Cellular sources of enhanced brain-derived neurotrophic factor production in a mouse model of allergic inflammation

Enhanced BDNF and ROS in Mucosa of Lower Motor Neuron Lesioned Dog Bladder Following Somatic Motor Nerve Transfer

Neurotrophic factors and reactive oxygen species (ROS) modulate neuronal plasticity. In a model of a lower motor neuron lesioned bladder, somatic nerve transfer was used as a reinnervation strategy. Levels of neurotrophins, ROS, and TNF-α in bladder mucosa and muscle layers collected from three groups of adult female dogs: (1) Decentralized, via bilateral transection of coccygeal and sacral spinal roots, lumbar 7 dorsal roots, and hypogastric nerves, then 6-21 mo recovery; (2) reinnervated (ObNT-Reinn), after similar decentralization for 12 mo, then bilateral obturator-to-vesical nerve transfer and 8-12 mo recovery; and (3) Controls. In mucosa, BDNF and ROS levels were highest in ObNT-Reinn bladders, GDNF and TNF-α levels were restored to Control levels in ObNT-Reinn bladders (lowest in Decentralized). NT-3 and ARTN were lower in ObNT-Reinn and Decentralized bladders versus Controls. In muscle, ROS was lower in ObNT-Reinn muscle versus Controls. BDNF mucosa levels correlated with bladder axonal density and detrusor layer thickness; and GDNF mucosal correlated with bladder contraction after vesical or transferred obturator nerve electrical stimulation, as did BDNF and GDNF muscle levels. The increased BDNF and GDNF in bladders that underwent somatic nerve transfer with subsequent recovery suggest that BDNF and GDNF may help promote the reestablishment of bladder innervation.

The effects of sex hormones on BDNF secretion in airway smooth muscle of patients with obstructive pulmonary disease

Obstructive pulmonary diseases, including asthma and chronic obstructive pulmonary disease, present significant global public health challenges and substantially impair patients' quality of life. Research indicates that sex hormones and brain-derived neurotrophic factor (BDNF) are pivotal in regulating airway function and inflammatory responses. Specifically, sex hormones modulate the expression and function of BDNF through their receptors, namely estrogen receptors and androgen receptors. Conversely, BDNF enhances cell survival and exerts anti-inflammatory and antioxidant effects, influencing the functionality of sex hormone receptors. This review elucidates the interactions between sex hormones and BDNF in obstructive pulmonary disease, emphasizing their synergistic roles in managing airway inflammation, facilitating tissue repair, and mitigating oxidative stress. Through a thorough examination of these mechanisms, this review aims to foster a more profound comprehension of the potential therapeutic implications for the management of these diseases.

Smoking-Dependent Association of Serum Brain-Derived Neurotrophic Factor with Pulmonary Function Parameters in Chronic Obstructive Pulmonary Disease

Background and Objectives: One of the members of the neurotrophin (NT) family is the brain-derived neurotrophic factor (BDNF). In addition to its role in the nerve system, it has been found to play a role in lung health and diseases. Materials and Methods: The serum concentrations of BDNF were assessed in 57 patients with COPD and in 19 control individuals and the possible associations of BDNF with the spirometric indexes and disease stages were explored. Results: We did not find a significant difference between the serum concentrations of BDNF of patients and controls (p = 0.521). A significant negative correlation of the serum BDNF levels with the age of the patients (Rho = -0.279, p = 0.036) was observed. In addition, a borderline negative correlation with the age of disease onset (Rho= -0.244, p = 0.063) was also found. When analyzing these correlations in different genders, we found stronger statistical significance in male patients (Rho = -0.398, p = 0.009; and Rho = -0.419, p = 0.006), while no such significance was found in females (p = 0.574 and p = 0.342). The analyses of the possible relations of serum BDNF concentration with the spirometric parameters in the whole group of patients did not reveal any significance (p = 0.231 for FEV1%pr. and p = 0.271 for FEV1/FVC%). However, when the patients were dichotomized on the basis of smoking habits, we obtained a strong positive correlation between BDNF and FEV1%pr. (Rho = 0.501, p = 0.048) in non-smokers, but strong negative correlations with FEV1%pr. (Rho = -0.468, p = 0.003) and with FEV1/FVC% (Rho = -0.331, p = 0.040) in ex/current smokers. Non-smokers with moderate disease (GOLD II) had higher BDNF serum concentrations than patients with GOLD stage III/IV (p = 0.031). In ex/current smokers, there was an opposite association (p = 0.045). Conclusions: The results of our study suggest that the expression and secretion of BDNF are changed in COPD, but its effects and functions may differ according to the smoking history of the patients.

Assessment and Management of Cough in Idiopathic Pulmonary Fibrosis: A Narrative Review

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and fatal disease with an unknown cause. It is characterized by symptoms such as cough and breathlessness, which significantly impact patients' quality of life. Cough, in particular, has emerged as a burdensome symptom for individuals with IPF. The etiology of cough in IPF patients is believed to be complex, involving factors related to the disease itself, such as increased sensitivity of cough nerves, lung structural changes, inflammation, and genetic factors, as well as comorbidities and medication effects. Unfortunately, effective treatment options for cough in IPF remain limited, often relying on empirical approaches based on studies involving chronic cough patients in general and the personal experience of physicians. Medications such as opioids and neuromodulators are commonly prescribed but have shown suboptimal efficacy, imposing significant physical, psychological, and economic burdens on patients. However, there is hope on the horizon, as specific purinergic P2 receptor ligand-gated ion channel (P2X3) inhibitors have demonstrated promising antitussive effects in ongoing clinical trials. This review aims to provide a comprehensive overview of the evaluation and management of cough in IPF patients, as well as highlight emerging pharmacological and non-pharmacological approaches that target the cough reflex and are currently being investigated in clinical settings.

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.

Four weeks of repetitive acute hypoxic preconditioning did not alleviate allergen-induced airway dysfunction in rats

Clinical case series suggest beneficial effects of low-dose intermittent hypoxia in asthma. We tested cardiopulmonary effects of repetitive acute hypoxic preconditioning (RAHP) during allergic inflammation. Brown Norway rats were sensitized to house dust mites (HDM) and exposed to 4-week RAHP or normoxia (SHAM), concurrent with weekly HDM or saline (SAL) challenges. We assessed methacholine responses and lung HIF-1α expression at endpoint, and weekly blood pressure (BP). RAHP relative to SHAM: 1) in HDM-challenged rats, showed no protection against HDM-induced airway dysfunction and did not significantly impact BP (week 4 mean BP difference = 10.51 mmHg, p = 0.09) or HIF-1α expression; 2) in SAL-challenged rats, attenuated airway responses to methacholine, reduced BP (week 4 mean BP average difference = -8.72 mmHg, p = 0.04) and amplified HIF-1α expression (p = 0.0086). Four weeks of RAHP did not mitigate the allergen-induced lower airway dysfunction and may detrimentally affect BP. However, it elicited beneficial cardiopulmonary responses in SAL-challenged rats, concurrent with increased HIF-1α expression.

Serum and plasma levels of brain-derived neurotrophic factor in individuals with eating disorders (EDs): a systematic review and meta-analysis

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is essential for neuronal survival, differentiation, development, and plasticity. Evidence suggests that fluctuations in peripheral levels (i.e., plasma or serum) of BDNF are associated with eating behaviors. Nevertheless, the findings are inconsistent. The purpose of this study is to determine if serum or plasma levels of BDNF are altered in individuals with eating disorders (EDs) compared to controls.

METHODS

We conducted a systematic search of the core electronic medical databases from inception to March 2022 and identified observational studies that compared individuals with EDs to controls without EDs on serum or plasma levels of BDNF. R version 4.0.4 was used for all visualizations and calculations.

