Abstract 14772: Induction of Adam17 via A Hypoxia Response Element Contributes to Perivascular Fibrosis but not Hypertension Induced by Angiotensin Ii Infusion in Mice
A metalloprotease, ADAM17, mediates HB-EGF generation and subsequent EGF receptor (EGFR) transactivation in vascular smooth muscle cells (VSMCs) induced by angiotensin II (AngII) leading to hypertrophy. However, the specific role of this ubiquitous protease in hypertensive end organ damages remains unclear. To test if vascular ADAM17 inhibition has therapeutic potential, we evaluated AngII-induced vascular remodeling in ADAM17 flox/flox mice expressing Cre under the control of sm22alpha promoter. After AngII infusion (1000 ng/kg/min) for 2 weeks, Cre-expressing mice showed reduced medial hypertrophy in aorta and carotid arteries, and perivascular fibrosis in heart was markedly suppressed (75% and 45% suppression for hypertrophy and fibrosis, respectively) compared with control littermates. Cardiac hypertrophy was also evident following the infusion but was only partially inhibited in Cre-expressing mice. AngII-induced hypertension assessed by telemetry was unaltered in Cre-expressing mice. AngII infused, Cre-expressing mice had diminished phospho-Tyr1068 EGFR staining in the vasculatures compared with control mice. AngII infusion also enhanced ADAM17 and nitroso-tyrosine staining in the arteries of control mice, but not in Cre-expressing mice. To test if AngII can induce ADAM17 protein expression in VSMCs, we stimulated VSMCs with 100 nM AngII and found that ADAM17 protein expression was increased (24h: 2.34±0.25 fold). Transcription reporter assay experiments showed that AngII stimulated ADAM17 promoter activity in VSMCs (24h: 2.90±0.17 fold). The ADAM17 promoter contains 6 putative hypoxia responsible elements (HREs). Experiments using deletion and mutation constructs suggest that the AngII response requires HRE4 located between -991 and -410 of the promoter. In addition, we observed that AngII increases expression of a luciferase reporter gene driven by the HRE from the erythropoietin gene. Induction of Hif1alpha by AngII was also confirmed in VSMCs and in vasculatures in vivo. These data suggest that ADAM17 induction mediated through Hif1 alpha/HRE in the vasculature significantly contributes to the end organ damages associated with the renin angiotensin system via the EGFR transactivation and oxidative stress.
- © 2012 by American Heart Association, Inc.