5-HT(2C) serotonin receptor blockade prevents tau protein hyperphosphorylation and corrects the defect in hippocampal synaptic plasticity caused by a combination of environmental stressors in mice.

Exposure to multimodal sensory stressors is an everyday occurrence and sometimes becomes very intense, such as during rave parties or other recreational events. A growing body of evidence suggests that strong environmental stressors might cause neuronal dysfunction on their own in addition to their synergistic action with illicit drugs. Mice were exposed to a combination of physical and sensory stressors that are reminiscent of those encountered in a rave party. However, this is not a model of rave because it lacks the rewarding properties of rave. A 14-h exposure to environmental stressors caused an impairment of hippocampal long-term potentiation (LTP) and spatial memory, and an enhanced phosphorylation of tau protein in the CA1 and CA3 regions. These effects were transient and critically depended on the activation of 5-HT2C serotonin receptors, which are highly expressed in the CA1 region. Acute systemic injection of the selective 5-HT2C antagonist, RS-102,221 (2 mg/kg, i.p., 2 min prior the onset of stress), prevented tau hyperphosphorylation and also corrected the defects in hippocampal LTP and spatial memory. These findings suggest that passive exposure to a combination of physical and sensory stressors causes a reversible hippocampal dysfunction, which might compromise mechanisms of synaptic plasticity and spatial memory for a few days. Drugs that block 5-HT2C receptors might protect the hippocampus against the detrimental effect of environmental stressors.

Gender differences in Parkinson's disease: focus on plasma α-synuclein.

Among promising biological markers proposed for Parkinson's disease (PD) and other disorders related to Lewy bodies, plasma alpha-synuclein assay has provided conflicting results mainly owing to the various laboratory assay techniques used and protein forms assayed. In this observational and exploratory cross-sectional study, using an immunoenzymatic technique, we assayed and compared total plasma alpha-synuclein concentrations in 69 patients with PD and 110 age-matched healthy control subjects. Two previously unreported findings concerned gender. First, plasma alpha-synuclein concentrations measured in the more advanced parkinsonian disease stages decreased in men, but not in women. Second, again only in men, plasma alpha-synuclein concentration was associated with cognitive impairments, hallucinations, and sleep disorders. These findings underline the gender-related differences in parkinsonian patients and indicate plasma alpha-synuclein expression as a potential biological marker for PD progression in men.

Targeting group II metabotropic glutamate (mGlu) receptors for the treatment of psychosis associated with Alzheimer's disease: selective activation of mGlu2 receptors amplifies beta-amyloid toxicity in cultured neurons, whereas dual activation of mGlu2 and mGlu3 receptors is neuroprotective.

Dual orthosteric agonists of metabotropic glutamate 2 (mGlu2) and mGlu3 receptors are being developed as novel antipsychotic agents devoid of the adverse effects of conventional antipsychotics. Therefore, these drugs could be helpful for the treatment of psychotic symptoms associated with Alzheimer's disease (AD). In experimental animals, the antipsychotic activity of mGlu2/3 receptor agonists is largely mediated by the activation of mGlu2 receptors and is mimicked by selective positive allosteric modulators (PAMs) of mGlu2 receptors. We investigated the distinct influence of mGlu2 and mGlu3 receptors in mixed and pure neuronal cultures exposed to synthetic ß-amyloid protein (Aß) to model neurodegeneration occurring in AD. The mGlu2 receptor PAM, N-4'-cyano-biphenyl-3-yl)-N-(3-pyridinylmethyl)-ethanesulfonamide hydrochloride (LY566332), devoid of toxicity per se, amplified Aß-induced neurodegeneration, and this effect was prevented by the mGlu2/3 receptor antagonist (2S,1'S,2'S)-2-(9-xanthylmethyl)-2-(2'-carboxycyclopropyl)glycine (LY341495). LY566332 potentiated Aß toxicity regardless of the presence of glial mGlu3 receptors, but it was inactive when neurons lacked mGlu2 receptors. The dual mGlu2/3 receptor agonist, (-)-2-oxa-4-aminobicyclo[3.1.0]exhane-4,6-dicarboxylic acid (LY379268), was neuroprotective in mixed cultures via a paracrine mechanism mediated by transforming growth factor-ß1. LY379268 lost its protective activity in neurons grown with astrocytes lacking mGlu3 receptors, indicating that protection against Aß neurotoxicity was mediated entirely by glial mGlu3 receptors. The selective noncompetitive mGlu3 receptor antagonist, (3S)-1-(5-bromopyrimidin-2-yl)-N-(2,4-dichlorobenzyl)pyrrolidin-3-amine methanesulfonate hydrate (LY2389575), amplified Aß toxicity on its own, and, interestingly, unmasked a neurotoxic activity of LY379268, which probably was mediated by the activation of mGlu2 receptors. These data indicate that selective potentiation of mGlu2 receptors enhances neuronal vulnerability to Aß, whereas dual activation of mGlu2 and mGlu3 receptors is protective against Aß-induced toxicity.

