Gallic acid activates hippocampal BDNF-Akt-mTOR signaling in chronic mild stress

Neurobiology, molecular pathways, and environmental influences in antisocial traits and personality disorders

Personality disorders (PDs) are psychiatric conditions characterized by enduring patterns of cognition, emotion, and behaviour that deviate significantly from cultural norms, causing distress or impairment. The aetiology of PDs is complex, involving both genetic and environmental factors. Genetic studies estimate the heritability of PDs at 30%-60%, implicating genes involved in neurotransmitter regulation, such as those for serotonin transporters and dopamine receptors. Environmental factors, including childhood trauma and chronic stress, interact with genetic predispositions to induce epigenetic modifications like DNA methylation and histone modifications, contributing to PD development. Neurobiological research has identified structural and functional abnormalities in brain regions related to emotional regulation and social cognition, such as the amygdala, prefrontal cortex, and limbic system. These abnormalities are linked to impaired emotion processing and interpersonal functioning in PDs. This review focuses on how environmental factors shape maladaptive behaviours and endophenotypes central to many PDs. It explores the interaction between the Ras-ERK, p38, and mTOR molecular pathways in response to environmental stimuli, and examines the role of oxidative stress and mitochondrial metabolism in these processes. Also reviewed are various types of PDs and existing animal models that replicate key endophenotypes, highlighting changes in neurotransmitters and neurohormones. Identifying molecular biomarkers can lead to the development of "enviromimetic" drugs, which mimic environmental influences to activate molecular pathways, facilitating targeted, personalized treatments based on the molecular profiles of individuals with PDs. Ultimately, understanding the molecular mechanisms of PDs promises to enhance diagnostic accuracy, prognosis, and therapeutic outcomes for affected individuals.

Psidium Exotic and Native Species from Brazil Abolish Depression-like Behavior and Oxidative Stress induced by Corticosterone in Mice

Depression is a highly prevalent neuropsychiatric disorder worldwide. One currently accepted hypothesis of this pathogenesis is the hypothalamic-pituitary-adrenal axis dysfunction, which involves oxidative stress and brain damage. Therefore, antioxidants, such as phenolic compounds, could be used in depression. In this study, we investigated the antidepressant-like and antioxidant effects of an aqueous extract of the leaves of three species of the genus Psidium, Myrtaceae family, in mice. The exotic Psidium guajava L. and the natives Psidium guineense Sw. and Psidium cattleianum Sabine (10, 1, and 0.1 mg/kg, respectively) and fluoxetine (10 mg/kg) were administered orally (p. o.) once daily for 21 days, with or without corticosterone (20 mg/kg). After behavioral assessments (tail suspension, splash, and open-field tests), the hippocampus, prefrontal cortex, liver, kidneys, and plasma were examined to determine the oxidative stress status. The three extracts and fluoxetine treatment decreased the immobility time and counteracted the oxidative stress induced by corticosterone administration. The phenolic compounds identified as major components of the extracts, quercetin in P. guajava and P. guineense and o-coumaric acid in P. cattleianum, may be involved in the biological activities. Therefore, the aqueous leaf extracts of P. guajava, P. cattleianum, and P. guineense could be potential antidepressants helpful in treating depression and other diseases with elevated nitro-oxidative stress.

The anti-depression effect and potential mechanism of the petroleum ether fraction of CDB: Integrated network pharmacology and metabolomics

The combination of Chaidangbo (CDB) is an antidepressant traditional Chinese medicine (TCM) prescription simplified by Xiaoyaosan (a classic antidepressant TCM prescription) through dismantling research, which has the effect of dispersing stagnated liver qi and nourishing blood in TCM theory. Although the antidepressant effect of CBD has been confirmed in animal studies, the material basis and possible molecular mechanism for antidepressant activity in CBD have not been clearly elucidated. Herein, we investigated the effects and potential mechanisms of CDB antidepressant fraction (petroleum ether fraction of CDB, PEFC) on chronic unpredictable mild stress (CUMS)-induced depression-like behavior in mice using network pharmacology and metabolomics. First, a UPLC-QE/MS was employed to identify the components of PEFC. To extract active ingredients, SwissADME screening was used to the real PEFC components that were found. Potential PEFC antidepressant targets were predicted based on a network pharmacology approach, and a pathway enrichment analysis was performed for the predicted targets. Afterward, a CUMS mouse depression model was established and LC-MS-based untargeted hippocampal metabolomics was performed to identify differential metabolites, and related metabolic pathways. Finally, the protein expressions in mouse hippocampi were determined by Western blot to validate the network pharmacology and metabolomics deduction. A total of 16 active compounds were screened in SwissADME that acted on 73 core targets of depression, including STAT3, MAPKs, and NR3C1; KEGG enrichment analysis showed that PEFC modulated signaling pathways such as PI3K-Akt signaling pathway, endocrine resistance, and MAPK to exert antidepressant effects. PEFC significantly reversed abnormalities of hippocampus metabolites in CUMS mice, mainly affecting the synthesis and metabolism of glycine, serine, and threonine, impacting catecholamine transfer and cholinergic synapses and regulating the activity of the mTOR signaling pathway. Furthermore, Western blot analysis confirmed that PEFC significantly influenced the main protein levels of the PI3K/Akt/mTOR signaling pathways in the hippocampus of mice subjected to CUMS. This study integrated metabolomics, network pharmacology and biological verification to explore the potential mechanism of PEFC in treating depression, which is related to the regulation of amino acid metabolism dysfunction and the activation of PI3K/Akt/mTOR signaling pathways in the hippocampus. The comprehensive strategy also provided a reasonable way for unveiling the pharmacodynamic mechanisms of multi-components, multi-targets, and multi-pathways in TCM with antidepressant effect.

