Effects of topical corticosteroids on inflammatory mediator-induced eicosanoid release by human airway epithelial cells

CC16-TNF-α negative feedback loop formed between Clara cells and normal airway epithelial cells protects against diesel exhaust particles exposure-induced inflammation

CC16 is almost exclusively expressed in non-ciliated epithelial Clara cells, and widely used as a Clara cell marker. Diesel exhaust particles (DEPs), the fine particulate matters produced by diesel engines, cause or exacerbate airway-related diseases. Our previous study documented that DEP inhibits the CC16 expression in the immortalized mouse Clara cell line through methylation of C/EBPα promoter. However, the molecular mechanism by which DEP regulates CC16 secretion is unclear. Here, we isolated CC16 containing Clara cells (CC16⁺) from human distal lung, and found that DEP inhibited CC16 secretion from CC16⁺ cells via methylation of C/EBPα and inhibition of Munc18b transcription. CC16⁺ cell conditioned media containing different concentrations of CC16 was prepared and used for culture of airway epithelial cells BEAS-2B with no expression of CC16. A positive correlation was observed between CC16 level and DEP-induced autophagy activity, and a negative correlation between CC16 level and DEP-induced pro-inflammatory cytokine TNF-α, IL-6, and IL-8 level, suggesting that CC16 might mitigate DEP-induced inflammation via promoting autophagy in BEAS-2B cells. This result was further confirmed by adding recombinant CC16 to BEAS-2B cells exposed to DEP. Moreover, CC16 level was significantly increased when CC16⁺ cells were cultured in BEAS-2B cell conditioned medium containing TNF-α or the normal medium supplemented with recombinant TNF-α, suggesting that TNF-α induced CC16 production and secretion from CC16⁺ cells. Collectively, these data point that CC16 and TNF-α form a negative feedback loop, and this negative feedback loop between Clara cells and normal airway epithelial cells protects against DEP exposure-induced inflammation.

Molecular Mechanisms of Lipid Metabolism Disorders in Infectious Exacerbations of Chronic Obstructive Pulmonary Disease

Exacerbations largely determine the character of the progression and prognosis of chronic obstructive pulmonary disease (COPD). Exacerbations are connected with changes in the microbiological landscape in the bronchi due to a violation of their immune homeostasis. Many metabolic and immune processes involved in COPD progression are associated with bacterial colonization of the bronchi. The objective of this review is the analysis of the molecular mechanisms of lipid metabolism and immune response disorders in the lungs in COPD exacerbations. The complex role of lipid metabolism disorders in the pathogenesis of some infections is only beginning to be understood, however, there are already fewer and fewer doubts even now about its significance both in the pathogenesis of infectious exacerbations of COPD and in general in the progression of the disease. It is shown that the lipid rafts of the plasma membranes of cells are involved in many processes related to the detection of pathogens, signal transduction, the penetration of pathogens into the cell. Smoking disrupts the normally proceeded processes of lipid metabolism in the lungs, which is a part of the COPD pathogenesis.

Non-steroidal anti-inflammatory drugs, prostaglandins, and COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of the novel coronavirus disease 2019 (COVID-19), a highly pathogenic and sometimes fatal respiratory disease responsible for the current 2020 global pandemic. Presently, there remains no effective vaccine or efficient treatment strategies against COVID-19. Non-steroidal anti-inflammatory drugs (NSAIDs) are medicines very widely used to alleviate fever, pain, and inflammation (common symptoms of COVID-19 patients) through effectively blocking production of prostaglandins (PGs) via inhibition of cyclooxyganase enzymes. PGs can exert either proinflammatory or anti-inflammatory effects depending on the inflammatory scenario. In this review, we survey the potential roles that NSAIDs and PGs may play during SARS-CoV-2 infection and the development and progression of COVID-19. LINKED ARTICLES: This article is part of a themed issue on The Pharmacology of COVID-19. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.21/issuetoc.

Anti-Inflammatory and Barrier-Stabilising Effects of Myrrh, Coffee Charcoal and Chamomile Flower Extract in a Co-Culture Cell Model of the Intestinal Mucosa

Recent clinical evidence suggests the efficacy of a traditional herbal medicinal product containing myrrh (Commiphora molmol Engl.), coffee charcoal (Coffea arabica L.) and chamomile flower dry extract (Matricaria chamomilla L.) in the therapy of inflammatory bowel diseases (IBD). However, the mechanisms of action in this context have not been entirely elucidated. The present study aimed to evaluate the effects of myrrh, coffee charcoal and chamomile flower extract on the inflammatory cross talk between immune and intestinal epithelial cells together with the resulting intestinal barrier disorders. A complex co-culture cell model consisting of intestinal epithelial cell (IEC) monolayers (Caco-2, HT29-MTX-E12) and macrophages (THP-1) was established for the simultaneous investigation of these two IBD characteristics. The lipopolysaccharide (LPS) activation of the macrophages led to a pro-inflammatory mediator release and thereby an inflammatory stimulation of IECs with chemokine release and reduced barrier function. The effects of the individual plant extracts and a ternary combination on inflammatory mediator release (IL-6, TNF, IL-8, MCP-1, PGE2) was quantified by ELISA. The transepithelial electrical resistance (TEER) of IEC monolayers was measured to evaluate the effects on the barrier function. Budesonide served as a positive control. All three plant extracts exhibited anti-inflammatory properties via the inhibition of the inflammatory mediator release to a varying extent. An intestinal barrier stabilising effect was observed for myrrh and coffee charcoal. Myrrh exerted the most distinct pharmacological activity. Dose reducing and synergistic interactions emerged within the threefold combination. Thus, our results provide a mechanistic basis for the use of the herbal combination of myrrh, coffee charcoal and chamomile flower extract in IBD treatment and underline the potential benefits of the phytotherapeutic multi-component/multi-target approach in this complex pathogenesis.

