Mechanisms of interleukin 1beta-induced human airway smooth muscle hyporesponsiveness to histamine. Involvement of p38 MAPK NF-kappaB

A high-throughput 3D cantilever array to model airway smooth muscle hypercontractility in asthma

Asthma is often characterized by tissue-level mechanical phenotypes that include remodeling of the airway and an increase in airway tightening, driven by the underlying smooth muscle. Existing therapies only provide symptom relief and do not improve the baseline narrowing of the airway or halt progression of the disease. To investigate such targeted therapeutics, there is a need for models that can recapitulate the 3D environment present in this tissue, provide phenotypic readouts of contractility, and be easily integrated into existing assay plate designs and laboratory automation used in drug discovery campaigns. To address this, we have developed DEFLCT, a high-throughput plate insert that can be paired with standard labware to easily generate high quantities of microscale tissues in vitro for screening applications. Using this platform, we exposed primary human airway smooth muscle cell-derived microtissues to a panel of six inflammatory cytokines present in the asthmatic niche, identifying TGF-β1 and IL-13 as inducers of a hypercontractile phenotype. RNAseq analysis further demonstrated enrichment of contractile and remodeling-relevant pathways in TGF-β1 and IL-13 treated tissues as well as pathways generally associated with asthma. Screening of 78 kinase inhibitors on TGF-β1 treated tissues suggests that inhibition of protein kinase C and mTOR/Akt signaling can prevent this hypercontractile phenotype from emerging, while direct inhibition of myosin light chain kinase does not. Taken together, these data establish a disease-relevant 3D tissue model for the asthmatic airway, which combines niche specific inflammatory cues and complex mechanical readouts that can be utilized in drug discovery efforts.

Targeting Airway Smooth Muscle Hypertrophy in Asthma: An Approach Whose Time Has Come

Airway smooth muscle (ASM) cell dysfunction is an important component of several obstructive pulmonary diseases, particularly asthma. External stimuli such as allergens, dust, air pollutants, and change in environmental temperatures provoke ASM cell hypertrophy, proliferation, and migration without adequate mechanistic controls. ASM cells can switch between quiescent, migratory, and proliferative phenotypes in response to extracellular matrix proteins, growth factors, and other soluble mediators. While some aspects of airway hypertrophy and remodeling could have beneficial effects, in many cases these contribute to a clinical phenotype of difficult to control asthma. In this review, we discuss the factors responsible for ASM hypertrophy and proliferation in asthma, focusing on cytokines, growth factors, and ion transporters, and discuss existing and potential approaches that specifically target ASM hypertrophy to reduce the ASM mass and improve asthma symptoms. The goal of this review is to highlight strategies that appear ready for translational investigations to improve asthma therapy.

Sustained exposure to prostaglandin D2 augments the contraction induced by acetylcholine via a DP1 receptor-mediated activation of p38 in bronchial smooth muscle of naive mice

Prostaglandin D₂ (PGD₂), one of the key lipid mediators of allergic airway inflammation, is increased in the airways of asthmatics. However, the role of PGD₂ in the pathogenesis of asthma is not fully understood. In the present study, effects of PGD₂ on smooth muscle contractility of the airways were determined to elucidate its role in the development of airway hyperresponsiveness (AHR). In a murine model of allergic asthma, antigen challenge to the sensitized animals caused a sustained increase in PGD₂ levels in bronchoalveolar lavage (BAL) fluids, indicating that smooth muscle cells of the airways are continually exposed to PGD₂ after the antigen exposure. In bronchial smooth muscles (BSMs) isolated from naive mice, a prolonged incubation with PGD₂ (10⁻⁵ M, for 24 h) induced an augmentation of contraction induced by acetylcholine (ACh): the ACh concentration-response curve was significantly shifted upward by the 24-h incubation with PGD₂. Application of PGD₂ caused phosphorylation of ERK1/2 and p38 in cultured BSM cells: both of the PGD₂-induced events were abolished by laropiprant (a DP₁ receptor antagonist) but not by fevipiprant (a DP₂ receptor antagonist). In addition, the BSM hyperresponsiveness to ACh induced by the 24-h incubation with PGD₂ was significantly inhibited by co-incubation with SB203580 (a p38 inhibitor), whereas U0126 (a ERK1/2 inhibitor) had no effect on it. These findings suggest that prolonged exposure to PGD₂ causes the BSM hyperresponsiveness via the DP₁ receptor-mediated activation of p38. A sustained increase in PGD₂ in the airways might be a cause of the AHR in allergic asthmatics.

Insights on the molecular mechanism of anti-inflammatory effect of formula from Islamic traditional medicine: An in-silico study

Background and aim

Traditional medicine is an important source for drug discovery. However, many challenges face the scientific community to develop novel drugs from it. To investigate the rationale behind the medical legacy of centuries of precious knowledge from traditional medicine, we aimed at performing virtual screening to identify potential leads from the middle-age textbook, The Canon of Medicine.

