title: Reactive oxygen species mediate thymoquinone-induced apoptosis and activate ERK and JNK signaling.
abstract: Thymoquinone (TQ), a component of black seed essential oil, is known to induce apoptotic cell death and oxidative stress, however, the direct involvement of oxidants in TQ-induced cell death has not been established yet. Here, we show that TQ inhibited the proliferation of a panel of human colon cancer cells (Caco-2, HCT-116, LoVo, DLD-1 and HT-29), without exhibiting cytotoxicity to normal human intestinal FHs74Int cells. Further investigation in DLD-1 revealed that apoptotic cell death is the mechanism for TQ-induced growth inhibition as confirmed by flow cytometry, M30 cytodeath and caspase-3/7 activation. Apoptosis was induced via the generation of reactive oxygen species (ROS) as evidenced by the abrogation of TQ apoptotic effect in cells preincubated with the strong antioxidant N-acetyl cysteine (NAC). TQ increased the phosphorylation states of the mitogen-activated protein kinases (MAPK) JNK and ERK, but not of p38. Their activation was completely abolished in the presence of NAC. Using PD98059 and SP600125, specific ERK and JNK inhibitors, the two kinases were found to possess pro-survival activities in TQ-induced cell death. These data present evidence linking the pro-oxidant effects of TQ with its apoptotic effects in colon cancer and prove a protective role of MAPK.
authors.affiliation: Department of Biology, American University of Beirut, Beirut, Lebanon.
authors.forename: Nahed
authors.initials: N
authors.lastname: El-Najjar
authors.forename: Manal
authors.initials: M
authors.lastname: Chatila
authors.forename: Hiba
authors.initials: H
authors.lastname: Moukadem
authors.forename: Heikki
authors.initials: H
authors.lastname: Vuorela
authors.forename: Matthias
authors.initials: M
authors.lastname: Ocker
authors.forename: Muktheshwar
authors.initials: M
authors.lastname: Gandesiri
authors.forename: Regine
authors.initials: R
authors.lastname: Schneider-Stock
authors.forename: Hala
authors.initials: H
authors.lastname: Gali-Muhtasib
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D016227:Benzoquinones / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003110:Colonic Neoplasms / Q000201:enzymology / Q000473:pathology; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D018384:Oxidative Stress / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D016227:Benzoquinones; D017382:Reactive Oxygen Species; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; C003466:thymoquinone; D000111:Acetylcysteine