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A J Moreno

Publications and source records attributed to A J Moreno.

At least 37 records · Page 2Linked to original sources
PubMed2000

Carvedilol inhibits the exogenous NADH dehydrogenase in rat heart mitochondria.

There are several reports on the oxidation of external NADH by an exogenous NADH dehydrogenase in the outer leaflet of the inner membrane of rat heart mitochondria. Until now, however, little was known about its physiological role in cellular metabolism. The present work shows that carvedilol (¿1-[carbazolyl-(4)-oxy]-3-[2-methoxyphenoxyethyl)amino]-pro - panol-(2)¿) is a specific inhibitor of an exogenous NADH dehydrogenase in rat heart mitochondria. Carvedilol does not affect oxygen consumption linked to the oxidation of succinate and internal NADH. It is also demonstrated that the inhibition of exogenous NADH dehydrogenase by carvedilol is accompanied by the inhibition of alkalinization of the external medium. In contrast to the addition of glutamate/malate or succinate, exogenous NADH does not generate a membrane potential in rat heart mitochondria, as observed with a TPP(+) electrode. It is also demonstrated that the oxygen consumption linked to NADH oxidation is not due to permeabilized mitochondria, but to actual oxidase activity in the inner membrane. The enzyme has a K(m) for NADH of 13 microM. Carvedilol is a noncompetitive inhibitor of this external NADH dehydrogenase with a K(i) of 15 microM. Carvedilol is the first inhibitor described to this organospecific enzyme. Since this enzyme was demonstrated to play a key role in the cardiotoxicity of anticancer drugs of the anthracycline family (e.g., adriamycin), we may suggest that the administration of carvedilol to tumor patients treated with adriamycin might be of great help in the prevention of the cardioselective toxicity of this antibiotic.

Animals↗
PubMed2000

Bile acids affect liver mitochondrial bioenergetics: possible relevance for cholestasis therapy.

It has been pointed out that intracellular accumulation of bile acids cause hepatocyte injury in cholestatic disease process. This study was aimed to test if cytotoxicity of these compounds is mediated through mitochondria dysfunction. Bile acids effects on isolated rat liver mitochondrial were analyzed by monitoring changes in membrane potential and mitochondrial respiration, as well as alterations in H(+) membrane permeability and mitochondrial permeability transition pore induction. Increasing concentrations of the bile acids litocholic (LCA), deoxycholic (DCA), ursodeoxycholic (UDCA), chenodeoxycholic (CDCA), glycochenodeoxycholic (GCDC), or taurochenodeoxycholic (TCDC) decrease transmembrane potential (delta psi) developed upon succinate energization. These compounds also decreased state 3 respiration and enhanced state 4. We have also demonstrated that the observed concentration-dependent stimulation of state 4 by LCA, DCA, CDCA, TCDC, and GCDC, is associated with an enhanced permeability of mitochondria to H(+). Addition of LCA, DCA, CDCA, TCDC, GCDC, and UDCA to mitochondria energized with succinate resulted in a dose-dependent membrane depolarization and stimulation of mitochondrial permeability transition. Tauroursodeoxycholate (TUDC) elicited no significant effect on succinate-supported mitochondrial bioenergetics. In contrast, in the presence of glycoursodeoxycholic (GUDC), delta psi increases as a function of bile salt concentration. The results of this investigation demonstrate that at toxicologically relevant concentrations, most but not all bile acids alter mitochondrial bioenergetics, so impairment of mitochondrial function can be clinically relevant for patients with cholestasis.

Adenosine Diphosphate↗
PubMed2000

Effects of carvedilol and its analog BM-910228 on mitochondrial function and oxidative stress.

