摘要
生物可降解塑料在自然环境中难以完全矿化,易在地表水体和土壤等介质中持续破碎形成微塑料,从而对生态系统健康构成潜在威胁。本研究以热带爪蟾(Xenopus tropicalis)为模型生物,系统评估了紫外老化聚己二酸/对苯二甲酸丁二酯(PBAT)微塑料在胚胎、蝌蚪和成蛙3个不同发育阶段的毒性差异。实验使用紫外老化程度相当于野外暴露半年后的PBAT微塑料[平均尺寸:(238±66.7)μm],设置覆盖环境相关至高风险预测范围的暴露浓度,并结合各阶段的生态习性,分别通过水体暴露(胚胎与蝌蚪)和食物暴露(成蛙)模拟真实环境场景。结果表明,PBAT微塑料的毒性具有明显的发育阶段依赖性。48 h胚胎暴露未导致孵化率、存活率及畸形率发生显著变化,可能由于绒毛膜对微米级颗粒具有物理阻隔作用。蝌蚪阶段为毒性敏感窗口。21 d水体暴露表现出典型的毒物兴奋效应(hormesis):中、高浓度导致存活率下降,而体长与体质量呈“低促高抑”趋势。肠道中微塑料呈剂量依赖性积累,并伴随肠壁分离及破损等组织病理损伤;同时氧化应激水平升高,促炎因子TNF-α基因表达上调,紧密连接蛋白Occludin与Claudin-1基因的表达发生改变。蝌蚪变态发育显著加速,提示其可能通过提前变态的发育策略以应对胁迫环境。潜在机制可能包括2条途径:一是物理性损伤,即摄入的微塑料在肠腔积累引起机械磨损和上皮结构破坏;二是化学性应激,源于整体暴露于含高浓度老化PBAT微塑料及其降解产物(如寡聚物、单体)的水体环境,从而诱导氧化应激、炎症反应及紧密连接蛋白相关基因的表达重塑。成蛙阶段在21 d食物暴露后表现出较强耐受性。尽管其微塑料摄入量高于蝌蚪,但仅在最高浓度组出现轻微肠道组织学变化,未引发生长或分子水平的显著扰动。这可能与成蛙更完善的解毒代谢系统及食物暴露方式对降解产物接触的限制有关。本研究强调,在评估生物可降解微塑料的生态风险时,需充分考虑不同发育阶段及暴露途径的差异。未来研究应重点关注其长期和跨代效应,并进一步解析纳米级颗粒与化学溶出物的相对毒性影响。
Biodegradable plastics are difficult to achieve complete mineralization in natural environments and tend to continuously fragment into microplastics(MPs)in surface waters and soils,posing potential threats to the health of ecosystem.In this study,Xenopus tropicalis was used as a model organism to systematically evaluate its stage-dependent toxic effects of ultraviolet(UV)-aged poly(butylene adipate-co-terephthalate)(PBAT)MPs during three key developmental stages,including embryo,tadpole,and adult ones.Tested PBAT MPs were of an aging degree approximately equivalent to six months of natural weathering.The average size was(238±66.7)μm.Exposure c oncentrations ranged from environmentally relevant to predicted high-risk levels,and exposure scenarios were d esigned according to the ecological habits of each stage:waterborne exposure for embryos and tadpoles,and d ietary exposure for adults to better simulate realistic environmental conditions.The results revealed a distinct d evelopmental stage-dependent toxicity of PBAT MPs.After a 48-hour embryonic exposure,no significant changes were observed in hatching,survival,or malformation rates,likely due to the physical barrier effect of the chorionic membrane against micrometer-sized particles.The tadpole stage represented a sensitive window:a 21-day w aterborne exposure induced a hormetic response,with decreased survival rates at medium and high concentrations and a“low-dose stimulation,high-dose inhibition”trend in body length and weight.PBAT MPs accumulated in the intestine in a dose-dependent manner,accompanied by histopathological lesions(e.g.,epithelial separation and structural disruption of the intestinal wall).Oxidative stress levels increased,TNF-α expression was up-regulated,and the tight-junction proteins Occludin and Claudin-1 were dysregulated.Metamorphosis was markedly accelerated,s uggesting a stress-induced developmental response.The two major potential mechanisms underlying these effects were physical injury,where ingested MPs accumulate in the intestinal lumen causing mechanical abrasion and epithelial damage,and chemical stress,resulting from exposure to water containing high concentrations of aged PBAT MPs and their degradation products(e.g.,oligomers and monomers),which induces oxidative stress,inflammatory responses,and alterations in tight-junction protein gene expression.In contrast,adult frogs showed greater tolerance after 21 days of dietary exposure:despite higher MPs intake than tadpoles,only mild intestinal histological changes were observed at the highest concentration,with no significant changes in growth or molecular biomarkers.This resilience may reflect a more developed detoxification capacity in adults and reduced contact with leachable degradation products under dietary exposure.This study highlights the importance of considering both developmental stage and exposure pathway when assessing the ecological risks of MPs.Future research should focus on their long-term and transgenerational effects and further elucidate the relative toxic contributions of nanoscale particles and chemical leachates.
作者
张雨
杜金玉
胡玲玲
ZHANG Yu;DU Jinyu;HU Lingling(Zhejiang Key Laboratory of Low-carbon Control Technology for Industrial Pollution,College of Environment,Zhejiang University of Technology,Hangzhou 310014,China)
出处
《生态毒理学报》
北大核心
2025年第6期13-24,共12页
Asian Journal of Ecotoxicology
基金
国家自然科学基金青年科学基金项目(42107296)
浙江省自然科学基金探索项目(LQ21D010010)。
关键词
生物可降解塑料
热带爪蟾
综合毒性
发育阶段特异性
biodegradable plastics
Xenopus tropicalis
comprehensive toxicity
different developmental stages
