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Abstract: PO1985

Knockout of the Neonatal Fc Receptor in Podocytes Ameliorates Nephritis by Reducing Glomerular Apoptosis

Session Information

  • Podocyte Biology
    October 22, 2020 | Location: On-Demand
    Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

  • 1204 Podocyte Biology

Authors

  • Blaine, Judith, University of Colorado, Aurora, Colorado, United States
  • Dylewski, James F., University of Colorado, Aurora, Colorado, United States
  • Lewis, Linda, University of Colorado, Aurora, Colorado, United States
  • Tonsawan, Pantipa, Khon Kaen University, Khon Kaen, Thailand
Background

There are few targeted treatments for immune mediated kidney diseases which can result in progressive renal failure. Podocytes express the neonatal Fc receptor (FcRn), a trafficking protein that sorts immune complexes (ICs) to the lysosome. In dendritic cells FcRn mediated trafficking of ICs to the lysosome is required for antigen processing and presentation on MHC II. We have found that podocyte specific knockout (KO) of FcRn ameliorates nephrotoxic serum (NTS) nephritis but that this protection occurs via a non-immune mediated mechanism. Here we show that KO of FcRn in podocytes results in a significant reduction in apoptosis both in vitro and in vivo after an immune challenge

Methods

Wild type (WT) and FcRn KO podocytes were cultured in the presence or absence of ICs. The intrinsic and extrinsic apoptotic pathways were assayed by Western blot and ELISA. RNA-seq was performed to evaluate changes in apoptotic pathways. NTS nephritis was induced in control and podocyte specific FcRn KO (podFcRn KO) mice. Glomerulosclerosis and crescent formation were quantitated on PAS sections. Flow cytometry was used to measure renal CD4+, CD8+ or FoxP3+ T cells. Glomerular apoptosis was assayed using the TUNEL assay.

Results

In vitro, after treatment with ICs, FcRn KO podocytes expressed significantly less caspase-3 and caspase-9 (intrinsic pathway caspases) and caspase-3 activity was significantly decreased in KO podocytes compared to WT. There was no difference in caspase-8 expression (a marker of extrinsic apoptosis) between WT and KO podocytes. RNA-seq analysis demonstrated significant downregulation of intrinsic apoptotic pathways in FcRn KO podocytes compared to WT.
In vivo, after induction of nephrotoxic serum nephritis, there was no change in renal CD4+, CD8+ or FoxP3+ T cells in podFcRn KO mice compared to controls but podFcRn KO mice had significantly less glomerulosclerosis and crescent formation. Podocyte-specific KO of FcRn also resulted in a significant reduction in the number of apoptotic cells within the glomerulus.

Conclusion

KO of FcRn reduces apoptosis via the intrinsic pathway in cultured podocytes after an immune challenge and ameliorates immune-mediated nephritis in vivo by reducing glomerular apoptosis.

Funding

  • NIDDK Support