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Kidney Week

Abstract: TH-PO032

Succinate Dehydrogenase Plays a Critical Role in Hypoxia/Reoxygenation-Induced Apoptosis in Renal Proximal Tubular Cells

Session Information

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • Chen, Xujiao, Department of Nephrology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
  • Hu, Ying, Department of Nephrology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
Background

Acute kidney injury (AKI) has become a worldwide public health problem because high risk of death and progression to chronic kidney disease. Renal ischemia-reperfusion (IR) injury is one of major causes of AKI. Many pathological factors and mechanisms are involved in I/R injury. Among them, overproduced reactive oxygen species (ROS) plays an important role in mitochondrial dysfunction and endoplasmic reticulum stress(ERS) which finally lead to the cell apoptosis. Succinate dehydrogenase (SDH) is an intermediate both of the mitochondrial citric acid cycle and electron cycle transport. Recent studies demonstrate that ischemia-related succinate accumulation followed by increased SDH activity after reperfusion as key drivers of ROS formation in heart and brain IR injury. But it is still unclear and controversial in kidney IR injury. We hypothesized that accumulated succinate during hypoxia and increase SDH activity during reoxygenation contribute to a large burst of ROS. Increased ROS levels induced mitochondrial damage and ERS which finally lead to cell apoptosis.

Methods

For hypoxia/reoxygenation, renal proximal tubular cells (RPTC) were cultured in hypoxic conditions for 4 hours followed by normoxic conditions for 2 hours. Succinate abundance, SDH activity were assessed by kits and mitochondrial ROS was assessed by confocal. Mitochondrial function and dynamics were assessed by measuring mitochondrial membrane potential(DYm), ATP content, Mfn2/Drp1 expression and mitochondrial morphometry. ERS were assessed through IRE1a-XBP1, PERK-eIF2α and ATF6 pathways. Cell apoptosis were determined by TUNEL assay and Caspase-3 activity.

Results

Succinate accumulated during hypoxia and SDH activity increased after reoxygenation. ROS production significantly increased in response to H/R and induced downstream of mitochondrial dysfunction(DYm and ATP content decreased) and mitochondrial fission(Mfn2 and mitochondrial morphometry decreased while Drp1 increased). ERS were also activated by ROS. Apoptosis ratio increased in response to H/R. Malonate can attenuates H/R-induced renal tubular epithelial cells injury through inhibiting SDH activity.

Conclusion

Inhibition of SDH activity can attenuate hypoxia/reoxygenation induced ROS overproduction, mitochondrial dysfunction, ERS and apoptosis in RPTC. Our findings provide a new perspective in treating renal ischemia-reperfusion injury.

Funding

  • Government Support - Non-U.S.