Review: Is lung inflammation associated with microbes and microbial toxins in cigarette tobacco smoke?

Perspective: The Lung, Particles, Fibers, Nanomaterials, and Autoimmunity

Studies have shown that a wide range of factors including drugs, chemicals, microbes, and other environmental agents can induce pre-clinical autoimmunity. However, only a few have been confidently linked to autoimmune diseases. Among these are exposures to inhaled particulates that are known to be associated with autoimmune diseases such as lupus and rheumatoid arthritis. In this article, the potential of particle, fiber, and nanomaterial exposures to induce autoimmunity is discussed. It is hypothesized that inhalation of particulate material known to be associated with human autoimmune diseases, such as cigarette smoke and crystalline silica, results in a complex interplay of a number of pathological processes, including, toxicity, oxidative stress, cell and tissue damage, chronic inflammation, post-translational modification of self-antigens, and the formation of lymphoid follicles that provide a milieu for the accumulation of autoreactive B and T cells necessary for the development and persistence of autoimmune responses, leading to disease. Although experimental studies show nanomaterials are capable of inducing several of the above features, there is no evidence that this matures to autoimmune disease. The procession of events hypothesized here provides a foundation from which to pursue experimental studies to determine the potential of other environmental exposures to induce autoimmunity and autoimmune disease.

Cigarette smoke and extracellular Hsp70 induce secretion of ATP and differential activation of NLRP3 inflammasome in monocytic and bronchial epithelial cells

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is an inflammatory disease mainly caused by smoking. Cigarette smoke damages airway epithelium and activates lung macrophages, causing inflammatory responses. It was suggested that nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome might have an important role in COPD development. Study aimed to explore whether cigarette smoke extract (CSE), extracellular heat shock protein 70 (eHsp70) or their combinations induce adenosine triphosphate (ATP) release and NLRP3 inflammasome activation.

METHODS

We detected NLRP3 and interleukin (IL)-1β mRNA expression, extracellular IL-1β and ATP concentrations as well as lactate dehydrogenase (LDH) activity. We used bronchial epithelial (NCI-H292, 16HBE and NHBE) and monocytic cells (monocyte-derived macrophages (MDMs) and THP-1) as representative of local airway and systemic compartments that could be affected in COPD.

RESULTS

CSE and eHsp70 increased NLRP3 and IL-1β mRNA expression as well as IL-1β and ATP secretion in all cells compared to untreated cells. Lytic cell death was observed in cell lines, especially those of bronchial epithelium origin, but not in primary cells (NHBE, MDMs). Regarding LDH activity, eHsp70 did not modulate CSE effects, except in NCI-H292 cell line. However, eHsp70 significantly affected CSE-provoked NLRP3 inflammasome activation by causing mostly antagonistic effects in airway epithelial cells and synergistic effects in MDMs.

CONCLUSION

We demonstrated that both CSE and eHsp70 induce ATP secretion and differential activation of NLRP3 inflammasome in bronchial epithelial and monocytic cells. We suggest that these mechanisms might be involved in pathophysiology of COPD by contributing to the propagation of inflammation.

Mentholation triggers brand-specific shifts in the bacterial microbiota of commercial cigarette products

Bacterial communities are integral constituents of tobacco products. They originate from tobacco plants and are acquired during manufacturing processes, where they play a role in the production of tobacco-specific nitrosamines. In addition, tobacco bacterial constituents may play an important role in the development of infectious and chronic diseases among users. Nevertheless, tobacco bacterial communities have been largely unexplored, and the influence of tobacco flavor additives such as menthol (a natural antimicrobial) on tobacco bacterial communities is unclear. To bridge this knowledge gap, time series experiments including 5 mentholated and non-mentholated commercially available cigarettes-Marlboro red (non-menthol), Marlboro menthol, Newport menthol box, Newport menthol gold, and Newport non-menthol-were conducted. Each brand was stored under three different temperature and relative humidity conditions. To characterize bacterial communities, total DNA was extracted on days 0 and 14. Resulting DNA was purified and subjected to PCR of the V3V4 region of the 16S rRNA gene, followed by sequencing on the Illumina HiSeq platform and analysis using the QIIME, phyloseq, metagenomeSeq, and DESeq software packages. Ordination analyses showed that the bacterial community composition of Marlboro cigarettes was different from that of Newport cigarettes. Additionally, bacterial profiles significantly differed between mentholated and non-mentholated Newports. Independently of storage conditions, tobacco brands were dominated by Proteobacteria, with the most dominant bacterial genera being Pseudomonas, unclassified Enterobacteriaceae, Bacillus, Erwinia, Sphingomonas, Acinetobacter, Agrobacterium, Staphylococcus, and Terribacillus. These data suggest that the bacterial communities of tobacco products differ across brands and that mentholation of tobacco can alter bacterial community composition of select brands. KEY POINTS: • Bacterial composition differed between the two brands of cigarettes. • Mentholation impacts cigarette microbiota. • Pseudomonas and Bacillus dominated the commercial cigarettes. Graphical abstract.

