Nicotine and alcoholic liver disease

摘要 酗酒是一个严重的全球性健康问题。长期饮酒可诱发酒精性肝病， 其范围从脂肪变性（脂肪肝）到脂肪性肝炎、纤维化和肝硬化。大约90%的重酒精 饮酒者会患上酒精性脂肪肝（AFL），这是酒精性肝病的一种表现。最近，我们发现， CYP 2A 5（人体中的CYP 2A 6）由慢性乙醇喂养诱导，而CYP 2A 6在酒精性饮食中升高。 患者CYP 2A 5/6是尼古丁的主要代谢酶。酒精和烟草经常被滥用， 吸烟可增加AFL。我们发现尼古丁，烟草烟雾中的一种主要的成瘾性碱性物质， 可增强AFL和高脂血症（HTG），这在WT小鼠中观察到，但在cyp 2a 5-/-小鼠中未观察到。 FGF 21是一种在肝脏中高度表达的新型代谢调节因子。我们观察到一种 cyp 2a 5-/-小鼠肝脏PPARα-FGF 21升高。在pparα-/-小鼠中观察到乙醇诱导的HTG， 极低的血清FGF 21可以通过rFGF 21的治疗来阻断。乙醇/尼古丁诱导的AFL 在肝脏特异性FGF 21 KO小鼠中更明显。这些结果表明，FGF 21可能发挥重要作用， FGF 21的作用通过FGF受体1（FR 1）调节细胞活性，FR 1主要在脂肪组织中表达， 组织和肝脏中的程度要小得多。我们没有观察到肝脏之间AFL和HTG的任何差异- 特异性FR 1 KO小鼠及其WT对照小鼠，表明在我们的模型中， 脂肪FR 1而非肝脏FR 1。肝脏FGF 21可以释放到血液中，以内分泌方式发挥作用。FGF21 能刺激脂肪细胞分泌脂联素，脂联素作用于肝脏，改善AFL。在AIM 1中，我们 将通过AAV 8将CYP 2A 5重新引入cyp 2a 5-/-小鼠，以验证CYP 2A 5在CYP 2a 5-/-小鼠中的重要作用。 尼古丁增强AFL和HTG，并应用可替宁和抗氧化剂来检查CYP 2A 5产生的作用。 尼古丁代谢产物和尼古丁增强的AFL和HTG中的氧化应激。在AIM 2中，我们将检查 通过应用pparα-/-/cyp 2a 5-/-小鼠，肝脏， 特异性FGF 21敲除小鼠和PPARα特异性激动剂WY-14，643。在AIM 3中，在细胞共- 将检查脂肪细胞和肝细胞的培养系统，以反映器官间的相互作用。 脂肪组织和肝脏。脂联素敲除小鼠将用rFGF 21处理以评估肝FGF 21 在脂肪组织中通过脂联素发挥作用，即PPARα-FGF 21-脂联素调节尼古丁- 增强AFL和HTG。最后，采用脂联素和CYP 2A 5双基因敲除小鼠进行研究 脂联素在观察中的作用，即在WT小鼠中观察到尼古丁增强AFL和HTG， 而不是在CYP 2A 5-/-小鼠中。

ABSTRACT Alcohol abuse is a significant global health problem. Chronic alcohol drinking can induce alcoholic liver disease, which ranges from steatosis (fatty liver) to steatohepatitis, fibrosis and cirrhosis. About 90% of heavy alcohol drinkers develop alcoholic fatty livers (AFL), an onset of alcoholic liver disease. Recently, we found that CYP2A5 (CYP2A6 in humans) is induced by chronic ethanol feeding and CYP2A6 is elevated in alcoholic patients. CYP2A5/6 is a major nicotine metabolic enzyme. Alcohol and tobacco are frequently co-abused and tobacco smoke can increase AFL. We found that nicotine, a major addictive forming alkaline in tobacco smoke, can enhance AFL and hypertriglyceridemia (HTG), which was observed in WT mice but not in cyp2a5-/- mice. PPARα-regulated FGF21 is a novel metabolic regulator highly expressed in liver. We observed a constitutive elevation of hepatic PPARα-FGF21 in cyp2a5-/- mice. Ethanol-induced HTG observed in pparα-/- mice with an extremely low serum FGF21 can be blocked by the treatment of rFGF21. Ethanol/nicotine-induced AFL was more pronounced in liver-specific FGF21 KO mice. These results suggest that FGF21 may play an important role in FGF21 modulates cellular activity through FGF receptor 1 (FR1), which is mainly expressed in adipose tissues and to a much lesser extent in liver. We didn’t observe any difference in AFL and HTG between liver- specific FR1 KO mice and their WT control mice, suggesting that in our model the more important might be adipose FR1 but not liver FR1. Liver FGF21 can be released into blood to act in an endocrine manner. FGF21 can stimulate adipocytes to secret adiponectin, which in turn acts on the liver to ameliorate AFL. In AIM 1, we will reintroduce CYP2A5 back to cyp2a5-/- mice via AAV8 to validate the essential role of CYP2A5 in the nicotine-enhanced AFL and HTG and apply cotinine and antioxidant to examine the role of CYP2A5-produced nicotine metabolites and oxidative stress in the nicotine-enhanced AFL and HTG. In AIM 2, we will examine the role of a PPARα-FGF21 axis in the nicotine-enhanced AFL and HTG by applying pparα-/-/cyp2a5-/- mice, liver- specific FGF21 knockout mice and PPARα specific agonist WY-14,643. In AIM 3, cell-cell interaction in cell co- culture system of adipocytes and hepatocytes will be examined to reflect organ-organ interaction between adipose tissue and liver. Adiponectin knockout mice will be treated with rFGF21 to evaluate if liver FGF21 exerts its action in adipose tissue through adiponectin i.e. the PPARα-FGF21-adiponectin to regulate nicotine- enhanced AFL and HTG. At last, adiponectin and CYP2A5 double knockout mice will be applied to investigate the role of adiponectin in the observation that nicotine-enhanced AFL and HTG was observed in WT mice but not in cyp2a5-/- mice.