Role of nerve growth factor in a mouse model of allergic airway inflammation and asthma

Role of neurogenic inflammation in the pathogenesis of alopecia areata

Alopecia areata refers to an autoimmune illness indicated by persistent inflammation. The key requirement for alopecia areata occurrence is the disruption of immune-privileged regions within the hair follicles. Recent research has indicated that neuropeptides play a role in the damage to hair follicles by triggering neurogenic inflammation, stimulating mast cells ambient the follicles, and promoting apoptotic processes in keratinocytes. However, the exact pathogenesis of alopecia areata requires further investigation. Recently, there has been an increasing focus on understanding the mechanisms of immune diseases resulting from the interplay between the nervous and the immune system. Neurogenic inflammation due to neuroimmune disorders of the skin system may disrupt the inflammatory microenvironment of the hair follicle, which plays a crucial part in the progression of alopecia areata.

Nerve growth factor mediates activation of transient receptor potential vanilloid 1 in neurogenic pruritus of psoriasis

Pruritus is a common and painful symptom in psoriasis with profoundly negative impacts on quality of life. The underlying mechanisms of pruritus are complex and multifactorial, and accumulating evidence suggests that pruritus induced by neurogenic inflammation predominates in psoriasis. Nerve growth factor (NGF) -mediated transient receptor potential vanilloid receptor 1(TRPV1) pathway has emerged as a crucial node in the regulation of neurogenic pruritus. TRPV1 appears coupled to most pruritus-specific molecules via the neuro-immune axis. While the modes of regulation differ for each axis, TRPV1 is involved in substantial biochemical crosstalk-causing feedback loops with significant effects on neurogenic pruritus. Therefore, TRPV1 has emerged as a target molecular in drug development for pruritus in psoriasis. However, no significant clinical progress occurred in the development of systemic TRPV1 antagonists due to elevated core temperature. Thus, topical application of TRPV1 antagonists and interference with mediators linked to the TRPV1 activation pathway may be promising therapeutic options to ameliorate pruritus. This Review focuses on recent advances in complicated regulation of NGF-mediated TRPV1 pathway in psoriatic neurogenic pruritus, as well as the therapeutic options that arise from the dissection of the pathway.

Neurotrophins: Neuroimmune Interactions in Human Atopic Diseases

Allergic diseases are accompanied by a variety of symptoms such as pruritus, coughing, sneezing, and watery eyes, which can result in severe physiological and even psychological impairments. The exact mechanisms of these conditions are not yet completely understood. However, recent studies demonstrated a high relevance of neurotrophins in allergic inflammation, as they induce cytokine release, mediate interaction between immune cells and neurons, and exhibit different expression levels in health and disease. In this review, we aim to give an overview of the current state of knowledge concerning the role of neurotrophins in atopic disorders such as atopic dermatitis, allergic asthma, and allergic rhinitis.

ProBDNF and its receptors in immune-mediated inflammatory diseases: novel insights into the regulation of metabolism and mitochondria

Immune-mediated inflammatory diseases (IMIDs) consist of a common and clinically diverse group of diseases. Despite remarkable progress in the past two decades, no remission is observed in a large number of patients, and no effective treatments have been developed to prevent organ and tissue damage. Brain-derived neurotrophic factor precursor (proBDNF) and receptors, such as p75 neurotrophin receptor (p75^NTR) and sortilin, have been proposed to mediate intracellular metabolism and mitochondrial function to regulate the progression of several IMIDs. Here, the regulatory role of proBDNF and its receptors in seven typical IMIDs, including multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, allergic asthma, type I diabetes, vasculitis, and inflammatory bowel diseases, was investigated.

Influenza A virus activates cellular Tropomyosin receptor kinase A (TrkA) signaling to promote viral replication and lung inflammation

Influenza A virus (IAV) infection causes acute respiratory disease with potential severe and deadly complications. Viral pathogenesis is not only due to the direct cytopathic effect of viral infections but also to the exacerbated host inflammatory responses. Influenza viral infection can activate various host signaling pathways that function to activate or inhibit viral replication. Our previous studies have shown that a receptor tyrosine kinase TrkA plays an important role in the replication of influenza viruses in vitro, but its biological roles and functional mechanisms in influenza viral infection have not been characterized. Here we show that IAV infection strongly activates TrkA in vitro and in vivo. Using a chemical-genetic approach to specifically control TrkA kinase activity through a small molecule compound 1NMPP1 in a TrkA knock-in (TrkA KI) mouse model, we show that 1NMPP1-mediated TrkA inhibition completely protected mice from a lethal IAV infection by significantly reducing viral loads and lung inflammation. Using primary lung cells isolated from the TrkA KI mice, we show that specific TrkA inhibition reduced IAV viral RNA synthesis in airway epithelial cells (AECs) but not in alveolar macrophages (AMs). Transcriptomic analysis confirmed the cell-type-specific role of TrkA in viral RNA synthesis, and identified distinct gene expression patterns under the TrkA regulation in IAV-infected AECs and AMs. Among the TrkA-activated targets are various proinflammatory cytokines and chemokines such as IL6, IL-1β, IFNs, CCL-5, and CXCL9, supporting the role of TrkA in mediating lung inflammation. Indeed, while TrkA inhibitor 1NMPP1 administered after the peak of IAV replication had no effect on viral load, it was able to decrease lung inflammation and provided partial protection in mice. Taken together, our results have demonstrated for the first time an important biological role of TrkA signaling in IAV infection, identified its cell-type-specific contribution to viral replication, and revealed its functional mechanism in virus-induced lung inflammation. This study suggests TrkA as a novel host target for therapeutic development against influenza viral disease.

Neuropeptides and neurohormones in immune, inflammatory and cellular responses to ultraviolet radiation

Humans are exposed to varying amounts of ultraviolet radiation (UVR) through sunlight. UVR penetrates into human skin leading to release of neuropeptides, neurotransmitters and neuroendocrine hormones. These messengers released from local sensory nerves, keratinocytes, Langerhans cells (LCs), mast cells, melanocytes and endothelial cells (ECs) modulate local and systemic immune responses, mediate inflammation and promote differing cell biologic effects. In this review, we will focus on both animal and human studies that elucidate the roles of calcitonin gene-related peptide (CGRP), substance P (SP), nerve growth factor (NGF), nitric oxide and proopiomelanocortin (POMC) derivatives in mediating immune and inflammatory effects of exposure to UVR as well as other cell biologic effects of UVR exposure.

MicroRNA-98 reduces nerve growth factor expression in nicotine-induced airway remodeling

Evolving evidence suggests that nicotine may contribute to impaired asthma control by stimulating expression of nerve growth factor (NGF), a neurotrophin associated with airway remodeling and airway hyperresponsiveness. We explored the hypothesis that nicotine increases NGF by reducing lung fibroblast (LF) microRNA-98 (miR-98) and PPARγ levels, thus promoting airway remodeling. Levels of NGF, miR-98, PPARγ, fibronectin 1 (FN1), endothelin-1 (EDN1, herein referred to as ET-1), and collagen (COL1A1 and COL3A1) were measured in human LFs isolated from smoking donors, in mouse primary LFs exposed to nicotine (50 μg/ml), and in whole lung homogenates from mice chronically exposed to nicotine (100 μg/ml) in the drinking water. In selected studies, these pathways were manipulated in LFs with miR-98 inhibitor (anti-miR-98), miR-98 overexpression (miR-98 mimic), or the PPARγ agonist rosiglitazone. Compared with unexposed controls, nicotine increased NGF, FN1, ET-1, COL1A1, and COL3A1 expression in human and mouse LFs and mouse lung homogenates. In contrast, nicotine reduced miR-98 levels in LFs in vitro and in lung homogenates in vivo Treatment with anti-miR-98 alone was sufficient to recapitulate increases in NGF, FN1, and ET-1, whereas treatment with a miR-98 mimic significantly suppressed luciferase expression in cells transfected with a luciferase reporter linked to the putative seed sequence in the NGF 3'UTR and also abrogated nicotine-induced increases in NGF, FN1, and ET-1 in LFs. Similarly, rosiglitazone increased miR-98 and reversed nicotine-induced increases in NGF, FN1, and ET-1. Taken together, these findings demonstrate that nicotine-induced increases in NGF and other markers of airway remodeling are negatively regulated by miR-98.

