These results demonstrate that upregulation of HO-1 by hemin ameliorated experimental colitis. Moreover, our study suggests a broader protective mechanism of hemin.

Heme oxygenase-1 (HO-1) is the rate-limiting enzyme of ferroheme metabolic pathway, which has the functions of anti-oxidation, anti-inflammatory, anti-apoptosis and anti-smooth muscle hyperplasia. Furthermore, HO-1 exerts a protective action in the diseases mediated by effector T lymphocytes such as T helper (Th) 1, Th2 and Th17. In addition, regulatory T cells (Treg) control the activity of CD4+CD25- effector cells in a suppressive manner. Numerous studies indicate that the protective action of HO-1 in diseases is through CD4+CD25+ Treg. This paper will review the current research and understanding of HO-1's role in T cells-mediated immunoregulation.