中文摘要：

目的探讨光敏剂MPPa（pyropheophorbide-a methyl ester）介导的光动力作用于人乳腺癌细胞MCF-7，诱导内质网应激途径凋亡的机制。方法给予不同浓度光敏剂MPPa（0、0.5、1、2、4 μmol/L），以及不同能量光照（0、0.9、1.8、2.7、3.6 J/cm^2）处理MCF-7细胞，用CCK-8法检测细胞活力。确定2 μmol/L MPPa及1.8 J/cm^2光能量为实验剂量。激光共聚焦显微镜观察光敏剂MPPa（2 μmol/L）内质网亚细胞器定位。将MCF-7细胞进行完全随机化分组，分为MPPa-PDT组（给予2 μmol/L MPPa及1.8 J/cm^2光能量）、空白对照组、单纯MPPa组（2 μmol/L MPPa）和单纯光照组（1.8 J/cm^2光能量）。应用Annexin V-FITC/PI双染流式细胞仪检测细胞的凋亡率。Flou-3/MA流式细胞仪检测细胞内Ca^2＋浓度变化。Western blot检测内质网应激标志蛋白BIP和内质网应激途径相关凋亡蛋白caspase-12、CHOP的表达。结果MPPa介导光动力对MCF-7细胞有显著杀伤作用，抑制其生长，且抑制作用呈明显的剂量效应关系（P〈0.05）；MPPa可富集在内质网上；MPPa-PDT组凋亡率显著高于各对照组（P〈0.05）；MPPa-PDT组细胞内Ca2＋荧光强度较对照组增高（P〈0.05）；Western blot检测发现BIP、caspase-12、CHOP蛋白在MPPa-PDT组中各时间点表达升高,而在各对照组中表达较低。结论MPPa介导的光动力可诱导MCF-7细胞发生内质网应激途径凋亡。

英文摘要：

Objective To investigate the mechanism of endoplasmic reticulum stress pathway in pyropheophorbide-a methyl ester （MPPa）-mediated photodynamic therapy （PDT） in inducement of breast cancer cells apoptosis.Methods The MCF-7 cells were randomly divided into the MPPa-PDT group and 3 control groups （the blank control group, the MPPa alone group, and the light alone group）. The cells were co-cultured with MPPa at different concentrations （0, 0.5, 1, 2 and 4 μmol/L） and exposed to the light of different energy intensities （0, 0.9, 1.8, 2.7 and 3.6 J/cm^2）. CCK-8 assay was used to measure the viability of MCF-7 cells. Confocal laser scanning with ER-tracker GREEN Probe uploading was used to observed the subcellular location of MPPa （2 μmol/L）. When the cells were treated with 2 μmol/L MPPa and exposed to 1.8 J/cm^2 light, flow cytometry with Annexin V-FITC/PI double-staining was used to assess the cell apoptosis. Flow cytometry with Flou-3/AM was used to measure the concentrations of free calcium ion in the cells. Western blotting was used to detect the protein levels of endoplasmic reticulum stress marker BIP, and its related apoptotic proteins, CHOP and caspase-12. Results Cell proliferation of MCF-7 cells was significantly inhibited by MPPa-PDT in an energy-dependent manner （P〈0.05）. MPPa was enriched in the endoplasmic reticulum. Flow cytometry showed the apoptotic rate and the Ca2＋ level were obviously higher in the MPPa-PDT treated cells than the control cells （P〈0.05）. Western blot analysis indicated that the expression levels of BIP, CHOP and caspase-12 were increased in the MPPa-PDT group at all time points, whereas those in the control groups were low. Conclusion MPPa-PDT induces apoptosis in the MCF-7 cells through endoplasmic reticulum stress pathway.