ANTIOXIDANT EFFECTS OF TAURINE, VITAMIN C, AND VITAMIN E ON OXIDATIVE DAMAGE IN HIPPOCAMPUS CAUSED BY THE ADMINISTRATION OF 3-NITROPROPIONIC ACID IN RATS

Effects of Moringa oleifera leaves extract, vitamin C, and taurine co-exposures on calcium and metallothionein levels, oxidative stress, and gill histopathological changes in Clarias gariepinus exposed to sub-lethal cadmium

Cadmium aquatic environmental pollution poses great threats to fish and their would-be consumers. The present work investigated the effects of ethyl acetate extract of Moringa oleifera leaves (EAEMOL), vitamin C, and taurine co-exposures on calcium and metallothionein levels, oxidative stress, and gill histopathological changes in Clarias gariepinus exposed to sub-lethal cadmium (CdCl₂) for 28 days. Fish were exposed to CdCl₂ only (1.048 mg/L) as well as co-exposed with EAEMOL (20 mg/L), vitamin C (5 mg/L), and taurine (5 mg/L) separately. There was significant (p < 0.05) deterioration in fish water quality with increasing exposure period but no significant (p > 0.05) changes occurred between the exposed groups. However, the co-exposure of EAEMOL, vitamin C, and taurine did not significantly (p > 0.05) improve the CdCl₂-induced fish water quality deterioration. Sub-lethal exposure to CdCl₂ only caused significant (p < 0.05) increase in the serum malondialdehyde (MDA) and liver metallothionein (MT) levels with significant (p < 0.05) decrease in serum catalase activity only. However, EAEMOL, vitamin C, and taurine co-exposures did not significantly (p > 0.05) improve the MDA, superoxide dismutase, catalase, and glutathione activities, as well as MT and calcium (Ca²⁺) levels, condition factor (CF), hepatosomatic index (HSI), and gill histopathological changes induced by the CdCl₂ exposure. Similarly, none of the present exposures, CdCl2 only or its co-exposures with EAEMOL, vitamin C, and taurine significantly (p > 0.05) altered the normal functioning of the gills despite the observed histopathological changes based on the degree of tissue change protocol. Therefore, EAEMOL, vitamin C, and taurine co-exposures, as administered in the present case, did not considerably alter the physicochemical parameters of the experimental fish water. However, outside significantly (p < 0.05) increasing MDA level, EAEMOL, vitamin C, and taurine co-exposures did not significantly (p > 0.05) improve the CdCl₂-induced Ca²⁺, MT, CF, HSI, and gill histopathological alterations by sub-lethal CdCl₂ exposure of C. gariepinus.

Epigallocatechin-3-gallate PEGylated poly(lactic-co-glycolic) acid nanoparticles mitigate striatal pathology and motor deficits in 3-nitropropionic acid intoxicated mice

Aim: To compare free and nanoparticle (NP)-encapsulated epigallocatechin-3-gallate (EGCG) for the treatment of Huntington's disease (HD)-like symptoms in mice. Materials & methods: EGCG was incorporated into PEGylated poly(lactic-co-glycolic) acid NPs with ascorbic acid (AA). HD-like striatal lesions and motor deficit were induced in mice by 3-nitropropionic acid-intoxication. EGCG and EGCG/AA NPs were co-administered and behavioral motor assessments and striatal histology performed after 5 days. Results: EGCG/AA NPs were significantly more effective than free EGCG in reducing motor disturbances and depression-like behavior associated with 3-nitropropionic acid toxicity. EGCG/AA NPs treatment also mitigated neuroinflammation and prevented neuronal loss. Conclusion: NP encapsulation enhances therapeutic robustness of EGCG in this model of HD symptomatology. Together with our previous findings, this highlights the potential of EGCG/AA NPs in the symptomatic treatment of neurodegenerative diseases.

Taurine Attenuates As2O3-Induced Autophagy in Cerebrum of Mouse Through Nrf2 Pathway

We previously reported that the impairment of cerebrum may relate with neurotoxicity induced by arsenic (As) exposure. In the present study, we investigated whether autophagy of the cerebrum neurons were responsible for As-induced neurotoxicity and the protective role of taurine (Tau). Forty mice were randomly divided into control group, Tau control group, As exposure group and Tau protection group. The results showed that LC3 II expression was elevated and P62 expression was lower after As exposure, whereas the effects were obviously attenuated by Tau treatment. More important, As induced increase of MDA level and decrease of Nrf2 expression were significantly inversed in protective group. In sum, autophagy inhibition might play a strong role in the neuroprotection of Tau in As-induced toxicity via Nrf2 pathway.

