The Prefrontal Dectin-1/AMPA Receptor Signaling Pathway Mediates The Robust and Prolonged Antidepressant Effect of Proteo-β-Glucan from Maitake

Microglia-Dependent Reversal of Depression-Like Behaviors in Chronically Stressed Mice by Administration of a Specific Immuno-stimulant β-Glucan

In recent years, the decline of microglia in the hippocampus has been shown to play a role in the development of depression, and its reversal shows marked antidepressant-like effects. β-glucan is a polysaccharide from Saccharomyces cerevisiae and has numerous beneficial effects on the nervous system, including improving axon regeneration and cognition. Considering its immuno-stimulatory activities in cultured microglia and brain tissues, we hypothesize that β-glucan may be a potential candidate to correct the functional deficiency of microglia and thereby alleviate depression-like behaviors in chronically stressed animals. An expected, our results showed that a single injection of β-glucan 5 h before behavioral tests at a dose of 10 or 20 mg/kg, but not at a dose of 5 mg/kg, reversed the depression-like behavior induced by chronic stress in mice in the tail suspension test, forced swimming test, and sucrose preference test. The effect of β-glucan (20 mg/kg) also showed time-dependent properties that were statistically significant 5 and 8, but not 3, hours after drug injection and persisted for at least 7 days. Fourteen days after β-glucan injection, no antidepressant-like effect was observed anymore. However, this effect was overcome by a second β-glucan injection (20 mg/kg) 14 days after the first β-glucan injection. Stimulation of microglia appeared to mediate the antidepressant-like effect of β-glucan, because both inhibition of microglia and their depletion prevented the antidepressant-like effect of β-glucan. Based on these effects of β-glucan, β-glucan administration could be developed as a new strategy for the treatment of depression.

The Dectin-1 Receptor Signaling Pathway Mediates the Remyelination Effect of Lentinan through Suppression of Neuroinflammation and Conversion of Microglia

Demyelinating diseases such as multiple sclerosis (MS) are chronic inflammatory autoimmune diseases and involve demyelination and axonal degeneration. Microglia rapidly respond to changes in the environment by altering morphotype and function during the progressive disease stage. Although substantial progress has been made in the drug development for MS, treatment of the progressive forms of the disease remains unsatisfactory. There is great interest in identifying novel agents for treating MS. Lentinus edodes is a traditional food, which can improve physiological function. Lentinan (LNT), a type of polysaccharide extracted from mushroom Lentinus edodes, is an anti-inflammatory and immunomodulatory agent. Here, we studied the remyelination effects of LNT and its therapeutic target in regulating the functions of neuroinflammation. We found that LNT enhanced remyelination and rescued motor deficiency by regulating dectin-1 receptor to inhibit neuroinflammation and microglial cell transformation. LNT promoted the conversion of microglial cells from the M1 status induced by LPS to the M2 status, enhanced the anti-inflammatory markers IL-10 and BDNF, inhibited inflammatory markers TNF-α and IL-1β, and downregulated the microglia activation and oligodendrocyte and astrocyte proliferation by modulating dectin-1. If we injected the dectin-1-specific inhibitor laminarin (Lam), the remyelination effects induced by LNT were completely abolished. Thus, these results suggest that LNT is a novel and potential therapeutic agent that can rescue MS neuroimmune imbalance and remyelination through a dectin-1 receptor-dependent mechanism.

Postsynaptic Proteins at Excitatory Synapses in the Brain—Relationship with Depressive Disorders

Depressive disorders (DDs) are an increasingly common health problem that affects all age groups. DDs pathogenesis is multifactorial. However, it was proven that stress is one of the most important environmental factors contributing to the development of these conditions. In recent years, there has been growing interest in the role of the glutamatergic system in the context of pharmacotherapy of DDs. Thus, it has become increasingly important to explore the functioning of excitatory synapses in pathogenesis and pharmacological treatment of psychiatric disorders (including DDs). This knowledge may lead to the description of new mechanisms of depression and indicate new potential targets for the pharmacotherapy of illness. An excitatory synapse is a highly complex and very dynamic structure, containing a vast number of proteins. This review aimed to discuss in detail the role of the key postsynaptic proteins (e.g., NMDAR, AMPAR, mGluR5, PSD-95, Homer, NOS etc.) in the excitatory synapse and to systematize the knowledge about changes that occur in the clinical course of depression and after antidepressant treatment. In addition, a discussion on the potential use of ligands and/or modulators of postsynaptic proteins at the excitatory synapse has been presented.

