Eosinophil Degranulation Research Articles

A205 EVALUATING THE ASSOCIATION BETWEEN PERIPHERAL BLOOD EOSINOPHILS AND DRUG RESPONSE IN CROHN'S DISEASE: CONTINUING ANALYSIS

Abstract Background Th2 cytokines, IL-5 and IL-13 enhance peripheral and mucosal eosinophil survival, recruitment and degranulation, facilitating inflammation in Crohn's Disease. In a preliminary analysis, peripheral eosinophilia (PBE) is seen to have an association with rates of steroid response and anti-TNF response in CD patients. Participants with high PBE (> 200 cells/μL) appear to be more steroid-responsive but less responsive to Th1-targeting anti-TNF therapies. We hypothesize the pattern of PBE at CD diagnosis can help identify distinct subsets within a larger CD population and correlate with response to treatments such as prednisone or anti-TNFs. Purpose We aim to evaluate the pattern of PBE of CD patients at time of diagnosis (prior to drug exposure) and with each subsequent treatment; and if baseline PBE or any changes seen with drug exposures are predictive of treatment response. Method A retrospective cohort study is ongoing with CD patients exposed to glucocorticoids and an anti-TNF seen at 3 hospitals affiliated with University of Western Ontario. Patients were identified using administrative databases and reviewed for biochemical data (complete blood count) and disease activity (Harvey Bradshaw Index) at baseline, before and after each drug exposure. Participants were classified as having high PBE (eosinophils>200 cells/μL) versus low PBE (eosinophils <200 cells/μL). To date, 350 patients have been screened. Subgroup analyses of PBE > 300 cells/μL, and differences between female and male patients will be carried out. Result(s) 46 of 200 CD patients are included in the continuing analysis with a mean age of 45 years. 26 had PBE >200 cells/μL at baseline and 20 did not. The median number therapies used was 4 (IQR=0.75). All received glucocorticoids followed by an anti-TNF. There was no difference in the occurrence of hospitalization or surgery between the two groups. Overall 50% participants with high PBE >200 and >300 cells/μL had clinical response to glucocorticoid exposure, seen as a 3-point decrease in HBI compared to 45%, 47% in the low PBE cohort (n=13/26 vs. n=9/20 p=0.77; n=6/12 vs. n=16/34 p=1.0 respectively). With subsequent anti-TNF exposure, PBE rebounded in 7 participants. 36% patients in the high PBE group required anti-TNF dose escalation versus 24% in the low PBE group (n=9/25 vs. n=5/21, p=0.52). The proportion of patients with anti-TNF discontinuation was similar in both groups (high PBE 19.2%, n=5/26 vs. low PBE 15%, n=3/20, p=1.0). Men had higher steroid response rates compared to women in both high and low PBE groups (n=6/8 vs. n=8/18 p=0.21; n=4/9 vs. 4/11 p=1.0 respectively). Conclusion(s) Peripheral eosinophilia is seen in varying degrees in CD patients. Participants with high PBE are more steroid-responsive. High PBE patients overall were less responsive to anti-TNF therapies, requiring more dose-escalation and discontinued anti-TNF treatment. Completion of this study will help clarify the association between PBE in CD and treatment response. Please acknowledge all funding agencies by checking the applicable boxes below None Disclosure of Interest None Declared

Bronchiectasis in severe asthma is associated with eosinophilic airway inflammation and activation.

Bronchiectasis is a common comorbidity in severe asthma; causative pathogenic mechanisms are not fully understood but may differ from other causes of bronchiectasis. The role of eosinophilic airway inflammation, a classic feature of asthma predominantly driven by IL-5 and IL-13, in bronchiectasis is unclear, but association with disruption of the airway epithelium through eosinophil degranulation and increased mucus production is plausible. We sought to describe the prevalence of bronchiectasis in an unselected population of patients with severe asthma, and the association with the airway eosinophilic inflammation and activation. All patients with severe asthma according to European Respiratory Society/American Thoracic Society criteria (high-dose inhaled corticosteroids/oral corticosteroids), attending 4 respiratory clinics over a 1-year period, were included. All patients underwent high-resolution computed tomography and induced sputum was collected and analyzed for a cell differential count, free eosinophilic granules, and airway messenger RNA expression of T2 inflammatory pathways. Bronchiectasis was present in 31% (34 of 108) of patients with severe asthma, and half (52%) of these patients had airway eosinophilia whereas only 16% of patients without bronchiectasis had airway eosinophilia. Patients with bronchiectasis had a significantly higher sputum eosinophil count (5.3 vs 0.8; P= .001) as well as more extensive eosinophil degranulation, compared with those without bronchiectasis (13% vs 2%; P= .05), suggesting a higher degree of eosinophil activation. Pairwise analyses identified significantly higher messenger RNA expression of Charcot-Leyden crystal galectin in patients with bronchiectasis (P= .02). Bronchiectasis in severe asthma was associated with eosinophilic airway inflammation and eosinophilic degranulation as well as messenger RNA expression of Charcot-Leyden crystal galectin.

