Inhibitors of protein kinase C prevent the toxicity of glutamate in primary neuronal cultures

Abstract

Glutamate-induced neurotoxicity has been proposed to depend on a sustained increase of intracellular free Ca 2+ levels. However, the molecular mechanism(s) involved are not well understood. Some results suggest that activation of protein kinase C by the increased levels of Ca 2+ could play a role in the mediation of glutamate neurotoxicity. To assess this hypothesis we have tested if the 1-(5-isoquinolinyl-sulfonyl)-2-methyl-piperazine (H7) and calphostin C, inhibitors of protein kinase C, are able to protect neurons in primary culture from glutamate-induced cell death. It is shown that both H7 and calphostin C prevent nearly completely the death of neurons from cerebellum, even when 2 mM glutamate was used. HA-1004, an inhibitor of cyclic nucleotide-dependent protein kinases, did not protect neurons. The protective effect was maximum at ≈ 10 μM H7 and at ≈ 10 nM calphostin C. The results reported support the hypothesis that protein kinase C plays a key role in the mediation of glutamate neurotoxicity.