Overexpression of functional TrkA receptors after internalisation in human airway smooth muscle cells

Genome-wide DNA methylation profiling after Ayurveda intervention to bronchial asthmatics identifies differential methylation in several transcription factors with immune process related function

BACKGROUND

The Indian traditional medicinal system, Ayurveda, describes several lifestyle practices, processes and medicines as an intervention to treat asthma. Rasayana therapy is one of them and although these treatment modules show improvement in bronchial asthma, their mechanism of action, particularly the effect on DNA methylation, is largely understudied.

OBJECTIVES

Our study aimed at identifying the contribution of DNA methylation changes in modulating bronchial asthma phenotype upon Ayurveda intervention.

MATERIALS AND METHODS

In this study, genome-wide methylation profiling in peripheral blood DNA of healthy controls and bronchial asthmatics before (BT) and after (AT) Ayurveda treatment was performed using array-based profiling of reference-independent methylation status (aPRIMES) coupled to microarray technique.

RESULTS

We identified 4820 treatment-associated DNA methylation signatures (TADS) and 11,643 asthma-associated DNA methylation signatures (AADS), differentially methylated [FDR (≤0.1) adjusted p-values] in AT and HC groups respectively, compared to BT group. Neurotrophin TRK receptor signaling pathway was significantly enriched for differentially methylated genes in bronchial asthmatics, compared to AT and HC subjects. Additionally, we identified over 100 differentially methylated immune-related genes located in the promoter/5'-UTR regions of TADS and AADS. Various immediate-early response and immune regulatory genes with functions such as transcription factor activity (FOXD1, FOXD2, GATA6, HOXA3, HOXA5, MZF1, NFATC1, NKX2-2, NKX2-3, RUNX1, KLF11), G-protein coupled receptor activity (CXCR4, PTGER4), G-protein coupled receptor binding (UCN), DNA binding (JARID2, EBF2, SOX9), SNARE binding (CAPN10), transmembrane signaling receptor activity (GP1BB), integrin binding (ITGA6), calcium ion binding (PCDHGA12), actin binding (TRPM7, PANX1, TPM1), receptor tyrosine kinase binding (PIK3R2), receptor activity (GDNF), histone methyltransferase activity (MLL5), and catalytic activity (TSTA3) were found to show consistent methylation status between AT and HC group in microarray data.

CONCLUSIONS

Our study reports the DNA methylation-regulated genes in bronchial asthmatics showing improvement in symptoms after Ayurveda intervention. DNA methylation regulation in the identified genes and pathways represents the Ayurveda intervention responsive genes and may be further explored as diagnostic, prognostic, and therapeutic biomarkers for bronchial asthma in peripheral blood.

Inflammation and Oxidative Stress Induce NGF Secretion by Pulmonary Arterial Cells through a TGF-β1-Dependent Mechanism

Expression of the nerve growth factor NGF is increased in pulmonary hypertension (PH). We have here studied whether oxidative stress and inflammation, two pathological conditions associated with transforming growth factor-β1 (TGF-β1) in PH, may trigger NGF secretion by pulmonary arterial (PA) cells. Effects of hydrogen peroxide (H2O2) and interleukin-1β (IL-1β) were investigated ex vivo on rat pulmonary arteries, as well as in vitro on human PA smooth muscle (hPASMC) or endothelial cells (hPAEC). TβRI expression was assessed by Western blotting. NGF PA secretion was assessed by ELISA after TGF-β1 blockade (anti-TGF-β1 siRNA, TGF-β1 blocking antibodies, TβRI kinase, p38 or Smad3 inhibitors). TβRI PA expression was evidenced by Western blotting both ex vivo and in vitro. H2O2 or IL-1β significantly increased NGF secretion by hPASMC and hPAEC, and this effect was significantly reduced when blocking TGF-β1 expression, binding to TβRI, TβRI activity, or signaling pathways. In conclusion, oxidative stress and inflammation may trigger TGF-β1 secretion by hPASMC and hPAEC. TGF-β1 may then act as an autocrine factor on these cells, increasing NGF secretion via TβRI activation. Since NGF and TGF-β1 are relevant growth factors involved in PA remodeling, such mechanisms may therefore be relevant to PH pathophysiology.

