Silver nanoparticle-induced hemoglobin decrease involves alteration of histone 3 methylation status

Abstract

a b s t r a c tSilver nanoparticles (nanosilver, AgNPs) have been shown to induce toxicity in vitro and in vivo; however, the molecular bases underlying the detrimental effects have not been thoroughly understood. Although there are numerous studies on its genotoxicity, only a few studies have investigated the epigenetic changes, even less on the changes of histone modifications by AgNPs. In the current study, we probed the AgNP-induced alterations to histone methylation that could be responsible for globin reduction in erythroid cells. AgNP treatment caused a significant reduction of global methylation level for histone 3 (H3) in erythroid MEL cells at sublethal concentrations, devoid of oxidative stress. The ChIP-PCR analyses demonstrated that methylation of H3 at lysine (Lys) 4 (H3K4) and Lys 79 (H3K79) on the b-globin locus was greatly reduced. The reduction in methylation could be attributed to decreased histone methyltransferase DOT-1L and MLL levels as well as the direct binding between AgNPs to H3/H4 that provide steric hindrance to prevent methylation as predicted by the all-atom molecular dynamics simulations. This direct interaction was further proved by AgNP-mediated pull-down assay and immunoprecipitation assay. These changes, together with decreased RNA polymerase II activity and chromatin binding at this locus, resulted in decreased hemoglobin production. By contrast, Ag ion-treated cells showed no alterations in histone methylation level. Taken together, these results showed a novel finding in which AgNPs could alter the methylation status of histone. Our study therefore opens a new avenue to study the biological effects of AgNPs at sublethal concentrations from the perspective of epigenetic mechanisms.

Nanomedicine and epigenome. Possible health risks

“…ZAC1 is an imprinted gene, critical in the control of embryonic growth . Sublethal AgNP concentrations induced a reduction in haemoglobin levels in mouse erythroleukemia cells through diminished H3K4me3 and H3K79me1 methylation, attributed to the inhibition of specific HMTs DOT-1L and MLL or to direct binding of AgNPs to histones H3/ H4 (Qian et al, 2015). In cells exposed to AgNPs, expression of hsamiR-219-5p was negatively correlated with the expression of MT1F and TRIB3 genes, involved in oxidative stress, cell cycle and apoptosis (Eom et al, 2014).…”

Silver_ nanoparticles inhibited erythrogenesis during zebrafish embryogenesis

“…Recently, AgNPs were found to block transcription of globin genes by inhibiting RNA polymerase activity and by altering histone 3 methylation status in erythroid progenitor cells (Qian et al, 2015;Wang et al, 2013). However, few studies reported toxic effects of AgNPs during vertebrate erythrogenesis by using an in vivo model.…”

Epigenetic modulation upon exposure of lung fibroblasts to TiO₂ and ZnO nanoparticles: alterations in DNA methylation

“…35,36 Similar study on silver NPs (AgNPs) shows that at sublethal levels AgNP can alter histone methylation, thereby effecting globin gene expression in red blood cells. 37 Copper oxide and gold NPs are shown to induce alterations in miRNA expression. [38][39][40] Recent study has reported that short-term exposure to engineered NPs leads to epigenetic alterations and an increase in L1 and Alu/SINEs mRNA transcripts in macrophages and lung epithelium.…”

“…Limited data suggest that exposure to some NPs, such as cadmium telluride quantum dots, SiO 2 , AgNP, gold NP, multiwalled carbon nanotubes, copper oxide, and engineered NPs adversely affect epigenetic landscape. [31][32][33][34][35][36][37][38][39][40][41] To our knowledge, global DNA methylation and Dnmt expression levels have not previously been investigated for TiO 2 and ZnO NP. Our results suggest that global hypomethylation is associated with concentration of NPs.…”