Nicotine strongly activates dendritic cell-mediated adaptive immunity: potential role for progression of atherosclerotic lesions

Ex vivo nicotine stimulation augments the efficacy of human peripheral blood mononuclear cell-derived dendritic cell vaccination via activating Akt-S6 pathway

Our previous studies showed that α7 nicotinic acetylcholine receptor (nAchR) agonist nicotine has stimulatory effects on murine bone marrow-derived semimature DCs, but the effect of nicotine on peripheral blood mononuclear cell- (PBMC-) derived human semimature dendritic cells (hu-imDCs) is still to be clarified. In the present study, hu-imDCs (cultured 4 days) were conferred with  ex vivo lower dose nicotine stimulation and the effect of nicotine on surface molecules expression, the ability of cross-presentation, DCs-mediated PBMC priming, and activated signaling pathways were determined. We could demonstrate that the treatment with nicotine resulted in increased surface molecules expression, enhanced hu-imDCs-mediated PBMC proliferation, upregulated release of IL-12 in the supernatant of cocultured DCs-PBMC, and augmented phosphorylation of Akt and ribosomal protein S6. Nicotine associated with traces of LPS efficiently enhanced endosomal translocation of internalized ovalbumin (OVA) and increased TAP-OVA colocalization. Importantly, the upregulation of nicotine-increased surface molecules upregulation was significantly abrogated by the inhibition of Akt kinase. These findings demonstrate that ex vivo nicotine stimulation augments hu-imDCs surface molecules expression via Akt-S6 pathway, combined with increased Ag-presentation result in augmented efficacy of DCs-mediated PBMC proliferation and Th1 polarization.

Nicotine exposure alters the mRNA expression of Notch ligands in dendritic cells and their response to Th1-/Th2-promoting stimuli

Dendritic cells (DCs) utilize polarizing signals to instruct the differentiation of T helper (Th) cells into Th1 and Th2 effector cells: antigen-specific 'signal 1', costimulatory 'signal 2' and polarizing cytokines 'signal 3'. Accumulating evidence suggests the involvement of an additional signal, the Notch signalling pathway. We reported that in response to Th1-promoting stimuli, both mouse and human DCs generated in the presence of the immune modulator nicotine (nicDCs) fail to support the development of effector memory Th1 cells. However, in response to Th2-promoting stimuli, these nicDCs preferentially support the differentiation of antigen-specific IL-4-producing Th2 effector cells. Here, we show that when compared to their control counterparts, immature mouse and human nicDCs display higher levels of the Notch ligands D1, D4 and J2 mRNA expression. In response to Th1- and Th2-promoting stimuli, mouse nicDCs display higher levels of the Notch ligands D1, D4 and J2, while human nicDCs show higher levels of D1, D4 and J1 mRNA expression. Furthermore, both stimulated mouse and human nicDCs express higher CD86 to CD80 ratio and produce lower amount of IL-12. Collectively, our data suggest that these changes in addition to an increase in Jagged expression correlate with the ability of nicDCs to modulate the Th1/Th2 balance in favour of Th2 generation.

Pulmonary Langerhans Cell Histiocytosis with Lytic Bone Involvement in an Adult Smoker: Regression following Smoking Cessation

Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm characterized by the proliferation and dissemination of histiocytes. These in turn may cause symptoms ranging from isolated, infiltrative lesions to severe multisystem disease. Pulmonary Langerhans cell histiocytosis (PLCH) presents as a localized polyclonal proliferation of Langerhans cells in the lungs causing bilateral cysts and fibrosis. In adults, this rare condition is considered a reactive process associated with cigarette smoking. Recently, clonal proliferation has been reported with the presence of BRAF V600E oncogenic mutation in a subset of PLCH patients. Spontaneous resolution was described; however, based on case series, smoking cessation remains the most effective way to achieve complete remission and prevent long term complications related to tobacco. Herein, we report the case of an adult woman with biopsy-proven PLCH presenting with thoracic (T8) vertebral bone destruction. Both the lung and the bone diseases regressed following smoking cessation, representing a rare case of synchronous disseminated PCLH with bone localization. This observation underscores the contribution of cigarette smoking as a systemic trigger of both pulmonary and extrapulmonary bone lesions. A review of similar cases in the literature is also presented.

Increased antigen presentation but impaired T cells priming after upregulation of interferon-beta induced by lipopolysaccharides is mediated by upregulation of B7H1 and GITRL

Dendritic cells are able to present Ag-derived peptides on MHC class I and II molecules and induce T cells priming. Lipopolysaccharides (LPS), an activator of Toll-like 4 receptor (TLR4) signaling, has been demonstrated to facilitate Ag-presentation, up-regulate surface molecules expression but impair T cells priming. In this study, we investigated the effect of LPS on nicotine-enhanced DCs-dependent T cells priming and the mechanisms of LPS orchestrating the immunosuppressive program. We could demonstrate that the treatment with LPS resulted in increased surface molecules expression, enhanced Ag-presentation, up-regulated release of TGF-beta, TNF-alpha, IL-6, and IFN-beta. Concomititantly, the upregulation of IFN-beta in DCs induces the up-regulation of coinhibitory molecules B7H1 and GITRL, which cause an impaired activation of naïve Ag-specific T cells and the induction of T cell tolerance by enhancing B7H1-PD-1 interactions and promoting GITRL-GITL facilitated Treg generation, respectively. These data provide a mechanistic basis for the immunomodulatory action of IFN-beta which might open new possibilities in the development of therapeutic approaches aimed at the control of excessive immune response and persistent infection.

Transcript levels of major interleukins in relation to the clinicopathological profile of patients with tuberculous intervertebral discs and healthy controls

Objectives

The purpose of the present study was to simultaneously examine the transcript levels of a large number of interleukins (ILs; IL-9, IL-10, IL-12, IL-13, IL-16, IL-17, IL-18, IL-26, and IL-27) and investigate their correlation with the clinicopathological profiles of patients with tuberculous intervertebral discs.

Methods

Clinical data were collected from 150 patients participating in the study from January 2013 to December 2013. mRNA expression levels in 70 tuberculous, 70 herniated, and 10 control intervertebral disc specimens were determined by real-time polymerase chain reaction.

