Aloe-emodin induces apoptosis of human nasopharyngeal carcinoma cells via caspase-8-mediated activation of the mitochondrial death pathway.
Aloe-emodin (AE), a natural, biologically active compound from the rhizome of Rheum palmatum, has been shown to induce apoptosis in several cancer cell lines in vitro. However, its molecular mechanism of action in the apoptosis induction of human nasopharyngeal carcinoma (NPC) cells has not been explored. This study shows that AE induced G(2)/M phase arrest by increasing levels of cyclin B1 bound to Cdc2, and also caused an increase in apoptosis of NPC cells, which was characterized by morphological changes, nuclear condensation, DNA fragmentation, caspase-3 activation, cleavage of poly (ADP-ribose) polymerase (PARP) and increased sub-G(1) population. Treatment of NPC cells with AE also resulted in a decrease in Bcl-X(L) and an increase in Bax expression. Ectopic expression of Bcl-X(L) but not Bcl-2 or small interfering RNA (siRNA)-mediated attenuation of Bax suppressed AE-induced apoptotic cell death. AE-induced loss of mitochondrial membrane potential (MMP) and increase in cellular Ca(++) content, reactive oxygen species (ROS) and apoptotic cell death were suppressed by the treatment of cyclosporin A (CsA) or caspase-8 inhibitor Z-IETD-FMK. Co-treatment with caspase-9 inhibitor Z-LEHD-FMK could inhibit AE-induced cell death and the activation of caspase-3 and -9. In addition, suppression of caspase-8 with the specific inhibitor Z-IETD-FMK inhibited AE-induced the activation of Bax, the cleavage of Bid, the translocation of tBid to the mitochondria and the release of cytochrome c, apoptosis-inducing factor (AIF) and Endo G from the mitochondria and subsequent apoptosis. Taken together, these results indicate that the caspase-8-mediated activation of the mitochondrial death pathway plays a critical role in AE-induced apoptosis of NPC cells.
Lin
Meng-Liang
ML
Department of Medical Laboratory Science and Biotechnology, Central Taiwan University of Science and Technology, Taichung, Taiwan.
Lu
Yao-Cheng
YC
Chung
Jing-Gung
JG
Li
Yi-Chen
YC
Wang
Shyang-Guang
SG
N G
Sue-Hwee
SH
Wu
Chia-Yin
CY
Su
Hong-Lin
HL
Chen
Shih-Shun
SS
D000880:Anthraquinones / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D016203:CDC2 Protein Kinase; D053148:Caspase 3 / Q000502:physiology; D053181:Caspase 8 / Q000502:physiology*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1 / Q000378:metabolism; D018844:Cyclin-Dependent Kinases; D006801:Humans; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D009303:Nasopharyngeal Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D017382:Reactive Oxygen Species / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000502:physiology; D051020:bcl-X Protein / Q000502:physiology
D000880:Anthraquinones; C494826:BAX protein, human; C494811:BCL2L1 protein, human; C534699:CCNB1 protein, human; D019926:Cyclin B; D056744:Cyclin B1; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; C518327:aloe emodin; D016203:CDC2 Protein Kinase; C528899:CDK1 protein, human; D018844:Cyclin-Dependent Kinases; D053148:Caspase 3; D053181:Caspase 8