Toxicological Aspects Associated with Consumption from Electronic Nicotine Delivery System (ENDS): Focus on Heavy Metals Exposure and Cancer Risk.

Tobacco smoking remains one of the leading causes of premature death worldwide. Electronic Nicotine Delivery Systems (ENDSs) are proposed as a tool for smoking cessation. In the last few years, a growing number of different types of ENDSs were launched onto the market. Despite the manufacturing differences, ENDSs can be classified as "liquid e-cigarettes" (e-cigs) equipped with an atomizer that vaporizes a liquid composed of vegetable glycerin (VG), polypropylene glycol (PG), and nicotine, with the possible addition of flavorings; otherwise, the "heated tobacco products" (HTPs) heat tobacco sticks through contact with an electronic heating metal element. The presence of some metals in the heating systems, as well as in solder joints, involves the possibility that heavy metal ions can move from these components to the liquid, or they can be adsorbed into the tobacco stick from the heating blade in the case of HTPs. Recent evidence has indicated the presence of heavy metals in the refill liquids and in the mainstream such as arsenic (As), cadmium (Cd), chromium (Cr), nickel (Ni), copper (Cu), and lead (Pb). The present review discusses the toxicological aspects associated with the exposition of heavy metals by consumption from ENDSs, focusing on metal carcinogenesis risk.

The Role of Extracellular Vesicles in Atopic Dermatitis.

Atopic dermatitis, or eczema, is the most common chronic skin disorder, characterized by red and pruritic lesions. Its etiology is multifaceted, involving an interplay of factors, such as the allergic immune response, skin barrier dysfunction, and dysbiosis of the skin microbiota. Recent studies have explored the role of extracellular vesicles (EVs), which are lipid bilayer-delimitated particles released by all cells, in atopic dermatitis. Examination of the available literature identified that most studies investigated EVs released by Staphylococcus aureus, which were found to impact the skin barrier and promote the release of cytokines that contribute to atopic dermatitis development. In addition, EVs released by the skin fungus, Malassezia sympodialis, were found to contain allergens, suggesting a potential contribution to allergic sensitization via the skin. The final major finding was the role of EVs released by mast cells, which were capable of activating various immune cells and attenuating the allergic response. While research in this area is still in its infancy, the studies examined in this review provide encouraging insights into how EVs released from a variety of cells play a role in both contributing to and protecting against atopic dermatitis.

Invariant NKT cells are more abundant in peanut-allergic adults and a subset of CD8+ iNKT cells are depleted after peanut oil exposure.

Introduction: Peanut allergy is one of the most prevalent food allergies globally. Currently, most research into the mechanisms involved in protein allergy focuses on the protein allergens under investigation, and information on the function of accompanying compounds, such as lipids, is scarce. Thus, this research investigates the role of peanut-associated lipids and invariant natural killer T (iNKT) cells in peanut allergy using a novel, human, in vitro assay. Methods: PBMCs from non-allergic and peanut-allergic subjects were stimulated with the glycolipid, α-Galactosylceramide (α-GalCer), over 14 days for iNKT cell expansion. Autologous dendritic cells (DCs) were stimulated with either peanut oil, the lipid-binding peanut allergen, Ara h 8, or both peanut oil and Ara h 8. The expanded iNKT cells were then immunomagnetically isolated and co-cultured for 5 h with autologous DCs, and cytokine expression was measured by flow cytometry. Results: A 5-fold higher iNKT cell population was observed in peanut-allergic subject peripheral blood compared to non-allergic controls. In all subjects, conventional flow analysis highlighted iNKTs co-cultured with autologous α-GalCer-pulsed DCs displayed increased IL-4 and IFN-y secretion within 5 hours of co-culture. A 10-parameter unsupervised clustering analysis of iNKT phenotype found significantly more CD3+CD8+CD25+IL-4+IL-5+IL-10+IFNγ+ cells in non-allergic adults following culture with peanut oil. Conclusion: For the first time, we show iNKT cells are more abundant in peanut-allergic adults compared to non-allergic adults, and peanut lipid-exposed iNKT cells resulted in the identification of a subset of CD8+ iNKT cells which was significantly lower in peanut-allergic adults. Thus, this study proposes a role for iNKT cells and peanut allergen-associated lipids in peanut allergy.

PBMC-derived extracellular vesicles in a smoking-related inflammatory disease model.

