Dopamine agonist cabergoline inhibits levodopa-induced caspase activation in 6-OHDA-lesioned mice

Levodopa therapy is the gold standard for symptomatic treatment of Parkinson's disease (PD), but levodopa and/or dopamine (DA)-induced neurotoxicity have been reported in both in vitro and in vivo experimental studies. To clarify the beneficial effects of combining DA agonists with levodopa in PD, the present study examines the effects of cabergoline, a DA agonist, on the levodopa-induced abnormal increase of lipid peroxidation (LPO) and caspase activities in 6-hydroxydopamine (6-OHDA)-lesioned mice. Daily treatments of levodopa/carbidopa for 7 days beginning at 1 day after 6-OHDA i.c.v. injection increased striatal DA levels and glutathione (GSH) contents. Furthermore, a high dose of levodopa/carbidopa (50/12.5 mg/kg) enhanced LPO and caspase-3, -8, and -9 activities in 6-OHDA-lesioned mouse brain. However, when levodopa/carbidopa (50/12.5 mg/kg) was combined with cabergoline (0.25 mg/kg), the effect reduced levodopa's enhancement of caspase-3, -8, and -9 activities in the 6-OHDA-lesioned mouse brain. In addition, the GSH-increasing effect of the combined cabergoline and levodopa/carbidopa treatment was stronger than that of the levodopa/carbidopa mono-treatment. Moreover, cabergoline prevented levodopa-induced abnormal increases of LPO in 6-OHDA-lesioned mice. These results indicate that such prevention is attributable mainly to the increase in GSH content and to the inhibition of caspase activities in 6-OHDA-lesioned mice.     

Molecular basis of 6-hydroxydopamine-induced caspase activations due to increases in oxidative stress in the mouse striatum

To clarify the possible role of in the in vivo toxic effects of 6-hydroxydopamine (6-OHDA), especially caspase activations, we examined its effects on striatal lipid peroxidation (LPO) and caspase activations in 6-OHDA-lesioned mice. Both dopamine (DA) levels and DA turnover were significantly changed by the 6-OHDA i.c.v. injection compared with the pre-injection level in the striatum. In addition, the striatal glutathione (GSH) content fluctuated and was significantly decreased both at 3 and 14 days after 6-OHDA i.c.v. injection. Moreover, superoxide dismutase (SOD) activity at 7 days after 6-OHDA i.c.v. injection was transiently and significantly increased compared with the pre-injection level. The levels of thiobarbituric acid-reactive substances (TBA-RS) were significantly increased at 1, 3 and 14 days. 6-OHDA significantly increased the activities of all three caspases, except for the caspase-3 activity at 7 days throughout the experimental period compared with the pre-injection level. In conclusion, 6-OHDA-induced dopaminergic dysfunction is mainly due to caspase activations by increases in oxidative stress in the mouse striatum.     

Aggravation of 6-hydroxydopamine-induced dopaminergic lesions in metallothionein-I and -II knock-out mouse brain

The effects of two major isoforms of metallothioneins (MTs), MT-I and -II, on dopaminergic neurotoxicity of 6-hydroxydopamine (6-OHDA) were examined using intracerebroventricularly 6-OHDA-injected MT-I, II knock-out (KO) mice. The loss of dopamine neurons in the substantia nigra pars compacta induced by the 6-OHDA injection was significantly aggravated in the MT-I, II KO mice, compared with that in the 6-OHDA-injected wild-type mice. The present results, taken together with the antioxidant properties of MT-I and -II suggest that MT-I and -II exert neuroprotective effects against the dopaminergic neurotoxicity of 6-OHDA at the nigral cell body by scavenging free radicals.     

The flavanoide caffeic acid phenethyl ester blocks 6-hydroxydopamine-induced neurotoxicity

Parkinson's disease (PD) is a neurodegenerative disorder characterized by progressive loss of dopaminergic (DA) neurons of the substantia nigra pars compacta. 6-Hydroxydopamine (6-OHDA) is specific to dopaminergic neurons in intrastriatal rodent models. It induces neuronal death either via uncoupling mitochondrial oxidative phosphorylation resulting in energy deprivation or alternatively, is associated with its ability to produce hydrogen peroxide, hydroxyl and superoxide radicals. Caffeic acid phenethyl ester (CAPE), an antioxidant flavanoid, has antiviral, anti-inflammatory, antioxidant, and immunomodulatory properties. Recent studies have shown that CAPE has also a neuroprotective effects in ischemia and low potassium-induced neuronal apoptotic models. In cerebellar granule neurons CAPE significantly blocks 6-OHDA mediated cell death (70 microM) in a dose-dependent manner. Furthermore, CAPE was able to modulate the Ca(2+)-induced release of cyctochrome c in isolated liver mitochondria. Caspase-3 activation following 6-OHDA treatment was markedly inhibited in the presence of CAPE. Although the molecular mechanisms associated with CAPE's neuroprotective effects remain to be elucidated in more detail, our results clearly demonstrate a considerable neuroprotective effect of CAPE. Since a mitochondrial insult is a major cause for the degeneration of nigral neurons in PD, we hypothesize that propolis derivatives, in particular CAPE, may have a neuroprotective effect on those cells and may be a promising drug candidate to be taken into in vivo models of PD.     

Manganese scavenges superoxide and hydroxyl radicals: an in vitro study in rats

The present study was designed to investigate the role of manganese (Mn) as an antioxidant element. In vitro experiments have been conducted to evaluate the ability of Mn in scavenging oxygen free radicals. Superoxide (O*-) and hydroxyl (OH*-) radicals were generated in vitro by using xanthine and xanthine oxidase system and fenton reactions respectively. Different concentrations of Mn (II) and Mn (III) were used in the reaction mixture to evaluate free radical scavenging ability of Mn. The results indicated that Mn scavenged superoxide radicals at nanomolar concentrations whereas hydroxyl radicals were scavenged at micromolar concentrations. In addition, Mn-superoxide dismutase (SOD) activity was measured in different regions of brain in adult male rats treated with MnCl2. The results showed that Mn-SOD activity increased in Mn treated animals. Therefore, the data support the hypothesis that Mn is one of the essential elements which can protect against oxidative damage, however, at higher concentrations Mn can be neurotoxic by generating the free radicals.     

Restorative potential of dopaminergic grafts in presence of antioxidants in rat model of Parkinson's disease

Free radical mediated damage has been reported to contribute significantly towards low survival (5–10%) of grafted dopaminergic neurons, post transplantation. In the present study, an attempt has been made to explore the neuroprotective potential of the combination of two major antioxidants ascorbic acid (AA) and glutathione (GSH) on ventral mesencephalic cells (VMC) and nigral dopamine (DA) neurons when co-transplanted together with VMC in rat model of Parkinson's disease (PD). GSH and AA have been reported to act co-operatively in the conditions of oxidative stress thereby helping in maintaining the cellular GSH/GSSG redox status. Functional recovery was assessed 12 weeks post transplantation, where a significant restoration (p < 0.001) in D-amphetamine induced circling behavior (62%), spontaneous locomotor activity (SLA; 64%), dopamine–D₂ receptor binding (63%), dopamine (65%) and 3,4-dihydroxy phenyl acetic acid (DOPAC) level (64%) was observed in co-transplanted animals as compared to lesioned and VMC alone grafted rats. VMC and GSH + AA co-transplanted animals exhibited a significantly higher surviving TH-immunoreactive (TH-ir) neurons number (p < 0.01), TH-ir fibers outgrowth (p < 0.05) in striatal graft and TH-ir neurons in substantia nigra pars compacta (SNpc) (p < 0.01), as compared to VMC alone transplanted rats. An attempt was made to further confirm our in vivo observations through in vitro experiments where following in vitro exposure to 6-OHDA, a higher cell survival (p < 0.01), TH-ir cell counts (p < 0.001) and DA and DOPAC levels (p < 0.01) were also observed in 8-day-old VMC culture in presence of GSH + AA as compared to VMC cultured in absence of antioxidants. The results suggest that GSH + AA when co-transplanted with VMC provide higher restoration probably by increasing the survival of grafted VMC and simultaneously supporting nigral TH-immunopositive neurons in rat model of PD.     

