Tumour necrosis factor-alpha gene polymorphisms in asbestos-induced diseases

Expression of microRNAs in leukocytes and serum of asbestosis patients

BACKGROUND

Although asbestos use is banned in many countries, long latency of asbestos-related diseases like pleural plaques or asbestosis mean it is still a public health issue. People suffering from these diseases have a higher risk of developing mesothelioma or lung cancer, which can progress quickly and aggressively. MicroRNAs were suggested as potential biomarkers in several diseases. However, in asbestosis, blood microRNAs are less explored. Since miR-32-5p, miR-143-3p, miR-145-5p, miR-146b-5p, miR-204-5p and miR-451a are involved in fibrotic processes and in cancer, expression of these microRNAs was analyzed in leukocytes and serum of asbestosis patients.

METHODS

MicroRNA expression was analyzed in leukocytes and serum of 36 patients (26 affected by pleural plaques and 10 by asbestosis) and 15 healthy controls by real-time RT-PCR. Additionally, data analyses were performed regarding disease severity based on ILO classification.

RESULTS

MicroRNA miR-146b-5p was significantly down-regulated in leukocytes of patients suffering from pleural plaques with a large effect indicated by η²_p = 0.150 and Cohen's f = 0.42, a value of difference of 0.725 and a 95% confidence interval of 0.070-1.381. In patients suffering from asbestosis miR-146b-5p was not significantly regulated. However, data analyses considering disease severity only, revealed that miR-146b-5p was significantly down-regulated in leukocytes of mildly diseased patients compared to controls with a large effect indicated by η²_p = 0.178 and Cohen's f = 0.465, a value of difference of 0.848 and a 95% confidence interval of 0.097-1.599. Receiver operating characteristic (ROC) curve and an area under the ROC curve value of 0.757 for miR-146b-5p indicated acceptable discrimination ability between patients suffering from pleural plaques and healthy controls. Less microRNAs were detectable in serum than in leukocytes, showing no significant expression differences in all participants of this study. Moreover, miR-145-5p was regulated significantly differently in leukocytes and serum. An R² value of 0.004 for miR-145-5p indicated no correlation in microRNA expression between leukocytes and serum.

CONCLUSION

Leukocytes seem more suitable than serum for microRNA analyses regarding disease and potentially cancer risk assessment of patients suffering from asbestos-related pleural plaques or asbestosis. Long-term studies may reveal whether down-regulation of miR-146b-5p in leukocytes might be an early indicator for an increased cancer risk.

Global DNA hypomethylation has no impact on lung function or serum inflammatory and fibrosis cytokines in asbestos-exposed population

PURPOSE

To examine the effect of asbestos exposure on global DNA methylation and determine whether lung function and inflammatory and fibrosis biomarkers are correlated with the methylation state.

METHODS

A total of 26 healthy subjects without asbestos exposure (Group 1), 47 healthy subjects with exposure (Group 2), and 52 subjects with benign asbestos-related disorders (ARDs) (Group 3) participated in this cross-sectional study. Blood global 5-methylcytosine (5mC) and serum TNF-α, collagen IV, CCL5 and CC16 concentrations were analyzed using enzyme-linked immunosorbent assay-like assays. Spirometric maneuvers were performed to assess lung function.

RESULTS

Decreased 5mC levels were observed in Groups 2 and 3 compared to Group 1, irrespective of lung function (p < 0.01). There was no significant change in 5mC between Groups 2 and 3. Overall, 5mC was negatively correlated with CCL5 and collagen IV (p < 0.05), but no significant inverse relationship was found between 5mC and CCL5 or collagen IV in each group. Additionally, both 5mC and CC16 were inversely associated with FEV1/FVC% (p = 0.001, adjusted R ² = 0.145) for non-smokers, and consistently significant inverse relationships were found between CC16 and FEV1/FVC%, independent of asbestos exposure.

CONCLUSIONS

Asbestos exposure causes global DNA hypomethylation. DNA hypomethylation has no influence on serum biomarkers and lung function in asbestos-exposed population with or without pleural and pulmonary parenchymal abnormalities.