Neurotrophic factors and nerve growth factor in ocular allergy

PURPOSE OF REVIEW

During allergic reaction, nervous and immune systems mutually interact through release of mediators, including neurotrophic factors and nerve growth factor (NGF). These mediators modulate allergic reaction through binding their receptors expressed by immune and structural cells and by stimulating neuropeptide release by nerves. The role of neuropeptides and NGF has been demonstrated in allergic asthma and rhinitis, and, to a lesser extent, in allergic conjunctivitis. The aim of this review are to elucidate the evidence of the role of NGF and neuropeptides in the pathogenesis of allergic conjunctivitis.

RECENT FINDINGS

NGF modulates allergic reaction by stimulating release of cytokines, inflammatory mediators and neuropeptides by immune and structural cells and nerve endings at the site of inflammation. Evidence showed that local and systemic NGF levels increase in patients with allergic conjunctivitis, including allergic rhinoconjuncivitis, vernal keratoconjunctivitis and atopic keratoconjunctivitis. We recently described an increase of conjunctival p75NTR expression in patients with allergic rhinoconjuncivitis, and an increase of tear levels of NGF after conjunctival provocation test with allergen.

SUMMARY

NGF modulates ocular allergic reaction. Increasing understanding of the role of neuropeptides in allergic conjunctivitis may pave the way to the development of novel therapeutic approaches and improvement of patients' management.

Activation of a nerve injury transcriptional signature in airway-innervating sensory neurons after lipopolysaccharide-induced lung inflammation

The lungs and the immune and nervous systems functionally interact to respond to respiratory environmental exposures and infections. The lungs are innervated by vagal sensory neurons of the jugular and nodose ganglia, fused together in smaller mammals as the jugular-nodose complex (JNC). Whereas the JNC shares properties with the other sensory ganglia, the trigeminal (TG) and dorsal root ganglia (DRG), these sensory structures express differential sets of genes that reflect their unique functionalities. Here, we used RNA sequencing (RNA-seq) in mice to identify the differential transcriptomes of the three sensory ganglia types. Using a fluorescent retrograde tracer and fluorescence-activated cell sorting, we isolated a defined population of airway-innervating JNC neurons and determined their differential transcriptional map after pulmonary exposure to lipopolysaccharide (LPS), a major mediator of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) after infection with gram-negative bacteria or inhalation of organic dust. JNC neurons activated an injury response program, leading to increased expression of gene products such as the G protein-coupled receptor Cckbr, inducing functional changes in neuronal sensitivity to peptides, and Gpr151, also rapidly induced upon neuropathic nerve injury in pain models. Unique JNC-specific transcripts, present at only minimal levels in TG, DRG, and other organs, were identified. These included TMC3, encoding for a putative mechanosensor, and urotensin 2B, a hypertensive peptide. These findings highlight the unique properties of the JNC and reveal that ALI/ARDS rapidly induces a nerve injury-related state, changing vagal excitability.

Airway Innervation and Plasticity in Asthma

Airway nerves represent a mechanistically and therapeutically important aspect that requires better highlighting in the context of diseases such as asthma. Altered structure and function (plasticity) of afferent and efferent airway innervation can contribute to airway diseases. We describe established anatomy, current understanding of how plasticity occurs, and contributions of plasticity to asthma, focusing on target-derived growth factors (neurotrophins). Perspectives toward novel treatment strategies and future research are provided.

Immunoregulatory Effects of Neuropeptides on Endothelial Cells: Relevance to Dermatological Disorders

Many skin diseases, including psoriasis and atopic dermatitis, have a neurogenic component. In this regard, bidirectional interactions between components of the nervous system and multiple target cells in the skin and elsewhere have been receiving increasing attention. Neuropeptides released by sensory nerves that innervate the skin can directly modulate functions of keratinocytes, Langerhans cells, dermal dendritic cells, mast cells, dermal microvascular endothelial cells and infiltrating immune cells. As a result, neuropeptides and neuropeptide receptors participate in a complex, interdependent network of mediators that modulate the skin immune system, skin inflammation, and wound healing. In this review, we will focus on recent studies demonstrating the roles of α-melanocyte-stimulating hormone, calcitonin gene-related peptide, substance P, somatostatin, vasoactive intestinal peptide, pituitary adenylate cyclase-activating peptide, and nerve growth factor in modulating inflammation and immunity in the skin through their effects on dermal microvascular endothelial cells.

Antiasthmatic potential of Zizyphus jujuba Mill and Jujuboside B. - Possible role in the treatment of asthma

Zizyphus jujuba Mill, a famous oriental traditional medicine, has been reported to exhibit diverse activities in biological systems including the respiratory system. However, a little information is available on its antiasthmatic activity. Jujuboside B (JB) is a natural saponin and one of the active constituent of fruits of Zizyphus jujuba. In the present investigation, JB was isolated from ethanolic extracts of fruits of Zizyphus jujuba (EZJF). EZJF and JB were then evaluated for anti-asthmatic activity using various screening methods. JB was additionally evaluated using ovalbumin (OVA) -induced allergic asthma in mice. Results obtained in the present study showed that EZJF and JB significantly inhibited clonidine-induced catalepsy, milk-induced leucocytosis and eosinophilia, clonidine-induced mast cell degranulation, and passive paw anaphylaxis. The number of inflammatory cells in bronchoalveolar lavage (BAL) fluid was considerably lowered and the severity of pulmonary inflammation was alleviated in the mice pretreated with JB. The high-level expression of T-helper type 2 (TH2) cytokines was markedly reduced in the serum, BAL fluid, and lung homogenates. Thus EZJF and JB showed potent anti-asthmatic activity. Hence EZJF and JB possess a potential role in the treatment of asthma.

Anti-nerve growth factor antibody improves airway hyperresponsiveness by down-regulating RhoA

BACKGROUND

The pathogenesis of asthma is complex and continues to be considered as a challenging subject. Some studies have shown that nerve growth factor (NGF) participates in the pathogenesis of asthma, but the mechanism of airway contraction caused by NGF is still unclear.

OBJECTIVE

Our aim was to discuss the effect of anti-NGF antibody on RhoA expression, and further explore the role of NGF in airway hyperresponsiveness (AHR).

METHODS

Thirty female BALB/c mice were divided into three groups randomly: control group (group C, n = 10), asthma group (group A, n = 10) and anti-NGF antibody intervention group (group N, n = 10). The asthmatic mice were stimulated by OVA suspension, the intervention mice were given nasal instillation of anti-NGF antibody before the stimulation. Airway responsiveness, eosinophils, IL-13, IFN-γ were measured. The protein expression and mRNA level of NGF and RhoA were detected by immunohistochemical and Real Time-PCR (RT-PCR) analyses.

RESULTS

Airway responsiveness, eosinophils and IL-13 levels in group A were significantly increased compare with the other groups, and significantly decreased in group N than those in group A. IFN-γ level was significantly reduced in group A and increased in group N. Immunohistochemistry and RT-PCR analyses showed that the protein expression and mRNA level of NGF and RhoA were significantly increased in group A and significantly decreased in group N.

CONCLUSION

NGF participates in the pathogenesis of asthma in mice. Anti-NGF antibody can inhibit airway inflammation and alleviate AHR by down-regulating the protein expression and mRNA level of RhoA.

