Mechanisms of BDNF regulation in asthmatic airway smooth muscle

Comparison of the effects of BDNF/TRKB signalling on metabolic biomarkers in the liver of sedentary and trained rats with normal and knockout BDNF genotypes

Introduction: The effect of brain-derived neurotrophic factor (BDNF) on the modulation of metabolic processes in the liver is poorly understood. Therefore, the aim of this study was to investigate whether hepatic concentrations or activities of metabolic biomarkers depend on altered BDNF/TrkB content in the liver, resulting from different BDNF genotypes of rats. In addition, it was assessed whether 5-week moderate endurance training modifies the levels of BDNF/Trk-B signaling and studied hepatic markers. Methods: Experiments were performed on wild-type and heterozygous BDNF knockout (HET, SD-Bdnf) rats, which were divided into four groups: control with normal genotype (Bdnf+/+), control with BDNF knockout genotype (Bdnf+/-), trained with normal genotype (Bdnf+/+T) and trained with BDNF knockout genotype (Bdnf +/-T). BDNF/TrkB concentrations as well as selected metabolic biomarkers including lipids-total cholesterol (CHOL), low-density lipoprotein (LDL), triglycerides (TG); enzymes-alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), gamma-glutamyl transferase (GGT), lactate dehydrogenase (LDH), alkaline phosphatase (ALP); hormones-insulin (INS) and leptin (LEPT) as well as interleukin-6 (IL-6) as regeneration indicator were measured directly in liver homogenates. Results and Discussion: The study showed that Bdnf+/- rats exhibited reduced BDNF/TrkB signaling (BDNF, p < 0.0001; Trk-B, p = 0.0005), altered lipid levels (CHOL, p < 0.0001; LDL, p < 0.0001; TG, p = 0.0006) and reduced hepatic ALAT (p = 0.0004) and GGT (p < 0.0001) activity, which may contribute to hepatic steatosis and obesity, as well as indicate impairment of specific metabolic pathways in the liver. Interestingly, endurance training did not alter hepatic BDNF and TrkB content, but improved ALAT (p = 0.0366) and ASAT (p = 0.0191) activities and increased hepatic IL-6 (p = 0.0422) levels in Bdnf +/- rats, suggesting enhanced liver regeneration in animals with BDNF allele loss.

Functional α7 nicotinic receptors in human airway smooth muscle increase intracellular calcium concentration and contractility in asthmatics

Although nicotinic acetylcholine receptors (nAChRs) are commonly associated with neurons in the brain and periphery, recent data indicate that they are also expressed in non-neuronal tissues. We recently found the alpha7 (α7nAChR) subunit is highly expressed in human airway smooth muscle (hASM) with substantial increase in asthmatics, but their functionality remains unknown. We investigated the location and functional role of α7nAChRs in hASM cells from normal versus mild-moderate asthmatic patients. Immunostaining and protein analyses showed α7nAChR in the plasma membrane including in asthmatics. In asthmatic hASM, patch-clamp recordings revealed significantly higher functional homomeric α7nAChR channels. Real-time fluorescence imaging showed nicotine, via α7nAChR, increases intracellular Ca2+ ([Ca2+]i) independent of ACh effects, particularly in asthmatic hASM, while cellular traction force microscopy showed nicotine-induced contractility including in asthmatics. These results indicate functional homomeric and heteromeric nAChRs that are increased in asthmatic hASM, with pharmacology that likely differ owing to different subunit interfaces that form the orthosteric sites. nAChRs may represent a novel target in alleviating airway hyperresponsiveness in asthma.NEW & NOTEWORTHY Cigarette smoking and vaping exacerbate asthma. Understanding the mechanisms of nicotine effects in asthmatic airways is important. This study demonstrates that functional alpha7 nicotinic acetylcholine receptors (α7nAChRs) are expressed in human airway smooth muscle, including from asthmatics, and enhance intracellular calcium and contractility. Although a7nAChRs are associated with neuronal pathways, α7nAChR in smooth muscle suggests inhaled nicotine (e.g., vaping) can directly influence airway contractility. Targeting α7nAChR may represent a novel approach to alleviating airway hyperresponsiveness in asthma.

