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Kidney Week

Abstract: TH-PO294

Elucidation of Mechanism for Indoxyl Sulfate (IS)-Promoted Renal Fibrotic Response in HK-2 Cells under Hypoxic Condition and Mice with Ischemia-Reperfusion (IR)-Induced AKI

Session Information

Category: Acute Kidney Injury

  • 001 AKI: Basic

Authors

  • Yamashita, Mami, Kumamoto University Graduate School of Pharmaceutical Sciences , Kumamoto, Japan
  • Eto, Moe, Kumamoto University Graduate School of Pharmaceutical Sciences , Kumamoto, Japan
  • Yoneda, Go, Kumamoto University Graduate School of Pharmaceutical Sciences , Kumamoto, Japan
  • Fujino, Rika, Kumamoto University Hospital, Kumamoto, Japan
  • Jono, Hirofumi, Kumamoto University Hospital, Kumamoto, Japan
  • Saito, Hideyuki, Kumamoto University Hospital, Kumamoto, Japan
Background

IR-induced acute kidney injury (AKI) is known to be a trigger for the development of renal fibrosis followed by the progression to chronic kidney disease. Under ischemia-caused hypoxia of the kidney, tubulointerstitial fibrosis is enhanced with the increased accumulation of matrix proteins such as collagen. A typical sulfate-conjugated uremic solute, IS, is known to be produced in the liver and accumulated in serum and renal tissue under IR-induced AKI, thereby promoting fibrotic responses. However, precise molecular mechanisms involved in IS-promoted renal fibrosis under hypoxia has not been elucidated. In this study, we examined the molecular biological effect of IS on fibrotic responses under hypoxic condition using HK-2 cells and IR-induced AKI model mice.

Methods

C57/BL6 mice (8-weeks old) were treated with IS or vehicle (control) intraperitoneally, after subjected to 20 min of renal IR. In IR-AKI mice, serum creatinine (SCr), BUN and serum IS levels were determined. HK-2 cells were cultivated in the medium with or without IS or vehicle. Hypoxic treatment of HK-2 cells was performed using AnaeroPack System™. mRNA expression of fibrosis-related gene including transforming growth factor (TGF)-β and plasminogen activator inhibitor (PAI)-1 were determined in the kidney of AKI mice and HK-2 cells cultivated under normal oxygen or hypoxic condition.

Results

IR treatment of murine kidney caused a marked elevation in SCr and BUN 24 hr after surgery. Administration of IS in IR-AKI mice synergistically enhanced these increases in SCr (2.2-fold vs control) and BUN (1.5-fold). Expression of PAI-1 mRNA was enhanced in IR-AKI mice (3.4-fold), and HK-2 cells (1.7-fold) under both hypoxic condition and IS treatments, compared with those under normal oxygen condition. GLUT1 mRNA expression, a downstream gene of hypoxia-inducible factor, was also elevated significantly under both hypoxia and IS treatments. By hypoxia and IS treatments, TGF-β expression was accelerated, whereas LY2157299, a TGF-β receptor inhibitor, suppressed dose-dependently PAI-1 expression induced by hypoxia with simultaneous addition of IS.

Conclusion

IS could play important roles in promoting renal fibrosis via TGF-β-mediated up-regulation of fibrotic gene expression under hypoxic condition.

Funding

  • Government Support - Non-U.S.