Extracellular vesicles (EVs) function as mediators of intercellular communication and as such influence the recipient cell function. EVs derived from immune cells can carry out many of the same functions as their parental cells, as they carry costimulatory molecules, antigens, and antigen-MHC complexes. As a result, there is a strong interest in understanding the composition and origin of immune cell-derived EVs in order to understand their role in the pathogenesis of diseases. This study aimed to optimize methodologies to study immune cell-derived EVs. Peripheral blood mononuclear cell-derived small EVs were isolated and observed using conventional transmission electron microscopy and sized by nanoparticle tracking analysis. They were then enumerated and profiled using imaging flow cytometry and were further characterized using a flow cytometric multiplex bead assay. These techniques were then applied to our current research, namely smoking-related inflammatory disease. We present here a comprehensive approach to analyze PBMC-derived small EVs in smoking-related inflammatory disease following the Minimal Information for Studies of Extracellular Vesicle 2018 guidelines.

The Role of Lipids in Allergic Sensitization: A Systematic Review.

Background: Immunoglobulin E (IgE)-mediated allergies are increasing in prevalence, with IgE-mediated food allergies currently affecting up to 10% of children and 6% of adults worldwide. The mechanisms underpinning the first phase of IgE-mediated allergy, allergic sensitization, are still not clear. Recently, the potential involvement of lipids in allergic sensitization has been proposed, with reports that they can bind allergenic proteins and act on immune cells to skew to a T helper type 2 (Th2) response. Objectives: The objective of this systematic review is to determine if there is strong evidence for the role of lipids in allergic sensitization. Methods: Nineteen studies were reviewed, ten of which were relevant to lipids in allergic sensitization to food allergens, nine relevant to lipids in aeroallergen sensitization. Results: The results provide strong evidence for the role of lipids in allergies. Intrinsic lipids from allergen sources can interact with allergenic proteins to predominantly enhance but also inhibit allergic sensitization through various mechanisms. Proposed mechanisms included reducing the gastrointestinal degradation of allergenic proteins by altering protein structure, reducing dendritic cell (DC) uptake of allergenic proteins to reduce immune tolerance, regulating Th2 cytokines, activating invariant natural killer T (iNKT) cells through CD1d presentation, and directly acting upon toll-like receptors (TLRs), epithelial cells, keratinocytes, and DCs. Conclusion: The current literature suggests intrinsic lipids are key influencers of allergic sensitization. Further research utilising human relevant in vitro models and clinical studies are needed to give a reliable account of the role of lipids in allergic sensitization.

Extracellular vesicles and chronic obstructive pulmonary disease (COPD): a systematic review.

BACKGROUND: Chronic Obstructive Pulmonary Disease (COPD) is a common inflammatory disease of the airways characterized by irreversible airflow limitation, ranking the third highest cause of death worldwide. Extracellular vesicles (EVs) are important intercellular communication mediators released by cells into their extracellular environment with the capacity to transfer biological signals. EVs involved in COPD hold great potential to understand disease pathogenesis and identify important biomarkers. This systematic review aims to examine all available research on EVs in the pathogenesis and diagnosis of COPD to identify existing knowledge and support further research within the field. METHODS: Publications were searched using PubMed and EMBASE with the search terms (Exosomes or extracellular vesicles or microvesicles or microparticles or ectosomes) AND (chronic obstructive pulmonary disease or COPD or emphysema or bronchitis). RESULTS: Initial search yielded 512 papers of which 142 were manually selected for review and 43 were eligible for analyses. The studies were divided into groups according to the role of EVs in pathogenesis, EV origin and cargo, their role in COPD exacerbations and their diagnostic utility. EVs were found to be involved in the mechanism of pathogenesis of COPD, derived from various cell types, as well as containing modified levels of miRNAs. EVs also varied according to the pathophysiological status of disease, therefore presenting a possible method for COPD diagnosis and progress monitoring. CONCLUSION: The current findings show the limited but good quality research looking at the role of EVs in COPD, demonstrating the need for more studies to better define and provide further insight into the functional characteristics of EV in COPD pathogenesis.

Mutations in the binding site of TNFR1 PLAD reduce homologous interactions but can enhance antagonism of wild-type TNFR1 activity.

