Effects of sodium arsenite on the cytoskeleton and cellular glutathione levels in cultured cells

Abstract

The effects of As 3+ (NaAsO 2) on the microtubule and microfilament organization, cytoskeletal protein synthesis, cytoskeletal and cytosolic (soluble) protein sulfhydryls, and cellular glutathione (GSH) levels were examined in Swiss 3T3 mouse cells. Exposure of cells to 2.5 μ m As 3+ for 16 hr resulted in apparent cell retraction and loss of thick cables of actin filaments. However, the cells still retained numerous thinner microfilaments distributed in a disorganized manner. Microtubule organization was relatively undisturbed. At higher doses (≥20 μ m), As 3+ treatment caused a severe loss of microtubules and the remaining dense finer actin filaments formed smearing clusters in perinuclear areas. Treatment of cells with As 3+ also induced a dose-dependent inhibition of cytoskeletal protein synthesis. Furthermore, As 3+ exposure enhanced cellular GSH synthesis since the elevated cellular GSH content in As 3+-treated cells could be abolished by treatment with buthionine sulfoximine, an inhibitor of γ-glutamylcysteine synthetase required for GSH biosynthesis. As determined by the N-[ 3H]-ethylmaleimide binding assay, As 3+ exposure also increased the amount of protein sulfhydryls in both the cytoskeletal and the cytosolic protein fractions. Moreover, a greater increase in protein sulfhydryls occurred in the cytoskeletal fraction than in the soluble fraction. These results indicate that the cytoskeleton could be a cellular target for injury by As 3+ exposure. The elevated cellular GSH content induced by As 3+ could provide a protective mechanism against further injury from this metal insult.