Influence of smoking on methylation and hydroxymethylation levels in global DNA and specific sites of KRT14 , KRT19 , MIR-9-3 and MIR-137 genes of oral mucosa

Polymorphism but not methylation status in the vitamin D receptor gene contributes to oral mucositis in children

OBJECTIVE

To investigate the relationship between the polymorphisms rs1544410 (BsmI), rs2228570 (FokI) and rs731236 (TaqI) and DNA methylation status in the VDR gene (vitamin D receptor) with oral mucositis (OM) in oncopaediatric patients treated with methotrexate (MTX®).

METHODS

The population comprised healthy patients with haematological malignancies aged between 5 and 19 years. An evaluation of oral conditions was performed using the Oral Assessment Guide. Demographic, clinical, biochemical and haematological data were obtained from medical records. Genomic DNA from oral mucosal cells was used for the analysis of polymorphisms (n = 102) (PCR-restriction fragment length polymorphism) and DNA methylation (n = 81) (methylation-specific PCR).

RESULTS

Males predominated (57.8%), and the mean age was 10.3 years (±4.7). OM affected 84.3% of patients, of which 53.1% developed severe oral mucositis (SOM). Patients with OM had lower platelet and leukocyte counts (p < 0.05). The G allele of rs1544410 (p = 0.040) and the CT genotype of rs2228570 polymorphisms were associated with SOM (p = 0.038). A partially methylated status in the VDR promoter was found in all patients.

CONCLUSION

OM is associated with lower leukocyte and platelet counts. SOM is associated with the rs1544410 and rs2228570 polymorphisms. The methylation status of the VDR is not associated with inflammation or exposure to MTX®.

Evaluation of salivary thiobarbituric acid reactive substances, total protein, and pH in children with various degrees of early childhood caries: a case-control study

PURPOSE

According to new studies, oxidative stress may play an important role in the beginning and progression of oral diseases. The aim of this study was the evaluation of thiobarbituric acid reactive substances (TBARS) as an indicator of lipid peroxidation, total protein, and pH of saliva in children with various degrees of early childhood caries in comparison with caries-free children.

METHODS

This case-control study was carried out on 90 children 3-5 years old in three equal groups, including caries-free children (CF), early childhood caries (ECC), and severe early childhood caries (S-ECC) who were age- and sex matched. Saliva pH was measured using a paper pH meter and TBARS and total protein were measured by spectrophotometer methods and data were statistically analysed.

RESULTS

TBARS and total protein levels in ECC and S-ECC groups were significantly higher than the CF group (p < 0.001), but pH was not significantly different between groups. There were no significant differences between ECC and S-ECC groups in any of the studied indicators.

CONCLUSION

Considering the limitations of the present study, the results showing the higher salivary TBARS levels in the S-ECC and ECC groups compared to caries-free children, lead to the conclusion that oxidative stress could be considered as a risk factor for early childhood caries.

Methylation Profile of miR-9-1 and miR-9-1/-9-3 as Potential Biomarkers of Diabetic Retinopathy

AIMS

Analysis of the relationship between the methylation profile of miR-9-1 or miRs -9-1 / -9-3 and diabetic retinopathy.

BACKGROUND

Diabetic Retinopathy (DR) is a frequent complication of Diabetes mellitus and it has a decisive impact on the quality of life, as it is one of the biggest causes of blindness in the adult population. Levels of microRNA-9 have been shown to be related to diabetes but little is known about its involvement with DR in humans.

OBJECTIVE

To analyze the relationship between the methylation profile of miR-9-1 or miRs -9-1/-9-3 and DR.

METHODS

103 patients diagnosed with diabetes for 5 to 10 years were analyzed. The data were categorized according to clinical, biochemical, lifestyle and anthropometric parameters. DNA extracted from leukocyte samples was used to determine the methylation profile of miRs-9-1 and -9-3 using a specific methylation PCR assay.

