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INTRODUCTION: A bacterial infection by Borrelia burgdorferi referred to as Lyme disease (LD) or borreliosis is transmitted mostly by a bite of the tick Ixodes scapularis in the USA and Ixodes ricinus in Europe. Various tests are used for the diagnosis of LD, but their results are often unreliable. We compiled a list of clinically visible and patient-reported symptoms that are associated with LD. Based on this list, we developed a novel scoring system. METHODOLOGY: Nutech functional Score (NFS), which is a 43 point positional (every symptom is subgraded and each alternative gets some points according to its position) and directional (moves in direction bad to good) scoring system that assesses the patient's condition. RESULTS: The grades of the scoring system have been converted into numeric values for conducting probability based studies. Each symptom is graded from 1 to 5 that runs in direction BAD â GOOD. CONCLUSION: NFS is a unique tool that can be used universally to assess the condition of patients with LD.
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Therapeutic targets in asthma are reduction of airway inflammation and remodelling, the latter is not affected by available drugs. Here we present data that inhibition of MAPK-activated protein kinase (MNK)-1 reduces inflammation and remodelling. MNK-1 regulates protein expression by controlling mRNA stability, nuclear export and translation through the eukaryotic initiation factor 4E (eIF4E). Airway smooth muscle cells were derived from asthmatic and non-asthmatic donors. Cells were pre-treated with CGP57380 (MNK-1 inhibitor) or MNK-1 siRNA, before TNF-α stimulation. Cytokine and protein expression was analysed by ELISA, real time PCR and immunoblotting. Proliferation was monitored by cell counts. TNF-α activated MNK-1 phosphorylation between 15 and 30min. and subsequently eIF4E between 15 and 60min. EIF4E activity was inhibited by CGP57380 dose-dependently. Inhibition of MNK-1 by CGP57380 or MNK-1 siRNA significantly reduced TNF-α induced CXCL10 and eotaxin mRNA expression and secretion, but had no effect on IL-8. However, CXCL10 mRNA stability or NF-κB activity were not affected by MNK-1 inhibition. Furthermore, eIF4E was detected in the cytosol and the nucleus, but TNF-α did not affected its export from the nucleus. Cytokine array assessment showed that in addition to eotaxin and CXCL10, asthma relevant GRO α and RANTES were down-regulated by MNK-1 inhibition. In addition, MNK-1 inhibition significantly reduced FCS and PDGF-BB induced cell proliferation. We are the first to report that MNK-1 controls chemokine secretion and proliferation in human airway smooth muscle cells. Therefore we suggest that MNK-1 inhibition may present a new target to limit inflammation and remodelling in asthmatic airways.
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Asma/metabolismo , Asma/patología , Factor 4E Eucariótico de Iniciación/metabolismo , Inflamación/metabolismo , Inflamación/patología , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Transducción de Señal , Transporte Activo de Núcleo Celular/efectos de los fármacos , Compuestos de Anilina/farmacología , Becaplermina , Núcleo Celular/efectos de los fármacos , Núcleo Celular/metabolismo , Proliferación Celular/efectos de los fármacos , Quimiocina CCL11/genética , Quimiocina CCL11/metabolismo , Quimiocina CXCL10/genética , Quimiocina CXCL10/metabolismo , Regulación hacia Abajo/efectos de los fármacos , Humanos , Péptidos y Proteínas de Señalización Intracelular/antagonistas & inhibidores , Cinética , Miocitos del Músculo Liso/efectos de los fármacos , Miocitos del Músculo Liso/metabolismo , FN-kappa B/metabolismo , Fosforilación/efectos de los fármacos , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Proteínas Proto-Oncogénicas c-sis/farmacología , Purinas/farmacología , Estabilidad del ARN/efectos de los fármacos , ARN Mensajero/genética , ARN Mensajero/metabolismo , ARN Interferente Pequeño/metabolismo , Transducción de Señal/efectos de los fármacos , Factor de Necrosis Tumoral alfa/farmacología , Proteínas Quinasas p38 Activadas por Mitógenos/metabolismoRESUMEN
BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with poor prognosis. The kinase inhibitor nintedanib specific for vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR) and fibroblast growth factor receptor (FGFR) significantly reduced the rate of decline of forced vital capacity versus placebo. AIM: To determine the in vitro effect of nintedanib on primary human lung fibroblasts. METHODS: Fibroblasts were isolated from lungs of IPF patients and from non-fibrotic controls. We assessed the effect of VEGF, PDGF-BB and basic FGF (bFGF) ± nintedanib on: (i) expression/activation of VEGFR, PDGFR, and FGFR, (ii) cell proliferation, secretion of (iii) matrix metalloproteinases (MMP), (iv) tissue inhibitor of metalloproteinase (TIMP), and (v) collagen. RESULTS: IPF fibroblasts expressed higher levels of PDGFR and FGFR than controls. PDGF-BB, bFGF, and VEGF caused a pro-proliferative effect which was prevented by nintedanib. Nintedanib enhanced the expression of pro-MMP-2, and inhibited the expression of TIMP-2. Transforming growth factor-beta-induced secretion of collagens was inhibited by nintedanib. CONCLUSION: Our data demonstrate a significant anti-fibrotic effect of nintedanib in IPF fibroblasts. This effect consists of the drug's anti-proliferative capacity, and on its effect on the extracellular matrix, the degradation of which seems to be enhanced.
