Mast cells and eosinophils: the hallmark of asthma

Potential Impact of SOD2 (rs4880; p.Val16Ala) Variant with the Susceptibility for Childhood Bronchial Asthma

Oxidative stress is a sophisticated situation that orignates from the accumulation of reactive free radicals within cellular compartments. The antioxidant mechanism of the MnSOD enzyme facilitates the removal of these lethal oxygen species from cellular components. The main goal of this pertained work is to study the contribution of the SOD2 (rs4880; p.Val16Ala) variant to the development of bronchial asthma among children. The study's design was carried out based on a total of 254 participants including 127 asthmatic children (91 atopic and 36 non-atopic) along with 127 unrelated healthy controls. Allelic discrimination analysis was executed using the T-ARMS-PCR protocol. This potential variant conferred a significant association with decreased risk of bronchial asthmatic children under allelic (OR = 0.56, P-value = 0.002), recessive (OR = 0.32, P-value = 0.011), and dominant (OR = 0.51, P-value = 0.040) models. Additionally, atopic and non-atopic asthmatic children indicated a protection against bronchial asthma development under allelic, and dominant models (p-value < 0.05). Our findings suggested that the SOD2*rs4880 variant was correlated with decreased risk of childhood bronchial asthma.

Co-exposure to lipopolysaccharide and desert dust causes exacerbation of ovalbumin-induced allergic lung inflammation in mice via TLR4/MyD88-dependent and -independent pathways

Background

Lipopolysaccharide (LPS) often presents in high concentrations in particulate matter (PM), few studies have reported the enhancing effects of both LPS and PM on airway inflammation in mice and the role of toll-like receptors (TLRs) in this process. Asian sand dust (ASD) is observed most frequently during the spring. This study aimed to clarify the role of TLRs in murine lung eosinophilia exacerbated by ASD and LPS.

Methods

The effects of LPS and ASD co-treatment on ovalbumin (OVA)-induced lung eosinophilia were investigated using wild-type (WT), TLR2^−/−, TLR4^−/−, and adaptor protein myeloid differentiation factor 88 (MyD88)^−/− BALB/c mice. ASD was heated (H-ASD) to remove the toxic organic substances. WT, TLR2^−/−, TLR4^−/− and MyD88^−/− BALB/c mice were intratracheally instilled with four different combinations of LPS, H-ASD and OVA treatment. Subsequently, the pathological changes in lungs, immune cell profiles in bronchoalveolar lavage fluid (BALF), inflammatory cytokines/chemokines levels in BALF and OVA-specific immunoglobulin (Ig) in serum were analyzed.

Results

In WT mice, H-ASD + LPS exacerbated OVA-induced lung eosinophilia. This combination of treatments increased the proportion of eosinophils and the levels of IL-5, IL-13, eotaxin in BALF, as well as the production of OVA-specific IgE and IgG1 in serum compared to OVA treatment alone. Although these effects were stronger in TLR2^−/− mice than in TLR4^−/− mice, the expression levels of IL-5, IL-13, eotaxin were somewhat increased in TLR4^−/− mice treated with OVA + H-ASD + LPS. In MyD88^−/− mice, this pro-inflammatory mediator-induced airway inflammation was considerably weak and the pathological changes in lungs were negligible.

Conclusions

These results suggest that LPS and H-ASD activate OVA-induced Th2 response in mice, and exacerbate lung eosinophilia via TLR4/MyD88, TLR4/TRIF and other TLR4-independent pathways.

Diagnostic Value of Serum Baseline Tryptase Levels in Childhood Asthma and Its Correlation with Disease Severity

BACKGROUND

The aim of this study was to explore whether serum baseline tryptase (sBT) levels might be a useful marker not only for the accurate diagnosis of childhood asthma, but also for the prediction of disease severity.

METHODS

A total of 114 asthmatic children were enrolled in this study, 36 of whom had mild intermittent asthma, 38 had mild persistent asthma, and 40 had moderate to severe persistent asthma. Additionally, 34 age-matched healthy children were enrolled as controls. The sBT levels of these populations were measured using a fluoroenzymeimmunoassay kit. The diagnostic performance of sBT levels and their correlation with asthma severity were systematically investigated using receiver operating characteristic (ROC) analysis and correlation analysis.

RESULTS

Children with mild and moderate to severe persistent asthma had significantly increased sBT levels as compared to those with mild intermittent asthma and healthy controls. ROC analysis further demonstrated that sBT levels not only appear to be highly sensitive and specific for distinguishing asthmatic children from healthy controls, but also show good accuracy for the differentiation of various asthmatic subgroups. Correlation analysis revealed that in all asthmatic subgroups sBT levels were significantly correlated with a variety of key markers that reflect the disease severity of asthma, including childhood asthma control test scores, serum IgE and interleukin-13 levels, blood eosinophil counts, and pulmonary test parameters.

CONCLUSIONS

sBT levels may have a potential use in supporting a diagnosis of asthma in children and as a predictor of disease severity.

Vitamin D decreases the secretion of eotaxin and RANTES in nasal polyp fibroblasts derived from Taiwanese patients with chronic rhinosinusitis with nasal polyps

Eosinophils are important inflammatory cells involved in the pathogenesis of chronic rhinosinusitis with nasal polyps (CRSwNP). Vitamin D and its derivatives, in addition to their classic role as regulators of electrolytes homeostasis, have modulatory effects in immunological and inflammatory responses. Such properties suggest that vitamin D might also play a role in inflammatory airway diseases such as CRSwNP. In this study, we investigated the effect of vitamin D derivatives (calcitriol and tacalcitol) on the secretion of eotaxin and Regulated on Activation, Normal T Cell Expressed and Secreted (RANTES), the two major eosinophil chemoattractants, in fibroblasts derived from the polyps of Taiwanese CRSwNP patients. Patients diagnosed with eosinophilic CRSwNP but without malignancies or asthma and undergoing elective endoscopic sinus surgery were recruited. Three primary fibroblast cultures were established using the polyp specimens obtained from these patients. The third to eighth passages of the fibroblasts were used for in vitro studies. Nasal polyp-derived fibroblasts were stimulated with IL-1β (10 ng/mL) for 24 hours, followed by replacement with media alone or with calcitriol or tacalcitol (10 μM) and incubation for another 24 hours. After the treatments, the levels of secreted eotaxin and RANTES were evaluated by ELISA assays. The results showed that IL-1β could substantially stimulate the secretion of eotaxin (p < 0.01) and RANTES (p < 0.01) in nasal polyp-derived fibroblasts. More importantly, this stimulatory effect was significantly suppressed by adding calcitriol (p ≤ 0.002 for eotaxin and p ≤ 0.008 for RANTES) or tacalcitol (p ≤ 0.009 for eotaxin and p ≤ 0.02 for RANTES). Therefore, the inhibitory effect of vitamin D derivatives on eotaxin and RANTES secretion might shed light not only on the disease mechanism, but also on the potential use of vitamin D in pharmacotherapy of Taiwanese patients with CRSwNP.

Janus kinase-3 dependent inflammatory responses in allergic asthma

Allergic asthma is a chronic inflammatory condition of the lung characterized by reversible airway obstruction, high serum immunoglobulin (Ig) E levels, and chronic airway inflammation. A number of cells including mast cells, T cells, macrophages and dendritic cells play a role in the pathogenesis of the disease. Janus kinase (JAK)-3, a non-receptor protein tyrosine kinase, traditionally known to mediate cytokine signaling, also regulates functional responses of these cells. In this review the role of JAK-3 in regulating various pathogenic processes in allergic asthma is discussed. We propose that targeting JAK-3 is a rationale approach to control the inflammatory responses of multiple cell types responsible for the pathogenesis of allergic asthma.

