Glucocorticoid-Driven NLRP3 Inflammasome Activation in Hippocampal Microglia Mediates Chronic Stress-Induced Depressive-Like Behaviors

Probiotic Bactolac alleviates depression-like behaviors by modulating BDNF, NLRP3 and MC4R levels, reducing neuroinflammation and promoting neural repair in rat model

Depression, a prevalent psychiatric disorder, exerts severe and debilitating impacts on an individual's mental and physical well-being, and it is considered a chronic mental illness. Chronic stress plays an important role in the pathophysiology of depression. Lactobacillus plantarum and Streptococcus thermophilus are psychobiotic bacteria and synthesize some neurotransmitters that play a role in the pathogenesis of depression. In this study, we aimed to investigate the therapeutic effects of Bactolac (Lactobacillus plantarum NBIMCC 8767  + Streptococcus thermophilus NBIMCC 8258) on chronic stress-induced depression in rats. Behavioral tests, including the sucrose preference test, elevated plus maze test, forced swim test, and three-chamber sociability test, were employed to assess depressive and anxiety-like behaviors. The expression level of the 5-HT1A, DRD1, ADRA-2A, GABA-A α1, CNR1, NR3C2, NOD1, NLRP3 and MC4R; BDNF levels, glial activity and intestinal permeability were determined in chronic stress-induced depression in rats. In conclusions, chronic stress decreased the expression levels of 5-HT1A, DRD1, ADRA-2A, GABA-A α1, CNR1, NR3C2, NOD1 and BDNF level; increased the expression levels of NLRP3 and MC4R, caused neurodegeneration and glial activity, ultimately led to depressive effects. Bactolac was effective in reducing depressive-like behaviors according to the results of behavioral tests. Bactolac treatment provided high neuronal survival rate increasing BDNF level, prevented the excessive release of pro-inflammatory cytokines by reducing the expression levels of NLRP3 and MC4R, therefore, prevented the excessive activation of the hypothalamus-pituitary-adrenal (HPA) axis and accordingly, reduced neurodegeneration and glial cell activation in depressed rats. We can suggest that Bactolac supplementation may be beneficial in coping with stress, alleviate the effects of chronic stress and help to protect mental health.

Zhizichi decoction alleviates depressive-like behaviors through modulating mitochondria-associated membrane via the IP3R3-GRP75-VDAC1 complex

ETHNOPHARMACOLOGICAL RELEVANCE

Zhizichi Decoction (ZZCD), a traditional Chinese medicine (TCM), is derived from the combination of Gardenia jasminoides J. Ellis [Rubiaceae] and Semen Sojae Praeparatum, a fermented derivative of Glycine max (L.) Merr. [Leguminosae]. ZZCD has demonstrated anti-inflammatory properties and the potential to promote neural plasticity. Neuroinflammation is believed to contribute to the development of depressive symptoms.

AIM OF THE STUDY

This study investigates the potential antidepressant effects of ZZCD, focusing on its role in regulating neuroinflammatory responses and mitochondria-associated membrane (MAM) structure.

MATERIALS AND METHODS

Using high-performance liquid chromatography (HPLC), we identified five active ingredients in ZZCD. We then evaluated its effect in a chronic social defeat stress (CSDS) mouse model. A combination of Network pharmacology analysis, Western-blot, immunostaining, enzyme-linked immunosorbent assay (ELISA), co-immunoprecipitation (CO-IP), mitochondrial transmembrane potential (ΔΨm), and transmission electron microscopy (TEM) was adopted to elucidate the mechanisms by which ZZCD improves MAM structure, inhibits neuroinflammation, and exerts antidepressant effects. Finally, according to the molecular docking results, a GRP75 overexpression viral vector was constructed to manipulate the MAM-related protein GRP75, further validating the mechanism of ZZCD's antidepressant effect.

