HOXA 13 exerts a beneficial effect in albumin-induced epithelial-mesenchymal transition via the glucocorticoid receptor signaling pathway in human renal tubular epithelial cells

Previous studies have suggested that albumin-induced renal tubular epithelial cell injury contributes to renal interstitial fibrosis. Epithelial‐mesenchymal transition (EMT) is known to be a key mechanism in the pathogenesis and progression of renal interstitial fibrosis. Homeobox protein HOX‐A13 (HOXA13) is a nuclear transcriptional factor that has been reported to be involved in renal fibrosis. However, the mechanism underlying the effect of HOXA13 in human serum albumin (HSA)‐induced EMT in HKC renal tubular epithelial cells remains to be elucidated. Thus, the aim of the present study was to investigate the role of HOXA13 in HSA‐induced EMT in HKC cells and the potential mechanism of the glucocorticoid receptor (GR) signaling pathway. The protein and mRNA expression levels of HOXA13, cytokeratin, and vimentin were determined by western blot analysis and reverse transcription-quantitative polymerase chain reaction in HKC cells, which were co‐incubated with HSA at different concentrations or for different time periods. The results demonstrated that HOXA13 mRNA and protein expression decreased in a dose‐ and time‐dependent manner when induced by HSA in HCK cells. The liposomal transfection experiment suggested that overexpression of HOXA13 activated the GR signal, which inhibits HSA‐induced EMT. HOXA13 is involved in HSA‐induced EMT in HKC cells and upregulation of HOXA13 exerts a beneficial effect in EMT, which may be associated with the GR signaling pathway. Introduction Interstitial fibrosis is a common pathway of progressive renal disease, leading to end-stage renal failure regardless of the etiology (1). Previous studies have indicated that the process of tubular epithelial-mesenchymal transition (EMT) contributes to the predominance of fibroblasts in idiopathic nephrotic syndrome (2). The pathological mechanism of EMT remains to be elucidated (3); however, recent studies have suggested that homeobox protein HOX‐A13 (HOXA13) is involved in urogenital development and renal fibrosis (4). Furthermore, Williams et al (5) reported that HOXA13 exerts an inhibitory effect on transforming growth factor-β1 (TGF‐β1) signaling, which has been widely demonstrated to induce EMT (6). Thus, HOXA13 is hypothesized to be involved in regulating EMT and renal fibrosis, however, the molecular mechanism underlying these effects remains to be elucidated. Resistance to glucocorticoid (GC) treatment is a key clinical problem in multiple diseases, including idiopathic nephrotic syndrome (7). The majority of the effects of GC are mediated by the glucocorticoid receptor (GR). GR is known to inhibit the activity of a number of immune-regulating transcription factors (8). Abnormalities in the number and affinity of GRs have been demonstrated to be associated with peripheral blood mononuclear cell (PBMC) proliferation and cytokine secretion, which are important in the development of idiopathic nephrotic syndrome and renal failure (7,9,10). However, the effect of GR signaling on EMT has not yet, to the best of our knowledge, been reported. Thus, the aim of the present study was to investigate the potential function of HOXA13 in human serum albumin (HSA)‐induced EMT and the GR signaling pathway in HKC human renal tubular epithelial cells. Materials and methods Reagents. Mouse anti-β-actin monoclonal antibody (cat no. 6008‐1), rabbit anti‐vimentin polyclonal antibody (cat no. 10366), rabbit anti‐cytokeratin (CK) polyclonal antibodies (cat no. 10830) and rabbit anti-GR polyclonal antibody (cat no. 23978) were obtained from ProteinTech Group, Inc. (Chicago, IL, USA). Rabbit anti‐HOXA13 polyclonal antibodies (cat no. sc-66922) were purchased from Santa Cruz Biotechnology, HOXA13 exerts a beneficial effect in albumin-induced epithelial-mesenchymal transition via the glucocorticoid receptor signaling pathway in human renal tubular epithelial cells LI PENG, QINGNAN HE, XIAOYAN LI, LANJUN SHUAI, HAIXIA CHEN, YONGZHEN LI and ZHUWEN YI Laboratory of Pediatric Nephrology, The Second Xiangya Hospital, Central South University and Hunan Clinical Center of Pediatric Nephrology, Changsha, Hunan 410011, P.R. China Received March 12, 2015; Accepted February 19, 2016 DOI: 10.3892/mmr.2016. 5247 Correspondence to: Professor Qingnan He, Laboratory of Pediatric Nephrology, The Second Xiangya Hospital, Central South University and Hunan Clinical Center of Pediatric Nephrology, 139 Middle Renmin Road, Furong District, Changsha, Hunan 410011, P.R. China E‐mail: heqn2629@163.com