Waterborne zinc pyrithione modulates immunity, biochemical, and antioxidant parameters in the blood of olive flounder

Male Reproductive Toxicity of Antifouling Chemicals: Insights into Oxidative Stress-Induced Infertility and Molecular Mechanisms of Zinc Pyrithione (ZPT)

Zinc pyrithione (ZPT), a widely utilized industrial chemical, is recognized for its versatile properties, including antimicrobial, antibacterial, antifungal, and antifouling activities. Despite its widespread use, recent research has shed light on its toxicity, particularly towards the male reproductive system. While investigations into ZPT's impact on male reproduction have been conducted, most of the attention has been directed towards marine organisms. Notably, ZPT has been identified as a catalyst for oxidative stress, contributing to various indicators of male infertility, such as a reduced sperm count, impaired sperm motility, diminished testosterone levels, apoptosis, and degenerative changes in the testicular tissue. Furthermore, discussions surrounding ZPT's effects on DNA and cellular structures have emerged. Despite the abundance of information regarding reproductive toxicity, the molecular mechanisms underlying ZPT's detrimental effects on the male reproductive system remain poorly understood. This review focuses specifically on ZPT, delving into its reported toxicity on male reproduction, while also addressing the broader context by discussing other antifouling chemicals, and emphasizing the need for further exploration into its molecular mechanisms.

Toxic effects and potential mechanisms of zinc pyrithione (ZPT) exposure on sperm and testicular injury in zebrafish

Zinc pyrithione (ZPT) is widely recognized for its beneficial properties as an antifouling, antibacterial, and antifungal agent. Despite its positive industrial contributions, ZPT has been proven to exhibit toxicity towards various ecosystems, particularly affecting marine life. However, there is still a dearth of comprehensive research on ZPT toxicity and its toxicological mechanism in reproductive systems of aquatic organisms. In our study, we conducted a thorough analysis and unveiled a multitude of abnormalities in zebrafish sperm and testicular tissue caused by ZPT exposure, including a dose-dependent diminishing of testosterone levels, various sperm deformities, decreased sperm concentration and motility, and ROS-induced testicular tissue DNA damage. In addition, our study suggested that ZPT-induced testicular damage is associated with heightened oxidative stress, apoptosis, and possible hyperpolarization of the mitochondrial membrane. Through RNA-seq analysis, a total of 409 DEGs associated with ZPT-induced testicular injury were identified, and the hub gene was determined using a protein-protein interaction network (PPI). The genes and pathways uncovered in this study point to potential mechanisms of ZPT exposure on sperm and testicular injury in zebrafish.

Effects of Zinc Status on Expression of Zinc Transporters, Redox-Related Enzymes and Insulin-like Growth Factor in Asian Sea Bass Cells

Since Asian sea bass is one of the economically most important fish, aquaculture conditions are constantly optimized. Evidence from feeding studies combined with the current understanding of the importance of zinc for growth and immune defense suggest that zinc supplementation may be a possible approach to optimize aquacultures of Asian sea bass. To investigate the effects of zinc deficiency and zinc supplementation, cells from Asian sea bass were incubated in culture medium with different zinc contents. The expression of genes, important for zinc homeostasis, redox metabolism, and growth hormones was analyzed using RT-PCR. Zinc deficiency induced the expression of certain zinc transporters (ZIP14, ZIP10, ZIP6, ZIP4, ZnT4, ZnT9) as well as of SOD1, IGF I and IGF II, while expression of ZnT1 and metallothionein (MT) was reduced. Zinc supplementation decreased the expression of ZIP10, while expression of ZnT1 and MT were elevated. No differences in the effects of zinc supplementation with zinc sulfate compared to supplementation with zinc amino acid complexes were observed. Thus, extracellular zinc conditions may govern the cellular zinc homeostasis, the redox metabolism and growth hormone expression in cells from Asian sea bass as reported for other fish species. Our data indicate that supplementing aquacultures with zinc may be recommended to avoid detriments of zinc deficiency.

Long-term exposure to antifouling biocide chlorothalonil modulates immunity and biochemical and antioxidant parameters in the blood of olive flounder

In this study, the potential effects of 30-day exposure to environmentally relevant concentrations of chlorothalonil (0, 5, 10, and 20 μg L^-l) were tested in the blood of the economically important olive flounder, Paralichthys olivaceus, using biochemical endpoints. Significant decreases in the enzymatic activities of immunity markers, alternative complements, and lysozymes were detected in the fish exposed to 10 or 20 μg L^-l of chlorothalonil at day 20 or 30. The total immunoglobulin content was lowered in response to 20 μg L^-l chlorothalonil at day 10 and 20, even when later exposed to 5 μg L^-l at day 30. Among the essential blood components, the cortisol level was increased in response to chlorothalonil throughout the study with a decrease in white blood cells, while no changes were observed in hemoglobin, red blood cells, total protein concentration, and glucose in all exposures. The enzymatic activities of the three hepatic toxicity markers, alanine transferases, aspartate transaminase, and alkaline phosphatase, increased by 10 and/or 20 μg L^-l of chlorothalonil. Significant oxidative stress was induced by chlorothalonil in the fish exposed to 10 or 20 μg L^-l of chlorothalonil, as revealed by increased malondialdehyde and fluctuating glutathione levels with increase in the enzymatic activities of antioxidant defense system, including catalase and superoxide dismutase, during exposure. Taken together, these results suggest that long-term exposure to environmentally relevant concentrations of chlorothalonil can affect susceptibility to pathogens through immunosuppression, hepatic toxicity, and oxidative stress in olive flounder. These results can contribute to the monitoring of aquatic environments and ecotoxicological research through the measurement of blood components against waterborne chlorothalonil.

