Functional extracellular eosinophil granules: novel implications in eosinophil immunobiology. Curr Opin Immunol. 2009;21:694-699. [PMID: 19709867 DOI: 10.1016/j.coi.2009.07.011]

Eosinophilic mucus diseases

Eosinophilic inflammation is primarily characterized by type 2 immune responses against parasitic organisms. In the contemporary human being especially in developed countries, eosinophilic inflammation is strongly associated with allergic/sterile inflammation, and constitutes an undesired immune reaction. This situation is in stark contrast to neutrophilic inflammation, which is indispensable for the host defense against bacterial infections. Among eosinophilic inflammatory disorders, massive accumulation of eosinophils within mucus is observed in certain cases, and is often linked to the distinctive clinical finding of mucus with high viscosity. Eosinophilic mucus is found in a variety of diseases, including chronic allergic keratoconjunctivitis, chronic rhinosinusitis encompassing allergic fungal sinusitis, eosinophilic otitis media, eosinophilic sialodochitis, allergic bronchopulmonary aspergillosis/mycosis, eosinophilic plastic bronchitis, and eosinophilic asthma. In these pathological conditions, chronic inflammation and tissue remodeling coupled with irreversible organ damage due to persistent adhesion of toxic substances and luminal obstruction may impose a significant burden on the body. Eosinophils aggregate in the hyperconcentrated mucus together with cell-derived crystals, macromolecules, and polymers, thereby affecting the biophysical properties of the mucus. This review focuses on the clinically significant challenges of mucus and discusses the consequences of activated eosinophils on the mucosal surface that impact mucus and persistent inflammation.

A Next-Generation Bacteria (Akkermansia muciniphila BAA-835) Presents Probiotic Potential Against Ovalbumin-Induced Food Allergy in Mice

Next-generation microorganisms have recently gained prominence in the scientific community, mainly due to their probiotic and postbiotic potentials. However, there are few studies that investigate these potentials in food allergy models. Therefore, the present study was designed to evaluate the probiotic potential of Akkermansia muciniphila BAA-835 in an ovalbumin food allergy (OVA) model and also analyse possible postbiotic potential. To access the probiotic potential, clinical, immunological, microbiological, and histological parameters were evaluated. In addition, the postbiotic potential was also evaluated by immunological parameters. Treatment with viable A. muciniphila was able to mitigate weight loss and serum levels of IgE and IgG1 anti-OVA in allergic mice. In addition, the ability of the bacteria to reduce the injury of the proximal jejunum, the eosinophil and neutrophil influx, and the levels of eotaxin-1, CXCL1/KC, IL4, IL6, IL9, IL13, IL17, and TNF, was clear. Furthermore, A. muciniphila was able to attenuate dysbiotic signs of food allergy by mitigating Staphylococcus levels and yeast frequency in the gut microbiota. In addition, the administration of the inactivated bacteria attenuated the levels of IgE anti-OVA and eosinophils, indicating its postbiotic effect. Our data demonstrate for the first time that the oral administration of viable and inactivated A. muciniphila BAA-835 promotes a systemic immunomodulatory protective effect in an in vivo model of food allergy to ovalbumin, which suggests its probiotic and postbiotic properties.

[Eosinophils in otorhinolaryngology: friend or foe?]

This article summarizes the essential aspects of current knowledge about eosinophils, classifies eosinophilia in terms of the dimensions healthy or harmful reaction, takes a specific look at eosinophils in the field of otorhinolaryngology, and gives recommendations for diagnostic workup and therapeutic intervention in case of proven eosinophilia, particularly as an adverse drug reaction. The thoughts are inspired by communications at the 29th Congress of the European Rhinologic Society in Sofia, Bulgaria, 2023.

Diagnosis and Management of Pediatric Hypereosinophilic Syndrome

Hypereosinophilic syndrome (HES) is a diverse group of disorders characterized by peripheral blood eosinophilia of 1.5 × 10⁹/L (1,500/μL) or greater with evidence of end-organ damage attributable to eosinophilia and no other cause of the end-organ damage. The HES is rare, especially in children. This review aims to provide best practices in diagnosis and treatment of HES in children, including how to differentiate between primary and secondary causes of hypereosinophilia; how to distinguish the differences in clinical presentation, treatment, and prognosis of HES in children and adults; and how to identify key steps in the evaluation and management of HES in children.

Halogenation Activity of Mammalian Heme Peroxidases

Mammalian heme peroxidases are fascinating due to their unique peculiarity of oxidizing (pseudo)halides under physiologically relevant conditions. These proteins are able either to incorporate oxidized halides into substrates adjacent to the active site or to generate different oxidized (pseudo)halogenated species, which can take part in multiple (pseudo)halogenation and oxidation reactions with cell and tissue constituents. The present article reviews basic biochemical and redox mechanisms of (pseudo)halogenation activity as well as the physiological role of heme peroxidases. Thyroid peroxidase and peroxidasin are key enzymes for thyroid hormone synthesis and the formation of functional cross-links in collagen IV during basement membrane formation. Special attention is directed to the properties, enzymatic mechanisms, and resulting (pseudo)halogenated products of the immunologically relevant proteins such as myeloperoxidase, eosinophil peroxidase, and lactoperoxidase. The potential role of the (pseudo)halogenated products (hypochlorous acid, hypobromous acid, hypothiocyanite, and cyanate) of these three heme peroxidases is further discussed.

Heme Peroxidases at Unperturbed and Inflamed Mucous Surfaces

In our organism, mucous surfaces are important boundaries against the environmental milieu with defined fluxes of metabolites through these surfaces and specific rules for defense reactions. Major mucous surfaces are formed by epithelia of the respiratory system and the digestive tract. The heme peroxidases lactoperoxidase (LPO), myeloperoxidase (MPO), and eosinophil peroxidase (EPO) contribute to immune protection at epithelial surfaces and in secretions. Whereas LPO is secreted from epithelial cells and maintains microbes in surface linings on low level, MPO and EPO are released from recruited neutrophils and eosinophils, respectively, at inflamed mucous surfaces. Activated heme peroxidases are able to oxidize (pseudo)halides to hypohalous acids and hypothiocyanite. These products are involved in the defense against pathogens, but can also contribute to cell and tissue damage under pathological conditions. This review highlights the beneficial and harmful functions of LPO, MPO, and EPO at unperturbed and inflamed mucous surfaces. Among the disorders, special attention is directed to cystic fibrosis and allergic reactions.