RESULTS

ZZCD treatment significantly ameliorated depressive-like behaviors induced by CSDS in mice and reversed adverse changes in endoplasmic reticulum (ER) stress, MAM structure, and mitochondria injury. In addition, ZZCD effectively reduced microglial inflammatory activation and suppressed the increased expression of pro-inflammatory cytokines. Finally, the antidepressant effects of ZZCD were primarily mediated through the IP3R3-GRP75-VDAC1 complex, as demonstrated by the overexpression of the GRP75 protein.

CONCLUSION

In summary, ZZCD exerts antidepressant effects in the CSDS model by improving the MAM structure, alleviating neuroinflammation, and enhancing mitochondrial function.

Novel insights into dietary bioactive compounds and major depressive disorders: evidence from animal studies and future perspectives

Clinical depression, including major depressive disorder (MDD), is a chronic mental illness characterized by persistent sadness and indifference. Depression is associated with neuroinflammation, oxidative stress, and neuronal apoptosis in the brain, resulting in microglial overactivation, decreased neuronal and glial proliferation, monoamine depletion, structural abnormalities, and aberrant biochemical activity via the hypothalamic-pituitary-adrenal axis. Recent studies have exhibited the role of dietary bioactive compounds in the mitigation of MDD progression. Here, in this narrative review, we reported the effects of commonly consumed bioactive compounds (curcumin, saffron, garlic, resveratrol, omega-3 fatty acids, ginger, blueberry, tea, and creatine) on MDD and MDD-related neuroinflammation and oxidative stress. The evidence reviewed here is almost exclusively from animal studies and strongly suggest that these commonly consumed bioactive compounds have anti-MDD effects as shown in anti-depression-like behaviors, such as increased immobility, sucrose preference, and social interaction. Based on the literature/studies reviewed, the proposed molecular mechanisms include (i) the reduction of neuroinflammation activation and oxidative stress, (ii) the enhancement of anti-inflammatory and anti-oxidant properties, (iii) the reduction of monoamine oxidase-A production, and (iv) the elevation of brain-derived neurotropic factor and neurogenesis. In the future, dietary bioactive compounds on clinical randomized controlled trials are warranted to confirm the findings of preclinical efficacies using bioactive compounds in individuals with MDD.

In situ dual-activated NIRF/PA carrier-free nanoprobe for diagnosis and treatment of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease threatening the life of millions people worldwide. Oxidative stress, mitochondrial dysfunction, and neuroinflammation are the pivotal causative elements of PD. Precise diagnosis enables timely monitoring initiation and progression of PD, thereby facilitating the formulation of customized and targeted treatment strategies. Optical imaging offers one alternative way for PD diagnosis. However, available diagnostic probes suffer from the inability to bypass the blood brain barrier (BBB). To accurately diagnose and effectively combat PD, there is an urgent need to develop an integrated diagnostic and therapeutic nanoprobe that can bypass the BBB and target the factors underlying degeneration of dopaminergic (DA) neurons. In present study, one integrated carrier-free nanoprobe HVCur-NPs towards those factors was designed and constructed. By modifying probe side chain with polypeptide, RVG29, we obtained brain-targeting HV-PEG-RVG29. It not only enables BBB penetration, but also produces near-infrared fluorescence (NIRF) and photoacoustic (PA) signals in cascade response to H2O2 and viscosity. The release of loaded curcumin (CUR) prevents oxidative stress, neuroinflammation and restore mitochondrial function so as to rescue PD phenotypes. In cellular PD model, HVCur-NPs generated NIRF/PA signals in response to elevated ROS and viscosity, and ameliorated cell apoptosis by eliminating ROS and restoring mitochondria function. Moreover, in mice PD model, HVCur-NPs realized in situ NIRF/PA imaging brain, and rescued DA neuron loss and restored the behavioral deficit of PD mice, without detectable biotoxicity. This carrier-free nanoprobe opens venues for integrated diagnosis and treatment of neurodegenerative diseases.

