Eosinophil survival and apoptosis in health and disease

Wnt Signaling in the Regulation of Immune Cell and Cancer Therapeutics

Wnt signaling is one of the important pathways to play a major role in various biological processes, such as embryonic stem-cell development, tissue regeneration, cell differentiation, and immune cell regulation. Recent studies suggest that Wnt signaling performs an essential function in immune cell modulation and counteracts various disorders. Nonetheless, the emerging role and mechanism of action of this signaling cascade in immune cell regulation, as well as its involvement in various cancers, remain debatable. The Wnt signaling in immune cells is very diverse, e.g., the tolerogenic role of dendritic cells, the development of natural killer cells, thymopoiesis of T cells, B-cell-driven initiation of T-cells, and macrophage actions in tissue repair, regeneration, and fibrosis. The purpose of this review is to highlight the current therapeutic targets in (and the prospects of) Wnt signaling, as well as the potential suitability of available modulators for the development of cancer immunotherapies. Although there are several Wnt inhibitors relevant to cancer, it would be worthwhile to extend this approach to immune cells.

Expression of eosinophil β chain-signaling cytokines receptors, outer-membrane integrins, and type 2 inflammation biomarkers in severe non-allergic eosinophilic asthma

Background

Severe non-allergic eosinophilic asthma (SNEA) is a rare asthma phenotype associated with severe clinical course, frequent exacerbations, and resistance to therapy, including high steroid doses. The key feature is type 2 inflammation with predominant airway eosinophilia. Eosinophil maturation, activation, survivability, and recruitment are mainly induced by interleukin (IL)-3, IL-5 and granulocyte–macrophage colony-stimulating factor (GM-CSF) through their receptors on eosinophil surface and related with integrins activation states. The aim of the study was to estimate the expression of eosinophil β chain-signaling cytokines receptors, outer-membrane integrins, and serum-derived type 2 inflammation biomarkers in SNEA.

Methods

We examined 8 stable SNEA patients with high inhaled steroid doses, 12 steroid-free patients with non-severe allergic asthma (AA), 12 healthy subjects (HS). Blood eosinophils were isolated using Ficol gradient centrifugation and magnetic separation. Eosinophils were lysed, and mRNA was isolated. Gene expressions of IL-5Rα, IL-3Rα, GM-CSFRα, and α4β1, αMβ2 integrins were analyzed using quantitative real-time reverse transcription polymerase chain reaction. Type 2 inflammation activity was evaluated measuring exhaled nitric oxide concentration (FeNO) collected with the electrochemical sensing device. Serum IL-5, IL-3, GM-CSF, periostin, chemokine ligand (CCL) 17 and eotaxin concentrations were assessed by enzyme-linked immunosorbent assay.

Results

Eosinophils from SNEA patients demonstrated significantly increased gene expression of IL-3Rα, IL-5Rα and GM-CSFRα as well as α4, β1 and αM integrin subunits compared with the AA group. The highest IL-5 serum concentration was in the SNEA group; it significantly differed compared with AA and HS. GM-CSF serum levels were similar in the SNEA and AA groups and were significantly lower in the HS group. No differences in serum IL-3 concentration were found among all groups. Furthermore, serum levels of eotaxin, CCL17 and FeNO, but not periostin, differed in all groups, with the highest levels in SNEA patients.

Conclusions

Eosinophil demonstrated higher expression of IL-3, IL-5, GM-CSF α-chain receptors and α4, β1, αM integrins subunits in SNEA compared with the AA group. Additionally, SNEA patients had increased serum levels of IL-5, eotaxin and CCL-17.

Trial registration

ClinicalTrials.gov Identifier NCT03388359.

Genetic Variation in Surfactant Protein-A2 Delays Resolution of Eosinophilia in Asthma

Surfactant protein-A (SP-A) is an important mediator of pulmonary immunity. A specific genetic variation in SP-A2, corresponding to a glutamine (Q) to lysine (K) amino acid substitution at position 223 of the lectin domain, was shown to alter the ability of SP-A to inhibit eosinophil degranulation. Because a large subgroup of asthmatics have associated eosinophilia, often accompanied by inflammation associated with delayed clearance, our goal was to define how SP-A mediates eosinophil resolution in allergic airways and whether genetic variation affects this activity. Wild-type, SP-A knockout (SP-A KO) and humanized (SP-A2 223Q/Q, SP-A2 223K/K) C57BL/6 mice were challenged in an allergic OVA model, and parameters of inflammation were examined. Peripheral blood eosinophils were isolated to assess the effect of SP-A genetic variation on apoptosis and chemotaxis. Five days postchallenge, SP-A KO and humanized SP-A2 223K/K mice had persistent eosinophilia in bronchoalveolar lavage fluid compared with wild-type and SP-A2 223Q/Q mice, suggesting an impairment in eosinophil resolution. In vitro, human SP-A containing either the 223Q or the 223K allele was chemoattractant for eosinophils whereas only 223Q resulted in decreased eosinophil viability. Our results suggest that SP-A aids in the resolution of allergic airway inflammation by promoting eosinophil clearance from lung tissue through chemotaxis, independent of SP-A2 Q223K, and by inducing apoptosis of eosinophils, which is altered by the polymorphism.

Eosinophils: Nemeses of Pulmonary Pathogens?

PURPOSE OF REVIEW

Eosinophils are short-lived granulocytes that contain a variety of proteins and lipids traditionally associated with host defense against parasites. The primary goal of this review is to examine more recent evidence that challenged this rather outdated role of eosinophils in the context of pulmonary infections with helminths, viruses, and bacteria.

RECENT FINDINGS

While eosinophil mechanisms that counter parasites, viruses, and bacteria are similar, the kinetics and impact may differ by pathogen type. Major antiparasitic responses include direct killing and immunoregulation, as well as some mechanisms by which parasite survival/growth is supported. Antiviral defenses may be as unembellished as granule protein-induced direct killing or more urbane as serving as a conduit for better adaptive immune responses to the invading virus. Although sacrificial, eosinophil DNA emitted in response to bacteria helps trap bacteria to limit dissemination. Herein, we discuss the current research redefining eosinophils as multifunctional cells that are active participants in host defense against lung pathogens. Eosinophils recognize and differentially respond to invading pathogens, allowing them to deploy innate defense mechanisms to contain and clear the infection, or modulate the immune response. Modern technology and animal models have unraveled hitherto unknown capabilities of this surreptitious cell that indubitably has more functions awaiting discovery.

Impact of blood storage and sample handling on quality of high dimensional flow cytometric data in multicenter clinical research

Obtaining reliable and reproducible high quality data in multicenter clinical research settings requires design of optimal standard operating procedures. While the need for standardization in sample processing and data analysis is well-recognized, the impact of sample handling in the pre-analytical phase remains underestimated. We evaluated the impact of sample storage time (≈transport time) and temperature, type of anticoagulant, and limited blood volume on reproducibility of flow cytometric studies. EDTA and Na-Heparin samples processed with the EuroFlow bulk lysis protocol, stained and stored at 4 °C showed fairly stable expression of cell surface markers and distribution of the major leukocyte populations for up to 72 h. Additional sample fixation (1% PFA, Fix & Perm) did not have any beneficial effects. Blood samples stored for <24 h at room temperature before processing and staining seemed suitable for reliable immunophenotyping, although losses in absolute cell numbers were observed. The major losses were observed in myeloid cells and monocytes, while lymphocytes seemed less affected. Expression of cell surface markers and population distribution were more stable in Na-Heparin blood than in EDTA blood. However, storage of Na-Heparin samples was associated with faster decrease in leukocyte counts over time. Whole blood fixation strategies (Cyto-Chex, TransFix) improved long-term population distribution, but were detrimental for expression of cellular markers. The main conclusions from this study on healthy donor blood samples were successfully confirmed in EDTA clinical (patient) blood samples with different time delays until processing. Finally, we recognized the need for adjustments in bulk lysis in case of insufficient blood volumes. Despite clear overall conclusions, individual markers and cell populations had different preferred conditions. Therefore, specific guidelines for sample handling should always be adjusted to the clinical application and the main target leukocyte population.

