Alpha-tocopherol in rat brain subcellular fractions is oxidized rapidly during incubations with low concentrations of peroxynitrite

β-Carotene and its physiological metabolites: Effects on oxidative status regulation and genotoxicity in in vitro models

Carotenoids are ubiquitously distributed in nature, β-carotene being the most frequently found carotenoid in the human diet. In the human body, β-carotene is absorbed, distributed and metabolized by enzymatic and/or non-enzymatic oxidant cleavage into several metabolites. Despite the broadly accepted biological value of β-carotene, it has also been considered a double-edged sword, mainly due to its potential antioxidant versus pro-oxidant behaviour. In this sense, the aim of this work was to scrutinize the antioxidant or pro-oxidant potential of β-carotene and its metabolites, namely trans-β-apo-8'-carotenal and β-ionone. Several parameters were evaluated in this study, viz. their effects on reactive species production, both in human whole blood and neutrophils; their effects on lipid peroxidation, in the absence and presence of peroxynitrite anion (ONOO^-) or hydrogen peroxide (H₂O₂), using a synaptosomal model; and finally, their putative genotoxic effects in the human hepatic HepG2 cell line. In general, depending on the cellular model and conditions tested, β-carotene and its metabolites revealed antioxidant effects to varying degrees without significant pro-oxidant or genotoxic effects.

The Effect of Alpha-Tocopherol on Morphine Tolerance-induced Expression of c-fos Proto-oncogene from a Biotechnological Perspective

BACKGROUND

The increase of oxidant compounds is the most well-known reasons for the tolerance to the analgesic properties of Morphine. Additionally, the production of proxy-nitrite impairs receptors, proteins and enzymes involved in the signaling pathways of analgesia, apoptosis and necrosis. Also, we revised all patents relating to opioid tolerance control methods.

OBJECTIVE

The aim of this study was to assess the effects of Alpha-tocopherol as an anti-oxidant agent to reduce Morphine tolerance.

METHOD

Forty male rats randomly divided into four groups. 10 mg/kg of morphine was injected subcutaneously to create the desired level of tolerance. After modeling, 70 mg/kg Alpha- Tocopherol was injected intraperitoneal. Also, the hot plate recorded pain threshold alterations was used to evaluate the behavioral test. All tissue samples were extracted from the spinal cord, thalamus and frontal cortex for molecular and gene expression evaluations. Also, the effect of Alpha- Tocopherol on the apoptosis and necrosis parameters was analyzed using nissl staining and tunel test.

RESULTS

The time latency results showed that there were no significant differences in the different days in groups treated with Morphine plus Alpha-Tocopherol. However, our data highlighted that the pain threshold and their time latency in respond to it had substantially increased in comparison with the control group. Furthermore, we found that the Alpha-Tocopherol obviously decreased c-fos gene expression, especially in the spinal cord.

CONCLUSION

Thus, co-administration of Alpha-Tocopherol with Morphine can decrease the adverse effects of nitrite proxy, which is released due to repeated injections of Morphine.

The Subcellular Distribution of Alpha-Tocopherol in the Adult Primate Brain and Its Relationship with Membrane Arachidonic Acid and Its Oxidation Products

The relationship between α-tocopherol, a known antioxidant, and polyunsaturated fatty acid (PUFA) oxidation, has not been directly investigated in the primate brain. This study characterized the membrane distribution of α-tocopherol in brain regions and investigated the association between membrane α-tocopherol and PUFA content, as well as brain PUFA oxidation products. Nuclear, myelin, mitochondrial, and neuronal membranes were isolated using a density gradient from the prefrontal cortex (PFC), cerebellum (CER), striatum (ST), and hippocampus (HC) of adult rhesus monkeys (n = 9), fed a stock diet containing vitamin E (α-, γ-tocopherol intake: ~0.7 µmol/kg body weight/day, ~5 µmol/kg body weight/day, respectively). α-tocopherol, PUFAs, and PUFA oxidation products were measured using high performance liquid chromatography (HPLC), gas chromatography (GC) and liquid chromatography-gas chromatography/mass spectrometry (LC-GC/MS) respectively. α-Tocopherol (ng/mg protein) was highest in nuclear membranes (p < 0.05) for all regions except HC. In PFC and ST, arachidonic acid (AA, µg/mg protein) had a similar membrane distribution to α-tocopherol. Total α-tocopherol concentrations were inversely associated with AA oxidation products (isoprostanes) (p < 0.05), but not docosahexaenoic acid oxidation products (neuroprostanes). This study reports novel data on α-tocopherol accumulation in primate brain regions and membranes and provides evidence that α-tocopherol and AA are similarly distributed in PFC and ST membranes, which may reflect a protective effect of α-tocopherol against AA oxidation.