Methylmercury alters the number and topography of NO-synthase positive neurons in embryonic retina: Protective effect of alpha-tocopherol

Vertebrate retina has been shown to be an important target for mercury toxicity and very studies have shown the effect of mercury on the retinal ontogenesis. The nitrergic system plays an important role in the retinal development. The current work studied the effects of methylmercury (MeHg) exposure on the NO-synthase positive neurons (NADPH-diaphorase neurons or NADPH-d+) of the chick retinal ganglion cell layer at embryonic E15 and postnatal P1 days. Retinal flat mounts were stained for NADPH-diaphorase histochemistry and mosaic properties of NADPH-d + were studied by plotting isodensity maps and employing density recovery profile technique. It was also evaluated the protective effect of alpha-tocopherol treatment on retinal tissues exposed to MeHg. MeHg exposure decreased the density of NADPH-d + neurons and altered cell mosaic properties at E15 but had very little or no effect at P1 retinas. Alpha-tocopherol has a protective effect against MeHg exposure at E15. MeHg alterations and alpha-tocopherol protective effect in embryonic retinas were demonstrated to be at work in experimental conditions. MeHg effect in the early phases of visual system development in natural conditions might use the nitrergic pathway and supplementary diet could have a protective effect. At later stages, this mechanism seems to be naturally protected.

Neuroprotective activity of tetramethylpyrazine against 3-nitropropionic acid induced Huntington's disease-like symptoms in rats

Huntington's disease (HD) is an autosomal neurodegenerative disease characterized by chorea, dystonia, motor ataxia, cognitive decline and psychiatric disorders with gradual loss of nerve cells and has no existing cure for the disease. In the present study, a mitochondrial toxin, 3-nitropropionic acid (3-NP) is used to induce HD like symptoms in rats. Tetramethylpyrazine is one of the active ingredients of Chuan Xiong which was reported to have neurotrophic and neuroprotective activities. The present study was designed to evaluate the role of TMP on 3-NP induced behavioral, biochemical, neurochemical, and histological alterations in the different regions of the brain. Animals were pretreated with normal saline/TMP for 7 days. From 8th day, the treatment groups were co-administered with 3-NP (10 mg/kg, i.p) and continued to the 21st day of the treatment protocol. At the end of the study, we found that the TMP improved all the behavioral performances of 3-NP induced neurotoxic rats, significantly. Further, oxidative stress parameters (lipid peroxidation, reduced glutathione, catalase, and superoxide dismutase), succinate dehydrogenase enzyme, and neurochemical (GABA and glutamate) estimations were done in the brain homogenate. In our study, the treatment with TMP ameliorated the 3-NP induced alterations, in the biochemical and neurochemical parameter in the brain homogenate, dose-dependently. The protective role of TMP further confirmed by measuring the lesion area with the 2,3,5-triphenyltetrazolium chloride staining of the brain slices and histopathological alteration in the hippocampus (CA1 and CA3) and striatal regions of the brain. Hence, the present findings suggest that the protective role of TMP against 3-NP induced behavioral, biochemical, neurochemical, and histological alterations in rats.

Protective effect of Convolvulus pluricaulis standardized extract and its fractions against 3-nitropropionic acid-induced neurotoxicity in rats

CONTEXT

Convolvulus pluricaulis Chois. (Convolvulaceae), a well-known Ayurvedic "Medhya Rasayana" (nervine tonic), is extensively used for different central nervous system (CNS) disorders.

OBJECTIVE

The objective of this study was to evaluate the protective effect of standardized hydro-methanol extract of C. pluricaulis (CPE) and its fractions, namely ethyl acetate (EAE), butanol (BE), and aqueous (AE), against 3-nitropropionic acid (3-NP) induced neurotoxicity in rats.

MATERIALS AND METHODS

The extract of the whole plant was standardized on the basis of scopoletin content (0.014%) using thin layer chromatography densitometric analysis. CPE (100 and 200 mg/kg) and its fractions, namely EAE (15 and 30 mg/kg), BE (25 and 50 mg/kg), and AE (50 and 100 mg/kg) were administered orally for 20 d. Their protective effect against 3-NP (10 mg/kg, i.p. for 14 d) was assessed by the effect on various behavioral parameters, namely body weight, locomotor activity, grip strength, gait pattern, and the effect on cognitive dysfunction. Biochemical parameters for oxidative damage were also assessed in the striatum and cortex regions of the brain.

