Inhibitors of the ATP/ADP antiporter suppress stimulation of mitochondrial respiration and H+ permeability by palmitate and anionic detergents

AbstractThe action of ATP/ADP-antiporter inhibitors upon the uncoupling effect of palmitate, detergents and ‘classical’ uncouplers has been studied. The uncoupling effect was estimated by stimulation of succinate oxidation and of H+ permeability of rat liver mitochondria in the presence of oligomycin. It is shown that carboxyatractylate (CAtr) and pyridoxal 5-phosphate (PLP) suppress the uncoupling induced by palmitate and the anionic detergents SDS and cholate, but do not affect that induced by the cationic detergents CTAB, by the non-ionic detergent Triton X-100, as well as by the ‘classical’ uncouplers FCCP and DNP. The results are discussed in terms of a concept assuming that the ATP/ADP-antiporter facilitates the electrophoretic export of hydrophobic anions from mitochondria

Light-dependent Δ\̄smNa-generation and utilization in the marine cyanobacterium Oscillatoria brevis

AbstractLight-dependent Na+ and H+ transports, membrane potential (Δψ) and motility have been studied in the cells of the marine cyanobacterium Oscillatoria brevis. In the presence of a protonophorous uncoupler, carbonyl cyanide-m-chlorophenylhydrazone, the intracellular Na+ level is shown to increase in the dark and decrease in the light. The Na+/H+ antiporter, monensin, stimulates the dark CCCP-dependent [Na+]in increase and abolishes the light-dependent [Na+]in decrease. Na+ ions are necessary for the fast light-induced Δψ generation and H+ uptake by the cells. This uptake is inhibited by monensin being resistant to CCCP. Monensin sensitizes the Δψ level and the motility rate to low CCCP concentrations. The obtained data are consistent with the assumption that O. brevis possesses a primary Na+ pump which utilizes (directly or indirectly) the light energy

Interrelations of mitochondrial fragmentation and cell death under ischemia/reoxygenation and UV-irradiation: Protective effects of SkQ1, lithium ions and insulin

AbstractMitochondria-targeted antioxidant 10-(6-plastoquinonyl)decyltriphenyl-phosphonium (SkQ1) as well as insulin and the inhibitor of glycogen-synthase kinase, Li+ are shown to (i) protect renal tubular cells from an apoptotic death and (ii) diminish mitochondrial fission (the thread-grain transition) induced by ischemia/reoxygenation. However, SkQ1 and LiCl protected the mitochondrial reticulum of skin fibroblasts from ultraviolet-induced fission but were ineffective in preventing a further cell death. This means that mitochondrial fission is not essential for apoptotic cascade progression

Mild depolarization of the inner mitochondrial membrane is a crucial component of an anti-aging program.

The mitochondria of various tissues from mice, naked mole rats (NMRs), and bats possess two mechanistically similar systems to prevent the generation of mitochondrial reactive oxygen species (mROS): hexokinases I and II and creatine kinase bound to mitochondrial membranes. Both systems operate in a manner such that one of the kinase substrates (mitochondrial ATP) is electrophoretically transported by the ATP/ADP antiporter to the catalytic site of bound hexokinase or bound creatine kinase without ATP dilution in the cytosol. One of the kinase reaction products, ADP, is transported back to the mitochondrial matrix via the antiporter, again through an electrophoretic process without cytosol dilution. The system in question continuously supports H <sup>+</sup> -ATP synthase with ADP until glucose or creatine is available. Under these conditions, the membrane potential, ∆ψ, is maintained at a lower than maximal level (i.e., mild depolarization of mitochondria). This ∆ψ decrease is sufficient to completely inhibit mROS generation. In 2.5-y-old mice, mild depolarization disappears in the skeletal muscles, diaphragm, heart, spleen, and brain and partially in the lung and kidney. This age-dependent decrease in the levels of bound kinases is not observed in NMRs and bats for many years. As a result, ROS-mediated protein damage, which is substantial during the aging of short-lived mice, is stabilized at low levels during the aging of long-lived NMRs and bats. It is suggested that this mitochondrial mild depolarization is a crucial component of the mitochondrial anti-aging system

Cytochrome d induction in Escherichia coli growing under unfavorable conditions

AbstractGrowth of E. Coli in the presence of the protonophorous uncoupler pentachlorophenol is shown to strongly enhance levels of cytochrome d, a putative Na+-motive oxidase. This effect was found to be arrested by chloramphenicol and stimulated by high Na+ concentration in the growth medium. The induction of cytochrome d takes place in a mutant deficient in the F0F1 ATP-synthase but does not occur in mutants deficient in either of two different components of the Arc system. Similar relationships were revealed when pentachlorophenol was replaced by ferricyanide and phenazine methosulfate, agents oxidizing the respiratory chain. Induction of cytochrome d is also shown to occur in riboflavin-deficient mutants growing in the presence of such low riboflavin concentrations as to be insufficient to maintain a high respiration rate. It is suggested (i) that it is Δ−μH+ decrease rather than reduction of the respiratory chain that is the signal for the induction of cytochrome d, and (ii) the Arc system is involved in this type of metabolic regulation

Reconstitution of Biological Molecular Generators of Electric Current Inorganic Pyrophosphatase

Proteoliposomes have been reconstituted from soy‐bean phospholipids (asolectin) and inorganic pyrophosphatase isolated from Rhodospirillum rubrum chromatophores. In the presence of Mg2+ ions, pyrophosphatase proteolinosomes were incorporated into a phospholipid‐impregnated Teflon filter separating two solutions of an identical electrolyte content. Addition of inorganic pyrophosphate to the same compartment as proteoliposomes was found to induce generation of an electric potential difference between the two filter‐separated compartments, the proteoliposomes‐containing compartment being negatively charged. An electric potential difference of 15 mV and a current of 20 pA were observed. The electrogenic effect required Mg2+ and proved to be sensitive to fluoride, an inorganic pyrophosphatase inhibitor. Treatment with 10 μM N,N′‐dicyclohexylcarbodiimide for several minutes was without influence upon pyrophosphate‐induced membrane potential generation. Similar results were obtained in experiments with a proteoliposome suspension and a penetrating anion, tetraphenyl borate, which is a probe for membrane potential. The obtained data are discussed in connection with the results of studies on other enzymes as molecular generators of electric current. Copyright © 1980, Wiley Blackwell. All rights reserve