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

Area of Science:

• Epigenetics
• Nanotoxicology
• Molecular Biology

Background:

• Silver nanoparticles (AgNPs) exhibit toxicity, but underlying molecular mechanisms, especially epigenetic changes like histone modifications, remain unclear.
• While genotoxicity of AgNPs is studied, their impact on histone methylation is less understood.
• Investigating AgNP-induced epigenetic alterations is crucial for understanding their biological effects.

Purpose of the Study:

• To investigate AgNP-induced alterations in histone methylation in erythroid cells.
• To determine if these epigenetic changes contribute to reduced globin production.
• To elucidate the molecular mechanisms behind AgNP-mediated epigenetic modifications.

Main Methods:

• Treatment of erythroid MEL cells with AgNPs at sublethal concentrations.
• Global methylation analysis of histone 3 (H3).
• Chromatin immunoprecipitation followed by PCR (ChIP-PCR) to analyze H3K4 and H3K79 methylation at the β-globin locus.
• All-atom molecular dynamics simulations to predict AgNP-histone interactions.
• AgNP-mediated pull-down and immunoprecipitation assays.
• Assessment of RNA polymerase II activity and chromatin binding.

Main Results:

• AgNP treatment significantly reduced global H3 methylation levels in erythroid cells, independent of oxidative stress.
• Methylation of H3 at lysine 4 (H3K4) and lysine 79 (H3K79) on the β-globin locus was markedly decreased.
• Reduced methylation correlated with decreased histone methyltransferase DOT-1L and MLL levels and direct binding of AgNPs to H3/H4, causing steric hindrance.
• AgNP-treated cells showed decreased RNA polymerase II activity and chromatin binding, leading to reduced hemoglobin production.
• Silver ions alone did not induce alterations in histone methylation.

Conclusions:

• AgNPs induce epigenetic alterations by modifying histone methylation status, specifically reducing H3K4 and H3K79 methylation.
• Direct interaction between AgNPs and histones (H3/H4) plays a role in preventing methylation.
• These epigenetic changes contribute to decreased hemoglobin synthesis, offering a novel perspective on AgNP toxicity at sublethal concentrations.