De Haan L H, Simons J W, Bos A T, Aarts J M, Denison M S, Brouwer A
Department of Toxicology, Agricultural University Wageningen, The Netherlands.
Toxicol Appl Pharmacol. 1994 Dec;129(2):283-93. doi: 10.1006/taap.1994.1253.
The effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and the coplanar 3,3',4,4'-tetrachlorobiphenyl (3,3',4,4'-TCB) and 3,3',4,4',5,5'-hexachlorobiphenyl (3,3',4,4',5,5'-HCB) on intercellular communication (IC) were determined in order to investigate the in vitro tumor promoting potency of these compounds. 2,3,7,8-TCDD and the two coplanar PCBs tested caused a rapid (2 hr) and a sustained inhibition (48 hr) of IC in the mouse hepatoma cell line (Hepa1c1c7) to 20 and 50% of the unexposed control, respectively. Inhibition of IC was dose dependent with an EC50 range of about 50-100 pM for 2,3,7,8-TCDD, 2-5 nM for 3,3',4,4'-TCB, and 10-15 nM for 3,3',4,4',5,5'-HCB, respectively. A comparison of the IC inhibitory effects of 2,3,7,8-TCDD and PCBs with a well-known aryl hydrocarbon receptor (AhR)-mediated response, the induction of ethoxyresorufin O-deethylase (EROD) activity, in the same cells revealed EROD induction by 2,3,7,8-TCDD, 3,3',4,4'-TCB, and 3,3',4,4',5,5'-HCB with EC50 ranges of 100-200 pM, 20-70 nM, and 5-10 nM, respectively. The time course of IC inhibition was paralleled by EROD induction, although the time of onset of the response was earlier for IC (1 hr) than for EROD (2.5 hr). A role of the AhR in the inhibition of IC by 2,3,7,8-TCDD and PCBs was demonstrated by the lack of inhibition in AhR-defective Hepa1c1c7 cells. Transient inhibition of IC was observed in the mutant cells only at early time points (within 2 hr of exposure). These results and the observation that alpha-naphtoflavone (an AhR antagonist) greatly reduced the 2,3,7,8-TCDD-dependent sustained inhibition of IC strongly support a role of the AhR in the sustained inhibition of IC by these compounds. Furthermore, these data suggest that the mouse Hepa1c1c7 cells may be a good model in which to study in vitro tumor promoting capacity of dioxins, PCBs, and related compounds.
为了研究2,3,7,8 - 四氯二苯并 - p - 二恶英（2,3,7,8 - TCDD）、共平面的3,3',4,4' - 四氯联苯（3,3',4,4' - TCB）和3,3',4,4',5,5' - 六氯联苯（3,3',4,4',5,5' - HCB）的体外促肿瘤能力，测定了这些化合物对细胞间通讯（IC）的影响。2,3,7,8 - TCDD以及所测试的两种共平面多氯联苯导致小鼠肝癌细胞系（Hepa1c1c7）中的IC迅速（2小时）且持续（48小时）受到抑制，分别降至未暴露对照组的20%和50%。IC的抑制呈剂量依赖性，2,3,7,8 - TCDD的EC50范围约为50 - 100 pM，3,3',4,4' - TCB为2 - 5 nM，3,3',4,4',5,5' - HCB为10 - 15 nM。将2,3,7,8 - TCDD和多氯联苯对IC的抑制作用与同一细胞中著名的芳烃受体（AhR）介导的反应——乙氧芴香豆素O - 脱乙基酶（EROD）活性的诱导进行比较，结果显示2,3,7,8 - TCDD、3,3',4,4' - TCB和3,3',4,4',5,5' - HCB均可诱导EROD，其EC50范围分别为100 - 200 pM、20 - 70 nM和5 - 10 nM。IC抑制的时间进程与EROD诱导平行，尽管IC反应的起始时间（1小时）早于EROD（2.5小时）。AhR缺陷的Hepa1c1c7细胞中缺乏抑制作用，这证明了AhR在2,3,7,8 - TCDD和多氯联苯对IC的抑制中起作用。仅在早期时间点（暴露后2小时内）在突变细胞中观察到IC的短暂抑制。这些结果以及α - 萘黄酮（一种AhR拮抗剂）大大降低了2,3,7,8 - TCDD对IC的持续抑制这一观察结果，有力地支持了AhR在这些化合物对IC的持续抑制中起作用。此外，这些数据表明小鼠Hepa1c1c7细胞可能是研究二恶英、多氯联苯及相关化合物体外促肿瘤能力的良好模型。
