Lipid peroxidation products and antioxidant proteins in plasma and cerebrospinal fluid from multiple sclerosis patients

Circulating antibodies directed against conjugated fatty acids in sera of patients with multiple sclerosis

Using an adapted ELISA assay, we have tested sera from multiple sclerosis (MS) patients for antibodies directed against ten fatty acids conjugated to bovine serum albumin. In serum samples from 68 MS patients and 20 patients suffering from rheumatoid arthritis (RA), a significant antibody titer elevation to the ten tested fatty acids was found when compared to sera of 40 healthy subjects and 82 patients with other neurological and autoimmune diseases. G-200 purified IgM of MS patients reacted specifically with the aliphatic chains with an avidity of 3 x 10(-7) M. These results suggest that in MS and RA, autoepitopes on cell membranes that are normally hidden from the immune system become immunogenic. This may arise because of previous membrane disruption by oxidative processes.

The effect of ascorbate and ubiquinone supplementation on plasma and CSF total antioxidant capacity

Free radicals are thought to be involved in the onset of neuronal disturbances such as Alzheimer's disease, Parkinson's disease, and neuronal ceroid lipofuscinosis. It is also assumed that they play a role in cerebral injury caused by ischemia or trauma. Plasma and cerebrospinal fluid (CSF), Total (peroxyl) Radical-trapping Antioxidant Parameter (TRAP), and the known antioxidant components of TRAP, for instance, ascorbic acid, uric acid, protein sulfhydryl groups, tocopherol, and ubiquinol were analyzed and the remaining unidentified fragment was calculated in five healthy volunteers before and after 4 weeks of ascorbate and ubiquinone (Q-10) supplementation. In CSF, TRAP was significantly lower than in plasma. The major contributor to plasma's antioxidant capacity was uric acid (UA), whereas in CSF it was ascorbic acid (AA). In CSF, AA concentrations were four times higher than in plasma. Oral supplementation of AA (500 mg/d first 2 weeks, 1,000 mg/d following 2 weeks) and Q-10 (100 mg/d first 2 weeks, 300 mg/d following 2 weeks) induced a significant increase in plasma AA and Q-10. Surprisingly, in spite of the high lipophilicity of Q-10, its concentration did not change in CSF. The supplementation of AA increased its concentration in CSF by 28% (p < .05). However, the increase in AA did not result in an increase in CSF TRAP. This indicates that AA had lost one-third of its radical trapping capacity as compared to that in plasma. The facts that AA is the highest contributor to CSF TRAP and its effect on TRAP is concentration dependent could indicate that the peroxyl radical-trapping capacity of CSF is buffered by AA.

Nitric oxide induces necrotic but not apoptotic cell death in oligodendrocytes

We have investigated the mechanism of nitric oxide-induced damage in glial cells. Genomic DNA isolated from astrocytes and microglia, treated for 18 h with varying concentrations of a nitric oxide donor, was analysed by electrophoresis. No DNA damage was evident. Oligodendrocytes, treated with 2 mM nitric oxide for 3-48 h, showed single stranded breaks at 48 h but no laddering of nucleosomic fragments of DNA. When analysed by electron microscopy, ultrastructural changes in oligodendrocytes treated with 1 mM nitric oxide for 24 h showed intact nuclei but alterations in membranes and organelles characteristic of necrosis, including disrupted mitochondria with dissolution of their christae. Astrocytes, a glial cell type that we have previously shown to be much less sensitive to nitric oxide-induced damage, did not show ultrastructural changes. DNA analysis by flow cytometry of glial cells treated with nitric oxide supported the apparent necrotic-type death in oligodendrocytes. Double staining of oligodendrocytes, using Hoechst 33342 and propidium iodide for the simultaneous assessment of both apoptotic and necrotic cells, demonstrated that, while the proportion of dead cells increased with time and increasing concentrations of nitric oxide, the death was due to necrosis and not apoptosis. In this study, we demonstrate that direct exposure to soluble nitric oxide, produced in vitro from a nitric oxide donor chemical, ultimately kills oligodendrocytes by necrosis. Microglia and astrocytes maintain DNA and organelle integrity when exposed to exogenous nitric oxide.

Nitric oxide as a potential pathological mechanism in demyelination: its differential effects on primary glial cells in vitro

Because we believe that macrophage-derived nitric oxide contributes to pathology of demyelinating diseases, we have determined the differential effects of nitric oxide on primary rat glial cells in vitro. Enriched cultures of microglia, astrocytes and oligodendrocytes were treated with S-nitroso,N-acetyl-DL-penicillamine, a nitric oxide-releasing chemical. There was a significantly decreased function of one of the ferrosulfur-containing mitochondrial enzymes after S-nitroso,N-acetyl-DL-penicillamine/nitric oxide treatment in oligodendrocytes and astrocytes compared to microglia, which were much less sensitive to S-nitroso,N-acetyl-DL-penicillamine/nitric oxide at all concentrations. At 0.5 mM S-nitroso,N-acetyl-DL-penicillamine/nitric oxide, astrocytes and oligodendrocytes suffered a 40% loss in succinate dehydrogenase activity, while microglia were unaffected. A control non-ferrosulfur-containing mitochondrial enzyme, isocitrate dehydrogenase, was not affected in any glial cell type. Although the per cent of mitochondrial damage in oligodendrocytes and astrocytes was the same for all concentrations of S-nitroso,N-acetyl-DL-penicillamine/nitric oxide, significant cell death occurred in oligodendrocytes at 1.0 mM; at this concentration there was no significant killing of microglia or astrocytes. Furthermore, at a 0.5 mM concentration of S-nitroso,N-acetyl-DL-penicillamine/nitric oxide, which inhibited mitochondrial respiration but did not kill oligodendrocytes, significant changes in oligodendrocyte morphology (e.g. retraction of processes) occurred. Morphological changes were not seen in microglia and astrocytes at any concentration of S-nitroso,N-acetyl-DL-penicillamine/nitric oxide. In addition, oligodendrocytes were more sensitive to S-nitroso,N-acetyl-DL-penicillamine/nitric oxide-induced single stranded DNA breaks than microglia or astrocytes. The mitochondrial damage was attributable to nitric oxide since N-acetyl-DL-penicillamine had no effect. Oxyhemoglobin, which competitively inhibits toxic effects of nitric oxide, protected these glial cells from mitochondrial damage, single stranded breaks in DNA and cell death in a time- and dose-dependent manner. Once again, oligodendrocytes were less easily rescued from nitric oxide effects by oxyhemoglobin than were astrocytes, suggesting greater vulnerability of the myelin-producing cell to nitric oxide. These findings suggest that there is differential sensitivity of glial cells to nitric oxide. Although oligodendrocytes and astrocytes are equally susceptible to nitric oxide-induced mitochondrial damage, oligodendrocytes are more sensitive to nitric oxide-induced single stranded DNA breaks, morphological changes and cell death. Compared to both oligodendrocytes and astrocytes, microglia, nitric oxide-producing cells, are resistant to nitric oxide-induced damage.

Neurotransmitters and cytokines in CNS pathology

In summary, we have demonstrated an in vitro model for oligodendrocyte cell death that may be relevant to events in formation of lesions in MS. It involves cell contact to oligodendrocytes with activated, viable microglia (or inflammatory macrophages), surface TNF-alpha, surface adhesion molecules, and production of NO. Precise mechanisms of TNF-alpha and ICAM-1/LFA-1 participation and the nature of the susceptibility of the oligodendrocyte are currently being studied.

Increased generation of superoxide radicals in the blood of MS patients

Increased generation of superoxide radical (O2-) in the blood stimulated with phorbol myristate acetate (PMA) has been found in multiple sclerosis (MS) patients. All the subjects studied were non-smokers and received the same hospital diet. In the MS group treated with prednisone superoxide radical generation was lower than in untreated patients, but was still above the level of O2- generation in controls. Plasma lipid peroxidation products, measured as thiobarbituric-reactive substances, were slightly elevated in both prednisone treated and non-treated MS patients in comparison with controls. Erythrocyte superoxide dismutase activity (SOD) was at the same level in MS and control groups. These results suggest that increased generation of reactive oxygen species may occur in MS patients during acute relapse. This phenomenon may be involved in the pathomechanism of demyelinating disorders.

In vitro lipid peroxidation of human serum catalyzed by cupric ion: antioxidant rather than prooxidant role of ascorbate

The dual role of ascorbate as an antioxidant and a prooxidant has been clearly documented in the literature. Ascorbate acts as an antioxidant by protecting human serum from lipid peroxidation induced by azo dye-generated free radicals. On the other hand, ascorbate is readily oxidized in the presence of transition metal ions, (especially cupric ion) and accelerates lipid peroxidation in tissue homogenates by producing free radicals. Interestingly, we observed an antioxidant rather than an expected prooxidant role of ascorbate when human serum supplemented with 1.2mmol/L ascorbate underwent lipid peroxidations initiated by 2mmol/L copper sulfate. The antioxidant role of ascorbate was confirmed by studying the conventional thiobarbituric acid reactive substances (TBARS) as well as by observing the protective effect of ascorbate on the copper-induced peroxidation of unsaturated and polyunsaturated fatty acids. The antioxidation protection provided by ascorbate was comparable to that of equimolar alpha-tocopherol when incubated for 24h. However, lipid peroxidation products were lower in serum supplemented with alpha-tocopherol after 48h of incubation. This effect may be attributed to the binding of copper by plpha-tocopherol after serum proteins, thus preventing direct interaction between cupric ions and ascorbate. This proposed mechanism is based on the observation that the concentration of ascorbate decreased more slowly in serum than in phosphate buffer at physiological pH. Our results also indicate an outstanding anti-oxidant property of human serum due to the chelation of transition metal ions (even at high concentrations) by various serum proteins.

Increased cerebrospinal fluid protein and lipid peroxidation products in patients with cerebral malaria

Membrane lipid peroxidation by reactive oxygen species leading to increased capillary permeability is considered an important event in the pathogenesis of severe malaria. A significant decrease in plasma albumin and increases in cerebrospinal fluid (CSF) protein and malondialdehyde (MDA) were observed in 73 patients with cerebral malaria, compared to values in 23 control patients. The greatest effect was noticed in the most severely ill patients. The ratio of CSF protein to plasma albumin was increased in the patients compared to the controls, and in fatal cases of cerebral malaria compared to non-fatal cases. Brain necropsies showed oedema, fibrin deposits and mononuclear cell infiltration. It is proposed that cerebral oedema due to enhanced permeability of vascular endothelium induced by increased lipid peroxidation plays a crucial role in the causation of cerebral malaria.

Natural and induced cytotoxicity of oligodendrocytes by microglia is inhibitable by TGF beta

Blood macrophages and brain macrophages (microglia) have been implicated in demyelination and destruction of the oligodendrocyte in multiple sclerosis (MS), a disease affecting primarily white matter of the central nervous system (CNS). In this study, we demonstrate that at high effector to target cell ratios, normal rat microglia exhibit a natural cytotoxicity against normal rat oligodendrocytes in vitro. The killing is not mediated by the release of soluble factors. The cytotoxic activity is upregulated by pretreatment of microglia with interferon gamma (IFN gamma) or phorbol myristate acetate (PMA). Both the natural and induced cytotoxicities are inhibitable by transforming growth factor beta (TGF beta). The increase in numbers and apposition of primed or activated microglia to oligodendrocytes in MS lesions may give rise to natural or induced killing from which oligodendrocytes may be protected by TGF beta.

High dose antioxidant supplementation to MS patients. Effects on glutathione peroxidase, clinical safety, and absorption of selenium

High-dose antioxidant supplementation has recently been recommended for multiple sclerosis (MS) patients. This study tests the clinical safety, the glutathione peroxidase (GSH-px) activity, and the absorption of selenium during such supplementation. Eighteen MS patients were given 6 tablets especially made for this study, equivalent to 6 mg sodium selenite, 2 g vitamin C, and 480 mg vitamin E a day for five wk. GSH-px, which was lower than in non-MS controls before the start of treatment, increased fivefold during 5 wk of treatment. Side effects were scarce. Ten MS patients were subjected to a 24-h selenium absorption study after ingestion of 2 active tablets, equivalent to 2 mg sodium selenite. Selenium, which was low initially, increased 24% during the first 3 h and then stabilized. It is concluded that the tested antioxidant treatment seems to be safe and that MS patients have low GSH-px, which may be increased by the tested antioxidant treatment.

