Anti-inflammatory and antinociceptive effects of 2,2`-dipyridyl diselenide through reduction of inducible nitric oxide synthase, nuclear factor-kappa B and c-Jun N-terminal kinase phosphorylation levels in the mouse spinal cord.

Appropriate treatment of pain requires analgesics and anti-inflammatory drugs generally associated with undesirable side effects and not fully effective in a significant proportion of patients. Organoselenium compounds elicit a plenty of pharmacological effects in different animal models. Among these compounds, the 2,2`-dipyridyl diselenide (DPD) has a potent antioxidant effect and low toxicity. In this way, the aim of this study was to investigate the possible DPD antinociceptive effect and its mechanism of action, as well as the safety of the compound. Female Swiss mice were treated with vehicle or DPD (0.01-50 mg/kg) intragastrically. Dose-response curve and time-course of the antinociceptive effect of DPD were performed on formalin and tail immersion tests. Morphine (2.5 mg/kg, subcutaneous, 15 min earlier) was used as a positive control in behavioral tests. The results showed that DPD presents a rapid antinociceptive effect in low doses, without changing the spontaneous locomotor activity and parameters of toxicity in mice. The DPD antinociceptive effect was also confirmed in male Swiss mice in both formalin and tail immersion tests. In addition, DPD reduced the paw edema induced by 2.5% formalin and ear edema induced by 2.5% croton oil. l-arginine (600 mg/kg, intraperitoneally) reduced the DPD antinociceptive effect in the first phase of the formalin test. Moreover, DPD attenuated the increase in iNOS, NF-κB and JNK phosphorylation in the spinal cord of mice injected with formalin. These results showed that DPD exerts peripheral and central nociceptive actions associated with anti-inflammatory effect and this organoselenium compound could be an interesting alternative therapy for pain treatment.

Antidepressant effects of creatine on amyloid ß1-40-treated mice: The role of GSK-3ß/Nrf2 pathway.

Alzheimer's disease (AD) is characterized by progressive synaptic dysfunction and neuronal lost in specific brain areas including hippocampus, resulting in memory/learning deficits and cognitive impairments. In addition, non-cognitive symptoms are reported in AD patients, such as anxiety, apathy and depressed mood. The current antidepressant drugs present reduced efficacy to improve depressive symptoms in AD patients. Here, we investigated the ability of creatine, a compound with neuroprotective and antidepressant properties, to counteract amyloid ß1-40 peptide-induced depressive-like behavior in mice. Moreover, we addressed the participation of the intracellular signaling pathway mediated by glycogen synthase kinase-3ß (GSK-3ß)/nuclear factor erythroid-2-related factor 2 (Nrf2) in the creatine effects. Aß1-40 administration (400 pmol/mouse, i.c.v.) increased the immobility time in the tail suspension test and decreased the grooming time and increased latency to grooming in the splash test, indicative of depressive-like behavior. These impairments were attenuated by creatine (0.01 and 10 mg/kg, p.o.) and fluoxetine (10 mg/kg, p.o., positive control). No significant alterations on locomotor performance were observed in the open field. Aß1-40 administration did not alter hippocampal phospho-GSK-3ß (Ser9)/total GSK-3ß, total GSK-3ß and heme oxygenase-1 (HO-1) immunocontents. However, Aß1-40-infused mice treated with creatine (0.01 mg/kg) presented increased phosphorylation of GSK-3ß(Ser9) and HO-1 immunocontent in the hippocampus. Fluoxetine per se increased GSK-3ß(Ser9) phosphorylation, but did not alter HO-1 levels. In addition, Aß1-40 administration increased hippocampal glutathione (GSH) levels as well as glutathione reductase (GR) and thioredoxin reductase (TrxR) activities, and these effects were abolished by creatine and fluoxetine. This study provides the first evidence of the antidepressive-like effects of creatine in Aß1-40-treated mice, which were accompanied by hippocampal inhibition of GSK-3ß and modulation of antioxidant defenses. These findings indicate the potential of creatine for the treatment of depression associated with AD.

Biochemical and histological evaluations of anti-inflammatory and antioxidant p-chloro-selenosteroid actions in acute murine models of inflammation.

