Neutrophil serine proteinases activate human nonepithelial cells to produce inflammatory cytokines through protease-activated receptor 2

Targeting of protease activator receptor-2 (PAR-2) antagonist FSLLRY-NH2 as an asthma adjuvant therapy

Asthma is a chronic inflammatory and multifactorial respiratory tract disease. It affects over 18 million adults and 6 million children in the USA with Puerto Ricans showing the highest prevalence (12%-19%). This airways illness can be triggered by an environmental stimulus such as grass pollen, fungi spores, cockroaches allergens, dust mites metabolic compounds, and importantly, by environmental proteases such as trypsin and tryptase. Because of the pivotal role of proteases in the onset of asthma pathophysiology, we focused this study on the serine Protease Activated Receptor-2 (PAR-2), a G-protein-coupled receptor widely expressed in cells across the respiratory tract. Herein, we measured the activation of PAR-2 on primary pulmonary bronchial/tracheal epithelial cells, human small airway epithelial cells, lung bronchial smooth muscle cells (with and without asthma). We tested human-derived eosinophils from 61 Puerto Rican participants (33 asthmatic and 28 non-asthmatic). As surrogate of PAR-2 activation or inhibition we used intracellular calcium mobilization assay. We hypothesized that following exposure of the PAR-2 agonist (AC264613), the studied human primary cell types will increase the mobilization of intracellular calcium levels. In contrast, we expected a decrease of the intracellular calcium levels upon exposure to a PAR-2 antagonist (FSLLRY-NH2). The Puerto Rican-derived eosinophils were analyzed for the proinflammatory markers MAPK/PI3K using flow cytometry (n = 8). As expected, the PAR-2 agonist significantly increased the activation of PAR-2 on the bronchial/tracheal epithelial cells, bronchial smooth muscle cells and human small airway epithelial cells (P = .01). The PAR-2 antagonist significantly decreased the intracellular calcium levels of these lung primary down to undetectable levels (P = .01). Remarkably, the asthmatic-derived eosinophils showed a striking 300% increase of intracellular calcium mobilization suggesting a severe response to the PAR-2 agonist stimuli in asthmatics. In contrast, there were no significant changes between groups after adding the PAR-2 antagonist. Our outcomes revealed that PAR-2 antagonist effectively inhibited the studied primary cells, expecting to decrease the immune response of eosinophils. Most importantly, our results reveal a promising role for the PAR-2 antagonist in targeting bronchial/tracheal epithelial cells, human small airway epithelial cells and bronchial smooth muscle cells with the potential to oblige an asthma adjuvant therapy.

Cathepsin G and Its Role in Inflammation and Autoimmune Diseases

Cathepsin G belongs to the neutrophil serine proteases family, known for its function in killing pathogens. Studies over the past several years indicate that cathepsin G has important effects on inflammation and immune reaction, and may be a key factor in the pathogenesis of some autoimmune diseases. In this article, we discuss the roles of cathepsin G in inflammation, immune reaction, and autoimmune diseases. To our knowledge, this is the first study providing important information about cathepsin G in the pathogenesis of autoimmune diseases and suggesting that cathepsin G may be a new biomarker or treatment target.

The role and mechanism of cathepsin G in dermatomyositis

Dermatomyositis (DM) is an idiopathic inflammatory myopathy characterized by CD4+ T cells and B cells infiltration in perivascular and muscle tissue. Although the infiltration of inflammatory cells plays a key role in muscle damage, the exact mechanism is not clear. Cathepsin G (CTSG) is a member of the serine proteases family and can increase the permeability of vascular endothelial cells and the chemotaxis of inflammatory cells. In this study, we found that the expression of CTSG was increased in peripheral blood mononuclear cells and muscle tissues of DM patients. The activity of CTSG was significantly increased in DM patients and correlated with disease activity. Serum CTSG induced the expression of protease activated receptor 2 (PAR2) and altered the cytoskeleton of human dermal microvascular endothelial cells. Our studies indicate, for the first time, that CTSG may play an important role in muscle inflammatory cells infiltration by increasing the permeability of vascular endothelial cells.

Expression of proteinase-activated receptor (PAR)-2 in monocytes from allergic patients and potential molecular mechanism

Serine proteases play an important role in inflammation via PARs. However, little is known of expression levels of PARs on monocytes of allergic patients, and influence of serine proteases and PARs on TNF-α secretion from monocytes. Using quantitative real-time PCR (qPCR) and flowcytometry techniques, we observed that the expression level of PAR-2 in monocytes of patients with allergic rhinitis and asthma was increased by 42.9 and 38.2 %. It was found that trypsin, thrombin, and tryptase induced up to 200, 320, and 310 % increase in TNF-α release from monocytes at 16 h, respectively. PAR-1 agonist peptide, SFLLR-NH₂, and PAR-2 agonist peptide tc-LIGRLO-NH₂ provoked up to 210 and 240 % increase in release of TNF-α. Since SCH 79797, a PAR-1 antagonist, and PD98059, an inhibitor of ERK inhibited thrombin- and SFLLR-NH₂-induced TNF-α release, the action of thrombin is most likely through a PAR-1- and ERK-mediated signaling mechanism. Similarly, because FSLLRN-NH₂, an inhibitor of PAR-2 diminished tryptase- and tc-LIGRLO-NH₂-induced TNF-α release, the action of tryptase appears PAR-2 dependent. Moreover, in vivo study showed that both recombinant cockroach major allergens Per a 1 and Per a 7 provoked upregulation of PAR-2 and PAR-1 expression on CD14+ cells in OVA-sensitized mouse peritoneum. In conclusion, increased expression of PAR-2 in monocytes of AR and asthma implicates that PAR-2 likely play a role in allergy. PAR-2- and PAR-1-mediated TNF-α release from monocytes suggests that these unique protease receptors are involved in the pathogenesis of inflammation.

Gastrointestinal Inflammation: A Central Component of Mucosal Defense and Repair

The mucosal layer of the gastrointestinal (GI) tract is able to resist digestion by the endogenous substances that we secrete to digest foodstuffs. So-called “mucosal defense” is multifactorial and can be modulated by a wide range of substances, many of which are classically regarded as inflammatory mediators. Damage to the GI mucosa, and its subsequent repair, are also modulated by various inflammatory mediators. In this article, we provide a review of some of the key Inflammatory mediators that modulate GI mucosal defense, Injury, and repair. Among the mediators discussed are nitric oxide, polyamines, the elcosanolds (prostaglandins and II-poxlns), protease-activated receptors, and cytokines. Many of these endogenous factors, or the enzymes involved in their synthesis, are considered potential therapeutic targets for the treatment of diseases of the digestive tract that are characterized by Inflammation and ulceration.

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.

