Background: The effects of FK506 on the endoplasmic reticulum (ER) mediated stress pathway accelerates CoCl2 - induced cytotoxicity in human hepatoma HepG2 cell line were investigated.
Methods: We examined the effects of FK506 on CoCl2 - induced cytotoxicity by western blottings of poly ADP-ribose polymerase(PARP), CHOP, GRP78, Nrf2, ATF4, ATF6, XBP-1, Bak, Bax, and Bcl-2. And the catalytic acitivity of caspase-3 and -12 caspase in HepG2 cells was also measured.
Results: FK506 and CoCl2 significantly induces the synergistic effect of HepG2 cytotoxicity in dose dependent manner. Increased active-PARP expression occurred at 24 hours after FK506 treatment on CoCl2-induced HepG2 cytotoxicity and peak activation of cleaved caspasec-3 was also observed at 24 hours. FK506 aggravates CoCl2-induced HepG2 cytotoxicity. GRP78 expression was increased 24 hours after FK506 treatment on CoCl2-induced HepG2 cytotoxicity. CHOP and caspase-12 expressions were increased 24 hours after FK506 treatment on CoCl2-induced HepG2 cytotoxicity. Expressions of ATF4 and ATF6 were same manners. Expression of XBP-1 was decreased beginning at 6 hours. FK506 exasperate endoplasmic reticulum stress by CoCl2-induced cytotoxicity. Bcl-2 protein expression decreased, but FK506 induces expression of Bak and Bax by CoCl2 induced cytotoxicity. Nrf2 expression was also noted.
Conclusions: FK506 and CoCl2 significantly induces the synergistic effect of cytotoxicity in dose dependent manner. FK506 aggravates CoCl2-induced cytotoxicity. FK506 exasperate endoplasmic reticulum stress by CoCl2 -induced cytotoxicity. FK506 accelerates expression of ER-stress related nuclear transcriptional factor.