Brain-derived neurotrophic factor promotes airway smooth muscle cell proliferation in asthma through regulation of transient receptor potential channel-mediated autophagy

OBJECTIVE

Increased proliferation of airway smooth muscle cells (ASMCs) is a key feature of airway remodeling in asthma. This study aims to determine whether brain-derived neurotrophic factor (BDNF) regulates ASMC proliferation and airway remodeling via the transient receptor potential channels (TRPCs)/autophagy axis.

METHODS

Human ASMCs were isolated and passively sensitized with human asthmatic serum. Protein levels of BDNF and its receptor TrkB, TRPC1/3/6, autophagy markers, intracellular Ca²⁺ concentration ([Ca²⁺]i), LC3 immunofluorescence, cell proliferation, cell cycle population were examined. Wistar rats were sensitized with OVA to establish asthma models.

RESULTS

In asthmatic serum-sensitized human ASMCs, BDNF overexpression or recombinant BDNF (rhBDNF) increased TrkB/TRPC1/3/6 axis, [Ca²⁺]i, autophagy level, cell proliferation, cell number in the S+G2/M phase and decreased cell number in the G0/G1 phase, whereas BDNF knockdown exerted the opposite effects. Furthermore, TRPC channel blocker SKF96365 and TRPC1/3/6 knockdown reversed the effects of the rhBDNF-mediated induction of [Ca²⁺]i, autophagy level, cell proliferation and cell number in the S+G2/M phase. Moreover, the autophagy inhibitor (3-MA) rescued the rhBDNF-mediated induction of cell proliferation and cell number in the S+G2/M phase. Further in vivo assays revealed that BDNF altered the pathology of airway remodeling, promoted the infiltration of inflammatory cells, promoted the proliferation of ASMCs, and upregulated the protein levels of TrkB, TRPC1/3/6, and autophagy markers in asthma model rats.

CONCLUSION

We conclude that BDNF promotes ASMCs proliferation in asthma through TRPC-mediated autophagy induction.

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.

The BDNF Val66Met Polymorphism is a Relevant, But not Determinant, Risk Factor in the Etiology of Neuropsychiatric Disorders - Current Advances in Human Studies: A Systematic Review

Brain-derived neurotrophic factor (BDNF) is the brain's most-produced neurotrophin during the lifespan, essentially involved in multiple mechanisms of nervous system development and function. The production/release of BDNF requires multi-stage processing that appears to be regulated at various stages in which the presence of a polymorphism "Val66Met" can exert a critical influence.

Aim

To synthesize the knowledge on the BDNF Val66Met polymorphism on intracellular processing and function of BDNF.

Methods

We performed a systematic review and collected all available studies on the post-translation processes of BDNF, regarding the Val66Met polymorphism. Searches were performed up to 21st March 2021.

Results

Out of 129 eligible papers, 18 studies addressed or had findings relating to BDNF post-translation processes and were included in this review.

Discussion

Compilation of experimental findings reveals that the Val66Met polymorphism affects BDNF function by slightly altering the processing, distribution, and regulated release of BDNF. Regarding the critical role of pro-BDNF as a pro-apoptotic factor, such alteration might represent a risk for the development of neuropsychiatric disorders.

Evidence for the presence and release of BDNF in the neuronal and non-neuronal structures of the internal anal sphincter

BACKGROUND

Data on the neuromodulatory effects of brain-derived neurotrophic factor (BDNF) in the gastrointestinal tract were recently reported, but there are still no data on the presence, distribution, and release of BDNF in the gastrointestinal tract, including the internal anal sphincter (IAS).

METHODS

We examined the presence and distribution of BDNF and its receptor TrkB in the different IAS structures (neuronal and non-neuronal) via immunohistochemical and immunocytochemical analyses. We also monitored the release of BDNF in an IAS muscle bath (consisting of smooth muscle cells [SMCs], myenteric plexus, and submucosal plexus) before and after different agonists, and electrical field stimulation in the absence and presence of neurotoxin tetrodotoxin.

KEY RESULTS

BDNF/TrkB was found to be present in all layers of the IAS, especially the smooth muscle, mucosa, myenteric plexus, and submucosal plexus. Detailed analyses revealed a significant colocalization between BDNF and TrkB in different structures, especially in the smooth muscle, the SMCs, and both plexuses. Data further showed higher levels of BDNF in the cytosol and that of TrkB toward the periphery of the SMCs.

