A novel interaction between extracellular vimentin and fibrinogen in fibrin formation

Annexin A2 Contributes to Release of Extracellular Vimentin in Response to Inflammation

Vimentin, an abundant intracellular cytoskeletal protein, is secreted into the extracellular space, where it can amplify tissue destruction in inflammatory diseases. The mechanisms by which inflammation promotes the release of extracellular vimentin (ECV) are not defined. In human subjects, we found > twofold higher levels of ECV in gingival crevicular fluid from periodontitis sites with inflammation compared with healthy sites. In cultures of human gingival fibroblasts (hGFs) treated with 1% serum or IL-1β (10 ng/mL) to model tissue injury or inflammation, respectively, we found that 1% serum increased ECV release > 11-fold while IL-1β further enhanced release 17-fold. Mass spectrometry of vimentin immunoprecipitates identified Annexin A2 (AnxA2), a Ca2+-dependent phospholipid-binding protein, as a potential binding protein of ECV, which was confirmed by immunoprecipitation of cultured hGFs and immunostaining of inflamed human gingiva. IL-1β treatment enhanced the abundance of AnxA2 and vimentin in membrane fractions prepared by sucrose gradients of hGF lysates. IL-1β increased colocalization of ECV and AnxA2 at the outer aspect of the plasma membrane of intact hGFs. Knockdown of AnxA2 with siRNA or inhibition of the unconventional secretory pathway reduced ECV release from hGFs. These findings indicate that the production of ECV by hGFs in response to inflammation is mediated by an AnxA2-dependent, unconventional secretory pathway that may play a role in amplification of the inflammatory response.

Structure and function of vimentin in the generation and secretion of extracellular vimentin in response to inflammation

The canonical functions of vimentin in cell mechanics and migration have been recently expanded by the discovery of new roles for extracellular vimentin (ECV) in immune responses to infection, injury and cancer. In contrast with the predominantly filamentous form of intracellular vimentin, ECV exists largely as soluble oligomers. The release of ECV from intact cells is dependent on mechanisms that regulate the assembly and disassembly of intracellular vimentin, which are influenced by discrete post-translational modifications. In this review we highlight the processes that promote the conversion of intracellular and insoluble vimentin filaments to ECV and secretion mechanisms. Insights into the regulation of ECV release from stromal and immune cells could provide new diagnostic and therapeutic approaches for assessing and controlling inflammatory diseases.

Proteomic analysis indicates lower abundance of platelet α-granule proteins in Glanzmann thrombasthenia

BACKGROUND

Glanzmann thrombasthenia (GT) is an inherited platelet function disorder caused by mutations in the fibrinogen receptor αIIbβ3. The deficiency can be quantitative (type I/II) or qualitative (type III). It causes lack of platelet aggregation and leads to a moderate to severe bleeding tendency. Besides the absence or functional alteration of the integrins αIIb and β3, little is known about the proteomic landscape of platelets from GT patients.

OBJECTIVES

To evaluate the platelet proteome in GT.

METHODS

Label-free quantification of platelet proteins was performed in 13 genetically confirmed GT patients (11 type I and 2 type III) and 13 healthy controls with liquid chromatography coupled with tandem mass spectrometry. αIIbβ3 expression was quantified with whole blood flow cytometry. Medical ethics committee approval was obtained and all participants provided informed consent.

RESULTS

Of 3664 identified proteins, 2677 were considered quantified. Dynamic range spanned 5 orders of magnitude, and the mean coefficient of variation was 1.2%, indicating data were robust. Flow cytometry-based αIIb expression correlated well with αIIb abundance according to liquid chromatography-tandem mass spectrometry. Twenty-nine proteins were less abundant, and 32 proteins were more abundant in GT patients than in controls. Downregulated proteins were enriched for α-granule proteins, including secreted protein acidic and cyteine rich, amyloid β precursor-like protein 2, TIMP metallopeptidase inhibitor 1, and TREM-like transcript-1, in addition to the subunits of integrin αIIbβ3, fibrinogen, and plasminogen. Upregulated proteins were mostly plasma proteins annotated to blood microparticles.

CONCLUSION

GT platelets show reduced abundance of specific platelet α-granule proteins compared with healthy controls.