This study investigated the potential p-chloro-selenosteroid (PCS) anti-inflammatory effect in different animal models of acute inflammation. In order to determine a time- and a dose-curve response of action, female adult Swiss mice (25-35g) were divided in different groups and pretreated by the intragastric route (i.g.) with PCS (5-10mg/kg) and after the specific times (5, 30 and 60min) the ear inflammation was induced with croton oil (2.5%, 20µl). The ear edema, myeloperoxidase (MPO) activity and histological analyses were performed. In a second experiment, the pleurisy model was used to determine the PCS protective effect (10mg/kg, i.g., 30min before induction) in the inflammatory and oxidative alterations induced by an intrapleural injection of a 1% carrageenan solution (0.1ml) in exudate and lung samples. Dexamethasone (1mg/kg, i.g.) was used as positive control for both models. Statistical analysis was performed through a One-Way ANOVA test followed by the Newman-Keuls' test. Pretreatment of 30min with PCS, only at a dose of 10mg/kg, decreased ear edema and the MPO activity as well as the histological alterations induced by croton oil. In the pleurisy model, PCS (10mg/kg, i.g.; 30min) reduced the leukocyte counts, histological alterations, MPO and adenosine deaminase activities, oxidative damage and the non-enzymatic antioxidant defense imbalance. PCS had a similar anti-inflammatory profile to dexamethasone; however, it showed a better antioxidant effect. PCS had anti-inflammatory and antioxidant actions in two well established inflammation models in mice.

2-Phenylethynyl-butyltellurium attenuates amyloid-ß peptide(25-35)-induced learning and memory impairments in mice.

Our previous study demonstrated that 2-phenylethynyl-butyltellurium (PEBT), an organotellurium compound, enhances memory in mice. In this study, the effects of PEBT on cognitive impairment induced by Aß25-35 were assessed by Morris water maze and step-down inhibitory avoidance tasks. Mice received a single intracerebroventricular injection of Aß25-35 (3 nmol/3 µl/per site) and a daily oral administration of PEBT (1 mg/kg, for 10 days). PEBT significantly improved Aß-induced learning deficits on the training session in the Morris water maze. At the probe trial session, PEBT significantly decreased the escape latency and increased the number of crossings in the platform local compared with the Aß-treated group. PEBT significantly improved Aß-induced memory impairment in the step-down inhibitory avoidance task. General locomotor activity was similar in all groups. This study showed that PEBT ameliorated the impairments of spatial and nonspatial long-term memory evaluated on Morris water maze and step-down inhibitory avoidance tasks, respectively. The results suggest that PEBT could be considered a candidate for the prevention of memory deficits such as those observed in Alzheimer's disease.

Hyperthermic seizures enhance responsiveness to pentylenetetrazole and induce cognitive dysfunction: protective effect of 3-alkynyl selenophene.

AIMS: In this study we investigated the effect of pre-treatment with 3-alkynyl selenophene (3-ASP) against the increase in responsiveness to pentylenetetrazole [PTZ seizure threshold] and cognitive dysfunction induced by experimental febrile seizures (FS). The effects of 3-ASP were compared to those of diazepam (DZP). MAIN METHODS: Young rats, at postnatal day 21, developed seizures after exposure to a stream of heated air to approximately 41°C. A non-spatial long-term memory and PTZ seizure threshold were determined 30 days after FS. The behavioural seizures were stereotyped followed by facial automatisms, often followed by body flexion. Young rats were pre-treated with 3-ASP (50 and 100mg/kg; per oral route), DZP (1 and 5mg/kg; intraperitoneally) or vehicle. KEY FINDINGS: 3-ASP and DZP pre-treatments were not effective in protecting against seizures induced by FS. 3-ASP pre-treatment protected against the increase in responsiveness to PTZ and cognitive dysfunction induced by FS. DZP pre-treatment was effective in protecting against the increase in responsiveness to PTZ, but not, against the impaired memory induced by FS. SIGNIFICANCE: 3-ASP pre-treatment protected against impairment of memory performance in the step-down passive avoidance task and the increase in the susceptibility to seizures caused by FS early in life of rats.

Diphenyl diselenide attenuates hepatic and hematologic toxicity induced by chlorpyrifos acute exposure in rats.

PURPOSE: In this study, we investigated the effect of diphenyl diselenide [(PhSe)(2)] on chlorpyrifos (CPF)-induced hepatic and hematologic toxicity in rats. METHODS: Rats were pre-treated with (PhSe)(2) (5 mg/kg) via the oral route (oral gavage) once a day for 7 days. On the eighth and ninth days, rats were treated with (PhSe)(2) (5 mg/kg) 30 min prior to CPF (50 mg/kg, by subcutaneous route). The aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase activities were determined in plasma of rats. Lipid peroxidation, protein carbonyl, and non-protein thiol levels as well as catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase, and gluthatione S-transferase activities were determined in livers of rats. Hematological parameters were also determined. RESULTS: The results showed that CPF caused hepatic oxidative damage, as demonstrated by an increase in lipid peroxidation and protein carbonyl levels which was associated with a decrease in antioxidant defenses. CPF exposure caused a reduction in the leukocyte, indicating hematologic toxicity. (PhSe)(2) was effective in attenuating these toxic effects caused by CPF exposure in rats. CONCLUSIONS: The results indicated that (PhSe)(2) was effective in protecting the hepatic and hematologic toxicity induced by acute CPF exposure in rats.

