Deficiency of GADD45α-R-Loop Pathway and Kidney Injury in Diabetic Nephropathy

Background: Diabetic nephropathy is a primary cause of kidney failure. Persistent hyperglycemia causes metabolic perturbations epigenetically dysregulating gene expression in renal cells, thereby leading to diabetic nephropathy pathogenesis. On analyzing the GEO database by using machine learning algorithms, our preliminary results demonstrated that growth arrest and DNA damage-inducible 45α (GADD45α) 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 GADD45α 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, GADD45α knockout, and renal tubule-specific GADD45α-overexpressing mice. The GADD45α lentivirus was used to induce the overexpression of GADD45α in HK-2 cells, while high-glucose treatment was applied to verify the mechanisms in vitro. Results: GADD45α expression was reduced in kidneys of diabetic nephropathy, correlating with kidney dysfunction. GADD45α knockout worsened kidney injuries, while overexpression mitigated them. Mechanistically, GADD45α interacted with R-loops on the STEAP4 promoter, recruiting TET1 to activate STEAP4 transcription. Deficiency in the GADD45α-R-loop pathway exacerbated mitochondrial injury, disrupted lipid metabolism, and increased oxidative stress in diabetic nephropathy. Conclusions: Deficiency of GADD45α exacerbates diabetic nephropathy by interacting with R-loops and inhibiting STEAP4 promoter demethylation. Targeting the GADD45α-R-loop pathway offers therapeutic potential against diabetic nephropathy.