title: Mechanism of apoptosis induced by a newly synthesized derivative of macrosphelides with a thiazole side chain.
abstract: The apoptosis-inducing ability of hybrid compounds composed of macrosphelide and thiazole-containing side chain of epothilones was investigated. Among the tested series of hybrid compounds the one containing thiazole side chain at C15 (MSt-2) showed the maximum potency to induce apoptosis, while another containing thiazole side chain at C3 (MSt-6) was less potent. MSt-2 was found to induce apoptosis in human lymphoma (U937) cells in a dose- and time-dependent manner as confirmed by DNA fragmentation analysis. MSt-2 treated cells showed rapid reactive oxygen species (ROS) formation and c-Jun N-terminal kinase (JNK) activation. Furthermore, significant activation of extrinsic pathway as evident by Fas expression and caspase-8 activation was also observed. MSt-2-mediated decreased expression of Bid is an important event for cross talk between intrinsic and extrinsic signaling. N-acetyl-l-cysteine pre-treatment rescued cells from MSt-2-induced ROS formation, mitochondrial membrane potential (Delta psi(m)) loss, Fas expression, caspase-8 and -3 activation and DNA fragmentation. Moreover, antioxidant enzymes catalase and/or superoxide dismutase conjugated with polyethylene glycol also inhibit MSt-2-induced ROS formation, apoptosis and Delta psi(m) loss suggesting thereby pro-oxidant effects of MSt-2. Furthermore, JNK and pan-caspase inhibitors also protect cells from MSt-2-induced apoptosis. In addition to this, MSt-2 was found to be more potent in human colon carcinoma (HCT116) and human gastric cancer (AGS) cells while it has no effect on human normal dermal fibroblast. The important structure-activity relationship observed in the current study which makes MSt-2 more potent than MSt-6 is the position of thiazole side chain and stereochemistry of position 3 in chemical structure. In short the results of our study demonstrate that MSt-2-induced rapid ROS generation and mitochondrial dysfunction in cells trigger events responsible for mitochondria-dependent apoptosis pathway.
authors.affiliation: Department of Radiological Sciences, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan.
authors.forename: Kanwal
authors.initials: K
authors.lastname: Ahmed
authors.forename: Yuji
authors.initials: Y
authors.lastname: Matsuya
authors.forename: Hideo
authors.initials: H
authors.lastname: Nemoto
authors.forename: Syed Faisal Haider
authors.initials: SF
authors.lastname: Zaidi
authors.forename: Toshiro
authors.initials: T
authors.lastname: Sugiyama
authors.forename: Yoko
authors.initials: Y
authors.lastname: Yoshihisa
authors.forename: Tadamichi
authors.initials: T
authors.lastname: Shimizu
authors.forename: Takashi
authors.initials: T
authors.lastname: Kondo
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D006571:Heterocyclic Compounds / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D048670:MAP Kinase Kinase 4 / Q000037:antagonists & inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D013844:Thiazoles / Q000737:chemistry*; D020298:U937 Cells
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; D006571:Heterocyclic Compounds; D047428:Protein Kinase Inhibitors; D017382:Reactive Oxygen Species; D013844:Thiazoles; D045304:Cytochromes c; D048670:MAP Kinase Kinase 4; D053148:Caspase 3; D053181:Caspase 8; D002118:Calcium; D000111:Acetylcysteine