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Giuseppina LEO

Personale tecnico amministrativo presso: Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze sede ex-Sc. Biomediche


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Pubblicazioni

2021 - Hsp90-mediated regulation of DYRK3 couples stress granule disassembly and growth via mTORC1 signaling [Articolo su rivista]
Mediani, L.; Antoniani, F.; Galli, V.; Vinet, J.; Carra, A. D.; Bigi, I.; Tripathy, V.; Tiago, T.; Cimino, M.; Leo, G.; Amen, T.; Kaganovich, D.; Cereda, C.; Pansarasa, O.; Mandrioli, J.; Tripathi, P.; Troost, D.; Aronica, E.; Buchner, J.; Goswami, A.; Sterneckert, J.; Alberti, S.; Carra, S.
abstract

Stress granules (SGs) are dynamic condensates associated with protein misfolding diseases. They sequester stalled mRNAs and signaling factors, such as the mTORC1 subunit raptor, suggesting that SGs coordinate cell growth during and after stress. However, the molecular mechanisms linking SG dynamics and signaling remain undefined. We report that the chaperone Hsp90 is required for SG dissolution. Hsp90 binds and stabilizes the dual-specificity tyrosine-phosphorylation-regulated kinase 3 (DYRK3) in the cytosol. Upon Hsp90 inhibition, DYRK3 dissociates from Hsp90 and becomes inactive. Inactive DYRK3 is subjected to two different fates: it either partitions into SGs, where it is protected from irreversible aggregation, or it is degraded. In the presence of Hsp90, DYRK3 is active and promotes SG disassembly, restoring mTORC1 signaling and translation. Thus, Hsp90 links stress adaptation and cell growth by regulating the activity of a key kinase involved in condensate disassembly and translation restoration.


2019 - Exosomes from astrocyte processes: Signaling to neurons [Articolo su rivista]
Venturini, A.; Passalacqua, M.; Pelassa, S.; Pastorino, F.; Tedesco, M.; Cortese, K.; Gagliani, M. C.; Leo, G.; Maura, G.; Guidolin, D.; Agnati, L. F.; Marcoli, M.; Cervetto, C.
abstract

It is widely recognized that extracellular vesicles subserve non-classical signal transmission in the central nervous system. Here we assess if the astrocyte processes, that are recognized to play crucial roles in intercellular communication at the synapses and in neuron-astrocyte networks, could convey messages through extracellular vesicles. Our findings indicate, for the first time that freshly isolated astrocyte processes prepared from adult rat cerebral cortex, can indeed participate to signal transmission in central nervous system by releasing exosomes that by volume transmission might target near or longdistance sites. It is noteworthy that the exosomes released from the astrocyte processes proved ability to selectively target neurons. The astrocyte-derived exosomes were proven positive for neuroglobin, a protein functioning as neuroprotectant against cell insult; the possibility that exosomes might transfer neuroglobin to neurons would add a mechanism to the potential astrocytic neuroprotectant activity. Notably, the exosomes released from the processes of astrocytes maintained markers, which prove their parental astrocytic origin. This potentially allows the assessment of the cellular origin of exosomes that might be recovered from body fluids.


2018 - A hydroxypyrone-based inhibitor of metalloproteinase-12 displays neuroprotective properties in both status epilepticus and optic nerve crush animal models [Articolo su rivista]
Vinet, J.; Costa, A. M.; Salinas-Navarro, M.; Leo, G.; Moons, L.; Arkens, L.; Biagini, G.
abstract

Recently, we showed that matrix metalloproteinase-12 (MMP-12) is highly expressed in microglia and myeloid infiltrates, which are presumably involved in blood–brain barrier (BBB) leakage and subsequent neuronal cell death that follows status epilepticus (SE). Here, we assessed the effects of a hydroxypyrone-based inhibitor selective for MMP-12 in the pilocarpine-induced SE rat model to determine hippocampal cell survival. In the hippocampus of rats treated with pilocarpine, intra-hippocampal injections of the MMP-12 inhibitor protected Cornu Ammonis 3 (CA3) and hilus of dentate gyrus neurons against cell death and limited the development of the ischemic-like lesion that typically develops in the CA3 stratum lacunosum-moleculare of the hippocampus. Furthermore, we showed that MMP-12 inhibition limited immunoglobulin G and albumin extravasation after SE, suggesting a reduction in BBB leakage. Finally, to rule out any possible involvement of seizure modulation in the neuroprotective effects of MMP-12 inhibition, neuroprotection was also observed in the retina of treated animals after optic nerve crush. Overall, these results support the hypothesis that MMP-12 inhibition can directly counteract neuronal cell death and that the specific hydroxypyrone-based inhibitor used in this study could be a potential therapeutic agent against neurological diseases/disorders characterized by an important inflammatory response and/or neuronal cell loss.


2018 - Untargeted rat brain metabolomics after oral administration of a single high dose of cannabidiol [Articolo su rivista]
Citti, Cinzia; Palazzoli, Federica; Licata, Manuela; Vilella, Antonietta; Leo, Giuseppina; Zoli, Michele; Vandelli, Maria Angela; Forni, Flavio; Pacchetti, Barbara; Cannazza, Giuseppe
abstract

Cannabidiol (CBD), for long time considered as a minor cannabinoid of Cannabis sativa, has recently gained much attention due to its antioxidant, anti-inflammatory, analgesic and anticonvulsant properties. A liquid chromatography coupled to mass spectrometry based method was developed for the quantitative determination of CBD and other cannabinoids (Δ9-tetrahydrocannabinol (THC), 11-hydroxy-THC and 11-nor-9-carboxy-THC) in rat brain samples after oral administration of a single high dose (50 mg/kg) of CBD. The main challenge of the present work was to study CBD pharmacokinetics in rat cortex: the identification of its metabolites and pharmacodynamics through the study of variations in endogenous compounds’ concentrations following CBD administration. An untargeted metabolomics approach revealed the formation of some CBD metabolites that are not commonly found in other body tissues or fluids. Lastly, the changes in some endogenous compounds’ concentrations were correlated with some of the pharmacological properties of this cannabinoid.


2017 - FosB/ΔFosB and p-ERK1/2 expression respectively identified the lateral amygdala and CA1 as critical regions involved in the progressive seizure aggravation observed in mice exposed to repeated 6-Hz corneal stimulation [Abstract in Atti di Convegno]
Costa, Am; Giordano, C; Lucchi, C; Curia, G; Piat, M; Leo, G; Vinet, J; Biagini, G
abstract

FosB/ΔFosB and p-ERK1/2 expression respectively identified the lateral amygdala and CA1 as critical regions involved in the progressive seizure aggravation observed in mice exposed to repeated 6-Hz corneal stimulation


2017 - Involvement of PPARγ in the anticonvulsant activity of EP-80317, a ghrelin receptor antagonist [Articolo su rivista]
Lucchi, Chiara; Costa, ANNA MARIA; Giordano, Carmela; Curia, Giulia; Piat, Marika; Leo, Giuseppina; Vinet, Jonathan; Brunel, Luc; Fehrentz, Jean Alain; Martinez, Jean; Torsello, Antonio; Biagini, Giuseppe
abstract

Ghrelin, des-acyl ghrelin and other related peptides possess anticonvulsant activities. Although ghrelin and cognate peptides were shown to physiologically regulate only the ghrelin receptor, some of them were pharmacologically proved to activate the peroxisome proliferator-activated receptor gamma (PPARγ) through stimulation of the scavenger receptor CD36 in macrophages. In our study, we challenged the hypothesis that PPARγ could be involved in the anticonvulsant effects of EP-80317, a ghrelin receptor antagonist. For this purpose, we used the PPARγ antagonist GW9662 to evaluate the modulation of EP-80317 anticonvulsant properties in two different models. Firstly, the anticonvulsant effects of EP-80317 were studied in rats treated with pilocarpine to induce status epilepticus (SE). Secondly, the anticonvulsant activity of EP-80317 was ascertained in the repeated 6-Hz corneal stimulation model in mice. Behavioral and video electrocorticographic (ECoG) analyses were performed in both models. We also characterized levels of immunoreactivity for PPARγ in the hippocampus of 6-Hz corneally stimulated mice. EP-80317 predictably antagonized seizures in both models. Pre-treatment with GW9662 counteracted almost all EP-80317 effects both in mice and rats. Only the effects of EP-80317 on power spectra of ECoGs recorded during repeated 6-Hz corneal stimulation were practically unaffected by GW9662 administration. Moreover, GW9662 alone produced a decrease in the latency of tonic-clonic seizures and accelerated the onset of SE in rats. Finally, in the hippocampus of mice treated with EP-80317 we found increased levels of PPARγ immunoreactivity. Overall, these results support the hypothesis that PPARγ is able to modulate seizures and mediates the anticonvulsant effects of EP-80317.


2016 - A Surveillance Function of the HSPB8-BAG3-HSP70 Chaperone Complex Ensures Stress Granule Integrity and Dynamism [Articolo su rivista]
Ganassi, Massimo; Mateju, Daniel; Bigi, Ilaria; Mediani, Laura; Poser, Ina; Lee, Hyun O.; Seguin, Samuel Joseph Andre'; Morelli, Federica Francesca; Vinet, Jonathan; Leo, Giuseppina; Pansarasa, Orietta; Cereda, Cristina; Poletti, Angelo; Alberti, Simon; Carra, Serena
abstract

Stress granules (SGs) are ribonucleoprotein complexes induced by stress. They sequester mRNAs and disassemble when the stress subsides, allowing translation restoration. In amyotrophic lateral sclerosis (ALS), aberrant SGs cannot disassemble and therefore accumulate and are degraded by autophagy. However, the molecular events causing aberrant SG formation and the molecular players regulating this transition are largely unknown. We report that defective ribosomal products (DRiPs) accumulate in SGs and promote a transition into an aberrant state that renders SGs resistant to RNase. We show that only a minor fraction of aberrant SGs is targeted by autophagy, whereas the majority disassembles in a process that requires assistance by the HSPB8-BAG3-HSP70 chaperone complex. We further demonstrate that HSPB8-BAG3-HSP70 ensures the functionality of SGs and restores proteostasis by targeting DRiPs for degradation. We propose a system of chaperone-mediated SG surveillance, or granulostasis, which regulates SG composition and dynamics and thus may play an important role in ALS.


