Serine protease inhibitors nafamostat mesilate and gabexate mesilate attenuate allergen-induced airway inflammation and eosinophilia in a murine model of asthma

Airborne indoor allergen serine proteases and their contribution to sensitisation and activation of innate immunity in allergic airway disease

Common airborne allergens (pollen, animal dander and those from fungi and insects) are the main triggers of type I allergic disorder in the respiratory system and are associated with allergic rhinitis, allergic asthma, as well as immunoglobulin E (IgE)-mediated allergic bronchopulmonary aspergillosis. These allergens promote IgE crosslinking, vasodilation, infiltration of inflammatory cells, mucosal barrier dysfunction, extracellular matrix deposition and smooth muscle spasm, which collectively cause remodelling of the airways. Fungus and insect (house dust mite and cockroaches) indoor allergens are particularly rich in proteases. Indeed, more than 40 different types of aeroallergen proteases, which have both IgE-neutralising and tissue-destructive activities, have been documented in the Allergen Nomenclature database. Of all the inhaled protease allergens, 85% are classed as serine protease activities and include trypsin-like, chymotrypsin-like and collagenolytic serine proteases. In this article, we review and compare the allergenicity and proteolytic effect of allergen serine proteases as listed in the Allergen Nomenclature and MEROPS databases and highlight their contribution to allergic sensitisation, disruption of the epithelial barrier and activation of innate immunity in allergic airways disease. The utility of small-molecule inhibitors of allergen serine proteases as a potential treatment strategy for allergic airways disease will also be discussed.

The Role of the Nuclear Factor-Kappa B (NF-κB) Pathway in SARS-CoV-2 Infection

COVID-19 is a global health threat caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and is associated with a significant increase in morbidity and mortality. The present review discusses nuclear factor-kappa B (NF-κB) activation and its potential therapeutical role in treating COVID-19. COVID-19 pathogenesis, the major NF-κB pathways, and the involvement of NF-κB in SARS-CoV-2 have been detailed. Specifically, NF-κB activation and its impact on managing COVID-19 has been discussed. As a central player in the immune and inflammatory responses, modulating NF-κB activation could offer a strategic avenue for managing SARS-CoV-2 infection. Understanding the NF-κB pathway's role could aid in developing treatments against SARS-CoV-2. Further investigations into the intricacies of NF-κB activation are required to reveal effective therapeutic strategies for managing and combating the SARS-CoV-2 infection and COVID-19.

House dust mite allergens, store-operated Ca2+ channels and asthma

The house dust mite is the principal source of aero-allergen worldwide. Exposure to mite-derived allergens is associated with the development of asthma in susceptible individuals, and the majority of asthmatics are allergic to the mite. Mite-derived allergens are functionally diverse and activate multiple cell types within the lung that result in chronic inflammation. Allergens activate store-operated Ca2+ release-activated Ca2+ (CRAC) channels, which are widely expressed in multiple cell types within the lung that are associated with the pathogenesis of asthma. Opening of CRAC channels stimulates Ca2+ -dependent transcription factors, including nuclear factor of activated T cells and nuclear factor-κB, which drive expression of a plethora of pro-inflammatory cytokines and chemokines that help to sustain chronic inflammation. Here, I describe drivers of asthma, properties of mite-derived allergens, how the allergens are recognized by cells, the signalling pathways used by the receptors and how these are transduced into functional effects, with a focus on CRAC channels. In vivo experiments that demonstrate the effectiveness of targeting CRAC channels as a potential new therapy for treating mite-induced asthma are also discussed, in tandem with other possible approaches.

Multicenter, single-blind, randomized controlled study of the efficacy and safety of favipiravir and nafamostat mesilate in patients with COVID-19 pneumonia

OBJECTIVES

To evaluate the efficacy and safety of nafamostat combined with favipiravir for the treatment of COVID-19.

METHODS

We conducted a multicenter, randomized, single-blind, placebo-controlled, parallel assignment study in hospitalized patients with mild-to-moderate COVID-19 pneumonia. Patients were randomly assigned to receive favipiravir alone (n = 24) or nafamostat with favipiravir (n = 21). The outcomes included changes in the World Health Organization clinical progression scale score, time to improvement in body temperature, and improvement in oxygen saturation (SpO₂).

RESULTS

There was no significant difference in the changes in the clinical progression scale between nafamostat with favipiravir and favipiravir alone groups (median, -0.444 vs -0.150, respectively; least-squares mean difference, -0.294; P = 0.364). The time to improvement in body temperature was significantly shorter in the combination group (5.0 days; 95% confidence interval, 4.0-7.0) than in the favipiravir group (9.0 days; 95% confidence interval, 7.0-18.0; P =0.009). The changes in SpO₂ were greater in the combination group than in the favipiravir group (0.526% vs -1.304%, respectively; least-squares mean difference, 1.831; P = 0.022). No serious adverse events or deaths were reported, but phlebitis occurred in 57.1% of the patients in the combination group.

CONCLUSION

Although our study showed no differences in clinical progression, earlier defervescence, and recovery of SpO₂ were observed in the combination group.

Nafamostat has anti-asthmatic effects associated with suppressed pro-inflammatory gene expression, eosinophil infiltration and airway hyperreactivity

Introduction

Asthma is characterized by an imbalance between proteases and their inhibitors. Hence, an attractive therapeutic option could be to interfere with asthma-associated proteases. Here we exploited this option by assessing the impact of nafamostat, a serine protease inhibitor known to neutralize mast cell tryptase.

Methods

Nafamostat was administered in a mouse model for asthma based on sensitization by house dust mite (HDM) extract, followed by the assessment of effects on airway hyperreactivity, inflammatory parameters and gene expression.

Results

We show that nafamostat efficiently suppressed the airway hyperreactivity in HDM-sensitized mice. This was accompanied by reduced infiltration of eosinophils and lymphocytes to the airways, and by lower levels of pro-inflammatory compounds within the airway lumen. Further, nafamostat had a dampening impact on goblet cell hyperplasia and smooth muscle layer thickening in the lungs of HDM-sensitized animals. To obtain deeper insight into the underlying mechanisms, a transcriptomic analysis was conducted. This revealed, as expected, that the HDM sensitization caused an upregulated expression of numerous pro-inflammatory genes. Further, the transcriptomic analysis showed that nafamostat suppressed the levels of multiple pro-inflammatory genes, with a particular impact on genes related to asthma.

Discussion

Taken together, this study provides extensive insight into the ameliorating effect of nafamostat on experimental asthma, and our findings can thereby provide a basis for the further evaluation of nafamostat as a potential therapeutic agent in human asthma.

Molecular and Immunomodulatory Actions of New Antiasthmatic Agents: Exploring the Diversity of Biologics in Th2 Endotype Asthma

Asthma is a major respiratory disorder characterised by chronic inflammation and airway remodelling. It affects about 1-8% of the global population and is responsible for over 461,000 deaths annually. Until recently, the pharmacotherapy of severe asthma involved high doses of inhaled corticosteroids in combination with β-agonist for prolonged action, including theophylline, leukotriene antagonist or anticholinergic yielding limited benefit. Although the use of newer agents to target Th2 asthma endotypes has improved therapeutic outcomes in severe asthmatic conditions, there seems to be a paucity of understanding the diverse mechanisms through which these classes of drugs act. This article delineates the molecular and immunomodulatory mechanisms of action of new antiasthmatic agents currently being trialled in preclinical and clinical studies to remit asthmatic conditions. The ultimate goal in developing antiasthmatic agents is based on two types of approaches: either anti-inflammatory or bronchodilators. Biologic and most small molecules have been shown to modulate specific asthma endotypes, targeting thymic stromal lymphopoietin, tryptase, spleen tyrosine kinase (Syk), Janus kinase, PD-L1/PD-L2, GATA-3, and CD38 for the treatment and management of Th2 endotype asthma.

