Effects of Ginkgo biloba extract on cell proliferation, cytokines and extracellular matrix of hepatic stellate cells.

BACKGROUND/AIMS: Hepatic fibrosis is the common wound-healing response to chronic liver injury. Ginkgo biloba extract (GbE) has been indicated to reverse hepatic fibrosis and exhibit therapeutic effects both in vitro and in vivo. This study aimed to investigate the underlying mechanism of GbE using HSC-T6 cells, a subline of hepatic stellate cells (HSC) as a model. METHODS: HSC-T6 cells were seeded into six-well plates and allowed to attach overnight. After exposure to different concentrations of GbE761 for 24 or 48 h, cell cycle analysis, semiquantitative RT-PCR, Western blotting analysis and analysis of ECM secretion were performed. RESULTS: It was revealed that GbE (1, 10, 100, 500 mg/l) suppressed HSC proliferation and caused G0/G1 phase arrest in a concentration-dependent manner. RT-PCR and Western blot assays were applied to detect the decline of transforming growth factor beta1(TGF-beta1) and connective tissue growth factor (CTGF) in both mRNA and protein levels after GbE treatment in HSC-T6 cells for 24 or 48 h. Meanwhile, GbE inhibited the synthesis of type I and type III collagens. Secretion of some extracellular matrix (ECM) proteins, such as type III procollagen (PC III), type IV collagen (collagen IV), laminin (LN), hyaluronic acid (HA), were all decreased in supernatant of GbE treated HSC cells. CONCLUSIONS: Our results suggest that GbE confers its anti-fibrosis effects through inhibiting HSC proliferation, reducing TGF-beta1 and CTGF expression and consequently suppressing the collagen production and ECM secretion.     

Inhibitory effect of human interferon-beta-1a on activated rat and human hepatic stellate cells

Background and Aims: Hepatic stellate cells (HSC) are the primary cell type mediating hepatic fibrosis. Although known for its antiviral effects, the inhibitory effects of interferon‐beta (IFN‐β) on HSC treatment have not yet been established. Methods: Both human and rat activated HSC cell lines were incubated with increasing concentrations of recombinant human IFN‐β1a (rhIFN‐β1a) for 24, 48 or 72 h. The effects of rhIFN‐β1a on α‐smooth muscle actin (α‐SMA), collagen types I and III, transforming growth factor‐β1 (TGF‐β1), platelet‐derived growth factor‐BB (PDGF‐BB), and mothers against decapentaplegic homolog (Smad4, Smad7) expression in HSC were examined using Western blotting and immunocytochemistry. Proliferation of HSC was evaluated via bromodeoxyuridine assay. Results: rhIFN‐β1a treatment had a dose‐dependent, inhibitory effect on α‐SMA and collagen type I protein expression. In addition, rhIFN‐β1a decreased the expression of collagen type III, TGF‐β1, PDGF‐BB and Smad4 protein expression in HSC compared with untreated cells. We also observed increased Smad7 protein expression and decreased proliferation in rhIFN‐β1a‐treated HSC. Conclusions: Our data suggest that rhIFN‐β1a treatment decreased α‐SMA and collagen expression and inhibited the activation of HSC through the inhibition of the TGF‐β and PDGF pathways.     

抗结缔组织生长因子小干扰RNA对肝星状细胞合成分泌细胞外基质的影响

目的 研究化学合成抗结缔组织生长因子(CTGF)小干扰RNA(siRNA)对肝星状细胞(HSC)CTGF基因表达及合成分泌细胞外基质(ECM)的影响。 方法 将化学合成抗CTGF siRNA以Oligofectamine包裹,转染HSC T6细胞,设空白对照,抽提孵育24、48、72 h细胞总RNA及蛋白质,并收集培养上清液,应用western blot和(或)逆转录聚合酶链反直检测HSC T6细胞CTGF及Ⅰ、Ⅲ型胶原基因表达,应用放射免疫法检测培养上清液中透明质酸及Ⅲ型前胶原含量。 结果 与空白对照相比,转染siRNA的HSC T6细胞CTGF及Ⅰ、Ⅲ型胶原基因表达水平显著下调,培养上清液中透明质酸及Ⅲ型前胶原含量24、48、72h分别降低46％±7％,52％±7％,53％±7％(F=157.45,P=0.0001)和29％±18％,29％±7％,27％±5％(F=10.77,P=0.0079)。 结论 化学合成抗CTGF siRNA能高效抑制HSC CTGF基因表达,显著减少HSC Ⅰ、Ⅲ型胶原及透明质酸等ECM的合成与分泌,抑制效应可持续72 h,提示化学合成CTGF siRNA具有预防及治疗肝纤维化的潜力并具有极好的开发前景。     

