Signaling-pathway-based preventative strategies for alcoholic liver disease

描述（由申请人提供）：酒精性肝损伤是一种常见的肝脏疾病，部分原因是脂质代谢失调和炎症。酒精性肝病（ALD）的发展经历四个病理阶段：脂肪变性、脂肪性肝炎、纤维化和肝硬化。脂质积累的严重程度与肝毒性的发展有着密切的联系。增加的肝脏脂质积累增强了肠道中产生的外源性和内毒素的能力，可能是通过增加炎症信号传导来增强酒精性肝炎和纤维化，这依赖于库普弗细胞/肝细胞和其他免疫细胞的相互作用。过氧化物酶体增殖物活化受体-a （PPARa）在肝脏脂肪酸分解代谢调节中具有重要作用。鉴于脂质积累在ALD病因学中的重要性，与表达功能PPARa的小鼠相比，PPARa缺失小鼠表现出恶化的ALD并不奇怪。与调节脂质分解代谢的PPARa相反，最近的研究表明，PPAR¿/d还通过诱导胰岛素诱导基因1 （Insig-1）的表达来抑制肝脏脂肪生成，从而调节肝脏脂质代谢，Insig-1是一种抑制SREBP激活的内质网蛋白。初步数据将确定PPAR¿/d可以防止毒素对肝脏的损害，支持PPAR¿/d也可以预防ALD的假设，这一观点迄今尚未得到证实。结合强有力的证据表明PPARa和PPAR¿/d具有有效的抗炎活性，本应用的重点是阐明PPARa和PPAR¿/d调节肝脏脂质积累和肝脏炎症的机制，这两个已知的途径在介导ALD中至关重要。Specific aim 1将使用Pparb -null和Pparb/d-null小鼠模型来区分靶向这些受体抑制早期和/或预先存在的ALD的适用性，以及PPARa和PPAR¿/d调节肝脏酒精诱导毒性的机制。这些模型中PPAR激动作用的评估将通过比较基因表达和靶向代谢组学特征与肝脏病理来评估，以机制地描述PPARa和PPAR¿/d如何调节ALD模型中的肝脏脂质代谢。特异性目标2将使用创新的转基因小鼠模型来确定炎症是否调节ppar依赖性的肝脏脂质积累以促进ALD，并区分体细胞介导的炎症（如肝细胞）和免疫细胞介导的炎症（如肝细胞）。Kupffer细胞，中性粒细胞，淋巴细胞)。这项应用的结果将决定结合PPARa和PPAR¿/d的配体激活和/或p38依赖性炎症的抑制是否会改善预防或治疗ALD的方法，并具有坚实的机制基础。该应用结合了Albert J. Fornace博士实验室（乔治城大学）和Jeffrey M. Peters博士（宾夕法尼亚州立大学）的独特专业知识和经验，定义了ALD所必需的PPAR调节和炎症依赖性诱导机制。

DESCRIPTION (provided by applicant): Alcohol-induced liver damage is a common liver disease that is due in part to dysregulated lipid metabolism and inflammation. Alcoholic liver disease (ALD) progresses through four pathological stages: steatosis, steatohepatitis, fibrosis and cirrhosis. There is a strong link between the severity of lipid accumulation and the development of liver toxicity. Increased hepatic lipid accumulation enhances the ability of xenobiotics and endotoxins produced in the gut to potentiate alcoholic hepatitis and fibrosis, likely by increased inflammatory signaling, which is dependent on Kupffer cell/hepatocyte interactions and other immune cells. Peroxisome proliferator-activated receptor-a (PPARa) has a central role in regulating fatty acid catabolism in liver. Given the significance of lipid accumulation in the etiology of ALD, it is not surprising that Ppara-null mice exhibit exacerbated ALD as compared to mice expressing a functional PPARa. In contrast to PPARa that regulates lipid catabolism, it was recently shown that PPAR¿/d also modulates hepatic lipid metabolism by inhibiting hepatic lipogenesis by inducing expression of insulin-induced gene-1 (Insig-1), an endoplasmic reticulum protein that inhibits SREBP activation. Preliminary data will establish that PPAR¿/d can protect against liver damage by toxins, supporting the hypothesis that PPAR¿/d will also protect against ALD, an idea that has not been examined to date. Coupled with strong evidence that PPARa and PPAR¿/d have potent anti- inflammatory activities, the focus of this application is on elucidating the mechanisms by which PPARa and PPAR¿/d regulate hepatic lipid accumulation and hepatic inflammation, two known pathways critical in mediating ALD. Specific aim 1 will use the Ppara-null and Pparb/d-null mouse models to distinguish between the suitability of targeting these receptors to inhibit early and/or pre-existing ALD and the mechanisms by which PPARa and PPAR¿/d modulate hepatic alcohol-induced toxicity. Evaluation of PPAR agonism in these models will be evaluated by comparing gene expression and targeted metabolomic profiles with liver pathology to mechanistically delineate how PPARa and PPAR¿/d regulate hepatic lipid metabolism in an ALD model. Specific aim 2 will use innovative and novel transgenic mouse models to determine if inflammation modulates PPAR-dependent hepatic lipid accumulation in promoting ALD and to distinguish between somatic cell- mediated inflammation (e.g. hepatocyte) versus immune cell-mediated inflammation (e.g,. Kupffer cell, neutrophils, lymphocytes). Results from this application will determine whether combining ligand activation of PPARa and PPAR¿/d and/or inhibition of p38-dependent inflammation will improve approaches to prevent or treat ALD with a solid mechanistic rationale. This application combines the unique expertise and experience of Dr. Albert J. Fornace's laboratory (Georgetown University) and Dr. Jeffrey M. Peters (Penn State University) to define the PPAR regulatory and inflammation-dependent inducing mechanisms that are essential for ALD. PUBLIC HEALTH RELEVANCE: Alcohol-induced liver damage is a common liver disease with important health and socioeconomic consequences that is due in part to dysregulated lipid metabolism and inflammation. This application combines the unique expertise and experience of Dr. Albert J. Fornace's laboratory (Georgetown University) and Dr. Jeffrey M. Peters (Penn State University) to define lipid metabolism regulatory and inflammation-dependent inducing mechanisms that are essential for alcoholic liver disease. Results will improve approaches to prevent or treat alcoholic liver disease with a solid mechanistic rationale.