Switch in the expression of mGlu1 and mGlu5 metabotropic glutamate receptors in the cerebellum of mice developing experimental autoimmune encephalomyelitis and in autoptic cerebellar samples from patients with multiple sclerosis (original) (raw)
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Cerebral Cortex, 2012
The metabotropic glutamate type 1 (mGlu1) and type 5 (mGlu5) receptors, the only members of group I mGlu receptors, are implicated in synaptic plasticity and mechanisms of feedback control of glutamate release. They exhibit nearly complementary distributions throughout the central nervous system, well evident in the cerebellum, where mGlu1 receptor is most intensely expressed while mGlu5 receptor is not. Despite their different distribution, they show a similar subcellular localization and use common transducing pathways. We recently described the Grm1 crv4 mouse with motor coordination deficits and renal anomalies caused by a spontaneous mutation inactivating the mGlu1 receptor. To define the neuropathological mechanisms in these mice, we evaluated expression and function of the mGlu5 receptor in cerebral and cerebellar cortices. Western blot and immunofluorescence analyses showed mGlu5 receptor overexpression. Quantitative reverse transcriptase-polymerase chain reaction results indicated that the up-regulation is already evident at RNA level. Functional studies confirmed an enhanced glutamate release from cortical cerebral and cerebellar synaptosomes when compared with wild-type that is abolished by the mGlu5 receptor-specific inhibitor, 2-methyl-6-(phenylethynyl) pyridine hydrochloride (MPEP). Finally, acute MPEP treatment of Grm1 crv4/crv4 mice induced an evident although incomplete improvement of motor coordination, suggesting that mGlu5 receptors enhanced activity worsens, instead of improving, the motor-coordination defects in the Grm1 crv4/crv4 mice.
Neurobiology of Disease, 2015
Enhancement of glial-derived neurotrophic factor (GDNF) is an established therapeutic target for amyotrophic lateral sclerosis (ALS). Activation of group II metabotropic glutamate (mGlu) receptors with the orthosteric agonist, LY379268, enhanced GDNF levels in cultured spinal cord astrocytes from wild-type mice and mGlu2 −/− mice, but not in astrocytes from mGlu3 −/− mice. LY379268 protected Sternberger monoclonal incorporated antibody-32 (SMI-32) + motor neurons against excitotoxic death in mixed cultures of spinal cord cells, and its action was abrogated by anti-GDNF antibodies. Acute systemic injection of LY379268 (0.5, 1 or 5 mg/kg, i.p.) enhanced spinal cord GDNF levels in wild-type and mGlu2 −/− mice, but not in mGlu3 −/− mice. No tolerance developed to the GDNF-enhancing effect of LY379268 when the drug was continuously delivered for 28 days by means of s.c. osmotic minipumps (0.5-5 mg/day). Double fluorescent immunostaining showed a colocalization of GDNF with the astrocyte marker, GFAP, but not with the neuronal marker, Neuronal Nuclear Antigen (NeuN), or with SMI-32. Continuous infusion of LY379268 also enhanced the expression of the glutamate transporter GLT-1, in the spinal cord. These data laid the groundwork for the study of LY379268 in ALS mice. Continuous treatment with 1 or 5 mg/kg/day with LY379268 had a beneficial effect on neurological disability in SOD1G93A mice. At day 40 of treatment, LY379268 enhanced spinal cord levels of GDNF and GLT-1, and rescued spinal cord motor neurons, as assessed by stereologic counting of SMI-32 + cells. LY379268 had no significant effect on the mortality rate of SODG93A. These findings encourage the development of selective mGlu3 receptor agonists/enhancers as neuroprotective agents in ALS.
International Journal of Molecular Sciences
Glutamate (Glu)-mediated excitotoxicity is a major cause of amyotrophic lateral sclerosis (ALS) and our previous work highlighted that abnormal Glu release may represent a leading mechanism for excessive synaptic Glu. We demonstrated that group I metabotropic Glu receptors (mGluR1, mGluR5) produced abnormal Glu release in SOD1G93A mouse spinal cord at a late disease stage (120 days). Here, we studied this phenomenon in pre-symptomatic (30 and 60 days) and early-symptomatic (90 days) SOD1G93A mice. The mGluR1/5 agonist (S)-3,5-Dihydroxyphenylglycine (3,5-DHPG) concentration dependently stimulated the release of [3H]d-Aspartate ([3H]d-Asp), which was comparable in 30- and 60-day-old wild type mice and SOD1G93A mice. At variance, [3H]d-Asp release was significantly augmented in 90-day-old SOD1G93A mice and both mGluR1 and mGluR5 were involved. The 3,5-DHPG-induced [3H]d-Asp release was exocytotic, being of vesicular origin and mediated by intra-terminal Ca2+ release. mGluR1 and mGluR5 ...
