German cockroach proteases regulate interleukin-8 expression via nuclear factor for interleukin-6 in human bronchial epithelial cells

German cockroach extract prevents IL-13-induced CCL26 expression in airway epithelial cells through IL-13 degradation

Inhaled aeroallergens can directly activate airway epithelial cells (AECs). Exposure to cockroach allergens is a strong risk factor for asthma. Cockroach allergens mediate some of their effects through their serine protease activity; protease activity is also a major contributor to allergenicity. The Th2 cytokine interleukin-13 (IL-13) induces upregulation of the eosinophil chemotactic factor CCL26. CCL26 induces eosinophil migration in allergic inflammation. In this work, we studied the effect of cockroach proteases on IL-13-induced effects. Immersed cultures of the human bronchial epithelial cell line BEAS-2B and air-liquid interface (ALI) cultures of primary normal human bronchial epithelial (NHBE) cells were stimulated with IL-13, Blattella Germanica cockroach extract (CE), or both. IL-13-induced genes were analyzed with qRT-PCR. IL-13 induced upregulation of CCL26, periostin, and IL-13Rα2 in bronchial epithelial cells which were decreased by CE. CE was heat-inactivated (HICE) or pre-incubated with protease inhibitors. HICE and CE preincubated with serine protease inhibitors did not prevent IL-13-induced CCL26 upregulation. CE-degraded IL-13 and specific cleavage sites were identified. CE also decreased IL-4-induced CCL26 upregulation and degraded IL-4. Other serine proteases such as bovine trypsin and house dust mite (HDM) serine proteases did not have the same effects on IL-13-induced CCL26. We conclude that CE serine proteases antagonize IL-13-induced effects in AECs, and this CE effect is mediated primarily through proteolytic cleavage of IL-13. IL-13 cleavage by cockroach serine proteases may modulate CCL26-mediated effects in allergic airway inflammation by interfering directly with the pro-inflammatory effects of IL-13 in vivo.

Protease allergens as initiators-regulators of allergic inflammation

Tremendous progress in the last few years has been made to explain how seemingly harmless environmental proteins from different origins can induce potent Th2-biased inflammatory responses. Convergent findings have shown the key roles of allergens displaying proteolytic activity in the initiation and progression of the allergic response. Through their propensity to activate IgE-independent inflammatory pathways, certain allergenic proteases are now considered as initiators for sensitization to themselves and to non-protease allergens. The protease allergens degrade junctional proteins of keratinocytes or airway epithelium to facilitate allergen delivery across the epithelial barrier and their subsequent uptake by antigen-presenting cells. Epithelial injuries mediated by these proteases together with their sensing by protease-activated receptors (PARs) elicit potent inflammatory responses resulting in the release of pro-Th2 cytokines (IL-6, IL-25, IL-1β, TSLP) and danger-associated molecular patterns (DAMPs; IL-33, ATP, uric acid). Recently, protease allergens were shown to cleave the protease sensor domain of IL-33 to produce a super-active form of the alarmin. At the same time, proteolytic cleavage of fibrinogen can trigger TLR4 signaling, and cleavage of various cell surface receptors further shape the Th2 polarization. Remarkably, the sensing of protease allergens by nociceptive neurons can represent a primary step in the development of the allergic response. The goal of this review is to highlight the multiple innate immune mechanisms triggered by protease allergens that converge to initiate the allergic response.

Comprehensive analysis of allergen-specific IgE in COPD: mite-specific IgE specifically related to the diagnosis of asthma-COPD overlap

Background

Although the relationship between allergic sensitization and increased respiratory symptoms of chronic obstructive pulmonary disease (COPD) has been suggested, which allergen has a significant effect on COPD pathology is unclear. This study aimed to identify the specific IgE related to clinical features of COPD and the diagnosis of asthma-COPD overlap (ACO).

Methods

We recruited 76 patients with COPD and analyzed 39 IgE using panel IgE test (View Allergy 39^®). ACO was diagnosed according to the Japanese Respiratory Society Guidelines.

Results

As for perennial aeroallergens, the positivity for moth (31.5%), Candida (23.7%), Dermatophagoides pteronyssinus (22.4%) and house dust (22.4%), and concerning pollen, Japanese cedar (35.5%) and Japanese cypress (22.2%) exceeded 20%. Only the positivity of IgE for Dermatophagoides pteronyssinus and house dust was significantly higher in ACO compared with that in non-ACO COPD. Moreover, it contributed to the diagnosis of ACO in an IgE class-dependent manner. Patients with cockroach IgE exhibited higher residual volume, whereas those with Japanese cedar IgE exhibited better diffusion capacity than negative patients. The contribution for ACO diagnosis by the receiver operating characteristic curve analysis was comparable among total IgE (cutoff value: 158 IU/mL), blood eosinophil count (234/μL), and fraction of exhaled nitric oxide (31.0 ppb).

Conclusions

The prominent role of mite-specific IgE in the diagnosis and pathology of ACO and the potentially detrimental effect of cockroach sensitization on air trapping in COPD were suggested. The finding highlights the future development of a treatment targeting IgE as a treatable trait in COPD.

Human airway trypsin-like protease enhances interleukin-8 synthesis in bronchial epithelial cells by activating protease-activated receptor 2

Human airway trypsin-like protease (HAT) localizes at human bronchial epithelial cells (HBECs). HAT enhanced release of interleukin-8 (IL-8) from HBECs at 10-100 mU/mL and the enhanced release was almost completely abolished by 50 μM leupeptin, a serine protease inhibitor. Previous reports suggested that HAT displays its physiological functions via protease-activated receptor 2 (PAR2). In the present study, we examined the mechanism whereby HAT upregulates IL-8 synthesis in HBECs with a focus on PAR2. Northern blot analysis revealed that HAT enhanced IL-8 mRNA expression at concentrations of 10-100 mU/mL. PAR2 activating peptide (PAR2 AP) also enhanced IL-8 release and IL-8 mRNA expression in HBECs at 50-1,000 μM at similar levels as HAT. Knockdown of PAR2 mRNA by siRNA methods showed that PAR2 mRNA expression was significantly depressed in primary HBECs, and both HAT- and PAR2 AP-induced IL-8 mRNA elevation was significantly depressed in PAR2 siRNA-transfected HBECs. Additionally, HAT cleaved the PAR2 activating site (R³⁶-S³⁷ bond) of synthetic PAR2 N-terminal peptide. These results indicate that HAT stimulates IL-8 synthesis in airway epithelial cells via PAR2 and could help to amplify inflammation in chronic respiratory tract disease.

