Biochemical assessment of intracellular signal transduction pathways in eosinophils: implications for pharmacotherapy

Exogenous interleukin-17A inhibits eosinophil differentiation and alleviates allergic airway inflammation

IL-17 is known to play important roles in immune and inflammatory disease, such as in asthma, but its functions in allergic airway inflammation are still controversial, and the molecular mechanisms mediating these functions remain unclear. Increased production of eosinophils in bone marrow and their emergence in the airway have been linked to the onset and progression of allergic asthma. In this study, we investigated the effects of exogenous IL-17 on allergic airway inflammation and explored the underlying molecular mechanisms through eosinophil generation. Exogenous IL-17 significantly attenuated the features of allergic inflammation induced by ovalbumin in mice. It inhibited eosinophil differentiation both in vivo and in vitro, accompanied by down-regulated expression of CC chemokine receptor 3, GATA binding protein 1 (GATA-1), and GATA binding protein 2 (GATA-2), as well as reduced formation of common myeloid progenitors and eosinophil progenitors, but without influencing eosinophil apoptosis. IL-17 also significantly decreased the number of eosinophils in IL-5-transgenic mice, although it notably increased the levels of IL-3, IL-5, and granulocyte/macrophage colony-stimulating factor. In addition, IL-17 had little effect on secretion of the inflammatory cytokines by eosinophils. Neutralization of endogenous IL-17 significantly augmented eosinophil recruitment in the airways. Together, these findings suggest that exogenous IL-17 protects against allergic airway inflammation, most likely through inhibition of the eosinophil differentiation in bone marrow.

Muramyl dipeptide mediated activation of human bronchial epithelial cells interacting with basophils: a novel mechanism of airway inflammation

Respiratory tract bacterial infection can amplify and sustain airway inflammation. Intracytosolic nucleotide-binding oligomerization domain-containing protein 2 (NOD2) is one member of the nucleotide binding and oligomerization domain (NOD)-like receptor (NLR) family, which senses the conserved structural peptidoglycan component muramyl dipeptide (MDP) in almost all bacteria. In the present study, activation of the NOD2 ligand MDP on primary human bronchial epithelial cells (HBE) co-cultured with human basophils was investigated. Cytokines, NOD2, adhesion molecules and intracellular signalling molecules were assayed by enzyme-linked immunosorbent assay or flow cytometry. The protein expression of NOD2 was confirmed in basophils/KU812 cells and HBE/human bronchial epithelial cell line (BEAS-2B) cells. MDP was found to up-regulate significantly the cell surface expression of intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 on basophils and HBE in the co-culture system with or without basophil priming by interleukin (IL)-33 (all P < 0·05). MDP could further enhance the release of inflammatory cytokine IL-6 and chemokine CXCL8, and epithelium-derived anti-microbial peptide β-defensin 2 in the co-culture. HBE cells were the major source for the release of IL-6, CXCL8 and β-defensin2 upon stimulation by MDP in the co-culture system. The expression of ICAM-1 and VCAM-1 and release of IL-6 and CXCL8 were suppressed by various signalling molecule inhibitors, implying that the interaction between basophils and primary human bronchial epithelial cells could be regulated differentially by the mitogen-activated protein kinase pathways and nuclear transcription factors. The results therefore provide a new insight into the functional role of basophils in innate immunity, and the link between respiratory bacteria-mediated innate immunity and subsequent amplification of allergic inflammation in the airway.

ORMDL3 promotes eosinophil trafficking and activation via regulation of integrins and CD48

ORM (yeast)-like protein isoform 3 (ORMDL3) has recently been identified as a candidate gene for susceptibility to asthma; however, the mechanisms by which it contributes to asthma pathogenesis are not well understood. Here we demonstrate a functional role for ORMDL3 in eosinophils in the context of allergic inflammation. Eosinophils recruited to the airways of allergen-challenged mice express ORMDL3. ORMDL3 expression in bone marrow eosinophils is localized in the endoplasmic reticulum and is induced by interleukin-3 and eotaxin-1. Overexpression of ORMDL3 in eosinophils causes increased rolling, distinct cytoskeletal rearrangement, extracellular signal-regulated kinase (1/2) phosphorylation and nuclear translocation of nuclear factor kappa B. Knockdown of ORMDL3 significantly inhibits activation-induced cell shape changes, adhesion and recruitment to sites of inflammation in vivo, combined with reduced expression of CD49d and CD18. In addition, ORMDL3 regulates interleukin-3-induced expression of CD48 and CD48-mediated eosinophil degranulation. These studies show that ORMDL3 regulates eosinophil trafficking, recruitment and degranulation, further elucidating a role for this molecule in allergic asthma and potentially other eosinophilic disorders.

Immunopathological roles of cytokines, chemokines, signaling molecules, and pattern-recognition receptors in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease with unknown etiology affecting more than one million individuals each year. It is characterized by B- and T-cell hyperactivity and by defects in the clearance of apoptotic cells and immune complexes. Understanding the complex process involved and the interaction between various cytokines, chemokines, signaling molecules, and pattern-recognition receptors (PRRs) in the immune pathways will provide valuable information on the development of novel therapeutic targets for treating SLE. In this paper, we review the immunopathological roles of novel cytokines, chemokines, signaling molecules, PRRs, and their interactions in immunoregulatory networks and suggest how their disturbances may implicate pathological conditions in SLE.

Molecular and clinical rationale for therapeutic targeting of interleukin-5 and its receptor

Interleukin-5 is a Th2 homodimeric cytokine involved in the differentiation, maturation, migration, development, survival, trafficking and effector function of blood and local tissue eosinophils, in addition to basophils and mast cells. The IL-5 receptor (IL-5R) consists of an IL-5-specific α subunit that interacts in conformationally dynamic ways with the receptor's βc subunit, an aggregate of domains it shares with binding sites of IL-3 and granulocyte-macrophage colony-stimulating factor. IL-5 and IL-5R drive allergic and inflammatory immune responses characterizing numerous diseases, such as asthma, atopic dermatitis, chronic obstructive pulmonary disease, eosinophilic gastrointestinal diseases, hyper-eosinophilic syndrome, Churg-Strauss syndrome and eosinophilic nasal polyposis. Although corticosteroid therapy is the primary treatment for these diseases, a substantial number of patients exhibit incomplete responses and suffer side-effects. Two monoclonal antibodies have been designed to neutralize IL-5 (mepolizumab and reslizumab). Both antibodies have demonstrated the ability to reduce blood and tissue eosinophil counts. One additional monoclonal antibody, benralizumab (MEDI-563), has been developed to target IL-5R and attenuate eosinophilia through antibody-dependent cellular cytotoxicity. All three monoclonal antibodies are being clinically evaluated. Antisense oligonucleotide technology targeting the common βc IL-5R subunit is also being used therapeutically to inhibit IL-5-mediated effects (TPI ASM8). Small interfering RNA technology has also been used therapeutically to inhibit the expression of IL-5 in animal models. This review summarizes the structural interactions between IL-5 and IL-5R and the functional consequences of such interactions, and describes the pre-clinical and clinical evidence supporting IL-5R as a therapeutic target.

Tanshinone II A attenuates inflammatory responses of rats with myocardial infarction by reducing MCP-1 expression

The root of Salvia miltiorrhiza Bunge, a well-known traditional Chinese medicine, has been used effectively for the treatment of cardiovascular diseases for a long time. The mechanisms underlying this therapeutic effect are not, however, fully understood. Tanshinone IIA (Tan IIA) is one of the major active components of this Chinese medicine. Therefore, the present study was performed to investigate whether Tan IIA, which has shown a cardio-protective capacity in myocardial ischemia, has an inhibitory effect on the inflammatory responses following myocardial infarction (MI) and its potential mechanisms. In an in vivo study, rat MI model was induced by permanent left anterior descending coronary artery (LAD) ligation. After the operation rats were divided into three groups (sham, MI and Tan IIA). Tan IIA was administered intragastrically at a dose of 60mg/kg body wt./day. One week later, rats were sacrificed and the hemodynamic, pathological and molecular biological indices were examined. In an in vitro study, the inflammatory model was established by TNF-alpha stimuli on cardiacmyocyte and cardiac fibroblasts. Tan IIA attenuates the MI pathological changes and improves heart function, and reduces expression of MCP-1, TGF-beta(1) and macrophage infiltration. Furthermore, Tan IIA could also decrease the expression of TNF-alpha and activation of nuclear transcription factor-kappa B (NF-kappaB). In vitro, Tan IIA could reduce MCP-1 and TGF-beta(1)secretion of cardiac fibroblasts. The present study demonstrated that the cardioprotective effects of Tan IIA might be attributed to its capacity for inhibiting inflammatory responses.

Activation profile of intracellular mitogen-activated protein kinases in peripheral lymphocytes of patients with systemic lupus erythematosus

INTRODUCTION

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease associated with aberrant activation of T and B lymphocytes. Abnormal activation of intracellular signaling molecules in lymphocytes by inflammatory cytokines can instigate the inflammation in SLE.

MATERIALS AND METHODS

The activation of extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) in inflammatory cytokine IL-18-activated monocytes, CD4+ T helper (Th) lymphocytes, CD8+ T lymphocytes, and CD19+ B lymphocytes in 22 SLE patients and 20 sex- and age-matched control subjects were measured by flow cytometry.

RESULTS AND DISCUSSION

The basal expressions of phospho-p38 MAPK in CD4+ T lymphocytes, CD8+ T lymphocytes, and B lymphocytes were significantly higher in SLE patients than controls (all p<0.05). The expression of phospho-p38 MAPK in CD4+ T lymphocytes, CD8+ T lymphocytes and B lymphocytes, and phospho-JNK in CD8+ T lymphocytes and B lymphocytes was also significantly elevated in SLE patients upon the activation by IL-18, exhibiting significant correlation with the plasma concentrations of Th1 chemokine CXCL10 (all p<0.05). The expression of phospho-JNK in IL-18 activated CD8+ T lymphocytes and the relative % fold increase of the expression of phospho-JNK upon IL-18 activation in B lymphocytes were significantly correlated with SLE disease activity index (both p<0.05).

CONCLUSION

The inflammation-mediated activation of JNK and p38 MAPK signaling pathways in T and B lymphocytes can be the underlying intracellular mechanisms causing lymphocyte hyperactivity in SLE.

Intracellular signaling mechanisms regulating the activation of human eosinophils by the novel Th2 cytokine IL-33: implications for allergic inflammation

The novel interleukin (IL)-1 family cytokine IL-33 has been shown to activate T helper 2 (Th2) lymphocytes, mast cells and basophils to produce an array of proinflammatory cytokines, as well as to mediate blood eosinophilia, IgE secretion and hypertrophy of airway epithelium in mice. In the present study, we characterized the activation of human eosinophils by IL-33, and investigated the underlying intracellular signaling mechanisms. IL-33 markedly enhanced eosinophil survival and upregulated cell surface expression of the adhesion molecule intercellular adhesion molecule (ICAM)-1 on eosinophils, but it suppressed that of ICAM-3 and L-selectin. In addition, IL-33 mediates significant release of the proinflammatory cytokine IL-6 and the chemokines CXCL8 and CCL2. We found that IL-33-mediated enhancement of survival, induction of adhesion molecules, and release of cytokines and chemokines were differentially regulated by activation of the nuclear factor (NF)-kappaB, p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) pathways. Furthermore, we compared the above IL-33 activities with two structurally and functionally related cytokines, IL-1beta and IL-18. IL-1beta, but not IL-18, markedly upregulated cell surface expression of ICAM-1. IL-1beta and IL-18 also significantly enhanced eosinophil survival, and induced the release of IL-6 and chemokines CXCL8 and CCL2 via the activation of the NF-kappaB, p38 MAPK and ERK pathways. Synergistic effects on the release of IL-6 were also observed in combined treatment with IL-1beta, IL-18 and IL-33. Taken together, our findings provide insight into IL-33-mediated activation of eosinophils via differential intracellular signaling cascades in the immunopathogenesis of allergic inflammation.

