基于代谢组学研究微囊藻毒素MCLR诱导大鼠认知损伤的毒性效应及机制

The animal and human health hazards from cyanobacterial secondary metabolites microcystins (MCs) have emerged as a major global environmental issue, due to the apparent global increase in occurrence of harmful cyanobacterial blooms. Mounting evidence have indicated that MCs have neurotoxicity and can cause cognitive impairment in mammals, but the impact on metabolome level and the exact molecular mechanisms of MCs-induced cognitive impairment remain largely unknown. In this project, rats will be chronically exposed to the most toxic MCs isomer microcystin-leucine-arginine (MCLR) to establish the rat model of the cognitive impairment; NMR- and HPLC-based metabonomics will be used to systematically analyze the effect of MCs on rat hippocampal metabolisms, thus deciphering the toxic effects at the functional level and identifying specific biomarkers related to the cognitive impairment; Further, systematical analysis of the gene expression, molecular metabolisms, cellular biochemistry, cellular ultra-structure, histopathology and individual behavior will be conducted to integrate the changes in different levels for better illustrating the mechanism of MCLR-induced cognitive impairment. This project will help to people's understanding of MCLR neurotoxicity and provide theoretical bases for diagnosis and precaution of MCLR-induce cognitive impairment.

随着蓝藻水华在世界范围内的大规模爆发，蓝藻次生代谢产物微囊藻毒素(Microcystin, MCs)对动物和人的健康危害已成为全球面临的重大环境问题之一。研究表明MCs具有神经毒性，能导致哺乳动物认知损伤，但MCs诱导的认知损伤在细胞功能水平(细胞代谢物水平)的毒性效应仍不清楚，MCs诱导认知损伤的分子机制缺乏深入研究。本项目拟以毒性较强的MCs异构体MCLR慢性染毒大鼠，建立认知损伤模型；运用基于核磁共振和液相色谱的代谢组学系统研究MCLR对大鼠海马代谢侧面的影响，从细胞功能水平阐释MCLR诱导的认知损伤效应，确定认知损伤的代谢标志物；同时，结合大鼠海马基因表达、细胞生化和超微结构、组织病理以及个体行为等多个水平的变化从系统生物学角度深入阐释MCLR诱导认知损伤的机制。该项目将有助于扩展人们对MCLR神经毒性的认识，为MCLR诱导的认知损伤的早期诊断预警和治疗提供理论依据和新的思路。

蓝藻次生代谢产物微囊藻毒素具有强烈的神经毒性，但其在细胞功能水平的神经毒性效应，尤其是对脂质代谢的影响仍不清楚，MC-LR染毒后不同脑区代谢变化是否存在差异也不清楚，这极大限制了对微囊藻毒素神经毒性机制的理解。本项目从脂类代谢的角度系统剖析环境低剂量MC-LR慢性染毒对小鼠海马和皮层两个区域脂质代谢侧面的影响，并结合组织病理和行为学等，解析认知损伤的分子机制。. 研究结果表明环境浓度MC-LR能够诱导小鼠海马和前额叶皮层组织病理改变，前额叶皮层出现凋亡，但海马组织细胞未观察到明显的凋亡；水迷宫和旷场实验等行为学研究表明低剂量MC-LR染毒能够导致小鼠空间学习、记忆能力及自主探索认知活动减弱，提示长期染毒会导致小鼠认知损伤等神经毒性。. 低浓度MC-LR慢性染毒显著影响了海马和前额叶皮层中脂质尤其是磷脂亚类分子的代谢，海马中大量磷脂含量及脂质不饱和度显著上升，这可缓解MC-LR对蛋白磷酸酶的抑制，抑制凋亡信号通路，降低氧化压力；而前额叶皮层中磷脂分子含量及脂肪酰不饱和度显著下降，加剧蛋白磷酸酶的抑制、可能促进凋亡信号通路以及氧化压力，这与前额叶皮层中观察到的凋亡损伤一致。前额叶皮层而非海马磷脂代谢紊乱可能在MC-LR诱导的神经毒性，如认知损伤过程中发挥了更大作用。以上结果也表明MC-LR对脑组织脂质代谢的影响具有区域特异性。