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Abstract: SA-PO750

SMPDL3b Modulates STING Activation in Podocytes

Session Information

Category: Glomerular Diseases

  • 1302 Glomerular Diseases: Immunology and Inflammation

Authors

  • Tolerico, Matthew, University of Miami Katz Family Division of Nephrology and Hypertension, Miami, Florida, United States
  • Fontanella, Antonio Miguel, University of Miami Katz Family Division of Nephrology and Hypertension, Miami, Florida, United States
  • Mallela, Shamroop Kumar, University of Miami Katz Family Division of Nephrology and Hypertension, Miami, Florida, United States
  • Gurumani, Margaret Zvido, University of Miami Katz Family Division of Nephrology and Hypertension, Miami, Florida, United States
  • Molina David, Judith T., University of Miami Katz Family Division of Nephrology and Hypertension, Miami, Florida, United States
  • Burke, George William, University of Miami Department of Surgery, Miami, Florida, United States
  • Merscher, Sandra M., University of Miami Katz Family Division of Nephrology and Hypertension, Miami, Florida, United States
  • Fornoni, Alessia, University of Miami Katz Family Division of Nephrology and Hypertension, Miami, Florida, United States
  • Mitrofanova, Alla, University of Miami Katz Family Division of Nephrology and Hypertension, Miami, Florida, United States
Background

Chronic kidney disease (CKD) is a major health problem with no definitive cure. Podocytes are specialized glomerular cells that maintain kidney filtration and are injured in CKD. Recent studies show that sphingomyelin phosphodiesterase acid-like 3b (SMPDL3b) is important for podocyte function and regulates innate immunity in macrophages. The stimulator of interferon genes (STING), a component of the innate immune system that detects cytosolic DNA, has been shown to regulate inflammation in mouse models of CKD. We tested the hypothesis that altered SMPDL3b expression leads to podocyte injury through chronic activation of STING.

Methods

Illumina sequencing RNA data analysis, qRT-PCR and Western blot were used to characterize immortalized human podocytes with knockdown (siSMP) or overexpression (SMP OE) of SMPDL3b. c-diAMP, a STING specific agonist, treatment (10μM) was performed for 24h. Glomeruli isolated from 8-week-old mice with podocyte specific Smpdl3b deficiency (pSMPfl/fl) or overexpression (pSMPTg) were used to evaluate STING activation. pSMPfl/fl and pSMPTg mice were injected I.P. with a single dose of c-diAMP, 25mg/kg or 5% DMSO and sacrificed 72h after injection, following by urinary albumin-to-creatinine ratio (ACR), histological and serum analyses. Two-tailed t-test or One-Way ANOVA followed by Tukey’s post-test were used to detect statistical changes.

Results

Illumina RNAseq analysis revealed altered DNA sensing pathways in SMP OE podocytes. siSMP podocytes have reduced phospho and total STING, while SMP OE podocytes have increased phospho and total STING compared to control podocytes. Treatment with c-diAMP resulted in increased STING phosphorylation in control and siSMP podocytes, but not in SMP OE cells. Glomerular STING was significantly decreased in pSMPfl/fl mice and increased in pSMPTg mice. While both pSMPfl/fl and pSMPTg mice do not develop proteinuria at the baseline, treatment with c-diAMP resulted in increased ACR in pSMPTg, but not in pSMPfl/fl mice.

Conclusion

Our data indicate that SMPDL3b overexpression leads to STING activation in podocytes in vitro and STING-dependent proteinuria in vivo. Targeting SMPDL3b in the podocytes may represent a novel approach to regulate podocyte innate immunity and to improve renal outcomes in patients with CKD.