Experimental procedure

A database of chemical constituents of plants mentioned within the book was built and docked against different molecular targets associated with inflammation such as phospholipase A2, p38 alpha mitogen activated protein kinase, cyclooxygenase-2 and leukotriene B4 dehydrogenase, after that literature survey was done to determine the consistency of traditional uses and molecular docking results with the current knowledge obtained from previous studies and reports.

Results and conclusion

The in-silico study revealed the ability of several chemical constituents, in the plants under investigation, to bind effectively to different targets associated with inflammation, which was consistent with previous reports, indicating that Islamic traditional medicine can be considered as a reliable promising source for developing new anti-inflammatory agents with low toxicity and minimal side effects.

Effect of budesonide and azelastine on histamine signaling regulation in human nasal epithelial cells

Both glucocorticoids and H1-antihistamines are widely used on patients with airway diseases. However, their direct effects on airway epithelial cells are not fully explored. Therefore, we use the primary culture of human nasal epithelial cells (HNEpC) to delineate in vitro mucosal responses to above two drugs. HNEpC cells were cultured with/without budesonide and azelastine. The growth rate at each group was recorded and measured as population double time (PDT). The histamine1-receptor (H1R), muscarinic1-receptor (M1R) and M3R were measured using immunocytochemistry and western blotting after 7-days treatment. Then, we used histamine and methacholine to stimulate the mucus secretion from HNEpC and observed the MUC5AC expression in culture supernatants. Concentration-dependent treatment-induced inhibition of HNEpC growth rate was observed. Cells incubated with azelastine proliferated significantly slower than that with budesonide and the combined use of those drugs led to significant PDT prolong. The immunocytochemistry showed the H1R, M1R and M3R were obviously located in the cell membrane without apparent difference after treatment. However, western blotting showed that budesonide can significantly up-regulate the H1R, M1R and M3R level while azelastine had opposite effects. Histamine and methacholine stimulated MUC5AC secretion was greater in cells treated with budesonide but was lesser in those treated with azelastine, as compared to controls. Our data suggest that both budesonide and azelastine can significantly inhibit HNEpC proliferation, and therefore, be helpful in against airway remodeling. Long-term use of budesonide might amplify histamine signaling and result in airway hyperreactivity to stimulants by enhancing H1R, M1R and M3R expression while azelastine can oppose this effect. Therefore, combined use of those two drugs in patients with chronic inflammatory airway diseases may be an ideal option.

Tumor Necrosis Factor Alpha Inhibits L-Type Ca(2+) Channels in Sensitized Guinea Pig Airway Smooth Muscle through ERK 1/2 Pathway

Tumor necrosis factor alpha (TNF-α) is a potent proinflammatory cytokine that plays a significant role in the pathogenesis of asthma by inducing hyperresponsiveness and airway remodeling. TNF-α diminishes the L-type voltage dependent Ca²⁺ channel (L-VDCC) current in cardiac myocytes, an observation that seems paradoxical. In guinea pig sensitized tracheas KCl responses were lower than in control tissues. Serum from sensitized animals (Ser-S) induced the same phenomenon. In tracheal myocytes from nonsensitized (NS) and sensitized (S) guinea pigs, an L-VDCC current (ICa) was observed and diminished by Ser-S. The same decrease was detected in NS myocytes incubated with TNF-α, pointing out that this cytokine might be present in Ser-S. We observed that a small-molecule inhibitor of TNF-α (SMI-TNF) and a TNF-α receptor 1 (TNFR1) antagonist (WP9QY) reversed ICa decrease induced by Ser-S in NS myocytes, confirming the former hypothesis. U0126 (a blocker of ERK 1/2 kinase) also reverted the decrease in ICa. Neither cycloheximide (a protein synthesis inhibitor) nor actinomycin D (a transcription inhibitor) showed any effect on the TNF-α-induced ICa reduction. We found that Ca_V1.2 and Ca_V1.3 mRNA and proteins were expressed in tracheal myocytes and that sensitization did not modify them. In cardiac myocytes, ERK 1/2 phosphorylates two sites of the L-VDCC, augmenting or decreasing ICa; we postulate that, in guinea pig tracheal smooth muscle, TNF-α diminishes ICa probably by phosphorylating the L-VDCC site that reduces its activity through the ERK1/2 MAP kinase pathway.

Statins Modulate Cyclooxygenase-2 and Microsomal Prostaglandin E Synthase-1 in Human Hepatic Myofibroblasts

Statins have been shown to exert anti-inflammatory and anti-fibrogenic properties in the liver. In the present study, we explored the mechanisms underlying anti-fibrogenic effects of statins in isolated hepatic myofibroblasts and focused on cyclooxyegnase-2, a major anti-proliferative pathway in these cells. We show that simvastatin and fluvastatin inhibit thymidine incorporation in hMF in a dose-dependent manner. Pretreatment of cells with NS398, a COX-2 inhibitor, partially blunted this effect. cAMP levels, essential to the inhibition of hMF proliferation, were increased by statins and inhibited by non-steroidal anti-inflammatory drugs. Since statins modify prenylation of some important proteins in gene expression, we investigated the targets involved using selective inhibitors of prenyltransferases. Inhibition of geranylgeranylation resulted in the induction of COX-2 and mPGES-1. Using gel retardation assays, we further demonstrated that statins potentially activated the NFκB and CRE/E-box binding for COX-2 promoter and the binding of GC-rich regions and GATA for mPGES-1. Together these data demonstrate that statin limit hepatic myofibroblasts proliferation via a COX-2 and mPGES-1 dependent pathway. These data suggest that statin-dependent increase of prostaglandin in hMF contributes to its anti-fibrogenic effect.

