Triterpenoid saponins, new metalloprotease snake venom inhibitors isolated from Pentaclethra macroloba.

We report here the antiproteolytic and antihemorrhagic properties of triterpenoid saponin inhibitors, named macrolobin-A and B, from Pentaclethra macroloba, against Bothrops snake venoms. The inhibitors were able to neutralize the hemorrhagic, fibrin(ogen)olytic, and proteolytic activities of class P-I and P-III metalloproteases isolated from B. neuwiedi and B. jararacussu venoms. Clotting and fibrinogenolytic activities induced by snake venoms and isolated thrombin-like enzymes were partially inhibited. Furthermore, the potential use of these inhibitors to complement antivenom therapy as an alternative treatment and/or used as molecular models for development of new therapeutical agents in the treatment of snake bite envenomations needs to be evaluated in future studies.     

C端序列的删除对非出血重组蛇毒纤溶酶的影响

[目的]研究C端序列对非出血重组纤溶酶(rFⅡ)特异性、活性和热敏感性的影响.[方法]通过SOEing PCR方法构建删除C端序列的突变体,突变体和rFⅡ分别在P.pastoris中诱导表达.表达和纯化的蛋白用SDS-PAGE和Westeren blot进行鉴定.之后分析其生化特性.[结果]rFⅡ及突变体通过SDS-PAGE和Westeren blot得到证实.生化分析揭示:①突变体对显色底物N-(p-Tosyl)-Gly-Pro-Lys-pNA的催化效率(Kcat/Km)是rFⅡ的1.9倍;②突变体和rFⅡ对氧化的胰岛素B链拥有共同的优先裂解位点,可是在随后的裂解中开始展现差异;③突变体显示了更高的纤(原)活性;④热处理表明突变体相较r FⅡ对温度的增加更敏感;⑤通过圆二色谱测量,突变体的螺旋比例有所增加.[结论]删除的序列参与rFⅡ的特异性、活性和热敏感性,该序列可作为下一步优化的候选序列.     

Synthesis of substrates and inhibitors of botulinum neurotoxin type A metalloprotease*

Abstract: Botulinum neurotoxin (BoNT) metalloproteases and related proteases are the most selective proteases known. X‐ray crystal structures suggest that the active sites of the native enzymes exist in catalytically incompetent forms that must be activated by substrate binding. In order to characterize the postulated substrate‐induced conformational changes for enzyme activation, we synthesized a series of transition‐state analog inhibitors in which the dipeptide cleavage site is replaced by tetrahedral intermediate analogs within the minimal substrate peptide sequence. In this paper, we report our efforts to design inhibitors of BoNT/A metalloprotease. We confirm that an effective substrate sequence for BoNT/A metalloprotease is a 17‐mer peptide corresponding to residues 187–203 of SNAP‐25. A more stable substrate, Nle²⁰²SNAP‐25 [187–203] was synthesized in order to develop an assay for proteolytic activity of BoNT/A metalloprotease that can be used to monitor time‐dependent inhibition. α‐Thiol amide analogs of Gln‐197 were incorporated via solid‐phase peptide synthesis into both 17‐mer minimal peptide substrate sequences. The synthesis, characterization and inhibition kinetics for the α‐thiol amide analogs of holotoxin A substrate are described. These substrate‐derived inhibitors were shown to be submicromolar inhibitors of BoNT/A catalytic activity.     

Inflammation Research Association: 12th international conference

The Inflammation Research Association held its 12th international meeting at the Sagamore at Bolton Landing in New York State (3 – 7 O-ctober 2004). These meetings were originally intended for scientists from the pharmaceutical industry to get together and discuss the latest developments in inflammation drug discovery, and it remains an industry-dominated affair. The conference covered some highly topical issues such as cyclooxygenase-2 inhibitors (rofecoxib/Vioxx® [Merck & Co., Inc.] was withdrawn from the market only a few days before the conference), along with areas of ongoing interest to the pharmaceutical and biotechnology industry, including p38 MAPK inhibitors, nuclear hormone receptor modulators and prostaglandin receptor antagonists. This review will cover the main themes that emerged during the meeting.     

Plasminogen activator inhibitor-1 is an aggregate response factor with pleiotropic effects on cell signaling in vascular disease and the tumor microenvironment

In hemostasis, the serine protease inhibitor (serpin) plasminogen activator inhibitor-1 (PAI-1) functions to stabilize clots via inhibition of tissue plasminogen activator (tPA) with subsequent inhibition of fibrinolysis. In tissues, PAI-1 functions to inhibit extracellular matrix degradation via inhibition of urokinase plasminogen activator (uPA). Elevated levels of PAI-1 in the vasculature and in tissues have long been known to be associated with thrombosis and fibrosis, respectively. However, there is emerging evidence that PAI-1 may participate in the pathophysiology of a number of diseases such as atherosclerosis, restenosis, and cancer. In many of these disease states, the canonical view of PAI-1 as an inhibitor of tPA and uPA cannot fully account for a mechanism whereby PAI-1 contributes to the disease. In these cases, one must consider recent data, which indicates PAI-1 can directly promote pro-proliferative and anti-apoptotic signaling in a variety of cell types. Given the wide variety of inflammatory, hormonal, and metabolic signals that increase PAI-1 expression, it is important to consider mechanisms by which PAI-1 can directly participate in disease etiology.     

