Effects of Single and Combined Ciprofloxacin and Lead Treatments on Zebrafish Behavior, Oxidative Stress, and Elements Content

Single and mixture exposure to atrazine and ciprofloxacin on Clarias gariepinus antioxidant defense status, hepatic condition and immune response

Atrazine (ATRA) and ciprofloxacin (CPRO) are widely detected, persistent and co-existing aquatic pollutants. This study investigated effects of 14-day single and joint ATRA and CPRO exposure on juvenile Clarias gariepinus. Standard bioassay methods were used to determine responses of oxidative stress, hepatic condition, and immunological biomarkers on days 7 and 14. Seven groups were used: Control, CPROEC, CPROSubl, ATRAEC, ATRASubl, CPROEC+ATRAEC, and CPROSubl+ATRASubl. The test substances caused decreased activity of superoxide dismutase, catalase, and glutathione peroxidase. Lipid peroxidation was elevated, especially in CPRO-ATRA mixtures. Serum aminotransferases (ALT, and AST), and alkaline phosphatase activity increased significantly. Total protein, albumin, total immunoglobulin, and respiratory burst decreased significantly. Therefore, single and joint exposure to CPRO and ATRA poses adverse consequences on aquatic life.

Reviewing the use of zebrafish for the detection of neurotoxicity induced by chemical mixtures through the analysis of behaviour

The knowledge and assessment of mixtures of chemical pollutants in the aquatic environment is a complex issue that is often challenging to address. In this review, we focused on the use of zebrafish (Danio rerio), a vertebrate widely used in biomedical research, as a model for detecting the effects of chemical mixtures with a focus on behaviour. Our aim was to summarize the current status of the ecotoxicological research in this sector. Specifically, we limited our research to the period between January 2012 and September 2023, including only those works aimed at detecting neurotoxicity through behavioural endpoints, utilizing zebrafish at one or more developmental stages, from egg to adult. Additionally, we gathered the findings for every group of chemicals involved and summarised data from all the works we included. At the end of the screening process 101 papers were considered eligible for inclusion. Results show a growing interest in zebrafish at all life stages for this kind of research in the last decade. Also, a wide variety of different assays, involving different senses, was used in the works we surveyed, with exposures ranging from acute to chronic. In conclusion, the results of this study show the versatility of zebrafish as a model for the detection of mixture toxicity although, for what concerns behavioural analysis, the lack of standardisation of methods and endpoints might still be limiting.

Enzymatic and transcriptional level changes induced by the co-presence of lead and procymidone in hook snout carp (Opsariichthys bidens)

Understanding the interactions between different environmental pollutants is necessary in ecotoxicology since environmental contaminants never appear as single components but rather in combination with other substances. Heavy metals and pesticides are commonly detected in the environment, but the characterization of their mixture toxicity has been inadequately explored. This research aimed to elucidate the mixture impacts of the heavy metal lead (Pb) and the pesticide procymidone (PCM) on the hook snout carp (Opsariichthys bidens) using an array of biomarkers. The data showed that Pb and PCM possessed almost equivalent acute toxicity to the animals, with 4-days LC50 values of 120.9 and 85.15 mg L-1, respectively. Combinations of Pb and PCM generated acute synergistic effects on O. bidens. The contents of malondialdehyde (MDA), antioxidative (SOD), apoptotic (caspase-9), and detoxifying enzymes glutathione S-transferase (GST) and cytochrome P450 (CYP450) significantly changed after most of the mixture exposures compared with the baseline level and the corresponding individual exposures. This suggests the induction of oxidative stress, cell damage, and detoxification dysfunction. The expressions of eight genes (mn-sod, cu-sod, p53, cas3, erβ1, esr, ap, and klf2α) associated with oxidative stress, cell apoptosis, immune response, and hormonal functions exhibited pronounced changes when challenged with the mixture compared to the individual treatments. This indicates the occurrence of immune dysregulation and endocrine disorder. These findings provide an overall understanding of fish upon the challenge of sublethal toxicity between Pb and PCM and can be adopted to evaluate the complicated toxic mechanisms in aquatic vertebrates when exposed to heavy metal and pesticide mixtures. Additionally, these results might guide environmental regulation tactics to protect the population of aquatic vertebrates in natural ecosystems.

Effects of environmental hypoxia on the goldfish skeletal muscle: Focus on oxidative status and mitochondrial dynamics

The skeletal muscle is a highly plastic tissue. Its ability to respond to external stimuli and challenges allows it to face the functional needs of the organism. In the goldfish Carassius auratus, a model of hypoxia resistance, exposure to reduced oxygen is accompanied by an improvement of the swimming performance, relying on a sustained contractile behavior of the skeletal muscle. At the moment, limited information is available on the mechanisms underlying these responses. We here evaluated the effects of short- (4 days) and long- (20 days) term exposure to moderate water hypoxia on the goldfish white skeletal muscle, focusing on oxidative status and mitochondrial dynamics. No differences in lipid peroxidation, measured as 2-thiobarbituric acid-reacting substances (TBARS), and oxidatively modified proteins (OMP) were detected in animals exposed to hypoxia with respect to their normoxic counterparts. Exposure to short-term hypoxia was characterized by an enhanced SOD activity and expression, paralleled by increased levels of Nrf2, a regulator of the antioxidant cell response, and HSP70, a chaperone also acting as a redox sensor. The expression of markers of mitochondrial biogenesis (TFAM) and abundance (VDAC) and of the mtDNA/nDNA ratio was similar under normoxia and under both short- and long-term hypoxia, thus excluding a rearrangement of the mitochondrial apparatus. Only an increase of PGC1α (a transcription factor involved in mitochondrial dynamics) was detected after 20 days of hypoxia. Our results revealed novel aspects of the molecular mechanisms that in the goldfish skeletal muscle may sustain the response to hypoxia, thus contributing to adequate tissue function to organism requirements.

Synergistic/antagonistic toxicity characterization and source-apportionment of heavy metals and organophosphorus pesticides by the biospectroscopy-bioreporter-coupling approach

Many anthropogenic chemicals are manufactured and eventually enter the surrounding environment, threatening food security and human health. Considering the additive or synergistic effects of pollutant mixtures, there is an expanding need for rapid, cost-effective and field-portable screening methods in environmental monitoring. This study used a recently developed biospectroscopy-bioreporter-coupling (BBC) approach to investigate the binary toxicity of Ag(I), Cr(VI) and four organophosphorus pesticides (dichlorvos, parathion, omethoate and monocrotophos). Ag(I) and Cr(VI) altered the toxicity mechanisms of pesticides, explained by the synergistic or antagonistic effect of Ag/Cr-induced cytotoxicity and pesticide-induced genotoxicity. The discriminating Raman spectral peaks associated with organophosphorus pesticides were 1585 and 1682 cm-1, but 750, 1004, 1306 and 1131 cm-1 were found in heavy metal and pesticide mixtures. More spectral alterations were related to pesticides rather than Ag(I) or Cr(VI), hinting at the dominant toxicity mechanisms of pesticides in mixtures. Ag(I) supplement significantly increased the levels of reactive oxygen species induced by organophosphorus pesticides, attributing to the increased permeability of cell membrane and entrance of toxic substances into the cells by the oligodynamic actions. This study lends deeper insights into the interactions between microbes and pollutant mixtures, offering clues to assess the cocktail effects of multiple pollutants comprehensively.

Occurrence, Bioaccumulation, Metabolism and Ecotoxicity of Fluoroquinolones in the Aquatic Environment: A Review

In recent years, there has been growing concern about antibiotic contamination in water bodies, particularly the widespread presence of fluoroquinolones (FQs), which pose a serious threat to ecosystems due to their extensive use and the phenomenon of "pseudo-persistence". This article provides a comprehensive review of the literature on FQs in water bodies, summarizing and analyzing contamination levels of FQs in global surface water over the past three years, as well as the bioaccumulation and metabolism patterns of FQs in aquatic organisms, their ecological toxicity, and the influencing factors. The results show that FQs contamination is widespread in surface water across the surveyed 32 countries, with ciprofloxacin and norfloxacin being the most heavy contaminants. Furthermore, contamination levels are generally higher in developing and developed countries. It has been observed that compound types, species, and environmental factors influence the bioaccumulation, metabolism, and toxicity of FQs in aquatic organisms. FQs tend to accumulate more in organisms with higher lipid content, and toxicity experiments have shown that FQs exhibit the highest toxicity to bacteria and the weakest toxicity to mollusk. This article summarizes and analyzes the current research status and shortcomings of FQs, providing guidance and theoretical support for future research directions.

Toxic effects of sirolimus and everolimus on the development and behavior of zebrafish embryos

Sirolimus and everolimus have been widely used in children. These mammalian target of rapamycin (mTOR) inhibitors have shown excellent efficacy not only in organ transplant patients as immunosuppressive agents but also in patients with some other diseases. However, whether mTOR inhibitors can affect the growth and development of children is of great concern. In this study, using zebrafish models, we discovered that sirolimus and everolimus could slow the development of zebrafish, affecting indicators such as survival, hatching, deformities, body length, and movement. In addition to these basic indicators, sirolimus and everolimus had certain slowing effects on the growth and development of the nervous system, blood vessels, and the immune system. These effects were dose dependent. When the drug concentration reached or exceeded 0.5 μM, the impacts of sirolimus and everolimus were very significant. More interestingly, the impact was transient. Over time, the various manifestations of experimental embryos gradually approached those of control embryos. We also compared the effects of sirolimus and everolimus on zebrafish, and we revealed that there was no significant difference between these drugs in terms of their effects. In summary, the dose of sirolimus and everolimus in children should be strictly controlled, and the drug concentration should be monitored over time. Otherwise, drug overdosing may have a certain impact on the growth and development of children.