Enterotoxigenic Bacteroides fragilis (ETBF) is a commensal bacterium of great importance to human health due to its ability to induce colitis and cause colon tumor formation in mice through the production of B. fragilis toxin (BFT). The formation of tumors is dependent on a pro‐inflammatory signaling cascade, which begins with the disruption of epithelial barrier integrity through cleavage of E‐cadherin. Here, we show that BFT increases levels of glucosylceramide, a vital intestinal sphingolipid, both in mice and in colon organoids (colonoids) generated from the distal colons of mice. When colonoids are treated with BFT in the presence of an inhibitor of glucosylceramide synthase (GCS), the enzyme responsible for generating glucosylceramide, colonoids become highly permeable, lose structural integrity, and eventually burst, releasing their contents into the extracellular matrix. By increasing glucosylceramide levels in colonoids via an inhibitor of glucocerebrosidase (GBA, the enzyme that degrades glucosylceramide), colonoid permeability was reduced, and bursting was significantly decreased. In the presence of BFT, pharmacological inhibition of GCS caused levels of tight junction protein 1 (TJP1) to decrease. However, when GBA was inhibited, TJP1 levels remained stable, suggesting that BFT‐induced production of glucosylceramide helps to stabilize tight junctions. Taken together, our data demonstrate a glucosylceramide‐dependent mechanism by which the colon epithelium responds to BFT.

中文翻译：

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葡萄糖神经酰胺的产生维持结肠完整性以响应脆弱拟杆菌毒素诱导的结肠上皮细胞信号传导

产肠毒素脆弱拟杆菌 (ETBF) 是一种对人类健康非常重要的共生细菌，因为它能够通过产生脆弱拟杆菌毒素 (BFT) 在小鼠中诱发结肠炎并导致结肠肿瘤形成。肿瘤的形成依赖于促炎信号级联反应，该级联反应始于通过 E-钙粘蛋白的切割破坏上皮屏障的完整性。在这里，我们展示了 BFT 增加了小鼠和小鼠远端结肠产生的结肠类器官（类结肠）中葡萄糖神经酰胺（一种重要的肠道鞘脂）的水平。当在存在葡萄糖神经酰胺合酶 (GCS) 抑制剂（负责产生葡萄糖神经酰胺的酶）的情况下用 BFT 处理结肠样时，结肠样变得高度渗透，失去结构完整性，并最终破裂，将它们的内容物释放到细胞外基质中。通过葡糖脑苷脂酶（GBA，一种降解葡糖神经酰胺的酶）抑制剂增加结肠样中的葡糖神经酰胺水平，结肠样通透性降低，爆裂显着降低。在存在 BFT 的情况下，GCS 的药理学抑制导致紧密连接蛋白 1 (TJP1) 的水平降低。然而，当 GBA 被抑制时，TJP1 水平保持稳定，这表明 BFT 诱导的葡萄糖神经酰胺的产生有助于稳定紧密连接。总之，我们的数据证明了结肠上皮对 BFT 反应的葡萄糖神经酰胺依赖性机制。结肠样通透性降低，爆裂明显减少。在存在 BFT 的情况下，GCS 的药理学抑制导致紧密连接蛋白 1 (TJP1) 的水平降低。然而，当 GBA 被抑制时，TJP1 水平保持稳定，这表明 BFT 诱导的葡萄糖神经酰胺的产生有助于稳定紧密连接。总之，我们的数据证明了结肠上皮对 BFT 反应的葡萄糖神经酰胺依赖性机制。结肠样通透性降低，爆裂明显减少。在存在 BFT 的情况下，GCS 的药理学抑制导致紧密连接蛋白 1 (TJP1) 的水平降低。然而，当 GBA 被抑制时，TJP1 水平保持稳定，这表明 BFT 诱导的葡萄糖神经酰胺的产生有助于稳定紧密连接。总之，我们的数据证明了结肠上皮对 BFT 反应的葡萄糖神经酰胺依赖性机制。