RESUMEN
Patients with chronic obstructive pulmonary disease (COPD) show abnormal adaptations of skeletal muscle redox status after exercise training. Increased skeletal muscle oxidative stress in COPD patients may prompt mitochondrial dysfunction. The present study explores the association between body composition and mitochondrial respiration in seven COPD patients with low body mass index (BMI(L)), eight COPD patients with normal body mass index (BMI(N)) and seven healthy controls. All of them underwent a vastus lateralis biopsy in which muscle structure, in vitro mitochondrial respiratory function, uncoupling protein 3 (UCP3) mRNA expression and glutathione levels in both isolated mitochondria and the whole muscle were determined. Mitochondrial respiratory function (assessed by acceptor control ratio (ACR)) was impaired in BMI(L) (2.2+/-0.6) compared with both BMI(N) (5.3+/-1.3) and controls (8.2+/-1.3). ACR significantly correlated with arterial oxygen tension and with muscle endurance but it showed a negative association with exercise-induced increase in blood lactate levels. UCP3 mRNA expression was reduced in BMI(L) patients. In conclusion, chronic obstructive pulmonary disease patients with low body mass index show electron transport chain dysfunction, which may contribute to low muscle endurance in the current subgroup of patients.
Asunto(s)
Mitocondrias Musculares/patología , Enfermedad Pulmonar Obstructiva Crónica/metabolismo , Anciano , Biopsia , Composición Corporal , Índice de Masa Corporal , Ejercicio Físico , Glutatión/metabolismo , Humanos , Masculino , Persona de Mediana Edad , Oxidación-Reducción , Resistencia Física , Enfermedad Pulmonar Obstructiva Crónica/patología , Músculo Cuádriceps/patología , ARN Mensajero/metabolismoRESUMEN
Post-training downregulation of muscle tumour necrosis factor (TNF)-alpha messenger ribonucleic acid (mRNA) expression and decrease in cellular TNF-alpha levels have been reported in the elderly. It is hypothesised that chronic obstructive pulmonary disease (COPD) patients may not show these adaptations due to their reduced ability to increase muscle antioxidant capacity with training. Eleven COPD patients (forced expiratory volume in one second 40 +/- 4.4% of the predicted value) and six age-matched controls were studied. Pre- and post-training levels of TNF-alpha, soluble TNF receptors (sTNFRs: sTNFR55 and sTNFR75) and interleukin (IL)-6 in plasma at rest and during exercise and vastus lateralis TNF-alpha mRNA were examined. Moderate-intensity constant-work-rate exercise (11 min at 40% of pretraining peak work-rate) increased pretraining plasma TNF-alpha levels in COPD patients (from 17 +/- 3.2 to 23 +/- 2.7 pg x mL(-1); p<0.005) but not in controls (from 19 +/- 4.6 to 19 +/- 3.2 pg x mL(-1)). No changes were observed in sTNFRs or IL-6 levels. After 8 weeks' endurance training, moderate-intensity exercise increased plasma TNF-alpha levels similarly to pretraining (from 16 +/- 3 to 21 +/- 4 pg x mL(-1); p<0.01). Pretraining muscle TNF-alpha mRNA expression was significantly higher in COPD patients than in controls (29.3 +/- 13.9 versus 5.0 +/- 1.5 TNF-alpha/18S ribonucleic acid, respectively), but no changes were observed after exercise or training. It is concluded that moderate-intensity exercise abnormally increases plasma tumour necrosis factor-alpha levels in chronic obstructive pulmonary disease patients without exercise-induced upregulation of the tumour necrosis factor-alpha gene in skeletal muscle.
