Recall helper T cell response: T helper 1 cell-resistant allergic susceptibility without biasing uncommitted CD4 T cells

Inhibitory Effects of Phellodendri Cortex Against Airway Inflammation and Hyperresponsiveness in Ovalbumin-Induced Murine Asthma Model

Phellodendri cortex (PC), the dried trunk bark of Phellodendron amurense RUPR, has traditionally been used to treat patients who suffer from gastroenteritis, abdominal pain or diarrhea. Its major bioactive compounds include alkaloids and limonin, and many physiological activities including anti-microbial, anti-ulcer and anti-cancer as well as anti-inflammation have been reported. Although PC is an effective anti-inflammatory natural substance that inhibits the inflammatory response, its effect on allergic asthma has not yet been investigated. The aim of this study was to evaluate the anti-asthmatic effects of PC in an ovalbumin (OVA)-induced murine model of asthma. As a result, PC inhibited airway eosinophil accumulation, the influx of inflammatory cells, airway hyperresponsiveness (AHR), production of Th2 cytokines (IL-4, IL-5 and IL-13) and tumor necrosis factor-α (TNF-α) in the bronchoalveolar lavage fluid and/or lung, as well as OVA-specific immunoglobulin E (IgE) in the serum. Furthermore, PC suppressed the gene expression of IL-4, IL-5, IL-13, TARC and CCR3, and attenuated unique histological changes that are associated with airway inflammatory reactions including the infiltration of various inflammatory cells, collagen deposition and goblet cell hyperplasia in lung tissues. These results indicate that PC may have preventive and/or therapeutic effects for allergic asthma via the inhibition of cytokines, chemokines and chemokine receptors associated with allergic inflammation.

CD38 and airway hyper-responsiveness: studies on human airway smooth muscle cells and mouse models

Asthma is an inflammatory disease in which altered calcium regulation, contractility, and airway smooth muscle (ASM) proliferation contribute to airway hyper-responsiveness and airway wall remodeling. The enzymatic activity of CD38, a cell-surface protein expressed in human ASM cells, generates calcium mobilizing second messenger molecules such as cyclic ADP-ribose. CD38 expression in human ASM cells is augmented by cytokines (e.g., TNF-α) that requires the activation of MAP kinases and the transcription factors, NF-κB and AP-1, and is post-transcriptionally regulated by miR-140-3p and miR-708 by binding to 3' Untranslated Region of CD38 as well as by modulating the activation of signaling mechanisms involved in its regulation. Mice deficient in Cd38 exhibit reduced airway responsiveness to inhaled methacholine relative to the response in wild-type mice. Intranasal challenge of Cd38-deficient mice with TNF-α or IL-13, or the environmental fungus Alternaria alternata, causes significantly attenuated methacholine responsiveness compared with wild-type mice, with comparable airway inflammation. Reciprocal bone marrow transfer studies revealed partial restoration of airway hyper-responsiveness to inhaled methacholine in the Cd38-deficient mice. These studies provide evidence for CD38 involvement in the development of airway hyper-responsiveness; a hallmark feature of asthma. Future studies aimed at drug discovery and delivery targeting CD38 expression and (or) activity are warranted.

Lymphocyte-based model systems for allergy research: a historic overview

During the last decades, a multitude of studies applying distinct in vitro and in vivo model systems have contributed greatly to our better understanding of the initiation and regulation of inflammatory processes leading to allergic diseases. Over the years, it has become evident that among lymphocytes, not only IgE-producing B cells and allergy-orchestrating CD4(+) helper cells but also cytotoxic CD8(+) T cells, γδ-T cells and innate lymphoid cells, as well as regulatory lymphocytes, might critically shape the immune response towards usually innocuous allergens. In this review, we provide a historic overview of pioneering work leading to the establishment of important lymphocyte-based model systems for allergy research. Moreover, we contrast the original findings with our currently more refined knowledge to appreciate the actual validity of the respective models and to reassess the conclusions obtained from them. Conflicting studies and interpretations are identified and discussed. The tables are intended to provide an easy overview of the field not only for scientists newly entering the field but also for the broader readership interested in updating their knowledge. Along those lines, herein we discuss in vitro and in vivo approaches to the investigation of lymphocyte effector cell activation, polarization and regulation, and describe depletion and adoptive transfer models along with gene knockout and transgenic (tg) methodologies. In addition, novel attempts to establish humanized T cell antigen receptor tg mouse models for allergy research are described and discussed.

