Exploring the effect of short-term exposure to non-functionalized polystyrene nanoparticles on selected chromatin determinants in human immune cells and plasmid DNA integrity

The effect of non-functionalized polystyrene nanoparticles (PS-NPs) with diameters of 29, 44, and 72 nm on plasmid DNA integrity and the expression of genes involved in the architecture of chromatin was investigated in human peripheral blood mononuclear cells (PBMCs). The cells were incubated with PS-NPs at concentrations ranging from 0.001 to 100 µg/mL for 24 hours. Gene expression profiling was carried out using quantitative real-time PCR for the following genes: those involved in DNA methylation (<i>DNMT1</i>, <i>DNMT3A</i>), DNA demethylation (<i>TET2</i>, <i>TET3</i>), and chromatin remodeling, including histone methylation (EHMT1, EHMT2) and histone deacetylation (<i>HDAC3</i>, <i>HDAC5</i>). Furthermore, the expression of selected epigenetic markers related to histone acetylation and methylation (H3ac, H3K4me3, H3K9me3) at the protein level was examined using Western blotting. To assess the potential direct interaction of PS-NPs with DNA, a plasmid relaxation assay was performed in an extracellular system. The results demonstrated that PS-NPs do not cleave plasmid DNA directly. The gene expression analysis indicated that PS-NPs did not alter the expression of <i>DNMT1</i>, <i>TET2</i>, <i>TET3</i>, <i>EHMT1</i>, <i>EHMT2</i>, <i>HDAC3</i>, or <i>HDAC5</i> in PBMCs. However, statistically significant changes in the expression of the <i>DNMT3A</i> gene were observed after exposure to 29 nm nanoparticles (<i>p</i> = 0.016, Kruskal-Wallis test), although post hoc comparisons did not reveal significant differences between individual treatment groups, and no clear dose-dependent trend was evident. PS-NPs induced a statistically significant decrease in post-translational histone modifications, specifically H3ac and H3K4me3. These findings suggest that PS-NPs may influence the epigenetic mechanisms involved in the regulation of chromatin architecture.