MAPK inhibitors and pifithrin-alpha block cinnamaldehyde-induced apoptosis in human PLC/PRF/5 cells.
Cinnamaldehyde (Cin) has been shown to be effective in inducing apoptotic cell death in a number of human cancer cells. The aim of this study was to investigate the effect of pifithrin-alpha (PFTalpha; a specific p53 inhibitor) and mitogen-activated protein kinases (MAPKs) inhibitors [namely SP600125 (a specific JNK inhibitor), SB203580 (a specific p38 inhibitor) and PD98059 (a specific ERK inhibitor)] on apoptotic signaling transduction mechanism induced by Cin in human hepatoma PLC/PRF/5 (CD95-negative) cells. Using XTT assay, Cin exhibited a powerful cytotoxic effect and apoptotic induction in PLC/PRF/5 cells. Apoptosis was elicited when cells were treated with 1 microM Cin as characterized by morphological changes and the appearance of phosphatidylserine on the outer surface of the plasma membrane. Cin down-regulated the expression of Bcl-(XL), up-regulated mutant p53 and Bax proteins and promoted caspase-3 to active forms, as well as cleaving poly (ADP-ribose) polymerase (PARP) in a time-dependent pattern. This could be supported by the activation and phosphorylation of MAPKs, including JNK, ERK and p38 kinases. Pre-incubation with PFTalpha and specific MAPK inhibitors significantly diminished the effect of Cin-induced apoptosis. The activities of anti-apoptotic (Bcl-(XL)) and pro-apoptotic (Bax) proteins were remarkably affected by PFTalpha and PD98059 pre-treatment. PFTalpha effectively blocked PARP cleavage in cells treated with Cin, and also markedly prevented the phosphorylation of JNK, p38 and ERK proteins. These results suggest that p53 induction and MAPK signaling pathways are required for Cin-mediated apoptosis in PLC/PRF/5 cells.
Wu
Shu-Jing
SJ
Department of Nutritional Health, Chia-Nan University of Pharmacy and Science, Tainan, Taiwan.
Ng
Lean-Teik
LT
D000873:Anthracenes / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects*; D052160:Benzothiazoles / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D045744:Cell Line, Tumor / Q000187:drug effects; D032904:Cinnamomum aromaticum; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D008517:Phytotherapy; D010936:Plant Extracts / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D014050:Toluene / Q000031:analogs & derivatives / Q000494:pharmacology
D000873:Anthracenes; D000972:Antineoplastic Agents, Phytogenic; D052160:Benzothiazoles; D004791:Enzyme Inhibitors; D005419:Flavonoids; D010936:Plant Extracts; C432165:pyrazolanthrone; D014050:Toluene; C121565:pifithrin; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one