Results

IL-10, IL-16, IL-17, IL-18, and IL-27 displayed stronger expression in tuberculous spinal disc tissue than in normal intervertebral disc tissue (P<0.05). Our results illustrated multiple correlations among IL-10, IL-16, IL-17, IL-18, and IL-27 mRNA expression in tuberculous samples. Smoking habits were found to have a positive correlation with IL-17 transcript levels and a negative correlation with IL-10 transcript levels (P<0.05). Pain intensity, symptom duration, C-reactive protein levels, and the erythrocyte sedimentation rate exhibited multiple correlations with the transcript levels of several ILs (P<0.05).

Conclusions

The experimental data imply a double-sided effect on the activity of ILs in tuberculous spinal intervertebral discs, suggesting that they may be involved in intervertebral discs destruction. Our findings also suggest that smoking may affect the intervertebral discs destruction process of spinal tuberculosis. However, further studies are necessary to elucidate the exact role of ILs in the intervertebral discs destruction process of spinal tuberculosis.

MCS-18, a natural product isolated from Helleborus purpurascens, inhibits maturation of dendritic cells in ApoE-deficient mice and prevents early atherosclerosis progression

INTRODUCTION

Inflammation accelerates both plaque progression and instability in the pathogenesis of atherosclerosis. The inhibition of dendritic cell (DC) maturation is a promising approach to suppress excessive inflammatory immune responses and has been shown to be protective in several autoimmune models. The aim of this study was to investigate the immune modulatory effects of the natural substance MCS-18, an inhibitor of DC maturation, regarding the progression of atherosclerosis in ApoE-deficient mice.

MATERIALS AND METHODS

ApoE-deficient mice were fed for twelve weeks with a Western-type diet (n = 32) or normal chow (control group; n = 16). Animals receiving high-fat diet were treated with MCS-18 (500 μg/kg body weight, n = 16) or saline (n = 16) twice a week. After 12 weeks, animals were transcardially perfused and sacrificed. The percentage of mature DCs (CD3(-)/CD19(-)/CD14(-)/NK1.1(-)/CD11c(+)/MHCII(+)/CD83(+)/CD86(+)) and T cell subpopulations (CD4(+)/CD25(+)/Foxp3(+), CD3/CD4/CD8) was analyzed in peripheral blood and in the spleen using flow cytometry. Plaque size was determined in the aortic root and the thoracoabdominal aorta using en-face staining. Immunohistochemical stainings served to detect inflammatory cells in the aortic root. Several cytokines and chemokines were determined in serum using multiplex assays.

RESULTS

In splenic cells derived from saline-treated atherosclerotic mice an increased DC maturation, reflected by the upregulation of CD83 and CD86 expression, was observed. The enhanced expression of both maturation markers was absent in MCS-18 treated atherosclerotic mice. While the percentage of splenic Foxp3 expressing Treg was increased in animals receiving MCS-18 compared to saline-treated atherosclerotic mice, cytotoxic T cells were reduced in the spleen and in atherosclerotic lesions of the aortic root. Furthermore, proatherogenic cytokines (e.g. IL-6 and IFN-γ) and chemokines (e.g. MIP-1β) were decreased in serum of MCS-18-treated animals when compared to saline-treated atherosclerotic mice. Also plaque size in the aortic root and the thoracoabdominal aorta was significantly lower following administration of MCS-18.

CONCLUSION

This study provides for the first time evidence that MCS-18 is able to prevent the onset of atherosclerosis in ApoE-deficient mice. The observed anti-atherogenic effect is associated with the suppression of DC maturation and an inhibited migration and proliferation of cytotoxic T cells.

Vagal nerve stimulation modulates the dendritic cell profile in posthemorrhagic shock mesenteric lymph

BACKGROUND

Previous studies have established that posthemorrhagic shock mesenteric lymph (PHSML) contains proinflammatory mediators, while the cellular basis of PHSML is less well characterized in acute models of injury. CD103 dendritic cells (DCs) have been identified in the mesenteric lymph (ML) in models of chronic intestinal inflammation, suggesting an important role in the gut response to injury. We have previously demonstrated the ability of vagal nerve stimulation (VNS) to prevent gut barrier failure after trauma/hemorrhagic shock (T/HS); however, the ability of VNS to alter ML DCs is unknown. We hypothesized that the CD103 MHC-II DC population would change in PHSML and that VNS would prevent injury-induced changes in this population in PHSML.

METHODS

Male Sprague-Dawley rats were randomly assigned to trauma/sham shock or T/HS. T/HS was induced by midline laparotomy and 60 minutes of HS (blood pressure, 35 mm Hg), followed by fluid resuscitation. A separate cohort of animals underwent cervical VNS after the HS phase. Gut tissue was harvested at 2 hours after injury for histologic analysis. ML was collected during the pre-HS, HS, and post-HS phase. For flow cytometric analysis, ML cells were subjected to staining with CD103 and MHC-II antibodies, and this cell population was compared in the pre-HS and post-HS phase from the same animal. The CD4Foxp3 cell (T reg) population in the ML node (MLN) was also tested to determine effects of CD103 DC modulation in the ML.

RESULTS

VNS reduced histologic gut injury and ML flow seen after injury. The CD103 MHC-II DC population in the PHSML was significantly decreased compared with pre-HS and was associated with decreased T reg expression in the MLN. VNS prevented the injury-induced decrease in the CD103 MHC-II+ DC population in the ML and restored the T reg population in the MLN.

CONCLUSION

These findings suggest that VNS mediates the inflammatory responses in ML DCs and MLN T reg cells by affecting the set point of T/HS responsiveness.

Nonneuronal Cholinergic System in Breast Tumors and Dendritic Cells: Does It Improve or Worsen the Response to Tumor?

Besides being the main neurotransmitter in the parasympathetic nervous system, acetylcholine (ACh) can act as a signaling molecule in nonneuronal tissues. For this reason, ACh and the enzymes that synthesize and degrade it (choline acetyltransferase and acetylcholinesterase) as well as muscarinic (mAChRs) and nicotinic receptors conform the non-neuronal cholinergic system (nNCS). It has been reported that nNCS regulates basal cellular functions including survival, proliferation, adhesion, and migration. Moreover, nNCS is broadly expressed in tumors and in different components of the immune system. In this review, we summarize the role of nNCS in tumors and in different immune cell types focusing on the expression and function of mAChRs in breast tumors and dendritic cells (DCs) and discussing the role of DCs in breast cancer.

