Induced Swelling Of Mitochondria Research Articles

Activation of glybenclamide-sensitive mitochondrial swelling under induction of cyclosporin of A-sensitive mitochondrial pore.

Induction of mitochondrial swelling and increased generation of reactive oxygen forms by Ca ions have been shown in suspension of mitochondria from rat uterus. These effects were suppressed by the blocker of mitochondrial Ca2+-uniporter ruthenium red and MPTP inhibitor cyclosporin A, that evidences that the induction of mitochondrial permeability transition pore by Ca ions takes place. Ca2+-induced mitochondrial swelling was blocked by ATP-sensitive channel blocker glybenclamide but only if K+ was present in the incubation medium. We also demonstrated that Ca2+-induced mitochondrial swelling can be eliminated in the presence of ROS scavengers N-acetyl cysteine and ascorbate. This effect of scavengers was also sensitive to K+ and was not revealed in the medium that contained equimolar NaCl instead of KCl. Thus, our data gave us grounds to assume that the induction of MPTP by Ca ions evokes the activation of mitochondrial ATPsensitive K+-channels, which are mediated by ROS.

The anti-cancer agent nemorosone is a new potent protonophoric mitochondrial uncoupler

Nemorosone, a natural-occurring polycyclic polyprenylated acylphloroglucinol, has received increasing attention due to its strong in vitro anti-cancer action. Here, we have demonstrated the toxic effect of nemorosone (1–25 μM) on HepG2 cells by means of the MTT assay, as well as early mitochondrial membrane potential dissipation and ATP depletion in this cancer cell line. In mitochondria isolated from rat liver, nemorosone (50–500 nM) displayed a protonophoric uncoupling activity, showing potency comparable to the classic protonophore, carbonyl cyanide m-chlorophenyl hydrazone (CCCP). Nemorosone enhanced the succinate-supported state 4 respiration rate, dissipated mitochondrial membrane potential, released Ca 2+ from Ca 2+-loaded mitochondria, decreased Ca 2+ uptake and depleted ATP. The protonophoric property of nemorosone was attested by the induction of mitochondrial swelling in hyposmotic K +-acetate medium in the presence of valinomycin. In addition, uncoupling concentrations of nemorosone in the presence of Ca 2+ plus ruthenium red induced the mitochondrial permeability transition process. Therefore, nemorosone is a new potent protonophoric mitochondrial uncoupler and this property is potentially involved in its toxicity on cancer cells.

Induction of mitochondrial swelling by mycotoxins in vitro

Induction of mitochondrial swelling by mycotoxins in vitro

Daphnetoxin Interacts with Mitochondrial Oxidative Phosphorylation and Induces Membrane Permeability Transition in Rat Liver

The effects of daphnetoxin on isolated rat liver mitochondria and freshly isolated rat hepatocytes were investigated. Daphnetoxin (in the microM range) increased mitochondrial state 4 respiration and decreased both state 3 and FCCP-uncoupled respiration. The transmembrane potential was strongly depressed by daphnetoxin in a concentration-dependent manner. The protonophoric activity of daphnetoxin was evidenced by the induction of mitochondrial swelling in hyposmotic K+ acetate medium in the presence of valinomycin. In isolated hepatocytes, daphnetoxin decreases intracellular ATP and simultaneously increases ADP and AMP concentrations. The addition of uncoupling concentrations of daphnetoxin to Ca2+-loaded mitochondria treated with Ruthenium Red results in non-specific membrane permeabilization, as evidenced by mitochondrial swelling in isosmotic sucrose medium. Mitochondrial swelling in the presence of Ca2+ was prevented by cyclosporine A and was drastically inhibited by catalase and dithiothreitol, indicating the participation of mitochondrial generated reactive oxygen species in this process. From this study we can conclude that the bioenergetic lesion promoted by daphnetoxin seems to be sufficient to explain the lethal hapatocyte injury.

