Date of Award
1-1-2015
Document Type
Dissertation
Degree Name
Ph.D. in Pharmaceutical Sciences
Department
Biomolecular Sciences
First Advisor
Kristine L. Willett
Second Advisor
Michael N. Lehman
Third Advisor
Asok K. Dasmahapatra
Relational Format
dissertation/thesis
Abstract
Benzo[a]pyrene (BaP) is a ubiquitous environmental contaminant that is both an endocrine disruptor and a carcinogen. Aromatase (CYP19) is a key enzyme in steroidogenesis playing a key role in the hypothalamus-pituitary-gonad feedback loop. We hypothesized that BaP would negatively impact cyp19a1b expression in zebrafish, in turn, adversely affecting development and physiology. Here, we consider whether the toxicities observed following BaP exposure are comparable to those following a transient morpholino (MO)-mediated CYP19a1b knockdown or exposure to an aromatase inhibitor (fadrozole) during early development. One-cell zebrafish embryos were injected with a CYP19a1b-MO or control-MO. Other non-injected embryos were exposed to nominal waterborne concentrations of BaP (0, 10 or 50 ?g/L) and fadrozole (0, 10 or 50 ?g/L) for 96 hours post-fertilization (hpf). Real-time PCR shoboth BaP concentrations significantly decreased cyp19a1b expression in 96 hpf zebrafish larvae homogenates. Likewise, concentrations of E2 in 48 hpf whole body larval homogenates were significantly decreased by BaP, fadrozole and CYP19a1b-MO. Cumulative mortality of zebrafish larvae was significantly increased following BaP and fadrozole exposure and CYP19a1b knockdown compared to controls. Estradiol (E2, 10 nM) co-treatment rescued mortality mediated by 10 μg/L BaP, 10 μg/L fadrozole, and CYP19a1b-MO. In a treatment-blinded morphological assessment of larvae at 96 hpf, several phenotypes were negatively impacted by BaP, fadrozole, and CYP19a1b knockdown including body length, optic vesicle size, swim bladder inflation, pericardial and abdominal edema, and incidence of normal larval tail shape and these effects were reversed by exogenous E2-cotreatment. Decreased incidence of normal pectoral fins was only impacted by BaP exposure. In conclusion, certain adverse developmental outcomes caused by BaP exposure are at least in part related to BaP-mediated CYP19a1b inhibition.
Recommended Citation
Alharthy, Khalid M., "Effects of benzo[a]pyrene and CYP19a1b knockdown on zebrafish development" (2015). Electronic Theses and Dissertations. 1482.
https://egrove.olemiss.edu/etd/1482
Concentration/Emphasis
Emphasis: Environmental Toxicology