Two fibrin zymography methods for analysis of plasminogen activators on gels

Lung lymphatic endothelial cells undergo inflammatory and prothrombotic changes in a model of chronic obstructive pulmonary disease

The lymphatic vasculature regulates lung homeostasis through drainage of fluid and trafficking of immune cells and plays a key role in the response to lung injury in several disease states. We have previously shown that lymphatic dysfunction occurs early in the pathogenesis of chronic obstructive pulmonary disease (COPD) caused by cigarette smoke (CS) and that this is associated with increased thrombin and fibrin clots in lung lymph. However, the direct effects of CS and thrombin on lymphatic endothelial cells (LECs) in COPD are not entirely clear. Studies of the blood vasculature have shown that COPD is associated with increased thrombin after CS exposure that causes endothelial dysfunction characterized by changes in the expression of coagulation factors and leukocyte adhesion proteins. Here, we determined whether similar changes occur in LECs. We used an in vitro cell culture system and treated human lung microvascular lymphatic endothelial cells with cigarette smoke extract (CSE) and/or thrombin. We found that CSE treatment led to decreased fibrinolytic activity in LECs, which was associated with increased expression of plasminogen activator inhibitor 1 (PAI-1). LECs treated with both CSE and thrombin together had a decreased expression of tissue factor pathway inhibitor (TFPI) and increased expression of adhesion molecules. RNA sequencing of lung LECs isolated from mice exposed to CS also showed upregulation of prothrombotic and inflammatory pathways at both acute and chronic exposure time points. Analysis of publicly available single-cell RNA sequencing of LECs as well as immunohistochemical staining of lung tissue from COPD patients supported these data and showed increased expression of inflammatory markers in LECs from COPD patients compared to those from controls. These studies suggest that in parallel with blood vessels, the lymphatic endothelium undergoes inflammatory changes associated with CS exposure and increased thrombin in COPD. Further research is needed to unravel the mechanisms by which these changes affect lymphatic function and drive tissue injury in COPD.

Silver-Stained Fibrin Zymography: Separation of Proteases and Activity Detection Using a Single Substrate-Containing Gel

Silver-stained fibrin zymography for separation of protease bands and activity detection using a single substrate gel was designed. The method takes advantage of the nano-scale sensitivity of both zymography and silver staining. After sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) in a gel containing fibrin (protease substrate), the gel was incubated in enzyme reaction buffer and the zymogram gel was silver-stained. Bands with protease activity were stained with silver in clear areas where the protein substrate had been degraded. The molecular sizes of proteases were accurately determined.

The tetraspanin CD81 protein increases melanoma cell motility by up-regulating metalloproteinase MT1-MMP expression through the pro-oncogenic Akt-dependent Sp1 activation signaling pathways

Despite the importance of multiple tetraspanin proteins in cancer invasion and metastasis, little is known about the role and significance of tetraspanin CD81 in these processes. In the present study, we examined CD81 effects on melanoma cell invasiveness and metastasis. Transfection of CD81 into melanoma cells lacking endogenous CD81 expression significantly enhanced the migrating, invasive, and metastatic abilities of melanoma cells. Interestingly, membrane type 1 matrix metalloproteinase (MT1-MMP) expression was found in CD81-expressing melanoma cells but not in CD81-deficient cells. siRNA knockdown of CD81 in melanoma cells with endogenous CD81 demonstrated decreased MT1-MMP levels and cell motility. Notably, CD81-induced cell migration was abrogated by antibody blocking and siRNA knockdown of MT1-MMP, indicating that MT1-MMP is responsible for CD81-stimulated melanoma cell migration. Promoter analysis revealed an essential role of the Sp1 transcription factor in CD81-induced MT1-MMP transcription. We also demonstrate that the Sp1-activating Akt pathway is involved in adhesion-dependent CD81 signaling to induce MT1-MMP expression and cell motility. Importantly, human skin cancer tissue specimens displayed a positive correlation of CD81 with MT1-MMP expression levels and a close association of CD81 with malignant melanomas. Taken together, these results strongly suggest that CD81 stimulates melanoma cell motility by inducing MT1-MMP expression through the Akt-dependent Sp1 activation signaling pathway, leading to increased melanoma invasion and metastasis.