Asunto(s)
Ejercicio Físico/fisiología , Enfermedad Pulmonar Obstructiva Crónica/metabolismo , Factor de Necrosis Tumoral alfa/metabolismo , Anciano , Expresión Génica , Humanos , Interleucina-6/sangre , Masculino , Persona de Mediana Edad , Músculo Esquelético/metabolismo , Enfermedad Pulmonar Obstructiva Crónica/sangre , ARN Mensajero , Receptores del Factor de Necrosis Tumoral/sangre , Factor de Necrosis Tumoral alfa/genéticaRESUMEN
The present study was undertaken to test whether endurance training in patients with COPD, along with enhancement of muscle bioenergetics, decreases muscle redox capacity as a result of recurrent episodes of cell hypoxia induced by high intensity exercise sessions. Seventeen patients with COPD (FEV(1), 38 +/- 4% pred; PaO2), 69 +/- 2.7 mm Hg; PaCO2, 42 +/- 1.7 mm Hg) and five age-matched control subjects (C) were studied pretraining and post-training. Reduced (GSH) and oxidized (GSSG) glutathione, lipid peroxidation, and gamma-glutamyl cysteine synthase heavy subunit chain mRNA expression (gammaGCS-HS mRNA) were measured in the vastus lateralis. Pretraining redox status at rest and after moderate (40% Wpeak) constant-work rate exercise were similar between groups. After training (DeltaWpeak, 27 +/- 7% and 37 +/- 18%, COPD and C, respectively) (p < 0.05 each), GSSG levels increased only in patients with COPD (from 0.7 +/- 0.08 to 1.0 +/- 0.15 nmol/ mg protein, p < 0.05) with maintenance of GSH levels, whereas GSH markedly increased in C (from 4.6 +/- 1.03 to 8.7 +/- 0.41 nmol/ mg protein, p < 0.01). Post-training gammaGCS-HS mRNA levels increased after submaximal exercise in patients with COPD. No evidence of lipid peroxidation was observed. We conclude that although endurance training increased muscle redox potential in healthy subjects, patients with COPD showed a reduced ability to adapt to endurance training reflected in lower capacity to synthesize GSH.
Asunto(s)
Ejercicio Físico/fisiología , Músculo Esquelético/metabolismo , Resistencia Física , Enfermedad Pulmonar Obstructiva Crónica/metabolismo , Enfermedad Pulmonar Obstructiva Crónica/fisiopatología , Anciano , Glutamato-Cisteína Ligasa/genética , Disulfuro de Glutatión/análisis , Disulfuro de Glutatión/metabolismo , Humanos , Peroxidación de Lípido , Masculino , Persona de Mediana Edad , Músculo Esquelético/química , Oxidación-Reducción , ARN Mensajero/análisis , ARN Mensajero/biosíntesisRESUMEN
Ceramide has been identified as a putative lipid messenger that mediates diverse cellular processes including cell death. Since glutathione (GSH) depletion is known to sensitize cells to many cytotoxic agents and as a result of the reported regulation of neutral sphyngomyelinase (NSMase) by GSH, the present study compared the role of individual SMases in the induction of oxidative stress, regulation of cellular GSH, and apoptosis of rat hepatocytes. Exposure of cultured rat hepatocytes to exogenous Bacillus cereus sphingomyelinase (bSMase), a neutral SMase, or human placenta sphingomyelinase (hSMase), an acidic SMase (ASMase), generated similar ceramide levels in a dose-dependent manner. However, whereas bSMase increased hepatocellular GSH levels, hSMase depleted GSH stores, an effect that was prevented by monensin and mannose 6-phosphate (M-6-P), suggesting that exogenous hSMase enters hepatocytes by endocytosis and is delivered to an endosomal/lysosomal acidic compartment. Interestingly, despite the differential effect of either SMases on cell GSH levels, both bSMase and hSMase increased gamma-glutamylcysteine synthetase heavy-subunit chain (gamma-GCS-HS) mRNA levels. Consistent with these findings on GSH regulation, hSMase, but not bSMase, generated reactive oxygen species (ROS), being accompanied by mitochondrial depolarization, suggesting that hSMase targeted mitochondria, leading to oxidative stress. Accordingly, hepatocytes displayed a selective sensitivity to hSMase in contrast to bSMase exposure, and depletion of GSH stores enhanced susceptibility to hSMase as a result of potentiation of ROS formation and caspase 3 activation. Thus, these findings reveal the ability of ASMase to induce oxidative stress as a result of the targeting of mitochondria, and that GSH depletion sensitizes hepatocytes to the ASMase-induced apoptosis.
