Role of Zn2+ in restoration of nonprotein thiol content in the cells under chemical stress induced by triclocarban

We have proposed that intracellular Zn2+ release during oxidative stress is a trigger to restore cellular thiol content that is decreased by oxidative stress. Recently, we found that the incubation with triclocarban for 1 h decreased cellular thiol content and increased intracellular Zn2+ concentration. It was reminiscent of the possibility that the increase in intracellular Zn2+ concentration by triclocarban could become a trigger to restore the cellular content of nonprotein thiols. To test the possibility, we cytometrically examined the effects of prolonged incubation (3 h) with triclocarban on the cellular content of nonprotein thiols, presumably glutathione, by the use of 5-chloromethylfluorescein (5-CMF) diacetate, a fluorescent indicator of cellular nonprotein thiols, in rat thymocytes. The intensity of 5-CMF fluorescence after the 3 h incubation with 300 nM triclocarban was significantly higher than that after the 1 h incubation. In the presence of a chelator of intracellular Zn2+, such a significant difference was not observed. The results suggest that the increase in intracellular Zn2+ concentration by triclocarban is one of triggers to restore cellular content that is decreased by triclocarban.