Antidepressant-like effect of Canavalia brasiliensis (ConBr) lectin in mice: Evidence for the involvement of the glutamatergic system

The lectin from Schinus terebinthifolia leaf (SteLL) reduces immobility of mice on the tail suspension test dependent on the monoaminergic and nitric oxide signaling

Depression underlies a common psychiatric disorder that has been rising in the diagnosis of long-term disabilities worldwide. Natural products have been studied as an antidepressant and anxiolytic agents aiming to make available new options for the daily basis treatment of those psychological disorders. SteLL is a lectin extracted from Schinus terebinthifolia leaf that has been revealed as an antimicrobial, immunomodulatory, antitumor, and antinociceptive agent. Nonetheless, the efficacy of SteLL in the treatment of depression has not yet been explored. In view of this, the aim of this study was to investigate the effect of SteLL in an acute protocol for symptoms of depression using the tail suspension test (TST) to assess despair. Administration of SteLL (1, 2 e 4 mg/kg) significantly diminished the immobility time of animals in the TST and this anti-immobility action was dependent on the carbohydrate-recognizing domain (CRD) since the prior incubation with casein (an inhibitor of SteLL carbohydrate-binding property) blocked the effect. SteLL effect was also reversed by pre-treatment with pharmacological antagonists of α2-adrenoceptor, 5-HT2A/2C serotonin receptor, and D1 dopamine receptor as well as by a selective inhibitor of iNOS (aminoguanidine). l-arginine, a precursor of NO, potentiated SteLL anti-immobility effect. In a subacute evaluation, the anti-immobility effect of SteLL persisted after seven days of treatment. Our findings suggest a role of SteLL in the modulation of depression mostly through monoaminergic and nitric oxide signaling.

A systematic review of studies investigating the acute effects of N-methyl-D-aspartate receptor antagonists on behavioural despair in normal animals suggests poor predictive validity

The ability of the N-methyl-D-aspartate receptor antagonist ketamine to induce a rapid and sustained antidepressant effect has led to a surge in pre-clinical studies investigating underlying mechanisms and seeking novel treatments. Animal models are key to this research as they can provide a behavioural readout linking underlying mechanisms to clinical benefits. However, quantifying depression-related behaviours in rodents represents a major challenge with the validity of traditional methods such as models of behavioural despair (forced swim test and tail suspension test) a topic of debate. While there is good evidence to support the value of using these behavioural readouts to study the effects of stress, these approaches have largely failed to detect reliable phenotypic effects in other disease models. In this systematic review, we identified publications which had tested N-methyl-D-aspartate receptor antagonists in normal animals using either the forced swim test or tail suspension test. We compared findings for different doses and time points and also drugs with different clinical profiles to investigate how well the outcomes in the rodent model predicted their effects in the clinic. Despite clear evidence that N-methyl-D-aspartate receptor antagonists reduce immobility time and hence exhibit an antidepressant profile in these tasks, we found similar effects with both clinically effective drugs as well as those which have failed to show efficacy in clinical trials. These findings suggest that behavioural despair tests in normal animals do not provide a good method to predict clinical efficacy of N-methyl-D-aspartate receptor antagonists.

Medicinal Plants in the Treatment of Depression: Evidence from Preclinical Studies

Medicinal plants and their extracts are natural remedies with enormous potential for treating various diseases, including depression and anxiety. In the case of depression, hundreds of plants have traditionally been used in folk medicine for generations. Different plant extracts and natural products have been analyzed as potential antidepressant agents with validated models to test for antidepressant-like effects in animals, although other complementary studies have also been employed. Most of these studies focus on the possible mediators implicated in these potential effects, with dopamine, serotonin, and noradrenaline being the principal neurotransmitters implicated, both through interference with receptors and with their metabolism by monoamino oxidases, as well as through neuro-endocrine and neuroprotective effects. There are approximately 650 reports of antidepressant-like medicinal plants in PubMed; 155 of them have been compiled in this review, with a relevant group yielding positive results. Saffron and turmeric are the most relevant species studied in both preclinical and clinical studies; St. John's wort or kava have also been tested extensively. To the best of our knowledge, no review to date has provided a comprehensive understanding of the biomolecular mechanisms of action of these herbs or of whether their potential effects could have real benefits. The purpose of this narrative review is to provide an update regarding medicinal plants from the year 2000 to the present to examine the therapeutic potential of these antidepressant-like plants in order to contribute to the development of new therapeutic methods to alleviate the tremendous burden that depression causes worldwide.