Effects of the neutrophil elastase inhibitor EL-17 in rat adjuvant-induced arthritis

OBJECTIVES

Neutrophil elastase (NE), a granule-associated enzyme, participates in connective tissue breakdown and promotes cytokine release and specific receptor activation during various inflammatory diseases like RA. NE is increased in the SF and cartilage of RA patients and represents a target for the development of new therapeutic possibilities. The present research aimed to evaluate the preclinical pharmacological profile of the N-benzoylpyrazole derivative EL-17, a potent and selective NE inhibitor, in a rat model of RA.

METHODS

Complete Freund's Adjuvant (CFA) was injected in the tibiotarsal joint and the effect of acute or repeated treatments with EL-17 (1-30 mg/kg by mouth) were evaluated.

RESULTS

On day 14 after CFA injection, a single administration of EL-17 significantly reduced CFA-dependent hypersensitivity to mechanical noxious stimuli and the postural unbalance related to spontaneous pain. To evaluate the preventive efficacy, EL-17 was administered daily starting from the day of CFA treatment. Behavioural measurements performed on days 7 and 14 showed a progressive efficacy of EL-17 against hypersensitivity to mechanical noxious and non-noxious stimuli, as well as a decrease of hind limb weight-bearing alterations. Histological evaluation of the tibiotarsal joint (day 14) demonstrated significant prevention of articular derangement after EL-17 (30 mg/kg) treatment. The protective effects of EL-17 directly correlated with a complete reversion of the plasma NE activity increase induced by CFA.

CONCLUSIONS

The NE inhibitor EL-17 relieved articular pain after acute administration. Furthermore, repeated treatment reduced the development of hypersensitivity and protected joint tissue, revealing a disease-modifying profile.

Gingival crevicular fluid levels of protease-activated receptors type 1 and type 2 in diabetic patients with periodontitis

BACKGROUND AND OBJECTIVE

Protease activated receptor type 1 (PAR1 ) seems to play a role in periodontal repair, while PAR2 is associated with periodontal inflammation. As diabetes is a known risk factor for periodontal disease, the aim of this study was to evaluate the influence of type 2 diabetes on PAR1 and PAR2 mRNA expression in the gingival crevicular fluid of patients with chronic periodontitis before and after non-surgical periodontal treatment.

MATERIAL AND METHODS

Gingival crevicular fluid samples and clinical parameters consisting of measuring probing depth, clinical attachment level, bleeding on probing and plaque index were collected from systemically healthy patients and patients with type 2 diabetes and chronic periodontitis, at baseline and after non-surgical periodontal therapy. PAR1 and PAR2 , as well as the presence of the proteases RgpB gingipain and neutrophil proteinase-3 were assessed by quantitative polymerase chain reaction in the gingival crevicular fluid.

RESULTS

The periodontal clinical parameters significantly improved after periodontal therapy (p < 0.01). Diabetes led to increased expression of PAR1 in gingival crevicular fluid, and in the presence of chronic periodontitis, it significantly decreased the expression of PAR1 and PAR2 (p < 0.05). Moreover, non-surgical periodontal treatment in diabetics resulted in increased expression of PAR1 and PAR2 (p < 0.05), and decreased expression of RgpB gingipain and proteinase-3 (p < 0.05).

CONCLUSION

The present data demonstrated that diabetes was associated with an altered expression of PAR1 and PAR2 in the gingival crevicular fluid cells of subjects with chronic periodontitis. Future studies are necessary to elucidate the effects of PAR1 upregulation in periodontally healthy sites and PAR2 downregulation in chronic periodontitis sites on the increased susceptibility and severity of periodontitis in diabetes.

Cyclosporine Does Not Prevent Microvascular Loss in Transplantation but Can Synergize With a Neutrophil Elastase Inhibitor, Elafin, to Maintain Graft Perfusion During Acute Rejection

The loss of a functional microvascular bed in rejecting solid organ transplants is correlated with fibrotic remodeling and chronic rejection; in lung allografts, this pathology is predicted by bronchoalveolar fluid neutrophilia which suggests a role for polymorphonuclear cells in microcirculatory injury. In a mouse orthotopic tracheal transplant model, cyclosporine, which primarily inhibits T cells, failed as a monotherapy for preventing microvessel rejection and graft ischemia. To target neutrophil action that may be contributing to vascular injury, we examined the effect of a neutrophil elastase inhibitor, elafin, on the microvascular health of transplant tissue. We showed that elafin monotherapy prolonged microvascular perfusion and enhanced tissue oxygenation while diminishing the infiltration of neutrophils and macrophages and decreasing tissue deposition of complement C3 and the membrane attack complex, C5b-9. Elafin was also found to promote angiogenesis through activation of the extracellular signal-regulated kinase (ERK) signaling pathway but was insufficient as a single agent to completely prevent tissue ischemia during acute rejection episodes. However, when combined with cyclosporine, elafin effectively preserved airway microvascular perfusion and oxygenation. The therapeutic strategy of targeting neutrophil elastase activity alongside standard immunosuppression during acute rejection episodes may be an effective approach for preventing the development of irreversible fibrotic remodeling.

Lack of cathelicidin processing in Papillon-Lefèvre syndrome patients reveals essential role of LL-37 in periodontal homeostasis

Background

Loss-of-function point mutations in the cathepsin C gene are the underlying genetic event in patients with Papillon-Lefèvre syndrome (PLS). PLS neutrophils lack serine protease activity essential for cathelicidin LL-37 generation from hCAP18 precursor.

Aim

We hypothesized that a local deficiency of LL-37 in the infected periodontium is mainly responsible for one of the clinical hallmark of PLS: severe periodontitis already in early childhood.

Methods

To confirm this effect, we compared the level of neutrophil-derived enzymes and antimicrobial peptides in gingival crevicular fluid (GCF) and saliva from PLS, aggressive and chronic periodontitis patients.

Results

Although neutrophil numbers in GCF were present at the same level in all periodontitis groups, LL-37 was totally absent in GCF from PLS patients despite the large amounts of its precursor, hCAP18. The absence of LL-37 in PLS patients coincided with the deficiency of both cathepsin C and protease 3 activities. The presence of other neutrophilic anti-microbial peptides in GCF from PLS patients, such as alpha-defensins, were comparable to that found in chronic periodontitis. In PLS microbial analysis revealed a high prevalence of Aggregatibacter actinomycetemcomitans infection. Most strains were susceptible to killing by LL-37.

Conclusions

Collectively, these findings imply that the lack of protease 3 activation by dysfunctional cathepsin C in PLS patients leads to the deficit of antimicrobial and immunomodulatory functions of LL-37 in the gingiva, allowing for infection with A. actinomycetemcomitans and the development of severe periodontal disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-014-0148-y) contains supplementary material, which is available to authorized users.