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Fibroblastos/efectos de los fármacos , Fibrosis Pulmonar Idiopática/enzimología , Indoles/farmacología , Pulmón/efectos de los fármacos , Inhibidores de Proteínas Quinasas/farmacología , Becaplermina , Estudios de Casos y Controles , Proliferación Celular/efectos de los fármacos , Células Cultivadas , Relación Dosis-Respuesta a Droga , Precursores Enzimáticos/metabolismo , Matriz Extracelular/metabolismo , Factor 2 de Crecimiento de Fibroblastos/farmacología , Fibroblastos/enzimología , Fibroblastos/patología , Gelatinasas/metabolismo , Humanos , Fibrosis Pulmonar Idiopática/patología , Pulmón/enzimología , Pulmón/patología , Fosforilación , Proteínas Proto-Oncogénicas c-sis/farmacología , Receptores de Factores de Crecimiento de Fibroblastos/efectos de los fármacos , Receptores de Factores de Crecimiento de Fibroblastos/metabolismo , Receptores del Factor de Crecimiento Derivado de Plaquetas/efectos de los fármacos , Receptores del Factor de Crecimiento Derivado de Plaquetas/metabolismo , Receptores de Factores de Crecimiento Endotelial Vascular/efectos de los fármacos , Receptores de Factores de Crecimiento Endotelial Vascular/metabolismo , Inhibidor Tisular de Metaloproteinasa-2/metabolismo , Factor A de Crecimiento Endotelial Vascular/farmacologíaRESUMEN
Sphingosine 1-phosphate (S1P) is a bioactive sphingolipid that plays an important proinflammatory role in asthmatic airways. Corticosteroids are first-line antiinflammatories in asthma; however, their repressive effects on S1P-induced cytokine secretion have not been investigated. To address this, our in vitro study reveals the molecular mechanisms by which corticosteroids inhibit S1P-induced IL-6 expression in the pivotal immunomodulatory cell type, airway smooth muscle (ASM). We first uncover the cellular signaling pathways responsible: S1P activates a cyclic adenosine monophosphate/cAMP response-element-binding protein (CREB)/CRE-dependent pathway to induce IL-6 transcription, concomitant with stimulation of the mitogen-activated protein kinase (MAPK) superfamily and downstream mitogen and stress-activated protein kinase 1 (MSK1) and histone H3 phosphorylation. In this way, S1P stimulates parallel signaling pathways to induce IL-6 secretion via CRE-driven transcription of the IL-6 gene promoter in a relaxed chromatin environment achieved through histone H3 phosphorylation. Second, we investigated how corticosteroids mediate their repressive effects. The corticosteroid dexamethasone inhibits S1P-induced IL-6 protein secretion and mRNA expression, but CREB/CRE transrepression, inhibition of IL-6 mRNA stability, or subcellular relocation of MSK1 were not responsible for the repressive effects of dexamethasone. Rather, we show that dexamethasone rapidly induces up-regulation of the MAPK deactivator MAPK phosphatase 1 (MKP-1) and that MKP-1 blocks the MAPK-driven activation of MSK1 and phosphorylation of histone H3. This was confirmed by treatment with triptolide, an inhibitor of MKP-1 up-regulation, where repressive effects of corticosteroids were reversed. Our study reveals the molecular mechanism underlying the antiinflammatory capacity of corticosteroids to repress proinflammatory functions induced by the potent bioactive sphingolipid S1P in the lung.
