Effects Of Inorganic Arsenic, Methylated Arsenicals, And Arsenobetaine On Atherosclerosis In The Apoeh(-/-) Mouse Model And The Role Of As3mt-Mediated Methylation

BACKGROUND: Arsenic is metabolized through a series of oxidative methylation reactions by arsenic (3) methyltransferase (As3MT) to yield methylated intermediates. Although arsenic exposure is known to increase the risk of atherosclerosis, the contribution of arsenic methylation and As3MT remains undefined.OBJECTIVES: Our objective was to define whether methylated arsenic intermediates were proatherogenic and whether arsenic biotransfor ation by As3MT was required for arsenic-enhanced atherosclerosis.METHODS: We utilized the apoE(-/-) mouse model to compare atherosclerotic plaque size and composition after inorganic arsenic, methylated arsenical, or arsenohetaine exposure in drinking water. We also generated apnE(-/-)/As3mf(-/-) double knockout mice to test whether As3MT-mediated hiotransformation was required for the proatherogenic effects of inorganic arsenite. Furthermore, As3MT expression and function were assessed in in vitro cultures of plaque-resident cells. Finally, hone marrow transplantation studies were performed to define the contribution of As3MT-mediated methylation in different cell types to the development of atherosclerosis alter inorganic arsenic exposure.RESULTS: We found that methylated arsenicals, but not arsenobetaine, are proatherogenic and that As3MT is required for arsenic to induce reactive oxygen species and promote atherosclerosis. Importantly, As3MT was expressed and functional in multiple plaque-resident cell types, and transplant studies indicated that As3MT is required in extrahcpatic tissues to promote atherosclerosis.CONCLUSION: Taken together, our findings indicate that As3MT acts to promote cardiovascular toxicity of arsenic and suggest that human AS3MT SNPs that correlate with enzyme function could predict those most at risk to develop atherosclerosis among the millions that are exposed to arsenic.