Abstract 1368: Overexpression of P22phox Subunit of Nadph Oxidase in Mice Accelerates Cardiac Fibrosis and Angiogenesis in Response to Angiotensin Ii
NADPH oxidases (Nox) are a major source of ROS in the heart and angiotensin II (Ang II) has been shown to activate these enzymes. In vitro, activation of Nox1, Nox2 and Nox4 by AngII requires p22phox. Transgenic mice which overexpress p22phox in smooth muscle cells and fibroblasts driven by the smooth muscle actin promoter (TGp22phox) have enhanced oxidative stress in response to Ang II. We hypothesized that p22phox-regulated NADPH oxidases accelerate Ang II-induced cardiac fibrosis in mice. Treatment with Ang II (100 nM) for 24 hours of murine cardiac fibroblasts isolated from WT or TGp22phox mice showed a dramatic upregulation of p22phox (10 fold±1. 5), Nox4 (8.3±1.4) and fibrosis markers (collagen I, fibronectin). Furthermore, downregulation of Nox4 with specific small interference RNA against Nox4 prevented induction of Nox4, collagen I, fibronectin and hydrogen peroxide in response to Ang II or TGF-β1. Next, we subjected wild-type (WT) and TGp22phox to hypertensive (1.4 mg/kg/day) of Ang II for four weeks. Surprisingly, TGp22phox mice exhibited enhanced vascularity and interstitial and perivascular cardiac fibrosis (2.2 fold ±0.5, n=8, p<0.05) as measured by Mason’s trichrome staining upon treatment with Ang II. In conclusion, overexpression of p22phox-based NADPH oxidases in cardiac fibroblasts and smooth muscled cells enhances cardiac fibrosis and angiogenesis in response to Ang II. Nox4 is a major contributor to cardiac fibrosis in vitro and may contribute in vivo in this murine model of cardiac fibrosis.
This research has received full or partial funding support from the American Heart Association, AHA National Center.