Oxygen-related processes in red blood cells exposed totert-butyl hydroperoxide

The flavonoids fisetin, apigenin, kaempferol, naringenin, naringin regulate respiratory activity and membrane potential of rat liver mitochondria and inhibit oxidative processes in erythrocytes

Flavonoids, secondary plant metabolites, represent the most abundant heterogeneous group of phytochemicals. The aim of this study to compare antioxidant activity and regulatory properties of several representatives of different classes of flavonoids, fisetin, apigenin, kaempferol, naringenin, naringin, using liver mitochondria and erythrocytes as research objects. In the concentration range of 2.5-25 μM fisetin, apigenin, kaempferol, naringenin, and naringin dose-dependently prevented oxidative damage of erythrocytes induced by 700 μM tert-butyl hydroperoxide: accumulation of lipid peroxidation (LPO) products and oxidation of glutathione GSH. The IC50 values corresponding to the flavonoid concentration inhibiting the LPO process in erythrocyte membranes by 50%, were 3.9±0.8 μM in the case of fisetin, 6.5±1.6 μM in the case of kaempferol, 8.1±2.1 μM in the case of apigenin, 37.8±4.4 μM in the case of naringenin, and 64.7±8.6 μM in the case of naringin. The antioxidant effect of flavonoids was significantly higher in the membrane structures compared to the cytoplasm of cells. All flavonoids studied (10-50 μM) effectively inhibited the respiratory activity of isolated rat liver mitochondria and, with the exception of kaempferol, stimulated Ca²⁺-induced dissipation of the mitochondrial membrane potential. Cyclosporine A and ruthenium red inhibited flavonoid-stimulated Ca²⁺-dependent membrane depolarization, thus indicating that the mitochondrial calcium uniporter and the mitochondrial permeability transition pore opening were involved in the flavonoid effects. Flavonoids, as the redox-active compounds with antioxidant properties, are able to regulate mitochondrial potential and respiratory activity, and prevent mitochondrial oxidative stress. They can be considered as effective pharmacological agents or nutraceuticals.

The Redox Potential of the β-93-Cysteine Thiol Group in Human Hemoglobin Estimated from In Vitro Oxidant Challenge Experiments

Glutathionyl hemoglobin is a minor form of hemoglobin with intriguing properties. The measurement of the redox potential of its reactive β-⁹³-Cysteine is useful to improve understanding of the response of erythrocytes to transient and chronic conditions of oxidative stress, where the level of glutathionyl hemoglobin is increased. An independent literature experiment describes the recovery of human erythrocytes exposed to an oxidant burst by measuring glutathione, glutathione disulfide and glutathionyl hemoglobin in a two-hour period. This article calculates a value for the redox potential E₀ of the β-⁹³-Cysteine, considering the erythrocyte as a closed system at equilibrium described by the Nernst equation and using the measurements of the literature experiment. The obtained value of E₀ of −121 mV at pH 7.4 places hemoglobin as the most oxidizing thiol of the erythrocyte. By using as synthetic indicators of the concentrations the electrochemical potentials of the two main redox pairs in the erythrocytes, those of glutathione–glutathione disulfide and of glutathionyl–hemoglobin, the mechanism of the recovery phase can be hypothesized. Hemoglobin acts as the redox buffer that scavenges oxidized glutathione in the oxidative phase and releases it in the recovery phase, by acting as the substrate of the NAD(P)H-cofactored enzymes.

Role of mitochondrial calcium in hypochlorite induced oxidative damage of cells

Hypochlorite (HOCl) is one of the most important mediators of inflammatory processes. Recent evidence demonstrates that changes in intracellular calcium pool play a significant role in the damaging effects of hypochlorite and other oxidants. Mitochondria are shown to be one of the intracellular targets of hypochlorite. But little is known about the mitochondrial calcium pool changes in HOCl-induced mitochondrial dysfunction. Using isolated rat liver mitochondria, we showed the oxidative damage of mitochondria (GSH oxidation and mixed protein-glutathione formation without membrane lipid peroxidation) and alterations in the mitochondrial functional parameters (decrease of respiratory activity and efficiency of oxidative phosphorylation, NADH and FADH coenzyme levels, and membrane potential) under hypochlorite action (50-300 μM). Simultaneously, the mitochondrial calcium release and swelling were demonstrated. In the presence of EGTA, the damaging effects of HOCl were less pronounced, reflecting direct involvement of mitochondrial Ca²⁺ in mechanisms of oxidant-induced injury. Furthermore, exposure of HeLa cells to hypochlorite resulted in a considerable increase in cytoplasmic calcium concentrations and a decrease in mitochondrial ones. Applying specific inhibitors of calcium transfer systems, we demonstrated that mitochondria play a key role in the redistribution of cytoplasmic Ca²⁺ ions under hypochlorite action and act as mediators of calcium release from the endoplasmic reticulum into the cytoplasm.

Modulation of Redox Signaling and Thiol Homeostasis in Red Blood Cells by Peroxiredoxin Mimetics

Red blood cell death or erythrocyte apoptosis (eryptosis) is generally mediated by oxidative stress, energy depletion, heavy metals exposure, or xenobiotics. As erythrocytes are a major target for oxidative stress due to their primary function as O₂-carrying cells, they possess an efficient antioxidant defense system consisting of glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), and peroxiredoxin 2 (Prx2). The oxidative stress-mediated activation of the Ca²⁺-permeable cation channel results in Ca²⁺ entry into the cells and subsequent cell death. Herein, we describe for the first time that selenium compounds having intramolecular diselenide or selenenyl sulfide moieties can prevent the oxidative stress-induced eryptosis by exhibiting an unusual Prx2-like redox activity under conditions when the cellular Prx2 and CAT enzymes are inhibited.

Erythrocyte and plasma oxidative stress appears to be compensated in patients with sickle cell disease during a period of relative health, despite the presence of known oxidative agents

Sickle cell disease (SCD) is a monogenetic disease that results in the formation of hemoglobin S. Due to more rapid oxidation of hemoglobin S due to intracellular heme and adventitious iron in SCD, it has been thought that an inherent property of SCD red cells would be an imbalance in antioxidant defenses and oxidant production. Less deformable and fragile RBC in SCD results in intravascular hemolysis and release of free hemoglobin (PFHb) in the plasma, which might be expected to produce oxidative stress in the plasma. Thus, we aimed to characterize intracellular and vascular oxidative stress in whole blood and plasma samples from adult SCD patients and controls recruited into a large study of SCD at Children's Hospital of Los Angeles. We evaluated the cellular content of metHb and several components of the antioxidant system in RBC as well as oxidation of GSH and Prx-2 oxidation in RBC after challenge with hydroperoxides. Plasma markers included PFHb, low molecular weight protein bound heme (freed heme), hemopexin, isoprostanes, and protein carbonyls. While GSH was slightly lower in SCD RBC, protein carbonyls, NADH, NAD+ and total NADP+ + NADPH were not different. Furthermore, GSH or Prx-2 oxidation was not different after oxidative challenge in SCD vs. Control. Elevated freed heme and PFHb had a significant negative, non-linear association with hemopexin. There appeared to be a threshold effect for hemopexin (200 μg/ml), under which the freed heme rose acutely. Plasma F2-isoprostanes were not significantly elevated in SCD. Despite significant release of Hb and elevation of freed heme in SCD when hemopexin was apparently saturated, there was no clear indication of uncompensated vascular oxidative stress. This somewhat surprising result, suggests that oxidative stress is well compensated in RBCs and plasma during a period of relative health.

Vascular-targeted particle binding efficacy in the presence of rigid red blood cells: Implications for performance in diseased blood

The field of drug delivery has taken an interest in combating numerous blood and heart diseases via the use of injectable vascular-targeted carriers (VTCs). However, VTC technology has encountered limited efficacy due to a variety of challenges associated with the immense complexity of the in vivo blood flow environment, including the hemodynamic interactions of blood cells, which impact their margination and adhesion to the vascular wall. Red blood cell (RBC) physiology, i.e., size, shape, and deformability, drive cellular distribution in blood flow and has been shown to impact VTC margination to the vessel wall significantly. The RBC shape and deformability are known to be altered in certain human diseases, yet little experimental work has been conducted towards understanding the effect of these alterations, specifically RBC rigidity, on VTC dynamics in physiological blood flow. In this work, we investigate the impact of RBCs of varying stiffnesses on the adhesion efficacy of particles of various sizes, moduli, and shapes onto an inflamed endothelial layer in a human vasculature-inspired, in vitro blood flow model. The blood rigid RBC compositions and degrees of RBC stiffness evaluated are analogous to conditions in diseases such as sickle cell disease. We find that particles of different sizes, moduli, and shapes yield drastically different adhesion patterns in blood flow in the presence of rigid RBCs when compared to 100% healthy RBCs. Specifically, up to 50% reduction in the localization and adhesion of non-deformable 2 μm particles to the vessel wall was observed in the presence of rigid RBCs. Interestingly, deformable 2 μm particles showed enhanced vessel wall localization and adhesion, by up to 85%, depending on the rigidity of RBCs evaluated. Ultimately, this work experimentally clarifies the importance of considering RBC rigidity in the intelligent design of particle therapeutics and highlights possible implications for a wide range of diseases relating to RBC deformability.

