Activation of diacylglycerol and protein kinase C by oxidants and advanced glycation end-products in vascular cells

Excessive activation of diacylglycerol (DAG)-protein kinase C (PKC) pathway can be important mechanism by which oxidants (H2O2) and advanced glycation end-products (AGE) can induce vascular dysfunction for the development of diabetic vascular complications. When the rat aortic smooth muscle cells (RASMC) were treated with H2O2 and AGE-BSA, in situ PKC activities were significantly increased. We have also found that H2O2 and AGE-BSA increased total DAG levels in RASMC. In RASMC containing labeled arachidonate (Ar) or palmitate (P), H2O2 increased Ar-DAG, while AGE-BSA increased Ar-DAG and P-DAG. We examined tyrosine phosphorylation of phospholipase C gamma (PLC-gamma) and phospholipase D (PLD), a marker of activation. H2O2 showed the increase of tyrosine phosphorylation of PLC-gamma, while AGE-BSA increased both tyrosine phosphorylation of PLC-gamma and PLD. Thus, oxidants and AGE may enhance the DAG-PKC pathway via PLC-gamma or PLD activation, indicating PKC activation by a novel signal transduction pathway.