Antioxidant responses and lipid peroxidation following intranasal 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration in rats: increased susceptibility of olfactory bulb

We evaluated an alternative method to investigate a possible involvement of environmental toxins in the pathology of Parkinson's disease (PD). There is considerable evidence supporting the role of oxidative stress in the toxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a neurotoxin largely used to modeling PD in primates and rodents. We have recently demonstrated that rats treated with intranasal (i.n.) infusion of MPTP suffer from progressive signs of PD that are correlated with time-dependent degeneration in dopaminergic neurons. In the present study, we investigated the time-dependent (2 h to 7 days) effect of a single i.n. administration of MPTP (0.1 mg/nostril) on the glutathione-related antioxidant status and lipid peroxidation (TBARS) in the adult Wistar rat brain. The effects were more pronounced in the olfactory bulb at 6 h after i.n. MPTP administration, as indicated by an increase in TBARS and total glutathione (GSH-t) levels, and also in the gamma-glutamyl transpeptidase (GGT) activity. Increased levels of TBARS, GSH-t and GGT activity were also observed at 6 h post-MPTP infusion in some structures (e.g. striatum, hippocampus and prefrontal cortex). No difference regarding glutathione reductase activity was observed in any of the brain structures analyzed, while a marked decrease in glutathione peroxidase activity was specifically observed in the substantia nigra 7 days after MPTP treatment. These results demonstrate that a single i.n. infusion of MPTP in rats induces significant alterations in the brain antioxidant status and lipid peroxidation, reinforcing the notion that the olfactory system represents a particularly sensitive route for the transport of neurotoxins into the central nervous system that may be related to the etiology of PD.     

Distribution, adaptation and physiological meaning of thiols from vertebrate hemoglobins

In the present review, the sequences of hemoglobins (Hb) of 267 adult vertebrate species belonging to eight major vertebrate taxa are examined for the presence and location of cysteinyl residues in an attempt at correlation with their ecophysiology. Essentially, all vertebrates have surface cysteinyl residues in Hb molecules whereby their thiol groups may become highly reactive. Thiol-rich Hbs may display eight or more thiols per tetramer. In vertebrates so far examined, the cysteinyl residues occur in 44 different sequence positions in alpha chains and 41 positions in beta chains. Most of them are conservatively located and occur in only a few positions in Teleostei, Aves and Mammalia, whereas they are dispersed in Amphibia. The internal cysteinyl residue alpha104 is ubiquitous in vertebrates. Residue beta93 is highly conserved in reptiles, birds and mammals. The number of cysteine residues per tetramer with solvent access varies in vertebrates, mammalians and bony fish having the lowest number of external residues, whereas nearly all external cysteine residues in Aves and Lepidosauria are of the surface crevice type. In cartilaginous fish, amphibians, Crocodylidae and fresh water turtles, a substantial portion of the solvent accessible thiols are of the totally external type. Recent evidence shows that some Hb thiol groups are highly reactive and undergo extensive and reversible S-thiolation, and that they may be implicated in interorgan redox equilibrium processes. Participation of thiol groups in nitric oxide ((*)NO) metabolism has also been proved. The evidence argues for a new physiologically relevant role for Hb via involvement in free radical and antioxidant metabolism.     

Diphenyl ditelluride targets brain selenoproteins in vivo: inhibition of cerebral thioredoxin reductase and glutathione peroxidase in mice after acute exposure

In this study, we investigated the effect of diphenyl ditelluride (PhTe)₂ administration (10 and 50?μmol/kg) on adult mouse behavioral performance as well as several parameters of oxidative stress in the brain and liver. Adult mice were injected with (PhTe)₂ or canola oil subcutaneously (s.c.) daily for 7?days. Results demonstrated that (PhTe)₂ induced prominent signs of toxicity (body weight loss), behavioral alterations and increased in lipid peroxidation in brain. 50?μmol/kg (PhTe)₂ inhibited blood δ-aminolevulinic acid dehydratase (δ-ALA-D), a redox sensitive enzyme. (PhTe)₂ caused an increase in cerebral non-protein thiol (NPSH) and protein thiol (PSH) groups. In the liver, 50?μmol/kg (PhTe)₂ decreased NPSH, but did not alter the content of protein thiol groups. (PhTe)₂ decreased cerebral antioxidant enzymes (catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), glutathione peroxidase (GPx), and thioredoxin reductase (TrxR). In liver, (PhTe)₂ increase SOD and GR and decreased GPx activity. Results obtained herein suggest that the brain was more susceptible to oxidative stress induced by (PhTe)₂ than the liver. Furthermore, we have demonstrated for the first time that TrxR is an in vivo target for (PhTe)_2. Combined, these results highlight a novel molecular mechanism involved in the toxicity of (PhTe)₂. In particular the inhibition of important selenoenzymes (TrxR and GPx) seems to be involved in the neurotoxicity associated with (PhTe)₂ exposure in adult mice.     