Leptin-mediated cytokine release and migration of eosinophils: Implications for immunopathophysiology of allergic inflammation

Leptin is a pleiotropic adipocyte-derived cytokine used in hypothalamic regulation of body weight and modulation of immune response by stimulating T cells, macrophages and neutrophils. Leptin has been shown to be an eosinophil survival factor. We examined the immunopathological mechanisms for the activation of human eosinophils from healthy volunteers by leptin in allergic inflammation. Adhesion molecules, cytokines and cell migration were assessed by flow cytometry, ELISA and Boyden chamber assay, respectively. Intracellular signaling molecules were investigated by membrane array and Western blot. Leptin could up-regulate cell surface expression of adhesion molecule ICAM-1 and CD18 but suppress ICAM-3 and L-selectin on eosinophils. Leptin could also stimulate the chemokinesis of eosinophils, and induce the release of inflammatory cytokines IL-1beta and IL-6, and chemokines IL-8, growth-related oncogene-alpha and MCP-1. We found that leptin-mediated induction of adhesion molecules, release of cytokines and chemokines, and chemokinesis were differentially regulated by the activation of ERK, p38 MAPK and NF-kappaB. In view of the above results and elevated production of leptin in patients with allergic diseases such as atopic asthma and atopic dermatitis, leptin could play crucial immunopathophysiological roles in allergic inflammation by activation of eosinophils via differential intracellular signaling cascades.

IL-25 regulates the expression of adhesion molecules on eosinophils: mechanism of eosinophilia in allergic inflammation

BACKGROUND

Interleukin-25 (IL-25) is a novel T-helper-2 (Th2) cytokine of the IL-17 family that plays a key role in allergic inflammation. Recent studies reported that over-expression of IL-25 in mouse induces eosinophilia. We investigated the effect of IL-25 on the expression of several adhesion molecules on human eosinophils and the underlying intracellular mechanisms.

METHODS

Viability of eosinophils was measured by annexin V-fluorescein isothiocyanate (FITC) assay. Gene expression and surface expression of intercellular adhesion molecule (ICAM)-1 (CD54), ICAM-3 (CD50), L-selectin (CD62L), leukocyte function-associated antigen (LFA-1) (CD11a/CD18) and very late antigen-4 (VLA-4, CD49d/CD29) on eosinophils were measured by reverse transcriptase-polymerase chain reaction (RT-PCR) and flow cytometry, respectively. Adhesion of eosinophils to fibronectin was assessed using the fibronectin-coated insert system.

RESULTS

Viability of eosinophils was significantly enhanced by IL-25 from 41% to 76% dose-dependently. IL-25 could significantly upregulate the surface expression of ICAM-1, but suppress those of ICAM-3 and L-selectin on eosinophils in a dose-dependent manner. Adhesion of eosinophils to fibronectin was also significantly enhanced by IL-25. Besides, pre-incubation with p38 mitogen-activated protein kinases (MAPK) inhibitor SB203580, C-Jun NH2-terminal protein kinases (JNK) inhibitor SP600125 and proteosome inhibitor MG-132 could significantly restrain the effects of IL-25 on surface expression of L-selectin, ICAM-1 and ICAM-3, respectively, and also on the adhesion of eosinophils onto fibronectin (all P < 0.05).

CONCLUSIONS

Our findings suggest an essential role of IL-25 in enhancing survival and regulating surface expression of ICAM-1, ICAM-3 and L-selectin on human eosinophils through the activation of p38 MAPK, JNK and nuclear factor (NF)-kappaB pathways, thereby shedding light on the molecular mechanisms of IL-25-induced eosinophilia in allergic inflammation.

Molecular mechanisms for the release of chemokines from human leukemic mast cell line (HMC)-1 cells activated by SCF and TNF-alpha: roles of ERK, p38 MAPK, and NF-kappaB

BACKGROUND

Mast cells play pivotal roles in IgE-mediated airway inflammation and other mast cell-mediated inflammation by activation and chemoattraction of inflammatory cells.