Neutrophil cathepsin G, but not elastase, induces aggregation of MCF-7 mammary carcinoma cells by a protease activity-dependent cell-oriented mechanism

We previously found that a neutrophil serine protease, cathepsin G, weakens adherence to culture substrates and induces E-cadherin-dependent aggregation of MCF-7 human breast cancer cells through its protease activity. In this study, we examined whether aggregation is caused by degradation of adhesion molecules on the culture substrates or through an unidentified mechanism. We compared the effect of treatment with cathepsin G and other proteases, including neutrophil elastase against fibronectin- (FN-) coated substrates. Cathepsin G and elastase potently degraded FN on the substrates and induced aggregation of MCF-7 cells that had been subsequently seeded onto the substrate. However, substrate-bound cathepsin G and elastase may have caused cell aggregation. After inhibiting the proteases on the culture substrates using the irreversible inhibitor phenylmethylsulfonyl fluoride (PMSF), we examined whether aggregation of MCF-7 cells was suppressed. PMSF attenuated cell aggregation on cathepsin G-treated substrates, but the effect was weak in cells pretreated with high concentrations of cathepsin G. In contrast, PMSF did not suppress cell aggregation on elastase-treated FN. Moreover, cathepsin G, but not elastase, induced aggregation on poly-L-lysine substrates which are not decomposed by these enzymes, and the action of cathepsin G was nearly completely attenuated by PMSF. These results suggest that cathepsin G induces MCF-7 aggregation through a cell-oriented mechanism.

Periodontal treatment downregulates protease-activated receptor 2 in human gingival crevicular fluid cells

Protease-activated receptor 2 (PAR2) is implicated in the pathogenesis of chronic inflammatory diseases, including periodontitis; it can be activated by gingipain and produced by Porphyromonas gingivalis and by neutrophil protease 3 (P3). PAR2 activation plays a relevant role in inflammatory processes by inducing the release of important inflammatory mediators associated with periodontal breakdown. The effects of periodontal treatment on PAR2 expression and its association with levels of proinflammatory mediators and activating proteases were investigated in chronic periodontitis patients. Positive staining for PAR2 was observed in gingival crevicular fluid cells and was reflective of tissue destruction. Overexpression of PAR2 was positively associated with inflammatory clinical parameters and with the levels of interleukin-6 (IL-6), IL-8, tumor necrosis factor alpha, matrix metalloprotease 2 (MMP-2), MMP-8, hepatocyte growth factor, and vascular endothelial growth factor. Elevated levels of gingipain and P3 and decreased levels of dentilisin and the protease inhibitors secretory leukocyte protease inhibitor and elafin were also associated with PAR2 overexpression. Healthy periodontal sites from individuals with chronic periodontitis showed diminished expression of PAR2 mRNA and the PAR2 protein (P < 0.05). Furthermore, periodontal treatment resulted in decreased PAR2 expression and correlated with decreased expression of inflammatory mediators and activating proteases. We concluded that periodontal treatment resulted in decreased levels of proteases and that proinflammatory mediators are associated with decreased PAR2 expression, suggesting that PAR2 expression is influenced by the presence of periodontal infection and is not a constitutive characteristic favoring periodontal inflammation.

Lipopolysaccharide-induced indoleamine 2,3-dioxygenase expression in the periodontal ligament

BACKGROUND AND OBJECTIVE

Indoleamine 2,3-dioxygenase (IDO) is a tryptophan-oxidizing enzyme with immune-inhibitory effects. The aim of this study was to investigate the expression of IDO by lipopolysaccharide (LPS), a component of gram-negative bacteria, in human periodontal ligament (PDL) cells.

MATERIAL AND METHODS

Human PDL cells and gingival fibroblasts (GFs) were prepared from explants of human PDLs and from gingival tissues of clinically healthy donors, respectively. Real-time RT-PCR, western blotting and the IDO enzyme assay were performed to determine the expression of IDO following LPS treatment of cells. LPS was injected into mice tail veins to evaluate the effects of LPS in vivo in the maxillary first molar. Immunofluorescence staining and histological analysis were followed to localize IDO in mouse PDL.

RESULTS

The level of expression of IDO mRNA in primary human PDL cells after LPS treatment was increased in a dose-dependent manner, reaching a peak 8 h after LPS treatment. The expression and activities of IDO protein were significantly increased in comparison with those of the control. In addition, the increased production of kynurenine in culture medium was observed 72 h after LPS treatment. In the immunofluorescence findings, stronger immunoreactivities were shown in PDL than in gingival tissues in the maxillae. In accordance with the immunofluorescence findings, LPS treatment induced a strong up-regulation of IDO mRNA in human PDL cells, whereas human GFs showed only a weak response to LPS.

CONCLUSION

These results clearly show that IDO was induced by LPS in primary human PDL cells, suggesting that PDL might be involved in the regulation of oral inflammatory disease.

Neutrophil elastase induces MUC5AC secretion via protease-activated receptor 2

Mucus hypersecretion is a major manifestation in patients with chronic inflammatory airway diseases, and mucin5AC (MUC5AC) protein is a major component of airway mucus. Previous studies have demonstrated that neutrophil elastase (NE) stimulates the secretion of MUC5AC from airway epithelial cells, however, the mechanism is poorly understood. NE is a known ligand for protein active receptors (PARs), which have been confirmed to participate in releasing MUC5AC in the airways. However, the role of PARs in NE-induced MUC5AC secretion remains unclear. We demonstrated that airway goblet-like Calu-3 cells express PAR1, PAR2, and PAR3 with a predominant level of PAR2. NE can increase PAR2 expression and MUC5AC release. In our study, we showed that NE binding to PAR2 can increase the cytosolic calcium concentration and subsequently activate PKC, leading to MUC5AC secretion. In order to investigate the mechanism of increased cytosolic calcium in Calu-3 cells, thapsigargin was used to exhaust the endoplasmic reticulum (ER) calcium pools, and 2-aminoethoxydiphenyl borate was used to inhibit the function of the store-operated calcium entry (SOCE) channels in the plasma membrane. We found that the NE-induced increase in intracellular calcium concentration is derived from release of the ER calcium pool and its subsequent calcium internal flux from the extracellular space via SOCE channels, which is dependent on sufficient levels of extracellular calcium.

Modulation of PAR expression and tryptic enzyme induced IL-4 production in mast cells by IL-29

Interleukin (IL)-29 is a relatively newly discovered cytokine, which has been shown to be actively involved in the pathogenesis of allergic inflammation. However, little is known of the effects of IL-29 on protease activated receptor (PAR) expression and potential mechanisms of cytokine production in mast cells. In the present study, we examined potential influence of IL-29 on PAR expression and cytokine production in P815 and bone marrow derived mast cells (BMMCs) by using flow cytometry analysis, quantitative real time PCR, and ELISA techniques. The results showed that IL-29 downregulated the expression of PAR-1 by up to 56.2%, but had little influence on the expression of PAR-2, PAR-3 and PAR-4. IL-29 also induced downregulation of expression of PAR-1 mRNA. However, when mast cells were pre-incubated with IL-29, thrombin-, trypsin- and tryptase-induced expression of PAR-2, PAR-3 and PAR-4 was upregulated, respectively. IL-29 provoked approximately up to 1.9-fold increase in IL-4 release when mast cells was challenged with IL-29. Administration of IL-29 blocking antibody, AG490 or LY294002 abolished IL-29-induced IL-4 release from P815 cells. It was found that IL-29 diminished trypsin- and tryptase-induced IL-4 release from P815 cells following 16 h incubation. In conclusion, IL-29 can regulate expression of PARs and tryptase- and trypsin-induced IL-4 production in mast cells, through which participates in the mast cell related inflammation.

