Myosin light chain kinase mediates eosinophil chemotaxis in a mitogen-activated protein kinase-dependent manner

Xenophagy in innate immunity: A battle between host and pathogen

Autophagy is a fundamental bulk intracellular degradation and recycling process that directly eliminates intracellular microorganisms through "xenophagy" in various types of cells, especially in macrophages. Meanwhile, bacteria have evolved strategies and cellular self-defense mechanisms to prevent autophagosomal degradation and even attack the immune system of host. The lack of knowledge about the roles of autophagy in innate immunity severely limits our understanding of host defensive system and the development of farmed industry consisting of aquaculture. Increasing evidence in recent decades has shown the importance of autophagy. This review focuses on the triggering of xenophagy, targeting of invading pathogens to autophagosomes and elimination in the autophagolysosomes during pathogen infection. How the pathogen can escape from the xenophagy pathway was also discussed. Overall, we aim to reduce diseases and improve industrial production in aquaculture by providing theoretical and technical guidance on xenophagy.

Bioactive Proteins in Channa striata Promote Wound Healing through Angiogenesis and Cell Proliferation

BACKGROUND

Channa striata are speculated to contain bioactive proteins with the ability to enhancing wound healing. It is commonly consumed after surgery for a faster recovery of the wound.

OBJECTIVE

To identify the bioactive proteins and evaluate their ability in cell proliferation and angiogenesis promotion.

MATERIAL AND METHODS

Freeze-Dried Water Extracts (FDWE) and Spray-Dried Water Extracts (SDWE) of C. striata were tested with MTT assay using EA.hy926 endothelial cell line and ex-vivo aortic ring assay. Later the proteins were fractionated and analysed using an LC-QTOF mass spectrometer. The data generated were matched with human gene database for protein similarity and pathway identification.

RESULTS

Both samples have shown positive cell proliferation and pro-angiogenic activity. Four essential proteins/genes were identified, which are collagen type XI, actin 1, myosin light chain and myosin heavy chain. The pathways discovered that related to these proteins are integrin pathway, Slit-Robo signalling pathway and immune response C-C Chemokine Receptor-3 signalling pathway in eosinophils, which contribute towards wound healing mechanism.

CONCLUSIONS

The results presented have demonstrated that C. striata FDWE and SDWE protein fractions contain bioactive proteins that are highly similar to human proteins and thus could be involved in the wound healing process via specific biological pathways.

Epstein-Barr Virus-induced Gene 2 Mediates Allergen-induced Leukocyte Migration into Airways

RATIONALE

Leukocyte recruitment to sites of allergic inflammation depends on the local production of priming cytokines, chemokines, and potentially other mediators. Previously, we showed that eosinophils (Eos) express numerous orphan G-protein-coupled receptors, including Epstein-Barr virus-induced gene 2 (EBI2). Despite its contribution to inflammatory diseases, the role of EBI2 in pulmonary eosinophilia is unknown.

OBJECTIVES

To determine whether oxysterol ligands for EBI2 are increased in asthma exacerbation, and if or how they promote Eos pulmonary migration.

METHODS

EBI2 ligands and pulmonary eosinophilia were measured in the bronchoalveolar lavage fluid from patients with mild asthma 48 hours after acute allergen challenge. In vitro, the ability of EBI2 ligands alone or in combination with IL-5 priming to induce the migration of human blood Eos was assessed.

MEASUREMENTS AND MAIN RESULTS

EBI2 was constitutively and stably expressed in peripheral blood Eos. Eos treated with the EBI2 ligands showed significantly increased transwell migration that was enhanced by priming with physiologic doses of IL-5. Migration was suppressed by inhibitors of the prolyl isomerase Pin1 or extracellular signal-regulated kinases (ERK) 1/2 or by pertussis toxin. EBI2 signaling activated Pin1 isomerase activity through a cascade that was sensitive to ERK inhibitors and pertussis toxin. The concentration of EBI2 ligands was significantly increased in the bronchoalveolar lavage fluid 48 hours after segmental allergen challenge and strongly correlated with the increased numbers of Eos, lymphocytes, and neutrophils in the airways.

