António Moreno - Academia.edu (original) (raw)

Papers by António Moreno

Research paper thumbnail of Quaternary ammonium surfactant structure determines selective toxicity towards bacteria: mechanisms of action and clinical implications in antibacterial prophylaxis

The Journal of antimicrobial chemotherapy, Jan 17, 2015

Broad-spectrum antimicrobial activity of quaternary ammonium surfactants (QAS) makes them attract... more Broad-spectrum antimicrobial activity of quaternary ammonium surfactants (QAS) makes them attractive and cheap topical prophylactic options for sexually transmitted infections and perinatal vertically transmitted urogenital infections. Although attributed to their high affinity for biological membranes, the mechanisms behind QAS microbicidal activity are not fully understood. We evaluated how QAS structure affects antimicrobial activity and whether this can be exploited for use in prophylaxis of bacterial infections. Acute toxicity of QAS to in vitro models of human epithelial cells and bacteria were compared to identify selective and potent bactericidal agents. Bacterial cell viability, membrane integrity, cell cycle and metabolism were evaluated to establish the mechanisms involved in selective toxicity of QAS. QAS toxicity normalized relative to surfactant critical micelle concentration showed n-dodecylpyridinium bromide (C12PB) to be the most effective, with a therapeutic index ...

Research paper thumbnail of Cardiac cytochrome c and cardiolipin depletion during anthracycline-induced chronic depression of mitochondrial function

Mitochondrion, Sep 13, 2016

It is still unclear why anthracycline treatment results in a cardiac-specific myopathy. We invest... more It is still unclear why anthracycline treatment results in a cardiac-specific myopathy. We investigated whether selective doxorubicin (DOX) cardiotoxicity involving mitochondrial degeneration is explained by different respiratory complexes reserves between tissues by comparing and contrasting treatment effects in heart vs liver and kidney. Alternatively, we have also explored if the degeneration is due to alterations of mitochondrial thresholds to incompatible states. Heart, liver and kidney mitochondria were isolated from male Wistar rats weekly injected with DOX during 7weeks. Global flux and isolated step curves were obtained for Complex I, III, IV, as well as for the adenine nucleotide translocator. We show treatment-related alterations in global flux curve for Complex III in all analyzed tissues and in Complex IV activity curve solely in heart. However, all mitochondrial threshold curves remained unchanged after treatment in the analyzed tissues. No treatment-related difference...

Research paper thumbnail of Measuring Mitochondrial Membrane Potential with a Tetraphenylphosphonium‐Selective Electrode

Current Protocols in Toxicology, 2015

Mitochondrial bioenergetics is based on the generation of the protonmotive force by the electron ... more Mitochondrial bioenergetics is based on the generation of the protonmotive force by the electron transport chain. The protonmotive force is used by mitochondria for different critical aspects of its normal function, ranging from calcium accumulation to the synthesis of ATP. The transmembrane electric potential (ΔΨ) is the major component of the protonmotive force and is also the main responsible for ATP synthesis by mitochondrial ATP synthase. Although several methods can be used to measure the ΔΨ, the use of the tetraphenylphosphonium cation (TPP(+) )-selective electrode is still a method of election due to its sensitivity. The method is based on the accumulation of TPP(+) by energized mitochondria, which develop a negative charge in the matrix due to the ejection of protons. This unit describes how to build a custom-made TPP(+) -selective electrode and how to establish the necessary set-up to follow ΔΨ fluctuations in isolated mitochondrial fractions. © 2015 by John Wiley & Sons, Inc.

Research paper thumbnail of Decreased susceptibility of heart mitochondria from diabetic GK rats to mitochondrial permeability transition induced by calcium phosphate

Type 2 diabetes (or non-insulin dependent diabetes mellitus, NIDDM) is a common metabolic disease... more Type 2 diabetes (or non-insulin dependent diabetes mellitus, NIDDM) is a common metabolic disease in man. The Goto-Kakizaki (GK) rat has been designed as a NIDDM model. Previous studies with this strain have shown differences at the mitochondrial level. The mitochondrial permeability transition (MPT) is a widely studied phenomenon but yet poorly understood, that leads to mitochondrial dysfunction and cell death. The aim of this work was to compare the differences in susceptibility of induction of the MPT with calcium phosphate in GK and Wistar rats. Our results show that heart mitochondria from GK rats are less susceptible to the induction of MPT, and show a larger calcium accumulation before the overall loss of mitochondrial impermeability.

Research paper thumbnail of Caffeine Enhances the Calcium-Dependent Cardiac Mitochondrial Permeability Transition: Relevance for Caffeine Toxicity

Toxicology and Applied Pharmacology, 2002

Caffeine (1,3,7-trimethylxanthine), a compound present in beverages such as tea and coffee, is kn... more Caffeine (1,3,7-trimethylxanthine), a compound present in beverages such as tea and coffee, is known to be toxic at high concentrations. Some of the observed clinical conditions include cardiovascular disease and reproductive disorders, among others. The possible toxic effects of caffeine on heart mitochondria are still poorly understood. The influence of caffeine on the mitochondrial permeability transition has not been clarified so far. The objective of this study was to investigate whether caffeine, at toxic concentrations, had any stimulating effect on the permeability transition of heart mitochondria isolated from Wistar rats, as well as whether it influenced mitochondrial respiratory parameters. Our results show that caffeine reduced mitochondrial ability to accumulate calcium by increasing the susceptibility of heart mitochondria to the opening of the transition pore. Caffeine not only hindered mitochondrial capacity to recover membrane potential after calcium addition but also increased the rate of calciumdependent mitochondrial swelling and calcium-induced calcium release. The increased swelling was also observed in nonenergized mitochondria. Caffeine also showed a complex array of effects on heart mitochondrial bioenergetics, as evaluated by respiratory parameter measurements. We observed an increase in state 4 respiration and a depression in state 3 respiration, although no effect was observed on succinate-sustained mitochondrial membrane potential in the absence of calcium. Our work may be relevant to cardiovascular problems linked to caffeine toxicity and also to in vitro experiences involving caffeine-induced calcium release from the sarcoplasmic reticulum and uptake by mitochondria.

