Combined exposure to microplastics and amitriptyline caused intestinal damage, oxidative stress and gut microbiota dysbiosis in zebrafish (Danio rerio).

The potential toxicity of microplastics (MPs) and hydrophilic pharmaceuticals to aquatic organisms has recently raised great public concern, yet their combined effects on aquatic organisms remain largely unknown. Herein, the combined effects of MPs and the commonly prescribed amitriptyline hydrochloride (AMI) on the intestinal tissue and gut microbiota of zebrafish (Danio rerio) were investigated. Adult zebrafish were exposed to microplastics (polystyrene, PS, 440 µg/L), AMI (2.5 µg/L), PS+AMI (440 µg/L PS + 2.5 µg/L AMI), and dechlorinated tap water (control) for 21 days, respectively. Our results showed that zebrafish rapidly ingested PS beads and accumulated them in the gut. Exposure to PS+AMI significantly enhanced the SOD and CAT activities compared to the control group, suggesting that combined exposure might increase ROS production in the zebrafish gut. Exposure to PS+AMI led to severe gut injuries, including cilia defects, partial absence and cracking of intestinal villi. Exposure to PS+AMI caused shifts in the gut bacterial communities, increasing the abundance of Proteobacteria and Actinobacteriota, and decreasing the abundance of Firmicutes, Bacteroidota and beneficial bacteria Cetobacterium, which caused dysbiosis in the gut microbiota, and subsequently may induce intestinal inflammation. Furthermore, exposure to PS+AMI disordered the predicted metabolic functions of gut microbiota, but functional changes in the PS+AMI group at KEGG level 1 and level 2 were not significantly different from those in the PS group. The results of this study extend our knowledge of the combined effects of MPs and AMI on the health of aquatic organisms, and will be helpful in assessing the combined effects of MPs and tricyclic antidepressants on aquatic organisms.

A transcriptomic-based analysis predicts the neuroendocrine disrupting effect on adult male and female zebrafish (Danio rerio) following long-term exposure to tetrabromobisphenol A bis(2-hydroxyethyl) ether.

Endocrine-disrupting chemicals (EDCs) are now ubiquitously distributed in the environment. Tetrabromobisphenol A bis(2-hydroxyethyl) ether (TBBPA-DHEE) pollution in environment media poses a significant threat to humans and aquatic organisms as a result of its potential neurotoxicity and endocrine-disrupting effect. The endocrine-disrupting effects of TBBPA-DHEE on aquatic organisms, however, have received limited attention. In this study, the neurotoxicity and reproductive endocrine-disruptive effect of TBBPA-DHEE was evaluated by observing the neurobehavioral changes, vitellogenin (VTG), testosterone, 17ß-estradiol and gene expression levels in adult male and female zebrafish exposed to TBBPA-DHEE (0.05, 0.2 and 0.3 mg/L) for 100 days. Furthermore, transcriptomic analysis was conducted to unravel other potential neuroendocrine-disrupting mechanism. Our result showed TBBPA-DHEE significantly (p < 0.05) altered the locomotor behavior and motor coordination abilities in both sexes. Steroid hormone and VTG levels were also altered indicating the neuroendocrine-disrupting effect of TBBPA-DHEE on the hypothalamic-pituitary-gonadal-axis. A total of 1568 genes were upregulated and 542 genes downregulated in males, whereas, 1265 upregulated and 535 downregulated genes were observed in females. The KEGG enrichment analysis showed that cell cycle and p55 signaling pathways were significantly enriched due to TBBPA-DHEE exposure. These pathways and its component genes are potential target of EDCs. The significant upregulation of genes in these pathways could partly explain the neuroendocrine disrupting effect of TBBPA-DHEE. The observed toxic effects of TBBPA-DHEE observed in this study is confirmation of the endocrine-disrupting toxicity of this chemical which would be valuable in biosafety evaluation and biomonitoring of TBBPA-DHEE for public health purposes.

Removal of Chromium(VI) by Nanoscale Zero-Valent Iron Supported on Melamine Carbon Foam.

The overuse of chromium (Cr) has significantly negatively impacted human life and environmental sustainability. Recently, the employment of nano zero-valent iron (nZVI) for Cr(VI) removal is becoming an emerging approach. In this study, carbonized melamine foam-supported nZVI composites, prepared by a simple impregnation-carbonization-reduction method, were assessed for efficient Cr(VI) removal. The prepared composites were characterized by XPS, SEM, TEM, BET and XRD. Batch experiments at different conditions revealed that the amount of iron added, the temperature of carbonization and the initial Cr(VI) concentration were critical factors. Fe@MF-12.5-800 exhibited the highest removal efficiency of 99% Cr(VI) (10 mg/L) at neutral pH among the carbonized melamine foam-supported nZVI composites. Its iron particles were effectively soldered onto the carbonaceous surfaces within the pore networks. Moreover, Fe@MF-12.5-800 demonstrated remarkable stability (60%, 7 days) in an open environment compared with nZVI particles.

Time-series responses in photosynthetic activity, 2-cysteine peroxiredoxin gene expression, and proteomics of Chattonella marina var. antiqua under different oxidative stress.