CONCLUSIONS & INFERENCES

These studies showed that BDNF/TrkB was present not only in the enteric nervous system (ENS), but also in the SMCs. For the neuromodulatory effects, BDNF is released locally from the ENS ((myenteric (10.01 ± 0.23 pg/ml) and submucosal plexus (9.05 ± 0.51 pg/ml)) and the SMCs (18.63 ± 1.63 pg/ml). Collectively, these findings have pathophysiological and therapeutic implications regarding the role of BDNF/TrkB in the IAS-associated rectoanal motility disorders.

Unlocking the secrets of long non-coding RNAs in asthma

Asthma is a very heterozygous disease, divided in subtypes, such as eosinophilic and neutrophilic asthma. Phenotyping and endotyping of patients, especially patients with severe asthma who are refractory to standard treatment, are crucial in asthma management and are based on a combination of clinical and biological features. Nevertheless, the quest remains to find better biomarkers that distinguish asthma subtypes in a more clear and objective manner and to find new therapeutic targets to treat people with therapy-resistant asthma. In the past, research to identify asthma subtypes mainly focused on expression profiles of protein-coding genes. However, advances in RNA-sequencing technologies and the discovery of non-coding RNAs as important post-transcriptional regulators have provided an entire new field of research opportunities in asthma. This review focusses on long non-coding RNAs (lncRNAs) in asthma; these are non-coding RNAs with a length of more than 200 nucleotides. Many lncRNAs are differentially expressed in asthma, and several have been associated with asthma severity or inflammatory phenotype. Moreover, in vivo and in vitro functional studies have identified the mechanisms of action of specific lncRNAs. Although lncRNAs remain not widely studied in asthma, the current studies show the potential of lncRNAs as biomarkers and therapeutic targets as well as the need for further research.

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.

BDNF rescues aging-associated internal anal sphincter dysfunction

Aging can lead to rectoanal incontinence due to internal anal sphincter (IAS) dysfunction, which is characterized by a decrease in IAS tone and contractility and an increase in nonadrenergic noncholinergic (NANC) relaxation. We aimed to determine whether brain-derived neurotropic factor (BDNF) rescues this aging-associated IAS dysfunction (AAID). To do so, we studied the effects of BDNF on the basal and G protein-coupled receptors (GPCR)-stimulated IAS smooth muscle tone and on NANC relaxation in Fischer 344 rats representing different age groups [26-mo-old (aging) vs. 6-mo-old (young)], before and after tyrosine kinase receptor B (TrkB) antagonist K252a. We also used isolated smooth muscle cells (SMCs) to determine the effects of BDNF before and after different agonists. For some studies, we monitored NO release using smooth muscle perfusates. BDNF reversed AAID by rescuing the basal IAS tone and agonists [thromboxane A₂ analog (U46619) and angiotensin II (ANG II)]-induced contractility, and NANC relaxation. These rescue effects of BDNF were selective as K252a attenuated the changes in the IAS without modifying the effects of K⁺depolarization. Because of the direct association between the basal and GPCR-stimulated IAS tone and RhoA/ROCK activation, we speculate that this pathway in the rescue effects of BDNF. Conversely, our data suggest that aging-associated increased NANC relaxation is reversed by decreased release of NO and decrease in the sensitivity of the released inhibitory neurotransmitter. In summary, BDNF rescue of AAID involves RhoA/ROCK and inhibitory neurotransmission. These data have direct implications for the role of BDNF in the pathophysiology and therapeutic targeting of aging-associated rectoanal motility disorders.NEW & NOTEWORTHY These studies demonstrate that brain-derived neurotropic factor (BDNF) rescues the aging-associated internal anal sphincter (IAS) dysfunction, characterized by a decrease in IAS tone, and increase in non-adrenergic noncholinergic relaxation. We determined the effects of BDNF on the basal and GPCR (TXA₂ and ANG II)-stimulated IAS tone, and on NANC relaxation, before and after TrkB inhibitor K252a. BDNF may have an important role in the pathophysiology and therapeutic targeting of certain rectoanal motility disorders.

