Abstract 426: Overexpression of Tissue-nonspecific Alkaline Phosphatase (TNAP) Accelerates Coronary Artery Disease in the Setting of Hypercholesterolemia in Mice

Abstract

Objective: Vascular calcification in asymptomatic individuals is an independent predictor of coronary heart disease (CHD). It is therefore plausible that vascular calcification plays a direct pathophysiological role in atherosclerosis, an underlying cause of CHD. The purpose of this study was to examine the contribution that vascular calcification has on the development of coronary atherosclerosis in a mouse model of familial hypercholesterolemia. Approach and Results: Calcification was induced by overexpression of tissue-nonspecific alkaline phosphatase (TNAP) in endothelial cells of mice harboring a point mutation in the low density lipoprotein receptor ( ldlr, wicked high cholesterol, WHC). Mice were fed an atherogenic diet; echocardiographic and biochemical data were collected longitudinally. Atherosclerosis and vascular calcification were analyzed histologically in the aorta, aortic sinus and coronary arteries. TNAP mice were also treated with a combination of an atherogenic diet and a specific inhibitor of TNAP (SBI-425). Combined with the ldlr mutation and an atherogenic diet, TNAP-driven arterial calcification led to severe atherosclerosis with 100% morbidity characterized by occlusive coronary artery disease, pathological cardiac hypertrophy with dilated LV and reduced ejection fraction (EF). We detected an interaction between vascular calcification and atherosclerosis in mice with endothelial TNAP overexpression. This interaction was particularly prominent in coronary circulation. Targeting TNAP activity therapeutically helped improve survival and heart function of endothelial TNAP overexpressor mice, however the incomplete inhibition of TNAP by SBI-425 was a limitation of this study. Conclusions: Vascular calcification via TNAP overexpression in endothelial cells promotes coronary atherosclerosis and is pathogenic under conditions of hypercholesterolemia.