Abstract 2080: Chip E3 Ligase Mediates Vascular Smooth Muscle Cell Proliferation And Migration By Regulating Mitochondrial Fission

Objective: Excessive mitochondrial fission promotes the proliferation and migration of vascular smooth muscle cells (VSMCs), leading to subsequent vascular disorders such as atherosclerosis and abdominal aortic aneurysms (AAAs). Therefore, targeting the signaling pathways linked to mitochondrial fission-driven VSMC dysfunction could be a promising therapy for vascular diseases. This study aims to explore novel target molecules and mechanisms underlying mitochondrial fission-induced VSMC phenotypic switching. Methods: To investigate the role of CHIP in VSMC function, VSMCs were isolated from the aorta of wild-type (WT) and CHIP-knock-out (KO) mice, and their proliferation and migration rates were compared. Western blotting, qRT-PCR analysis, MitoTracker staining, JC-1 staining, MitoSOX staining, and a luciferase assay were employed to elucidate the molecular mechanisms. Results: We found that angiotensin II (Ang II)-induced VSMC migration and proliferation were reduced by CHIP-KO. Consistently, CHIP deficiency rescued the effects of Ang II on MMP2, MMP9, PCNA, and cyclin D1, as observed in both protein and mRNA levels. Notably, the localization of DRP1 phosphorylation (Ser616) in mitochondria and the mitochondrial fragmentation induced by Ang II were inhibited in CHIP-KO cells. The inactivation of DRP1 using mitochondrial division inhibitor 1 (Mdivi-1) inhibited Ang II-induced KLF4 protein expression and promoter activity. Furthermore, DRP1 inhibition significantly suppressed Ang II-induced VSMC migration and proliferation. Interestingly, Ang II-induced transcriptional activity and protein expression of KLF4 were prevented by CHIP inhibition. Concomitantly, the inhibition of DRP1 or CHIP prevented Ang II from increasing intracellular and mitochondrial ROS production. Consistent with the in vitro data, the CHIP KO and Mdivi-1 treatment group did not show abdominal aortic aneurysm (AAA) formation when challenged with Ang II infusion (1000 ng/kg/min) and β-aminopropionitrile (1 mg/ml in drinking water). Conclusions: Ang II-increased CHIP expression promotes DRP1-dependent mitochondrial fission, leading to activation of p90RSK/KLF4 signaling pathway to VSMC proliferation and migration.