Dermatophagoides pteronyssinus 2 regulates nerve growth factor release to induce airway inflammation via a reactive oxygen species-dependent pathway

Group 2 allergen of Dermatophagoides pteronyssinus 2 (Der p2) induces airway inflammation without protease activity, and elevated nerve growth factor (NGF) levels are also found in this inflammation. How the allergen Der p2 regulates NGF release via reactive oxygen species (ROS) to induce inflammation remains unclear. In the present study, intratracheal administration of Der p2 to mice led to inflammatory cell infiltration, mucus gland hyperplasia, and NGF upregulation in the bronchial epithelium, as well as elevated ROS and NGF production in bronchoalveolar lavage fluids. In addition, Der p2 caused fibrocyte accumulation and mild fibrosis. p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK) inhibitors inhibited Der p2-induced NGF release in LA4 lung epithelial cells and MLg lung fibroblasts. Pretreatment with an antioxidant, tiron, reduced the Der p2-induced ROS production, NGF expression and release, p38 MAPK or JNK phosphorylation, and airway inflammation. These results suggest that Der p2 allergen-induced airway inflammation and elevated NGF release were through increasing ROS production and a MAPK-dependent pathway. The use of an antioxidant, tiron, may provide a new therapeutic modality for the treatment of allergic asthma.     

Monocytes of allergics and non-allergics produce, store and release the neurotrophins NGF, BDNF and NT-3

INTRODUCTION: Recent studies have shown that neurotrophins (NTs) are involved in inflammatory processes. Elevated plasma levels of NTs were found allergic diseases with the highest levels in allergic asthma. However, the exact cellular sources involved in the regulation and release of neurotrophins in allergic inflammation are still not well defined. OBJECTIVE: The aim of this study was to assess whether monocytes of allergic and non-allergic subjects produce, store and release the neurotrophins NGF, BDNF and NT-3. METHODS: Monocytes of allergic and non-allergic donors were purified by immunomagnetic selection. APAAP-staining for the presence of NTs and their receptors was performed. RT-PCR and Western blot evaluated the production and storage of NTs. Monocytes were incubated and supernatants were collected for measurement of neurotrophic factors after stimulation with lipopolysaccharide (LPS) as inflammatory stimulus. The neurotrophin content in lysates and cell culture supernatants was determined by ELISA. RESULTS: Human monocytes express the neurotrophins NGF, BDNF and NT-3 but also their specific receptors TrkA, TrkB and TrkC. RT-PCR amplification of isolated mRNA demonstrated expression of the examined neurotrophins. Proteins were detectable by Western blot. NTs were found in the monocyte lysates and supernatants at different levels in allergic and non-allergic donors. Cell stimulation with LPS leads to release of NGF and NT3. CONCLUSIONS: Monocytes, produce, store and release NGF, BDNF and NT-3. They are a possible source of elevated neurotrophin levels found in allergy and asthma.     

FIZZ1, a novel cysteine-rich secreted protein associated with pulmonary inflammation, defines a new gene family

Bronchoalveolar lavage fluid from mice with experimentally induced allergic pulmonary inflammation contains a novel 9.4 kDa cysteine-rich secreted protein, FIZZ1 (found in inflammatory zone). Murine (m) FIZZ1 is the founding member of a new gene family including two other murine genes expressed, respectively, in intestinal crypt epithelium and white adipose tissue, and two related human genes. In control mice, FIZZ1 mRNA and protein expression occur at low levels in a subset of bronchial epithelial cells and in non-neuronal cells adjacent to neurovascular bundles in the peribronchial stroma, and in the wall of the large and small bowel. During allergic pulmonary inflammation, mFIZZ1 expression markedly increases in hypertrophic, hyperplastic bronchial epithelium and appears in type II alveolar pneumocytes. In vitro, recombinant mFIZZ1 inhibits the nerve growth factor (NGF)-mediated survival of rat embryonic day 14 dorsal root ganglion (DRG) neurons and NGF-induced CGRP gene expression in adult rat DRG neurons. In vivo, FIZZ1 may modulate the function of neurons innervating the bronchial tree, thereby altering the local tissue response to allergic pulmonary inflammation.     

