Cytosolic zinc mediates the cytotoxicity of thiol-reactive electrophiles in rat vascular smooth muscle cells

Abstract

The aberrant increase or dysregulation of cytosolic Zn²⁺ concentration ([Zn²⁺]_cyt) has been associated with cellular dysfunction and cytotoxicity. In this study, we postulated that Zn²⁺ mediates the cytotoxicity of thiol-reactive electrophiles. This notion was grounded on earlier research, which revealed that thiol-reactive electrophiles may disrupt Zn²⁺-binding motifs, consequently causing Zn²⁺ to be released from Zn²⁺-binding proteins, and leading to a surge in [Zn²⁺]_cyt. The thiol-reactive electrophiles N-ethylmaleimide (NEM) and diamide were observed to induce an increase in [Zn²⁺]_cyt, possibly through the impairment of Zn²⁺-binding motifs, and subsequent stimulation of reactive oxygen species (ROS) formation, resulting in cytotoxicity in primary cultured rat vascular smooth muscle cells. These processes were negated by the thiol donor N-acetyl-L-cysteine and the Zn²⁺ chelator TPEN. Similar outcomes were detected with co-treatment involving Zn²⁺ and Zn²⁺ ionophores such as pyrithione or disulfiram. Moreover, TPEN was found to inhibit cytotoxicity triggered by short-term exposure to various thiol-reactive electrophiles including hydrogen peroxide, acrylamide, acrylonitrile, diethyl maleate, iodoacetic acid, and iodoacetamide. In conclusion, our findings suggest that cytosolic Zn²⁺ acts as a universal mediator in the cytotoxic effects produced by thiol-reactive electrophiles.

Keywords: Cytotoxicity; Electrophiles; Thiol; Zinc.