RESUMEN
Betalains are natural pigments recently considered as compounds with potential antioxidative properties. In this work, ex vivo plasma spiking of pure either betanin or indicaxanthin, followed by isolation of low density lipoprotein (LDL), and measurement of its resistance to copper-induced oxidation, has been used to research if these betalains can bind to LDL and prevent oxidation of LDL lipids. When pooled human plasma from 10 healthy volunteers was incubated in the presence of 25-100 microM either betanin or indicaxanthin, incorporation of both compounds in LDL was observed, with a maximum binding of 0.52 +/- 0.08, and 0.51 +/- 0.06 nmoles of indicaxanthin and betanin, respectively, per mg LDL protein. Indicaxanthin-enriched and betanin-enriched LDL were more resistant than homologous native LDL to copper-induced oxidation, as assessed by the elongation of the induction period. The incorporated indicaxanthin, however, appeared twice as effective as betanin in increasing the length of the lag phase, while both compounds did not affect the propagation rate. Both betalains were consumed during the inhibition period of lipid oxidation, and delayed consumption of LDL-beta carotene. Indicaxanthin, but not betanin, prevented vitamin E consumption at the beginning of LDL oxidation, and prolonged the time of its utilization. The resistance of LDL to oxidation when vitamin E and indicaxanthin acted separately in a sequence, was lower than that measured when they were allowed to act in combination, indicating some synergistic interaction between the two molecules. No prooxidant effect over a large concentration range of either betanin or indicaxanthin was observed, when either betalain was added to the LDL system undergoing a copper-induced oxidation. These results show than indicaxanthin and betanin may bind to LDL, and are highly effective in preventing copper-induced lipid oxidation. Interaction with vitamin E appears to add a remarkable potential to indicaxanthin in the protection of LDL. Although molecular mechanisms remain uncompletely understood, various aspects of the action of betanin and indicaxanthin in preventing LDL lipid oxidation are discussed.
Asunto(s)
Lipoproteínas LDL/química , Oxígeno/metabolismo , Compuestos de Amonio Cuaternario/farmacología , Antioxidantes/química , Antioxidantes/farmacología , Betalaínas , Relación Dosis-Respuesta a Droga , Humanos , Peróxido de Hidrógeno/química , Modelos Químicos , Unión Proteica , Pyrus , Factores de TiempoRESUMEN
Melatonin has been shown to act as a radical scavenger in various chemical and biological model systems in vitro. Kinetic evidence is now provided showing that melatonin inhibits the irreversible degradation of hemoglobin (Hb), when incubated with red blood cells exposed to the oxidant activity of cumene hydroperoxide (cumOOH). A decrease of heme loss and accumulation of soluble methemoglobin (met-Hb) are explained in terms of the interaction of the indoleamine with perferryl Hb (Hb[Fe(IV)=O]), a highly reactive Hb-derived radical species responsible for the irreversible Hb degradation. A kinetic study, in pure chemical solution, showed that melatonin can effectively reduce the oxoferryl heme group of perferryl-Hb, thus forming met-Hb. The reducing activity of melatonin is of the same order as that of Trolox, the water-soluble vitamin E analog. This novel radical-scavenging activity of melatonin may contribute to the previously observed protective effects of melatonin in ischemia-reperfusion injury.
Asunto(s)
Eritrocitos/metabolismo , Hemoglobinas/química , Hemoglobinas/metabolismo , Melatonina/metabolismo , Animales , Antioxidantes/metabolismo , Bovinos , Depuradores de Radicales Libres/metabolismo , Radicales Libres/metabolismo , Humanos , Técnicas In Vitro , Melatonina/sangre , Metahemoglobina/metabolismo , Oxidación-Reducción , Desnaturalización ProteicaRESUMEN
Fifteen beta-thalassemia intermedia patients, not requiring chronic transfusional therapy, were monitored in order to check their antioxidant status, and the lipid oxidation products in plasma, LDL, and erythrocytes before and during a 9-month oral treatment with 600 mg/day vitamin E. The low level of vitamin E, and high level of malondialdehyde in plasma clearly tended to normalize after three months (P < .001), and were quite similar to control after six months. The abnormally low level of vitamin E in LDL and the four times higher than control basal level of conjugated dienes (LDL-CD), were not modified after three months of treatment. Significant changes of LDL-VE (P < .05) and of the basal LDL-CD (P < .001) were evident after six months. LDL-VE was within the normal range after nine months, whereas LDL-CD still appeared twice as higher than control. Plasma vitamin A, ascorbate, beta-carotene, and lycopene increased markedly at the end of the trial (P < .005). The level of vitamin E in red blood cells was normalized after six months of supplementation. A decrease of the baseline value of conjugated dienes was observed after nine months, although it remained 1.4-fold higher than control. The RBC count and hematocrit appeared higher at the end of the trial (P < .05 and P < .001, respectively). The hemoglobin value did not show variations. A shift to normal of the resistance of erythrocytes to osmotic lysis was observed. Our findings provide evidence that an oral treatment with vitamin E improves the antioxidant/oxidant balance in plasma, LDL particles, and red blood cells, and counteracts lipid peroxidation processes in beta-thalassemia intermedia patients.
Asunto(s)
Eritrocitos/metabolismo , Lipoproteínas LDL/metabolismo , Vitamina E/uso terapéutico , Talasemia beta/sangre , Talasemia beta/tratamiento farmacológico , Administración Oral , Adolescente , Adulto , Antioxidantes/metabolismo , Estudios de Casos y Controles , Niño , Eritrocitos/efectos de los fármacos , Femenino , Humanos , Lípidos/sangre , Lipoproteínas LDL/efectos de los fármacos , Masculino , Persona de Mediana Edad , Concentración Osmolar , Estrés Oxidativo/efectos de los fármacos , Valores de Referencia , Vitamina A/sangre , Vitamina E/sangre , beta Caroteno/sangreRESUMEN
Reaction of melatonin with the hypervalent iron centre of oxoferryl hemoglobin, produced in aqueous solution from methemoglobin and H2O2, has been investigated at 37 degrees C and pH 7.4, by absorption spectroscopy. The reaction results in reduction of the oxoferryl moiety with formation of a heme-ferric containing hemoprotein. Stopped-flow spectrophotometric measurements provide evidence that the reduction of oxoferryl-Hb by melatonin is first-order in oxoferryl-Hb and first-order in melatonin. The bimolecular reaction constant at pH 7.4 and 37 degrees C is 112 +/- 1.0 M(-1) s(-1). Two major oxidation products from melatonin have been found by gas chromatography-mass spectroscopy: the cyclic compound 1,2,3,3a,8,8a-hexahydro-1-acetyl-5-methoxy-3a-hydroxypyrrolo[2,3-b]indole (cyclic 3-hydroxy-melatonin), and N-acetyl-N'-formyl 5-methoxykynuramine (AFMK). The percentage yield of the two major products appears dependent on the ratio [oxoferryl-Hb]:[melatonin]--the higher the ratio the higher the yield of AFMK. The observed stoichiometry oxoferryl-Hb(reduced):melatonin(consumed) is 2, when the ratio [oxoferryl-Hb]:[melatonin] is 1:1, but appears >2 at higher molar ratios. The reduction of the hypervalent iron of the oxoferryl moiety may be consistent with an oxidation of melatonin by two one-electron steps.
Asunto(s)
Cloro/metabolismo , Hemoglobinas/metabolismo , Melatonina/metabolismo , Óxidos/metabolismo , Animales , Bovinos , Cromatografía de Gases y Espectrometría de Masas , Peróxido de Hidrógeno/metabolismo , Cinética , Kinuramina/análogos & derivados , Kinuramina/metabolismo , Espectroscopía de Resonancia Magnética , Metahemoglobina/metabolismo , Oxidación-Reducción , Espectrofotometría Ultravioleta , Factores de TiempoRESUMEN
Lipid peroxidation products, lipid antioxidants, and hematologic and blood chemistry changes were evaluated in plasma of patients after acute burning injury involving 10% (n=8), 20% (n=8), and 40% (n=5) of total body surface area (TBSA), 24 h after burning (baseline) up to 30 days after. Markedly increased plasma levels of malondialdehyde (MDA) were observed at baseline in all patients, according to the extent of the injury, then the values declined progressively. However, levels of MDA remained above normal up to 30 days even in less injured patients. On the other hand, the plasma level of conjugated diene lipid hydroperoxides was only slightly higher than control at the baseline, then dropped under the control value in all patients. Cholesterol showed a marked fall at baseline, followed by a rapidly progressive decrease, indicating a massive loss of circulating lipids by the acute thermal injury. Because of such an extensive and rapidly spreading oxidative degradation of lipids, decomposition of conjugated diene hydroperoxides, produced in early stages of the peroxidation process, occurs, so these compounds cannot be a suitable index to value lipid oxidation in burned patients. Aldehydic products of lipid peroxidation act as endotoxins, causing damage to various tissues and organs. Damage to liver and decrease of erythrocyte survival were assessed by increased plasma levels of asparate and alanine transaminases, within 7-15 days after injury, and by a decreased number of red blood cells, which remained under the normal value at 30 days. A marked decrease of lipid antioxidants, beta-carotene, vitamin A and vitamin E was observed at baseline. The level of beta-carotene remained low in all patients at the end of the 30-day observation. A complete recovery of vitamin A did not occur at 30 days post-burn, even in the patients with 10% of burned TBSA. Plasma levels of vitamin E decreased significantly in 1-7 days after burn in all patients, but these levels increased thereafter, with almost total recovery at 30 days. These data show evidence of a marked, long-lasting oxidant/antioxidant imbalance in burned patients, in accordance with the severity of the injury, which is also reflected as systemic oxidant stress.
Asunto(s)
Quemaduras/sangre , Peróxidos Lipídicos/sangre , Estrés Oxidativo , Adolescente , Adulto , Anciano , Alanina Transaminasa/sangre , Aspartato Aminotransferasas/sangre , Niño , Colesterol/sangre , Recuento de Eritrocitos , Eritrocitos/patología , Humanos , Peroxidación de Lípido , Hígado/patología , Malondialdehído/sangre , Persona de Mediana Edad , Factores de Tiempo , Vitamina A/sangre , Vitamina E/sangre , beta Caroteno/sangreRESUMEN
Antioxidant activity of melatonin in human erythrocytes, exposed to oxidative stress by cumene hydroperoxide (cumOOH), was investigated. CumOOH at 300 microM progressively oxidized a 1% suspension of red blood cells (RBCs), leading to 100% hemolysis in 180 min. Malondialdehyde and protein carbonyls in the membrane showed a progressive increase, as a result of the oxidative damage to membrane lipids and proteins, reaching peak values after 30 and 40 min, respectively. The membrane antioxidant vitamin E and the cytosolic reduced glutathione (GSH) were totally depleted in 20 min. As a consequence of the irreversible oxidative damage to hemoglobin (Hb), hemin accumulated into the RBC membrane during 40 min. Sodium dodecyl sulfate (SDS) gel electrophoresis of membrane proteins showed a progressive loss of the cytoskeleton proteins and formation of low molecular weight bands and protein aggregates, with an increment of the intensity of the Hb band. Melatonin at 50 microM strongly enhanced the RBC resistance to oxidative lysis, leading to a 100% hemolysis in 330 min. Melatonin had no effect on the membrane lipid peroxidation, nor prevented the consumption of glutathione (GSH) or vitamin E. However, it completely inhibited the formation of membrane protein carbonyls for 20 min and hemin precipitation for 10 min. The electrophoretic pattern provided further evidence that melatonin delayed modifications to the membrane proteins and to Hb. In addition, RBCs incubated for 15 min with 300 microM cumOOH in the presence of 50 microM melatonin were less susceptible, when submitted to osmotic lysis, than cells incubated in its absence. Extraction and high-performance liquid chromatography (HPLC) analysis showed a much more rapid consumption of melatonin during the first 10 min of incubation, then melatonin slowly decreased up to 30 min and remained stable thereafter. Equilibrium partition experiments showed that 15% of the melatonin in the incubation mixture was recovered in the RBC cytosol, and no melatonin was extracted from RBC membrane. However, 35% of the added melatonin was consumed during RBC oxidation. Hydroxyl radical trapping agents, such as dimethylsulfoxide or mannitol, added into the assay in a 1,000 times molar excess, did not vary melatonin consumption, suggesting that hydroxyl radicals were not involved in the indole consumption. Our results indicate that melatonin is actively taken up into erythrocytes under oxidative stress, and is consumed in the defence of the cell, delaying Hb denaturation and release of hemin. RBCs are highly exposed to oxygen and can be a site for radical formation, under pathological conditions, which results in their destruction. A protective role of melatonin should be explored in hemolytic diseases.
Asunto(s)
Eritrocitos/efectos de los fármacos , Depuradores de Radicales Libres/farmacología , Hemólisis/efectos de los fármacos , Melatonina/farmacología , Derivados del Benceno/toxicidad , Dimetilsulfóxido/farmacología , Membrana Eritrocítica/efectos de los fármacos , Membrana Eritrocítica/metabolismo , Eritrocitos/metabolismo , Depuradores de Radicales Libres/metabolismo , Glutatión/sangre , Hemina/metabolismo , Humanos , Radical Hidroxilo/metabolismo , Técnicas In Vitro , Peroxidación de Lípido/efectos de los fármacos , Manitol/farmacología , Melatonina/metabolismo , Fragilidad Osmótica/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacosRESUMEN
Melatonin is now known to be a multifaceted free radical scavenger and antioxidant. It detoxifies a variety of free radicals and reactive oxygen intermediates including the hydroxyl radical, peroxynitrite anion, singlet oxygen and nitric oxide. Additionally, it reportedly stimulates several antioxidative enzymes including glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and superoxide dismutase; conversely, it inhibits a prooxidative enzyme, nitric oxide synthase. Melatonin also crosses all morphophysiological barriers, e.g., the blood-brain barrier, placenta, and distributes throughout the cell; these features increase the efficacy of melatonin as an antioxidant. Melatonin has been shown to markedly protect both membrane lipids and nuclear DNA from oxidative damage. In every experimental model in which melatonin has been tested, it has been found to resist macromolecular damage and the associated dysfunction associated with free radicals.
Asunto(s)
Antioxidantes/metabolismo , Melatonina/metabolismo , Oxidantes/metabolismo , Animales , Depuradores de Radicales Libres/metabolismo , Radicales Libres/metabolismo , Humanos , Melatonina/farmacología , Glándula Pineal/metabolismo , Especies Reactivas de Oxígeno/metabolismoRESUMEN
Several tryptophan derivatives function as free radical scavengers and antioxidants. The molecule that has been most widely investigated in this regard is N-acetyl-5-methoxytryptamine (melatonin); however, pinoline (6-methoxy-1,2,3,4-tetrahydro-beta-carboline) and N-acetylserotonin also possess free radical scavenging activity. Experimental studies have shown that melatonin directly scavenges the hydroxy radical, peroxyl radical, peroxynitrite anion, and singlet oxygen. Furthermore, this tryptophan derivative stimulates a number of antioxidative enzymes and stabilizes cell membranes; this latter action helps membranes to resist free radical damage. While the antioxidative actions of most molecules are limited by their specific intracellular distribution, e.g., vitamin E in lipid-rich membranes, melatonin's antioxidative actions include the protection of lipids in the cell membrane, proteins in the cytosol, and DNA in the nucleus. Furthermore, melatonin crosses all morphophysiological barriers and enters equally well all cells in the organism.
Asunto(s)
Antioxidantes/farmacología , Depuradores de Radicales Libres/farmacología , Melatonina/análogos & derivados , Melatonina/fisiología , Triptófano/análogos & derivados , Triptófano/fisiología , Animales , Membrana Celular/efectos de los fármacos , Membrana Celular/fisiología , Radicales Libres/metabolismo , Humanos , Melatonina/farmacología , Oxígeno/metabolismo , Triptófano/farmacologíaRESUMEN
We investigated the oxidative state of low-density lipoprotein (LDL) in patients with beta-thalassemia to determine whether there was an association with atherogenesis. Conjugated diene lipid hydroperoxides (CD) and the level of major lipid antioxidants in LDL, as well as modified LDL protein, were evaluated in 35 beta-thalassemia intermedia patients, aged 10 to 60, and compared with age-matched healthy controls. Vitamin E and beta-carotene levels in LDL from patients were 45% and 24% of that observed in healthy controls, respectively. In contrast, the mean amount of LDL-CD was threefold higher and lysil residues of apo B-100 were decreased by 17%. LDL-CD in thalassemia patients showed a strong inverse correlation with LDL vitamin E (r = -0.784; P <.0001), while a negative trend was observed with LDL-beta-carotene (r = -0.443; P =.149). In the plasma of thalassemia patients, malondialdehyde (MDA), a byproduct of lipid peroxidation, was increased by about twofold, while vitamin E showed a 52% decrease versus healthy controls. LDL-CD were inversely correlated with plasma vitamin E (r = -0.659; P <.0001) and correlated positively with plasma MDA (r = 0.621; P <. 0001). Plasma ferritin was positively correlated with LDL-CD (r = 0.583; P =.0002). No correlation was found between the age of the patients and plasma MDA or LDL-CD. The LDL from thalassemia patients was cytotoxic to cultured human fibroblasts and cytotoxicity increased with the content of lipid peroxidation products. Clinical evidence of mild to severe vascular complications in nine of the patients was then matched with levels of LDL-CD, which were 36% to 118% higher than the mean levels of the patients. Our results could account for the incidence of atherogenic vascular diseases often reported in beta-thalassemia patients. We suggest that the level of plasma MDA in beta-thalassemia patients may represent a sensitive index of the oxidative status of LDL in vivo and of its potential atherogenicity.
Asunto(s)
Arteriosclerosis/epidemiología , Lipoproteínas LDL/química , Talasemia beta/metabolismo , Adolescente , Adulto , Apolipoproteína B-100 , Apolipoproteínas B/sangre , Arteriosclerosis/etiología , Arteriosclerosis/prevención & control , Células Cultivadas , Niño , Susceptibilidad a Enfermedades , Ferritinas/sangre , Fibroblastos/efectos de los fármacos , Humanos , Hipertensión Pulmonar/etiología , Incidencia , Peroxidación de Lípido , Lipoproteínas LDL/sangre , Lipoproteínas LDL/toxicidad , Malondialdehído/sangre , Persona de Mediana Edad , Oxidación-Reducción , Estrés Oxidativo , Riesgo , Tretinoina/sangre , Vitamina E/sangre , Talasemia beta/complicacionesRESUMEN
The alteration of the oxidant/antioxidant balance may affect the susceptibility of low density lipoproteins (LDL) to oxidation in haemolytic disorders such as thalassemia. Thirty patients affected by beta-thalassemia intermedia were examined, and compared with age-matched healthy controls. The mean amount of vitamin E in the thalassemic LDL was lower than control (p < 0.0001), either when it was calculated on the base of LDL protein (61% decrease) or cholesterol (25% decrease). The LDL resistance to Cu2+-induced oxidation, evaluated as the length of the lag phase before the onset of conjugated diene (CD) lipid hydroperoxide production, was 20% lower than control. Other parameters of LDL susceptibility to oxidation, such as the rate of lipid peroxidation, Rp, and the total amount of conjugated dienes produced, CDmax, were only slightly lower than control, which can be explained by a lower content of peroxidable lipids in the thalassemic LDL. Total LDL cholesterol was 1.08 x 10(3) and 2.07 x 10(3) mol/mol LDL in thalassemic and in control LDL, respectively. The length of the lag phase in thalassemic LDL shows a strongly positive correlation with its vitamin E content (r = 0.732; p < 0.0001). The r2-value of 0.53 provides evidence that more than 50% of the lag phase is determined by vitamin E. Oxidizability of LDL lipids may explain 22-24% of the lag phase, as calculated by the inverse correlation between the length of the lag phase and CDmax (r = -0.474; p = 0.008; r2 = 0.22) and Rp (r = -0.499; p = 0.005; r2 = 0.24). In multiple regression analysis, the lag phase was predictable to 66% by vitamin E plus CDmax, and to 60% by vitamin E plus Rp. Plasma vitamin E was 53% lower in thalassemia patients compared to control and positively correlated with vitamin E in the LDL (r = 0.677; p < 0.0001). None of the correlations above were observed in control subjects. In conclusion, beta-thalassemia is associated with very low levels of vitamin E in plasma and in LDL, a condition that renders these particles more susceptible to in vitro oxidative modification and may account for atherogenesis-related vascular diseases described in thalassemia. The present data on a statistically significant correlation between abnormally low vitamin E and oxidizability of LDL contribute substantially to the hypothesis that vitamin E is a pathophysiologically important determinant of antioxidative protection of LDL.
