Introduction
In fish culture setting grounds, exogenous steroids input is a matter of concern. Recently, we unveiled that in the gilthead seabream (Sparus aurata), the G-protein-coupled estrogen receptor agonist G-1 (G1) and the endocrine disruptor 17α-ethinylestradiol (EE2) are potent modulators in polyreactive natural antibodies production. However, the integral role of the microbiota upon antibody production under the effect of EE2 remains largely unexplored.
Material and Methods
Here, 240 juvenile seabreams continuously exposed for 84 days to oral G1 or EE 2 at a fixed dose (5 μg /g food) were i.p. vaccinated on day 42 with the model antigen keyhole lymphet hemocyanin (KLH). A critical panel of systemic and mucosal immune markers, serum vitellogenin, humoral enzymatic, and bacteriolytic activities were recorded and correlated with the gut bacterial microbiome 16S rRNA status one day post priming (dpp ). Besides, 15 dpp animals received a boost to explore the systemic- and mucosal-specific anti-KLH titers production by the end of the trial.
Results and Conclusion
EE 2 but not G1 induced a significant shift in the serum vitellogenin level one dpp. Simultaneously, in the serum and gut mucus of the EE 2 treated group, we recorded significant changes in some immune enzymatic activities. While we only inferred an attenuated profile in the immunized groups. The gut genes qPCR analysis exhibited a related pattern only emphasized by the significant shift on the EE 2 group il1b expression. The gut bacterial microbiome undergoes dynamic changes in alpha diversity indices, but only with exposure to dietary G1, supporting functional alterations on cellular processes, signaling, and lipid metabolism. By the same token, the immunization in both treated groups decreased the relative abundance of Fusobacteria and remarkably promoted changes in the estrogen-associated bacterial genera. Besides, systemic and mucosal KLH-specific IgM/T titers observed significant changes after 84 days of estrogenic oral administration.
In summary, these are the first results highlighting the intrinsic relationship between estrogens and their associated receptors in the ubiquitous fish immune regulation and the subtle but significant crosstalk with the gut endobolome.
Acknowledgements
This study was funded by Fundación Séneca , Coordination Center for Research, CARM (04538/GERM/06). The Spanish Ministry of Science and Innovation (AGL2008-04575-C02-01 co-funded with Fondos Europeos de Desarrollo Regional/European Regional Development Funds). Ministerio de Ciencia e Innovación and FEDER (AGL2017-85978-C2-1-R). The Fundación Séneca (CARM) (19883/GERM/15) .