Effects of transforming growth factor-[beta] and budesonide on mitogen-activated protein kinase activation and apoptosis in airway epithelial cells

Oleic acid attenuates asthma pathogenesis via Th1/Th2 immune cell modulation, TLR3/4-NF-κB-related inflammation suppression, and intrinsic apoptotic pathway induction

WHO reported that asthma was responsible for 455,000 deaths in 2019 and asthma patients was evaluated 262 million in May 2023. The incidence is expected to increase as the average life expectancy increases, highlighting asthma as a significant health challenge in an aging society. The etiology of asthma is linked to an imbalance of Th1 and Th2 cells, respiratory inflammation, and pulmonary cell proliferation. The purpose of this study is to investigate the anti-asthmatic effect and potential mechanism of oleic acid. The anti-inflammatory effect of oleic acid was evaluated in an LPS-induced RAW 264.7 cell model, and immune modulation and the anti-apoptotic effect were measured in an ovalbumin-induced BALB/c mouse model. A variety of analytical procedures, such as MTT, qPCR, ELISA, Western blotting, immunofluorescence, gene transfection, immunohistochemistry, and several staining methods (Diff Quik, H&E, PAS), were used to evaluate the effectiveness and mechanisms of these methods. The results from in vitro experiments showed that oleic acid could reduce the levels of inflammatory cytokines (TNF-α, IL-6, and IL-1β), and molecular docking studies suggested that oleic acid could interact with TLR3 and TLR4 proteins to form ligand-protein complexes, showing good binding affinity. Additionally, oleic acid attenuated the expression of MAPK pathway components (JNK, p38 MAPK) and NF-κB pathway constituents (IκB, NF-κB, COX-2, PGE2). In vivo results indicated that oleic acid reduced the levels of inflammatory cells (WBCs and eosinophils) and IgE activity, reduced the expression of the Th2 cell transcription factor GATA-3, and decreased the levels of Th2/Th17-related cytokines (IL-4, TNF-α, and IL-6). Oleic acid also alleviated OVA-induced pathological changes in the lung, such as epithelial cell proliferation, inflammatory cell infiltration, and mucus hypersecretion. OVA restored apoptosis in lung epithelial cells by modulating the expression of Bcl-2 and Bax. In summary, oleic acid has potential as a novel candidate for asthma treatment through its ability to regulate immune cells, exert anti-inflammatory effects, and promote apoptosis, thereby ameliorating asthma manifestations.

CAR-NKT Cells in Asthma: Use of NKT as a Promising Cell for CAR Therapy

NKT cells, unique lymphocytes bridging innate and adaptive immunity, offer significant potential for managing inflammatory disorders like asthma. Activating iNKT induces increasing IFN-γ, TGF-β, IL-2, and IL-10 potentially suppressing allergic asthma. However, their immunomodulatory effects, including granzyme-perforin-mediated cytotoxicity, and expression of TIM-3 and TRAIL warrant careful consideration and targeted approaches. Although CAR-T cell therapy has achieved remarkable success in treating certain cancers, its limitations necessitate exploring alternative approaches. In this context, CAR-NKT cells emerge as a promising approach for overcoming these challenges, potentially achieving safer and more effective immunotherapies. Strategies involve targeting distinct IgE-receptors and their interactions with CAR-NKT cells, potentially disrupting allergen-mast cell/basophil interactions and preventing inflammatory cytokine release. Additionally, targeting immune checkpoints like PDL-2, inducible ICOS, FASL, CTLA-4, and CD137 or dectin-1 for fungal asthma could further modulate immune responses. Furthermore, artificial intelligence and machine learning hold immense promise for revolutionizing NKT cell-based asthma therapy. AI can optimize CAR-NKT cell functionalities, design personalized treatment strategies, and unlock a future of precise and effective care. This review discusses various approaches to enhancing CAR-NKT cell efficacy and longevity, along with the challenges and opportunities they present in the treatment of allergic asthma.

Drug Development from Natural Products Based on the Pathogenic Mechanism of Asthma

Asthma is a chronic inflammatory disease of the pulmonary system associated with many wheeze-to-sleep apnea complications that may lead to death. In 2019, approximately 262 million patients suffered from asthma, and 455 thousand died from the disease worldwide. It is a more severe health problem in children and older adults, and as the aging of society intensifies, the problem will continue to worsen. Asthma inducers can be classified as indoor and outdoor allergens and can cause asthma due to their repeated invasion. There are several theories about asthma occurrence, such as the imbalance between Th1 and Th2, inflammation in the pulmonary system, and the abnormal apoptosis/cell proliferation of cells related to asthma. Although there are many medications for asthma, as it is an incurable disease, the purpose of the drugs is only to suppress the symptoms. The current drugs can be divided into relievers and controllers; however, as they have many adverse effects, such as immune suppression, growth retardation, promotion of cataracts, hyperactivity, and convulsions, developing new asthma drugs is necessary. Although natural products can have adverse effects, the development of asthma drugs from natural products may be beneficial, as some have anti-asthmatic effects such as immune modulation, anti-inflammation, and/or apoptosis modulation.

Polymer-Functionalized Mitochondrial Transplantation to Fibroblasts Counteracts a Pro-Fibrotic Phenotype

Fibroblast-to-myofibroblast transition (FMT) leads to excessive extracellular matrix (ECM) deposition-a well-known hallmark of fibrotic disease. Transforming growth factor-β (TGF-β) is the primary cytokine driving FMT, and this phenotypic conversion is associated with mitochondrial dysfunction, notably a metabolic reprogramming towards enhanced glycolysis. The objective of this study was to examine whether the establishment of favorable metabolic phenotypes in TGF-β-stimulated fibroblasts could attenuate FMT. The hypothesis was that mitochondrial replenishment of TGF-β-stimulated fibroblasts would counteract a shift towards glycolytic metabolism, consequently offsetting pro-fibrotic processes. Isolated mitochondria, functionalized with a dextran and triphenylphosphonium (TPP) (Dex-TPP) polymer conjugate, were administered to fibroblasts (MRC-5 cells) stimulated with TGF-β, and effects on bioenergetics and fibrotic programming were subsequently examined. Results demonstrate that TGF-β stimulation of fibroblasts led to FMT, which was associated with enhanced glycolysis. Dex-TPP-coated mitochondria (Dex-TPP/Mt) delivery to TGF-β-stimulated fibroblasts abrogated a metabolic shift towards glycolysis and led to a reduction in reactive oxygen species (ROS) generation. Importantly, TGF-β-stimulated fibroblasts treated with Dex-TPP/Mt had lessened expression of FMT markers and ECM proteins, as well as reduced migration and proliferation. Findings highlight the potential of mitochondrial transfer, as well as other strategies involving functional reinforcement of mitochondria, as viable therapeutic modalities in fibrosis.

Effects of early vitamin D supplementation on the prevention of bronchopulmonary dysplasia in preterm infants

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a respiratory dysfunction caused by poor lung bronchial development, which may lead to long-term lung disease, threatening the lives of children. Studies have shown that premature infants with low vitamin D are highly associated with BPD. In this study, we aim to obtain insights into whether early vitamin D supplementation could prevent BPD in preterm infants.

METHODS

A total of 112 preterm infants were randomly divided into two groups: the control and vitamin D supplementation (VD) group. The VD group received vitamin D (800 IU/day) within 48 h at birth for consecutively 28 days. The serum levels of 25(OH)D₃ and C-reactive protein (CRP), IL6, and TNF-α were measured using ELISA assay. The arterial partial pressure of oxygen (PaO₂ ) and carbon dioxide (PaCO₂ ) was measured using an i-STAT analyzer.

RESULTS

The occurrence of BPD was decreased in the VD group compared with the control. The decreased serum 25(OH)D₃ was significantly elevated by supplementation with vitamin D. In addition, the serum inflammation factors (CRP, IL6, and TNF-α) were significantly reduced by vitamin D supplementation.

