Hemin reduces postoperative ileus in a heme oxygenase 1-dependent manner while dimethyl fumarate does without heme oxygenase 1-induction.

Background Postoperative ileus (POI), the impairment of gastrointestinal motility after abdominal surgery, is mainly due to intestinal muscular inflammation. Carbon monoxide (CO)-releasing compounds were shown to exert an anti-inflammatory effect in murine POI partially through induction of heme oxygenase-1 (HO-1). The influence of hemin and dimethyl fumarate (DMF), currently used for multiple sclerosis (MS), was therefore tested in murine POI. Methods C57BL/6J mice were anesthetized and after laparotomy, POI was induced via intestinal manipulation (IM). Animals were treated with either 30 mg kg(-1) hemin intraperitoneally (ip), 30 mg kg(-1) DMF ip, or 100 mg kg(-1) intragastrically (ig) 24 hours before IM. Intestinal transit was assessed 24 hours postoperatively and mucosa-free muscularis or whole segments of the small intestine were stored for later analysis. Intestinal HO-1 protein expression was studied at 6, 12, and 24 hours after administration of hemin or DMF in non-manipulated mice. Key results Pretreatment with hemin and DMF, both ig and ip, prevented the delayed transit seen after IM. Concomitantly, both hemin and DMF significantly reduced the increased interleukin-6 levels and the elevated leukocyte infiltration in the muscularis. Hemin but not DMF caused a significant increase in intestinal HO-1 protein expression and co-administration of the HO-1 inhibitor chromium mesoporphyrin abolished the protective effects of hemin on POI; DMF reduced the IM-induced activation of NF-kappa B and ERK 1/2. Conclusions and Inferences Both hemin and DMF improve the delayed transit and inflammation seen in murine POI, but only hemin does so in a HO-1-dependent manner.