RESULTS

Administration of 3-NP induced HD-like symptoms that were indicated by reduced body weight, locomotor activity, memory, grip strength, and oxidative defense. CPE (200 mg/kg), EAE (30 mg/kg), and BE (50 mg/kg) significantly (p < 0.001) attenuated 3-NP induced reduction in locomotor activity, grip strength, memory, body weight, and oxidative defense in comparison with 3-NP-treated animals on 10 and 15 d.

CONCLUSION

The present study suggested that CPE has a protective action against 3-NP-induced neurotoxicity and can be further explored for its efficacy against Huntington's disease.

Neuroprotective effect of hemeoxygenase-1/glycogen synthase kinase-3β modulators in 3-nitropropionic acid-induced neurotoxicity in rats

The present study has been designed to explore the possible interaction between hemeoxygenase-1 (HO-1) and glycogen synthase kinase-3β (GSK-3β) pathway in 3-nitropropionic acid (3-NP)-induced neurotoxicity in rats. 3-NP produces neurotoxicity by inhibition of the mitochondrial complex II (enzyme succinate dehydrogenase) and by sensitizing the N-methyl-D-aspartate receptor. Recent studies have reported the therapeutic potential of HO-1/GSK-3β modulators in different neurodegenerative disorders. However, their exact role is yet to be explored. The present study is an attempt to investigate the effect of pharmacological modulation of HO-1/GSK-3β pathway against 3-NP-induced behavioral, biochemical and molecular alterations in rat. Behavioral observation, oxidative stress, pro-inflammatory [tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β)], HO-1 and GSK-3β activity were evaluated post 3-NP treatment. Findings of the present study demonstrate a significant alteration in the locomotor activity, motor coordination, oxidative burden (increased lipid peroxidation, nitrite concentration and decreased endogenous antioxidants), pro-inflammatory mediators [TNF-α, IL-1β], HO-1 and GSK-3β activity in 3-NP-treated animals. Further, administration of hemin (10- and 30-mg/kg; i.p.) and lithium chloride (LiCl) (25- and 50-mg/kg; i.p.) prevented the alteration in body weight, motor impairments, oxidative stress and cellular markers. In addition, combined administration of hemin (10-mg/kg) and LiCl (25-mg/kg) showed synergistic effect on 3-NP-treated rats. Pretreatment with Tin (IV) protoporphyrin (40 μM/kg), HO-1 inhibitor reversed the beneficial effect of LiCl and hemin. Outcomes of the present study suggest that HO-1 and GSK-3β enzymes are involved in the pathophysiology of HD. The modulators of both the pathways might be used as adjuvants or prophylactic therapy for the treatment of HD-like symptoms.

Ebselen protects against behavioral and biochemical toxicities induced by 3-nitropropionic acid in rats: correlations between motor coordination, reactive species levels, and succinate dehydrogenase activity

The protective effect of ebselen was investigated against 3-nitropropionic acid (3-NP)-induced behavioral and biochemical toxicities in rats. Ebselen (10 or 25 mg/kg, intragastrically) was administered to rats 30 min before 3-NP (20 mg/kg, intraperitoneally) once a day for a period of 4 days. Locomotor activity, motor coordination, and body weight gain were determined. The striatal content of reactive oxygen species (ROS), reduced glutathione (GSH), ascorbic acid (AA), and protein carbonyl as well as catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione-S-transferase (GST) activities was determined 24 h after the last dose of 3-NP. Na(+)/ K(+)-ATPase, succinate dehydrogenase (SDH), and δ-aminolevulinic dehydratase (δ-ALA-D) activities were also determined. The results demonstrated that ebselen at a dose of 25 mg/kg, but not at 10 mg/kg, protected against (1) a decrease in locomotor activity, motor coordination impairment, and body weight loss; (2) striatal oxidative damage, which was characterized by an increase in ROS levels, protein carbonyl content, and GR activity, an inhibition of CAT and GPx activities, and a decrease in GSH levels; and (3) an inhibition of SDH and Na(+)/K(+)-ATPase activities, induced by 3-NP. GST activity and AA levels were not modified by ebselen or 3-NP. Ebselen was not effective against the inhibition of δ-ALA-D activity induced by 3-NP. The results revealed a significant correlation between SDH activity and ROS levels, and SDH activity and latency to fall (rotarod test). The present study highlighted the protective effect of ebselen against 3-NP-induced toxicity in rats.