Cytokine and Chemokine Profiling in Patients with Hand, Foot and Mouth Disease in Singapore and Malaysia

Hand, foot and mouth disease (HFMD) is a prevalent contagious childhood disease typically associated with fever, oral lesions and limb exanthema. While HFMD is caused by a plethora of serotypes of viruses under the genus Enterovirus within the Picornaviridae family, Coxsackievirus A16 (CV-A16) and Enterovirus 71 (EV-A71) are considered the main etiological agents. In recent years however, other viruses have also been isolated in considerable numbers from infected individuals in many regions, joining the legion commonly associated with HFMD. The present study investigated the cytokine and chemokine profiles of HFMD patients from Singapore and Malaysia for the first time. Comparative cohort studies of EV-A71-associated HFMD cases revealed that the Malaysia cohort had a distinct profile from the Singapore cohort, and this could be partly attributed by different EV-A71 genotypes. As the isolation of CV-A6, instead of CV-A16, had become prevalent in the Singapore cohort, it was also of particular interest to study the differential cytokine and chemokine profiles. Our data revealed that overlapping as well as unique profiles exist between the two major causative clinical isolates in the Singapore cohort. Having a better understanding of the respective immunological profiles could be useful for more accurate HFMD diagnosis, which is imperative for disease transmission control until multi-valent vaccines and/or broad-spectrum anti-viral drugs become available.

Mechanisms of nerve growth factor signaling in bone nociceptors and in an animal model of inflammatory bone pain

Sequestration of nerve growth factor has been used successfully in the management of pain in animal models of bone disease and in human osteoarthritis. However, the mechanisms of nerve growth factor-induced bone pain and its role in modulating inflammatory bone pain remain to be determined. In this study, we show that nerve growth factor receptors (TrkA and p75) and some other nerve growth factor-signaling molecules (TRPV1 and Nav1.8, but not Nav1.9) are expressed in substantial proportions of rat bone nociceptors. We demonstrate that nerve growth factor injected directly into rat tibia rapidly activates and sensitizes bone nociceptors and produces acute behavioral responses with a similar time course. The nerve growth factor-induced changes in the activity and sensitivity of bone nociceptors we report are dependent on signaling through the TrkA receptor, but are not affected by mast cell stabilization. We failed to show evidence for longer term changes in expression of TrkA, TRPV1, Nav1.8 or Nav1.9 in the soma of bone nociceptors in a rat model of inflammatory bone pain. Thus, retrograde transport of NGF/TrkA and increased expression of some of the common nerve growth factor signaling molecules do not appear to be important for the maintenance of inflammatory bone pain. The findings are relevant to understand the basis of nerve growth factor sequestration and other therapies directed at nerve growth factor signaling, in managing pain in bone disease.

Neurotrophin Receptor p75NTR Regulates Immune Function of Plasmacytoid Dendritic Cells

Plasmacytoid dendritic cells (pDCs) regulate innate and adaptive immunity. Neurotrophins and their receptors control the function of neuronal tissue. In addition, they have been demonstrated to be part of the immune response but little is known about the effector immune cells involved. We report, for the first time, the expression and immune-regulatory function of the low affinity neurotrophin receptor p75 neurotrophin receptor (p75NTR) by the antigen-presenting pDCs, mediated by toll-like receptor (TLR) 9 activation and differential phosphorylation of interferon regulatory factor 3 and 7. The modulation of p75NTR on pDCs significantly influences disease progression of asthma in an ovalbumin-induced mouse model mediated by the TLR9 signaling pathway. p75NTR activation of pDCs from patients with asthma increased allergen-specific T cell proliferation and cytokine secretion in nerve growth factor concentration-dependent manner. Further, p75NTR activation of pDCs delayed the onset of autoimmune diabetes in RIP-CD80GP mice and aggravated graft-versus-host disease in a xenotransplantation model. Thus, p75NTR signaling on pDCs constitutes a new and critical mechanism connecting neurotrophin signaling and immune response regulation with great therapeutic potential for a variety of immune disorders.

The relationship of Chlamydophila pneumoniae with schizophrenia: The role of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) in this relationship

Several pathogens have been suspected of playing a role in the pathogenesis of schizophrenia. Chronic inflammation has been proposed to occur as a result of persistent infection caused by Chlamydophila pneumoniae cells that reside in brain endothelial cells for many years. It was recently hypothesized that brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) may play prominent roles in the development of schizophrenia. NT-3 and BDNF levels have been suggested to change in response to various manifestations of infection. Therefore, we aimed to elucidate the roles of BDNF and NT3 in the schizophrenia-C. pneumoniae infection relationship. RT-PCR, immunofluorescence and ELISA methods were used. Fifty patients suffering from schizophrenia and 35 healthy individuals were included as the patient group (PG) and the healthy control group (HCG), respectively. We detected persistent infection in 14 of the 50 individuals in the PG and in 1 of the 35 individuals in the HCG. A significant difference was found between the two groups (p<0.05). Twenty-two individuals in the PG and 13 in the HCG showed seropositivity for past C. pneumoniae infection, and no difference was observed between the groups (p>0.05). C. pneumoniae DNA was not detected in any group. A significant difference in NT-3 levels was observed between the groups, with very low levels in the PG (p<0.001). A significant difference in BDNF levels was also found, with lower levels in the PG (p<0.05). The mean serum NT-3 level was higher in the PG cases with C. pneumoniae seropositivity than in seronegative cases; however, this difference was not statistically significant (p>0.05). In conclusion, we suggest that NT-3 levels during persistent C. pneumoniae infection may play a role in this relationship.

The nervous system of airways and its remodeling in inflammatory lung diseases

Inflammatory lung diseases are associated with bronchospasm, cough, dyspnea and airway hyperreactivity. The majority of these symptoms cannot be primarily explained by immune cell infiltration. Evidence has been provided that vagal efferent and afferent neurons play a pivotal role in this regard. Their functions can be altered by inflammatory mediators that induce long-lasting changes in vagal nerve activity and gene expression in both peripheral and central neurons, providing new targets for treatment of pulmonary inflammatory diseases.

The Role of Neurotrophins in Inflammation and Allergy

Allergic inflammation is the result of a specific pattern of cellular and humoral responses leading to the activation of the innate and adaptive immune system, which, in turn, results in physiological and structural changes affecting target tissues such as the airways and the skin. Eosinophil activation and the production of soluble mediators such as IgE antibodies are pivotal features in the pathophysiology of allergic diseases. In the past few years, however, convincing evidence has shown that neurons and other neurosensory structures are not only a target of the inflammatory process but also participate in the regulation of immune responses by actively releasing soluble mediators. The main products of these activated sensory neurons are a family of protein growth factors called neurotrophins. They were first isolated in the central nervous system and identified as important factors for the survival and differentiation of neurons during fetal and postnatal development as well as neuronal maintenance later in life. Four members of this family have been identified and well defined: nerve growth factor, brain-derived neurotrophic factor, neurotrophin 3, and neurotrophin 4/5. Neurotrophins play a critical role in the bidirectional signaling mechanisms between immune cells and the neurosensory network structures in the airways and the skin. Pruritus and airway hyperresponsiveness, two major features of atopic dermatitis and asthma, respectively, are associated with the disruption of the neurosensory network activities. In this chapter, we provide a comprehensive description of the neuroimmune interactions underlying the pathophysiological mechanisms of allergic and inflammatory diseases.

Activation of Bcl-2-Caspase-9 Apoptosis Pathway in the Testis of Asthmatic Mice

BACKGROUND

Apoptosis plays a critical role in controlling the proliferation and differentiation of germ cells during spermatogenesis. Dysregulation of the fine-tuned balance may lead to the onset of testicular diseases. In this study, we investigated the activation status of apoptosis pathways in the testicular tissues under the background of an asthmatic mouse model.

METHODS

Ten BALB/c mice were divided into two groups: the acute asthma group and the control group. In the acute asthma group, ovalbumin (OVA)-sensitized mice were challenged with aerosolized OVA for 7 days, while the control group was treated with physiological saline. After that, both epididymis and testis were collected to determine the sperm count and motility. Apoptosis in the testis was evaluated by DNA ladder, immunochemistry and further by PCR array of apoptosis-related genes. Finally, the cleavage of caspase-3 and poly ADP-ribose polymerase (PARP) was determined by western blot and the enzymatic activities of caspase-9 and 3/7 were assessed using Caspase-Glo kits.