New Insights into Cockroach Allergens

PURPOSE OF REVIEW

This review addresses the most recent developments on cockroach allergen research in relation to allergic diseases, especially asthma.

RECENT FINDINGS

The number of allergens relevant to cockroach allergy has recently expanded considerably up to 12 groups. New X-ray crystal structures of allergens from groups 1, 2, and 5 revealed interesting features with implications for allergen standardization, sensitization, diagnosis, and therapy. Cockroach allergy is strongly associated with asthma particularly among children and young adults living in inner-city environments, posing challenges for disease control. Environmental interventions targeted at reducing cockroach allergen exposure have provided conflicting results. Immunotherapy may be a way to modify the natural history of cockroach allergy and decrease symptoms and asthma severity among sensitized and exposed individuals. The new information on cockroach allergens is important for the assessment of allergen markers of exposure and disease, and for the design of immunotherapy trials.

Airway epithelium interactions with aeroallergens: role of secreted cytokines and chemokines in innate immunity

Airway epithelial cells are the first line of defense against the constituents of the inhaled air, which include allergens, pathogens, pollutants, and toxic compounds. The epithelium not only prevents the penetration of these foreign substances into the interstitium, but also senses their presence and informs the organism’s immune system of the impending assault. The epithelium accomplishes the latter through the release of inflammatory cytokines and chemokines that recruit and activate innate immune cells at the site of assault. These epithelial responses aim to eliminate the inhaled foreign substances and minimize their detrimental effects to the organism. Quite frequently, however, the innate immune responses of the epithelium to inhaled substances lead to chronic and high level release of pro-inflammatory mediators that may mediate the lung pathology seen in asthma. The interactions of airway epithelial cells with allergens will be discussed with particular focus on interactions-mediated epithelial release of cytokines and chemokines and their role in the immune response. As pollutants are other major constituents of inhaled air, we will also discuss how pollutants may alter the responses of airway epithelial cells to allergens.

Per a 10 activates human derived epithelial cell line in a protease dependent manner via PAR-2

BACKGROUND

Protease activity of Per a 10 has been shown to modulate dendritic cells toward Th-2 polarization and to induce airway inflammation.

OBJECTIVE

To elucidate the role of serine protease activity of Per a 10 in inducing biochemical responses in epithelial cells.

METHODS

Per a 10 was inactivated by heat treatment (ΔPer a 10) or AEBSF (iPer a 10). A549 cells were exposed to either enzymatically active/inactive Per a 10. The supernatant was analyzed for the secretion of proinflammatory cytokines by ELISA. Ca(2+) mobilization was analyzed by flow cytometry. A PAR-2 derived synthetic peptide 28GTNRSSKGRSLIGKVDGTSHVTGKGVTC54 was incubated with Per a 10 and the resultant cleaved products were analyzed by LC-MS. PAR-2 activation was inhibited by PAR-2 cleavage inhibiting antibody.

RESULTS

ΔPer a 10 was completely inactivated whereas iPer a 10 showed some residual activity. nPer a 10 having protease activity increased the secretion of IL-6, IL-8 and GMCSF from A549 in a dose and time dependent manner whereas iPer a 10 has reduced cytokine secretion. ΔPer a 10 and rPer a 10 were unable to activate the cells. nPer a 10 mobilized intracellular Ca(2+). nPer a 10 cleaved the PAR-2 derived peptide between arginine and serine residues (36R-S37) to expose PAR-2 ligand SLIGKV, as determined by LC-MS. Incubating with anti-PAR-2 cleavage antibody showed diminished cytokine secretion when treated with nPer a 10.

CONCLUSION

Serine protease activity of Per a 10 activates A549 cells to secrete proinflammatory cytokines by PAR-2 activation and Ca(2+)mobilization and can be exploited therapeutically.

Investigating cockroach allergens: aiming to improve diagnosis and treatment of cockroach allergic patients

Cockroach allergy is an important health problem associated with the development of asthma, as a consequence of chronic exposure to low levels of allergens in susceptible individuals. In the last 20 years, progress in understanding the disease has been possible, thanks to the identification and molecular cloning of cockroach allergens and their expression as recombinant proteins. Assays for assessment of environmental allergen exposure have been developed and used to measure Bla g 1 and Bla g 2, as markers of cockroach exposure. IgE antibodies to cockroach extracts and to specific purified allergens have been measured to assess sensitization and analyze association with exposure and disease. With the development of the field of structural biology and the expression of recombinant cockroach allergens, insights into allergen structure, function, epitope mapping and allergen-antibody interactions have provided further understanding of mechanisms of cockroach allergic disease at the molecular level. This information will contribute to develop new approaches to allergen avoidance and to improve diagnosis and therapy of cockroach allergy.

Functional interaction of cockroach allergens and mannose receptor (CD206) in human circulating fibrocytes

BACKGROUND

The innate pattern recognition C-type-lectin receptors (CLRs), including mannose receptor (MRC1; CD206), have been suggested to functionally interact with allergens and are critical in controlling immune response. Fibrocytes have been considered to play a role in allergic asthma. Here we sought to investigate the functional interaction of cockroach allergens with CD206 in fibrocytes.

METHODS

Profiling of N-linked glycans from natural purified cockroach allergen Bla g 2 was accomplished by MALDI-MS. The binding activity of cockroach allergens to CD206 was determined by solid-phase binding assays. Levels of CD206 expression on human fibrocytes and CD206 mediated signaling and cytokine production in Bla g 2 treated fibrocytes were determined.