Meta-analysis of the associations between TNF-α or IL-6 gene polymorphisms and susceptibility to lung cancer

BACKGROUND

Several studies have indicated an association between tumor necrosis factor-alpha (TNF-α) or interleukin (IL)-6 gene polymorphisms and lung cancer risk. However, the conclusions remain controversial.

METHODS

An English literature screening about case-control trials with regard to TNF-α (-308G/A) or IL-6 (174G/C) polymorphisms and lung cancer susceptibility was performed on PubMed, EMBASE, and EBSCO until November 2012. The pooled odds ratio (OR) and 95% confidence intervals (CI) were calculated using STATA 11.0. Sensitivity analysis was performed by sequential omission of individual studies. Publication bias was evaluated by Egger's linear regression test and funnel plots.

RESULTS

Eight eligible studies, including 1,690 patients and 1,974 controls, were identified in this meta-analysis. Compared with the control, no significant association was revealed between TNF-α-308G/A (GG + GC vs. CC: OR = 1.10, 95% CI: 0.73 to 1.64; GG vs. GC + CC: OR = 1.02, 95% CI: 0.81 to 1.27; GC vs. CC: OR = 1.13, 95% CI: 0.73 to 1.77; GG vs. CC: OR = 1.04, 95% CI: 0.80 to 1.36; G vs. C: OR = 1.03, 95% CI: 0.90 to 1.18) or IL-6 174G/C (GG + GC vs. CC: OR = 1.10, 95% CI: 0.73 to 1.64; GG vs. GC + CC: OR = 1.02, 95% CI: 0.81 to 1.27; GC vs. CC: OR = 1.13, 95% CI: 0.73 to 1.77; GG vs. CC: OR = 1.04, 95% CI: 0.80 to 1.36; G vs. C: OR = 1.03, 95% CI: 0.90 to 1.18) and lung cancer risk. The pooled OR remained unchanged after removing the maximum-weight study and no publication bias was observed.

CONCLUSIONS

The study raises the possibility of no correlation between the polymorphisms of the two genes and lung cancer susceptibility. However, further researches with large-sample or subgroup analyses are necessary to validate the conclusions.

Association between TNF-α gene 308G>A polymorphism and lung cancer risk: a meta-analysis

Many studies have investigated the association between tumor necrosis factor alpha (TNF-α) gene 308G/A polymorphism and lung cancer risk, but the results were inconsistent. We thus comprehensively searched the PubMed, EMBASE, and BIOSIS Previews databases and extracted data from all eligible articles to estimate the association between TNF-α gene 308G/A polymorphism and lung cancer risk. The pooled odds ratio (OR) with 95 % confidence intervals (CIs) were calculated. Twelve case-control studies in 11 articles involving 2,436 cases and 2,573 controls were included in the meta-analysis to assess the association between TNF-α gene 308G>A polymorphism and susceptibility to lung cancer. Overall, TNF-α gene 308G>A polymorphism was significantly associated with an increased risk of lung cancer for A vs. G (OR = 1.13, 95 % CI 1.00 ~ 1.27, P = 0.04). Subgroup analysis by ethnicity showed that there was a significant association between TNF-α gene 308G>A polymorphism and increased risk of lung cancer in Asians, but not in Caucasians. In subgroup analysis by tumor type, there were significant associations between TNF-α gene 308G>A polymorphism and increased risk of lung cancer in small cell lung cancer (SCLC) for AA+AG vs. GG, in non-small cell lung cancer (NSCLC) for A vs. G, AA vs. GG, and AA+AG vs. GG. No association between the genotypes and different stages of lung cancer was detected. The meta-analysis suggests that TNF-α gene 308G>A polymorphism is associated with an increased risk of lung cancer, particularly among Asians, both for SCLC and NSCLC, considering tumor type.