Neuroprotection by Polyherbal Medicine Divya-Medha-Vati Against Scopolamine-Induced Cognitive Impairment Through Modulation of Oxidative Stress, Acetylcholine Activity, and Cell Signaling

Alzheimer disease is associated with cognitive impairments and neuronal damages. In this study, Scopolamine, a model drug used for the generation of Alzheimer-like symptoms induced cognitive dysfunction in C57BL/6 mice. It also elevated acetylcholine esterase (AcHE) activity, and reduced antioxidant (superoxide dismutase and catalase) activity in cortex tissue. Scop reduced neuronal density and increased pyknotic neurons in hippocampus tissue. In mouse neuroblastoma (Neuro2a) cells, Scop triggered a dose-dependent loss of cell viability and neurite outgrowth reduction. Scop-treated Neuro2a cells showed oxidative stress and reduction in mRNA expression for brain-derived neurotrophic factor (BDNF), nerve growth factor-1 (NGF-1), and Synapsin-1 (SYN-1) genes. Mice treated with Divya-Medha-Vati (DMV), an Ayurvedic polyherbal medicine showed protection against Scop-induced cognitive impairment (Morris Water Maze Escape Latency, and Elevated Plus Maze Transfer Latency). DMV protected against Scop-induced AcHE activity, and loss of antioxidant activities in the mice brain cortex while sustaining neuronal density in the hippocampus region. In the Neuro2a cells, DMV reduced Scop-induced loss of cell viability and neurite outgrowth loss. DMV protected the cells against induction of oxidative stress and promoted mRNA expression of BDNF, NGF-1, and SYN-1 genes. Phytochemical profiling of DMV showed the presence of Withanolide A, Withanolide B, Bacopaside II, Jujubogenin, Apigenin, Gallic acid, Caffeic acid, and Quercetin that are associated with antioxidant and neurostimulatory activities. In conclusion, the study showed that Divya-Medha-Vati was capable of promoting neuronal health and inhibiting Alzheimer-like cognitive dysfunction through enhanced antioxidant activities and modulation of neuronal activities.

Neuroprotective Effects of Polysaccharides and Gallic Acid from Amauroderma rugosum against 6-OHDA-Induced Toxicity in SH-SY5Y Cells

The pharmacological activity and medicinal significance of Amauroderma rugosum (AR) have rarely been documented. We examined the antioxidant and neuroprotective effects of AR on 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in an SH-SY5Y human neuroblastoma cell model of Parkinson's disease (PD) and explored the active ingredients responsible for these effects. The results showed that the AR aqueous extract could scavenge reactive oxygen species and reduce SH-SY5Y cell death induced by 6-OHDA. In addition, the AR aqueous extract increased the survival of Caenorhabditis elegans upon juglone-induced toxicity. Among the constituents of AR, only polysaccharides and gallic acid exhibited antioxidant and neuroprotective effects. The AR aqueous extract reduced apoptosis and increased the expression of phospho-Akt, phospho-mTOR, phospho-MEK, phospho-ERK, and superoxide dismutase-1 in 6-OHDA-treated SH-SY5Y cells. The polysaccharide-rich AR extract was slightly more potent than the aqueous AR extract; however, it did not affect the expression of phospho-Akt or phospho-mTOR. In conclusion, the AR aqueous extract possessed antioxidant and neuroprotective properties against 6-OHDA-induced toxicity in SH-SY5Y cells. The mechanism of action involves the upregulation of the Akt/mTOR and MEK/ERK-dependent pathways. These findings indicate the potential utility of AR and its active ingredients in preventing or treating neurodegenerative disorders associated with oxidative stress such as PD.

