Serum levels of eosinophil cationic protein reflect the state of in vitro degranulation of blood hypodense eosinophils in atopic dermatitis

Eosinophilic airway diseases: basic science, clinical manifestations and future challenges

Eosinophils have a broad range of functions, both homeostatic and pathological, mediated through an array of cell surface receptors and specific secretory granules that promote interactions with their microenvironment. Eosinophil development, differentiation, activation, survival and recruitment are closely regulated by a number of type 2 cytokines, including interleukin (IL)-5, the key driver of eosinophilopoiesis. Evidence shows that type 2 inflammation, driven mainly by interleukin (IL)-4, IL-5 and IL-13, plays an important role in the pathophysiology of eosinophilic airway diseases, including asthma, chronic rhinosinusitis with nasal polyps, eosinophilic granulomatosis with polyangiitis and hypereosinophilic syndrome. Several biologic therapies have been developed to suppress type 2 inflammation, namely mepolizumab, reslizumab, benralizumab, dupilumab, omalizumab and tezepelumab. While these therapies have been associated with clinical benefits in a range of eosinophilic diseases, their development has highlighted several challenges and directions for future research. These include the need for further information on disease progression and identification of treatable traits, including clinical characteristics or biomarkers that will improve the prediction of treatment response. The Nordic countries have a long tradition of collaboration using patient registries and Nordic asthma registries provide unique opportunities to address these research questions. One example of such a registry is the NORdic Dataset for aSThmA Research (NORDSTAR), a longitudinal population-based dataset containing all 3.3 million individuals with asthma from four Nordic countries (Denmark, Finland, Norway and Sweden). Large-scale, real-world registry data such as those from Nordic countries may provide important information regarding the progression of eosinophilic asthma, in addition to clinical characteristics or biomarkers that could allow targeted treatment and ensure optimal patient outcomes.

The emerging roles of eosinophils: Implications for the targeted treatment of eosinophilic-associated inflammatory conditions

Eosinophils have multiple relevant biological functions, including the maintenance of homeostasis, host defense against infectious agents, innate immunity activities, immune regulation through Th1/Th2 balance, anti-inflammatory, and anti-tumorigenic effects. Eosinophils also have a main role in tissue damage through eosinophil-derived cytotoxic mediators that are involved in eosinophilic inflammation, as documented in Th2-high asthma and other eosinophilic-associated inflammatory conditions.

Recent evidence shows that these multiple and apparently conflicting functions may be attributed to the existence of different eosinophil subtypes (i.e.: tissue resident and inducible eosinophils). Therapeutic intervention with biological agents that totally deplete tissues and circulating eosinophils or, vice versa, maintain a minimal proportion of eosinophils, particularly the tissue-resident ones, could therefore have a very different impact on patients, especially when considering the administration of these therapies for prolonged time. In addition, the characterization of the predominant pathway underlying eosinophilic inflammation by surrogate biomarkers (circulating eosinophils, organ-specific eosinophils levels such as eosinophil count in sputum, bronchoalveolar lavage, tissue biopsy; total circulating IgE levels, or the use of FeNO) in the single patient with an eosinophilic-associated inflammatory condition could help in choosing the treatment.

These observations are crucial in light of the increasing therapeutic armamentarium effective in modulating eosinophilic inflammation through the inhibition in different, yet complementary ways of eosinophil pathways, such as the interleukin-5 one (with mepolizumab, benralizumab, reslizumab) or the interleukin-4/13 one (with dupilumab and lebrikizumab), in severe T2-high asthma as well as in other systemic eosinophilic associated diseases, such as eosinophilic granulomatosis with polyangiitis and hypereosinophilic syndrome.

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Recent evidence pointed out the existence of different eosinophil subtypes, i.e. tissue resident and inducible eosinophils, with different and apparently conflicting functions.

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Biological therapies with different mechanisms can deplete completely tissues and circulating eosinophils or maintain a minimal proportion of eosinophils, particularly the tissue-resident ones, and this could therefore have a different impact on patients, especially when considering the administration of these therapies for prolonged time.