Modulation of RhoGTPases improves the behavioral phenotype and reverses astrocytic deficits in a mouse model of Rett syndrome

RhoGTPases are crucial molecules in neuronal plasticity and cognition, as confirmed by their role in non-syndromic mental retardation. Activation of brain RhoGTPases by the bacterial cytotoxic necrotizing factor 1 (CNF1) reshapes the actin cytoskeleton and enhances neurotransmission and synaptic plasticity in mouse brains. We evaluated the effects of a single CNF1 intracerebroventricular inoculation in a mouse model of Rett syndrome (RTT), a rare neurodevelopmental disorder and a genetic cause of mental retardation, for which no effective therapy is available. Fully symptomatic MeCP2-308 male mice were evaluated in a battery of tests specifically tailored to detect RTT-related impairments. At the end of behavioral testing, brain sections were immunohistochemically characterized. Magnetic resonance imaging and spectroscopy (MRS) were also applied to assess morphological and metabolic brain changes. The CNF1 administration markedly improved the behavioral phenotype of MeCP2-308 mice. CNF1 also dramatically reversed the evident signs of atrophy in astrocytes of mutant mice and restored wt-like levels of this cell population. A partial rescue of the overexpression of IL-6 cytokine was also observed in RTT brains. CNF1-induced brain metabolic changes detected by MRS analysis involved markers of glial integrity and bioenergetics, and point to improved mitochondria functionality in CNF1-treated mice. These results clearly indicate that modulation of brain RhoGTPases by CNF1 may constitute a totally innovative therapeutic approach for RTT and, possibly, for other disorders associated with mental retardation.

Ketones prevent synaptic dysfunction induced by mitochondrial respiratory complex inhibitors

Ketones have previously shown beneficial effects in models of neurodegenerative disorders, particularly against associated mitochondrial dysfunction and cognitive impairment. However, evidence of a synaptic protective effect of ketones remains lacking. We tested the effects of ketones on synaptic impairment induced by mitochondrial respiratory complex (MRC) inhibitors using electrophysiological, reactive oxygen species (ROS) imaging and biochemical techniques. MRC inhibitors dose-dependently suppressed both population spike (PS) and field potential amplitudes in the CA1 hippocampus. Pre-treatment with ketones strongly prevented changes in the PS, whereas partial protection was seen in the field potential. Rotenone (Rot; 100 nmol/L), a MRC I inhibitor, suppressed synaptic function without altering ROS levels and PS depression by Rot was unaffected by antioxidants. In contrast, antioxidant-induced PS recovery against the MRC II inhibitor 3-nitropropionic acid (3-NP; 1 mmol/L) was similar to the synaptic protective effects of ketones. Ketones also suppressed ROS generation induced by 3-NP. Finally, ketones reversed the decreases in ATP levels caused by Rot and 3-NP. In summary, our data demonstrate that ketones can preserve synaptic function in CA1 hippocampus induced by MRC dysfunction, likely through an antioxidant action and enhanced ATP generation.

Protective effects of epigallocatechin gallate following 3-nitropropionic acid-induced brain damage: possible nitric oxide mechanisms

INTRODUCTION

The role of oxidative stress has been well known in neurodegenerative disorders. 3-Nitropropionic acid (3-NP) is a plant-based mycotoxin that produces HD like symptoms in animals. Oxidative stress and nitric oxide mechanisms have been recently proposed in the 3-NP-induced neurotoxicity. Epigallocatechin gallate (EGCG) is one of the major components of green tea, known for its potent antioxidant activity. Besides, neuroprotective effect of EGCG has also been suggested in different experimental models.

OBJECTIVES

The present study has been designed to examine possible effect of EGCG against 3-NP induced behavioral, oxidative stress, mitochondrial dysfunction, and striatal damage in rats and its possible interaction with nitric oxide modulators.

MATERIAL AND METHODS

Systemic 3-NP (10 mg/kg) administration for 14 days significantly reduced locomotor activity, body weight, grip strength, oxidative defense (raised levels of lipid peroxidation, nitrite concentration, depletion of antioxidant enzyme), and mitochondrial enzymes activity in striatum, cortex, and hippocampal regions of the brain.

RESULTS

Fourteen days of EGCG pretreatment (10, 20, and 40 mg/kg) significantly attenuated behavioral alterations, oxidative damage, mitochondrial complex enzymes dysfunction, and striatal damage in 3-NP-treated animals. L-arginine (50 mg/kg) pretreatment with sub-effective dose of EGCG (20 mg/kg) significantly reversed the protective behavioral, biochemical, cellular, and histological effects of EGCG. However, L-NAME (10 mg/kg) pretreatment with EGCG (20 mg/kg) significantly potentiated the protective effect of EGCG which was significant as compared to their effect per se.

CONCLUSION

The present study shows that EGCG attenuate 3-NP-induced neurotoxicity, and nitric oxide modulation might be involved in its protective action.