Potent elastase inhibitors from cyanobacteria: structural basis and mechanisms mediating cytoprotective and anti-inflammatory effects in bronchial epithelial cells

We discovered new structural diversity to a prevalent, yet medicinally underappreciated, cyanobacterial protease inhibitor scaffold and undertook comprehensive protease profiling to reveal potent and selective elastase inhibition. Structure-activity relationship (SAR) studies and X-ray cocrystal structure analysis allowed a detailed assessment of critical and tunable structural elements. To realize the therapeutic potential of these cyclodepsipeptides, we probed the cellular effects of a novel and representative family member, symplostatin 5 (1), which attenuated the downstream cellular effects of elastase in an epithelial lung airway model system, alleviating clinical hallmarks of chronic pulmonary diseases such as cell death, cell detachment, and inflammation. This compound attenuated the effects of elastase on receptor activation, proteolytic processing of the adhesion protein ICAM-1, NF-κB activation, and transcriptomic changes, including the expression of pro-inflammatory cytokines IL1A, IL1B, and IL8. Compound 1 exhibited activity comparable to the clinically approved elastase inhibitor sivelestat in short-term assays and demonstrated superior sustained activity in longer-term assays.

Inhibition of neutrophil elastase attenuates airway hyperresponsiveness and inflammation in a mouse model of secondary allergen challenge: neutrophil elastase inhibition attenuates allergic airway responses

BACKGROUND

Chronic asthma is often associated with neutrophilic infiltration in the airways. Neutrophils contain elastase, a potent secretagogue in the airways, nonetheless the role for neutrophil elastase as well as neutrophilic inflammation in allergen-induced airway responses is not well defined. In this study, we have investigated the impact of neutrophil elastase inhibition on the development of allergic airway inflammation and airway hyperresponsiveness (AHR) in previously sensitized and challenged mice.

METHODS

BALB/c mice were sensitized and challenged (primary) with ovalbumin (OVA). Six weeks later, a single OVA aerosol (secondary challenge) was delivered and airway inflammation and airway responses were monitored 6 and 48 hrs later. An inhibitor of neutrophil elastase was administered prior to secondary challenge.

RESULTS

Mice developed a two-phase airway inflammatory response after secondary allergen challenge, one neutrophilic at 6 hr and the other eosinophilic, at 48 hr. PAR-2 expression in the lung tissues was enhanced following secondary challenge, and that PAR-2 intracellular expression on peribronchial lymph node (PBLN) T cells was also increased following allergen challenge of sensitized mice. Inhibition of neutrophil elastase significantly attenuated AHR, goblet cell metaplasia, and inflammatory cell accumulation in the airways following secondary OVA challenge. Levels of IL-4, IL-5 and IL-13, and eotaxin in BAL fluid 6 hr after secondary allergen challenge were significantly suppressed by the treatment. At 48 hr, treatment with the neutrophil elastase inhibitor significantly reduced the levels of IL-13 and TGF-β1 in the BAL fluid. In parallel, in vitro IL-13 production was significantly inhibited in spleen cells from sensitized mice.

CONCLUSION

These data indicate that neutrophil elastase plays an important role in the development of allergic airway inflammation and hyperresponsiveness, and would suggest that the neutrophil elastase inhibitor reduced AHR to inhaled methacholine indicating the potential for its use as a modulator of the immune/inflammatory response in both the neutrophil- and eosinophil-dominant phases of the response to secondary allergen challenge.

Role of Proteases in Inflammatory Lung Diseases

Proteases are enzymes that have the capacity to hydrolyze peptide bonds and degrade other proteins. Proteases can promote inflammation by regulating expression and activity of different pro-inflammatory cytokines, chemokines and other immune components in the lung compartment. They are categorized in three major subcategories: serine proteases, metalloproteases and cysteine proteases especially in case of lung diseases. Neutrophil-derived serine proteases (NSPs), metalloproteases and some mast cell-derived proteases are mainly focused here. Their modes of actions are different in different diseases for e.g. NE induces the release of IL-8 from lung epithelial cells through a MyD88/IRAK/TRAF-6-dependent pathway and also through EGFR MAPK pathway. NSPs contribute to immune regulation during inflammation through the cleavage and activation of specific cellular receptors. MMPs can also influence the progression of various inflammatory processes and there are many non-matrix substrates for MMPs, such as chemokines, growth factors and receptors. During lung inflammation interplay between NE and MMP is an important significant phenomenon. They have been evaluated as therapeutic targets in several inflammatory lung diseases. Here we review the role of proteases in various lung inflammatory diseases with emphasis on their mode of action and contribution to immune regulation during inflammation.

Induction of tumor necrosis factor (TNF) release from subtypes of T cells by agonists of proteinase activated receptors

Serine proteinases have been recognized as playing an important role in inflammation via proteinase activated receptors (PARs). However, little is known about the influence of serine proteinases and PARs on TNF secretion from highly purified T cells. We challenged T cells from human peripheral blood with serine proteinases and agonist peptides of PARs and measured the levels of TNF in culture supernatants by ELISA. The results showed that thrombin and trypsin, but not tryptase, stimulated approximately up to 2.5-fold increase in TNF release from T cells following 16 h incubation. Proteinase inhibitors and PAR-1 antagonist SCH 79797 almost completely abolished thrombin- and trypsin-induced TNF release from T cells. Agonist peptides of PAR-1, but not PAR-2 induced TNF release from T cells. Moreover, trypsin- and thrombin-induced upregulated expression of TNF was observed in CD4+, IL-4+, or CD25+ T cells, but not in IFN+ or IL-17+ T cells. The signaling pathways MAPK/ERK and PI3K/Akt are involved in the thrombin- and trypsin-induced TNF release from T cells. In conclusion, thrombin and trypsin can induce TNF release from IL-4+ and CD25+ T cells through activation of PAR-1 and therefore contribute to regulation of immune response and inflammation of the body.

