Atherogenic Activation of Human Vascular Smooth Muscle Cells by Monosodium Urate Crystals

Abstract

Gout is strongly associated with atherosclerosis and other cardiovascular comorbidities. Furthermore, sites of extra-articular monosodium urate (MSU) crystal deposits in gout can include heart valves and atherosclerotic artery plaques, but with unclear effects therein. Hence, we seminally explored cultured vascular smooth muscle cell (VSMC) responsiveness to MSU crystals. To limit confounding effects, we cultured human aortic VSMCs under serum-free conditions to assess MSU crystal effects on VSMC differentiation and function, differentially expressed genes (DEGs) via RNA sequencing, and selected atherogenic changes in cytokines and the lipidome. MSU crystals induced p38 phosphorylation, IL-6, and VSMC vacuolization with dysregulated autophagy. MSU-crystal-induced DEGs included decreased late-stage autophagosome maturation mediator GABARAPL1, decreased physiologic VSMC differentiation regulators (LMOD1 and SYNPO2), increased ATF4, CHOP, and the intrinsic apoptosis signaling pathway in response to ER stress, and neointimal atherogenic nuclear receptors (NR4A1 and NR4A3). MSU crystals alone increased the levels of cholesterol biosynthetic intermediates 14-demethyl-lanosterol (14-DML), desmosterol, and zymosterol. Adding MSU crystals increased oxidized LDL’s capacity to increase intracellular 27-OH cholesterol, and MSU crystals and oxidized LDL synergistically induced a marked release of arachidonate. In conclusion, MSU crystals deposited in arterial media and neointima have the potential to dysregulate VSMC differentiation and proteostasis, and to induce further atherogenic effects, which include enhanced VSMC loading of oxidized cholesterol intermediates and release of IL-6 and arachidonic acid (AA).