Ion flux in the lung: virus-induced inflammasome activation

Innate immunity has a primary role in lung antimicrobial defenses. The inflammasome has evolved for this purpose and is an important surveillance system that, when triggered, fights infection and eliminates pathogens. However, there is growing evidence that the inflammasome also plays a role in the pathogenesis of acute and chronic respiratory disease. Inflammasomes contribute to both the clearance of the pathogen as well as its pathogenesis - depending on the amount of inflammation triggered. How respiratory viruses trigger inflammasome activation remains unclear. Emerging evidence shows that ion flux is responsible for triggering inflammasome activation in the lung, causing lung pathology and disease exacerbations. Viroporins, encoded by all common respiratory viruses, are responsible for the changes in intracellular ion homeostasis that modulate inflammasome activation. This is a novel mechanism by which respiratory viral infection activates inflammasomes, and identifies sensing of disturbances in intracellular ionic concentrations as a novel pathogen-recognition pathway in the lung.

Airway smooth muscle in asthma: just a target for bronchodilation?

Airway smooth muscle (ASM) has long been recognized as the main cell type responsible for bronchial hyperresponsiveness. It has, thus, been considered as a target for bronchodilation. In asthma, however, there is a complex relationship between ASM and inflammatory cells, such as mast cells and T lymphocytes. Moreover, the increased ASM mass in asthmatic airways is one of the key features of airway remodeling. This article aims to review the main concepts about the 3 possible roles of ASM in asthma: (1) contractile tone, (2) inflammatory response, and (3) remodeling.

Does airway smooth muscle express an inflammatory phenotype in asthma?

In addition to hyperresponsiveness in asthma, airway smooth muscle (ASM) also manifests an inflammatory phenotype characterized by augmented expression of mediators that enhance inflammation, contribute to tissue remodelling and augment leucocyte trafficking and activity. Our present review summarizes contemporary understanding of ASM-derived mediators and their paracrine and autocrine actions in airway diseases.

Mechanisms altering airway smooth muscle cell Ca+ homeostasis in two asthma models

BACKGROUND

Asthma is characterized by airway remodeling, altered mucus production and airway smooth muscle cell (ASMC) contraction causing extensive airway narrowing. In particular, alterations of ASMC contractility seem to be of crucial importance. The elevation of the cytoplasmic Ca(2+) concentration is a key event leading to ASMC contraction and changes in the agonist-induced Ca(2+) increase in ASMC have been reported in asthma.

OBJECTIVE

The aim of this study was to investigate mechanisms underlying these changes.

METHODS

Murine tracheal smooth muscle cells (MTSMC) from T-bet KO mice and human bronchial smooth muscle cells (HBSMC) incubated with IL-13 and IL-4 served as asthma models. Acetylcholine-induced changes in the cytoplasmic Ca(2+) concentration were recorded using fluorescence microscopy and the expression of Ca(2+) homeostasis regulating proteins was investigated with Western blot analysis.

RESULTS

Acetylcholine-induced Ca(2+) transients were elevated in both asthma models. This correlated with an increased Ca(2+) content of the sarcoplasmic reticulum (SR). In MTSMC from T-bet KO mice, the expression of the SR Ca(2+) buffers calreticulin and calsequestrin was higher compared to wild-type mice. In HBSMC incubated with IL-13 or IL-4, the expression of ryanodine receptors, inositol-3-phosphate receptors and sarcoplasmic/endoplasmic reticulum Ca(2+) ATPases 2 was increased compared to HBSMC without incubation with interleukins. The enlarged acetylcholine-induced Ca(2+) transients could be reversed by blocking inositol-3-phosphate receptors.

CONCLUSIONS

We conclude that in the murine asthma model the SR Ca(2+) buffer capacity is increased, while in the human asthma model the expression of SR Ca(2+) channels is altered. The investigation of the Ca(2+) homeostasis of ASMC has the potential to provide new therapeutical options in asthma.

