Inducible NOS And Interstitial Cells Of Cajal Play Important Role In Postoperative Ileus In Rats

Background：Postoperative ileus (POI), which prevent the postoperative rehabilitation, is a verycommon gastrointestinal motility disordered with various duration from2days to7days oreven more. The pathophysiological mechanism of POI is not completely clear, but it hasclose relationship with anesthesia, surgical trauma, stress, drugs and postoperative pain.Recent studies have found that postoperative gastrointestinal inflammation, especially theinflammatory mediators, play a key role in the continuation of POI.It has been shown that, during the POI, the expression of inducible nitric oxidesynthase (iNOS) is upregulated due to the activation of macrophages, which producesexcessive nitric oxide (NO) have relationship with gastrointestinal motility abnormalities.NO is one of the most important inhibitory neurotransmitter in enteric nervoussystem(ENS), which plays an important role in the regulation of gastrointestinal motility.NO has to bind with soluble guanylate cyclase (sGC) producing cGMP to induce a series ofbiological effects. It has been reported recently that interstitial cells of Cajal(ICC) isimmunoreaction positive for sGC, and this implied that ICC could be one of the primarytarget cells of NO.ICC is the pacemaker cell of slow wave in the gastrointestinal tract. Its processesformed network structure widely distributing in gastrointestinal tract. ICC is locatedbetween ENS and smooth muscle cells (SMC). It is believed that ICC plays an importantrole in the neurotransmission of ENS signal. In many inflammatory gastrointestinaldiseases such as ulcerative colitis, Crohn’s disease, the morphology and amount of ICC isabnormal in the intestinal lamina muscularis. Animal experiments in the mechanicalintestinal obstruction also found that the amount of ICC in the proximal intestine isabnormal. However during POI, the change of ICC in the intestine isn’t reported until now.whether it is due to excessive NO production is unknown. Based on the above, we hypothesized that the expression of NO is upregulated byiNOS during POI, which in turn result in abnormality of ICC, leading to intestinal motilitydysfunction. To protect ICC function through blocking the NO signal pathway, which mayprevent POI in the future.Objective: To establish the POI rat models, detect the gastrointestinal motility in ratmodels with POI; To investigate the distribution and expression of iNOS and ICC in smallintestine; To observe the ICC changes and intestinal motility after administration iNOSinhibitor in POI rats. To explore the mechanism of iNOS and ICC in the POI.Method：1. Establishment of the POI rat models. Detection of the gastrointestinal transitfunction.2. The distribution of intestinal iNOS and c-kit(ICC specific marker) immunoreactivitywere observed by immunohistochemistry in small intestine. Real time RT-PCR techniquewas employed to determine the expression of iNOS and c-kit mRNA.3. After administration of iNOS inhibitor, the gastrointestinal transit rate was measured,and the distribution of intestinal iNOS and c-kit immunoreactivity were examined byimmunohistochemistry, and the expression of iNOS and c-kit mRNA were studied by realtime RT-PCR technique.Result：1. The gastrointestinal transit study showed that the gastrointestinal transit rate in POImodel rats significantly decreased when compared with the control rats(P <0.05).2. Immunohistochemical results displayed that, the iNOS immune positive reaction isnegative in the small intestine in control rats, while it is significantly increased in the smallintestine in POI rats (P<0.05), which mainly distribute in the mucosa and submucosa layer.The c-kit positive cells mainly distribute in the circular muscle layer, longitudinal musclelayers, myenteric plexus and submucosa layer. Compared with the control group, the c-kitimmunoreactivity is significantly decreased in the POI models(P<0.05).3. Real time RT-PCR results showed that, compared with the control group, theexpression of c-kit mRNA in small intestine in POI rats were significantly reduced (P <0.05), while the expression of iNOS mRNA were significantly enhanced (P <0.05).4. After application of iNOS inhibitor, the gastrointestinal transit rate were significantly increased compared with the POI model rats (P<0.05); Immunohistochemicalstudy displayed that, comparison with the POI rats, the immunoreactivity of iNOSsignificantly decreased (P<0.05), while the c-kit increased (P <0.05); Real time RT-PCRresults displayed that, after application of iNOS inhibitor, the small intestine iNOS mRNAexpression significantly decreased, while the c-kit mRNA expression were significantlyincreased (P <0.05).Conclusion：1. The gastrointestinal transit rate in POI rats are much lower than the control rats; Theexpression of iNOS in the POI rats increased, while c-kit expression decreased, whichindicate that the abnormal change of iNOS and ICC may play an important role in thegastrointestinal motility abnormalities of POI.2. After application iNOS inhibitor in POI, the gastrointestinal transit rate weresignificantly increased. The iNOS expression were significantly reduced in POI, while thec-kit expression were increased. This indicate that the iNOS overexpression can lead toabnormal ICC distribution, the alteration of iNOS and ICC plays an important role in thegastrointestinal motility dysfunction in POI. Inhibition of NO pathways can promote therecovery of ICC number and morphology, which is one potential method of the clinicalprevention and treatment of POI gastrointestinal motility disorder.