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Corticoesteroides/farmacología , Fosfatasa 1 de Especificidad Dual/efectos de los fármacos , Interleucina-6/biosíntesis , Lisofosfolípidos/farmacología , Fosfatasas de la Proteína Quinasa Activada por Mitógenos/metabolismo , Músculo Liso/efectos de los fármacos , Proteínas Quinasas S6 Ribosómicas 90-kDa/metabolismo , Esfingosina/análogos & derivados , AMP Cíclico , Proteína de Unión a Elemento de Respuesta al AMP Cíclico , Humanos , Interleucina-6/metabolismo , Músculo Liso/metabolismo , Fosforilación , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Esfingosina/farmacología , Proteínas Quinasas p38 Activadas por Mitógenos/metabolismoRESUMEN
Asthma is a chronic inflammatory disease of the airways, which results from the deregulated interaction of inflammatory cells and tissue forming cells. Beside the derangement of the epithelial cell layer, the most prominent tissue pathology of the asthmatic lung is the hypertrophy and hyperplasia of the airway smooth muscle cell (ASMC) bundles, which actively contributes to airway inflammation and remodeling. ASMCs of asthma patients secrete proinflammatory chemokines CXCL10, CCL11, and RANTES which attract immune cells into the airways and may thereby initiate inflammation. None of the available asthma drugs cures the disease--only symptoms are controlled. Dimethylfumarate (DMF) is used as an anti-inflammatory drug in psoriasis and showed promising results in phase III clinical studies in multiple sclerosis patients. In regard to asthma therapy, DMF has been anecdotally reported to reduce asthma symptoms in patients with psoriasis and asthma. Here we discuss the potential use of DMF as a novel therapy in asthma on the basis of in vitro studies of its inhibitory effect on ASMC proliferation and cytokine secretion in ASMCs.
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Antiinflamatorios/uso terapéutico , Asma/tratamiento farmacológico , Fumaratos/uso terapéutico , Dimetilfumarato , Humanos , Miocitos del Músculo Liso/efectos de los fármacos , Miocitos del Músculo Liso/metabolismoRESUMEN
CXCL10 stimulates mast cell infiltration into airway smooth muscle bundles and, thus, activate cytokine secretion and airway smooth muscle cell (ASMC) proliferation. Dimethylfumarate (DMF) reduces cytokine secretion by lymphocytes and ASMC proliferation through haem oxygenase (HO)-1. Therefore, we investigated the potency of DMF to inhibit tumour necrosis factor (TNF)-α- and interferon (IFN)-γ-induced CXCL10 secretion by human ASMCs. Human primary ASMCs were pre-incubated with DMF and/or fluticasone and/or glutathione ethylester before cells were stimulated with IFN-γ and/or TNF-α. DMF inhibited CXCL10 secretion and increased HO-1 levels, and p38 mitogen-activated protein kinase (MAPK) inhibition reduced DMF-dependent HO-1 expression. The DMF effect on CXCL10 secretion was abrogated by pre-treatment with HO-1 small interfering RNA (siRNA). Glutathione supplementation reversed all DMF effects on CXCL10 secretion and p38 MAPK phosphorylation. Importantly, combining DMF with fluticasone further reduced CXCL10 secretion. In addition, DMF inhibited IFN-γ-induced CXCL10 secretion. This effect was compensated by glutathione supplementation or by pre-treatment with HO-1 siRNA. In addition, DMF reduced TNF-α-induced granulocyte colony-stimulating factor (G-CSF) secretion but had no effect on INF-γ-induced G-CSF secretion. In human primary ASMCs, DMF inhibits CXCL10 secretion by reducing the cellular glutathione level and by activation of p38 MAPK and HO-1. Therefore, DMF may reduce airway inflammation in asthma by a glucocorticoid-independent pathway.
