Plasminogen-stimulated inflammatory cytokine production by airway smooth muscle cells is regulated by annexin A2

Sensory neurons: An integrated component of innate immunity

The sensory nervous system possesses the ability to integrate exogenous threats and endogenous signals to mediate downstream effector functions. Sensory neurons have been shown to activate or suppress host defense and immunity against pathogens, depending on the tissue and disease state. Through this lens, pro- and anti-inflammatory neuroimmune effector functions can be interpreted as evolutionary adaptations by host or pathogen. Here, we discuss recent and impactful examples of neuroimmune circuitry that regulate tissue homeostasis, autoinflammation, and host defense. Apparently paradoxical or conflicting reports in the literature also highlight the complexity of neuroimmune interactions that may depend on tissue- and microbe-specific cues. These findings expand our understanding of the nuanced mechanisms and the greater context of sensory neurons in innate immunity.

Role of Perturbated Hemostasis in MASLD and Its Correlation with Adipokines

The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) continues to rise, making it one of the most prevalent chronic liver disorders. MASLD encompasses a range of liver pathologies, from simple steatosis to metabolic dysfunction-associated steatohepatitis (MASH) with inflammation, hepatocyte damage, and fibrosis. Interestingly, the liver exhibits close intercommunication with fatty tissue. In fact, adipose tissue could contribute to the etiology and advancement of MASLD, acting as an endocrine organ that releases several hormones and cytokines, with the adipokines assuming a pivotal role. The levels of adipokines in the blood are altered in people with MASLD, and recent research has shed light on the crucial role played by adipokines in regulating energy expenditure, inflammation, and fibrosis in MASLD. However, MASLD disease is a multifaceted condition that affects various aspects of health beyond liver function, including its impact on hemostasis. The alterations in coagulation mechanisms and endothelial and platelet functions may play a role in the increased vulnerability and severity of MASLD. Therefore, more attention is being given to imbalanced adipokines as causative agents in causing disturbances in hemostasis in MASLD. Metabolic inflammation and hepatic injury are fundamental components of MASLD, and the interrelation between these biological components and the hemostasis pathway is delineated by reciprocal influences, as well as the induction of alterations. Adipokines have the potential to serve as the shared elements within this complex interrelationship. The objective of this review is to thoroughly examine the existing scientific knowledge on the impairment of hemostasis in MASLD and its connection with adipokines, with the aim of enhancing our comprehension of the disease.

Tranexamic acid: Beyond antifibrinolysis

Tranexamic acid (TXA) is a popular antifibrinolytic drug widely used in hemorrhagic trauma patients and cardiovascular, orthopedic, and gynecological surgical patients. TXA binds plasminogen and prevents its maturation to the fibrinolytic enzyme plasmin. A number of studies have demonstrated the broad life-saving effects of TXA in trauma, superior to those of other antifibrinolytic agents. Besides preventing fibrinolysis and blood loss, TXA has been reported to suppress posttraumatic inflammation and edema. Although the efficiency of TXA transcends simple inhibition of fibrinolysis, little is known about its mechanisms of action besides the suppression of plasmin maturation. Understanding the broader effects of TXA at the cell, organ, and organism levels are required to elucidate its potential mechanisms of action transcending antifibrinolytic activity. In this article, we provide a brief review of the current clinical use of TXA and then focus on the effects of TXA beyond antifibrinolytics such as its anti-inflammatory activity, protection of the endothelial and epithelial monolayers, stimulation of mitochondrial respiration, and suppression of melanogenesis.

