Cellular oxygen sensing in health and disease.

To avoid localised problems resulting from excess or inadequate oxygen, all cells and tissues have the ability to sense and respond to changes in oxygen levels. Despite their rich blood supply, the kidneys have unique properties with respect to oxygen that enable them to act as specialised organs, sensing oxygen delivery as well as rendering them prone to hypoxic injury. Essential to normal growth and development, as well as the control of energy metabolism, angiogenesis and erythropoiesis, cellular oxygen homoeostasis is central to the pathophysiology of anaemia, ischaemia, inflammation and cancer, both within the kidney and more generally. A major transcriptional pathway, predominantly regulated by hypoxia-inducible factor (HIF), controls many hundreds of genes, either directly or indirectly, that serve to modulate both the supply and consumption of oxygen. Recent advances have illuminated the mechanisms underlying the regulation of HIF by oxygen and have defined novel therapeutic targets. The challenge now is for us to understand the complexities generated by multiple isoforms of the various components of oxygen sensing, the identification of additional levels of control, and the tissue specific responses to activation of the HIF pathway.