Little cigars and cigarillos harbor diverse bacterial communities that differ between the tobacco and the wrapper

Despite their potential importance with regard to infectious and chronic diseases among tobacco users, microbial constituents of tobacco products lack characterization. Specifically, to our knowledge, there are no data describing the bacterial diversity of little cigars or cigarillos. To address this knowledge gap, we tested four brands of little cigars and cigarillos. Tobacco and wrapper subsamples (n = 132) were separately subjected to DNA extraction, followed by PCR amplification of the V3V4 hypervariable region of the 16S rRNA gene, and sequencing using Illumina HiSeq. Sequences were analyzed using QIIME and Phyloseq implemented in R. We identified 2,681 operational taxonomic units across all products. Significant differences in alpha and beta diversity were observed between Swisher Sweets and Cheyenne products. Alpha and beta diversity was also significantly different between tobacco and wrapper subsamples within the same product. Beta diversity analyses of only tobacco samples identified no significant differences in the bacterial microbiota of different lots of the same products; however, the microbiota in the wrapper differed significantly across lots for all brands. Overall, Firmicutes were found to dominate in the wrapper, whereas Proteobacteria were most abundant in the tobacco. At the genus level, Bacillus and Lactobacillus dominated in the wrappers, and Staphylococcus and Pseudomonas dominated in the tobacco. Our findings suggest that the bacterial microbiota of little cigars and cigarillos is diverse and differs significantly between the tobacco and the wrapper, and across brands. Future work is necessary to evaluate the potential public health implications of these findings.

The Contribution of Small Airway Obstruction to the Pathogenesis of Chronic Obstructive Pulmonary Disease

The hypothesis that the small conducting airways were the major site of obstruction to airflow in normal lungs was introduced by Rohrer in 1915 and prevailed until Weibel introduced a quantitative method of studying lung anatomy in 1963. Green repeated Rohrer's calculations using Weibels new data in 1965 and found that the smaller conducting airways offered very little resistance to airflow. This conflict was resolved by seminal experiments conducted by Macklem and Mead in 1967, which confirmed that a small proportion of the total lower airways resistance is attributable to small airways <2 mm in diameter. Shortly thereafter, Hogg, Macklem, and Thurlbeck used this technique to show that small airways become the major site of obstruction in lungs affected by emphysema. These and other observations led Mead to write a seminal editorial in 1970 that postulated the small airways are a silent zone within normal lungs where disease can accumulate over many years without being noticed. This review provides a progress report since the 1970s on methods for detecting chronic obstructive pulmonary disease, the structural nature of small airways' disease, and the cellular and molecular mechanisms that are thought to underlie its pathogenesis.

Exacerbation of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a disease with high prevalence and substantial associated economical burden. A significant determinant of quality of life, long-term survival, and health care costs is an acute exacerbation of COPD. Acute exacerbations are provoked by respiratory viruses, altered airway microbiome, and environmental factors. The current treatment options are limited. In order to develop specific therapeutic measures, it is important to understand how acute exacerbations evolve. This review focuses on pathophysiology of stable and exacerbated COPD.

Lung inflammation caused by inhaled toxicants: a review

Exposure of the lungs to airborne toxicants from different sources in the environment may lead to acute and chronic pulmonary or even systemic inflammation. Cigarette smoke is the leading cause of chronic obstructive pulmonary disease, although wood smoke in urban areas of underdeveloped countries is now recognized as a leading cause of respiratory disease. Mycotoxins from fungal spores pose an occupational risk for respiratory illness and also present a health hazard to those living in damp buildings. Microscopic airborne particulates of asbestos and silica (from building materials) and those of heavy metals (from paint) are additional sources of indoor air pollution that contributes to respiratory illness and is known to cause respiratory illness in experimental animals. Ricin in aerosolized form is a potential bioweapon that is extremely toxic yet relatively easy to produce. Although the aforementioned agents belong to different classes of toxic chemicals, their pathogenicity is similar. They induce the recruitment and activation of macrophages, activation of mitogen-activated protein kinases, inhibition of protein synthesis, and production of interleukin-1 beta. Targeting either macrophages (using nanoparticles) or the production of interleukin-1 beta (using inhibitors against protein kinases, NOD-like receptor protein-3, or P2X7) may potentially be employed to treat these types of lung inflammation without affecting the natural immune response to bacterial infections.

