Neutrophil airway inflammation in childhood asthma

Th17 Lymphocytes in Children with Asthma: Do They Influence Control?

Background: Allergic asthma was considered as an inflammation mediated by specific CD4+ helper lymphocytes (Th2); however, this paradigm changed in 2005, when a third group of helper cells called Th17 cells were identified. Th17 lymphocytes are the main source of interleukin (IL)-17A-F, IL-21, and IL-22; however, their physiological role in children is unclear. This study aimed to determine the percentage of Th17 cells and IL-17A in pediatric patients diagnosed with asthma and to associate it with disease control using a validated questionnaire. Methods: This cross-sectional, prospective, comparative study included 92 asthma-diagnosed children 4-18 years of age. The Asthma Control Test was used as an assessment measure to classify patients as controlled (n = 30), partially controlled (n = 31), and uncontrolled (n = 31). Th17 cells and IL-17A were analyzed by flow cytometry. Patients receiving inhaled steroid therapy as monotherapy or associated with a long-acting bronchodilator were included. Results: The mean percentage of Th17 cells in the participants was 4.55 ± 7.34 (Controlled), 5.50 ± 8.09 (Partially Controlled), and 6.14 ± 7.11 (Uncontrolled). There was no significant difference between the 3 groups (P = 0.71). The mean percentage of IL-17A in all the participants was 9.84 ± 9.4 (Controlled), 10.10 ± 10.5 (Partially Controlled), and 11.42 ± 8.96 (Uncontrolled); no significant difference between the 3 groups (P = 0.79) was observed. Th17 lymphocyte levels were similar among the 3 groups and the same trend was observed with IL-17A. A significant correlation between Th17 or IL-17A and the degree of asthma control (Th17, P = 0.24; IL-17A, P = 0.23) was not found. Conclusions: The percentages of both Th17 lymphocytes and IL-17A found in children with asthma were not significantly different in the 3 groups, which suggests that they do not play an important role in asthma control. Our findings may contribute to the knowledge related to non-Th2 inflammation in children. Clinical-Trials.gov ID: 2015-2102-85.

Semaphorin3E/plexinD1 Axis in Asthma: What We Know So Far!

Semaphorin3E belongs to the large family of semaphorin proteins. Semaphorin3E was initially identified as axon guidance cues in the neural system. It is universally expressed beyond the nervous system and contributes to regulating essential cell functions such as cell migration, proliferation, and adhesion. Binding of semaphorin3E to its receptor, plexinD1, triggers diverse signaling pathways involved in the pathogenesis of various diseases from cancer to autoimmune and allergic disorders. Here, we highlight the novel findings on the role of semaphorin3E in airway biology. In particular, we highlight our recent findings on the function and potential mechanisms by which semaphorin3E and its receptor, plexinD1, impact airway inflammation, airway hyperresponsiveness, and remodeling in the context of asthma.

Necrostatin-1 Ameliorates Neutrophilic Inflammation in Asthma by Suppressing MLKL Phosphorylation to Inhibiting NETs Release

Neutrophilic inflammation occurs during asthma exacerbation, and especially, in patients with steroid-refractory asthma, but the underlying mechanisms are poorly understood. Recently, a significant accumulation of neutrophil extracellular traps (NETs) in the airways of neutrophilic asthma has been documented, suggesting that NETs may play an important role in the pathogenesis. In this study, we firstly demonstrated that NETs could induce human airway epithelial cell damage in vitro. In a mouse asthmatic model of neutrophil-dominated airway inflammation, we found that NETs were markedly increased in bronchoalveolar lavage (BAL), and the formation of NETs exacerbated the airway inflammation. Additionally, a small-molecule drug necrostatin-1 (Nec-1) shown to inhibit NETs formation was found to alleviate the neutrophil-dominated airway inflammation. Nec-1 reduced total protein concentration, myeloperoxidase activity, and the levels of inflammatory cytokines in BAL. Finally, further experiments proved that the inhibition of Nec-1 on NETs formation might be related to its ability to inhibiting mixed lineage kinase domain-like (MLKL) phosphorylation and perforation. Together, these results document that NETs are closely associated with the pathogenesis of neutrophilic asthma and inhibition of the formation of NETs by Nec-1 may be a new therapeutic strategy to ameliorate neutrophil-dominated airway inflammation.

