Nitroxyl (HNO) suppresses vascular Nox2 oxidase activity

Nox2 oxidase activity underlies the oxidative stress and vascular dysfunction associated with several vascular-related diseases. We have reported that nitric oxide (NO center dot) decreases reactive oxygen species production by endothelial Nox2. This study tested the hypothesis that nitroxyl (HNO), the redox sibling of NO center dot, also suppresses vascular Nox2 oxidase activity. Specifically, we examined the influence of two well-characterized HNO donors, Angeli's salt and isopropylamine NONOate (IPA/NO), on Nox2-dependent responses to angiotensin II (reactive oxygen species production and vasoconstriction) in mouse cerebral arteries. Angiotensin II (0.1 mu mol/L)-stimulated superoxide (measured by lucigenin-enhanced chemiluminescence) and hydrogen peroxide (Amplex red fluorescence) levels in cerebral arteries (pooled basilar and middle cerebral (MCA)) from wild-type (WT) mice were similar to 60% lower (P < 0.05) in the presence of either Angeli's salt (1 mu mol/L) or IPA/NO (1 mu mol/L). Similarly, phorbyl 12,13-dibutyrate (10 mu mol/L; Nox2 activator)-stimulated hydrogen peroxide levels were similar to 40% lower in the presence of IPA/NO (1 mu mol/L; P < 0.05). The ability of IPA/NO to decrease superoxide levels was reversible and abolished by the HNO scavenger L-cysteine (3 mmol/L; P < 0.05), but was unaffected by hydroxocobalamin (100 mu mol/L; NO center dot scavenger), ODQ (10 mu mol/L; soluble guanylyl cyclase (sGC) inhibitor), or Rp-8-pCPT-cGMPS (10 mu mol/L; cyclic guanosine monophosphate (cGMP)-dependent protein kinase inhibitor). Angiotensin II-stimulated superoxide was substantially less in arteries from Nox2-deficient (Nox2(-/y)) versus WT mice (P < 0.05). In contrast to WT, IPA/NO (1 mu mol/L) had no effect on superoxide levels in arteries from Nox2(-/y) mice.