Mitochondrial Probe Methyltriphenylphosphonium (TPMP) Inhibits the Krebs Cycle Enzyme 2-Oxoglutarate Dehydrogenase (original) (raw)
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Mitochondrially targeted compounds and their impact on cellular bioenergetics
Redox biology, 2013
Mitochondria are recognized as critical sites of localized injury in a number of chronic pathologies which has led to the development of organelle directed therapeutics. One of the approaches employed to target molecules to the mitochondrion is to conjugate a delocalized cation such as triphenylphosphonium (TPP þ ) to various redox active compounds. Mitochondrially targeted antioxidants have also been used in numerous cell culture based studies as probes of the contribution of the mitochondrial generation of reactive oxygen species on cell signaling events. However, concentrations used in vitro are typically 10-100 times greater than those generated from oral dosing in a wide range of animal models and in humans. In the present study, we determined the effects of mitochondrial targeted antioxidants, MitoQ, MitoTempol, and MitoE on cellular bioenergetics of mesangial cells in culture and compared these to TPP þ conjugated compounds which lack the antioxidant functional group. We found that all TPP þ compounds inhibited oxidative phosphorylation to different extents independent of the antioxidant functional groups. These findings show that the TPP þ moiety can disrupt mitochondrial function at concentrations frequently observed in cell culture and this behavior is dependent on the linker group and independent of antioxidant properties. Moreover, the TPP þ moiety alone is unlikely to achieve the concentrations needed to contribute to the protective mechanisms of the mitochondrially targeted compounds that have been reported in vivo.
Tetraphenylphosphonium inhibits oxidation of physiological substrates in heart mitochondria
Molecular and cellular biochemistry, 1997
We show that tetraphenylphosphonium inhibits oxidation of palmitoylcarnitine, pyruvate, malate, 2-oxoglutarate and glutamate in heart mitochondria in the range of concentration (1-5 microM) commonly used for the determination of mitochondrial membrane potential. The inhibition of 2-oxoglutarate (but not other substrate) oxidation by tetraphenylphosphonium is dependent on the concentration of 2-oxoglutarate and on extramitochondrial free calcium, and the kinetic plots are consistent with a mixed type of inhibition. Our results indicate that tetraphenylphosphonium interacts with enzymes, specifically involved in the oxidation of 2-oxoglutarate, most possibly, 2-oxoglutarate dehydrogenase.
Cytometry. Part A : the journal of the International Society for Analytical Cytology, 2003
Determination of mitochondrial membrane potential (DeltaPsim) is widely used to characterize cellular metabolism, viability, and apoptosis. Changes of DeltaPsim induced by inhibitors of oxidative phosphorylation characterize respective contributions of mitochondria and glycolysis to adenosine triphosphate (ATP) synthesis. DeltaPsim in BSC-40 and HeLa G cell lines was determined by flow cytometry and spectrofluorometry. Its changes induced by specific mitochondrial inhibitors were evaluated using 3,3'-dihexyloxacarbocyanine iodide (DiOC6(3)), tetramethylrhodamine ethyl ester, and MitoTracker Red. Mitochondrial function was further characterized by oxygen consumption. Inhibition of respiration by antimycin A or uncoupling of mitochondria by FCCP decreased DeltaPsim in both cell lines. Inhibition of ATP production by oligomycin or atractyloside induced a moderate decrease of DeltaPsim in HeLa G cells and an increase of DeltaPsim in BSC-40 cells. Statistically significant difference...
Biochemistry (Moscow), 2012
Artificial (not naturally occurring) penetrating ions were originally synthesized and successfully used by E. A. Liberman and V. P. Skulachev [1-3] to demonstrate the validity of Mitchell's chemiosmotic hypothesis. Cations with delocalized charge depolarized the inner mitochondrial membrane (decreased the membrane potential) using the transmembrane electric potential difference generated by the respiratory chain as a driving force, precisely in conformity with predictions of Mitchell's hypothesis. Later, the penetrating ions were dubbed "Skulachev ions" by David E. Green [4]. There is now ample evidence that mitochondria are the principle generators of reactive oxygen species (ROS) in cells and that many pathologies and aging arise from oxidative damage to key cellular compounds (DNA, especially mitochondrial DNA (mDNA), lipids, and proteins) [5]. The idea arose to employ penetrating cations with delocalized charge as "electric locomotive molecules" targeting antioxidants conjugated to these ions to the cellular and mitochondrial interior [6-10]. Mitochondria-targeted (i.e. being accumulated predominantly, if not exclusively into mitochondria) lipophilic antioxidants offer advantages over conventional watersoluble antioxidants as they are transported into and accumulated within cells and mitochondria in conformi
Amine fluorescamine compounds inhibit oxidative phosphorylation in rat liver mitochondria
Archives of Biochemistry and Biophysics, 1984
The reaction of fluorescamine with ammonia, benzylamine, o,p-dimethylbenzylamine, 2-phenylethylamine, p-aminobenzoic acid, and the mycosamine-containing macrolide antibiotic, amphotericin B, yield compounds which induce significant effects on mitochondrial activities. From their effects on energy-yielding processes which lead to transmembranous proton movements, the compounds may be divided into three classes. While all modifiers significantly inhibit proton movement induced by both ATP hydrolysis and electron transfer in mitochondria, their influence on the primary energy yielding steps are quite different. Class I modifiers, e.g., the compound made from amphotericin B, inhibit electron transfer but have no effect on the Pi release associated with ATP hydrolysis. Class II modifiers, e.g., the compound made from benzylamine, inhibit respiration but stimulate Pi release. Class III modifiers, e.g., the compound made from p-aminobenzoic acid, on the other hand, only slightly increase Pi release but have no effect on redox reactions. These and other effects of the modifiers are taken to mean that the proton movements and their associated energy-yielding processes are only linked indirectly. The effects of the modifiers on State 3 mitochondrial activities were also investigated. Although all the modifiers decrease the rates of both State 3 respiration and its coupled ATP synthesis, the efficiency of energy conversion measured by the P/O ratio remains unaltered.
