肠道屏障在维持稳态中起着关键作用，通常由机械屏障、化学屏障、免疫屏障和生物屏障组成。然而，铅（Pb）对禽鸟肠道屏障的影响仍不清楚。因此，本研究旨在确定铅对一种生物模型——日本鹌鹑（Coturnix japonica）回肠屏障的毒性作用。一周龄的鹌鹑暴露在0、50、500和1000 ppm铅的饮用水中，持续5周。结果表明，回肠的机械屏障受到破坏，表现为上皮细胞脱落、绒毛收缩、杯状细胞减少，以及线粒体肿胀、紧密连接模糊和微绒毛减少等超微结构变化。与此同时，Pb处理组的肠紧密连接相关基因表达下调，表明紧密连接功能障碍。此外，少量粘液和粘液蛋白2（Muc2）和Kruppel-like factor 4（Klf4）表达下调表明化学屏障受到Pb干扰。此外，微生物多样性的改变和病原菌的出现表明Pb干扰了回肠的生物屏障。此外，Pb通过促进炎性因子白细胞介素1β（IL-1β）、白细胞介素6（IL-6）、干扰素γ（IFN-γ）、肿瘤坏死因子α（TNF-α）和核因子κB（NF-κB）的表达，并抑制抗炎因子白细胞介素10（IL-10）的表达，导致回肠的免疫功能失调。本研究表明，Pb可能通过破坏肠道屏障对禽鸟的健康构成风险。 版权所有 © 2023 The Authors. Elsevier Inc. 版权所有。

The gut barrier plays an essential role in maintaining homeostasis and is usually composed of a mechanical barrier, a chemical barrier, an immune barrier, and a biological barrier. However, the impacts of lead (Pb) exposure on avian gut barrier are still unclear. Therefore, the present study tried to determine the toxic effects of Pb on ileal barrier of a biological model-Japanese quail (Coturnix japonica). One-week old quails were exposed to 0, 50, 500 and 1000 ppm Pb in drinking water for 5 weeks. The results showed mechanic barrier in the ileum was disrupted with microstructural deformation featured by epithelial cell abscission, villi contractions and goblet cells reduction as well as ultrastructural changes characterized by swollen mitochondria, blurry tight junctions and microvilli subtraction. Meanwhile, the expression of genes associated with intestinal tight junctions was downregulated in Pb-treated groups indicating tight junction malfunction. Moreover, less mucus and downregulation of expression of mucin2 (Muc2) and Krüppel-like factor 4 (Klf4) indicated chemical barrier disturbance by Pb. In addition, the alteration of microbial diversity and emergence of pathogen bacteria suggested ileal biological barrier disruption by Pb. Furthermore, Pb caused immune dysfunction in the ileum through promoting the expression of pro-inflammatory factors including interleukin 1 beta (IL-1β), interleukin 6 (IL-6), Interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α) and nuclear factor kappa B (NF-κB) and inhibiting the expression of anti-inflammatory factor interleukin 10 (IL-10). The present study demonstrated that Pb may pose health risks to birds through gut barrier damages.Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.