CONCLUSION

We demonstrated that early vitamin D supplementation could significantly reduce BPD incidence in preterm infants. We showed that early vitamin D supplementation could significantly increase serum level of 25(OH)D₃ and reduce inflammatory response thereby preventing and reducing neonatal BPD.

LIMITATION

Firstly, a larger sample size will be needed to be included to gain a comprehensive understanding of the protective effects of vitamin D and BPD mechanistically in preterm infants. Secondly, the pathophysiological process of BPD will need to be studied. In addition, the pathways that vitamin D is responsible for, need to be further researched.

Role of p38 Mitogen-Activated Protein Kinase in Asthma and COPD: Pathogenic Aspects and Potential Targeted Therapies

Among the various members of the mitogen-activated protein kinase (MAPK) family, p38 MAPK subgroup is the most involved in airway and lung inflammation underlying asthma and chronic obstructive pulmonary disease (COPD). In particular, several environmental agents including aeroallergens, cigarette smoke, airborne pollutants, viral and bacterial pathogens activate the p38α isoform which in turn up-regulates the expression of multiple proinflammatory cytokines and chemokines, as well as the production of some fibrogenic factors. Therefore, p38 MAPK-induced bronchial inflammation and remodelling significantly contribute to the development, persistence and amplification of airflow limitation, which is the hallmark of asthma and COPD. Such advances in our understanding of p38 role in the pathobiology of the above widespread, chronic obstructive respiratory diseases, have led to consider p38 MAPK as a suitable molecular target for novel treatment strategies. Indeed, many studies have been carried out in both animal and clinical settings, with the aim of evaluating the potential therapeutic effects of p38 MAPK inhibitors in both asthma and COPD.

Clinical relevance of understanding mitogen-activated protein kinases involved in asthma

Introduction: Mitogen-activated protein kinases (MAPKs) are a large family of evolutionary conserved intracellular enzymes that play a pivotal role in signaling pathways mediating the biologic actions of a wide array of extracellular stimuli.Areas covered: MAPKs are implicated in most pathogenic events involved in asthma, including both inflammatory and structural changes occurring in the airways. Indeed, MAPKs are located at the level of crucial convergence points within the signal transduction networks activated by many cytokines, chemokines, growth factors, and other inducers of bronchial inflammation and remodeling such as immunoglobulin E (IgE) and oxidative stress.Expert opinion: Therefore, given the growing importance of MAPKs in asthma pathobiology, these signaling enzymes are emerging as key intracellular pathways whose upstream activation can be inhibited by biological drugs such as anti-cytokines and anti-IgE.

Physiological Roles of Mast Cells: Collegium Internationale Allergologicum Update 2019

Mast cells are immune cells which have a widespread distribution in nearly all tissues. These cells and their mediators are canonically viewed as primary effector cells in allergic disorders. However, in the last years, mast cells have gained recognition for their involvement in several physiological and pathological conditions. They are highly heterogeneous immune cells displaying a constellation of surface receptors and producing a wide spectrum of inflammatory and immunomodulatory mediators. These features enable the cells to act as sentinels in harmful situations as well as respond to metabolic and immune changes in their microenvironment. Moreover, they communicate with many immune and nonimmune cells implicated in several immunological responses. Although mast cells contribute to host responses in experimental infections, there is no satisfactory model to study how they contribute to infection outcome in humans. Mast cells modulate physiological and pathological angiogenesis and lymphangiogenesis, but their role in tumor initiation and development is still controversial. Cardiac mast cells store and release several mediators that can exert multiple effects in the homeostatic control of different cardiometabolic functions. Although mast cells and their mediators have been simplistically associated with detrimental roles in allergic disorders, there is increasing evidence that they can also have homeostatic or protective roles in several pathophysiological processes. These findings may reflect the functional heterogeneity of different subsets of mast cells.

Topical Corticosteroid Pretreatment Mitigates Cellular Damage After Caustic Injury to the Nasal Upper Airway Epithelium

BACKGROUND

Topical corticosteroids are currently employed to reduce established airway inflammation; their prophylactic use might help limit cellular damage against harmful stimuli.

OBJECTIVES

To determine the effects of a prophylactic topical application of budesonide (BD) on an in vivo nasal epithelium injury model induced by trichloroacetic acid (TCA).

METHODS

C57Bl/6 mice were exposed to intranasal TCA topical application. Three groups received topical intranasal BD, saline solution, or no intervention prior to a single topical exposure to TCA. Controls were not exposed to TCA. Whole nasal cavity coronal sections were analyzed at 1, 3, and 6 days postinjury at tissue and cellular levels using histopathological analysis, immunofluorescent staining, and fresh tissue RNA microarray analysis.

RESULTS

Prophylactic topical corticosteroid exposure protected the nasal epithelium from acute damage, maintaining epithelial thickness and cell survival. Six days following TCA exposure, epithelial and cellular changes were less pronounced on the BD-treated group compared to all exposure groups. The microarray analysis was used to evaluate the gene transcripts in all treatment groups. Ciliary tip protein, Sentan, and submucosal protein S100b were identified as potential factors in epithelial airway protection; immunofluorescent staining corroborated their presence and location within the respiratory epithelium.

CONCLUSION

Topical corticosteroid treatment to the nasal epithelium can mitigate several of the early deleterious effects of acute epithelial damage in experimental airway injuries caused by TCA. These findings suggest a novel, direct cytoprotective effect of corticosteroids on the nasal epithelium, and the potential of expanding the use of prophylactic periprocedural topical corticosteroids for respiratory epithelial tissues.

Cortisol limits selected actions of synthetic glucocorticoids in the airway epithelium

Cortisol, a physiologic glucocorticoid (GC), is essential for growth and differentiation of the airway epithelium. Epithelial function influences inflammation in chronic respiratory diseases. Synthetic GCs, including inhaled corticosteroids, exert anti-inflammatory effects in airway epithelium by transactivation of genes and by inhibition of proinflammatory cytokine release. We examined the effect of cortisol on the actions of synthetic GCs in the airway epithelium, demonstrating that cortisol acts like a partial agonist at the GC receptor (GR), limiting GC-induced GR-dependent transcription in the BEAS-2B human bronchial epithelial cell line. Cortisol also limited the inhibition of granulocyte macrophage colony-stimulating factor release by synthetic GCs in TNF-α-activated BEAS-2B cells. The relevance of these findings is supported by observations on tracheal epithelium obtained from mice treated for 5 d with systemic GC, showing limitations in selected GC effects, including inhibition of IL-6. Moreover, gene transactivation by synthetic GCs was compromised by standard air-liquid interface (ALI) growth medium cortisol concentration (1.4 μM) in the ALI-differentiated organotypic culture of primary human airway epithelial cells. These findings suggest that endogenous corticosteroids may limit certain actions of synthetic pharmacological GCs and contribute to GC insensitivity, particularly when corticosteroid levels are elevated by stress.-Prodanovic, D., Keenan, C. R., Langenbach, S., Li, M., Chen, Q., Lew, M. J., Stewart, A. G. Cortisol limits selected actions of synthetic glucocorticoids in the airway epithelium.

Fibroblast-derived exosomes promote epithelial cell proliferation through TGF-β2 signalling pathway in severe asthma

BACKGROUND

Bronchial fibroblasts play a key role in airway remodelling in asthma. They regulate epithelial cell functions such as proliferation through growth factors, cytokines, chemokines and exosomes. The role of exosomes in the communication between epithelial cells and fibroblasts by vehiculing these mediators in asthma remains to be determined.

OBJECTIVE

To evaluate the role of exosomes released by bronchial fibroblasts on epithelial cell proliferation in severe asthma.

