硒对大鼠肝细胞核糖体相关蛋白质含量的影响

本文通过高、超速差速分步离心肝组织匀浆,并用高浓度盐溶液洗涤核糖体沉淀得核糖体相关蛋白质粗制品,然后经 Sephadex 柱层析,SDS—PAGE 电泳将其分离。结果显示,低硒组大鼠肝核糖体相关蛋白质的种类和数量均此西安组低,加硒能一定程度改善上述变化。从而说明,硒可以通过改变机体核糖体相关蛋白质而影响其蛋白质的合成。     

Structural changes of proteins in liver cirrhosis and consequential changes in their function

The liver is the site of synthesis of the majority of circulating proteins. Besides initial polypeptide synthesis, sophisticated machinery is involved in the further processing of proteins by removing parts of them and/or adding functional groups and small molecules tailoring the final molecule to suit its physiological purpose. Posttranslational modifications (PTMs) design a network of molecules with the common protein ancestor but with slightly or considerably varying activity/localization/purpose. PTMs can change under pathological conditions, giving rise to aberrant or overmodified proteins. Undesired changes in the structure of proteins most often accompany undesired changes in their function, such as reduced activity or the appearance of new effects. Proper protein processing is essential for the reactions in living beings and crucial for the overall quality control. Modifications that occur on proteins synthesized in the liver whose PTMs are cirrhosis-related are oxidation, nitration, glycosylation, acetylation, and ubiquitination. Some of them predominantly affect proteins that remain in liver cells, whereas others predominantly occur on proteins that leave the liver or originate from other tissues and perform their function in the circulation. Altered PTMs of certain proteins are potential candidates as biomarkers of liver-related diseases, including cirrhosis. This review will focus on PTMs on proteins whose structural changes in cirrhosis exert or are suspected to exert the most serious functional consequences.     

Association between thrombotic risk factors and extent of fibrosis in patients with non-alcoholic fatty liver diseases

AIM: To evaluate the prevalence of genetic and acquired prothrombotic risk factors and their association with the extent of fibrosis and fatty infiltration in patients with nonalcoholic fatty liver disease (NAFLD). METHODS: Forty-four patients with chronic hepatitis (28 men and 16 women, with mean age of 45±11 and 49±12 years, respectively) constituted the patient population of this study. The groups were divided as follows: 15 patients with fatty liver (FL); 15 with non-alcoholic steatohepatitis (NASH); 14 with chronic viral hepatitis (CH) diagnosed by histology and liver technetium scan or ultrasound; and 10 healthy individuals. Thrombophilic, coagulation factors and genetic mutations were diagnosed by standard hemostatic and molecular coagulation assays. RESULTS: Activated protein C (APC) resistance and protein S were the most prevalent thrombotic risk factors (6% and 10% in NAFLD vs 21% and 14% in CH; P<0.01 and P<0.05, respectively). One thrombotic risk factor was identified in 41% of patients (23% mild fibrosis, 18% severe fibrosis) and two thrombotic risk factors in 6% of patients with NAFLD and severe fibrosis. While no differences in APC ratio, lupus anticoagulant, fibrinogen, factor V Leiden, prothrombin, and MTHFR mutation were found. Protein S levels were significantly lower in NASH patients than in patients with FL alone (92±19 vs 106±2, P<0.01). Protein C levels were markedly higher in patients with NAFLD and mild or severe fibrosis as compared to the patients with CH, respectively (128±40 vs 96±14, P<0.001 or 129±36 CONCLUSION: Up to 46% of patients with NAFLD may have thrombotic risk factors, and the presence of thrombotic risk factors is correlated with the extent of hepatic fibrosis, suggesting a crucial role of the coagulation system in the pathogenesis of hepatic fibrosis.     

