During the Vietnam War, the United States military sprayed over 74 million litres of Agent Orange (AO) to destroy forest cover as a counterinsurgency tactic in Vietnam, Laos and Cambodia. The main ingredient was contaminated by 2,3,7,8-tetrachlorodibenzo-paradioxin (TCDD). DNA methylation (DNAm) differences are potential biomarker of environmental toxicants exposure. The aim of this study was to perform a preliminary investigation of the DNAm levels from peripheral blood of the present-day Vietnamese population, including individuals whose parents, according to historical data, were exposed to AO/TCDD during the war. 94 individuals from heavily sprayed areas (cases) and 94 individuals from non-sprayed areas (controls) were studied, and historical data on alleged exposure of parents collected. 94 cases were analysed considering those whose father/parents participated in the war (N = 29) and considering the place of residence of both parents (64 living in sprayed areas versus 30 in non-contaminated areas). DNAm levels in CYP1A1 and IGF2 genes were measured (MALDI-TOF technology). The analyses showed that: 1) one CpG site in the CYP1A1 and one in the IGF2 gene showed significant differences in DNAm levels between cases and controls; 2) the CYP1A1 region resulted to be hypomethylated (in 9 out of 16 sites/units; p-val<0.01) in 29 individuals whose father/parents participated in the war in the spray zones; 3) we showed that the place of residence of both parents influenced methylation levels of the CYP1A1 and IGF2 genes (p-val<0.05). In conclusion this study indicates that past environmental exposure to dioxin (AO/TCDD) shapes the DNAm profile of CYP1A1 and that the place of living for parents in former spray zones influences DNAm of CYP1A1 and IGF2 genes. These results open the way to new applications of DNAm as potential biomarker(s) of past human exposure to dioxin.

在越南战争期间，美国军队喷洒了超过7400万升的特工Orange（AO），以摧毁森林覆盖，这是越南，老挝和柬埔寨的一种平叛策略。主要成分被2,3,7,8-四氯二苯并-对二恶英（TCDD）污染。DNA甲基化（DNAm）差异是环境有毒物质暴露的潜在生物标志物。这项研究的目的是对当今越南人口的外周血DNAm水平进行初步调查，其中包括根据历史数据其父母在战争期间暴露于AO / TCDD的个体。研究了来自大量喷洒地区（病例）的94个人和来自非喷洒地区（对照）的94个人，并收集了据称父母暴露的历史数据。对94例病例进行了分析，考虑了父亲/父母参加战争的人（N = 29）并考虑了父母双方的居住地（64人居住在喷雾区，而30人生活在未受污染的区）。测定CYP1A1和IGF2基因的DNAm水平（MALDI-TOF技术）。分析表明：1）CYP1A1的一个CpG位点和IGF2的一个CpG位点在病例和对照之间的DNAm水平上显示出显着差异；2）CYP1A1区域被低甲基化（在16个位点/单位中有9个位点； p-val <0.01），其29个父母/父母参加了喷雾区的战争。3）我们发现父母双方的居住地都会影响CYP1A1和IGF2基因的甲基化水平（p-val <0.05）。总而言之，这项研究表明，过去暴露于二恶英（AO / TCDD）的环境影响了CYP1A1的DNAm分布，父母在前喷雾区的居住地影响了CYP1A1和IGF2基因的DNAm。这些结果为DNAm作为过去人类暴露于二恶英的潜在生物标志物的新应用开辟了道路。