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Background & Aims Postoperative ileus, an iatrogenic complication of abdominal surgery, is mediated by severe inflammation of the tunica muscularis. Macrophages that reside in the muscularis have important roles in initiating the inflammation. We investigated whether activation of the p38 mitogen-activated protein kinase (MAPK) and stress-activated protein kinase is involved in the genesis of postoperative ileus, and whether p38-MAPK inhibition by the macrophage-specific inhibitor semapimod prevents intestinal dysmotility. Methods Postoperative ileus was induced by intestinal manipulation of the small bowel in mice. Protein kinase phosphorylation was assessed by immunoblotting of muscularis externa preparations. Proinflammatory gene expression was quantified by real-time polymerase chain reaction. Myeloperoxidase histochemistry for neutrophils was performed in jejunal segments. Nitric oxide production was measured by Griess reaction in smooth-muscle organ culture supernatants. Jejunal contractility was assessed within an organ bath setup. Intestinal motility was analyzed by gastrointestinal and colonic transit measurements. Results High levels of p38-MAPK and stress-activated protein kinase phosphorylation were observed immediately after intestinal manipulation. Semapimod treatment led to a significant decrease of p38-MAPK phosphorylation in macrophages; proinflammatory gene expression of macrophage inflammatory protein-1α, interleukin-6, monocyte chemoattractant protein-1, and intercellular adhesion molecule-1; and neutrophil infiltration. Furthermore, semapimod completely abrogated nitric oxide production within the tunica muscularis. Subsequently, semapimod prevented the suppression of smooth muscle contractility and small intestinal and colonic motility after intestinal manipulation. Conclusion A single preoperative semapimod administration prevents intestinal macrophage activation and subsequent gastrointestinal dysmotility induced by abdominal surgery. Semapimod inhibits p38-MAPK and nitric oxide production in macrophages, making it a promising strategy for prophylaxis of postoperative ileus.

neuromuscular function by increasing basal tone and response to cholinergic stimulus. These effects are not reversible after short-term observation. It is known that temperature affects both the ionic conductances and the rate constants modulating the action potential propagation in giant squid axon. We hypothesize that temperature gradients, by changing the ion dynamics, could influence the electrochemical behaviour of intestinal muscle, with a memory effect which should require long time to be deleted. Further studies are needed to establish the exact involved mechanisms in order to better understand clinical consequences of hypothermia during abdominal surgery.

Hirschsprung's disease (HD) is a congenital disorder characterized by aganglionosis in the distal intestine. The zebrafish mutant, lessen (lsn), has HD phenotypic characteristics. We use the lsn mutant as an experimental model to unravel underlying developmental mechanisms for HD. This study aims to compare the neurochemical content of enteric neurons and gastrointestinal (GI)-motility patterns between wild-type zebrafish and lsn mutants to further validate this mutant as a suitable model for HD research. Immunofluorescence staining was used to detect specific neurochemical markers from 3 to 6 days post-fertilization (dpf) in the proximal (PI), mid (MI) and distal intestine (DI) of both wild-type and mutant embryos. Contractile activity of the GI-tract was filmed and the frequency and direction of contractions in each intestinal region were analyzed. Both mutant and wild-type embryos showed an increase in enteric neuron numbers over time. In mutants, the number of enteric neurons at each embryonic stage was significantly reduced in DI (absent at 3dpf) and MI, but less in PI. The proportion of nitrergic neurons was significantly reduced in all regions at 3dpf, but nearly unaffected in PI and MI at 4 and 5dpf. In mutants, serotonin, calretinin and calbindin showed a delayed expression and a decrease in both number and proportion at all points of time and in each intestinal region. In both mutant and wild-type embryos, galanin, vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP) were only detected in nerve fibers. In wild-type, VIP/PACAP-positive and galaninpositive fibers were present at all time points and in each region. Mutants only showed a few immunoreactive fibers at 3dpf in PI, while at 4dpf immunostained fibers appeared in MI and at 5dpf in DI, showing a delayed expression of these neuropeptides. GI-contractility analyses revealed that wild-type animals have defined motility patterns by 4dpf. When comparing motility patterns, the PI showed little change in when comparing wild-type to mutants. In contrast, we observed a decreased contractility in the MI and DI of mutants. The present study reveals abnormalities in the number and proportions of neurons expressing various neurochemical markers in the lsn mutant. These results are similar to previously reported data in the intestine proximal to the aganglionic segment and in the aganglionic segment of the lethal spotted mutant mice, an experimental HD model. Furthermore, in lessen GI-contractility is significantly perturbed inMI and DI. So, this study supports previous studies indicating that the zebrafish mutant lessen is a suitable model for HD research.