Eosinophil-derived cytokines in allergic inflammation and asthma

Comparison of serum eosinophil-derived neurotoxin levels between wheezing and non-wheezing groups in children with respiratory tract infection

Objective: Eosinophil-derived neurotoxin (EDN) is associated with recurrent wheezing episodes after bronchiolitis, childhood asthma, and allergic rhinitis. We investigated if there is a measurable difference between serum EDN levels in children with wheezing and non-wheezing respiratory infections.Methods: 171 children who visited a university hospital with respiratory infections were enrolled in the study. Subjects were divided into two groups: wheezing (n = 46) and non-wheezing (n = 125). Serum EDN levels were compared.Results: Serum EDN levels in the wheezing group were significantly higher than in the non-wheezing group (P < 0.001). The non-wheezing group was divided into three sub-groups: pneumonia, common cold, and tonsillitis. Serum EDN levels in the wheezing group were significantly higher than in the pneumonia, common cold, or tonsillitis subgroups (P < 0.001). There was no significant difference in serum EDN levels among the pneumonia, common cold, and tonsillitis subgroups.Conclusions: These findings suggest that elevated serum EDN levels could be a distinctive feature of respiratory infections with wheezing. EDN's utility as a biomarker for wheezing-associated disease should be explored through further study.

Connexin 43 expression on peripheral blood eosinophils: role of gap junctions in transendothelial migration

Eosinophils circulate in the blood and are recruited in tissues during allergic inflammation. Gap junctions mediate direct communication between adjacent cells and may represent a new way of communication between immune cells distinct from communication through cytokines and chemokines. We characterized the expression of connexin (Cx)43 by eosinophils isolated from atopic individuals using RT-PCR, Western blotting, and confocal microscopy and studied the biological functions of gap junctions on eosinophils. The formation of functional gap junctions was evaluated measuring dye transfer using flow cytometry. The role of gap junctions on eosinophil transendothelial migration was studied using the inhibitor 18-a-glycyrrhetinic acid. Peripheral blood eosinophils express Cx43 mRNA and protein. Cx43 is localized not only in the cytoplasm but also on the plasma membrane. The membrane impermeable dye BCECF transferred from eosinophils to epithelial or endothelial cells following coculture in a dose and time dependent fashion. The gap junction inhibitors 18-a-glycyrrhetinic acid and octanol did not have a significant effect on dye transfer but reduced dye exit from eosinophils. The gap junction inhibitor 18-a-glycyrrhetinic acid inhibited eosinophil transendothelial migration in a dose dependent manner. Thus, eosinophils from atopic individuals express Cx43 constitutively and Cx43 may play an important role in eosinophil transendothelial migration and function in sites of inflammation.

Eosinophils regulate dendritic cells and Th2 pulmonary immune responses following allergen provocation

Reports have recently suggested that eosinophils have the potential to modulate allergen-dependent pulmonary immune responses. The studies presented expand these reports demonstrating in the mouse that eosinophils are required for the allergen-dependent Th2 pulmonary immune responses mediated by dendritic cells (DCs) and T lymphocytes. Specifically, the recruitment of peripheral eosinophils to the pulmonary lymphatic compartment(s) was required for the accumulation of myeloid DCs in draining lymph nodes and, in turn, Ag-specific T effector cell production. These effects on DCs and Ag-specific T cells did not require MHC class II expression on eosinophils, suggesting that these granulocytes have an accessory role as opposed to direct T cell stimulation. The data also showed that eosinophils uniquely suppress the DC-mediated production of Th17 and, to smaller degree, Th1 responses. The cumulative effect of these eosinophil-dependent immune mechanisms is to promote the Th2 polarization characteristic of the pulmonary microenvironment after allergen challenge.