Targeted disruption of Smad3 confers resistance to the development of dimethylnitrosamine‐induced hepatic fibrosis in mice

Background: Hepatic fibrosis is characterized by a progressive accumulation of fibrillar extracellular matrix (ECM) proteins including collagen, which occurs in most types of chronic liver diseases. Transforming growth factor‐β (TGF‐β)/Smad3 signalling plays a central role in tissue fibrogenesis, acting as a potent stimulus of ECM accumulation. Aim: To evaluate the potential protective role of Smad3 deficiency in the pathogenesis of liver fibrosis induced by dimethylnitrosamine (DMN) in Smad3 null mice. Methods: Chronic hepatitis‐associated fibrosis was induced in 13 Smad3 null and 13 wild‐type (WT) mice by intraperitoneal DMN administration (10 μg/g body weight/day) for three consecutive days per week for 6 weeks. The liver was excised for macroscopic examination and histological, morphometric and immunohistochemical (IHC) analyses. For IHC, α‐smooth muscle actin (α‐SMA), collagen types I–III, TGF‐β1, connective tissue growth factor (CTGF), Smad3, Smad7 and CD3 antibodies were used. Results: At macroscopic examination, the liver of DMN‐treated Smad3 WT appeared harder with a dark brown colouring and necrotic areas compared with that from null mice. Histological and morphometric evaluation revealed a significantly higher degree of hepatic fibrosis and accumulation of connective tissue in the Smad3 WT compared with null mice. IHC evaluation showed a marked increase in α‐SMA, CTGF, collagen I‐III, TGF‐β and Smad3 staining in the liver of Smad3 WT compared with that in null mice, whereas Smad7 was increased only in null mice. Conclusions: The results indicate that Smad3 loss confers resistance to the development of DMN‐induced hepatic fibrosis. The reduced fibrotic response appears to be due to a reduction of fibrogenic myofibroblast activation and ECM production and accumulation. Smad3 could be a novel target for potential treatment of fibrosis complicating chronic hepatitis.     

沉默结缔组织生长因子对鼠转化生长因子β/Smads信号的影响

目的 研究小干扰RNA(siRNA)沉默结缔组织生长因子(CTGF)对大鼠转化生长因子(TGF)β/Smads信号通路的影响.方法 将化学合成CTGF siRNA转染肝星状细胞(HSC)T6和经门静脉注入CCl4诱导6周的肝纤维化大鼠,设空白及随机siRNA对照,抽提HSC T6及大鼠肝组织总RNA和蛋白质,应用Western blot和RT-PCR检测HSC T6及肝组织CTGF及TGF β1,Smad2、3、7蛋白质和基因表达. 结果与空白对照组相比,siRNA能显著下调HSC T6 CTGF蛋白表达,以48 h最明显,CTGF蛋白表达下调94%±4%(t=46.196,P<0.01),而TGF β1、Smad2,3,7 mRNA表达差异无统计学意义;模型组及对照siRNA组,CCl4诱导的大鼠肝组织CTGF和TGF β1蛋白表达明显上调,与模型组相比,CTGF siRNA组大鼠肝组织CTGF及TGF β1蛋白表达分别下调95%±2%(F=21.234,P<0.01)和74%±8%(F=13.464,P<0.05),但Smad2和Smad7蛋白表达无明显改变. 结论沉默CTGF基因表达对大鼠肝TGF β/Smads信号具有阻抑作用.     

Connective tissue growth factor: a fibrogenic master switch in fibrotic liver diseases

Connective tissue growth factor (CTGF=CCN2), one of six members of cysteine‐rich, secreted, heparin‐binding proteins with a modular structure, is recognized as an important player in fibrogenic pathways as deduced from findings in non‐hepatic tissues and emerging results from liver fibrosis. Collectively, the data show strongly increased expression in fibrosing tissues and transforming growth factor (TGF‐β)‐stimulated expression in hepatocytes, biliary epithelial cells and stellate cells. Functional activity as a mediator of fibre–fibre, fibre–matrix and matrix–matrix interactions, as an enhancer of profibrogenic TGF‐β and several secondary effects owing to TGF‐β enhancement, and as a down‐modulator of the bioactivity of bone morphogenetic protein‐7 has been proposed. By changing the activity ratio of TGF‐β to its antagonist bone‐morphogenetic protein‐7, CTGF is proposed as a fibrogenic master switch for epithelial–mesenchymal transition. Consequently, knockdown of CTGF considerably attenuates experimental liver fibrosis. The spill‐over of CTGF from the liver into the blood stream proposes this protein as a non‐invasive reporter of TGF‐β bioactivity in this organ. Indeed, CTGF‐levels in sera correlate significantly with fibrogenic activity. The data suggest CTGF as a multifaceted regulatory protein in fibrosis, which offers important translational aspects for diagnosis and follow‐up of hepatic fibrogenesis and as a target for therapeutic interventions. In addition, CTGF‐promoter polymorphism might be of importance as a prognostic genetic marker to predict the progression of fibrosis.     

