The role of Stim1 in the progression of lupus nephritis in mice.

OBJECTIVE To investigate the expression of Stim1 in the kidneys of mice with lupus, and the effect of Stim1 on the progression of renal interstitial fibrosis. METHODS Mice (MRL/lpr) with spontaneous lupus nephritis (LN) and normal control mice (C57/BL) were selected. Immunohistochemistry and Masson staining were used to determine the degree of renal interstitial fibrosis in kidney tissues. The expression of Stim1 and fibronectin in tissues was measured by qRT-PCR, western blotting, and immunohistochemistry. Urine protein, blood urea nitrogen, and serum creatinine levels in the mice were analyzed, and Spearman analysis was conducted to determine the correlation with Stim1 expression levels. Mouse renal tubular epithelial cells (mRTECs) were chosen as the experimental objects. After various treatments, the cells were divided into the blank control group, lipopolysaccharide (LPS) treatment group, LPS+siRNA-NC group and LPS+siRNA-Stim1 group. Western blotting and immunofluorescence were used to measure epithelial-mesenchymal transition (EMT)-related protein levels. RESULTS There was significant interstitial fibrosis in the kidneys of LN mice. Compared with that in normal mice, the expression of Stim1 in the kidney tissues of LN mice was significantly increased, and Stim1 expression was positively correlated with fibronectin, urine protein, blood urea nitrogen and serum creatinine levels. LPS induced the expression of Stim1, fibronectin, and α-SMA in mRTECs and decreased the protein level of E-CA, while silencing Stim1 effectively alleviated the effects of LPS. CONCLUSION Stim1 is significantly increased in the kidneys of lupus mice, and it is possible to promote EMT in renal tubular epithelial cells and renal interstitial fibrosis by elevating fibronectin, which ultimately contributes to renal damage.