Cigarette smoke is a major cause of chronic obstructive pulmonary disease (COPD). Airway epithelial cells and macrophages are the first defense cells against cigarette smoke and these cells are an important source of pro-inflammatory cytokines. These cytokines play a role in progressive airflow limitation and chronic airways inflammation. Furthermore, the chronic colonization of airways by Gram-negative bacteria, contributes to the persistent airways inflammation and progression of COPD. The current study addressed the effects of cigarette smoke along with lipolysaccharide (LPS) in airway epithelial cells as a representative in vitro model of COPD exacerbations. Furthermore, we evaluated the effects of PDE4 inhibitor, the roflumilast N-oxide (RNO), in this experimental model. A549 cells were stimulated with cigarette smoke extract (CSE) alone (0.4% to 10%) or in combination with a low concentration of LPS (0.1 µg/ml) for 2 h or 24 h for measurement of chemokine protein and mRNAs and 5–120 min for protein phosphorylation. Cells were also pre-incubated with MAP kinases inhibitors and Prostaglandin E2 alone or combined with RNO, before the addition of CSE+LPS. Production of cytokines was determined by ELISA and protein phosphorylation by western blotting and phospho-kinase array. CSE did not induce production of IL-8/CXCL8 and Gro-α/CXCL1 from A549 cells, but increase production of CCL2/MCP-1. However the combination of LPS 0.1 µg/ml with CSE 2% or 4% induced an important production of these chemokines, that appears to be dependent of ERK1/2 and JAK/STAT pathways but did not require JNK and p38 pathways. Moreover, RNO associated with PGE2 reduced CSE+LPS-induced cytokine release, which can happen by occur through of ERK1/2 and JAK/STAT pathways. We report here an in vitro model that can reflect what happen in airway epithelial cells in COPD exacerbation. We also showed a new pathway where CSE+LPS can induce cytokine release from A549 cells, which is reduced by RNO.
Chronic airway inflammation is a cardinal feature of chronic obstructive pulmonary disease (COPD), a destructive cigarette smoke-induced lung disease. Although it is apparent that dendritic cells (DCs) are an important constituent of the chronic inflammatory cell influx found in airways of COPD patients, the functional roles of DCs in the pathogenesis of smoking-induced emphysema are unknown. We postulated that DCs activated by cigarette smoke constituents directly participate in the chronic inflammation that characterizes COPD airways. Concordant with this hypothesis, we observed that incubation of DCs with cigarette smoke extract (CSE), and chronic exposure of mice to cigarette smoke, both augmented the generation of neutrophilic chemokines by immature and lipopolysaccharide (LPS) or CD40L-matured DCs. The generation of interleukin-8 (CXCL8/IL-8) by human DCs conditioned with CSE was suppressed by the anti-oxidant n-acetyl cysteine (NAC), implying the involvement of oxidant sensitive pathways as a primary mechanism involved in the enhanced CXCL8/IL-8 generation. Cigarette smoke extract and nicotine also augment the production of secreted prostaglandin E2 and intracellular cyclo-oxygenase-2 (COX-2) in maturing DCs. Whereas NAC suppressed production of CXCL8 by CSE-conditioned DCs, it augmented production of PGE2 and cellular COX-2 levels in maturing DCs. These studies indicate that the stimulation of DCs by cigarette smoke-induced oxidative stress and nicotine promote the generation of pro-inflammatory responses that promote chronic inflammation in smokers. Certain pharmacologic strategies such as anti-oxidant therapy may be only partially effective in mitigating cigarette smoke-induced pro-inflammatory DC-mediated responses in smokers.
Smoking; dendritic cell; oxidative stress; neutrophil; chemokines; prostaglandins
Cigarette smoke is the leading risk factor for the development of chronic obstructive pulmonary disease (COPD) an inflammatory condition characterised by neutrophilic inflammation and release of proinflammatory mediators such as interleukin-8 (IL-8). Human airway smooth muscle cells (HASMC) are a source of proinflammatory cytokines and chemokines. We investigated whether cigarette smoke could directly induce the release of chemokines from HASMC.
HASMC in primary culture were exposed to cigarette smoke extract (CSE) with or without TNFα. Chemokines were measured by enzyme-linked immunosorbent assay (ELISA) and gene expression by real time polymerase chain reaction (PCR). Data were analysed using one-way analysis of variance (ANOVA) followed by Bonferroni's t test
CSE (5, 10 and 15%) induced IL-8 release and expression without effect on eotaxin or RANTES release. At 20%, there was less IL-8 release. TNFα enhanced CSE-induced IL-8 release and expression. However, CSE (5–30%) inhibited TNFα-induced eotaxin and RANTES production. The effects of CSE on IL-8 release were inhibited by glutathione (GSH) and associated with the induction of the oxidant sensing protein, heme oxygenase-1.
Cigarette smoke may directly cause the release of IL-8 from HASMC, an effect enhanced by TNF-α which is overexpressed in COPD. Inhibition of eotaxin and RANTES by cigarette smoke is consistent with the predominant neutrophilic but not eosinophilic inflammation found in COPD.
