Improved health-span and lifespan in mtDNA mutator mice treated with the mitochondrially targeted antioxidant SkQ1

MtDNA mutator mice exhibit marked features of premature aging. We find that these mice treated from age of ≈100 days with the mitochondria-targeted antioxidant SkQ1 showed a delayed appearance of traits of aging such as kyphosis, alopecia, lowering of body temperature, body weight loss, as well as ameliorated heart, kidney and liver pathologies. These effects of SkQ1 are suggested to be related to an alleviation of the effects of an enhanced reactive oxygen species (ROS) level in mtDNA mutator mice: the increased mitochondrial ROS released due to mitochondrial mutations probably interact with polyunsaturated fatty acids in cardiolipin, releasing malondialdehyde and 4-hydroxynonenal that form protein adducts and thus diminishes mitochondrial functions. SkQ1 counteracts this as it scavenges mitochondrial ROS. As the results, the normal mitochondrial ultrastructure is preserved in liver and heart; the phosphorylation capacity of skeletal muscle mitochondria as well as the thermogenic capacity of brown adipose tissue is also improved. The SkQ1-treated mice live significantly longer (335 versus 290 days). These data may be relevant in relation to treatment of mitochondrial diseases particularly and the process of aging in general.

Derivatives of the cationic plant alkaloids berberine and palmatine amplify protonophorous activity of fatty acids in model membranes and mitochondria

Previously it has been shown by our group that berberine and palmatine, penetrating cations of plant origin, when conjugated with plastoquinone (SkQBerb and SkQPalm), can accumulate in isolated mitochondria or in mitochondria of living cells and effectively protect them from oxidative damage. In the present work, we demonstrate that SkQBerb, SkQPalm, and their analogs lacking the plastoquinone moiety (C10Berb and C10Palm) operate as mitochondria-targeted compounds facilitating protonophorous effect of free fatty acids. These compounds induce proton transport mediated by small concentrations of added fatty acids both in planar and liposomal model lipid membranes. In mitochondria, such an effect can be carried out by endogenous fatty acids and the adenine nucleotide translocase.

Derivatives of rhodamine 19 as mild mitochondria-targeted cationic uncouplers

A limited decrease in mitochondrial membrane potential can be beneficial for cells, especially under some pathological conditions, suggesting that mild uncouplers (protonophores) causing such an effect are promising candidates for therapeutic uses. The great majority of protonophores are weak acids capable of permeating across membranes in their neutral and anionic forms. In the present study, protonophorous activity of a series of derivatives of cationic rhodamine 19, including dodecylrhodamine (C(12)R1) and its conjugate with plastoquinone (SkQR1), was revealed using a variety of assays. Derivatives of rhodamine B, lacking dissociable protons, showed no protonophorous properties. In planar bilayer lipid membranes, separating two compartments differing in pH, diffusion potential of H(+) ions was generated in the presence of C(12)R1 and SkQR1. These compounds induced pH equilibration in liposomes loaded with the pH probe pyranine. C(12)R1 and SkQR1 partially stimulated respiration of rat liver mitochondria in State 4 and decreased their membrane potential. Also, C(12)R1 partially stimulated respiration of yeast cells but, unlike the anionic protonophore FCCP, did not suppress their growth. Loss of function of mitochondrial DNA in yeast (grande-petite transformation) is known to cause a major decrease in the mitochondrial membrane potential. We found that petite yeast cells are relatively more sensitive to the anionic uncouplers than to C(12)R1 compared with grande cells. Together, our data suggest that rhodamine 19-based cationic protonophores are self-limiting; their uncoupling activity is maximal at high membrane potential, but the activity decreases membrane potentials, which causes partial efflux of the uncouplers from mitochondria and, hence, prevents further membrane potential decrease.

Mitochondria-targeted plastoquinone derivatives as tools to interrupt execution of the aging program. 1. Cationic plastoquinone derivatives: synthesis and in vitro studies

Synthesis of cationic plastoquinone derivatives (SkQs) containing positively charged phosphonium or rhodamine moieties connected to plastoquinone by decane or pentane linkers is described. It is shown that SkQs (i) easily penetrate through planar, mitochondrial, and outer cell membranes, (ii) at low (nanomolar) concentrations, posses strong antioxidant activity in aqueous solution, BLM, lipid micelles, liposomes, isolated mitochondria, and cells, (iii) at higher (micromolar) concentrations, show pronounced prooxidant activity, the "window" between anti- and prooxidant concentrations being very much larger than for MitoQ, a cationic ubiquinone derivative showing very much lower antioxidant activity and higher prooxidant activity, (iv) are reduced by the respiratory chain to SkQH2, the rate of oxidation of SkQH2 being lower than the rate of SkQ reduction, and (v) prevent oxidation of mitochondrial cardiolipin by OH*. In HeLa cells and human fibroblasts, SkQs operate as powerful inhibitors of the ROS-induced apoptosis and necrosis. For the two most active SkQs, namely SkQ1 and SkQR1, C(1/2) values for inhibition of the H2O2-induced apoptosis in fibroblasts appear to be as low as 1x10(-11) and 8x10(-13) M, respectively. SkQR1, a fluorescent representative of the SkQ family, specifically stains a single type of organelles in the living cell, i.e. energized mitochondria. Such specificity is explained by the fact that it is the mitochondrial matrix that is the only negatively-charged compartment inside the cell. Assuming that the Deltapsi values on the outer cell and inner mitochondrial membranes are about 60 and 180 mV, respectively, and taking into account distribution coefficient of SkQ1 between lipid and water (about 13,000 : 1), the SkQ1 concentration in the inner leaflet of the inner mitochondrial membrane should be 1.3x10(8) times higher than in the extracellular space. This explains the very high efficiency of such compounds in experiments on cell cultures. It is concluded that SkQs are rechargeable, mitochondria-targeted antioxidants of very high efficiency and specificity. Therefore, they might be used to effectively prevent ROS-induced oxidation of lipids and proteins in the inner mitochondrial membrane in vivo.