Trolox ameliorates 3-nitropropionic acid-induced neurotoxicity in rats

3-nitropropionic acid (3-NPA) is a naturally occurring neurotoxin produced by legumes of the genus Astragalus and Arthrium fungi. Acute exposure to 3-NPA results in striatal astrocytic death and variety of behavior dysfunction in rats. Oxidative stress has been reported to play an important role in 3-NPA-induced neurotoxicity. Trolox is a potent free radical chain breaking antioxidant which has been shown to restore structure and function of the nervous system following oxidative stress. This rapid and efficient antioxidant property of trolox was attributed to its enhanced water solubility as compared with alpha-tocopherol. This investigation was aimed to study the effect of trolox against 3-NPA-induced neurotoxicity in female Wistar rats. The animals received trolox (0, 40 mg, 80 mg and 160 mg/kg, orally) daily for 7 days. 3-NPA (25mg/kg, i.p.) was administered daily 30 min after trolox for the same duration. One additional group of rats served as control (vehicle only). On day 8, the animals were observed for neurobehavioral performance. Immediately after behavioral studies, the animal's brains were dissected out for histological studies. Lesions in the striatal dopaminergic neurons were assessed by immunohistochemical method using tyrosine hydroxylase immunostaining. Administration of 3-NPA alone caused significant depletion of striatal dopamine and glutathione, whereas, the levels of thiobarbituric acid reactive substance (TBARS) and nitric oxide (NO) were significantly increased suggesting an elevated level of oxidative stress. Trolox significantly and dose-dependently protected animals against 3-NPA-induced neurobehavioral, neurochemical and structural abnormalities. These results clearly suggest that protective effect of trolox against 3-NPA-induced neurotoxicity is mediated through its free radical scavenging activity.

EFFECT OF COLLOIDAL SILVER AGAINST THE CYTOTOXICITY OF HYDROGEN PEROXIDE AND NAPHTHAZARIN ON PRIMARY CULTURED CORTICAL ASTROCYTES

One major pathogenesis in degenerative disorders of the central nervous system (CNS), including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and ischemia, is the oxidative stress induced by reactive oxygen species (ROS). The present study investigated the protective effect of colloidal silver, which is widely marketed as a dietary supplement for diseases like diabetes, AIDS, cancer, and various infections, upon the oxidative brain damage induced by H(2)O(2) or naphthazarin treatment. LDH release from primary cultured astrocytes was enhanced by naphthazarin treatment, and this elevation of the LDH concentration in medium was blocked by colloidal silver treatment. However, hydrogen peroxide was little affected by the colloidal silver. Fluorescence of DCF (peroxides) increased in astrocytes incubated with hydrogen peroxide or naphthazarin compared to the control. When exposed to naphthazarin-induced cells, ROS formation appeared to be reduced by colloidal silver. However, intracellular ROS formation in hydrogen peroxide-treated cells slightly reduced by colloidal silver. These results suggest that colloidal silver has a protective activity against the oxidative stress induced by naphthazarin, but not by hydrogen peroxide.

Heme oxygenase-1 induction prevents neuronal damage triggered during mitochondrial inhibition: role of CO and bilirubin

Heme oxygenase (HO) catalyzes the breakdown of heme to iron, carbon monoxide (CO), and biliverdin, the latter being further reduced to bilirubin (BR). A protective role of the inducible isoform, HO-1, has been described in pathological conditions associated with reactive oxygen species (ROS) and oxidative damage. The aim of this study was to investigate the role of HO-1 in the neurotoxicity induced by the mitochondrial toxin 3-nitropropionic acid (3-NP) in primary cultures of cerebellar granule neurons (CGNs). Toxicity of 3-NP is associated with ROS production, and this metabolic toxin has been used to mimic pathological conditions such as Huntington's disease. We found that cell death caused by 3-NP exposure was exacerbated by inhibition of HO with tin mesoporphyrin (SnMP). In addition, HO-1 up-regulation induced by the exposure to cobalt protoporphyrin (CoPP) before the incubation with 3-NP, prevented the cell death and the increase in ROS induced by 3-NP. Interestingly, addition of SnMP to CoPP-pretreated CGNs exposed to 3-NP, abolished the protective effect of CoPP suggesting that HO activity was responsible for this protective effect. This was additionally supported by the fact that CORM-2, a CO-releasing molecule, and BR, were able to protect against cell death and the increase in ROS induced by 3-NP. Our data clearly show that HO-1 elicits in CGNs a neuroprotective action against the neurotoxicity of 3-NP and that CO and BR may be involved, at least in part, in this protective effect. The present results increase our knowledge about the role of HO-1 in neuropathological conditions.