The role of dendritic cells in the pathogenesis of cigarette smoke-induced emphysema in mice

Chronic Obstructive Pulmonary Disease (COPD) is an important lung and airway disease which affects the lives of around 200 million people worldwide. The pathological hallmark of COPD is emphysema and bronchiolitis and is based on the inflammatory response of the innate and adaptive immune system to the inhalation of toxic particles and gases. The inflamed airways of COPD patients contain several inflammatory cells including neutrophils, macrophages, T lymphocytes, and dendritic cells (DC). The potential role of DCs as mediators of inflammation in the airways of smokers and COPD patients is poorly understood. The current study investigated the role of DC subsets in an animal model of cigarette smoke-induced lung emphysema through the expansion or depletion of DC subsets. Expansion of both myeloid DC (mDC) and plasmacytoid DC (pDC) by Flt3L treatment induced a decline in macrophage numbers and increased the levels of fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF) in the bronchoalveolar lavage (BAL) fluid of smoke-exposed animals. The increase in the mean linear intercept (Lm) following Flt3L treatment was decreased by pDC depletion. In conclusion, pharmacological modulation of DC subsets may have an effect on the development of airway responses and emphysema as indicated by the decline in macrophage numbers and the increase in FGF and VEGF levels in the bronchoalveolar lavage fluid. Moreover, the depletion of pDCs decreased the Lm which might suggest a role for pDC in the pathogenesis of lung emphysema.

General mechanisms of nicotine-induced fibrogenesis

Cigarette smoking contributes to the development of cancer, and pathogenesis of other diseases. Many chemicals have been identified in cigarettes that have potent biological properties. Nicotine is especially known for its role in addiction and plays a role in other physiological effects of smoking and tobacco use. Recent studies have provided compelling evidence that, in addition to promoting cancer, nicotine also plays a pathogenic role in systems, such as the lung, kidney, heart, and liver. In many organ systems, nicotine modulates fibrosis by altering the functions of fibroblasts. Understanding the processes modulated by nicotine holds therapeutic potential and may guide future clinical and research decisions. This review discusses the role of nicotine in the general fibrogenic process that governs fibrosis and fibrosis-related diseases, focusing on the cellular mechanisms that have implications in multiple organ systems. Potential research directions for the management of nicotine-induced fibrosis, and potential clinical considerations with regard to nicotine-replacement therapy (NRT) are presented.

Cigarette smoke-induced accumulation of lung dendritic cells is interleukin-1α-dependent in mice

Background

Evidence suggests that dendritic cells accumulate in the lungs of COPD patients and correlate with disease severity. We investigated the importance of IL-1R1 and its ligands IL-1α and β to dendritic cell accumulation and maturation in response to cigarette smoke exposure.

Methods

Mice were exposed to cigarette smoke using a whole body smoke exposure system. IL-1R1-, TLR4-, and IL-1α-deficient mice, as well as anti-IL-1α and anti-IL-1β blocking antibodies were used to study the importance of IL-1R1 and TLR4 to dendritic cell accumulation and activation.

Results

Acute and chronic cigarette smoke exposure led to increased frequency of lung dendritic cells. Accumulation and activation of dendritic cells was IL-1R1/IL-1α dependent, but TLR4- and IL-1β-independent. Corroborating the cellular data, expression of CCL20, a potent dendritic cells chemoattractant, was IL-1R1/IL-1α-dependent. Studies using IL-1R1 bone marrow-chimeric mice revealed the importance of IL-1R1 signaling on lung structural cells for CCL20 expression. Consistent with the importance of dendritic cells in T cell activation, we observed decreased CD4⁺ and CD8⁺ T cell activation in cigarette smoke-exposed IL-1R1-deficient mice.

Conclusion

Our findings convey the importance of IL-1R1/IL-1α to the recruitment and activation of dendritic cells in response to cigarette smoke exposure.

Nicotine up-regulated 4-1BBL expression by activating Mek-PI3K pathway augments the efficacy of bone marrow-derived dendritic cell vaccination

PURPOSE

To explore the role of 4-1BBL in nicotine-treated immature dendritic cells (imDCs) mediated anti-tumor effects.

METHODS

Bone marrow-derived imDCs were stimulated with nicotine and 4-1BBL expression was determinated by flow cytometry, Western blot and RT-PCR respectively. Then, the roles of 4-1BBL in nicotine-augmented DCs-dependent T cell proliferation, CTL priming and anti-tumor effects were investigated by BrdU cell proliferation assay, enzyme-linked immunospot assay and in vivo preventive effect on tumor development, respectively. Finally, using relative kinase inhibitors, the mechanism of 4-1BBL up-regulation by nicotine stimulation and the roles of Mek-PI3K signal pathways in nicotine-augmented DCs-dependent T cell proliferation were explored by Western blot and BrdU cell proliferation assay, respectively.

RESULTS

Firstly, nicotine could up-regulate 4-1BBL expression in both protein and mRNA levels. Secondly, the effects of nicotine-augmented DCs-dependent T-cell proliferation, CTL priming and anti-tumor effects could be significantly abolished by blocking CD80, CD86 and 4-1BBL activity, respectively. Thirdly, the combined blockages of CD80/CD86, CD80/4-1BBL, CD86/4-1BBL or CD80/CD86/4-1BBL signals could decrease 53.2 %, 29.6 %, 27.9 % and 54.5 % nicotine-enhanced T cell proliferation, respectively. Importantly, nicotine-induced 4-1BBL up-regulation could be decreased by the usage of Mek-PI3K pathway kinase inhibitors. The pre-treatment of Mek-p38-PI3K kinase inhibitors could obviously abolish nicotine-augmented DCs-dependent T cell proliferation.

CONCLUSIONS

CD80/CD86 and 4-1BBL are critical for nicotine augmented DCs-mediated anti-tumor effects. 4-1BBL and CD80/CD86 could be considered as potential candidates for preventive and therapeutic tumor vaccination.

Nicotinic acetylcholine receptor signaling in atherogenesis

Smoking is a major risk factor for the development of atherosclerosis, stroke and myocardial infarction. Cigarette smoke consists of a complex mixture of about 4000 compounds. Out of these, polycyclic hydrocarbons, tobacco-specific nitrosamines, oxidizing agents and carbon monoxide have been implicated in the development of atherosclerosis. Recent studies have shown that nicotine (the addictive component of cigarettes) binds to high affinity cell-surface receptors and accelerates the atherogenic process. These receptors are called nicotinic acetylcholine receptors (nAChRs) and are expressed ubiquitously in almost all cells existing in the blood vessels. The present review summarizes the pro-atherogenic effects of nAChR ligands such as nicotine and tobacco nitrosamines. The contribution of different nAChR subunits in plaque growth, progression and neovascularization are discussed in detail. The signaling pathways underlying the actions of the nAChRs ligands in blood vessels are also described. Finally, the feasibility of nAChR ligands as therapeutic targets for atherosclerosis is summarized. We believe that the information presented in this review is relevant for atherosclerosis patients who are active smokers, exposed to environmental tobacco smoke or use nicotine patches or gums for smoking cessation.

