Mollugin induces apoptosis in human Jurkat T cells through endoplasmic reticulum stress-mediated activation of JNK and caspase-12 and subsequent activation of mitochondria-dependent caspase cascade regulated by Bcl-xL.
Exposure of Jurkat T cells to mollugin (15-30 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-12, -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-12 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-12 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-12, 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.
Kim
Sun Mi
SM
Laboratory of Immunobiology, School of Life Science and Biotechnology, College of Natural Sciences, Kyungpook National University, Daegu 702-701, Korea.
Park
Hae Sun
HS
Jun
Do Youn
DY
Woo
Hyun Ju
HJ
Woo
Mi Hee
MH
Yang
Chae Ha
CH
Kim
Young Ho
YH
D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D053454:Caspase 12 / Q000096:biosynthesis*; D045304:Cytochromes c / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016195:G2 Phase / Q000187:drug effects; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000096:biosynthesis*; D019169:Jurkat Cells; D008928:Mitochondria / Q000502:physiology*; D018517:Plant Roots; D011714:Pyrans / Q000494:pharmacology*; D045470:Rubia; D051020:bcl-X Protein / Q000096:biosynthesis*
D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D011714:Pyrans; D051020:bcl-X Protein; C046245:rubimaillin; D045304:Cytochromes c; D048031:JNK Mitogen-Activated Protein Kinases; D053454:Caspase 12