蛇毒抗肿瘤转移的研究现状

蛇毒含有多种酶和多种不同生理、药理活性蛋白。人们对纯化的蛇毒制品和非纯化的蛇毒制品已有了较深入的研究。本针对血小板、解离素、粘附分子、纤维蛋白以及血管生成等方面，并首重对蛇毒抗肿瘤转移作了简要综述。     

蛇毒解离素对肿瘤侵袭、转移的影响

解离素是蛇毒中的一类活性蛋白质,因含特异性RGD(精-甘-天冬氨酸,Arg—Gly—Asp)或KGD(精-甘-天冬氨酸,Lys—Gly—Asp)基序,可阻断细胞膜表面的整合素与其配体结合,具有抑制血小板聚集、影响细胞迁移和抑制血管生成等作用,从而在多个环节遏制肿瘤细胞的侵袭和转移。     

整合素连接激酶(ILK)在肾脏疾病中的研究进展

整合素连接激酶（integrin-linked kinase,ILK）是一种丝氨酸/苏氨酸蛋白激酶,可与整合素β1、β3亚基胞浆域结合,参与整合素、生长因子、Wnt及TGF-β/Smad等多种信号转导,在调节细胞黏附、凋亡、转移、生长、细胞周期、肿瘤形成等过程中起重要作用。细胞中ILK表达异常,将引发病理变化。本文综述了ILK的生物学活性及其与肾脏疾病的关系,提示ILK的表达调控可能成为治疗肾脏疾病的新途径。     

蛇毒解离素的结构特征及其与生物学活性的关系

目前已从蛇毒中分离出 80余种解离素多肽,根据其结构及来源可分为五大类,即短链、中链、长链解离素、金属蛋白酶P Ⅲ的类解离素区释放的解离素以及二聚体解离素。不同解离素的分子结构共同点包括RGD活性中心、半胱氨酸残基配对形成的二硫键、RGD三肽的C 端和N 端的氨基酸序列以及解离素多肽分子的C 末端。这些结构决定了解离素的抑制血小板聚集、抑制细胞粘附以及血管形成等生物学活性。     

外源性RGD肽在肿瘤诊断与治疗中的应用研究进展

多种肿瘤细胞表面存在高表达的αvβ3、αvβ5等整合素,这些整合素可以与含精氨酸-甘氨酸-天冬氨酸(Arg-Gly-Asp,RGD)三肽结构单元的肽特异性结合,且与肿瘤细胞的黏附、转移、侵袭及血管新生过程密切相关。因此,人们合成了多种含RGD三肽结构单元的外源性多肽,将其与肿瘤显影示踪剂或抗肿瘤活性分子结合,竞争性抑制含RGD结构单元的内源性物质,提高肿瘤显影示踪剂的定位准确性或增强抗肿瘤活性分子的治疗作用,为肿瘤的诊断和治疗提供了新的方向。本文主要介绍了一些外源性RGD肽,并概述其在肿瘤诊断及靶向抗肿瘤方面应用的研究进展。     

蛇毒解离素抗肿瘤血管生成的研究

血管生成是肿瘤细胞生长、浸润、转移过程中的一个重要环节。肿瘤血管不仅为肿瘤细胞生长提供了充足的营养,而且为肿瘤细胞的转移提供了通道。通过抑制肿瘤血管形成,切断肿瘤细胞的营养供应,可抑制其生长并能减少肿瘤浸润转移的机会。蛇毒解离素抗肿瘤的研究是当前蛇毒研究的热点之一,本文就近年来蛇毒解离素抗肿瘤血管生成方面的研究进展予以综述。     

细胞粘附分子研究和开发的新进展

多种生理过程包括细胞的激活、迁移、增殖、分化以及其它的过程需要细胞之间、细胞与细胞外基质之间的直接接触。细胞与细胞和细胞与细胞外基质之间的相互作用是通过几种不同家族的细胞粘附分子所介导的，它们包括整合素、选择素、钙粘着蛋白和免疫球蛋白。细胞粘附分子的商业和治疗潜力在不断提高，新发现的细胞粘附分子以及某些疾病状态下整合素、选择素、免疫球蛋白新作用的发现为诊断性和治疗性药物的研究和开发提供了很好的机会     

