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Kidney Week

Abstract: FR-PO144

Ceramides as Mediators of Mitochondrial Dysfunction Driving Kidney Injury

Session Information

  • AKI: Mechanisms - II
    November 04, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
    Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • Nicholson, Rebekah, University of Utah Health, Salt Lake City, Utah, United States
  • Li, Ying, University of Utah Health, Salt Lake City, Utah, United States
  • Maschek, John A., University of Utah Health, Salt Lake City, Utah, United States
  • Stuart, Deborah, University of Utah Health, Salt Lake City, Utah, United States
  • Ramkumar, Nirupama, University of Utah Health, Salt Lake City, Utah, United States
  • Summers, Scott, University of Utah Health, Salt Lake City, Utah, United States
Background

Perturbations in proximal tubule mitochondrial function and lipid metabolism potentiate kidney injury and failed repair following ischemia reperfusion or obstruction. Sphingolipids such as ceramides are recognized as lipotoxic drivers of metabolic dysfunction. We investigate mechanisms of ceramides driving proximal tubule pathology and assess the efficacy of ceramide-lowering therapeutics to combat AKI.

Methods

We lowered whole-body ceramides via Degs1 inducible global knockout (Degs1iGKO) in male C57Bl/6J mice prior to challenge with warm bilateral IRI (22 minute ischemia) or UUO and compared clinical and histopathological outcomes versus Degs1fl/fl littermate controls 24 hours after kidney reperfusion or 7 days after obstruction. In vitro, we examined effects of ceramide accrual on mitochondrial function in human immortalized proximal tubule epithelial cells treated with palmitate or C2-ceramide with an Agilent Seahorse Analyzer.

Results

Degs1 global knockout decreased total cortex ceramide levels by 57%, preventing the 21% and 18% increase in ceramides in Degs1fl/fl surgery vs. sham groups following IRI or UUO, respectively. Degs1iGKO animals had improved blood urea nitrogen [49.82±6.34(KO) vs. 81.02±2.13(fl/fl) mg/dL], plasma creatinine [0.32±0.11(KO) vs. 1.28±0.4(fl/fl) mg/dL], and cortex Lcn2 expression [5.31±4.61(KO) vs. 36.36±21.50(fl/fl) relative to fl/fl sham] following IRI. Following UUO, Degs1iGKO kidneys were less fibrotic with lower expression of fibrosis (Col1a1, Col3a1, Fn1), inflammation (Il6), and injury (Havcr1) markers. Treatment of HK2 cells for 24 hours with 500mM palmitate, the primary substrate of ceramide biosynthesis, decreased basal and maximal mitochondrial respiration by 24% and 30%, respectively, vs. vehicle-treated controls. Co-treatment with 10mM myriocin, a ceramide synthesis inhibitor, prevented ceramide accumulation and rescued mitochondrial function. Treating cells with 15mM C2-ceramide, but not dihydroceramide lacking a double bond essential for lipid bioactivity, elicited similar impairments in mitochondrial oxygen consumption and acutely depleted mitochondrial ATP production.

Conclusion

Renal ceramides are implicated as drivers of kidney injury and mitochondrial dysfunction. Ceramide-lowering interventions may be effective strategies to prevent AKI.

Funding

  • NIDDK Support