CONCLUSIONS

Oxysterols are increased in inflamed airways after allergen challenge and, through G-protein subunit α, ERK, and Pin1 signaling, likely participate in the regulation of Eos migration into the lung in people with asthma.

Integrins are Mechanosensors That Modulate Human Eosinophil Activation

Eosinophil migration to the lung is primarily regulated by the eosinophil-selective family of eotaxin chemokines, which mobilize intracellular calcium (Ca²⁺) and orchestrate myriad changes in cell structure and function. Eosinophil function is also known to be flow-dependent, although the molecular cognate of this mechanical response has yet to be adequately characterized. Using confocal fluorescence microscopy, we determined the effects of fluid shear stress on intracellular calcium concentration ([Ca²⁺]_i) in human peripheral blood eosinophils by perfusing cells in a parallel-plate flow chamber. Our results indicate that fluid perfusion evokes a calcium response that leads to cell flattening, increase in cell area, shape change, and non-directional migration. None of these changes are seen in the absence of a flow stimulus, and all are blocked by chelation of intracellular Ca²⁺ using BAPTA. These changes are enhanced by stimulating the cells with eotaxin-1. The perfusion-induced calcium response (PICR) could be blocked by pre-treating cells with selective (CDP-323) and non-selective (RGD tripeptides) integrin receptor antagonists, suggesting that α₄β₇/α₄β₁ integrins mediate this response. Overall, our study provides the first pharmacological description of a molecular mechanosensor that may collaborate with the eotaxin-1 signaling program in order to control human eosinophil activation.

Moving towards a paradigm: common mechanisms of chemotactic signaling in Dictyostelium and mammalian leukocytes

Chemotaxis, or directed migration of cells along a chemical gradient, is a highly coordinated process that involves gradient sensing, motility, and polarity. Most of our understanding of chemotaxis comes from studies of cells undergoing amoeboid-type migration, in particular the social amoeba Dictyostelium discoideum and leukocytes. In these amoeboid cells the molecular events leading to directed migration can be conceptually divided into four interacting networks: receptor/G protein, signal transduction, cytoskeleton, and polarity. The signal transduction network occupies a central position in this scheme as it receives direct input from the receptor/G protein network, as well as feedback from the cytoskeletal and polarity networks. Multiple overlapping modules within the signal transduction network transmit the signals to the actin cytoskeleton network leading to biased pseudopod protrusion in the direction of the gradient. The overall architecture of the networks, as well as the individual signaling modules, is remarkably conserved between Dictyostelium and mammalian leukocytes, and the similarities and differences between the two systems are the subject of this review.

The effect of pharmacological PI3Kγ inhibitor on eotaxin-induced human eosinophil functions

BACKGROUND

Asthma is characterized by chronic inflammation caused by activation of immune cells including Th2 lymphocytes and eosinophils. Phosphoinositide 3-kinase (PI3K) γ deficient asthmatic mice did not develop lung eosinophilia, although the detailed mechanisms are not well known. A CC chemokine eotaxin (CCL11) plays a prominent role in developing eosinophilic inflammation through CCR3. In this study, we tested the roles of PI3Kγ in eotaxin-induced eosinophil functions using a pharmacological inhibitor.

METHOD

Human peripheral blood eosinophils were isolated by CD16-negative selection method. The effect of AS605240, synthetic PI3Kγ inhibitor on eotaxin-induced adhesion, chemotaxis, and degranulation were studied using intracellular adhesion molecule-1 (ICAM-1)-coated plates, Boyden chamber system, ELISA for eosinophil-derived neurotoxin (EDN) levels in the culture supernatant, respectively. CCR3 expression levels and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation were assessed by flowcytometry. Involvement of PI3Kγ in spontaneous apoptosis was studied using flowcytometry.

