Hewitt Rebecca, Forero Albert, Luncsford Paz J, Martin Francis L
Biomedical Sciences Unit, Lancaster University, Lancaster, United Kingdom.
Environ Health Perspect. 2007 Dec;115 Suppl 1(Suppl 1):129-36. doi: 10.1289/ehp.9361.
Within mixtures, interactions between different xenobiotics may occur to give rise to additive, synergistic, inhibitory and/or stimulatory effects in target cells. The role that xenobiotics individually or in mixtures, and at environmental concentrations, play in the etiology of common human diseases often remains obscure.
In the presence or absence of lindane, chromosomal aberrations were detected in MCF-7 cells after 24-hr treatment with benzo[a]pyrene (B[a]P) or 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) using the cytokinesis-block micronucleus assay. Micronuclei were scored in 1,000 binucleate cells/treatment. We investigated intracellular responses using quantitative gene expression analyses of cyclin-dependent kinase inhibitor 1A [CDKN1A (P21(WAF1/CIP1))], B-cell leukemia/lymphoma 2 (BCL-2), BCL-2-associated X (BAX), and isoforms of cytochrome P450 (CYP), CYP1A1, CYP1A2, and CYP1B1. Immunocytochemical analyses of p53, p21(Waf1/Cip1), Bcl-2 and Bax protein expression in MCF-7 cells were also carried out.
After exposure to binary mixtures of B[a]P plus lindane or PhIP plus lindane, a 10-fold increase in micronucleus formation resulted; these test agents individually induced 2- to 5-fold increases. Lindane increased the ratio of Bcl-2:Bax, as did 17beta-estradiol (E(2)). Although treatment with B[a]P alone was found to elevate expression of P21(WAF1/CIP1)and CYP isoenzymes, it reduced the ratio of BCL-2:BAX mRNA transcripts. Treatment with a binary mixture of 10(-8) M B[a]P plus 10(-12) M lindane or 10(-10) M E(2) reversed B[a]P-induced reductions in the ratio of Bcl-2- to Bax-positive cells. In contrast, treatments with PhIP (known to possess hormonelike properties) plus lindane or E(2) resulted in profound reductions in Bcl-2:Bax ratio.
Our results suggest that low-dose treatments (i.e., close to environmental levels) may increase DNA damage while influencing survival in exposed cells and that these effects may depend on the endocrine activity of test agents.
在混合物中，不同外源性物质之间可能发生相互作用，从而在靶细胞中产生相加、协同、抑制和/或刺激作用。外源性物质单独或混合存在且处于环境浓度时，在常见人类疾病病因学中所起的作用往往仍不清楚。
在有或没有林丹存在的情况下，使用胞质分裂阻滞微核试验，在用苯并[a]芘（B[a]P）或2-氨基-1-甲基-6-苯基咪唑[4,5-b]吡啶（PhIP）处理24小时后，检测MCF-7细胞中的染色体畸变。对每个处理组的1000个双核细胞进行微核计数。我们使用细胞周期蛋白依赖性激酶抑制剂1A[CDKN1A（P21（WAF1/CIP1））]、B细胞白血病/淋巴瘤2（BCL-2）、BCL-2相关X蛋白（BAX）以及细胞色素P450（CYP）的同工酶CYP1A1、CYP1A2和CYP1B进行定量基因表达分析，以研究细胞内反应。还对MCF-7细胞中的p53、p21（Waf1/Cip1）、Bcl-2和Bax蛋白表达进行了免疫细胞化学分析。
暴露于B[a]P与林丹或PhIP与林丹的二元混合物后，微核形成增加了10倍；这些受试物单独作用时诱导微核形成增加2至5倍。林丹增加了Bcl-2:Bax的比例，17β-雌二醇（E₂）也有同样的作用。虽然发现单独用B[a]P处理可提高P21（WAF1/CIP1）和CYP同工酶的表达，但它降低了BCL-2:BAX mRNA转录本的比例。用10⁻⁸M B[a]P加10⁻¹²M林丹或10⁻¹⁰M E₂的二元混合物处理可逆转B[a]P诱导的Bcl-2阳性细胞与Bax阳性细胞比例的降低。相比之下，用PhIP（已知具有类激素特性）加林丹或E₂处理导致Bcl-2:Bax比例大幅降低。
我们的结果表明，低剂量处理（即接近环境水平）可能会增加DNA损伤，同时影响暴露细胞的存活，并且这些影响可能取决于受试物的内分泌活性。
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