Cigarette smoke effects on innate immune mechanisms in the nasal mucosa. Potential effects on the microbiome

It is well established that exposure to cigarette smoke (CS), through active smoking and through exposure to secondhand smoke, has immunosuppressive effects, yet how this might affect the microbiome is not known. In this manuscript we focus on the effects of CS on innate host defense response, with particular emphasis on the role of epithelial cells and mucosal immune responses in the nose and the potential effects on the microbiome. The studies described here briefly summarize the effects of CS on specific innate immune cells, such as neutrophils, macrophages/monocytes, natural killer cells, and dendritic cells. A detailed description of how CS affects epithelial cells and why we consider this to be a central defect in the overall immunosuppressive effects of CS in the lung is provided. We summarize data on the role of the "epimmunome" in the context of CS exposure, including the effects on soluble mediator production, such as cytokines, chemokines, and antimicrobial defense mediators. Separate emphasis is put on the expression of ligands on epithelial cells, which directly interact with receptors on immune cells, and the effects of CS on these interactions. We introduce the nose and nasal mucosa as a model to study the effects of CS exposure on host defense responses and changes in the microbiome in humans in vivo. Understanding the dynamics of a healthy microbiome and how CS affects this balance is important to uncovering the mechanisms of CS-induced disease.

Cigarette smoking and mechanisms of susceptibility to infections of the respiratory tract and other organ systems

The predisposition of cigarette smokers for development of oral and respiratory infections caused by microbial pathogens is well recognised, with those infected with the human immunodeficiency virus (HIV) at particularly high risk. Smoking cigarettes has a suppressive effect on the protective functions of airway epithelium, alveolar macrophages, dendritic cells, natural killer (NK) cells and adaptive immune mechanisms, in the setting of chronic systemic activation of neutrophils. Cigarette smoke also has a direct effect on microbial pathogens to promote the likelihood of infective disease, specifically promotion of microbial virulence and antibiotic resistance. In addition to interactions between smoking and HIV infection, a number of specific infections/clinical syndromes have been associated epidemiologically with cigarette smoking, including those of the upper and lower respiratory tract, gastrointestinal tract, central nervous and other organ systems. Smoking cessation benefits patients in many ways, including reduction of the risk of infectious disease.

Bacterial and fungal markers in tobacco smoke

Previous research has demonstrated that cigarette smoke contains bacterial and fungal components including lipopolysaccharide (LPS) and ergosterol. In the present study we used gas chromatography-mass spectrometry to analyze tobacco as well as mainstream and second hand smoke for 3-hydroxy fatty acids (3-OH FAs) of 10 to 18 carbon chain lengths, used as LPS markers, and ergosterol, used as a marker of fungal biomass. The air concentrations of LPS were 0.0017 n mol/m(3) (N=5) and 0.0007/m(3) (N=6) in the smoking vs. non-smoking rooms (p=0.0559) of the studied private houses, and 0.0231 n mol/m(3) (N=5) vs. 0.0006 n mol/m(3) (N=5) (p=0.0173), respectively, at the worksite. The air concentrations of ergosterol were also significantly higher in rooms with ongoing smoking than in rooms without smoking. A positive correlation was found between LPS and ergosterol in rooms with smoking but not in rooms without smoking. 3-OH C14:0 was the main 3-OH FA, followed by 3-OH C12:0, both in mainstream and second hand smoke and in phenol:water smoke extracts prepared in order to purify the LPS. The Limulus activity of the phenolic phase of tobacco was 3900 endotoxin units (EU)/cigarette; the corresponding amount of the smoke, collected on filters from 8 puffs, was 4 EU/cigarette. Tobacco smoking has been associated with a range of inflammatory airway conditions including COPD, asthma, bronchitis, alveolar hypersensitivity etc. Significant levels of LPS and ergosterol were identified in tobacco smoke and these observations support the hypothesis that microbial components of tobacco smoke contribute to inflammation and airway disease.

