Detection of chemical-induced unscheduled DNA synthesis in cultures of normal adult human keratinocytes

Chitosan Oligosaccharide inhibits203HgCl2-induced genotoxicity in mice: Micronuclei occurrence and chromosomal aberration

The purpose of this study was to investigate the safety of chitosan oligosaccharide and the effects of chitosan oligosaccharide on mercury induced genotoxicity in mice using the micronuclei and chromosome aberration. The micronuclei test was performed by microscopic examination (x1,000, stained using a May-Grunwald solution) after administering 0.01, 0.1, and 1% (10 mg/mL) chitosan oligosaccharide for 7, 60, and 180 days ad libitum in mice. Total micronuclei of 1,000 polychromatic erythrocytes were recorded for each group. There was no difference between the untreated and experimental groups. The intake periods and concentrations of chitosan oligosaccharide did not affect the occurrence of micronuclei in bone marrow cells (P>0.05). The chromosomal aberration test was performed by microscopic examination (x1,000, stained using a 4% Giemsa solution) after administering the same concentration of chitosan oligosaccharide to mice, in F1, F2, F3 generations and parents. The frequency of chromosomal aberrations was defined as [Ydr = (D+R)/total number of counted lymphocytes]. Similar to the micronuclei test, there was no difference between the untreated and treated groups. These results showed that the intake periods and concentrations of chitosan oligosaccharide did not affect chromosomal aberrations in bone marrow cells (P>0.05). To investigate the effect of chitosan oligosaccharide on mercury-induced chromosome aberration, mice in each condition were supplied with 203HgCl2 and chitosan oligosaccharide ad libitum. Chitosan oligosaccharide significantly inhibited 203HgCl2-induced chromosome aberration in mice. Based on the results of this study, it may be concluded that the chitosan oligosaccharide is a nontoxic material that could be used as a suppressor of heavy metal-induced genotoxicity.

Chemically-induced unscheduled DNA synthesis in cultures of adult human epidermal keratinocytes

Skin is a major target organ for many experimental carcinogens that exist in our environment and the majority of previous carcinogenicity studies have utilised animal derived models. In view of the fact, that many of these environmental chemicals exhibit species- and tissue-specific metabolism, a human skin tissue derived model would be a distinct advantage. Squamous epithelial carcinoma is a predominant form of skin cancer in man and, in theory, human epidermal keratinocytes present an appropriate target cell to employ as an in vitro system to study epidermal carcinogenesis. This report demonstrates the valuable potential of human keratinocyte cultures as a suitable model for mechanistic studies on factors which may influence DNA damage and, hence, the subsequent development of cancer in human epidermis. Keratinocytes were serially cultivated from adult human skin samples and maintained in culture for at least 3 passages. Tertiary cultures, isolated from 3 separate individuals, were exposed to the direct-acting experimental carcinogen, methyl methanesulphonate (CAS No. 66-27-3), and benzo[a]pyrene (CAS No. 50-32-8), which requires metabolic activation. DNA repair was assessed by a quantitative autoradiographic technique. Methyl methanesulphonate and benzo[a]pyrene both elicited a dose-related increase in unscheduled DNA synthesis in cultures prepared from each individual. Inter-individual variation in the response was observed for each chemical, but this was greater in the case of benzo[a]pyrene, which indicates inter-individual variation in both xenobiotic metabolism activity and DNA repair capacity.