Endothelial de novo nucleotide synthesis in atherosclerosis

Baylor College Of Medicine, Houston TX

Investigators

Abstract

PROJECT SUMMARY Atherosclerotic risk factors, including disturbed flow (d-flow), induce endothelial cell (EC) DNA damage and the subsequent EC death, compromise the integrity of the endothelial barrier, and ultimately lead to the formation of atherosclerotic lesions. Metabolism such as glycolysis and fatty acid metabolism are reprogrammed to accommodate ECs to the atherosclerotic environment. Nucleotide metabolism, including purine and pyrimidine synthesis, has been reported to regulate DNA repair and cell proliferation in cancer cells. However, the role of endothelial purine and pyrimidine synthesis in atherosclerosis has not been investigated. 5-aminoimidazole-4- carboxamide ribonucleotide formyltransferase/inosine monophosphate cyclohydrolase (ATIC) and Carbamoyl- phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase (CAD) are critical enzymes for de novo purine synthesis (DNPS) and de novo pyrimidine synthesis, respectively. Recently, I have demonstrated the pivotal role of ATIC in vascular smooth muscle cells in proliferative arterial disease in rodent models. However, it remains unclear in the role of ATIC or CAD-mediated de novo nucleotide metabolism in ECs in the development of atherosclerosis. My preliminary data show that (1) DNA damage response was increased in ECs exposed to disturbed flow, and this was accompanied by increased ATIC-mediated DNPS and CAD-mediated de novo pyrimidine synthesis; (2) Knockdown of ATIC with siRNA aggravated EC DNA damage and apoptosis induced by d-flow; (3) The atherosclerotic lesion size was markedly increased in EC-specific Atic deficient mice in d-flow-induced mouse atherosclerosis. These data allow me to hypothesize that ATIC-mediated DNPS and CAD-mediated de novo pyrimidine synthesis in ECs supply nucleotides to repair DNA damage and preserve EC barrier integrity in vulnerable atheroprone regions and ultimately protect against the development and progression of atherosclerosis. To test my hypothesis, I have generated endothelial Atic or Cad deficient mice (AticΔVEC and CadΔVEC) and crossed the mice with ApoE-/- mice to generate ApoE-/-;AticΔVEC and ApoE-/-;CadΔVEC mice. I will investigate the effect of endothelial Atic or Cad deficiency in the formation of atherosclerotic lesions using specific genetic tools with an integrated approach of in vivo and in vitro models. The results of this study will provide insights into how metabolic reprogramming of purine and pyrimidine synthesis in endothelial cells is involved in the development of atherosclerosis, offering new strategies for its prevention and treatment. This grant will be critical for me to achieve the following short- and long-term objectives: 1) to acquire additional scientific training both methodologically and conceptually; 2) to merge the yet distinct metabolism and atherosclerosis fields with the goals toward opening up new avenues of discovery; 3) to establish an independent research program; 4) publish high-impact corresponding author articles and develop a highly competitive R01 grant application. I have assembled a multidisciplinary team to guide my career toward independence and assist with the completion of the proposed research study.