title: Keto amphetamine toxicity-focus on the redox reactivity of the cathinone designer drug mephedrone.
abstract: The β-keto amphetamine (cathinone, β-KA) designer drugs such as mephedrone (4-methylmethcathinone, 4-MMC) show a large degree of structural similarity to amphetamines like methamphetamine (METH). However, little is currently known about whether these substances also share the potential neurotoxic properties of their non-keto amphetamine counterparts, or what mechanisms could be involved. Here, we evaluate the cytotoxicity of β-KAs in SH-SY5Y cells using lactate dehydrogenase (LDH) assays, assess the redox potential of a range of β-KAs and non-keto amphetamines using the sensitive redox indicator 2-(4-Iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium (WST-1), and explore the effect of 4-MMC on the formation of protein adducts using ultra-high performance liquid chromatography/high-resolution time-of-flight mass spectrometry (UHPLC-HR-TOFMS) and on the mitochondrial respiratory chain using high-resolution respirometry. We show that treatment with β-KAs increases LDH release. Further, we demonstrate that even under physiological pH, β-KAs are effective and selective-as compared with their non-keto analogues-reductants in the presence of electron acceptors. Increased pH (range 7.6-8.0) greatly enhanced the reactivity up to sixfold. We found no evidence of protein adduct formation, suggesting the reactivity is due to direct electron transfer by the β-KAs. Finally, we show that 4-MMC and METH produce dissimilar effects on the respiratory chain. Our results indicate that β-KAs such as 4-MMC possess cytotoxic properties in vitro. Furthermore, in the presence of an electron-accepting redox partner, the ketone moiety of β-KAs is vital for pH-dependent redox reactivity. Further work is needed to establish the importance of β-KA redox properties and its potential toxicological importance in vivo.
authors.affiliation: Institute of Biomedicine, Pharmacology, Biomedicum Helsinki, Haartmaninkatu 8, FI-00014 University of Helsinki, Finland denhollander.bjornar@gmail.com.
authors.forename: Bjørnar
authors.initials: B
authors.lastname: den Hollander
authors.affiliation: Hjelt Institute, Department of Forensic Medicine, Kytösuontie 11, FI-00014 University of Helsinki, Finland.
authors.forename: Mira
authors.initials: M
authors.lastname: Sundström
authors.affiliation: Hjelt Institute, Department of Forensic Medicine, Kytösuontie 11, FI-00014 University of Helsinki, Finland.
authors.forename: Anna
authors.initials: A
authors.lastname: Pelander
authors.affiliation: Hjelt Institute, Department of Forensic Medicine, Kytösuontie 11, FI-00014 University of Helsinki, Finland.
authors.forename: Ilkka
authors.initials: I
authors.lastname: Ojanperä
authors.affiliation: Institute of Biomedicine, Pharmacology, Biomedicum Helsinki, Haartmaninkatu 8, FI-00014 University of Helsinki, Finland.
authors.forename: Eero
authors.initials: E
authors.lastname: Mervaala
authors.affiliation: Institute of Biomedicine, Pharmacology, Biomedicum Helsinki, Haartmaninkatu 8, FI-00014 University of Helsinki, Finland.
authors.forename: Esa Risto
authors.initials: ER
authors.lastname: Korpi
authors.affiliation: Institute of Biomedicine, Pharmacology, Biomedicum Helsinki, Haartmaninkatu 8, FI-00014 University of Helsinki, Finland.
authors.forename: Esko
authors.initials: E
authors.lastname: Kankuri
mesh_terms: D000470:Alkaloids / Q000737:chemistry*; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D015198:Designer Drugs / Q000737:chemistry / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008297:Male; D008694:Methamphetamine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000633:toxicity; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000187:drug effects; D023701:Smegmamorpha; D013778:Tetrazolium Salts / Q000737:chemistry
chemical_list: C110656:2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium; D000470:Alkaloids; D000596:Amino Acids; D015198:Designer Drugs; D013778:Tetrazolium Salts; D008694:Methamphetamine; C023665:cathinone; C548233:mephedrone
keywords: cathinones; mephedrone; methamphetamine; neurotoxicity; protein adducts; reducing agent; respiratory chain; β-keto amphetamine