METHODS

Exosomes were obtained from culture media of primary bronchial fibroblasts and characterized using Western blot, electron microscopy and flow cytometry. Uptake profile of fluorescent-labelled exosomes in epithelial cells was assessed by flow cytometry. Exosome cytokine content was analysed by Cytokine Arrays. Bronchial epithelial cell proliferation was evaluated by BrdU incorporation test. Exosome biogenesis/release was blocked using sphingomyelinase inhibitor. Plasmid transfection was used to modulate transforming growth factor beta 2 (TGF-β2) gene expression.

RESULTS

We showed that bronchial fibroblasts secreted exosomes, which were internalized by bronchial epithelial cells. Exosomes of severe asthmatic subjects' fibroblasts showed a lower level of TGF-β2 and significantly increased the epithelial cell proliferation of both healthy and severe asthmatic subjects compared to healthy controls' exosomes. Overexpression of TGF-β2 in severe asthmatics' fibroblasts induced enhanced TGF-β2 in exosomes leading to a reduced proliferation of epithelial cells, whereas knockdown of TGF-β2 enhanced epithelial cell proliferation.

CONCLUSION

Our study shows that exosomes are involved in fine-tuning intercellular communication in asthma. Exosomes of severe eosinophilic asthmatics' fibroblasts can contribute to airway remodelling, at least in part, by modulating epithelial cell proliferation observed in severe asthma.

Biological mechanisms underlying the clinical effects of allergen-specific immunotherapy in asthmatic children

INTRODUCTION

Allergen-specific immunotherapy (AIT) is indicated for patients with allergic asthma and/or allergic rhinitis, and can be implemented by either subcutaneous injection (SCIT) or sublingual administration (SLIT). AIT reduces asthma symptoms, lowers the use of pharmacologic controller therapy, and decreases the need for rescue medications. SLIT appears to be safer than SCIT, but SCIT seems to be more efficacious and acts earlier in allergic asthmatic children.

AREAS COVERED

This review looks at the pathobiology of allergic asthma as well as the role of regulatory T and B cells in allergen tolerance. It also reviews the immunological mechanisms underlying the clinical effects induced by AIT in allergic asthmatic children.

EXPERT OPINION

AIT is very effective in allergic asthmatic children, who can significantly benefit from this particular type of immunotherapy in order to achieve a better control of their disease. AIT is also capable of modifying the natural history of allergic asthma. Furthermore, AIT can potentially represent a valuable therapeutic tool within the context of precision medicine, as recombinant allergen technology might allow the creation of targeted extracts able to be effective against specific proteins to which individual asthmatic children are allergic, thus helping to implement a personalized approach to treatment.

Azithromycin ameliorates airway remodeling via inhibiting airway epithelium apoptosis

AIMS

Azithromycin can benefit treating allergic airway inflammation and remodeling. In the present study, we hypothesized that azithromycin alleviated airway epithelium injury through inhibiting airway epithelium apoptosis via down regulation of caspase-3 and Bax/Bcl2 ratio in vivo and in vitro.

MAIN METHODS

Ovalbumin induced rat asthma model and TGF-β1-induced BEAS-2B cell apoptosis model were established, respectively. In vivo experiments, airway epithelium was stained with hematoxylin and eosin (HE) and periodic acid-Schiff (PAS) to histologically evaluate the airway inflammation and remodeling. Airway epithelium apoptotic index (AI) was further analyzed by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), while expression of apoptosis related gene (Bax, Bcl2, Caspase-3) in lungs were measured by qRT-PCR and western blotting, respectively. In vitro experiments, apoptosis were evaluated by Flow cytometry (FCM) and TUNEL. Above apoptosis related gene were also measured by qRT-PCR and western blotting.

KEY FINDINGS

Compared with the OVA group, azithromycin significantly reduced the inflammation score, peribronchial smooth muscle layer thickness, epithelial thickening and goblet cell metaplasia (P<0.05), and effectively suppressed AI of airway epithelium (P<0.05). Moreover, the increasing mRNA and protein expressions of Caspase-3 and Bax/Bcl-2 ratio in lung tissue were all significantly decreased in azithromycin-treated rats (P<0.05). In vitro, azithromycin significantly suppressed TGF-β1-induced BEAS-2B cells apoptosis (P<0.05) and reversed TGF-β1 elevated Caspase-3 mRNA level and Bax/Bcl-2 ratio (P<0.05).

SIGNIFICANCE

Azithromycin is an attractive treatment option for reducing airway epithelial cell apoptosis by improving the imbalance of Bax/Bcl-2 ratio and inhibiting Caspase-3 level in airway epithelium.

Biomass Smoke Exposure Enhances Rhinovirus-Induced Inflammation in Primary Lung Fibroblasts

Biomass smoke is one of the major air pollutants and contributors of household air pollution worldwide. More than 3 billion people use biomass fuels for cooking and heating, while other sources of exposure are from the occurrence of bushfires and occupational conditions. Persistent biomass smoke exposure has been associated with acute lower respiratory infection (ALRI) as a major environmental risk factor. Children under the age of five years are the most susceptible in developing severe ALRI, which accounts for 940,000 deaths globally. Around 90% of cases are attributed to viral infections, such as influenza, adenovirus, and rhinovirus. Although several epidemiological studies have generated substantial evidence of the association of biomass smoke and respiratory infections, the underlying mechanism is still unknown. Using an in vitro model, primary human lung fibroblasts were stimulated with biomass smoke extract (BME), specifically investigating hardwood and softwood types, and human rhinovirus-16 for 24 h. Production of pro-inflammatory mediators, such as IL-6 and IL-8, were measured via ELISA. Firstly, we found that hardwood and softwood smoke extract (1%) up-regulate IL-6 and IL-8 release (p ≤ 0.05). In addition, human rhinovirus-16 further increased biomass smoke-induced IL-8 in fibroblasts, in comparison to the two stimulatory agents alone. We also investigated the effect of biomass smoke on viral susceptibility by measuring viral load, and found no significant changes between BME exposed and non-exposed infected fibroblasts. Activated signaling pathways for IL-6 and IL-8 production by BME stimulation were examined using signaling pathway inhibitors. p38 MAPK inhibitor SB239063 significantly attenuated IL-6 and IL-8 release the most (p ≤ 0.05). This study demonstrated that biomass smoke can modulate rhinovirus-induced inflammation during infection, which can alter the severity of the disease. The mechanism by which biomass smoke exposure increases inflammation in the lungs can be targeted and inhibited via p38 MAP kinase pathway.

Molecular and cellular mechanisms underlying the therapeutic effects of budesonide in asthma

Inhaled glucocorticoids are the mainstay of asthma treatment. Indeed, such therapeutic agents effectively interfere with many pathogenic circuits underpinning asthma. Among these drugs, during the last decades budesonide has been probably the most used molecule in both experimental studies and clinical practice. Therefore, a large body of evidence clearly shows that budesonide, either alone or in combination with long-acting bronchodilators, provides a successful control of asthma in many patients ranging throughout the overall spectrum of disease severity. These excellent therapeutic properties of budesonide basically depend on its molecular mechanisms of action, capable of inhibiting within the airways the activity of multiple immune-inflammatory and structural cells involved in asthma pathobiology.

Flunisolide attenuates nitric oxide-induced DNA damage in rat trachea epithelial cells

In asthma the bronchial epithelium is highly abnormal, with various structural changes. As a consequence, the epithelium becomes an important source of inflammatory mediators that contribute to the ongoing inflammation and remodeling responses occurring in asthma. Compared with normal individuals, the fraction of exhaled nitric oxide (NO) is elevated in patients with asthma, and these levels have been shown to vary with disease activity. Thus, in asthma, epithelial cells may be exposed to large amounts of NO. Increased NO production is associated with the formation of various nitrosating species capable of promoting DNA damage. In this study we investigated the effect of NO on DNA of rat trachea epithelial cells in the presence or absence of flunisolide. Rat airway epithelial cells were prepared and incubated with the NO donor S-nitroso-L-glutathione monoethyl ester (GSNO-MEE). DNA damage was evaluated using single cell gel electrophoresis 'comet assay.' The parameters used as an index of DNA damage were tail length, tail intensity, and tail moment. Results of our study demonstrated that NO induced significant DNA damage in rat airway epithelial cells. Flunisolide in amounts of 11-110 mumol/L significantly reduced all the considered parameters indicating DNA damage. These data indicate that flunisolide may protect epithelial cells from the NO-mediated DNA damage. NO overproduction could contribute to epithelial injury in asthma, and flunisolide seems to attenuate this damage.

