Cholesterol Paradigm and Beyond in Atherosclerotic Cardiovascular Disease: Cholesterol, Sterol Regulatory Element-Binding Protein, Inflammation, and Vascular Cell Mobilization in Vasculopathy
Ruihai Zhou, George A. Stouffer, William H. Frishman
Abstract
Hypercholesterolemia is a well-established risk factor for atherosclerotic cardiovascular disease (ASCVD). How cholesterol and its carrier lipoproteins are involved in ASCVD is still under extensive investigation. Satins are thus far the best-proven class of cholesterol-lowering medications to improve the clinical outcomes of ASCVD. Statins specifically inhibit the rate-limiting enzyme 3-hydroxy-3-methylglutaryl-CoA reductase of the mevalonate pathway for cholesterol biosynthesis. The widely accepted theory is that statins inhibit the hepatic cholesterol synthesis causing upregulation of hepatocyte low-density lipoprotein (LDL) receptor; receptor-mediated LDL uptake and metabolism in the liver results in reduction of circulating LDL cholesterol, which subsequently reduces vascular deposition and retention of cholesterol or LDL in atherogenesis. Nevertheless, cholesterol biosynthesis is ubiquitous, also in extrahepatic cells including those in vascular wall, under tight regulation by sterol regulatory element-binding protein (SREBP), the master gene transcription factor governing cholesterol biosynthesis. Studies have shown that SREBP can be upregulated in vascular wall subject to injury or stent implantation. SREBP can be activated by proinflammatory and mitogenic factors in vascular cells, leading to hyperactive mevalonate pathway, which promotes vascular cell mobilization, further proinflammatory and mitogenic factor release from vascular cells, and vascular inflammation. In this article, we review the cellular cholesterol homeostasis regulation by SREBP and SREBP-mediated vascular hyperactive cholesterol biosynthesis, we term vascular hypercholesterolism, in the pathogenesis of ASCVD and vasculopathy. SREBP functions as a platform bridging cholesterol, inflammation, and vascular cell mobilization in ASCVD pathogenesis. Targeting vascular hypercholesterolism could open a new avenue in fighting against ASCVD.