环境浓度下壬基酚对秀丽隐杆线虫时间依赖性的毒性兴奋效应

为研究暴露时间对壬基酚生态毒理学效应的影响,选取秀丽隐杆线虫(Caenorhabditis elegans)作为受试生物,采用急性(24 h和72 h)、慢性(10 d) 3个不同时间点,进行壬基酚环境浓度下(0、0.0001、0.001、0.01、0.1、0.2 mg·L~(-1))的暴露实验,以秀丽隐杆线虫的生理指标(体长、运动行为)、生化指标(氧化应激、细胞凋亡、脂褐素)为终点进行评估。结果表明:急性暴露24 h后,活性氧自由基(ROS)在0.01 mg·L~(-1)时即出现了明显的下降,其他生理生化指标无统计学意义上的明显变化。72 h暴露条件下,体长随壬基酚浓度的增加呈现倒U型趋势,在0.0001 mg·L-1时表现出最大刺激效应,比对照组高出26.4%(P0.01);头部摆动频率和身体弯曲频率在2个较高浓度(0.1和0.2 mg·L~(-1))时表现出明显的刺激效应;细胞凋亡水平在0.0001 mg·L~(-1)时显著性下降,呈现负剂量-效应关系(P0.05),在0.2 mg·L~(-1)时表现出最大刺激效应,比对照组降低了45.5%; ROS及脂褐素在壬基酚暴露浓度范围内呈正相关性增加。慢性暴露条件下,脂褐素在0.001 mg·L~(-1)时表现出最大效应,和对照组相比下降了65.4%,并且随着壬基酚浓度的增加呈现U型趋势;其他生理生化指标随着壬基酚浓度的增加表现出明显的负面效应。研究揭示了环境浓度水平的壬基酚对秀丽隐杆线虫的生态毒理效应是时间依赖性的,急性暴露以引起刺激作用为主,表现为毒性兴奋效应,而长期暴露后壬基酚对生理生化指标的负面效应更为明显。上述结果为进行壬基酚的毒性评价及更好地理解其毒性作用机理提供基础数据。

Time-dependent Hormetic Effects of Nonylphenol on Caenorhabditis elegans under Environmental Concentrations

In order to investigate time-dependent ecotoxicological effects of nonylphenol (NP), Caenorhabditis elegans, as the model organism, was exposed under different time against the background of environmental concentrations of NP (0, 0.0001, 0.001, 0.01, 0.1, 0.2 mg L^-1), including acute (24 h and 72 h), chronic (10 d) exposure. The physiological indicators (body length, locomotive behaviors), biochemical indicators (oxidative stress, apoptosis, lipofuscin) of Caenorhabditis elegans were evaluated as endpoints. The results indicated that under acute exposure condition (24 h), the level of reactive oxygen species (ROS) at 0.01 mg L^-1 NP displayed a significant decrease, but other physiological and biochemical indexes did not show statistically significant changes. Under 72 h exposure condition, body length showed an inverted U-shaped trend with the increase of NP concentration and the maximum stimulatory effect was observed at 0.0001 mg L^-1, which was 26.4% higher than the control group (P<0.01); the frequency of head threshes and body bends showed significantly stimulatory effect at 0.1 and 0.2 mg L^-1; the apoptosis was significantly decreased at 0.0001 mg L^-1, displaying a negative dose-effect relationship (P<0.05), and the maximum stimulatory effect was observed at 0.2 mg L^-1 which was 45.5% lower than the control group. Under chronic exposure condition, lipofuscin content showed a U-shaped tendency with the increase of NP concentration exhibiting the maximum effect at 0.001 mg L^-1, which was 65.4% lower compared to the control group; however, other physiological and biochemical indexes showed a negative effect with the increase of NP concentration. The present study revealed that the environmental toxicological effects of NP on Caenorhabditis elegans were time-dependent. The influence after acute exposure of NP for C. elegans were mainly stimulatory and showed hormetic effects. However, the negative effect on physiological and biochemical indicators after chronic exposure was more pronounced. The results provide basic data for evaluating toxicity of nonylphenol and better understanding its toxic mechanism.