Expression of interleukin-17A in lung tissues of irradiated mice and the influence of dexamethasone

Purpose. To investigate the expressions of IL-17A in different phases of radiation-induced lung injury and the effect of dexamethasone. Methods. The thorax of C57BL/6 mice was irradiated with 15 Gy rays. Mice from dexamethasone-treated group were injected intraperitoneally with dexamethasone (0.42 mg/kg/day) every day for the first month after irradiation. IL-17A in lung tissues was detected by immunohistochemistry. IL-17A, TGF-β1, and IL-6 in bronchoalveolar lavage fluid were detected by ELISA. Lung inflammation and collagen deposition were observed by H&E and Masson methods. The degree of alveolitis and fibrosis was judged according to scoring. Results. IL-17A expression was appreciable at 1 week, peaked at 4 weeks, and subsequently declined at 8 weeks after irradiation. IL-17A was reduced after dexamethasone application at all the observation periods. Dexamethasone also inhibited expressions of TGF-β, IL-6, and TNF-α in bronchoalveolar lavage fluid. Moreover, dexamethasone attenuated the severity of lung injury by reducing the infiltration of inflammatory cells and collagen deposition. Terms of survival and the time of death in mice of treatment group were postponed and survival rate was improved. Conclusions. IL-17A plays an important role in the process of radiation-induced lung injury. And dexamethasone may provide a protective role in lung injury induced by radiation.

Arsenic trioxide induces cardiac fibroblast apoptosis in vitro and in vivo by up-regulating TGF-β1 expression

Arsenic trioxide (As2O3; ATO) is clinically effective in treating acute promyelocytic leukemia (APL); however, it frequently causes cardiotoxic effects. This study was designed to investigate whether ATO could induce apoptosis of cardiac fibroblasts (CFs) that play very important roles in maintaining the structure integrity and function of the heart. Cardiac fibroblasts from guinea pigs administered with ATO (1mg/kgbw) were used to test the pro-apoptotic role of ATO in vivo. The current study demonstrated that ATO induced morphological characteristics of apoptosis and Caspase-3 activation in CFs of guinea pigs along with a significant up-regulation in TGF-β1 protein expression, Bax/Bcl-2 ratio and ERK1/2 phosphorylation. In vitro MTT assay showed that ATO remarkably reduced the viability of cultured cardiac fibroblasts (NRCFs) from neonatal rat in a concentration- and time-dependent manner. Consistent with the notions in vivo, ATO significantly induced the apoptosis in NRCFs, dramatically up-regulated TGF-β1 protein level and Bax/Bcl-2 ratio in a time-dependent fashion and activated Caspase-3 and ERK1/2. Finally, pretreatment with LY364947, an inhibitor of TGF-β signaling could apparently reverse these changes. We therefore conclude that TGF-β is functionally linked to ERK1/2 and that TGF-β signaling is responsible for ATO-induced CFs apoptosis, which provides a novel mechanism of ATO related cardiac toxicology.

The emerging role of C/EBPs in glucocorticoid signaling: lessons from the lung

Glucocorticoids (GCs) have been successfully used in the treatment of inflammatory diseases for decades. However, there is a relative GC resistance in several inflammatory lung disorders, such as chronic obstructive pulmonary disease (COPD), but still the mechanism(s) behind this unresponsiveness remains unknown. Interaction between transcription factors and the GC receptor contribute to GC effects but may also provide mechanisms explaining steroid resistance. CCAAT/enhancer-binding protein (C/EBP) transcription factors are important regulators of pulmonary gene expression and have been implicated in inflammatory lung diseases such as asthma, pulmonary fibrosis, cystic fibrosis, sarcoidosis, and COPD. In addition, several studies have indicated a role for C/EBPs in mediating GC effects. In this review, we discuss the different mechanisms of GC action as well as the function of the lung-enriched members of the C/EBP transcription factor family. We also summarize the current knowledge of the role of C/EBP transcription factors in mediating the effects of GCs, with emphasis on pulmonary effects, and their potential role in mediating GC resistance.

Apoptosis and the airway epithelium

The airway epithelium functions as a barrier and front line of host defense in the lung. Apoptosis or programmed cell death can be elicited in the epithelium as a response to viral infection, exposure to allergen or to environmental toxins, or to drugs. While apoptosis can be induced via activation of death receptors on the cell surface or by disruption of mitochondrial polarity, epithelial cells compared to inflammatory cells are more resistant to apoptotic stimuli. This paper focuses on the response of airway epithelium to apoptosis in the normal state, apoptosis as a potential regulator of the number and types of epithelial cells in the airway, and the contribution of epithelial cell apoptosis in important airways diseases.

TGFβ1 induces IL-6 and inhibits IL-8 release in human bronchial epithelial cells: the role of Smad2/3

Human bronchial epithelial (HBE) cells contribute to asthmatic airway inflammation by secreting cytokines, chemokines, and growth factors, including interleukin (IL)-6, IL-8 and transforming growth factor (TGF) β1, all of which are elevated in asthmatic airways. This study examines the signaling pathways leading to TGFβ1 induced IL-6 and IL-8 in primary HBE cells from asthmatic and non-asthmatic volunteers. HBE cells were stimulated with TGFβ1 in the presence or absence of signaling inhibitors. IL-6 and IL-8 protein and mRNA were measured by ELISA and real-time PCR respectively, and cell signaling kinases by Western blot. TGFβ1 increased IL-6, but inhibited IL-8 production in both asthmatic and non-asthmatic cells; however, TGF induced significantly more IL-6 in asthmatic cells. Inhibition of JNK MAP kinase partially reduced TGFβ1 induced IL-6 in both cell groups. TGFβ1 induced Smad2 phosphorylation, and blockade of Smad2/3 prevented both the TGFβ1 modulated IL-6 increase and the decrease in IL-8 production in asthmatic and non-asthmatic cells. Inhibition of Smad2/3 also increased basal IL-8 release in asthmatic cells but not in non-asthmatic cells. Using CHIP assays we demonstrated that activated Smad2 bound to the IL-6, but not the IL-8 promoter region. We conclude that the Smad2/3 pathway is the predominant TGFβ1 signaling pathway in HBE cells, and this is altered in asthmatic bronchial epithelial cells. Understanding the mechanism of aberrant pro-inflammatory cytokine production in asthmatic airways will allow the development of alternative ways to control airway inflammation.

