Rapamycin attenuates renal ischemia–reperfusion injury and early profibrotic responses

Renal ischemia–reperfusion (I/R) injury is a major cause of acute kidney injury and contributes to subsequent renal dysfunction and profibrotic responses. Rapamycin, an Mechanistic Target of Rapamycin inhibitor, has been reported to modulate autophagy and inflammatory responses; however, its effects on renal I/R injury and early profibrotic signaling remain incompletely understood. In this study, a rat renal I/R injury model was established by 45 min ischemia followed by 3 or 7 days of reperfusion. The experiment utilized 6- to 8-week-old male and female Sprague–Dawley rats, with a sample size of n = 6 in each group, comprising 3 males and 3 females. Starting one day prior to modeling, the rats received daily gavage of rapamycin at low (1 mg/kg) or high (2 mg/kg) doses. Renal injury was assessed through renal histopathological staining, TUNEL apoptosis detection, and the measurement of oxidative stress, inflammatory factors, and fibrosis markers. Additionally, the molecular mechanisms underlying the renal protective effects of rapamycin were investigated using RNA sequencing. Rapamycin treatment significantly reduced tubular injury and apoptosis following renal I/R injury. In addition, rapamycin decreased oxidative stress markers (ROS and MDA) and pro-inflammatory cytokines (TNF-α and IL-6), while enhancing antioxidant defenses (SOD and GSH). Expression of profibrotic markers was also reduced after rapamycin treatment. Rapamycin treatment resulted in alterations in the expression of autophagy-related markers, such as LC3B. RNA sequencing and subsequent validation experiments revealed a correlation between the expression level of Col6a6 and the aforementioned protective indicators. In conclusion, the current findings suggest that rapamycin can mitigate renal ischemia–reperfusion injury, accompanied by changes in autophagy, oxidative stress, and inflammatory responses, and is linked to the attenuation of early activation of pro-fibrotic signaling pathways in the kidneys. However, the causal relationship of this association and whether Col6a6 directly mediates the protective effect necessitate further experimental validation.