Neurotrophic Natural Products

Neurotrophins (NGF, BDNF, NT3, NT4) can decrease cell death, induce differentiation, as well as sustain the structure and function of neurons, which make them promising therapeutic agents for the treatment of neurodegenerative disorders. However, neurotrophins have not been very effective in clinical trials mostly because they cannot pass through the blood-brain barrier owing to being high-molecular-weight proteins. Thus, neurotrophin-mimic small molecules, which stimulate the synthesis of endogenous neurotrophins or enhance neurotrophic actions, may serve as promising alternatives to neurotrophins. Small-molecular-weight natural products, which have been used in dietary functional foods or in traditional medicines over the course of human history, have a great potential for the development of new therapeutic agents against neurodegenerative diseases such as Alzheimer's disease. In this contribution, a variety of natural products possessing neurotrophic properties such as neurogenesis, neurite outgrowth promotion (neuritogenesis), and neuroprotection are described, and a focus is made on the chemistry and biology of several neurotrophic natural products.

Mediterranean Shrub Species as a Source of Biomolecules against Neurodegenerative Diseases

Neurodegenerative diseases are associated with oxidative stress, due to an imbalance in the oxidation-reduction reactions at the cellular level. Various treatments are available to treat these diseases, although they often do not cure them and have many adverse effects. Therefore, it is necessary to find complementary and/or alternative drugs that replace current treatments with fewer side effects. It has been demonstrated that natural products derived from plants, specifically phenolic compounds, have a great capacity to suppress oxidative stress and neutralize free radicals thus, they may be used as alternative alternative pharmacological treatments for pathological conditions associated with an increase in oxidative stress. The plant species that dominate the Mediterranean ecosystems are characterized by having a wide variety of phenolic compound content. Therefore, these species might be important sources of neuroprotective biomolecules. To evaluate this potential, 24 typical plant species of the Mediterranean ecosystems were selected, identifying the most important compounds present in them. This set of plant species provides a total of 403 different compounds. Of these compounds, 35.7% are phenolic acids and 55.6% are flavonoids. The most relevant of these compounds are gallic, vanillic, caffeic, chlorogenic, p-coumaric, and ferulic acids, apigenin, kaempferol, myricitrin, quercetin, isoquercetin, quercetrin, rutin, catechin and epicatechin, which are widely distributed among the analyzed plant species (in over 10 species) and which have been involved in the literature in the prevention of different neurodegenerative pathologies. It is also important to mention that three of these plant species, Pistacea lentiscus, Lavandula stoechas and Thymus vulgaris, have most of the described compounds with protective properties against neurodegenerative diseases. The present work shows that the plant species that dominate the studied geographic area can provide an important source of phenolic compounds for the pharmacological and biotechnological industry to prepare extracts or isolated compounds for therapy against neurodegenerative diseases.

Interplay between stress, sleep, and BDNF in a high-risk sample of young adults

Children in institutional care have a high risk to experience childhood adversities (CAs), with consequences for physical and mental well-being. The long-term effects of CAs on the brain, including consequences for neuronal plasticity and sleep, are poorly understood. This study examined the interplay between stress (including CAs), sleep, and brain-derived neurotrophic factor (BDNF), a prominent marker for neuronal plasticity. Participants (N = 131, mean age = 26.3±3.4 years, 40 females) with residential youth-care history completed questionnaires measuring CAs (Childhood Trauma Questionnaire, CTQ), psychological well-being (World Health Organization-Five Well-Being Index, WHO-5), and sleep disturbances (Pittsburgh Sleep Quality Inventory, PSQI). Hair cortisol and serum BDNF concentration were measured using enzyme-linked immunosorbent assays. The analyses were conducted by using bootstrap regression models. There was no association of stress parameters or sleep with BDNF concentration. However, we found a significant association of CAs and well-being with sleep disturbances. Last, we found an association between CAs and BDNF in sleep-healthy but not sleep-disturbed participants. Our findings indicated a role of sleep disturbance in the association between stress and BDNF. Still, further studies are warranted using vulnerable groups at-risk to understand long-term effects on mental health and sleep.

Clerodendrum viscosum leaves attenuate lead-induced neurotoxicity through upregulation of BDNF-Akt-Nrf2 pathway in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Clerodendrum viscosum is an important medicinal plant in Ayurveda in Bangladesh and its leaves are used as a remedy for various diseases such as anti-inflammatory, antibacterial, hyperglycemic, hepatoprotective effects.

