*Purpose: Allograft interstitial fibrosis and fibrogenesis significantly exacerbate the progression of chronic allograft disease (CAD) and are essential therapeutic targets. Epithelial‐mesenchymal transition (EMT) is recognized as an important source of myofibroblasts contributing to the pathogenesis of allograft interstitial fibrosis. We previously demonstrated that tumor necrosis factor‐alpha (TNF‐α) induced EMT via the TNF-α/Akt/Smurf2 signaling pathways in renal proximal tubule epithelial (HK-2) cells. Bortezomib (BZM) is a proteasome inhibitor used for the treatment of multiple myeloma (MM). Several studies have demonstrated that BZM prevents the progression of fibrosis in organs including kidney.

*Methods: To investigate the effect of BZM on allograft interstitial fibrosis and its mechanism both in vivo and in vitro. We used rat renal transplantation model and HK2 cell line treated with TNF-α to examine their response to BZM by assessing changes on morphology, renal function, expression of fibrosis/EMT related markers and evaluating cell movement. Besides, we explored the effect of BZM on TNF-α/Akt/Smurf2 signaling pathways. RNA sequencing was applied to assess the mechanism by which BZM inhibits the EMT. Based on RNA sequencing data, we further detected changes on NF-κB pathway.

*Results: BZM significantly attenuated renal allograft interstitial fibrosis and prevented allograft renal function impairment in vivo. In HK2 cell line, BZM inhibited the development of TNF-α-induced EMT as well as the abilities of motility and migration. In addition to blocking of Akt/mTOR/P70S6K/Smurf2 pathway, the antifibrotic effect of BZM on the EMT was associated with inhibition of NF-κB pathway by stabilizing IκBα protein.

*Conclusions: Our study suggests that BZM attenuates the development of TNF-α-induced EMT and renal allograft interstitial fibrosis, which provides novel insights into renal interstitial fibrosis and CAD following kidney transplantation. The results also highlight the therapeutic potential of BZM via its effect on NF-κB/TNF-α/Akt/mTOR/P70S6K/Smurf2 signaling pathways by stabilizing IκBα protein.

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