Departments of Nutrition and Environmental Toxicology, University of California, Davis, CA, USA.
Departments of Nutrition and Environmental Toxicology, University of California, Davis, CA, USA; Fisicoquímica, Facultad de Farmacia y Bioquímica, Instituto de Bioquímica y Medicina Molecular (IBIMOL), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina.
Redox Biol. 2020 Jan;28:101360. doi: 10.1016/j.redox.2019.101360. Epub 2019 Oct 22.
Secondary bile acids promote gastrointestinal (GI) tract permeabilization both in vivo and in vitro. Consumption of high fat diets increases bile acid levels in the GI tract which can contribute to intestinal permeabilization and consequent local and systemic inflammation. This work investigated the mechanisms involved in bile acid (deoxycholic acid (DCA))-induced intestinal epithelial cell monolayer permeabilization and the preventive capacity of (-)-epicatechin (EC). While EC prevented high fat diet-induced intestinal permeabilization in mice, it did not mitigate the associated increase in fecal/cecal total and individual bile acids. In vitro, using differentiated Caco-2 cells as a model of epithelial barrier, EC and other NADPH oxidase inhibitors (VAS-2870 and apocynin) mitigated DCA-induced Caco-2 monolayer permeabilization. While EC inhibited DCA-mediated increase in cell oxidants, it did not prevent DCA-induced mitochondrial oxidant production. Prevention of DCA-induced ERK1/2 activation with EC, VAS-2870, apocynin and the MEK inhibitor U0126, also prevented monolayer permeabilization, stressing the key involvement of ERK1/2 in this process and its redox regulation. Downstream, DCA promoted myosin light chain (MLC) phosphorylation which was related to MLC phosphatase (MLCP) inhibition by ERK1/2. DCA also decreased the levels of the tight junction proteins ZO-1 and occludin, which can be related to MMP-2 activation and consequent ZO-1 and occludin degradation. Both events were prevented by EC, NADPH oxidase and ERK1/2 inhibitors. Thus, DCA-induced Caco-2 monolayer permeabilization occurs mainly secondary to a redox-regulated ERK1/2 activation and downstream disruption of TJ structure and dynamic. EC's capacity to mitigate in vivo the gastrointestinal permeabilization caused by consumption of high-fat diets can be in part related to its capacity to inhibit bile-induced NADPH oxidase and ERK1/2 activation.
次级胆汁酸在体内和体外均可促进胃肠道（GI）道通透性。高脂饮食会增加 GI 道中的胆汁酸水平，这可能导致肠道通透性增加，并进而导致局部和全身炎症。本研究旨在探讨胆汁酸（脱氧胆酸（DCA））诱导的肠道上皮细胞单层通透性的机制，以及（-）-表儿茶素（EC）的预防能力。虽然 EC 可预防高脂肪饮食诱导的小鼠肠道通透性，但它不能减轻相关的粪便/盲肠总胆汁酸和个体胆汁酸的增加。在体外，使用分化的 Caco-2 细胞作为上皮屏障模型，EC 和其他 NADPH 氧化酶抑制剂（VAS-2870 和 apocynin）可减轻 DCA 诱导的 Caco-2 单层通透性。虽然 EC 抑制了 DCA 介导的细胞氧化剂增加，但它不能防止 DCA 诱导的线粒体氧化剂产生。用 EC、VAS-2870、apocynin 和 MEK 抑制剂 U0126 预防 DCA 诱导的 ERK1/2 激活，也可防止单层通透性，这强调了 ERK1/2 在该过程及其氧化还原调节中的关键作用。下游，DCA 促进肌球蛋白轻链（MLC）磷酸化，这与 ERK1/2 抑制 MLC 磷酸酶（MLCP）有关。DCA 还降低了紧密连接蛋白 ZO-1 和闭合蛋白的水平，这可能与 MMP-2 激活和随后的 ZO-1 和闭合蛋白降解有关。这两种情况都被 EC、NADPH 氧化酶和 ERK1/2 抑制剂所阻止。因此，DCA 诱导的 Caco-2 单层通透性的发生主要是由于氧化还原调节的 ERK1/2 激活以及随后 TJ 结构和动态的破坏。EC 减轻高脂肪饮食引起的胃肠道通透性的能力，部分可能与其抑制胆汁诱导的 NADPH 氧化酶和 ERK1/2 激活的能力有关。