Nerve growth factor

Nerve growth factor (NGF) is widely recognized as a target-derived factor responsible for the survival and maintenance of the phenotype of specific subsets of peripheral neurons and basal forebrain cholinergic nuclei during development and maturation. Other NGF-responsive cells are now known to belong to the hemopoietic-immune system and to populations in the brain involved in neuroendocrine functions. The concentration of NGF is elevated in a number of inflammatory and autoimmune states in conjunction with increased accumulation of mast cells. Mast cells and NGF appear to be involved in neuroimmune interactions and tissue inflammation. Mast cells themselves are capable of producing and responding to NGF, suggesting that alterations in mast cell behavior may trigger maladaptive neuroimmune tissue responses, including those of an autoimmune nature. Moreover, NGF exerts a modulatory role on sensory nociceptive nerve physiology in the adult, and appears to correlate with hyperalgesic phenomena occurring in tissue inflammation. NGF can thus be viewed as a multifactorial modulator of neuroimmune-endocrine functions.     

Interleukin-10 and nerve growth factor have reciprocal upregulatory effects on intestinal epithelial cells

The intestinal mucosa is in a constant state of controlled inflammation, but the processes whereby this occurs are poorly understood. The aims of this study were to look at the role of IL-10 and nerve growth factor (NGF) in intestinal epithelial cell regulation. The human colon epithelial cell lines T84, HT-29, and CACO-2 were used. RT-PCR, flow cytometry analysis, and immunohistochemistry were applied to measure the cytokine changes in epithelial cells induced by recombinant cholera toxin and its B subunit, IL-10, and NGF. Cholera toxin B subunit caused selective dose-dependent increased mRNA for IL-10 in T84 cells and the protein in T84, HT-29, and CACO-2 cells. IL-10 dose dependently selectively increased NGF mRNA in T84 cells and intracellular protein synthesis in all three epithelial cell lines. The effect of NGF was reciprocal, selective, and dose dependent because it increased mRNA for IL-10 and IL-10 synthesis. Our results suggest that the epithelium may actively participate in downregulation through innate mechanisms involving IL-10 and NGF. The reciprocal interaction suggests for the first time that NGF may be involved in local downregulation by mucosal epithelium and thus may play a potent protective role in response to injury, by prevention of undue inflammation.     

The roles of autotaxin/lysophosphatidic acid in immune regulation and asthma

Lysophosphatidic acid (LPA) species are present in almost all organ systems and play diverse roles through its receptors. Asthma is an airway disease characterized by chronic allergic inflammation where various innate and adaptive immune cells participate in establishing Th2 immune response. Here, we will review the contribution of LPA and its receptors to the functions of immune cells that play a key role in establishing allergic airway inflammation and aggravation of allergic asthma.     

The two faces of mast cells in food allergy and allergic asthma: The possible concept of Yin Yang

The purpose of this review is to discuss the role of mast cells in allergic inflammation. We have focused on inflammation associated with allergic asthma and food allergy. Mast cells are ‘first line of defense’ innate/adaptive immune cells and are widely distributed in tissues in surfaces exposed to the environment. Especially in allergic settings mast cells are extensively studied, as they can be activated to release a wide range of mediators by allergen-IgE specific triggers. In addition, in allergic inflammation mast cells can also be activated non-allergic triggers. Recent studies revealed that mast cells, besides the classical role of pro-inflammatory effector cell, have also emerged as modulators of allergic sensitization and down-regulators of allergic inflammation. Therefore, mast cells can be regarded as ‘Ying Yan’ modulators in allergic responses in intestinal tract and airways. This article is part of a Special Issue entitled: Mast Cells in Inflammation.     

