Diphenyl Diselenide Attenuates Mitochondrial Damage During Initial Hypoxia and Enhances Resistance to Recurrent Hypoxia.

Hypoxia plays a significant role in the development of various cerebral diseases, many of which are associated with the potential risk of recurrence due to mitochondrial damage. Conventional drug treatments are not always effective for hypoxia-related brain diseases, necessitating the exploration of alternative compounds. In this study, we investigated the potential of diphenyl diselenide [(PhSe)2] to ameliorate locomotor impairments and mitigate brain mitochondrial dysfunction in zebrafish subjected to hypoxia. Additionally, we explored whether these improvements could confer resistance to recurrent hypoxia. Through a screening process, an appropriate dose of (PhSe)2 was determined, and animals exposed to hypoxia received a single intraperitoneal injection of 100 mg/kg of the compound or vehicle. After 1 h from the injection, evaluations were conducted on locomotor deficits, (PhSe)2 content, mitochondrial electron transport system, and mitochondrial viability in the brain. The animals were subsequently exposed to recurrent hypoxia to assess the latency time to hypoxia symptoms. The findings revealed that (PhSe)2 effectively crossed the blood-brain barrier, attenuated locomotor deficits induced by hypoxia, and improved brain mitochondrial respiration by modulating complex III. Furthermore, it enhanced mitochondrial viability in the telencephalon, contributing to greater resistance to recurrent hypoxia. These results demonstrate the beneficial effects of (PhSe)2 on both hypoxia and recurrent hypoxia, with cerebral mitochondria being a critical target of its action. Considering the involvement of brain hypoxia in numerous pathologies, (PhSe)2 should be further tested to determine its effectiveness as a potential treatment for hypoxia-related brain diseases.

Effects of caffeine on brain antioxidant status and mitochondrial respiration in acetaminophen-intoxicated mice.

Hepatic encephalopathy is a pathophysiological complication of acute liver failure, which may be triggered by hepatotoxic drugs such as acetaminophen (APAP). Although APAP is safe in therapeutic concentration, APAP overdose may induce neurotoxicity, which is mainly associated with oxidative stress. Caffeine is a compound widely found in numerous natural beverages. However, the neuroprotective effect of caffeine remains unclear during APAP intoxication. The present study aimed to investigate the possible modulatory effects of caffeine on brain after APAP intoxication. Mice received intraperitoneal injections of APAP (250 mg/kg) and/or caffeine (20 mg/kg) and, 4 h after APAP administration, samples of brain and blood were collected for the biochemical analysis. APAP enhanced the transaminase activity levels in plasma, increased oxidative stress biomarkers (lipid peroxidation and reactive oxygen species), promoted an imbalance in endogenous antioxidant system in brain homogenate and increased the mortality. In contrast, APAP did not induce dysfunction of the mitochondrial bioenergetics. Co-treatment with caffeine modulated the biomarkers of oxidative stress as well as antioxidant system in brain. Besides, survival assays demonstrated that caffeine protective effects could be dose- and time-dependent. In addition, caffeine promoted an increase of mitochondrial bioenergetics response in brain by the enhancement of the oxidative phosphorylation, which could promote a better energy supply necessary for brain recovery. In conclusion, caffeine prevented APAP-induced biochemical alterations in brain and reduced lethality in APAP-intoxicated mice, these effects may relate to the preservation of the cellular antioxidant status, and these therapeutic properties could be useful in the treatment of hepatic encephalopathy induced by APAP intoxication.

A single muscle contusion promotes an immediate alteration in mitochondrial bioenergetics response in skeletal muscle fibres with different metabolism.