Synergy of Interleukin (IL)-5 and IL-18 in eosinophil mediated pathogenesis of allergic diseases

Eosinophils are circulating granulocytes that have pleiotropic effects in response to inflammatory signals in the body. In response to allergens or pathogens, exposure eosinophils are recruited in various organs that execute pathological immune responses. IL-5 plays a key role in the differentiation, development, and survival of eosinophils. Eosinophils are involved in a variety of allergic diseases including asthma, dermatitis and various gastrointestinal disorders (EGID). IL-5 signal transduction involves JAK-STAT-p38MAPK-NFκB activation and executes extracellular matrix remodeling, EMT transition and immune responses in allergic diseases. IL-18 is a classical cytokine also involved in immune responses and has a critical role in inflammasome pathway. We recently identified the IL-18 role in the generation, transformation, and maturation of (CD101+CD274+) pathogenic eosinophils. In, addition, several other cytokines like IL-2, IL-4, IL-13, IL-21, and IL-33 also contribute in advancing eosinophils associated immune responses in innate and adaptive immunity. This review discusses with a major focus (1) Eosinophils and its constituents, (2) Role of IL-5 and IL-18 in eosinophils development, transformation, maturation, signal transduction of IL-5 and IL-18, (3) The role of eosinophils in allergic disorders and (4) The role of several other associated cytokines in promoting eosinophils mediated allergic diseases.

Long-term effects of biologic therapies on peripheral blood eosinophils in patients with psoriasis: a 3-year single-center study

Background: Biologic therapies (BTs), etanercept, infliximab, adalimumab, and ustekinumab, are generally well-tolerated and safe agents in psoriasis management.Objectives: To determine the overall effect of BTs on peripheral blood eosinophil count (PBEc) and percentage (PBEp), peripheral blood basophil count (PBBc) and percentage (PBBp), white blood cell count (WBCc), erythrocyte sedimentation rate (ESR), and serum C-reactive protein (s-CRP) level during a 3-year follow-up in patients with psoriasis.Methods: This retrospective cohort study included 200 patients (116 men; 84 women) treated continuously with BTs for 3 years for plaque-type, pustular, or nail psoriasis. Patient data were reviewed from medical charts. During routine laboratory investigation at baseline and every 3 months thereafter up to 3 years, the PBEp, PBEc, PBBp, PBBc, WBCc, ESR, and s-CRP level were monitored. Generalized estimating equations were used to compare consecutive data.Results: Seventy patients received infliximab (35%); 34 (17%), etanercept; 44 (22%), adalimumab; and 52 (26%), ustekinumab. The mean PBEp and PBEc significantly increased starting from 3 months after BT (both p<.001). The mean PBEp and PBEc significantly increased during follow-up compared with the baseline values (PBEp (%): 1.49 ± 0.1 (1st month) vs. 2.29 ± 0.14 (3rd month), p<.001 and 1.49 ± 0.1 (1st month) vs. 2.17 ± 0.18 (36th month), p=.004; PBEc (×10³/µL): 115.80 ± 6.32 (1st month) vs. 174.9 ± 10.08 (3rd month), p<.001 and 115.80 ± 6.32 (1st month) vs. 162.9 ± 12.86 (36th month), p<.001). However, the mean PBBp, PBBc, WBCc, ESR, and s-CRP level did not change significantly.Conclusions: The PBEc and PBEp increase with BTs up to 3 years in patients with psoriasis. This increase is observed at as early as 3 months of BT and maintained thereafter.

Active vaccination against interleukin-5 as long-term treatment for insect-bite hypersensitivity in horses

Background

Insect‐bite hypersensitivity (IBH) in horses is a chronic allergic dermatitis caused by insect bites. Horses suffer from pruritic skin lesions, caused by type‐I/type‐IV allergic reactions accompanied by prominent eosinophil infiltration into the skin. Interleukin‐5 (IL‐5) is the key cytokine for eosinophils and we have previously shown that targeting IL‐5 by vaccination reduces disease symptoms in horses.

Objective

Here, we analyzed the potential for long‐term therapy by assessing a second follow‐up year of the previously published study.

Methods

The vaccine consisted of equine IL‐5 (eIL‐5) covalently linked to a cucumber mosaic virus‐like particle (VLP) containing a universal T cell epitope (CuMV_TT) using a semi‐crossover design to follow vaccinated horses during a second treatment season. Thirty Icelandic horses were immunized with 300 μg of eIL‐5‐CuMV_TT without adjuvant.

Results

The vaccine was well tolerated and did not reveal any safety concerns throughout the study. Upon vaccination, all horses developed reversible anti‐eIL‐5 auto‐antibody titers. The mean course of eosinophil levels was reduced compared to placebo treatment leading to significant reduction of clinical lesion scores. Horses in their second vaccination year showed a more pronounced improvement of disease symptoms when compared to first treatment year, most likely due to more stable antibody titers induced by a single booster injection. Hence, responses could be maintained over two seasons and the horses remained protected against disease symptoms.

Conclusion

Yearly vaccination against IL‐5 may be a long‐term solution for the treatment of IBH and other eosinophil‐mediated diseases in horses and other species including humans.

Childhood asthma clusters reveal neutrophil-predominant phenotype with distinct gene expression

BACKGROUND

Childhood asthma comprises different phenotypes with complex pathophysiology. Different asthma phenotypes evoke various clinical symptoms and vary in their responses to treatments.

METHODS

We applied k-means clustering algorithm of twelve objective laboratory tests among 351 asthmatic children enrolled in the Taiwanese Consortium of Childhood Asthma Study (TCCAS). We constructed gene expression profiles of peripheral blood mononuclear cells (PBMC) from children with different asthma phenotypes.

RESULTS

Five distinct phenotypes of childhood asthma were identified and can be characterized by either eosinophil-predominant or neutrophil-predominant inflammatory characteristics. In the gene expression profile analysis, significant differences were noted for neutrophil-predominant asthma, compared with samples from all the other asthma phenotypes. The vast majority of the differentially expressed genes in neutrophil-predominant asthma was associated with corticosteroid response. From an independent inhaled corticosteroid (ICS) response cohort, we also found neutrophils could be activated in this severe asthma phenotype and neutrophil-predominant asthma may be associated with corticosteroid nonresponsiveness.

CONCLUSION

Phenotype clustering of childhood asthma can be helpful to identify clinically relevant patients and reveal different inflammatory characteristics in asthmatic children. Neutrophil-predominant asthma is the most severe asthma phenotype with poor corticosteroid response. Gene expression profile of different asthma phenotypes not only improve our knowledge of childhood asthma, but also can guide asthma precision medicine.

Risks and management of long-term corticosteroid use in chronic rhinosinusitis

PURPOSE OF REVIEW

The purpose of this review is to provide an update on the use and risks of long-term corticosteroids in the management of chronic rhinosinusitis (CRS).

RECENT FINDINGS

Long-term use of systemic corticosteroids is not indicated in the management of CRS due to the associated side effects and potential complications. Therefore, recent research has focused on the safety and efficacy of topical corticosteroid, particularly second-generation corticosteroids, and their modes of administration. Second-generation corticosteroids are more potent and have less systemic bioavailability than their first-generation counterparts. However, caution must be taken with concomitant use of more than two types of corticosteroids (topical, systemic, inhaled etc.) and also with their dosage and frequency of administration to avoid adrenal suppression, growth suppression in children, elevated intraocular pressure or epistaxis. Research is ongoing into therapies that may reduce corticosteroid resistance which has been demonstrated in some nasal polyps.

SUMMARY

Corticosteroids play an essential role in the management of CRS; however, use must be tailored to the patient-specific disease and requires ongoing review and regular reevaluation by their physician.

