Background: We previously reported that impaired autophagic activation after renal ischemia-reperfusion (I/R) underlies aggravation of acute kidney injury (AKI) in type 2 diabetes (T2D). We also found that suppression of autophagy promotes necroptosis, one type of programed cell death, in the cardiomyocyte. Here, we examined whether necroptosis signaling is enhanced by suppression of autophagy in diabetic kidney after I/R.
Methods and Results: AKI was induced by unilateral nephrectomy and 30-min renal artery occlusion/24-hr reperfusion in the contralateral kidney in OLETF, T2D rats, and its control rats, LETO. In LETO, rats were pretreated with a vehicle or chloroquine (CQ; 10 mg/kg/day, 7 days), an autophagy inhibitor. In OLETF, a vehicle or rapamycin (0.25 kg/kg, IP), an activator of autophagy, was administered 30-min before reperfusion. After I/R, serum creatinine (sCr) levels were higher in OLETF than LETO. CQ pretreatment also increased sCr level in LETO. In contrast, rapamycin treatment decreased sCr levels in OLETF. Western blot analysis showed that renal levels of RIPK1, RIPK3, and MLKL, major signal proteins related to necroptosis, were increased after I/R in both LETO and OLETF. RIPK3 protein levels after I/R were higher in OLETF than LETO. In addition, RIPK3 protein levels after I/R were increased by CQ treatment in LETO. On the other hand, rapamycin treatment reduced RIPK1 and RIPK3 protein levels in OLETF.
Conclusion: The results suggest that suppression of autophagy contributes to enhanced necroptosis signals in diabetic kidney after I/R.