RESULTS

The current meta-analysis comprised 15 studies that fulfilled the inclusion criteria. Subjects with EDs (n = 795) showed lower BDNF levels compared to non-EDs controls (n = 552) (SMD: - 0.49, 95% CI [- 0.89; - 0.08], p-value = 0.01). Moreover, subgroup analysis was conducted based on the specimen (plasma and serum), which revealed no statistically significant difference in the levels of BDNF between the two subgroups (p-value = 0.92). Additionally, meta-regression results revealed that publication year, mean age of the individuals with EDs, NOS scores, and the number of individuals with EDs collectively accounted for 25.99% percent of the existing heterogeneity.

CONCLUSION

Lower BDNF levels are associated with EDs.

Effect of BDNF on airway inflammation in a rat model of COPD

Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation that is not fully reversible. The airflow limitation is usually progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases. The present study aimed to investigate the effect of brain-derived neurotrophic factor (BDNF) on lung function and airway inflammation in a rat model of COPD. A rat model of COPD was established in this study, and anti-BDNF antibody was injected to observe the effect of BDNF on pulmonary function and airway inflammation. Lung function and hematoxylin and eosin staining analyses were performed. BDNF in the airway was examined using immunohistochemistry, western blotting and enzyme-linked immunosorbent assay. Levels of oxidant stress and inflammatory cytokines were measured. After long-term heavy cigarette exposure, pulmonary inflammation and emphysema were observed, while lung function had deteriorated in the COPD, COPD + anti-BDNF and COPD + normal saline groups. Levels of BDNF expression, malondialdehyde, tumor necrosis factor-α and interleukin-6 were increased in rats with COPD compared with control rats, while levels of superoxide dismutase and glutathione peroxidase were decreased. Anti-BDNF intervention improved airway inflammation. To conclude, anti-BDNF intervention could alleviate inflammation and improve any imbalance between oxidation and antioxidation in the airway.

Pituitary adenylate cyclase activating polypeptide concentrations in the sheep mammary gland, milk, and in the lamb blood plasma after suckling

Pituitary adenylate cyclase activating polypeptide (PACAP) is involved in development and reproduction. We previously described elevated PACAP levels in the milk compared to the plasma, and the presence of its specific PAC1 receptor in the mammary gland. This study aimed to determine PACAP and vasoactive intestinal peptide (VIP) levels in female suckling lambs compared to ewe plasma and mammary gland, as well as their age-dependent alterations. mRNA expressions of PACAP, VIP, PAC1 receptor and brain-derived neurotrophic factor (BDNF) were quantified in the milk whey and mammary gland. PACAP38-like immunoreactivity (PACAP38-LI) was measured in plasma, milk whey and mammary gland by radioimmunoassay, VIP-LI by enzyme-linked immunoassay. PACAP38-LI was 5, 6 times higher in the milk compared to the plasma of lactating sheep. It significantly increased in the lamb plasma 1 h, but returned to basal level 2 h after suckling. However, VIP mRNA was not present in the mammary gland, we detected the VIP protein in the milk whey. BDNF mRNA significantly decreased with age to approximately 60% and 25% in the 3- and 10-year-old sheep respectively, compared to the 3-month-old lambs. No differences were found between mammary and jugular vein plasma PACAP and VIP concentrations, or during the daily cycle. We propose a rapid absorption of PACAP38 from the milk and/or its release in suckling lambs. PACAP accumulated in the milk might be synthesized in the mammary gland or secreted from the plasma of the mothers. PACAP is suggested to have differentiation/proliferation promoting and immunomodulatory effects in the newborns and/or a local function in the mammary gland.

Antidepressants Promote and Prevent Cancers

The review states that antidepressants (ADs) increase brain-derived neurotrophic factor (BDNF) transmission concomitantly in the brain and the blood: ADs increasing BDNF synthesis in specific areas of the central nervous system (CNS) could presumably affect megakaryocyte's production of platelets. ADs increase BDNF levels in the CNS and improve mood. In the blood, ADs increase BDNF release from platelets. The hypothesis presented here is that the release of BDNF from platelets contributes to the ADs effects on neurogenesis and on tumor growth in the cancer disease. Oncological studies indicate that chemicals ADs exert an aggravating effect on the cancer disease, possibly by promoting proplatelets formation and enhancing BDNF release from platelets in the tumor.

Exploring the role of nerves in asthma; insights from the study of cough

Cough in asthma predicts disease severity, prognosis, and is a common and troublesome symptom. Cough is the archetypal airway neuronal reflex, yet little is understood about the underlying neuronal mechanisms. It is generally assumed that symptoms arise because of airway hyper-responsiveness and/or airway inflammation, but despite using inhaled corticosteroids and bronchodilators targeting these pathologies, a large proportion of patients have persistent coughing. This review focuses on the prevalence and impact of cough in asthma and explores data from pre-clinical and clinical studies which have explored neuronal mechanisms of cough and asthma. We present evidence to suggest patients with asthma have evidence of neuronal dysfunction, which is further heightened and exaggerated by both bronchoconstriction and airway eosinophilia. Identifying patients with excessive coughing with asthma may represent a neuro-phenotype and hence developing treatment for this symptom is important for reducing the burden of disease on patients' lives and currently represents a major unmet clinical need.

Upregulation of proBDNF in the Mesenteric Lymph Nodes in Septic Mice

The immune status in the lymphatic system, especially mesenteric lymph nodes (MLNs), is critical to regulate the septic shock. Brain-derived neurotrophic factor (BDNF) in the enteric system has been reported to regulate enteric immunity. However, the role of its precursor, proBDNF, in the immune status of MLNs under sepsis condition is still unclear. This study aimed to characterize the expression pattern of proBDNF in MLNs after lipopolysaccharide (LPS) stimulation, and to investigate the association of pathogenesis of sepsis. LPS (20 mg/kg) was intraperitoneally injected to induce sepsis in mice. Survival curve analysis, routine blood tests, and liver and kidney function tests were performed to evaluate the severity of sepsis. QPCR and histological staining were performed to assess the mRNA levels of proinflammatory cytokines and degree of immune-inflammatory response in the MLNs. Furthermore, Western blotting, flow cytometry, and immunofluorescence were performed to examine the key molecules expression of proBDNF signaling. Intraperitoneal LPS injection significantly decreased the number of lymphocytes in blood but increased the number of T lymphocytes in MLNs. Serum alanine transaminase, aspartate transaminase, and blood urea nitrogen levels were increased in LPS-challenged mice compared to control mice. LPS administration upregulated proinflammatory cytokine gene expression and induced histological changes in the MLNs. LPS injection increased BDNF, proBDNF, and its receptor pan neutrophin receptor 75 (p75^NTR) expression in MLNs. The increased proBDNF was mainly localized on CD3⁺ and CD4⁺ T cells in the medulla of MLNs. LPS-induced sepsis upregulated proBDNF expression in medulla T cells of MLNs. ProBDNF upregulation may be involved in the pathogenesis of septic shock.

Peripheral blood brain-derived neurotrophic factor level and tyrosine kinase B expression on T lymphocytes in systemic lupus erythematosus: Implications for systemic involvement

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) has been reported to be involved in the pathogenesis of autoimmune diseases and tyrosine kinase B (TrkB) is the specific receptor for BDNF. Our aim in this study was to investigate serum BDNF level and TrkB expression on peripheral blood T cell surface in patients with systemic lupus erythematosus (SLE) and explore potential relationship between serum BDNF and SLE.

METHODS

Samples from fifty SLE patients and thirty healthy controls were evaluated. Serum BDNF level was measured by enzyme-linked immunosorbent assay (ELISA) and the percentages of TrkB expression on the surface of CD3 + CD4 + and CD3 + CD8 + T lymphocytes were measured by flow cytometry. The SLE patients were divided into subgroups according to whether they exhibited brain, kidney or lung involvement, and whether the disease was active or inactive.

