Channel Catfish (Ictalurus punctatus) White Blood Cells are Functionally Modulated by Estrogens

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Estrogens are recognized as modulators of immune responses in mammals, but how these effects might occur in fish was not understood. U.S. Geological Survey (USGS) scientists published findings that fish white blood cells (leukocytes) have specific estrogen receptors (ERs)—a discovery that moves scientists one step closer to understanding the connection between exposure to estrogenic substances and disease susceptibility in fish.

A diagram of how estrogens interact with estrogen receptors

A diagram of how estrogens, such as 17βestradiol, interact with estrogen receptors ERα and ERβ2 of white blood cells. Once activated by estrogenic chemicals the estrogen receptors interact with the cell's DNA. The immune system functions in a delicate balance which can be disrupted by estrogens with the potential to affect disease susceptibility. In the background is an electron micrograph of channel catfish macrophages (42TA cell line). Photo Credit: Jan Lovy, New Jersey Division of Fish and Wildlife, as modified by David W. Morganwalp, USGS.

USGS scientists confirmed that channel catfish (Ictalurus punctaus) leukocytes express ERα and ERβ2. Activation of these receptors changed leukocyte responses when tested in the laboratory. Also, the expression of these receptors changed upon activation of leukocytes following exposure to immunostimulants. This research identifies dynamic relationships between estrogens and the cellular responses within the immune system.

Estrogens are one class of compounds that can cause endocrine disruption in fishes. While estrogens are known to disrupt reproductive physiology, less is known about the effects these compounds might have on the immune response. Interestingly, periodic fish mortality and suggestions of immune impairment have been observed in aquatic ecosystems where estrogenic compounds have been found and where female characteristics have been identified in the testes of male fish—evidence of endocrine disruption. This research establishes baseline evidence that these endocrine disrupting compounds not only change reproductive physiology but may also make fish more prone to disease.

This research was funded by the USGS Ecosystems Mission Area’s Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology), Contaminant Biology and Priority Ecosystems Science, and Fisheries: Aquatic and Endangered Resources Program.