Eosinophils and eosinophil-associated disorders: immunological, clinical, and molecular complexity

Eosinophils and their mediators play a crucial role in various reactive states such as bacterial and viral infections, chronic inflammatory disorders, and certain hematologic malignancies. Depending on the underlying pathology, molecular defect(s), and the cytokine- and mediator-cascades involved, peripheral blood and tissue hypereosinophilia (HE) may develop and may lead to organ dysfunction or even organ damage which usually leads to the diagnosis of a HE syndrome (HES). In some of these patients, the etiology and impact of HE remain unclear. These patients are diagnosed with idiopathic HE. In other patients, HES is diagnosed but the etiology remains unknown — these patients are classified as idiopathic HES. For patients with HES, early therapeutic application of agents reducing eosinophil counts is usually effective in avoiding irreversible organ damage. Therefore, it is important to systematically explore various diagnostic markers and to correctly identify the disease elicitors and etiology. Depending on the presence and type of underlying disease, HES are classified into primary (clonal) HES, reactive HES, and idiopathic HES. In most of these patients, effective therapies can be administered. The current article provides an overview of the pathogenesis of eosinophil-associated disorders, with special emphasis on the molecular, immunological, and clinical complexity of HE and HES. In addition, diagnostic criteria and the classification of eosinophil disorders are reviewed in light of new developments in the field.

Exosomes: A Key Piece in Asthmatic Inflammation

Asthma is a chronic disease of the airways that has an important inflammatory component. Multiple cells are implicated in asthma pathogenesis (lymphocytes, eosinophils, mast cells, basophils, neutrophils), releasing a wide variety of cytokines. These cells can exert their inflammatory functions throughout extracellular vesicles (EVs), which are small vesicles released by donor cells into the extracellular microenvironment that can be taken up by recipient cells. Depending on their size, EVs can be classified as microvesicles, exosomes, or apoptotic bodies. EVs are heterogeneous spherical structures secreted by almost all cell types. One of their main functions is to act as transporters of a wide range of molecules, such as proteins, lipids, and microRNAs (miRNAs), which are single-stranded RNAs of approximately 22 nucleotides in length. Therefore, exosomes could influence several physiological and pathological processes, including those involved in asthma. They can be detected in multiple cell types and biofluids, providing a wealth of information about the processes that take account in a pathological scenario. This review thus summarizes the most recent insights concerning the role of exosomes from different sources (several cell populations and biofluids) in one of the most prevalent respiratory diseases, asthma.

Atomic Force Microscopy Is a Potent Technique to Study Eosinophil Activation

Eosinophils are multifunctional cells with several functions both in healthy individuals, and those with several diseases. Increased number and morphological changes in eosinophils have been correlated with the severity of an acute asthma exacerbation. We measured eosinophils obtained from healthy controls and individuals with acute asthma using atomic force microscopy (AFM). In the control samples, cells showed more rounded morphologies with some spreading, while activated cells from symptomatic individuals were spreading, and presenting emission of multiple pseudopods. Eosinophils presenting separate granules close to the cells suggesting some degranulation was also increased in asthma samples. In comparison to histopathological techniques based on brightfield microscopy, AFM showed considerably more details of these morphological changes, making the technique much more sensitive to detect eosinophil morphological changes that indicate functional alteration of this cell. AFM could be an important tool to evaluate diseases with alterations in eosinophil functions.

Eosinophils in the gastrointestinal tract and their role in the pathogenesis of major colorectal disorders

Eosinophils are currently regarded as versatile mobile cells controlling and regulating multiple biological pathways and responses in health and disease. These cells store in their specific granules numerous biologically active substances (cytotoxic cationic proteins, cytokines, growth factors, chemokines, enzymes) ready for rapid release. The human gut is the main destination of eosinophils that are produced and matured in the bone marrow and then transferred to target tissues through the circulation. In health the most important functions of gut-residing eosinophils comprise their participation in the maintenance of the protective mucosal barrier and interactions with other immune cells in providing immunity to microbiota of the gut lumen. Eosinophils are closely involved in the development of inflammatory bowel disease (IBD), when their cytotoxic granule proteins cause damage to host tissues. However, their roles in Crohn’s disease and ulcerative colitis appear to follow different immune response patterns. Eosinophils in IBD are especially important in altering the structure and protective functions of the mucosal barrier and modulating massive neutrophil influx to the lamina propria followed by transepithelial migration to colorectal mucus. IBD-associated inflammatory process involving eosinophils then appears to expand to the mucus overlaying the internal gut surface. The author hypothesises that immune responses within colorectal mucus as well as ETosis exerted by both neutrophils and eosinophils on the both sides of the colonic epithelial barrier act as additional pathogenetic factors in IBD. Literature analysis also shows an association between elevated eosinophil levels and better colorectal cancer (CRC) prognosis, but mechanisms behind this effect remain to be elucidated. In conclusion, the author emphasises the importance of investigating colorectal mucus in IBD and CRC patients as a previously unexplored milieu of disease-related inflammatory responses.

The Immunomodulatory and Antimicrobial Properties of the Vertebrate Ribonuclease A Superfamily

The Ribonuclease A Superfamily is composed of cationic peptides that are secreted by immune cells and epithelial tissues. Although their physiological roles are unclear, several members of the vertebrate Ribonuclease A Superfamily demonstrate antimicrobial and immune modulation activities. The objective of this review is to provide an overview of the published literature on the Ribonuclease A Superfamily with an emphasis on each peptide’s regulation, antimicrobial properties, and immunomodulatory functions. As additional insights emerge regarding the mechanisms in which these ribonucleases eradicate invading pathogens and modulate immune function, these ribonucleases may have the potential to be developed as a novel class of therapeutics for some human diseases.

Immune Modulation by Human Secreted RNases at the Extracellular Space

The ribonuclease A superfamily is a vertebrate-specific family of proteins that encompasses eight functional members in humans. The proteins are secreted by diverse innate immune cells, from blood cells to epithelial cells and their levels in our body fluids correlate with infection and inflammation processes. Recent studies ascribe a prominent role to secretory RNases in the extracellular space. Extracellular RNases endowed with immuno-modulatory and antimicrobial properties can participate in a wide variety of host defense tasks, from performing cellular housekeeping to maintaining body fluid sterility. Their expression and secretion are induced in response to a variety of injury stimuli. The secreted proteins can target damaged cells and facilitate their removal from the focus of infection or inflammation. Following tissue damage, RNases can participate in clearing RNA from cellular debris or work as signaling molecules to regulate the host response and contribute to tissue remodeling and repair. We provide here an overall perspective on the current knowledge of human RNases’ biological properties and their role in health and disease. The review also includes a brief description of other vertebrate family members and unrelated extracellular RNases that share common mechanisms of action. A better knowledge of RNase mechanism of actions and an understanding of their physiological roles should facilitate the development of novel therapeutics.

