2-NITROSOAMINO-3-METHYLIMIDAZO[4,5-F]QUINOLINE STABILITY AND REACTIVITY

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。N-亚硝胺和亚硝胺会引发癌症。这些研究评估了2-nitrosoamino-3-methylimidazo[4，5-f]quinoline(N-NO-IQ)的稳定性和反应性，以评估其在2-氨基-3-甲基咪唑并[4，5-f]喹啉(IQ)引发结肠癌中的可能作用。将14C-N-NO-IQ与不同的溶剂和PHS在亲核剂存在和不存在的情况下孵育，并用高效液相色谱法进行分析。电喷雾电离质谱仪鉴定的产物包括2-氯-3-甲基咪唑[4，5-f]喹啉(2-Cl-IQ)、2，2‘-偶氮-3，3’-二甲基咪唑[4，5-f]喹啉(AZO-IQ)、2-叠氮基-IQ(2-N3-IQ)、3-甲基咪唑[4，5-f]喹啉(脱氨基-IQ)和IQ。用0.1NHCl对多种有机溶剂进行了测定。所有溶剂酸化后生成2-氯-IQ和IQ。偶氮智商仅在甲醇中生成。除甲醇外，在所有被测试的醇中形成的主要产物是脱氨基-IQ。在5min内将N-NO-IQ完全转化为N-NO-IQ的酸性条件下(乙腈加0.1N HCl)，用二甲基亚砜取代乙腈30min后，N-NO-IQ的残留率为62%。N-NO-IQ在生理pH为5.5-9.0范围内稳定，在pH为7.4和37℃的条件下，4 h内不与亲核性物质发生反应，在酸性pH(pH 2.0)中反应30 min，37℃时，N-NO-IQ形成不稳定的亲和体(S)，与生物相关的亲核性物质结合。N-NO-IQ在pH为2.0时的反应符合一级反应动力学(t1/2=10？2min)，在10 mM NaN3中反应速率显著增加(t1/2=2？0.1min)。2-N3-IQ是后一种孵育的主要产物。在pH为2.0时，N-NO-IQ与DNA的结合比在pH为7.4时高100倍。在pH 2.0时，10 mM NaN3对90%以上的结合有抑制作用。因此，N-NO-IQ在酸性pH下形成反应性电泳体(S)，与DNA结合。N-NO-IQ反应产物可能取决于细胞或组织的pH值和疏水环境。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. N-Nitrosamines and nitrosamides can initiate cancer. These studies evaluated the stability and reactivity of 2-nitrosoamino-3-methylimidazo[4,5-f]quinoline (N-NO-IQ) to assess its possible role in the initiation of colon cancer by 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). 14C-N-NO-IQ was incubated with different solvents and pHs in the presence and in the absence of nucleophiles and analyzed by HPLC. The products identified by electrospray ionization mass spectrometry include 2-chloro-3-methylimidazo[4,5-f]quinoline (2-Cl-IQ), 2,2'-azo-3,3'-dimethylimidazo[4,5-f]quinoline (AZO-IQ), 2-azido-IQ (2-N3-IQ), 3-methylimidazo[4,5-f]quinoline (deamino-IQ), and IQ. A variety of organic solvents were tested with 0.1 N HCl. 2-Cl-IQ and IQ were formed following acidification of all solvents. AZO-IQ was only formed in methanol. Deamino-IQ was the major product formed in all of the alcohols tested, except for methanol. Under acidic conditions that completely convert N-NO-IQ in 5 min (acetonitrile with 0.1 N HCl), 62% of N-NO-IQ remains after 30 min if dimethyl sulfoxide is substituted for acetonitrile. N-NO-IQ was stable in the physiologic pH range of 5.5-9.0 and did not react with nucleophiles over a 4 h period at pH 7.4 and 37 C. At acidic pH (pH 2.0) for 30 min and 37 C, N-NO-IQ becomes labile forming electrophile(s), which combine with biologically relevant nucleophiles. The reaction of N-NO-IQ at pH 2.0 followed first-order kinetics (t1/2 = 10 ¿ 2 min) and was significantly increased in 10 mM NaN3 (t1/2 = 2 ¿ 0.1 min). 2-N3-IQ was the major product observed in the latter incubation. N-NO-IQ binding to DNA at pH 2.0 is 100-fold more than that at pH 7.4. At pH 2.0, greater than 90% of the binding was inhibited by 10 mM NaN3. Thus, N-NO-IQ forms a reactive electrophile(s) at acidic pH, which binds DNA. N-NO-IQ reaction products may depend on the pH and the hydrophobic milieu of cells or tissues.