Abstract 241: Nicotinamide Nucleotide Transhydrogenase Regulates Mitochondrial Function And Oxldl Induced Macrophage Endothelial Interaction.

Abstract

Atherosclerosis is a chronic inflammatory disease effecting large and medium sized arteries that leads to the buildup of plaque that contributes to myocardial infraction, stroke, and other pathologies. Mounting evidence has identified mitochondrial reactive oxygen species (ROS) as a key contributor to plaque formation and progression. A inner mitochondrial membrane enzyme Nicotinamide nucleotide transhydrogenase (NNT) sustains NADPH pools required for the mitochondrial antioxidant systems. We have observed that the expression of NNT is decreased in severe human atherosclerotic plaques leading us to hypothesize that the loss of NNT contributes to increased mitochondrial ROS and drives the progression of atherosclerosis by enhancing endothelial and vascular dysfunction. Utilizing AAV/PCSK9 and HFD induced models of early and late-stage atherosclerosis, we found that NNT knockout (NNT KO) mice display significantly increased VCAM-1 expression in aortic endothelial cells during early atherosclerosis and significantly larger necrotic cores in late-stage atherosclerosis. Additionally, NNT KO mice displayed a significantly thinner fibrous cap in late-stage plaques. Similar results were observed in vitro where the loss of NNT in human aortic endothelial cells exacerbated oxLDL induced VCAM-1 expression that was associated with decreased mitochondrial NADPH levels, glutathione peroxidase (Gpx2) activity, and increased H 2 O 2 production. The observed increase in necrotic core area in NNT KO mice is suggestive of increased inflammatory cell recruitment to the plaque. Furthermore, bone marrow derived macrophages (BMDM) from NNT KO mice display decreased lipid content, poor lipid uptake and a predisposition to differentiate into a proinflammatory M1 phenotype. Based on these studies, we conclude that the loss of NNT contributes to unstable plaques with large necrotic cores, mitochondrial ROS driven endothelial dysfunction, increased inflammatory cell recruitment, and enhanced M1 macrophage activity. The novel relationship between vascular NNT expression and plaque severity in human samples implicates NNT as a novel clinical target in atherosclerosis.