Involvement of GABAergic and glutamatergic systems in the anticonvulsant activity of 3-alkynyl selenophene in 21 day-old rats.

In this study, we investigated the role of GABAergic and glutamatergic systems in the anticonvulsant action of 3-alkynyl selenophene (3-ASP) in a pilocarpine (PC) model of seizures. To this purpose, 21 day-old rats were administered with an anticonvulsant dose of 3-ASP (50 mg/kg, per oral, p.o.), and [(3)H]γ-aminobutyric acid (GABA) and [(3)H]glutamate uptakes were carried out in slices of cerebral cortex and hippocampus. [(3)H]GABA uptake was decreased in cerebral cortex (64%) and hippocampus (58%) slices of 21 day-old rats treated with 3-ASP. In contrast, no alteration was observed in [(3)H]glutamate uptake in cerebral cortex and hippocampus slices of 21 day-old rats that received 3-ASP. Considering the drugs that increase synaptic GABA levels, by inhibiting its uptake or catabolism, are effective anticonvulsants, we further investigated the possible interaction between sub-effective doses of 3-ASP and GABA uptake or GABA transaminase (GABA-T) inhibitors in PC-induced seizures in 21 day-old rats. For this end, sub-effective doses of 3-ASP (10 mg/kg, p.o.) and DL-2,4-diamino-n-butyric acid hydrochloride (DABA, an inhibitor of GABA uptake--2 mg/kg, intraperitoneally; i.p.) or aminooxyacetic acid hemihydrochloride (AOAA; a GABA-T inhibitor--10 mg/kg, i.p.) were co-administrated to 21 day-old rats before PC (400 mg/kg; i.p.) treatment, and the appearance of seizures was recorded. Results demonstrated that treatment with AOAA and 3-ASP or DABA and 3-ASP significantly abolished the number of convulsing animals induced by PC. The present study indicates that 3-ASP reduced [(3)H]GABA uptake, suggesting that its anticonvulsant action is related to an increase in inhibitory tonus.

2-phenylethynyl-butyltellurium improves memory in mice.

The present study was conducted to evaluate the effect of 2-phenylethynyl-butyltellurium (PEBT), an organotellurium compound, at doses of 5 and 10 mg/kg on memory, employing the step-down inhibitory avoidance task in mice. Moreover, the involvement of glutamate uptake and release in cerebral cortex and hippocampus of mice was investigated. A single oral administration (p.o.) of PEBT at the dose of 10 mg/kg 1h before training (acquisition), immediately after training (consolidation) or 1 h before the test session (retrieval) of the step-down inhibitory avoidance task increased the step-through latency time in comparison to the control mice. In the open-field test, no significant differences in the number of crossings and rearings were observed among groups. The [(3)H]glutamate uptake by cerebral cortex and hippocampal slices of mice was significantly inhibited after 1h of treatment with PEBT. After 24h of PEBT exposure, only the hippocampal [(3)H]glutamate uptake was inhibited. The [(3)H]glutamate release by cerebral cortex and hippocampal synaptosomes of mice was not altered. These results suggest that PEBT improved memory stages (acquisition, consolidation and retrieval) in the step-down inhibitory avoidance task in mice. The improvement of memory by PEBT seems most likely to be mediated through an interaction with the amino acid transporters of the glutamatergic system.

Repeated malathion exposure induces behavioral impairment and AChE activity inhibition in brains of rat pups.

The present study evaluated if repeated malathion administration would cause behavioral impairment in rat pups. Na+K+ ATPase and acetylcholinesterase (AChE) activities were investigated in brains of rat pups. Malathion was administered (100 or 200 mg/kg) orally (p.o.), once a day for four consecutive days. Rat pups were submitted to behavioral tests on the 5th day, 24 h after the last malathion administration. Malathion at the dose of 200 mg/kg caused a significant increase in the negative geotaxis latency and a decrease in the rotarod latency of rat pups. Rat pups exposed to malathion at both doses showed a significant decrease in the forelimb support latency and an inhibition of brain AChE activity. Repeated exposure of rat pups to malathion caused a decrease in motor coordination, vestibular function and muscular strength/coordination. The brain activity of AChE is involved in the behavioral alterations caused by malathion in rat pups.

Antidepressant-like effect of m-trifluoromethyl-diphenyl diselenide in the mouse forced swimming test involves opioid and serotonergic systems.