Protective efficiacy of taurine against pulmonary edema progression: experimental study

Re-expansion pulmonary edema (RPE) is an acute, rare and potentially lethal complication [1,2]. Its beginning is sudden and dramatic. The mechanism is not yet fully understood [1]. Some authors suggest that it may occur after rapid re-inflation of a collapsed lung [1]. It was reported by other authors that it may relate to surfactant depletion or may result from hypoxic capillary damage, leading to increased capillary permeability [1,3]. In RPE, unilateral lung injury is initiated by cytotoxic oxygen metabolites and temporally associated with an influx of polymorphonuclear neutrophils [1]. These toxic oxygen products are the results of re-oxygenation of a collapsed lung. Treatment of re-expansion pulmonary edema is basically preventive [4].

Oxidative stress modulates membrane bound ATPases in brain regions of PCB (Aroclor 1254) exposed rats: Protective role of α-tocopherol

Polychlorinated biphenyls (PCBs) are a class of widely dispersed and environmentally persistent organic compounds. PCBs exhibit a wide range of toxicological effects including neurotoxicity. Vitamin E (alpha-tocopherol) is an important lipid soluble antioxidant placed in a special region of membranes. Large amounts of energy are required to maintain the signaling activities of the cells in the central nervous system (CNS). Membrane proteins that control ion gradients across organellar and plasma membranes appear to be particularly susceptible to oxidation-induced changes. The aim of this study was to determine the protective role of vitamin E on Aroclor 1254 induced modulation in membrane bound ATPases in brain regions of rats. One group of rats received corn oil as vehicle for 30days as control. The other group of rats were administered Aroclor 1254 at a dose of 2mgkg(-1) bwday(-1) intraperitoneally for 30days. One group of rats received vitamin E (50mgkg(-1) bwday(-1)) orally simultaneously with Aroclor 1254 for 30days. After 30days, the animals were euthanized and the brain was dissected to hypothalamus and hippocampus to determine the following parameters. Hydrogen peroxide (H2O2), Lipid peroxidation (LPO) and the activities of Na+K+-ATPase, Ca2+-ATPase and Mg2+-ATPase were determined. Reduced glutathione (GSH) level was also determined. Activities of all the enzymes were decreased while an increase in H2O2 and LPO were observed in selected brain regions of PCB treated animals. Simultaneous vitamin E treatment in PCB exposed animals restored all the parameters significantly. These results suggest that oxidative stress is involved in the inhibitory effect of PCB (Aroclor 1254) on membrane bound ATPases in selected brain regions. alpha-tocopherol acts against PCB induced neurotoxicity by decreasing oxidative stress.

PCB (Aroclor 1254) enhances oxidative damage in rat brain regions: protective role of ascorbic acid

PCBs are one of the environmental toxicants and neurotoxic compounds which induce the production of free radicals leading to oxidative stress. Oxidative stress is a contributing factor to alteration caused in neurodegenerative processes. The ability of Vitamin C to retard oxidative processes has been recognized for many years. Therefore, the present experiment was carried out to determine the antioxidant role of ascorbate on Aroclor 1254 induced oxidative stress in brain regions of albino rats. One group of rats received corn oil as vehicle for 30 days as control. The other group of rats were administered Aroclor 1254 at a dose of 2 mg/kg bw/day intraperitoneally for 30 days. One group of rats received Vitamin C (100 mg/kg bw/day) orally simultaneously with Aroclor 1254 for 30 days. The brain was dissected to cerebral cortex (Cc), cerebellum (C) and hippocampus (H). Enzymatic and non-enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST), reduced glutathione (GSH) and Vitamin C were estimated. Hydrogen peroxide (H(2)O(2)), lipid peroxidation (LPO) and acetylcholine esterase activity (AchE) were determined. Activities of SOD, CAT, GPx, GST, AchE and the concentration of GSH, Vitamin C were decreased while an increase in H(2)O(2) and LPO were observed in brain regions of PCB treated animals. Vitamin C administration retrieved all the parameters except GST, significantly. These results suggest that PCB induces oxidative stress in rat brain by decreasing the activities of antioxidant enzymes, which can be protected by Vitamin C treatment.