Ferutinin Induces Membrane Depolarization, Permeability Transition Pore Formation, and Respiration Uncoupling in Isolated Rat Liver Mitochondria by Stimulation of Ca2+-Permeability

It is well known that the terpenoid ferutinin (4-oxy-6-(4-oxybenzoyloxy) dauc-8,9-en), isolated from the plant Ferula tenuisecta, considerably increases the permeability of artificial and cellular membranes to Ca²⁺-ions and produces apoptotic cell death in different cell lines in a mitochondria-dependent manner. The present study was designed for further evaluation of the mechanism(s) of mitochondrial effects of ferutinin using isolated rat liver mitochondria. Our findings provide evidence for ferutinin at concentrations of 5-27 µM to decrease state 3 respiration and the acceptor control ratio in the case of glutamate/malate as substrates. Ferutinin alone (10-60 µM) also dose-dependently dissipated membrane potential. In the presence of Ca²⁺-ions, ferutinin (10-60 µM) induced considerable depolarization of the inner mitochondrial membrane, which was partially inhibited by EGTA, and permeability transition pore formation, which was diminished partly by cyclosporin A, and did not influence markedly the effect of Ca²⁺ on mitochondrial respiration. Ruthenium Red, a specific inhibitor of mitochondrial calcium uniporter, completely inhibited Ca²⁺-induced mitochondria swelling and membrane depolarization, but did not affect markedly the stimulation of these Ca²⁺-dependent processes by ferutinin. We concluded that the mitochondrial effects of ferutinin might be primarily induced by stimulation of mitochondrial membrane Ca²⁺-permeability, but other mechanisms, such as driving of univalent cations, might be involved.

Presence of Rigid Red Blood Cells in Blood Flow Interferes with the Vascular Wall Adhesion of Leukocytes

The symptoms of many blood diseases can often be attributed to irregularities in cellular dynamics produced by abnormalities in blood cells, particularly red blood cells (RBCs). Contingent on the disease and its severity, RBCs can be afflicted with increased membrane rigidity as seen in malaria and sickle cell disease. Despite this understanding, little experimental work has been conducted toward understanding the effect of RBC rigidity on cellular dynamics in physiologic blood flow. Though many have computationally modeled complex blood flow to postulate how RBC rigidity may disrupt normal hemodynamics, to date, there lacks a clear understanding of how rigid RBCs affect the blood cell segregation behavior in blood flow, known as margination, and the resulting change in the adhesion of white blood cells (WBCs). In this work, we utilized an in vitro blood flow model to examine how different RBC rigidities and volume fractions of rigid RBCs impact cell margination and the downstream effect on white blood cell (WBC) adhesion in blood flow. Healthy RBC membranes were rigidified and reconstituted into whole blood and then perfused over activated endothelial cells under physiologically relevant shear conditions. Rigid RBCs were shown to reduce WBC adhesion by up to 80%, contingent on the RBC rigidity and the fraction of treated RBCs present in blood flow. Furthermore, the RBC core was found to be slightly expanded with the presence of rigid RBCs, by up to ∼30% in size fully composed of rigid RBCs. Overall, the obtained results demonstrate an impact of RBC rigidity on cellular dynamics and WBC adhesion, which possibly contributes to the pathological understanding of diseases characterized by significant RBC rigidity.

Redox regulation of mitochondrial functional activity by quinones

Quinones are among the rare compounds successfully used as therapeutic agents to correct mitochondrial diseases and as specific regulators of mitochondrial function within cells. The aim of the present study was to elucidate the redox-dependent effects of quinones on mitochondrial function. The functional parameters [respiratory activity, membrane potential, and reactive oxygen species (ROS) generation] of isolated rat liver mitochondria and mitochondria in intact cells were measured in the presence of eight exogenously applied quinones that differ in lipophilicity and one-electron reduction potential. The quinones affected the respiratory parameters of mitochondria, and dissipated the mitochondrial membrane potential as well as influenced (either decreased or enhanced) ROS generation, and restored the electron flow during electron transport chain inhibition. The stimulation of ROS production by juglone and 2,5-di-tert-butyl-1,4-benzoquinone was accompanied by a decrease in the acceptor control and respiration control ratios, dissipation of the mitochondrial membrane potential and induction of the reverse electron flow under succinate oxidation in isolated mitochondria. Menadione and 2,3,5-trimethyl-1,4-benzoquinone, which decreased the mitochondrial ROS generation, did not affect the mitochondrial potential and, vice versa, were capable of restoring electron transport during Complex I inhibition. In intact C6 cells, all the quinones, except for coenzyme Q10, decreased the mitochondrial membrane potential. Juglone, 1,4-benzoquinone, and menadione showed the most pronounced effects. These findings indicate that quinones with the reduction potential values E1/2 in the range from −99 to −260 mV were effective redox regulators of mitochondrial electron transport.