Effects of budesonide on P38 MAPK activation, apoptosis and IL-8 secretion, induced by TNF-alpha and Haemophilus influenzae in human bronchial epithelial cells

Non-typeable Haemophilus influenzae (NTHi) is one of the most frequently involved pathogens in bacterial exacerbations of chronic obstructive pulmonary disease (COPD). In the airways, the main tissue target of NTHi is bronchial epithelium, where this pathogen can further amplify the inflammatory and structural changes induced by proinflammatory cytokines such as tumour necrosis factor-alpha (TNF-alpha). Therefore, the aim of this study is to investigate, in primary cultures of human bronchial epithelial cells, the effects of NTHi on signal transduction pathways, apoptotic events and chemokine production activated by TNF-alpha. Moreover, we also evaluated the effects exerted on such cellular and molecular phenomena by a corticosteroid drug. p38 mitogen-activated protein kinase (MAPK) phosphorylation was analyzed by Western blotting, using an anti-phospho-p38 MAPK monoclonal antibody. Apoptosis was assayed by active caspase-3 expression. Interleukin-8 (IL-8/CXCL8) was detected in cell-free culture supernatants by ELISA. TNF-alpha induced a significant increase in p38 MAPK phosphorylation. NTHi was able to potentiate the stimulatory actions of TNF-alpha on caspase-3 expression and, to a lesser extent, on IL-8 secretion. These effects were significantly (P less than 0.01) inhibited by a pharmacological pre-treatment with budesonide. These results suggest that TNF-alpha is able to stimulate, via activation of p38 MAPK signalling pathway, IL-8 release and airway epithelial cell apoptosis; the latter effect can be markedly potentiated by NTHi. Furthermore, budesonide can be very effective in preventing, through inhibition of p38 MAPK phosphorylation, both structural and proinflammatory changes elicited in bronchial epithelium by TNF-alpha and NTHi.

The role of Nox4 in oxidative stress-induced MUC5AC overexpression in human airway epithelial cells

Mucus hypersecretion is a prominent manifestation in patients with chronic inflammatory airway diseases, and MUC5AC is a major airway mucin. It is well known that reactive oxygen species (ROS) may be involved in the pathogenesis of various inflammatory airway diseases. The purpose of this study was to identify which secreted mucin genes are induced by exogenous hydrogen peroxide and the mechanism by which these genes are up-regulated in normal human nasal epithelial (NHNE) cells. Exogenous H(2)O(2) induced the ligand-independent activation of epidermal growth factor receptors (EGFR) and the subsequent activation of ERK1 mitogen-activated protein kinase, resulting in the induction of intracellular ROS generation. Through this signal pathway, exogenous H(2)O(2) markedly induced overexpression of the MUC5AC gene alone. In addition, Nox4, a subtype of nonphagocytic NADPH oxidase, was found to play a key role in intracellular ROS generation and exogenous H(2)O(2)-induced MUC5AC gene expression in NHNE cells.

Simvastatin attenuates release of neutrophilic and remodeling factors from primary bronchial epithelial cells derived from stable lung transplant recipients

Obliterative bronchiolitis (OB), the major cause of chronic lung allograft dysfunction, is characterized by airway neutrophilia, inflammation, and remodeling, with progressive fibroproliferation and obliteration of small airways that ultimately leads to patient death. Statins have potential anti-inflammatory effects and have been demonstrated to confer a survival advantage in lung transplant patients. We postulated that the beneficial effects of simvastatin in lung transplantation are in part due to inhibition of the epithelial production of key mediators of neutrophil chemotaxis, inflammation, and airway remodeling. Our objective was to assess the effect of simvastatin on a unique population of primary bronchial epithelial cells (PBECs) derived from stable lung allografts, with specific reference to airway neutrophilia and remodeling. PBEC cultures were stimulated with IL-17 or transforming growth factor (TGF)-β, with and without simvastatin. Supernatant levels of factors critical to driving airway neutrophilia and remodeling were measured. IL-17 upregulated IL-8, IL-6, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor (GM-CSF), and VEGF, whereas TGF-β increased IL-6, GM-CSF, matrix metalloproteinase (MMP)-2, and MMP-9. Simvastatin attenuated effects of both IL-17 and TGF-β. We have demonstrated the ability of simvastatin to attenuate release of airway neutrophilic and remodeling mediators and to inhibit their upregulation by TGF-β and IL-17. These data illustrate the potential of simvastatin to alleviate neutrophilic airway inflammation and remodeling in the transplanted lung and may have additional relevance to other neutrophilic airway conditions, such as chronic obstructive pulmonary disease.

Effect of inhalation of single dose of beclomethasone on airway epithelium

Inhaled corticosteroids are being recommended for the treatment of bronchial asthma for their anti-inflammatory properties and reduction of airway hyperreactivity. The first tissue coming to the contact with all inhaled substances is the airway epithelium. In this experiment, the immediate effect of a single MDI dose of beclomethasone on the ultrastructure of the tracheal and bronchiolar epithelium was studied. Due to the beclomethasone administration, the secretory elements were highly affected. The tracheal goblet cells were damaged, mucus release was significantly accelerated, and the mechanism of secretion was influenced. The bronchiolar Clara cells revealed signs of the pathological alteration. Their secretory granules were usually stored in the cytoplasm. Occasionally, degenerating Clara cells were found after the beclomethasone administration. The injury of ciliated cells in both locations was only mild and this fact was reflected in slight impairment of the tracheal ciliary border. As a morphological sign of impaired self-cleaning ability, inspissated secretion was discovered among cilia. According to this evaluation, the inhalation of the single dose of beclomethasone caused a moderate damage to the tracheal epithelium and a mild one to the epithelium of terminal bronchioles. The results draw attention to the adverse effects of otherwise therapeutically beneficial inhaled glucocorticosteroids.

Activation of extracellular signal-regulated kinase by TGF-beta1 via TbetaRII and Smad7 dependent mechanisms in human bronchial epithelial BEP2D cells

Transforming growth factor-beta1 (TGF-beta1) can activate mitogen-activated protein kinases (MAPKs) in many types of cells. The mechanism of this activation is not well elucidated. Here, we explore the role of TGF-beta/Smads signaling compounds in TGF-beta1-mediated activation of extracellular signal-regulated kinase (ERK) MAPK in human papillomavirus (HPV)-18 immortalized human bronchial epithelial cell line BEP2D and the role of TGF-beta1-induced phosphorylation of ERK in proliferation and apoptosis of BEP2D. The cell models of siRNA-mediated silencing of TGF-beta receptor type II (TbetaRII), Smad2, Smad3, Smad4, and Smad7 were employed in this study. Our results demonstrate that TGF-beta1 activates ERK in a time-dependent manner with a maximum effect at 60 min; overexpression of Smad7 increased this TGF-beta1-mediated phosphorylation of the ERK; and siRNA-mediated silencing of TbetaRII, Smad3, Smad4, and Smad7 abrogated this effect. Moreover, we observed that overexpression of Smad7 restored TGF-beta1-mediated ERK phosphorylation in Smad4 knockdown cells but not in TbetaRII knockdown cells. In BEP2D cells, TGF-beta1 treatment effectively inhibited cells' proliferation and induced their apoptosis. Pretreatment with U0126, an inhibitor of ERK1/2, significantly enhanced the TGF-beta1-mediated antiproliferative and apoptosis induction effects in BEP2D cells. These data revealed that TbetaRII and Smad7 play the critical roles in TGF-beta1-mediated activation of ERK; Smad3 and Smad4 can play an indirect role through up-regulating Smad7 expression; and TGF-beta1-induced phosphorylation of ERK may participate in BEP2D cell proliferation and apoptosis regulation.

Toluene diisocyanate (TDI) induces production of inflammatory cytokines and chemokines by bronchial epithelial cells via the epidermal growth factor receptor and p38 mitogen-activated protein kinase pathways

Toluene diisocyanate (TDI) is known as one of causes of occupational asthma and hypersensitivity pneumonitis. To investigate the stimulatory effect on bronchial epithelial cells in response to TDI, the authors examined production of cytokines by the bronchial epithelial cell line BEAS-2B and intercellular signal transduction stimulated by TDI-human serum albumin (HSA) conjugate. The production of interleukin (IL)-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), and regulated on activation normal T cell expressed and secreted (RANTES) from the bronchial epithelial cells were augmented by the TDI-HSA conjugate. Extracellular signal-regulated kinase (Erk) 1/2 and p38 mitogen-activated protein kinase (MAPK) were phosphorylated by the TDI-HSA conjugate. AG1478, SB203580, and dexamethasone prevented augmentation of these cytokine production. TDI-HSA conjugate did not augment release of epidermal growth factor (EGF) ligands from BEAS-2B. These results suggest that TDI directly induces production of proinflammatory cytokines and chemokines through p38 MAPK and EGF receptor (EGFR)-Erk pathway without an autocrine mechanism. Thus, TDI was shown to have a stimulatory effect on bronchial epithelial cells, suggesting the potent role of bronchial epithelial cells in TDI-induced asthma.

