紫草素对DNA拓扑异构酶Ⅰ活性的抑制作用和诱导人白血病K562细胞的凋亡

目的：研究紫草素对DNA拓扑异构酶I催化活性和K562白血病细胞凋亡的影响。方法：从K562白血病细胞提取拓扑异构酶I，通过DNA解螺旋试验评价该药对拓扑异构酶I催化活性的抑制作用。用MTT法测定了该药对K562白血病细胞增殖的抑制作用。应用流式细胞术和琼脂糖凝胶电泳观察了该药对细胞凋亡的诱导作用。结果：紫草素可显著抑制拓扑异构酶I的解螺旋活性(IC50=75．Oμmol/L)。该药能显著抑制K562的细胞增殖，并随剂量增大而抑制作用增强。紫草素O．3～3μmol/L对K562细胞作用24h后，其凋亡率为20％～70％。琼脂糖凝胶电泳出现典型的DNA“lad-der”。结论：紫草素显著抑制拓扑异构酶I的催化活性，并能诱导K562白血病细胞凋亡。

Shikonin Inhibiting the Catalytic Activity of DNA Topoisomerase I and Inducing the Apoptosis of K562 Leukemia Cells

AIM:To study the effects of shikonin on the catalytic activity of DNA topoisomerase I and apoptosis of K562 leukemia cells. METHOD: Topoisomerase I was extracted from K562 cells and the inhibitory effect of shikonin on the catalytic activity was estimated by DNA relaxation assay. MTT assay was used to measure the inhibition of K562 cells proliferation. The amount of apoptotics cells was determined by flow cytometry (FCM). DNA fragmentation was analyzed by agarose gel electrophoresis. RESULT:Shikonin remarkadly inhibited the catalytic activity of topoisomerase I with IC50 value of 75.0 μmol/L. K562 cells proliferation was inhibited by shikonin in a concentration-dependent manner. The analysis with flow cytometry showed that the percentage of apoptotic cells was about 20%～70% after K562 cells were treated by 0.3～3 μmol/L shikonin for 24 h, and DNA ladder can be observed by electrophoretic analysis. CONCLUSION: This study showed that shikonin might inhibit the catalytic activity of DNA topoisomerase I and have apoptosis-induced activity for K562 leukemia cells.