Peroxisome Proliferator-Activated Receptor γ Activation Alleviates Postoperative Ileus in Mice by Inhibition of Egr-1 Expression and Its Downstream Target Genes

Postoperative ileus, a major cause of morbidity after abdominal surgery, is characterized by intestinal dysmotility and a complex inflammatory cascade within the intestinal muscularis. Treatment with carbon monoxide (CO)—inhaled or intraperitoneal—has been shown to ameliorate bowel dysmotility caused by surgical manipulation of the gut in experimental animals. Recent evidence indicates that CO exerts its anti-inflammatory effects through the induction of peroxisome proliferator-activated receptor (PPAR)-γ, a nuclear receptor whose activation has been linked to several physiological pathways, including those related to the regulation of intestinal inflammation. The purpose of this study was to evaluate pharmacological activation of PPARγ in a murine model of postoperative ileus by use of the PPARγ agonist rosiglitazone. Postoperative bowel dysmotility was induced by surgical manipulation of the colon. The functional severity of postoperative ileus was significantly ameliorated in mice pretreated with rosiglitazone (0.3 to 10 mg/kg i.p.); this was associated with a down-regulation of pro-inflammatory cytokines/chemokines, inducible nitric oxide synthase activity, cyclooxygenase-2 activity, as well as a decrease in leukocyte recruitment into the muscularis of both colon and jejunum. These anti-inflammatory effects were preceded by a PPARγ-dependent down-regulation of early growth response (Egr)-1, a key regulator of inflammatory gene expression. In conclusion, these results indicate that rosiglitazone significantly attenuates postoperative ileus in mice by suppression of the muscularis inflammatory cascade through a PPARγ-dependent down-regulation of Egr-1 and encourage the further clinical evaluation of synthetic PPARγ agonists as pharmacological tool to prevent this postoperative event.