Research paper thumbnail of Sildenafil citrate concentrations not affecting oxidative phosphorylation depress H2O2 generation by rat heart mitochondria

Molecular and Cellular Biochemistry, 2007

Sildenafil citrate (Viagra) is a potent and specific inhibitor of cyclic guanosine monophosphate ... more Sildenafil citrate (Viagra) is a potent and specific inhibitor of cyclic guanosine monophosphate (cGMP)specific phosphodiesterase type 5 (PDE5), which exhibits cardioprotective action against ischemia/reperfusion injury in intact and isolated heart. The mechanism of its cardioprotective action is not completely understood, but some results suggested that sildenafil exerts cardioprotection through the opening of mitochondrial ATP-sensitive K + channels (mitoK ATP). However, the impact of sildenafil citrate per se on isolated heart mitochondrial function is unknown. The goal of this study was to investigate the influence of the compound on mitochondrial function (bioenergetics, Ca 2+-induced mitochondrial permeability transition, and hydrogen peroxide (H 2 O 2) generation) in an attempt to correlate its known actions with effects on heart mitochondria. It was observed that sildenafil citrate concentrations of up to 50 lM did not significantly affect glutamate/malate-supported respiration in states 2, 3, 4, oligomycin-inhibited state 3, and uncoupled respiration. The respiratory control ratio (RCR), the ADP to oxygen ratio (ADP/O), the transmembrane potential (DW), the phosphorylation rate, and the membrane permeability to H + , K + and Ca 2+ were not affected either. However, sildenafil citrate decreased H 2 O 2 generation by mitochondria respiring glutamate/malate, and also decreased the formation of superoxide radical (O 2 •-) generated in a hypoxantine/xantine oxidase system. It was concluded that sildenafil citrate concentrations of up to 50 lM do not affect either rat heart mitochondrial bioenergetics or Ca 2+induced mitochondrial permeability transition, but it depresses H 2 O 2 generation by acting as a superoxide dismutase (SOD)-mimetic. By preventing reactive oxygen species (ROS) generation, sildenafil citrate may preserve heart mitochondrial function.

Research paper thumbnail of Sanguinarine cytotoxicity on mouse melanoma K1735-M2 cells—Nuclear vs. mitochondrial effects

Biochemical Pharmacology, 2008

Sanguinarine (SANG, 13-methyl-benzodioxolo-[5,6-c]-1,3dioxolo[4,5-i]phenanthridinium) [1,2] is an... more Sanguinarine (SANG, 13-methyl-benzodioxolo-[5,6-c]-1,3dioxolo[4,5-i]phenanthridinium) [1,2] is an alkaloid derived from the root of Sanguinaria canadensis and other plants from the Papaveraceae family. SANG is a benzophenanthridine structural homologue of chelerythrine [3]. A positive moiety is present in the aromatic ring of the molecule (Fig. 1). b i o c h e m i c a l p h a r m a c o l o g y 7 6 (2 0 0 8) 1 4 5 9-1 4 7 5

Research paper thumbnail of Inhibition of heart mitochondrial lipid peroxidation by non-toxic concentrations of carvedilol and its analog BM-91022811Abbreviations: TBARS, thiobarbituric acid-reactive substances; ROS, reactive oxygen species; TPP+, tetraphenylphosphonium ion; ΔΨ, mitochondrial membrane potential

Biochemical Pharmacology, 2001

Carvedilol, a non-selective ␤-adrenoreceptor blocker, has been shown to possess a high degree of ... more Carvedilol, a non-selective ␤-adrenoreceptor blocker, has been shown to possess a high degree of cardioprotection in experimental models of myocardial damage. Reactive oxygen species have been proposed to be implicated in such situations, and antioxidants have been demonstrated to provide partial protection to the reported damage. The purpose of our study was to investigate the antioxidant effect of carvedilol and its metabolite BM-910228 by measuring the extent of lipid peroxidation in a model of severe oxidative damage induced by ADP/FeSO 4 in isolated rat heart mitochondria. Carvedilol and BM-910228 inhibited the thiobarbituric acid-reactive substance formation and oxygen consumption associated with lipid peroxidation with IC 50 values of 6 and 0.22 M, respectively. Under the same conditions, the IC 50 values of ␣-tocopheryl succinate and Trolox were 125 and 31 M, respectively. As expected, the presence of carvedilol and BM-910228 preserved the structural and functional integrity of mitochondria under oxidative stress conditions for the same concentration range shown to inhibit lipid peroxidation, since they prevented the collapse of the mitochondrial membrane potential (⌬⌿) induced by ADP/FeSO 4 in respiring mitochondria. It should be stressed that neither carvedilol nor BM-910228 induced any toxic effect on mitochondrial function in the concentration range of the compounds that inhibits the peroxidation of mitochondrial membranes. In conclusion, the antioxidant properties of carvedilol may contribute to the cardioprotective effects of the compound, namely through the preservation of mitochondrial functions whose importance in myocardial dysfunction is clearly documented. Additionally, its hydroxylated analog BM-910220, with its notably superior antioxidant activity, may significantly contribute to the therapeutic effects of carvedilol.

Research paper thumbnail of Carvedilol in heart mitochondria

Life Sciences, 2001

Carvedilol ({1–[carbazolyl–(4)-oxy]-3-[2-methoxyphenoxyethyl) amino]-propanol-(2)}) has been show... more Carvedilol ({1–[carbazolyl–(4)-oxy]-3-[2-methoxyphenoxyethyl) amino]-propanol-(2)}) has been shown to protect cardiac mitochondria from oxidative stress. In this work we examined the mechanisms responsible for an observed depressive effect in the mitochondrial transmembrane potential (ΔΨ). Two possible mechanisms were considered: a protonophoretic activity and the opening of mitochondrial ATP-sensitive potassium channels. We show that carvedilol increases mitochondrial inner membrane permeability to protons, but

Research paper thumbnail of Carvedilol reduces mitochondrial damage induced by hypoxanthine/xanthine oxidase: Relevance to hypoxia/reoxygenation injury

Cardiovascular Toxicology, 2001

The cardioprotective properties of new pharmaceuticals such as carvedilol might be explained by e... more The cardioprotective properties of new pharmaceuticals such as carvedilol might be explained by enhanced mitochondrial protection. The aim of this work was to determine the role of carvedilol in the protection of heart mitochondria from oxidative damage induced by hypoxanthine/xanthine oxidase, a known source of oxidative stress in the vascular system. Carvedilol reduced oxidative-stress-induced mitochondrial injury, as seen by the delay in the loss of the mitochondrial transmembranar potential (DY), the decrease in mitochondrial swelling, and the increase in mitochondrial calcium uptake. Carvedilol improved the mitochondrial respiratory activity in state III and offered an overall protection in the respiratory control and in the P/O ratios in mitochondria under oxidative stress. The data indicated that carvedilol was able to partly protect heart mitochondria from oxidative stress-induced damage. Our results suggest that mitochondria can be important targets for some cardioprotective pharmaceuticals.

Research paper thumbnail of Chenodeoxycholate is a potent inducer of the permeability transition pore in rat liver mitochondria

Bioscience Reports, 2001

Several reports support the concept that bile acids may be cytotoxic during cholestatic disease p... more Several reports support the concept that bile acids may be cytotoxic during cholestatic disease process by causing mitochondrial dysfunction. Here we report additional data and findings aimed at a better understanding of the involvement of the permeability transition pore (PTP) opening in bile acids toxicity. The mitochondrial PTP is implicated as a mediator of cell injury and death in many situations. In the presence of calcium and phosphate, chenodeoxycholic acid (CDCA) induced a permeability transition in freshly isolated rat liver mitochondria, characterized by membrane depolarization, release of matrix calcium, and osmotic swelling. All these events were blocked by cyclosporine A (CyA) and the calcium uniporter inhibitor ruthenium red (RR). The results suggest that CDCA increases the sensitivity of isolated mitochondria in ûitro to the calcium-dependent induction of the PTP.

