Study On Immune Toxicity And Mechanism Of Bisphenol A To Carp(Cyprinus Carpio)

Bisphenol A (BPA) is a well-known endocrine disrupting chemical (EDCs) withestrogen-like effects on human and other animals, which is ubiquitous in water,sediments, aquatic organisms and other aquatic environmental media. As an importantindustrial chemical, BPA was widely employed as a plastic monomer and plasticizerin the manufacture. In recent years, BPA has obtained great public attentions due toits detrimental effects on human health and ecosystem as a consequence of globallylarge-scale production and extensive application in the consumer products. Using redcarp (Cyprinus carpio), a typical fresh fish species in China as a model, the presentstudy investigated the adverse effects of long-term exposure to BPA at environmentalrelevant concentrations on the antioxidative defense system and the innate immunesystem of red carp. Also, the impact of acute exposure to BPA on the antioxidativedefense system and the innate immune-related gene expression in primarymacrophages of red carp was determined. Furthermore, to explore the actionmechanism of BPA in fish immune cells, the co-exposures of BPA at differentconcentrations combined with anti-estrogen were set. The results were shown asfollows:1. The long-term exposure (30d) to BPA at environmental relevant levels (0.1,1,10,100, and1,000μg/L) significantly inhibited the activities of antioxidant enzymesincluding catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase(GPx), and increased the content of malondialdehyde (MDA) in red carp livers. Ourresults indicated that the chronic exposure to environmental relevant levels of BPAinhibited the antioxidant enzyme activities, which might lead to an accumulation ofreactive oxygen species in red carp, and thus induced lipid peroxidation and affectedthe oxidation defense system in red carp.2. The long-term exposure (30d) to environmental relevant levels of BPA (0.1,1,10,100, or1,000μg/L) induced the immunoglobulin content but inhibited thecomplement C3content, and the lysozyme activity and the respiratory burst in serumwere affected upon the exposure. Our results showed that the chronic exposure to environmental relevant levels of BPA might have adverse effects on the innateimmune system of red carp.3. Primary macrophages from the head kidney of red carp were successfullycultured in vitro and the culture conditions were optimized including the optimumculture medium, the optimum pH (7.2-7.4), the optimum temperature (26℃), theoptimum cell density(1×107cells/well) and optimum adherent time (24h). Thecultured cells were verified as monocyte macrophages by trypan blue, non-specificesterase and Wright Giemsa Staining methods. The acute exposure (6h) toenvironmental relevant levels of BPA (0.1,1,10,100, or1,000μg/L) significantlyinduced CAT and SOD activities but decreased the MDA content in primarymacrophages. These results suggested that the acute exposure to BPA might changethe redox status in macrophages and lead to an increase of reactive oxygen species(ROS), which might promote antioxidant enzyme activities as a positive feedback toeliminate the ROS, and thus lead to a decrease of MDA content. Meanwhile, theresults showed that in the10μg/L BPA exposure group, all the tested oxidative stressparameters were significantly affected by the exposure, which therefore might be athreshold of BPA toxicity to macrophages of red carp.4. To determine the impact of BPA exposure on the immune-related geneexpression in primary macrophages of red carp, acute exposure to BPA for6h at arelatively low and a relatively high concentrations of BPA were set at10and5×104μg/L, respectively. The results showed that the interleukin genes (IL-1β, IL-10, M17)were induced in primary macrophages upon the exposure but the tumor necrosisfactor genes (TNF-α1, TNF-α2) were restrained. These observations implied thatacute BPA exposure might promote the innate immune reactions in macrophages toenhance their immune functions to resist the environmental stress. Furthermore,co-exposures of BPA combined with an estrogen receptor inhibitor ICI182,780wereset to explore the action mechanism of BPA toxicity in immune cells. The resultsindicated that the co-exposure with ICI182,780significantly minimized the effects ofBPA on the immune related gene expression in the relatively high BPA co-exposuregroup; however it did not have significant influence in the relatively low BPA co-exposure group. Thus, it was speculated that the action mechanism of BPA in fishmacrophates might be different at low concentrations from that at high concentrations.In conclusion, the present study indicated that the environmental relevant levelsof BPA exposure significantly affected the antioxidant defense system and the innateimmune system functions in red carp. Also, the results revealed a susceptibility ofinnate immune system of fish to estrogenic EDCs and suggested a different actionmechanism of BPA at the low concentration from that at the high concentration inimmune cells. In addition, we provided an in vitro culture method of primarymacrophages from fish, which might be useful for the risk assessment ofimmunotoxicity and further investigation of action mechanisms of exogenouspollutants in the aquatic environment.