Microglia Sing the Prelude of Neuroinflammation-Associated Depression

Major depressive disorder (MDD) is a psychiatric condition characterized by sadness and anhedonia and is closely linked to chronic low-grade neuroinflammation, which is primarily induced by microglia. Nonetheless, the mechanisms by which microglia elicit depressive symptoms remain uncertain. This review focuses on the mechanism linking microglia and depression encompassing the breakdown of the blood-brain barrier, the hypothalamic-pituitary-adrenal axis, the gut-brain axis, the vagus and sympathetic nervous systems, and the susceptibility influenced by epigenetic modifications on microglia. These pathways may lead to the alterations of microglia in cytokine levels, as well as increased oxidative stress. Simultaneously, many antidepressant treatments can alter the immune phenotype of microglia, while anti-inflammatory treatments can also have antidepressant effects. This framework linking microglia, neuroinflammation, and depression could serve as a reference for targeting microglia to treat depression.

Chronic Stress-Associated Depressive Disorders: The Impact of HPA Axis Dysregulation and Neuroinflammation on the Hippocampus-A Mini Review

Chronic stress significantly contributes to the development of depressive disorders, with the hypothalamic-pituitary-adrenal (HPA) axis playing a central role in mediating stress responses. This review examines the neurobiological alterations in the hippocampus linked to HPA axis dysregulation in chronic stress-associated depressive disorders. The prolonged activation of the HPA axis disrupts cortisol regulation, leading to the decline of both physical and mental health. The chronic stress-induced HPA axis dysfunction interacts with inflammatory pathways and generates oxidative stress, contributing to cellular damage and neuroinflammation that further aggravates depressive symptoms. These processes result in structural and functional alterations in the hippocampus, which is essential for emotional regulation and cognitive function. Comprehending the impact of chronic stress on the HPA axis and associated neurobiological pathways is essential for formulating effective interventions for depressive disorders. This review summarises the existing findings and underscores the necessity for future investigations into intervention strategies to improve physical and psychological wellbeing targeting at HPA axis dysregulation for the betterment of psychological wellbeing and human health.

How does chronic psychosocial distress induce pain? Focus on neuroinflammation and neuroplasticity changes

Chronic primary pain including fibromyalgia for the musculoskeletal system persists for more than 3 months. Its etiological factors and the pathophysiological mechanisms are not known, and therefore, there is no satisfactory therapy, it is an unmet medical need condition. The only etiological and aggravating factor is chronic psychosocial distress, which is known to cause neuroimmune and endocrine changes both in the periphery and the central nervous system. In this short review, we introduce our research perspective by summarizing the recent literature on the interactions between chronic pain, stress, and commonly co-morbid mood disorders. Immune activation, autoimmunity, neuro-immune-vascular crosstalks and neuroinflammation play roles in the pathophysiology of these conditions. Data on stress-induced neuroplasticity changes at cellular and molecular levels were also collected in relation to chronic primary pain both from clinical studies and animal experiments of translational relevance. Understanding these mechanisms could help to identify novel therapeutic targets for chronic primary pain including fibromyalgia.

Effects and mechanisms of Apelin in treating central nervous system diseases

Apelin, an endogenous ligand of G protein-coupled receptor APJ, is widely distributed in the central nervous system (CNS). It can be divided into such subtypes as Apelin-13, Apelin-17, and Apelin-36 as they have different amino acid structures. All Apelin is widely studied as an adipokine, showing a significant protective effect through regulating apoptosis, autophagy, oxidative stress, angiogenesis, inflammation, and other pathophysiological processes. As an adipokine, Apelin has been found to play a crucial role in cardiovascular disease development. In this paper, we reviewed the effects and mechanisms of Apelin in treating CNS diseases, such as neurotrauma, stroke, spinal cord injury, primary tumors, neurodegenerative diseases, psychiatric diseases, epilepsy, and pain.