Identification of ANXA2 on epithelial cells as a new receptor for secretory IgA using immunoprecipitation and mass spectrometry

Secretory immunoglobulin A plays an important role in the protection against exogenous pathogens and antigens, but it has also been reported to have pathogenic potential. We previously found that secretory immunoglobulin A accumulated in the peripheral lungs during idiopathic pulmonary fibrosis and that transferrin receptor/CD71 was partially involved in secretory immunoglobulin A-induced inflammatory cytokine production in A549 cells. This study aimed to identify the receptor responsible for the induction of cytokine production by secretory immunoglobulin A-stimulated airway epithelial cells. To this end, immunoprecipitation followed by time-of-flight mass spectrometry and peptide mass fingerprinting were performed and Annexin A2 was detected as a novel receptor for secretory immunoglobulin A. Enzyme-linked immunosorbent assay demonstrated binding of secretory immunoglobulin A to Annexin A2, and flow cytometry showed robust expression of Annexin A2 on the surface of BEAS-2B cells, A549 cells, and normal human bronchial/tracheal epithelial cells. Experiments in A549 cells using Annexin A2 small interfering RNA and neutralizing antibodies suggested that Annexin A2 was partially involved in the production of interleukin-8/CXCL8 and C-C motif chemokine ligand 2/monocyte chemoattractant protein-1 induced by secretory immunoglobulin A. Immunohistochemistry using lung sections revealed clear expression of Annexin A2 on airway epithelial cells, although the staining remained equivalent in idiopathic pulmonary fibrosis, asthma, and healthy control lungs. In conclusion, we identified that Annexin A2 expressed in airway epithelial cells is a novel receptor for secretory immunoglobulin A, which is involved in cytokine synthesis.

Molecular Insights on the Possible Role of Annexin A2 in COVID-19 Pathogenesis and Post-Infection Complications

Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) has infected >235 million people and killed over 4.8 million individuals worldwide. Although vaccines have been developed for prophylactic management, there are no clinically proven antivirals to treat the viral infection. Continuous efforts are being made all over the world to develop effective drugs but these are being delayed by periodic outbreak of mutated SARS-CoV-2 and a lack of knowledge of molecular mechanisms underlying viral pathogenesis and post-infection complications. In this regard, the involvement of Annexin A2 (AnxA2), a lipid-raft related phospholipid-binding protein, in SARS-CoV-2 attachment, internalization, and replication has been discussed. In addition to the evidence from published literature, we have performed in silico docking of viral spike glycoprotein and RNA-dependent RNA polymerase with human AnxA2 to find the molecular interactions. Overall, this review provides the molecular insights into a potential role of AnxA2 in the SARS-CoV-2 pathogenesis and post-infection complications, especially thrombosis, cytokine storm, and insulin resistance.

Fibrinolysis and COVID-19: A plasmin paradox

The COVID-19 pandemic has provided many challenges in the field of thrombosis and hemostasis. Among these is a novel form of coagulopathy that includes exceptionally high levels of D-dimer. D-dimer is a marker of poor prognosis, but does this also imply a causal relationship? These spectacularly raised D-dimer levels may actually signify the failing attempt of the fibrinolytic system to remove fibrin and necrotic tissue from the lung parenchyma, being consumed or overwhelmed in the process. Indeed, recent studies suggest that increasing fibrinolytic activity might offer hope for patients with critical disease and severe respiratory failure. However, the fibrinolytic system can also be harnessed by coronavirus to promote infectivity and where antifibrinolytic measures would also seem appropriate. Hence, there is a clinical paradox where plasmin formation can be either deleterious or beneficial in COVID-19, but not at the same time. Hence, it all comes down to timing.

