Active oxygen in neuromuscular disorders

Dynamic thiol-disulphide homeostasis in patients with Guillain-Barre Syndrome

OBJECTIVE

The aim of this study was to evaluate dynamic thiol-disulphide homeostasis as a novel oxidative stress parameter in patients with Guillain-Barre syndrome (GBS).

METHODS

A total of 130 participants were included in this study, 70 of whom were diagnosed with GBS. Total thiol (-SH+-S-S-) and native thiol (-SH) levels in serum were measured in all patients and healthy individuals. Amount of dynamic disulphide bond were calculated from these values. In the GBS patients, disability status was determined by the Hughes and Medical Research Center (MRC) sum scores at the time of admission and 3 months thereafter.

RESULTS

Total and native thiol levels were significantly lower in patients with GBS compared with healthy individuals. There was no statistically significant difference in the number of dynamic disulphide bonds between groups. There was a negative correlation between total thiol levels in patients with GBS and Hughes scores at month 3.

DISCUSSION

Oxidative stress is among the molecular changes underlying the pathogenesis of GBS. In this study, we have investigated the dynamic thiol-disulfide homeostasis in patients with epilepsy using a new method in the literature. Also, functional recovery in Guillain-Barré syndrome patients could be promoted by increasing antioxidant activity.

Low serum levels of uric acid and albumin in patients with Guillain-Barre syndrome

Free radical toxicity due to poorly maintained cellular redox levels is crucial events that have been associated with the pathogenesis of Guillain-Barre syndrome (GBS) patients. Uric acid (UA) and albumin correlate with oxidative stress in some degree. We aimed to evaluate the relationship between GBS and serum levels of UA and albumin in the present study.The serum levels of UA and albumin were determined in 203 individuals including 88 patients with GBS and 153 healthy controls (HC).We found that serum levels of UA and albumin in patients with GBS were significantly lower than those in HC group. Besides, similar phenomenon was observed when the male and female subgroups were estimated, respectively. Additionally, we found that there is no statistic difference among subgroups of GBS regarding UA and albumin. The univariate analysis revealed that both the high UA and high albumin were protective factors for patients with GBS (odds ratio [OR] 0.140; 95% confidence interval [CI]: 0.074-0.264; P < .001 and OR 0.016; 95% CI: 0.006-0.038; P < .001, respectively). It was further confirmed by the multivariable logistic regression analysis after adjusting for other potential confounding factors (OR 0.168; 95% CI: 0.055-0.514; P = .002 and OR 0.027; 95% CI: 0.011-0.071; P < .001, respectively).In conclusion, we found that patients with GBS had significantly low serum UA and albumin levels. Moreover, we demonstrated that both the high UA and high albumin were protective factors for patients with GBS.

An evidence-based systematic review of vanadium by the Natural Standard Research Collaboration

An evidence-based systematic review of vanadium by the Natural Standard Research Collaboration consolidates the safety and efficacy data available in the scientific literature using a validated, reproducible grading rationale. This article includes written and statistical analysis of clinical trials, plus a compilation of expert opinion, folkloric precedent, history, pharmacology, kinetics/dynamics, interactions, adverse effects, toxicology, and dosing.

Antioxidant status of bilirubin and uric acid in patients with myasthenia gravis

Oxidative stress and changes in antioxidant status have been implicated in the pathogenesis of inflammatory and autoimmune diseases, and free radicals can cause considerable damage to the acetylcholine receptors. 388 individuals, including 97 patients with myasthenia gravis (MG), 135 patients with multiple sclerosis (MS) and 156 healthy controls, were assessed for serum levels of bilirubin and uric acid (UA), in order to determine the levels of these natural antioxidants in the serum. We found that serum UA levels in patients with MG were significantly lower (266.03 ± 93.09 μmol/l) compared with those of the healthy control group (338.87 ± 107.10 μmol/l, p = 0.001). However, there was no significant difference of serum UA levels between patients with MG and those with MS (p = 0.071). We also found that serum levels of total, direct and indirect bilirubin in patients with MG were significantly lower, compared with those in the healthy control group, whether male or female. From this study, we conclude that serum levels of bilirubin and UA are lower in MG patients.

