Cell-specific role for ε- and βI-protein kinase C isozymes in protecting cortical neurons and astrocytes from ischemia-like injury

Abstract

Activation of ϵ protein kinase C (ϵPKC) has been shown to protect cardiac myocytes against ischemia and reperfusion injury. However, the role of PKC in ischemic brain injury is less well defined. Western blot analysis of murine neurons and astrocytes in primary culture demonstrated ϵ- and βIPKC expression in both cell types. Activation of ϵPKC increased in neuronal cultures in response to the ischemia-like insult of oxygen–glucose deprivation (OGD). Isozyme-specific peptide activators or inhibitors of PKC were applied at various times before, during and after the OGD period. Neuron–astrocyte mixed cultures pretreated with a selective ϵPKC activator peptide showed a significant reduction in neuronal injury after OGD and reperfusion, compared to cultures pretreated with control peptide. The ϵPKC activator peptide counteracted the increased damage induced by pretreatment with the ϵPKC-selective inhibitor peptide in relatively pure neuronal cultures subjected to OGD. Neither ϵPKC activator nor inhibitor peptides affected injury of neurons when applied after OGD onset. In contrast, the βIPKC-selective inhibitor peptide increased injury in astrocyte cultures exposed to OGD at all application times tested. Our data demonstrate protection of neurons by selective activation of ϵPKC but enhanced astrocyte cell death with selective inhibition of βIPKC. Thus PKC isozymes exhibit cell type-specific effects on ischemia-like injury.