氟中毒大鼠脑组织和PC12细胞中脂质和尼古丁受体的改变

Changes of lipids and nicotinic receptors in rat brains and Pheochromocytoma with fluorosis

目的观察氟中毒对大鼠脑组织和神经细胞中细胞膜性脂质和神经型尼古丁受体的影响．探讨氟中毒引起神经系统功能紊乱的分子作用机制。方法用不同剂量氟饲养大鼠和处理体外培养的大鼠嗜铬神经细胞瘤细胞株(PC12神经细胞),用生物化学方法测定细胞3-4,5-二甲基噻唑-2,5-二酚基四唑溴化物 (MTT)还原能力、脂质过氧化和蛋白氧化水平,用高效液相色谱方法测定细胞膜性脂质,用放射核素标记放射性配体-受体实验方法测定不同的尼古丁受体类型,用蛋白印迹方法测定α3、α4、α7和β2尼古丁受体亚单位蛋白水平。结果经氟处理的神经细胞中MTT水平降低36％,氟中毒大鼠和高浓度氟处理的神经细胞中氧化应激水平升高55％-89％,细胞膜性磷脂减少24％-34％,辅酶Q减少13％-30％,含α3、α4和α7亚单位的尼古丁受体类型在受体-配体结合率和蛋白水平均降低20％-44％,用抗氧化剂处理可减弱氟中毒对受体的损害作用。结论氟中毒导致神经型尼古丁受体水平降低,其原因可能与氟中毒时氧化应激水平升高及所引起的细胞膜性脂质结构异常改变有关,这些可能是氟中毒时神经系统功能紊乱的重要发生机制。

Objective To observe the influence of fluorosis on cellular membrane lipids and nicotinic acetylcholine receptors （nAChRs） in rat brain and neurons, and to investigate the mechanisins of nervous system disorder induced by fluorosis. Methods Rats and Pheochromocytoma cells （PC12 cells） were treated by different concentrations of fluoride. The MTT [3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyhetrazoliumbromide] reduction, lipid peroxidation and protein oxidation were detected by biochemistry methods; contents of lipids were measured by high performance liquid-chromatography; the numbers of nAChRs were analyzed by receptor binding assay and the subunits of these receptors by Western blotting. Results In the group with higher-dose of iluoride as compared to control, the decreased MTT reduction （36%）, high level of oxidative stress （55% -89%）, decreased phospholipids （24% - 34%）, decreased ubiquinone （13% - 30%）,and decreased nAChRs （20% - 32%） were observed. Prior treatment with antioxidant resulted in preventing the decrease of nAChRs in the cells exposed to higher concentration of fluoride. Conclusions Decreased nAChRs resulted from fluorosis might be due to the attack by oxidative stress and consequently influenced by changed cellular membrane lipid composition, which may be involved in the important pathogenesis of nervous system disorder.