Contaminant-Related Thyroid Disruption In Wild Fish In Southern And Northern California: Cause And Effect Evaluations Website
Kevin M. Kelley - California State University, Long Beach
Jesus A. Reyes - Pacific Coast Environmental Conservancy
Jeffrey L. Armstrong - Environmental Laboratory and Ocean Monitoring Division, Orange County Sanitation District
Period: 2/1/2012 -
|Federal Funds:||State Funds:|
In the urban ocean and estuarine environments of California, wildlife and humans are exposed to a wide variety of anthropogenic chemicals, both domestic and industrial in origin. Many chemicals are persistent and can bio-accumulate in animals, yet knowledge of their physiological effects is extremely limited. One class of mechanisms by which chemicals may act, is by perturbing endocrine systems. This may include changing the gene expression and secretion of hormones, modulating hormone actions at their target tissues, and/or affecting hormone clearance, and it can lead to dysregulation of physiological functions essential to homeostasis, adaptation, & survival. Understanding which environmental contaminants are active in animals, and the extent of their maladaptive effects, is critical to effective management of our coastal environments.
In preliminary work in both northern and southern California coastal environments, we have found that that the thyroid endocrine system is significantly disrupted in certain populations of wild fishes, including shiner surfperch and Pacific staghorn sculpin in San Francisco Bay and flatfish living offshore of Los Angeles and Orange Counties. Part of this work was recently published (Brar et al. 2010) and implicated certain kinds of anthropogenic contaminants in the thyroid disruption including polychlorinated biphenyls (PCBs) and certain chlorinated pesticides.
Among vertebrate hormones, thyroid hormones are unique in that they exert physiological effects on almost every tissue, and their target receptors are found in all cell types. Thyroid hormones are particularly involved in the regulation of growth and development, as well as metabolism, and they interact with other endocrine systems (e.g., growth endocrine system). Since changes in thyroid status can have significant physiological and developmental impacts, disruption of this system by persistent environmental chemicals presents a significant concern for wildlife living in the impacted coastal environments identified by the preliminary work.
Based on the preliminary work and current scientific literature, the overall hypothesis of the proposed study is that environmental contaminants will be significantly associated with disruption of the thyroid endocrine system and directly related to specific functional components within the HPT axis. An associated secondary hypothesis is that disruption of the thyroid endocrine system will be correlated to maladaptive alterations in important physiological systems, including growth and intermediary metabolism.
To address these hypotheses, there are three principal objectives in the proposed study:
1) To identify underlying mechanisms (molecular, physiological) of the environmental thyroid endocrine disruption. This work is also expected to lead to new measures (e.g., molecular) that will be useful in future efforts to screen for this type of endocrine disruption in fish, and to identify specific active EDCs
2) To determine which environmental contaminants (EDCs) are associated with the environmental thyroid endocrine deficits. Accumulated environmental chemicals in fish will be correlated with thyroid disruption parameters. This work is expected to lead to candidate EDCs that can then be laboratory tested for their direct actions on thyroid endocrine parameters, in order to begin to establish cause & effect relationships.
3) To evaluate the extent to which important thyroid regulated physiological functions exhibit maladaptive alteration, in order to predict greater impacts relevant to ecosystem-based management. This work is expected to determine the nature of the relationships between thyroid endocrine disruption and associated impacts on physiological performance (growth, metabolism).
A key objective of the proposed study is to characterize the nature of this environment-related disruption on multiple functional components of the thyroid endocrine system, in order to understand the mechanism(s) by which this environmental effect is manifested in wild fish of Californias urban ocean. We will compare three different fish species (surfperch, sculpin, English sole) and different locations where the thyroid disruption occurs in both southern and northern California. The study sites provide a variety of conditions (contaminated-industrial to remote-uncontaminated) under which indices of thyroid function can be assessed, in Phase I of the study. Incidence and magnitude of alterations in plasma thyroid hormones, thyroid glandular functions, and peripheral enzyme systems involved in thyroid hormone regulation (deiodinases) will be evaluated. Phase II studies will use these data to identify study groups for additional molecular physiological analyses (see next paragraph). Liver samples will also be prepared for measurement of organic and metal contaminant concentrations, which will be carried out at an instrumentation core facility next to the laboratory (www.iirmes.org).
