Mutual activation of pulmonary fibroblasts and eosinophils, and modulation by drugs in relation to asthma

Identification of toxicity-induced biomarkers in human non-immune airway cells exposed to respiratory sensitizers: A mechanistic approach

Occupational asthma covers a group of work-related diseases whose clinical manifestations include airway hyperresponsiveness and airflow limitation. Although the chemical respiratory allergy (CRA) induced by Low Molecular Weight (LMW) sensitizers is a major concern, especially in terms of the regulatory framework, to date there are no methods available for preclinically addressing this toxicological outcome, as its mechanistic background is not fully understood at molecular or cellular levels. This paper proposes a mechanistic study applying New Approach Methodologies (NAM) of the pro-inflammatory and functional effects triggered by LMW respiratory allergens in different respiratory tract cell lines, including bronchial epithelial (BEAS-2B), lung fibroblast (MRC-5), and endothelial cells (EA.hy926), and an analysis of the capacity of such chemicals to interact with the mucin protein, to address certain toxicodynamic aspects of such compounds. The results showed that some of the sensitizers evaluated interact with mucin, the main protein mucus component, but the toxicant-mucin complex formation does not seem to be a common feature of different chemical classes of allergens. At a cellular level, sensitizers promoted an increase in IL-8, IL-6, and IL-1β production in the evaluated cell types. It also impaired the MUC1 expression by bronchial cells and activated endothelial cells, thereby increasing the ICAM-I surface expression. Taken together, our results showed that these aforementioned cell types participate in the CRA Adverse Outcome Pathway and must be considered when developing preclinical testing strategies, particularly investigating danger signal production after exposure to LMW sensitizers in different tissue compartments.

The Predictive Value of Eosinophil Indices for Major Cardiovascular Events in Patients with Acute Decompensated HFrEF

Background and Objectives: Heart failure is a chronic disease with a high risk of mortality and morbidity. In these patients, inflammatory markers have been shown to be associated with cardiovascular adverse outcomes and disease progression. To investigate the relationships between eosinophil indices and major cardiovascular events (MACE) in patients with acute decompensated heart failure (ADHF) with reduced ejection fraction. Materials and Methods: A total of 395 consecutive patients admitted to the intensive care unit (ICU) with ADHF and reduced ejection fraction between January 2017 and December 2021 were enrolled in this retrospective study. MACE was defined as the composite of death and re-hospitalization for ADHF within 6 months of index hospitalization. All-cause mortality and MACE were assessed with respect to relationships with eosinophil indices, including neutrophil-to-eosinophil ratio (NER), leukocyte-to-eosinophil ratio (LER), eosinophil-to-lymphocyte ratio (ELR), and eosinophil-to-monocyte ratio (EMR). Results: NER and LER were significantly higher in subjects with MACE. Absolute eosinophil, lymphocyte and basophil count, hemoglobin, serum Na+, albumin, and CRP, and EMR and ELR were significantly lower in subjects with MACE compared to those without. NT-proBNP (OR: 1.682, 95% CI: 1.106−2.312, p = 0.001), Na+ (OR: 0.932, 95% CI: 0.897−0.969, p < 0.001), NER (OR: 2.740, 95 % CI: 1.797−4.177, p < 0.001), LER (OR: 2.705, 95% CI: 1.752−4.176, p < 0.001), EMR (OR:1.654, 95% CI 1.123−2.436, p = 0.011), ELR (OR: 2.112, 95% CI 1.424−3.134, p < 0.001), and eosinophil count (OR: 1.833, 95% CI 1.276−2.635) were independent predictors for development of MACE. Conclusions: Patients with ADHF and reduced ejection fraction who developed MACE within the first six months of index hospitalization had lower levels of absolute eosinophil and lymphocyte counts, and EMR and ELR values, whereas NER and LER were higher compared to those without MACE. The eosinophil indices were independently associated with mortality and MACE development. The eosinophil indices may be used to estimate MACE likelihood with acceptable sensitivity and specificity.

Apolipoprotein A-IV acts as an endogenous anti-inflammatory protein and is reduced in treatment-naïve allergic patients and allergen-challenged mice

Background

Recent studies pointed to a crucial role for apolipoproteins in the pathogenesis of inflammatory diseases. However, the role of apolipoprotein‐IV (ApoA‐IV) in allergic inflammation has not been addressed thoroughly thus far.

Objective

Here, we explored the anti‐inflammatory effects and underlying signaling pathways of ApoA‐IV on eosinophil effector function in vitro and in vivo.