Constitutive Ret signaling is protective for dopaminergic cell bodies but not for axonal terminals

Ret is the canonical signaling receptor for glial cell line-derived neurotrophic factor (GDNF), which has been shown to have neuroprotective effects when administered prior to neurotoxic challenge. A missense Meth918Thr mutation causes the constitutive activation of Ret, resulting in multiple endocrine neoplasia type 2 B (MEN2B). To clarify the role of Ret signaling in neuroprotection, we studied the effects of the neurotoxins 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA) on the dopaminergic system of mice carrying the MEN2B mutation. We found that MEN2B mice were significantly more resistant to nigral tyrosine hydroxylase (TH)-positive cell loss induced by unilateral striatal 6-OHDA than Wt mice. However, 6-OHDA caused profound dopamine (DA) depletion in the striatum of both MEN2B and Wt mice. Systemic MPTP caused similar DA depletion and a decrease in TH-immunostaining in the striatum of MEN2B and Wt mice. Neither neurotoxin induced a compensatory increase in striatal metabolite/DA ratios in the MEN2B mice, possibly contributing to an increased amphetamine-induced turning behavior observed in behavioral assessments of these mice. Thus, our data suggest that activated Ret protects DA cell bodies in the substantia nigra pars compacta, but does not protect DA axons in the striatum.     

Lung antioxidant enzymes, peroxidation, glutathione system and oxygen consumption in catalase inactivated young and old Rana perezi frogs

In the lung of Rana perezi no differences as a function of age have been found for any of the five major antioxidant enzymes, reduced (GSH), oxidized (GSSG) or glutathione ratio (GSSG/GSH), oxygen consumption (VO2) and for in vivo or in vitro stimulated tissue peroxidation. This frog shows a moderate rate of oxygen consumption and a life span substantially longer than that of rats and mice. Chronic (2.5 months) catalase depletion in the lung did not affect survival or any additional antioxidant enzyme, GSH, GSSG or in vivo and in vitro lung peroxidation in any age group. Only the GSSG/GSH ratio and the VO2 were elevated in catalase depleted old but not young frogs. After comparison of these results with those obtained in other animal species by other authors we suggest the possibility that decreases in antioxidant capacity in old age be restricted to species with high basal metabolic rates. Nevertheless, scavenging of oxygen radicals can not be 100% effective in any species. Thus, aging can still be due to the continuous presence of small concentrations of O2 radicals in the tissues throughout the life span in animals with either high or low metabolic rates.     

Herbal (Phyllanthus niruri) protein isolate protects liver from nimesulide induced oxidative stress.

Present study was conducted to evaluate the role of a protein fraction (PI, protein isolate) of the herb, Phyllanthus niruri (P. niruri) against nimesulide-induced oxidative stress in vivo using a murine model. Mice were intraperitoneally treated with that at a dose of 5mg/kg body weight for 7 days before and separately 1-5 days after nimesulide (at a dose of 10mg/kg body weight for 7 days) administration to evaluate its preventive and curative role. Levels of reduced glutathione (GSH), antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), as well as thiobarbituric acid reactive substances (TBARS) were measured in the liver homogenates of all study groups. Pretreatment with isolated P. niruri protein fraction significantly enhanced nimesulide-induced reduced levels of antioxidant enzymes and GSH as well as reduced the enhanced level of lipid peroxidation. Post-treatment studies showed that the recovery after nimesulide induced oxidative stress was more rapid if PI was administered compared to the spontaneous recovery of liver. Histological studies also suggest that this protein fraction could prevent as well as cure liver from nimesulide induced oxidative stress. DPPH radical scavenging assay showed that it could scavenge free radicals. Its antioxidant property was compared with that of a known potent antioxidant, Vitamin E. Besides, the effect of a non-relevant protein, BSA, was also included in the study. Heat treatment and trypsin digestion destroyed the biological activity of this protein fraction. In conclusion, data obtained suggest that the P. niruri protein fraction may protect liver from nimesulide-induced oxidative stress probably via promotion of antioxidant defense.     