RESULTS

miR-9-1 methylation was related to diabetic retinopathy, indicating that methylation of this miR increases the chances of presenting retinopathy up to 5 times. In our analyses, diabetics with lower levels of creatinine and CRP showed significant reductions (99% and 97%) in presenting DR. Methylation of both miRs-9-1 and 9-3 methylated increases the chances of presenting DR by 8 times; in addition, a sedentary lifestyle can increase the risk for the same complication by up to 6 times.

CONCLUSION

Our results suggest that both methylation of miR-9-1 and e miRs-9-1 / 9-3 favors DR in patients with diabetes in a period of 5 to 10 years of diagnosis.

Changes in global DNA methylation and hydroxymethylation in oral mucosa according to tobacco smoke exposure

OBJECTIVE

This prospective clinical study comparatively investigated the effects of tobacco smoking on global methylation and hydroxymethylation in oral epithelial cells.

METHODS

Buccal cells from the inside of the cheeks were collected from 47 individuals, including smokers, former smokers, and never smokers. DNA was extracted using dedicated kits. Methylated and hydroxymethylated DNA fractions were measured using assays similar to enzyme-linked immunosorbent assays. The levels of methylation and hydroxymethylation were compared among groups using unpaired two-tailed t-tests or the Mann-Whitney U test; P < 0.05 was considered statistically significant.

RESULTS

There was no statistically significant difference in the average number of cigarettes between smoker and former smoker groups. Although methylation levels were lower for smokers (3.1%) and former smokers (2.16%), compared with never smokers (4.16%), these differences were not statistically significant. There was a two-fold increase in hydroxymethylation level in never smokers, compared with smokers.

CONCLUSIONS

Our findings suggest that smoking leads to global reductions in both methylation and hydroxymethylation levels in oral epithelial cells in a manner influenced by the intensity and length of exposure to tobacco smoke.

Hepatitis B virus X protein boosts hepatocellular carcinoma progression by downregulating microRNA-137

BACKGROUND

Hepatocellular carcinoma (HCC) is a frequent diagnosed malignancy. microRNAs (miRs) are involved in various cellular processes during cancer development. This study attempted to probe the miR-based mechanism in hepatitis B virus X protein (HBx) small interfering RNA (siRNA)-treated HCC cells.

METHODS

HBx expression in hepatocyte and HCC cells was detected, and cells with highest HBx expression were screened out and transfected with HBx-siRNAs. Then the effect of HBx on HCC cell proliferation was detected. miRs differentially expressed in HBx-siRNA-transfected MHCC97H cells were analyzed and verified. miR-137 methylation was analyzed by bioinformatics, and miR-137 restoration was detected after Aza treatment. Furthermore, miR-137 methylation in MHCC97H cells with HBx knockdown or HBx overexpression was detected by methylation specific PCR. The targeting relationship between miR-137 and Notch1 was verified. Then the gain-and-loss functions of miR-137 or/and Notch1 were performed to estimate their roles in HCC cell proliferation. The effects of HBx-siRNA and overexpressed miR-137 in vivo were observed by tumor xenograft in nude mice and immunohistochemistry.

RESULTS

HBx-siRNA weakened MHCC97H cell proliferation and tumor growth. miR-137 was highly expressed in HBx-siRNA-treated HCC cells and targeted Notch1. HBx knockdown decreased miR-137 methylation and restored miR-137 expression. miR-137 overexpression prevented HCC cell proliferation and tumor growth, while miR-137 downregulation reversed the repressing effects of HBx-siRNA on HCC cell proliferation. Inhibition of Notch1 reversed HCC cell proliferation induced by miR-137 downregulation.

CONCLUSION

Overexpression of miR-137 blocks HCC cell proliferation in HBx-siRNA-treated MHCC97H cells by targeting Notch1. This study may offer novel target for HCC treatment.

miR-9-1 gene methylation and DNMT3B (rs2424913) polymorphism may contribute to periodontitis

BACKGROUND

Genetic and epigenetic changes have been associated with periodontitis in various genes; however, little is known about genes involved in epigenetic mechanisms and in oxidative stress.

