Epigenetics and environmental chemicals.
OBJECTIVE
Epigenetics investigates heritable changes in gene expression occurring without changes in DNA sequence. Several epigenetic mechanisms, including DNA methylation, histone modifications, and microRNA expression, can change genome function under exogenous influence. Here, we review current evidence indicating that epigenetic alterations mediate toxicity from environmental chemicals.


RESULTS
In-vitro, animal, and human investigations have identified several classes of environmental chemicals that modify epigenetic marks, including metals (cadmium, arsenic, nickel, chromium, and methylmercury), peroxisome proliferators (trichloroethylene, dichloroacetic acid, and TCA), air pollutants (particulate matter, black carbon, and benzene), and endocrine-disrupting/reproductive toxicants (diethylstilbestrol, bisphenol A, persistent organic pollutants, and dioxin). Most studies conducted so far have been centered on DNA methylation, whereas only a few investigations have studied environmental chemicals in relation to histone modifications and microRNA.


CONCLUSIONS
For several exposures, it has been proved that chemicals can alter epigenetic marks, and that the same or similar epigenetic alterations can be found in patients with the disease of concern or in diseased tissues. Future prospective investigations are needed to determine whether exposed individuals develop epigenetic alterations over time and, in turn, which such alterations increase the risk of disease. Also, further research is needed to determine whether environmental epigenetic changes are transmitted transgenerationally.
Baccarelli
Andrea
A
Laboratory of Environmental Epigenetics, Center of Molecular and Genetic Epidemiology, Department of Environmental and Occupational Health, University of Milan, Via San Barnaba 8, Milan, Italy. andrea.baccarelli@unimi.it
Bollati
Valentina
V
D000818:Animals; D004781:Environmental Exposure; D044127:Epigenesis, Genetic / Q000187:drug effects*; D020022:Genetic Predisposition to Disease; D006801:Humans; D007287:Inorganic Chemicals / Q000633:toxicity*; D009930:Organic Chemicals / Q000633:toxicity*; D012307:Risk Factors
D007287:Inorganic Chemicals; D009930:Organic Chemicals