Lung MRI for experimental drug research

Current techniques to evaluate the efficacy of potential treatments for airways diseases in preclinical models are generally invasive and terminal. In the past few years, the flexibility of magnetic resonance imaging (MRI) to obtain anatomical and functional information of the lung has been explored with the scope of developing a non-invasive approach for the routine testing of drugs in models of airways diseases in small rodents. With MRI, the disease progression can be followed in the same animal. Thus, a significant reduction in the number of animals used for experimentation is achieved, as well as minimal interference with their well-being and physiological status. In addition, under certain circumstances the duration of the observation period after disease onset can be shortened since the technique is able to detect changes before these are reflected in parameters of inflammation determined using invasive procedures. The objective of this article is to briefly address MRI techniques that are being used in experimental lung research, with special emphasis on applications. Following an introduction on proton techniques and MRI of hyperpolarized gases, the attention is shifted to the MRI analysis of several aspects of lung disease models, including inflammation, ventilation, emphysema, fibrosis and sensory nerve activation. The next subject concerns the use of MRI in pharmacological studies within the context of experimental lung research. A final discussion points towards advantages and limitations of MRI in this area.

Pulmonary inflammation monitored noninvasively by MRI in freely breathing rats

A detailed analysis has been carried out of the correlation between the signals detected by MRI in the rat lung after allergen or endotoxin challenge and parameters of inflammation determined in the broncho-alveolar lavage (BAL) fluid. MRI signals after allergen correlated highly significantly with the BAL fluid eosinophil number, eosinophil peroxidase activity and protein concentration. Similar highly significant correlations were seen when the anti-inflammatory glucocorticosteroid, budesonide, manifested against allergen. In contrast, following endotoxin challenge, mucus was the sole BAL fluid parameter that correlated significantly with the long lasting signal detected by MRI. Since edema is an integral component of pulmonary inflammation, MRI provides a noninvasive means of monitoring the course of the inflammatory response and should prove invaluable in profiling anti-inflammatory drugs in vivo. Further, the prospect of noninvasively detecting a sustained mucus hypersecretory phenotype in the lung brings an important new perspective to models of chronic obstructive pulmonary diseases.

Which factors predict success after discontinuation of inhaled budesonide therapy in children with asthma?

Urinary eosinophil protein X (UEPX) concentration, lung function, and nonspecific bronchial hyperreactivity were determined in 40 asthmatic children (asymptomatic for 6.4 +/- 3.0 months) (mean age 9.8 +/- 2.9 years) receiving inhaled budesonide, in order to establish whether measurement of these parameters is useful in determining discontinuation of inhaled corticosteroid therapy. After the discontinuation of therapy, patients were asked to come to the Outpatient Clinic if symptoms recurred and did not respond to beta2 mimetic usage in 24 hr. Otherwise they were to be seen 2-3 months later for a follow-up visit. UEPX concentration was determined and spirometry was performed on this visit. While UEPX concentrations had increased (p < 0.0001), FEV1, FEF 25-75 and PEF had decreased significantly 2.3 +/- 0.53 months after the cessation of inhaled budesonide therapy in all children (p = 0.004, p = 0.02, p = 0.02, respectively). Due to clinical deterioration, inhaled corticosteroid therapy had to be restarted in 19 (48%) of the children (Group I), while the remaining 21 (52%) (Group II) continued to be asymptomatic during the 2.3 +/- 0.5 months follow-up period. Although the initial UEPX concentrations, spirometer variables, and methacholine PC20 values of these two groups were not statistically different, the duration of clinical remission before discontinuation of budesonide prophylaxis was significantly longer in group II (p = 0.0037). We concluded that, in determining discontinuation of inhaled corticosteroid prophylaxis, duration of clinical remission seems to be a more useful criterion than measurement of UEPX levels, lung function test, and assessment of bronchial hyperreactivity.

Human recombinant histamine-releasing factor activates human eosinophils and the eosinophilic cell line, AML14-3D10

