Neuregulin-1β (NRG-1β) is critical for cardiac development and repair, and recombinant forms are currently being assessed as possible therapeutics for systolic heart failure. We previously demonstrated that recombinant NRG-1β reduces cardiac fibrosis in an animal model of cardiac remodeling and heart failure, suggesting that there may be direct effects on cardiac fibroblasts. Here we show that NRG-1β receptors (ErbB2, ErbB3, and ErbB4) are expressed in normal human cardiac ventricular (NHCV) fibroblast cell lines. Treatment of NHCV fibroblasts with recombinant NRG-1β induced activation of the AKT pathway, which was phosphoinositide 3-kinase (PI3K)-dependent. Moreover, the NRG-1β-induced PI3K/AKT signaling in these cells required phosphorylation of both ErbB2 and ErbB3 receptors at tyrosine (Tyr)1248 and Tyr1289 respectively. RNASeq analysis of NRG-1β-treated cardiac fibroblasts obtained from three different individuals revealed a global gene expression signature consistent with cell growth and survival. We confirmed enhanced cellular proliferation and viability in NHCV fibroblasts in response to NRG-1β, which was abrogated by PI3K, ErbB2, and ErbB3 inhibitors. NRG-1β also induced production and secretion of cytokines (interleukin-1α and interferon-γ) and pro-reparative factors (angiopoietin-2, brain-derived neurotrophic factor, and crypto-1), suggesting a role in cardiac repair through the activation of paracrine signaling.
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