Elevation of intracellular Zn2+ level by nanomolar concentrations of triclocarban in rat thymocytes

It was recently reported that nanomolar concentrations of triclocarban, an antimicrobial agent, were detected in human blood after the use of soap containing triclocarban. Due to the widespread use of triclocarban in adult and infant personal care products, the report prompted us to study its cytotoxicity. The cytotoxicity of triclocarban was examined in rat thymocytes by using a cytometric technique with propidium iodide for examining cell lethality, FluoZin-3-AM for monitoring the intracellular Zn2+ level, and 5-chloromethylfluorescencein diacetate for estimating the cellular content of non-protein thiol. The incubation with triclocarban at nanomolar concentrations (50–500 nM) for 1 h did not affect cell lethality but significantly elevated the intracellular Zn2+ level. The elevation of the intracellular Zn2+ level by triclocarban was not significantly dependent on external Zn2+ level. There was a negative correlation (r = −0.9225) between the effect on the intracellular Zn2+ level and that on the cellular content of non-protein thiol. These results suggest that nanomolar concentrations of triclocarban decrease the cellular content of non-protein thiol, leading to intracellular Zn2+ release. Since zinc plays physiological roles in mammalian cells, the percutaneous absorption of triclocarban from soap may, therefore, affect some cellular functions.

► Triclocarban, an antimicrobial agent, is contained in personal care products.
► Triclocarban was reported to be detected in human blood after showering.
► Triclocarban at relevant concentrations increased cellular Zn2+ level in rat thymocytes.
► Triclocarban may affect immunity because zinc has physiological roles in lymphocytes.