The Emerging Roles of Surfactant Protein-A in Asthma

Asthma remains one of the most common respiratory diseases in both children and adults affecting up to 10% of the US population. Asthma is characterized by persistent symptoms, airway inflammation, airflow limitation and frequent exacerbations. Eosinophils are a key immune cell present in a large majority of asthmatics and their presence and dysregulation are clinically associated with more severe asthma. Surfactant protein A (SP-A) provides a first-line of defense in pulmonary innate immunity by virtue of its role in pathogen opsonization. SP-A is known to specifically bind to Mycoplasma pneumoniae (Mp), a pathogen associated with asthma exacerbations, and functions to attenuate Mp pathogenicity and abrogate lung inflammation. In addition, SP-A has been shown to inhibit Mp-induced eosinophil peroxidase (EPO) release, a toxic product that can compromise the integrity of the delicate airway epithelia. We have determined that genetic variation in SP-A2 at position 223 that results in a glutamine (Q) to a lysine (K) substitution alters the ability of SP-A to inhibit EPO release and may offer a mechanistic explanation as to why some SP-A extracted from subjects with asthma is unable to carry out normal immune regulatory functions.

Emergence of Leptin in Infection and Immunity: Scope and Challenges in Vaccines Formulation

Deficiency of leptin (ob/ob) and/or desensitization of leptin signaling (db/db) and elevated expression of suppressor of cytokine signaling-3 (SOCS3) reported in obesity are also reported in a variety of pathologies including hypertriglyceridemia, insulin resistance, and malnutrition as the risk factors in host defense system. Viral infections cause the elevated SOCS3 expression, which inhibits leptin signaling. It results in immunosuppression by T-regulatory cells (Tregs). The host immunity becomes incompetent to manage pathogens' attack and invasion, which results in the accelerated infections and diminished vaccine-specific antibody response. Leptin was successfully used as mucosal vaccine adjuvant against Rhodococcus equi. Leptin induced the antibody response to Helicobacter pylori vaccination in mice. An integral leptin signaling in mucosal gut epithelial cells offered resistance against Clostridium difficile and Entameoba histolytica infections. We present in this review, the intervention of leptin in lethal diseases caused by microbial infections and propose the possible scope and challenges of leptin as an adjuvant tool in the development of effective vaccines.

Severe, eosinophilic asthma in primary care in Canada: a longitudinal study of the clinical burden and economic impact based on linked electronic medical record data

Background

Stratification of patients with severe asthma by blood eosinophil counts predicts responders to anti-interleukin (IL)-5 (mepolizumab and reslizumab) and anti-IL-5 receptor α (benralizumab) therapies. This study characterized patients with severe asthma who could qualify for these biologics in a primary care setting.

Methods

We retrospectively selected patients from July 1, 2010, to June 30, 2014, using a linked electronic medical records (EMR) database (IMS Evidence 360 EMR Canada) for > 950,000 patients in primary care in Ontario, Canada. Patients aged ≥ 12 years with ≥ 2 documented asthma diagnoses were identified as having severe asthma based on prescriptions for high-dosage inhaled corticosteroids (ICS) plus either a leukotriene receptor antagonist, long-acting β₂-agonist (LABA), or theophylline filled on the same day. Patients’ asthma was considered severe also if they received a prescription for ICS with oral corticosteroids (OCS) or an additional prescription for omalizumab. Patient characteristics, asthma-related medications, and blood eosinophil counts were captured using observed care patterns for the year prior to ICS/LABA and/or OCS prescription. Health care resource use (HCRU) and costs were captured throughout the 1-year follow-up period.

Results

We identified 212 patients who met the criteria for severe asthma. These patients required an average of 6.5 physician visits during the 1-year follow-up period (95% confidence interval 5.7–7.3), and 20 (9%) were referred to respiratory specialists. Overall, 56 patients (26%) with severe asthma had complete blood counts, of whom 23 (41%) had blood eosinophil counts ≥ 300 cells/μL and might be considered for anti-eosinophil therapies. Patients with severe asthma and blood eosinophil counts ≥ 300 cells/μL had more respiratory specialist referrals (17% vs. 12%) than patients with blood eosinophils < 300 cells/μL.

Conclusions

Our data suggest that during 2010–2014, Ontario primary care patients with severe asthma and high blood eosinophil counts had greater HRCU than those with lower counts. Approximately 41% of patients with severe asthma could qualify for anti-eosinophil drugs based on blood eosinophil counts. However, the eosinophilic status of most patients was unknown. It is appropriate to increase awareness of the use of blood eosinophil counts to identify patients who could be considered for anti-eosinophil therapies.

Treating insect-bite hypersensitivity in horses with active vaccination against IL-5

BACKGROUND

Insect-bite hypersensitivity is the most common allergic dermatitis in horses. Excoriated skin lesions are typical symptoms of this seasonal and refractory chronic disease. On a cellular level, the skin lesions are characterized by massive eosinophil infiltration caused by an underlying allergic response.

OBJECTIVE

To target these cells and treat disease, we developed a therapeutic vaccine against equine IL-5 (eIL-5), the master regulator of eosinophils.

METHODS

The vaccine consisted of eIL-5 covalently linked to a virus-like particle derived from cucumber mosaic virus containing the tetanus toxoid universal T-cell epitope tt830-843 (CMV_TT). Thirty-four Icelandic horses were recruited and immunized with 400 μg of eIL-5-CMV_TT formulated in PBS without adjuvant (19 horses) or PBS alone (15 horses).

RESULTS

The vaccine was well tolerated and did not reveal any safety concerns but was able to induce anti-eIL-5 autoantibody titers in 17 of 19 horses. This resulted in a statistically significant reduction in clinical lesion scores when compared with previous season levels, as well as levels in placebo-treated horses. Protection required a minimal threshold of anti-eIL-5 antibodies. Clinical improvement by disease scoring showed that 47% and 21% of vaccinated horses reached 50% and 75% improvement, respectively. In the placebo group no horse reached 75% improvement, and only 13% reached 50% improvement.

CONCLUSION

Our therapeutic vaccine inducing autoantibodies against self IL-5 brings biologics to horses, is the first successful immunotherapeutic approach targeting a chronic disease in horses, and might facilitate development of a similar vaccine against IL-5 in human subjects.

Marrow Adiposity and Hematopoiesis in Aging and Obesity: Exercise as an Intervention

PURPOSE OF REVIEW

Changes in the bone marrow microenvironment, which accompany aging and obesity, including increased marrow adiposity, can compromise hematopoiesis. Here, we review deleterious shifts in molecular, cellular, and tissue activity and consider the potential of exercise to slow degenerative changes associated with aging and obesity.

RECENT FINDINGS

While bone marrow hematopoietic stem cells (HSC) are increased in frequency and myeloid-biased with age, the effect of obesity on HSC proliferation and differentiation remains controversial. HSC from both aged and obese environment have reduced hematopoietic reconstitution capacity following bone marrow transplant. Increased marrow adiposity affects HSC function, causing upregulation of myelopoiesis and downregulation of lymphopoiesis. Exercise, in contrast, can reduce marrow adiposity and restore hematopoiesis. The impact of marrow adiposity on hematopoiesis is determined mainly through correlations. Mechanistic studies are needed to determine a causative relationship between marrow adiposity and declines in hematopoiesis, which could aid in developing treatments for conditions that arise from disruptions in the marrow microenvironment.

The diversity of myeloid immune cells shaping wound repair and fibrosis in the lung

In healthy circumstances the immune system coordinates tissue repair responses in a tight balance that entails efficient inflammation for removal of potential threats, proper wound closure, and regeneration to regain tissue function. Pathological conditions, continuous exposure to noxious agents, and even ageing can dysregulate immune responses after injury. This dysregulation can lead to a chronic repair mechanism known as fibrosis. Alterations in wound healing can occur in many organs, but our focus lies with the lung as it requires highly regulated immune and repair responses with its continuous exposure to airborne threats. Dysregulated repair responses can lead to pulmonary fibrosis but the exact reason for its development is often not known. Here, we review the diversity of innate immune cells of myeloid origin that are involved in tissue repair and we illustrate how these cell types can contribute to the development of pulmonary fibrosis. Moreover, we briefly discuss the effect of age on innate immune responses and therefore on wound healing and we conclude with the implications of current knowledge on the avenues for future research.