2016 - Progressive Seizure Aggravation in the Repeated 6-Hz Corneal Stimulation Model Is Accompanied by Marked Increase in Hippocampal p-ERK1/2 Immunoreactivity in Neurons [Articolo su rivista]
Giordano, Carmela; Costa, ANNA MARIA; Lucchi, Chiara; Leo, Giuseppina; Brunel, Luc; Fehrentz, Jean Alain; Martinez, Jean; Torsello, Antonio; Biagini, Giuseppe
abstract

The 6-Hz corneal stimulation test is used to screen novel antiepileptic molecules to overcome the problem of drug refractoriness. Although recognized as a standard test, it has been evaluated only recently in the attempt to characterize the putative neuronal networks involved in seizures caused by corneal stimulation. In particular, by recording from the CA1 region we previously established that the hippocampus participates to propagation of seizure activity. However, these findings were not corroborated by using markers of neuronal activation such as FosB/ΔFosB antigens. In view of this discrepancy, we performed new experiments to characterize the changes in levels of phosphorylated extracellular signal-regulated kinases1/2 (p-ERK1/2), which are also used as markers of neuronal activation. To this aim, mice underwent corneal stimulation up to three different times, in three sessions separated by an interval of 3 days. To characterize a group in which seizures could be prevented by pharmacological treatment, we also considered pretreatment with the ghrelin receptor antagonist EP-80317 (330 μg/kg). Control mice were sham-treated. Video electrocorticographic (ECoG) recordings were obtained from mice belonging to each group of treatment. Animals were finally used to characterize the immunoreactivity for FosB/ΔFosB and p-ERK1/2 in the hippocampus. As previously shown, FosB/ΔFosB levels were highly increased throughout the hippocampus by the first induced seizure but, in spite of the progressively increased seizure severity, they were restored to control levels after the third stimulation. At variance, corneal stimulation caused a progressive increase in p-ERK1/2 immunoreactivity all over the hippocampus, especially in CA1, peaking in the third session. Predictably, EP-80317 administration reduced both duration and severity of seizures, prevented the increase in FosB/ΔFosB levels in the first session, and partially counteracted the increase in p-ERK1/2 levels in the third session. The vast majority of p-ERK1/2 immunopositive cells were co-labeled with FosB/ΔFosB antibodies, suggesting the existence of a relationship between the investigated markers in a subpopulation of neurons activated by seizures. These findings suggest that p-ERK1/2 are useful markers to define the aggravation of seizures and the response to anticonvulsant treatments. In particular, p-ERK1/2 expression clearly identified the involvement of hippocampal regions during seizure aggravation in the 6-Hz model.


2015 - Acute isoproterenol induces anxiety-like behavior in rats and increases plasma content of extracellular vesicles [Articolo su rivista]
Leo, Giuseppina; Guescini, Michele; Genedani, Susanna; Stocchi, Vilberto; Carone, Chiara; Filaferro, Monica; Sisti, Davide; Marcoli, Manuela; Maura, Guido; Cortelli, Pietro; Guidolin, Diego; Fuxe, Kjell; Agnati, Luigi Francesco
abstract

Several clinical observations have demonstrated a link between heart rate and anxiety or panic disorders. In these patients, β-adrenergic receptor function was altered. This prompted us to investigate whether the β-adrenergic receptor agonist isoproterenol, at a dose that stimulates peripheral β-adrenergic system but has no effects at the central nervous system, can induce anxiety-like behavior in rats. Moreover, some possible messengers involved in the peripheral to brain communication were investigated. Our results showed that isoproterenol (5 mg kg(-1) i.p.) increased heart rate, evoked anxiety-like behavior, did not result in motor impairments and increased extracellular vesicle content in the blood. Plasma corticosterone level was unmodified as well as vesicular Hsp70 content. Vesicular miR-208 was also unmodified indicating a source of increased extracellular vesicles different from cardiomyocytes. We can hypothesize that peripheral extracellular vesicles might contribute to the β-adrenergic receptor-evoked anxiety-like behavior, acting as peripheral signals in modulating the mental state.


2015 - In vitro effects of cocaine on tunneling nanotube formation and extracellular vesicle release in glioblastoma cell cultures [Articolo su rivista]
Carone, Chiara; Genedani, Susanna; Leo, Giuseppina; Filaferro, Monica; Fuxe, Kjell; Agnati, Luigi Francesco
abstract

The effects of cocaine (150 nM, 300 nM, and 150 μM) on human glioblastoma cell cultures were studied on tunneling nanotube formation (1-h cocaine treatment) and extracellular vesicle release (1-, 3-, and 8-h cocaine treatment). Cocaine significantly increased the number of tunneling nanotubes only at the lowest concentration used. The release of extracellular vesicles (mainly exosomes) into the medium was stimulated by cocaine at each concentration used with a maximum effect at the highest concentration tested (150 μM). Moreover, cocaine (150 nM) significantly increased the number of vesicles with 61-80 nm diameter while at concentrations of 300 nM and 150 μM, and the smaller vesicles (30-40 nm diameter) were significantly increased with a reduction of the larger vesicles (41-60 nm diameter). A time dependence in the release of extracellular vesicles was observed. In view of the proposed role of these novel intercellular communication modes in the glial-neuronal plasticity, it seems possible that they can participate in the processes leading to cocaine addiction. The molecular target/s involved in these cocaine effects could be specific molecular components of plasma membrane lipid rafts and/or cocaine-induced modifications in cytoplasmic lipid composition.


2014 - Information handling by the brain: proposal of a new "paradigm" involving the roamer type of volume transmission and the tunneling nanotube type of wiring transmission [Articolo su rivista]
Agnati, Luigi F; Guidolin, Diego; Maura, Guido; Marcoli, Manuela; Leo, Giuseppina; Carone, Chiara; De Caro, Raffaele; Genedani, Susanna; Borroto Escuela, Dasiel O; Fuxe, Kjell
abstract

The current view on the organization of the central nervous system (CNS) is basically anchored to the paradigm describing the brain as formed by networks of neurons interconnected by synapses. Synaptic contacts are a fundamental characteristic for describing CNS operations, but increasing evidence accumulated in the last 30 years pointed to a refinement of this view. A possible overcoming of the classical "neuroscience paradigm" will be here outlined, based on the following hypotheses: (1) the basic morpho-functional unit in the brain is a compartment of tissue (functional module) where different resident cells (not only neurons) work as an integrated unit; (2) in these complex networks, a spectrum of intercellular communication processes is exploited, that can be classified according to a dichotomous criterion: wiring transmission (occurring through physically delimited channels) and volume transmission (exploiting diffusion in the extracellular space); (3) the connections between cells can themselves be described as a network, leading to an information processing occurring at different levels from cell network down to molecular level; (4) recent evidence of the existence of specialized structures (microvesicles and tunneling nanotubes) for intercellular exchange of materials, could allow a further type of polymorphism of the CNS networks based on at least transient changes in cell phenotype. When compared to the classical paradigm, the proposed scheme of cellular organization could allow a strong increase of the degrees of freedom available to the whole system and then of its plasticity. Furthermore, long range coordination and correlation can be more easily accommodated within this framework.


2012 - Microvesicle and tunneling nanotube mediated intercellular transfer of g-protein coupled receptors in cell cultures. [Articolo su rivista]
Guescini, M; Leo, Giuseppina; Genedani, Susanna; Carone, C; Pederzoli, Francesca; Ciruela, F; Guidolin, D; Stocchi, V; Mantuano, M; Borroto Escuela, Do; Fuxe, K; Agnati, L. F.
abstract

Recent evidence shows that cells exchange collections of signals via microvesicles (MVs) and tunneling nano-tubes (TNTs). In this paper we have investigated whether in cell cultures GPCRs can be transferred by means of MVs and TNTs from a source cell to target cells. Western blot, transmission electron microscopy and gene expression analyses demonstrate that A(2A) and D(2) receptors are present in released MVs. In order to further demonstrate the involvement of MVs in cell-to-cell communication we created two populations of cells (HEK293T and COS-7) transiently transfected with D(2)R-CFP or A(2A)R-YFP. These two types of cells were co-cultured, and FRET analysis demonstrated simultaneously positive cells to the D(2)R-CFP and A(2A)R-YFP. Fluorescence microscopy analysis also showed that GPCRs can move from one cell to another also by means of TNTs. Finally, recipient cells pre-incubated for 24h with A(2A)R positive MVs were treated with the adenosine A(2A) receptor agonist CGS-21680. The significant increase in cAMP accumulation clearly demonstrated that A(2A)Rs were functionally competent in target cells. These findings demonstrate that A(2A) receptors capable of recognizing and decoding extracellular signals can be safely transferred via MVs from source to target cells.


