Innate immune mechanism in allergic asthma

Harshness and unpredictability: Childhood environmental links with immune and asthma outcomes

The environment has pervasive impacts on human development, and two key environmental conditions - harshness and unpredictability - are proposed to be instrumental in tuning development. This study examined (1) how harsh and unpredictable environments related to immune and clinical outcomes in the context of childhood asthma, and (2) whether there were independent associations of harshness and unpredictability with these outcomes. Participants were 290 youth physician-diagnosed with asthma. Harshness was assessed with youth-reported exposure to violence and neighborhood-level murder rate. Unpredictability was assessed with parent reports of family structural changes. Youth also completed measures of asthma control as well as asthma quality of life and provided blood samples to assess immune profiles, including in vitro cytokine responses to challenge and sensitivity to inhibitory signals from glucocorticoids. Results indicated that harshness was associated with more pronounced pro-inflammatory cytokine production following challenge and less sensitivity to the inhibitory properties of glucocorticoids. Furthermore, youth exposed to harsher environments reported less asthma control and poorer quality of life. All associations with harshness persisted when controlling for unpredictability. No associations between unpredictability and outcomes were found. These findings suggest that relative to unpredictability, harshness may be a more consistent correlate of asthma-relevant immune and clinical outcomes.

Pulmonary neuroendocrine cells: physiology, tissue homeostasis and disease

Mammalian lungs have the ability to recognize external environments by sensing different compounds in inhaled air. Pulmonary neuroendocrine cells (PNECs) are rare, multi-functional epithelial cells currently garnering attention as intrapulmonary sensors; PNECs can detect hypoxic conditions through chemoreception. Because PNEC overactivation has been reported in patients suffering from respiratory diseases – such as asthma, chronic obstructive pulmonary disease, bronchopulmonary dysplasia and other congenital diseases – an improved understanding of the fundamental characteristics of PNECs is becoming crucial in pulmonary biology and pathology. During the past decade, murine genetics and disease models revealed the involvement of PNECs in lung ventilation dynamics, mechanosensing and the type 2 immune responses. Single-cell RNA sequencing further unveiled heterogeneous gene expression profiles in the PNEC population and revealed that a small number of PNECs undergo reprogramming during regeneration. Aberrant large clusters of PNECs have been observed in neuroendocrine tumors, including small-cell lung cancer (SCLC). Modern innovation of imaging analyses has enabled the discovery of dynamic migratory behaviors of PNECs during airway development, perhaps relating to SCLC malignancy. This Review summarizes the findings from research on PNECs, along with novel knowledge about their function. In addition, it thoroughly addresses the relevant questions concerning the molecular pathology of pulmonary diseases and related therapeutic approaches.

Summary: This Review highlights the physiological relevance of pulmonary neuroendocrine cells, rare airway epithelial cells that form intrapulmonary sensory organs, abnormalities of which are associated with several pulmonary disorders, such as asthma and lung cancer.

Short ragweed pollen promotes M2 macrophage polarization via TSLP/TSLPR/OX40L signaling in allergic inflammation

This study was to explore the role and mechanism of macrophages in pollen-triggered allergic inflammation. A murine model of short ragweed (SRW) pollen-induced experimental allergic conjunctivitis (EAC), and bone marrow (BM)-macrophages cultures were used. Typical allergic manifestations and TSLP-stimulated Th2 hyperresponse were observed in ocular surface of EAC model in wild-type (WT) mice induced by SRW. The M2 phenotype markers, Arg1, Ym1 and FIZZ1, were highly expressed by conjunctiva and draining cervical lymph nodes (CLNs) of WT-EAC mice when compared with controls, as evaluated by RT-qPCR and Immunofluorescent double staining with macrophage marker F4/80. The stimulated expression of TSLPR and OX40L by macrophage was detected in conjunctiva and CLNs by RT-qPCR, double staining, and flow cytometry. M2 macrophages were found to produce TARC and MDC. In contrast, EAC model with TSLPR^-/- mice did not show allergic signs and any increase of Th2 cytokines (IL-4, IL-5 and IL-13) and M2 markers. In vitro cultures confirmed that SRW extract stimulates expression of TSLPR, OX40L, TARC, MDC, and three M2 markers by BM-macrophages from WT mice, but not from TSLPR^-/- mice. These findings demonstrate that SRW pollen primes macrophage polarization toward to M2 phenotype via TSLP/TSLPR/OX40L signaling to amplify allergic inflammation.

