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Abstract: PO1723

Role of Plin5 Deficiency in Podocyte Lipotoxicity and the Progression of Alport Syndrome

Session Information

Category: Glomerular Diseases

  • 1201 Glomerular Diseases: Fibrosis and Extracellular Matrix

Authors

  • Kim, Jin Ju, University of Miami School of Medicine, Miami, Florida, United States
  • Wilbon, Sydney S., University of Miami School of Medicine, Miami, Florida, United States
  • Molina David, Judith T., University of Miami School of Medicine, Miami, Florida, United States
  • Merscher, Sandra M., University of Miami School of Medicine, Miami, Florida, United States
  • Fontanesi, Flavia, University of Miami School of Medicine, Miami, Florida, United States
  • Miner, Jeffrey H., Washington University in Saint Louis School of Medicine, Saint Louis, Missouri, United States
  • Fornoni, Alessia, University of Miami School of Medicine, Miami, Florida, United States
Background

Alport Syndrome (AS) is a hereditary disease caused by mutations in collagen type IV. We and others have demonstrated pathogenic renal lipid accumulation in experimental AS (Col4a3KO mice). Excess lipids stored in lipid droplets (LD) as cholesterol ester and triglyceride (TG) are known to cause lipotoxicity. Excessive FFA catabolism resulting from excessive lipolysis of TG is a major contributor to cell lipotoxicity in obesity and diabetes. Perilipin 5 (PLIN5) is a LD-related protein that plays a critical role in the regulation of triglyceride lipase activity and in the interactions between LD and mitochondria, where it protects mitochondria from excessive exposure to FFA. Here we test the hypothesis that PLIN5 is express in podocytes and that excessive TG breakdown occur in AS podocytes as a consequence of PLIN5 deficiency.

Methods

Immortalized AS podocytes (AS podocyte) and WT podocytes were established and characterized in our laboratory by breeding the Col4a3KO mice (Jackson Laboratory) to Immorto mice (Charles River). PLIN5 expression was determined by RT-PCR and western blot analysis in podocytes from Col4a3KO mice when compared to controls. TG lipolysis and FFA quantification were determined and normalized to protein content. Mitochondrial function was determined by utilizing Seahorse XF cell mito stress kit. To determine ATP linked respiration and proton leak, 1.5uM Oligomycin was injected to cells and analyzed by Seahorse XF96 Analyzer (Agilent).

Results

We demonstrate that PLIN5 is expressed in podocytes and the expression of PLIN5 is significantly decreased in AS podocytes when compared to WT podocytes (p<0.01). AS podocytes also showed significantly increased rates of TG lipolysis (p<0.05), intracellular free fatty acids (p<0.05) and apoptosis (p<0.01) when compared to WT podocytes. AS podocytes had increased proton leak, implying that the FFA may uncouple the mitochondria, leading to mitochondrial dysfunction and apoptosis. Moreover, ezetimibe, which in vivo improved kidney function, was found to in vitro restorePLIN5 expression in a dose-dependent manner.

Conclusion

Our study suggests that podocyte PLIN5 deficiency may cause podocyte injury in AS through excessive TG lipolysis and mitochondrial dysfunction.