Glial-derived neurotrophic factor in human airway smooth muscle

Airway smooth muscle (ASM) cells modulate the local airway milieu via production of inflammatory mediators and growth factors including classical neurotrophins, such as brain-derived neurotrophic factor (BDNF). The glial cell-derived neurotrophic factor (GDNF) family of ligands (GFLs) are nonclassical neurotrophins and their role in the airway is barely understood. The major GFLs, GDNF and Neurturin (NRTN) bind to GDNF family receptor (GFR) α1 and α2 respectively that pair with Ret receptor to accomplish signaling. In this study, we found GDNF is expressed in human lung and increased in adult asthma, while human ASM expresses GDNF and its receptors. Accordingly, we used human ASM cells to test the hypothesis that ASM expression and autocrine signaling by GFLs regulate [Ca²⁺ ]_i . Serum-deprived ASM cells from non-asthmatics were exposed to 10 ng/ml GDNF or NRTN for 15 min (acute) or 24 h (chronic). In fura-2 loaded cells, acute GDNF or NRTN alone induced [Ca²⁺ ]_i responses, and further enhanced responses to 1 µM ACh or 10 µM histamine. Ret inhibitor (SPP86; 10 µM) or specific GDNF chelator GFRα1-Fc (1 µg/ml) showed roles of these receptors in GDNF effects. In contrast, NRTN did not enhance [Ca²⁺ ]_i response to histamine. Furthermore, conditioned media of nonasthmatic and asthmatic ASM cells showed GDNF secretion. SPP86, Ret inhibitor and GFRα1-Fc chelator markedly decreased [Ca²⁺ ]_i response compared with vehicle, highlighting autocrine effects of secreted GDNF. Chronic GDNF treatment increased histamine-induced myosin light chain phosphorylation. These novel data demonstrate GFLs particularly GDNF/GFRα1 influence ASM [Ca²⁺ ]_i and raise the possibility that GFLs are potential targets of airway hyperresponsiveness.

Neurotrophin Regulation and Signaling in Airway Smooth Muscle

Structural and functional aspects of bronchial airways are key throughout life and play critical roles in diseases such as asthma. Asthma involves functional changes such as airway irritability and hyperreactivity, as well as structural changes such as enhanced cellular proliferation of airway smooth muscle (ASM), epithelium, and fibroblasts, and altered extracellular matrix (ECM) and fibrosis, all modulated by factors such as inflammation. There is now increasing recognition that disease maintenance following initial triggers involves a prominent role for resident nonimmune airway cells that secrete growth factors with pleiotropic autocrine and paracrine effects. The family of neurotrophins may be particularly relevant in this regard. Long recognized in the nervous system, classical neurotrophins such as brain-derived neurotrophic factor (BDNF) and nonclassical ligands such as glial-derived neurotrophic factor (GDNF) are now known to be expressed and functional in non-neuronal systems including lung. However, the sources, targets, regulation, and downstream effects are still under investigation. In this chapter, we discuss current state of knowledge and future directions regarding BDNF and GDNF in airway physiology and on pathophysiological contributions in asthma.

[Extracellular molecules controlling the contraction of airway smooth muscle and their potential contribution to bronchial hyperresponsiveness]

INTRODUCTION

A significant portion of symptoms in some lung diseases results from an excessive constriction of airways due to the contraction of smooth muscle and bronchial hyperresponsiveness. A better understanding of the extracellular molecules that control smooth muscle contractility is necessary to identify the underlying causes of the problem.

STATE OF KNOWLEDGE

Almost a hundred molecules, some of which newly identified, influence the contractility of airway smooth muscle. While some molecules activate the contraction, others activate the relaxation, thus acting directly as bronchoconstrictors and bronchodilators, respectively. Other molecules do not affect contraction directly but rather influence it indirectly by modifying the effect of bronchoconstrictors and bronchodilators. These are called bronchomodulators. Some of these bronchomodulators increase the contractile effect of bronchoconstrictors and could thus contribute to bronchial hyperresponsiveness.

PROSPECTS

Considering the high number of molecules potentially involved, as well as the level of functional overlap between some of them, identifying the extracellular molecules responsible for excessive airway constriction in a patient is a major contemporary challenge.