Eozinofilni ezofagitis

Eosinophilic esophagitis (EoE) is an inflammatory disorder characterized by intraepithelial eosinophilic infiltration followed by esophageal dysfunction. Pathophysiological mechanism of EoE is still not well understood, with several factors that may contribute, such as host immunity, environmental and genetic factors. Modern diagnostic for EoE should include: esophageal dysfunction, esophageal biopsy with at least 15 eosinophils per high power field and absence of other pathology characterized by increased number of eosinophils. The most common presenting symptoms in adults are dysphagia, heartburn, food impaction and chest pain. Children are usually presented with nausea and vomiting, anorexia, heartburn, regurgitation, chest burn and abdominal pain. Endoscopically, patients with EoE are characterized by longitudinal furrows (vertical lines, darker than surrounding mucosa), esophageal trachealization (numerous transversal rings, as in trachea), exudate (white plaques), edema (decreased mucosal vascularization), strictures and crepe-paper mucosa (mucosal friability and tearing during endoscopy). Histological features of EoE could be separated into major and minor criteria. Major criteria include: intraepithelial infiltration by eosinophils (>15 eosinophils/HPF), eosinophilic microabscesses (≥4 eosinophils in a collection), eosinophils occupying outer layer of the squamous epithelium, epithelial sloughing and eosinophil degranulation. Minor criteria include: basal zone hyperplasia, lengthening of the epithelial papillae, intracellular edema and subepithelial fibrosis. In order to set adequate diagnosis, all other conditions related to increased number of eosinophils should be excluded. The most common and the most important differential is gastroesophageal reflux disease (GERD). Treatment of the EoE encompasses: proton pump inhibitors (PPI), corticosteroids (topical and systemic), elimination diet and esophageal dilation.

High Discovery Rate of Duodenal and Gastric Eosinophilia in Patients With Unexplained Moderate–Severe Abdominal Symptoms: A Prospective US Multisite Study

High Discovery Rate of Duodenal and Gastric Eosinophilia in Patients With Unexplained Moderate–Severe Abdominal Symptoms: A Prospective US Multisite Study

Knockdown of CCR3 gene inhibits Proliferation, migration and degranulation of eosinophils in mice by downregulating the PI3K/Akt pathway.

This study aimed to investigate the effects of CCR3 knockdown (CCR3-/-) on the proliferation, migration, and degranulation of the bone marrow eosinophils (EOS) in mice. Bone marrow cells from wild-type mice (WT) were harvested for primary culture and differentiated into mature EOS, which were then randomly divided into the control, 740Y-P, and LY294002 group. The effects of different concentrations of LY294002 (PI3K inhibitor) and 740Y-P (PI3K agonist) on the proliferation viability of EOS, expressions of EPO, Akt, and p-Akt proteins, and migration changes of EOS were detected. CCR3-/- mice were identified. Then, bone marrow cells of WT and CCR3-/- mice were differentiated into mature EOS and grouped into WT EOS, WT EOS+eotaxin (100ng/mL), CCR3-/- EOS, and CCR3-/- EOS+eotaxin (100ng/mL) group. The changes in EOS proliferation, migration, as well as expressions of EPO, Akt, and p-Akt proteins were detected. The number of migrated cells (P<0.01) and expression of EPO (p<0.05) in the 740Y-P group were higher than those in the control group, while opposite trends were observed for the LY294002 group. Expression levels of p-Akt and Akt in the LY294002 group were significantly lower than in the control group (all P<0.01). Also, the expression of p-Akt in the 740Y-P group was significantly higher than that in the control group (p<0.05). The proliferative activity of EOS, expression of EPO and p-Akt, and the number of migrated cells in the WT EOS group were higher than those in CCR3-/- EOS group (all P<0.05). After adding eotaxin, the WT EOS group was higher than the other three groups (all P<0.05). Mechanistically, CCR3-/- inhibited EOS's proliferation, migration, and degranulation by downregulating PI3K/Akt pathway. This data suggests that the knockout of the CCR3 gene in bone marrow cells may inhibit the function of EOS by downregulating the PI3K/Akt pathway, thereby affecting AR; thus, the CCR3 gene may be a target gene for AR therapy.