Interactions of mast cells with the nervous system —Recent advances

This article reviews recent advances in the understanding of mast cell-nervous system interactions. It is drawn largely from work published within the last ten years, and discusses the anatomical and biochemical evidence of a functional connection between mast cells and the nervous system, and the implications that such a relationship may have for normal and abnormal physiological functioning. Mast cells are found at varying levels of association with the nervous system; in CNS parenchyma (mainly thalamus), in connective tissue coverings (e.g. meninges, endonerium), and in close apposition to peripheral nerve endings in a variety of tissues. There is, as yet, no clearly defined role for mast cells in nervous system function, or vice-versa, and it seems most likely that their interactions fulfil mutually modulatory roles. By extension, pathological situations where one of the partners in this relationship is overly stimulated may lead to a dysregulation of the other, and contribute to disease symptomatology.Abbreviations ACh acetylcholine - BMMC bone marrow-derived mast cells - CGRP calcitonin gene-related peptide - EAE experimental allergic encephalomyelitis - EAN experimental allergic neuritis - 5-HT serotonin - IgE immunoglobulin E - IL-3 interleukin-3 - MS multiple sclerosis - NA noradrenaline - NF neurofibromatosis - NGF nerve growth factor - VIP Vasoactive intestinal polypeptide Special issue dedicated to Dr. Alan N. Davison.     

The multitasking mast cell: positive and negative roles in the progression of autoimmunity

Among the potential outcomes of an aberrantly functioning immune system are allergic disease and autoimmunity. Although it has been assumed that the underlying mechanisms mediating these conditions are completely different, recent evidence shows that mast cells provide a common link. Mast cells reside in most tissues, are particularly prevalent at sites of Ag entry, and act as sentinel cells of the immune system. They express many inflammatory mediators that affect both innate and adaptive cellular function. They contribute to pathologic allergic inflammation but also serve an important protective role in bacterial and parasite infections. Given the proinflammatory nature of autoimmune responses, it is not surprising that studies using murine models of autoimmunity clearly implicate mast cells in the initiation and/or progression of autoimmune disease. In this review, we discuss the defined and hypothesized mechanisms of mast cell influence on autoimmune diseases, including their surprising and newly discovered role as anti-inflammatory cells.     

Long-term protective and antigen-specific effect of heat-killed Mycobacterium vaccae in a murine model of allergic pulmonary inflammation

This report examines the effect of heat-killed Mycobacterium vaccae in a mouse model of allergic pulmonary inflammation. The s.c. administration of M. vaccae 3 wk before the immunization significantly reduced Ag-induced airway hyperreactivity and the increase in the numbers of eosinophils observed in the bronchoalveolar lavage fluid, blood, and bone marrow, even though no detectable changes in either cytokine (IL-4, IL-13, IL-5, and IFN-gamma) or total IgE levels were observed. Furthermore, transfer of splenocytes from OVA-immunized and M. vaccae-treated mice into recipient, OVA-immunized mice significantly reduced the allergen-induced eosinophilia by an IFN-gamma-independent mechanism, clearly indicating that the mechanism by which M. vaccae induces its inhibitory effect is not due to a redirection from a predominantly Th2 to a Th1-dominated immune response. The protective effect of M. vaccae on the allergen-induced eosinophilia lasted for at least 12 wk after its administration, and the treatment was also effective in presensitized mice. Moreover, the allergen specificity of the inhibitory effect could be demonstrated using a double-immunization protocol, where M. vaccae treatment before OVA immunization had no effect on the eosinophilic inflammation induced by later immunization and challenge with cockroach extract Ag. Taken together, these results clearly demonstrate that M. vaccae is effective in blocking allergic inflammation by a mechanism independent of IFN-gamma, induces long term and Ag-specific protection, and therefore has both prophylactic and therapeutic potential for the treatment of allergic diseases.     

