2-chloro-5-hydroxyphenylglycine and 4-hydroxyphenylglycine

Opposite effects of nuclear factor-kappaB (NF-kappaB) on neuron survival rely on activation of diverse NF-kappaB factors. While p65 is necessary for glutamate-induced cell death, c-Rel mediates prosurvival effects of interleukin-1beta. However, it is unknown whether activation of c-Rel-dependent pathways reduces neuron vulnerability to amyloid-beta (Abeta), a peptide implicated in Alzheimer's disease pathogenesis. We show that neuroprotection elicited by activation of metabotropic glutamate receptors type 5 (mGlu5) against Abeta toxicity depends on c-Rel activation. Abeta peptide induced NF-kappaB factors p50 and p65. The mGlu5 agonists activated c-Rel, besides p50 and p65, and the expression of manganese superoxide dismutase (MnSOD) and Bcl-X(L). Targeting c-Rel expression by RNA interference suppressed the induction of both antiapoptotic genes. Targeting c-Rel or Bcl-X(L) prevented the prosurvival effect of mGlu5 agonists. Conversely, c-Rel overexpression or TAT-Bcl-X(L) addition rescued neurons from Abeta toxicity. These data demonstrate that mGlu5 receptor activation promotes a c-Rel-dependent antiapoptotic pathway responsible for neuroprotection against Abeta peptide.

Topics: Amyloid beta-Peptides; Animals; Cell Line, Tumor; Cell Survival; Cells, Cultured; Cerebral Cortex; Enzyme Inhibitors; Excitatory Amino Acid Agonists; Gene Deletion; Gene Silencing; Glycine; Humans; Mice; Mice, Inbred C57BL; Neurons; Neuroprotective Agents; NF-kappa B; Phenylacetates; Proto-Oncogene Proteins c-rel; Receptors, Metabotropic Glutamate; RNA, Small Interfering; Superoxide Dismutase

We have investigated the binding properties of [(3)H]quisqualate to rat metabotropic glutamate (mGlu) 1a and 5a receptors and to rat and human brain sections. Saturation isotherms gave K:(D) values of 27 +/- 4 and 81 +/- 22 nM: for mGlu1a and mGlu5a receptors, respectively. Several compounds inhibited the binding to mGlu1a and mGlu5a receptors concentration-dependently. (S:)-4-Carboxyphenylglycine, (S:)-4-carboxy-3-hydroxyphenylglycine, and (R,S)-1-aminoindan-1,5-dicarboxylic acid, which completely inhibited [(3)H]quisqualate binding to the mGlu5a receptor, were inactive in a functional assay using this receptor. The distribution and abundance of binding sites in rat and human brain sections were studied by quantitative receptor radioautography and image analysis. Using 10 nM: [(3)H]quisqualate, a high density of binding was detected in various brain regions with the following rank order of increasing levels: medulla, thalamus, olfactory bulb, cerebral cortex, spinal cord dorsal horn, olfactory tubercle, dentate gyrus molecular layer, CA1-3 oriens layer of hippocampus, striatum, and cerebellar molecular layer. The ionotropic component of this binding could be inhibited by 30 microM: kainate, revealing the distribution of mGlu1+5 receptors. The latter were almost completely inhibited by the group I agonist (S:)-3,5-dihydroxyphenylglycine. The binding profile correlated well with the cellular sites of synthesis and regional expression of the respective group I receptor proteins revealed by in situ hybridization histochemistry and immunohistochemistry, respectively.

Topics: Animals; Binding, Competitive; Brain; Calcium; Cells, Cultured; Dose-Response Relationship, Drug; Enzyme Inhibitors; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Glycine; Humans; Imidazoles; Indans; Intracellular Fluid; Kainic Acid; Male; Organ Specificity; Quinazolines; Quisqualic Acid; Rats; Rats, Inbred Strains; Receptor, Metabotropic Glutamate 5; Receptors, Metabotropic Glutamate; Recombinant Proteins; Spinal Cord; Transfection