Eosinophilic dermatoses

Eosinophilic dermatoses are aheterogeneous group of rare diseases that histopathologically display the defining pattern of an eosinophil-rich dermal infiltrate. In these eosinophilic dermatoses, ahistopathologic pattern called flame figures, which result from degranulation of eosinophils in the tissue, can be observed. Although eosinophil granulocytes can also be detected in other dermatoses such as atopic dermatitis, urticaria, prurigo and bullous pemphigoid, the eosinophil-rich infiltrate is decisive for classic eosinophilic dermatoses. Accordingly, eosinophilic dermatoses include hypereosinophilic syndrome, eosinophilic fasciitis, granuloma faciale, pustular sterile eosinophilia, and angiolymphoid hyperplasia with eosinophilia. These eosinophilic dermatoses display clinical different patterns and are discussed in this article, as well as the interesting eosinophils and novel therapeutic options.

OMALIZUMAB: A POTENTIAL LONG-TERM THERAPEUTIC ALTERNATIVE FOR REFRACTORY DELAYED PRESSURE URTICARIA?

<h3>Introduction</h3> Delayed pressure urticaria (DPU) can go unrecognized due to its delayed onset. While most are antihistamine resistant, this case illustrates a complete response to omalizumab as a potential long-term therapeutic alternative. <h3>Case Description</h3> A 44 year-old man who works at a weapons disposal arsenal presents for chronic spontaneous delayed pressure urticaria. Exam reveals lesions on his trunk and extremities with redness and oozing blisters. Triggers include using his hands, wearing a respirator backpack, or leaning against an object for longer than 5 minutes. Skin biopsy reveals nonspecific eosinophilic infiltrate and labs showed mildly elevated CRP. He is treated with cephalexin for presumed cellulitis and high dose antihistamines, famotidine, and montelukast without relief. Given recurrent episodes, the patient is started on monthly omalizumab with complete resolution after the first injection. <h3>Discussion</h3> DPU is a physical urticaria that presents with erythematous, pruritic painful swellings, occasionally with blisters, after prolonged pressure on the skin. The incidence is 2% and occurs in up to 37% of patients with chronic spontaneous urticaria (CSU). Pathophysiology is due to late phase reaction from mast cell activation and upregulation of E selectin leading to an inflammatory response with cytokines and cellular infiltrates. Management is generally unsatisfactory and consists mainly of antihistamine, NSAIDs, colchicine, TNF-a blocker, IVIG, and montelukast. Oral steroids are the most effective treatment, but should not be used long-term. This case illustrates a favorable response to omalizumab, normally used in CSU. Proposed mechanism in a bullous DPU case involves inhibition of cutaneous mast cells, resulting in decreased eosinophil degranulation.

Autoantibody-mediated Macrophage Dysfunction in Patients with Severe Asthma with Airway Infections.

Rationale: Localized autoimmune responses have been reported in patients with severe eosinophilic asthma, characterized by eosinophil degranulation and airway infections. Objective: To determine the presence of autoantibodies against macrophage scavenger receptors within the airways and their effects on macrophage function and susceptibility to infection. Methods: Anti-EPX (eosinophil peroxidase), anti-MARCO (macrophage receptor with collagenous structure) IgG titers, and T1 and T2 (type 1/2) cytokines were measured in 221 sputa from 143 well-characterized patients with severe asthma. Peripheral monocytes and MDMs (monocyte-derived macrophages) isolated from healthy control subjects were treated with immunoprecipitated immunoglobulins from sputa with high anti-MARCO titers or nonspecific IgG to assess uptake of Streptococcus pneumoniae or response to the bacterial product LPS. Measurements and Main Results: Anti-MARCO IgG was detected in 36% of patients, with significantly higher titers (up to 1:16) in patients with mixed granulocytic sputa, indicative of airway infections. Multivariate regression analysis confirmed increased frequency of degranulation (free eosinophil granules), increased blood eosinophils (indicative of high T2 burden), increased sputum total cell count, peripheral blood leukocytes (indicative of infection), and lymphopenia were associated with increased anti-MARCO IgG titers; IL-15 (odds ratio [OR], 1.79; confidence interval [CI], 1.19-2.70), IL-13 (OR, 1.06; CI, 1.02-1.12), and IL-12p70 (OR, 3.34; CI, 1.32-8.40) were the associated cytokines. Patients with anti-MARCO antibodies had higher chances of subsequent infective versus eosinophilic exacerbations (P = 0.01). MDMs treated with immunoprecipitated immunoglobulins (anti-MARCO+ sputa) had reduced bacterial uptake by 39% ± 15% and significantly reduced release of IL-10 and granulocyte-macrophage colony-stimulating factor (GM-CSF) (P < 0.05) in response to an LPS stimulus. Conclusions: Autoantibodies against macrophage scavenger receptors in eosinophilic asthma airways may impede effective host defenses and lead to recurrent infective bronchitis.