Amburoside A, a glucoside from Amburanacearensis, protects mesencephalic cells against 6-hydroxydopamine-induced neurotoxicity

This study evaluates the potential neuroprotective properties of amburoside A, a glucoside isolated from Amburana cearensis, on rat mesencephalic cell cultures exposure to the neurotoxin 6-hydroxydopamine (6-OHDA). The parameters determined were cell viability by the 3[4,5-dimethylthiazole-2-il]-2,5-diphenyltetrazolium bromide (MTT) method, nitric oxide (NO) and free radical formation by the measurement of nitrite concentration and thiobarbituric acid reacting substance (TBARS) formation as an indication of cellular lipid peroxidation. The results showed that AMB was less effective as a curative agent in the MTT assay, since its addition after 6-OHDA did not reverse the neurotoxin's effect, except at the highest concentration (AMB, 100 microg/ml). Similarly, the higher nitrite levels observed after exposure of the cells to 6-OHDA were only partially reversed by AMB, at this highest concentration. However, when AMB (0.5, 1, 10 and 100 microg/ml) was added before the toxin, it appeared to protect neuronal cells against 6-OHDA toxicity in a concentration-dependent manner, as shown by MTT assay. AMB also prevented free radical formation indicated by the increased nitrite concentration induced by 6-OHDA. Cells exposed to 6-OHDA showed a 3.4 times increase in TBARS concentration as compared to controls, and this effect was inhibited from 24% up to 64% by AMB (0.1-100 microg/ml), indicative of a neuroprotective effect. In conclusion, we show that AMB, acting as an antioxidant compound, presents a significant neuroprotective effect, suggesting that this compound could provide benefits as a therapeutic agent in neurodegenerative disease such as Parkinson's.     

Free radical reactions might contribute to severe alpha amanitin hepatotoxicity--a hypothesis

Alpha amanitin is a powerful natural hepatotoxin that belongs to the amatoxins isolated from deadly poisonous Amanita phalloides mushroom. The basic molecular mechanism of their toxicity was attributed to inhibition of RNA polymerase II of the eukaryotic cells. At present, the most effective clinical antidote to acute Amanita phalloides mushroom poisoning is silybin, an antioxidant possessing free radical scavenger activity and inhibiting lipid peroxidation, stabilizing membrane structure and protecting enzymes under conditions of oxidative stress. Bearing in mind the biological mechanism of silybin action and the fact that for different amatoxins (alpha, beta, and est. amanitins) does not established straight correlation between their in vivo LD50 and inhibitory constants (Ki) toward RNA polymerase III in vitro determined we supposed some additional toxic effects of these toxins might contribute to their severe hepatotoxicity. Our formerly in vitro experiments demonstrated that alpha amanitin could act either as an antioxidant or as a prooxidant depending on the treatment conditions and toxin concentration. By UV-visible spectroscopy we also shown that alpha amanitin was sensitive to oxidation by a system of lactoperoxidase/H(2)O(2) and assumed formation of free radical toxin intermediates. Having in mind some exogenic compounds including natural toxins can induce increased production of reactive oxygen species (ROS) we suggested similar generation of ROS provoked by alpha amanitin. Our recently in vitro studies have demonstrated that the alpha amanitin could increase superoxide dismutase (SOD) activity and inhibit catalase (CAT) activity to a considerable degree after together incubation of the toxin with any of enzymes. We have also shown that in vitro increased SOD activity was due to superoxide anion radical scavenging activity (SSA) of the toxin. This therefore informed the decision to study the in vivo effect of alpha amanitin on SOD and CAT activity and the level of lipid peroxidation (LPO) products in liver homogenates isolated from mice treated with the toxin. Statistical significant increased level of LPO products was found at the 6th day comparing to the 20th hour after mice treatment with a subletal dose of the toxin. Based on our previous in vitro and present in vivo studies we have made a hypothesize that in vivo during liver accumulation of the toxin it might be transformed to free radical intermediates causing increase in ROS levels. As a result a peroxidative process in hepatocytes might contribute to the severe alpha amanitin hepatotoxicity.     

Hepatocytes are protected by herb Phyllanthus niruri protein isolate against thioacetamide toxicity.

