The neurotoxicity of phosphorylated tau protein (P-tau) and mitochondrial dysfunction play a significant role in the pathophysiology of Alzheimer's disease (AD). In vitro studies of the effects of P-tau oligomers on mitochondrial bioenergetics and reactive oxygen species production will allow us to evaluate the direct influence of P-tau on mitochondrial function. We measured the in vitro effect of P-tau oligomers on oxygen consumption and hydrogen peroxide production in isolated brain mitochondria. An appropriate combination of specific substrates and inhibitors of the phosphorylation pathway enabled the measurement and functional analysis of the effect of P-tau on mitochondrial respiration in defined coupling control states achieved in complex I-, II-, and I&II-linked electron transfer pathways. At submicromolar P-tau concentrations, we found no significant effect of P-tau on either mitochondrial respiration or hydrogen peroxide production in different respiratory states. The titration of P-tau showed a nonsignificant dose-dependent decrease in hydrogen peroxide production for complex I- and I&II-linked pathways. An insignificant in vitro effect of P-tau oligomers on both mitochondrial respiration and hydrogen peroxide production indicates that P-tau-induced mitochondrial dysfunction in AD is not due to direct effects of P-tau on the efficiency of the electron transport chain and on the production of reactive oxygen species.

• Keywords
• Alzheimer’s disease, hydrogen peroxide, isolated mitochondria, mitochondrial dysfunction, phosphorylated tau, respiratory state,
• MeSH
• Cell Respiration MeSH
• Phosphorylation MeSH
• Rats MeSH
• Humans MeSH
• Mitochondria * metabolism   MeSH
• Brain metabolism   MeSH
• Hydrogen Peroxide * metabolism   MeSH
• tau Proteins * metabolism   MeSH
• Reactive Oxygen Species metabolism   MeSH
• Oxygen Consumption MeSH
• Electron Transport MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Hydrogen Peroxide * MeSH
• tau Proteins * MeSH
• Reactive Oxygen Species MeSH

Mitochondria are targets of newly synthesized drugs and being tested for the treatment of various diseases caused or accompanied by disruption of cellular bioenergetics. In drug development, it is necessary to test for drug-induced changes in mitochondrial enzyme activity that may be related to therapeutic or adverse drug effects. Measurement of drug effect on mitochondrial oxygen consumption kinetics and/or protective effects of drugs against calcium-induced inhibition of the mitochondrial respiration can be used for the study mitochondrial toxicity and neuroprotective effects of drugs. Supposing that the drug-induced inhibition of the mitochondrial respiratory rate and/or individual mitochondrial complexes is associated with adverse drug effects, the effects of drugs on mitochondrial respiration in isolated mitochondria allow selection of novel molecules that are relatively safe for mitochondrial toxicity.

• Keywords
• Drug development, High-resolution respirometry, Isolated mitochondria, Mitochondrial respiration, Mitochondrial toxicity, Pig brain,
• MeSH
• Mitochondria drug effects   metabolism   MeSH
• Brain cytology   MeSH
• Swine MeSH
• Drug Evaluation, Preclinical instrumentation   methods   MeSH
• Electron Transport Complex I metabolism   MeSH
• Electron Transport Complex III metabolism   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Electron Transport Complex I MeSH
• Electron Transport Complex III MeSH

