Protein kinase C-δ modulates apoptosis induced by hyperglycemia in adult ventricular myocytes

Abstract

We evaluated the direct effect of hyperglycemia on apoptosis of adult rat ventricular myocytes (ARVM) in vitro. Hyperglycemia (16.5 mM) for 24 h increased apoptosis by greater than threefold (48.2 ± 4.4%, by the TdT-mediated dUTP nick-end labeling method) compared with baseline (14.7 ± 2.5%). Hyperosmolarity with mannitol (11.0 mM) in the presence of 5.5 mM glucose also increased apoptosis by approximately twofold of baseline. Both glucose and mannitol treatment resulted in the membrane translocation of protein kinase C (PKC)-δ, and the activation of PKC-δ was confirmed by immune complex kinase assay. PKC-δ-specific translocation inhibitor peptide (δV1-1) attenuated only apoptosis induced by hyperglycemia but not by mannitol. A PKC-ɛ-specific translocation inhibitor peptide (ɛV1-1) affected neither type of apoptosis. Moderate overexpression of PKC-δ by adenovirus gene transfer prevented the antiapoptotic effect of δV1-1. Furthermore, δV1-1 attenuated the production of reactive oxygen species (ROS) by glucose. Taken together, our results indicate that increased ROS production regulated by PKC-δ is in part responsible for the induction of apoptosis by hyperglycemia and that apoptosis by hyperglycemia is mechanistically different from that by hyperosmolarity.