title: Naphthoquinoxaline metabolite of mitoxantrone is less cardiotoxic than the parent compound and it can be a more cardiosafe drug in anticancer therapy.
abstract: Mitoxantrone (MTX) is an antineoplastic agent used to treat several types of cancers and on multiple sclerosis, which shows a high incidence of cardiotoxicity. Still, the underlying mechanisms of MTX cardiotoxicity are poorly understood and the potential toxicity of its metabolites scarcely investigated. Therefore, this work aimed to synthesize the MTX-naphthoquinoxaline metabolite (NAPHT) and to compare its cytotoxicity to the parent compound in 7-day differentiated H9c2 cells using pharmacological relevant concentrations (0.01-5 µM). MTX was more toxic in equivalent concentrations in all cytotoxicity tests performed [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide reduction, neutral red uptake, and lactate dehydrogenase release assays] and times tested (24 and 48 h). Both MTX and NAPHT significantly decreased mitochondrial membrane potential in 7-day differentiated H9c2 cells after a 12-h incubation. However, energetic pathways were affected in a different manner after MTX or NAPHT incubation. ATP increased and lactate levels decreased after a 24-h incubation with MTX, whereas for the same incubation time and concentrations, NAPHT did not cause any significant effect. The increased activity of ATP synthase seems responsible for MTX-induced increases in ATP levels, as oligomycin (an inhibitor of ATP synthase) abrogated this effect on 5 µM MTX-incubated cells. 3-Methyladenine (an autophagy inhibitor) was the only molecule to give a partial protection against the cytotoxicity produced by MTX or NAPHT. To the best of our knowledge, this was the first broad study on NAPHT cardiotoxicity, and it revealed that the parent drug, MTX, caused a higher disruption in the energetic pathways in a cardiac model in vitro, whereas autophagy is involved in the toxicity of both compounds. In conclusion, NAPHT is claimed to largely contribute to MTX-anticancer properties; therefore, this metabolite should be regarded as a good option for a safer anticancer therapy since it is less cardiotoxic than MTX.
authors.affiliation: UCIBIO-REQUIMTE (Rede de Química e Tecnologia), Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313, Porto, Portugal. afreis.mendes@gmail.com.
authors.forename: A
authors.initials: A
authors.lastname: Reis-Mendes
authors.affiliation: UCIBIO-REQUIMTE, Laboratory of Microbiology, Department of Biological Sciences, Faculty of Pharmacy, University of Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313, Porto, Portugal.|Lab. Química Orgânica e Farmacêutica, Dep. Química, Faculdade de Farmácia, U. Porto, Porto, Portugal.
authors.forename: A S
authors.initials: AS
authors.lastname: Gomes
authors.affiliation: Centre for Functional Ecology, Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, Coimbra, Portugal.
authors.forename: R A
authors.initials: RA
authors.lastname: Carvalho
authors.affiliation: UCIBIO-REQUIMTE (Rede de Química e Tecnologia), Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313, Porto, Portugal.
authors.forename: F
authors.initials: F
authors.lastname: Carvalho
authors.affiliation: UCIBIO-REQUIMTE (Rede de Química e Tecnologia), Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313, Porto, Portugal.
authors.forename: F
authors.initials: F
authors.lastname: Remião
authors.affiliation: Lab. Química Orgânica e Farmacêutica, Dep. Química, Faculdade de Farmácia, U. Porto, Porto, Portugal.|CIIMAR - Interdisciplinary Centre of Marine and Environmental Research, Porto, Portugal.
authors.forename: M
authors.initials: M
authors.lastname: Pinto
authors.affiliation: UCIBIO-REQUIMTE (Rede de Química e Tecnologia), Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313, Porto, Portugal.
authors.forename: M L
authors.initials: ML
authors.lastname: Bastos
authors.affiliation: Lab. Química Orgânica e Farmacêutica, Dep. Química, Faculdade de Farmácia, U. Porto, Porto, Portugal.|CIIMAR - Interdisciplinary Centre of Marine and Environmental Research, Porto, Portugal.
authors.forename: E
authors.initials: E
authors.lastname: Sousa
authors.affiliation: UCIBIO-REQUIMTE (Rede de Química e Tecnologia), Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313, Porto, Portugal. veramcosta@ff.up.pt.
authors.forename: V M
authors.identifier: http://orcid.org/0000-0002-0471-2756
authors.initials: VM
authors.lastname: Costa
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000378:metabolism / Q000633:toxicity*; D001343:Autophagy / Q000187:drug effects; D066126:Cardiotoxicity / Q000209:etiology* / Q000473:pathology; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D019344:Lactic Acid / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008942:Mitoxantrone / Q000008:administration & dosage / Q000378:metabolism / Q000633:toxicity*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000473:pathology; D011810:Quinoxalines / Q000378:metabolism / Q000633:toxicity; D051381:Rats; D013997:Time Factors
chemical_list: D000970:Antineoplastic Agents; D011810:Quinoxalines; D019344:Lactic Acid; C025946:3-methyladenine; D000255:Adenosine Triphosphate; D008942:Mitoxantrone; D000225:Adenine
keywords: Autophagy; Cardiotoxicity; Differentiated H9c2 cells; Mitoxantrone; Naphthoquinoxaline