Chronic unpredictable mild stress decreases BDNF and NGF levels and Na+,K+-ATPase activity in the hippocampus and prefrontal cortex of mice: Antidepressant effect of chrysin

Comparing the effect of fluoxetine, escitalopram, and sertraline, on the level of BDNF and depression in preclinical and clinical studies: a systematic review

Brain-derived neurotrophic factor (BDNF) dysfunction is one of the most important mechanisms underlying depression. It seems that selective serotonin reuptake inhibitors (SSRIs) improve depression via affecting BDNF level. In this systematic review, for the first time, we aimed to review the effect of three SSRIs including fluoxetine, escitalopram, and sertraline, on both depression and BDNF level in preclinical and clinical studies. PubMed electronic database was searched, and 193 articles were included in this study. After reviewing all manuscripts, only one important difference was found: subjects. We found that SSRIs induce different effects in animals vs. humans. Preclinical studies showed many controversial effects, while human studies showed only two effects: improvement of depression, with or without the improvement of BDNF. However, most studies used chronic SSRIs treatment, while acute SSRIs were not effectively used and evaluated. In conclusion, it seems that SSRIs are reliable antidepressants, and the improvement effect of SSRIs on depression is not dependent to BDNF level (at least in human studies).

Sildenafil prevents chronic psychosocial stress-induced working memory impairment: Role of brain-derived neurotrophic factor

Background

Psychosocial stress, a common feature in modern societies, impairs cognitive functions. It is suggested that stress hormones and elevated excitatory amino acids during stress are responsible for stress-induced cognitive deficits. Reduced brain-derived neurotrophic factor (BDNF) levels, increased oxidative stress, and alteration of synaptic plasticity biomarkers are also possible contributors to the negative impact of stress on learning and memory. Sildenafil citrate is a selective phosphodiesterase type 5 (PDE5) inhibitor and the first oral therapy for the treatment of erectile dysfunction. It has been shown that sildenafil improves learning and memory and possesses antioxidant properties. We hypothesized that administering sildenafil to stressed rats prevents the cognitive deficit induced by chronic psychosocial stress.

Methods

Psychosocial stress was generated using the intruder model. Sildenafil 3 mg/kg/day was administered intraperitoneally to animals. Behavioral studies were conducted to test spatial learning and memory using the radial arm water maze. Then, the hippocampal BDNF level and several antioxidant markers were assessed.

Results

This study revealed that chronic psychosocial stress impaired short-term but not long-term memory. The administration of sildenafil prevented this short-term memory impairment. Chronic psychosocial stress markedly reduced the level of hippocampal BDNF (P˂0.05), and this reduction in BDNF was normalized by sildenafil treatment. In addition, neither chronic psychosocial stress nor sildenafil significantly altered the activity of measured oxidative parameters (P > 0.05).

Conclusion

Chronic psychosocial stress induces short-term memory impairment. The administration of sildenafil citrate prevented this impairment, possibly by normalizing the level of BDNF.

BDNF Unveiled: Exploring Its Role in Major Depression Disorder Serotonergic Imbalance and Associated Stress Conditions

Brain-derived neurotrophic factor (BDNF) is a neurotrophin that plays a significant role in the survival and development of neurons, being involved in several diseases such as Alzheimer's disease and major depression disorder. The association between BDNF and major depressive disorder is the subject of extensive research. Indeed, numerous studies indicate that decreased levels of BDNF are linked to an increased occurrence of depressive symptoms, neuronal loss, and cortical atrophy. Moreover, it has been observed that antidepressive therapy can help restore BDNF levels. In this review, we will focus on the role of BDNF in major depression disorder serotonergic imbalance and associated stress conditions, particularly hypothalamic-pituitary-adrenal (HPA) axis dysregulation and oxidative stress. All of these features are highly connected to BDNF signaling pathways in the context of this disease, and exploring this topic will aim to advance our understanding of the disorder, improve diagnostic and treatment approaches, and potentially identify new therapeutic targets to alleviate the heavy burden of depression on society.

Chronic infection by atypical Toxoplasma gondii strain induces disturbance in microglia population and altered behaviour in mice

Toxoplasma gondii chronic infection is characterized by the establishment of tissue cysts in the brain and increased levels of IFN-γ, which can lead to brain circuitry interference and consequently abnormal behaviour in mice. In this sense, the study presented here sought to investigate the impact of chronic infection by two T. gondii strains in the brain of infection-resistant mice, as a model for studying the involvement of chronic neuroinflammation with the development of behavioural alterations. For that, male BALB/c mice were divided into three groups: non-infected (Ni), infected with T. gondii ME49 clonal strain (ME49), and infected with TgCkBrRN2 atypical strain (CK2). Mice were monitored for 60 days to establish the chronic infection and then submitted to behavioural assessment. The enzyme-linked immunosorbent assay was used for measurement of specific IgG in the blood and levels of inflammatory cytokines and neurotrophic factors in the brain, and the cell's immunophenotype was determined by multiparametric flow cytometry. Mice infected with ME49 clonal strain displayed hyperlocomotor activity and memory deficit, although no signs of depressive- and/or anxiety-like behaviour were detected; on the other hand, chronic infection with CK2 atypical strain induced anxiety- and depressive-like behaviour. During chronic infection by CK2 atypical strain, mice displayed a higher number of T. gondii brain tissue cysts and inflammatory infiltrate, composed mainly of CD3⁺ T lymphocytes and Ly6C^hi inflammatory monocytes, compared to mice infected with the ME49 clonal strain. Infected mice presented a marked decrease of microglia population compared to non-infected group. Chronic infection with CK2 strain produced elevated levels of IFN-γ and TNF-ɑ in the brain, decreased NGF levels in the prefrontal cortex and striatum, and altered levels of fractalkine (CX3CL1) in the prefrontal cortex and hippocampus. The persistent inflammation and the disturbance in the cerebral homeostasis may contribute to altered behaviour in mice, as the levels of IFN-γ were shown to be correlated with the behavioural parameters assessed here. Considering the high incidence and life-long persistence of T. gondii infection, this approach can be considered a suitable model for studying the impact of chronic infections in the brain and how it impacts in behavioural responses.

Short-Term Irisin Treatment Enhanced Neurotrophin Expression Differently in the Hippocampus and the Prefrontal Cortex of Young Mice

As a result of physical exercise, muscle releases multiple exerkines, such as "irisin", which is thought to induce pro-cognitive and antidepressant effects. We recently demonstrated in young healthy mice the mitigation of depressive behaviors induced by consecutive 5 day irisin administration. To understand which molecular mechanisms might be involved in such effect, we here studied, in a group of mice previously submitted to a behavioral test of depression, the gene expression of neurotrophins and cytokines in the hippocampus and prefrontal cortex (PFC), two brain areas frequently investigated in the depression pathogenesis. We found significantly increased mRNA levels of nerve growth factor (NGF) and fibroblast growth factor 2 (FGF-2) in the hippocampus and brain-derived growth factor (BDNF) in the PFC. We did not detect a difference in the mRNA levels of interleukin 6 (IL-6) and IL-1β in both brain regions. Except for BDNF in the PFC, two-way ANOVA analysis did not reveal sex differences in the expression of the tested genes. Overall, our data evidenced a site-specific cerebral modulation of neurotrophins induced by irisin treatment in the hippocampus and the PFC, contributing to the search for new antidepressant treatments targeted at single depressive events with short-term protocols.

Dose-dependent toxic effects of di-(2-ethylhexyl) phthalate in male rats: Focus on behavioral alterations and inducing TLR4/NF-κB signaling pathway

Di -(2-ethylhexyl) phthalate (DEHP) is a widely used phthalate that possesses a public health concern. Different concentrations of DEHP, including 50, 300, and 750 mg/kg, were administrated orally for 28 days in male rats. Body weight and vital organs weight were measured as well as anxiety-like behavior, short and long-term memory were investigated. Brain inflammatory cytokines, including IL-1β, TLR4, NF-κB, TNF-α, and IL1-6, were assessed. Brain caspase-3, neuropeptide-Y (NPY), and brain histopathology were also evaluated. DEHP triggers the release of pro-inflammatory cytokines via inducing the nuclear translocation of the signaling pathway; TLR 4/ NF-κB leads to cognitive impairment and neurodegeneration, which is confirmed by the impaired brain architecture. Also, DEHP upgrades the expression levels of brain caspase-3 and NPY. In conclusion, exposure to high doses of DEHP persuades great toxicity visualized by behavioral, biochemical, and histological impairments when compared to the low dose.

The 5-HT1A receptor biased agonist, NLX-204, shows rapid-acting antidepressant-like properties and neurochemical changes in two mouse models of depression

Activation of cortical serotonin 5-HT_1A receptors may be a promising strategy to achieve rapid-acting antidepressant (RAAD) activity. NLX-204 is a selective 5-HT_1A receptor biased agonist that, in naïve mice, robustly decreases immobility in the forced swim test (FST), and preferentially phosphorylates extracellular signal-regulated kinase (ERK1/2), involved in antidepressant activity. Here, we evaluated the properties of NLX-204 in two mouse models of depression. Male CD-1 mice were subjected to unpredictable chronic mild stress (UCMS) for 4-weeks or to repeated corticosterone (CORT, 20 mg/kg s.c./day) for 3-weeks before receiving acute administration of NLX-204 (2 mg/kg, p.o.). Depressive-like behavior was assessed in the FST, anhedonia-like behavior in the sucrose preference test (SPT) and locomotor activity was also recorded. Phosphorylation of ERK1/2 (pERK1/2) and cAMP response binding element (pCREB) were measured ex vivo in hippocampus and prefrontal cortex (PFC). UCMS or CORT treatment increased immobility in the FST, elicited a sucrose preference deficit, and decreased pERK1/2 and pCREB levels in PFC and hippocampus. NLX-204 reduced depressive-like behavior in the FST in CORT and UCMS mice, and normalized sucrose preference in CORT mice, suggesting anti-anhedonic activity. NLX-204 increased pERK1/2 levels in PFC of UCMS mice. NLX-204 also increased pCREB levels in PFC of CORT mice. These data suggest that NLX-204 has RAAD-like properties not only in naïve mice, but also in mice in a "depressive-like" state, and that these involve changes in PFC and hippocampal pERK1/2 and pCREB levels. These data provide additional evidence that activation of 5-HT_1A receptors by selective biased agonists, such as NLX-204, may constitute a promising RAAD strategy.

Antidepressant-like effect of endogenous SO2 on depression caused by chronic unpredictable mild stress

Sulfur dioxide (SO₂) is a toxic gas with harmful effects on various organs. However, recent studies have confirmed the protective effect of SO₂ on ischemic heart disease, atherosclerosis, and lung infections. Therefore, the present study was designed to investigate the effect of endogenous SO₂ on depression. The chronic unpredictable mild stress (CUMS) model was performed to cause depression. Depression-like behaviors in animals were determined using an open-field test, forced swimming test, and sucrose consumption. Animal spatial learning and memory were also assessed using the Morris water maze. Besides, the oxidative status of the hippocampus and serum corticosterone level were evaluated. A reduction in the tendency to consume sucrose, mobility, and curiosity, as well as learning and memory disorders were observed in CUMS animals. Depressed animals treated with SO₂ revealed a significant improvement in behavioral and cognitive functions. SO₂ also reduced neuronal damage and lipid peroxidation of the hippocampus and serum corticosterone level in the CUMS group. Various shreds of evidence support a mutual relationship between inflammation and depression; also, growing studies show the role of oxidative stress in the pathogenesis of mood-related disorders such as depression. This study indicated that increased hippocampal malondialdehyde (MDA) and serum corticosterone levels can be due to the existence of oxidative stress and possible activation of inflammatory processes. SO₂ donors diminished MDA and corticosterone levels in depressed animals. According to the study results, SO₂ may be able to reduce tissue damage and eventually behavioral disorders caused by depression by lowering oxidative stress and inflammation.

Therapeutic treatment with fluoxetine using the chronic unpredictable stress model induces changes in neurotransmitters and circulating miRNAs in extracellular vesicles

The most widely prescribed antidepressant, fluoxetine (FLX), is known for its antioxidant and anti-inflammatory effects when administered post-stress. Few studies have evaluated the effects of FLX treatment when chronic stress has induced deleterious effects in patients. Our objective was to evaluate FLX treatment (20 mg/kg/day, i.v.) once these effects are manifested, and the drug's relation to extracellular circulating microRNAs associated with inflammation, a hedonic response (sucrose intake), the forced swim test (FST), and corticosterone levels (CORT) and monoamine concentrations in limbic areas. A group of Wistar rats was divided into groups: Control; FLX; CUMS (for six weeks of exposure to chronic, unpredictable mild stress); and CUMS + FLX, a mixed group. After CUMS, the rats performed the FST, and serum levels of CORT and six microRNAs (miR-16, -21, -144, -155, -146a, -223) were analyzed, as were levels of dopamine, noradrenaline, and serotonin in the prefrontal cortex, hippocampus, and hypothalamus. CUMS reduced body weight, sucrose intake, and hippocampal noradrenaline levels, but increased CORT, immobility behavior on the FST, dopamine concentrations in the prefrontal cortex, and all miRNAs except miR-146a expression. Administering FLX during CUMS reduced CORT levels and immobility behavior on the FST and increased the expression of miR-16, -21, -146a, -223, and dopamine. FLX protects against the deleterious effects of stress by reducing CORT and has an antidepressant effect on the FST, with minimally-modified neurotransmitter levels. FLX increased the expression of miRNAs as part of the antidepressant effect. It also regulates both neuroinflammation and serotoninergic neurotransmission through miRNAs, such as the miR-16.

Behavioral Despair Is Blocked by the Flavonoid Chrysin (5,7-Dihydroxyflavone) in a Rat Model of Surgical Menopause

Women have a high susceptibility to the negative effects of stress. Hormonal changes experienced throughout their reproductive life partially contribute to a higher incidence of anxiety and depression symptoms, particularly, during natural or surgical menopause. In preclinical research, the flavonoid chrysin (5,7-dihydroxyflavone) exerts anxiolytic- and anti-despair-like effects; however, it is unknown whether chrysin exerts a protective effect against the behavioral changes produced by acute stress on locomotor activity and behavioral despair in rats at 12-weeks post-ovariectomy. Ovariectomized female Wistar rats were assigned to eight groups: vehicle group (10% DMSO), three groups with chrysin and three groups with the same dose of allopregnanolone (0.5, 1, and 2 mg/kg), and one group with diazepam (2 mg/kg). The treatments were administered for seven consecutive days and the effects were evaluated in the locomotor activity and swimming tests. Chrysin (2 mg/kg) increased the latency to first immobility and decreased the total immobility time in the swimming test as the reference drugs allopregnanolone and diazepam (2 mg/kg); while locomotor activity prevented the behavioral changes produced by swimming. In conclusion, chrysin exerts a protective effect against the behavioral changes induced by acute stress, similarly to the neurosteroid allopregnanolone and the benzodiazepine diazepam in rats subjected to a surgical menopause model.

Hydroalcoholic Extract of Rabbiteye Blueberry (Vaccinium ashei) Leaves Mitigates Unpredictable Chronic Mild Stress Model Inducing Depressive-Like Behavior in Rats

Several studies reported that rabbiteye blueberry (Vaccinium ashei Reade) leaves present promising biological properties. To the best of our knowledge, no study investigated the possible application of their hydroalcoholic extract for treating mood disorders. Herein, we evaluated if the hydroalcoholic extract of rabbiteye blueberry (Vaccinium ashei Reade) leaves (HEV) promotes an antidepressant-like effect in rodents using chronic experimental approaches. The effect of repeated administration of HEV (50 mg/kg, p.o.) on the immobility time was assessed in the forced swimming test (FST) in an unpredictable chronic mild stress (UCMS) model. Repeated treatment with HEV reversed the depressive-like behavior induced by UCMS by reducing the immobility time. Besides, the exposure to HEV caused no changes in relative organ weights in rats submitted to UCMS. The results indicated that HEV administration presented antidepressant-like action devoid of toxic effects. Thus, it is possible to suggest its potential as a safe and accessible therapeutic tool in the management of depression and other related mood disorders.

Participation of the Serotonergic System and Brain-Derived Neurotrophic Factor in the Antidepressant-like Effect of Flavonoids

Depressive disorders are among the most disabling diseases experienced around the world, and their incidence has significantly increased over the last few decades due to multiple environmental, social, and biological factors. The search for new pharmacological alternatives to treat depression is a global priority. In preclinical research, molecules obtained from plants, such as flavonoids, have shown promising antidepressant-like properties through several mechanisms of action that have not been fully elucidated, including crossing of the blood brain barrier (BBB). This review will focus on discussing the main findings related to the participation of the serotonergic system and brain-derived neurotrophic factor (BDNF) on the antidepressant-like effect of some flavonoids reported by behavioral, neurochemical, and molecular studies. In this sense, evidence shows that depressive individuals have low levels of serotonin and BDNF, while flavonoids can reverse it. Finally, the elucidation of the mechanism used by flavonoids to modulate serotonin and BDNF will contribute to our understanding of the neurobiological bases underlying the antidepressant-like effects produced by these natural compounds.

Activating PPARβ/δ Protects against Endoplasmic Reticulum Stress-Induced Astrocytic Apoptosis via UCP2-Dependent Mitophagy in Depressive Model

As energy metabolism regulation factor, peroxisome proliferator-activated receptor (PPAR) is thought to be a potential target for the treatment of depression. The present study was performed to evaluate the effects of activating PPARβ/δ, the most highly expressed subtype in the brain, in depressive in vivo and in vitro models. We observed that PPARβ/δ agonist GW0742 significantly alleviated depressive behaviors in mice and promoted the formation of autophagosomes around the damaged mitochondria in hippocampal astrocytes. Our in vitro experiments showed that GW0742 could reduce mitochondrial oxidative stress, and thereby attenuate endoplasmic reticulum (ER) stress-mediated apoptosis pathway via inhibiting IRE1α phosphorylation, subsequently protect against astrocytic apoptosis and loss. Furthermore, we found that PPARβ/δ agonist induces astrocytic mitophagy companied with the upregulated UCP2 expressions. Knocking down UCP2 in astrocytes could block the anti-apoptosis and pro-mitophagy effects of GW0742. In conclusion, our findings reveal PPARβ/δ activation protects against ER stress-induced astrocytic apoptosis via enhancing UCP2-mediated mitophagy, which contribute to the anti-depressive action. The present study provides a new insight for depression therapy.

Propolis: An update on its chemistry and pharmacological applications

Propolis, a resinous substance produced by honeybees from various plant sources, has been used for thousands of years in traditional medicine for several purposes all over the world. The precise composition of propolis varies according to plant source, seasons harvesting, geography, type of bee flora, climate changes, and honeybee species at the site of collection. This apiary product has broad clinical applications such as antioxidant, anti-inflammatory, antimicrobial, anticancer, analgesic, antidepressant, and anxiolytic as well asimmunomodulatory effects. It is also well known from traditional uses in treating purulent disorders, improving the wound healing, and alleviating many of the related discomforts. Even if its use was already widespread since ancient times, after the First and Second World War, it has grown even more as well as the studies to identify its chemical and pharmacological features, allowing to discriminate the qualities of propolis in terms of the chemical profile and relative biological activity based on the geographic place of origin. Recently, several in vitro and in vivo studies have been carried out and new insights into the pharmaceutical prospects of this bee product in the management of different disorders, have been highlighted. Specifically, the available literature confirms the efficacy of propolis and its bioactive compounds in the reduction of cancer progression, inhibition of bacterial and viral infections as well as mitigation of parasitic-related symptoms, paving the way to the use of propolis as an alternative approach to improve the human health. However, a more conscious use of propolis in terms of standardized extracts as well as new clinical studies are needed to substantiate these health claims.

LPS-induced impairment of Na+/K+-ATPase activity: ameliorative effect of tannic acid in mice

Acetylcholine is an excitatory neurotransmitter that modulates synaptic plasticity and communication, and it is essential for learning and memory processes. This neurotransmitter is hydrolyzed by acetylcholinesterase (AChE), which plays other cellular roles in processes such as inflammation and oxidative stress. Ion pumps, such as Na⁺/K⁺-ATPase and Ca²⁺-ATPase, are highly expressed channels that derive energy for their functions from ATP hydrolysis. Impairment of the cholinergic system and ion pumps is associated with neuropsychiatric diseases. Major depressive disorder (MDD) is an example of a complex disease with high morbidity and a heterogenous etiology. Polyphenols have been investigated for their therapeutic effects, and tannic acid (TA) has been reported to show neuroprotective and antidepressant-like activities. Animal models of depression-like behavior, such as lipopolysaccharide (LPS)-induced models of depression, are useful for investigating the pathophysiology of MDD. In this context, effects of TA were evaluated in an LPS-induced mouse model of depression-like behavior. Animals received TA for 7 days, and on the last day of treatment, LPS (830 μg/kg) was administered intraperitoneally. In vitro exposure of healthy brain to TA decreased the AChE activity. Additionally, this enzyme activity was decreased in cerebral cortex of LPS-treated mice. LPS injection increased the activity of Ca²⁺-ATPase in the cerebral cortex but decreased the enzyme activity in the hippocampus. LPS administration decreased Na⁺/K⁺-ATPase activity in the cerebral cortex, hippocampus, and striatum; however, TA administration prevented these changes. In conclusion, tannins may affect Na⁺/K⁺-ATPase and Ca²⁺-ATPase activities, which is interesting in the context of MDD.

Selection of the Male or Female Sex in Chronic Unpredictable Mild Stress-Induced Animal Models of Depression

Depression is a serious public health problem and an important factor leading to disease-related disability. Influenced by many factors, such as psychological, hormonal, and genetic factors, the incidence rate of depression in females is approximately two times that in males. However, in preclinical neuroscience research, the selection of the animals' sex for use in depression models has been controversial. At present, in most preclinical studies, the animals generally chosen in depression models have been male rodents rather than female rodents. It remains doubtful whether the data obtained from male animals can be generalized to female animals. The performance of female animals in preclinical studies of depression has been inconclusive. Based on a review of a large number of original studies in the PubMed database, it was found that although male rodents are more commonly used in the study of depression, the use of female animals also shows good modeling of depression and has its advantages. The influence of the animals' sex in the chronic unpredictable mild stress (CUMS) model needs further research.

Chrysin-Loaded Chitosan Nanoparticle-Mediated Neuroprotection in Aβ1-42-Induced Neurodegenerative Conditions in Zebrafish

Amyloid β plaques and neurofibrillary tangles are the characteristic features of Alzheimer's disease (AD). Plaques of amyloid β play a pivotal role in affecting cognitive functions and memory. Alzheimer's disease is a progressive neurodegenerative disease and is one of the leading causes of dementia worldwide. Several treatment strategies focusing on the amyloid cascade have been implemented to treat AD. The blood-brain barrier (BBB) poses the main obstructive barrier by refraining drugs from penetrating the brain. Nanotechnology is a promising research field for brain drug delivery using nanosized particles. Zebrafish is emerging as a model of interest to elaborate on brain targeting and nanotechnology-based therapeutics for neurodegenerative diseases. In the current study, we have synthesized and characterized chrysin-loaded chitosan nanoparticles (Chr-Chi NPs) and evaluated them for neuroprotection against amyloid-β-induced toxicity. We find that treatment with Chr-Chi NPs helps to retain memory, cognition, and synaptic connections, which are otherwise compromised due to Aβ_1-42 toxicity. The NPs further help in reducing aggregates of amyloid β, thus decreasing neuronal death and generation of reactive oxygen species (ROS). Taken together, our study brings to light a novel strategy for treating AD by a combined action on the neurons and amyloid aggregates mediated by chrysin and chitosan, respectively. Chr-Chi NPs, therefore, have the potential to provide a beneficial combinatorial treatment strategy for AD.

Pharmacological, Neurochemical, and Behavioral Mechanisms Underlying the Anxiolytic- and Antidepressant-like Effects of Flavonoid Chrysin

Chrysin (5,7-dihydroxyflavone) is a flavonoid isolated from plants, such as Passiflora coerulea, Passiflora incarnata, and Matricaria chamomilla. This natural molecule exerts diverse pharmacological effects, which includes antioxidant, anti-inflammatory, anti-cancer, neuroprotective, and anti-apoptotic effects. Additionally, in brain structures, such as the hippocampus, prefrontal cortex, raphe nucleus, and striatum, involved in the physiopathology of anxiety and depression disorders, several neuropharmacological activities, including the activation of neurotransmitter systems (GABAergic, serotonergic, dopaminergic, and noradrenergic), neurotrophic factors, such as brain-derived neurotrophic factor and the nerve growth factor, and some signaling pathways are affected. The results showed that the anxiolytic and antidepressant-like effects of chrysin occurs through its interaction with specific neurotransmitter systems, principally the GABAergic and the serotonergic, and activation of other neurotrophic factors. However, it is not possible to discard the antioxidant and anti-inflammatory activities of chrysin while producing its anxiolytic- and antidepressant-like effects. Although these results have been obtained principally from pre-clinical research, they consistently demonstrate the potential therapeutic use of flavonoid chrysin as an anxiolytic and antidepressant agent. Therefore, this flavonoid could be considered as a promising novel therapy for anxiety and depression disorders.

