Interleukin-33 promotes the epithelial-mesenchymal transition of renal tubular epithelial cells via the NF-κB/Twist1 signalling pathway

Objectives: Epithelial-mesenchymal transition (EMT) of renal tubular epithelial cells (RTECs) is a pathogenic factor for renal interstitial fibrosis (RIF). Interleukin-33 (IL-33) is related to the occurrence and development of RIF, but the underlying mechanism remains unclear. Here, we investigated whether IL-33 mediates the EMT of RTECs by activating the NF-κB/Twist1 signalling pathway. Methods: In vivo, the RIF animal model induced by unilateral ureteral obstruction (UUO) was established. The effects of exogenous IL-33 and anti-IL-33 antibodies were evaluated. In vitro, the EMT of RTECs was induced by IL-33. The inhibition of the nuclear factor kappa-B (NF-κB) by the pyrrolidine dithiocarbamate (PDTC) and the knockdown of the suppression of tumorigenicity 2 (ST2) by small interference RNA were used to observe whether IL-33 mediates the EMT of RTECs through the NF-κB/Twist1 signaling pathway. Results: In vivo, exogenous IL-33 significantly aggravated UUO-induced pathological damage and collagen deposition, down-regulated E-cadherin expression, and up-regulated α-smooth muscle actin and Vimentin expressions. Moreover, exogenous IL-33 increased the levels of phospho-IκB-α (p-IκB-α) and phospho-NF-κB p65 (p-NF-κB p65), NF-κB p65 nuclear translocation, and Twist1 nuclear expression. However, these effects were reversed by the anti-IL-33 antibody. In vitro , the increases in the levels of p-IκB-α, p-NF-κB p65, NF-κB p65 nuclear translocation, and Twist1 nuclear expression induced by IL-33 were inhibited by the knockdown of PDTC or ST2. IL-33-mediated EMT of RTECs was also significantly reversed. However, NF-κB inhibitor PDTC had no significant effect on ST2 expression. Conclusions: The IL-33/ST2 axis may up-regulate the expression of Twist1 through the NF-κB signalling pathway, thereby inducing the EMT of RTECs and leading to RIF.