基于报告基因检测的PXR、FXR和LXRα激动剂高通量筛选模型的建立

目的建立基于报告基因法的高通量筛选细胞模型,用来发现PXR、FXR和LXRα受体激动剂。方法利用Real-time定量PCR方法比较HEK293、Hep G2和LS174T细胞中内源性核受体PXR、FXR和LXRα的表达量,将p SG5-h PXR和p GL3-XREM-CYP3A4、p EGFP-N3-h FXR和EcRETK-Luc、p CMX-FLAG-h LXRα和p GL3-XREM-CYP3A4等质粒分别共转染到工具细胞中,优化共转染比例,并考察阳性药与萤光素酶报告基因表达强度的量效关系、模型特异性和稳定性。结果 1根据Real-time定量PCR结果,模型选用低表达PXR、FXR和LXRα的HEK293细胞作为工具细胞;2根据不同共转染比例对报告基因活性的结果,PXR、FXR和LXRα报告基因药物筛选模型的报告基因和过表达质粒比例,最终分别选择1∶1、2∶1和2∶1;3模型中,报告基因活性均与相应阳性药物(PXR/Rif、FXR/CDCA和LXRα/T0901317)呈剂量依赖性增长;4仅PXR激动剂Rif、FXR激动剂CDCA和LXRα激动剂T0901317可分别明显增加相应筛选模型的报告基因活性,分别重复5次试验后,计算得Z'值分别为0.58、0.66和0.63。结论该研究建立的PXR、FXR和LXRα激动剂高通量筛选模型,具有良好的特异性和稳定性,适用于对PXR、FXR和LXRα受体激动剂的筛选,进而开发以核受体作为药物靶点的药物。     

FXR信号通路介导何首乌导致脂质沉积的作用及机理研究

目的 探索何首乌对肝细胞脂质沉积的影响及其机制。方法 利用永生化肝细胞系LO2,采用1 mmol/L游离脂肪酸（FFA）处理,建立脂肪肝沉积细胞模型。同时加入不同浓度的何首乌提取物处理（0、2.5、5、10 μg/mL）,采用油红O染色以观察何首乌对LO2细胞脂肪沉积的作用;采用实时荧光定量PCR进行实验组LO2细胞内法尼酯X受体（FXR）基因及其下游通路胆盐输出泵（BSEP）、小分子异源二聚体伴侣（SHP）、胆固醇7α-羟化酶1（CYP7A1）关键基因的检测;并采用蛋白免疫印迹法检测FXR及其下游通路关键蛋白的表达水平。结果 何首乌处理后的LO2细胞中,油红O的染色量会随着药物浓度增加而增加;FXR的mRNA表达下降,而FXR蛋白诱导促进的下游基因BSEP、SHP的表达相应下降,而其下游抑制基因CYP7A1的表达则上升（P均<0.05）。何首乌处理的LO2肝细胞中,FXR的蛋白水平明显降低,蛋白激酶C （PKC）蛋白磷酸化水平明显降低,而PKC总蛋白表达水平无明显改变,SHP的蛋白水平也明显下降。结论 何首乌可通过抑制FXR-PKC/SHP信号转导通路,从而促进LO2肝细胞内的脂质沉积。为何首乌导致胆汁淤积所引起的肝损伤的治疗提供新的理论依据。     

The roles and interaction of FXR and PPARs in the pathogenesis of nonalcoholic fatty liver disease

Background and study aimsTo identify the roles and interaction of farnesoid X receptor (FXR) and peroxisome proliferator activated receptors (PPARs) in Non-alcoholic fatty liver disease (NAFLD) pathogenesis.Material and Methods16 C57/BL male FXR knockout (KO) mice and sex- and age-matched C57/BL wild type mice were received either standard rodent chow or high-fat and sucrose diet (Blank control, NAFLD, FXR KO and FXR KO NAFLD) for 8 weeks. After that, all mice were sacrificed. Liver tissues and blood samples were collected for laboratory and RT-PCR examination.ResultsNAFLD, FXR KO and FXR KO NAFLD mouse models were successful established. Compared with blank control, FXR and PPAR-α mRNA expression decreased significantly (P < 0.05), PPAR-β expression increased slightly (P > 0.05), PPAR-γ expression increased significantly in NAFLD (P < 0.05). Slight increased PPAR-α mRNA expression (P > 0.05) and markedly decreased PPAR-β and PPAR-γ expression (P < 0.05) were found in FXR KO. Compared with FXR KO group, there was a slight increase in PPAR-αand PPAR-βmRNA expression (P > 0.05) and significant increase in PPAR-γ expression (P < 0.05) in FXR KO NAFLD group. Comparison with NAFLD, PPAR-α mRNA expression increased slightly (P > 0.05), PPAR-β and PPAR-γ expression decreased significantly (P < 0.05) in FXR KO NAFLD.ConclusionFXR and PPARs interaction may play important roles in NAFLD pathogenesis.     

Bile acids,obesity, and the metabolic syndrome

Bile acids are increasingly recognized as key regulators of systemic metabolism. While bile acids have long been known to play important and direct roles in nutrient absorption, bile acids also serve as signalling molecules. Bile acid interactions with the nuclear hormone receptor farnesoid X receptor (FXR) and the membrane receptor G-protein-coupled bile acid receptor 5 (TGR5) can regulate incretin hormone and fibroblast growth factor 19 (FGF19) secretion, cholesterol metabolism, and systemic energy expenditure. Bile acid levels and distribution are altered in type 2 diabetes and increased following bariatric procedures, in parallel with reduced body weight and improved insulin sensitivity and glycaemic control. Thus, modulation of bile acid levels and signalling, using bile acid binding resins, TGR5 agonists, and FXR agonists, may serve as a potent therapeutic approach for the treatment of obesity, type 2 diabetes, and other components of the metabolic syndrome in humans.