A Study of Fibrin Zymography Method for the Assay of Plasminogen Activators

Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) is the most important and widely used technology which is mainly used to analyze the protein molecular weight. Fibrin zymography based on the SDS-PAGE is the best method for qualitative analysis of unknown plasminogen activators (PAs), especially for the analysis of molecular weight. In electrophoresis technique, molecular weight marker is the most important factor. However, it is difficult to detect protein molecular weight markers in fibrin zymography. In this study, some important factors, such as concentrations of fibrinogen and plasminogen, are discussed. Our results provide an efficient and convenient method which can clearly exhibit the dark blue bands of protein molecular weight (MW) markers and the transparent bands of PAs against the light blue background on one gel at the same time, and show high sensitivity.

Purification and characterization of a novel anticoagulant and fibrinolytic enzyme produced by endophytic bacterium Paenibacillus polymyxa EJS-3

INTRODUCTION

Endophytes may become a new source of thrombolytic agents for thrombosis treatment.

MATERIALS AND METHODS

A novel fibrinolytic enzyme from Paenibacillus polymyxa EJS-3 (PPFE-I) was purified with ammonium sulfate precipitation, hydrophobic chromatography, ion exchange and gel filtration chromatography. The characterization of the enzyme was investigated by means of fibrinolysis plate, hydrolysis of fibrinogen and anticoagulant effect in vitro.

RESULTS

The fibrinolytic enzyme is purified to homogeneity with a purification of 14.5 fold and a recovery of 3.3%. The enzyme was shown to have a molecular mass of 63.3kDa by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The optimum temperature and pH value were 37°C and 7.5, respectively. Results from the fibrinolysis pattern showed that the enzyme rapidly hydrolyzed the Aα-chain of fibrinogen, followed by the Bβ-chains. It also hydrolyzed the γ-chains, but more slowly. It was activated by metal ions such as Zn(2+), Mg(2+), and Fe(2+), but inhibited by Ca(2+) and Cu(2+). Furthermore, PPFE-I activity was inhibited strongly by PMSF, and it was found to exhibit a higher specificity for the synthetic substrate N-succinyl-Ala-Ala-Pro-Phe-pNA for chymotrypsin, indicating that the enzyme is a chymotrypsin-like serine protease. Additionly, PPFE-I showed a significant anticoagulant effect in vitro.

CONCLUSION

The fibrinolytic enzyme PPFE-I from endophytic bacterium Paenibacillu polymyxa EJS-3 exhibits a profound fibrinolytic activity.

Inhibition of human breast cancer cell invasion by siRNA against urokinase-type plasminogen activator

Urokinase plasminogen activator (uPA) correlates closely with breast cancer metastasis via triggering the degradation of divergent matrix proteins. Here, uPA was selectively knocked down in breast carcinoma MDA-MB-231 cells by siRNAs. The in vitro migration of MDA-MB-231 cells was effectively suppressed accompanied by a decrease in extracellular MMP-9 activities. The colony formation ability of MDA-MB-231 cells was inhibited following uPA knockdown, while the proliferation was not affected. The uPA knockdown in MDA-MB-231 cells caused significantly suppressed tumor metastasis in nude mice. Thus, siRNAs targeted to uPA have implications in the development of novel approaches to preventing breast cancer metastasis.

Isolation and Identification of an Endophytic Strain EJS-3 Producing Novel Fibrinolytic Enzymes

An endophytic strain EJS-3, which produces a novel fibrinolytic enzyme, was screened from root tissue of Stemona japonica (Blume) Miq, a chinese traditional medicine. This strain was identified as Paenibacillus polymyxa (DQ120522) by morphological, physiological, and biochemical tests and 16S rRNA gene sequence analysis. Two serine-type fibrinolytic enzymes with a relative molecular weight about 118 and 49 kDa, respectively, which are larger than known fibrinolytic enzymes, were found by the SDS-fibrin zymogram or by fibrin-inhibitor zymography gels. No work on P. polymyxa-producing fibrinolytic enzymes has been reported.