Silencing of ADAM33 restrains proliferation and induces apoptosis of airway smooth muscle cells in ovalbumin-induced asthma model

A defibrinogen and metalloproteinase 33 (ADAM33) was reported to play an important role in asthma. Furthermore, ADAM33 may play a possible role in airway remodeling due to its high expression in myo-/fibroblasts, epithelium, as well as the airway smooth muscle cells (ASMCs). Thus, the study is supposed to investigate the effect of the downregulation of ADAM33 on the proliferation and apoptosis of ASMCs in allergic asthma. An ovalbumin-induced asthma model in rats was established for investigating the function of the silencing of ADAM33. ASMCs were cultured and divided into four groups after transfection. The messenger RNA and protein expressions of ADAM33 were measured by reverse transcription quantitative polymerase chain reaction and Western blot analysis. Cell proliferation was tested by cell counting kit-8 and cell apoptosis by TdT-mediated dUTP nick-end labeling. The allergic asthma rats showed a large number of inflammatory cell infiltration, airway smooth muscle hypertrophy and hyperplasia, and increased WA _t , WA _m , and numbers of bronchial smooth muscle nucleus. Additionally, increased numbers of eosinophils and neutrophils, expressions of immunoglobulin E and interleukin-4, content of airway air pressure, and NO, although decreased in expression of interferon-γ, were exhibited in rats with allergic asthma. In our study, upregulated ADAM33 was found, and after the silencing of ADAM33, decreased proliferation and increased apoptosis of ASMCs were observed. The study evidences that silencing of ADAM33 can decrease the proliferation and increase the apoptosis of ASMCs in a rat model of allergic asthma, suggesting ADAM33 represents a potential investigative focus target aiding allergic asthma.

Does lung microbiome play a causal or casual role in asthma?

Asthma is the most common chronic disease in childhood. The pathogenesis of asthma is multifactorial and is thought to include environmental factors interacting with genetics during pregnancy and in the first years of life. In the last decades, a possible role of gut microbiota in allergic disease pathogenesis has been demonstrated. Next generation sequencing techniques have allowed the identification of a distinct microbiome in the healthy lungs. The lung microbiome is characterized by the prevalence of bacteria belonging to the phylum Bacteroidetes (mostly Prevotella and Veilonella spp) in healthy subjects and to the phylum Proteobacteria in asthmatics (mostly Haemophilus, Moraxella, and Neisseria spp). In asthma, as well as in other diseases, the lung microbiome composition changes due to a disruption of the delicate balance between immigration and elimination of bacteria. The lung microbiome can interact with the immune system, thus influencing inflammation. Early infections with viruses, such as respiratory syncytial virus, may alter lung microbiome composition favoring the emergence of Proteobacteria, a phylum which is also linked to severity of asthma and bronchial hyperreactivity. Lastly, antibiotics may alter the gut and lung microbiota and potentially disturb the relationship between microbiota and host. Therefore, antibiotics should be prescribed with increasing awareness of their potential harmful effect on the microbiota in young children with and without asthma. The potential effects of probiotics and prebiotics on lung microbiome are unknown.

Exposure to diisodecyl phthalate exacerbated Th2 and Th17-mediated asthma through aggravating oxidative stress and the activation of p38 MAPK

Diisodecyl phthalate (DIDP) is considered to be one of the less toxic phthalates. However epidemiological studies suggest that DIDP is associated with the occurrence of asthma. The effect of DIDP exposure on allergic asthma and the underlying mechanism have not been fully elucidated. Here, mice were exposed to DIDP and sensitization with OVA. The results demonstrated that DIDP exposure aggravated allergic asthma. Exposure to 15 mg/kg/day DIDP markedly exacerbated airway remodeling and promoted airway hyperresponsiveness (AhR). The study suggests that exposure to DIDP not only promotes a predominant Th2 response, but also induces Th17-type immunity. The induced allergic asthma was accompanied by elevation of IgE, an increase in TSLP expression and exacerbation of oxidative stress. Inhibition of oxidative stress by Vitamin E effectively alleviated the airway remodeling and AhR induced by DIDP and OVA sensitization. Treatment with Vitamin E inhibited the Th2 response and the production of TSLP. Blocking the activation of p38 MAPK by SB203580 prevented elevation of IL-1β and IL-17A induced by DIDP and OVA sensitization and effectively alleviated Th17 type asthmatic lesions. These results suggest that exposure to DIDP exacerbates the Th2 and Th17 response through aggravating oxidative stress and activation of the p38 MAPK pathway.

The Potential for Emerging Microbiome-Mediated Therapeutics in Asthma

PURPOSE OF REVIEW

In terms of immune regulating functions, analysis of the microbiome has led the development of therapeutic strategies that may be applicable to asthma management. This review summarizes the current literature on the gut and lung microbiota in asthma pathogenesis with a focus on the roles of innate molecules and new microbiome-mediated therapeutics.

RECENT FINDINGS

Recent clinical and basic studies to date have identified several possible therapeutics that can target innate immunity and the microbiota in asthma. Some of these drugs have shown beneficial effects in the treatment of certain asthma phenotypes and for protection against asthma during early life. Current clinical evidence does not support the use of these therapies for effective treatment of asthma. The integration of the data regarding microbiota with technologic advances, such as next generation sequencing and omics offers promise. Combining comprehensive bioinformatics, new molecules and approaches may shape future asthma treatment.

The cAMP response element modulator (CREM) regulates TH2 mediated inflammation

A characteristic feature of allergic diseases is the appearance of a subset of CD4⁺ cells known as T_H2 cells, which is controlled by transcriptional and epigenetic mechanisms. We aimed to analyze the role of CREM, a known transcriptional activator of T cells, with regard to T_H2 responses and allergic diseases in men and mice. Here we demonstrate that T cells of asthmatic children and PBMCs of adults with atopy express lower mRNA levels of the transcription factor CREM compared to cells from healthy controls. CREM deficiency in murine T cells results in enhanced T_H2 effector cytokines in vitro and in vivo and CREM^−/− mice demonstrate stronger airway hyperresponsiveness in an OVA-induced asthma model. Mechanistically, both direct CREM binding to the IL-4 and IL-13 promoter as well as a decreased IL-2 dependent STAT5 activation suppress the T_H2 response. Accordingly, mice selectively overexpressing CREMα in T cells display decreased T_H2 type cytokines in vivo and in vitro, and are protected in an asthma model. Thus, we provide evidence that CREM is a negative regulator of the T_H2 response and determines the outcome of allergic asthma.

Properdin Contributes to Allergic Airway Inflammation through Local C3a Generation

Complement is implicated in asthma pathogenesis, but its mechanism of action in this disease remains incompletely understood. In this study, we investigated the role of properdin (P), a positive alternative pathway complement regulator, in allergen-induced airway inflammation. Allergen challenge stimulated P release into the airways of asthmatic patients, and P levels positively correlated with proinflammatory cytokines in human bronchoalveolar lavage (BAL). High levels of P were also detected in the BAL of OVA-sensitized and challenged but not naive mice. Compared with wild-type (WT) mice, P-deficient (P(-/-)) mice had markedly reduced total and eosinophil cell counts in BAL and significantly attenuated airway hyperresponsiveness to methacholine. Ab blocking of P at both sensitization and challenge phases or at challenge phase alone, but not at sensitization phase alone, reduced airway inflammation. Conversely, intranasal reconstitution of P to P(-/-) mice at the challenge phase restored airway inflammation to wild-type levels. Notably, C3a levels in the BAL of OVA-challenged P(-/-) mice were significantly lower than in wild-type mice, and intranasal coadministration of an anti-C3a mAb with P to P(-/-) mice prevented restoration of airway inflammation. These results show that P plays a key role in allergen-induced airway inflammation and represents a potential therapeutic target for human asthma.

Inhaled environmental allergens and toxicants as determinants of the asthma phenotype