Human rhinovirus (HRV) triggers exacerbations of asthma and chronic obstructive pulmonary disease (COPD). Cigarette smoking is the leading risk factor for the development of COPD and 25% of asthmatics smoke. Smoking asthmatics have worse symptoms and more frequent hospitalizations compared to non-smoking asthmatics. The degree of neutrophil recruitment to the airways correlates with disease severity in COPD and during viral exacerbations of asthma. We have previously shown that HRV and cigarette smoke, in the form of cigarette smoke extract (CSE), each induce expression of the neutrophil chemoattractant and activator, CXCL8, in human airway epithelial cells. Additionally, we demonstrated that the combination of HRV and CSE induces expression of levels of CXCL8 that are at least additive relative to induction by each stimulus alone, and that enhancement of CXCL8 expression by HRV+CSE is regulated, at least in part, via mRNA stabilization. Here we further investigate the mechanisms by which HRV+CSE enhances CXCL8 expression.
Primary human bronchial epithelial cells were cultured and treated with CSE alone, HRV alone or the combination of the two stimuli. Stabilizing/destabilizing proteins adenine/uridine-rich factor-1 (AUF-1), KH-type splicing regulatory protein (KHSRP) and human antigen R (HuR) were measured in cell lysates to determine expression levels following treatment. siRNA knockdown of each protein was used to assess their contribution to the induction of CXCL8 expression following treatment of cells with HRV and CSE.
We show that total expression of stabilizing/de-stabilizing proteins linked to CXCL8 regulation, including AUF-1, KHSRP and HuR, are not altered by CSE, HRV or the combination of the two stimuli. Importantly, however, siRNA-mediated knock-down of HuR, but not AUF-1 or KHSRP, abolishes the enhancement of CXCL8 by HRV+CSE. Data were analyzed using one-way ANOVA with student Newman-Keuls post hoc analysis and values of p≤ 0.05 were considered significant.
Induction of CXCL8 by the combination of HRV and CSE is regulated by mRNA stabilization involving HuR. Thus, targeting the HuR pathway may be an effective method of dampening CXCL8 production during HRV-induced exacerbations of lower airway disease, particularly in COPD patients and asthmatic patients who smoke.
Airway epithelium; Rhinovirus; Cigarette smoke; CXCL8; HuR; Post-transcriptional gene regulation; COPD; Asthma
Respiratory syncytial viral (RSV) infections are a frequent cause of chronic obstructive pulmonary disease (COPD) exacerbations, which are a major factor in disease progression and mortality. RSV is able to evade antiviral defenses to persist in the lungs of COPD patients. Though RSV infection has been identified in COPD, its contribution to cigarette smoke-induced airway inflammation and lung tissue destruction has not been established. Here we examine the long-term effects of cigarette smoke exposure, in combination with monthly RSV infections, on pulmonary inflammation, protease production and remodeling in mice. RSV exposures enhanced the influx of macrophages, neutrophils and lymphocytes to the airways of cigarette smoke exposed C57BL/6J mice. This infiltration of cells was most pronounced around the vasculature and bronchial airways. By itself, RSV caused significant airspace enlargement and fibrosis in mice and these effects were accentuated with concomitant smoke exposure. Combined stimulation with both smoke and RSV synergistically induced cytokine (IL-1α, IL-17, IFN-γ, KC, IL-13, CXCL9, RANTES, MIF and GM-CSF) and protease (MMP-2, -8, -12, -13, -16 and cathepsins E, S, W and Z) expression. In addition, RSV exposure caused marked apoptosis within the airways of infected mice, which was augmented by cigarette smoke exposure. RSV and smoke exposure also reduced protein phosphatase 2A (PP2A) and protein tyrosine phosphates (PTP1B) expression and activity. This is significant as these phosphatases counter smoke-induced inflammation and protease expression. Together, these findings show for the first time that recurrent RSV infection markedly enhances inflammation, apoptosis and tissue destruction in smoke-exposed mice. Indeed, these results indicate that preventing RSV transmission and infection has the potential to significantly impact on COPD severity and progression.
The pulmonary innate immune system is heavily implicated in the perpetual airway inflammation and impaired host defense characterizing Chronic Obstructive Pulmonary Disease (COPD). The airways of patients suffering from COPD are infiltrated by various immune and inflammatory cells including macrophages, neutrophils, T lymphocytes, and dendritic cells. While the role of macrophages, neutrophils and T lymphocytes is well characterized, the contribution of dendritic cells to COPD pathogenesis is still the subject of emerging research. A paper by Botelho and colleagues in the current issue of Respiratory Research investigates the importance of dendritic cell recruitment in cigarette-smoke induced acute and chronic inflammation in mice. Dendritic cells of the healthy lung parenchyma and airways perform an important sentinel function and regulate immune homeostasis. During inflammatory responses the function and migration pattern of these cells is dramatically altered but the underlying mechanisms are incompletely understood. Botelho and colleagues demonstrate here the importance of IL-1R1/IL-1α related mechanisms including CCL20 production in cigarette-smoke induced recruitment of dendritic cells and T cell activation in the mouse lung.
