Abstract: TH-OR019

Inhibition of Endothelial PHD2 Protects against Ischemic Kidney Injury through HIF-1 Dependent Suppression of Neutrophilic Inflammation

Session Information

Category: Acute Kidney Injury

  • 001 AKI: Basic

Authors

  • Rajendran, Ganeshkumar, KANSAS UNIVERSITY MEDICAL CENTER, KANSAS CITY, Kansas, United States
  • Schonfeld, Michael P., KUMC - University of Kansas Medical Center, Kansas City, Kansas, United States
  • Torosyan, Rafael, University of Kansas Medical Center, Kansas City, Kansas, United States
  • Kapitsinou, Pinelopi P., University of Kansas Medical Center, Kansas City, Kansas, United States
Background

Peritubular endothelial cells (ECs) are major determinants in renal ischemia reperfusion injury (IRI) but the molecular mechanisms remain undefined. Key regulators of hypoxic vascular responses are Hypoxia-Inducible-Factors (HIF)-1 and -2, transcription factors whose activity is inhibited by prolyl-hydroxylase domain proteins 1 to 3 (PHD1 to PHD3), PHD2 being the main oxygen sensor. We previously reported that deficiency of endothelial HIF-2 exacerbated renal IRI, while inactivation of endothelial PHD2 provided renoprotection. Here, we investigated the contribution of HIF1/HIF2 in renoprotection induced by endothelial PHD2 loss.

Methods

EC-specific HIF activation was achieved by crossing Vecadherin (Cdh5)-Cre transgenics to Phd2 floxed mice (ePHD2), while the contribution of each HIF isoform was assessed by generating double mutants lacking PHD2 and HIF-2 (ePHD2HIF2) or PHD2 and HIF-1 (ePHD2HIF1) in ECs. IRI was induced by unilateral renal artery clamping.

Results

Deletion of HIF-1 in endothelial PHD2 deficient background completely reversed the renoprotection conferred by endothelial PHD2 loss as indicated by histological injury scores and Kim1 mRNA levels in kidney homogenates (Day 3 post IRI, n=8 mice). In contrast, double ePHD2HIF2 mutants had attenuated kidney injury with ~1.7 fold down-regulation in Kim1 transcript levels compared to controls. CD45 staining showed comparable inflammatory cell infiltration in ePHD2HIF1 injured kidneys with Cre-, while ePHD2HIF2 kidneys had significantly less CD45+ve area than their corresponding controls. Consistently, FACs analysis indicated significant reduction in neutrophils in ePHD2HIF2 kidneys while no difference was detected in ePHD2HIF1 compared to controls. To assess how endothelial PHD2/HIF-1 suppressed post-ischemic inflammation, we examined the expression of EC-adhesion molecules and chemokines known to regulate neutrophil recruitment. We found that Icam1, Tnfa, Cxcl1 and Cxcl2 mRNA levels were significantly reduced in ePHD2HIF2 post-ischemic kidneys compared to controls, while no differences were noted for ePHD2HIF1 kidneys.

Conclusion

Our data establish that endothelial HIF-1 mediates the renoprotective effects generated by endothelial PHD2 deficiency through suppression of leukocyte recruitment and adhesion to endothelium.

Funding

  • Other NIH Support