Increased β2-adrenoceptor phosphorylation in airway smooth muscle in severe asthma: possible role of mast cell-derived growth factors

The purpose of this study was to investigate whether growth factors produced by activated human lung mast cells (HLMCs) impair β₂ -adrenoceptor (β₂ -AR) function in human airway smooth muscle (ASM) cells. Protein array analysis confirmed the presence of various growth factors, including transforming growth factor (TGF)-β1, in the supernatants of high-affinity IgE receptor (FcεRI)-activated HLMCs which, when applied to ASM cells, impaired albuterol-induced cyclic adenosine monophosphate (cAMP) production, an effect that was prevented following neutralization of TGF-β1. This blunted β₂ -AR response was reproduced by treating ASM cells with TGF-β1 or fibroblast growth factor (FGF)-2, which induced β₂ -AR phosphorylation at tyrosine residues Tyr¹⁴¹ and Tyr³⁵⁰ , and significantly reduced the maximal bronchorelaxant responses to isoproterenol in human precision cut lung slices (PCLS). Finally, ASM cells isolated from severe asthmatics displayed constitutive elevated β₂ -AR phosphorylation at both Tyr¹⁴¹ and Tyr³⁵⁰ and a reduced relaxant response to albuterol. This study shows for the first time that abnormal β₂ -AR phosphorylation/function in ASM cells that is induced rapidly by HLMC-derived growth factors, is present constitutively in cells from severe asthmatics.

Optimising experimental research in respiratory diseases: an ERS statement

Experimental models are critical for the understanding of lung health and disease and are indispensable for drug development. However, the pathogenetic and clinical relevance of the models is often unclear. Further, the use of animals in biomedical research is controversial from an ethical perspective.The objective of this task force was to issue a statement with research recommendations about lung disease models by facilitating in-depth discussions between respiratory scientists, and to provide an overview of the literature on the available models. Focus was put on their specific benefits and limitations. This will result in more efficient use of resources and greater reduction in the numbers of animals employed, thereby enhancing the ethical standards and translational capacity of experimental research.The task force statement addresses general issues of experimental research (ethics, species, sex, age, ex vivo and in vitro models, gene editing). The statement also includes research recommendations on modelling asthma, chronic obstructive pulmonary disease, pulmonary fibrosis, lung infections, acute lung injury and pulmonary hypertension.The task force stressed the importance of using multiple models to strengthen validity of results, the need to increase the availability of human tissues and the importance of standard operating procedures and data quality.

Tropomyosin receptor kinase: a novel target in screened neuroendocrine tumors

Tropomyosin receptor kinase (Trk) inhibitors are investigated as a novel targeted therapy in various cancers. We investigated the in vitro effects of the pan-Trk inhibitor GNF-5837 in human neuroendocrine tumor (NET) cells. The human neuroendocrine pancreatic BON1, bronchopulmonary NCI-H727 and ileal GOT1 cell lines were treated with GNF-5837 alone and in combination with everolimus. Cell viability decreased in a time- and dose-dependent manner in GOT1 cells in response to GNF-5837 treatment, while treatment in BON1 and NCI-H727 cells showed no effect on cellular viability. Trk receptor expression determined GNF-5837 sensitivity. GNF-5837 caused downregulation of PI3K-Akt-mTOR signaling, Ras-Raf-MEK-ERK signaling, the cell cycle and increased apoptotic cell death. The combinational treatment of GNF-5837 with everolimus showed a significant enhancement in inhibition of cell viability vs single substance treatments, due to a cooperative PI3K-Akt-mTOR and Ras-Raf-MEK-ERK pathway downregulation, as well as an enhanced cell cycle component downregulation. Immunohistochemical staining for Trk receptors were performed using a tissue microarray containing 107 tumor samples of gastroenteropancreatic NETs. Immunohistochemical staining with TrkA receptor and pan-Trk receptor antibodies revealed a positive staining in pancreatic NETs in 24.2% (8/33) and 33.3% (11/33), respectively. We demonstrated that the pan-Trk inhibitor GNF-5837 has promising anti-tumoral properties in human NET cell lines expressing the TrkA receptor. Immunohistochemical or molecular screening for Trk expression particularly in pancreatic NETs might serve as predictive marker for molecular targeted therapy with Trk inhibitors.

