NMDA receptor-mediated modulation on glutamine synthetase and glial glutamate transporter GLT-1 is involved in the antidepressant-like and neuroprotective effects of guanosine.

Guanosine has been reported to elicit antidepressant-like responses in rodents, but if these actions are associated with its ability to afford neuroprotection against glutamate-induced toxicity still needs to be fully understood. Therefore, this study investigated the antidepressant-like and neuroprotective effects elicited by guanosine in mice and evaluated the possible involvement of NMDA receptors, glutamine synthetase, and GLT-1 in these responses. We found that guanosine (0.05 mg/kg, but not 0.01 mg/kg, p. o.) was effective in producing an antidepressant-like effect and protecting hippocampal and prefrontocortical slices against glutamate-induced damage. Our results also unveiled that ketamine (1 mg/kg, but not 0.1 mg/kg, i. p, an NMDA receptor antagonist) effectively elicited antidepressant-like actions and protected hippocampal and prefrontocortical slices against glutamatergic toxicity. Furthermore, the combined administration of sub-effective doses of guanosine (0.01 mg/kg, p. o.) with ketamine (0.1 mg/kg, i. p.) promoted an antidepressant-like effect and augmented glutamine synthetase activity and GLT-1 immunocontent in the hippocampus, but not in the prefrontal cortex. Our results also showed that the combination of sub-effective doses of ketamine and guanosine, at the same protocol schedule that exhibited an antidepressant-like effect, effectively abolished glutamate-induced damage in hippocampal and prefrontocortical slices. Our in vitro results reinforce that guanosine, ketamine, or sub-effective concentrations of guanosine plus ketamine protect against glutamate exposure by modulating glutamine synthetase activity and GLT-1 levels. Finally, molecular docking analysis suggests that guanosine might interact with NMDA receptors at the ketamine or glycine/d-serine co-agonist binding sites. These findings provide support for the premise that guanosine has antidepressant-like effects and should be further investigated for depression management.

Guanosine boosts the fast, but not sustained, antidepressant-like and pro-synaptogenic effects of ketamine by stimulating mTORC1-driven signaling pathway.

The mTORC1-dependent dendritic spines formation represents a key mechanism for fast and long-lasting antidepressant responses, but it remains to be determined whether this mechanism may account for the ability of guanosine in potentiating ketamine's actions. Here, we investigated the ability of ketamine plus guanosine to elicit fast and sustained antidepressant-like and pro-synaptogenic effects in mice and the role of mTORC1 signaling in these responses. The combined administration of subthreshold doses of ketamine (0.1 mg/kg, i.p.) and guanosine (0.01 mg/kg, p.o.) caused a fast (1 h - 24 h), but not long-lasting (7 days) reduction in the immobility time in the tail suspension test. This behavioral effect was paralleled by a rapid (started in 1 h) and transient (back to baseline in 24 h) increase on BDNF, p-Akt (Ser473), p-GSK-3ß (Ser9), p-mTORC1 (Ser2448), p-p70S6K (Thr389) immunocontent in the hippocampus, but not in the prefrontal cortex. Conversely, ketamine plus guanosine increased PSD-95 and GluA1 immunocontent in the prefrontal cortex, but not the hippocampus after 1 h, whereas increased levels of these proteins in both brain structures were observed after 24 h, but these effects did not persist after 7 days. The combined administration of ketamine plus guanosine raised the dendritic spines density in the ventral hippocampal DG and prefrontal cortex after 24 h Rapamycin (0.2 nmol/site, i.c.v.) abrogated the antidepressant-like effect and pro-synaptogenic responses triggered by ketamine plus guanosine. These results indicate that guanosine may boost the antidepressant-like effect of ketamine for up to 24 h by a mTORC1-dependent mechanism.

Low doses of ketamine and guanosine abrogate corticosterone-induced anxiety-related behavior, but not disturbances in the hippocampal NLRP3 inflammasome pathway.