OBJECTIVE

This study aims to investigate the association of polymorphisms C677T in MTHFR (rs1801133) and -149C→T in DNMT3B (rs2424913), as well as the methylation profiles of MTHFR, miR-9-1, miR-9-3, SOD1, and CAT with periodontitis. The association between polymorphisms and DNA methylation profiles was also analyzed.

METHODOLOGY

The population studied was composed of 100 nonsmokers of both sexes, divided into healthy and periodontitis groups. Genomic DNA was extracted from the epithelial buccal cells, which were collected through a mouthwash. Polymorphism analysis was performed through polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), while methylation-specific PCR (MSP) or combined bisulfite restriction analysis techniques were applied for methylation analysis.

RESULTS

For DNMT3B, the T allele and the TT genotype were detected more frequently in the periodontitis group, as well as the methylated profile on the miR-9-1 promoter region. There was also a tendency towards promoter region methylation on the CAT sequence of individuals with periodontal disease.

CONCLUSION

The polymorphism -149C→T in DNMT3B (rs2424913) and the methylated profile of the miR-9-1 promoter region are associated with periodontitis.

A systematic review of smoking-related epigenetic alterations

The aim of this study is to provide a systematic review of the known epigenetic alterations caused by cigarette smoke; establish an evidence-based perspective of their clinical value for screening, diagnosis, and treatment of smoke-related disorders; and discuss the challenges and ethical concerns associated with epigenetic studies. A well-defined, reproducible search strategy was employed to identify relevant literature (clinical, cellular, and animal-based) between 2000 and 2019 based on AMSTAR guidelines. A total of 80 studies were identified that reported alterations in DNA methylation, histone modifications, and miRNA expression following exposure to cigarette smoke. Changes in DNA methylation were most extensively documented for genes including AHRR, F2RL3, DAPK, and p16 after exposure to cigarette smoke. Likewise, miR16, miR21, miR146, and miR222 were identified to be differentially expressed in smokers and exhibit potential as biomarkers for determining susceptibility to COPD. We also identified 22 studies highlighting the transgenerational effects of maternal and paternal smoking on offspring. This systematic review lists the epigenetic events/alterations known to occur in response to cigarette smoke exposure and identifies the major genes and miRNAs that are potential targets for translational research in associated pathologies. Importantly, the limitations and ethical concerns related to epigenetic studies are also highlighted, as are the effects on the ability to address specific questions associated with exposure to tobacco/cigarette smoke. In the future, improved interpretation of epigenetic signatures will lead to their increased use as biomarkers and/or in drug development.

Association of Bisphenol A Exposure with LINE-1 Hydroxymethylation in Human Semen

Bisphenol A (BPA), an exogenous endocrine-disrupting chemical, has been shown to alter DNA methylation. However, little information is available about the effect of BPA exposure on DNA hydroxymethylation in humans. The objective of the present study was to examine whether BPA exposure was associated with DNA hydroxymethylation in human semen samples. We measured urine BPA levels and LINE-1 hydroxymethylation in 158 male factory workers selected from an occupational cohort study conducted in China between 2004 and 2008. Among them, there were 72 male workers with occupational BPA exposure (BPA-exposed group) and 86 male workers without occupational BPA exposure (unexposed group). Multivariate linear regression models were used to examine the association of exposure to BPA with LINE-1 hydroxymethylation. LINE-1 was more highly hydroxymethylated in the BPA-exposed group than in the unexposed group (median 12.97% vs. 9.68%, respectively; p < 0.05), after adjusting for the potential confounders. The medians of 5-hydroxymethylcytosine (5hmC) generally increased with increasing urine BPA levels: 8.79%, 12.16%, 11.53%, and 13.45%, for undetected BPA and corresponding tertiles for the detected BPA, respectively. After analysis using data at individual level, our findings indicated that BPA exposure was associated with alterations of sperm LINE-1 hydroxymethylation, which might have implications for understanding the mechanisms underlying BPA-induced adverse effects on male reproductive function.