2011 - Possible new targets for GPCR modulation: allosteric interactions, plasma membrane domains, intercellular transfer and epigenetic mechanisms. [Articolo su rivista]
Agnati, Lf; Guidolin, D; Leo, Giuseppina; Guescini, M; Pizzi, M; Stocchi, V; Spano, Pf; Ghidoni, R; Ciruela, F; Genedani, Susanna; Fuxe, K.
abstract

It has been estimated that at least 50% of the drugs available on the market act on G-protein coupled receptors (GPCRs) and most of these are basically or agonists or antagonists of this type of receptors. Herein, we propose new putative targets for drug development based on recent data on GPCR allosterism and on the existence of receptor mosaics (RMs). The main target for drug development is still GPCRs, but the focus is not the orthosteric binding pocket. According to the mosaic model of the plasma membrane, we mainly discuss the possibility of indirect modulatory pharmacological actions on expression/function of GPCRs. In particular, the following two new targets will be analyzed: a) The possibility of pharmacological interventions on the roamer-type of volume transmission (VT), which allow the intercellular transfer of set of signal molecules such as GPCRs, tetraspanins and ribonucleic acids. Thus, there is the possibility of pharmacological interventions on the decoding capabilities of neurons and/or glial cells by means of an action on composition and release of micro-vesicles. b) The possibility of pharmacological interventions on epigenetic mechanisms by taking into account their inter-relationships with GPCRs. As a matter of fact, there are epigenetic changes that are characteristic of periods of developmental plasticity that could provide a target for therapeutic intervention in the event of brain damage. We believe that almost all the biochemical knowledge presently available on GPCRs can be used in the development of these new pharmacological approaches.


2010 - A New Hypothesis of Pathogenesis Based on the Divorce between Mitochondria and their Host Cells: Possible Relevances for the Alzheimer's Disease. [Articolo su rivista]
Agnati, Luigi Francesco; D., Guidolin; F., BaluskaF; Leo, Giuseppina; P. W., Barlow; Carone, Chiara; Genedani, Susanna
abstract

On the basis of not only the endosymbiotic theory of eukaryotic cell organization and evolution but also of observations of transcellular communication via Tunneling NanoTubes (TNTs), the hypothesis is put forward that when mitochondria, which were once independently living prokaryote-like organisms, are subjected to detrimental genetic, toxic, or environmental conditions, including age-related endogenous factors, they can regress towards their original independent state. At that point, they can become potentially pathogenic intruders within their eukaryotic host cell. Because of the protoplasmic disequilibrium caused by an altered, or mutated, mitochondral population, certain host cells with a minimal capacity for self-renewal, such as dopaminergic neurons, risk a loss of function and degenerate. It is also proposed that altered mitochondria, as well as their mutated mtDNA, can migrate, via TNTs, into adjacent cells. In this way, neurodegenerative states are propagated between cells (glia and/or neurons) of the Central Nervous System (CNS) and that this leads to conditions such as Alzheimer's and Parkinson's disease. This proposal finds indirect support from observations on rotenone-poisoned glioblastoma cells which have been co-cultured with non-poisoned cells. Immunocytochemical techniques revealed that mitochondria, moving along the TNTs, migrated from the poisoned cells towards the healthy cells. It has also been demonstrated by means of immunocytochemistry that, in glioblastoma cell cultures, Amyloid Precursor Protein (APP) is present in TNTs, hence it may migrate from one cell to neighbouring cells. This datum may be of high relevance for a better understanding of Alzheimer's Disease (AD) since molecular, cellular, and animal model studies have revealed that the formation of amyloid beta (Abeta) and other derivatives of the APP are key pathogenic factors in AD, causing mitochondrial dysfunction, free radical generation, oxidative damage, and inflammation. Furthermore, the present data demonstrate the presence of alpha-synuclein (alpha-syn) within TNTs, hence a similar pathogenic mechanism to the one surmised for AD, but centred on alpha-syn rather than on Abeta, may play a role in Parkinson's Disease (PD). As a matter of fact, alpha-syn can enter mitochondria and interact with complex I causing respiratory deficiency and increased oxygen free radical production. In agreement with this view, it has been demonstrated that, in comparison with normal subjects, PD patients show a significant accumulation of alpha-syn at Substantia Nigra and Striatal level, predominantly associated with the inner mitochondrial membrane,. These observations suggest that potentially neuropathogenic proteins, such as Abeta and alpha-syn, can not only diffuse via the extracellular space but also move from cell to cell also via TNTs where they can cause mitochondrial damage and cell degeneration. A mathematical model (see Appendix) is proposed to simulate the pathogenic consequences of the migration of altered mitochondria and/or of their mtDNA via TNTs. The results of the present simulation is compatible with the proposal that mutated mitochondrial agents behave as though they were infectious particles migrating through a continuum of interconnected cells.


2010 - Beta-amyloid fibrillation and/or hyperhomocysteinemia modify striatal patterns of hyaluronic acid and dermatan sulfate: possible role in the pathogenesis of Alzheimer's disease. [Articolo su rivista]
Genedani, Susanna; Agnati, Luigi Francesco; Leo, Giuseppina; Buzzega, D.; Maccari, Francesca; Carone, Chiara; Andreoli, Nicola; Filaferro, Monica; Volpi, Nicola
abstract

A key event in Alzheimer's disease (AD) pathogenesis is the formation of insoluble peptides -amyloid aggregates and this process is favoured by a condition of hyperhomocysteinemia. To date, there is growing evidence that implicates glycosaminoglycans (GAGs) in the pathophysiology of amyloidosis but no data are available on the characterization of brain GAGs involved in the enhancing -amyloid fibrillogenesis in relationship to their structure and physico-chemical properties. Furthermore, few studies have been performed on the relationship between hyperhomocysteinemia and extracellular matrix (ECM) modifications. The aim of this study was to evaluate the amount and chemical structure of GAGs in rat striatal areas where -amyioid fibrillogenesis was induced, and in conditions of hyperhomocysteinemia. The intrastriatal injection of -amyloid produced a significant decrease (-40.8%) in the hyaluronic acid (HA) percentage and an increase (+14.5%) in the dermatan sulfate (DS) with a total charge density increasing of 14.9%. A significant decrease (-19.5%) in the HA percentage and an increase (+6.9%) in the DS % was also observed in striata obtained from the hyperhomocysteinemic animals. The total charge density increased by 6.8%. Quite the same trend was observed in rats after intrastriatal injection of -amyloid and in a condition of hyperhomocysteinemia. The observed increase of DS concentration and the correspondent decrease of the nonsulfated polymer HA after in vivo treatment with -amyloid and in a condition of hyperhocysteinemia support the hypothesis that an increase in local production of sulfated GAGs may reduce -amyloid neurotoxicity. However, the consequent modification of the ECM network might impair the extracellular diffusion pathways of different signal molecules and participate in the progression of AD.


2010 - Homocysteine potentiates seizures and cell loss induced by pilocarpine treatment [Articolo su rivista]
Baldelli, Enrica; Leo, Giuseppina; Andreoli, Nicola; K., Fuxe; Biagini, Giuseppe; Agnati, Luigi Francesco
abstract

Patients affected by recurrent seizures frequently present increased homocysteine plasma levels in consequence of treatment with antiepileptic drugs. Homocysteine is proconvulsant and can affect the response to antiepileptic drugs. In addition, high homocysteine plasma levels represent a risk factor for cardiovascular and neurodegenerative diseases. To better define the role of increased homocysteine in epilepsy, we analyzed the effects of homocysteine pretreatment in the pilocarpine model of status epilepticus (SE), which is used to mimic temporal lobe epilepsy (TLE) in rodents. Precisely, we investigated whether a moderate hyperhomocysteinemia, unable to cause seizures, could sensitize rats to pilocarpine and cooperate in inducing brain lesions. We found that a subthreshold dose of pilocarpine (200 mg/kg) is sufficient to induce SE in the majority (approximately 90%) of rats pretreated with homocysteine for 2 weeks, whereas only 40% of saline-treated controls developed SE following the same pilocarpine dose. Furthermore, homocysteine pretreatment led to a significant increase in neuronal cell loss evaluated by counting toluidine blue-stained or Fluoro-Jade-positive cells in hippocampal and parahippocampal regions. Pilocarpine augmented amyloid beta expression in both animal groups. However, pretreatment with homocysteine favored the intraneuronal fibrillar conformation of amyloid beta, thus promoting neurodegeneration. These findings indicate that increased homocysteine levels enhance seizure activity and neurodegeneration in pilocarpine-treated rats and suggest that similar detrimental effects may occur in patients affected by TLE.


2010 - Receptor-receptor interactions: A novel concept in brain integration. [Articolo su rivista]
Agnati, Luigi Francesco; D., Guidolin; Leo, Giuseppina; Carone, Chiara; Genedani, Susanna; K., Fuxe
abstract

A brief historical presentation of the hypothesis on receptor-receptor interactions as an important integrative mechanism taking place at plasma membrane level is given. Some concepts derived from this integrative mechanism especially the possible assemblage of receptors in receptor mosaics (high-order receptor oligomers) and their relevance for the molecular networks associated with the plasma membrane are discussed. In particular, the Rodbell's disaggregation theory for G-proteins is revisited in the frame of receptor mosaic model. The paper also presents some new indirect evidence on A2A;D2 receptor interactions obtained by means of Atomic Force Microscopy on immunogold preparations of A2A and D2 receptors in CHO cells. These findings support previous data obtained by means of computer-assisted confocal laser microscopy. The allosteric control of G-protein coupled receptors is examined in the light of the new views on allosterism and recent data on a homocysteine analogue capable of modulating D2 receptors are shown. Finally, the hypothesis is introduced on the existence of check-points along the amino acid pathways connecting allosteric and orthosteric binding sites of a receptor and their potential importance for drug development.


2009 - Common key-signals in learning and neurodegeneration: focus on excito-amino acids, beta-amyloid peptides and alpha-synuclein. [Articolo su rivista]
Agnati, Luigi Francesco; Leo, Giuseppina; Genedani, Susanna; L., Piron; A., Rivera; D., Guidolin; K., Fuxe
abstract

In this paper a hypothesis that some special signals (“key-signals” excito-amino acids, β-amyloid peptides and α-synuclein) are not only involved in information handling by the neuronal circuits, but also trigger out substantial structural and/or functional changes in the Central Nervous System (CNS) is introduced. This forces the neuronal circuits to move from one stable state towards a new state, but in doing so these signals became potentially dangerous. Several mechanisms are put in action to protect neurons and glial cells from these potentially harmful signals. However, in agreement with the Red Queen Theory of Ageing (Agnati et al. in Acta Physiol Scand 145:301–309, 1992), it is proposed that during ageing these neuroprotective processes become less effective while, in the meantime, a shortage of brain plasticity occurs together with an increased need of plasticity for repairing the wear and tear of the CNS. The paper presents findings supporting the concept that such key-signals in instances such as ageing may favour neurodegenerative processes in an attempt of maximizing neuronal plasticity.