Role of Autophagy in Lung Inflammation

Autophagy is a cellular recycling system found in almost all types of eukaryotic organisms. The system is made up of a variety of proteins which function to deliver intracellular cargo to lysosomes for formation of autophagosomes in which the contents are degraded. The maintenance of cellular homeostasis is key in the survival and function of a variety of human cell populations. The interconnection between metabolism and autophagy is extensive, therefore it has a role in a variety of different cell functions. The disruption or dysfunction of autophagy in these cell types have been implicated in the development of a variety of inflammatory diseases including asthma. The role of autophagy in non-immune and immune cells both lead to the pathogenesis of lung inflammation. Autophagy in pulmonary non-immune cells leads to tissue remodeling which can develop into chronic asthma cases with long term effects. The role autophagy in the lymphoid and myeloid lineages in the pathology of asthma differ in their functions. Impaired autophagy in lymphoid populations have been shown, in general, to decrease inflammation in both asthma and inflammatory disease models. Many lymphoid cells rely on autophagy for effector function and maintained inflammation. In stark contrast, autophagy deficient antigen presenting cells have been shown to have an activated inflammasome. This is largely characterized by a T_H17 response that is accompanied with a much worse prognosis including granulocyte mediated inflammation and steroid resistance. The cell specificity associated with changes in autophagic flux complicates its targeting for amelioration of asthmatic symptoms. Differing asthmatic phenotypes between T_H2 and T_H17 mediated disease may require different autophagic modulations. Therefore, treatments call for a more cell specific and personalized approach when looking at chronic asthma cases. Viral-induced lung inflammation, such as that caused by SARS-CoV-2, also may involve autophagic modulation leading to inflammation mediated by lung resident cells. In this review, we will be discussing the role of autophagy in non-immune cells, myeloid cells, and lymphoid cells for their implications into lung inflammation and asthma. Finally, we will discuss autophagy's role viral pathogenesis, immunometabolism, and asthma with insights into autophagic modulators for amelioration of lung inflammation.

Tissue-type plasminogen activator neutralizes LPS but not protease-activated receptor-mediated inflammatory responses to plasmin

Tissue-type plasminogen activator (tPA) activates fibrinolysis and also suppresses innate immune system responses to LPS in bone marrow-derived macrophages (BMDMs) and in vivo in mice. The objective of this study was to assess the activity of tPA as a regulator of macrophage physiology in the presence of plasmin. Enzymatically active and enzymatically inactive (EI) tPA appeared to comprehensively block the response to LPS in BMDMs, including expression of proinflammatory cytokines such as TNF-α and IL-1β and anti-inflammatory cytokines such as IL-10 and IL-1 receptor antagonist. The activity of EI-tPA as an LPS response modifier was conserved in the presence of plasminogen. By contrast, in BMDMs treated with tPA and plasminogen or preactivated plasmin, in the presence or absence of LPS, increased proinflammatory cytokine expression was observed and tPA failed to reverse the response. Plasmin independently activated NF-κB, ERK1/2, c-Jun N-terminal kinase, and p38 mitogen-activated protein kinase in BMDMs, which is characteristic of proinflammatory stimuli. Plasmin-induced cytokine expression was blocked by ε-aminocaproic acid, aprotinin, and inhibitors of the known plasmin substrate, Protease-activated receptor-1 (PAR-1), but not by N-methyl-d-aspartate receptor inhibitor, which blocks the effects of tPA on macrophages. Cytokine expression by BMDMs treated with the PAR-1 agonist, TFLLR, was not inhibited by EI-tPA, possibly explaining why EI-tPA does not inhibit macrophage responses to plasmin and providing evidence for specificity in the ability of tPA to oppose proinflammatory stimuli. Regulation of innate immunity by the fibrinolysis system may reflect the nature of the stimulus and a balance between the potentially opposing activities of tPA and plasmin.

TRPC3 overexpression and intervention in airway smooth muscle of ovalbumin-induced hyperresponsiveness and remodeling

Transient receptor potential canonical channel 3 (TRPC3) proteins function as non-voltage-gated Ca²⁺ -permeable channels and play divergent roles in many processes of pathophysiology. The purpose of this study was to determine the relationship between TRPC3 expression and airway hyperresponsiveness and remodeling in ovalbumin-induced asthmatic Kunming mice. Mice were sensitized and challenged by ovalbumin to establish asthmatic model. Hematoxylin-eosin staining, hydroxyproline assay, and isometric tracheal ring force measurement were used to evaluate airway remodeling and hyperresponsiveness in asthmatic mice. Western blot was performed to detect the expression of TRPC3 proteins. MTT assay was used to measure the proliferation of airway smooth muscle cells. TRPC3 protein expression increased in airway smooth muscle of asthmatic mice. GdCl₃ , a nonspecific TRPC blocker, attenuated the contractile force of airway smooth muscle. Fetal bovine serum stimulated airway smooth muscle cells proliferation and augmented TRPC3 protein expression. Both TRPC3 blockade by GdCl₃ or specific TRPC3 antibodies and gene silencing by siRNA inhibited the proliferation of airway smooth muscle cells. In contrast, the current drugs treatment for asthma such as Dexamethasone and Aminophylline had no effects on TRPC3 protein overexpression. Therefore, TRPC3 protein overexpression may be involved in airway smooth muscle hyperresponsiveness and remodeling in asthmatic mice, providing evidence for a new direction of asthma pathogenesis research and a new target for drug intervention.