The herb, Phyllanthus niruri has been known to possess protective activity against various drugs and toxins induced hepatic disorders. Present study was conducted to evaluate the role of the protein isolate of the herb against thioacetamide (TAA)-induced cytotoxicity in mice hepatocytes. In vitro cell viability, lactate dehydrogenase (LDH) and alanine amino transferase (ALT) leakage were measured as the indicators of cell damage. In addition, measurement of the level of non-protein thiol, glutathione (GSH); activities of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) as well as the extent of lipid peroxidation were carried out to evaluate the prooxidant-antioxidant status of the cell. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay was performed to determine the radical scavenging activity of the protein isolate. Results showed that the administration of the protein isolate prior to TAA exposure significantly reduced the release of LDH and ALT leakage and enhanced the cell viability in a dose-dependent manner in hepatocytes. Besides, the protein isolate appeared to prevent the alterations in GSH levels and activities of the anti-oxidant enzymes related to prooxidant-antioxidant status of hepatocytes. It also reduced the TAA-induced lipid peroxidation significantly as demonstrated by the reduction of malondialdehyde (MDA) production. DPPH radical scavenging assay showed that the protein isolate possessed radical scavenging activity. Combining, the data suggest that the protein isolate could protect hepatocytes from TAA-induced cellular injury probably by its antioxidative and radical scavenging properties.     

Neural stem/progenitor cells initiate the formation of cellular networks that provide neuroprotection by growth factor-modulated antioxidant expression

Recent studies indicate that transplanted neural stem/progenitor cells (NSPs) can interact with the environment of the central nervous system and stimulate protection and regeneration of host cells exposed to oxidative stress. Here, a set of animals grafted with NSPs and treated with 3-nitropropionic acid (3-NP) exhibited reduced behavioral symptoms and less severe damage of striatal cytoarchitecture than sham transplanted controls including better survival of neurons. Sites of tissue sparing correlated with the distribution pattern of donor cells in the host brain. To investigate the cellular and molecular bases of this phenomenon, we treated cocultures of NSPs and primary neural cell cultures with 3-NP to induce oxidative stress and to study NSP-dependent activation of antioxidant mechanisms and cell survival. Proactive presence of NSPs significantly improved cell viability by interfering with production of free radicals and increasing the expression of neuroprotective factors. This process was accompanied by elevated expression of ciliary neurotrophic factor (CNTF) and vascular endothelial growth factor (VEGF) in a network of NSPs and local astrocytes. Intriguingly, both in vitro and in vivo, enhanced growth factor secretion stimulated a robust upregulation of the antioxidant enzyme superoxide dismutase 2 (SOD2) in neurons and resulted in their improved survival. Our findings thus reveal a so far unrecognized mechanism of interaction between NSPs and surrounding cells accompanying neuroprotection: through mutual, NSP-triggered stimulation of growth factor production and activation of antioxidant mechanisms, cellular networks may shield the local environment from the arriving impact of oxidative stress.     

Clozapine prolongs hypotonic immobility in rats with bilateral 6-hydroxydopamine lesions of the striatum

Clozapine does not induce classical catalepsy. One explanation is that endogenous dopamine (DA) readily displaces clozapine from postsynaptic striatal DA receptors. If the latter were true, then depletion of striatal DA should permit clozapine to induce classical catalepsy. Rats received bilateral sham or 6-hydroxydopamine (6-OHDA) lesions of the striatum. Catalepsy using the bar test was assessed on days 21, 28 and 35 after i.p. vehicle, haloperidol (0.75 mg/kg) or clozapine (20 mg/kg). Brains were harvested on day 36 and striatal DA was assayed. A 97% depletion of striatal DA was associated with a significant increase in the duration of immobility after haloperidol or clozapine administration. Both in sham as well as in 6-OHDA lesioned animals, however, the duration of immobility was greater after haloperidol than after clozapine. Furthermore, clozapine-treated animals were hypotonic and did not show the classic rigidity of haloperidol catalepsy. While clozapine's low propensity to induce immobility in animals and extrapyramidal symptoms in man may depend in part on endogenous striatal DA, other mechanisms must also be involved.     

GDNF reduces oxidative stress in a 6-hydroxydopamine model of Parkinson's disease

Many current theories of Parkinson's disease (PD) suggest that oxidative stress is involved in the neurodegenerative process. Potential neuroprotective agents could protect neurons through inherent antioxidant properties or through the upregulation of the brain's antioxidant defenses. Glial cell line-derived neurotrophic factor (GDNF) has been shown to protect and restore dopamine neurons in experimental models of PD and to improve motor function in human patients. This study was designed to investigate GDNF's effect on oxidative stress in a model of PD. GDNF or vehicle was injected into the right striatum of male Fischer-344 rats. Three days later 6-OHDA or saline was injected into the same striatum. The striatum and substantia nigra from both sides of the brain were removed 24h after 6-OHDA or saline injection and analyzed for the oxidative stress markers protein carbonyls and 4-hydroxynonenal. Both markers were significantly reduced in GDNF+6-OHDA treated animals compared to vehicle+6-OHDA treated animals. In addition, in animals allowed to recover for 3.5-4 weeks after the 6-OHDA administration, the GDNF led to significant protection against loss of striatal and nigral tissue levels of dopamine. These results suggest that the protective effects of GDNF against 6-OHDA involve a reduction in oxidative stress.     

Protective role of aminoguanidine on gentamicin-induced acute renal failure in rats

The toxicity of aminoglycosides including gentamicin (GEN), the most widely used drug in this category, is believed to be related to the generation of reactive oxygen species (ROS) in the kidney. Aminoguanidine (AG) is known as an effective antioxidant and its free radical scavenger effects may protect GEN-induced acute renal failure (ARF). Therefore, this study was focused on investigating the possible protective effect of AG against GEN-induced nephrotoxicity in an in vivo rat model. We investigated the effects of AG on GEN-induced changes in renal tissue malondialdehyde (MDA) levels; nitric oxide (NO) generation; glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and catalase (CAT) activities; glutathione (GSH) content; serum creatinine (Cr) and blood urea nitrogen (BUN) levels. Morphological changes in the kidney were also examined using light microscopy. GEN administration to control group rats increased renal MDA and NO levels but decreased GSH-Px, SOD, CAT activities and GSH content. AG administration with GEN injection resulted in significantly decreased MDA, NO generation and increased GSH-Px, SOD, CAT activities and GSH content when compared with GEN alone. Serum levels of Cr and BUN significantly increased as a result of nephrotoxicity. Also, AG significantly decreased Cr and BUN levels. Morphological changes in the kidney, including tubular necrosis, intracellular edema, glomerular and basement membrane alterations were evaluated qualitatively. Both biochemical findings and histopathological evidence showed that administration of AG reduced the GEN-induced kidney damage. We propose that AG acts in the kidney as a potent scavenger of free radicals to prevent the toxic effects of GEN both at the biochemical and histological level.     

Changes in expression of the antioxidant enzyme SOD3 occur upon differentiation of human bone marrow-derived mesenchymal stem cells in vitro

The discovery that mesenchymal stem cells (MSCs) secrete SOD3 may help explain studies in which MSCs have direct antioxidant activities both in vivo and in vitro. SOD3 is an antioxidant enzyme that dismutes toxic free radicals produced during inflammatory processes. Therefore, MSC production and secretion of active and therapeutically significant levels of SOD3 would further support the use of MSCs as a cellular based antioxidant therapy. The aim of this study was therefore to investigate in vitro if MSC differentiation down the adipogenic, chondrogenic, and osteogenic lineages influences the expression of the antioxidant molecule SOD3. Human bone marrow MSCs and their differentiated progeny were cultured under standard conditions and both the SOD3 gene and protein expression examined. Following adipogenesis, cultures demonstrated that both SOD3 protein and gene expression are significantly increased, and conversely, following chondrogenesis SOD3 protein and gene expression is significantly decreased. Following osteogenesis there were no significant changes in SOD3 protein or gene expression. This in vitro study describes the initial characterization of SOD3 expression and secretion by differentiated MSCs. This should help guide further in vivo work establishing the therapeutic and antioxidative potential of MSC and their differentiated progeny.     