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The identification of the predominant pathway underlying eosinophilic inflammation by surrogate biomarkers (circulating eosinophils, organ-specific eosinophils levels such as eosinophil count in sputum, bronchoalveolar lavage, tissue biopsy; total circulating IgE levels, or the use of FeNO) should be sought in the single patient with an eosinophilic-associated inflammatory condition.

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These considerations may help in choosing the best anti-eosinophilic treatment, considering the increasing therapeutic armamentarium effective in modulating eosinophilic inflammation through the inhibition of the interleukin-5 one (with mepolizumab, benralizumab, reslizumab) or the interleukin-4/13 one (with dupilumab and lebrikizumab)

The multiple functions and subpopulations of eosinophils in tissues under steady-state and pathological conditions

Eosinophils not only play a critical role in the pathogenesis of eosinophil-associated diseases, but they also have multiple important biological functions, including the maintenance of homeostasis, host defense against infections, immune regulation through canonical Th1/Th2 balance modulation, and anti-inflammatory and anti-tumorigenic activities. Recent studies have elucidated some emerging roles of eosinophils in steady-state conditions; for example, eosinophils contribute to adipose tissue metabolism and metabolic health through alternatively activated macrophages and the maintenance of plasma cells in intestinal tissue and bone marrow. Moreover, eosinophils exert tissue damage through eosinophil-derived cytotoxic mediators that are involved in eosinophilic airway inflammation, leading to diseases including asthma and chronic rhinosinusitis with nasal polyps characterized by fibrin deposition through excessive response by eosinophils-induced. Thus, eosinophils possessing these various effects reflect the heterogenous features of these cells, which suggests the existence of distinct different subpopulations of eosinophils between steady-state and pathological conditions. Indeed, a recent study demonstrated that instead of dividing eosinophils by classical morphological changes into normodense and hypodense eosinophils, murine eosinophils from lung tissue can be phenotypically divided into two distinct subtypes: resident eosinophils and inducible eosinophils gated by Siglec-F^int CD62L⁺ CD101^low and Siglec-F^high CD62L^- CD101^high, respectively. However, it is difficult to explain every function of eosinophils by rEos and iEos, and the relationship between the functions and subpopulations of eosinophils remains controversial. Here, we overview the multiple roles of eosinophils in the tissue and their biological behavior in steady-state and pathological conditions. We also discuss eosinophil subpopulations.

An extragranular compartment of blood eosinophils contains eosinophil protein X/eosinophil-derived neurotoxin (EPX/EDN)

Serum and plasma profiles of eosinophil protein X (EPX/EDN) and those of other eosinophil proteins differ in various conditions, suggesting a different mobilisation from storage granules. This work studied the subcellular localisation of EPX/EDN in non-primed and in vivo primed blood eosinophils from healthy and allergic subjects, during and out of the pollen season. Primed eosinophils contain easily mobilisable secretory proteins. By fractionation on sucrose density gradients, EPX/EDN localised in the specific granules as well as in a cytoplasmic extra-granular compartment of low equilibrium density that partially overlapped with vesicular structures, cytosolic proteins and plasma membranes. This compartment was clearly separate from the low density peak of ECP that increases during the pollen season. There were no significant differences in the amounts of EPX/EDN present in the low density peak of healthy and allergic subjects. Immuno-gold labelling electron microscopy showed EPX/EDN in specific granules, cytoplasm and associated to plasma membranes. In conclusion, substantial amounts of EPX/EDN localise in an extra-granular, low equilibrium density compartment of human eosinophils.

Probiotics for the treatment or prevention of atopic dermatitis: a review of the evidence from randomized controlled trials