Asunto(s)
Apoptosis/efectos de los fármacos , Glutatión/metabolismo , Hígado/metabolismo , Estrés Oxidativo/efectos de los fármacos , Placenta/enzimología , Esfingomielina Fosfodiesterasa/farmacología , Animales , Células Cultivadas , Ceramidas/análisis , Glutamato-Cisteína Ligasa/metabolismo , Humanos , Hígado/citología , Magnesio/farmacología , Ratas , Especies Reactivas de Oxígeno/metabolismoRESUMEN
Because reactive oxygen species (ROS) have been implicated as mediators of inflammatory bowel disease (IBD), the purpose of the present work was to determine the functional role of mucosal GSH in the trinitrobenzenesulfonic acid in 50% ethanol (TNBS+ethanol)-induced colitis in rats. Mucosal samples were taken to evaluate the temporal relationship between the extent of injury, the levels of glutathione (GSH) during acute colitis induced by TNBS+ethanol, and the effect of N-acetylcysteine (NAC) administration. In vitro assays revealed the interaction of TNBS with GSH leading to the almost instantaneous disappearance of GSH, while the reductive metabolism of TNBS by GSSG reductase generated ROS. Mucosal samples from TNBS+ethanol-treated rats indicated a direct correlation between GSH depletion and injury detected as soon as 30 minutes after TNBS+ethanol administration that persisted 24 hours post treatment. Although, short term depletion of mucosal GSH per se by diethylmaleate did not result in mucosal injury, the oral administration of NAC (40 mM) 4 hours after TNBS+ethanol treatment increased GSH stores (2-fold), decreasing the extent of mucosal injury (60-70%) examined at 24 hours post treatment. However, an equimolar dose of dithiothreitol failed to increase GSH levels and protect mucosa from TNBS+ethanol-induced injury. Interestingly, GSH levels in TNBS+ethanol-treated rats recovered by 1-2 weeks, an effect that was accounted for by an increase of gamma-glutamylcysteine synthetase (gamma-GCS) activity due to an induction of gamma-GCS-heavy subunit chain mRNA. Thus, TNBS promotes two independent mechanisms of injury, GSH depletion and ROS generation, both being required for the manifestation of mucosal injury as GSH limitation renders intestine susceptible to the TNBS-induced ROS overgeneration. Accordingly, in vivo administration of NAC attenuates the acute colitis through increased mucosal GSH levels, suggesting that GSH precursors may be of relevance in the acute relapse of IBD.
Asunto(s)
Colitis/metabolismo , Glutatión/fisiología , Mucosa Intestinal/fisiología , Acetilcisteína/farmacología , Enfermedad Aguda , Animales , Etanol/toxicidad , Enfermedades Inflamatorias del Intestino/etiología , Mucosa Intestinal/efectos de los fármacos , Masculino , Ratas , Ratas Sprague-Dawley , Especies Reactivas de Oxígeno , Factores de Tiempo , Ácido Trinitrobencenosulfónico/toxicidadRESUMEN
BACKGROUND/AIMS: The mechanisms underlying the initial graft dysfunction in liver transplantation are not completely understood, although much of the liver graft injury derives from the ischemia/reperfusion-induced oxidative stress. Thus, the purpose of our study was to determine the involvement of oxidative stress in the initial graft dysfunction in human liver transplantation. METHODS: Liver biopsies were taken at different times of the transplantation procedure, at the organ donor laparatomy (T1), before graft reperfusion (T2), and 5-60 min after graft reperfusion (T3), determining the levels of GSH, GSSG, as well as peroxides and malondialdehyde in liver homogenates. RESULTS: Patients were graded into two groups depending on whether the peak serum alanine aminotransferases within the first 3 postoperative days were lower (group A, mild to moderate injury: 32 patients) or higher (group B, severe injury: 5 patients) than 2500 U/l. The levels of GSH at time intervals T1-T3 were similar for groups A and B, with a trend to lower GSSG levels in group B at T2 and T3 samples. This outcome was accompanied by unchanged levels of malondialdehyde and hydrogen peroxide in the same samples in both groups of patients. No patient developed primary graft nonfunction. One-year cumulative survival was 81% and 60% in groups A and B, respectively (p>0.05). CONCLUSIONS: These findings indicate a lack of significant generation of reactive oxygen species and consequent oxidative stress as a major factor involved in the pathogenesis of the initial graft dysfunction in human liver transplantation.
