Stahle Jessica A, Vunta Hema, Channa Reddy C, Sandeep Prabhu K
Undergraduate Program in Animal Biosciences, The Pennsylvania State University, University Park, PA, 16802 USA.
Eur J Nutr. 2009 Aug;48(5):283-90. doi: 10.1007/s00394-009-0012-3. Epub 2009 Mar 18.
Cardiomyopathy is common to areas with low selenium (Se) intake and in patients receiving total parenteral nutrition. Although controversial, a few studies have suggested a protective role for Se in coronary heart disease on the basis of modulation of high-density lipoproteins (HDL).
In this study, the role of Se as a positive regulator of expression of a key HDL, apolipoprotein A-I (apoA-I), has been evaluated in human hepatoblastoma (HepG2) cell culture model. We further examined if the transcription of apoA-I, driven by the nuclear hormone receptor, peroxisome-proliferator activated receptor, PPARalpha, was trans-repressed by the presence of the oxidative stress-responsive transcription factor, NF-kappaB.
Modulation of expression of apoA-I and activation of nuclear NF-kappaB subunit p65 and PPARalpha by Se status were evaluated by Western blot and luciferase-based assays. Interaction of p65 with PPARalpha was evaluated by immunoprecipitation.
HepG2 cultured in media with Se (100 nM) demonstrated an increase in the expression of apoA-I when compared to Se-deficient cells. A similar trend was also seen in mice that were supplemented with 0.4 ppm of Se as sodium selenite. Treatment of Se-supplemented cells with bacterial lipopolysaccharide (LPS) showed induction of apoA-I. Supplementation of hepatocytes with Se decreased the nuclear levels of p65, which prevented its interaction with PPARalpha to modulate apoA-I transcription.
Our results suggest that supplementation of hepatocytes with Se mitigates oxidative stress-dependent repression of apoA-I expression by suppressing the NF-kappaB pathway, which allows PPARalpha to effectively drive the expression of apoA-I.
心肌病在硒（Se）摄入量低的地区以及接受全胃肠外营养的患者中很常见。尽管存在争议，但一些研究表明，基于对高密度脂蛋白（HDL）的调节作用，硒在冠心病中具有保护作用。
在本研究中，已在人肝癌细胞（HepG2）培养模型中评估了硒作为关键HDL载脂蛋白A-I（apoA-I）表达的正向调节因子的作用。我们进一步研究了由核激素受体过氧化物酶体增殖物激活受体PPARα驱动的apoA-I转录是否会被氧化应激反应转录因子NF-κB的存在反式抑制。
通过蛋白质免疫印迹和基于荧光素酶的检测评估硒状态对apoA-I表达的调节以及核NF-κB亚基p65和PPARα的激活。通过免疫沉淀评估p65与PPARα的相互作用。
与缺硒细胞相比，在含硒（100 nM）培养基中培养的HepG2细胞中apoA-I的表达增加。在补充了0.4 ppm亚硒酸钠的小鼠中也观察到了类似趋势。用细菌脂多糖（LPS）处理补硒细胞显示apoA-I被诱导。用硒补充肝细胞可降低p65的核水平，从而阻止其与PPARα相互作用来调节apoA-I转录。
我们的结果表明，用硒补充肝细胞可通过抑制NF-κB途径减轻氧化应激依赖性的apoA-I表达抑制，这使得PPARα能够有效地驱动apoA-I的表达。