[Mitochondrial dysfunction and compensatory mechanisms in liver cells during acute carbon tetrachloride-induced rat intoxication]

Electron-transport chain and redox-balance of mitochondria are important targets that are damaged during intoxication. The aim of the present work was to estimate the role of impairments in cellular bioenergetic function in the development of liver damage during acute carbon tetrachloride intoxication in rats and to elucidate possible compensatory mechanisms. Acute CCl4-induced rat intoxication (0.8 g/kg or 4 g/kg) resulted in considerable impairments of respiratory and synthetic mitochondrial functions; their manifestations depended on the dose of the toxic agent and the duration of the intoxication increased and accompanied by complete uncoupling of oxidation and phosphorylation processes in liver mitochondria. The intoxication induced considerable liver damage and accumulation of NO in blood plasma and liver tissue. The changes of some parameters of liver mitochondrial functional activity demonstrate an oscillative pattern, reflecting compensatory mechanisms during intoxication that involved increased reduced glutathione level and enhanced succinate dehydrogenase activity.

Oxidative damage of rat liver mitochondria during exposure to t-butyl hydroperoxide. Role of Ca²⁺ ions in oxidative processes

AIMS

The present study was designed for further evaluation of the biochemical mechanism of hepatic mitochondrial dysfunction under oxidative damages induced by organic hydroperoxide, tert-butyl hydroperoxide (tBHP), for estimation of the molecular targets impaired during oxidative stress, and for investigation of the role of Ca(2+) ions in mitochondrial oxidative reactions and of the protective effect of melatonin during mitochondrial peroxidative damage.

MAIN METHODS

Mitochondria were isolated by differential centrifugation from the rat liver. The effects of tBHP exposure, EDTA, Ca(2+) ions and melatonin on mitochondrial respiratory activity, mitochondrial enzyme activities and redox status were measured.

KEY FINDINGS

The present study provides evidence that tBHP (at low concentrations of 0.02-0.065mM, in EDTA-free medium) induced uncoupling of the oxidation and phosphorylation processes and decreased the efficiency of the phosphorylation reaction. This effect depended on the respiratory substrate used. The presence of EDTA prevented oxidative impairment of mitochondrial respiration, but Ca(2+) ions in the medium enhanced oxidant-induced mitochondrial damage considerably. In the presence of 0.5mM EDTA, tBHP (at high concentrations, 0.5-2mM) considerably oxidized mitochondrial reduced glutathione, enhanced accumulation of membrane lipid peroxidation products and mixed protein-glutathione disulfides and led to an inhibition of oxoglutarate dehydrogenase and succinate dehydrogenase.

SIGNIFICANCE

Direct oxidative modification of enzymatic complexes of the respiratory chain and mitochondrial matrix, mitochondrial reduced glutathione depletion, protein glutathionylation, membrane lipid peroxidation and Ca(2+) overload are the main events of mitochondrial peroxidative damages. Experiments in vitro demonstrated that melatonin inhibited the mitochondrial peroxidative damage, preventing redox-balance changes and succinate dehydrogenase inactivation.

Corrections by melatonin of liver mitochondrial disorders under diabetes and acute intoxication in rats

The aim of the present work was to investigate the mechanisms of oxidative damage of the liver mitochondria under diabetes and intoxication in rats as well as to evaluate the possibility of corrections of mitochondrial disorders by pharmacological doses of melatonin. The experimental (30 days) streptozotocin-induced diabetes mellitus caused a significant damage of the respiratory activity in rat liver mitochondria. In the case of succinate as a respiratory substrate, the ADP-stimulated respiration rate V₃ considerably decreased (by 25%, p < 0·05) as well as the acceptor control ratio (ACR) V₃/V₂ markedly diminished (by 25%, p < 0·01). We observed a decrease of the ADP-stimulated respiration rate V₃ by 35% (p < 0·05), with glutamate as substrate. In this case, ACR also decreased (by 20%, p < 0·05). Surprisingly, the phosphorylation coefficient ADP/O did not change under diabetic liver damage. Acute rat carbon tetrachloride-induced intoxication resulted in considerable decrease of the phosphorylation coefficient because of uncoupling of the oxidation and phosphorylation processes in the liver mitochondria. The melatonin administration during diabetes (10 mg·kg⁻¹ body weight, 30 days, daily) showed a considerable protective effect on the liver mitochondrial function, reversing the decreased respiration rate V₃ and the diminished ACR to the control values both for succinate-dependent respiration and for glutamate-dependent respiration. The melatonin administration to intoxicated animals (10 mg·kg⁻¹ body weight, three times) partially increased the rate of succinate-dependent respiration coupled with phosphorylation. The impairment of mitochondrial respiratory plays a key role in the development of liver injury under diabetes and intoxication. Melatonin might be considered as an effector that regulates the mitochondrial function under diabetes.