三氯乙烯诱导人表皮角质形成细胞凋亡的实验研究

目的 探讨有机溶剂三氯乙烯(TCE)诱导正常人表皮角质形成细胞(NHEK)凋亡的可能机制.方法 TCE处理NHEK后,分光光度法测细胞上清中半胱氨酸蛋白水解酶(Caspase)-3、8和9的活性,膜联蛋白V/碘化丙啶(PI)双染后流式细胞仪(FCM)测细胞凋亡,Rh123/PI双染后FCM测线粒体膜电位(△Ψm);用Caspase-3抑制剂或Caspase-9抑制剂预处理NHEK 1 h,验证Caspase的活化.结果 不同浓度TCE处理NHEK 4 h后培养不同时间,Caspase-3和9活性呈剂量和时间依赖的升高,培养12、24 h,各TCE处理组Caspase-3和9活性与溶剂对照比差异均有统计学意义(均P<0.05),而Caspase-8活性变化不明显.0.125、0.25、0.5、1.0和2.0 mmol/L TCE处理NHEK 4 h后培养12 h,膜联蛋白V~+/PI~-为(20.1±4.1)%、(30.0±7.5)%、(42.1±8.2)%、(56.0±6.1)%和(79.1±4.3)%,除0.125 mmol/L组外,其余组与溶剂对照组(9.4±3.0)%比较,差异均有统计学意义(均P<0.05).膜联蛋白V~+/PI~-与Caspase-3和9活性都呈正相关(r=0.786、0.736,均P<0.05),Caspase-3活性与Caspase~活性也呈正相关(r=0.845,P<0.05),膜联蛋白V~+/PI~-和Caspase-3活性均与Caspase-8活性无相关.100 μmol/L Z-DEVD-FMK预处理使2.0 mmol/L TCE处理的NHEK中Caspase-3活性从(0.963±0.043)nmol pNA·min~(-1)·ml~(-1)下降为(0.349±0.045)nmol pNA·min~(-1)·ml~(-1),膜联蛋白V~+/PI~-从(80.0±5.5)%下降为(16.3±3.2)%(P<0.01),Caspase-9活性变化不大(P>0.05).100μmol/L的Z-LEHD-FMK预处理不仅使得2.0 mmol/L TCE处理的NHEK中Caspase-3活性下降为(0.338±0.011)nmol pNA·min~(-1)·ml~(-1),膜联蛋白V~+/PI~-下降为(16.1±1.7)%,而且Caspase-9活性也从(0.821±0.031)nmol pNA·min~(-1)·ml~(-1)下降为(0.240±0.043)nmol pNA·min~(-1)·ml~(-1),差异有统计学意义(P<0.01).2.0 mmol/L的TCE处理NHEK 4 h后,Rh123荧光强度在培养4、8、12、24 h时均明显低于0 h(18.7±0.5,均P<0.01);0.125、0.5和2.0 mmol/L的TCE处理NHEK 4 h后培养8 h,Rh123荧光强度为16.1±0.5、12.1±0.6和8.1±0.6,均低于溶剂对照组(18.1±0.5,均P<0.01).结论 TCE诱导NHEK凋亡中,包括线粒体膜电位下降和Caspse-9依赖的Caspase-3的激活在内的内部凋亡途径可能发挥重要作用.

Mechanisms of apoptosis induced by trichloroethylene in normal human epidermis keratinocytes

Objective To explore the potential mechanism of trichloroethylene (TCE) -induced apoptosis in normal human epidermis keratinocyte (NHEK) by assaying the Caspase activities, mitochondrial membrane potential (△Ψm) and apoptosis in vitro. Methods NHEK was exposed to TCE and Caspases-3, 8 and 9 activities were determined using a commercial assay kit. Apoptosis and △Ψm were detected by flow cytometry (FCM) after double-stained with annexin-V and PI, Rh123 and PI respectively. NHEK was pretreated with inhibitor of Caspase-3 or 9 to verify the activation of Caspases by TCE treatment. Results Various dose of TCE exposure could increase the Caspases-3 and 9 activities in dose- and time-dependent way. There was marked difference between TCE-treated group and control at 12 or 24 h. But no significant influence of Caspase-8 activity was evoked. 0.125, 0.25, 0.5, 1.0 and 2.0 mmol/L TCE treated NHEK 4 h then cultured for 12 h. Annexin-V~+/PI~- proportion were (20.1±4.1) %, (30.0± 7.5) %, (42.1±8.2) %, (56.0±6.1) % and (79.1±4.3) % respectively. There was marked difference between TCE-treated group except for 0.125 mmol/L and control (9.4±3.0) % (all P < 0.05 ). FITC~+/ PI~- proportion were marked positive correlation with Caspase-3 and 9 activities, r =0.786, 0.736(both P < 0.05). Caspase-3 activities had also a marked positive correlation with Caspase-9 activities, r=0.845 (P < 0.05). There was no correlation with Caspase-8 activities. Pretreatment for 1 h with 100 μmol/L Z-DEVD-annexin-V~+/PI~- proportion decreased from (80.0±5.5)% to (16.3±3.2)% in 2.0 mmol/L TCE treated NHEK with a significant difference (P < 0.01), but there was no change of Caspase-9 activities. 100 treatment with 2.0 mmol/L TCE. Rhod123 fluorescence intensity (FI) were respectively with a marked decrease as compared with 0 h(18.7±0.5, all P < 0.01). At 0.125, 0.5 and 2.0 mmol/L TCE treated NHEK for 4 h then cultured 8 h, Rh123 FI were 16.1±0.5, 12.1±0.6 and 8.1±0.6 with a marked decrease as compared with control(18.1±0.5, all P < 0.01). Conclusion TCE-induced NHEK apoptosis is mediated intrinsically through the mitochondrial pathway of the decrease of ΔΨm and the Caspase-9 dependent activation of Caspase-3.