Chattonella spp. are known to produce large amounts of reactive oxygen species (ROS); however, little is known about the mechanisms involved in mitigating the intracellular accumulation of ROS. In this study, a time-series of biological responses in C. marina var. antiqua under different oxidative stress conditions, induced by adding H2O2 at the initial concentrations of 100 and 500 µM, was investigated. Although the added exogenous H2O2 was rapidly consumed at 3 h post-exposure (hpe), intracellular ROS levels were enhanced in the 500 µM H2O2 group but decreased in the 100 µM H2O2 group. Accompanied by increased intracellular ROS levels, the photosynthetic activity of C. marina var. antiqua was considerably inhibited in the 500 µM H2O2 group, but not in the 100 µM H2O2 group. The Fv/Fm ratio and PIABS were negatively correlated with the intracellular ROS level, while the ABS/RC, TR0/RC, and DI0/RC were positively correlated with the intracellular ROS level. Expression of the gene encoding 2-cysteine peroxiredoxin (2-Cys Prx) was up-regulated in 100 µM H2O2 group at 6 hpe, but was down-regulated in 100 µM H2O2 group at 3 and 6 hpe. A negative relationship between the 2-Cys Prx transcript levels and intracellular ROS levels was detected. Results of the 2-DE proteomic analysis confirmed that the 500 µM H2O2 treatment down-regulated the expression of 2-Cys Prx and induced more damage to photosynthetic abilities of C. marina var. antiqua.

Transcriptomic analysis reveals potential mechanisms of toxicity in a combined exposure to dibutyl phthalate and diisobutyl phthalate in zebrafish (Danio rerio) ovary.

Phthalate esters (PAEs), which are notable plasticizers, can be prolific contaminants in aquatic environments, and have been shown to induce reproductive toxicity. However, the studies concerning their toxicity towards aquatic species are based on individual chemicals, and the combined toxicity of PAEs to aquatic organisms remains unclear. The aim of this study was to explore the potential toxicity mechanisms associated with combined exposure to dibutyl phthalate (DBP) and diisobutyl phthalate (DiBP) in adult female zebrafish ovaries. Zebrafish were exposed to DBP, DiBP and their mixtures for 30 days, and their effects on ovarian histology, plasma sex hormones and ovarian transcriptomics were investigated. Plasma estradiol (E2) levels were significantly decreased by 38.9% in the DBP-1133 exposure group and 41.0% in the DiBP-1038 exposure group. The percentage of late/mature oocytes was also significantly decreased by 17.3% under DBP-1133 exposure and 16.2% under DiBP-1038 exposure, while that under combined exposure was not significantly affected. Nevertheless, transcriptome sequencing revealed 2564 differentially expressed genes (DEGs) in zebrafish ovaries after exposure to the mixtures. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that the DEGs were involved in the neuroactive ligand-receptor interaction, GnRH, progesterone-mediated oocyte maturation, oocyte meiosis and steroid hormone biosynthesis signaling pathways. These results revealed that combined exposure exerts potential reproductive toxicity at the molecular level.

Thiobencarb herbicide reduces growth, photosynthetic activity, and amount of Rieske iron-sulfur protein in the diatom Thalassiosira pseudonana.

We investigated the effects of the herbicide thiobencarb on the growth, photosynthetic activity, and expression profile of photosynthesis-related proteins in the marine diatom Thalassiosira pseudonana. Growth rate was suppressed by 50% at a thiobencarb concentration of 1.26 mg/L. Growth and photosystem II activity (Fv /Fm ratio) were drastically decreased at 5 mg/L, at which the expression levels of 13 proteins increased significantly and those of 11 proteins decreased significantly. Among these proteins, the level of the Rieske iron-sulfur protein was decreased to less than half of the control level. This protein is an essential component of the cytochrome b6 f complex in the photosynthetic electron transport chain. Although the mechanism by which thiobencarb decreased the Rieske iron-sulfur protein level is not clear, these results suggest that growth was inhibited by interruption of the photosynthetic electron transport chain by thiobencarb.

Growth-phase dependent variation in photosynthetic activity and cellular protein expression profile in the harmful raphidophyte Chattonella antiqua.

This study investigated temporal variations in the potential maximum quantum yield of photosystem II (F(v)/F(m) ratio) and growth-phase dependent cellular protein expressions of Chattonella antiqua under laboratory conditions. Despite the culture conditions, significant positive correlations between the F(v)/F(m) ratio and daily growth rate were observed. Threshold F(v)/F(m) ratios associated with positive cell growth were calculated to be >0.44, >0.44, and >0.37, and those associated with active cell growth (growth rate >0.5 div. d(-1)) were >0.58, >0.60, and >0.49 under control culture, low nutrient and intense light conditions, respectively. Proteome profiles obtained by two-dimensional gel electrophoresis (2-DE) indicated that 42 protein spots were differentially expressed at various growth phases of C. antiqua, which indicates changes in cellular physiological status throughout the growth cycle, and suggests that oxygen evolving enhancer 1 and 2-cysteine peroxiredoxin play roles in maintaining the positive growth of C. antiqua.