Blood vessel occlusion with erythrocyte aggregates causes burn injury progression-microvasculature dilation as a possible therapy.

Burns are dynamic injuries characterized by progressive tissue death and continuous severe pain over the course of several days. The extent of burn injury progression determines the ultimate patient outcome. Initial burns result in a central zone of necrosis surrounded by a potentially viable zone of ischemia. Several mechanisms have been proposed to explain injury progression, including oxidant and cytokine stress resulting from either ischemia/reperfusion and/or inflammation, but no proven therapy has emerged. To address the unmet need to limit burn injury progression, the root cause of this process must be delineated. For this reason, we have recently focused on post-burn blood vessel occlusion, currently ascribed to microthrombi. We have found that blood vessel occlusion is initially, mainly and persistently caused by erythrocyte aggregation. Although thermal-induced cell necrosis is the immediate cause of cell death, apoptotic cells from persistent ischemia/anoxia, admixed with inflammatory cells, form a band between viable and nonviable tissue 24 hours later. The delayed cell death by apoptosis appears to be the main attractant for inflammatory cells. Finally, we posit that fibrinogen elevation arising from inflammation provides stimulus for additional erythrocyte aggregation, further extending blood vessel occlusion. In our view this persistent occlusion with resultant prolonged tissue ischemia/anoxia, not ischemia/reperfusion, is the root cause of burn injury progression concomitant with associated severe and persistent pain. Epiviosamines, a new class of peptides, appear to selectively dilate microvasculature, and may provide therapy for burn injury progression.

The antileukemic activity of modified fibrinogen-methotrexate conjugate.

BACKGROUND: The search for new, innovative methods to treat all types of diseases, especially cancer-related ones, is a challenge taken by pharmaceutical companies and academic institutions. The use of conjugates containing widely-known and widely-used bioactive substances is one of the ways to solve this problem. Research into drug binding with macromolecular carrier systems has joined the search for new therapeutic strategies. METHODS: The main goal of this paper is the potential offered by the use of fibrinogen derivatives as an antileukemic drug carrier. Physicochemical properties of the obtained conjugate were analyzed, characterizing alterations in relation to the starting carrier and analyzing biological implications. The intraperitoneally (i.p.) inoculated P388 mouse leukemia model for in vivo studies was used. RESULTS AND CONCLUSIONS: Conjugates consisting of a fibrinogen derivative with a covalently bound anticancer drug were developed. Carrier preparation and a conjugate synthesis in aqueous solution were formulated, as well as purification of the conjugate was performed. The study showed that the survival of leukemia mice treated with FH-MTX conjugate was indeed significantly longer than survival in both untreated animals (control) and mice treated with unbound MTX. A significant increase in the antileukemic activity of MTX conjugated with hydrolysed fibrinogen was observed as compared with the unconjugated drug. Reported data suggest that hydrolysed fibrinogen can serve as a carrier molecule for the MTX drug with the aim of enhancing its antileukemic activity. GENERAL SIGNIFICANCE: Conjugates consisting of a fibrinogen derivative with a covalently bound anticancer drug seem to be a promising anticancer drug.

Characterization of fibrinogen glycosylation and its importance for serum/plasma N-glycome analysis.

The majority of proteins present in human serum/plasma are glycoproteins, validating this fluid as an ideal starting material for N-glycan analysis and discovery of potential biomarkers. The glycoprotein content for both serum and plasma is very similar, except for proteins removed in the coagulation process, including fibrinogen. Our aim was to characterize fibrinogen glycosylation in order to determine its contribution to differences between serum and plasma N-glycomes. N-Glycans from human fibrinogen were released, labeled, and analyzed by HILIC-HPLC and MS. Structural characterization of fibrinogen subunits revealed that the α chain was not N-glycosylated, whereas ß and γ contained identical oligosaccharide structures, mainly biantennary digalactosylated monosialylated structures (A2G2S1) and biantennary digalactosylated disialylated structures (A2G2S2). Blood was collected from five healthy volunteers into four testing tubes: silicone-coated glass for serum and EDTA, Na-heparin, and Li-heparin glass tubes for plasma. N-Glycans were analyzed using the high-throughput HILIC-HPLC method. N-Glycan profiles from serum and plasma samples differed largely in glycans identified in fibrinogen, suggesting that this glycoprotein represents a major factor distinguishing these body fluids. This result emphasizes the important of consistent body fluid collection practices in biomarker discovery studies.

From artificial red blood cells, oxygen carriers, and oxygen therapeutics to artificial cells, nanomedicine, and beyond.

The first experimental artificial red blood cells have all three major functions of red blood cells (rbc). However, the first practical one is a simple polyhemoglobin (PolyHb) that only has an oxygen-carrying function. This is now in routine clinical use in South Africa and Russia. An oxygen carrier with antioxidant functions, PolyHb-catalase-superoxide dismutase, can fulfill two of the three functions of rbc. Even more complete is one with all three functions of rbc in the form of PolyHb-catalase-superoxide dismutase-carbonic anhydrase. The most advanced ones are nanodimension artificial rbc with either PEG-lipid membrane or PEG-PLA polymer membrane. Extensions into oxygen therapeutics include a PolyHb-tyrosinase that suppresses the growth of melanoma in a mice model. Another is a PolyHb-fibrinogen that is an oxygen carrier with platelet-like function. Research has now extended well beyond the original research on artificial rbc into many areas of artificial cells. These include nanoparticles, nanotubules, lipid vesicles, liposomes, polymer-tethered lipid vesicles, polymersomes, microcapsules, bioencapsulation, nanocapules, macroencapsulation, synthetic cells, and others. These are being used in nanotechnology, nanomedicine, regenerative medicine, enzyme/gene therapy, cell/stem cell therapy, biotechnology, drug delivery, hemoperfusion, nanosensers, and even by some groups in agriculture, industry, aquatic culture, nanocomputers, and nanorobotics.

The effect of glycaemic control on fibrin network structure of type 2 diabetic subjects.

Diabetic subjects have been shown to have altered fibrin network structures. One possible cause may be fibrinogen glycation resulting in altered structure/function properties. We investigated the effect of glucose control on fibrinogen glycation and fibrin network structure in type 2 diabetes. Blood samples were taken from twenty uncontrolled diabetic subjects at baseline to determine the levels of fibrinogen glycation and fibrin network structures. The subjects were then treated with insulin until blood glucose control was achieved before end blood samples were taken. Twenty age- and BMI-matched non-diabetic subjects were included as a reference group. The diabetic subjects had significantly higher mean fibrinogen glycation at baseline than the non-diabetic subjects (7.84 vs. 3.89 mol glucose / mol fibrinogen; p < 0.001). This was significantly reduced during the intervention (7.84 to 5.24 mol glucose / mol fibrinogen; p < 0.0002) in the diabetic group. Both groups had high mean fibrinogen concentrations (4.25 and 4.02 g/l, diabetic and non-diabetic subjects respectively). There was no difference in fibrinogen concentration, porosity, compaction and kinetics of clot formation between the diabetic subjects and non-diabetic subjects at baseline, nor were there any changes during the intervention despite the reduced fibrinogen glycation. Fibrin network characteristics correlated well with fibrinogen but not with any markers of glycaemic control. Improved glycaemic control resulted in decreased fibrinogen glycation but not fibrinogen concentration. It seems as though porosity, compaction and kinetics of clot formation are more related to fibrinogen concentration than fibrinogen glycation in this model.

Purification of desmoglein II: a method for the preparation and fractionation of desmosomal components.

We have developed rapid and efficient methods for the isolation of desmosomes and the fractionation of their components. These methods involve the use of 6 M guanidine HCl to isolate the desmosomes from bovine epidermis, followed by hydroxyapatite column chromatography in the presence of SDS to fractionate the desmosomal components. All of the desmoplakins and desmogleins were purified at least partially by these procedures, and desmoglein II was purified to apparent homogeneity. We expect these procedures to facilitate a detailed biochemical analysis of the molecular components of desmosomes. In addition, these methods may be applicable to the purification of other plasma membrane domains involved in cell adhesion.

In vivo magnetic resonance imaging of coronary thrombosis using a fibrin-binding molecular magnetic resonance contrast agent.