Effect of cytokine treatment on the expression and secretion of brain derived neurotrophic factor in the smooth muscle of the rat colon

The production of pro-inflammatory cytokines and chemokines is increased during inflammatory bowel disease (IBD). Previously, it was demonstrated that brain derived neurotrophic factor (BDNF) expression is increased in experimental models of colitis. BDNF is partially responsible for the structural and functional changes that take place during IBD. However, the exact mechanisms underlying the upregulation of BDNF during gut inflammation are unknown. The aim of the present study was to determine the effects of direct treatment of smooth muscle cells with inflammatory cytokines on the synthesis and secretion of BDNF. BDNF expression and secretion levels were measured using ELISA kits on tissue lysates and on incubation media used to culture the rat colon smooth muscle tissues treated for 24 h with either tumor necrosis factor (TNF)-α or interleukin (IL)-1β. Compared with the control tissue samples, treatment with TNF-α and IL-1β resulted in a significant increase in the protein expression levels of BDNF in the incubated smooth muscle tissue. TNF-α and IL-1β also stimulated the secretion of BDNF. Chelation of intracellular Ca²⁺ with BABTA-AM prevented the TNF-α and IL-1β-induced increase in BDNF protein expression and secretion levels. Furthermore, inhibition of protein kinase A (PKA) significantly reduced BDNF expression levels when treated with cytokines but not secretion. In conclusion, proinflammatory cytokines that are upregulated during IBD, directly stimulated BDNF expression and secretion in a Ca²⁺ dependent manner. Considering the ability of BDNF to enhance smooth muscle contraction and pain sensation, this autocrine loop may partially explain the characteristic hypercontractility and hypersensitivity associated with IBD.

Role of Differential Estrogen Receptor Activation in Airway Hyperreactivity and Remodeling in a Murine Model of Asthma

Evidence suggests that airway hyperresponsiveness (AHR) is a characteristic feature of asthma. Epidemiological studies have confirmed that the severity of asthma is greater in women, suggesting a critical role of female sex steroid hormones (especially estrogen). Very few in vivo studies have examined the role of sex steroid hormones in asthma, and the sequence of events that occur through differential activation of estrogen receptors (ERs) remains to be determined in asthmatic airways. Our recent in vitro findings indicated that ERβ had increased expression in asthmatic airway smooth muscle (ASM), and that its activation by an ERβ-specific agonist downregulated airway remodeling. In this study, we translated the in vitro findings to a murine asthma model and examined the differential role of ER activation in modulating lung mechanics. C57BL/6J male, female, and ovariectomized mice were exposed to mixed allergen (MA) and subcutaneously implanted with sustained-release pellets of placebo, an ERα agonist (4,4',4″-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol [PPT]), and/or an ERβ agonist (WAY-200070). We then evaluated the effects of these treatments on airway mechanics, biochemical, molecular, and histological parameters. Mice exposed to MA showed a significant increase in airway resistance, elastance, and tissue damping, and a decrease in compliance; pronounced effects were observed in females. Compared with PPT, WAY treatment significantly reversed the MA-induced changes. The increased mRNA/protein expression of ERα, ERβ, and remodeling genes observed in MA-treated mice was significantly reversed in WAY-treated mice. This novel study indicates that activation of ERβ signaling downregulates AHR and airway remodeling, and is a promising target in the development of treatments for asthma.

Aging reduces succinate dehydrogenase activity in rat type IIx/IIb diaphragm muscle fibers