Research paper thumbnail of Carvedilol Inhibits the Mitochondrial Permeability Transition by an Antioxidant Mechanism

Cardiovascular Toxicology, 2004

It was previously shown that carvedilol, a b-adrenergic receptor antagonist with antioxidant prop... more It was previously shown that carvedilol, a b-adrenergic receptor antagonist with antioxidant properties, was able to inhibit the mitochondrial permeability transition (MPT). In the present work, the hypothesis was that the negative impact of carvedilol on the MPT was specifically the result of its antioxidant effect. For the current investigation, we used three different MPT inducers. MPT-associated events were tested to study the protective effect of both carvedilol and cyclosporin-A, the known MPT inhibitor. Carvedilol inhibited mitochondrial swelling with calcium plus phosphate and with calcium plus t-butylhydroperoxide, but not with calcium plus carboxyatractyloside. Carvedilol inhibited the oxidation of thiol groups with calcium plus phosphate (p < 0.01) and with calcium plus t-butylhydroperoxide (p < 0.05), but not with calcium plus carboxyatractyloside-in opposition to the full protection afforded by cyclosporin-A when using calcium and carboxyatractyloside. Our results showed that carvedilol was effective only when the MPT was triggered by a primary oxidative process. This finding implies that the antioxidant properties of carvedilol are crucial for the observed effects and reinforces the advantageous use of carvedilol in cardiac pathologies associated with enhanced cellular oxidative stress.

Research paper thumbnail of Serpentine endophytic bacterium Pseudomonas azotoformans ASS1 accelerates phytoremediation of soil metals under drought stress

Chemosphere, Jan 3, 2017

This study evaluates the potential of serpentine endophytic bacterium to foster phytoremediation ... more This study evaluates the potential of serpentine endophytic bacterium to foster phytoremediation efficiency of Trifolium arvense grown on multi-metal (Cu, Zn and Ni) contaminated soils under drought stress. A drought resistant endophytic bacterial strain ASS1 isolated from the leaves of Alyssum serpyllifolium grown in serpentine soils was identified as Pseudomonas azotoformans based on biochemical tests and partial 16S rRNA gene sequencing. P. azotoformans ASS1 possessed abiotic stress resistance (heavy metals, drought, salinity, antibiotics and extreme temperature) and plant growth promoting (PGP) properties (phosphate solubilization, nitrogen fixation, production of 1-aminocyclopropane-1-carboxylate deaminase, siderophore and ammonia). Inoculation of T. arvense with ASS1 considerably increased the plant biomass and leaf relative water content in both roll towel assay and pot experiments in the absence and presence of drought stress (DS). In the pot experiments, ASS1 greatly enhanc...

Research paper thumbnail of Amyloid β-peptide promotes permeability transition pore in brain mitochondria

Bioscience Reports, 2001

In this work the effect of the neurotoxic amino acid sequence, Aβ 25-35 , on brain mitochondrial ... more In this work the effect of the neurotoxic amino acid sequence, Aβ 25-35 , on brain mitochondrial permeability transition pore (PTP) was studied. For the purpose, the mitochondrial transmembrane potential (∆Ψm), mitochondrial respiration and the calcium fluxes were examined. It was observed that Aβ 25-35 , in the presence of Ca 2+ , decreased the ∆Ψm, the capacity of brain mitochondria to accumulate calcium and led to a complete uncoupling of the respiration. However, the reverse sequence of the peptide Aβ 25-35 (Aβ 35-25) did not promote the PTP. The alterations promoted by Aβ 35-25 and͞or Ca 2+ could be reversed when Ca 2+ was removed by EGTA or when ADP plus oligomycin were present. The pretreatment with CsA or ADP plus oligomycin prevented the ∆Ψm drop and preserved the capacity of mitochondria to accumulate Ca 2+. These results suggest that Aβ 25-35 can promote the PTP induced by Ca 2+ .

Research paper thumbnail of Effects of hyperglycemia on sperm and testicular cells of Goto-Kakizaki and streptozotocin-treated rat models for diabetes

Theriogenology, 2006

Diabetes mellitus is a degenerative disease that has deleterious effects on male reproductive fun... more Diabetes mellitus is a degenerative disease that has deleterious effects on male reproductive function, possibly through an increase in oxidative stress. This study was conducted in order to clarify the mechanisms by which oxidative stress influences animal models for both type 1 (streptozotocin-treated rats, STZ) and type 2 (Goto-Kakizaki (GK) rats) diabetes. We determined the extent of lipid peroxidation, protein oxidation, lactate levels, adenine nucleotides, adenylate energy charge and the activity of glutathione peroxidase, glutathione reductase and lactate dehydrogenase, in isolated testicular cells of control and diabetic rats. We have also correlated these parameters with sperm count and motility. Sperm concentration and motility were decreased in STZtreated rats. ATP levels were lower in rats treated with STZ for 3 months, in contrast to GK and rats treated with STZ for 1 month, suggesting an adaptative response. STZ-treated rats showed increased lipid peroxidation after 1 week and 3 months of treatment. Glutathione reductase (G-red) activity was found to be higher in GK rats. Glutathione peroxidase activity was lower in GK and rats treated with STZ for 1 month, which is in accordance with the proposal of functional recovery in these animals. We conclude that hyperglycemia has an adverse effect in sperm concentration and motility via changes in energy production and free radical management. Furthermore, both animal models, particularly GK rats and rats treated with STZ for 1 month, present some metabolic adaptations, increasing the efficiency of mitochondrial ATP production, in order to circumvent the deleterious effects promoted by the disease.

