内质网应激反应在二十碳五烯酸对胶质瘤U87细胞替莫唑胺化疗敏感性影响中的作用

Eicosapentaenoic acid enhances the sensitivity of glioma cell line U87 to temozolomide via inhibiting en-

目的探讨二十碳五烯酸（EPA）对胶质瘤U87细胞替莫唑胺（TMZ）化疗敏感性的影响及其机制。方法胶质瘤U87根据不同药物干预分为：对照组、TMZ组、EPA±TMZ组、EPA±TMZ±应激诱导剂衣霉素（TM）组（EPA±TMZ±TM组）。采用MTr法和流式细胞仪检测各组胶质瘤U87细胞增殖抑制率和细胞凋亡率；Westernblot法检测各组胶质瘤U87细胞凋亡因子（半胱氨酸蛋白酶-3、Bax）和内质网应激相关因子[葡萄糖调节蛋白78（GRP78）、磷酸化肌醇需要酶1（IRE-1）]的蛋白表达。结果MMT检测显示浓度〉50moWLEPA对胶质瘤U87的细胞增殖抑制呈浓度和时间依赖性（P均：0．00）。EPA可提高胶质瘤U87TMZ化疗敏感性。相对于TMZ组，EPA±TMZ组对胶质瘤U87的细胞增殖抑制率明显升高[（56．27±6．15）％比（42．32±4．12）％，P均=0．03）]，凋亡率也明显升高[（49．78±5．94）％比（37．74±4．24）％，P=0．04]。Westernblot检测显示，与TMz组相比，EPA±TMZ组凋亡因子半胱氨酸蛋白酶-3和Bax蛋白表达明显增加，内质网应激因子GRP78和IRE．1蛋白表达明显减少（P均=0．01）；内质网应激诱导剂TM抵消EPA抑制内质网应激的作用，逆转EPA提高胶质瘤U87细胞TMZ化疗敏感性的作用。结论EPA预处理可提高胶质瘤细胞对TMZ的化疗敏感性，其机制可能是通过抑制癌细胞内质网应激起作用。

Objective To investigate the effect of Eicosapentaenoic scid （EPA） on the sensitivity of glioma cell line U87 to temozolomide （TMZ） and the mechanism behind this effect. Methods U87 ceils were randomly divided into four groups： control group, TMZ group, EPA ±TMZ group and endoplasmic reticulum stress （ERS） activation tunicamycin group （EPA±TMZ±TM group）. MTI＂ method was used to evaluate inhibi- tion ratio of cell proliferation. The apoptotic ratio was examined by flow eytometry. Western blot was used to de- tect the protein expressions of apoptosis cytokines （caspase-3 and Bax） and ERS cytokines [ glucose-regulated protein 78 （GRP78） and inositol-requiring enzyme 1 （IRE-1 ） ]. Results EPA causes concentration-de- pendent and time-dependent inhibition of the cell proliferation （ all P = 0. 00）. EPA significantly enhanced the sensitivity of glioma cell line U87 to temozolomide. Compared to TMZ treatment alone, the inhibition ratio [ （56.27±6. 15）% vs. （42.32±4. 12）%, P=0.03] and apoptotic ratio [ （49.78±5.94）% vs. （37.74± 4. 24）%, P= 0. 04] of U87 ceils were enhanced by EPA±TMZ treatment. Western blot showed that the expres-sion of apoptotic factor easpase-3 and Bax proteins were increased by EPA±TMZ treatment, while the protein ex- pressions of ERS-related factors （GRP78 and IRE-1 ） were significantly inhibited （P = 0. 01 ）. However, the salu- tary effects of EPA were reversed by ERS activation tunicamycin. Conclusion EPA enhances the sensitivity of glioma cell line U87 to temozolomide, the mechanism of which may be the suppression of ERS response.