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Kidney Week

Abstract: PO0399

Endothelial and Not Proximal Tubule Epithelial Pannexin 1 Plays a Critical Role in Fibrosis Progression After AKI

Session Information

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • Poudel, Nabin, University of Virginia School of Medicine, Charlottesville, Virginia, United States
  • Nash, William, University of Virginia School of Medicine, Charlottesville, Virginia, United States
  • Skrypnyk, Nataliya, University of Virginia School of Medicine, Charlottesville, Virginia, United States
  • Zheng, Shuqiu, University of Virginia School of Medicine, Charlottesville, Virginia, United States
  • Goggins, Eibhlin, University of Virginia School of Medicine, Charlottesville, Virginia, United States
  • Okusa, Mark D., University of Virginia School of Medicine, Charlottesville, Virginia, United States
Background

Activation of pannexin-1 (Panx1) channels during acute kidney injury (AKI) and Panx1-mediated release of tissue messengers facilitates the recruitment and activation of immune cells to the site of injury. Lack of Panx1 in the proximal tubules (PT) or in the endothelial cells (EC) significantly reduces AKI. Metabolites released from Panx1 affect a number of biological processes that regulate inflammation and cellular metabolism. Thus, we investigated the role of PT or EC Panx1 during AKI to chronic kidney disease (AKI-CKD) transition by inducing deletion of Panx1 from PT or EC before or after an established AKI.

Methods

AKI was induced by unilateral ischemia-reperfusion injury (IRI), folic acid, or bilateral IRI. Cell-type specific deletion of Panx1 was achieved by injecting tamoxifen before or after AKI to Panx1 floxed (Panx1fl/fl) animals expressing either PT (SLC34a1GCE) (provided by B. Humphreys, Washington University) or EC (Cdh5CreER) specific inducible Cre-recombinase to generate either PT (SLC34a1GCEPanx1-/-) or EC (Cdh5CreERPanx1-/-) specific Panx1 knockout animals. Kidneys were analyzed for extent of fibrosis by measuring mRNA expression of fibrotic markers and Masson’s trichrome staining and for immune cell infiltration by flow cytometry.

Results

Deletion of Panx1 before AKI globally, in PT, or in EC attenuated renal fibrosis. Deletion of Panx1 after AKI did not alter the extent of fibrosis in SLC34a1GCEPanx1-/- animals compared to SLC34a1+/+Panxfl/fl controls that received tamoxifen, however, deletion of Panx1 after AKI significantly increased fibrosis in Cdh5CreERPanx1-/-compared to Cdh5CreERPanx1fl/fl controls. Tamoxifen itself did not alter the extent of fibrosis. Flow cytometry revealed robust immune cells recruitment including neutrophils, macrophages, dendritic cells, and T-cells in injured kidneys post-AKI. While there was no significant difference in other immune cell proportions at day 3 and day 7 post AKI, Cdh5CreERPanx1-/- animals had a significantly higher CD103-positive dendritic cell population at day 10 post AKI.

Conclusion

Our data show that while Panx1 from PT or EC play crucial role during AKI, Panx1 from EC is vital for limiting extent of fibrosis during AKI-CKD potentially by releasing metabolites that regulate immune cell function and fibrosis/repair.

Funding

  • NIDDK Support