RESULTS

Serum BDNF levels in SLE patients were decreased when compared to the controls (p < 0.001). Comparing with the SLE individuals without systemic involvement, the BDNF levels were decreased in SLE patients with lupus nephritis (p = 0.042) and in SLE patients with neuropsychiatric manifestations (p = 0.04). On the other hand, the BDNF level was significantly increased in the inactive SLE group (p < 0.001) compared to the active SLE group. In addition, the percentages of TrkB expression on CD3 + CD4 + and CD3 + CD8 + T cell surface in SLE were significantly higher (p < 0.001; p < 0.001, respectively) than that in the controls.

CONCLUSIONS

Serum BDNF level combined with TrkB expression on T cell surface can reflect SLE activity. It is possible that BDNF may be used as a potential serological biomarker for disease activity of SLE. In addition, the significant decrease in serum BDNF level may imply systemic involvement of SLE, as well as, possibly, differentiate neuropsychiatric SLE from hormone-induced mental disorders.

Smooth muscle brain-derived neurotrophic factor contributes to airway hyperreactivity in a mouse model of allergic asthma

Recent studies have demonstrated an effect of neurotrophins, particularly brain-derived neurotrophic factor (BDNF), on airway contractility [ via increased airway smooth muscle (ASM) intracellular calcium [Ca2+]i] and remodeling (ASM proliferation and extracellular matrix formation) in the context of airway disease. In the present study, we examined the role of BDNF in allergen-induced airway inflammation using 2 transgenic models: 1) tropomyosin-related kinase B (TrkB) conditional knockin (TrkBKI) mice allowing for inducible, reversible disruption of BDNF receptor kinase activity by administration of 1NMPP1, a PP1 derivative, and 2) smooth muscle-specific BDNF knockout (BDNFfl/fl/SMMHC11Cre/0) mice. Adult mice were intranasally challenged with PBS or mixed allergen ( Alternaria alternata, Aspergillus fumigatus, house dust mite, and ovalbumin) for 4 wk. Our data show that administration of 1NMPP1 in TrkBKI mice during the 4-wk allergen challenge blunted airway hyperresponsiveness (AHR) and reduced fibronectin mRNA expression in ASM layers but did not reduce inflammation per se. Smooth muscle-specific deletion of BDNF reduced AHR and blunted airway fibrosis but did not significantly alter airway inflammation. Together, our novel data indicate that TrkB signaling is a key modulator of AHR and that smooth muscle-derived BDNF mediates these effects during allergic airway inflammation.-Britt, R. D., Jr., Thompson, M. A., Wicher, S. A., Manlove, L. J., Roesler, A., Fang, Y.-H., Roos, C., Smith, L., Miller, J. D., Pabelick, C. M., Prakash, Y. S. Smooth muscle brain-derived neurotrophic factor contributes to airway hyperreactivity in a mouse model of allergic asthma.

Neurons and Glia in the Enteric Nervous System and Epithelial Barrier Function

The intestinal epithelial barrier is the largest exchange surface between the body and the external environment. Its functions are regulated by luminal, and also internal, components including the enteric nervous system. This review summarizes current knowledge about the role of the digestive "neuronal-glial-epithelial unit" on epithelial barrier function.

The pathogenetic mechanisms of cough in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis is a peripheral subpleural interstitial lung disorder limited to the lung not involving the airways. It has a poor prognosis (survival less than 5 years) and commonly an interstitial pneumonia radiological pattern. Patients complain of a chronic dry cough in 80% of cases. A cough is often the first symptom of this rare disease, preceding dyspnea by years, and is associated with a poor prognosis, high dyspnea scores and low FVC percentages. The pathogenetic mechanisms leading to coughing in IPF are unclear. This review focuses on recent evidence of cough pathophysiology in this disease. Gastroesophageal reflux may promote coughing in IPF patients; bile salts and pepsin may be abundant in BAL of these patients, inducing overproduction of TGF-β by airway epithelial cells and mesenchymal transition with fibroblast recruitment/activation and extracellular matrix deposition. Patients have an enhanced cough reflex to capsaicin and substance P with respect to control subjects. Moreover, patients with the MUC5B polymorphism show more severe coughing as MUC5B encodes for the dominant mucin in the honeycomb cysts of IPF patients. Comorbidities, including asthma, gastroesophageal reflux, hypersensitivity pneumonitis, bronchiectasis, chronic obstructive pulmonary disease and emphysema, can induce coughing in IPF patients. There is no clear explanation of the causes of coughing in IPF. Further research into the pathophysiology of IPF and the pathogenetic mechanisms of coughing is necessary to improve survival and quality of life.

Brain-Derived Neurotrophic Factor in Patients With Age-Related Macular Degeneration and Its Correlation With Retinal Layer Thicknesses

PURPOSE

To determine brain-derived neurotrophic factor (BDNF) levels in serum and aqueous humor (AH) and to assess the relationship between BDNF levels and retinal layer thicknesses in age-related macular degeneration (AMD).

METHODS

A total of 48 AMD patients (AMD group) that was composed of twenty-three nonexudative and 25 exudative patients and 26 control subjects (control group) were included in the study. Serum and AH BDNF levels were assessed by ELISA method. Retinal layer thicknesses were calculated by segmentation analysis of optical coherence tomography.

RESULTS

The mean BDNF levels in AH were found to be significantly lower in both the nonexudative and exudative AMD groups than in the control group (P = 0.003 and P < 0.001, respectively). Optical coherence tomography segmentation analysis revealed that the total average retina pigment epithelium thickness was statistically significantly thinner in the nonexudative AMD group compared with the exudative AMD and control groups (P = 0.001 and P = 0.040, respectively). The total average outer nuclear layer (ONL) thicknesses of nonexudative and exudative AMD cases were reduced compared to control group; however, the decrement was statistically significant only in the nonexudative AMD group (P = 0.009). In the correlation analysis of BDNF levels with retinal layer thicknesses, statistically significant correlations exist between BDNF levels of AH with ONL thicknesses in cases of AMD and with retina pigment epithelium thicknesses in the nonexudative AMD group.

CONCLUSIONS

BDNF concentrations in AH decreased in the AMD group and this decrease correlates with outer retinal layer thicknesses. Low BDNF levels detected in the AMD group may be insufficient to protect the photoreceptors, resulting in thinning of ONL.

Neurotrophins in Asthma

PURPOSE OF REVIEW

Asthma is a chronic airway disease that affects more than 300 million people worldwide. Current treatment focuses on symptomatic relief by temporally dampening inflammation and relaxing the airway. Novel combative strategies against asthma and hopefully a cure are yet to be developed. The goal of this review is to summarize recent literature on neurotrophins (NTs) in experimental models and clinical settings of asthma research.

RECENT FINDINGS

We highlight studies of early phases of asthma that collectively reveal a profound impact of elevated NT levels following initial detrimental insults on long-term airway dysfunction. We hope this review will foster insights into the complex interaction between NTs, nerves, immune cells, and airway structural cells during a critical time window of development and disease susceptibility. Future studies are required to better understand the role of NTs in asthma pathophysiology and to evaluate whether NTs and their receptors may serve as new drug targets.

Brain-derived neurotrophic factor and airway fibrosis in asthma

Airway remodeling in asthma driven by inflammation involves proliferation of epithelial cells and airway smooth muscle (ASM), as well as enhanced extracellular matrix (ECM) generation and deposition, i.e., fibrosis. Accordingly, understanding profibrotic mechanisms is important for developing novel therapeutic strategies in asthma. Recent studies, including our own, have suggested a role for locally produced growth factors such as brain-derived neurotrophic factor (BDNF) in mediating and modulating inflammation effects. In this study, we explored the profibrotic influence of BDNF in the context of asthma by examining expression, activity, and deposition of ECM proteins in primary ASM cells isolated from asthmatic vs. nonasthmatic patients. Basal BDNF expression and secretion, and levels of the high-affinity BDNF receptor TrkB, were higher in asthmatic ASM. Exogenous BDNF significantly increased ECM production and deposition, especially of collagen-1 and collagen-3 (less so fibronectin) and the activity of matrix metalloproteinases (MMP-2, MMP-9). Exposure to the proinflammatory cytokine TNFα significantly increased BDNF secretion, particularly in asthmatic ASM, whereas no significant changes were observed with IL-13. Chelation of BDNF using TrkB-Fc reversed TNFα-induced increase in ECM deposition. Conditioned media from asthmatic ASM enhanced ECM generation in nonasthmatic ASM, which was blunted by BDNF chelation. Inflammation-induced changes in MMP-2, MMP-9, and tissue inhibitor metalloproteinases (TIMP-1, TIMP-2) were reversed in the presence of TrkB-Fc. These novel data suggest ASM as an inflammation-sensitive source of BDNF within human airways, with autocrine effects on fibrosis relevant to asthma.

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.

Correlation of 5-HTT, BDNF and NPSR1 gene polymorphisms with anxiety and depression in asthmatic patients

Asthmatic patients are known to have a higher risk of anxiety and depression. In the present study, we aimed to explore the association of serotonin transporter (5-HTT), brain-derived neurotrophic factor (BDNF) and neuropeptide S receptor 1 (NPSR1) gene polymorphisms with anxiety and depression in asthmatic patients. This was a cross-sectional study conducted on 143 asthmatic patients and 175 healthy volunteers. Of the asthmatic patients, 49 suffered from anxiety and 12 exhibited signs of depression. Patients with a lower level of education were more prone to depression. Both anxiety and depression were associated with poor asthma control as evaluated by the Asthma Control Test (ACT) score. The association of single nucleotide polymorphisms of BDNF, NPSR1 and 5-HTT with anxiety and depression in asthamtic patients was evaluated. The distribution of 5-HTT gene polymorphisms in the healthy group, the group with asthma but without anxiety, and the group with asthma and anxiety had significant differences. Females with asthma and anxiety were more prone to BDNF polymorphism. Also, BDNF gene distribution exhibited significant differences among those in the healthy group, the group with asthma but no depression, and the group with asthma and depression; however, NPSR1 gene distribution did not vary greatly between the groups. The anxiety score was significantly affected by the interaction between 5-HTT (LL, S⁺) and BDNF (A⁺, GG) (H=5.99, P=0.015). The depression score was significantly affected by the interaction between BDNF (A⁺, GG) and NPSR1 (AA, T⁺). We noted that both anxiety and depression led to poor asthma control. The interaction between 5-HTT (LL) and BDNF (A⁺) increased the risk of anxiety, and the interaction between BDNF (A⁺, GG) and NPSR1 (AA, T⁺) increased the risk of depression in asthmatic patients.

Steroid Treatment Reduces Allergic Airway Inflammation and Does Not Alter the Increased Numbers of Dendritic Cells and Calcitonin Gene-Related Peptide-Expressing Neurons in Airway Sensory Ganglia

OBJECTIVES

Our previous data demonstrated that allergic airway inflammation induces migration of dendritic cells (DC) into airway sensory jugular and nodose ganglia (jugular-nodose ganglion complex; JNC). Here we investigated the effects of steroid treatment regarding the expression and migration of DC and calcitonin gene-related peptide (CGRP)-immunoreactive neurons of vagal sensory ganglia during allergic airway inflammation.

METHODS

A house dust mite (HDM) model for allergic airway inflammation was used. The mice received 0.3 mg fluticasone propionate per kilogram of body weight in the last 9 days. JNC slices were analyzed on MHC II, the neuronal marker PGP9.5, and the neuropeptide CGRP.

RESULTS

Allergic airway inflammation increased the numbers of DC and CGRP-expressing neurons in the JNC significantly in comparison to the controls (DC/neurons: HDM 44.58 ± 1.6% vs. saline 33.29 ± 1.6%, p < 0.05; CGRP-positive neurons/total neurons: HDM 30.65 ± 1.9% vs. saline 19.49 ± 2.3%, p < 0.05). Steroid treatment did not have any effect on the numbers of DC and CGRP-expressing neurons in the JNC compared to HDM-treated mice.

CONCLUSIONS

The present findings indicate an important role of DC and CGRP-containing neurons in the pathogenesis of allergic airway inflammation. However, steroid treatment did not have an effect on the population of DC and neurons displaying CGRP in the JNC, whereas steroid treatment was found to suppress allergic airway inflammation.

Association between Val66Met polymorphisms in brain-derived neurotrophic factor gene and asthma risk: a meta-analysis

OBJECTIVE

The Val66Met polymorphisms in brain-derived neurotrophic factor (BDNF) gene have been reported to be associated with asthma risk, while the results are inconclusive. Considering a single study may lack the power to provide reliable conclusion, we performed a meta-analysis to investigate the association between the Val66Met polymorphisms and asthma susceptibility.

METHODS

A comprehensive literature search of PubMed, Embase, China National Knowledge Infrastructure (CNKI) and Wanfang databases was conducted before February 12, 2015. The pooled odds ratio (OR) with 95 % confidence intervals (CIs) were calculated.

RESULTS

Six eligible studies with a total of 3501 subjects were finally included in this meta-analysis. Overall, a significantly increased risk was detected in the Val66Met G allele (G vs. A: OR 1.33, 95 % CI 1.19-1.49, P = 5.61E-07; GG vs. GA + AA: OR 1.48, 95 % CI 1.20-1.83, P = 3.14E-04; GG vs. GA: OR 1.48, 95 % CI 1.17-1.89, P = 0.001; GG vs. AA: OR 1.62, 95 % CI 1.20-2.19, P = 0.002). Moreover, stratification by ethnicity indicated marked association between the Val66Met G allele and asthma risk in Caucasians (G vs. A: OR 1.29, 95 % CI 1.12-1.49, P = 0.001; GG + GA vs. AA: OR 1.59, 95 % CI 1.03-2.46, P = 0.039; GG vs. GA + AA: OR 1.32, 95 % CI 1.11-1.57, P = 0.001; GG vs. GA: OR 1.28, 95 % CI 1.07-1.53, P = 0.007; GG vs. AA: OR 1.72, 95 % CI 1.11-2.68, P = 0.015).

CONCLUSION

Our present meta-analysis suggests that the Val66Met polymorphisms in BDNF gene are potentially associated with asthma risk in Caucasians. Further well-designed case-control studies with larger sample size and more ethnic groups are needed to confirm these conclusions.

Peripheral BDNF: a candidate biomarker of healthy neural activity during learning is disrupted in schizophrenia

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is an important regulator of synaptogenesis and synaptic plasticity underlying learning. However, a relationship between circulating BDNF levels and brain activity during learning has not been demonstrated in humans. Reduced brain BDNF levels are found in schizophrenia and functional neuroimaging studies of probabilistic association learning in schizophrenia have demonstrated reduced activity in a neural network that includes the prefrontal and parietal cortices and the caudate nucleus. We predicted that brain activity would correlate positively with peripheral BDNF levels during probabilistic association learning in healthy adults and that this relationship would be altered in schizophrenia.

METHOD

Twenty-five healthy adults and 17 people with schizophrenia or schizo-affective disorder performed a probabilistic association learning test during functional magnetic resonance imaging (fMRI). Plasma BDNF levels were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

We found a positive correlation between circulating plasma BDNF levels and brain activity in the parietal cortex in healthy adults. There was no relationship between plasma BDNF levels and task-related activity in the prefrontal, parietal or caudate regions in schizophrenia. A direct comparison of these relationships between groups revealed a significant diagnostic difference.