Modulation of Brain Glutathione Reductase and Peroxiredoxin 2 by α-Tocopheryl Phosphate

α-Tocopheryl phosphate (αTP) is a phosphorylated form of α-tocopherol. Since it is phosphorylated in the hydroxyl group that is essential for the antioxidant property of α-tocopherol, we hypothesized that αTP would modulate the antioxidant system, rather than being an antioxidant agent per se. α-TP demonstrated antioxidant activity in vitro against iron-induced oxidative stress in a mitochondria-enriched fraction preparation treated with 30 or 100 µM α-TP. However, this effect was not observed ex vivo with mitochondrial-enriched fraction from mice treated with an intracerebroventricular injection of 0.1 or 1 nmol/site of αTP. Two days after treatment (1 nmol/site αTP), peroxiredoxin 2 (Prx2) and glutathione reductase (GR) expression and GR activity were decreased in cerebral cortex and hippocampus. Glutathione content, glutathione peroxidase, and thioredoxin reductase activities were not affected by αTP. In conclusion, the persistent decrease in GR and Prx2 protein content is the first report of an in vivo effect of αTP on protein expression in the mouse brain, potentially associated to a novel and biologically relevant function of this naturally occurring compound.     

Antioxidant effect of diphenyl diselenide against sodium nitroprusside (SNP) induced lipid peroxidation in human platelets and erythrocyte membranes: an in vitro evaluation

An in vitro evaluation on the antioxidant effect of diphenyl diselenide (PhSe)(2), an organochalcogenide, against sodium nitroprusside (SNP)-induced lipid peroxidation (LPO) was conduced. Human platelets and erythrocyte membranes (ghosts), as well as rat brain homogenates (S(1)), were pre-incubated with different concentrations of SNP (0-10 microM). All SNP concentrations tested significantly increased LPO in human platelets and S(1). Platelets were more sensitive to SNP-induced peroxidative damage when compared to S(1). SNP 10 microM decreased glutathione peroxidase (GPx) activity and did not affect glutathione reductase (GR) and catalase (CAT) activities in human platelets. However, ghosts were insensitive to SNP-induced LPO and no changes on GPx, GR and CAT activities were observed. Diphenyl diselenide significantly protected human platelets against SNP-induced LPO and recovered GPx inactivation. This effect was more evident at (PhSe)(2) concentrations above 2 microM. The presented results indicate that (PhSe)(2) exerts protective effects on SNP-induced oxidative damage in human blood components and in rat brain. These phenomena seem to be related to its thiol peroxidase-like activity and to a possible direct interaction with SNP and derivatives. Based on our results and on literature, diphenyl diselenide can be pointed as a promising antioxidant molecule.     

Antioxidant enzymes and thiol/disulfide status in the digestive gland of the brown mussel Perna perna exposed to lead and paraquat

Lead (Pb) and paraquat (PQ) have different toxic mechanisms associated with cell damage. Pb may induce alterations in zinc containing proteins, including the known inhibitory effect on the enzyme delta-aminolevulinic acid dehydratase, disrupting the heme-synthesis pathway. During PQ biotransformation, redox cycle reactions enhance oxyradical production, which may lead to pro-oxidative conditions. In this study, we analyzed the effects of Pb and PQ on antioxidant enzymes and thiol status, using the digestive glands of the mussel Perna perna collected in a mussel farm on Santa Catarina Island. Mussels were exposed to Pb (1 ppm) and PQ (10 ppm), either separately or concomitantly, for 48 h. We were unable to detect an effect of Pb treatment on the enzymes, catalase, glucose 6-phosphate dehydrogenase (G6PDH), glutathione S-transferase (GST) and glutathione reductase (GSSG-reductase), which contrasts to the effect of PQ, increasing GSSG-reductase and G6PDH, but decreasing GST activity. The thiol status showed a pro-oxidative trend, observed mainly through a decrease in the reduced/oxidized glutathione ratio, despite the total-glutathione increase. Protein-mixed disulfides and protein thiols did not change by the treatments. The observed effects of PQ and Pb were consistent with literature. Pb had a suppressive effect on the enzymatic changes elicited by PQ, while the changes in the thiol/disulfide parameters were retained.     

Effects of High-Intensity Swimming on Lung Inflammation and Oxidative Stress in a Murine Model of DEP-Induced Injury