Nafamostat mesylate as a broad-spectrum candidate for the treatment of flavivirus infections by targeting envelope proteins

Epidemics caused by flaviviruses occur globally; however, no antiviral drugs treating flaviviruses infections have yet been developed. Nafamostat (NM) is a protease inhibitor approved for pancreatitis and anti-coagulation. The anti-flavivirus potential of NM has yet to be determined. Here, utilizing in vitro and in vivo infection assays, we present that NM effectively inhibits Zika virus (ZIKV) and other flaviviruses in vitro. NM inhibited the production of ZIKV viral RNA and proteins originating from Asia and African lineage in human-, mouse- and monkey-derived cell lines and the in vivo anti-ZIKV efficacy of NM was verified. Mode-of-action analysis using time-of-drug-addition assay, infectivity inhibition assay, surface plasmon resonance assay, and molecular docking revealed that NM interacted with viral particles and blocked the early stage of infection by targeting the domain III of ZIKV envelope protein. Analysing the anti-flavivirus effects of NM-related compounds suggested that the antiviral effect depended on the unique structure of NM. These findings suggest the potential use of NM as an anti-flavivirus candidate, and a novel drug design approach targeting the flavivirus envelope protein.

Pulmonary Eosinophils at the Center of the Allergic Space-Time Continuum

Eosinophils are typically a minority population of circulating granulocytes being released from the bone-marrow as terminally differentiated cells. Besides their function in the defense against parasites and in promoting allergic airway inflammation, regulatory functions have now been attributed to eosinophils in various organs. Although eosinophils are involved in the inflammatory response to allergens, it remains unclear whether they are drivers of the asthma pathology or merely recruited effector cells. Recent findings highlight the homeostatic and pro-resolving capacity of eosinophils and raise the question at what point in time their function is regulated. Similarly, eosinophils from different physical locations display phenotypic and functional diversity. However, it remains unclear whether eosinophil plasticity remains as they develop and travel from the bone marrow to the tissue, in homeostasis or during inflammation. In the tissue, eosinophils of different ages and origin along the inflammatory trajectory may exhibit functional diversity as circumstances change. Herein, we outline the inflammatory time line of allergic airway inflammation from acute, late, adaptive to chronic processes. We summarize the function of the eosinophils in regards to their resident localization and time of recruitment to the lung, in all stages of the inflammatory response. In all, we argue that immunological differences in eosinophils are a function of time and space as the allergic inflammatory response is initiated and resolved.

The find of COVID-19 vaccine: Challenges and opportunities

Severe acute respiratory syndrome coronavirus (SARS-CoV-2), a novel corona virus, causing COVID-19 with Flu-like symptoms is the first alarming pandemic of the third millennium. SARS-CoV-2 belongs to beta coronavirus as Middle East respiratory syndrome coronavirus (MERS-CoV). Pandemic COVID-19 owes devastating mortality and destructively exceptional consequences on Socio-Economics life around the world. Therefore, the current review is redirected to the scientific community to owe comprehensive visualization about SARS-CoV-2 to tackle the current pandemic. As systematically shown through the current review, it indexes unmet medical problem of COVID-19 in view of public health and vaccination discovery for the infectious SARS-CoV-2; it is currently under-investigational therapeutic protocols, and next possible vaccines. Furthermore, the review extensively reports the precautionary measures to achieve" COVID-19/Flatten the curve". It is concluded that vaccines formulation within exceptional no time in this pandemic is highly recommended, via following the same protocols of previous pandemics; MERS-CoV and SARS-CoV, and excluding some initial steps of vaccination development process.

Effective drugs used to combat SARS-CoV-2 infection and the current status of vaccines

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a causal factor of the coronavirus disease 2019 (COVID-19). Drug repurposing, portraying patented drugs as a successful drug development technique, could shorten the period and minimize costs relative to de novo drug exploration. Recently several drugs have been used as anti-SARS-CoV-2 such as Remdesivir, Favipiravir, Hydroxychloroquine, Azithromycin, Lopinavir/Ritonavir, Nafamostat mesylate and so on. Despite such efforts, there is currently no successful broad-spectrum antiviral countermeasures to combat SARS-CoV-2 or possibly potential CoVs pandemic. Therefore it is desperately important to recognize and test widely efficient, reliable anti-CoV therapies now and in the future. Remdesivir and Favipiravir were more promising despite having side effects; it had prominent efficacy and efficiency while still not yet approved as the official anti-viral drug for SARS CoV-2. In this review, we summarizes the current drug and vaccine discovery status against SARS-CoV-2, predicting that these efforts will help create effective drugs and vaccines for SARS-CoV-2.

Targeting Crucial Host Factors of SARS-CoV-2

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread worldwide since its first incidence in Wuhan, China, in December 2019. Although the case fatality rate of COVID-19 appears to be lower than that of SARS and Middle East respiratory syndrome (MERS), the higher transmissibility of SARS-CoV-2 has caused the total fatality to surpass other viral diseases, reaching more than 1 million globally as of October 6, 2020. The rate at which the disease is spreading calls for a therapy that is useful for treating a large population. Multiple intersecting viral and host factor targets involved in the life cycle of the virus are being explored. Because of the frequent mutations, many coronaviruses gain zoonotic potential, which is dependent on the presence of cell receptors and proteases, and therefore the targeting of the viral proteins has some drawbacks, as strain-specific drug resistance can occur. Moreover, the limited number of proteins in a virus makes the number of available targets small. Although SARS-CoV and SARS-CoV-2 share common mechanisms of entry and replication, there are substantial differences in viral proteins such as the spike (S) protein. In contrast, targeting cellular factors may result in a broader range of therapies, reducing the chances of developing drug resistance. In this Review, we discuss the role of primary host factors such as the cell receptor angiotensin-converting enzyme 2 (ACE2), cellular proteases of S protein priming, post-translational modifiers, kinases, inflammatory cells, and their pharmacological intervention in the infection of SARS-CoV-2 and related viruses.

The Anticoagulant Nafamostat Potently Inhibits SARS-CoV-2 S Protein-Mediated Fusion in a Cell Fusion Assay System and Viral Infection In Vitro in a Cell-Type-Dependent Manner

Although infection by SARS-CoV-2, the causative agent of coronavirus pneumonia disease (COVID-19), is spreading rapidly worldwide, no drug has been shown to be sufficiently effective for treating COVID-19. We previously found that nafamostat mesylate, an existing drug used for disseminated intravascular coagulation (DIC), effectively blocked Middle East respiratory syndrome coronavirus (MERS-CoV) S protein-mediated cell fusion by targeting transmembrane serine protease 2 (TMPRSS2), and inhibited MERS-CoV infection of human lung epithelium-derived Calu-3 cells. Here we established a quantitative fusion assay dependent on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) S protein, angiotensin I converting enzyme 2 (ACE2) and TMPRSS2, and found that nafamostat mesylate potently inhibited the fusion while camostat mesylate was about 10-fold less active. Furthermore, nafamostat mesylate blocked SARS-CoV-2 infection of Calu-3 cells with an effective concentration (EC)50 around 10 nM, which is below its average blood concentration after intravenous administration through continuous infusion. On the other hand, a significantly higher dose (EC50 around 30 mM) was required for VeroE6/TMPRSS2 cells, where the TMPRSS2-independent but cathepsin-dependent endosomal infection pathway likely predominates. Together, our study shows that nafamostat mesylate potently inhibits SARS-CoV-2 S protein-mediated fusion in a cell fusion assay system and also inhibits SARS-CoV-2 infection in vitro in a cell-type-dependent manner. These findings, together with accumulated clinical data regarding nafamostat's safety, make it a likely candidate drug to treat COVID-19.

Immune response in COVID-19: addressing a pharmacological challenge by targeting pathways triggered by SARS-CoV-2

To date, no vaccines or effective drugs have been approved to prevent or treat COVID-19 and the current standard care relies on supportive treatments. Therefore, based on the fast and global spread of the virus, urgent investigations are warranted in order to develop preventive and therapeutic drugs. In this regard, treatments addressing the immunopathology of SARS-CoV-2 infection have become a major focus. Notably, while a rapid and well-coordinated immune response represents the first line of defense against viral infection, excessive inflammatory innate response and impaired adaptive host immune defense may lead to tissue damage both at the site of virus entry and at systemic level. Several studies highlight relevant changes occurring both in innate and adaptive immune system in COVID-19 patients. In particular, the massive cytokine and chemokine release, the so-called "cytokine storm", clearly reflects a widespread uncontrolled dysregulation of the host immune defense. Although the prospective of counteracting cytokine storm is compelling, a major limitation relies on the limited understanding of the immune signaling pathways triggered by SARS-CoV-2 infection. The identification of signaling pathways altered during viral infections may help to unravel the most relevant molecular cascades implicated in biological processes mediating viral infections and to unveil key molecular players that may be targeted. Thus, given the key role of the immune system in COVID-19, a deeper understanding of the mechanism behind the immune dysregulation might give us clues for the clinical management of the severe cases and for preventing the transition from mild to severe stages.

The emerging role of mast cell proteases in asthma

It is now well established that mast cells (MCs) play a crucial role in asthma. This is supported by multiple lines of evidence, including both clinical studies and studies on MC-deficient mice. However, there is still only limited knowledge of the exact effector mechanism(s) by which MCs influence asthma pathology. MCs contain large amounts of secretory granules, which are filled with a variety of bioactive compounds including histamine, cytokines, lysosomal hydrolases, serglycin proteoglycans and a number of MC-restricted proteases. When MCs are activated, e.g. in response to IgE receptor cross-linking, the contents of their granules are released to the exterior and can cause a massive inflammatory reaction. The MC-restricted proteases include tryptases, chymases and carboxypeptidase A3, and these are expressed and stored at remarkably high levels. There is now emerging evidence supporting a prominent role of these enzymes in the pathology of asthma. Interestingly, however, the role of the MC-restricted proteases is multifaceted, encompassing both protective and detrimental activities. Here, the current knowledge of how the MC-restricted proteases impact on asthma is reviewed.

Comparing the Protection Imparted by Different Fraction Extracts of Garlic (Allium sativum L.) against Der p-Induced Allergic Airway Inflammation in Mice

Garlic (Allium sativum L.) has been used extensively as a food ingredient and medicinally, but the effect on asthmatic airway inflammation has not been studied in detail. We accordingly explored the protective effects exerted by various garlic fraction extracts against airway inflammation with Dermatophagoides pteronyssinus (Der p)-induced allergic asthma in vivo and in vitro. Garlic extraction was realized using n-hexane, dichloromethane, ethylacetate, n-butanol, and water in sequence to obtain different fraction extracts. Mice were orally administered different fractions (80 mg/kg) daily for four weeks. The histological results showed that the water fraction could ameliorate lung-based goblet cell hyperplasia, inflammatory cell infiltration, and mucus hypersecretion. The water fraction extracts decreased IgE and IgG1, and they decreased inflammatory cells as quantified in bronchoalveolar lavage fluid (BALF); however, they increased IgG2a in serum. Moreover, the water fraction extracts increased IFN-γ and IL-12 (both constituting Th1 cytokines) in BALF, but they reduced IL-13, -4, and -5 (all constituting Th2 cytokines), and also inhibited the expression of IL-1β, IL-6, and TNF-α. The water fraction also inhibited the PI3K/Akt/NF-κB signal pathways in A549 cells. These findings suggest that water fraction extracts of garlic have a clear anti-inflammatory effect on Der p-induced allergic asthma.

Dengue virus-elicited tryptase induces endothelial permeability and shock

Dengue virus (DENV) infection causes a characteristic pathology in humans involving dysregulation of the vascular system. In some patients with dengue hemorrhagic fever (DHF), vascular pathology can become severe, resulting in extensive microvascular permeability and plasma leakage into tissues and organs. Mast cells (MCs), which line blood vessels and regulate vascular function, are able to detect DENV in vivo and promote vascular leakage. Here, we identified that a MC-derived protease, tryptase, is consequential for promoting vascular permeability during DENV infection, through inducing breakdown of endothelial cell tight junctions. Injected tryptase alone was sufficient to induce plasma loss from the circulation and hypovolemic shock in animals. A potent tryptase inhibitor, nafamostat mesylate, blocked DENV-induced vascular leakage in vivo. Importantly, in two independent human dengue cohorts, tryptase levels correlated with the grade of DHF severity. This study defines an immune mechanism by which DENV can induce vascular pathology and shock.

Mast Cells and Their Progenitors in Allergic Asthma

Mast cells and their mediators have been implicated in the pathogenesis of asthma and allergy for decades. Allergic asthma is a complex chronic lung disease in which several different immune cells, genetic factors and environmental exposures influence the pathology. Mast cells are key players in the asthmatic response through secretion of a multitude of mediators with pro-inflammatory and airway-constrictive effects. Well-known mast cell mediators, such as histamine and bioactive lipids are responsible for many of the physiological effects observed in the acute phase of allergic reactions. The accumulation of mast cells at particular sites of the allergic lung is likely relevant to the asthma phenotype, severity and progression. Mast cells located in different compartments in the lung and airways have different characteristics and express different mediators. According to in vivo experiments in mice, lung mast cells develop from mast cell progenitors induced by inflammatory stimuli to migrate to the airways. Human mast cell progenitors have been identified in the blood circulation. A high frequency of circulating human mast cell progenitors may reflect ongoing pathological changes in the allergic lung. In allergic asthma, mast cells become activated mainly via IgE-mediated crosslinking of the high affinity receptor for IgE (FcεRI) with allergens. However, mast cells can also be activated by numerous other stimuli e.g. toll-like receptors and MAS-related G protein-coupled receptor X2. In this review, we summarize research with implications on the role and development of mast cells and their progenitors in allergic asthma and cover selected activation pathways and mast cell mediators that have been implicated in the pathogenesis. The review places an emphasis on describing mechanisms identified using in vivo mouse models and data obtained by analysis of clinical samples.

The Allergen Der p3 from House Dust Mite Stimulates Store-Operated Ca2+ Channels and Mast Cell Migration through PAR4 Receptors

The house dust mite is the principal source of perennial aeroallergens in man. How these allergens activate innate and adaptive immunity is unclear, and therefore, there are no therapies targeting mite allergens. Here, we show that house dust mite extract activates store-operated Ca²⁺ channels, a common signaling module in numerous cell types in the lung. Activation of channel pore-forming Orai1 subunits by mite extract requires gating by STIM1 proteins. Although mite extract stimulates both protease-activated receptor type 2 (PAR2) and PAR4 receptors, Ca²⁺ influx is more tightly coupled to the PAR4 pathway. We identify a major role for the serine protease allergen Der p3 in stimulating Orai1 channels and show that a therapy involving sub-maximal inhibition of both Der p3 and Orai1 channels suppresses mast cell activation to house dust mite. Our results reveal Der p3 as an important aeroallergen that activates Ca²⁺ channels and suggest a therapeutic strategy for treating mite-induced asthma.

Toxoplasma gondii serine-protease inhibitor-1: A new adjuvant candidate for asthma therapy

Serine-proteases are important players in the pathogenesis of asthma, promoting inflammation and tissue remodeling. It’s also known that many serine protease inhibitors display immunomodulatory properties. TgPI-1 is a Toxoplasma gondii protein that exhibits broad spectrum inhibitory activity against serine proteases. In view of the increased prevalence of atopic disorders and the need to develop new treatment strategies we sought to investigate the potential of TgPI-1 for treating respiratory allergies. For this purpose, we developed a therapeutic experimental model. BALB/c mice were rendered allergic by intraperitoneal ovalbumin-alum sensitization and airway-challenged. Once the asthmatic phenotype was achieved, mice were intranasally treated with rTgPI-1 alone or with a mixture of rTgPI-1 and ovalbumin (OVA). A week later mice were given a secondary aerosol challenge. Treatment with rTgPI-1 alone or co-administered with OVA diminished bronchoalveolar eosinophilia, mucus production and peribronchial lung infiltration. This effect was accompanied by a lung resistance reduction of 26.3% and 50.3% respectively. Both treatments resulted in the production of lower levels of IL-4, IL-5, IFN-γ and regulatory IL-10 by thoracic lymph node cells stimulated with OVA. Interestingly, significant decreases in OVA specific IgE and T cell proliferation, and increases in FoxP3⁺ T cells at local and systemic levels were only detected when the inhibitor was administered along with OVA. These results show that both rTgPI-1 treatments reduced asthma hallmarks. However, co-administration of the inhibitor with the allergen was more effective. Hence, rTgPI-1 emerges as a novel adjuvant candidate for asthma treatment.

