Distinct regulatory profiles of interleukins and chemokines in response to cigarette smoke condensate in normal human bronchial epithelial (NHBE) cells

IL-36 expression is increased in NSCLC with IL-36 stimulation of lung cancer cells promoting a pro-tumorigenic phenotype

The IL-36 cytokines are a recently described subset of the IL-1 family of cytokines, and have been shown to play a role in the pathogenesis of respiratory diseases such as asthma and COPD. Given the common aetiological links between COPD and lung cancer development, as well as the involvement of other IL-1 family members in lung tumorigenesis, the aim of this work was to investigate the role of IL-36 cytokines in the pathogenesis of lung cancer. In this study we demonstrate that expression of IL-36 cytokines and receptor mRNA and protein are significantly increased in lung cancer tissue compared to adjacent non-tumour tissue. In vitro assays showed that stimulation of two lung cancer cell lines, SKMES-1 human squamous cell and LLC murine lung cancer, with IL-36R agonists resulted in increased cellular migration and proliferation. All IL-36 cytokines induced the expression of pro-inflammatory chemokines in both lung cancer cell lines with synergistic effects identified upon co-stimulation of cells with IL-17, IL-22 and TNFα. Furthermore, we report that IL-36 cytokines induce protein expression of the immune checkpoint inhibitor protein PD-L1 on lung cancer cells. Taken together, this data indicates that targeting IL-36R signalling may be a useful targeted therapy for lung cancer patients with IL-36R⁺ cancer cells.

Imbalance between IL-36 receptor agonist and antagonist drives neutrophilic inflammation in COPD

Current treatments fail to modify the underlying pathophysiology and disease progression of chronic obstructive pulmonary disease (COPD), necessitating alternative therapies. Here, we show that COPD subjects have increased IL-36γ and decreased IL-36 receptor antagonist (IL-36Ra) in bronchoalveolar and nasal fluid compared to control subjects. IL-36γ is derived from small airway epithelial cells (SAEC) and further induced by a viral mimetic, whereas IL-36RA is derived from macrophages. IL-36γ stimulates release of the neutrophil chemoattractants CXCL1 and CXCL8, as well as elastolytic matrix metalloproteinases (MMPs) from small airway fibroblasts (SAF). Proteases released from COPD neutrophils cleave and activate IL-36γ thereby perpetuating IL-36 inflammation. Transfer of culture media from SAEC to SAF stimulated release of CXCL1, that was inhibited by exogenous IL-36RA. The use of a therapeutic antibody that inhibits binding to the IL-36 receptor (IL-36R) attenuated IL-36γ driven inflammation and cellular cross talk. We have demonstrated a mechanism for the amplification and propagation of neutrophilic inflammation in COPD and that blocking this cytokine family via a IL-36R neutralizing antibody could be a promising new therapeutic strategy in the treatment of COPD.

Interleukin-36 Cytokines in Infectious and Non-Infectious Lung Diseases

The IL-36 family of cytokines were identified in the early 2000’s as a new subfamily of the IL-1 cytokine family, and since then, the role of IL-36 cytokines during various inflammatory processes has been characterized. While most of the research has focused on the role of these cytokines in autoimmune skin diseases such as psoriasis and dermatitis, recent studies have also shown the importance of IL-36 cytokines in the lung inflammatory response during infectious and non-infectious diseases. In this review, we discuss the biology of IL-36 cytokines in terms of how they are produced and activated, as well as their effects on myeloid and lymphoid cells during inflammation. We also discuss the role of these cytokines during lung infectious diseases caused by bacteria and influenza virus, as well as other inflammatory conditions in the lungs such as allergic asthma, lung fibrosis, chronic obstructive pulmonary disease, cystic fibrosis and cancer. Finally, we discuss the current therapeutic advances that target the IL-36 pathway and the possibility to extend these tools to treat lung inflammatory diseases.

IL-36 in chronic inflammation and fibrosis - bridging the gap?

