Regulation of mitochondrial oxidative stress by β-arrestins in cultured human cardiac fibroblasts

• Main Authors: Jennifer L. Philip (Author), Md. Abdur Razzaque (Author), Mei Han (Author), Jinju Li (Author), Tiju Theccanat (Author), Xianyao Xu (Author), Shahab A. Akhter (Author)
• Format: Book
• Published: The Company of Biologists, 2015-12-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.
• Notes: 1754-8411; 1754-8403; 10.1242/dmm.019968
• Keywords: β-arrestin; Oxidative stress; NADPH oxidase; Heart failure; Cardiac fibroblast; Collagen; Myocardial fibrosis; Medicine; R; Pathology; RB1-214
• Source: Disease Models & Mechanisms, Vol 8, Iss 12, Pp 1579-1589 (2015)

Oxidative stress in cardiac fibroblasts (CFs) promotes transformation to myofibroblasts and collagen synthesis leading to myocardial fibrosis, a precursor to heart failure (HF). NADPH oxidase 4 (Nox4) is a major source of cardiac reactive oxygen species (ROS); however, mechanisms of Nox4 regulation are unclear. β-arrestins are scaffold proteins that signal in G-protein-dependent and -independent pathways; for example, in ERK activation. We hypothesize that β-arrestins regulate oxidative stress in a Nox4-dependent manner and increase fibrosis in HF. CFs were isolated from normal and failing adult human left ventricles. Mitochondrial ROS/superoxide production was quantitated using MitoSox. β-arrestin and Nox4 expressions were manipulated using adenoviral overexpression or short interfering RNA (siRNA)-mediated knockdown. Mitochondrial oxidative stress and Nox4 expression in CFs were significantly increased in HF. Nox4 knockdown resulted in inhibition of mitochondrial superoxide production and decreased basal and TGF-β-stimulated collagen and α-SMA expression. CF β-arrestin expression was upregulated fourfold in HF. β-arrestin knockdown in failing CFs decreased ROS and Nox4 expression by 50%. β-arrestin overexpression in normal CFs increased mitochondrial superoxide production twofold. These effects were prevented by inhibition of either Nox or ERK. Upregulation of Nox4 seemed to be a primary mechanism for increased ROS production in failing CFs, which stimulates collagen deposition. β-arrestin expression was upregulated in HF and plays an important and newly identified role in regulating mitochondrial superoxide production via Nox4. The mechanism for this effect seems to be ERK-mediated. Targeted inhibition of β-arrestins in CFs might decrease oxidative stress as well as pathological cardiac fibrosis.