State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao, China; and Zhuhai UM Science & Technology Research Institute, Zhuhai, China.
State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao, China; and Zhuhai UM Science & Technology Research Institute, Zhuhai, China
Drug Metab Dispos. 2018 Mar;46(3):292-302. doi: 10.1124/dmd.117.079046. Epub 2018 Jan 8.
UDP-glucuronosyltransferase 1A1 (UGT1A1) constitutes an important part of intestinal epithelial barrier and catalyzes glucuronidation of many endogenous compounds and drugs. Downregulation of UGT1A1 in inflammation has been reported, whereas the association with gut dysbiosis is poorly defined. This study verified the involvement of gut microbiota in intestinal UGT1A1 regulation using dextran sulfate sodium (DSS)-induced rat colitis model plus fecal microbiota transplantation (FMT). Generally, both DSS induction and colitis-to-normal FMT suppressed mRNA and protein expressions of UGT1A1 and nuclear xenobiotic receptors (NRs) in colon, but enhanced mRNA and decreased protein of rat UGT1A1/rat NRs in small intestine. Normal-to-colitis FMT alleviated DSS-induced changes. Bacterial outer membrane vesicles (OMVs) from colitis rats and rats receiving colitis feces reduced both mRNA and protein of human UGT1A1 (hUGT1A1)/human NRs (hNRs) in Caco-2 cells. Interestingly, using deoxycholate to reduce lipopolysaccharide, normal OMVs upregulated hUGT1A1/hNRs, whereas colitis OMVs decreased, indicating the involvement of other OMVs components in UGT1A1 regulation. The 10- to 50-kDa fractions from both normal and colitis OMVs downregulated hUGT1A1, human PXR, and human PPAR-, whereas >50-kDa fractions from normal rats upregulated hUGT1A1 and human CAR. Additionally, the conditioned medium from OMVs-stimulated rat primary macrophages also reduced hUGT1A1/hNRs expression. Both Toll-like receptor (TLR)2 and TLR4 were activated by DSS, colitis-to-normal FMT, and the opposite, whereas only TLR4 was increased in OMVs-treated cells. TLR4 small interfering RNA blocked hUGT1A1/hNRs downregulation and phosphatidylinositol 3-kinase/Akt, extracellular signal-regulated kinase, and nuclear factor B phosphorylation evoked by bacterial OMVs. Taken together, this study demonstrated that gut microbiota regulate intestinal UGT1A1 partially through secreting OMVs, which interact with intestinal epithelial cells directly or via activating macrophage.
UDP-葡糖醛酸基转移酶 1A1（UGT1A1）是肠道上皮屏障的重要组成部分，可催化许多内源性化合物和药物的葡醛酸化。已有报道称，UGT1A1 在炎症中下调，但其与肠道菌群失调的关联尚不清楚。本研究使用葡聚糖硫酸钠（DSS）诱导的大鼠结肠炎模型加粪便微生物群移植（FMT）验证了肠道微生物群在肠道 UGT1A1 调节中的作用。通常，DSS 诱导和结肠炎到正常 FMT 均抑制了结肠中 UGT1A1 和核异生素受体（NRs）的 mRNA 和蛋白表达，但增强了小肠中大鼠 UGT1A1/大鼠 NRs 的 mRNA 并降低了其蛋白。正常到结肠炎 FMT 减轻了 DSS 诱导的变化。结肠炎大鼠和接受结肠炎粪便的细菌外膜囊泡（OMVs）降低了 Caco-2 细胞中人类 UGT1A1（hUGT1A1）/人类 NRs（hNRs）的 mRNA 和蛋白。有趣的是，使用去氧胆酸钠降低脂多糖后，正常 OMVs 上调了 hUGT1A1/hNRs，而结肠炎 OMVs 下调了 hUGT1A1/hNRs，表明 UGT1A1 调节中涉及其他 OMVs 成分。来自正常和结肠炎 OMVs 的 10-50kDa 馏分下调了 hUGT1A1、人 PXR 和人 PPAR-，而来自正常大鼠的>50kDa 馏分上调了 hUGT1A1 和人 CAR。此外，来自 OMVs 刺激的大鼠原代巨噬细胞的条件培养基也降低了 hUGT1A1/hNRs 的表达。DSS、结肠炎到正常 FMT 以及相反情况下均激活了 Toll 样受体（TLR）2 和 TLR4，而 OMVs 处理的细胞中仅 TLR4 增加。TLR4 小干扰 RNA 阻断了细菌 OMVs 引起的 hUGT1A1/hNRs 下调以及磷酸肌醇 3-激酶/Akt、细胞外信号调节激酶和核因子 B 磷酸化。综上所述，本研究表明肠道微生物群通过分泌 OMVs 部分调节肠道 UGT1A1，这些 OMVs 直接或通过激活巨噬细胞与肠道上皮细胞相互作用。
