Cleavage of fibrinogen by human platelet calcium-activated protease

In lysates of washed human platelets produced by sonication or by addition of nonionic detergent, fibrinogen (Mr 340,000) was rapidly degraded, under conditions favorable to activation of the endogenous calcium-activated protease (CAP), to a core derivative (Mr 280-290,000) composed of partially degraded A alpha chains (Mr 47,000, 46,000, and 34,000) and B beta chains (Mr 56,000), and apparently intact gamma chains (Mr 53-54,000). Extensive degradation occurred within one minute at 4 degrees C, ambient temperature or at 37 degrees C, and was inhibited by leupeptin, EDTA, EGTA, or N-Ethylmaleimide, but not by soybean trypsin inhibitor, hirudin, aprotonin, benzamidine, phenylmethylsulfonyl fluoride or epsilon-aminocaproic acid. Purified plasma fibrinogen exposed to lysates containing active protease was cleaved in an identical fashion. The cleavage pattern of A alpha chains produced by this platelet protease activity is different from that produced by plasmin in vitro or that found in fibrinogen catabolites in vivo, and is unlike that produced by any cellular fibrinolytic enzyme yet described. In view of this finding, as well as the striking differential inhibitory effect of the agents cited above, we conclude that the degradation of platelet fibrinogen observed in these studies is due to direct proteolysis by platelet CAP.     

The viscosity of fibrinogen subfractions and of EDTA denatured fibrinogen do not differ from that of native fibrinogen

INTRODUCTION: Fibrinogen is a major determinant of plasma viscosity. The increased risk of atherothrombotic disease associated with a high fibrinogen concentration may partly be attributed to its effect on viscosity. Since the ratio between the three main fibrinogen subfractions high molecular weight (HMW)-, low molecular weight (LMW)-, and very low molecular weight (LMW')-fibrinogen is altered during acute phase conditions, and an increased HMW/LMW-fibrinogen ratio is associated with increased thromboembolic risk, we have examined how these subfractions affect viscosity. The viscosity of plasma is usually determined in ethylenediaminetetra-acetic acid (EDTA) plasma at 37 degrees C. Under such conditions the clotting properties of fibrinogen is affected due to denaturation. Denaturation of plasma proteins may affect their viscosity. Therefore, we have also investigated the effects of EDTA on the viscosity of fibrinogen. MATERIALS AND METHODS: Purified fibrinogen was obtained by beta-alanine precipitation of plasma from healthy donors. Separation of the fibrinogen fractions was performed by gradual precipitation of purified fibrinogen by ammonium sulphate. The viscosity was determined using a Haake Microvisco 2 viscometer. RESULTS: There was no statistically significant difference between the viscosity of native fibrinogen and the three fibrinogen subfractions. A substantial prolongation of the thrombin clotting time was observed in the fibrinogen solution containing EDTA at 37 degrees C compared to 20 degrees C. However, the viscosity of EDTA anticoagulated purified fibrinogen and plasma samples did not differ from that of heparin anticoagulated samples. CONCLUSION: The viscosity of the main fibrinogen subfractions HMW-, LMW- and LMW-fibrinogen did not differ from that of native fibrinogen, and the use of EDTA as anticoagulant did not significantly affect the viscosity of fibrinogen at 37 degrees C.     

Proteomic comparison between human young and old brains by two-dimensional gel electrophoresis and identification of proteins

To investigate molecular mechanisms of human brain aging, brain proteins were isolated from postmortem human young and old brains and profiled by two-dimensional gel electrophoresis (2-DE). With the help of special software, five down-regulated protein spots in two-dimensional gel electrophoresis gels of old brains were found compared with young brains, four of which was identified as a protein similar to peroxiredoxin 2 (accession-numbered as gi | 13631440), two of stathmin (phosphoprotein p19) and apolipoprotein A-I precursor (apo-AI) by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Eight common proteins, whose expressions were not altered between young and old brains, were also identified. The possible relevance of changes was analyzed. This study shows that the contribution of proteomics could be valuable in experimental gerontology field.     

