半胱氨酸蛋白酶-3／-9在大肠埃希菌诱导的人巨噬细胞系U937细胞凋亡中的作用

Effect of Caspase-3/-9 on Apoptosis Induced by E. coli in Human Monocytic U937 Cells

目的探讨大肠埃希菌(E.coli)感染时人巨噬细胞系U937细胞凋亡与半胱氨酸蛋白酶-3/-9(caspase-3/-9)的关系。方法以流式细胞仪检测为指标,研究E.coli感染对U937细胞凋亡的诱导作用。ELISA方法检测caspase-3/-9蛋白酶活性。结果当U937细胞∶E.coli为1∶20时,E.coli感染U937细胞0,10,20,30,60,90min时细胞凋亡百分率分别为(3.02±0.78)%,(6.67±1.34)%,(10.56±1.02)%,(33.92±2.66)%,(46.98±3.12)%和(69.02±4.69)%,呈时间依赖性。感染30,60,90min时,细胞凋亡率与对照组相比明显增高(P<0.01)。caspase-3/-9蛋白酶活性随着培养时间延长也逐渐增高,与细胞凋亡程度基本一致。caspase-3/-9蛋白酶的抑制剂Z-DEVD-FMK和Z-LEHD-FMK能够抑制E.coli诱导的U937细胞凋亡。结论人巨噬细胞系U937细胞在E.coli感染过程中存在凋亡,caspase-3/-9参与了该凋亡过程并发挥了重要的作用。

Objective To study the relationship between human monocytic U937 cell apoptosis and the activity of caspase-3 and 9 when infected with E. coli. Methods The U937 apoptosis induced by E. coli was detected with PI assay. ELISA was used to measure easpase-3 and 9 activity in E. coli-indueed apoptosis in human U937 cells. Results After U937 cells were exposed to E. coli at an MOI of 20：1 for 0,10 min,20 min,30 min,60 min and 90 min,the percentage of apoptosis was （3.02±0.78）%, （6.67±1.34）%, （10.56±1.02）%, （33.92± 2.66）%, （46.98±3.12）% and （69.02±4.69）%,respectively. The U937 apoptosis rates in infection groups at 30 min,60 min and 90 min were significantly higher than that in the control group （P 〈 0.01 ）. Moreover,exposure of U937 cells to E. coli led to the increase of easpase-3 and 9 activity. The results were further confirmed by the observation that the easpase inhibitors Z-DEVD-FMK and Z-LEHD-FMK could block E. coli induced U937 apoptosis. Conclusion Caspase-3 and 9 are involved and play an important role in U937 apoptosis induced by E. coli.