A novel 3-dimensional culture system as an in vitro model for studying oral cancer cell invasion

Tissue microenvironment plays a critical role in tumour growth and invasion. This study established a novel 3-dimensional (3-D) cell invasion model for direct microscopic observation of oral cancer cell invasion into the underlying basement membrane and connective tissue stroma. A multilayer cell construct was developed using the OptiCell chamber, consisting of a lower layer of oral mucosa fibroblasts embedded in collagen gel and an overlaying upper layer of oral cancer cells. The two layers are separated by a basement membrane composed of reconstituted extracellular matrix. To verify the applicability of the cell invasion model, multilayer cell constructs of oral squamous cell carcinoma and oral mucosal fibroblasts were exposed to extrinsic urokinase-type plasminogen activator (uPA) or plasminogen activator inhibitor (PAI-1), which are known effectors of cell migration. In addition, the constructs were exposed to both normoxic and hypoxic culture conditions. Microscopic study showed that the presence of uPA enhanced cell invasion, while PAI-1 inhibited cell migration. Western blot and zymographic analysis demonstrated that hypoxia up-regulated uPA and matrix metalloproteinases (MMPs) expression and activity; conversely, PAI-1 level was down-regulated in response to hypoxic challenge as compared to normoxic condition. Our results indicated that the novel 3-D invasion model could serve as an excellent in vitro model to study cancer cell invasion and to test conditions or mediators of cellular migration.

Double-layer fluorescent zymography for processing protease detection

We have developed a novel double-layer zymographic method for the detection of specific processing proteases of a target proprotease using a specific fluorescent substrate. The target processing proteases were separated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the gel was subsequently incubated with the target proenzyme used as the substrate. A cellulose acetate membrane was immersed in 10% glycerol and then soaked in the fluorescent substrate solution. The slab gel of the processing protease was covered with the fluorescent substrate membrane, making a double layer. The double layer was incubated at 37 degrees C, and the released fluorescent band, in which the processing protease was located, was detected using UV light. The advantages of the double-layer fluorescent zymographic method are as follows: (i) the specific detection of target proprotease using a specific substrate, (ii) a relatively rapid and sensitive method, (iii) effective detection using small amounts of crude material, and (iv) wide applications that include the detection of processing proteases and activators for target proteases. Typical examples used for the detection of the processing proteases, such as plasminogen activator, chymotrypsinogen activator, procaspase-3 processing protease and caspase-3 activators, using this new method are described in this article.

A Method for Direct Application of Human Plasmin on a Dithiothreitol-containing Agarose Stacking Gel System

A new simplified procedure for identifying human plasmin was developed using a DTT copolymerized agarose stacking gel (ASG) system. Agarose (1 %) was used for the stacking gel because DTT inhibits the polymerization of acrylamide. Human plasmin showed the lowest activity at pH 9.0. There was a similar catalytically active pattern observed under acidic conditions (pH 3.0) to that observed under alkaline conditions (pH 10.0 or 11.0). Using the ASG system, the primary structure of the heavy chain could be established at pH 3.0. This protein was found to consist of three fragments, 45 kDa, 23 kDa, and 13 kDa. These results showed that the heavy chain has a similar structure to the autolysed plasmin (Wu et al., 1987b) but there is a different start amino acid sequence of the N-termini.

Confirmation of Vpr as a fibrinolytic enzyme present in extracellular proteins of Bacillus subtilis

We have previously reported a proteomic approach to detect fibrinolytic enzymes from the secreted proteins of Bacillus subtilis 168 and identified two extracellular fibrinolytic enzymes of Bacillus, namely, Vpr and WprA. In this study, to confirm the fibrinolytic activity of Vpr, we cloned the vpr gene and expressed it in Escherichia coli, where it is predominantly localized to inclusion bodies. After affinity purification and desalting steps, the expressed Vpr is auto-processed to an active form. Interestingly, after the desalting step, several additional bands with fibrinolytic activity were detected in zymography gel along with a mature form (68 kDa) of Vpr. MALDI-TOF analyses of these bands revealed that Vpr could exist in multiple forms.

