Tissue factor- and factor X-dependent activation of protease-activated receptor 2 by factor VIIa

Coagulation and Inflammation in COVID-19: Reciprocal Relationship between Inflammatory and Coagulation Markers

The coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), formerly known as 2019-nCoV. Numerous cellular and biochemical issues arise after COVID-19 infection. The severe inflammation that is caused by a number of cytokines appears to be one of the key hallmarks of COVID-19. Additionally, people with severe COVID-19 have coagulopathy and fulminant thrombotic events. We briefly reviewed the COVID-19 disease at the beginning of this paper. The inflammation and coagulation markers and their alterations in COVID-19 illness are briefly discussed in the parts that follow. Next, we talked about NETosis, which is a crucial relationship between coagulation and inflammation. In the end, we mentioned the two-way relationship between inflammation and coagulation, as well as the factors involved in it. We suggest that inflammation and coagulation are integrated systems in COVID-19 that act on each other in such a way that not only inflammation can activate coagulation but also coagulation can activate inflammation.

Coagulation Protease-Driven Cancer Immune Evasion: Potential Targets for Cancer Immunotherapy

Blood coagulation and cancer are intrinsically connected, hypercoagulation-associated thrombotic complications are commonly observed in certain types of cancer, often leading to decreased survival in cancer patients. Apart from the common role in coagulation, coagulation proteases often trigger intracellular signaling in various cancers via the activation of a G protein-coupled receptor superfamily protease: protease-activated receptors (PARs). Although the role of PARs is well-established in the development and progression of certain types of cancer, their impact on cancer immune response is only just emerging. The present review highlights how coagulation protease-driven PAR signaling plays a key role in modulating innate and adaptive immune responses. This is followed by a detailed discussion on the contribution of coagulation protease-induced signaling in cancer immune evasion, thereby supporting the growth and development of certain tumors. A special section of the review demonstrates the role of coagulation proteases, thrombin, factor VIIa, and factor Xa in cancer immune evasion. Targeting coagulation protease-induced signaling might be a potential therapeutic strategy to boost the immune surveillance mechanism of a host fighting against cancer, thereby augmenting the clinical consequences of targeted immunotherapeutic regimens.

The protease activated receptor 2 - CCAAT/enhancer-binding protein beta - SerpinB3 axis inhibition as a novel strategy for the treatment of non-alcoholic steatohepatitis

OBJECTIVE

The serine protease inhibitor SerpinB3 has been described as critical mediator of liver fibrosis and it has been recently proposed as an additional hepatokine involved in NASH development and insulin resistance. Protease Activated Receptor 2 has been identified as a novel regulator of hepatic metabolism. A targeted therapeutic strategy for NASH has been investigated, using 1-Piperidine Propionic Acid (1-PPA), since this compound has been recently proposed as both Protease Activated Receptor 2 and SerpinB3 inhibitor.

METHODS

The effect of SerpinB3 on inflammation and fibrosis genes was assessed in human macrophage and stellate cell lines. Transgenic mice, either overexpressing SerpinB3 or carrying Serpinb3 deletion and their relative wild type strains, were used in experimental NASH models. Subgroups of SerpinB3 transgenic mice and their controls were also injected with 1-PPA to assess the efficacy of this compound in NASH inhibition.

RESULTS

1-PPA did not present significant cell and organ toxicity and was able to inhibit SerpinB3 and PAR2 in a dose-dependent manner. This effect was associated to a parallel reduction of the synthesis of the molecules induced by endogenous SerpinB3 or by its paracrine effects both in vitro and in vivo, leading to inhibition of lipid accumulation, inflammation and fibrosis in experimental NASH. At mechanistic level, the antiprotease activity of SerpinB3 was found essential for PAR2 activation, determining upregulation of the CCAAT Enhancer Binding Protein beta (C/EBP-β), another pivotal regulator of metabolism, inflammation and fibrosis, which in turn determined SerpinB3 synthesis.

CONCLUSIONS

1-PPA treatment was able to inhibit the PAR2 - C/EBP-β - SerpinB3 axis and to protect from NASH development and progression, supporting the potential use of a similar approach for a targeted therapy of NASH.

Endotoxemia and Platelets: 2 Players of Intrahepatic Microthrombosis in NAFLD

Gut dysbiosis-related intestinal barrier dysfunction with increased translocation of bacterial products such as lipopolysaccharide (LPS) into systemic circulation is emerging as pathogenic factor of nonalcoholic fatty liver disease (NAFLD). Experimental and clinical studies suggested a potential role of LPS as a trigger eliciting in situ liver inflammation upon interaction with its receptor toll-like receptor 4. Also, LPS has been reported to prime platelets to respond to the common agonists indicating that it behaves as a prothrombotic molecule. Of note, recent studies suggested platelet-related intrahepatic thrombosis triggered by LPS as a mechanism implicated in the process of liver inflammation. This review describes: 1) the impact of gut barrier dysfunction and endotoxemia in the process of NAFLD; 2) the relationship between endotoxemia and platelet activation in NAFLD; 3) clinical evidence for the use of antiplatelet drugs in NAFLD/nonalcoholic steatohepatitis patients; and 4) the potential therapeutic approach to modulate endotoxemia and eventually platelet activation.

Protease-Activated Receptors (PARs): Biology and Therapeutic Potential in Perioperative Stroke

Perioperative stroke is a devastating complication that occurs during surgery or within 30 days following the surgical procedure. Its prevalence ranges from 0.08 to 10% although it is most likely an underestimation, as sedatives and narcotics can substantially mask symptomatology and clinical presentation. Understanding the underlying pathophysiology and identifying potential therapeutic targets are of paramount importance. Protease-activated receptors (PARs), a unique family of G-protein-coupled receptors, are widely expressed throughout the human body and play essential roles in various physiological and pathological processes. This review elucidates the biology and significance of PARs, outlining their diverse functions in health and disease, and their intricate involvement in cerebrovascular (patho)physiology and neuroprotection. PARs exhibit a dual role in cerebral ischemia, which underscores their potential as therapeutic targets to mitigate the devastating effects of stroke in surgical patients.

Coagulation Factor Xa Has No Effects on the Expression of PAR1, PAR2, and PAR4 and No Proinflammatory Effects on HL-1 Cells

Atrial fibrillation (AF), characterised by irregular high-frequency contractions of the atria of the heart, is of increasing clinical importance. The reasons are the increasing prevalence and thromboembolic complications caused by AF. So-called atrial remodelling is characterised, among other things, by atrial dilatation and fibrotic remodelling. As a result, AF is self-sustaining and forms a procoagulant state. But hypercoagulation not only appears to be the consequence of AF. Coagulation factors can exert influence on cells via protease-activated receptors (PAR) and thereby the procoagulation state could contribute to the development and maintenance of AF. In this work, the influence of FXa on Heart Like-1 (HL-1) cells, which are murine adult atrial cardiomyocytes (immortalized), was investigated. PAR1, PAR2, and PAR4 expression was detected. After incubations with FXa (5-50 nM; 4-24 h) or PAR1- and PAR2-agonists (20 µM; 4-24 h), no changes occurred in PAR expression or in the inflammatory signalling cascade. There were no time- or concentration-dependent changes in the phosphorylation of the MAP kinases ERK1/2 or the p65 subunit of NF-κB. In addition, there was no change in the mRNA expression of the cell adhesion molecules (ICAM-1, VCAM-1, fibronectin). Thus, FXa has no direct PAR-dependent effects on HL-1 cells. Future studies should investigate the influence of FXa on human cardiomyocytes or on other cardiac cell types like fibroblasts.

Coagulation factor VIIa enhances programmed death-ligand 1 expression and its stability in breast cancer cells to promote breast cancer immune evasion

BACKGROUND

Immunotherapy for breast cancer has not gained significant success. Coagulation factor VIIa (FVIIa)-tissue factor (TF) mediated activation of protease-activated receptor 2 (PAR2) is shown to promote metastasis and secretion of the immune-modulatory cytokines but the role of FVIIa in cancer immunology is still not well understood.

OBJECTIVES

Here, we aim to investigate whether FVIIa protects breast cancer cells from CD8 T-cell-mediated killing.

METHODS

Peripheral blood mononuclear cell-derived CD8 T cells were cocultured with vehicle or FVIIa pretreated MDAMB468 cells. The proliferation and activity of CD8 T cells were measured by flow cytometry and ELISA. An allograft model, using wild-type or TF/PAR2-deleted 4T1 cells, was employed to determine the effect of FVIIa on breast cancer immune evasion in vivo.