Axonal Damage in Traumatic Brain Injury

Axonal damage is one of the most common and important pathologic features of traumatic brain injury. Severe diffuse axonal injury, resulting from inertial forces applied to the head, is associated with prolonged unconsciousness and poor outcome. The susceptibility of axons to mechanical injury appears to be due to both their viscoelastic properties and their highly organized structure in white matter tracts. Although axons are supple under normal conditions, they become brittle when exposed to rapid deformations associated with brain trauma. Accordingly, rapid stretch of axons can damage the axonal cytoskeleton, resulting in a loss of elasticity and impairment of axoplasmic transport. Subsequent swelling of the axon occurs in discrete bulb formations or in elongated varicosities that accumulate organelles. Calcium entry into damaged axons is thought to initiate further damage by the activation of proteases and the induction of mitochondrial swelling and dysfunction. Ultimately, swollen axons may become disconnected and contribute to additional neuropathologic changes in brain tissue. However, promising new therapies that reduce proteolytic activity or maintain mitochondrial integrity may attenuate progressive damage of injured axons following experimental brain trauma. Future advancements in the prevention and treatment of traumatic axonal injury will depend on our collective understanding of the relationship between the biomechanics and pathophysiology of various phases of axonal trauma.

4,6-Dinitro- o-cresol uncouples oxidative phosphorylation and induces membrane permeability transition in rat liver mitochondria

The effect of the herbicide 4,6-dinitro- o-cresol (DNOC), a structural analogue of the classical protonophore 2,4-dinitrophenol, on the bioenergetics and inner membrane permeability of isolated rat liver mitochondria was studied. We observed that DNOC (10–50 μM) acts as a classical uncoupler of oxidative phosphorylation in rat liver mitochondria, promoting both an increase in succinate-supported mitochondrial respiration in the presence or absence of ADP and a decrease in transmembrane potential. The protonophoric activity of DNOC was evidenced by the induction of mitochondrial swelling in hyposmotic K +-acetate medium, in the presence of valinomycin. At higher concentrations ( > 50 μM), DNOC also induces an inhibition of succinate-supported respiration, and a decrease in the activity of the succinate dehydrogenase can be observed. The addition of uncoupling concentrations of DNOC to Ca 2+-loaded mitochondria treated with Ruthenium Red results in non-specific membrane permeabilization, as evidenced by mitochondrial swelling in isosmotic sucrose medium. Cyclosporin A, which inhibits mitochondrial permeability transition, prevented DNOC-induced mitochondrial swelling in the presence of Ca 2+, which was accompanied by a decrease in mitochondrial membrane protein thiol content, owing to protein thiol oxidation. Catalase partially inhibits mitochondrial swelling and protein thiol oxidation, indicating the participation of mitochondrial-generated reactive oxygen species in this process. It is concluded that DNOC is a potent protonophore acting as a classical uncoupler of oxidative phosphorylation in rat liver mitochondria by dissipating the proton electrochemical gradient. Treatment of Ca 2+-loaded mitochondria with uncoupling concentrations of DNOC results in mitochondrial permeability transition, associated with membrane protein thiol oxidation by reactive oxygen species.

On the mechanism of phosphate and dicarboxylate transport in mitochondria

Studies on the swelling of mitochondria in isoosmotic solutions of the ammonium salts of phosphoric acid and of various dicarboxylic and tricarboxylic acids, led to the postulation of 3 functionallyrelated but separate anion transporters in the inner mitochondrial membrane [ 1,2] : a phosphate/OH-, a phosphate/dicarboxylate and a dicarboxylate/tricarboxylate antiporter. In further studies [3-61, using the swelling technique [7-91, or more direct methods to study the transport of anions [lo-l 51, the main conclusions were further substantiated (reviewed [17-211). Although the 2 transport systems for phosphate could be distinguished by the discovery of the specific inhibitors N-ethylmaleimide for phosphate/OHexchange [5,1 l] and butylmalonate for phosphate/ dicarboxylate exchange [3 ,l 1 ] , experiments on the effect of the 2 inhibitors on mitochondrial phosphate and dicarboxylate exchanges, led to the proposition that the inner mitochondrial membrane contains only 1 carrier for phosphate and dicarboxylates [22,23] . Kinetic analysis by a modified Hill-plot of the effect of N-ethylmaleimide and butylmalonate on 32P uptake in m’ o rt chondria clearly demonstrated a mutual interdependence of both inhibitor binding sites [24]. in an investigation on the induction of mitochondrial swelling in NH4 -malate by the phosphate analogues thiophosphate, monoand di-fluorophosphate, we concluded that the uptake of malate into mitochondria does not occur via an exchange with phosphate, but by activation of the transporter by phosphate [ 251.