Functional inhibition of PAR2 alleviates allergen-induced airway hyperresponsiveness and inflammation

BACKGROUND

Proteinase-activated receptor 2 (PAR2 ) is a G protein-coupled receptor activated by trypsin-like serine proteinases. PAR2 activation has been associated with inflammation including allergic airway inflammation. We have also shown that PAR2 activation in the airways leads to allergic sensitization. The exact contribution of PAR2 in the development of eosinophilic inflammation and airway hyperresponsiveness (AHR) in sensitized individuals is not clear.

OBJECTIVE

To investigate whether functional inhibition of PAR2 during allergen challenge of allergic mice would inhibit allergen-induced AHR and inflammation in mouse models of asthma.

METHODS

Mice were sensitized and challenged with ovalbumin (OVA) or cockroach extract (CE). To investigate the role of PAR2 in the development of AHR and airway inflammation, we administered blocking anti-PAR2 antibodies, or a cell permeable peptide inhibitor of PAR2 signalling, pepducin, i.n. before allergen challenges and then assessed AHR and airway inflammation.

RESULTS

Administration of anti-PAR2 antibodies significantly inhibited OVA- and CE-induced AHR and airway inflammation. In particular, two anti-PAR2 antibodies, the monoclonal SAM-11 and polyclonal B5, inhibited AHR, airway eosinophilia, the increase of cytokines in the lung tissue and antigen-specific T cell proliferation, but had no effect on antigen-specific IgG and IgE levels. Pepducin was also effective in inhibiting AHR and airway inflammation in an OVA model of allergic airway inflammation.

CONCLUSIONS AND CLINICAL RELEVANCE

Functional blockade of PAR2 in the airways during allergen challenge improves allergen-induced AHR and inflammation in mice. Therefore, topical PAR2 blockade in the airways, through anti-PAR2 antibodies or molecules that interrupt PAR2 signalling, has the potential to be used as a therapeutic option in allergic asthma.

PI3K and ERK1/2 kinase inhibition potentiate protease inhibitor to attenuate allergen induced Th2 immune response in mouse

Proteases affect immune response by activating PI3K, ERK1/2 and p38 kinase. In present study, therapeutic effect of PI3K, ERK1/2 and p38 kinase inhibitor in combination with serine protease inhibitor was evaluated in cockroach extract (CE) induced airway inflammatory disease. Mice were sensitized on day 0, 7 and 14 and challenged on day 27, 28 and 29 with CE. Mice were given PI3K, ERK1/2 and the p38 kinase inhibitor (iPI3K, iERK1/2 and the ip38) alone or with serine protease inhibitor 4-(2-Aminoethyl) benzenesulfonyl fluoride hydrochloride (AEBSF), 1h before challenge. On day 30 airway resistance of mice were determined and euthanized to collect blood, BAL fluid and lung for analysis. CE immunized mice showed PI3K, ERK1/2 and p38 kinase activation, increased airway resistance, cellular infiltration, Th2 cytokines IgE and IgG1. AEBSF given to mice reduced the CE induced allergic response. AEBSF given in combination of iPI3K/iERK1/2 reduced cellular infiltration in lungs. Furthermore, iPI3K/iERK1/2 with AEBSF significantly reduced the CE induced Th2 cytokines in comparison to monotherapy of kinase inhibitor and AEBSF (P<0.05). The combination of iPI3K/iERK1/2 with AEBSF enhanced IL-12 level that could further provide a mean of Th2 reduction. Best effect in reduction of allergic response in mice was observed on administration of AEBSF with iPI3K. Conclusively, the combination of PI3K kinase inhibitor with AEBSF reduced allergen induced airway response and has therapeutic potential for add-on therapy in allergic airway disease.

Development of recombinant stable house dust mite allergen Der p 3 molecules for component-resolved diagnosis and specific immunotherapy

BACKGROUND

The allergen Der p 3 is underrepresented in house dust mite (HDM) extracts probably due to autolysis. Recombinant stable molecule of the allergen is thus needed to improve the diagnosis of allergy and the safety and efficacy of immunotherapy.

OBJECTIVE

The current study reports the immunological characterization of two recombinant molecules of the HDM allergen Der p 3 as useful tools for diagnosis and immunotherapy.

METHODS

Recombinant mature (rDer p 3) and immature (proDer p 3) Der p 3 and their corresponding S196A mutants were produced in Pichia pastoris and purified. The stability, IgE-binding capacity and allergenicity of the different proteins were analysed and compared with those of the major mite allergen Der p 1 used as a reference. Additionally, the immunogenicity of the different allergens was evaluated in a murine model of Der p 3 sensitization.

RESULTS

Compared to the IgE reactivity to recombinant and natural Der p 3 (nDer p 3), the mean IgE binding of patient's sera to rDer p 3-S196A (50%) was higher. The poorly binding to nDer p 3 or rDer p 3 was due to autolysis of the allergen. Contrary to Der p 3, proDer p 3 displayed very weak IgE reactivity, as measured by sandwich ELISA and competitive inhibition, rat basophil leukaemia degranulation and human basophil activation assays. Moreover, proDer p 3 induced a TH 1-biased immune response that prevented allergic response in mice but retained Der p 3-specific T-cell reactivity.

CONCLUSION

rDer p 3-S196A should be used for the diagnosis of HDM allergy elicited by Der p 3, and proDer p 3 may represent a hypoallergen of Der p 3.

Protease inhibitor reduces airway response and underlying inflammation in cockroach allergen-induced murine model

Protease(s) enhances airway inflammation and allergic cascade. In the present study, effect of a serine protease inhibitor was evaluated in mouse model of airway disease. Mice were sensitized with cockroach extract (CE) or Per a 10 and treated with 4-(2-aminoethyl) benzenesulfonyl fluoride hydrochloride (AEBSF) 1 h before or after challenge to measure airway response. Mice were euthanized to collect bronchoalveolar lavage fluid (BALF), blood, and lung to evaluate inflammation. AEBSF treatment significantly reduced the AHR in allergen-challenged mice in dose-dependent manner (p≤ 0.01). IgE (p≤0.05) and Th2 cytokines (p≤0.05) were significantly reduced in treated mice. AEBSF treatment lowered total cell (p≤0.05), eosinophil (p≤0.05), and neutrophil (p≤0.05) in BALF and lung tissue. Oxidative stress parameters were impaired on treatment in allergen-challenged mice (p≤0.05). AEBSF had therapeutic effect in allergen-induced airway resistance and underling inflammation and had potential for combination or as add-on therapy for respiratory diseases.

Divergent Inhibitor Susceptibility among Airway Lumen-Accessible Tryptic Proteases

Tryptic serine proteases of bronchial epithelium regulate ion flux, barrier integrity, and allergic inflammation. Inhibition of some of these proteases is a strategy to improve mucociliary function in cystic fibrosis and asthmatic inflammation. Several inhibitors have been tested in pre-clinical animal models and humans. We hypothesized that these inhibitors inactivate a variety of airway protease targets, potentially with bystander effects. To establish relative potencies and modes of action, we compared inactivation of human prostasin, matriptase, airway trypsin-like protease (HAT), and β-tryptase by nafamostat, camostat, bis(5-amidino-2-benzimidazolyl)methane (BABIM), aprotinin, and benzamidine. Nafamostat achieved complete, nearly stoichiometric and very slowly reversible inhibition of matriptase and tryptase, but inhibited prostasin less potently and was weakest versus HAT. The IC₅₀ of nafamostat’s leaving group, 6-amidino-2-naphthol, was >10⁴-fold higher than that of nafamostat itself, consistent with suicide rather than product inhibition as mechanisms of prolonged inactivation. Stoichiometric release of 6-amidino-2-naphthol allowed highly sensitive fluorometric estimation of active-site concentration in preparations of matriptase and tryptase. Camostat inactivated all enzymes but was less potent overall and weakest towards matriptase, which, however was strongly inhibited by BABIM. Aprotinin exhibited nearly stoichiometric inhibition of prostasin and matriptase, but was much weaker towards HAT and was completely ineffective versus tryptase. Benzamidine was universally weak. Thus, each inhibitor profile was distinct. Nafamostat, camostat and aprotinin markedly reduced tryptic activity on the apical surface of cystic fibrosis airway epithelial monolayers, suggesting prostasin as the major source of such activity and supporting strategies targeting prostasin for inactivation.

