Perfluoroalkyl substances (PFASs), a class of man-made chemicals, are widely used in daily and industrial products because of their water-, oil-, stain and heat resistant properties, such as food wrappers and non-stick cookware. PFASs are stable and persistent in the environment and in many species, range from wildlife, plants and humans. PFASs have been suggested to be carcinogenic without DNA damage and are believed to act as non-genotoxic agents. Many non-genotoxic xenobiotics have been found to induce toxicity by altering DNA methylation patterns. Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) related adverse effects may be induced through changing DNA methylation status.
DNA methylation is a mechanism of epigenetic regulation and is essential for the development of mammals, involves the addition of a methyl group to the 5-position of a CpG dinucleotide. Early embryonic development may be particularly susceptible to epigenetic dysregulation caused by environmental exposures because DNA methylation patterns are being established and cell division rates are high. Change of DNA methylation level may affect genomic stability and gene expression without directly changing DNA sequence. Global DNA hypomethylation is generally associated with genomic instability and is commonly observed in many complex diseases.
A recent study led by Dr. Chen-yu Liu at the National Taiwan University College of Public Health, examined the prenatal PFASs exposures effects at global DNA methylation estimated in Alu and LINE-1 repeated elements in a birth cohort study in Taiwan. The study used the subjects from Taiwan Birth Panel birth cohort study, including all pregnant women who gave birth between July 2004 and June 2005 in four hospitals in Taipei city and New Taipei City. A total of 363 mother-infant pairs were included in the final analyses. PFOA, PFOS, PFNA (perfluorononanoic acid) and PFUA (perfluoroundecanoic acid) were measured by UPLC-MS/MS in cord blood. LINE-1 and Alu repeated elements from cord blood was used to represent global DNA methylation levels.
Results showed that Alu methylation levels decreased with the increase of PFOS exposure measurement (β = −0.33, 95 percent CI = (−0.63, −0.02) by using a multivariable models adjusting for parental education level, maternal BMI, maternal age, delivery method (vaginal delivery or cesarean section), parity, infant sex, gestational age, and cotinine levels in cord blood. No significant effects between PFOA, PFNA, PFUA and methylation levels in the multivariable regression models were observed.
These findings were published online in the May issue of International Journal of Environmental Research and Public Health.
Liu, C. Y., P. C. Chen, P. C. Lien, and Y. P. Liao. “Prenatal Perfluorooctyl Sulfonate Exposure and Alu DNA Hypomethylation in Cord Blood” Int J Environ Res Public Health 15, no. 6 (May 24 2018).