Todorovic R, Devanesan P, Higginbotham S, Zhao J, Gross M L, Rogan E G, Cavalieri E L
Eppley Institute for Research in Cancer and Allied Diseases, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, USA.
Carcinogenesis. 2001 Jun;22(6):905-11. doi: 10.1093/carcin/22.6.905.
Estrone (E1) and 17beta-estradiol (E2) are metabolized to catechol estrogens (CE), which may be oxidized to semiquinones and quinones (CE-Q). CE-Q can react with glutathione (GSH) and DNA, or be reduced to CE. In particular, CE-3,4-Q react with DNA to form depurinating adducts (N7Gua and N3Ade), which are cleaved from DNA to leave behind apurinic sites. We report the determination of 22 estrogen metabolites, conjugates and adducts in the urine of male Syrian golden hamsters treated with 4-hydroxyestradiol (4-OHE2). After initial purification, urine samples were analyzed by HPLC with multichannel electrochemical detection and by capillary HPLC/tandem mass spectrometry. 4-Hydroxyestrogen-2-cysteine [4-OHE1(E2)-2-Cys] and N-acetylcysteine [4-OHE1(E2)-2-NAcCys] conjugates, as well as the methoxy CE, were identified and quantified by HPLC, whereas the 4-OHE1(E2)-1-N7Gua depurinating adducts and 4-OHE1(E2)-2-SG conjugates could only be identified by the mass spectrometry method. Most of the administered 4-OHE2 was metabolically converted to 4-OHE1. Formation of thioether (GSH, Cys and NAcCys) conjugates and depurinating adducts [4-OHE1(E2)-1-N7Gua] indicates that oxidation of 4-CE to CE-3,4-Q and subsequent reaction with GSH and DNA, respectively, do occur. The major conjugates in the urine were 4-OHE1(E2)-2-NACCYS: The oxidative pathway of 4-OHE1(E2) accounted for approximately twice the level of products compared with those from the methylation pathway. The metabolites and methoxy CE were excreted predominantly (>90%) as glucuronides, whereas the thioether conjugates were not further conjugated. These results provide strong evidence that exposure to 4-OHE1(E2) leads to the formation of E1(E2)-3,4-Q and, subsequently, depurinating DNA adducts. This process is a putative tumor initiating event. The estrogen metabolites, conjugates and adducts can be used as biomarkers for detecting enzymatic oxidation of estrogens to reactive electrophilic metabolites and possible susceptibility to estrogen-induced cancer.
雌酮（E1）和17β-雌二醇（E2）可代谢生成儿茶酚雌激素（CE），后者可被氧化为半醌和醌（CE-Q）。CE-Q可与谷胱甘肽（GSH）和DNA反应，或被还原为CE。特别是，CE-3,4-Q与DNA反应形成脱嘌呤加合物（N7鸟嘌呤和N3腺嘌呤），这些加合物从DNA上裂解下来，留下无嘌呤位点。我们报告了在用4-羟基雌二醇（4-OHE2）处理的雄性叙利亚金仓鼠尿液中22种雌激素代谢物、结合物和加合物的测定情况。经过初步纯化后，尿液样本通过高效液相色谱-多通道电化学检测以及毛细管高效液相色谱/串联质谱进行分析。4-羟基雌激素-2-半胱氨酸[4-OHE1（E2）-2-Cys]和N-乙酰半胱氨酸[4-OHE1（E2）-2-NAcCys]结合物以及甲氧基CE通过高效液相色谱进行鉴定和定量，而4-OHE1（E2）-1-N7鸟嘌呤脱嘌呤加合物和4-OHE1（E2）-2-SG结合物只能通过质谱法进行鉴定。大部分给予的4-OHE2在代谢上转化为4-OHE1。硫醚（GSH、半胱氨酸和N-乙酰半胱氨酸）结合物和脱嘌呤加合物[4-OHE1（E2）-1-N7鸟嘌呤]的形成表明，4-CE分别氧化为CE-3,4-Q以及随后与GSH和DNA反应确实发生。尿液中的主要结合物是4-OHE1（E2）-2-NACCYS：4-OHE1（E2）的氧化途径产生的产物水平约为甲基化途径的两倍。代谢物和甲氧基CE主要（>90%）以葡萄糖醛酸苷的形式排泄，而硫醚结合物则不再进一步结合。这些结果提供了强有力的证据，表明暴露于4-OHE1（E2）会导致E1（E2）-3,4-Q的形成，并随后导致脱嘌呤DNA加合物的形成。这一过程是一种假定的肿瘤起始事件。雌激素代谢物、结合物和加合物可作为生物标志物，用于检测雌激素酶促氧化为反应性亲电代谢物以及对雌激素诱导癌症的可能易感性。
