Ethylbenzene induces microsomal oxygen free radical generation: antibody-directed characterization of the responsible cytochrome P450 enzymes.
Ethylbenzene induces microsomal oxygen free radical generation: antibody-directed characterization of the responsible cytochrome P450 enzymes.
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DOI：
10.1006/taap.2000.8910
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发表时间：
2000-05
影响因子：
3.8
通讯作者：
S. C. Serron;N. Dwivedi;W. Backes
中科院分区：
文献类型：
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作者：
S. C. Serron;N. Dwivedi;W. Backes
小分子芳香烃通过调节细胞色素P450酶的水平引起氧化代谢的变化，这些酶的变化导致芳香烃代谢的质变。这项研究的目的是确定暴露于小分子烷基苯乙苯(EB)是否会导致肝脏自由基产量的增加。给雄性F344大鼠ip EB(10 mmol/kg)，并与玉米油对照组进行比较。通过测定2‘，7’-二氯二乙酸酯荧光素(DCFH-DA)向其荧光产物2‘，7’-二氯荧光素(DCF)的转化来检测肝脏自由基的产生。观察到EB治疗后荧光DCF产量显著增加，尽管对总体细胞色素P450水平没有影响。这一过程可被P450的抑制剂美曲酮所抑制。过氧化氢酶也抑制了DCF的产生，表明过氧化氢(H(2)O(2))是EB介导的活性氧物种(ROS)形成过程中的一种活性氧中间体。有趣的是，超氧化物歧化酶(SOD)并不抑制玉米油处理的大鼠DCF的产生，但在EB处理的组中是一种有效的抑制作用。为了确定ROS产生的增加是否与特定的P450酶的变化有关，在存在抗CYP2B、抗CYP2C11、抗CYP2E1和抗CYP3A2抑制抗体的情况下，测量了DCF的产生。在EB处理组，抗CYP2B抗体抑制DCF的产生，但不抑制玉米油处理组的DCF产生，这与该酶的低组成水平以及EB对其的诱导相一致。数据还表明，CYP2B对ROS的产生有贡献。抗CYP2C11抗体对两组DCF的产生均无影响。玉米油处理的大鼠和乙苯处理的大鼠的ROS形成也被抗CYP2E1和抗CYP3A2的抗体抑制。这些结果表明，CYP2C11似乎不影响自由基的产生，EB处理大鼠自由基产生的增加与EB介导的CYP2B、CyP2E1和CyP3A2的升高是一致的。碳氢化合物处理后自由基生成的这种变化可能会导致这些化合物的毒性。
Small aromatic hydrocarbons cause changes in oxidative metabolism by modulating the levels of cytochrome P450 enzymes, with the changes in these enzymes being responsible for qualitative changes in aromatic hydrocarbon metabolism. The goal of this study was to determine if exposure to the small alkylbenzene ethylbenzene (EB) leads to an increase in hepatic free radical production. Male F344 rats were treated with ip injections of EB (10 mmol/kg) and compared to corn oil controls. Hepatic free radical production was examined by measuring the conversion of 2',7'-dichlorofluorescin diacetate (DCFH-DA) to its fluorescent product 2',7'-dichlorofluorescein (DCF). A significant elevation of fluorescent DCF production was observed after treatment with EB, despite the lack of effect on overall cytochrome P450 levels. This process was shown to be inhibitable by metyrapone, an inhibitor of P450. DCF production was also inhibited by catalase, suggesting that hydrogen peroxide (H(2)O(2)) is one of the reactive oxygen intermediates involved in EB-mediated reactive oxygen species (ROS) formation. Interestingly, superoxide dismutase (SOD) did not inhibit DCF production in corn oil-treated rats but was an effective inhibitor in the EB-treated groups. In an effort to determine if the increase in ROS production was related to changes in specific P450 enzymes, DCF production was measured in the presence of anti-CYP2B, anti-CYP2C11, anti-CYP2E1, and anti-CYP3A2 inhibitory antibodies. Anti-CYP2B antibodies inhibited DCF production in EB-treated, but not corn oil groups, which is consistent with the low constitutive levels of this enzyme and its induction by EB. The data also demonstrate that CYP2B contributes to ROS production. Anti-CYP2C11 did not influence DCF production in either group. ROS formation in corn oil-treated rats as well as in ethylbenzene-treated rats was also inhibited with antibodies to anti-CYP2E1 and anti-CYP3A2. These results suggest that CYP2C11 does not appear to influence free radical production and that the increase in free radical production in EB treated rats is consistent with the EB-mediated elevation of CYP2B, CYP 2E1, and CYP3A2. Such alterations in free radical generation in response to hydrocarbon treatment may contribute to the toxicity of these compounds.