Activation of SIRT1 Reduces Renal Tubular Epithelial Cells Fibrosis in Hypoxia Through SIRT1-FoxO1-FoxO3-Autophagy Pathway

Heart failure-induced renal tubular epithelial cell fibrosis is an important pathological process that leads to chronic kidney disease. This study is to investigate the regulatory mechanism of over-expression or knock-down SIRT1 gene, alleviating hypoxia-induced HK2 cell fibrosis in heart failure. The focus is on the SIRT1-FoxO1-FoxO3-Autophagy pathway. In vitro experiments are performed by HK2cell line to simulate the normal oxygen state (Normoxia) and the hypoxia state (Hypoxia) caused by heart failure, SIRT1 gene over-expression by transfected vectors, knock-down and Rapamycin (RAPA)-induced cellular autophagy, and the cell models are divided into four subgroups, named control group, oeSIRT1, siSIRT1 and siSIRT1+RAPA. Western blotting (WB), real-time qPCR, immunofluorescence (IF), ELISA, and transmission electron microscopy are used to quantitatively or semi-quantitatively analyze the expression of FoxO1, FoxO3, SIRT1, Beclin1, LC-3, alpha-SMA, E- Cadherin, and collagen-I in cells or supernatants. It is demonstrated that activation of SIRT1 regulates the expression and activity of FoxO1 and FoxO3, thereby affecting autophagy. This modulation leads to a reduction in HK2 fibrosis markers (alpha-SMA and E-cadherin) and extracellular matrix deposition (collagen I), which ultimately attenuates renal tubular epithelial cell fibrosis. These findings provide new insights into potential therapeutic strategies for treating heart failure-induced renal tubular epithelial cell fibrosis by targeting the SIRT1-FoxO1-FoxO3-Autophagy pathway.