Liquiritin apioside attenuates laryngeal chemoreflex but not mechanoreflex in rat pups

Liquiritin apioside (LA), a main flavonoid component of licorice, reportedly suppresses cough responses to inhalation of aerosolized capsaicin [CAP; a stimulant to transient receptor potential vanilloid 1 (TRPV1)] in conscious guinea pigs via acting on peripheral nerves. However, the evidence of LA having a direct effect on airway sensory fibers is lacking. Considering the important role laryngeal chemoreceptors and mechanoreceptors play in triggering apnea and cough, we studied whether LA suppressed the apneic responses to stimulation of these receptors via directly acting on the superior laryngeal nerve (SLN). Intralaryngeal delivery of chemical [CAP, HCl, and distilled water (DW)] and mechanical [an air-pulse (AP)] stimulations was applied in anesthetized rat pups to evoke the apnea. These stimuli were repeated after intralaryngeal LA treatment or peri-SLN LA treatment to determine the direct effect of LA on the SLN. Our results showed that all stimuli triggered an immediate apnea. Intralaryngeal LA treatment significantly attenuated the apneic response to chemical but not mechanical stimulations. The same attenuation was observed after peri-SLN LA treatment. Owing that TRPV1 receptors of laryngeal C fibers are responsible for the CAP-triggered apneas, the LA impact on the activity of laryngeal C neurons retrogradely traced by DiI was subsequently studied using a patch-clamp approach. LA pretreatment significantly altered the electrophysiological kinetics of CAP-induced currents in laryngeal C neurons by reducing their amplitudes, increasing the rise times, and prolonging the decay times. In conclusion, our results, for the first time, reveal that LA suppresses the laryngeal chemoreceptor-mediated apnea by directly acting on the SLN (TRPV1 receptors of laryngeal C fibers).

Synergistic Effect of H1-Antihistamines on Topical Corticosteroids for Pruritus in Atopic Dermatitis: A Systematic Review and Meta-Analysis

Background

Although oral antihistamines (H1-histamine receptor antagonists) are the main treatment option for pruritus in general skin dermatosis, their effect in treating pruritus of atopic dermatitis (AD) has not yet been established.

Objective

We conducted a systematic review and meta-analysis to evaluate the effectiveness of combined therapy of H1-antihistamines and topical steroids.

Methods

We systematically searched MEDLINE, Embase, and CENTRAL databases for articles published from 1967 to 2015. We identified 1,206 studies and assessed their titles, abstract, and full-text. Random effects meta-analysis was used to calculate mean differences (MD) with 95% confidence intervals (CI).

Results

Two studies satisfying the inclusion criteria of antihistamine therapy with mandatory topical steroid use were selected. Comparing antihistamine monotherapy with combination therapy, patients treated with the addition of antihistamine to topical corticosteroids showed a statistically significant clinical improvement (standard MD, −0.24; 95% CI, −0.42 to −0.05; p=0.01).

Conclusion

H1-antihistamines may have a synergistic effect when combined with topical steroids by influencing various associative factors of chronic pruritus in AD.

Prostaglandins in asthma and allergic diseases

Prostaglandins are synthesized through the metabolism of arachidonic acid via the cyclooxygenase pathway. There are five primary prostaglandins, PGD₂, PGE₂, PGF₂, PGI₂, and thromboxane B₂, that all signal through distinct seven transmembrane, G-protein coupled receptors. The receptors through which the prostaglandins signal determines their immunologic or physiologic effects. For instance, the same prostaglandin may have opposing properties, dependent upon the signaling pathways activated. In this article, we will detail how inhibition of cyclooxygenase metabolism and regulation of prostaglandin signaling regulates allergic airway inflammation and asthma physiology. Possible prostaglandin therapeutic targets for allergic lung inflammation and asthma will also be reviewed, as informed by human studies, basic science, and animal models.