Oral application of 1,7-dimethylxanthine (paraxanthine) attenuates the formation of experimental cholestatic liver fibrosis

Aim: Several epidemiological studies suggest a beneficial effect of coffee consumption on the formation and progression of fibrogenic diseases, particularly of the liver. Recent data now point to a modulation of transforming growth factor‐β (TGF‐β) signaling by paraxanthine (1,7‐dimethylxanthine [1,7‐DMX]), the demethylated primary metabolite of caffeine Methods: Twenty adult Sprague–Dawley rats were bile duct ligated (BDL) or sham operated with or without concomitant oral 1,7‐DMX (1 mM) application. Serum was investigated by standard biochemical analysis, in‐house connective tissue growth factor (CTGF), enzyme linked immunosorbent assay (ELISA) or liquid chromatography‐mass spectrometry analysis. Liver tissue was stained using hematoxylin‐eosin (HE) and Sirius‐red staining. Whole liver lysates, primary rat hepatocytes (PC) and hepatic stellate cells (HSC) were investigated by CTGF, and total Smad2/3 Western blot analysis, CTGF reporter gene assay or an in‐house malondialdehyde ELISA. Results: The in vitro 50% inhibitory dose (ID50) of 1,7‐DMX was 0.95 mM by for CTGF promoter activity and protein expression in PC and 1.25 mM for protein expression in HSC. Oral 1,7‐DMX application (1 mM) attenuated cholestatic hepatocellular injury in vivo as determined by biochemical serum analysis and reduced intercellular collagen deposition in the cholestatic rat liver (HE‐ and Sirius‐red staining). Western Blot analysis of whole liver lysates revealed a reduction of intrahepatic concentrations of Smad2/3 and CTGF following oral 1,7‐DMX intake. However, serum CTGF concentrations were not reduced in 1,7‐DMX treated BDL rats. Oral 1,7‐DMX furthermore led to a reduction of intrahepatic lipid peroxidation (malondialdehyde concentrations) as markers of oxidative stress in BDL rats. Conclusion: Our pilot study warrants further studies of 1,7‐DMX as a potential new drug to fight fibrotic processes, not just of the liver.     

蛋白激酶C及转化生长因子β1信号通路对肝星状细胞激活的影响

目的探讨蛋白激酶C（PKC）活性改变对HSC表达TGF β1的影响及在HSC激活中的作用。方法将肝星状细胞系rHSC-99分为3组：对照组（A组），PKC激动剂佛波酯0．5μmol／L组（B组），PKC抑制剂Calphostin C 100nmol／L组（C组）。加药后0、3、6、12h和24h分别检测各组细胞PKC活性的变化；作用24h后，采用Western blot和RT—PCR方法检测各组细胞TGF β1，Smad 4，Ⅰ、Ⅲ型胶原和α-平滑肌肌动蛋白的表达；采用MTT法检测细胞的增殖情况。结果 佛波酯作用后PKC的活性显著增强，而Calphostin C则抑制PKC的活性。PKC活性增强后，与对照组相比TGF β1及其下游信号分子Smad 4的表达分别升高了4．8倍和13．1倍（P〈0．01）；HSC的Ⅰ、Ⅲ型胶原和α-平滑肌肌动蛋白的表达分别升高了2．4倍、1．8倍和1．3倍（P〈0．01），并促进HSC的增殖；PKC活性被抑制后则能抑制以上作用。结论PKC活性的改变能调控HSC中TGF β1的表达，在HSC的激活中发挥调节作用。     

大黄素抗肝纤维化的细胞学机制

研究大黄素抗肝纤维化的细胞学机制。分离、培养大鼠肝星状细胞(HSC)并分别以不同剂量的大黄素(大、中、小剂量组分别为(20、10、5)mg/L)干预,测定各组HSC细胞增殖和胶原合成,并测定HSC培养上清液中透明质酸(HA)和层粘连蛋白(LN)含量,结果大黄素干预的HSC增殖、胶原合成、HA及LN合成明显低于正常对照组,且具有剂量依赖关系,结果提示,大黄素对HSC增殖、细胞外基质合成的直接抑制作用可能是其抗肝纤维化的主要作用机制。     

