Cloning, Expression and Polyclonal Antibody Preparation of the Asialoglycoprotein Receptor of Marmota Himalayan

The objective of this study is to express the carbohydrate recognition domain （CRD） of the asialoglycoprotein receptor （ASGPR） H1 and H2 subunits of Marmota himalayan in vitro, and develop polyclonal antibodies against the recombinant proteins. RT-PCR was used to amplify ASGPR CRDH1 and CRDH2 from the liver tissue of Marmota himalayan. The products of amplification were subcloned into prokaryotic expression vector pRSET-B, and expressed in E.coli BL21（DE3）plysS. The recombinant proteins were purified using Ni-NTA spin column. The purified proteins were inoculated into BALB/c mice to develop polyclonal antibodies. The sensitivity and specificity of antibodies were evaluated by enzyme-linked immunosorbent assay （ELISA）, Western blotting and immunohistochemical staining （IHC）. The polyclonal antibodies showed high sensitivity and specificity against both denaturated and native ASGPR proteins. We successfully amplified and expressed the ASGPR CRDs of Marmota himalayan. The nucleic sequences of ASGPR CRDH1 and CRDH2 of Marmota himalayan have been submitted to Genbank and the sequence ID are DQ 845465 and DQ845466, respectively. The proteins and antibodies prepared can be used for targeting gene therapy in a new animal model-Marrnota himalayan—— for the research of infectious diseases of hepatitis viruses and liver cancer treatment.

Feasibility on Systemic Delivery of Asialoorosomucoid Complex to Hepatic Origin Cells Mediated by Asialoglycoprotein Receptor

Receptor mediated gene delivery is a new gene transfer strategy. Asialoglycoprotein receptor (ASGP-R), the receptor of asialoorosomucoid (Asor), is specially expressed on the surface of hepatocyte. In this paper, the nuclide 131I was combined with Asor to form a kind of soluble nuclide-protein complex, which can be specifically endocytosed into hepatocyte by ASGP-R. After intravenous injection of the complex into experimental animals, the deposition of Asor in vivo and the targeting quality of hepatocyte was detected by ECT. This research testified the feasibility of targeting Asor complex delivery to hepatocyte mediated by ASGP-R in vivo, and provided foundation for the genetic diagnosis and gene therapy of hepatic cell-related diseases.

Constant serum levels of secreted asialoglycoprotein receptor sH2a and decrease with cirrhosis

AIM: To investigate the existence and levels of sH2a, a soluble secreted form of the asialoglycoprotein receptor in human serum. METHODS: Production of recombinant sH2a and development of a monoclonal antibody and an enzyme-linked immunosorbent assay (ELISA). This assay was used to determine the presence and concentration of sH2a in human sera of individuals of both sexes and a wide range of ages. RESULTS: The recombinant protein was produced successfully and a specific ELISA assay was developed. The levels of sH2a in sera from 62 healthy individuals variedminimally (147 ± 19 ng/mL). In contrast, 5 hepatitis C patients with cirrhosis showed much decreased sH2a levels (50 ± 9 ng/mL). CONCLUSION: Constant sH2a levels suggest constitutive secretion from hepatocytes in healthy individuals. This constant level and the decrease with cirrhosis suggest a diagnostic potential.

Synthesis and biological evaluation of ^(18)F-FB-NGA as a hepatic asialoglycoprotein receptor PET imaging agent

Asialoglycoprotein receptor(ASGP-R)is a hepatic membrane receptor that uniquely exists on the surface of mammalian hepatocytes,and has been used as target of liver functional imaging agents for many years.We labeled the Galactosyl-neoglycoalbumin(NGA)with 18F to get a PET molecular probe 18F-FB-NGA and evaluated its ability as a liver functional PET imaging agent.The 18F-FB-NGA was prepared with NGA by conjugation with Nsuccinimidyl-4-18F-fluorobenzoate(18F-SFB)and purified with PD-10 desalting column.The radiolabeling yield and radiochemical purity of 18F-FB-NGA were determined by radio-HPLC.Starting with 18F-F–,the total time for 18F-FB-NGA was about 120±10 min.The decay-corrected radiochemical yield is about 25–30%.The radiochemical purity of purified 18F-FB-NGA was more than 98%.Labeled with 185–1850 MBq 18F-SFB,the specific activity of 18F-FBNGA was estimated to be 7.83–78.3 TBq/mmol.Biodistribution of 18F-FB-NGA in normal mice was investigated after injection through the tail vein.The results showed that the liver accumulated 39.47±3.42 and 12.12±6.11%ID/g at 10 and 30 min after injection,respectively.Dynamic MicroPET images in mice were acquired with and without block after injection of the radiotracer,respectively.High liver activity accumulation was observed at 5 min after injection in normal group.On the contrary,the liver accumulation was significantly lower after block,indicating the specific binding to ASGP-R.18F-FB-NGA is probably a potential PET liver imaging agent.