Enteric parasites can disturb leptin and adiponectin levels in children

INTRODUCTION

Infection by intestinal parasites in childhood may be the main cause of many health-related problems in developed countries such as anemia, anorexia, loss of appetite, retarded growth and development. The aim of the present study was to assess the effect of different intestinal parasites on white adipose tissue hormones.

MATERIAL AND METHODS

Eighty-one children infected by different parasites and 35 apparently healthy children were enrolled in this study. All patients and controls were subjected to clinical examination, measurement of body mass index (BMI) and laboratory examination.

RESULTS

For BMI percentiles, there was a significant increase in serum leptin level (p = 0.042) and a significant decrease in serum adiponectin level (p = 0.039) in uninfected children, whereas there were no significant changes in the infected group (p = 0.068 and 0.082 respectively). A significant increase in leptin and decrease in adiponectin levels were observed for E. histolytica, Strongyloides and E. histolytica and Giardia infections compared to the control group (p = 0.047, 0.035 and 0.019 for leptin, and p = 0.025, 0.038 and 0.041 for adiponectin, respectively).

CONCLUSIONS

The infection by some intestinal parasites may deregulate the secretion of leptin and adiponectin and also affect the absorption of some nutrients which can disturb the BMI and cause anorexia.

MHC Class II Activation and Interferon-γ Mediate the Inhibition of Neutrophils and Eosinophils by Staphylococcal Enterotoxin Type A (SEA)

Staphylococcal enterotoxins are classified as superantigens that act by linking T-cell receptor with MHC class II molecules, which are expressed on classical antigen-presenting cells (APC). Evidence shows that MHC class II is also expressed in neutrophils and eosinophils. This study aimed to investigate the role of MHC class II and IFN-γ on chemotactic and adhesion properties of neutrophils and eosinophils after incubation with SEA. Bone marrow (BM) cells obtained from BALB/c mice were resuspended in culture medium, and incubated with SEA (3–30 ng/ml; 1–4 h), after which chemotaxis and adhesion were evaluated. Incubation with SEA significantly reduced the chemotactic and adhesive responses in BM neutrophils activated with IL-8 (200 ng/ml). Likewise, SEA significantly reduced the chemotactic and adhesive responses of BM eosinophils activated with eotaxin (300 ng/ml). The inhibitory effects of SEA on cell chemotaxis and adhesion were fully prevented by prior incubation with an anti-MHC class II blocking antibody (2 μg/ml). SEA also significantly reduced the intracellular Ca²⁺ levels in IL-8- and eotaxin-activated BM cells. No alterations of MAC-1, VLA4, and LFA-1α expressions were observed after SEA incubation. In addition, SEA elevated by 3.5-fold (P < 0.05) the INF-γ levels in BM cells. Incubation of BM leukocytes with IFN-γ (10 ng/ml, 2 h) reduced both neutrophil and eosinophil chemotaxis and adhesion, which were prevented by prior incubation with anti-MHC class II antibody (2 μg/ml). In conclusion, SEA inhibits neutrophil and eosinophil by MHC class II-dependent mechanism, which may be modulated by concomitant release of IFN-γ.

Helminth antigens counteract a rapid high-fat diet-induced decrease in adipose tissue eosinophils

Brown adipose tissue (BAT) activation and white adipose tissue (WAT) beiging can increase energy expenditure and have the potential to reduce obesity and associated diseases. The immune system is a potential target in mediating brown and beige adipocyte activation. Type 2 and anti-inflammatory immune cells contribute to metabolic homeostasis within lean WAT, with a prominent role for eosinophils and interleukin (IL)-4-induced anti-inflammatory macrophages. We determined eosinophil numbers in epididymal WAT (EpAT), subcutaneous WAT (ScAT) and BAT after 1 day, 3 days or 1 week of high-fat diet (HFD) feeding in C57Bl/6 mice. One day of HFD resulted in a rapid drop in eosinophil numbers in EpAT and BAT, and after 3 days, in ScAT. In an attempt to restore this HFD-induced drop in adipose tissue eosinophils, we treated 1-week HFD-fed mice with helminth antigens from Schistosoma mansoni or Trichuris suis and evaluated whether the well-known protective metabolic effects of helminth antigens involves BAT activation or beiging. Indeed, antigens of both helminth species induced high numbers of eosinophils in EpAT, but failed to induce beiging. In ScAT, Schistosoma mansoni antigens induced mild eosinophilia, which was accompanied by slightly more beiging. No effects were observed in BAT. To study type 2 responses on brown adipocytes directly, T37i cells were stimulated with IL-4. This increased Ucp1 expression and strongly induced the production of eosinophil chemoattractant CCL11 (+26-fold), revealing that brown adipocytes themselves can attract eosinophils. Our findings indicate that helminth antigen-induced eosinophilia fails to induce profound beiging of white adipocytes.

Interleukin-5 Inhibitors for Severe Asthma: Rationale and Future Outlook

In this review, we outline the pathophysiology of severe asthma and discuss the role of anti-interleukin (IL)-5 inhibitors for the treatment of asthma. Anti-IL-5 treatments have shown efficacy in reducing the rate of severe asthma attacks in eosinophilic asthma. We review the history of the development of these agents, lessons learnt about severe asthma along the way and key clinical trials supporting efficacy of the three anti-IL-5 treatments that are clinically available or undergoing clinical trials in asthma.

The Innate Immune Cross Talk between NK Cells and Eosinophils Is Regulated by the Interaction of Natural Cytotoxicity Receptors with Eosinophil Surface Ligands

Previous studies suggested that the cross talk between NK cells and other cell types is crucial for the regulation of both innate and adaptive immune responses. In the present study, we analyzed the phenotypic and functional outcome of the interaction between resting or cytokine-activated NK cells and eosinophils derived from non-atopic donors. Our results provide the first evidence that a natural cytotoxicity receptor (NCR)/NCR ligand-dependent cross talk between NK cells and eosinophils may be important to upregulate the activation state and the effector function of cytokine-primed NK cells. This interaction also promotes the NK-mediated editing process of dendritic cells that influence the process of Th1 polarization. In turn, this cross talk also resulted in eosinophil activation and acquisition of the characteristic features of antigen-presenting cells. At higher NK/eosinophil ratios, cytokine-primed NK cells were found to kill eosinophils via NKp46 and NKp30, thus suggesting a potential immunoregulatory role for NK cells in dampening inflammatory responses involving eosinophils.

The effect of size-segregated ambient particulate matter on Th1/Th2-like immune responses in mice

Background

Particulate matter (PM) has been associated with increased pulmonary and cardiovascular mortality and morbidity. Additionally, PM is known to exacerbate asthma. However, whether ambient PM exposure contributes to the onset of asthma, especially in non-atopic children and adults, is less conclusive. The current study aimed to evaluate the effects of size-fractioned PM on lung immune responses in healthy BALB/c mice.

Methods and principal findings

We collected PM₁₀, PM_2.5, PM₁ and PM_0.1 samples from October 2012 to August 2013 in the Taipei Basin. These PM samples were representative of urban traffic pollution. The samples were extracted and sonicated in phosphate-buffered saline (PBS). Female BALB/c mice were exposed to the samples via intratracheal instillation at three different doses: 1.75 mg/kg (35 μg/per mouse), 5 mg/kg (100 μg/per mouse), and 12.5 mg/kg (250 μg/per mouse). The mice were exposed on days 0 and 7, and PBS alone was used as a control. Following the exposures, the expression profiles of inflammatory cells and cytokines in bronchoalveolar lavage fluid (BALF) were assessed. Exposure to PM₁₀ resulted in inflammatory responses, including the recruitment of neutrophils and the induction of T helper 1 (Th1) cell-related cytokine release, such as TNF-α and IFN-γ. Furthermore, an allergic immune response, including the recruitment of eosinophils and the up-regulation of T helper 2 (Th2) cell-related cytokine release, such as IL-5 and IL-13, was also observed in the BALF of mice exposed to PM₁₀.

