PKC activation impairs endothelium‐dependent NO‐mediated dilation of coronary arterioles via enhanced superoxide production from xanthine oxidase

Abstract

We examined the role of PKC‐mediated pathway in eliciting endothelial dysfunction using isolated and pressurized porcine coronary arterioles. Diameter changes were recorded using videomicroscopic techniques. Superoxide production was detected with dihydroethidium (DHE) staining. Incubation of coronary arterioles with the PKC activator phorbol 12, 13‐dibutyrate (PDBu) (1 nM, 60 minutes) attenuated arteriolar dilation to the endothelium‐dependent, NO‐mediated agonists adenosine and serotonin, but not the NO donor sodium nitroprusside. In the presence of superoxide scavenger TEMPOL (1 mM), xanthine oxidase inhibitor allopurinol (10 μM), c‐Jun N‐terminal kinase (JNK) inhibitor SP600125 (5 μM) or Rho‐kinase inhibitor Y‐27632 (0.1 μM), the adverse effects of PDBu on adenosine‐ and serotonin‐induced dilations were prevented. Nevertheless, the inhibitory effects of PDBu were insensitive to H2O2 scavenger PEG‐catalase (500 units/ml), NAD(P)H oxidase inhibitor apocynin (100 μM) or p38 kinase inhibitor SB203580 (0.1 μM). DHE staining revealed that PDBu generated TEMPOL‐sensitive superoxide production in the coronary arteriolar smooth muscle. In conclusion, activation of vascular PKC with PDBu inhibits endothelium‐dependent, NO‐mediated dilation in coronary arterioles by producing superoxide from xanthine oxidase, which appears to be linked with JNK and RhoA/Rho kinase activation.