Cyclic GMP/cyclic GMP-dependent protein kinase system prevents excitotoxicity in an immortalized oligodendroglial cell line

Previously, we have demonstrated that excitotoxicity of oligodendrocyte-lik e cells (OLC), differentiated from immortalized rat O-2A progenitor cells ( CG-4 cells), is prevented by cyclic AMP-elevating agents. We now report tha t some agents that elevate cyclic GMP prevent OLC excitotoxicity. Kainate-i nduced injury was prevented by cyclic GMP analogues (8-bromo-cyclic GMP and dibutyryl cyclic GMP), a guanylate cyclase activator [atrial natriuretic p eptide (ANP)], and phosphodiesterase inhibitors [3-isobutyl-1-methylxanthin e (IBMX), ibudilast, propentofylline, and rolipram]. When both forskolin an d 8-bromo-cyclic GMP were added, kainate-induced injury was additively prev ented. There was a strong positive correlation between suppression of kaina te-induced Ca2+ influx and prevention of injury by these chemicals. The mea surement of intracellular cyclic AMP and cyclic GMP by radioimmunoassay dem onstrated the following: an increase of cyclic GMP with treatment with 8-br omo-cyclic GMP, dibutyryl cyclic GMP, and ANP; an increase of cyclic AMP wi th treatment with ibudilast and rolipram; and an increase of both cyclic AM P and cyclic GMP with treatment with IBMX and propentofylline. Kainate-indu ced Ca2+ influx was decreased by 8-(4-chlorophenylthiol)-guanosine-3',5'-mo nophosphate, an activator of cyclic GMP-dependent protein kinase (PKG), or okadaic acid, an inhibitor of protein phosphatases 1 and 2A, RT-PCR and wes tern blotting of OLC demonstrated transcription of PKG II gene and translat ion of PKG I beta mRNA, but no:translation of PKG I alpha mRNA, Therefore, we concluded that the cyclic GMP/PKG system prevents OLC excitotoxicity.