Potential Therapeutic Benefits of Honey in Neurological Disorders: The Role of Polyphenols

Honey is the principal premier product of beekeeping familiar to Homo for centuries. In every geological era and culture, evidence can be traced to the potential usefulness of honey in several ailments. With the advent of recent scientific approaches, honey has been proclaimed as a potent complementary and alternative medicine for the management and treatment of several maladies including various neurological disorders such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and multiple sclerosis, etc. In the literature archive, oxidative stress and the deprivation of antioxidants are believed to be the paramount cause of many of these neuropathies. Since different types of honey are abundant with certain antioxidants, primarily in the form of diverse polyphenols, honey is undoubtedly a strong pharmaceutic candidate against multiple neurological diseases. In this review, we have indexed and comprehended the involved mechanisms of various constituent polyphenols including different phenolic acids, flavonoids, and other phytochemicals that manifest multiple antioxidant effects in various neurological disorders. All these mechanistic interpretations of the nutritious components of honey explain and justify the potential recommendation of sweet nectar in ameliorating the burden of neurological disorders that have significantly increased across the world in the last few decades.

Serum NGF and BDNF in Long-COVID-19 Adolescents: A Pilot Study

COVID-19 (COronaVIrus Disease 19) is an infectious disease also known as an acute respiratory syndrome caused by the SARS-CoV-2. Although in children and adolescents SARS-CoV-2 infection produces mostly mild or moderate symptoms, in a certain percentage of recovered young people a condition of malaise, defined as long-COVID-19, remains. To date, the risk factors for the development of long-COVID-19 are not completely elucidated. Neurotrophins such as NGF (Nerve Growth Factor) and BDNF (Brain-Derived Neurotrophic Factor) are known to regulate not only neuronal growth, survival and plasticity, but also to influence cardiovascular, immune, and endocrine systems in physiological and/or pathological conditions; to date only a few papers have discussed their potential role in COVID-19. In the present pilot study, we aimed to identify NGF and BDNF changes in the serum of a small cohort of male and female adolescents that contracted the infection during the second wave of the pandemic (between September and October 2020), notably in the absence of available vaccines. Blood withdrawal was carried out when the recruited adolescents tested negative for the SARS-CoV-2 (“post-infected COVID-19”), 30 to 35 days after the last molecular test. According to their COVID-19 related outcomes, the recruited individuals were divided into three groups: asymptomatics, acute symptomatics and symptomatics that over time developed long-COVID-19 symptoms (“future long-COVID-19”). As a control group, we analyzed the serum of age-matched healthy controls that did not contract the infection. Inflammatory biomarkers (TNF-α, TGF-β), MCP-1, IL-1α, IL-2, IL-6, IL-10, IL-12) were also analyzed with the free oxygen radicals’ presence as an oxidative stress index. We showed that NGF serum content was lower in post-infected-COVID-19 individuals when compared to healthy controls; BDNF levels were found to be higher compared to healthy individuals only in post-infected-COVID-19 symptomatic and future long-COVID-19 girls, leaving the BDNF levels unchanged in asymptomatic individuals if compared to controls. Oxidative stress and inflammatory biomarkers were unchanged in male and female adolescents, except for TGF-β that, similarly to BDNF, was higher in post-infected-COVID-19 symptomatic and future long-COVID-19 girls. We predicted that NGF and/or BDNF could be used as early biomarkers of COVID-19 morbidity in adolescents.

GABAA/Benzodiazepine Receptor Complex in the Dorsal Hippocampus Mediates the Effects of Chrysin on Anxiety-Like Behaviour in Female Rats

Systemic injections of the flavonoid chrysin (5,7-dihydroxyflavone) exert anxiolytic-like effects in ovariectomised and cycling female rats through actions on gamma-aminobutyric acid-A (GABA_A) receptors; however, it is unknown if chrysin directly acts on brain structures that are involved in regulating emotional processes, such as the hippocampus. The present study evaluated the effects of intrahippocampal microinjections of 0.25, 0.5, and 1 μg of chrysin on anxiety-like behaviour in the elevated plus maze (EPM) and locomotor activity test (LAT) in female rats in proestrus and dioestrus. Similar doses of the neurosteroid allopregnanolone were used as a reference GABAergic anxiolytic drug. The participation of the GABA_A/benzodiazepine receptor complex was evaluated by administering the antagonists picrotoxin, bicuculline and flumazenil. In proestrus, 0.5 and 1 μg of chrysin and allopregnanolone induced anxiogenic-like behaviour. In dioestrus, chrysin, and allopregnanolone (0.5 μg) induced anxiolytic-like effects. Picrotoxin, bicuculline and flumazenil prevented the effects of chrysin and allopregnanolone in both proestrus and dioestrus. None of the treatments significantly affected locomotor activity. These results indicate that the GABA_A/benzodiazepine receptor complex in the dorsal hippocampus regulates the effects of chrysin on anxiety-like behaviour, similar to the actions of allopregnanolone. The divergent effects of treatments across the oestrous cycle phases suggest complex interactions between GABA_A receptors and compounds with an anxiolytic potential.

Analysis of Antidepressant-like Effects and Action Mechanisms of GSB-106, a Small Molecule, Affecting the TrkB Signaling

Induction of BDNF-TrkB signaling is associated with the action mechanisms of conventional and fast-acting antidepressants. GSB-106, developed as a small dimeric dipeptide mimetic of BDNF, was previously shown to produce antidepressant-like effects in the mouse Porsolt test, tail suspension test, Nomura water wheel test, in the chronic social defeat stress model and in the inflammation-induced model of depression. In the present study, we evaluated the effect of chronic per os administration of GSB-106 to Balb/c mice under unpredictable chronic mild stress (UCMS). It was observed for the first time that long term GSB-106 treatment (1 mg/kg, 26 days) during ongoing UCMS procedure ameliorated the depressive-like behaviors in mice as indicated by the Porsolt test. In addition, chronic per os administration of GSB-106 resulted in an increase in BDNF levels, which were found to be decreased in the prefrontal cortex and hippocampus of mice after UCMS. Furthermore, prolonged GSB-106 treatment was accompanied by an increase in the content of pTrkB^706/707 in the prefrontal cortex and by a pronounced increase in the level of pTrkB⁸¹⁶ in both studied brain structures of mice subjected to UCMS procedure. In summary, the present data show that chronic GSB-106 treatment produces an antidepressant-like effect in the unpredictable chronic mild stress model, which is likely to be associated with the regulation of the BDNF-TrkB signaling.

Emerging Role of Flavonoids as the Treatment of Depression

Depression is one of the most frequently observed psychological disorders, affecting thoughts, feelings, behavior and a sense of well-being in person. As per the WHO, it is projected to be the primitive cause of various other diseases by 2030. Clinically, depression is treated by various types of synthetic medicines that have several limitations such as side-effects, slow-onset action, poor remission and response rates due to complicated pathophysiology involved with depression. Further, clinically, patients cannot be given the treatment unless it affects adversely the job or family. In addition, synthetic drugs are usually single targeted drugs. Unlike synthetic medicaments, there are many plants that have flavonoids and producing action on multiple molecular targets and exhibit anti-depressant action by affecting multiple neuronal transmissions or pathways such as noradrenergic, serotonergic, GABAnergic and dopaminergic; inhibition of monoamine oxidase and tropomyosin receptor kinase B; simultaneous increase in nerve growth and brain-derived neurotrophic factors. Such herbal drugs with flavonoids are likely to be useful in patients with sub-clinical depression. This review is an attempt to analyze pre-clinical studies, structural activity relationship and characteristics of reported isolated flavonoids, which may be considered for clinical trials for the development of therapeutically useful antidepressant.

