Hypoxia and Inflammation

Mammals have oxygen-sensing mechanisms that help them adapt quickly to hypoxia by increasing respiration, blood flow, and survival responses.If an inadequate supply of oxygen persists, additional mechanisms attempt to restore oxygenation or help the body adapt to hypoxia. 1 These other mechanisms rely on oxygen-sensing prolyl hydroxylases (PHDs), which hydroxylate prolines in the alpha subunit of the hypoxia-inducible transcription factor (HIF).This transcription factor is a heterodimer with two subunits: HIF-1α or HIF-2α and HIF-1β (or aryl hydrocarbon receptor nuclear translocator [ARNT] protein).HIF-1α is ubiquitous, whereas HIF-2α is restricted to certain tissues. 1 In this review, we show the ways in which the PHD-HIF system affects inflammatory processes.We discuss the regulation of immune responses by hypoxia-induced signaling, outline molecular aspects of the cross-talk between hypoxia and inflammation, and illustrate the link between hypoxia and inflammation in inflammatory bowel disease, certain cancers, and infections.