Studies have reported that exposure to diesel exhaust particles (DEPs) induces lung inflammation and increases oxidative stress, and both effects are susceptible to changes via regular aerobic exercise in rehabilitation programs. However, the effects of exercise on lungs exposed to DEP after the cessation of exercise are not clear. Therefore, the aim of this study was to evaluate the effects of high-intensity swimming on lung inflammation and oxidative stress in mice exposed to DEP concomitantly and after exercise cessation. Male Swiss mice were divided into 4 groups: Control (n = 12), Swimming (30 min/day) (n = 8), DEP (3 mg/mL—10 μL/mouse) (n = 9) and DEP+Swimming (n = 8). The high-intensity swimming was characterized by an increase in blood lactate levels greater than 1 mmoL/L between 10th and 30th minutes of exercise. Twenty-four hours after the final exposure to DEP, the anesthetized mice were euthanized, and we counted the number of total and differential inflammatory cells in the bronchoalveolar fluid (BALF), measured the lung homogenate levels of IL-1β, TNF-α, IL-6, INF-ϫ, IL-10, and IL-1ra using ELISA, and measured the levels of glutathione, non-protein thiols (GSH-t and NPSH) and the antioxidant enzymes catalase and glutathione peroxidase (GPx) in the lung. Swimming sessions decreased the number of total cells (p<0.001), neutrophils and lymphocytes (p<0.001; p<0.05) in the BALF, as well as lung levels of IL-1β (p = 0.002), TNF-α (p = 0.003), IL-6 (p = 0.0001) and IFN-ϫ (p = 0.0001). However, the levels of IL-10 (p = 0.01) and IL-1ra (p = 0.0002) increased in the swimming groups compared with the control groups, as did the CAT lung levels (p = 0.0001). Simultaneously, swimming resulted in an increase in the GSH-t and NPSH lung levels in the DEP group (p = 0.0001 and p<0.002). We concluded that in this experimental model, the high-intensity swimming sessions decreased the lung inflammation and oxidative stress status during DEP-induced lung inflammation in mice.     

Hemoglobin S-thiolation during peroxide-induced oxidative stress in chicken blood

Protein S-thiolation or protein-glutathione mixed disulfide (PSSG) occurs when cells are exposed to oxidative stress, and has been implicated in several cellular functions. The S-thiolation of hemoglobin as well as other abundant proteins is proposed to participate as a redox buffer, being part of the antioxidant protection system of the cell during the oxidative challenge. We studied the oxidative stress caused by peroxides (H(2)O(2), cumene and tert-butyl hydroperoxide) on chicken blood by measuring the thiol/disulfide status. Chicken blood under peroxide treatment showed a time- and concentration-dependent increase in glutathione disulfide (GSSG) and PSSG. GSSG peaked immediately after treatment (1 min), while PSSG increased progressively over time, showing a maximum after about 30 min. The system recovered after 140 min of incubation, with GSSG and PSSG then barely reaching control values. The S-thiolation of hemoglobin was monitored under nondenaturing PAGE, and the fraction of S-thiolated hemoglobin, or Hb A1, rose in a dose-dependent fashion and was proportional to total S-thiolation, measured as PSSG. This significant correlation indicates that hemoglobin is the major S-thiolated protein in chicken erythrocytes treated with peroxides. The present work shows the behavior of chicken blood under peroxide treatment; it anticipated that chicken hemoglobin thiol groups can actively participate in the redox processes of erythrocytes exposed to oxidative stress, and that hemoglobin is the major S-thiolated protein. This further corroborates the hypothesis that abundant proteins, such as hemoglobin, may take part in the cellular antioxidant defense system.     

A study of the relative importance of the peroxiredoxin-, catalase-, and glutathione-dependent systems in neural peroxide metabolism

Cells are endowed with several overlapping peroxide-degrading systems whose relative importance is a matter of debate. In this study, three different sources of neural cells (rat hippocampal slices, rat C6 glioma cells, and mouse N2a neuroblastoma cells) were used as models to understand the relative contributions of individual peroxide-degrading systems. After a pretreatment (30 min) with specific inhibitors, each system was challenged with either H₂O₂ or cumene hydroperoxide (CuOOH), both at 100 μM. Hippocampal slices, C6 cells, and N2a cells showed a decrease in the H₂O₂ decomposition rate (23-28%) by a pretreatment with the catalase inhibitor aminotriazole. The inhibition of glutathione reductase (GR) by BCNU (1,3-bis(2-chloroethyl)-1-nitrosourea) significantly decreased H₂O₂ and CuOOH decomposition rates (31-77%). Inhibition of catalase was not as effective as BCNU at decreasing cell viability (MTT assay) and cell permeability or at increasing DNA damage (comet test). Impairing the thioredoxin (Trx)-dependent peroxiredoxin (Prx) recycling by thioredoxin reductase (TrxR) inhibition with auranofin neither potentiated peroxide toxicity nor decreased the peroxide-decomposition rate. The results indicate that neural peroxidatic systems depending on Trx/TrxR for recycling are not as important as those depending on GSH/GR. Dimer formation, which leads to Prx2 inactivation, was observed in hippocampal slices and N2a cells treated with H₂O₂, but not in C6 cells. However, Prx-SO₃ formation, another form of Prx inactivation, was observed in all neural cell types tested, indicating that redox-mediated signaling pathways can be modulated in neural cells. These differences in Prx2 dimerization suggest specific redox regulation mechanisms in glia-derived (C6) compared to neuron-derived (N2a) cells and hippocampal slices.