ABSTRACT
PURPOSE: Polycarpine from ascidian Polycarpa aurata was previously found to be active against different human tumor cells. In this study, we investigated the antitumor mechanisms of polycarpine and its synthetic derivative, desmethoxyethoxy-polycarpine (dimethylpolycarpine), through the induction of apoptosis. This new knowledge regarding the proapoptotic action of polycarpine and dimethylpolycarpine should lead to a better understanding of their effects and development of a new class of anticancer drugs. METHODS: Apoptosis was clearly observed by flow cytometry and Western blotting using an antibody against cleaved caspase-3 as an apoptotic marker. RESULTS: Polycarpines differentially activated p38 kinase, JNKs, and ERKs in JB6 Cl 41 cells. The polycarpines-induced apoptosis was decreased in cells expressing a dominant-negative mutant of JNK. Both compounds stimulated p53-dependent transcriptional activity and phosphorylation. Induction of p53-phosphorylation at serine 15 was suppressed in JNKI and JNK2 knockout cells. Furthermore, polycarpines were unable to induce apoptosis in p53-deficient MEFs in contrast to a strong induction of apoptosis in wild type MEFs, suggesting that p53 is involved in apoptosis induced by polycarpines. The p53 phosphorylation in turn was mediated by activated JNKs. CONCLUSIONS: These results indicate that all three MAPK signaling pathways are involved in the response of JB6 cells to treatment with polycarpines. Evidence also supports a proapoptotic role of the JNKs signaling pathway in vivo and clearly indicates that JNKs are required for phosphorylation of c-Jun, activation of p53, and subsequent apoptosis induced by polycarpines.
Subject(s)
Alkaloids/chemical synthesis , Alkaloids/pharmacology , Apoptosis/drug effects , Caspases/biosynthesis , Imidazoles/chemical synthesis , Imidazoles/pharmacology , Tumor Suppressor Protein p53/biosynthesis , Urochordata , Alkaloids/chemistry , Animals , Apoptosis/physiology , Caspase 3 , Cell Line , Cell Survival/drug effects , Cell Survival/physiology , Dose-Response Relationship, Drug , Mice , Signal Transduction/drug effects , Signal Transduction/physiologyABSTRACT
Long-chain N-acylethanolamines (NAE), including the endocannabinoid, anandamide, accumulate in mammalian tissues under a variety of pathological conditions. They have also been shown to inhibit the growth of various cancer cell lines in vitro. Here, we report the presence, in widely differing amounts (3.88-254.46 pmol/micromol lipid P), of NAE and their precursor phospholipids in various human tumors and some adjacent unaffected tissues. Anandamide ranged from 1.5 to 48% of total NAE, and incubation of tissue homogenates suggested possible NAE biosynthesis by both the established transacylation-phosphodiesterase pathway via N-acyl PE and by direct N-acylation of ethanolamine.
Subject(s)
Arachidonic Acids/analysis , Ethanolamines/analysis , Neoplasms/chemistry , Tissue Extracts/chemistry , Arachidonic Acids/metabolism , Endocannabinoids , Ethanolamines/metabolism , Humans , Neoplasms/metabolism , Polyunsaturated Alkamides , Tissue Extracts/metabolism , Tumor Cells, CulturedABSTRACT
The major endocannabinoids, anandamide (N-arachidonoylethanolamide, 20:4n-6 N-acylethanolamine) and 2-arachidonoylglycerol (2-AG) are structurally and functionally similar, but they are produced by different metabolic pathways and their levels must therefore be regulated by different mechanisms. Both endocannabinoids are accompanied by cannabinoid receptor-inactive, saturated and mono- or di-unsaturated congeners which can influence their metabolism and function. Here we review published data on the presence and production of anandamide and 2-AG and their congeners in mammalian cells and discuss this information in terms of their proposed signaling functions.
Subject(s)
Arachidonic Acids/physiology , Glycerides/physiology , Signal Transduction/physiology , Animals , Arachidonic Acids/chemistry , Arachidonic Acids/metabolism , Arachidonic Acids/pharmacology , Biological Transport , Cannabinoid Receptor Modulators , Cannabinoids/metabolism , Cell Line , Endocannabinoids , Glycerides/chemistry , Glycerides/metabolism , Glycerides/pharmacology , Humans , Membrane Proteins/metabolism , Mitogen-Activated Protein Kinase Kinases/metabolism , Polyunsaturated Alkamides , Receptors, Cannabinoid , Receptors, Drug/metabolismABSTRACT
Cannabinoids are known to downregulate immune response but the role for cannabinoid receptors in cannabinoid-induced immunosuppression is still unclear. To address this question, the interference of CB1 and CB2 receptor antagonists with the inhibition of TNF-alpha production by synthetic cannabinoid WIN 55,212-2 was studied using human peripheral blood mononuclear cells (PBMC) in vitro. CB2 (SR 144528) but not CB1 (SR 141716A) receptor antagonist dose dependently interfered with WIN 55,212-2-induced inhibition of TNF-alpha synthesis. Also, WIN 55,212-2 decreased fMLP-induced reactive oxygen species generation in lipopolysaccharide (LPS)-primed PBMC. However, the high concentrations of cannabinoid receptor ligands needed to achieve significant effects suggest that the observed effects may be in part cannabinoid receptor independent.
