DNA damage evaluated by γH2AX foci formation by a selective group of chemical/physical stressors

It has been reported that the phosphorylated form of histone variant H2AX (gamma H2AX) plays an important role in the recruitment of DNA repair and checkpoint proteins to sites of DNA damage, particularly at double strand breaks (DSBs). Using gamma H2AX foci formation as an indicator for DNA damage, several chemical s/stress factors were chosen to assess their ability to induce gamma H2AX foci in a 24 It time frame in a human amnion FL cell line. Two direct-acting genotoxins, methyl methanesulfonate (MMS) and N-ethyl-N-nitrosourea (ENU), can induce gamma H2AX foci formation in a time- and dose-dependent manner. Similarly, an indirect-acting genotoxin, benzo[a]pyrene (BP), also induced the formation of gamma H2AX foci in a time- and dose-dependent manner. Another indirect genotoxin, 2-acetyl-aminofluorene (AAF), did not induce gamma H2AX foci formation in FL cells; however, AAF can induce gamma H2AX foci formation in Chinese hamster CHL cells. Neutral comet assays also revealed the induction of DNA strand breaks by these agents. In contrast, epigenetic carcinogens azathioprine and cyclosporine A, as well as non-carcinogen dimethyl sulfoxide, did not induce gamma H2AX foci fort-nation in FL cells. In addition, heat shock and hypertonic saline did not induce gamma H2AX foci. Cell survival analyses indicated that the induction of gamma H2AX is not correlated with the cytotoxic effects of these agents/factors. Taken together, these results suggest that gamma H2AX foci formation could be used for evaluating DNA damage; however, the different cell types used may play an important role in determining gamma H2AX foci formation induced by a specific agent. (c) 2005 Elsevier B.V. All rights reserved.