Beneficial effects of the heme oxygenase-1/carbon monoxide system

It has been reported that the blood level of carboxyhemoglobin (CO-Hb) is increased in critically ill patients such as those with sepsis or multiple trauma [1,2]. Because carbon monoxide (CO) is one of the metabolites of heme catabolism, it has been suggested that there may be increased breakdown of heme in these patients. Heme oxygenase (HO) is the enzyme involved in the rate-limiting step for catabolism of heme-containing proteins. It was recently reported that HO-1 acts as a potent anti-inflammatory agent and antioxidant through its products [3]. HO-1 may therefore be an inducible defense against cellular stress that occurs during the inflammatory process [1,4]. Against this background, we decided to evaluate the relation among the blood level of CO, HO-1 expression by monocytes, oxidative stress, and the outcome of sepsis.