RATIONALE: Guanosine has been shown to potentiate ketamine's antidepressant-like actions, although its ability to augment the anxiolytic effect of ketamine remains to be determined. OBJECTIVE: This study investigated the anxiolytic-like effects of a single administration with low doses of ketamine and/or guanosine in mice subjected to chronic administration of corticosterone and the role of NLRP3-driven signaling. METHODS: Corticosterone (20 mg/kg, p.o.) was administered for 21 days, followed by a single administration of ketamine (0.1 mg/kg, i.p.), guanosine (0.01 mg/kg, p.o.), or ketamine (0.1 mg/kg, i.p.) plus guanosine (0.01 mg/kg, p.o.). Anxiety-like behavior and NLRP3-related targets were analyzed 24 h following treatments. RESULTS: Corticosterone reduced the time spent in the open arms and the central zone in the elevated plus-maze test and open-field test, respectively. Corticosterone raised the number of unsupported rearings and the number and time of grooming, and decreased the latency to start grooming in the open-field test. Disturbances in regional distribution (increased rostral grooming) and grooming transitions (increased aborted and total incorrect transitions) were detected in corticosterone-treated mice. These behavioral alterations were accompanied by increased immunocontent of Iba-1, ASC, NLRP3, caspase-1, TXNIP, and IL-1ß in the hippocampus, but not in the prefrontal cortex. The treatments with ketamine, guanosine, and ketamine plus guanosine were effective to counteract corticosterone-induced anxiety-like phenotype, but not disturbances in the hippocampal NLRP3 pathway. CONCLUSIONS: Our study provides novel evidence that low doses of ketamine and/or guanosine reverse corticosterone-induced anxiety-like behavior and shows that the NLRP3 inflammasome pathway is likely unrelated to this response.

A low-dose combination of ketamine and guanosine counteracts corticosterone-induced depressive-like behavior and hippocampal synaptic impairments via mTORC1 signaling.

Ketamine exhibits rapid and sustained antidepressant responses, but its repeated use may cause adverse effects. Augmentation strategies have been postulated to be useful for the management/reduction of ketamine's dose and its adverse effects. Based on the studies that have suggested that ketamine and guanosine may share overlapping mechanisms of action, the present study investigated the antidepressant-like effect of subthreshold doses of ketamine and guanosine in mice subjected to repeated administration of corticosterone (CORT) and the role of mTORC1 signaling for this effect. The ability of the treatment with ketamine (0.1 mg/kg, i.p.) plus guanosine (0.01 mg/kg, p.o.) to counteract the depressive-like behavior induced by CORT (20 mg/kg, p.o., for 21 days) in mice, was paralleled with the prevention of the CORT-induced reduction on BDNF levels, Akt (Ser473) and GSK-3ß (Ser9) phosphorylation, and PSD-95, GluA1, and synapsin immunocontent in the hippocampus. No changes on mTORC1 and p70S6K immunocontent were found in the hippocampus and prefrontal cortex of any experimental group. No alterations on BDNF, Akt/GSK-3ß, mTORC1/p70S6K, and synaptic proteins were observed in the prefrontal cortex of mice. The antidepressant-like and pro-synaptogenic effects elicited by ketamine plus guanosine were abolished by the pretreatment with rapamycin (0.2 nmol/site, i.c.v., a selective mTORC1 inhibitor). Our results showed that the combined administration of ketamine and guanosine at low doses counteracted CORT-induced depressive-like behavior and synaptogenic disturbances by activating mTORC1 signaling. This study supports the notion that the combined administration of guanosine and ketamine may be a useful therapeutic strategy for the management of MDD.

Ketamine, but not guanosine, as a prophylactic agent against corticosterone-induced depressive-like behavior: Possible role of long-lasting pro-synaptogenic signaling pathway.