The enigmatic role of the neutrophil in asthma: Friend, foe or indifferent?

Whilst severe asthma has classically been categorized as a predominantly Th2-driven pathology, there has in recent years been a paradigm shift with the realization that it is a heterogeneous disease that may manifest with quite disparate underlying inflammatory and remodelling profiles. A subset of asthmatics, particularly those with a severe, corticosteroid refractory disease, present with a prominent neutrophilic component. Given the potential of neutrophils to impart extensive tissue damage and promote inflammation, it has been anticipated that these cells are closely implicated in the underlying pathophysiology of severe asthma. However, uncertainty persists as to why the neutrophil is present in the asthmatic lung and what precisely it is doing there, with evidence supporting its role as a protagonist of pathology being primarily circumstantial. Furthermore, our view of the neutrophil as a primitive, indiscriminate killer has evolved with the realization that neutrophils can exhibit a marked anti-inflammatory, pro-resolving and wound healing capacity. We suggest that the neutrophil likely exhibits pleiotropic and potentially conflicting roles in defining asthma pathophysiology-some almost certainly detrimental and some potentially beneficial-with context, timing and location all critical confounders. Accordingly, indiscriminate blockade of neutrophils with a broad sword approach is unlikely to be the answer, but rather we should first seek to understand their complex and multifaceted roles in the disease state and then target them with the same subtleties and specificity that they themselves exhibit.

The effect of rhinovirus on airway inflammation in a murine asthma model

PURPOSE

The aim of the present study was to investigate the differences in lower airway inflammatory immune responses, including cellular responses and responses in terms of inflammatory mediators in bronchoalveolar lavage fluid (BALF) and the airway, to rhinovirus (RV) infection on asthma exacerbation by comparing a control and a murine asthma model, with or without RV infection.

METHODS

BALB/c mice were intraperitoneally injected with a crude extract of Dermatophagoides farinae (Df) or phosphate buffered saline (PBS) and were subsequently intranasally treated with a crude extract of Df or PBS. Airway responsiveness and cell infiltration, differential cell counts in BALF, and cytokine and chemokine concentrations in BALF were measured 24 hours after intranasal RV1B infection.

RESULTS

RV infection increased the enhanced pause (Penh) in both the Df sensitized and challenged mice (Df mice) and PBS-treated mice (PBS mice) (P<0.05). Airway eosinophil infiltration increased in Df mice after RV infection (P<0.05). The levels of interleukin (IL) 13, tumor necrosis factor alpha, and regulated on activation, normal T cells expressed and secreted (RANTES) increased in response to RV infection in Df mice, but not in PBS mice (P<0.05). The level of IL-10 significantly decreased following RV infection in Df mice (P<0.05).

CONCLUSION

Our findings suggest that the augmented induction of proinflammatory cytokines, Th2 cytokines, and chemokines that mediate an eosinophil response and the decreased induction of regulatory cytokines after RV infection may be important manifestations leading to airway inflammation with eosinophil infiltration and changes in airway responsiveness in the asthma model.

Elevated inflammatory markers at preschool age precede persistent wheezing at school age

BACKGROUND

  Wheeze is a heterogeneous symptom in preschool children. At preschool age it is hard to predict whether symptoms will pass or persist and develop into asthma. Our objective is to prospectively study whether inflammatory markers in exhaled breath condensate (EBC) and pre- and post-bronchodilator interrupter resistance (Rint) assessed at preschool age, are associated with wheezing phenotypes at school age.

METHODS

  Children (N = 230) were recruited from the Asthma DEtection and Monitoring (ADEM) study. At preschool age [mean (SE): 3.3 (0.1) yr], pre- and post-bronchodilator Rint was assessed. EBC was collected using a closed glass condenser. Inflammatory markers (IL-2, IL-4, IL-8, IL-10, sICAM) were measured using multiplex immunoassay. Wheezing phenotypes at 5 yr of age were determined based on longitudinal assessment. Children were classified as: never (N = 47), early-transient (N = 89) or persistent wheezers (N = 94).

RESULTS

  Persistent wheezers had elevated levels of all interleukins at preschool age compared to children who never wheezed (p < 0.05). EBC markers did not differ between the persistent and transient wheezers. There was no marked difference in Rint between wheezing phenotypes.