Lack of correlation between 3-hydroxy-3-methylglutaryl coenzyme A reductase activity and lovastatin resistance in nerve growth factor treated PC-12 cells

Summary 1. The relationships among the mevalonic acid (MVA) forming enzyme, 3-hydroxy-3-methylglutaryl coenzyme A (CoA) reductase, cell growth and differentiation, and the cytotoxic effects of the reductase inhibitor lovastatin were studied in PC-12 cells, exposed to growth factors.2. When added individually, nerve growth factor (NGF), basic fibroblast growth factor, and epidermal growth factor induce an increase in HMG-CoA reductase activity in cells grown in serum-containing medium. In the presence of serum, the effect of NGF on HMG-CoA reductase is persistent.3. Short-term serum starvation and long-term NGF treatment, in combination, have an additive effect, resulting in a high reductase activity.4. Unlike serum and MVA, which downregulate levels of HMG-CoA reductase by accelerating its degradation, NGF upregulates reductase by slowing the rate of its degradation. This mechanism, however, appears to operate only in the presence of serum, as after prolonged growth with NGF in serum-free medium, cells have a low reductase activity.5. PC-12 cells grown in the absence of NGF are highly sensitive to lovastatin (25 µM) and more than 70% of the cells die after 48 hr. NGF confers lovastatin resistance on cells grown in the presence or in the absence of serum (only 30–40% cell death after 48 hr with lovastatin).6. NGF-induced resistance on lovastatin develops with time and is apparent only in the well-differentiated PC-12 cells whether or not the cells express a high reductase activity.7. Thus, levels of HMG-CoA reductase activity and lovastatin resistance in PC-12 cells are not directly correlated, though clearly inversed lovastatin cytotoxicity and elevated reductase activities are expressed during the period of cell proliferation.8. These data suggest that fully differentiated neuronal cells may not be affected by prolonged high doses of lovastatin.     

Nerve growth factor: two receptors,multiple functions

Nerve growth factor (NGF) was characterized over 4 decades ago, and like the other neurotrophins subsequently discovered, it is best known for its trophic role, including the prevention of programmed cell death in specific populations of neurones in the peripheral nervous system. This property can be accounted for by the activation of a tyrosine kinase receptor. NGF also regulates neuronal function, as illustrated by its role in pain and inflammation, and in synaptic plasticity. Finally, NGF recently was shown to activate the neurotrophin receptor p75 (p75^NTR), a receptor with no intrinsic catalytic activity and with similarities to members of the tumor necrosis factor receptor family. During normal development, the activation of p75^NTR by NGF actually kills cells in the central nervous system. One remarkable property of NGF is then that it controls cell numbers in opposite ways in the developing nervous system, a result of its unique ability to activate two different receptor types. BioEssays 20:137–145, 1998. © 1998 John Wiley & Sons, Inc.     

Nerve growth factor and nerve growth factor receptors in respiratory syncytial virus-infected lungs

Nerve growth factor (NGF) controls sensorineural development and responsiveness and modulates immunoinflammatory reactions. Respiratory syncytial virus (RSV) potentiates the proinflammatory effects of sensory nerves in rat airways by upregulating the substance P receptor, neurokinin 1 (NK(1)). We investigated whether the expression of NGF and its trkA and p75 receptors in the lungs is age dependent, whether it is upregulated during RSV infection, and whether it affects neurogenic inflammation. Pathogen-free rats were killed at 2 (weanling) to 12 (adult) wk of age; in addition, subgroups of rats were inoculated with RSV or virus-free medium. In pathogen-free rats, expression of NGF and its receptors in the lungs declined with age, but RSV doubled expression of NGF, trkA, and p75 in weanling and adult rats. Exogenous NGF upregulated NK(1) receptor expression in the lungs. Anti-NGF antibody inhibited NK(1) receptor upregulation and neurogenic inflammation in RSV-infected lungs. These data indicate that expression of NGF and its receptors in the lungs declines physiologically with age but is upregulated by RSV and is a major determinant of neurogenic inflammation.     