IL-36 is a member of the IL-1 superfamily and consists of three agonists and one receptor antagonist (IL-36Ra). The three endogenous agonists, IL-36α, -β, and -γ, act primarily as proinflammatory cytokines, and their signaling through the IL-36 receptor (IL-36R) promotes immune cell infiltration and secretion of inflammatory and chemotactic molecules. However, IL-36 signaling also fosters secretion of profibrotic soluble mediators, suggesting a role in fibrotic disorders. IL-36 isoforms and IL-36 have been implicated in inflammatory diseases including psoriasis, arthritis, inflammatory bowel diseases, and allergic rhinitis. Moreover, IL-36 has been connected to fibrotic disorders affecting the kidney, lung, and intestines. This review summarizes the expression, cellular source, and function of IL-36 in inflammation and fibrosis in various organs, and proposes that IL-36 modulation may prove valuable in preventing or treating inflammatory and fibrotic diseases and may reveal a mechanistic link between inflammation and fibrosis.

IL-36 Cytokines Promote Inflammation in the Lungs of Long-Term Smokers

Chronic obstructive pulmonary disease (COPD) is a progressive inflammatory lung disease with high morbidity and mortality. The IL-36 family are proinflammatory cytokines that are known to shape innate immune responses, including those critical to bacterial pneumonia. The objective of this study was to determine whether IL-36 cytokines promote a proinflammatory milieu in the lungs of long-term smokers with and without COPD. Concentrations of IL-36 cytokines were measured in plasma and BAL fluid from subjects in a pilot study (n = 23) of long-term smokers with and without COPD in vivo and from a variety of lung cells (from 3-5 donors) stimulated with bacteria or cigarette smoke components in vitro. Pulmonary macrophages were stimulated with IL-36 cytokines in vitro, and chemokine and cytokine production was assessed. IL-36α and IL-36γ are produced to varying degrees in murine and human lung cells in response to bacterial stimuli and cigarette smoke components in vitro. Moreover, whereas IL-36γ production is upregulated early after cigarette smoke stimulation and wanes over time, IL-36α production requires a longer duration of exposure. IL-36α and IL-36γ are enhanced systemically and locally in long-term smokers with and without COPD, and local IL-36α concentrations display a positive correlation with declining ventilatory lung function and increasing proinflammatory cytokine concentrations. In vitro, IL-36α and IL-36γ induce proinflammatory chemokines and cytokines in a concentration-dependent fashion that requires IL-36R and MyD88. IL-36 cytokine production is altered in long-term smokers with and without COPD and contributes to shaping a proinflammatory milieu in the lungs.

IL36 is a critical upstream amplifier of neutrophilic lung inflammation in mice

IL-36, which belongs to the IL-1 superfamily, is increasingly linked to neutrophilic inflammation. Here, we combined in vivo and in vitro approaches using primary mouse and human cells, as well as, acute and chronic mouse models of lung inflammation to provide mechanistic insight into the intercellular signaling pathways and mechanisms through which IL-36 promotes lung inflammation. IL-36 receptor deficient mice exposed to cigarette smoke or cigarette smoke and H1N1 influenza virus had attenuated lung inflammation compared with wild-type controls. We identified neutrophils as a source of IL-36 and show that IL-36 is a key upstream amplifier of lung inflammation by promoting activation of neutrophils, macrophages and fibroblasts through cooperation with GM-CSF and the viral mimic poly(I:C). Our data implicate IL-36, independent of other IL-1 family members, as a key upstream amplifier of neutrophilic lung inflammation, providing a rationale for targeting IL-36 to improve treatment of a variety of neutrophilic lung diseases.

Interleukin-36 Cytokine/Receptor Signaling: A New Target for Tissue Fibrosis

Tissue fibrosis is a major unresolved medical problem, which impairs the function of various systems. The molecular mechanisms involved are poorly understood, which hinders the development of effective therapeutic strategies. Emerging evidence from recent studies indicates that interleukin 36 (IL-36) and the corresponding receptor (IL-36R), a newly-characterized cytokine/receptor signaling complex involved in immune-inflammation, play an important role in the pathogenesis of fibrosis in multiple tissues. This review focuses on recent experimental findings, which implicate IL-36R and its associated cytokines in different forms of organ fibrosis. Specifically, it outlines the molecular basis and biological function of IL-36R in normal cells and sums up the pathological role in the development of fibrosis in the lung, kidney, heart, intestine, and pancreas. We also summarize the new progress in the IL-36/IL-36R-related mechanisms involved in tissue fibrosis and enclose the potential of IL-36R inhibition as a therapeutic strategy to combat pro-fibrotic pathologies. Given its high association with disease, gaining new insight into the immuno-mechanisms that contribute to tissue fibrosis could have a significant impact on human health.

