Abstract: SA-PO395

Albuminuria and Podocytopathy Induced by Podocyte-Specific Deletion of Acid Ceramidase α Subunit

Session Information

Category: Chronic Kidney Disease (Non-Dialysis)

  • 301 CKD: Risk Factors for Incidence and Progression

Authors

  • Li, Guangbi, Virginia Commonwealth University, Richmond, Virginia, United States
  • Boini, Krishna M, Virginia Commonwealth University, Richmond, Virginia, United States
  • Gehr, Todd W., Virginia Commonwealth University, Richmond, Virginia, United States
  • Li, Pin-lan, Virginia Commonwealth University, Richmond, Virginia, United States
Background

Acid ceramidase (AC) as a lysosomal enzyme has been shown to be critical for the metabolism of sphingolipid, ceramide, which regulate lysosome function and related cellular activities such as autophagy and vesicle or molecular trafficking. It remains unknown whether AC is involved in the control of podocyte function and in the development of glomerular disease. In the present study, we generated a mouse line with podocyte-specific deletion of α subunit in Asah1 gene (AC gene code in mouse), a main subunit for its activity in lysosomes using Cre-Lox recombination technology. This AC flox/podocyte Cre (Asah1fl/fl/podoCre) mouse colony was characterized by several genetic, molecular and biochemical approaches. By PCR genotyping, detection of both homozygous floxed gene Asah1 and Cre recombinase gene was considered as homozygous mice with Cre expression. If neither floxed Asah1 gene nor Cre recombinase gene was detected, mice are wild type (WT/WT). If only floxed Asah1 gene was detected without Cre recombinase gene, the mice were Asah1 flox control without podocyte specific deletion (Asah1fl/fl/WT). Immunofluorescent staining and immunohistochemistry showed that ACα was not detactable in podocytes in glomeruli of Asah1fl/fl/podoCre mice, compared to Asah1fl/fl/WT and WT/WT mice. Although Periodic acid-Schiff staining showed no significant increase in glomerular damage index in Asah1fl/fl/podoCre mice compared with other two types of mice, there were severe proteinuria and albuminuria found in Asah1fl/fl/podoCre mice even started at 6 weeks old. Correspondingly, compared Asah1fl/fl/WT and WT/WT mice at the same ages, hypoalbuminemia and edema were observed in Asah1fl/fl/podoCre mice when they grew to 12 weeks old. Under electron microscope, Asah1fl/fl/podoCre mice were found to have foot process effacement, vacuolation, and microvillus formation in podocytes. In cultured mouse podocytes, we also found that inhibition of AC activity by carmofur, a selective AC inhibitor, remarkably decreased the expression of podocin. These results suggest that AC and associated metabolism of ceramide are essential for the maintenance of podocyte structural and functional integrity and that the defect or deficiency of AC expression and function may result in podocytopathy and related glomerular disease such as minimal change disease.

Funding

  • NIDDK Support