基于Nrf2信号通路探讨桑葚多酚类物质对壬基酚神经行为毒性的干预机制

Nonylphenol (NP) is a typical environmental endocrine disruptor. It can enter human body through drinking water or food chain and pose a risk to human health. Facing the potential threat, it would be a trend to seek for strategic methods of active toxicity intervention in the future. Plant polyphenols are important secondary metabolites of plants, which have many physiological functions, such as antioxidation, antitumor, antibacterial and so on. Our previous study found that NP not only had the neurobehavioral toxicity, but also could downregulate the expression level of Nrf2 mRNA in the rat liver, while crude extract of mulberry polyphenol could significantly upregulate the expression level of Nrf2 mRNA. This founding suggested that they might have antagonistic effect on Nrf2 pathway. The project is designed to investigate the inhibitory effects of NP on Nrf2 signaling pathway firstly, then carry out an intervention trial to test the detoxication effects of mulberry polyphenols on neurobehavioral toxicity in rats exposed to NP. The intervention effects and mechanisms will be analysed in single, combined or mixed mode of mulberry polyphenols adminsitration through the Nrf2 signaling pathway and related route of Thyroid hormon action. The proposed study will have meaningful theoretical and practical implications for further exploring potential benefits of mulberry and the implementation of the toxicity intervention programs based on the foods of " medicine and food homology” or their active ingredients.

壬基酚（NP）是典型的环境内分泌干扰物，可通过水源、食物链等途径进入人体，对健康带来潜在危害。面对此类健康威胁，寻求主动的毒性干预策略在未来将成为一种趋势。植物多酚是植物体内重要的次生代谢产物，具有抗氧化、抗肿瘤、抑菌等多种生理功能。我们前期研究发现NP不仅具有神经行为毒性，而且能使大鼠肝脏抗氧化调节因子Nrf2 mRNA表达水平降低，而桑葚多酚粗提液则能显著上调肝脏Nrf2 mRNA表达，暗示两者对Nrf2信号通路可能存在对抗效应。本项目拟在研究NP对Nrf2信号通路抑制效应的基础上，采用桑葚多酚类物质对NP染毒大鼠进行干预，从Nrf2信号通路及与之相关的甲状腺激素途径探讨桑葚多酚在单一、联合或混合组分模式下对NP所诱导的神经行为毒性的干预效果及机制。研究结果不仅有利于进一步挖掘桑葚的潜在价值，而且对实施以药食同源类食物或其活性成分为基础的毒性干预计划也具有重要的理论意义和应用价值。

壬基酚（Nonylphenol, NP）广泛应用于农业和工业领域并造成严重污染，对机体具有一定的毒害作用，同时桑葚具有一定的解毒作用，其主要活性成分花青素和白藜芦醇的抗氧化活性也被广泛研究。本项目通过连续28天NP染毒实验和神经行为学测试技术（旷场实验、高架十字迷宫实验）发现NP暴露导致大鼠生成过量ROS，通过抑制Keap1-Nrf2信号通路而对大鼠肝脏、大脑皮层造成一定氧化损伤，并诱导大鼠的焦虑情绪；NP暴露对该信号通路的抑制作用具有一定的剂量-效应以及时间-效应关系。在此基础上继续以桑葚粗提液以及桑葚的主要活性成分花青素、白藜芦醇及其混合成分作为干预物质对NP暴露大鼠进行干预，从神经行为学指标、甲状腺功能指标、氧化应激指标以及Keap1-Nrf2信号通路、MAPK通路的相关蛋白水平探讨桑葚多酚类物质对NP暴露大鼠的干预作用及机制。结果表明，桑葚粗提液能有效减轻NP暴露导致的一般毒性、神经行为毒性、甲状腺激素紊乱以及氧化应激损伤，其主要活性成分花青素和白藜芦醇对此也有一定的干预效果。其中的干预机制可能是桑葚及其多酚类物质可激活MAPK通路，使Nrf2活化并进入细胞核中激活II相解毒酶（GST、UGT及其亚型），从而降低氧化产物（ROS、8-iso-PGF2α）水平，缓解NP染毒大鼠的焦虑状态，达到减轻神经行为毒性与氧化应激损伤的目的。研究结果对进一步挖掘桑葚及其多酚类物质的保健价值以及相关保健品的开发利用具有较好的理论指导意义。