Data generated from Phase I of the study will be used to evaluate site-associated differences in thyroid endocrine status, and their correlative relationships with fish exposures to environmental contaminant chemicals. Of interest will be the comparability between different fish species and between the locations in both northern and southern California, in terms of the kinds and classes of chemical exposures associated with the thyroid disruption (are PCBs a common problem?) and the nature of the disruptive effects (implication of thyroid glandular function, peripheral deiodinase alterations).
The Phase I results will guide Phase II analyses. For example, where T3/T4 ratios implicate potential differences in peripheral 5-deiodinase activity, we will measure 5-deiodinase activity; we recently established a sensitive assay in which 5-deiodinase activity is highly correlated with T3/T4 ratio (R=0.97), for use in these studies. In addition, we are establishing an assay to measure rT3, to determine whether D3 deiodinase may be operative in thyroid hormone turnover. If the generated data indicate significant changes in deiodinase activity, we will pursue cloning cDNAs for D1-D3, to develop qPCR assays to measure mRNA expression, an approach repeatedly used in our laboratory.
Where Phase I results implicate thyroid glandular function, we will assess potential impacts in three ways, by histomorphological analysis of thyroid follicles in the fish, by analysis of protein expression changes using proteomic approaches, and measurement of enzymes involved in thyroid hormone turnover (including phase II enzymes).
Hepatic contaminant concentrations, measured in the same fish, will be correlated with all indices of thyroid function (hormone concentrations, histological measures, deiodinase and other enzymatic measures, thyroid synthetic responsiveness) and also evaluated using multivariate statistical approaches to understand relationships among environmental constituents and the phenotypic measures. These analyses is aimed at identifying the specific relationships among disrupted components of thyroid endocrine system function and specific environmental contaminant(s) to which the fish have been exposed.
The study will also evaluate the relationships between the thyroid disrupted condition and measures of growth and intermediary metabolism, potentially very important physiological effects. Thyroid hormones are important regulators for maintaining normal growth in all vertebrates including fish.
These studies will ascertain whether the thyroid disruption is associated with additional deficits in physiologically important growth and metabolic indices.
In total, this study strives to bridge the gap between observed environment chemicals and metals, accumulated contaminants in fish, and biological effects. The study will also provide indicators of wider impacts (physiological performance) more directly relevant to ecosystem-based management. Through all of the studies proposed here, a highly integrative analytical approach will be taken, with the same individuals being measured for a large number of parameters (e.g., hormones, protein expression and activity, contaminants, physiological), enabling analyses to identify relationships among environmental contaminants, measured factors and phenotypic changes.
Results from this study are expected to shed light on the affected targets of contaminants in the thyroid endocrine system, which is important for determining the mechanism(s) of action of the operative environmental agents as well as to identify possible specific bioassays (biomarkers) that can be used in screening in subsequent environmental monitoring efforts. Additionally, the findings will establish the extent to which the observed environmental disruption of thyroid function may be translated into impaired physiological performance indices in the fish.
Our preliminary work uncovered significant thyroid system disruption in wild fish in association with contaminated locations in northern and southern California. The study will directly study this important water quality problem and is aimed at providing critical information relevant to management of marine resources, including characterizing the nature of the effect in the fish, identification of related environmental contaminants, and providing key data on the larger ecologically relevant impacts on physiological performance. This project brings together an academic research laboratory with expertise in fish endocrinology and toxicology, an important regional agency (Orange County Sanitation District), and a minority-owned non-for-profit environmental organization (Pacific Coast Environmental Conservancy); these partners are providing important non-federal match for this projects successful outcome.
The objectives of the proposed work are directly relevant to State and regional environmental managers, as they work toward effective ecological-based management, which has traditionally developed water quality objectives based on concentrations of contaminants alone. The support letters from Orange County and the PCEC attest to this relevance and benefit of our proposed project to their evolving needs. There is a critical need for scientifically based understanding of impacts of water quality on wildlife in the urban ocean habitats of coastal California, and the proposed project directly addresses this need.
Publications & other print media:
Analysis of endocrine disruption in southern California coastal fish using an aquatic multi-species microarray. 2008. ME Baker, B Ruggeri, J Sprague, C Eckhardt, J Lapira, I Wick, L Soverchia, M Ubaldi, AM Polzonetti-Magni, DE Vidal-Dorsch, SM Bay, JR Gully, JA Reyes, KM Kelley, D Schlenk, EC Breen, R, G Hardiman. pp. 65-78 in: SB Weisberg and K Miller (eds.), Southern California Coastal Water Research Project 2008 Annual Report. Southern California Coastal Water Research Project. Costa Mesa, CA.
Video, electronic, and computer products: