[Heme oxygenase-1 - more than the cytoprotection]

Heme oxygenase-1 (HO-1) is an enzyme degrading heme to three products - ferrous ions, carbon monoxide and biliverdin. Its function extends, however, far beyond removal of pro-oxidative heme from microenvironment. During the last few decades it was proven that apart from cytoprotective and antioxidative properties HO-1 regulates also a variety of cellular processes. It exerts an impact on both innate and adaptive immune response. HO-1 accelerates development of new blood vessels in a process called angiogenesis. Moreover, it controls cell cycle and depending on a cell type increases or decreases the rate of cell division. Finally, the most recent data indicate, that HO-1 regulates also differentiation of various stem and progenitor cells. Interestingly, that aspect of HO-1 function seems also to depend on cell type. In this review, both effects and mechanisms of above-mentioned processes in different cell types are discussed.