Circadian clock gene BMAL1 is involved in transforming growth factor β1‐induced fibrotic response in NRK‐49F cells

The transcription factor brain and muscle Arnt-like protein-1 (BMAL1) is a clock protein involved in various diseases, including atherosclerosis and cancer. However, BMAL1's involvement in kidney fibrosis and the underlying mechanisms remain largely unknown, a gap addressed in this study. Analysis through Masson's trichrome and Sirius red staining revealed that all groups exposed to unilateral ureteral obstruction showed increased BMAL1 protein expression accompanied by increased TGF-β1 expression and elevated key fibrosis markers, including α-SMA, compared with sham groups. Although TGF-β1 induced BMAL1 protein expression accompanied by increased α-SMA expression in NRK-49F cells, the REV-ERBα agonist GSK4112, a transcriptional repressor of BMAL1, or siRNA targeting BMAL1 significantly inhibited TGF-β1-induced α-SMA expression. Furthermore, BMAL1 knockdown significantly suppressed TGF-β1-induced NOX4/ROS/p38 pathways in NRK-49F cells. Thus, BMAL1 positively regulates TGF-β1-induced signaling associated with fibrotic responses via the NOX4/ROS/p38 pathway. Overall, this study uncovers BMAL1 as a promising therapeutic target for preventing and treating kidney fibrosis, potentially preventing renal failure.