Date of Award

12-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Environmental Toxicology

Advisor

Rice, Charles D

Committee Member

Bain , Lisa J.

Committee Member

Schwedler , Thomas E.

Committee Member

Hurk , Peter V.

Abstract

Atlantic killifish, Fundulus heteroclitus, have adapted to, or at least developed a level of resistance to creosote-based polycyclic aromatic hydrocarbons (PAHs) found at the Atlantic Wood (AW) superfund site in the southern branch of the Elizabeth River, VA USA. Historically, 90+% of the mummichogs at this site have hepatic lesions of varying severity, and 30+% of these fish have tumors of various origin. Many xenobiotics, including select PAHs found at the Atlantic Wood site, are ligands for the aryl hydrocarbon receptor (AhR), which is a promiscuous ligand-dependent transcription factor involved in developmental regulation, environmental sensing, and induction of a suite of phase I, II, and III drug metabolizing enzymes. Subsequent to the discovery of the AW killifish population, investigators demonstrated that these fish were recalcitrant to AhR activation and CYP1A induction following exposure to model PAHs. Moreover, killifish embryos collected from the AW site are still resistant to the cardiac and craniofacial deformities typically associated with exposure to PAHs and sediments collected from the AW site. In this study, the issue of CYP1A inducibility in AW fish collected in situ was re-examined nearly 2 decades after first discovery, and shown that the gene expression of this sentinel biomarker of AhR activation was significantly higher in intestines in comparison to a reference population. The livers of AW mummichogs were examined by IHC to discover that CYP1A and AhR2 protein patterns reflect tissue damage from lesions, and/or intrinsic cellular physiology of tumors, rather than recalcitrant induction of CYP1A. Gene expression profiles also indicated that liver COX-2 is elevated in livers of these fish. A monoclonal antibody was then generated against COX-2 (mAb CX53-1) and used to observe the possible role of COX-2 and inflammation in Atlantic Wood fish liver lesions. COX-2 protein expression was very high in macrophage aggregates and surrounding tumors, suggesting chronic inflammation. Further characterization of the gut innate immune system focusing on eosinophilic cell infiltration and lysozyme levels demonstrated higher activity. Overall, these findings suggest that AW fish are not necessarily recalcitrant to CYP1A induction, and thus seem to have active functional AhR2 protein(s) in non-damaged tissues. These fish are also under chronic inflammatory stress.

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