Université de Liège, Laboratoire de Chimie Médicale, Institut de Pathologie, B35, Centre Hospitalier Universitaire, B-4000 San Tilman, Belgium.
Environ Toxicol Pharmacol. 1996 Jul 15;1(4):249-56. doi: 10.1016/1382-6689(96)00018-X.
Endosulfan, a chlorinated cyclodiene insecticide, is known to cause a significant enhancement of altered hepatic foci in rats and to be a potent inhibitor of gap-junctional intercellular communication in vitro. Both of these features are common to many tumor promoters. However, long-term studies in rodents provide no evidence that it is carcinogenic or genotoxic. In the present study, endosulfan genotoxicity is evaluated and the formation of DNA adducts is investigated in three types of cultured hepatic cells (rodent, bird, and human). DNA-adduct formation in response to endosulfan treatment is measured by the (32)P-postlabelling method. The results have shown a high genotoxicity of endosulfan only in rat and human cells. Therefore, to better understand these findings and because nothing is known about the xenobiotic-metabolizing enzymes involved in endosulfan metabolism, we have attempted to identify the cytochromes P450 induced, which can transform endosulfan into reactive intermediates capable of interacting with DNA. To examine if endosulfan induces CYP1A-, CYP2B-, or CYP3A-family transcripts, we measured transcript levels by Northern blot and RT-PCR analyses. Endosulfan appears to selectively induce expression of the CYP3A gene family. It is a potent inducer of CYP3A1 mRNA in rat and is also shown, by RT-PCR. to increase the CYP3A7 transcript level in Hep G2 human hepatoma cells. In contrast, in fetal quail hepatocytes, CYP3A is not expressed and no endosulfan-DNA adducts are formed.
硫丹，一种氯化环戊二烯类杀虫剂，已知可显著增强大鼠肝病变焦点，并体外强力抑制细胞间隙连接通讯。这两个特点都是许多肿瘤促进剂所共有的。然而，啮齿动物的长期研究并未提供证据表明它具有致癌性或遗传毒性。在本研究中，评估了硫丹的遗传毒性，并研究了三种类型的培养肝细胞（啮齿动物、鸟类和人类）中 DNA 加合物的形成。通过（32）P-后标记法测量硫丹处理后 DNA 加合物的形成。结果表明，硫丹仅在大鼠和人类细胞中具有高遗传毒性。因此，为了更好地理解这些发现，并且因为人们对参与硫丹代谢的异生物质代谢酶一无所知，我们试图鉴定出可以将硫丹转化为能够与 DNA 相互作用的反应性中间产物的诱导细胞色素 P450。为了检查硫丹是否诱导 CYP1A、CYP2B 或 CYP3A 家族转录本，我们通过 Northern blot 和 RT-PCR 分析测量了转录本水平。硫丹似乎选择性地诱导 CYP3A 基因家族的表达。它是大鼠 CYP3A1 mRNA 的强力诱导剂，并且通过 RT-PCR 还表明它增加了 Hep G2 人肝癌细胞中的 CYP3A7 转录本水平。相比之下，在胎禽肝细胞中，CYP3A 不表达，也没有形成硫丹-DNA 加合物。