Decreased proteasome activity is associated with increased severity of liver pathology and oxidative stress in experimental alcoholic liver disease

BACKGROUND: Because of its role in degrading the bulk of intracellular proteins and eliminating damaged proteins, the proteasome is important in maintaining cell viability. Previously, we showed a 35-40% decrease in proteasome peptidase activity when ethanol was administered to rats by intragastric infusion. We hypothesized that this reduction was caused by ethanol-elicited oxidative stress, the degree of which varies depending on the method of ethanol administration. This study examined the relationship of proteasome activity and content with ethanol-induced oxidative stress and the degree of liver injury. METHODS: Rats were given ethanol or isocaloric dextrose-containing liquid diets by intragastric infusion for 1 month. The diets contained medium-chain triglycerides (MCT), palm oil (PO), corn oil (CO), or fish oil (FO) as the principal source of fat. RESULTS: Rats given ethanol and MCT exhibited no significant liver pathology, whereas cumulative pathology scores in ethanol-fed rats given PO, CO, or FO were 2.5, 5.4 and 7.0, respectively, indicating that ethanol and FO caused the greatest liver damage. The severity of liver pathology in the last three groups of animals correlated with levels of lipid peroxides and serum 8-isoprostanes. Alpha smooth muscle actin, an indicator of stellate cell activation, was increased relative to controls in the livers of all ethanol-fed rats except FO-fed animals, in which both control and ethanol-fed rats had similar levels of this protein. In livers of CO and FO ethanol-fed rats, proteasome chymotrypsin-like activity was decreased by 55-60%, but there was no quantitative alteration in 20S proteasome subunit content. In contrast, ethanol affected neither proteasome activity nor its content in MCT- and PO-treated animals. CONCLUSIONS: Our findings indicate that the severity of liver injury and ethanol-induced oxidative stress is associated with a reduction in proteasome catalysis.     

乙型肝炎病毒X蛋白在不同肝细胞定位及表达的特性

目的探讨乙型肝炎病毒X蛋白(HBx)在肝细胞的分布特点及蛋白表达的规律。方法常规分子克隆技术构建HBx及其各种突变体的表达载体,Western blot验证HBx蛋白的表达;荧光共聚集扫描技术观察HBx蛋白在肝细胞中的分布特点;谷光甘肽S转移酶(GST)-Sepharose 4B亲和层析方法纯化GST-HBx融合蛋白。结果成功构建了全长HBx及其各种缺失突变体表达载体;HBx蛋白在肝细胞核内均匀分布,在细胞质内呈颗粒状聚集分布; 在优化蛋白表达及纯化条件下,突变体HBx(73～120 aa)的GST融合蛋白极易降解。结论为从蛋白水平探讨HBx 的生物学功能提供了有利的材料。     

肥大细胞及蛋白酶激活受体-2在大鼠实验性肝纤维化中的变化

目的观察肝纤维化大鼠的肥大细胞(MC)数量变化和蛋白酶激活受体-2(PAR-2)在肝脏中表达及其与肝纤维化的关系。方法建立大鼠肝纤维化模型,以甲苯胺蓝染色显示MC,运用碱水解法测定肝脏羟脯氨酸含量,采用逆转录聚合酶链反应(RT-PCR)方法检测正常对照组及造模2、4、8、12周组大鼠肝组织中PAR-2 mRNA的表达,免疫组织化学方法检测PAR-2蛋白的表达及定位。结果正常对照组大鼠肝组织中MC数量极少,仅(2．5±1．0)个,主要沿肝脏汇管区分布；模型组MC数量：2周为(9．1±0．5)个,4周为(15．7±3．0)个,8周为(32．0±3．3)个。造模组2周与正常组比较,P=0．038,造模组组间比较,F=58．553,P＜0．01,差异均有统计学意义。MC在汇管区、中央静脉周围密集分布。随着造模时间的延长,肝脏羟脯氨酸的含量逐渐升高。PAR-2 mRNA检测结果,PAR- 2/β-肌动蛋白(β-actin)：正常对照组几乎不表达；造模2周肝组织可有少量PAR-2 mRNA表达,为0．15±0．01,4周为0．35±0．02,8周为0．80±0．02。PAR-2蛋白检测结果,阳性信号灰度：正常对照组为156．0±0．5；造模2周为162．5±1．3,4周为174．8±1．3,8周为185．7±2．1,12周为207．7±4．4,模型组与对照组比较和模型组组间比较,F=429．389,P＜<0．01,差异均有统计学意义。结论PAR-2 mRNA和蛋白的表达水平与MC数量、羟脯氨酸含量的增加一致,可能在肝纤维化的发生发展过程中起重要作用。     

