Epigenetic mechanisms in Transgenerational Effects of an Environmental Pollutant

摘要 新生儿期的细菌感染导致高发病率和死亡率，并在发展中 国家应为26%的死亡负责。众所周知，怀孕期间存在的环境因素 影响包括葡萄球菌在内的新生儿的危及生命的感染。金黄色葡萄球菌感染，尽管其机制是 不清楚。摘要四氯二苯并对二恶英(TCDD)是一种通过细胞质作用的环境污染物。 芳香烃受体(AhR)。虽然AhR因其在调节毒性方面的作用而被很好地描述 最近，在TCDD的介导下，AhR的激活被证明调节T细胞分化为Tregs或Th17 细胞。我们已经产生了令人兴奋的初步数据，表明TCDD激活AhR抑制T细胞 对葡萄球菌肠毒素B(SEB)的反应，这是由表观遗传途径介导的，包括 激活的T细胞中microRNA(MiR)表达、DNA甲基化和组蛋白修饰的失调。 更重要的是，我们的研究表明，TCDD可能对T细胞产生跨代表观遗传效应 细胞。基于上面讨论的葡萄球菌感染的重要性，我们将使用SEB作为抗原来 验证这一中心假设，即TCDD对Vβ8+T细胞AhR激活在减少 促炎症Th1/Th17细胞以及增加抗炎树突状细胞及其亚群 调节miR的表达，这可能取决于DNA甲基化、组蛋白修饰和 可以跨代传递的染色质重塑。由于SEB可激活Vβ8+ T细胞占外周T细胞的30%，我们的研究旨在确定TCDD诱导的 在怀孕期间母亲接触TCDD或TCDD后，F0、F1、F2和F3世代的变化持续存在 交配前母亲/父亲接触(F0)。在目标1中，我们将确定 TCDD对SEB诱导的CD4+T细胞分化的影响我们将测试TCDD对TCR克隆性和 Vβ8+T细胞应答(Th1、2、17、Tregs)的多样性在目标2中，我们将研究特定的 MIR在F0-F3代CD4+T细胞分化中的作用此外，将特异性miR基因导入T细胞 将进行模拟或反交配子来逆转TCDD诱导的T细胞分化，并确定 这种影响将代代相传。在目标3中，我们将确定全基因组和特定位点的作用 调节Th/Treg差异表达的特异性miR启动子上CpG位点的DNA甲基化 世世代代对SEB的反应。目标4将阐明组蛋白的允许和抑制修饰 TCDD介导的参与CD4+T细胞miR跨代异常的染色质可及性 差异化。最后，将评估这些变化是通过男性还是女性生殖系留下的。 所提出的研究在TCDD介导的免疫毒性的新的表观遗传途径方面具有重要意义 跨越几代人将被识别。此外，了解AhR配体如何通过 表观遗传途径将导致创新预防和治疗模式的发展。

Abstract Bacterial infections during neonatal phase cause high rates of morbidity and mortality, and in developing countries are responsible for 26% of deaths. Environmental factors present during pregnancy are known to impact life-threatening infections in newborns, including Staph. aureus infections, although the mechanisms are unclear. Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental pollutant, which acts through the cytosolic aryl hydrocarbon receptor (AhR). While AhR has been well characterized for its role in regulating toxicity mediated by TCDD, recently, AhR activation was shown to regulate T cell differentiation into T regs or Th17 cells. We have generated exciting preliminary data indicating that AhR activation by TCDD suppresses T cell response to Staphylococcal enterotoxin B (SEB) and that this is mediated by epigenetic pathways including dysregulation in microRNA (miR) expression, DNA methylation, and histone modifications in activated T cells. More importantly, our studies have suggested that TCDD may exert transgenerational epigenetic effects on T cells. Based on the importance of Staph infections discussed above, we will use SEB as an antigen to test the central hypothesis that AhR activation of Vβ8+ T cells by TCDD, plays a crucial role in reducing pro-inflammatory Th1/Th17 cells as well as increasing anti-inflammatory Tregs and its subsets by modulating miR expression, and that this may depend on DNA methylation, histone modifications and chromatin remodeling that could be transmitted transgenerationally. Inasmuch as, SEB can activate Vβ8+ T cells which constitute ~30% of peripheral T cells, our studies are aimed at determining whether TCDD-induced changes persist in F0, F1, F2, and F3 generations following maternal exposure during pregnancy to TCDD or maternal/paternal exposure prior to mating (F0). In Aim 1, we will determine the transgenerational effects of TCDD on SEB-induced CD4+ T cell differentiation. We will test the effect of TCDD on the TCR clonality and diversity of the Vβ8+ CD4+ T cell response (Th1, 2, 17, Tregs) to SEB. In Aim 2, we will study the role of specific miRs in CD4+ T cell differentiation in F0-F3 generations. Furthermore, transfection of T cells with specific miR mimics or antagomirs will be performed to reverse T cell differentiation induced by TCDD and determine whether the effects persist across generations. In Aim 3, we will determine the role of genome-wide and locus-specific DNA methylation on CpG sites on promoters of specific miR that regulate differential expression of Th/Treg response to SEB across the generations. Aim 4 will elucidate the permissive and repressive histone modification and chromatin accessibility in TCDD-mediated transgenerational dysregulation of miR involved in CD4+ T cell differentiation. Lastly, whether these changes are imprinted through male or female germline will be assessed. The proposed studies are highly significant in that novel epigenetic pathways of TCDD-mediated immunotoxicity across generations will be identified. Also, understanding how AhR ligands mediate differential effects through epigenetic pathways would lead to development of innovative preventive and therapeutic modalities.