Pharmacodynamic and pharmacokinetic considerations in choosing an inhaled corticosteroid

Inhaled corticosteroids are effective in controlling airway inflammation. Their anti-inflammatory effect is primarily topical, at the site of deposition in the airways. Consequently, traditional pharmacodynamic and pharmacokinetic concepts, which rely on measuring blood concentrations of drug, have limited applicability for evaluating the efficacy of topically acting inhaled corticosteroids. Important factors affecting efficacy of inhaled corticosteroids are: (i) intrinsic properties of the drugs, particularly their affinity for the corticosteroid receptor; and (ii) the newer pharmacodynamic concept of deposition characteristics of the drug formulation. Small particle formulations, especially those developed in the metered-dose inhaler with the new hydrofluoroalkane propellant, deposit to a much greater extent in the lung and may consequently have improved clinical efficacy. Lipid conjugation of inhaled corticosteroids within the lung may allow prolonged duration of effect, enabling once-daily administration. Pharmacodynamic and pharmacokinetic principles probably do not play a role in describing upper airway adverse effects occurring with inhaled corticosteroids. These are probably also determined by intrinsic properties of the drug and deposition characteristics. However, pharmacodynamic and pharmacokinetic principles seem to be important in addressing systemic safety concerns with inhaled corticosteroids. Those inhaled corticosteroids with a longer serum half-life, especially if they have higher affinity for the corticosteroid receptor, may be associated with greater systemic effects. A new pharmacokinetic concept suggests that increased protein binding within the systemic circulation and high systemic clearance of an inhaled corticosteroid may reduce the risk for systemic effects. These new pharmacodynamic and pharmacokinetic concepts provide a useful framework for identifying the characteristics of an inhaled corticosteroid with an improved benefit-to-risk profile. Increased lung deposition and reduced deposition in the upper airway should result in an inhaled corticosteroid with favorable clinical efficacy and a decreased risk for topical upper airway adverse effects. An inhaled corticosteroid with high plasma protein binding and rapid clearance might pose much less risk for systemic adverse effects than currently available drugs in this class.

Anti-inflammatory and membrane-stabilizing properties of two semisynthetic derivatives of oleanolic acid

Acetylation and methylation semisynthesis of oleanolic acid (OA) isolated from Syzygium aromaticum L. yielded two compounds: 3-acetoxyoleanolic acid (3-AOA) and 3-acetoxy, 28-methylester oleanolic acid (3-A,28-MOA). Anti-inflammatory properties of these compounds were assessed using the serotonin and fresh egg albumin-induced inflammatory test models in male Wistar rats weighing 250-300 g. Furthermore, erythrocyte membrane-stabilizing property of these compounds was evaluated in the heat- and hypotonicity-induced in vitro hemolysis test models. The two semisynthetic compounds significantly (p < 0.05) inhibited albumin-induced inflammation better than OA and indomethacin from 1-5 h post administration. Both compounds were membrane stabilizing in heat-induced hemolysis test while only 3-AOA showed membrane-stabilizing effects in a hypotonic milieu. Semisynthesis of OA yielded two compounds which had better in vivo anti-inflammatory and in vitro membrane-stabilizing properties.

Therapeutic effects of topical netrin-4 in a corneal acute inflammatory model

AIM

To evaluate the therapeutic effect of netrin-4 on the early acute phase of inflammation in the alkali-burned eye.

METHODS

Eye drops containing netrin-4 or phosphate buffered saline (PBS) were administered to a alkali-burn-induced corneal acute inflammatory model four times daily. The clinical evaluations, including fluorescein staining and inflammatory index, were performed on day 1, 4 and 7 using slit lamp microscopy. Global specimens were collected on day 7 and processed for immunofluorescent staining. The levels of inflammatory mediators in the corneas were determined by real-time polymerase chain reaction (PCR).

RESULTS

Exogenous netrin-4 administered on rat ocular surfaces showed more improvements in decreasing fluorescein staining on day 4 and 7, and resolved alkali burn-induced corneal inflammation index on day 7 (P<0.01). The levels of IL-1β, IL-6, intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), monocyte chemotactic protein-1 (MCP-1) and macrophage inflammatory protein-1 (MIP-1) in corneas were decreased in netrin-4-treated groups (P<0.05). In addition, netrin-4 significantly reduced the expression of leukocyte common antigen 45 (CD45) in the alkali-burn cornea (P<0.001).

CONCLUSION

Topical netrin-4 accelerated wound healing and reduced the inflammation on alkali-burn rat model, suggesting a potential as an anti-inflammatory agent in the clinical to treat the acute inflammation.

The role of prostaglandins in allergic lung inflammation and asthma

Prostaglandins (PGs) are products of the COX pathway of arachidonic acid metabolism. There are five primary PGs, PGD₂, PGE₂, PGF₂, PGI₂ and thromboxane A₂, all of which signal through distinct seven transmembrane, G-protein coupled receptors. Some PGs may counteract the actions of others, or even the same PG may have opposing physiologic or immunologic effects, depending on the specific receptor through which it signals. In this review, we examine the effects of COX activity and the various PGs on allergic airway inflammation and physiology that is associated with asthma. We also highlight the potential therapeutic benefit of targeting PGs in allergic lung inflammation and asthma based on basic science, animal model and human studies.

Managing Sjögren's Syndrome and non-Sjögren Syndrome dry eye with anti-inflammatory therapy

Dry eye from Sjögren’s syndrome is a multifactorial disease that results in dysfunction of the lacrimal functional unit. Studies have shown changes in tear composition, including inflammatory cytokines, chemokines, and metalloproteinase. T-lymphocytes have been shown to increase in the conjunctiva and lacrimal glands in patient and animal models. This inflammation is in part responsible for the pathogenesis of the disease, which results in symptoms of eye irritation, ocular surface epithelial disease, and loss of corneal barrier function. There are a number of anti-inflammatory approaches for treating this disease. The current study reviews details of immune response and anti–inflammatory therapies used to control this disease.

