Procaterol inhibits lung fibroblast migration

Fibroblasts are important cells that are involved in modulation of fibrosis after injuries. In some uncontrollable inflammatory processes, excess fibroblasts migrate around the small airway. The pathogenesis of chronic obstructive pulmonary disease is related to fibrosis around the small airways. The aim of the current study was to investigate the effect of procaterol, a second-generation beta (2)-agonist, on migration of human fetal lung fibroblasts (HFL-1) induced by human plasma fibronectin (HFn). Using the blindwell chamber technique, 10(-8) M procaterol inhibited migration of HFL-1 (control, 100%; 10(-8) M, 73.2 +/- 4.9%; n = 6, p < 0.05). The inhibitory effect of procaterol was concentration-dependent. Although a beta 2-receptor inhibitor, ICI 181551, blocked the inhibitory effect of procaterol, a beta 1-receptor inhibitor, atenolol, did not. Because a cyclic AMP-dependent protein kinase (PKA) inhibitor, KT5720, blocked the effect of procaterol, the cyclic AMP-PKA pathway may be involved in the migration inhibitory process. Procaterol, which is prescribed mainly for treatment of bronchial asthma, might be a useful drug for inhibiting lung fibrosis following injuries to the lung.

Tumor necrosis factor-alpha enhances both epithelial-mesenchymal transition and cell contraction induced in A549 human alveolar epithelial cells by transforming growth factor-beta1

Recently, epithelial-mesenchymal transition (EMT) has been reported to contribute to tissue fibrosis through enhanced transforming growth factor (TGF)-beta1 signaling. Tumor necrosis factor (TNF)-alpha has also been implicated in tissue fibrosis. Therefore, the authors investigated whether TNF-alpha affected TGF-beta1-induced EMT. Cultured alveolar epithelial cells (A549 cells) were stimulated with TGF-beta1 (5 ng/mL), with/without TNF-alpha (10 ng/mL). TGF-beta1 induced EMT of A549 cells, with loss of E-cadherin and acquisition of vimentin. Combination of TNF-alpha with TGF-beta1 enhanced EMT, causing morphological changes, while quantitative polymerase chain reaction (PCR) showed suppression of E-cadherin mRNA and expression of vimentin mRNA. In addition, the gel contraction method revealed that cells that had undergone EMT acquired cell contractility, which is a feature of mesenchymal cells. Stimulation with TGF-beta1 induced cell contraction, as did TNF-alpha. Moreover, costimulation with TGF-beta1 and TNF-alpha enhanced the cell contraction. Although IFN-gamma suppressed spontaneous cell contraction, it did not suppress cell contraction, which was induced by TGF-beta1. In conclusion, TNF-alpha enhances not only EMT but also cell contraction induced by TGF-beta1. EMT might contribute to tissue fibrosis through induction of cell contraction.

Leukotriene D4 potentiates fibronectin-induced migration of human lung fibroblasts

Fibroblasts play an important role in the repair and remodeling processes following injury. Leukotriene D4 (LTD4) is a potent mediator in inflammatory processes, but the direct effect of cysteinyl leukotrienes on fibroblast migration remains unelucidated. In this study, the effect of the LTD4 on normal human lung fibroblasts (NHLF) chemotaxis induced by human plasma fibronectin (HFn) was investigated using the modified Boyden's chamber technique. LTD4 potentiated NHLF chemotaxis to HFn in concentration-dependent manner. A specific cysteinyl leukotriene receptor type 1 antagonist, pranlukast inhibited this effect, indicating that LTD4 affected cell migration via its specific receptor. The potentiating effect of LTD4 on fibroblast chemotaxis was completely abolished by pertussis toxin (PTX), suggesting that LTD4-induced effect was dependent on PTX-sensitive Gi/o signaling. These findings suggest that LTD4 has a potential to augment fibroblast chemotaxis, and to contribute to regulation of the wound healing and following remodeling in fibrotic processes of the lung.