Inflammatory and Oxidative Stress Markers in Experimental Allergic Asthma

Ovalbumin-induced allergic lung inflammation (ALI) is a condition believed to be mediated by cytokines, extracellular matrix remodeling, and redox imbalance. In this study, we evaluated pulmonary function together with inflammatory markers as interleukin-4 (IL-4), myeloperoxidase (MPO), eosinophil cells, and redox markers in the lungs of BALB/c mice after ovalbumin (OVA) sensitization and challenge. Our results showed an increase in bronchial hyperresponsiveness stimulated by methacholine (Mch), inflammatory cell influx, especially eosinophils together with an increase of high mobility group box 1 (HMGB1) and altered lipid peroxidation (LP) and antioxidant defenses in the OVA group compared to the control group (p ≤ 0.5). Thus, we demonstrated that OVA-induced ALI altered redox status concomitantly with impaired lung function, which was associated with HMGB1 expression and proteolytic remodeling. Taken together all results found here, we may suggest HMGB1 is an important therapeutic target for asthma, once orchestrates the redox signaling, inflammation, and remodeling that contribute to the disease development.

Eosinophil Development, Disease Involvement, and Therapeutic Suppression

Human eosinophils have characteristic morphologic features, including a bilobed nucleus and cytoplasmic granules filled with cytotoxic and immunoregulatory proteins that are packaged in a specific manner. Eosinophil production in the bone marrow is exquisitely regulated by timely expression of a repertoire of transcription factors that work together via collaborative and hierarchical interactions to direct eosinophil development. In addition, proper granule formation, which occurs in a spatially organized manner, is an intrinsic checkpoint that must be passed for proper eosinophil production to occur. In eosinophil-associated disorders, eosinophils and their progenitors can be recruited in large numbers into tissues where they can induce proinflammatory organ damage in response to local signals. Eosinophils are terminally differentiated and do not proliferate once they leave the bone marrow. The cytokine IL-5 specifically enhances eosinophil production and, along with other mediators, promotes eosinophil activation. Indeed, eosinophil depletion with anti-IL-5 or anti-IL-5Rα is now proven to be clinically beneficial for several eosinophilic disorders, most notably severe asthma, and several therapeutics targeting eosinophil viability and production are now in development. Significant progress has been made in our understanding of eosinophil development and the consequences of tissue eosinophilia. Future research efforts focused on basic eosinophil immunobiology and translational efforts to assist in the diagnosis, treatment selection, and resolution of eosinophil-associated disorders will likely be informative and clinically helpful.

Cysteinyl Leukotrienes in Eosinophil Biology: Functional Roles and Therapeutic Perspectives in Eosinophilic Disorders

Cysteinyl leukotrienes (cysLTs), LTC4, and its extracellular metabolites, LTD4 and LTE4, have varied and multiple roles in mediating eosinophilic disorders including host defense against parasitic helminthes and allergic inflammation, especially in the lung and in asthma. CysLTs are known to act through at least 2 receptors termed cysLT1 receptor (CysLT1R) and cysLT2 receptor (CysLT2R). Eosinophils contain a dominant population of cytoplasmic crystalloid granules that store various preformed proteins. Human eosinophils are sources of cysLTs and are known to express the two known cysLTs receptors (CysLTRs). CysLTs can have varied functions on eosinophils, ranging from intracrine regulators of secretion of granule-derived proteins to paracrine/autocrine roles in eosinophil chemotaxis, differentiation, and survival. Lately, it has been recognized the expression of CysLTRs in the membranes of eosinophil granules. Moreover, cysLTs have been shown to evoke secretion from isolated cell-free eosinophil granules operating through their receptors expressed on granule membranes. In this work, we review the functional roles of cysLTs in eosinophil biology. We review cysLTs biosynthesis, their receptors, and argue the intracrine and paracrine/autocrine responses induced by cysLTs in eosinophils and in isolated free extracellular eosinophil granules. We also examine and speculate on the therapeutic relevance of targeting CysLTRs in the treatment of eosinophilic disorders.

Ferulic acid supresses Th2 immune response and prevents remodeling in ovalbumin-induced pulmonary allergy associated with inhibition of epithelial-derived cytokines

Asthma is characterized by intermittent airway obstruction and chronic inflammation, orchestrated primarily by Th2 cytokines. There is a strong rationale for developing new asthma therapies, since current treatment protocols present side effects and may not be effective in cases of difficult-to-control asthma. The purpose of this study was to evaluate the effect of ferulic acid, a phenolic acid commonly present in plants, in the ovalbumin-induced pulmonary allergy murine model.

METHODS

BALB/c mice were sensitized and challenged with ovalbumin, and treatments were provided by gavage. Six groups of mice (n = 6) were studied, labeled as: control, pulmonary allergy, dexamethasone, and 3 receiving ferulic acid (at 25, 50, and 100 mg/kg). Lung tissue, bronchoalveolar lavage fluid and serum were collected for analysis.

RESULTS

Ferulic acid treatment inhibited an established allergic Th2-response by decreasing the key features of pulmonary allergy, including lung and airway inflammation, eosinophil infiltration, mucus production and serum levels of OVA-specific IgE. These results were associated with lower levels of CCL20, CCL11 and CCL5 chemokines and IL-4, IL-5, IL-13, TSLP, IL-25 and IL-33 cytokines in lung tissue homogenate.

CONCLUSIONS

In this study it was demonstrated for the first time that ferulic acid treatment is able to suppress one of the main features of the airway remodeling, indicated by reduction of mucus production, besides the Th2 pathogenic response on ovalbumin-induced pulmonary allergy. Taken together, results shows that the immunopathological mechanism underlying these effects is linked to a reduction of the epithelial-derived chemokines and cytokines, suggesting that ferulic acid may be useful as a potential therapeutic agent for asthma.

Role of Eosinophil Granulocytes in Allergic Airway Inflammation Endotypes

Eosinophil granulocytes are intriguing members of the innate immunity system that have been considered important defenders during parasitic diseases as well as culprits during allergy-associated inflammatory diseases. Novel studies have, however, found new homoeostasis-maintaining roles for the cell. Recent clinical trials blocking different Th2 cytokines have uncovered that asthma is heterogeneous entity and forms different characteristic endotypes. Although eosinophils are present in allergic asthma with early onset, the cells may not be essential for the pathology. The cells are, however, likely disease causing in asthma with a late onset, which is often associated with chronic rhinosinusitis. Assessment of eosinophilia, fraction exhaled nitric oxide (FeNO) and periostin are markers that have emerged useful in assessing and monitoring asthma severity and endotype. Current scientific knowledge suggests that eosinophils are recruited by the inflammatory environment, activated by the innate interleukin (IL)-33 and prevented from apoptosis by both lymphocytes and innate immune cells such as type two innate immune cells. Eosinophils contain four specific granule proteins that exhibit an array of toxic and immune-modulatory activates. The granule proteins can be released by different mechanisms. Additionally, eosinophils contain a number of inflammatory cytokines and lipid mediators as well as radical oxygen species that might contribute to the disease both by the recruitment of other cells and the direct damage to supporting cells, leading to exacerbations and tissue fibrosis. This review aimed to outline current knowledge how eosinophils are recruited, activated and mediate damage to tissues and therapies used to control the cells.