RESULTS

Although AS605240 did not affect the eosinophil spontaneous apoptosis, eotaxin-induced chemotaxis, adhesion to ICAM-1 coated plate, and EDN release were inhibited by AS605240. AS605240 also inhibited the eotaxin-induced ERK1/2 phosphorylation without down-regulation of surface CCR3 expression.

CONCLUSION

These results indicate that PI3Kγ inhibitor attenuates eotaxin-induced eosinophil functions by suppressing the downstream signaling of CCR3 without significant cytotoxicity. PI3Kγ plays an important role in the development of eosinophilic inflammation and blockade of PI3Kγ might be a therapeutic strategy for treatment of eosinophil-related diseases including asthma.

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.

The signaling mechanism of eosinophil activation

Eosinophils play an important role in certain aspects of asthma pathogenesis. This review focuses on the mechanism of activation of eosinophils by the growth factor interleukin-5 and the CC chemokine receptor-3. Interleukin-5 activates members of the Janus and Src family of kinases. The latter kinases are largely responsible for the generation of initial signaling events. CC chemokine receptor-3, in contrast, signals through heterotrimeric G-proteins. Subsequently, various signaling pathways are activated, which converge on four major pathways - the mitogen-activated protein kinase pathway, the phosphoinositide-3 kinase pathway, the calcium signaling pathway and the Janus-signal transducer and activator of transcription signaling pathway. The biologic consequences of many of these signaling pathways are also discussed.

Phagocytosis of heat-killed Staphylococcus aureus by eosinophils: comparison with neutrophils

Eosinophils are characterized by several functional properties, such as chemotaxis, adhesion, superoxide anion production, and degranulation. In this article, we have studied the role of bacterial ingestion by eosinophils in comparison with that by neutrophils. Eosinophils and neutrophils were purified by using the Percoll gradient method followed by selection with CD16-coated immunomagnetic beads and centrifugation through a Ficoll-Hypaque gradient combined with dextran sedimentation, respectively. Both cells were preincubated with anti-FcgammaRIIa mAb (CD32 mAb), anti-FcgammaRIIIb mAb (CD16 mAb), anti-CR3 (CD11b mAb), or anti-CR1 (CD35 mAb) before being examined for phagocytosis of opsonized heat-killed Staphylococcus aureus (S. aureus). Phagocytosis and production of hydrogen peroxide were simultaneously measured by flow cytometry using S. aureus labeled with propidium iodide and stained with 2',7'-dichlorofluorescein diacetate. Eosinophils showed significantly lower activity than neutrophils in both phagocytosis and hydrogen peroxide production. Phagocytosis by both cells was decreased by heat-inactivated serum. Phagocytosis by neutrophils was significantly inhibited by CD16 mAb and CD32 mAb, whereas that by eosinophils was only inhibited by CD35 mAb. Whereas the mechanism of phagocytosis by neutrophils was mediated by CD16 and CD32, that of eosinophils was modulated by complement receptor 1 (CD35).

MYLK polymorphism associated with blood eosinophil level among asthmatic patients in a Korean population

The myosin light chain kinase (MYLK) gene encodes both smooth muscle and nonmuscle cell isoforms. Recently, polymorphisms in MYLK have been reported to be associated with several diseases. To examine the genetic effects of polymorphisms on the risk of asthma and related phenotypes, we scrutinized MYLK by re-sequencing/genotyping and statistical analysis in Korean population (n = 1,015). Seventeen common polymorphisms located in or near exons, having pairwise r ( 2 ) values less than 0.25, were genotyped. Our statistical analysis did not replicate the associations with the risk of asthma and log-transformed total IgE levels observed among African descendant populations. However, two SNPs in intron 16 (+89872C > G and +92263T >C), which were in tight LD (|D'| = 0.99), revealed significant association with log-transformed blood eosinophil level even after correction multiple testing (P = 0.002/P( corr )= 0.01 and P = 0.002/P( corr ) = 0.01, respectively). The log-transformed blood eosinophil levels were higher in individuals bearing the minor alleles for +89872C > G and +92263T > C, than in those bearing other allele. In additional subgroup analysis, the genetic effects of both SNPs were much more apparent among asthmatic patients and atopic asthma patients. Among atopic asthma patients, the log-transformed blood eosinophil levels were proportionally increased by gene-dose dependent manner of in both +89872C > G and +92263T > C (P = 0.0002 and P = 0.00007, respectively). These findings suggest that MYLK polymorphisms might be among the genetic factors underlying differential increases of blood eosinophil levels among asthmatic patients. Further biological and/or functional studies are needed to confirm our results.

Nonkinase activity of MLCK in elongated filopodia formation and chemotaxis of vascular smooth muscle cells toward sphingosylphosphorylcholine

The actin-myosin interaction of vascular smooth muscle cells (VSMCs) is regulated by myosin light chain kinase (MLCK), which is a fusion protein of the central catalytic domain with the N-terminal actin-binding and C-terminal myosin-binding domains. In addition to the regulatory role of kinase activity mediated by the catalytic domain, nonkinase activity that derives from both terminals is able to exert a regulatory role as reviewed by Nakamura et al. (32). We previously showed that nonkinase activity mediated the filopodia upon the stimulation by sphingosylphosphorylcholine (SPC) (25). To explore the regulatory role of nonkinase activity in chemotaxis, we constructed VSMCs where the expression of MLCK was totally abolished by using a lentivirus-mediated RNAi system. We hypothesized that the MLCK-downregulated VSMCs were unable to form filopodia and to migrate upon SPC stimulation and confirmed the hypothesis. We further constructed a kinase-inactive mutant from bovine cDNA coding wild-type (WT) MLCK by mutating the ATP-binding sites located in the catalytic domain, followed by confirming the presence (absence) of the kinase activity of WT (kinase-inactive mutant). We transfected WT and the mutant into MLCK-downregulated VSMCs. We expected that the transfected VSMCs will recover the ability to induce filopodia and chemotaxis toward SPC and found both constructs rescued the ability. Because they share the actin- and myosin-binding domains, we concluded nonkinase activity plays a major role for SPC-induced migration.

Polymorphisms in the myosin light chain kinase gene that confer risk of severe sepsis are associated with a lower risk of asthma

BACKGROUND

Myosin light chain kinase (MYLK) is a multifunctional protein involved in regulation of airway hyperreactivity and other activities relevant to asthma.

OBJECTIVE

To determine the role of MYLK gene variants in asthma among African Caribbean and African American populations.

METHODS

We performed association tests between single nucleotide polymorphisms (SNPs) in the MYLK gene and asthma susceptibility and total serum IgE concentrations in 2 independent, family-based populations of African descent. Previously we identified variants/haplotypes in MYLK that confer risk for sepsis and acute lung injury; we compared findings from our asthma populations to findings in the African American sepsis and acute lung injury groups.

RESULTS

Significant associations between MYLK SNPs and asthma and total serum IgE concentrations were observed in the African Caribbean families: a promoter SNP (rs936170) in the smooth muscle form gave the strongest association (P = .009). A haplotype including rs936170 corresponding to the actin-binding activity of the nonmuscle and smooth muscle forms was negatively associated with asthma (eg, decreased risk) in both the American (P = .005) and Caribbean families (P = .004), and was the same haplotype that conferred risk for severe sepsis (P = .002). RNA expression studies on PBMCs and rs936170 suggested a significant decrease in MYLK expression among patients with asthma with this variant (P = .025).

CONCLUSION

MYLK polymorphisms may function as a common genetic factor in clinically distinct diseases involving bronchial smooth muscle contraction and inflammation.

CLINICAL IMPLICATIONS

Genetic variants in MYLK are significantly associated with both asthma and sepsis in populations of African ancestry.

Autoantigen signalling through chemokine receptors

PURPOSE OF REVIEW

Recent studies have shown that disease-associated self-antigens activate chemokine receptors. This review focuses on the mechanics of autoantigen interaction with select chemokine receptors, how these migratory signals are amplified and discusses the possibility that chemokine receptors can be valuable therapeutic targets in the prevention and treatment of autoimmune disease.

