Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Mizuho-ku, Nagoya, Japan.
J Physiol. 2024 Oct;602(19):4803-4820. doi: 10.1113/JP286258. Epub 2024 Sep 17.
Upon epithelial barrier dysfunction, lipopolysaccharide (LPS) stimulates glucagon-like peptide-1 (GLP-1) secretion from enteroendocrine L cells by activating Toll-like receptor 4 (TLR4). Because GLP-1 accelerates peristalsis in the proximal colon, the present study aimed to explore whether LPS facilitates colonic peristalsis by stimulating L cell-derived GLP-1 release. In isolated segments of rat proximal colon that were serosally perfused with physiological salt solution and luminally perfused with 0.9% saline, peristaltic wall motion was video recorded and converted into spatio-temporal maps. Fluorescence immunohistochemistry was also carried out. Intraluminal administration of LPS (100 or 1 µg mL but not 100 ng mL) increased the frequency of oro-aboral propagating peristaltic contractions. The LPS-induced acceleration of colonic peristalsis was blocked by TAK-242 (the TLR4 antagonist), exendin-3 (the GLP-1 receptor antagonist) or BIBN4096 (the calcitonin gene-related peptide receptor antagonist). GLP-1-positive epithelial cells co-expressed TLR4 immunoreactivity. In aspirin-pretreated preparations where epithelial barrier function had been impaired, a lower dose of LPS (100 ng mL) became capable of accelerating peristalsis. By contrast, luminally applied dimethyl sulphoxide, a reactive oxygen species scavenger that protects epithelial integrity, attenuated the prokinetic effects of a higher dose of LPS (100 µg mL). In colonic segments of a stress rat model leading to a leaky gut, LPS induced more pronounced prokinetic effects. Colonic L cells may well sense luminal LPS via TLR4 triggering the release of GLP-1 that stimulates calcitonin gene-related peptide-containing neurons. The resultant acceleration of peristalsis would facilitate excretion of Gram-negative bacteria from the intestine, and thus L cells may have a protective role against intestinal bacterial infections. KEY POINTS: Colonic epithelial cells form a barrier against bacterial invasion but also may contribute more actively to the exclusion of luminal pathogen by stimulating colonic motility. Luminal lipopolysaccharide (LPS) accelerated colonic peristalsis by stimulating calcitonin gene-related peptide-containing neurons. The prokinetic effect of LPS was mediated by the secretion of glucagon-like peptide-1 from enteroendocrine L cells in which Toll-like receptor 4 was expressed. The LPS-mediated acceleration of peristalsis depended on epithelial barrier integrity. L cells have a defensive role against Gram-negative bacterial infections by facilitating faecal excretion, and could be a potential therapeutic target for gastrointestinal infections.
在肠上皮屏障功能障碍的情况下，脂多糖（LPS）通过激活 Toll 样受体 4（TLR4）从肠内分泌 L 细胞中刺激胰高血糖素样肽-1（GLP-1）的分泌。由于 GLP-1 加速了近端结肠的蠕动，因此本研究旨在探讨 LPS 是否通过刺激 L 细胞衍生的 GLP-1 释放来促进结肠蠕动。在用生理盐水经浆膜腔灌注并经腔用 0.9%生理盐水灌注的大鼠近端结肠分离段上，视频记录蠕动壁运动，并将其转换为时空图谱。还进行了荧光免疫组织化学检查。腔内给予 LPS（100 或 1μg mL，但不是 100ng mL）可增加口-肛传播蠕动收缩的频率。TLR4 拮抗剂 TAK-242、GLP-1 受体拮抗剂 exendin-3 或降钙素基因相关肽受体拮抗剂 BIBN4096 阻断了 LPS 诱导的结肠蠕动加速。GLP-1 阳性上皮细胞共表达 TLR4 免疫反应性。在预先用阿司匹林处理的制剂中，上皮屏障功能受损，较低剂量的 LPS（100ng mL）即可加速蠕动。相比之下，腔内给予二甲亚砜，一种可保护上皮完整性的活性氧清除剂，可减弱较高剂量 LPS（100μg mL）的促动力作用。在导致漏肠的应激大鼠模型的结肠段中，LPS 引起更明显的促动力作用。结肠 L 细胞很可能通过 TLR4 触发 GLP-1 的释放来感知腔内容 LPS，从而刺激含有降钙素基因相关肽的神经元。由此产生的蠕动加速将有助于从肠道中排出革兰氏阴性菌，因此 L 细胞可能在防止肠道细菌感染方面具有保护作用。关键点：结肠上皮细胞形成了针对细菌入侵的屏障，但通过刺激结肠蠕动，也可以更积极地有助于将腔内容物病原体排出。腔内容 LPS 通过刺激含有降钙素基因相关肽的神经元来加速结肠蠕动。LPS 的促动力作用是通过表达 Toll 样受体 4 的肠内分泌 L 细胞分泌胰高血糖素样肽-1介导的。LPS 介导的蠕动加速取决于上皮屏障完整性。L 细胞通过促进粪便排泄在防止革兰氏阴性细菌感染方面具有防御作用，并且可能是胃肠道感染的潜在治疗靶点。
