Abstract：
Hexavalent chromium (Cr(VI)) exposure has been linked with gastrointestinal toxicity, whereas the molecular pathways and key targets remain elusive. Computational toxicology analysis predicted the correlation between protein phosphatase 2A (PP2A) and genes regarding Cr(VI)-induced intestinal injury. Here, we generated a mouse model with intestinal epithelium-specific knock out of Ppp2r1a (encoding PP2A Aα subunit) to investigate the mechanisms underlying Cr(VI)-induced small intestinal toxicity. Heterozygous (HE) mice and matched WT littermates were administrated with Cr(VI) at 0, 5, 20, and 80 mg/l for 28 successive days. Cr(VI) treatment led to crypt hyperplasia, epithelial cell apoptosis, and intestinal barrier dysfunction, accompanied by the decline of goblet cell counts and Occludin expression in WT mice. Notably, these effects were aggravated in HE mice, indicating that PP2A Aα deficiency conferred mice with susceptibility to Cr(VI)-induced intestinal injury. The combination of data analysis and biological experiments revealed Cr(VI) exposure could decrease YAP1 phosphorylation at Ser127 but increase protein expression and activity, together with elevated transcriptional coactivator with PDZ-binding motif protein driving epithelial crypt cells proliferation following damage, suggesting the involvement of Hippo/YAP1 signaling pathway in Cr(VI)-induced intestinal toxicity. Nevertheless, the enhanced phosphorylation of YAP1 in HE mice resulted in proliferation/repair defects in intestinal epithelium, thereby exacerbating Cr(VI)-induced gut barrier dysfunction. Notably, by molecular docking and further studies, we identified urolithin A, a microbial metabolite, attenuated Cr(VI)-induced disruption of intestinal barrier function, partly by modulating YAP1 expression and activity. Our findings reveal the novel molecular pathways participated in Cr(VI)-caused small intestinal injury and urolithin A could potentially protect against environmental hazards-induced intestinal diseases.
摘要：
六价铬（Cr（VI））暴露与胃肠道毒性有关，而分子途径和关键靶标仍然难以捉摸。计算毒理学分析预测了蛋白磷酸酶2A（PP2A）与Cr（VI）引起的肠损伤基因之间的相关性。这里,我们建立了肠上皮特异性敲除Ppp2r1a（编码PP2AAα亚基）的小鼠模型，以研究Cr（VI）诱导的小肠毒性的潜在机制。杂合小鼠（HE）和匹配的野生型（WT）同窝以0、5、20、80mg/L连续28天给予Cr（VI）。Cr（VI）治疗导致隐窝增生，上皮细胞凋亡，和肠屏障功能障碍，伴随着WT小鼠杯状细胞计数和Occludin表达的下降。值得注意的是,这些效应在HE小鼠中加重，表明PP2AAα缺乏使小鼠对Cr（VI）引起的肠损伤具有易感性。综合数据分析和生物学实验表明，Cr（VI）暴露可以降低Ser127处的YAP1磷酸化，但增加蛋白质的表达和活性。与升高的TAZ蛋白一起驱动损伤后的上皮隐窝细胞增殖，提示Hippo/YAP1信号通路参与Cr(VI)诱导的肠毒性。然而，HE小鼠中YAP1的磷酸化增强导致肠上皮的增殖/修复缺陷，从而加剧Cr(VI)诱导的肠屏障功能障碍。值得注意的是,通过分子对接和进一步的研究，我们鉴定了尿脂素A,微生物代谢产物,减弱Cr(VI)诱导的肠屏障功能破坏，部分通过调节YAP1的表达和活性。我们的发现揭示了新的分子途径参与了Cr（VI）引起的小肠损伤，尿石素A可以潜在地预防环境危害引起的肠道疾病。
