ABSTRACT
Multiple Sclerosis (MS) is a chronic disease of the central nervous system (CNS) characterized by autoimmune and neurodegenerative pathologies for which there is no cure and no defined etiology. Although several, modestly effective, disease modifying drugs are available to treat MS, there are presently no treatments that offer neuroprotection and prevent clinical progression. Therapies are needed that control immune homeostasis, prevent disease progression, and stimulate regeneration in the CNS. Components of the renin-angiotensin-system (RAS) have recently been identified as chemical mediators in the CNS and in neurological disease. Here we show the beneficial effect of therapeutic treatment with the Mas receptor agonist and metabolite of the protective arm of RAS, angiotensin 1-7 (A(1-7)), in the experimental autoimmune encephalomyelitis (EAE) animal model of MS. Therapeutic treatment with A(1-7) caused a dose-dependent reduction both in clinical disease severity and progression, and was dependent on Mas receptor activation. Further analysis of the most optimal dose of A(1-7) treatment revealed that the reductions in clinical disease course were associated with decreased immune infiltration and demyelination, axonal loss and oxidative stress in the spinal cord. In addition A(1-7) treatment was also associated with increases in circulating alternatively activated monocytes/macrophages.
Subject(s)
Angiotensin I/therapeutic use , Encephalomyelitis, Autoimmune, Experimental/drug therapy , Neuroprotection/drug effects , Neuroprotective Agents/therapeutic use , Peptide Fragments/therapeutic use , Angiotensin I/administration & dosage , Animals , Cell Proliferation/drug effects , Disease Progression , Dose-Response Relationship, Drug , Encephalomyelitis, Autoimmune, Experimental/diagnosis , Encephalomyelitis, Autoimmune, Experimental/metabolism , Male , Mice , Neuroprotective Agents/administration & dosage , Peptide Fragments/administration & dosage , Proto-Oncogene Mas , Proto-Oncogene Proteins/metabolism , Receptors, G-Protein-Coupled/metabolism , Severity of Illness Index , Treatment OutcomeABSTRACT
Recent data indicate that (2S,4R)-4-methylglutamate is a selective agonist for low affinity (GluR5 and GluR6) kainate receptor subunits. In the present study, we have employed [(3)H](2S,4R)-4-methylglutamate to examine low affinity kainate receptor distribution in mouse brain. [(3)H](2S,4R)-4-Methylglutamate labelled a single site in murine cerebrocortical membranes (K(d)=9.9+/-2.7 nM, B(max)=296.3+/-27.1 fmol mg protein(-1)). The binding of 8 nM [(3)H](2S,4R)-4-methylglutamate was displaced by several non-NMDA receptor ligands (K(i)+/-S.E.M.): domoate (1.1+/-0.2 nM)>kainate (7.1+/-1.1 nM) >> L-glutamate (187.6+/-31.9 nM) >> (S)-alpha-amino-3-hydroxy-5-methyl-4-isoazolepropionic acid (AMPA) (>50 microM). [(3)H](2S,4R)-4-Methylglutamate autoradiography revealed a widespread regional distribution of low affinity kainate receptors. Highest binding densities occurred within deep layers of the cerebral cortex, olfactory bulb, basolateral amygdala and hippocampal CA3 subregion. Moderate labelling was also evident in the nucleus accumbens, dentate gyrus, caudate putamen, hypothalamus and cerebellar granule cell layer. These data show that [(3)H](2S,4R)-4-methylglutamate is a useful radioligand for selectively labelling low affinity kainate receptors.
Subject(s)
Brain/physiology , Glutamates/analysis , Receptors, Kainic Acid/analysis , Animals , Autoradiography , Binding Sites , Brain/metabolism , Brain Mapping , Mice , TritiumABSTRACT
Oligodendrocyte progenitor cells were found to be vulnerable to kainate excitotoxic insults, an effect inhibited by either the selective alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist (1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine (GYKI 52466)) or the selective group I metabotropic glutamate (mGlu) receptor agonist, (S)-3,5-dihydroxyphenylglycine. The protective effects of (S)-3,5-dihydroxyphenylglycine were reversed by the selective mGlu receptor antagonist, (S)-alpha-methyl-4-carboxyphenylglycine. These data suggest that group I mGlu receptors may limit oligodendrocyte progenitor cell degeneration during acute brain insults.
