title: Brd4 inhibition attenuates unilateral ureteral obstruction-induced fibrosis by blocking TGF-β-mediated Nox4 expression.
abstract: Uncovering new therapeutic targets for renal fibrosis holds promise for the treatment of chronic kidney diseases. Bromodomain and extra-terminal (BET) protein inhibitors have been shown to effectively ameliorate pathological fibrotic responses. However, the pharmacological effects and underlying mechanisms of these inhibitors in renal fibrosis remain elusive. In this study, we determined that the inhibition of Brd4, a BET family member, with a selective potent chemical inhibitor, JQ1, could prevent the development of renal fibrosis and block the progression of fibrosis in rats that have undergone unilateral ureteral obstruction (UUO). Inhibiting Brd4 with either JQ1 or genetic knockdown resulted in decreased expression of fibrotic genes such as α-smooth muscle actin, collagen IV and fibronectin both in UUO-induced fibrosis and upon TGF-β1 stimulation in HK-2 cells. Brd4 inhibition also suppressed the oxidative stress induced by UUO in vivo or by TGF-β1 in HK-2 cells. Moreover, Nox4, which is constitutively active in renal cells and is involved in the generation of hydrogen peroxide, was up-regulated during UUO-mediated fibrosis and induced by TGF-β1 in HK-2 cells, and this up-regulation could be blunted by Brd4 inhibition. Consistently, Nox4-mediated ROS generation and fibrotic gene expression were attenuated upon Brd4 inhibition. Further, the transcriptional activity of Nox4 was suppressed by JQ1 or siRNA against Brd4. Additionally, Smad3 and ERK1/2 phosphorylation, which are upstream signals of Nox4 expression, were inhibited both in JQ1-administered UUO rats and Brd4-inhibited HK-2 cells. In conclusion, these results indicated that the inhibition of Brd4 might protect against renal fibrosis by blocking the TGF-β-Nox4-ROS-fibrosis axis, suggesting that Brd4 could be a promising therapeutic target.
authors.affiliation: Department of Nephrology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China.
authors.forename: Baoshang
authors.initials: B
authors.lastname: Zhou
authors.affiliation: Department of Nephrology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China.
authors.forename: Jiao
authors.initials: J
authors.lastname: Mu
authors.affiliation: Department of Nephrology, Southwest Hospital, Third Military Medical University, Chongqing 400038, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Gong
authors.affiliation: Department of Nephrology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China.
authors.forename: Caibao
authors.initials: C
authors.lastname: Lu
authors.affiliation: Department of Urology, Chengdu Military General Hospital, Chengdu 610083, China.
authors.forename: Youguang
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of Nephrology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China.
authors.forename: Ting
authors.initials: T
authors.lastname: He
authors.affiliation: Department of Cardiology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China. Electronic address: zhexueqin@126.com.
authors.forename: Zhexue
authors.initials: Z
authors.lastname: Qin
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001381:Azepines / Q000494:pharmacology*; D018797:Cell Cycle Proteins; D002461:Cell Line, Transformed; D024141:Collagen Type IV / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D005353:Fibronectins / Q000235:genetics / Q000378:metabolism; D005355:Fibrosis / Q000209:etiology / Q000235:genetics / Q000473:pathology / Q000517:prevention & control*; D006801:Humans; D007668:Kidney / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism; D000074663:NADPH Oxidase 4 / Q000235:genetics* / Q000378:metabolism; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000037:antagonists & inhibitors / Q000494:pharmacology; D014230:Triazoles / Q000494:pharmacology*; D014517:Ureteral Obstruction / Q000150:complications / Q000378:metabolism / Q000473:pathology / Q000601:surgery; D000092468:Bromodomain Containing Proteins
chemical_list: D000199:Actins; D000975:Antioxidants; D001381:Azepines; D018797:Cell Cycle Proteins; D024141:Collagen Type IV; D005353:Fibronectins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D000074663:NADPH Oxidase 4; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D051900:Smad3 Protein; D014157:Transcription Factors; D053773:Transforming Growth Factor beta1; D014230:Triazoles; C561695:(+)-JQ1 compound; C441289:BRD4 protein, human; D000092468:Bromodomain Containing Proteins; C497787:Smad3 protein, rat; C498862:Acta2 protein, rat; C498911:Nox4 protein, rat; C535150:MAPK1 protein, human
keywords: Brd4; Nox4; Renal fibrosis; TGF-β1