Fibrinogen-to-albumin ratio is associated with the prognosis of patients with septic acute kidney injury

Background

The fibrinogen-to-albumin ratio (FAR), a novel inflammatory biomarker, is strongly associated with the incidence of sepsis. Nonetheless, there is a lack of research regarding the FAR and prognosis in individuals with septic acute kidney injury (SAKI). The aim of this study was to assess the correlation between the FAR upon intensive care unit (ICU) admission and overall mortality in patients with SAKI.

Methods

All patient information was retrieved from the Medical Information Mart for Intensive Care-IV (MIMIC-IV) database. All patients were divided into four distinct categories according to the FAR. The primary endpoints for this study were the 30-day and 365-day all-cause death rates, whereas the secondary endpoints were the 60-day, 90-day and 180-day all-cause death rates. The FAR was quartile, and the Kaplan-Meier curve was used to evaluate the outcomes across the groups. To evaluate the correlation between the FAR and outcomes, we used a Cox proportional hazards regression model and restricted cubic splines (RCSs).

Results

Among the 6208 participants, the average age was 65 years, with 3659 (58.94%) identified as male. Patients exhibiting elevated FAR values demonstrated an increased risk of all-cause mortality at 30, 60, 90, 180 and 365 days, as evidenced by the Kaplan-Meier curves (log-rank P < .001). SAKI patients with elevated FAR values had a greater risk of all-cause mortality at 30, 60, 90, 180 and 365 days than did those with lower FAR values, as demonstrated by Cox proportional hazards regression analysis. With inflection points at 35.14 for 30-day mortality and 34.8 for 365-day mortality, the RCS analysis revealed that the FAR and all-cause mortality were related in an inverted N-type pattern. In instances where FAR levels were below 35.14 mg/g, a reduction of 1 unit in the FAR correlated with a 6.5% increase in the risk of 30-day all-cause mortality [hazard ratio (HR) 0.935; 95% confidence interval (CI) 0.923, 0.948]. In instances where FAR levels were below 34.8 mg/g, a reduction of 1 unit in the FAR correlated with a 6.2% increase in the risk of 365-day all-cause mortality (HR 0.938; 95% CI 0.927, 0.949).

Conclusion

In severely ill patients with SAKI, elevated FAR levels are strongly correlated with an increased risk of all-cause mortality at 30, 60, 90, 180 and 365 days. FAR may serve as a reliable metric for assessing and managing patients with SAKI in the ICU.

The unconventional role of vimentin intermediate filaments

Vimentin, a type III intermediate filament (IF) protein, is well-recognized for its role at the intersection of structural biology and cellular dynamics, influencing various pathways that determine cell fate and function. While these functions have been extensively characterized, there is still limited understanding of vimentin's broader impact beyond its traditional cytoskeletal roles in regulating a spectrum of cellular processes. This review explores the novel and unconventional roles of vimentin, with a focus on its extracellular functions, membrane receptor properties, and regulatory influence on gene expression and cellular metabolism.

Low-Dose Dabigatran for Venous Sinus Thromboembolism Associated with Hereditary Dysfibrinogenemia: A Case Report

Dabigatran, an anticoagulant, may increase the risk of bleeding in patients with dysfibrinogenemia because of coagulation irregularities, especially at high doses. Cranial Magnetic Resonance Imaging (MRI) and Magnetic Resonance Venography (MRV) were used in the diagnosis of venous sinus thromboembolism in a 42-year-old woman with hereditary dysfibrinogenemia, as documented in our case report. Cranial MRI suggested thrombosis in the venous sinuses, which was confirmed by MRV as thromboses in the superior sagittal, straight, left transverse, and sigmoid sinuses. Instead of the usual fixed-dose, we gave the patient dabigatran based on how the coagulation indicators changed. Forty-six days after treatment, the patient's clinical symptoms had largely resolved. Follow-up cranial MR showed that most of the venous sinus thromboses had disappeared, with some mural thrombi still present in the superior sagittal sinus and left sigmoid sinus. In this report, we optimized the dabigatran regimen adjusted to thrombin time, ensuring efficacy with low bleeding risk.

Extracellular vimentin is a damage-associated molecular pattern protein serving as an agonist of TLR4 in human neutrophils

BACKGROUND

Vimentin is a type III intermediate filament protein that plays an important role in cytoskeletal mechanics. It is now known that vimentin also has distinct functions outside the cell. Recent studies show the controlled release of vimentin into the extracellular environment, where it functions as a signaling molecule. Such observations are expanding our current knowledge of vimentin as a structural cellular component towards additional roles as an active participant in cell signaling.

