We conducted a two-year inhalation study of butyl methacrylate using F344/DuCrlCrlj rats and B6D2F₁/Crl mice. Rats were exposed to 0, 30, 125 and 500 ppm (v/v) and mice were exposed to 0, 8, 30 and 125 ppm (v/v) using whole-body inhalation chambers. Non-neoplastic lesions developed in the nasal cavities of both rats and mice, but neoplastic lesions were not found. There was also a positive trend in the incidence of large granular lymphocytic (LGL) leukemia in the spleen of male rats. No changes were observed in female rats. Overall, there is some evidence of carcinogenicity in male rats, but there is no evidence of carcinogenicity in female rats. In male mice, there was a positive trend by Peto’s test in the incidence of hepatocellular adenomas, and the incidence of hepatocellular adenomas and hepatocellular carcinomas combined was significantly increased compared to the controls by Fisher’s exact test in the 30 ppm exposed male group. In female mice, the incidence of hemangiosarcoma in all organs combined showed a positive trend by Peto’s test. Therefore, there is some evidence of carcinogenicity in male mice, and there is equivocal evidence of carcinogenicity in female mice.

The interaction between sunlight and drugs can lead to phototoxicity in patients who have received such drugs. Phototoxicity assessment is a regulatory requirement globally and one of the main toxicity screening steps in the early stages of drug discovery. An in silico-in vitro approach has been utilized mainly for toxicology assessments at these stages. Although several quantitative structure-activity relationship (QSAR) models for phototoxicity have been developed, in silico technology to evaluate phototoxicity has not been well established. In this study, we attempted to develop an artificial intelligence (AI) model to predict the in vitro Neutral Red Uptake Phototoxicity Test results from a chemical structure and its derived information. To accomplish this, we utilized an open-source software library, kMoL. kMoL employs a graph convolutional neural networks (GCN) approach, which allows it to learn the data for the specified chemical structure. kMoL also utilizes the integrated gradient (IG) method, enabling it to visually display the substructures contributing to any positive results. To construct this AI model, we used only the chemical structure as a basis, then added the descriptors and the HOMO-LUMO gap, which was obtained from quantum chemical calculations. As a result, the assortment of chemical structures and the HOMO-LUMO gap produced an AI model with high discrimination performance, and an F1 score of 0.857. Additionally, our AI model could visualize the substructures involved in phototoxicity using the IG method. Our AI model can be applied as a toxicity screening method and could enhance productivity in drug development.

The biliary excretion of pharmaceutical and food-related compounds is an important factor for assessing pharmacokinetics and toxicities in humans, and a highly predictive in vitro method for human biliary excretion is required. We have developed a simple in vitro culture method for generating extended and functional bile canaliculi using cryopreserved human hepatocytes. We evaluated the uptake of compounds by hepatocytes and bile canaliculi, and the biliary excretion index (BEI) was calculated. After 21 days of culture, the presence of extended and functional bile canaliculi was confirmed by the uptake of two fluorescent substrates. Positive BEIs were observed for taurocholic acid-d₄, rosuvastatin, pitavastatin, pravastatin, valsartan, olmesartan, and topotecan (reported biliary-excreted compounds in humans), but no difference in BEI was observed for salicylic acid (a nonbiliary-excreted compound). Furthermore, 8 of 21 food-related compounds with specific structures and reported biliary transporter involvement exhibited positive BEIs. The developed in vitro system was characterized by functional bile canaliculus-like structures, and it could be applied to the prediction of the biliary excretion of pharmaceutical and food-related compounds.

Glycation products are generated during the Maillard reaction, a non-enzymatic reaction between reducing sugars and the amino groups of proteins, which accumulate in the body with aging and cause many diseases. Herein, we have focused on dihydropyrazines (DHPs), which are glycation products formed by the dimerization of D-glucosamine or 5-aminolevulinic acid, and have reported that DHPs can produce several kinds of radicals and induce cytotoxicity via oxidative stress. To advance our understanding of DHP-mediated cytotoxicity, we selected a DHP, 3-hydro-2,2,5,6-tetramethylpyrazine (DHP-3), and two major Maillard reaction products, N^ε-(carboxymethyl)-L-lysine (CML) and acrylamide, and performed comparative experiments focusing on their cytotoxicity and their ability to induce oxidative stress. The order of increasing cytotoxicity was DHP-3, acrylamide, and CML, and the LC₅₀ value could be calculated only for DHP-3 (0.53 mM), indicating that DHP-3 is more toxic than the other Maillard reaction products. However, their toxicities were significantly lower than those of common toxic chemicals. Further, the results of their cytotoxicity assay were consistent with the results of intracellular reactive oxygen species production and activation of oxidative stress response signaling. These results indicate that the acute toxicity of Maillard reaction products is closely related to their ability to induce oxidative stress, and that DHP-3 is a particularly strong inducer of oxidative stress and thus exhibits high cytotoxicity among Maillard reaction products. In addition, we have shown that a comprehensive analysis comparing multiple Maillard reaction products is effective for elucidating their complex and diverse toxicities.