The tumour necrosis factor receptor superfamily (TNFRSF) members contain cysteine-rich domains (CRD) in their extracellular regions, and the membrane-distal CRD1 forms homologous interactions in the absence of ligand. The CRD1 is therefore termed a pre-ligand assembly domain (PLAD). The role of PLAD-PLAD interactions in the induction of signalling as a consequence of TNF-TNFR binding led to the development of soluble PLAD domains as antagonists of TNFR activation. In the present study, we generated recombinant wild-type (WT) PLAD of TNFR1 and mutant forms with single alanine substitutions of amino acid residues thought to be critical for the formation of homologous dimers and/or trimers of PLAD (K19A, T31A, D49A and D52A). These mutated PLADs were compared with WT PLAD as antagonists of TNF-induced apoptosis or the activation of inflammatory signalling pathways. Unlike WT PLAD, the mutated PLADs showed little or no homologous interactions, confirming the importance of particular amino acids as contact residues in the PLAD binding region. However, as with WT PLAD, the mutated PLADs functioned as antagonists of TNF-induced TNFR1 activity leading to induction of cell death or NF-κB signalling. Indeed, some of the mutant PLADs, and K19A PLAD in particular, showed enhanced antagonistic activity compared with WT PLAD. This is consistent with the reduced formation of homologous multimers by these PLAD mutants effectively increasing the concentration of PLAD available to bind and antagonize WT TNFR1 when compared to WT PLAD acting as an antagonist. This may have implications for the development of antagonistic PLADs as therapeutic agents.

Array-based measurements of aero-allergen-specific IgE correlate with skin-prick test reactivity in asthma regardless of specific IgG4 or total IgE measurements.

Skin prick testing (SPT) and measurement of serum allergen-specific IgE (sIgE) are used to investigate asthma and other allergic conditions. Measurement of serum total IgE (tIgE) and allergen-specific IgG4 (sIgG4) may also be useful. The aim was to ascertain the correlation between these serological parameters and SPT. Sera from 60 suspected asthmatic patients and 18 healthy controls were assayed for sIgE and sIgG4 reactivity against a panel of 70 SPT allergen preparations, and for tIgE. The patients were also assessed by skin prick tests for reactivity to cat, dog, house dust mite and grass allergens. Over 50% of the patients had tIgE levels above the 75th percentile of the controls. 58% of patients and 39% of controls showed sIgE reactivity to ≥1 allergen. The mean number of allergens detected by sIgE was 3.1 in suspected asthma patients and 0.9 in controls. 58% of patients and 50% of controls showed sIgG4 reactivity to ≥1 allergen. The mean number of allergens detected by sIgG4 was 2.5 in patients and 1.7 in controls. For the patients, a strong correlation was observed between clinical SPT reactivity and serum sIgE levels to cat, dog, house dust mite (HDM) and grass allergens. SPT correlations using sIgE/sIgG4 or sIgE/tIgE ratios were not markedly higher. The measurement of serum sIgE by microarray using SPT allergen preparations showed good correlation with clinical SPT reactivity to cat, dog, HDM and grass allergens. This concordance was not improved by measuring tIgE or sIgG4.

The role of CD8 + T lymphocytes in chronic obstructive pulmonary disease: a systematic review.

OBJECTIVE AND DESIGN: This systematic review aims to establish the role of CD8 + T lymphocytes in COPD. METHODS: Forty-eight papers published in the last 15 years were identified for inclusion. RESULTS: CD8 + T-cells are increased in the lungs of patients with COPD (17 studies, 16 positive) whereas in the circulation, findings were inconclusive. Activation of CD8 + T-cells was enhanced in lungs (four studies, three positive) but cell phenotype was unclear. There was substantial evidence of a higher proportion of type 1 CD8 + (Tc1) cells in COPD (11 studies, 9 positive), though the population of type 2 (Tc2) cells was also increased (5 studies, 4 positive). CD8 + T-cells in COPD exhibited greater expression of cytotoxic proteins (five studies, five positive). Studies assessed a variety of questions so evidence was insufficient to draw firm conclusions. The role of CD8 + T-cells at acute exacerbation of COPD and also their contribution to alveolar destruction can only be hypothesised at this stage. CONCLUSIONS: Not only is the number of CD8 + T-cells increased in COPD, these cells have increased capacity to exert effector functions and are likely to contribute to disease pathogenesis. Several mechanisms highlighted show promise for future investigation to consolidate current knowledge.

Electronic cigarette vapour moderately stimulates pro-inflammatory signalling pathways and interleukin-6 production by human monocyte-derived dendritic cells.