Dysfibrinogen Kagoshima with the amino acid substitution gammaThr-314 to Ile: analyses of molecular abnormalities and thrombophilic nature of this abnormal molecule

INTRODUCTION: Emerging lines of evidence have suggested that certain dysfibrinogens present a significant risk of thrombosis. PATIENT/METHODS: The thrombophilic nature of a new-type of dysfibrinogen Kagoshima identified in a 36-year-old female with deep vein thrombosis during the postpartum period was studied. RESULTS/DISCUSSION: Based on the analyses of the patient fibrinogen and the fibrinogen genes, fibrinogen Kagoshima was shown to have the amino acid substitution of gammaThr-314 to Ile that resulted in impaired function and hypofibrinogenemia. Polymerization of fibrin monomers derived from patient fibrinogen was severely impaired with a partial correction in the presence of calcium ions, causing very low clottability and delayed cross-linking of patient fibrin catalyzed by activated factor XIII. Because of the low clottability, a large amount of soluble fibrin was formed upon thrombin treatment, resulting in an increase of thrombin in the soluble fraction. Additionally, tPA-mediated plasmin generation on fibrin was impaired and calcium-ion-dependent integrity of the gamma-chain D domain of Kagoshima fibrinogen was perturbed. The presence of many tapered-fiber ends inside the tangled fibrin networks, observed by scanning electron microscopy, suggested early termination of fibrin polymerization and the structural alteration. CONCLUSION: These data suggest that fibrinogen Kagoshima is dysfunctional, giving rise to formation of fibrinolysis-resistant soluble fibrin polymers and entrance of soluble fibrin associating with thrombin to the circulation, partly accounting for the thrombophilic nature of the affected fibrinogen and fibrin molecules.     

Separation and purification of rat fibrinogen degradation products D1 and E by chromatofocusing

The use of chromatofocusing as a single-step method for separation of fibrinogen degradation products D₁ and E is described. The method provides good resolution and a high yield.     

建立人肾小管上皮细胞蛋白质组双向电泳的分离体系

背景：双向电泳分离技术是蛋白质组学研究的核心技术之一,但蛋白质样品的分离效果受各种实验条件的影响较大。因此,针对不同来源的蛋白样品进行实验条件的优化可获得具有较高分辨率的双向电泳图谱。 目的：拟建立优化的人肾小管上皮细胞株蛋白质组双向电泳分离体系。 方法：常规培养人肾小管上皮细胞株HK-2细胞并裂解提取全蛋白,按标准条件对蛋白质进行双向电泳分离,并对各个关键因素进行优化。等电聚焦采用缓慢升压模式,电泳参数根据Bio-Rad公司的预设方案进行调整。改良硝酸银法进行蛋白质斑点染色。采集电泳图谱并分析双向电泳图谱中蛋白斑点的数量、图像分辨率及背景条纹的变化。 结果与结论：通过对实验条件的筛选和优化,成功建立了具有较高的分辨率和重复性的人肾小管上皮细胞蛋白质组双向电泳分离体系。其中,优化后的裂解液配方成分为1% TBP,4%CHAPS,0.2% Bio-Lyte,40 mmol/L Tris,8 mol/L尿素,2 mol/L硫脲;采用pH 4~7的IPG胶条;上样方式选择被动的水化上样。等电聚焦过程中使用预设的缓慢升压模式,充分聚焦后选用合适的电压模式进行SDS-PAGE电泳,然后采用改良硝酸银法进行染色,最终获得了满意的蛋白质组双向电泳图谱。     