Uncoupling effect of lauryl sulfate on mitochondria can be mediated by release of bound endogenous fatty acids

The mechanism of uncoupling by lauryl sulfate (LS) has been studied. The very fact that uncoupling by low concentration of LS (a strong acid) resembles very much that by fatty acids (weak acids) was used as an argument against the fatty acid cycling scheme of uncoupling where protonated fatty acids operate as a protonophore. We have found that rat liver and heart muscle mitochondria can be uncoupled by low (70 microM) LS concentration in a fashion completely arrested by the ATP/ADP antiporter inhibitor carboxyatractylate (CAtr). On the other hand, uncoupling by two-fold higher LS concentration is not sensitive to CAtr. Addition of oleate desensitizes mitochondria to low LS so that addition of bovine serum albumin becomes necessary to recouple mitochondria. The data are accounted for assuming that low LS releases endogenous fatty acids from some mitochondrial depots, and these fatty acids are responsible for uncoupling. As to high LS, it causes a nonspecific (CAtr-insensitive) damage to the mitochondrial membrane.

Effects of lipophilic dications on planar bilayer phospholipid membrane and mitochondria

In this paper, we studied effects of phosphonium dications P2C5 and P2C10 on bilayer planar phospholipid membrane (BLM) and rat liver mitochondria. In line with our previous observations [M.F. Ross, T. Da Ros, F.H. Blaikie, T.A. Prime, C.M. Porteous, I.I. Severina, V.P. Skulachev, H.G. Kjaergaard, R.A. Smith, M.P. Murphy, Accumulation of lipophilic dications by mitochondria and cells, Biochem. J. 400 (2006) 199-208], we showed both P2C5 and P2C10 are cationic penetrants for BLM. They generated transmembrane diffusion potential (Delta Psi), the compartment with a lower dication concentration positive. However, the Delta Psi values measured proved to be lower that the Nernstian. This fact could be explained by rather low BLM conductance for the cations at their small concentrations and by induction of some BLM damage at their large concentrations. The damage in question consisted in appearance of non-Ohmic current/voltage relationships which increased in time. Such a non-Ohmicity was especially strong at Delta Psi >100 mV. Addition of penetrating lipophilic anion TPB, which increases the BLM conductance for lipophilic cations, yielded the Nernstian Delta Psi, i.e. 30 mV per ten-fold dication gradient. In the State 4 mitochondria, dications stimulated respiration and lowered Delta Psi. Moreover, they inhibited the State 3 respiration with succinate or glutamate and malate (but not with TMPD and ascorbate) in an uncoupler-sensitive fashion. Effect on the in State 4 mitochondria, similarly to that on BLM, was accounted for by a time-dependent membrane damage. On the other hand, the State 3 effect was most probably due to inhibition of the respiratory chain Complex I and/or Complex III. The damaging and inhibitory activities of lipophilic dications should be taken into account when one considers a possibility to use them as a vehicle to target antioxidants or other compounds to mitochondria.

Hydrogen peroxide produced inside mitochondria takes part in cell-to-cell transmission of apoptotic signal

In monolayer of HeLa cells treated with tumor necrosis factor (TNF), apoptotic cells formed clusters indicating possible transmission of apoptotic signal via the culture media. To investigate this phenomenon, a simple method of enabling two cell cultures to interact has been employed. Two coverslips were placed side by side in a Petri dish, one coverslip covered with apoptogen-treated cells (the inducer) and another with non-treated cells (the recipient). TNF, staurosporine, or H2O2 treatment of the inducer cells is shown to initiate apoptosis on the recipient coverslip. This effect is increased by a catalase inhibitor aminotriazole and is arrested by addition of catalase or by pre-treatment of either the inducer or the recipient cells with nanomolar concentrations of mitochondria-targeted cationic antioxidant MitoQ (10-(6 -ubiquinolyl)decyltriphenylphosphonium), which specifically arrests H2O2-induced apoptosis. The action of MitoQ is abolished by an uncoupler preventing accumulation of MitoQ in mitochondria. It is concluded that reactive oxygen species (ROS) produced by mitochondria in the apoptotic cells initiate the release of H2O2 from these cells. The H2O2 released is employed as a long-distance cell suicide messenger. In processing of such a signal by the recipient cells, mitochondrial ROS production is also involved. It is suggested that the described phenomenon may be involved in expansion of the apoptotic region around a damaged part of the tissue during heart attack or stroke as well as in "organoptosis", i.e. disappearance of organs during ontogenesis.

