Prenatal Damage from Dioxin Shown to Involve microRNAs

A new study by researchers from the University of Carolina, recently published in the journal PLOS ONE, identified novel mechanisms through which dioxin, a well-known environmental contaminant, can alter physiological functions. The research team, which included Narendra Singh, Mitzi Nagarkatti and Prakash Nagarkatti of the USC School of Medicine, demonstrated that exposure to dioxin (TCDD) during pregnancy in an experimental mouse model can cause significant toxicity to the foetus, and specifically to the organs that produce the immune cells that fight infections. They found that dioxin alters small molecules called microRNAs, which can affect the expression of a large number of genes. During the study, the researchers examined over 608 microRNAs, and 78 of these were significantly altered following exposure to dioxin. On the basis of the pattern of changes in these molecules, the team was also able to predict that dioxin can alter several genes that regulate cancer. Many other physiological systems were also affected, including those involved in reproductive, gastrointestinal, haematological, inflammation, renal and urological diseases as well as genetic, endocrine and developmental disorders. Dioxin is a highly toxic chemical produced as a by-product of industrial processes, such as the manufacture of herbicides or pesticides or the bleaching of paper. Because it degrades slowly in the environment and is soluble in fats, dioxin can bio-accumulate in the food chain and is often found in high concentrations in the milk and fat of animals in contaminated regions. “Our results lend more credence to the hypothesis that foetal exposure to environmental contaminants can have life-long effects,” said Mitzi Nagarkatti. “Prenatal damage to the expression of microRNAs in the immune system could well impact the adult immune response.”

Science Daily, 17 September 2012 ;http://www.sciencedaily.com ;