COPD; Dendritic cells; IL-1R1; IL-1α; Cigarette smoke exposure; Mice
Exposure to cigarette smoke is associated with a significant increase in the risk for respiratory viral infections. The airway epithelium is the primary target for both cigarette smoke and respiratory viral infection. We investigated the effects of cigarette smoke on the response of airway epithelial cells to rhinovirus infection. We found that pre-exposure of BEAS-2B cells or primary normal human bronchial epithelial cells (NHBEs) to cigarette smoke extract (CSE) reduced the induction of mRNA of the chemokines CXCL10 and CCL5 by either the viral mimic polyinosine–polycytidylic acid (Poly I:C) or human rhinovirus 16 (HRV-16) infection. The HRV-16–induced release of CXCL10 and CCL5 was also significantly suppressed by CSE. Activation of the IFN mediator STAT-1 and the activation of JNK by poly I:C and HRV-16 were partially suppressed by pre-exposure to CSE. In contrast, the poly I:C–induced and HRV-16–induced phosphorylation of ERK1/2 was unaffected by CSE. HRV-16–stimulated IFN-β mRNA was also significantly reduced by CSE. Because suppression of the IFN response to viral infection was associated with increased viral production, we assessed HRV-16 RNA concentrations. Exposure to CSE resulted in an increase in HRV-16 RNA at 48 hours after the infection of BEAS-2B cells. These data demonstrate that exposure to CSE alters the response of airway epithelial cells to HRV infection, leading to decreased activation of the IFN–STAT-1 and SAP–JNK pathways, the suppression of CXCL10 and CCL5 production, and increased viral RNA. A diminished, early epithelial-initiated antiviral response to rhinovirus infection could contribute to the increased susceptibility of subjects to prolonged respiratory viral infections after exposure to cigarette smoke.
cigarette smoke; respiratory infections; rhinovirus; epithelial cells
Cigarette smoke-induced release of pro-inflammatory cytokines including interleukin-8 (IL-8) from inflammatory as well as structural cells in the airways, including airway smooth muscle (ASM) cells, may contribute to the development of chronic obstructive pulmonary disease (COPD). Despite the wide use of pharmacological treatment aimed at increasing intracellular levels of the endogenous suppressor cyclic AMP (cAMP), little is known about its exact mechanism of action. We report here that next to the β2-agonist fenoterol, direct and specific activation of either exchange protein directly activated by cAMP (Epac) or protein kinase A (PKA) reduced cigarette smoke extract (CSE)-induced IL-8 mRNA expression and protein release by human ASM cells. CSE-induced IκBα-degradation and p65 nuclear translocation, processes that were primarily reversed by Epac activation. Further, CSE increased extracellular signal-regulated kinase (ERK) phosphorylation, which was selectively reduced by PKA activation. CSE decreased Epac1 expression, but did not affect Epac2 and PKA expression. Importantly, Epac1 expression was also reduced in lung tissue from COPD patients. In conclusion, Epac and PKA decrease CSE-induced IL-8 release by human ASM cells via inhibition of NF-κB and ERK, respectively, pointing at these cAMP effectors as potential targets for anti-inflammatory therapy in COPD. However, cigarette smoke exposure may reduce anti-inflammatory effects of cAMP elevating agents via down-regulation of Epac1.
Cigarette smoking induces inflammatory responses in all smokers and is the major risk factor for lung disease such as chronic obstructive pulmonary disease (COPD). In this progressive disease, chronic inflammation in the lung contributes to lung tissue destruction leading to the formation of chemotactic collagen fragments such as N-acetylated Proline-Glycine-Proline (N-ac-PGP). The generation of this tripeptide is mediated by a multistep pathway involving matrix metalloproteases (MMPs) 8 and 9 and prolyl endopeptidase (PE). Here we investigated whether cigarette smoke extract (CSE) stimulates human PMNs to breakdown whole matrix collagen leading to the generation of the chemotactic collagen fragment N-ac-PGP.
Incubating PMNs with CSE led to the release of chemo-attractant CXCL8 and proteases MMP8 and MMP9. PMNs constitutively expressed PE activity as well as PE protein. Incubating CSE-primed PMNs with collagen resulted in collagen breakdown and in N-ac-PGP generation. Incubation of PMNs with the tripeptide N-ac-PGP resulted in the release of CXCL8, MMP8 and MMP9. Moreover, we tested whether PMNs from COPD patients are different from PMNs from healthy donors. Here we show that the intracellular basal PE activity of PMNs from COPD patients increased 25-fold compared to PMNs from healthy donors. Immunohistological staining of human lung tissue for PE showed that besides neutrophils, macrophages and epithelial cells express PE.
This study indicates that neutrophils activated by cigarette smoke extract can breakdown collagen into N-ac-PGP and that this collagen fragment itself can activate neutrophils, which may lead in vivo to a self-propagating cycle of neutrophil infiltration, chronic inflammation and lung emphysema. MMP-, PE- or PGP-inhibitors can serve as an attractive therapeutic target and may open new avenues towards effective treatment of COPD.
CXCL14, a recently described epithelial cytokine, plays putative multiple roles in inflammation and carcinogenesis. In the context that chronic obstructive pulmonary disease (COPD) and lung cancer are both smoking-related disorders associated with airway epithelial disorder and inflammation, we hypothesized that the airway epithelium responds to cigarette smoking with altered CXCL14 gene expression, contributing to the disease-relevant phenotype. Using genome-wide microarrays with subsequent immunohistochemical analysis, the data demonstrate that the expression of CXCL14 is up-regulated in the airway epithelium of healthy smokers and further increased in COPD smokers, especially within hyperplastic/metaplastic lesions, in association with multiple genes relevant to epithelial structural integrity and cancer. In vitro experiments revealed that the expression of CXCL14 is induced in the differentiated airway epithelium by cigarette smoke extract, and that epidermal growth factor mediates CXCL14 up-regulation in the airway epithelium through its effects on the basal stem/progenitor cell population. Analyses of two independent lung cancer cohorts revealed a dramatic up-regulation of CXCL14 expression in adenocarcinoma and squamous-cell carcinoma. High expression of the COPD-associated CXCL14-correlating cluster of genes was linked in lung adenocarcinoma with poor survival. These data suggest that the smoking-induced expression of CXCL14 in the airway epithelium represents a novel potential molecular link between smoking-associated airway epithelial injury, COPD, and lung cancer.