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Bronquios/fisiología , Quimiocina CXCL10/antagonistas & inhibidores , Fumaratos/farmacología , Hemo-Oxigenasa 1/efectos de los fármacos , Hemo-Oxigenasa 1/fisiología , Inmunosupresores/farmacología , Músculo Liso/fisiología , Bronquios/citología , Células Cultivadas , Dimetilfumarato , Humanos , Interferón gamma/efectos de los fármacos , Interferón gamma/fisiología , Músculo Liso/citología , Factor de Necrosis Tumoral alfa/efectos de los fármacos , Factor de Necrosis Tumoral alfa/fisiología , Proteínas Quinasas p38 Activadas por Mitógenos/efectos de los fármacos , Proteínas Quinasas p38 Activadas por Mitógenos/fisiologíaRESUMEN
BACKGROUND: Activated mast cells are present within airway smooth muscle (ASM) bundles in eosinophilic asthma. ASM production of the chemokine CXCL10 plays a role in their recruitment. Thus the effects of glucocorticoids (fluticasone, budesonide), long-acting ß2-agonists (salmeterol, formoterol) and thiazolidinediones (ciglitazone, rosiglitazone) on CXCL10 production by ASM cells (ASMC) from people with and without asthma were investigated in vitro. METHODS: Confluent serum-deprived cells were treated with the agents before and during cytokine stimulation for 0-24 h. CXCL10 protein/mRNA, IκB-α levels and p65 activity were measured using ELISA, RT PCR, immunoblotting and p65 activity assays respectively. Data were analysed using ANOVA followed by Fisher's post-hoc test. RESULTS: Fluticasone and/or salmeterol at 1 and 100 nM inhibited CXCL10 release induced by IL-1ß and TNF-α, but not IFNγ or all three cytokines (cytomix). The latter was also not affected by budesonide and formoterol. In asthmatic ASMC low salmeterol, but not formoterol, concentrations increased cytomix-induced CXCL10 release and at 0.01 nM enhanced NF-κB activity. Salmeterol 0.1 nM together with fluticasone 0.1 and 10 nM still increased CXCL10 release. The thiazolidinediones ciglitazone and rosiglitazone (at 25 and 100 µM) inhibited cytomix-induced CXCL10 release but these inhibitory effects were not prevented by the PPAR-g antagonist GW9662. Ciglitazone did not affect early NF-κB activity and CXCL10 mRNA production. CONCLUSIONS: Thus the thiazolidinediones inhibited asthmatic ASMC CXCL10 release under conditions when common asthma therapies were ineffective or enhanced it. They may provide an alternative strategy to reduce mast cell-ASM interactions and restore normal airway physiology in asthma.
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Antiasmáticos/administración & dosificación , Asma/tratamiento farmacológico , Asma/metabolismo , Quimiocina CXCL10/metabolismo , Pulmón/metabolismo , Músculo Liso/metabolismo , Tiazolidinedionas/administración & dosificación , Adulto , Humanos , Técnicas In Vitro , Pulmón/efectos de los fármacos , Masculino , Persona de Mediana Edad , Músculo Liso/efectos de los fármacosRESUMEN
Hyperplasia of airway smooth muscle (ASM) is a feature of the remodelled airway in asthmatics. We examined the antiproliferative effectiveness of the corticosteroid dexamethasone on expression of the key regulator of G(1) cell cycle progression-cyclin D1-in ASM cells from nonasthmatics and asthmatics stimulated with the mitogen platelet-derived growth factor BB. While cyclin D1 mRNA and protein expression were repressed in cells from nonasthmatics in contrast, cyclin D1 expression in asthmatics was resistant to inhibition by dexamethasone. This was independent of a repressive effect on glucocorticoid receptor translocation. Our results corroborate evidence demonstrating that corticosteroids inhibit mitogen-induced proliferation only in ASM cells from subjects without asthma and suggest that there are corticosteroid-insensitive proliferative pathways in asthmatics.
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Airway inflammation and respiratory infections are important factors contributing to disease exacerbation in chronic airway diseases such as asthma and chronic obstructive pulmonary disease. Airway smooth muscle (ASM) cells express Toll-like receptors (TLRs) and may be involved in the amplification of airway inflammatory responses during infectious exacerbations. We determined whether infectious stimuli (mimicked using Pam3CSK4, a synthetic bacterial lipopeptide that binds to TLR2/TLR1) further enhance ASM cell inflammatory responses to TNFα in vitro and the signaling pathways involved. Human ASM cells were pretreated for 1 h with Pam3CSK4 (1 µg/ml) in the absence or presence of TNFα (10 ng/ml), and IL-6 and IL-8 release was measured after 24 h. As expected, stimulation with Pam3CSK4 or TNFα alone induced significant IL-6 and IL-8 release. Furthermore, Pam3CSK4 significantly increased TNFα-induced IL-6 and IL-8 mRNA expression and protein release and neutrophil chemotactic activity. The potentiating effect of Pam3CSK4 on TNFα-induced inflammatory responses was not due to enhanced TLR2 expression nor did it involve augmentation of NF-κB or MAPK signaling pathways. Rather, Pam3CSK4 induced cAMP response element (CRE) binding protein phosphorylation and induced CRE-mediated transcriptional regulation, suggesting that Pam3CSK4 and TNFα are acting in concert to enhance ASM cytokine secretion via parallel transcriptional pathways. Our findings suggest that ASM cells may be involved in the amplification of airway inflammatory responses during infectious exacerbations in chronic airway disease.
