Evidence that reduced nitric oxide signal contributes to cutaneous microvascular dysfunction in peripheral arterial disease

Peripheral arterial disease (PAD) is associated with cutaneous microvascular dysfunction and an increased risk of arterial ulceration in the affected lower-limb(s). The purpose of this study was to investigate the role of nitric oxide (NO) in cutaneous microvascular dysfunction in patients with PAD. Using laser-Doppler flowmetry, we measured skin blood flow (SkBF) in 5 patients with unilateral symptomatic PAD and 10 age-matched healthy controls at baseline and during 40 min of local skin heating to 42°C at 1) untreated lower-leg sites, and 2) lower-leg sites treated with 20 mM N(G)-nitro-L-arginine methyl ester (L-NAME) to inhibit NO synthase activity. SkBF was expressed as laser-Doppler flux (LDF) and normalized to maximal LDF (%LDF(max)) achieved through localized heating to 44°C and concomitant infusion of 56 mM sodium nitroprusside. Pharmacological agents and control treatments (lactated Ringer's) were administered using intradermal microdialysis. The plateau LDF response to local skin warming at the untreated skin sites was significantly (P < 0.05) lower in the diseased limb of the PAD patients (70.3 ± 13.6 %max) compared to the non-diseased contralateral limb (85.0 ± 10.2 %max) and the response observed for the control participants (89.0 ± 5.2 %max). The NO contribution to the plateau SkBF response tended to be lower in the diseased limb of the PAD patients (45.1 ± 16.4% versus 56.1 ± 10.7% [P = 0.12] and 55.4 ± 11.5% [P = 0.13], respectively). The results suggest that PAD impairs downstream cutaneous microvascular vasodilatory function and that the microvascular dysfunction is probably explained, at least in part, by a reduced NO signal