Research paper thumbnail of Effect of amyloid ?-peptide on permeability transition pore: A comparative study

Journal of Neuroscience Research, 2002

A potentially central factor in neurodegeneration is the permeability transition pore (PTP). Beca... more A potentially central factor in neurodegeneration is the permeability transition pore (PTP). Because of the tissuespecific differences in pore properties, we directly compared isolated brain and liver mitochondria responses to the neurotoxic A␤ peptides. For this purpose, the following parameters were examined: mitochondrial membrane potential (⌬⌿m), respiration, swelling, ultrastructural morphology, and content of cytochrome c. Both peptides, A␤ 25-35 (50 M) and A␤ 1-40 (2 M), had a similar toxicity, exacerbating the effects of Ca 2ϩ , although, per se, they did not induce (PTP). In liver mitochondria, A␤ led to a drop in ⌬⌿m and potentiated matrix swelling and disruption induced by Ca 2ϩ. In contrast, brain mitochondria, exposed to the same conditions, demonstrated a higher capacity to accumulate Ca 2ϩ before the ⌬⌿m drop and a slight increase of mitochondrial swelling compared with liver mitochondria. Furthermore, mitochondrial respiratory state 3 was depressed in the presence of A␤, whereas state 4 was unaltered, resulting in an uncoupling of respiration. In both types of mitochondria, A␤ did not affect the content of cytochrome c. The ⌬⌿m drop was reversed when Ca 2ϩ was removed by EGTA or when ADP plus oligomycin was present. Pretreatment with cyclosporin A or ADP plus oligomycin prevented the deleterious effects promoted by A␤ and/or Ca 2ϩ. It can be concluded that brain and liver mitochondria show a different susceptibility to the deleterious effect of A␤ peptide, brain mitochondria being more resistant to the potentiation by A␤ of Ca 2ϩ-induced PTP.

Research paper thumbnail of Tamoxifen and Estradiol Interact with the Flavin Mononucleotide Site of Complex I Leading to Mitochondrial Failure

Journal of Biological Chemistry, 2006

This study evaluated the action of tamoxifen and estradiol on the function of isolated liver mito... more This study evaluated the action of tamoxifen and estradiol on the function of isolated liver mitochondria. We observed that although tamoxifen and estradiol per se did not affect mitochondrial complexes II, III, or IV, complex I is affected, this effect being more drastic (except for state 4 of respiration) when mitochondria were coincubated with both drugs. Furthermore, using two respiratory chain inhibitors, rotenone and diphenyliodonium chloride, we identified the flavin mononucleotide site of complex I as the target of tamoxifen and/or estradiol action(s). Tamoxifen (25 M) per se induced a significant increase in hydrogen peroxide production and state 4 of respiration. Additionally, a significant decrease in respiratory control ratio, transmembrane, and depolarization potentials were observed. Estradiol per se decreased carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP)-stimulated respiration, state 3 of respiration, and respiratory control ratio and increased lag phase of repolarization. With the exception of state 4 of respiration whose increase induced by tamoxifen was reversed by the presence of estradiol, the effects of tamoxifen were highly exacerbated when estradiol was present. We observed that 10 M tamoxifen in the presence of estradiol affected mitochondria significantly by decreasing FCCP-stimulated respiration, state 3 of respiration, respiratory control ratio, and ADP depolarization and increasing the lag phase of repolarization. All of the deleterious effects induced by 25 M tamoxifen were highly exacerbated in the presence of estradiol. Furthermore, we observed that the effects of both compounds were independent of estrogen receptors because the pure estrogen antagonist ICI 182,780 did not interfere with tamoxifen and/or estradiol detrimental effects. Altogether, our data provide a mechanistic explanation for the multiple cytotoxic effects of tamoxifen including its capacity to destroy tamoxifen-resistant breast cancer cells in the presence of estradiol. This new piece of information provides a basis for the development of new and promising anticancer therapeutic strategies.

Research paper thumbnail of Protection against post-ischemic mitochondrial injury in rat liver by silymarin or TUDC

Hepatology Research, 2003

Background: Hepatic ischemia/reperfusion (I/R) injury is characterized by features such as choles... more Background: Hepatic ischemia/reperfusion (I/R) injury is characterized by features such as cholestasis. Mitochondria become susceptible to damage during ischemia and after reperfusion. The aim of this study was to determine if silymarin and tauroursodeoxycholic acid (TUDC), would prevent impairment of liver mitochondrial function following I/R injury. Methods: Livers of male Wistar rats were subjected to 45 min of hepatic ischemia. During the 90 min of reperfusion, livers were perfused with either vehicle, silymarin, or TUDC. Changes in membrane potential, mitochondrial respiration as well as susceptibility to mitochondrial permeability transition (MPT) induction were evaluated and endogenous adenine nucleotides were measured. Results: In rats subjected to I/R, compared with the control group, a severe impairment of mitochondrial bioenergetics was observed. State 3 respiration was decreased and state 4 enhanced, associated with lower membrane potential developed following succinate energization. An increased susceptibility to MPT induction by calcium/phosphate was also observed. The effects of I/R injury were ameliorated in the presence of silymarin but not TUDC. Similarly, ATP levels following I/R were lower, in comparison with the control group and the silymarin treatment but not TUDC. Conclusion: Thus, silymarin, but not TUDC, prevents the most significant changes that occur in mitochondria during I/R, and probably, the associated cell dysfunction, through their central role in cellular bioenergetics.

Research paper thumbnail of Inhibitory effect of carvedilol in the high-conductance state of the mitochondrial permeability transition pore

European Journal of Pharmacology, 2001

The mitochondrial permeability transition is a widely studied, but poorly understood, phenomenon ... more The mitochondrial permeability transition is a widely studied, but poorly understood, phenomenon in mitochondrial bioenergetics. It has been recognised that this phenomenon is related to the opening of a protein pore in the inner mitochondrial membrane, and that opening of this pore is the cause of some forms of mitochondrial dysfunction. In this work, we propose that carvedilol, a multi-role cardioprotective compound, may act as an inhibitor of the high-conductance state of the mitochondrial permeability transition pore, a conclusion supported by the finding that carvedilol provides differential protection against mitochondrial swelling in sucrose and KCl-based media, and that it is unable to protect against calcium-induced depolarisation of the mitochondrial membrane. We also show that carvedilol inhibits the oxidation of mitochondrial thiol groups and that, beyond causing a slight depression of the membrane potential, it has no inhibitory effect on mitochondrial calcium uptake. A decrease in the number of oxidised protein thiol groups may be the main mechanism responsible for this selective inhibition of the permeability transition pore in heart mitochondria. These effects may be important for the role of carvedilol in some cardiac pathologies.

Research paper thumbnail of Dioxin-induced acute cardiac mitochondrial oxidative damage and increased activity of ATP-sensitive potassium channels in Wistar rats

Environmental Pollution, 2013

The environmental dioxin 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is classified as a Group 1 hu... more The environmental dioxin 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is classified as a Group 1 human carcinogen and teratogenic agent. We hypothesize that TCDD-induced oxidative stress may also interfere with mitochondrial ATP-sensitive potassium channels (mitoKATP), which are known to regulate and to be regulated by mitochondrial redox state. We investigated the effects of an acute treatment of male Wistar rats with TCDD (50 mg/kg i.p.) and measured the regulation of cardiac mitoKATP. While the function of cardiac mitochondria was slightly depressed, mitoKATP activity was 52% higher in animals treated with TCDD. The same effects were not observed in liver mitochondria isolated from the same animals. Our data also shows that regulation of mitochondrial ROS production by mitoKATP activity is different in both groups. To our knowledge, this is the first report to show that TCDD increases mitoKATP activity in the heart, which may counteract the increased oxidative stress caused by the dioxin during acute exposure.

