Gallagher J, Heinrich U, George M, Hendee L, Phillips D H, Lewtas J
Health Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711.
Carcinogenesis. 1994 Jul;15(7):1291-9. doi: 10.1093/carcin/15.7.1291.
Exposure of rats to diesel emissions results in the development of lung tumors. The objective of this study was to determine whether the polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs or other polycyclic organic matter adsorbed to diesel particles induces the formation of DNA adducts in the lung when compared to particles with little or no adsorbed organic matter. Rats were exposed to diesel emissions containing particles with over 30% solvent-extractable adsorbed organic matter and to particles with < 0.1% adsorbed organic matter (carbon black particles and TiO2). Wistar rats were exposed to diesel emissions (7.5 mg/m3) for 2 months, 6 months and 2 years and for 2 years to carbon black (11.3 mg/m3) and TiO2 particles (10.4 mg/m3) to compare tumorigenic response and DNA adduct formation in the lung. Two versions of the 32P-postlabeling assay for the detection of DNA adducts were used to tentatively identify nitrated-amine or arylamine adducts formed relative to other nitro PAH based on the demonstrated sensitivity of these adducts to nuclease P1 treatment. Total adduct levels were determined for peripheral lung tissue DNA as detected in a diagonal radioactive zone. One major adduct which migrated outside this region (adduct 1) and a nuclease P1-sensitive adduct (adduct 2) were quantitated separately. Adduct 1 increased significantly over time in the filtered air exposed animals but decreased markedly at the 2 year time points regardless of particle type, presumably as a result of adduct dilution through de novo cell synthesis or cell proliferation invoked in response to particle loading and/or effect on the endogenous synthesis or degradation of DNA reactive moieties. The nuclease sensitive adduct (adduct 2), possibly resulting from exposure to nitro-PAHs, was detected in diesel-exposed rats but was not detected in the rats exposed to TiO2 and carbon black. No significant elevation in PAH-derived adducts, relative to the filtered air controls, was observed in the rodents exposed to diesel emission. Our data suggest that long-term contact with these particles may result in a cell proliferative response, enhanced degradation of I-compounds not related to cell proliferation, and/or synthesis of I-compounds, irrespective of the differences in organic content associated with the three particle types. This response may be an important factor in explaining the reported similarity in tumorigenic response in rodents exposed to diesel emissions, carbon black and TiO2 particles.
将大鼠暴露于柴油废气中会导致肺部肿瘤的发生。本研究的目的是确定与吸附很少或没有有机物的颗粒相比，吸附在柴油颗粒上的多环芳烃（PAHs）、硝基多环芳烃或其他多环有机物是否会在肺部诱导形成DNA加合物。将大鼠暴露于含有超过30%可溶剂萃取吸附有机物的柴油废气颗粒以及吸附有机物<0.1%的颗粒（炭黑颗粒和二氧化钛）中。将Wistar大鼠暴露于柴油废气（7.5毫克/立方米）中2个月、6个月和2年，并将其暴露于炭黑（11.3毫克/立方米）和二氧化钛颗粒（10.4毫克/立方米）中2年，以比较肺部的致瘤反应和DNA加合物的形成。使用两种版本的32P后标记分析法检测DNA加合物，根据这些加合物对核酸酶P1处理的敏感性，初步鉴定相对于其他硝基PAH形成的硝化胺或芳胺加合物。测定外周肺组织DNA在对角放射性区域中检测到的总加合物水平。分别对迁移出该区域的一种主要加合物（加合物1）和一种核酸酶P1敏感加合物（加合物2）进行定量。加合物1在暴露于过滤空气的动物中随时间显著增加，但在2年时间点时无论颗粒类型如何均显著下降，这可能是由于通过从头细胞合成或因颗粒负荷引起的细胞增殖以及/或者对DNA反应性部分内源性合成或降解的影响导致加合物稀释的结果。在暴露于柴油的大鼠中检测到可能因接触硝基多环芳烃而产生的核酸酶敏感加合物（加合物2），但在暴露于二氧化钛和炭黑的大鼠中未检测到。相对于过滤空气对照组，在暴露于柴油废气的啮齿动物中未观察到PAH衍生加合物有显著升高。我们的数据表明，长期接触这些颗粒可能导致细胞增殖反应、与细胞增殖无关的I类化合物降解增强以及/或者I类化合物的合成，而与三种颗粒类型相关的有机含量差异无关。这种反应可能是解释在暴露于柴油废气、炭黑和二氧化钛颗粒的啮齿动物中报告的致瘤反应相似性的一个重要因素。