CONCLUSIONS

This is the first study to show a relationship between peripheral BDNF levels and cortical activity during learning, suggesting that plasma BDNF levels may reflect learning-related brain activity in healthy humans. The lack of relationship between plasma BDNF and task-related brain activity in patients suggests that circulating blood BDNF may not be indicative of learning-dependent brain activity in schizophrenia.

Riluzole stimulates BDNF release from human platelets

Brain-derived neurotrophic factor (BDNF) has several functions in the central nervous system, where it contributes to brain development and its functionality through affecting neuronal survival and activity and also modulating neurotransmitter levels. This neurotrophin is also found in the serum, but its origin and peripheral function remain unknown. Although the source of circulating BDNF is uncertain, it is stored in platelets and can be released through pharmacological treatment. Decreased levels of BDNF in the serum have been related to the pathophysiology of depression, and this relationship is reinforced by the reversal of this condition by treatment with antidepressants. Recently, riluzole has been proposed for the treatment of depression because it has the ability to lower extracellular glutamate levels and increase BDNF expression; and both mechanisms could be associated with its antidepressant action. Considering that riluzole enhances BDNF levels in the serum of patients, we investigated if treatment with this drug could stimulate the release of this neurotrophin from human platelets obtained from healthy subjects. When platelets were incubated with riluzole for 4 h, the basal value of BDNF (92.9 ± 11.1 pg 10(-6) platelets) was significantly increased (P < 0.05, n = 27). This stimulatory effect was achieved at low concentrations of riluzole (from 10 µM) and was not observed when platelets were incubated with the drug for 24 h. The direct action of riluzole evoking BDNF release from human platelets at therapeutic concentrations is important and may contribute to the understanding of its mechanisms of action in the treatment of depression.

Allergic airway inflammation induces the migration of dendritic cells into airway sensory ganglia

BACKGROUND

A neuroimmune crosstalk between dendritic cells (DCs) and airway nerves in the lung has recently been reported. However, the presence of DCs in airway sensory ganglia under normal and allergic conditions has not been explored so far. Therefore, this study aims to investigate the localisation, distribution and proliferation of DCs in airway sensory ganglia under allergic airway inflammation.

METHODS

Using the house dust mite (HDM) model for allergic airway inflammation BALB/c mice were exposed to HDM extract intranasally (25 μg/50 μl) for 5 consecutive days a week over 7 weeks. With the help of the immunohistochemistry, vagal jugular-nodose ganglia complex (JNC) sections were analysed regarding their expression of DC-markers (MHC II, CD11c, CD103), the neuronal marker PGP 9.5 and the neuropeptide calcitonin gene-related peptide (CGRP) and glutamine synthetase (GS) as a marker for satellite glia cells (SGCs). To address the original source of DCs in sensory ganglia, a proliferation experiment was also carried in this study.

RESULTS

Immune cells with characteristic DC-phenotype were found to be closely located to SGCs and vagal sensory neurons under physiological conditions. The percentage of DCs in relation to neurons was significantly increased by allergic airway inflammation in comparison to the controls (HDM 51.38 ± 2.38% vs. control 28.16 ± 2.86%, p < 0.001). The present study also demonstrated that DCs were shown to proliferate in jugular-nodose ganglia, however, the proliferation rate of DCs is not significantly changed in the two treated animal groups (proliferating DCs/ total DCs: HDM 0.89 ± 0.38%, vs. control 1.19 ± 0.54%, p = 0.68). Also, increased number of CGRP-positive neurons was found in JNC after allergic sensitisation and challenge (HDM 31.16 ± 5.41% vs. control 7.16 ± 1.53%, p < 0.001).

CONCLUSION

The present findings suggest that DCs may migrate from outside into the ganglia to interact with sensory neurons enhancing or protecting the allergic airway inflammation. The increase of DCs as well as CGRP-positive neurons in airway ganglia by allergic airway inflammation indicate that intraganglionic DCs and neurons expressing CGRP may contribute to the pathogenesis of bronchial asthma. To understand this neuroimmune interaction in allergic airway inflammation further functional experiments should be carried out in future studies.

Neurotrophin receptor TrkB promotes lung adenocarcinoma metastasis

Lung cancer is notorious for its ability to metastasize, but the pathways regulating lung cancer metastasis are largely unknown. An in vitro system designed to discover factors critical for lung cancer cell migration identified brain-derived neurotrophic factor, which stimulates cell migration through activation of tropomyosin-related kinase B (TrkB; also called NTRK2). Knockdown of TrkB in human lung cancer cell lines significantly decreased their migratory and metastatic ability in vitro and in vivo. In an autochthonous lung adenocarcinoma model driven by activated oncogenic Kras and p53 loss, TrkB deficiency significantly reduced metastasis. Hypoxia-inducible factor-1 directly regulated TrkB expression, and, in turn, TrkB activated Akt signaling in metastatic lung cancer cells. Finally, TrkB expression was correlated with metastasis in patient samples, and TrkB was detected more often in tumors that did not have Kras or epidermal growth factor receptor mutations. These studies demonstrate that TrkB is an important therapeutic target in metastatic lung adenocarcinoma.

Participation of the neutrophin brain-derived neurotrophic factor in neuropsychiatric systemic lupus erythematosus

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) is associated with the pathogenesis of several neuropsychiatric (NP) diseases, but there are few studies involving SLE. The aim of this study was to investigate whether plasma BDNF levels are associated with disease activity in SLE patients with severe NPSLE and non-NPSLE manifestations.

METHODS

We assessed 131 SLE patients and 24 randomly selected healthy individuals. SLE patients were evaluated in a cross-sectional study allocated according to the presence or not of NP manifestations and disease activity: (i) active NPSLE (n = 40), (ii) inactive NPSLE (n = 26), (iii) active SLE (n = 29) and (iv) inactive SLE (n = 36). In addition, NPSLE patients (n = 40) were evaluated before and after treatment. Disease activity was assessed according to the SLEDAI score. The plasma BDNF was measured by ELISA.

RESULTS

BDNF levels were increased in inactive NPSLE when compared with active SLE and controls (P < 0.0001). We observed similar findings in inactive SLE when compared with active SLE (P < 0.0001). In addition, we found an inverse correlation between plasma BDNF levels and the SLEDAI (r = -0.54, P < 0.0001) and a positive correlation with complement levels. We also observed an increase in BDNF levels in parallel with the improvement in NP symptoms.

CONCLUSION

Plasma BDNF level is increased in SLE patients and this increase is independent of the occurrence of NP manifestations. In addition, plasma BDNF levels increased with control of SLE activity, which points to the potential use of BDNF as a biomarker of response to treatment.

Effects of fluoxetine on brain-derived neurotrophic factor serum concentration and cognition in patients with vascular dementia

Background

Selective serotonin reuptake inhibitors improve cognition in patients with stroke and increase the expression of brain-derived neurotrophic factor (BDNF) in the rat hippocampus. However, the effects of selective serotonin reuptake inhibitors on cognition and serum BDNF levels in patients with vascular dementia are largely unknown. We performed an open-label study to investigate the effects of fluoxetine, a selective serotonin reuptake inhibitor, on cognition and serum BDNF levels in patients with vascular dementia.

Methods

Fifty patients with vascular dementia were randomly allocated to receive fluoxetine (20 mg/day; n=25) or no fluoxetine (control group; n=25) for 12 weeks. Both groups received secondary prevention of stroke. Serum BDNF level, Mini-Mental State Examination (MMSE) score, Ten-Point Clock Drawing score, and Digit Span Test and Verbal Fluency Test scores were measured at baseline and at week 12 in the both groups.