Asunto(s)
Trasplante de Hígado/patología , Trasplante de Hígado/fisiología , Estrés Oxidativo , Adolescente , Adulto , Anciano , Alanina Transaminasa/sangre , Biopsia , Femenino , Glutatión/metabolismo , Disulfuro de Glutatión/metabolismo , Supervivencia de Injerto , Hepatectomía , Humanos , Peróxido de Hidrógeno/metabolismo , Hígado/patología , Masculino , Malondialdehído/metabolismo , Persona de Mediana Edad , Daño por Reperfusión , Donantes de Tejidos , Recolección de Tejidos y ÓrganosRESUMEN
BACKGROUND & AIMS: The molecular mechanisms responsible for leukocyte recruitment in experimental colitis are poorly understood. The aims of this study were to measure expression of endothelial intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) and to determine their role in leukocyte recruitment in experimental colitis. METHODS: Rats with trinitrobenzene sulfonic acid (TNBS)-induced colitis and control rats were studied 1, 7, or 21 days after treatment. ICAM-1 and VCAM-1 expressions were measured by the double radiolabeled antibody technique. Leukocyte-endothelial cell interactions were determined in colonic venules by fluorescence intravital microscopy. Therapeutic effects of treatment with anti-VCAM-1 antibodies were also assessed. RESULTS: Colonic endothelial ICAM-1 was constitutively expressed and did not increase in colitic animals. In contrast, constitutive expression of VCAM-1 was low but markedly increased (6-fold) 1 and 7 days after induction of colitis. Increased colonic expression of VCAM-1 paralleled macroscopic damage score, myeloperoxidase activity, and increased leukocyte adhesion in colonic venules. The latter was significantly decreased by immunoneutralization of ICAM-1 and completely abrogated by immunoneutralization of VCAM-1. Long-term administration of anti-VCAM-1 antibody resulted in significant attenuation of colitis. CONCLUSIONS: Induction of colitis in rats by TNBS is followed by up-regulation of endothelial VCAM-1. VCAM-1 and constitutive ICAM-1 are major determinants of leukocyte recruitment to the inflamed intestine.
Asunto(s)
Colitis/patología , Endotelio Vascular/fisiología , Molécula 1 de Adhesión Intercelular/fisiología , Leucocitos/fisiología , Molécula 1 de Adhesión Celular Vascular/fisiología , Animales , Anticuerpos Monoclonales/uso terapéutico , Adhesión Celular , Endotelio Vascular/citología , Molécula 1 de Adhesión Intercelular/análisis , Masculino , Ratas , Ratas Sprague-Dawley , Ácido Trinitrobencenosulfónico , Molécula 1 de Adhesión Celular Vascular/análisisRESUMEN
BACKGROUND & AIMS: Tumor necrosis factor (TNF)-alpha induces cell injury by generating oxidative stress from mitochondria. The purpose of this study was to determine the effect of ethanol on the sensitization of hepatocytes to TNF-alpha. METHODS: Cultured hepatocytes from ethanol-fed (ethanol hepatocytes) or pair-fed (control hepatocytes) rats were exposed to TNF-alpha, and the extent of oxidative stress, gene expression, and viability were evaluated. RESULTS: Ethanol hepatocytes, which develop a selective deficiency of mitochondrial glutathione (mGSH), showed marked susceptibility to TNF-alpha. The susceptibility to TNF-alpha, manifested as necrosis rather than apoptosis, was accompanied by a progressive increase in hydrogen peroxide that correlated inversely with cell survival. Nuclear factor kappaB activation by TNF-alpha was significantly greater in ethanol hepatocytes than in control hepatocytes, an effect paralleled by the expression of cytokine-induced neutrophil chemoattractant. Similar sensitization of normal hepatocytes to TNF-alpha was obtained by depleting the mitochondrial pool of GSH with 3-hydroxyl-4-pentenoate. Restoration of mGSH by S-adenosyl-L-methionine or by GSH-ethyl ester prevented the increased susceptibility of ethanol hepatocytes to TNF-alpha. CONCLUSIONS: These results indicate that mGSH controls the fate of hepatocytes in response to TNF-alpha. Its depletion caused by alcohol consumption amplifies the power of TNF-alpha to generate reactive oxygen species, compromising mitochondrial and cellular functions that culminate in cell death.