Skeletal muscle is the most abundant tissue in the human body and mechanical injuries are common; these are frequently of mechanical origins, such as contusion. However, the immediate mitochondrial response to injury and energetic substrate utilisation is still unclear. We evaluated the acute response in mitochondrial function after a single muscle contusion, either in fast twitch fibres (glycolytic metabolism), fast and slow twitch (oxidative and glycolytic metabolism), or slow twitch fibres (oxidative metabolism). Rats were assigned to two groups: control and Lesion (muscle contusion). We collected the gastrocnemius and soleus muscles. The fibres were analysed for mitochondrial respiration, lactate dehydrogenase (LDH), citrate synthase (CS) activity, Ca2+ uptake, and H2O2 production. We found that muscle injury was able to increase ATP synthesis-dependent and OXPHOS oxygen flux in the oxidative fibres when stimulated by complex I + II substrates. On the other hand, the muscle injury increased hydrogen peroxide (H2O2) production when compared to control fibres, and reduced citrate synthase activity; however, it did not change Ca2+ uptake. Surprisingly, injury in mixed fibres increased the OXPHOS and ATP synthesis oxygen consumption, and H2O2 production, but it reduced Ca2+ uptake. The injury in glycolytic fibres did not affect oxygen flux coupled to ATP synthesis, citrate synthase, and lactate dehydrogenase activity, but did reduce Ca2+ uptake. Finally, we demonstrated distinct mitochondrial responses between the different muscle fibres, indicating that the mitochondrial dynamics is related to flexibilities in metabolism, and that reactive oxygen species directly affect physiology and normal function.

Neurochemical mechanisms underlying acute and chronic ethanol-mediated responses in zebrafish: The role of mitochondrial bioenergetics.

Ethanol (EtOH) is a socially-accepted drug, whose consumption is a risk factor for non-intentional injuries, development of pathologies, and addiction. In the brain, EtOH affects redox signaling and increases reactive oxygen species (ROS) production after acute and chronic exposures. Here, using a high-resolution respirometry assay, we investigated whether changes in mitochondrial bioenergetics play a role in both acute and chronic EtOH-mediated neurochemical responses in zebrafish. For the first time, we showed that acute and chronic EtOH exposures differently affect brain mitochondrial function. Acutely, EtOH stimulated mitochondrial respiration through increased baseline state, CI-mediated OXPHOS, OXPHOS capacity, OXPHOS coupling efficiency, bioenergetic efficiency, and ROX/ETS ratio. Conversely, EtOH chronically decreased baseline respiration, complex I- and II-mediated ETS, as well as increased ROX state and ROX/ETS ratio, which are associated with ROS formation. Overall, we observed that changes in mitochondrial bioenergetics play a role, at least partially, in both acute and chronic effects of EtOH in the zebrafish brain. Moreover, our findings reinforce the face, predictive, and construct validities of zebrafish models to explore the neurochemical bases involved in alcohol abuse and alcoholism.

Drosophila melanogaster: A model to study obesity effects on genes expression and developmental changes on descendants.

Maternal obesity and metabolic diseases are two of the most important potential dangers to offspring, given that impaired offspring may cause deficiencies that impair the adult life and health. This study evaluated the oxidative damage, the enzymatic antioxidant defenses, and the enzymes of fatty acid metabolism, such as Acyl-CoA Synthetase and Acetyl-CoA Synthetase (mRNA expression levels), as well as the modulation of cell stress signaling pathway, as Hsp83, and gene expression and insulin-like peptide DILP6 in Drosophila melanogaster models that received a high fat diet (HFD) (10% and 20% of coconut oil) throughout their development period. After 7 days, the progenitor flies were removed and, the remaining eggs were monitored daily, until the eclosion. The descendants were then exposed to a regular diet (RD). The results revealed that the HFD caused a decrease in the proportion of eclosion, lifespan, MTT reduction in mitochondrial enriched fractions, AceCS1 levels, mRNA expression levels (SOD and CAT), and in catalase activity a decrease was only observed in the group that received the highest concentration of coconut oil. In parallel, it was demonstrated an increase in the upregulation of HSP83 mRNA levels, but only when 10% of coconut oil was added, and an increase in glucose and triglyceride levels, as well as in DILP6 mRNA levels in larger concentration of coconut oil tested (20%). In conclusion, flies that have progenitors fed with HFD can develop metabolic dysfunctions, causing oxidative insults, which are involved in the shortening of lifespan.

Treatment with pentylenetetrazole (PTZ) and 4-aminopyridine (4-AP) differently affects survival, locomotor activity, and biochemical markers in Drosophila melanogaster.