PR3 and elastase alter PAR1 signaling and trigger vWF release via a calcium-independent mechanism from glomerular endothelial cells

Neutrophil proteases, proteinase-3 (PR3) and elastase play key roles in glomerular endothelial cell (GEC) injury during glomerulonephritis. Endothelial protease-activated receptors (PARs) are potential serine protease targets in glomerulonephritis. We investigated whether PAR1/2 are required for alterations in GEC phenotype that are mediated by PR3 or elastase during active glomerulonephritis. Endothelial PARs were assessed by flow cytometry. Thrombin, trypsin and agonist peptides for PAR1 and PAR2, TFLLR-NH(2) and SLIGKV-NH(2,) respectively, were used to assess alterations in PAR activation induced by PR3 or elastase. Endothelial von Willebrand Factor (vWF)release and calcium signaling were used as PAR activation markers. Both PR3 and elastase induced endothelial vWF release, with elastase inducing the highest response. PAR1 peptide induced GEC vWF release to the same extent as PR3. However, knockdown of PARs by small interfering RNA showed that neither PAR1 nor PAR2 activation caused PR3 or elastase-mediated vWF release. Both proteases interacted with and disarmed surface GEC PAR1, but there was no detectable interaction with cellular PAR2. Neither protease induced a calcium response in GEC. Therefore, PAR signaling and serine protease-induced alterations in endothelial function modulate glomerular inflammation via parallel but independent pathways.

Host-bacteria crosstalk at the dentogingival junction

The dentogingival junction is of crucial importance in periodontal host defense both structurally and functionally. Oral bacteria exert a constant challenge to the host cells and tissues at the dentogingival junction. The host response is set up to eliminate the pathogens by the innate and adaptive defense mechanisms. In health, the commensal bacteria and the host defense mechanisms are in a dynamic steady state. During periodontal disease progression, the dental bacterial plaque, junctional epithelium (JE), inflammatory cells, connective tissue, and bone all go through a series of changes. The tissue homeostasis is turned into tissue destruction and progression of periodontitis. The classical study of Slots showed that in the bacterial plaque, the most remarkable change is the shift from gram-positive aerobic and facultatively anaerobic flora to a predominantly gram-negative and anaerobic flora. This has been later confirmed by several other studies. Furthermore, not only the shift of the bacterial flora to a more pathogenic one, but also bacterial growth as a biofilm on the tooth surface, allows the bacteria to communicate with each other and exert their virulence aimed at favoring their growth. This paper focuses on host-bacteria crosstalk at the dentogingival junction and the models studying it in vitro.

Proteinase-activated receptor-2 is required for normal osteoblast and osteoclast differentiation during skeletal growth and repair

Proteinase-activated receptor-2 (PAR(2)) is a G-protein coupled receptor expressed by osteoblasts and monocytes. PAR(2) is activated by a number of proteinases including coagulation factors and proteinases released by inflammatory cells. The aim of the current study was to investigate the role of PAR(2) in skeletal growth and repair using wild type (WT) and PAR(2) knockout (KO) mice. Micro computed tomography and histomorphometry were used to examine the structure of tibias isolated from uninjured mice at 50 and 90 days of age, and from 98-day-old mice in a bone repair model in which a hole had been drilled through the tibias. Bone marrow was cultured and investigated for the presence of osteoblast precursors (alkaline phosphatase-positive fibroblastic colonies), and osteoclasts were counted in cultures treated with M-CSF and RANKL. Polymerase chain reaction (PCR) was used to determine which proteinases that activate PAR(2) are expressed in bone marrow. Regulation of PAR(2) expression in primary calvarial osteoblasts from WT mice was investigated by quantitative PCR. Cortical and trabecular bone volumes were significantly greater in the tibias of PAR(2) KO mice than in those of WT mice at 50 days of age. In trabecular bone, osteoclast surface, osteoblast surface and osteoid volume were significantly lower in KO than in WT mice. Bone marrow cultures from KO mice showed significantly fewer alkaline phosphatase-positive colony-forming units and osteoclasts compared to cultures from WT mice. Significantly less new bone and significantly fewer osteoclasts were observed in the drill sites of PAR(2) KO mice compared to WT mice 7 days post-surgery. A number of activators of PAR(2), including matriptase and kallikrein 4, were found to be expressed by normal bone marrow. Parathyroid hormone, 1,25 dihydroxyvitamin D(3), or interleukin-6 in combination with its soluble receptor down-regulated PAR(2) mRNA expression, and fibroblast growth factor-2 or thrombin stimulated PAR(2) expression. These results suggest that PAR(2) activation contributes to determination of cells of both osteoblast and osteoclast lineages within bone marrow, and thereby participates in the regulation of skeletal growth and bone repair.

Periodontal pathogens affect the level of protease inhibitors in gingival crevicular fluid

In periodontitis, an effective host-response is primarily related to neutrophils loaded with serine proteases, including elastase (NE) and protease 3 (PR3), the extracellular activity of which is tightly controlled by endogenous inhibitors. In vitro these inhibitors are degraded by gingipains, cysteine proteases produced by Porphyromonas gingivalis. The purpose of this study was to determine the level of selected protease inhibitors in gingival crevicular fluid (GCF) in relation to periodontal infection. The GCF collected from 31 subjects (nine healthy controls, seven with gingivitis, five with aggressive periodontitis and 10 with chronic periodontitis) was analyzed for the levels of elafin and secretory leukocyte protease inhibitor (SLPI), two main tissue-derived inhibitors of neutrophil serine proteases. In parallel, activity of NE, PR3 and arginine-specific gingipains (Rgps) in GCF was measured. Finally loads of P. gingivalis, Aggregatibacter actinomycetemcomitans, Tannerella forsythia and Treponema denticola were determined. The highest values of elafin were found in aggressive periodontitis and the lowest in controls. The quantity of elafin correlated positively with the load of P. gingivalis, Ta. forsythia and Tr. denticola, as well as with Rgps activity. In addition, NE activity was positively associated with the counts of those bacterial species, but not with the amount of elafin. In contrast, the highest concentrations of SLPI were found in periodontally healthy subjects whereas amounts of this inhibitor were significantly decreased in patients infected with P. gingivalis. Periodontopathogenic bacteria stimulate the release of NE and PR3, which activities escape the control through degradation of locally produced inhibitors (SLPI and elafin) by host-derived and bacteria-derived proteases.

Local regulation of neutrophil elastase activity by endogenous α1-antitrypsin in lipopolysaccharide-primed hematological cells

Neutrophil elastase released from activated neutrophils contributes in combating bacterial infection. While chronic inflammation results in anemia and decreased bone marrow activities, little is known about the effect of neutrophil elastase on hematological cell growth in severe inflammatory states. Here, we demonstrated that α1-antitrypsin, a physiological inhibitor of neutrophil elastase, functions as a regulator for cell growth by neutralizing neutrophil elastase activity in lipopolysaccharide-primed hematological cells. HL-60 cells were resistant to neutrophil elastase, as they also expressed α1-antitrypsin. The growth of HL-60 cells transduced with a LentiLox-short hairpin α1-antitrypsin vector was significantly suppressed by neutrophil elastase or lipopolysaccharide. When CD34(+) progenitor cells were differentiated towards a granulocytic lineage, they concomitantly expressed neutrophil elastase and α1-antitrypsin and prevented neutrophil elastase-induced growth inhibition. These results suggest that granulocytes might protect themselves from neutrophil elastase-induced cellular damage by efficiently neutralizing its activity through the simultaneous secretion of endogenous α1-antitrypsin.

