Membrane damage by MBP-1 is mediated by pore formation and amplified by mtDNA.

Eosinophils play a crucial role in host defense while also contributing to immunopathology through the release of inflammatory mediators. Characterized by distinctive cytoplasmic granules, eosinophils securely store and rapidly release various proteins exhibiting high toxicity upon extracellular release. Among these, major basic protein 1 (MBP-1) emerges as an important mediator in eosinophil function against pathogens and in eosinophil-associated diseases. While MBP-1 targets both microorganisms and host cells, its precise mechanism remains elusive. We demonstrate that formation of small pores by MBP-1 in lipid bilayers induces membrane permeabilization and disrupts potassium balance. Additionally, we reveal that mitochondrial DNA (mtDNA) present in eosinophil extracellular traps (EETs) amplifies MBP-1 toxic effects, underscoring the pivotal role of mtDNA in EETs. Furthermore, we present evidence indicating that absence of CpG methylation in mtDNA contributes to the regulation of MBP-1-mediated toxicity. Taken together, our data suggest that the mtDNA scaffold within extracellular traps promotes MBP-1 toxicity.

Sustained Effectiveness of Benralizumab in Naïve and Biologics-Experienced Severe Eosinophilic Asthma Patients: Results from the ANANKE Study.

Purpose: Severe eosinophilic asthma (SEA) patients often present overlapping inflammatory features rendering them eligible for multiple biologic therapies; switching biologic treatment is a strategy adopted to optimize asthma control when patients show partial or no response to previous biologics. Patients and Methods: ANANKE is a retrospective, multicenter Italian study (NCT04272463). Here, we outline the characteristics and long-term clinical outcomes in naïve-to-biologics and biologics-experienced patients treated with benralizumab for up to 96 weeks. Bio-experienced patients were split into omalizumab and mepolizumab subsets according to the type of biologic previously used. Results: A total of 124 (76.5%) naïve and 38 (23.5%) bio-experienced patients were evaluated at index date; 13 patients (34.2%) switched from mepolizumab, 21 patients (55.3%) switched from omalizumab, and four patients (10.5%) received both biologics. The mepolizumab subset was characterized by the longest SEA duration (median of 4.6 years), the highest prevalence of chronic rhinosinusitis with nasal polyposis (CRSwNP) (76.5%), and the greatest oral corticosteroid (OCS) daily dosage (median of 25 mg prednisone equivalent). The omalizumab group showed the highest severe annual exacerbation rate (AER) (1.70). At 96 weeks, treatment with benralizumab reduced any and severe AER by more than 87% and 94%, respectively, across all groups. Lung function was overall preserved, with major improvements observed in the mepolizumab group, which also revealed a 100% drop of the median OCS dose. Asthma Control Test (ACT) score improved in the naïve group while its increment was more variable in bio-experienced patients; among these, a marked difference was noticed between omalizumab and mepolizumab subsets (median ACT score of 23.5 and 18, respectively). Conclusion: Benralizumab promotes durable and profound clinical benefits in naïve and bio-experienced groups, indicating that a nearly complete depletion of eosinophils is highly beneficial in the control of SEA, independently of previous biologic use.

In-Depth Review of Loeffler Endocarditis: What Have We Learned?

Loeffler endocarditis, eosinophilic endocarditis or eosinophilic endomyocardial disease are conditions associated with hypereosinophilia and they affect the heart function. Loeffler endocarditis is a rare endomyocardial disorder thought to be caused by eosinophilic damage. The disorder is characterized by inflammatory infiltration, formation of thrombus within cardiovascular system, and ultimately fibrosis of the afflicted area. It can lead to multiple severe complications, including thromboembolic disease, thickening of fibrous tissue in the endocardium of ventricles, valve involvement, apical obliteration, and various heart disorders. Although early clinical intervention can lead to remission, the underlying mechanisms of the disorder remain unresolved. In the present article, we summarise the existing literature concerning Loeffler endocarditis based on PubMed, Web of Science, and other medical databases to conduct an in-depth review of the epidemiology, etiology, pathophysiological mechanisms, staging, diagnosis, treatment and prognosis of Loeffler endocarditis. Meanwhile, we provide novel patients data and clinical figures of Loeffler endocarditis to supplement the understanding of this cardiac disorder. The findings presented in this article provide a basis for further studies and can be used to improve management of the disorder.

[Correlation study of NCF2 in chronic rhinosinusitis with nasal polyps].