CXCL14; airway epithelium; smoking; COPD; lung cancer
Abnormal immune responses are believed to be highly relevant in the pathogenesis of chronic obstructive pulmonary disease (COPD). Dendritic cells provide a critical checkpoint for immunity by their capacity to both induce and suppress immunity. Although evident that cigarette smoke, the primary cause of COPD, significantly influences dendritic cell functions, little is known about the roles of dendritic cells in the pathogenesis of COPD.
The extent of dendritic cell infiltration in COPD tissue specimens was determined using immunohistochemical localization of CD83+ cells (marker of matured myeloid dendritic cells), and CD1a+ cells (Langerhans cells). The extent of tissue infiltration with Langerhans cells was also determined by the relative expression of the CD207 gene in COPD versus control tissues. To determine mechanisms by which dendritic cells accumulate in COPD, complimentary studies were conducted using monocyte-derived human dendritic cells exposed to cigarette smoke extract (CSE), and dendritic cells extracted from mice chronically exposed to cigarette smoke.
In human COPD lung tissue, we detected a significant increase in the total number of CD83+ cells, and significantly higher amounts of CD207 mRNA when compared with control tissue. Human monocyte-derived dendritic cells exposed to CSE (0.1-2%) exhibited enhanced survival in vitro when compared with control dendritic cells. Murine dendritic cells extracted from mice exposed to cigarette smoke for 4 weeks, also demonstrated enhanced survival compared to dendritic cells extracted from control mice. Acute exposure of human dendritic cells to CSE induced the cellular pro-survival proteins heme-oxygenase-1 (HO-1), and B cell lymphoma leukemia-x(L) (Bcl-xL), predominantly through oxidative stress. Although activated human dendritic cells conditioned with CSE expressed diminished migratory CCR7 expression, their migration towards the CCR7 ligand CCL21 was not impaired.
These data indicate that COPD is associated with increased numbers of cells bearing markers associated with Langerhans cells and mature dendritic cells, and that cigarette smoke promotes survival signals and augments survival of dendritic cells. Although CSE suppressed dendritic cell CCR7 expression, migration towards a CCR7 ligand was not diminished, suggesting that reduced CCR7-dependent migration is unlikely to be an important mechanism for dendritic cell retention in the lungs of smokers with COPD.
Cigarette smoke is a profound pro-inflammatory stimulus that contributes to acute lung injuries and to chronic lung disease including COPD (emphysema and chronic bronchitis). Until recently, it was assumed that resolution of inflammation was a passive process that occurred once the inflammatory stimulus was removed. It is now recognized that resolution of inflammation is a bioactive process, mediated by specialized lipid mediators, and that normal homeostasis is maintained by a balance between pro-inflammatory and pro-resolving pathways. These novel small lipid mediators, including the resolvins, protectins and maresins, are bioactive products mainly derived from dietary omega-3 and omega-6 polyunsaturated fatty acids (PUFA). We hypothesize that resolvin D1 (RvD1) has potent anti-inflammatory and pro-resolving effects in a model of cigarette smoke-induced lung inflammation.
Primary human lung fibroblasts, small airway epithelial cells and blood monocytes were treated with IL-1β or cigarette smoke extract in combination with RvD1 in vitro, production of pro-inflammatory mediators was measured. Mice were exposed to dilute mainstream cigarette smoke and treated with RvD1 either concurrently with smoke or after smoking cessation. The effects on lung inflammation and lung macrophage populations were assessed.
RvD1 suppressed production of pro-inflammatory mediators by primary human cells in a dose-dependent manner. Treatment of mice with RvD1 concurrently with cigarette smoke exposure significantly reduced neutrophilic lung inflammation and production of pro-inflammatory cytokines, while upregulating the anti-inflammatory cytokine IL-10. RvD1 promoted differentiation of alternatively activated (M2) macrophages and neutrophil efferocytosis. RvD1 also accelerated the resolution of lung inflammation when given after the final smoke exposure.
RvD1 has potent anti-inflammatory and pro-resolving effects in cells and mice exposed to cigarette smoke. Resolvins have strong potential as a novel therapeutic approach to resolve lung injury caused by smoke and pulmonary toxicants.