Nasal protein profiles in work-related asthma caused by different exposures

BACKGROUND

The mechanisms of work-related asthma (WRA) are incompletely delineated. Nasal cell samples may be informative about processes in the lower airways. Our aim was to determine the nasal protein expression profiles of WRA caused by different kind of exposures.

METHODS

We collected nasal brush samples from 82 nonsmoking participants, including healthy controls and WRA patients exposed to (i) protein allergens, (ii) isocyanates and (iii) welding fumes the day after relevant exposure. The proteome changes in samples were analysed by two-dimensional difference gel electrophoresis, and the differentially regulated proteins found were identified by mass spectrometry. Immunological comparison was carried out using Western blot.

RESULTS

We detected an average of 2500 spots per protein gel. Altogether, 228 protein spots were chosen for identification, yielding 77 different proteins. Compared to the controls, exposure to protein allergens had the largest effects on the proteome. Hierarchical clustering revealed that protein allergen- and isocyanate-related asthma had similar profiles, whereas asthma related to welding fumes differed. The highly overrepresented functional categories in the asthma groups were defence response, protease inhibitor activity, inflammatory and calcium signalling, complement activation and cellular response to oxidative stress. Immunological analysis confirmed the found abundance differences in galectin 10 and protein S100-A9 between the groups.

CONCLUSIONS

Work-related asthma patients exposed to protein allergens and isocyanates elicit similar nasal proteome responses and the profiles of welders and healthy controls were alike. Revealed biological activities of the protein expression changes are associated with allergic inflammation and asthma.

The fibrogenic actions of the coagulant and plasminogen activation systems in pulmonary fibrosis

Fibrosis causes irreversible damage to lung structure and function in restrictive lung diseases such as idiopathic pulmonary fibrosis (IPF). Extravascular coagulation involving fibrin formation in the intra-alveolar compartment is postulated to have a pivotal role in the development of pulmonary fibrosis, serving as a provisional matrix for migrating fibroblasts. Furthermore, proteases of the coagulation and plasminogen activation (plasminergic) systems that form and breakdown fibrin respectively directly contribute to pulmonary fibrosis. The coagulants, thrombin and factor Xa (FXa) evoke fibrogenic effects via cleavage of the N-terminus of protease-activated receptors (PARs). Whilst the formation and activity of plasmin, the principle plasminergic mediator is suppressed in the airspaces of patients with IPF, localized increases are likely to occur in the lung interstitium. Plasmin-evoked proteolytic activation of factor XII (FXII), matrix metalloproteases (MMPs) and latent, matrix-bound growth factors such as epidermal growth factor (EGF) indirectly implicate plasmin in pulmonary fibrosis. Another plasminergic protease, urokinase plasminogen activator (uPA) is associated with regions of fibrosis in the remodelled lung of IPF patients and elicits fibrogenic activity via binding its receptor (uPAR). Plasminogen activator inhibitor-1 (PAI-1) formed in the injured alveolar epithelium also contributes to pulmonary fibrosis in a manner that involves vitronectin binding. This review describes the mechanisms by which components of the two systems primarily involved in fibrin homeostasis contribute to interstitial fibrosis, with a particular focus on IPF. Selectively targeting the receptor-mediated mechanisms of coagulant and plasminergic proteases may limit pulmonary fibrosis, without the bleeding complications associated with conventional anti-coagulant and thrombolytic therapies.

