Curcumin induces apoptosis through mitochondrial hyperpolarization and mtDNA damage in human hepatoma G2 cells.
Curcumin, a major pigment of turmeric, is a natural antioxidant possessing a variety of pharmacological activities and therapeutic properties. But its mechanisms are unknown. In our previous study, we found that a 2-h exposure to curcumin induced DNA damage to both the mitochondrial DNA (mtDNA) and the nuclear DNA (nDNA) in HepG2 cells and that mtDNA damage was more extensive than nDNA damage. Therefore, experiments were initiated to evaluate the role of mtDNA damage in curcumin-induced apoptosis. The results demonstrated that HepG2 cells challenged with curcumin for 1 h showed a transient elevation of the mitochondrial membrane potential (DeltaPsim), followed by cytochrome c release into the cytosol and disruption of DeltaPsim after 6 h exposure to curcumin. Apoptosis was detected by Hoechst 33342 and annexin V/PI assay after 10 h treatment. Interestingly, the expression of Bcl-2 remained unchanged. A resistance to apoptosis for the corresponding rho0 counterparts confirmed a critical dependency for mitochondria during the induction of apoptosis in HepG2 cells mediated by curcumin. The effects of PEG-SOD in protecting against curcumin-induced cytotoxicity suggest that curcumin-induced cytotoxicity is directly dependent on superoxide anion O2- production. These data suggest that mitochondrial hyperpolarization is a prerequisite for curcumin-induced apoptosis and that mtDNA damage is the initial event triggering a chain of events leading to apoptosis in HepG2 cells.
Cao
Jun
J
Department of Toxicology, Dalian Medical University, Dalian 116027, China.
Liu
Yong
Y
Jia
Li
L
Zhou
Hui-Min
HM
Kong
Ying
Y
Yang
Guang
G
Jiang
Li-Ping
LP
Li
Qiu-Juan
QJ
Zhong
Lai-Fu
LF
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000648:ultrastructure; D003474:Curcumin / Q000494:pharmacology*; D045304:Cytochromes c / Q000378:metabolism; D004249:DNA Damage; D004272:DNA, Mitochondrial / Q000187:drug effects*; D016166:Free Radical Scavengers / Q000494:pharmacology; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism
D000970:Antineoplastic Agents; D004272:DNA, Mitochondrial; D016166:Free Radical Scavengers; D019253:Proto-Oncogene Proteins c-bcl-2; D013481:Superoxides; D045304:Cytochromes c; D003474:Curcumin