Polymerisation of fibrin αC-domains promotes endothelial cell migration and proliferation

The sequence 581Ser-610Val in the fibrinogen Aα chain is responsible for the formation of complexes between plasminogen and αC-regions of fibrin(ogen)

Objective

This study aimed to identify the binding sites for plasminogen (Pg) and its kringle-containing fragments within the αC-region of fibrin(ogen). This investigation is crucial while the conversion of fibrinogen into fibrin induces conformational changes that expose binding sites for Pg and tissue-type Pg activator (tPA), facilitating effective zymogen activation on the fibrin surface.

Methods

Two C-terminal fragments of the Aα chain ‒ 45 kDa (225Val-610Val) and 40 kDa (225Val-580Lys), were obtained through plasmin hydrolysis of human fibrinogen and subsequently characterized using MALDI TOF mass spectrometry. The interactions of Glu-Pg and Lys-Pg, as well as Pg kringle fragments (K1-3, K4, and K5), with the obtained αC truncated polypeptides were analyzed using ELISA and Western blot techniques with the use of specific antibodies.

Results

It was demonstrated that Pg and its fragments K1-3, K4, and K5 interact exclusively with the 45-kDa fragment (225Val-610Val) of the αC region of fibrinogen with high affinity in a concentration-dependent manner (Kd values for Glu-Pg = 7.10 × 10-9 M, Lys-Pg = 6.01 × 10-9 M, K1-3 = 1.08 × 10-7 M, K4 = 5.06 × 10-7 M, and K5 = 2.50 × 10-7 M). This fragment, unlike the 40-kDa polypeptide (225Val-580Lys), contains the α581Ser-610Val sequence.

Conclusions

It was shown that the sequence 581Ser-610Val of fibrinogen Aα-chain, which becomes exposed during the conversion of fibrinogen to fibrin, is essential for the formation of complexes between Pg and αC regions of fibrin(ogen), thereby contributing to the initiation and regulation of fibrinolysis.

Scaffold Adhering to Peptide-Based Biomimetic Extracellular Matrix Composite Nanobioglass Promotes the Proliferation and Migration of Skin Fibroblasts Through the GSK-3β/β-Catenin Signaling Axis

Introduction

Nano-mesoporous bioactive glass and RGD peptide-coated collagen membranes have great potential in wound healing. However, the application of their compound has not been further studied. Our purpose is to prepare a novel bioactive collagen scaffold containing both NMBG stent and adhesion peptides (BM), which then proves its promising prospect the assessment of physical properties, biocompatibility, GSK-3β/β-catenin signaling axis and toxicological effects.

Methods

The structural and morphological changes of BM were analyzed using scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). In vivo, wound healing of BM was assessed in SD rats through dynamic monitoring and calculation of wound healing rate. Immunohistofluorescence (IHF), H&E, and Masson staining were utilized; in vitro, primary cell culture, and a variety of assays including CCK-8, Transwell, Scratch, Immunocytofluorescence (ICF), and Western blot (WB) were performed, both for morphology and molecular analysis.

Results and Discussion

Preparation of BM involved attaching NMBG to RGD-exposed collagen while avoiding the use of toxic chemical reagents. BM exhibited a distinctive superficial morphology with increased Si content, indicating successful NMBG attachment. In vivo studies on SD rats demonstrated the superior wound healing capability of BM, as evidenced by accelerated wound closure, thicker epithelial layers, and enhanced collagen deposition compared to the NC group. Additionally, BM promoted skin fibroblast migration and proliferation, possibly through activation of the GSK-3β/β-catenin signaling axis, which was crucial for tissue regeneration. This study underscored the potential of BM as an effective wound-healing dressing.

Conclusion

A new method for synthesizing ECM-like membranes has been developed using nano-mesoporous bioactive glass and collagen-derived peptides. This approach enhances the bioactivity of biomaterials through surface functionalization and growth factor-free therapy.