RESULTS

Here, we demonstrate that TF-FVIIa induces programmed death-ligand 1 (PD-L1) in breast cancer cells by activating PAR2. PAR2 activation triggers large tumor suppressor kinase 1 (LATS1) inactivation leading to loss of yes-associated protein (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) phosphorylation and subsequent nuclear localization of YAP/TAZ. YAP/TAZ inhibition reduces PD-L1 expression and increases CD8 T-cell activity. We further demonstrate that, apart from transcriptional induction of PD-L1, PAR2 activation also increases PD-L1 stability by enhancing its glycosylation through N-glycosyltransferases STT3A and STT3B.

CONCLUSION

In a mouse model of breast cancer, tumor cell-specific PAR2 depletion leads to PD-L1 downregulation and increases anti-PD-1 immunotherapy efficacy. In conclusion, we showed that FVIIa-mediated signaling cascade in cancer cells serves as a tumor intrinsic mechanism of immunosuppression to promote cancer immune evasion.

Current Medical Therapy and Revascularization in Peripheral Artery Disease of the Lower Limbs: Impacts on Subclinical Chronic Inflammation

Peripheral artery disease (PAD), coronary artery disease (CAD), and cerebrovascular disease (CeVD) are characterized by atherosclerosis and inflammation as their underlying mechanisms. This paper aims to conduct a literature review on pharmacotherapy for PAD, specifically focusing on how different drug classes target pro-inflammatory pathways. The goal is to enhance the choice of therapeutic plans by considering their impact on the chronic subclinical inflammation that is associated with PAD development and progression. We conducted a comprehensive review of currently published original articles, narratives, systematic reviews, and meta-analyses. The aim was to explore the relationship between PAD and inflammation and evaluate the influence of current pharmacological and nonpharmacological interventions on the underlying chronic subclinical inflammation. Our findings indicate that the existing treatments have added anti-inflammatory properties that can potentially delay or prevent PAD progression and improve outcomes, independent of their effects on traditional risk factors. Although inflammation-targeted therapy in PAD shows promising potential, its benefits have not been definitively proven yet. However, it is crucial not to overlook the pleiotropic properties of the currently available treatments, as they may provide valuable insights for therapeutic strategies. Further studies focusing on the anti-inflammatory and immunomodulatory effects of these treatments could enhance our understanding of the mechanisms contributing to the residual risk in PAD and pave the way for the development of novel therapies.

ADNP is associated with immune infiltration and radiosensitivity in hepatocellular carcinoma for predicting the prognosis

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most lethal diseases due to its high faculty of invasiveness and metastasis. Activity-dependent neuroprotective protein (ADNP) has been regarded as an oncogene in bladder cancer and ovarian cancer. However, the role of ADNP in the regulation of tumor immune response, development, and treatment resistance in HCC remains unknown and is worth exploring.

METHODS

The correlation between ADNP and prognosis, immune cell infiltration, immune checkpoints, chemokines, tumor mutation burden, microsatellite instability, and genomic mutation of pan-cancer cohorts in The Cancer Genome Atlas was analyzed. ADNP expression in HCC cell lines, HCC and the adjacent normal tissues was measured by western blotting and immunochemistry. Nomogram was constructed to predict the survival of patients with HCC based on the ADNP expression and significant clinical characteristics. The potential biological functions and impacts on radiotherapy of ADNP in HCC cell lines were verified by vitro experiments.

RESULTS

ADNP was upregulated in most cancers and patients with elevated ADNP expression were related to poor survival in several types of cancers including HCC. Functional enrichment analysis showed ADNP participated in the pathways correlated with coagulation cascades and DNA double strand break repair. Further, ADNP exhibited a negative correlation with the immune score, stromal score, estimated score, and chemokines, and a positive correlation with cancer-associated fibroblasts, myeloid-derived suppressor cells, neutrophils, regulatory T cells, and endothelial cells. Immunochemistry and western blotting results demonstrated ADNP was up-regulated in HCC. Vitro experiments verified that suppressing the ADNP expression significantly inhibited the proliferation, invasion and migration and elevated the radiosensitivity via decreasing DNA damage repair in HCC.

CONCLUSION

ADNP might play an oncogene and immunosuppression role in tumor immune infiltration and response, thus influencing the prognosis. Its downregulation could attenuate the proliferation, invasion, migration, radioresistance of HCC. Our results indicated the potential of ADNP as a promising biomarker to predict the survival of HCC patients, providing a theoretical basis for novel integrative strategies.

Tissue factor (coagulation factor III): a potential double-edge molecule to be targeted and re-targeted toward cancer

Tissue factor (TF) is a protein that plays a critical role in blood clotting, but recent research has also shown its involvement in cancer development and progression. Herein, we provide an overview of the structure of TF and its involvement in signaling pathways that promote cancer cell proliferation and survival, such as the PI3K/AKT and MAPK pathways. TF overexpression is associated with increased tumor aggressiveness and poor prognosis in various cancers. The review also explores TF's role in promoting cancer cell metastasis, angiogenesis, and venous thromboembolism (VTE). Of note, various TF-targeted therapies, including monoclonal antibodies, small molecule inhibitors, and immunotherapies have been developed, and preclinical and clinical studies demonstrating the efficacy of these therapies in various cancer types are now being evaluated. The potential for re-targeting TF toward cancer cells using TF-conjugated nanoparticles, which have shown promising results in preclinical studies is another intriguing approach in the path of cancer treatment. Although there are still many challenges, TF could possibly be a potential molecule to be used for further cancer therapy as some TF-targeted therapies like Seagen and Genmab's tisotumab vedotin have gained FDA approval for treatment of cervical cancer. Overall, based on the overviewed studies, this review article provides an in-depth overview of the crucial role that TF plays in cancer development and progression, and emphasizes the potential of TF-targeted and re-targeted therapies as potential approaches for the treatment of cancer.

Long COVID: pathophysiological factors and abnormalities of coagulation

Acute COVID-19 infection is followed by prolonged symptoms in approximately one in ten cases: known as Long COVID. The disease affects ~65 million individuals worldwide. Many pathophysiological processes appear to underlie Long COVID, including viral factors (persistence, reactivation, and bacteriophagic action of SARS CoV-2); host factors (chronic inflammation, metabolic and endocrine dysregulation, immune dysregulation, and autoimmunity); and downstream impacts (tissue damage from the initial infection, tissue hypoxia, host dysbiosis, and autonomic nervous system dysfunction). These mechanisms culminate in the long-term persistence of the disorder characterized by a thrombotic endothelialitis, endothelial inflammation, hyperactivated platelets, and fibrinaloid microclots. These abnormalities of blood vessels and coagulation affect every organ system and represent a unifying pathway for the various symptoms of Long COVID.

Protease-activated receptors in kidney diseases: A comprehensive review of pathological roles, therapeutic outcomes and challenges

Studies have demonstrated that protease-activated receptors (PARs) with four subtypes (PAR1-4) are mainly expressed in the renal epithelial, endothelial, and podocyte cells. Some endogenous and urinary proteases, namely thrombin, trypsin, urokinase, and kallikrein released during diseased conditions, are responsible for activating different subtypes of PARs. Each PAR receptor subtype is involved in kidney disease of distinct aetiology. PAR1 and PAR2 have shown differential therapeutic outcomes in rodent models of type-1 and type-2 diabetic kidney diseases due to the distinct etiological basis of each disease type, however such findings need to be confirmed in other diabetic renal injury models. PAR1 and PAR2 blockers have been observed to abolish drug-induced nephrotoxicity in rodents by suppressing tubular inflammation and fibrosis and preventing mitochondrial dysfunction. Notably, PAR2 inhibition improved autophagy and prevented fibrosis, inflammation, and remodeling in the urethral obstruction model. Only the PAR1/4 subtypes have emerged as a therapeutic target for treating experimentally induced nephrotic syndrome, where their respective antibodies attenuated the podocyte apoptosis induced upon thrombin activation. Strikingly PAR2 and PAR4 subtypes involvement has been tested in sepsis-induced acute kidney injury (AKI) and renal ischemia-reperfusion injury models. Thus, more studies are required to delineate the role of other subtypes in the sepsis-AKI model. Evidence suggests that PARs regulate oxidative, inflammatory stress, immune cell activation, fibrosis, autophagic flux, and apoptosis during kidney diseases.

Peripheral blood mononuclear cell tissue factor (F3 gene) transcript levels and circulating extracellular vesicles are elevated in severe coronavirus 2019 (COVID-19) disease

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with excessive coagulation, thrombosis, and mortality.

OBJECTIVE

To provide insight into mechanisms that contribute to excessive coagulation in coronavirus 2019 (COVID-19) disease.

PATIENTS/METHODS

Blood from COVID-19 patients was investigated for coagulation-related gene expression and functional activities.