Oxidative damage in Huntington's disease pathogenesis

Huntington's disease (HD) is a devastating neurodegenerative disorder characterized by the progressive development of involuntary choreiform movements, cognitive impairment, neuropsychiatric symptoms, and premature death. These phenotypes reflect neuronal dysfunction and ultimately death in selected brain regions, the striatum and cerebral cortex being principal targets. The genetic mutation responsible for the HD phenotype is known, and its protein product, mutant huntingtin (mhtt), identified. HD is one of several "triplet repeat" diseases, in which abnormal expansions in trinucleotide repeat domains lead to elongated polyglutamine stretches in the affected gene's protein product. Mutant htt-mediated toxicity in the brain disrupts a number of vital cellular processes in the course of disease progression, including energy metabolism, gene transcription, clathrin-dependent endocytosis, intraneuronal trafficking, and postsynaptic signaling, but the crucial initiation mechanism induced by mhtt is still unclear. A large body of evidence, however, supports an early and critical involvement of defects in mitochondrial function and CNS energy metabolism in the disease trigger. Thus, downstream death-effector mechanisms, including excitotoxicity, apoptosis, and oxidative damage, have been implicated in the mechanism of selective neuronal damage in HD. Here we review the current evidence supporting a role for oxidative damage in the etiology of neuronal damage and degeneration in HD.

Effect of N-acetylcysteine, allopurinol and vitamin E on jaundice-induced brain oxidative stress in rats

We examined the possible protective effect of certain antioxidants (N-acetylcysteine, allopurinol and vitamin E) against the oxidative stress of brain tissue induced by experimental obstructive jaundice in rats. Thirty-six male Wistar rats were randomly divided into six groups; group I control, group II sham operated, group III bile duct ligated and groups IV, V, and VI in which the rats, after bile duct ligation, were given every day an intraperitoneal injection with N-acetylcysteine, allopurinol and Vit-E respectively. All rats were sacrificed on the tenth day by exsanguination and the oxidative state in samples from cortex, midbrain and cerebellum was assessed by measuring the thiol redox state and lipid peroxidation quantified by MDA measurements. The main finding was that all three antioxidants decrease lipid peroxidation in the three brain areas. Cysteine levels increased and protein thiol levels were reserved only in the group treated with N-acetylcysteine, whereas oxidized glutathione increased dramatically in the group treated with allopurinol, suggesting that each antioxidant agent had a certain influence profile on the different antioxidant defense systems. The observed effects of the antioxidants in this experimental model could also provide insight into some aspects of jaundice-induced hepatic encephalopathy in humans.

S-Allylcysteine prevents the rat from 3-nitropropionic acid-induced hyperactivity, early markers of oxidative stress and mitochondrial dysfunction

We investigated the effects of S-allylcysteine (SAC) on early behavioral alterations, striatal changes in superoxide dismutase (SOD) activity, lipid peroxidation (LP) and mitochondrial dysfunction induced by the systemic infusion of 3-nitropropionic acid (3-NPA) to rats. SAC (300 mg/kg, i.p.), given to animals 30 min before 3-NPA (30 mg/kg, i.p.), prevented the hyperkinetic pattern evoked by the toxin. In addition, 3-NPA alone produced decreased activities of manganese- (Mn-SOD) and copper/zinc-dependent superoxide dismutase (Cu,Zn-SOD), increased LP (evaluated as the formation of lipid fluorescent products) and produced mitochondrial dysfunction in the striatum (measured as decreased 3-(3,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction). In contrast, pretreatment of 3-NPA-injected rats with SAC resulted in a significant prevention of all these markers. Our findings suggest that the protective actions of SAC are related with its antioxidant properties, which in turn may be accounting for the preservation of SOD activity and primary mitochondrial tasks.

Protective effect of taurine on myocardial antioxidant status in isoprenaline-induced myocardial infarction in rats

We have examined the protective effect of taurine on the myocardial antioxidant defense system in isoprenaline (isoproterenol)-induced myocardial infarction in rats, an animal model of myocardial infarction in man. Levels of diagnostic marker enzymes in plasma, lipid peroxides and reduced glutathione, and the activity of glutathione-dependent antioxidant enzymes and anti-peroxidative enzymes in the heart tissue were determined. Intraperitoneal administration of taurine significantly prevented the isoprenaline-induced increases in the levels of alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and creatine phosphokinase in the plasma of rats. Taurine exerted an antioxidant effect against isoprenaline-induced myocardial infarction by preventing the accumulation of lipid peroxides and by maintaining the level of reduced glutathione and the activity of glutathione peroxidase, glutathione-S-transferase, catalase and superoxide dismutase at near normality. The results indicated that the cardioprotective potential of taurine was probably due to the increase of the activity of the free radical enzymes, or to a counteraction of free radicals by its antioxidant nature, or to a strengthening of myocardial membrane by its membrane stabilizing property.