RESULTS

Profiling of N-linked glycans from Bla g 2 revealed a predominance of small, mannose-terminated glycans with and without fucose. Significant binding of Bla g 2 to CD206 was observed, which was inhibited by yeast mannan (a known CD206 ligand), free mannose, and a blocking antibody (anti-hMR). Flow cytometric analyses of human fibrocytes (CD45(+) and collagen-1(+)) showed selective expression of CD206 on fibrocytes. Functionally, a concentration-dependent uptake of FITC labeled Bla g 2 by fibrocytes was observed, but was significantly inhibited by anti-hMR. Bla g 2 can stimulate up-regulation of inflammatory cytokines including TNF-alpha and IL-6 and activation of nuclear factor kappa B (NF-kB/p65), p38 mitogen-activated protein kinase (p38), ERK, and JNK in cultured fibrocytes. This increased secretion of TNF-alpha and IL-6 and activation of NF-kB, ERK, and JNK was significantly inhibited by the addition of either mannan or mannose. Furthermore, Bla g 2 induced increase in TNF-alpha and IL-6 production was also inhibited by the use of NF-kB, ERK, and JNK inhibitors.

CONCLUSION

These results provide evidence supporting the existence of a functional cockroach allergen-CD206 axis in human fibrocytes, suggesting a role for CD206 in regulating allergen induced allergic responses in asthma.

Role of cockroach proteases in allergic disease

Allergic asthma is on the rise in developed countries, and cockroach exposure is a major risk factor for the development of asthma. In recent years, a number of studies have investigated the importance of allergen-associated proteases in modulating allergic airway inflammation. Many of the studies have suggested the importance of allergen-associated proteases as having a direct role on airway epithelial cells and dendritic cells. In most cases, activation of the protease activated receptor (PAR)-2 has been implicated as a mechanism behind the potent allergenicity associated with cockroaches. In this review, we focus on recent evidence linking cockroach proteases to activation of a variety of cells important in allergic airway inflammation and the role of PAR-2 in this process. We will highlight recent data exploring the potential mechanisms involved in the biological effects of the allergen.

Dendritic cell-derived tumor necrosis factor α modifies airway epithelial cell responses

Mucosal dendritic cells (DC) are intimately associated with the airway epithelium and thus are ideally situated to be first responders to pathogens. We hypothesize that DC drive innate immune responses through early release of tumor necrosis factor (TNF) α, which drives airway epithelial cell responses. In a mouse model, TNFα release was significantly increased following a single exposure to German cockroach (GC) frass, an event independent of neutrophil recruitment into the airways. While lung epithelial cells and alveolar macrophages failed to release TNFα following GC frass exposure, bone marrow-derived DC (BMDC) produced substantial amounts of TNFα suggesting their importance as early responding cells. This was confirmed by flow cytometry of pulmonary myeloid DC. Addition of GC frass-pulsed BMDC or conditioned media from GC frass-pulsed BMDC to primary mouse tracheal epithelial cells (MTEC) or MLE-15 cells induced chemokine (C-C) motif ligand (CCL) 20 and granulocyte macrophage (GM) colony-stimulating factor (CSF), both of which are important for DC recruitment, survival and differentiation. Importantly, DC do not produce CCL20 or GM-CSF following allergen exposure. Blocking TNFα receptor 1 (TNFR1) completely abolished chemokine production, suggesting that BMDC-derived TNFα induced airway epithelial cell activation and enhancement of the innate immune response. Lastly, blocking TNFR1 in vivo resulted in significantly decreased CCL20 and GM-CSF production in the lungs of mice. Together, our data strongly suggest that DC-derived TNFα plays a crucial role in the initiation of innate immune responses through the modification of airway epithelial cell responses.

Role of Allergen Source-Derived Proteases in Sensitization via Airway Epithelial Cells

Protease activity is a characteristic common to many allergens. Allergen source-derived proteases interact with lung epithelial cells, which are now thought to play vital roles in both innate and adaptive immune responses. Allergen source-derived proteases act on airway epithelial cells to induce disruption of the tight junctions between epithelial cells, activation of protease-activated receptor-2, and the production of thymic stromal lymphopoietin. These facilitate allergen delivery across epithelial layers and enhance allergenicity or directly activate the immune system through a nonallergic mechanism. Furthermore, they cleave regulatory cell surface molecules involved in allergic reactions. Thus, allergen source-derived proteases are a potentially critical factor in the development of allergic sensitization and appear to be strongly associated with heightened allergenicity.

Sensitization to cockroach allergen: immune regulation and genetic determinants

Asthma is a major public health concern. Cockroach allergen exposure and cockroach allergic sensitization could contribute to the higher prevalence of asthma. However, the underlying immune mechanism and the genetic etiology remain unclear. Recent advances have demonstrated that several receptors (PAR-2, TLRs, CLRs) and their pathways mediate antigen uptake from the environment and induce allergies by signaling T cells to activate an inappropriate immune response. Cockroach-derived protease can disturb airway epithelial integrity via PAR-2 and leads to an increased penetration of cockroach allergen, resulting in activation of innate immune cells (e.g., DCs) via binding to either TLRs or CLRs. The activated DCs can direct cells of the adaptive immune system to facilitate promotion of Th2 cell response and subsequently increase risk of sensitization. Mannose receptor (MR), as a CLR, has been shown to mediate Bla g2 (purified cockroach allergen) uptake by DCs and to determine allergen-induced T cell polarization. Additionally, genetic factors may play an important role in conferring the susceptibility to cockroach sensitization. Several genes have been associated with cockroach sensitization and related phenotypes (HLA-D, TSLP, IL-12A, MBL2). In this review, we have focused on studies on the cockroach allergen induced immunologic responses and genetic basis for cockroach sensitization.