2008 - Structural plasticity in G-protein coupled receptors as demonstrated by the allosteric actions of homocysteine and computer-assisted analysis of disordered domains [Articolo su rivista]
Agnati, Luigi Francesco; Leo, Giuseppina; Genedani, Susanna; Andreoli, Nicola; D., Marcellino; A., Woods; L., Piron; D., Guidolin; K., Fuxe
abstract

Structural plasticity of G-protein coupled receptors (GPCRs) is of basic importance for their interactions with ligands, in particular with other proteins such as receptors or receptor-modifying proteins that can lead to different functions for the same GPCR. In the present paper, structural plasticity of GPCRs has been investigated discussing allosteric modulatory actions of Homocysteine (Hcy) on D2 receptors together with data obtained by computer-assisted analysis of the presence of disordered domains in GPCRs. Previous evidence for a modulatory action of Hcy on D2 receptors has been further extended by means of experiments on the effects of Hcy local intrastriatal injection on rotational behaviour. Altogether the present data allow considering under a new angle the well known proposal of A2A antagonists as new therapeutic agents in Parkinson's disease (PD). Furthermore, they point out to not only the importance of drugs capable of reducing Hcy brain levels, but also to the potential therapeutic impact of drugs capable of regionally blocking (for PD) or enhancing (for some schizophrenic syndromes) Hcy allosteric action on D2 receptors.As far as the investigations on GPCR plastic domains, extracellular, intracellular and transmembrane domains of 14 GPCRs have been considered and propensity of each of these domains for a structured or unstructured conformation has been evaluated by means of ad hoc computer programs. It has been shown that the N- and C-terminals as well as intracellular loop 3 have a high propensity towards an unstructured conformation, hence they are potentially very plastic domains, which can undergo easily to interactions with other ligands, particularly with other protein domains. This aspect is obviously of the greatest importance not only for the function of single GPCRs, but also for their interactions either with other receptors (receptor–receptor interactions) or, more generally, for formation of clusters of membrane associated proteins, hence of “protein mosaics”, where the GPCRs could represent the input unit of the supra-molecular device.


2008 - The novel cyclooxygenase-2 inhibitor GW637185X protects against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxicity. [Articolo su rivista]
J. A., Aguirre; Leo, Giuseppina; R., Cueto; B., Andbjer; A., Naylor; A. D., Medhurst; Agnati, Luigi Francesco; Fuxe, K.
abstract

The possible neuroprotective role of a novel and highly selective cyclooxygenase-2 inhibitor GW637185X was studied in a model of acute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced injury of nigrostriatal dopaminergic (DA) neurons in the mouse. Stereological and microdensitometrical analysis of nigral tyrosine hydroxylase-immunoreactive cell bodies and striatal tyrosine hydroxylase-immunoreactive terminals, respectively, showed that GW637185X exerted a full protection against MPTP-induced degeneration of the nigro-striatal pathway. In contrast to earlier studies, these findings demonstrate that acute inhibition of cyclooxygenase-2 can result in a full neuroprotective effect not only on nigral DA cell bodies, but also on striatal DA terminals in the mouse MPTP model.


2007 - A beta peptides as one of the crucial volume transmission signals in the trophic units and their interactions with homocysteine. Physiological implications and relevance for Alzheimer's disease [Articolo su rivista]
Agnati, Luigi Francesco; Genedani, Susanna; Leo, Giuseppina; Forni, Arrigo; A. S., Woods; Filaferro, Monica; R., Franco; K., Fuxe
abstract

Amyloid peptides (Aβ) can operate as volume transmission (VT) signals since they are continuously released from cells of the central nervous system and diffuse in the extra-cellular space of the brain. They have both regulatory and trophic functions on cellular networks. In agreement with Aβ regulatory actions on glial-neuronal networks, the present paper reports new findings demonstrating that intrastriatal injections of Aβ peptides reduce striatal tyrosine hydroxylase, increase striatal GFAP immunoreactivities and lower pain threshold in experimental rats. Furthermore, it has been demonstrated that exogenous homocysteine (Hcy) binds Aβ(1-40) favouring its β-sheet conformation both in vitro and in vivo and hence the formation of β-fibrils and development of neurotoxicity.Thus, the hypothesis is discussed that Aβ peptides represent crucial VT-signals in the brain and their action is altered by dysmetabolic signals such as high Hcy extra-cellular levels, known to be an important risk factor for Alzheimer’s disease.


2007 - A boolean network modelling of receptor mosaics relevance of topology and cooperativity [Articolo su rivista]
Agnati, Luigi Francesco; Guidolin, D; Leo, Giuseppina; Fuxe, K.
abstract

In the last five years data have been obtained showing that a functional cross-talk among G Protein Coupled receptors (GPCR) exists at the plasma membrane level where they can dimerise and are able to generate high order oligomers. These findings are in agreement with the receptor mosaic (RM) hypothesis that claims the existence of clusters of receptor proteins at the plasma membrane level, where they establish mutual interactions and work as 'intelligent interfaces' between the extra-cellular and the intra-cellular environments. Individual receptor dimers can be considered to have two stable conformational states with respect to the macromolecular effectors: one active, one inactive. Owing to receptor-receptor interactions, however, a state change of a given receptor will change the probability of changing the state for the adjacent receptors in the RM and the effect will propagate throughout the cluster, leading to a complex cooperative behaviour. In this study we explore the properties of a RM on the basis of an equivalence with a Boolean network, a mathematical framework able to describe how complex properties may emerge from systems characterized by deterministic local interactions of many simple components acting in parallel. Computer simulations of receptor clusters arranged according to topologies consistent with available experimental ultrastructural data were performed. They indicated that RMs after a stimulation can achieve a limited number of specific temporary equilibrium configurations (attractors), characterized by the presence of receptor units frozen in the active state. They could be interpreted as a form of information storage and a role of RM in learning and memory could be hypothesized. Moreover, they seem to be at the basis of very common 'macroscopical' properties of a receptor system, such as a sigmoidal response curve to an extracellular ligand, the sensitivity of the mosaic being modulated by changes in the topology and/or in the level of cooperativity among receptors.


2007 - From the Golgi-Cajal mapping to the transmitter-based characterization of the neuronal networks leading to two modes of brain communication: Wiring and volume transmission. [Articolo su rivista]
Fuxe, K; Dahlstrom, A; Hoistad, M; Marcellino, D; Jansson, A; Rivera, A; DIAZ CABIALE, Z; Jacobsen, K; TINNER STAINES, B; Hagman, B; Leo, Giuseppina; Staines, W; Guidolin, D; Kehr, J; Genedani, Susanna; Belluardo, N; Agnati, Luigi Francesco
abstract

After Golgi–Cajal mapped neural circuits, the discovery and mapping of the central monoamine neurons opened up for a new understanding of interneuronal communication by indicating that another form of communication exists. For instance, it was found that dopamine may be released as a prolactin inhibitory factor from the median eminence, indicating an alternative mode of dopamine communication in the brain. Subsequently, the analysis of the locus coeruleus noradrenaline neurons demonstrated a novel type of lower brainstem neuron that monosynaptically and globally innervated the entire CNS. Furthermore, the ascending raphe serotonin neuron systems were found to globally innervate the forebrain with few synapses, and where deficits in serotonergic function appeared to play a major role in depression. We propose that serotonin reuptake inhibitors may produce antidepressant effects through increasing serotonergic neurotrophism in serotonin nerve cells and their targets by transactivation of receptor tyrosine kinases (RTK), involving direct or indirect receptor/RTK interactions. Early chemical neuroanatomical work on the monoamine neurons, involving primitive nervous systems and analysis of peptide neurons, indicated the existence of alternative modes of communication apart from synaptic transmission. In 1986, Agnati and Fuxe introduced the theory of two main types of intercellular communication in the brain: wiring and volume transmission (WT and VT). Synchronization of phasic activity in the monoamine cell clusters through electrotonic coupling and synaptic transmission (WT) enables optimal VT of monoamines in the target regions. Experimental work suggests an integration of WT and VT signals via receptor–receptor interactions, and a new theory of receptor–connexin interactions in electrical and mixed synapses is introduced. Consequently, a new model of brain function must be built, in which communication includes both WT and VT and receptor–receptor interactions in the integration of signals. This will lead to the unified execution of information handling and trophism for optimal brain function and survival.


