Abstract: FR-PO156

Clearance of Damaged Mitochondria via Mitophagy Plays an Important Role in the Protective Effect of Renal Ischemic Preconditioning

Session Information

  • Mitochondriacs and More
    November 03, 2017 | Location: Hall H, Morial Convention Center
    Abstract Time: 10:00 AM - 10:00 AM

Category: Acute Kidney Injury

  • 001 AKI: Basic

Authors

  • Livingston, Man J., Augusta University Medical College of Georgia, Augusta, Georgia, United States
  • Dong, Zheng, Augusta University Medical College of Georgia, Augusta, Georgia, United States
Background

Ischemic preconditioning (IPC) affords tissue protective effects in organs including the kidney; however, the underlying mechanism remains unclear. Autophagy is induced in renal tubular cells during acute kidney injury (AKI) and plays a protective role, but whether autophagy contributes to the protective effect of IPC is unknown.

Methods

This study has examined the role of autophagy in the renoprotection of IPC using both in vivo and in vitro ischemic AKI models. IPC was induced in mice by mild (15 minutes) renal ischemia followed by 1-hour reperfusion. The mice were then subjected to more severe (27 minutes) renal ischemia to examine kidney injury. In in vitro, IPC was induced in proximal tubular cells (RPTC) by 30 minutes of “chemical ischemia” with CCCP followed by 40-minute recovery. The cells were then incubated with CCCP for 3 hours followed by 2-hour recovery (CCCP3h/R2h) to examine injury.

Results

IPC suppressed subsequent ischemic AKI. Autophagy was induced in kidneys by IPC. Notably, the renoprotective effect of IPC was abolished by autophagy inhibitors and also in kidney proximal tubule-specific Atg7 knockout mice, suggesting the dependence of IPC renoprotection on autophagy. Along with autophagy induction, the mitophagy regulator Pink1 was activated and there was a remarkable loss of mitochondrial proteins following ischemic AKI, suggesting that autophagy may protect kidneys by activating mitophagy. Consistent with in vivo observations, IPC in RPTC cells showed protective effects, which were abrogated by autophagy inhibition. Interestingly, IPC in RPTC cells induced a significant increase in the colocalization of autophagosomes with mitochondria, suggesting mitophagy induction. Moreover, IPC increased the delivery of mitochondria to lysosomes as shown by Cox8-EGFP-mCherry mitophagy reporter assay. Consistently, IPC induced higher levels of mitochondrial loss or clearance during subsequent CCCP treatment that was suppressed by autophagy inhibitors. IPC-induced clearance of mitochondria was associated with the reduction of ROS generation during subsequent CCCP treatment.

Conclusion

Together, these results suggest that autophagy, especially mitophagy, plays an important role in the protective effect of IPC.

Funding

  • NIDDK Support