从肠肌间神经丛抑制性神经递质的改变探讨IBS不同亚型的发病机制

Changes in Enteric Neurons of Small Intestine in a Rat Model of Irritable Bowel Syndrome with Diarrhea

Background/Aims

Physical and/or emotional stresses are important factors in the exacerbation of symptoms in irritable bowel syndrome (IBS). Several lines of evidence support that a major impact of stress on the gastrointestinal tract occurs via the enteric nervous system. We aimed to evaluate histological changes in the submucosal plexus (SMP) and myenteric plexus (MP) of the distal ileum in concert with the intestinal motor function in a rat model of IBS with diarrhea.

Methods

The rat model was induced by heterotypic chronic and acute stress (CAS). The intestinal transit was measured by administering powdered carbon by gastric gavage. Double immunohistochemical fluorescence staining with whole-mount preparations of SMP and MP of enteric nervous system was used to assess changes in expression of choline acetyltransferase, vasoactive intestinal peptide, or nitric oxide synthase in relation to the pan neuronal marker, anti-Hu.

Results

The intestinal transit ratio increased significantly from control values of 50.8% to 60.6% in the CAS group. The numbers of enteric ganglia and neurons in the SMP were increased in the CAS group. The proportions of choline acetyltransferase- and vasoactive intestinal peptide-immunoreactive neurons in the SMP were increased (82.1 ± 4.3% vs. 76.0 ± 5.0%, P = 0.021; 40.5 ± 5.9% vs 28.9 ± 3.7%, P = 0.001), while nitric oxide synthase-immunoreactive neurons in the MP were decreased compared with controls (23.3 ± 4.5% vs 32.4 ± 4.5%, P = 0.002).

Conclusions

These morphological changes in enteric neurons to CAS might contribute to the dysfunction in motility and secretion in IBS with diarrhea.

Effect of Huangshu Enema on mast cells and substance P in rats with diarrhea-predominant irritable bowel syndrome

AIM: To evaluate the effect of Huangshu Enema (HSE) on mast cells in the ileocecal junction and levels of substance P in serum and tissue homogenate of the ileocecal junction in rats with diarrhea-predominant irritable bowel syndrome (D-IBS).

METHODS: Thirty-six female Sprague-Dawley rats were randomly divided into normal control group (n = 9), model control group (n = 9), HSE treatment group (n =9) and Dicetel treatment group (n = 9). A rat model of D-IBS was created by intracolonic instillation of acetic acid and restraint stress. The changes in the number of mast cells in the ileocecal junction of rats were evaluated by the improved Toluidine blue staining method. The contents of substance P in serum and tissue homogenate of the ileocecal junction were determined by ELISA.

RESULTS: The number of mast cells in the ileocecal junction was significantly higher in the model control group than in the normal control group (3.07 ± 0.56 vs 1.47 ± 0.26; t = 7.787, P < 0.01). The contents of substance P in serum and tissue homogenate of the ileocecal junction were significantly higher in the model control group than in the normal control group (600.38 ± 175.25 vs 181.12 ± 40.03, 194.01 ± 35.54 vs 60.01 ± 9.33; t = 6.997, t = 10.943, both P < 0.01). The number of mast cells in the ileocecal junction and the contents of substance P in serum and tissue homogenate of the ileocecal junction were significantly lower in the HSE treatment group than in the model control group (1.53 ± 0.26 vs 3.07 ± 0.56, 237.86 ± 19.75 vs 600.38 ± 175.25, 88.29 ± 5.51 vs 194.01 ± 35.54; all P < 0.01). The number of mast cells in the ileocecal junction and the content of substance P in serum had no significant difference between the HSE treatment group and the Dicetel treatment group (both P > 0.05). The content of substance P in tissue homogenate of the ileocecal junction was significantly lower in the HSE treatment group than in the Dicetel treatment group (88.29 ± 5.51 vs 135.11 ± 34.66, P < 0.05).

CONCLUSION: HSE can reduce the number of mast cells in the ileocecal junction and the contents of substance P in serum and ileocecal junction, thereby exerting a therapeutic effect on D-IBS.

Proteomic analysis of colonic mucosa in a rat model of irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most common functional disorders of the gastrointestinal tract. It is characterized by abdominal pain and changes in bowel habits. Various studies have investigated the pathophysiologic processes underlying IBS, but the mechanism remains poorly understood. In the present study, we established an IBS model and identified differentially expressed proteins in colon tissue of IBS rats compared with healthy controls by 2-D gel electrophoresis, MALDI-TOF-MS, and Western blot analysis. Our results showed that 13 of the 1396 protein spots on 2-D gel were differently expressed between the IBS and control groups. Ontological analysis of these proteins revealed primary roles in catalytic activity (protein disulfide-isomerase A3, glyoxalase I, cathepsin S, alpha-enolase), structural support (cytokeratin 8), antioxidant activity (peroxiredoxin-6), protein binding (transgelin, serpin peptidase inhibitor B5), and signal transduction (40S ribosomal protein SA). Protein disulfide-isomerase A3 and cytokeratin 8 overexpression in IBS were confirmed by Western blot. The findings indicate that multiple proteins are involved in IBS processes that influence intestinal tract immunity, inflammation, and nerve regulation. Our study provides useful candidate genes and proteins for further investigation.