METHODS

Our study investigates the immunological roles of extracellular vimentin (eVim) and its citrullinated form (CitVim) as a damage-associated molecular pattern (DAMP) engaging the Toll-like receptor 4 (TLR4) of human neutrophils. We used in vitro assays to study neutrophil migration through endothelial cell monolayers and activation markers such as NADPH oxidase subunit 2 (NOX2/gp91phox). The comparison of eVim with CitVim and its effect on human neutrophils was extended to the induction of extracellular traps (NETs) and phagocytosis of pathogens.

RESULTS

Both eVim and CitVim interact with and trigger TLR4, leading to increased neutrophil migration and adhesion. CitVim stimulated the enhanced migratory ability of neutrophils, activation of NF-κB, and induction of NET formation mainly mediated through reactive oxygen species (ROS)-dependent and TLR4-dependent pathways. In contrast, neutrophils exposed to non-citrullinated vimentin exhibited higher efficiency in favoring pathogen phagocytosis, such as Escherichia coli and Candida albicans, compared to CitVim.

CONCLUSIONS

Our study identifies new functions of eVim in its native and modified forms as an extracellular matrix DAMP and highlights its importance in the modulation of immune system functions. The differential effects of eVim and CitVim on neutrophil functions highlight their potential as new molecular targets for therapeutic strategies aimed at regulation of neutrophil activity in different pathological conditions. This, in turn, opens new windows of therapeutic intervention in inflammatory and immunological diseases characterized by immune system dysfunction, in which eVim and CitVim play a key role.

Extracellular vimentin amplifies inflammation: Perspectives for immune injury and therapeutics for periodontitis

Periodontitis is an inflammatory disease triggered by microbial biofilms that promote immune dysfunction and tissue destruction of tooth-supporting tissues. The search for soluble mediators that amplify inflammatory responses and matrix degradation in periodontal tissues has implicated extracellular vimentin (ECV) as a signaling ligand and damage-associated molecular pattern in the pathogenesis of periodontitis. Intracellular vimentin filaments are essential for the structural integrity of cells and the preservation of matrix homeostasis. These are important determinants of health in the periodontium and many other organs. But in inflamed tissues, intracellular vimentin filaments are disassembled. Vimentin is subsequently released from cells into the extracellular space in a soluble form where it drives immune signaling and tissue destruction. We discuss the role of ECV as a signaling molecule in several tissues. We apply these data to understand how in inflammatory diseases like periodontitis, ECV amplifies immune responses that contribute to disease progression. Arising from these data, we consider novel therapeutic opportunities for limiting tissue destruction by targeting ECV for treatment of inflammatory disorders like periodontitis.

Cellular vimentin interacts with VP70 protein of goose astrovirus genotype 2 and acts as a structural organizer to facilitate viral replication

The fatal gouty disease caused by goose astrovirus genotype 2 (GAstV-2) still seriously endangers the goose industry in China, causing great economic losses. However, research on its infection mechanism has progressed relatively slowly. VP70 is the structural protein of GAstV-2 and is closely related to virus invasion and replication. To better understand the role of VP70 during GAstV-2 infection, we used immunoprecipitation and mass spectrometry to identify host proteins that interact with VP70. Here, we report that cellular vimentin (VIM) is a host binding partner of VP70. Site-directed mutagenesis showed that amino acid residues 399 to 413 of VP70 interacted with VIM. Using reverse genetics, we found that VP70 mutation disrupts the interaction of VP70 with VIM, which is essential for viral replication. Overexpression of VIM significantly promoted GAstV-2 replication, while knockdown of VIM significantly inhibited GAstV-2 replication. Laser confocal microscopy showed that VP70 protein expression induced the rearrangement of VIM, gradually aggregating from the original uniform grid to the side of the nucleus, and aggregated the originally dispersed GAstV-2 RNA in VIM. This rearrangement was associated with increased VIM phosphorylation caused by GAstV-2. Meanwhile, blocking VIM rearrangement with acrylamide substantially inhibited viral replication. These results indicate that VIM interacts with VP70 and positively regulates GAstV-2 replication, and VIM-VP70 interaction and an intact VIM network are needed for GAstV-2 replication. This study provides a theoretical basis and novel perspective for the further characterization of the pathogenic mechanism of GAstV-2-induced gouty disease in goslings.

