Andiara E. Freitas

Ascorbic acid treatment, similarly to fluoxetine, reverses depressive-like behavior and brain oxidative damage induced by chronic unpredictable stress

Reactive oxygen species (ROS) have been shown to play a role in the pathophysiology of depression. Taking into account that experimental chronic unpredictable stress (CUS) induces depressive-like behavior and that ascorbic acid has antidepressant-like effect in animals, the objective of this study was to investigate the influence of ascorbic acid on depressive-like behavior induced by CUS paradigm, serum corticosterone levels and markers of oxidative stress in cerebral cortex and hippocampus of mice. Animals were submitted to CUS procedure during 14 days. From the 8th to the 14th day mice received ascorbic acid (10 mg/kg) or fluoxetine (10 mg/kg, conventional antidepressant, positive control) once a day by oral route. On 15th day behavioral and biochemical parameters were analyzed. CUS exposure caused a depressive-like behavior evidenced by the increased immobility time in the tail suspension test and decreased time in which mice spent grooming in the splash test. Depressive-like behavior induced by CUS was accompanied by a significant increased lipid peroxidation (cerebral cortex and hippocampus), decreased catalase (CAT) (cerebral cortex and hippocampus) and glutathione reductase (GR) (hippocampus) activities and reduced levels of glutathione (cerebral cortex). Repeated ascorbic acid or fluoxetine administration significantly reversed CUS-induced depressive-like behavior and oxidative damage. No alteration was observed in locomotor activity, corticosterone levels and glutathione peroxidase (GPx) activity. These findings indicate a rapid and robust effect of ascorbic acid in reversing behavioral and biochemical alterations induced by CUS in mice, suggesting that this vitamin may be an alternative approach for the management of depressive symptoms.

α-Tocopherol administration produces an antidepressant-like effect in predictive animal models of depression.

This study investigated the antidepressant potential of alpha-tocopherol, the most active and abundant form of vitamin E, in the forced swim test (FST) and tail suspension test (TST). The acute oral treatment with alpha-tocopherol at the doses of 30 and 100mg/kg reduced the immobility time in the FST and in the TST. A single i.c.v. administration of alpha-tocopheryl phosphate, a water-soluble analogue of alpha-tocopherol, also reduced the immobility time in the FST (0.1 and 1 nmol/site) and in the TST (0.1 nmol/site). In addition, the long-term treatment (28 days) with alpha-tocopherol (10mg/kg, p.o.) significantly reduced the immobility time in the FST. Moreover, a subeffective dose of alpha-T (10mg/kg, p.o.) potentiated the effect of fluoxetine (10mg/kg, p.o.) in the FST. The long-term treatment with alpha-T was able to increase the glutathione (GSH) antioxidant defense system, while the acute treatment was not. The long-term treatment with alpha-tocopherol (10mg/kg) increased the GSH levels in the hippocampus and in the prefrontal cortex and increased the glutathione peroxidase and glutathione reductase activity in the hippocampus (10mg/kg) and in the prefrontal cortex (10-100mg/kg). The long-term treatment with fluoxetine (10mg/kg, p.o.), a positive control, was also able to increase the GSH levels in the hippocampus, but failed to alter the activity of both enzymes. Besides the specific antidepressant-like effect, long-term, but not the acute treatment with alpha-T, especially in the doses that produced an antidepressant-like effect (10mg/kg), improved the antioxidant defenses in the mouse hippocampus and prefrontal cortex, two structures closely implicated in the pathophysiology of depression.

Antidepressant-like action of the ethanolic extract from Tabebuia avellanedae in mice: evidence for the involvement of the monoaminergic system.