mGlu2 metabotropic glutamate receptors restrain inflammatory pain and mediate the analgesic activity of dual mGlu2/mGlu3 receptor agonists.

Group II metabotropic glutamate receptors (mGluRs) couple to the inhibitory G-protein Gi. The group II mGluRs include two subtypes, mGlu2 and mGlu3, and their pharmacological activation produces analgesic effects in inflammatory and neuropathic pain states. However, the specific contribution of each one of the two subtypes has not been clarified due to the lack of selective orthosteric ligands that can discriminate between mGlu2 and mGlu3 subtypes.In this study we used mGlu2 or mGlu3 knock-out mice to dissect the specific role for these two receptors in the endogenous control of inflammatory pain and their specific contribution to the analgesic activity of mixed mGlu2/3 receptor agonists.Our results showed that mGlu2⁻(/)⁻ mice display a significantly greater pain response compared to their wild type littermates. Interestingly the increased pain sensitivity in mGlu2⁻(/)⁻ mice occurred only in the second phase of the formalin test. No differences were observed in the first phase. In contrast, mGlu3⁻(/)⁻ mice did not significantly differ from their wild type littermates in either phase of the formalin test.When systemically injected, a single administration of the mGlu2/3 agonist, LY379268 (3 mg/kg, ip), showed a significant reduction of both phases in wild-type mice and in mGlu3⁻(/)⁻ but not in mGlu2⁻(/)⁻ mice. However tolerance to the analgesic effect of LY379268 (3 mg/kg, ip) in mGlu3⁻(/)⁻ mice developed following 5 consecutive days of injection.Taken together, these results demonstrate that: (i) mGlu2 receptors play a predominant role over mGlu3 receptors in the control of inflammatory pain in mice; (ii) the analgesic activity of mixed mGlu2/3 agonists is entirely mediated by the activation of the mGlu2 subtype and (iii) the development of tolerance to the analgesic effect of mGlu2/3 agonists develops despite the lack of mGlu3 receptors.

Maternal stress programs accelerated aging of the basal ganglia motor system in offspring.

Early-life stress involved in the programming of stress-related illnesses can have a toxic influence on the functioning of the nigrostriatal motor system during aging. We examined the effects of perinatal stress (PRS) on the neurochemical, electrophysiological, histological, neuroimaging, and behavioral correlates of striatal motor function in adult (4 months of age) and old (21 months of age) male rats. Adult PRS offspring rats showed reduced dopamine (DA) release in the striatum associated with reductions in tyrosine hydroxylase-positive (TH+) cells and DA transporter (DAT) levels, with no loss of striatal dopaminergic terminals as assessed by positron emission tomography analysis with fluorine-18-l-dihydroxyphenylalanine. Striatal levels of DA and its metabolites were increased in PRS rats. In contrast, D2 DA receptor signaling was reduced and A2A adenosine receptor signaling was increased in the striatum of adult PRS rats. This indicated enhanced activity of the indirect pathway of the basal ganglia motor circuit. Adult PRS rats also showed poorer performance in the grip strength test and motor learning tasks. The aged PRS rats also showed a persistent reduction in striatal DA release and defective motor skills in the pasta matrix and ladder rung walking tests. In addition, the old rats showed large increases in the levels of SNAP-25 and synaptophysin, which are synaptic vesicle-related proteins in the striatum, and in the PRS group only, reductions in Syntaxin-1 and Rab3a protein levels were observed. Our findings indicated that the age-dependent threshold for motor dysfunction was lowered in PRS rats. This area of research is underdeveloped, and our study suggests that early-life stress can contribute to an increased understanding of how aging diseases are programmed in early-life.