Effect of Agaricus blazei Murill on exploratory behavior of mice-model

Increased anxiety and depressive symptoms have reported to be its association with long term illness. Because of having unwanted effects of newly available drugs, patients administering anxiolytic drugs usually discontinue the treatment before they are completely recovered. Therefore, there is a serious need to develop new anxiolytic drugs. The anxiolytic effect of hydro-alcoholic extract of Agaricus blazei in animal models was assessed. 24 male mice (Mus musculus genus) were included in the study. Four groups were prepared and each group contained six animals. The groups were vehicle control, positive control (diazepam 1.0 mg/kg, i.p.) as well as two treatment groups receiving Agaricus blazei hydro-alcoholic extract at a dose of 136.50 mg/kg and 273.0 mg/kg orally. The Marble burying test, Nestlet shredding test and Light and Dark box test used to assess anxiolytic activity. Mice administered with diazepam 1.0 mg/kg, i.p. while hydro-alcoholic extract of AbM (136.50 and 273.0 mg/kg, respectively) was administered via oral route which exhibited marked reduction in number of marbles-burying as compared to vehicle control group. Mice administered with diazepam 1.0 mg/kg, i.p. and Oral administration of hydro-alcoholic extract of AbM (136.50 and 273.0 mg/kg, respectively) exhibited significant decrease in nestlet shredding in comparison to vehicle control group. The oral administration of hydro-alcoholic extract at a dose of 136.5mg/kg and 273mg/kg showed elevation in time spent in light box and was comparable to standard treated group while time spent by mice following oral administration of hydro-alcoholic extract of Agaricus blazei at a dose of 273.0 mg/kg also showed elevation and was found to be more near to standard treated group (diazepam 1 mg/kg, i.p.).

Discovering the Potentials of Medicinal Mushrooms in Combating Depression - A Review

Depression is the most common form of mental illness and the major cause of disability worldwide. Symptoms of depression, including feelings of intense sadness and hopelessness, may occur after a specific event or in response to a gradual decline in health and functional status, often associated with aging. Current therapies for treating these symptoms include antidepressant drugs, counseling and behavioral therapy. However, antidepressant drugs are associated with mild to severe adverse effects, which has prompted the need for better treatment options. Medicinal mushrooms are valuable sources of food and medicine and are increasingly being used as supplements or as alternative medicines in standard healthcare. Numerous studies have provided insights into the neuroprotective effects of medicinal mushrooms, which are attributed to their antioxidant, anti-neuroinflammatory, cholinesterase inhibitory and neuroprotective properties. In this review, we comprehensively examine the role of these medicinal mushrooms in the treatment of depression. However, to apply these natural products in clinical settings, the therapeutic agent needs to be properly evaluated, including the active ingredients, the presence of synergistic effects, efficient extraction methods, and stabilization of the active ingredients for delivery into the body as well as crossing the blood-brain barrier.

Ganoderma lucidum polysaccharides ameliorated depression-like behaviors in the chronic social defeat stress depression model via modulation of Dectin-1 and the innate immune system

Major depressive disorder (MDD) is a prevalent, chronic, and recurrent disease. At least one-third of patients have treatment-resistant depression; therefore, there is an urgent need for novel drug development. Cumulative studies have suggested an inflammatory mechanism for the pathophysiology of MDD. Ganoderma lucidum polysaccharides (GLP) is an anti-inflammatory and immunomodulatory agent. Here, we found that an injection of GLP led to a rapid and robust antidepressant effect after 60 min in the tail suspension test. This antidepressant effect remained after 5 days of treatment with GLP in the forced swim test. Unlike psychostimulants, GLP did not show a hyperactive effect in the open field test. After 60 min or 5 days of treatment, GLP exhibited an antidepressant effect in a chronic social defeat stress (CSDS) depression animal model. Moreover, after 5 days of treatment, GLP attenuated the expression of the proinflammatory cytokines IL-1β and TNF-α, enhanced the expression of the anti-inflammatory cytokine IL-10 and the neurotrophic factor BDNF, and inhibited the activation of microglia and proliferation of astrocytes in the hippocampus of CSDS mice. In addition, after 5 days of treatment, GLP significantly enhanced GluA1 S845 phosphorylation as well as GluA1 and GluA2 expression levels in the hippocampus of CSDS mice. To determine whether the antidepressant effect was mediated by Dectin-1, we found that GLP treatment enhanced Dectin-1 expression in the hippocampus in CSDS mice, and the Dectin-1-specific inhibitor laminarin almost completely blocked the antidepressant effect of GLP. This study identified GLP, an agonist of Dectin-1, as a novel and rapid antidepressant with clinical potential and multiple beneficial mechanisms, particularly in regulating the neuroimmune system and, subsequently, AMPA receptor function.

From bench to bedside - translational approaches in anti-fungal immunology

Invasive fungal infections mainly occur in patients suffering from impaired immunity. Their associated mortality is high despite antifungal treatment. Thus, several efforts have been made to translate our knowledge on protective antifungal immunity into clinical application. Since the first attempts with transfusion of neutrophilic granulocytes, these approaches have become more refined and include administration of cytokines to booster antifungal immune responses or selective stimulation of pattern recognition receptors. Recently, novel tools that have proven effective in the treatment of cancer have offered new options for enhancing antifungal immunity. These approaches include checkpoint inhibitors as well as T-cell based therapies, including chimeric antigen receptor T-cells.

