The annual meeting of the Superfund Research Program (SRP) brings together researchers, trainees, and administrators from SRP research centers to share their latest research on environmental health problems and toxic waste remediation.

Two University of Iowa graduate students received special recognition for their research findings during the 2011 Superfund Annual Meeting in Lexington, Ky. Fabian Grimm received first-place honors in the biomedical poster session, and Richard Meggo was honored with the third-place award among those with non-biomedical posters.

Over 70 trainees presented their biomedical and non-biomedical research at the conference.

Grimm, a Ph.D. student in the Interdisciplinary Graduate Program in Human Toxicology, presented his poster, “Sulfated Metabolites of Polychlorinated Biphenyls are High-Affinity Ligands for Human Transthyretin” at the conference. His mentor is Michael Duffel, professor of medicinal and natural products chemistry in the College of Pharmacy and faculty member in the Human Toxicology Program.

Richard Meggo, a Ph.D. candidate in civil and environmental engineering, presented his poster titled, "Rhizosphere Biotransformation Products of Selected PCB Congeners.” His mentor is Jerry Schnoor, professor of civil and environmental engineering in the College of Engineering and faculty member in the Human Toxicology Program.

Grimm has found that sulfated metabolites of polychlorinated biphenyls (PCBs) bind to a protein found in blood plasma called transthyretin. Transthyretin is a transporter of the thyroid hormone thyroxine in the blood and the brain.

Using an optimized, fluorescence-based method to derive binding constants, consisting of two molecules at equilibrium, Grimm hypothesized that sulfated metabolites of PCBs may interfere with the proper delivery of thyroid hormones to certain tissues. Thyroid hormones are responsible for regulation of metabolism.

“We are arguing that these PCBs are able to bind to transthyretin in the plasma and the cerebrospinal fluid, thereby interfering with the proper delivery of thyroid hormones, particularly to target sites in the central nervous system,” Grimm says.

Transthyretin carries thyroxine from the thyroid gland through the blood and is believed necessary for the transport of thyroid hormones across the blood-brain barrier. Exposure to PCBs has been related to decreased cognitive function in children, and it has been hypothesized that this may, at least in part, be caused by PCB-induced hypothyroidism. Displacement of thyroxine from its binding sites on transthyretin could be a contributing mechanism since transthyretin is the only thyroxine transport protein in the brain.  

“People would generally assume that sulfated metabolites of PCBs will be excreted, but we have shown that these sulfates bind to transthyretin, a fact that indicates for the first time their potential toxicological relevance, particularly with respect to thyroid hormone disruption,” Grimm says.