The Trace Kynurenine, Cinnabarinic Acid, Displays Potent Antipsychotic-Like Activity in Mice and Its Levels Are Reduced in the Prefrontal Cortex of Individuals Affected by Schizophrenia.

Cinnabarinic acid (CA) is a kynurenine metabolite that activates mGlu4 metabotropic glutamate receptors. Using a highly sensitive ultra-performance liquid chromatography/tandem mass spectrometry (UPLC/MS-MS) method, we found that CA is present in trace amounts in human brain tissue. CA levels were largely reduced in the prefrontal cortex (PFC) of individuals affected by schizophrenia. This reduction did not correlate with age, sex, duration of the disease, and duration and type of antipsychotic medication and might, therefore, represent a trait of schizophrenia. Interestingly, systemic treatment with low doses of CA (<1 mg/kg, i.p.) showed robust efficacy in several behavioral tests useful to study antipsychotic-like activity in mice and rats and attenuated MK-801-evoked glutamate release. CA failed to display antipsychotic-like activity and inhibit excitatory synaptic transmission in mice lacking mGlu4 receptors. These findings suggest that CA is a potent endogenous antipsychotic-like molecule and reduced CA levels in the PFC might contribute to the pathophysiology of schizophrenia.

Dickkopf-3 Causes Neuroprotection by Inducing Vascular Endothelial Growth Factor.

Dickkopf-3 (Dkk3) is an atypical member of the Dkk family of Wnt inhibitors, which has been implicated in the pathophysiology of neurodegenerative disorders. However, the role of Dkk3 in mechanisms of cell degeneration and protection is unknown. We used Dkk3 knockout mice to examine how endogenous Dkk3 influences ischemic brain damage. In addition, we used primary cultures of astrocytes or mixed cultures of astrocytes and neurons to investigate the action of Dkk3 on cell damage and dissect the underlying molecular mechanisms. In a model of focal brain ischemia induced by permanent middle cerebral artery (MCA) occlusion (MCAO) Dkk3-/- mice showed a significantly greater infarct size with respect to their wild-type counterparts at all time points investigated (1, 3 and 7 days after MCAO). Immunohistochemical analysis showed that Dkk3 expression was enhanced at the borders of the ischemic focus, and was predominantly detected in astrocytes. This raised the possibility that Dkk3 produced by astrocytes acted as a protective molecule. We tested this hypothesis using either primary cultures of cortical astrocytes or mixed cortical cultures containing both neurons and astrocytes. Genetic deletion of Dkk3 was permissive to astrocyte damage induced by either oxidative stress or glucose deprivation. In addition, application of human recombinant Dkk3 (hrDkk3) was highly protective against oxidative stress in cultured astrocytes. We tested the hypothesis that the protective activity of Dkk3 was mediated byvascular endothelial growth factor (VEGF). Interestingly, glucose deprivation up-regulated both Dkk3 and VEGF in cultured astrocytes prepared from wild-type mice. VEGF induction was not observed in astrocytes lacking Dkk3 (i.e., in cultures prepared from Dkk3-/- mice). In mixed cultures of cortical cells, excitotoxic neuronal death induced by a brief pulse with N-methyl-D-aspartate (NMDA) was significantly enhanced when Dkk3 was lacking in astrocytes, whereas post-NMDA addition of hrDkk3 was neuroprotective. Neuroprotection by hrDkk3 was significantly reduced by pharmacological blockade of type-2 VEGF receptors and was mimicked by hrVEGF. These data offer the first evidence that Dkk3 protects both neurons and astrocytes against a variety of toxic insults, and at least in culture, protection involves VEGF induction.