Nascent endothelium initiates Th2 polarization of asthma

Asthma airway remodeling is linked to Th2 inflammation. Angiogenesis is a consistent feature of airway remodeling, but its contribution to pathophysiology remains unclear. We hypothesized that nascent endothelial cells in newly forming vessels are sufficient to initiate Th2-inflammation. Vascular endothelial (VE)-cadherin is a constitutively expressed endothelial cell adhesion molecule that is exposed in its monomer form on endothelial tip cells prior to adherens junction formation. Abs targeted to VE-cadherin monomers inhibit angiogenesis by blocking this adherens junction formation. In this study, VE-cadherin monomer Ab reduced angiogenesis in the lungs of the allergen-induced murine asthma model. Strikingly, Th2 responses including, IgE production, eosinophil infiltration of the airway, subepithelial fibrosis, mucus metaplasia, and airway-hyperreactivity were also attenuated by VE-cadherin blockade, via mechanisms that blunted endothelial IL-25 and proangiogenic progenitor cell thymic stromal lymphopoietin production. The results identify angiogenic responses in the origins of atopic inflammation.

Hyaluronan deposition and correlation with inflammation in a murine ovalbumin model of asthma

Asthma is a chronic inflammatory disease of the airways characterized by airway remodeling, which includes changes in the extracellular matrix (ECM). However the role of the ECM in mediating these changes is poorly understood. Hyaluronan (HA), a major component of the ECM, has been implicated in asthma as well as in many other biological processes. Our study investigates the processes involved in HA synthesis, deposition, localization and degradation during an acute and chronic murine model of ovalbumin (OVA)-induced allergic pulmonary inflammation. Mice were sensitized, challenged to OVA and sacrificed at various time points during an 8-week challenge protocol. Bronchoalveolar lavage (BAL) fluids, blood, and lung tissue were collected for study. RNA, HA, protein and histopathology were analyzed. Analyses of lung sections and BAL fluids revealed an early deposition and an increase in HA levels within 24 h of antigen exposure. HA levels peaked at day 8 in BAL, while inflammatory cell recovery peaked at day 6. Hyaluronan synthase (HAS)1 and HAS2 on RNA levels peaked within 2 h of antigen exposure, while hyaluronidase (HYAL)1 and HYAL2 on RNA levels decreased. Both inflammatory cell infiltrates and collagen deposition co-localized with HA deposition within the lungs. These data support a role for HA in the pathogenesis of inflammation and airway remodeling in a murine model of asthma. HA deposition appears largely due to up regulation of HAS1 and HAS2. In addition, HA appears to provide the scaffolding for inflammatory cell accumulation as well as for new collagen synthesis and deposition.

Pathogens and immunologic memory in asthma: what have we learned?

Animal models and clinical studies of asthma have generated important insights into the first effector phase leading to the development of allergic airway disease and bronchial hyper-reactivity. In contrast, mechanisms related to asthma chronicity or persistence are less well understood. The CD4(+) T-helper 2 lymphocytes are known initiators of the inflammatory response associated with asthma. There is now increasing evidence that memory T-cells, sensitized against allergenic, occupational or viral antigens, are also involved in the persistence of asthma. Additionally, the role of pathogens in asthma has been linked to both the initial susceptibility to and flares of this disease. This review will discuss the potential links between infection and asthma, the role of the memory T-cells in asthma, and the potential mechanisms by which these factors interact to lead to the development and/or persistence of asthma.

Allergen-induced, eotaxin-rich, proangiogenic bone marrow progenitors: a blood-borne cellular envoy for lung eosinophilia

BACKGROUND

Eosinophilic inflammation is closely related to angiogenesis in asthmatic airway remodeling. In ovalbumin (OVA)-sensitized mice bone marrow-derived, proangiogenic endothelial progenitor cells (EPCs) are rapidly recruited into the lungs after OVA aerosol challenge and promptly followed by mobilization and recruitment of eosinophils.

OBJECTIVE

We hypothesized that bone marrow-derived EPCs initiate the recruitment of eosinophils through expression of the eosinophil chemoattractant eotaxin-1.

METHODS

EPCs were isolated from an OVA murine model of allergic airway inflammation and from asthmatic patients. Endothelial and smooth muscle cells were isolated from mice. Eotaxin-1 expression was analyzed by means of immunofluorescence, real-time PCR, or ELISA. In vivo recruitment of eosinophils by EPCs was analyzed in mice.