Serotonergic and opioid systems have been implicated in major depression and in the action mechanism of antidepressants. The organoselenium compound m-trifluoromethyl-diphenyl diselenide (m-CF(3)-PhSe)(2) shows antioxidant and anxiolytic activities and is a selective inhibitor of monoamine oxidase A activity. The present study was designed to investigate the antidepressant-like effect of (m-CF(3)-PhSe)(2) in female mice, employing the forced swimming test. The involvement of the serotonergic and opioid systems in the antidepressant-like effect of (m-CF(3)-PhSe)(2) was appraised. (m-CF(3)-PhSe)(2) at doses of 50 and 100mg/kg (p.o.) exhibited antidepressant-like action in the forced swimming test. The effect of (m-CF(3)-PhSe)(2) (50mg/kg p.o.) was prevented by pretreatment of mice with WAY100635 (0.1mg/kg, s.c. a selective 5-HT(1A) receptor antagonist), ritanserin (4 mg/kg, i.p., a non-selective 5HT(2A/2C) receptor antagonist), ondansetron (1mg/kg, i.p., a selective 5-HT(3) receptor antagonist) and naloxone (1mg/kg, i.p., a non-selective antagonist of opioid receptors). These results suggest that (m-CF(3)-PhSe)(2) produced an antidepressant-like effect in the mouse forced swimming test and this effect seems most likely to be mediated through an interaction with serotonergic and opioid systems.

Diphenyl diselenide and diphenyl ditelluride: neurotoxic effect in brain of young rats, in vitro.

This study examined whether maturity of rat brain may be relevant for the sensitivity to diphenyl diselenide (PhSe)(2) and diphenyl ditelluride (PhTe)(2) on [(3)H]glutamate uptake and release, in vitro. Brain synaptosomes were isolated from young (14- and 30-day-old) and adult rats and incubated at different concentrations of (PhSe)(2) or (PhTe)(2). The results demonstrated that the highest concentration (100 microM) of (PhSe)(2) and (PhTe)(2) inhibited the [(3)H]glutamate uptake by synaptosomes of brain at all ages. In the adult brain, (PhSe)(2) did not inhibit the [(3)H]glutamate uptake at the lowest concentration (10 microM). The highest concentration of (PhTe)(2) inhibited the [(3)H]glutamate uptake more in the 14-day-old than in the 30-day-old rats or adult rats. In the 30-day-old animals, the highest concentration of (PhSe)(2), and the lowest concentration of (PhTe)(2), increased the basal [(3)H]glutamate release. At the highest concentration, (PhTe)(2) increased the basal and K(+)-stimulated glutamate release on all ages evaluated. The results suggest that (PhSe)(2) and (PhTe)(2) caused alterations on the homeostasis of the glutamatergic system at the pre-synaptic level. These alterations were age-, concentration-, and compound-dependent. The maturity of rat brain is relevant for the glutamatergic system sensitivity to (PhSe)(2) and (PhTe)(2) .

Oral administration of diphenyl diselenide potentiates hepatotoxicity induced by carbon tetrachloride in rats.

Carbon tetrachloride (CCl4) is a model for studying free radical-induced liver injury and screening hepato-protective drugs. Numerous studies have reported the involvement of oxidative stress in CCl4-induced liver damage and the hepato-protective effects mediated by different antioxidants. The present study examined the effects of diphenyl diselenide, (PhSe)2, on hepatotoxicity induced by CCl4 in rats. To this end, male Wistar rats received (PhSe)2 by oral route at the dosage of 31.2 mg/kg for one or two days. After the second day of treatment, rats received CCl4 orally in a single dose. The liver and kidney were utilized for determination of histopathology, biochemical [aspartate (ALT) and alanine (AST) aminotransferases, alkaline phosphatase (ALP), total bilirrubin (TB) and gamaglutamyl transferase (GGT)] and toxicological parameters [thiobarbituric reactive species (TBARS) levels, catalase activity, ascorbic acid, nonprotein thiols (NPSH) and aminolevulinate dehydratase (-ALA-D) activity]. Repeated administration of (PhSe)2 caused a marked potentiation of hepatotoxicity induced by CCl4 exposure, as manifested by an increase in biochemical parameters (AST, ALT, ALP, GGT and BT) and severe alteration in histopathology. This study also demonstrated a potentiation of TBARS levels and a consequent depletion of important antioxidant defenses including catalase and ascorbic acid. Pre-treatment with a single dose of (PhSe)2 prevented the effect of strychnine, a substrate for CYPs, abolishing lethality in mice. This result indicates that (PhSe)2 prevented animal death, suggesting an activator action of (PhSe)2 in CYPs. This study clearly indicates that (PhSe)2 potentiated acute hepatic damage induced by CCl4.