title: Microtubules as a critical target for arsenic toxicity in lung cells in vitro and in vivo.
abstract: To understand mechanisms for arsenic toxicity in the lung, we examined effects of sodium m-arsenite (As³⁺) on microtubule (MT) assembly in vitro (0-40 µM), in cultured rat lung fibroblasts (RFL6, 0-20 µM for 24 h) and in the rat animal model (intratracheal instillation of 2.02 mg As/kg body weight, once a week for 5 weeks). As³⁺ induced a dose-dependent disassembly of cellular MTs and enhancement of the free tubulin pool, initiating an autoregulation of tubulin synthesis manifest as inhibition of steady-state mRNA levels of βI-tubulin in dosed lung cells and tissues. Spindle MT injuries by As³⁺ were concomitant with chromosomal disorientations. As³⁺ reduced the binding to tubulin of [³H]N-ethylmaleimide (NEM), an -SH group reagent, resulting in inhibition of MT polymerization in vitro with bovine brain tubulins which was abolished by addition of dithiothreitol (DTT) suggesting As³⁺ action upon tubulin through -SH groups. In response to As³⁺, cells elevated cellular thiols such as metallothionein. Taxol, a tubulin polymerization agent, antagonized both As³⁺ and NEM induced MT depolymerization. MT-associated proteins (MAPs) essential for the MT stability were markedly suppressed in As³⁺-treated cells. Thus, tubulin sulfhydryls and MAPs are major molecular targets for As³⁺ damage to the lung triggering MT disassembly cascades.
authors.affiliation: Department of Biochemistry, Boston University School of Medicine, 72 East Concord Street, Boston, MA 02118, USA. yinzhi@bu.edu
authors.forename: Yinzhi
authors.initials: Y
authors.lastname: Zhao
authors.forename: Paul
authors.initials: P
authors.lastname: Toselli
authors.forename: Wande
authors.initials: W
authors.lastname: Li
mesh_terms: D000818:Animals; D001151:Arsenic / Q000633:toxicity*; D015153:Blotting, Western; D002460:Cell Line; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects*; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000187:drug effects*; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D001151:Arsenic