Results

The baseline serum BDNF level correlated significantly with the MMSE score. MMSE score, Ten-Point Clock Drawing score, and serum BDNF level increased significantly in the fluoxetine group but not in the control group. The increase in serum BDNF level correlated with the increase in MMSE score in the fluoxetine group.

Conclusion

Fluoxetine may potentially improve cognition in patients with vascular dementia and requires further investigation. BDNF may play an important role in cognitive recovery.

TRPC3 regulates release of brain-derived neurotrophic factor from human airway smooth muscle

Exogenous brain-derived neurotrophic factor (BDNF) enhances Ca(2+) signaling and cell proliferation in human airway smooth muscle (ASM), especially with inflammation. Human ASM also expresses BDNF, raising the potential for autocrine/paracrine effects. The mechanisms by which ASM BDNF secretion occurs are not known. Transient receptor potential channels (TRPCs) regulate a variety of intracellular processes including store-operated Ca(2+) entry (SOCE; including in ASM) and secretion of factors such as cytokines. In human ASM, we tested the hypothesis that TRPC3 regulates BDNF secretion. At baseline, intracellular BDNF was present, and BDNF secretion was detectable by enzyme linked immunosorbent assay (ELISA) of cell supernatants or by real-time fluorescence imaging of cells transfected with GFP-BDNF vector. Exposure to the pro-inflammatory cytokine tumor necrosis factor-alpha (TNFα) (20ng/ml, 48h) or a mixture of allergens (ovalbumin, house dust mite, Alternaria, and Aspergillus extracts) significantly enhanced BDNF secretion and increased TRPC3 expression. TRPC3 knockdown (siRNA or inhibitor Pyr3; 10μM) blunted BDNF secretion, and prevented inflammation effects. Chelation of extracellular Ca(2+) (EGTA; 1mM) or intracellular Ca(2+) (BAPTA; 5μM) significantly reduced secreted BDNF, as did the knockdown of SOCE proteins STIM1 and Orai1 or plasma membrane caveolin-1. Functionally, secreted BDNF had autocrine effects suggested by phosphorylation of high-affinity tropomyosin-related kinase TrkB receptor, prevented by chelating extracellular BDNF with chimeric TrkB-Fc. These data emphasize the role of TRPC3 and Ca(2+) influx in the regulation of BDNF secretion by human ASM and the enhancing effects of inflammation. Given the BDNF effects on Ca(2+) and cell proliferation, BDNF secretion may contribute to altered airway structure and function in diseases such as asthma.

Association between brain-derived neurothropic factor variants and asthma in Chinese Han children

AIM

To identify the markers contributing to genetic susceptibility to asthma in Chinese Han children.

METHODS

This study examined the potential association between childhood asthma and seven single nucleotide polymorphisms of Brain-derived Neurotrophic Factor (BDNF) - SNPs, rs16917204, rs6265, rs7103873, rs16917237, rs56164415, rs13306221 and rs10767664 - using the MassARRAY system. The participants, recruited between May 2009 and July 2012, were 319 children with asthma (mean age 9.82 ± 1.57 years) recruited from a hospital paediatric department and 309 healthy controls (mean age 10.25 ± 1.36 years), recruited from the medical examination centre at the same hospital.

RESULTS

We observed a significant association for rs6265 (χ(2)  = 9.851, p = 0.002, OR = 1.427, 95% CI = 1.143-1.783), located in exon 4 of the BDNF. Another potential association was observed for rs13306221 (χ(2)  = 4.316, p = 0.038, OR = 1.604, 95% CI = 1.024-2.512) in the promoter region of the BDNF. Strong linkage disequilibrium was observed in block 1 (D' > 0.9). Significantly more G-G-G haplotypes in block 1 were found in children with asthma.

CONCLUSIONS

These findings point to a role for BDNF polymorphisms in Chinese Han children with asthma and may inform future genetic or biological studies on childhood asthma.

Stage-dependent association of BDNF and TGF-β1 with lung function in stable COPD

Background

Chronic Obstructive Pulmonary Disease (COPD) is characterised by complex inflammatory, neuronal and fibrotic changes. Brain-derived Neurotrophic Factor (BDNF) is a key regulator of neuronal plasticity, whereas Transforming Growth Factor-β₁ (TGF-β₁) plays a crucial role in tissue repair and emphysema pathogenesis. Both mediators are stored in platelets and released from platelets in inflammatory conditions and during serum preparation. In patients with asthma, it was previously shown that elevated serum BDNF concentrations correlate with disease severity, whereas TGF-β₁ concentrations were normal.

Methods

In the present study, 63 patients with stable COPD (spirometric GOLD stages 2–4) and 17 age- and comorbidity-matched controls were studied. Lung function, smoking history, medication, platelet concentrations in peripheral blood and serum concentrations of BDNF, TGF-β₁ and Serotonin (5-HT) were assessed in all participants.

Results

Serum levels of both BDNF and TGF-β₁ (but not concentrations of platelets in peripheral blood) were significantly elevated in all stages of COPD as compared to controls. Highest BDNF concentrations were found in spirometric GOLD stage 3, whereas highest TGF-β₁ serum levels were found in spirometric GOLD stage 4. There were specific, stage-dependent correlations of these mediators with lung function parameters of the patients.

Conclusions

Taken together, we show that, in contrast to asthma, COPD is characterised by elevated concentrations of both BDNF and TGF-β₁ in serum. The stage-dependent association with lung function supports the hypothesis that these platelet mediators may play a role in the pathogenesis of COPD.

BDNF gene therapy induces auditory nerve survival and fiber sprouting in deaf Pou4f3 mutant mice

Current therapy for patients with hereditary absence of cochlear hair cells, who have severe or profound deafness, is restricted to cochlear implantation, a procedure that requires survival of the auditory nerve. Mouse mutations that serve as models for genetic deafness can be utilized for developing and enhancing therapies for hereditary deafness. A mouse with Pou4f3 loss of function has no hair cells and a subsequent, progressive degeneration of auditory neurons. Here we tested the influence of neurotrophin gene therapy on auditory nerve survival and peripheral sprouting in Pou4f3 mouse ears. BDNF gene transfer enhanced preservation of auditory neurons compared to control ears, in which nearly all neurons degenerated. Surviving neurons in treated ears exhibited pronounced sprouting of nerve fibers into the auditory epithelium, despite the absence of hair cells. This enhanced nerve survival and regenerative sprouting may improve the outcome of cochlear implant therapy in patients with hereditary deafness.

A Review of Brain-derived Neurotrophic Factor as a Candidate Biomarker in Schizophrenia

Brain-derived neurotrophic factor (BDNF), a neurotrophin known to be responsible for development, regeneration, survival and maintenance of neurons has been implicated in the pathophysiology of schizophrenia. This review seeks to complement previous reviews on biological roles of BDNF and summarizes evidence on the involvement of BDNF in the pathophysiology of schizophrenia with an emphasis on clinical relevance. The expressions of BDNF were altered in patients with schizophrenia and were found to be correlated with psychotic symptomatology. Antipsychotics appeared to have differential effects on expression of BDNF but did not restore BDNF expression of patients with schizophrenia to normal levels. In addition, evidence suggests that BDNF is involved in the major neurotransmitter systems and is associated with disruptions in brain structure, neurodevelopmental process, cognitive function, metabolic and immune systems commonly associated with schizophrenia. Besides that, BDNF has been demonstrated to be tightly regulated with estrogen which has also been previously implicated in schizophrenia. Evidence gathered in this review confirms the relevance of BDNF in the pathophysiology of schizophrenia and the potential utility of BDNF as a suitable biomarker for diagnostic and prognostic purposes for disease outcome and other co-morbidities. However, further investigations are warranted to examine the specificity of BDNF in schizophrenia compared to other neurodegenerative disorders and other neuropsychiatric illness. Longitudinal prospective studies will also be of added advantage for evaluation of prognostic utility of BDNF in schizophrenia.

