ABSTRACT

Here we report epigenomic and transcriptomic changes in a prototypical J774 macrophage after engulfing talc or titanium dioxide particles in presence of estrogen. Macrophages are the first immune cells to engage and clear particles of various nature. A novel paradigm is emerging, that exposure to so-called ‘inert’ particulates that are considered innocuous is not really free of consequences. We hypothesized that especially the insoluble, non-digestible particles that do not release a known hazardous chemical can be underappreciated agents acting to affect the regulation inside macrophages upon phagocytosis. We performed gene chip microarray profiling and found that talc alone, and especially with oestrogen, has induced a substantially more prominent gene expression change than titanium dioxide; the affected genes were involved in pathways of cell proliferation, immune response and regulation, and, unexpectedly, enzymes and proteins of epigenetic regulation. We therefore tested the DNA methylation profiles of these cells via epigenome-wide bisulphite sequencing and found vast epigenetic changes in hundreds of loci, remarkably after a very short exposure to particles; ELISA assay for methylcytosine levels determined the particles induced an overall decrease in DNA methylation. We found a few loci where both the transcriptional changes and epigenetic changes occurred in the pathways involving immune and inflammatory signalling. Some transcriptomic and epigenomic changes were shared between talc and titanium dioxide, however, it is especially interesting that each of the two particles of similar size and insoluble nature has also induced a specific pattern of gene expression and DNA methylation changes which we report here.

摘要

在这里，我们报告了在雌激素存在下吞噬滑石粉或二氧化钛颗粒后原型 J774 巨噬细胞的表观基因组和转录组变化。巨噬细胞是第一个参与和清除各种性质颗粒的免疫细胞。一种新的范式正在出现，即暴露于被认为是无害的所谓“惰性”颗粒并非真的没有后果。我们假设，特别是不释放已知危险化学物质的不溶性、不可消化颗粒可能是被低估的药剂，它们在吞噬作用时影响巨噬细胞内部的调节。我们进行了基因芯片微阵列分析，发现单独的滑石粉，特别是与雌激素一起，比二氧化钛诱导了明显更显着的基因表达变化。受影响的基因参与细胞增殖、免疫反应和调节的途径，以及出乎意料的表观遗传调节的酶和蛋白质。因此，我们通过表观基因组范围内的亚硫酸氢盐测序测试了这些细胞的 DNA 甲基化谱，发现数百个基因座发生了巨大的表观遗传变化，尤其是在很短的时间暴露于粒子之后。甲基胞嘧啶水平的 ELISA 测定确定颗粒诱导 DNA 甲基化的总体降低。我们发现了一些基因座，其中转录变化和表观遗传变化都发生在涉及免疫和炎症信号传导的途径中。然而，滑石粉和二氧化钛之间共有一些转录组和表观基因组变化，