The antioxidant effects of carvedilol and its analog BM-910228 (also known as SB 211475) were studied in rat liver mitochondria as well as their action on mitochondrial bioenergetics. Carvedilol and BM-910228 inhibited ADP/Fe(2+)-initiated lipid peroxidation (measured in mitochondrial membranes as thiobarbituric acid reactive substances and oxygen consumption) with IC(50) values of 10.9 and 0. 33 microM, respectively. Under the same conditions, the IC(50) value for Trolox C was 18.8 microM. At the same concentration range showing antioxidant activity both compounds prevent the collapse of transmembranar electric potential induced by ADP/Fe(2+) on respiring mitochondria. Furthermore, both carvedilol and BM-910228 do not display toxic effects on mitochondria up to the concentration showing maximal antioxidant effects ( approximately 40 microM for carvedilol and approximately 1 microM for BM-910228). At higher concentrations of carvedilol (>40 microM), however, the phosphorylation efficiency of mitochondria is depressed as deduced from a decrease in respiratory control and in the ADP/oxygen ratio. The Brand approach was used to assess the effects of carvedilol on oxidative phosphorylation. We found that carvedilol stimulated membrane proton leak and inhibited substrate oxidation, but had no measurable effect on phosphorylation reactions. Because carvedilol exerts its antioxidant properties for nontoxic concentrations, its therapeutic interest is reinforced because it may potentially prevent mitochondrial dysfunctions associated to cell death in several pathophysiological states where excessive production of reactive oxygen species by mitochondria is well documented (e.g., ischemia/reperfusion). Additionally, its hydroxylated analog BM-910228 with notable superior antioxidant activity may significantly contribute to the known therapeutic effects of carvedilol.

Adenosine Diphosphate↗
PubMed1998

Tamoxifen inhibits induction of the mitochondrial permeability transition by Ca2+ and inorganic phosphate.

Tamoxifen (TAM) is a synthetic, nonsteroidal antiestrogenic agent that is widely prescribed in the treatment of estrogen-dependent neoplasias, including breast cancer. The mechanism of action has yet to be defined, but likely is independent of estrogen receptor binding. In light of its high lipophilicity and peroxyl radical scavenging activities, we hypothesized that TAM might be an effective inhibitor of the mitochondrial permeability transition (MPT), which is widely implicated in the mechanisms of chemical-induced tissue injury and apoptosis. The MPT was induced in vitro by incubating freshly isolated rat liver mitochondria in 1 mM Pi with increasing concentrations of calcium. Induction of the MPT was characterized by the calcium-dependent depolarization of mitochondrial membrane potential, release of matrix calcium, and large amplitude swelling. Membrane potential and calcium release were measured with ion-selective electrodes; mitochondrial swelling was monitored spectrophotometrically. Preincubation with either cyclosporine A or TAM prevented, in a dose-dependent manner, the calcium-induced MPT. TAM also inhibited the calcium-induced release of matrix glutathione. TAM caused a time-dependent reversal of both the calcium-induced membrane depolarization and calcium release, suggesting that the effect was on the permeability transition pore and not due to inhibition of the mitochondrial calcium uniport. The results suggest that TAM mimics cyclosporine A to inhibit induction of the MPT and that this activity is not related to the antioxidant properties of TAM.

Animals↗
PubMed1998

Acrylic acid induces the glutathione-independent mitochondrial permeability transition in vitro.

Acrylic acid (AA) is used widely in the synthesis of esters essential in the production of paints, adhesives, plastics, and coatings. The minimal systemic toxicity of AA is attributed to its rapid oxidation to acetyl-CoA and CO2 via the vitamin B12-independent beta-oxidation pathway. This oxidation is localized to the mitochondria and preliminary evidence suggests a possible inhibition of mitochondrial metabolism by acrylic acid. The purpose of this investigation was to evaluate whether AA interferes with mitochondrial bioenergetics in vitro. Incubation of isolated rat liver mitochondrial with AA resulted in a dose-dependent induction of the mitochondrial permeability transition (MPT). This was evidenced by an increased sensitivity to calcium-induced stimulation of state 4 oxygen consumption, depolarization of membrane potential, and swelling, all of which were prevented by preincubating the mitochondrial with cyclosporine A, a potent and specific inhibitor of the mitochondrial permeability transition pore. Both N-ethylmaleimide (NEM) and dithiothreitol (DTT) showed only partial protection against induction of the MPT by AA. Associated with the induction of the MPT by AA was the loss of mitochondrial glutathione (GSH), which was due to efflux from the matrix rather than oxidation to GSSG. Cyclosporine A, by inhibiting the permeability transition, prevented the AA-induced loss of mitochondrial GSH. In conclusion, AA increases the sensitivity of isolated mitochondria in vitro to the calcium-dependent induction of the MPT. Although the molecular mechanism has yet to be defined, it does not appear to be related to the oxidation of critical thiols.

Acrylates↗
PubMed1998

The use of the mitochondrial transmembrane electric potential as an effective biosensor in ecotoxicological research.