Chrysin restores memory deficit in hypothyroidism mice: Behavioral, neurochemical and computational approaches involving the neurotrophinergic system

Hypothyroidism is a condition that affects multiple systems, including the central nervous system, causing, for example, cognitive deficits closely related to Alzheimer's disease. The flavonoid chrysin is a natural compound associated with neuronal improvement in several experimental models. Here, we evaluated the effect of chrysin on cognitive impairment in hypothyroid female mice by exploring neuroplasticity. Hypothyroidism was induced by continuous exposure to 0.1% methimazole (MTZ) in drinking water for 31 days. On the 32nd day, the animals showed low plasma levels of thyroid hormones (hypothyroid mice) than the control group (euthyroid mice). Subsequently, mice were intragastrically administered with vehicle or chrysin (20 mg/kg) once a day for 28 consecutive days. At the end of the treatments, behavioral tests were performed: open-field test (OFT) and morris water maze (MWM). Then, the levels of neurotrophins (BDNF and NGF) in the hippocampus and prefrontal cortex were measured and tested the affinity of chrysin with neurotrophinergic receptors through molecular docking. Hypothyroid mice showed memory deficit in the MWM and reduced neurotrophins levels in the hippocampus and prefrontal cortex, meanwhile, the chrysin treatment was able to reversed the deficit of spatial memory function and increased the levels of BDNF in hipocamppus and NGF in both structures. Additionally, molecular docking analysis showed that chrysin potentially binds to the active site of the TrkA, TrkB, and p75NTR receptors. Together, these findings suggest that chrysin reversed behavioral and neurochemical alterations associated with memory deficit induced by hypothyroidism, possibly by modulating synaptic plasticity in the neurotrophinergic system.

Antidepressant-like effect of Ganoderma lucidum spore polysaccharide-peptide mediated by upregulation of prefrontal cortex brain-derived neurotrophic factor

A 28-kDa polysaccharide-peptide (PGL) with antidepressant-like activities was isolated from spores of the mushroom Ganoderma lucidum. It was unadsorbed on DEAE-cellulose. Its internal amino acid sequences manifested pronounced similarity with proteins from the mushrooms Lentinula edodes and Agaricus bisporus. The monosaccharides present in 28-kDa PGL comprised predominantly of glucose (over 90%) and much fewer galactose, mannose residues, and other residues. PGL manifested antidepressant-like activities as follows. It enhanced viability and DNA content in corticosterone-injured PC12 cells(a cell line derived from a pheochromocytoma of the rat adrenal medulla with an embryonic origin from the neural crest containing a mixture of neuroblastic cells and eosinophilic cells) and reduced LDH release. A single acute PGL treatment shortened the duration of immobility of mice in both tail suspension and forced swimming tests. PGL treatment enhanced sucrose preference and shortened the duration of immobility in mice exposed to chronic unpredictable mild stress (CUMS). Chronic PGL treatment reversed the decline in mouse brain serotonin and norepinephrine levels but did not affect dopamine levels. PGL decreased serum corticosterone levels and increased BDNF mRNA and protein levels and increased synapsin I and PSD95 levels in the prefrontal cortex. This effect was completely blocked by pretreatment with the BDNF antagonist K252a, indicating that PGL increased synaptic proteins in a BDNF-dependent manner.Key points• An antidepressive polysaccharide-peptide PGL was isolated from G. lucidum spores.• PGL protected PC12 nerve cells from the toxicity of corticosterone.• PGL upregulated BDNF expression and influenced key factors in the prefrontal cortex.

Neuroprotective Potential of Chrysin: Mechanistic Insights and Therapeutic Potential for Neurological Disorders

Chrysin, a herbal bioactive molecule, exerts a plethora of pharmacological effects, including anti-oxidant, anti-inflammatory, neuroprotective, and anti-cancer. A growing body of evidence has highlighted the emerging role of chrysin in a variety of neurological disorders, including Alzheimer’s and Parkinson’s disease, epilepsy, multiple sclerosis, ischemic stroke, traumatic brain injury, and brain tumors. Based on the results of recent pre-clinical studies and evidence from studies in humans, this review is focused on the molecular mechanisms underlying the neuroprotective effects of chrysin in different neurological diseases. In addition, the potential challenges, and opportunities of chrysin’s inclusion in the neurotherapeutics repertoire are critically discussed.

Musk (Moschus moschiferus) Attenuates Changes in Main Olfactory Bulb of Depressed Mice: Behavioral, Biochemical, and Histopathological Evidence

BACKGROUND

Musk (Moschus moschiferus) has been described to have a significant impact on the central nervous system, as well as anticonvulsion and antidepressant effects. This study was designed to evaluate the efficacy of musk in alleviating alterations induced in olfactory bulb of depressed mice exposed to chronic stress and identify the mechanism behind it.

METHODS

Fifty male albino mice were divided into five groups (n = 10 each): control, musk, chronic unpredictable mild stress (CUMS), fluoxetine-treated, and musk-treated groups were included in this study. Behavioral changes and serum levels of corticosterone and proinflammatory cytokines included tumor necrosis factor α, interleukin 6, and oxidant/antioxidant profile were assessed at the end of the experiment. Main olfactory bulb (MOB) has been processed for histopathological examination. Gene expression of caspase-3, glial fibrillary acidic protein, and Ki67 were assessed in the MOB using quantitative real-time polymerase chain reaction.

RESULTS

The study showed that musk inhalation significantly reduced (p < 0.001) corticosterone level, immobility time, inflammatory cytokines, and oxidative stress markers in CUMS-exposed mice compared to the untreated CUMS group. Musk lessened CUMS-associated neuronal alterations in the MOB and significantly reduced apoptosis and enhanced neural cell proliferation (p < 0.001) comparable to fluoxetine. Musk significantly enhanced the level of antioxidants in the serum and significantly reduced inflammatory cytokines. The anti-inflammatory and antioxidant activity of musk and its constituents seemed to be behind its neuroprotective effect observed in this study.

CONCLUSION

Musk effectively ameliorated the chronic stress-induced behavioral, biochemical, and neuronal structural changes in MOB mostly through its antioxidant and anti-inflammatory effect.

5-HT Receptors and the Development of New Antidepressants

Serotonin modulates several physiological and cognitive pathways throughout the human body that affect emotions, memory, sleep, and thermal regulation. The complex nature of the serotonergic system and interactions with other neurochemical systems indicate that the development of depression may be mediated by various pathomechanisms, the common denominator of which is undoubtedly the disturbed transmission in central 5-HT synapses. Therefore, the deliberate pharmacological modulation of serotonergic transmission in the brain seems to be one of the most appropriate strategies for the search for new antidepressants. As discussed in this review, the serotonergic system offers great potential for the development of new antidepressant therapies based on the combination of SERT inhibition with different pharmacological activity towards the 5-HT system. The aim of this article is to summarize the search for new antidepressants in recent years, focusing primarily on the possibility of benefiting from interactions with various 5-HT receptors in the pharmacotherapy of depression.

Defining Valid Chronic Stress Models for Depression With Female Rodents

Women are twice as likely to experience depression than men, yet until recently, preclinical studies in rodents have focused almost exclusively on males. As interest in sex differences and sex-specific mechanisms of stress susceptibility increases, chronic stress models for inducing depression-relevant behavioral and physiological changes in male rodents are being applied to females, and several new models have emerged to include both males and females, yet not all models have been systematically validated in females. An increasing number of researchers seek to include female rodents in their experimental designs, asking the question "what is the ideal chronic stress model for depression in females?" We review criteria for assessing female model validity in light of key research questions and the fundamental distinction between studying sex differences and studying both sexes. In overviewing current models, we explore challenges inherent to establishing an ideal female chronic stress model, with particular emphasis on the need for standardization and adoption of validated behavioral tests sensitive to stress effects in females. Taken together, these considerations will empower female chronic stress models to provide a better understanding of stress susceptibility and allow the development of efficient sex-specific treatments.

The selective 5-HT1A receptor biased agonists, F15599 and F13714, show antidepressant-like properties after a single administration in the mouse model of unpredictable chronic mild stress

RATIONALE

The prevalence of depression is ever-increasing throughout the population. However, available treatments are ineffective in around one-third of patients and there is a need for more effective and safer drugs.

OBJECTIVES

The antidepressant-like and procognitive effects of the "biased agonists" F15599 (also known as NLX-101) which preferentially targets postsynaptic 5-HT1A receptors and F13714, which targets 5-HT1A autoreceptors, were investigated in mice.

METHODS

Antidepressant-like properties of the compounds and their effect on cognitive functions were assessed using the forced swim test (FST) and the novel object recognition (NOR), respectively. Next, we induced a depressive-like state by an unpredictable chronic mild stress (UCMS) procedure to test the compounds' activity in the depression model, followed by measures of sucrose preference, FST, and locomotor activity. Levels of phosphorylated cyclic AMP response element-binding protein (p-CREB) and phosphorylated extracellular signal-regulated kinase (p-ERK1/2) were also determined.