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Interleucina-6/metabolismo , Interleucina-8/metabolismo , Lipopéptidos/farmacología , Receptor Toll-Like 2/agonistas , Factor de Necrosis Tumoral alfa/fisiología , Regulación hacia Arriba , Transporte Activo de Núcleo Celular , Bronquios/inmunología , Bronquios/patología , Bronquios/fisiología , Células Cultivadas , Quimiotaxis/efectos de los fármacos , Expresión Génica , Humanos , Inflamación/metabolismo , Interleucina-6/genética , Interleucina-8/genética , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Miocitos del Músculo Liso/efectos de los fármacos , Miocitos del Músculo Liso/metabolismo , FN-kappa B/metabolismo , Neutrófilos , Cultivo Primario de Células , Transducción de Señal , Receptor Toll-Like 2/genética , Receptor Toll-Like 2/metabolismoRESUMEN
Airway smooth muscle (ASM) plays an important immunomodulatory role in airway inflammation in asthma. In our previous in vitro studies in ASM cells delineating the pro-inflammatory mitogen-activated protein kinase (MAPK) signaling pathways activated by tumor necrosis factor α (TNFα), we observed that TNFα concomitantly induces the rapid, but transient, upregulation of the anti-inflammatory protein-mitogen-activated protein kinase phosphatase 1 (MKP-1). As this was suggestive of a negative feedback loop, the aim of this study was to investigate the molecular mechanisms of MKP-1 upregulation by TNFα and to determine whether MKP-1 is a negative feedback effector that represses MAPK-mediated pro-inflammatory signaling pathways and cytokine secretion in ASM cells. Herein, we show that TNFα increases MKP-1 mRNA expression and protein upregulation in a p38 MAPK-dependent manner. TNFα does not increase MKP-1 transcription (measured by MKP-1 promoter activity); rather, we found that TNFα-induced MKP-1 mRNA stability is regulated by the p38 MAPK pathway. Inhibiting MKP-1 upregulation (with triptolide) demonstrated the precise temporal control exerted on MAPK signaling by MKP-1. In the absence of MKP-1, downstream phosphoprotein targets of MAPKs (such as MSK-1 and histone H3) are not turned off at the right time, allowing pro-inflammatory pathways to continue in an unrestrained manner. This is confirmed by knocking-down MKP-1 by siRNA where enhanced secretion of the neutrophil chemoattractant cytokine-interleukin 8 was detected in the absence of MKP-1. Thus, by activating p38 MAP kinase, TNFα concomitantly upregulates the MAPK deactivator MKP-1 to serve as an important negative feedback effector, limiting the extent and duration of pro-inflammatory MAPK signaling and cytokine secretion in ASM cells.
