Exfoliated buccal and microdissected lung cell expression of antioxidant enzymes

Quantitation by Liquid Chromatography-Nanoelectrospray Ionization-High-Resolution Tandem Mass Spectrometry of Multiple DNA Adducts Related to Cigarette Smoking in Oral Cells in the Shanghai Cohort Study

We developed a liquid chromatography-nanoelectrospray ionization-high-resolution tandem mass spectrometry (LC-NSI-HRMS/MS) method for simultaneous quantitative analysis of 5 oral cell DNA adducts associated with cigarette smoking: (8R/S)-3-(2'-deoxyribos-1'-yl)-5,6,7,8-tetrahydro-8-hydroxypyrimido[1,2-a]purine-10(3H)-one (γ-OH-Acr-dGuo, 1) from acrolein; (6S,8S and 6R,8R)-3-(2'-deoxyribos-1'-yl)-5,6,7,8-tetrahydro-8-hydroxy-6-methylpyrimido[1,2-a]purine-10(3H)-one [(6S,8S)γ-OH-Cro-dGuo, 2; and (6R,8R)γ-OH-Cro-dGuo, 3] from crotonaldehyde; 1,N⁶-etheno-dAdo (4) from acrylonitrile, vinyl chloride, lipid peroxidation, and inflammation; and 8-oxo-dGuo (5) from oxidative damage. Oral cell DNA was isolated in the presence of glutathione to prevent artifact formation. Clear LC-NSI-HRMS/MS chromatograms were obtained allowing quantitation of each adduct using the appropriately labeled internal standards. The accuracy and precision of the method were validated, and the assay limit of quantitation was 5 fmol/μmol dGuo for adducts 1-4 and 20 fmol/μmol for adduct 5. The assay was applied to 80 buccal cell samples selected from those collected in the Shanghai Cohort Study: 40 from current smokers and 40 from never smokers. Significant differences were found in all adduct levels between smokers and nonsmokers. Levels of 8-oxo-dGuo (5) were at least 3000 times greater than those of the other adducts in both smokers and nonsmokers, and the difference between amounts of this adduct in smokers versus nonsmokers, while significant (P = 0.013), was not as great as the differences of the other DNA adducts between smokers and nonsmokers (P-values all less than 0.001). No significant relationship of adduct levels to risk of lung cancer incidence was found. This study provides a new LC-NSI-HRMS/MS methodology for the quantitation of diverse DNA adducts resulting from exposure to the α,β-unsaturated aldehydes acrolein and crotonaldehyde, inflammation, and oxidative damage which are all associated with carcinogenesis. We anticipate application of this assay in ongoing studies of the molecular epidemiology of cancers of the lung and oral cavity related to cigarette smoking.

Short-term exposure to PM2.5 and vanadium and changes in asthma gene DNA methylation and lung function decrements among urban children

Background

Both short and long-term exposure to traffic-related air pollutants have been associated with asthma and reduced lung function. We hypothesized that short-term indoor exposure to fine particulate matter <2.5 μm (PM_2.5) and vanadium (V) would be associated with altered buccal cell DNA methylation of targeted asthma genes and decreased lung function among urban children in a nested subcohort of African American and Dominican children.

Methods

Six day integrated levels of air pollutants were measured from children’s homes (age 9–14; n = 163), repeated 6 months later (n = 98). Buccal samples were collected repeatedly during visits. CpG promoter loci of asthma genes (i.e., interleukin 4 (IL4), interferon gamma (IFNγ), inducible nitric oxide synthase (NOS2A), arginase 2 (ARG2)) were pyrosequenced and lung function was assessed.

Results

Exposure to V, but not PM_2.5, was associated with lower DNA methylation of IL4 and IFNγ. In exploratory analyses, V levels were associated with lower methylation of the proinflammatory NOS2A-CpG⁺⁵⁰⁹⁹ among asthmatic overweight or obese children but not nonasthmatics. Short-term exposure to PM_2.5, but not V, appeared associated with lower lung function (i.e., reduced z-scores for forced expiratory volume in one second (FEV₁, FEV₁/ forced vital capacity [FEV₁/FVC] and forced expiratory flow at 25–75% of FVC [FEF_25–75]).

Conclusions

Exposure to V was associated with altered DNA methylation of allergic and proinflammatory asthma genes implicated in air pollution related asthma. However, short-term exposure to PM_2.5, but not V, appeared associated with decrements in lung function among urban children.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-017-0550-9) contains supplementary material, which is available to authorized users.

Oral Cell DNA Adducts as Potential Biomarkers for Lung Cancer Susceptibility in Cigarette Smokers

This perspective considers the use of oral cell DNA adducts, together with exposure and genetic information, to potentially identify those cigarette smokers at highest risk for lung cancer, so that appropriate preventive measures could be initiated at a relatively young age before too much damage has been done. There are now well established and validated analytical methods for the quantitation of urinary and serum metabolites of tobacco smoke toxicants and carcinogens. These metabolites provide a profile of exposure and in some cases lung cancer risk, but they do not yield information on the critical DNA damage parameter that leads to mutations in cancer growth control genes such as KRAS and TP53. Studies demonstrate a correlation between changes in the oral cavity and lung in cigarette smokers, due to the field effect of tobacco smoke. Oral cell DNA is readily obtained in contrast to DNA samples from the lung. Studies in which oral cell DNA and salivary DNA have been analyzed for specific DNA adducts are reviewed; some of the adducts identified have also been previously reported in lung DNA from smokers. The multiple challenges of developing a panel of oral cell DNA adducts that could be routinely quantified by mass spectrometry are discussed.