Hypochlorous acid modifies calcium release channel function from skeletal muscle sarcoplasmic reticulum

We have previously demonstrated that H2O2 at millimolar concentrations induces Ca(2+) release from actively loaded sarcoplasmic reticulum (SR) vesicles and induces biphasic [(3)H]ryanodine binding behavior. Considering that hypochlorous acid (HOCl) is a related free radical and has been demonstrated to be a more effective oxidant of proteins, we evaluated the effects of HOCl on sarcoplasmic reticulum Ca(2+)-channel release mechanism. In a concentration-dependent manner, HOCl activates the SR Ca(2+) release channel and induces rapid release of Ca from actively loaded vesicles. HOCl-induced Ca(2+) release is inhibited in the presence of millimolar concentrations of DMSO. High-affinity [(3)H]ryanodine binding is also enhanced at concentrations from 10 to 100 microM. At HOCl concentrations of >100 microM, equilibrium binding is inhibited. HOCl stimulation of binding is inhibited by the addition of dithiothreitol. The direct interaction between HOCl and the Ca(2+) release mechanism was further demonstrated in single-channel reconstitution experiments. HOCl, at 20 microM, activated the Ca(2+) release channel after fusion of a SR vesicle to a bilayer lipid membrane. At 40 microM, Ca(2+)-channel activity was inhibited. Pretreatment of SR vesicles with HOCl inhibited the fluorescence development of a fluorogenic probe specific to thiol groups critical to channel function. These results suggest that HOCl at micromolar concentrations can modify SR Ca(2+) handling.

In vivo fatiguing contraction of rat diaphragm produces hydroxyl radicals

It is suggested that free radical generation is a cause of muscle fatigue from in vitro studies. We examined whether hydroxyl radical would be generated in an in vivo fatiguing contraction of the diaphragm. Diaphragmatic fatigue was induced in rats by the in vivo rhythmic electrical stimulation of the diaphragm under mechanical ventilation for 30 min. The force-frequency relationship of a diaphragmatic muscle strip was assessed, and the production of hydroxyl radical in muscle strip was evaluated by measuring the metabolites of a reaction of salicylate with hydroxyl radical (2,3- and 2,5-dihydroxybenzoate [DHBA]). After fatiguing contraction, the contractile force of the diaphragm was decreased by approximately 58% at all stimulating frequencies (P < 0.01). There was more 2,3-DHBA in the fatigued muscles compared with the control muscle (219 +/- 22 ng/g tissue versus 109 +/- 17, respectively, P < 0.01) and 2,5-DHBA (198 +/- 23 ng/g tissue versus 84 +/- 14, respectively, P < 0.01). There was a significant relationship between contractile force and the sum of 2,3- and 2,5-DHBA (r = -0.71, P < 0.01). These results suggest that the development of fatigue in the diaphragm is related to the generation of hydroxyl radical.

Hydrogen peroxide stimulates the Ca2+ release channel from skeletal muscle sarcoplasmic reticulum