Dendritic cells (DCs) are professional antigen presenting cells that play a critical role in bridging innate and adaptive immunity. Numerous studies have shown that tobacco constituents present in conventional cigarettes affect the phenotype and function of DCs; however, no studies have examined the effects of vapour from E-cigarettes on human DCs. Here, the effects of E-cigarette vapour extract (ECVE) on the phenotype and function of DCs were investigated by creating an in vitro cell culture model using human monocyte-derived DCs (MoDCs). Immature DCs were generated from peripheral blood monocytes and mature DCs were then produced by treatment with LPS or Poly I:C for 24 h. For LPS-matured DCs, 3% ECVE treatment slightly suppressed HLA-DR and CD86 expression, whereas 1% ECVE treatment enhanced IL-6 production. The overall expression of 29 signalling molecules and other cytoplasmic proteins (mainly associated with DC activation) was significantly upregulated in immature DCs by 1% ECVE, and in LPS-treated DCs by 3% ECVE. In particular, the condition that induced IL-6 production also upregulated MAPK pathway activation. These findings indicate that E-cigarette vapour moderately affects human DCs, but the effects are less pronounced than those reported for tobacco smoke.

Correction to: Atopic dermatitis and autoimmunity: the occurrence of autoantibodies and their association with disease severity.

Two of the references included in this review concern antigens derived from the fungus Malassezia globosa that have also been found in human sweat.

Extracellular vesicles and asthma: A review of the literature.

Asthma is a chronic, recurrent and incurable allergy-related respiratory disease characterized by inflammation, bronchial hyperresponsiveness and narrowing of the airways. Extracellular vesicles (EVs) are a universal feature of cellular function and can be detected in different bodily fluids. Recent evidence has shown the possibility of using EVs in understanding the pathogenesis of asthma, including their potential as diagnostic and therapeutic tools. Studies have reported that EVs released from key cells involved in asthma can induce priming and activation of other asthma-associated cells. A literature review was conducted on all current research regarding the role and function of EVs in the pathogenesis of asthma via the PRISMA statement method. An electronic search was performed using EMBASE and PubMed through to November 2018. The EMBASE search returned 76 papers, while the PubMed search returned 211 papers. Following duplicate removal, titles and abstracts were screened for eligibility with a total of 34 studies included in the final qualitative analysis. The review found evidence of association between the presence of EVs and physiological changes characteristic of asthma, suggesting that EVs are involved in the pathogenesis, with the weight of evidence presently favouring deleterious effects of EVs in asthma. Numerous studies highlighted differences in exosomal contents between EVs of healthy and asthmatic individuals, which could be employed as potential diagnostic markers. In some circumstances, EVs were also found to be suppressive to disease, but more often promote inflammation and airway remodelling. In conclusion, EVs hold immense potential in understanding the pathophysiology of asthma, and as diagnostic and therapeutic markers. While more research is needed for definitive conclusions and their application in medical practice, the literature presented in this review should encourage further research and discovery within the field of EVs and asthma.

Autoantibodies in chronic obstructive pulmonary disease: A systematic review.

Chronic Obstructive Pulmonary Disease (COPD) is a major cause of death worldwide in which the involvement of autoimmunity has been widely investigated and debated. The role of autoantibodies in COPD has been extensively researched in recent years. The aim of this systematic review is to assess the association between autoantibodies and COPD and analyse whether autoantibody levels correlate with disease severity and/or phenotype. PubMed, Embase, OpenGrey and the reference lists of articles were searched. The strongest evidence for an association between autoantibodies and COPD lies with anti-endothelial/epithelial cell autoantibodies (7 studies, all positive), rheumatoid factor autoantibodies (4 studies, all positive), anti-cytokeratin autoantibodies (3 studies, all positive), anti-nuclear autoantibodies (8 studies, 7 positive) and anti-collagen autoantibodies (10 studies, 6 positive). This review also identifies several other autoantibodies which had both positive and negative associations with COPD, however the evidence for these was not as strong and/or the number of studies is low, and further research is required. In particular, a clear case can be made for the potential importance of autoantibodies to carbonylated proteins. The relationship between autoantibody levels and disease severity requires further research with only 17/43 studies investigating this; however, 12 of the studies did show a positive association, making it a promising area for future research. There was also not enough evidence available on the relationship between autoantibody levels and disease phenotype to draw any conclusions, with only 2 studies investigating it (1 positive and 1 negative). This review has shown very promising evidence for the association of several autoantibodies in COPD and has identified those autoantibodies which require further research.