PTZ is a convulsive agent that acts via selective blockage of GABAA receptor channels, whereas 4-AP leads to a convulsive episode via blockage of K+ channels. However, the mechanism(s) by which pentylenetetrazole (PTZ) and 4-aminopyridine (4-AP) cause toxicity to Drosophila melanogaster needs to be properly explored, once it will help in establishing an alternative model for development of proper therapeutic strategies and also to counteract the changes associated with exposure to both epileptic drugs. For the purpose, we investigated the effects of exposure (48 h) to PTZ (60 mM) and/or 4-AP (20 mM) on survival, locomotor performance, and biochemical markers in the body and/or head of flies. 4-AP-fed flies presented a higher incidence of mortality and a worse performance in the open field test as compared to non-treated flies. 4-AP also caused a significant increase in the reactive species (RS) and protein carbonyl (PC) content in the body and head. Also a significant increase in catalase and acetylcholinesterase (AChE) activities was observed in the body. In the same vein, PTZ exposure resulted in a significant increase in RS, thiobarbituric acid reactive substances (TBARS), PC content, and catalase activity in the body. PTZ exposure also caused a significant increase in AChE activity both in body and head. It is important to note that PTZ-treated flies also down-regulated the NRF2 expression. Moreover, both 4AP- and PTZ-fed flies presented a significant decrease in MTT reduction, down-regulation, and inhibition of SOD in body. However, SOD was significantly more active in the head of both 4-AP and PTZ-treated flies. Our findings provide evidence regarding the toxicological potential of both PTZ and/or 4-AP to flies. This model will help in decoding the underlying toxicological mechanisms of the stated drugs. It will also help to properly investigate the therapeutic strategies and to counteract the drastic changes associated with both epileptogenic drugs.

Caffeine and acetaminophen association: Effects on mitochondrial bioenergetics.

AIMS: Many studies have been demonstrating the role of mitochondrial function in acetaminophen (APAP) hepatotoxicity. Since APAP is commonly consumed with caffeine, this work evaluated the effects of the combination of APAP and caffeine on hepatic mitochondrial bioenergetic function in mice. MAIN METHODS: Mice were treated with caffeine (20mg/kg, intraperitoneal (i.p.)) or its vehicle and, after 30minutes, APAP (250mg/kg, i.p.) or its vehicle. Four hours later, livers were removed, and the parameters associated with mitochondrial function and oxidative stress were evaluated. Hepatic cellular oxygen consumption was evaluated by high-resolution respirometry (HRR). KEY FINDINGS: APAP treatment decreased cellular oxygen consumption and mitochondrial complex activities in the livers of mice. Additionally, treatment with APAP increased swelling of isolated mitochondria from mice livers. On the other hand, caffeine administered with APAP was able to improve hepatic mitochondrial bioenergetic function. Treatment with APAP increased lipid peroxidation and reactive oxygen species (ROS) production and decreased glutathione levels in the livers of mice. Caffeine administered with APAP was able to prevent lipid peroxidation and the ROS production in mice livers, which may be associated with the improvement of mitochondrial function caused by caffeine treatment. SIGNIFICANCE: We suggest that the antioxidant effects of caffeine and/or its interactions with mitochondrial bioenergetics may be involved in its beneficial effects against APAP hepatotoxicity.

Reversal of bioenergetics dysfunction by diphenyl diselenide is critical to protection against the acetaminophen-induced acute liver failure.

Physiopathological conditions such as acute liver failure (ALF) induced by acetaminophen (APAP) can often impair the mitochondrial bioenergetics. Diphenyl diselenide [(PhSe)2] has been shown protects against APAP-induced ALF. The present study aimed to clarify the signaling mechanism involved in the protection of bioenergetics dysfunction associated with ALF-induced by APAP overdose. Mice received APAP (600mg/kg) or (PhSe)2 (15.6mg/kg) alone, or APAP+(PhSe)2, all the solutions were administered by the intraperitoneal (i.p.). Samples of liver, blood and liver mitochondria were collected at 2 and 4h after APAP administration. APAP-induced ALF was able to induce ALF by means of alteration on liver injury biomarkers, increased Nitrite and Nitrate levels and the impairment of oxidative phosphorylation capacity (OXPHOS). In parallel, APAP overdose promoted activation of nuclear factor erythroid 2-related factor 2 (Nrf2) and Heat shock protein 70 (HSP70) expression. (PhSe)2 was able to abolish the APAP-induced decline of OXPHOS and changes on the Nrf2-ARE pathway. In addition, (PhSe)2 elevated the levels of peroxisome proliferator-activated receptor-γ coactivator (PGC-1α), helping to restore the levels of nuclear respiratory factor 1 (NRF1) associated with mitochondrial biogenesis. In summary, the treatment with (PhSe)2 maintained mitochondrial function, promoted genes related to mitochondrial dynamic and demonstrating to play critical role in the modulation of cellular protective responses during ALF.

