Genotoxicity of acrylamide and glycidamide

Background: Acrylamide, a known rodent carcinogen, is found in the human diet. However, the mechanism by which acrylamide exerts its carcinogenic effects remains unclear. Methods: Normal human bronchial epithelial cells and Big Blue mouse embryonic fibroblasts that carry a lambda phage cII transgene were treated in vitro with acrylamide, its primary epoxide metabolite glycidamide, or water (control) and then subjected to terminal transferase-dependent polymerase chain reaction to map the formation of DNA adducts within the human gene encoding p53 (TP53) and the cII transgene. The frequency and spectrum of glycidamide-induced mutations in cII were examined by using a lambda phage-based mutation detection system and DNA sequence analysis, respectively. All statistical tests were two-sided. Results: Acrylamide and glycidamide formed DNA adducts at similar specific locations within TP53 and cII, and DNA adduct formation was more pronounced after glycidamide treatment than after acrylamide treatment at all doses tested. Acrylamide-DNA adduct formation was saturable, whereas the formation of most glycidamide-DNA adducts was dose-dependent. Glycidamide treatment dose-dependently increased the frequency of cII mutations relative to control treatment (P<.001). Glycidamide was more mutagenic than acrylamide at any given dose. The spectrum of glycidamide-induced cII mutations was statistically significantly different from the spectrum of spontaneously occurring mutations in the control-treated cells (P = .038). Compared with spontaneous mutations in control cells, cells treated with glycidamide or acrylamide had more A-->G transitions and G-->C transversions and glycidamide-treated cells had more G-->T transversions (P<.001). Conclusion: The mutagenicity of acrylamide in human and mouse cells is based on the capacity of its epoxide metabolite glycidamide to form DNA adducts.