RESULTS

F15599 reduced immobility time in the FST over a wider dose-range (2 to 16 mg/kg po) than F13714 (2 and 4 mg/kg po), suggesting accentuated antidepressant-like properties in mice. F15599 did not disrupt long-term memory consolidation in the NOR at any dose tested, while F13714 impaired memory formation, notably at higher doses (4-16 mg/kg). In UCMS mice, a single administration of F15599 and F13714 was sufficient to robustly normalize depressive-like behavior in the FST but did not rescue disrupted sucrose preference. Both F15599 and F13714 rescued cortical and hippocampal deficits in p-ERK1/2 levels of UCMS mice but did not influence the p-CREB levels.

CONCLUSIONS

Our studies showed that 5-HT1A receptor biased agonists such as F13714 and especially F15599, due to its less pronounced side effects, might have potential as fast-acting antidepressants.

An updated review on the versatile role of chrysin in neurological diseases: Chemistry, pharmacology, and drug delivery approaches

Neurological diseases are responsible for a large number of morbidities and mortalities in the world. Flavonoids are phytochemicals that possess various health-promoting impacts. Chrysin, a natural flavonoid isolated from diverse fruits, vegetables, and even mushrooms, has several pharmacological activities comprising antioxidant, anti-inflammatory, antiapoptotic, anticancer, and neuroprotective effects. The current study was designed to review the relationship between chrysin administration and neurological complications by discussing the feasible mechanism and signaling pathways. Herein, we mentioned the sources, pharmacological properties, chemistry, and drug delivery systems associated with chrysin pharmacotherapy. The role of chrysin was discussed in depression, anxiety, neuroinflammation, Alzheimer's disease, Parkinson's disease, Huntington's disease, epilepsy, cerebral ischemia, spinal cord injury, neuropathy, Multiple Sclerosis, and Guillain-Barré Syndrome. The findings indicate that chrysin has protective effects against neurological conditions by modulating oxidative stress, inflammation, and apoptosis in animal models. However, more studies should be done to clear the neuroprotective effects of chrysin.

Hydroalcoholic extract from Abelmoschus manihot (Linn.) Medicus flower reverses sleep deprivation-evoked learning and memory deficit

Previous researches have indicated that sleep plays a vital role in cognitive functions. Sleep deprivation (SD) causes learning and memory damage, which is associated with oxidative stress. This study was performed to investigate the neuroprotective effects of an extract of Abelmoschus manihot flower (EAM) against memory deficit induced by SD in mice. The SD model was evoked by multiple platform method for 5 days, successively. The learning and memory-improving effects of EAM were assessed by behavioral trials and the underlying mechanism was investigated by measuring the oxidative stress alteration. Our findings indicated that the SD-induced memory deficit and the EAM treatment improved the cognitive functions of mice in the object location recognition test and passive avoidance task. In addition, EAM effectively improved the activities of the antioxidant enzyme, decreased the content of malondialdehyde (MDA), and restored the protein expression of the brain-derived neurotrophic factor (BDNF), tyrosine kinase B (TrkB) and glutamate receptor 1 (GluR1) in brain tissues. In conclusion, EAM could improve the SD-evoked learning and memory impairments. The possible underlying mechanisms of EAM may be related to its antioxidant capacity and enhanced BDNF/TrkB/GluR1 levels in the hippocampal memory.

Therapeutic effects of saffron extract on different memory types, anxiety, and hippocampal BDNF and TNF-α gene expressions in sub-chronically stressed rats

Objective: While stress reportedly impairs memory, saffron enhances it. This study investigated the therapeutic effects of saffron extract on different memory types, anxiety-like behavior, and expressions of BDNF and TNF-α genes in sub-chronically stressed rats.Methods: Rats were randomly assigned to control, restraint stress (6 h/day/7 days), two 7-days saffron treatments with 30 and 60 mg/kg, and two stress-saffron groups (30 and 60 mg/kg/7 post-stress days). Serum cortisol level and hippocampal BDNF and TNF-α gene expressions were measured. Open field, passive avoidance, novel object recognition, and object location tests were performed to assess anxiety-like behavior and avoidance as well as cognitive and spatial memories, respectively.Results: The low saffron dose in the sub-chronic stressed group led to a significant increase in passive avoidance latency from day 3 onward whereas this effect was observed after 7 days under the high-dose treatment that simultaneously led to a significant decline in serum cortisol level. While the low saffron dose led to a sharp drop in hippocampal TNF-α gene expression, the high dose significantly increased the hippocampal BDNF gene expression in the sub-chronic stress group. Finally, both saffron doses reduced anxiety in the stressed groups.Conclusion: Compared to the low saffron dose, the high dose had a latent but long-lasting impact. Cognitive and spatial memories remained unaffected by either stress or saffron treatment. In addition, only the high saffron dose reversed anxiety in the sub-chronically stressed group. These findings suggest that various doses of saffron act differently on different brain functions under sub-chronic stress conditions.Abbreviations: Brain derived neurotrophic factor (BDNF), tumor necrosis factor-α (TNF-α), hypothalamic-pituitary-adrenal axis (HPA), novel object recognition task (NORT), novel object location task (NOLT), open field test (OFT), passive avoidance (PA).

Nerve Growth Factor, Stress and Diseases

Stress is a constant threat for homeostasis and is represented by different extrinsic and intrinsic stimuli (stressors, Hans Selye's "noxious agents"), such as aggressive behavior, fear, diseases, physical activity, drugs, surgical injury, and environmental and physiological changes. Our organisms respond to stress by activating the adaptive stress system to activate compensatory responses for restoring homeostasis. Nerve Growth Factor (NGF) was discovered as a signaling molecule involved in survival, protection, differentiation, and proliferation of sympathetic and peripheral sensory neurons. NGF mediates stress with an important role in translating environmental stimuli into physiological and pathological feedbacks since NGF levels undergo important variations after exposure to stressful events. Psychological stress, lifestyle stress, and oxidative stress are well known to increase the risk of mental disorders such as schizophrenia, major depressive disorders, bipolar disorder, alcohol use disorders and metabolic disorders such as metabolic syndrome. This review reports recent works describing the activity of NGF in mental and metabolic disorders related to stress.

Natural Compounds as Medical Strategies in the Prevention and Treatment of Psychiatric Disorders Seen in Neurological Diseases

Psychiatric disorders are frequently encountered in many neurological disorders, such as Alzheimer’s and Parkinson diseases along with epilepsy, migraine, essential tremors, and stroke. The most common comorbid diagnoses in neurological diseases are depression and anxiety disorders along with cognitive impairment. Whether the underlying reason is due to common neurochemical mechanisms or loss of previous functioning level, comorbidities are often overlooked. Various treatment options are available, such as pharmacological treatments, cognitive-behavioral therapy, somatic interventions, or electroconvulsive therapy. However oral antidepressant therapy may have some disadvantages, such as interaction with other medications, low tolerability due to side effects, and low efficiency. Natural compounds of plant origin are extensively researched to find a better and safer alternative treatment. Experimental studies have shown that phytochemicals such as alkaloids, terpenes, flavonoids, phenolic acids as well as lipids have significant potential in in vitro and in vivo models of psychiatric disorders. In this review, various efficacy of natural products in in vitro and in vivo studies on neuroprotective and their roles in psychiatric disorders are examined and their neuro-therapeutic potentials are shed light.

Cardiac glycosaminoglycans and structural alterations during chronic stress-induced depression-like behavior in mice

Major depressive disorder (MDD) is an independent risk factor for cardiovascular disease (CVD) and its complications; however, causal mechanisms remain unclear. In the present study, we investigate cardiac structural and functional alterations and associated changes in myocardial glycosaminoglycans (GAGs) disaccharide profile in mice that exhibit depression-like behavior. Mice were assigned to the chronic mild stress (CMS) group and nonstress control group (CT). The CMS group was exposed to a series of mild, unpredictable stressors for 7 wk. Mice in the CMS group show a significant decrease in protein expression of hippocampal brain-derived neurotrophic factor (BDNF) and exhibit depression-like behavioral changes, such as learned helplessness and decreased exploration behavior, as compared with the control group. Although cardiac function remained unchanged between the groups, echocardiography analysis showed slightly increased left ventricular wall thickness in the CMS group. Furthermore, the CMS group shows an increase in cardiomyocyte cross-sectional area and an associated decrease in BDNF protein expression and increase in IL-6 mRNA expression, when compared with control mice. GAG disaccharide analysis of the left ventricles of the CMS and CT mice revealed an elevation in heparan (HS) and chondroitin sulfate (CS) content in the CMS hearts (35.3% and 17.9%, respectively, vs. control group). Furthermore, we also observed that unsulfated or monosulfated disaccharides were the most abundant units; however, we did not find any significant difference in mole percent or sulfation pattern of HS/CS disaccharides between the groups. The current investigation highlights a need for further research to explore the relationship between cardiac GAGs biology and myocardial remodeling as a causal mechanism that underlie cardiovascular complications in patients with MDD.NEW & NOTEWORTHY Comorbidity between depression and CVD is well established, whereas its etiology, especially the role of nonfibrous components (proteoglycans/GAGs) of the extracellular matrix, is unexplored. To the best of our knowledge, this is the first study to characterize cardiac proteoglycan/glycosaminoglycan profile in response to depression-like behavioral changes in mice. We observed that chronic mild stress (CMS)-induced depression-like behavior and alterations in glycosaminoglycan profile were associated with structural changes in the heart.

