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application/pdf, Genes and Environment. 2020, 42,(Article number: 12), P.1-6

Umu test have been widely used to predict the detection and assessment of DNA- damaging chemicals in environmental genotoxicity field for three decades. This test system is more useful with respect to simplicity, sensitivity, rapidity, and reproducibility. A review of the literature on the development of the umu test is presented in this article. The contents of this article are included a description of numerous data using the umu test. This test have been fully evaluated and used in many directions. Different genetically engineered umu systems introducing bacterial and rat or human drug metabolizing enzymes into the umu tester strains, have been successfully established and are considered as useful tools for genotoxicity assays to study the mechanisms of biotransformation in chemical carcinogenesis. Actually, we developed that two types of bacterial metabolizing enzymes and 4 types of rat and human metabolizing enzyme DNAs are expressed in these strains such as nitroreductase and O-acetyltransferase, cytochrome P450, N-acetyltransferases, sulfotransferases, and glutathione S-transferases, respectively. Due to increasing numbers of minute environmental samples and new pharmaceuticals, a high-throughput umu test system using Salmonella typhimurium TA1535/pSK1002, NM2009, and NM3009 strains provides a useful for these genotoxicity screening. I also briefly describe the first attempts to incorporate such umu tester strain into photo-genotoxicity test.

3-Nitrobenzanthrone (3-NBA) is a mutagenic and carcinogenic compound identified in diesel exhaust, airborne particulate matter, soil, and water. To address whether 3-NBA shows genotoxic effects through any metabolic activation pathway, we determined the genotoxicity of 3-NBA using the parental strain Salmonella enterica serovar Typhimurium (S. typhimurium) TA1535/pSK1002, nitroreductase (NR)-deficient strain NM1000, the O-acetyltransferase (O-AT)-deficient strain NM2000, bacterial O-AT-overexpressing strain NM2009, and bacterial NR- and O-AT-overexpressing strain NM3009 established in our laboratory. In order to further clarify the role of human cytochrome P450 (P450 or CYP) enzyme in the bioactivation of 3-NBA to genotoxic metabolites, umu tester strains S. typhimurium OY1022/1A1, OY1022/1A2, OY1022/1B1, and OY1022/3A4, which express four respective human cytochrome P450 enzymes, NADPH-cytochrome P450 reductases (NPR) and O-AT were established by introducing two plasmids into S. typhimurium TA1535NR/1,8-DNP (nitroreductase-deficient and resistant to 1,8-dinitropyrene, probably due to functional loss of O-AT), one carrying both P450 and reductase cDNA in a biocistronic construct under control of an IPTG-inducible double tac promoter and the other, pOA102, carrying O-AT and umuC'-'lacZ fusion genes. Induction of umuC gene expression could be monitored by measuring the cellular β-galactosidase activity produced by the umuC'-'lacZ fusion gene. Although the induction of umuC by 3-NBA was weak in TA1535/pSK1002, NM1000, and NM2000 strains, the induction was considerably potent in NM2009 and NM3009 strains. 3-NBA was also found to induce umuC gene expression in OY1022/1A1 and OY1022/3A4 strains and, to a lesser extent, OY1022/1A2 and OY1022/1B1 strains, at a much higher rate than the parental OY1022/pCW strain. Collectively, these results suggest nitroreduction and O-acetylation by bacterial NR and O-AT, respectively, and nitroreduction by human CYP1A1, 3A4, 1A2, and 1B1 and NPR could contribute to the genotoxic activation of 3-NBA to produce reactive metabolites.