German cockroach proteases and protease-activated receptor-2 regulate chemokine production and dendritic cell recruitment

We recently showed that serine proteases in German cockroach (GC) feces (frass) decreased experimental asthma through the activation of protease-activated receptor (PAR)-2. Since dendritic cells (DCs) play an important role in the initiation of asthma, we queried the role of GC frass proteases in modulating CCL20 (chemokine C-C motif ligand 20) and granulocyte macrophage colony-stimulating factor (GM-CSF) production, factors that regulate pulmonary DCs. A single exposure to GC frass resulted in a rapid, but transient, increase in GM-CSF and a steady increase in CCL20 in the airways of mice. Instillation of protease-depleted GC frass or instillation of GC frass in PAR-2-deficient mice significantly decreased chemokine release. A specific PAR-2-activating peptide was also sufficient to induce CCL20 production. To directly assess the role of the GC frass protease in chemokine release, we enriched the protease from GC frass and confirmed that the protease was sufficient to induce both GM-CSF and CCL20 production in vivo. Primary airway epithelial cells produced both GM-CSF and CCL20 in a protease- and PAR-2-dependent manner. Finally, we show a decreased percentage of myeloid DCs in the lung following allergen exposure in PAR-2-deficient mice compared to wild-type mice. However, there was no difference in GC frass uptake. Our data indicate that, through the activation of PAR-2, allergen-derived proteases are sufficient to induce CCL20 and GM-CSF production in the airways. This leads to increased recruitment and/or differentiation of myeloid DC populations in the lungs and likely plays an important role in the initiation of allergic airway responses.

Mucosal allergic sensitization to cockroach allergens is dependent on proteinase activity and proteinase-activated receptor-2 activation

We have shown that proteinase-activated receptor-2 (PAR(2)) activation in the airways leads to allergic sensitization to concomitantly inhaled Ags, thus implicating PAR(2) in the pathogenesis of asthma. Many aeroallergens with proteinase activity activate PAR(2). To study the role of PAR(2) in allergic sensitization to aeroallergens, we developed a murine model of mucosal sensitization to cockroach proteins. We hypothesized that PAR(2) activation in the airways by natural allergens with serine proteinase activity plays an important role in allergic sensitization. Cockroach extract (CE) was administered to BALB/c mice intranasally on five consecutive days (sensitization phase) and a week later for four more days (challenge phase). Airway hyperresponsiveness (AHR) and allergic airway inflammation were assessed after the last challenge. To study the role of PAR(2), mice were exposed intranasally to a receptor-blocking anti-PAR(2) Ab before each administration of CE during the sensitization phase. Mucosal exposure to CE induced eosinophilic airway inflammation, AHR, and cockroach-specific IgG1. Heat-inactivated or soybean trypsin inhibitor-treated CE failed to induce these effects, indicating that proteinase activity plays an important role. The use of an anti-PAR(2) blocking Ab during the sensitization phase completely inhibited airway inflammation and also decreased AHR and the production of cockroach-specific IgG1. PAR(2) activation by CE acts as an adjuvant for allergic sensitization even in the absence of functional TLR4. We conclude that CE induces PAR(2)-dependent allergic airway sensitization in a mouse model of allergic airway inflammation. PAR(2) activation may be a general mechanism used by aeroallergens to induce allergic sensitization.

Mucosal sensitization to German cockroach involves protease-activated receptor-2

BACKGROUND

Allergic asthma is on the rise in developed countries. A common characteristic of allergens is that they contain intrinsic protease activity, and many have been shown to activate protease-activated receptor (PAR)-2 in vitro. The role for PAR-2 in mediating allergic airway inflammation has not been assessed using a real world allergen.

METHODS

Mice (wild type or PAR-2-deficient) were sensitized to German cockroach (GC) feces (frass) or protease-depleted GC frass by either mucosal exposure or intraperitoneal injection and measurements of airway inflammation (IL-5, IL-13, IL-17A, and IFNgamma levels in the lung, serum IgE levels, cellular infiltration, mucin production) and airway hyperresponsiveness were performed.

RESULTS

Following systemic sensitization, GC frass increased airway hyperresponsiveness, Th2 cytokine release, serum IgE levels, cellular infiltration and mucin production in wild type mice. Interestingly, PAR-2-deficient mice had similar responses as wild type mice. Since these data were in direct contrast to our finding that mucosal sensitization with GC frass proteases regulated airway hyperresponsiveness and mucin production in BALB/c mice (Page et. al. 2007 Resp Res 8:91), we backcrossed the PAR-2-deficient mice into the BALB/c strain. Sensitization to GC frass could now occur via the more physiologically relevant method of intratracheal inhalation. PAR-2-deficient mice had significantly reduced airway hyperresponsiveness, Th2 and Th17 cytokine release, serum IgE levels, and cellular infiltration compared to wild type mice when sensitization to GC frass occurred through the mucosa. To confirm the importance of mucosal exposure, mice were systemically sensitized to GC frass or protease-depleted GC frass via intraperitoneal injection. We found that removal of proteases from GC frass had no effect on airway inflammation when administered systemically.

CONCLUSIONS

We showed for the first time that allergen-derived proteases in GC frass elicit allergic airway inflammation via PAR-2, but only when allergen was administered through the mucosa. Importantly, our data suggest the importance of resident airway cells in the initiation of allergic airway disease, and could make allergen-derived proteases attractive therapeutic targets.