The driving environmental factors behind the development of the asthma phenotype remain incompletely studied and understood. Here, we present an overview of inhaled allergic/atopic and mainly nonallergic/nonatopic or toxicant shapers of the asthma phenotype, which are present in both the indoor and outdoor environment around us. The inhaled allergic/atopic factors include fungus, mold, animal dander, cockroach, dust mites, and pollen; these allergic triggers and shapers of the asthma phenotype are considered in the context of their ability to drive the immunologic IgE response and potentially induce interactions between the innate and adaptive immune responses, with special emphasis on the NADPH-dependent reactive oxygen-species-associated mechanism of pollen-associated allergy induction. The inhaled nonallergic/nonatopic, toxicant factors include gaseous and volatile agents, such as sulfur dioxide, ozone, acrolein, and butadiene, as well as particulate agents, such as rubber tire breakdown particles, and diesel exhaust particles. These toxicants are reviewed in terms of their relevant chemical characteristics and hazard potential, ability to induce airway dysfunction, and potential for driving the asthma phenotype. Special emphasis is placed on their interactive nature with other triggers and drivers, with regard to driving the asthma phenotype. Overall, both allergic and nonallergic environmental factors can interact to acutely exacerbate the asthma phenotype; some may also promote its development over prolonged periods of untreated exposure, or possibly indirectly through effects on the genome. Further therapeutic considerations should be given to these environmental factors when determining the best course of personalized medicine for individuals with asthma.

Increase in the mediators of asthma in obesity and obesity with type 2 diabetes: reduction with weight loss

OBJECTIVE

To determine whether the expression of key asthma related genes, IL-4, LIGHT, LTBR, MMP-9, CCR-2, and ADAM-33 in mononuclear cells and the plasma concentration of nitric oxide metabolites (NOM) and MMP-9 are increased in the obese, obese type 2 diabetics (T2DM) and in morbidly obese patients prior to and after gastric bypass surgery (RYGB).

DESIGN AND METHODS

The expression of these genes in MNC and plasma concentrations of these indices was measured in healthy lean and in obese with and without T2DM and following RYGB in obese T2DM.

RESULTS

The expression of IL-4, MMP-9, LIGHT and CCR-2 and plasma NOM concentrations was significantly higher in the obese subjects and in obese T2DM patients than in normal subjects. The expression of IL-4, LIGHT, MMP-9, and CCR-2 expression was related to BMI and HOMA-IR. The expression of IL-4, LIGHT, LTBR, ADAM-33, MMP-9, and CCR-2 fell after RYGB surgery as did plasma concentrations of MMP-9 and NOM.

CONCLUSIONS

Obesity with and without T2DM is associated with an increase in the expression of IL-4, LIGHT, MMP-9 and CCR-2; plasma NOM and MMP-9 concentrations are also increased. Following RYGB surgery and weight loss, the expression of these factors in MNC and plasma concentrations falls significantly.

Lung dendritic cell developmental programming, environmental stimuli, and asthma in early periods of life

Dendritic cells (DCs) are important cells of our innate immune system. Their role is critical in inducing adaptive immunity, tolerance, or allergic response in peripheral organs—lung and skin. The lung DCs are not developed prenatally before birth. The DCs develop after birth presumably during the first year of life; exposures to any foreign antigen or infectious organisms during this period can significantly affect DC developmental programming and generation of distinct DC phenotypes and functions. These changes can have both short-term and long-term health effects which may be very relevant in childhood asthma and predisposition for a persistent response in adulthood. An understanding of DC development at molecular and cellular levels can help in protecting neonates and infants against problematic environmental exposures and developmental immunotoxicity. This knowledge can eventually help in designing novel pharmacological modulators to skew the DC characteristics and immune responses to benefit the host across a lifetime.

Role of NOD1-mediated signals in a mouse model of allergic rhinitis

OBJECTIVES

The purpose of the present study was to investigate the effect of nucleotide-binding oligomerization domain 1 (NOD1), an innate immune sensor, on allergic inflammation and induction of regulatory T cells in a mouse model of allergic rhinitis. We also aimed to explore whether there were differences in the effect of NOD1 ligand according to the timing of administration. Study Design An in vivo study using an animal model.

SETTING

Catholic Research Institutes of Medical Science.

SUBJECTS AND METHODS

Forty BALB/c mice were divided into 4 groups: control, OVA, pre-NOD1, and post-NOD1. Ovalbumin (OVA) was used for sensitization and challenge. The pre-NOD1 group received NOD1 ligand intranasally before sensitization, whereas the post-NOD1 group received it after sensitization. The effects of allergic inflammation and regulatory T cells were compared among the groups.

RESULTS

In the post-NOD1 group, serum OVA-specific IgE, eosinophil counts, interleukin (IL)-13 levels, and GATA-3 mRNA expression were significantly increased and Foxp3(+) mRNA expression and CD4(+) Foxp3(+) T cells were decreased compared with the OVA group. In the pre-NOD1 group, Foxp3 mRNA expression and CD4(+) Foxp3(+) T cells were significantly decreased compared with the OVA group. Although not significant, the pre-NOD1 group showed increases in serum OVA-specific IgE, eosinophil counts, IL-13 levels, and GATA-3 mRNA expression compared with the OVA group.