Cx43 hemichannels and gap junction channels in astrocytes are regulated oppositely by proinflammatory cytokines released from activated microglia

Astrocytes have a role in maintaining normal neuronal functions, some of which depend on connexins, protein subunits of gap junction channels and hemichannels. Under inflammatory conditions, microglia release cytokines, including interleukin-1beta and tumor necrosis factor-alpha, that reduce intercellular communication via gap junctions. Now, we demonstrate that either conditioned medium harvested from activated microglia or a mixture of these two cytokines enhances the cellular exchange with the extracellular milieu via Cx43 hemichannels. These changes in membrane permeability were not detected in astrocytes cultured from Cx43 knock-out mice and were abrogated by connexin hemichannel blockers, including La3+, mimetic peptides, and niflumic acid. Both the reduction in gap junctional communication and the increase in membrane permeability were mediated by a p38 mitogen-activated protein kinase-dependent pathway. However, the increase in membrane permeability, but not the gap junction inhibition, was rapidly reversed by the sulfhydryl reducing agent dithiothreitol, indicating that final regulatory mechanisms are different. Treatment with proinflammatory cytokines reduced the total and cell surface Cx43 levels, suggesting that the increase in membrane permeability was attributable to an increase in hemichannels activity. Indeed, unitary events of approximately 220 pS corresponding to Cx43 hemichannels were much more frequent in astrocytes treated with microglia conditioned medium than under control conditions. Finally, the effect of cytokines enhanced the uptake and reduced the intercellular diffusion of glucose, which might explain changes in the metabolic status of astrocytes under inflammatory conditions. Accordingly, this opposite regulation may affect glucose trafficking and certainly will modify the metabolic status of astrocytes involved in brain inflammation.

Salmeterol and cytokines modulate inositol-phosphate signalling in human airway smooth muscle cells via regulation at the receptor locus

Background

Airway hyper-responsiveness (AHR) is a key feature of asthma and a causal relationship between airway inflammation and AHR has been identified. The aim of the current study was to clarify the effect of proinflammatory cytokines and asthma medication on primary human airway smooth muscle (ASM) inositol phosphate (IPx) signalling and define the regulatory loci involved.

Methods

Primary Human ASM cells were isolated from explants of trachealis muscle from individuals with no history of respiratory disease. The effect of cytokine or asthma medication on histamine or bradykinin induced IPx signalling was assessed by [³H] inositol incorporation. Quantitative Real Time PCR was used to measure mRNA levels of receptors and downstream signalling components. Transcriptional mechanisms were explored using a combination of 5'Rapid Amplification of cDNA Ends (5'RACE) and promoter-reporter techniques.

Results

Treatment of Human ASM cells with IL-13, IFNγ or salmeterol for 24 hours lead to a modest augmentation of histamine induced IPx responses (144.3 +/- 9.3, 126.4 +/- 7.5 and 117.7 +/- 5.2%, p < 0.05). Similarly, TNFα, IFNγ or salmeterol treatment augmented bradykinin induced IPx responses (127.4 +/- 8.3, 128.0 +/- 8.4 and 111.7 +/- 5.0%, P < 0.05). No treatment significantly influenced sodium fluoride induced IPx responses suggesting regulation occurs at the receptor locus. Analyses of mRNA expression of components of the IPx pathway i.e. H1 Histamine Receptor (HRH1), B2 Bradykinin Receptor (BDKRB2), Gαq/11 and PLC-β1 identified that a significant induction of receptor mRNA (>2 fold) was a feature of these responses explaining the cytokine and spasmogen specificity. The HRH1 and BDKRB2 promoter regions were mapped in ASM and promoter-reporter analyses identified that salmeterol can induce HRH1 (>2 fold) and BDKRB2 (2–5 fold) transcription. The effect of cytokines on HRH1 and BDKRB2 promoter-reporter expression suggested a more complex regulation of mRNA expression involving additional loci to the core promoter.

Conclusion

Our results indicate that the spasmogen specific receptor locus may be a key site of regulation determining the magnitude of spasmogen mediated ASM IPx responses during airway inflammation or following asthma medication. These data provide further insight into the molecular basis of AHR and extend our understanding of potentially detrimental effects associated with existing therapies used in the treatment of asthma.

Targeting G protein-coupled receptor signaling in asthma

The complex disease asthma, an obstructive lung disease in which excessive airway smooth muscle (ASM) contraction as well as increased ASM mass reduces airway lumen size and limits airflow, can be viewed as a consequence of aberrant airway G protein-coupled receptor (GPCR) function. The central role of GPCRs in determining airway resistance is underscored by the fact that almost every drug used in the treatment of asthma directly or indirectly targets either GPCR-ligand interaction, GPCR signaling, or processes that produce GPCR agonists. Although many airway cells contribute to the regulation of airway resistance and architecture, ASM properties and functions have the greatest impact on airway homeostasis. The theme of this review is that GPCR-mediated regulation of ASM tone and ASM growth is a major determinant of the acute and chronic features of asthma, and multiple strategies targeting GPCR signaling may be employed to prevent or manage these features.

Airway smooth muscle as a regulator of immune responses and bronchomotor tone

The traditional view of airway smooth muscle (ASM) in asthma, as a purely contractile tissue, seems to be inadequate. Compelling evidence now suggests that ASM plays an important role in regulating bronchomotor tone, in perpetuating airway inflammation, and in remodeling of the airways. This article reviews three distinct functions of ASM cells: the process of excitation-contraction coupling, with a particular focus on the role of cytokines in modulating calcium responses; the processes of smooth muscle cell proliferation and migration; and the synthetic and immunomodulatory function of ASM cells. This article also discusses how altered synthetic function contributes to airway remodeling.