Decrease of the DNA methylation levels of the ADRB3 gene in leukocytes is related with serum folate in eutrophic adults

Background

DNA methylation has been evidenced as a potential epigenetic mechanism related to various candidate genes to development of obesity. Therefore, the objective of this study was to evaluate the DNA methylation levels of the ADRB3 gene by body mass index (BMI) in a representative adult population, besides characterizing this population as to the lipid profile, oxidative stress and food intake.

Methods

This was a cross-sectional population-based study, involving 262 adults aged 20–59 years, of both genders, representative of the East and West regions of the municipality of João Pessoa, Paraíba state, Brazil, in that were evaluated lifestyle variables and performed nutritional, biochemical evaluation and DNA methylation levels of the ADRB3 gene using high resolution melting method. The relationship between the study variables was performed using analyses of variance and multiple regression models. All results were obtained using the software R, 3.3.2.

Results

From the stratification of categories BMI, was observed a difference in the average variables values of age, waist-to-height ratio, waist-to-hip ratio, waist circumference, triglycerides and intake of trans fat, which occurred more frequently between the categories “eutrophic” and “obesity”. From the multiple regression analysis in the group of eutrophic adults, it was observed a negative relationship between methylation levels of the ADRB3 gene with serum levels of folic acid. However, no significant relation was observed among lipid profile, oxidative stress and food intake in individuals distributed in the three categories of BMI.

Conclusions

A negative relationship was demonstrated between methylation levels of the ADRB3 gene in eutrophic adults individuals with serum levels of folic acid, as well as with the independent gender of BMI, however, was not observed relation with lipid profile, oxidative stress and variables of food intake. Regarding the absence of relationship with methylation levels of the ADRB3 gene in the categories of overweight, mild and moderate obesity, the answer probably lies in the insufficient amount of body fat to initiate inflammatory processes and oxidative stress with a direct impact on methylation levels, what is differently is found most of the times in exacerbated levels in severe obesity.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1529-0) contains supplementary material, which is available to authorized users.

Perkinsus infection is associated with alterations in the level of global DNA methylation of gills and gastrointestinal tract of the oyster Crassostrea gasar

Bivalves are filter feeders that obtain food from seawater that may contain infectious agents, such as the protozoan parasites Perkinsus marinus and P. olseni that are associated with massive mortalities responsible for losses in the aquaculture industry. Despite all physical and chemical barriers, microorganisms cross epithelia and infect host tissues to cause pathologies. Epigenetics mechanisms play important roles in a variety of human processes, from embryonic development to cell differentiation and growth. It is currently emerging as crucial mechanism involved in modulation of host-parasite interactions and pathogenesis, promoting discovery of targets for drug treatment. In bivalves, little is known about epigenetic mechanism in host parasite interactions. The objective of the present study was to evaluate the effect of Perkinsus sp. infections on DNA methylation levels in tissues of Crassostrea gasar oysters. Samples were collected in 2015 and 2016 in the Mamanguape River estuary (PB). Oyster gills were removed and used for Perkinsus sp.

DIAGNOSIS

Gills (G) and gastrointestinal tract (GT), as well as cultured P. marinus trophozoites were preserved in 95% ethanol for DNA extractions. DNA methylation levels were estimated from G and GT tissues of uninfected (n=60) and infected oysters (n=60), and from P. marinus trophozoites, by ELISA assays. Results showed that the mean prevalence of Perkinsus sp. infections was high (87.3%) in 2015 and moderate (59.6%) in 2016. DNA methylation levels of G and GT tissues were significantly lower in infected oyster than in uninfected oysters, suggesting that infections are associated with hypomethylation. Methylation level was significantly higher in G than in GT tissues, indicating a likely tissue-specific mechanism. P. marinus trophozoites showed 33% methylation. This was the first study that confirms alterations of DNA methylation in two tissues of C. gasar oysters in association with Perkinsus sp. infections.