Nicotine stimulated bone marrow-derived dendritic cells could augment HBV specific CTL priming by activating PI3K-Akt pathway

Our previous studies have revealed that nicotine-treated immature dendritic cells (imDCs) have anti-tumor effects in murine lymphoma models. The present study is to explore HBV-specific CTL priming and its cytolytic activities of nicotine-treated murine DCs, the mechanism of α7 nicotinic acetylcholine receptor (nAChR) up-regulation by nicotine and the efficiency of nicotine with other cytokines. To address these hypotheses, bone marrow-derived imDCs were stimulated by nicotine and expression of α7 nAChR was firstly determined by flow cytometry and Western blot. Then, DCs-dependent HBV-specific T cell proliferation and IL-12 secretion were secondly determined by BrdU cell proliferation assay and ELISA, respectively. The HBV-specific CTL priming and its activities were further explored by intraperitoneal transfer of nicotine treated imDCs. The mechanism of nicotine up-regulating α7 nAChR was finally explored by Western blot. The results showed that: first, the maximal activation of PI3K and Akt was reached at 30 and 60-120 min respectively after nicotine stimulation. Nicotine up-regulated the expression of α7 nAChR by activating PI3K-Akt pathway in murine DCs; secondly, nicotine stimulation could enhance DCs' ability of HBV-specific T cell proliferation and IL-12 secretion; thirdly, adoptive transfer of nicotine stimulated DCs could induce HBV specific CTL priming in vivo and those CTL had cytolytic activities; fourthly, nicotine had equal efficiencies to 2 ng/ml IFN-γ in DCs-mediated T cell proliferation. All these data presented here indicated that nicotine treated imDCs might be considered as a potential candidate for HBV immunotherapy.

Smoking and risk of incident psoriasis among women and men in the United States: a combined analysis

The authors evaluated the association between smoking and the incidence of psoriasis among 185,836 participants from a cohort of older women (the Nurses' Health Study, 1996-2008), a cohort of younger women (the Nurses' Health Study II, 1991-2005), and a cohort of men (Health Professionals' Follow-up Study, 1986-2006). Information on smoking was collected biennially during follow-up. The authors identified a total of 2,410 participants with incident psoriasis. Compared with never smokers, past smokers had a relative risk of incident psoriasis of 1.39 (95% confidence interval (CI): 1.27, 1.52) and current smokers had a relative risk of 1.94 (95% CI: 1.64, 2.28). For current smokers who smoked 1-14 cigarettes/day, the relative risk was 1.81 (95% CI: 1.38, 2.36); for those who smoked 15-24 cigarettes/day, the relative risk was 2.04 (95% CI: 1.68, 2.47); and for those who smoked 25 or more cigarettes/day, the relative risk was 2.29 (95% CI: 1.74, 3.01). There was a trend toward an increased risk of psoriasis with increasing pack-years or duration of smoking (P(trend) < 0.0001). The risk was highest among smokers who had 65 or more pack-years of smoking (relative risk = 2.72, 95% CI: 2.05, 3.60) and among those with a smoking duration of 30 or more years (relative risk = 1.99, 95% CI: 1.75, 2.25). The authors observed a graded reduction of risk with an increase in time since smoking cessation (P(trend) <0.0001). In this study, smoking was found to be an independent risk factor for psoriasis in both women and men. Psoriasis risk was particularly augmented for heavy smokers and persons with longer durations of smoking.

Nicotine modulates the immunological function of dendritic cells through peroxisome proliferator-activated receptor-γ upregulation

We examined the effects of nicotine on differentiation and function of monocyte-derived human dendritic cells (DCs). NiDCs, which were the DCs differentiated in the presence of nicotine, showed lower levels of CD1a. Secretion of IL-12 and TNF-α by lipopolysaccharide (LPS)-stimulated NiDCs was significantly suppressed compared to monocyte-derived DCs grown without nicotine. NiDCs displayed a diminished capacity to induce allogeneic T cell proliferation with a reduced production of IFN-γ, and maintained/enhanced LPS-mediated expression of coinhibitory molecules. Interestingly, NiDCs enhanced the expression of nuclear receptor peroxisome proliferator-activated receptors γ (PPAR γ), which has immunomodulatory properties. Expression of PPAR γ and PPAR γ-target genes was significantly inhibited by pretreatment with d-tubocurarine, antagonist of non-selective nicotinic acetylcholine receptors (nAChR). In addition, reduction of Th1 responses was inhibited after blocking nAChR-mediated signal. These data suggest the effect of nicotine on altering DC immunogenicity by impeding Th1 immunity is partially mediated by upregulation of PPAR γ.

Exposure to nicotine adversely affects the dendritic cell system and compromises host response to vaccination

The magnitude of Th1 cells response to vaccination is a critical factor in determining protection from clinical disease. Our previous in vitro studies suggested that exposure to the nicotine component of cigarette smoke skews the differentiation of both human and mouse dendritic cell (DC) precursors into atypical DCs (DCs differentiated ex vivo in the presence of nicotine) lacking parameters essential for the development of Th1-mediated immunity. In this study, we determined the causal relationship between nicotine-induced DC alterations and host response to vaccines. We show that animals exposed to nicotine failed to develop and maintain Ag-specific effector memory Th1 cells and Ab production to protein-based vaccine formulated with Th1 adjuvants. Accordingly, both prophylactic and therapeutic vaccines failed to protect and cure the nicotine-exposed mice from disease. More importantly, we demonstrate the nicotine-induced defects in the biological activities of in vivo DCs as an underlying mechanism. Indeed, i.v. administration of DCs differentiated in the presence of nicotine preferentially promoted the development of Ag-specific IL-4-producing effector cells in the challenged mice. In addition, DC subsets isolated from mice exposed to nicotine produced significantly less cytokines in response to Th1 adjuvants and inadequately supported the development of Ag-specific Th1 cells. Collectively, our studies suggest that nicotine-induced defects in the DC system compromises vaccine efficacy in smokers.