CONCLUSIONS

  We demonstrated that 5 yr old children with persistent wheeze already had elevated exhaled inflammatory markers at preschool age compared to never wheezers, indicating augmented airway inflammation in these children.

Can exhaled inflammatory markers predict a steroid response in wheezing preschool children?

BACKGROUND

The efficacy of inhaled corticosteroids (ICS) varies among wheezing preschool children. Currently, it is not possible to predict which fraction of wheezing children will benefit from an ICS treatment.

OBJECTIVE

We explored whether fractional exhaled nitric oxide (FeNO) and inflammatory markers in exhaled breath condensate (EBC) can predict an ICS response in preschool wheezers.

METHODS

An 8-week ICS study (registered at Clinicaltrial.gov: NCT 00422747; 200 μg; beclomethasone extra-fine daily) was performed in 93 wheezing children (age range 2.0-4.4 years). At baseline, FeNO was determined off-line. EBC was collected using a closed glass-condenser. The acidity of EBC was determined and other EBC markers [interleukin (IL)-1α, IL-2, IL-4, IL-5, IL-10, soluble intercellular adhesion molecule, interferon-γ, eotaxin] were measured using a multiplex immunoassay. The change in airway resistance (Rint) and symptom score following ICS treatment was related to atopy (positive Phadiatop Infant test), FeNO and EBC markers.

RESULTS

Airway resistance and symptoms mildly improved after ICS treatment [median (IQR): 1.4 (1.2-1.7) to 1.3 (1.1-1.5) kPa s/L, symptom score: 26 (23-28) to 28 (24-29), P < 0.01, respectively]. Only IL-10 and atopy had limited predictive value regarding a change in symptoms [β (SE) =-0.13 (0.07), P = 0.08, β (SE) = 2.05 (1.17), P = 0.08, respectively].

CONCLUSIONS AND CLINICAL RELEVANCE

We did not find convincing evidence that FeNO and EBC markers could predict an ICS response in preschool wheezers. Recommendations for future studies on this topic are given.

Immunobiology of asthma

Asthma is characterized by chronic inflammation of the airways in which there is an overabundance of eosinophils, mast cells, and activated T helper lymphocytes. These inflammatory cells release mediators that then trigger bronchoconstriction, mucus secretion, and remodeling. The inflammatory mediators that drive this process include cytokines, chemokines, growth factors, lipid mediators, immunoglobulins, and histamine. The inflammation in allergic asthma can be difficult to control. This is mainly due to the development of an adaptive immunity to an allergen, leading to immunological memory. This leads to recall reactions to the allergen, causing persistent inflammation and damage to the airways. Generally, in asthma inflammation is directed by Th2 cytokines, which can act by positive feedback mechanisms to promote the production of more inflammatory mediators including other cytokines and chemokines. This review discusses the role of cytokines and chemokines in the immunobiology of asthma and attempts to relate their expression to morphological and functional abnormalities in the lungs of asthmatic subjects. We also discuss new concepts in asthma immunology, in particular the role of cytokines in airway remodeling and the interaction between cytokines and infection.

Exhaled nitric oxide after a single dose of intramuscular triamcinolone in children with difficult to control asthma

In a previous study, we reported that intramuscular (IM) triamcinolone improves symptoms in children with difficult asthma. In 2005, we revised our difficult asthma protocol to include assessment of airway inflammation, both directly using sputum induction and indirectly by measurement of exhaled nitric oxide (eNO). In this retrospective review, we aimed to describe (i) the changes in eNO and symptoms after a single 60 mg dose of IM triamcinolone and (ii) the changes in inflammatory markers in the subgroup with non-eosinophilic asthma (i.e., an induced sputum eosinophil differential count <2.0%). Seven children received IM triamcinolone during the study period. In all children, symptom scores fell in the week following the IM injection (P < 0.01 vs. the pre-treatment week), and remained reduced for up to 6 weeks. eNO also fell within a week after IM therapy (P < 0.01), and remained reduced for up to 4 weeks. Non-eosinophilic asthma was definitively identified in three children, and in this group, eNO and symptoms fell after the IM injection. We conclude that IM triamcinolone therapy reduces both eNO and symptoms for up to 4 weeks in children with difficult asthma. Our data provide preliminary evidence that IM triamcinolone is an effective anti-inflammatory therapy in children with induced sputum non-eosinophilic asthma.