Critical role of IL-6 in dendritic cell-induced allergic inflammation of asthma

Interleukin (IL)-6 plays important roles in autoimmunity and inflammation and is essential for T helper (Th) 2 and Th17 differentiation. However, whether it is involved in the development and function of dendritic cells (DCs) during allergen-induced airway inflammation and airway hyper-reactivity (AHR) remains undefined. In this study, Dermatophagoides pteronyssinus (Der p)-induced airway inflammation and AHR were studied in IL-6 knockout (KO) mice. Der p-loaded bone marrow-derived DCs (BMDCs) from IL-6 KO mice were used to assaying their ability to induce airway inflammation in naïve wild-type mice. Our results showed that IL-6 KO mice showed reduced AHR, significant decreases in inflammatory cell recruitment and Th2 and Th17 cytokine production in the airways, and lowered Der p-specific immunoglobulin G1 after Der p exposure. Further exploration of BMDCs from IL-6 KO mice revealed decreased activity of phagocytosis and reduced expression of MHC class II and CD86 after Der p stimulation. Adoptive transfer of Der p-loaded BMDCs from IL-6 KO mice also showed a functional defect in their inability to induce Th2 and Th17 immune responses and trigger airway inflammation and AHR in recipient mice. Finally, in allergic asthmatics, DCs that differentiated from monocytes treated with anti-IL-6 receptor antibody (tocilizumab) had poor capacity for eliciting Th2 polarization as compared to DCs generated from monocytes without antibody treatment. In conclusion, IL-6 signaling in DCs is essential for their uptake of allergens, maturation, and initiation of Th2/Th17-mediated airway inflammation and AHR in asthma, thus providing a new potential target for treating allergic asthma.

KEY MESSAGES

IL-6 signaling is important for DCs to take up allergens and to initiate Th2/Th17-mediated airway inflammation. DCs from allergic asthmatics treated with anti-IL-6 receptor antibody had poor capacity for eliciting Th2 polarization. Anti-IL-6 treatment may provide a new potential target for treating allergic asthma.

Mast cell proteases as pharmacological targets

Mast cells are rich in proteases, which are the major proteins of intracellular granules and are released with histamine and heparin by activated cells. Most of these proteases are active in the granule as well as outside of the mast cell when secreted, and can cleave targets near degranulating mast cells and in adjoining tissue compartments. Some proteases released from mast cells reach the bloodstream and may have far-reaching actions. In terms of relative amounts, the major mast cell proteases include the tryptases, chymases, cathepsin G, carboxypeptidase A3, dipeptidylpeptidase I/cathepsin C, and cathepsins L and S. Some mast cells also produce granzyme B, plasminogen activators, and matrix metalloproteinases. Tryptases and chymases are almost entirely mast cell-specific, whereas other proteases, such as cathepsins G, C, and L are expressed by a variety of inflammatory cells. Carboxypeptidase A3 expression is a property shared by basophils and mast cells. Other proteases, such as mastins, are largely basophil-specific, although human basophils are protease-deficient compared with their murine counterparts. The major classes of mast cell proteases have been targeted for development of therapeutic inhibitors. Also, a human β-tryptase has been proposed as a potential drug itself, to inactivate of snake venins. Diseases linked to mast cell proteases include allergic diseases, such as asthma, eczema, and anaphylaxis, but also include non-allergic diseases such as inflammatory bowel disease, autoimmune arthritis, atherosclerosis, aortic aneurysms, hypertension, myocardial infarction, heart failure, pulmonary hypertension and scarring diseases of lungs and other organs. In some cases, studies performed in mouse models suggest protective or homeostatic roles for specific proteases (or groups of proteases) in infections by bacteria, worms and other parasites, and even in allergic inflammation. At the same time, a clearer picture has emerged of differences in the properties and patterns of expression of proteases expressed in human mast cell subsets, and in humans versus other mammals. These considerations are influencing prioritization of specific protease targets for therapeutic inhibition, as well as options of pre-clinical models, disease indications, and choice of topical versus systemic routes of inhibitor administration.

The effect of serine protease inhibitors on airway inflammation in a chronic allergen-induced asthma mouse model

Serine protease inhibitors reportedly attenuated airway inflammation and had antioxidant in multiorgan. However, the effects of the serine protease inhibitors nafamostat mesilate (FUT), gabexate mesilate (FOY), and ulinastatin (UTI) on a long-term challenged mouse model of chronic asthma are unclear. BALB/c mice (6 mice/group) were intratracheally inoculated with five doses of Dermatophagoides pteronyssinus (Der p; 50 μL, 1 mg/mL) at one-week intervals. Therapeutic doses of FUT (0.0625 mg/kg), FOY (20 mg/kg), or UTI (10,000 U/kg) were, respectively, injected intraperitoneally into these mice. Control mice received sterile PBS. At 3 days after the last challenge, mice were sacrificed to assess airway hyperresponsiveness (AHR), remodeling, and inflammation; lung histological features; and cytokine expression profiles. Compared with untreated controls, mice treated with FUT, FOY, and UTI had decreased AHR and goblet cell hyperplasia, decreased eosinophil and neutrophil infiltration, decreased Der p-induced IL-4 levels in serum and IL-5, IL-6, IL-13, and IL-17 levels in bronchoalveolar lavage fluid, and inhibited nuclear factor (NF)-κB activity in lung tissues. The serine protease inhibitors FUT, FOY, and UTI have potential therapeutic benefits for treating asthma by downregulating Th2 cytokines and Th17 cell function and inhibiting NF-κB activation in lung tissue.

Escherichia coli heat-labile detoxified enterotoxin modulates dendritic cell function and attenuates allergic airway inflammation

Various mutant forms of Escherichia coli heat-labile enterotoxin (LT) have been used as a mucosal adjuvant for vaccines, as it enhances immune responses to specific antigens including antigen-specific IgA antibodies when administrated intranasally or orally. We hypothesized that a detoxified mutant form of LT, LTS61K, could modulate dendritic cell (DC) function and alleviate allergen-induced airway inflammation. Two protocols, preventative and therapeutic, were used to evaluate the effects of LTS61K in a Dermatophagoides pteronyssinus (Der p)-sensitized and challenged murine model of asthma. LTS61K or Der p-primed bone marrow-derived dendritic cells (BMDCs) were also adoptively transferred into Der p-sensitized and challenged mice. Intranasal inoculations with LTS61K or LTS61K/Der p decreased allergen-induced airway inflammation and alleviated systemic T_H2-type immune responses. Bronchoalveolar lavage fluid (BALF) and sera from LTS61K/Der p-treated mice also had higher concentrations of Der p-specific immunoglobulin (Ig) A than those of other groups. In vitro, BMDCs stimulated with Der p underwent cellular maturation and secreted proinflammatory cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)α In contrast, Der p-stimulated BMDCs that were pretreated with LTS61K showed decreased IL-6 and TNFα production and were less mature. Intratracheal adoptive transfer of LTS61K- or LTS61K/Der p-primed BMDCs into Der p-sensitized mice reduced inflammatory cell infiltration and T_H2-type chemokines in BALF and alleviated airway inflammation in treated mice. LTS61K influenced DC maturation and decreased inflammatory cytokine production. Moreover, LTS61K/Der p induced increased Der p-specific IgA production to decrease allergic T_H2 cytokine responses and alleviated airway inflammation in Der p-sensitized mice. These results suggest that the immunomodulatory effects of LTS61K may have clinical applications for allergy and asthma treatment.

Therapeutic potential of the peptide leucine arginine as a new nonplant bowman-birk-like serine protease inhibitor

The peptide leucine arginine (pLR) belongs to a new class of cyclic peptides isolated from frog skin. Its primary sequence is similar to the reactive loop of plant Bowman-Birk inhibitors (BBI), and the recently discovered circular sunflower trypsin inhibitor-1 (SFTI-1). The conformational properties of pLR in solution were determined by NMR spectroscopy and revealed excellent structural similarity to BBI and SFTI-1. Moreover, pLR is a highly potent trypsin inhibitor, with Ki values in the nanomolar range, and, due to its small size, a potential inhibitor of the serine protease tryptase. Since tryptase plays a crucial role in the development of allergic airway inflammation, the therapeutic potential of pLR in a murine asthma model was investigated. Treatment of ovalbumin-sensitized mice with pLR during allergen challenge reduced the acute asthma phenotype. Most importantly, application even at the end of a long-lasting chronic asthma model decreased the development of chronic airway inflammation and tissue remodeling.