Elevated level of extracellular vimentin is associated with an increased fibrin formation potential in sepsis: ex vivo swine study

BACKGROUND

Sepsis can lead to coagulopathy and microvascular thrombosis. Prior studies, including ours, reported an increased level of extracellular vimentin in blood derived from septic patients. Moreover, we identified the contribution of extracellular vimentin to fibrin formation and to the fibrin clot structure ex vivo in plasma from septic patients. Here, we tested the status of plasma vimentin and its impact on fibrin clots using our recently described swine model of methicillin-resistant Staphylococcus aureus (MRSA) sepsis-induced coagulopathy.

RESULTS

We employed ELISA, size-exclusion chromatography, vimentin antibodies, confocal microscopy, and turbidity assays on piglet plasma obtained at pre- and post-MRSA inoculation. Plasma vimentin level at 70 h post-MRSA inoculation was on average twofold higher compared to pre-infection (0 h) level in the same animal. Anti-vimentin antibody effectively reduced fibrin formation ex vivo and increased porosity in the fibrin clot structure generated from septic piglet plasma. In contrast to plasma at 0 h, the size-exclusion chromatography revealed that phosphorylated vimentin was in-complex with fibrinogen in septic piglet plasma.

CONCLUSIONS

Thus, our swine model of sepsis-induced coagulopathy, reproduced increased extracellular circulating vimentin and subsequent potentiation of fibrin formation, often observed in septic patient. These outcomes validate the use of large animal models to investigate the dysregulated host immune response to infection leading to coagulopathy, and to develop new therapies for sepsis-induced disseminated microvascular thrombosis.

Mechanobiology in Metabolic Dysfunction-Associated Steatotic Liver Disease and Obesity

With the ongoing obesity epidemic, the prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) is expected to rise and necessitates a greater understanding of how the disease proceeds from benign excess lipid in hepatocytes to liver fibrosis and eventually to liver cancer. MASLD is caused, at least in part, by hepatocytes' storage of free fatty acids (FAs) that dysfunctional adipocytes are no longer able to store, and therefore, MASLD is a disease that involves both the liver and adipose tissues. The disease progression is not only facilitated by biochemical signals, but also by mechanical cues such as the increase in stiffness often seen with fibrotic fatty livers. The change in stiffness and accumulation of excess lipid droplets impact the ability of a cell to mechanosense and mechanotranduce, which perpetuates the disease. A mechanosensitive protein that is largely unexplored and could serve as a potential therapeutic target is the intermediate filament vimentin. In this review, we briefly summarize the recent research on hepatocyte and adipocyte mechanobiology and provide a synopsis of studies on the varied, and sometimes contradictory, roles of vimentin. This review is intended to benefit and encourage future studies on hepatocyte and adipocyte mechanobiology in the context of MASLD and obesity.

Vimentin at the core of wound healing

As a member of the large family of intermediate filaments (IFs), vimentin has emerged as a highly dynamic and versatile cytoskeletal protein involved in many key processes of wound healing. It is well established that vimentin is involved in epithelial-mesenchymal transition (EMT) during wound healing and metastasis, during which epithelial cells acquire more dynamic and motile characteristics. Moreover, vimentin participates in multiple cellular activities supporting growth, proliferation, migration, cell survival, and stress resilience. Here, we explore the role of vimentin at each phase of wound healing, with focus on how it integrates different signaling pathways and protects cells in the fluctuating and challenging environments that characterize a healing tissue.

Extracellular vimentin as a modulator of the immune response and an important player during infectious diseases

Vimentin, an intermediate filament protein primarily recognized for its intracellular role in maintaining cellular structure, has recently garnered increased attention and emerged as a pivotal extracellular player in immune regulation and host-pathogen interactions. While the functions of extracellular vimentin were initially overshadowed by its cytoskeletal role, accumulating evidence now highlights its significance in diverse physiological and pathological events. This review explores the multifaceted role of extracellular vimentin in modulating immune responses and orchestrating interactions between host cells and pathogens. It delves into the mechanisms underlying vimentin's release into the extracellular milieu, elucidating its unconventional secretion pathways and identifying critical molecular triggers. In addition, the future perspectives of using extracellular vimentin in diagnostics and as a target protein in the treatment of diseases are discussed.