Proteinase-activated receptors induce interleukin-8 expression by intestinal epithelial cells through ERK/RSK90 activation and histone acetylation

Proteinase-activated receptors (PARs) are involved in both inflammation and tumorigenesis in epithelial cells. Interleukin (IL)-8 is a potent chemoattractant and is also involved in angiogenesis. The molecular mechanism whereby PARs induce epithelial IL-8 expression is not known. In HT-29 colonic epithelial cells, PAR(1) or PAR(2) agonists stimulated the expression of IL-8 through a NF-kappaB-dependent pathway without inducing IkappaB degradation and disassociation of IkappaB from NF-kappaB. Further studies revealed that PAR activation induced the phosphorylation of p65 at Ser-276 in the nucleus, which increased the recruitment of histone acetyltransferase (HAT) p300 to p50. Inhibition of ERK activation completely blocked PAR-induced IL-8 expression, phosphorylation of p65 and HAT activity. We also demonstrated that RSK p90 was the downstream kinase that mediated ERK-induced nuclear p65 phosphorylation. In conclusion, activation of either PAR(1) or PAR(2) stimulated the transcriptional up-regulation of IL-8 in HT-29 colonic epithelial cells through a pathway that involved ERK/RSK p90, NF-kappaB phosphorylation, and HAT activity. These studies provide evidence of a new role for serine proteinases and PARs in the regulation of gene expression in colonic inflammation and tumorigenesis.

Extracellular Hsp72, an endogenous DAMP, is released by virally infected airway epithelial cells and activates neutrophils via Toll-like receptor (TLR)-4

Background

Neutrophils play an important role in the pathophysiology of RSV, though RSV does not appear to directly activate neutrophils in the lower airways. Therefore locally produced cytokines or other molecules released by virally-infected airway epithelial cells are likely responsible for recruiting and activating neutrophils. Heat shock proteins (HSPs) are generally regarded as intracellular proteins acting as molecular chaperones; however, HSP72 can also be released from cells, and the implications of this release are not fully understood.

Methods

Human bronchial epithelial cells (16HBE14o-) were infected with RSV and Hsp72 levels were measured by Western blot and ELISA. Tracheal aspirates were obtained from critically ill children infected with RSV and analyzed for Hsp72 levels by ELISA. Primary human neutrophils and differentiated HL-60 cells were cultured with Hsp72 and supernatants analyzed for cytokine production. In some cases, cells were pretreated with polymyxin B prior to treatment with Hsp72. IκBα was assessed by Western blot and EMSA's were performed to determine NF-κB activation. HL-60 cells were pretreated with neutralizing antibody against TLR4 prior to Hsp72 treatment. Neutrophils were harvested from the bone marrow of wild type or TLR4-deficient mice prior to treatment with Hsp72.

Results

Infection of 16HBE14o- with RSV showed an induction of intracellular Hsp72 levels as well as extracellular release of Hsp72. Primary human neutrophils from normal donors and differentiated HL-60 cells treated with increasing concentrations of Hsp72 resulted in increased cytokine (IL-8 and TNFα) production. This effect was independent of the low levels of endotoxin in the Hsp72 preparation. Hsp72 mediated cytokine production via activation of NF-κB translocation and DNA binding. Using bone marrow-derived neutrophils from wild type and TLR4-mutant mice, we showed that Hsp72 directly activates neutrophil-derived cytokine production via the activation of TLR4.

Conclusion

Collectively these data suggest that extracellular Hsp72 is released from virally infected airway epithelial cells resulting in the recruitment and activation of neutrophils.

Hsp72 induces inflammation and regulates cytokine production in airway epithelium through a TLR4- and NF-kappaB-dependent mechanism

Heat shock proteins are generally regarded as intracellular proteins acting as molecular chaperones; however, Hsp72 is also detected in the extracellular compartment. Hsp72 has been identified in the bronchoalveolar lavage fluid (BALF) of patients with acute lung injury. To address whether Hsp72 directly activated airway epithelium, human bronchial epithelial cells (16HBE14o-) were treated with recombinant Hsp72. Hsp72 induced a dose-dependent increase in IL-8 expression, which was inhibited by the NF-kappaB inhibitor parthenolide. Hsp72 induced activation of NF-kappaB, as evidenced by NF-kappaB trans-activation and by p65 RelA and p50 NF-kappaB1 binding to DNA. Endotoxin contamination of the Hsp72 preparation was not responsible for these effects. Next, BALB/c mice were challenged with a single intratracheal inhalation of Hsp72 and killed 4 h later. Hsp72 induced significant up-regulation of KC, TNF-alpha, neutrophil recruitment, and myeloperoxidase in the BALF. A similar challenge with Hsp72 in TLR4 mutant mice did not stimulate the inflammatory response, stressing the importance of TLR4 in Hsp72-mediated lung inflammation. Last, cultured mouse tracheal epithelial cells (MTEC) from BALB/c and TLR4 mutant and wild-type mice were treated ex vivo with Hsp72. Hsp72 induced a significant increase in KC expression from BALB/c and wild-type MTEC in an NF-kappaB-dependent manner; however, TLR4 mutant MTEC had minimal cytokine release. Taken together, these data suggest that Hsp72 is released and biologically active in the BALF and can regulate airway epithelial cell cytokine expression in a TLR4 and NF-kappaB-dependent mechanism.

Regulation of German cockroach extract-induced IL-8 expression in human airway epithelial cells

BACKGROUND

Cockroaches have been known as a cause of respiratory allergies such as asthma. IL-8 plays an integral role in the coordination and persistence of the inflammatory process in the chronic inflammation of the airways in asthma.

OBJECTIVE

We investigated the mechanism by which German cockroach extract (GCE) triggers IL-8 release from human airway epithelial cells.

METHODS

Chemical inhibitors were pretreated before addition of GCE for promoter activity and protein synthesis of IL-8. The Transcriptional activity of IL-8 promoter was analysed by mutational, deletional anaylsis and electrophoretic mobility shift assay (EMSA).

RESULTS

Stimulation of H292 cells with GCE resulted in a time- and concentration-dependent induction of IL-8 transcription and protein synthesis. IL-8 promoter deletion analysis indicated that position -132 to +41 was essential for GCE-induced IL-8 transcription, and mutants with substitutions in activator protein (AP)-1, nuclear factor (NF)-IL6 and NF-kappaB-binding sites revealed a requirement for NF-kappaB and NF-IL6, but not AP-1, in GCE-induced activation of the IL-8 promoter. The DNA-binding activities of NF-kappaB and NF-IL6 were induced by GCE, as determined by EMSA. The chemical inhibition of extracellular signal-regulated kinase (ERK) attenuated GCE-induced transcriptional activity and protein synthesis. In addition, through aprotinin treatment and PAR2 small interfering RNA transfection, it was proven that protease of GCE is consistent with the regulation of GCE-induced IL-8.