整合素阻断剂抗肿瘤药物研究进展

整合素是存在于细胞表面的跨膜糖蛋白受体,能介导细胞间的黏附,参与血管生成和肿瘤转移,与肿瘤的发生发展密切相关。以整合素为靶点进行抗肿瘤治疗,可有效抑制肿瘤的生长和转移。本文主要从抗肿瘤生长类药物、抗肿瘤转移类药物、抗血管生成类药物等方面对近年来整合素阻断剂抗肿瘤药物研究进展进行综述,并对整合素靶向给药的剂量问题进行了讨论。     

P-选择素对黑色素瘤细胞整合素β_1表达的影响

目的：研究P-选择素对黑色素瘤细胞整合素β1表达的影响,探讨P-选择素在肿瘤转移中的作用。方法：培养黑色素瘤细胞B16F10,在加或不加p38丝裂原活化蛋白激酶（MAPK）抑制剂SB203580的情况下,用P-选择素蛋白进行刺激,用蛋白质印迹（Western Blot）检测刺激后B16F10细胞整合素β1蛋白表达及p38 MAPK信号分子磷酸化水平的改变,用MTT法检测黏附细胞数目的变化。结果：P-选择素刺激B16F10细胞导致p38 MAPK磷酸化水平增高,整合素β1表达上调,用特异性阻断剂阻断p38 MAPK活化可以抑制P-选择素的诱导作用。MTT检测结果显示P-选择素刺激可增加细胞与整合素β1配基纤维粘连蛋白的黏附能力,说明细胞整合素β1表达增高。结论：P-选择素可以通过激活p38 MAPK途径诱导黑色素瘤B16F10细胞整合素β1的表达,提高肿瘤细胞的黏附能力,这可能是其促进肿瘤转移的机制之一。     

L-选择素与动脉粥样硬化相关性的研究进展

细胞黏附分子（CAMs）是泛指一类介导细胞与细胞或细胞与细胞基质间相互结合,起黏附作用的糖蛋白,主要位于血管内皮细胞和白细胞表面。黏附分子的种类很多,根据其化学结构和功能特点分为五大类：（1）选择素家族;（2）整合素家族;（3）免疫球蛋白超家族;（4）钙黏附素家族;（5）尚未被归类的细胞黏附分子,如：CD33、CD36等。1983年,     

以整合素为作用靶点的精氨酸-甘氨酸-天冬氨酸模体毒素研究进展

整合素为一类αβ异源二聚体膜蛋白,调节细胞外基质与胞内细胞骨架间的相互作用。精氨酸-甘氨酸-天冬氨酸（RGD）序列为整合素的结合位点,存在于多种重要的细胞外基质蛋白中。整合素与RGD序列结合可调节多种细胞生理活动,RGD模体还存在于来自蛇毒和其他物种来源的多种毒素蛋白中,这些RGD模体毒素能够特异性抑制整合素与细胞外基质的结合,从而成为整合素的强效拮抗剂。本文对整合素的结构与功能、去整合素作为整合素拮抗剂的结构特征做一综述,并对整合素和以RGD为模体结构作为潜在药物靶点的应用加以讨论。     

ADAM-Integrin Interactions: potential integrin regulated ectodomain shedding activity

ADAMs (a disintegrin and metalloprotease) are a family of cell surface proteins related to the Class III snake venom metalloproteases (SVMP). ADAMs are members of the Metazincin family which includes the matrix matalloproteases and the ADAMTS proteins. Unlike their snake venom relatives, ADAMs are expressed as transmembrane cell surface proteins. The domain structure of ADAMs suggests that these proteins posses both proteolytic and adhesive functions. Several members of the ADAM protein family have been shown to be involved in ectodomain shedding of many important cell surface proteins resulting in the release of biologically active soluble factors. The carboxyl-terminal domains, especially the disintegrin-like domain of ADAMs, have been demonstrated to support cell adhesion. The disintegrin-like domains of many ADAMs are capable of acting as integrin ligands. Integrins known to interact with ADAM disintegrin-like domains include alpha4beta1, alpha4beta7, alpha5beta1, alpha6beta1, alpha9beta1, alphavbeta3, and alphavbeta5. This integrin mediated interaction of the disintegrin-like domains with the cell surface suggests that ADAMs may function as cellular counter receptors. In this review we discuss the individual functions ascribed to members of the ADAM family especially those related to integrin interactions and the potential for integrin mediated regulation of ectodomain shedding.     

