Center for Environmental Health, Department of Pharmacology and Toxicology, Indiana University School of Medicine, 980 W. Walnut Street, C132, Indianapolis, IN 46202, USA.
Toxicology. 2010 Apr 11;270(2-3):131-6. doi: 10.1016/j.tox.2010.02.006. Epub 2010 Feb 11.
2-Butoxyethanol increases hemangiosarcomas selectively in male mouse liver after chronic inhalation through mechanisms that have not fully been elucidated. Hemolysis, a primary toxic effect associated with 2-butoxyethanol exposure in rodents, increased hemosiderin (iron) deposition in Kupffer cells in the liver. These findings, along with the induction of hepatic neoplastic lesions, led to our hypothesis that the induction hemangiosarcomas by 2-butoxyethanol is due to the activation of Kupffer cells, subsequent to hemolysis, that results in the induction of DNA synthesis in target cells (endothelial cells); allowing for the selective proliferation of preneoplastic target cells and/or the promotion of new initiated cells. The present studies were conducted to determine whether Kupffer cells contributed to 2-butoxyethanol-induced endothelial DNA synthesis in the liver, thereby determining whether a linkage exists between these events. Male B6C3F1 mice were treated with 450 and 900 mg/kg 2-butoxyethanol (via daily gavage; 5x/week) for 7 days in the presence or absence of Kupffer cell depletion (via clodronate-encapsulated liposomes). 2-Butoxyethanol (450 and 900 mg/kg/day) increased the number of F4/80 stained cells (Kupffer cells) compared to controls (approximately 1.3- and approximately 1.6-fold over control, respectively). Clodronate liposome treatment reduced the number of Kupffer cells by >90%, as assessed by F4/80 immunohistochemistry. Increased hemolysis, measured by increases in relative spleen weights and decreased hematocrit was confirmed in 2-butoxyethanol treated mice. The percentage of iron-stained endothelial cells increased by approximately 11-fold over control, and endothelial cell DNA synthesis increased approximately 1.7-fold over control in 2-butoxyethanol exposed mice. Importantly, Kupffer cell depletion reduced 2-butoxyethanol-induced iron staining and hepatic endothelial cell DNA synthesis. These studies provide evidence supporting the hypothesis that the Kupffer cell modulates 2-butoxyethanol-induced endothelial cell DNA synthesis, and therefore may contribute to hemangiosarcoma induction by 2-butoxyethanol.
2-丁氧基乙醇通过尚未完全阐明的机制，在雄性小鼠肝脏中经慢性吸入选择性增加血管肉瘤。溶血，与啮齿动物 2-丁氧基乙醇暴露相关的主要毒性作用，增加了肝脏库普弗细胞中的血铁黄素（铁）沉积。这些发现，以及肝肿瘤病变的诱导，导致我们的假设，即 2-丁氧基乙醇诱导血管肉瘤是由于溶血后库普弗细胞的激活，导致靶细胞（内皮细胞）中的 DNA 合成诱导；允许前肿瘤靶细胞的选择性增殖和/或新起始细胞的促进。进行本研究是为了确定库普弗细胞是否有助于 2-丁氧基乙醇诱导肝脏内皮细胞的 DNA 合成，从而确定这些事件之间是否存在联系。雄性 B6C3F1 小鼠用 450 和 900 mg/kg 2-丁氧基乙醇（通过每日灌胃；每周 5 次）处理，在存在或不存在库普弗细胞耗竭（通过氯膦酸盐包裹的脂质体）的情况下处理 7 天。与对照组相比，2-丁氧基乙醇（450 和 900 mg/kg/天）增加了 F4/80 染色细胞（库普弗细胞）的数量（分别约为对照的 1.3 倍和 1.6 倍）。F4/80 免疫组织化学评估表明，氯膦酸盐脂质体处理使库普弗细胞数量减少了>90%。通过相对脾脏重量增加和红细胞压积降低证实了 2-丁氧基乙醇处理小鼠的溶血增加。与对照组相比，铁染色的内皮细胞百分比增加了约 11 倍，2-丁氧基乙醇暴露小鼠的内皮细胞 DNA 合成增加了约 1.7 倍。重要的是，库普弗细胞耗竭减少了 2-丁氧基乙醇诱导的铁染色和肝内皮细胞 DNA 合成。这些研究提供了证据支持库普弗细胞调节 2-丁氧基乙醇诱导的内皮细胞 DNA 合成的假设，因此可能有助于 2-丁氧基乙醇诱导血管肉瘤。
