BHMT Prevents Renal Ischemia/Reperfusion Injury via Suppressing ROS-induced Apoptosis by Targeting NOX4.

BACKGROUND Ischemia/reperfusion injury (IRI) is a major cause of acute kidney injury (AKI), primarily driven by the increased production of reactive oxygen species (ROS). Elevated ROS levels can lead to cell apoptosis. However, effective therapeutic targets for IRI remain limited.

PURPOSE This study aims to investigate the potential mechanisms by which BHMT modulates IRI.

METHODS RT-qPCR and Western blot were used to assess RNA and protein expression levels. MTT assay, flow cytometry, and ROS-related assays were employed to evaluate renal cell injury in vitro. Mechanistic studies were conducted to explore molecular interactions, while in vivo assays were used to assess IRI.

RESULTS Betaine-homocysteine S-methyltransferase (BHMT) was found to be downregulated in both ischemia/reperfusion (I/R) and hypoxia/reoxygenation (H/R) models. BHMT overexpression mitigated the effects of H/R or I/R on ROS production and cell apoptosis. Mechanistically, BHMT enhanced the synthesis of S-adenosylmethionine (SAM), which in turn increased DNA-methyltransferase (DNMT) activity. This facilitated methylation of the NADPH Oxidase 4 (NOX4) promoter, suppressing NOX4 transcription and expression. Rescue assays confirmed that BHMT reduced ROS production and cell apoptosis in H/R-treated renal cells by downregulating NOX4. Furthermore, elevated expression of Samd4a in I/R accelerated renal fibrosis progression through activation of the Wnt/β-catenin signaling pathway.

CONCLUSION BHMT reduces ROS-induced apoptosis by downregulating NOX4, offering protection against renal IRI. Additionally, targeting Samd4a expression may provide a therapeutic approach for preventing chronic kidney disease in kidney injury models.