Dry eye disease: A review of diagnostic approaches and treatments

Dry eye (DE) is a common ocular disease that results in eye discomfort, visual disturbance and substantially affects the quality of life. It has a multifactorial etiology involving tear film instability, increased osmolarity of the tear film and inflammation of the ocular surface with potential damage to the ocular surface. This review discusses the classification, diagnostic approaches and treatments of DE.

Dry eye disease: an immune-mediated ocular surface disorder

Dry eye disease is a multifactorial disorder of the tears and ocular surface characterized by symptoms of dryness and irritation. Although the pathogenesis of dry eye disease is not fully understood, it is recognized that inflammation has a prominent role in the development and propagation of this debilitating condition. Factors that adversely affect tear film stability and osmolarity can induce ocular surface damage and initiate an inflammatory cascade that generates innate and adaptive immune responses. These immunoinflammatory responses lead to further ocular surface damage and the development of a self-perpetuating inflammatory cycle. Herein, we review the fundamental links between inflammation and dry eye disease and discuss the clinical implications of inflammation in disease management.

Selective prostacyclin receptor agonism augments glucocorticoid-induced gene expression in human bronchial epithelial cells

Prostacyclin receptor (IP-receptor) agonists display anti-inflammatory and antiviral activity in cell-based assays and in preclinical models of asthma and chronic obstructive pulmonary disease. In this study, we have extended these observations by demonstrating that IP-receptor activation also can enhance the ability of glucocorticoids to induce genes with anti-inflammatory activity. BEAS-2B bronchial epithelial cells stably transfected with a glucocorticoid response element (GRE) luciferase reporter were activated in a concentration-dependent manner by the glucocorticoid dexamethasone. An IP-receptor agonist, taprostene, increased cAMP in these cells and augmented luciferase expression at all concentrations of dexamethasone examined. Analysis of the concentration-response relationship that described this effect showed that taprostene increased the magnitude of transcription without affecting the potency of dexamethasone and was, thus, steroid-sparing in this simple system. RO3244794, an IP-receptor antagonist, and oligonucleotides that selectively silenced the IP-receptor gene, PTGIR, abolished these effects of taprostene. Infection of BEAS-2B GRE reporter cells with an adenovirus vector encoding a highly selective inhibitor of cAMP-dependent protein kinase (PKA) also prevented taprostene from enhancing GRE-dependent transcription. In BEAS-2B cells and primary cultures of human airway epithelial cells, taprostene and dexamethasone interacted either additively or cooperatively in the expression of three glucocorticoid-inducible genes (GILZ, MKP-1, and p57(kip2)) that have anti-inflammatory potential. Collectively, these data show that IP-receptor agonists can augment the ability of glucocorticoids to induce anti-inflammatory genes in human airway epithelial cells by activating a cAMP/PKA-dependent mechanism. This observation may have clinical relevance in the treatment of airway inflammatory diseases that are either refractory or respond suboptimally to glucocorticoids.

Phospholipase A2 subclasses in acute respiratory distress syndrome

Phospholipases A2 (PLA2) catalyse the cleavage of fatty acids esterified at the sn-2 position of glycerophospholipids. In acute lung injury-acute respiratory distress syndrome (ALI-ARDS) several distinct isoenzymes appear in lung cells and fluid. Some are capable to trigger molecular events leading to enhanced inflammation and lung damage and others have a role in lung surfactant recycling preserving lung function: Secreted forms (groups sPLA2-IIA, -V, -X) can directly hydrolyze surfactant phospholipids. Cytosolic PLA2 (cPLA2-IVA) requiring Ca2+ has a preference for arachidonate, the precursor of eicosanoids which participate in the inflammatory response in the lung. Ca(2+)-independent intracellular PLA2s (iPLA2) take part in surfactant phospholipids turnover within alveolar cells. Acidic Ca(2+)-independent PLA2 (aiPLA2), of lysosomal origin, has additionally antioxidant properties, (peroxiredoxin VI activity), and participates in the formation of dipalmitoyl-phosphatidylcholine in lung surfactant. PAF-AH degrades PAF, a potent mediator of inflammation, and oxidatively fragmented phospholipids but also leads to toxic metabolites. Therefore, the regulation of PLA2 isoforms could be a valuable approach for ARDS treatment.

Topical glucocorticoids downregulate COX-1 positive cells in nasal polyps

BACKGROUND

Influx of inflammatory cells is one of the hallmarks of nasal polyposis. As glucocorticoids (GC) are known to exhibit strong anti-inflammatory effects, these drugs are frequently used in the treatment of the disease. Part of the anti-inflammatory effects of GC is attributed to their interference with prostanoid synthesis. As cyclooxygenases (COX) are key enzymes in the synthesis of both pro- (COX-1, COX-2) and anti-inflammatory prostanoids (COX-2), we investigated the role of topical GC on COX-1, COX-2 and inflammatory markers in nasal polyps (NP).

METHODS

Immunohistochemical analysis of inflammatory markers (CD68, CD117, MBP, elastase, IgE, BB-1, IL-4, IL-5 and IL-6), COX-1 and COX-2 was performed on normal nasal mucosa (NM) (n = 18), non-GC treated NP (n = 27) and topical GC treated NP (n = 12). NP groups were matched for allergy, asthma and ASA intolerance.