Impact of asialoglycoprotein receptor deficiency on the development of liver injury

The asialoglycoprotein (ASGP) receptor is a wellcharacterized hepatic receptor that is recycled via the common cellular process of receptor-mediated endocytosis (RME). The RME process plays an integral part in the proper traff icking and routing of receptors and ligands in the healthy cell. Thus, the missorting or altered transport of proteins during RME is thought to play a role in several diseases associated with hepatocyte and liver dysfunction. Previously, we examined in detail alterations that occur in hepatocellular RME and associated receptor functions as a result of one particular liver injury, alcoholic liver disease (ALD). The studies revealed profound ethanolmediated impairments to the ASGP receptor and the RME process, indicating the importance of this receptor and the maintenance of proper endocytic events in normal tissue. To further clarify these observations, studies were performed utilizing knockout mice (lacking a functional ASGP receptor) to which were administered several liver toxicants. In addition to alcohol, we examined the effects following administration of antiFas (CD95) antibody, carbon tetrachloride (CCl4) and lipopolysaccharide (LPS)/galactosamine. The results of these studies demonstrated that the knockout mice sustained enhanced liver injury in response to all of the treatments, as shown by increased indices of liver damage, such as enhancement of serum enzyme levels, histopathological scores, as well as hepatocellular death. Overall, the work completed to date suggests a possible link between hepatic receptors and liver injury. In particular, adequate function and content of the ASGP receptor may provide protection against various toxinmediated liver diseases.

Asialoglycoprotein receptor and liposome synergistically mediate the gene transfer into primary rat hepatocytes

Gene transfer into primary rat hepatocytes was performed by employing cationic liposome as DNA carrier and the specific ligand of hepatic asialoglycoprotein receptor (ASGPR), asialofetuin, as liver-targeting ligand. The resuits showed that asialofetuin, when added to the gene transfer complexes, could significantly increase the hepatocyte transfeetion efficiency, and alleviate the cellular toxicity of Lipofectin. Several synthetic ligands of ASGPR (galactosyl albumin) could also increase the transfection efficiency of hepatocyte like asialofetuin. It was proved that ASGPR and cationic liposome could synergistically mediate the gene transfer into primary rat hepatoeytes. This novel gene delivery system provided a safer, more simple and efficient gene transfer method for primary hepatocytes, and showed prospecting application in hepatic gene therapy.