Snake venom modulators of platelet adhesion receptors and their ligands.

In thrombosis, platelet aggregation is initiated by a specific membrane glycoprotein (GP) Ib-IX-V complex binding to its adhesive ligand, von Willebrand factor, in the matrix of ruptured atherosclerotic plaques or in plasma exposed to high hydrodynamic shear stress. This process closely resembles normal haemostasis at high shear, where GP Ib-IX-V-dependent platelet adhesion to von Willebrand factor in the injured blood vessel wall initiates platelet activation and integrin alphaIIb beta3 (GP IIb-IIIa)-dependent platelet aggregation. At low shear, other receptors such as those that bind collagen, the integrin alpha2beta1 (GP Ia-IIa) or GP VI, mediate platelet adhesion. Recently, snake venom proteins have been identified that selectively modulate platelet function, either promoting or inhibiting platelet aggregation by targeting GP Ib-IX-V, alpha2beta1, GP VI, alphaIIb beta3, or their respective ligands. Interestingly, these venom proteins typically belong to one of two major protein families, the C-type lectin family or the metalloproteinase-disintegrins. This review focuses on recent insights into structure-activity relationships of snake venom proteins that regulate platelet function, and the ways in which these novel probes have contributed in unexpected ways to our understanding of the molecular mechanisms underlying thrombosis.     

Integrins in drug targeting-RGD templates in toxins

Integrins are a family of heterodimeric receptors, which modulate many cellular processes including: growth, death (apoptosis), adhesion, migration, and invasion by activating several signaling pathways. Integrin-binding RGD (arginine-glycine-aspartic acid) is found in several important extracellular matrix proteins which serve as adhesive integrin ligands. The RGD motif has also been found in many toxins from snake venom and other sources that specifically inhibit integrin binding function and serve as potent integrin antagonists, particularly of platelet aggregation and integrin-mediated cell adhesion. Many of these proteins have potential as therapeutic agents which can target integrins directly. Structural and functional studies of several RGD-containing toxins suggest that the inhibitory potency of these proteins lies in subtle positional requirements of the tripeptide RGD at the tip of a flexible loop, a structural feature for binding to integrins. In addition, amino acid residues in this loop in close vicinity to the RGD-motif determine the integrin-binding specificity and selectivity. This review will present a review of integrin structure and function, and of disintegrin structural features responsible for their activity as antagonists of integrin function. The use of integrins in drug targeting and integrins as targets for drug delivery by using the RGD as a template structure will also be discussed.     

蛇毒蛋白基因的大肠杆菌表达研究进展

蛇毒是多种生物活性蛋白和多肽的混合物，由于蛇毒在基础医学和临床上的特殊作用以及天然蛇毒蛋白获取方法的局限性，采用生物工程方法规模化生产高纯度的蛇毒蛋白已成为当前及今后的研究方向。该文就蛇毒蛋白基因在大肠杆菌中表达的研究近况进行介绍。     