Hemodialysis decreases serum brain-derived neurotrophic factor concentration in humans

In the present study we have evaluated the effect of a single hemodialysis session on the brain-derived neurotrophic factor levels in plasma [BDNF](pl) and in serum [BDNF](s) as well as on the plasma isoprostanes concentration [F(2) isoprostanes](pl), plasma total antioxidant capacity (TAC) and plasma cortisol levels in chronic kidney disease patients. Twenty male patients (age 69.8 ± 2.9 years (mean ± SE)) with end-stage renal disease undergoing maintenance hemodialysis on regular dialysis treatment for 15-71 months participated in this study. A single hemodialysis session, lasting 4.2 ± 0.1 h, resulted in a decrease (P = 0.014) in [BDNF](s) by ~42 % (2,574 ± 322 vs. 1,492 ± 327 pg ml(-1)). This was accompanied by an increase (P < 10(-4)) of [F(2)-Isoprostanes](pl) (38 ± 3 vs. 116 ± 16 pg ml(-1)), decrease (P < 10(-4)) in TAC (1,483 ± 41 vs. 983 ± 35 trolox equivalents, μmol l(-1)) and a decrease (P = 0.004) in plasma cortisol level (449.5 ± 101.2 vs. 315.3 ± 196.3 nmol l(-1)). No changes (P > 0.05) in [BDNF](pl) and the platelets count were observed after a single dialysis session. Furthermore, basal [BDNF](s) in the chronic kidney disease patients was significantly lower (P = 0.03) when compared to the age-matched control group (n = 23). We have concluded that the observed decrease in serum BDNF level after hemodialysis accompanied by elevated [F(2)-Isoprostanes](pl) and decreased plasma TAC might be caused by enhanced oxidative stress induced by hemodialysis.

Are mouse models of asthma appropriate for investigating the pathogenesis of airway hyper-responsiveness?

Whether mouse models of chronic asthma can be used to investigate the relationship between airway inflammation/remodeling and airway hyper-responsiveness (AHR) is a vexed question. It raises issues about the extent to which such models replicate key features of the human disease. Here, we review some of the characteristic pathological features of human asthma and their relationship to AHR and examine some limitations of mouse models that are commonly used to investigate these relationships. We compare these conventional models with our mouse model of chronic asthma involving long-term low-level inhalational challenge and review studies of the relationship between inflammation/remodeling and AHR in this model and its derivatives, including models of an acute exacerbation of chronic asthma and of the induction phase of childhood asthma. We conclude that while extrapolating from studies in mouse models to AHR in humans requires cautious interpretation, such experimental work can provide significant insights into the pathogenesis of airway responsiveness and its molecular and cellular regulation.

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.

TRPV1 induction in airway vagal low-threshold mechanosensory neurons by allergen challenge and neurotrophic factors

We addressed the hypothesis that allergic inflammation in guinea pig airways leads to a phenotypic switch in vagal tracheal cough-causing, low-threshold mechanosensitive Aδ neurons, such that they begin expressing functional transient receptor potential vanilloid (TRPV1) channels. Guinea pigs were actively sensitized to ovalbumin (OVA) and beginning 21 days later exposed via aerosol to OVA daily for 3 days. Tracheal-specific neurons were identified in the nodose ganglion using retrograde tracing techniques. Tracheal specific neurons were isolated, and mRNA expression was evaluated at the single-neuron level using RT-PCR analysis. Electrophysiological studies have revealed that the vast majority of vagal nodose afferent nerves innervating the trachea are capsaicin-insensitive Aδ-fibers. Consistent with this, we found <20% of these neurons express TRPV1 mRNA or respond to capsaicin in a calcium assay. Allergen exposure induced de novo TRPV1 mRNA in a majority of the tracheal-specific nodose neurons (P < 0.05). The allergen-induced TRPV1 induction was mimicked by applying either brain-derived neurotrophic factor (BDNF) or glial-derived neurotrophic factor (GDNF) to the tracheal lumen. The BDNF-induced phenotypic change observed at the level of mRNA expression was mimicked using a calcium assay to assess functional TRPV1 ion channels. Finally, OVA exposure induced BDNF and GDNF production in the tracheal epithelium, the immediate vicinity of the nodose Aδ -fibers terminations. The induction of TRPV1 in nodose tracheal Aδ -fibers would substantively expand the nature of stimuli capable of activating these cough-causing nerves.

Functional biomarkers of depression: diagnosis, treatment, and pathophysiology

Major depressive disorder (MDD) is a heterogeneous illness for which there are currently no effective methods to objectively assess severity, endophenotypes, or response to treatment. Increasing evidence suggests that circulating levels of peripheral/serum growth factors and cytokines are altered in patients with MDD, and that antidepressant treatments reverse or normalize these effects. Furthermore, there is a large body of literature demonstrating that MDD is associated with changes in endocrine and metabolic factors. Here we provide a brief overview of the evidence that peripheral growth factors, pro-inflammatory cytokines, endocrine factors, and metabolic markers contribute to the pathophysiology of MDD and antidepressant response. Recent preclinical studies demonstrating that peripheral growth factors and cytokines influence brain function and behavior are also discussed along with their implications for diagnosing and treating patients with MDD. Together, these studies highlight the need to develop a biomarker panel for depression that aims to profile diverse peripheral factors that together provide a biological signature of MDD subtypes as well as treatment response.

Early reactions of brain-derived neurotrophic factor in plasma (pBDNF) and outcome to acute antidepressant treatment in patients with Major Depression

In Major Depressive Disorder, a growing data base suggests that the onset of antidepressants' action can be detected by improvement of depressive symptoms in the first 10-14 days of treatment. Previous studies showed that the mean concentration of the brain-derived neurotrophic factor (BDNF) in blood increases during antidepressant treatment and positively correlates with amelioration of MDD symptoms. We previously showed an association between very early changes of the serum BDNF concentration and treatment outcome (Tadić et al., 2011. Prog Neuropsychopharmacol Biol Psychiatry 35, 415-420). However, no study has yet investigated whether BDNF concentration in plasma increases in the early course of treatment and enables the prediction of final treatment outcome. The goal of this study was to investigate in MDD patients, whether the change of pBDNF in the early course of treatment is a specific and sensitive marker for final treatment outcome. For this purpose, we performed a naturalistic pilot study with 39 inpatients with MDD according to DSM-IV. Depression severity and pBDNF were measured in weekly intervals from baseline (EP) to endpoint (EP, max. week six) with the 21-item Hamilton Depression Rating Scale (HAMD-21) and enzyme-linked immunosorbent assay (ELISA), respectively. According to ROC-analysis, the best cut-off value for the prediction of response at EP is an increase of 338 pg/ml or 126%, respectively, of pBDNF between BL and day 7. The single markers pBDNF change and HAMD-21 improvement from BL-d7 predicted later treatment outcome with moderate to high sensitivity and specificity (pBDNF: 42% and 96%, resp.; HAMD improvement: 83% and 65%, resp.). The combined marker early pBDNF change plus HAMD-21 improvement at day 7 increased the specificity for response to 100%. Our data provide first preliminary evidence that an early change of pBDNF in conjunction with early improvement might be a peripheral marker predictive for treatment outcome in patients with MDD. This has to be confirmed in further investigations. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Genetic variation in BDNF is associated with allergic asthma and allergic rhinitis in an ethnic Chinese population in Singapore