RESULTS

Compared with control mice, significant decreases in the body weight, testis weight, sperm count and motility were seen in the experimental group. DNA ladder and immunochemistry showed significant increase in apoptotic index of the asthmatic testis, whereas a decrease in mRNA expression of Bcl-2 and increases in Bax, BNIP3, caspase-9, and AIF were observed in the asthma group. Furthermore, protein levels of AIF were significantly upregulated, while the translational expression of Bcl-2 was downregulated markedly. Consistently, caspase-9 activity in the testis of asthma mice was significantly higher than that of the control group.

CONCLUSION

Collectively, these results showed that Bcl-2-caspase-9 apoptosis pathway was clearly activated in the testis of asthmatic mice with the increased expression of apoptosis-related genes and proteins. To our knowledge, this is the first report demonstrating that asthma could lead to the activation of the mitochondrial apoptosis signaling pathway in the mouse testis.

Role of Nerve Growth Factor in Development and Persistence of Experimental Pulmonary Hypertension

RATIONALE

Pulmonary hypertension (PH) is characterized by a progressive elevation in mean pulmonary arterial pressure, often leading to right ventricular failure and death. Growth factors play significant roles in the pathogenesis of PH, and their targeting may therefore offer novel therapeutic strategies in this disease.

OBJECTIVES

To evaluate the nerve growth factor (NGF) as a potential new target in PH.

METHODS

Expression and/or activation of NGF and its receptors were evaluated in rat experimental PH induced by chronic hypoxia or monocrotaline and in human PH (idiopathic or associated with chronic obstructive pulmonary disease). Effects of exogenous NGF were evaluated ex vivo on pulmonary arterial inflammation and contraction, and in vitro on pulmonary vascular cell proliferation, migration, and cytokine secretion. Effects of NGF inhibition were evaluated in vivo with anti-NGF blocking antibodies administered both in rat chronic hypoxia- and monocrotaline-induced PH.

MEASUREMENTS AND MAIN RESULTS

Our results show increased expression of NGF and/or increased expression/activation of its receptors in experimental and human PH. Ex vivo/in vitro, we found out that NGF promotes pulmonary vascular cell proliferation and migration, pulmonary arterial hyperreactivity, and secretion of proinflammatory cytokines. In vivo, we demonstrated that anti-NGF blocking antibodies prevent and reverse PH in rats through significant reduction of pulmonary arterial inflammation, hyperreactivity, and remodeling.

CONCLUSIONS

This study highlights the critical role of NGF in PH. Because of the recent development of anti-NGF blocking antibodies as a possible new pain treatment, such a therapeutic strategy of NGF inhibition may be of interest in PH.

Myenteric expression of nerve growth factor and the p75 neurotrophin receptor regulate axonal remodeling as a consequence of colonic inflammation in mice

Nerve growth factor (NGF) levels increase in response to inflammation of the mammalian colon. The precise cellular sources of colonic NGF synthesis, however, remain elusive. Using lines of transgenic mice that express enhanced green fluorescent protein (EGFP) under the control of the NGF promoter, we found a subpopulation of adendritic EGFP(+) neurons in the myenteric plexus. These colonic EGFP(+) neurons display positive immunostaining for calretinin but not nitric oxide synthase 1 (NOS1) two biomarkers of mouse myenteric neurons. A loss of NGF expression in null mutant postnatal mice does not affect the survival of these EGFP(+) neurons. Induction of colonic inflammation confirms local increases in NGF mRNA/protein levels, which coincide with heightened detection of EGFP by myenteric neurons. Though NOS1(+) myenteric neurons display positive immunostaining for trkA (the receptor required for NGF binding/signaling), transgenic overexpression of NGF by smooth muscle cells in the colon does not alter the survival, somal size, or axonal density of trkA-expressing NOS1(+) myenteric neurons. Mice lacking functional p75NTR (the second receptor required for NGF binding) exhibit significantly less axonal damage among NOS1(+) myenteric neurons, in response to chemically induced colonic inflammation. Likewise, trkA-expressing sympathetic axons that innervate the myenteric ganglia display less damage in the absence of p75NTR. These data are the first to implicate calretinin(+) myenteric neurons as a source of NGF in the murine colon, and that in response to colonic inflammation, increases in NGF can exaggerate damage of intrinsic NOS1(+) axons and extrinsic sympathetic axons that co-express trkA and p75NTR.

Val66Met polymorphism in the BDNF gene in children with bronchial asthma

OBJECTIVES

Bronchial asthma is a chronic respiratory disease characterized by airway inflammation. There is increasing evidence that neurotrophins play an important role in the development and maintenance of neurogenic airway inflammation in chronic allergic diseases.

WORKING HYPOTHESIS

Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family and has several important functions in the airways. There are only a few reports on the association between genetic variations in the BDNF gene and various allergic diseases, and the results are generally conflicting. Therefore, we aimed to study the functional polymorphism Val66Met (also called rs6265 or G196A) in the BDNF gene in a group of asthmatic children and healthy controls.

STUDY DESIGN, PATIENT-SELECTION, AND METHODOLOGY

We studied 248 asthmatic patients (aged 12.28 ± 0.24 years) and 249 healthy children (aged 13.14 ± 0.48 years). Analysis of the Val66Met polymorphism of the BDNF gene was performed by polymerase chain reaction (PCR) and PCR products were digested by PmlI.

RESULTS

The prevalence of the Val66Met polymorphisms (Val/Val, Val/Met, and Met/Met) was 61.7%, 33.5%, and 4.8% in asthmatics, respectively, and 47.0%, 51.8%, and 1.2% in healthy subjects, respectively. We observed a significant association of the Met/Met variant genotype with asthmatics (OR = 4.17, 95% CI = 1.16-14.96, P = 0.018). The Val/Met genotype was protective against bronchial asthma (OR = 0.69, 95% CI = 0.48-0.99, P = 0.045), especially in girls (OR = 0.34, 95% CI = 0.20-0.59, P = 0.001).

CONCLUSION

Specific BDNF gene polymorphism may contribute to bronchial asthma susceptibility. Our study suggested the positive association between selected functional BDNF polymorphism (rs6265) and asthma in children.

Mast cells in airway diseases and interstitial lung disease

Mast cells are major effector cells of inflammation and there is strong evidence that mast cells play a significant role in asthma pathophysiology. There is also a growing body of evidence that mast cells contribute to other inflammatory and fibrotic lung diseases such as chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis. This review discusses the role that mast cells play in airway diseases and highlights how mast cell microlocalisation within specific lung compartments and their cellular interactions are likely to be critical for their effector function in disease.

Ozone exposure initiates a sequential signaling cascade in airways involving interleukin-1beta release, nerve growth factor secretion, and substance P upregulation

Previous studies demonstrated that interleukin-1β (IL-1β) and nerve growth factor (NGF) increase synthesis of substance P (SP) in airway neurons both after ozone (O3) exposure and by direct application. It was postulated that NGF mediates O3-induced IL-1β effects on SP. The current study specifically focused on the influence of O3 on IL-1β, NGF, and SP levels in mice bronchoalveolar lavage fluid (BALF) and whether these mediators may be linked in an inflammatory-neuronal cascade in vivo. The findings showed that in vivo O3 exposure induced an increase of all three proteins in mouse BALF and that O3-induced elevations in both NGF and SP are mediated by the inflammatory cytokine IL-1β. Further, inhibition of NGF reduced O3 induced increases of SP in both the lung BALF and lung tissue, demonstrating NGF serves as a mediator of IL-1β effects on SP. These data indicate that IL-1β is an early mediator of O3-induced rise in NGF and subsequent SP release in mice in vivo.