Effect of glucocorticoids on stem cell factor expression in human asthmatic bronchi

BACKGROUND

Stem cell factor (SCF) is a major mast cell growth factor promoting differentiation, chemotaxis as well as inhibition of apoptosis of mast cells. Regulation of SCF expression by glucocorticoids has not yet been reported in human asthmatic bronchi.

OBJECTIVE

To evaluate SCF mRNA and protein expression in biopsy specimen and bronchoalveolar lavage fluid, respectively, and to determine the mast cell numbers in biopsy sections from control and asthmatic subjects treated or not with glucocorticoids.

METHODS

Volunteers were recruited out of pollen season. Asthmatic patients were allergic to common allergen extracts including grass and tree pollen, cat, dog or mite; three volunteers had non-allergic asthma. Mast cell numbers were counted after anti-human tryptase immunolabelling. SCF mRNA was quantified by real-time fluorescent PCR (LightCycler) after reverse transcription, and SCF protein was measured by ELISA.

RESULTS

Asthmatic patients not treated with glucocorticoids showed a 5.8-, 1.8- and 3.1-fold significant increase in SCF mRNA, protein levels and mast cell numbers, respectively, compared with healthy volunteers of the control group (7.8 and 1.3 pg/mug SCF mRNA/GAPDH; 99.8+/-11.5 and 56.0+/-11.0 pg/mL SCF protein; 103+/-21 and 33+/-8 mast cells/mm(2), respectively; P<0.05). In asthmatic patients treated with glucocorticoids, a significant decrease of SCF mRNA, protein levels and mast cell numbers was observed as compared with untreated asthmatic patients (1.1 pg/microg mRNA; 62.0+/-10.3 pg/mL SCF protein and 39+/-13 mast cells/mm(2); P<0.05), reaching levels comparable to those of the control group.

CONCLUSION

Our study shows that SCF is expressed in the bronchus in humans in vivo. This expression is increased in asthma, and is parallel to the increased mast cell numbers in the airways. Both increases were normalized in glucocorticoid-treated patients, strongly suggesting an involvement of SCF in the mast cell-associated asthmatic disease.

Importance of p38 mitogen-activated protein kinase pathway in allergic airway remodelling and bronchial hyperresponsiveness

p38 mitogen-activated protein kinase (MAPK) plays an important role in the activation of inflammatory cells and in the proliferation of airway structural cells. We investigated the role of p38 MAPK by using a selective inhibitor of p38 alpha and beta isoforms, SD282, in a chronic model of 15 ovalbumin exposures in sensitised mice using two doses (30 and 90 mg/kg). Allergen exposure induced bronchial hyperresponsiveness to methacholine as measured by the concentration of methacholine needed to increase pulmonary resistance by 200% (PC200), eosinophilia in bronchoalveolar lavage fluid and increase in airway smooth muscle area and goblet cell hyperplasia. In addition, p38 MAPK activity as measured by phosphorylated p38 expression on Western blots was increased after allergen challenge, which was suppressed by SD282 at both doses. SD282 inhibited bronchial hyperresponsiveness, but had no effect on eosinophils in bronchoalveolar lavage fluid. It also reduced airway smooth muscle and goblet cell hyperplasia, but had no effect on serum immunoglobulin E. p38 MAPK is involved in the pathogenesis of bronchial hyperresponsiveness but not in eosinophilic inflammation or the allergic response; however, remodelling features such as airway smooth muscle or goblet cell hyperplasia are regulated through p38 MAPK. Furthermore, bronchial hyperresponsiveness induced by chronic allergen exposure may be related to the development of airway wall remodelling.

Budesonide effects on Clara cell under normal and allergic inflammatory condition

Clara cells are nonciliated secretory cells implicated in lung homeostasis by the synthesis of immunomodulatory and host defense products, being one of the most important the CC16 protein. In this study, we compared the effects of budesonide (BUD), an inhaled corticoid, on Clara cell biology and its ability to reverse morphofunctional changes induced in an allergic airway hyper-responsiveness mouse model. In normal mice, exposure to BUD induced morphological changes compatible with a state of maximal differentiation on CC16 positive cells which developed a prominent cupola filled up with numerous mitochondria rich in CYP2E1, a member of the cytochrome P450 family. Consequently, CYP2E1 expression raised significantly. Exposure to OVA provoked hypertrophy of Clara cells and an increment in their number per millimeter of basal membrane. These cells acquired a mucous cell phenotype characterized by a notorious expansion of the secretory granular content. Synthesis of CC16 was greatly up-regulated concurrent to the finding of MUC5AC expression and the increment of epidermal growth factor receptor (EGFR). Mitochondrial content decreased significantly with a consequent reduction in CYP2E1 expression. After BUD treatment of OVA-challenged animals, the majority of Clara cells regained their normal morphology and functional characteristics; CYP2E1 levels raised when compared to the OVA exposed group. The BUD potential to differentiate Clara cells appeared to be important for the regression of the profound changes generated by the allergic injury. These results demonstrated the wide range of stimuli that can modify different aspects of Clara cell biology, and highlighted the effects of budesonide as a modulator of P450 enzymes, which probably contributes to a complementary antiinflamatory activity.

Roles of apoptosis in airway epithelia

The airway epithelium functions primarily as a barrier to foreign particles and as a modulator of inflammation. Apoptosis is induced in airway epithelial cells (AECs) by viral and bacterial infections, destruction of the cytoskeleton, or by exposure to toxins such as high oxygen and polycyclic hydrocarbons. Various growth factors and cytokines including TGF-beta, IFN-gamma, or the activators of the death receptors, TNF-alpha and FasL, also induce apoptosis in AECs. However, cell death is observed in maximally 15% of AECs after 24 h of treatment. Preincubation with IFN-gamma or a zinc deficiency increases the percentage of apoptotic AECs in response to TNF-alpha or FasL, suggesting that AECs have mechanisms to protect them from cell death. Apoptosis of AECs is a major mechanism in reducing cell numbers after hyperplastic changes in airway epithelia that may arise due to major injuries in response to LPS or allergen exposures. Resolution of hyperplastic changes or changes during prolonged exposure to an allergen is primarily regulated by the Bcl-2 family of proteins. Fas and FasL are both expressed in AECs, and their main function may be to control inflammation by inducing Fas-induced death in inflammatory cells without inducing apoptosis in neighboring cells. Furthermore, AECs engulf dying eosinophils to clear them by phagocytosis. Therefore, in the airway epithelium apoptosis serves three main roles: (1) to eliminate damaged cells; (2) to restore homeostasis following hyperplastic changes; and (3) to control inflammation, and thereby support the barrier and anti-inflammatory functions.

