title: Curcuminoid binding to embryonal carcinoma cells: reductive metabolism, induction of apoptosis, senescence, and inhibition of cell proliferation.
abstract: Curcumin preparations typically contain a mixture of polyphenols, collectively referred to as curcuminoids. In addition to the primary component curcumin, they also contain smaller amounts of the co-extracted derivatives demethoxycurcumin and bisdemethoxycurcumin. Curcuminoids can be differentially solubilized in serum, which allows for the systematic analysis of concentration-dependent cellular binding, biological effects, and metabolism. Technical grade curcumin was solubilized in fetal calf serum by two alternative methods yielding saturated preparations containing either predominantly curcumin (60%) or bisdemethoxycurcumin (55%). Continual exposure of NT2/D1 cells for 4-6 days to either preparation in cell culture media reduced cell division (1-5 µM), induced senescence (6-7 µM) or comprehensive cell death (8-10 µM) in a concentration-dependent manner. Some of these effects could also be elicited in cells transiently exposed to higher concentrations of curcuminoids (47 µM) for 0.5-4 h. Curcuminoids induced apoptosis by generalized activation of caspases but without nucleosomal fragmentation. The equilibrium binding of serum-solubilized curcuminoids to NT2/D1 cells incubated with increasing amounts of curcuminoid-saturated serum occurred with apparent overall dissociation constants in the 6-10 µM range. However, the presence of excess free serum decreased cellular binding in a hyperbolic manner. Cellular binding was overwhelmingly associated with membrane fractions and bound curcuminoids were metabolized in NT2/D1 cells via a previously unidentified reduction pathway. Both the binding affinities for curcuminoids and their reductive metabolic pathways varied in other cell lines. These results suggest that curcuminoids interact with cellular binding sites, thereby activating signal transduction pathways that initiate a variety of biological responses. The dose-dependent effects of these responses further imply that distinct cellular pathways are sequentially activated and that this activation is dependent on the affinity of curcuminoids for the respective binding sites. Defined serum-solubilized curcuminoids used in cell culture media are thus suitable for further investigating the differential activation of signal transduction pathways.
authors: Department of Psychiatry and Behavioral Science, State University of New York at Stony Brook, Stony Brook, New York, United States of America. wolfgang.quitschke@sbumed.org
authors: Wolfgang W
authors: WW
authors: Quitschke
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D016922:Cellular Senescence / Q000187:drug effects*; D003470:Culture Media / Q000737:chemistry; D003474:Curcumin / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D054278:Embryonal Carcinoma Stem Cells / Q000187:drug effects / Q000473:pathology*; D006801:Humans; D012995:Solubility / Q000187:drug effects; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors
chemical_list: D003470:Culture Media; D003474:Curcumin