Environmentally relevant concentrations of benzophenones exposure disrupt intestinal homeostasis, impair the intestinal barrier, and induce inflammation in mice

The aim of this study is to investigate the adverse effects of benzophenones (BPs) on the intestinal tract of mice and the potential mechanism. F1-generation ICR mice were exposed to BPs (benzophenone-1, benzophenone-2, and benzophenone-3) by breastfeeding from birth until weaning, and by drinking water after weaning until maturity. The offspring mice were executed on postnatal day 56, then their distal colons were sampled. AB-PAS staining, HE staining, immunofluorescence, Transmission Electron Microscope, immunohistochemistry, western blot and RT-qPCR were used to study the effects of BPs exposure on the colonic tissues of offspring mice. The results showed that colonic microvilli appeared significantly deficient in the high-dose group, and the expression of tight junction markers Zo-1 and Occludin was significantly down-regulated and the number of goblet cells and secretions were reduced in all dose groups, and the expression of secretory cell markers MUC2 and KI67 were decreased, as well as the expression of intestinal stem cell markers Lgr5 and Bmi1, suggesting that BPs exposure caused disruption of intestinal barrier and imbalance in the composition of the intestinal stem cell pool. Besides, the expression of cellular inflammatory factors such as macrophage marker F4/80 and tumor necrosis factor TNF-α was elevated in the colonic tissues of all dose groups, and the inflammatory infiltration was observed, which means the exposure of BPs caused inflammatory effects in the intestinal tract of F1-generation mice. In addition, the contents of Notch/Wnt signaling pathway-related genes, such as Dll-4, Notch1, Hes1, Ctnnb1and Sfrp2 were significantly decreased in each high-dose group (P < 0.05), suggesting that BPs may inhibit the regulation of Notch/Wnt signaling pathway. In conclusion, exposure to BPs was able to imbalance colonic homeostasis, disrupt the intestinal barrier, and trigger inflammation in the offspring mice, which might be realized through interfering with the Notch/Wnt signaling pathway.

Combined Effects of Micro- and Nanoplastics at the Predicted Environmental Concentration on Functional State of Intestinal Barrier in Caenorhabditis elegans

The possible toxicity caused by nanoplastics or microplastics on organisms has been extensively studied. However, the unavoidably combined effects of nanoplastics and microplastics on organisms, particularly intestinal toxicity, are rarely clear. Here, we employed Caenorhabditis elegans to investigate the combined effects of PS-50 (50 nm nanopolystyrene) and PS-500 (500 nm micropolystyrene) at environmentally relevant concentrations on the functional state of the intestinal barrier. Environmentally, after long-term treatment (4.5 days), coexposure to PS-50 (10 and 15 μg/L) and PS-500 (1 μg/L) resulted in more severe formation of toxicity in decreasing locomotion behavior, in inhibiting brood size, in inducing intestinal ROS production, and in inducting intestinal autofluorescence production, compared with single-exposure to PS-50 (10 and 15 μg/L) or PS-500 (1 μg/L). Additionally, coexposure to PS-50 (15 μg/L) and PS-500 (1 μg/L) remarkably caused an enhancement in intestinal permeability, but no detectable abnormality of intestinal morphology was observed in wild-type nematodes. Lastly, the downregulation of acs-22 or erm-1 expression and the upregulation expressions of genes required for controlling oxidative stress (sod-2, sod-3, isp-1, clk-1, gas-1, and ctl-3) served as a molecular basis to strongly explain the formation of intestinal toxicity caused by coexposure to PS-50 (15 μg/L) and PS-500 (1 μg/L). Our results suggested that combined exposure to microplastics and nanoplastics at the predicted environmental concentration causes intestinal toxicity by affecting the functional state of the intestinal barrier in organisms.

Fluoroquinolone Residues in the Environment Rapidly Induce Heritable Fluoroquinolone Resistance in Escherichia coli

Extensive antibiotic use increases the environmental presence of their residues and may accelerate the development of antibiotic resistance, although this remains poorly understood at environmentally relevant concentrations. Herein, susceptible Escherichia coli K12 was continuously exposed to five antibiotics at such concentrations for 100 days. The de novo-evolved mutants rapidly obtained fluoroquinolone resistance within 10 days, as indicated by the 4- and 16-fold augmentation of minimum inhibitory concentrations against enrofloxacin and ciprofloxacin, respectively. Moreover, the mutants maintained heritable fluoroquinolone resistance after the withdrawal of antibiotics for 30 days. Genomic analysis identified Asp87Gly or Ser83Leu substitutions in the gyrA gene in the mutants. Transcriptomics data showed that the transcriptional response of the mutants to fluoroquinolones was primarily involved in biofilm formation, cellular motility, porin, oxidative stress defense, and energy metabolism. Homologous recombination and molecular docking revealed that mutations of gyrA primarily mainly conferred fluoroquinolone resistance, while mutations at different positions of gyrA likely endowed different fluoroquinolone resistance levels. Collectively, this study revealed that environmentally relevant concentrations of antibiotics could rapidly induce heritable antibiotic resistance; therefore, the discharge of antibiotics into the environment should be rigorously controlled to prevent the development of antibiotic resistance.

Do Polystyrene Nanoplastics Have Similar Effects on Duckweed (Lemna minor L.) at Environmentally Relevant and Observed-Effect Concentrations?

Although the biological effects of nanoplastics (<100 nm in size) in aquatic environments have been increasingly investigated, almost all such studies have been performed at observed-effect concentrations (higher than 1 μg/mL). The use of observed-effect concentrations of nanoplastics can provide essential data for evaluating the potential risks, but how these results apply to the effects of concentrations of nanoplastics observed in the environment remains unclear. Here, we show that exposure to both positively and negatively charged nanoplastics at the observed-effect concentration (ranging from 0 to 50 μg/mL) can result in physiological changes of Lemna minor L., a typical flowering aquatic plant species, inducing H₂O₂ and O₂^- accumulation and even cell death. However, the nanoplastics at environmentally relevant concentrations (lower than 0.1 μg/mL) had no obvious effects on phenotype of L. minor. Moreover, nanoplastics at both observed-effect and environmentally relevant concentrations were adsorbed onto the roots and fronds of the plants, whereas uptake by the roots and fronds occurred only at the observed-effect concentration. Although no phenotypic changes across 30 generations of cultivation were observed when the plants were exposed to 0.015 μg/mL nanoplastics, the expression of genes related to the response to stimuli and to oxidative and osmotic stress was upregulated under both observed-effect and environmentally relevant concentrations. Our findings suggest that the long-term presence of nanoplastics at environmentally relevant concentrations might induce some variations in the transcription level and have potential threat to floating microphytes and aquatic ecosystems.