对氨基水杨酸钠对铅致海马神经炎症的干预机制

Lead (Pb) poisoning results in impairments of learning and memory ability. The results of T1-weighted magnetic resonance imaging (MRI) and hydrogen proton magnetic resonance spectroscopy (1H-MRS) showed that occupational Pb exposure decreased hippocampcal volume and the N-acetyl aspartate to creatine ratio, but elevated lipid to creatine ratio. It suggested that Pb may damage the cell membrane and nerve cell，and subsequently induce impairment of memory ability. The pathogenesis could be associated with neuroinflammation. Our preliminary study found that sodium para-aminosalicylic acid (PAS-Na) has antagonistic effects on the Pb-induced impairments of learning and memory ability, and the hippocampal neurons injuries. Therefore, the present research, by combining methods of in vivo and in vitro toxicology and a case-control study of Pb-exposed workers, aims to 1) observe the promoting effects of PAS-Na on Pb excretion in Pb-exposed rats by using atomic absorption spectrometry; 2) investigate the interventional mechanisms of PAS-Na on the Pb induced inflammation in hippocampus by using techniques of immunohistochemical staining, single cell gel electrophoresis，enzyme-linked immunosorbent assay，real-time PCR and Western Blotting; 3) determine the nerve inflammation in Pb-exposed workers and the interventional effect of PAS-Na in Pb poisoning worker. By studying the effects of Pb-induced hippocampal injuries as a breakthrough point, the present research will help develop and improve an direct, noninvasive technical platform of MRI and 1H-MRS brain imaging in evaluating Pb-induced neurotoxicity, and also lay a scientific foundation for early diagnosis, prevention and treatment of Pb poisoning.

铅中毒会引起学习记忆力下降。磁共振成像（MRI）和氢质子磁共振波谱(1H-MRS)检查显示，铅作业工人血铅增高，海马体积和N-乙酰天冬氨酸/肌酸（Cr）比值变小，脂质/Cr比值变大，提示铅可能损害神经细胞、细胞膜，以致记忆力降低。发病机制可能与神经炎症有关。我们研究发现，对氨基水杨酸钠（PAS-Na）对铅致大鼠学习记忆力及其海马神经元受损有拮抗作用。本项目通过体内外毒理学实验和职业人群调查相结合的研究方法，采用原子吸收光谱法观察PAS-Na对铅中毒小鼠的促排作用；用免疫组化、单细胞凝胶电泳、实时定量荧光和蛋白质印迹法等技术探讨铅致大鼠海马炎症反应及PAS-Na的干预作用机制；探讨职业性铅暴露致工人神经炎症反应以及PAS-Na治疗中毒病人的效果。并以铅致海马损害为突破口，发展、完善直观、无创性检测铅致脑损害的MRI和1H-MRS技术平台，为铅中毒早期诊断与防治工作提供科学依据。

铅中毒能损害海马神经细胞、细胞膜，以致学习记忆力降低，其毒作用机制可能与神经炎症有关。本项目在对氨基水杨酸钠（PAS-Na）对染铅大鼠海马神经元和学习记忆力受损有拮抗作用的基础上，探讨PAS-Na对染铅小鼠的促排铅作用，探讨铅中毒致大鼠海马炎症反应及PAS-Na的干预作用机制。结果发现，PAS-Na治疗对急性染铅小鼠纹状体、血铅有促排作用。体外染铅可经NLRP3/caspase-1介导神经细胞焦亡，引起阿尔兹海默病（AD）标志性蛋白增多，出现AD样病变。体内染铅可激活大鼠海马神经元NLRP3/caspase-1炎症体，使CaMKII/CREB通路受阻或紊乱。PAS-Na可通过抑制铅诱导的NLRP3/Caspase-1炎症体活性，恢复CaMKII/CREB通路，对铅中毒性神经退行性病变产生拮抗作用。铅可引起原代海马神经元凋亡、细胞内钙离子紊乱，引起IP3R-Ca2+信号通路紊乱，PAS-Na对铅神经元毒性有拮抗效应。亚慢性染铅使大鼠海马细胞凋亡、学习记忆能力受损，PAS-Na可能经IP3R、ASK1-p38信号通路产生拮抗作用。短期染铅使大鼠海马CA2区神经元受损，海马ERK1/2-p90RSK、p65磷酸化和IL-1β水平增高，PAS-Na可经ERK1/2-p90RSK/NF-κB通路抑制大鼠海马神经炎症，使铅致学习记忆功能障碍减轻。体外染铅可经SIRT1/NF-κB通路损伤大鼠皮层神经元，使炎症因子含量增高，PAS-Na干预有抗炎作用。铅可抑制CREB/BDNF通路来降低学习记忆能力，PAS-Na治疗可激活该通路来对染铅大鼠学习记忆受损产生拮抗作用。染铅大鼠皮层可经SIRT1/NF-κB通路介导炎症反应，PAS-Na可经该通路的调节抑制神经炎症反应，使染铅大鼠学习记忆好转或恢复。PAS-Na对染铅大鼠大脑皮层自噬引起的学习记忆能力下降有拮抗作用。本研究表明，铅中毒可使大鼠产生神经炎症，诱导海马神经退行性病变，且可能与AD发病有关。PAS-Na对铅中毒大鼠海马炎症反应有明显的拮抗作用，其机制可能与PAS-Na可以改善铅中毒性神经信号通路有关。与广西铅作业的主要职业危害是粉尘、噪声、铅、镉及其化合物，作业场所空气铅及其化合物浓度超标是影响工人血铅水平的主要因素。