RESULTS

Single-cell RNA sequencing (scRNA-seq) of peripheral blood mononuclear cells from severe COVID-19 patients revealed a 5.2-fold increase in tissue factor (TF [F3 gene]) transcript expression levels (P < .05), the trigger of extrinsic coagulation; a 7.7-fold increase in C1-inhibitor (SERPING1 gene; P < .01) transcript expression levels, an inhibitor of intrinsic coagulation; and a 4.4-fold increase in anticoagulant thrombomodulin (TM [THBD gene]) transcript expression levels (P < .001). Bulk RNA-seq analysis of sorted CD14⁺ monocytes on an independent cohort of COVID-19 patients confirmed these findings (P < .05). Indicative of excessive coagulation, 41% of COVID-19 patients' plasma samples contained high D-dimer levels (P < .0001); of these, 19% demonstrated extracellular vesicle TF activity (P = .109). COVID-19 patients' ex vivo plasma-based thrombin generation correlated positively with D-dimer levels (P < .01). Plasma procoagulant extracellular vesicles were elevated ∼9-fold in COVID-19 patients (P < .01). Public scRNA-seq data sets from bronchoalveolar lung fluid and our peripheral blood mononuclear cell scRNA-seq data show CD14⁺ monocytes/macrophages TF transcript expression levels are elevated in severe but not mild or moderate COVID-19 patients.

CONCLUSIONS

Beyond local lung injury, SARS-CoV-2 infection increases systemic TF (F3) transcript levels and elevates circulating extracellular vesicles that likely contribute to disease-associated coagulation, thrombosis, and related mortality.

An Emerging Role for Type I Interferons as Critical Regulators of Blood Coagulation

Type I interferons (IFNs) are central mediators of anti-viral and anti-bacterial host defence. Detection of microbes by innate immune cells via pattern recognition receptors (PRRs), including Toll-like receptors (TLRs) and cGAS-STING, induces the expression of type I IFN-stimulated genes. Primarily comprising the cytokines IFN-α and IFN-β, type I IFNs act via the type I IFN receptor in an autocrine or exocrine manner to orchestrate rapid and diverse innate immune responses. Growing evidence pinpoints type I IFN signalling as a fulcrum that not only induces blood coagulation as a core feature of the inflammatory response but is also activated by components of the coagulation cascade. In this review, we describe in detail recent studies identifying the type I IFN pathway as a modulator of vascular function and thrombosis. In addition, we profile discoveries showing that thrombin signalling via protease-activated receptors (PARs), which can synergize with TLRs, regulates the host response to infection via induction of type I IFN signalling. Thus, type I IFNs can have both protective (via maintenance of haemostasis) and pathological (facilitating thrombosis) effects on inflammation and coagulation signalling. These can manifest as an increased risk of thrombotic complications in infection and in type I interferonopathies such as systemic lupus erythematosus (SLE) and STING-associated vasculopathy with onset in infancy (SAVI). We also consider the effects on coagulation of recombinant type I IFN therapies in the clinic and discuss pharmacological regulation of type I IFN signalling as a potential mechanism by which aberrant coagulation and thrombosis may be treated therapeutically.

The Tissue Factor Pathway in Cancer: Overview and Role of Heparan Sulfate Proteoglycans

Historically, the only focus on tissue factor (TF) in clinical pathophysiology has been on its function as the initiation of the extrinsic coagulation cascade. This obsolete vessel-wall TF dogma is now being challenged by the findings that TF circulates throughout the body as a soluble form, a cell-associated protein, and a binding microparticle. Furthermore, it has been observed that TF is expressed by various cell types, including T-lymphocytes and platelets, and that certain pathological situations, such as chronic and acute inflammatory states, and cancer, may increase its expression and activity. Transmembrane G protein-coupled protease-activated receptors can be proteolytically cleaved by the TF:FVIIa complex that develops when TF binds to Factor VII (PARs). The TF:FVIIa complex can activate integrins, receptor tyrosine kinases (RTKs), and PARs in addition to PARs. Cancer cells use these signaling pathways to promote cell division, angiogenesis, metastasis, and the maintenance of cancer stem-like cells. Proteoglycans play a crucial role in the biochemical and mechanical properties of the cellular extracellular matrix, where they control cellular behavior via interacting with transmembrane receptors. For TFPI.fXa complexes, heparan sulfate proteoglycans (HSPGs) may serve as the primary receptor for uptake and degradation. The regulation of TF expression, TF signaling mechanisms, their pathogenic effects, and their therapeutic targeting in cancer are all covered in detail here.

Structural and functional properties of the Kunitz-type and C-terminal domains of Amblyomin-X supporting its antitumor activity

Amblyomin-X is a Kunitz-type FXa inhibitor identified through the transcriptome analysis of the salivary gland from Amblyomma sculptum tick. This protein consists of two domains of equivalent size, triggers apoptosis in different tumor cell lines, and promotes regression of tumor growth, and reduction of metastasis. To study the structural properties and functional roles of the N-terminal (N-ter) and C-terminal (C-ter) domains of Amblyomin-X, we synthesized them by solid-phase peptide synthesis, solved the X-Ray crystallographic structure of the N-ter domain, confirming its Kunitz-type signature, and studied their biological properties. We show here that the C-ter domain is responsible for the uptake of Amblyomin-X by tumor cells and highlight the ability of this domain to deliver intracellular cargo by the strong enhancement of the intracellular detection of molecules with low cellular-uptake efficiency (p15) after their coupling with the C-ter domain. In contrast, the N-ter Kunitz domain of Amblyomin-X is not capable of crossing through the cell membrane but is associated with tumor cell cytotoxicity when it is microinjected into the cells or fused to TAT cell-penetrating peptide. Additionally, we identify the minimum length C-terminal domain named F2C able to enter in the SK-MEL-28 cells and induces dynein chains gene expression modulation, a molecular motor that plays a role in the uptake and intracellular trafficking of Amblyomin-X.

The effect of rivaroxaban on biomarkers in blood and plasma: a review of preclinical and clinical evidence

Rivaroxaban is a direct, oral factor Xa inhibitor that is used for the prevention and treatment of various thromboembolic disorders. Several preclinical and clinical studies have utilized specific molecules as biomarkers to investigate the potential role of rivaroxaban beyond its anticoagulant activity and across a range of biological processes. The aim of this review is to summarize the existing evidence regarding the use of blood-based biomarkers to characterize the effects of rivaroxaban on coagulation and other pathways, including platelet activation, inflammation and endothelial effects. After a literature search using PubMed, almost 100 preclinical and clinical studies were identified that investigated the effects of rivaroxaban using molecular biomarkers. In agreement with the preclinical data, clinical studies reported a trend for reduction in the blood concentrations of D-dimers, thrombin-antithrombin complex and prothrombin fragment 1 + 2 following treatment with rivaroxaban in both healthy individuals and those with various chronic conditions. Preclinical and also some clinical studies have also reported a potential impact of rivaroxaban on the concentrations of platelet activation biomarkers (von Willebrand factor, P-selectin and thrombomodulin), endothelial activation biomarkers (matrix metalloproteinase-9, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1) and inflammation biomarkers (interleukin-6, tumor necrosis factor-α and monocyte chemoattractant protein-1). Based on the results of biomarker studies, molecular biomarkers can be used in addition to traditional coagulation assays to increase the understanding of the anticoagulation effects of rivaroxaban. Moreover, there is preliminary evidence to suggest that rivaroxaban may have an impact on the biological pathways of platelet activation, endothelial activation and inflammation; however, owing to paucity of clinical data to investigate the trends reported in preclinical studies, further investigation is required to clarify these observations.

Computational modeling of hypercoagulability in COVID-19

Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has infected more than 100 million people worldwide and claimed millions of lives. While the leading cause of mortality in COVID-19 patients is the hypoxic respiratory failure from acute respiratory distress syndrome, there is accumulating evidence that shows excessive coagulation also increases the fatalities in COVID-19. Thus, there is a pressing demand to understand the association between COVID-19-induced hypercoagulability and the extent of formation of undesired blood clots. Mathematical modeling of coagulation has been used as an important tool to identify novel reaction mechanisms and to identify targets for new drugs. Here, we employ the coagulation factor data of COVID-19 patients reported from published studies as inputs for two mathematical models of coagulation to identify how the concentrations of coagulation factors change in these patients. Our simulation results show that while the levels of many of the abnormal coagulation factors measured in COVID-19 patients promote the generation of thrombin and fibrin, two key components of blood clots, the increased level of fibrinogen and then the reduced level of antithrombin are the factors most responsible for boosting the level of fibrin and thrombin, respectively. Altogether, our study demonstrates the potential of mathematical modeling to identify coagulation factors responsible for the increased clot formation in COVID-19 patients where clinical data is scarce.

Protease-activated receptors in health and disease

Proteases are signaling molecules that specifically control cellular functions by cleaving protease-activated receptors (PARs). The four known PARs are members of the large family of G protein-coupled receptors. These transmembrane receptors control most physiological and pathological processes and are the target of a large proportion of therapeutic drugs. Signaling proteases include enzymes from the circulation; from immune, inflammatory epithelial, and cancer cells; as well as from commensal and pathogenic bacteria. Advances in our understanding of the structure and function of PARs provide insights into how diverse proteases activate these receptors to regulate physiological and pathological processes in most tissues and organ systems. The realization that proteases and PARs are key mediators of disease, coupled with advances in understanding the atomic level structure of PARs and their mechanisms of signaling in subcellular microdomains, has spurred the development of antagonists, some of which have advanced to the clinic. Herein we review the discovery, structure, and function of this receptor system, highlight the contribution of PARs to homeostatic control, and discuss the potential of PAR antagonists for the treatment of major diseases.

Gut-derived low-grade endotoxaemia, atherothrombosis and cardiovascular disease

Systemic inflammation has been suggested to have a pivotal role in atherothrombosis, but the factors that trigger systemic inflammation have not been fully elucidated. Lipopolysaccharide (LPS) is a component of the membrane of Gram-negative bacteria present in the gut that can translocate into the systemic circulation, causing non-septic, low-grade endotoxaemia. Gut dysbiosis is a major determinant of low-grade endotoxaemia via dysfunction of the intestinal barrier scaffold, which is a prerequisite for LPS translocation into the systemic circulation. Experimental studies have demonstrated that LPS is present in atherosclerotic arteries but not in normal arteries. In atherosclerotic plaques, LPS promotes a pro-inflammatory status that can lead to plaque instability and thrombus formation. Low-grade endotoxaemia affects several cell types, including leukocytes, platelets and endothelial cells, leading to inflammation and clot formation. Low-grade endotoxaemia has been described in patients at risk of or with overt cardiovascular disease, in whom low-grade endotoxaemia was associated with atherosclerotic burden and its clinical sequelae. In this Review, we describe the mechanisms favouring the development of low-grade endotoxaemia, focusing on gut dysbiosis and changes in gut permeability; the plausible biological mechanisms linking low-grade endotoxaemia and atherothrombosis; the clinical studies suggesting that low-grade endotoxaemia is a risk factor for cardiovascular events; and the potential therapeutic tools to improve gut permeability and eventually eliminate low-grade endotoxaemia.

Protease- and cell type-specific activation of protease-activated receptor 2 in cutaneous inflammation

BACKGROUND

Protease-activated receptor 2 (PAR2) signaling controls skin barrier function and inflammation, but the roles of immune cells and PAR2-activating proteases in cutaneous diseases are poorly understood.

OBJECTIVE

To dissect PAR2 signaling contributions to skin inflammation with new genetic and pharmacological tools.

METHODS/RESULTS

We found markedly increased numbers of PAR2+ infiltrating myeloid cells in skin lesions of allergic contact dermatitis (ACD) patients and in the skin of contact hypersensitivity (CHS) in mice, a murine ACD model for T cell-mediated allergic skin inflammation. Cell type-specific deletion of PAR2 in myeloid immune cells as well as mutation-induced complete PAR2 cleavage insensitivity significantly reduced skin inflammation and hapten-specific Tc1/Th1 cell response. Pharmacological approaches identified individual proteases involved in PAR2 cleavage and demonstrated a pivotal role of tissue factor (TF) and coagulation factor Xa (FXa) as upstream activators of PAR2 in both the induction and effector phase of CHS. PAR2 mutant mouse strains with differential cleavage sensitivity for FXa versus skin epithelial cell-expressed proteases furthermore uncovered a time-dependent regulation of CHS development with an important function of FXa-induced PAR2 activation during the late phase of skin inflammation.

CONCLUSIONS

Myeloid cells and the TF-FXa-PAR2 axis are key mediators and potential therapeutic targets in inflammatory skin diseases.

GPR97 triggers inflammatory processes in human neutrophils via a macromolecular complex upstream of PAR2 activation

Neutrophils play essential anti-microbial and inflammatory roles in host defense, however, their activities require tight regulation as dysfunction often leads to detrimental inflammatory and autoimmune diseases. Here we show that the adhesion molecule GPR97 allosterically activates CD177-associated membrane proteinase 3 (mPR3), and in conjugation with several protein interaction partners leads to neutrophil activation in humans. Crystallographic and deletion analysis of the GPR97 extracellular region identified two independent mPR3-binding domains. Mechanistically, the efficient binding and activation of mPR3 by GPR97 requires the macromolecular CD177/GPR97/PAR2/CD16b complex and induces the activation of PAR2, a G protein-coupled receptor known for its function in inflammation. Triggering PAR2 by the upstream complex leads to strong inflammatory activation, prompting anti-microbial activities and endothelial dysfunction. The role of the complex in pathologic inflammation is underscored by the finding that both GPR97 and mPR3 are upregulated on the surface of disease-associated neutrophils. In summary, we identify a PAR2 activation mechanism that directs neutrophil activation, and thus inflammation. The PR3/CD177/GPR97/PAR2/CD16b protein complex, therefore, represents a potential therapeutic target for neutrophil-mediated inflammatory diseases.

Studies on activation and regulation of the coagulation cascade in chronic rhinosinusitis with nasal polyps

BACKGROUND

Increased activation of the coagulation cascade and diminished fibrinolysis combine to promote fibrin deposition and polyp formation in chronic rhinosinusitis (CRS) with nasal polyps (CRSwNP). More information is needed concerning mechanisms of coagulation in CRSwNP.

OBJECTIVE

We investigated the mechanisms as well as the initiation and regulation of coagulation cascade activation in CRS.

METHODS

Samples were collected from 135 subjects with CRSwNP, 80 subjects with chronic CRS without nasal polyps (NP), and 65 control subjects. The levels of activated factor X (FXa), prothrombin fragment 1+2 (F1+2), thrombin-antithrombin complex, tissue factor (TF), and TF pathway inhibitor (TFPI) were monitored in CRS by real-time PCR, ELISA, immunohistochemistry, or immunofluorescence. Heteromeric complexes of TF with activated factor VII (FVII) and TF with activated FVII and FXa were assessed by coimmunoprecipitation and Western blotting.

RESULTS

Increased levels of FXa, F1+2, and thrombin-antithrombin complex were detected in NP tissue compared to uncinate tissue from CRS and control subjects. Although free TF protein levels were not increased in NP, immunoprecipitation of TF in NP tissue revealed increased complexes of TF with FVII. Local expression of FVII was detected in sinonasal mucosa, and the ratio of TFPI to FXa was lower in NP tissue.

CONCLUSION

The coagulation cascade is associated with NP compared to control and uncinate tissue from CRS patients, and TF and FVII are produced locally in sinonasal mucosa in patients. TF and FVII can activate the extrinsic coagulation pathway, suggesting that this pathway may activate fibrin deposition in CRSwNP. Reduced formation of the complex of FXa and TFPI in NP may reduce natural suppression of the extrinsic coagulation pathway in CRSwNP.

Role of protease-activated receptor-1 (PAR-1) in the glomerular filtration barrier integrity

Protease-activated receptors (PAR) play an important role in the regulation of cellular function by the coagulation system, and they are activated by thrombin. PAR-1 is expressed in both endothelial cells and podocytes in the kidney. The role of PAR1 in the maintenance of the glomerular filtration barrier is not clear. Anticoagulant-related nephropathy (ARN) is a kidney disease with glomerular hematuria and red blood cell tubular casts. We validated 5/6 nephrectomy (5/6NE) in rats as a model of ARN and had demonstrated that direct thrombin inhibitor (dabigatran) induces ARN. The aim of this study was to investigate the role of PAR-1 in the ARN pathogenesis. 5/6NE rats were treated with dabigatran (150 mg/kg/day), PAR-1 inhibitor SCH79797 (1 and 3 mg/kg/day) and PAR-1 agonist TFLLR-NH2 (0.25 and 0.50 µmol/kg/day) for 7 days. Serum creatinine and hematuria were assessed daily. Kidney morphology was evaluated at the end of the study. In 5/6NE rats treated with either dabigatran or combination with a PAR-1 modulator, there was an elevation in serum creatinine, glomerular hematuria, red blood casts in the tubules, and acute tubular epithelial cell injury. Interestingly, both PAR-1 modulators in a dose-depended manner had similar effects on the serum creatinine levels and hematuria as those of dabigatran. Dabigatran-induced increase in the systolic blood pressure was not affected by PAR-1 modulators. In conclusion, the normal function of PAR-1 is crucial to maintain the glomerular filtration barrier integrity. Either activation or blockage of PAR-1 leads to glomerular hematuria and subsequent acute tubular epithelial cell injury.