Neuronal activity regulated pentraxin (narp) and GluA4 subunit of AMPA receptor may be targets for fluoxetine modulation

Fluoxetine is the foremost prescribed antidepressant. Drugs acting on monoaminergic system may also regulate glutamatergic system. Indeed, the investigation of proteins associated with this system, such as Narp (neuronal activity-dependent pentraxin) and GluA4 subunit of AMPA receptor may reveal poorly explored modulations triggered by conventional antidepressants. This study aimed to uncover neurochemical mechanisms underlying the chronic fluoxetine treatment, mainly by evaluating these protein targets in the prefrontal cortex and in the hippocampus. Mice received a daily administration of fluoxetine (0.1, 1 or 10 mg/kg, p.o.) or potable water (vehicle group) for 21 days. These animals were submitted to the forced swim test (FST) to verify antidepressant-like responses and the open-field test (OFT) to assess locomotor activity. Modulation of signaling proteins was analyzed by western blot. Chronic treatment with fluoxetine (1 and 10 mg/kg) was effective, since it reduced the immobility time in the FST, without altering locomotor activity. Fluoxetine 10 mg/kg increased CREB phosphorylation and BDNF expression in the prefrontal cortex and hippocampus. Noteworthy, in the hippocampus fluoxetine also promoted Akt activation and augmented Narp expression. In the prefrontal cortex, a significant decrease in the expression of the GluA4 subunit and Narp were observed following fluoxetine administration (10 mg/kg). The results provide evidence of novel molecular targets potentially involved in the antidepressant effects of fluoxetine, since in mature rodents Narp and GluA4 are mainly expressed in the GABAergic parvalbumin-positive (PV+) interneurons. This may bring new insights into the molecular elements involved in the mechanisms underlying the antidepressant effects of fluoxetine.

ConBr lectin modulates MAPKs and Akt pathways and triggers autophagic glioma cell death by a mechanism dependent upon caspase-8 activation

Glioblastoma multiforme is the most aggressive type of glioma, with limited treatment and poor prognosis. Despite some advances over the last decade, validation of novel and selective antiglioma agents remains a challenge in clinical pharmacology. Prior studies have shown that leguminous lectins may exert various biological effects, including antitumor properties. Accordingly, this study aimed to evaluate the mechanisms underlying the antiglioma activity of ConBr, a lectin extracted from the Canavalia brasiliensis seeds. ConBr at lower concentrations inhibited C6 glioma cell migration while higher levels promoted cell death dependent upon carbohydrate recognition domain (CRD) structure. ConBr increased p38^MAPK and JNK and decreased ERK1/2 and Akt phosphorylation. Moreover, ConBr inhibited mTORC1 phosphorylation associated with accumulation of autophagic markers, such as acidic vacuoles and LC3 cleavage. Inhibition of early steps of autophagy with 3-methyl-adenine (3-MA) partially protected whereas the later autophagy inhibitor Chloroquine (CQ) had no protective effect upon ConBr cytotoxicity. ConBr also augmented caspase-3 activation without affecting mitochondrial function. Noteworthy, the caspase-8 inhibitor IETF-fmk attenuated ConBr induced autophagy and C6 glioma cell death. Finally, ConBr did not show cytotoxicity against primary astrocytes, suggesting a selective antiglioma activity. In summary, our results indicate that ConBr requires functional CRD lectin domain to exert antiglioma activity, and its cytotoxicity is associated with MAPKs and Akt pathways modulation and autophagy- and caspase-8- dependent cell death.

