Deficiency of Growth Arrest and DNA Damage–Inducible 45α-R-Loop Pathway and Kidney Injury in Diabetic Nephropathy

Key Points Growth arrest and DNA damage–inducible 45 α (GADD45 α ) is crucial for maintaining kidney health by enhancing six-transmembrane epithelial antigen of the prostate 4 expression through promoter demethylation. In diabetic nephropathy, lower GADD45 α levels hinder R-loop formation, leading to decreased six-transmembrane epithelial antigen of the prostate 4 demethylation and expression. Targeting the GADD45 α -R-loop pathway holds promise for innovative diabetic nephropathy treatment strategies. Background Diabetic nephropathy is a primary cause of kidney failure. Persistent hyperglycemia causes metabolic perturbations epigenetically dysregulating gene expression in kidney cells, thereby leading to diabetic nephropathy pathogenesis. On analyzing the Gene Expression Omnibus database by using machine learning algorithms, our preliminary results demonstrated that growth arrest and DNA damage–inducible 45 α (GADD45 α ) might serve as key regulators in diabetic nephropathy. Furthermore, emerging evidence has shown that R-loops, the three-stranded DNA–RNA structures, are crucial to gene expression during diabetic nephropathy. Therefore, this study aimed to investigate the role of GADD45 α in diabetic nephropathy by modulating epigenetic alterations through interaction with R-loops. Methods A diabetic mouse model was established by injecting streptozotocin intraperitoneally into mice. Kidney histology and biochemical markers were analyzed in wild-type, GADD45 α knockout, and renal tubule–specific GADD45 α -overexpressing mice. The GADD45 α lentivirus was used to induce the overexpression of GADD45 α in human kidney-2 (a proximal tubular epithelial cell line) cells, while high-glucose treatment was applied to verify the mechanisms in vitro . Results GADD45 α expression was reduced in kidneys of diabetic nephropathy, correlating with kidney dysfunction. GADD45 α knockout worsened kidney injuries, while overexpression mitigated them. Mechanistically, GADD45 α interacted with R-loops on the six-transmembrane epithelial antigen of the prostate 4 ( STEAP4 ) promoter, recruiting ten eleven translocation 1 to activate STEAP4 transcription. Deficiency in the GADD45 α -R-loop pathway exacerbated mitochondrial injury, disrupted lipid metabolism, and increased oxidative stress in diabetic nephropathy. Conclusions Deficiency of GADD45 α exacerbates diabetic nephropathy by interacting with R-loops and inhibiting STEAP4 promoter demethylation. Targeting the GADD45 α -R-loop pathway offers therapeutic potential against diabetic nephropathy.