Inhalation of diesel exhaust for three months affects major cytokine expression and induces bronchus-associated lymphoid tissue formation in murine lungs

The authors investigated the effects of exposure to diesel exhaust (DE) on murine lung tissues in vivo. BALB/c and C57BL/6 mice were exposed to DE with low (100 microg/m(3)) and high (3 mg/m(3)) DE particle levels for 3 months. The authors then examined morphological changes and the expression of mRNAs for various cytokines (tumor necrosis factor [TNF]-alpha, interleukin [IL]-1beta, IL-4, IL-6, IL-10, IL-12p40, and interferon [IFN]-gamma) and inducible nitric oxide synthase (iNOS) in the lungs, as well as TNF-alpha, IL-1beta, IL-10, IL-12p40, and Mac-1 mRNA expression in alveolar macrophages (AMs). TNF-alpha, IL-12p40, IL-4, and IL-10 mRNA expression were mildly increased, whereas IL-1beta mRNA and iNOS expression were slightly decreased, in the low- and high-level exposure groups. Flow cytometry of bronchoalveolar lavage fluid revealed a significant increase in Mac-1-positive cells in the high-level exposure group. On histological examination, bronchus-associated lymphoid tissue (BALT), containing B and T lymphocytes, had developed only in the high-level exposure group. Chronic inhalation of DE influences cytokine expression in the murine lung, and induces phagocytosis and BALT development. These findings suggest that DE may provoke immunological responses by acting as a foreign body in the lung, and that even low-level exposure may induce allergic reactions.

Molecular mechanisms of anti-inflammatory action of erythromycin in human bronchial epithelial cells: possible role in the signaling pathway that regulates nuclear factor-kappaB activation

Long-term macrolide therapy has been proven to improve survival in patients with diffuse panbronchiolitis. Although its mechanisms remain unknown, previous studies have suggested the effects of macrolide might be anti-inflammatory rather than antibacterial. To elucidate the molecular mechanisms of its action, we studied here the effects of erythromycin (EM) and its new derivative, EM703, which shows no antibacterial action, on the activation of the transcription factor nuclear factor-kappaB (NF-kappaB) in human bronchial epithelial cells. Western blotting analysis showed that EM did not inhibit the degradation of IkappaBalpha, suggesting the molecular target for EM was not the dissociation of NF-kappaB from IkappaB. An electrophoretic mobility shift assay showed that EM did not interrupt the NF-kappaB DNA-binding activity in the nucleus under the conditions tested. Moreover, not only EM but also EM703 suppressed the activation of NF-kappaB and the production of interleukin-8, demonstrating that the anti-inflammatory action of the macrolide is independent of its antibacterial activity. Taken together, these data suggest EM has an anti-inflammatory action, presumably via an interaction with the NF-kappaB signaling pathway in the downstream of the dissociation from IkappaB, resulting in the inhibition of NF-kappaB.

Methotrexate induces interleukin-8 production by human bronchial and alveolar epithelial cells

Methotrexate (MTX) has been widely used for the treatment of a variety of tumours as well as for inflammatory diseases. MTX-induced pneumonitis has been a serious unpredictable side effect of the treatment and an important clinical problem. However, its mechanism remains largely unclear. Possible causes include allergic, cytotoxic or immunologic reactions to this agent. To elucidate the proinflammatory mechanism of MTX-induced pneumonitis, we evaluated the effect of MTX on the production of IL (interleukin)-8 by human bronchial and alveolar epithelial cells in vitro and the role of p38 MAPK (mitogen-activated protein kinase) in order to clarify the intracellular signal regulating IL-8 expression. MTX induced IL-8 secretion by human bronchial and alveolar epithelial cells in a dose- and time-dependent manner within the range of the clinically observed serum concentrations. Although addition of LPS (lipopolysaccharide) and glucose showed no significant enhancing effect, addition of IL-1β or TNF-α (tumour necrosis factor-α) with MTX to bronchial epithelial cells showed a significant augmenting effect. SB203580, the specific inhibitor of p38 MAPK, inhibited MTX-induced IL-8 production. MTX induced the phosphorylation of Thr180 and Tyr182 on p38 MAPK. These results suggest that MTX activates bronchial and alveolar epithelial cells to induce IL-8 production through p38 MAPK, which might play an important role as one of the mechanisms of MTX-induced lung inflammation.