Lipopolysaccharide and dose of nicotine determine the effects of nicotine on murine bone marrow-derived dendritic cells

The reported effects of nicotine on dendritic cells (DCs) are controversial. To investigate the factors which determine the effects of nicotine on DCs, immature dendritic cells (imDCs) induced from murine bone marrow were treated with different doses of nicotine with or without lipopolysaccharides (LPS). The morphology and expression of the co-stimulatory molecules CD80, CD86, CD40 and CD54 were observed and determined by microscopy and flow cytometry, respectively. The results showed that, firstly, nicotine treatment promoted the development of DC precursors into imDCs with a semi-mature phenotype revealed by a higher expression of CD11c and more branched projections. Secondly, lower doses of nicotine (16.5 ng/ml), but not higher (200 μg/ml), up-regulated the expression of the co-stimulatory molecules CD80, CD40 and CD54 on imDCs. Co-administration of LPS and nicotine revealed differential effects on co-stimulatory molecule expression on imDCs. Thirdly and importantly, treatment with lower doses of nicotine (16.5 ng/ml) did not augment expression of the CD80, CD86, CD40 and CD54 molecules in mature DCs. Fourthly and interestingly, high doses of nicotine (more than 165 μg/ml) revealed pro-apoptotic activity but lower doses of nicotine (16.5–0.165 ng/ml) achieved an anti-apoptotic effect on imDCs. All data presented here indicate that the controversial effects of nicotine on DCs may be due to the LPS of the nicotinic environment and the dose of nicotine used.

Smoking and pathogenesis of psoriasis: a review of oxidative, inflammatory and genetic mechanisms

Recent studies suggest that cigarette smoking may trigger the development of psoriasis through oxidative, inflammatory and genetic mechanisms. Smoking initiates formation of free radicals that stimulate cell signalling pathways active in psoriasis including mitogen-activated protein kinase (MAPK), nuclear factor-κB (NF-κB) and Janus kinase/signal transducers and activators of transcription (JAK-STAT). Smoking damages the skin by increasing formation of reactive oxygen species and decreasing the gene expression of antioxidants. Nicotine also stimulates innate immune cells integral to the pathogenesis of psoriasis including dendritic cells, macrophages and keratinocytes. These cells release cytokines that activate T lymphocytes and perpetuate a cycle of chronic inflammation. Smoking also enhances expression of genes known to confer an increased risk of psoriasis, including HLA-Cw6, HLA-DQA1*0201 and CYP1A1. Improved understanding of the possible link between smoking and psoriasis pathogenesis may provide further insight into mechanisms underlying smoking, psoriasis and risk of subsequent cardiovascular disease.

Role of α7 nicotinic acetylcholine receptors in regulating tumor necrosis factor-α (TNF-α) as revealed by subtype selective agonists

Immunological responses to protect against excessive inflammation can be regulated by the central nervous system through the cholinergic anti-inflammatory pathway wherein acetylcholine released from vagus nerves can inhibit inflammatory cytokines. Although a role for the α7 nicotinic acetylcholine receptor (α7 nAChR) in mediating this pathway has been suggested, pharmacological modulation of the pathway by selective agonists remains to be further elucidated. In this study, the role of α7 nAChRs in the regulation of TNF-α release was investigated using high affinity and selective α7 nAChR agonists in mouse peritoneal macrophage and human whole blood in vitro, and in mouse serum in vivo. In mouse peritoneal macrophages, LPS-induced TNF-α release in vitro was inhibited by a selective α7 nAChR agonist, A-833834 (5-[6-(5-Methyl-hexahydro-pyrrolo[3,4-c]pyrrol-2-yl)-pyridazin-3-yl]-1H-indole), and that effect was attenuated by α7 nAChR antagonist methyllycaconitine. The inhibitory effect of A-833834 on LPS-induced TNF-α release was also observed in human whole blood in vitro. I.v. LPS-induced TNF-α release in mouse serum was attenuated following i.p. administration of A-833834. Similarly, i.v. LPS-induced TNF-α release in mouse serum was also attenuated following i.p. administration of A-585539, another α7 nAChR agonist with limited brain penetration, suggesting that these effects are mediated by peripheral α7 nAChRs. A-833834 was also efficacious in suppressing TNF-α release in mouse serum following oral administration in zymosan-induced peritonitis. These studies collectively demonstrate that selectively targeting α7 nAChRs could offer a novel therapeutic modality to treat acute and chronic inflammatory disease states.

Cytokine-induced alterations of α7 nicotinic receptor in colonic CD4 T cells mediate dichotomous response to nicotine in murine models of Th1/Th17- versus Th2-mediated colitis

Ulcerative colitis (UC) and Crohn's disease (CD) are two forms of chronic inflammatory bowel disease. CD4 T cells play a central role in the pathogenesis of both diseases. Smoking affects both UC and CD but with opposite effects, ameliorating UC and worsening CD. We hypothesized that the severity of gut inflammation could be modulated through T cell nicotinic acetylcholine receptors (nAChRs) and that the exact clinical outcome would depend on the repertoire of nAChRs on CD4 T cells mediating each form of colitis. We measured clinical and immunologic outcomes of treating BALB/c mice with oxazolone- and trinitrobenzene sulfonic acid (TNBS)-induced colitides by nicotine. Nicotine attenuated oxazolone colitis, which was associated with an increased percentage of colonic regulatory T cells and a reduction of Th17 cells. TCR stimulation of naive CD4(+)CD62L(+) T cells in the presence of nicotine upregulated expression of Foxp3. In marked contrast, nicotine worsened TNBS colitis, and this was associated with increased Th17 cells among colonic CD4 T cells. Nicotine upregulated IL-10 and inhibited IL-17 production, which could be abolished by exogenous IL-12 that also abolished the nicotine-dependent upregulation of regulatory T cells. The dichotomous action of nicotine resulted from the up- and downregulation of anti-inflammatory α7 nAChR on colonic CD4 T cells induced by cytokines characteristic of the inflammatory milieu in oxazolone (IL-4) and TNBS (IL-12) colitis, respectively. These findings help explain the dichotomous effect of smoking in patients with UC and CD, and they underscore the potential for nicotinergic drugs in regulating colonic inflammation.