RESULTS

Increased numbers of eosinophils, IL-5+ cells and IgE+ cells and decreased numbers of mastcells are striking features of NP inflammation (P < 0.05). In addition, increased numbers of COX-1+ cells are observed in NP epithelium compared to NM (P < 0.05).

CONCLUSION

Topical GC significantly reduce the number of COX-1+ NP cells (P < 0.05), but have no significant effect on COX-2+ NP cells. No significant reduction in the number of eosinophils is observed for GC treated NP. The number of IL-5+ cells is however increased significantly upon GC treatment (P < 0.05).

Glucocorticoid actions on airway epithelial responses in immunity: functional outcomes and molecular targets

Research on the biology of airway epithelium in the last decades has progressively uncovered the many roles of this cell type during the immune response. Far from the early view of the epithelial layer simply as a passive barrier, the airway epithelium is now considered a central player in mucosal immunity, providing innate mechanisms of first-line host defense as well as facilitating adaptive immune responses. Alterations of the epithelial phenotype are primarily involved in the pathogenesis of allergic airways disease, particularly in severe asthma. Appreciation of the epithelium as target of glucocorticoid therapy has also grown, because of studies defining the pathways and mediators affected by glucocorticoids, and studies illustrating the relevance of the control of the response from epithelium in the overall efficacy of topical and systemic therapy with glucocorticoids. Studies of the mechanism of action of glucocorticoids within the biology of the immune response of the epithelium have uncovered mechanisms of gene regulation involving both transcriptional and posttranscriptional events. The view of epithelium as therapeutic target therefore has plenty of room to evolve, as new knowledge on the role of epithelium in immunity is established and novel pathways mediating glucocorticoid regulation are elucidated.

Influence of dexamethasone on protease-activated receptor 2-mediated responses in the airways

Stimulants of protease-activated receptor (PAR)(2) promote the generation of the bronchoprotective prostanoid prostaglandin (PG) E(2) by airway epithelial cells. In contrast, glucocorticoids reduce the levels of PGE(2) in airway epithelial cell cultures by concomitantly inhibiting pathways required for PGE(2) synthesis and facilitating pathways involved in PGE(2) inactivation. The aim of this study was to determine whether glucocorticoids inhibited PAR(2)-mediated, PGE(2)-dependent responses in epithelial cell cultures, in intact airway preparations, and in whole animals. In cultures of A549 cells, a PAR(2)-activating peptide SLI-GRL-NH(2) produced concentration and time-dependent increases in PGE(2) levels, which were significantly enhanced after exposure to lipopolysaccharide (LPS). However, SLIGRL-NH(2)-induced increases in PGE(2) levels were abolished by pretreatment of cells with the glucocorticoid, dexamethasone. In mouse isolated tracheal preparations, SLIGRL-NH(2) and PGE(2) induced concentration-dependent relaxation responses that were unaffected by dexamethasone, irrespective of whether dexamethasone exposure occurred in vitro or in vivo. Intranasal administration of LPS produced a pronounced increase in the numbers of neutrophils recovered from the bronchoalveolar lavage fluid of BALB/c mice. Numbers of recovered neutrophils were 40 to 60% lower in mice that received f-LIGRL-NH(2) (PAR(2)-activating peptide, 30 microg intranasally), PGE(2) (10 mugintranasally), or dexamethasone (1 mg/kg i.p.). In the combined presence of dexamethasone and f-LIGRL-NH(2) or dexamethasone and PGE(2), the number of neutrophils was suppressed further (80-83% lower). Thus, although dexamethasone abolished PAR(2)-mediated generation of PGE(2) in A549 cells, neither the smooth muscle relaxant nor the anti-inflammatory effects of PAR(2)-activating peptides (and PGE(2)) were diminished by in vitro or in vivo exposure to dexamethasone.

Anti-inflammatory therapy of dry eye

As tear secretion and tear clearance decrease in the dry eye, an inflammatory response is initiated on the ocular surface that appears to involve both soluble and cellular mediators. Although the traditional approach to treating dry eye is to hydrate and lubricate the ocular surface with artificial tears, symptoms and/or sight-threatening corneal disease may persist in some patients on such aqueous enhancement therapies. In these patients, treatment with anti-inflammatory agents, such as cyclosporin A, corticosteroids, tetracyclines, or autologous serum, may be considered. Results of studies investigating the use of these agents are discussed. During treatment, patients should be conscientiously monitored for adverse effects.

Attenuation of human lung mast cell degranulation by bronchial epithelium

BACKGROUND

Human lung mast cells (HLMC) lie in close proximity to the bronchial epithelium in asthma and adhere with high affinity to bronchial epithelial monolayers in vitro. We investigated the consequences of this adhesive interaction on HLMC activation in response to Fc epsilon RI cross-linking.

METHODS

Human lung mast cells were cultured with the bronchial epithelial cell line BEAS-2B or plastic control for either 30 min or 16 h and then activated with anti-IgE. Histamine was measured by radioenzymatic assay.

