Abstract P157: Role of P47 phox in Angiotensin II Induced Cardiac Hypertrophy and Fibrosis in Mice

Abstract

NADPH oxidase mediated ROS production has been recognized to be an important contributory mechanism for hypertension and left ventricular hypertrophy (LVH). However, the regulatory role of NADPH oxidase mediated superoxide production in Angiotensin II (AngII) induced cardiac fibrosis and macrophage infiltration is still elusive. In the present study, we investigated the role of phagocytic NADPH oxidase enzyme system in cardiac remodelling induced by AngII in young adult (2-3 months old) male mice deficient in p47 phox , a cytosolic subunit of the NADPH oxidase (KO, n=13) and age-matched wild-type littermates (WT, n=9). Animals were infused with AngII pressor dose (1500 ng/kg/min, s.c) or saline via osmotic minipump (Alzet 2002, USA) for 14 consecutive days and then, subjected to echocardiography (VEVO 1100, Canada). Further animals were sacrificed and hearts was harvested for histological studies and gene expression analysis. AngII treatment in WT and KO mice showed prominent alterations in echocardiographic measurements with no changes in E/A, EF and FS. However, KO mice showed aggravated cardiac hypertrophic response (LVAWd: WT, 1.20±0.09 vs. KO, 1.42±0.04, p<0.05; LVIDd: WT, 3.02±0.20 vs. KO, 2.60±0.07, p<0.05; LVPWd: WT, 1.49±0.06 vs. KO, 1.78±0.06, p<0.05). Histologically, AngII infused KO mice also showed increased cardiomyocyte diameter compared to AngII infused WT mice (WT, 388±16.37 vs. KO, 560.3±41.28 μm 2 ; p<0.01 respectively). Further, AngII infused KO mice showed elevated immune cell infiltration, which were positive for Mac-3 staining compared to AngII infused WT mice (WT, 2.61±0.32 vs. KO, 4.09±0.44 %; p<0.05). Besides, AngII infused KO mice showed augmented interstitial fibrosis (WT, 11.11±0 0.67 vs. KO, 20.85± 3.63 %; p<0.05), thick collagen fibres deposition (WT, 28.93± 0.94 vs. KO, 37.60± 2.49 %; p<0.05) compared to AngII infused WT mice. Moreover, AngII infused KO mice also showed upregulated gene expression of hypertrophic and fibrotic markers, including Nppa, Nppb, Acta1, Myh6, TGF-β1, collagen (I and III) and α-sma compared to AngII infused WT mice. Together, these data suggest that NADPH oxidase and its subunit p47 phox play a pivotal role in AngII induced LVH by regulating fibrotic machinery and macrophage infiltration.