CONCLUSION

We conclude that GCE with protease activity-induced IL-8 expression is regulated by transcriptional activation of NF-kappaB and NF-IL6 coordinating with the ERK pathway in human airway epithelial cells.

PAR-2 activation regulates IL-8 and GRO-alpha synthesis by NF-kappaB, but not RANTES, IL-6, eotaxin or TARC expression in nasal epithelium

BACKGROUND

The effects of protease-activated receptor-2 (PAR-2) stimulation on inflammation mechanisms of chronic rhinosinusitis (CRS) are still unknown.

METHODS

PAR-2 receptor expression was investigated by immunohistochemistry and Taqman mRNA analysis in the mucosa of different rhinosinusitis entities. In primary nasal epithelial cell cultures, the function of PAR-2 and its ability to produce CXC, CC chemokines, and IL-6 were measured by calcium mobilization and stimulation tests. Inhibition tests were performed using cortisone, serine protease inhibitors, cysteine protease inhibitors, Pertussis toxin (PTX) and nuclear transcription factor (NF-kappaB) inhibition (BAY 11-7085). Signal transduction pathways were analysed by electromobility shift assays (EMSA) and NF-kappaB binding studies.

RESULTS

The expression of PAR-2 was found to be increased in CRS specimens. The activation of PAR by trypsin or PAR-2-specific activating peptide (AP) caused an increase in cytosolic calcium, as well as the release of the CXC chemokines IL-8 and growth-related oncogene (GRO)-alpha, but not the release of CC chemokines or IL-6. AP-induced CXC chemokine was sensitive to PTX and activation of NF-kappaB was inhibited by BAY11-7085. Furthermore, a serine protease inhibitor significantly inhibited chemokine synthesis stimulated by trypsin and culture supernatants of staphylococci, whereas steroids and cysteine protease inhibitors had little effect.

CONCLUSION

PAR-2 plays a role in serine protease-mediated regulation - staphylococcal and non-staphylococcal origin - of IL-8 and GRO-alpha in nasal epithelial cells, but not in the regulation of CC chemokines. PAR-2 may therefore be involved in the pathophysiology of CRS and NP at different sites of activation, namely (i) proteases, (ii) the PAR-2 receptor itself or (iii) the application of novel agents that block NF-kappaB/IkappaB-alpha signalling.

A novel therapeutic target in various lung diseases: Airway proteases and protease-activated receptors

Protease-activated receptors (PAR), which are G protein-coupled receptors, have 4 members, PAR-1 to PAR-4. PARs are activated by proteolysis of a peptide bond at the N-terminal domain of the receptor. PARs are widely distributed throughout the airways. Their activity is modulated by airway proteases of endogenous and exogenous origin, which can either activate or disable the receptors. The regulation of PAR activity by proteases is important under pathological conditions when the activity of proteases is increased. Moreover, various inflammatory mediators, such as cytokines, growth factors, or prostanoids, alter the PAR expression level. Elevated PAR levels are observed in various lung disorders, and their significance in the development of pathological situations in the lung is currently intensively investigated. Consequences of PAR activation can be either beneficial or deleterious, depending on the PAR subtype. PAR-1 has been shown to be an important player in the development of pulmonary fibrosis. Thus, PAR-1 represents an exciting target for clinical intervention in fibrotic diseases. PAR-2 contributes to allergic airway inflammation. However, the question whether the impact of PAR-2 is beneficial or deleterious is still under intensive discussion. Therefore, precise information concerning the participation of PAR-2 in various lesions is required. Moreover, it is necessary to generate selective PAR- and organ-targeted approaches for treating the diseases. A thorough understanding of PAR-induced cellular events and the consequences of receptor blockade may help in the development of novel therapeutic strategies targeted to prevent lung destruction and to avoid deterioration of conditions of patients with inflammatory or fibrotic lung diseases.

Calcium-calmodulin mediates house dust mite-induced ERK activation and IL-8 production in human respiratory epithelial cells

BACKGROUND

House dust mites (HDM) have been shown to be important sources of indoor allergens associated with asthma and other allergic conditions. While exogenous proteases from allergens have a direct proinflammatory role in the respiratory tract, the precise mechanisms underlying the release of cytokines from the respiratory epithelium are unclear.

OBJECTIVES

The present study examines that extracellular signal-regulated kinase (ERK) activated downstream of the Ca(2+)-sensitive tyrosine kinase plays an important role in the efficient activation of the HDM-induced IL-8 signaling pathway.

METHODS

We examined the effect of HDM, and the role of the Ca(2+)/calmodulin system and mitogen-activated protein kinases, on IL-8 expression in human lung epithelial cells.

RESULTS

In H292 cells, HDM induced IL-8 release in a time- and/or dose-dependent manner. This IL-8 release was abolished by treatment with intracellular Ca(2+) chelator (BAPTA-AM), but not by EGTA or nifedipine. Calmodulin inhibitor (calmidazolium) and tyrosine kinase inhibitor (genistein) almost completely blocked IL-8 release by HDM. PD98,059, an ERK pathway inhibitor, completely abolished HDM-induced IL-8 release. Moreover, PD98,059, BAPTA-AM, calmidazolium and genistein suppressed the HDM-induced ERK phosphorylation.

CONCLUSIONS

HDM-induced IL-8 production is predominantly regulated by Ca(2+)/calmodulin signaling, and ERK plays an important role in signal transmission for efficient activation of the HDM-induced IL-8 signaling pathway.