Transglutaminase II/MicroRNA-218/-181a Loop Regulates Positive Feedback Relationship between Allergic Inflammation and Tumor Metastasis

The molecular mechanism of transglutaminase II (TGaseII)-mediated allergic inflammation remains largely unknown. TGaseII, induced by antigen stimulation, showed an interaction and co-localization with FcϵRI. TGaseII was necessary for in vivo allergic inflammation, such as triphasic cutaneous reaction, passive cutaneous anaphylaxis, and passive systemic anaphylaxis. TGaseII was necessary for the enhanced metastatic potential of B16F1 melanoma cells by passive systemic anaphylaxis. TGaseII was shown to be a secreted protein. Recombinant TGaseII protein increased the histamine release and β-hexosaminidase activity, and enhanced the metastatic potential of B16F1 mouse melanoma cells. Recombinant TGaseII protein induced the activation of EGF receptor and an interaction between EGF receptor and FcϵRI. Recombinant TGaseII protein displayed angiogenic potential accompanied by allergic inflammation. R2 peptide, an inhibitor of TGaseII, exerted negative effects on in vitro and in vivo allergic inflammation by regulating the expression of TGaseII and FcϵRI signaling. MicroRNA (miR)-218 and miR-181a, decreased during allergic inflammation, were predicted as negative regulators of TGaseII by microRNA array and TargetScan analysis. miR-218 and miR-181a formed a negative feedback loop with TGaseII and regulated the in vitro and in vivo allergic inflammation. TGaseII was necessary for the interaction between mast cells and macrophages during allergic inflammation. Mast cells and macrophages, activated during allergic inflammation, were responsible for the enhanced metastatic potential of tumor cells that are accompanied by allergic inflammation. In conclusion, the TGaseII/miR-218/-181a feedback loop can be employed for the development of anti-allergy therapeutics.     

Neurotrophins and lung disease

Neurotrophins are growth factors that exert multiple actions on neuronal and nonneuronal cells. Neurotrophin receptors are expressed on central and peripheral neurons, lymphocytes, monocytes, mast cells, and fibroblasts. In accordance with the distribution of their receptors, neurotrophins control the development and function of neurons and regulate inflammatory processes. Production of neurotrophins is altered in asthma, lung cancer, and pulmonary fibrosis. Evidence from animal models has implicated nerve growth factor (NGF) as a mediator of pulmonary inflammation, bronchoconstriction, and airway hyperreactivity, all of which are hallmarks of asthma. NGF regulates the growth of lung tumor cells and cultured lung fibroblasts. Thus neurotrophins, particularly NGF, are candidate molecules for regulating disease processes in asthma, lung cancer, and pulmonary fibrosis.     

Cyclooxygenase inhibition during allergic sensitization increases STAT6-independent primary and memory Th2 responses

Immune sensitization and memory generation are required for the development of allergic inflammation. Our previous studies demonstrate that the cyclooxygenase (COX) metabolic pathway is actively involved in allergic responses and COX inhibition increases allergic airway inflammation in a STAT6-independent fashion. To test the hypothesis that COX inhibition augments allergic inflammation by enhancing immune sensitization and memory, we sensitized STAT6 knockout mice with an i.p. injection of OVA with aluminum hydroxide as an adjuvant and treated the mice with the COX inhibitor indomethacin or vehicle for analyses of the primary and memory immune responses. We found that COX inhibition during immune sensitization, but not the allergic challenge phase, was necessary and sufficient to increase allergic inflammation. COX inhibition during sensitization increased the numbers of mature dendritic cells and activated CD4 T cells in the spleen and augmented OVA-specific IL-5 and IL-13 responses of the splenic CD4 T cells at day 5 after sensitization. COX inhibition during sensitization also augmented allergic Th2 response to OVA challenge 90 days after the sensitization. Therefore, COX inhibition during allergic sensitization augments allergic responses by enhancing Th2 cell activation and memory generation and the proallergic effect is STAT6-independent. These findings provide a mechanistic explanation for the increased allergic inflammation previously shown in the mice treated with COX inhibitors and in COX-deficient mice and suggest that use of COX-inhibiting drugs during initial allergen exposure may increase the risk of developing allergic responses.     