应用差异荧光双向凝胶电泳法进行大鼠局灶性脑缺血早期蛋白质组学研究

目前对缺血性脑血管病发病的危险因素研究较多,但从蛋白质水平对其发病机制进行研究并不多见[1],国内外应用蛋白质组学方法对缺血性脑血管病研究多集中于对血浆[2, 3]、体液[4]的研究,而对于脑组织研究只是刚刚起步[5]。由于局部脑血流被阻断或者减少,而使脑缺血对于基因表达起到强大的刺激作用[6],势必导致蛋白质水平发生相应变化。因此,本研究应用先进的荧光差异双向凝胶电泳(two-dimensional differential in-gel electrophoresis, 2D DIGE)蛋白质组学方法, 对大鼠脑缺血大脑中动脉(MCAO)模型进行研究,揭示脑缺血发病的病理生理机制,寻找缺血性脑血管病早期作为疾病标志物的蛋白质,为发现新型的脑缺血治疗药物靶点提供线索。     

Precipitation of fibrinogen, fibrinogen degradation products and fibrin monomer by histone H3

Incubation of histone H3 with normal citrated plasma resulted in the formation of insoluble aggregates, as determined by turbidity measurements. The precipitate was subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis, confirming that fibrinogen was a major component. Purified fibrinogen precipitated rapidly as determined with turbidity experiments and experiments with radioiodinated protein. The amount of fibrinogen precipitation was strongly dependent on H3 concentration. Variation of ionic strength (0.2-0.84) and pH (5.3-7.4), however, had little or no effect on the reaction. Fibrinogen subjected to gelatin-Sepharose chromatography or dialysis against 3.3M urea reacted equivalently with H3. Precipitation of 125I-fibrinogen by H3 was strongly favored by increasing temperature (4 degrees-45 degrees C). Precipitation of fibrinogen by protamine was maximized by decreasing the temperature. In addition, formation of insoluble fibrinogen-protamine aggregates was highly dependent on ionic strength and pH, suggesting that different types of protein-interaction are involved in the two studied precipitation reactions. Of the fibrinogen degradation products, only fragment X precipitated significantly when incubated with H3. Radioiodinated fibrin monomer also precipitated when incubated with H3 in solutions of sufficient ionic strength to prevent spontaneous polymerization. The extent of precipitation was equivalent for fibrin monomer and fibrinogen. Fragment D inhibited the precipitation of fibrinogen by H3 or protamine. These studies indicate that the proteins termed "paracoagulants" are not all equivalent and that the hydrophobic domain of H3 plays a critical role in fibrinogen precipitation.     

Cytokine-induced cell death in human oligodendroglial cell lines. II: Alterations in gene expression induced by interferon-gamma and tumor necrosis factor-alpha

Cytokines, such as interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha), can initiate dual effects resulting in either cell growth or cell death. In this study, the human oligodendroglial cell lines HOG and MO3.13 were used as a model to study the molecular mechanisms of cytokine-induced cell death in human oligodendrocytes. We have previously shown that TNF-alpha and IFN-gamma induce apoptosis in both oligodendroglial cell lines within 72 hr. In the present study, the cell death pathways operating within these cells were further investigated at the gene expression level. Both cell lines express a broad repertoire of caspases and apoptosis-related genes. Some of these genes are specifically up-regulated by cytokine treatment; e.g., caspase-1 is up-regulated by IFN-gamma. In addition to direct cytotoxic effects, IFN-gamma and TNF-alpha also enhance the expression of Fas, TNFR1, and MHC class I molecules in both cell lines. This suggests that cytokines can make oligodendrocytes more vulnerable to different cell death pathways in an inflammatory environment. cDNA microarray analysis of the HOG cell line revealed that TNF-alpha induces genes that regulate apoptosis, survival, inflammation, cell metabolism, and cell signaling. The data suggest that oligodendroglial cells activate both death and survival pathways upon cytokine challenges. However, the survival pathways seem to be unable to compete with the death signal after more than 24 hr of cytokine treatment. These results may contribute to the development of therapeutic strategies aimed at interfering with cytokine-induced cell death of oligodendrocytes in patients with multiple sclerosis.     

