Brd4-p300 inhibition downregulates Nox4 and accelerates lung fibrosis resolution in aged mice.

Victor J Thannickal,Zheyi Xiang,Yan Y Sanders,Steven M Rowe,Denise Stanford,Q Jennifer Zhou,Sandeep Bodduluri,Xing Lyv

doi:10.1172/jci.insight.137127

Abstract

Tissue regeneration capacity declines with aging in association with heightened oxidative stress. Expression of the oxidant-generating enzyme, NADPH oxidase 4 (Nox4), is elevated in aged mice with diminished capacity for fibrosis resolution. Bromodomain-containing protein 4 (Brd4) is a member of the bromodomain and extraterminal (BET) family of proteins that function as epigenetic "readers" of acetylated lysine groups on histones. In this study, we explored the role of Brd4 and its interaction with the p300 acetyltransferase in the regulation of Nox4 and the in vivo efficacy of a BET inhibitor to reverse established age-associated lung fibrosis. BET inhibition interferes with the association of Brd4, p300, and acetylated histone H4K16 with the Nox4 promoter in lung fibroblasts stimulated with the profibrotic cytokine, TGF-β1. A number of BET inhibitors, including I-BET-762, JQ1, and OTX015, downregulate Nox4 gene expression and activity. Aged mice with established and persistent lung fibrosis recover capacity for fibrosis resolution with OTX015 treatment. This study implicates epigenetic regulation of Nox4 by Brd4 and p300 and supports BET/Brd4 inhibition as an effective strategy for the treatment of age-related fibrotic lung disease.

Highlights

Idiopathic pulmonary fibrosis (IPF) is an age-related, progressive, and usually fatal lung disease with limited treatment options [1]
We investigated the effects of a bromodomain and extraterminal (BET)/Bromodomain-containing protein 4 (Brd4) inhibition on p300 and H4K16ac in regulating NADPH oxidase 4 (Nox4) expression in response to TGF-β1 and in the constitutive activation of IPF fibroblasts; we examined the efficacy of the BET inhibitor, OTX015, in the treatment of established and persistent lung fibrosis in aged mice
Nox4 is downregulated in IPF myofibroblasts by Brd4 inhibition

Summary

Introduction

Idiopathic pulmonary fibrosis (IPF) is an age-related, progressive, and usually fatal lung disease with limited treatment options [1]. IPF is characterized by the aberrant tissue remodeling associated with declining lung function and progressive respiratory failure [1]. The pathogenesis of IPF is incompletely understood, our group and others have demonstrated that accumulation/persistence of activated fibroblasts/myofibroblasts is a hallmark of nonresolving fibrosis [4, 5]. Increased levels of the profibrotic cytokine, TGF-β1, have been implicated in persistent myofibroblast differentiation/activation that leads to this aberrant wound-healing process [8]. TGF-β1 differentiates lung fibroblasts into myofibroblasts [9] and markedly upregulates Nox expression [5]. Nox is constitutively upregulated in activated myofibroblasts and in lung tissues of humans with IPF [5]. Nox expression is constitutively upregulated in senescent (myo)fibroblasts, in part, through epigenetic regulation involving histone acetylation [10]. Epigenetic mechanisms that control Nox expression in IPF fibroblasts and in response to TGF-β1 remain unclear

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Results

Conclusion