USP25-PKM2-Glycolysis axis participates in ischemia reperfusion-induced acute kidney injury by promoting M1 macrophage polarization and proinflammatory response

Abstract M1 macrophage, characterized by the production of proinflammatory cytokines, has been reported to exert a critical role in ischemia-reperfusion (I/R)-induced acute kidney injury (AKI). Recently, increasing evidence suggests that aerobic glycolysis plays an important role in the M1 polarization of macrophages. However, the M1 polarization area still needs continuous studies although it has been developed a lot. Here, we found that the upregulation of ubiquitin-specific protease 25 (USP25), a deubiquitinase, was correlated with renal function in patients with acute kidney tubular injury. In the model of murine I/R-induced AKI, the expression of USP25 was increased in the kidney, and USP25 knockout lowered murine I/R-induced AKI and reduced the infiltration of M1 macrophages in the kidney. In vitro, USP25 was highly expressed in LPS-induced M1 macrophages. Silencing of USP25 expression efficiently suppressed the levels of M1 polarization and proinflammatory response. This suppression was restored by plasmid-mediated overexpression of wild-type USP25, but not by an enzyme-inactivated mutant USP25 (C178S). By performing rapid immunoprecipitation mass spectrometry of endogenous proteins, we screened out M2 isoform of pyruvate kinase, muscle (PKM2) as a target substrate of USP25. By USP25 knockout and overexpression, we showed that USP25 cleaved the K48-linked ubiquitin chain from PKM2. We furthermore confirmed that USP25 affected the aerobic glycolysis during M1 polarization using extracellular acidification rate and determination of lactate production. By PKM2 inhibition and supplement of USP25−/− BMDMs with PKM2, we derived that the USP25-PKM2-aerobic glycolysis axis positively regulated M1 polarization and proinflammatory response, and exacerbated murine I/R induced AKI. Our data suggest that the USP25-PKM2-aerobic glycolysis axis was expected to be a therapeutic target for AKI.