Specific Induction of Protein Kinase Cδ Subspecies after Transient Middle Cerebral Artery Occlusion in the Rat Brain: Inhibition by MK-801

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Abstract
Protein kinase C (PKC) consists of a family of closely related Ca2+/phospholipid-dependent phosphotransferase isozymes, most of which are present in the brain and are differentially activated by second messengers. Calcium-dependent PKC activity may cause neuronal degeneration after ischemic insult. PKC is also involved in trophic-factor signaling, indicating that activity of some PKC subspecies may be beneficial to the injured brain. Therefore, we screened long-term changes in the expression of multiple PKC subspecies after focal brain ischemia. Middle cerebral artery occlusion was produced by using an intraluminal suture for 30 min or 90 min. Inin situhybridization experiments, mRNA levels of PKCα, -β, -γ, -δ, -ε and -ζ were decreased in the infarct core 4 hr after ischemia and were lost completely 12 hr after ischemia. In areas surrounding the core, PKCδ mRNA was specifically induced 4, 12, and 24 hr after ischemia in the cortex. At 3 and 7 d, the core and a rim around it showed increased mRNA levels of PKCδ. No other subspecies were induced. At 2 d, immunoblotting demonstrated increased levels of PKCδ protein in the perifocal tissue, and immunocytochemistry revealed an increased number of PKCδ-positive neurons in the perifocal cortex. In the core, PKCδ-positive macrophages and endothelial cells were seen. Pretreatment with MK-801, an NMDA antagonist, inhibited cortical PKCδ mRNA induction. The data show that focal brain ischemia induces PKCδ mRNA and protein but not other PKC subspecies through the activation of NMDA receptors and that the upregulation lasts for several days in neurons of the perifocal zone.