Antioxidant effect of ascorbic acid on PCB (Aroclor 1254) induced oxidative stress in hypothalamus of albino rats

BACKGROUND

PCBs are one of the environmental toxicants and neurotoxic compounds which induce the production of free radicals leading to oxidative stress. Vitamin C is well known as an outstanding antioxidant. We determined the protective role of ascorbate on hypothalamic antioxidant system of Aroclor 1254 exposed rats.

METHODS

The rats were injected Aroclor 1254 at a dose of 2 mg/kg bw/day intraperitoneally for 30 days. One group of rats received vitamin C (100 mg/kg bw/day) orally simultaneously with Aroclor 1254 for 30 days. Twenty-four hours after last treatment, the animals were killed and hypothalamic region was separated from brain tissue. Enzymatic and non-enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and vitamin C were estimated. Hydrogen peroxide (H(2)O(2)), lipid peroxidation (LPO) and acetylcholine esterase (AchE) activity were determined. Serum gonadotropins such as luteinizing hormone (LH) and follicle stimulating hormone (FSH) were also assayed.

RESULTS

Activities of SOD, CAT, GPx, GR, AchE and the concentration of vitamin C were decreased while an increase in H(2)O(2) and LPO were observed in hypothalamus of PCB treated animals. LH and FSH concentrations were also decreased in serum of PCB exposed animals. Vitamin C administration retrieved all the parameters significantly except serum hormonal profiles.

CONCLUSION

PCB induces oxidative stress in hypothalamus by decreasing the activities of antioxidant enzymes, which can be protected by vitamin C treatment.

Immunohistochemical study of the distribution of sodium-dependent vitamin C transporters in adult rat brain

Sodium-dependent vitamin C transporters (SVCTs) is known to transport the reduced form of ascorbic acid into the cell, whereas the oxidized form of vitamin C (VC) is moved through a facilitative sugar transporter, such as glucose transporter (GLUT). With regard to the distribution of SVCT1 and -2 within the various organs, they were reported to be expressed in different types of cells. Especially in the central nervous system, only SVCT2 mRNA was expressed mainly in neurons and some types of neuroglial cells. However, data on the expression of SVCT proteins in the brain are scant. Therefore, we tried to develop comprehensive data on the distribution of SVCT proteins in adult rat brain by using immunohistochemical techniques for the first time. In our study, SVCT2 immunoreactivities (IRs) were intensely localized in the neurons of cerebral cortex, hippocampus, and Purkinje cells of cerebellum, and much weaker SVCT2 IRs were found in the other brain regions. Judging from double-immunohistochemical data, most of the cells expressing SVCT2 IRs were likely to be neurons or microglia, even though the cells in choroids plexus or ependymal cells around the ventricles also exhibited SVCT2 IRs. Complete mapping of the distribution of SVCT2 IRs was available by using a semiquantitative method. The subcellular localization of SVCT proteins is necessary for understanding the exact role of the protein, so the current overall mapping of SVCT IRs in the rat brain could be the basis for further studies on related subjects.

Neuroprotective effect of taurine in 3-nitropropionic acid-induced experimental animal model of Huntington's disease phenotype

An experimental animal model of Huntington's disease (HD) phenotype was induced using the mycotoxin 3-nitropropionic acid (3-NP) and was well characterized behaviorally, neurochemically, morphometrically and histologically. Administration of 3-NP caused a reduction in prepulse inhibition (PPI) of acoustic startle response, locomotor hyper- and/or hypoactivity, bilateral striatal lesions, brain oxidative stress, and decreased striatal gamma-aminobutyric acid (GABA) levels. Taurine is a semi-essential beta-amino acid that was demonstrated to have both antioxidant and GABA-A agonistic activity. In this study, treatment with taurine (200 mg/kg daily for 3 days) prior to 3-NP administration reversed both reduced PPI response and locomotor hypoactivity caused by 3-NP injection. Taurine pretreatment also caused about 2-fold increase in GABA concentration compared to 3-NP-treated animals. In addition, taurine demonstrated antioxidant activity against oxidative stress induced by 3-NP administration as evidenced by the reduced striatal malondialdehyde (MDA) and elevated striatal glutathione (GSH) levels. Histochemical examination of striatal tissue showed that prior administration of taurine ahead of 3-NP challenge significantly increased succinate dehydrogenase (SDH) activity compared to 3-NP-treated animals. Histopathological examination further affirmed the neuroprotective effect of taurine in 3-NP-induced HD in rats. Taken together, one may conclude that taurine has neuroprotective role in the current HD paradigm due, at least partly, to its indirect antioxidant effect and GABA agonistic action.