Multiple cellular targets involved in the antidepressant-like effect of glutathione

A previous study demonstrated that glutathione (GSH) produces specific antidepressant-like effect in the forced swimming test (FST), a predictive test of antidepressant activity. The present study investigated the involvement of multiple cellular targets implicated in the antidepressant-like effect of GSH in the FST. The antidepressant-like effect of GSH (300 nmol/site, icv) lasted up to 3 h when mice were submitted to FST. The central administration of oxidized GSH (GSSG, 3-300 nmol/site) did not alter the behavior of mice submitted to the FST. Furthermore, the combined treatment of sub-effective doses of GSH (100 nmol/site, icv) with a sub-effective dose of classical antidepressants (fluoxetine 10 mg/kg, and imipramine 5 mg/kg, ip) presented synergistic effect by decreasing the immobility time in the FST. The antidepressant-like effect of GSH was abolished by prazosin (1 mg/kg, ip, α₁-adrenoceptor antagonist), baclofen (1 mg/kg, ip, GABAB receptor agonist), bicuculline (1 mg/kg, ip, GABAA receptor antagonist), l-arginine (750 mg/kg, ip, NO precursor), SNAP (25 μg/site, icv, NO donor), but not by yohimbine (1 mg/kg, ip, α₂-adrenoceptor antagonist). The NMDA receptor antagonists, MK-801(0.001 mg/kg, ip) or GMP (0.5 mg/kg, ip), potentiated the effect of a sub-effective dose of GSH in the FST. These results suggest that the antidepressant-like effect induced by GSH is connected to the activation of α1 adrenergic and GABAA receptors, as well as the inhibition of GABAB and NMDA receptors and NO biosyntesis. We speculate that redox-mediated signaling on the extracelular portion of cell membrane receptors would be a common mechanism of action of GSH.

Neuropharmacological Characterization of Dioclea altissima Seed Lectin (DAL) in Mice: Evidence of Anxiolytic-like Effect Mediated by Serotonergic, GABAergic Receptors and NO Pathway

BACKGROUND

Plant lectins have shown promising biological activities in the central nervous system (CNS).

OBJECTIVE

This study evaluated the effect of DAL, a lectin isolated from the seeds of the Dioclea altissima species, having binding affinity to D-glucose or D-mannose residues, on mice behavior.

METHODS

Mice (n=6/group) were treated (i.p.) with DAL (0.25, 0.5 or 1 mg/kg) or vehicle and subjected to several tests (open field/OFT, marble-burying/MBT, hole-board/HBT, elevated plus maze/PMT, tail suspension/ TST, forced swimming/FST or rotarod/RRT). Pizotifen, cyproheptadine, flumazenil, L-NAME, 7-NI, Larginine or yohimbine were administered 15 min before DAL (0.5 mg/kg) and the animals were evaluated on PMT. It was also verified whether the DAL effect depended on its structural integrity and ability to interact with carbohydrates.

RESULTS

The results showed there were no neurobehavioral changes in the mice at the RRT, FST and locomotion in the OFT. DAL (0.25, 0.5 or 1 mg/kg) increased the behavior of grooming and rearing in the OFT, head dips in the HBT, pedalling in the TST and decreased the number of marbles hidden in the MBT. In the PMT, DAL (0.25, 0.5 and 1 mg/kg) and Diazepam increased the frequency of entries in the open arms and the time of permanence in the open arms without affecting the locomotor activity. The effect of DAL was dependent on carbohydrate interaction and protein structure integrity and it prevented by pizotifen, cyproheptadine, flumazenil, L-NAME and 7-NI, but not by L-arginine or yohimbine.