CONCLUSION

The innate immune response through NOD1 enhances allergen-specific Th2 response and suppresses induction of regulatory T cells in a mouse model of allergic rhinitis, and the effects are different depending on the timing of exposure to NOD1 ligand.

Epidemiology of stress and asthma: from constricting communities and fragile families to epigenetics

Several epidemiologic frameworks, exemplified through extant research examples, provide insight into the role of stress in the expression of asthma and other allergic disorders. Biologic, psychological, and social processes interact throughout the life course to influence disease expression. Studies exploiting a child development framework focus on critical periods of exposure, including the in utero environment, to examine the influence of stress on disease onset. Early stress effects that alter the normal course of morphogenesis and maturation that affect both structure and function of key organ systems (eg, immune, respiratory) may persist into adult life underscoring the importance of a life course perspective. Other evidence suggests that maternal stress influences programming of integrated physiologic systems in their offspring (eg, neuroendocrine, autonomic, immune function) starting in pregnancy; consequently stress effects may be transgenerational. A multilevel approach that includes an ecological perspective may help to explain heterogeneities in asthma expression across socioeconomic and geographic boundaries that to date remain largely unexplained. Evolving studies incorporating psychological, behavioral, and physiologic correlates of stress more specifically inform underlying mechanisms operating in these critical periods of development. The role of genetics, gene by environment interactions, and epigenetic mechanisms of gene expression have been sparsely examined in epidemiologic studies on stress and asthma although overlapping evidence provides proof of concept for such studies in the future.

T lymphocyte apoptosis in asthma

The paper describes the possible role of apoptosis of T lymphocytes in asthma pathogenesis. The authors focused on resistance against Fas-mediated programed cell death and the role of Bcl-2 protein in impaired programed cell death process. The reports from the literature regarding the imbalance of Th1 and Th2, caused by impaired apoptosis of T cells, in asthma pathogenesis are reviewed.

Perinatal stress and early life programming of lung structure and function

Exposure to environmental toxins during critical periods of prenatal and/or postnatal development may alter the normal course of lung morphogenesis and maturation, potentially resulting in changes that affect both structure and function of the respiratory system. Moreover, these early effects may persist into adult life magnifying the potential public health impact. Aberrant or excessive pro-inflammatory immune responses, occurring both locally and systemically, that result in inflammatory damage to the airway are a central determinant of lung structure-function changes throughout life. Disruption of neuroendocrine function in early development, specifically the hypothalamic-pituitary-adrenal (HPA) axis, may alter functional status of the immune system. Autonomic nervous system (ANS) function (sympathovagal imbalance) is another integral component of airway function and immunity in childhood. This overview discusses the evidence linking psychological factors to alterations in these interrelated physiological processes that may, in turn, influence childhood lung function and identifies gaps in our understanding.

Prenatal maternal stress and cord blood innate and adaptive cytokine responses in an inner-city cohort

RATIONALE

Stress-elicited disruption of immunity begins in utero.

OBJECTIVES

Associations among prenatal maternal stress and cord blood mononuclear cell (CBMC) cytokine responses were prospectively examined in the Urban Environment and Childhood Asthma Study (n = 557 families).

METHODS

Prenatal maternal stress included financial hardship, difficult life circumstances, community violence, and neighborhood/block and housing conditions. Factor analysis produced latent variables representing three contexts: individual stressors and ecological-level strains (housing problems and neighborhood problems), which were combined to create a composite cumulative stress indicator. CBMCs were incubated with innate (lipopolysaccharide, polyinosinic-polycytidylic acid, cytosine-phosphate-guanine dinucleotides, peptidoglycan) and adaptive (tetanus, dust mite, cockroach) stimuli, respiratory syncytial virus, phytohemagglutinin, or medium alone. Cytokines were measured using multiplex ELISAs. Using linear regression, associations among increasing cumulative stress and cytokine responses were examined, adjusting for sociodemographic factors, parity, season of birth, maternal asthma and steroid use, and potential pathway variables (prenatal smoking, birth weight for gestational age).