Conclusions

Our study showed that exposure to PM alone caused mixed Th1/Th2 inflammatory responses in healthy mice. These findings support the hypothesis that PM may contribute to the onset of asthma.

Myeloid Cells in Asthma

Asthma is a heterogeneous chronic inflammatory disorder of the airways, and not surprisingly, many myeloid cells play a crucial role in pathogenesis. Antigen-presenting dendritic cells are the first to recognize the allergens, pollutants, and viruses that are implicated in asthma pathogenesis, and subsequently initiate the adaptive immune response by migrating to lymph nodes. Eosinophils are the hallmark of type 2 inflammation, releasing toxic compounds in the airways and contributing to airway remodeling. Mast cells and basophils control both the early- and late-phase allergic response and contribute to alterations in smooth muscle reactivity. Finally, relatively little is known about neutrophils and macrophages in this disease. Although many of these myeloid cells respond well to treatment with inhaled steroids, there is now an increasing armamentarium of targeted biologicals that can specifically eliminate only one myeloid cell population, like eosinophils. It is only with those new tools that we will be able to fully understand the role of myeloid cells in chronic asthma in humans.

Immune Cell Responses and Mucosal Barrier Disruptions in Chronic Rhinosinusitis

Chronic rhinosinusitis (CRS) is one of the most common presentations of upper airway illness and severely affects patient quality of life. Its frequency is not surprising given levels of environmental exposure to microbes, pollutants, and allergens. Inflammatory cells, inflammatory cytokine and chemokine production, and airway remodeling have been detected in the sinonasal mucosae of CRS patients, although the precise pathophysiological mechanisms causing such persistent inflammation remain unclear. Given its high prevalence and considerable associated morbidity, continued research into CRS is necessary to increase our understanding of factors likely to contribute to its pathogenesis, and facilitate the development of novel therapeutic strategies to improve treatment. The purpose of this review is to summarize the current state of knowledge regarding immune cell responses and epithelial alterations in CRS.

Bcl-2 inhibitors reduce steroid-insensitive airway inflammation

BACKGROUND

Asthmatic inflammation is dominated by accumulation of either eosinophils, neutrophils, or both in the airways. Disposal of these inflammatory cells is the key to disease control. Eosinophilic airway inflammation is responsive to corticosteroid treatment, whereas neutrophilic inflammation is resistant and increases the burden of global health care. Corticosteroid-resistant neutrophilic asthma remains mechanistically poorly understood and requires novel effective therapeutic strategies.

OBJECTIVE

We sought to explore the underlying mechanisms of airway inflammation persistence, as well as corticosteroid resistance, and to investigate a new strategy of effective treatment against corticosteroid-insensitive neutrophilic asthma.

METHODS

Mouse models of either eosinophil-dominated or neutrophil-dominated airway inflammation were used in this study to test corticosteroid sensitivity in vivo and in vitro. We also used vav-Bcl-2 transgenic mice to confirm the importance of granulocytes apoptosis in the clearance of airway inflammation. Finally, the Bcl-2 inhibitors ABT-737 or ABT-199 were tested for their therapeutic effects against eosinophilic or neutrophilic airway inflammation and airway hyperresponsiveness.

RESULTS

Overexpression of Bcl-2 protein was found to be responsible for persistence of granulocytes in bronchoalveolar lavage fluid after allergic challenge. This was important because allergen-induced airway inflammation aggravated and persisted in vav-Bcl-2 transgenic mice, in which nucleated hematopoietic cells were overexpressed with Bcl-2 and resistant to apoptosis. The Bcl-2 inhibitors ABT-737 or ABT-199 play efficient roles in alleviation of either eosinophilic or corticosteroid-resistant neutrophilic airway inflammation by inducing apoptosis of immune cells, such as eosinophils, neutrophils, T_H2 cells, T_H17 cells, and dendritic cells. Moreover, these inhibitors were found to be more efficient than steroids to induce granulocyte apoptosis ex vivo from patients with severe asthma.

CONCLUSION

Apoptosis of inflammatory cells is essential for clearance of allergen-induced airway inflammation. The Bcl-2 inhibitors ABT-737 or ABT-199 might be promising drugs for the treatment of airway inflammation, especially for corticosteroid-insensitive neutrophilic airway inflammation.

Prognostic Value of Eosinophil to Leukocyte Ratio in Patients with ST-Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

Aim: Leukocyte profile has been related to clinical outcome in patients with ST-segment elevation (STE) myocardial infarction (MI). However, whether eosinophil to leukocyte ratio (ELR) predicts clinical outcome in patients who have undergone primary percutaneous coronary intervention (PCI) remains unclear. Therefore, we examined the prognostic value of ELR in this patient population.

Methods: We retrospectively analyzed the data of 331 consecutive patients who underwent primary PCI for STEMI between January 2009 and March 2015. All leukocyte types were counted and ELR was calculated for all patients 24 h after hospital admission. The primary study endpoint was major adverse cardiac events (MACEs) within up to one year of follow-up duration.

Results: MACEs including cardiac deaths in 9.4% of the patients, MI in 1.5%, and target lesion or vessel revascularization in 10.3%, occurred within one year in 68 patients (20.5%). The mean ELR was significantly lower in patients with MACEs than in patients without MACEs (0.20 ± 0.51 vs. 0.49 ± 0.66, respectively; p < 0.001). An ELR < 0.1 at 24 h was identified as the best cut-off value for mortality prediction. Multivariate analysis identified that an ELR < 0.1 (odds ratio [OR] = 0.38; 95% confidence interval [CI] = 0.22–0.67; p < 0.001) and chronic kidney disease (OR = 2.38; CI = 1.33–4.24; p = 0.003) are independent predictors of MACEs.

Conclusion: In primary PCI patients with STEMI, ELR at 24 h was an independent predictor of MACEs in addition to the usual coronary risk factors and commonly used biomarkers.

The LINA Study: Higher Sensitivity of Infant Compared to Maternal Eosinophil/Basophil Progenitors to Indoor Chemical Exposures

Purpose. Enhanced eosinophil/basophil (Eo/B) progenitor cell levels are known to be associated with allergic inflammation and atopy risk. The aim of the present study was to investigate the influence of different indoor exposures on the recruitment and differentiation of Eo/B progenitors in mother-child pairs. Methods. In 68 mother-child pairs of the LINA study peripheral blood mononuclear cells were used to assess Eo/B colony forming units (CFUs). Information about disease outcomes and indoor exposures was obtained from questionnaires. Indoor concentrations of volatile organic compounds (VOCs) were measured by passive sampling. Results. Infant's Eo/B CFUs were positively associated with exposure to tobacco smoke, disinfectants, or VOCs. In contrast, for maternal Eo/B CFUs, only a few associations were seen. Higher numbers of infant Eo/B CFUs were observed in children with wheezing symptoms within the second year of life. Conclusions. We demonstrate that infant's hematopoietic cells seem to respond with more sensitivity to environmental exposure compared to maternal cells. At least in infants, an activation of these hematopoietic cells by environmental exposure could contribute to an enhanced risk for the development of respiratory outcomes.

Berberine improves airway inflammation and inhibits NF-κB signaling pathway in an ovalbumin-induced rat model of asthma

OBJECTIVES

Berberine has been reported for its various activities including anti-inflammatory effects and has been used in treating many diseases. However, its effects on airway inflammation in asthma have not been investigated. This study mainly aimed to detect its effects on the airway inflammation and the nuclear factor-κB (NF-κB) signaling pathway activity in a rat model of asthma.