Anti-Inflammatory and Anti-Hyperuricemic Effects of Chrysin on a High Fructose Corn Syrup-Induced Hyperuricemia Rat Model via the Amelioration of Urate Transporters and Inhibition of NLRP3 Inflammasome Signaling Pathway

Hyperuricemia is the main cause of gout and involved in the occurrence of many other diseases such as hyperlipidemia and hypertension correlated with metabolic disorders. Chrysin is a flavonoid compound found naturally in honey, propolis, and mushrooms and has anti-inflammatory and antioxidant effects. However, its mechanism of action is not clear yet. This study investigated the mechanism of chrysin’s anti-hyperuricemic effect in hyperuricemia-induced rats fed with high-fructose corn syrup. Orally administrated chrysin for 28 consecutive days effectively decreased uric acid by inhibiting the activity of xanthine oxidase (XO) in the liver. Moreover, chrysin markedly downregulated the protein expression of uric acid transporter 1 (URAT1) and glucose transporter type 9 (GLUT9) and upregulated the protein expression of organic anion transporter 1 (OAT1) and human ATP-binding cassette subfamily G-2 (ABCG2). In addition, chrysin showed prominent anti-oxidative and inflammatory effects as the malondialdehyde (MDA) and interleukin 1 beta (IL-1β) concentration was reduced in both rat kidney and serum, which aligned with the inhibition of NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome signaling pathway activation. Collectively, our results strongly suggest that chrysin exhibits potent anti-hyperuricemic and anti-inflammatory effects that may yield new adjuvant treatments for gout.

Nootkatone improves anxiety- and depression-like behavior by targeting hyperammonemia-induced oxidative stress in D-galactosamine model of liver injury

Acute or chronic liver injury is closely related to hyperammonemia, which will result in oxidative stress and damage to nerve cells, and these factors are vital to the development of anxiety and depression. In this study, the effect of Nootkatone (NKT) on the anxiety- and depression-like behavioral changes in mice induced by liver injury was investigated. Liver injury was induced by D-galactosamine (D-GalN; 350 mg/kg) three times a week for 4 weeks. NKT (5 mg/kg or 10 mg/kg) was given as co-treatment daily for 4 weeks. NKT (5 mg/kg) co-treatment remarkably ameliorates D-GalN-induced anxiety- and depression-like behaviors as evident from the results of sucrose preference test, forced swimming test, tail suspension test, and novelty suppressed feeding test. Results showed that NKT could induce an elevation in serum alanine transaminase and aspartate transaminase level, alleviate the oxidative stress induced by hyperammonemia through activating Keap1/Nrf2/HO-1 antioxidant pathways, decrease the expression of inducible nitric oxide synthase and NOX2 in hippocampus and prefrontal cortex, enhance the vitality of superoxide dismutase, catalase, and glutathione levels in serum, liver, and brain, and significantly reduce the generation of malondialdehyde. At the same time, NKT also reduces the level of ammonia in serum and brain and upgrades the activity of glutamine synthetase in the hippocampus and prefrontal cortex. Taken together, the present results suggested that NKT has a significant antidepressant effect through modulation of oxidative stress induced by D-GalN administration.

Expression of Selected Genes Involved in Neurogenesis in the Etiopathogenesis of Depressive Disorders

(1) Background: The neurogenic theory suggests that impaired neurogenesis within the dentate gyrus of the hippocampus is one of the factors causing depression. Immunology also has an impact on neurotrophic factors. The aim of the study was to assess the importance of selected genes involved in the process of neurogenesis i.e., nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial-derived neurotrophic factor (GDNF) and neuron-restrictive silencer factor (REST gene) in the etiopathogenesis of depressive disorders. (2) Methods: A total of 189 subjects took part in the study (95 depressed patients, 94 healthy controls). Sociodemographic data were collected. The severity of depressive symptoms was assessed using the Hamilton Depression Rating Scale (HDRS). RT-PCR was used to assess gene expression at the mRNA levels, while Enzyme-Linked Immunosorbent Assay (ELISA) was used to assess gene expression at the protein level. (3) Results: Expression of NGF, BDNF, REST genes is lower in depressed patients than in the control group, whereas the expression of GDNF gene is higher in patients with depressive disorders than in the group of healthy volunteers. (4) Conclusions: The expression of selected genes might serve as a biomarker of depression.

Relaxation Response in Stressed Volunteers: Psychometric Tests and Neurotrophin Changes in Biological Fluids

Background: To evaluate the beneficial effects of relaxation response (RR) training in adult stressed subjects by evaluating the psychometric response recorded at relaxation session. Cortisol as well as nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) mediators were quantified in both saliva and tears, and their levels were related to each other and to the psychometric response. Methods: Stressed subjects (n = 23; 10M/13F; age range 21-53 years old) were voluntarily enrolled in the study. RR training sessions were carried out for 2 months, 1 day per week, at the same time (3-5 p.m.). Two different psychological questionnaires, the Perceived Stress Scale-10 (PSS-10) and the Beck Depression Inventory - Short Form (BDI-SF) and Ocular Surface Disease Index (OSDI) tests, were administered before each session. Saliva and tears were sampled for cortisol (EIA), NGF (ELISA), and BDNF (ELISA) quantifications. Questionnaires' data were analyzed and compared to biochemical ones. Results: All subjects reported beneficial effects from training. RR significantly reduced the psychological stress indexes (p = 0.039 for PSS-10 and p = 0.001 for BDI-SF). Specifically, RR training lowered the perception of Perceived Helplessness (items 1, 3, 10; p < 0.05) in PSS-10 and increased the Perceived Self-Efficacy (p < 0.05). OSDI score was in the normal range (0-25). Biochemically, a decrease in cortisol, a trend to a decrease in NGF, and an increase in BDNF levels were observed in saliva samples after RR treatment. Furthermore, a trend to a decrease in NGF and an increase in BDNF were quantified in tear samples. A correlation between PSS-10 total score and saliva NGF variation (%) as well as between BDI-SF total score and BDNF tear levels were also observed. Conclusion: RR training appeared useful to lowering psychological, mental, and physical stress, as supported by both psychological total and single scores. The finding on biochemical levels of BDNF in saliva and tears are sustained by previous studies while those of NGF require further investigation. Overall, these data on a small population highlight the potential use of RR training and potential neurotrophic changes in biological fluids, in stressed volunteers.

A Load to Find Clinically Useful Biomarkers for Depression

Depression is heterogeneous and complex disease with diverse symptoms. Its neurobiological underpinning is still not completely understood. For now, there are still no validated, easy obtainable, clinically useful noninvasive biomarker(s) or biomarker panel that will be able to confirm a diagnosis of depression, its subtypes and improve diagnostic procedures. Future multimodal preclinical and clinical research that involves (epi)genetic, molecular, cellular, imaging, and other studies is necessary to advance our understanding of the role of monoamines, GABA, HPA axis, neurotrophins, metabolome, and glycome in the pathogenesis of depression and their potential as diagnostic, prognostic, and treatment response biomarkers. These studies should be focused to include the first-episode depression and antidepressant drug-naïve patients with large sample sizes to reduce variability in different biological and clinical parameters. At present, metabolomics study revealed with high precision that a neurometabolite panel consisting of plasma metabolite biomarkers (GABA, dopamine, tyramine, kynurenine) might represent clinically useful biomarkers of MDD.

