Elevation of Intracellular Ca~(2+) Level by Triclosan in Rat Thymic Lymphocytes: Increase in Membrane Ca~(2+) Permeability and Induction of Intracellular Ca~(2+) Release

摘要

Triclosan is an antibacterial agent used in household items and personal care products. Because wild animals and humans can harbor this compound in their systems, the toxic effects of triclosan are a possibility and are suspected. Therefore, we examined the effects of triclosan on intracellular Ca~(2+) concentration in rat thymocytes by cytometric techniques using fluorescent probes. Triclosan doses of 1-10 uM significantly increased the intensity of Ca~(2+)-detecting Fluo-3 fluorescence, indicating an increase in intracellular Ca~(2+) concentrations. The augmentation of Fluo-3 fluorescence became more profound in a dose-dependent manner after the addition of an external source of Ca~(2+). Conversely, the removal of external Ca~(2+) greatly attenuated the triclosan-induced augmentation of Fluo-3 fluorescence. These results suggest that triclosan treatment allows external Ca~(2+) to pass through cell membranes. This phenomenon was not specific for Ca~(2+) because external Mn~(2+) quenched the triclosan-induced augmentation of Fluo-3 fluorescence, indicating that triclosan can also mediate Mn~(2+) permeation across membranes. Therefore, these results suggest that triclosan increases membrane permeability to divalent metal cations. Furthermore, triclosan induces Ca~(2+) release from intracellular stores because the Fluo-3 fluorescence inten-sity still increased slightly after triclosan treatment, even under conditions free from external Ca~(2+). Additionally, triclosan did not increase the intensity of Fluo-3 fluorescence when Ca~(2+) was depleted from intracellular Ca~(2+) stores by A23187 under the external Ca~(2+)-free condition. Taken together, these data suggest that micromolar concentrations of triclosan affect intracellular Ca~(2+) homeostasis in thymocytes, possibly resulting in cellular malfunction.