Doxorubicin triggers bioenergetic failure and p53 activation in mouse stem cell-derived cardiomyocytes.

Doxorubicin (DOX) is a widely used anticancer drug that could be even more effective if its clinical dosage was not limited because of delayed cardiotoxicity. Beating stem cell-derived cardiomyocytes are a preferred in vitro model to further uncover the mechanisms of DOX-induced cardiotoxicity. Our objective was to use cultured induced-pluripotent stem cell(iPSC)-derived mouse cardiomyocytes (Cor.At) to investigate the effects of DOX on cell and mitochondrial metabolism, as well as on stress responses. Non-proliferating and beating Cor.At cells were treated with 0.5 or 1 µM DOX for 24 h, and morphological, functional and biochemical changes associated with mitochondrial bioenergetics, DNA-damage response and apoptosis were measured. Both DOX concentrations decreased ATP levels and SOD2 protein levels and induced p53-dependent caspase activation. However, differential effects were observed for the two DOX concentrations. The highest concentration induced a high degree of apoptosis, with increased nuclear apoptotic morphology, PARP-1 cleavage and decrease of some OXPHOS protein subunits. At the lowest concentration, DOX increased the expression of p53 target transcripts associated with mitochondria-dependent apoptosis and decreased transcripts related with DNA-damage response and glycolysis. Interestingly, cells treated with 0.5 µM DOX presented an increase in PDK4 transcript levels, accompanied by an increase in phospho-PDH and decreased PDH activity. This was accompanied by an apparent decrease in basal and maximal oxygen consumption rates (OCR) and in basal extracellular acidification rate (ECAR). Cells pre-treated with the PDK inhibitor dichloroacetate (DCA), with the aim of restoring PDH activity, partially recovered OCR and ECAR. The results suggest that the higher DOX concentration mainly induces p53-dependent apoptosis, whereas for the lower DOX concentration the cardiotoxic effects involve bioenergetic failure, unveiling PDH as a possible therapeutic target to decrease DOX cardiotoxicity.

Acute effects of cocaine, morphine and their combination on bioenergetic function and susceptibility to oxidative stress of rat liver mitochondria.

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 bioenergetics and oxidative stress-related parameters by using Clark O2, Ca(2+), TPP(+) and pH electrodes and by measuring thiobarbituric acid reactive substances (TBARS) and H2O2 production. KEY FINDINGS: Cocaine and Mor+Coc at the higher concentrations (1mM) similarly increased O2 consumption at state 2, state 4 and state oligomycin. In these conditions, maximum respiration was decreased only upon glutamate/malate energization, suggesting an involvement of complex I. Morphine (1mM) 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 O2 consumption and in TBARS upon ADP/Fe(2+) stimulus, and a decrease in H2O2 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.

Disruption of striatal glutamatergic/GABAergic homeostasis following acute methamphetamine in mice.

Methamphetamine leads to functional changes in basal ganglia that are linked to impairment in motor activity. Previous studies from our group and others have shown that a single high-methamphetamine injection induces striatal dopaminergic changes in rodents. However, striatal glutamatergic, GABAergic and serotoninergic changes remain elusive under this methamphetamine regimen. Moreover, nothing is known about the participation of the receptor for advanced glycation end-products (RAGE), which is overexpressed upon synaptic dysfunction and glial response, on methamphetamine-induced striatal dysfunction. The aim of this work was to provide an integrative characterization of the striatal changes in amino acids, monoamines and astroglia, as well as in the RAGE levels, and the associated motor activity profile of C57BL/6 adult mice, 72 h after a single-high dose of methamphetamine (30 mg/kg, i.p.). Our findings indicate, for the first time, that methamphetamine decreases striatal glutamine, glutamate and GABA levels, as well as glutamine/glutamate and GABA/glutamate ratios, while serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels remain unchanged. This methamphetamine regimen also produced dopaminergic terminal degeneration in the striatum, as evidenced by dopamine and tyrosine hydroxylase depletion. Consistently, methamphetamine decreased the locomotor activity of mice, in the open field test. In addition, increased levels of glutamine synthase and glial fibrillary acidic protein were observed. Nevertheless, methamphetamine failed to change RAGE levels. Our results show that acute methamphetamine intoxication induces pronounced changes in the striatal glutamatergic/GABAergic and dopaminergic homeostasis, along with astrocyte activation. These neurochemical and glial alterations are accompanied by impairment in locomotor activity.