Objective:After selecting NCF2 based on bioinformatics, clinical experiments were conducted to verify the expression of NCF2 in chronic rhinosinusitis with nasal polyps to study its correlation. Methods:The differentially expressed genes（DEGs） between CRSwNP and non-CRS patients were explored using the CRS-related dataset from the gene expression omnibus GEO database. The weighted gene co-expression network（WGCNA） was used for cluster analysis. The expression and cell distribution of NCF2 in the tissues were determined by single gene enrichment analysis（GSEA）, immune inflammatory infiltration analysis, and principal component（PCA） analysis. The expression degree of NCF2 in the tissues of the subjects was determined by immunohistochemistry, and the percentage of EOS in the peripheral blood of the subjects was detected and the correlation was analyzed. EOS in the tissues of the subjects were counted under a microscope and compared. Results:①The Venn diagram was obtained by crossing the module with the highest correlation between DEGs and WGCNA to determine the core gene NCF2. ②GSEA analysis showed that NCF2 was significantly related to the immunological processes such as allogeneic rejection and asthma. ③The area under the ROC curve was 1, indicating that NCF2 had diagnostic value for CRSwNP. ④NCF2 was highly expressed in nasal polyps, mainly distributed in monocytes and eosinophils. ⑤HE staining showed that the number of EOS in ECRSwNP tissues and the percentage of eosinophils in peripheral blood were higher than those in nonECRSwNP and control groups. ⑥The immunohistochemistry results showed that NCF2 was significantly expressed in the nasal polyps of ECRSwNP patients, which was higher than that in the nasal mucosa of nonECRSwNP group and control group. ⑦The expression of NCF2 in tissues was positively correlated with EOS count in ECRSwNP group and EOS expression in peripheral blood. Conclusion:The expression of NCF2 is increased in eosinophilic chronic rhinosinusitis with nasal polyps, and it is significantly correlated with the expression of eosinophils in peripheral blood and tissues, suggesting that NCF2 may be used as a basis for the intrinsic classification of ECRSwNP and a reference index for clinical diagnosis and treatment.

Dupilumab's impact on nasal citology: Real life experience after 1 year of treatment.

BACKGROUND: Biologic agents are considered a new revolutionized therapy for severe and recurrent forms of CRSwNP which disease burden is not sufficiently controlled by conservative and/or surgical treatments. Recent Research has focused on evaluating their real-life efficacy in CRSwNP, as only limited reports on real-life data are available. However, in most studies, the response to treatment is evaluated in terms of improvement in Nasal Polyp Score (NPS) or in Sino-Nasal Outcome test (SNOT-22) scores. However, both criteria do not consider nasal immunophlogosis, which can be easily assessed by nasal cytology. The aim of our study was to evaluate changings in the nasal inflammatory infiltrate of CRSwNP patients treated with Dupilumab for 12 months. METHODS: 27 patients suffering from severe CRSwNP treated with Dupilumab were recruited. Nasal cytology findings, NPS, SNOT-22, ACT scores and blood eosinophil count at T0 (before treatment) and at T1 (after 1 year of treatment) were compared. RESULTS: After 1 year of biological therapy with Dupilumab, NPS, SNOT-22 and, among the 17 asthmatic patients, ACT scores improved significantly. At T1, a statistically significant percentage of patients showed negative citology. Moreover, a significant reduction in the mast cell-eosinophilic pattern and an increase of neutrophils and bacteria was reported. CONCLUSIONS: The response to treatment can be considered both in the case of negative nasal cytology and in the case of the appearance of neutrophils and bacteria. In this context, eosinophils, the specific target of biological therapies, play a crucial role in regulating tissue homeostasis and, consequently, the nasal immunophlogosis.

Histopathology of Eosinophilic Esophagitis.

Microscopic examination of esophageal biopsies is essential to diagnose eosinophilic esophagitis (EoE). Eosinophil inflammation is the basis for the diagnosis, but additional abnormalities may contribute to persistent symptoms and epithelial barrier dysfunction. Both peak eosinophil count and assessments of additional features should be included in pre-therapy and post-therapy pathology reports. Pathologic abnormalities identified in esophageal biopsies of EoE are reversible in contrast to esophageal strictures.

Role of Mast Cells in Eosinophilic Gastrointestinal Diseases.