Ketamine has been reported to exert a prophylactic effect against stress-induced depressive-like behavior by modulating the guanosine-based purinergic system. However, the molecular pathways underlying its prophylactic effect and whether guanosine also elicits a similar effect remain to be determined. Here, we investigated the prophylactic effect of ketamine and guanosine against corticosterone (CORT - 20 mg/kg, p.o.)-induced depressive-like behavior in mice. Furthermore, we characterized if the prophylactic response may be associated with mTORC1-driven signaling in the hippocampus and prefrontal cortex. A single administration of ketamine (5 mg/kg, i.p.), but not guanosine (1 or 5 mg/kg, p.o.), given 1 week before the pharmacological stress prevented CORT-induced depressive-like behavior in the tail suspension test (TST) and splash test (SPT). Fluoxetine treatment for 3 weeks did not prevent CORT-induced behavioral effects. A single administration of subthreshold doses of ketamine (1 mg/kg, i.p.) plus guanosine (5 mg/kg, p.o.) partially prevented the CORT-induced depressive-like behavior in the SPT. Additionally, CORT reduced Akt (Ser473) and GSK-3ß (Ser9) phosphorylation and PSD-95, GluA1, and synapsin immunocontent in the hippocampus, but not in the prefrontal cortex. No alterations on mTORC1/p70S6K immunocontent were found in both regions in any experimental group. CORT-induced reductions on PSD-95, GluA1, and synapsin immunocontent were prevented only by ketamine treatment. Collectively, these findings suggest that ketamine, but not guanosine, exerts a prophylactic effect against depressive-like behavior, an effect associated with the stimulation of long-lasting pro-synaptogenic signaling in the hippocampus.

Guanosine potentiates the antidepressant-like effect of subthreshold doses of ketamine: Possible role of pro-synaptogenic signaling pathway.

Background Augmentation therapies may be effective strategies to potentiate the ketamine's actions with lower potential for knock-on effects. Thus, this study investigated the ability of combined administration of guanosine plus ketamine to elicit an antidepressant-like effect associated with mTOR pathway modulation. The ability of this combined administration to exert an antidepressant-like effect in a model of depression was also evaluated. Methods Mice were administered with subthreshold doses of ketamine (0.1 mg/kg, i.p.) and guanosine (0.01 mg/kg, p.o.) and submitted to the tail suspension test, and immunoblotting analyses (p-mTOR, p-p70S6K, PSD-95, GluA1, and synapsin) in the hippocampus and prefrontal cortex. The antidepressant-like effect of ketamine plus guanosine in mice subjected to administration of corticosterone (20 mg/kg, p.o., 21 days) was also evaluated. Results Ketamine plus guanosine treatment elicited an antidepressant-like effect, which was associated with increased mTOR (Ser2448) and p70S6K (Thr389) phosphorylation in the hippocampus, but not in the prefrontal cortex. Furthermore, increased PSD-95 and GluA1 immunocontent were observed in the prefrontal cortex, but not in the hippocampus of ketamine plus guanosine-treated mice. Reinforcing the notion that guanosine may potentiate the ketamine's behavioral response, a single administration of subthreshold doses of ketamine plus guanosine counteracted the corticosterone-induced depressive-like behavior. Conclusions Our results indicate that guanosine potentiates the antidepressant-like effect of subthreshold doses of ketamine, an effect likely associated with the stimulation of synaptogenic pathway in the hippocampus and prefrontal cortex, although with a different profile. The augmentation effect of ketamine by guanosine could have therapeutic relevance for patients with treatment-resistant depression.

Red cabbage (Brassica oleracea L.) extract reverses lipid oxidative stress in rats.

Red cabbage (Brassica oleracea L. var. capitata f. rubra DC.) extract has been demonstrated hypolipidemic and antioxidant capacity. Herein, we investigated the effect of red cabbage aqueous extract (RC) or fenofibrate (FF) in oxidative stress induced by Triton WR-1339 in rats. The antioxidant capacity was evaluated through the superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities and, thiobarbituric reactive species (TBARS) and protein carbonyl (PC) levels in erythrocytes, liver, kidneys, cerebral cortex and hippocampus of male rats. The alterations promoted by Triton WR-1339 in enzymatic antioxidant defense in the liver, kidneys and hippocampus were reversed by RC or FF treatments. The TBARS and PC levels increased in the liver, cerebral cortex and hippocampus of hyperlipidemic rats were decreased by the treatments with RC or FF. These findings demonstrated that RC is a potential therapy to treat diseases not only involving dyslipidemic condition but also oxidative stress.