In aged rats, diaphragm muscle (DIAm) reduced specific force and fiber cross-sectional area, sarcopenia, is selective for vulnerable type IIx and/or IIb DIAm fibers, with type I and IIa fibers being resilient. In humans, the oxidative capacity [as measured by maximum succinate dehydrogenase (SDH_max) activity] of fast-type muscle is reduced with aging, with slow-type muscle being unaffected. We hypothesized that in aged Fischer rat DIAm exhibiting sarcopenia, reduced SDH_max activity would occur in type IIx and/or IIb fibers. Rats obtained from the NIA colony (6, 18, and 24 mo old) were euthanized, and ~2-mm-wide DIAm strips were obtained. For SDH_max and fiber type assessments, DIAm strips were stretched (approximately optimal length), fresh frozen in isopentane, and sectioned on a cryostat at 6 μm. SDH_max, quantified by intensity of nitroblue tetrazolium diformazan precipitation, was assessed in a fiber type-specific manner by comparing serial sections labeled with myosin heavy chain (MyHC) antibodies differentiating type I (MyHC_Slow), IIa (MyHC_2A), and IIx and/or IIb fibers. Isometric DIAm force and fatigue were assessed in DIAm strips by muscle stimulation with supramaximal pulses at a variety of frequencies (5-100 Hz) delivered in 1-s trains. By 24 mo, DIAm sarcopenia was apparent and SDH_max in type IIx and/or IIb fibers activity was reduced ~35% compared with 6-mo-old control DIAm. These results underscore the remarkable fiber type selectivity of type IIx and/or IIb fibers to age-associated perturbations and suggest that reduced mitochondrial oxidative capacity is associated with DIAm sarcopenia.NEW & NOTEWORTHY We examined the oxidative capacity as measured by maximum succinate dehydrogenase activity in older (18 or 24 mo old) Fischer 344 rat diaphragm muscle (DIAm) compared with young rats (6 mo old). In 24-mo-old rats, SDH activity was reduced in type IIx/b DIAm fibers. These SDH changes were concomitant with sarcopenia (reduced specific force and atrophy of type IIx/b DIAm fibers) at 24 mo old. At 18 mo old, there was no change in SDH activity and no evidence of sarcopenia.

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.

Uncovering the mechanism of Maxing Ganshi Decoction on asthma from a systematic perspective: A network pharmacology study

Maxing Ganshi Decoction (MXGSD) is used widely for asthma over thousands of years, but its underlying pharmacological mechanisms remain unclear. In this study, systematic and comprehensive network pharmacology was utilized for the first time to reveal the potential pharmacological mechanisms of MXGSD on asthma. Specifically, we collected 141 bioactive components from the 600 components in MXGSD, which shared 52 targets common to asthma-related ones. In-depth network analysis of these 52 common targets indicated that asthma might be a manifestation of systemic neuro-immuno-inflammatory dysfunction in the respiratory system, and MXGSD could treat asthma through relieving airway inflammation, improving airway remodeling, and increasing drug responsiveness. After further cluster and enrichment analysis of the protein-protein interaction network of MXGSD bioactive component targets and asthma-related targets, we found that the neurotrophin signaling pathway, estrogen signaling pathway, PI3K-Akt signaling pathway, and ErbB signaling pathway might serve as the key points and principal pathways of MXGSD gene therapy for asthma from a systemic and holistic perspective, and also provides a novel idea for the development of new drugs for asthma.

Chronic asthma-induced behavioral and hippocampal neuronal morphological changes are concurrent with BDNF, cofilin1 and Cdc42/RhoA alterations in immature mice

INTRODUCTION

Recent studies have found that persistent hypoxia caused by chronic asthma, especially during childhood, affects the development and function of the brain, but the mechanism is unclear. In the present study, BDNF and its signal pathway was investigated in mediating chronic asthma induced-neuronal changes that lead to behavior alterations.

METHODS

The chronic asthma model was induced by sensitization with ovalbumin for more than 9 weeks in immature mice. Morris water maze test (MWMT), open field test (OFT) and elevated plus maze test (EPMT) were used to conduct behavioral evaluation. Neuronal morphology in hippocampal CA1, CA3 and DG was assessed using ImageJ's Sholl plugin and RESCONSTRUCT software. BDNF signaling pathway related molecules was determined by Western blotting.

RESULTS

Chronic asthma does affect the behavioral performances of immature mice evaluated in MWMT, OFT, and EPMT. The analysis by three-dimensional reconstruction software found that following the behavioral alteration of asthmatic mice, dendritic changes also occurred in hippocampal neurons, including shortened dendrite length, significantly reduced number of dendritic branches, decreased density of dendritic spines, and reduced percentage of functional dendritic spine types. At the same time, by immunofluorescence and western blotting, we also found that alterations in dendritic morphology were consistent with activation of cofilin1 and changes in BDNF-Cdc42/RhoA levels. Some of the changes mentioned above can be alleviated by intranasal administration of budesonide.