2007 - Hyper-homocysteinemia alters amyloid peptide-clusterin interactions and neuroglial network morphology and function in the caudate after intrastriatal injection of amyloid peptides. [Articolo su rivista]
Leo, Giuseppina; Genedani, Susanna; Filaferro, Monica; Carone, Chiara; Andreoli, Nicola; Astancolle, Serenella; Davalli, Pierpaola; Fuxe, K; Agnati, Luigi Francesco
abstract

Amyloid peptides (Aβ) are fragments of the Amyloid Precursor Protein (APP), an integral membrane protein. Aβ peptides are continuously generated by neurons and non-neuronal cells via sequential cleavage of APP by secretases. In particular, Aβ1-42 is the main component of the senile plaques associated with Alzheimer's disease (AD). Glial cells participate in the uptake of soluble extra-cellular Aβ and in the clearance of this material at localized sites where the Aβ are concentrated. It has been shown that clusterin (Apo J) and apolipoprotein E (ApoE) exert important additive effects in reducing Aβ deposition. In agreement with the fact that homocysteine (Hcy) potentiates Aβ peptide neurotoxicity, and Hcy brain levels increase with age, it has been demonstrated that high plasma levels of Hcy are a risk factor for AD.In the present paper, we used animals subjected to chronic intake of methionine (1 g/kg/day) in the drinking water, since this treatment can increase plasma Hcy levels by 30%. By means of this animal model, interactions between the Aβ β- sheet rich fibrils and clusterin, have been evaluated in striata of animals after Aβ injection. Furthermore, it has been demonstrated that Aβ peptides are not only signals capable of activating astrocytes but also capable of reducing tyrosinehydroxylase immunoreactivity in the basal ganglia probably leading to a reduction of volume transmission. These alterations in the neuroglial network morphology and function can, at least in part, explain the enhanced pain threshold observed in the Aβ intra-striatally injected animals.


2007 - Intramembrane receptor-receptor interactions: a novel principle in molecular medicine [Articolo su rivista]
K., Fuxe; M., Canals; M., Torvinen; D., Marcellino; A., Terasmaa; Genedani, Susanna; Leo, Giuseppina; D., Guidolin; Z., Diaz Cabiale; A., Rivera; L., Lundstrom; U., Langel; J., Narvaez; S., Tanganelli; C., Lluis; S., Ferre; A., Woods; R., Franco; Agnati, Luigi Francesco
abstract

In 1980/81 Agnati and Fuxe introduced the concept of intramembrane receptor-receptor interactions and presented the first experimental observations for their existence in crude membrane preparations. The second step was their introduction of the receptor mosaic hypothesis of the engram in 1982. The third step was their proposal that the existence of intramembrane receptor-receptor interactions made possible the integration of synaptic (WT) and extrasynaptic (VT) signals. With the discovery of the intramembrane receptor-receptor interactions with the likely formation of receptor aggregates of multiple receptors, so called receptor mosaics, the entire decoding process becomes a branched process already at the receptor level in the surface membrane. Recent developments indicate the relevance of cooperativity in intramembrane receptor-receptor interactions namely the presence of regulated cooperativity via receptor-receptor interactions in receptor mosaics (RM) built up of the same type of receptor (homo-oligomers) or of subtypes of the same receptor (RM type1). The receptor-receptor interactions will to a large extent determine the various conformational states of the receptors and their operation will be dependent on the receptor composition (stoichiometry), the spatial organization (topography) and order of receptor activation in the RM. The biochemical and functional integrative implications of the receptor-receptor interactions are outlined and long-lived heteromeric receptor complexes with frozen RM in various nerve cell systems may play an essential role in learning, memory and retrieval processes. Intramembrane receptor-receptor interactions in the brain have given rise to novel strategies for treatment of Parkinson's disease (A2A and mGluR5 receptor antagonists), schizophrenia (A2A and mGluR5 agonists) and depression (galanin receptor antagonists). The A2A/D2, A2A/D3 and A2A/mGluR5 heteromers and heteromeric complexes with their possible participation in different types of RM are described in detail, especially in the cortico-striatal glutamate synapse and its extrasynaptic components, together with a postulated existence of A2A/D4 heteromers. Finally, the impact of intramembrane receptor-receptor interactions in molecular medicine is discussed outside the brain with focus on the endocrine, the cardiovascular and the immune systems.


2007 - Loss of high-affinity nicotinic receptors increases the vulnerability to excitotoxic lesion and decreases the positive effects of an enriched environment [Articolo su rivista]
Zanardi, Alessio; Ferrari, Rosaria; Leo, Giuseppina; U., Maskos; J. P., Changeux; Zoli, Michele
abstract

Pharmacological activation of nicotinic acetylcholine receptors (nAChRs) exerts neuroprotective effects in cultured neurons and the intact animal. Much less is known about a physiological protective role of nAChRs. In order to understand whether endogenous activation of beta2* nAChRs contributes to the maintenance of the functional and morphological integrity of neural tissue, adult beta2-/- mice were subjected to in vivo challenges which cause neurodegeneration and cognitive impairment (intrahippocampal injection of the excitotoxin quinolinic acid), or neuroprotection and cognitive potentiation (2 month-exposure to an enriched environment). The excitotoxic insult caused an increased deficit in the Morris water maze learning curve and increased loss of hippocampal pyramidal cells in beta2-/- mice. Exposure to an enriched environment improved performance in contextual and cued fear conditioning and object recognition tests in beta2+/+ whereas the improvement was absent in beta2-/- mice. In addition, beta2+/+, but not beta2-/-, mice exposed to an enriched environment showed a significant hypertrophy of the CA1/3 regions. Thus, lack of beta2* nAChRs increased susceptibility to an excitotoxic insult and diminished the positive effects of an enriched environment. These results may be relevant to understanding the pathophysiological consequences of the marked decrease in nAChRs that occurs in neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease.


2007 - One century of progress in neuroscience founded on Golgi and Cajal's outstanding experimental and theoretical contributions [Articolo su rivista]
Agnati, Luigi Francesco; Genedani, Susanna; Leo, Giuseppina; Rivera, A; Guidolin, D; Fuxe, K.
abstract

Since the discovery and mapping of the neuronal circuits of the brain by Golgi and Cajal neuroscientists have clearly spelled the fundamental questions which should be answered to delineate the arena for a scientific understanding of brain function:• How neurons communicate with each other in a network?• Is there some basic principle according to which brain networks are organised?• Is it possible to map out brain regions specialised in carrying out some specific task?As far as the first point is concerned it is well known that Golgi and Cajal had opposite views on the interneuronal communication. Golgi suggested protoplasmic continuity and/or electrotonic spreading of currents between neurons. Cajal proposed the so-called “neuron doctrine”, which maintained that neurons could communicate only via a specialised region of contiguity, namely the synapse.The present paper has the first and second points as main topics and last century progresses in these fields are viewed as developments of Golgi and Cajal's findings and above all, hypotheses. Thus, we will briefly discuss these topics moving from the transmitter based mapping, which brought neurochemistry into the Golgi–Cajal mapping of the brain with silver impregnation techniques. The mapping of transmitter-identified neurons in the brain represents one of the major foundations for neuropsychopharmacology and a reference frame for the biochemical and behavioural investigations of brain function. Biochemical techniques allowed giving evidence for multiple transmission lines in synapses interacting via receptor–receptor interactions postulated to be based on supramolecular aggregates, called receptor mosaics. Immunocytochemical and autoradiographic mapping techniques allowed the discovery of extra-synaptic receptors and of transmitter–receptor mismatches leading to the introduction of the volume transmission concept by Agnati–Fuxe teams. The Volume Transmission theory proposed the existence of a three-dimensional diffusion of e.g. transmitter and ion signals, released by any type of cell, in the extra-cellular space and the cerebrospinal fluid of the brain. Thus, a synthesis between Golgi and Cajal's views became possible, by considering two main modes of intercellular communication: volume transmission (VT) and wiring transmission (WT) (a prototype of the latter one is synaptic transmission) and two types of networks (cellular and molecular networks) in the central nervous system. This was the basis for the suggestion of two fundamental principles in brain morphological and functional organisation, the miniaturisation and hierarchic organisation.Finally, moving from Apathy's work, a new model of brain networks has recently been proposed. In fact, it has been proposed that a network of fibrils enmeshes the entire CNS forming a global molecular network (GMN) superimposed on the cellular networks.


2007 - Possible relevance of receptor-receptor interactions between viral- and host-coded receptors for viral-induced disease. [Articolo su rivista]
Agnati, Luigi Francesco; Leo, Giuseppina; Genedani, Susanna; Guidolin, D; Andreoli, Nicola; Fuxe, K.
abstract

It has been demonstrated that some viruses, such as the cytomegalovirus, code for G-protein coupled receptors not only to elude the immune system, but also to redirect cellular signaling in the receptor networks of the host cells. In view of the existence of receptor-receptor interactions, the hypothesis is introduced that these viral-coded receptors not only operate as constitutively active monomers, but also can affect other receptor function by interacting with receptors of the host cell. Furthermore, it is suggested that viruses could also insert not single receptors (monomers), but clusters of receptors (receptor mosaics), altering the cell metabolism in a profound way. The prevention of viral receptor–induced changes in host receptor networks may give rise to novel antiviral drugs that counteract viral-induced disease.


2007 - Role of cooperativity in protein folding and protein mosaic assemblage relevance for protein conformational diseases [Articolo su rivista]
Agnati, Luigi Francesco; D., Guidolin; Leo, Giuseppina; Genedani, Susanna; P., Arhem; Forni, Arrigo; Andreoli, Nicola; K., Fuxe
abstract

Biological systems are organized in intricate and highly structured networks with hierarchies and multiple scales. Cells can be considered as “meso-scale level” systems placed between the “macro-scale level ” (systems of cellular networks) and the “micro-scale level” (systems of molecular networks). In fact, cells represent complex biochemical machineries made by networks of molecules connected by biochemical reactions. Thus, the brain should be studied as a system of “networks of networks”. Recently, the existence of a Global Molecular Network (GMN) enmeshing the entire CNS was proposed. This proposal is based on the evidence that the extra-cellular matrix is a dynamic molecular structure capable of storing and releasing signals and of interacting with receptors and proteins on the cell membranes. Proteins have a special role in molecular networks since they can be assembled into high-order molecular complexes, which have been defined as Protein Mosaics (PM). Protein monomers in a PM (the “tesserae” of the mosaic) can interact via classical and non-classical cooperativity behaviour involving allosteric interactions.In the present paper, new features of allostery and cooperativity for protein folding, assemblage and topological features of PM will be discussed. Against this background, alterations in PM via allosteric modulations and non-classical cooperativity mechanisms may lead to protein aggregates like beta amyloid fibrils. Such aggregates cause pathological changes in the GMN structure and function leading to neurodegenerative diseases such as Alzheimer's disease. Thus, a novel view of the so called Protein Conformational Diseases (PCD) is proposed.