Comparative Study of Enzyme Activity and Stability of Bovine and Human Plasmins in Electrophoretic Reagents, β-mercaptoethanol, DTT, SDS, Triton X-100, and Urea

Effects of common electrophoretic reagents, reducing agents (beta-mercaptoethanol [BME] and DTT), denaturants (SDS and urea), and non-ionic detergent (Triton X-100), on the activity and stability of bovine plasmin (b-pln) and human plasmin (h-pln) were compared. In the presence of 0.1% SDS (w/v), all reagents completely inhibited two plns, whereas SDS (1%) and urea (1 M) denatured plns recovered their activities after removal of SDS by treatment of 2.5% Triton X-100 (v/v). However, reducing agents (0.1 M of BME and DTT) treated plns did not restore their activities. Based on a fibrin zymogram gel, five (from b-pln) and four (from h-pln) active fragments were resolved. Two plns exhibited unusual stability in concentrated SDS and Triton X-100 (final 10%) and urea (final 6 M) solutions. Two bands, heavy chain-2 (HC-2) and cleaved heavy chain-2 (CHC-2), of b-pln were completely inhibited in 0.5% SDS or 3 M urea, whereas no significant difference was found in h-pln. Interestingly, 50 kDa (cleaved heavy chain-1, CHC-1) of b-pln and two fragments, 26 kDa (light chain, LC) and 29 kDa (microplasmin, MP), of h-pln were increased by SDS in a concentration dependent manner. We also found that the inhibition of SDS against both plns was reversible.

Nano-scale Proteomics Approach Using Two-dimensional Fibrin Zymography Combined with Fluorescent SYPRO Ruby Dye

In general, a SYPRO Ruby dye is well known as a sensitive fluorescence-based method for detecting proteins by one-or two-dimensional SDS-PAGE (1-DE or 2-DE). Based on the SYPRO Ruby dye system, the combined two-dimensional fibrin zymography (2-D FZ) with SYPRO Ruby staining was newly developed to identify the Bacillus sp. proteases. Namely, complex protein mixtures from Bacillus sp. DJ-4, which were screened from Doen-Jang (Korean traditional fermented food), showed activity on the zymogram gel. The gel spots on the SYPRO Ruby gel, which corresponded to the active spots showing on the 2-D FZ gel, were analyzed by a matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometric analysis. Five intracellular fibrinolytic enzymes of Bacillus sp. DJ-4 were detected through 2-D FZ. The gel spots on the SYPRO Ruby dye stained 2-D gel corresponding to 2-D FZ were then analyzed by MALID-TOF MS. Three of the five gel spots proved to be quite similar to the ATP-dependent protease, extracellular neutral metalloprotease, and protease of Bacillus subtilis. Also, the extracellular proteases of Bacillus sp. DJ-4 employing this combined system were identified on three gels (e.g., casein, fibrin, and gelatin) and the proteolytic maps were established. This combined system of 2-D zymography and SYPRO Ruby dye should be useful for searching the specific protease from complex protein mixtures of many other sources (e.g., yeast and cancer cell lines).

Dynamic compression of chondrocyte-seeded fibrin gels: effects on matrix accumulation and mechanical stiffness

OBJECTIVE

Various strategies have been tested to direct and control matrix synthesis in tissue engineered cartilage, including mechanical stimulation of the construct both before and after implantation. This study examined the effects of oscillatory compression on chondrocytes in a fibrin-based tissue engineered cartilage.

DESIGN

Chondrocyte-seeded fibrin gels were cultured under unconfined mechanical compression for 10 or 20 days (free-swelling, 10% static, or 10+/-4% at 0.1 or 1Hz). During the culture period, accumulation of nitrite, sGAG, and proteolytic enzymes in the culture media were monitored. Following culture, the mechanical stiffness and biochemical content of the gels (DNA, sGAG, and hydroxyproline content and GAG Delta-disaccharide composition) were assessed.

RESULTS

Compared to free-swelling conditions, static compression had little effect on the mechanical stiffness or biochemical content of the gels. Compared to static compression, oscillatory compression produced softer gels, inhibited sGAG and hydroxyproline accumulation in the gels, and stimulated accumulation of nitrite and sGAG in the culture media. Minimal differences were observed in DNA content and Delta-disaccharide composition across treatment conditions.