RECENT FINDINGS

We have recently shown that most autoantigens are chemotactic for immature dendritic cells, suggesting that autoantigens have the potential to bridge the innate and adaptive immune systems. Autoantigens also induce other leukocytes expressing their responsive chemokine receptor to migrate. These newly recruited leukocytes, in response to proinflammatory mediators, simulate the surrounding tissues to release chemokines. Several groups have reported increases in both select chemokines and chemokine receptors in inflamed tissues. Taken together, these studies suggest that autoantigens initiate leukocyte migration into damaged and inflamed tissue that leads to the subsequent amplification of the inflammatory response.

SUMMARY

Most autoantigens induce chemokine receptor mediated cell migration, therefore targeting chemokine receptors for either prevention or therapy has great potential to limit autoimmune diseases.

Intracellular signal transduction for migration and actin remodeling in vascular smooth muscle cells after sphingosylphosphorylcholine stimulation

Molecular mechanisms underlying migration of vascular smooth muscle cells (VSMCs) toward sphingosylphosphorylcholine (SPC) were analyzed in light of the hypothesis that remodeling of the actin cytoskeleton should be involved. After SPC stimulation, mitogen-activated protein kinases (MAPKs), including p38 MAPK (p38) and p42/44 MAPK (p42/44), were found to be phosphorylated. Migration of cells toward SPC was reduced in the presence of SB-203580, an inhibitor of p38, but not PD-98059, an inhibitor of p42/44. Pertussis toxin (PTX), a Giprotein inhibitor, induced an inhibitory effect on p38 phosphorylation and VSMC migration. Myosin light chain (MLC) phosphorylation occurred after SPC stimulation with or without pretreatment with SB-203580 or PTX. The MLC kinase inhibitor ML-7 and the Rho kinase inhibitor Y-27632 inhibited MLC phosphorylation but only partially inhibited SPC-directed migration. Complete inhibition was achieved with the addition of SB-203580. After SPC stimulation, the actin cytoskeleton formed thick bundles of actin filaments around the periphery of cells, and the cells were surrounded by elongated filopodia, i.e., magunapodia. The peripheral actin bundles consisted of α- and β-actin, but magunapodia consisted exclusively of β-actin. Such a remodeling of actin was reversed by addition of SB-203580 and PTX, but not ML-7 or Y-27632. Taken together, our biochemical and morphological data confirmed the regulation of actin remodeling and suggest that VSMCs migrate toward SPC, not only by an MLC phosphorylation-dependent pathway, but also by an MLC phosphorylation-independent pathway.

The Role of Platelet-Derived Growth Factor Receptor in Eotaxin Signaling of Eosinophils

BACKGROUND

Receptor tyrosine kinases (RTKs) such as epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor (PDGFR) are capable of eliciting kinase activity after ligand binding. In several cells, RTKs are activated via the G-protein-coupled receptor independent of the ligand-RTK interaction. We have previously found that EGFR is transactivated via CC chemokine receptor 3 in bronchial epithelial cells and that this pathway is important for mitogen-activated protein (MAP) kinase activation and cytokine production. It has recently been suggested that hypereosinophilic syndrome results from the fusion tyrosine kinase FIP1L1-PDGFRA. Although it is possible that the PDGFR signal is involved in eosinophil function, the details are still unclear.

METHODS

Blood eosinophils were purified using Percoll and anti-CD16 antibody-coated magnetic beads. Expression of PDGFR mRNA was examined by RT-PCR. After stimulating eosinophils with eotaxin, the phosphorylation of MAP kinases was examined by Western blotting with the antiphosphospecific MAP kinase antibody. The eotaxin-induced eosinophil chemotaxis was studied using Boyden chambers.

RESULTS

Eosinophils expressed PDGFRbeta mRNA in 4 out of 8 donors, while PDGFRalpha mRNA was expressed in only 1 donor. Protein expression of PDGFR was also detectable in eosinophils from some donors. AG1295, a specific inhibitor of PDGFR, showed dose-dependent inhibition of eotaxin-induced MAP kinase phosphorylation in the eosinophils expressing PDGFRbeta mRNA. The chemotaxis of these eosinophils was significantly inhibited by AG1295 (n = 3).