Eugenia uniflora leaf essential oil promotes mitochondrial dysfunction in Drosophila melanogaster through the inhibition of oxidative phosphorylation.

Eugenia uniflora L. (Myrtaceae family) has demonstrated several properties of human interest, including insecticide potential, due to its pro-oxidant properties. These properties likely result from the effects on its mitochondria, but the mechanism of this action is unclear. The aim of this work was to evaluate the mitochondrial bioenergetics function in Drosophila melanogaster exposed to E. uniflora leaf essential oil. For this, we used a high-resolution respirometry (HRR) protocol. We found that E. uniflora promoted a collapse of the mitochondrial transmembrane potential (ΔΨm). In addition the essential oil was able to promote the disruption of respiration coupled to oxidative phosphorylation (OXPHOS) and inhibit the respiratory electron transfer system (ETS) established with an uncoupler. In addition, exposure led to decreases of respiratory control ratio (RCR), bioenergetics capacity and OXPHOS coupling efficiency, and induced changes in the substrate control ratio. Altogether, our results suggested that E. uniflora impairs the mitochondrial function/viability and promotes the uncoupling of OXPHOS, which appears to play an important role in the cellular bioenergetics failure induced by essential oil in D. melanogaster.

Reproductive dysfunction after mercury exposure at low levels: evidence for a role of glutathione peroxidase (GPx) 1 and GPx4 in male rats.

Mercury is a ubiquitous environmental pollutant and mercury contamination and toxicity are serious hazards to human health. Some studies have shown that mercury impairs male reproductive function, but less is known about its effects following exposure at low doses and the possible mechanisms underlying its toxicity. Herein we show that exposure of rats to mercury chloride for 30 days (first dose 4.6µgkg-1, subsequent doses 0.07µgkg-1day-1) resulted in mean (±s.e.m.) blood mercury concentrations of 6.8±0.3ngmL-1, similar to that found in human blood after occupational exposure or released from removal of amalgam fillings. Even at these low concentrations, mercury was deposited in reproductive organs (testis, epididymis and prostate), impaired sperm membrane integrity, reduced the number of mature spermatozoa and, in the testes, promoted disorganisation, empty spaces and loss of germinal epithelium. Mercury increased levels of reactive oxygen species and the expression of glutathione peroxidase (GPx) 1 and GPx4. These results suggest that the toxic effects of mercury on the male reproductive system are due to its accumulation in reproductive organs and that the glutathione system is its potential target. The data also suggest, for the first time, a possible role of the selenoproteins GPx1 and GPx4 in the reproductive toxicity of mercury chloride.

The Impact of Previous Physical Training on Redox Signaling after Traumatic Brain Injury in Rats: A Behavioral and Neurochemical Approach.

Throughout the world, traumatic brain injury (TBI) is one of the major causes of disability, which can include deficits in motor function and memory, as well as acquired epilepsy. Although some studies have shown the beneficial effects of physical exercise after TBI, the prophylactic effects are poorly understood. In the current study, we demonstrated that TBI induced by fluid percussion injury (FPI) in adult male Wistar rats caused early motor impairment (24 h), learning deficit (15 days), spontaneous epileptiform events (SEE), and hilar cell loss in the hippocampus (35 days) after TBI. The hippocampal alterations in the redox status, which were characterized by dichlorofluorescein diacetate oxidation and superoxide dismutase (SOD) activity inhibition, led to the impairment of protein function (Na(+), K(+)-adenosine triphosphatase [ATPase] activity inhibition) and glutamate uptake inhibition 24 h after neuronal injury. The molecular adaptations elicited by previous swim training protected against the glutamate uptake inhibition, oxidative stress, and inhibition of selected targets for free radicals (e.g., Na(+), K(+)-ATPase) 24 h after neuronal injury. Our data indicate that this protocol of exercise protected against FPI-induced motor impairment, learning deficits, and SEE. In addition, the enhancement of the hippocampal phosphorylated nuclear factor erythroid 2-related factor (P-Nrf2)/Nrf2, heat shock protein 70, and brain-derived neurotrophic factor immune content in the trained injured rats suggests that protein expression modulation associated with an antioxidant defense elicited by previous physical exercise can prevent toxicity induced by TBI, which is characterized by cell loss in the dentate gyrus hilus at 35 days after TBI. Therefore, this report suggests that previous physical exercise can decrease lesion progression in this model of brain damage.