Mast cells play a central role in the pathogenesis of eosinophilic gastrointestinal disorders (EGIDs), including eosinophilic esophagitis. Their interactions with immune and structural cells, involvement in tissue remodeling, and contribution to symptoms make them attractive targets for therapeutic intervention. More is being discovered regarding the intricate interplay of mast cells and eosinophils. Recent studies demonstrating that depletion of eosinophils is insufficient to improve symptoms of EGIDs have raised the question of whether other cells may play a role in symptomatology and pathogenesis of EGIDs.

Multiple lymphadenopathies in eosinophilic granulomatosis with polyangiitis: differentiating from IgG4-related lymphadenopathy.

We report a case of eosinophilic granulomatosis with polyangiitis (EGPA) in a 75-year-old man who developed mononeuritis multiplex and purpura in the lower legs concomitantly presenting with lymphadenopathies. Biopsied lymph node tissue pathologically demonstrated fibrinoid necrotizing vasculitis with perivascular eosinophil infiltration, resulting in EGPA diagnosis. Additionally, abundant IgG4-positive plasma cell infiltration exhibiting >70% IgG4/IgG ratio, without storiform pattern fibrosis and obliterative phlebitis, was observed in the biopsied lymph node. Clinical improvement was observed after corticosteroid therapy. IgG4-related lymphadenopathy (IgG4-LAD) has been defined as a distinct clinical category regardless of fulfilling IgG4-related disease classification criteria. However, some autoimmune diseases, including EGPA, can develop lymphadenopathy pathologically similar to IgG4-LAD.

Allergic Phenotypes and Sarcopenia: Evidence from Observational Studies and Mendelian Randomization Analysis.

Commonly affected in early-life population, the impact of allergic phenotypes on mid- or late-life health is less discussed. This study is to explore the association of allergic phenotypes including atopic dermatitis (AD), asthma, eosinophils count (EC), and sarcopenia. We conducted observational studies and mendelian randomization (MR) analysis based on UK Biobank (UKB), the China Health and Retirement Longitudinal Study (CHARLS) and data from genome-wide association study (GWAS). Based on the UKB data, AD, asthma and EC were positively correlated with pre-sarcopenia and decreased skeletal muscle mass index and hand grip in fully adjusted model. Asthma and EC were significantly associated with sarcopenia while AD was marginally associated (p = 0.095). Based on the CHARLS cohort, asthma significantly added 109.4% risk for pre-sarcopenia in adjusted model (relative risk = 2.094; p = 0.002), respectively. Both asthma (ß = 0.100, p = 0.006) and EC (ß = 0.023, p = 0.017) exerted significantly casual effects on pre-sarcopenia. However, as for sarcopenia, merely EC exhibited a significantly casual effect (ß = 0.005, p = 0.048). Significant casual effects of AD (ß = - 0.027, p = 0.003), asthma (ß = - 0.029, p = 0.027) and EC (ß = - 0.041, p < 0.001) on decreased appendicular lean mass (ALM) were observed using the inverse-variance weighted method and the Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) method. Our results revealed a contributory role of AD, asthma and EC on sarcopenia, especially in terms of decreased ALM, an indicator for sarcopenia diagnosis. The findings of our study will raise the awareness of preventing aging-related disorders or geriatric syndromes among allergic populations. Supplementary Information: The online version contains supplementary material available at 10.1007/s43657-023-00110-4.

Can the ADO Index Be Used as a Predictor of Mortality from COVID-19 in Patients with COPD?

Background: Several studies have shown that the risk of mortality due to COVID-19 is high in patients with COPD. However, evidence on factors predicting mortality is limited. Research Question: Are there any useful markers to predict mortality in COVID-19 patients with COPD?. Study Design and Methods: A total of 689 patients were included in this study from the COPET study, a national multicenter observational study investigating COPD phenotypes consisting of patients who were followed up with a spirometry-confirmed COPD diagnosis. Patients were also retrospectively examined in terms of COVID-19 and their outcomes. Results: Among the study patients, 105 were diagnosed with PCR-positive COVID-19, and 19 of them died. Body mass index (p= 0.01) and ADO (age, dyspnoea, airflow obstruction) index (p= 0.01) were higher, whereas predicted FEV1 (p< 0.001) and eosinophil count (p= 0.003) were lower in patients who died of COVID-19. Each 0.755 unit increase in the ADO index increased the risk of death by 2.12 times, and each 0.007 unit increase in the eosinophil count decreased the risk of death by 1.007 times. The optimum cut-off ADO score of 3.5 was diagnostic with 94% sensitivity and 40% specificity in predicting mortality. Interpretation: Our study suggested that the ADO index recorded in the stable period in patients with COPD makes a modest contribution to the prediction of mortality due to COVID-19. Further studies are needed to validate the use of the ADO index in estimating mortality in both COVID-19 and other viral respiratory infections in patients with COPD.