CONCLUSIONS

Our results suggest that PDGFR modifies the CCR3-MAP kinase signaling pathway and chemotactic response in some donors. The pharmacological targeting of PDGFR may be a new strategy to treat eosinophilic disorders.

CD28 and secretory immunoglobulin A-dependent activation of eosinophils: inhibition of mediator release by the anti-allergic drug, suplatast tosilate

BACKGROUND

Eosinophils are major effector cells in allergic diseases. After their recruitment to sites of inflammation, they contribute to the pathophysiology of the disease by releasing granule proteins and cytokines. Suplatast tosilate (IPD-1151T), a new anti-allergic agent, has shown beneficial effect in the treatment of asthma, associated with reduced bronchoalveolar lavage eosinophil infiltration and eosinophilic cationic protein (ECP) release in serum and sputum.

OBJECTIVE

We investigated whether suplatast tosilate could exert direct effects on human eosinophil activation.

METHODS

Eosinophils from hypereosinophilic patients or normal donors were purified by Percoll gradient and the magnetic cell separation system. Chemotaxis was studied using the Boyden chamber technique using three chemoattractants, formyl-methionine-leucine-phenylalanine (fMLP), IL-5 and eotaxin. Oxidative metabolism was determined by a luminol-dependent chemiluminescence assay after activation with eotaxin or secretory IgA (sIgA). The release of ECP and eosinophil derived neurotoxin (EDN) was measured by radioimmunoassay and cytokine production was determined by ELISA following activation with sIgA or anti-CD28.

RESULTS

The chemotactic response to fMLP, IL-5 and eotaxin was significantly inhibited by IPD-1151T. Suplatast tosilate was partially inhibiting the release of reactive oxygen species (ROS) induced by eotaxin and sIgA. Activation by sIgA and CD28 ligation resulted in the release of ECP and EDN, which was inhibited by IPD-1151T. Upon activation by anti-CD28, only IL-13 production was inhibited by IPD-1151T, whereas release of IL-2 and IFN-gamma was not affected. IL-10 release induced by sIgA was also inhibited by IPD-1151T. Additionally, the pro-inflammatory cytokine IL-6, which was secreted following anti-CD28 and sIgA stimulation, was strongly inhibited by IPD-1151T.

CONCLUSION

Through inhibition of chemotaxis, IPD-1151T might limit the number of eosinophils at the inflammation site. Furthermore, it could reduce the pathological potential of eosinophils by inhibiting the release of ROS and cationic proteins, main inflammatory mediators produced by eosinophils. Moreover, the inhibition of immunoregulatory cytokines released by eosinophils could locally modify the immune response.

Inhaled p38alpha mitogen-activated protein kinase antisense oligonucleotide attenuates asthma in mice

The p38 mitogen-activated protein kinase (MAPK) plays a critical role in the activation of inflammatory cells. Therefore, we investigated the antiinflammatory effects of a respirable p38alpha MAPK antisense oligonucleotide (p38alpha-ASO) in a mouse asthma model. A potent and selective p38alpha-ASO was characterized in vitro. Inhalation of aerosolized p38alpha-ASO using an aerosol chamber dosing system produced measurable lung deposition of ASO and significant reduction of ovalbumin (OVA-)-induced increases in total cells, eosinophils, and interleukin 4 (IL-4), IL-5, and IL-13 levels in bronchoalveolar lavage fluid, and dose-dependent inhibition of airway hyperresponsiveness in allergen-challenged mice. Furthermore, inhaled p38alpha-ASO markedly inhibited OVA-induced lung tissue eosinophilia and airway mucus hypersecretion. Quantitative polymerase chain reaction analysis of bronchoalveolar lavage fluid cells and peribronchial lymph node cells showed that p38alpha-ASO significantly reduced p38alpha MAPK mRNA expression. Nose-only aerosol exposure of mice verified the p38alpha-ASO-induced inhibition of OVA-induced pulmonary eosinophilia, mucus hypersecretion, and airway hyperresponsiveness. None of the effects of the p38alpha-ASO were produced by a six-base mismatched control oligonucleotide. These findings demonstrate antisense pharmacodynamic activity in the airways after aerosol delivery and suggest that a p38alpha MAPK ASO approach may have therapeutic potential for asthma and other inflammatory lung diseases.