RESULTS

After co-culture for 30 min, IgE-dependent histamine release from HLMC was identical on both BEAS-2B and plastic. After 16 h of co-culture, there was a marked decrease in constitutive and IgE-dependent histamine release from HLMC cultured on BEAS-2B compared with those cultured on plastic or fibronectin. In contrast, the Ca(2+)/ATPase inhibitor thapsigargin produced concentration-dependent histamine release that was significantly increased on BEAS-2B compared with plastic. IgE-dependent degranulation was not significantly affected by BEAS-2B-conditioned medium.

CONCLUSIONS

BEAS-2B bronchial epithelial cells attenuate IgE-dependent but not thapsigargin-induced histamine release from HLMC. The differential effect with anti-IgE compared with thapsigargin suggests that the mechanism includes interference with the proximal Fc epsilon RI signalling pathway.

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

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

Pathogenesis and management of aspirin-intolerant asthma

In 2-23% of adults with asthma, and rarely in children with asthma, aspirin (acetylsalicylic acid) and non-steroidal anti-inflammatory drugs (NSAIDs) cause asthma exacerbations. Within 3 hours of ingestion of aspirin/NSAIDs, individuals with aspirin-intolerant asthma (AIA) develop bronchoconstriction, often accompanied by rhinorrhea, conjunctival irritation, and scarlet flush. In severe cases, a single therapeutic dose of aspirin/NSAIDs can provoke violent bronchospasm, loss of consciousness, and respiratory arrest. In order to diagnose AIA, oral, inhaled, nasal or intravenous aspirin challenge tests are performed in facilities where experienced physicians are present and emergency treatment is available. The exact differences in the pathogenesis of AIA and other types of asthma are not fully understood. The interference of aspirin/NSAIDs with arachidonic acid metabolism in the lungs plays an important role in the mechanism of AIA; inhibition of cyclo-oxygenase is accompanied by overproduction of cysteinyl leukotrienes (cys-LTs). It has been proposed that overproduction of cys-LTs, together with removal by aspirin/NSAIDs of the 'brake' imposed by the bronchodilator prostaglandin E2, may cause an asthma attack in patients with AIA. Development of a suitable animal model to investigate the pathogenesis of AIA would help to clarify this question. Although it is still controversial whether leukotriene modifiers are more effective in patients with AIA compared with other types of asthma, because LT plays an important role in the pathogenesis of AIA, leukotriene modifiers are the preferred medication for the long-term control of AIA. Add-on efficacy of leukotriene modifiers has been confirmed in patients with AIA already treated with inhaled corticosteroids. However, this does not mean that aspirin/NSAIDs can be safely taken by aspirin-sensitive patients treated with leukotriene modifiers. To prevent attacks of AIA, sensitive patients should avoid the use of aspirin/NSAIDs or use selective cyclo-oxygenase 2 inhibitors when required. When patients with AIA need aspirin for specific situations they should receive aspirin desensitization therapy or treatment with selective cyclo-oxygenase 2 inhibitors.

Oral corticosteroid-sparing effects of inhaled corticosteroids in the treatment of persistent and acute asthma

OBJECTIVE

To review the efficacy and safety of inhaled corticosteroids (ICSs) when used to reduce daily oral corticosteroid (OCS) requirements in patients with severe persistent asthma and periodic requirements in patients with acute asthma exacerbations.

DATA SOURCES

Clinical studies of the OCS-sparing effects of ICSs were located by searching MEDLINE databases from 1966 onward using the terms oral, steroid, and asthma in combination with the generic names for each marketed ICS.

STUDY SELECTION

Studies reporting on the use of ICSs to reduce OCS requirements in patients with persistent and acute asthma are included.

RESULTS

Clinical study results consistently show that ICSs significantly improve asthma control and reduce OCS requirements among adults, children, and infants with persistent asthma. A dose reduction or complete discontinuation of use of OCSs is possible in most patients without loss of asthma control. ICSs also can control asthma during acute asthma exacerbations and reduce the need for short courses of OCSs. With many ICSs, the reductions in OCS use are accompanied by recovery of hypothalamic-pituitary-adrenal axis function, indicating that the safety of asthma therapy is improved when OCS requirements are decreased with ICSs. Of the available ICSs that may reduce OCS needs, budesonide appears to be the most intensively studied.

CONCLUSIONS

ICSs can reduce OCS requirements in adults and children with persistent asthma and during acute asthma exacerbations. The reduced systemic corticosteroid activity associated with ICS treatment improves the overall safety of asthma therapy.

[Role of the innate immune response in sepsis]

