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

The Expressions of TSLP, IL-33, and IL-17A in Monocyte Derived Dendritic Cells from Asthma and COPD Patients are Related to Epithelial-Macrophage Interactions

BACKGROUND

The cross-talk between the external and internal environment in the respiratory tract involves macrophage/dendritic cell (DC) transepithelial network. Epithelium triggers dendritic cell-mediated inflammation by producing thymic stromal lymphopoietin (TSLP), IL-33, and IL-17A. The study aimed to evaluate the expression of TSLP, IL-33, and IL-17A in human monocyte derived dendritic cells (moDCs) co-cultured with respiratory epithelium and monocyte derived macrophages (moMφs) in asthma, chronic obstructive pulmonary disease (COPD) and healthy controls.

METHODS

The study used a triple-cell co-culture model, utilizing nasal epithelial cells, along with moMφs and moDCs. Cells were cultured in mono-, di-, and triple-co-cultures for 24 h.

RESULTS

Co-culture with epithelium and moMφs significantly increased TSLP in asthma and did not change IL-33 and IL-17A mRNA expression in moDCs. moDCs from asthmatics were characterized by the highest TSLP mRNA expression and the richest population of TSLPR, ST2, and IL17RA expressed cells. A high number of positive correlations between the assessed cytokines and CHI3L1, IL-12p40, IL-1β, IL-6, IL-8, TNF in moDCs was observed in asthma and COPD.

CONCLUSION

TSLP, IL-33, and IL-17A expression in moDCs are differently regulated by epithelium in asthma, COPD, and healthy subjects. These complex cell-cell interactions may impact airway inflammation and be an important factor in the pathobiology of asthma and COPD.

A Novel Murine Chronic Obstructive Pulmonary Disease Model and the Pathogenic Role of MicroRNA-21

Chronic obstructive pulmonary disease (COPD) is a multi-pathogenesis chronic lung disease. The mechanisms underlying COPD have not been adequately illustrated. Many reseachers argue that microRNAs (miRs) could play a crucial role in COPD. The classic animal model of COPD is both time consuming and costly. This study proposes a novel mice COPD model and explores the role of miR-21 in COPD. A total of 50 wide-type (WT) C57BL/6 mice were separated into five euqlly-sized groups—(1) control group (CG), (2) the novel combined method group (NCM, cigarette smoke (CS) exposure for 28 days combined with cigarette smoke extract (CSE) intraperitoneal injection), (3) the short-term CS exposure group (SCSE, CS exposure for 28 days), (4) the CSE intraperitoneal injection group (CSEII, 28 days CSE intraperitoneal injection), and (5) the long-term CS exposure group (LCSE, CS exposure).The body weight gain of mice were recorded and lung function tested once the modeling was done. The pathological changes and the inflammation level by hematoxylin eosin (H&E) staining and immunohistochemical staining (IHS) on the lung tissue sections were also evaluated. The level of miR-21 in the mice lungs of the mice across all groups was detected by RT-qPCR and the effects of miR-21 knock-down in modeled mice were observed. The mice in LCSE and NCM exhibited the most severe inflammation levels and pathological and pathophysiological changes; while the changes for the mice in SCSE and CSEII were less, they remained more severe than the mice in the CG. The level of miR-21 was found to be negatively correlated with lung functions. Moreover, knocking miR-21 down from the modeled mice, ameliorated all those tested COPD-related changes. Our novel modeling method detected virtually the same changes as those detected in the classic method in WT mice, but in less time and cost. Further, it was determined that the level of miR-21 in the lungs could be an indicator of COPD severity and blocking functions of miR-21 could be a potential treatment for early stage COPD.

MicroRNA-21 aggravates chronic obstructive pulmonary disease by promoting autophagy

MicroRNAs and autophagy play important roles in chronic obstructive pulmonary disease (COPD). This study was designed to explore the role of microRNA-21 (miR-21) induced autophagy in COPD. Using the C57BL/6, miR-21-/- mice and human bronchial epithelial (16HBE) cell line, we found that in the lung tissues of mice, the level of autophagy in the COPD model group was significantly higher than that in the control group. However, compared to the COPD model, the level of autophagy was significantly lower in the miR-21-/- CSE+CS group. In the COPD model, miR-21 was overexpressed. Moreover, in human bronchial epithelial (16HBE) cells exposed to cigarette smoke extract (CSE), miR-21 expression was upregulated and autophagy was notably increased. In addition, pretreatment of 16HBE cells with miR-21 inhibitor significantly inhibited autophagy activity and decreased apoptosis, indicating that miR-21 is involved in CSE-induced autophagy and apoptosis. The results showed that miR-21 could increase autophagy and promote the apoptosis of 16HBE cells in COPD. This information contributes to our further understanding of COPD.

Dendritic Cell Trafficking and Function in Rare Lung Diseases

Dendritic cells (DCs) are highly specialized immune cells that capture antigens and then migrate to lymphoid tissue and present antigen to T cells. This critical function of DCs is well defined, and recent studies further demonstrate that DCs are also key regulators of several innate immune responses. Studies focused on the roles of DCs in the pathogenesis of common lung diseases, such as asthma, infection, and cancer, have traditionally driven our mechanistic understanding of pulmonary DC biology. The emerging development of novel DC reagents, techniques, and genetically modified animal models has provided abundant data revealing distinct populations of DCs in the lung, and allow us to examine mechanisms of DC development, migration, and function in pulmonary disease with unprecedented detail. This enhanced understanding of DCs permits the examination of the potential role of DCs in diseases with known or suspected immunological underpinnings. Recent advances in the study of rare lung diseases, including pulmonary Langerhans cell histiocytosis, sarcoidosis, hypersensitivity pneumonitis, and pulmonary fibrosis, reveal expanding potential pathogenic roles for DCs. Here, we provide a review of DC development, trafficking, and effector functions in the lung, and discuss how alterations in these DC pathways contribute to the pathogenesis of rare lung diseases.

Cigarette smoke promotes COPD by activating platelet-activating factor receptor and inducing neutrophil autophagic death in mice

Neutrophils are the most important effector cells during the development of chronic obstructive pulmonary disease (COPD). Although neutrophil elastase is critical in cigarette smoke (CS)-induced lung parenchyma, the mechanism by which CS triggers elastase release from neutrophils remains unclear. Here we report that CS induction of autophagy in neutrophils by activating platelet- activating factor receptor (PAFR) promotes COPD progression in mouse. We found that the dead neutrophils were increased in bronchoalveolar lavage fluid from CS-exposed mice. Blocking PAFR suppressed the CS-induced autophagy in neutrophils, protected neutrophils from death, and reduced elastase release. Mechanistically, CS enhanced ROS production and High mobility group box 1 (HMGB1) expression through activation of PAFR. The elevated HMGB1 interacted with beclin1, which promoted the dissociation of Bcl-2 from beclin1 and the assembly of autophagy core complex. Moreover, the antagonism of PAFR by rupatadine, a prescription PAFR inhibitor, protected against the development of emphysema, and reduced the autophagic death of neutrophils after CS exposure. These results suggest that CS contributes to the pathogenesis of COPD partly by inducing a PAFR-dependent autophagic death of neutrophils. Therefore, PAFR may be a therapeutic target for COPD and inhibition of PAFR may provide potential therapeutic benefits in the treatment of patients with COPD.

The Role of Innate and Adaptive Immune Cells in the Immunopathogenesis of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a chronic and progressive inflammatory disease of the airways and lungs that results in limitations of continuous airflow and is caused by exposure to noxious gasses and particles. A major cause of morbidity and mortality in adults, COPD is a complex disease pathologically mediated by many inflammatory pathways. Macrophages, neutrophils, dendritic cells, and CD8+ T-lymphocytes are the key inflammatory cells involved in COPD. Recently, the non-coding small RNA, micro-RNA, have also been intensively investigated and evidence suggest that it plays a role in the pathogenesis of COPD. Here, we discuss the accumulated evidence that has since revealed the role of each inflammatory cell and their involvement in the immunopathogenesis of COPD. Mechanisms of steroid resistance in COPD will also be briefly discussed.

Cigarette smoke differentially modulates dendritic cell maturation and function in time

Background

Dendritic cells (DCs) as professional antigen presenting cells (APCs) play a critical role in the regulation of host immune responses. DCs evolve from immature, antigen-capturing cells, to mature antigen-presenting cells. The relative contribution of DCs to cigarette smoke-induced inflammation is not well documented. In the current study, we investigated a modulatory effect of cigarette smoke extract (CSE) on differentiation, maturation and function of DCs.

Methods

Primary murine DCs were grown from bone marrow cells with GM-CSF. Development of DC was analyzed by expression of CD11c, MHCII, CD86, CD40 and CD83 using flow cytometry. Murine DC’s and human L428 cells were co-cultured with CSE for various periods of time. Functional activity was analyzed by measuring FITC-dextran uptake, cytokine production and the ability to stimulate T cell activation in a mixed lymphocyte reaction.

Results

Our results show that short-term CSE stimulation (~24 h) influence the maturation status of newly differentiated and immature DCs towards more mature cells as revealed by upregulation of MHCII, CD83, CD86, CD40, reduction in antigen up-take capacity and enhanced secretion of pro-inflammatory (IL-12, IL-6 and TNF-α) cytokines. Interestingly, long-term CSE exposure, time- and concentration-dependently, suppressed the development of functional DCs. This suppression was demonstrated by a decline in CD11c/MHCII, CD83, CD86 and CD40 expression, the production of cytokines and ability to stimulate T lymphocytes. Moreover, CSE significantly suppressed the endocytosis function of mouse DCs which was not due to diminished DC viability. Similar to mouse DCs, long-term co-culturing of the human L428 DC cell line with CSE time-dependently suppressed the expression of CD54.

