Objective The present study aims to investigate the role of protein kinase C 5 subtype （PKCS） phosphorylation in the process of 6-hydroxydopamine （6-OHDA）-induced dopaminergic cell death, and demonstrate the molecular basis of neurological disorders, such as Parkinson＇ s disease. Methods The pheochromocytoma （PC 12） cell line was employed in the present study. Cells were treated with 2 μmol/L PKC5 inhibitor Rottlerin, 10 nmol/L protein kinase C α subtype （PKCα） inhibitor bisindolylmaleimide 1, or 5 nmol/L G66976 that could specifically inhibit the calcium-dependent PKC isoforms, respectively. PKC8 activator phorbol-12-myristate-13-acetate （PMA, 100 nmol/L） was also used in this study. All these agents were added to the medium before cells were incubated with 6-OHDA. Cells with no treatment served as control. The cytotox- icity of 6-OHDA was determined by methyl thiazolyl tetrazolium （MTT） reduction assay and PKCδ phosphorylation levels in various groups were measured by western blotting. Results Bisindolylmaleimide I and Go6976 exerted no significant attenuation on the cytotoxicity of 6-OHDA, nor any effects on PKCδ phosphorylation in PC 12 cells. However, Rottlerin could inhibit the phosphorylation of PKC5 and attenuate 6-OHDA-induced cell death, and the cell viability was raised to 69.6 ±2.63% of that in control group （P 〈 0.05）. In contrast, PMA induced a significant increase in PKC5 phosphorylation and also strengthened the cytotoxic effects of 6-OHDA. The cell viability of PMA-treated PC12 cells decreased to 49.8±5.06% of that in control group （P 〈 0.001）. Conclusion Rottlerin can protect PC 12 cells from cytotoxicity of 6-OHDA probably by inhibiting PKC δ phosphorylation. The results suggest that PKCδ may be a key regulator of neuron loss in Parkinson＇s disease.