2006 - Allosteric modulation of dopamine D-2 receptors by homocysteine [Articolo su rivista]
Agnati, Luigi Francesco; S., Ferre; Genedani, Susanna; Leo, Giuseppina; D., Guidolin; Filaferro, Monica; P., Carriba; V., Casado; C., Lluis; R., Franco; A. S., Woods; K., Fuxe
abstract

It has been suggested that L-DOPA-induced hyperhomocysteinemia can increase the risk of stroke, heart disease, and dementia and is an additional pathogenetic factor involved in the progression of Parkinson's disease. In Chinese hamster ovary (CHO) cells stably cotransfected with adenosine A(2A) and dopamine D-2 receptors, homocysteine selectively decreased the ability of D-2 receptor stimulation to internalize adenosine A(2A)-dopamine D-2 receptor complexes. Radioligand-binding experiments in the same cell line demonstrated that homocysteine acts as an allosteric D-2 receptor antagonist, by selectively reducing the affinity of D-2 receptors for agonists but not for antagonists. Mass spectrometric analysis showed that, by means of an arginine (Arg)-thiol electrostatic interaction, homocysteine forms noncovalent complexes with the two Arg-rich epitopes of the third intracellular loop of the D-2 receptor, one of them involved in A(2A)-D-2 receptor heteromerization. However, homocysteine was unable to prevent or disrupt A(2A)-D-2 receptor heteromerization, as demonstrated with Fluorescence Resonance Energy Transfer (FRET) experiments in stably cotransfected HEK cells. The present results could have implications for Parkinson's disease.


2006 - Studies on the effects of homocysteine (hcy) and Aβ peptides on human glioma cells [Poster]
Agnati, L. f.; Genedani, Susanna; Filaferro, M.; Carone, C.; Coppi, A.; Andreoli, N.; Rocchi, M.; Rossi, T.; Volpi, Nicola; Woods, A.; Fuxe, J.; Leo, G.; Fuxe, K.
abstract

Studies on the effects of homocysteine (hcy) and Aβ peptides on human glioma cells


2006 - Volume transmission and wiring transmission from cellular to molecular networks: history and perspectives [Articolo su rivista]
Agnati, Luigi Francesco; Leo, Giuseppina; Zanardi, Alessio; Genedani, Susanna; A., Rivera; K., Fuxe; D., Guidolin
abstract

The present paper deals with a fundamental issue in neuroscience: the inter-neuronal communication. The paper gives a brief account of our previous and more recent theoretical contributions to the subject and also reports new recent data that support some aspects of our proposal on two major modes of communication in the central nervous system: the wiring and the volume transmission. There exist two competing theories on inter-neuronal communication: the neuron doctrine and the theory of the diffuse nerve network, supported by Cajal and Golgi, respectively (see their respective Nobel Lectures). The present paper gives a brief account of a view on inter-neuronal communication in the brain, the volume and wiring transmission concept that to a great extent reconcile these two theories. Thus, the theory of volume and wiring transmission are summarized and its recent developments that allow to extend these two modes of communication from the cellular network to the molecular network level is also briefly illustrated. The explanatory value of this broadened view is further enhanced by our recent proposal on the existence of a Global Molecular Network enmeshing the entire central nervous system. It may be interesting to note that also the Global Molecular Network theory is reminiscent of the old reticular theory of Apathy. Finally, the so-called 'tide hypothesis' for diffusion of signals in the brain is briefly discussed and its possible extension to the molecular level is for the first time introduced. Early indirect evidence supporting volume transmission in the brain was the discovery of transmitter-receptor mismatches. Thus, as an experimental part of the present paper a new approach to evaluate transmitter-receptor mismatches is given and evidence for inter-relationships between temperature micro-gradients and mismatches is provided.


2005 - Computer-assisted image analysis of Caveolin-1 involvement in the iternalization process of adenosine A2A-dopamine D2 Receptor heterodimers [Articolo su rivista]
Genedani, Susanna; D., Guidolin; Leo, Giuseppina; Filaferro, Monica; M., Torvinen; A. S., Woods; K., Fuxe; S., Ferre; Agnati, Luigi Francesco
abstract

A functional aspect of horizontal molecular networks has been investigated experimentally, namely the heteromerization between adenosine A(2A) and doparnine D-2 receptors and the possible role of caveolin-1 in the cotrafficking of these molecular complexes. This study has been carried out by means of computer-assisted image analysis procedure of laser images of membrane immunoreactivity of caveolin-1, A(2A), D-1, and D-2 receptors obtained in two clones of Chinese hamster ovary cells-one transfected with A(2A) and dopamine D, receptors and the other one with A(2A) and D-2 receptors. Cells were treated for 3 h with 10 mu M D-1 receptor agonist SKF 38393,50 mu M D-2-D-3 receptor agonist quinpirole, and 200 nM A(2A) receptor agonist CGS 21680. In A(2A)-D-1-cotransfected cells, caveolin-1 was found to colocalize with both A2A and D, receptors and treatment with SKF 38393 induced internalization of caveolin-1 and D-1 receptors, with a preferential internalization of D, receptors colocalized. with caveolin-1. In A(2A)-D-2-cotransfected cells, caveolin-1 was found to colocalize with both A2A and D2 receptors and either CGS 21680 or quinpirole treatment induced internalization of caveolin-1 and A2A and D2 receptors, with a preferential internalization of A2A and D2 receptors colocalized with caveolin-1. The results suggest that A2A and D2 receptors and caveolin-1 likely interact forming a macrocomplex that internalizes upon agonist treatment. These observations are discussed in the frame of receptor oligomerization and of the possible functional role of caveolin-1 in the process of co-internalization and, hence, in controlling the permanence of receptors at the plasma membrane level (prerequisite for receptor mosaic organization and plastic adjustments) and in the control of receptor desensitization.


2005 - Dynamics of volume transmission in the brain. Focus on catecholamine and opioid peptide communication and the role of uncoupling protein 2 [Articolo su rivista]
K., Fuxe; A., Rivera; K. X., Jacobsen; M., Hoistad; Leo, Giuseppina; T. L., Horvath; W., Staines; A., De la Calle; Agnati, Luigi Francesco
abstract

This review focuses on transmitter-receptor mismatches in the brain, which is one of the hallmarks of the Volume Transmission (VT) concept, and how this phenomenon may be related to local temperature gradients created by brain uncoupling protein 2 (UCP2), which uncouples oxidative phosphorylation from ATP synthesis, hereby generating heat. Recent studies on transmitter-receptor mismatches have revealed dopamine and opioid peptide receptor mismatches in the intercalated islands of the amygdala, which are GABAergic cell clusters regulating amygdaloid output. Such mismatches have also been found in regions belonging to the extended amygdala and the nucleus accumbens shell. Now substantial UCP2 immunoreactivity has been found within the above transmitter-receptor mismatch regions, suggesting that UCP2 may enhance diffusion and convection of DA and opioid peptides in such regions by generation of local temperature gradients, thereby contributing to a dynamic regulation of VT.


2005 - Energy gradients for the homeostatic control of brain ECF composition and for VT signal migration: introduction of the tide hypothesis [Articolo su rivista]
Agnati, Luigi Francesco; Genedani, Susanna; Pl, Lenzi; Leo, Giuseppina; F., Mora; S., Ferre; K., Fuxe
abstract

The present paper enlightens a new point of view on brain homeostasis and communication, namely how the brain takes advantage of different chemical-physical phenomena such as pressure waves, and temperature and concentration gradients to allow the renewal of the extra-cellular fluid (i.e., the homeostasis of the brain internal milieu) as well as some forms of intercellular communications (Volume Transmission) at an energy cost much lower than the classical synaptic transmission (the prototype of Wiring Transmission). In particular, the possible functional meaning of the intracranial pressure waves is discussed in the frame of the so called tide hypothesis which maintains that the pressure waves, created by the cardiac pump, modulate the cerebro-spinal fluid flow from and towards the subarachnoid space as well as towards and from the Virchow-Robin spaces. These fluid push-pull movements favor both the migration of signals and the extra-cellular fluid renewal, especially in the cerebral cortex.


2005 - New methods to evaluate colocalization of fluorophores in immunocytochemical preparations as exemplified by a study on A(2A) and D-2 receptors in Chinese hamster ovary cells [Articolo su rivista]
Agnati, Luigi Francesco; K., Fuxe; M., Torvinen; Genedani, Susanna; R., Franco; S., Watson; Gg, Nussdorfer; Leo, Giuseppina; D., Guidolin
abstract

An important aspect of the image analysis of immunocytochemical preparations is the evaluation of colocalization of different molecules. The aim of the present study is to introduce image analysis methods to identify double-labeled locations exhibiting the highest association of two fluorophores and to characterize their pattern of distribution. These methods will be applied to the analysis of the cotrafficking of adenosine A(2A) and dopamine D-2 receptors belonging to the G protein-coupled receptor family and visualized by means of fluorescence immunocytochemistry in Chinese hamster ovary cells after agonist treatment. The present procedures for colocalization have the great advantage that they are, to a large extent, insensitive to the need for a balanced staining with the two fluorophores. Thus, these procedures involve image processing, visualization, and analysis of colocalized events, using a covariance method and a multiply method and the evaluation of the identified colocalization patterns. Moreover, the covariance method offers the possibility of detecting and quantitatively characterizing anticorrelated patterns of intensities, whereas the immediate detection of colocalized clusters with a high concentration of labeling is a possibility offered by the multiply method. The present methods offer a new and sensitive approach to detecting and quantitatively characterizing strongly associated fluorescence events, such as those generated by receptor-receptor interaction, and their distribution patterns in dual-color confocal laser microscopy.