High-Risk Human Papillomavirus and Tobacco Smoke Interactions in Epithelial Carcinogenesis

Cervical, anogenital, and some head and neck cancers (HNC) are etiologically associated with high-risk human papillomavirus (HR-HPV) infection, even though additional cofactors are necessary. Epidemiological studies have established that tobacco smoke (TS) is a cofactor for cervical carcinogenesis because women who smoke are more susceptible to cervical cancer when compared to non-smokers. Even though such a relationship has not been established in HPV-related HNC, a group of HPV positive patients with this malignancy are smokers. TS is a complex mixture of more than 4500 chemical compounds and approximately 60 of them show oncogenic properties such as benzo[α]pyrene (BaP) and nitrosamines, among others. Some of these compounds have been evaluated for carcinogenesis through experimental settings in collaboration with HR-HPV. Here, we conducted a comprehensive review of the suggested molecular mechanisms involved in cooperation with both HR-HPV and TS for epithelial carcinogenesis. Furthermore, we propose interaction models in which TS collaborates with HR-HPV to promote epithelial cancer initiation, promotion, and progression. More studies are warranted to clarify interactions between oncogenic viruses and chemical or physical environmental factors for epithelial carcinogenesis.

Interleukin-23 pathway at the enthesis: The emerging story of enthesitis in spondyloarthropathy

The inflammatory disorders collectively termed the seronegative spondyloarthropathies (SpA) include ankylosing spondylitis (AS), psoriatic arthritis (PsA), reactive arthritis, the arthritis associated with inflammatory bowel disease including Crohn's disease and ulcerative colitis, the arthritis related to anterior uveitis, and finally, somewhat controversially Behcet's disease. All of these diseases are associated with SNPs in the IL-23R or the interleukin-23 (IL-23) cytokine itself and related downstream signaling JAK pathway genes and the interleukin-17 (IL-17) pathway. In rheumatoid arthritis, the target of the immune response is the synovium but the SpA disorders target the tendon, ligament, and joint capsule skeletal anchorage points that are termed entheses. The discovery that IL-23R-expressing cells were ensconced in healthy murine enthesis, and other extraskeletal anchorage points including the aortic root and the ciliary body of the eye and that systemic overexpression of IL-23 resulted in a severe experimental SpA, confirmed a fundamentally different immunobiology to rheumatoid arthritis. Recently, IL-23R-expressing myeloid cells and various innate and adaptive T cells that produce IL-17 family cytokines have also been described in the human enthesis. Blockade of IL-23 pathway with either anti-p40 or anti-p19 subunits has resulted in some spectacular therapeutic successes in psoriasis and PsA including improvement in enthesitis in the peripheral skeleton but has failed to demonstrate efficacy in AS that is largely a spinal polyenthesitis. Herein, we discuss the known biology of IL-23 at the human enthesis and highlight the remarkable emerging story of this unique skeletal tissue.

Regulation and function of interleukin-36 cytokines

The interleukin (IL)-36 cytokines include 3 agonists, IL-36α, IL-36β, and IL-36γ that bind to a common receptor composed of IL-36R and IL-1RAcP to stimulate inflammatory responses. IL-36Ra is a natural antagonist that binds to IL-36R, but does not recruit the co-receptor IL-1RAcP and does not stimulate any intracellular responses. The IL-36 cytokines are expressed predominantly by epithelial cells and act on a number of cells including immune cells, epithelial cells, and fibroblasts. Processing of the N-terminus is required for full agonist or antagonist activity for all IL-36 members. The role of IL-36 has been extensively demonstrated in the skin where it can act on keratinocytes and immune cells to induce a robust inflammatory response that has been implicated in psoriatic disorders. Emerging data also suggest a role for this cytokine family in pulmonary and intestinal physiology and pathology.

