Decreased expression of serotonin in the jejunum and increased numbers of mast cells in the terminal ileum in patients with irritable bowel syndrome.
OBJECTIVE
To investigate if there are changes in serotonin (5-HT) levels, enterochromaffin (EC) cells and mast cells in small intestinal mucosa of patients with irritable bowel syndrome (IBS).


METHODS
Diarrhea-predominant (IBS-D, n = 20), or constipation-predominant (IBS-C, n = 18) IBS patients and healthy controls (n = 20) underwent colonoscopy and peroral small intestinal endoscopy, and mucosal samples were obtained at the descending part of the duodenum, proximal end of jejunum and terminal ileum. High-performance liquid chromatography-electrochemistry and immunohistochemical methods were used to detect 5-HT content, EC cells and mast cells.


RESULTS
(1) There were no differences in the number and distribution of EC cells between IBS patients and the normal group. (2) The mucosal 5-HT contents at the duodenum, jejunum and ileum in IBS-C patients were 182 +/- 90, 122 +/- 54, 61 +/- 35 ng/mg protein, respectively, which were all lower than those in the normal group (256 +/- 84, 188 +/- 91, and 93 +/- 45 ng/mg protein, respectively), with a significant difference at the jejunum (P < 0.05). There were no differences in the small intestinal mucosal 5-HT contents between IBS-D patients and the normal group. The mucosal 5-HT contents at the duodenum were significantly higher than those at the ileum in the three groups (P < 0.001). (3) The numbers of mast cells in patients with IBS-C and IBS-D at the ileum were 38.7 +/- 9.4 and 35.8 +/- 5.5/high power field (hpf), respectively, which were significantly more than that in the normal group (29.8 +/- 4.4/hpf) (P < 0.001). There was no significant difference in the numbers of mast cells at the other two parts between IBS patients and the normal group. The numbers of mast cells in IBS-C, IBS-D, and normal groups were all significantly higher at the ileum (38.7 +/- 9.4, 35.8 +/- 5.5, 29.8 +/- 4.4/hpf, respectively) than at the duodenum (19.6 +/- 4.7, 18.5 +/- 6.3, 19.2 +/- 3.3/hpf, respectively, P < 0.001).


CONCLUSIONS
The changes in the 5-HT signaling pathway at the jejunum of IBS-C patients and the increase in mast cells in patients with IBS at the terminal ileum may offer evidence to explain the pathogenesis of IBS.
Wang
Shen-Hao
SH
Department of Gastroenterology, Second Hospital of Xi'an Jiaotong University, 157, Xi 5 Road, Xi'an 710004, Shaanxi Province, China.
Dong
Lei
L
Luo
Jin-Yan
JY
Gong
Jun
J
Li
Lu
L
Lu
Xiao-Lan
XL
Han
Shui-Ping
SP
D000328:Adult; D000368:Aged; D004759:Enterochromaffin Cells; D005260:Female; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000473:pathology; D007421:Intestine, Small / Q000378:metabolism* / Q000473:pathology; D043183:Irritable Bowel Syndrome / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008407:Mast Cells; D008875:Middle Aged; D012701:Serotonin / Q000378:metabolism*
D012701:Serotonin