Abstract P355: Involvement Of Nlrp3 Inflammasome In Vascular Injury-induced Neointimal Formation And PDGF-BB Stimulated Monocyte Retention And Pyroptosis In Arterial Smooth Muscle Cells

Abstract

Intimal hyperplasia due to pathological vascular remodeling is a common feature of cardiovascular diseases such as atherosclerosis and restenosis after angioplasty. Nlrp3 inflammasome has been reported to trigger endothelial injury leading to pathological vascular remodeling in metabolic diseases. This study aimed to elucidate whether the Nlrp3 inflammasome in smooth muscle cells (SMCs) per se is involved in their phenotypic regulation and thereby contributes to pathological vascular remodeling. The ligation injury-induced neointimal hyperplasia model was established in hypercholesterolemic mice. Mice received a single intravenous injection of AAV encoding mutant mPCSK9 (rAAV8-D377Y-mPCSK9). Then mice received partial ligation surgery in left carotid artery (LCA) and consumed a high fat, high cholesterol diet for 4 weeks. The neointimal formation and various markers related to synthetic phenotype and Nlrp3 inflammasome pathways were assessed in ligated LCA. The collateral un-ligated right carotid artery (RCA) served as controls. Our data revealed that ligation injury induced neointimal formation in Nlrp3 +/+ mice, which was markedly attenuated in Nlrp3 -/- mice (intima area: Nlrp3 +/+ 15.97±4.07 μm 2 vs. Nlrp3 -/- 4.31±1.27 μm 2 ). Ligation injury drastically increased Nlrp3 inflammasome activation, monocyte adhesion, pyroptosis, and synthetic phenotype trans-differentiation in LCAs of Nlrp3 +/+ mice. These changes were largely limited in the SMC-enriched neointimal region and abrogated in Nlrp3 -/- mice. PDGF-BB, a ligation injury-associated factor promoting SMC synthetic phenotype transition, activated Nlrp3 inflammasomes in cultured SMCs. Inhibition of inflammasome-dependent caspase-1 by Ac-YVAD-cmk attenuated PDGF-BB-induced SMC-monocyte interaction and pyroptosis, whereas proliferation and migration of SMCs were unaffected. Together, these results suggest that in arterial SMCs, activation of Nlrp3 inflammasomes and subsequent events including induction of pyroptosis and adhesion of monocytes are essential for ligation injury-induced neointimal formation. These results provide new insight into the mechanisms of Nlrp3 inflammasome action in SMCs in pathological vascular remodeling in hypercholesterolemia.