Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Skip Bertman Drive, Baton Rouge, LA United States of America.
Department of Pharmacology, Toxicology, and Neuroscience, LSU Health Sciences Center-Shreveport, Shreveport, LA United States of America.
PLoS One. 2018 Oct 11;13(10):e0205412. doi: 10.1371/journal.pone.0205412. eCollection 2018.
Particulate matter (PM) is emitted during the combustion of fuels and wastes. PM exposure exacerbates pulmonary diseases, and the mechanism may involve oxidative stress. At lower combustion temperatures such as occurs in the cool zone of a flame, aromatic compounds chemisorb to the surface of metal-oxide-containing PM, resulting in the formation of surface-stabilized environmentally persistent free radicals (EPFR). Prior studies showed that PM-containing EPFR redox cycle to produce reactive oxygen species (ROS), and after inhalation, EPFR induce pulmonary inflammation and oxidative stress. Our objective was to elucidate mechanisms linking EPFR-induced oxidant injury with increased cytokine production by pulmonary epithelial cells. We thus treated human bronchial epithelial cells with EPFR at sub-toxic doses and measured ROS and cytokine production. To assess aryl hydrocarbon receptor (AhR) activity, cells were transfected with a luciferase reporter for xenobiotic response element activation. To test whether cytokine production was dependent upon AhR activation or oxidative stress, some cells were co-treated with an antioxidant or an AhR antagonist. EPFR increased IL-6 release in an ROS and AhR- and oxidant-dependent manner. Moreover, EPFR induced an AhR activation that was dependent upon oxidant production, since antioxidant co-treatment blocked AhR activation. On the other hand, EPFR treatment increased a cellular ROS production that was at least partially attenuated by AhR knockdown using siRNA. While AhR activation was correlated with an increased expression of oxidant-producing enzymes like cytochrome P450 CYP1A1, it is possible that AhR activation is both a cause and effect of EPFR-induced ROS. Finally, lipid oxidation products also induced AhR activation. ROS-dependent AhR activation may be a mechanism for altered epithelial cell responses after EPFR exposure, potentially via formation of bioactive lipid or protein oxidation products.
颗粒物（PM）是在燃料和废物燃烧过程中排放的。PM 暴露会加重肺部疾病，其机制可能涉及氧化应激。在较低的燃烧温度下，例如火焰的冷区，芳香族化合物化学吸附到含金属氧化物的 PM 表面，导致表面稳定的环境持久性自由基（EPFR）的形成。先前的研究表明，含有 EPFR 的 PM 会进行氧化还原循环以产生活性氧物质（ROS），并且在吸入后，EPFR 会引起肺部炎症和氧化应激。我们的目标是阐明将 EPFR 诱导的氧化剂损伤与肺部上皮细胞中细胞因子产生增加联系起来的机制。因此，我们用亚毒性剂量的 EPFR 处理人支气管上皮细胞，并测量 ROS 和细胞因子的产生。为了评估芳基烃受体（AhR）的活性，将细胞用异生物质反应元件激活的荧光素酶报告基因转染。为了测试细胞因子的产生是否依赖于 AhR 激活或氧化应激，一些细胞用抗氧化剂或 AhR 拮抗剂共同处理。EPFR 以 ROS、AhR 和氧化剂依赖性方式增加 IL-6 的释放。此外，EPFR 诱导了 AhR 激活，该激活依赖于氧化剂的产生，因为抗氧化剂共处理阻断了 AhR 激活。另一方面，EPFR 处理增加了细胞 ROS 的产生，该产生至少部分被使用 siRNA 的 AhR 敲低所减弱。虽然 AhR 激活与细胞色素 P450 CYP1A1 等产氧化剂酶的表达增加相关，但 AhR 激活可能是 EPFR 诱导的 ROS 的原因和结果。最后，脂质氧化产物也诱导了 AhR 激活。ROS 依赖性 AhR 激活可能是 EPFR 暴露后上皮细胞反应改变的一种机制，可能是通过形成生物活性脂质或蛋白质氧化产物。