C-Type Lectins in Veterinary Species: Recent Advancements and Applications

C-type lectins (CTLs), a superfamily of glycan-binding receptors, play a pivotal role in the host defense against pathogens and the maintenance of immune homeostasis of higher animals and humans. CTLs in innate immunity serve as pattern recognition receptors and often bind to glycan structures in damage- and pathogen-associated molecular patterns. While CTLs are found throughout the whole animal kingdom, their ligand specificities and downstream signaling have mainly been studied in humans and in model organisms such as mice. In this review, recent advancements in CTL research in veterinary species as well as potential applications of CTL targeting in veterinary medicine are outlined.

A Maitake (Grifola frondosa) polysaccharide ameliorates Alzheimer's disease-like pathology and cognitive impairments by enhancing microglial amyloid-β clearance

Alzheimer's disease (AD) is characterized by the deposition of amyloid-β (Aβ) plaques, neuronal loss and neurofibrillary tangles. In addition, neuroinflammatory processes are thought to contribute to AD pathophysiology. Maitake (Grifola frondosa), an edible/medicinal mushroom, exhibits high nutritional value and contains a great amount of health-beneficial, bioactive compounds. It has been reported that proteo-β-glucan, a polysaccharide derived from Maitake (PGM), possesses strong immunomodulatory activities. However, whether PGM is responsible for the immunomodulatory and neuroprotection effects on APPswe/PS1ΔE9 (APP/PS1) transgenic mice, a widely used animal model of AD, remains unclear. In the present study, the results demonstrated that PGM could improve learning and memory impairment, attenuate neuron loss and histopathological abnormalities in APP/PS1 mice. In addition, PGM treatment could activate microglia and astrocytes and promote microglial recruitment to the Aβ plaques. Also, PGM could enhance Aβ phagocytosis, and thereby alleviate Aβ burden and the pathological changes in the cortex and hippocampus in APP/PS1 mice. Moreover, PGM showed no significant effect on mice body weight. In conclusion, these findings indicated that administration of PGM could improve memory impairment via immunomodulatory action, and dietary supplementation with PGM may provide potential benefits on brain aging related memory dysfunction.

Griflola frondosa (GF) produces significant antidepressant effects involving AMPA receptor activation in mice

CONTEXT

Griflola frondosa (Fr) S.F. Gray (Meripilaceae) (GF) is a medical mushroom, and its regulation of the immune system is of interest for the treatment of mood disorders. α-Amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors are the central mediator for the treatment of depression.

OBJECTIVE

This study examines the antidepressant effects of GF and the role of AMPA in these antidepressant effects.

MATERIALS AND METHODS

The CD-1 mice were fed with GF- or Pleurotus ostreatus [(Jacq.: Fr) Kumm (Pleurotaceae)] (PO)-containing food for 1 day or 5 days. The antidepressant effects was determined in the tail suspension test (TST), forced swim test (FST), and open field test (OFT). The involvement of AMPA receptors was determined by the application of the AMPA-specific blocker GYKI 52466.

RESULTS

Treatments with 20%, 33% or 50% of GF-containing food significantly decreased the immobility time (63.6, 56.9, and 52.0% in TST; and 50.8, 43.2, and 38.2% in FST) after 1 day and (62.3, 51.8, and 52.8% in TST; and 49.5, 45.1, and 40.3% in FST) after 5 days. GF-containing food did not cause hyperactive effects in the OFT. The antidepressant effects of the 33% of GF-containing food (down-to 51.3% in 1-day TST and 46.8% in 5-day FST) were significantly stronger than that of the 33% of PO-containing food (down-to 85.5% in 1-day TST and 82.0% in 5-day FST). AMPA-specific blocker GYKI 52466 was able to block the antidepressant effects of the GF-containing food.

CONCLUSION

GF demonstrated the potential as a safe medical food supplement for the patient with depression.

Lentinan produces a robust antidepressant-like effect via enhancing the prefrontal Dectin-1/AMPA receptor signaling pathway

Lentinan (LNT) is an immune regulator and its potential and mechanism for the treatment of mood disorder is of our interest. Dectin-1 is a β-glucan (including LNT) receptor that regulates immune functions in many immune cell types. Cumulative evidence has suggested that the glutamatergic system seems to play an important role in the treatment of depression. Here, we studied the antidepressant-like effects of LNT and its therapeutical target in regulating the functions of AMPA receptors. We found that 60min treatment with LNT leads to a significant antidepressant-like effect in the tail suspension test (TST) and the forced swim test (FST) in mice. The antidepressant-like effects of LNT in TST and FST remained after 1day or 5days of injections. Additionally, LNT did not show a hyperactive effect in the open field test. Dectin-1 receptor levels were increased after LNT treatment for 5days and the specific Dectin-1 inhibitor laminarin was able to block the antidepressant-like effects of LNT. After 5days of treatment, LNT enhanced p-GluR1 (S845) in the prefrontal cortex (PFC); however, the total GluR1, GluR2, and GluR3 expression levels remained unchanged. We also found that the AMPA-specific blocker GYKI 52466 was able to block the antidepressant-like effects of LNT. This study identified LNT as a novel antidepressant with clinical potential and a new antidepressant mechanism for regulating prefrontal Dectin-1/AMPA receptor signaling.