Antioxidants and polyunsaturated fatty acids in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). Oligodendrocyte damage and subsequent axonal demyelination is a hallmark of this disease. Different pathomechanisms, for example, immune-mediated inflammation, oxidative stress and excitotoxicity, are involved in the immunopathology of MS. The risk of developing MS is associated with increased dietary intake of saturated fatty acids. Polyunsaturated fatty acid (PUFA) and antioxidant deficiencies along with decreased cellular antioxidant defence mechanisms have been observed in MS patients. Furthermore, antioxidant and PUFA treatment in experimental allergic encephalomyelitis, an animal model of MS, decreased the clinical signs of disease. Low-molecular-weight antioxidants may support cellular antioxidant defences in various ways, including radical scavenging, interfering with gene transcription, protein expression, enzyme activity and by metal chelation. PUFAs may not only exert immunosuppressive actions through their incorporation in immune cells but also may affect cell function within the CNS. Both dietary antioxidants and PUFAs have the potential to diminish disease symptoms by targeting specific pathomechanisms and supporting recovery in MS.

Inhibition of inducible nitric oxide synthase reduces lipopolysaccharide-induced renal injury in the rat

1. Gram-negative bacterial lipopolysaccharide (LPS) release and subsequent septic shock is a major cause of death in intensive care units. Lipopolysaccharide has been reported to increase the production of nitric oxide (NO) and the formation of oxygen-derived free radicals (OFR) in different organs. The aim of the present study was to evaluate the role of an inducible form of NO synthase (iNOS) and OFR production in LPS-induced renal impairment. 2. Measurement of vitamin E as the most important fat-soluble anti-oxidant was used as a marker of tissue oxidative stress. Lipopolysaccharide (10 mg/kg), L-iminoethyl lysine (L-Nil; 3 mg/kg, i.p.; a specific inhibitor of iNOS activity) and dimethyl thiourea (DMTU; 500 mg/kg i.p.; a well-known OFR scavenger) were used. Four groups of eight rats were studied. One group received LPS, whereas a second group received LPS + L-Nil. A third group received LPS + DMTU and the fourth group, receiving saline, acted as a control group. To evaluate renal function, plasma creatinine and blood urea nitrogen (BUN) were measured. High-pressure liquid chromatography and ultraviolet detection were used to measure plasma and tissue vitamin E levels. Light microscopy was used to examine histopathological changes in the four groups. 3. Lipopolysaccharide markedly decreased the vitamin E content of renal plasma and tissue (P < 0.05). Administration of L-Nil attenuated renal dysfunction and preserved vitamin E levels. However, DMTU failed to prevent renal injury, as indicated by plasma BUN levels and renal histology, despite the fact that it maintained renal vitamin E levels and increased plasma vitamin E levels. Thus, the overproduction of NO by iNOS may have a role in this model of LPS-induced renal impairment.

Oxidative stress and inhibition of oxidative phosphorylation induced by peroxynitrite and nitrite in rat brain subcellular fractions

Nitrite and nitrate, two endogenous oxides of nitrogen, are toxic in vivo. Furthermore, the reaction of superoxide (produced by all aerobic cells) with nitric oxide (NO) generates peroxynitrite, a potent oxidizing agent, that can cause biological oxidative stress. Using subcellular fractions from rat brain hemispheres we studied oxidative stress induced by these nitrogen compounds with special emphasis on nitrite. The consumption of Vitamin C (ascorbate) and Vitamin E (alpha tocopherol), two of the important nutritional antioxidants, was followed in synaptosomes (nerve-ending particles) and mitochondria along with changes in parameters of mitochondrial oxidative phosphorylation. Nitrite, but not nitrate, oxidized ascorbate without oxidizing alpha tocopherol in both synaptosomes and mitochondria whereas peroxynitrite oxidized both ascorbate and alpha tocopherol. Functionally, both nitrite and peroxynitrite inhibited mitochondrial oxidative phosphorylation. Nitrite was less potent than peroxynitrite when the effects of equal concentrations of the two were compared. However, since nitrite is much more stable than peroxynitrite the impact of nitrite as an oxidant in vivo could be as much or even more significant than peroxynitrite. Nitrate would not have similar action unless it is reduced to nitrite. It is possible that nitrite may impair oxidative phosphorylation through modulating levels of nitric oxide, changing the activity of heme proteins or a mild uncoupling of mitochondria.