The human recombinant histamine-releasing factor (HrHRF) was previously shown to induce histamine release from human basophils from a subset of donors. The ability of HrHRF to directly induce histamine release from only certain basophils was thought to involve interaction between HrHRF and a particular kind of IgE, termed IgE+, on the surface of these cells. Recent studies disproved the hypothesis that the IgE molecule or its high-affinity receptor, FcεRI, is involved in secretion of histamine and cytokines by basophils stimulated with HrHRF. Rather, data suggest that HrHRF is a cytokine that stimulates basophils by binding to a cell-surface structure other than the IgE molecule. This report describes the effects of HrHRF on another inflammatory cell type: eosinophils from mildly allergic donors. In purified eosinophils primed with granulocyte-macrophage colony-stimulating factor, both tumor necrosis factor α (TNF-α) and HrHRF induced increased secretion of interleukin (IL) 8. In addition, both HrHRF and IL-5 enhanced secretion of IL-8 stimulated by TNF-α. Secretion of IL-8 reached a plateau level in less than 24 hours, was inhibited by cycloheximide, and required the presence of HrHRF throughout the culture period. In some eosinophil preparations, HrHRF induced calcium mobilization that was inhibited by pertussis toxin. Additionally, HrHRF caused secretion of IL-8 from the human eosinophilic cell line, AML14-3D10, which does not possess the α chain of FcεRI. These data provide evidence that HrHRF contributes to activation of eosinophils and thus suggest an additional role for HrHRF in the pathophysiologic mechanisms of allergic disease.

Human recombinant histamine-releasing factor activates human eosinophils and the eosinophilic cell line, AML14-3D10

The human recombinant histamine-releasing factor (HrHRF) was previously shown to induce histamine release from human basophils from a subset of donors. The ability of HrHRF to directly induce histamine release from only certain basophils was thought to involve interaction between HrHRF and a particular kind of IgE, termed IgE+, on the surface of these cells. Recent studies disproved the hypothesis that the IgE molecule or its high-affinity receptor, FcεRI, is involved in secretion of histamine and cytokines by basophils stimulated with HrHRF. Rather, data suggest that HrHRF is a cytokine that stimulates basophils by binding to a cell-surface structure other than the IgE molecule. This report describes the effects of HrHRF on another inflammatory cell type: eosinophils from mildly allergic donors. In purified eosinophils primed with granulocyte-macrophage colony-stimulating factor, both tumor necrosis factor α (TNF-α) and HrHRF induced increased secretion of interleukin (IL) 8. In addition, both HrHRF and IL-5 enhanced secretion of IL-8 stimulated by TNF-α. Secretion of IL-8 reached a plateau level in less than 24 hours, was inhibited by cycloheximide, and required the presence of HrHRF throughout the culture period. In some eosinophil preparations, HrHRF induced calcium mobilization that was inhibited by pertussis toxin. Additionally, HrHRF caused secretion of IL-8 from the human eosinophilic cell line, AML14-3D10, which does not possess the α chain of FcεRI. These data provide evidence that HrHRF contributes to activation of eosinophils and thus suggest an additional role for HrHRF in the pathophysiologic mechanisms of allergic disease.

Cell-specific expression of RANTES, MCP-1, and MIP-1alpha by lower airway epithelial cells and eosinophils infected with respiratory syncytial virus

Respiratory syncytial virus (RSV) is the major cause of acute bronchiolitis in infancy, a syndrome characterized by wheezing, respiratory distress, and the pathologic findings of peribronchial mononuclear cell infiltration and release of inflammatory mediators by basophil and eosinophil leukocytes. Composition and activation of this cellular response are thought to rely on the discrete target cell selectivity of C-C chemokines. We demonstrate that infection in vitro of human epithelial cells of the lower respiratory tract by RSV induced dose- and time-dependent increases in mRNA and protein secretion for RANTES (regulated upon activation, normal T-cell expressed and presumably secreted), monocyte chemotactic protein-1 (MCP-1), and macrophage inflammatory protein-1alpha (MIP-1alpha). Production of MCP-1 and MIP-1alpha was selectively localized only in epithelial cells of the small airways and lung. Exposure of epithelial cells to gamma interferon (IFN-gamma), in combination with RSV infection, induced a significant increase in RANTES production that was synergistic with respect to that obtained by RSV infection or IFN-gamma treatment alone. Epithelial cell-derived chemokines exhibited a strong chemotactic activity for normal human blood eosinophils. Furthermore, eosinophils were susceptible to RSV and released RANTES and MIP-1alpha as a result of infection. Therefore, the inflammatory process in RSV-induced bronchiolitis appears to be triggered by the infection of epithelial cells and further amplified via mechanisms driven by IFN-gamma and by the secretion of eosinophil chemokines.