Hydrogen peroxide (H2O2) at millimolar concentrations induces Ca2+ release from actively loaded sarcoplasmic reticulum vesicles and induces biphasic [3H]ryanodine binding behavior. High affinity [3H]ryanodine binding is enhanced at concentrations from 100 microM to 10 mM (3-4 fold). At H2O2 concentrations greater than 10 mM, equilibrium binding is inhibited. H2O2 decreased the kd for [3H]ryanodine binding by increasing its association rate, while having no effect on the rate of dissociation of [3H]ryanodine from its receptor. H2O2 (1 mM) also reduced the EC50 for Ca2+ activation from 632 nM to 335 nM. These effects were completely abolished in the presence of catalase, ruthenium red, and/or Mg2+ (Mm). H2O2-stimulated [3H]ryanodine binding is not further enhanced by either doxorubicin or caffeine. The direct interaction between H2O2 and the Ca2+ release mechanism was further demonstrated in single-channel reconstitution experiments. Peroxide, at submillimolar concentrations, activated the Ca2+ release channel following fusion of a sarcoplasmic reticulum vesicle to a bilayer lipid membrane. At millimolar concentrations of peroxide, Ca2+ channel activity was inhibited. Peroxide stimulation of Ca2+ channel activity was reversed by the thiol reducing agent dithiothreitol. Paralleling peroxide induced activation of ryanodine binding, Ca2+ transport, and single Ca2+ channel activity, it was observed that the ryanodine receptor formed large disulfide-linked protein complexes that dissociated upon addition of dithiothreitol.

Nitric oxide synthase complexed with dystrophin and absent from skeletal muscle sarcolemma in Duchenne muscular dystrophy

Nitric oxide (NO) is synthesized in skeletal muscle by neuronal-type NO synthase (nNOS), which is localized to sarcolemma of fast-twitch fibers. Synthesis of NO in active muscle opposes contractile force. We show that nNOS partitions with skeletal muscle membranes owing to association of nNOS with dystrophin, the protein mutated in Duchenne muscular dystrophy (DMD). The dystrophin complex interacts with an N-terminal domain of nNOS that contains a GLGF motif. mdx mice and humans with DMD evince a selective loss of nNOS protein and catalytic activity from muscle membranes, demonstrating a novel role for dystrophin in localizing a signaling enzyme to the myocyte sarcolemma. Aberrant regulation of nNOS may contribute to preferential degeneration of fast-twitch muscle fibers in DMD.

Action of reactive oxygen species and their antagonists on twitch tension of the rat phrenic nerve-diaphragm

Reactive oxygen species have been implicated in normal and pathological processes of many tissues, including skeletal muscle. I extended previous studies by examining the effect of these intermediates and eight of their antagonists (superoxide dismutase, catalase, deferoxamine, [Cu(II)]2(3,5-diisopropylsalicylate)4, 1,2-dimethyl-3-hydroxy-pyridone, 1,3-dimethyl-2-thiourea, N-(2-mercaptopropionyl)-glycine, vitamin E) on indirectly stimulated twitch tension of an in vitro neuroskeletomuscular preparation, the phrenic nerve-diaphragm of the rat. In the absence of exogenous reactive oxygen species, none of the antagonists potentiated twitch tension, and all but one (N-[2-mercaptopropionyl]-glycine) of the membrane-permeant antagonists attenuated twitch tension. The reactive oxygen intermediate-generating system of purine plus xanthine oxidase reduced indirectly stimulated twitch tension by 36% while having no effect on directly stimulated twitch tension. Catalase (but not superoxide dismutase or deferoxamine) eliminated the reduction in twitch tension, indicating that hydrogen peroxide played a role in the reduction. The membrane-permeant antagonists [Cu(II)]2(3,5-diisopropylsalicylate)4 and 1,2-dimethyl-3-hydroxy-pyridone also eliminated the reduction in twitch tension caused by reactive oxygen species, suggesting that hydrogen peroxide could have acted intracellularly through an iron-catalyzed Haber-Weiss reaction to produce hydroxyl radical, which in turn reacted with intracellular components, thereby reducing twitch tension.