Chronic exposure to sublethal concentrations of saxitoxin reduces antioxidant activity and immunity in zebrafish but does not affect reproductive parameters

Saxitoxin produced by dinoflagellates and cyanobacteria can be transferred to humans through intoxicated organisms such as fish, but limited research has addressed the adverse effects of this toxin on aquatic organisms. In this study, we measured the potential effects of a 90-day exposure to saxitoxin (0.1 or 1 µg·L ^- 1) on body weight and length, antioxidant defense system, immunity, sex hormones, and genes involved in associated key metabolic pathways in zebrafish (Danio rerio). Significant impairments in body weight and length were observed in response to 1 µg·L ^- 1 saxitoxin in both male and female zebrafish. A significant increase in the levels of malondialdehyde, together with decreased enzymatic activities of catalase and superoxide dismutase, was observed in fish of both sexes exposed to 1 µg·L ^- 1 saxitoxin, indicating the occurrence of lipid peroxidation and oxidative stress. Immune parameters such as alternative complement activity, lysozyme activity, and immunoglobulin content were also significantly reduced. However, exposure of male and female zebrafish to saxitoxin for 90 days did not significantly affect reproductive parameters such as the gonadosomatic index and plasma concentrations of vitellogenin, estradiol, and 11-keto testosterone. Transcriptional responses showed similar trends to those of the biochemical parameters, as genes involved in the antioxidant defense system and immunity were downregulated, whereas the transcription of genes related to reproductive metabolism showed no significant change upon treatment with 1 µg·L ^- 1 saxitoxin. Our findings indicate that long-term exposure to a sublethal concentration of saxitoxin can inhibit growth through induction of oxidative stress and immunosuppression, while the reproductive parameters of zebrafish are not a main target of this toxin at sublethal concentrations.

Development and Evaluation of Olive Flounder cyp1a1-Luciferase Assay for Effective Detection of CYP1A-Inducing Contaminants in Coastal Sediments

Flounders have been widely used as indicator species for monitoring the benthic environment of marine coastal regions owing to their habitat and feeding preferences in or on sandy sediments. Here, a single-step, sensitive, specific, and simple luciferase assay was developed, using the olive flounder cyp1a1 gene, for effective detection of CYP1A-inducing contaminants in coastal sediments. The developed cyp1a1-luciferase assay was highly sensitive to the widely used CYP1A inducers 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), benzo[a]pyrene (B[a]P), and 3,3',4,4',5-pentachlorobiphenyl (PCB 126). In the case of TCDD, significant dose-dependent increases in luciferase activity (0.3-300 ng/L) were detected. The assay was more sensitive to PCB 126 than to B[a]P. The assay also involved the highly sensitive expression of luciferase to extracted mixtures of PCBs and polycyclic aromatic hydrocarbons (PAHs) collected from coastal sediments. PCBs were more capable of cyp1a1 induction in the assay system at small doses than PAHs in environmental samples. Using the cyp1a1-luciferase assay along with water or sediment chemistry will certainly aid in diagnosing CYP1A-inducing contaminants in coastal environments.

Inorganic nitrogen compounds reduce immunity and induce oxidative stress in red seabream

In this study, the effect of ammonia derived from different stocking densities on immunological, hematological, and oxidative stress parameters was analyzed in the blood or liver of red seabream. Density- and time-dependent increases in inorganic nitrogen compounds were measured for 20 days by analyzing the three major inorganic nitrogen compounds, total ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen. Three immunity parameters, alternative complement activity, lysozyme activity, and total immunoglobulin content were significantly decreased in the blood at the highest stocking density (10 kg m^-3). The concentrations of hemoglobin and white blood cells were significantly decreased at 10 kg m^-3, while there was no significant change in red blood cells. The significant increases in cortisol level and the enzymatic activities of alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase at 10 kg m^-3 clearly supported inorganic nitrogen compounds-triggered stress. A significant elevation of lipid peroxidation value and depletion of intracellular glutathione were observed at 5 and/or 10 kg m^-3 in the liver tissue. The hepatic enzymatic activities of antioxidant defense enzymes, catalase and superoxide dismutase were also significantly increased. When a protein skimmer removes the inorganic nitrogen compounds at the highest density, most parameters showed no significant change. Taken together, these results suggest that accumulated inorganic nitrogen compounds at the highest stocking density inhibit innate immunity and induce oxidative stress in red seabream. This information will be helpful to maintain homeostasis of red seabream by controlling immunity and oxidative status through inorganic nitrogen compounds removal in intensive culture condition.