Morus nigra leaves extract revokes the depressive-like behavior, oxidative stress, and hippocampal damage induced by corticosterone: a pivotal role of the phenolic syringic acid.

The pathophysiology of depression includes glucocorticoids excess, glutamatergic excitotoxicity, and oxidative stress impairment. Previous study demonstrated Morus nigra L. leaves extract and syringic acid (4-hydroxy-3,5-dimethoxybenzoic acid), its major phenolic compound, administered orally for 7 days, decreased the immobility time in the tail suspension test, without locomotor alteration. Therefore, the purpose of this study was to investigate the antidepressant-like effects, antioxidant effects, and neuroprotective effects of M. nigra leaves extract and syringic acid in an animal model of depression induced by corticosterone. Herein, corticosterone administered in male Swiss mice, 60-90 days of age, at 20 mg/kg, once a day, for 21 days, was effective to induce depressive-like phenotype. This alteration was accompanied by the increase of oxidative stress markers (lipid peroxidation, nitrite, and protein carbonyl) and the decrease in nonprotein thiols level, besides impairment in the hippocampus. Conversely, the treatment with M. nigra leaves extract (10 mg/kg), syringic acid (1 mg/kg), or fluoxetine (10 mg/kg), administered once a day for the last 7 days of the corticosterone treatment, was able to abolish the behavioral alterations elicited by corticosterone, reinforcing evidence of the M. nigra leaves extract and syringic acid having antidepressant-like effect. Both treatments also exerted antioxidant property in the mice's brain, reducing the amount of oxidative stress and abolishing the corticosterone-induced damage in the hippocampal slices. In addition, the treatments protected the hippocampus against the damage induced by the association between corticosterone administration and glutamate excess. In conclusion, M. nigra leaves extract and syringic acid revoke depressive-like behavior induced by corticosterone via inhibition of oxidative stress and hippocampal damage.

Evaluation of phenolic compounds and lipid-lowering effect of Morus nigra leaves extract.

Morus nigra L. (Moraceae) is a tree known as black mulberry and the leaves are used in folk medicine in the treatment of diabetes, high cholesterol and menopause symptoms. The aim of this study was to evaluate the M. nigra leaves phytochemical profile in different extractions and the hypolipidemic effect of the infusion comparing to the fenofibrate. Morus nigra infusion (MN) showed higher amounts of phenolics and flavonoids (83.85 mg/g and 79.96 µg/g, respectively), as well as antioxidant activity (83.85%) than decoction or hydromethanolic extracts. Although, decoction showed the best result for ascorbic acid (4.35 mg/100 g) than hydromethanolic or infusion (2.51 or 2.13 mg/100 g, respectively). The phenolic acids gallic, chlorogenic and caffeic and the flavonoids quercetin, rutin and catechin were found in the M. nigra extracts. Hyperlipidemic rats treated with 100, 200 or 400 mg/kg of MN decreased serum cholesterol, triglycerides and normalized lipoproteins. Furthermore, MN inhibited lipid peroxidation in liver, kidney and brain of hyperlipidemic rats. This study provides evidence that M. nigra leaves extracts are rich in polyphenols, mainly chlorogenic acid, which normalized hyperlipidemic disturbance. The results suggest a potential therapeutic effect of the M. nigra leaves infusion on dislipidemic condition and related oxidative stress.

Evaluation of phenolic compounds and lipid-lowering effect of Morus nigra leaves extract

ABSTRACT Morus nigra L. (Moraceae) is a tree known as black mulberry and the leaves are used in folk medicine in the treatment of diabetes, high cholesterol and menopause symptoms. The aim of this study was to evaluate the M. nigra leaves phytochemical profile in different extractions and the hypolipidemic effect of the infusion comparing to the fenofibrate. Morus nigra infusion (MN) showed higher amounts of phenolics and flavonoids (83.85 mg/g and 79.96 µg/g, respectively), as well as antioxidant activity (83.85%) than decoction or hydromethanolic extracts. Although, decoction showed the best result for ascorbic acid (4.35 mg/100 g) than hydromethanolic or infusion (2.51 or 2.13 mg/100 g, respectively). The phenolic acids gallic, chlorogenic and caffeic and the flavonoids quercetin, rutin and catechin were found in the M. nigra extracts. Hyperlipidemic rats treated with 100, 200 or 400 mg/kg of MN decreased serum cholesterol, triglycerides and normalized lipoproteins. Furthermore, MN inhibited lipid peroxidation in liver, kidney and brain of hyperlipidemic rats. This study provides evidence that M. nigra leaves extracts are rich in polyphenols, mainly chlorogenic acid, which normalized hyperlipidemic disturbance. The results suggest a potential therapeutic effect of the M. nigra leaves infusion on dislipidemic condition and related oxidative stress.

Evidence of the involvement of the monoaminergic systems in the antidepressant-like effect of Aloysia gratissima.

ETHNOPHARMACOLOGICAL RELEVANCE: Aloysia gratissima (Verbenaceae) is an aromatic plant distributed in South America and, employed in folk medicine for the treatment of nervous systems illness, including depression. The neuroprotective and antidepressant-like activities of the aqueous extract of Aloysia gratissima (AE) administered orally has already been demonstrated.In this study the involvement of monoaminergic systems in the antidepressant-like effect of the AE was investigated. MATERIALS AND METHODS: The implication of the monoaminergic systems in the antidepressant-like activity of Aloysia gratissima was evaluated using different pharmacological antagonists that were administered previously to the acute oral administration of AE (10 mg/kg). The antidepressant-like effect was assessed in the TST and locomotor activity was evaluated in the open-field test in mice. RESULTS: The anti-immobility effect elicited by AE in the TST was prevented by the pre-treatment of mice with the antagonists, NAN-190 (5-HT(1A) receptor), ketanserin (5-HT(2A/2C) receptor), prazosin (α1-adrenoceptor), yohimbine (α2-adrenoceptor), SCH23390 (dopamine D1 receptor), or sulpiride (dopamine D2 receptor). CONCLUSIONS: These results indicate that the antidepressant-like effect of AE in the TST is dependent on its interaction with the serotonergic (5-HT(1A) and 5-HT(2A/2C)), noradrenergic (α1 and α2-adrenoceptors) and dopaminergic (D1 and D2 receptors) systems, suggesting that this specie might act as a new potential resource for developing antidepressants to treat depressive disorders.

Acute atorvastatin treatment exerts antidepressant-like effect in mice via the L-arginine-nitric oxide-cyclic guanosine monophosphate pathway and increases BDNF levels.

Atorvastatin is a synthetic and lipophilic statin that presents a good effect in decreasing cholesterol levels and is safe and well tolerated. Population-based studies have suggested a positive role of statins in reducing depression risk. This study aimed at investigating the atorvastatin effect in the tail suspension test (TST) and in the forced swimming test (FST). The participation of NMDA receptors and L-arginine-NO-cGMP in an atorvastatin antidepressant-like effect in the TST was evaluated. Acute atorvastatin administration (0.1-30 mg/kg) reduced the immobility time both in TST and FST. A similar effect was observed by using imipramine as a positive control in the TST and FST (1 and 0.1-1 mg/kg, p.o., respectively). An atorvastatin (0.1 mg/kg) antidepressant-like effect was prevented by the pretreatment of mice with NMDA (0.1 pmol/site, i.c.v.), L-arginine (750 mg/kg, i.p.) or sildenafil (5 mg/kg, i.p.). The administration of MK-801 (0.001 mg/kg, i.p.), ketamine (0.1 mg/kg, i.p.), 7-nitroindazole (50 mg/kg, i.p.), methylene blue (20 mg/kg, i.p.), or ODQ (30 pmol/site i.c.v.) in combination with a subeffective dose of atorvastatin (0.01 mg/kg, p.o.) reduced the immobility time in the TST compared to drugs alone, showing the participation of the pathway L-arginine-NO-cGMP. The administration of drugs did not produce any significant alteration in locomotor activity in the open-field test. Acute atorvastatin treatment (0.1-10.0 mg/kg, v.o.) increased the hippocampal BDNF levels, which is an effect that has not been observed in imipramine-treated mice. These results demonstrate that atorvastatin exerts an antidepressant-like effect and point to dependence on the inhibition of NMDA receptors and NO-cGMP synthesis, and on the increase of hippocampal BDNF levels.