The antidepressant-like effect of the ethanolic extract obtained from barks of Tabebuia avellanedae, a plant widely employed in folk medicine, was investigated in two predictive models of depression: forced swimming test (FST) and tail suspension test (TST) in mice. Additionally, the mechanisms involved in this antidepressant-like action and the effects of the association of the extract with the antidepressants fluoxetine, desipramine and bupropion in the TST were investigated. The extract from T. avellanedae produced an antidepressant-like effect, in the FST (100 mg/kg, p.o.) and in the TST (10-300 mg/kg, p.o.), without accompanying changes in ambulation when assessed in the open-field test. The anti-immobility effect of the extract (30 mg/kg, p.o.) in the TST was prevented by pre-treatment of mice with ketanserin (5 mg/kg, i.p., a preferential 5-HT(2A) receptor antagonist), prazosin (1 mg/kg, i.p., an alpha(1)-adrenoceptor antagonist), yohimbine (1 mg/kg, i.p., an alpha(2)-adrenoceptor antagonist), propranolol (2 mg/kg, i.p., a beta-adrenoceptor antagonist), sulpiride (50 mg/kg, i.p., a dopamine D(2) receptor antagonist) and SCH23390 (0.05 mg/kg, s.c., a dopamine D(1) receptor antagonist). The combined administration of a subeffective dose of WAY100635 (0.1 mg/kg, s.c., a selective 5-HT(1A) receptor antagonist) and a subeffective dose of the extract (1 mg/kg, p.o.) produced a significant reduction in the immobility time in the TST. In addition, the combination of fluoxetine (1 mg/kg, p.o.), desipramine (0.1 mg/kg, p.o.), or bupropion (1 mg/kg, p.o.) with a subeffective dose of the extract (1 mg/kg, p.o.) produced a synergistic antidepressant-like effect in the TST, without causing hyperlocomotion in the open-field test. It may be concluded that the extract from T. avellanedae produces an antidepressant-like effect in the FST and in the TST that is dependent on the monoaminergic system. Taken together, our results suggest that T. avellanedae deserves further investigation as a putative alternative therapeutic tool that could help the conventional pharmacotherapy of depression.

Agmatine abolishes restraint stress-induced depressive-like behavior and hippocampal antioxidant imbalance in mice.

Agmatine has been recently emerged as a novel candidate to assist the conventional pharmacotherapy of depression. The acute restraint stress (ARS) is an unavoidable stress situation that may cause depressive-like behavior in rodents. In this study, we investigated the potential antidepressant-like effect of agmatine (10mg/kg, administered acutely by oral route) in the forced swimming test (FST) in non-stressed mice, as well as its ability to abolish the depressive-like behavior and hippocampal antioxidant imbalance induced by ARS. Agmatine reduced the immobility time in the mouse FST (1-100mg/kg) in non-stressed mice. ARS caused an increase in the immobility time in the FST, indicative of a depressive-like behavior, as well as hippocampal lipid peroxidation, and an increase in the activity of hippocampal superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR) activities, reduced catalase (CAT) activity and increased SOD/CAT ratio, an index of pro-oxidative conditions. Agmatine was effective to abolish the depressive-like behavior induced by ARS and to prevent the ARS-induced lipid peroxidation and changes in SOD, GR and CAT activities and in SOD/CAT activity ratio. Hippocampal levels of reduced glutathione (GSH) were not altered by any experimental condition. In conclusion, the present study shows that agmatine was able to abrogate the ARS-induced depressive-like behavior and the associated redox hippocampal imbalance observed in stressed restraint mice, suggesting that its antidepressant-like effect may be dependent on its ability to maintain the pro-/anti-oxidative homeostasis in the hippocampus.

Involvement of nitric oxide–cGMP pathway in the antidepressant-like effect of ascorbic acid in the tail suspension test

Clinical and preclinical data reported that ascorbic acid has antidepressant properties. The present study was designed to investigate the participation of l-arginine-NO-cGMP pathway in the antidepressant-like effect of ascorbic acid in the tail suspension test (TST) in mice. The antidepressant-like effect of ascorbic acid (1mg/kg, p.o.) in the TST was prevented by the pre-treatment of mice with NMDA (0.1pmol/site, i.c.v.), l-arginine (750mg/kg, i.p., a substrate for nitric oxide synthase) or sildenafil (5mg/kg, i.p., a phosphodiesterase 5 inhibitor). The administration of MK-801 (0.001mg/kg, i.p), 7-nitroindazole (25mg/kg, i.p., a neuronal nitric oxide synthase inhibitor) or ODQ (30pmol/site i.c.v., a soluble guanylate cyclase inhibitor) in combination with a sub-effective dose of ascorbic acid (0.1mg/kg, p.o.) reduced the immobility time in the TST test when compared with either drug alone. None of the results in the TST appears to be due to a nonspecific locomotor effect. Our findings provide evidence that the effect of ascorbic acid in the TST involve an interaction with NMDA receptors and l-arginine-NO-cGMP pathway, contributing to the understanding of the mechanisms underlying the antidepressant-like effect of this vitamin.