吡格列酮对转化生长因子β诱导的大鼠肝星状细胞的影响

目的观察吡格列酮对TGFβ诱导的大鼠HSC形态和结缔组织生长因子(CTGF)表达的影响,探讨吡格列酮抑制肝纤维化的机制。方法将大鼠HSC进行体外培养,并分为空白组、TGFβ组、TGFβ 不同剂量吡格列酮组。观察HSC细胞发生的形态学改变,并用免疫组织化学、流式细胞仪定性及定量检测CTGF的表达;ELISA法测定培养细胞上清液中Ⅲ型胶原的含量。结果TGFβ可以诱导大鼠HSC细胞形态发生改变和表达CTGF,且TGFβ组细胞上清液中Ⅲ型胶原含量增加(P<0.05);吡格列酮组可以不同程度抑制TGFβ诱导的细胞形态学改变,各组CTGF的表达水平以及Ⅲ型胶原分泌均低于TGFβ组(P<0.05),且呈剂量依赖性(P<0.05)。结论吡格列酮能够抑制TGFβ诱导的大鼠HSC细胞形态改变、CTGF表达及Ⅲ型胶原的分泌,对肝纤维化具有抑制作用。     

Attenuated liver fibrosis after bile duct ligation and defective hepatic stellate cell activation in neural cell adhesion molecule knockout mice

Aim: Neural cell adhesion molecule (N‐CAM) is expressed by activated hepatic stellate cells (HSC), portal fibroblasts, cholangiocytes and hepatic progenitor cells during liver injury. Its functional role in liver disease and fibrogenesis is unknown. The aim of this study was to investigate the role of N‐CAM in liver fibrogenesis. Methods: To induce fibrosis, N‐CAM knockout mice and wild‐type controls were subjected to bile duct ligation (BDL) or repeated carbon tetrachloride (CCl₄) injections. Fibrosis was quantified by hydroxyproline, immunhistochemistry staining and image analysis. Protein levels were determined with immunoblotting. HSCs were isolated by ultracentrifugation in a Larcoll gradient and thereafter in vitro stimulated with recombinant transforming growth factor (TGF)‐β1. Results: Two weeks after BDL, wild‐type mice had developed pronounced liver fibrosis while N‐CAM?/? mice had less such alterations. N‐CAM?/? mice had less deposition of collagen and fibronectin seen in immunhistochemistry. The protein levels of fibronectin were higher in the liver from the wild type, while laminin were unaltered. CCl₄‐treated N‐CAM?/? and wild‐type mice showed no significant difference in the extent of liver fibrosis or the expression levels of the above‐mentioned genes. HSC isolated from N‐CAM?/? mice showed declined levels of smooth muscle actin and desmin after stimulation in vitro with TGF‐β1. Conclusions: Loss of N‐CAM results in decreased hepatic collagen and fibronectin deposition in mice subjected to BDL, but not in animals exposed to repeated CCl₄ injections. HSC isolated from N‐CAM null mice show impaired activation in vitro. This indicates a role of N‐CAM in cholestatic liver disease and HSC activation.     

促肝细胞生长素及其类似物的生物活性研究

目的 研究促肝细胞生长素(pHGF)对肝细胞及肝星状细胞生物活性的影响。方法 以人肝细胞株及大鼠肝星状细胞株为研究靶细胞,采用MTT法研究pHGF对细胞增殖活性的影响,放免法检测透明质酸(HA),细胞基因转染结合报告基因测活检测Ⅰ型胶原基因转录活性的变化,SDS-PAGE分析pHGF主要成分。结果 pHGF具有明确促进肝细胞增生及抑制肝纤维化主要形成细胞肝星状细胞系增殖的作用,能抑制细胞外间质成分HA的产生,抑制Ⅰ型胶原基因启动子样活性。研究的12种pHGF中仅1种在15％SDS-PAGE中具有明确的蛋白条带。结论 pHGF具有促进肝细胞再生及抗纤维化作用,结构-功能关系需进一步研究。     

Hypoxia and transforming growth factor-beta 1 act independently to increase extracellular matrix production by placental fibroblasts

