Abstract 5462: Dual Effects of Nox2-NADPH Oxidase During Atherosclerotic Plaque Development in Apolipoprotein E-Null Mice

Abstract

The reactive oxygen species (ROS) -producing NADPH oxidases are implicated in atherogenesis, although the relative contribution of the different isoforms of these enzymes to plaque development has not been established. We investigated the role of the ‘classical’ Nox2-containing NADPH oxidase in atherogenesis in apolipoprotein E-null (ApoE −/− ) mice. Nox2 expression (Western blotting) and localisation (immunohistochemistry), ROS production (L012-enhanced chemiluminescence), nitric oxide (NO) bioavailability (isometric contractions to N γ -nitro-L-arginine methyl ester) and atherosclerotic lesion development along the luminal surface of the aorta and in the aortic sinus, were measured in 12, 19 and 26 week-old wild-type, ApoE −/− and Nox2 −/− /ApoE −/− mice maintained on a Western style diet (21% fat, 0.15% cholesterol). Nox2 expression was elevated in the endothelium of ApoE −/− mice prior to lesion formation and this was associated with elevated ROS production. In developing plaques, macrophages were also a source of Nox2. The absence of Nox2 in 12 and 19 week-old Nox2 −/− /ApoE −/− mice had minimal effects on plasma lipids but was associated with a marked reduction in vascular ROS production and an increase in NO bioavailability. En face lesion coverage of the aorta from the arch to the iliac bifurcation was also markedly reduced in 12 and 19 week-old Nox2 −/− /ApoE −/− versus ApoE −/− mice. However, in 26 week-old mice, differences in en face lesion area were no longer apparent between strains and, surprisingly, intimal thickening in the aortic sinus was more pronounced in the Nox2 −/− /ApoE −/− mice. Thus, we have described, for the first time, that Nox2-NADPH oxidase plays dual roles in atherosclerotic plaque development in ApoE −/− mice, being pro-atherogenic in early stages, and possibly protective in later stages of the disease.