Objective: To investigate the effects and mechanisms of equol and its enantiomers on urethane-induced lung cancer in mice.
Methods: A total of 120 5-week-old male C57BL/6 mice were randomly divided into 8 groups: lung cancer tumor control group (CG), genistein control group (GCG), low dose racemic equol group (LEG), high dose racemic equol group (HEG), low dose R-equol group (LRE), high dose R-equol group (HRE), low dose S-equol group (LSE) and high dose S-equol group (HSE). Urethane was injected subcutaneously twice a week for 4 weeks to induce lung cancer and then the mice were fed for 4 months. The body weight and food intake of each group were measured and recorded weekly. After the mice were sacrificed, the blood, livers and lungs of the mice were collected. The incidence of lung cancer in each group was recorded. The concentration of serum superoxide dismutase (SOD), malondialdehyde (MDA) and 8-hydroxydeoxygunosine (8-OHdG) were detected by the corresponding kits. Western blotting was used to detect the expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) in the livers. Between-group differences in body weight and food intake of the mice were compared using repeated measures ANOVA, and ANOVA for the differences between non-repeated measurements, with post hoc analysis using Tukey's method if there were between-group differences. Comparisons of categorical data were performed by chi-square test, and if there were differences between the groups, the Bonferroni method was used for pairwise comparison.
Results: A total of 49 in the 120 mice developed lung cancer. The overall incidence of lung cancer was 40.8%. Compared with the control group, the incidence of lung cancers in each experimental group was lower, and the difference was statistically significant. The incidence of lung cancer in the high-dose experimental group was significantly lower than that in the low-dose experimental group. However, the incidence of lung cancer was similar in the three equol groups and the genistein group at the same dose. Compared with the control group, the high-dose experimental group had higher serum SOD concentration, lower MDA and 8-OHdG concentrations, and the differences were statistically significant. Western blotting analysis showed that the expression levels of Nrf2 protein in the experimental groups were higher than those in the control group except the low-dose racemic equol group, and the Nrf2 protein expression level in the high-dose equol groups was higher than that in the low-dose equol groups.
Conclusion: Racemic equol and its enantiomers mayinhibit lung carcinogenesis through antioxidant effects.
目的: 探讨外消旋雌马酚及其对应异构体对乌拉坦诱导小鼠肺癌的影响及其可能机制。
方法: 120只小鼠随机分为8组，实验组予以染料木素或不同剂量的雌马酚，每周2次连续4周皮下注射乌拉坦后测量并记录各组小鼠体质量、摄食量和肺癌发生率。处死小鼠后收集小鼠血液、肝和肺，用相应的试剂盒检测血清中超氧化物歧化酶(superoxide dismutase, SOD)、丙二醛(malondialdehyde, MDA)和8-羟基脱氧鸟嘌呤(8-hydroxydeoxygunosine, 8-OHdG)的含量，蛋白免疫印迹法检测肝中核因子红系2相关因子2[nuclear factor(erythroid-derived 2)-like 2, Nrf2]的表达。
结果: 120只小鼠中49只出现肺癌，肺癌总体发生率为40.8%。与喂养基础饲料的对照组相比，各实验组肺癌发生率均更低，且差异具有统计学意义，同种药物高剂量实验组肺癌发生率显著低于低剂量实验组，但是同等剂量下3种雌马酚组和染料木素组小鼠肺癌发生率相当。与对照组相比，高剂量实验组小鼠血清中SOD含量更高，MDA和8-OHdG的含量更低，且差异具有统计学意义。蛋白免疫印迹检测结果显示，除低剂量外消旋雌马酚组外其余各组小鼠的Nrf2蛋白表达水平均高于对照组小鼠，并且同种药物高剂量雌马酚组的Nrf2蛋白表达水平高于低剂量雌马酚组。
结论: 雌马酚及其对应异构体可能通过抗氧化效应抑制肺癌的发生。
Keywords: Antioxidant activity; Equol; Equol enantiomers; Lung cancer; Nuclear factor (erythroid-derived 2)-like 2 (Nrf2).