Optical detection of preneoplastic lesions of the central airways

Current routine diagnosis of premalignant lesions of the central airways is hampered due to a limited sensitivity (white light bronchoscopy) and resolution (computer tomography (CT), positron emission tomography (PET)) of currently used techniques. To improve the detection of these subtle mucosal abnormalities, novel optical imaging bronchoscopic techniques have been developed over the past decade. In this review we highlight the technological developments in the field of endoscopic imaging, and describe their advantages and disadvantages in clinical use.

Dual role of Toll-like receptors in asthma and chronic obstructive pulmonary disease

During the last decade, significant research has been focused on Toll-like receptors (TLRs) in the pathogenesis of airway diseases. TLRs are pattern recognition receptors that play pivotal roles in the detection of and response to pathogens. Because of the involvement of TLRs in innate and adaptive immunity, these receptors are currently being exploited as possible targets for drug development. Asthma and chronic obstructive pulmonary disease (COPD) are chronic inflammatory airway diseases in which innate and adaptive immunity play an important role. To date, asthma is the most common chronic disease in children aged 5 years and older. COPD is prevalent amongst the elderly and is currently the fifth-leading cause of death worldwide with still-growing prevalence. Both of these inflammatory diseases result in shortness of breath, which is treated, often ineffectively, with bronchodilators and glucocorticosteroids. Symptomatic treatment approaches are similar for both diseases; however, the underlying immunological mechanisms differ greatly. There is a clear need for improved treatment specific for asthma and for COPD. This review provides an update on the role of TLRs in asthma and in COPD and discusses the merits and difficulties of targeting these proteins as novel treatment strategies for airway diseases. TLR agonist, TLR adjuvant, and TLR antagonist therapies could all be argued to be effective in airway disease management. Because of a possible dual role of TLRs in airway diseases with shared symptoms and risk factors but different immunological mechanisms, caution should be taken while designing pulmonary TLR-based therapies.

Cigarette smoke induces the release of CXCL-8 from human bronchial epithelial cells via TLRs and induction of the inflammasome

COPD is a chronic airway disease associated with inflammation and cigarette smoking. Airway epithelial cells are the first cells exposed to cigarette smoke (CS) and can release CXCL-8 and IL-1β. These cytokines are involved in acute and chronic inflammatory processes in COPD. The aim of this study was to investigate whether toll-like receptors (TLRs) located in/on epithelial cells were involved in cigarette smoke-induced cytokine production. Here we demonstrate that CS induces the release of CXCL-8 and IL-1β from human bronchial epithelial cells (HBE-14o). CS-induced CXCL-8 production was inhibited by an antibody against TLR4 and by inhibitory ODN suggesting the involvement of TLR4 and TLR9. In addition, exposure of HBE-14o cells to TLR4 or TLR9 ligands resulted in the release of CXCL-8 and IL1β. TLR4 and also TLR9 were present on the cell surface and the expression of both receptors decreased after CS exposure. The molecular mechanism of the CS-induced CXCL-8 production by the epithelial cells was further investigated. It was found that P2X7 receptors and reactive oxygen species were involved. Interestingly, the inflammasome activator monosodium urate crystals (MSU) induced the release of CXCL-8 and IL-1β and the caspase-1 inhibitor Z-VADDCB suppressed the CS-induced release of CXCL-8. In addition, CS, CpGODN, lipopolysaccharide and MSU all increased the expression of caspase-1 and IL-1β. In conclusion, our results demonstrate that CS releases CXCL-8 from HBE-14o cells via TLR4 and TLR9 and inflammasome activation. Therefore, inflammasome signaling in airway epithelial cells may play an important role in pathogenesis of diseases like COPD.

