title: The antiestrogen 4-hydroxytamoxifen protects against isotretinoin-induced permeability transition and bioenergetic dysfunction of liver mitochondria: comparison with tamoxifen.
abstract: The combination of isotretinoin (13-cis-retinoic acid) with antiestrogens seems to be a promising strategy for cancer chemotherapy. The aim of the study was to evaluate the effects of isotretinoin alone or in combination with 4-hydroxytamoxifen (OHTAM) and with its prodrug tamoxifen (TAM), on the functions of rat liver mitochondria, i.e., mitochondrial permeability transition (MPT), bioenergetic functions and adenine nucleotide translocase (ANT). Isotretinoin (5 nmol/mg protein) induced the Ca²⁺-dependent MPT pore opening in mitochondria energized with succinate, which was prevented by OHTAM, cyclosporine A, TAM and ANT ligands. When mitochondria were energized with glutamate/malate and in the absence of added Ca²⁺ isotretinoin decreased the state 3 respiration, the ATP levels, the active ANT content and increased the lag phase of the phosphorylation cycle, demonstrating that isotretinoin decreased the mitochondrial phosphorylation efficiency. These changes of isotretinoin in bioenergetic parameters were not significant in the presence of succinate. The effects of isotretinoin at 5 nmol/mg protein on the Ca²⁺-dependent MPT and phosphorylative efficacy may be related with interactions with the ANT. Above 10 nmol/mg protein isotretinoin strongly diminished the active ANT content, decreased the Δψ, inhibited the complex I and induced proton leak through the Fo fraction of complex V. The combination of OHTAM with isotretinoin only induced significant changes in the energy production systems at concentrations ≥5 nmol isotretinoin/mg protein. Therefore, our results suggest that isotretinoin-associated liver toxicity is possibly related with mitochondrial dysfunctions and that the combination with OHTAM may contribute to decrease its toxicity.
authors.affiliation: Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.
authors.forename: Filomena S G
authors.initials: FS
authors.lastname: Silva
authors.forename: Mariana P C
authors.initials: MP
authors.lastname: Ribeiro
authors.forename: Maria S
authors.initials: MS
authors.lastname: Santos
authors.forename: Petronila
authors.initials: P
authors.lastname: Rocha-Pereira
authors.forename: Alice
authors.initials: A
authors.lastname: Santos-Silva
authors.forename: José B A
authors.initials: JB
authors.lastname: Custódio
mesh_terms: D000818:Animals; D018931:Antineoplastic Agents, Hormonal / Q000008:administration & dosage / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D002463:Cell Membrane Permeability / Q000187:drug effects; D004195:Disease Models, Animal; D004347:Drug Interactions; D004734:Energy Metabolism; D020847:Estrogen Receptor Modulators / Q000008:administration & dosage / Q000494:pharmacology*; D015474:Isotretinoin / Q000008:administration & dosage / Q000494:pharmacology*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D000226:Mitochondrial ADP, ATP Translocases / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism; D000083162:Mitochondrial Permeability Transition Pore; D010085:Oxidative Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D013629:Tamoxifen / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology*
chemical_list: D018931:Antineoplastic Agents, Hormonal; D020847:Estrogen Receptor Modulators; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D013629:Tamoxifen; C016601:afimoxifene; D000226:Mitochondrial ADP, ATP Translocases; D015474:Isotretinoin