Protein phosphatase 2A (PP2A) is the primary serine-threonine phosphatase of eukaryotic cells, and changes in its activity have been linked to neoplastic and neurodegenerative diseases. However, the role of PP2A in noncancerous lung diseases such as chronic obstructive pulmonary disease (COPD) has not been previously examined. This study determined that PP2A activity was significantly increased in the lungs of advanced emphysema subjects compared with age-matched controls. Furthermore, we found that cigarette smoke exposure increases PP2A activity in mouse lung in vivo and in primary human small airway epithelial (SAE) cells in vitro. In mice, intratracheal transfection of PP2A protein prior to cigarette smoke exposure prevented acute smoke–induced lung inflammation. Conversely, inhibiting PP2A activity during smoke exposure exacerbated inflammatory responses in the lung. To further determine how PP2A modulates the responses to cigarette smoke in the lung, enzyme levels were manipulated in SAE cells using protein transfection and short hairpin RNA (shRNA) techniques. Increasing PP2A activity in SAE cells via PP2A protein transfection downregulated cytokine expression and prevented the induction of proteases following cigarette smoke extract (CSE) treatment. Conversely, decreasing enzymatic activity by stably transfecting SAE cells with shRNA for the A subunit of PP2A exacerbated these smoke-mediated responses. This study establishes that PP2A induction by cigarette smoke modulates immune and proteolytic responses to cigarette smoke exposure. Together, these findings suggest that manipulation of PP2A activity may be a plausible means to treat COPD and other inflammatory diseases.
phosphatase; inflammation; emphysema
The tachykinins, substance P and neurokinin A, present in sensory nerves and inflammatory cells such as macrophages and dendritic cells, are considered as pro-inflammatory agents. Inflammation of the airways and lung parenchyma plays a major role in the pathogenesis of chronic obstructive pulmonary disease (COPD) and increased tachykinin levels are recovered from the airways of COPD patients. The aim of our study was to clarify the involvement of the tachykinin NK1 receptor, the preferential receptor for substance P, in cigarette smoke (CS)-induced pulmonary inflammation and emphysema in a mouse model of COPD.
Tachykinin NK1 receptor knockout (NK1-R-/-) mice and their wild type controls (all in a mixed 129/sv-C57BL/6 background) were subjected to sub acute (4 weeks) or chronic (24 weeks) exposure to air or CS. 24 hours after the last exposure, pulmonary inflammation and development of emphysema were evaluated.
Sub acute and chronic exposure to CS resulted in a substantial accumulation of inflammatory cells in the airways of both WT and NK1-R-/- mice. However, the CS-induced increase in macrophages and dendritic cells was significantly impaired in NK1-R-/- mice, compared to WT controls, and correlated with an attenuated release of MIP-3α/CCL20 and TGF-β1. Chronic exposure to CS resulted in development of pulmonary emphysema in WT mice. NK1-R-/- mice showed already enlarged airspaces upon air-exposure. Upon CS-exposure, the NK1-R-/- mice did not develop additional destruction of the lung parenchyma. Moreover, an impaired production of MMP-12 by alveolar macrophages upon CS-exposure was observed in these KO mice. In a pharmacological validation experiment using the NK1 receptor antagonist RP 67580, we confirmed the protective effect of absence of the NK1 receptor on CS-induced pulmonary inflammation.
These data suggest that the tachykinin NK1 receptor is involved in the accumulation of macrophages and dendritic cells in the airways upon CS-exposure and in the development of smoking-induced emphysema. As both inflammation of the airways and parenchymal destruction are important characteristics of COPD, these findings may have implications in the future treatment of this devastating disease.
Tobacco smoking irritates and damages the respiratory tract and contributes to a higher risk of developing lung emphysema. At present, smoking cessation is the only effective treatment for reducing the progression of lung emphysema, however, there is hardly anything known about the effects of smoking cessation on cytokine and chemokine levels in the airways. To the best of our knowledge, this is the first reported in vivo study in which cytokine profiles were determined after cessation of cigarette smoke exposure.
The severity of airway remodeling and inflammation was studied by analyzing alveolar enlargement, heart hypertrophy, inflammatory cells in the bronchoalveolar lavage fluid (BALF) and lung tissue and by determining the cytokine and chemokine profiles in the BALF of A/J mice exposed to cigarette smoke for 20 weeks and 8 weeks after smoking cessation.
The alveolar enlargement and right ventricle heart hypertrophy found in smoke-exposed mice remained unchanged after smoking cessation. Although the neutrophilic inflammation in the BALF of cigarette smoke-exposed animals was reduced after smoking cessation, a sustained inflammation in the lung tissue was observed. The elevated cytokine (IL-1α and TNF-α) and chemokine (CCL2 and CCL3) levels in the BALF of smoke-exposed mice returned to basal levels after smoking cessation, while the increased IL-12 levels did not return to its basal level. The cigarette smoke-enhanced VEGF levels did not significantly change after smoking cessation. Moreover, IL-10 levels were reduced in the BALF of smoke-exposed mice and these levels were still significantly decreased after smoking cessation compared to the control animals.
The inflammatory changes in the airways caused by cigarette smoke exposure were only partially reversed after smoking cessation. Although smoking cessation should be the first step in reducing the progression of lung emphysema, additional medication could be provided to tackle the sustained airway inflammation.
In this study, we evaluated the anti-inflammatory effect of PM014 on cigarette smoke induced lung disease in the murine animal model of chronic obstructive pulmonary disease (COPD).
Mice were exposed to cigarette smoke (CS) for 2 weeks to induce COPD-like lung inflammation. Two hours prior to cigarette smoke exposure, the treatment group was administered PM014 via an oral injection. To investigate the effects of PM014, we assessed PM014 functions in vivo, including immune cell infiltration, cytokine profiles in bronchoalveolar lavage (BAL) fluid and histopathological changes in the lung. The efficacy of PM014 was compared with that of the recently developed anti-COPD drug, roflumilast.