Ganoderic Acid A-Mediated Modulation of Microglial Polarization is Involved in Depressive-Like Behaviors and Neuroinflammation in a Rat Model of Post-Stroke Depression

BACKGROUND

Post-stroke depression (PSD) is a common complication after stroke. Ganoderic acid A (GAA), one of the main bioactive Ganoderma triterpenoids, exerts preventive and therapeutic effects in many diseases. However, the function of GAA in PSD has not been well studied.

METHODS

PSD model was established via stimulating rats with chronic unpredictable mild stress stimulations (CUMS) after middle cerebral artery occlusion (MCAO). Rats were treated with GAA before CUMS. Depressive-like behaviors were investigated by body weight alteration, open field test (OFT), and sucrose preference test (SPT). Neuronal damage was evaluated by hematoxylin and eosin (HE) staining and Western blotting. Inflammation was detected by enzyme-linked immunosorbent assay (ELISA) and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). Microglial polarization was analyzed via qRT-PCR and Western blotting. The extracellular signal-regulated kinase (ERK)/cAMP-response element-binding protein (CREB) pathway was analyzed by Western blotting, and inactivated by the inhibitor PD98059 (PD).

RESULTS

GAA attenuated PSD-induced depressive-like behaviors in rats. GAA mitigated PSD-induced neuronal damage and reduced BDNF and NGF levels in the cerebral hippocampus. GAA weakened PSD-induced inflammatory response in the cerebral hippocampus. GAA prevented pro-inflammatory (M1) polarization and promoted anti-inflammatory (M2) polarization, as indicated by decreased iNOS and CD86 levels and increased Arg-1 and CD206 levels. GAA restored the PSD-induced inactivation of the ERK/CREB pathway. GAA regulated M1/M2 microglial polarization by activating the ERK/CREB pathway.

CONCLUSION

GAA alleviated the depressive-like behaviors and brain inflammation in PSD rats, indicating its potential for PSD therapy.

Evaluation of the Effect of Hypericum triquetrifolium Turra on Memory Impairment Induced by Chronic Psychosocial Stress in Rats: Role of BDNF

BACKGROUND

Chronic psychosocial stress impairs memory function and leads to a depression-like phenotype induced by a persistent status of oxidative stress. Hypericum perforatum L. (St. John's wort) is widely used to relieve symptoms of anxiety and depression; however, its long-term use is associated with adverse effects. Hypericum triquetrifolium Turra is closely related to H. perforatum. Both plants belong to Hypericaceae family and share many biologically active compounds. Previous work by our group showed that methanolic extracts of H. triquetrifolium have potent antioxidant activity as well as high hypericin content, a component that proved to have stress-relieving and antidepressant effects by other studies. Therefore, we hypothesized that H. triquetrifolium would reduce stress-induced cognitive impairment in a rat model of chronic stress.

OBJECTIVE

To determine whether chronic treatment with H. triquetrifolium protects against stress-associated memory deficits and to investigate a possible mechanism.

METHODS

The radial arm water maze (RAWM) was used to test learning and memory in rats exposed to daily stress using the resident-intruder paradigm. Stressed and unstressed rats received chronic H. triquetrifolium or vehicle. We also measured levels of brain-derived neurotrophic factor (BDNF) in the hippocampus, cortex and cerebellum.

RESULTS

Neither chronic stress nor chronic H. triquetrifolium administration affected performance during acquisition. However, memory tests in the RAWM showed that chronic stress impaired different post-encoding memory stages. H. triquetrifolium prevented this impairment. Furthermore, hippocampal BDNF levels were markedly lower in stressed animals than in unstressed animals, and chronic administration of H triquetrifolium chronic administration protected against this reduction. No significant difference was observed in the effects of chronic stress and/or H. triquetrifolium treatment on BDNF levels in the cerebellum and cortex.

CONCLUSION

H. triquetrifolium extract can oppose stress-associated hippocampus-dependent memory deficits in a mechanism that may involve BDNF in the hippocampus.

Involvement of kynurenine pathway in depressive-like behaviour induced by nandrolone decanoate in mice

Nandrolone decanoate (ND) belongs to the class II of anabolic-androgenic steroids (AAS), which is composed of 19-nor-testosterone-derivatives. AAS represent a group of synthetic testosterone that is used in clinical treatment. However, these drugs are widely abused among individuals as a means of promoting muscle growth or enhancing athletic performance. AAS in general and ND in particular have been associated with several behavioral disturbances, such as anxiety, aggressiveness and depression. A factor that contributes to the development of depression is the brain activation of indoleamine 2,3-dioxygenase (IDO), the rate-limiting enzyme of kynurenine pathway (KP). In the present study, we examined the involvement of KP in depressive phenotype induced by a ND treatment (10 mg/kg/day/s.c., for 28 days) that mimics human abuse system (e.g. supraphysiological doses) in C57B/6J mice. Our results showed that ND caused depressive like-behavior in the tail suspension test and anhedonic-like state measured in the sucrose preference test. ND administration decreased the levels of brain-derived neurotrophic factor and neurotrophin-3 and reduced Na⁺,K⁺-ATPase activity in the hippocampus, striatum and prefrontal cortex. We also found that ND elicited KP activation, as reflected by the increase of IDO activity and kynurenine levels in these brain regions. Moreover, ND decreased serotonin levels and increased 5-hydroxyindoleacetic acid levels in the brain. Treatment with IDO inhibitor 1-methyl-dl-trypthophan (1 mg/kg/i.p.) reversed the behavioral and neurochemical alterations induced by ND. These results indicate for the first time that KP plays a key role in depressive-like behavior and neurotoxicity induced by supraphysiologicaldoses of ND in mice.

Is neurotrophin-3 (NT-3): a potential therapeutic target for depression and anxiety?

Introduction: Neurotrophin-3 (NT-3) is thought to play a role in the neurobiological processes implicated in mood and anxiety disorders. NT-3 is a potential pharmacological target for mood disorders because of its effects on monoamine neurotransmitters, regulation of synaptic plasticity and neurogenesis, brain-derived neurotrophic factor (BDNF) signaling boosting, and modulation of the hypothalamic-pituitary-adrenal (HPA) axis. The mechanisms underlying NT-3 anxiolytic properties are less clear and require further exploration and definition. Areas covered: The evidence that supports NT-3 as a pharmacological target for anxiety and mood disorders is presented and this is followed by a reflection on the quandaries, stumbling blocks, and future perspectives for this novel target. Expert opinion: There is evidence for miRNAs being key post-transcriptional regulators of neurotrophin-3 receptor gene (NTRK3) in anxiety disorders; however, the anxiolytic properties of NT-3 need further examination and delineation. Moreover, NT-3 expression by non-neuronal cells and its role in brain circuits that participate in anxiety and mood disorders require further scrutiny. Further work is vital before progression into clinical trials can be realized.

Unfolding the Role of BDNF as a Biomarker for Treatment of Depression

Depression is a well-known disabling mental illness characterized by sadness, loss of interest in activities, and decreased energy. The symptoms of depression are usually recurrent in vulnerable individuals, and persistence of symptoms significantly impairs individuals' quality of life. The exact pathophysiology of depression remains ambiguous, though many hypotheses have been proposed. Brain-derived neurotrophic factor (BDNF) has recently been reported to play a vital role in the pathophysiology of depression. BDNF is an important neurotrophic factor found in the human brain and is involved in neuronal growth and proliferation, synaptic neurotransmission, and neuroplasticity. The neurotrophic theory of depression proposes that depression results from reduced BDNF levels in the brain, which can be treated with antidepressants to alleviate depressive behavior and increase BDNF levels. The aim of this review is to provide broad insight into the role of BDNF in the pathogenesis of depression and in antidepressant therapy. The studies mentioned in this review article greatly support the role of BDNF in the pathogenesis of depression and treatment of this disorder with antidepressants. Since abnormalities in BDNF levels lead to the production of diverse insults that amplify the development or progression of depression, it is important to study and explore BDNF impairment in relation to depression, neuroplasticity, and neurogenesis, and increasing BDNF levels through antidepressant therapy, showing positive response in the management of depression.

Chaperone Sigma1R and Antidepressant Effect

This review analyzes the current scientific literature on the role of the Sigma1R chaperone in the pathogenesis of depressive disorders and pharmacodynamics of antidepressants. As a result of ligand activation, Sigma1R is capable of intracellular translocation from the endoplasmic reticulum (ER) into the region of nuclear and cellular membranes, where it interacts with resident proteins. This unique property of Sigma1R provides regulation of various receptors, ion channels, enzymes, and transcriptional factors. The current review demonstrates the contribution of the Sigma1R chaperone to the regulation of molecular mechanisms involved in the antidepressant effect.