An open microfluidic coculture model of fibroblasts and eosinophils to investigate mechanisms of airway inflammation.

Interactions between fibroblasts and immune cells play an important role in tissue inflammation. Previous studies have found that eosinophils activated with interleukin-3 (IL-3) degranulate on aggregated immunoglobulin G (IgG) and release mediators that activate fibroblasts in the lung. However, these studies were done with eosinophil-conditioned media that have the capacity to investigate only one-way signaling from eosinophils to fibroblasts. Here, we demonstrate a coculture model of primary normal human lung fibroblasts (HLFs) and human blood eosinophils from patients with allergy and asthma using an open microfluidic coculture device. In our device, the two types of cells can communicate via two-way soluble factor signaling in the shared media while being physically separated by a half wall. Initially, we assessed the level of eosinophil degranulation by their release of eosinophil-derived neurotoxin (EDN). Next, we analyzed the inflammation-associated genes and soluble factors using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and multiplex immunoassays, respectively. Our results suggest an induction of a proinflammatory fibroblast phenotype of HLFs following the coculture with degranulating eosinophils, validating our previous findings. Additionally, we present a new result that indicate potential impacts of activated HLFs back on eosinophils. This open microfluidic coculture platform provides unique opportunities to investigate the intercellular signaling between the two cell types and their roles in airway inflammation and remodeling.

Taking a Breather: Advances in Interleukin 5 Inhibition for Asthma Relief.

Interleukin 5 (IL-5) is a major cytokine responsible for eosinophil proliferation, migration and degranulation. Eosinophils play a considerable role in the manifestation of type 2 asthma, and therefore this makes IL-5 a unique and clinically important target for therapeutic intervention. Due to the critical role that IL-5 plays in all areas of eosinophil activity, it has been identified and targeted by three therapeutics, Mepolizumab, Benralizumab and Reslizumab. This review describes the IL-5 pathway and presents the clinical trial history of the three IL-5 inhibitors, to provide insight into the role of IL-5 in clinical asthma presentation. Additionally, this review aims to foster further investigation into the IL-5 pathway by describing current novel therapeutic discovery strategies with monoclonal antibodies.

In Vivo ETosis of Human Eosinophils: The Ultrastructural Signature Captured by TEM in Eosinophilic Diseases.