PM014 substantially inhibited immune cell infiltration (neutrophils, macrophages, and lymphocytes) into the airway. In addition, IL-6, TNF-α and MCP-1 were decreased in the BAL fluid of PM014-treated mice compared to cigarette smoke stimulated mice. These changes were more prominent than roflumilast treated mice. The expression of PAS-positive cells in the bronchial layer was also significantly reduced in both PM014 and roflumilast treated mice.
These data suggest that PM014 exerts strong therapeutic effects against CS induced, COPD-like lung inflammation. Therefore, this herbal medicine may represent a novel therapeutic agent for lung inflammation in general, as well as a specific agent for COPD treatment.
COPD; CS; PM014; Neutrophil; IL-6; TNF-α; MCP-1
Chronic obstructive pulmonary disease (COPD) is a progressive condition characterized by chronic airway inflammation and airspace remodeling, leading to airflow limitation that is not completely reversible. Smoking is the leading risk factor for compromised lung function stemming from COPD pathogenesis. First- and second-hand cigarette smoke contain thousands of constituents, including several carcinogens and cytotoxic chemicals that orchestrate chronic lung inflammation and destructive alveolar remodeling. Receptors for advanced glycation end-products (RAGE) are multi-ligand cell surface receptors primarily expressed by diverse lung cells. RAGE expression increases following cigarette smoke exposure and expression is elevated in the lungs of patients with COPD. RAGE is responsible in part for inducing pro-inflammatory signaling pathways that culminate in expression and secretion of several cytokines, chemokines, enzymes, and other mediators. In the current review, new transgenic mouse models that conditionally over-express RAGE in pulmonary epithelium are discussed. When RAGE is over-expressed throughout embryogenesis, apoptosis in the peripheral lung causes severe lung hypoplasia. Interestingly, apoptosis in RAGE transgenic mice occurs via conserved apoptotic pathways also known to function in advanced stages of COPD. RAGE over-expression in the adult lung models features of COPD including pronounced inflammation and loss of parenchymal tissue. Understanding the biological contributions of RAGE during cigarette smoke-induced inflammation may provide critically important insight into the pathology of COPD.
RAGE; COPD; tobacco; mouse model
Myeloid and plasmacytoid dendritic cells (mDCs, pDC) are crucial to the immune system, detecting microorganisms and linking the innate and adaptive immunity. pDC are present in small quantities in tissues that are in contact with the external environment; mainly the skin, the inner lining of the nose, lungs, stomach and intestines. They produce large amounts of IFN-α after stimulation and are pivotal for the induction of antiviral responses. Chronic obstructive pulmonary disease (COPD) patients are known to be more susceptible to viral infections. We have demonstrated that exposure of mDC to cigarette smoke extract (CSE) leads to the release of chemokines, however, not much is known about the role of pDC in COPD. In this study, we addressed several key questions with respect to the mechanism of action of CSE on human pDC in an in vitro model. Human pDCs were isolated from normal healthy volunteers and subjected to fresh CSE and the levels of IL-8, TNF-α, IP-10, IL-6, IL-1, IL-12 and IL-10 and IFN-α were studied by both ELISA and real time PCR methods. We observed that CSE augmented the production of IL-8 and suppressed the release of TNF-α, IL-6 and IFN-α. Moreover, CSE suppressed PI3K/Akt signalling in pDC. In conclusion, our data indicate that CSE has both the potential to diminish anti-viral immunity by downregulating the release of IFN-α and other pro-inflammatory cytokines while, at the same time, augmenting the pathogenesis of COPD via an IL-8 induced recruitment of neutrophils.
Cigarette smoke is the major risk factor associated with the development of chronic obstructive pulmonary disease (COPD). Recent studies propose a link between endoplasmic reticulum (ER) stress and emphysema, demonstrated by increased ER stress markers under smoking conditions. Here, we investigate whether cigarette smoke-induced ER stress is cell specific and correlates with acute and chronic cigarette smoke exposure.
Gene and protein expression changes in human primary lung cell cultures following cigarette smoke extract (CSE) exposure were monitored by qPCR and Western blot analysis. Mice and guinea pigs were exposed to cigarette smoke and ER stress markers examined in whole lung homogenates. Inflammatory cells from the bronchoalveolar lavage fluid of 10 days smoke exposed mice were also examined.
Cigarette smoke induced a trend increase in the ER stress response through an activating transcription factor 4 (ATF4) mediated induction of C/EBP homologous protein (CHOP) in primary small airway epithelial cells. Bronchial epithelial cells and macrophages responded similarly to CSE. Wild-type mice and guinea pigs exposed to acute levels of cigarette smoke exhibited increased levels of CHOP but not at significant levels. However, after long-term chronic cigarette smoke exposure, CHOP expression was reduced. Interestingly, inflammatory cells from smoke exposed mice had a significant increase in CHOP/ATF4 expression.
A trend increase in CHOP levels appear in multiple human lung cell types following acute cigarette smoke exposure in vitro. In vivo, inflammatory cells, predominately macrophages, demonstrate significant cigarette smoke-induced ER stress. Early induction of CHOP in cigarette smoke may play a pivotal role in early induction of lung disease, however in vivo long-term cigarette smoke exposure exhibited a reduction in the ER stress response.
COPD; ER stress; cigarette smoke; CHOP
Cigarette smoking is the main risk factor for the development of chronic obstructive pulmonary disease (COPD), a major cause of morbidity and mortality worldwide. Despite this, the cellular and molecular mechanisms that contribute to COPD pathogenesis are still poorly understood.