Journal of Neuroscience, 2013
In fact, brief incubation of IL-1 in normal cerebellar slices replicated EAE modifications through a rapid GLAST/EAAT1 downregulation, whereas incubation of an IL-1 receptor antagonist (IL-1ra) in EAE slices reduced spontaneous EPSC alterations. Finally, EAE mice treated with intracerebroventricular IL-1ra showed normal glutamatergic and GABAergic transmissions, along with GLAST/EAAT1 normalization, milder inflammation, and reduced motor deficits. These results highlight the crucial role played by the proinflammatory IL-1 in triggering molecular and synaptic events involved in neurodegenerative processes that characterize neuroinflammatory diseases such as MS.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2013
Cerebellar deficit contributes significantly to disability in multiple sclerosis (MS). Several clinical and experimental studies have investigated the pathophysiology of cerebellar dysfunction in this neuroinflammatory disorder, but the cellular and molecular mechanisms are still unclear. In experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, proinflammatory cytokines, together with a degeneration of inhibitory neurons, contribute to impair GABAergic transmission at Purkinje cells (PCs). Here, we investigated glutamatergic transmission to gain insight into the pathophysiology of cerebellar dysfunction in EAE. Electrophysiological recordings from PCs showed increased duration of spontaneous excitatory postsynaptic currents (EPSCs) during the symptomatic phase of EAE, suggesting an alteration of glutamate uptake played by Bergmann glia. We indeed observed an impaired functioning of the glutamate-aspartate transporter/excitatory amino acid transporter 1 (GLAST/EAAT1) in EAE cerebellum caused by protein downregulation and in correlation with prominent astroglia activation. We have also demonstrated that the proinflammatory cytokine interleukin-1β (IL-1β), released by a subset of activated microglia/macrophages and infiltrating lymphocytes, was involved directly in such synaptic alteration. In fact, brief incubation of IL-1β in normal cerebellar slices replicated EAE modifications through a rapid GLAST/EAAT1 downregulation, whereas incubation of an IL-1 receptor antagonist (IL-1ra) in EAE slices reduced spontaneous EPSC alterations. Finally, EAE mice treated with intracerebroventricular IL-1ra showed normal glutamatergic and GABAergic transmissions, along with GLAST/EAAT1 normalization, milder inflammation, and reduced motor deficits. These results highlight the crucial role played by the proinflammatory IL-1β in triggering molecular and synaptic events involved in neurodegenerative processes that characterize neuroinflammatory diseases such as MS.
Neuropharmacology, 2017
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder due to loss of upper and lower motor neurons (MNs). The mechanisms of neuronal death are largely unknown, thus prejudicing the successful pharmacological treatment. One major cause for MN degeneration in ALS is represented by glutamate(Glu)-mediated excitotoxicity. We have previously reported that activation of Group I metabotropic Glu receptors (mGluR1 and mGluR5) at glutamatergic spinal cord nerve terminals produces abnormal Glu release in the widely studied SOD1(G93A) mouse model of ALS. We also demonstrated that halving mGluR1 expression in the SOD1(G93A) mouse had a positive impact on survival, disease onset, disease progression, and on a number of cellular and biochemical readouts of ALS. We generated here SOD1(G93A) mice with reduced expression of mGluR5 (SOD1(G93A)Grm5(-/+)) by crossing the SOD1(G93A) mutant mouse with the mGluR5 heterozigous Grm5(-/+) mouse. SOD1(G93A)Grm5(-/+) mice showed prolonged s...
Neuropharmacology, 2013
Amyotrophic lateral sclerosis Glutamate release Pre-synaptic mGlu1 receptors Pre-synaptic mGlu5 receptors Neurotoxicity SOD1/G93A mice a b s t r a c t Glutamate-mediated excitotoxicity plays a major role in ALS and reduced astrocytic glutamate transport was suggested as a cause. Based on previous work we have proposed that abnormal release may represent another source of excessive glutamate. In this line, here we studied the modulation of glutamate release in ALS by Group I metabotropic glutamate (mGlu) receptors, that comprise mGlu1 and mGlu5 members. Synaptosomes from the lumbar spinal cord of SOD1/G93A mice, a widely used murine model for human ALS, and controls were used in release, confocal or electron microscopy and Western blot experiments. Concentrations of the mGlu1/5 receptor agonist 3,5-DHPG >0.3 mM stimulated the release of [ 3 H]Daspartate, used to label the releasing pools of glutamate, both in control and SOD1/G93A mice. At variance, 0.3 mM 3,5-DHPG increased [ 3 H]D-aspartate release in SOD1/G93A mice only. Experiments with selective