Yalcin E B, Tong M, de la Monte S M
Liver Research Center, Division of Gastroenterology and Department of Medicine, Rhode Island Hospital and the Alpert Medical School of Brown University, USA.
Departments of Neurology, Neurosurgery and Pathology, Rhode Island Hospital and the Alpert Medical School of Brown University, USA.
Austin Liver. 2016;1(1). Epub 2016 Dec 1.
Chronic feeding plus binge administration of ethanol causes very high blood alcohol concentrations. However, its co-administration with tobacco Nicotine-Derived Nitrosamine Ketone (NNK) results in somewhat lower blood alcohol levels, suggesting that NNK and therefore smoking, alters alcohol metabolism in the liver. To explore this hypothesis, we examined effects of ethanol and/or NNK exposures on the expression and activity levels of enzymes that regulate their metabolism in liver.
This study utilized a 4-way model in which Long Evans rats were fed liquid diets containing 0% or 26% ethanol for 8 weeks, and respectively i.p injected with saline or 2 g/kg of ethanol 3 times/week during Weeks 7 and 8. The control and ethanol-exposed groups were each sub-divided and further i.p treated with 2 mg/kg of NNK or saline (3×/week) in Weeks 3-8. ADH, catalase and ALDH activities were measured using commercial kits. CYP450 mRNA levels (17 isoforms) were measured by qRT-PCR analysis.
Ethanol significantly increased hepatic ADH but not catalase or ALDH activity. NNK had no effect on ADH, ALDH, or catalase, but when combined with ethanol, it increased ADH activity above the levels measured in all other groups. Ethanol increased CYP2C7, while NNK increased CYP2B1 and CYP4A1mRNA levels relative to control. In contrast, dual ethanol + NNK exposures inhibited CYP2B1 and CYP4A1 expression relative to NNK. Conclusion: Dual exposures to ethanol and NNK increase hepatic ethanol metabolism, and ethanol and/or NNK exposures alter the expression of CYP450 isoforms that are utilized in NNK and fatty acid metabolism.
长期喂食并暴饮乙醇会导致血液中酒精浓度极高。然而，将其与烟草中的尼古丁衍生亚硝胺酮（NNK）共同使用时，血液中的酒精水平会有所降低，这表明NNK以及吸烟会改变肝脏中的酒精代谢。为了探究这一假设，我们研究了乙醇和/或NNK暴露对肝脏中调节其代谢的酶的表达和活性水平的影响。
本研究采用四因素模型，对Long Evans大鼠喂食含0%或26%乙醇的液体饲料8周，并在第7周和第8周分别每周3次腹腔注射生理盐水或2 g/kg乙醇。在第3 - 8周，将对照组和乙醇暴露组再各自细分，并进一步腹腔注射2 mg/kg NNK或生理盐水（每周3次）。使用商业试剂盒测量乙醇脱氢酶（ADH）、过氧化氢酶和乙醛脱氢酶（ALDH）的活性。通过定量逆转录聚合酶链反应（qRT-PCR）分析测量细胞色素P450（CYP450）mRNA水平（17种亚型）。
乙醇显著增加肝脏ADH活性，但对过氧化氢酶或ALDH活性无影响。NNK对ADH、ALDH或过氧化氢酶无影响，但与乙醇联合使用时，它使ADH活性高于所有其他组测得的水平。相对于对照组，乙醇增加了CYP2C7，而NNK增加了CYP2B1和CYP4A1 mRNA水平。相比之下，乙醇 + NNK联合暴露相对于NNK抑制了CYP2B1和CYP4A1的表达。结论：乙醇和NNK联合暴露增加肝脏乙醇代谢，乙醇和/或NNK暴露改变了参与NNK和脂肪酸代谢的CYP450亚型的表达。
