Metabolic mechanisms of naphthalene toxicity in lung

描述（由申请人提供）：萘（NA）是一种普遍存在的污染物，人类广泛暴露于其中。NA在大鼠和小鼠中引起肿瘤，并已被归类为可能的人类致癌物。NA致癌性的机制被认为涉及NA诱导的急性肺损伤和修复的重复循环。NA细胞毒性的先决条件是其通过细胞色素P450（NA-O）酶的生物活化;形成的反应性代谢物，其衍生自NA-环氧化物（NA-O），可以耗尽细胞谷胱甘肽（GSH），并且在较高浓度下，共价结合至组织蛋白。NA-O可以由肺和肝产生。在小鼠中负责NA生物活化的主要酶包括CYP 2A 5和CYP 2F 2; Cyp 2f 2缺失小鼠对NA肺毒性具有高度抗性，而Cyp 2a 5缺失小鼠对NA鼻毒性具有部分保护作用。人肺和人肝都能够代谢NA，尽管微粒体NA代谢和生物活化的速率存在较大的个体间差异。然而，人CYP 2A 13和CYP 2F 1（分别为小鼠CYP 2A 5和CYP 2F 2的直系同源物）在NA生物活化中的作用尚未充分了解，肝脏P450功能变化对个体发生NA介导的肺毒性风险的潜在影响仍不明确。本申请的目的是确定CYP 2A 13和CYP 2F 1在CYP 2A 13/2F 1人源化小鼠肺中NA生物活化和毒性中的作用;鉴定富含CYP 2A 13/2F 1表达的人肺区域;并确定肝脏中P450介导的NA生物活化和/或解毒是否会导致或以其他方式影响NA肺毒性。中心假设是NA有可能引起人类肺毒性，并且NA在肺和肝脏中的代谢影响个体的结果。将在两个特定目的中检验该假设，即：1）确定CYP 2A 13和CYP 2F 1在NA生物活化和肺毒性中的作用; 2）确定肝脏NA代谢是否会影响NA肺毒性的风险。我们将采用体内和体外方法相结合，并利用一些遗传修饰的小鼠模型，以及人体组织和细胞，以解决特定的目标。这些研究的长期目标是确定影响实验动物和人类NA介导的肺毒性的代谢机制。

DESCRIPTION (provided by applicant): Naphthalene (NA) is a ubiquitous pollutant to which humans are widely exposed. NA causes tumors in rats and mice, and has been classified as a Possible Human Carcinogen. The mechanism of NA carcinogenicity is believed to involve repeated cycles of NA-induced acute lung injury and repair. A prerequisite for NA cytotoxicity is its bioactivation by cytochrome P450 (CYP) enzymes; the reactive metabolites formed, which derive from the NA-epoxide (NA-O), can deplete cellular glutathione (GSH) and, at higher concentrations, bind covalently to tissue proteins. NA-O can be produced by both lung and liver. The major enzymes responsible for NA bioactivation in the mouse include CYP2A5 and CYP2F2; Cyp2f2-null mice are highly resistant to NA lung toxicity, whereas Cyp2a5-null mice are partially protected against NA nasal toxicity. Both human lung and human liver are capable of metabolizing NA, although large interindividual variations exist in the rates of microsomal NA metabolism and bioactivation. However, the roles of human CYP2A13 and CYP2F1 (orthologs of mouse CYP2A5 and CYP2F2, respectively) in NA bioactivation are not well understood, and the potential impact of variations in hepatic P450 function on an individual's risks of developing NA- mediated lung toxicity remains undefined. The objectives of this application are to define the role of CYP2A13 and CYP2F1 in NA bioactivation and toxicity in the lungs of CYP2A13/2F1-humanized mice; identify human lung regions that are enriched in CYP2A13/2F1 expression; and determine whether P450- mediated NA bioactivation and/or detoxification in the liver could contribute to, or otherwise influence, NA lung toxicity. The central hypothesis is that NA has the potential to cause lung toxicity in humans and that the metabolism of NA in both lung and liver influence the outcome on an individual basis. This hypothesis will be tested in two specific aims that will 1) define the role of CYP2A13 and CYP2F1 in NA bioactivation and toxicity in the lung; 2) define whether hepatic NA metabolism could influence the risks of NA lung toxicity. We will employ a combination of in vivo and in vitro approaches, and utilize a number of genetically modified mouse models, as well as human tissues and cells, to address the specific aims. The long-term goal of these studies is to define the metabolic mechanisms that influence NA-mediated lung toxicity in experimental animals and humans.