The neuropeptide NMU amplifies ILC2-driven allergic lung inflammation

Type 2 innate lymphoid cells (ILC2s) both contribute to mucosal homeostasis and initiate pathologic inflammation in allergic asthma. However, the signals that direct ILC2s to promote homeostasis versus inflammation are unclear. To identify such molecular cues, we profiled mouse lung-resident ILCs using single-cell RNA sequencing at steady state and after in vivo stimulation with the alarmin cytokines IL-25 and IL-33. ILC2s were transcriptionally heterogeneous after activation, with subpopulations distinguished by expression of proliferative, homeostatic and effector genes. The neuropeptide receptor Nmur1 was preferentially expressed by ILC2s at steady state and after IL-25 stimulation. Neuromedin U (NMU), the ligand of NMUR1, activated ILC2s in vitro, and in vivo co-administration of NMU with IL-25 strongly amplified allergic inflammation. Loss of NMU-NMUR1 signalling reduced ILC2 frequency and effector function, and altered transcriptional programs following allergen challenge in vivo. Thus, NMUR1 signalling promotes inflammatory ILC2 responses, highlighting the importance of neuro-immune crosstalk in allergic inflammation at mucosal surfaces.

Annexin A2 contributes to lung injury and fibrosis by augmenting factor Xa fibrogenic activity

In lung injury and disease, including idiopathic pulmonary fibrosis (IPF), extravascular factor X is converted into factor Xa (FXa), a coagulant protease with fibrogenic actions. Extracellular annexin A2 binds to FXa, augmenting activation of the protease-activated receptor-1 (PAR-1). In this study, the contribution of annexin A2 in lung injury and fibrosis was investigated. Annexin A2 immunoreactivity was observed in regions of fibrosis, including those associated with fibroblasts in lung tissue of IPF patients. Furthermore, annexin A2 was detected in the conditioned media and an EGTA membrane wash of human lung fibroblast (LF) cultures. Incubation with human plasma (5% vol/vol) or purified FXa (15–50 nM) evoked fibrogenic responses in LF cultures, with FXa increasing interleukin-6 (IL-6) production and cell number by 270 and 46%, respectively ( P < 0.05, n = 5–8). The fibrogenic actions of plasma or FXa were attenuated by the selective FXa inhibitor apixaban (10 μM, or antibodies raised against annexin A2 or PAR-1 (2 μg/ml). FXa-stimulated LFs from IPF patients ( n = 6) produced twice as much IL-6 as controls ( n = 10) ( P < 0.05), corresponding with increased levels of extracellular annexin A2. Annexin A2 gene deletion in mice reduced bleomycin-induced increases in bronchoalveolar lavage fluid (BALF) IL-6 levels and cell number (* P < 0.05; n = 4–12). Lung fibrogenic gene expression and dry weight were reduced by annexin A2 gene deletion, but lung levels of collagen were not. Our data suggest that annexin A2 contributes to lung injury and fibrotic disease by mediating the fibrogenic actions of FXa. Extracellular annexin A2 is a potential target for the treatment of IPF.

Collagen-binding nanoparticles for extracellular anti-inflammatory peptide delivery decrease platelet activation, promote endothelial migration, and suppress inflammation

Peripheral artery disease is an atherosclerotic stenosis in the peripheral vasculature that is typically treated via percutaneous transluminal angioplasty. Deployment of the angioplasty balloon damages the endothelial layer, exposing the underlying collagen and allowing for the binding and activation of circulating platelets which initiate an inflammatory cascade leading to eventual restenosis. Here, we report on collagen-binding sulfated poly(N-isopropylacrylamide) nanoparticles that are able to target to the denuded endothelium. Once bound, these nanoparticles present a barrier that reduces cellular and platelet adhesion to the collagenous surface by 67% in whole blood and 59% in platelet-rich plasma under biologically relevant shear rates. In vitro studies indicate that the collagen-binding nanoparticles are able to load and release therapeutic quantities of anti-inflammatory peptides, with the particles reducing inflammation in endothelial and smooth muscle cells by 30% and 40% respectively. Once bound to collagen, the nanoparticles increased endothelial migration while avoiding uptake by smooth muscle cells, indicating that they may promote regeneration of the damaged endothelium while remaining anchored to the collagenous matrix and locally releasing anti-inflammatory peptides into the injured area. Combined, these collagen-binding nanoparticles have the potential to reduce inflammation, and the subsequent restenosis, while simultaneously promoting endothelial regeneration following balloon angioplasty.