BACKGROUND: The advent of fibrin-binding molecular magnetic resonance (MR) contrast agents and advances in coronary MRI techniques offers the potential for direct imaging of coronary thrombosis. We tested the feasibility of this approach using a gadolinium (Gd)-based fibrin-binding contrast agent, EP-2104R (EPIX Medical Inc), in a swine model of coronary thrombus and in-stent thrombosis. METHODS AND RESULTS: Ex vivo and in vivo sensitivity of coronary MR thrombus imaging was tested by use of intracoronarily delivered Gd-DTPA-labeled fibrinogen thrombi (n=6). After successful demonstration, in-stent coronary thrombosis was induced by x-ray-guided placement of thrombogenic-coated, MR-lucent stents (n=5). After stent placement, 60 micromol of EP-2104R was injected via the left main coronary artery. Free-breathing, navigator-gated 3D coronary MR angiography and thrombus imaging were performed (1) before and after stent placement and (2) before and after EP-2104R. Thrombi were confirmed by x-ray angiography and autopsy. Fibrinogen thrombi: 5 of 6 intracoronarily delivered Gd-labeled fibrinogen clots (approximately 250 micromol/L Gd) were visible on MRI and subsequently confirmed by x-ray angiography. In-stent thrombi: in-stent thrombosis was observed in all stents after EP-2104R. Four of 5 thrombi were confirmed by x-ray angiography. Chemical analysis of 2 thrombi demonstrated 99 to 147 micromol/L Gd. CONCLUSIONS: We demonstrate the feasibility of MRI of coronary thrombus and in-stent thrombosis using a novel fibrin-binding molecular MR contrast agent. Potential applications include detection of coronary in-stent thrombosis or thrombus burden in patients with acute coronary syndromes.

Molecular cloning and comparative analysis of fibrinogen-related proteins from the soft tick Ornithodoros moubata and the hard tick Ixodes ricinus.

Among disease-vectors, the evolution of the tick innate immune system is still lagging when compared to insects. Such an investigation, which was initiated, by first cloning and sequencing lectins associated in the innate immunity of invertebrates and having fibrinogen related domains, helped in the sequencing of cDNA encoding for OMFREP from the soft tick, Ornithodoros moubata. Also obtained were Ixoderin A and Ixoderin B cDNA sequences from the hard tick Ixodes ricinus. Tissue-specific expression of OMFREP showed that it was present primarily in the hemocytes and salivary glands. Ixoderin A besides sharing a similar expression profile was also expressed in the midgut. Both showed significantly high homology to the lectin Dorin M, from O. moubata. Further, phylogenetic comparisons between these molecules of the soft and hard ticks showed their relatedness to Tachylectins 5A and 5B, involved in the innate immunity of Tachypleus tridentatus and ficolins from both vertebrates and invertebrates. Ixoderin B showing tissue-specific expression only in the salivary glands and the sequence displaying certain motif differences in homology point towards a possible function different from the other two molecules. This is the first report of lectin-like sequences, with a fibrinogen-domain, from the hard tick I. ricinus and a preliminary phylogenetic study of these tick sequences with related fibrinogen-domain containing sequences highlights a possible role for them in the innate immunity of the ticks.

Antileukemic activity of glycated fibrinogen-methotrexate conjugates.

BACKGROUND: The aim of the study was to compare the antileukemic activity of methotrexate (MTX) conjugates with native and glycated fibrinogen. We expected that conjugates based on glycated fibrinogen would reveal higher antileukemic activity because of decreased plasmin digestibility and a higher retention rate of glycated fibrinogen in the body. MATERIALS AND METHODS: Fibrinogen was glycated using a high-temperature procedure at 65-85 degrees C. Glycated fibrinogens were examined with respect to their ability to clot and susceptibility to plasmin digestion. Native fibrinogen (F) and fibrinogens glycated at 65 and 73 degrees C (F65 and F73) were conjugated with MTX and tested in mice bearing P388 leukemia, at a dose of 40 mg of MTX per kg of body weight. RESULTS: Glycated fibrinogens retained their ability to clot. Compared to native fibrinogen, they were more resistant to digestion by plasmin. All tested conjugates revealed higher antitumor activity than the free drug. Increases in average lifespan over the control group were 34% for free MTX, 137% for F-MTX, 151% for F65-MTX and 91% for F73-MTX. The differences between the antitumor activities of all conjugates were not statistically significant. CONCLUSION: It seems necessary to compare the antitumor activities of MTX conjugates based on native and glycated fibrinogen in different tumor models, to demonstrate the expected differences.

The intravascular generation of fibrinogen derivatives and the blood vessel wall in venous thrombosis and disseminated intravascular coagulation.

Both deep venous thrombosis and DIC are intermediate mechanisms of disease--both are a consequence of the deposition of fibrin-rich material in blood vessels some distance from the primary site of tissue destruction. The great difference in the sites of fibrin deposition may depend on the extent and site of activation of the clotting mechanism. DIC likely occurs in the fluid phase of the blood as a consequence of massive fibrin formation while thrombosis results from limited fibrin formation at the interface between blood and vessel wall. Leukocytes may be essential for attaching thrombi to the vessel wall in many places.

Cytotoxic and antitumor effect of fibrinogen-methotrexate conjugate.

