Yuya Deguchi

Genotoxicity and Estrogenic Activity of 3,3'-Dinitrobisphenol A in Goldfish

3,3′-Dinitrobisphenol A (dinitro-BPA) is formed in a mixture of bisphenol A (BPA) and nitrite under acidic conditions. It shows genotoxicity in male ICR mice on a micronucleus test, but its estrogenic activity has not been examined in vivo. We examined its estrogenic activity using goldfish (Carassius auratus) by measuring plasma levels of vitellogenin (VTG) by the ELISA method. Expression of VTG didn’t increase in the plasma of goldfish intraperitoneal injected with dinitro-BPA at a dose of 10 mg/kg of body weight. We also examined the genotoxicity of dinitro-BPA by single-cell gel electrophoresis (comet assay) and a micronucleus test using goldfish. The DNA tail moment of blood cells increased after intraperitoneal injection of dinitro-BPA. Dinitro-BPA at the same dose significantly increased micronucleus frequency in gills of goldfish. On the other hand, BPA did not significantly increase the frequency of micronucleated cells. In conclusion, we found that dinitro-BPA did not show estrogenic activity, but had genotoxic potency stronger than that of BPA.

Leaf extract of Wasabia japonica relieved oxidative stress induced by Helicobacter pylori infection and stress loading in Mongolian gerbils.

Infection with Helicobacter pylori (H. pylori) can induce gastric disorders, and though its presence cannot explain disease pathogenesis and does not have associations with other factors, it is well known that H. pylori infection causes stomach inflammation following oxidative stress. We examined the suppressive effects of a leaf extract of Wasabia japonica on H. pylori infection and on stress loading in Mongolian gerbils. Following oral administration of wasabi extract of 50 and 200 mg/kg B.W./d for 10 d, the animals were exposed to restraint stress for 90 and 270 min. As for the results, the level of 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) in the stomach and oxidative DNA damage in peripheral erythrocytes at 270 min significantly increased. That elevation was significantly suppressed by the addition of the leaf extract. We concluded that the simultaneous loading of H. pylori infection and physical stress loading might induce oxidative DNA damage additively, while a leaf extract attenuated this DNA damage in the stomach as well as the peripheral erythrocytes.

Application of a new bioassay technique using goldfish for assessment of water toxicity.

There are a variety of chemicals in aquatic environment, so it is important to assess the toxicity. The biomarkers such as induction of DNA damage, micronuclei, vitellogenin, and hepatic P450 in fish are known to be effective for monitoring genotoxic and/or estrogenic chemicals. However, there is little study to use these biomarkers in same fish. Goldfish (Carassius auratus) is widely used and is suitable in size to collect blood or organs. In this study, validity of multiple‐biomarkers in goldfish was checked using standard chemicals and applied in the river water. Ho River, which flows through the textile dyeing factory in Shizuoka Prefecture, Japan, was reported to show genotoxicity toward Salmonella typhimurium TA98 and YG1024. When the goldfish were exposed to Ho River, DNA damage, estrogenic activity, and CYP1A induction were observed. Through the study, it was assumed that not only mutagens/carcinogens but also endocrine disrupting chemicals and poly aromatic hydrocarbons were present in Ho River. Therefore, chemical identification should be required. We could evaluate both genotoxicity and estrogenic activity simultaneously, so goldfish might be a good experimental model for estimation of chemical contamination levels in aquatic environment.

Changes in the Mutagenic and Estrogenic Activities of 17β-Estradiol after Treatment with Nitrite

We determined the changes in the mutagenic and estrogenic activities of 17β-estradiol after a nitrite treatment. Nitrite-treated 17β-estradiol showed mutagenic activities toward Salmonella typhimurium strains TA 100 and TA 98. We confirmed that nitrite-treated 17β-estradiol generated radicals from the results of an analysis of electron spin resonance. By applying an instrumental analysis, we identified 2-nitro-17β-estradiol to have been formed in the reaction mixture. 2-Nitro-17β-estradiol did not exhibit mutagenic activities toward Salmonella typhimurium strains, suggesting that other mutagens might have been formed in the reaction mixture. The clastogenic properties of nitrite-treated 17β-estradiol and 2-nitro-17β-estradiol were analyzed by a micronucleus test with male ICR mice. Nitrite-treated 17β-estradiol and 2-nitro-17β-estradiol induced a significantly higher frequency of micronucleated reticulocytes in mice. The estrogenic activity of 2-nitro-17β-estradiol was found to be lower than that of 17β-estradiol. These data suggest that a daily oral intake of 17β-estradiol and nitrite might induce the formation of mutagenic compounds in our body.

Seasonal Fluctuation of Endotoxin and Protein Concentrations in Outdoor Air in Sasebo, Japan

To determine the levels of endotoxin, which is a major component of outer membrane of Gram-negative bacteria, and protein in the atmosphere in Sasebo, Japan, we measured these biological materials in fine (aerodynamic diameter ≤2.5 µm) and coarse (≥2.5 µm) particles collected for 81 weeks (September 2014 to May 2016). The monthly concentrations (i.e., the mean value of weekly concentrations for each month) of endotoxin were higher in coarse particles than in fine particles. Fluctuations in monthly endotoxin concentrations were large in both fine (0.0005-0.0208 EU/m3) and coarse (0.0032-0.1164 EU/m3) particles. Furthermore, the endotoxin concentrations in coarse particles were highest in October 2014 and 2015 as well as September 2014 (0.0407-0.1164 EU/m3). However, the monthly protein concentrations were higher in fine particles than in coarse particles. Compared to the endotoxin concentrations, the fluctuations in the monthly protein concentrations were smaller in both coarse and fine particles. To our knowledge, this study is the first to report long-term atmospheric concentrations of endotoxin and protein in Japan. Since the endotoxin concentrations in coarse particles were positively associated with the concentrations of Na+ and Cl-, it suggests the involvement of Gram-negative bacteria from seawater to the endotoxin levels in the atmosphere. For fine particles, the protein concentrations were positively associated with the concentrations of particles, NO3- and SO42-. These results suggest that combustion of organic materials, such as biomass burning, may be a contributor to atmospheric protein during this study period.