RESULTS

Circulating EPCs of asthmatic patients had higher levels of eotaxin-1 compared with those seen in control subjects. In the murine model OVA allergen exposure augmented eotaxin-1 mRNA and protein levels in EPCs. The EPCs from OVA-sensitized and OVA-challenged mice released high levels of eotaxin-1 on contact with lung endothelial cells from sensitized and challenged mice but not from control animals and not on contact with cardiac or hepatic endothelial cells from sensitized and challenged mice. Intranasal administration of the eotaxin-rich media overlying cultures of EPCs caused recruitment into the lungs, confirming functional chemoattractant activity.

CONCLUSIONS

Bone marrow-derived EPCs are early responders to environmental allergen exposures and initiate a parallel switch to a proangiogenic and proeosinophilic environment in the lungs of asthmatic patients.

Airway hyperresponsiveness is associated with activated CD4+ T cells in the airways

It is widely accepted that atopic asthma depends on an allergic response in the airway, yet the immune mechanisms that underlie the development of airway hyperresponsiveness (AHR) are poorly understood. Mouse models of asthma have been developed to study the pathobiology of this disease, but there is considerable strain variation in the induction of allergic disease and AHR. The aim of this study was to compare the development of AHR in BALB/c, 129/Sv, and C57BL/6 mice after sensitization and challenge with ovalbumin (OVA). AHR to methacholine was measured using a modification of the forced oscillation technique in anesthetized, tracheostomized mice to distinguish between airway and parenchymal responses. Whereas all strains showed signs of allergic sensitization, BALB/c was the only strain to develop AHR, which was associated with the highest number of activated (CD69(+)) CD4(+) T cells in the airway wall and the highest levels of circulating OVA-specific IgG(1). AHR did not correlate with total or antigen-specific IgE. We assessed the relative contribution of CD4(+) T cells and specific IgG(1) to the development of AHR in BALB/c mice using adoptive transfer of OVA-specific CD4(+) T cells from DO11.10 mice. AHR developed in these mice in a progressive fashion following multiple OVA challenges. There was no evidence that antigen-specific antibody had a synergistic effect in this model, and we concluded that the number of antigen-specific T cells activated and recruited to the airway wall was crucial for development of AHR.

Flexibility accompanies commitment of memory CD4 lymphocytes derived from IL-4 locus-activated precursors

Differentiation of T helper (Th) subset 2 effector lymphocytes is thought to foreclose on IFN-gamma gene expression. Using an IL-4 locus modified to detect transcriptional induction of this effector cytokine gene in developing Th2 cells, we show here that these cells contributed effectively to a long-term memory population. A memory CD4 subset formed efficiently from an activated population after transcriptional induction of the IL-4 locus and differentiation into an IL-4-producing subset with Th2 characteristics. Memory lymphocytes derived from Th2 cells with IL-4 locus activation remained committed to transcriptional competence of Th2 cytokine genes when reactivated and cultured under strong Th1-polarizing conditions. This commitment to transcriptional competence at Th2 cytokine gene loci upon recall activation indicates that linear differentiation is a substantial component of type 2 memory. Strikingly, however, descendants of the Th2 population could turn on IFN-gamma expression when reactivated after a quiescent period, revealing an unexpected flexibility allowing activation of the forbidden IFN-gamma gene after reactivation and growth.

Plasminogen is an important regulator in the pathogenesis of a murine model of asthma

RATIONALE

Asthma is a syndrome whose common pathogenic expression is inflammation of the airways. Plasminogen plays an important role in cell migration and is also implicated in tissue remodeling, but its role in asthma has not been defined.

OBJECTIVES

To test whether plasminogen is a critical component in the development of asthma.

METHODS

We used a mouse model of ovalbumin-induced pulmonary inflammation in Plg(+/+), Plg(+/-), and Plg(-/-) mice.

MEASUREMENTS AND MAIN RESULTS

The host responses measured included lung morphometry, and inflammatory mediators and cell counts were assessed in bronchoalveolar lavage fluid. Bronchoalveolar lavage demonstrated a marked increase in eosinophils and lymphocytes in ovalbumin-treated Plg(+/+) mice, which were reduced to phosphate-buffered saline-treated control levels in Plg(+/-) or Plg(-/-) mice. Lung histology revealed peribronchial and perivascular leukocytosis, mucus production, and increased collagen deposition in ovalbumin-treated Plg(+/+) but not in Plg(+/-) or Plg(-/-) mice. IL-5, tumor necrosis factor-alpha, and gelatinases, known mediators of asthma, were detected in bronchoalveolar lavage fluid of ovalbumin-treated Plg(+/+) mice, yet were reduced in Plg(-/-) mice. Administration of the plasminogen inhibitor, tranexamic acid, reduced eosinophil and lymphocyte numbers, mucus production, and collagen deposition in the lungs of ovalbumin-treated Plg(+/+) mice.