不同亚型Numb蛋白对肝纤维化相关信号通路的影响

肝纤维化是各种慢性肝病发展为肝硬化的必经之路,是一个可逆的病理状态。但如何阻抑或逆转肝纤维化的发生与发展,仍是临床需要解决的重要科学问题。Numb,一个重要的细胞命运决定子,已被发现与多种疾病的发生密切相关。在肝纤维化环境中,由于Numb基因的选择性剪切作用,翻译出不同亚型的Numb蛋白,其对不同信号通路的活化以及肝干细胞的分化具有不同的调节作用。目前关于Numb蛋白不同亚型在肝纤维化中的作用报道较少。综述了不同亚型Numb蛋白对Notch、Hedgehog、P53信号通路以及对肝干细胞的调控作用,阐释其在肝纤维化治疗中的潜在应用前景。     

p38信号转导途径对离体肝脏缺血再灌注损伤的影响

目的 研究离体肝脏缺血再灌注期间p38信号转导途径的激活对其损伤程度的影响。 方法 通过自行建立的兔离体肝脏缺血再灌注模型,将一定剂量的特异性p38丝裂原激活蛋白激酶(MAPK)抑制剂SB202190加入到保存液中,根据原位灌注液及保存液中加入SB202190的剂量再将离体肝分为A、B、C、D4组。分别于冷保存前、冷保存末及再灌注5、10、15、30、60、120 min获取离体肝组织及受体兔静脉血液标本。分别应用免疫印迹杂交和免疫沉淀法测定离体肝组织磷酸化p38M A P K的活性。用全自动生化分析仪测定离体兔肝功酶学含量;并测定再灌注120 min内的胆汁分泌总量。 结果 在正常肝组织中p38 MAPK即有一定的基础活性;经冷保存后有一定的升高,再灌注10 min时达到峰值,然后逐渐下降,至再灌注120 min时降低至正常水平,而在冷保存液中加入SB202190后,再灌注期间p38 MAPK的活性受到显著性抑制,其中B、C、D组p38 MAPK活性峰值仅分别为A组的53.9％,12.8％,9.6％;再灌注期间各组受体肝酶学水平均表现为A>B>C>D,而胆汁分泌量表现为A相似文献   

Cloning and expression of special F protein from human liver

AIM: To clone human liver special F protein and to express it in a prokaryotic system. METHODS: Total RNA was isolated from human liver tissue and first-strand cDNA was reverse transcribed using the PCR reverse primer. Following this, cDNA of the F protein was ligated into the clone vector pUCm-T. The segment of F protein's cDNA was subcloned into the expression vector pET-15b and transformed into E. coli BL21 (DE3) pLyss. Isopropy-β-D-thiogalactoside (IPTG) was then used to induce expression of the target protein. RESULTS: The cDNA clone of human liver special F protein (1134bp) was successfully produced, with the cDNA sequence being published in Gene-bank: DQ188836. We confirmed the expression of F protein by Western blot with a molecular weight of 43 kDa. The expressed protein accounted for 40% of the total protein extracted. CONCLUSION: F protein expresses cDNA clone in a prokaryotic system, which offers a relatively simple way of producing sufficient quantities of F protein and contributes to understanding the principal biological functions of this protein.     

