低氧联合TNF-α通过激活STAT3而非ERK1/2途径介导人肺微血管内皮细胞凋亡

Hypoxia combined with TNF-α induces apoptosis of cultured human pulmonary microvascular endothelial cells via activation of the STAT3 rather than ERK1/2signaling pathway

目的探讨低氧联合肿瘤坏死因子α(TNF-α)介导人肺微血管内皮细胞(HPMVEC)凋亡的信号通路。方法低氧6、12、24 h及(10、20、50、100)ng/m L TNF-α分别处理HPMVEC,使用MTT比色法检测各组的细胞活性;选用最佳的低氧时间及TNF-α剂量联合刺激HPMVEC,流式细胞术检测caspase-3的活性,异硫氰酸荧光素标记的膜联素Ⅴ/碘化丙啶(annexinⅤ-FITC/PI)检测各组细胞的凋亡情况,采用Western blot法检测各组细胞中磷酸化信号转导子与转录因子3(p STAT3)及磷酸化胞外信号调节激酶1/2(pERK1/2)的水平。结果 MTT法显示,低氧24 h组的相对细胞活性最低,100 ng/m L TNF-α处理组的相对细胞活性明显降低且对细胞活性的抑制呈现剂量依赖性;选用低氧24 h及100 ng/mL TNF-α作为联合处理组,与空白对照组及单独处理组相比,联合处理组的caspase-3活性及细胞凋亡率均升高。Western blot结果显示,与空白对照组相比,联合处理组的p STAT3表达明显升高,而p ERK1/2的变化无统计学意义。而STAT3通路阻断剂S3I-201可使联合处理组的细胞凋亡率下降。结论低氧状态联合TNF-α通过激活STAT3而非ERK1/2介导HPMVEC凋亡。

Objective To explore the effect of combined hypoxia and tumor necrosis factor a （TNF-α） on the apoptosis of human pulmonary microvascular endothelial cells （HPMVECs） and the involved signaling pathway mechanism. Methods Some HPMVECs were treated with hypoxia within 6, 12, or 24 hours, and the other cells were treated with TNF-α at the concentrations of 10, 20, 50, or 100 ng/mL. Cell activity was determined by MTT assay in each group to determine the best combined stimulatory conditions. Under the optimal costimulatory condition, the activity of caspase-3 was detected by flow cytometry, annexin V-FITC/PI double staining combined with flow cytometry was used to detect the apoptosis, Western blotting was performed to test the level of phosphorylated signal transducer and activator of transcription 3 （pSTAT3） and phosphorylated extracellular signal-regulated kinase 1/2 （pERK1/2）. Results The cell activity was the lowest in 24-hour hypoxia group and 100 ng/mL TNF-α group. Therefore, we confirmed the combination of hypoxia for 24 hours and 100 ng/mL TNF-α as the costimulatory conditions. The caspase-3 activity and apoptosis rate in the combined treatment group were higher, compared with the other groups. The expression of pSTAT3, rather than pERK1/2, increased in the combined treatment group, compared with the control group. Moreover, the STAT3 inhibitor s31-201 reduced the apoptosis rate in the combined treatment group. Conclusion Combined hypoxia and TNF-α could promote HPMVEC apoptosis by activating STAT3 rather than ERK1/2.