The procoagulant properties of purified fibrinogen concentrate are enhanced by carbon monoxide releasing molecule-2

Introduction

Fibrinogen concentrate has been demonstrated to enhance coagulation in vitro and in several clinical settings of coagulopathy. We have recently demonstrated that carbon monoxide releasing molecule-2 (tricarbonyldichlororuthenium (II) dimer; CORM-2) enhances fibrinogen as a substrate for thrombin via an attached heme. The objective of this study was to determine if CORM-2 modified fibrinogen concentrate would enhance coagulation more effectively than CORM-2 naïve fibrinogen concentrate.

Materials and Methods

In the first series of experiments, fibrinogen concentrate (final concentration 300 mg/dl) was exposed to 0, 50 or 100 μM CORM-2 for 5 min at 37 °C prior to being added to citrated, fibrinogen depleted plasma. In another series of experiments, citrated plasma obtained from 12 normal subjects was 50% diluted with crystalloid to which was added fibrinogen concentrate (final concentration 300 mg/dl) exposed to 0 or 100 μM CORM-2. Coagulation was activated with tissue factor (n = 8 per condition). Thrombus growth was monitored with thrombelastography for 15 min.

Results and Conclusions

CORM-2 modification of fibrinogen concentrate significantly enhanced the velocity of clot formation (30-50%) and strength (15-31%) in fibrinogen deficient plasma. Similarly, while diluted plasma-derived thrombi demonstrated a marked decrease in velocity of formation (54%) and strength (61%), fibrinogen concentrate significantly enhanced velocity (217%) and strength (171%); however, CORM-2 modified fibrinogen concentrate significantly increased velocity (303%) and strength (205%) to a greater extent. Additional in vitro investigation and in vivo preclinical assessments of the hemostatic efficacy of CORM-2 modified fibrinogen concentrate are warranted.     

The release of B beta 1-42 from fibrinogen and fibrin by plasmin

The balance between thrombin and plasmin action has been postulated to be an important determinant of thrombosis. Measurement of plasma concentrations of fibrinopeptide A (FPA), which reflect thrombin action on the NH₂-terminal end of the A chain, and of Bβ 1–42 (thrombin-increasable fibrinopeptide B immunoreactivity - TIFPB) which reflect plasmin action on the NH₂-terminal end of the Bβ chain have shown systematic changes in the relative concentrations of the two peptides in thrombotic states. This paper reports kinetic data for TIFPB release by plasmin using fibrinogen, fibrin I monomer, and fibrin I polymer as substrates. For fibrinogen and fibrin I monomer the data fit the Michaelis-Menten equation. Experiments were performed with human proteins in 0.15M Trisbuffered saline at pH 7.4 and at 37°C. With fibrinogen as substrate the K_m was calculated to be 0.87 μM and the V_max 3.75 × 10⁻⁵ M/min/unit of plasmin. With fibrin I monomer as the substrate the K_m was calculated to be 1.25 μM and the V_max 5.5 × 10⁻⁵ M/min/unit of plasmin. With fibrin I polymer as substrate the data did not fit the Michaelis-Menten equation but there appeared to be no dramatic differences in rates from those obtained with the other two substrates. The influence of factor XIIIa-induced cross-linking of fibrin was not examined. It is concluded from these findings that fibrinogen and non-cross-linked fibrin I are equally good substrates for plasmin cleavage of the NH₂-terminal end of the Bβ chain.     