Cholinergic modulation of dendritic cell function

Dendritic cells (DCs) are highly specialized antigen-presenting cells with a unique ability to activate resting T lymphocytes. Acetylcholine (ACh) is the primary parasympathetic neurotransmitter and also a non-neural paracrine factor produced by different cells. Here, we analyzed the expression of the cholinergic system in DCs. We found that DCs express the muscarinic receptors M(3), M(4) and M(5), as well as the enzymes responsible for the synthesis and degradation of ACh, choline acetyltransferase (ChAT) and acetylcholinesterase (AChE), respectively. Differentiation of DCs in the presence of the cholinergic agonist carbachol, the synthetic analog of ACh, resulted in an increased expression of HLA-DR and CD86 and the stimulation of TNF-α and IL-8 production. All these effects were prevented by atropine, a muscarinic ACh receptor (mAChR) antagonist. Carbachol, was also able to modulate the function of DCs when added after the differentiation is accomplished; it increased the expression of HLA-DR, improved the T cell priming ability of DCs, and stimulated the production of TNF-α but not IL-12 or IL-10. By contrast, carbachol significantly inhibited the stimulation of HLA-DR expression and the enhancement in the T cell priming ability of DCs triggered by LPS. Interestingly, the TNF-α antagonist etanercept completely prevented the increased expression of HLA-DR induced by carbachol, suggesting that it promotes the phenotypic maturation of DCs by stimulating the production of TNF-α. ACh induced similar effects than carbachol; it stimulated the expression of HLA-DR and the production of TNF-α, while inhibiting the stimulation of HLA-DR expression and IL-12 production triggered by LPS. Similarly, neostigmine, an inhibitor of AChE, also stimulated the expression of HLA-DR and the production of TNF-α by DCs while inhibiting the production of TNF-α and IL-12 triggered by LPS. These results support the existence of an autocrine/paracrine loop through which ACh modulates the function of DCs.

Tristetraprolin mediates anti-inflammatory effects of nicotine in lipopolysaccharide-stimulated macrophages

Nicotine inhibits the release of TNF-α from macrophage through activation of STAT3. Tristetraprolin (TTP) is known to destabilize pro-inflammatory transcripts containing AU-rich elements (ARE) in 3'-untranslated region (3'-UTR). Here we show that in LPS-stimulated human macrophages the anti-inflammatory action of nicotine is mediated by TTP. Nicotine induced activation of STAT3 enhanced STAT3 binding to the TTP promoter, increased TTP promoter activity, and increased TTP expression resulting in the suppression of LPS-stimulated TNF-α production. Overexpression of a dominant negative mutant of STAT3 (R382W) or down-regulation of STAT3 by siRNA abolished nicotine-induced TTP expression and suppression of LPS-stimulated TNF-α production. Nicotine enhanced the decay of TNF-α mRNA and decreased luciferase expression of a TNF-α 3'-UTR reporter plasmid in U937 cells. However, siRNA to TTP abrogated these effects of nicotine. In this experiment, we are reporting for the first time the involvement of TTP in the cholinergic anti-inflammatory cascade consisting of nicotine-STAT3-TTP-dampening inflammation.

Nicotine-induced differential modulation of autoimmune arthritis in the Lewis rat involves changes in interleukin-17 and anti-cyclic citrullinated peptide antibodies

OBJECTIVE

Rheumatoid arthritis (RA) is a debilitating autoimmune disease, and smoking is an important environmental factor in a subset of RA patients. A role of the cholinergic antiinflammatory pathway in autoimmune inflammation is increasingly being realized. Nicotine is a major component of cigarette smoke, and it stimulates the α7 nicotinic acetylcholine receptors. Therefore, defining the mechanisms underlying the immunomodulatory effects of nicotine on arthritis is of high relevance. The purpose of this study was to address this issue using the rat adjuvant-induced arthritis (AIA) model of human RA.

METHODS

Lewis rats were immunized subcutaneously with heat-killed Mycobacterium tuberculosis H37Ra for disease induction. Rats were treated with nicotine intraperitoneally either before (pretreatment) or after (posttreatment) the onset of AIA. Control rats received the vehicle (buffer) in place of nicotine. The severity of arthritis was assessed and graded. The draining lymph node cells were tested for T cell proliferative and cytokine responses against the disease-related antigen mycobacterial heat-shock protein 65. The sera were tested for anti-cyclic citrullinated peptide (anti-CCP) antibodies and anti-mycobacterial Hsp65 antibodies.

RESULTS

Nicotine pretreatment aggravated the arthritis, whereas nicotine posttreatment suppressed the disease. This altered severity of AIA directly correlated with the levels of the anti-CCP antibodies, of the Th1/Th17 cytokines, and of the corresponding dendritic cell-derived cytokines. The majority of these effects on cellular responses could be replicated in vitro.

CONCLUSION

Nicotine-induced modulation of AIA involves specific alterations in the disease-related cellular and humoral immune responses in AIA. These results are of significance in advancing our understanding of the pathogenesis of RA.

Environmental risk factors in pediatric psoriasis: a multicenter case-control study

To analyze the effect of possible risk factors, including breastfeeding, on the development of childhood-onset psoriasis, a multicenter case-control study with prospective collection of data was performed. Using a standard questionnaire, personal and specific variables including family history of psoriasis, maternal and environmental tobacco smoke exposure, body mass index (BMI), exclusive and partial breastfeeding for at least 3 and 12 months, cow's milk intake before 1 year, birth delivery method, and stressful life events were collected during 2009 from 537 patients with psoriasis and 511 controls younger than 18. Overall, patients more frequently reported exposure to environmental tobacco smoke at home and stressful life events in the year preceding the diagnosis than controls. The odds ratios (OR) for smoking and stressful life events were 2.90 (95% confidence interval [CI]=2.27-3.78) and 2.94 (95% CI=2.28-3.79), respectively. In addition, children with psoriasis were more likely to have a higher BMI (>26) than controls (OR=2.52; 95% CI=1.42-4.49). High BMI, environmental tobacco smoke exposure at home, and stressful life events may influence the development of pediatric psoriasis.