miR-181b过表达对胶质瘤U87细胞中MT1-MMP和TIMP3蛋白表达和细胞侵袭能力的影响

目的:探讨微小RNA-181b(miR-181b)过表达对人胶质瘤细胞中膜型基质金属蛋白酶1(MT1-MMP)和金属蛋白酶组织抑制剂3(TIMP3)表达的调控作用及对细胞侵袭能力的影响。方法:将培养于DMEM培养基的人胶质瘤U87细胞分为阴性对照组(不做任何处理)、空载组(转染Lipofetamine 2000)、乱序组(转染乱序has-miR-181b寡核苷酸)和miR-181b组(转染has-miR-181b寡核苷酸)。qRT-PCR法检测各组细胞中miR-181b基因表达水平,Western blotting法检测各组细胞中MT1-MMP和TIMP3蛋白的相对表达水平,基质胶侵袭试验检测各组细胞的侵袭能力,测定各组细胞的趋化运动抑制率、迁移率和细胞黏附率;生物信息学数据库预测miR-181b的侯选靶基因。结果:miR-181b组U87细胞中miR-181b基因表达水平明显高于其他各组(P<0.01),呈过表达。miR-181b组U87细胞中MT1-MMP蛋白表达水平低于其他各组(P<0.01),miR-181b与MT1-MMP蛋白表达水平呈负相关关系(r=-0.787,P<0.05);miR-181b组U87细胞中TIMP3蛋白表达水平高于其他各组(P<0.01),miR-181b与TIMP3蛋白表达水平呈正相关关系(r=0.801,P<0.05)。基质胶侵袭试验中miR-181b组穿膜细胞数明显低于其他各组(P<0.05)。与其他3组比较,miR-181b组U87细胞的趋化运动抑制率升高、迁移率和细胞黏附率降低(P<0.05)。生物信息学数据库预测,在MT1-MMP的3'非翻译区(3'UTR)有1个与miR-181b的结合位点,在TIMP3的3'UTR有2个与miR-181b的结合位点。结论:miR-181b过表达可下调MT1-MMP和上调TIMP3蛋白的表达,从而抑制胶质瘤细胞的侵袭能力;miR-181b作为关键性调节miR,可能成为胶质瘤治疗的重要靶标。     

Branching out: a molecular fingerprint of endothelial differentiation into tube-like structures generated by Affymetrix oligonucleotide arrays

The process of endothelial differentiation into a network of tube-like structures with patent lumens requires an integrated program of gene expression. To identify genes upregulated in endothelial cells during the process of tube formation, RNA was prepared from several different time points (0, 4, 8, 24, 40, and 48 hours) and from three different experimental models of human endothelial tube formation: in collagen gels and fibrin gels driven by the combination of PMA (80), bFGF (40 ng/ml) and bFGF (40 ng/ml) or in collagen gels driven by the combination of HGF (40 ng/ml) and VEGF (40 ng/ml). Gene expression was evaluated using Affymetrix Gene Chip oligonucleotide arrays. Over 1000 common genes were upregulated greater than twofold over baseline at one or more time points in the three different models. In the present study, we discuss the identified genes that could be assigned to major functional classes: apoptosis, cytoskeleton, proteases, matrix, and matrix turnover, pumps and transporters, membrane lipid turnover, and junctional molecules or adhesion proteins.     

Evaluation of a chromogenic commercial assay using VWF-73 peptide for ADAMTS13 activity measurement

Introduction

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy (TMA), related to a severe functional deficiency of ADAMTS13 activity (< 10% of normal). ADAMTS13 activity is thus crucial to confirm the clinical suspicion of TTP, to distinguish it from other TMAs, and to perform the follow-up of TTP patients.

Material and methods

We compared the performance of the commercial chromogenic assay Technozym® ADAMTS13 Activity ELISA (chromogenic VWF73 substrate, Chr-VWF73, Technoclone, Vienna, Austria), to that of our in-house FRETS-VWF73 used as reference method. A large group of 247 subjects (30 healthy volunteers and 217 patients with miscellaneaous TMAs) was studied.

Results

The lower limit of detection of the Chr-VWF73 was 3%, which is well adapted to the clinically relevant threshold for TTP diagnosis (10%). Our results showed a reasonable agreement between FRETS-VWF73 and Chr-VWF73 assays to distinguish samples with an ADAMTS13 activity < 10% from those with an ADAMTS13 activity > 10%. However, Chr-VWF73 assay provided false negative results in ~ 12% of acute TTP patients. Inversely, the Chr-VWF73 assay globally underestimated ADAMTS13 activity in detectable values ranging from 11 to 100% (with a great variability compared to FRETS-VWF73), which may be a concern for the follow-up of TTP patients in remission.

Conclusion

In-house assays developed and performed by expert laboratories remain the reference methods that should be used without limitation to control values provided by commercial assays when needed. Also, the development of an international reference preparation will be crucial to improve standardization.