title: Heme synthesis increases artemisinin-induced radical formation and cytotoxicity that can be suppressed by superoxide scavengers.
abstract: Artemisinin (ART) is a sesquiterpene lactone natural product that is widely used to treat multi-drug resistant strains of malaria. Artemisinin and its derivatives are also selectively cytotoxic to cancer cells, which can be modulated by altering heme synthesis. Cytotoxicity to cancer cells is thought to involve generation of oxidative stress, although conflicting data exist. We have analyzed reactive oxygen species (ROS) generation using the fluorescent probes 2',7'-dichlorodihydrofluorescein diacetate (DCF) and dihydroethidine (HET) upon exposure to dihydroartemisinin (DHA) in Molt-4 leukemia cells. HET fluorescence correlated with dose-dependent DHA-induced cytotoxicity, increased within 30 min of DHA exposure, and was significantly enhanced by increasing heme synthesis. Protein levels of copper, zinc-superoxide dismutase (CuZnSOD), manganese-superoxide dismutase (MnSOD), catalase, and glutathione peroxidases 1/2 were also found to increase with DHA exposure. 4-hydroxy-tempol (TEMPOL) and DF-Mn, MnSOD mimetics, could significantly inhibit ROS generation and reduce cell death. Production of superoxide appears to be a central mediator of cytotoxicity from DHA.
authors.affiliation: Weis Center for Research, Geisinger Clinic, 100 North Academy Avenue, Danville, PA 17822, USA. szhang1@geisinger.edu
authors.forename: Shiming
authors.initials: S
authors.lastname: Zhang
authors.forename: Hui
authors.initials: H
authors.lastname: Chen
authors.forename: Glenn S
authors.initials: GS
authors.lastname: Gerhard
mesh_terms: D000962:Antimalarials / Q000494:pharmacology*; D037621:Artemisinins / Q000494:pharmacology*; D002374:Catalase / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D003603:Cytotoxins / Q000494:pharmacology*; D003997:Dicarbethoxydihydrocollidine / Q000031:analogs & derivatives; D005452:Fluoresceins; D016166:Free Radical Scavengers / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D006418:Heme / Q000378:metabolism*; D006801:Humans; D007938:Leukemia / Q000188:drug therapy / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism
chemical_list: C110400:2',7'-dichlorodihydrofluorescein diacetate; D000962:Antimalarials; D037621:Artemisinins; D003603:Cytotoxins; D005452:Fluoresceins; D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; C514241:dihydroethidine; D013481:Superoxides; D006418:Heme; D003997:Dicarbethoxydihydrocollidine; C039060:artenimol; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase