Tetrandrine-induced apoptosis is mediated by activation of caspases and PKC-delta in U937 cells.
Tetrandrine, which is isolated from Chinese herb Stephania tetrandrae, possesses anti-inflammatory, immunosuppressive, and cytoprotective properties. Though it was previously shown that tetrandrine causes a G1 blockade and apoptosis in various cell types, however, the mechanism by which tetrandrine initiates apoptosis remains poorly understood. In present study, we investigated the mechanisms of apoptosis induced by tetrandrine in U937 leukemia cells. Tetrandrine inhibited U937 cell growth by inducing apoptosis. After treatment of U937 cells with tetrandrine (10microM) for 24h, alteration of cell morphology, chromatin fragmentation, cytochrome c release, and caspase activation were observed. Tetrandrine also induced early oxidative stress, which resulted in activation of JNK, but not ERK and p38 MAPK. A broad-spectrum caspase inhibitor and antioxidants significantly blocked tetrandrine-induced caspase-3 activation. However, inhibition of the JNK activity with SP600125 did not block tetrandrine-induced apoptosis. Tetrandrine-induced apoptosis of U937 cells also required activity of PKC-delta, because pretreatment with a specific PKC-delta inhibitor greatly blocked tetrandrine-induced caspase-3 activation. In addition, the apoptotic response to tetrandrine was significantly attenuated in dominant-negative PKC-delta transfected MCF-7 cells, suggesting that PKC-delta plays an important role in tetrandrine-induced apoptosis and can induce caspase activation. These results suggest that tetrandrine induces oxidative stress, JNK activation, and caspase activation. However, JNK activation by ROS is not involved in the tetrandrine-induced apoptosis. In addition, tetrandrine induces caspase-dependent generation of a catalytically active fragment of PKC-delta, and this fragment also appears to play a role in the activation of caspases.
Jang
Byeong-Churl
BC
Chronic Disease Research Center, Institute for Medical Science, School of Medicine, Keimyung University, Daegu 700-712, South Korea.
Lim
Ki-Jo
KJ
Paik
Ji-Hye
JH
Cho
Jae-We
JW
Baek
Won-Ki
WK
Suh
Min-Ho
MH
Park
Jae-Bok
JB
Kwon
Taek Kyu
TK
Park
Jong-Wook
JW
Kim
Sang-Pyo
SP
Shin
Dong-Hoon
DH
Song
Dae-kyu
DK
Bae
Jae-Hoon
JH
Mun
Kyo-Cheol
KC
Suh
Seong-Il
SI
D000470:Alkaloids / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D044182:Benzylisoquinolines / Q000494:pharmacology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology; D011493:Protein Kinase C / Q000378:metabolism*; D051745:Protein Kinase C-delta; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D020298:U937 Cells
D000470:Alkaloids; D000970:Antineoplastic Agents; D044182:Benzylisoquinolines; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; C030193:immunosuppressive acidic protein; C009438:tetrandrine; C497258:PRKCD protein, human; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases