Background & Aims

Irritable bowel syndrome (IBS) is associated with intestinal dysbiosis and symptoms of IBS develop following gastroenteritis. We aimed to study the passage of live bacteria through the colonic epithelium, and determine the role of mast cells (MCs) and vasoactive intestinal polypeptide (VIP) in barrier regulation in IBS and healthy individuals.

Methods

Colon biopsies from 32 women with IBS and 15 age-matched healthy women (controls) were mounted in Ussing chambers; we measured numbers of fluorescently labeled Escherichia coli HS and Salmonella typhimurium that passed through from the mucosal side to the serosal side of the tissue. Some biopsies were exposed to agents that block the VIP receptors (VPAC1 and VPAC2) or MCs. Levels of VIP and tryptase were measured in plasma and biopsy lysates. Number of MCs and MCs that express VIP or VIP receptors were quantified by immunofluorescence. Biopsies from an additional 5 patients with IBS and 4 controls were mounted in chambers and Salmonella were added; we studied passage routes through the epithelium by transmission electron microscopy and expression of tight junctions by confocal microscopy.

Results

In colon biopsies from patients with IBS, larger numbers of E coli HS and S typhimurium passed through the epithelium than in biopsies from controls (P < .0005). In transmission electron microscopy analyses, bacteria were found to cross the epithelium via only the transcellular route. Bacterial passage was reduced in biopsies from patients with IBS and controls after addition of antibodies against VPACs or ketotifen, which inhibits MCs. Plasma samples from patients with IBS had higher levels of VIP than plasma samples from controls. Biopsies from patients with IBS had higher levels of tryptase, larger numbers of MCs, and a higher percentage of MCs that express VPAC1 than biopsies from controls. In biopsies from patients with IBS, addition of Salmonella significantly reduced levels of occludin; subsequent addition of ketotifen significantly reversed this effect.

Conclusions

We found that colonic epithelium tissues from patients with IBS have increased translocation of commensal and pathogenic live bacteria compared with controls. The mechanisms of increased translocation include MCs and VIP.

中文翻译：

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肠易激综合征患者血管活性肠多肽和肥大细胞调节结肠细菌的通过增加

背景与目标

肠易激综合症（IBS）与肠道营养不良有关，肠胃炎后会出现IBS症状。我们旨在研究活细菌通过结肠上皮的传播，并确定肥大细胞（MCs）和血管活性肠多肽（VIP）在IBS和健康个体的屏障调节中的作用。

方法

将32例IBS妇女和15例年龄相匹配的健康妇女（对照组）的结肠活检安装在Ussing室中。我们测量了荧光标记的大肠杆菌HS和鼠伤寒沙门氏菌的数量从组织的粘膜侧穿过到浆膜侧。一些活组织检查暴露于阻断VIP受体（VPAC1和VPAC2）或MC的药物。在血浆和活检裂解物中测量VIP和类胰蛋白酶的水平。通过免疫荧光定量表达VIP或VIP受体的MC和MC的数量。将另外5例IBS患者和4例对照患者的活组织检查安装在小室中，并添加沙门氏菌。我们通过透射电子显微镜研究了上皮的通过途径，并通过共聚焦显微镜研究了紧密连接的表达。

结果

在IBS患者的结肠活检中，穿过上皮的大肠杆菌HS和鼠伤寒沙门氏菌数量要比对照活检中的数量大（P<.0005）。在透射电子显微镜分析中，发现细菌仅通过跨细胞途径穿过上皮。添加抗VMC的抗VPAC或酮替芬的抗体后，IBS和对照患者的活检中细菌传代减少。IBS患者的血浆样品的VIP含量高于对照组的血浆样品。与对照组的活检相比，IBS患者的活检具有较高的类胰蛋白酶水平，大量的MC和表达VPAC1的MC百分比较高。在IBS患者的活检中，沙门氏菌的添加显着降低了闭合蛋白的水平。随后加入酮替芬可显着逆转此效应。

结论

我们发现，与对照组相比，IBS患者的结肠上皮组织的共生和致病性活细菌易位增加。易位的机制包括MC和VIP。