Research paper thumbnail of Quaternary ammonium surfactant structure determines selective toxicity towards bacteria: mechanisms of action and clinical implications in antibacterial prophylaxis

The Journal of antimicrobial chemotherapy, Jan 17, 2015

Broad-spectrum antimicrobial activity of quaternary ammonium surfactants (QAS) makes them attract... more Broad-spectrum antimicrobial activity of quaternary ammonium surfactants (QAS) makes them attractive and cheap topical prophylactic options for sexually transmitted infections and perinatal vertically transmitted urogenital infections. Although attributed to their high affinity for biological membranes, the mechanisms behind QAS microbicidal activity are not fully understood. We evaluated how QAS structure affects antimicrobial activity and whether this can be exploited for use in prophylaxis of bacterial infections. Acute toxicity of QAS to in vitro models of human epithelial cells and bacteria were compared to identify selective and potent bactericidal agents. Bacterial cell viability, membrane integrity, cell cycle and metabolism were evaluated to establish the mechanisms involved in selective toxicity of QAS. QAS toxicity normalized relative to surfactant critical micelle concentration showed n-dodecylpyridinium bromide (C12PB) to be the most effective, with a therapeutic index ...

Research paper thumbnail of Cardiac cytochrome c and cardiolipin depletion during anthracycline-induced chronic depression of mitochondrial function

Mitochondrion, Sep 13, 2016

It is still unclear why anthracycline treatment results in a cardiac-specific myopathy. We invest... more It is still unclear why anthracycline treatment results in a cardiac-specific myopathy. We investigated whether selective doxorubicin (DOX) cardiotoxicity involving mitochondrial degeneration is explained by different respiratory complexes reserves between tissues by comparing and contrasting treatment effects in heart vs liver and kidney. Alternatively, we have also explored if the degeneration is due to alterations of mitochondrial thresholds to incompatible states. Heart, liver and kidney mitochondria were isolated from male Wistar rats weekly injected with DOX during 7weeks. Global flux and isolated step curves were obtained for Complex I, III, IV, as well as for the adenine nucleotide translocator. We show treatment-related alterations in global flux curve for Complex III in all analyzed tissues and in Complex IV activity curve solely in heart. However, all mitochondrial threshold curves remained unchanged after treatment in the analyzed tissues. No treatment-related difference...

Research paper thumbnail of Measuring Mitochondrial Membrane Potential with a Tetraphenylphosphonium‐Selective Electrode

Current Protocols in Toxicology, 2015

Mitochondrial bioenergetics is based on the generation of the protonmotive force by the electron ... more Mitochondrial bioenergetics is based on the generation of the protonmotive force by the electron transport chain. The protonmotive force is used by mitochondria for different critical aspects of its normal function, ranging from calcium accumulation to the synthesis of ATP. The transmembrane electric potential (ΔΨ) is the major component of the protonmotive force and is also the main responsible for ATP synthesis by mitochondrial ATP synthase. Although several methods can be used to measure the ΔΨ, the use of the tetraphenylphosphonium cation (TPP(+) )-selective electrode is still a method of election due to its sensitivity. The method is based on the accumulation of TPP(+) by energized mitochondria, which develop a negative charge in the matrix due to the ejection of protons. This unit describes how to build a custom-made TPP(+) -selective electrode and how to establish the necessary set-up to follow ΔΨ fluctuations in isolated mitochondrial fractions. © 2015 by John Wiley &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp; Sons, Inc.

Research paper thumbnail of Decreased susceptibility of heart mitochondria from diabetic GK rats to mitochondrial permeability transition induced by calcium phosphate

Type 2 diabetes (or non-insulin dependent diabetes mellitus, NIDDM) is a common metabolic disease... more Type 2 diabetes (or non-insulin dependent diabetes mellitus, NIDDM) is a common metabolic disease in man. The Goto-Kakizaki (GK) rat has been designed as a NIDDM model. Previous studies with this strain have shown differences at the mitochondrial level. The mitochondrial permeability transition (MPT) is a widely studied phenomenon but yet poorly understood, that leads to mitochondrial dysfunction and cell death. The aim of this work was to compare the differences in susceptibility of induction of the MPT with calcium phosphate in GK and Wistar rats. Our results show that heart mitochondria from GK rats are less susceptible to the induction of MPT, and show a larger calcium accumulation before the overall loss of mitochondrial impermeability.

Research paper thumbnail of Caffeine Enhances the Calcium-Dependent Cardiac Mitochondrial Permeability Transition: Relevance for Caffeine Toxicity

Toxicology and Applied Pharmacology, 2002

Caffeine (1,3,7-trimethylxanthine), a compound present in beverages such as tea and coffee, is kn... more Caffeine (1,3,7-trimethylxanthine), a compound present in beverages such as tea and coffee, is known to be toxic at high concentrations. Some of the observed clinical conditions include cardiovascular disease and reproductive disorders, among others. The possible toxic effects of caffeine on heart mitochondria are still poorly understood. The influence of caffeine on the mitochondrial permeability transition has not been clarified so far. The objective of this study was to investigate whether caffeine, at toxic concentrations, had any stimulating effect on the permeability transition of heart mitochondria isolated from Wistar rats, as well as whether it influenced mitochondrial respiratory parameters. Our results show that caffeine reduced mitochondrial ability to accumulate calcium by increasing the susceptibility of heart mitochondria to the opening of the transition pore. Caffeine not only hindered mitochondrial capacity to recover membrane potential after calcium addition but also increased the rate of calciumdependent mitochondrial swelling and calcium-induced calcium release. The increased swelling was also observed in nonenergized mitochondria. Caffeine also showed a complex array of effects on heart mitochondrial bioenergetics, as evaluated by respiratory parameter measurements. We observed an increase in state 4 respiration and a depression in state 3 respiration, although no effect was observed on succinate-sustained mitochondrial membrane potential in the absence of calcium. Our work may be relevant to cardiovascular problems linked to caffeine toxicity and also to in vitro experiences involving caffeine-induced calcium release from the sarcoplasmic reticulum and uptake by mitochondria.