JunB is required for IgE-mediated degranulation and cytokine release of mast cells

Mast cells are effector cells of IgE-mediated immune responses frequently found at the vicinity of blood vessels, the margins of diverse tumors and at sites of potential infection and inflammation. Upon IgE-mediated stimulation, mast cells produce and secrete a broad spectrum of cytokines and other inflammatory mediators. Recent work identified JunB, a member of the AP-1 transcription factor family, as critical regulator of basal and induced expression of inflammatory mediators in fibroblasts and T cells. To study the impact of JunB on mast cell biology, we analyzed JunB-deficient mast cells. Mast cells lacking JunB display a normal in vivo maturation, and JunB-deficient bone marrow cells in vitro differentiated to mast cells show no alterations in proliferation or apoptosis. But these cells exhibit impaired IgE-mediated degranulation most likely due to diminished expression of SWAP-70, Synaptotagmin-1, and VAMP-8, and due to impaired influx of extracellular calcium. Moreover, JunB-deficient bone marrow mast cells display an altered cytokine expression profile in response to IgE stimulation. In line with these findings, the contribution of JunB-deficient mast cells to angiogenesis, as analyzed in an in vitro tube formation assay on matrigel, is severely impaired due to limiting amounts of synthesized and secreted vascular endothelial growth factor. Thus, JunB is a critical regulator of intrinsic mast cell functions including cross-talk with endothelial cells.

Free immunoglobulin light chains as target in the treatment of chronic inflammatory diseases

Immunoglobulin free light chains were long considered irrelevant bystander products of immunoglobulin synthesis by B lymphocytes. To date, different studies suggest that free light chains may have important functional activities. For instance, it has been shown that immunoglobulin free light chains can elicit mast cell-driven hypersensitivity responses leading to asthma and contact sensitivity. Free light chains also show other biologic actions such as anti-angiogenic and proteolytic activities or can be used as specific targeting vehicles. Levels of free light chain levels in body fluids increase markedly in diseases such as multiple sclerosis, rheumatoid arthritis, and systemic lupus erythematosus. In this review, we will focus on the unexpected biological activities of immunoglobulin free light chains with special attention to its possible role in the induction of chronic inflammatory diseases.

Mast cell activation and leukotriene secretion in wheezing infants. Relation to respiratory syncytial virus and outcome

The persistence of wheezing after early wheezing episodes in infancy may be related to the virus involved and to the type of inflammation during the initial wheezing. The role of mast cell activation and leukotriene secretion in wheezing, and the relation to outcome, is not known. Our objective was to study markers of mast cell activation and leukotriene secretion from wheezing infants, and the relation to respiratory syncytial virus (RSV) infection and persistent wheezing. Urinary 9alpha,11beta-PGF(2), a marker of mast cell activation, and urinary leukotriene E4 were measured in 106 infants hospitalized for wheezing during their first year of life. Results were related to the presence of RSV infection and the persistence of wheezing at follow-up 20 months later. Levels of 9alpha,11beta-PGF(2) were higher in infants positive for RSV than in those with RSV negative wheezing, but both groups had higher levels than controls. Leukotriene E4 levels were higher in wheezing infants than in controls. Urinary 9alpha,11beta-PGF(2) levels were higher in infants with transient compared with persistent wheezing. We found a positive correlation between 9alpha,11beta-PGF(2) and leukotriene E4, strongest in infants with RSV negative disease and in infants with persistent wheezing. The results suggest that mast cells play an important role in infant wheezing, and may be a major source of leukotriene secretion in these infants. Mast cell activation and leukotriene secretion were not associated with persistent wheezing.

Adenosine receptors and the control of endothelial cell function in inflammatory disease

The nucleoside adenosine accumulates in many tissues following the onset of ischaemia and inflammation. This initiates a series of protective mechanisms in target cells upon binding and activation of a family of four G-protein-coupled cell surface adenosine receptor (AR) proteins. The magnitude and duration of adenosine's effects are dictated by the identity and expression levels of each receptor subtype on individual cell types within the hypoxic microenvironment. Given the key role of endothelial cells (ECs) in the development of inflammatory diseases, such as sepsis, rheumatoid arthritis (RA) and atherosclerosis, ARs represent attractive targets for therapeutic intervention in these conditions. In this review, we examine several critical aspects of endothelial function in vivo, assess the role of individual AR subtypes in these events and, where known, discuss the molecular mechanisms by which specific ARs exert their effects.