Mar Almar

Antioxidant enzyme status in biliary obstructed rats: effects of N-acetylcysteine

BACKGROUND/AIMS N-acetylcysteine (NAC) is a modulator of thiol levels that protects against hepatotoxic agents. The aim of this study was to investigate whether NAC might improve hepatic antioxidant defenses in chronically biliary obstructed rats. METHODS Secondary biliary cirrhosis was induced by 28 days of bile-duct obstruction. Groups of control and cirrhotic animals received NAC (50 mumol .kg-1.d-1 i.m.) through the experimental period. RESULTS Bile-duct obstruction resulted in decreased liver glutathione concentrations. Dichlorofluorescein (DCF) and thiobarbituric acid reactive substances (TBARS) concentrations, measured as markers of production of reactive oxygen species and lipid peroxidation, respectively, were significantly increased. Microsomal and mitochondrial membrane fluidity and the activities of catalase, cytosolic and mitochondrial superoxide dismutase (SOD), glutathione S-transferase, and cytosolic and mitochondrial Se-dependent and Se-independent glutathione peroxidase (GPx) were significantly reduced. NAC corrected the reduction in glutathione concentration and partially prevented the increases in DCF and TBARS concentrations. In addition, NAC treatment resulted in significant preservation of membrane fluidity and of the activities of catalase, mitochondrial SOD and the different forms of GPx. CONCLUSIONS Our data indicate that NAC maintains antioxidant defenses in biliary obstructed rats. These effects of NAC suggest that it may be a useful agent to preserve liver function in patients with biliary obstruction.

Differential effects of dietary flavonoids on reactive oxygen and nitrogen species generation and changes in antioxidant enzyme expression induced by proinflammatory cytokines in Chang Liver cells.

This study was aimed to investigate the differential protective effect of dietary flavonoids against oxidative stress induced by proinflammatory stimuli in parenchymal liver cells. Chang Liver cells were incubated with a cytokine mixture (CM) supplemented with the flavonols quercetin and kaempferol, the flavanone taxifolin and the flavone apigenin (5-50 microM). Concentrations of oxidised and reduced glutathione, generation of different ROS/RNS, and expression of antioxidant enzymes were measured. Oxidised glutathione concentration and the oxidised/reduced glutathione ratio were increased by the CM. These effects were significantly prevented by quercetin, kaempferol and taxifolin at all tested concentrations. Effects of apigenin reached a lesser extent and were not significant at 25 microM. Treatment with quercetin and kaempferol prevented the production of peroxides, superoxide anion and nitric oxide induced by CM. Taxifolin 50 microM and apigenin 25-50 microM caused a significant increase in peroxides and nitric oxide generation. Protein concentration of the different antioxidant enzymes was generally reduced by kaempferol and quercetin in comparison to CM, although quercetin 25 and 50 microM increased Mn SOD protein concentration. GPx protein level was significantly increased by apigenin 25 and 50 microM. Changes in mRNA tended to be parallel to those in protein concentration. Our study reveals that important differences exist between flavonoids with different structural features in their capacity to abrogate the generation of different ROS/RNS, and suggests that the modulation of antioxidant enzymes by flavonoids may be also important in their antioxidant effects in liver cells.

Changes in oxidative stress markers and NF-κB activation induced by sprint exercise

This study was aimed to investigate changes in blood markers of oxidative damage induced by short-term supramaximal anaerobic exercise and to determine whether oxidative stress was associated to activation of the redox-sensitive transcription factor nuclear factor-κB (NF-κB). Both a single Wingate test (WAnT) test and series of four WAnTs separated by 60 min rest intervals were carried out by eight professional cyclists. Leukocyte 8-OH-2-deoxyguanosine levels were significantly elevated 24 h after both exercise protocols. A significant decrease in blood reduced glutathione (GSH) concentration was observed immediately after and at 15, 60 and 120 min of the single WAnT, followed by a return to basal value after 24 h. This decrease was parallel to a significant increase of the oxidised/reduced glutathione (GSSG/GSH) ratio, to an activation of NF-κB and to a significant decrease in the protein level of its inhibitor IκB. GSH concentration and the GSSG/GSH ratio changed significantly for the first three of the WAnTs series and normalised thereafter. A significant activation of NF-κB and a decrease in the IκB protein level were also detected. We conclude that short-term supramaximal anaerobic exercise induces oxidative stress, as evidenced by non cumulative damage to macromolecules and changes in the glutathione status. Our data also indicate that high intensity anaerobic work gives rise to an activation of the transcription factor NF-κB accompanied by a degradation of IκB.