Functional properties of individual sub-domains of the fibrin(ogen) αC-domains

Background

Fibrinogen is a large polyfunctional plasma protein consisting of a number of structural and functional domains. Among them, two αC-domains, each formed by the amino acid residues Аα392-610, are involved in fibrin polymerization, activation of fibrinolysis, platelet aggregation, and interaction with different cell types. Previous study revealed that each fibrinogen αC-domain consists of the N-terminal and C-terminal sub-domains. The major objections of the present study were to test functional role of these sub-domains in the above mentioned processes.

Methods

To achieve these objections, we used specific proteases to prepare two truncated forms of fibrinogen, fibrinogen desAα505-610 and fibrinogen desAα414-610, missing their N-terminal and both N- and C-terminal sub-domains, respectively.

Results

Our study with these truncated forms using turbidity measurements and electron microscopy revealed that the N- and C-terminal subdomains both contribute to protofibril formation and their lateral aggregation into fibers during fibrin polymerization process. These two sub-domains also contributed to platelet aggregation with the N-terminal sub-domains playing a more significant role in this process. At the same time, the C-terminal sub-domains make the major contribution to the plasminogen activation process. Further, our experiments revealed that the C-terminal sub-domains are involved in endothelial cell viability and migration of cancer cells.

Conclusions

Thus, the results obtained establish the functional role of individual sub-domains of the αC-domains in fibrin polymerization, activation of fibrinolytic system, platelet aggregation, and cellular interactions.

General significance

The present study expands our understanding of the functional role of individual fibrinogen domains and their specific portions in various fibrin(ogen)-dependent processes.

The Story of the Fibrin(ogen) αC-Domains: Evolution of Our View on Their Structure and Interactions

Although much has been established concerning the overall structure and function of fibrinogen, much less has been known about its two αC regions, each consisting of an αC-connector and an αC-domain, but new information has been accumulating. This review summarizes the state of our current knowledge of the structure and interactions of fibrinogen's αC regions. A series of studies with isolated αC regions and their fragments demonstrated that the αC-domain forms compact ordered structures consisting of N- and C-terminal subdomains including β sheets and suggested that the αC-connector has a poly(L-proline) type II structure. Functionally, the αC-domains interact intramolecularly with each other and with the central region of the molecule, first demonstrated by electron microscopy and then quantified by optical trap force spectroscopy. Upon conversion of fibrinogen into fibrin, the αC-domains switch from intra- to intermolecular interactions to form ordered αC polymers. The formation of αC polymers occurs mainly through the homophilic interaction between the N-terminal subdomains; interaction between the C-terminal subdomains and the αC-connectors also contributes to this process. Considerable evidence supports the idea that the αC-regions accelerate fibrin polymerization and affect the final structure of fibrin clots. The interactions between αC-regions are important for the mechanical properties of clots, increasing their stiffness and extensibility. Conversion of fibrinogen into fibrin results in exposure of multiple binding sites in its αC regions, providing interaction of fibrin with different proteins and cell types during hemostasis and wound healing. This heretofore mysterious part of the fibrinogen molecule is finally giving up its secrets.

LIMITED PROTEOLYSIS OF FIBRINOGEN BY PROTEASE OF Gloydius halys halys SNAKE VENOM

Aim. One of the approaches for studying structure and functions of proteins is their limited proteolysis. Proteolytic fragments of macromolecules can preserve the biological activity and can be used for the study of their structural and functional peculiarities. Thus, the characterization of new proteolytic enzymes and determination of the specificity of their action can be of interest for exploration. In the present work, we focused on the action of protease from the venom of Gloydius halys halys on fibrinogen, the crucial protein of blood coagulation system. Methods. Products of fibrinogen hydrolysis by protease from the venom of G. halys halys were studied by SDS-PAGE electrophoresis and western-blot analysis using monoclonal antibodies ІІ-5 Сand 1-5A targeted to 20‒78 and 549‒610 fragments of fibrinogen Aα-chain. Molecular weights of hydrolytic products were determined using MALDI-TOF analysis on Voyager DE PRO (USA). Sequence of hydrolytic products were predicted by «Peptide Mass Calculator» soft ware. Results. SDS-PAGE showed that protease from the venom of Gloydius halys halys initially cleaved Аα-chain of fibrinogen molecule. Western-blot analysis confirmed that this protease specifically cleaves off fragment of C-terminal parts of Аα-chain with apparent molecular weight of 22 kDa. Cleaved fragment was identified by MALDI-TOF analysis as the 21.1 kDa polypeptide. «Peptide Mass Calculator» predicted that such a fragment corresponded to Аα414-610 residue of fibrinogen molecule. Thus, we showed that studied protease cleaved peptide bond AαK413-L414 with the formation of stable partly hydrolyzed fibrinogen desAα414-610. Conclusions. The use of protease from the venom of Gloydius halys halys would allow obtaining the unique partly hydrolyzed fibrinogen des Aα 414‒610 that is suitable for the study of structure and functions of fibrinogen αС-regions.

Serum peptides as putative modulators of inflammation in psoriasis

BACKGROUND

Psoriasis is a refractory inflammatory disease, however, its pathophysiology is still not fully understood.

OBJECTIVE

We tried to identify novel serum peptides associated with the pathophysiology of psoriasis.

METHODS

Serum peptides from 24 patients with psoriasis vulgaris (PV), 10 patients with psoriatic arthritis (PsA), 14 patients with atopic dermatitis (AD), and 23 healthy control (HC) subjects were analyzed by mass spectrometry. The effects of some peptides on the secretion of humoral factors from dermal cells were investigated by cytokine arrays and ELISAs.

RESULTS

A total of 93 peptides were detected. 24, 20, 23, and 2 peptides showed at least 1.2-fold difference in ion intensity between the psoriasis (PV+PsA) and HC groups, between the PV+PsA and AD groups, between the PV and PsA groups, and between patients with severe-to-moderate PV (n=6) and those with mild PV (n=18), respectively (p<0.05). 13 out of 27 peptides that showed at least 1.5-fold ion intensity difference in the abovementioned 4 comparisons were identified. The parent proteins of the identified peptides included a coagulation factor, proteins involved in the maintenance of skin, and a protein relating to cytoskeleton. We focused on 2 peptides that were increased in the PV+PsA group: a fibrinogen α chain-derived peptide (1462m/z), the unmodified form of which was fibrinopeptide A-des-alanine (FPAdA), and a filaggrin (FLG)-derived peptide (1977m/z), a modified form of FLG_2099-2118 (Q₂₀₉₉pE, Q₂₁₁₅E; FLG-pEE). FPAdA stimulation increased the secretion of GROα from dermal microvascular endothelial cells (dMVECs) and decreased the secretion of lipocalin-2 from keratinocytes in comparison to FPAdA-resequenced peptide stimulation (GROα, 280.9±7.3pg/mL vs. 229.6±5.0pg/mL, p<0.001; lipocalin-2, 273±13pg/mL vs. 350±10pg/mL, p<0.01). Interestingly, FLG-pEE stimulation decreased the secretion of GROα, IL-8, and MCP-1 from dMVECs in comparison to FLG-derived control peptide stimulation (GROα, 844.3±47.5pg/mL vs. 1038.5±96.9pg/mL, p<0.05; IL-8, 2240.1±172.6pg/mL vs. 3221.8±523.7pg/mL, p<0.05; MCP-1, 4057.8±157.2pg/mL vs. 4619.1±213.4pg/mL, p<0.05).

CONCLUSIONS

The results suggested that some serum peptides are involved in the pathophysiology of psoriasis, regulating the secretion of inflammatory chemokines and an antimicrobial protein. The modulation of serum peptides may be a potential therapeutic strategy for psoriasis.

Structural properties of fracture haematoma: current status and future clinical implications

Blood clots (haematomas) that form immediately following a bone fracture have been shown to be vital for the subsequent healing process. During the clotting process, a number of factors can influence the fibrin clot structure, such as fibrin polymerization, growth factor binding, cellular infiltration (including platelet retraction), protein concentrations and cytokines. The modulation of the fibrin clot structure within the fracture site has important clinical implications and could result in the development of multifunctional scaffolds that mimic the natural structure of a haematoma. Artificial haematoma structures such as these can be created from the patient's own blood and can therefore act as an ideal bone defect filling material for potential clinical application to accelerate bone regeneration. Copyright © 2016 John Wiley & Sons, Ltd.