Diesel exhaust particles upregulate eotaxin gene expression in human bronchial epithelial cells via nuclear factor-kappa B-dependent pathway

Fine particles derived from diesel engines, diesel exhaust particles (DEP), have been shown to augment gene expression of several inflammatory cytokines in human airway epithelial cells in vitro. However, it remains unclear whether or not DEP have any effect on the expression and production of eotaxin, an important chemokine involved in eosinophil recruitment into the airways. We studied the effects of DEP by using a conventional suspended DEP and by a recently established in vitro cell exposure system to diesel exhaust (Abe S, Takizawa H, Sugawara I, and Kudoh S, Am J Respir Cell Mol Biol 22: 296-303, 2000). DEP showed a dose-dependent stimulatory effect on eotaxin production by normal human peripheral airway epithelial cells as well as by bronchial epithelial cell line BET-1A as assessed by specific ELISA. mRNA levels increased by DEP were shown by RT-PCR. DEP showed an additive effect on IL-13-stimulated eotaxin expression. DEP induced NF-kappaB activation by EMSA as previously reported but did not induce signal transducer and activator of transcription (STAT) 6 activation according to Western blot analysis. Finally, antioxidant agents (N-acetyl cysteine and pyrrolidine dithiocarbamate), which inhibited NF-kappaB activation but failed to affect STAT6 activation, almost completely attenuated DEP-induced eotaxin production, whereas these agents failed to attenuate IL-13-induced eotaxin production. These findings suggested that DEP stimulated eotaxin gene expression via NF-kappaB-dependent, but STAT6-independent, pathways.

Role of interferon-gamma in the development of murine bronchus-associated lymphoid tissues induced by silica in vivo

Exposure to silica is associated with the development of chronic airflow obstruction as well as pulmonary fibrosis, probably mediated in part by silica-induced small airway disease. To elucidate the mechanism of mucosal immune responses in the small airways, we analyzed the roles of interferon-gamma (IFN-gamma) using mice deficient of this cytokine in silicotic lung. IFN-gamma knockout mice (-/-) and wild-type C57BL/6 mice were treated with either a single fibrogenic dose of silica or an equivalent volume of saline and euthanized 21 days after intratracheal instillation. Total cell counts in bronchoalveolar lavage fluids increased in silica-instilled mice compared to saline-instilled mice, but there were no significant differences between IFN-gamma knockout mice and wild-type mice treated with silica. Morphometric estimation for fibrotic lesions within the lung did not show any differences between these mice. However, bronchus-associated lymphoid tissues (BALT), which are known to be involved in the mucosal immune responses, were significantly larger in the lungs of IFN-gamma knockout mice than in those of wild-type mice treated with silica. In addition, we evaluated the development of BALT in interleukin 4 (IL-4) knockout mice in order to clarify the effect of Th2 cytokine. Morphometric estimation for BALT did not show any differences between IL-4 knockout mice and wild-type mice in silicotic lung. These results suggest that IFN-gamma has an inhibitory effect on the development of BALT and may be involved in small airway disease in silicotic lung.

Benzene-extracted components are important for the major activity of diesel exhaust particles: effect on interleukin-8 gene expression in human bronchial epithelial cells

Epidemiologic and experimental studies suggest that diesel exhaust particles (DEPs) may be related to increasing respiratory mortality and morbidity. We have shown that DEPs augmented the production of inflammatory cytokines by human airway epithelial cells in vitro. To better understand the mechanisms of their proinflammatory activities, we studied the effects of several components extracted from DEPs on interleukin (IL)-8 expression in human bronchial epithelial cell line BEAS-2B and normal human airway epithelial cells obtained from very peripheral airways by an ultrathin bronchoscope. We used several agents active on signal transduction pathways in cytokine expression, such as the protein kinase C inhibitor staurosporin, antioxidant agents including N-acetyl cysteine (NAC) and pyrrolidine dithiocarbamate (PDTC), and p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580. Benzene-extracted components showed effects mimicking DEPs on IL-8 gene expression, release of several cytokines (IL-8; granulocyte macrophage colony-stimulating factor; and regulated on activation, normal T cells expressed and secreted) and nuclear factor (NF)-kappa B activation. We also found that NAC, PDTC, and SB203580 suppressed the activities of DEPs and their benzene extracts, suggesting the roles of oxidants-mediated NF-kappa B activation and p38MAPK pathways. Finally, benzo[a]pyrene, one of the important compounds included in the benzene component, replicated the activities shown by DEPs.

