二氧化钛饲料添加剂与脂多糖联合作用对慢性暴露后小鼠肠道屏障功能的影响。

OBJECTIVE: Up to 44% of particulates of food-grade titanium dioxide (TiO) are in nanoscale, while the effect and combined effect of which with other substances on intestinal barrier haven't been fully understood yet. This study is aimed to study the effect of two kinds of TiO nanoparticles (TiO NPs and TiO MPs) on intestinal barrier functions, to reveal the combined effect of TiO NPs and Lipopolysaccharide (LPS) on intestinal barrier. METHODS: Male ICR mice were randomly divided into 18 groups (3 feed types * 3 exposure length * 2 LPS dosage) and were fed with normal or TiO-mixed feed (containing 1% (mass fraction, w/w) TiO NPs or TiO MPs) for 1, 3, 6 months, followed by a single oral administration of 0 or 10 mg/(kg body weight) LPS. Four hours later, the transportation of TiO, the intestinal barrier functions and the inflammatory response were evaluated. RESULTS: Both TiO notably increased the intestinal villi height / crypt depth ratios after 1 and 3 months of exposure, and increased the expression of ileal tight junction proteins (ZO-1 and occludin) after 1 month of exposure. After 6 months of exposure, TiO NPs led to reduced feed consumption, TiO MPs caused spare microvilli in small intestine and elevated Ti content in the blood cells. The intestinal permeability didn't change in both TiO exposed groups. After LPS administration, we observed altered intestinal villi height / crypt depth ratios, lowered intestinal permeability (DAO) and upregulated expression of ileal ZO-1 in both (TiO +LPS) exposed groups. There are no significant changes of ileal or serum cytokines except for a higher serum TNF-α level in LPS treated group. The antagonistic effect was found between TiO NPs and LPS, but there are complicated interactions between TiO MPs and LPS. CONCLUSION: Long-term intake of food additive TiO could alter the intestinal epithelial structure without influencing intestinal barrier function. Co-exposure of TiO and LPS would enhance intestinal barrier function without causing notable inflammatory responses, and there is antagonistic effect between TiO NPs and LPS. All the minor effects observed might associate with the gentle exposure method where TiO being ingested with feed.

目的：食品级二氧化钛（TiO）的颗粒中，有 44%可达纳米级，但其与其他物质共同作用对肠道屏障的影响尚未完全阐明。本研究旨在研究两种 TiO 纳米颗粒（TiO NPs 和 TiO MPs）对肠道屏障功能的影响，揭示 TiO NPs 与脂多糖（LPS）联合作用对肠道屏障的影响。

方法：雄性 ICR 小鼠随机分为 18 组（3 种饲料类型×3 种暴露时间×2 种 LPS 剂量），分别用正常饲料或含 1%（质量分数，w/w）TiO NPs 或 TiO MPs 的 TiO 混合饲料喂养 1、3、6 个月，随后单次口服 0 或 10 mg/（kg 体重）LPS。4 小时后，评估 TiO 的转运、肠道屏障功能和炎症反应。

结果：暴露 1 和 3 个月后，TiO 显著增加了回肠绒毛高度/隐窝深度比值，暴露 1 个月后增加了回肠紧密连接蛋白（ZO-1 和 occludin）的表达。暴露 6 个月后，TiO NPs 导致摄食量减少，TiO MPs 导致小肠微绒毛稀疏和血细胞中 Ti 含量升高。两种 TiO 暴露组的肠道通透性均无变化。LPS 处理后，我们观察到（TiO+LPS）暴露组回肠绒毛高度/隐窝深度比值改变，肠道通透性（DAO）降低，回肠 ZO-1 表达上调。除 LPS 处理组血清 TNF-α水平升高外，回肠或血清细胞因子无明显变化。TiO NPs 和 LPS 之间存在拮抗作用，但 TiO MPs 和 LPS 之间存在复杂的相互作用。

结论：长期摄入食品添加剂 TiO 可能会改变肠道上皮结构，而不会影响肠道屏障功能。TiO 和 LPS 的共同暴露会增强肠道屏障功能，而不会引起明显的炎症反应，TiO NPs 和 LPS 之间存在拮抗作用。所有观察到的轻微影响可能与 TiO 随饲料摄入的温和暴露方法有关。