Oxidation and methylation status determine the effects of arsenic on the mitotic apparatus
Source: Molecular and Cellular Biochemistry, Volume 279, Numbers 1-2, November 2005 , pp. 113-121(9)
Abstract:We investigated the spindle inhibitory properties of six arsenicals differing in their methylation or oxidation state. Human lymphoblasts were exposed for 6 h to either sodium arsenate (NaAsV), sodium arsenite (NaAsIII), monomethylarsonic acid (MMAV), monomethylarsonous acid (MMAIII), dimethylarsinic acid (DMAV), or dimethylarsinous acid (DMAIII). After exposure slides were prepared, and the mitotic indices (MI) were assessed. We also exposed tubulin directly to each arsenical and spectrophotometrically measured its effect on polymerization. NaAsV caused a small but significant increase in MI. MMAV also caused only a slight increase in MI that just reached statistical significance. In contrast, DMAV caused a significant increase in MI, producing ∼75% the MI of demecolcine and ∼4 times the MI of the control. NaAsIII had no significant effect on MI and was quite toxic. MMAIII induced more than a twofold increase in MI compared to the control, which was about 40% that caused by demecolcine. On a micromolar basis, MMAIII was the most potent of the arsenicals tested. DMAIII gave inconsistent results. None of the pentavalent arsenicals had a substantial effect (either inhibition or enhancement) on GTP-induced polymerization of tubulin. In contrast, NaAsIII inhibited polymerization at concentrations of 1 mM and above and MMAIII and DMAIII at 10 M and above. Taken together, these results present a complex picture of how arsenicals may affect cells. These studies demonstrate that the metabolites of arsenic are active not only as chromosome breaking and DNA damaging agents but can also interfere with cell division via tubulin disruption.
Document Type: Research Article
Affiliations: 1: Environmental Carcinogenesis Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina, USA, Email: email@example.com 2: Environmental Carcinogenesis Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina, USA,
Publication date: 2005-11-01