中文摘要：

[目的]探讨不同浓度纳米二氧化钛（nanosized titanium dioxide,Nano-TiO2）颗粒对人肺上皮细胞（A549细胞）增殖的影响及其可能机制。[方法]采用不同粒径（5、10和40 nm）和浓度（0、0.125、0.25、0.5、1、2、4、8、16 mg/L）的Nano-TiO2处理A549细胞24 h,用四甲基偶氮唑盐（MTT）法和细胞计数法观察Nano-TiO2对细胞增殖的影响;用流式细胞术检测Nano-TiO2对细胞凋亡的影响;用蛋白质免疫印记法（Western Blot）测定Nano-TiO2对细胞外调节蛋白激酶（extracellular-receptor kinase,ERK）的影响。并采用ERK特异性抑制剂PD98059（20μmol/L）对细胞进行预处理30 min后,MTT法观察ERK抑制剂对低浓度Nano-TiO2（0.5 mg/L）调节细胞增殖的影响。[结果]不同粒径的Nano-TiO2均表现出较低浓度（≤4 mg/L）促进细胞增殖,较高浓度（≥8 mg/L）抑制细胞活力的作用,而更高浓度Nano-TiO2（16 mg/L）可引起细胞凋亡的发生。进一步研究发现,低浓度Nano-TiO2（0.5 mg/L）可引起细胞磷酸化ERK表达增强,ERK抑制剂PD98059可明显抑制低浓度Nano-TiO2（0.5 mg/L）的促细胞增殖作用。[结论]低浓度Nano-TiO2可通过激活ERK促进细胞增殖,较高浓度Nano-TiO2则引发细胞凋亡发挥其抑制细胞活力的作用;不同粒径Nano-TiO2的效应之间没有明显差异。

英文摘要：

[ Objective ] To estimate the effects of nanosized titanium dioxide （Nano-TiO2） at different concentrations on A549 human lung epithelial cell line proliferation and the potential mechanisms. [ Methods ] A549 cells were exposed to Nano-TiO2 with different sizes （5, 10, and 4ohm） at different concentrations （0, 0.125, 0.25, 0.5, 1, 2, 4, 8, and 16rag/L） for 24h. After 24 h exposure, cell proliferation was detected by tetrazolium （MTY） assay and cell number determination. Cell apoptosis and extracellular-receptor kinases （ERK） expression were determined by flow cytometry and Western Blot, respectively. MTI＇ assay was also used to detect the effect of ERK inhibitor PD98059 （20gmol/L） on cell proliferation induced by 0.5 mg/L Nano-TiO2. [ Results ] The Nano-TiO2 with different sizes （5, 10, and 40 nm） showed biphasic effects on the A549 cell proliferation, namely, stimulating proliferation at lower concentrations （ ≤ 4 mg/mL）, while inhibiting cell viability at higher concentrations （ ≥ 8 mg/mL）. The Nano-TiO2 at 16 mg/L induced significant increases in cell apoptosis. The results of Western Blot analysis showed that 0.5 mg/L Nano-TiO2 exposure significantly increased the expression of phosphorylated-ERK. The cell proliferation induced by 0.5 mg/L Nano-TiO2 was significantly blocked by ERK inhibitor PD98059. [ Conclusion ] Nano-TiO2 stimulate cell proliferation at low concentrations, while inhibite cell viability at higher concentrations. The low-concentration stimulatory effects of Nano-TiO2 could be mediated by ERK signal transduction pathway. These effects show no significant differences among Nano-TiO2 with different sizes.