Research paper thumbnail of Sildenafil citrate concentrations not affecting oxidative phosphorylation depress H2O2 generation by rat heart mitochondria

Molecular and Cellular Biochemistry, 2007

Sildenafil citrate (Viagra) is a potent and specific inhibitor of cyclic guanosine monophosphate ... more Sildenafil citrate (Viagra) is a potent and specific inhibitor of cyclic guanosine monophosphate (cGMP)specific phosphodiesterase type 5 (PDE5), which exhibits cardioprotective action against ischemia/reperfusion injury in intact and isolated heart. The mechanism of its cardioprotective action is not completely understood, but some results suggested that sildenafil exerts cardioprotection through the opening of mitochondrial ATP-sensitive K + channels (mitoK ATP). However, the impact of sildenafil citrate per se on isolated heart mitochondrial function is unknown. The goal of this study was to investigate the influence of the compound on mitochondrial function (bioenergetics, Ca 2+-induced mitochondrial permeability transition, and hydrogen peroxide (H 2 O 2) generation) in an attempt to correlate its known actions with effects on heart mitochondria. It was observed that sildenafil citrate concentrations of up to 50 lM did not significantly affect glutamate/malate-supported respiration in states 2, 3, 4, oligomycin-inhibited state 3, and uncoupled respiration. The respiratory control ratio (RCR), the ADP to oxygen ratio (ADP/O), the transmembrane potential (DW), the phosphorylation rate, and the membrane permeability to H + , K + and Ca 2+ were not affected either. However, sildenafil citrate decreased H 2 O 2 generation by mitochondria respiring glutamate/malate, and also decreased the formation of superoxide radical (O 2 •-) generated in a hypoxantine/xantine oxidase system. It was concluded that sildenafil citrate concentrations of up to 50 lM do not affect either rat heart mitochondrial bioenergetics or Ca 2+induced mitochondrial permeability transition, but it depresses H 2 O 2 generation by acting as a superoxide dismutase (SOD)-mimetic. By preventing reactive oxygen species (ROS) generation, sildenafil citrate may preserve heart mitochondrial function.

Research paper thumbnail of Sanguinarine cytotoxicity on mouse melanoma K1735-M2 cells—Nuclear vs. mitochondrial effects

Biochemical Pharmacology, 2008

Sanguinarine (SANG, 13-methyl-benzodioxolo-[5,6-c]-1,3dioxolo[4,5-i]phenanthridinium) [1,2] is an... more Sanguinarine (SANG, 13-methyl-benzodioxolo-[5,6-c]-1,3dioxolo[4,5-i]phenanthridinium) [1,2] is an alkaloid derived from the root of Sanguinaria canadensis and other plants from the Papaveraceae family. SANG is a benzophenanthridine structural homologue of chelerythrine [3]. A positive moiety is present in the aromatic ring of the molecule (Fig. 1). b i o c h e m i c a l p h a r m a c o l o g y 7 6 (2 0 0 8) 1 4 5 9-1 4 7 5

Research paper thumbnail of Inhibition of heart mitochondrial lipid peroxidation by non-toxic concentrations of carvedilol and its analog BM-91022811Abbreviations: TBARS, thiobarbituric acid-reactive substances; ROS, reactive oxygen species; TPP+, tetraphenylphosphonium ion; ΔΨ, mitochondrial membrane potential

Biochemical Pharmacology, 2001

Carvedilol, a non-selective ␤-adrenoreceptor blocker, has been shown to possess a high degree of ... more Carvedilol, a non-selective ␤-adrenoreceptor blocker, has been shown to possess a high degree of cardioprotection in experimental models of myocardial damage. Reactive oxygen species have been proposed to be implicated in such situations, and antioxidants have been demonstrated to provide partial protection to the reported damage. The purpose of our study was to investigate the antioxidant effect of carvedilol and its metabolite BM-910228 by measuring the extent of lipid peroxidation in a model of severe oxidative damage induced by ADP/FeSO 4 in isolated rat heart mitochondria. Carvedilol and BM-910228 inhibited the thiobarbituric acid-reactive substance formation and oxygen consumption associated with lipid peroxidation with IC 50 values of 6 and 0.22 M, respectively. Under the same conditions, the IC 50 values of ␣-tocopheryl succinate and Trolox were 125 and 31 M, respectively. As expected, the presence of carvedilol and BM-910228 preserved the structural and functional integrity of mitochondria under oxidative stress conditions for the same concentration range shown to inhibit lipid peroxidation, since they prevented the collapse of the mitochondrial membrane potential (⌬⌿) induced by ADP/FeSO 4 in respiring mitochondria. It should be stressed that neither carvedilol nor BM-910228 induced any toxic effect on mitochondrial function in the concentration range of the compounds that inhibits the peroxidation of mitochondrial membranes. In conclusion, the antioxidant properties of carvedilol may contribute to the cardioprotective effects of the compound, namely through the preservation of mitochondrial functions whose importance in myocardial dysfunction is clearly documented. Additionally, its hydroxylated analog BM-910220, with its notably superior antioxidant activity, may significantly contribute to the therapeutic effects of carvedilol.

Research paper thumbnail of Carvedilol in heart mitochondria

Life Sciences, 2001

Carvedilol ({1–[carbazolyl–(4)-oxy]-3-[2-methoxyphenoxyethyl) amino]-propanol-(2)}) has been show... more Carvedilol ({1–[carbazolyl–(4)-oxy]-3-[2-methoxyphenoxyethyl) amino]-propanol-(2)}) has been shown to protect cardiac mitochondria from oxidative stress. In this work we examined the mechanisms responsible for an observed depressive effect in the mitochondrial transmembrane potential (ΔΨ). Two possible mechanisms were considered: a protonophoretic activity and the opening of mitochondrial ATP-sensitive potassium channels. We show that carvedilol increases mitochondrial inner membrane permeability to protons, but

Research paper thumbnail of Carvedilol reduces mitochondrial damage induced by hypoxanthine/xanthine oxidase: Relevance to hypoxia/reoxygenation injury

Cardiovascular Toxicology, 2001

The cardioprotective properties of new pharmaceuticals such as carvedilol might be explained by e... more The cardioprotective properties of new pharmaceuticals such as carvedilol might be explained by enhanced mitochondrial protection. The aim of this work was to determine the role of carvedilol in the protection of heart mitochondria from oxidative damage induced by hypoxanthine/xanthine oxidase, a known source of oxidative stress in the vascular system. Carvedilol reduced oxidative-stress-induced mitochondrial injury, as seen by the delay in the loss of the mitochondrial transmembranar potential (DY), the decrease in mitochondrial swelling, and the increase in mitochondrial calcium uptake. Carvedilol improved the mitochondrial respiratory activity in state III and offered an overall protection in the respiratory control and in the P/O ratios in mitochondria under oxidative stress. The data indicated that carvedilol was able to partly protect heart mitochondria from oxidative stress-induced damage. Our results suggest that mitochondria can be important targets for some cardioprotective pharmaceuticals.

Research paper thumbnail of Chenodeoxycholate is a potent inducer of the permeability transition pore in rat liver mitochondria

Bioscience Reports, 2001

Several reports support the concept that bile acids may be cytotoxic during cholestatic disease p... more Several reports support the concept that bile acids may be cytotoxic during cholestatic disease process by causing mitochondrial dysfunction. Here we report additional data and findings aimed at a better understanding of the involvement of the permeability transition pore (PTP) opening in bile acids toxicity. The mitochondrial PTP is implicated as a mediator of cell injury and death in many situations. In the presence of calcium and phosphate, chenodeoxycholic acid (CDCA) induced a permeability transition in freshly isolated rat liver mitochondria, characterized by membrane depolarization, release of matrix calcium, and osmotic swelling. All these events were blocked by cyclosporine A (CyA) and the calcium uniporter inhibitor ruthenium red (RR). The results suggest that CDCA increases the sensitivity of isolated mitochondria in ûitro to the calcium-dependent induction of the PTP.