Lung dendritic cells undergo maturation and polarization towards a T helper type 2-stimulating phenotype in a mouse model of asthma: Role of nerve growth factor

Nerve growth factor (NGF) and dendritic cells (DCs) have been hypothesized to modulate T cell responses in a mouse model of asthma. However, whether NGF plays a role in regulating the maturation and polarization of lung DCs remains unclear. In the present study, the effect of NGF inhibition on the maturation and phenotype of lung DCs was investigated in a mouse model of asthma. BALB/c mice were sensitized and challenged with ovalbumin (OVA), and subsequently received anti-NGF treatment. At 24 h following the last challenge, airway responsiveness and inflammation were examined. The concentrations of NGF, interferon (IFN)-γ and interleukin (IL)-4 were analyzed. In addition, maturation and CD103 expression in the lung DCs were investigated. Anti-NGF treatment was found to significantly reduce airway hyperreactivity and inflammation in asthmatic mice. In addition, a subdued T helper 2 (Th2) response was observed, characterized by the downregulation of IL-4 and the upregulation of IFN-γ. Furthermore, the expression of the DC surface molecules, CD80, CD86 and major histocompatibility complex class II, as well as the proportion of lung CD103⁺ DCs, decreased in the OVA-sensitized and challenged mice. The proportion of lung CD103⁺ DCs also exhibited a positive correlation with the levels of plasma NGF in the mice. These results may provide an explanation for the role of NGF in amplifying the Th2 response in allergic diseases. Therefore, NGF may promote the maturation and polarization towards a Th2-stimulating phenotype of activated DCs, contributing to an amplification of the Th2 response in asthma.

Nerve growth factor reduces amiloride-sensitive Na+ transport in human airway epithelial cells

Nerve growth factor (NGF) is overexpressed in patients with inflammatory lung diseases, including virus infections. Airway surface liquid (ASL), which is regulated by epithelial cell ion transport, is essential for normal lung function. No information is available regarding the effect of NGF on ion transport of airway epithelium. To investigate whether NGF can affect ion transport, human primary air‐interface cultured epithelial cells were placed in Ussing chambers to obtain transepithelial voltage (−7.1 ± 3.4 mV), short‐circuit current (I_sc, 5.9 ± 1.0 μA), and transepithelial resistance (750 Ω·cm²), and to measure responses to ion transport inhibitors. Amiloride (apical, 3.5 × 10⁻⁵ mol/L) decreased I_sc by 55.3%. Apically applied NGF (1 ng/mL) reduced I_sc by 5.3% in 5 min; basolaterally applied NGF had no effect. The response to amiloride was reduced (41.6%) in the presence of NGF. K‐252a (10 nmol/L, apical) did not itself affect Na⁺ transport, but it attenuated the NGF‐induced reduction in Na⁺ transport, indicating the participation of the trkA receptor in the NGF‐induced reduction in Na⁺ transport. PD‐98059 (30 μmol/L, apical and basolateral) did not itself affect Na⁺ transport, but attenuated the NGF‐induced reduction in Na⁺ transport, indicating that trkA activated the Erk 1/2 signaling cascade. NGF stimulated phosphorylation of Erk 1/2 and the β‐subunit of ENaC. K‐252a and PD‐98059 inhibited these responses. NGF had no effect on I_sc in the presence of apical nystatin (50 μmol/L). These results indicate that NGF inhibits Na⁺ transport through a trkA‐Erk 1/2‐activated signaling pathway linked to ENaC phosphorylation.

Nerve growth factor (apical, 1 ng/mL) reduced amiloride‐sensitive Na⁺ transport in human cultured bronchial epithelial cells. We determined that this reduction in Na⁺ transport occurred through NGF‐mediated activation of the trkA receptor and Erk 1/2 signaling cascade to cause phosphorylation of ENaC.

Small interfering RNA targeting nerve growth factor alleviates allergic airway hyperresponsiveness

Airway hyperresponsiveness is the hallmark of allergic asthma and caused by multiple factors. Nerve growth factor (NGF), a neurotrophin, is originally known for regulation of neural circuit development and function. Recent studies indicated that NGF contributes to airway hyperresponsiveness and pathogenesis of asthma. The objective of this study is to develop a small interfering RNA against NGF to attenuate airway hyperresponsiveness and further elucidate the underlying mechanism. In a murine model of allergic asthma, the ovalbumin-sensitized mice were intratracheally delivered small interfering RNA against NGF or administered an inhibitor targeting NGF receptor, tropomyosin-related kinase A, as a positive treatment control. In this study, knockdown NGF derived from pulmonary epithelium significantly reduced airway resistance in vivo. The levels of NGF, proinflammatory cytokines and infiltrated eosinophils in airway were decreased in small interfering RNA against NGF group but not in tropomyosin-related kinase A inhibitor and mock siRNA group. Furthermore, induction of neuropeptide (substance P) and airway innervation were mediated by NGF/tropomyosin-related kinase A pathway. These findings suggested that NGF targeting treatment holds the potential therapy for antigen-induced airway hyperresponsiveness via attenuation of airway innervation and inflammation in asthma.

Expression of neuronal protein Kidins220/ARMS in the spleen and peripheral blood of mice following airway allergen challenge

Nerve growth factor (NGF), combined with the high-affinity tyrosine kinase receptor A (TrkA), has been reported to be involved in the pathogenesis of asthma. Ankyrin-rich membrane spanning/transmembrane substrate of protein kinase D (ARMS/Kidins220), a TrkA‑binding protein, modulates the NGF signaling pathway. The aim of the present study was to investigate the expression of Kidins220/ARMS and the effect NGF has on the protein in the spleen and peripheral blood, following airway allergen challenge in mice. BALB/c mice were sensitized and challenged with ovalbumin. The effects of NGF on Kidins220/ARMS in the spleen and peripheral blood of mice were assessed by administering anti-NGF antibody. Expression of ARMS, interleukin (IL)-1β and IL-4 in the spleen and peripheral blood was observed by reverse transcription-polymerase chain reaction, western blot analysis and immunohistochemistry. Pathological changes in the bronchi and lung tissues were examined by hematoxylin and eosin staining. Results showed that Kidins220/ARMS, IL-1β and IL-4 were overexpressed in the spleen and peripheral blood following allergen challenge, compared with the control mice. Moreover, following treatment with anti-NGF, the levels of Kidins220/ARMS, IL-1β and IL-4 in the mice were downregulated. Therefore, the results of the present study showed that Kidins220/ARMS is expressed in the spleen and peripheral blood of normal BALB/c mice and may participate in the immuno-inflammation of asthma through the NGF-mediated signaling pathway.

Interleukin and neurotrophin up-regulation correlates with severity of H1N1 infection in children: a case-control study

OBJECTIVE

To evaluate the correlation between cytokine and neurotrophin expression and clinical findings, disease severity, and outcome of children with H1N1 influenza infection.

METHODS

A prospective observational clinical study was performed on 15 children with H1N1 infection, 15 controls with lower respiratory tract infections (LRTI), and 15 non-infected children. Plasma levels of interleukin (IL)-1β, IL-6, and neurotrophic factor (nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), and glial derived neurotrophic factor (GDNF)) were measured using immunoenzymatic assays.

RESULTS

Significantly higher levels of IL-1β, IL-6, BDNF, and NGF were detected in patients with H1N1 infection compared to LRTI controls, while there was no significant variation in GDNF in the two groups. IL-1β, IL-6, BDNF, and NGF levels were significantly higher in H1N1 patients with more severe clinical manifestations compared to H1N1 patients with mild clinical manifestations. Of note, IL-6 was significantly correlated with the severity of respiratory compromise and fever, while NGF up-regulation was associated with the duration of cough. No correlation was found between interleukin and neurotrophic factor expression and outcome.

CONCLUSIONS

H1N1 infection induces an early and significant IL-1β, IL-6, BDNF, and NGF up-regulation. The over-expression of these molecular markers is likely to play a neuroimmunomodulatory role in H1N1 infection and may contribute to airway inflammation and bronchial hyper-reactivity in infected children.