Asthma: is it due to an abnormal airway smooth muscle cell?

Asthma is an airway disease highly prevalent in westernized countries and of unknown etiology. Often, asthma is associated with atopy, but not all atopic individuals have asthma. Some patients with asthma outgrow symptoms, whereas many others acquire asthma later in life. Still other patients suffer from asthma their entire life. How can we explain these different patterns? It may be that asthma should be regarded as the clinical manifestation of a group of diseases with similar pathology due to a common factor. In this Pulmonary Perspective, we propose that an aberrant phenotype of airway smooth muscle (ASM) cells could be sufficient to explain the pathology of asthma. We will argue an abnormal ASM cell is a prerequisite to the development of asthma. Our postulate is that inadequate levels of C/EBPalpha, a protein that is pivotal for the suppression of both inflammation and proliferation responses, confer on ASM cells an activated phenotype that is more susceptible to mitogenic and contractile stimuli.

Regulatory features of interleukin-1β-mediated prostaglandin E2 synthesis in airway smooth muscle

Exposure of airway smooth muscle (ASM) cells to the cytokine IL-1β results in an induction of PGE2 synthesis that affects numerous cell functions. Current dogma posits induction of COX-2 protein as the critical, obligatory event in cytokine-induced PGE2 production, although PGE2 induction can be inhibited without a concomitant inhibition of COX-2. To explore other putative regulatory features we examined the role of phospholipase A2 (PLA2) and PGE synthase (PGES) enzymes in IL-1β-induced PGE2 production. Treatment of human ASM cultures with IL-1β caused a time-dependent induction of both cytosolic PLA2 (cPLA2) and microsomal PGES (mPGES) similar to that observed for COX-2. Regulation of COX-2 and mPGES induction was similar, being significantly reduced by inhibition of p42/p44 or p38, whereas cPLA2 induction was only minimally reduced by inhibition of p38 or PKC. COX-2 and mPGES induction was subject to feed-forward regulation by PKA, whereas cPLA2 induction was not. SB-202474, an SB-203580 analog lacking the ability to inhibit p38 but capable of inhibiting IL-1β-induced PGE2 production, was effective in inhibiting mPGES but not COX-2 or cPLA2 induction. These data suggest that although COX-2, cPLA2, and mPGES are all induced by IL-β in human ASM cells, regulatory features of cPLA2 are dissociated, whereas those of COX-2 and mPGES are primarily associated, with regulation of PGE2 production. mPGES induction and, possibly, cPLA2 induction appear to cooperate with COX-2 to determine IL-1β-mediated PGE2 production in human ASM cells.

Ca2+-signaling in airway smooth muscle cells is altered in T-bet knock-out mice

BACKGROUND

Airway smooth muscle cells (ASMC) play a key role in bronchial hyperresponsiveness (BHR). A major component of the signaling cascade leading to ASMC contraction is calcium. So far, agonist-induced Ca2+-signaling in asthma has been studied by comparing innate properties of inbred rat or mouse strains, or by using selected mediators known to be involved in asthma. T-bet knock-out (KO) mice show key features of allergic asthma such as a shift towards TH2-lymphocytes and display a broad spectrum of asthma-like histological and functional characteristics. In this study, we aimed at investigating whether Ca2+-homeostasis of ASMC is altered in T-bet KO-mice as an experimental model of asthma.

METHODS

Lung slices of 100 to 200 microm thickness were obtained from T-bet KO- and wild-type mice. Airway contraction in response to acetylcholine (ACH) was measured by video-microscopy and Ca2+-signaling in single ASMC of lung slices was assessed using two-photon-microscopy.

RESULTS

Airways from T-bet KO-mice showed increased baseline airway tone (BAT) and BHR compared to wild-type mice. This could be mimicked by incubation of lung slices from wild-type mice with IL-13. The increased BAT was correlated with an increased incidence of spontaneous changes in intracellular Ca2+-concentrations, whereas BHR correlated with higher ACH-induced Ca2+-transients and an increased proportion of ASMC showing Ca2+-oscillations. Emptying intracellular Ca2+-stores using caffeine or cyclopiazonic acid induced higher Ca2+-elevations in ASMC from T-bet KO- compared to wild-type mice.

CONCLUSION

Altered Ca2+-homeostasis of ASMC contributes to increased BAT and BHR in lung slices from T-bet KO-mice as a murine asthma model. We propose that a higher Ca2+-content of the intracellular Ca2+-stores is involved in the pathophysiology of these changes.