CONCLUSION

DAL was found to have an anxiolytic-like effect mediated by the 5-HT and GABAergic receptors and NO pathway.

Dioclea violacea lectin modulates the gentamicin activity against multi-resistant strains and induces nefroprotection during antibiotic exposure

Gentamicin is an aminoglycoside antibiotic used to treat infections of various origins. In the last few decades, the constant use of gentamicin has resulted in increased bacterial resistance and nephrotoxicity in some cases. In this study, we examined the ability of Dioclea violacea lectin (DVL) in modulate the antimicrobial activity of gentamicin and reduce the nephrotoxicity induced by this drug. The minimum inhibitory concentration (MIC) obtained for DVL against all strains studied was not clinically relevant (MIC ≥ 1024 μg/mL). However, when DVL was combined with gentamicin, a significant increase in antibiotic action was observed against Staphylococcus aureus and Escherichia coli. DVL also reduced antibiotic tolerance in S. aureus during 10 days of continuous treatment. In addition, DVL presented a nephroprotective effect, reducing sodium excretion, N-Gal expression and urinary protein, that are important markers of glomerular and tubular injuries. Taken together, studies of inhibition of hemagglutinating activity, fluorescence spectroscopy and molecular docking revealed that gentamicin can interact with DVL via the carbohydrate recognition domain (CRD), suggesting that the results obtained in this study may be directly related to the interaction of DVL-gentamicin and with the ability of the lectin to interact with glycans present in the cells of the peritoneum.

Animal Galectins and Plant Lectins as Tools for Studies in Neurosciences

Lectins are proteins or glycoproteins of non-immunological origin capable of reversibly and specifically binding to glycoconjugates. They exist in free form or associated with cells and are widely distributed in nature, being found in plants, microorganisms, and animals. Due to their characteristics and mainly due to the possibility of reversible binding to glycoconjugates, lectins have stood out as important tools in research involving Neurobiology. These proteins have the ability to modulate molecular targets in the central nervous system (CNS) which may be involved with neuroplasticity, neurobehavioral effects, and neuroprotection. The present report integrates existing information on the activity of animal and plant lectins in different areas of Neuroscience, presenting perspectives to direct new research on lectin function in the CNS, providing alternatives for understanding neurological diseases such as mental disorders, neurodegenerative, and neuro-oncological diseases, and for the development of new drugs, diagnoses and therapies in the field of Neuroscience.

Pharmacological evidence for the relationship between the NMDA receptor and nitric oxide pathway and the antidepressant-like effects of glucagon-like peptide-2 in the mouse forced-swim test

We previously demonstrated that glucagon-like peptide-2 (GLP-2) exerted antidepressant-like effects in mice. The aim of the present study was to investigate the relationship between N-methyl-_D-aspartate (NMDA) receptor-nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway and the antidepressant-like effects of GLP-2 in the forced-swim test (FST) in mice. Intracerebroventricularly administered GLP-2 (3 μg/mouse) decreased the immobility time in the FST. The pretreatment of mice with l-arginine (750 mg/kg, i.p.), a substrate for nitric oxide synthase, sildenafil (5 mg/kg, i.p.), a phosphodiesterase 5 inhibitor, or d-serine (300 mg/kg, i.p.), a NMDA receptor co-agonist, inhibited the antidepressant-like effects of GLP-2 (3 μg/mouse) in the FST. Meanwhile, l-nitroarginine methyl ester (10 mg/kg, i.p.), a non-specific nitric oxide synthase (NOS) inhibitor, 7-nitroindazole (30 mg/kg, i.p.), a neuronal NOS inhibitor, methylene blue (10 mg/kg, i.p.), an inhibitor of both NOS and soluble guanylate cyclase (sGC), ODQ (30 pmol/site, i.c.v.), a sGC inhibitor, or MK-801 (0.05 mg/kg, i.p.), an NMDA receptor antagonist, in combination with a sub-effective dose of GLP-2 (1.5 μg/mouse) also decreased the immobility time in the FST. The present study provided evidence for the synergistic antidepressant-like effects of GLP-2 and inhibition of the NMDA receptor-l-arginine-NO-cGMP pathway in the FST, thereby contributing to our understanding of the mechanisms underlying the antidepressant-like effects of GLP-2.