Eosinophilic diseases, also termed eosinophil-associated diseases (EADs), are characterized by eosinophil-rich inflammatory infiltrates and extensive eosinophil degranulation with clinically relevant organ pathology. Recent evidence shows that eosinophil cytolytic degranulation, that is, the release of intact, membrane-delimited granules that arises from the eosinophil cytolysis, occurs mainly through ETosis, meaning death with a cytolytic profile and extrusion of nucleus-originated DNA extracellular traps (ETs). The ultrastructural features of eosinophil ETosis (EETosis) have been studied mostly in vitro after stimulation, but are still poorly understood in vivo. Here, we investigated in detail, by transmission electron microscopy (TEM), the ultrastructure of EETosis in selected human EADs affecting several tissues and organ systems. Biopsies of patients diagnosed with eosinophilic chronic rhinosinusitis/ECRS (frontal sinus), ulcerative colitis/UC (intestine), and hypereosinophilic syndrome/HES (skin) were processed for conventional TEM. First, we found that a large proportion of tissue-infiltrated eosinophils in all diseases (~45-65% of all eosinophils) were undergoing cytolysis with release of free extracellular granules (FEGs). Second, we compared the morphology of tissue inflammatory eosinophils with that shown by in vitro ETosis-stimulated eosinophils. By applying single-cell imaging analysis, we sought typical early and late EETosis events: chromatin decondensation; nuclear delobulation and rounding; expanded nuclear area; nuclear envelope alterations and disruption; and extracellular decondensed chromatin spread as ETs. We detected that 53% (ECRS), 37% (UC), and 82% (HES) of all tissue cytolytic eosinophils had ultrastructural features of ETosis in different degrees. Eosinophils in early ETosis significantly increased their nuclear area compared to non-cytolytic eosinophils due to excessive chromatin decondensation and expansion observed before nuclear envelope disruption. ETosis led not only to the deposition of intact granules, but also to the release of eosinophil sombrero vesicles (EoSVs) and Charcot-Leyden crystals (CLCs). Free intact EoSVs and CLCs were associated with FEGs and extracellular DNA nets. Interestingly, not all cytolytic eosinophils in the same microenvironment exhibited ultrastructure of ETosis, thus indicating that different populations of eosinophils might be selectively activated into this pathway. Altogether, our findings captured an ultrastructural signature of EETosis in vivo in prototypic EADs highlighting the importance of this event as a form of eosinophil degranulation and release of inflammatory markers (EoSVs and CLCs).

Airway autoantibodies are determinants of asthma severity.

Local airway autoimmune responses may contribute to steroid dependence and persistent eosinophilia in severe asthma. Auto-IgG antibodies directed against granule proteins such as eosinophil peroxidase (EPX), macrophage scavenger receptor with collagenous structure (MARCO) and nuclear/extranuclear antigens (antinuclear antibodies (ANAs)) have been reported. Our objective was to describe the prevalence and clinical characteristics of asthmatic patients with airway autoreactivity, and to assess if this could be predicted from clinical history of autoreactivity. We analysed anti-EPX, anti-MARCO and ANAs in 218 sputum samples collected prospectively from 148 asthmatic patients, and evaluated their association with lung function parameters, blood/airway inflammation, severity indices and exacerbations. Additionally, 107 of these patients consented to fill out an autoimmune checklist to determine personal/family history of systemic autoimmune disease and symptoms. Out of the 148 patients, 59 (40%) were anti-EPX IgG+, 53 (36%) were anti-MARCO IgG+ and 64 out of 129 (50%) had ≥2 nuclear/extranuclear autoreactivities. A composite airway autoreactivity score (CAAS) demonstrated that 82 patients (55%) had ≥2 airway autoreactivities (considered as CAAS+). Increased airway eosinophil degranulation (OR 15.1, 95% CI 1.1-199.4), increased blood leukocytes (OR 3.5, 95% CI 1.3-10.1) and reduced blood lymphocytes (OR 0.19, 95% CI 0.04-0.84) predicted CAAS+. A third of CAAS+ patients reported an exacerbation, associated with increased anti-EPX and/or anti-MARCO IgG (p<0.05). While no association was found between family history or personal diagnosis of autoimmune disease, 30% of CAAS+ asthmatic patients reported sicca symptoms (p=0.02). Current anti-inflammatory (inhaled/oral corticosteroids and/or adjunct anti-interleukin-5 biologics) treatment does not attenuate airway autoantibodies, irrespective of eosinophil suppression. We report 55% of moderate-severe asthmatic patients to have airway autoreactivity that persists despite anti-inflammatory treatment and is associated with exacerbations.

Eosinophils Decrease Pulmonary Metastatic Mammary Tumor Growth.

Metastatic breast cancer is challenging to effectively treat, highlighting the need for an improved understanding of host factors that influence metastatic tumor cell colonization and growth in distant tissues. The lungs are a common site of breast cancer metastasis and are host to a population of tissue-resident eosinophils. Eosinophils are granulocytic innate immune cells known for their prominent roles in allergy and Th2 immunity. Though their presence in solid tumors and metastases have been reported for decades, the influence of eosinophils on metastatic tumor growth in the lungs is unclear. We used transgenic mouse models characterized by elevated pulmonary eosinophils (IL5Tg mice) and eosinophil-deficiency (ΔdblGATA mice), as well as antibody-mediated depletion of eosinophils, to study the role of eosinophils in EO771 mammary tumor growth in the lungs. We found that IL5Tg mice exhibit reduced pulmonary metastatic colonization and decreased metastatic tumor burden compared to wild-type (WT) mice or eosinophil-deficient mice. Eosinophils co-cultured with tumor cells ex vivo produced peroxidase activity and induced tumor cell death, indicating that eosinophils are capable of releasing eosinophil peroxidase (EPX) and killing EO771 tumor cells. We found that lung eosinophils expressed phenotypic markers of activation during EO771 tumor growth in the lungs, and that metastatic growth was accelerated in eosinophil-deficient mice and in WT mice after immunological depletion of eosinophils. Our results highlight an important role for eosinophils in restricting mammary tumor cell growth in the lungs and support further work to determine whether strategies to trigger local eosinophil degranulation may decrease pulmonary metastatic growth.

