Electronic Theses and Dissertations

Title

Synthesis and Evaluation of Naturally Occuring Halogenated Bipyrroles in a Relevant Marine Species, Fundulus Heteroclitus

Date of Award

2012

Document Type

Dissertation

Degree Name

M.S. in Engineering Science

First Advisor

Kimberly S. Foster

Second Advisor

Marc Slattery

Third Advisor

Kristine Willett

Abstract

Halogenated dimethyl-2-2'-bipyrroles (HDBPs) have recently been discovered in seabird eggs and have been shown to bioaccumulate in trophic organisms. HDBPs are suspected to be biogenic in nature, derived from evidence of marine natural products that are persistent in the environment and widespread in the Pacific and Atlantic Ocean. The HDBPs exhibit chlorinated and brominated substitution patterns that closely resemble anthropogenic pollutants like the polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs), and polybrominated diphenyl ethers (PBDEs). Environmental health concerns exists regarding these naturally occurring HDBPs because several of these analogs were shown to induce the cytochrome P4501A (CYP1A) gene through activation of the AhR signaling pathway, similar to other anthropogenic pollutants. They also result in porphyrin accumulation in chicken embryo hepatocytes. Based on these studies, we have focused our efforts on examining the effects of HDBP's to inhibit heme oxygenase (HO), the enzyme responsible for the catalytic oxidation of heme, which may account for the accumulation of porphryrins in hepatocyte models. Within the current study we have synthesized and characterized several natural product halogenated bipyrroles, and examined their effect on heme oxygenase-1, utilizing assays performed on liver lysates obtained from mice treated with the heme oxygenase-1 inducer, cobalt protoporphyrin. The ability of the halogenated bipyrroles to inhibit HO was evaluated by measuring the amount of bilirubin formed from the HO-catalyzed oxidation of hemin. Several of the analogs were found to be modest inhibitors of HO, and these results suggest that porphyrin accumulation from halogenated bipyrrole exposure may be mediated by the direct inhibition of heme oxgyenase-1. We have also focused our efforts on examining the developmental toxicity in a marine relevant species, Fundulus heteroclitus. We measured also the induction of the cytochrome P4501A (CYP1A) gene through activation of AhR signaling pathway by HDBPs. Fundulus are considered to be the "premier teleost model" in marine biology research, having several functionalized genes capable of tolerating exposure to many environmental contaminants. Exposure of three HDBP's to Fundulus revealed that several of these analogs exhibited significant EROD induction, to negative and positive controls DMSO and PCB126, respectively.

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