N-Acetylcysteine does not protect behavioral and biochemical toxicological effect after acute exposure of diphenyl ditelluride.

Diphenyl ditelluride (PhTe)2 is a versatile molecule used in the organic synthesis and it is a potential prototype for the development of novel biologically active molecules. The mechanism(s) involved in (PhTe)2 toxicity is(are) elusive, but thiol oxidation of critical proteins are important targets. Consequently, the possible remedy of its toxicity by thiol-containing compounds is of experimental and clinical interest. The present study aimed to investigate putative mechanisms underlying the toxicity of (PhTe)2 in vivo. We assessed behavioral and oxidative stress parameters in mice, including the modulation of antioxidant enzymatic defense systems. In order to mitigate such toxicity, N-acetylcysteine (NAC) was administered before (3 d) and simultaneously with (PhTe)2 (7 d). Mice were separated into six groups receiving daily injections of (1) TFK (2.5 ml/kg, intraperitonealy (i.p.)) plus canola oil (10 ml/kg, subcutaneously (s.c.)), (2) NAC (100 mg/kg, i.p.) plus canola oil s.c., (3) TFK i.p. plus (PhTe)2 (10 µmol/kg, s.c.), (4) TFK i.p. plus (PhTe)2 (50 µmol/kg, s.c.), (5) NAC plus (PhTe)2 (10 µmol/kg, s.c.), and (6) NAC plus (PhTe)2 (50 µmol/kg, s.c.). (PhTe)2 treatment started on the fourth day of treatment with NAC. Results demonstrated that (PhTe)2 induced behavioral alterations and inhibited important selenoenzymes (thioredoxin reductase and glutathione peroxidase). Treatments produced no or minor effects on the activities of antioxidant enzymes catalase and glutathione reductase. Contrary to expected, NAC co-administration did not protect against the deleterious effects of (PhTe)2. Other low-molecular-thiol containing molecules should be investigated to determine whether or not they can be effective against ditellurides.

Sub-acute administration of (S)-dimethyl 2-(3-(phenyltellanyl) propanamido) succinate induces toxicity and oxidative stress in mice: unexpected effects of N-acetylcysteine.

The organic tellurium compound (S)-dimethyl 2-(3-(phenyltellanyl) propanamide) succinate (TeAsp) exhibits thiol-peroxidase activity that could potentially offer protection against oxidative stress. However, data from the literature show that tellurium is a toxic agent to rodents. In order to mitigate such toxicity, N-acetylcysteine (NAC) was administered in parallel with TeAsp during 10 days. Mice were separated into four groups receiving daily injections of (A) vehicle (PBS 2.5 ml/kg, i.p. and DMSO 1 ml/kg, s.c.), (B) NAC (100 mg/kg, i.p. and DMSO s.c.), (C) PBS i.p. and TeAsp (92.5 µmol/kg, s.c), or (D) NAC plus TeAsp. TeAsp treatment started on the fourth day. Vehicle or NAC-treated animals showed an increase in body weight whereas TeAsp caused a significant reduction. Contrary to expected, NAC co-administration potentiated the toxic effect of TeAsp, causing a decrease in body weight. Vehicle, NAC or TeAsp did not affect the exploratory and motor activity in the open-field test at the end of the treatment, while the combination of NAC and TeAsp produced a significant decrease in these parameters. No DNA damage or alterations in cell viability were observed in leukocytes of treated animals. Treatments produced no or minor effects on the activities of antioxidant enzymes catalase, glutathione peroxidase and glutathione reductase, whereas the activity of the thioredoxin reductase was decreased in the brain and increased the liver of the animals in the groups receiving TeAsp or TeAsp plus NAC. In conclusion, the toxicity of TeAsp was potentiated by NAC and oxidative stress appears to play a central role in this process.

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.

Evaluation of the biological effects of (S)-dimethyl 2-(3-(phenyltellanyl) propanamido) succinate, a new telluroamino acid derivative of aspartic acid.

(S)-dimethyl 2-(3-(phenyltellanyl) propanamido) succinate, a new telluroamino acid derivative, showed remarkable glutathione peroxidase (GPx)-like activity, attesting to its antioxidant potential. However, the stability and toxicity of this compound has not yet been investigated. The present study was designed to investigate the pharmacological/toxicological properties of this compound in vitro and in vivo. In vitro, this telluroamino acid derivative significantly blocked spontaneous and Fe(II)-induced TBARS formation in rat brain homogenates, demonstrating high antioxidant activity. In addition, it exhibited GPx-like and thiol oxidase activities. However, when subcutaneously administered to mice, (S)-dimethyl 2-(3-(phenyltellanyl) propanamido) succinate indicated genotoxic and mutagenic effect in adult male mice. Considering the differential effects of (S)-dimethyl 2-(3-(phenyltellanyl) propanamido) succinate in vitro and in vivo, additional experiments are needed to elucidate the mechanism(s) by which this compound displays its antioxidant/toxicological effects.

Structure-activity relationship of flavonoids derived from medicinal plants in preventing methylmercury-induced mitochondrial dysfunction.

In the present study, we investigated the potential protective effects of three flavonoids (myricetin, myricitrin and rutin) derived from medicinal plants against methyl mercury (MeHg)-induced mitochondrial dysfunction in vitro. Incubation of mouse brain mitochondria with MeHg induced a significant decrease in mitochondrial function, which was correlated with decreased glutathione (GSH) levels and increased generation of reactive oxygen species (ROS) and lipid peroxidation. The co-incubation of mouse brain mitochondria with myricetin or myricitrin caused a concentration-dependent decrease of MeHg-induced mitochondrial dysfunction and oxidative stress. The flavonoid rutin was ineffective in counteracting MeHg toxicity. Among the three tested flavonoids, myricetin was the most efficient in protecting against MeHg-induced mitochondrial dysfunction. Moreover, myricetin completely blocked MeHg-induced ROS formation and lipid peroxidation and partially prevented MeHg-induced GSH depletion. The ability of myricetin to attenuate MeHg-induced mitochondrial dysfunction and oxidative stress appears to be related to its higher scavenging capability when compared to myricitrin and rutin. Overall, the results suggest that MeHg-induced mitotoxicity is associated with oxidative stress. The ability of myricetin to prevent MeHg-induced oxidative damage in brain mitochondria renders this flavonoid a promising molecule for further in vivo studies in the search for potential antidotes to counteract MeHg-induced neurotoxicity.

Folic acid administration prevents ouabain-induced hyperlocomotion and alterations in oxidative stress markers in the rat brain.

OBJECTIVE: Bipolar disorder (BD) is a chronic, prevalent, and highly debilitating psychiatric illness. Folic acid has been shown to have antidepressant-like effects in preclinical and clinical studies and has also been suggested to play a role in BD. The present work investigates the therapeutic value of folic acid supplementation in a preclinical animal model of mania induced by ouabain. METHODS: Male Wistar rats were treated twice daily for seven days with folic acid (10, 50, and 100 mg/kg, p.o.) or the mood stabilizer lithium chloride (LiCl) (45 mg/kg, p.o.). One day after the last dose was given, the animals received an i.c.v. injection of ouabain (10 microM), a Na(+),K(+)-ATPase-inhibiting compound. Locomotor activity was assessed in the open-field test. Thiobarbituric acid-reactive substance (TBARS) levels, glutathione peroxidase (GPx), and glutathione reductase (GR) activities were measured in the cerebral cortex and hippocampus. RESULTS: Ouabain (10 microM, i.c.v.) significantly increased motor activity in the open-field test, and seven days of pretreatment with folic acid (50 mg/kg, p.o.) or LiCl (45 mg/kg, p.o.) completely prevented this effect. Ouabain treatment elicited lipid peroxidation (increased TBARS levels) and reduced GPx activity in the hippocampus. GR activity was decreased in the cerebral cortex and hippocampus. These effects were prevented by pretreatment with folic acid and LiCl. CONCLUSIONS: Our results show that folic acid, similarly to LiCl, produces a clear antimanic action and prevents the neurochemical alterations indicative of oxidative stress in an animal model of mania.