Eccentric training impairs NF-κB activation and over-expression of inflammation-related genes induced by acute eccentric exercise in the elderly

The present study was aimed to investigate in elderly humans changes in NF-kappaB activation and in the expression of the inflammation-related genes inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and interleukin-6 (IL-6) induced in peripheral blood mononuclear cells (PBMC) by acute eccentric exercise and by submaximal eccentric training. Eleven subjects, aged 66-75 years, carried out 2 bouts of eccentric exercise separated by 8 weeks of training. Following the first bout, NF-kappaB activation, and protein level of p50/p65 subunits, phospho-IkappaBalpha and phospho-IKKalpha increased, while IkappaBalpha protein level was significantly reduced. This was accompanied by a significant increase in iNOS, COX-2 and IL-6 mRNA protein level and protein content. Changes were significantly attenuated following the second exercise bout. In conclusion, acute eccentric exercise increases NF-kappaB activation and the expression of several inflammation-related genes in PBMC from elderly individuals. Regular eccentric training might be an effective method of preventing undesirable inflammatory responses induced by eccentric exercise.

Urinary Levels of 8-Hydroxydeoxyguanosine as a Marker of Oxidative Damage in Road Cycling

We have determined the urinary 8-hydroxydeoxyguanosine (8-OHdG) levels of eight professional cyclists during a 4-day and a 3-week stage races. Monitoring of heart rates was used to establish zones corresponding to different intensities of exercise. The urinary 8-OHdG excretion, expressed by body weight, increased significantly in the first day or the first week of each race, respectively, and did not show further increases thereafter. Maximum 8-OHdG levels were reached in parallel to longer times spent at high intensities of exercise. Urinary excretion of creatinine increased with exercise, and changes in 8-OHdG levels were not detected when corrected by creatinine excretion. Serum glutathione concentrations did not change significantly at any point during exercise. We conclude that road cycling courses with an oxidative damage to DNA, which is sustained as long as the exercise is repeated. Both adaptation of antioxidant defenses and a decreased capacity to maintain a high intensity of effort may contribute to explain the absence of progressive increases in 8-OHdG excretion. The results of this study also confirm that the correction procedure using the amount of creatinine excreted should not be used when studying effects of exercise on urinary 8-OHdG.

Microsomal function in biliary obstructed rats: effects of S-adenosylmethionine

BACKGROUND/AIMS S-adenosylmethionine has been reported to have beneficial effects in the treatment of different chronic liver diseases and to protect against different hepatotoxic agents. The aim of this study was to investigate whether S-adenosylmethionine treatment might contribute to improved microsomal function in chronically biliary obstructed rats. METHODS Secondary biliary cirrhosis was induced by 28 days of bile duct obstruction. Groups of control and cirrhotic animals received S-adenosylmethionine (10 mg/kg per day) through the experimental period. RESULTS Bile duct obstruction resulted in a marked increase in lipid peroxidation levels and decreases in glutathione concentration, microsomal membrane fluidity, microsomal cytochrome P-450 content, NADPH-cytochrome P-450 reductase activity and the activities of the aniline hydroxylase, aminopyrine demethylase and ethoxycoumarin deethylase. Reductions in glutathione and cytochrome P-450 concentration were not corrected by S-adenosylmethionine, but lipid peroxidation, the decrease in the activities of the various microsomal monooxygenases and the reduction in microsomal membrane fluidity were partially prevented. A significant relationship was found between membrane fluidity and aniline hydroxylase, aminopyrine demethylase or ethoxycoumarin deethylase activities. CONCLUSIONS S-adenosylmethionine administration partially preserves microsomal function. This effect could be associated to the protection of membrane function by restoring transmethylation reactions.

Effects of strength and endurance training on antioxidant enzyme gene expression and activity in middle-aged men

This study was aimed at investigating the effects of a 21‐week period of progressive strength or endurance training on peripheral blood mononuclear cells (PBMC) antioxidant enzyme gene expression and activity in healthy middle‐aged untrained men. Strength (n=11) and endurance (n=12) training were performed twice a week, including resistance exercises to activate all the main muscle groups or cycle‐ergometer pedaling, respectively. mRNA levels of catalase, glutathione peroxidase (GPx), mitochondrial superoxide dismutase (MnSOD) and cytosolic superoxide dismutase (CuZnSOD) were increased after 21 weeks of strength training, while endurance training induced significant changes only in MnSOD and GPx mRNA levels. CuZnSOD protein content was significantly increased only in strength‐trained subjects. The program of strength or endurance exercise training had no significant effects on the activity of any of the antioxidant enzymes. In conclusion, in a middle‐aged population, 21 weeks of strength or endurance training was a sufficient stimulus to up‐regulate mRNA levels of PBMC antioxidant enzymes, the strength training being a more optimal stimulus. However, the discrepancies between enzyme protein and mRNA levels suggest that the present systematic strength or endurance training period had no beneficial effects on enzymatic antioxidant defense mechanisms in previously untrained middle‐aged men.