Protease-activated receptor-2: Role in asthma pathogenesis and utility as a biomarker of disease severity

PAR₂, a receptor activated by serine proteases, has primarily pro-inflammatory roles in the airways and may play a role in asthma pathogenesis. PAR₂ exerts its effects in the lungs through activation of a variety of airway cells, but also activation of circulating immune cells. There is evidence that PAR₂ expression increases in asthma and other inflammatory diseases, although the regulation of PAR₂ expression is not fully understood. Here we review the available literature on the potential role of PAR₂ in asthma pathogenesis and propose a model of PAR₂-mediated development of allergic sensitization. We also propose, based on our previous work, that PAR₂ expression on peripheral blood monocyte subsets has the potential to serve as a biomarker of asthma severity and/or control.

Venous Thromboembolism in Sepsis: From Bench to Bedside

Septic patients were commonly affected by coagulation disorders; thus, they are at high risk of thrombotic complications. In the last decades, novel knowledge has emerged about the interconnected and reciprocal influence of immune and coagulation systems. This phenomenon is called immunothrombosis, and it indicates an effective response whereby immune cells and the coagulation cascade cooperate to limit pathogen invasion and endothelial damage. When this network becomes dysregulated due to a systemic inflammatory activation, as occurs during sepsis, it can result in pathological thrombosis. Endothelium, platelets and neutrophils are the main characters involved in this process, together with the TF and coagulation cascade, playing a critical role in both the host defense and in thrombogenesis. A deeper understanding of this relationship may allow us to answer the growing need for clinical instruments to establish the thrombotic risk and treatments that consider more the connection between coagulation and inflammation. Heparin remains the principal therapeutical response to this phenomenon, although not sufficiently effective. To date, no other significant alternatives have been found yet. In this review, we discuss the role of sepsis-related inflammation in the development and resolution of venous thromboembolism and its clinical implications, from bench to bedside.

Thrombotic complications in patients with cancer: Advances in pathogenesis, prevention, and treatment—A report from ICTHIC 2021

Venous thromboembolism (VTE) is a common complication in cancer patients, resulting in deep vein thrombosis (DVT) or pulmonary embolism (PE), and is responsible for high morbidity and mortality. This article discusses evidence and future perspectives on pathogenesis and prevention and treatment of thrombotic complications in patients with cancer. In April 2021, international basic researchers and clinicians met for the virtual edition of the 10th International Conference on Thrombosis & Hemostasis Issues in Cancer. Pathogenic mechanisms, markers and scores for risk assessment, diagnosis and therapy issues, current prophylaxis recommendations, and special settings, such as palliative care, pediatrics, and COVID‐19 patients were discussed. Emerging areas of interest in cancer associated VTE are the role of immunotherapy, platelet activation markers, genetic alterations and real‐world systems‐based approaches to prevention and treatment.

Put out the fire: The pleiotropic anti-inflammatory action of non-vitamin K oral anticoagulants

Non-vitamin K antagonist oral anticoagulants (NOACs) should be the preferred anticoagulant strategy for preventing ischemic stroke in patients with atrial fibrillation (AF) at increased thromboembolic risk and for treating deep venous thromboembolism (DVT) in the general population. Beyond their inhibiting action on the activated factor X (FXa) or thrombin (FIIa), NOACs showed some pleiotropic anti-inflammatory effects. The present review aimed to describe the role of FXa and FIIa in the inflammation pathway and the potential anti-inflammatory effects of NOACs.

Mice expressing fluorescent PAR2 reveal that endocytosis mediates colonic inflammation and pain

G protein-coupled receptors (GPCRs) regulate many pathophysiological processes and are major therapeutic targets. The impact of disease on the subcellular distribution and function of GPCRs is poorly understood. We investigated trafficking and signaling of protease-activated receptor 2 (PAR₂) in colitis. To localize PAR₂ and assess redistribution during disease, we generated knockin mice expressing PAR₂ fused to monomeric ultrastable green fluorescent protein (muGFP). PAR₂-muGFP signaled and trafficked normally. PAR₂ messenger RNA was detected at similar levels in Par₂-mugfp and wild-type mice. Immunostaining with a GFP antibody and RNAScope in situ hybridization using F2rl1 (PAR₂) and Gfp probes revealed that PAR₂-muGFP was expressed in epithelial cells of the small and large intestine and in subsets of enteric and dorsal root ganglia neurons. In healthy mice, PAR₂-muGFP was prominently localized to the basolateral membrane of colonocytes. In mice with colitis, PAR₂-muGFP was depleted from the plasma membrane of colonocytes and redistributed to early endosomes, consistent with generation of proinflammatory proteases that activate PAR₂ PAR₂ agonists stimulated endocytosis of PAR₂ and recruitment of Gα_q, Gα_i, and β-arrestin to early endosomes of T84 colon carcinoma cells. PAR₂ agonists increased paracellular permeability of colonic epithelial cells, induced colonic inflammation and hyperalgesia in mice, and stimulated proinflammatory cytokine release from segments of human colon. Knockdown of dynamin-2 (Dnm2), the major colonocyte isoform, and Dnm inhibition attenuated PAR₂ endocytosis, signaling complex assembly and colonic inflammation and hyperalgesia. Thus, PAR₂ endocytosis sustains protease-evoked inflammation and nociception and PAR₂ in endosomes is a potential therapeutic target for colitis.

Protease Activated Receptors: A Pathway to Boosting Mesenchymal Stromal Cell Therapeutic Efficacy in Acute Respiratory Distress Syndrome?

Acute Respiratory Distress Syndrome is the most common cause of respiratory failure among critically ill patients, and its importance has been heightened during the COVID-19 pandemic. Even with the best supportive care, the mortality rate in the most severe cases is 40–50%, and the only pharmacological agent shown to be of possible benefit has been steroids. Mesenchymal stromal cells (MSCs) have been tested in several pre-clinical models of lung injury and been found to have significant therapeutic benefit related to: (a) potent immunomodulation; (b) secretion of epithelial and endothelial growth factors; and (c) augmentation of host defense to infection. Initial translational efforts have shown signs of promise, but the results have not yielded the anticipated outcomes. One potential reason is the relatively low survival of MSCs in inflammatory conditions as shown in several studies. Therefore, strategies to boost the survival of MSCs are needed to enhance their therapeutic effect. Protease-activated receptors (PARs) may represent one such possibility as they are G-protein coupled receptors expressed by MSCs and control several facets of cell behavior. This review summarizes some of the existing literature about PARs and MSCs and presents possible future areas of investigation in order to develop potential, PAR-modified MSCs with enhanced therapeutic efficiency.

Mechanisms of cytokine release syndrome and neurotoxicity of CAR T-cell therapy and associated prevention and management strategies

Chimeric antigen receptor (CAR) T-cell therapy has yielded impressive outcomes and transformed treatment algorithms for hematological malignancies. To date, five CAR T-cell products have been approved by the US Food and Drug Administration (FDA). Nevertheless, some significant toxicities pose great challenges to the development of CAR T-cell therapy, most notably cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). Understanding the mechanisms underlying these toxicities and establishing prevention and treatment strategies are important. In this review, we summarize the mechanisms underlying CRS and ICANS and provide potential treatment and prevention strategies.

Coagulation, Protease-Activated Receptors, and Diabetic Kidney Disease: Lessons from eNOS-Deficient Mice

Endothelial nitric oxide synthase (eNOS) dysfunction is known to exacerbate the progression and prognosis of diabetic kidney disease (DKD). One of the mechanisms through which this is achieved is that low eNOS levels are associated with hypercoagulability, which promotes kidney injury. In the extrinsic coagulation cascade, the tissue factor (factor III) and downstream coagulation factors, such as active factor X (FXa), exacerbate inflammation through activation of the protease-activated receptors (PARs). Recently, it has been shown that the lack of or reduced eNOS expression in diabetic mice, as a model of advanced DKD, increases renal tissue factor levels and PAR1 and 2 expression in their kidneys. Furthermore, pharmaceutical inhibition or genetic deletion of coagulation factors or PARs ameliorated inflammation in DKD in mice lacking eNOS. In this review, we summarize the relationship between eNOS, coagulation, and PARs and propose a novel therapeutic option for the management of patients with DKD.