METHODS

Asthma was induced by ovalbumin (OVA) sensitization and challenge. The asthmatic rats were respectively treated with vehicle PBS or berberine (100 mg/kg or 200 mg/kg) for 28 days. The control rats were treated with PBS. Inflammatory cells in bronchoalveolar lavage fluid (BALF) were counted and the lung inflammation was scored. Levels of NF-κB p65 (mRNA and protein), phosphorylated NF-κB p65 (p-NF-κB p65), inhibitory κB alpha (IκBα) (mRNA and protein) and phosphorylated IκBα (p-IκBα), as well as NF-κB p65 DNA-binding activity, were measured to assess the activity of NF-κB signaling pathway. Levels of the downstream inflammatory mediators of NF-κB signaling, IL-1β, IL-4, IL-5, IL-6, IL-13 and IL-17 in BALF, were measured. Besides, the serum levels of OVA-specific immunoglobulin (Ig)E were measured.

RESULTS

Results showed that OVA increased the number of inflammatory cells in BALF, elevated lung inflammation scores, enhanced the NF-κB signaling activity and promoted the production of IgE in rats. Berberine dose-dependently reversed the alterations induced by OVA in the asthmatic rats.

CONCLUSIONS

The findings suggested a therapeutic potential of berberine on OVA- induced airway inflammation. The ameliorative effects on the OVA-induced airway inflammation might be associated with the inhibition of the NF-κB signaling pathway.

Clinical implications of mucosal remodeling from chronic rhinosinusitis

BACKGROUND

Prognostic implications of mucosal remodeling in chronic rhinosinusitis (CRS) remain unclear. Remodeling of respiratory mucosa in asthma is associated with greater medication use and decreased function. This study investigates the implications of mucosal remodeling on long-term clinical outcomes in patients with CRS.

METHODS

A case-control study of adult patients with CRS undergoing endoscopic sinus surgery (ESS) was performed. Mucosal remodeling was defined by squamous metaplasia, subepithelial fibrosis, and/or basement membrane thickening. The presence of remodeling changes were assessed relative to clinical and treatment outcomes at a minimum of 12 months postoperatively. Clinical outcomes were assessed at baseline and 12 months using a Nasal Symptom Score (NSS) and 22-item Sino-Nasal Outcome Test (SNOT-22). Treatment outcomes were assessed by oral corticosteroid usage (burst/continuous), topical corticosteroid irrigation frequency, and further surgical intervention.

RESULTS

A total of 110 patients (48.73 ± 14.75 years, 48.2% female) were assessed. Significant improvements where seen for the entire population, in both NSS (2.64 ± 1.06 to 1.34 ± 1.08, p < 0.001) and SNOT-22 (2.05 ± 0.96 to 1.06 ± 0.79, p < 0.001). Patients with remodeling (n = 88) were younger (47.2 ± 14.8 vs 54.7 ± 13.5 years, p = 0.03), but had similar symptom scores. Remodeling was seen in CRS with nasal polyposis (CRSwNP) (54.5%) and eosinophilic chronic rhinosinusitis (eCRS) (59.8%). Symptom improvement at 12 months was similar between remodeled and non-remodeled groups (NSS: Δ1.34 ± 1.20 vs Δ1.12 ± 1.31, p = 0.395; SNOT-22: Δ1.05 ± 0.91 vs Δ0.73 ± 0.95, p = 0.124); however, patients with remodeling had greater corticosteroid irrigation frequency (64.0% vs 31.6% daily use, Kendall's tau-b p = 0.004).

CONCLUSION

Established mucosal remodeling predicts a greater reliance on topical therapies to reach similar clinical endpoints as those without remodeling.

Zinc oxide nanoparticles induce eosinophilic airway inflammation in mice

Zinc oxide nanoparticles (ZnO NPs) have been widely used in industry. The metal composition of PM2.5 might contribute to the higher prevalence of asthma. To investigate the effects of ZnO NPs on allergic airway inflammation, mice were first exposed to different concentrations of ZnO NPs (0.1 mg/kg, 0.5 mg/kg) or to a combination of ZnO NPs and chicken egg ovalbumin (OVA) by oropharyngeal aspiration on day 0 and day 7 and then were sacrificed 5 days later. The subsequent time course of airway inflammation in the mice after ZnO NPs exposure was evaluated on days 1, 7, and 14. To further determine the role of zinc ions, ZnCl2 was also administered. The inflammatory cell count, cytokine levels in the bronchoalveolar lavage fluid (BALF), and lung histopathology were examined. We found significant neutrophilia after exposure to high-dose ZnO NPs on day 1 and significant eosinophilia in the BALF at 7 days. However, the expression levels of the T helper 2 (Th2) cytokines IL-4, IL-5, and IL-13 increased significantly after 24h of exposure to only ZnO NPs and then decreased gradually. These results suggested that ZnO NPs could cause eosinophilic airway inflammation in the absence of allergens.

Transcription Factor Repertoire of Homeostatic Eosinophilopoiesis

The production of mature eosinophils (Eos) is a tightly orchestrated process with the aim to sustain normal Eos levels in tissues while also maintaining low numbers of these complex and sensitive cells in the blood. To identify regulators of homeostatic eosinophilopoiesis in mice, we took a global approach to identify genome-wide transcriptome and epigenome changes that occur during homeostasis at critical developmental stages, including Eos-lineage commitment and lineage maturation. Our analyses revealed a markedly greater number of transcriptome alterations associated with Eos maturation (1199 genes) than with Eos-lineage commitment (490 genes), highlighting the greater transcriptional investment necessary for differentiation. Eos-lineage-committed progenitors (EoPs) were noted to express high levels of granule proteins and contain granules with an ultrastructure distinct from that of mature resting Eos. Our analyses also delineated a 976-gene Eos-lineage transcriptome that included a repertoire of 56 transcription factors, many of which have never previously been associated with Eos. EoPs and Eos, but not granulocyte-monocyte progenitors or neutrophils, expressed Helios and Aiolos, members of the Ikaros family of transcription factors, which regulate gene expression via modulation of chromatin structure and DNA accessibility. Epigenetic studies revealed a distinct distribution of active chromatin marks between genes induced with lineage commitment and genes induced with cell maturation during Eos development. In addition, Aiolos and Helios binding sites were significantly enriched in genes expressed by EoPs and Eos with active chromatin, highlighting a potential novel role for Helios and Aiolos in regulating gene expression during Eos development.

Staphylococcal enterotoxin A regulates bone marrow granulocyte trafficking during pulmonary inflammatory disease in mice

Pulmonary neutrophil infiltration produced by Staphylococcal enterotoxin A (SEA) airway exposure is accompanied by marked granulocyte accumulation in bone marrow (BM). Therefore, the aim of this study was to investigate the mechanisms of BM cell accumulation, and trafficking to circulating blood and lung tissue after SEA airway exposure. Male BALB/C mice were intranasally exposed to SEA (1μg), and at 4, 12 and 24h thereafter, BM, circulating blood, bronchoalveolar lavage (BAL) fluid and lung tissue were collected. Adhesion of BM granulocytes and flow cytometry for MAC-1, LFA1-α and VLA-4 and cytokine and/or chemokine levels were assayed after SEA-airway exposure. Prior exposure to SEA promoted a marked PMN influx to BAL and lung tissue, which was accompanied by increased counts of immature and/or mature neutrophils and eosinophils in BM, along with blood neutrophilia. Airway exposure to SEA enhanced BM neutrophil MAC-1 expression, and adhesion to VCAM-1 and/or ICAM-1-coated plates. Elevated levels of GM-CSF, G-CSF, INF-γ, TNF-α, KC/CXCL-1 and SDF-1α were detected in BM after SEA exposure. SEA exposure increased production of eosinopoietic cytokines (eotaxin and IL-5) and BM eosinophil VLA-4 expression, but it failed to affect eosinophil adhesion to VCAM-1 and ICAM-1. In conclusion, BM neutrophil accumulation after SEA exposure takes place by integrated action of cytokines and/or chemokines, enhancing the adhesive responses of BM neutrophils and its trafficking to lung tissues, leading to acute lung injury. BM eosinophil accumulation in SEA-induced acute lung injury may occur via increased eosinopoietic cytokines and VLA-4 expression.

