Abstract Cotinine is the main metabolite of nicotine, which is metabolized in the liver through a cytochrome P450 enzyme. Different studies point to genetic instability caused by nicotine, such as single and double DNA strand breaks and micronuclei formation, but little is known about the effect of cotinine. Therefore, the present in vitro study assessed the effects of cotinine on cell viability and DNA damage in SH-SY5Y neuroblastoma cells, as well as genotoxicity related to oxidative stress mechanisms. Comparisons with nicotine were also performed. An alkaline comet assay modified by repair endonucleases (FPG, OGG1, and Endo III) was used to detect oxidized nucleobases. SH-SY5Y neuronal cells were cultured under standard conditions and exposed for 3 h to different concentrations of cotinine and nicotine. Cytotoxicity was observed at higher doses of cotinine and nicotine in the MTT assay. In the trypan blue assay, cells showed viability above 80% for both compounds. Alkaline comet assay results demonstrated a significant increase in damage index and frequency for cells treated with cotinine and nicotine, presenting genotoxicity. The results of the enzyme-modified comet assay suggest a DNA oxidative damage induced by nicotine. Unlike other studies, our results demonstrated genotoxicity induced by both cotinine and nicotine. The similar effects observed for these two pyridine alkaloids may be due to the similarity of their structures.

中文翻译：

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使用人神经母细胞瘤细胞 (SH-SY5Y) 对可替宁进行细胞毒性和基因毒性评估

摘要 可替宁是尼古丁的主要代谢产物，通过细胞色素 P450 酶在肝脏中代谢。不同的研究指出尼古丁引起的遗传不稳定性，例如单双 DNA 链断裂和微核形成，但对可替宁的影响知之甚少。因此，目前的体外研究评估了可替宁对 SH-SY5Y 神经母细胞瘤细胞活力和 DNA 损伤的影响，以及与氧化应激机制相关的基因毒性。还进行了与尼古丁的比较。通过修复核酸内切酶（FPG、OGG1 和 Endo III）改进的碱性彗星试验用于检测氧化的核碱基。SH-SY5Y 神经元细胞在标准条件下培养并暴露于不同浓度的可替宁和尼古丁中 3 小时。在 MTT 试验中，在较高剂量的可替宁和尼古丁下观察到细胞毒性。在台盼蓝试验中，两种化合物的细胞存活率均高于 80%。碱性彗星试验结果表明，用可替宁和尼古丁处理的细胞的损伤指数和频率显着增加，表现出基因毒性。酶修饰彗星试验的结果表明尼古丁诱导了 DNA 氧化损伤。与其他研究不同，我们的结果证明了可替宁和尼古丁均诱导的基因毒性。对这两种吡啶生物碱观察到的相似效果可能是由于它们的结构相似。碱性彗星试验结果表明，用可替宁和尼古丁处理的细胞的损伤指数和频率显着增加，表现出基因毒性。酶修饰彗星试验的结果表明尼古丁诱导了 DNA 氧化损伤。与其他研究不同，我们的结果证明了可替宁和尼古丁均诱导的基因毒性。对这两种吡啶生物碱观察到的相似效果可能是由于它们的结构相似。碱性彗星试验结果表明，用可替宁和尼古丁处理的细胞的损伤指数和频率显着增加，表现出基因毒性。酶修饰彗星试验的结果表明尼古丁诱导了 DNA 氧化损伤。与其他研究不同，我们的结果证明了可替宁和尼古丁均诱导的基因毒性。对这两种吡啶生物碱观察到的相似效果可能是由于它们的结构相似。