Research paper thumbnail of Carvedilol Inhibits the Mitochondrial Permeability Transition by an Antioxidant Mechanism

Cardiovascular Toxicology, 2004

It was previously shown that carvedilol, a b-adrenergic receptor antagonist with antioxidant prop... more It was previously shown that carvedilol, a b-adrenergic receptor antagonist with antioxidant properties, was able to inhibit the mitochondrial permeability transition (MPT). In the present work, the hypothesis was that the negative impact of carvedilol on the MPT was specifically the result of its antioxidant effect. For the current investigation, we used three different MPT inducers. MPT-associated events were tested to study the protective effect of both carvedilol and cyclosporin-A, the known MPT inhibitor. Carvedilol inhibited mitochondrial swelling with calcium plus phosphate and with calcium plus t-butylhydroperoxide, but not with calcium plus carboxyatractyloside. Carvedilol inhibited the oxidation of thiol groups with calcium plus phosphate (p < 0.01) and with calcium plus t-butylhydroperoxide (p < 0.05), but not with calcium plus carboxyatractyloside-in opposition to the full protection afforded by cyclosporin-A when using calcium and carboxyatractyloside. Our results showed that carvedilol was effective only when the MPT was triggered by a primary oxidative process. This finding implies that the antioxidant properties of carvedilol are crucial for the observed effects and reinforces the advantageous use of carvedilol in cardiac pathologies associated with enhanced cellular oxidative stress.

Research paper thumbnail of Serpentine endophytic bacterium Pseudomonas azotoformans ASS1 accelerates phytoremediation of soil metals under drought stress

Chemosphere, Jan 3, 2017

This study evaluates the potential of serpentine endophytic bacterium to foster phytoremediation ... more This study evaluates the potential of serpentine endophytic bacterium to foster phytoremediation efficiency of Trifolium arvense grown on multi-metal (Cu, Zn and Ni) contaminated soils under drought stress. A drought resistant endophytic bacterial strain ASS1 isolated from the leaves of Alyssum serpyllifolium grown in serpentine soils was identified as Pseudomonas azotoformans based on biochemical tests and partial 16S rRNA gene sequencing. P. azotoformans ASS1 possessed abiotic stress resistance (heavy metals, drought, salinity, antibiotics and extreme temperature) and plant growth promoting (PGP) properties (phosphate solubilization, nitrogen fixation, production of 1-aminocyclopropane-1-carboxylate deaminase, siderophore and ammonia). Inoculation of T. arvense with ASS1 considerably increased the plant biomass and leaf relative water content in both roll towel assay and pot experiments in the absence and presence of drought stress (DS). In the pot experiments, ASS1 greatly enhanc...

Research paper thumbnail of Amyloid β-peptide promotes permeability transition pore in brain mitochondria

Bioscience Reports, 2001

In this work the effect of the neurotoxic amino acid sequence, Aβ 25-35 , on brain mitochondrial ... more In this work the effect of the neurotoxic amino acid sequence, Aβ 25-35 , on brain mitochondrial permeability transition pore (PTP) was studied. For the purpose, the mitochondrial transmembrane potential (∆Ψm), mitochondrial respiration and the calcium fluxes were examined. It was observed that Aβ 25-35 , in the presence of Ca 2+ , decreased the ∆Ψm, the capacity of brain mitochondria to accumulate calcium and led to a complete uncoupling of the respiration. However, the reverse sequence of the peptide Aβ 25-35 (Aβ 35-25) did not promote the PTP. The alterations promoted by Aβ 35-25 and͞or Ca 2+ could be reversed when Ca 2+ was removed by EGTA or when ADP plus oligomycin were present. The pretreatment with CsA or ADP plus oligomycin prevented the ∆Ψm drop and preserved the capacity of mitochondria to accumulate Ca 2+. These results suggest that Aβ 25-35 can promote the PTP induced by Ca 2+ .

Research paper thumbnail of Effects of hyperglycemia on sperm and testicular cells of Goto-Kakizaki and streptozotocin-treated rat models for diabetes

Theriogenology, 2006

Diabetes mellitus is a degenerative disease that has deleterious effects on male reproductive fun... more Diabetes mellitus is a degenerative disease that has deleterious effects on male reproductive function, possibly through an increase in oxidative stress. This study was conducted in order to clarify the mechanisms by which oxidative stress influences animal models for both type 1 (streptozotocin-treated rats, STZ) and type 2 (Goto-Kakizaki (GK) rats) diabetes. We determined the extent of lipid peroxidation, protein oxidation, lactate levels, adenine nucleotides, adenylate energy charge and the activity of glutathione peroxidase, glutathione reductase and lactate dehydrogenase, in isolated testicular cells of control and diabetic rats. We have also correlated these parameters with sperm count and motility. Sperm concentration and motility were decreased in STZtreated rats. ATP levels were lower in rats treated with STZ for 3 months, in contrast to GK and rats treated with STZ for 1 month, suggesting an adaptative response. STZ-treated rats showed increased lipid peroxidation after 1 week and 3 months of treatment. Glutathione reductase (G-red) activity was found to be higher in GK rats. Glutathione peroxidase activity was lower in GK and rats treated with STZ for 1 month, which is in accordance with the proposal of functional recovery in these animals. We conclude that hyperglycemia has an adverse effect in sperm concentration and motility via changes in energy production and free radical management. Furthermore, both animal models, particularly GK rats and rats treated with STZ for 1 month, present some metabolic adaptations, increasing the efficiency of mitochondrial ATP production, in order to circumvent the deleterious effects promoted by the disease.

Research paper thumbnail of Effect of amyloid ?-peptide on permeability transition pore: A comparative study

Journal of Neuroscience Research, 2002

A potentially central factor in neurodegeneration is the permeability transition pore (PTP). Beca... more A potentially central factor in neurodegeneration is the permeability transition pore (PTP). Because of the tissuespecific differences in pore properties, we directly compared isolated brain and liver mitochondria responses to the neurotoxic A␤ peptides. For this purpose, the following parameters were examined: mitochondrial membrane potential (⌬⌿m), respiration, swelling, ultrastructural morphology, and content of cytochrome c. Both peptides, A␤ 25-35 (50 M) and A␤ 1-40 (2 M), had a similar toxicity, exacerbating the effects of Ca 2ϩ , although, per se, they did not induce (PTP). In liver mitochondria, A␤ led to a drop in ⌬⌿m and potentiated matrix swelling and disruption induced by Ca 2ϩ. In contrast, brain mitochondria, exposed to the same conditions, demonstrated a higher capacity to accumulate Ca 2ϩ before the ⌬⌿m drop and a slight increase of mitochondrial swelling compared with liver mitochondria. Furthermore, mitochondrial respiratory state 3 was depressed in the presence of A␤, whereas state 4 was unaltered, resulting in an uncoupling of respiration. In both types of mitochondria, A␤ did not affect the content of cytochrome c. The ⌬⌿m drop was reversed when Ca 2ϩ was removed by EGTA or when ADP plus oligomycin was present. Pretreatment with cyclosporin A or ADP plus oligomycin prevented the deleterious effects promoted by A␤ and/or Ca 2ϩ. It can be concluded that brain and liver mitochondria show a different susceptibility to the deleterious effect of A␤ peptide, brain mitochondria being more resistant to the potentiation by A␤ of Ca 2ϩ-induced PTP.