IL-36γ Is a Strong Inducer of IL-23 in Psoriatic Cells and Activates Angiogenesis

The IL-1 family member cytokine IL-36γ is recognised as key mediator in the immunopathology of psoriasis, hallmarks of which involve the activation of both resident and infiltrating inflammatory myeloid cells and aberrant angiogenesis. This research demonstrates a role for IL-36γ in both myeloid activation and angiogenesis. We show that IL-36γ induces the production of psoriasis-associated cytokines from macrophages (IL-23 and TNFα) and that this response is enhanced in macrophages from psoriasis patients. This effect is specific for IL-36γ and could not be mimicked by other IL-1 family cytokines such as IL-1α. IL-36γ was also demonstrated to induce endothelial tube formation and branching, in a VEGF-A-dependent manner. Furthermore, IL-36γ-stimulated macrophages potently activated endothelial cells and led to increased adherence of monocytes, effects that were markedly more pronounced for psoriatic macrophages. Interestingly, regardless of stimulus, psoriasis monocytes showed increased adherence to both the stimulated and unstimulated endothelium when compared with monocytes from healthy individuals. Collectively, these findings show that IL-36γ has the potential to enhance endothelium directed leucocyte infiltration into the skin and strengthen the IL-23/IL-17 pathway adding to the growing evidence of pathogenetic roles for IL-36γ in psoriatic responses. Our findings also point to a cellular response, which could potentially explain cardiovascular comorbidities in psoriasis in the form of endothelial activation and increased monocyte adherence.

IL-36 induces cytokine IL-6 and chemokine CXCL8 expression in human lung tissue cells: Implications for pulmonary inflammatory responses

IL-36α, IL-36β and IL-36γ are cytokine members of IL-1 family. Although IL-36 expression was observed in human lung during pulmonary infections, it remains unknown whether IL-36 could act directly on lung tissue cells during pulmonary inflammatory responses. In this study, we showed that IL-36 receptor was expressed in human lung fibroblasts and bronchial epithelial cells. Correspondingly, IL-36α, IL-36β or IL-36γ up-regulated gene expression of cytokine IL-6 and chemokine CXCL8 in human lung fibroblasts and bronchial epithelial cells, and promoted IL-6 and CXCL8 release from human lung fibroblasts and bronchial epithelial cells. The production of IL-6 and CXCL8 in these lung tissues cells induced by IL-36α, IL-36β or IL-36γ was regulated by p38MAPK, ERK or Akt signaling pathways. Taken together, the above results suggest that IL-36-mediated IL-6 and CXCL8 production in human lung fibroblasts and bronchial epithelial cells may be involved in pulmonary inflammation especially caused by bacterial or viral infections.

The IL-1 cytokine family and its role in inflammation and fibrosis in the lung

The IL-1 cytokine family comprises 11 members (7 ligands with agonist activity, 3 receptor antagonists and 1 anti-inflammatory cytokine) and is recognised as a key mediator of inflammation and fibrosis in multiple tissues including the lung. IL-1 targeted therapies have been successfully employed to treat a range of inflammatory conditions such as rheumatoid arthritis and gouty arthritis. This review will introduce the members of the IL-1 cytokine family, briefly discuss the cellular origins and cellular targets and provide an overview of the role of these molecules in inflammation and fibrosis in the lung.

Neutrophil Elastase-mediated proteolysis activates the anti-inflammatory cytokine IL-36 Receptor antagonist

The interleukin-36 receptor antagonist (IL-36Ra) which regulates IL-36α, -β and -γ is linked to psoriatic inflammation, especially loss-of-function mutations in pustular psoriasis subtypes. As observed with other IL-1 superfamily proteins, the IL-36 members require N-terminal cleavage for full biological activity but the mechanisms of IL-36Ra activation remain poorly defined. Using different blood leukocyte and skin resident cell preparations, and recombinant proteins, we have identified that neutrophil elastase, but not other neutrophil derived proteases, cleaves IL-36Ra into its highly active antagonistic form. The activity of this processed form of IL-36Ra was confirmed in human primary dermal fibroblasts and keratinocytes and in skin equivalents. A significant dose dependent reduction of IL-36γ induced IL-8 and chemokine ligand 20 (CCL20) levels were detected following addition of the cleaved IL-36Ra compared to full length IL-36Ra. By activating IL-36Ra, the neutrophil derived protease can inhibit IL-36 induced chemokine production, including IL-8 and CCL20, and reduce further inflammatory cell infiltration. These findings strongly indicate neutrophil elastase to be a key enzyme in the biological function of IL-36Ra and that neutrophils can play a regulatory role in psoriatic inflammation with regard to balancing the pro-inflammatory activity of IL-36.

