TP23 Environmental Hypoxia
Tuesday, 15 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(HEN-1117-574289) Cross-talk between pyrene and hypoxia signaling pathways in embryonic Cyrpinodon variegatus.

Hendon, L¹, Carlson, E¹, Manning, S¹, Brouwer, M¹, ¹ Department of Coastal Sciences, University of Southern Mississippi, Ocean Springs, MS, United States

ABSTRACT- The aryl hydrocarbon nuclear translocator (ARNT) is a general dimeric partner for the aryl hydrocarbon receptor (AhR) and hypoxia-inducible factor one alpha (HIF1-). The AhR/ARNT complex binds to promoters in target genes, such as CYP1A1, resulting in alterations in gene expression, while the HIF1-/ARNT heterodimer binds to hypoxia response elements in target genes, such as VEGF. While AhR is activated by PAHs, such as pyrene, HIF1- is activated by hypoxia. Since ARNT is a general dimeric partner for both AhR and HIF1-, possible cross-talk may exist between the two pathways in which the activation of one results in inhibition of the other. The objective of this study is to determine if pyrene-activation of AhR2 or hypoxia-activation of HIF1- can sequester the ARNT protein away from HIF1- and AhR2, respectiviely, resulting in reduced developmental toxicity associated with hypoxia or pyrene alone in embryonic Cyprinodon variegatus. As a first step to examine this hypothesis, we cloned AhR2, CYP1A1 (PAH-activated gene), and VEGF (HIF-activated gene). Next, pyrene (20, 60, and 150 ppb) and hypoxia's (1-2 ppm) individual developmental toxicity endpoints were determined, together with CYP1A1 and VEGF expression levels using real-time quantitative RT-PCR. Combined treatments of pyrene and hypoxia are examined in order to determine sequestration of the ARNT protein and developmental toxicity endpoints. Results demonstrate that pyrene-treated embryos alone develop toxicity endpoints such as pericardial edema and dorsal body curvature. Hypoxia-treated embryos alone display delayed hatching and less-developed characteristics in comparative to normoxic treatments. This research addresses the individual combined effects of PAHs and low DO concentrations in embryonic development and provides a clearer understanding of the mechanisms that cause these responses.

Key words: AhR2, ARNT, hypoxia, pyrene