Food restriction markedly increases dopamine D2 receptor (D2R) in a rat model of obesity as assessed with in-vivo muPET imaging ([11C] raclopride) and in-vitro ([3H] spiperone) autoradiography

Introduction: Dopamine (DA) regulates food intake by modulating food reward and motivation but its involvement in obesity is much less understood. Recent evidence points to the involvement of leptin in the DA‐related modulation of food intake. Here we assess DA D2 receptors (D2R) in a genetic rodent obesity model characterized by leptin‐receptor deficiency and assess the influence of food restriction on these receptors. Methods: We compared D2R levels between Zucker Obese (fa/fa) and Lean (Fa/Fa) rats at 1 and 4 months of age and in two different feeding conditions (restricted and unrestricted food access) using in‐vivo μPET imaging ([¹¹C] raclopride, which is a method sensitive to competition with endogenous DA) and in‐vitro ([³H] spiperone washed to ensure no competition with endogenous DA) autoradiography (ARG). Results: Both ARG and μPET showed that D2R were higher at 1 month than at 4 months of age and that food restricted animals had higher D2R than unrestricted animals. However there were significant differences in the results obtained at 4 months between ARG and μPET. ARG showed that at 1 month and at 4 months unrestricted lean rats (Le U) had significantly higher D2R binding than obese unrestricted rats (Ob U) but showed no differences between restricted obese (Ob R) and restricted lean rats (Le R). It also showed that D2R decline between 1 and 4 months of age was significantly attenuated in food restricted rats [both obese and lean]. In contrast, μPET showed that at 4 months of age, Ob U showed greater D2R availability than Le U rats but like ARG showed no differences between Ob R and Le R rats. Conclusion: The lower D2R binding in Ob U than Le U rats observed with ARG most likely reflects decreases in striatal D2 receptors levels whereas the increased availability observed with μPET is likely to reflect reduced DA release (resulting in decreased competition with endogenous DA). Lack of a significant difference between Ob R and Le R suggests that the differences in dopamine activity and D2R levels between Ob and Le Zucker rats are modulated by access to food. The ARG finding of an attenuation of the age‐related loss of D2R binding corroborates previous studies of the salutary effects of food restriction in the aging process. Because [¹¹C] raclopride is sensitive to competition with endogenous DA, the higher D2R binding in obese rats with raclopride despite the lower D2R levels shown with spiperone could reflect lower extracellular DA in the Ob rats and merits further investigation. Synapse 62:50–61, 2008. Published 2007 Wiley‐Liss, Inc.     

Relationships between fibrinogen, plasminogen activator inhibitor-1, and their gene polymorphisms in current smokers with essential hypertension

Background: To elucidate the role of some haemostatic gene polymorphisms and environmental factors, we studied fibrinogen (Fb), plasminogen activator inhibitor-1 (PAI-1), and tissue plasminogen activator (t-PA) levels with respect to Fb G455A and PAI-1 4G/5G gene polymorphisms in smokers and nonsmokers with essential hypertension. Material and methods: The study was done in 90 patients (including 30 smokers) with essential hypertension (HT) and 40 controls (including 8 smokers). Fb and PAI-1 genotypes were PCR identified. The groups did not differ significantly as to genotype frequencies. Results: When allele A455 carriers were compared, HT patients had significantly higher Fb (p=0.015) and t-PA levels (p=0.013). Comparison of 4G allele carriers (4G/4G homozygotes) revealed significantly higher Fb (p=0.045), PAI-1 (p=0.009), and t-PA levels (p=0.007) in HT patients than controls. Interactions of Fb and PAI-1 gene polymorphisms with smoking were disclosed in HT patients only. Allele A455-carrying HT smokers compared with nonsmokers had significantly higher t-PA (12.1±5.8 vs. 7.4±3.1 ng/ml; p=0.002) and tendency to higher Fb (3.36±0.74 vs. 2.95±0.70 g/l; p=0.075) levels. Higher Fb levels were disclosed in 4G/4G smokers than nonsmokers (3.31±0.81 vs. 2.84±0.85 g/l; p=0.064). Finally, in smokers, significantly higher levels of PAI-1 were found in 4G/4G (42.1±29.4 ng/ml) as compared with 4G/5G (18.6±13.7 ng/ml; p=0.025) and 5G/5G (14.4±10.8 ng/ml; p=0.044) genotypes. Conclusions: Smoking potentiates the prothrombotic effect of allele A455 and PAI-1 4G/4G genotype in untreated essential hypertension, reflected by increased levels of haemostatic risk factors and accelerated progression of cardiovascular diseases.     

