Division of General Surgery, Peking University First Hospital, Peking University, 8 Xi Shiku Street, Beijing, 100034, People's Republic of China.
Inflammation. 2015 Feb;38(1):375-83. doi: 10.1007/s10753-014-0041-9.
Lipopolysaccharide was found to be elevated in the plasma of necrotizing enterocolitis (NEC) and inflammatory bowel disease (IBD) patients and may play an important role in the pathogenesis and propagation of these intestinal diseases. To illustrate the destructive effect of lipopolysaccharide (LPS) and to test the protective effect of 1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) on LPS-induced barrier injury, an in vitro intestinal epithelia barrier model was established with Caco-2 monolayers and treated with clinically relevant concentrations (1-10 ng/ml) of LPS with or without 1,25(OH)2D3. Transepithelial electrical resistance (TEER) and FITC-Dextran 40kda (FD-40) flux were measured to reflect monolayer permeability. We found that LPS at clinically relevant concentrations increased intestinal permeability by downregulating and redistributing tight junction (TJ) proteins. 1,25(OH)2D3 added at baseline or at day 4 abrogated the destructive effect of LPS on monolayer permeability by restoring the expression and localization of TJ proteins. LPS, at clinically relevant concentrations, also downregulated the expression of vitamin D receptor (VDR); 1,25 (OH)2D3, however, could restore the expression of VDR. Our findings illustrate the mechanism underlying the destructive effect of clinically relevant concentrations of LPS on intestinal TJ barrier and provide evidence for the clinical application of vitamin D in LPS-related intestinal barrier dysfunction.
脂多糖（LPS）被发现存在于坏死性小肠结肠炎（NEC）和炎症性肠病（IBD）患者的血浆中，可能在这些肠道疾病的发病机制和传播中发挥重要作用。为了说明脂多糖（LPS）的破坏作用，并测试 1,25-二羟维生素 D3（1,25(OH)2D3）对 LPS 诱导的屏障损伤的保护作用，我们用 Caco-2 单层细胞建立了体外肠上皮屏障模型，并使用临床相关浓度（1-10ng/ml）的 LPS 进行处理，同时加入或不加入 1,25(OH)2D3。通过测量跨上皮电阻（TEER）和 FITC-葡聚糖 40kda（FD-40）通量来反映单层通透性。我们发现，LPS 在临床相关浓度下通过下调和重新分布紧密连接（TJ）蛋白来增加肠道通透性。在基线或第 4 天加入 1,25(OH)2D3 可以通过恢复 TJ 蛋白的表达和定位来消除 LPS 对单层通透性的破坏作用。LPS 在临床相关浓度下还下调了维生素 D 受体（VDR）的表达；然而，1,25(OH)2D3 可以恢复 VDR 的表达。我们的研究结果说明了临床相关浓度的 LPS 对肠道 TJ 屏障的破坏作用的机制，并为维生素 D 在 LPS 相关的肠道屏障功能障碍的临床应用提供了证据。