Depressive-like behavior induced by tumor necrosis factor-α is abolished by agmatine administration.

Agmatine, an endogenous cationic amine, has been shown to exert antidepressant-like effects. This study investigated the ability of agmatine administered orally to abolish the depressive-like behavior induced by the administration of the pro-inflammatory cytokine, tumor necrosis factor (TNF-α) in mice. In control animals, agmatine (0.001, 0.01, 0.1, and 1 mg/kg) reduced the immobility time in the tail suspension test (TST). Acute administration of TNF-α (0.001 fg/mouse, i.c.v.) increased immobility time in the TST, indicative of a depressive-like behavior, and agmatine (0.0001, 0.1, and 1 mg/kg) prevented this effect. Additionally, we examined the effects of the combined administration of sub-effective doses of agmatine with antidepressants, the NMDA receptor antagonist MK-801 and the neuronal nitric oxide synthase inhibitor 7-nitroindazole (7-NI) in mice exposed to either TNF-α or saline. In control mice, administration of a sub-effective dose of agmatine (0.0001 mg/kg) combined with sub-effective doses of either fluoxetine (5 mg/kg, p.o.), imipramine (0.1 mg/kg, p.o.), bupropion (1 mg/kg, p.o.), MK-801 (0.001 mg/kg, p.o.) or 7-NI (25 mg/kg, i.p.) produced a synergistic antidepressant-like effect in the TST. All these administrations prevented the increased immobility time induced by TNF-α. The effect of agmatine in the TNF-α model of depression appears to be associated, at least partially, with an activation of the monoaminergic systems and inhibition of NMDA receptors and nitric oxide synthesis, although converging signal transduction pathways that may underlie the effect of agmatine should be further investigated. This set of results indicates that agmatine may constitute a new therapeutic alternative for the treatment of depression associated with inflammation.

Fluoxetine modulates hippocampal cell signaling pathways implicated in neuroplasticity in olfactory bulbectomized mice.

The olfactory bulbectomy (OB) animal model of depression is a well-established model that is capable of detecting antidepressant activity following chronic drug therapy, and the surgery results in behavioral and biochemical changes that are reminiscent of various symptoms of depression. In the present study, we investigated the degree to which 14 days of p.o. administration of the classic antidepressant fluoxetine (10mg/kg) were able to reverse OB-induced changes in behavior (namely, hyperactivity in the open-field test and reduced motivational and self-care behaviors in the splash test) and in the activation of hippocampal cell signaling pathways that are thought to be involved in synaptic plasticity. OB caused significant increases in ERK1 and CREB (Ser(133)) phosphorylation and in the expression of BDNF immunocontent, all of which were prevented by fluoxetine administration. Moreover, fluoxetine administration also caused a significant decrease in ERK2 phosphorylation in mice that had undergone OB. Neither Akt nor GSK-3β phosphorylation was altered in any experimental condition. In conclusion, the present study shows that OB can induce significant behavioral changes that are accompanied by the activation of hippocampal signaling pathways, namely the ERK1/CREB/BDNF pathway, which is involved in the synaptic plasticity. Conversely, fluoxetine prevented these OB-induced behavioral changes and avoided the activation of ERK1/CREB/BDNF in the hippocampus. Taken together, our results extend the data from the existing literature regarding OB-induced behavioral and neurochemical changes, and suggest a possible underlying mechanism that can account for the antidepressant effect of fluoxetine in this model.

Involvement of PI3K, GSK-3β and PPARγ in the antidepressant-like effect of folic acid in the forced swimming test in mice

Preclinical and clinical studies indicate that deficiency in folic acid plays a role in the pathophysiology of depression. Considering that alterations in the signaling pathways that regulate neuroplasticity and cellular survival are implicated in depressive disorders, the present study investigated the involvement of the phosphoinositide 3-kinase (PI3K), glycogen synthase kinase-3 (GSK-3β), and peroxisome proliferator-activated receptor-γ (PPARγ) in the antidepressant-like effect of folic acid in the forced swimming test (FST). The intracerebroventricular (i.c.v.) pre-treatment of mice with LY294002 (10 nmol/site, a PI3K inhibitor) or GW-9662 (1 µg/site, a PPARγ antagonist) prevented the antidepressant-like effect of folic acid (50 mg/kg, p.o.) in the FST. In addition, the administration of subeffective doses of the selective GSK-3β inhibitor, AR-A014418 (3 mg/kg, i.p.), a non-selective GSK-3β inhibitor, lithium chloride (10 mg/kg, p.o) or a PPARγ agonist, rosiglitazone (1 µg/site, i.c.v.) in combination with a subeffective dose of folic acid (10 mg/kg, p.o.) significantly reduced the immobility time in the FST as compared with either drug alone, without altering the locomotor activity. These results indicate that the antidepressant-like effect of folic acid in the FST might be dependent on inhibition of GSK-3β and activation of PPARγ, reinforcing the notion that these are important targets for antidepressant activity.