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Fosfatasa 1 de Especificidad Dual/genética , Retroalimentación Fisiológica , Miocitos del Músculo Liso/metabolismo , Proteínas Quinasas p38 Activadas por Mitógenos/metabolismo , Antiinflamatorios no Esteroideos/farmacología , Bronquios/citología , Bronquios/metabolismo , Diterpenos/farmacología , Fosfatasa 1 de Especificidad Dual/antagonistas & inhibidores , Fosfatasa 1 de Especificidad Dual/deficiencia , Compuestos Epoxi/farmacología , Regulación de la Expresión Génica , Histonas/genética , Histonas/metabolismo , Humanos , Imidazoles/farmacología , Inflamación/genética , Inflamación/metabolismo , Interleucina-8/biosíntesis , Miocitos del Músculo Liso/citología , Fenantrenos/farmacología , Cultivo Primario de Células , Regiones Promotoras Genéticas , Piridinas/farmacología , Estabilidad del ARN/efectos de los fármacos , ARN Interferente Pequeño/genética , Proteínas Quinasas S6 Ribosómicas 90-kDa/genética , Proteínas Quinasas S6 Ribosómicas 90-kDa/metabolismo , Transducción de Señal , Factor de Necrosis Tumoral alfa/farmacología , Proteínas Quinasas p38 Activadas por Mitógenos/genéticaRESUMEN
UNLABELLED: QUESTION UNDER STUDY/PRINCIPLES: Dimethylfumarate (DMF) had been reported to reduce asthma symptoms and to improve the quality of life of asthma patients. Therefore, we assessed the anti-inflammatory and anti-remodeling effect of DMF on isolated lung fibroblasts, which are relevant to inflammatory lung diseases. We determined the effect of DMF on platelet derived growth factor (PDGF)-BB induced proliferation, as well as on PDGF-BB and tumor necrosis factor (TNF)-α induced interleukin (IL)-6 secretion and on activation of activated protein (AP)-1 and nuclear factor kappaB (NF-ĸB). METHODS: Confluent lung fibroblasts were incubated with DMF (0.1-100 µM) 1 hour before stimulation with PDGF-BB or TNF-α (both 10 ng/ml). IL-6 secretion was measured by ELISA. NF-ĸB and AP-1 activation was determined by immuno-blotting and EMSA. Cell proliferation was assessed by [3H]-thymidine incorporation in subconfluent fibroblasts. RESULTS: PDGF-BB but not TNF-α induced fibroblast proliferation. This was dose dependently reduced by DMF in a concentration range of 10-100 µM. PDGF-BB and TNF-α induced IL-6 secretion by lung fibroblasts and this was inhibited by DMF in a dose-dependent manner. However, PDGF-BB induced IL-6 secretion did not correlate with NF-ĸB activity, while TNF-α did. DMF inhibited the TNF-α induced NF-ĸB-DNA binding, but had neither an inhibitory effect on NF-ĸB nuclear entry nor on the degradation of IκB-α. PDGF-BB and TNF-α activated AP-1, which was also inhibited by DMF. CONCLUSIONS: Our data suggest that DMF down-regulates TNF-α-induced IL-6 secretion and proliferation by inhibiting NF-ĸB and AP-1 activity, indicating its potential beneficial use for the treatment of inflammatory lung diseases.
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Proliferación Celular/efectos de los fármacos , Regulación hacia Abajo/efectos de los fármacos , Fibroblastos/citología , Fibroblastos/efectos de los fármacos , Fumaratos/farmacología , Interleucina-6/metabolismo , FN-kappa B/antagonistas & inhibidores , Factor de Transcripción AP-1/antagonistas & inhibidores , Células Cultivadas , Dimetilfumarato , Humanos , Pulmón/citologíaRESUMEN
BACKGROUND: Airway wall remodelling is an important pathology of asthma. Growth factor induced airway smooth muscle cell (ASMC) proliferation is thought to be the major cause of airway wall thickening in asthma. Earlier we reported that Dimethylfumarate (DMF) inhibits platelet-derived growth factor (PDGF)-BB induced mitogen and stress activated kinase (MSK)-1 and CREB activity as well as IL-6 secretion by ASMC. In addition, DMF altered intracellular glutathione levels and thereby reduced proliferation of other cell types. METHODS: We investigated the effect of DMF on PDGF-BB induced ASMC proliferation, on mitogen activated protein kinase (MAPK) activation; and on heme oxygenase (HO)-1 expression. ASMC were pre-incubated for 1 hour with DMF and/or glutathione ethylester (GSH-OEt), SB203580, hemin, cobalt-protoporphyrin (CoPP), or siRNA specific to HO-1 before stimulation with PDGF-BB (10 ng/ml). RESULTS: PDGF-BB induced ASMC proliferation was inhibited in a dose-dependant manner by DMF. PDGF-BB induced the phosphorylation of ERK1/2 and p38 MAPK, but not of JNK. DMF enhanced the PDGF-BB induced phosphorylation of p38 MAPK and there by up-regulated the expression of HO-1. HO-1 induction inhibited the proliferative effect of PDGF-BB. HO-1 expression was reversed by GSH-OEt, or p38 MAPK inhibition, or HO-1 siRNA, which all reversed the anti-proliferative effect of DMF. CONCLUSION: Our data indicate that DMF inhibits ASMC proliferation by reducing the intracellular GSH level with subsequent activation of p38 MAPK and induction of HO-1. Thus, DMF might reduce ASMC and airway remodelling processes in asthma.