AIM OF THE STUDY

The present study aimed to evaluate the protective effect of aqueous extract of C. viscosum leaves against Pb-induced neurobehavioral and biochemical changes in mice.

MATERIALS AND METHODS

Swiss albino mice were divided as a) control, b) lead treated (Pb) and c) C. viscosum leaves (Cle) d) Pb plus Cle groups. Pb-acetate (10 mg/kg body weight) was given to Pb and Pb + Cle groups mice, and water extract of leaves (50 mg/kg body weight) was provided as supplementation to Cle and Pb + Cle groups mice for 30 days. Elevated plus maze and Morris water maze tests were used for evaluating anxiety, spatial memory and learning, respectively. Status of cholinesterase, SOD, GSH enzyme activity and neurotoxicity markers such BDNF and Nrf2 levels were analyzed in the brain tissue of experimental mice.

RESULTS

Poorer learning, inferior spatial memory, and increased anxiety-like behavior in Pb-exposure mice were noted when compared to control mice in Morris water maze and elevated plus maze test, respectively. In addition, expression of BDNF and Nrf2, cholinesterase activity along with antioxidant activity were significantly reduced compared to control group (p < 0.01). Interestingly, C. viscosum leaves' aqueous extract supplementation in Pb-exposed mice provide a significant improved neurochemical and antioxidant properties through the augmentation of activity of cholinergic enzymes, and upregulation of BDNF and Nrf2 levels in the brain tissue compared to Pb-exposed mice.

CONCLUSIONS

This study suggested that C. viscosum leaves restore the cognitive dysfunction and reduce anxiety-like behavior through upregulation of BDNF mediated Akt-Nrf2 pathway in Pb-exposure mice.

Phytochemicals That Act on Synaptic Plasticity as Potential Prophylaxis against Stress-Induced Depressive Disorder

Depression is a neuropsychiatric disorder associated with persistent stress and disruption of neuronal function. Persistent stress causes neuronal atrophy, including loss of synapses and reduced size of the hippocampus and prefrontal cortex. These alterations are associated with neural dysfunction, including mood disturbances, cognitive impairment, and behavioral changes. Synaptic plasticity is the fundamental function of neural networks in response to various stimuli and acts by reorganizing neuronal structure, function, and connections from the molecular to the behavioral level. In this review, we describe the alterations in synaptic plasticity as underlying pathological mechanisms for depression in animal models and humans. We further elaborate on the significance of phytochemicals as bioactive agents that can positively modulate stress-induced, aberrant synaptic activity. Bioactive agents, including flavonoids, terpenes, saponins, and lignans, have been reported to upregulate brain-derived neurotrophic factor expression and release, suppress neuronal loss, and activate the relevant signaling pathways, including TrkB, ERK, Akt, and mTOR pathways, resulting in increased spine maturation and synaptic numbers in the neuronal cells and in the brains of stressed animals. In clinical trials, phytochemical usage is regarded as safe and well-tolerated for suppressing stress-related parameters in patients with depression. Thus, intake of phytochemicals with safe and active effects on synaptic plasticity may be a strategy for preventing neuronal damage and alleviating depression in a stressful life.

Physical exercise mediates a cortical FMRP-mTOR pathway to improve resilience against chronic stress in adolescent mice

Aerobic exercise effectively relieves anxiety disorders via modulating neurogenesis and neural activity. The molecular mechanism of exercise-mediated anxiolysis, however, remains incomplete. On a chronic restrain stress (CRS) model in adolescent mice, we showed that 14-day treadmill exercise profoundly maintained normal neural activity and axonal myelination in the medial prefrontal cortex (mPFC), in association with the prevention of anxiety-like behaviors. Further interrogation of molecular mechanisms revealed the activation of the mechanistic target of the rapamycin (mTOR) pathway within mPFC under exercise training. At the upstream of mTOR, exercise-mediated brain RNA methylation inhibited the expression of Fragile X mental retardation protein (FMRP) to activate the mTOR pathway. In summary, treadmill exercise modulates an FMRP-mTOR pathway to maintain cortical neural activity and axonal myelination, contributing to improved stress resilience. These results extended our understanding of the molecular substrate of exercise-mediated anxiolytic effect during adolescent period.

Unveiling behavioral and molecular neuroadaptations related to the antidepressant action of cannabidiol in the unpredictable chronic mild stress model

Introduction: This study aims to further characterize cannabidiol's pharmacological and molecular profile as an antidepressant. Methods: Effects of cannabidiol (CBD), alone or combined with sertraline (STR), were evaluated in male CD1 mice (n = 48) exposed to an unpredictable chronic mild stress (UCMS) procedure. Once the model was established (4 weeks), mice received CBD (20 mg·kg-1, i.p.), STR (10 mg·kg-1, p.o.) or its combination for 28 days. The efficacy of CBD was evaluated using the light-dark box (LDB), elevated plus maze (EPM), tail suspension (TS), sucrose consumption (SC) and novel object recognition (NOR) tests. Gene expression changes in the serotonin transporter, 5-HT1A and 5-HT2A receptors, BDNF, VGlut1 and PPARdelta, were evaluated in the dorsal raphe, hippocampus (Hipp) and amygdala by real-time PCR. Besides, BDNF, NeuN and caspase-3 immunoreactivity were assessed in the Hipp. Results: CBD exerted anxiolytic and antidepressant-like effects at 4 and 7 days of treatment in the LDB and TS tests, respectively. In contrast, STR required 14 days of treatment to show efficacy. CBD improved cognitive impairment and anhedonia more significantly than STR. CBD plus STR showed a similar effect than CBD in the LBD, TST and EPM. However, a worse outcome was observed in the NOR and SI tests. CBD modulates all molecular disturbances induced by UCMS, whereas STR and the combination could not restore 5-HT1A, BDNF and PPARdelta in the Hipp. Discussion: These results pointed out CBD as a potential new antidepressant with faster action and efficiency than STR. Particular attention should be given to the combination of CBD with current SSRI since it appears to produce a negative impact on treatment.

Protective effect of gallic acid on doxorubicin-induced ovarian toxicity in mouse

The aims of the present study were to evaluate the protective effects of gallic acid against doxorubicin-induced ovarian toxicity in mice, and to verify the possible involvement of PI3K and mTOR signaling pathway members (PTEN, Akt, FOXO3a and rpS6) in the gallic acid protective actions. Mice were pretreated with NaCl (0.15 M, p.o.) (control and doxorubicin groups) or gallic acid (50, 100 or 200 mg/kg body weight, p.o.) once daily, for 5 days, and on the third day of treatment, after 1 h of treatment administration, the mice received saline solution (i.p.) (control group) or doxorubicin (10 mg/kg of body weight, i.p.). Next, the ovaries were harvested for histological (follicular morphology and activation), fluorescence (GSH and mitochondrial activity), and immunohistochemical (PCNA, cleaved caspase-3, TNF-α, p-PTEN, Akt, p-Akt, p-rpS6 and p-FOXO3a) analyses. The results showed that cotreatment with 50 mg/kg gallic acid plus doxorubicin preserved the percentage of normal follicles and cell proliferation, reduced the percentage of cleaved caspase-3 follicles, prevented inflammation, and increased GSH concentrations and mitochondrial activity compared to doxorubicin treatment alone. Furthermore, cotreatment 50 mg/kg gallic acid plus doxorrubicin increased expression of Akt, p-Akt, p-rpS6 and p-FOXO3a compared to the doxorubicin alone. In conclusion, 50 mg/kg gallic acid protects the mouse ovary against doxorubicin-induced damage by improving GSH concentrations and mitochondrial activity and cellular proliferation, inhibiting inflammation and apoptosis, and regulating PI3K and mTOR signaling pathway.

Prophylactic efficacy of ketamine, but not the low-trapping NMDA receptor antagonist AZD6765, against stress-induced maladaptive behavior and 4E-BP1-related synaptic protein synthesis impairment

Ketamine enhances the resilience against stress-induced depressive-like behavior, but its prophylactic efficacy in anxiety-related behaviors remains to be elucidated. Moreover, there is a need for developing novel preventive strategies against depressive- and anxiety-like behavior. AZD6765, a low-trapping NMDA receptor antagonist, shares with ketamine common molecular targets and produces rapid-onset antidepressant effects, suggesting that it could be a prophylactic agent. Therefore, this study investigated the prophylactic effect of ketamine against the depressive- and anxiety-like behavior induced by chronic restraint stress (2 h/day, for 10 days) in mice. We also investigated if AZD6765 exerts a resilience-enhancing response against these maladaptive behaviors. The contribution of 4E-BP1-related synaptic proteins synthesis (PSD-95/GluA1) in the possible pro-resilience efficacy of ketamine and AZD6765 was investigated. A single administration of ketamine (5 mg/kg, i.p.), but not AZD6765 (1 or 5 mg/kg, i.p.), given 1 week before the stress protocol, was effective in preventing stress-induced depressive-like behavior in the tail suspension test and splash test. Ketamine administered at 1 and 5 mg/kg (i.p.), but not AZD6765 (1 or 5 mg/kg, i.p.), prevented stress-induced anxiety-related self-grooming alterations. Stress-induced reduction on 4E-BP1 phosphorylation and PSD-95 and GluA1 immunocontent in the prefrontal cortex was prevented by ketamine (5 mg/kg, i.p.), but not AZD6765 (1 or 5 mg/kg, i.p.). The results indicate that ketamine, but not AZD6765, exerts a pro-resilience response against stress-induced maladaptive behavior, reinforcing that it could be a prophylactic agent to manage individuals at-risk to develop MDD and anxiety.

Comorbidity of osteoporosis and Alzheimer's disease: Is `AKT `-ing on cellular glucose uptake the missing link?

Osteoporosis and Alzheimer's disease (AD) are both degenerative diseases. Osteoporosis often proceeds cognitive deficits, and multiple studies have revealed common triggers that lead to energy deficits in brain and bone. Risk factors for osteoporosis and AD, such as obesity, type 2 diabetes, aging, chemotherapy, vitamin deficiency, alcohol abuse, and apolipoprotein Eε4 and/or Il-6 gene variants, reduce cellular glucose uptake, and protective factors, such as estrogen, insulin, exercise, mammalian target of rapamycin inhibitors, hydrogen sulfide, and most phytochemicals, increase uptake. Glucose uptake is a fine-tuned process that depends on an abundance of glucose transporters (Gluts) on the cell surface. Gluts are stored in vesicles under the plasma membrane, and protective factors cause these vesicles to fuse with the membrane, resulting in presentation of Gluts on the cell surface. This translocation depends mainly on AKT kinase signaling and can be affected by a range of factors. Reduced AKT kinase signaling results in intracellular glucose deprivation, which causes endoplasmic reticulum stress and iron depletion, leading to activation of HIF-1α, the transcription factor necessary for higher Glut expression. The link between diseases and aging is a topic of growing interest. Here, we show that diseases that affect the same biochemical pathways tend to co-occur, which may explain why osteoporosis and/or diabetes are often associated with AD.

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-3β (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-3β, 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.

Phenolic profile, antidepressant-like and neuroprotective effects of Maclura tinctoria leaves extract

Considering the drawbacks elicited by the conventional antidepressants, the interest in natural products for the management of major depressive disorder has increased in the last years. Therefore, this study investigated the phenolic profile of Maclura tinctoria leaf aqueous extract (MtAE) and its possible antidepressant-like effect in mice. The LC-MS/MS analysis demonstrated MtAE has epicatechin as the major phenolic, followed by catechin, gallic acid, quercetin, syringaldehyde, ferulic acid, and syringic acid. Moreover, the acute treatment of MtAE elicited an antidepressant-like response in mice. Importantly, this antidepressant-like effect produced by MtAE was reinforced in the chronic corticosterone (20 mg/kg p.o.) administration model. MtAE treatment was also effective to protect hippocampal and cerebrocortical slices against glutamatergic excitotoxicity. Our results indicated that MtAE displayed antidepressant-like and neuroprotective effects and these responses could be associated with the presence of the phenolic compounds identified.

Natural products attenuate PI3K/Akt/mTOR signaling pathway: A promising strategy in regulating neurodegeneration

BACKGROUND

As common, progressive, and chronic causes of disability and death, neurodegenerative diseases (NDDs) significantly threaten human health, while no effective treatment is available. Given the engagement of multiple dysregulated pathways in neurodegeneration, there is an imperative need to target the axis and provide effective/multi-target agents to tackle neurodegeneration. Recent studies have revealed the role of phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) in some diseases and natural products with therapeutic potentials.

PURPOSE

This is the first systematic and comprehensive review on the role of plant-derived secondary metabolites in managing and/or treating various neuronal disorders via the PI3K/Akt/mTOR signaling pathway.

STUDY DESIGN AND METHODS

A systematic and comprehensive review was done based on the PubMed, Scopus, Web of Science, and Cochrane electronic databases. Two independent investigators followed the PRISMA guidelines and included papers on PI3K/Akt/mTOR and interconnected pathways/mediators targeted by phytochemicals in NDDs.

RESULTS

Natural products are multi-target agents with diverse pharmacological and biological activities and rich sources for discovering and developing novel therapeutic agents. Accordingly, recent studies have shown increasing phytochemicals in combating Alzheimer's disease, aging, Parkinson's disease, brain/spinal cord damages, depression, and other neuronal-associated dysfunctions. Amongst the emerging targets in neurodegeneration, PI3K/Akt/mTOR is of great importance. Therefore, attenuation of these mediators would be a great step towards neuroprotection in such NDDs.

CONCLUSION

The application of plant-derived secondary metabolites in managing and/or treating various neuronal disorders through the PI3K/Akt/mTOR signaling pathway is a promising strategy towards neuroprotection.

The effectiveness of continuous and interval exercise preconditioning against chronic unpredictable stress: Involvement of hippocampal PGC-1α/FNDC5/BDNF pathway

Various exercise-training types are known to prevent depression, but mechanisms underlying their beneficial effects remain unknown. In the present study, the preconditioning effect of continuous and interval exercise on stress-induced depression was evaluated. Adult male Wistar rats in the exercise groups were made to run on a motorized treadmill, five sessions per week for six weeks. After that, to induce the depression model, the rats were exposed to chronic unpredictable stress for three weeks. Behavioral tests were assessed by open field, elevated plus maze, and forced swim tests. Hippocampal PGC-1α, FNDC5, and BDNF protein expression by Western blot and serum corticosterone by ELISA were detected. In the present results, after continuous and interval exercise periods, locomotor activity, the number of entries and time spent in the open arms were increased, and immobility time was significantly reduced. PGC-1α, FNDC5, and BDNF protein levels had a significant increase, and serum corticosterone did not change. Also, interval exercise training increased PGC-1α and FNDC5 more than continuous. Chronic unpredictable stress reduced the positive changes caused by exercise training, although, except FNDC5, exercise preconditioned groups experienced less significant adverse changes in most variables. These findings showed that both continuous and interval exercise preconditioning with increasing hippocampal PGC-1α, FNDC5, and BDNF proteins and improve the anxiety- and depression-like behaviors have a protective effect against chronic unpredictable stress.

Physical exercise stimulates hippocampal mTORC1 and FNDC5/irisin signaling pathway in mice: Possible implication for its antidepressant effect

Several lines of evidence have consistently indicated that physical exercise has antidepressant effects by improving hippocampal function, although the signaling pathways underpinning these responses are not well established. Therefore, this study investigated the role of mechanistic target of rapamycin complex 1 (mTORC1) and fibronectin type III domain-containing protein 5 (FNDC5)/irisin signaling in the antidepressant-like effect of physical exercise. We showed that physical exercise (treadmill running - 45 min/day/5 days/week for 4 weeks) produced an antidepressant-like effect as indicated by a reduction on the immobility time in mice subjected to the forced swimming test (FST) without altering locomotor activity in the open field test (OFT). Rapamycin (a selective mTORC1 inhibitor, 0.2 nmol/site, i.c.v.) administration completely abolished the antidepressant-like effect of physical exercise in the FST, suggesting that mTORC1 activation plays a role for its behavioral effect. Accordingly, physical exercise increased the number of phosphorylated mTORC1 (Ser2448)-positive cells in the entire and ventral subgranular zone of the hippocampal dentate gyrus. Physical exercise was also effective in augmenting the hippocampal FNDC5/irisin immunocontent, but rapamycin administration did not alter this effect. Our results reinforce the notion that physical exercise exerts an antidepressant-like effect and identifies the mTORC1-mediated signaling pathway as a target for its behavioral effects. This study provides additional evidence that physical exercise increases hippocampal FNDC5/irisin immunocontent, but this effect seems to be independent on hippocampal mTORC1 activation. Altogether the results contribute to elucidate possible molecular targets implicated in the antidepressant effects of physical exercise and highlight the role of mTORC1 signaling for its behavioral response.

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-3β (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.

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CORT induces depressive-like behavior and hippocampal synaptogenic markers deficits.

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Ketamine prevents CORT-induced behavioral and hippocampal synaptogenic alterations.

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Guanosine or fluoxetine are unable to prevent the alterations induced by CORT.

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Ketamine plus guanosine partially prevent CORT-induced reduced self-care behavior.