Serratia marcescens serralysin induces inflammatory responses through protease-activated receptor 2

The Serratia marcescens-derived protease serralysin is considered to play an important role in the pathogenesis of infection. Protease-activated receptor 2 (PAR-2) is activated by trypsin and also several other trypsin-like serine proteases, leading to the modulation of inflammatory and immune responses. However, little is known about the activation of PAR-2 by bacterial proteases and its roles in bacterial infection. In this study, we investigated whether S. marcescens serralysin activates host inflammatory responses through PAR-2. Our results demonstrated that serralysin induces interleukin-6 (IL-6) and IL-8 mRNA expression in a human lung squamous cell carcinoma, EBC-l cells. In addition, serralysin activated activator protein 1 (AP-1)-, CCAAT/enhancer-binding protein (C/EBP)-, and nuclear factor-kappaB (NF-kappaB)-driven promoters in EBC-1 cells. An electrophoretic mobility shift assay showed that serralysin activates the binding of AP-1, C/EBPbeta, and NF-kappaB in the cells. Inactivation of serralysin resulted in the failure of transactivation of AP-1-, C/EBP-, and NF-kappaB-driven promoters in the cells. Furthermore, serralysin activated AP-1-, C/EBP-, and NF-kappaB-driven promoters via PAR-2 in HeLa cells. PAR-2 antagonist peptides decreased serralysin-induced transactivation of AP-1-, C/EBP-, and NF-kappaB-driven promoters in EBC-1 cells. Considered together, these results suggest that serralysin requires PAR-2 to activate the critical transcription factors AP-1, C/EBPbeta, and NF-kappaB for host inflammatory responses.

Der p, IL-4, and TGF-beta cooperatively induce EGFR-dependent TARC expression in airway epithelium

Thymus and Activation-Regulated Chemokine (TARC) may be critical in Th2 cell recruitment in allergic inflammation; however, the mechanisms of allergen-induced TARC release are unclear. Since airway epithelium is the first line of defense to inhaled allergens, we questioned whether house dust mite allergen (Der p) can induce TARC expression in bronchial epithelial cells, how this is regulated at the molecular level, and if micro-environmental cytokines augment this effect. We examined the effects of Der p and the cytokines IL-4 and TGF-beta on TARC expression in 16HBE cells and primary bronchial asthma epithelium. Real-time PCR and immunofluorescence demonstrated that Der p induces TARC expression in bronchial epithelium. Supernatants from Der p-stimulated 16HBE cells were able to induce TARC-dependent T cell trafficking. IL-4 and TGF-beta cooperatively enhanced Der p-induced TARC expression in 16HBE cells. Specific inhibitors, immunodetection, and gel-shifts revealed that these effects are mediated by phosphorylation of the epidermal growth factor receptor (EGFR), mitogen-activated protein kinase (MAPK) signaling and subsequent nuclear factor (NF)-kappaB activation. A Disintegrin And Metalloproteinase (ADAM), a family of proteins involved in shedding of various growth factors, was shown to be responsible for EGFR activation. The increase in TARC production by direct interaction of Der p with the bronchial epithelium may be an important initial step in the generation of allergic inflammation, which is further potentiated by micro-environmental cytokines. Interference with ADAM or EGFR activity may be a novel promising target to prevent TARC release and subsequent allergic inflammation.

German cockroach proteases regulate matrix metalloproteinase-9 in human bronchial epithelial cells

BACKGROUND

Matrix metalloproteinases (MMPs) digest extracellular matrix proteins and may play a role in the pathogenesis of bronchial asthma. MMP-9 levels are increased in the bronchoalveolar lavage fluid and sputum of asthmatics compared with that of controls. As exposure to cockroaches is an environmental risk factor for asthma, we sought to investigate the role of German cockroach fecal remnants (frass) on MMP-9 expression.

METHODS

Human bronchial epithelial cells (16HBE14o-) and primary normal human bronchial epithelial cells were treated with cockroach frass in the absence or presence of tumor necrosis factor (TNF)alpha. MMP-9 mRNA, protein levels and pro-MMP-9 activity were determined using real-time polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA) and zymogram assays. Pretreatment of frass with aprotinin abolished protease activity. PD98059, a chemical inhibitor of extracellular signal regulated kinase (ERK), and SLIGKV, an activator of protease-activated receptor (PAR)-2 were also used. AP-1DNA binding was determined by electrophoretic mobility shift assay (EMSA) and ERK phosphorylation by Western blot analysis.

RESULTS

Cockroach frass augmented TNFalpha-mediated MMP-9 mRNA and protein expression by a mechanism dependent on active serine proteases within frass and not on endogenous endotoxin. Frass increased ERK phosphorylation, and chemical inhibition of ERK attenuated cockroaches' effects on MMP-9. Serine proteases are known to activate the PAR-2 receptor. We found that selective activation of PAR-2 using the peptide SLIGKV augmented TNFalpha-induced MMP-9 protein levels and increased ERK phosphorylation. Frass and SLIGKV each increased AP-1 translocation and DNA binding.

CONCLUSIONS

These data suggest that German cockroach frass contains active serine proteases which augment TNFalpha-induced MMP-9 expression by a mechanism involving PAR-2, ERK and AP-1.

Induction of CXC chemokines in A549 airway epithelial cells by trypsin and staphylococcal proteases - a possible route for neutrophilic inflammation in chronic rhinosinusitis