The Eosinophil in Infection

First described by Paul Ehrlich in 1879, who noted its characteristic staining by acidophilic dyes, for many years, the eosinophil was considered to be an end-effector cell associated with helminth infections and a cause of tissue damage. Over the past 30 years, research has helped to elucidate the complexity of the eosinophil's function and establish its role in host defense and immunity. Eosinophils express an array of ligand receptors which play a role in cell growth, adhesion, chemotaxis, degranulation, and cell-to-cell interactions. They play a role in activation of complement via both classical and alternative pathways. Eosinophils synthesize, store and secrete cytokines, chemokines, and growth factors. They can process antigen, stimulate T cells, and promote humoral responses by interacting with B cells. Eosinophils can function as antigen presenting cells and can regulate processes associated with both T1 and T2 immunity. Although long known to play a role in defense against helminth organisms, the interactions of eosinophils with these parasites are now recognized to be much more complex. In addition, their interaction with other pathogens continues to be investigated. In this paper, we review the eosinophil's unique biology and structure, including its characteristic granules and the effects of its proteins, our developing understanding of its role in innate and adaptive immunity and importance in immunomodulation, and the part it plays in defense against parasitic, viral, fungal and bacterial infections. Rather than our worst enemy, the eosinophil may, in fact, be one of the most essential components in host defense and immunity.

Monoclonal antibody therapy for the treatment of asthma and chronic obstructive pulmonary disease with eosinophilic inflammation

Eosinophils have been linked with asthma for more than a century, but their role has been unclear. This review discusses the roles of eosinophils in asthma and chronic obstructive pulmonary disease (COPD) and describes therapeutic antibodies that affect eosinophilia. The aims of pharmacologic treatments for pulmonary conditions are to reduce symptoms, slow decline or improve lung function, and reduce the frequency and severity of exacerbations. Inhaled corticosteroids (ICS) are important in managing symptoms and exacerbations in asthma and COPD. However, control with these agents is often suboptimal, especially for patients with severe disease. Recently, new biologics that target eosinophilic inflammation, used as adjunctive therapy to corticosteroids, have proven beneficial and support a pivotal role for eosinophils in the pathology of asthma. Nucala® (mepolizumab; anti-interleukin [IL]-5) and Cinquair® (reslizumab; anti-IL-5), the second and third biologics approved, respectively, for the treatment of asthma, exemplifies these new treatment options. Emerging evidence suggests that eosinophils may contribute to exacerbations and possibly to lung function decline for a subset of patients with COPD. Here we describe the pharmacology of therapeutic antibodies inhibiting IL-5 or targeting the IL-5 receptor, as well as other cytokines contributing to eosinophilic inflammation. We discuss their roles as adjuncts to conventional therapeutic approaches, especially ICS therapy, when disease is suboptimally controlled. These agents have achieved a place in the therapeutic armamentarium for asthma and COPD and will deepen our understanding of the pathogenic role of eosinophils.

Cyclophilin D regulates necrosis, but not apoptosis, of murine eosinophils

Eosinophil degranulation and clusters of free extracellular granules are frequently observed in diverse diseases, including atopic dermatitis, nasal polyposis, and eosinophilic esophagitis. Whether these intact granules are released by necrosis or a biochemically mediated cytolysis remains unknown. Recently, a peptidyl-prolyl isomerase located within the mitochondrial matrix, cyclophilin D (PPIF), was shown to regulate necrotic, but not apoptotic, cell death in vitro in fibroblasts, hepatocytes, and cardiomyocytes. Whether cyclophilin D regulates necrosis in hematopoietic cells such as eosinophils remains unknown. We used PPIF-deficient (Ppif(-/-)) mice to test whether cyclophilin D is required for regulating eosinophil necrosis. PPIF deficiency did not affect eosinophil development or maturation at baseline. After in vitro ionomycin or H2O2 treatment, Ppif(-/-) eosinophils were significantly protected from Ca(2+) overload- or oxidative stress-induced necrosis. Additionally, Ppif(-/-) eosinophils demonstrated significantly decreased necrosis, but not apoptosis, in response to Siglec-F cross-linking, a stimulus associated with eosinophil-mediated processes in vitro and in vivo. When treated with apoptosis inducers, Ppif(+/+) and Ppif(-/-) eosinophils exhibited no significant difference in apoptosis or secondary necrosis. Finally, in a dextran sodium sulfate-induced colitis model, although levels of colitogenic cytokines and eosinophil-selective chemokines were comparable between Ppif(+/+) and Ppif(-/-) mice, the latter exhibited decreased clinical outcomes. This correlated with significantly reduced eosinophil cytolysis in the colon. Collectively, our present studies demonstrate that murine eosinophil necrosis is regulated in vitro and in vivo by cyclophilin D, at least in part, thus providing new insight into the mechanism of eosinophil necrosis and release of free extracellular granules in eosinophil-associated diseases.

Multifaceted roles of cysteinyl leukotrienes in eliciting eosinophil granule protein secretion

Cysteinyl leukotrienes (cysLTs) are cell membrane-impermeant lipid mediators that play major roles in the pathogenesis of eosinophilic inflammation and are recognized to act via at least 2 receptors, namely, cysLT1 receptor (cysLT1R) and cysLT2 receptor (cysLT2R). Eosinophils, which are granulocytes classically associated with host defense against parasitic helminthes and allergic conditions, are distinguished from leukocytes by their dominant population of cytoplasmic crystalloid (also termed secretory, specific, or secondary) granules that contain robust stores of diverse preformed proteins. Human eosinophils are the main source of cysLTs and are recognized to express both cysLTs receptors (cysLTRs) on their surface, at the plasma membrane. More recently, we identified the expression of cysLTRs in eosinophil granule membranes and demonstrated that cysLTs, acting via their granule membrane-expressed receptors, elicit secretion from cell-free human eosinophil granules. Herein, we review the multifaceted roles of cysLTs in eliciting eosinophil granule protein secretion. We discuss the intracrine and autocrine/paracrine secretory responses evoked by cysLTs in eosinophils and in cell-free extracellular eosinophil crystalloid granules. We also discuss the importance of this finding in eosinophil immunobiology and speculate on its potential role(s) in eosinophilic diseases.

