Free Radical Mechanism in Obesity Potentiation of Environmental Hepatotoxicity

肥胖相关的非酒精性脂肪性肝炎（NASH），已成为一个日益增长的公共卫生问题，在美国的肥胖人口增加。从脂肪变性（脂肪肝）到脂肪性肝炎（脂肪肝伴炎症）的进展被认为需要第二次打击。这种第二次打击可以通过环境暴露于肝毒素来提供，所述肝毒素被还原性代谢以形成反应性自由基。虽然直接暴露于高剂量的环境肝毒素是罕见的，从环境中的低暴露更常见。正常健康个体可能对低剂量耐受良好，但可能是肥胖人群中脂肪性肝炎等炎性肝损伤的潜在风险因素。因此，本研究项目的长期目标是检验以下假设：环境中的低肝毒素暴露可增强肥胖小鼠脂肪性肝炎进展的风险。该假设将在三个特定的目标，包括调查的自由基形成和蛋白质的翻译后氧化加合物在肥胖小鼠响应消毒副产物（DBP）溴二氯甲烷（BDCM）的机制进行测试。通过使用酶（如NADPH氧化酶和Cyp 450同工酶CYP 2 E1）的抑制剂以及缺乏这些酶中的每一种的敲除小鼠，将实现特定的目的。肥胖症的所有研究将在饮食诱导的肥胖（DIG）小鼠中进行，并与饮食限制的瘦对照进行比较。在目标2中，1将检查初始脂质过氧化、干扰素-γ（IFN-γ）和粒细胞巨噬细胞集落刺激因子（GMCSF）如何导致巨噬细胞活化，并促进BDCM暴露后第二波自由基损伤和TNF-α分泌。这一目标将通过使用体内和体外系统的实验来实现。在目标3中，我将研究促炎脂肪细胞因子瘦素在协同环境肝毒素如溴二氯甲烷（DBP）的作用中的作用。这一目标将通过研究瘦素敲除小鼠中自由基诱导的巨噬细胞活化和细胞死亡以及使用针对瘦素的中和抗体来实现。

Obesity associated Nonalcoriolic steatohepatitis (NASH), has become a growing public health concern with increased obesity population in the United States. Progression from steatosis (fatty liver) to steatohepatitis (fatty liver with inflammation) is thought to require a second hit. This second hit can be provided by environmental exposure to hepatotoxins that are reductively metaboiized to form reactive free radicals. Although direct exposure to high doses of environmental hepatotoxins is rare, low exposure from the environment is more com.mon. Low doses may be well tolerated by normal healthy individuals but can be potential risk factors for inflammatory liver injuries like steatohepatitis in obese persons. Thus the long term objective of this research project is to test the hypothesis that low hepatotoxin exposure from the environment can potentiate the risk of progression of steatohepatitis in obese mice. The hypothesis will be tested in three specific aims that include investigating the mechanism of free radical formation and post-translation oxidation adducts of proteins in obese mice in response to the disinfection byproduct (DBP) bromodichloromethane (BDCM). The specific aims will be achieved by using inhibitors of enzymes such as NADPH oxidase and the Cyp450 isozyme CYP2E1 and with knockout mice lacking each of these enzymes. All studies in obesity will be carried out in diet-induced obese (DIG) mice and compared to diet-restricted lean controls. In Aim 2, 1 shall examine how initial lipid peroxidation, interferon-gamma (IFN-y) and granulocyte macrophage colony stimulating factor (GMCSF) lead to activation of macrophages and contribute to the second wave of generation of free radical damage and TNF-alpha secretion following BDCM exposure. This aim will be achieved through experiments using both in vivo and in vitro systems, in aim 3, I shall investigate the role of the proinflammatory adipocytokine leptin in synergizing the effect of environmental hepatotoxins such as bromodichloromethane, a DBP, This aim will be achieved by investigating free radical-induced macrophage activation and cell death in Ieptin knockout mice and using neutralizing antibodies against Ieptin.