Probiotics are defined as live microorganisms which, when administered in adequate amounts, confer a health benefit on the host. To synthesize the evidence for the effectiveness of probiotics in the treatment or prevention of atopic dermatitis (AD) in children, we reviewed the results of 13 relevant randomized (placebo)-controlled trials (RCTs), 10 of which evaluated probiotics as treatment and 3 for prevention of AD. The main outcome measure in 9 RCTs was the change in SCORAD (SCORing Atopic Dermatitis). Four RCTs suggested that there was a statistically significant decrease in SCORAD after probiotic administration to infants or children with AD for 1 or 2 months compared with that after placebo, while in two RCTs SCORAD was significantly reduced after treatment with lactobacilli only in children with IgE-associated AD. In four of these six RCTs, clinical improvement was associated with a change in some inflammatory markers. In three RCTs, the change in SCORAD was not statistically significant between probiotic- and placebo-treated children, although in one of these trials SCORAD was significantly lower after probiotic than with placebo treatment in food-sensitized children. In most RCTs, probiotics did not cause a statistically significant change in interferon-gamma, interleukin-4, tumor necrosis factor-alpha, eosinophil cationic protein or transforming growth factor-beta compared with placebo. Regarding the effectiveness of probiotics in the prevention of AD, in two RCTs, infants at high risk for atopy who received probiotics developed AD significantly less frequently during the first 2 years of life than infants who received placebo. In these studies, mothers were administered Lactobacillus rhamnosus GG with or without other probiotics perinatally, followed by treatment of the infants with the same probiotics for the first 6 months of life. However, in another trial, neither the frequency nor the severity of AD during the first year of life were significantly different between infants with atopic mothers who received L. acidophilus for the first 6 months of life compared with infants who received placebo.Probiotics, especially L. rhamnosus GG, seem to be effective for the prevention of AD. They were also found to reduce the severity of AD in approximately half of the RCTs evaluated, although they were not found to change significantly most of the inflammatory markers measured in the majority of the RCTs evaluated. More RCTs need to be conducted to elucidate whether probiotics are useful for the treatment or prevention of AD.

Activation of humoral immunity and eosinophils in neuromyelitis optica

OBJECTIVE

To study immunologic alterations in patients with neuromyelitis optica (NMO).

METHODS

The authors studied 8 patients with NMO together with 16 healthy subjects, 16 patients with relapsing remitting multiple sclerosis (RRMS), and 16 patients with secondary progressive MS (SPMS), matched for age and sex, as controls. Because recent histopathologic studies have demonstrated that active NMO lesions consist of perivascular immunoglobulin (Ig) deposition and eosinophil infiltration, IL-5, IL-6, IL-12, IgG, and IgM production by anti-myelin oligodendrocyte glycoprotein (MOG) mononuclear cells in peripheral blood and CSF were selected for study using ELISPOT. Eotaxin-2 (Eo-2) and eotaxin-3 (Eo-3) levels were also assessed using ELISA and eosinophil cationic protein (ECP) levels by radioimmunoassay.

RESULTS

MOG-specific responses in CSF showed significant increase in IL-5, IL-6, IgG, and IgM secreting cells in NMO patients compared with patients with RRMS, SPMS and healthy subjects. Interestingly, numbers of IgM secreting cells were significantly higher than identical specificity IgG secreting ones. Moreover, CSF Eo-2, Eo-3, and ECP levels were also significantly higher in NMO patients compared to all three control populations. Anti-MOG IL-12 secreting cells were increased in CSF and peripheral blood from NMO, RRMS, and SPMS patients when compared to healthy subjects.

CONCLUSIONS

These observations suggest that neuromyelitis optica is associated with a major humoral immune response (particularly anti-MOG IgM production) and eosinophil activation present exclusively in CSF.

Eosinophil infiltration, gastric juice and serum eosinophil cationic protein levels in Helicobacter pylori-associated chronic gastritis and gastric ulcer

INTRODUCTION: Helicobacter pylori is one of the main causes of gastroduodenal diseases, such as chronic gastritis and peptic ulcer. It has been shown that eosinophils increase in the stomach in H. pylori infection. Eosinophilic cationic protein (ECP) is a cytotoxic molecule secreted by the activated eosinophils. However, there are no sufficient data about the role of ECP in H. pylori infection and its effect on ulcer development. In this study we investigated the gastric eosinophilic infiltration, gastric juice and serum ECP levels in patients with chronic gastritis and gastric ulcer associated with H. pylori. MATERIALS AND METHODS: Forty-four H. pylori-positive and 20 H. pylori-negative patients who underwent upper gastrointestinal system endoscopy after admitting with dyspeptic complaints were enrolled in the study. Twenty-one of the H. pylori-positive patients had gastric ulcer while 23 patients had none. During endoscopy, multiple gastric biopsies and juices were taken. In gastric biopsies, H. pylori and eosinophilic infiltration were assessed. Additionally, gastric juice and serum ECP levels were measured. RESULTS: Eosinophil infiltration, gastric juice ECP levels, and gastric juice/serum ECP ratios in the H. pylori-positive group were greater than in the H. pylori-negative group (p < 0.01). There was no statistically significant difference regarding serum ECP levels between the two groups (p > 0.05). When H. pylori-positive patients were compared with regard to gastric ulcer presence, however, there was no significant difference in gastric eosinophil infiltration, gastric juice ECP levels, serum ECP levels, and gastric juice/serum ECP ratios (p > 0.05). CONCLUSION: The results of this study suggest that eosinophils and eosinophil-released ECP may contribute to inflammatory changes seen in chronic gastritis, whereas there is no proof that they play a role in ulcer development.

