乙醇诱导脂肪肝过程中肝组织一氧化氮合酶的表达及作用

Expression and function of nitric oxide synthase in liver tissues in process of ethanol-induced fatty liver formation

目的 观察乙醇诱导脂肪肝过程中肝组织一氧化氮合酶 (NOS)的表达 ,探讨不同亚型NOS表达与脂质过氧化的关系。方法 在大鼠饮水中加入乙醇建立乙醇性脂肪肝模型 ,采用免疫组化和逆转录多聚酶链反应 (RT PCR)的方法动态观察肝组织中NOS的蛋白及基因表达 ,同时检测肝组织中一氧化氮 (NO)、丙二醛 (MDA)含量。结果 成功建立乙醇性脂肪肝大鼠模型。与正常对照组相比 ,造模大鼠肝组织在第 4周时诱导型一氧化氮合酶 (iNOS)表达已显著增加 (P <0 .0 5 ) ,第 12周达高峰 ,而后有所下降 ,第 2 0周时又明显上升 (P <0 .0 1)。内皮型一氧化氮合酶 (eNOS)在第 4周时表达无明显改变 (P >0 .0 5 ) ,随造模时间延长而逐渐降低 (P <0 .0 5 )。肝组织中NO水平在第 4周时无明显升高 (P>0 .0 5 ) ,以后显著增加 ,第 12周达高峰 ,而后有所下降 ,第 2 0周时又明显上升 (P <0 .0 1)。肝组织中MDA含量在第 4周已显著升高 (P <0 .0 5 ) ,随饮用乙醇时间延长进行性增加。肝组织中NO、MDA含量与iNOS表达成正相关 (P <0 .0 1) ,与eNOS表达成负相关 (P <0 .0 1)。结论 乙醇诱导脂肪肝过程中肝组织NO水平升高主要与iNOS的活化有关 ,iNOS产生的NO可能与脂质过氧化损伤有关 ,而eNOS产生的NO可能起抗脂质过氧化损伤的保护作用。

Objective To investigate the expression of nitric oxide synthase(NOS) in the liver tissues during ethanol-induced fatty liver and to explore the relationship between the expression of different NOS isoforms and lipid peroxidation. Methods Rat models with alcoholic fatty liver were established with ethanol-containing drinking water. The expression of protein and mRNA of NOS in the liver was dynamically detected with immunohistochemistry and reverse transcription polymerase chain reaction. Meanwhile, hepatic nitric oxide (NO), malondialehyde(MDA) contents were measured. Results Rat models of alcoholic fatty liver were established successfully. Compared to pair-fed controls, the expression of inducible NOS(iNOS) in alcoholic fatty liver rat model at 4th week was significantly increased ( P<0.05), peak was reached at 12th week and at 20th week (P<0.01). The expression of endothelial NOS(eNOS) in liver tissues showed no significant changes at 4th week(P>0.05), then decreased gradually (P<0.05 or P<0.01). The NO level in the liver tissues at 4th week was similar to that of pair-fed controls, significant increasing was observed at 12th week (P<0.05) and at 20th week (P<0.01). MDA contents in liver tissues at 4th week were higher(P< 0.05), and it kept increasing within the duration of alcohol feeding . Positive correlation existed between iNOS expression and NO,MDA contents (P<0.01), and negative correlation was found between eNOS expression and NO,MDA contents (P<0.01). Conclusions The elevated NO level in the liver tissues mainly resulted from iNOS activation. NO produced by iNOS may be involved in lipid peroxidation injury, however, NO derived from eNOS may possibly protect against lipid peroxidation injury.