MEASUREMENTS AND MAIN RESULTS

Mothers were primarily minorities (Black [71%], Latino [19%]) with an income less than $15,000 (69%). Mothers with the highest cumulative stress were older and more likely to have asthma and deliver lower birth weight infants. Higher prenatal stress was related to increased IL-8 production after microbial (CpG, PIC, peptidoglycan) stimuli and increased tumor necrosis factor-alpha to microbial stimuli (CpG, PIC). In the adaptive panel, higher stress was associated with increased IL-13 after dust mite stimulation and reduced phytohemagglutinin-induced IFN-gamma.

CONCLUSIONS

Prenatal stress was associated with altered innate and adaptive immune responses in CBMCs. Stress-induced perinatal immunomodulation may impact the expression of allergic disease in these children.

The role of Epac proteins, novel cAMP mediators, in the regulation of immune, lung and neuronal function

Chronic degenerative inflammatory diseases, such as chronic obstructive pulmonary disease and Alzheimer's dementia, afflict millions of people around the world, causing death and debilitation. Despite the global impact of these diseases, there have been few innovative breakthroughs into their cause, treatment or cure. As with many debilitating disorders, chronic degenerative inflammatory diseases may be associated with defective or dysfunctional responses to second messengers, such as cyclic adenosinemonophosphate (cAMP). The identification of the cAMP-activated guanine nucleotide exchange factors for Ras-like GTPases, Epac1 (also known as cAMP-GEF-I) and Epac2 (also known as cAMP-GEF-II), profoundly altered the prevailing assumptions concerning cAMP signalling, which until then had been solely associated with protein kinase A (PKA). Studies of the molecular mechanisms of Epac-related signalling have demonstrated that these novel cAMP sensors regulate many physiological processes either alone and/or in concert with PKA. These include calcium handling, cardiac and smooth muscle contraction, learning and memory, cell proliferation and differentiation, apoptosis, and inflammation. The diverse signalling properties of cAMP might be explained by spatio-temporal compartmentalization, as well as A-kinase anchoring proteins, which seem to coordinate Epac signalling networks. Future research should focus on the Epac-regulated dynamics of cAMP, and, hopefully, the development of compounds that specifically interfere with the Epac signalling system in order to determine the precise significance of Epac proteins in chronic degenerative inflammatory disorders.

Chronic inflammation and asthma

Allergic asthma is a complex and chronic inflammatory disorder which is associated with airway hyper-responsiveness and tissue remodelling of the airway structure. Although originally thought to be a Th2-driven inflammatory response to inhaled innocuous allergen, the immune response in asthma is now considered highly heterogeneous. There are now various in vivo systems which have been designed to examine the pathways leading to the development of this chronic immune response and reflect, in part this heterogeneity. Furthermore, the emergence of endogenous immunoregulatory pathways and active pro-resolving mediators hold great potential for future therapeutic intervention. In this review, the key cellular and molecular mediators relating to chronic allergic airway disease are discussed, as well as emerging players in the regulation of chronic allergic inflammation.

Immunopathogenesis of bronchial asthma

Bronchial asthma is a common immune-mediated disorder characterized by reversible airway inflammation, mucus production, and variable airflow obstruction with airway hyperresponsiveness. Allergen exposure results in the activation of numerous cells of the immune system, of which dendritic cells (DCs) and Th2 lymphocytes are of paramount importance. Although the epithelium was initially considered to function solely as a physical barrier, it is now evident that it plays a central role in the Th2-cell sensitization process due to its ability to activate DCs. Cytokines are inevitable factors in driving immune responses. To the list of numerous cytokines already known to be involved in the regulation of allergic reactions, new cytokines were added, such as TSLP, IL-25, and IL-33. IgE is also a central player in the allergic response. The activity of IgE is associated with a network of proteins, especially with its high- and low-affinity Fc receptors. Understanding the cellular and molecular mechanisms of allergic reactions helps us not only to understand the mechanisms of current treatments, but is also important for the identification of new targets for biological intervention. An IgE-specific monoclonal antibody, omalizumab, has already reached the clinic and similar biological agents will surely follow.

A low dose of Mycoplasma pneumoniae infection enhances an established allergic inflammation in mice: the role of the prostaglandin E2 pathway

BACKGROUND

Over 40% of chronic stable asthma patients have evidence of respiratory Mycoplasma pneumoniae (Mp) infection as detected by PCR, but not by serology and culture, suggesting that a low-level Mp is involved in chronic asthma. However, the role of such a low-level Mp infection in the regulation of allergic inflammation remains unknown.