Pharmacological activation of mGlu4 metabotropic glutamate receptors reduces nigrostriatal degeneration in mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine.

We examined whether selective activation of mGlu4 metabotropic glutamate receptors attenuates 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced nigrostriatal damage in mice. C57BL mice were treated with a single dose of MPTP (30 mg/kg, i.p.) preceded, 30 min earlier, by a systemic injection of the mGlu4 receptor enhancer N-phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxamide (PHCCC). PHCCC was injected either subcutaneously in cremophor EL or intraperitoneally in saline containing 50% DMSO. PHCCC treatment (3 or 10 mg/kg) significantly reduced MPTP toxicity, as assessed by measurements of the striatal levels of dopamine and its metabolites and by tyrosine hydroxylase, dopamine transporter, and glial fibrillary acidic protein immunostaining in the corpus striatum and substantia nigra. In another set of experiments, a higher cumulative dose of MPTP (80 mg/kg divided into four injections with 2 h of interval) was injected to mGlu4-/- mice and their Sv129/CD1 wild-type controls. A higher dose was used in these experiments because Sv129/CD1 mice are less sensitive to MPTP toxicity. Systemic administration of PHCCC was protective in wild-type mice but failed to affect nigrostriatal damage in mGlu4-/- mice. Finally, unilateral infusion of PHCCC in the external globus pallidus protected the ipsilateral nigrostriatal pathway against MPTP toxicity. These data support the view that mGlu4 receptors are potential targets for the experimental treatment of parkinsonism.

Reduced activity of cortico-striatal fibres in the R6/2 mouse model of Huntington's disease.

We have used the R6/2 mice to study cortico-striatal glutamatergic transmission by microdialysis in freely moving mice. Basal extracellular striatal glutamate concentrations were lower in R6/2 mice at 12 weeks of age, but not at 6 weeks of age, when neurological symptoms start to develop. In contrast, K-induced glutamate release was blunted in the striatum of R6/2 mice at both 6 and 12 weeks of age as compared with age-matched controls. We also found a substantial reduction in striatal pro-BDNF (brain derived neurotrophic factor) levels associated with no changes in the mature form of BDNF, as assessed by immunoblotting, in 12-week-old R6/2 mice, suggesting a reduced turnover rate of BDNF in the striatum of these mice. These data support the hypothesis of a cortico-striatal dysfunction in Huntington's disease.

Genetic deletion of mGlu2 metabotropic glutamate receptors improves the short-term outcome of cerebral transient focal ischemia.

We have recently shown that pharmacological blockade of mGlu2 metabotropic glutamate receptors protects vulnerable neurons in the 4-vessel occlusion model of transient global ischemia, whereas receptor activation amplifies neuronal death. This raised the possibility that endogenous activation of mGlu2 receptors contributes to the pathophysiology of ischemic neuronal damage. Here, we examined this possibility using two models of transient focal ischemia: (i) the monofilament model of middle cerebral artery occlusion (MCAO) in mice, and (ii) the model based on intracerebral infusion of endothelin-1 (Et-1) in rats. Following transient MCAO, mGlu2 receptor knockout mice showed a significant reduction in infarct volume and an improved short-term behavioural outcome, as assessed by a neurological disability scale and the "grip test". Following Et-1 infusion, Grm2 gene mutated Hannover Wistar rats lacking mGlu2 receptors did not show changes in the overall infarct volume as compared to their wild-type counterparts, although they showed a reduced infarct area in the agranular insular cortex. Interestingly, however, mGlu2 receptor-deficient rats performed better than wild-type rats in the adhesive tape test, in which these rats did not show the laterality preference typically observed after focal ischemia. These findings support the hypothesis that activation of mGlu2 receptors is detrimental in the post-ischemic phase, and support the use of mGlu2 receptor antagonists in the experimental treatment of brain ischemia.

Microtubule alterations occur early in experimental parkinsonism and the microtubule stabilizer epothilone D is neuroprotective.