ConA-Like Lectins: High Similarity Proteins as Models to Study Structure/Biological Activities Relationships

Lectins are a widely studied group of proteins capable of specific and reversible binding to carbohydrates. Undoubtedly, the best characterized are those extracted from plants of the Leguminosae family. Inside this group of proteins, those from the Diocleinae subtribe have attracted attention, in particular Concanavalin A (ConA), the best-studied lectin of the group. Diocleinae lectins, also called ConA-like lectins, present a high similarity of sequence and three-dimensional structure and are known to present inflammatory, vasoactive, antibiotic, immunomodulatory and antitumor activities, among others. This high similarity of lectins inside the ConA-like group makes it possible to use them to study structure/biological activity relationships by the variability of both carbohydrate specificity and biological activities results. It is in this context the following review aims to summarize the most recent data on the biochemical and structural properties, as well as biological activities, of ConA-like lectins and the use of these lectins as models to study structure/biological activity relationships.

Pathologic role of nitrergic neurotransmission in mood disorders

Mood disorders are chronic, recurrent mental diseases that affect millions of individuals worldwide. Although over the past 40 years the biogenic amine models have provided meaningful links with the clinical phenomena of, and the pharmacological treatments currently employed in, mood disorders, there is still a need to examine the contribution of other systems to the neurobiology and treatment of mood disorders. This article reviews the current literature describing the potential role of nitric oxide (NO) signaling in the pathophysiology and thereby the treatment of mood disorders. The hypothesis has arisen from several observations including (i) altered NO levels in patients with mood disorders; (ii) antidepressant effects of NO signaling blockers in both clinical and pre-clinical studies; (iii) interaction between conventional antidepressants/mood stabilizers and NO signaling modulators in several biochemical and behavioral studies; (iv) biochemical and physiological evidence of interaction between monoaminergic (serotonin, noradrenaline, and dopamine) system and NO signaling; (v) interaction between neurotrophic factors and NO signaling in mood regulation and neuroprotection; and finally (vi) a crucial role for NO signaling in the inflammatory processes involved in pathophysiology of mood disorders. These accumulating lines of evidence have provided a new insight into novel approaches for the treatment of mood disorders.

Neuropharmacological characterization of frutalin in mice: Evidence of an antidepressant-like effect mediated by the NMDA receptor/NO/cGMP pathway

In this study we evaluated the effect of frutalin (FTL) on mouse behavior. Mice (n=6/group) were treated (i.p.) with FTL (0.25; 0.5 or 1mg/kg) or vehicle and submitted to several tests (hole-board/HBT, elevated plus maze/PMT, open field/OFT, tail suspension/TST, or forced swimming/FST). Yohimbine, ketamine, l-NAME, aminoguanidine, 7-NI, methylene blue, l-arginine or dl-serine was administered 30min before FTL (0.5mg/kg). To evaluate the subchronic effect, animals were injected with FTL or vehicle for 7days and submitted to the FST. Molecular docking was simulated using FTL against NOS and the NMDA receptor. No changes were observed in the HBT or the OFT. FTL (0.25mg/kg) increased the number of entries into enclosed arms in the PMT. FTL reduced immobility in the TST (0.25 and 0.5mg/kg) and the FST (0.25mg/kg; 0.5mg/kg). The effect of FTL was dependent on carbohydrate interaction and protein structure integrity and was reduced by ketamine, l-NAME, aminoguanidine, 7-NI and methylene blue, but not by l-arginine, yohimbine or dl-serine. The antidepressant-like effect remained after subchronic treatment. The molecular docking study revealed a strong interaction between FTL and NOS and NMDA. FTL was found to have an antidepressant-like effect mediated by the NMDA receptor/NO/cGMP pathway.