ASGR1在肝细胞癌中的意义及机制研究

目的·探究去唾液酸糖蛋白受体1(asialoglycoprotein receptor 1,ASGR1)在肝细胞癌(hepatocellular carcinoma,HCC)中的意义及潜在机制。方法·通过R语言分析癌症基因组图谱(The Cancer Genome Atlas,TCGA)数据库中ASGR1在肝癌患者中的表达情况并绘制相关生存曲线。利用人类蛋白质图谱(The Human Protein Atlas,HPA)数据库获得人体正常肝组织和肝癌组织的免疫组织化学(immunohistochemistry,IHC)数据来分析ASGR1的蛋白表达情况。利用流体动力学尾静脉注射(hydrodynamic tail vein injection,HTVI)递送方法,在免疫完全的小鼠肝脏中敲除Asgr1探究其在体内的致瘤功能,并通过蛋白免疫印迹法(Western blotting,WB)验证基因敲除效率。利用R语言进行京都基因与基因组百科全书(Kyoto Encyclopedia of Genes and Genomes,KEGG)通路富集分析及相关性分析,利用基因探针富集(Gene Set Enrichment Analysis,GSEA)软件进行GSEA hallmark相关通路分析,利用实时荧光定量PCR(quantitative real-time PCR,qPCR)在小鼠肝癌组织中验证糖酵解关键基因表达水平。结果·ASGR1在肝癌组织中显著低表达,在肝癌患者中ASGR1的低表达与患者较差的总体生存期(overall survival,OS)、无疾病间隔(disease free interval,DFI)、无进展间隔期(progression free interval,PFI)和疾病特异性生存期(disease specific survival,DSS)相关;肿瘤分级程度越高的肝癌患者ASGR1基因表达水平越低。人体正常肝组织ASGR1蛋白的表达显著高于肝癌组织。在免疫完全的肝细胞癌小鼠模型中,小鼠内源性Asgr1敲除可增加肝组织中肿瘤结节的大小和数量。TCGA数据库中ASGR1低表达组肝癌患者富集到多条癌症及代谢相关通路,ASGR1表达与部分糖酵解关键基因表达呈负相关,Asgr1敲除组的小鼠肝癌组织中糖酵解水平高于对照组,提示ASGR1低表达很可能促进肝癌的生长发展,加强代谢重编程促进肿瘤的合成代谢发展。结论·ASGR1在肝癌患者中表达显著降低,与患者的预后呈正相关;小鼠体内敲除Asgr1可促进肝细胞癌的发生发展;ASGR1可以作为肝癌预后不良的潜在生物标志物和潜在治疗新靶点。

去唾液酸糖蛋白受体介导甘草次酸壳聚糖微球的质量评价

目的:甘草次酸具有多种药理作用,如抗肿瘤、抗炎和抗病毒等。对甘草次酸进行修饰,制成靶向缓释制剂可以使药物准确到达作用部位,降低对其他组织的伤害。实验制备去唾液酸糖蛋白受体介导的甘草次酸壳聚糖微球,并对所制备的微球进行表征和质量评价。方法:采用乳化交联法制备,并对壳聚糖微球的粒径、Zeta电位、红外光谱图、包封率和载药量、体外释放度及稳定性等方面进行考察。结果:制备的微球粒径为1.106~1.718μm,Zeta电位为(15.13±1.76)mV,包封率为82.4%,载药量为1.02%,24 h体外释放度为77.09%,稳定性有待提高。结论:去唾液酸糖蛋白受体介导的甘草次酸壳聚糖微球,可为研制靶向肝药物提供一定的理论依据和实践基础。

半乳糖修饰人血清白蛋白的质谱分析

研究发现,存在于哺乳动物肝细胞膜上的血浆无唾液酸糖蛋白受体(asialoglycoprotein receptor,ASGP-R)是一种肝结合蛋白(hepatic binding protein,HBP),能专一性识别分子末端带有半乳糖残基的糖蛋白并与之结合,定向转到肝细胞内的溶酶体进行代谢[1],针对ASGP-R作为靶点的肝靶向药物载体半乳糖化人血白蛋白偶合物(galactosyl-neoglycoalbumin,NGA),已引起药物研究工作者的极大重视[2,3].将药物与带有半乳糖残基的蛋白偶合,可提高药物的肝靶向性,提高治疗指数,减少非靶器官的毒副作用.……

甲氨喋呤-乳糖酰基壳聚糖的制备及其体外实验

制备了不同乳糖酰基取代度的N-乳糖酰基壳聚糖(LCH),并通过红外光谱(IR)及核磁共振氢谱(1H NMR)对其进行了结构表征.体外放射性配基竞争结合实验结果显示,当乳糖酰基取代度为15·5%～38·9%时,LCH对肝实质细胞膜表面去唾液酸糖蛋白受体(ASGPR)具有特异亲和性,即具有潜在的肝靶向性.将甲氨喋呤(MTX)与壳聚糖以酰胺键偶联,制备MTX-壳聚糖(MTX-CH),再与乳糖酸反应生成目标产物MTX-乳糖酰基壳聚糖(MTX-LCH),并通过紫外分光光度法(UV)检测MTX的取代度为5·6%,乳糖酰基取代度为33·8%.溶解性实验结果显示,MTX-LCH溶于pH=1～14的水溶液;体外释放实验结果表明,MTX-LCH性质稳定,能明显延缓MTX的释放.