Cigarette smoking differentially affects immunoglobulin class levels in serum and saliva: An investigation and review.

The aim of the present study was to compare concentrations of IgG, IgA, IgM and IgD in both serum and saliva samples from smoking and non-smoking individuals using a protein microarray assay. The findings were also compared to previous studies. Serum and saliva were collected from 48 smoking male individuals and 48 age-matched never-smoker male individuals. The protein microarray assays for detection of human IgG, IgM, IgA and IgD were established and optimized using Ig class-specific affinity-purified goat anti-human Ig-Fc capture antibodies and horseradish peroxidase (HRP)-conjugated goat anti-human Ig-Fc detection antibodies. The Ig class specificity of the microarray assays was verified, and the optimal dilutions of serum and saliva samples were determined for quantification of Ig levels against standard curves. We found that smoking is associated with reduced IgG concentrations and enhanced IgA concentrations in both serum and saliva. By contrast, smoking differentially affected IgM concentrations-causing increased concentrations in serum, but decreased concentrations in saliva. Smoking was associated with decreased IgD concentrations in serum and did not have a significant effect on the very low IgD concentrations in saliva. Thus, cigarette smoking differentially affects the levels of Ig classes systemically and in the oral mucosa. Although there is variation between the results of different published studies, there is a consensus that smokers have significantly reduced levels of IgG in both serum and saliva. A functional antibody deficiency associated with smoking may compromise the body's response to infection and result in a predisposition to the development of autoimmunity.

Immunological and pathological effects of electronic cigarettes.

Electronic cigarettes (E-cigarettes) are considered a preferable alternative to conventional cigarettes due to the lack of combustion and the absence of tobacco-specific toxicants. E-cigarettes have rapidly gained in popularity in recent years amongst both existing smokers and previous non-smokers. However, a growing literature demonstrates that E-cigarettes are not as safe as generally believed. Here, we discuss the immunological, and other, deleterious effects of E-cigarettes on a variety of cell types and host defence mechanisms in humans and in murine models. We review not only the effects of complete E-cigarette liquids, but also each of the main components-nicotine, humectants and flavourings. This MiniReview thus highlights the possible role of E-cigarettes in the pathogenesis of disease and raises awareness of the potential harm that E-cigarettes may cause.

Atopic dermatitis and autoimmunity: the occurrence of autoantibodies and their association with disease severity.

Atopic dermatitis (AD) is a widespread condition that appears to be increasing in prevalence and severity worldwide, yet the underlying mechanisms are not well understood. Recent research has identified various similarities between AD and autoimmune conditions, as well as indicating that there may be an association between AD and autoimmunity. This systematic review evaluates the association between AD and autoimmunity, as well as between severity of disease in AD and autoimmunity, with an emphasis on the associations with autoantibodies. MEDLINE (1946 to December 2017) and Embase (1974 to December 2017) databases were searched. Further relevant articles were retrieved from reference lists. Only studies measuring direct indicators of autoimmunity, in humans, were included. Qualitative analysis was carried out for all studies. In addition, quantitative analysis was used to evaluate prevalence of IgE autoantibodies and anti-nuclear antibodies (ANAs) in AD patients and control subjects. The Mantel-Haenszel method was used with a random-effects model. 28 studies assessed the occurrence of autoantibodies in AD patients and 16 studies were used to evaluate association between disease severity and autoantibodies. Pooled analysis from 14 studies, involving 986 AD patients and 441 control subjects, showed that IgE autoantibodies were significantly more prevalent in patients with AD (P < 0.00001) than control subjects. Similar analysis was carried out for ANAs, with eight studies that involved 1045 AD patients and 1273 control subjects. ANAs were significantly more prevalent in patients with AD (P = 0.003). This quantitative analysis supported an association between AD and IgE autoantibodies, as well as between AD and ANAs. There was insufficient data to make similar conclusions for other indicators of autoimmunity. The weight of evidence also suggests an association between IgE autoantibodies and disease severity. There was insufficient evidence to make this link for other indicators of autoimmunity.

Tobacco smoke and nicotine suppress expression of activating signaling molecules in human dendritic cells.