2005 - Protection but maintained dysfunction of nigral dopaminergic nerve cell bodies and striatal dopaminergic terminals in MPTP-lesioned mice after acute treatment with the mGluR5 antagonist MPEP [Articolo su rivista]
J. A., Aguirre; J., Kehr; T., Yoshitake; F. L., Liu; A., Rivera; S., Fernandez Espinola; B., Andbjer; Leo, Giuseppina; A. D., Medhurst; Agnati, Luigi Francesco; K., Fuxe
abstract

The mGluR5 antagonist MPEP was used to study the role of mGluR5 in MPTP-induced injury of the nigrostriatal DA neurons. The findings indicate that acute blockade of mGluR5 may result in neuroprotective actions against MPTP neurotoxicity on nigral DA cell bodies and striatal DA terminals using stereological analysis of TH immunoreactivity and microdensitometry. Biochemical analysis showed no restoration of DA levels and metabolism indicating a maintained reduction of DA transmission.


2004 - Acute intermittent nicotine treatment produces a reduction in the total number of FGF-2 immunoreactive astroglial cells in the substantia nigra of the rat: a stereological analysis [Articolo su rivista]
Liu, Fl; Fuxe, K; Belluardo, N; Leo, Giuseppina; Agnati, Luigi Francesco; Aguirre, Ja
abstract

To understand the morphological substrate of the nicotine effect on nigral FGF-2 expression, a stereological analysis of FGF-2 immunoreactive neuronal and glial profiles has been performed in the substantia nigra of the rat after acute intermittent nicotine treatment. The major finding of this paper is the demonstration that this type of nicotine treatment produces a significant reduction in the total number of nuclear FGF-2 immunoreactive astroglial profiles in the substantia nigra. A parallel analysis of nigral FGF-1 and FGF-5 immunoreactivities showed no effect of this type of nicotine treatment. The results may be explained by an inhibition of FGF-2 synthesis in a subpopulation of nigral astroglia by nicotinic receptor activation, favouring a reduction of astroglial neurotrophism in the substantia nigra. (C) 2003 Elsevier Ireland Ltd. All rights reserved.


2004 - Energy gradients for VT-signal migration in the CNS: studies on melanocortin receptors, mitochondrial uncoupling proteins and food intake [Articolo su rivista]
Agnati, Luigi Francesco; Vergoni, Anna Valeria; Leo, Giuseppina; Genedani, Susanna; R., Franco; Bertolini, Alfio; K., Fuxe
abstract

The present paper enlightens a new point of view on brain homeostasis and communication, namely how the brain takes advantage of different chemical-physical phenomena such as pressure waves, and temperature and concentration gradients to allow the homeostasis of the brain internal milieu as well as some forms of intercellular communications (volume transmission, VT) at an energy cost much lower than the classical synaptic transmission (the prototype of wiring transmission, WT). The possible melanocortin control of uncoupling protein 2 (UCP2) expression (hence of local brain temperature gradients) has been studied in relation to food intake in male Wistar rats. Osmotic minipumps were subcutaneously (sc) implanted in the midscapular region for intracerebroventricular (icv) infusion. The control rats received an icv infusion of 0.5 microl/h of artificial cerebrospinal fluid (ACSF), while experimental rats received either an icv infusion of 0.16 nmol/h of HS024 or of 0.16 nmol/h of adrenocorticotropin-(1-24) [ACTH-(1-24)]. The ACTH-treated group ate significantly less than the ACSF-treated group during the first three days of infusion, while, subsequently, food intake of the two groups was similar. On the other hand, the HS024-treated group ate significantly more (up to 153% of the control value) than ACSF- and ACTH-treated rats during the entire period. UCP2 mRNA analysis in arcuate nuclei of ACTH, HS024 and ACSF-treated animals showed a significant 75% decrease (p<0.05 vs saline) of the total specific mRNA level in the HS024-treated group vs ACSF-treated animals (control group), while no significant change was observed between ACTH- and ACSF-treated animals. Melanocortin antagonist HS024 via blockade of MCR4 increases food intake and via a reduction of UCP2 expression enhances the food consumption ratio. This result underlines the fact that UCP2 expression and food intake can be differentially regulated. In other words, via a peptidergic control the central nervous system (CNS) can modulate the energy stored from the amount of the food that the animal has eaten and also uncouple the thermal micro-gradients (dependent on UCP2 expression) and hence the VT-signal micro-migrations from the food intake. It should also be noticed that the control of the thermal gradients affects also the neuronal firing rate and hence the transmitter release (likely above all the release of peptides such as neuropeptide Y (NPY), melanin-concentrating hormone (MCH) and beta-endorphin, e.g., in the arcuate nucleus representing signals relevant to energy homeostasis). Thus, WT and VT are both modulated by peptidergic signals that affect thermal gradients.


2004 - Neuroprotective effect of L-DOPA co-administered with the adenosine A(2A) receptor agonist CGS 21680 in an animal model of Parkinson's disease [Articolo su rivista]
Agnati, Luigi Francesco; Leo, Giuseppina; Vergoni, Anna Valeria; E., Martinez; J., Hockemeyer; C., Lluis; R., Franco; K., Fuxe; S., Ferre
abstract

Adenosine A(2A) receptors are a new target for drug development in Parkinson´s disease. Some experimental and clinical data suggest that A(2A) receptor antagonists can provide symptomatic improvement by potentiating the effects of (L)-DOPA as well as a decrease in secondary effects such as (L)-DOPA-induced dyskinesia. (L)-DOPA-induced behavioral sensitization in unilateral 6-hydroxydopamine-lesioned rats is frequently used as an experimental model of (L)-DOPA-induced dyskinesia. In the present work this model was used to evaluate the effect of the A(2A) receptor agonist CGS 21680 and the AA receptor antagonist MSX-3 on (L)-DOPA-induced behavioral sensitization and 6-hydroxydopamine-induced striatal dopamine denervation. (L)-DOPA-induced behavioral sensitization was determined as an increase in (L)-DOPA-induced abnormal involuntary movements and enhancement of apomorphine-induced turning behavior. Striatal dopamine innervation was determined by measuring tyro sine-hydroxylase immunoreactivity. Chronic administration of MSX-3 was not found to be effective at counteracting (L)-DOPA-induced behavioral sensitization. On the other hand, CGS 21680 completely avoided the development of (L)-DOPA-induced behavioral sensitization. The analysis of the striatal dopamine innervation showed that (L)-DOPA-CGS 21680 co-treatment conferred neuroprotection to the toxic effects of 6-hydroxydopamine. This neuroprotective effect was dependent on A(2A) and D-2 receptor stimulation, since it was counteracted by MSX-3 and by the D-2 receptor antagonist haloperidol. These results open new therapeutic avenues in early events in Parkinson´s disease.


2004 - On the molecular basis of the receptor mosaic hypothesis of the engram [Articolo su rivista]
Agnati, Luigi Francesco; S., Ferre; Leo, Giuseppina; C., Lluis; El, Canela; R., Franco; K., Fuxe
abstract

This paper revisits the so-called receptor mosaic hypothesis for memory trace formation in the light of recent findings in functional ( or interaction) proteomics. The receptor mosaic hypothesis maintains that receptors may form molecular aggregates at the plasma membrane level representing part of the computational molecular networks. 2. Specific interactions between receptors occur as a consequence of the pattern of transmitter release from the source neurons, which release the chemical code impinging on the receptor mosaics of the target neuron. Thus, the decoding of the chemical message depends on the receptors forming the receptor mosaics and on the type of interactions among receptors and other proteins in the molecular network with novel long-term mosaics formed by their stabilization via adapter proteins formed in target neurons through the incoming neurotransmitter code. The internalized receptor heteromeric complexes or parts of them may act as transcription factors for the formation of such adapter proteins. 3. Receptor mosaics are formed both at the pre- and postsynaptic level of the plasma membranes and this phenomenon can play a role in the Hebbian behavior of some synaptic contacts. The appropriate matching of the pre- with the postsynaptic receptor mosaic can be thought of as the clamping of the synapse to the external teaching signal. According to our hypothesis the behavior of the molecular networks at plasma membrane level to which the receptor mosaics belong can be set in a frozen conformation (i.e. in a frozen functional state) and this may represent a mechanism to maintain constant the input to a neuron. 4. Thus, we are suggesting that molecular networks at plasma membrane level may display multiple attractors each of which stores the memory of a specific neurotransmitter code due to a unique firing pattern. Hence, this mechanism may play a role in learning processes where the input to a neuron is likely to remain constant for a while.


2004 - On the nested hierarchical organization of CNS: basic characteristics of neuronal molecular networks [Relazione in Atti di Convegno]
Agnati, Luigi Francesco; L., Santarossa; Genedani, Susanna; Ei, Canela; Leo, Giuseppina; R., Franco; A., Woods; C., Lluis; S., Ferr; K., Fuxe
abstract

NON DISPONIBILE


2003 - Ontogeny and tissue-specific regulation of ghrelin mRNA expression suggest that ghrelin is primarily involved in the control of extraendocrine functions in the rat. [Articolo su rivista]
Torsello, A; Scibona, B; Leo, Giuseppina; Bresciani, E; Avallone, R; Bulgarelli, I; Luoni, M; Zoli, Michele; Rindi, G; Cocchi, D; Locatelli, V.
abstract

Ghrelin is a 28-amino-acid gastric peptide that potently stimulates growth hormone (GH) secretion in vivo and in vitro. Ghrelin-expressing cells have been found in the oxyntic region of the stomach and in the arcuate nucleus of the hypothalamus. The aim of this work was to investigate the regional distribution and developmental changes in ghrelin mRNA levels in the pituitary, hypothalamus and gastrointestinal (GI) tract of the rat using a semiquantitative RT-PCR assay. We also describe the effects of ghrelin immunoneutralization in late gestation and those resulting from induction of an isolated GH deficiency in adult rats. Ghrelin mRNA was already expressed in the fetus by embryonic day 12 (E12), by E17 most of ghrelin mRNA was in the trunk. At E17, in situ hybridization did not reveal a clear expression of ghrelin mRNA in fetal stomach but showed high ghrelin mRNA levels in the placenta. In the pituitary gland, levels of ghrelin mRNA were high after birth but declined significantly with puberty, whereas in the hypothalamus they were barely detectable at birth and remained very low at all subsequent time points tested. In the GI tract, ghrelin mRNA levels were high from birth to 270 days of life. Immunoneutralization of ghrelin at E16 had no effect on survival or development. Rats showed normal somatotropic function, ghrelin expression and onset of puberty. In young adult rats, passive immunization against GHRH did not affect ghrelin mRNA levels in the pituitary, hypothalamus and stomach. Only a 72-hour fasting period induced a significant increase in ghrelin mRNA levels in the stomach, but not in the pituitary and hypothalamus. These results strongly indicate that ghrelin is an important GI hormone expressed early in life and primarily sensitive to nutritional status.