Drugs acting on mitochondrial pathways
International Journal of Basic & Clinical Pharmacology, 2017
Mitochondrion, “the power house” of the cell plays a vital role in generating energy for the intricate functions of the cells. Mitochondria also play important roles in various apoptotic pathways. Around 80-90% of the ATP generated in cells is contributed by these organelles through the process of oxidative phosphorylation. Though this process is essential for the functioning of cells it also generates various Reactive Oxygen Species (ROS), which are toxic to cells. Hence mitochondrial dysfunction is hypothesized to be an important factor in the occurrence of disorders related to aging such as neurodegeneration and malignancies. Several commonly used drugs in clinical practice exert their action by interacting with mitochondrial pathways. This review attempts to focus on the various groups of drugs which act on mitochondria and are utilized for therapy of conditions like cancer, diabetes mellitus, neurodegeneration and so on.
Chemico-biological Interactions, 2008
The 1,4-dihydropyridines OSI-1210, OSI-1211 (etaftoron), and OSI-3802 are compounds with similar chemical structure. They differ by the length of the alkoxyl chain in positions 3 and 5 of the dihydropyridine (DHP) ring and by their pharmacological action characteristics. However, as far as we know, a clear relationship between the effects of these compounds and the length of the alkoxyl chain in positions 3 and 5 of the DHP has not been established. The goal of this study was to compare the influence of OSI-1210, OSI-1211 (etaftoron), and OSI-3802 on rat liver mitochondrial bioenergetics and on the physical properties of membrane lipid bilayers, correlating their actions with the length of the alkoxyl chain in positions 3 and 5 of the DHP ring. Using either glutamate/malate or succinate as respiratory substrates, all the compounds, in concentrations of up to 500 M, depressed state 3 and uncoupled respiration, respiratory control (RCR) and ADP/O ratios, and phosphorylation rate, whereas state 4 respiration was stimulated. However, the stimulatory effect on state 4 induced by OSI-3802, the compound with the longest chain in positions 3 and 5 of the DHP ring, as well as its inhibitory effects on RCR and ADP/O ratios and phosphorylation rate were more pronounced than that induced by OSI-1210 and OSI-1211 (etaftoron), the compounds with the shortest and intermediate chains, respectively. Moreover, OSI-3802 maximized state 4 stimulation and minimized RCR and ADP/O ratios, and phosphorylation rate at a concentration of 100 M, whereas low graduate effects were detected with OSI-1210 and OSI-1211 (etaftoron) for concentrations of up to 500 M. At low concentrations (≤30 M), OSI-3802, like its analogue OSI-1212 (cerebrocrast), reduced the phase transition temperature, the cooperative unit size, and the enthalpy associated with the phase transition temperature of dimyristoylphosphatidylcholine (DMPC) membrane bilayers. A good correlation was established between the effects of 200 M OSI-1210, OSI-1211 (etaftoron), and OSI-3802 on glutamate/malate-and succinate-dependent RCR of rat liver mitochondria and on the enthalpy change ( H) for the thermotropic profile of DMPC membrane bilayers at a 0.2 drug/DMPC molar ratio, indicating that the changes induced by these compounds on both mitochondrial membrane integrity and physical properties of DMPC membrane bilayers are strongly related to the length of the alkoxyl chain in positions 3 and 5 of the DHP ring. A putative relationship between membrane physical perturbation, bioenergetics impairment and the molecular characteristics of the compounds will be established as an approach to better understand their differentiated toxicological and pharmacological actions.
TCMS inhibits ATP synthesis in mitochondria: A systematic analysis of the inhibitory mechanism
The interactions of the antifouling compound TCMS (2,3,5,6-tetrachloro-4-methylsulphonyl pyridine) with rat liver mitochondria have been investigated. The results indicate that the compound inhibits ATP synthesis. Further investigations regarding the ATP synthesis mechanism suggest that TCMS inhibits succinic dehydrogenase of the mitochondrial respiratory chain. As the respiratory chain is similar in all living organisms, it can be concluded that the toxic effect of TCMS most likely depend on the different bioavailability of the compound and on the different importance of mitochondria in the ATP production in the animal species.