摘要

微生物和纳米塑料在水生环境中的广泛存在和积累已成为全球日益关注的问题。通常，天然水生群体的特征在于多种多结构化年龄组，其生理和生化反应通常不同。淡水枝角类水蚤（Daphnia pulex）是一种在环境监测研究和生态毒理学试验中广泛使用的模式物种。这里，测量了聚苯乙烯纳米塑料对该淡水蚤中生理变化（即存活）和应激防御基因（即，编码抗氧化介导和热休克蛋白的那些）的表达水平的影响。来自急性生物测定的结果用于确定五个年龄组（1天，4天，7天，14天和21天的个体）的相应纳米塑性LC50值：获得的1天和21天的值 - 旧的D. pulex组相似（即没有显着差异）。编码关键应激防御酶和蛋白质-SOD，CAT，GST，GPx，HSP70和HSP90-的基因的表达水平受所有年龄组中纳米塑料的影响，但对于每种年龄组不同。在暴露于纳米塑料后，在编码能量敏感酶AMPK（腺苷一磷酸激活的蛋白激酶）α，β和γ的基因的表达中观察到所有年龄组之间的显着差异。此外，相对于对照组，暴露于纳米塑性的1日龄，7日龄和21日龄个体中AMPKα的表达显着增加。总之，这些结果表明，D。pulex的年龄影响其个体对该纳米塑料的污染的敏感性，主要是通过改变生命和生物化学过程，例如细胞能量稳态和氧化，这在体内得到证实。我们推测这种与年龄相关的影响可能会扩展到D. pulex中的其他纳米塑料和污染形式以及类似的海洋生物。

The widespread occurrence and accumulation of micro- and nanoplastics in aquatic environments has become a growing global concern. Generally, natural aquatic populations are characterized by a variety of multi-structured age groups, for which physiological and biochemical responses typically differ. The freshwater cladoceran, Daphnia pulex, is a model species used extensively in environmental monitoring studies and ecotoxicology testing. Here, the effects of a polystyrene nanoplastic on the physiological changes (i.e., survival) and expression levels of stress defense genes (i.e., those encoding antioxidant-mediated and heat shock proteins) in this freshwater flea were measured. Results from acute bioassays were used to determine the respective nanoplastic LC50 values for five age groups (1-, 4-, 7-, 14- and 21-day-old individuals): the obtained values for the 1- and 21-day-old D. pulex groups were similar (i.e., not significantly different). The expression levels of genes encoding key stress defense enzymes and proteins-SOD, CAT, GST, GPx, HSP70, and HSP90-were influenced by the nanoplastic in all the age groups, but not in the same way for each. Significant differences were observed among all age groups in their expression of the gene encoding the energy-sensing enzyme AMPK (adenosine monophosphate-activated protein kinase) α, β, and γ following exposure to the nanoplastic. Moreover, the expression of AMPK α was significantly increased in the 1-, 7-, and 21-day-old individuals exposed to nanoplastic relative to the control group. Together, these results indicate that age in D. pulex affects the sensitivity of its individuals to pollution from this nanoplastic, primarily via alterations to vital physiological and biochemical processes, such as cellular energy homeostasis and oxidation, which were demonstrated in vivo. We speculate that such age-related effects may extend to other nanoplastics and forms of pollution in D. pulex and perhaps similar marine organisms.

https://www.ncbi.nlm.nih.gov/pubmed/30153596