The rats reared by attentive mothers had different levels of corticoid gene expression and lower levels of stress hormones than those reared by inattentive mothers. Szyf found he could cure the stressed rats by injecting a chemical called TSA into their brains, which reversed the inappropriate methylation caused by inattentive mothering.
This understanding of epigenetics may lead to new medications for treating human problems. By using approaches similar to those used in the rat study, Szyf is hoping to find drugs that will help alleviate human psychiatric conditions.
Szyf also studied the preserved brains of suicide victims and of people who died suddenly from causes other than suicide. He found that certain genes in the suicide victims were methylated, or turned off. In contrast, those same genes were not methylated in the victims who died by other means. Abnormal methylation patterns could cause depression in some people, he said.
Some compounds, such as nickel, chromium and arsenic, are well-known carcinogens—not because they are toxic to cells but because of their epigenetic effect, said Max Costa, a New York University professor of environmental medicine and pharmacology. They increase DNA methylation, which results in gene silencing and cell transformation and leads to cancer, he explained.
Researchers at the meeting spent a great deal of time discussing whether and how to test chemicals for their ability to cause epigenetic changes.
Most researchers there agreed that compounds need to be tested for epigenetic effects. But practical testing of the 80,000 or so chemicals in commerce would require rapid screens that would prioritize the compounds into high, medium, and low-risk groups. Those at high risk for epigenetic effects could then be subjected to more definitive and expensive tests.
John M. Greally, associate professor at the Albert Einstein College of Medicine in New York City, pointed out that no single test is ideal for detecting epigenetic effects.
“All of the assays have drawbacks,” he said. For example, one assay requires immediate sample processing so it cannot be used on stored samples.
Nevertheless, many researchers said that testing chemicals for epigenetic changes can begin soon.