CONCLUSIONS

The decreased inflammation in the lungs of Plg(-/-) mice and its blockade with a plasminogen inhibitor indicate that plasminogen plays an important role in orchestrating the asthmatic response and suggests that plasminogen may be a therapeutic target for the treatment of asthma.

Th1- and Th2-dependent endothelial progenitor cell recruitment and angiogenic switch in asthma

Increased numbers of submucosal vessels are a consistent pathologic component of asthmatic airway remodeling. However, the relationship between new vessel formation and asthmatic inflammatory response is unknown. We hypothesized that angiogenesis is a primary event during the initiation of airway inflammation and is linked to the recruitment of bone marrow-derived endothelial progenitor cells (EPC). To test this hypothesis, circulating EPC and EPC-derived endothelial cell colony formation of individuals with asthma or allergic rhinitis and health controls was evaluated. Circulating EPC were increased in asthma, highly proliferative, and exhibited enhanced incorporation into endothelial cell tubes as compared with controls. In an acute allergen challenge murine asthma model, EPC mobilization occurred within hours of challenge and mobilized EPC were selectively recruited into the challenged lungs of sensitized animals, but not into other organs. EPC recruitment was Th1 and Th2 dependent and was temporally associated with an increased microvessel density that was noted within 48 h of allergen challenge, indicating an early switch to an angiogenic lung environment. A chronic allergen challenge model provided evidence that EPC recruitment to the lung persisted and was associated with increasing microvessel density over time. Thus, a Th1- and Th2-dependent angiogenic switch with EPC mobilization, recruitment, and increased lung vessel formation occurs early but becomes a sustained and cumulative component of the allergen-induced asthmatic response.

Adoptively transferred allergen-specific T cells cause maternal transmission of asthma risk

In addition to genetics and environment, maternal asthma is an identified risk factor for developing the disease during childhood. The mechanisms of this maternal effect remain poorly understood. We tested the role of allergen-specific T cells in the maternal transmission of asthma risk by modifying a model where offspring of asthmatic mothers are more prone to develop asthma after an intentionally suboptimal asthma induction. Normal BALB/c females were injected with allergen-specific T cells from ovalbumin-specific T cell receptor (TCR) transgenic DO11.10 donors before mating. Using the protocol of suboptimal asthma induction, offspring of normal and recipient mothers were tested for their susceptibility to develop asthma. Only pups of recipient mothers showed increased airway responsiveness (Penh), allergic airway inflammation with eosinophilia, and local Th2-skewed cytokine production. Although recipient mothers did not develop asthma, serum levels of interferon-gamma, interleukin (IL)-4, IL-10, and IL-13 were significantly increased during pregnancy. Consistent with this finding, a subset of DO11.10 T cells persisted in the spleen and placenta of expectant recipient mothers. We conclude that allergen-specific T cells are sufficient to orchestrate the maternal transmission of asthma risk. Because overt maternal asthma was not required, our results suggest that similar maternal-fetal interactions may occur in other allergic disorders.

Nitrotyrosine proteome survey in asthma identifies oxidative mechanism of catalase inactivation

Reactive oxygen species and reactive nitrogen species produced by epithelial and inflammatory cells are key mediators of the chronic airway inflammation of asthma. Detection of 3-nitrotyrosine in the asthmatic lung confirms the presence of increased reactive oxygen and nitrogen species, but the lack of identification of modified proteins has hindered an understanding of the potential mechanistic contributions of nitration/oxidation to airway inflammation. In this study, we applied a proteomic approach, using nitrotyrosine as a marker, to evaluate the oxidation of proteins in the allergen-induced murine model of asthma. Over 30 different proteins were targets of nitration following allergen challenge, including the antioxidant enzyme catalase. Oxidative modification and loss of catalase enzyme function were seen in this model. Subsequent investigation of human bronchoalveolar lavage fluid revealed that catalase activity was reduced in asthma by up to 50% relative to healthy controls. Analysis of catalase isolated from asthmatic airway epithelial cells revealed increased amounts of several protein oxidation markers, including chloro- and nitrotyrosine, linking oxidative modification to the reduced activity in vivo. Parallel in vitro studies using reactive chlorinating species revealed that catalase inactivation is accompanied by the oxidation of a specific cysteine (Cys(377)). Taken together, these studies provide evidence of multiple ongoing and profound oxidative reactions in asthmatic airways, with one early downstream consequence being catalase inactivation. Loss of catalase activity likely amplifies oxidative stress, contributing to the chronic inflammatory state of the asthmatic airway.