Estimation of protein intake using urinary urea nitrogen in patients with early-stage liver cirrhosis

Purpose Evaluation of protein intake of patients with liver cirrhosis (LC) would facilitate optimal nutritional support. However, it has never been done on the basis of urinary urea nitrogen (UUN). The aim of this study, therefore, is to determine the usefulness of the estimated protein intake (EPI) based on UUN in patients with LC. Methods A total of 42 patients with early-stage LC were enrolled in this study. The actual protein intake (API) was defined as the dietary protein intake (1.0 g/kg/d) plus supplementation of any enteral diets containing branched-chain amino acids (BCAA). We calculated EPI from UUN using the formula [UUN (g/d) + 0.031 × body weight (kg)] × 0.625. We examined the correlation between EPI and API, the EPI/API ratio (EAR), and the correction based on the results. Results A significant positive correlation was found between API and EPI (r = 0.703, p < 0.001). The EAR in all patients was 0.84 ± 0.11. EPI times 1.2 was the correction needed to adjust EAR to 1. The corrected EPI was correlated with API (r = 0.704, p < 0.001). The corrected EAR of all 42 patients was 1.01 ± 0.13. Conclusion In conclusion, for patients with early-stage LC, an EPI calculated from UUN may be a useful tool for optimal nutritional support. The corrected EPI would be very useful for improved monitoring of early-stage LC.     

黄芩苷调节高脂饲养大鼠肝脏脂质代谢及其机制

近年来,非酒精性脂肪性肝病(NAFLD)发病率有逐年上升的趋势,但目前对NAFLD尚无有效的疗法,减少肝脏细胞内脂质含量有望减轻高脂饮食对肝脏的危害.有研究结果表明,黄芩苷对肝脏具有较好的保护作用,但其机制不明.腺苷酸活化蛋白激酶(AMPK)是脂质调节的关键靶蛋白,参与脂肪酸、甘油三酯(TG)及胆固醇的调节.本研究主要探讨黄芩苷对高脂喂养大鼠肝脏脂质代谢的影响及AMPK信号通路是否参与该调控.     

内毒素血症时肝窦内皮细胞脂多糖受体CD14蛋白表达的观察

目的观察内毒素血症时肝窦内皮细胞(LSECs)中CD14蛋白合成和CD14 基因的表达,以及CD14蛋白在内毒素介导LSECs激活中的作用. 方法经尾静脉注入脂多糖(LPS,E coli O111B4)5mg/kg,建立大鼠内毒素血症动物模型,分别于术后0(对照组)、3、6、12、24h活杀取材.用兔抗鼠CD14抗体和异硫氢酸荧光素(FITC)标记的羊抗兔IgG对LSECs进行孵育后,流式细胞仪测定LSECs的平均荧光强度(MFI)及FITC阳性细胞数;用原位杂交法测定LSEC中CD14 mRNA的表达.用原位胶原酶灌注法分离大鼠LSECs,用不同浓度LPS(0、0.01、1、10、100μg/ml)刺激LSECs.并用CD14抗体阻断LSECs的 CD14蛋白后,再用不同浓度LPS(0、0.01、1、10、100μg/ml)刺激LSECs.测定LPS介导LSECs肿瘤坏死因子(TNF)-α及白细胞介素-6(IL-6)分泌及CD14抗体对LSECs细胞因子分泌的影响. 结果内毒素血症大鼠3、6、12和24h 时LSECs的MFI明显增加;FITC阳性细胞数也明显增多,分别为54.32%、65.83%、85.61%和45.65%,与对照组的4.45%比较差异有非常显著意义(P＜0.01).原位杂交显示,内毒素血症大鼠LSECs中CD14 mRNA的表达明显增强,而对照组CD14 mRMA无阳性表达.LPS组TNF-α的含量(pg/ml)分别为54.49±6.02、84.65±10.16、206.54±23.55、349.87±39.47和365.76±40.31;CD14阻断组TNF-α的含量(pg/ml)分别为55.93±6.95、63.32±7.81、85.34±9.72、112.75±13.54、198.66±21.54;两组间比较差异有非常显著意义(P＜0.01).LPS组IL-6的含量(pg/ml)分别为103.34±12.52、187.39±20.31、243.87±27.83、289.51±30.15、298.53±31.94;CD14阻断组IL-6的含量(pg/ml)分别为104.37±11.49、125.02±13.58、164.59±19.47、183.47±20.17、221.76±26.43;两组间比较差异有非常显著意义(P＜0.01). 结论内毒素血症时LSECs能合成CD14蛋白及表达CD14基因;抗CD14抗体对LPS诱导LSECs TNF-α和IL-6的分泌有抑制作用;CD14蛋白的表达在内毒素介导LSECs激活中可能起重要作用.     

