Corthals Stacy M, Kamendulis Lisa M, Klaunig James E
Department of Pharmacology and Toxicology, Division of Toxicology, Indiana University School of Medicine, Indianapolis, 46202, USA.
Toxicol Sci. 2006 Aug;92(2):378-86. doi: 10.1093/toxsci/kfl007. Epub 2006 May 4.
Chronic exposure to 2-butoxyethanol increased liver hemangiosarcomas in male mice. The mechanism for the selective induction of hemangiosarcomas by 2-butoxyethanol is unknown but has been suggested to occur through non-DNA-reactive mechanisms. The occurrence of liver hemangiosarcomas in male mice has been linked to oxidative damage subsequent to RBC hemolysis and iron deposition and activation of macrophages (Kupffer cells) in the liver, events that exhibit a threshold in both animals and humans. 2-Butoxyethanol is metabolized to 2-butoxyacetaldehyde and 2-butoxyacetic acid, and although the aldehyde metabolite is short lived, the potential exists for this metabolite to cause DNA damage. The present study examined whether 2-butoxyethanol and its metabolites, 2-butoxyacetaldehyde and 2-butoxyacetic acid, damaged mouse endothelial cell DNA using the comet assay. No increase in DNA damage was observed following 2-butoxyethanol (1-10mM), 2-butoxyacetaldehyde (0.1-1.0mM), or 2-butoxyacetic acid (1-10mM) in endothelial cells after 2, 4, or 24 h of exposure. Additional studies examined the involvement of hemolysis and macrophage activation in 2-butoxyethanol carcinogenesis. DNA damage was produced by hemolyzed RBCs (10 x 10(6), 4 h), ferrous sulfate (0.1-1.0 microM; 2-24 h), and hydrogen peroxide (50-100 microM; 1-4 h) in endothelial cells. Hemolyzed RBCs also activated macrophages, as evidenced by increased tumor necrosis factor (TNF) alpha, while neither 2-butoxyethanol nor butoxyacetic acid increased TNF-alpha from macrophages. The effect of activated macrophages on endothelial cell DNA damage and DNA synthesis was also studied. Coculture of endothelial cells with activated macrophages increased endothelial cell DNA damage after 4 or 24 h and increased endothelial cell DNA synthesis after 24 h. These data demonstrate that 2-butoxyethanol and related metabolites do not directly cause DNA damage. Supportive evidence also demonstrated that damaged RBCs, iron, and/or products from macrophage activation (possibly reactive oxygen species) produce DNA damage in endothelial cells and that activated macrophages stimulate endothelial cell proliferation. These events coupled together provide the events necessary for the induction of hemangiosarcomas by 2-butoxyethanol.
长期接触2-丁氧基乙醇会增加雄性小鼠肝脏血管肉瘤的发生。2-丁氧基乙醇选择性诱导血管肉瘤的机制尚不清楚，但有人认为其通过非DNA反应性机制发生。雄性小鼠肝脏血管肉瘤的发生与红细胞溶血、铁沉积以及肝脏中巨噬细胞（库普弗细胞）激活后的氧化损伤有关，这些事件在动物和人类中均表现出阈值。2-丁氧基乙醇代谢为2-丁氧基乙醛和2-丁氧基乙酸，虽然醛代谢产物寿命短暂，但该代谢产物仍有可能导致DNA损伤。本研究使用彗星试验检测了2-丁氧基乙醇及其代谢产物2-丁氧基乙醛和2-丁氧基乙酸是否会损伤小鼠内皮细胞DNA。在内皮细胞暴露2、4或24小时后，未观察到2-丁氧基乙醇（1-10mM）、2-丁氧基乙醛（0.1-1.0mM）或2-丁氧基乙酸（1-10mM）导致DNA损伤增加。其他研究检测了溶血和巨噬细胞激活在2-丁氧基乙醇致癌过程中的作用。溶血红细胞（10×10⁶，4小时）、硫酸亚铁（0.1-1.0微摩尔；2-24小时）和过氧化氢（50-100微摩尔；1-4小时）在内皮细胞中产生了DNA损伤。溶血红细胞还激活了巨噬细胞，肿瘤坏死因子（TNF）α增加即为证据，而2-丁氧基乙醇和丁氧基乙酸均未使巨噬细胞的TNF-α增加。还研究了激活的巨噬细胞对内皮细胞DNA损伤和DNA合成的影响。内皮细胞与激活的巨噬细胞共培养4或24小时后，内皮细胞DNA损伤增加，24小时后内皮细胞DNA合成增加。这些数据表明，2-丁氧基乙醇及其相关代谢产物不会直接导致DNA损伤。支持性证据还表明，受损的红细胞、铁和/或巨噬细胞激活产物（可能是活性氧）在内皮细胞中产生DNA损伤，且激活的巨噬细胞刺激内皮细胞增殖。这些事件共同构成了2-丁氧基乙醇诱导血管肉瘤所需的条件。