Serum eosinophil derived neurotoxin may reflect more strongly disease severity in childhood atopic dermatitis than eosinophil cationic protein

Serum levels of eosinophil cationic protein (ECP) have been shown to be a good parameter of the disease severity of patients with atopic dermatitis (AD). However, the relationship between the disease severity and the eosinophil derived neurotoxin (EDN) has not been established in AD patients. The purpose of this study is to examine serum ECP and EDN levels in relation to the disease severity in AD children. Serum ECP and EDN levels were assessed in relation to the skin scores in 34 AD children (18 boys and 16 girls; age 0.6 to 7years: mean+/-S.D. 2.2+/-1.9) and six non-atopic control children (three boys and three girls; age 1 to 3years: mean+/-S.D. 1.7+/-0.9). Serum ECP and EDN levels of the patients with AD were significantly increased compared with the non-atopic controls. Serum EDN levels of the patients were also related to the disease severity. The skin scores were more significantly correlated with serum EDN levels than ECP levels. We concluded that serum EDN may reflect more strongly disease severity as eosinophilic activation in AD children than serum ECP.

Piecemeal degranulation of peripheral blood eosinophils: a study of allergic subjects during and out of the pollen season

The variability of serum and plasma levels of eosinophil granule proteins in different clinical conditions, interpreted as the result of different patterns of cytokine priming, suggests a selective mobilization of granule proteins. Inasmuch as piecemeal degranulation (PM) is the mechanism proposed for the differential release of eosinophil granule proteins, we decided to investigate whether blood eosinophils from allergic subjects show characteristics of PM during natural allergen challenge. Eosinophils from three birch-sensitive subjects were studied before and during the pollen season. Electron microscopy analysis showed that during the season, eosinophils presented morphologic features of PM. By immunogold labeling, eosinophil cationic protein (ECP) was detected not only in normal specific granules but also in the cytoplasm, in the vicinity of partially lucent specific granules. These results were confirmed by subcellular fractionation, where the amount of ECP associated with compartments containing small vesicles increased 2-fold during the pollen season. A study of the distribution of ECP, eosinophil peroxidase, and hexosaminidase in eosinophils of different densities showed that the profile of each of these proteins differed depending on cell density. All of these proteins decreased in the specific granule of hypodense cells and increased in other cell compartments. We conclude that allergen exposure causes PM of the peripheral blood eosinophils of allergic subjects, and that the density of these cells reflects the degree of degranulation. Our results provide novel information for the understanding of the selective mobilization of granule proteins into the circulation.

Urinary eosinophil protein X in children with atopic dermatitis: relation to atopy and disease activity

BACKGROUND

Parameters of eosinophil inflammation have been suggested as markers of disease activity in atopic dermatitis (AD), but the value of urinary eosinophil protein X (U-EPX) in children with AD, as well as the influence of allergic sensitization, is not known.

METHODS

We measured U-EPX in 59 atopic and 29 nonatopic children with mild (n = 32), moderate (n = 34), and severe (n = 22) AD, as well as in 64 controls.

RESULTS

U-EPX was increased in children with AD (110; 67-164 microg/mmol creatinine, median; quartiles) compared to controls (62; 41-95, P<0.001). Children with mild (97; 63-164, P < 0.01), moderate (108; 67-157, P < 0.01), and severe disease (152; 99-202, P < 0.001) had levels of U-EPX higher than controls. U-EPX was significantly higher in children with severe AD than in mild and moderate disease (P < 0.05 for both). Children with AD and a positive skin prick test (120; 81-176) had higher levels of U-EPX than children with a negative skin prick test (87; 56-155, P<0.05).