Cellular mechanisms underlying eosinophilic and neutrophilic airway inflammation in asthma

Asthma is a phenotypically heterogeneous chronic disease of the airways, characterized by either predominant eosinophilic or neutrophilic, or even mixed eosinophilic/neutrophilic inflammatory patterns. Eosinophilic inflammation can be associated with the whole spectrum of asthma severity, ranging from mild-to-moderate to severe uncontrolled disease, whereas neutrophilic inflammation occurs mostly in more severe asthma. Eosinophilic asthma includes either allergic or nonallergic phenotypes underlying immune responses mediated by T helper (Th)2 cell-derived cytokines, whilst neutrophilic asthma is mostly dependent on Th17 cell-induced mechanisms. These immune-inflammatory profiles develop as a consequence of a functional impairment of T regulatory (Treg) lymphocytes, which promotes the activation of dendritic cells directing the differentiation of distinct Th cell subsets. The recent advances in the knowledge of the cellular and molecular mechanisms underlying asthmatic inflammation are contributing to the identification of novel therapeutic targets, potentially suitable for the implementation of future improvements in antiasthma pharmacologic treatments.

Domestic exposure to volatile organic compounds in relation to asthma and allergy in children and adults

Over the past decades, the prevalence of asthma, allergic disease and atopy has increased significantly and in parallel with the increased use of products and materials emitting volatile organic compounds (VOCs) in the indoor environment. The purpose of this review is to examine the evidence of the relationship between quantitatively measured domestic exposure to VOCs and allergic diseases and allergy in children and adults. Sources, potential immune-inflammatory mechanisms and risks for development and severity of asthma and allergy have been addressed. Available evidence is based on studies that have mainly used observational designs of variable quality. Total, aromatic, aliphatic, microbial VOCs and aldehydes have been the most widely investigated VOC classes, with formaldehyde being the most commonly examined single compound. Overall, the evidence is inadequate to draw any firm conclusions. However, given indicative evidence from a few high-quality studies and significant potential for improvements in asthma outcomes in those with established disease, there is a need to consider undertaking further investigation of the relationship between domestic VOC exposure and asthma/allergy outcomes that should encompass both high-quality, robust observational studies and ultimately clinical trials assessing the impact of interventions that aim to reduce VOC exposure in children and adults with asthma.

Adult asthma biomarkers

PURPOSE OF REVIEW

A variety of novel asthma treatments have been developed based on phenotypes, and the clinical trial results show promising responses. This review summarizes the current knowledge of biomarkers for the determination of asthma phenotypes.

RECENT FINDINGS

Eosinophilic inflammation is the most focused phenotype because most novel asthma treatments have targeted T-helper type 2 (Th2) pathway. Fractional-exhaled nitric oxide (FeNO) is a new method that represents an eosinophilic airway inflammation with a significant correlation with sputum eosinophilia and asthma severity instead of sputum eosinophil count that easily influenced by corticosteroid therapy. However, some reports indicated the discordance between treatment response or adjustment and FeNO levels. Serum periostin is a strong serum biomarker for eosinophilic airway inflammation and an indicator of Th2-targeted therapy (such as lebrikizumab or omalizumab) and airflow limitation. YKL-40 is associated with asthma severity and airway remodeling. In addition, genetic and metabolomic approaches have been made to determine asthma phenotypes and severity.

SUMMARY

Biomarkers such as FeNO and serum periostin represent eosinophilic airway inflammation, together with eosinophil-derived neurotoxin and osteopontin (OPN) needed more replication studies. Periostin, YKL-40, OPN and some metabolites (choline, arginine, acetone and protectin D1) are related to asthma severity and airflow limitation.

Eosinophils as a pharmacological target for the treatment of allergic diseases

Eosinophils are innate immune cells and active players in inflammatory responses. Their activation and increased levels in the blood and at specific sites are associated with parasitic infections and several inflammatory conditions, notably allergic diseases in which eosinophils are considered to be damaging cells. Intervention targeting eosinophils is thought to prevent and/or limit irreversible organ damage and other eosinophil-associated disorders like hypereosinophilic syndromes, some cancers and autoimmune diseases. Several eosinophil-targeted therapeutic agents which block specific steps in eosinophil differentiation, migration and activation have recently been developed, showing encouraging results and new insights into their specific role in allergy. Here, we review some potentially effective drug compounds, their drawbacks and future prospective focusing on allergic diseases.

Eosinophils in the lung - modulating apoptosis and efferocytosis in airway inflammation

Due to the key role of the lung in efficient transfer of oxygen in exchange for carbon dioxide, a controlled inflammatory response is essential for restoration of tissue homeostasis following airway exposure to bacterial pathogens or environmental toxins. Unregulated or prolonged inflammatory responses in the lungs can lead to tissue damage, disrupting normal tissue architecture, and consequently compromising efficient gaseous exchange. Failure to resolve inflammation underlies the development and/or progression of a number of inflammatory lung diseases including asthma. Eosinophils, granulocytic cells of the innate immune system, are primarily involved in defense against parasitic infections. However, the propagation of the allergic inflammatory response in chronic asthma is thought to involve excessive recruitment and impaired apoptosis of eosinophils together with defective phagocytic clearance of apoptotic cells (efferocytosis). In terms of therapeutic approaches for the treatment of asthma, the widespread use of glucocorticoids is associated with a number of adverse health consequences after long-term use, while some patients suffer from steroid-resistant disease. A new approach for therapeutic intervention would be to promote the resolution of inflammation via modulation of eosinophil apoptosis and the phagocytic clearance of apoptotic cells. This review focuses on the mechanisms underpinning eosinophil-mediated lung damage, currently available treatments and therapeutic targets that might in future be harnessed to facilitate inflammation resolution by the manipulation of cell survival and clearance pathways.

The LINA cohort: Cord blood eosinophil/basophil progenitors predict respiratory outcomes in early infancy

RATIONALE

Cord blood eosinophil/basophil progenitor cells (Eo/B) of high risk infants have been shown to predict respiratory illnesses in infancy. Here we investigated this association in a population-based cohort. Furthermore, we analysed whether newborns Th1/Th2 balance and prenatal environmental exposure impact Eo/B recruitment.

METHODS

In a sub-cohort of the LINA study cord blood mononuclear cells were used for methylcellulose assays to assess Eo/B differentiation. Questionnaires were recorded during pregnancy and annually thereafter. Volatile organic compounds were measured during pregnancy and cord blood cytokines after ex vivo stimulation.

RESULTS

Cord blood IL-4 and IL-13 positively correlated with Eo/B. Tobacco smoke related benzene was also positively associated with Eo/B. Enhanced Eo/B numbers increased the risk for wheezing within the first 24 months.

CONCLUSIONS

The association between cord blood Eo/B and respiratory illnesses is not restricted to high-risk children. Prenatal environmental exposure and a Th2 milieu at birth contribute to Eo/B recruitment.

