The roles of protein kinase C (PKC) epsilon and tetrahydrobiopterin (BH4)/dihydrobiopterin (BH2) related to endothelial nitric oxide synthase (eNOS) coupling/uncoupling in ischemia/reperfusion (I/R)

Abstract

The roles of coupled or uncoupled eNOS mediating nitric oxide (NO) or hydrogen peroxide (H2O2) release respectively in I/R have not been evaluated in vivo. The effects of PKC epsilon activator or inhibitor peptides, which can increase or decrease eNOS activity respectively, combined with BH4 or BH2 were tested in isolated perfused rat hearts (ex vivo) and femoral arteries/veins (in vivo) that were subjected to I(20 min)/R(45 min). When given during reperfusion, the PKC epsilon activator combined with BH4 restored post‐reperfused cardiac function (p<0.05), increased NO release (p<0.05) and reduced H2O2 release in femoral veins (p<0.01) compared to controls, but when combined with BH2 resulted in compromised post‐reperfused cardiac function, decreased NO and increased H2O2 release in femoral veins compared to controls (p<0.05). The results suggest that the combination of PKC epsilon activator and BH4 promoted eNOS to function in its coupled state producing NO. However, the combination of PKC epsilon inhibitor with BH2 or BH4 significantly improved post‐reperfused cardiac function (p<0.05), reduced H2O2 release (p<0.05) and increased NO release (p<0.05) in femoral veins compared to controls. These results suggest that inhibition of eNOS uncoupling following I/R attenuates H2O2 release. This study was supported by NHLBI Grant 2R15HL‐76235‐02 and the Center for the Chronic Disorders of Aging at PCOM.