Combined Ischemic Postconditioning and Ozone Postconditioning Provides Synergistic Protection Against Renal Ischemia and Reperfusion Injury Through Inhibiting Pyroptosis

Abstract

To investigate whether ischemic postconditioning (IPO) and ozone postconditioning (OP) could synergistically attenuate renal ischemia-reperfusion (I/R) injury and its possible mechanism. An in vivo rat model of renal I/R injury was established, and the serum and kidneys were harvested after reperfusion to assess renal function and histologic changes. For the in vitro study, the cultured NRK-52E cells were subjected to 3 hours of hypoxia (5% CO2, 1% O2, and 94% N2) followed by 24 hours of reoxygenation (5% CO2, 21% O2, and 74% N2). The mRNA expression levels were analyzed by real-time polymerase chain reaction, and the protein expression levels were analyzed by using Western blot, immunofluorescence staining and enzyme-linked immunosorbent assay. Kidneys undergone I/R showed characteristic renal dysfunction and pyroptosis. IPO or OP could prevent the elevated blood urea nitrogen and creatinine, renal damage, as well as pyroptosis, however, the combined application of them had more obvious protection. Oxidative stress and pyroptosis were increased in hypoxia and reoxygenation (H/R) model using NRK-52E cells. The combination of hypoxic postconditioning and OP had more protective effects on oxidative abnormalities and pyroptosis compared with the single application of hypoxic postconditioning or OP. Our in vivo and in vitro studies show the combination of IPO and OP synergistically prote-cted the kidney from I/R by attenuating pyroptosis in kidney cells.