肝靶向抗病毒药NGA－ACV的制备及其趋肝性

以无唾液酸糖蛋白受体（ａｓｉａｌｏｇｌｙｃｏｐｒｏｔｅｉｎｒｅｃｅｐｔｏｒ，ＡＳＧＰＲ）的特异性配体半乳糖基拟糖白蛋白（ｎｅｏｇｌｙｃｏａｌｂｕｍｉｎ，ＮＧＡ）为载体，通过丁二酰基桥将抗病毒药无环鸟苷（ａｃｙｃｌｏｖｉｒ，ＡＣＶ）与ＮＧＡ偶联，得到肝靶向抗病毒药ＮＧＡＡＣＶ。差热分析和高效液相色谱分析结果表明，ＮＧＡＡＣＶ是共价键偶联物，且在血液中稳定性很好。将偶联物用１３１Ｉ标记后进行家兔放射性显像比较研究。结果，高、低药密度ＮＧＡＡＣＶ的肝脏放射性分别是全身放射性的８１．６％和８６．６％，其趋肝性无明显差别。研究小鼠体内高药密度１３１ＩＮＧＡＡＣＶ的分布，在５ｍｉｎ时肝脏放射性达到峰值，为注入量的８１．７±１０．４％。受体竞争抑制实验表明ＮＧＡＡＣＶ的肝靶向机理为受体介导的主动靶向过程。初步体外抗乙肝病毒比较研究表明，ＮＧＡＡＣＶ较ＡＣＶ的抗病毒剂量有明显降低。

^99mTc-DTPA-半乳糖人血清白蛋白在不同小鼠肝损伤模型中肝功能显像的应用

目的明确肝显像剂99mTc-DTPA-半乳糖人血清白蛋白(99mTc-GSA)在3种不同类型肝细胞损伤小鼠模型中不同的摄取和生物分布情况。方法3种小鼠模型分别为肝硬化、淤胆性肝损伤和肝肿瘤模型。肝硬化模型用腹腔内注射CCl4完成(每48小时腹腔注射0.4 ml 10%CCl4,共48 d);淤胆性肝损伤模型以结扎胆总管72 h建立;肝肿瘤模型用H22肿瘤细胞株种植肝包膜下10 d建立。各模型组小鼠和正常对照组小鼠均以0.1 ml(0.37 MBq)99mTc-GSA(2μg)注射尾静脉,5 min后断头处死,取出各重要器官或组织(肝脏、心脏、肺脏、肾脏、脾脏、胃、血液、骨骼、肌肉、肠道)称量,测定其放射性计数。同时血清学及肝脏病理学检查验证肝脏损伤。结果3个模型组和对照组中99mTc-GSA在小鼠肝脏均有显著浓聚(均>40%ID.g-1),但与对照组(90.05±10.55)%ID.g-1相比,肝损伤模型组的浓聚度均显著下降(P<0.001)。病理检查结果和建立模型时预期的病变相符;血清肝功能显示肝硬化模型组的损伤[天冬氨酸转氨酶为(235.3±14.7)U/L]轻于淤胆性肝损伤模型以及肝肿瘤模型[天冬氨酸转氨酶分别为(841.3±68.7)和(1 060.3±208.3)U/L];但肝硬化模型的浓聚度(72.20±2.13)%ID.g-1较淤胆性肝损伤模型(56.72±5.92)%ID.g-1及肝肿瘤模型(42.80±6.05)%ID.g-1显著增高(P<0.001)。结论99mTc-GSA在肝脏有显著浓聚,其浓聚程度与肝功能受损情况呈负相关。99mTc-GSA可能成为临床上反映肝功能的显像剂,如与三维扫描技术相结合,有希望建立评估肝脏区段功能的三维成像系统。

半乳糖基新糖白蛋白的制备及其对肝特异性受体结合试验的研究

作者用半乳糖经乙酰化、溴代、缩合、置换及加成反应制得2-亚氨基-2-甲氧基乙基-1-硫代-β-D-半乳吡喃糖苷,最后与人血清白蛋白偶连后得不同糖密度的半乳糖基新糖白蛋白(NGA),并用^(90)mTc标记后进行了动物及临床试验。结果^(99m)Tc-NGA-21的肝最大摄取率为82.6％,肝显像清晰。

