铝对大鼠脑部和PC12细胞中肥胖相关蛋白及脑源性神经营养因子表达的影响

Effects of aluminum on expressions of fat mass and obesity-associated protein and brain-derived neurotrophic factor in rat brain and PC12 cells

[背景]RNA化学修饰是表观遗传学领域新近研究的热点,但有关RNA化学修饰的研究在铝神经毒性的具体机制中尚未见报道。[目的]观察染铝对大鼠不同脑区及大鼠肾上腺髓质嗜铬细胞瘤分化细胞(PC12细胞)内6-甲基腺嘌呤(m^(6)A)去甲基化酶肥胖相关蛋白(FTO)和脑源性神经营养因子(BDNF)表达的影响。[方法]动物实验:健康雄性SD大鼠24只,按体重随机分为对照组(生理盐水)和10、20、40μmol·kg^(-1)剂量组,每组6只,采用腹腔注射麦芽酚铝[Al(mal)_(3)]染毒,隔天注射,染毒3个月。细胞实验:分为对照组和100、200、400μmol·L^(-1)剂量组,Al(mal)_(3)染毒PC12细胞24 h。染毒结束后,水迷宫实验检测大鼠学习记忆能力;水迷宫实验结束后,Western blotting法测定大鼠皮质(n=6)和海马区(n=6)及PC12细胞(n=5)的FTO及BDNF蛋白表达量。[结果]水迷宫实验结果显示,40μmol·kg^(-1)Al(mal)_(3)组大鼠的逃避潜伏期在训练的第3、4、5天均比对照组、10μmol·kg^(-1)和20μmol·kg^(-1)Al(mal)_(3)组增加(P<0.05),其目标象限停留时间也比对照组减少(P<0.05),即染铝可造成大鼠学习记忆能力损害。Western blotting结果显示:在皮质区,与对照组相比,染铝各组大鼠FTO及BDNF蛋白表达水平均降低(P<0.05);在海马区,与对照组相比,20μmol·kg^(-1)和40μmol·kg^(-1)Al(mal)_(3)组FTO及BDNF蛋白表达水平降低(P<0.05);在PC12细胞中,与对照组相比,染铝各组细胞FTO及BDNF蛋白表达水平均降低(P<0.05)。[结论]铝引起的学习记忆损害与FTO和BDNF蛋白表达同时降低有关,提示m^(6)A甲基化修饰可能参与其中。

[Background]Chemical modification of RNA is a recent hotspot in the field of epigenetics,but the specific mechanism of chemical modification of RNA in aluminum neurotoxicity has not been fully reported.[Objective]To investigate the alterations of fat mass and obesity-associated protein(FTO),that demethylates N6-methyladenosine(m^(6)A),and brain-derived neurotrophic factor(BDNF)in different brain regions of rats and rat adrenal pheochromocytoma differentiated cells(PC12 cells)following aluminum exposure.[Methods]Animal experiment:Twenty-four healthy male SD rats were randomly divided into a control group(normal saline)and 10,20,and 40μmol·kg^(-1)exposure groups according to body weight,with 6 rats in each group.Maltol aluminum[Al(mal)_(3)]was injected intraperitoneally every other day for 3 months.Cell experiment:PC12 cells were divided into a control group and 100,200,and 400μmol·L^(−1)exposure groups exposed to Al(mal)_(3) for 24 h.After exposure,the learning and memory ability of rats was measured by water maze experiment,and the protein expression levels of FTO and BDNF in rat cortex(n=6)and hippocampus(n=6)samples as well as in PC12 cells(n=5)were determined by Western blotting.[Results]The results of water maze test showed that the escape latency of the 40μmol·kg^(-1)Al(mal)_(3) group was higher than those of the control group,the 10μmol·kg^(−1) Al(mal)_(3) group,and the 20μmol·kg^(−1) Al(mal)_(3)􀀁group on day 3,4,and 5 of training(P<0.05).The retention time of the target quadrant of the 40μmol·kg^(-1)Al(mal)_(3) group was also reduced compared with that of the control group(P<0.05),indicating that aluminum exposure damaged the learning and memory ability of the rats.The Western blotting results showed that in the cortex,compared with the control group,the protein expression levels of FTO and BDNF in the aluminum treated groups were decreased(P<0.05).In the hippocampus,compared with the control group,the protein expression levels of FTO and BDNF in the 20μmol·kg^(-1)and the 40μmol·kg^(−1) Al(mal)_(3) groups were decreased(P<0.05).In PC12 cells,compared with the control group,the protein expression levels of FTO and BDNF in the aluminum treated groups were decreased(P<0.05).[Conclusion]Aluminum-induced learning and memory impairment is related to a simultaneous reduction of FTO and BDNF protein expressions,suggesting that m^(6)A methylation may be involved.