In this work, the mitochondrial transmembrane electric potential (delta psi) of isolated mitochondria was used to evaluate the toxicity of some chemicals (endosulfan, 3,4-dichloroaniline, parathion, tributyltin and cadmium) and wastewater. Mitochondria were isolated from rat liver, and the delta psi measured in a suitable assay medium, using a sensitive tetraphenylphosphonium (TPP+) electrode. The test substance was pre-incubated in a rotenone-containing medium during 3 min with 1.0 mg of mitochondrial protein. Mitochondria were energised with succinate and after the establishment of a constant maximal potential ADP was added to induce the phosphorylative cycle. Chosen endpoints were the membrane potential from mitochondria oxidising succinate and the depolarisation induced by ADP. After the appropriate transformations the EC50 (effective concentration) was calculated for each toxicant. Even very low concentrations of a toxicant were able to affect the delta psi, thus showing its suitability as a biosensor in ecotoxicology and results were reproducible between tests. The utilisation of delta psi in screening tests of pure substances and wastewater seems to be very effective and can be carried out routinely.

Aniline Compounds↗
PubMed1998

Ischemic heart disease: the role of mitochondria--carvedilol prevents lipid peroxidation of mitochondrial membranes.

Depriving heart tissue of their blood supply leads to a decrease in high-energy compounds and many metabolic disturbances. Following short periods of ischemia, heart can recover their physiological functions after reperfusion, but prolonged ischemia injures heart irreversibly. Mitochondrial disfunction is one of the most critical events associated to injury irreversibility because regeneration of a high ATP level is indispensable for recovery of cellular functions. Reperfusion injury is also implicated in the irreversible damage of the ischemic heart. Even after a period of ischemia that is too short to injure the heart, reperfusion can cause further irreversible damage. The formation of oxygen radicals caused by reintroduction of O2 is probably the most important factor of this phenomenon. The mitochondrial redox chain is one of the main sources of O2 radicals responsible for causing damage to mitochondria, and thus mitochondria can be damaged during reperfusion. Most probably the opening of the mitochondrial permeability transition pore due to increased production of oxygen radicals is associated with the irreversible disruption of mitochondria for oxidative phosphorylation. Carvedilol, a potent antioxidant, prevents the lipoperoxidation of mitochondrial membranes what suggest a strong contribution to the known cardioprotective activity of this compound through protection of mitochondrial functions.

Animals↗
PubMed1997

Interactions of 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene with mitochondrial oxidative phosphorylation.

The effects of DDE (2,2-bis(p-chlorophenyl)-1,1-dichloroethylene), the major metabolite of DDT (2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane), on rat liver mitochondrial bioenergetic activities were examined. The approach developed by M. D. Brand (Biochim Biophys Acta 1018: 128-133, 1990) was used to assess the effects of DDE because it is possible to discriminate the sites of action of compounds having pleiotypic effects on oxidative phosphorylation. Data were further confirmed using a "classical" approach, including measurements of transmembrane potential, respiratory indexes, enzymatic activities and membrane permeability to protons. DDE up to 40 nmol/mg protein affected the proton motive force generating system. In fact, DDE interacted with succinate dehydrogenase (complex II), decreasing respiration and membrane potential. In this concentration range, the permeability of the inner membrane to protons remained intact. Only higher concentrations (> or = 80 nmol/mg) increased permeability to protons, uncoupling oxidation from phosphorylation. The phosphorylative system was not affected because the rate of ATP synthesis was unchanged. In addition, data from carbonyl cyanide m-chlorophenylhydrazone-uncoupled rotenone-inhibited preparations or submitochondrial particles indicated that F0F1 ATPase activity is not affected by DDE. Therefore, DDE inhibition of complex II and putative inhibition of succinate translocation explain the depression of mitochondrial respiration. The use of appropriate substrates and assay conditions indicates that complexes I, III and IV were not affected by DDE. The uncoupling of oxidative phosphorylation at high concentrations (> 80 nmol DDE/mg protein) was probably related to deleterious effects on the integrity of the mitochondrial membrane. We confirmed that the technique originally proposed by Brand is useful for characterizing the effects of xenobiotics on oxidative phosphorylation. In addition, data provided by this technique closely agree with data from classical studies.

Adenosine Triphosphate↗
PubMed1996

Continuous monitoring of mitochondrial membrane potential in hepatocyte cell suspensions.