Misdiagnosis of lymphoma as vasculitis: A case report.

NK/T-cell lymphoma (NKTCL) is a highly aggressive malignant tumour with a very poor prognosis, which often poses diagnostic difficulties due to the non-specificity of its clinical presentation. NK/T-cell lymphoma with eosinophilic hyperplasia syndrome is extremely rare. This article describes a patient with NKTCL misdiagnosed as vasculitis who presented with sinusitis, abdominal pain, anorexia, and lung shadows. Additionally, the patient exhibited extremely high eosinophilia levels, which led to a further misdiagnosis of eosinophilic granuloma. We describe the clinical features, diagnostic methods and differential diagnosis of lymphoma and highlights the importance of a multidisciplinary approach in accurate diagnosis and treatment.

Identification of neutrophils and eosinophils in upper airway mucosa with immunofluorescence multiplex image cytometry.

Characterization of inflammation in chronic rhinosinusitis with (CRSwNP) and without nasal polyps (CRSsNP) is an ongoing research process. To overcome limitations of current cytologic techniques, we investigated whether immunofluorescence multiplex image cytometry could quantify intact neutrophils, eosinophils, and other immune cells in solid upper airway mucosa. We used a four-channel immunofluorescence-microscopy technique for the simultaneous detection of the leukocyte marker CD45, the neutrophil marker myeloperoxidase, two eosinophil markers, i.e., major basic protein and eosinophil peroxidase, and DAPI (4',6-diamidin-2-phenylindole), in formalin-fixed paraffin-embedded upper airway tissue samples of patients with CRSwNP and CRSsNP, as well as of patients free of CRS with inferior turbinate hypertrophy (controls). Image acquisition and analysis were performed with TissueFAXS and StrataQuest (TissueGnostics, Vienna, Austria), respectively. Positive and negative immunostaining were differentiated with a specific fluorescence signal/background signal ratio. Isotype controls were used as negative controls. In six controls, nine patients with CRSsNP, and 11 patients with CRSwNP, the median area scanned and median cell count per patient were 14.2 mm2 and 34,356, respectively. In CRSwNP, the number of eosinophils was three times higher (23%) than that of neutrophils (7%). Three times more immune cells were encountered in CRSwNP (33%) compared to CRSsNP (11%). In controls, inflammation was balanced between the epithelial layer and lamina propria, in contrast to CRS (three times more pronounced inflammation in the lamina propria). The quantification of intact neutrophils, eosinophils, and other immune cells in solid tissue with undisrupted architecture seems feasible with immunofluorescence multiplex image cytometry.

Eosinophils exhibit a unique transcriptional signature and increased sensitivity to IL-3-induced activation in response to colorectal cancer cells.

Eosinophils have been mainly studied in allergic diseases and parasitic infections. Nonetheless, eosinophils accumulate in a variety of solid tumors, including colorectal cancer, where their presence is associated with improved prognosis. Eosinophils can promote anti-tumor immunity through various mechanisms, including direct cytotoxicity towards tumor cells and promoting T cell activation. However, the mechanisms by which tumor cells regulate eosinophil activities are largely unknown. Herein, we characterized the potential interactions between eosinophils and colorectal cancer cells using an unbiased transcriptomic and proteomic analyses approach. Human eosinophils were stimulated with colorectal cancer cell-conditioned media, containing tumor cell-secreted factors from multiple cancer cell lines. RNA sequencing analysis identified a "core" signature consisting of 101 genes that characterize a baseline transcriptional program for the response of human eosinophils to colorectal cancer cells. Among these, the increased expression of IL-3Rα and its ßc chain was identified and validated at the protein level. Secreted factors from tumor cells potentiated IL-3-induced expression of the adhesion molecule CD11a in eosinophils. Combining proteomics analysis of tumor cell-secreted factors with RNA sequencing revealed potential ligand-receptor pairs between tumor cells and eosinophils and the potential involvement of the adhesion molecule CD18 and F2RL3/PAR4. Subsequent functional analyses demonstrated that F2RL3/PAR4 suppresses eosinophil migration in response tumor cell-secreted factors. These findings add to the growing body of evidence that eosinophils are conditioned by their local microenvironment. Identifying mechanisms by which eosinophils interact with tumor cells could lead to the development of new immunotherapies for colorectal cancer and other solid tumors.

