Kidney Week

Abstract: SA-OR016

Inhibition of Orai1-Mediated Ca2+ Signaling Ameliorates AKI-to-CKD Transition Following Ischemia and High Salt Diet

Session Information

• AKI: Inflammation and Regeneration
  October 27, 2018 | Location: 6B, San Diego Convention Center
  Abstract Time: 05:30 PM - 05:42 PM

Category: Acute Kidney Injury

• 103 AKI: Mechanisms

Authors

• Mehrotra, Purvi, Indiana School of Medicine, Indianapolis, Indiana, United States

Purvi Mehrotra, PhD

• Sturek, Michael, Indiana University School of Medicine, Indianapolis, Indiana, United States

Michael Sturek,

• Basile, David P., Indiana University School of Medicine , Indianapolis, Indiana, United States

David P. Basile,

Background

Store-operated Ca²⁺entry (SOCE) through Orai1 channels raise intracellular Ca²⁺concentrations in T cells, which induce proliferation and cytokine production in immune cells. The Orai-1 gene has been linked to SCID, and loss-of-function mutation of Orai-1 in murine T cells shown to be protective in models of autoimmune disease, due to impaired production of the cytokine IL-17.

T-helper 17 (Th17) cells increase following renal injury and exposure to high-salt diet and IL-17 blockade reduces AKI-to-CKD progression. We have recently identified Orai-1 expression in AKI primed renal T cells and hypothesize that Orai1-mediated Ca²⁺signaling may influence Th17 differentiation and modulate CKD progression.

Methods

Rats were allowed to recover from renal ischemia for 1 week and CD4+ lymphocytes were analyzed for Ca²⁺and IL-17 responses in vitro. In other studies, rats were subjected to bilateral I/R and allowed to recover 24 hours with or without SOCE antagonist YM-58483 (1mg/kg). To study CKD progression, rats following unilateral ischemia were allowed to recover for 5 weeks 0.4% NaCl diet. CKD was hastened by Unx and elevated dietary NaCl (4%) for 4 weeks. In this study, rats were fed YM-58483 or vehicle daily during the high salt treatment.

Results

AKI primed CD4+ lymphocytes manifested an induction of IL-17 production in vitro to angiotensin II and 170 mMol/L Na⁺while ~30% of cells manifested an increase in cytosolic Ca²⁺; these responses were blocked by 10mM YM-58483. Rats treated with YM-58483 were protected from bilateral ischemia as indicated by lower serum creatinine (vehicle 3.3±0.4; YM-58483 2.2±0.5 mg/dl; p£0.05) and significantly reduced by ~40% Th17 infiltration. When post ischemic rats were exposed to 4% dietary salt, there was an increase in inflammatory cells and fibrosis. YM 58483 initiated during high salt feeding significantly attenuated renal CD4+, CD8+, B cells and dendritic/macrophage cells by ~50%. Th17 cells (CD4+/IL17+) were also reduced significantly (vehicle 19425±23086, YM-58483 6494±1146 cells/g; p£0.05). In addition, YM-58343 treatment also attenuated the development of interstitial fibrosis by ~86% relative to vehicle (p< 0.05).

Conclusion

Taken together, these data suggest that Orai1 activity is enhanced by renal ischemia and that Orai1-mediated Ca²⁺signaling increases Th17 activity and AKI-CKD progression.

Funding

• NIDDK Support