Linking work factors to neck myalgia: the nitric oxide/oxygen ratio hypothesis

The pathophysiological link between work-related exposures and neck myalgia remains a puzzle. According to the hypothesis presented here, neck myalgia is evoked when low-level contractions in the trapezius muscle are combined with sympathetic vasoconstriction due to psychological stress or prolonged head-down neck flexion at work. These ischemic contractions increase nitric oxide/oxygen concentration ratio in the muscle fibres, enhancing herewith the reversible inhibition of mitochondrial cytochrome oxidase by nitric oxide. The result is depletion of adenosine triphosphate, which elicits production/efflux of lactic acid, in turn activating and sensitising proton-sensitive nociceptive fibres in the connective tissue, causing myalgic pain and tenderness. High estrogen-level, which gives a high expression of nitric oxide synthase in the muscle, accentuates the situation. During episodes of sustained inhibition of cytochrome oxidase by nitric oxide, peroxynitrite may be produced and cause irreversible inactivation of several enzymes in the mitochondrial electron-carrier chain. With repeated episodes, an increasing part of the enzymatic capacity for cellular respiration is inactivated. Even if this process only takes place within a small portion of the muscle fibres, it may contribute to frequent exacerbations of pain. Effects of peroxinitrite may also explain the mitochondrial abnormalities found in the trapezius muscle of many neck myalgia patients. Adrenergic antagonists and nitric oxide synthase inhibitors could reduce symptoms. Ascorbic acid, alpha tocopherol, and flavonoids, which are safe and effective scavengers of peroxynitrite, could prevent chronicity. The most effective non-pharmacological measure may be to reduce exposure to prolonged head-down neck flexions and psychosocial stress at work.

5-Aminosalicylic acid protection against oxidative damage to synaptosomal membranes by alkoxyl radicals in vitro

The antioxidant properties of 5-aminosalicylic acid in vitro were evaluated in a synaptosomal membrane system prepared from gerbil cortical synaptosomes using EPR spin labeling and spectroscopic techniques. MAL-6 (2,2,6,6-tetramethyl-4-maleimidopiperidin-1-oxyl) and 5-NS (5-nitroxide stearate) spin labels were used to assess changes in protein oxidation and membrane lipid fluidity, respectively. Synaptosomal membranes were subjected to oxidative stress by incubation with 1 mM azo-bis(isobutyronitrile) (AIBN) or 1 mM 2,2'-azobis(amidino propane) dihydrochloride (AAPH) at 37 degrees C for 30 minutes. The EPR analyses of the samples showed significant oxidation of synaptosomal proteins and a decrease in membrane fluidity. 5-Aminosalicylic acid also was evaluated by means of FRAP (the ferric reducing ability of plasma) test as a potential antioxidant. 5-Aminosalicylic acid also showed protection against the oxidation in gerbil cortical synaptosomes system caused by AIBN and AAPH. These results are consistent with the notion of antioxidant protection against free radical induced oxidative stress in synaptosomal membrane system by this agent.

Intervention du monoxyde d'azote, NO, et de ses dérivés oxydés, particulièrement chez les mammifères

