Vanadium-induced Nuclear Factor of Activated T Cells Activation through Hydrogen Peroxide

Chuanshu Huang,Min Ding,Jingxia Li,Stephen S Leonard,Yongyut Rojanasakul,Vincent Castranova,Val Vallyathan,Gong Ju,Xianglin Shi

doi:10.1074/jbc.m010828200

Abstract

The present study investigated the role of reactive oxygen species (ROS) in activation of nuclear factor of activated T cells (NFAT), a pivotal transcription factor responsible for regulation of cytokines, by vanadium in mouse embryo fibroblast PW cells or mouse epidermal Cl 41 cells. Exposure of cells to vanadium led to the transactivation of NFAT in a time- and dose-dependent manner. Scavenging of vanadium-induced H(2)O(2) with N-acety-L-cyteine (a general antioxidant) or catalase (a specific H(2)O(2) inhibitor) or the chelation of vanadate with deferoxamine, resulted in inhibition of NFAT activation. In contrast, an increase in H(2)O(2) generation by the addition of superoxide dismutase or NADPH enhanced vanadium-induced NFAT activation. This vanadate-mediated H(2)O(2) generation was verified by both electron spin resonance and fluorescence staining assay. These results demonstrate that H(2)O(2) plays an important role in vanadium-induced NFAT transactivation in two different cell types. Furthermore, pretreatment of cells with nifedipine, a calcium channel blocker, inhibited vanadium-induced NFAT activation, whereas and ionomycin, two calcium ionophores, had synergistic effects with vanadium for NFAT induction. Incubation of cells with cyclosporin A (CsA), a pharmacological inhibitor of the phosphatase calcineurin, blocked vanadium-induced NFAT activation. All data show that vanadium induces NFAT activation not only through a calcium-dependent and CsA-sensitive pathway but also involved H(2)O(2) generation, suggesting that H(2)O(2) may be involved in activation of calcium-calcineurin pathways for NFAT activation caused by vanadium exposure.

Highlights

Vanadium is a transition metal widely distributed in the environment
We investigated the possible involvement of H2O2 in nuclear factor of activated T cells (NFAT) activation of fibroblasts and epidermal cells in response to vanadium
These results strongly suggest that vanadium is able to induce NFAT activation

Summary

Introduction

Vanadium is a transition metal widely distributed in the environment. Occupational exposure to vanadium is common in oil-fired electrical generating plants and the petrochemical, steel, and mining industries [1]. The activation of NFAT in T cells includes dephosphorylation, nuclear translocation, and an increase in affinity for DNA binding [15]. Stimuli that elicit calcium mobilization result in rapid dephosphorylation of NFAT proteins and their translocation to the nucleus These dephosphorylated proteins show increased affinity for DNA binding [15]. Growing evidence indicates that NFAT is a T cellspecific transcriptional factor and is expressed in a variety of lymphoid cells and in non-lymphoid tissue [15, 32, 33], NFAT involvement is reasonably well established for the production of IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, IL-8, IL-10, IL-13, IL-18, TNF-␣, interferon ␥, and granulocyte macrophage-colony-stimulating factor in a variety of cell types [15]. The objective of the present study was to determine if activation of NFAT occurred in response to vanadium and if so to investigate the molecular mechanism, by which lead to NFAT activation

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Conclusion