OBJECTIVE

We investigated the intracellular signaling mechanisms regulating chemokine release from human mast cell line-1 (HMC-1) cells activated by stem cell factor (SCF) or tumor necrosis factor (TNF)-alpha.

METHODS

Chemokine gene expressions were assessed by reverse transcription-polymerase chain reaction, while the releases of chemokines were determined by flow cytometry or enzyme-linked immunosorbent assay (ELISA). To elucidate the intracellular signal transduction regulating the chemokine expression, phosphorylated-extracellular signal-regulated kinase (ERK), phosphorylated-p38 mitogen-activated protein kinase (MAPK) and nuclear translocated nuclear factor (NF)-kappaB-DNA binding were quantitatively assessed by ELISA.

RESULTS

Either SCF or TNF-alpha could induce release from HMC-1 cells of interleukin (IL)-8, monocyte chemoattractant protein (MCP)-1, regulated upon activation normal T-cell expressed and secreted (RANTES), and I-309, while SCF and TNF-alpha induced release of macrophage inflammatory protein (MIP)-1beta and interferon-gamma-inducible protein-10 (IP-10), respectively. Using various selective inhibitors for signaling molecules, we found that the inductions of IL-8, MCP-1, and I-309 were mediated by either SCF-activated ERK or TNF-alpha-activated p38 MAPK, while the induction of IP-10 by TNF-alpha was mediated by both activated p38 MAPK and NF-kappaB. The induction of RANTES by SCF or TNF-alpha was mediated by ERK and NF-kappaB, respectively, and SCF induced MIP-1beta release was mediated by ERK.

CONCLUSION

The above results therefore elucidated the different intracellular signaling pathways regulating the release of different chemokines from SCF and TNF-alpha-activated mast cells, thereby shedding light for the immunopathological mechanisms of mast cell-mediated diseases.

Secretory IgA induces antigen-independent eosinophil survival and cytokine production without inducing effector functions

BACKGROUND

Eosinophils in human beings reside in tissues, especially the mucosal tissues of the gastrointestinal tract and inflamed airways. Secretory IgA (S-IgA) is the predominant antibody secreted by these tissues and likely plays a role in the innate immune response.

OBJECTIVE

Because eosinophils and S-IgA are often colocalized in mucosal tissues, we examined the potential regulatory effects of S-IgA without antigens on survival, gene expression, and effector functions of human eosinophils.

METHODS

Eosinophils were incubated with S-IgA in solution without antigens (soluble S-IgA) or with S-IgA immobilized to mimic multivalent antigen cross-linking. Eosinophil activation was monitored by superoxide anion generation and degranulation. Survival was assessed between 24 and 96 hours. Gene and protein expression were examined by microarray and ELISA. Eosinophil lysates were examined by immunoblot for extracellular signal-regulated kinase (ERK) phosphorylation.

RESULTS

Immobilized S-IgA stimulated eosinophil superoxide production and degranulation; soluble S-IgA did not. Although immobilized S-IgA inhibited eosinophil survival in vitro, soluble S-IgA enhanced survival; this involved autocrine production of GM-CSF. Soluble S-IgA without antigens induced increases in mRNA levels of various cytokines, chemokines, signal transduction molecules, antiapoptotic factors, and cell surface markers. By using ELISA, we confirmed protein expression of selected mediators. Eosinophil interaction with soluble S-IgA likely involves FcalphaRI (CD89) and ERK pathway activation.

CONCLUSION

Secretory IgA without multivalent antigens may regulate survival and gene expression of eosinophils. Eosinophils in mucosal tissues can be either primed for action (cytokine production and survival) or fully activated (degranulation and superoxide release) by different forms of S-IgA.

Hypereosinophilic syndrome: an update

Hypereosinophilic syndrome (HES) is a rare disorder that is characterized by persistent and marked eosinophilia combined with organ system dysfunction. HES has substantial clinical heterogeneity but can be fatal without treatment, especially in patients who present with a myelodysplastic variant of the disorder. Although the pathophysiology of HES is poorly defined, dysregulation of cytokines (interleukin 5 [IL-5], IL-3, granulocyte-macrophage colony-stimulating factor [GM-CSF]) responsible for the maturation of eosinophils is a primary feature. Of these cytokines, IL-5 appears to have the greatest role in the regulation of eosinophil maturation. There is no Food and Drug Administration-approved treatment for HES as yet; current strategies are designed to lower blood eosinophils and attempt to limit end-organ damage. Historically, corticosteroids and cytotoxic agents have been the mainstays of therapy, with biological response modifiers such as interferon-alpha also effective in some patients. However, despite improvements in survival, available agents have significant limitations in terms of efficacy, tolerability, and long-term toxicity. More recently, new agents directed at specific targets in the pathogenesis of HES have been developed. These include imatinib mesylate, a tyrosine kinase inhibitor, and more recently, mepolizumab, an anti-IL-5 monoclonal antibody. In a small case series of patients, these agents have been shown to produce hematological and clinical responses in patients with HES, although they may be effective in different subsets of patients. These targeted therapies have the potential to improve clinical outcomes and to further the understanding the pathophysiology of this difficult-to-treat condition.

Interleukin-25–Induced Chemokines and Interleukin-6 Release from Eosinophils Is Mediated by p38 Mitogen-Activated Protein Kinase, c-Jun N-Terminal Kinase, and Nuclear Factor-κB

Interleukin (IL)-25, a novel Th2 cytokine, is capable of amplifying allergic inflammation. We investigated the modulation of nuclear factor (NF)-kappaB and mitogen-activated protein kinases (MAPK) pathways in IL-25-activated eosinophils, the principal effector cells of allergic inflammation, for the in vitro release of chemokines including monocyte chemoattractant protein-1 (MCP-1), IL-8, and macrophage inflammatory protein (MIP)-1alpha, and inflammatory cytokine IL-6. Gene expression of chemokines and IL-6 was evaluated by RT-PCR, and concentrations of chemokines and cytokine were measured by cytokine protein array, cytometric bead array, and enzyme-linked immunosorbent assay. NF-kappaB, c-Jun amino-terminal kinase (JNK), and p38 MAPK activities in eosinophils were assessed by electrophoretic mobility shift assay and Western blot. IL-25 was found to upregulate the gene expression of chemokines MCP-1, MIP-1alpha, and IL-8, and cytokine IL-6, in eosinophils, and to significantly increase the release of the above chemokines and IL-6 from eosinophils. IL-25 could also activate the JNK, p38 MAPK, and NF-kappaB activities of eosinophils, while inhibitor of IkappaB-alpha phosphorylation (BAY11-7082), JNK (SP600125), and p38 MAPK (SB203580) could suppress the release of IL-8, MIP-1alpha, MCP-1, and IL-6. Together, the above results showed that the induction of MCP-1, MIP-1alpha, IL-8, and IL-6 in IL-25-activated eosinophils are regulated by JNK, p38 MAPK, and NF-kappaB pathways.

Effects of a single intratracheal administration of phenanthraquinone on murine lung

Although several studies have reported that diesel exhaust particles (DEP) affect cardiorespiratory health in animals and humans, the responsible components in DEP for the effects remain to be defined. Diesel exhaust particles contain quinones that can catalyse the generation of reactive oxygen species, resulting in the induction of oxidative stress. Oxidative stress can correlate with a variety of diseases and health effects. In the present study, we investigated the effects of phenanthraquinone--a relatively abundant quinone in DEP--on lung inflammation and the local expression of cytokine proteins in mice as a measure of oxidative damage. The animals were randomized into two experimental groups that received vehicle or phenanthraquinone by intratracheal instillation. The cellular profiles of bronchoalveolar lavage fluid (BALF) and local expression of cytokines were evaluated 24 and 48 h after the instillation. Phenanthraquinone challenge revealed an increase in the numbers of neutrophils and eosinophils in BALF as compared to vehicle challenge (P < 0.05 at 48 h post-instillation). Phenanthraquinone induced the lung expression of interleukin (IL)-5 and eotaxin 48 h and 24 h after the challenge, respectively. These results indicate that intratracheal exposure to phenanthraquinone induces recruitment of inflammatory cells, at least partly, through the local expression of IL-5 and eotaxin.