体外培养的肝癌细胞株与正常肝细胞株蛋白质的差异表达

目的:运用SELDI蛋白质芯片技术分析体外培养的肝癌细胞株(HepG2)与正常肝细胞株(L02)蛋白质表达差异．方法:在体外培养HepG2和L02细胞株,收获细胞,将细胞用细胞裂解液裂解后,采用SELDI蛋白质芯片技术用IMAC3 及WCX2芯片检测HepG2、L02的蛋白质谱．结果:体外培养的肝癌细胞株与正常肝细胞株的蛋白质存在差异表达,IMAC3芯片共捕获61个蛋白,发现差异峰7个,与 L02细胞相比,其中3个差异蛋白在肝癌细胞中高表达,4个差异蛋白在肝癌细胞中低表达．WCX2芯片共捕获91个蛋白, 发现差异峰14个,其中3个差异蛋白在肝癌细胞中高表达,11 个差异蛋白在肝癌细胞中低表达．结论:SELDI蛋白芯片技术检测肝癌细胞株与正常肝细胞株蛋白质的差异表达方法简便,敏感性高,重复性好．     

Effect of 40% restriction of dietary amino acids (except methionine) on mitochondrial oxidative stress and biogenesis, AIF and SIRT1 in rat liver

Previous studies have shown that the decrease in mitochondrial reactive oxygen species (mitROS) generation and oxidative damage to mitochondrial DNA (mtDNA) that occurs during life extending dietary restriction also occurs during protein or methionine restriction, whereas it does not take place during carbohydrate or lipid restriction. In order to study the possible effects of other amino acids, in this investigation all the dietary amino acids, except methionine, were restricted by 40% in male Wistar rats (RESTAAS group). After 6–7 weeks, experimental parameters were measured in the liver. Amino acid restriction did not change the levels of the methionine metabolites S-adenosylmethionine and S-adenosylhomocysteine, mitochondrial oxygen consumption and ROS generation, oxidative damage to mtDNA, amounts of the respiratory complexes I–IV, and the mitochondrial biogenesis factors PGC-1α and NRF-2. On the other hand, adenylate energy charge, mitochondrial protein oxidation, lipooxidation and glycooxidation, the degree of mitochondrial fatty acid unsaturation, and the amount of the apoptosis inducing factor (AIF) were decreased in the RESTAAS group. Amino acid restriction also increased SIRT1 protein. These results, together with previous ones, strongly suggest that the decrease in mitROS generation and oxidative damage to mtDNA that occurs during dietary restriction is due to restriction of a single aminoacid: methionine. They also show for the first time that restriction of dietary amino acids different from methionine decreases mitochondrial protein oxidative modification and AIF, and increases SIRT1, in rat liver.     

Late post liver transplant protein losing enteropathy: Rare complication of incisional hernia

Development of oedema and hypoproteinaemia in a liver transplant recipient may be the first signs of graft dysfunction and should prompt a full assessment. We report the novel case of a patient who, years after liver transplantation developed a functional blind loop in an incisional hernia, which manifested as oedema and hypoproteinaemia secondary to protein losing enteropathy. After numerous investigations, the diagnosis was made by flurodeoxyglucose positron emmision tomography (FDG-PET) imaging. Surgical repair of the incisional hernia was followed several months later by resolution of the protein loss, and confirmed at a post operative FDG-PET scan at one year.     

