TRPM7 function in ischemia-reperfusion renal injury and its regulatory mechanism of PARthanatos

PARthanatos is one of the dominant forms of renal tubular epithelial cell death in ischemia–reperfusion renal injury (RIRI). Studies have shown that TRPM7 is positively correlated with the activation of PARP1, but its role and mechanism in the RIRI phenotype remain unclear. Rat models of in vivo RIRI and oxygen–glucose deprivation/reoxygenation (OGD/R) models of HK-2 in vitro were established. Interventions included TRPM7 silencing via sh-TRPM7, TRPM7 overexpression via oe-TRPM7, transfection of wild-type TRPM7 or α-kinase inactive TRPM7 mutant, and treatment with an ERK2 phosphorylation inhibitor. Co-immunoprecipitation (Co-IP), immunofluorescence staining, hematoxylin and eosin (H&E) staining, TUNEL staining, reactive oxygen species (ROS) quantification, cell apoptosis assays, LDH cytotoxicity detection, enzyme-linked immunosorbent assay (ELISA), quantitative real-time polymerase chain reaction (qRT-PCR), and Western blot were utilized to detect phenotypic characteristics and corresponding molecular indicators in each experimental group. In the RIRI model, TRPM7, PARP1, and PAR expression was upregulated in rat renal tissues, accompanied by glomerular atrophy and necrosis, renal tubular dilation, renal interstitial fibrosis, inflammatory cell infiltration, enhanced oxidative stress, and aggravated DNA damage. In the OGD/R model, HK-2 cell viability was decreased; TRPM7/PARP1/PAR expression was upregulated; mitochondrial–nuclear translocation of AIF was increased; and oxidative stress and cell death were exacerbated. TRPM7 silencing reversed the aforementioned injuries, leading to restored cell viability. Co-IP-MS confirmed that ERK2 is a specific interacting protein of TRPM7. TRPM7 overexpression further upregulated PARP1 activity, induced AIF nuclear translocation and PARthanatos, and exacerbated injuries by activating ERK2. The ERK2 phosphorylation inhibitor specifically reversed the pathological effects mediated by TRPM7 overexpression, confirming that ERK2 phosphorylation is an essential link in this regulatory process. TRPM7 phosphorylates ERK2 via its α-kinase domain, thereby activating the PARthanatos pathway and exacerbating RIRI.