MYO9A deficiency in motor neurons is associated with reduced neuromuscular agrin secretion

Congenital myasthenic syndromes (CMS) are a group of rare, inherited disorders characterized by compromised function of the neuromuscular junction, manifesting with fatigable muscle weakness. Mutations in MYO9A were previously identified as causative for CMS but the precise pathomechanism remained to be characterized. On the basis of the role of MYO9A as an actin-based molecular motor and as a negative regulator of RhoA, we hypothesized that loss of MYO9A may affect the neuronal cytoskeleton, leading to impaired intracellular transport. To investigate this, we used MYO9A-depleted NSC-34 cells (mouse motor neuron-derived cells), revealing altered expression of a number of cytoskeletal proteins important for neuron structure and intracellular transport. On the basis of these findings, the effect on protein transport was determined using a vesicular recycling assay which revealed impaired recycling of a neuronal growth factor receptor. In addition, an unbiased approach utilizing proteomic profiling of the secretome revealed a key role for defective intracellular transport affecting proper protein secretion in the pathophysiology of MYO9A-related CMS. This also led to the identification of agrin as being affected by the defective transport. Zebrafish with reduced MYO9A orthologue expression were treated with an artificial agrin compound, ameliorating defects in neurite extension and improving motility. In summary, loss of MYO9A affects the neuronal cytoskeleton and leads to impaired transport of proteins, including agrin, which may provide a new and unexpected treatment option.

β2-Adrenoceptor Function in Asthma

β2-adrenoceptor agonists, often used in combination with corticosteroids, have been extensively used for the treatment of asthma. However, concerns have been raised regarding their adverse effects and safety including poor asthma control, life-threatening exacerbations, exacerbations that often require hospitalization, and asthma-related deaths. The question as to whether these adverse effects relate to the loss of their bronchoprotective action remains an interesting possibility. In the chapter, we will review the experimental evidence that describes the different potential factors and associated mechanisms that can blunt the therapeutic action of β2-adrenoceptor agonists in asthma. We show here evidence that various key inflammatory cytokines, growth factors, some respiratory viruses, certain allergens, unknown factors present in serum from atopic asthmatics have the capacity to impair β2-adrenoceptor function in airway smooth muscle, the main target of these drugs. More importantly, we present our latest research describing the role played by mast cells in impairing β2-adrenoceptor function. Although no definitive conclusion could be made regarding the implication of one single mechanism, receptor uncoupling, or receptor desensitization due to phosphorylation represents the main inhibitory pathways associated with a loss of β2-adrenoceptor function in airway smooth muscle. Targeting the pathways leading to β2-adrenoceptor dysfunction will likely provide novel therapies to improve the efficacy of β2-agonists in asthma.

Abnormal corticosteroid signalling in airway smooth muscle: mechanisms and perspectives for the treatment of severe asthma

Growing in vivo evidence supports the concept that airway smooth muscle produces various immunomodulatory factors that could contribute to asthma pathogenesis via the regulation of airway inflammation, airway narrowing and remodelling. Targeting ASM using bronchial thermoplasty has provided undeniable clinical benefits for patients with uncontrolled severe asthma who are refractory to glucocorticoid therapy. The present review will explain why the failure of glucocorticoids to adequately manage patients with severe asthma could derive from their inability to affect the immunomodulatory potential of ASM. We will support the view that ASM sensitivity to glucocorticoid therapy can be blunted in severe asthma and will describe some of the factors and mechanisms that could be responsible for glucocorticoid insensitivity.

Cross-talk between lysophosphatidic acid receptor 1 and tropomyosin receptor kinase A promotes lung epithelial cell migration

