Abstract 9: Involvement of Caveolin-1 in Vascular Remodeling and Inflammation Induced by Angiotensin II

Abstract

We have recently reported that caveolin-1 (Cav1) enriched membrane microdomains in vascular smooth muscle cells (VSMC) mediate a metalloprotease ADAM17-dependent EGF receptor (EGFR) transactivation, which is linked to vascular remodeling induced by AngII. We have tested our hypothesis that Cav1, a major structural protein of caveolae, plays a critical role for development of vascular remodeling by AngII via regulation of ADAM17 and EGFR. Here, 8 week old male Cav1-/- and control Cav+/+ wild-type mice (WT) were infused with AngII (1 μg/kg/min) for 2 weeks to induce vascular remodeling and hypertension. Upon AngII infusion, histological assessments demonstrated medial hypertrophy and perivascular fibrosis of coronary and renal arteries in WT mice compared with saline-infused control mice. The AngII-infused WT mice also showed a phenotype of cardiac hypertrophy with increased HW/BW ratio (mg/g: 8.0±0.6 vs 5.7±0.7 p<0.01) compared with WT control. In contrast to AngII-infused WT mice, Cav1-/- mice with AngII showed attenuation of vascular remodeling but not cardiac hypertrophy ; HW/BW ratio (8.6±0.5 vs 6.4±0.2 p<0.05). Similar levels of AngII-induced hypertension were observed in both WT and Cav1-/- mice assessed by telemetry (MAP mmHg: 142±9 vs 154±20). In WT mice, Ang II enhanced ADAM17 expression and phospho-Tyr EGFR staining in heart and kidney vasculature. These events were attenuated in vessels from Cav1-/- mice infused with AngII. In addition, IHC analysis revealed less ER stress in heart and kidney vasculature of AngII-infused Cav1-/- mice compared with WT mice. Enhanced Cav1 and VCAM-1 expression were also observed in the aorta from AngII-infused WT mice but not in Cav1-/- aorta. These data suggest that Cav1 and presumably vascular caveolae play critical roles for vascular remodeling and inflammation via induction of ADAM17 and activation of EGFR independent of blood pressure or cardiac hypertrophy regulation.