Effects of TGF-β and glucocorticoids on map kinase phosphorylation, IL-6/IL-11 secretion and cell proliferation in primary cultures of human lung fibroblasts

Transforming growth factor-beta1 (TGF-beta1) is crucially involved in the fibrotic events characterizing interstitial lung diseases (ILDs), as well as in the airway remodeling process typical of asthma. Within such a context, the aim of our study was to investigate, in primary cultures of normal and fibrotic human lung fibroblasts (HLFs), the effects of TGF-beta1 on mitogen-activated protein kinase (MAPK) phosphorylation, cell proliferation, and production of interleukins 6 (IL-6) and 11 (IL-11), in the presence or absence of a pretreatment with budesonide (BUD). MAPK phosphorylation was detected by Western blotting, cell viability and proliferation were evaluated using Trypan blue staining and [(3)H]-thymidine incorporation assay, respectively, and the release of IL-6 and IL-11 into cell culture supernatants was assessed by ELISA. TGF-beta1 (10 ng/ml) significantly stimulated MAPK phosphorylation (P < 0.01), and also enhanced cell proliferation as well as the secretion of both IL-6 and IL-11, which reached the highest increases at the 72nd h of cell exposure to this growth factor. All such effects were prevented by BUD (10(-8) M) and, with the exception of IL-6 release, also by a mixture of MAPK inhibitors. Therefore, our findings suggest that the fibrotic action exerted by TGF-beta1 in the lung is mediated at least in part by MAPK activation and by an increased synthesis of the profibrogenic cytokines IL-6 and IL-11; all these effects appear to be prevented by corticosteroids via inhibition of MAPK phosphorylation.

Biological targets for therapeutic interventions in COPD: clinical potential

COPD is a widespread inflammatory respiratory disorder characterized by a progressive, poorly reversible airflow limitation. Currently available therapies are mostly based on those used to treat asthma. However, such compounds are not able to effectively reduce the gradual functional deterioration, as well as the ongoing airway and lung inflammation occurring in COPD patients. Therefore, there is an urgent need to improve the efficacy of the existing drug classes and to develop new treatments, targeting the main cellular and molecular mechanisms underlying disease pathogenesis. These therapeutic strategies will be highlighted in the present review.

Zinc modulates airway epithelium susceptibility to death receptor-mediated apoptosis

The accelerated loss of lung epithelium through activation of extrinsic apoptosis is believed to play a causative role in lung pathogenesis. Previous investigations have shown that zinc is required to sustain lung epithelial cell viability under stress conditions and that depletion of intracellular zinc predisposes cells to apoptosis. In this investigation, we determined whether intracellular zinc deficiency enhanced the susceptibility of primary, differentiated cultures of human lung epithelium to death receptor-mediated apoptosis, leading to barrier dysfunction. Cultures obtained from multiple donors were exposed to stimuli that provoke death receptor-mediated apoptosis and depleted of intracellular zinc with a zinc-specific chelating agent. Transepithelial resistance, paracellular transport, caspase-8 and caspase-3 activity, and apoptosis were measured. Activation of extrinsic apoptosis or zinc chelation alone resulted in a nominal increase in caspase function and apoptosis without major evidence of barrier disruption. Activation of extrinsic apoptosis in addition to zinc depletion resulted in an abrupt decrease in transepithelial resistance, a substantial increase in apoptosis, and an increased paracellular leak. Cultures were rescued by supplementation with zinc sulfate. Further analysis revealed that exogenous zinc facilitates cell survival through activation of the phosphatidylinositol 3-kinase/Akt signaling pathway. We conclude that intracellular zinc is a vital factor in lung epithelium that protects cells from death receptor-mediated apoptosis and barrier dysfunction.

Respiratory infections and asthma

Respiratory tract infections caused by both viruses and/or atypical bacteria are involved in the pathogenesis of asthma. In particular, several viruses such as respiratory syncytial virus, rhinovirus and influenza/parainfluenza viruses may favour the expression of the asthmatic phenotype, being also implicated in the induction of disease exacerbations. Within this pathological context, a significant role can also be played by airway bacterial colonizations and infections due to Chlamydiae and Mycoplasms. All these microbial agents probably interfere with complex immunological pathways, thus contributing to induce and exacerbate asthma in genetically predisposed individuals.

Stimulus-dependent glucocorticoid-resistance of GM-CSF production in human cultured airway smooth muscle

For a subpopulation of asthmatics, symptoms persist even with high doses of glucocorticoids. Glucocorticoids reduce the levels of the proinflammatory and fibrogenic cytokine, granulocyte-macrophage colony-stimulating factor (GM-CSF) produced by human cultured airway smooth muscle (ASM). We have contrasted the effects of a synthetic glucocorticoid, dexamethasone, on thrombin- and IL-1alpha-stimulated GM-CSF production in human ASM cells. Although IL-1alpha stimulated three-fold higher levels of GM-CSF mRNA and protein compared to thrombin, dexamethasone concentration-dependently reduced IL-1alpha-stimulated GM-CSF more potently and to a greater extent than the response to thrombin. This pattern of glucocorticoid regulation was also observed at the GM-CSF mRNA level and was reproduced with other glucocorticoids such as fluticasone propionate. IL-1alpha and thrombin stimulated NF-kappa B-dependent luciferase expression equally. Dexamethasone treatment reduced luciferase expression stimulated by both IL-1alpha and thrombin. The GM-CSF mRNA half life was markedly prolonged by IL-1alpha compared to thrombin. This IL-1alpha-induced GM-CSF mRNA stability was prevented by either dexamethasone or the p38(MAPK) inhibitor, SB203580, neither of which influenced GM-CSF mRNA stability in thrombin-treated cells. Dexamethasone inhibited p38(MAPK) phosphorylation in IL-1alpha-stimulated ASM, whereas thrombin does not stimulate p38(MAPK) phosphorylation. These data suggest that the mechanism underlying the greater potency and efficacy of glucocorticoids in reducing GM-CSF synthesis stimulated by IL-1alpha depends on inhibition of the involvement of p38(MAPK)-induced increases in GM-CSF message stability.

Airway wall remodelling: the influence of corticosteroids

PURPOSE OF THE REVIEW

We have attempted to bring together recent findings, mainly from airway endobronchial biopsies, on the structural changes that constitute 'remodelling' in airway disease, with a particular focus on asthma. We have tried to put this into the context of classic studies on the asthma pathological phenotype. Having described these basic changes, we have then given an update on recent studies investigating the effects of corticosteroid medication on the different manifestations of remodelled airways.

RECENT FINDINGS

The effects of corticosteroid on airway remodelling seem to vary a great deal; some aspects are steroid responsive while others are not, or less so. It is likely that different manifestations of remodelling require different doses and timescales for treatment to be effective.

SUMMARY

Further longitudinal interventional studies are required, with multiple airway sampling times, to fully elucidate the full potential for corticosteroids to benefit remodelling of the airways in chronic inflammatory diseases. There needs to be more attention to pathophysiological and clinical correlations in such studies. It is likely that even when used optimally corticosteroids will have limited efficacy overall in this aspect of asthma pathogenesis. The search is on for newer and better treatments.

Mitogen-activated protein kinases and asthma

Mitogen-activated protein kinases (MAPKs) are evolutionary conserved enzymes which play a key role in signal transduction mediated by cytokines, growth factors, neurotransmitters and various types of environmental stresses. In the airways, these extracellular stimuli elicit complex inflammatory and structural changes leading to the typical features of asthma including T cell activation, eosinophil and mast cell infiltration, as well as bronchial hyperresponsiveness and airway remodelling. Because MAPKs represent an important point of convergence for several different signalling pathways, they affect multiple aspects of normal airway function and also significantly contribute to asthma pathophysiology. Therefore, this review focuses on the crucial involvement of MAPKs in asthma pathogenesis, thus also discussing their emerging role as molecular targets for anti-asthma drugs.

Potential genetic influences on the response to asthma treatment

Genetic factors play a key role in determining the widely heterogeneous response to pharmacological treatment detectable among asthmatics. In particular, polymorphisms of the genes encoding relevant anti-asthma drug targets contribute significantly to such a variability. Therefore, it is very important to characterize asthmatic patient's genotypes and the related phenotypic patterns, in order to predict the individual therapeutic outcome. This pharmacogenetic approach will eventually help clinicians to optimize and personalize anti-asthma treatment, and will also provide useful information with regard to pre- and post-marketing evaluation of both effectiveness and side effects of newly introduced drugs.