Detecting gene expression in buccal mucosa in subjects with asthma versus subjects without asthma

BACKGROUND

Differences in mRNA expression for inflammatory markers have been observed between subjects with asthma vs. controls and in relation to corticosteroid response. However, these studies utilized methods (e.g., bronchoscopy) that are too invasive to be used routinely in children and in the clinic. The primary purpose of this study was to determine the feasibility of obtaining RNA of adequate quantity and quality from buccal mucosa of children and adults for gene expression studies. Secondly, this study aimed to determine whether gene expression patterns in buccal mucosa are similar to those that have been observed in respiratory epithelium.

METHODS

We enrolled 94 subjects with and without asthma between 5 and 54 years of age. Relative gene expression in buccal mucosa was determined with quantitative RT-PCR for the following genes: CCL2, EDN1, FKBP5, IL8, IFNAR2, NFKB1, RELA, SERPINB2, DENND1B, HRH1, ICAM1, ORMDL3, NR3C1, CLCA1, CRHR1, MUC5B, FCER2, POSTN, GAPDH, PPIA.

RESULTS

mRNA Expression of the following genes was detected in buccal mucosa: CCL2, EDN1, FKBP5, IL8, IFNAR2, NFKB1, RELA, SERPINB2, DENND1B, HRH1, ICAM1, ORMDL3, NR3C1, GAPDH, PPIA. HRH1 was differentially expressed in adults with asthma vs. controls (p = 0.04), and EDN1 was differentially expressed in children with asthma vs. controls 12-18 years old (p = 0.03). A similar trend for HRH1 was observed in children 12-18 years old.

CONCLUSIONS

Buccal mucosa sampling is a reliable method for detecting changes in gene expression in patients with asthma. This non-invasive technique may serve as a valuable tool for diagnosing asthma and evaluating therapeutic response.

RNA from brush oral cytology to measure squamous cell carcinoma gene expression

BACKGROUND

RNA expression analysis of oral keratinocytes can be used to detect early stages of disease such as oral cancer or to monitor on-going treatment responses of the same or other oral diseases. A limitation is the inability to obtain high quality RNA from oral tissue without using biopsies. While oral cytology cell samples can be obtained from patients in a minimally invasive manner they have not been validated for quantitative analysis of RNA expression.

METHODS

As a starting point in the analysis of tumor markers in oral squamous cell carcinoma (OSCC), we examined RNA in brush cytology samples from hamsters treated with dibenzo[a,l]pyrene to induce oral carcinoma. Three separate samples from each animal were assessed for expression of candidate marker genes and control genes measured with real-time RT-PCR.

RESULTS

Brush oral cytology samples from normal mucosa were shown to consist almost exclusively of epithelial cells. Remarkably, ss-2 microglobulin and cytochrome p450, 1B1 (CYP1B1) RNA showed potential utility as markers of OSCC in samples obtained in this rapid and non-surgical manner.

CONCLUSION

Brush oral cytology may prove useful as a source of RNA for gene expression analysis during the progression of diseases of the oral epithelium such as OSCC.

Haplotype-environment interactions that regulate the human glutathione S-transferase P1 promoter

Phase II detoxification of carcinogens is reported to mediate some of the anticarcinogenesis effects of candidate chemopreventive agents. We explored the interaction between sequence variation in the GSTP1 gene promoter and candidate chemopreventive exposure in regulating human GSTP1 expression. Polymorphisms along 1.8 kb of the GSTP1 promoter were identified in leukocytes [peripheral blood mononuclear cells (PBMC)] from 40 Caucasian subjects. Ten promoter polymorphisms (9 previously unreported) displayed strong linkage disequilibrium, yielding identification of three frequently observed haplotypes [HAP1 (43%), HAP2 (36%), and HAP3 (8%)]. Each haplotype was cloned into luciferase reporter constructs and transfected into normal human bronchial epithelial cells. Basal HAP3 reporter activity was significantly elevated (1.8-fold) but decreased to the same levels as HAP2 and HAP1 with increasing concentrations of sulforaphane, benzyl isothiocyanate (BITC), and epigallocatechin gallate (EGCG). To confirm native HAP3 functionality, we quantitated mRNA expression in uncultured PBMCs and in laser microdissected normal lung epithelial cells (MNLEC) from the same patients. Basal mRNA expression was higher in HAP3 individuals [1.8-fold (PBMC) and 4-fold (MNLEC) for HAP3 heterozygotes and 2.3-fold (PBMC), and 15-fold (MNLEC) for the HAP3 homozygote] than in the other genotypes. PBMC GSTP1 mRNA expression correlated to MNLEC expression (R2 = 0.77). After culture and in vitro exposure to sulforaphane, BITC, or EGCG, the elevated GSTP1 mRNA expression of PBMCs from HAP3 individuals decreased to common expression levels. Elevated HAP3 function was confirmed at the protein level in PBMCs (5-fold higher for HAP3 heterozygotes and 7.6-fold for the HAP3 homozygote). These data suggest a potentially protective GSTP1 promoter haplotype and unpredicted inhibitory chemopreventive agent-haplotype interactions.