In vivo visualization of eosinophil secretion in eosinophilic granulomatosis with polyangiitis: An ultrastructural study

BackgroundAlthough eosinophilic granulomatosis with polyangiitis (EGPA) has been considered as a single disease entity belonging to anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, several studies have suggested that in addition to the mechanisms associated with ANCA, those associated with eosinophils play a vital role in tissue damage. Nevertheless, the morphological bases underlying eosinophil-associated lesions have not been completely elucidated. MethodsWe investigated the electron microscopic findings of sural nerve biopsy specimens obtained from 18 patients with EGPA by focusing on the behavior of eosinophils, particularly the mode of secretion. ResultsEosinophils tended to be located at sites close to endothelial cells within the lumina of epineurial small vessels. Attachment of eosinophils to endothelial cells was observed, particularly at the junction between neighboring endothelial cells, and some of these eosinophils appeared to escape from the vascular lumen to migrate into the extravascular interstitium. Furthermore, we observed eosinophil degranulation via piecemeal degranulation and cytolysis. Degranulating eosinophils were identified in both intravascular and extravascular compartments. Some of the small vessels appeared to be occluded by numerous eosinophils, and eosinophils attached by platelets were also observed, suggesting that coagulopathy occurs in EGPA. ConclusionsBoth extravascular and intravascular eosinophils can induce tissue damage unrelated to classical necrotizing vasculitis associated with ANCA in patients with EGPA. Further research is necessary to elucidate the molecular basis of the induction of these fine structural changes, which will contribute to the development of targeted therapies based on specific mechanisms of eosinophil-related diseases.

Menthone Inhalation Alleviates Local and Systemic Allergic Inflammation in Ovalbumin-Sensitized and Challenged Asthmatic Mice.

Menthone is rich in Mentha × Piperita L. essential oil and it has anti-inflammatory properties; research shows that it is useful, via percutaneous absorption, in treating inflammation-related diseases. However, anti-allergic inflammatory effects of volatile menthone have not yet been used to treat allergic asthma, in vivo. We hypothesized that menthone inhalation may have anti-inflammatory and anti-allergic effects in patients with allergic asthma. Therefore, in our study, menthone inhalation was used to treat ovalbumin (OVA)-sensitized and challenged asthmatic mice. Allergic inflammation mediator changes in the lungs and airways, sera, splenocytes, and peritoneal macrophages of the mice were measured. Relative expression amounts of six receptor genes related to allergic inflammation of the lungs and airways were quantitated using a two-step real time quantitative polymerase chain reaction (qPCR). Results showed that menthone inhalation increased serum OVA-specific IgG2a/IgG1 and IgG2a/IgE ratios, increased Th1-type cytokine production in the bronchoalveolar lavage fluid, and decreased nitric oxide, protein, and eotaxin levels. Menthone inhalation inhibited mast cell and eosinophil degranulation, and chemokine (C-C motif) receptor 3 (Ccr3) gene expression amounts, but (relatively) increased Th1 cytokine secretion by splenocytes. Our results evidence that menthone inhalation alleviates local and systemic allergic inflammation in asthmatic mice.

Proposed Pathogenesis of Diffuse Alveolar Hemorrhage in Idiopathic Pulmonary Hemosiderosis.

