Vermeer Ingrid T M, Henderson Laila Y, Moonen Edwin J C, Engels Leopold G J B, Dallinga Jan W, van Maanen Jan M S, Kleinjans Jos C S
Department of Health Risk Analysis and Toxicology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands.
Toxicol Lett. 2004 Dec 30;154(3):175-82. doi: 10.1016/j.toxlet.2004.07.013.
In order to study neutrophil-mediated formation of carcinogenic N-nitroso compounds as a mechanism of inflammation-related colon carcinogenesis, we designed an in vitro model for intestinal inflammation, consisting of a coincubation system with human colon cells (Caco-2 cells) and activated human neutrophils (PMN), as important immunoreactive cells. We investigated whether nitrosamines and nitrosamides could be formed upon addition of dimethylamine, morpholine and methylurea to the coincubations as nitrosatable precursors, which are known to produce carcinogenic N-nitroso compounds. Incubations of pure nitric oxide with dimethylamine and morpholine showed that NO-mediated formation of nitrosodimethylamine and nitrosomorpholine is possible under the incubation conditions. During the coincubations of activated PMN and Caco-2 cells, 0.34 nmol nitrite/10(6) PMN was produced. Dose-dependent formation of NMOR was observed in this PMN/Caco-2 system; addition of 5mM morpholine resulted in a significantly increased NMOR formation of 4.2 nM. However, no detectable NDMA and methylnitrosourea were formed in this coincubation system. These results suggest that activated human neutrophils are able to synthesize carcinogenic N-nitrosamines, e.g. NMOR, which implies a risk of colon carcinogenesis during chronic inflammation. However, the observed relatively low level of nitrosation suggests that also other risk factors are contributing to the association between chronic inflammation and colon cancer risk.
为了研究中性粒细胞介导的致癌性N-亚硝基化合物的形成作为炎症相关结肠癌发生的机制，我们设计了一种肠道炎症的体外模型，该模型由人结肠细胞（Caco-2细胞）与活化的人中性粒细胞（PMN）（作为重要的免疫反应细胞）共同孵育系统组成。我们研究了在共同孵育体系中加入二甲胺、吗啉和甲基脲作为可亚硝化前体（已知可产生致癌性N-亚硝基化合物）后是否能形成亚硝胺和亚硝酰胺。纯一氧化氮与二甲胺和吗啉的孵育表明，在孵育条件下，NO介导的亚硝基二甲胺和亚硝基吗啉的形成是可能的。在活化的PMN和Caco-2细胞共同孵育期间，产生了0.34 nmol亚硝酸盐/10(6) PMN。在该PMN/Caco-2系统中观察到NMOR呈剂量依赖性形成；加入5mM吗啉导致NMOR形成显著增加至4.2 nM。然而，在该共同孵育系统中未检测到NDMA和甲基亚硝基脲的形成。这些结果表明，活化的人中性粒细胞能够合成致癌性N-亚硝胺，例如NMOR，这意味着在慢性炎症期间存在结肠癌发生的风险。然而，观察到的相对较低的亚硝化水平表明，其他风险因素也在慢性炎症与结肠癌风险之间的关联中起作用。