Biochemical studies on peptide alkaloids: induction of ion selective mitochondrial swelling.

The effect of frangulanine, a cyclopeptide alkaloid isolated from Hovenia dulcis Thunb., on mitochondrial swelling was studied. Frangulanine induced mitochondrial swelling in 0.15 M KCl solution at the concentration of 6.5 muM. The alkaloid showed ion selectivity on the induction of mitochondrial swelling. Upon addition of frangulanine, mitochondria underwent swelling in 0.15 M KCl or RbCl solution but in neither NaCl nor LiCl solution.

Effect of subacute toxic levels of dietary cyclopropenoid fatty acids upon membrane function and fatty acid composition in the rat.

AbstractThe effect of subacute toxicity levels of dietary cyclopropenoid fatty acids upon several physiological parameters was determined in the rat. Diets containing 2% corn oil, 2%Sterculia foetida oil or 2% hydrogenatedSterculia foetida oil were fed.Sterculia foetida oil (50% cyclopropenoid fatty acids) fed rats exhibited retarded growth, elevated organ to body wt ratios, increased saturation of tissue lipid, and abnormal histopathology when compared to corn oil and hydrogenatedSterculia foetida oil fed rats. Growth was retarded 50%, liver/body wt doubled, and the percentage of saturated fatty acids in adipose tissue increased 2.5‐fold forSterculia foetida oil vs. corn oil comparisons. Three membrane systems were examined in corn oil andSterculia foetida oil fed rats. Erythrocyte hemolysis rate in 0.3 M glycerol was increased by 30%; induction of mitochondrial swelling by reduced glutathione was inhibited completely and microsomal codeine demethylase activity was depressed nearly 50% inSterculia foetida oil fed rats. The ability of cyclopropenoid fatty acids to inhibit fatty acyl desaturase and influence tissue and membrane lipid composition is discussed. Most of the detrimental effects observed in cyclopropenoid fatty acids fed rats may be associated with alteration of normal lipid metabolism and membrane function.

Pathophysiology of staphylococcal enterotoxin, Type B, (SEB) toxemia after intravenous administration to monkeys

Type B staphylococcal enterotoxin (SEB) is a single-chain protein of known amino acid composition and sequence. In highly purified form, SEB given orally to rhesus monkeys caused non-lethal illness characteristic of staphylococcal food poisoning. In contrast, after its intravenous administration, SEB produced fever and leukopenia followed by leukocytosis, and shock. Shock developed through pathophysiologic mechanisms generally similar to those which accompanied bacterial lipopolysaccharide endotoxemia, i.e. a pooling of blood in peripheral capillaries. After its intravenous administration, purified SEB disappeared rapidly from plasma. A major portion of the toxin was cleared by the kidneys, accumulating within proximal tubular cells. SEB toxemia could be prevented by prior administration of specific antitoxin, or treated after its onset by antitoxin. The purified SEB also produced in vitro effects on single cells which included: (a) induction of mitosis in lymphocytes, (b) generation of a chemotactic factor for neutrophiles, (c) inhibition of macrophage migration, (d) cytotoxicity in selected tissue cultures, and (e) induction of mitochondrial swelling in hepatocytes. Each of these effects of SEB on single cells was blocked by the inclusion of antitoxin in the reaction media. Although the primary site of SEB toxicity remains unknown, vascular endothelial cells may be a primary target.

Induction of mitochondrial swelling by the fungicide captan

The fungicide captan induces large-amplitude swelling in rat liver mitochondria. In the absence of an energy source, initial swelling, but not later swelling, can be inhibited by 2,4-dinitrophenol and KCN, suggesting two phases in the process—the first energy-linked, the second passive. Sucrose inhibits both phases of swelling. Though sucrose prevents swelling, it does not prevent captan inhibition of state 3 respiration. Captan does not prevent P i-induced swelling, indicating that captan inhibition of oxidative phosphorylation is not due to interference with the transport of P i into the mitochondria. Two moieties of the captan molecule (trichloromethylthiol moiety and tetrahydrophthalimide) were tested for their abilities to induce swelling; only the former compound proved active. The results suggest that captan interacts with mitochondrial membranes, presumably with sulfhydryl groups, altering their permeability to endogenous and exogenous ions.