CONCLUSIONS

U-EPX is significantly increased in children with AD and may reflect disease activity. U-EPX may also reflect differences in eosinophil activation between those sensitized and those not sensitized to common allergens.

Soluble E-selectin and eosinophil cationic protein are distinct serum markers that differentially represent clinical features of atopic dermatitis

The serum levels of eosinophil cationic protein (ECP), soluble E-selectin (sE-selectin), soluble CD14 (sCD14) and interleukin (IL)-4 are known to be elevated in patients with atopic dermatitis (AD). However, little is known of the mutual relationship between these factors. To elucidate the clinical and mutual relevance of these markers, we examined the serum levels of ECP, sE-selectin, sCD14 and IL-4 as compared with eruption scores, itch scores, total IgE and numbers of peripheral eosinophils in patients with AD (n = 43), non-atopic eczema (n = 24) and urticaria (n = 13) and in normal individuals (n = 45). In 27 patients with AD the levels of these markers were compared before and after treatment. Levels of ECP were elevated only in the patients with AD, whereas the sE-selectin levels were higher not only in AD but also in non-atopic eczema in a severity-dependent manner. The levels of both markers significantly diminished after treatment. Significant correlations existed between ECP levels and numbers of eosinophils, sE-selectin levels and itch scores, and sE-selectin levels and IgE levels. No significant changes were observed in the sCD14 and IL-4 levels. Taken together, sE-selectin and ECP are good but distinct serum markers that reflect different clinical features of AD.

Serum eosinophil cationic protein: distribution and reproducibility in a randomly selected sample of men living in rural Norfolk, UK

BACKGROUND

It has been proposed that serum levels of eosinophil cationic protein (ECP) may be a clinically useful measure in allergic illness. The aim of this report is to describe the distribution and reproducibility of serum ECP levels in a population sample and to examine its relationship with other markers of disease.

METHODS

The study was conducted in rural areas of Norfolk, UK in a random sample of men aged 20-44 years enriched with subjects drawn from general practice 'asthma registers'. Asthma symptoms were assessed using the EC Respiratory Health Survey questionnaire. Atopy was measured by skin prick tests and serum IgE. Airway hyperresponsiveness (AHR) was tested by methacholine challenge test. Serum IgE and ECP was measured by fluoroimmunoassay using the Pharmacia CAP system. Reference equations were derived in subjects from the random sample who did not have symptoms of asthma, abnormal lung function or AHR. The relation of serum ECP with various clinical characteristics was examined in the whole study population. Reproducibility of serum ECP measurement was assessed in 57 subjects 4 weeks after the initial test.

RESULTS

The study population comprised 311 from the random sample and 58 from the asthma sample. The reference equation for serum ECP for healthy men was log10 ECP = 1.3966 - [(age - 20) x 0.0057]. The estimated mean serum ECP for a 20-year-old man was 25 microg/L. Current smokers have higher serum ECP levels that non-smokers (P = 0.014). ECP levels were not related to the skin prick test reactivity, serum IgE, a questionnaire-based diagnosis of asthma, or impaired lung function (all P > 0.05). Levels were higher in subjects with AHR (P = 0.003) and those who reported wheeze (P = 0.017) but there was no clinically useful separation in ECP levels between subjects classified by these criteria. The test was moderately reproducible over a 4-week period (intraclass correlation coefficient = 0.62).

DISCUSSION

Serum ECP levels were higher in this rural English population than reported in a comparable population in Sweden. Serum ECP is a reproducible test but cross-sectionally does not relate in any clinically useful way to markers of asthma. The meaning of between- subject differences in ECP levels requires further exploration.

