Mercury exposure induces the release of neutrophil extracellular traps and apoptosis in carp neutrophils

Abstract Mercury, an important toxic contaminant, has been reported to have toxic effects on fish and mammals. Neutrophil extracellular traps (NETs) not only plays an important role in defending against infection but also leads to the damage of the tissues. In this study, we aimed to investigate the effects of mercury exposure on the formation of NETs in carp neutrophils. Neutrophils were isolated from the blood of common carps and incubated with different concentrations of mercury chloride. The formation of NETs were observed by laser confocal microscopy and quantitatively measured by picoGreen. The results showed that mercury chloride significantly induced the formation of NETs in carp neutrophils, which was a DNA-based network structure modified with myeloperoxidase (MPO) and histone (H3). Meanwhile, treatment of mercury chloride increased the production of reactive oxygen species (ROS), and decreased the activities of SOD and CAT. Furthermore, mercury treatment could induce the apoptosis of carp neutrophils. In addition, the results showed that mercury chloride-induced NETs were not inhibited by NADPH oxidase inhibitor DPI, AMPK inhibitor Compound C and p38 inhibitor SB202190, suggesting it was independent of ROS, AMPK, and p38. In conclusion, the results indicated that mercury chloride could induce the formation of NETs, which plays an important foundation for further study on the influence and mechanism of mercury chloride on the immune system.