Villous fibrosis is associated with oxygen deprivation in placental pathology, but the signaling networks and growth factors involved in activating the relevant cellular repair mechanisms are largely unknown. TGF is a powerful enhancer of extracellular matrix (ECM) production and an important immune suppressor that has been linked with fibrosis in several tissues. Here, cell culture methods were used to investigate possible links between hypoxia, elevated TGF beta 1, and altered ECM production in placenta. Term placental fibroblasts were isolated and cultured under hypoxia (3% O(2)) or in the presence of TGF beta 1, and the expression of fibronectin, collagen I, and collagen IV was examined using immunohistochemistry, ELISA of cell monolayers with associated ECM, and real-time RT-PCR. The effect of hypoxia on endogenous production of TGF beta 1-3 was also examined. Both TGF beta 1 and hypoxia increased fibronectin, collagen I, and collagen IV protein and mRNA in placental fibroblasts. However, TGF beta 1-3 production was not increased by culturing the cells under hypoxic conditions for 5 d. Thus, increased ECM expression under hypoxia was not mediated directly by increased TGF beta. We conclude that ECM production can be stimulated independently by hypoxia and TGF beta 1.     

All‐trans‐retinoic acid ameliorates carbon tetrachloride‐induced liver fibrosis in mice through modulating cytokine production

Background/Aims: Liver fibrosis with any aetiology, induced by the transdifferentiation and proliferation of hepatic stellate cells (HSCs) to produce collagen, is characterized by progressive worsening in liver function, leading to a high incidence of death. We have recently reported that all‐trans‐retinoic acid (ATRA) suppresses the transdifferentiation and proliferation of lung fibroblasts and prevents radiation‐ or bleomycin‐induced lung fibrosis. Methods: We examined the impact of ATRA on carbon tetrachloride (CCl₄)‐induced liver fibrosis. We performed histological examinations and quantitative measurements of transforming growth factor (TGF)‐β1 and interleukin (IL)‐6 in CCl₄‐treated mouse liver tissues with or without the administration of ATRA, and investigated the effect of ATRA on the production of the cytokines in quiescent and activated HSCs. Results: CCl₄‐induced liver fibrosis was attenuated in histology by intraperitoneal administration of ATRA, and the overall survival rate at 12 weeks was 26.5% without ATRA (n=25), whereas it was 75.0% (n=24) in the treatment group (P=0.0187). In vitro studies disclosed that the administration of ATRA reduced (i) the production of TGF‐β1, IL‐6 and collagen from HSCs, (ii) TGF‐β‐dependent transdifferentiation of the cells and IL‐6‐dependent cell proliferation and (iii) the activities of nuclear factor‐κB p65 and p38mitogen‐activated protein kinase, which stimulate the production of TGF‐β1 and IL‐6, which could be the mechanism underlying the preventive effect of ATRA on liver fibrosis. Conclusions: Our findings indicate that ATRA ameliorates liver fibrosis. As the oral administration of the drug results in good compliance, ATRA could be a novel approach in the treatment of liver fibrosis.     

Cell survival,activation and apoptosis of hepatic stellate cells: modulation by extracellular matrix proteins

Aim: Cytokines and growth factors released by various hepatic cells exert both paracrine and autocrine effects on hepatic stellate cell (HSC) activation during liver injury. The aim of the present study was to examine whether the surrounding extracellular matrix (ECM) influences the activation, transdifferentiation and survival of HSCs. Methods: An in vitro model system of isolated HSCs maintained in culture on different matrix protein substrata was employed. Results: The rate of loss of HSC‐specific retinol uptake activity and gain of myofibroblast‐like activity such as ³⁵[S] proteoglycan synthesis varied in cells maintained on different matrix proteins and was in the order collagen I > collagen IV ≥ laminin. ³[H]‐thymidine incorporation by HSCs maintained on different matrix proteins varied and was in the order collagen I > collagen IV > laminin. MTT assay revealed that the growth inhibition in response to curcumin was significantly low in cells maintained on collagen I. Apoptotic marker activities such as DNA fragmentation, 4′,6′‐diamidino‐2‐phenylindole dihydrochloride (DAPI) staining, annexin staining and caspase‐3 activities showed that cells maintained on collagen I showed minimal apoptosis than those maintained on collagen IV, laminin and polylysine, showing the influence of ECM on HSC apoptosis. Experiments using blocking antibodies showed that the collagen I effect was mediated through α₂β₁ integrin. Conclusions: These results indicate that ECM influences activation, transdifferentiation and survival of HSCs, and suggest that apart from diffusible factors, the surrounding ECM also influences HSC behavior critical in both the progression of the fibrosis and the restitution of the liver during recovery after hepatic injury.