背景:柴油机废气(DE)在实验暴露的人类中诱导嗜中性粒细胞增多和淋巴细胞增多。这些反应与NF-κB和c-Jun的核迁移平行发生,丝裂原活化蛋白激酶的活化和炎症介质的产生增加。关于DE对内源性抗氧化剂和外源性生物防御的影响仍然存在不确定性,分别由核因子红系2相关因子2(Nrf2)和芳烃受体(AhR)介导,以及细胞抗氧化剂适应对DE不利影响的保护程度。
方法:使用免疫组织化学,我们在一项随机双盲研究中,研究了健康受试者暴露于DE(PM10,300µg/m3)后6小时与过滤后的空气相比,支气管粘膜活检上皮中Nrf2和AhR的核定位。作为激活的标志。细胞色素P450的细胞质表达,家族1,亚族A,多肽1(CYP1A1)和亚家族B,检查多肽1(CYP1B1)以确认AhR激活;随着aldo-keto还原酶(AKR1A1,AKR1C1和AKR1C3)的表达,环氧化物水解酶和NAD(P)H脱氢酶醌1(NQO1)也定量。检查了炎症和氧化应激标志物,以了解观察到的反应。
结果:DE暴露导致中性粒细胞流入支气管气道表面(p=0.013),以及支气管粘膜下中性粒细胞增加(p<0.001),淋巴细胞(p=0.007)和肥大细胞(p=0.002)数量。此外,DE暴露增强了AhR的核易位,并增加了支气管上皮中CYP1A1的表达(分别为p=0.001和p=0.028)。AhR的核易位在粘膜下白细胞中也增加(p<0.001)。上皮核AhR表达与DE后支气管粘膜下CD3数量呈负相关(r=-0.706,p=0.002)。相比之下,DE没有增加Nrf2的核转位,并且与支气管上皮细胞中NQO1的减少有关(p=0.02),不影响CYP1B1,aldo-keto还原酶,或环氧化物水解酶蛋白表达。
结论:这些体内人体数据证实了早期基于细胞和动物的柴油机尾气诱导AhR和CYP1A1的观察结果。在暴露后6小时的研究时间点,在没有诱导抗氧化剂或II期异生物防御的情况下,发生了I期异生物反应的诱导。这表明DE相关化合物,如多环芳烃(PAHs),可能会诱导急性炎症并改变解毒酶,而不会伴随人类气道中的保护性细胞适应。
BACKGROUND: Diesel exhaust (DE) induces neutrophilia and lymphocytosis in experimentally exposed humans. These responses occur in parallel to nuclear migration of NF-κB and c-Jun, activation of mitogen activated protein kinases and increased production of inflammatory mediators. There remains uncertainty regarding the impact of DE on endogenous antioxidant and xenobiotic defences, mediated by nuclear factor erythroid 2-related factor 2 (Nrf2) and the aryl hydrocarbon receptor (AhR) respectively, and the extent to which cellular antioxidant adaptations protect against the adverse effects of DE.
METHODS: Using immunohistochemistry we investigated the nuclear localization of Nrf2 and AhR in the epithelium of endobronchial mucosal biopsies from healthy subjects six-hours post exposure to DE (PM10, 300 µg/m3) versus post-filtered air in a randomized double blind study, as a marker of activation. Cytoplasmic expression of cytochrome P450s, family 1, subfamily A, polypeptide 1 (CYP1A1) and subfamily B, Polypeptide 1 (CYP1B1) were examined to confirm AhR activation; with the expression of aldo-keto reductases (AKR1A1, AKR1C1 and AKR1C3), epoxide hydrolase and NAD(P)H dehydrogenase quinone 1 (NQO1) also quantified. Inflammatory and oxidative stress markers were examined to contextualize the responses observed.
RESULTS: DE exposure caused an influx of neutrophils to the bronchial airway surface (p = 0.013), as well as increased bronchial submucosal neutrophil (p < 0.001), lymphocyte (p = 0.007) and mast cell (p = 0.002) numbers. In addition, DE exposure enhanced the nuclear translocation of the AhR and increased the CYP1A1 expression in the bronchial epithelium (p = 0.001 and p = 0.028, respectively). Nuclear translocation of AhR was also increased in the submucosal leukocytes (p < 0.001). Epithelial nuclear AhR expression was negatively associated with bronchial submucosal CD3 numbers post DE (r = -0.706, p = 0.002). In contrast, DE did not increase nuclear translocation of Nrf2 and was associated with decreased NQO1 in bronchial epithelial cells (p = 0.02), without affecting CYP1B1, aldo-keto reductases, or epoxide hydrolase protein expression.
CONCLUSIONS: These in vivo human data confirm earlier cell and animal-based observations of the induction of the AhR and CYP1A1 by diesel exhaust. The induction of phase I xenobiotic response occurred in the absence of the induction of antioxidant or phase II xenobiotic defences at the investigated time point 6 h post-exposures. This suggests DE-associated compounds, such as polycyclic aromatic hydrocarbons (PAHs), may induce acute inflammation and alter detoxification enzymes without concomitant protective cellular adaptations in human airways.