Acute effects of cocaine, morphine and their combination on bioenergetic function and susceptibility to oxidative stress of rat liver mitochondria Teresa Cunha-Oliveira a, ⁎ , 1 , Lisbeth Silva a, 1 , Ana Maria Silva a , António J. Moreno c , Catarina R. Oliveira a, b , Maria S. Santos a, c a CNC — Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517 Coimbra, Portugal b Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal c Life Sciences Department, Faculty of Sciences and Technology, University of Coimbra, Apartado 3046, 3001-401 Coimbra, Portugal abstract article info Article history: Received 2 February 2013 Accepted 29 April 2013 Keywords: Cocaine Morphine Speedball Mitochondria Liver Oxidative stress Bioenergetics Aims: Cocaine and heroin are frequently co-abused in a combination known as speedball. Despite the relevance of the liver in the metabolism and detoxification of these drugs, little is known about the impact of speedball on liver function. Main methods: In this work, we evaluated the effects of cocaine, morphine and morphine + cocaine (Mor + Coc) combination (1:1) in isolated rat liver mitochondria, upon glutamate/malate or succinate energization, on bioen- ergetics and oxidative stress-related parameters by using Clark O 2 , Ca 2+ , TPP + and pH electrodes and by measur- ing thiobarbituric acid reactive substances (TBARS) and H 2 O 2 production. Key findings: Cocaine and Mor + Coc at the higher concentrations (1 mM) similarly increased O 2 consumption at state 2, state 4 and state oligomycin. In these conditions, maximum respiration was decreased only upon glu- tamate/malate energization, suggesting an involvement of complex I. Morphine (1 mM) only increased state 2 respiration. Cocaine and Mor + Coc induced a similar decrease in maximum mitochondrial membrane potential and in ADP-induced depolarization, whereas morphine had no effect. The drugs and their combination similarly decreased mitochondrial ATPase activity and had no effect on Ca 2+ -induced permeability transition. Morphine and Mor + Coc prevented lipid peroxidation, since in these conditions there was a decrease in O 2 consumption and in TBARS upon ADP/Fe 2+ stimulus, and a decrease in H 2 O 2 formation, suggesting an antioxidant effect. Interestingly, heroin did not share morphine antioxidant properties. Significance: Our results show that the sequential direct exposure of liver mitochondria to morphine and cocaine does not alter the effects observed in the presence of each drug alone. © 2013 Elsevier Inc. All rights reserved. Introduction Cocaine and heroin are two of the most problematic illicit drugs of abuse (Nutt et al., 2007). Cocaine is the second most used illicit drug in Europe (after cannabis) and heroin use accounts for the greatest share of morbidity and mortality related to drug use in the European Union (European Monitoring Center for Drugs and Drug Addiction, 2012). Polydrug abuse is a widespread phenomenon among drug ad- dicts, with serious health consequences (European Monitoring Center for Drugs and Drug Addiction, 2009). Co-consumption of cocaine and heroin is very common since these drugs have complementary effects (stimulant and sedative, respectively), thereby reducing the secondary effects of one another, and may occur either sequentially or simulta- neously (Leri et al., 2003). In mixtures of cocaine and heroin, chemical interactions between cocaine and morphine (heroin metabolite) may occur, resulting in the formation of adducts between the two molecules at a 1:1 proportion (Garrido et al., 2007), which may modify the molec- ular effects of speedball. We have previously shown that acute exposure to both cocaine (Cunha-Oliveira et al., 2006a) and heroin (Cunha-Oliveira et al., 2007) induces neurotoxicity in rat cortical neurons, in a process involving mitochondrial dysfunction and cell death by apoptosis. We have also shown that cocaine–heroin combinations induced mitochondrial depo- larization, ATP loss and cytochrome c release in rat cortical neurons (Cunha-Oliveira et al., 2010). Thus, the cytotoxicity of cocaine and/or heroin seems to involve mitochondrial dysfunction, pointing out the mitochondria as a main intracellular target of the cytotoxicity of these drugs. Heroin has a very short half-life and is rapidly metabolized into 6-acetylmorphine and morphine, which mediate many of heroin's effects in the organism (Cunha-Oliveira et al., 2008). Cocaine and mor- phine, as most drugs, are metabolized in the liver, with mitochondria playing a central role, and this organ is highly affected by each of these drugs (Bekheet, 2010; Van Thiel and Perper, 1992). Since little is Life Sciences 92 (2013) 1157–1164 ⁎ Corresponding author. Tel.: +351 239 820 190; fax: +351 239 822 776. E-mail addresses: mteroliv@cnc.cj.uc.pt, teresa.oliveira@gmail.com (T. Cunha-Oliveira). 1 These authors contributed equally to this work. 0024-3205/$ – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.lfs.2013.04.016 Contents lists available at SciVerse ScienceDirect Life Sciences journal homepage: www.elsevier.com/locate/lifescie