In this paper we describe the chemical procedure of fibrinogen-methotrexate (F-MTX) conjugate preparation and its in vitro and in vivo antitumor activity. F-MTX conjugates were synthesized in reaction of fibrinogen with MTX N-hydroxysuccynimide ester. The conjugates were not cross-linked and were soluble in water. The results of the in vitro and in vivo studies have shown: (1) a lower in vitro cytotoxicity of the F-MTX conjugate as compared with MTX alone; (2) a significantly higher in vivo antitumor activity of the F-MTX conjugate in mice with P388 leukemia as compared with MTX alone; (3) a significantly increased in vivo lethal toxicity of F-MTX as compared with MTX. The results suggest the therapeutic utility of the fibrinogen-methotrexate conjugate and the usefulness of fibrinogen as a chemotherapeutic drug carrier. However, a new effort in the preparation of F-MTX conjugate should be made to decrease its in vivo toxicity.

The polymerization of fibrinogen under the influence of diazomethane modification.

To study the effect of the acidic amino acid residues on the physiological polymerization and clot formation of fibrinogen, the fibrinogen system was polymerized by interaction with diazomethane, a specific group reagent which modifies the carboxylic acid residues via the process of methylation. The extent of methylation of fibrinogen by diazomethane was estimated by methoxyl determination on the modified fibrinogen. Under the present experimental conditions, no significant amounts of ammonia were detected as a result of amide hydrolysis concomitant with esterification of the fibrinogen. Chemical methylation of approximately 214 residues resulted in polymerization of the fibrinogen molecule to a product which resembled the physiological clot formation. The application of paper chromatographic techniques identified the modification of other amino acid residues in addition to the methylation of the carboxylic acid groups of glutamic and aspartic acids. These results are interpreted in terms of methylation of carboxylic acid groups in fibrinogen by diazomethane providing a reduction of both negative charge and intermolecular repulsion, thereby enabling the modified fibrinogen molecules to polymerize.

Chromatographic isolation and identification of methylated derivatives obtained from modified fibrinogen.

Polymerization was accomplished in the fibrinogen system by methylation with diazomethane, thionyl chloride and dimethyl sulphate. The duration and extent of polymerization were dependent on the modifying agent which was applied to the fibrinogen system. When fibrinogen was methylated with a very narrow range group-specific methylating agent, like dimethyl sulphate, the polymerization process was accelerated and proceeded with a reduction in the extent of modification of that obtained with the other methylating reagents utilized in these experiments. Chromatographic analysis revealed that diazomethane and thionyl chloride induced both O-methylation and N-methylation, as well as esterification of the carboxylate groups of aspartic and glutamic acid in fibrinogen. However, dimethyl sulphate resulted primarily in esterification accompanied by a small amount of histidine methylation. The proposed mechanism for the polymerization is through the esterification of the aspartic and glutamic acid residues which produces an increased protein-protein interaction resulting in polymer formation.

New strategy of thrombolysis. Conjunctive effect of plasminogen activators with different pharmacokinetic profile.

Combined actions of native and prolonged thrombolytics allow the use of lower doses and simplified schemes of administration, thus yielding significant results in experimental therapy regarding the efficacy and safety of thrombolysis. Development of prolonged forms of plasminogen activators and testing their effect in combination with the thrombolysis trigger are well founded and of current interest. Thrombolytic compositions on the basis of short- and long-term-acting plasminogen activators appear to be promising and potentially eligible for bolus administration.

Liposome transduction into cells enhanced by haptotactic peptides (Haptides) homologous to fibrinogen C-termini.

Haptides are 19-21mer cell-binding peptides equivalent to sequences on the C-termini of fibrinogen beta chain (Cbeta), gamma chain (preCgamma) and the extended alphaE chain of fibrinogen (CalphaE). In solution, Haptides accumulated in cells by non-saturable kinetics [Exp. Cell Res. 287 (2003) 116]. This study describes Haptide interactions with liposomes and Haptide-mediated liposome uptake by cells. Haptides became incorporated into negatively charged liposomes, changing their zeta potential. Atomic force microscopy and particle sizing by light scattering showed that the liposomes dissolved Haptide nanoparticles and absorbed them from solution. Pre-mixing fluorescent rhodamine-containing liposomes or "stealth" doxorubicin (DOX)-containing liposomes (Doxil) with Cbeta, preCgamma or to a lesser degree CalphaE, significantly enhanced their uptake by fibroblasts and endothelial cells. Confocal microscopy showed Haptide-induced liposome uptake saturated above approximately 40 microM Haptide. Cytotoxicity tests with lower concentrations of Doxil liposomes indicated that premixing with approximately 40 microM Cbeta or preCgamma increased their toxicity by one order of magnitude. It was evident that the liposomes complexed with an amphiphilic Haptide are transduced through cell membranes, probably by a non-receptor-mediated process. These results suggest that Cbeta or pre-Cgamma could be employed to augment the cellular uptake of drugs in liposomal formulations.

