| Objective: To investigate the expression of aquaporin-8 (AQP8) and Vasoactive Intestinal Peptide(VIP), somatostatin (SS) protein in human colonic mucosa with irritable bowel syndrome(IBS), and elucidate their possible roles in the pathogenesis of IBSMethods: Based on Romeâ…¢criteria, 56 IBS patients, including 31 IBS-D, 25 IBS-C and 15 healthy subjects were enrolled from November 2006 to February 2007 in Shanxi Provincial People's Hospital in the study. The expression of AQP8mRNA in colonic mucosa was measured by transcription polymerase chain reaction(RT-PCR), and AQP8,VIP,SS in ascend and descend colonic mucosa were measured by immunohistochemistry(IHC).Results:1. There were all expression of AQP8 in human colonic mucosa with IBS and normal group. AQP8 was strongly expressed in the apical membrane and the basolateral membrane, and there was litter expression in cytoplasm in colonic epithelial cells.2. There were all expression of AQP8 in ascend and descend colonic mucosa with IBS-D, IBS-C and normal group. Compared with normal control group, the level of AQP8 in IBS-D was significantly reduced and the level of AQP8 in IBS-C was obviously increased(p<0.05), and the expression of AQP8 in IBS-C group was significantly higher than that of the IBS-D group(p<0.05). However, there was no significant difference in ascend and descend colonic mucosa of normal group and IBS-C group(p>0.05). only in IBS-D group, the expression of AQP8 of the ascend colon was significantly higher than that of the descending colon(p<0.05).3. There were all expression of the gut hormone of VIP, SS in human ascend and descend colonic mucosa with IBS and normal group. VIP and SS was mainly expressed in the endocrine cells of the mucous layer and lamina propria of the colonic mucosa.4. There were all expression of VIP in ascend and descend colonic mucosa with IBS-D, IBS-C and normal group. Compared with normal control group, the level of VIP in IBS-D and IBS-C were all significantly increased(p<0.05), and the expression of VIP in IBS-C group was significantly higher than that of the IBS-D group(p<0.05). However, there was no significant difference in ascend and descend colonic mucosa of each group(p>0.05).5. There were all expression of SS in ascend and descend colonic mucosa with IBS-D, IBS-C and normal group. Compared with normal control group, the leyel of SS in IBS-C was significantly increased(p<0.05), the expression of SS in IBS-C group was significantly higher than that of the IBS-D group and normal group(p<0.05), and the level of SS in IBS-D was only slightly increased but not significantly in IBS-D group(p>0.05). However, there was also no significant difference in ascend and descend colonic mucosa of each group(p>0.05).Conclusion:1,There were all expression of AQP8, VIP and SS in human ascend and descend colonic mucosa with IBS and normal group.2,AQP8 may play a major role in water movement through the colonic epithelial cells, and probably involve in the regulation of water in colonic mucosa with IBS. The change of the AQP8 may be one of the factors which result in diarrhea or constipation in IBS.3,The gut hormones including VIP and SS may play an important role in the pathogenesis of IBS. It is probably becoming new proof for the neuro-endocrine-immune network regulation theory.
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