Eccentric exercise induces nitric oxide synthase expression through nuclear factor-κB modulation in rat skeletal muscle

This study aimed to investigate the effect of eccentric exercise on the expression of the different nitric oxide synthase (NOS) isoforms in rat deep vastus lateralis muscle. Twenty-four rats were allocated to four experimental groups: rested control group, acutely exercised group after an intermittent downhill protocol for 90 min, acutely exercised group treated with pyrrolidine dithiocarbamate (100 mg/kg ip) for 24 and 1 h before the acute exercise bout, and acutely exercised group with a previous submaximal eccentric training of 8 wk. Acutely exercised rats showed increased levels of protein tyrosine nitration, NF-kappaB binding, and phospho-I kappaB alpha content. A significant increase was observed in mRNA level and protein content of neuronal NOS, inducible NOS, and endothelial NOS. The binding of NF-kappaB to the NOS isoform promoters, measured by a chromatin immunoprecipitation assay, was undetectable in rested rats, whereas it was evident in acutely exercised animals. All of these effects were partially abolished by pyrrolidine dithiocarbamate treatment and by training. In summary, our findings provide a direct link between the NF-kappaB signaling cascade and NOS expression in skeletal muscle following eccentric exercise and suggest a modulation of the expression of the three NOS isoforms by this transcription factor.

Role of Toll-like receptor 2 and 4 signaling pathways on the inflammatory response to resistance training in elderly subjects

This study assessed the effects of a resistance exercise training program on the inflammatory response associated with Toll-like receptor (TLR) 2 and TLR4 signaling pathways in senior participants. Twenty-six healthy subjects (age, 69.5 ± 1.3) were randomized to a training (TG; n = 16) or a control (CG; n = 10) group. TG performed an 8-week resistance training program, while CG followed their daily routines. Peripheral blood mononuclear cells were isolated from blood samples obtained before and after the intervention, and levels of proteins involved in the TLR2, TLR4, and myeloid differentiation primary response gene 88 (MyD88)-dependent and MyD88-independent pathways were analyzed. The inflammatory status was evaluated through messenger RNA (mRNA) and protein content of interleukin (IL)-10 and tumor necrosis factor alpha (TNF-α) and plasma levels of C-reactive protein (CRP). After the 8-week resistance training, TLR2 and TLR4 protein expression was reduced in TG. MyD88, p65, phospho-p38, TIR domain-containing adaptor inducing interferon (TRIF), IKKi/IKKε, phospho-interferon regulatory factor (IRF) 3, and phosho-IRF7 were also downregulated in TG after the intervention. The training program induced an increase of phospho-extracellular signal-regulated kinases 1 and 2 (ERK1/2) and Hsp70 and a reduction of Hsp60. While TNF-α mRNA and protein values remained unchanged in both TG and CG, IL-10 mRNA and protein content were upregulated in TG after the intervention. CRP values decreased in TG only. The increase in Hsp70 negatively correlated with TLR2 and TLR4 downregulation. These data suggest that resistance exercise may represent an effective tool to ameliorate the pro-inflammatory status of old participants through an attenuation of MyD88-dependent and MyD88-independent TLR2 and TLR4 signaling pathways.

Monitoring biological and psychological measures throughout an entire season in male handball players

Abstract The aim of this study was to monitor biological markers of inflammation and oxidative stress, mood states, and recovery-stress states throughout an entire season in male handball players. Fourteen handball players (age 20.1±2.5 years) with a regular training and competitive background in handball (11.0±3.7 years) from the same club volunteered to participate. All participants completed 40 weeks of training. The training load was increased progressively throughout the season. Blood samples were collected and questionnaires were administered during preparatory, competitive, and recovery periods. Blood C-reactive protein and oxidized glutathione (GSSG) concentrations increased during periods of high load, while the reduced/oxidized glutathione ratio (GSH/GSSG) decreased. These changes were accompanied by a significant increase in total leukocyte count. Positive correlations were found between C-reactive protein, GSSG, GSH/GSSG ratio, and training load. No changes were observed in the Total Mood Disturbance score of the Profile of Mood States (POMS). However, scores on some Recovery-Stress Questionnaire for Athletes subscales, such as Injury, Physical Recovery, and Being in Shape, correlated with training load. Findings indicate that during periods of high training load, handball players developed a low grade of inflammation and oxidative state. Results support the usefulness of monitoring psychological and biological markers of inflammation, oxidative stress, and training load during season.