Abstract 209: NAD(P)H Oxidase-Derived Superoxide Contributes to Impaired Cutaneous Microvascular Function in Chronic Kidney Disease

Abstract

Endothelial dysfunction occurs in chronic kidney disease (CKD) and cardiovascular disease is the most common cause of death in these patients. Oxidative stress has been shown to be a mechanism of vascular dysfunction in CKD. We utilized the cutaneous circulation to test the hypothesis that superoxide derived from NAD(P)H oxidase and xanthine oxidase impair nitric oxide (NO)-dependent cutaneous vasodilation patients with CKD. Twenty subjects, 10 stage 3 and 4 CKD patients (61±4 years; 5 male/5 female; eGFR: 39 ± 4 ml·min -1 ·1.73m -2 ) and 10 healthy controls (HC) (55±2 years; 4 male/6 female; eGFR: >60 ml·min -1 ·1.73m -2 ) were instrumented with 4 intradermal microdialysis fibers in the forearm for the local delivery of 1) Ringers solution (Control), 2) 10 μM Tempol to scavenge superoxide, 3) 100 μM apocynin to inhibit NAD(P)H oxidase, and 4) 10 μM allopurinol to inhibit xanthine oxidase. Red blood cell (RBC) flux was measured via laser Doppler flowmetry during standardized local heating (42°C). After the local heating response was established, 10 mM L-NAME was infused into all four sites to quantify the NO-dependent portion of the response. Cutaneous vascular conductance (CVC) was calculated as RBC flux/mean arterial pressure and all data are presented as a percentage of maximum CVC achieved during 28mM sodium nitroprusside infusion at 43°C. The plateau in cutaneous vasodilation was attenuated in CKD at the control site (CKD: 77±3 vs. HC: 88±3 %, p<0.05). Tempol and apocynin augmented the plateau in cutaneous vasodilation in CKD patients (Tempol: 88±2, apocynin: 91±2 %, p<0.05 vs. CKD control site) but had no effect in the healthy control group. The NO-dependent portion of the response was reduced in CKD at the control site (CKD: 41±4 vs. HC: 58±2 %, p<0.05). Tempol and apocynin augmented NO-dependent portion of the response in CKD patients (Tempol: 58±3, apocynin: 58±4 %, p<0.05 vs. CKD control site) but had no effect in the healthy control group. Inhibition of xanthine oxidase did not alter the plateau in cutaneous vasodilation in either group (p>0.05). These data suggest that NAD(P)H oxidase is a source of superoxide and contributes to microvascular dysfunction in CKD.