Free Radical Mechanism in Obesity Potentiation of Environmental Hepatotoxicity

随着美国肥胖人口的增加，肥胖相关的非酒精性脂肪性肝炎(NASH)已成为一个日益严重的公共卫生问题。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。这第二次打击可以通过暴露于环境中的肝毒素来提供，这些毒素被还原代谢形成反应性自由基。虽然直接接触高剂量的环境肝毒素很少见，但从环境中低剂量暴露更常见。低剂量可能是正常健康人很好的耐受性，但可能是肥胖者脂肪性肝炎等炎症性肝损伤的潜在危险因素。因此，这项研究项目的长期目标是检验这样一个假设，即环境中低肝毒素暴露可以增强肥胖小鼠脂肪性肝炎的进展风险。这一假设将在三个特定目标下进行验证，其中包括研究肥胖小鼠体内自由基的形成机制和蛋白质对消毒副产物溴二氯甲烷(BDCM)的反应后的翻译后氧化加合物。具体的目的将通过使用酶的抑制剂，如NADPH氧化酶和CYP450同工酶CYP2E1，以及缺乏这些酶的基因敲除小鼠来实现。所有关于肥胖的研究都将在饮食诱导肥胖(DIG)小鼠身上进行，并与饮食限制的瘦身对照组进行比较。在目标2中，1将研究初始脂质过氧化、干扰素-γ(干扰素-γ)和粒细胞巨噬细胞集落刺激因子(GMCSF)如何导致巨噬细胞激活，并在BDCM暴露后导致第二波自由基损伤和肿瘤坏死因子-α的分泌。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，我将研究促炎症脂肪细胞因子瘦素在协同环境肝毒素如溴二氯甲烷、一种DBP的作用，这一目标将通过研究自由基诱导的巨噬细胞激活和细胞死亡在Ieptin基因敲除小鼠中被实现，并使用针对Ieptin的中和抗体。

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.