Complex methylmercury-cysteine alters mercury accumulation in different tissues of mice.

Methylmercury (MeHg) can cause deleterious effects in vertebrate tissues, particularly in the central nervous system. MeHg interacts with sulfhydryl groups from low and high molecular weight thiols in the blood, which can facilitate MeHg uptake into different tissues. The purpose of this study was to examine the effect of MeHg-Cysteine (MeHg-Cys) complex administration on Hg-uptake in cerebral areas (cortex and cerebellum), liver and kidney of adult mice. Animals were divided into four groups: control (1 mL/kg distilled water), MeHg (2 mg/kg), Cys (2 mg/kg) and MeHg-Cys complex (0.8 molar ratio). Mice received one intraperitoneal injection per day for 60 consecutive days. Treatment with MeHg significantly increased mercury concentrations in all tissues analysed when compared with the control group. The accumulation of mercury in brain and in liver was further increased in animals that received MeHg-Cys complex when compared with the MeHg alone group. However, renal Hg decreased in MeHg-Cys treated mice, when compared with the group treated only with MeHg. In summary, the transport of MeHg-Cys complex was tissue-specific, and we observed an increase in its uptake by liver and brain as well as a decrease in kidney.

Expression of tyrosine hydroxylase increases the resistance of human neuroblastoma cells to oxidative insults.

In this study, we demonstrate that human neuroblastoma SH-SY5Y cells transfected with human tyrosine hydroxylase isoform 1 (SH + TH cells) were substantially more resistant to cell death induced by hydrogen peroxide and 6-hydroxydopamine when compared to wild-type SH-SY5Y cells (SH cells). SH + TH cells exhibit increased levels of dopamine (DA) compared to SH cells. Incubation with hydrogen peroxide or 6-hydroxydopamine (10-100microM) for 24 h caused a significant reduction in cell viability and increased apoptosis in both cell types. However, these effects were significantly reduced in the SH + TH cells when compared to the SH cells. The SH + TH cells showed an improved ability to detoxify peroxide, which correlated with an increase in glutathione peroxidase and glutathione reductase activities, while catalase activity was unchanged. Our data suggest that a preconditioning-like mechanism linked to higher DA levels increased the resistance of SH + TH cells against oxidative insults, which is at least in part related to an augmentation in the activity of glutathione-related antioxidant enzymes.

Manganese induces sustained Ser40 phosphorylation and activation of tyrosine hydroxylase in PC12 cells.

Manganese (Mn2+) is an essential metal involved in normal functioning of a range of physiological processes. However,occupational overexposure to Mn2+ causes neurotoxicity. The dopaminergic system is a particular target for Mn2+ neurotoxicity.Tyrosine hydroxylase (TH) is the rate limiting enzyme for dopamine synthesis and is regulated acutely by phosphorylation at Ser40 and chronically by protein synthesis. In this study we used pheochromocytoma 12 cells to investigate the effects of Mn2+ exposure on the phosphorylation and activity of TH. Mn2+ treatment for 24 h caused a sustained increase in Ser40 phosphorylation and TH activity at a concentration of 100 lM, without altering the level of TH protein orPC12 cell viability. Inhibition of protein kinase A and protein kinase C and protein kinases known to be involved in sustained phosphorylation of TH in response to other stimuli didnot block the effects of Mn2+ on Ser40 phosphorylation.A substantial increase in H2O2 production occurred in response to 100 lM Mn2+. The antioxidant Trolox completely inhibited H2O2 production but did not block TH phosphorylation at Ser40, indicating that oxidative stress was not involved. Sustained TH phosphorylation at Ser40 and the consequent activation of TH both occurred at low concentrations of Mn2+ and this provides a potential new mechanism for Mn2+-induced neuronal action that does not involve H2O2-mediated cell death.