Eosinophil expression of Triggering receptor expressed on myeloid cells-1 (TREM-1) restricts type 2 lung inflammation.

Asthma affects 25 million Americans and recent advances in treatment are effective for only a portion of severe asthma patients. Triggering Receptor Expressed on Myeloid cells 1 (TREM-1), an innate receptor that canonically amplifies inflammatory signaling in neutrophils and monocytes, plays a central role in regulating lung inflammation. It is unknown how TREM-1 contributes to allergic asthma pathology. Utilizing a murine model of asthma, flow cytometry revealed TREM-1+ eosinophils in the lung tissue and airway during allergic airway inflammation. TREM-1 expression was restricted to recruited, inflammatory eosinophils. Expression was induced on bone marrow derived eosinophils by incubation with IL-33, LPS, or GM-CSF. Compared to TREM-1- airway eosinophils, TREM-1+ eosinophils were enriched for pro-inflammatory gene sets including migration, respiratory burst, and cytokine production. Unexpectedly, eosinophil-specific ablation of TREM-1 exacerbated airway IL-5 production, airway MUC5AC production, and lung tissue eosinophil accumulation. Further investigation of transcriptional data revealed apoptosis and superoxide generation related gene sets were enriched in TREM-1+ eosinophils. Consistent with these findings, Annexin V and Caspase 3/7 staining demonstrated higher rates of apoptosis among TREM-1+ eosinophils compared to TREM-1- eosinophils in the inflammatory airway. In vitro, Trem1/3-/- bone marrow derived eosinophils consumed less oxygen than WT in response to PMA, suggesting that TREM-1 promotes superoxide generation in eosinophils. These data reveal protein level expression of TREM-1 by eosinophils, define a population of TREM-1+ inflammatory eosinophils, and demonstrate that eosinophil TREM-1 restricts key features of type 2 lung inflammation.

Eosinophil granulocytes in chronic inflammatory respiratory diseases and CRSwNP: Function, immunological basis, and clinical significance.

INTRODUCTION: Eosinophils play an important regulatory and immunomodulatory role in airway mucosa and have antiparasitic and antiviral properties as well as pro-inflammatory effects that may also cause persistence of inflammation with tissue remodeling. The number of eosinophils and the detection of specific mediators in biological samples from, e.g., blood, nasal secretions, and bronchial fluid can serve as biomarkers that reflect the underlying pathophysiology of certain diseases, predict treatment success, and detect therapy effects. MATERIALS AND METHODS: A literature search was conducted to determine the immunologic basis, mode of action, clinical significance, and available evidence for therapeutic approaches using eosinophil-targeted monoclonal antibodies by searching Medline, Pubmed, and the national and international trial database (ClinicalTrials.gov) and guideline registries as well as the Cochrane Library. Human studies published on the topic in the period up to and including 10/2023 were considered. RESULTS: Based on the international literature and previous experience, the results are summarized, and recommendations are given. CONCLUSION: The important role of eosinophils in immunological processes in the airway mucosa is comprehensively analyzed and can serve as a basis for current and future treatment approaches.

EGPA: Eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome) as a special presentation of chronic rhinosinusitis with nasal polyps (CRSwNP).

INTRODUCTION: Eosinophilic granulomatosis with polyangiitis (EGPA) was formerly known as Churg-Strauss syndrome. The condition is characterized by disseminated necrotizing vasculitis with extravascular granulomas associated with hypereosinophilia. The vasculitides affect small vessels and are associated with antineutrophil cytoplasmic antibodies (ANCAs) detectable in the blood. Distinguishing between type 2-mediated chronic airway inflammation such as chronic rhinosinusitis with nasal polyps (CRSwNP) without vasculitis can be clinically challenging and should be considered. MATERIALS AND METHODS: Immunological background, diagnosis, and therapy of EGPA were identified through literature searches in Medline, PubMed, as well as national and international studies (ClinicalTrials.gov) and the Cochrane Library. Human studies published up to and including 10/2023 on the topic were considered. RESULTS: In cases of deteriorating general health with previously known eosinophilic inflammation of the upper and lower airways, EGPA and its interdisciplinary investigation should be considered. Various types of eosinophilic inflammation and syndromes must be considered differentially. CONCLUSION: Characterization of mucosal airway inflammation through biomarker determination is meaningful and occasionally makes the difference for targeted therapy.