Das angeborene („innate“) Immunsystem bekämpft erfolgreich den größten Teil unserer Infektionen, noch bevor das erworbene Immunsystem aktiviert wird. Genauere Kenntnisse über Wirkmechanismen des angeborenen Immunsystems lassen uns die Pathophysiologie systemischer Infektionen, wie der Sepsis, besser verstehen und dienen der Entwicklung neuer Therapiestrategien. Das angeborene Immunsystem ist für die erste Abwehrreaktion auf eine Infektion verantwortlich. Darüber hinaus aktiviert und interagiert es mit dem erworbenen Immunsystem. Wechselwirkungen werden über Immunzellen, wie Makrophagen und dendritische Zellen, sowie lösliche Faktoren, wie Zytokine, vermittelt. Aufgrund neuer Erkenntnisse aus Tiermodellen, die neben der Inflammation auch ein Fortschreiten der Bakterienabwehr berücksichtigen, mussten bisherige Erkenntnisse überprüft und korrigiert werden. Die Vorstellung von Sepsis als überwiegende „Überreaktion auf eine Entzündung“ wich neuen Theorien. Die Zellen des angeborenen Immunsystems erkennen Eindringlinge mit Hilfe spezieller Rezeptoren. Nach Rezeptorinteraktion führen intrazelluläre Signalkaskaden zur Zellaktivierung, durch die zahlreiche Zytokine und antimikrobielle Substanzen freigesetzt werden. Im Verlauf einer Sepsis kommt es durch verschiedene Regelkreise zu zunehmender Immunsuppression. Mit dem angeborenen Immunsystem verknüpft ist die Migration von Leukozyten in entzündetes Gewebe. Chemokine und Adhäsionsmoleküle übernehmen dabei Schlüsselrollen. Auch die Blutgerinnung ist mit dem angeborenen Immunsystem eng verzahnt. Immunzellen sezernieren „tissue factor“; dies führt über eine Kaskade u. a. zur Bildung von Thrombin. Dieses kann unter den besonderen Bedingungen der Sepsis eine disseminierte intravasale Gerinnung verursachen. Umgekehrt werden durch Thrombin auch Endothelzellen zur Freisetzung von Chemokinen und Adhäsionsmolekülen angeregt; dies stellt einen positiven „Feedback-Mechanismus“ für die angeborene Immunantwort dar. Neue Therapieansätze zur Sepsis versuchen diese Regelkreise zu durchbrechen und durch Blockade von Zytokinen, Rezeptoren oder durch Aktivierung immunstimulierender Systeme eine ausgewogene Reaktion des angeborenen Immunsystems ohne Suppression der antibakteriellen Funktion zu erzielen.

Antiinflammatory therapy for dry eye

PURPOSE

To present evidence establishing the relationship between inflammation and dry eye and supporting the use of antiinflammatory therapy for dry eye.

DESIGN

Analysis of literature.

METHODS

Research studies that evaluated inflammation in dry eye pathogenesis and clinical trials of antiinflammatory therapies for dry eye were reviewed.

RESULTS

There is increasing evidence that decreased tear secretion, decreased tear turnover, and desiccation promote inflammation on the ocular surface. An increase in soluble mediators (cytokines and proteases) in the tear fluid, adhesion molecule expression by the conjunctival epithelium, and T-cell infiltration of the conjunctiva have been observed in dry eye patients. This inflammation appears to have a role in the pathogenesis of the ocular surface epithelial disease, termed keratoconjunctivitis sicca (KCS), that develops in dry eye. Clinical improvement of KCS has been observed after therapy with antiinflammatory agents including corticosteroids, cyclosporin and doxycycline. Cyclosporin A emulsion was approved by the Food and Drug Administration as therapy for dry eye. Randomized placebo-controlled FDA clinical trials showed that cyclosporine A was superior to vehicle in stimulating aqueous tear production, decreasing corneal punctuate fluorescein staining, reducing symptoms of blurred vision, and decreasing artificial tear use in patients with KCS. No ocular or systemic toxicity was observed from this medication.

CONCLUSIONS

Ocular surface and lacrimal gland inflammation has been identified in dry eye that plays a role in the pathogenesis of KCS. Antiinflammatory therapy has efficacy for treating KCS. Cyclosporin A is the first FDA approved therapy for this indication. It improved signs and symptoms of KCS, and it is safe for long-term use.

Corticosteroids in sepsis: from bench to bedside?

The use of corticosteroids in patients with septic shock has been recently revisited and the use of low dose corticosteroids led to very promising results, particularly in patients with corticosteroid insufficiency. We review the different mechanisms that can account for their beneficial effects in patients. Glucocorticoids display a wide spectrum of anti-inflammatory properties that have been identified in in vitro and in vivo experimental models (e.g., inhibition of production of pro-inflammatory cytokines, free radicals, prostaglandins and inhibition of chemotaxis, and adhesion molecule expressions.) In addition, glucocorticoids have profound effects on the cardiovascular system (e.g., increasing mean blood pressure, increasing pressor sensitivity, and therefore decreasing the duration of use of catecholamines during septic shock.) Through these anti-inflammatory and cardiovascular effects, low doses of glucorticoids may improve septic shock survival.

Increased exhaled cysteinyl-leukotrienes and 8-isoprostane in aspirin-induced asthma