The gastrointestinal (GI) tract is more vulnerable to effects by the outside environment, and experiences oxidative stress. A wide diversity of GI disorders can be partially attributed to oxidative stress. However, the mechanism of oxidative stress-caused GI pathological changes is not clear. In the present study, human gastric epithelial cells (hGECs) were treated with hydrogen peroxide (H₂O₂), and oxidative stress was determined. The effect of oxidative stress on the levels of some antioxidative enzymes, proliferation, nuclear DNA damage, apoptosis, expression of ten-eleven translocation (TET), and level of DNA methylation was determined in these cells. The results showed that H₂O₂ treatment caused oxidative stress, increased the levels of superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA), decreased the level of glutathione (GSH), inhibited proliferation, caused nuclear DNA damage and apoptosis, upregulated the expression of TET1 gene, and ultimately led to active DNA demethylation in hGECs. The present study presents a mechanism by which oxidative stress induces active DNA demethylation in hGECs. We propose that TET inhibitors can be used to restore the oxidative stress-induced DNA demethylation, and thus inhibit possible malignant transformation of GI cells.

Chemical plants must handle a wide variety of hazardous substances. To ensure safety in such plants, it is necessary to conduct extensive and highly accurate risk assessments. In this study, we aimed at developing a method that enables flexible and accurate risk assessment. We combined two different simulation tools to reproduce the phenomena of toxic gas leakage and diffusion as well as its impact on human health. The atmospheric diffusion after the leakage of toxic gas was simulated by computational fluid dynamics (CFD). Assuming the movement line of the person, toxic gas absorption and subsequent metabolism were calculated by a physiologically based pharmacokinetic (PBPK) model. From this, changes in blood concentration of toxic substances with time were simulated and we evaluated the effects of toxic gases on human body. Ethanol was selected as a toxic gas in this study. Based on the assumed scenario, the diffusion of leaked ethanol gas was calculated by CFD leading to the confirmation that the concentration of ethanol gas varies significantly with wind speed, human position, and elapsed time. The PBPK model showed that the maximum blood concentration of ethanol was 161 µmol/L, which is sufficiently low compared to that of ethanol poisoning (i.e., 10,900 µmol/L). These results suggest that the effects on the human body are relatively low and the evacuation can be performed safely. Compared to conventional methods of risk assessment, our new method allows the risk assessment of multiple scenarios, namely interindividual differences, activity status and the used of protective equipment.

As a common environmental endocrine disruptor, monobutyl phthalate (MBP) has been connected to reports of ROS accumulation, sperm destruction and reproductive damage. However, the specific mechanism of reproductive injury caused by MBP remains uncertain. Ferroptosis is a non-apoptotic, controlled oxidative damage-related cell death that is usually connected with reactive oxygen species and lipid peroxidation. In this work, to evaluate the mechanism of MBP-induced ferroptosis in reproductive damage, bioinformation analysis and experimental validation were used. Based on bioinformatics analysis, the interleukin-6 (IL-6) and signal transducer and activator of transcription 3 (STAT3) genes may be involved in the tumor necrosis factor (TNF) signaling pathway, which controls inflammation. Experimental study validated the significance of IL6 and STAT3 in MBP-induced ferroptosis. Western blotting and quantitative real-time PCR revealed that Acyl-CoA Synthetase Long Chain Family Member 4 (ACSL4), Tumor necrosis factor-α (TNF-α), IL6, and STAT3 were all elevated with treatment of MBP, but Glutathione peroxidase 4 was significantly decreased. To determine the participation of IL6/STAT3, we added the ferroptosis inhibitor Ferrastain-1 (Fer-1) and the IL6/STAT3 pathway inhibitor Angoline. In conclusion, we found that MBP induced ferroptosis in TM3 cells to damage male reproductive system through the TNF/IL6/STAT signal pathway, resulting in lipid peroxidation and iron metabolite degradation.