TLR4 protein contributes to cigarette smoke-induced matrix metalloproteinase-1 (MMP-1) expression in chronic obstructive pulmonary disease

Cigarette smoke is the major risk factor associated with the development of chronic obstructive pulmonary disease and alters expression of proteolytic enzymes that contribute to disease pathology. Previously, we reported that smoke exposure leads to the induction of matrix metalloproteinase-1 (MMP-1) through the activation of ERK1/2, which is critical to the development of emphysema. To date, the upstream signaling pathway by which cigarette smoke induces MMP-1 expression has been undefined. This study demonstrates that cigarette smoke mediates MMP-1 expression via activation of the TLR4 signaling cascade. In vitro cell culture studies demonstrated that cigarette smoke-induced MMP-1 was regulated by TLR4 via MyD88/IRAK1. Blockade of TLR4 or inhibition of IRAK1 prevented cigarette smoke induction of MMP-1. Mice exposed to acute levels of cigarette smoke exhibited increased TLR4 expression. To further confirm the in vivo relevance of this signaling pathway, rabbits exposed to acute cigarette smoke were found to have elevated TLR4 signaling and subsequent MMP-1 expression. Additionally, lungs from smokers exhibited elevated TLR4 and MMP-1 levels. Therefore, our data indicate that TLR4 signaling, through MyD88 and IRAK1, plays a predominant role in MMP-1 induction by cigarette smoke. The identification of the TLR4 pathway as a regulator of smoke-induced protease production presents a series of novel targets for future therapy in chronic obstructive pulmonary disease.

Induction of the unfolded protein response by cigarette smoke is primarily an activating transcription factor 4-C/EBP homologous protein mediated process

PURPOSE

Cigarette smoke is the major risk factor associated with the development of chronic obstructive pulmonary disease (COPD). Recent studies propose a link between endoplasmic reticulum (ER) stress and emphysema, demonstrated by increased ER stress markers under smoking conditions. Here, we investigate whether cigarette smoke-induced ER stress is cell specific and correlates with acute and chronic cigarette smoke exposure.

METHODS

Gene and protein expression changes in human primary lung cell cultures following cigarette smoke extract (CSE) exposure were monitored by qPCR and Western blot analysis. Mice and guinea pigs were exposed to cigarette smoke and ER stress markers examined in whole lung homogenates. Inflammatory cells from the bronchoalveolar lavage fluid of 10 days smoke exposed mice were also examined.

RESULTS

Cigarette smoke induced a trend increase in the ER stress response through an activating transcription factor 4 (ATF4) mediated induction of C/EBP homologous protein (CHOP) in primary small airway epithelial cells. Bronchial epithelial cells and macrophages responded similarly to CSE. Wild-type mice and guinea pigs exposed to acute levels of cigarette smoke exhibited increased levels of CHOP but not at significant levels. However, after long-term chronic cigarette smoke exposure, CHOP expression was reduced. Interestingly, inflammatory cells from smoke exposed mice had a significant increase in CHOP/ATF4 expression.

CONCLUSION

A trend increase in CHOP levels appear in multiple human lung cell types following acute cigarette smoke exposure in vitro. In vivo, inflammatory cells, predominately macrophages, demonstrate significant cigarette smoke-induced ER stress. Early induction of CHOP in cigarette smoke may play a pivotal role in early induction of lung disease, however in vivo long-term cigarette smoke exposure exhibited a reduction in the ER stress response.

Cigarette filter-based assays as proxies for toxicant exposure and smoking behavior--a literature review

BACKGROUND

Cigarettes are being marketed with filters that differ in composition and design. The filters have different toxicant trapping efficiencies, and smoking stains reflect variations in smoking behavior. Presented herein are the results of a structured literature review that was done to identify cigarette filter-based assays that may serve as proxies for mouth-level exposure and assessing smoking methods.

METHODS

A search of the published scientific literature and internal tobacco company documents from 1954 to 2009 was carried out.

RESULTS

The literature search identified diverse schemes for assessing cigarette filters, including visual inspection and digital imaging of smoked-stained spent filters, and quantitative determinations for total particulate matter (TPM), nicotine, and solanesol. The results also showed that: (a) there are sufficient data to link filter-based chemical measures to standardized smoking machine-measured yields of tar and nicotine; (b) TPM eluted from filters or in chemical digest of filters can be used to estimate the efficiency of the filter for trapping smoke solids; (c) visual and digital inspection of spent filters is useful in finding indicators of variations in smoking behaviors; and (d) there is a correlation between solanesol and nicotine measured in filters and exposure biomarkers in smokers.

CONCLUSIONS

The cigarette filter may prove useful in estimating smoking behaviors such as filter vent blocking and puffing intensity, and may have utility as proxy measures of mouth-level smoke exposure in clinical trials. Additional investigations are needed to compare the different proposed assay schemes and the assay results with measurements of human biomarker assays of smoke exposure.