Chlorella vulgaris extract ameliorates carbon tetrachloride-induced acute hepatic injury in mice

The possible protective effects of Chlorella vulgaris extract (CVE) on carbon tetrachloride (CCl₄)-induced acute hepatic injury in mice and the mechanism underlying these effects was investigated. CCl₄ administration caused a marked increase in the levels of serum aminotransferases, lipid peroxidation and cytochrome P450-2E1 (CYP450) expression. Also, decreased glutathione (GSH) content and activities of cellular antioxidant defense enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase and glutathione-S-transferase (GST) were found after CCl₄ exposure. All of these phenotypes were markedly reversed by preadministration of the mice with CVE. In addition, CVE exhibited antioxidant effects on FeCl₂–ascorbate induced lipid peroxidation in mouse liver homogenates, and on superoxide radical scavenging activity. Taken together, these results suggest that CVE produced a protective action on CCl₄-induced acute hepatic injury in mice, presumably through blocking CYP-mediated CCl₄ bioactivation, inducing the GSH levels, antioxidant enzyme activities and free radical scavenging effect. Therefore, CVE may be an effective hepatoprotective agent and viable candidate for treating hepatic disorders and other oxidative stress-related diseases.     

Overexpression of Cu-Zn superoxide dismutase protects neuroblastoma cells against dopamine cytotoxicity accompanied by increase in their glutathione level

Dopamine (DA) was shown to exert toxic effects on cultured neurons through autoxidation or oxidative deamination, followed by formation of highly reactive quinone compounds and superoxide radicals. In the present study, therefore, any involvement of Cu-Zn superoxide dismutase (SOD) in DA toxicity was evaluated by transfection of Cu-Zn SOD cDNA. The transient transfection of Cu-Zn SOD cDNA inhibited the DA-induced decrease of dopaminergic neuroblastoma cells. Moreover, Cu-Zn SOD cDNA-transfection significantly increased the glutathione (GSH) level when the cells were exposed to DA. However, such Cu-Zn SOD-overexpression failed to show any protective effects against hydrogen peroxide. The Cu-Zn SOD-overexpressing cells also showed significantly higher levels of GSH upon DA exposure than did the empty vector-transfected cells. The increase in the GSH level in response to hydrogen peroxide remained almost identical in empty vector-transfected or Cu-Zn SOD-overexpressed cells. The level of GSH in DA-treated Cu-Zn SOD-overexpressing cells was 2.5-fold higher than that increased by hydrogen peroxide exposure. The catechol structure of DA molecule is probably involved in the mechanism of increasing GSH level. Furthermore, the Cu-Zn SOD-overexpressing cells inhibited the activation of caspase-3 upon DA exposure. Therefore, Cu-Zn SOD overexpression may temporarily inhibit or delay DA autoxidation and consequently increase the GSH level, which then prevents the activation of apoptotic pathway and subsequent cell death.     

Antioxidant properties of fruit and vegetable juices: more to the story than ascorbic acid

Dietary supplements such as vitamin C have become popular for their perceived ability to enhance the body's antioxidant defenses. Reactive oxygen species (ROS) have been shown to cause a broad spectrum of damage to biological systems. Scavenging of ROS is part of a healthy, well-balanced, antioxidant defense system. The present study used the Fenton reaction as a source of hydroxyl radicals and xanthine/xanthine oxidase as a source of superoxide radicals to investigate the scavenging capabilities of various fruit and vegetable juices against these radicals. Electron spin resonance (ESR) spin trapping was used for free radical detection and measurement. Using a colormetric assay, the present study also investigated the protective effects of fruit and vegetable juices against lipid peroxidation induced in cell membranes by hydroxyl radicals. The present study showed that the free radical scavenging capability of each individual juice, but not its ascorbic acid content, is correlated with its protective effect on free radical induced lipid peroxidation. The results indicate that ascorbic acid is only one facet of the protective effect of fruit and vegetable juices. It appears that consumption of whole fruits and vegetables would be superior to an ascorbic acid supplement for antioxidant effectiveness.