Abstract: FR-PO375

Pharmacological Induction of ARNT/HIF1β Attenuates Chronic Organ Failure

Session Information

Category: Chronic Kidney Disease (Non-Dialysis)

  • 308 CKD: Mechanisms of Tubulointerstitial Fibrosis

Authors

  • Zeisberg, Michael, University Medical Center Goettingen, Goettingen, Germany
  • Tampe, Desiree, University Medical Center Goettingen, Goettingen, Germany
  • Mueller, Gerhard A., University Medical Center Goettingen, Goettingen, Germany
  • Tampe, Bjoern, University Medical Center Goettingen, Goettingen, Germany
Background

Injury in any organ triggers a complex signaling cascade, ultimately culminating in tissue fibrosis and organ failure. Prompted by various studies across multiple organs demonstrating that preconditioning regimens to pre-emptively induce endogenous regenerative mechanisms protect from later incurring injury, we here aimed to gain insights into the molecular mechanisms underlying successful preconditioning, and to explore whether such pathways could be utilized to inhibit progression of chronic organ injury.

Methods

The effect of picomolar versus nanomolar FK506 was assessed in multiple models of chronic injury in the kidney (UUO), heart (AT II infusion) and liver (CCl4 injection). Using murine and human cell cultures, molecular mechanisms were analyzed by qRT-PCR, immunostaining and Western blotting.

Results

Based on existing transcriptional profiling data, enrichment analysis and array-based screening, we identified a novel protective mechanism that is controlled by the transcription factor ARNT (synonym HIF1β), which effectively inhibits progression of chronic kidney injury in both, preconditioning as well as interventional regimens. We further report that ARNT expression itself is controlled by the FKBP12/YY1 transcriptional repressor complex, and that disruption of such FKBP12/YY1 complexes by either depletion of FKBP12 or YY1, or by picomolar FK506 concentrations at sub-immunosuppressive doses increases ARNT expression, leading to transcriptional ARNT induction. On a molecular level, we provide evidence that supraphysiological ARNT levels induce formation of distinct ARNT homodimers independent of hypoxia or xenobiotic signaling. For the first time, we detect ARNT homodimer formation in mammalian cells, facilitating unique transcriptional properties of ARNT/ARNT by direct targeting of a palindromic E-box binding motifs (5'-CACGTG core sequence) within the proximal ALK3 promoter. Subsequent activation of ALK3-dependent canonical BMP signaling responses attenuate chronic organ failure in models of chronic kidney, cardiac and liver injuries.

Conclusion

We report a novel organ protective mechanism that depends on ARNT/HIF1β homodimers, which can be pharmacologically modulated and targeted by immunophilin ligand FK506.