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Abstract: SA-PO084

The Protective Effects of Novel HIF-Hydroxylase Inhibitors in Renal Tubules

Session Information

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • Grampp, Steffen, Universitätsklinikum Erlangen, Erlangen, Germany
  • Lauer, Victoria, Universitätsklinikum Erlangen, Erlangen, Germany
  • Schödel, Johannes, Universitätsklinikum Erlangen, Erlangen, Germany
Background

Acute kidney injury (AKI) has an increasing incidence. To date there are no specific pharmacological treatment options for AKI. Results from multiple rodent models of AKI suggest that the pre-conditional stabilization of hypoxia-inducible factors (HIFs) in renal tubular epithelial cells leads to improved kidney function. However, so far it is unclear whether these effects can be translated into human disease, and the underlying molecular mechanisms are poorly understood. HIF protein stability is regulated by prolyl hydroxylases (PHD) and HIF transcriptional activity is regulated by the Factor Inhibiting HIF (FIH). Novel inhibitors of PHDs (PHDi) have been developed to treat the anemia in chronic kidney disease by increasing EPO levels. Here we evaluate the effects of some of the novel selective PHDi on the HIF-response in human primary renal tubular cells and contrast them with effects of pan-hydroxylase inhibition.

Methods

Human primary renal tubular cells (hPTC) were isolated from kidney of patients undergoing tumour nephrectomy. hPTC were exposed to different hydroxylase inhibitors and HIF levels, HIF DNA-interactions as well as target gene induction were measured by western blotting, ChIP experiments and RNA analyses, respectively. We employed an in vitro model of cisplatin induced apoptosis to screen for protective effects of HIF stabilization in hPTC.

Results

PHDi stabilize HIF-1α protein to levels comparable to pan-hydroxylase inhibition by dimethyl oxalylglycine (DMOG) in hPTC. ChIP analyses confirmed comparable HIF-binding to selected gene loci under PHDi and DMOG. In contrast to equal protein levels and DNA-binding, transcriptional activation of selected HIF targets (CA9, EGLN3) was more pronounced in cells treated with DMOG suggesting that the additional inhibition of FIH increases the HIF response. PHDi led to reduced apoptosis in the cisplatin AKI in vitro model. However, combined inhibition of PHDs and FIH either by siRNA mediated knock-down or with a selective FIH-inhibition further increased target gene expression and cell protection.

Conclusion

Novel PHDi lead to a remarkable HIF-response in hPTC and have protective effects upon toxic stimuli. Additional inhibition of FIH which regulates HIF activity further improves cell survival. Therefore, pan-HIF hydroxylase inhibition is protective in tubular cells and might open a novel route into AKI treatment.

Funding

  • Government Support - Non-U.S.