大黄素诱导白血病U937细胞凋亡及机制初探

目的研究中药大黄素(Emodin)对人髓系白血病细胞株U937细胞增殖及凋亡的影响,探讨bcl-2/bax比值变化和procaspase-3(CPP32)的激活在其中的作用。方法MTT法绘制细胞生长曲线;克隆形成试验观察大黄素对U937细胞增殖的影响;线粒体膜电位检测、DNA倍体分析及DNA凝胶电泳分析细胞凋亡;PCR及检测大黄素作用前后bcl-2/bax基因及蛋白表达的变化;流式细胞术测定大黄素作用前后caspase-3活性变化及检测CPP32的蛋白表达的变化。结果大黄素能抑制U937细胞增殖,作用72h的半数抑制浓度(IC50)约为30μmol·L-1;线粒体膜电位、亚G1峰(凋亡峰)及DNA片段化的检出证实大黄素能诱导U937细胞凋亡,并呈量效关系。大黄素作用后G0/G1期细胞比例较对照组增高,S期比例下降,且与药物浓度呈正相关。大黄素作用后U937细胞bcl-2/bax基因及蛋白的表达水平比值下降,被激活的caspase-3阳性细胞增多,CPP32蛋白表达水平下降,并呈时效关系。结论大黄素能通过诱导凋亡来抑制U937细胞增殖,bcl-2/bax比值的降低及CPP32的活化可能参与了大黄素抑制U937细胞增殖和诱导凋亡的过程。

Emodin induced leukemic U937 cells apoptosis and its underlying mechanism

Aim To investigate the effects of Emodin on proliferation inhibition and apoptosis induction in human myeloid leukemia cell line U937 cells and on bcl-2/bax and the activation of procaspase-3(CPP32). Methods U937 cells were exposed to Emodin at different dosages. Proliferation inhibition was detected by MTT assay and clone formation assay. The ability of Emodin to induce apoptosis of U937 cells was examined by flow cytometry, MitoCapture apoptosis detection and DNA fragmentation. Bax and bcl-2 mRNA and protein expressions were detected by RT-PCR and Western-blot. The activation of caspase-3 was detected by flow cytometry, and CPP32 protein expressions by Western-blot. Results Emodin remarkably inhibited the U937 cells proliferation, with an IC50 value of 30 μmol·L-1 after 72 hours of treatment. Concomitantly, apoptosis was induced in U937 cells, as measured by detection of sub-G1 apoptotic peak and DNA fragmentation. These showed that Emodin induced apoptosis in U937 cells in dose-dependent manners. Compared with the control group, the percentage of the treated cells in G0/G1 phase increased,while that in S phase decreased. Moreover, the expressions of bcl-2/bax mRNA and protein in treated U937 cells decreased. The activated caspase-3 in treated U937 cells increased,with decreased expressions of CPP32 protein. Conclusion Emodin can efficiently induce proliferation inhibition and apoptosis in U937 cells. Bcl-2/bax and the activation of CPP32 may be involved in these processes.