Elevated lipid peroxidation products and depleted transferrin levels in the plasma of kidney transplant recipients

Lipid peroxidation products were measured in the plasma of 24 kidney transplant patients and 12 healthy volunteers (controls) by: (1) 2-thiobarbituric acid assay and (2) the intensity of fluorescence products of malonaldehyde cross-linked proteins. Plasma levels of creatinine, ceruloplasmin, transferrin, prealbumin, albumin and total protein were also measured. Elevated lipid peroxidation products and lowered transferrin levels were observed in transplant patients compared to controls. Ceruloplasmin levels were slightly but significantly elevated in recent transplant recipients (less than 6 months, n = 12, Group A) while no difference was observed between older transplant recipients (greater than 6 months, n = 12, Group B) and controls. Serum, creatinine levels were also slightly but significantly elevated in both groups of patients compared to controls. Serum prealbumin, albumin and total protein levels in both groups of transplant recipients were not different from controls or reference range values.

Serum selenium concentration, glutathione peroxidase activity and lipid peroxides in a co-twin control study on multiple sclerosis

Serum selenium concentration, glutathione peroxidase activity and lipid peroxides were determined in patients with multiple sclerosis (MS). The series consisted of 13 same-sexed twin pairs derived from the Finnish Twin Cohort of 15,815 pairs. Fourteen subjects had a definite and 1 a probable MS, and their 11 co-twins showed no evidence of central nervous system disease. No statistical differences were observed, but the 3 patients with active progressive MS had a higher mean level of lipid peroxides than the rest of the patients. We suggest that serum lipid peroxidation may be involved in the activity of MS.

Measurement of free radical scavengers in the spinal cord of rats with experimental autoimmune encephalomyelitis

Antioxidants (ascorbic acid, glutathione, cysteine, alpha-tocopherol) and uric acid were measured using two high-pressure liquid chromatographic methods in 3 regions (cervical, thoracic, lumbar) of the spinal cord and in blood of Lewis rats during the attack and recovery of experimental autoimmune encephalomyelitis (EAE). Uric acid, which is thought to be a marker of free radical release, was greatly increased and glutathione correspondingly decreased in lumbar and thoracic regions. Cysteine and ascorbic acid were practically unchanged, whereas alpha-tocopherol was significantly increased during attack and recovery. Results, which could have therapeutic implications, generally support the hypothesis that free radicals are released during EAE.

In vitro study of mediators of inflammation in multiple sclerosis

Prostaglandin E levels have previously been demonstrated to be elevated in multiple sclerosis (MS). We have further investigated other products of activated macrophages related to inflammation. We report here on prostaglandin E and its relationship to interleukin 1, tumor necrosis factor, and leukotriene B4 produced by macrophages from blood and cerebrospinal fluid of MS patients and controls in vitro. Interleukin and tumor necrosis factor are elevated significantly after stimulation in MS, while leukotriene B4 production by blood macrophages is depressed compared to other neurological disease and normal healthy controls. In 40% of MS patients tested, peripheral blood macrophages spontaneously produced elevated levels of interleukin 1. All mediators of inflammation are produced in increased amounts by MS cerebrospinal fluid leukocytes after stimulation. Macrophages from MS blood are not as sensitive as controls to nonsteroidal inhibitors specific for lipoxygenase or cyclo-oxygenase pathways. Positive correlations of elevations in production of such mediators of inflammation as prostaglandin E, interleukin 1, and tumor necrosis factor in MS were significant. Elevated production of these mediators in combination with insensitivity to inhibitors of inflammation suggests a role for activated macrophages in the demyelination process.

Free malondialdehyde determination in human plasma by high-performance liquid chromatography

A high-performance liquid chromatographic method was developed for quantification of malondialdehyde (MDA) in human plasma. Deproteinized samples were injected onto a Waters carbohydrate analysis column which was eluted with 20% (v/v) 0.03 M Tris buffer, pH 7.4, in acetonitrile. Peak absorbancy was measured at 267 nm. In contrast to data already published, we did not detect any free MDA in normal human plasma. This suggests that the classical thiobarbituric acid test is not suitable for the determination of MDA in human plasma.