Research paper thumbnail of Tamoxifen and Estradiol Interact with the Flavin Mononucleotide Site of Complex I Leading to Mitochondrial Failure

Journal of Biological Chemistry, 2006

This study evaluated the action of tamoxifen and estradiol on the function of isolated liver mito... more This study evaluated the action of tamoxifen and estradiol on the function of isolated liver mitochondria. We observed that although tamoxifen and estradiol per se did not affect mitochondrial complexes II, III, or IV, complex I is affected, this effect being more drastic (except for state 4 of respiration) when mitochondria were coincubated with both drugs. Furthermore, using two respiratory chain inhibitors, rotenone and diphenyliodonium chloride, we identified the flavin mononucleotide site of complex I as the target of tamoxifen and/or estradiol action(s). Tamoxifen (25 M) per se induced a significant increase in hydrogen peroxide production and state 4 of respiration. Additionally, a significant decrease in respiratory control ratio, transmembrane, and depolarization potentials were observed. Estradiol per se decreased carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP)-stimulated respiration, state 3 of respiration, and respiratory control ratio and increased lag phase of repolarization. With the exception of state 4 of respiration whose increase induced by tamoxifen was reversed by the presence of estradiol, the effects of tamoxifen were highly exacerbated when estradiol was present. We observed that 10 M tamoxifen in the presence of estradiol affected mitochondria significantly by decreasing FCCP-stimulated respiration, state 3 of respiration, respiratory control ratio, and ADP depolarization and increasing the lag phase of repolarization. All of the deleterious effects induced by 25 M tamoxifen were highly exacerbated in the presence of estradiol. Furthermore, we observed that the effects of both compounds were independent of estrogen receptors because the pure estrogen antagonist ICI 182,780 did not interfere with tamoxifen and/or estradiol detrimental effects. Altogether, our data provide a mechanistic explanation for the multiple cytotoxic effects of tamoxifen including its capacity to destroy tamoxifen-resistant breast cancer cells in the presence of estradiol. This new piece of information provides a basis for the development of new and promising anticancer therapeutic strategies.

Research paper thumbnail of Protection against post-ischemic mitochondrial injury in rat liver by silymarin or TUDC

Hepatology Research, 2003

Background: Hepatic ischemia/reperfusion (I/R) injury is characterized by features such as choles... more Background: Hepatic ischemia/reperfusion (I/R) injury is characterized by features such as cholestasis. Mitochondria become susceptible to damage during ischemia and after reperfusion. The aim of this study was to determine if silymarin and tauroursodeoxycholic acid (TUDC), would prevent impairment of liver mitochondrial function following I/R injury. Methods: Livers of male Wistar rats were subjected to 45 min of hepatic ischemia. During the 90 min of reperfusion, livers were perfused with either vehicle, silymarin, or TUDC. Changes in membrane potential, mitochondrial respiration as well as susceptibility to mitochondrial permeability transition (MPT) induction were evaluated and endogenous adenine nucleotides were measured. Results: In rats subjected to I/R, compared with the control group, a severe impairment of mitochondrial bioenergetics was observed. State 3 respiration was decreased and state 4 enhanced, associated with lower membrane potential developed following succinate energization. An increased susceptibility to MPT induction by calcium/phosphate was also observed. The effects of I/R injury were ameliorated in the presence of silymarin but not TUDC. Similarly, ATP levels following I/R were lower, in comparison with the control group and the silymarin treatment but not TUDC. Conclusion: Thus, silymarin, but not TUDC, prevents the most significant changes that occur in mitochondria during I/R, and probably, the associated cell dysfunction, through their central role in cellular bioenergetics.

Research paper thumbnail of Inhibitory effect of carvedilol in the high-conductance state of the mitochondrial permeability transition pore

European Journal of Pharmacology, 2001

The mitochondrial permeability transition is a widely studied, but poorly understood, phenomenon ... more The mitochondrial permeability transition is a widely studied, but poorly understood, phenomenon in mitochondrial bioenergetics. It has been recognised that this phenomenon is related to the opening of a protein pore in the inner mitochondrial membrane, and that opening of this pore is the cause of some forms of mitochondrial dysfunction. In this work, we propose that carvedilol, a multi-role cardioprotective compound, may act as an inhibitor of the high-conductance state of the mitochondrial permeability transition pore, a conclusion supported by the finding that carvedilol provides differential protection against mitochondrial swelling in sucrose and KCl-based media, and that it is unable to protect against calcium-induced depolarisation of the mitochondrial membrane. We also show that carvedilol inhibits the oxidation of mitochondrial thiol groups and that, beyond causing a slight depression of the membrane potential, it has no inhibitory effect on mitochondrial calcium uptake. A decrease in the number of oxidised protein thiol groups may be the main mechanism responsible for this selective inhibition of the permeability transition pore in heart mitochondria. These effects may be important for the role of carvedilol in some cardiac pathologies.

Research paper thumbnail of Dioxin-induced acute cardiac mitochondrial oxidative damage and increased activity of ATP-sensitive potassium channels in Wistar rats

Environmental Pollution, 2013

The environmental dioxin 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is classified as a Group 1 hu... more The environmental dioxin 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is classified as a Group 1 human carcinogen and teratogenic agent. We hypothesize that TCDD-induced oxidative stress may also interfere with mitochondrial ATP-sensitive potassium channels (mitoKATP), which are known to regulate and to be regulated by mitochondrial redox state. We investigated the effects of an acute treatment of male Wistar rats with TCDD (50 mg/kg i.p.) and measured the regulation of cardiac mitoKATP. While the function of cardiac mitochondria was slightly depressed, mitoKATP activity was 52% higher in animals treated with TCDD. The same effects were not observed in liver mitochondria isolated from the same animals. Our data also shows that regulation of mitochondrial ROS production by mitoKATP activity is different in both groups. To our knowledge, this is the first report to show that TCDD increases mitoKATP activity in the heart, which may counteract the increased oxidative stress caused by the dioxin during acute exposure.