Antidepressant-like effect of ascorbic acid is associated with the modulation of mammalian target of rapamycin pathway

The present study investigated the involvement of the PI3K, GSK-3β, heme oxygenase-1 (HO-1) and mTOR in the antidepressant-like effect of ascorbic acid in the tail suspension test (TST). Male Swiss mice were pretreated with ascorbic acid (1 mg/kg, p.o.) or vehicle and 45 min after, LY294002 (10 μg/site, i.c.v., reversible PI3K inhibitor), rapamycin (0.2 nmol/site, i.c.v., selective mTOR inhibitor), zinc protoporphyrin (ZnPP - 10 ng/site, i.c.v., HO-1 inhibitor) or vehicle was administered. We also investigated the synergistic effect of ascorbic acid (0.1 mg/kg, p.o., sub-effective dose in the TST) with lithium chloride (10 mg/kg, p.o., non-selective GSK-3β inhibitor), AR-A014418 (0.01 μg/site, i.c.v., selective GSK-3β inhibitor) or cobalt protoporphyrin (CoPP - 0.01 μg/site, i.c.v., HO-1 inducer) in the TST. The antidepressant-like effect of ascorbic acid (1 mg/kg, p.o.) was prevented by the treatment of mice with LY294002, rapamycin or ZnPP. In addition, sub-effective doses of lithium chloride, AR-A014418 or CoPP, combined with a sub-effective dose of ascorbic acid produced a synergistic antidepressant-like effect. We also demonstrated that 1 h after its administration, ascorbic acid increased the phosphorylation of p70S6K and the immunocontent of PSD-95 in the hippocampus of mice. These results indicate that the antidepressant-like effect of ascorbic acid in the TST might be dependent on the activation of PI3K and mTOR, inhibition of GSK-3β as well as induction of HO-1, reinforcing the notion that these are important targets for antidepressant activity and contributing to better elucidate the mechanisms underlying the antidepressant-like effect of ascorbic acid.

Antidepressant-like effect of α-tocopherol in a mouse model of depressive-like behavior induced by TNF-α.

Taking into account that pro-inflammatory cytokines and oxidative and nitrosative stress are implicated in the pathogenesis of depression and that α-tocopherol has antidepressant, anti-inflammatory and antioxidant properties, this study investigated the ability of α-tocopherol to abolish the depressive-like behavior induced by i.c.v. administration of TNF-α in the mouse TST. Additionally, we investigated the occurrence of changes in the levels of Bcl2 and Bax and phosphorylation of GSK-3β (Ser9) in the hippocampus of mice. The administration of TNF-α (0.001fg/site, i.c.v.) increased the immobility time in the TST, which was prevented by the administration of α-tocopherol at the doses of 10, 30 and 100mg/kg (p.o.). Subeffective doses of α-tocopherol (10mg/kg, p.o.) and/or the antidepressants fluoxetine (5mg/kg, p.o.), imipramine (0.1mg/kg, p.o.) and bupropion (1mg/kg, p.o.), the NMDA receptor antagonist MK-801 (0.001mg/kg, p.o.) or the neuronal nitric oxide synthase inhibitor 7-nitroindazole (25mg/kg, i.p.) prevented the depressive-like effect induced by TNF-α. None of the treatments altered the locomotor activity of mice. Treatment with TNF-α and/or α-tocopherol did not alter the levels of Bax and Bcl2 or the phosphorylation of GSK-3β in the hippocampus of mice. Together, our results show a synergistic antidepressant-like effect of α-tocopherol with antidepressants against the depressive-like behavior induced by an inflammatory insult, suggesting that this vitamin may be useful to optimize conventional pharmacotherapy of depression, including depressive states associated with inflammatory conditions.