Lysophosphatidic acid (LPA) is a bioactive lysophospholipid, which plays a crucial role in the regulation of cell proliferation, migration, and differentiation. LPA exerts its biological effects mainly through binding to cell-surface LPA receptors (LPA1-6), which belong to the G protein-coupled receptor (GPCR) family. Recent studies suggest that cross-talk between receptor tyrosine kinases (RTKs) and GPCRs modulates GPCRs-mediated signaling. Tropomyosin receptor kinase A (TrkA) is a RTK, which mediates nerve growth factor (NGF)-induced biological functions including cell migration in neuronal and non-neuronal cells. Here, we show LPA1 transactivation of TrkA in murine lung epithelial cells (MLE12). LPA induced tyrosine phosphorylation of TrkA in both time- and dose-dependent manners. Down-regulation of LPA1 by siRNA transfection attenuated LPA-induced phosphorylation of TrkA, suggesting a cross-talk between LPA1 and TrkA. To investigate the molecular regulation of the cross-talk, we focused on the interaction between LPA1 and TrkA. We found that LPA induced interaction between LPA1 and TrkA. The LPA1/TrkA complex was localized on the plasma membrane and in the cytoplasm. The C-terminus of LPA1 was identified as the binding site for TrkA. Inhibition of TrkA attenuated LPA-induced phosphorylation of TrkA and LPA1 internalization, as well as lung epithelial cell migration. These studies provide a molecular mechanism for the transactivation of TrkA by LPA, and suggest that the cross-talk between LPA1 and TrkA regulates LPA-induced receptor internalization and lung epithelial cell migration.

Effects of nerve growth factor antagonist K252a on peritoneal mast cell degranulation: implications for rat postoperative ileus

Stabilization of mast cell (MC) degranulation has been proposed to prevent postoperative ileus (POI). Nerve growth factor (NGF) mediates MC degranulation. The aim of the study was to evaluate whether NGF receptor antagonist K252a acts as a MC stabilizer in vitro and in vivo model of POI. Peritoneal mast cells (PMCs) were obtained from Sprague-Dawley rats and were incubated with K252a and exposed to NGF or Compound 48/80 (C48/80). MC degranulation was assessed by β-hexosaminidase assay. POI was induced in rats by intestinal manipulation (IM). Rats were pretreated with K252a (100 μg/kg sc) 20 min prior to POI induction. At 20 min after IM, release of rat mast cell protease 6 (RMCP-6) was evaluated in peritoneal lavage. At 24 h, intestinal transit (IT) and gastric emptying (GE) were evaluated. Ileal inflammation was assessed by myeloperoxidase (MPO) activity, expression of IL-6, NGF, TrkA, RMCP-2 and 6, and MC density within the full-thickness ileum. C48/80 and NGF evoked degranulation of PMCs in a dose-dependent manner. K252a prevented NGF-evoked, but not C48/80-evoked, MC degranulation. IM evoked the release of peritoneal RMCP-6 and subsequently delayed IT and GE. IM increased MPO activity and expression of IL-6. In IM rats, K252a prevented upregulation of IL-6 expression and reduced TrkA. IT, GE, and inflammation were not affected by K252a. K252a inhibited NGF-evoked degranulation of PMCs in vitro. In vivo, K252a decreased IL-6 and PMC degranulation. This may be of relevance for the development of new therapeutic targets for POI.

Diagnostic value of neurotrophin expression in malignant pleural effusions

Neurotrophins (NTs) modulate the growth of human malignancies, including lung cancers. Our prospective study evaluated the accuracy of pleural NTs [nerve growth factor, brain-derived neurotrophic factor (BDNF), neurotrophin 3 (nT3) and 4 (nT4)] levels for differentiating benign from malignant pleural exudates. Levels of NTs were measured by ELISA in 170 patients with non-neutrophilic (<50%) exudative benign or malignant pleurisies diagnosed by pleuroscopy. Fifty-nine benign (9 infections and 50 inflammatory diseases) and 111 malignant (50 extrathoracic tumors, 51 lung cancers and 10 mesotheliomas) pleural exudates were diagnosed by thoracoscopy. Levels of BDNF were significantly higher in malignant than in benign effusions [17 pg/ml (0-367) vs. 8 pg/ml (0-51), p<0.05]. ROC analysis showed an area under the curve of 0.609 (p=0.012; best threshold 44 pg/ml). Pleural BDNF levels were significantly higher in pleural metastasis of pulmonary tumors and in mesothelioma than in pleural benign effusions. Finally, a higher proportion of pleural nT3 was detected in squamous cell lung carcinoma in comparison to that in non-squamous cell lung carcinoma (72.7 vs. 10%, p<0.0001). NTs and particularly BDNF may play a role in the pathogenesis of malignant pleural effusions.