Heme oxygenase (HO-1) enzyme controls the initial and rate-limiting step in heme catabolism, cleaving heme to biliverdine then to bilirubin. Iron is released when the heme ring is opened, while CO is liberated. Therefore, HO enzyme down-regulates all cellular homoproteins. Heme molecule plays a centarl role in diverse biological processes in different systems, in cell respiration, energy generation, growth differentiation processes, oxidative biotransformation and generating inflammatory mediators as eicosaoids and NO synthase (NOS) .The finding of high-level expression of HO-2 in cell populations not involved in haemoglobin heme degradation, such as neurons and germ cells, led to the suggestion that it has function(s) aside from heme degradation.