Exosome secretion by eosinophils: A possible role in asthma pathogenesis

BACKGROUND

Eosinophils secrete several granules that are involved in the propagation of inflammatory responses in patients with pathologies such as asthma.

OBJECTIVE

We hypothesized that some of these granules are exosomes, which, when transferred to the recipient cells, could modulate asthma progression.

METHODS

Eosinophils were purified from peripheral blood and cultured with or without IFN-γ or eotaxin. Multivesicular bodies (MVBs) in eosinophils were studied by using fluorescence microscopy, transmission electron microscopy (TEM), and flow cytometry. Exosome secretion was measured and exosome characterization was performed with TEM, Western blotting, and NanoSight analysis.

RESULTS

Generation of MVBs in eosinophils was confirmed by using fluorescence microscopy and flow cytometry and corroborated by means of TEM. Having established that eosinophils contain MVBs, our aim was to demonstrate that eosinophils secrete exosomes. To do this, we purified exosomes from culture medium of eosinophils and characterized them. Using Western blot analysis, we demonstrated that eosinophils secreted exosomes and that the discharge of exosomes to extracellular media increases after IFN-γ stimulation. We measured exosome size and quantified exosome production from healthy and asthmatic subjects using nanotracking analysis. We found that exosome production was augmented in asthmatic patients.

CONCLUSION

Our findings are the first to demonstrate that eosinophils contain functional MVBs and secrete exosomes and that their secretion is increased in asthmatic patients. Thus exosomes might play an important role in the progression of asthma and eventually be considered a biomarker.

Eosinophil-Specific Granules in Tumor Cell Cytoplasm: Unusual Ultrastructural Findings in a Case of Diffuse-Type Gastric Carcinoma

A case of desmoplastic variant of diffuse-type gastric carcinoma in a 72-year-old woman is reported. Microscopic findings included poorly cohesive tumor cells, resembling mononuclear inflammatory cells, prominent diffuse desmoplasia, and tumor-associated tissue eosinophilia. Electron microscopy confirmed the undifferentiated phenotype of tumor cells and disclosed activated eosinophils in the tumor stroma. Eosinophil-specific granules were found either free in the tumor stroma or within the cytoplasm of some tumor cells. Electron microscopy provided also circumstantial evidence of phagocytosis of apoptotic eosinophils by tumor cells. Extracellular, membrane-bound, eosinophil-specific granules have been long recognized in tissues associated with eosinophilia, including allergic diseases, inflammatory responses to helminths, and in stroma of some neoplasms. Our ultrastructural study now extends these findings and provides additional morphological evidence of eosinophil-specific granules within the cytoplasm of gastric carcinoma cells.

Eosinophil secretion of granule-derived cytokines

Eosinophils are tissue-dwelling leukocytes, present in the thymus, and gastrointestinal and genitourinary tracts of healthy individuals at baseline, and recruited, often in large numbers, to allergic inflammatory foci and sites of active tissue repair. The biological significance of eosinophils is vast and varied. In health, eosinophils support uterine and mammary gland development, and maintain bone marrow plasma cells and adipose tissue alternatively activated macrophages, while in response to tissue insult eosinophils function as inflammatory effector cells, and, in the wake of an inflammatory response, promote tissue regeneration, and wound healing. One common mechanism driving many of the diverse eosinophil functions is the regulated and differential secretion of a vast array of eosinophil-derived cytokines. Eosinophils are distinguished from most other leukocytes in that many, if not all, of the over three dozen eosinophil-derived cytokines are pre-synthesized and stored within intracellular granules, poised for very rapid, stimulus-induced secretion. Eosinophils engaged in cytokine secretion in situ utilize distinct pathways of cytokine release that include classical exocytosis, whereby granules themselves fuse with the plasma membrane and release their entire contents extracellularly; piecemeal degranulation, whereby granule-derived cytokines are selectively mobilized into vesicles that emerge from granules, traverse the cytoplasm and fuse with the plasma membrane to release discrete packets of cytokines; and eosinophil cytolysis, whereby intact granules are extruded from eosinophils, and deposited within tissues. In this latter scenario, extracellular granules can themselves function as stimulus-responsive secretory-competent organelles within the tissue. Here, we review the distinctive processes of differential secretion of eosinophil granule-derived cytokines.

The role of airway epithelial cells and innate immune cells in chronic respiratory disease

An abnormal immune response to environmental agents is generally thought to be responsible for causing chronic respiratory diseases, such as asthma and chronic obstructive pulmonary disease (COPD). Based on studies of experimental models and human subjects, there is increasing evidence that the response of the innate immune system is crucial for the development of this type of airway disease. Airway epithelial cells and innate immune cells represent key components of the pathogenesis of chronic airway disease and are emerging targets for new therapies. In this Review, we summarize the innate immune mechanisms by which airway epithelial cells and innate immune cells regulate the development of chronic respiratory diseases. We also explain how these pathways are being targeted in the clinic to treat patients with these diseases.

Primary lysis of eosinophils in severe desquamative asthma

Primary lysis of eosinophils liberates free eosinophil granules (FEGs) releasing toxic proteins in association with bronchial epithelial injury repair. Eosinophil lysis may be significantly pathogenic. Bronchial mucosal FEGs are associated with uncontrolled asthma, severe asthma, aspirin-sensitive asthma, and lethal asthma. FEGs in the bronchial wall may characterize severe asthma without sputum eosinophilia. Excessive numbers of sputum FEGs occur in severe exacerbations of asthma and are reduced along with clinical improvement. Occurrence of FEGs affects interpretation of other sputum biomarkers including numbers of eosinophils, ECP, and eosinophil-stained macrophages. Thus, eosinophil lysis produces FEGs as bronchial biomarkers of severe asthma. Blood eosinophils in severe asthma seem primed exhibiting a propensity to lyse that is greater the more severe the asthma. Proclivity of blood eosinophils to lyse also distinguished three levels of severity among children with exacerbations of asthma. Numerous FEGs releasing toxic proteins occur in association with grave derangement and shedding of epithelium in severe asthma. Subepithelial FEGs correlate negatively with intact bronchial epithelium in clinically uncontrolled asthma. Significant correlations between sputum ECP, Creola bodies, and severity of asthma exacerbations have also been demonstrated. Hence, eosinophil lysis apparently causes epithelial desquamation in severe asthma. Exaggerated epithelial repair in turn would contribute to inflammatory and remodelling features of severe asthma. Perseverance of FEGs together with maintained disease activity, despite treatment with 'eosinophil-depleting' steroids and anti-IL5 biologicals, agrees with the possibility that eosinophil lysis is worthy target for novel anti-asthma drugs. Priming and lysis of eosinophils, and protein release from FEGs, are regulated and can be targeted. Eosinophil lysis and FEGs belong to the disease picture of severe asthma and need consideration in asthma studies concerned with phenotypes, biomarkers, roles of epithelial injury/repair, and targeting novel drugs.