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

Allergic asthma and allergic rhinitis are inflammatory diseases of the airway. Cytokines and chemokines produced by T helper (Th) type 2 cells (GM-CSF, IL-4, IL-5, IL-6, IL-9, IL-10 and IL-13), eotaxin, transforming growth factor-beta, and IL-11 orchestrate most pathophysiological processes of the late-phase allergic reaction, including the recruitment, activation, and delayed apoptosis of eosinophils, as well as eosinophilic degranulation to release eosinophilic cationic protein, major basic protein, and eosinophil-derived neurotoxin. These processes are regulated through an extensive network of interactive intracellular signal transduction pathways that have been intensively investigated recently. Our present review updates the cytokine and chemokine-mediated signal transduction mechanisms including the RAS-RAF-mitogen-activated protein kinases, Janus kinases (signal transducers and activators of transcription), phosphatidylinositol 3-kinase, nuclear factor-kappa B, activator protein-1, GATA, and cyclic AMP-dependent pathways, and describes the roles of different signaling pathways in the regulation of eosinophil differentiation, recruitment, degranulation, and expression of adhesion molecules. We shall also discuss different biochemical methods for the assessment of various intracellular signal transduction molecules, and various antagonists of receptors, modulators, and inhibitors of intracellular signaling molecules, many of which are potential therapeutic agents for treating allergic diseases.

A new model for studying eosinophil migration across cultured intestinal epithelial monolayers

OBJECTIVE

Eosinophils play an important role in some gastrointestinal inflammatory conditions. Stimulated eosinophils migrate across the vascular endothelial wall and into the intestinal epithelium where by-products such as proteases may contribute to intestinal epithelial damage. Little is known about the epithelial migration of the eosinophils in the gut. The lack of data is attributable in part to the scarcity of human eosinophils for studies. HL-60-differentiated eosinophils present a means to perform studies on eosinophil function and chemotaxis. HL-60 clone 15 can be induced to differentiate into cells closely resembling human eosinophils. The authors describe a novel model for studying eosinophil migration across the intestinal epithelium.

METHODS

Fluorescent-labeled HL-60 eosinophils were incubated for 150 minutes on the basolateral surface of confluent and inverted T-84 monolayers separated by fluoroblock insert membranes. Chemotactic gradients of n-formyl methionyl leucyl phenylalanine (fMLP), eotaxin, and platelet aggregating factor (PAF) were used in variable concentrations. Changes in transepithelial electrical resistance (TEER) were compared with baseline values.

RESULTS

Differentiated HL-60 eosinophils undergo migration in response to fMLP, PAF, and eotaxin. Migration is associated with a drop in TEER.

CONCLUSION

In this model, HL-60-differentiated eosinophils migrate in response to stimulants chemotactic for human eosinophils. The transepithelial migration of eosinophils is associated with epithelial barrier dysfunction, which may contribute to the development of disease.

Signaling molecules as therapeutic targets in allergic diseases

A molecular understanding of physiologic and pathologic processes requires complete knowledge about the signal transduction mechanism of involved cells. Signal transduction research is a rapidly growing field in basic science. Unlike intercellular inflammatory mediators, signaling molecules show less functional redundancy. This allows inhibition of multiple cytokines/mediators by blocking one common signaling molecule. Interference with signaling pathways has shown significant potential for inhibition of fundamental processes as well as clinical phenotype of allergic diseases. The purpose of this review was to provide a theoretical classification of signaling molecules based on their function and to analyze various strategies for developing effective signaling inhibitors for allergic diseases.