Autophagy Inhibition Sensitizes Renal Tubular Epithelial Cell to G1 Arrest Induced by Transforming Growth Factor beta (TGF-β)
Chen Yang, Hong-luan Wu, Zhi-hang Li, Xiao-cui Chen, Hong-yong Su, Xiao-yan Guo, Ning An, Kai-peng Jing, Qing-jun Pan, Hua-feng Liu
Key Laboratory of Prevention and Management of Chronic Kidney Disease of Zhanjiang City, Institute of Nephrology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, Guangdong, China (mainland)
Med Sci Monit 2020; 26:e922673
Available online: 2020-04-07
Cell cycle arrest and autophagy have been demonstrated to be involved in various transforming growth factor (TGF)-ß-mediated phenotype alterations of tubular epithelial cells (TECs) and tubulointerstitial fibrosis. But the relationship between cell cycle arrest and the autophagy induced by TGF-ß has not been explored well.
MATERIAL AND METHODS: The effects of autophagy inhibition on TGF-ß-induced cell cycle arrest in TECs were explored in vitro. Human kidney-2 (HK-2) cells were stimulated by TGF-ß with or without a combined treatment of autophagy inhibitor chloroquine (CQ) or bafilomycin A1 (Baf).
RESULTS: Autophagy inhibition by CQ or Baf promotes the suppression of growth in TGF-ß-treated HK-2 cells, as detected by the Cell Counting Kit-8 (CCK-8) method. In addition, CQ or Baf stimulation enhances G1 arrest in TGF-ß treated HK-2 cells, as investigated using propidium iodide (PI) staining and flow cytometry, which was further confirmed by a decrease in the expression of phosphorylated retinoblastoma protein (p-RB) and cyclin-dependent kinase 4 (CDK4). The upregulation of p21 induced by CQ or Baf may mediate an enhanced G1 arrest in TGF-ß treated HK-2 cells. Western blot analysis showed that TGF-ß-induced expression of extracellular matrix fibronectin was notably upregulated in the presence of autophagy inhibitors.
CONCLUSIONS: Inhibition of autophagy sensitizes the TECs to G1 arrest and proliferation suppression induced by TGF-ß that contributes to the induction of tubulointerstitial fibrosis.
Keywords: Autophagy, Epithelial Cells, Fibrosis, G1 Phase Cell Cycle Checkpoints, Transforming Growth Factor beta