Exposure to 17α-Ethinylestradiol Results in Differential Susceptibility of Largemouth Bass (Micropterus salmoides) to Bacterial Infection

[Image: see text] Disease outbreaks, skin lesions, mortality events, and reproductive abnormalities have been observed in wild populations of centrarchids. The presence of estrogenic endocrine disrupting compounds (EEDCs) has been implicated as a potential causal factor for these effects. The effects of prior EEDC exposure on immune response were examined in juvenile largemouth bass (Micropterus salmoides) exposed to a potent synthetic estrogen (17α-ethinylestradiol, EE2) at a low (EE2(Low), 0.87 ng/L) or high (EE2(High), 9.08 ng/L) dose for 4 weeks, followed by transfer to clean water and injection with an LD(40) dose of the Gram-negative bacteria Edwardsiella piscicida. Unexpectedly, this prior exposure to EE2(High) significantly increased survivorship at 10 d post-infection compared to solvent control or EE2(Low)-exposed, infected fish. Both prior exposure and infection with E. piscicida led to significantly reduced hepatic glycogen levels, indicating a stress response resulting in depletion of energy stores. Additionally, pathway analysis for liver and spleen indicated differentially expressed genes associated with immunometabolic processes in the mock-injected EE2(High) treatment that could underlie the observed protective effect and metabolic shift in EE2(High)-infected fish. Our results demonstrate that exposure to a model EEDC alters metabolism and immune function in a fish species that is ecologically and economically important in North America.