Protein Kinase B (PKB) and Protein Kinase C (PKC) in N-Methyl-D-Aspartate(NMDA)-Induced Excitotoxicity in Rats

Abstract

Abstract: : Purpose: To investigate the possible involvement of PKB and PKC in the inner retina after NMDA-induced excitotoxicity in rats. Methods: Excitotoxicity in retinal cells was induced by intravitreal injection of 2 µl. of 0.2 mM neutralized NMDA in 0.1 M phosphate buffered saline (PBS) in albino Lewis rats. The animals were euthanized at 0,3,9 and 18 hours after NMDA injection and the eyes were fixed, processed, embedded in paraffin and sectioned. To localize PKB and PKC, we performed immunohistochemistry using antibodies against phosphorylated PKB and PKC. Quantitative real-time PCR for PKB was also performed. Results: Immunohistochemistry revealed staining of phosphorylated PKB and PKC in both normal retina and those retinas in which excitotoxicity was induced; it was localized primarily to the inner part of inner plexiform layer (IPL) and less so to the outer IPL and to the retinal ganglion cell layer. However, there were no significant differences among the normal, 3, and 9 hour retinas. The 18 hour retinas showed a noticeable decrease in both phosphorylated PKB and PKC immunoreactivity. Quantitative real-time PCR for PKB also showed a decrease in PKB mRNA at 18 hours. Conclusions: PKB and PKC were down-regulated in the retina after NMDA excitotoxicity and may be involved in RGC survival.

Keywords: excitatory amino acid receptors • apoptosis/cell death • retina