肝靶向配体半乳糖基白蛋白和多聚谷氨酸

化学合成两类去唾液酸糖蛋白受体（ＡＳＧＰＲ）的人工配体———半乳糖基白蛋白（ＧａｌｎＨＳＡ）和半乳糖基多聚Ｌ谷氨酸（ＧａｌｎＰＬＧＡ），并以１２５Ｉ标记的去唾液酸胎球蛋白（ＡＳＦ）为标准配体，测定了合成配体抑制１２５ＩＡＳＦ与大鼠肝细胞膜ＡＳＧＰＲ结合的ＩＣ５０值．结果表明，Ｇａｌ１２ＨＳＡ、Ｇａｌ１５ＨＳＡ、Ｇａｌ２６ＨＳＡ、Ｇａｌ３０ＨＳＡ和Ｇａｌ３４ＰＬＧＡ均能够有效地抑制１２５ＩＡＳＦ与ＡＳＧＰＲ的结合，且前者与ＡＳＧＰＲ的亲和力随半乳糖基化程度的增加而增加．这些合成配体来源丰富、制备简单，适合于作为药物或基因肝靶向运送的导向配体．

脂质体的乳糖化修饰及其肝脏靶向性研究

目的探讨乳糖化白蛋白－脂质体交联物（简称交联物）作为肝脏靶向性药物载体的可行性。方法应用生物化学技 术合成交联物并对大鼠进行体内实验，了解交联物在动物肝脏的聚集量以及预先注射乳糖化白蛋白对交联物肝脏聚集 性的抑制作用；比较交联物、普通脂质体分别包裹的 α－干扰素及游离 α－干扰素在 ２．２．１５细胞中的抗乙型肝炎病毒效 应。结果交联物在肝脏的聚集量是脾脏的２倍以上，是其他脏器的４－９倍；预先注射乳糖化白蛋白后交联物的肝脏聚 集性减弱，与脾脏聚集量无显著差异；交联物包裹干扰素后抗乙肝病毒效应较普通脂质体包裹的干扰素及游离干扰素 显著提高，相当于普通脂质体干扰素１／４剂量、游离干扰素１／８剂量的抗病毒效应。结论文联物通过去唾液酸糖蛋白受 体实现肝脏聚集性，可望成为理想的肝脏靶向性药物载体。

肝靶向抗病毒药Lac-PLL-ACV的制备及其趋肝性研究

目的 减少抗病毒药阿昔洛韦 (Acyclovir ,ACV)在治疗乙型肝炎中的肝外毒副作用 ,获得肝靶向ACV偶联物。方法 多聚赖氨酸 (Poly L lysine ,PLL)在氰硼酸钠的催化作用下与乳糖反应生成乳糖化多聚赖氨酸 ,乳糖化多聚赖氨酸与咪唑化阿昔洛韦在 3 7℃pH 9 5的条件下反应合成偶联物乳糖化多聚赖氨酸 阿昔洛韦 (Lactosaminatedpoly L lysine acyclovir ,Lac PLL ACV)。偶联物经尾静脉注射进入小鼠体内后 ,收集小鼠血浆及肝脏样品 ,用高效液相色谱法测定药物浓度 ,研究偶联物的体内分布和药代动力学。结果 HPLC检测证实Lac PLL ACV在血浆中十分稳定 ,不易解离出ACV。偶联物的肝最大摄取率约为 60 % ,是ACV组的 10倍以上 ,偶联物肝中的T1/ 2 ,AUC ,CL分别为ACV的 4 2倍 ,5 6 6倍和 1/ 5 7,具有明显的肝靶向性。结论 乳糖化多聚赖氨酸作为肝去唾液酸糖蛋白受体 (Asialoglycoproteinreceptor ,ASGPR)介导的一种药物载体 。

