Abstract 19686: Nox4-Dependent Increase in Mitochondrial Reactive Oxygen Species Levels Contributes to Aging-Associated Increase in Cardiovascular Disease

Abstract

The incidence of cardiovascular diseases (CVD) increases with age. Elevated ROS levels and resulting vascular inflammation were implicated in this process. We previously reported that inhibition of Nox1/Nox2 NADPH oxidases in p47phox deficient apoE-/- mice was not sufficient to reduce aging-associated increase in vascular reactive oxygen species (ROS) levels and atherosclerosis, aortic stiffness and cardiac dysfunction. This loss of protection is associated with increased total as well as mitochondrial ROS (mtROS) levels in the vasculature of aged apoE-/- and apoE-/-/p47phox-/- mice. Here we investigated the mechanisms and impact of aging-associated increase in oxidative stress in mouse and human CVD. Vascular smooth muscle cells (VSMC) isolated from aged wild-type and p47phox-/- mice had higher total and mtROS levels compared to VSMC from respective young mice (p<0.01 for both total and mtROS). Nox4 expression was increased in the aortic wall of aged apoE-/- and apoE-/-/p47phox-/- mice and in mitochondria of VSMC from both aged mice (p<0.05). Nox4 knockdown with shRNA resulted in decreased mtROS levels in aged wild-type VSMC (p<0.05). Increased oxidation and dysfunction of mitochondrial proteins were observed in VSMC from aged mice. Vcam1 expression, which was increased in the aged VSMC was abrogated on treatment with MitoTEMPO, a mitochondria targeted antioxidant (p<0.05). Increased mtROS levels in aortic VSMC from aged subjects were associated with enhanced mitochondrial Nox4 expression. Expression of Nox4 in the human carotid artery wall correlated with subjects’ age (r2 = 0.59, p<0.0001) and atherosclerotic lesion complexity (p< 0.0001). In addition, a significant association was observed between mitochondrial DNA damage index and CVD (r=0.45, p=0.013). In conclusion, Nox4-dependent increase in mitochondrial oxidative stress may contribute to mitochondrial DNA damage, mitochondrial dysfunction, vascular inflammation and increased incidence of CVD in aging, suggesting that selective targeting of mtROS in aging is beneficial.