[Cytotoxic action of polymorphonuclear leukocytes on tumor and normal cells during ascite tumor development in vitro and in vivo]

A vast number of studies, including the authors' own research, support the important role polymorphonuclear leukocytes (PMNL) in the development of ascite tumors. The method of luminol-dependent chemiluminescence (CL) was used to show the presence of two functionally different PMNL pools in a tumor-bearing organism: 1) "primed" PMNL, which circulate in the blood stream, and 2) "activated" PMNL, which are accumulated in the tumor zone and are capable of spontaneous CL. The purpose of the present investigation was to compare cytotoxic effects of primed and activated PMNL on tumor cells (ascite Ehrlich carcinoma (AEC), ascite Zajdel hepatoma) upon co-cultivation, as well as on normal cells of the organism, erythrocytes in vitro and in vivo. Upon stimulation with phorbol myristate acetate (PMA), PMNL effectively damaged AEC cells within the first 24 h until PMNL apoptosis occurred. Upon further co-cultivation, the tumor cells grew in number, which suggest the participation of PMNL in tumor protection. When stimulated with PMNL, pools suppressed tumor growth in vitro, since in this case the cytotoxicity was due to both reactive oxygen species and proteolytic enzymes. As it has been shown earlier by the authors, the functional potential of PMNL increases many times during tumor growth, and we suggested that not only tumor but also normal cells could be damaged. In this connection, we have studied the cytotoxic effect of primed and activated PMNL on rat erythrocytes in vitro on their co-cultivation. On stimulation with PMA, the rate of lysis of erythrocytes by primed PMNL increase many times compared to the norm. The fMLP-stimulated cytotoxity was 1.5-2.0 times higher than in the norm. Activated PMNL without stimulation are capable of producing only a partial lysis of erythrocytes (5-7 %). In order to assess the cytotoxic action of PMNL on erythrocytes in vivo, the hemoglobin content in erythrocytes and blood plasm of rats was measured in the course of tumor growth. The hemoglobin content in erythocytes during growth tumor decreased from 135 +/- 10 to 85 +/- 5 g/l, whereas in the blood plasm the hemoglobin content gradually increased by almost two times. The results enable us to suggest that one of death causes of tumor-bearing organisms may be the cytotoxic action of PMNL on normal cells of the organism caused by hyperproduction of ROS.

Generation of reactive oxygen species by polymorphonuclear leukocytes and its modulation by calcium ions during tumor growth

The generation of reactive oxygen species (ROS) by polymorphonuclear leukocytes (PMNL) and the role of Ca2+ in regulating their activity during Zajdela hepatoma growth in the animal peritoneal cavity were studied. We found a marked increase in the ROS-generating activity of PMNL in circulating blood, the result of increases in both the specific activity of leukocytes and total number of PMNL in circulating blood. The ROS-generating activity of PMNL was substantially activated by Ca2+ ions and a calcium ionophore (ionomycin), but this effect virtually completely disappeared during tumor growth. Perhaps the high ROS-generating activity of PMNL and the lack of the sensitivity to extracellular Ca2+ during tumor growth in the organism are due to an accumulation of intracellular Ca2+ ions.

[Generation of reactive forms of oxygen by polymorphonuclear leukocytes during hepatoma growth in the peritoneal cavity of animals]

In the present work, an attempt was made to analyse generation of reactive oxygen species (ROS) by polymorphonuclear leucocytes (PMN) in the course of tumour growth, using chemiluminescence (CL). A multiple increase in the capacity of polymorphonuclear leucocytes of generating active forms of oxygen in the course of tumor growth was discovered. Two causes of this process were found. 1) the increase in specific activity of leucocytes; 2) the increase in the total quantity of PMN circulating in the blood. Leucocytes were also found in the ascite liquid. PMN leucocytes were shown to participate in the antitumor defence of the organism.

[The effect of catecholamines on the luminol-dependent chemiluminescence of rat polymorphonuclear leukocytes]

The effects of catecholamines on reactive oxygen species (ROS) generation by polymorphonuclear leucocytes were studied using chemiluminescence (CL). It has been found that catecholamines in 10(-9)-10(-10) M concentration range are able to increase reactive oxygen species generation. Within the micromolar concentration range (10(-6)-10(-5) M) cetacholamines (CA) strongly suppress CL intensity and ROS production. The efficiency of inhibitory action of CA: noradrenaline > adrenaline > dopamine > L-DOPA correspond to their redox properties. A conclusion is made that peroxidase is one of the main targets of CA effect.