Demonstration of the essential role of protein kinase C isoforms in hyperglycemia-induced embryonic malformations

To address the role of PKC isoforms in hyperglycemia-induced apoptosis and malformations in the embryos of diabetic pregnancies, expression of PKC alpha, beta 1, beta 2, gamma, delta, epsilon, and zeta was examined in the neural tube of rat embryos and showed to overlap with the regions of increased apoptosis. Levels of activated (Phosphorylated) PKC alpha, beta 2, and delta were increased in the embryos of diabetic dams whereas those of PKC epsilon and zeta were decreased when compared with those in control groups. Cytosolic phospholipase A(2) (cPLA(2)) was also activated. Blocking the activity of PKC alpha, beta 2, and delta using isoform-specftic inhibitors in embryos cultured in hyperglycemia (40 mM) reduced malformation rates when compared with those in untreated hyperglycemic and euglycemic (8.3 mM) groups. These observations demonstrate that PKC alpha, beta 2, and delta play an essential role in diabetic embryopathy. Activation of cPLA(2) was also decreased, suggesting that PKCs mediate the hyperglycemic effects through the cPLA2 -phospholipid pcroxidation pathway.