The potent anti-cancer activity of Dioclea lasiocarpa lectin

The lectin DLasiL was isolated from seeds of the Dioclea lasiocarpa collected from the northeast coast of Brazil and characterized for the first time by mass spectrometry, DNA sequencing, inductively coupled plasma-mass spectrometry, electron paramagnetic resonance, and fluorescence spectroscopy. The structure of DLasiL lectin obtained by homology modelling suggested strong conservation of the dinuclear Ca/Mn and sugar-binding sites, and dependence of the solvent accessibility of tryptophan-88 on the oligomerisation state of the protein. DLasiL showed highly potent (low nanomolar) antiproliferative activity against several human carcinoma cell lines including A2780 (ovarian), A549 (lung), MCF-7 (breast) and PC3 (prostate), and was as, or more, potent than the lectins ConBr (Canavalia brasiliensis), ConM (Canavalia maritima) and DSclerL (Dioclea sclerocarpa) against A2780 and PC3 cells. Interestingly, DLasiL lectin caused a G2/M arrest in A2780 cells after 24h exposure, activating caspase 9 and delaying the on-set of apoptosis. Confocal microscopy showed that fluorescently-labelled DLasiL localized around the nuclei of A2780 cells at lectin doses of 0.5-2× IC₅₀ and gave rise to enlarged nuclei and spreading of the cells at high doses. These data reveal the interesting antiproliferative activity of DLasiL lectin, and suggest that further investigations to explore the potential of DLasiL as a new anticancer agent are warranted.

Contribution of NMDA, GABAA and GABAB receptors and l-arginine-NO-cGMP, MEK1/2 and CaMK-II pathways in the antidepressant-like effect of 7-fluoro-1,3-diphenylisoquinoline-1-amine in mice

It has been reported that the antidepressant-like effect of 7-fluoro-1,3-diphenylisoquinoline-1-amine (FDPI) may result from the modulation of brain monoaminergic systems. However, the mechanisms of FDPI action are not fully understood. The aim of this study was to investigate the contribution of N-methyl-d-aspartate (NMDA) and gamma-aminobutyric acid (GABA) systems as well as l-arginine-nitric oxide-(NO)-cyclic guanosine monophosphate-(cGMP), mitogen-activated protein/extracellular signal-regulated kinase (MEK1/2) and Ca(2+)/calmodulin-dependent protein kinase II (CaMK-II) signaling pathways in the antidepressant-like effect of FDPI in the mouse forced swimming test (FST). The levels of NO and uptake of [(3)H]glutamate and [(3)H]GABA were determined in prefrontal cortices of Swiss mice. Pretreatments with NMDA (0.1 pmol/site, i.c.v., a NMDA receptor agonist), bicuculline (1mg/kg, i.p., a GABAA receptor antagonist), phaclofen (2mg/kg, i.p., a GABAB receptor antagonist) and l-arginine (750mg/kg, i.p., a NO precursor), KN-62 (1μg/site, a CaMK-II inhibitor), U0126 (5μg/site, a MEK1/2 inhibitor) and PD09058 (5μg/site, a MEK1/2 inhibitor) blocked the antidepressant-like effect of FDPI, at a dose of 1mg/kg, in the FST. ODQ (30 pmol/site, i.c.v., a soluble guanylate cyclase (sGC) inhibitor) in combination with a sub-effective dose of FDPI (0.1mg/kg, i.g.) reduced the immobility time in the FST. The administration of FDPI (50mg/kg) to mice increased the glutamate uptake and reduced NO levels in the prefrontal cortex of mice. The results suggest a contribution of NMDA, GABAA and GABAB receptors and l-arginine-NO-cGMP pathway in the antidepressant-like action of FDPI in mice, and this effect is related to CaMK-II and MEK 1/2 activation.