Transforming growth factor-beta2 induces bronchial epithelial mucin expression in asthma

The transforming growth factor (TGF)-beta family is important for tissue repair in pathological conditions including asthma. However, little is known about the impact of either TGF-beta1 or TGF-beta2 on asthmatic airway epithelial mucin expression. We evaluated bronchial epithelial TGF-beta1 and TGF-beta2 expression and their effects on mucin expression, and the role of TGF-beta1 or TGF-beta2 in interleukin (IL)-13-induced mucin expression. Epithelial TGF-beta1, TGF-beta2, and mucin expression were evaluated in endobronchial biopsies from asthmatics and normal subjects. The effects of TGF-beta1 or TGF-beta2 on mucin MUC5AC protein and mRNA expression, and the impact of IL-13 on epithelial TGF-beta1, TGF-beta2, and MUC5AC were determined in cultured bronchial epithelial cells from endobronchial brushings of both subject groups. In biopsy tissue, epithelial TGF-beta2 expression levels were higher than TGF-beta1 in both asthmatics and normals. TGF-beta2, but not TGF-beta1, was increased in asthmatics compared with normals, and significantly correlated with mucin expression. TGF-beta2, but not TGF-beta1, increased mucin expression in cultured epithelial cells from both subject groups. IL-13 increased the release of TGF-beta2, but not TGF-beta1, from epithelial cells. A neutralizing TGF-beta2 antibody partially inhibited IL-13-induced mucin expression. These data suggest that TGF-beta2 production by asthmatic bronchial epithelial cells may increase airway mucin expression. IL-13-induced mucin expression may occur in part through TGF-beta2 up-regulation.

Soluble tumor necrosis factor (TNF) receptor-1 induces apoptosis via reverse TNF signaling and autocrine transforming growth factor-beta1

The pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) plays a central role in inflammatory disorders. Transmembrane TNF-alpha and its two receptors are cleaved by the proteinase TNF-alpha converting enzyme (TACE), resulting in appreciable serum levels of soluble TNF-alpha and soluble TNF-alpha receptors (sTNFR1 and -2). The only known functions of sTNFR1 are to antagonize and buffer circulating TNF-alpha. Here, we present evidence that sTNFR1 exerts immunoregulatory functions by induction of apoptosis in monocytes through reverse signaling via transmembrane TNF-alpha. sTNFR1-induced apoptosis is independent of death receptor pathways but depends on autocrine transforming growth factor (TGF)-beta1 signaling through the mitogen-activated protein kinase p38alpha. This novel mechanism has implications for understanding the physiological role of sTNFR1 and for TNF-alpha-blocking therapies of autoimmune diseases.

Early growth response gene 1-mediated apoptosis is essential for transforming growth factor beta1-induced pulmonary fibrosis

Fibrosis and apoptosis are juxtaposed in pulmonary disorders such as asthma and the interstitial diseases, and transforming growth factor (TGF)-β₁ has been implicated in the pathogenesis of these responses. However, the in vivo effector functions of TGF-β₁ in the lung and its roles in the pathogenesis of these responses are not completely understood. In addition, the relationships between apoptosis and other TGF-β₁–induced responses have not been defined. To address these issues, we targeted bioactive TGF-β₁ to the murine lung using a novel externally regulatable, triple transgenic system. TGF-β₁ produced a transient wave of epithelial apoptosis that was followed by mononuclear-rich inflammation, tissue fibrosis, myofibroblast and myocyte hyperplasia, and septal rupture with honeycombing. Studies of these mice highlighted the reversibility of this fibrotic response. They also demonstrated that a null mutation of early growth response gene (Egr)-1 or caspase inhibition blocked TGF-β₁–induced apoptosis. Interestingly, both interventions markedly ameliorated TGF-β₁–induced fibrosis and alveolar remodeling. These studies illustrate the complex effects of TGF-β₁ in vivo and define the critical role of Egr-1 in the TGF-β₁ phenotype. They also demonstrate that Egr-1–mediated apoptosis is a prerequisite for TGF-β₁–induced fibrosis and remodeling.

Effects of hydrogen peroxide on MAPK activation, IL-8 production and cell viability in primary cultures of human bronchial epithelial cells

The airway epithelium is continuously exposed to inhaled oxidants, including airborne pollutants and cigarette smoke, which can exert harmful proinflammatory and cytotoxic effects. Therefore, the aim of our study was to investigate, in primary cultures of human bronchial epithelial cells (HBEC), the signal transduction pathways activated by increasing concentrations (0.25, 0.5, and 1 mM) of hydrogen peroxide (H(2)O(2)), as well as their effects on IL-8 production and cell viability. The reported results show that H(2)O(2) elicited, in a concentration-dependent fashion, a remarkable increase in phosphorylation-dependent activation of mitogen-activated protein kinases (MAPKs), associated with a significant induction of IL-8 synthesis and a dramatically enhanced cell death. Pre-treatment of HBEC with MAPK inhibitors was able to significantly inhibit the effects of H(2)O(2) on IL-8 secretion, and to effectively prevent cell death. Therefore, these findings suggest that MAPKs play a key role as molecular transducers of the airway epithelial injury triggered by oxidative stress, as well as potential pharmacologic targets for indirect antioxidant intervention.

Smad and p38-MAPK signaling mediates apoptotic effects of transforming growth factor-beta1 in human airway epithelial cells

Transforming growth factor-beta1 (TGF-beta1) belongs to a family of multifunctional cytokines that regulate a variety of biological processes, including cell differentiation, proliferation, and apoptosis. The effects of TGF-beta1 are cell context and cell cycle specific and may be signaled through several pathways. We examined the effect of TGF-beta1 on apoptosis of primary human central airway epithelial cells and cell lines. TGF-beta1 protected human airway epithelial cells from apoptosis induced by either activation of the Fas death receptor (CD95) or by corticosteroids. This protective effect was blocked by inhibition of the Smad pathway via overexpression of inhibitory Smad7. The protective effect is associated with an increase in the cyclin-dependent kinase inhibitor p21 and was blocked by the overexpression of key gatekeeper cyclins for the G1/S interface, cyclins D1 and E. Blockade of the Smad pathway by overexpression of the inhibitory Smad7 permitted demonstration of a TGF-beta-mediated proapoptotic pathway. This proapoptotic effect was blocked by inhibition of the p38 MAPK kinase signaling with the inhibitor SB-203580 and was associated with an increase in p38 activity as measured by a kinase assay. Here we demonstrate dual signaling pathways involving TGF-beta1, an antiapoptotic pathway mediated by the Smad pathway involving p21, and an apoptosis-permissive pathway mediated in part by p38 MAPK.

Constitutive activation of MAPK cascade in acute quadriplegic myopathy

Acute quadriplegic myopathy (AQM; also called "critical illness myopathy") shows acute muscle wasting and weakness and is experienced by some patients with severe systemic illness, often associated with administration of corticosteroids and/or neuroblocking agents. Key aspects of AQM include muscle atrophy and myofilament loss. Although these features are shared with neurogenic atrophy, myogenic atrophy in AQM appears mechanistically distinct from neurogenic atrophy. Using muscle biopsies from AQM, neurogenic atrophy, and normal controls, we show that both myogenic and neurogenic atrophy share induction of myofiber-specific ubiquitin/proteosome pathways (eg, atrogin-1). However, AQM patient muscle showed a specific strong induction of transforming growth factor (TGF)-beta/MAPK pathways. Atrophic AQM myofibers showed coexpression of TGF-beta receptors, p38 MAPK, c-jun, and c-myc, including phosphorylated active forms, and these same fibers showed apoptotic features. Our data suggest a model of AQM pathogenesis in which stress stimuli (sepsis, corticosteroids, pH imbalance, osmotic imbalance) converge on the TGF-beta pathway in myofibers. The acute stimulation of the TGF-beta/MAPK pathway, coupled with the inactivity-induced atrogin-1/proteosome pathway, leads to the acute muscle loss seen in AQM patients.