Abstract: SA-OR008

APOL1 Risk Variant Induced Kidney Injury in Podocytes Is Mediated by Caspase-1

Session Information

  • A View on the Glomerulus
    November 04, 2017 | Location: Room 294, Morial Convention Center
    Abstract Time: 05:54 PM - 06:06 PM

Category: Glomerular

  • 1002 Glomerular: Basic/Experimental Pathology

Authors

  • Laczko, Dorottya, University of Pennsylvania, Philadelphia, Pennsylvania, United States
  • Beckerman, Pazit, University of Pennsylvania, Philadelphia, Pennsylvania, United States
  • Bi Karchin, Jing, University of Pennsylvania, Philadelphia, Pennsylvania, United States
  • Chinga, Frank S., University of Pennsylvania, Philadelphia, Pennsylvania, United States
  • Susztak, Katalin, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Background

Coding variants of APOL1 (termed as G1 and G2) are associated with increased risk of kidney disease in African Americans. Recently, we developed a new mouse model that recapitulates APOL1 associated renal disease by conditional inducible expression of G1 and G2 APOL1 variants in podocytes. While these animals develop albuminuria, glomerulosclerosis and azotemia, the exact pathomechanism of APOL1 variant induced kidney disease remains poorly understood. Here, we tested whether caspase-1 (Cas1) / IL-1β mediated pyroptotic cell death play a role in disease development.

Methods

Podocyte specific G2 APOL1 transgenic mice was generated by crossing TRE-G2 APOL1 animals with mice carrying the nephrin rtTA. Transgene expression was controled by doxycycline. To test the role of Cas1, we crossed nephrin rtTA/TRE-G2 APOL1 with Cas1 knock-out (KO) mice. To test the role of IL-1β we treated mice with IL-1β neutralizing antibody Anakinra. Histological changes were evaluated by PAS staining and the level of proteinuria was determined by albumin specific ELISA. The mRNA levels of kidney injury markers (KIM1, Col4a1, SMA) were analyzed by qPCR. For in vitro testing cells with inducible G2 APOL1 expression were generated, and the effect of pan-caspase, Cas1 and -3 were tested.

Results

In vitro expression of G2 APOL1 resulted in increased cleaved Cas1 and IL-1β levels. Pan-caspase and Cas1 inhibitors ameliorated cell death induced by G2 APOL1. In vivo, Anakinra injection for 21 days failed to significantly reduce albuminuria or glomerulosclerosis of G2 APOL1 mice. In line with these findings, no change in the transcript level of kidney injury markers was observed after neutralization of IL-1β compared to their control saline injected littermates. In contrast, renal disease was ameliorated in G2 APOL1 Cas1 KO mice as evidenced by decreasing level of proteinuria over the 21 days doxycycline treatment period as opposed to their Cas1 wild type littermates. In addition to this, Cas1 KO mice displayed marked reduction of kidney fibrosis confirmed by PAS staining.

Conclusion

Our initial data suggest that Cas1 plays a crucial role in the development of G2 APOL1 induced kidney damage, albeit the mechanism still needs to be elucidated. We propose that inhibition of Cas1 can offer a potential therapeutic target for APOL1 associated kidney damage.

Funding

  • Other NIH Support