Methodology and Principal Findings
The objective of this study was to assess IL-1 α and β expression in COPD patients and to investigate their respective roles in perpetuating cigarette smoke-induced inflammation. Functional studies were pursued in smoke-exposed mice using gene-deficient animals, as well as blocking antibodies for IL-1α and β. Here, we demonstrate an underappreciated role for IL-1α expression in COPD. While a strong correlation existed between IL-1α and β levels in patients during stable disease and periods of exacerbation, neutrophilic inflammation was shown to be IL-1α-dependent, and IL-1β- and caspase-1-independent in a murine model of cigarette smoke exposure. As IL-1α was predominantly expressed by hematopoietic cells in COPD patients and in mice exposed to cigarette smoke, studies pursued in bone marrow chimeric mice demonstrated that the crosstalk between IL-1α+ hematopoietic cells and the IL-1R1+ epithelial cells regulates smoke-induced inflammation. IL-1α/IL-1R1-dependent activation of the airway epithelium also led to exacerbated inflammatory responses in H1N1 influenza virus infected smoke-exposed mice, a previously reported model of COPD exacerbation.
Conclusions and Significance
This study provides compelling evidence that IL-1α is central to the initiation of smoke-induced neutrophilic inflammation and suggests that IL-1α/IL-1R1 targeted therapies may be relevant for limiting inflammation and exacerbations in COPD.
Thymic stromal lymphopoietin (TSLP) is a newly identified IL-7–like cytokine known to be expressed in airway biopsies of patients with asthma and chronic obstructive pulmonary disease. As both diseases may be induced or exacerbated by cigarette smoking, it is possible that TSLP represents an important link between cigarette smoke exposure and inflammatory signaling in the airways. In this regard, TSLP appears to also be expressed in airway smooth muscle (ASM); however, its role is unknown. In the current study, we examined TSLP and the TSLP receptor (TSLP-R) expression and function in human ASM cells under normal conditions and following exposure to cigarette smoke extract (CSE). Western blot analysis of human ASM cells showed significant expression of TSLP and TSLP-R, with increased expression of both by overnight exposure to 1 or 2% CSE. Furthermore, CSE increased TSLP release by ASM. In parallel experiments using enzymatically dissociated human ASM cells loaded with the Ca2+ indicator fura 2-AM and imaged using fluorescence microscopy, we evaluated the effects of CSE exposure on intracellular Ca2+ ([Ca2+]i) responses to agonist stimulation. [Ca2+]i responses to histamine were increased with overnight CSE exposure. Exposure to TSLP also resulted in elevated responses, which were blunted by TSLP and TSLP-R Abs. Importantly, the enhancing effects of CSE on [Ca2+]i responses were also blunted by these Abs. These effects were associated with CSE- and TSLP-induced changes in STAT5 phosphorylation. Overall, these novel data suggest that cigarette smoke, TSLP, and ASM are functionally linked and that cigarette smoke-induced increase in airway contractility may be mediated via ASM-derived increases in TSLP signaling.
Cigarette smoke, the major risk factor for COPD, is known to activate matrix metalloproteinases in airway epithelium. We investigated whether metalloproteinases, particularly A Disintegrin and Metalloproteinase (ADAM)17, contribute to increased pro-inflammatory epithelial responses with respect to the release of IL-8 and TGF-α, cytokines implicated in COPD pathogenesis.
We studied the effects of cigarette smoke extract (CSE) and metalloproteinase inhibitors on TGF-α and IL-8 release in primary bronchial epithelial cells (PBECs) from COPD patients, healthy smokers and non-smokers.
We observed that TGF-α was mainly shed by ADAM17 in PBECs from all groups. Interestingly, IL-8 production occurred independently from ADAM17 and TGF-α shedding, but was significantly inhibited by broad-spectrum metalloproteinase inhibitor TAPI-2. CSE did not induce ADAM17-dependent TGF-α shedding, while it slightly augmented the production of IL-8. This was accompanied by reduced endogenous inhibitor of metalloproteinase (TIMP)-3 levels, suggesting that CSE does not directly but rather indirectly alter activity of ADAM17 through the regulation of its endogenous inhibitor. Furthermore, whereas baseline TGF-α shedding was lower in COPD PBECs, the early release of IL-8 (likely due to its shedding) was higher in PBECs from COPD than healthy smokers. Importantly, this was accompanied by lower TIMP-2 levels in COPD PBECs, while baseline TIMP-3 levels were similar between groups.
Our data indicate that IL-8 secretion is regulated independently from ADAM17 activity and TGF-α shedding and that particularly its early release is differentially regulated in PBECs from COPD and healthy smokers. Since TIMP-2-sensitive metalloproteinases could potentially contribute to IL-8 release, these may be interesting targets to further investigate novel therapeutic strategies in COPD.
