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17β-estradiol reshapes the reproductive dose–response to polystyrene nanoplastics in the rotifer Brachionus calyciflorus
Original title: 17β-estradiol reshapes the reproductive dose–response to polystyrene nanoplastics in the rotifer Brachionus calyciflorus
Summary
Scientists found that tiny plastic particles (nanoplastics) can have surprisingly different effects on reproduction in tiny water animals depending on whether hormone-disrupting chemicals like estrogen are also present—small amounts of plastic actually boosted offspring numbers, while slightly higher amounts sharply reduced them. This matters because plastics rarely act alone in real-world water systems; they mix with other chemicals like hormones from pharmaceuticals or personal care products, and this study shows those combinations can produce unpredictable health effects that wouldn't show up if scientists only tested plastic pollution by itself
Nanoplastics (NPs) sorb co-occurring contaminants, yet how endocrine-disrupting chemicals condition NP toxicity remains poorly resolved. Using the freshwater rotifer Brachionus calyciflorus, we combined a full-factorial design of 70 nm polystyrene NPs and 17β-estradiol (E2) with a focused NP concentration gradient under a fixed E2 background of 300 μg L. Two-way ANOVA revealed significant E2 × NPs interactions for lifespan, total offspring, and final population density, indicating background-dependent NP effects. At E2 = 300 μg L, low-dose NPs (1 μg mL) increased total offspring by 18.29 % relative to E300N0, whereas 5 μg mL decreased total offspring by 32.20 %, producing a non-monotonic dose-response curve. A Gaussian fit located the stimulation peak at 1.11 μg mL and an approximate transition point at 2.50 μg mL. Corrected relative internal fluorescence during 0-4 h post-transfer was higher in E300N5 than in N5. Oil Red O staining and triglyceride assays indicated neutral lipid depletion across treatments, and qPCR showed tor downregulation specific to E300N5, alongside suppression of rar/rxr and the reproduction-related markers vasa and nanos. Collectively, these findings identify endocrine background as a state variable capable of reshaping nanoplastic reproductive toxicity, with implications for mixture-risk assessment in aquatic invertebrates.