Impacts of endocrine-disrupting compounds in fish

By Charlotte Stevenson, USC Sea Grant

If you can’t see something with your eyes, can it leave fingerprints?  According to Professor Kevin Kelley of California State University, Long Beach, something invisible indeed leaves fingerprints. To find them, just use the right tools and know where to look.

Worldwide, and especially in urban coastal waters like those of Southern California, wildlife and humans are exposed to increasing quantities and types of persistent industrial, domestic, and pharmaceutical chemicals. Many of these contaminants, classified as endocrine-disrupting compounds (EDCs), significantly alter endocrine systems and consequently disrupt important physiological functions and health. 

With the support of The University of Southern California (USC) Sea Grant Program and the California Ocean Protection Council, Dr. Kelley has pioneered the use of a cutting-edge technology—proteomics—to see the “fingerprints” or impacts of EDCs in fish.

Traditionally, scientists determine endocrine disruption by picking one biomarker (usually a particular protein affected by a suspected EDC) and by testing for its presence or absence (or increase or decrease) in a population of organisms suspected of EDC exposure. This approach often requires trial and error and provides a limited picture of what actually is happening inside a fish.

Alternatively, Dr. Kelley’s proteomics technique simultaneously assesses the expression of 1000s of biomarkers in a single tissue sample. His research has produced proteomics maps for each species of fish he studies, showing all the proteins expressed in a given endocrine tissue (e.g., liver, adrenal gland, testes, ovary). Each protein has its own specific position in the map. By lining up the proteome map of a test fish with the proteome map of a reference fish from a non-contaminated site, Dr. Kelley and his team can characterize the molecular and physiological effects associated with contaminant exposures and endocrine disruption. In other words, they can pinpoint the “fingerprints” left by endocrine-disrupting contaminants. 

For an environmental manager, proteomics is powerful and valuable as a screening tool as more protein biomarkers are identified and added into the proteomics map. Not only can mangers test to see if fish are being affected by the usual suspects of contamination (e.g. DDT, PCBs), but they can also see the effects of trace contaminants, the synergistic effects of contaminant combinations, the effects of yet unknown (“new”) chemicals, and even the effects associated with environmental changes such as ocean acidification, hypoxic events, and changes in water temperature due to climate change. If the endocrine system is being affected in any way, Dr. Kelley can see it on the proteome map.

Dr. Kelley’s work provides a valuable, real-time, direct link between academic science and the regulatory community by collaborating with Dr. Jeffrey Armstrong, Environmental Supervisor at the Orange County Sanitation District. “Our collaborations with Dr. Kelley and his students have given us valuable information about potential effects from our discharge that we would have otherwise missed,” says Dr. Armstrong. “Plus, his work in other areas of Southern California allows us to put our results into a regional context, which is very helpful from a potential regulatory perspective.”

Moreover, environmental managers have based water quality objectives on measuring contaminant concentration alone and assuming risk for marine life based upon limited published laboratory studies. But simply knowing that a contaminant is present in the water does not help managers understand if and how it is affecting wildlife. There is a critical need for a scientifically-based understanding of the impacts of water quality on wildlife. Further development of bioanalytical technologies such as endocrine and proteomic screening methods—like those pioneered by Dr. Kelley’s Sea Grant research—could allow water quality agencies and managers to develop objectives in a more ecosystem-based manner by linking endocrine disruption directly to the anthropogenic contaminants causing the disruption.

For more information on Dr. Kelley’s research