Sell Mollugin

Description

Exposure of Jurkat T cells to mollugin (****0 microM), purified from the roots of Rubia cordifolia L., caused cytotoxicity and apoptotic DNA fragmentation along with mitochondrial membrane potential disruption, mitochondrial cytochrome c release, phosphorylation of c-Jun N-terminal kinase (JNK), activation of caspase**2, *9, *7, *3, and *8, cleavage of FLIP and Bid, and PARP degradation, without accompanying necrosis. While these mollugin-induced cytotoxicity and apoptotic events including activation of caspase*8 and mitochondria-dependent activation of caspase cascade were completely prevented by overexpression of Bcl-xL, the activation of JNK and caspase**2 was prevented to much lesser extent. Pretreatment of the cells with the pan-caspase inhibitor (z-VAD-fmk), the caspase*9 inhibitor (z-LEHD-fmk), the caspase*3 inhibitor (z-DEVD-fmk) or the caspase**2 inhibitor (z-ATAD-fmk) at the minimal concentration to prevent mollugin-induced apoptosis appeared to completely block the activation of caspase*7 and *8, and PARP degradation, but failed to block the activation of caspase*9 and *3 with allowing a slight enhancement in the level of JNK phosphorylation. Both FADD-positive wild-type Jurkat clone A3 and FADD-deficient Jurkat clone I2.1 exhibited a similar susceptibility to the cytotoxicity of mollugin, excluding involvement of Fas/FasL system in triggering mollugin-induced apoptosis. Normal peripheral T cells were more refractory to the cytotoxicity of mollugin than were Jurkat T cells. These results demonstrated that mollugin-induced cytotoxicity in Jurkat T cells was mainly attributable to apoptosis provoked via endoplasmic reticulum (ER) stress-mediated activation of JNK and caspase**2, and subsequent mitochondria-dependent activation of caspase*9 and *3, leading to activation of caspase*7 and *8, which could be regulated by Bcl-xL.