Conclusions

The present study provides evidence that CSE modulates DC-mediated immune responses via affecting both the function and maturation of DCs. The suppressive effects of cigarette smoke on DC function might lead to impaired immune responses to various infections.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0291-6) contains supplementary material, which is available to authorized users.

Dendritic cells inversely regulate airway inflammation in cigarette smoke-exposed mice

The recruitment and activation of inflammatory cells into the respiratory system is considered a crucial feature in the pathophysiology of chronic obstructive pulmonary disease (COPD). Because dendritic cells (DCs) have a pivotal role in the onset and regulation of immune responses, we investigated the effect of modulating DC subsets on airway inflammation by acute cigarette smoke (CS) exposure. CS-exposed mice (5 days) were treated with fms-like tyrosine kinase 3 ligand (Flt3L) and 120g8 antibody to increase total DC numbers and deplete plasmacytoid DCs (pDCs), respectively. Flt3L treatment decreased the number of inflammatory cells in the bronchoalveolar lavage (BALF) of the smoke-exposed mice and increased these in lung tissue. DC modulation reduced IL-17 and increased IL-10 levels, which may be responsible for the suppression of the BALF cells. Furthermore, depletion of pDCs led to increased infiltration of alveolar macrophages while restricting the presence of CD103(+) DCs. This study suggests that DC subsets may differentially and compartment-dependent influence the inflammation induced by CS. pDC may play a role in preventing the pathogenesis of CS by inhibiting the alveolar macrophage migration to lung and increasing CD103(+) DCs at inflammatory sites to avoid extensive lung tissue damage.

Comparison between cigarette smoke-induced emphysema and cigarette smoke extract-induced emphysema

Background and objective

Emphysema is the main pathological feature of COPD and also is the focus of the related research. Although several emphysema animal models have been established, exact comparison of findings is seldom. The present study aimed to compare cigarette smoke (CS) exposure-induced emphysema model and intraperitoneal injection of cigarette smoke extract (CSE)-induced emphysema model to evaluate the effectiveness of the two different modeling methods.

Methods

Six-week-old male C57BL/6 J mice were used and randomly divided into two groups: CS exposure and intraperitoneal injection of CSE. Each group was subdivided into two subgroups: control and CS or CSE. Lung function, mean linear intercept (MLI), destructive index (DI), apoptotic index (AI), total and differential cells count in broncholavolar lavage fluid (BALF), SOD and IL-6 concentration in serum were measured.

Results

Compared with their respective controls, lung function was significantly decreased in CS and CSE groups (P < 0.01); MLI, DI, and AI of lung tissue were significantly higher in CS and CSE groups (P < 0.01); total number of leukocytes, the number and percentage of neutrophils (NEUs), and the number of macrophages (MAC) in BALF were significantly higher in CS and CSE groups (P < 0.01); SOD concentration in serum was significantly decreased in CS and CSE groups (P < 0.01); IL-6 concentration in serum was significantly increased in in CS and CSE groups (P < 0.01). There was no significant difference between CS group and CSE group in any of the parameters described above.

Conclusions

Both CS exposure and intraperitoneal injection of CSE could induce emphysema and the effectiveness of the two different modeling methods were equal.

Toll-like receptor 9 dependent interferon-α release is impaired in severe asthma but is not associated with exacerbation frequency

Patients with asthma and chronic obstructive pulmonary disease (COPD) are susceptible to exacerbations, often caused by microbial pathogens. We hypothesised that intracellular Toll-like receptor (TLR) function in blood mononuclear cells (PBMCs) from these subjects would be impaired and that this impairment is related to exacerbation frequency. PBMCs stimulated with a TLR-9 agonist (but not TLR-3 or 7/8) produced significantly less IFN-α in asthma (26 [3-696]pg/ml) compared to control (943 [164-1651]) and COPD (597 [127-1186]) subjects (p = 0.0019) but this was not related to the number of exacerbations per year in asthma or COPD. In COPD, IFN-α levels were related to KCO (% predicted) in COPD (r = -0.41, p = 0.01). IFN-α was derived from plasmacytoid dendritic cells (pDCs) and their frequency was lower in asthma compared to control subjects (control 0.48% [0.33-0.64] versus asthma 0.29% [0.13-0.34], p = 0.019) whereas pDC function per se was not significantly impaired between groups. The mechanism underlying reduced IFN-α production and the clinical consequences in severe asthma remains to be established.