Nuclear factor-kappa b activation in silica-induced interleukin 8 production by human bronchial epithelial cells

Recent studies indicate that interleukin 8 (IL-8) plays an important role in interstitial lung diseases including silica-induced lung inflammation. To investigate the regulation of IL-8 expression and production in human bronchial epithelial cells, we examined the effects of silica on NF-kappaB activation. Human bronchial epithelial cell line BET-1A was cultured with hormonally defined Ham's F12 medium. The administration of silica induced IL-8 production in BET-1A dose-dependently and time-dependently. Northern blot analysis demonstrated that silica upregulated IL-8 expression in BET-1A. Moreover, electrophoretic mobility shift assays revealed that NF-kappaB activation occurred in the presence of silica, which was inhibited by antioxidants such as N-acetylcysteine (NAC). These data suggest that reactive oxygen species may be involved in the activation of NF-kappaB induced by silica.

Diesel exhaust particles up-regulate expression of intercellular adhesion molecule-1 (ICAM-1) in human bronchial epithelial cells

Epidemiological and experimental studies suggest that diesel exhaust particles (DEP) may play an active role in the increased respiratory mortality and morbidity. We have shown that DEP augmented the production of inflammatory cytokines by human airway epithelial cells in vitro. ICAM-1 has been shown to play an important role in the local accumulation of inflammatory cells. We studied the effect of DEP on ICAM-1 gene expression and surface expression in human bronchial epithelial cell line BEAS-2B. DEP (5-50 microg/ml) showed a stimulatory effect on ICAM-1 mRNA levels as evaluated by reverse transcription-polymerase chain reaction (RT-PCR). Flow cytometric analysis demonstrated an increased ICAM-1 expression on the epithelial cell surfaces. The soluble form of ICAM-1 molecules was also increased by the stimulation of DEP. In vitro neutrophil attachment onto DEP-stimulated epithelial cells was augmented, which was partially blocked by anti-ICAM-1 neutralizing antibody. Finally, these events were significantly inhibited by pretreatment with anti-oxidants pyrrolidine dithiocarbamate and N-acetyl cysteine, and p38 mitogen activated protein kinase (MAPK) inhibitor SB203580. These findings suggested that DEP induced up-regulation of ICAM-1 gene, and this process might be largely dependent on oxidant-mediated NF-kappaB activation and p38-MAPK pathways.

Erythromycin suppresses nuclear factor-kappaB and activator protein-1 activation in human bronchial epithelial cells

Erythromycin (EM), and related 14-member macrolide antibiotics, has attracted attention for its effectiveness in airway diseases including diffuse panbronchiolitis and sinobronchial syndrome. However, its molecular mechanisms remain unknown. We evaluated the effects of EM on activation of several transcription factors, including nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) in human bronchial epithelial cell line BET-1A, which are known to regulate the expression of many proinflammatory cytokines and chemokines such as interleukin-8 (IL-8). BET-1A cells were cultured with hormonally defined Ham's F12 medium, and were stimulated by phorbol myristate acetate (PMA). EM suppressed mRNA expression as well as the release of IL-8 at therapeutic and noncytotoxic concentrations (% inhibition of IL-8 protein release: 42.2 +/- 5.5%, at 10(-6) M). Furthermore, electrophoretic mobility shift assays revealed that EM inhibited the activations of NF-kappaB and AP-1 induced by PMA in BET-1A cells. These data indicate that EM has inhibitory effects not only on the mRNA expression and release of IL-8, but also on the activation of transcription factors NF-kappaB and AP-1. Our findings support the concept that the recruitment of neutrophils in airway diseases may be regulated by NF-kappaB and AP-1.

Diesel Exhaust Particles Induce NF-κB Activation in Human Bronchial Epithelial Cells In Vitro: Importance in Cytokine Transcription

Fine particles derived from diesel engines (diesel exhaust particles, DEP) have attracted attention, since their density in industrial countries seems related to the increased prevalence of pulmonary diseases. Previous studies have suggested that DEP have a potential to directly activate airway epithelial cells to produce and release inflammatory cytokines and mediators, and thus facilitate inflammatory responses in the lung. To elucidate the molecular mechanisms of their action, we studied here IL-8 gene expression, one of the important cytokines in inflammatory responses, by Northern blot analysis and run-on transcription assay. Suspended DEP (1–50 μg/ml) increased the steady state levels of IL-8 mRNA, which was suggested to be largely due to increased transcriptional rates. Electrophoretic mobility shift assay demonstrated that DEP induced increased binding to the specific motif of NF-κB, but not of transcription factor AP-1. The luciferase reporter gene assay using wild-type and mutated NF-κB-binding sequences showed that DEP-induced NF-κB activation was involved in IL-8 transcription. Finally, both N-acetylcysteine and pyrrolidine dithiocarbamate attenuated the action of DEP on IL-8 mRNA expression, suggesting that oxidant-mediated pathway might be involved in its processes. These results suggested that DEP activate NF-κB, which might be an important mechanism of its potential to increase the expression of inflammatory cytokines in vitro.

Diesel exhaust particles induce NF-kappa B activation in human bronchial epithelial cells in vitro: importance in cytokine transcription

Fine particles derived from diesel engines (diesel exhaust particles, DEP) have attracted attention, since their density in industrial countries seems related to the increased prevalence of pulmonary diseases. Previous studies have suggested that DEP have a potential to directly activate airway epithelial cells to produce and release inflammatory cytokines and mediators, and thus facilitate inflammatory responses in the lung. To elucidate the molecular mechanisms of their action, we studied here IL-8 gene expression, one of the important cytokines in inflammatory responses, by Northern blot analysis and run-on transcription assay. Suspended DEP (1-50 microgram/ml) increased the steady state levels of IL-8 mRNA, which was suggested to be largely due to increased transcriptional rates. Electrophoretic mobility shift assay demonstrated that DEP induced increased binding to the specific motif of NF-kappa B, but not of transcription factor AP-1. The luciferase reporter gene assay using wild-type and mutated NF-kappa B-binding sequences showed that DEP-induced NF-kappa B activation was involved in IL-8 transcription. Finally, both N-acetylcysteine and pyrrolidine dithiocarbamate attenuated the action of DEP on IL-8 mRNA expression, suggesting that oxidant-mediated pathway might be involved in its processes. These results suggested that DEP activate NF-kappa B, which might be an important mechanism of its potential to increase the expression of inflammatory cytokines in vitro.

Erythromycin and clarithromycin attenuate cytokine-induced endothelin-1 expression in human bronchial epithelial cells

Erythromycin and its fourteen-member macrolide analogues have attracted attention for their efficacy in bronchial asthma. However, their mechanisms of action remain unclear. We evaluated the effects of the macrolide antibiotics on endothelin-1 (ET-1) expression in normal and transformed human bronchial epithelial cells, one of the sources of this potent bronchoconstrictor important in the pathogenesis of asthma. Human bronchial epithelial cells were obtained from the resected bronchi, and the effect of several antimicrobial and antiasthmatic drugs on the production and messenger ribonucleic acid (mRNA) levels of ET-1 was evaluated. Bronchoepithelial cells were also isolated from the mucosa of asthmatic patients under fibreoptic bronchoscopy, and the modulating effects of the drugs were studied. Erythromycin and clarithromycin uniquely suppressed mRNA levels as well as the release of ET- at therapeutic and non-cytotoxic concentrations (percentage inhibition of ET-1 protein release: 26.4+/-5.22% and 31.2+/-7.45%, respectively, at 10(-6) M). Furthermore, erythromycin and clarithromycin inhibited ET-1 expression in bronchoepithelial cells from patients with chronic, stable asthma. A glucocorticosteroid, dexamethasone, also inhibited ET-1 expression. In contrast, theophylline, salbutamol and FK506 had no effect on ET-1 production. Our findings demonstrated that these fourteen-member macrolide antibiotics had an inhibitory effect on endothelin-1 expression in human bronchial epithelial cells. Moreover, this new mode of action may have some relevance to their clinical efficacy in bronchial asthma.

