title: Indirubin-3'-oxime impairs mitochondrial oxidative phosphorylation and prevents mitochondrial permeability transition induction.
abstract: Indirubin, a red colored 3,2'-bisindole isomer, is a component of Indigo naturalis and is an active ingredient used in traditional Chinese medicine for the treatment of chronic diseases. The family of indirubin derivatives, such as indirubin-3'-oxime, has been suggested for various therapeutic indications. However, potential toxic interactions such as indirubin effects on mitochondrial bioenergetics are still unknown. This study evaluated the action of indirubin-3'-oxime on the function of isolated rat liver mitochondria contributing to a better understanding of the biochemical mechanisms underlying the multiple effects of indirubin. Indirubin-3'-oxime incubated with isolated rat liver mitochondria, at concentrations above 10microM, significantly depresses the phosphorylation efficiency of mitochondria as inferred from the decrease in the respiratory control and ADP/O ratios, the perturbations in mitochondrial membrane potential and in the phosphorylative cycle induced by ADP. Furthermore, indirubin-3'-oxime at up to 25microM stimulates the rate of state 4 respiration and inhibits state 3 respiration. The increased lag phase of repolarization was associated with a direct inhibition of the mitochondrial ATPase. Indirubin-3'-oxime significantly inhibited the activity of complex II and IV thus explaining the decreased FCCP-stimulated mitochondrial respiration. Mitochondria pre-incubated with indirubin-3'-oxime exhibits decreased susceptibility to calcium-induced mitochondrial permeability transition. This work shows for the first time multiple effects of indirubin-3'-oxime on mitochondrial bioenergetics thus indicating a potential mechanism for indirubin-3'-oxime effects on cell function.
authors.affiliation: Center for Neurosciences and Cell Biology, Department of Zoology, University of Coimbra, 3004-517 Coimbra, Portugal.
authors.forename: Ana T
authors.initials: AT
authors.lastname: Varela
authors.forename: Ana P
authors.initials: AP
authors.lastname: Gomes
authors.forename: Anabela M
authors.initials: AM
authors.lastname: Simões
authors.forename: João S
authors.initials: JS
authors.lastname: Teodoro
authors.forename: Filipe V
authors.initials: FV
authors.lastname: Duarte
authors.forename: Anabela P
authors.initials: AP
authors.lastname: Rolo
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Palmeira
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D019069:Cell Respiration / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004365:Drugs, Chinese Herbal / Q000737:chemistry; D007211:Indoles / Q000008:administration & dosage / Q000633:toxicity*; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects*; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D010085:Oxidative Phosphorylation / Q000187:drug effects*; D010091:Oximes / Q000008:administration & dosage / Q000633:toxicity*; D010100:Oxygen / Q000378:metabolism; D010539:Permeability / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar
chemical_list: D004365:Drugs, Chinese Herbal; D007211:Indoles; D010091:Oximes; C474021:indirubin-3'-monoxime; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D000244:Adenosine Diphosphate; D000251:Adenosine Triphosphatases; D010100:Oxygen; D002118:Calcium