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Kidney Week

Abstract: PO0635

Interaction Between the Na-K-ATPase and CD40 Signaling in Proximal Tubule Epithelial Cells (PTECs) Contributes to Renal Inflammation and Fibrosis

Session Information

  • CKD Mechanisms - 2
    October 22, 2020 | Location: On-Demand
    Abstract Time: 10:00 AM - 12:00 PM

Category: CKD (Non-Dialysis)

  • 2103 CKD (Non-Dialysis): Mechanisms

Authors

  • Haller, Steven T., Department of Medicine University of Toledo College of Medicine and Life Sciences, Toledo, Ohio, United States
  • Zhang, Shungang, Department of Medicine University of Toledo College of Medicine and Life Sciences, Toledo, Ohio, United States
  • Nie, Ying, Marshall University Joan C. Edward School of Medicine, Huntington, West Virginia, United States
  • Shapiro, Joseph I., Marshall University Joan C. Edward School of Medicine, Huntington, West Virginia, United States
  • Liu, Jiang, Marshall University Joan C. Edward School of Medicine, Huntington, West Virginia, United States
Background

We have demonstrated that signaling through the Na/K-ATPase-α1 subunit/c-Src kinase (NKA-α1/c-Src) complex and activation of the pro-inflammatory receptor, CD40 induce renal inflammation and fibrosis in both clinical and experimental models of ischemic and chronic kidney disease (CKD). Circulating cardiotonic steroids (specific ligands of Na/K-ATPase) are significantly elevated in CKD that not only stimulate NKA-α1/c-Src signaling, but also regulate CD40 signaling by upregulation of CD40 expression in PTECs. Furthermore, soluble CD40 ligand (sCD40L)-stimulated CD40 signaling in PTECs is dependent on NKA-α1/c-Src signaling. However, the interplay between Na/K-ATPase and CD40 signaling-induced renal inflammation and fibrosis has not been thoroughly investigated.

Methods

RNA sequencing was performed on pig PTECs with and without a functional NKA-α1/c-Src signaling complex (Ly-α2 cells and Lx-α2 cells, respectively) following treatment with sCD40L (100ng/mL) for 24hrs. In pig PTECs LLC-PK1 cells treated with the cardiotonic steroid telocinobufagin (TCB), immunoprecipitation was performed to detect protein-protein interaction.

Results

Treatment with sCD40L in Ly-α2 cells demonstrated a significant increase in gene expression of pro-inflammatory and pro-fibrotic mediators [CXCL9, CXCL10, IL1R1, complement C3, and COL1A2 (all > 5-fold increase)] compared to Lx-α2 cells. In LLC-PK1 cells, short-term TCB treatments (up to 1 hr) stimulates interaction between NKA-α1 and CD40 that presents under resting conditions. Long-term TCB treatment (24 hr) still shows the NKA-α1 and CD40 interaction, but reduced NKA-α1 and CD40 interaction was also observed in comparison to control, suggesting a possible endocytosis of NKA-α1 (by the cardiotonic steroid) and CD40.

Conclusion

In renal proximal tubular cells, CD40-induced pro-inflammatory and pro-fibrotic signaling is dependent on the NKA-α1/c-Src complex, and there is an interaction between NKA-α1 and CD40 that was enhanced by activation of the NKA-α1/c-Src signaling. A regulation through expression level and/or endocytosis of NKA-α1 and CD40 might be involved to control signaling strength.

Funding

  • NIDDK Support