Alpha-melanocyte-stimulating hormone inhibits allergic airway inflammation

Alpha-melanocyte-stimulating hormone (alpha-MSH) is a neuropeptide controlling melanogenesis in pigmentary cells. In addition, its potent immunomodulatory and immunosuppressive activity has been recently described in cutaneous inflammatory disorders. Whether alpha-MSH is also produced in the lung and might play a role in the pathogenesis of inflammatory lung conditions, including allergic bronchial asthma, is unknown. Production and functional role of alpha-MSH were investigated in a murine model of allergic airway inflammation. alpha-MSH production was detected in bronchoalveolar lavage fluids. Although aerosol challenges stimulate alpha-MSH production in nonsensitized mice, this rapid and marked stimulation was absent in allergic animals. Treatment of allergic mice with alpha-MSH resulted in suppression of airway inflammation. These effects were mediated via IL-10 production, because IL-10 knockout mice were resistant to alpha-MSH treatment. This study provides evidence for a novel function of alpha-MSH linking neuroimmune functions in allergic airway inflammation.     

Cutting edge: invariant V alpha 14 NKT cells are required for allergen-induced airway inflammation and hyperreactivity in an experimental asthma model

Airway hyperreactivity (AHR), eosinophilic inflammation with a Th2-type cytokine profile, and specific Th2-mediated IgE production characterize allergic asthma. In this paper, we show that OVA-immunized Jalpha18(-/-) mice, which are exclusively deficient in the invariant Valpha14(+) (iValpha14), CD1d-restricted NKT cells, exhibit impaired AHR and airway eosinophilia, decreased IL-4 and IL-5 production in bronchoalveolar lavage fluid, and reduced OVA-specific IgE compared with wild-type (WT) littermates. Adoptive transfer of WT iValpha14 NKT cells fully reconstitutes the capacity of Jalpha18(-/-) mice to develop allergic asthma. Also, specific tetramer staining shows that OVA-immunized WT mice have activated (CD69(+)) iValpha14 NKT cells. Importantly, anti-CD1d mAb treatment blocked the ability of iValpha14 T cells to amplify eosinophil recruitment to airways, and both Th2 cytokine and IgE production following OVA challenge. In conclusion, these findings clearly demonstrate that iValpha14 NKT cells are required to participate in allergen-induced Th2 airway inflammation through a CD1d-dependent mechanism.     

Prostaglandin D2 receptors DP and CRTH2 in the pathogenesis of asthma

Prostaglandin D2 (PGD2) is a major prostanoid produced mainly by mast cells in allergic diseases, including bronchial asthma. However, its role in the pathogenesis of asthma remains unclear. PGD2-induced vasodilatation and increased permeability are well-known classical effects that may facilitate transendothelial migration of inflammatory cells, such as eosinophils, mast cells, lymphocytes, and monocytes in allergic inflammation. These effects are initiated via a PGD2 receptor, D prostanoid receptor (DP), and are referred to as DP-mediated vasodilation-extravasation. Recently, novel functions of DP have been identified. Furthermore, a novel and different receptor of PGD2, CRTH2, has been discovered. To date, DP and CRTH2 have been shown to be major PGD(2)-related receptors that have pivotal roles in mediating allergic diseases by effects such as directly regulating the migration of inflammatory cells and controlling the production of cytokines and lipid mediators. Available evidence suggests that CRTH2 and DP may collaborate in allergic inflammation. This review focuses on the novel roles of DP and CRTH2 in the initiation and maintenance of allergy.