Idiopathic pulmonary hemosiderosis (IPH) is a rare disease that causes diffuse alveolar hemorrhage (DAH). The latest data suggests an immunologic origin of IPH, and a new name, immune mediated pulmonary hemosiderosis (ImPH), has been proposed. However, the exact immunologic mechanism has remained elusive for nearly eight decades despite extensive research, including detailed histopathologic analysis. Although several hypotheses have been proposed to describe the pathobiology of IPH, none of them explain the clinical and histopathologic findings conclusively. In this manuscript, we have presented a new hypothesis for the pathogenesis of DAH in IPH. We hypothesize that DAH in IPH is not immunocomplex mediated but due to histamine, eosinophilic cationic protein (ECP), and possibly vascular endothelial growth factor (VEGF). These bioactive proteins induce endothelial and alveolar epithelial damage, leading to the peri-capillary and intraalveolar escape of RBCs. The deformability of the RBC likely also plays a role. The supranormal secretion of histamine, ECP and VEGF occurs in genetically predisposed individuals with an aberrant immunologic response. The histamine is released from the basophils and possibly the mast cells in response to cytokines secreted by activated lymphocytes. The lymphocyte activation occurs after exposure to a known (gluten) or unknown antigen. The same lymphocyte-derived cytokines also induce eosinophilic degranulation of ECP and VEGF in the pulmonary circulation. We believe that our hypothesis unifies the observed clinical variabilities and histopathologic findings in IPH, and we hope that would promote future research in the field of IPH.

A163 EVALUATING THE ASSOCIATION BETWEEN PERIPHERAL BLOOD EOSINOPHILS AND DRUG RESPONSE IN CROHN’S DISEASE: A PRELIMINARY REPORT

BackgroundTh1, Th2, and Th17 immune pathways are variably activated in inflammatory bowel disease (IBD). The degree to which pathway having a more dominant role in propagating Crohn’s disease (CD) is not considered when selecting a treatment strategy. Th2 cytokines, IL-5 and IL-13 enhance eosinophil survival, recruitment and degranulation, facilitating inflammation. Mucosal eosinophilia has been documented in CD and its presence is a surrogate marker of Th2 pathway activation. Peripheral eosinophilia has an established role in asthma to help prognosticate treatment response to Th2-cytokine-specific therapies. We hypothesize the pattern of peripheral blood eosinophils (PBE) at CD diagnosis will identify distinct subsets within a larger CD population and correlate with response to treatments such as prednisone or anti-TNFs.AimsWe aim to evaluate the pattern of PBE of CD patients at time of diagnosis (prior to drug exposure) and with each subsequent treatment; and if baseline PBE or any changes seen with drug exposures are predictive of treatment response.MethodsA retrospective cohort study is ongoing with CD patients exposed to glucocorticoids and an anti-TNF seen at one of 3 hospitals affiliated with University of Western Ontario. Patients were identified using administrative databases and reviewed for biochemical data (complete blood count) and disease activity (Harvey Bradshaw Index) at baseline as well as before and after each drug exposure. Participants were classified as having high PBE (eosinophils >200 cells/μl) versus low PBE (eosinophils <200 cells/μl).ResultsTo date,10 of 200 CD patients are included in the preliminary analyses with a mean age of 47. 8 had PBE >200 cells/μL at baseline, while 2 did not. The median number therapies used was 4 (IQR=0.75). All received glucocorticoids followed by an anti-TNF. There was no difference in the occurrence of hospitalization or surgery between the two cohorts. Overall 75% (n=6/8) participants with high PBE had clinical response to glucocorticoid exposure, seen as a 3-point decrease in HBI compared to 0% (n=0/2, p=0.5) in the low PBE cohort. With subsequent anti-TNF exposure, PBE rebounded in 6 participants. More patients in the high PBE group required anti-TNF dose escalation versus the low PBE group (63%, n=5/8 versus 50%, n=1/2, p=0.99). The proportion of patients with anti-TNF discontinuation was similar in both groups (high PBE, 50%, n=4/8 versus low PBE, 50%, n=1/2, p=1.00).ConclusionsPeripheral eosinophilia is seen in varying degrees in CD patients. Participants with high PBE appear to be more steroid-responsive which is typical for Th2-mediated pathways. They were less responsive to Th1-targeting anti-TNF therapies, requiring more dose-escalation and discontinued anti-TNF treatment. Completion of this study will help clarify the association between PBE in CD and treatment response.Funding AgenciesNone

Siglec-F Promotes IL-33-Induced Cytokine Release from Bone Marrow-Derived Eosinophils Independently of the ITIM and ITIM-like Motif Phosphorylation.