Cigarette smoke has significant toxic effects on the immune system, and increases the risk of developing autoimmune diseases; one immunosuppressive effect of cigarette smoke is that it inhibits the T cell-stimulating, immunogenic properties of myeloid dendritic cells (DCs). As the functions of DCs are regulated by intra-cellular signaling pathways, we investigated the effects of cigarette smoke extract (CSE) and nicotine on multiple signaling molecules and other regulatory proteins in human DCs to elucidate the molecular basis of the inhibition of DC maturation and function by CSE and nicotine. Maturation of monocyte-derived DCs was induced with the TLR3-agonist poly I:C or with the TLR4-agonist lipopolysaccharide, in the absence or presence of CSE or nicotine. Reverse-phase protein microarray was used to quantify multiple signaling molecules and other proteins in cell lysates. Particularly in poly I:C-matured DCs, cigarette smoke constituents and nicotine suppressed the expression of signaling molecules associated with DC maturation and T cell stimulation, cell survival and cell migration. In conclusion, constituents of tobacco smoke suppress the immunogenic potential of DCs at the signaling pathway level.

Characterization of Behavioral, Signaling and Cytokine Alterations in a Rat Neurodevelopmental Model for Schizophrenia, and Their Reversal by the 5-HT6 Receptor Antagonist SB-399885.

Post-weaning social isolation of rats produces neuroanatomical, neurochemical and behavioral alterations resembling some core features of schizophrenia. This study examined the ability of the 5-HT6 receptor antagonist SB-399885 to reverse isolation-induced cognitive deficits, then investigated alterations in hippocampal cell proliferation and hippocampal and frontal cortical expression of selected intracellular signaling molecules and cytokines. Male Lister hooded rats (weaned on post-natal days 21-24 and housed individually or in groups of 3-4) received six i.p. injections of vehicle (1% Tween 80, 1 mL/kg) or SB-399885 (5 or 10 mg/kg) over a 2-week period starting 40 days post-weaning, on the days that locomotor activity, novel object discrimination (NOD), pre-pulse inhibition of acoustic startle and acquisition, retention and extinction of a conditioned freezing response (CFR) were assessed. Tissue was collected 24 h after the final injection for immunohistochemistry, reverse-phase protein microarray and western blotting. Isolation rearing impaired NOD and cue-mediated CFR, decreased cell proliferation within the dentate gyrus, and elevated hippocampal TNFα levels and Cdc42 expression. SB-399885 reversed the NOD deficit and partially normalized CFR and cell proliferation. These effects were accompanied by altered expression of several members of the c-Jun N-terminal Kinase (JNK) and p38 MAPK signaling pathways (including TAK1, MKK4 and STAT3). Although JNK and p38 themselves were unaltered at this time point hippocampal TAK1 expression and phosphorylation correlated with visual recognition memory in the NOD task. Continued use of this neurodevelopmental model could further elucidate the neurobiology of schizophrenia and aid assessment of novel therapies for drug-resistant cognitive symptoms.

Prophylactic Antibiotic Use in COPD and the Potential Anti-Inflammatory Activities of Antibiotics.

Antibiotics have previously demonstrated anti-inflammatory properties, and they have been linked to therapeutic benefit in several pulmonary conditions that feature inflammation. Previous research suggests that these anti-inflammatory properties may be beneficial in the treatment of COPD. This review assesses the potential benefit of prophylactic, long-term, and low-dose antibiotic therapy in COPD, and whether any effects seen are anti-inflammatory in nature. Randomized, controlled trials comparing antibiotic therapy with placebo in subjects with stable COPD were evaluated. Twelve trials involving 3,784 participants and a range of antibiotics were included: azithromycin (6 studies, 1,972 participants), clarithromycin (1 study, 67 participants), erythromycin (3 studies, 254 participants), roxithromycin (1 study, 191 participants), and moxifloxacin (2 studies, 1,198 participants). In vitro, in vivo, and ex vivo experimental study designs exploring the mechanisms via which antibiotics may act in subjects with stable COPD were evaluated. Azithromycin and erythromycin showed the greatest effect in subjects with COPD, with evidence suggesting improvement in exacerbation-related outcomes and health status, as measured by the St George Respiratory Questionnaire. An increase in antibiotic resistance was reported in 2 studies. The macrolide class of antibiotics exhibited convincing anti-inflammatory properties with relevance to COPD, implicating several pathways as potential mechanisms of action. In conclusion, the therapeutic benefit of macrolide antibiotics in subjects with stable COPD is consistent with anti-inflammatory properties, and macrolides should be considered as a potential therapy in COPD. Safety concerns regarding antibiotic resistance need to be addressed before widespread use in clinical practice.