Chronic ethanol consumption alters the glutathione/glutathione peroxidase-1 system and protein oxidation status in rat liver

BACKGROUND: Alcohol-induced liver damage is associated with oxidative stress, which might be linked to disturbances in liver antioxidant defense mechanisms. The effect of chronic ethanol consumption on the mitochondrial and cytosolic glutathione/glutathione peroxidase-1 (GSHPx-1) system and oxidative modification of proteins was therefore studied in the rat. METHODS: Male Sprague-Dawley rats were fed liquid diets that provided 36% total calories as ethanol for at least 31 days. Pair-fed controls received isocaloric diets with ethanol calories substituted with maltose-dextrins. Mitochondrial and cytosolic fractions were prepared from livers and assayed for GSHPx-1 and glutathione reductase activities and total and oxidized concentrations of glutathione. Catalase activity was measured in the postmitochondrial supernatant. Levels of GSHPx-1, lactate dehydrogenase, and the beta subunit of the F1 portion of the ATP synthase protein were determined by western blot analysis. Concentrations of mitochondrial and cytosolic protein carbonyls were measured to assess ethanol-induced oxidation of proteins. RESULTS: Chronic ethanol consumption significantly decreased cytosolic and mitochondrial GSHPx-1 activities by 40% and 30%, respectively. Levels of GSHPx-1 protein in cytosol were unaffected by ethanol feeding, whereas there was a small decrease in GSHPx-1 protein levels in mitochondria isolated from ethanol-fed rats. Glutathione reductase activities were increased in both intracellular compartments and catalase activity was increased as a consequence of ethanol exposure. Cytosolic total glutathione was mildly decreased, whereas ethanol feeding increased mitochondrial levels of total glutathione. Chronic ethanol feeding significantly increased both cytosolic and mitochondrial concentrations of protein carbonyls by 30% and 60%, respectively. CONCLUSIONS: This study demonstrates that chronic ethanol-induced alterations in the glutathione/GSHPx-1 antioxidant system might promote oxidative modification of liver proteins, namely those of the mitochondrion, which could contribute to the adverse effects of ethanol on the liver.     

Multiple subcellular localizations and functions of protein kinase Cδ in liver cancer

Protein kinase Cδ (PKCδ) is a member of the PKC family, and its implications have been reported in various biological and cancerous processes, including cell proliferation, cell death, tumor suppression, and tumor progression. In liver cancer cells, accumulating reports show the bi-functional regulation of PKCδ in cell death and survival. PKCδ function is defined by various factors, such as phosphorylation, catalytic domain cleavage, and subcellular localization. PKCδ has multiple intracellular distribution patterns, ranging from the cytosol to the nucleus. We recently found a unique extracellular localization of PKCδ in liver cancer and its growth factor-like function in liver cancer cells. In this review, we first discuss the structural features of PKCδ and then focus on the functional diversity of PKCδ based on its subcellular localization, such as the nucleus, cell surface, and extracellular space. These findings improve our knowledge of PKCδ involvement in the progression of liver cancer.     

Thrombin activation and liver inflammation in advanced hepatitis C virus infection

Hepatitis C virus(HCV) infection is associated with increased thrombotic risk. Several mechanisms are involved including direct endothelial damage by the HCV virus, with activation of tissue factor, altered fibrinolysis and increased platelet aggregation and activation. In advanced stages, chronic HCV infection may evolve to liver cirrhosis, a condition in which alterations in the portal microcirculation may also ultimately lead to thrombin activation, platelet aggregation, and clot formation. Therefore in advanced HCV liver disease there is an increased prevalence of thrombotic phenomena in portal vein radicles. Increased thrombin formation may activate hepatic stellate cells and promote liver fibrosis. In addition, ischemic changes derived from vascular occlusion by microthrombi favor the so called parenchymal extinction, a process that promotes collapse of hepatocytes and the formation of gross fibrous tracts. These reasons may explain why advanced HCV infection may evolve more rapidly to end-stage liver disease than other forms of cirrhosis.