Evaluation of chemical phototoxicity, focusing on phosphorylated histone H2AX.
Bottom Line: Therefore, γ-H2AX is currently attracting attention as a new biomarker for detecting various genotoxic insults.We have determined the toxic impact of various environmental stresses such as chemicals, light and/or their coexposure using γ-H2AX, and found that the γ-H2AX assay exhibited high sensitivity and a low false-positive rate as a detection system of genotoxic potential.In this review, we introduced our recent findings concerning the evaluation of chemical phototoxicity, focusing on γ-H2AX.
Affiliation: Graduate Division of Nutritional and Environmental Sciences, University of Shizuoka, Shizuoka, Japan email@example.com.Show MeSH
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Mentions: Figure 7 shows the detection limits for the phototoxic effects of the chemicals assessed using (i) γ-H2AX (4 h after the treatments), (ii) DSBs detected by BSFGE (4 h after the treatments), and (iii) cell viability (24 h after the treatments) (edited figure from J Invest Dermatol 2011;131:1313–21 ). A total of 11 kinds of chemicals: 8-MOP, bithionol (BT), 6-MC, promethazine hydrochloride (PM), 5-methoxypsoralen (5-MOP), chlorpromazine hydrochloride (CPZ), neutral red (NR), rose bengal sodium salt (RB), tetracycline (TC), SDS, and L-histidine (L-his), as shown in Fig. 4, were compared. The most suitable concentrations for the detection of phototoxicity were expressed by wide bars and dark colors. For example, in the case of 8-MOP, the detectable concentrations for cell death and DSBs using gel electrophoresis were over 10−6 M, and the higher doses were more suitable. γ-H2AX could be detected even at a concentration of 10−9 M and strongly at the higher concentrations. The phototoxicity of the weak phototoxic chemical, 6-MC, was detectable only by γ-H2AX from 10−7 M, and not by survival and gel electrophoresis. On the other hand, in the cases of PM, CPZ and NR, the sensitivity of the detection of γ-H2AX was less at the excessively high concentrations. This may be due to a decrease in cellular responses (phosphorylation) by acute phototoxicity. We concluded that the limits of detection of phototoxicity using γ-H2AX were 100–1000 times lower than that using cell viability and DNA gel electrophoresis. In addition, neither of the non-phototoxic chemicals, SDS and L-His, generated γ-H2AX. This result means that the detection of γ-H2AX as a photogenotoxic marker is a method with a low false-positive rate, even at high concentrations, which is an essential requirement for phototoxicity testing.
Affiliation: Graduate Division of Nutritional and Environmental Sciences, University of Shizuoka, Shizuoka, Japan firstname.lastname@example.org.