CONCLUSION

Our data suggest that response similar to nicotine withdrawal or/and hypoxia induced by childhood chronic asthma enhances the BDNF-Cdc42/RhoA signaling pathway and activates cofilin1, leading to the remodeling of actin, causing the loss of dendritic spines and atrophy of dendrites, eventually resulting in behavioral alterations.

Pro-inflammatory role of transient receptor potential canonical channel 6 in the pathogenesis of chronic rhinosinusitis with nasal polyps

BACKGROUND

The pathogenesis of chronic rhinosinusitis with nasal polyps (CRSwNP) has not been fully elucidated. This study sought to explore the role and mechanism of transient receptor potential canonical channel 6 (TRPC6) in the pathogenesis of CRSwNP.

METHODS

Immunohistochemistry (IHC) was employed to evaluate TRPC6 immunolabeling. Real-time polymerase chain reaction (PCR) was conducted to assay TRPC6, stromal interaction molecule 1 (STIM1), and calcium release-activated calcium channel protein 1 (Orai1) messenger RNA (mRNA) levels in 70 patients with CRSwNP, including eosinophilic CRSwNP (ECRSwNP) or non-eosinophilic CRSwNP (nECRSwNP), and 28 control subjects. The concentrations of inflammatory mediators, including interleukin (IL)-1β, IL-5, and IL-25, were assayed by enzyme-linked immunosorbent assay (ELISA). In experiments on human nasal epithelial cell (HNEC) culture and stimulation, the mean fluorescence intensity (MFI) of intracellular Ca²⁺ was assayed by flow cytometry. Western blotting, real-time PCR, and ELISA were also conducted to assess the effects and mechanisms of TRPC6 activator 1-oleoyl-2-acetyl-glycerol (OAG) and TRPC6 inhibitor 1-[2-(4-methoxyphenyl)-2-[3-(4-methoxyphenyl) propoxy]ethyl-1H-imidazole (SKF-96365) on HNECs.

RESULTS

Upregulation of TRPC6, STIM1, and Orai1 levels was found in CRSwNP patients, particularly in those with ECRSwNP. TRPC6-positive cells correlated positively with the numbers of eosinophils and neutrophils, respectively. Moreover, TRPC6 mRNA was positively correlated with STIM1 and Orai1 mRNA levels. The concentrations of inflammatory mediators, including IL-1β, IL-5, and IL-25, were elevated in CRSwNP, especially in ECRSwNP. In cultured HNECs, TRPC6, STIM1, Orai1, Ca²⁺ MFI levels, and inflammatory mediators were upregulated by lipopolysaccharide (LPS) and OAG but were inhibited by SKF-96365.

CONCLUSION

TRPC6 plays a pro-inflammatory role in the pathogenesis of CRSwNP via regulating Ca²⁺ flow.

The combined effects of three-dimensional cell culture and natural tissue extract on neural differentiation of P19 embryonal carcinoma stem cells

Tissue engineering, as a novel transplantation therapy, aims to create biomaterial scaffolds resembling the extracellular matrix in order to regenerate the damaged tissues. Adding bioactive factors to the scaffold would improve cell-tissue interactions. In this study, the effect of chitosan polyvinyl alcohol nanofibres containing carbon nanotube scaffold with or without active bioglass (BG⁺ /BG^- ), in combination with neonatal rat brain extract on cell viability, proliferation, and neural differentiation of P19 embryonic carcinoma stem cells was investigated. To induce differentiation, the cells were cultured in α-MEM supplemented with neonatal rat brain extract on the scaffolds. The expression of undifferentiated stem cell markers as well as neuroepithelial and neural-specific markers was evaluated and confirmed by real-time Reverse transcription polymerase chain reaction (RT-PCR) and immunofluorescence procedures. Finally, the three-dimensional (3D) cultured cells were implanted into the damaged neural tubes of chick embryos, and their fates were followed in ovo. Based on the histological and immunofluorescence observations, the transplanted cells were able to survive, migrate, and penetrate into the host embryonic tissues. Gene network analysis suggested the possible involvement of neurotransmitters as a downstream target of synaptophysin and tyrosine hydroxylase. Overall, the results of this study indicated that combining the effects of 3D cell culture and natural brain tissue extract can accelerate the differentiation of P19 embryonic carcinoma cells into neuronal phenotype cells.