Clinical impact of tumor-infiltrating inflammatory cells in primary small cell esophageal carcinoma

Primary small cell esophageal carcinoma is a rare and aggressive type of gastrointestinal cancer with poor prognosis. In the present study, the impact of tumour infiltrating inflammatory cells on clinico-pathological characteristics and the patients' prognosis were analysed. A total of 36 small cell esophageal carcinomas, 19 adjacent normal tissues and 16 esophageal squamous cell carcinoma samples were collected. Qualified pathologists examined eosinophils, neutrophils, lymphocytes and macrophages on histochemical slides. The infiltration of eosinophils and macrophages in small cell esophageal carcinoma was significantly increased as compared with tumor adjacent normal tissues, and was significantly less in esophageal squamous cell carcinoma. Macrophage count was significantly associated with (p = 0.015) lymph node-stage in small cell esophageal carcinoma. When we grouped patients into two groups by counts of infiltrated inflammatory cells, Kaplan-Meier analysis revealed that high macrophage infiltration group (p = 0.004) and high eosinophil infiltration group (p = 0.027) had significantly enhanced survival. In addition, multivariate analysis unveiled that eosinophil count (p = 0.002) and chemotherapy (Yes vs. No, p = 0.001) were independent prognostic indicators. Taken together, infiltration of macrophages and eosinophils into the solid tumor appear to be important in the progression of small cell esophageal carcinoma and patients' prognosis.

Functional extracellular eosinophil granules: a bomb caught in a trap

Eosinophils store a wide range of preformed proteins, including cationic proteins and cytokines, within their morphologically unique granules. Recently, we have demonstrated that cell-free eosinophil granules are functional, independent, secretory organelles and that clusters of cell-free granules are commonly found at tissue sites associated with various pathologic conditions. Cytolytic release of intact eosinophil granules produces extracellular organelles that are fully capable of ligand-elicited, active, secretory responses and are hence able to act as 'cluster bombs' that amplify the differential secretory properties of eosinophils. Herein, we review recent progress in elucidating the molecular mechanisms involved in the cytolytical release of intact cell-free functional eosinophil granules in a process associated with the liberation of eosinophil DNA traps (nets), a known aspect of the innate response recognized in various immune cells and pathological conditions. We also discuss the importance of clusters of cell-free eosinophil granules trapped in eosinophil DNA nets in disease and speculate on their potential role(s) in immunity as well as compare available data on DNA-releasing neutrophils.

Morphological changes in eosinophils are reliable markers of the severity of an acute asthma exacerbation in children

BACKGROUND

Early identification of the severity of asthma exacerbation would be helpful for the management of patients. We aimed to evaluate the correlation of morphological change in activated eosinophils and the severity of an asthma exacerbation.

METHODS

Blood was collected from 55 asthmatic children: 40 of whom were having an exacerbation, 15 symptom-free, and 15 healthy controls. The percentage of eosinophils with morphological changes (emission of single or multiple pseudopods, presence of cytoplasmic vacuoles, releasing a small, moderate, or large quantity of granules, spreading, eosinophil death, and presence of cluster of free eosinophil granules) was quantified after the adherence to a slide and compared using the Mann-Whitney test. The correlation between the severity of the asthma exacerbation and the percentage changed eosinophils was tested with Spearman's correlation.

RESULTS

The proportion of activated eosinophils was higher in asthmatic symptom-free children than in the control group, and acute asthma exacerbation produced an additional increase in eosinophil activation (P < 0.01). More significantly increased morphological changes were emissions of multiple pseudopods, presence of cytoplasmic vacuoles, spreading, and presence of a cluster of free eosinophil granules (P < 0.001). The following were correlated with the severity of an asthma exacerbation: ≥14% of eosinophils emitting single pseudopod, 8% emitting multiple pseudopods, 17% with vacuoles, 28% eosinophils releasing a large quantity of granules, and 66% of spread eosinophils.

CONCLUSIONS

Quantifying the morphological changes in eosinophils is a feasible, easy, and reliable manner to identify the severity of an asthma exacerbation and therefore might improve the clinical management of asthmatic children.

Eosinophil-derived cytokines in health and disease: unraveling novel mechanisms of selective secretion

Over the past two decades, our understanding of eosinophils has evolved from that of categorically destructive effector cells to include active participation in immune modulation, tissue repair processes, and normal organ development, in both health and disease. At the core of their newly appreciated functions is the capacity of eosinophils to synthesize, store within intracellular granules, and very rapidly secrete a highly diverse repertoire of cytokines. Mechanisms governing the selective secretion of preformed cytokines from eosinophils are attractive therapeutic targets and may well be more broadly applicable to other immune cells. Here, we discuss recent advances in deciphering pathways of cytokine secretion, both from intact eosinophils and from tissue-deposited cell-free eosinophil granules, extruded from eosinophils undergoing a lytic cell death.

Targeting eosinophils in allergy, inflammation and beyond

Eosinophils can regulate local immune and inflammatory responses, and their accumulation in the blood and tissue is associated with several inflammatory and infectious diseases. Thus, therapies that target eosinophils may help control diverse diseases, including atopic disorders such as asthma and allergy, as well as diseases that are not primarily associated with eosinophils, such as autoimmunity and malignancy. Eosinophil-targeted therapeutic agents that are aimed at blocking specific steps involved in eosinophil development, migration and activation have recently entered clinical testing and have produced encouraging results and insights into the role of eosinophils. In this Review, we describe recent advances in the development of first-generation eosinophil-targeted therapies and highlight strategies for using personalized medicine to treat eosinophilic disorders.