The role of microtubule (MT) dysfunction in Parkinson's disease is emerging. It is still unknown whether it is a cause or a consequence of neurodegeneration. Our objective was to assess whether alterations of MT stability precede or follow axonal transport impairment and neurite degeneration in experimental parkinsonism induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in C57Bl mice. MPTP induced a time- and dose-dependent increase in fibres with altered mitochondria distribution, and early changes in cytoskeletal proteins and MT stability. Indeed, we observed significant increases in neuron-specific ßIII tubulin and enrichment of deTyr tubulin in dopaminergic neurons. Finally, we showed that repeated daily administrations of the MT stabilizer Epothilone D rescued MT defects and attenuated nigrostriatal degeneration induced by MPTP. These data suggest that alteration of ΜΤs is an early event specifically associated with dopaminergic neuron degeneration. Pharmacological stabilization of MTs may be a viable strategy for the management of parkinsonism.

Resveratrol improves vascular function in patients with hypertension and dyslipidemia by modulating NO metabolism.

Epidemiological studies have demonstrated that the Mediterranean diet, which is rich in resveratrol, is associated with a significantly reduced risk of cardiovascular disease. However, the molecular mechanisms that underlie the beneficial effects of resveratrol on cardiovascular function remain incompletely understood. Therefore, we set out to identify the molecular target(s) mediating the protective action of resveratrol on vascular function. To this end, we performed vascular reactivity studies to evaluate the effects of resveratrol on superior thyroid artery obtained from 59 patients with hypertension and dyslipidemia. We found that resveratrol evoked vasorelaxation and reduced endothelial dysfunction through the modulation of NO metabolism via (1) an 5' adenosine monophosphate-activated protein kinase-mediated increase in endothelial NO synthase activity; (2) a rise in tetrahydrobiopterin levels, which also increases endothelial NO synthase activity; and (3) attenuation of vascular oxidative stress, brought about by overexpression of manganese superoxide dismutase via an nuclear factor erythroid-derived 2-like 2-dependent mechanism. The effects of resveratrol on acetylcholine vasorelaxation were also tested in vessels from patients with nonhypertensive nondyslipidemia undergoing thyroid surgery. In this setting, resveratrol failed to exert any effect. Thus, our finding that resveratrol reduces endothelial dysfunction, an early pathophysiological feature and independent predictor of poor prognosis in most forms of cardiovascular disease, supports the concept that the risk of vascular events could be further reduced by adherence to a set of dietary and behavioral guidelines.

Role of the intravitreal growth factors in the pathogenesis of idiopathic epiretinal membrane.

PURPOSE: The aim of the present study is to evaluate the roles of TGFs ß1 and ß2, glial cell line-derived neurotrophic factor (GDNF), and nerve growth factor (NGF) in the pathogenesis of idiopathic epiretinal membrane (ERM). METHODS: Eight patients, six males and two females, with an average age of 60.25 ± 17.16 years (range, 33-75 years) who were affected by idiopathic ERM were enrolled in the study. All patients underwent standard pars plana vitrectomy surgery with membrane removal and specific ELISA was performed to evaluate TGFß1, TGFß2, GDNF, and NGF in the vitreous samples. This was repeated after acidification of the samples with hydrochloric acid. RESULTS: Before acidification, ELISA analysis revealed a significant increase of TGFß2 in the samples with idiopathic ERM (327.98 ± 99.58 pg/mL; range, 206.864-466.235 pg/mL) compared to the control group (187.17 ± 58.20 pg/mL; range, 132.758-271.707 pg/mL; t = 3.4; P < 0.05). A statistically significant difference was also obtained after acidification of the samples (618.15 ± 201.43 pg/mL; range, 409.795-866.215 pg/mL compared to 265.04 ± 98.15 pg/mL; range, 152.478-352.101 pg/mL; t = 4.5; P < 0.05). Notably, before acidification the differences in NGF between the two groups were not statistically significant (t = 0.79; P = 0.46), while after acidification a significant increase of the NGF levels in ERM samples was found in comparison with the control group (723.41 ± 235.4 vs. 242.84 ± 104.61; t = 3; P < 0.05). CONCLUSIONS: The present study reveals that TGFß2 and NGF are associated with idiopathic ERMs, suggesting a novel compensatory mechanism so far never proposed.