Diversity of glycine receptors in the mouse retina: localization of the alpha2 subunit

Gamma-aminobutyric acid (GABA) and glycine are the major inhibitory neurotransmitters in the retina, glycine being produced in approximately half of all amacrine cells. Whereas retinal cell types expressing the glycine receptor (GlyR) alpha1 and alpha3 subunits have been mapped, the role of the alpha2 subunit in retinal circuitry remains unclear. By using immunocytochemistry, we localized the alpha2 subunit in the inner plexiform layer (IPL) in brightly fluorescent puncta, which represent postsynaptically clustered GlyRs. This was shown by doubly labeling sections for GlyR alpha2 and bassoon (a presynaptic marker) or gephyrin (a postsynaptic marker). Synapses containing GlyR alpha2 were rarely found on ganglion cell dendrites but were observed on bipolar cell axon terminals and on amacrine cell processes. Recently, an amacrine cell type has been described that is immunopositive for glycine and for the vesicular glutamate transporter vGluT3. The processes of this cell type were presynaptic to GlyR alpha2 puncta, suggesting that vGluT3 amacrine cells release glycine. Double labeling of sections for GlyR alpha1 and GlyR alpha2 subunits showed that they are clustered at different synapses. In sections doubly labeled for GlyR alpha2 and GlyR alpha3, approximately one-third of the puncta were colocalized. The most abundant GlyR subtype in retina contains alpha3 subunits, followed by those containing GlyR alpha2 and GlyR alpha1 subunits.     

Synthesis and release of neurotoxic kynurenine metabolites by human monocyte-derived macrophages

We studied the regulation of the kynurenine pathway of tryptophan metabolism in human monocyte-derived macrophages (MDM) with the aim of evaluating macrophage involvement in inflammatory neurological disorders.

Cultured MDM metabolized tryptophan and released kynurenine metabolites, including the excitotoxin quinolinic acid (QUIN). Lipopolysaccharides (LPS) or the pro-inflammatory cytokines INFγ and TNF increased, while IL 4 or IL 10 inhibited the rate of tryptophan metabolism and the release of QUIN.

The incubation media of INFγ-exposed MDM caused neuronal death in primary cultures of mixed cortical cells. Glutamate receptor antagonists or poly(ADP-ribose) polymerase inhibitors significantly reduced this death, thus suggesting new possibilities for the treatment of neuronal damage in neuroinflammatory disorders.     

Elevated dopamine D2High receptors in alpha-1b-adrenoceptor knockout supersensitive mice

Although amphetamine induces hyperactivity by releasing dopamine (DA), mice that lack alpha1b-adrenoceptors do not release DA in response to amphetamine and do not, therefore, exhibit locomotor supersensitivity to amphetamine. However, such mice reveal hyperlocomotion to p-chloroamphetamine (PCA). Because these alpha1b-adrenoceptor knockout mice have no alterations in the striatal densities of DA D1 or D2 receptors, the basis for any possible dopaminergic contribution to the PCA-induced hyperlocomotion to PCA is unclear. Therefore, because supersensitive animals are generally known to have a higher proportion of DA D2 receptors in the high-affinity state for DA D2(High), we investigated whether there was any change in the alpha1b-adrenoceptor knockout striata in the proportion of DA D2(High) receptors to determine whether there could be a DA-based contribution to the PCA-induced hyperlocomotion. We found that the proportion of D2(High) in the wild type striata was 23 +/- 3.3%, whereas that in the alpha1b-adrenoceptor knockout striata was 52 +/- 2.9%, an increase of 2.3-fold. This elevation agrees with other types of DA-supersensitive animal striata and could assist in eliciting a supersensitive response in these alpha1b-adrenoceptor knockout mice.