Tacrolimus (FK506) Induced Apoptotic Signal Transduction Pathway

ABSTRACT

PURPOSE: This study examined the effects of Tacrolimus (FK506) on the expression of the apoptotic signal transduction proteins of Jurkat human T-lymphocytes. METHODS: The cell viability was examined by a MTT assay, DAPI stain, enzyme activity of caspase family proteins, and western blotting for Bcl-2, Bak, Fas, and Fas-L. The cells were cultured in the presence or absence of FK506. FK506 induced cell death was confirmed to be apoptosis by the observation of nuclear fragmentation. RESULTS: The viability of Jurkat cells was decreased by the addition of FK506 in a dose- and time- dependent manner. The FK506 induced activation of caspase-3 protease was observed. FK506 didn't increase the catalytic activity of caspase -6, -8, and -9 proteases of Jurkat cells in a time-dependent manner. The viability was improved when a caspase-3 inhibitor was added. However, the caspase-9 inhibitor did not affect the viability. Bak protein expression was increased, and the Bcl-2 protein was decreased for some time. The expression of Fas and Fas-L were unaffected by FK506. CONCLUSION: FK506 induces dose- and time-dependent apoptotic cell death, and enhances the apoptosis of Jurkat cell by increasing the expression of Bak and caspase-3.