Facile potentiometric sensing of gallic acid in edible plants based on molecularly imprinted polymer

Molecularly imprinted polymers (MIPs) have become a valuable material in the field of electrochemical sensors, due to their selective recognition capabilities towards target molecules. A low-cost potentiometric sensor based on molecular imprinting was developed for the measurement of gallic acid (GA) in edible plants. The imprinted polymer was synthesized by bulk polymerization in the presence of trimethylolpropane triacrylate as the cross-linker and 2,2'-azo-bisisobutyronitrile as the initiator. The sensing component of the sensor was fabricated by the incorporation of MIPs in a polyvinyl chloride matrix. The species and amount of MIPs were optimized, and the imprinted poly(methacrylic acid) sensor was examined and characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and potential response. The proposed sensor exhibited a fast near-Nernst response to GA in the range of 1 × 10^-5 to 3.2 × 10^-4 mol/L. The potentiometric measurement of GA in edible plants was checked by high-performance liquid chromatography, and the two test results showed no significant difference (P > 0.05). The imprinted sensor is applicable to the electrochemical determination of GA in edible plants. PRACTICAL APPLICATION: The proposed MIP-based potentiometric sensor provided a low-cost, efficient, and green tool for the rapid determination of the bioactive ingredient GA in edible plants. The knowledge obtained will offer useful reference to the quality control and bioactive assessment of botanical food.

Gallic acid affects blood-brain barrier permeability, behaviors, hippocampus local EEG, and brain oxidative stress in ischemic rats exposed to dusty particulate matter

Dust storms are environmental natural events that transport high concentrations of particulate matter (PM) in living spaces. Recent epidemiological studies have shown that air pollution is associated with stroke. In the present study we aimed to investigate the probable protective effects of gallic acid (GA) on blood-brain barrier (BBB) disruption, brain oxidative stress, anxiety, depression, locomotion behaviors, and changes of hippocampal local electroencephalogram (local EEG) power induced by 4-vessel transient occlusion (4VO I/R) following exposure to dusty PM in rats. Male Wistar rats were divided randomly into eight groups: (1) vehicle+Sham (Veh + Sh), (2) vehicle+4VO I/R (Veh + I/R), (3) gallic acid+sham (GA + Sh), (4) gallic acid+4VO I/R (GA + I/R), (5) vehicle+PM (Veh + PM), (6) PM + 4VO I/R (PM + I/R), (7) gallic acid+PM + Sham (GA + PM + Sh), and (8) gallic acid+PM + 4Vo I/R (GA + PM + I/R). 4VO type of I/R was induced after 10 days of pretreatment by GA 100 mg/kg/2 ml/ip, or 2 ml/kg/ip, normal saline as vehicle (Veh) and exposure to dust storm composed of dusty PM (DPM, 2000-8000 μg/m3), 60 min daily for consecutive 10 days) simultaneously. Seventy-two hours after I/R induction, all behavioral tests and BBB permeability evaluation were done. Hippocampus local EEG was recorded just before and 72 h after I/R induction, and finally brain tissue oxidative stress was assayed. Data showed that 4VO I/R following exposure to DPM increased BBB permeability (p < 0.001), brain oxidative stress (p < 0.001), induced anxiety (p < 0.001), depression (p < 0.01), locomotion impairment (p < 0.001), superoxide dismutase (SOD) activity, and local EEG power also were decreased in PM + Sh (p < 0.001). Pretreatment with GA reversed BBB permeability and MDA. Our findings suggest that GA is a probable protective agent against adverse effects of both I/R and exposure to DPM and also in I/R subjects exposed to DPM. The beneficial effects of GA may induce by its antioxidative and anti-inflammatory properties.

Gallic acid improves recognition memory and decreases oxidative-inflammatory damage in the rat hippocampus with metabolic syndrome

Metabolic syndrome (MS) results from excessive consumption of high-calorie foods and sedentary lifestyles. Clinically, insulin resistance, abdominal obesity, hyperglycemia, dyslipidemia, and hypertension are observed. MS has been considered a risk factor in the development of dementia. In the brain, a metabolically impaired environment generates oxidative stress and excessive production of pro-inflammatory cytokines that deteriorate the morphology and neuronal function in the hippocampus, leading to cognitive impairment. Therapeutic alternatives suggest that phenolic compounds can be part of the treatment for neuropathies and metabolic diseases. In recent years, the use of Gallic Acid (GA) has demonstrated antioxidant and anti-inflammatory effects that contribute to neuroprotection and memory improvement in animal models. However, the effect of GA on hippocampal neurodegeneration and memory impairment under MS conditions is still unclear. In this work, we administered GA (20 mg/kg) for 60 days to rats with MS. The results show that GA treatment improved zoometric and biochemical parameters, as well as the recognition memory, in animals with MS. Additionally, GA administration increased hippocampal dendritic spines and decreased oxidative stress and inflammation. Our results show that GA treatment improves metabolism: reducing the oxidative and inflammatory environment that facilitates the recovery of the neuronal morphology in the hippocampus of rats with MS. Consequently, the recognition of objects by these animals, suggesting that GA could be used therapeutically in metabolic disorders that cause dementia.