A review of the genetic epidemiology of resistance to parasitic disease and atopic asthma: common variants for common phenotypes?

PURPOSE OF REVIEW

An inverse relationship between resistance to certain parasitic diseases and measures of atopy and asthma has long been observed. A possible explanation is that genetic determinants which confer protection against detrimental worm burdens are the same determinants involved in atopic asthma. The focus of this review is to consider the potential candidate genes that have been elucidated as part of molecular, genomic and genetic studies of parasite biology, host-parasite interactions and classic genetic epidemiology studies on parasitic disease and allergic asthma.

RECENT FINDINGS

Comparative studies of the Plasmodium and Schistosoma spp. genomes have revealed a number of proteins that are homologous to humans. A number of linkage and association studies on susceptibility/resistance to parasitic diseases, including malaria and schistosomiasis, overlap with associations that have been identified for susceptibility to atopy and asthma.

SUMMARY

In response to parasitic approaches in maintaining survival, the human host has evolved genetic adaptations that minimize severe manifestations of disease, which conversely appear to contribute to allergic disease. A clearer understanding of this process will elucidate the complex pathways and mechanisms involved in these traits.

Chlamydophila pneumoniae and Mycoplasma pneumoniae: a role in asthma pathogenesis?

The potential role of atypical bacterial infection in the pathogenesis of asthma is a subject of continuing debate. There is an increasing body of literature concerning the association between the atypical bacteria Chlamydophila pneumoniae and Mycoplasma pneumoniae and asthma pathogenesis; however, many studies investigating such a link have been uncontrolled and have provided conflicting evidence, in part due to the difficulty in accurately diagnosing infection with these atypical pathogens. This article reviews the evidence for an association between atypical bacterial respiratory pathogens and the pathogenesis of asthma, and discusses the biological mechanisms that could account for such a link. The possible role of antibacterial therapy in the management of asthma and the need for well-designed studies to investigate this is also discussed.

Targeting memory Th2 cells for the treatment of allergic asthma

Th2 memory cells play an important role in the pathogenesis of allergic asthma. Evidence from patients and experimental models indicates that memory Th2 cells reside in the lungs during disease remission and, upon allergen exposure, become activated effectors involved in disease exacerbation. The inhibition of memory Th2 cells or their effector functions in allergic asthma influence disease progression, suggesting their importance as therapeutic targets. They are allergen specific and can potentially be suppressed or eliminated using this specificity. They have distinct activation, differentiation, cell surface phenotype, migration capacity, and effector functions that can be targeted singularly or in combination. Furthermore, memory Th2 cells residing in the lungs can be treated locally. Capitalizing on these unique attributes is important for drug development for allergic asthma. The aim of this review is to present an overview of therapeutic strategies targeting Th2 memory cells in allergic asthma, emphasizing Th2 generation, differentiation, activation, migration, effector function, and survival.

Susceptibility to allergic lung disease regulated by recall responses of dual-receptor memory T cells

BACKGROUND

Microbial infections are associated with the initial susceptibility to and flares of asthma. However, immunologic mechanisms whereby infections might alter the asthmatic phenotype are lacking.

OBJECTIVE

To test the hypothesis that memory T cells specific both for a viral antigen and an allergen could influence the pathogenesis of allergic disease in vivo .

METHODS

We developed a system in which 2 distinct T-cell receptors coexist on the T-cell surface, 1 specific for a virus and the other for an inhaled antigen.

RESULTS

We show that a population of dual-receptor T cells, polarized through a virus-specific T-cell receptor to contain T(H)1 or T(H)2 cells, can be reactivated through an unrelated T-cell receptor in recall responses in vivo . Quiescent memory cells derived from a T(H)1-polarized effector population blocked the development of airway hyperreactivity in a model of allergic lung disease, in association with decreased induction of chemokines and eosinophil recruitment. Conversely, reactivation of quiescent T(H)2 cells after inhalation of antigen or virus infection was sufficient to lead to the development of airway hyperresponsiveness and allergic pulmonary inflammation in mice whose lungs were previously normal.

CONCLUSION

These data provide evidence that dual-receptor memory T cells can regulate allergic disease susceptibility and suggest that they may play a role in mediating the influence of microbes on asthma pathogenesis.