Tgf-β1 induces autophagy and promotes apoptosis in renal tubular epithelial             cells.
Transforming growth factor-β1 (TGF-β1) is a multifunctional cytokine that             regulates cell growth, differentiation, apoptosis and autophagy in various cell             types. It has been shown that TGF-β1-driven autophagy represents a novel mechanism             of tubular decomposition, leading to renal interstitial fibrosis. However, the             exact mechanism by which TGF-β1 regulates autophagy is still poorly understood.             In the present study, we investigated the effects of exogenous TGF-β1 on cultured             human renal proximal tubular epithelial cells (HRPTEpiCs). Presence of TGF-β1             in the medium induced accumulation of autophagosomes in a time- and dose-dependent             manner as seen by monitoring the marker LC3 by confocal fluorescence microscopy             and immunoblotting. In addition, TGF-β1 induced upregulation of autophagy-related             genes, Atg5, Atg7 and Beclin1. Importantly, increased generation of reactive oxygen             species (ROS) and enhanced expression of NADPH oxidases were found to be associated             with the TGF-β1-induced autophagy. Conversely, treatment with inhibitors of NADPH             oxidase markedly reversed the autophagic effects of TGF-β1. Apoptotic effects             were evaluated by the TUNEL assay, measuring mitochondrial membrane potential             and monitoring expression of the pro- and anti-apoptotic genes, Bim and Bcl-2,             respectively. Transcriptional silencing of the above three autophagy-related genes             in HRPTEpiCs caused attenuation of TGF-β1-mediated apoptosis. Similarly, when             autophagy was prevented at an early stage by application of 3-methyladenine, the             pro-apoptotic effects of TGF-β1 were attenuated. These observations suggest that             in HRPTEpiCs TGF-β1 promotes autophagy through the generation of ROS, which contributes             to its proapoptotic effect.
Department of Nephrology, First Affiliated Hospital, Fujian Medical University, Fuzhou 350005, P.R. China. xuyanfang99@hotmail.com
Yanfang
Y
Xu
Shuyu
S
Yang
Jiyi
J
Huang
Shiwei
S
Ruan
Zhang
Z
Zheng
Jiumao
J
Lin
D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D017209:Apoptosis; D001343:Autophagy / Q000187:drug effects; D000071187:Autophagy-Related Protein 5; D000071193:Autophagy-Related Protein 7; D002460:Cell Line; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007684:Kidney Tubules / Q000166:cytology* / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial; D008869:Microtubule-Associated Proteins / Q000235:genetics; D019255:NADPH Oxidases / Q000378:metabolism; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*; D044764:Ubiquitin-Activating Enzymes / Q000235:genetics
C502778:ATG5 protein, human; D000071187:Autophagy-Related Protein 5; D008869:Microtubule-Associated Proteins; D017382:Reactive Oxygen Species; D053773:Transforming Growth Factor beta1; C025946:3-methyladenine; D019255:NADPH Oxidases; C509349:ATG7 protein, human; D000071193:Autophagy-Related Protein 7; D044764:Ubiquitin-Activating Enzymes; D000225:Adenine