Peptides and monoclonal antibodies which bind to platelet glycoproteins IIb and/or IIIa inhibit clot retraction.

The rate of clot retraction in platelet-rich plasma was decreased by synthetic peptide analogues of fibrinogen and monoclonal antibodies each of which bind to the platelet plasma membrane glycoproteins IIb and/or IIIa. These and related data demonstrate that intact complexes of the glycoproteins IIb and IIIa are required for platelet-mediated clot retraction.

The effect of fucoidan, heparin and cyanogen bromide-fibrinogen on the activation of human glutamic-plasminogen by tissue plasminogen activator.

Earlier studies on the stimulatory effect of fucoidan, heparin, and cyanogen bromide (CNBr)-fibrinogen digest on the in-vitro activation of glutamic type plasminogen by tissue plasminogen activator, which were performed using subphysiologic ionic strengths of buffers, gave inconsistent results because of the variation in the ionic strengths of the buffers used. Studies were therefore conducted on the effect of these cofactors using 0.05 mol/l Tris buffer containing a physiologic concentration of sodium chloride. The double reciprocal plots of the activation of glutamic type plasminogen by tissue plasminogen activator in the presence of fucoidan and 6-aminohexanoic acid (6-AH) or heparin and 6-AH showed a four- to six-fold increase in K(cat), while the K(m) remained unchanged. On the other hand, there was greater than six-fold lowering of K(m) from 0.213 to 0.035 micromol/l in the presence of CNBr-fibrinogen, while K(cat) was only slightly increased. The ratios of the initial rate of plasmin generation in the presence or absence of the cofactors were plotted against the inverse of the volume fraction of glutamic type plasminogen or of tissue plasminogen activator after serial dilution. The results suggested that the enhancements by fucoidan and 6-AH or CNBr-fibrinogen were due to their interactions directed towards glutamic type plasminogen, while for heparin and 6-AH, the interaction was directed towards tissue plasminogen activator. Circular dichroism studies in the near ultraviolet range (250-308 nm) showed that 6-AH enhanced the circular dichroism spectra of glutamic type plasminogen around certain chromophores, while fucoidan and heparin had no effect, suggesting that the enhancement by the cofactors may be related to the favorable conformational changes of glutamic type plasminogen by 6-AH.

The effect of fibrinogen-methotrexate derivatives on HeLa cell growth.

Proteolytic cleavage of bovine fibrinogen with covalently bound methotrexate (MTX) was studied using four different proteolytic enzymes--trypsin, chymotrypsin, pepsin, and cathepsin D and the interaction of the modified fibrinogen (or fibrin) with HeLa cells was investigated. The presence of fibrin-MTX derivative did not induce any significant morphological alternations of cells. The fibrin-MTX derivative in the gel form was solubilized easily by the action of all proteinases investigated, hydrolysis of highly crosslinked denatured fibrin-MTX in suspension proceeded slower. The solubilized fibrin-MTX degradation products had a strong inhibiting effect on the growth of HeLa cells cultured in monolayer indicating the liberation of chemotherapeutically active MTX from its fibrin derivative.

[Microcalorimetric studies of temperature transitions in fibrinogen and its proteolytic fragments]. / Mikrokalorimetricheskie issledovaniia temperaturnykh perekhodov v fibrinogene i ego proteoliticheskikh fragmentakh.

Melting of fibrinogen and its proteolytic fragments has been studied by differential scanning microcalorimetry. It has been shown that the fibrinogen molecule contains at least nine cooperative regions. One of them pertains to the central structural block (domain E), two of them are formed by the structures removed at proteolytic fragmentation and the others make part of the terminal structural blocks (domains D). A scheme of localization of melting regions in the fibrinogen molecule is proposed on the basis of the results obtained.

[Combined thrombolysis by pharmacokinetically different plasminogen activators]. / Sochetannyi trombolizis farmakokineticheski razlichnymi aktivatorami plazminogena.

Prospects for the search for thrombolytic compositions on the basis of short-term and long-term acting plasminogen activators were shown. These will be useful as potential ambulance remedies for effective prehospital treatment. Combined proteolysis by plasminogen activators with complementary action mechanisms and significantly different pharmacokinetic behavior was suggested for this purpose.