Eosinophil extracellular DNA trap cell death mediates lytic release of free secretion-competent eosinophil granules in humans

Eosinophils release their granule proteins extracellularly through exocytosis, piecemeal degranulation, or cytolytic degranulation. Findings in diverse human eosinophilic diseases of intact extracellular eosinophil granules, either free or clustered, indicate that eosinophil cytolysis occurs in vivo, but the mechanisms and consequences of lytic eosinophil degranulation are poorly understood. We demonstrate that activated human eosinophils can undergo extracellular DNA trap cell death (ETosis) that cytolytically releases free eosinophil granules. Eosinophil ETosis (EETosis), in response to immobilized immunoglobulins (IgG, IgA), cytokines with platelet activating factor, calcium ionophore, or phorbol myristate acetate, develops within 120 minutes in a reduced NADP (NADPH) oxidase-dependent manner. Initially, nuclear lobular formation is lost and some granules are released by budding off from the cell as plasma membrane-enveloped clusters. Following nuclear chromatolysis, plasma membrane lysis liberates DNA that forms weblike extracellular DNA nets and releases free intact granules. EETosis-released eosinophil granules, still retaining eosinophil cationic granule proteins, can be activated to secrete when stimulated with CC chemokine ligand 11 (eotaxin-1). Our results indicate that an active NADPH oxidase-dependent mechanism of cytolytic, nonapoptotic eosinophil death initiates nuclear chromatolysis that eventuates in the release of intact secretion-competent granules and the formation of extracellular DNA nets.

Eosinophils: changing perspectives in health and disease

Eosinophils have been traditionally perceived as terminally differentiated cytotoxic effector cells. Recent studies have profoundly altered this simplistic view of eosinophils and their function. New insights into the molecular pathways that control the development, trafficking and degranulation of eosinophils have improved our understanding of the immunomodulatory functions of these cells and their roles in promoting homeostasis. Likewise, recent developments have generated a more sophisticated view of how eosinophils contribute to the pathogenesis of different diseases, including asthma and primary hypereosinophilic syndromes, and have also provided us with a more complete appreciation of the activities of these cells during parasitic infection.

Eosinophils: changing perspectives in health and disease

Eosinophils have been traditionally perceived as terminally differentiated cytotoxic effector cells. Recent studies have profoundly altered this simplistic view of eosinophils and their function. New insights into the molecular pathways that control the development, trafficking and degranulation of eosinophils have improved our understanding of the immunomodulatory functions of these cells and their roles in promoting homeostasis. Likewise, recent developments have generated a more sophisticated view of how eosinophils contribute to the pathogenesis of different diseases, including asthma and primary hypereosinophilic syndromes, and have also provided us with a more complete appreciation of the activities of these cells during parasitic infection.

Pathogenesis and classification of eosinophil disorders: a review of recent developments in the field

Eosinophils and their products play an essential role in the pathogenesis of various reactive and neoplastic disorders. Depending on the underlying disease, molecular defect and involved cytokines, hypereosinophilia may develop and may lead to organ damage. In other patients, persistent eosinophilia is accompanied by typical clinical findings, but the causative role and impact of eosinophilia remain uncertain. For patients with eosinophil-mediated organ pathology, early therapeutic intervention with agents reducing eosinophil counts can be effective in limiting or preventing irreversible organ damage. Therefore, it is important to approach eosinophil disorders and related syndromes early by using established criteria, to perform all appropriate staging investigations, and to search for molecular targets of therapy. In this article, we review current concepts in the pathogenesis and evolution of eosinophilia and eosinophil-related organ damage in neoplastic and non-neoplastic conditions. In addition, we discuss classifications of eosinophil disorders and related syndromes as well as diagnostic algorithms and standard treatment for various eosinophil-related disorders.

Eosinophil crystalloid granules: structure, function, and beyond

Eosinophils are granulocytes associated with host defense against parasitic helminths with allergic conditions and more recently, with immunoregulatory responses. Eosinophils are distinguished from leukocytes by their dominant population of cytoplasmic crystalloid (also termed secretory, specific, or secondary) granules that contain robust stores of diverse, preformed cationic proteins. Here, we provide an update on our knowledge about the unique and complex structure of human eosinophil crystalloid granules. We discuss their significance as rich sites of a variety of receptors and review our own recent research findings and those of others that highlight discoveries concerning the function of intracellular receptors and their potential implications in cell signaling. Special focus is provided on how eosinophils might use these intracellular receptors as mechanisms to secrete, selectively and rapidly, cytokines or chemokines and enable cell-free extracellular eosinophil granules to function as independent secretory structures. Potential roles of cell-free eosinophil granules as immune players in the absence of intact eosinophils will also be discussed.

CCL11 elicits secretion of RNases from mouse eosinophils and their cell-free granules

Rapid secretion of eosinophil-associated RNases (EARs), such as the human eosinophilic cationic protein (ECP), from intracellular granules is central to the role of eosinophils in allergic diseases and host immunity. Our knowledge regarding allergic inflammation has advanced based on mouse experimental models. However, unlike human eosinophils, capacities of mouse eosinophils to secrete granule proteins have been controversial. To study mechanisms of mouse eosinophil secretion and EAR release, we combined an RNase assay of mouse EARs with ultrastructural studies. In vitro, mouse eosinophils stimulated with the chemokine eotaxin-1 (CCL11) secreted enzymatically active EARs (EC(50) 5 nM) by piecemeal degranulation. In vivo, in a mouse model of allergic airway inflammation, increased airway eosinophil infiltration (24-fold) correlated with secretion of active RNases (3-fold). Moreover, we found that eosinophilic inflammation in mice can involve eosinophil cytolysis and release of cell-free granules. Cell-free mouse eosinophil granules expressed functional CCR3 receptors and secreted their granule proteins, including EAR and eosinophil peroxidase in response to CCL11. Collectively, these data demonstrate chemokine-dependent secretion of EARs from both intact mouse eosinophils and their cell-free granules, findings pertinent to understanding the pathogenesis of eosinophil-associated diseases, in which EARs are key factors.

Polymorphisms in the RNASE3 gene are associated with susceptibility to cerebral malaria in Ghanaian children

Background

Cerebral malaria (CM) is the most severe outcome of Plasmodium falciparum infection and a major cause of death in children from 2 to 4 years of age. A hospital based study in Ghana showed that P. falciparum induces eosinophilia and found a significantly higher serum level of eosinophil cationic protein (ECP) in CM patients than in uncomplicated malaria (UM) and severe malaria anemia (SA) patients. Single nucleotide polymorphisms (SNPs) have been described in the ECP encoding-gene (RNASE3) of which the c.371G>C polymorphism (rs2073342) results in an arginine to threonine amino acid substitution p.R124T in the polypeptide and abolishes the cytotoxicity of ECP. The present study aimed to investigate the potential association between polymorphisms in RNASE3 and CM.

Methodology/Principal Findings

The RNASE3 gene and flanking regions were sequenced in 206 Ghanaian children enrolled in a hospital based malaria study. An association study was carried out to assess the significance of five SNPs in CM (n = 45) and SA (n = 56) cases, respectively. The two severe case groups (CM and SA) were compared with the non-severe control group comprising children suffering from UM (n = 105). The 371G allele was significantly associated with CM (p = 0.00945, OR = 2.29, 95% CI = 1.22–4.32) but not with SA. Linkage disequilibrium analysis demonstrated significant linkage between three SNPs and the haplotype combination 371G/*16G/*94A was strongly associated with susceptibility to CM (p  = 0.000913, OR = 4.14, 95% CI = 1.79–9.56), thus, defining a risk haplotype. The RNASE3 371GG genotype was found to be under frequency-dependent selection.

