Mechanistic insights into hexavalent chromium-induced ferroptosis in mRTECs: a novel MTF1-IREB2-FTH1/DMT1 axis-mediated iron homeostasis dysregulation

• Cr(VI) induces an increase in MTF1 expression and enhances nuclear translocation. • MTF1 binds IREB2 at 5′-TGCACAC-3′, driving Cr(VI)-induced ferroptosis in mRTECs. • IREB2 stabilizes DMT1 mRNA, degrades FTH1 mRNA, disrupting iron homeostasis. • Free Fe 2+ enters the mitochondria, causing mitochondrial damage. • Mitochondrial damage leads to the accumulation of ROS, exacerbating lipid peroxidation. • The MTF1-IREB2-FTH1/DMT1 axis links Cr(VI) exposure to renal injury. Hexavalent Chromium [Cr(VI)], a Group 1 carcinogen designated by the International Agency for Research on Cancer (IARC), is a pervasive environmental pollutant. The kidneys are particularly vulnerable to Cr(VI)-induced damage, and emerging evidence suggests that ferroptosis plays a pivotal role in Cr(VI) toxicity. This study aimed to investigate the role of ferroptosis in Cr(VI)-induced injury of mouse renal tubular epithelial cells (mRTECs), and to delineate the underlying molecular mechanisms. The cytotoxicity of Cr(VI) on mRTECs was assessed using CCK-8 assays. A comprehensive approach, including Western blot analysis, immunofluorescence, flow cytometry, gene knockdown, overexpression, and malondialdehyde (MDA) detection, was employed to evaluate ferroptosis-related markers, including protein expression, lipid peroxidation, Fe 2+ levels, mitochondrial Fe 2+ (Mito-Fe 2+ ) levels, reactive oxygen species (ROS) levels, and mitochondrial damage. The transcriptional regulation of IREB2 by metal regulatory transcription factor 1 (MTF1) was validated using a dual-luciferase reporter assay and site-directed mutagenesis. Cr(VI) exposure induced nuclear translocation of MTF1, which transcriptionally upregulated IREB2 expression. We identified a specific MTF1 binding site (5′-TGCACAC-3′) in the IREB2 promoter, and its functional role was confirmed through site-directed mutagenesis and dual-luciferase reporter assays. IREB2 upregulation increased divalent metal transporter 1 (DMT1) expression while decreasing ferritin heavy chain 1 (FTH1) levels, leading to elevated intracellular free Fe 2+ . The excess Fe 2+ was transported into mitochondria, causing mitochondrial damage, increased ROS production, and exacerbated lipid peroxidation, ultimately triggering ferroptosis in mRTECs. Our findings reveal a novel MTF1-IREB2-FTH1/DMT1 axis through which Cr(VI) induces ferroptosis in mRTECs by disrupting iron homeostasis, promoting mitochondrial damage, and enhancing lipid peroxidation. This study uncovers a critical molecular mechanism underlying Cr(VI)-induced kidney injury and provides new insights for developing preventive and therapeutic strategies against Cr(VI)-associated public health diseases.