Lin Ching-Yu, Huang Feng-Peng, Ling Yee Soon, Liang Hao-Jan, Lee Sheng-Han, Hu Mei-Yun, Tsao Po-Nien
Institute of Environmental Health, College of Public Health, National Taiwan University, Taipei 100, Taiwan.
Department of Pediatrics, National Taiwan University Hospital, Taipei 100, Taiwan.
PLoS One. 2015 Apr 7;10(4):e0120429. doi: 10.1371/journal.pone.0120429. eCollection 2015.
Naphthalene, the most common polycyclic aromatic hydrocarbon, causes airway epithelium injury in mice. Repeated exposure of mice to naphthalene induces airway epithelia that are resistant to further injury. Previous studies revealed that alterations in bioactivation enzymes and increased levels of gamma-glutamylcysteine synthase in the bronchioles protect tolerant mice from naphthalene and its reactive metabolites. In our current study, tolerance was induced in male ICR mice using a total of 7 daily intraperitoneal injections of naphthalene (200 mg/kg). Both naphthalene-tolerant and non-tolerant mice were challenged with a dose of 300 mg/kg naphthalene on day 8 to investigate metabolite differences. The lungs, liver, and kidneys were collected for histopathology 24 h after the challenge dose. Bronchial alveolar lavage fluid (BALF) and both hydrophilic and hydrophobic extracts from each organ were analyzed using nuclear magnetic resonance (NMR)-based metabolomics. The histological results showed no observable injuries to the airway epithelium of naphthalene-tolerant mice when compared with the control. In contrast, airway injuries were observed in mice given a single challenge dose (injury mice). The metabolomics analysis revealed that the energy metabolism in the lungs of tolerant and injury mice was significantly perturbed. However, antioxidant metabolites, such as glutathione and succinate, were significantly increased in the lungs of tolerant mice, suggesting a role for these compounds in the protection of organs from naphthalene-induced electrophilic metabolites and free radicals. Damage to the airway cellular membrane, as shown by histopathological results and increased acetone in the BALF and perturbation of hydrophobic lung extracts, including cholesterol, phosphorylcholine-containing lipids, and fatty acyl chains, were observed in injury mice. Consistent with our histopathological results, fewer metabolic effects were observed in the liver and kidney of mice after naphthalene treatments. In conclusion, NMR-based metabolomics reveals possible mechanisms of naphthalene tolerance and naphthalene-induced toxicity in the respiratory system of mice.
萘是最常见的多环芳烃，可导致小鼠气道上皮损伤。小鼠反复接触萘会诱导产生对进一步损伤具有抗性的气道上皮。先前的研究表明，生物活化酶的改变以及细支气管中γ-谷氨酰半胱氨酸合成酶水平的升高可保护耐受小鼠免受萘及其活性代谢产物的影响。在我们目前的研究中，通过总共7天每天腹腔注射萘（200毫克/千克）诱导雄性ICR小鼠产生耐受性。在第8天，对萘耐受和不耐受的小鼠均用300毫克/千克的萘剂量进行攻击，以研究代谢产物差异。攻击剂量后24小时收集肺、肝和肾用于组织病理学检查。使用基于核磁共振（NMR）的代谢组学分析支气管肺泡灌洗液（BALF）以及每个器官的亲水性和疏水性提取物。组织学结果显示，与对照组相比，萘耐受小鼠的气道上皮没有观察到损伤。相比之下，在给予单次攻击剂量的小鼠（损伤小鼠）中观察到气道损伤。代谢组学分析表明，耐受和损伤小鼠肺中的能量代谢受到显著干扰。然而，耐受小鼠肺中的抗氧化代谢产物，如谷胱甘肽和琥珀酸，显著增加，表明这些化合物在保护器官免受萘诱导的亲电代谢产物和自由基的影响中发挥作用。在损伤小鼠中观察到气道细胞膜损伤，这通过组织病理学结果以及BALF中丙酮增加和肺疏水性提取物（包括胆固醇、含磷酸胆碱的脂质和脂肪酰链）的扰动得以体现。与我们的组织病理学结果一致，萘处理后小鼠肝脏和肾脏中的代谢影响较少。总之，基于NMR的代谢组学揭示了小鼠呼吸系统中萘耐受和萘诱导毒性的可能机制。