Methods

Migratory responsiveness, Ca²⁺‐flux and apoptosis of human peripheral blood eosinophils were assessed in vitro. Allergen‐driven airway inflammation was assessed in a mouse model of acute house dust mite‐induced asthma. ApoA‐IV serum levels were determined by ELISA.

Results

Recombinant ApoA‐IV potently inhibited eosinophil responsiveness in vitro as measured by Ca²⁺‐flux, shape change, integrin (CD11b) expression, and chemotaxis. The underlying molecular mechanism involved the activation of Rev‐ErbA‐α and induced a PI3K/PDK1/PKA‐dependent signaling cascade. Systemic application of ApoA‐IV prevented airway hyperresponsiveness (AHR) and airway eosinophilia in mice following allergen challenge. ApoA‐IV levels were decreased in serum from allergic patients compared to healthy controls.

Conclusion

Our data suggest that ApoA‐IV is an endogenous anti‐inflammatory protein that potently suppresses effector cell functions in eosinophils. Thus, exogenously applied ApoA‐IV may represent a novel pharmacological approach for the treatment of allergic inflammation and other eosinophil‐driven disorders.

Antileukotriene reverts the early effects of inflammatory response of distal parenchyma in experimental chronic allergic inflammation

Aims. Compare the effects of montelukast or dexamethasone in distal lung parenchyma and airway walls of guinea pigs (GP) with chronic allergic inflammation. Methods. GP have inhaled ovalbumin (OVA group-2x/week/4weeks). After the 4th inhalation, GP were treated with montelukast or dexamethasone. After 72 hours of the 7th inhalation, GP were anesthetised, and lungs were removed and submitted to histopathological evaluation. Results. Montelukast and dexamethasone treatments reduced the number of eosinophils in airway wall and distal lung parenchyma compared to OVA group (P < 0.05). On distal parenchyma, both treatments were effective in reducing RANTES, NF-κB, and fibronectin positive cells compared to OVA group (P < 0.001). Montelukast was more effective in reducing eotaxin positive cells on distal parenchyma compared to dexamethasone treatment (P < 0.001), while there was a more expressive reduction of IGF-I positive cells in OVA-D group (P < 0.001). On airway walls, montelukast and dexamethasone were effective in reducing IGF-I, RANTES, and fibronectin positive cells compared to OVA group (P < 0.05). Dexamethasone was more effective in reducing the number of eotaxin and NF-κB positive cells than Montelukast (P < 0.05). Conclusions. In this animal model, both treatments were effective in modulating allergic inflammation and remodeling distal lung parenchyma and airway wall, contributing to a better control of the inflammatory response.

Caffeic acid phenethyl ester suppresses the induction of eotaxin in human lung fibroblast cells

BACKGROUND

Eotaxin, a CC chemokine, plays an important role in inflammation of airway allergic diseases. The authors investigated the activities of caffeic acid phenethyl ester (CAPE), the active component of propolis, in regulating eotaxin production in human lung fibroblast.

MATERIAL AND METHODS

The authors used human lung fibroblasts, CCD-11Lu cells, stimulated with interleukin-13 (IL-13) and tumor necrosis factor-alpha (TNF-alpha), to induce eotaxin secretion. The cells were treated with CAPE of different concentrations and pretreatment duration to check its inhibition in eotaxin production. Enzyme-linked immunosorbent assay (ELISA) was used to measure eotaxin secretion; electrophoretic mobility shift assay (EMSA) to check nuclear factor kappa B (NF-kappaB)-promoter binding; and Western blot to quantitate the cyplasmic inhibitor of NF-kappaB (IkappaB) and nuclear NF-kappaB p65.

RESULTS

CAPE inhibited the production of eotaxin in CCD-11Lu cells stimulated by IL-13 and TNF-alpha combination in a dose- and time-dependent manner. The authors also demonstrated CAPE to be able to inhibit NF-kappaB activation in CCD-11Lu cells.

CONCLUSION

The authors suggest that CAPE is a promising agent in controlling eosinophils influx in human airway.

Inflammatory effect of environmental proteases on airway mucosa

Proteases--both endogenous proteases from the coagulation cascade, mast cells, and respiratory epithelial trypsin, and exogenous proteases from parasites, insects, mites, molds, pollens, and other aeroallergens--stimulate a tissue response that includes attraction and activation of eosinophils and neutrophils, degranulation of eosinophils and mast cells, increased response of afferent neurons, smooth muscle contraction, angiogenesis, fibrosis, and production of immunoglobulin E. This response to exogenous proteases can be considered a form of innate immunity directed against multicellular organisms. The response of the airways to environmental proteases very closely resembles the response to airborne allergens. Although clinical research in this area is just beginning, the response to environmental proteases appears to be important in the pathogenesis of rhinitis and asthma developing from damp, water-damaged buildings, and intrinsic asthma with its associated rhinosinusitis and polyps.

