Investigating the Toxicity of Dioxin

By Michelle Werts posted 03-26-2014 17:45


“I consider this to be our award. I share it with all of the members of my lab at University of Wisconsin-Madison and other colleagues and partners who have worked on this research.” That was how this year’s SOT Distinguished Toxicology Scholar began his 2014 Award Lecture titled “Investigating the Toxicity of Dioxin.”

This sincere, humble moment was followed by a lecture that highlighted Dr. Richard Peterson’s studies into dioxin—work that SOT Past President William Slikker in his speaker introduction said led to a paradigm shift that allowed aquatic animals to be used to study human health issues.

SOT_14_bg_0630.jpgDr. Peterson began by describing his early research into dioxin, which focused on the effect of exposure in rats. Specifically, studies were conducted around in utero and lactational TCDD, a type of dioxin, exposure. In these studies, the researchers discovered a couple of key things. First, it was discovered that TCDD exposure affected the male reproductive system. The second was that the timing of the dioxin exposure was critical to determining how sensitive the rats were to dioxin exposure.

The team then moved onto studies in mice, wondering if they would see similar effects in to the prostate—the main target organ of the dioxin in the rats. Dr. Peterson discovered ventral prostate agenesis in mice from dioxin exposure and that dioxin inhibits ventral prostatic bud formation.

The next organism that Dr. Peterson studied in relation to dioxin was lake trout in Lake Ontario. The fish had become extinct in the lake by the 1950s, leading researchers to posit a number of theories into the fish’s decline while restocking efforts occurred in the 1960s and 70s. In the 70s, scientists observed a lake of natural recruitment during the reproductive process—a lack which continued into the 80s. Dr. Peterson and team decided to investigate if environmental contaminants were a factor in this phenomenom.

In the early 90s, they discovered that lake trout were one of the most sensitive invertebrates to dioxin-induced mortality. To discover if this might have been a factor in the species decline in Lake Ontario, a collaborative team collected sediment cores from the bottom of Lake Ontario and tested them for chemical levels. The results showed that Lake Ontario’s dioxin exposure levels represented a bell curve—with the chemical showing up in the 40s, reaching its peak by the 60s before declining into the 80s.

From this research, Dr. Peterson began to wonder if studying dioxin heart toxicity in another invertebrate, zebrafish, could be used to understand human heart conditions from dioxin exposure. Through his research, he found that effects in zebrafish hearts to diseases observed in humans were very similar.

After listening to the highlights from decades of evolving research, it was no surprise to me that the Society chose to award Dr. Peterson with its Distinguished Toxicology Scholar Award, as his contributes to our understanding of the effects of environmental dioxin exposure are significant.