Toxic effects of long-term dual or single exposure to oxytetracycline and arsenic on Xenopus tropicalis living in duck wastewater

Study on toxicity responses in Xenopus tropicalis long-term exposure to norfloxacin, oxytetracycline and arsenic

The presence of residues of antibiotics and heavy metals in the global aquatic environment is a widespread potential environmental risk. Here, we studied their effect on Xenopus tropicalis by analysing the hepatotoxic effects of norfloxacin (NOR), oxytetracycline (OTC), and arsenic (As) on its histology, lipidomics, proteases, and cytokines. The results showed that development was inhibited, and additional vacuolation, sinusoids, pyknosis, nuclei, cell lysis, and leukocyte infiltration were observed in the liver after 72 days of exposure to NOR (0.1-4.0 mg L-1), OTC (0.1-4.0 mg L-1), and/or As (0.3-3.5 μg L-1). In addition, the size and number of lipid droplets increased with the superposition of drugs, disrupting lipid droplet homeostasis. Lipidomics proved that the intensity of lipid responses related to lipid metabolism was disrupted, especially for CerP and TAG. In addition, the lipotoxicity induced by joint exposure was more potent than that induced by a single exposure. Compared with the controls, the ROS levels in the liver were 7.21%-37.18% greater, which promoted oxidative stress damage. By revealing the underlying mechanisms involved, we found that the liver can resist oxidative stress and lipid peroxidation by regulating the expression of multiple cytokines. Our study provides new insights into the hepatotoxicity and underlying mechanisms in aquatic amphibians caused by long-term exposure to low concentrations of NOR, OTC, and/or As.

Effects of triclosan adsorption on intestinal toxicity and resistance gene expression in Xenopus tropicalis with different particle sizes of polystyrene

Microplastics (MPs) are commonly found with hydrophobic contaminants in the water column and pose a serious threat to aquatic organisms. The effects of polystyrene microplastics of different particle sizes on the accumulation of triclosan in the gut of Xenopus tropicalis, its toxic effects, and the transmission of resistance genes were evaluated. The results showed that co-exposure to polystyrene (PS-MPs) adsorbed with triclosan (TCS) caused the accumulation of triclosan in the intestine with the following accumulation capacity: TCS + 5 µm PS group > TCS group > TCS + 20 µm PS group > TCS + 0.1 µm PS group. All experimental groups showed increased intestinal inflammation and antioxidant enzyme activity after 28 days of exposure to PS-MPs and TCS of different particle sizes. The TCS + 20 µm PS group exhibited the highest upregulated expression of pro-inflammatory factors (IL-10, IL-1β). The TCS + 20 µm group showed the highest increase in enzyme activity compared to the control group. PS-MPs and TCS, either alone or together, altered the composition of the intestinal microbial community. In addition, the presence of more antibiotic resistance genes than triclosan resistance genes significantly increased the expression of tetracycline resistance and sulfonamide resistance genes, which may be associated with the development of intestinal inflammation and oxidative stress. This study refines the aquatic ecotoxicity assessment of TCS adsorbed by MPs and provides informative information for the management and control of microplastics and non-antibiotic bacterial inhibitors.

Nuclear abnormalities and DNA damage indicate different genotoxic stress responses of marsh frogs (Pelophylax ridibundus, Pallas 1771) to industrial and agricultural water pollution in South Bulgaria

Amphibians are continuously exposed to pollutants and anthropogenic stressors in their natural habitats, representing a significant challenge to their survival. This study aimed to quantify the extent of DNA damage caused by chronic industrial and agrochemical surface water pollution in wild populations of the marsh frog (Pelophylax ridibundus). The observed genotoxic effects on the marsh frog DNA, manifesting as abnormalities in erythrocyte nuclei, micronuclei, and DNA strand breaks, demonstrate a clear cause-and-effect relationship with surface water parameters, heavy metals, metalloids, and pesticides. The most prevalent nuclear abnormalities observed were notched and blebbed nuclei and nuclear buds, indicative of chromosomal instability. The significant correlation between cadmium, lead, and copper contamination and the increased frequency of DNA breakage in the marsh frogs from the industrial site indicates that heavy metal contamination has a higher genotoxic potential than pesticide contamination. These findings underscore the vulnerability of amphibians inhabiting heavy metal-contaminated wetlands to genotoxic stress due to their lower tolerance to environmental genotoxins. Therefore, using in situ assays to detect erythrocyte nuclear abnormalities and DNA damage in P. ridibundus could serve as a reliable indicator of environmental quality and provide early detection of anthropogenic pollution.

In situ synthesis of oxygen-doped carbon quantum dots embedded in MIL-53(Fe) for efficient degradation of oxytetracycline

Introducing carbon quantum dots (CQDs) into photocatalysts is believed to boost the charge transfer rate and reduce charge complexation. Doping heteroatoms such as N, S, or P enable CQDs to have an uplifting electron transfer capability. However, the application of oxygen-doped CQDs to improve the performance of photocatalysts has rarely been reported. Herein, a type of carbon-oxygen quantum dots (COQDs) was in situ embedded into MIL-53(Fe) to aid peroxydisulfate (PDS)-activated degradation of oxytetracycline (OTC) under visible light irradiation. The successful embedding of COQDs was confirmed by XRD, FT-IR, XPS, SEM, and TEM techniques. Photoelectrochemical testing confirmed its better performance. The prepared COQDs1/MIL-53(Fe) showed 88.2% decomposition efficiency of OTC in 60 min, which was 1.45 times higher than that of pure MIL-53(Fe). In addition, the performance of the material was tested at different pH, OTC concentrations, catalyst dosing, and PDS dosing. It was also subjected to cyclic testing to check stability. Moreover, free radical trapping experiments and electron paramagnetic resonance were conducted to explore the possible OTC deterioration mechanism. Our work provides a new idea for the development of MOFs for water treatment and remediation.

Intestinal toxicity and resistance gene threat assessment of multidrug-resistant Shigella: A novel biotype pollutant

Multidrug-resistant bacteria, especially pathogens, pose a serious threat to disease treatment and recovery, but their potential toxicity to animal development is not entirely clear. As the most important site for nutrient absorption, we studied the intestinal microbiome of Xenopus tropicalis by analyzing the effect of multidrug-resistant Shigella on its intestinal health. Unlike in the control, Shigella intake promoted the secretion of neutral mucus and inhibited intestinal development and weight gain. Following 60 days of exposure, intestinal crypt atrophy, intestinal villus shortening, internal cavity enlargement, and external mucosal muscle disintegration were observed. The circular and longitudinal intestinal muscles became thinner with increasing pathogen exposure. In addition, the presence of Shigella altered the expression of multiple cytokines and classic antioxidant enzyme activities in the gut, which may have caused the intestinal lesions that we observed. 16 S rDNA sequencing analysis of intestinal samples showed that exposure to Shigella destroyed the normal gut microbial abundance and diversity and increased the functional bacterial ratio. Notably, the increased abundance of intestinal antibiotic resistance genes (ARGs) may imply that the resistance genes carried by Shigella easily migrate and transmit within the intestine. Our results expand existing knowledge concerning multidrug-resistant Shigella-induced intestinal toxicity in X. tropicalis and provide new insights for the threat assessment of resistance genes carried by drug-resistant pathogens.