Interleukin-17-Induced Interleukin-8 Release in Human Airway Smooth Muscle Cells: Role for Mitogen-Activated Kinases and Nuclear Factor-κB

BACKGROUND

It has recently become clear that interleukin (IL)-8 plays a role in chronic neutrophilic inflammatory disorders, such as chronic rejection after lung transplantation. We have shown that IL-17--stimulated human airway smooth muscle cells (HASMC) are able to produce IL-8. The aim of this study was to determine whether p38 mitogen-activated protein kinase (MAPK), c-Jun amino-terminal kinase (JNK), p42/p44 extracellular signal-related kinase (ERK) and nuclear factor-kappaB (NF-kappaB) are involved in IL-17--induced IL-8 production in HASMC in vitro.

METHODS

We used human airway smooth muscle cells in culture. Western blotting was done to obtain data regarding activation of MAPK. Furthermore, we used specific inhibitors of MAPK to investigate their involvement in IL-17--induced IL-8 release, which was measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Western blotting clearly demonstrated that p38 MAPK, JNK and p42/p44 ERK were activated by IL-17 in HASMC. Using SB203580, a specific inhibitor of p38 MAPK, we detected a concentration-dependent inhibition of IL-17--induced IL-8 production with a maximal decrease of 63 +/- 5% (n=8, p<0.01). Curcumin, a specific inhibitor of JNK, also concentration-dependently reduced IL-17--induced IL-8 production, with a maximal decrease of 82+/-4% (n=8, p<0.01). U0126, a specific inhibitor of p42/p44 ERK, induced a maximal decrease of 84+/-5% (n=8, p<0.001). Pyrrolydine dithiocarbamate (PDTC), an inhibitor of NF-kappaB, caused a 70+/-5% (n=8, p<0.01) decrease in IL-17--induced IL-8 production.

CONCLUSIONS

We found that IL-17 induces activation of p38MAPK, JNK and p42/p44ERK in HASMC. We also found that p38MAPK, JNK, p42/p44 ERK and NF-kappaB play an important role in IL-17--induced IL-8 production in HASMC in vitro. This may open up new opportunities for further treatment of this disease.

Inhibition of Early Airway Neutrophilia Does Not Affect Development of Airway Hyperresponsiveness

The effect of modifying early neutrophil-mediated inflammation on the development of airway hyperresponsiveness (AHR) was investigated using an interleukin (IL)-1 receptor antagonist (IL-1Ra), an anti-IL-18 antibody (anti-IL-18) or a p38 mitogen-activated protein kinase (MAPK) inhibitor (M39). Balb/c mice were sensitized to ovalbumin (OVA) and challenged with a single intranasal dose of OVA. Treatment with the IL-1Ra or anti-IL-18 was initiated 20 min before challenge, whereas M39 was administered 4 h before the challenge. Eight hours after challenge, sensitized mice showed significantly higher numbers of neutrophils in bronchoalveolar lavage (BAL) fluid; treatment with IL-1Ra, anti-IL-18, or M39 significantly decreased the influx of neutrophils. At 48 h, none of the treatments affected eosinophil inflammation in BAL fluid and lung tissue, goblet cell hyperplasia, or cytokine levels (IL-4, IL-5, IL-12, IL-13, interferon-gamma) in BAL fluid. Anti-IL-18 or IL-1Ra had no effect on the development of AHR, whereas M39-treated mice showed a decrease in methacholine responsiveness. These results demonstrate that early neutrophil influx following allergen challenge is mediated by IL-1, IL-18, and p38 MAPK. However, neutralization of IL-1 and IL-18 did not affect the later development of AHR and eosinophilic airway inflammation. The effects of inhibiting p38 MAPK in decreasing AHR indicate activities independent of its prevention of neutrophil accumulation.

MAPK regulation of gene expression in airway smooth muscle

Mitogen-activated protein kinases (MAPK) are important components of signaling modules activated by neurotransmitters, cytokines, and growth factors, as well as chemical and mechanical stressors. In the airway, these external signals produce acute responses that modify smooth muscle contraction and may also induce chronic responses that modify airway structure. Both acute and chronic events in airway remodeling result from altered expression of multiple genes encoding protein mediators of cell-cell signaling, extracellular matrix remodeling, cell cycle control and intracellular signaling pathways. This review will focus on inflammatory and growth factor mediators of cell-cell signaling regulated by the ERK and p38 MAPK pathways in airway smooth muscle (ASM). These signaling mediators affect ASM tissue mechanics, cell migration, and gene expression patterns in a paracrine and autocrine fashion, although the relative importance of each MAPK pathway varies with the stimulus. These events thereby contribute to normal airway function and participate in pathological changes in ASM that accompany symptoms of asthma.