TGF-β1 induces proteinase-activated receptor 2 (PAR2) expression in endometriotic stromal cells and stimulates PAR2 activation-induced secretion of IL-6

BACKGROUND

Proteinase-activated receptor 2 (PAR2) is a G-protein-coupled receptor that is activated by several serine proteases. PAR2 activation in endometriotic stromal cells (ESCs) has been implicated in the development of endometriosis but the regulatory mechanism of PAR2 expression in ESC is unknown. Our objective was to study the mechanism by which PAR2 expression may be regulated in endometriotic lesions.

METHODS

Primary cultures of ESCs were treated with transforming growth factor-β (TGF-β) 1, tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), and the expression of PAR2 was examined by real-time quantitative PCR. ESCs pretreated with or without TGF-β1 were treated with PAR2 agonist peptide (PAR2AP) and the secretion of the pro-endometriotic cytokine, IL-6, was measured using a specific enzyme-linked immunosorbent assay. Effects of TGF-β type 1 inhibitor, SB431542, and PAR2 small interfering RNA (siRNA) on the TGF-β1 stimulation of PAR2 gene expression and PAR2AP-induced IL-6 secretion were also evaluated. To study intracellular signaling, effects of inhibitors of mitogen-activated protein kinases (MAPKs) and phosphoinositide 3-kinase (PI3K) and of Smad4 siRNA on the TGF-β1-induced PAR2 gene expression were studied.

RESULTS

Only TGF-β1, but neither TNF-α nor IL-1β, increased gene expression of PAR2. Activation of PAR2 with PAR2AP increased the secretion of IL-6 from ESCs. As expected, TGF-β1 pretreatment dose-dependently enhanced the PAR2AP-induced increase in IL-6 secretion from ESCs. Treatment of ESCs with the TGF-β type 1 inhibitor, SB431542, inhibited both TGF-β1-stimulation of PAR2 gene expression and PAR2AP-induced IL-6 secretion. Transfection of ESCs with PAR2 siRNA produced a similar inhibition of IL-6 secretion. The TGF-β1-induced increase in PAR2 gene expression was repressed by inhibition of p38 MAPK, p42/44 MAPK or PI3K, but not by knockdown of Smad4 expression.

CONCLUSIONS

In view of significant roles of PAR2 and IL-6 in endometriosis, the TGF-β1-induced increase in PAR2 expression may be an elaborate mechanism that augments the progression of the disease.

Neutrophil elastase, proteinase 3, and cathepsin G as therapeutic targets in human diseases

Polymorphonuclear neutrophils are the first cells recruited to inflammatory sites and form the earliest line of defense against invading microorganisms. Neutrophil elastase, proteinase 3, and cathepsin G are three hematopoietic serine proteases stored in large quantities in neutrophil cytoplasmic azurophilic granules. They act in combination with reactive oxygen species to help degrade engulfed microorganisms inside phagolysosomes. These proteases are also externalized in an active form during neutrophil activation at inflammatory sites, thus contributing to the regulation of inflammatory and immune responses. As multifunctional proteases, they also play a regulatory role in noninfectious inflammatory diseases. Mutations in the ELA2/ELANE gene, encoding neutrophil elastase, are the cause of human congenital neutropenia. Neutrophil membrane-bound proteinase 3 serves as an autoantigen in Wegener granulomatosis, a systemic autoimmune vasculitis. All three proteases are affected by mutations of the gene (CTSC) encoding dipeptidyl peptidase I, a protease required for activation of their proform before storage in cytoplasmic granules. Mutations of CTSC cause Papillon-Lefèvre syndrome. Because of their roles in host defense and disease, elastase, proteinase 3, and cathepsin G are of interest as potential therapeutic targets. In this review, we describe the physicochemical functions of these proteases, toward a goal of better delineating their role in human diseases and identifying new therapeutic strategies based on the modulation of their bioavailability and activity. We also describe how nonhuman primate experimental models could assist with testing the efficacy of proposed therapeutic strategies.

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.

Tailor-made inflammation: how neutrophil serine proteases modulate the inflammatory response

Neutrophil granulocytes are important mediators of innate immunity, but also participate in the pathogenesis of (auto)inflammatory diseases. Neutrophils express a specific set of proteolytic enzymes, the neutrophil serine proteases (NSPs), which are stored in cytoplasmic granules and can be secreted into the extra- and pericellular space upon cellular activation. These NSPs, namely cathepsin G (CG), neutrophil elastase (NE), and proteinase 3 (PR3), have early been implicated in bacterial defense. However, NSPs also regulate the inflammatory response by specifically altering the function of cytokines and chemokines. For instance, PR3 and NE both inactivate the anti-inflammatory mediator progranulin, which may play a role in chronic inflammation. Here, we provide a concise update on NSPs as modulators of inflammation and discuss the biological and pathological significance of this novel function of NSPs. Mounting evidence support an important proinflammatory function for PR3, which may have been underestimated in the past.

Protease-activated Receptor-2 (par2) in Human Periodontitis

No evidence for the role of protease-activated receptor-2 (PAR2) in human periodontal disease has been demonstrated so far. Thus, we sought to investigate the expression of PAR2 mRNA in chronic periodontitis, and to examine whether its expression is related to the presence of PAR2 potential activators. Microbiological and gingival crevicular fluid samples were collected from individuals with chronic periodontitis and control individuals, and the presence of neutrophil serine proteinase 3 (P3) and Porphyromonas gingivalis was evaluated. PAR2 mRNA expression was higher (p < 0.001) in those with chronic periodontitis compared with control individuals, and it was statistically decreased (p = 0.0006) after periodontal treatment. Furthermore, those with chronic periodontitis presented higher (p < 0.05) levels of IL-1α, IL-6, IL-8, and TNF-α, total proteolytic activity, P. gingivalis prevalence, and P3mRNA expression compared with control individuals. We conclude that PAR2 mRNA expression and its potential activators are elevated in human chronic periodontitis, therefore suggesting that PAR2 may play a role in periodontal inflammation.

PAR-2 regulates dental pulp inflammation associated with caries

Protease-activated receptors (PARs) are G-protein-coupled receptors that are activated enzymatically by proteolysis of an N-terminal domain. The cleavage and activation of PARs by serine proteases represent a novel mechanism by which such enzymes could influence the host inflammatory response. The aim of this study was to determine whether PAR-2 expression and activation were increased in dental caries. Using immunohistochemistry, we showed PAR-2 to be localized to pulp cells subjacent to caries lesions, but minimally expressed by healthy pulp tissue. Trypsin and the PAR-2 agonist (PAR2-AP) activated PAR-2 in an in vitro functional assay. Endogenous molecules present in pulp cell lysates from carious teeth specifically activated PAR-2, but those from healthy teeth failed to do so. The activation of PAR-2 in vitro was shown to increase the expression of the pro-inflammatory mediator cyclo-oxygenase-2 (COX-2), providing a mechanism whereby PAR-2 could modulate pulpal inflammation.