Conclusions/Significance

The 371G allele of RNASE3 is associated with susceptibility to CM and forms part of a risk associated haplotype GGA defined by the markers: rs2073342 (G-allele), rs2233860 (G-allele) and rs8019343 (A-allele) respectively. Collectively, these results suggest a hitherto unrecognized role for eosinophils in CM pathogenesis.

Innate immunity in allergic disease

The innate immune system consists of multiple cell types that express germline-encoded pattern recognition receptors that recognize pathogen-associated molecular patterns (PAMPs) or danger-associated molecular patterns (DAMPs). Allergens are frequently found in forms and mixtures that contain PAMPs and DAMPs. The innate immune system is interposed between the external environment and the internal acquired immune system. It is also an integral part of the airways, gut, and skin. These tissues face continuous exposure to allergens, PAMPs, and DAMPs. Interaction of allergens with the innate immune system normally results in immune tolerance but, in the case of allergic disease, this interaction induces recurring and/or chronic inflammation as well as the loss of immunologic tolerance. Upon activation by allergens, the innate immune response commits the acquired immune response to a variety of outcomes mediated by distinct T-cell subsets, such as T-helper 2, regulatory T, or T-helper 17 cells. New studies highlighted in this review underscore the close relationship between allergens, the innate immune system, and the acquired immune system that promotes homeostasis versus allergic disease.

Eosinophils are necessary for pulmonary arterial remodeling in a mouse model of eosinophilic inflammation-induced pulmonary hypertension

There is increasing evidence that inflammation plays a pivotal role in the pathogenesis of some forms of pulmonary hypertension (PH). We recently demonstrated that deficiency of adiponectin (APN) in a mouse model of PH induced by eosinophilic inflammation increases pulmonary arterial remodeling, pulmonary pressures, and the accumulation of eosinophils in the lung. Based on these data, we hypothesized that APN deficiency exacerbates PH indirectly by increasing eosinophil recruitment. Herein, we examined the role of eosinophils in the development of inflammation-induced PH. Elimination of eosinophils in APN-deficient mice by treatment with anti-interleukin-5 antibody attenuated pulmonary arterial muscularization and PH. In addition, we observed that transgenic mice that are devoid of eosinophils also do not develop pulmonary arterial muscularization in eosinophilic inflammation-induced PH. To investigate the mechanism by which APN deficiency increased eosinophil accumulation in response to an allergic inflammatory stimulus, we measured expression levels of the eosinophil-specific chemokines in alveolar macrophages isolated from the lungs of mice with eosinophilic inflammation-induced PH. In these experiments, the levels of CCL11 and CCL24 were higher in macrophages isolated from APN-deficient mice than in macrophages from wild-type mice. Finally, we demonstrate that the extracts of eosinophil granules promoted the proliferation of pulmonary arterial smooth muscle cells in vitro. These data suggest that APN deficiency may exacerbate PH, in part, by increasing eosinophil recruitment into the lung and that eosinophils could play an important role in the pathogenesis of inflammation-induced PH. These results may have implications for the pathogenesis and treatment of PH caused by vascular inflammation.

SIRPα/CD172a regulates eosinophil homeostasis

Eosinophils are abundant in the lamina propria of the small intestine, but they rarely show degranulation in situ under steady-state conditions. In this study, using two novel mAbs, we found that intestinal eosinophils constitutively expressed a high level of an inhibitory receptor signal regulatory protein α (SIRPα)/CD172a and a low, but significant, level of a tetraspanin CD63, whose upregulation is closely associated with degranulation. Cross-linking SIRPα/CD172a on the surface of wild-type eosinophils significantly inhibited the release of eosinophil peroxidase induced by the calcium ionophore A23187, whereas this cross-linking effect was not observed in eosinophils isolated from mice expressing a mutated SIRPα/CD172a that lacks most of its cytoplasmic domain (SIRPα Cyto(-/-)). The SIRPα Cyto(-/-) eosinophils showed reduced viability, increased CD63 expression, and increased eosinophil peroxidase release with or without A23187 stimulation in vitro. In addition, SIRPα Cyto(-/-) mice showed increased frequencies of Annexin V-binding eosinophils and free MBP(+)CD63(+) extracellular granules, as well as increased tissue remodeling in the small intestine under steady-state conditions. Mice deficient in CD47, which is a ligand for SIRPα/CD172a, recapitulated these phenomena. Moreover, during Th2-biased inflammation, increased eosinophil cell death and degranulation were obvious in a number of tissues, including the small intestine, in the SIRPα Cyto(-/-) mice compared with wild-type mice. Collectively, our results indicated that SIRPα/CD172a regulates eosinophil homeostasis, probably by interacting with CD47, with substantial effects on eosinophil survival. Thus, SIRPα/CD172a is a potential therapeutic target for eosinophil-associated diseases.

Effects of aqueous extract of Echinodorus grandiflorus on the immune response in ovalbumin-induced pulmonary allergy

BACKGROUND

Asthma is a disease characterized by intermittent obstruction of the airways and chronic inflammation that affects approximately 300 million people worldwide. The immune response in asthma is predominantly T(H)2, with high levels of total and allergen-specific IgE and bronchial eosinophilia. Asthma treatment is aimed at controlling the disease, and the drugs used currently have systemic adverse effects and generally are not effective in difficult-to-control cases.

OBJECTIVE

To investigate the effect of aqueous extract of Echinodorus grandiflorus, a plant used in folk medicine for its diuretic and anti-inflammatory properties, in a model of pulmonary allergy.

METHODS

BALB/c mice were intraperitoneally sensitized and nasally challenged with ovalbumin. Aqueous extract and dexamethasone treatments (0.1 mL/d per mouse) were initiated on day 32 and concluded on day 40. Eight hours after the last challenge evaluations, of serum, bronchoalveolar lavage, and lung tissue were performed.

RESULTS

Oral treatment with the extract markedly reduced the number of total cells and eosinophils in bronchoalveolar lavage. The eosinophil peroxidase activity in lung tissue, the levels of ovalbumin-specific IgE in serum, the levels of CCL11, and the gene expression of interleukin 4 and interleukin 13 in lung tissue were also lower after treatment.

CONCLUSIONS

These results suggest that the aqueous extract of E grandiflorus is able to modulate allergic pulmonary inflammation and may be useful as a potential therapeutic agent for asthma.