Molecular cytogenetic analysis of buccal cells and lymphocytes from benzene-exposed workers

Abstract

Benzene is a well-characterized human carcinogen and clastogen still present in both the occupational and general environment. However, the levels of benzene encountered today are, in most cases, relatively low and new methods, more specific and sensitive than classical cytogenetics, are probably needed to assess if current benzene exposures pose a genotoxic risk to human health. Bearing in mind the leukaemogenic action of benzene, blood lymphocytes appear to be a suitable cell system for biomonitoring studies. Buccal epithelium is an alternative source of tissue for monitoring human exposure to inhaled occupational and environmental genotoxicants. New molecular cytogenetic techniques allowing us to specifically study clastogenic or aneugenic events in human cells may provide the additional sensitivity required. In the present study, fluorescence in situ hybridization was used to examine the content of micronuclei (MN) (using the pan-centromeric DNA probe SO-alphaAllCen) in lymphocytes and buccal cells and to detect numerical abnormalities of chromosome 9 (using a chromosome 9 centromere-specific alphoid DNA probe) in buccal cells from a population occupationally exposed to benzene in an Estonian petrochemical plant. Age-matched Estonian volunteers were used as a control group. Individual benzene exposure levels were estimated to be around 1 p.p.m. (8 h time-weighted average). No increases in the frequency of total MN, MN harbouring whole chromosomes or acentric chromosomal fragments or chromosome 9 numerical abnormalities were detected in relation to benzene exposure in the present study. The lack of positive results was consistent in both buccal cells and lymphocytes, indicating that the benzene exposure levels encountered did not induce detectable clastogenic or aneugenic effects in the exposed workers. Other variables and confounding factors, such as age, smoking or alcohol consumption, did not influence any of the multiple cytogenetic biomarkers analysed.

The Nature of Chromosomal Aberrations Detected in Humans Exposed to Benzene

“…The MN assay has been applied in studies of benzene exposure only during the last decade (Table 6) (Carere et al, 1995;Carere et al, 1998a;Gao et al, 1994;Högstedt et al, 1991;Holland et al, 1999;Liu et al, 1996;Nise et al, 1991;Surrallés et al, 1997;Xu et al, 1995;Zhang, 1996a). More than half of these studies found no association between increased MN frequency and exposure to benzene (Carere et al, 1995;Carere et al, 1998a;Högstedt et al, 1991;Holland et al, 1999;Nise et al, 1991;Surrallés et al, 1997), but almost all of these negative studies involved relatively low levels of exposure (< 5 ppm) (Carere et al, 1995;Carere et al, 1998a;Högstedt et al, 1991;Nise et al, 1991;Surrallés et al, 1997).…”

“…More than half of these studies found no association between increased MN frequency and exposure to benzene (Carere et al, 1995;Carere et al, 1998a;Högstedt et al, 1991;Holland et al, 1999;Nise et al, 1991;Surrallés et al, 1997), but almost all of these negative studies involved relatively low levels of exposure (< 5 ppm) (Carere et al, 1995;Carere et al, 1998a;Högstedt et al, 1991;Nise et al, 1991;Surrallés et al, 1997). On the other hand, increased MN frequencies in pokeweed mitogen (PWM) stimulated lymphocytes of exposed workers were detected in two studies (Högstedt et al, 1991;Nise et al, 1991).…”

“…No increased levels of hyperdiploidy were detected in any chromosome; in fact, slightly lower levels in comparison with controls were observed. Similarly, no increase in hyperdiploidy of chromosome 9 was detected in the buccal cells of workers exposed to 1 ppm benzene (Surrallés et al, 1997). Hyperdiploidy and breakage of chromosomes 1 and 9 were examined in different cell populations of workers exposed to about 1 to 2 ppm benzene in a recent study (Carere et al, 1998a;Marcon et al, 1999).…”

Molecular Epidemiology Studies on Occupational and Environmental Exposure to Mutagens and Carcinogens, 1997-1999

“…Effects of exposure were observed with PAHs (18,19), benzene (28), epichlorohydrin (40), pesticides (44), fluorides (47), cytostatics (50), and cosmic radiation (54). No effects were induced by VOCs (23,24), benzene (26,33), styrene (36), BD (37), malathion (46), or cosmic radiation (55).…”

Exfoliated Buccal Mucosa Cells as a Source of DNA to Study Oxidative Stress

“…The use of buccal mucosa cells (BMC) as study material offers a number of advantages, which include the following: (a) chemotherapeutic agents and radiation therapy limit the proliferative ability of the epithelium, producing thinning and ulceration manifested predominantly in gastrointestinal and oral mucosa (23); (b) the BMC lining serves as a mirror for health status, reflecting changes in the systemic conditions, such as oxidative stress (24), nutrient deficiency (25)(26)(27), or human exposure to genotoxins (28)(29)(30)(31); (c) 90% of all cancers arise from epithelial tissue (32) and the use of oral exfoliated cells is therefore considered a powerful diagnostic tool for monitoring genetic damage in human populations (33); (d) BMCs are directly exposed to xenobiotics in food and the environment, making them the most interesting cell type to explore different aspects of oxidative stress and carcinogenesis. The ease of harvest and biochemical analysis (34) of good quantity and quality DNA (35) makes them an excellent indicator cell for the extent of DNA damage that the epithelium may be experiencing.…”