Blockade of ankyrin repeat-rich membrane spanning protein modulates extracellular signal-regulated kinase expression and inhibits allergic inflammation in ovalbumin-sensitized mice

Ankyrin repeat-rich membrane spanning protein (ARMS), also known as kinase D-interacting substrate of 220 kDa (Kidins220), is a transmembrane protein that has been reported to be involved in the pathogenesis of asthma through the nerve growth factor (NGF)/tyrosine kinase A (TrkA) receptor signaling pathway. To investigate whether NGF/TrkA-Kidins220/ARMS-extracellular signal-regulated kinase (ERK) signaling is activated in airway inflammation of asthma, BALB/c mice were sensitized and challenged with ovalbumin (OVA). The effects of Kidins220/ARMS on ERK, interleukin (IL)-1β, IL-4 and tumor necrosis factor (TNF)-α in lung tissues following the allergic airway challenge in mice were assessed by administering anti-ARMS antibody to the mice. Pathological changes in the bronchi and lung tissues were examined via hematoxylin and eosin staining. The phosphorylated ERK, IL-1β, IL-4 and TNF-α levels were determined using western blot analysis and ELISA and were found to be overexpressed in lung tissues following the allergen challenge. Moreover, after the mice were treated with anti-NGF, anti-TrkA or anti-ARMS, the levels of Kidins220/ARMS, phosphorylated ERK, IL-1β, IL-4, TNF-α and allergen-induced airway inflammation were downregulated. These results suggested that NGF/TrkA-Kidins220/ARMS-ERK signaling was activated in airway inflammation induced by the allergic airway challenge, possibly representing a new mechanism in asthma.

Increased nerve growth factor serum levels in top athletes

OBJECTIVE

The nerve growth factor (NGF) is the main neurotrophin, which, besides being an important growth factor for nerves, plays an important role as a mediator of inflammation. Nerve growth factor has been shown to increase in relation to stress stimuli and in allergic diseases in humans as well as after physical exercise in animal models. This study aims at evaluating NGF serum levels in top athletes, a population sample in which allergic and neuro-immune diseases are reported with a significantly increased prevalence.

DESIGN

Observational, cross-sectional, multicenter study.

SETTING

Institutional, tertiary care.

PARTICIPANTS

Ninety-six Italian pre-Olympic athletes (44 allergic and 52 nonallergic) and 49 matched controls selected within the Italian National Olympic delegation (n = 435).

INDEPENDENT VARIABLES

Nerve growth factor serum levels determined through an enzyme-linked immunosorbent assay.

MAIN OUTCOME MEASURES

Parametric or nonparametric tests were used for comparing NGF serum levels among different study groups depending on value distributions.

RESULTS

Nerve growth factor serum levels were significantly higher in athletes than in controls independently from the presence of allergy. Nerve growth factor mean values were 368.3 ± 776.3 pg/mL in the sample of athletes and 174.1 ± 483.7 pg/mL in the control group (P < 0.001).

CONCLUSIONS

This is the first study showing that intense and prolonged physical exercise is associated with an increase of NGF serum levels in athletes. Whether the increased NGF production might be linked to the prevalent Th2 response observed in allergic diseases and after physical exercise and whether it might be related to the patophysiology of neuro-immune disorders as such amyotrophic lateral sclerosis, reported with a higher prevalence in athletes, should deserve further investigations.

TRPV1 inhibition attenuates IL-13 mediated asthma features in mice by reducing airway epithelial injury

Even though neurogenic axis is well known in asthma pathogenesis much attention had not been given on this aspect. Recent studies have reported the importance of TRP channels, calcium-permeable ion channels and key molecules in neurogenic axis, in asthma therapeutics. The role of TRPV1 channels has been underestimated in chronic respiratory diseases as TRPV1 knockout mice of C57BL/6 strains did not attenuate the features of these diseases. However, this could be due to strain differences in the distribution of airway capsaicin receptors. Here, we show that TRPV1 inhibition attenuates IL-13 induced asthma features by reducing airway epithelial injury in BALB/c mice. We found that IL-13 increased not only the lung TRPV1 levels but also TRPV1 expression in bronchial epithelia in BALB/c rather than in C57BL/6 mice. TRPV1 knockdown attenuated airway hyperresponsiveness, airway inflammation, goblet cell metaplasia and subepithelial fibrosis induced by IL-13 in BALB/c mice. Further, TRPV1 siRNA treatment reduced not only the cytosolic calpain and mitochondrial calpain 10 activities in the lung but also bronchial epithelial apoptosis indicating that TRPV1 siRNA might have corrected the intracellular and intramitochondrial calcium overload and its consequent apoptosis. Knockdown of IL-13 in allergen induced asthmatic mice reduced TRPV1, cytochrome c, and activities of calpain and caspase 3 in lung cytosol. Thus, these findings suggest that induction of TRPV1 with IL-13 in bronchial epithelia could lead to epithelial injury in in vivo condition. Since TRPV1 expression is correlated with human asthma severity, TRPV1 inhibition could be beneficial in attenuating airway epithelial injury and asthma features.

Strategies for local gene therapy of corneal allograft rejection

Penetrating keratoplasty is the most common type of tissue transplant in humans. Irreversible immune rejection leads to loss of vision and graft failure. This complex immune response further predisposes future corneal transplants to rejection and failure. A diverse armamentarium of surgical and pharmacologic tools is available to improve graft survival. In this review, we will discuss the various gene therapeutic strategies aimed at potentiating the anterior chamber-associated immune deviation to extend graft survival.

Blockage of nerve growth factor modulates T cell responses and inhibits allergic inflammation in a mouse model of asthma

OBJECTIVE

Blockage of nerve growth factor (NGF) by anti-NGF antibodies can inhibit allergic airway hyper-responsiveness in mice. This study was aimed at determining the mechanisms underlying the action of anti-NGF in vivo.

METHODS

BALB/c mice were sensitized with ovalbumin (OVA) and treated with anti-NGF. At 1 day after the last challenge, their airway responsiveness and inflammation were examined and the levels of cytokine and transcription factor mRNA transcripts in the lungs and cytokines in the bronchoalveolar lavage fluid were determined. The frequency of different functional T cells and the levels of serum OVA-specific antibodies were measured.

RESULTS

OVA challenge induced severe airway resistance, inflammation, higher levels of IL-4, TNFα, IL-17A, TGFβ, GATA-3 and RORγT expression and increased Th2 and Th17 cells and IgE responses, but decreased IFNγ and IL-10 responses, T-bet and Foxp3 expression and Th1 and Tregs. Treatment with anti-NGF significantly reduced allergic airway resistance and inflammation, up-regulated IFNγ, IL-10, TGFβ, T-bet, and Foxp3 expression, increased Th1 and Tregs, but down-regulated IL-4, TNFα, IL-17A, RORγT and GATA-3 expression and reduced Th2 and Th17 cells, accompanied by increased serum IgG2a.

CONCLUSIONS

Anti-NGF inhibits allergic airway inflammation by modulating the balance of pro- and anti-asthmatic T cell responses in the lungs of mice.

Multilocus analysis of candidate genes involved in neurogenic inflammation in pediatric asthma and related phenotypes: a case-control study

OBJECTIVES

Asthma is a heterogenous complex disorder caused by chronic inflammation of the airways. The key issue in genetic association studies of complex disorders is the identification of multiple low-risk genes that individually have little impact on the phenotype, but in combination account for the clinical manifestation of asthma. Since neurogenic inflammation is emerging as a candidate factor in the pathogenesis of asthma, the aim of the study was to investigate whether genetic variants of neurotrophin genes are associated with asthma disease severity or asthma-related phenotypes in a pediatric population.

METHODS

We genotyped 27 polymorphisms located in neurotrophin genes, using TaqMan SNP genotyping assays or Polymerase Chain Reaction - Restriction Fragments Lengths Polymorphism (PCR-RFLP) in 200 children diagnosed with asthma and 226 controls. Interactions between 27 polymorphic loci and asthma-related phenotypes were determined using the Multifactor Dimensionality Reduction (MDR) method.