[[Eosinophilic fasciitis: From pathophysiology to therapeutics]]. / Fasciite à éosinophiles : actualités physiopathologiques et nouvelles voies thérapeutiques.

Eosinophilic fasciitis (EF) is a rare connective tissue disorder characterized by painful edema and induration of the limbs and trunk, likely associated with hypereosinophilia and hypergammaglobulinemia. EF causes arthralgia and range of motion limitation, leading to significant functional impairment and poor quality of life. Since its description by Shulman in 1974, over 300 cases have been reported. We present here a review of the latest diagnostic, pathophysiological and therapeutic developments in this disease. Magnetic resonance imaging appears useful to guide diagnosis and biopsy. Diagnosis is based on a deep skin biopsy involving the fascia, which will reveal edema, sclerofibrosis of the muscular fascia and subcutaneous tissue, and an inflammatory infiltrate sometimes composed of eosinophilic polynuclear cells. EF may occur in patients treated with immune checkpoint inhibitors and the diagnosis should be raised in case of cutaneous sclerosis in these patients. The pathophysiology of the disease remains poorly understood, and its management lacks randomized, controlled, blinded trials. First-line treatment consists in oral corticosteroid therapy, sometimes combined with an immunosuppressant, mainly methotrexate. A better understanding of the pathophysiology has opened new therapeutic perspectives and clarified the role of targeted therapies in the management of EF, such as interleukin-6 inhibitors, whose efficacy has been reported in several cases.

Patient education needs in severe asthma, a pilot study.

BACKGROUND: Severe asthma is characterized by frequent exacerbations, altered lung function, and impaired quality of life. Tailored patient education allows for the improvement of both asthma management and quality of life. Our study aimed to assess the needs of severe asthma patient in therapeutic education, according to previous therapeutic patient education background and asthma phenotype. METHODS: Consecutive patients monitored for severe asthma in a tertiary referral center were considered for inclusion and answered a questionnaire detailing their patient education needs and the topics they would like to discuss. Asthma history, clinical and biological data, and lung function results were recorded. RESULTS: Fifty-three patients were included and 47 (88.7%) expressed at least one need. The most frequently selected topics were "life with asthma" (83%), "treatment use" (68%), and "exacerbation management" (60%), independent of previous participation in a patient education program dedicated to asthma. Patients of older age at inclusion, uncontrolled asthma, and T2-high phenotypes were associated with different profiles of patient education needs. CONCLUSION: Our study identified frequent and various patient educational needs among severe asthmatics, highlighting the importance of an in-depth assessment of severe asthmatics expectations and the crucial need for the development of dedicated educational tools.

The role of mitochondria in eosinophil function: implications for severe asthma pathogenesis.

Mitochondria are key metabolic hubs involved in cellular energy production and biosynthesis. ATP is generated primarily by glucose and fatty acid oxidation through the tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS) in the mitochondria. During OXPHOS there is also production of reactive oxygen species (ROS), which are involved in the regulation of cellular function. Mitochondria are also central in the regulating cell survival and death, particularly in the intrinsic apoptosis pathway. Severe asthma is a heterogeneous disease driven by various immune mechanisms. Severe eosinophilic asthma entails a type 2 inflammatory response and peripheral and lung eosinophilia, associated with severe airflow obstruction, frequent exacerbations and poor response to treatment. Mitochondrial dysfunction and altered metabolism have been observed in airway epithelial and smooth muscle cells from patients with asthma. However, the role of mitochondria in the development of eosinophilia and eosinophil-mediated inflammation in severe asthma is unknown. In this review, we discuss the currently limited literature on the role of mitochondria in eosinophil function and how it is regulated by asthma-relevant cytokines, including interleukin (IL)-5 and granulocyte-macrophage colony-stimulating factor (GM-CSF), as well as by corticosteroid drugs. Moreover, we summarise the evidence on the role of mitochondria in the regulation of eosinophils apoptosis and eosinophil extracellular trap formation. Finally, we discuss the possible role of altered mitochondrial function in eosinophil dysfunction in severe asthma and suggest possible research avenues in order to better understand their role in disease pathogenesis, and identify novel therapeutic targets.