C-reactive protein inhibits endothelium-dependent NO-mediated dilation in coronary arterioles by activating p38 kinase and NAD(P)H oxidase

Objective-Elevated levels of C-reactive protein (CRP), a proinflammatory marker, are associated with reduced systemic endothelium-dependent NO-mediated dilation in patients with coronary artery disease; however, the direct effect of CRP on coronary microvascular reactivity remains unknown. Herein, we examined whether CRP can modulate endothelium-dependent NO-mediated dilation of coronary arterioles and whether proinflammatory signaling pathways such as stress-activated protein kinases (p38 and c-Jun N-terminal kinase [JNK]) and oxidative stress are involved in the CRP-mediated effect. Methods and Results-Porcine coronary arterioles were isolated and pressurized without flow for in vitro study. Intraluminal treatment with a clinically relevant concentration of CRP (7 mu g/mL; 1 hour) significantly attenuated the NO release and vasodilation to serotonin. Further incubation with the NO precursor L-arginine (3 mmol/L) partially restored serotonin-induced vasodilation. In the presence of superoxide scavenger 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL), NAD(P)H oxidase inhibitor apocynin, or p38 kinase (an upstream activator of NAD( P) H oxidase) inhibitor SB203850, but not xanthine oxidase inhibitor allopurinol or JNK inhibitor SP600125, the detrimental effect of CRP on serotonin-induced dilation was prevented. Dihydroethidium staining showed that CRP produced SB203850- and TEMPOL-sensitive superoxide production in the arteriolar endothelium. CRP treatment of coronary arterioles significantly increased NAD(P)H oxidase activity. Conclusions-CRP inhibits endothelium-dependent NO-mediated dilation in coronary arterioles by producing superoxide from NAD(P)H oxidase via p38 kinase activation. By impairing endothelium-dependent NO-mediated vasoreactivity, CRP could facilitate the initiation of numerous cardiovascular diseases.