CXCL14 as an emerging immune and inflammatory modulator

CXCL14, a relatively novel chemokine, is a non-ELR (glutamic acid-leucine-arginine) chemokine with a broad spectrum of biological activities. CXCL14 mainly contributes to the regulation of immune cell migration, also executes antimicrobial immunity. The identity of the receptor for CXCL14 still remains obscure and therefore the intracellular signaling pathway is not entirely delineated. The present review summarizes the contribution of CXCL14 in these two aspects and discusses the biological mechanisms regulating CXCL14 expression and potential CXCL14 mediated functional implications in a variety of cells.

Limited Contribution of IL-36 versus IL-1 and TNF Pathways in Host Response to Mycobacterial Infection

IL-36 cytokines are members of the IL-1 family of cytokines that stimulate dendritic cells and T cells leading to enhanced T helper 1 responses in vitro and in vivo; however, their role in host defense has not been fully addressed thus far. The objective of this study was to examine the role of IL-36R signaling in the control of mycobacterial infection, using models of systemic attenuated M. bovis BCG infection and virulent aerogenic M. tuberculosis infection. IL-36γ expression was increased in the lung of M. bovis BCG infected mice. However, IL-36R deficient mice infected with M. bovis BCG showed similar survival and control of the infection as compared to wild-type mice, although their lung pathology and CXCL1 response were transiently different. While highly susceptible TNF-α deficient mice succumbed with overwhelming M. tuberculosis infection, and IL-1RI deficient mice showed intermediate susceptibility, IL-36R-deficient mice controlled the infection, with bacterial burden, lung inflammation and pathology, similar to wild-type controls. Therefore, IL-36R signaling has only limited influence in the control of mycobacterial infection.

Regulation of gene expression by tobacco product preparations in cultured human dermal fibroblasts

Skin fibroblasts comprise the first barrier of defense against wounds, and tobacco products directly contact the oral cavity. Cultured human dermal fibroblasts were exposed to smokeless tobacco extract (STE), total particulate matter (TPM) from tobacco smoke, or nicotine at concentrations comparable to those found in these extracts for 1h or 5h. Differences were identified in pathway-specific genes between treatments and vehicle using qRT-PCR. At 1h, IL1α was suppressed significantly by TPM and less significantly by STE. Neither FOS nor JUN was suppressed at 1h by tobacco products. IL8, TNFα, VCAM1, and NFκB1 were suppressed after 5h with STE, whereas only TNFα and NFκB1 were suppressed by TPM. At 1h with TPM, secreted levels of IL10 and TNFα were increased. Potentially confounding effects of nicotine were exemplified by genes such as ATF3 (5h), which was increased by nicotine but suppressed by other components of STE. Within 2h, TPM stimulated nitric oxide production, and both STE and TPM increased reactive oxygen species. The biological significance of these findings and utilization of the gene expression changes reported herein regarding effects of the tobacco product preparations on dermal fibroblasts will require additional research.

Combustible and non-combustible tobacco product preparations differentially regulate human peripheral blood mononuclear cell functions

Natural killer (NK) cells and T cells play essential roles in innate and adaptive immune responses in protecting against microbial infections and in tumor surveillance. Although evidence suggests that smoking causes immunosuppression, there is limited information whether the use of smokeless tobacco (ST) products affects immune responses. In this study, we assessed the effects of two preparations of cigarette smoke, ST extract and nicotine on T cell and NK cell responses using Toll-like receptor-ligand stimulated human peripheral blood mononuclear cells (PBMCs). The tobacco product preparations (TPPs) tested included whole smoke conditioned media (WS-CM), total particulate matter (TPM) and a ST product preparation in complete artificial saliva (ST/CAS). The PBMCs were stimulated with polyinosinic:polycytidylic acid (poly I:C) and lipopolysaccharide (LPS). A marked reduction of the expression of intracellular IFN-γ and TNF-α was evident in NK cells and T cells treated with WS-CM and TPM. Consistently, attenuation of ligand-induced secretion of cytokines (IL-1β, IL-10, IL-12 and TNF-α) from PBMCs treated with WS-CM and TPM were observed. While the treatment with TPPs did not alter the expression of the maturation marker CD69, WS-CM and TPM inhibited the cytolytic activity of human PBMCs. Suppression of perforin by WS-CM was also detected. Although interference from the vehicle confounded the interpretation of effects of ST/CAS, some effects were evident only at high concentrations. Nicotine treatment minimally impacted expression of cytokines and cytolytic activity. Data presented herein suggests that the function of NK cells and T cells is influenced by exposure to TPPs (based on equi-nicotine units) in the following order: WS-CM>TPM>ST/CAS. These findings are consistent with the hypothesis put forward by others that chronic smoking leads to immunosuppression, an effect that may contribute to increased microbial infections and cancer incidence among smokers.

In vitro and clinical studies examining the expression of osteopontin in cigarette smoke-exposed endothelial cells and cigarette smokers

Background

Cigarette smoking is a leading cause of mortality and morbidity and is associated with cardiovascular disease via contributory processes such as endothelial dysfunction, inflammation and thrombosis. Cigarette smoke both contains and stimulates the production of cellular oxidants and it may also promote vascular inflammation. Osteopontin is a non-collagenous matrix protein first identified in bone and there is increasing evidence for its role in inflammation and cardiovascular disease via its action as a soluble cytokine.

Methods

In this study we have examined the mechanisms underlying the expression of osteopontin in human vascular endothelial cells in vitro following exposure to cigarette smoke particulate matter (PM), using PCR, electrochemiluminescence, immunostaining and Western blotting. We further determined if serum osteopontin levels changed in humans who quit smoking.

Results

Non-cytotoxic concentrations of PM increased osteopontin levels in cultured human endothelial cells and this effect was reduced in the presence of ascorbate, suggesting a role for oxidants in the response to PM. However, oxidant production played no role in the PM-evoked induction MMP-3, an enzyme which cleaves osteopontin. In smokers who quit smoking for 5 days, serum osteopontin levels were significantly lowered compared to those measured prior to smoking cessation.

Conclusions

In vitro cigarette smoke extract exposure induced osteopontin expression in human endothelial cells in an oxidative stress-dependent manner, which may involve MMP-3 cleavage. In humans, serum osteopontin was decreased with short-term smoking cessation. Endothelial-derived osteopontin may contribute to inflammation in smokers, and may also contribute to atherosclerosis and cardiovascular disease-related processes.

Extractable organic matter of standard reference material 1649a influences immunological response induced by pathogen-associated molecular patterns

BACKGROUND, AIM, AND SCOPE

Lungs are permanently and simultaneously challenged by airborne microorganisms and airborne pollutants. Temporal increase of airborne particulate matter (APM), a potential carrier for extractable organic matter (EOM), degrades the situation of pulmonary patients. The Ah receptor (AhR) has been described as an important factor influencing the immunological challenge by viral infections. Molecular mechanisms underlying epidemiological observations are not well understood. Cytokine secretion (IL-6, IL-8, and TGF-beta) from human bronchial epithelial cells (Beas2B) was determined as an indicator for immune responses upon co-stimulation with an artificial analog of viral dsRNA [polyinosinic/polycytidylic acid, (PIC)] and EOM of Standard Reference Material 1649a (SRM). Since polycyclic aromatic hydrocarbons are major components of APM usually acting via the AhR, particular focus was on AhR involvement.

MATERIALS AND METHODS

Cytokine secretion was demonstrated by enzyme-linked immunosorbent assay. To mimic the activation of organic matter during contact of particles with the human lung, Soxhlet extraction of SRM was performed. In some experiments, the AhR was blocked by alpha-naphthoflavone.

RESULTS

Microbial stimulation (PIC) induced Beas2B cytokine release, whereas isolated exposure to EOM of APM did not. Co-stimulation with EOM and PIC increased IL-8 secretion, whereas neither IL-6 nor TGF-beta was affected. Blocking of the AhR suppressed the release of IL-8.

DISCUSSION

Organic compounds adsorbed on airborne particulate matter influence the cytokine secretion of lung epithelial cells induced by pathogen-associated molecular patterns.

RECOMMENDATIONS AND PERSPECTIVES

Further investigation of these observations is required to understand the molecular mechanisms underlying adverse health effects of APM reported in epidemiological studies.

