Smoking-induced expression of the GPR15 gene indicates its potential role in chronic inflammatory pathologies

Gene expression profiles associated with cigarette smoking and moist snuff consumption

Background

Among the different tobacco products that are available on the US market, cigarette smoking is shown to be the most harmful and the effects of cigarette smoking have been well studied. US epidemiological studies indicate that non-combustible tobacco products are less harmful than smoking and yet very limited biological and mechanistic information is available on the effects of these alternative tobacco products. For the first time, we characterized gene expression profiling in PBMCs from moist snuff consumers (MSC), compared with that from consumers of cigarettes (SMK) and non-tobacco consumers (NTC).

Results

Microarray analysis identified 100 differentially expressed genes (DEGs) between the SMK and NTC groups and 46 DEGs between SMK and MSC groups. However, we found no significant differences in gene expression between MSC and NTC. Both hierarchical clustering and principle component analysis revealed that MSC and NTC expression profiles were more similar than to SMK. Random forest classification identified a subset of DEGs which predicted SMK from either NTC or MSC with high accuracy (AUC 0.98).

Conclusions

PMBC gene expression profiles of NTC and MSC are similar to each other, while SMK exhibit distinct profiles with alterations in immune related pathways. In addition to discovering several biomarkers, these studies support further understanding of the biological effects of different tobacco products.

Trial registration

ClinicalTrials.gov. Identifier: NCT01923402. Date of Registration: August 14, 2013. Study was retrospectively registered.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3565-1) contains supplementary material, which is available to authorized users.

Tobacco smoking and smoking-related DNA methylation are associated with the development of frailty among older adults

Tobacco smoking is a preventable environmental factor that contributes to a wide spectrum of age-related health outcomes; however, its association with the development of frailty is not yet well established. We examined the associations of self-reported smoking indicators, serum cotinine levels and smoking-related DNA methylation biomarkers with a quantitative frailty index (FI) in 2 independent subsets of older adults (age 50-75) recruited in Saarland, Germany in 2000 - 2002 (discovery set: n = 978, validation set: n = 531). We obtained DNA methylation profiles in whole blood samples by Illumina HumanMethylation450 BeadChip and calculated the FI according to the method of Mitnitski and Rockwood. Mixed linear regression models were implemented to assess the associations between smoking indicators and the FI. After controlling for potential covariates, current smoking, cumulative smoking exposure (pack-years), and time after smoking cessation (years) were significantly associated with the FI (P-value < 0.05). In the discovery panel, 17 out of 151 previously identified smoking-related CpG sites were associated with the FI after correction for multiple testing (FDR < 0.05). Nine of them survived in the validation phase and were designated as frailty-associated loci. A smoking index (SI) based on the 9 loci manifested a monotonic association with the FI. In conclusion, this study suggested that epigenetic alterations could play a role in smoking-associated development of frailty. The identified CpG sites have the potential to be prognostic biomarkers of frailty and frailty-related health outcomes. Our findings and the underlying mechanisms should be followed up in further, preferably longitudinal studies.

Childhood Leukemia: A Preventable Disease

In contrast to most pediatric cancers, there is a growing body of literature, nationally and internationally, that has implicated the role of several environmental indoor and outdoor hazards in the etiology of childhood leukemia. For example, exposures to solvents, traffic, pesticides, and tobacco smoke have consistently demonstrated positive associations with the risk of developing childhood leukemia. Intake of vitamins and folate supplementation during the preconception period or pregnancy has been demonstrated to have a protective effect. Despite the strength of these findings, the dissemination of this knowledge to clinicians has been limited. Some children may be more vulnerable than others as documented by the high and increasing incidence of childhood leukemia in Hispanics. To protect children's health, it is prudent to establish programs to alter exposure to those factors with well-established associations with leukemia risk rather than to suspend judgment until no uncertainty remains. This is particularly true because other serious health outcomes (both negative and positive) have been associated with the same exposures. We draw from historical examples to put in perspective the arguments of association versus causation, as well as to discuss benefits versus risks of immediate and long-term preventive actions.

Comparison and combination of blood DNA methylation at smoking-associated genes and at lung cancer-related genes in prediction of lung cancer mortality

Epigenome-wide association studies have established methylation patterns related to smoking, the major risk factor of lung cancer (LC), which are distinct from methylation profiles disclosed in LC patients. This study simultaneously investigated associations of smoking-associated and LC-related methylation markers with LC mortality. DNA methylation was determined by HM450K assay in baseline blood samples of 1,565 older adults in a population-based case-cohort study. The associations of 151 smoking-associated CpGs (smoCpGs) and 3,806 LC-related CpGs (caCpGs) with LC mortality were assessed by weighted Cox regression models, controlling for potential confounders. Multi-loci methylation scores were separately constructed based on smoCpGs and caCpGs. During a median follow-up of 13.8 years, 60 participants who had a first diagnosis of LC died from LC. The average time between sample collection and LC diagnosis was 5.8 years. Hypomethylation at 77 smoCpGs and 121 caCpGs, and hypermethylation at 4 smoCpGs and 66 caCpGs were associated with LC mortality. The associations were much stronger for smoCpGs than for caCpGs. Hazard ratios (95% CI) were 7.82 (2.91-21.00) and 2.27 (0.75-6.85), respectively, for participants in highest quartile of Score I (based on 81 smoCpGs) and Score II (based on 187 caCpGs), compared with participants in the corresponding lower three quartiles. Score I outperformed Score II, with an optimism-corrected C-index of 0.87 vs. 0.77. In conclusion, although methylation changes of both smoking-associated and LC-related genes are associated with LC mortality, only smoking-associated methylation markers predict LC mortality with high accuracy, and may thus serve as promising candidates to identify high risk populations for LC screening.

