Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona 85721.
Wadsworth Center, New York State Department of Health, and School of Public Health, State University of New York at Albany, Albany, New York 12201.
Toxicol Sci. 2020 Oct 1;177(2):334-346. doi: 10.1093/toxsci/kfaa114.
Previous studies have established that cytochrome P450 enzymes (CYPs) in both liver and lung are capable of bioactivating naphthalene (NA), an omnipresent air pollutant and possible human carcinogen, in vitro and in vivo. The aim of this study was to examine the specific contribution of pulmonary CYPs in airway epithelial cells to NA-induced airway toxicity. We used a lung-Cpr-null mouse model, which undergoes doxycycline-induced, Cre-mediated deletion of the Cpr (a redox partner of all microsomal CYPs) gene specifically in airway epithelial cells. In 2-month-old lung-Cpr-null mice, Cpr deletion occurred in 75%-82% of epithelial cells of conducting airways. The extent of NA-induced acute lung toxicity (as indicated by total protein concentration and lactate dehydrogenase activity in bronchoalveolar lavage fluid collected at 24-h after initiation of a 4-h, nose-only, 10-ppm NA inhalation exposure) was substantially lower (by 37%-39%) in lung-Cpr-null mice, compared with control littermates. Moreover, the extent of cellular proliferation (as indicated by 5-bromo-2'-deoxyuridine incorporation) was noticeably lower in both proximal and distal airways (by 59% and 65%, respectively) of NA-treated lung-Cpr-null mice, compared with control littermates, at 2-day post-NA inhalation exposure. A similar genotype-related difference in the extent of postexposure cell proliferation was also observed in mice exposed to NA via intraperitoneal injection at 200 mg/kg. These results directly validate the hypothesis that microsomal CYP enzymes in airway epithelial cells play a large role in causing injury to airway epithelia following exposure to NA via either inhalation or intraperitoneal route.
先前的研究已经证实，肝和肺中的细胞色素 P450 酶（CYPs）在体外和体内均能使无处不在的空气污染物和可能的人类致癌物萘（NA）生物活化。本研究的目的是研究气道上皮细胞中的肺 CYP 对 NA 诱导的气道毒性的特定贡献。我们使用了肺-Cpr 基因敲除小鼠模型，该模型可在气道上皮细胞中经强力霉素诱导、Cre 介导的 Cpr（所有微粒体 CYP 的氧化还原伴侣）基因缺失。在 2 月龄的肺-Cpr 基因敲除小鼠中，上皮细胞中有 75%-82%的细胞发生 Cpr 缺失。在启动 4 小时、仅鼻吸入 10ppm NA 暴露 24 小时后收集的支气管肺泡灌洗液中总蛋白浓度和乳酸脱氢酶活性表明，NA 诱导的急性肺毒性程度（作为指示）在肺-Cpr 基因敲除小鼠中显著降低（降低 37%-39%），与对照同窝仔鼠相比。此外，在 NA 处理的肺-Cpr 基因敲除小鼠的近端和远端气道（分别降低 59%和 65%）中，细胞增殖程度（以 5-溴-2'-脱氧尿苷掺入表示）明显低于对照同窝仔鼠，在 NA 吸入暴露后 2 天。在通过腹腔注射 200mg/kg 暴露于 NA 的小鼠中也观察到类似的与基因型相关的细胞增殖程度差异。这些结果直接验证了这样一个假设，即在通过吸入或腹腔途径暴露于 NA 后，气道上皮细胞中的微粒体 CYP 酶在引起气道上皮细胞损伤方面发挥着重要作用。
