金属硫蛋白抑制阿霉素引起的心肌细胞凋亡作用研究

目的 研究锌诱导的金属硫蛋白(MT)对阿霉素(DOX)所致心肌细胞凋亡的的抑制作用并探讨其作用机制.方法 雄性C57BL小鼠随机分成4组(每组7只),即对照组、锌处理组、给药组和锌预处理给药组.各组小鼠连续2 d皮下给予ZnSO4 300 μmol/kg(锌处理组和锌预处理给药组)或等量生理盐水(对照组和给药组),第3 d单次腹腔注射DOX 15 mg/kg(给药组和锌预处理给药组)或等量生理盐水(对照组和锌处理组).DOX给药后第4 d处死小鼠,采用血红素镉饱和法测定心脏组织MT含量,ELISA法测定心肌凋亡指数,蛋白印迹分析(Western blot)测定心肌组织凋亡相关蛋白Bax、Bcl-2的表达水平.结果 与对照组相比,DOX引起小鼠心脏质量下降10%,且显著引起小鼠心肌细胞凋亡;经锌诱导后,心脏组织MT水平提高约25倍,且MT高表达能抑制DOX引起的凋亡细胞增加;进一步的研究发现,Bax蛋白表达水平在DOX给药后明显升高,而MT高表达抑制了Bax的表达升高;Bcl-2蛋白表达水平各组间的差异无统计学意义.结论 锌诱导的MT高表达能抑制DOX引起的心肌细胞凋亡,其作用机制主要与抑制DOX引起的Bax蛋白表达升高以及Bax/Bcl-2比值增加有关.

Metallothionein Inhibited DOX-induced Cardiac Apoptosis in Mice

OBJECTIVE: To investigate the inhibitive effect of metallothionein (MT) on DOX-induced cardiac apoptosis and the involved possible mechanisms. METHODS: Adult male C57BL mice (6-8 weeks old) were randomly assigned into four groups and given the following treatment: Zinc (ZnSO4, 300 micromol/kg, s.c., once a day for 2 days) or equal volume of physiological saline prior to a single dose of DOX (15 mg/kg, i.p.) or equal volume of saline. Animals were sacrificed on the 4th day after DOX administration and hearts were excised for further studies, including cadmium-hemoglobin affinity assay for MT concentration, ELISA detection of DNA fragmentation and Western blot analysis of Bax and Bcl-2. RESULTS: DOX administration decreased heart weight by 10% and caused remarkable cardiac apoptosis as demonstrated by DNA fragments, while Zinc pretreatment significantly increased the MT levels and therefore inhibited the cardiac apoptotic effect of DOX. Elevated expression of Bax was obviously observed after DOX treatment, while this elevation was prevented by MT induction by Zinc. On the contrary, Bcl-2 protein level was not altered significantly among each group. CONCLUSION: These findings suggest that metallothionein induced by Zinc exhibits protective effects on the cardiac apoptosis of DOX, which might be mediated through the prevention of Bax protein up-regulation by DOX and associated elevation of Bax/Bcl-2 ratio.