Malondialdehyde–Deoxyguanosine Adducts among Workers of a Thai Industrial Estate and Nearby Residents

Background: Humans living near industrial point emissions can experience high levels of exposures to air pollutants. Map Ta Phut Industrial Estate in Thailand is the location of the largest steel, oil refinery, and petrochemical factory complexes in Southeast Asia. Air pollution is an important source of oxidative stress and reactive oxygen species, which interact with DNA and lipids, leading to oxidative damage and lipid peroxidation, respectively. Objective: We measured the levels of malondialdehyde-deoxyguanosine (dG) adducts, a biomarker of oxidative stress and lipid peroxidation, in petrochemical workers, nearby residents, and subjects living in a control district without proximity to industrial sources. Design: We conducted a cross-sectional study to compare the prevalence of malondialdehyde-dG adducts in groups of subjects experiencing various degrees of air pollution. Results: The multivariate regression analysis shows that the adduct levels were associated with occupational and environmental exposures to air pollution. The highest adduct level was observed in the steel factory workers. In addition, the formation of DNA damage tended to be associated with tobacco smoking, but without reaching statistical significance. A non significant increase in DNA adducts was observed after 4-6 years of employment among the petrochemical complexes. Conclusions: Air pollution emitted from the Map Ta Phut Industrial Estate complexes was associated with increased adduct levels in petrochemical workers and nearby residents. Considering the mutagenic potential of DNA lesions in the carcinogenic process, we recommend measures aimed at reducing the levels of air pollution

Opisthorchis viverrini infestation and endogenous nitrosamines as risk factors for cholangiocarcinoma in Thailand

Cholanglocarcinoma (CCA) is one of the most common cancers In north-east Thailand and has been associated with infestation by the liver fluke Opisthorchis viverrini (OV). Two samples of 12-hr overnight urine (after dosing with proline and ascorbic acid or proline alone) were collected from 20 Inhabitants from each of 5 contrasting incidence areas for CCA. The incidence of CCA was not correlated with either the amount of NPRO or other nitrosamino acids, endogenous nitrosation potential (difference in NPRO levels between proline dose and proline and ascorbic dose), or nitrate level. However, when urinary levels of nitrosamino acids were compared in subjects living in high-risk areas, subjects who were positive for OV antibody excreted significantly more (P < 0.01) NPRO (12.3 ± 18.7 μg/12 hr) after proline ingestion than those who were negative (3.5 ± 3.2 μg/12 hr). After ingestion of ascorbic acid, the NPRO levels in the positive subjects were significantly reduced (p < 0.01) to 2.4 ± 2.0 μg/12 hr, suggesting that endogenous nitrosation of proline was inhibited. Thus, endogenous nitrosation potential estimated from the difference between NPRO and the sum of nitrosamino acids excreted in the 2 urine samples was significantly higher in subjects positive for the OV antibody. Small amounts of pre-formed nitrosamines were found in fermented fish and pork food items, which are consumed frequently in the high-risk area for CCA. These results suggest that the interaction between chemical carcinogens, especially nitrosamines, and OV infestation may play a role in the development of cholangiocarcinoma in Thailand

Liver cancer in Thailand. I. A case-control study of cholangiocarcinoma

Potential risk factors for cholangiocarcinoma were investigated in a case-control study among inhabitants of north-east Thailand, which included 103 cases from 3 hospitals, with age-and sex-matched controls. A clear association with past or present infection with Opisthorchis viverrini, as indicated by raised serum antibodies, was found (o.r. 5.0), and at least two-thirds of cases can be attributed to this cause. The results suggest that males may be at higher risk than females. There was no association with hepatitis B infection, with aflatoxin Intake as estimated from albumin adducts in serum or with any particular dietary patterns. Alcohol consumption was very low in the population, and the risk associated with regular drinking was non-significant. Regular users of betel nut—predominantly female—had a high risk (o.r. 6.4), a possible mechanism being through their increased exposure to nitro-samines

Liver cancer in Thailand. II. A case-control study of hepatocellular carcinoma

Potential risk factors for hepatocellular carcinoma were investigated in a case-control study among inhabitants of north east Thailand. Sixty-five cases from 3 hospitals, with matched controls, were included. Infection with hepatitis-B virus was the major risk factor—chronic carriers of HB surface antigen had an estimated relative risk of 15.2. Infection with hepatltis-C virus appeared to be rare. No increase In risk was found with recent aflatoxin intake, as estimated by consumption of possibly contaminated foods, or by measuring aflatoxin-albumln adducts in serum. Regular use of alcohol (2 or more glasses of spirits per week) was associated with a nonsignificant elevation in risk (o.r. = 3.4, 95% c.i. 0.8–14.6), but the number of regular drinkers in the population was small. The meaning of an apparent protection conferred by certain food items is uncertain, but a possible role of betel nut in the aetiology deserves further investigation

The role of infection by opisthorchis viverrini, hepatitis B virus, and aflatoxin exposure in the etiology of liver cancer in Thailand. A correlation study

The incidence of the two principle types of liver cancer (hepatocellular carcinoma and cholangiocarcinoma) in five different areas of Thailand was compared with the prevalence of exposure to the main risk factors in samples of the population. Cholangiocarcinoma showed striking variations in incidence, which correlated closely with markers of exposure to the liver fluke, Opisthorchis viverrini. However, there was little geographic variation in incidence of hepatocellular carcinoma or in prevalence of the major risk factors (chronic carriage of hepatitis B virus and exposure to aflatoxin), and apparently there was little relationship between them

Characteristic expression of MSX1, MSX2, TBX2 and ENTPD1 in dental pulp cells

Dental pulp cells (DPCs) are a promising source of transplantable cells in regenerative medicine. However, DPCs have not been fully characterized at the molecular level. The aim of the present study was to distinguish DPCs from various source‑derived mesenchymal stem cells (MSCs), fibroblasts (FBs) and other cells by the expression of several DPC‑characteristic genes. DPCs were isolated from human pulp tissues by the explant method or the enzyme digestion method, and maintained with media containing 10% serum or 7.5% platelet‑rich plasma. RNA was isolated from the cells and from dental pulp tissue specimens. The mRNA levels were determined by DNA microarray and quantitative polymerase chain reaction analyses. The msh homeobox 1, msh homeobox 2, T‑box 2 and ectonucleoside triphosphate diphosphohydrolase 1 mRNA levels in DPCs were higher than that of the levels identified in the following cell types: MSCs derived from bone marrow, synovium and adipose tissue; and in cells such as FBs, osteoblasts, adipocytes and chondrocytes. The enhanced expression in DPCs was consistently observed irrespective of donor age, tooth type and culture medium. In addition, these genes were expressed at high levels in dental pulp tissue in vivo. In conclusion, this gene set may be useful in the identification and characterization of DPCs in basic studies and pulp cell‑based regeneration therapy