Dosage effects of curcumin on cell death types in a human osteoblast cell line.
Curcumin, the yellow pigment of Curcuma longa, is known to have antioxidant and anti-inflammatory properties, as well as their ability to either induce or prevent cell apoptosis. However, the precise molecular mechanisms of these effects are unknown. Here, we demonstrate that curcumin can induce apoptotic changes, including JNK activation, caspase-3 activation, and cleavage of PARP and PAK2, at treatment concentrations lower than 25 microM in human osteoblast cells. In contrast, treatment with 50-200 microM of curcumin does not induce apoptosis, but rather triggers necrotic cell death in human osteoblasts. Using the cell permeable dye 2',7'-dichlorofluorescin diacetate (DCF-DA) as an indicator of reactive oxygen species (ROS) generation, we found that while treatment with 12.5-25 microM curcumin directly increased intracellular oxidative stress, 50-200 microM curcumin had far less effect. Pretreatment of cells with N-acetyl cysteine or alpha-tocopherol, two well known ROS scavengers, attenuated the intracellular ROS levels increases and converted the apoptosis to necrosis induced by 12.5-25 microM curcumin. Moreover, we observed a dose-dependent decrease in intracellular ATP levels after treatment of osteoblast cells with curcumin and pretreatment of cells with antimycin or 2-deoxyglucose to cause ATP depletion significantly converted 12.5-25 microM curcumin-induced apoptosis to necrosis, indicating that ATP (a known mediator of apoptotic versus necrotic death) is most likely involved in the switching mechanism. Overall, our results signify that curcumin dosage treatment determines the possible effect on ROS generation, intracellular ATP levels, and cell apoptosis or necrosis in osteoblast cells.
Chan
Wen-Hsiung
WH
Department of Bioscience Technology and Center for Nanotechnology, Chung Yuan Christian University, Chung Li, Taiwan.
Wu
Hsiao-Yun
HY
Chang
Walter H
WH
D000255:Adenosine Triphosphate / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003474:Curcumin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D016166:Free Radical Scavengers / Q000494:pharmacology; D006801:Humans; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D018613:Microscopy, Confocal; D051336:Mitochondrial Membranes / Q000187:drug effects; D009336:Necrosis; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D054462:p21-Activated Kinases
D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D000255:Adenosine Triphosphate; D011065:Poly(ADP-ribose) Polymerases; C515907:PAK2 protein, human; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D048670:MAP Kinase Kinase 4; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D003474:Curcumin