Erythromycin modulates IL-8 expression in normal and inflamed human bronchial epithelial cells

Erythromycin (EM) and its 14-member macrolide analogues have attracted attention for its effectiveness in a variety of airway diseases, including diffuse panbronchiolitis (DPB), sinobronchial syndrome, and chronic sinusitis. However, its mechanisms of action remain unelucidated. We evaluated the effects of several antibiotics on IL-8 expression by normal and transformed human bronchial epithelial cells, an important source of this potent chemokine involved in cell recruitment into the airways. EM and clarithromycin (CAM) uniquely suppressed mRNA levels as well as the release of IL-8 at the therapeutic and noncytotoxic concentrations (% inhibition of IL-8 protein release: 25.0 +/- 5.67% and 37.5 +/- 8.99%, respectively, at 10(-6) M). The other antimicrobes, including a 16-member macrolide josamycin, showed no effect. Bronchial epithelial cells from very peripheral airways as well as from main bronchi were obtained from patients with chronic airway inflammatory diseases, and EM and CAM inhibited IL-8 release from these cells. Among five patients who underwent bronchoscopy before and after macrolide treatment, four showed decreased levels of IL-8 expression in airway epithelium as assessed by reverse transcription and polymerase chain reaction. Our findings showed these 14-member macrolides had inhibitory effect on IL-8 expression in human bronchial epithelial cells, and this new mode of action may have relevance to their clinical effectiveness in airway diseases.

Erythromycin suppresses interleukin 6 expression by human bronchial epithelial cells: a potential mechanism of its anti-inflammatory action

We evaluated the effects of several antibiotics on IL-6 expression by human bronchial epithelial cells, potent sources of this proinflammatory cytokine important in airway inflammation. Among those tested, erythromycin (EM) and clarithromycin (CAM) uniquely suppressed mRNA levels as well as the release of IL-6 at the therapeutic and non-cytotoxic concentration (10(-6)M). Our findings suggested that these macrolide antibiotics had suppressive effect on cytokine expression in human cells, and this new mode of action may have relevance to their clinical effectiveness in airway inflammatory diseases.

[Systemic necrotizing vasculitis with pulmonary hemorrhage and gastrointestinal bleeding]

A 61-year-old man was admitted to our hospital with pain and weakness in both lower legs. Eosinophil count was abnormally high (6800/mm3). Chest X-ray film revealed multiple infiltrates in both lung fields. A specimen obtained by transbronchial lung biopsy demonstrated pulmonary hemorrhage. Vasculitis syndrome was suspected and 1 g per day of methylprednisolone was administered for 3 days. Pulmonary infiltrates quickly disappeared, but 2 weeks later massive intestinal hemorrhage occurred. Emergency ilectomy was done, but the patient died of bleeding from other intestinal lesions. Microscopic examination of the resected ileum revealed mucosal ulceration and necrotizing vasculitis in small arteries. This case is important in that vascular occlusion and ischemia progressed soon after vascular inflammation was relieved by administration of corticosteroid hormone.

[A case of pulmonary alveolar proteinosis with elevated serum angiotensin-converting enzyme activity]

A 45-year-old man with diffuse infiltrates on the chest X-ray film was admitted to the hospital. At first, sarcoidosis was suspected due to the elevated serum angiotensin-converting enzyme (ACE) activity. Transbronchial lung biopsy and bronchoalveolar lavage, however, did not lead to that diagnosis. Pulmonary alveolar proteinosis (PAP) was diagnosed after an open lung biopsy. The diffuse infiltrates on his chest X-ray film diminished spontaneously. Two years later, diffuse infiltrates increased again with an elevated serum ACE activity. In this case, it seemed that the severity of PAP was associated with serum ACE activity. We review the literature on the relationship between serum ACE activity and dysfunction of alveolar macrophages in PAP.