2003 - Receptor heteromerization in adenosine A2A receptor signaling [Articolo su rivista]
Fuxe, K.; Agnati, Luigi Francesco; Jacobsen, K.; Hillion, J.; Canals, M.; Torvinen, M.; Tinnerstaines, B.; Staines, W.; Rosin, D.; Terasmaa, A.; Popoli, P.; Leo, Giuseppina; Vergoni, Anna Valeria; Lluis, C.; Ciruela, F.; Franco, R.; Ferre', S.
abstract

Recently evidence has been presented that adenosine A2A and dopamine D2 receptors form functional heteromeric receptor complexes as demonstrated in human neuroblastoma cells and mouse fibroblast Ltk- cells. These A2A/D2 heteromeric receptor complexes undergo coaggregation, cointernalization, and codesensitization on D2 or A2A receptor agonist treatments and especially after combined agonist treatment. It is hypothesized that the A2A/D2 receptor heteromer represents the molecular basis for the antagonistic A2A/D2 receptor interactions demonstrated at the biochemical and behavioral levels. Functional heteromeric complexes between A2A and metabotropic glutamate 5 receptors (mGluR5) have also recently been demonstrated in HEK-293 cells and rat striatal membrane preparations. The A2A/mGluR5 receptor heteromer may account for the synergism found after combined agonist treatments demonstrated in different in vitro and in vivo models. D2, A2A, and mGluR5 receptors are found together in the dendritic spines of the striatopallidal GABA neurons. Therefore, possible D2/A2A/mGluR5 multimeric receptor complexes and the receptor interactions within them may have a major role in controlling the dorsal and ventral striatopallidal GABA neurons involved in Parkinson's disease and in schizophrenia and drug addiction, respectively.


2002 - Diet-induced changes in hypothalamic pro-opio-melanocortin mRNA in the rat hypothalamus [Articolo su rivista]
C., Torri; Pedrazzi, Patrizia; Leo, Giuseppina; E. E., Muller; D., Cocchi; Agnati, Luigi Francesco; Zoli, Michele
abstract

Hypothalamic mRNA and peptide levels of pro-opio-melanocortin (POMC) and other neuropeptides were studied in rats that either develop obesity (diet-induced obese, DIO), when fed a palatable and hypercaloric diet (cafeteria diet, caf) or do not develop obesity (diet resistant, DR), when fed the same diet. cafDIO rats showed a significant increase in POMC, but not in melanin concentrating hormone, mRNA levels as determined by semiquantitative in situ hybridization. cafDR and cafDIO rats showed no change in POMC-derived peptide levels, whereas neuropeptide Y immunoreactivity was significantly increased in cafDR rats. POW mRNA levels were also studied in high-fat diet-fed rats but no significant change was observed. Altered hypothalamic transmission by POMC-derived peptides may contribute to the susceptibility of cafDIO rats to the weight promoting action of caf diet.


2002 - Nicotine and neurodegeneration in ageing [Articolo su rivista]
Zanardi, Alessio; Leo, Giuseppina; Biagini, Giuseppe; Zoli, Michele
abstract

Impairment in cholinergic systems is a highly consistent finding in human dementia. Among cholinergic markers, marked decreases in nicotine binding have been most consistently observed in the telencephalic regions of demented patients and are thought to contribute to the cognitive deficits associated with ageing and age-related neurodegenerative diseases. New evidence that the cholinergic system has a specific pathogenic role in the neurodegenerative alterations of aged and, especially, demented patients is fast accumulating. Both in vivo and in culture, nicotine protects striatal, hippocampal and cortical neurons against the neurotoxicity induced by excitotoxic amino acids as well as the toxicity caused by beta-amyloid, the major component of senile plaques. Further support for the implication of nicotinic receptors in brain ageing is come from recent studies on transgenic animals lacking nicotinic receptor subtypes, which shed light on the mechanisms of nicotine neuroprotection and neurotoxicity. (C) 2002 Published by Elsevier Science Ireland Ltd.


2002 - Pharmacological manipulation of brain galaninergic system and sexual behavior in male mice [Articolo su rivista]
Benelli, Augusta; Bertolini, Alfio; Zoli, Michele; Leo, Giuseppina; Filaferro, Monica; S., Saltini; Genedani, Susanna
abstract

Available data suggest a complex role for the brain galaninergic system in male sexual behavior; however, the results so far obtained in animals with either galanin or galanin antagonists are conflicting. Objective: To define the better influence of galanin on male sexual behavior by studying, in mice, (i) the effect of galanin and of the chimeric galanin peptide M40 on the copulatory performance, and (ii) galanin mRNA levels in hypothalamic arcuate and dorso-medial nuclei. Methods: For the behavioral testing, only sexually sluggish male mice were used. Galanin mRNA levels were studied in both sexually potent and impotent mice by means of in situ hybridization. Standard behavioral parameters for sexual behavior were recorded or calculated. Synthetic galanin (0.05, 0.1 or 1 mug/mouse) and M40 (5 or 20 mug/mouse) were intracerebroventricularly (ICV) injected, 15 min before the copulatory test. Galanin mRNA levels were evaluated. Results: In sexually sluggish male mice, both galanin (0.1 and 1 mug/mouse ICV) and M40 (20 mug/mouse ICV), significantly increased intromission frequency and ejaculation latency; M40 also improved copulatory efficacy. On the other hand, in the hypothalamic arcuate and dorso-medial nuclei, the levels of galanin mRNA were not significantly different in sexually potent and impotent male mice. Conclusions.-These results show that in sexually sluggish male mice the ICV injection of either galanin or the chimeric analogue M40 greatly prolongs the duration of the copulation; without a reduction of the sexual drive or of the copulatory performance. On the other hand, the hybridization experiments seem to rule out an important physiological role of the brain galaninergic system in the regulation of male sexual behavior, at least in mice.


2002 - Preferential alterations in the mesolimbic dopamine pathway of heterozygous reeler mice: an emerging animal-based model of schizophrenia [Articolo su rivista]
M., Ballmaier; Zoli, Michele; Leo, Giuseppina; Agnati, Luigi Francesco; P., Spano
abstract

Based on a number of neuroanatomical and behavioural similarities, recent evidence suggests that heterozygous reeler mice, haploinsufficient for reelin expression, represent a useful model of psychosis vulnerability. As brain mesolimbic dopamine pathways have been proposed to be associated with the pathophysiology of psychotic disorders, we thought it would be of interest to examine whether these animals present disturbances in the mesolimbic dopamine system. To this end we studied by immunocytochemical, in situ hybridization procedures and receptor autoradiography, several markers of the mesotelencephalic dopamine pathway in heterozygous reeler mice and controls. We report that heterozygous reeler mice exhibit a reduction in the number of tyrosine hydroxylase-immunoreactive cell bodies and tyrosine hydroxylase mRNA levels in the ventral tegmental area, as well as a reduction of tyrosine hydroxylase and dopamine transporter immunoreactivity in the dopamine terminal fields of the limbic striatum. In these areas we also observed a reduction of dopamine D2 receptor mRNA. Finally, a marked increase in D3 receptor mRNA levels was observed concomitant with a significant increase in D3 binding sites. On the contrary, the nigrostriatal pathway did not show any significant alteration in heterozygous reeler mice with regards to the dopaminergic markers examined in substantia nigra cell bodies and dorsal striatum dopamine terminal fields. These results suggest a specific link between reelin-related neuronal pathology and dopamine involvement in the pathophysiology of psychotic disorders.


1999 - Changes in nicotinic acetylcholine receptor subunit mRNAs and nicotinic binding in spontaneously hypertensive stroke prone rats [Articolo su rivista]
R., Ferrari; A., Frasoldati; Leo, Giuseppina; C., Torri; Zini, Isabella; Agnati, Luigi Francesco; Zoli, Michele
abstract

We have studied nicotinic acetylcholine receptors in spontaneously hypertensive 'stroke prone' (SHsp) rats. We found a significant decrease in I-125-alpha-bungarotoxin binding and alpha 7 subunit mRNA levels in cortical areas of the SHsp rats with respect to Wistar Kyoto (WKy) normotensive rats. Antihypertensive drug treatment counteracted these changes in cerebral cortex but not in hippocampus. No significant change was instead found in [H-3]-epibatidine binding and alpha 4 and beta 2 subunit mRNA levels. SHsp rats showed decreased latency at the active avoidance test and transiently increased threshold at both hot-plate and tail-flick tests in comparison with WKy rats. None of these behavioral parameters was correlated with I-125-alpha-bungarotoxin binding in cortical areas. In conclusion, present data show a preferential impairment of alpha-bungarotoxin sensitive nAChRs in SHsp rats. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.