Effects of Environmental Pollutants on Gene Expression

Stephanie McPherson

While at first glance breast milk and fish may seem to have little in common, Associate Professor of Veterinary and Animal Sciences Kathleen Arcaro sees a relationship in these seemingly disparate areas of study. For the past six years, Arcaro and her team have been studying the effects of environmental pollutants on gene expression in fish and the health of cells present in human breast milk. “Fish serve as sentinels for water quality, while the breast milk and cells present in the milk provide biomarkers of human exposure and effect. In both cases we’re particularly interested in those pollutants that have hormonal activity,” Arcaro says.

Arcaro has several projects underway with the Japanese Medaka, a small freshwater fish. She has teamed with Professor of Civil and Environmental Engineering David Reckhow to monitor the effects of aquatic pollutants with a particular focus on personal care products and pharmaceuticals in water. Reckhow gathers samples from water treatment plants from across the nation and prepares extracts. Then Arcaro places the fish in fresh water with the extracts and studies the effectiveness of the water treatment processes. “Does their treatment remove any compounds that might have hormonal activity, like an estrogen that causes cells to grow and divide?”, Arcaro asks. After the fish have been exposed to the water, Arcaro checks certain tissues, particularly the liver, for unusual changes. For example, if a male fish is exposed to estrogen he will start to produce the protein vitellogenin, which is the precursor to forming eggs.

Arcaro’s research is valuable for detecting classes of contaminants with a known effect, rather than for identifying the contaminant. “I couldn’t tell you what was in the water, but I could tell you that it had this effect,” she says. It is a good method of determining whether or not a full chemical screening is necessary. “If you screen very quickly the 20 water samples [with the fish] and they have no effect, then you don’t want to go on and do the more expensive chemical analysis. But if you screen one and it has an effect, then you better go find out what’s there,” she says.

In another related line of research involving fish studies, Arcaro and several of her colleagues at UMass Amherst - Professors of Chemistry Vincent Rotello, Richard Vachet and Julian Tyson, and Professor of Sociology Douglas Anderton – are cooperating on a study in which Arcaro is exposing fish to monolayer-protected gold nanoparticles in an effort to understand the fate, transport, and bioavailability of nanoparticles in the environment. The widespread use of nanoparticles in all types of products assures that they will be released into the environment, yet little is known about how and where nanoparticles will accumulate and their effects on the health of wildlife and humans.

“The first step is just to see where these nanoparticles go,” says Arcaro. “They’re in the water, so they can potentially be taken up by the fish and spread through the body.” After 24 or 48 hours of exposure, the team harvests a variety of tissues including the gills, intestine, liver, gonads, brain and muscles. “It looks as if the nanoparticles accumulate first in the intestines and gills and then slowly pass to the gonads and liver.” Arcaro says. Then, through the same methods used for the analysis of vitellogenin, the team looks closely to see if nanoparticles affect the performance of the tissues.

Arcaro adds the human element to her research with her studies of breast milk. “Many of the pollutants in our environment, including pesticides, plasticizers, and flame retardants are lipophilic, “fat loving”, and so accumulate in fatty tissue such as breast milk while other compounds from our diet or environment are present in the liquid portion of milk,” say Arcaro. Breast milk can give us information about a lifetime of exposure as well as what a woman ate for dinner. Arcaro and her colleagues have assessed the levels of various pollutants in milk from women living in western Massachusetts. The good news is that levels of some pollutants such as the banned polychlorinated biphenyls have greatly decreased in the last 20 years. Unfortunately the levels of other compounds, such the flame retardants and synthetic musks, are slowly increasing.
As we produce and release more and more chemicals into the environment we need to monitor breast milk, not because we know that the chemicals get into the breast milk and cause harm, but rather because we don’t know where the chemicals end up. Arcaro states, ““I think it’s so important to study breast milk because infants are at the very top of the food chain.”

Breast milk not only allows us to monitor pollutant levels, the millions of cells present in human milk provide a window into the breast and a means to assess the health of the breast cells. Arcaro has ongoing studies that will examine levels of pollutants in breast milk donated from women across the country. In addition, the cells from these breast milk samples will be utilized as a potential screen for changes in DNA indicative of breast cancer risk. Breast milk can be used as a tool to measure pollutant load, and may one day be used as a noninvasive method to detect breast cancer risk.