Plasticity of the murine spleen T-cell cholinergic receptors and their role in in vitro differentiation of naïve CD4 T cells toward the Th1, Th2 and Th17 lineages

Acetylcholine (ACh) regulates vital functions of T cells by acting on the nicotinic and muscarinic classes of cholinergic receptors, nAChR and mAChRs, respectively. This study was performed in murine splenic T cells. In freshly isolated CD4 and CD8 T cells, we detected mRNAs encoding α5, α9, α10, β1, β2, β4 nAChR subunits and M₁, M₃, M₄ and M₅ mAChR subtypes, whereas α2 was detected only in CD8 T cells. In vitro activation of CD4 T cells through T-cell receptor (TCR)/CD3 cross-linking was associated with the appearance of α4 and α7, upregulation of α5, α10, β4, M₁ and M₅ and downregulation of α9 and β2, whereas in vitro activation of CD8 T cells also featured the appearance of α4 and α7, as well as upregulation of α2, α5, β4, M₁ and M₄, and downregulation of α10, β1, β2 and M₃. In vitro polarization toward T helper (Th) 1 lineage was associated with a decrease of β2, β4 and M₃ expression; that toward Th2 cells with downregulation of α9 and M₃, and upregulation of M₁ and M₅; and that toward Th17 phenotype with downregulation of α9, α10, β2 and M₃ mAChR. Polarized T cells also expressed α4, but not α1, α2, α3, α6, β3 or M₂. To determine the role of cholinergic receptors in mediating the immunoregulatory action of autocrine/paracrine ACh, we analyzed the effects of nicotinic and muscarinic agonists±antagonists on cytokine production in the CD4+CD62L+ T cells co-stimulated via TCR/CD3 cross-linking. The nicotinergic stimulation upregulated interferon-γ (IFN-γ) and downregulated interleukin (IL)-17 secretion, whereas the muscarinic stimulation enhanced IL-10 and IL-17 and inhibited INF-γ secretion. These results demonstrated plasticity of the T-cell cholinergic system.

Decreased numbers of peripheral blood dendritic cells in patients with coronary artery disease are associated with diminished plasma Flt3 ligand levels and impaired plasmacytoid dendritic cell function

We investigated whether activation of circulating DCs (dendritic cells) or levels of Flt3L (FMS-like tyrosine kinase 3 ligand) and GM-CSF (granulocyte/macrophage colony-stimulating factor), haematopoietic growth factors important for DC differentiation, could account for reduced blood DC numbers in CAD (coronary artery disease) patients. Concentrations of Flt3L and GM-CSF were measured in plasma from CAD patients (n = 15) and controls (n = 12). Frequency and phenotype of mDCs (myeloid dendritic cells) and pDCs (plasmacytoid dendritic cells) were analysed by multicolour flow cytometry in fresh blood, and after overnight incubation with TLR (Toll-like receptor)-4 or -7 ligands LPS (lipopolysaccharide) or IQ (imiquimod). DC function was measured by IL (interleukin)-12 and IFN (interferon)-α secretion. Circulating numbers of CD11c+ mDCs and CD123+ pDCs and frequencies of CD86+ and CCR-7+ (CC chemokine receptor type 7) mDCs, but not pDCs, were declined in CAD. In addition, plasma Flt3L, but not GM-CSF, was lower in patients and positively correlated with blood DC counts. In response to LPS, mDCs up-regulated CD83 and CD86, but CCR-7 expression and IL-12 secretion remained unchanged, similarly in patients and controls. Conversely, pDCs from patients had lower CD83 and CCR-7 expression after overnight incubation and had a weaker IQ-induced up-regulation of CD83 and IFN-α secretion. In conclusion, our results suggest that reduced blood DC counts in CAD are, at least partly, due to impaired DC differentiation from bone marrow progenitors. Decreased levels of mDCs are presumably also explained by activation and subsequent migration to atherosclerotic plaques or lymph nodes. Although mDCs are functioning normally, pDCs from patients appeared to be both numerically and functionally impaired.

Up-regulation of TNF-alpha secretion by cigarette smoke is mediated by Egr-1 in HaCaT human keratinocytes

Many epidemiologic studies have pointed to a significant association between cigarette smoking and inflammatory skin disease such as psoriasis. Cigarette smoke induces expression of regulators of inflammation such as interleukin (IL)-1, IL-6, IL-8 and tumor necrosis factor (TNF)-alpha. It was recently demonstrated that early growth response-1 (Egr-1) transcription factor is significantly up-regulated in the skin lesions of patients with psoriasis. The mechanism by which cigarette smoke extract (CSE) regulates inflammatory cytokine expression in keratinocyte was still unknown. The aim of this study was to investigate the signalling of CSE-induced Egr-1 expression and the role for Egr-1 in CSE-induced TNF-alpha expression. Cytotoxicity of CSE in HaCaT cells was measured by thiazolyl blue tetrazolium bromide (MTT) assay. CSE-induced Egr-1 expression was investigated by western blot, luciferase reporter assay and confocal microscopy. TNF-alpha expression was measured by reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. Involvement of Egr-1 in CSE-induced TNF-alpha secretion was determined by using Egr-1 specific siRNA. CSE increases the Egr-1 expression, promoter activity and its nuclear translocation in human HaCaT keratinocytes. CSE activates mitogen-activated protein kinase (MAPK) pathways including extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK). Up-regulation of Egr-1 expression by CSE stimulation was found to be inhibited by an ERK and JNK but not p38 inhibitor. CSE increases TNF-alpha expression and secretion. This increase is mediated by CSE-induced Egr-1 expression. Our results showed that CSE induces Egr-1 expression via MAPK pathway in human keratinocytes and TNF-alpha expression by Egr-1. This pathway may contribute to the development of inflammatory disease such as psoriasis.

Nicotine stimulated dendritic cells could achieve anti-tumor effects in mouse lung and liver cancer

INTRODUCTION

Our previous studies have revealed that nicotine-treated immature dendritic cells (imDCs) have anti-tumor effects in murine lymphoma models. The present study is to explore the preventive and therapeutic anti-tumor effects of nicotine-treated imDCs in murine lung and liver cancer.

MATERIALS AND METHODS

To address this objection, bone marrow-derived imDCs were firstly stimulated by nicotine in vitro and the expressions of CD80, CD86, CD40, CD11b, MHC class I and II were determined by flow cytometry. Then, DCs-dependent tumor-lysate-specific T cell proliferation, IL-12(p40+p70) secretion were determined by BrdU cell proliferation assay and enzyme-linked immunosorbent assay, respectively. The anti-tumor effects of such imDCs were further explored by intraperitoneal transfer against tumor challenge or implantation. By using kinase inhibitors, the mechanism of nicotine upregulating CD80 was finally explored by flow cytometry.

RESULTS

The results showed that: firstly, nicotine could upregulate the expressions of CD80, CD86, CD40,CD11b, MHC class I and II molecules in imDCs. Secondly, nicotine could promote imDCs-dependent T cell priming and IL-12 secretion. Most importantly, systemic transfer of ex vivo nicotine-stimulated imDCs, which enhanced CD80 expression through PI3K activation, could reveal preventive and effectively therapeutic effects on tumor development.