While various microorganisms have been recovered from patients with chronic rhinosinusitis, the inflammatory impact of virulence factors, in particular proteases from Staphylococcus aureus and coagulase negative staphylococci on the nasal epithelium, has not yet been investigated. Expression of CXC chemokines was determined in the epithelium of patients with chronic rhinosinusitis by immunohistochemistry. In a cell culture system of A549 respiratory epithelial cells, chemokine levels were quantified by enzyme-linked immunosorbent assay (ELISA) after stimulation with supernatants originating from three different staphylococcal strains or with trypsin, representing a serine protease. Inhibition experiments were performed with prednisolone, with the serine protease inhibitor 4-(2-aminoethyl)-benzenesulphonylfluoride (AEBSF) and with the nuclear transcription factor (NF)-kappaBeta inhibitor (2E)-3-[[4-(1,1-dimethylethyl)phenyl]sulphonyl]-2-propenenitrite (BAY) 11-7085. Electromobility shift assays (EMSA) were used to demonstrate NF-kappaB-dependent protein synthesis. CXC chemokines interleukin (IL)-8, growth-related oncogene alpha (GRO-alpha) and granulocyte chemotactic protein-2 (GCP-2) were expressed in the patients' epithelium whereas epithelial cell-derived neutrophil attractant 78 (ENA-78) was rarely detected. In A549 cells, chemokines IL-8, ENA-78 and GRO-alpha but not GCP-2 were induced by trypsin and almost equal levels were induced by staphylococcal supernatants. IL-8, GRO-alpha and ENA-78 synthesis was suppressed almost completely by AEBSF and BAY 11-7085, whereas prednisolone reduced chemokine levels differentially dependent on the supernatant added. CXC chemokines were detectable in the epithelium of patients with chronic rhinosinusitis. Staphylococcal serine proteases induced CXC chemokines in A549 cells, probably by the activation of proteases activated receptors, and thus might potentially be involved in neutrophilic inflammation in chronic sinusitis.

CpG DNA modulates interleukin 1beta-induced interleukin-8 expression in human bronchial epithelial (16HBE14o-) cells

Background

Recognition of repeat unmethylated CpG motifs from bacterial DNA through Toll-like receptor (TLR-9) has been shown to induce interleukin (IL)-8 expression in immune cells. We sought to investigate the role of CpG oligodeoxynucleotides (ODN) on a human bronchial epithelial cells.

Methods

RT-PCR and Western blot analysis were used to determine expression of TLR-9 in human bronchial epithelial cells (16HBE14o-). Cells were treated with CpG ODN in the presence or absence of IL-1β and IL-8 protein was determined using ELISA. In some cases cells were pretreated with chloroquine, an inhibitor of TLR-9 signaling, or SB202190, an inhibitor of the mitogen activated protein kinase p38, prior to treatment with IL-1β and CpG. TLR9 siRNA was used to silence TLR9 prior to treatment with IL-1β and CpG. IκBα and p38 were assessed by Western blot, and EMSA's were performed to determine NF-κB activation. To investigate IL-8 mRNA stability, cells were treated with IL-1β in the absence or presence of CpG for 2 h and actinomycin D was added to induce transcriptional arrest. Cells were harvested at 15 min intervals and Northern blot analysis was performed.

Results

TLR-9 is expressed in 16HBE14o- cells. CpG synergistically increased IL-1β-induced IL-8 protein abundance, however treatment with CpG alone had no effect. CpC (a control ODN) had no effect on IL-1β-induced IL-8 levels. In addition, CpG synergistically upregulated TNFα-induced IL-8 expression. Silencing TLR9 using siRNA or pretreatment of cells with chloroquine had little effect on IL-1β-induced IL-8 levels, but abolished CpG-induced synergy. CpG ODN had no effect on NF-κB translocation or DNA binding in 16HBE14o- cells. Treatment with CpG increased phosphorylation of p38 and pretreatment with the p38 inhibitor SB202190 attenuated the synergistic increase in IL-8 protein levels. Analysis of the half-life of IL-8 mRNA revealed that IL-8 mRNA had a longer half-life following the co-treatment of CpG and IL-1β compared to treatment with IL-1β alone.

Conclusion

Together, these data demonstrate that CpG modulates IL-8 synthesis in the presence of a pro-inflammatory mediator utilizing TLR9 and post-transcriptional mechanisms involving the activation of p38 and stabilization of IL-8 mRNA.

The protease-activated receptor2 (PAR2)-prostaglandin E2-prostanoid EP receptor axis: a potential bronchoprotective unit in the respiratory tract?

Protease-activated receptor2 (PAR2) is a subtype of G protein-coupled receptor that is widely expressed within the respiratory tract. Stimulation of PAR2 by proteases such as trypsin and tryptase, or by small peptidic activators induces a complex array of effects within the airways. One such PAR2-mediated effect by basal airway epithelial cells is the generation of prostaglandin E2. Prostaglandin E2 produces a raft of anti-inflammatory effects within the airways, principally through the activation of the prostanoid EP2 and EP3 receptor subtypes. This article reviews the PAR2-prostaglandin E2-prostanoid EP receptor axis and discusses approaches through which its activation may provide beneficial effects in respiratory disease.

IL-4 regulates MEK expression required for lysophosphatidic acid-mediated chemokine generation by human mast cells

IL-4 and mast cells (MCs) mediate mucosal defense against helminths and are central to allergic inflammation. Lysophosphatidic acid (LPA), an abundant, potent lipid growth factor, stimulates the growth of cultured human MCs (hMCs) in vitro through a pathway involving LPA receptors 1 and 3 (termed the LPA(1) and LPA(3) receptors, respectively) and peroxisome proliferator-activated receptor-gamma. We now report that LPA potently induces the generation of proinflammatory chemokines (MIP-1beta, IL-8, and MCP-1) by hMCs by a mechanism that absolutely requires IL-4. The de novo expression of chemokine mRNA and protein generation involves synergistic actions of calcium flux-dependent NFAT transcription factors and ERK. ERK phosphorylation and chemokine production in response to LPA require IL-4-dependent up-regulation of MEK-1 expression by a pathway involving PI3K. Although receptor-selective agonists for both the LPA(2) and LPA(3) receptors induce calcium fluxes by hMCs, only the LPA(2) receptor-selective agonist fatty alcohol phosphate-12 mimics the IL-4-dependent effect of LPA on chemokine generation. The fact that LPA, an endogenous lipid mediator, activates hMCs by an LPA(2) receptor-dependent pathway indicates functional distinctions between different LPA receptor family members that are expressed constitutively by cells of a single hemopoietic lineage. Moreover, the regulation of MEK-dependent signaling is a mechanism by which IL-4 could amplify inflammation in mucosal immune responses through receptor systems for endogenous ligands such as LPA.