Allergic diseases affect more than 25% of the world population and result from a complex interplay between genetic and environmental factors. Recent evidence has shown that BDNF (Brain Derived Neurotrophic Factor) could serve as an important marker of allergic disease. Increased levels of BDNF in blood, bronchoalveolar lavage fluid and nasal lavage fluid positively correlate with disease activity and severity in patients with allergic rhinitis (AR), asthma and atopic eczema. However, reports on the association between genetic variation in BDNF and allergic disease have been controversial. This study therefore aims to clarify the relationship between single nucleotide polymorphisms (SNPs) in BDNF and a genetic predisposition to AR and asthma in an ethnic Chinese population of Singapore. Volunteers with a self-reported history of asthma (718 subjects) or a history of AR as determined by a researcher-administered questionnaire (795 subjects) were used in this study, alongside controls with no personal or family history of allergy (717 subjects). The association results identified a significant association for the tagSNP rs10767664 with a significant PDominant=0.0007 and OR=1.3 for AR and PDominant=0.0005 and OR=1.3 for asthma (using a dominant model of association). The haplotype based analysis also identified a significant association further confirming the single SNP association. The SNP rs10767664 is strongly linked (r2=0.95) to the functional polymorphism rs6265 (Val66Met), which has previously been reported to be associated to allergic phenotypes and also shown to affect BDNF expression. BDNF is a therefore a key molecular player in allergy. Further studies on polymorphisms within BDNF may shed light on its role in the pathogenesis of allergic diseases and potentially serve as biomarkers for allergic disease.

The lighter side of BDNF

Brain-derived neurotrophic factor (BDNF) mediates energy metabolism and feeding behavior. As a neurotrophin, BDNF promotes neuronal differentiation, survival during early development, adult neurogenesis, and neural plasticity; thus, there is the potential that BDNF could modify circuits important to eating behavior and energy expenditure. The possibility that "faulty" circuits could be remodeled by BDNF is an exciting concept for new therapies for obesity and eating disorders. In the hypothalamus, BDNF and its receptor, tropomyosin-related kinase B (TrkB), are extensively expressed in areas associated with feeding and metabolism. Hypothalamic BDNF and TrkB appear to inhibit food intake and increase energy expenditure, leading to negative energy balance. In the hippocampus, the involvement of BDNF in neural plasticity and neurogenesis is important to learning and memory, but less is known about how BDNF participates in energy homeostasis. We review current research about BDNF in specific brain locations related to energy balance, environmental, and behavioral influences on BDNF expression and the possibility that BDNF may influence energy homeostasis via its role in neurogenesis and neural plasticity.

Peripheral BDNF produces antidepressant-like effects in cellular and behavioral models

Recent clinical studies demonstrate that serum levels of brain-derived neurotrophic factor (BDNF) are significantly decreased in patients with major depressive disorder (MDD) and that antidepressant treatments reverse this effect, indicating that serum BDNF is a biomarker of MDD. These findings raise the possibility that serum BDNF may also have effects on neuronal activity and behavior, but the functional significance of altered serum BDNF is unknown. To address this issue, we determined the influence of peripheral BDNF administration on depression- and anxiety-like behavior, including the forced swim test (FST), chronic unpredictable stress (CUS)/anhedonia, novelty-induced hypophagia (NIH) test, and elevated-plus maze (EPM). Furthermore, we examined adult hippocampal neurogenesis as well as hippocampal and striatal expression of BDNF, extracellular signal-regulated kinase (ERK) and cAMP response element-binding protein (CREB), in order to determine whether peripherally administered BDNF produces antidepressant-like cellular responses in the brain. Peripheral BDNF administration increased mobility in the FST, attenuated the effects of CUS on sucrose consumption, decreased latency in the NIH test, and increased time spent in the open arms of an EPM. Moreover, adult hippocampal neurogenesis was increased after chronic, peripheral BDNF administration. We also found that BDNF levels as well as expression of pCREB and pERK were elevated in the hippocampus of adult mice receiving peripheral BDNF. Taken together, these results indicate that peripheral/serum BDNF may not only represent a biomarker of MDD, but also have functional consequences on molecular signaling substrates, neurogenesis, and behavior.

BDNF Val66Met polymorphism and brain volumes in multiple sclerosis

Brain derived neurotrophic factor (BDNF) regulates several CNS physiological and pathological processes. To investigate in multiple sclerosis (MS) patients, the relationship between the Val66Met polymorphism of BDNF and clinical markers of disease activity and MRI markers of focal and diffuse brain pathologies. 45 MS patients and 34 healthy controls (HCs) were genotyped and subjected to clinical-MRI examination. Global white matter fraction (gWM-f), gray matter-f (GM-f), cerebrospinal fluid-f (CSF-f), and abnormal WM-f were measured. We studied 26 Val/Val and 19 Val/Met patients and 23 Val/Val and 11 Val/Met HCs. We found that Val/Val patients had lower GM-f and higher CSF-f than Val/Val HCs; such differences were not statistically significant comparing Val/Met patients to HCs. The regression analysis showed that both Val/Met genotype and relapse number were associated with lower CSF-f. Our data suggest that Met allele might be a protective factor against MS as it is associated to a lower brain atrophy.

Plasma brain-derived neurotrophic factor levels are associated with clinical severity in school age children with asthma

BACKGROUND

Asthma is characterized by chronic inflammation of the airways with significant changes in leucocyte trafficking, cellular activation and tissue remodelling. Brain-derived neurotrophic factor (BDNF) has been involved with asthma and allergic diseases but its role as a severity marker in paediatric asthma has not been clinically assessed.

OBJECTIVES

To evaluate plasma BDNF and inflammatory markers in order to address their relationships with disease severity in children (6-15 years) with controlled persistent asthma.

METHODS

Children with persistent asthma were selected and lung function and skin prick tests were performed in all patients. Plasma BDNF levels and various inflammatory markers (CCL3, CCL11, CCL22, CCL24, CXCL8, CXCL9, CXCL10, soluble TNF receptors) were assessed by ELISAs.

RESULTS

Subjects with moderate and severe asthma had higher BDNF levels than mild asthma and controls (P<0.001). The chemokines studied and soluble TNF receptors did not differ between the studied groups.

CONCLUSION AND CLINICAL RELEVANCE

Our results indicate BDNF as a potential biomarker for clinical severity in children with asthma.

Peripheral BDNF produces antidepressant-like effects in cellular and behavioral models

Recent clinical studies demonstrate that serum levels of brain-derived neurotrophic factor (BDNF) are significantly decreased in patients with major depressive disorder (MDD) and that antidepressant treatments reverse this effect, indicating that serum BDNF is a biomarker of MDD. These findings raise the possibility that serum BDNF may also have effects on neuronal activity and behavior, but the functional significance of altered serum BDNF is unknown. To address this issue, we determined the influence of peripheral BDNF administration on depression- and anxiety-like behavior, including the forced swim test (FST), chronic unpredictable stress (CUS)/anhedonia, novelty-induced hypophagia (NIH) test, and elevated-plus maze (EPM). Furthermore, we examined adult hippocampal neurogenesis as well as hippocampal and striatal expression of BDNF, extracellular signal-regulated kinase (ERK) and cAMP response element-binding protein (CREB), in order to determine whether peripherally administered BDNF produces antidepressant-like cellular responses in the brain. Peripheral BDNF administration increased mobility in the FST, attenuated the effects of CUS on sucrose consumption, decreased latency in the NIH test, and increased time spent in the open arms of an EPM. Moreover, adult hippocampal neurogenesis was increased after chronic, peripheral BDNF administration. We also found that BDNF levels as well as expression of pCREB and pERK were elevated in the hippocampus of adult mice receiving peripheral BDNF. Taken together, these results indicate that peripheral/serum BDNF may not only represent a biomarker of MDD, but also have functional consequences on molecular signaling substrates, neurogenesis, and behavior.