CONCLUSIONS

Ex vivo nicotine stimulation can significantly improve imDCs efficacy for adaptive therapy of cancer. Nicotine-treated imDCs might be considered as a potential candidate for therapeutic tumor immunotherapy for lung and liver cancer.

Neurogenic regulation of dendritic cells in the intestine

Antigen presenting cells like dendritic cells (DC) are responsible for the initiation of adaptive immune responses via the T helper cells they activate. The type of T cell responses DC induce is dependent on the local immunological environment where antigen has been taken up. In the gut, resident DC are phenotypically and functionally shaped by epithelial and stromal cell derived signals, the cytokine microenvironment, and neuronal products. These factors can control the activation state of DC thereby inducing tolerance for food and commensal organisms or immunity against pathogenic microbes. The enteric nervous system (ENS) is increasingly recognized as an important regulatory factor in intestinal immune cell control. Neurotransmitters and neuropeptides like acetylcholine (ACh), norepinephrine (NE) and vasoactive intestinal peptide (VIP) are released by neurons of the ENS and can affect the function of DC and subsequent immune responses. The critical balance between tolerance and protective immunity is disrupted in inflammatory bowel disease, which results in an exaggerated immune response against commensal bacteria. In this review we discuss the effects of ACh, VIP, and NE on DC function. DC express various receptors for these neuron derived products and can alter DC co-stimulatory molecule expression, cytokine release and subsequent T cell activation in an anti-inflammatory fashion. Knowledge about these interactions will help find new drug targets and may facilitate the development of specific therapies for diseases like inflammatory bowel disease (IBD).

Dendritic cells and their role in atherogenesis

Dendritic cells (DCs) are the most potent professional antigen-presenting cells with the unique ability of primary immune response initiation. DCs originate from bone marrow progenitors, which circulate in the peripheral blood and subsequently penetrate peripheral tissues, where they give rise to immature DCs. In peripheral tissues, DCs continuously monitor the microenvironment and, when the cells encounter 'danger' signals, DCs undergo differentiation and maturation. Maturing DCs usually migrate to lymphatic tissues, where they form contacts with T cells to initiate a primary immune response. DCs were identified in arteries in 1995 and since then, further knowledge has been gained about the peculiarities of vascular-associated DCs and their role in atherosclerosis. Immune reactions toward modified lipoproteins and other factors ignited by resident vascular DCs as well as by newly arrived DCs, which originate from blood monocytes, are believed to destabilize arterial homeostasis from very earlier stages of atherogenesis. There is a remarkable heterogeneity of DCs in atherosclerotic lesions. Some DCs mature and become capable of forming clusters with T cells directly within the arterial wall. The predictive value of the numbers of circulating DC precursors in coronary artery disease and in atherosclerosis has been assessed, and it has been shown that DCs have a role in plaque destabilization. Over recent decades, DCs have proven to be a valuable instrument in immunotherapy approaches against cancer and various autoimmune diseases, and this explains the demand that the accumulated knowledge be applied to the field of atherosclerosis immunotherapy.

Smoking and atherosclerotic cardiovascular disease: part II: role of cigarette smoking in cardiovascular disease development

Potential mechanisms and biomarkers of atherosclerosis related to cigarette smoking - a modifiable risk factor for that disease - are discussed in this article. These include smoking-associated inflammatory markers, such as leukocytes, high-sensitivity C-reactive protein, serum amyloid A, ICAM-1 and IL-6. Other reviewed markers are indicative for smoking-related impairment of arterial endothelial function (transcapillary leakage of albumin, inhibition of endogenous nitric oxide synthase activity and reduced endothelium-dependent vasodilation) or point to oxidative stress caused by various chemicals (cholesterol oxidation, autoantibodies to oxidized low-density lipoprotein, plasma levels of malondialdehyde and F(2)-isoprostanes and reduced antioxidant capacity). Smoking enhances platelet aggregability, increases blood viscosity and shifts the pro- and antithrombotic balance towards increased coagulability (e.g., fibrinogen, von Willebrand factor, ICAM-1 and P-selectin). Insulin resistance is higher in smokers compared with nonsmokers, and hemoglobin A1c is dose-dependently elevated, as is homocysteine. Smoke exposure may influence the kinetics of markers with different response to transient or chronic changes in cigarette smoking behavior.

Update on the epidemiology and systemic treatment of psoriasis

Recent epidemiological observations reveal that the prevalence of psoriasis increases more rapidly in young women compared with young men, and that the prevalence of psoriasis may decrease in the elderly. Emerging evidence suggests that some potentially modifiable exposures, such as smoking, stress and obesity, may increase a patient's risk of developing psoriasis. The evolving literature suggests that psoriasis is associated with multiple other diseases, including cancer, cardiovascular disease, diabetes and psychiatric disease, and that psoriasis itself may be an independent risk factor for developing atherosclerosis and myocardial infarction. The treatment of moderate-to-severe psoriasis is undergoing a revolution with the advent of biological therapies that target the immunopathogenesis of psoriasis, such as tumor necrosis factor-alpha and T-cell function. The pharmacokinetics, pharmacodynamics, efficacy and safety profiles vary among biologicals and, therefore, drug and patient factors are important in selecting the optimum therapy. In this article, we focus on recent developments in the epidemiology and systemic treatment of psoriasis.

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.

Effects of tobacco smoke on immunity, inflammation and autoimmunity

Smoking is a central factor in many pathological conditions. Its role in neoplasm, lung and cardiovascular diseases has been well established for years. However it is less acknowledged the cigarette smoking affects both the innate and adoptive immune arms. Cigarette smoke was shown to augment the production of numerous pro-inflammatory cytokines such as TNF-alpha, IL-1, IL-6, IL-8 GM-CSF and to decrease the levels of anti-inflammatory cytokines such as IL-10. Tobacco smoke via multiple mechanisms leads to elevated IgE concentrations and to the subsequent development of atopic diseases and asthma. Cigarette smoke has also been shown activate in many ways macrophage and dendritic cell activity. While it is better evident how cigarette smoke evokes airway diseases more mechanisms are being revealed linking this social hazard to autoimmune disorders, for instance via the production of antibodies recognizing citrullinated proteins in rheumatoid arthritis or by the elevation of anti-dsDNA titers in systemic lupus erythematosus. The current review underlines the importance of smoking prevention and eradication not only in respiratory disorders but also in autoimmune conditions as well.