Prospective randomized controlled study on the effects of perioperative administration of a neutrophil elastase inhibitor to patients undergoing video-assisted thoracoscopic surgery for thoracic esophageal cancer

Sivelestat sodium hydrate (Ono Pharmaceutical Co., Osaka, Japan) is a selective inhibitor of neutrophil elastase (NE) and is effective in reducing acute lung injury associated with systemic inflammatory response syndrome (SIRS). We conducted a prospective randomized controlled study to investigate the efficacy of perioperative administration of sivelestat sodium hydrate to prevent postoperative acute lung injury in patients undergoing thoracoscopic esophagectomy and radical lymphadenectomy. Twenty-two patients with thoracic esophageal cancer underwent video-assisted thoracoscopic esophagectomy with extended lymph node dissection in our institution between April 2007 and November 2008. Using a double-blinded method, these patients were randomly assigned to one of two groups preoperatively. The active treatment group received sivelestat sodium hydrate intravenously for 72 hours starting at the beginning of surgery (sivelestat-treated group; n= 11), while the other group received saline (control group; n= 11). All patients were given methylprednisolone immediately before surgery. Postoperative clinical course was compared between the two groups. Two patients (one in each group) were discontinued from the study during the postoperative period because of surgery-related complications. Of the remaining 20 patients, 2 patients who developed pneumonia within a week after surgery were excluded from some laboratory analyses, so data from 18 patients (9 patients in each group) were analyzed based on the arterial oxygen pressure/fraction of inspired oxygen ratio, white blood cell count, serum C-reactive protein level, plasma cytokine levels, plasma NE level, and markers of alveolar type II epithelial cells. In the current study, the incidence of postoperative morbidity did not differ between the two groups. The median duration of SIRS in the sivelestat-treated group was significantly shorter than that in the control group: 17 (range 9-36) hours versus 49 (15-60) hours, respectively (P= 0.009). Concerning the parameters used for the diagnosis of SIRS, the median heart rates on postoperative day (POD) 2 were significantly lower in the sivelestat-treated group than in the control group (P= 0.007). The median arterial oxygen pressure/fraction of inspired oxygen ratio of the sivelestat-treated group were significantly higher than those of the control group on POD 1 and POD 7 (POD 1: 372.0 [range 284.0-475.0] vs 322.5 [243.5-380.0], respectively, P= 0.040; POD 7: 377.2 [339.5-430.0] vs 357.6 [240.0-392.8], P= 0.031). Postoperative white blood cell counts, serum C-reactive protein levels, plasma interleukin-1beta, tumor necrosis factor-alpha levels, and plasma NE levels did not differ significantly between the two groups at any point during the postoperative course, nor did serum Krebs von den Lungen 6, surfactant protein-A, or surfactant protein-D levels, which were used as markers of alveolar type II epithelial cells to evaluate the severity of lung injury. Plasma interleukin-8 levels were significantly lower in the sivelestat-treated group than in the control group on POD 3 (P= 0.040). In conclusion, perioperative administration of sivelestat sodium hydrate (starting at the beginning of surgery) mitigated postoperative hypoxia, partially suppressed postoperative hypercytokinemia, shortened the duration of SIRS, and stabilized postoperative circulatory status after thoracoscopic esophagectomy.

Protease-activated receptor 2 has pivotal roles in cellular mechanisms involved in experimental periodontitis

The tissue destruction seen in chronic periodontitis is commonly accepted to involve extensive upregulation of the host inflammatory response. Protease-activated receptor 2 (PAR-2)-null mice infected with Porphyromonas gingivalis did not display periodontal bone resorption in contrast to wild-type-infected and PAR-1-null-infected mice. Histological examination of tissues confirmed the lowered bone resorption in PAR-2-null mice and identified a substantial decrease in mast cells infiltrating the periodontal tissues of these mice. T cells from P. gingivalis-infected or immunized PAR-2-null mice proliferated less in response to antigen than those from wild-type animals. CD90 (Thy1.2) expression on CD4(+) and CD8(+) T-cell-receptor beta (TCRbeta) T cells was significantly (P < 0.001) decreased in antigen-immunized PAR-2-null mice compared to sham-immunized PAR-2-null mice; this was not observed in wild-type controls. T cells from infected or antigen-immunized PAR-2-null mice had a significantly different Th1/inflammatory cytokine profile from wild-type cells: in particular, gamma interferon, interleukins (interleukin-2, -3, and -17), granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor alpha demonstrated lower expression than wild-type controls. The absence of PAR-2 therefore appears to substantially decrease T-cell activation and the Th1/inflammatory response. Regulation of such proinflammatory mechanisms in T cells and mast cells by PAR-2 suggests a pivotal role in the pathogenesis of the disease.

Over-expression and localization of a host protein on the membrane of Cryptosporidium parvum infected epithelial cells

The genus Cryptosporidium includes several species of intestinal protozoan parasites which multiply in intestinal epithelial cells. The impact of this infection on the transcriptome of cultured host cells was investigated using DNA microarray hybridizations. The expression of 14 genes found to be consistently up- or down-regulated in infected cell monolayers was validated with RT PCR. Using immunofluorescence we examined the expression of Protease Activated Receptor-2, which is encoded by one of the up-regulated genes. In infected cells this receptor localized to the host cell membrane which covers the intracellular trophozoites and meronts. This observation indicates that the composition of the host cell membrane is affected by the developing trophozoite, a phenomenon which has not been described previously.

Neutrophil granule proteins tune monocytic cell function

Polymorphonuclear leukocytes (PMNs) release the contents of granules during their migration to inflammatory sites. On liberation from the first leukocyte to enter injured tissue, the granule proteins play a central role in the early inflammatory response. In particular, mononuclear phagocytes interact intimately with PMNs and their secretion products. PMN granule proteins enhance the adhesion of monocytes to the endothelium and stimulate subsequent extravasation of inflammatory monocytes. At the site of inflammation, PMN granule proteins activate macrophages to produce and release cytokines and to phagocytose IgG-opsonized bacteria. Furthermore, by direct cell-cell contacts, PMNs activate monocyte-derived dendritic cells, thereby enhancing antigen presentation. Efforts in this field might lead to the development of drugs for specific modulation of innate immune functions.

