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

Abstract

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 μM) 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 μM) abolished the neuroprotective action of (2S,1′R,2R′,3R′)-2(2,3-dicarboxycyclopropyl)glycine (30 μM) 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.