In vivo assessment of respiratory burst inhibition by xenobiotic exposure using larval zebrafish

Adaptation of the in vivo respiratory burst assay for fathead minnow larvae (Pimephales promelas)

Initial innate immune responses such as the respiratory burst response of phagocytes present the first line of defense in response to exposure to pathogens. Several respiratory burst assays have been developed in mammals, cell cultures, and whole zebrafish embryos as a reliable indicator of the innate immune response of a host, and these assays are being used to screen various environmental contaminants for their immunotoxic potential. While zebrafish are a common laboratory fish used in toxicology studies geared towards human health effects, fathead minnows are commonly used as an ecotoxicological indicator species for North America. In this technical note, we describe how we adapted the zebrafish in vivo respiratory burst assay for use in fathead minnow larvae. This assay provides promising expansion of using in vivo respiratory burst responses in different species of larval fish for future comparative immunotoxicity assays, as well as laying the groundwork for studies that can better define the development of the innate and adaptive immune responses of fathead minnow larvae.

Per- and polyfluoroalkyl substances alter innate immune function: evidence and data gaps

Per- and polyfluoroalkyl substances (PFASs) are a large class of compounds used in a variety of processes and consumer products. Their unique chemical properties make them ubiquitous and persistent environmental contaminants while also making them economically viable and socially convenient. To date, several reviews have been published to synthesize information regarding the immunotoxic effects of PFASs on the adaptive immune system. However, these reviews often do not include data on the impact of these compounds on innate immunity. Here, current literature is reviewed to identify and incorporate data regarding the effects of PFASs on innate immunity in humans, experimental models, and wildlife. Known mechanisms by which PFASs modulate innate immune function are also reviewed, including disruption of cell signaling, metabolism, and tissue-level effects. For PFASs where innate immune data are available, results are equivocal, raising additional questions about common mechanisms or pathways of toxicity, but highlighting that the innate immune system within several species can be perturbed by exposure to PFASs. Recommendations are provided for future research to inform hazard identification, risk assessment, and risk management practices for PFASs to protect the immune systems of exposed organisms as well as environmental health.

A study on the effectiveness of sodium selenite in treating cadmium and perfluoro octane sulfonic (PFOS) poisoned zebrafish (Danio rerio)

Perfluoro octane sulfonate (PFOS) and cadmium (Cd) are toxic elements in the environment. As a micronutrient trace element, selenium (Se) can mitigate the adverse effects induced by PFOS and Cd. However, few studies have examined the correlation between Se, PFOS and Cd in fish. The present study focused on the antagonistic effects of Se on PFOS+Cd-induced accumulation in the liver of zebrafish. The fish was exposed to PFOS (0.08mg/L), Cd (1mg/L), PFOS+ Cd (0.08 mg/L PFOS+1 mg/L Cd), L-Se (0.07mg/L Sodium selenite +0.08mg/L PFOS+1mg/L Cd), M-Se (0.35mg/L Sodium selenite + 0.08mg/L PFOS+ 1 mg/L Cd), H-Se (1.75 mg/L Sodium selenite + 0.08 mg/L PFOS+ 1mg/L Cd) for 14d. The addition of selenium to fish exposed to PFOS and Cd has been found to have significant positive effects. Specifically, selenium treatments can alleviate the adverse effects of PFOS and Cd on fish growth, with a 23.10% improvement observed with the addition of T6 compared to T4. In addition, selenium can alleviate the negative effects of PFOS and Cd on antioxidant enzymes in zebrafish liver, thus reducing the liver toxicity caused by PFOS and Cd. Overall, the supplementation of selenium can reduce the health risks to fish and mitigate the injuries caused by PFOS and Cd in zebrafish.

Legacy and emerging per- and polyfluoroalkyl substances suppress the neutrophil respiratory burst

Per- and polyfluoroalkyl substances (PFASs) are used in a multitude of processes and products, including nonstick coatings, food wrappers, and fire-fighting foams. These chemicals are environmentally-persistent, ubiquitous, and can be detected in the serum of 98% of Americans. Despite evidence that PFASs alter adaptive immunity, few studies have investigated their effects on innate immunity. The report here presents results of studies that investigated the impact of nine environmentally-relevant PFASs [e.g. perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid potassium salt (PFOS-K), perfluorononanoic acid (PFNA), perfluorohexanoic acid (PFHxA), perfluorohexane sulfonic acid (PFHxS), perfluorobutane sulfonic acid (PFBS), ammonium perfluoro(2-methyl-3-oxahexanoate) (GenX), 7H-perfluoro-4-methyl-3,6-dioxa-octane sulfonic acid (Nafion byproduct 2), and perfluoromethoxyacetic acid sodium salt (PFMOAA-Na)] on one component of the innate immune response, the neutrophil respiratory burst. The respiratory burst is a key innate immune process by which microbicidal reactive oxygen species (ROS) are rapidly induced by neutrophils in response to pathogens; defects in the respiratory burst can increase susceptibility to infection. The study here utilized larval zebrafish, a human neutrophil-like cell line, and primary human neutrophils to ascertain whether PFAS exposure inhibits ROS production in the respiratory burst. It was observed that exposure to PFHxA and GenX suppresses the respiratory burst in zebrafish larvae and a human neutrophil-like cell line. GenX also suppressed the respiratory burst in primary human neutrophils. This report is the first to demonstrate that these PFASs suppress neutrophil function and support the utility of employing zebrafish larvae and a human cell line as screening tools to identify chemicals that may suppress human immune function.