Nitric oxide (NO) is a natural and stable free radical produced in soil and water by the bacteriological reduction of nitrites and nitrates and in animals by the enzyme oxidation of L-arginine. NO is biosynthesised by finely regulated enzymatic systems called NO-synthases and readily diffuses through tissues. It reacts rapidly with hemoproteins and iron-sulphur centers to form nitrosylated compounds. It oxidises more slowly to form nitrogen oxides that nitrosate thiols into thionitrite. NO is transported in these various forms and released spontaneously or through yet unclear mechanisms into most cells; it also regulates oxygen consumption at the mitochondrial respiratory chain level through interaction with cytochrome oxidase. In the cardiovascular system, NO lowers blood pressure by activating a hemoprotein, the guanylate cyclase present in muscle cells; through such interaction it acts also as a neuromediator and neuromodulator in the nervous system. However, many of NO's roles result from rapid coupling to other radicals; for example, it reacts with the superoxide anion (O–2) to form oxoperoxinitrate (ONOO–, also known as peroxynitrite). This strong oxidant of metallic centers, thiols, and antioxidants is also able to convert tyrosine to 3-nitrotyrosine and to act upon tyrosine residues contained in proteins. The biological aspects of the roles of NO are presented with particular respect to the rapid interactions of NO with hemoproteins' iron and other radicals. Concurrently, NO oxidation enables nitrosation reactions primarily of thiols but ultimately of nucleic bases. The thionitrite function (R-S-NO) thus formed and the dimerisation and nitration of tyrosine residues are protein post-translational modifications that are being investigated in animals.Key words: nitric oxide, peroxynitrite, nitration, nitrosation, nitrosylation. [Translated by the editors.]

A novel human tocopherol-associated protein: cloning, in vitro expression, and characterization

Vitamin E (alpha-tocopherol) is an essential dietary nutrient for humans and animals. The mechanisms involved in cellular regulation as well as in the preferential cellular and tissue accumulation of alpha-tocopherol are not yet well established. We previously reported (Stocker, A., Zimmer, S., Spycher, S. E., and Azzi, A. (1999) IUBMB Life 48, 49-55) the identification of a novel 46-kDa tocopherol-associated protein (TAP) in the cytosol of bovine liver. Here, we describe the identification, the molecular cloning into Escherichia coli, and the in vitro expression of the human homologue of bovine TAP, hTAP. This protein appears to belong to a family of hydrophobic ligand binding proteins, which have the CRAL (cis-retinal binding motif) sequence in common. By using a biotinylated alpha-tocopherol derivative and the IASys resonant mirror biosensor, the purified recombinant protein was shown to bind tocopherol at a specific binding site with K(d) 4.6 x 10(-7) m. Northern analyses showed that hTAP mRNA has a size of approximately 2800 base pairs and is ubiquitously expressed. The highest amounts of hTAP message are found in liver, brain, and prostate. In conclusion, hTAP has sequence homology to proteins containing the CRAL_TRIO structural motif. TAP binds to alpha-tocopherol and biotinylated tocopherol, suggesting the existence of a hydrophobic pocket, possibly analogous to that of SEC14.

Elevated, sustained peroxynitrite levels as the cause of chronic fatigue syndrome

The etiology of chronic fatigue syndrome (CFS) has been both obscure and highly contentious, leading to substantial barriers to both clear diagnosis and effective treatment. I propose here a novel hypothesis of CFS in which either viral or bacterial infection induces one or more cytokines, IL-1beta IL-6, TNF-alpha and IFN-gamma. These induce nitric oxide synthase (iNOS), leading to increased nitric oxide levels. Nitric oxide, in turn, reacts with superoxide radical to generate the potent oxidant peroxynitrite. Multiple amplification and positive feedback mechanisms are proposed by which once peroxynitrite levels are elevated, they tend to be sustained at a high level. This proposed mechanism may lower the HPA axis activity and be maintained by consequent lowered glucocorticoid levels. Similarities are discussed among CFS and autoimmune and other diseases previously shown to be associated with elevated peroxynitrite. Multiple pharmacological approaches to the treatment of CFS are suggested by this hypothesis.

Procyanidins extracted from pine bark protect alpha-tocopherol in ECV 304 endothelial cells challenged by activated RAW 264.7 macrophages: role of nitric oxide and peroxynitrite

A co-culture system was used to study the effect of reactive nitrogen species (RNS) generated by RAW 264.7 macrophages grown on filters and activated by lipopolysaccharide and interferon-gamma, on the alpha-tocopherol levels in ECV 302 endothelial cells. The results indicate that: RNS generated by activated macrophages or by direct administration of peroxynitrite lead to a significant loss of alpha-tocopherol in endothelial cells; pre-incubation with procyanidin extracted from pine bark (Pycnogenol) protects alpha-tocopherol of endothelial cells and enhances by about 15% basal endogenous levels of alpha-tocopherol. These results demonstrate flavonoids participate in the cellular antioxidant network and suggest that Pycnogenol may play an important role in the protection of endothelium from oxidative stress induced by reactive nitrogen species.