Cigarette smoke; ADAM17; IL-8; TGF-α; TIMP-2
Small sputum macrophages represent highly active cells that increase in the airways of patients with inflammatory diseases such as chronic obstructive pulmonary disease (COPD). It has been reported often that levels of cytokines, chemokines and pro-teases are increased in sputum supernatants of these patients. In COPD, the small sputum macrophages may contribute to these supernatant proteins and recruit additional cells via specific chemokine expression patterns. We therefore investigated the expression profile of chemokines in sputum macrophages obtained from COPD patients in comparison to cells from healthy donors and cells isolated after inhalation of lipopolysaccharide (LPS). We used the minimally invasive procedure of sputum induction and have purified macrophages with the RosetteSep technology. Using macrophage purification and flow cytometry we show that in COPD small sputum macrophages account for 85.9% ± 8.3% compared with 12.9% ± 7.1% of total macrophages in control donors. When looking at chemokine expression we found, for the small macrophages in COPD, increased transcript and protein levels for CCL2, CCL7, CCL13 and CCL22 with a more than 100-fold increase for CCL13 mRNA (P < 0.001). Looking at active smokers without COPD, there is a substantial increase of small macrophages to 60% ± 15% and, here, chemokine expression is increased as well. In a model of airway inflammation healthy volunteers inhaled 20 μg of lipopolysaccharide (LPS), which resulted in an increase of small sputum macrophages from 18% ± 19% to 64% ± 25%. The pattern of chemokine expression was, however, different with an upregulation for CCL2 and CCL7, while CCL13 was downregulated three-fold in the LPS-induced small macrophages. These data demonstrate that sputum macrophages in COPD show induction of a specific set of CCL chemokines, which is distinct from what can be induced by LPS.
Chronic obstructive pulmonary disease (COPD) is an inflammatory disorder marked by relative resistance to steroids. The IL-17 superfamily, which mediates cross-talk between the adaptive and innate immune systems, has been associated with diminished responses to steroids. Increasing evidence supports elevated IL-17 expression in the lung of COPD subjects. However, whether cells of the immune system (systemic) and/or local lung cells are contributing to the elevated IL-17 remains unclear. To address this issue, we utilized a human parenchymal lung tissue explant culture system with cigarette smoke exposure to investigate the expression of IL-17 and the mechanisms involved.
Parenchymal lung tissue removed from 10 non-COPD and 8 COPD patients was sectioned and cultured with different concentrations of cigarette smoke extract (CSE) for 3 or 6 hours. Tissue viability was evaluated by LDH (lactate dehydrogenase) in culture supernatants. Western blot and real-time PCR were performed to evaluate IL-17A/F expression. To investigate the mechanisms, pharmacological inhibitors for MAPK p38, ERK1/2, NF-κB and PI3K pathways were added into the culture media.
No tissue damage was observed after the cigarette smoke exposure for 3 h or 6 h compared with the control media. At the protein level, the expression of both IL-17A (2.4 ± 0.6 fold) and IL-17 F (3.7 ± 0.7 fold) in the tissue from non-COPD subjects was significantly increased by 5% of CSE at 3 h. For COPD subjects, IL-17A/F expression were significantly increased only at 6 h with 10% of CSE (IL-17A: 4.2 ± 0.8 fold; IL-17 F: 3.3 ± 0.8 fold). The increased expression of IL-17A/F is also regulated at the mRNA level. The inhibitors for NF-κB and PI3K pathways significantly inhibited CSE-induced IL-17A/F expression from lung tissue of non-COPD subjects.
We found the evidence that the expression of both IL-17A and IL-17 F is increased by the cigarette smoke exposure in explants from both non-COPD and COPD subjects, supporting that local lung cells contribute IL-17 production. The elevated IL-17A/F expression is dependent on NF-κB and PI3K pathways. These observations add to the growing evidence which suggests that Th17 cytokines play a significant role in COPD.
COPD; IL-17; Cigarette smoke; Tissue explants
Chronic obstructive pulmonary disease (COPD) is a heterogeneous syndrome characterized by varying degrees of airflow limitation and diffusion impairment. There is increasing evidence to suggest that COPD is also characterized by systemic inflammation. The primary goal of this study was to identify soluble proteins in plasma that associate with the severity of airflow limitation in a COPD cohort with stable disease. A secondary goal was to assess whether unique markers associate with diffusion impairment, based on diffusion capacity of carbon monoxide (DLCO), independent of the forced expiratory volume in 1 second (FEV1).
A cross sectional study of 73 COPD subjects was performed in order to examine the association of 25 different plasma proteins with the severity of lung function impairment, as defined by the baseline measurements of the % predicted FEV1 and the % predicted DLCO. Plasma protein concentrations were assayed using multiplexed immunobead-based cytokine profiling. Associations between lung function and protein concentrations were adjusted for age, gender, pack years smoking history, current smoking, inhaled corticosteroid use, systemic corticosteroid use and statin use.
Plasma concentrations of CCL2/monocyte chemoattractant protein-1 (CCL2/MCP-1), CCL4/macrophage inflammatory protein-1β (CCL4/MIP -1β), CCL11/eotaxin, and interleukin-13 (IL-13) were inversely associated with the % FEV1. Plasma concentrations of soluble Fas were associated with the % DLCO, whereas CXCL9/monokine induced by interferon-γ (CXCL9/Mig), granulocyte- colony stimulating factor (G-CSF) and IL-13 showed inverse relationships with the % DLCO.
Systemic inflammation in a COPD cohort is characterized by cytokines implicated in inflammatory cell recruitment and airway remodeling. Plasma concentrations of IL-13 and chemoattractants for monocytes, T lymphocytes, and eosinophils show associations with increasing severity of disease. Soluble Fas, G-CSF and CXCL9/Mig may be unique markers that associate with disease characterized by disproportionate abnormalities in DLCO independent of the FEV1.