Mechanisms of inflammation-mediated airway smooth muscle plasticity and airways remodeling in asthma

Recent evidence points to progressive structural change in the airway wall, driven by chronic local inflammation, as a fundamental component for development of irreversible airway hyperresponsiveness. Acute and chronic inflammation is orchestrated by cytokines from recruited inflammatory cells, airway myofibroblasts and myocytes. Airway myocytes exhibit functional plasticity in their capacity for contraction, proliferation, and synthesis of matrix protein and cytokines. This confers a principal role in driving different components of the airway remodeling process, and mediating constrictor hyperresponsiveness. Functional plasticity of airway smooth muscle (ASM) is regulated by an array of environmental cues, including cytokines, which mediate their effects through receptors and a number of intracellular signaling pathways. Despite numerous studies of the cellular effects of cytokines on cultured airway myocytes, few have identified how intracellular signaling pathways modulate or induce these cellular responses. This review summarizes current understanding of these concepts and presents a model for the effects of inflammatory mediators on functional plasticity of ASM in asthma.

p38 MAPK and NF-kappaB mediate COX-2 expression in human airway myocytes

We have previously demonstrated that p38 and extracellular signal-regulated protein kinase (ERK) mitogen-activated protein kinases (MAPK) are components of proinflammatory induced cytokine expression in human airway myocytes. The experiments described here further these studies by examining p38 MAPK and NF-kappaB regulation of cyclooxygenase-2 (COX-2) expression in response to a complex inflammatory stimulus consisting of 10 ng/ml interleukin (IL)-1beta, tumor necrosis factor-alpha (TNF-alpha), and interferon (IFN)-gamma. COX-2 expression was induced with this stimulus in a time-dependent manner, with maximal expression seen 12-20 h after treatment. Semiquantitative RT-PCR and immunoblotting experiments demonstrate decreased COX-2 expression following treatment with the p38 MAPK inhibitor SB-203580 (25 microM) or the proteosome inhibitor MG-132 (1 microM). SB-203580 did not affect cytokine-stimulated IkappaBalpha degradation, NF-kappaB nuclear binding activity, or NF-kappaB-dependent signaling from the COX-2 promoter, indicating that p38 MAPK and NF-kappaB may affect COX-2 expression via separate signaling pathways. SB-203580, but not MG-132, also increased the initial rate of COX-2 mRNA decay, indicating p38 MAPK, but not NF-kappaB, participates in the regulation of COX-2 mRNA stability. These findings suggest that although p38 MAPK and NF-kappaB signaling regulate steady-state levels of COX-2 expression, p38 MAPK additionally affects stability of COX-2 mRNA in cytokine-stimulated human airway myocytes.

Do inflammatory mediators influence the contribution of airway smooth muscle contraction to airway hyperresponsiveness in asthma?

It is now accepted that a host of cytokines, chemokines, growth factors, and other inflammatory mediators contributes to the development of nonspecific airway hyperresponsiveness in asthma. Yet, relatively little is known about how inflammatory mediators might promote airway structural remodeling or about the molecular mechanisms by which they might exaggerate smooth muscle shortening as observed in asthmatic airways. Taking a deep inspiration, which provides relief of bronchodilation in normal subjects, is less effective in asthmatic subjects, and some have speculated that this deficiency stems directly from an abnormality of airway smooth muscle and results in airway hyperresponsiveness to constrictor agonists. Here, we consider some of the mechanisms by which inflammatory mediators might acutely or chronically induce changes in the contractile apparatus that in turn might contribute to hyperresponsive airways in asthma.

TNF-[alpha] modulates murine tracheal rings responsiveness to G-protein-coupled receptor agonists and KCl

Although the mechanisms that underlie airway hyperresponsiveness in asthma are complex and involve a variety of factors, evidence now suggests that intrinsic abnormalities in airway smooth muscle (ASM) may play an important role. We previously reported that TNF-alpha, a cytokine involved in asthma, augments G-protein-coupled receptor (GPCR) agonist-evoked calcium responses in cultured ASM cells. Here we have extended our previous studies by investigating whether TNF-alpha also modulates the contractile and relaxant responses to GPCR activation using cultured murine tracheal rings. We found that in tracheal rings treated with 50 ng/ml TNF-alpha, carbachol-induced isometric force was significantly increased by 30% compared with those treated with diluent alone (P < 0.05). TNF-alpha also augmented KCl-induced force generation by 70% compared with rings treated with diluent alone (P < 0.01). The enhancing effect of TNF-alpha on carbachol-induced isometric force generation was completely abrogated in the tracheal rings obtained from TNF-alpha receptor (TNFR)1-deficient mice and in control rings treated with a TNF-alpha mutant that solely activates TNFR2. TNF-alpha also attenuated relaxation responsiveness to isoproterenol but not to PGE2 or forskolin. TNF-alpha modulatory effects on GPCR-induced ASM responsiveness were completely abrogated by pertussis toxin, an inhibitor of Gialpha proteins. Taken together, these data suggest that TNF-alpha may participate in the development of airway hyperresponsiveness in asthma via the modulation of ASM responsiveness to both contractile and beta-adrenoceptor GPCR agonists.