去唾液酸糖蛋白受体特异性单链抗体的优化表达及亲和常数的测定

目的:表达及纯化抗去唾液酸糖蛋白受体(ASG-PR)的单链抗体的可溶性,并测定其亲和常数。方法:用噬菌体C1克隆感染E.coliHB2151,挑取单个菌落接种于2×TY培养基中,于37℃震荡培养过夜。将培养物作1∶100稀释并转种后,用终浓度为0.25、0.5、1.0mmol/L的IPTG,分别在37℃、25℃和20℃下诱导表达过夜。取其培养上清,用饱和硫酸铵沉淀后,以120g/LSDS-PAGE分析。另外,将饱和硫酸铵沉淀物用30mLPBS重新溶解、透析除盐后,用Ni2+螯合柱进行纯化,再以120g/LSDS-PAGE鉴定纯化scFvC1的纯度。用非竞争酶免疫法测定scFv的亲和常数。结果:用0.5mmol/LIPTG在25℃诱导过夜,表达的scFvC1的量较多,其相对分子质量(Mr)约为28000,以可溶性的形式存在于培养基中。通过Ni2+亲和柱纯化后scFvC1的纯度在95%以上,产量约为0.8mg/L。scFv的亲和常数为(2.31±0.36)×10-7mol/L。结论:以筛选的C1噬菌体感染E.coliHB2151后可表达低亲和力的可溶性scFv,对肝癌的基因治疗具有潜在的应用价值。

肝癌细胞膜上转铁蛋白受体和去唾液酸糖蛋白受体数量的变化

目的:研究肝癌细胞膜摄取转铁蛋白受体的变化。方法：采用免疫组化及配体受体结合法分别测定正常肝脏、肝癌组织及癌旁肝组织转铁蛋白受体及去唾液酸糖蛋白受体的含量。结果：肝癌组织中转铁蛋白受体的含量高于癌旁及正常肝组织，而去唾液酸糖蛋白受体却明显低于癌旁及正常肝组织。结论：该变化有利于肝癌细胞对转铁蛋白的有效提取，也增加了肝癌细胞对高度唾液酸化的转铁蛋白的相对特异性摄取。

肝细胞表面去唾液酸糖蛋白受体的流式细胞分析

建立肝细胞表面去唾液酸糖蛋白受体 (ASGPR)的流式细胞分析方法 (FCM ) ,对正常及损伤鼠肝细胞、肝癌细胞 (BEL 740 2 )表面的ASGPR作同步比较分析 .以异硫氰酸荧光素标记的新半乳糖白蛋白 (FITC NGA)为ASGPR的特异性配体 ,以培养的正常肝细胞 (L 0 2 )为靶细胞 ,建立肝细胞表面ASGPR的FCM .测定并计算正常及损伤鼠肝细胞 ,BEL 740 2细胞与同一浓度的FITC NGA同步反应后的平均荧光强度 (MIF)值 .FITC NGA与L 0 2细胞表面ASGPR趋近饱和结合的浓度为 0 4mg/L ,该浓度下正常及损伤鼠肝细胞 ,BEL 740 2细胞的MIF值分别为 2 2 8 7、 5 81、 1 13.该结合可以被至少 5 0倍于FITC NGA的NGA或10mmol/L的EDTA完全抑制 .FCM能够良好地揭示FITC NGA同ASGPR之间的受配体结合特性 .该方法证实BEL 740 2细胞表面几乎没有ASGPR ,损伤鼠肝细胞表面ASGPR的数量较正常鼠肝细胞显著减少 .

半乳糖配体介导多烯紫杉醇脂质体靶向性研究

目的:研究经半乳糖配体修饰后的多烯紫杉醇脂质体(docetaxel liposomes modified with galactose ligand,Gal-DOC-L)在小鼠体内的组织分布,探讨Gal-DOC-L对肝脏的靶向作用。方法:采用高效液相色谱法(high performance liquid chromatogra-phy,HPLC)测定各组织中多烯紫杉醇的药物浓度,以多烯紫杉醇普通脂质体(docetaxel liposomes,DOC-L)为对比,分别采用相对摄取率re、峰浓度比Ce和靶向效率te作为评价参数,对Gal-DOC-L的肝靶向性进行评价。结果:DOC-L和Gal-DOC-L的re分别为2.80和4.34,Ce分别为1.67和2.38,te分别为28.44%和38.91%。结论:药物经脂质体包封后对肝脏具有一定的靶向效应,而半乳糖配体的引入可进一步提高脂质体对肝脏的靶向性。