Re-expression of CXCL14, a common target for epigenetic silencing in lung cancer, induces tumor necrosis

Chemokines are important regulators of directional cell migration and tumor metastasis. A genome-wide transcriptome array designed to uncover novel genes silenced by methylation in lung cancer identified the CXC-subfamily of chemokines. Expression of eleven of the sixteen known human CXC-chemokines was increased in lung adenocarcinoma cell lines after treatment with 5-aza-2deoxycytidine (DAC). Tumor-specific methylation leading to silencing of CXCL5, 12 and 14 was found in over 75% of primary lung adenocarcinomas and DAC treatment restored expression of each silenced gene. Forced expression of CXCL14 in H23 cells where this gene is silenced by methylation increased cell death in vitro and dramatically reduced in vivo growth of lung tumor xenografts through necrosis of up to 90% of the tumor mass. CXCL14 re-expression had a profound effect on the genome altering the transcription of over 1,000 genes, including increased expression of 30 cell cycle inhibitor and pro-apoptosis genes. In addition, CXCL14 methylation in sputum from asymptomatic early stage lung cancer cases was associated with a 2.9-fold elevated risk for this disease compared to controls, substantiating its potential as a biomarker for early detection of lung cancer. Together these findings identify CXCL14 as an important tumor suppressor gene epigenetically silenced during lung carcinogenesis.

Cigarette smoke promotes dendritic cell accumulation in COPD; a Lung Tissue Research Consortium study

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Interleukin-1 family member 9 stimulates chemokine production and neutrophil influx in mouse lungs

Interleukin-1 (IL-1) is a proinflammatory cytokine that signals through the Type I IL-1 receptor (IL-1RI). Novel IL-1-like cytokines were recently identified. Their functions in lung disease remain unclear. Interleukin-1 family member-9 (IL-1F9) is one such IL-1-like cytokine, expressed in the lungs of humans and mice. IL-1F9 signals through IL-1 receptor-related protein 2 (IL-1Rrp2/IL-1RL2), which is distinct from IL-1RI. We sought to determine if IL-1F9 acts as a proinflammatory cytokine in lung disease. IL-1F9 protein was increased in lung homogenates of house dust mite-challenged A/J mice compared with controls, and expression was seen in airway epithelial cells. The intratracheal administration of recombinant mouse IL-1F9 increased airway hyperresponsiveness and induced neutrophil influx and mucus production, but not eosinophilic infiltration in the lungs of mice. In addition, IL-1α protein levels in bronchoalveolar lavage fluid, chemokines, and chemokine-receptor mRNA expression in the lungs were increased after the instillation of intratracheal IL-1F9. Consistent with these changes, NF-κB transcription factor activity was increased in the lungs of mice challenged with IL-1F9 and in a macrophage cell line treated with IL-1F9. These data suggest that IL-1F9 is upregulated during inflammation, and acts as a proinflammatory cytokine in the lungs.

Comparison of two in vitro models of cigarette smoke exposure

Cigarette smoke is associated with a high morbidity and mortality, and affects particularly the respiratory tract. Various in vitro models have been developed to study the effects of cigarette smoke on bronchial epithelial cells. To identify an adequate exposure model of cigarette smoke, we analysed the effects of cigarette smoke extract (CSE) and a smoking chamber on bronchial epithelial cells. The release of monocyte chemoattractant protein (MCP)-1, interleukin (IL)-10, and vascular endothelial growth factor (VEGF) was measured. Bronchial epithelial cells isolated from Sprague-Dawley rat (NRBE) were exposed to 3% CSE or air control every day for 3 days. In the second model, NRBE were placed in an air/liquid interface and exposed, in a smoking chamber, to whole smoke from 2 cigarettes, twice daily for 3 days. Levels of MCP-1, IL-10, and VEGF were measured by enzyme-linked immunosorbent assay (ELISA), 24 h after the last exposure. The pattern of MCP-1 production by bronchial epithelial cells was different between the two models. MCP-1 release was increased after 3 days of exposure in the CSE model, but was inhibited using the smoking chamber model. Production of IL-10 by NRBE was reduced after 3 days in both models. Finally, no difference was observed in the production of VEGF between the two models. CSE and the smoking chamber differently modulate bronchial epithelial cell mediator production, demonstrating that the model of cigarette smoke exposure used can influence the data obtained.