Eosinophils are potent innate effector cells associated mainly with type 2 immune responses elicited by helminths and allergens. Their activity needs to be tightly controlled to prevent severe inflammation and tissue damage. Eosinophil degranulation and secretion of inflammatory effector molecules, including cytokines, chemokines, and lipid mediators, can be regulated by activating and inhibitory receptors on the cell surface. In this study, we investigated the modulation of proliferation, apoptosis, gene expression, and cytokine/chemokine secretion from IL-33-activated Mus musculus eosinophils on cross-linking of the transmembrane receptor Sialic acid-binding Ig-like lectin F (Siglec-F). Siglec-F contains an ITIM plus an ITIM-like motif in its intracellular tail and is mainly regarded as an inhibitory and apoptosis-inducing receptor. In vitro costimulation of bone marrow-derived eosinophils with anti-Siglec-F and IL-33 compared with treatment with either alone led to enhanced STAT6 phosphorylation, stronger induction of hypoxia/glycolysis-related proinflammatory genes, and elevated secretion of type 2 cytokines (IL-4, IL-13) and chemokines (CCL3, CCL4) with only minor effects on proliferation and apoptosis. Using a competitive mixed bone marrow chimera approach with wild-type and Siglec-F-deficient eosinophils, we observed no evidence for Siglec-F-regulated inhibition of Aspergillus fumigatus-elicited lung eosinophilia. Truncation of the Siglec-F cytoplasmic tail, but not mutation of the ITIM and ITIM-like motifs, ablated the effect of enhanced cytokine/chemokine secretion. This provides evidence for an ITIM phosphorylation-independent signaling pathway from the cytoplasmic tail of the Siglec-F receptor that enhances effector molecule release from activated eosinophils.

203 Small Intestinal Inflammatory Microenvironments In The Murine Model of Psoriasis

Although gastrointestinal microbiome has been receiving attention to affect skin inflammation, changes in intestinal microenvironment remain largely unknown, particularly in psoriasis. In this study, we evaluated the changes in the skin and intestine of an imiquimod (IMQ)-induced murine model of psoriasis. In IMQ-treated mice, weight and energy intake was significantly decreased, while fecal protein and intestinal permeability was significantly increased. The composition of small intestinal microbiome was also altered with increased diversity. With IMQ-induced stimulation, IL-17-producing T cells were significantly increased in the skin. In contrast, IL-17 expression was significantly decreased with increased expression of IL-1beta, IL-6, TNF, and S100a8, and decreased intestinal tight junction molecules in small intestine. Interestingly, there was a marked decrease of eosinophils in the small intestine of IMQ-treated mice, with a significant upregulation of the eosinophil degranulation markers. The expression of tight junction and mucus molecules was significantly upregulated in the small intestine of IMQ-treated ΔdblGATA mice, in which eosinophil lineage is depleted, suggesting that the activation and degranulation of small intestinal eosinophils could affect pathogenesis of psoriatic inflammation by damaging intestinal barrier integrity.

Effect of TGF-β1 on eosinophils to induce cysteinyl leukotriene E4 production in aspirin-exacerbated respiratory disease.

Cysteinyl leukotriene (cysLT) overproduction and eosinophil activation are hallmarks of aspirin-exacerbated respiratory disease (AERD). However, pathogenic mechanisms of AERD remain to be clarified. Here, we aimed to find the significance of transforming growth factor beta 1 (TGF-β1) in association with cysteinyl leukotriene E4 (LTE4) production, leading to eosinophil degranulation. To evaluate levels of serum TGF-β1, first cohort enrolled AERD (n = 336), ATA (n = 442) patients and healthy control subjects (HCs, n = 253). In addition, second cohort recruited AERD (n = 34) and ATA (n = 25) patients to investigate a relation between levels of serum TGF-β1 and urinary LTE4. The function of TGF-β1 in LTE4 production was further demonstrated by ex vivo (human peripheral eosinophils) or in vivo (BALB/c mice) experiment. As a result, the levels of serum TGF-β1 were significantly higher in AERD patients than in ATA patients or HCs (P = .001; respectively). Moreover, levels of serum TGF-β1 and urinary LTE4 had a positive correlation (r = 0.273, P = .037). In the presence of TGF-β1, leukotriene C4 synthase (LTC4S) expression was enhanced in peripheral eosinophils to produce LTE4, which sequentially induced eosinophil degranulation via the p38 pathway. When mice were treated with TGF-β1, significantly induced eosinophilia with increased LTE4 production in the lung tissues were noted. These findings suggest that higher levels of TGF-β1 in AERD patients may contribute to LTE4 production via enhancing LTC4S expression which induces eosinophil degranulation, accelerating airway inflammation.