The pathogenesis of aspirin-induced asthma (AIA) has not yet been clearly elucidated, although eicosanoid metabolites appear to play an important role. We hypothesized that levels of eicosanoids in exhaled air condensate are abnormal in patients with AIA and that they change in patients receiving steroid therapy. We measured cysteinyl-leukotrienes (cys-LTs), prostaglandin E(2) (PGE(2)), and leukotriene B(4) (LTB(4)), and also 8-isoprostane as a marker of oxidative stress, by enzyme immunoassay in exhaled breath condensate from patients with AIA (17 steroid naive; mean age, 41 +/- 23 years; FEV(1), 63%pred), 26 patients with aspirin-tolerant asthma (ATA) (11 steroid naive; mean age, 47 +/- 18 years; FEV(1), 69%pred), and 16 healthy subjects (mean age, 45 +/- 17 years; FEV(1), 93%pred). Cys-LTs were significantly higher in steroid-naive patients with AIA compared with steroid-naive patients with ATA and healthy subjects (152.3 +/- 30.4 and 36.6 +/- 7.1 versus 19.4 +/- 2.8 pg/ml; p < 0.05 and p < 0.05, respectively). Steroid-naive patients with AIA also had higher levels of 8-isoprostane than normal subjects (131.8 +/- 31.0 versus 21.9 +/- 4.5 pg/ml; p < 0.05). There were significantly lower levels of both cys-LTs and 8-isoprostanes in steroid-treated patients with AIA. There was no difference in either the PGE(2) or LTB(4) level between the patient groups. This is the first study to show that cys-LTs and 8-isoprostanes are elevated in expired breath condensate of steroid-naive patients with AIA, and that cys-LTs are decreased in steroid-treated patients. Exhaled PGE(2) levels are not reduced, so that it is unlikely that a deficiency of PGE(2) is an important mechanism, whereas exhaled LTB(4) levels are unchanged, indicating an abnormality beyond 5-lipoxygenase.

Neuroimmune alterations in the complex regional pain syndrome

This review focuses on some clinical aspects of the complex regional pain syndrome, such as oedema, local temperature changes and chronic pain, as a result of supposed neurogenic inflammation. Involvement of the immune system could imply the subsequent release of neuropeptides, pro-inflammatory cytokines and eicosanoids, which in turn leads to a complex cross-talk of primary and secondary generated mediators of inflammation. The development and application of drugs that act through selective receptor antagonism or enzymatic synthesis inhibition to prevent further stimulation of this cascade that could inevitably lead to chronicity of this disease are extensively discussed.

Corticosteroids for septic shock

OBJECTIVE

To gather the data to provide a rationale for using replacement therapy with hydrocortisone in septic shock patients.

DATA SOURCES

The Medline and the Cochrane Library databases.

STUDY SELECTION

Studies in animals and in humans were considered when significant data were available about the mechanisms of action of corticosteroids or about their use in severe sepsis.

DATA SUMMARY

Corticosteroids were the first anti-inflammatory drugs tested in septic patients. Randomized trials clearly showed that a short course of a large dose of anti-inflammatory steroids is ineffective and potentially harmful in patients with severe sepsis. Recent demonstrations of altered hypothalamic-pituitary-adrenal axis response to septic insult have led to a reappraisal of the use of steroids in septic shock. Randomized trials in catecholamine-dependent septic shock patients strongly suggest that replacement therapy with hydrocortisone may alleviate the symptoms of systemic inflammatory response, reduce the duration of shock, and favorably affect survival.

CONCLUSIONS

Current evidence that the therapeutic interest of replacement therapy with corticosteroids increases suggests that low doses of hydrocortisone should be offered to patients with catecholamine-dependent septic shock.

Safety of inhaled and intranasal corticosteroids: lessons for the new millennium

Although inhaled and intranasal corticosteroids are first-line therapy for asthma and allergic rhinitis, there has recently been an increasing awareness of their propensity to produce systemic adverse effects. The availability of more potent and lipophilic corticosteroids and new chlorofluorocarbon (CFC)-free formulations has focused attention on these safety issues. The main determinant of systemic bioavailability of these drugs is direct absorption from the lung or nose, where there is no first-pass inactivation. Consequently, the systemic bioavailability of inhaled corticosteroids is greatly influenced by the efficiency of the inhaler device. Thus, when comparing different inhaled corticosteroids it is imperative to consider the unique drug/device interaction. The pharmacokinetic profile is important in determining the systemic bioactivity of inhaled and intranasal corticosteroids. For highly lipophilic drugs, such as fluticasone propionate or mometasone furoate, there is preferential partitioning into the systemic tissue compartment, and consequently a large volume of distribution at steady state. In contrast, drugs with lower lipophilicity, such as triamcinolone acetonide or budesonide, have a smaller volume of distribution. The systemic tissue compartment may act as a slow release reservoir, resulting in a long elimination half-life for the lipophilic drugs. For intranasal corticosteroids, a high degree of lipophilicity diminishes water solubility in mucosa and therefore increases the amount of drug swept away by mucociliary clearance before it can gain access to tissue receptor sites. This may reduce the anti-inflammatory efficacy in the nose, but might also reduce the propensity for direct systemic absorption from the nasal cavity. The hydrofluoroalkane (HFA) formulations of beclomethasone dipropionate are solutions and exhibit a much higher respirable fine particle dose than do the CFC formulations. Dose-response studies with one of the HFA formulations have shown therapeutic equivalence at half the dosage, with little evidence of adrenal suppression at dosages up to 800 microg/day. A lack of similar studies for another of the available HFA formulations has led to a discrepancy in the recommendations for equivalence. Although in vitro studies have pointed to a similar fine particle distribution for the HFA and CFC formulations of fluticasone propionate, this is not supported by in vivo data for lung bioavailability, suggesting that care will be required when switching these formulations. Prescribers of inhaled and intranasal corticosteroids should be aware of the potential for long term systemic effects. The safest way to use these drugs is to 'step-down' to achieve the lowest possible effective maintenance dosage.