Snake venoms and the hemostatic system

Snake venoms are complex mixtures containing many different biologically active proteins and peptides. A number of these proteins interact with components of the human hemostatic system. This review is focused on those venom constituents which affect the blood coagulation pathway, endothelial cells, and platelets. Only highly purified and well characterized snake venom proteins will be discussed in this review. Hemostatically active components are distributed widely in the venom of many different snake species, particularly from pit viper, viper and elapid venoms. The venom components can be grouped into a number of different categories depending on their hemostatic action. The following groups are discussed in this review: (i) enzymes that clot fibrinogen; (ii) enzymes that degrade fibrin(ogen); (iii) plasminogen activators; (iv) prothrombin activators; (v) factor V activators; (vi) factor X activators; (vii) anticoagulant activities including inhibitors of prothrombinase complex formation, inhibitors of thrombin, phospholipases, and protein C activators; (viii) enzymes with hemorrhagic activity; (ix) enzymes that degrade plasma serine proteinase inhibitors; (x) platelet aggregation inducers including direct acting enzymes, direct acting non-enzymatic components, and agents that require a cofactor; (xi) platelet aggregation inhibitors including: -fibrinogenases, 5′-nucleotidases, phospholipases, and disintegrins. Although many snake venoms contain a number of hemostatically active components, it is safe to say that no single venom contains all the hemostatically active components described here. Several venom enzymes have been used clinically as anticoagulants and other venom components are being used in pre-clinical research to examine their possible therapeutic potential. The disintegrins are an interesting group of peptides that contain a cell adhesion recognition motif, Arg–Gly–Asp (RGD), in the carboxy-terminal half of their amino acid sequence. These agents act as fibrinogen receptor (integrin GPIIb/IIIa) antagonists. Since this integrin is believed to serve as the final common pathway leading to the formation of platelet–platelet bridges and platelet aggregation, blockage of this integrin leads to inhibition of platelet aggregation regardless of the stimulating agent. Clinical trials suggest that platelet GPIIb/IIIa blockade is an effective therapy for the thrombotic events and restenosis frequently accompanying cardiovascular and cerebrovascular disease. Therefore, because of their clinical potential, a large number of disintegrins have been isolated and characterized.     

Snake venom: kill and cure

Snake venom is a natural biological resource that contains several components, which are not only responsible for death but also have a potential therapeutic activity. The use of snake venom for medicinal purposes dates back to ancient times, now many drugs and clinical diagnostic kits have derived from components of snake venom. The scientists can extract, purify and identify new components of venom that may serve as starting point for structure–function relationship studies leading to design new medications. This review will highlight the activities of snake venoms and their components against cancer, microbes, parasitic infections and platelet aggregation.     

Snake venom toxin inhibits cell growth through induction of apoptosis in neuroblastoma cells

Snake venom toxin from Vipera lebetina turanica can induce apoptosis in many cancer cell lines, but there is no study about the apoptotic effect of snake venom toxin on human neuroblastoma cells. In this study, we investigated the apoptotic effect of snake venom toxin in human neuroblastoma SK-N-MC and SK-N-SH cells. Our result showed that cell detachment and apoptotic cell death were increased by snake venom toxin (1.25–10 μg/mL), but normal neuronal cells were not affected. Consistent with the induction of apoptosis, the level of reactive oxygen species (ROS) was increased, but mitochondrial membrane potential (MMP) was disrupted by treatment with snake venom toxin. However, the glutathione prevented snake venom toxin-induced cell growth inhibition. Snake venom toxin also increased the expression of pro-apoptotic protein Bax, but down-regulated anti-apoptotic protein Bcl-2. Therefore, these results showed that snake venom toxin from Vipera lebetina turanica causes apoptotic cell death of neuroblastoma cells through ROS dependent MMP disruption, and suggested that snake venom toxin may be applicable as an anti-cancer agent for neuroblastoma.     

Functional characteristic of snake venom disintegrins: potential therapeutic implication

Snake venom disintegrins are the natural products that have been investigated as potent inhibitors of various integrins. Functionally, disintegrins can be divided into three groups according to their integrin selectivity and presence of specific, active motifs. This classification includes RGD-disintegrins, MLD-disintegrins, and KTS-disintegrins. RGD-disintegrins have been the most intensively investigated, and their research resulted in design and synthesis of new pharmaceutical compounds, eptifibatide and tirofiban that are currently being evaluated for the therapy of acute coronary ischaemic syndrome. MLD- and KTS-disintegrins are specific for leukocyte integrins and collagen receptors, respectively, and are being investigated in the new fields of pharmaceutical research. This review summarizes the biological activities of snake venom disintegrins, as well as discusses their potential in the study of the pharmacology of various human diseases.