The Prognostic Value of ADAMTS-13 and von Willebrand Factor in COVID-19 Patients: Prospective Evaluation by Care Setting

Background: Endothelial dysfunction, coupled with inflammation, induces thrombo-inflammation. In COVID-19, this process is believed to be associated with clinical severity. Von Willebrand factor (VWF), and a disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS-13), are strong markers of endothelial dysfunction. We evaluated the impact of the VWF/ADAMTS-13 fraction on COVID-19 severity and prognosis. Materials and methods: A cohort study including 74 COVID-19 patients, with 22 admitted to the intensive care unit (ICU) and 52 to the medical ward (MW), was carried out. We also evaluated, in a group of 54 patients who were prospectively observed, whether variations in VWF/ADAMTS-13 correlated with the degree of severity and routine blood parameters. Results: A VWF:RCo/ADAMTS-13 fraction above 6.5 predicted in-hospital mortality in the entire cohort. At admission, a VWF:RCo/ADAMTS-13 fraction above 5.7 predicted admission to the ICU. Furthermore, the VWF:RCo/ADAMTS-13 fraction directly correlated with C-reactive protein (CRP) (Spearman r: 0.51, p < 0.0001) and D-dimer (Spearman r: 0.26, p = 0.03). In the prospective cohort, dynamic changes in VWF:RCo/ADAMTS-13 and the CRP concentration were directly correlated (Spearman r, p = 0.0014). This relationship was significant in both groups (ICU: p = 0.006; MW: p = 0.02).Conclusions: The present findings show that in COVID-19, the VWF/ADAMTS-13 fraction predicts in-hospital mortality. The VWF/ADAMTS-13 fraction may be a helpful tool to monitor COVID-19 patients throughout hospitalization.

Biomaterial and cellular implants:foreign surfaces where immunity and coagulation meet

Exposure of blood to a foreign surface in the form of a diagnostic or therapeutic biomaterial device or implanted cells or tissues, elicits an immediate, evolutionarily conserved thrombo-inflammatory response by the host. Primarily designed to protect against invading organisms following an injury, this innate response features instantaneous activation of several blood-borne, highly interactive and well-orchestrated cascades and cellular events that limit bleeding, destroy and eliminate the foreign substance/cells, and promote healing and a return to homeostasis via delicately balanced regenerative processes. In the setting of blood-contacting synthetic or natural biomaterials and implantation of foreign cells/tissues, innate responses are robust, albeit highly context-specific. Unfortunately, they tend to be less than adequately regulated by the host's natural anti-coagulant/anti-inflammatory pathways, thereby jeopardizing the functional integrity of the device, as well as the health of the host. Strategies to achieve biocompatibility with a sustained return to homeostasis, particularly while the device remains in situ and functional, continue to elude scientists and clinicians. In this review, some of the complex mechanisms by which biomaterials and cellular transplants provide a "hub" for activation and amplification of coagulation and immunity - thrombo-inflammation - will be discussed, with a view toward the development of innovative means of overcoming the innate challenges.

The development of proteinase-activated receptor-2 modulators and the challenges involved

Protease-activated receptor-2 (PAR2) has been extensively studied since its discovery in the mid-1990. Despite the advances in understanding PAR2 pharmacology, it has taken almost 25 years for the first inhibitor to reach clinical trials, and so far, no PAR2 antagonist has been approved for human use. Research has employed classical approaches to develop a wide array of PAR2 agonists and antagonists, consisting of peptides, peptoids and antibodies to name a few, with a surge in patent applications over this period. Recent breakthroughs in PAR2 structure determination has provided a unique insight into proposed PAR2 ligand binding sites. Publication of the first crystal structures of PAR2 resolved in complex with two novel non-peptide small molecule antagonists (AZ8838 and AZ3451) revealed two distinct binding pockets, originally presumed to be allosteric sites, with a PAR2 antibody (Fab3949) used to block tethered ligand engagement with the peptide-binding domain of the receptor. Further studies have proposed orthosteric site occupancy for AZ8838 as a competitive antagonist. One company has taken the first PAR2 antibody (MEDI0618) into phase I clinical trial (NCT04198558). While this first-in-human trial is at the early stages of the assessment of safety, other research into the structural characterisation of PAR2 is still ongoing in an attempt to identify new ways to target receptor activity. This review will focus on the development of novel PAR2 modulators developed to date, with an emphasis placed upon the advances made in the pharmacological targeting of PAR2 activity as a strategy to limit chronic inflammatory disease.

Factor VIIa Regulates the Level of Cell-Surface Tissue Factor through Separate but Cooperative Mechanisms

Simple Summary

Under normal conditions, blood coagulation is suppressed to prevent thrombosis. However, during inflammatory conditions such as injury or disease conditions, the protein “tissue factor (TF)” is expressed on the surface of the cells and is also released into the bloodstream within cell-derived vesicles called “microvesicles”. TF appears first at the site of trauma which makes TF suitable for determining the extent of damage and instructing cells to proliferate and repair, or if severely damaged, to die. The relationship between cancer and thrombosis was reported in the early part of the 19th century. Cancer cells and particularly those with aggressive tendencies have the ability to produce, and then optimise the amount of TF on the cell, in order to maximise the pro-survival and proliferative properties of this protein. This study has demonstrated some of the mechanisms by which cells control excessive amounts of TF, to levels ideal for tumour survival and growth.

Abstract

Procoagulant activity of tissue factor (TF) in response to injury or inflammation is accompanied with cellular signals which determine the fate of cells. However, to prevent excessive signalling, TF is rapidly dissipated through release into microvesicles, and/or endocytosis. To elucidate the mechanism by which TF signalling may become moderated on the surface of cells, the associations of TF, fVII/fVIIa, PAR2 and caveolin-1 on MDA-MB-231, BxPC-3 and 786-O cells were examined and compared to that in cells lacking either fVII/fVIIa or TF. Furthermore, the localisation of labelled-recombinant TF with cholesterol-rich lipid rafts was explored on the surface of primary human blood dermal endothelial cells (HDBEC). Finally, by disrupting the caveolae on the surface of HDBEC, the outcome on TF-mediated signalling was examined. The association between TF and PAR2 was found to be dependent on the presence of fVIIa. Interestingly, the presence of TF was not pre-requisite for the association between fVII/fVIIa and PAR2 but was significantly enhanced by TF, which was also essential for the proliferative signal. Supplementation of HDBEC with exogenous TF resulted in early release of fVII/fVIIa from caveolae, followed by re-sequestration of TF-fVIIa. Addition of labelled-TF resulted in the accumulation within caveolin-1-containing cholesterol-rich regions and was also accompanied with the increased assimilation of cell-surface fVIIa. Disruption of the caveolae/rafts in HDBEC using MβCD enhanced the TF-mediated cellular signalling. Our data supports a hypothesis that cells respond to the exposure to TF by moderating the signalling activities as well as the procoagulant activity of TF, through incorporation into the caveolae/lipid rafts.

Thrombosis in Psoriasis: Cutaneous Cytokine Production as a Potential Driving Force of Haemostatic Dysregulation and Subsequent Cardiovascular Risk

Psoriasis (PsO) is a common T cell-mediated inflammatory disorder of the skin with an estimated prevalence of 2%. The condition manifests most commonly as erythematous plaques covered with scales. The aetiology of PsO is multifactorial and disease initiation involves interactions between environmental factors, susceptibility genes, and innate and adaptive immune responses. The underlying pathology is mainly driven by interleukin-17. In addition, various inflammatory mediators from specific T helper (T_H) cell subsets, namely T_H1, T_H17, and T_H22, are overexpressed in cutaneous lesions and may also be detected in the peripheral blood of psoriatic patients. Moreover, these individuals are also at greater risk, compared to the general population, of developing multiple comorbid conditions. Cardiovascular disease (CVD) has been recognised as a prominent comorbidity of PsO. A potential mechanism contributing to this association may be the presence of a hypercoagulable state in these individuals. Inflammation and coagulation are closely related. The presence of chronic, low-grade systemic inflammation may promote thrombosis – one of the major determinants of CVD. A pro-inflammatory milieu may induce the expression of tissue factor, augment platelet activity, and perturb the vascular endothelium. Altogether, these changes will result in a prothrombotic state. In this review, we describe the aetiology of PsO, as well as the pathophysiology of the condition. We also consider its relationship to CVD. Given the systemic inflammatory nature of PsO, we evaluate the potential contribution of prominent inflammatory mediators (implicated in PsO pathogenesis) to establishing a prothrombotic state in psoriatic patients.

