In vitro profiling of epigenetic modifications underlying heavy metal toxicity of tungsten-alloy and its components

Authors

Ranjana Verma, Uniformed Services University of the Health SciencesFollow
Xiufen Xu, Uniformed Services University of the Health SciencesFollow
Manoj K. Jaiswal, Uniformed Services University of the Health SciencesFollow
Cara Olsen, Uniformed Services University of the Health SciencesFollow
David Mears, Uniformed Services University of the Health SciencesFollow
Giuseppina Caretti, University of MilanFollow
Zygmunt Galdzicki, Uniformed Services University of the Health SciencesFollow

Date of this Version

2011

Comments

Published in Toxicology and Applied Pharmacology 253 (2011) 178–187; doi:10.1016/j.taap.2011.04.002

Abstract

Tungsten-alloy has carcinogenic potential as demonstrated by cancer development in rats with intramuscular implanted tungsten-alloy pellets. This suggests a potential involvement of epigenetic events previously implicated as environmental triggers of cancer. Here, we tested metal induced cytotoxicity and epigenetic modifications including H3 acetylation, H3-Ser10 phosphorylation and H3-K4 trimethylation. We exposed human embryonic kidney (HEK293), human neuroepithelioma(SKNMC), and mousemyoblast (C2C12) cultures for 1-day and hippocampal primary neuronal cultures for 1-week to 50–200 μg/ml of tungsten-alloy (91% tungsten/6% nickel/3% cobalt), tungsten, nickel, and cobalt. We also examined the potential role of intracellular calcium in metal mediated histone modifications by addition of calciumchannel blockers/chelators to the metal solutions. Tungsten and its alloy showed cytotoxicity at concentrations N50 μg/ml, while we found significant toxicity with cobalt and nickel for most tested concentrations. Diverse cell-specific toxic effects were observed, with C2C12 being relatively resistant to tungsten-alloy mediated toxic impact. Tungsten-alloy, but not tungsten, caused almost complete dephosphorylation of H3-Ser10 in C2C12 and hippocampal primary neuronal cultures with H3-hypoacetylation in C2C12. Dramatic H3-Ser10 dephosphorylation was found in all cobalt treated cultures with a decrease in H3 pan-acetylation in C2C12, SKNMC and HEK293. Trimethylation of H3-K4 was not affected. Both tungsten-alloy and cobalt mediated H3-Ser10 dephosphorylation were reversed with BAPTA-AM, highlighting the role of intracellular calcium, confirmedwith 2-photon calciumimaging. In summary, our results for the first time reveal epigeneticmodifications triggered by tungsten-alloy exposure in C2C12 and hippocampal primary neuronal cultures suggesting the underlying synergistic effects of tungsten, nickel and cobalt mediated by changes in intracellular calcium homeostasis and buffering.