Induction of IL-4 release and upregulated expression of protease activated receptors by GM-CSF in P815 cells

GM-CSF has been showed to be able to induce up-regulated receptor and cytokine expression in mast cells in inflammatory conditions. However, little is known of its effects on protease activated receptor (PAR) expression and Th2 cytokine secretion from mast cells. In the present study, we examined potential influence of GM-CSF on mast cell PAR expression and IL-4 and IL-10 release by using flow cytometry analysis, quantitative real time PCR, ELISA and cellular activation of signaling ELISA (CASE) techniques. The results showed that GM-CSF induced up to 3.0-fold increase in IL-4 release from P815 cells, and FSLLRY-NH(2) and trans-cinnamoyl (tc)-YPGKF-NH(2) did not affect GM-CSF induced IL-4 release. GM-CSF reduced tryptase and trypsin induced IL-4 release by up to approximately 55.8% and 70.3%, respectively. GM-CSF elicited the upregulated expression of PAR-1, PAR-2, PAR-3 and PAR-4 mRNAs, but enhanced only PAR-4 protein expression in P815 cells. U0126, PD98059 and LY204002 almost completely abolished GM-CSF induced IL-4 release when they were preincubated with P815 cells for 30 min, indicating ERK and Akt cell signaling pathways may be involved in the event. In conclusion, GM-CSF can stimulate IL-4 release from mast cells through an ERK and Akt cell signaling pathway dependent, but PAR independent mechanism. GM-CSF may serve as a regulator for IL-4 production in mast cells and through which participates in the mast cell related inflammation.

PR3-ANCA in Wegener's granulomatosis prime human mononuclear cells for enhanced activation via TLRs and NOD1/2

Background

Anti-neutrophil cytoplasmic antibodies (ANCA) is autoantibodies characteristic of vasculitis diseases. A connection between ANCA and Wegener's granulomatosis was well established. The interaction of both ANCA phenotypes (PR3-ANCA and MPO-ANCA) with leukocytes provoked cell activation, which might be involved in the pathogenesis of ANCA-related Wegener's granulomatosis.

Methods

In this study, we examined whether PR3-ANCA sera and purified immunoglobulins from patients with Wegener's granulomatosis prime human monocytic cells for enhanced responses to microbial components in terms of production of proinflammatory cytokines.

Results

Flow cytometry demonstrated that stimulation with antibodies to proteinase 3 enhanced the expression of TLR2, 3, 4, 7, and 9, NOD1, and NOD2 in human mononuclear cells. The sera and purified immunoglobulins significantly primed human mononuclear cells to secrete interleukin-8 in response to microbial components via TLRs and NODs. Priming effects were also observed for the production of interleukin-6, monocyte chemoattractant protein-1, and tumor necrosis factor-α. On the other hand, PR3-ANCA-negative sera from patients with polyarteritis nodosa which possibly related to MPO-ANCA and aortitis syndrome as well as control sera from a healthy volunteer did not have any priming effects on PBMCs.

Conclusion

In conclusion, PR3-ANCA prime human mononuclear cells to produce cytokines upon stimulation with various microbial components by up-regulating the TLR and NOD signaling pathway, and these mechanisms may partially participate in the inflammatory process in Wegener's granulomatosis.

Modulation of expression of innate immunity markers CXCL5/ENA-78 and CCL20/MIP3alpha by protease-activated receptors (PARs) in human gingival epithelial cells

Protease-activated receptors (PARs) are G-protein-coupled receptors with an active role in host defense. The two most highly expressed members of the PAR family in gingival epithelial cells (GECs) are PAR1 and PAR2. The major virulence factors of periodontal pathogen Porphyromonas gingivalis are its proteases which can activate PAR2. However, little is known about the function of PARs in GECs when they are activated by their endogenous agonist enzymes. The purpose of this study was to characterize how the expression of innate immune markers is modulated when PAR1 and PAR2 are activated by their agonist enzymes, thrombin and trypsin, respectively. Here, we report that activation of PAR1 and PAR2 induces cell proliferation at low concentration. Activation of PAR via proteolytic activity of thrombin and trypsin induces expression of CXCL5/ENA-78 and CCL20/MIP3alpha in a concentration-dependent manner. Induction of CXCL5 via PAR1 was inhibited in the presence of PAR1 cleavage blocking antibodies and by PAR1 siRNA. The induction of CXCL5 and CCL20 via PAR2 was inhibited by PAR2 siRNA. These findings indicate an active role in innate immune responses by PAR1 and PAR2 in GECs. Modulation of innate immunity by PARs may contribute to co-ordinated and balanced immunosurveillance in GECs.

Neuroprotective activities of activated protein C mutant with reduced anticoagulant activity

The anticoagulant activated protein C (APC) protects neurons and endothelium via protease activated receptor (PAR)1, PAR3 and endothelial protein C receptor. APC is neuroprotective in stroke models. Bleeding complications may limit the pharmacologic utility of APC. Here, we compared the 3K3A-APC mutant with 80% reduced anticoagulant activity and wild-type (wt)-APC. Murine 3K3A-APC compared with wt-APC protected mouse cortical neurons from N-methyl-D-aspartate-induced apoptosis with twofold greater efficacy and more potently reduced N-methyl-D-aspartate excitotoxic lesions in vivo. Human 3K3A-APC protected human brain endothelial cells (BECs) from oxygen/glucose deprivation with 1.7-fold greater efficacy than wt-APC. 3K3A-APC neuronal protection required PAR1 and PAR3, as shown by using PAR-specific blocking antibodies and PAR1- and PAR3-deficient cells and mice. BEC protection required endothelial protein C receptor and PAR1. In neurons and BECs, 3K3A-APC blocked caspase-9 and -3 activation and induction of p53, and decreased the Bax/Bcl-2 pro-apoptotic ratio. After distal middle cerebral artery occlusion (dMCAO) in mice, murine 3K3A-APC compared with vehicle given 4:00 h after dMCAO improved the functional outcome and reduced the infarction volume by 50% within 3 days. 3K3A-APC compared with wt-APC multi-dosing therapy at 12:00 h, 1, 3, 5 and 7 days after dMCAO significantly improved functional recovery and reduced the infarction volume by 75% and 38%, respectively, within 7 days. The wt-APC, but not 3K3A-APC, significantly increased the risk of intracerebral bleeding as indicated by a 50% increase in hemoglobin levels in the ischemic hemisphere. Thus, 3K3A-APC offers a new approach for safer and more efficacious treatments of neurodegenerative disorders and stroke with APC.

Protease-activated receptors as drug targets in inflammation and pain

Proteases have been shown to signal to cells through the activation of a novel class of receptors coupled to G proteins: the protease-activated receptors (PARs). Those receptors are expressed in a wide range of cells, which ultimately are all involved in mechanisms of inflammation and pain. Numerous studies have considered the role of PARs in cells, organ systems or in vivo, highlighting the fact that PAR activation results in signs of inflammation. A growing body of evidences discussed here suggests that these receptors, and the proteases that activate them, interfere with inflammation and pain processes. Whether a role for PARs has been clearly defined in inflammatory and pain pathologies is discussed in this review. Further, the pros and cons for considering PARs as targets for the development of therapeutic options for the treatment of inflammation and pain are discussed.