CONCLUSIONS

In this study, oscillatory compression inhibited formation of cartilage-like tissues by chondrocytes in fibrin gels. These results suggest that the effects of mechanical stimuli on tissue engineered cartilage may vary substantially between different scaffold systems.

Skeletal muscle dictates the fibrinolytic state after exercise training in overweight men with characteristics of metabolic syndrome

While there is indisputable evidence supporting the beneficial role of aerobic exercise in reducing cardiovascular risk factors, there are few dose-response studies of this relationship. Increasingly, it is thought that the cardiovascular benefits of exercise are significantly influenced by adaptations within skeletal muscle and its vasculature. However, little is known about the molecular mechanisms underlying these adaptations. To address this need, we initiated a study utilizing longitudinal, microarray-based gene expression profiling of serial skeletal muscle biopsies obtained from the study of targeted risk reduction intervention through defined exercise (STRRIDE). STRRIDE participants were overweight and exhibited symptoms characteristic of the metabolic syndrome that typically precedes type II diabetes such as insulin resistance, abnormal lipids and glucose intolerance. Expression data were statistically filtered and sorted into exercise training-responsive clusters based on gene product knowledge. One such cluster included genes that promote the degradation of fibrin clots such as tissue plasminogen activator (t-PA), connective tissue activation peptide III (CTAP III) and tetranectin. The fibrinolytic activity and protein levels of tetranectin, and t-PA and its endogenous inhibitor PAI-1, were subsequently shown to change significantly in both skeletal muscle and serum in response to exercise training. Our data show that the rigors of exercise directly induce fibrinolytic genes and protein cascades, both within muscle, and in the systemic circulation. This finding is particularly significant given that the metabolic syndrome is an independent risk factor for peripheral vascular disease and thrombotic events within the heart and brain. We conclude that aerobic exercise training induces both local and systemic changes in fibrinolysis and vascular homeostasis that are probably protective against cardiovascular disease.

Activation of human meprin-alpha in a cell culture model of colorectal cancer is triggered by the plasminogen-activating system

The activation of latent proenzymes is an important mechanism for the regulation of localized proteolytic activity. Human meprin-alpha, an astacin-like zinc metalloprotease expressed in normal colon epithelial cells, is secreted as a zymogen into the intestinal lumen. Here, meprin is activated after propeptide cleavage by trypsin. In contrast, colorectal cancer cells secrete meprin-alpha in a non-polarized way, leading to accumulation and increased activity of meprin-alpha in the tumor stroma. We have analyzed the activation mechanism of promeprin-alpha in colorectal cancer using a co-culture model of the intestinal mucosa composed of colorectal adenocarcinoma cells (Caco-2) cultivated on filter supports and intestinal fibroblasts grown in the companion dish. We provide evidence that meprin-alpha is activated by plasmin and show that the presence of plasminogen in the basolateral compartment of the co-cultures is sufficient for promeprin-alpha activation. Analysis of the plasminogen-activating system in the co-cultures revealed that plasminogen activators produced and secreted by fibroblasts converted plasminogen to active plasmin, which in turn generated active meprin-alpha. This activation mechanism offers an explanation for the observed meprin-alpha activity in the tumor stroma, a prerequisite for a potential role of this protease in colorectal cancer.

A functional proteomic analysis of secreted fibrinolytic enzymes from Bacillus subtilis 168 using a combined method of two-dimensional gel electrophoresis and zymography

Here we describe a proteomic approach to detect fibrinolytic enzymes from the culture supernatant of Bacillus subtilis 168. Following isoelectric focusing without dithiothreitol, two gels, one for sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and the other for zymography, were run in parallel. After silver staining of SDS-PAGE and activity staining of zymography gel, the two gels were superimposed to detect protein spots that coincided with clear zones on the zymography gel. We identified four protein spots and characterized them with matrix-assisted laser desorption/ionization mass spectrometry. Database search revealed that four spots contained at least one of the extracellular serine proteases such as WprA and Vpr. This combined method of two-dimensional gel and zymography can be used as a powerful tool to detect proteases from various organisms.