The trends of novel AD therapeutics are focused on multitarget-directed ligands (MTDLs), which combine cholinesterase inhibition with additional biological properties such as antioxidant properties to positively affect neuronal energy metabolism as well as mitochondrial function. We examined the in vitro effects of 10 novel MTDLs on the activities of mitochondrial enzymes (electron transport chain complexes and citrate synthase), mitochondrial respiration, and monoamine oxidase isoform (MAO-A and MAO-B) activity. The drug-induced effects of 7-MEOTA-adamantylamine heterodimers (K1011, K1013, K1018, K1020, and K1022) and tacrine/7-MEOTA/6-chlorotacrine-trolox heterodimers (K1046, K1053, K1056, K1060, and K1065) were measured in pig brain mitochondria. Most of the substances inhibited complex I- and complex II-linked respiration at high concentrations; K1046, K1053, K1056, and K1060 resulted in the least inhibition of mitochondrial respiration. Citrate synthase activity was not significantly inhibited by the tested substances; the least inhibition of complex I was observed for compounds K1060 and K1053, while both complex II/III and complex IV activity were markedly inhibited by K1011 and K1018. MAO-A was fully inhibited by K1018 and K1065, and MAO-B was fully inhibited by K1053 and K1065; the other tested drugs were partial inhibitors of both MAO-A and MAO-B. The tacrine/7-MEOTA/6-chlorotacrine-trolox heterodimers K1046, K1053, and K1060 seem to be the most suitable molecules for subsequent in vivo studies. These compounds had balanced inhibitory effects on mitochondrial respiration, with low complex I and complex II/III inhibition and full or partial inhibition of MAO-B activity.

• Keywords
• Alzheimer’s disease, Cholinesterase inhibitors, Electron transport chain complexes, Mitochondrial respiration, Monoamine oxidase, Multitarget-directed ligands,
• MeSH
• Alzheimer Disease drug therapy   MeSH
• Cell Respiration drug effects   MeSH
• Energy Metabolism * drug effects   MeSH
• Monoamine Oxidase Inhibitors pharmacology   MeSH
• Mitochondria drug effects   enzymology   metabolism   MeSH
• Monoamine Oxidase metabolism   MeSH
• Swine MeSH
• Electron Transport Complex II metabolism   MeSH
• Tacrine chemistry   pharmacology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Monoamine Oxidase Inhibitors MeSH
• Monoamine Oxidase MeSH
• Electron Transport Complex II MeSH
• Tacrine MeSH

The aim of this study was to investigate changes in the activity of individual mitochondrial respiratory chain complexes (I, II/III, IV) and citrate synthase induced by pharmacologically different cannabinoids. In vitro effects of selected cannabinoids on mitochondrial enzymes were measured in crude mitochondrial fraction isolated from pig brain. Both cannabinoid receptor agonists, Δ(9)-tetrahydrocannabinol, anandamide, and R-(+)-WIN55,212-2, and antagonist/inverse agonists of cannabinoid receptors, AM251, and cannabidiol were examined in pig brain mitochondria. Different effects of these cannabinoids on mitochondrial respiratory chain complexes and citrate synthase were found. Citrate synthase activity was decreased only by Δ(9)-tetrahydrocannabinol and AM251. Significant increase in the complex I activity was induced by anandamide. At micromolar concentration, all the tested cannabinoids inhibited the activity of electron transport chain complexes II/III and IV. Stimulatory effect of anandamide on activity of complex I may participate on distinct physiological effects of endocannabinoids compared to phytocannabinoids or synthetic cannabinoids. Common inhibitory effect of cannabinoids on activity of complex II/III and IV confirmed a non-receptor-mediated mechanism of cannabinoid action on individual components of system of oxidative phosphorylation.

• MeSH
• Cannabinoid Receptor Antagonists pharmacology   MeSH
• Citrate (si)-Synthase metabolism   MeSH
• Cannabinoids pharmacology   MeSH
• Mitochondria drug effects   metabolism   MeSH
• Brain drug effects   metabolism   MeSH
• Swine MeSH
• Electron Transport Complex I metabolism   MeSH
• Electron Transport Complex II metabolism   MeSH
• Electron Transport Complex III metabolism   MeSH
• Electron Transport Complex IV metabolism   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Cannabinoid Receptor Antagonists MeSH
• Citrate (si)-Synthase MeSH
• Cannabinoids MeSH
• Electron Transport Complex I MeSH
• Electron Transport Complex II MeSH
• Electron Transport Complex III MeSH
• Electron Transport Complex IV MeSH