The role of SCCA1 in asthma related physiological events in the airway epithelium and the effect of promoter variants on asthma and gene function

BACKGROUND

Even though the systemic level of SCCA1, a serine protease inhibitor, was shown to be elevated in asthma, its physiological role is unknown.

OBJECTIVE

We sought to determine the effect of SCCA1 on apoptosis, cytokine expression and mucus production by A549 cells and define the effect of promoter variants on gene expression and association with asthma.

METHODS

SCCA levels were measured by ELISA. Promoter variants were determined by direct sequencing. 442 asthmatic children and 191 controls were genotyped by RFLP. The functional effect of the polymorphisms was assessed in transient transfection experiments using reporter constructs. A transcription factor ELISA was used for differential binding of GATA proteins to the variant region. The effects of SCCA1 on cytokine synthesis, mucus production and apoptosis were determined in A549 cells transfected with SCCA1 pcDNA vector. MUC5AC expression in A549 cells was determined with RT-PCR.

RESULTS

SCCA1 protein level was significantly higher in asthmatic children compared to healthy controls. Four polymorphisms SCCA1 promoter that were in linkage disequilibrium were associated with skin test positivity in asthmatic children and showed higher promoter activity and higher binding of GATA-2 and GATA-3 after IL-4 + IL-13 stimulation. IL-6, IL-8 levels were significantly higher in cells transfected with SCCA1 whereas RANTES increased only after IL-4 stimulation. Transfection of A549 cells with SCCA1 resulted in decreased MUC5AC expression and conferred protection against apoptosis.

CONCLUSION

Our results showed that SCCA1 has diverse effects on many of the cellular events that characterize asthma and its role extends beyond protease inhibition.

The innate immune response in house dust mite-induced allergic inflammation

Hypersensitivity to house dust mite (HDM; Dermatophagoides sp.) allergens is one of the most common allergic responses, affecting up to 85% of asthmatics. Sensitization to indoor allergens is the strongest independent risk factor associated with asthma. Additionally, >50% of children and adolescents with asthma are sensitized to HDM. Although allergen-specific CD4⁺ Th2 cells orchestrate the HDM allergic response through induction of IgE directed toward mite allergens, activation of innate immunity also plays a critical role in HDM-induced allergic inflammation. This review highlights the HDM components that lead to activation of the innate immune response. Activation may due to HDM proteases. Proteases may be recognized by protease-activation receptors (PARs), Toll-like receptors (TLRs), or C-type lectin receptors (CTRs), or act as a molecular mimic for PAMP activation signaling pathways. Understanding the role of mite allergen-induced innate immunity will facilitate the development of therapeutic strategies that exploit innate immunity receptors and associated signaling pathways for the treatment of allergic asthma.

Effect of a serine protease inhibitor on the progression of chronic renal failure

The number of the chronic renal failure (CRF) patients is increasing explosively. Hypertension, proteinuria, inflammation, fibrosis, and oxidative stress are intertwined in a complicated manner that leads to the progression of CRF. However, the therapeutic strategies to delay its progression are limited. Since serine proteases are involved in many processes that contribute to these risk factors, we investigated the effects of a synthetic serine protease inhibitor, camostat mesilate (CM), on the progression of CRF in 5/6 nephrectomized (Nx) rats. Eighteen male Sprague-Dawley rats were divided into three groups: a sham-operated group ( n = 6), a vehicle-treated Nx group ( n = 6), and a CM-treated Nx group ( n = 6). Following the 9-wk study period, both proteinuria and serum creatinine levels were substantially increased in the vehicle-treated Nx group, and treatment with CM significantly reduced proteinuria and serum creatinine levels. The levels of podocyte-associated proteins in glomeruli, such as nephrin and synaptopodin, were markedly decreased by 5/6 nephrectomy, and this was significantly ameliorated by CM. CM also suppressed the levels of inflammatory and fibrotic marker mRNAs including transforming growth factor-β1, TNF-α, collagen types I, III, and IV, and reduced glomerulosclerosis, glomerular hypertrophy, and interstitial fibrosis in histological studies. Furthermore, CM decreased the expression of NADPH oxidase component mRNAs, as well as reactive oxygen species generation and advanced oxidative protein product levels. Our present results strongly suggest the possibility that CM could be a useful therapeutic agent against the progression of CRF.

Serine protease inhibitor attenuates ovalbumin induced inflammation in mouse model of allergic airway disease

Background

Serine proteases promote inflammation and tissue remodeling by activating proteinase-activated receptors, urokinase, metalloproteinases and angiotensin. In the present study, 4-(2-Aminoethyl) benzenesulfonyl fluoride (AEBSF) a serine protease inhibitor was evaluated for prophylactic and therapeutic treatment in mouse model of airway allergy.

Methods

BALB/c mice were sensitized by i.p route and challenged with ovalbumin. They were treated i.n. with 2, 10 and 50 µg of AEBSF, one hour before or after challenge and euthanized to collect BALF (bronchoalveolar lavage fluid), blood and lungs. Proteolytic activity, total cell/eosinophil/neutrophil count eosinophil peroxidase activity (EPO), IL-4, IL-5, IL-10, IL-13, cysteinyl leukotrienes and 8-isoprostane were determined in BALF and immunoglobulins were measured in serum. H&E and PAS stained lung sections were examined for cellular infiltration and airway inflammation.

Results

Mice exposed to ovalbumin and treated with PBS showed increased cellular infiltration in lungs and higher serum IgE, IgG1 and IgG2a levels as compared to sham mice. Treatment with AEBSF reduced total cells/eosinophil/neutrophil infiltration. Both prophylactic and therapeutic AEBSF treatment of 10 or 50 µg reduced serum IgE and IgG1 significantly (p<0.05) than control. AEBSF treatment reduced the proteolytic activity in BALF. IL-4 IL-5 and IL-13 levels decreased significantly (p<0.05) after AEBSF treatment while IL-10 levels increased significantly (p<0.05) in BALF. Airway inflammation and goblet cell hyperplasia reduced as demonstrated by lung histopathology, EPO activity and cysteinyl leukotrienes in BALF after treatment. AEBSF treatment also suppressed oxidative stress in terms of 8-isoprostane in BALF. Among the treatment doses, 10 or 50 µg of AEBSF were most effective in reducing the inflammatory parameters.

Conclusions

Prophylactic and therapeutic treatment with serine protease inhibitor attenuates the airway inflammation in mouse model of airway allergy and have potential for adjunct therapy.

Fungi linking the pathophysiology of chronic rhinosinusitis with nasal polyps and allergic asthma

The immunologic reaction to fungal stimuli has long been thought to be a contributor to the development of sinonasal disease. We aim to review the role of fungi in upper and lower airway inflammatory diseases. The immune response to fungi in the pathogenicity of specific respiratory inflammatory diseases such as allergic bronchopulmonary aspergillosis and a subtype of CRS known as allergic fungal rhinosinusitis has been relatively well described. Fungi are thought to serve both as immunogenic antigens and as adjuncts to inflammation through protease activity. Development of a recent murine mouse model of asthma bypassing the pre-sensitization of allergen further suggests a broader role for fungi in allergic asthma. The literature is lacking in defining a clear presence of fungi within the inflamed sinus cavity of CRS patients and its potential immunologic effects, as well as the utility of antifungal therapy for CRS management. We will review these data and potential common molecular mechanisms activated by fungi in the common pathway toward upper and lower airway inflammatory pathology.

Protease phenotype of constitutive connective tissue and of induced mucosal mast cells in mice is regulated by the tissue

Mouse mast cells (MCs) express a large number of serine proteases including tryptases, mouse mast cell protease (mMCP)-6 and -7; chymases, mMCP-1, -2, and -4; and an elastase, mMCP-5; along with carboxypeptidase-A3 (CPA3). In helminth-infected mouse intestine, distinct protease phenotypes are observed for connective tissue MCs (CTMCs) (mMCP-4(+)-7(+), and CPA3(+)) and mucosal MCs (MMCs) (mMCP-1(+) and 2(+)). To determine whether the protease phenotype was regulated by the tissue, we compared the phenotype of constitutive CTMCs and induced MMCs in trachea and large airways in antigen-sensitized unchallenged and challenged mice to MCs in skin and helminthic-infected intestine. We found that in the trachea, unlike in skin and intestine, CTMCs and MMCs both express all six serine proteases and CPA3 (mMCP-1(+), -2(+), 4(+)-7(+), CPA3(+)). This phenotype also holds for the lung CTMCs in the proximal bronchi, whereas the induced MMCs express only four proteases, mMCP-1, -2, -6, and -7. Thus, the T-cell-dependent induction of MMCs in trachea, large bronchi, and small intestine provides numbers but does not determine the protease phenotype. Furthermore, the CTMCs, which are constitutive, also show striking differences at these tissue sites, supporting the view that the differences in expression are tissue directed and not dependent on inflammation.

Mast cell proteases as protective and inflammatory mediators

Proteases are the most abundant class of proteins produced by mast cells. Many of these are stored in membrane-enclosed intracellular granules until liberated by degranulating stimuli, which include cross-linking of high affinity IgE receptor F(c)εRI by IgE bound to multivalent allergen. Understanding and separating the functions of the proteases is important because expression differs among mast cells in different tissue locations. Differences between laboratory animals and humans in protease expression also influence the degree of confidence with which results obtained in animal models of mast cell function can be extrapolated to humans. The inflammatory potential of mast cell proteases was the first aspect of their biology to be explored and has received the most attention, in part because some of them, notably tryptases and chymases, are biomarkers of local and systemic mast cell degranulation and anaphylaxis. Although some of the proteases indeed augment allergic inflammation and are potential targets for inhibition to treat asthma and related allergic disorders, they are protective and even anti-inflammatory in some settings. For example, mast cell tryptases may protect from serious bacterial lung infections and may limit the "rubor" component of inflammation caused by vasodilating neuropeptides in the skin. Chymases help to maintain intestinal barrier function and to expel parasitic worms and may support blood pressure during anaphylaxis by generating angiotensin II. In other life-or-death examples, carboxypeptidase A3 and other mast cell peptidases limit systemic toxicity of endogenous peptideslike endothelin and neurotensin during septic peritonitis and inactivate venom-associated peptides. On the other hand, mast cell peptidase-mediated destruction of protective cytokines, like IL-6, can enhance mortality from sepsis. Peptidases released from mast cells also influence nonmast cell proteases, such as by activating matrix metalloproteinase cascades, which are important in responses to infection and resolution of tissue injury. Overall, mast cell proteases have a variety of roles, inflammatory and anti-inflammatory, protective and deleterious, in keeping with the increasingly well-appreciated contributions of mast cells in allergy, tissue homeostasis and innate immunity.

Targeted treatment of pruritus: a look into the future

Recent advances in pruritus research have elucidated mediators and neuronal pathways involved in itch transmission, and this fast emerging knowledge may possibly be translated into new therapies in the near future. In the skin and peripheral nerves, potential mediator and receptor therapeutic targets include the H4 histamine receptor, protease-activated receptor 2, serine proteases, cathepsin S, peripheral mu- and kappa-opioid receptors, interleukin-31, transient receptor potential vanilloid 1 and 3, fatty acid amide hydrolase, nerve growth factor and its receptor, acetylcholine, and the Mas-related G protein-coupled receptors. In the spinal cord, gastrin-related peptide and its receptor, as well as substance P and its receptor neurokinin receptor-1 serve as potential therapeutic targets. In the brain, reduction of itch perception and modulation of emotions may possibly be achieved through drugs acting on the anterior cingulate cortex. Clinically, management of pruritus should be instituted early and should address the skin pathology, peripheral neuropathy, central sensitization, and the cognito-affective aspects of the disease.

Targeted treatment of pruritus: a look into the future

Recent advances in pruritus research have elucidated mediators and neuronal pathways involved in itch transmission, and this fast emerging knowledge may possibly be translated into new therapies in the near future. In the skin and peripheral nerves, potential mediator and receptor therapeutic targets include the H4 histamine receptor, protease-activated receptor 2, serine proteases, cathepsin S, peripheral mu- and kappa-opioid receptors, interleukin-31, transient receptor potential vanilloid 1 and 3, fatty acid amide hydrolase, nerve growth factor and its receptor, acetylcholine, and the Mas-related G protein-coupled receptors. In the spinal cord, gastrin-related peptide and its receptor, as well as substance P and its receptor neurokinin receptor-1 serve as potential therapeutic targets. In the brain, reduction of itch perception and modulation of emotions may possibly be achieved through drugs acting on the anterior cingulate cortex. Clinically, management of pruritus should be instituted early and should address the skin pathology, peripheral neuropathy, central sensitization, and the cognito-affective aspects of the disease.

Epitope mapping and structural analysis of the anti-Der p 1 monoclonal antibody: insight into therapeutic potential

Group 1 allergen from Dermatophagoid pteronyssinus (Der p 1) belongs to the papain-like cysteine protease family and is a major cause of allergic rhinitis and asthma. An anti-Der p 1 monoclonal antibody, mAb W108, was selected and isolated from Der p-specific IgG2b-producing hybridoma clones. Two-dimensional electrophoresis and immunoblotting showed that mAb W108 reacted with four components of Der p extracts with a molecular mass of 35 kDa and pI values varying from 4 to 6; it also reacted with IgE antibodies in the sera of Der p-sensitive patients. In the competitive assay and using azocasein as a substrate, we found that mAb W108 inhibited not only the binding of Der p 1, but also its cysteine protease activity in a dose-dependent manner. The two peptide segments of Der p 1 identified by mAb W108 (aa 151-197 and 286-320) were parts of inter-connecting loops located in the substrate-binding cleft and on the surface of the domain comprising mainly β-sheets. From the predicted interaction between the amino acid sequence in the CDR3 of mAb W108 and Der p 1-binding epitopes, the possible binding sites for mAb W108 to Der p 1 may sterically hinder the IgE epitope and the active site of cysteine protease activity. Administration of mAb W108 in the Der p-sensitized murine model of asthma alleviated allergen-induced airway inflammation and the Th2 cytokine immune response, suggesting its therapeutic potential. These findings can provide new insights into understanding IgE-mediated disease and the design of modified allergen vaccines for future allergen-specific immunotherapy.

Nafamostat mesilate, a potent tryptase inhibitor, modulates periodontitis in rats

Previous reports have demonstrated increased tryptase-like proteolytic activity in the crevicular fluid of patients with periodontal disease. In the present study, we have investigated the effect of tryptase inhibition with nafamostat mesilate (NM, 6-amino-2-naphtlyl p-guanidinobenzoate dimethansulfonate) on the development of experimental periodontitis in rats. Eighty (80) male Wistar rats were randomly separated into four groups: Control group, NM group (daily 0.1 mg/kg body weight of NM, i.p.), Ligature group (ligature placed at lower right first molars), and NM+Ligature group. The amount of alveolar bone loss (ABL) around the mesial root surface of the first mandibulary molar, as well as the myeloperoxidase (MPO) activity, and total proteolytic activity [N-benzoyl-L: -arginine-p-nitroanilide (BApNA) substrate] were determined at 7 and 14 days. NM led to significantly (p < 0.05) decreased ABL in animals subjected to ligature-induced periodontitis. Tryptase inhibition prevented the onset of significant ABL at 7 days of experiment (0.44 ± 0.16 and 0.60 ± 0.22, p > 0.05, NM+Ligature and Control, respectively) and significantly decreased the ABL at 14 days (0.97 ± 0.17 versus 1.82 ± 0.26, p < 0.001, NM+Ligature versus Ligature, respectively). In addition, NM significantly decreased MPO and total proteolytic activity at 14 days (p < 0.05). These data provided evidence that tryptase inhibition with NM attenuates gingival granulocyte infiltration and ABL in an experimental model of periodontitis in rats.

Protease inhibitors in respiratory disease: focus on asthma and chronic obstructive pulmonary disease

Respiratory diseases, such as asthma and chronic obstructive pulmonary disease (COPD), are a major health burden on society and current treatment modalities for these diseases have not significantly changed over the past 40 years. The only major pharmacological advancement for the treatment of these diseases has been to increase the duration of action of bronchodilators (asthma: salmeterol; COPD: tiotropium bromide) and glucocorticosteroids (asthma: fluticasone propionate) and, increasingly, to formulate these agents in the same delivery device. Despite our increasing understanding of the cell and molecular biology of these diseases, the development of novel treatments remains beyond the reach of the scientific community. Proteases are a family of proteins with diverse biological activity, which are found in abundance within the airways of asthma and COPD, and have been implicated in the pathogenesis of these diseases. The targeting of proteases, including mast cell tryptase, neutrophil elastase and matrix metalloprotease with low-molecular-weight inhibitors, has highlighted the potential role of these enzymes in mediating certain aspects of the disease process in preclinical studies. Several challenges remain regarding the development of protease inhibitors, including the synthesis of highly potent and specific inhibitors, and target validation in man.

New insights into innate immune mechanisms underlying allergenicity

Allergic diseases, which have reached epidemic proportions, are caused by inappropriate immune responses to a relatively small number of environmental proteins. The molecular basis for the propensity of specific proteins to promote maladaptive, allergic responses has been difficult to define. Recent data suggest that the ability of such proteins to promote allergic responses in susceptible hosts is a function of their ability to interact with diverse pathways of innate immune recognition and activation at mucosal surfaces. This review highlights recent insights into innate immune activation by allergens--through proteolytic activity, engagement of pattern recognition receptors, molecular mimicry of TLR signaling complex molecules, lipid-binding activity, and oxidant potential--and the role of such activation in inducing allergic disease. A greater understanding of the fundamental origins of allergenicity should help define new preventive and therapeutic targets in allergic disease.

Enhancement of ovalbumin-induced pulmonary eosinophilia by intranasal administration of alpha1-proteinase inhibitor type 2 antisense oligonucleotides

To identify asthma-susceptibility genes, we did proteome analyses of the lung from control and ovalbumin-sensitized BALB/c mice. Among the 6 up-regulated proteins is alpha(1)-protease inhibitor (alpha(1)-PI) type 2, which is a member of the serine protease inhibitor superfamily of protease inhibitors that participate in a variety of physiological functions, including extracellular matrix remodeling and inflammation. The up-regulated expression of alpha(1)-PI type 2 was confirmed by real-time PCR. Then we examined mRNA expression of five members of the alpha(1)-PI family genes (alpha(1)-PI types 1-5) in several organs of BALB/c mice and found that in addition to the liver, all the organs tested also expressed different isoforms of alpha(1)-PI in a tissue-specific manner, albeit to a lesser extent compared with the liver. When a similar study was performed with C57BL/6 mice, which have been shown to be more susceptible to ovalbumin-induced asthma than BALB/c mice, a pair of remarkable differences between the mouse strains were revealed: (1) the magnitude of alpha(1)-PI type 2 mRNA in all the organs was much higher in BALB/c than in C57BL/6 mice and (2) alpha(1)-PI type 2 is the only isoform expressed in the lung of BALB/c, but not of C57BL/c mice. Using the antisense oligonucleotide technology to specifically down-regulate expression of alpha(1)-PI type 2, we demonstrated that pulmonary infiltration of eosinophils was significantly increased by intranasal administration of alpha(1)-PI type 2 antisense oligonucleotides in OVA-sensitized mice, suggesting that alpha(1)-PI type 2 may suppress the progress of asthma, probably by acting on neutrophil elastase, which can produce many of the pathological features of asthma.

Serine protease inhibitor nafamostat given before reperfusion reduces inflammatory myocardial injury by complement and neutrophil inhibition

Animal data strongly support a role for inflammation in myocardial ischemia reperfusion injury. Attempts at cardioprotection by immunomodulation (such as with the specific C5 antibody pexelizumab) in humans have been disappointing. We hypothesized that a broader spectrum antiinflammatory agent might yield successful cardioprotection. The serine protease inhibitor nafamostat (FUT-175), which is already in clinical use, is a potent antiinflammatory synthetic serine protease inhibitor with anticomplement activity that we tested in a well-established rabbit model of 1 hour of myocardial ischemia followed by 3 hours of reperfusion. Compared to vehicle-treated animals, nafamostat (1 mg/kg of body weight) administered 5 minutes before reperfusion significantly reduced myocardial injury assessed by plasma creatine kinase activity (38.1 +/- 6.0 versus 57.9 +/- 3.7I U/g protein; P < 0.05) and myocardial necrosis (23.6 +/- 3.1% versus 35.7 +/- 1.0%; P < 0.05) as well as myocardial leukocyte accumulation (P < 0.05). In parallel in vitro studies, Nafamostat was a significantly more potent broad spectrum complement suppressor than C1 inhibitor. Nafamostat appears to have capability as an inhibitor of both complement pathways and as a broad-spectrum antiinflammatory agent by virtue of its serine protease inhibition. Administration of nafamostat before myocardial reperfusion after ischemia produced significant, dose-dependent cardioprotection. Reduced leukocyte accumulation and complement activity seem involved in the mechanism of this cardioprotective effect.

Nafamostat mesilate, a potent serine protease inhibitor, inhibits airway eosinophilic inflammation and airway epithelial remodeling in a murine model of allergic asthma

To clarify the involvement of serine proteases in the development of allergic airway inflammation, we investigated the effect of nafamostat mesilate, a serine protease inhibitor, in a murine model of allergic asthma. Mice were sensitized to ovalbumin (OA) with alum and then exposed to 1% OA for 30 min, three times every 4th day. Nafamostat mesilate was administered orally for 10 days during the allergen challenge. In sensitized mice, repeated allergen challenge induced an increase in tryptase proteolytic activity in bronchoalveolar lavage fluid (BALF). In addition, marked increases in the numbers of inflammatory cells, levels of T helper type 2 (Th2) cytokines and eotaxin in BALF, numbers of goblet cells in the epithelium, and level of OA-specific IgE in serum were observed after repetitive allergen inhalation. Treatment with nafamostat mesilate significantly inhibited not only increased proteolytic activities, but also increases in the numbers of eosinophils and lymphocytes in the BALF. Nafamostat mesilate also dose-dependently inhibited increases in the levels of interleukin-13 and eotaxin in BALF and goblet cell hyperplasia. These findings suggest that increased serine protease activity in the airways is involved in the development of antigen-induced allergic eosinophilic inflammation and epithelial remodeling in bronchial asthma.

Evidence for the role of neurogenic inflammation components in trypsin-elicited scratching behaviour in mice

BACKGROUND AND PURPOSE

We investigated the mechanisms underlying the pruritogenic response induced by trypsin in mice, to assess the relevance of neurogenic inflammation components in this response.

EXPERIMENTAL APPROACH

Itching was induced by an intradermal injection of trypsin in the mouse neck. The animals were observed for 40 min and their scratching behaviour was quantified.

KEY RESULTS

Trypsin-induced itching was blocked by the lima bean trypsin inhibitor, the selective proteinase-activated receptor-2 (PAR-2) antagonist FSLLRY and PAR-2 receptor desensitization. An important involvement of mast cells was observed, as chronic pretreatment with the mast cell degranulator compound 48/80 or the mast cell stabilizer disodium cromoglycate prevented scratching. Also, trypsin response was inhibited by the selective COX-2 inhibitor celecoxib and by the selective kinin B2 (FR173657) and B1 (SSR240612) receptor antagonists. Moreover, an essential role for the mediators of neurogenic inflammation was established, as the selective NK1 (FK888), NK3 (SR142801) and calcitonin gene-related peptide (CGRP(8-37) fragment) receptor antagonists inhibited trypsin-induced itching. Similarly, blockade of transient receptor potential vanilloid 1 (TRPV1) receptors by the selective TRPV1 receptor antagonist SB366791, or by genetic deletion of TRPV1 receptor reduced this behaviour in mice. C-fibre desensitization showed a very similar result.

CONCLUSIONS AND IMPLICATIONS

Trypsin intradermal injection proved to be a reproducible model for the study of itching and the involvement of PAR-2 receptors. Also, trypsin-induced itching seems to be widely dependent on neurogenic inflammation, with a role for TRPV1 receptors. In addition, several other mediators located in the sensory nerves and skin also seem to contribute to this process.