The role of genotoxicity in asbestos-induced mesothelioma: an explanation for the differences in carcinogenic potential among fiber types

The mechanism(s) underlying asbestos toxicity associated with the pathogenesis of mesothelioma has been a challenge to unravel for more than 60 years. A significant amount of research has focused on the characteristics of different fiber types and their potential to induce mesothelioma. These mechanistic studies of fiber toxicity have proceeded along two lines: those demonstrating biochemical mechanisms by which fibers induce disease and those investigating human susceptibility. Most recent studies focused on in vitro genotoxic effects induced by asbestos as the mechanism responsible for asbestos-induced disease. Although asbestos exerts a genotoxic effect at certain concentrations in vitro, a positive response in these tests does not indicate that the chemical is likely to produce an increased risk of carcinogenesis in exposed human populations. Thus far, findings from studies on the effects of fiber type in mesothelial cells are seriously flawed by a lack of a dose response relationship. The common limitation of these in vitro experiments is the lack of attention paid to the complexities of the human anatomy, biochemistry and physiology, which make the observed effects in these experimental systems difficult to extrapolate to persons in the workplace. Mechanistic differences between carcinogenic and genotoxic processes indicate why tests for genotoxicity do not provide much insight regarding the ability to predict carcinogenic potential in workers exposed to asbestos doses in the post-Occupational Safety and Health Administration era. This review discusses the existing literature on asbestos-induced genotoxicity and explains why these studies may or may not likely help characterize the dose-response curve at low dose.

Genes involved in innate immunity associated with asbestos-related fibrotic changes

Objectives

To determine whether genetic polymorphisms in several candidate genes related to innate immunity and protease–antiprotease balance modify individual susceptibility to develop asbestos-related fibrotic pleuropulmonary changes.

Methods

Sixteen polymorphisms from nine genes (NLRP3, CARD8, TNF, TGFB1, GC, MMP1, MMP9, MMP12 and TIMP2) were genotyped from 951 Finnish asbestos-exposed workers. The genotype/haplotype data were compared to signs of fibrosis and pleural thickenings using linear and logistic regression analysis adjusted for potential confounders.

Results

A functional polymorphism (Q705K; rs35829419) in the NLRP3 gene was associated with interstitial lung fibrosis (p=0.013), and the TGFB1 rs2241718 SNP with visceral pleural fibrosis (VPF) (p=0.044). In stratified analysis, the carriage of at least one NLRP3 variant allele conferred a 2.5-fold increased risk for pathological interstitial lung fibrosis (OR 2.44, 95% CI 0.97 to 6.14). Conversely, the carriage of at least one TGFB1 rs2241718 variant allele protected against VPF (OR 0.62, 95% CI 0.39 to 0.98). The TIMP2 rs2277698 SNP and a haplotype consisting of the TGFB1 rs1800469 and rs1800470 SNPs were associated with the degree of pleural thickening calcification (p=0.037 and p=0.035), and the CARD8 rs2043211 SNP with the greatest thickness of pleural plaques (p=0.015).

Conclusions

Our results support the hypothesis that the NLRP3 inflammasome is important in the development of fibrotic lung disease by associating the NLRP3 rs35829419 variant allele with increased risk of asbestos-related interstitial lung fibrosis, and the TGFB1 rs2241718 variant allele with decreased risk of asbestos-related VPF. Polymorphisms in CARD8 and TIMP2 are proposed to modify the development and/or calcification of pleural thickenings.