Tumour necrosis factor-α regulates human eosinophil apoptosis via ligation of TNF-receptor 1 and balance between NF-κB and AP-1

Eosinophils play a central role in asthma. The present study was performed to investigate the effect of tumour necrosis factor-α (TNF-α) on longevity of isolated human eosinophils. In contrast to Fas, TNF-α inhibited eosinophil apoptosis as evidenced by a combination of flow cytometry, DNA fragmentation assay and morphological analyses. The effect of TNF-α on eosinophil apoptosis was reversed by a TNF-α neutralising antibody. The anti-apoptotic effect of TNF-α was not due to autocrine release of known survival-prolonging cytokines interleukins 3 and 5 or granulocyte-macrophage-colony-stimulating factor as their neutralisation did not affect the effect of TNF-α. The anti-apoptotic signal was mediated mainly by the TNF-receptor 1. TNF-α induced phosphorylation and degradation of IκB and an increase in NF-κB DNA-binding activity. The survival-prolonging effect of TNF-α was reversed by inhibitors of NF-κB pyrrolidinedithiocarbamate and gliotoxin and by an inhibitor of IκB kinase, BMS-345541. TNF-α induced also an increase in AP-1 DNA-binding activity and the antiapoptotic effect of TNF-α was potentiated by inhibitors of AP-1, SR 11302 and tanshinone IIA and by an inhibitor of c-jun-N-terminal kinase, SP600125, which is an upstream kinase activating AP-1. Our results thus suggest that TNF-α delays human eosinophil apoptosis via TNF-receptor 1 and the resulting changes in longevity depend on yin-yang balance between activation of NF-κB and AP-1.

Regulation of spontaneous eosinophil apoptosis-a neglected area of importance

Asthma is characterized by the accumulation of eosinophils in the airways in most phenotypes. Eosinophils are inflammatory cells that require an external survival-prolonging stimulus such as granulocyte macrophage-colony-stimulating factor (GM-CSF), interleukin (IL)-5, or IL-3 for survival. In their absence, eosinophils are programmed to die by spontaneous apoptosis in a few days. Eosinophil apoptosis can be accelerated by Fas ligation or by pharmacological agents such as glucocorticoids. Evidence exists for the relevance of these survival-prolonging and pro-apoptotic agents in the regulation of eosinophilic inflammation in inflamed airways. Much less is known about the physiological significance and mechanisms of spontaneous eosinophil apoptosis even though it forms the basis of regulation of eosinophil longevity by pathophysiological factors and pharmacological agents. This review concentrates on discussing the mechanisms of spontaneous eosinophil apoptosis compared to those of glucocorticoid- and Fas-induced apoptosis. We aim to answer the question whether the external apoptotic stimuli only augment the ongoing pathway of spontaneous apoptosis or truly activate a specific pathway.

Neutrophil and macrophage apoptosis in bronchoalveolar lavage fluid from healthy horses and horses with recurrent airway obstruction (RAO)

BACKGROUND

Dysregulation of apoptosis has been implicated in a range of diseases including tumors, neurodegenerative and autoimmune diseases, as well as allergic asthma and chronic obstructive pulmonary disease (COPD) in humans. Although it has a different pathophysiology, delayed apoptosis of various inflammatory cells may play a pivotal role in the development of recurrent airway obstruction (RAO) in horses. Reduction of inflammatory cell apoptosis or a dysregulation of this process could lead to chronic inflammation and tissue injury. Therefore, the aim of this study was to investigate the rate of apoptosis and necrosis of neutrophils and macrophages in bronchoalveolar lavage fluid obtained from seven horses suffering from RAO (study group) and seven control horses.

RESULTS

We demonstrated that neutrophil/macrophage apoptosis is altered in RAO-affected horses compared with the control group in the BAL fluid. We found a significant difference between the median percentage of early and late apoptosis of neutrophils between the study and control group of horses. Moreover, we found a positive correlation between the rate of apoptosis and the median percentage of macrophages in RAO-affected horses.

CONCLUSION

The findings suggest that apoptosis dysregulation may play a significant role in the pathogenesis of RAO. However, further studies are needed to clarify the role of altered apoptosis in the course of equine recurrent airway obstruction.

Assays of eosinophil apoptosis and phagocytic uptake

Eosinophilic inflammation plays an important role in driving a variety of inflammatory and allergic conditions. Delineating the mechanisms by which these terminally differentiated granulocytes undergo programmed cell death (apoptosis) and their subsequent clearance by surrounding phagocytes are central to understanding disease pathogenesis and development of novel pharmacological agents. Dysregulation of the processes of either apoptosis or phagocytosis can result in chronic inflammation and disease progression due to either increased eosinophil life-span or cell necrosis with loss of cell membrane integrity and release of toxic intracellular mediators. A variety of in vitro methods have therefore been developed to understand these mechanisms in isolated primary human eosinophils. Here we describe the key assays used to study eosinophil apoptosis and the intracellular signalling pathways involved as well as phagocytic clearance of these cells.

Eosinophil apoptosis as a therapeutic target in allergic asthma

Asthma is a chronic inflammatory disease of the airways manifesting in many different phenotypes. Allergic asthma, comprising approximately half of patients with asthma, is characterized by the accumulation of eosinophils into the lungs. Eosinophils release factors that damage the surrounding cells and participate in the maintenance and exacerbation of inflammation. In the absence of any inflammatory survival-prolonging factors, eosinophils die by apoptosis in few days but in inflamed airways, eosinophil survival is thought to be prolonged due to the surrounding pro-inflammatory factors such as IL-5, IL-3 and GM-CSF. Resolution of eosinophilic inflammation is an important goal in the treatment of allergic asthma. Apoptosis is a physiological and non-inflammatory way to eliminate these harmful cells, and development of drugs targeting eosinophil apoptosis is one possible strategy for the therapy of allergic asthma. Importance of this strategy is supported by the fact that promotion of eosinophil apoptosis is a property of many anti-asthmatic agents such as glucocorticoids, the current main anti-inflammatory therapy of asthma, theophylline and leukotriene modifiers. β2 agonists have been shown to modulate eosinophil longevity by increasing survival. Also, anti-IL-5 antibody mesolizumab has shown efficacy in reducing asthma exacerbations in patients with severe eosinophilic asthma. Many potential future anti-asthmatic agents, such as Siglec-8 activating antibody and novel humanized anti-IL-5 antibody MEDI-563, have the property of inducing eosinophil apoptosis. This MiniReview aims to present eosinophil apoptosis as a therapeutic target in the treatment of allergic asthma. We summarize the effects and mechanisms of current and potential future anti-asthmatic drugs on eosinophil apoptosis and additionally, discuss the potential factors that promote eosinophil longevity in the lungs.

A case of idiopathic hypereosinophilic syndrome presenting with acute respiratory distress syndrome

Although idiopathic hypereosinophilic syndrome(IHES) commonly involves the lung, it is rarely associated with acute respiratory distress syndrome (ARDS). Here we describe a case of IHES presented in conjunction with ARDS. A 37-year-old male visited the emergency department at Samsung Medical Center, Seoul, Korea, with a chief complaint of dyspnea. Blood tests showed profound peripheral eosinophilia and thrombocytopenia. Patchy areas of consolidation with ground-glass opacity were noticed in both lower lung zones on chest radiography. Rapid progression of dyspnea and hypoxia despite supplement of oxygen necessitated the use of mechanical ventilation. Eosinophilic airway inflammation was subsequently confirmed by bronchoalveolar lavage, leading to a diagnosis of IHES. High-dose corticosteroids were administered, resulting in a dramatic clinical response.

Living and dying for inflammation: neutrophils, eosinophils, basophils

Neutrophils, eosinophils, and basophils play essential roles during microbe-induced and sterile inflammation. The severity of such inflammatory processes is controlled, at least in part, by factors that regulate cell death and survival of granulocytes. In recent years, major progress has been made in understanding the molecular mechanisms of granulocyte cell death and in identifying novel damage- and pathogen-associated molecular patterns as well as regulatory cytokines impacting granulocyte viability. Furthermore, an increased interest in innate immunity has boosted our overall understanding of granulocyte biology. In this review, we describe and compare factors and mechanisms regulating neutrophil, eosinophil, and basophil lifespan. Because dysregulation of death pathways in granulocytes can contribute to inflammation-associated immunopathology, targeting granulocyte lifespan could be therapeutically promising.