Apocynin reduces infarct volume following cerebral ischemia in mice

Abstract

We tested the effect of apocynin, an NADPH oxidase inhibitor, on cerebral artery production of superoxide (O2‐) and hydrogen peroxide (H2O2), and on stroke outcome in C57Bl6/J and Nox2 KO mice. Apocynin (300 μM) inhibited NADPH‐induced O2‐ production by ∼40% (n=9, P<0.05), and reduced H2O2 levels by ∼80% (n=6, P<0.05), in cerebral arteries. Interestingly, apocynin also reduced detectable H2O2 by >80% in the absence of arterial tissue. Ischemic stroke was induced by 30 min middle cerebral artery occlusion (n=79). Mice received vehicle (0.1% DMSO), 2.5 or 5 mg/kg apocynin ip 30 min before ischemia. Mortality at 24 h was 12% in vehicle controls, and 0% (P=0.24) and 41% (P<0.05) in mice treated with 2.5 and 5 mg/kg apocynin, respectively. Infarct volume was reduced by 2.5 mg/kg apocynin by ∼50% (n=8; P<0.05), whereas 5 mg/kg apocynin was ineffective (n=13). Apocynin (2.5 mg/kg) had no effect on infarct volume in Nox2 KO mice, suggesting its protective effect is Nox2‐dependent. Thus, apocynin inhibits cerebral NADPH oxidase, directly scavenges H2O2, and has a narrow therapeutic window for stroke. As H2O2 is an endogenous cerebral vasodilator, high dose apocynin could compromise blood flow.