Involvement of p38 MAPK, JNK, p42/p44 ERK and NF-kappaB in IL-1beta-induced chemokine release in human airway smooth muscle cells

Asthma is an inflammatory disease, in which eotaxin, MCP-1 and MCP-3 play a crucial role. These chemokines have been shown to be expressed and produced by IL-1beta-stimulated human airway smooth muscle cells (HASMC) in culture. In the present study we were interested to unravel the IL-1beta-induced signal transduction leading to chemokine production. Using Western blot, we observed an activation of p38 MAPK, JNK kinase and p42/p44 ERK when HASMC were stimulated with IL-1beta. We also observed a significant decrease in the expression and the release of eotaxin, MCP-1 and MCP-3 in the presence of SB203580, an inhibitor of p38 MAPK (71 +/- 6%, P < 0.05, n = 8 and 39 +/- 10% P < 0.01, n = 10 respectively), curcumin, an inhibitor of JNK kinase (83 +/- 4.9% and 88 +/- 3.4% respectively, P < 0.01, n = 4). U0126, an inhibitor of p42/p44 ERK, also produced a significant decrease in chemokine production (46.3 +/- 9%, P < 0.01 n = 10 and 67.8 +/- 12%, P < 0.01, n = 12). Pyrrolydine dithiocarbamate, an inhibitor of NF-kappaB was also able to reduce the eotaxin, MCP-1 and MCP-3 expression and production (50 +/- 13%, P < 0.05, n = 10 and 23 +/- 7%, P < 0.05, n = 12). We conclude that p38 MAPK, JNK kinase, ERK and NF-kappaB are involved in the IL-1beta-induced eotaxin, MCP-1, and MCP-3 expression and release in HASMC.

Down-regulated circulating PMN function after injury despite enhanced p38 MAPK activity

BACKGROUND

Neutrophils (PMN) are initially primed by injury. However, remaining PMN found in the circulation postinjury demonstrate a down-regulated phenotype with inhibited apoptosis, CXCR2 expression, and endotoxin (LPS) responsiveness that may contribute to infectious complications and organ dysfunction. The p38 mitogen activated protein kinase (MAPK) signal transduction pathway has been implicated in regulating each of these PMN functions. We, therefore, hypothesize that p38 signaling is similarly down-regulated in postinjury circulating PMN.

MATERIALS AND METHODS

PMN were isolated from trauma patients (ISS > 20, postinjury day 3) and concurrently from healthy volunteers (control). PMN were cultured with LPS (100 ng/mL) and p38 activity assessed by Western blotting of cell lysates using a dual phosphospecific antibody for phosphorylated, active p38. In separate experiments, PMN from healthy volunteers were cultured in plasma from either healthy or injured subjects +/- LPS and p38 activity assessed by a cell-free in vitro kinase assay using the transcription factor, ATF-2, as a substrate. Apoptosis and IL-1beta secretion of the cultured PMN from each experimental condition were also quantified.

RESULTS

Circulating PMN from trauma patients have an upregulated LPS signaled p38 MAPK response (threefold) compared to PMN from healthy volunteers (p < 0.05). Furthermore, circulating factors present in trauma plasma can transfer this response to normal PMN. There was no significant alteration in apoptosis following LPS treatment between control and trauma patient's PMN (control: 62 +/- 3% vs. trauma: 55 +/- 5%), but there was decreased secretion of IL-1beta (control: 100 +/- 28 pg/mL vs. trauma: 12 +/- 5 pg/mL, p < 0.05).

CONCLUSION

We conclude that injury down-regulates selective PMN function despite enhanced p38 activity. These results suggest a shift in the role of PMN p38 signal transduction following injury with additional critical regulation of LPS responses downstream to p38 MAPK activity.

Effects of cytokines on contractile and dilator responses of airway smooth muscle

1. Increased bronchoconstrictor responses to contractile agonists and decreased dilator responses to beta-adrenoceptor agonists are characteristics of human asthma. One explanation for these features of asthma is that cytokines released in the asthmatic airway have direct effects on airway smooth muscle cells that alter their phenotype. 2. The present review summarizes data indicating that inflammatory cytokines, such as interleukin (IL)-1 beta and tumour necrosis factor-alpha, T helper (h) 1 cytokines, such as interferon-gamma, and Th2 cytokines, such as IL-13 and IL-5, have the capacity to enhance contractile responses and/or decrease relaxant responses of airway smooth muscle. These effects are observed in smooth muscle from human airways and airway smooth muscle of other species. 3. Understanding the mechanistic basis for the effects of these cytokines may prove to be an important step in improving the efficacy of beta-adrenoceptor agonists for the treatment of asthma.

Modulation of calcium homeostasis as a mechanism for altering smooth muscle responsiveness in asthma

Airway hyperresponsiveness remains a defining characteristic of asthma. Traditional views assert that airway smooth muscle is an important structural effector cell in the bronchi that modulates bronchomotor tone induced by contractile agonists. New evidence, however, suggests that abnormalities in airway smooth muscle functions, induced by variety of extracellular stimuli, may play an important role in the development of airway hyperresponsiveness. Studies using isolated bronchial preparations or cultured cells show that inflammatory mediators and cytokines may alter calcium homeostasis in airway smooth muscle and render the cells nonspecifically hyperreactive to agonists.