Acute Aquatic Toxicity to Zebrafish and Bioaccumulation in Marine Mussels of Antimony Tin Oxide Nanoparticles

Antimony tin oxide (Sb₂O₅/SnO₂) is effective in the absorption of infrared radiation for applications, such as skylights. As a nanoparticle (NP), it can be incorporated into films or sheets providing infrared radiation attenuation while allowing for a transparent final product. The acute toxicity exerted by commercial Sb₂O₅/SnO₂ (ATO) NPs was studied in adults and embryos of zebrafish (Danio rerio). Our results suggest that these NPs do not induce an acute toxicity in zebrafish, either adults or embryos. However, some sub-lethal parameters were altered: heart rate and spontaneous movements. Finally, the possible bioaccumulation of these NPs in the aquacultured marine mussel Mytilus sp. was studied. A quantitative analysis was performed using single particle inductively coupled plasma mass spectrometry (sp-ICP-MS). The results indicated that, despite being scarce (2.31 × 10⁶ ± 9.05 × 10⁵ NPs/g), there is some accumulation of the ATO NPs in the mussel. In conclusion, commercial ATO NPs seem to be quite innocuous to aquatic organisms; however, the fact that some of the developmental parameters in zebrafish embryos are altered should be considered for further investigation. More in-depth analysis of these NPs transformations in the digestive tract of humans is needed to assess whether their accumulation in mussels presents an actual risk to humans.

Exposure to polycyclic aromatic hydrocarbons and the associations with oxidative stress in waste incineration plant workers from South China

Waste incineration is one of the most common emission sources of polycyclic aromatic hydrocarbons (PAHs), causing potential occupational exposure in waste incineration workers. However, relative investigations among waste incineration plant workers are still very limited, particularly in China. Therefore, we collected urine specimens from 77 workers in a waste incineration plant as the exposed group, and 101 residents as the control group in Shenzhen, China. Nine mono-hydroxylated PAH metabolites (OH-PAHs) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were measured, and their internal relationships were explored. The urinary levels of most OH-PAHs and 8-OHdG in the exposed group exhibited high levels versus another group (p < 0.05). We found negative associations between OH-PAHs and 8-OHdG in the control group (p < 0.05), while most of OH-PAHs were not associated with 8-OHdG in the exposed group, which indicated that the exposure to waste incineration could enlarge the level of individual oxidative stress damage. Nevertheless, PAHs were less likely to trigger obvious health risks in exposed workers through estimation of human intake and exposure risks. This study provides a reference for occupational PAH exposure and strengthen the need of health monitoring among incineration workers.

Leaching of PAHs from rubber modified asphalt pavements

The present study aimed to, for the first time, quantify the total content of 16 priority EPA PAHs in end-of-life tyre derived crumb rubber granulates and various manufactured rubberised asphalt mix designs. After identifying the availability of 16 EPA PAHs, the leaching behaviour of rubberised asphalt specimens, were evaluated using the Dynamic Surface Leaching Test (DSLT) based on CEN/TS 16637-2:2014 standard. This was prior to modelling the release mechanisms of PAHs by utilizing a mathematical diffusion-controlled leaching model. According to the results, the total content of 16 EPA PAHs in crumb rubber granulates ranged between 0.061 and 8.322 μg/g, which were associated with acenaphthene and pyrene, respectively. The total content of PAHs in rubberised asphalt specimens varied between 0.019 and 4.992 μg/g depending on the volume of crumb rubber granulates in the asphalt concrete mix design, and type of binder. Results of the leaching experiments revealed that the highest leached PAHs were benzo[b]fluoranthene, benzo[k]fluoranthene and naphthalene with a 64-days cumulative release per specimen surface area > 1 μg/m². Acenaphthylene, fluoranthene, fluorene and indeno[1,2,3-c,d]pyrene were released in cumulative concentrations between 0.1 and 1 μg/m². The PAHs with a cumulative release potential below 0.1 μg/m² during DSLT were benzo[a]anthracene, benzo[a]pyrene, benzo[g,h,i]perylene and chrysene. The diffusion coefficients, which were calculated by mathematical modelling of DSLT data, revealed that the leaching process of 16 EPA PAHs from surface of rubberised asphalt concrete mix designs fitted all the criteria set by the NEN 7345 standard for diffusion-controlled leaching during all stages of leaching experiments.

A review of human and animals exposure to polycyclic aromatic hydrocarbons: Health risk and adverse effects, photo-induced toxicity and regulating effect of microplastics

Polycyclic aromatic hydrocarbons (PAHs) are one of the most widely distributed persistent organic pollutants (POPs) in the environmental media. PAHs have been widely concerned due to their significant health risk and adverse effects to human and animals. Currently, the main sources of PAHs in the environment are the incomplete combustion of fossil fuels, as well as municipal waste incineration and agricultural non-surface source emissions. In this work, the scope of our attention includes 16 typical PAHs themselves without involving their metabolites and industrial by-products. Exposure of human and animals to PAHs can lead to a variety of adverse effects, including carcinogenicity and teratogenicity, genotoxicity, reproductive- and endocrine-disrupting effects, immunotoxicity and neurotoxicity, the type and severity of which depend on a variety of factors. On the other hand, the regulatory effect of microplastics (MPs) on the bio-toxicity and bioaccumulation capacity of PAHs has now gradually attracted attention. We critically reviewed the adsorption capacity and mechanisms of MPs on PAHs as well as the effects of MPs on PAHs toxicity, thus highlighting the importance of paying attention to the joint bio-toxicity caused by PAHs-MPs interactions. In addition, due to the extensive nature of the common exposure pathway of PAHs and ultraviolet ray, an accurate understanding of biological processes exposed to both PAHs and UV light is necessary to develop effective protective strategies. Finally, based on the above critical review, we highlighted the research gaps and pointed out the priority of further studies.