Hepatocellular bioactivation and cytotoxicity of the synthetic endoperoxide antimalarial arteflene.
Arteflene is a synthetic endoperoxide antimalarial. Its peroxide bridge undergoes iron(II)-mediated reduction in vitro which yields a carbon-centered cyclohexyl radical and a mixture of cis- and trans-alpha,beta-unsaturated ketones (enones). The enones are biliary metabolites in rats and therefore surrogate markers of bioactivation. Arteflene is reported to be more cytotoxic to primary rat hepatocytes than some non-endoperoxide antimalarials. Hepatic metabolism of arteflene was investigated in recirculating isolated perfused rat livers, and the drug's metabolism and cytotoxicity were compared using hepatocytes from male rats. Both preparations metabolized [(14)C]arteflene to cis- and trans-[(14)C]enone, 8-hydroxyarteflene glucuronide and an unassigned isomeric glucuronide. During a 2 h liver perfusion, the cis- and trans-enones recovered in bile represented 8.1 +/- 3.4 and 11.3 +/- 4.6% (mean +/- S.D., N=6), respectively, of the [(14)C]arteflene (52 microM) added to the perfusate. After a 3 h incubation of [(14)C]arteflene (10 microM) with hepatocytes in suspension, the cis- and trans-enones comprised, respectively, 14.8 +/- 7.1 and 2.1 +/- 1.0% (N = 4) of the recovered radioactivity; the corresponding data for cultured hepatocytes being 18.6 +/- 6.9 and 3.3 +/- 2.2%. Arteflene was significantly (P < 0.05) toxic to isolated hepatocytes with reference to extramitochondrial reductase activity (tetrazolium reduction) but not enzyme leakage when the cells were exposed to drug concentrations > or =50 microM for 24 h. Cellular glutathione was depleted under these conditions. Therefore arteflene was acutely cytotoxic, though only at relatively high concentrations, when it was metabolized via a pathway which generates carbon-centered radicals.
Maggs
James L
JL
Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool L69 3GE, UK. j.l.maggs@liv.ac.uk
Bishop
Laurence P D
LP
Batty
Kevin T
KT
Dodd
Charlotte C
CC
Ilett
Kenneth F
KF
O'Neill
Paul M
PM
Edwards
Geoffrey
G
Kevin Park
B
B
D000818:Animals; D000962:Antimalarials / Q000378:metabolism* / Q000633:toxicity; D037621:Artemisinins / Q000378:metabolism* / Q000633:toxicity; D001646:Bile / Q000737:chemistry / Q000378:metabolism; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000378:metabolism* / Q000633:toxicity; D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D005978:Glutathione / Q000032:analysis / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D008297:Male; D010477:Perfusion; D051381:Rats; D017208:Rats, Wistar; D013343:Styrenes / Q000378:metabolism* / Q000633:toxicity
D000962:Antimalarials; D037621:Artemisinins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002250:Carbon Radioisotopes; D013343:Styrenes; C090720:arteflene; D005978:Glutathione