Detection of free radicals in blood by electron spin resonance in a model of respiratory failure in the rat

Previous work has suggested that a free radical mechanism is involved in some types of muscle fatigue and that there can be free radicals released extracellularly. Because muscle fatigue may be an important factor in respiratory failure, the authors tested the hypothesis that increased concentrations of free radicals could be detected in the blood of animals undergoing severe resistive loading to respiratory failure. An ex vivo spin trapping technique with alpha-phenyl-N-tert-butylnitrone (PBN) was used to investigate the possible formation of free radicals in systemic blood samples by electron spin resonance (ESR) spectrometry. After 2.5-3 h of severe inspiratory resistive loading with 70% supplemental inspired oxygen, free radical levels in the form of PBN-adducts were found to rise significantly over the control group breathing room air and the control group breathing 70% oxygen (p < 0.05, N = 8). There were no significant differences between control groups breathing room air and control groups breathing 70% oxygen. This study presents direct evidence that free radicals are produced ex vivo and that they can be detected in the systemic circulation due to excessive resistive loading of the respiratory muscles.

Changes in heat shock protein 70 and ubiquitin mRNA levels in C1300 N2A mouse neuroblastoma cells following treatment with iron

We have shown that following heat shock (42.5 degree C for 30 min), mouse-derived C1300 N2A neuroblastoma cells contain increased levels of mRNA coding for the inducible form of heat shock protein 70 and for ubiquitin. Incubation of C1300 cells with iron also induces an elevation in content of mRNAs coding for the same two proteins that can be blocked by alpha-tocopherol and desferrioxamine. Iron was shown to increase mitochondrial and lysosomal activities in differentiated C1300 N2A cultures, as shown by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and neutral red cytotoxicity assays. These responses were not initially associated with any loss of viability, as assessed by the lactate dehydrogenase release assay. These results suggest that there is production of cytoprotective heat shock proteins in response to iron-mediated cell damage, probably involving free radical generation, in neural cells. The apparent stress response of vulnerable neurones in human neurodegenerative diseases, particularly Parkinson's disease, may be induced by iron-mediated free radical production in degenerating neurones, making investigation of the mechanism of free radical-induced responses in neuronal cells of special interest.

The role of reactive oxygen species, antioxidants and phytopharmaceuticals in human immunodeficiency virus activity

Currently, several prominent researchers are investigating the role of reactive oxygen and free radicals in the activation of latent HIV in infected individuals. Early clinical applications of free radical scavengers and plant-based antioxidant systems have shown promise of efficacy in altering this process. This manuscript demonstrates a premise for the existence of 'oxidative stress' as an important element in HIV progression and a basis for the use of these phytopharmaceutical substances.

Free radicals as mediators of tissue injury and disease

A radical is any molecule that contains one or more unpaired electrons. Radicals are normally generated in many metabolic pathways. Some of these radicals can exist in a free form and subsequently interact with various tissue components resulting in dysfunction. The potential role of oxygen- or xenobiotic-derived free radicals in the pathology of several human diseases has stimulated extensive research linking the toxicity of numerous xenobiotics and disease processes to a free radical mechanism. However, because free radical-mediated changes are pervasive and often poorly understood, the question of whether such species are a major cause of tissue injury and human disease remains equivocal. This review discusses cellular sources of various radical species and their reactions with vital cellular constituents. Examples of purported free radical-mediated disorders are discussed in detail to provide insights into the controversy over whether free radicals are important mediators of tissue injury.

Protection by beta-carotene and related compounds against oxygen-mediated cytotoxicity and genotoxicity: implications for carcinogenesis and anticarcinogenesis

beta-Carotene protects against photooxidative dermatitis in porphyric humans and mice by quenching of photoactivated species. Other actions of beta-carotene in vivo are explained on the basis of its ability to scavenge free radicals in vitro. For example, in guinea pigs treated with CCl4, beta-carotene decreases pentane and ethane production. Epidemiological studies link low serum beta-carotene levels to elevated risk of lung and other cancers, and in intervention trials, beta-carotene diminishes preneoplastic lesions. However, the dose/response relationships are not well established, and antineoplastic mechanisms await clarification. Given a radical quenching mechanism, beta-carotene should block tumor promotion, but more typically the site of action is progression and an even later role in invasion has not been ruled out. Some antineoplastic actions of carotenoids (such as increased rejection of fibrosarcomas in mice) are attributed to immunoenhancement; others may reflect conversion to retinoids and subsequent gene regulation. Carotenoids other than beta-carotene may act at an earlier stage of carcinogenesis or be more effective as anticarcinogens at certain target sites. As scavengers of hydroxyl radicals, canthaxanthin and astaxanthin are more effective than beta-carotene. Canthaxanthin is sometimes more effective than beta-carotene in chemoprevention, but it is sometimes completely ineffective. Lycopene quenches singlet oxygen more than twice as effectively as beta-carotene. However, the antineoplastic actions of lycopene or astaxanthin remain untested. Explorations of the interactions of carotenoids with other nutrients are just beginning. Dietary fat increases absorption of carotene but decreases antineoplastic effectiveness. Research is hampered by technical problems, including the unavailability of rigorous controls, the instability of carotenoids, and the heterogeneous phase structure induced by hydrophobic compounds in aqueous media. Areas of current controversy and promising approaches for future research are identified.

Drug antioxidant effects. A basis for drug selection?

A free radical is any species capable of independent existence that contains one or more unpaired electrons. Free radical reactions have been implicated in the pathology of more than 50 human diseases. Radicals and other reactive oxygen species are formed constantly in the human body, both by deliberate synthesis (e.g. by activated phagocytes) and by chemical side-reactions. They are removed by enzymic and nonenzymic antioxidant defence systems. Oxidative stress, occurring when antioxidant defences are inadequate, can damage lipids, proteins, carbohydrates and DNA. A few clinical conditions are caused by oxidative stress, but more often the stress results from the disease. Sometimes it then makes a significant contribution to the disease pathology, and sometimes it does not. Several antioxidants are available for therapeutic use. They include molecules naturally present in the body [superoxide dismutase (SOD), alpha-tocopherol, glutathione and its precursors, ascorbic acid, adenosine, lactoferrin and carotenoids] as well as synthetic antioxidants [such as thiols, ebselen (PZ51), xanthine oxidase inhibitors, inhibitors of phagocyte function, iron ion chelators and probucol]. The therapeutic efficacy of SOD, alpha-tocopherol and ascorbic acid in the treatment of human disease is generally unimpressive to date although dietary deficiencies of the last two molecules should certainly be avoided. Xanthine oxidase inhibitors may be of limited relevance as antioxidants for human use. Exciting preliminary results with probucol (antiatherosclerosis), ebselen (anti-inflammatory), and iron ion chelators (in thalassaemia, leukaemia, malaria, stroke, traumatic brain injury and haemorrhagic shock) need to be confirmed by controlled clinical trials. Clinical testing of N-acetylcysteine in HIV-1-positive subjects may also be merited. A few drugs already in clinical use may have some antioxidant properties, but this ability is not widespread and drug-derived radicals may occasionally cause significant damage.

Age-related down regulation of hepatic cytochrome P1-450, P3-450, catalase and CuZn-superoxide dismutase RNA

The influence of age on liver gene expression was investigated in two strains of H-2 congenic mice. In B10.RIII mice (H-2r), basal P1- and P3-450 RNA levels progressively decreased 65 and 95%, respectively, between 4 and 28 months of age (P less than or equal to 0.05). Polyaromatic hydrocarbon (PAH) induced P1- and P3-450 RNA levels decreased about 50% during this time (P less than or equal to 0.05). In contrast, in C57BL/10 mice (H-2b) little or no change was detected in basal or induced P1- or P3-450 RNA levels. CuZn-superoxide dismutase RNA decreased 80 to 90% between 4 and 9 months of age in B10.RIII mice, while a quantitatively smaller decrease of 50 to 65% was found in C57BL/10 mice (P less than or equal to 0.05). Catalase RNA decreased approximately 80% between 4 and 9 months of age in B10.RIII mice, and a similar decrease was found in C57BL/10 mice. Down regulation of these genes may explain the reduced activities of the cognate hepatic enzymes, and reduced xenobiotic metabolism found in older animals.