Interleukin gene polymorphisms in pneumoconiosis

Inhaled asbestos fibres are known to cause inflammation processes with the result of lung or pleural fibrosis and malignancies. Interleukins (IL), such as IL-1β, IL-6 and IL-10, have various functions in the regulation of the inflammatory response and in proliferative processes after inhalation of silica dust and can, therefore, influence the pathogenesis of asbestos-induced fibrosis and carcinogenesis. Polymorphisms within these genes may be associated with susceptibility to silica and asbestos-induced lung diseases. Thus, IL-1β, IL-6 and IL-10 polymorphisms were examined to determine an association with asbestos or silica-induced fibrosis or malignancies. Association studies were performed in 1180 individuals, using control subjects (n=177), fibrosis patients (n=605), lung cancer (LC) patients (n=364) and malignant mesothelioma (MM) patients (n=34). IL-1β (C-511T; C+3954T), IL-6 (G-174C) as well as IL-10 (G-1082A) polymorphisms were investigated. Compared to a healthy (control) group, a higher risk was seen for malignant mesothelioma patients in all investigated polymorphisms. The IL-6 -174C allele showed a tendency towards a higher risk for fibrosis or asbestos-induced lung cancer (ORasbestosis, 1.338; 95% CI, 0.71-2.53; ORsilicosis, 1.226; 95% CI, 0.54-2.81; ORfibrosis other aetiology, 1.313; 95% CI, 0.58-2.98 and ORLC asbestos, 2.112; 95% CI, 0.75-5.92). The IL-10 -1082A carrier seemed to be at higher risk for silicosis (ORsilicosis, 2.064; 95% CI, 0.78-5.49) but not for asbestosis. In summary, this study did not reveal sufficient evidence for a significant association of the investigated interleukin polymorphisms with asbestos or silica-induced diseases in the population studied.

TNF-α mRNA expression correlates with TGF-β mRNA expression in vivo

TNF-α is postulated to play a significant role in regulating TGF-β(1) expression. In lung fibroblasts, for example, TNF-α is supposed to induce TGF-β(1) via AP-1 activation. TNF-α receptor, knock-out mice are resistant to induced fibrosis and over-expression of TNF-α causes increased TGF-β(1) production in mice. Therefore, we investigated whether TNF-α mRNA levels are associated with the TGF-β(1) mRNA levels of blood leucocytes in humans. Quantitative real-time PCR of TNF-α and TGF-β(1) was performed in 118 Germans. Calculations of expression were made with the 2(-ΔΔCT) method. When the investigated population was divided in two groups (TNF-α low and TNF-α high) by the median of the determined TNF-α expression, highly significant (p < 0.0001) differences of TGF-β1 mRNA expression were revealed. Additionally, dividing the investigated population into quartiles of the determined TNF-α expression showed significantly different TGF-β1 mRNA expressions. Comparing the determined CT-values of TNF-α in context with these of TGF-β1, a coefficient of determination R(2) = 0.4635 was calculated. In this study we demonstrated in vivo a significant association of the relative TNF-α/B2M mRNA expression and the relative TGF-β(1)/B2M mRNA expression in 118 Germans.

TNF alpha antagonist therapy and safety monitoring

OBJECTIVES

To develop and/or update fact sheets about TNFα antagonists treatments, in order to assist physicians in the management of patients with inflammatory joint disease.

METHODS

1. selection by a committee of rheumatology experts of the main topics of interest for which fact sheets were desirable; 2. identification and review of publications relevant to each topic; 3. development and/or update of fact sheets based on three levels of evidence: evidence-based medicine, official recommendations, and expert opinion. The experts were rheumatologists and invited specialists in other fields, and they had extensive experience with the management of chronic inflammatory diseases, such as rheumatoid. They were members of the CRI (Club Rhumatismes et Inflammation), a section of the Société Francaise de Rhumatologie. Each fact sheet was revised by several experts and the overall process was coordinated by three experts.

RESULTS

Several topics of major interest were selected: contraindications of TNFα antagonists treatments, the management of adverse effects and concomitant diseases that may develop during these therapies, and the management of everyday situations such as pregnancy, surgery, and immunizations. After a review of the literature and discussions among experts, a consensus was developed about the content of the fact sheets presented here. These fact sheets focus on several points: 1. in RA and SpA, initiation and monitoring of TNFα antagonists treatments, management of patients with specific past histories, and specific clinical situations such as pregnancy; 2. diseases other than RA, such as juvenile idiopathic arthritis; 3. models of letters for informing the rheumatologist and general practitioner; 4. and patient information.

CONCLUSION

These TNFα antagonists treatments fact sheets built on evidence-based medicine and expert opinion will serve as a practical tool for assisting physicians who manage patients on these therapies. They will be available continuously at www.cri-net.com and updated at appropriate intervals.