RESULTS

In single marker analysis, we observed an association of MAP3K1 gene polymorphisms (rs702689 and rs889312) with asthma. We also observed that four Single Nucleotide Polymorphisms (SNPs) were associated with severe asthma. Analysis stratified by asthma-related phenotype revealed an association between atopy and NGFR (rs3785931), while BDNF (rs7124442), NTRK2 (rs1212171), NGFR (rs2072446), and FYN (rs3730353) variants were associated with increased exhaled nitric oxide (exNO). In addition, gene-gene interaction analysis revealed a significant epistatic interaction between MAPK (rs889312) and NGF (rs11102930) variants in asthma susceptibility.

CONCLUSIONS

Our results suggest that genetic variants of MAP3K1 and NGF genes involved in the regulation of neurogenic inflammation may contribute to asthma, possibly via enhanced NGF expression and MAPK signaling pathway activation.

Pneumocystis elicits a STAT6-dependent, strain-specific innate immune response and airway hyperresponsiveness

It is widely held that exposure to pathogens such as fungi can be an agent of comorbidity, such as exacerbation of asthma or chronic obstructive pulmonary disease. Although many studies have examined allergic responses to fungi and their effects on pulmonary function, the possible pathologic implications of the early innate responses to fungal pathogens have not been explored. We examined early responses to the atypical fungus Pneumocystis in two common strains of mice in terms of overall immunological response and related pathology, such as cell damage and airway hyperresponsiveness (AHR). We found a strong strain-specific response in BALB/c mice that included recruitment of neutrophils, NK, NKT, and CD4 T cells. This response was accompanied by elevated indicators of lung damage (bronchoalveolar lavage fluid albumin and LDH) and profound AHR. This early response was absent in C57BL/6 mice, although both strains exhibited a later response associated with the clearance of Pneumocystis. We found that this AHR could not be attributed exclusively to the presence of recruited neutrophils, NKT, NK, or CD4 cells or to the actions of IFN-γ or IL-4. However, in the absence of STAT6 signaling, AHR and inflammatory cell recruitment were virtually absent. Gene expression analysis indicated that this early response included activation of several transcription factors that could be involved in pulmonary remodeling. These results show that exposure to a fungus such as Pneumocystis can elicit pulmonary responses that may contribute to morbidity, even without prior sensitization, in the context of certain genetic backgrounds.

Cyclosporine A induces nerve growth factor expression via activation of MAPK p38 and NFAT5

PURPOSE

We investigated the effects of cyclosporine A (CsA) on the mechanism of nerve growth factor (NGF) expression using a cultured human corneal epithelial cell line (HCECL).

METHODS

NGF transcription and production levels were assessed after treatment of cells with various concentrations of CsA. Activities of mitogen-activated protein kinase (MAPK), nuclear factor Kappa B (NF-κB), activator protein-1 (AP-1), and nuclear factor of activated T cells (NFATs) influenced by CsA were determined using a luciferase assay. The translocation activity of NFAT5 was assessed by confocal microscopy and Western immunoblotting after CsA treatment. Transcriptional activity of NGF was measured after pretreatment of cells with SB20429 (a p38 inhibitor) and NFAT5 small interfering RNA.

RESULTS

NGF was induced after treatment with CsA, but not dexamethasone, in the HCECL. NGF expression was mediated via p38 phosphorylation and NFAT5 activation. Transcriptional activities of NF-κB, AP-1, and NFAT1 were not stimulated by CsA; however, nuclear translocation of NFAT5 was markedly upregulated by CsA. CsA-induced NGF production was markedly decreased on inhibition of NFAT5 or SB20429.

CONCLUSIONS

CsA is a potent inducer of NGF in the HCECL. These results suggest that CsA mediates NGF expression through activation of p38 and NFAT5.

Nerve growth factor is associated with islet graft failure following intraportal transplantation

Nerve growth factor (NGF) has recently been recognized as an angiogenic factor with an important regulatory role in pancreatic β-cell function. We previously showed that treatment of pancreatic islets with NGF improved their quality and viability. Revascularization and survival of islets transplanted under the kidney capsule were improved by NGF. However, the usefulness of NGF in intraportal islet transplantation was not previously tested. To resolve this problem, we transplanted syngeneic islets (360 islet equivalents per recipient) cultured with or without NGF into the portal vein of streptozotocin-induced diabetic BALB/c mice. Analysis revealed that 44.4% (4/9) of control and 12.5% (1/8) of NGF-treated mice attained normoglycemia (≤ 200 mg/dL) (p = 0.195). NGF-treated islets led to worse graft function (area under the curve of intraperitoneal glucose tolerance tests (IPGTT) on post-operative day (POD) 30, control; 35,800 ± 3,960 min*mg/dl, NGF-treated; 47,900 ± 3,220 min*mg/dl: *p = 0.0348). NGF treatment of islets was also associated with increased graft failure [the percentage of TdT-mediated dUTP-biotin nick-end labeling (TUNEL)-positive and necrotic transplanted islets on POD 5, control; 23.8% (5/21), NGF-treated; 52.9% (9/17): p = 0.0650] following intraportal islet transplantation. Nonviable (TUNEL-positive and necrotic) islets in both groups expressed vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1α (HIF-1α). On the other hand, viable (TUNEL-negative and not necrotic) islets in both groups did not express VEGF and HIF-1α. In the present study, pre-transplant NGF treatment was associated with impaired survival and angiogenesis of intraportal islet grafts. The effect of NGF on islet transplantation may significantly vary according to the transplant site.

Nerve growth factor derived from bronchial epithelium after chronic mite antigen exposure contributes to airway hyperresponsiveness by inducing hyperinnervation, and is inhibited by in vivo siRNA

BACKGROUND

Bronchial asthma is a chronic allergic airway inflammatory disease. Neurotrophins, including nerve growth factor (NGF), play an important role in the pathogenesis of asthma. However, the effects of NGF derived from epithelium on airway hyperresponsiveness (AHR) after antigen sensitization/exposure remain uncertain.

OBJECTIVE

In this study, we examined the role of NGF on AHR after chronic antigen exposure and the effect of inhibiting NGF by in vivo siRNA on AHR exacerbation.

METHODS

We generated chronic mouse models of bronchial asthma using house-dust mite antigen (Dermatophagoides pteronyssinus; Dp). NGF concentrations in bronchoalveolar lavage fluid (BALF), lung histopathology, hyperresponsiveness, and related neuronal peptides and cytokines in supernatants of lung homogenates were determined.

RESULTS

NGF in BALF was increased in a dose- and time-dependent manner, and was expressed primarily in bronchial epithelium. Nerve fibres and substance P-positive fibres were detected in subepithelium of Dp-sensitized and challenged mice over 4 weeks of mite antigen exposure. AHR was positively correlated with NGF concentration and nerve fibre innervation. AHR, modulation of innervation, and increased substance P were inhibited by in vivo administration of siRNA that targeted NGF, although the inhibition of NGF did not affect allergic inflammation and subepithelial fibrosis.

CONCLUSION AND CLINICAL RELEVANCE

These findings suggest that NGF derived from bronchial and alveolar epithelium plays an important role in AHR after chronic exposure to mite antigen. NGF inhibition could potentially manage bronchial asthma, including AHR.