OBJECTIVE

To determine the impact of a low-level Mp infection in mice with established airway allergic inflammation on allergic responses such as eosinophilia and chemokine eotaxin-2, and the underlying mechanisms [i.e. the prostaglandin E(2) (PGE(2)) pathway] since PGE(2) inhalation before an allergen challenge suppressed the eosinophil infiltration in human airways.

METHODS

BALB/c mouse models of ovalbumin (OVA)-induced allergic asthma with an ensuing low- or high-dose Mp were used to assess IL-4 expression, bronchoalveolar lavage (BAL) eosinophil, eotaxin-2 and PGE(2) levels, and lung mRNA levels of microsomal prostaglandin E synthase-1 (mPGES-1). Primary alveolar macrophages (pAMs) from naïve BALB/c mice were cultured to determine whether Mp-induced PGE(2) or exogenous PGE(2) down-regulates IL-4/IL-13-induced eotaxin-2.

RESULTS

Low-dose Mp in allergic mice significantly enhanced IL-4 and eotaxin-2, and moderately promoted lung eosinophilia, whereas high-dose Mp significantly reduced lung eosinophilia and tended to decrease IL-4 and eotaxin-2. Moreover, in both OVA-naïve and allergic mice, lung mPGES-1 mRNA and BAL PGE(2) levels were elevated in mice infected with high-dose, but not low-dose Mp. In pAMs, IL-4/IL-13 significantly increased eotaxin-2, which was reduced by Mp infection accompanied by dose-dependent PGE(2) induction. Exogenous PGE(2) inhibited IL-4/IL-13-induced eotaxin-2 in a dose-dependent manner.

CONCLUSIONS

This study highlights a novel concept on how different bacterial loads in the lung modify the established allergic airway inflammation and thus interact with an allergen to further induce Th2 responses. That is, unlike high-level Mp, low-level Mp fails to effectively induce PGE(2) to down-regulate allergic responses (e.g. eotaxin-2), thus maintaining or even worsening allergic inflammation in asthmatic airways.

Moving towards making social toxins mainstream in children's environmental health

PURPOSE OF REVIEW

Although traditional disciplinary research theory and methods have focused separately on how social and physical environmental factors affect children's health, evolving research underscores important integrated effects.

RECENT FINDINGS

This review outlines the specific reasons why social determinants should be considered mainstream in children's environmental health research with particular focus on interactive effects between social and physical hazards. These include sensitivity of overlapping physiological systems, via epigenesis, programming, and plasticity to social and physical environmental moderation that may impact health across the life span; ways in which social environmental vulnerabilities moderate the effects of physical environmental factors, providing specific examples related to respiratory health and neurodevelopment; overlapping exposure distribution profiles; and relevance to pediatric health disparities.

SUMMARY

Because of the covariance across exposures, and evidence that social stress and other environmental toxins (e.g., pollutants, tobacco smoke) may influence common physiological pathways (e.g., oxidative stress, proinflammatory immune pathways, autonomic disruption), understanding the potential synergistic effects promises to more completely inform children's environmental health risk. Although this discussion focuses around the respiratory and neurological systems, these concepts extend more broadly to children's psychological and physical development.

The adaptor protein CIKS/Act1 is essential for IL-25-mediated allergic airway inflammation

IL-17 is the signature cytokine of recently discovered Th type 17 (Th17) cells, which are prominent in defense against extracellular bacteria and fungi as well as in autoimmune diseases, such as rheumatoid arthritis and experimental autoimmune encephalomyelitis in animal models. IL-25 is a member of the IL-17 family of cytokines, but has been associated with Th2 responses instead and may negatively cross-regulate Th17/IL-17 responses. IL-25 can initiate an allergic asthma-like inflammation in the airways, which includes recruitment of eosinophils, mucus hypersecretion, Th2 cytokine production, and airways hyperreactivity. We demonstrate that these effects of IL-25 are entirely dependent on the adaptor protein CIKS (also known as Act1). Surprisingly, this adaptor is necessary to transmit IL-17 signals as well, despite the very distinct biologic responses that these two cytokines elicit. We identify CD11c(+) macrophage-like lung cells as physiologic relevant targets of IL-25 in vivo.