We report a simple fluorometric method for the continuous monitoring of mitochondrial membrane potential and cell viability in suspensions of hepatocytes exposed in vitro to cytotoxic agents. Suspensions of freshly isolated hepatocytes (10(6) cells/mL) preloaded with rhodamine 123 (Rh 123, 100 mumol/L) are transferred to a thermostatically controlled mixed cuvette to which the desired cytotoxic agent is added. Rh 123 is a cationic fluorophore that is actively accumulated by cells in direct proportion to the mitochondrial membrane potential. Cell viability was estimated by monitoring propidium iodide (PI) fluorescence. Exposure of cell suspensions to the mitochondrial uncoupling agent FCCP caused an immediate and titratable increase in Rh 123 fluorescence. Subsequent treatment with digitonin did not change Rh 123 fluorescence, suggeseting that Rh 123 equilibrates rapidly across the intact cell membrane. Likewise, treatment of hepatocyte suspensions with inhibitors of mitochondrial respiration (rotenone, cyanide, or menadione) caused an immediate increase in Rh 123 fluorescence. This was accompanied by a progressive increase in PI fluorescence, suggesting a causal relationship between mitochondrial depolarization and cell injury. In contrast, 1,4-benzoquinone caused a time-dependent and linear increase in PI fluorescence that paralleled changes in Rh 123 fluorescence. Comparing the time courses for changes in PI and Rh 123 fluorescence suggests that for benzoquinone, the depolarization of the mitochondria is a consequence rather than a cause of the cell injury. This modified procedure provides a simple and specific technique for continuously monitoring mitochondrial membrane potential and cell viability in suspensions of freshly isolated hepatocytes. The advantage is that there is no need to separate cells from the incubation medium, making it possible to record real-time changes in mitochondrial membrane potential and cell viability throughout the in vitro exposure period.

Animals↗
PubMed1996

Renal oncocytoma: preoperative diagnosis using technetium 99m sestamibi imaging.

OBJECTIVES: To determine if 99mTc-sestamibi (technetium 99m-methoxyisobutylisonitrile) can be used preoperatively to differentiate renal oncocytomas from other renal masses. METHODS: We performed 99mTc-sestamibi scans on 6 patients with various renal masses, using a standard technique. The diagnosis in each patient was determined either by radiologic methods. RESULTS: There was significantly increased uptake in the patient with the renal oncocytoma, whereas the other lesions had decreased uptake in comparison to normal kidney. This was determined visually and by mean pixel analysis. CONCLUSIONS: Technetium 99m sestamibi scanning appears to have a potential role in the nonoperative diagnosis of renal oncocytomas, in combination with pathologic fine-needle biopsy confirmation. More definitive pathologic experience is required before recommending standard use.

Adenoma, Oxyphilic↗
PubMed1996

Relationships between ATP depletion, membrane potential, and the release of neurotransmitters in rat nerve terminals. An in vitro study under conditions that mimic anoxia, hypoglycemia, and ischemia.

BACKGROUND AND PURPOSE: It is known that the extracellular accumulation of glutamate during anoxia/ischemia is responsible for initiating neuronal injury. However, little information is available on the release of monoamines and whether the mechanism of its release resembles that of glutamate, which may itself influence the release of monoamines by activating presynaptic receptors. This study was designed to characterize the release of both amino acids and monoamines under chemical conditions that mimic anoxia, hypoglycemia, and ischemia. METHODS: The contents of synaptosomes in adenine nucleotides (ATP, ADP, and AMP), amino acids (aspartate, glutamate, taurine, and gamma-aminobutyric acid), and monoamines (dopamine, noradrenaline, and 5-hydroxytryptamine) were measured by high-performance liquid chromatography, after the synaptosomes were subjected to anoxia (KCN + oligomycin), hypoglycemia (2 mmol/L 2-deoxyglucose in glucose-free medium), and ischemia (anoxia plus hypoglycemia). RESULTS: The anoxia- and ischemia-induced release or noradrenaline, dopamine, 5-hydroxytryptamine, and glutamate correlated well with ATP depletion. The correlation observed between glutamate levels and the release of dopamine and 5-hydroxytryptamine in ischemic conditions suggests a functional linkage between the two transmitter systems. However, the antagonists of presynaptic glutamate receptors failed to alter the amount of monoamines released. The inhibition of Na+,K+-ATPase by ouabain had an effect similar to that produced by ischemia. CONCLUSIONS: The decrease in Na+ and K+ gradients resulting from the energy depletion of the synaptosomes under ischemic conditions or resulting from the inhibition of Na+, K+-ATPase by ouabain promotes the reversal of the neurotransmitter transporters. The decrease in uptake of neurotransmitters may also contribute to the rise in the extracellular concentration of different transmitters observed during brain ischemia.

Adenosine Diphosphate↗