Silencing IL-23 expression by a small hairpin RNA protects against asthma in mice

To determine the impact of IL-23 knockdown by RNA interference on the development and severity of ovalbumin (OVA)-induced asthmatic inflammation, and the potential mechanisms in mice, the IL-23-specific RNAi-expressing pSRZsi-IL-23p19 plasmid was constructed and inhaled into OVA-sensitized mice before each challenge, as compared with that of control mice treated with alum or budesonide. Inhalation of the pSRZsi-IL-23p19, significantly reduced the levels of OVA-challenge induced IL-23 in the lung tissues by nearly 75%, determined by RT-PCR. In addition, knockdown of IL-23 expression dramatically reduced the numbers of eosinophils and neutrophils in BALF and mitigated inflammation in the lungs of asthmatic mice. Furthermore, knockdown of IL-23 expression significantly decreased the levels of serum IgE, IL-23, IL-17, and IL-4, but not IFNgamma, and its anti-inflammatory effects were similar to or better than that of treatment with budesonide in asthmatic mice. Our data support the notion that IL-23 and associated Th17 responses contribute to the pathogenic process of bronchial asthma. Knockdown of IL-23 by RNAi effectively inhibits asthmatic inflammation, which is associated with mitigating the production of IL-17 and IL-4 in asthmatic mice.

Stress, atopy and allergy: A re-evaluation from a psychoneuroimmunologic persepective

Since the early days of psychosomatic thinking, atopic disease was considered exemplary. In the 70s and 80s numerous reports stated increased anxiety, depression or ill stresscoping in atopics in correlation with enhanced disease activity. Employed patient groups however were small and diverse and controls rare. Therefore, the question remained, whether psychopathological findings in atopics were of pathogenetic relevance or an epiphenomenon of chronic inflammatory disease. Recently, the discussion has been revived and refocused by psychoneuroimmunological findings. We now know that atopic disease is characterized by an imbalance of the classical stress-axis response along the hypothalamus-pituitary-adrenal axis (HPA) and the sympathetic axis (SA). This imbalance can be found shoulder-to-shoulder with enhanced expression of newly emerging neuroendocrine stress mediators such as substance P (SP) and nerve growth factor that form up to a third stress axis (neurotrophin neuropeptide axis: NNA). Together they can alter the inflammatory as well as the neuroendocrine stress-response on several levels. In skin, the immediate inflammatory response to stress involves neuropeptide release and mast cell degranulation, in short neurogenic inflammation. Systemically, antigen-presentation and TH2 cytokine bias are promoted under the influence of cortisol and neuropeptides. Imbalanced stress-responsiveness may therefore be at the core of exacerbated allergic disease and deserves re-evaluation of therapeutic options such as neutralization of SP-signaling by antagonists against its receptor NK1, cortisol treatment as supplementation and relaxation techniques to balance the stress-response.

Proliferation of sensory C-fibers and subsequent neurogenic inflammation in rat airway induced by inhaled lipopolysaccharide

Lipopolysaccharide (LPS) is associated with the development and exacerbation of airway inflammation. Increases in innervation of sensory C-fibers and tachykinin receptors, which mainly involve overproduction of neurotrophins such as nerve growth factor (NGF), may enhance neurogenic inflammation. Expression of NGF and its receptors in rat lungs is known to decline with age. We examined whether inhaled LPS causes proliferation of sensory C-fibers, increased expression of tachykinin receptors and subsequent enhancement of neurogenic inflammation in the airways of preweaning rats. Wistar male rats aged 2 weeks inhaled aerosolized LPS derived from Escherichia coli (0.1mg/ml) for 30 min. Evans blue dye leakage into the trachea induced by gaseous formaldehyde or intravenous capsaicin was measured as an index of tachykinin NK1 receptor-mediated vascular permeability. Expression of substance P-immunoreactive nerves, tachykinin NK1 receptors, tumor necrosis factor (TNF)-α and NGF in the trachea was also assessed immunohistochemically. Neurogenic plasma leakage in the trachea increased significantly between 7 and 21 days after LPS inhalation. Expression of TNF-α, NGF, substance P-immunoreactive nerves and tachykinin NK1 receptors was enhanced, peaking at 28 h, 7 days, 14 days and 14 days after LPS inhalation, respectively. Pretreatment with infliximab, a blocking antibody for TNF-α, almost completely abolished the airway changes seen after LPS inhalation. In conclusion, inhaled LPS increased innervation of sensory C-fibers and expression of tachykinin NK1 receptors in the airway, probably resulting in enhancement of neurogenic airway inflammation. These airway responses may be caused by overproduction of neurotrophins including NGF, mainly through a TNF-α-mediated pathway.

NGF/TrkA-mediated Kidins220/ARMS signaling activated in the allergic airway challenge in mice

BACKGROUND

Nerve growth factor (NGF), combined with its high-affinity receptor tyrosine kinase receptor A (TrkA), has been reported to be involved in the pathogenesis of asthma.

OBJECTIVE

To investigate whether the downstream protein ankyrin-rich membrane spanning (ARMS), a novel transmembrane substrate of protein kinase D (Kidins220), is activated in the pathogenesis of asthma.

METHODS

The asthmatic model was established by the inhalation of ovalbumin in BALB/c mice. The effects of NGF and TrkA on Kidins220/ARMS in an allergic airway challenge were assessed by administering anti-NGF or anti-TrkA antibody to the mice. Pathologic changes in the bronchi and lung tissues were examined by means of hematoxylin and eosin staining; the inflammatory cells in the bronchoalveolar lavage fluid (BALF) were counted; and co-expression of ARMS and TrkA in BALF cells was observed by means of immunofluorescence. In addition, Kidins220/ARMS, CrkL, NGF, TrkA protein, and Kidins220 messenger RNA levels were determined using Western blot or quantitative reverse transcription-polymerase chain reaction.

RESULTS

Using fluorescence microscopy, we found that Kidins220 and TrkA were co-expressed on the membranes of the BALF cells of asthmatic mice. Compared with expression in control animals, Kidins220/ARMS, CrkL, NGF, and TrkA were overexpressed in the lungs after allergen challenge. Moreover, after the mice were treated with anti-NGF or anti-TrkA, the Kidins220/ARMS levels and allergen-induced airway inflammation decreased.

CONCLUSIONS

These results suggest that Kidins220/ARMS partly participates in the pathogenesis of asthma through the NGF-TrkA signaling pathway, possibly representing a new mechanism in asthma.

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.

Neurotrophins and neurotrophin receptors in pulmonary sarcoidosis - granulomas as a source of expression

Background

Pulmonary sarcoidosis is an inflammatory disease, characterized by an accumulation of CD4⁺ lymphocytes and the formation of non-caseating epithelioid cell granulomas in the lungs. The disease either resolves spontaneously or develops into a chronic disease with fibrosis. The neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) have been suggested to be important mediators of inflammation and mediate tissue remodelling. In support of this, we have recently reported enhanced NGF levels in the airways of patients with pulmonary sarcoidosis. However, less is known about levels of BDNF and NT-3, and moreover, knowledge in the cellular sources of neurotrophins and the distribution of the corresponding neurotrophin receptors in airway tissue in sarcoidosis is lacking.

Methods

The concentrations of NGF, BDNF and NT-3 in bronchoalveolar lavage fluid (BALF) of 41 patients with newly diagnosed pulmonary sarcoidosis and 27 healthy controls were determined with ELISA. The localization of neurotrophins and neurotrophin receptors were examined by immunohistochemistry on transbronchial lung biopsies from sarcoidosis patients.

Results

The sarcoidosis patients showed significantly enhanced NT-3 and NGF levels in BALF, whereas BDNF was undetectable in both patients and controls. NT-3 levels in BALF were found higher in patients with non-Löfgren sarcoidosis as compared to patients with Löfgren's syndrome, and in more advanced disease stage. Epithelioid cells and multinucleated giant cells within the sarcoid granulomas showed marked immunoreactivity for NGF, BDNF and NT-3. Also, immunoreactivity for the neurotrophin receptor TrkA, TrkB and TrkC, was found within the granulomas. In addition, alveolar macrophages showed positive immunoreactivity for NGF, BDNF and NT-3 as well as for TrkA, TrkB and TrkC.

Conclusions

This study provides evidence of enhanced neurotrophin levels locally within the airways of patients with sarcoidosis. Findings suggest that sarcoid granuloma cells and alveolar macrophages are possible cellular sources of, as well as targets for, neurotrophins in the airways of these patients.