STATEMENT OF SIGNIFICANCE

In this manuscript, we present our work on the development and characterization of a novel temperature sensitive collagen-binding nanoparticle system. We demonstrate that when bound to a collagenous matrix, the nanoparticles are able to promote endothelial migration while avoiding cellular uptake. We also show that the nanoparticles are able to reduce inflammation via the release of anti-inflammatory peptides which, when combined with its ability to inhibit platelet binding, could lead to reduced intimal hyperplasia following balloon angioplasty. The drug delivery platform presented represents a unique dual therapy biomaterial wherein the nanoparticle itself plays a crucial role in the system's overall therapeutic potential while simultaneously releasing anti-inflammatory peptides.

The Membrane Phospholipid Binding Protein Annexin A2 Promotes Phagocytosis and Nonlytic Exocytosis of Cryptococcus neoformans and Impacts Survival in Fungal Infection

Cryptococcus neoformans is a fungal pathogen with a unique intracellular pathogenic strategy that includes nonlytic exocytosis, a phenomenon whereby fungal cells are expunged from macrophages without lysing the host cell. The exact mechanism and specific proteins involved in this process have yet to be completely defined. Using murine macrophages deficient in the membrane phospholipid binding protein, annexin A2 (ANXA2), we observed a significant decrease in both phagocytosis of yeast cells and the frequency of nonlytic exocytosis. Cryptococcal cells isolated from Anxa2-deficient (Anxa2(-/-)) bone marrow-derived macrophages and lung parenchyma displayed significantly larger capsules than those isolated from wild-type macrophages and tissues. Concomitantly, we observed significant differences in the amount of reactive oxygen species produced between Anxa2(-/-) and Anxa2(+/+) macrophages. Despite comparable fungal burden, Anxa2(-/-) mice died more rapidly than wild-type mice when infected with C. neoformans, and Anxa2(-/-) mice exhibited enhanced inflammatory responses, suggesting that the reduced survival reflected greater immune-mediated damage. Together, these findings suggest a role for ANXA2 in the control of cryptococcal infection, macrophage function, and fungal morphology.

The Coagulant Factor Xa Induces Protease-Activated Receptor-1 and Annexin A2-Dependent Airway Smooth Muscle Cytokine Production and Cell Proliferation

During asthma exacerbation, plasma circulating coagulant factor X (FX) enters the inflamed airways and is activated (FXa). FXa may have an important role in asthma, being involved in thrombin activation and an agonist of protease-activated receptor-1 (PAR-1). Extracellular annexin A2 and integrins are also implicated in PAR-1 signaling. In this study, the potential role of PAR-1 in mediating the effects of FXa on human airway smooth muscle (ASM) cell cytokine production and proliferation was investigated. FXa (5-50 nM), but not FX, stimulated increases in ASM IL-6 production and cell number after 24- and 48-hour incubation, respectively (P < 0.05; n = 5). FXa (15 nM) also stimulated increases in the levels of mRNA for cytokines (IL-6), cell cycle-related protein (cyclin D1), and proremodeling proteins (FGF-2, PDGF-B, CTGF, SM22, and PAI-1) after 3-hour incubation (P < 0.05; n = 4). The actions of FXa were insensitive to inhibition by hirudin (1 U/ml), a selective thrombin inhibitor, but were attenuated by SCH79797 (100 nM), a PAR-1 antagonist, or Cpd 22 (1 μM), an inhibitor of integrin-linked kinase. The selective targeting of PAR-1, annexin A2, or β1-integrin by small interfering RNA and/or by functional blocking antibodies also attenuated FXa-evoked responses. In contrast, the targeting of annexin A2 did not inhibit thrombin-stimulated ASM function. In airway biopsies of patients with asthma, FXa and annexin A2 were detected in the ASM bundle by immunohistochemistry. These findings establish FXa as a potentially important asthma mediator, stimulating ASM function through actions requiring PAR-1 and annexin A2 and involving integrin coactivation.

Exhaled breath condensate annexin A5 levels in exercise-induced bronchoconstriction in asthma: A preliminary study

BACKGROUND AND OBJECTIVE

The pathogenesis of exercise-induced bronchoconstriction (EIB) in asthma is incompletely understood. The role of exhaled breath condensate (EBC) annexin A5, which is an anti-inflammatory mediator, has not been investigated. The purpose of this study is to evaluate EBC annexin A5 levels in EIB in asthmatic children.

METHODS

Two groups of children were enrolled in this study: asthmatic children with positive (n=11) and negative (n=7) responses to exercise. The levels of pre- and post-exercise EBC annexin A5 were determined with using enzyme-linked immunosorbent assay (ELISA).

RESULTS

We observed significant higher pre-exercise EBC annexin A5 levels in the challenge test negative children than in the challenge test positive children (p<0.05). No significant difference was observed in the post-exercise EBC annexin A5 levels between the groups (p>0.05). Also, no significant difference was observed between pre- and post-exercise EBC annexin A5 levels within each group (p>0.05). There was an inverse correlation between annexin A5 levels and a reduction in forced expiratory volume at one second percent (FEV1%) (p=0.009, r=-0.598).

CONCLUSIONS

Our preliminary study showed that EBC annexin A5 may have a possible preventive role in EIB in asthma. Annexin A5 and related compounds may provide novel therapeutic approaches to the treatment of EIB in asthma.

The inflammatory actions of coagulant and fibrinolytic proteases in disease

Aside from their role in hemostasis, coagulant and fibrinolytic proteases are important mediators of inflammation in diseases such as asthma, atherosclerosis, rheumatoid arthritis, and cancer. The blood circulating zymogens of these proteases enter damaged tissue as a consequence of vascular leak or rupture to become activated and contribute to extravascular coagulation or fibrinolysis. The coagulants, factor Xa (FXa), factor VIIa (FVIIa), tissue factor, and thrombin, also evoke cell-mediated actions on structural cells (e.g., fibroblasts and smooth muscle cells) or inflammatory cells (e.g., macrophages) via the proteolytic activation of protease-activated receptors (PARs). Plasmin, the principle enzymatic mediator of fibrinolysis, also forms toll-like receptor-4 (TLR-4) activating fibrin degradation products (FDPs) and can release latent-matrix bound growth factors such as transforming growth factor-β (TGF-β). Furthermore, the proteases that convert plasminogen into plasmin (e.g., urokinase plasminogen activator) evoke plasmin-independent proinflammatory actions involving coreceptor activation. Selectively targeting the receptor-mediated actions of hemostatic proteases is a strategy that may be used to treat inflammatory disease without the bleeding complications of conventional anticoagulant therapies. The mechanisms by which proteases of the coagulant and fibrinolytic systems contribute to extravascular inflammation in disease will be considered in this review.

Regulation of pulmonary inflammation by mesenchymal cells

Pulmonary inflammation and tissue remodelling are common elements of chronic respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and pulmonary hypertension (PH). In disease, pulmonary mesenchymal cells not only contribute to tissue remodelling, but also have an important role in pulmonary inflammation. This review will describe the immunomodulatory functions of pulmonary mesenchymal cells, such as airway smooth muscle (ASM) cells and lung fibroblasts, in chronic respiratory disease. An important theme of the review is that pulmonary mesenchymal cells not only respond to inflammatory mediators, but also produce their own mediators, whether pro-inflammatory or pro-resolving, which influence the quantity and quality of the lung immune response. The notion that defective pro-inflammatory or pro-resolving signalling in these cells potentially contributes to disease progression is also discussed. Finally, the concept of specifically targeting pulmonary mesenchymal cell immunomodulatory function to improve therapeutic control of chronic respiratory disease is considered.