Eosinophils: singularly destructive effector cells or purveyors of immunoregulation?

Eosinophils are granulocytes typically associated with immune responses to a limited number of specific insults, including helminth infection and exposure to various allergens. Moreover, the overwhelming consensus from the literature is that eosinophils evolved as uniquely destructive leukocytes with cytotoxic activities as an adaptation for host defense. However, recent studies now suggest that the parochial caricature of eosinophils as effector cells with nonspecific killing abilities that evolved as a host defense mechanism against large nonphagotizable parasites is incomplete. A new paradigm has emerged describing eosinophils as initial responders to cell death/tissue damage that are a part of remodeling/repair processes and, more importantly, significant contributors to localized innate and acquired immune responses as well as systemic adaptive immunity. Significantly, this new paradigm does not preclude roles for eosinophils in host defense leading to tissue damage but instead suggests the equal importance of eosinophil-associated regulatory mechanisms modulating local tissue immune responses. The goal of this review is to summarize the data in support of this new paradigm. In turn, we believe that this expanded role provides a probable explanation for the presence of eosinophils in diverse disease settings such as asthma, allergy, cancer, transplant rejection, gastrointestinal inflammation, and viral or helminth infection.

The influence of intravenous hydrocortisone on cytokine levels in children with asthma

Nocturnal airway obstruction occurs frequently in childhood asthma and results from increased airway inflammation. Lymphocytes are believed to be key effector cells of airway wall inflammation, releasing pro-inflammatory mediators and cytokines. A previous study showed that hydrocortisone infusion, an effective anti-inflammatory treatment, improves nocturnal and daytime FEV(1) values. This study in 16 children with moderate asthma was designed to assess whether there exists day and night differences in IL-4, IL-5, IL-8, and IFN-gamma production of concanavaline A stimulated peripheral blood mononuclear cells. Furthermore, we investigated whether substitution of low serum cortisol levels with intravenous hydrocortisone would affect those parameters. Saline (as a placebo) or hydrocortisone (30 microg/m(2) body surface area/24 h) was intravenously administered in a randomized, double blind, cross-over design. Measurements under saline or hydrocortisone infusions were separated by 1 wk. At 04:00 and 16:00 hours 10 ml blood was taken for determination of peripheral blood mononuclear cell isolation and stimulation, and an eosinophil count. Hydrocortisone infusion significantly reduced the nocturnal fall in FEV(1). Median values of IFNgamma, IL-4, IL-5, and IL-8 produced by peripheral blood mononuclear cells did not significantly differ at 04:00 and 16:00 hours, both with saline and hydrocortisone infusion. Our results suggest that FEV(1) improvement is not due to suppression of circulating peripheral blood mononuclear cell activation. We hypothesize that it is rather due to its effect on local lung tissue epithelial and/or fibroblasts thereby reducing airway inflammation and vascular leakage.

Regulation of activin A expression in mast cells and asthma: its effect on the proliferation of human airway smooth muscle cells

Activin A, a homodimeric protein (betaAbetaA) and a member of the TGF-beta superfamily, is involved in the inflammatory repair process. Using cDNA microarray analysis, we discovered strong induction of the activin betaA gene in human mast cells (MC) on stimulation with PMA and calcium ionophore (A23187). Activin betaA mRNA was also highly induced in primary cultured murine bone marrow MC (BMMC) after stimulation by IgE receptor cross-linking. Secretion of activin A was evident in human mast cell-1 line cells 3 h after stimulation and progressively increased over time. Activin A was present in the cytoplasm of activated but not unstimulated murine bone marrow MC as demonstrated by immunofluorescence studies, suggesting that secretion of activin A by MC was due to de novo synthesis rather than secretion of preformed protein. Activin A also colocalized with human lung MC from patients with asthma by double-immunofluorescence staining. Furthermore, secretion of activin A was significantly increased in the airway of wild-type mice after OVA sensitization followed by intranasal challenge. Secretion of activin A, however, was greatly reduced in MC-deficient WBB6F(1)-W/W(v) mice as compared with wild-type mice, indicating that MC are an important contributor of activin A in the airways of a murine asthma model. Additionally, activin A promoted the proliferation of human airway smooth muscle cells. Taken together, these data suggest that MC-derived activin A may play an important role in the process of airway remodeling by promoting the proliferation of airway smooth muscle.