DOI： 10.3390/ijms26135955

PubMed

DOI： 10.3390/cancers17132212

PubMed

DOI： 10.3390/nu17040645

PubMed

<p>The use of alternative <i>in vitro</i> methods for assessing acute inhalation toxicity instead of animal testing is currently an important issue and aligns with the 3Rs concept (reduction, refinement, and replacement). This study aimed to develop a neutral red uptake (NRU) assay using human lung adenocarcinoma cells (A549-NRU) to predict acute inhalation toxicity in animal models. LC₅₀ values of 49 chemicals were evaluated and their correlations with LD₅₀ values from 4-hour rat inhalation studies were analyzed. The LC₅₀ values from A549-NRU showed significantly negative correlation with their physicochemical properties (molecular weight and octanol-water partition coefficient). A significantly positive correlation between LC₅₀ values from A549-NRU and LD₅₀ values from 4-hour rat inhalation of water-soluble chemicals was observed. Among all chemicals, those containing aldehyde and ketone groups, as well as chemicals containing alcohol, ether, and epoxide groups, exhibited significant positive correlation between LC₅₀ values from A549-NRU and LD₅₀ values from 4-hour rat inhalation. Furthermore, compared to the standard NRU assay using mouse fibroblast cells (3T3), the LC₅₀ values from the A549-NRU assay exhibited stronger positive correlation with the LD₅₀ values from 4-hour rat inhalation studies. These findings indicate that physicochemical properties and chemical structures are key determinants in the A549-NRU assay, supporting its potential as a promising <i>in vitro</i> alternative for predicting acute inhalation toxicity in rats.</p>

DOI： 10.14869/toxpt.52.1.0_p-391

CiNii Research

<p>Tobacco smoking is a major risk factor for human cancers including urinary bladder carcinoma. In a previous study, nicotine was shown to enhance rat urinary bladder carcinogenesis in a two-stage carcinogenesis model. In this study, we examined the progressive effects of nicotine on bladder carcinogenesis in F344 rats treated with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN). Nicotine, administered in drinking water for 52 weeks following 4 weeks of BBN treatment, significantly increased the incidence and multiplicity of invasive urothelial carcinoma in a dose-dependent manner. The Ki67 labeling index of bladder papillomas was significantly increased by nicotine in a dose-dependent manner. However, nicotine treatment did not affect the incidence or total number of tumors, and nicotine administration alone for 52 weeks did not result in any neoplastic lesions. These data suggest that while nicotine does not initiate carcinogenesis, it has the potential to promote invasive urinary cancers.</p>

DOI： 10.1293/tox.2024-0087

PubMed

CiNii Research

<p> Occupational exposure to aromatic amines is a major risk factor for urinary bladder cancer. Our previous studies showed that acetoaceto-<i>o</i>-toluidine, which is produced using <i>o</i>-toluidine as a raw material, promotes urinary bladder carcinogenesis in rats. We also found high concentrations of <i>o</i>-toluidine, a human bladder carcinogen, in the urine of acetoaceto-<i>o</i>-toluidine-treated rats, indicating that urinary <i>o</i>-toluidine derived from acetoaceto-<i>o</i>-toluidine may play an important role in bladder carcinogenesis. However, this has not been investigated in humans. In the present study, we used non-humanized (F1-TKm30 mice) and humanized-liver mice established by human hepatocyte transplantation to compare differences in urinary acetoaceto-<i>o</i>-toluidine metabolites produced by human and mouse liver cells. We also examined the changes in acetoaceto-<i>o</i>-toluidine-induced mRNA expression in the liver and the proliferative effects on the bladder epithelium. Urinary <i>o</i>-toluidine was detected in both non-humanized and humanized mice. Acetoaceto-<i>o</i>-toluidine metabolites in the urine, cell proliferation activities, and DNA damage in the bladder urothelium were similar in non-humanized and humanized-liver mice. RNA expression analysis revealed that CYP1A2 expression increased in the livers of humanized-liver mice, and Cyp2c29 expression (equivalent to human CYP2C9/19) increased in the livers of non-humanized mice. These data suggest that acetoaceto-<i>o</i>-toluidine may be a human carcinogen, as evidenced by the detection of urinary <i>o</i>-toluidine in acetoaceto-<i>o</i>-toluidine-treated humanized-liver mice. This animal model is important for extrapolating toxicity data from animals to humans.</p>

DOI： 10.1293/tox.2024-0042

PubMed

CiNii Research

DOI： 10.1093/toxsci/kfae119

PubMed

DOI： 10.1002/adtp.202400348

DOI： 10.1016/j.jff.2024.106391

DOI： 10.1007/s00204-024-03755-w

PubMed

DOI： 10.1007/s00204-024-03750-1

PubMed

DOI： 10.3390/biom14010036

<p>Introduction</p><p>The acute inhalation toxicity of chemicals is traditionally determined using LD50 values from animal testing. There is a growing call for alternative evaluation methods that rely on <i>in vitro</i> testing and adhere to the 3Rs principle (Replacement, Reduction, and Refinement). This study aims to introduce a new in vitro assay for selecting doses in Trans-Tracheal Intrapulmonary Spraying (TIPS) administration for rats.</p><p></p><p>Methods</p><p>We modified the Neutral Red Uptake Cytotoxicity Assay (OECD GD 129), typically used for predicting oral toxicity, by replacing mouse fibroblast 3T3 cells with the human lung adenocarcinoma cell line A549, thus creating the A549 NRU assay. We established optimal conditions for this assay and evaluated IC50 values for 30 chemicals.</p><p></p><p>Results</p><p>The A549 NRU assay successfully provided IC50 values for 30 chemicals with high reproducibility. Importantly, for six chemicals (Acetylacetone, 1,2-Dichloroethane, N,N-Dimethylacetamide, N-Dimethylformamide, Glycidol, and Polyacrylic Acid 5000), there was a significant correlation between IC50 values from the assay and LD50 values derived from the TIPS method.</p><p></p><p>Conclusion</p><p>The A549 NRU assay demonstrates significant promise as an effective <i>in vitro</i> methodology for dose selection in the administration of TIPS. This assay aligns with the 3Rs principle, offering a more ethical and potentially more efficient approach to determining acute inhalation toxicity.</p>

DOI： 10.14869/toxpt.51.1.0_p-299

CiNii Research