Extracellular vimentin: Battle between the devil and the angel

Vimentin, an intracellular cytoskeletal protein, can be secreted by various cells in response to conditions such as injury, stress, senescence, and cancer. Once vimentin is secreted outside of the cell, it is called extracellular vimentin. This extracellular vimentin is significantly involved in pathological conditions, particularly in the areas of viral infection, cancer, immune response, and wound healing. The effects of extracellular vimentin can be either positive or negative, for example it can enhance axonal repair but also mediates SARS-CoV-2 infection. In this review, we categorize the functional implications of extracellular vimentin based on its localization outside the cell. Specifically, we classify extracellular vimentin into two distinct forms: surface vimentin, which remains bound to the cell surface, and secreted vimentin, which refers to the free form that is completely released outside the cell. Overall, extracellular vimentin has a dual nature that encompasses both beneficial and detrimental effects on the functionality of cells, organs and whole organisms. Here, we summarize its effects in viral infection, cancer, immune response and wound healing. We find that surface vimentin is often associated with negative consequences, whereas secreted vimentin manifests predominantly with positive influences. We found that the observed effects of extracellular vimentin strongly depend on the specific circumstances under which its expression occurs in cells.

Vimentin takes a hike - Emerging roles of extracellular vimentin in cancer and wound healing

Vimentin is a cytoskeletal protein important for many cellular processes, including proliferation, migration, invasion, stress resistance, signaling, and many more. The vimentin-deficient mouse has revealed many of these functions as it has numerous severe phenotypes, many of which are found only following a suitable challenge or stress. While these functions are usually related to vimentin as a major intracellular protein, vimentin is also emerging as an extracellular protein, exposed at the cell surface in an oligomeric form or secreted to the extracellular environment in soluble and vesicle-bound forms. Thus, this review explores the roles of the extracellular pool of vimentin (eVIM), identified in both normal and pathological states. It focuses specifically on the recent advances regarding the role of eVIM in wound healing and cancer. Finally, it discusses new technologies and future perspectives for the clinical application of eVIM.

Transmit and protect: The mechanical functions of intermediate filaments

New aspects of the unique mechanical properties of intermediate filaments (IFs) continue to emerge from studies that illuminate the structure and mechanical response of single filaments, the interaction of intermediate filaments with each other or with other cytoskeletal elements, and the viscoelasticity of the networks that these intermediate filaments form. The relation of purified IF network mechanics to the role of IFs in cells and tissues is a particularly active area, with several new demonstrations of the unique and essential role that intermediate filament networks play in determining the mechanical response of biological materials, especially to large deformations, and the mechanisms by which intermediate filaments protect the nucleus from mechanical stresses that cells and tissues encounter in vivo.

Extracellular vimentin as a versatile immune suppressive protein in cancer

The interest in finding new targets in the tumor microenvironment for anti-cancer therapy has increased rapidly over the years. More specifically, the tumor-associated blood vessels are a promising target. We recently found that the intermediate filament protein vimentin is externalized by endothelial cells of the tumor vasculature. Extracellular vimentin was shown to sustain angiogenesis by mimicking VEGF and supporting cell migration, as well as endothelial cell anergy, the unresponsiveness of the endothelium to proinflammatory cytokines. The latter hampers immune cell infiltration and subsequently provides escape from tumor immunity. Other studies showed that extracellular vimentin plays a role in sustained systemic and local inflammation. Here we will review the reported roles of extracellular vimentin with a particular emphasis on its involvement in the interactions between immune cells and the endothelium in the tumor microenvironment. To this end, we discuss the different ways by which extracellular vimentin modulates the immune system. Moreover, we review how this protein can alter immune cell-vessel wall adhesion by altering the expression of adhesion proteins, attenuating immune cell infiltration into the tumor parenchyma. Finally, we discuss how vimentin-targeting therapy can reverse endothelial cell anergy and promote immune infiltration, supporting anti-tumor immunity.

An updated overview of some factors that influence the biological effects of nanoparticles

Nanoparticles (NPs) can be extremely effective in the early diagnosis and treatment of cancer due to their properties. The nanotechnology industry is developing rapidly. The number of multifunctional NPs has increased in the market and hundreds of NPs are in various stages of preclinical and clinical development. Thus, the mechanism underlying the effects of NPs on biological systems has received much attention. After NPs enter the body, they interact with plasma proteins, tumour cell receptors, and small biological molecules. This interaction is closely related to the size, shape, chemical composition and surface modification properties of NPs. In this review, the effects of the size, shape, chemical composition and surface modification of NPs on the biological effects of NPs were summarised, including the mechanism through which NPs enter cells, the resulting oxidative stress response, and the interaction with proteins. This review of the biological effects of NPs can not only provide theoretical support for the preparation of safer and more efficient NPs but also lay the foundation for their clinical application.