Abstract 248: Role of Mitochondrial Heat-Shock Protein 90 (HSP90) in Regulation of Vascular Smooth Muscle Cell (VSMC) Apoptosis and Vascular Remodeling in-vivo

Abstract

Introduction Apoptosis of VSMC is a common feature of vascular remodeling. Mitochondrial apoptosis is regulated by an organelle-specific network including Hsp90 family proteins. Gamitrinib (G4) is a small molecule that selectively targets mitochondrial Hsp90 and has shown antitumor activity. We investigated the effects of G4 on mitochondrial membrane potential (MMP) and apoptosis in VSMC, and on vascular remodeling in vivo. Methods Primary cultured human VSMCs were treated with G4, 17-AAG (inhibits cytosolic Hsp90), or vehicle. MMP (TMRM assay), apoptosis (Annexin V/PI flow cytometry) and cell viability (MTT assay) were measured. For in vivo studies, a mouse carotid artery ligation model was used. Mice (N= 45) were treated with systemic G4 (10 mg/kg IP daily) vs. control, and sacrificed at 3 or 14 days. Results Pre-treatment of VSMC with G4 (1 uM) resulted in a rapid, dose-dependent loss of MMP upon exposure to peroxynitrite (PN;25-200 uM), compared to 17-AAG or vehicle. G4 (25 uM) sensitized VSMC to apoptotic death (17.5% vs 8.8%, p=.02) following exposure to PN (300 uM, 4 hrs). In-vivo, G4 treatment resulted in increased apoptosis (TUNEL) in the ligated carotid artery (21% vs 4 %, p=.02) at 3 days, with no discernible difference in proliferation (Ki67 and BrdU). At 14 days, G4 treatment resulted in improved remodeling, with reduced intimal thickness (25%, p=.04) and increased radius:wall thickness ratio (50%; p=.008; Figure). Conclusions Selective targeting of mitochondrial Hsp90 sensitizes VSMC to mitochondrial depolarization and apoptosis, and alters vascular remodeling in-vivo. This may represent a new molecular target to modulate vascular injury.