Metabolic mechanisms of naphthalene toxicity in lung

描述(申请人提供)：萘(NA)是一种普遍存在的污染物，人类广泛接触。NA会导致大鼠和小鼠的肿瘤，并已被归类为可能的人类致癌物质。NA的致癌机制被认为涉及NA诱导的急性肺损伤和修复的反复循环。NA细胞毒性的先决条件是它被细胞色素P450(CYP)酶激活；由NA-环氧化物(NA-O)产生的反应性代谢产物可以耗尽细胞内的谷胱甘肽(GSH)，在较高浓度时，它与组织蛋白共价结合。肺和肝都能产生Na-O。在小鼠体内，负责NA生物激活的主要酶包括CYP2A5和CYP2F2；Cyp2f2缺失的小鼠对NA肺部毒性具有高度的抵抗力，而Cyp2a5缺失的小鼠对NA鼻毒性具有部分保护作用。人的肺和肝都能代谢NA，尽管微体NA的代谢率和生物活性在个体间存在很大的差异。然而，人类细胞色素P450 A13和细胞色素P450 F1(分别与小鼠细胞色素P450 A5和细胞色素P450 F2同源)在NA生物激活中的作用尚不清楚，肝脏P450功能变异对个体发生NA介导的肺毒性风险的潜在影响仍不明确。本应用的目的是确定细胞色素P450-A13和细胞色素P450-1在细胞色素P450-A13/2F1人源化小鼠肺内NA生物激活和毒性中的作用；确定人类肺组织中表达丰富的CYP2A13/2F1区域；以及确定肝脏中P450介导的NA生物激活和/或解毒是否有助于或以其他方式影响NA的肺毒性。中心假设是NA有可能导致人类的肺部毒性，NA在肺和肝脏中的代谢影响个体的结果。这一假设将在两个特定的目标下进行检验，这两个目标将1)确定CYP2A13和CYP2F1在NA在肺中的生物激活和毒性中的作用；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相结合的方法，并利用一些转基因小鼠模型以及人类组织和细胞来解决特定的目标。这些研究的长期目标是确定在实验动物和人类中影响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.