CRS-related coagulopathy in BCMA targeted CAR-T therapy: a retrospective analysis in a phase I/II clinical trial

Chimeric antigen receptor (CAR) T-cell therapy that targets B-cell maturation antigen (BCMA) has shown promising effects in the treatment of patients with refractory/relapsed multiple myeloma (R/R MM) patients. In this retrospective analysis of phase I/II clinical trial (ChiCTR1800017404), 37 patients with R/R MM received their first BCMA-targeted CAR T-cells following lymphodepletion chemotherapy. The response rate was high (97%), while accompanied by a high incidence of adverse events including coagulation dysfunction. Of 37 patients, all (100%) had cytokine release syndrome (CRS) and 34 (91%) developed at least one abnormal coagulation parameter. The values of coagulation parameters were positively correlated with the severity of CRS as well as with the levels of some cytokines, such as interleukin (IL)-6, IL-10, and interferon (IFN)-γ, etc. Furthermore, levels of the plasma tissue factor (TF), Factor X (FX), Factor XII (FXII), and P-selectin also showed a positive correlation with severity of CRS as well as some specific cytokines, which indicates that these factors are likely to play important roles in CRS-related coagulopathy. Our study suggests that there exists relationship in some extent between coagulation disorder and CRS. Moreover, coagulation dysfunction can be managed with daily monitoring and early intervention despite high incidence.

Antisense Tissue Factor Oligodeoxynucleotides Protected Diethyl Nitrosamine/Carbon Tetrachloride-Induced Liver Fibrosis Through Toll Like Receptor4-Tissue Factor-Protease Activated Receptor1 Pathway

Tissue factor (TF) is a blood coagulation factor that has several roles in many non-coagulant pathways involved in different pathological conditions such as angiogenesis, inflammation and fibrogenesis. Coagulation and inflammation are crosslinked with liver fibrosis where protease-activated receptor1 (PAR1) and toll-like receptor4 (TLR4) play a key role. Antisense oligodeoxynucleotides are strong modulators of gene expression. In the present study, antisense TF oligodeoxynucleotides (TFAS) was evaluated in treating liver fibrosis via suppression of TF gene expression. Liver fibrosis was induced in rats by a single administration of N-diethyl nitrosamine (DEN, 200 mg/kg; i. p.) followed by carbon tetrachloride (CCl4, 3 ml/kg; s. c.) once weekly for 6 weeks. Following fibrosis induction, liver TF expression was significantly upregulated along with liver enzymes activities and liver histopathological deterioration. Alpha smooth muscle actin (α-SMA) and transforming growth factor-1beta (TGF-1β) expression, tumor necrosis factor-alpha (TNF-α) and hydroxyproline content and collagen deposition were significantly elevated in the liver. Blocking of TF expression by TFAS injection (2.8 mg/kg; s. c.) once weekly for 6 weeks significantly restored liver enzymes activities and improved histopathological features along with decreasing the elevated α-SMA, TGF-1β, TNF-α, hydroxyproline and collagen. Moreover, TFAS decreased the expression of both PAR1 and TLR4 that were induced by liver fibrosis. In conclusion, we reported that blockage of TF expression by TFAS improved inflammatory and fibrotic changes associated with CCl4+DEN intoxication. In addition, we explored the potential crosslink between the TF, PAR1 and TLR4 in liver fibrogenesis. These findings offer a platform on which recovery from liver fibrosis could be mediated through targeting TF expression.

Tissue factor promotes airway pathological features through epithelial-mesenchymal transition of bronchial epithelial cells in mice with house dust mite-induced asthma

It has recently been shown that expression levels of tissue factor (TF) are high in the serum and peripheral blood mononuclear cells of patients with asthma. However, whether TF impacts airway inflammation and remodelling in asthma remains unknown. The aim of this study was to investigate the effect of TF in asthma airway inflammation and remodelling using a house dust mite (HDM)-induced chronic asthma model and human bronchial epithelial (16HBE) cells. A chronic asthma model was constructed in BALB/c mice by the intranasal instillation of HDM. Mice were treated with short hairpin TF (shTF), and airway inflammation and remodelling features of asthma and epithelial-mesenchymal transition (EMT) were assessed. 16HBE cells were induced by transforming growth factor-β1 (TGF-β1) and HDM in the presence or absence of shTF; then, EMT markers and invasion and migration ability were determined. TF expression increased in the lung tissue and 16HBE cells when exposed to HDM. TF downregulation in the lung significantly reduced airway hyperresponsiveness, eosinophil inflammation, the EMT process, and levels of interleukin (IL)-4, IL-6, IL-13, and TGF-β1 in bronchoalveolar lavage fluid of asthmatic mice. Moreover, TF downregulation inhibited migration and incursion and decreased the expression levels of fibronectin 1 and TGF-β1, but increased the expression of E-cadherin in HDM- and TGF-β1-stimulated 16HBE cells. These results demonstrated that TF promoted airway pathological features by enhancing the EMT of bronchial epithelial cells both in vitro and in mice with house dust mite-induced asthma.

Platelets, immune cells and the coagulation cascade; friend or foe of the circulating tumour cell?

Cancer cells that transit from primary tumours into the circulatory system are known as circulating tumour cells (CTCs). These cancer cells have unique phenotypic and genotypic characteristics which allow them to survive within the circulation, subsequently extravasate and metastasise. CTCs have emerged as a useful diagnostic tool using "liquid biopsies" to report on the metastatic potential of cancers. However, CTCs by their nature interact with components of the blood circulatory system on a constant basis, influencing both their physical and morphological characteristics as well as metastatic capabilities. These properties and the associated molecular profile may provide critical diagnostic and prognostic capabilities in the clinic. Platelets interact with CTCs within minutes of their dissemination and are crucial in the formation of the initial metastatic niche. Platelets and coagulation proteins also alter the fate of a CTC by influencing EMT, promoting pro-survival signalling and aiding in evading immune cell destruction. CTCs have the capacity to directly hijack immune cells and utilise them to aid in CTC metastatic seeding processes. The disruption of CTC clusters may also offer a strategy for the treatment of advance staged cancers. Therapeutic disruption of these heterotypical interactions as well as direct CTC targeting hold great promise, especially with the advent of new immunotherapies and personalised medicines. Understanding the molecular role that platelets, immune cells and the coagulation cascade play in CTC biology will allow us to identify and characterise the most clinically relevant CTCs from patients. This will subsequently advance the clinical utility of CTCs in cancer diagnosis/prognosis.

PAR2 Activation on Human Kidney Tubular Epithelial Cells Induces Tissue Factor Synthesis, That Enhances Blood Clotting

Coagulation abnormalities and increased risk of atherothrombosis are common in patients with chronic kidney diseases (CKD). Mechanisms that alter renal hemostasis and lead to thrombotic events are not fully understood. Here we show that activation of protease activated receptor-2 (PAR2) on human kidney tubular epithelial cells (HTECs), induces tissue factor (TF) synthesis and secretion that enhances blood clotting. PAR-activating coagulation-associated protease (thrombin), as well as specific PAR2 activators (matriptase, trypsin, or synthetic agonist 2f-LIGRLO-NH₂ (2F), induced TF synthesis and secretion that were potently inhibited by PAR2 antagonist, I-191. Thrombin-induced TF was also inhibited by a PAR1 antagonist, Vorapaxar. Peptide activators of PAR1, PAR3, and PAR4 failed to induce TF synthesis. Differential centrifugation of the 2F-conditoned medium sedimented the secreted TF, together with the exosome marker ALG-2 interacting protein X (ALIX), indicating that secreted TF was associated with extracellular vesicles. 2F-treated HTEC conditioned medium significantly enhanced blood clotting, which was prevented by pre-incubating this medium with an antibody for TF. In summary, activation of PAR2 on HTEC stimulates synthesis and secretion of TF that induces blood clotting, and this is attenuated by PAR2 antagonism. Thrombin-induced TF synthesis is at least partly mediated by PAR1 transactivation of PAR2. These findings reveal how underlying hemostatic imbalances might increase thrombosis risk and subsequent chronic fibrin deposition in the kidneys of patients with CKD and suggest PAR2 antagonism as a potential therapeutic strategy for intervening in CKD progression.

Platelet Membrane Receptor Proteolysis: Implications for Platelet Function

The activities of adhesion and signaling receptors in platelets are controlled by several mechanisms. An important way of regulation is provided by proteolytic cleavage of several of these receptors, leading to either a gain or a loss of platelet function. The proteases involved are of different origins and types: (i) present as precursor in plasma, (ii) secreted into the plasma by activated platelets or other blood cells, or (iii) intracellularly activated and cleaving cytosolic receptor domains. We provide a comprehensive overview of the proteases acting on the platelet membrane. We describe how these are activated, which are their target proteins, and how their proteolytic activity modulates platelet functions. The review focuses on coagulation-related proteases, plasmin, matrix metalloproteinases, ADAM(TS) isoforms, cathepsins, caspases, and calpains. We also describe how the proteolytic activities are determined by different platelet populations in a thrombus and conversely how proteolysis contributes to the formation of such populations.