Asunto(s)
Etanol/metabolismo , Glutatión/metabolismo , Hígado/citología , Hígado/fisiología , Mitocondrias/metabolismo , Factor de Necrosis Tumoral alfa/fisiología , Animales , Hígado/efectos de los fármacos , Masculino , Ratas , Ratas Sprague-Dawley , S-Adenosilmetionina/farmacología , Factores de TiempoRESUMEN
Increasing evidence has unraveled a dual functional role of mitochondria as suppliers of the energy required for cell viability, and critical players in the pathway leading to cell death. Consequence of their physiological role in the oxidative phosphorylation is the generation of reactive oxygen species (ROS) as byproducts of the consumption of molecular oxygen in the electron transport chain. Superoxide anion and hydrogen peroxide produced during aerobic respiration are precursors of hydroxyl radical by the participation of transition metals. Glutathione (GSH) in mitochondria is the only defense available to metabolize hydrogen peroxide. A small fraction of the total cellular pool of GSH is sequestered in mitochondria by the action of a carrier that transports GSH from cytosol to the mitochondrial matrix. Recent evidence position mitochondria as subcellular targets of cytokines leading to overproduction of ROS induced by ceramide, a lipid intermediate of cytokine action. Chronic ethanol-fed cells are selectively depleted of GSH in mitochondria due to a defective operation of the carrier responsible for the transport of GSH from cytosol into the mitochondrial matrix. Its limitation sensitizes alcohol hepatocytes to the prooxidant effects of cytokines and prooxidants generated by the oxidative metabolism of ethanol. One of the mechanisms leading to the onset of selective defect in the mitochondrial transport of GSH induced by chronic ethanol exposure is mediated by decreased fluidity of the mitochondrial inner membrane. Its fluidization by SAM treatment normalizes the steady state levels of GSH in mitochondria contributing to withstand the oxidative stress derived by the oxidative metabolism of ethanol.
Asunto(s)
Glutatión/metabolismo , Mitocondrias/fisiología , Estrés Oxidativo/fisiología , Animales , Apoptosis/efectos de los fármacos , Muerte Celular , Ceramidas/fisiología , Humanos , Especies Reactivas de Oxígeno/metabolismo , Factor de Necrosis Tumoral alfa/toxicidadRESUMEN
Nuclear factor kappB (NFkappaB) is a transcription factor that controls several genes important for immunity and inflammation. The aim of this study was to assess if activation of NFkappaB plays a role in the pathogenesis of inflammatory bowel disease (IBD), and whether steroid treatment affects NFkappaB activation. Activation of NFkappaB was analysed in colon biopsy samples of 13 patients with active IBD (8 Crohn's colitis, 5 ulcerative colitis) by electrophoretic mobility-shift assays, under basal conditions and 3 weeks after treatment with 0.75 mg kg(-1) day(-1) prednisolone. The presence of interleukin-8 mRNA in biopsies was assessed by RT-PCR. A specific NFkappaB band was present in all nuclear extracts from inflamed mucosa, whereas the band was barely detectable in uninflamed colonic mucosa. NFkappaB bands were super-shifted by antibodies against p50 subunit, whereas antibodies against p65, p52, c-Rel, or Rel B did not modify the mobility of the band. Increased interleukin-8 mRNA was detected at the same sites of NFkappaB activation. Steroid-induced healing of colonic inflammation was associated with disappearance of NFkappaB from nuclear extracts. These results support the notion that NFkappaB plays an important role in the pathogenesis of IBD, and that blockade of NFkappaB activation is one of the mechanisms by which steroids suppress the inflammatory cascade in IBD.