Tobacco smoking differently influences cell types of the innate and adaptive immune system-indications from CpG site methylation

Background

Tobacco smoke is worldwide one of the main preventable lifestyle inhalative pollutants causing severe adverse health effects. Epidemiological studies revealed association of tobacco smoking with epigenetic changes at single CpGs in blood. However, the biological relevance of the often only marginal methylation changes remains unclear.

Results

Comparing genome-wide changes in CpG methylation of three recently reported epidemiological datasets, two obtained on whole blood and one on peripheral blood mononuclear cells (PBMCs), it becomes evident that the majority of methylation changes (86.7 and 93.3 %) in whole blood account for changes in granulocytes. Analyzing, in more detail, seven highly significant reported smoking-induced methylation changes at single CpGs in different blood cell types of healthy volunteers (n = 32), we confirmatively found a strong cell-type specificity. Two CpGs in GFI1 and F2RL3 were significantly hypomethylated in granulocytes (−11.3 %, p = 0.001; −8.7 %, p = 0.001, respectively) but not in PBMCs of smokers while two CpGs in CPOX and GPR15 were found to be hypomethylated in PBMC (−4.3 %, p = 0.003; −4.2 %, P = 0.009, respectively) and their subtypes of GPR15 non-expressing (−3.2 %, p = 0.027; −2.5 %, p = 0.032, respectively) and smoking-evoked GPR15 expressing T cells (−15.8 %, p < 0.001; −13.8 %, p = 0.018, respectively) but not in granulocytes. In contrast, cg05575921 within AHRR was hypomethylated in every analyzed cell type of smokers, but with a different degree. Both, hypomethylation at cg05575921 in granulocytes (−55.2 % methylation change in smokers, p < 0.001) and the frequency of GPR15+ T cells (9.8–37.1 % in smokers), possessing a specific hypomethylation at cg19859270, were strongly associated with smoking behavior at individual level and could therefore serve as valuable biomarkers indicating a disturbed homeostasis in smokers.

In contrast to the reported long-term persistent methylation changes in adult smokers after cessation, the hypomethylation at cg05575921 in prenatally tobacco smoke-exposed children (n = 13) from our LINA cohort was less stable and disappeared already within 2 years after birth.

Conclusions

Studying cell type-specific methylation changes provides helpful information regarding the biological relevance of epigenetic modifications. Here, we could show that smoking differently affects both cells of the innate and adaptive immune systems.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-016-0249-7) contains supplementary material, which is available to authorized users.

Smoking and Air Pollution as Pro-Inflammatory Triggers for the Development of Rheumatoid Arthritis

INTRODUCTION

Smoking is now well recognized not only as a risk factor for rheumatoid arthritis (RA), but also as a determinant of disease activity, severity, response to therapy, and possibly mortality.

METHODS

Studies, mostly recent, which have provided significant insights into the molecular and cellular mechanisms which underpin the pathogenesis of smoking-related RA, as well as the possible involvement of other types of outdoor and indoor pollution form the basis of this review.

RESULTS

Smoking initiates chronic inflammatory events in the lungs. These, in turn, promote the release of the enzymes, peptidylarginine deiminases 2 and 4 from smoke-activated, resident and infiltrating pulmonary phagocytes. Peptidylarginine deiminases mediate conversion of various endogenous proteins to putative citrullinated autoantigens. In genetically susceptible individuals, these autoantigens trigger the production of anti-citrullinated peptide, pathogenic autoantibodies, an event which precedes the development of RA.

CONCLUSIONS

An increasing body of evidence has linked chronic inflammatory events in the lungs of smokers, to the production of anti-citrullinated peptide autoantibodies and development of RA. Creation of awareness of the associated risks, assessment of smoking status and implementation of compelling antismoking strategies must be included in the routine clinical management of patients presenting with suspected RA.

IMPLICATIONS

Chronic inflammatory mechanisms operative in the lungs of smokers lead to the production of anti-citrullinated protein antibodies which, in turn, drive the development of RA. These mechanistic insights not only reinforce the association between smoking and risk for RA, but also the necessity to increase the level of awareness in those at highest risk.

DNA methylation changes of whole blood cells in response to active smoking exposure in adults: a systematic review of DNA methylation studies

Active smoking is a major preventable public health problem and an established critical factor for epigenetic modification. In this systematic review, we identified 17 studies addressing the association of active smoking exposure with methylation modifications in blood DNA, including 14 recent epigenome-wide association studies (EWASs) and 3 gene-specific methylation studies (GSMSs) on the gene regions identified by EWASs. Overall, 1460 smoking-associated CpG sites were identified in the EWASs, of which 62 sites were detected in multiple (≥3) studies. The three most frequently reported CpG sites (genes) in whole blood samples were cg05575921 (AHRR), cg03636183 (F2RL3), and cg19859270 (GPR15), followed by other loci within intergenic regions 2q37.1 and 6p21.33. These significant smoking-related genes were further assessed by specific methylation assays in three GSMSs and reflected not only current but also lifetime or long-term exposure to active smoking. In conclusion, this review summarizes the evidences for the use of blood DNA methylation patterns as biomarkers of smoking exposure for research and clinical practice. In particular, it provides a reservoir for constructing a smoking exposure index score which could be used to more precisely quantify long-term smoking exposure and evaluate the risks of smoking-induced diseases.