Division of Pathology, National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki, 210-9501, Japan.
Laboratory of Veterinary Pathology, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, 183-8509, Japan.
Arch Toxicol. 2019 Mar;93(3):753-762. doi: 10.1007/s00204-019-02396-8. Epub 2019 Jan 17.
Although aromatic amines are widely used as raw materials for dyes, some of them have been concerned about carcinogenicity in the urinary bladder. We examined early changes in histopathology and the formation of γ-H2AX, a biomarker of DNA damage, in the urinary bladder of rats to investigate the mechanisms of mucosal damage induced by monocyclic aromatic amines. 6-week-old male F344 rats were administered 0.4% or 0.8% o-toluidine, 0.3% or 1.0% o-anisidine, 0.4% 2,4-xylidine, 0.2% p-toluidine, or 0.6% aniline in the diet for 4 weeks. Animals were sequentially killed from day 2 to after 2 weeks of recovery, and histopathological and immunohistochemical analyses were performed. In the 0.8% o-toluidine group, there was sequential progression of bladder lesions, characterized by edematous changes and intramucosal hemorrhage at day 2 and formation of granulation tissue with mononuclear cell infiltration at week 1, followed by diffuse hyperplasia at weeks 2 and 4. In the 1.0% o-anisidine group, simple hyperplasia only with slight inflammation was detected from week 1. Whereas γ-H2AX-positive bladder epithelial cells in the 1.0% o-anisidine group were significantly increased in a time-dependent manner, transient increases in γ-H2AX-positive cells were detected at day 2 and week 1 in the 0.8% o-toluidine group. No apparent bladder lesions or increases in γ-H2AX formation were observed in any other groups. These results revealed different mechanisms of bladder mucosal damage associated with o-toluidine and o-anisidine. Moreover, immunohistochemical analysis for γ-H2AX suggested that both compounds may induce DNA damage in epithelial cells, mainly basal cells, of the bladder mucosa.
尽管芳香胺被广泛用作染料的原料，但其中一些已被关注到具有膀胱癌致癌性。我们研究了单环芳香胺诱导的膀胱黏膜损伤的机制，检查了大鼠膀胱组织病理学的早期变化和 DNA 损伤生物标志物 γ-H2AX 的形成。我们给 6 周龄雄性 F344 大鼠喂食含 0.4%或 0.8%邻甲苯胺、0.3%或 1.0%邻茴香胺、0.4%2,4-二甲氧基甲苯、0.2%对甲苯胺或 0.6%苯胺的饲料，持续 4 周。动物在第 2 天到恢复后 2 周期间依次处死，进行组织病理学和免疫组织化学分析。在 0.8%邻甲苯胺组中，膀胱病变呈顺序进展，表现为第 2 天的水肿变化和黏膜内出血，第 1 周形成有单核细胞浸润的肉芽组织，随后第 2 周和第 4 周出现弥漫性增生。在 1.0%邻茴香胺组中，从第 1 周开始仅检测到单纯增生，伴有轻微炎症。而在 1.0%邻茴香胺组中，γ-H2AX 阳性膀胱上皮细胞呈时间依赖性显著增加，在 0.8%邻甲苯胺组中，第 2 天和第 1 周检测到 γ-H2AX 阳性细胞的短暂增加。在任何其他组中均未观察到明显的膀胱病变或 γ-H2AX 形成增加。这些结果揭示了与邻甲苯胺和邻茴香胺相关的不同膀胱黏膜损伤机制。此外，γ-H2AX 的免疫组织化学分析表明，这两种化合物可能会诱导膀胱黏膜上皮细胞（主要是基底细胞）中的 DNA 损伤。