Asunto(s)
Antiinflamatorios/farmacología , Enfermedades Inflamatorias del Intestino/metabolismo , FN-kappa B/metabolismo , Adulto , Antiinflamatorios/uso terapéutico , Electroforesis en Gel de Poliacrilamida , Humanos , Enfermedades Inflamatorias del Intestino/tratamiento farmacológico , Interleucina-8/biosíntesis , Mucosa Intestinal/efectos de los fármacos , Mucosa Intestinal/metabolismo , Reacción en Cadena de la Polimerasa , Prednisolona/farmacología , Prednisolona/uso terapéutico , ARN Mensajero/biosíntesisRESUMEN
Tumor necrosis factor (TNF) is an inflammatory cytokine that causes cell injury by generation of oxidative stress. Since glutathione (GSH) is a key cellular antioxidant that detoxifies reactive oxygen species, the purpose of our work was to examine the regulation of cellular GSH, the expression of heavy subunit chain of gamma-glutamylcysteine synthetase (gamma-GCS-HS), and control of intracellular generation of reactive oxygen species in cultured rat hepatocytes treated with TNF. Exposure of cells to TNF (10,000 units/ml) resulted in depletion of cellular GSH levels (50-70%) and overproduction of hydrogen peroxide (2-3-fold) and lipid peroxidation. However, cells treated with lower doses of TNF (250-500 units/ml) exhibited increased levels of GSH (60-80% over control). TNF treatment increased (70-100%) the levels of gamma-GCS-HS mRNA, the catalytic subunit of the regulating enzyme in GSH biosynthesis. Furthermore, intact nuclei isolated from hepatocytes treated with TNF transcribed the gamma-GCS-HS gene to a greater extent than control cells, indicating that TNF regulates gamma-GCS-HS at the transcriptional level. The capacity to synthesize GSH de novo determined in cell-free extracts incubated with GSH precursors was greater (50-70%) in hepatocytes that were treated with TNF; however, the activity of GSH synthetase remained unaltered by TNF treatment indicating that TNF selectively increased the activity of gamma-GCS. Despite activation of nuclear factor-kappaB (NF-kappaB) by TNF, this transcription factor was not required for TNF-induced transcription of gamma-GCS-HS as revealed by deletion constructs of the gamma-GCS-HS promoter subcloned in a chloramphenicol acetyltransferase reporter vector and transfected into HepG2 cells. In contrast, a construct containing AP-1 like/metal response regulatory elements increased chloramphenicol acetyltransferase activity upon exposure to TNF. Thus, TNF increases hepatocellular GSH levels by transcriptional regulation of gamma-GCS-HS gene, probably through AP-1/metal response element-like binding site(s) in its promoter, which may constitute a protective mechanism in the control of oxidative stress induced by inflammatory cytokines.
Asunto(s)
Glutamato-Cisteína Ligasa/genética , Glutatión/metabolismo , Hígado/metabolismo , Factor de Necrosis Tumoral alfa/farmacología , Animales , Células Cultivadas , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , FN-kappa B/metabolismo , Oxidación-Reducción , Regiones Promotoras Genéticas , ARN Mensajero/genética , Ratas , Especies Reactivas de Oxígeno/metabolismo , Rotenona/farmacología , Tenoiltrifluoroacetona/farmacología , Transcripción Genética/efectos de los fármacosRESUMEN
Mitochondria generate reactive oxygen species (ROS) as byproducts of molecular oxygen consumption in the electron transport chain. Most cellular oxygen is consumed in the cytochrome-c oxidase complex of the respiratory chain, which does not generate reactive species. The ubiquinone pool of complex III of respiration is the major site within the respiratory chain that generates superoxide anion as a result of a single electron transfer to molecular oxygen. Superoxide anion and hydrogen peroxide, derived from the former by superoxide dismutase, are precursor of hydroxyl radical through the participation of transition metals. Glutathione (GSH) in mitochondria is the only defense available to metabolize hydrogen peroxide. A small fraction of the total cellular GSH pool is sequestered in mitochondria by the action of a carrier that transports GSH from the cytosol to the mitochondrial matrix. Mitochondria are not only one of the main cellular sources of ROS, they also are a key target of ROS. Mitochondria are subcellular targets of cytokines, especially tumor necrosis factor (TNF); depletion of GSH in this organelle renders the cell more susceptible to oxidative stress originating in mitochondria. Ceramide generated during TNF signaling leads to increased production of ROS in mitochondria. Chronic ethanol-fed hepatocytes are selectively depleted of GSH in mitochondria due to a defective operation of the carrier responsible for transport of GSH from the cytosol into the mitochondrial matrix. Under these conditions, limitation of the mitochondrial GSH pool represents a critical contributory factor that sensitizes alcoholic hepatocytes to the prooxidant effects of cytokines and prooxidants generated by oxidative metabolism of ethanol. S-adenosyl-L-methionine prevents development of the ethanol-induced defect. The mitochondrial GSH carrier has been functionally expressed in Xenopus laevis oocytes microinjected with mRNA from rat liver. This critical carrier displays functional characteristics distinct from other plasma membrane GSH carriers, such as its ATP dependency, inhibitor specificity, and the size class of mRNA that encode the corresponding carrier, suggesting that the mitochondrial carrier of GSH is a gene product distinct from the plasma membrane transporters.
Asunto(s)
Etanol/farmacología , Glutatión/metabolismo , Mitocondrias/metabolismo , Estrés Oxidativo/fisiología , Factor de Necrosis Tumoral alfa/fisiología , Animales , Transporte Biológico , Citosol/metabolismo , Complejo III de Transporte de Electrones/metabolismo , Humanos , Hígado/efectos de los fármacos , Hígado/metabolismo , Mitocondrias/efectos de los fármacos , Mitocondrias Hepáticas/efectos de los fármacos , Mitocondrias Hepáticas/metabolismo , Modelos Biológicos , Ratas , Factor de Necrosis Tumoral alfa/farmacologíaRESUMEN
BACKGROUND & AIMS: Spontaneous gastric damage occurs in diabetic rats, but the mechanism is unknown. The aim of this study was to assess the role of glutathione metabolism and gastric mucosal blood flow (GMBF) in the development of such spontaneous gastric damage. METHODS: Mucosal damage, GMBF, glutathione metabolism, and lipid peroxidation were measured in the stomach of diabetic and control rats. RESULTS: Spontaneous gastric damage occurred in fasted diabetic rats 4 weeks after streptozotocin administration or pancreatectomy. This was accompanied by a 50% decrement in mucosal content of glutathione; 48 hours after streptozotocin, the decrement of glutathione was only of 25% and no gastric damage was observed. Fed diabetic rats (4 weeks after streptozotocin) had normal glutathione levels and no damage; however, a 30% glutathione depletion achieved by buthionine-sulfoximine administration promoted significant damage. Gastric glutathione synthetic rate, levels of adenosine triphosphate, oxidized glutathione, and malonyldialdehyde were similar in all groups, whereas cysteine concentration was reduced in fasted diabetic animals. Exogenous cysteine attenuated the gastric damage. GMBF was not influenced by diabetes. CONCLUSIONS: Spontaneous gastric damage in fasted diabetic rats seems to be related to glutathione depletion as a result of limited availability of cysteine and not to increased glutathione oxidation. GMBF changes are not involved.
Asunto(s)
Diabetes Mellitus Experimental/patología , Mucosa Gástrica/patología , Glutatión/fisiología , Animales , Glucemia/análisis , Peso Corporal , Mucosa Gástrica/irrigación sanguínea , Mucosa Gástrica/metabolismo , Masculino , Estrés Oxidativo , Ratas , Ratas Sprague-Dawley , EstreptozocinaRESUMEN
It has been widely postulated that age-dependent changes in the mitochondrial genetic system may contribute to the human aging process. We recently reported unchanged specific activities of mitochondrial respiratory chain enzymes and a decrease in oxidation capacity of different substrates with aging, due, in part, to some confounding variables such as physical activity or tobacco consumption. The present study deals with age-related changes in muscle mtDNA structure and its biogenesis in humans. We found a low prevalence of mtDNA rearrangements with aging, only detected by PCR. The mtDNA content increased significantly with age (b = 0.0115, P < 0.0001). Also, an unchanged steady-state level of mitochondrial transcripts, a reduced transcription rate (P < 0.0001), and an increase in mitochondrial membrane lipid peroxidation (P < 0.0001) were observed in aging. These data demonstrate that minor structural mtDNA changes appear during the human aging process. By contrast, alterations in mitochondrial homeostasis ultimately producing modifications in mitochondrial biogenesis rates could play a role in the process of human senescence.