Asunto(s)
Peroxidación de Lípido/fisiología , Lipoproteínas LDL/sangre , Vitamina E/sangre , Talasemia beta/sangre , Adulto , Colesterol/sangre , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Oxidación-Reducción , Estrés Oxidativo , Análisis de RegresiónRESUMEN
Lipoperoxyl radical-scavenging activity of retinol in unilamellar soybean phosphatidylcholine liposomes was studied under a variety of conditions to appreciate to what extend retinol may be considered an effective antioxidant. Peroxidation, initiated by 2 mM 2,2'-azobis(amidino-propane)hydrochloride (AAPH), was carried out at 160 torr O2 or at 15 torr O2, in the absence or in the presence of 10 to 40 mM retinol. As evaluated by the length of the inhibition periods, t(inh), and by the ratio between the inhibition and propagation rate, R(inh)/R(p), the antioxidant activity of retinol was higher at 15 torr O2 than at 160 torr O2. The consumption rate of retinol was markedly faster at 160 torr O2 than at 15 torr O2 and increased with the increase of retinol concentration under both oxygen tensions. When liposome peroxidation was carried out under N2, retinol consumption was independent of retinol concentration. Peroxyl radicals oxidize retinol to 5,6-retinol epoxide. The ratio between 5,6-epoxide formed and the retinol consumed was markedly higher at 15 torr O2 than under air and decreased with the increased retinol concentrations. When butylated hydroxytoluene was included into the liposomal suspension, most of the consumed retinol was converted into 5,6-epoxide. Liposomes were incubated at 15 torr O2, in the presence of 0.5 to 10 mM AAPH. The antioxidant effectiveness of 40 mM retinol, as measured by the R(inh)/R(p) ratio, increased with the increase of the radical fluxes. The results suggest, besides radical trapping, that a major consumption of retinol during lipid oxidation occurs through self-oxidation reactions, which are concentration- and oxygen-dependent. A decreased self-oxidation makes retinol a better lipoperoxyl radical scavenger at low, rather than at high partial pressure of oxygen. However, when self-oxidation of retinol is prevented, only a minor fraction of the antioxidant is allowed to effectively act as a radical scavenger, suggesting that the radical-trapping reactions are rate-limiting for the antioxidant process. Peroxyl radical concentration, by shifting the route of the retinol activity toward radical scavenging, brings about an increasingly more efficient radical trapping. It is concluded that all-trans retinol behaves as a more effective antioxidant at low oxygen partial pressure, low retinol concentrations, and high radical flux.
Asunto(s)
Antioxidantes/química , Membrana Dobles de Lípidos , Oxígeno/química , Fosfolípidos/química , Retinaldehído/química , Carbono/química , Diterpenos , Depuradores de Radicales Libres , Radicales Libres , Liposomas , Vitamina A/análogos & derivados , Vitamina A/síntesis químicaRESUMEN
Melatonin, at 5 to 500 microM was incorporated in unilamellar soybean phosphatidylcholine (PC) liposomes, the peroxidation of which was induced by 2,2'-azobis (2-amidinopropane-hydrochloride) (AAPH), and measured as production of conjugated diene lipid hydroperoxides. Concentration as low as 5 and 10 microM were poorly effective in reducing lipid peroxidation. Melatonin at 30 to 500 microM caused short inhibition periods, increasing with, but not linearly related to concentration, with a concurrent net decrease of the propagation rate. The time course of melatonin oxidation, measured as loss of fluorescence, was studied during the AAPH-stimulated peroxidation of soybean PC liposomes, or when melatonin was incorporated in nonperoxidable unilamellar dimirystoyl phosphatidylcholine (DMC) liposomes. Consumption kinetics of 30 microM melatonin were linear with time in DMC liposomes and disappearance of melatonin occurred at a rate of 0.058 M(-8) s(-1). On the other hand, the consumption of melatonin during the oxidation of soybean PC liposomes, was not linear with time. The rate of disappearance was calculated as 0.19 M(-8) s(-1) at the beginning of the propagation phase, then it slowed down to reach the same rate observed in DMC liposomes. This evidence suggests a reaction with lipid-derived peroxyl radicals, possibly in addition to reaction with peroxyl radicals derived from AAPH. Scavenging of lipoperoxyl radicals by melatonin was also evident in experiments where melatonin was incorporated in multilamellar soybean PC liposomes and peroxidation was initiated by 2,2 '-azobis (2,4-dimethyl-valeronitrile). The antioxidant activity of melatonin in soybean PC liposomes is much lower than that of alpha-tocopherol, under comparable assay conditions. However, a combination of melatonin and alpha-tocopherol, at 5 microM, resulted in a synergistic antioxidant effect. Time course of alpha-tocopherol consumption, monitored in the absence and in the presence of melatonin, showed a significant decrease of the consumption rate when compounds were combined, indicating some protection by melatonin. Regeneration mechanisms were not evident and depletion of alpha-tocopherol was coincident with the inhibition time.
Asunto(s)
Depuradores de Radicales Libres/metabolismo , Membrana Dobles de Lípidos/metabolismo , Peroxidación de Lípido , Peróxidos Lipídicos/metabolismo , Melatonina/metabolismo , Fosfatidilcolinas/metabolismo , Sinergismo Farmacológico , Radicales Libres/metabolismo , Cinética , Oxidación-Reducción , Vitamina E/metabolismoRESUMEN
Because of continuous blood transfusions, thalassemia patients are subjected to peroxidative tissue injury by the secondary iron overload. In accordance, analysis of serum from 42 beta-thalassemia patients, aged 4 to 40 years, showed that the mean concentrations of conjugated diene lipid hydroperoxides (CD), lipoperoxides evaluated as malondialdehyde/ thiobarbituric acid (MDA/TBA) adducts, and protein carbonyls increased about twofold with respect to control. Ferritin levels were positively correlated with the amount of MDA (r = .41; P = .007) and showed a positive trend with CD (r = .31; P = .07) and protein carbonyls (r = .35; P = .054), as further evidence of the deleterious effects of high tissue iron levels. Marked changes in the antioxidant pattern were also observed in all patients. Evidence is presented of a net drop in the concentration of ascorbate (-44%), vitamin E (-42%), vitamin A(-44%), beta-carotene (-29%), and lycopene (-67%). On the other hand, an increase of uric acid and bilirubin was observed, whereas serum albumin and glutathione were in the normal range in all patients. As a result, the total serum antioxidant potential, measured as trolox equivalent antioxidant capacity appeared significantly decreased by 14%. Serum levels of vitamin E were inversely correlated with ferritin (r = -.45; P = .003), suggesting a major consumption of this antioxidant under iron overload. Nontransferrin bound iron (NTBI) was in the range 4.5 to 54.8 micrograms/dL (mean, 21.8 +/- 13.9). Although NTBI had a positive trend with ferritin (r = .37, P = .03), no clear correlation was found with either MDA or vitamin E. A mild to severe hepatic damage, as assessed by serum transaminases, was shown in 24 of 42 patients. Serum levels of vitamin E (r = -.49, P = .015), vitamin A (r = -.48, P = .016) and lycopene (r = -.47, P = .020), were inversely correlated with the levels of transminases. On the other hand, lipid-soluble antioxidants in thalassemia patients were depleted to the same extent in hepatitis C virus (HCV)-infected (31 subjects) and in HCV-uninfected (10 subjects), while in the normal range in serum from 30 nonthalassemic patients with HCV-related chronic hepatitis. These results point out that the iron-induced liver damage in thalassemia may play a major role in the depletion of lipid-soluble antioxidants. The variations of the parameters evaluated in the present study were not correlated with the age of the patients. Our results suggest that the measurement of peroxidation products, matched with evaluation of antioxidants, may be a simple measure of iron toxicity in thalessemia, in addition to the conventional indices of iron status.
Asunto(s)
Antioxidantes/metabolismo , Hemosiderosis/sangre , Talasemia beta/sangre , Adolescente , Adulto , Niño , Preescolar , Femenino , Hemosiderosis/etiología , Humanos , Hígado/metabolismo , Hígado/patología , Masculino , Estrés Oxidativo , Reacción a la Transfusión , Talasemia beta/patología , Talasemia beta/terapiaRESUMEN
Interactions between alpha-tocopherol and all-trans retinol in suppressing lipid peroxidation were studied in a unilamellar liposomal system of phosphatidylcholine from either egg or soybean, in which peroxidation was initiated by the water-soluble azo initiator 2,2-azobis(2-amidino-propane)hydrochloride and peroxidation was measured as production of conjugated diene hydroperoxides. While all-trans retinol alone was poorly effective, the combination of all-trans retinol with alpha-tocopherol caused an inhibition period far beyond the sum of the inhibition periods observed with individual antioxidants, providing evidence of synergistic interactions. Furthermore, the inhibition rate calculated in the presence of both all-trans retinol and alpha-tocopherol, Rinh(E+A), was lower than Rinh(E) observed with alpha-tocopherol alone, suggesting that the extension of the inhibition time cannot be ascribed only to the antioxidant activity of alpha-tocopherol. The extent of synergism was linear with a molar ratio all-trans retinol/alpha-tocopherol ranging from 0.1 to 1.0, whereas a drop was observed at a ratio of 2.0. Synergistic antioxidant interactions between all-trans retinol and alpha-tocopherol were also evident when peroxidation was evaluated as production of malondialdehyde. A time course study, in which peroxidation of liposomes and depletion of antioxidants were concomitantly monitored, while showing that most of alpha-tocopherol was consumed to bring about the inhibition period, indicated that autooxidative reactions substantially contributed to the rapid depletion of all-trans retinol, when the antioxidants were allowed to act separately. On the other hand, when alpha-tocopherol and all-trans retinol were combined, the consumption of both antioxidants was significantly delayed, indicating reciprocal protection. Regeneration mechanisms cannot be accounted for by our results. The observed synergism between all-trans retinol and alpha-tocopherol does not appear as the result of specific structural interactions in the lipid bilayer. Combination of all-trans retinol with butylated hydroxytoluene, which reduced markedly all-trans retinol oxidation, resulted in a synergistic antioxidant activity greater than that observed with comparable amounts of alpha-tocopherol. In light of the known antioxidant mechanism of retinoids, the data suggest that by limiting autooxidation of all-trans retinol, alpha-tocopherol strongly promotes its antioxidant effectiveness. The concerted radical scavenging action in turn results in a synergistic protection of the lipid system against peroxidative stress and, ultimately, slows down the alpha-tocopherol consumption.
Asunto(s)
Peroxidación de Lípido , Liposomas , Vitamina A/metabolismo , Vitamina E/metabolismo , Sinergismo Farmacológico , Fosfatidilcolinas , Vitamina A/química , Vitamina E/químicaRESUMEN
During this decade, diagnosis and treatment of coronary heart disease (CHD) have become far more aggressive and invasive than in prior decades. This study documents rates of hospitalization, use of various treatment options, a case fatality in the state of Massachusetts during 4 of the first 5 years of this decade (1980, 1982, 1983, and 1984). The data base was that of the Massachusetts Health Data Consortium (MHDC), covering all hospital discharges in the state, a total of 3.8 million discharge records for this period. Of these, about 190,000 (5%) fell into two active symptomatic categories of CHD: chronic active coronary disease (CACD) and acute myocardial infarction (AMI). Total hospitalization rate for these CHD categories increased by 17%; this was due both to an increased rate of hospital transfers (or readmissions) and to a larger cohort of patients under care. The case fatality rate for hospitalized CHD decreased approximately 16%, from 9.7% (1980) to 8.1% (1984). In CACD the frequency of coronary angiography (CA) rose; the use of percutaneous transluminal coronary angioplasty (PTCA) increased much faster than the rate of coronary artery bypass grafting (CABG), with a resultant increase in PTCA as a fraction of total interventions. Similar findings were recorded for AMI, but with much more marked changes, the total intervention rate increasing almost twenty-fold from 1980 to 1984. The statewide mortality rate for hospitalized CHD patients remained essentially unchanged at 71 to 74 hospital deaths per 100,000 population.
Asunto(s)
Enfermedad Coronaria/mortalidad , Angiografía/estadística & datos numéricos , Angioplastia Coronaria con Balón/estadística & datos numéricos , Angiografía Coronaria , Puente de Arteria Coronaria/estadística & datos numéricos , Enfermedad Coronaria/terapia , Hospitalización , Humanos , Massachusetts/epidemiología , Infarto del Miocardio/mortalidad , Infarto del Miocardio/terapiaRESUMEN
This article presents an analysis of over 140,000 selected surgical procedures performed in Massachusetts in 1980, giving the per capita rates of 14 common procedures and of four less frequently performed procedures. The analysis defines 172 geographic areas for the commonly performed procedures and 45 for the less frequently performed procedures. Per capita surgical rates among the defined areas are significantly different from both a statistical and a clinical point of view. Twofold and threefold variations occur frequently across geographic areas. In certain areas, some surgical services appear to be provided at rates substantially different from the statewide rate. We discuss the importance of these data for physicians as well as the implications for the distribution and quality of clinical care and for containment of medical care costs.
Asunto(s)
Procedimientos Quirúrgicos Operativos/estadística & datos numéricos , Costos y Análisis de Costo , Tiempo de Internación , Massachusetts , Revisión de Utilización de Recursos/métodosRESUMEN
The effect of the Massachusetts second-opinion program on the volume of elective surgery in the Medicaid population was assessed using two approaches: a study of the program experience and surgery decisions of 2,501 program referrals, and an analysis of Medicaid surgery rates before and after program implementation. Nonconfirmation rates, which averaged 14.5 per cent, varied by procedure from 4 per cent for cholecystectomy to 26 per cent for disc surgery. The patient's surgery decision was related to the outcome of the second-opinion consultation: 85.5 per cent of the confirmed patients had the originally proposed operation, as compared with 31 per cent of the nonconfirmed patients. In the year after program implementation, the program was associated with a 20 per cent reduction in the volume of those procedures covered by the program. The greatest percentage declines were for hysterectomies, meniscectomies, hemorrhoidectomies and tonsillectomies/adenoidectomies. The decline in surgery rates was attributed both to a direct effect on patients referred to the program and to a sentinel effect whereby fewer operations were proposed. We conclude that the mandatory second-opinion program in Massachusetts saved Medicaid $3 to $4 for every dollar spent.