Ferulic acid exerts antidepressant-like effect in the tail suspension test in mice: evidence for the involvement of the serotonergic system.

Ferulic acid (4-hydroxy-3-methoxycinnamic acid) is a phenolic compound present in several plants with claimed beneficial effects in prevention and treatment of disorders linked to oxidative stress and inflammation. In this study, we aimed to verify the possible antidepressant-like effect of acute oral administration of ferulic acid in the forced swimming test (FST) and tail suspension test (TST) in mice. Additionally, the mechanisms involved in the antidepressant-like action and the effects of the association of ferulic acid with the antidepressants fluoxetine, paroxetine, and sertraline in the TST were investigated. Ferulic acid produced an antidepressant-like effect in the FST and TST (0.01-10 mg/kg, p.o.), without accompanying changes in ambulation. The pretreatment of mice with WAY100635 (0.1 mg/kg, s.c., a selective 5-HT(1A) receptor antagonist) or ketanserin (5 mg/kg, i.p., a 5-HT(2A) receptor antagonist) was able to reverse the anti-immobility effect of ferulic acid (0.01 mg/kg, p.o.) in the TST. The combination of fluoxetine (5 mg/kg, p.o.), paroxetine (0.1 mg/kg, p.o.) or sertraline (1 mg/kg, p.o.) with a sub-effective dose of ferulic acid (0.001 mg/kg, p.o.) produced a synergistic antidepressant-like effect in the TST, without causing hyperlocomotion in the open-field test. Taken together, these results demonstrate that ferulic acid exerts antidepressant-like effect in the FST and TST in mice through modulation of the serotonergic system.

Hypotriglyceridemic effect of Morus alba L., Moraceae, leaves in hyperlipidemic rats / Efeito hipotrigliceridêmico de folhas de Morus alba L., Moraceae, em ratos hiperlipidêmicos

Mulberry Morus alba L., Moraceae, leaves are used in Brazil medicines against fever, to protect the liver, to lower the blood pressure and cholesterol. The aqueous extract of leaves of M. alba given by oral route to hyperlipidemic rats with diet enriched by cholesterol (1 percent by weight) with dose of 150 mg/kg/day for forteen days reduced significantly by 55,01 percent the plasma triglycerides level. Therefore, the treatment not only decreased the plasma level of triglycerides but also affected a hepatic enzyme tested supportting the fact that the extracts of Morus alba that have been used by folk medicine have a great potential to be further developed into a phytomedicine.

As folhas de amoreira branca Morus alba L., Moraceae, são utilizadas no Brasil na medicina popular para tratar febre, como protetor do fígado, para baixar a pressão e o colesterol. O extrato aquoso de folhas de M. alba foi administrado via oral através de gavagem em ratos hiperlipidêmicos com uma dieta enriquecida com colesterol (1 por cento) com uma dose de 150 mg/kg/dia por quatorze dias que reduziu significativamente em 55,01 por cento o nível de triglicerídios plasmáticos. Desta forma, o tratamento diminuiu o nível de triglicerídios e uma enzima hepática testada, demonstrando que extratos de Morus alba que tem sido popularmente utilizados possuem um grande potencial para se tornar um fitomedicamento.