A serine loop in tissue factor mediates substrate selectivity by the tissue factor-factor VIIa complex

Essentials How the tissue factor-factor VIIa complex selects between different substrates is not well understood. We investigated a serine loop in tissue factor and its role in substrate selectivity. The tissue factor serine loop is selective for factor X over factor IX. Substrate selectivity is facilitated by differential regulation of the nearby tissue factor exosite. ABSTRACT: Background The tissue factor-factor VIIa (TF-FVIIa) complex is the physiologic activator of blood clotting and plays a major role in many thrombotic diseases. TF-FVIIa drives clotting through proteolytic cleavage of its major protein substrates, factor IX (FIX) and factor X (FX). However, it remains unclear how TF-FVIIa exhibits selectivity between these substrates. We previously showed that TF residues adjacent to the putative substrate binding site of TF ("exosite") facilitate FX activation, but the role of these residues in substrate selectivity had not been tested. Objectives We hypothesized that a TF serine loop (residues S160-S163) mediates substrate selectivity by the TF-FVIIa complex. Methods We generated TF serine loop and exosite mutants. The mutants were tested in FIX and FX enzyme activation assays as well as thrombin generation assays. Results Changes in the length of the serine loop affected rates of FIX and FX activation very differently. FX activation was decreased by up to 200-fold when the loop length was changed by just one residue. In contrast, FIX activation was largely unaffected. Substrate selectivity was also detected in thrombin generation assays. Activation assays with TF serine loop and exosite double mutants revealed that the serine loop has no effect on the exosite during FIX activation. In contrast, the serine loop regulates the exosite during FX activation. Conclusions Our results provide new insights into how the TF-FVIIa complex actively selects between its major protein substrates, which is mediated by a TF serine loop.

The PAR2 inhibitor I-287 selectively targets Gαq and Gα12/13 signaling and has anti-inflammatory effects

Protease-activated receptor-2 (PAR2) is involved in inflammatory responses and pain, therefore representing a promising therapeutic target for the treatment of immune-mediated inflammatory diseases. However, as for other GPCRs, PAR2 can activate multiple signaling pathways and those involved in inflammatory responses remain poorly defined. Here, we describe a new selective and potent PAR2 inhibitor (I-287) that shows functional selectivity by acting as a negative allosteric regulator on Gα_q and Gα_12/13 activity and their downstream effectors, while having no effect on G_i/o signaling and βarrestin2 engagement. Such selective inhibition of only a subset of the pathways engaged by PAR2 was found to be sufficient to block inflammation in vivo. In addition to unraveling the PAR2 signaling pathways involved in the pro-inflammatory response, our study opens the path toward the development of new functionally selective drugs with reduced liabilities that could arise from blocking all the signaling activities controlled by the receptor.

Avet et al. characterize I-287, an inhibitor to protease-activated receptor 2 using BRET-assays. They find that I-287 selectively inhibits Gα_q and Gα_12/13 without affecting the activation of G_i/o or the recruitment of βarrestin2 and that it blocks inflammation in vitro and in vivo.

Thromboinflammatory mechanisms in sickle cell disease - challenging the hemostatic balance

Sickle cell disease (SCD) is an inherited hemoglobinopathy that is caused by the presence of abnormal hemoglobin S (HbS) in red blood cells, leading to alterations in red cell properties and shape, as the result of HbS dexoygenation and subsequent polymerization. SCD pathophysiology is characterized by chronic inflammatory processes, triggered by hemolytic and vaso-occlusive events, which lead to the varied complications, organ damage and elevated mortality seen in individuals with the disease. In association with activation of the endothelium and leukocytes, hemostatic alterations and thrombotic events are well-documented in SCD. Here we discuss the role for inflammatory pathways in modulating coagulation and inducing platelet activation in SCD, due to tissue factor activation, adhesion molecule expression, inflammatory mediator production and the induction of innate immune responses, amongst other mechanisms. Thromboinflammatory pathways may play a significant role in some of the major complications of SCD, such as stroke, venous thromboembolism and possibly acute chest syndrome, besides exacerbating the chronic inflammation and cellular interactions that trigger vaso-occlusion, ischemia-reperfusion processes, and eventually organ damage.

The domino effect triggered by the tethered ligand of the protease activated receptors

Protease activated receptors (PARs) are G-protein coupled receptors (GPCRs) that have a unique activation mechanism. Unlike other GPCRs that can be activated by free ligands, under physiological conditions, PARs are activated by the tethered ligand, which is a part of their N-terminus that is unmasked by proteolysis. It has been 30 years since the first member of the family, PAR1, was identified. In this review, we will discuss this unique tethered ligand mediate receptor activation of PARs in detail: how they interact with the proteases, the complex structural rearrangement of the receptors upon activation, and the termination of the signaling. We also summarize the structural studies of the PARs and how single nucleotide polymorphisms impact the receptor reactivity. Finally, we review the current strategies for inhibiting PAR function with therapeutic targets for anti-thrombosis. The focus of this review is PAR1 and PAR4 as they are the thrombin signal mediators on human platelets and therapeutics targets. We also include the structural studies of PAR2 as it informs the mechanism of action for PARs in general.

The Emerging Threat of (Micro)Thrombosis in COVID-19 and Its Therapeutic Implications

The recent emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the ensuing global pandemic has presented a health emergency of unprecedented magnitude. Recent clinical data has highlighted that coronavirus disease 2019 (COVID-19) is associated with a significant risk of thrombotic complications ranging from microvascular thrombosis, venous thromboembolic disease, and stroke. Importantly, thrombotic complications are markers of severe COVID-19 and are associated with multiorgan failure and increased mortality. The evidence to date supports the concept that the thrombotic manifestations of severe COVID-19 are due to the ability of SARS-CoV-2 to invade endothelial cells via ACE-2 (angiotensin-converting enzyme 2), which is expressed on the endothelial cell surface. However, in patients with COVID-19 the subsequent endothelial inflammation, complement activation, thrombin generation, platelet, and leukocyte recruitment, and the initiation of innate and adaptive immune responses culminate in immunothrombosis, ultimately causing (micro)thrombotic complications, such as deep vein thrombosis, pulmonary embolism, and stroke. Accordingly, the activation of coagulation (eg, as measured with plasma D-dimer) and thrombocytopenia have emerged as prognostic markers in COVID-19. Given thrombotic complications are central determinants of the high mortality rate in COVID-19, strategies to prevent thrombosis are of critical importance. Several antithrombotic drugs have been proposed as potential therapies to prevent COVID-19-associated thrombosis, including heparin, FXII inhibitors, fibrinolytic drugs, nafamostat, and dipyridamole, many of which also possess pleiotropic anti-inflammatory or antiviral effects. The growing awareness and mechanistic understanding of the prothrombotic state of COVID-19 patients are driving efforts to more stringent diagnostic screening for thrombotic complications and to the early institution of antithrombotic drugs, for both the prevention and therapy of thrombotic complications. The shifting paradigm of diagnostic and treatment strategies holds significant promise to reduce the burden of thrombotic complications and ultimately improve the prognosis for patients with COVID-19.

Trypsin activity governs increased susceptibility to pancreatitis in mice expressing human PRSS1R122H

Currently, an effective targeted therapy for pancreatitis is lacking. Hereditary pancreatitis (HP) is a heritable, autosomal-dominant disorder with recurrent acute pancreatitis (AP) progressing to chronic pancreatitis (CP) and a markedly increased risk of pancreatic cancer. In 1996, mutations in PRSS1 were linked to the development of HP. Here, we developed a mouse model by inserting a full-length human PRSS1R122H gene, the most commonly mutated gene in human HP, into mice. Expression of PRSS1R122H protein in the pancreas markedly increased stress signaling pathways and exacerbated AP. After the attack of AP, all PRSS1R122H mice had disease progression to CP, with similar histologic features as those observed in human HP. By comparing PRSS1R122H mice with PRSS1WT mice, as well as enzymatically inactivated Dead-PRSS1R122H mice, we unraveled that increased trypsin activity is the mechanism for R122H mutation to sensitize mice to the development of pancreatitis. We further discovered that trypsin inhibition, in combination with anticoagulation therapy, synergistically prevented progression to CP in PRSS1R122H mice. These animal models help us better understand the complex nature of this disease and provide powerful tools for developing and testing novel therapeutics for human pancreatitis.