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Abstract: FR-OR100

SMPDL3b Modulates Podocyte Innate Immunity via Stimulator of Interferon Genes (STING) Activation in CKD

Session Information

Category: Glomerular Diseases

  • 1403 Podocyte Biology

Authors

  • Fontanella, Antonio Miguel, University of Miami School of Medicine, Miami, Florida, United States
  • Semenova, Veronika, University of Miami School of Medicine, Miami, Florida, United States
  • Molina David, Judith T., University of Miami School of Medicine, Miami, Florida, United States
  • Mallela, Shamroop Kumar, University of Miami School of Medicine, Miami, Florida, United States
  • Burke, George William, University of Miami School of Medicine, Miami, Florida, United States
  • Merscher, Sandra M., University of Miami School of Medicine, Miami, Florida, United States
  • Fornoni, Alessia, University of Miami School of Medicine, Miami, Florida, United States
  • Mitrofanova, Alla, University of Miami School of Medicine, Miami, Florida, United States
Background

Chronic kidney disease (CKD) is a global problem with rising incidence, prevalence and poor understood pathogenesis. Our prior studies support the hypothesis that sphingolipids are major determinants of podocyte function and survival, where sphingomyelin phosphodiesterase acid like 3b (SMPDL3b) plays an important role. Sphingolipids are known regulators of inflammation, also a major contributor to CKD progression. We reported that activation of the stimulator of interferon genes (STING), an important innate immune signaling protein, contributes to alterations in podocyte foot processes, proteinuria, and CKD progression. Here we test the hypothesis that increased SMPDL3b expression leads to podocyte injury through activation of STING.

Methods

Immortalized control or overexpression (SMP OE) human podocytes were used. Illumina sequencing RNA data analysis, qRT-PCR and Western blot analysis were used to characterize the cells. 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 intraperitoneally injected with a single dose of c-diAMP, 50mg/kg or 5% DMSO and sacrificed 72h after, followed 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

Genes involved in the cytosolic DNA sensing pathways in SMP OE podocytes are significantly regulated. In vitro and in vivo studies demonstrated that SMP OE podocytes and glomeruli isolated from pSMPTg mice have increased levels of STING phosphorylation (pSTING). Treatment with c-diAMP resulted in increased pSTING in control, but not in SMP OE podocytes. While both pSMPfl/fl and pSMPTg mice did not develop proteinuria at the baseline, treatment with c-diAMP resulted in significantly increased ACR in pSMPTg, but not in pSMPfl/fl mice. No changes in serum BUN and creatinine levels were observed in pSMPfl/fl and pSMPTg mice treated with c-diAMP.

Conclusion

Our data indicate that SMPDL3b overexpression is associated with STING activation in podocytes in vitro and STING-dependent proteinuria in vivo.

Funding

  • NIDDK Support