Metabotropic glutamate receptor agonists protect from oxygen-glucose deprivation- and colchicine-induced apoptosis in primary cultures of cerebellar granule cells.

The effects of the metabotropic glutamate receptor agonists against apoptosis induced by oxygen-glucose deprivation or colchicine were studied in the primary cultures of mature cerebellar granule cells. Oxygen-glucose deprivation (90 min) or addition of colchicine (1 microM) resulted in neuronal damage as revealed by Trypan Blue assay 12 h later. Further analysis demonstrated that the cells exposed to oxygen-glucose deprivation or colchicine exhibit typical features of apoptosis: internucleosomal DNA fragmentation, condensation and fragmentation of chromatin and typical DNA ladder on agarose gel electrophoresis. Metabotropic glutamate receptor agonist, (1S,3R)-1-aminocycloheptane-trans-1,3-dicarboxylic acid, acting at group I and II receptors, and selective agonist, (2S,1'R,2R',3R')-2(2,3-dicarboxycyclopropyl)glycine, acting at group II receptors, added to cells recovering from oxygen-glucose deprivation exerted neuroprotective action against oxygen-glucose deprivation-induced apoptosis. Similar neuroprotective effects of metabotropic glutamate receptor agonists were observed against colchicine-induced apoptosis. The results thereby provide evidence that metabotropic glutamate receptor agonists have therapeutic potential in the treatment of pathologies associated with increased neuronal apoptosis. The selective protein kinase C inhibitor bisindolylmaleimide (100 nM) abolished the neuroprotective action of (1S,3R)-1-aminocycloheptane-trans-1,3-dicarboxylic acid, whereas the activator of adenylyl cyclase forskolin (10 microM) abolished the neuroprotective action of (2S,1'R,2R',3R')-2(2,3-dicarboxycyclopropyl)glycine (30 microM) against colchicine-induced apoptosis. It is concluded that both phosphoinositide hydrolysis with consequent activation of protein kinase C and inhibition of adenylyl cyclase seem to contribute to the neuroprotective action of metabotropic glutamate receptor agonists against neuronal apoptosis in the primary culture of cerebellar granule cells.