Correlation of house dust mite-specific lymphocyte proliferation with IL-5 production, eosinophilia, and the severity of symptoms in infants with atopic dermatitis

Because house dust mite (HDM)-specific IgE antibody (IgE-RAST) is usually not detectable in infants with atopic dermatitis (AD), HDM has not been regarded as the cause of infantile AD. The level of HDM-specific lymphocyte proliferation (expressed as stimulation index measured by flow cytometry [SIF]), however, was found to be markedly elevated in AD infants. This suggests that the sensitization of T cells to HDM extract occurs even in infancy. Moreover, the level of HDM-SIF is correlated closely with the severity of infantile AD, suggesting that HDM is a major cause of this disease not only in adults and children but also in infants. Although the level of HDM-SIF did not correlate with the level of HDM-specific IgE-RAST in infants with AD, it did intimately correlate with the absolute number of peripheral blood eosinophils. Because T lymphocytes are known to secrete some cytokines, such as IL-5, that enhance the proliferation of eosinophils, we measured the IL-5 production by peripheral blood mononuclear cells in infants with AD on stimulation with HDM extract. The amount of IL-5 production is significantly higher in infants with AD, as well as in children with AD, than that found in nonatopic control subjects. Moreover, the level of IL-5 production is correlated closely with the level of HDM-SIF in infants with AD. Taken together, these results suggest that HDMs play an important role in the development of infantile AD by inducing IL-5 production from HDM-specific T lymphocytes.

Monitoring of serologic immune parameters in inflammatory skin diseases

This paper deals with the correlation of clinical scoring and serologic markers of inflammation in atopic dermatitis and psoriasis. Serum eosinophil cationic protein (ECP), soluble interleukin-2 receptor (sIL-2R), total serum IgE, IgG and IgM anti-IgE antibodies, and IgE immune complexes were evaluated in monitoring inflammatory skin diseases such as atopic dermatitis and psoriasis. Well-established clinical activity scores were used as standards in recording skin improvement under treatment in a clinical setting. Serum ECP was found to be increased in both atopic dermatitis and psoriasis patients compared to normal controls; sIL-2R and IgE immune complexes were increased only in atopics with increased serum IgE. Anti-IgE antibodies did not show any deviation in both groups of patients. There was a significant elevation of sIL-2R and IgE immune complexes and a nonsignificant elevation of ECP in high-IgE atopics in comparison to those with normal serum IgE. In both groups of patients, there was a significant reduction of ECP and sIL-2R accompanying the improving skin condition. Serum IgE and the other immune parameters failed to respond. In contrast to other studies, serum ECP failed to correspond significantly with disease activity in our study. Our results showed measurable changes of ECP and sIL-2R for atopic dermatitis and/or psoriasis under treatment, but comparison to clinical scores remains difficult due to the different basis of the two systems. The only significant correlation was established for relative changes in sIL-2R and psoriasis area and intensity (PASI), a correlation which might be a useful approach in psoriasis.

Effects of rapamycin, cyclosporin A, and dexamethasone on interleukin 5-induced eosinophil degranulation and prolonged survival

Interleukin-5 (IL-5) enhances eosinophil degranulation and prolongs eosinophil survival. Rapamycin, cyclosporin A, and dexamethasone have been shown to influence either cytokine transcription, cytokine-mediated signalling, or degranulation by granulocytes. The study aimed to determine whether these agents inhibited IL-5-enhanced eosinophil survival or degranulation. Peripheral blood eosinophils were isolated from atopic subjects. The effects of serial dilutions (10(-6)-10(-9) M) of these drugs or vehicle control on 1) the viability of eosinophils cultured (1-5 days) in the presence and absence of recombinant human IL-5, as measured by propidium iodide staining and flow cytometry, and 2) degranulation of eosinophils preincubated (45 min) with rhIL-5 or medium control, as measured by eosinophil cationic protein (ECP) release after stimulation with serum-coated Sephadex beads, were assessed. Dexamethasone and rapamycin produced significant, concentration-dependent inhibition of IL-5-enhanced eosinophil survival at pharmacologic concentrations, whereas cyclosporin A did not. Prior incubation of eosinophils with IL-5, as compared with medium control, significantly enhanced ECP release by eosinophils on subsequent exposure to serum-coated Sephadex beads. Cyclosporin A and rapamycin significantly inhibited IL-5-enhanced ECP release in a concentration-dependent fashion, whereas dexamethasone did not. All three drugs had no significant effect on eosinophil survival and degranulation in the absence of IL-5. Our results suggest that immunosuppressive drugs may inhibit IL-5-mediated mechanisms in eosinophils which result in enhanced survival and release of granule contents. These findings may be relevant to the further development of therapeutic strategies in allergic diseases.