TRPC3 overexpression and intervention in airway smooth muscle of ovalbumin-induced hyperresponsiveness and remodeling

Transient receptor potential canonical channel 3 (TRPC3) proteins function as non-voltage-gated Ca²⁺ -permeable channels and play divergent roles in many processes of pathophysiology. The purpose of this study was to determine the relationship between TRPC3 expression and airway hyperresponsiveness and remodeling in ovalbumin-induced asthmatic Kunming mice. Mice were sensitized and challenged by ovalbumin to establish asthmatic model. Hematoxylin-eosin staining, hydroxyproline assay, and isometric tracheal ring force measurement were used to evaluate airway remodeling and hyperresponsiveness in asthmatic mice. Western blot was performed to detect the expression of TRPC3 proteins. MTT assay was used to measure the proliferation of airway smooth muscle cells. TRPC3 protein expression increased in airway smooth muscle of asthmatic mice. GdCl₃ , a nonspecific TRPC blocker, attenuated the contractile force of airway smooth muscle. Fetal bovine serum stimulated airway smooth muscle cells proliferation and augmented TRPC3 protein expression. Both TRPC3 blockade by GdCl₃ or specific TRPC3 antibodies and gene silencing by siRNA inhibited the proliferation of airway smooth muscle cells. In contrast, the current drugs treatment for asthma such as Dexamethasone and Aminophylline had no effects on TRPC3 protein overexpression. Therefore, TRPC3 protein overexpression may be involved in airway smooth muscle hyperresponsiveness and remodeling in asthmatic mice, providing evidence for a new direction of asthma pathogenesis research and a new target for drug intervention.

Hypoxia and Local Inflammation in Pulmonary Artery Structure and Function

Hypoxia is recognized as a contributor to pulmonary vascular diseases such as pulmonary hypertension. Hypoxia-induced inflammatory changes can enhance structural and functional changes in pulmonary artery (PA) in the context of PH. Accordingly, understanding how hypoxia and inflammation are linked in the context of pulmonary artery structure and function could be relevant towards development of novel therapies for PH. In this regard, factors such as thymic stromal lymphopoietin (TSLP), an inflammatory cytokine, and brain-derived neurotrophic factor (BDNF), a neurotrophin, have been found critical for nonvascular systems such as airway and asthma. While TSLP canonically affects the immune system, in nonvascular systems, noncanonical effects such as altered [Ca²⁺]_i and cell proliferation have been noted: aspects also relevant to the PA, where there is currently little to no data. Similarly, better known in the nervous system, there is increasing evidence that BDNF is locally produced by structural cells of the airway and can contribute to asthma pathophysiology. In this chapter, we summarize the potential relevance of factors such as TSLP and BDNF to the PA and in the context of hypoxia influences towards development of PH. We focus on cell sources and targets such as PA endothelial cells (PAECs) and smooth muscle cells (PASMCs), and the effects of TSLP or BDNF on intracellular Ca²⁺ responses to vasoconstrictor agonist, cell proliferation, and potential signaling cascades involved.

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.

Emerging concepts in smooth muscle contributions to airway structure and function: implications for health and disease

Airway structure and function are key aspects of normal lung development, growth, and aging, as well as of lung responses to the environment and the pathophysiology of important diseases such as asthma, chronic obstructive pulmonary disease, and fibrosis. In this regard, the contributions of airway smooth muscle (ASM) are both functional, in the context of airway contractility and relaxation, as well as synthetic, involving production and modulation of extracellular components, modulation of the local immune environment, cellular contribution to airway structure, and, finally, interactions with other airway cell types such as epithelium, fibroblasts, and nerves. These ASM contributions are now found to be critical in airway hyperresponsiveness and remodeling that occur in lung diseases. This review emphasizes established and recent discoveries that underline the central role of ASM and sets the stage for future research toward understanding how ASM plays a central role by being both upstream and downstream in the many interactive processes that determine airway structure and function in health and disease.