Hypoxia-inducible factor prolyl-4-hydroxylase-1 is a convergent point in the reciprocal negative regulation of NF-\u03baB and p53 signaling pathways

Karim Ullah,Ann-Helen Rosendahl,Valerio Izzi,Johanna Myllyharju,Joni M Mäki,Ulrich Bergmann,Taina Pihlajaniemi

doi:10.1038/s41598-017-17376-0

Abstract

Hypoxia-inducible factor 1α (HIF1α) induces the expression of several hundred genes in hypoxia aiming at restoration of oxygen homeostasis. HIF prolyl-4-hydroxylases (HIF-P4Hs) regulate the stability of HIF1α in an oxygen-dependent manner. Hypoxia is a common feature in inflammation and cancer and the HIF pathway is closely linked with the inflammatory NF-κB and tumor suppressor p53 pathways. Here we show that genetic inactivation or chemical inhibition of HIF-P4H-1 leads to downregulation of proinflammatory genes, while proapoptotic genes are upregulated. HIF-P4H-1 inactivation reduces the inflammatory response under LPS stimulus in vitro and in an acute skin inflammation model in vivo. Furthermore, HIF-P4H-1 inactivation increases p53 activity and stability and hydroxylation of proline 142 in p53 has an important role in this regulation. Altogether, our data suggest that HIF-P4H-1 inhibition may be a promising therapeutic candidate for inflammatory diseases and cancer, enhancing the reciprocal negative regulation of the NF-κB and p53 pathways.

Highlights

Under compromized oxygenation, a hypoxia response pathway is induced by hypoxia-inducible factors (HIFs) that activate >100 genes for hypoxic adaptation[1,2]
Expression of inflammatory and apoptotic genes is altered in Hif-p4h-1−/− mouse embryonic fibroblasts (MEFs)
Of these ~2.7% were genes that are involved in positive regulation of acute inflammatory response and 72.5% of these were downregulated in Hif-p4h-1−/− MEFs relative to wt (Fig. 1a, supplementary Table 1)

Summary

Introduction

A hypoxia response pathway is induced by hypoxia-inducible factors (HIFs) that activate >100 genes for hypoxic adaptation[1,2]. HIF-P4Hs hydroxylate HIF1α in normoxia, leading to its ubiquitination and proteasomal degradation. Hypoxia inhibits HIF-P4Hs resulting in HIF1α stabilization and assembly of active HIF1 αβ dimer. Hypoxia-induced increase in p53 mRNA, translation, protein stability and activity, and decreased proteasomal p53 degradation, have been reported. P53 is present at low baseline levels in a complex with MDM2 that blocks p53 activity and directs it to ubiquitination and proteasomal degradation, but p53 is stabilized and activated in response to DNA damage and other adverse stimuli[29]. To study the potential of HIF-P4H-1 being a common regulator of hypoxia, inflammatory and p53 pathways, we analyzed gene expression in Hif-p4h-1−/− mouse embryonic fibroblasts (MEFs) and found that proinflammatory genes were downregulated, while proapoptotic genes were upregulated. Our data suggest that HIF-P4H-1 inhibition enhances reciprocal negative regulation of the NF-κB and p53 pathways and may be a promising therapeutic candidate for inflammatory diseases and cancer

Methods

Results

Conclusion