The cross-talk between NF-κB and HIF-1: further evidence for a significant liaison

Abstract

HIF-1 (hypoxia-inducible factor-1) has been shown to essentially control the cellular response to hypoxia. Hypoxia stabilizes the inducible α-subunit, preventing post-translational hydroxylation and subsequent degradation via the proteasome. In recent years, clear evidence has emerged that HIF-1α is also responsive to many stimuli under normoxic conditions, including thrombin, growth factors, vasoactive peptides, insulin, lipopolysaccharide and cytokines such as TNF-α (tumour necrosis factor-α), and in many cases reactive oxygen species are involved. One important mechanism underlying these responses is the transcriptional regulation of HIF-1α by the redox-sensitive transcription factor NF-κB (nuclear factor κB), which binds at a distinct element in the proximal promoter of the HIF-1α gene. More recently, NF-κB binding to this site in the HIF-1α promoter has been shown also under hypoxic conditions. Thus these two major pathways regulating the responses to inflammation and oxidative stress on the one hand, and hypoxia on the other hand, appear to be intimately linked. In this issue of the Biochemical Journal, a study by van Uden et al. has supported these findings further, in which they have confirmed the binding of several proteins of the NF-κB family at the previously identified consensus site in the HIF-1α promoter and shown that TNF-α can also transcriptionally induce HIF-1α by this previously described pathway. The identification of HIF-1α as a target gene of NF-κB will have important implications for a variety of disorders related to hypoxia–ischaemia and/or inflammation and oxidative stress.