Microglia-Derived Vitamin D Binding Protein Mediates Synaptic Damage and Induces Depression by Binding to the Neuronal Receptor Megalin

Vitamin D binding protein (VDBP) is a potential biomarker of major depressive disorder (MDD). This study demonstrates for the first time that VDBP is highly expressed in core emotion-related brain regions of mice susceptible to chronic unpredictable mild stress (CUMS). Specifically, the overexpression of microglia (MG)-derived VDBP in the prelimbic leads to depression-like behavior and aggravates CUMS-induced depressive phenotypes in mice, whereas conditional knockout of MG-derived VDBP can reverse both neuronal damage and depression-like behaviors. Mechanistically, the binding of MG-derived VDBP with the neuronal receptor megalin mediates the downstream SRC signaling pathway, leading to neuronal and synaptic damage and depression-like behaviors. These events may be caused by biased activation of inhibitory neurons and excitatory-inhibitory imbalance. Importantly, this study has effectively identified MG-derived VDBP as a pivotal mediator in the interplay between microglia and neurons via its interaction with the neuronal receptor megalin and intricate downstream impacts on neuronal functions, thus offering a promising therapeutic target for MDD.

Flavins and Flavoproteins in the Neuroimmune Landscape of Stress Sensitization and Major Depressive Disorder

Major Depressive Disorder (MDD) is a common and severe neuropsychiatric condition resulting in irregular alterations in affect, mood, and cognition. Besides the well-studied neurotransmission-related etiologies of MDD, several biological systems and phenomena, such as the hypothalamic-pituitary-adrenal (HPA) axis, reactive oxygen species (ROS) production, and cytokine signaling, have been implicated as being altered and contributing to depressive symptoms. However, the manner in which these factors interact with each other to induce their effects on MDD development has been less clear, but is beginning to be understood. Flavins are potent biomolecules that regulate many redox activities, including ROS generation and energy production. Studies have found that circulating flavin levels are modulated during stress and MDD. Flavins are also known for their importance in immune responses. This review offers a unique perspective that considers the redox-active cofactors, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), as vital substrates for linking MDD-related maladaptive processes together, by permitting stress-induced enhancement of microglial interleukin-1 beta (IL-1β) signaling.

Neuroprotective Role of Selenium Nanoparticles Against Behavioral, Neurobiochemical and Histological Alterations in Rats Subjected to Chronic Restraint Stress

Chronic stress induces changes in the prefrontal cortex and hippocampus. Selenium nanoparticles (SeNPs) showed promising results in several neurological animal models. The implementation of SeNPs in chronic restraint stress (CRS) remains to be elucidated. This study was done to determine the possible protective effects of selenium nanoparticles on behavioral changes and brain oxidative stress markers in a rat model of CRS. 50 rats were divided into three groups; control group (n = 10), untreated CRS group (n = 10) and CRS-SeNPs treated group (n = 30). Restraint stress was performed 6 h./day for 21 days. Rats of CRS-SeNPs treated group received 1, 2.5 or 5 mg/kg SeNPs (10 rats each) by oral gavage for 21 days. Rats were subjected to behavioral assessments and then sacrificed for biochemical and histological analysis of the prefrontal cortex and hippocampus. Prefrontal cortical and hippocampal serotonin levels, oxidative stress markers including malondialdehyde (MDA), reduced glutathione (GSH) and glutathione peroxidase (GPx), tumor necrosis factor alpha (TNF-α) and caspase-3 were assessed. Accordingly, different doses of SeNPs showed variable effectiveness in ameliorating disease parameters, with 2.5 mg/kg dose of SeNPs showing the best improving results in all studied parameters. The present study exhibited the neuroprotective role of SeNPs in rats subjected to CRS and proposed their antioxidant, anti-inflammatory and anti-apoptotic effects as the possible mechanism for increased prefrontal cortical and hippocampal serotonin level, ameliorated anxiety-like and depressive-like behaviors and improved prefrontal cortical and hippocampal histological architecture.

Stress-induced obesity in mice causes cognitive decline associated with inhibition of hippocampal neurogenesis and dysfunctional gut microbiota

Effects of stress on obesity have been thoroughly studied in high-fat diet fed mice, but not in normal diet fed mice, which is important to clarify because even on a normal diet, some individuals will become obese under stress conditions. Here we compared mice that showed substantial weight gain or loss under chronic mild stress while on a normal diet; we compared the two groups in terms of cognitive function, hypothalamic-pituitary-adrenal signaling, neurogenesis and activation of microglia in hippocampus, gene expression and composition of the gut microbiome. Chronic mild stress induced diet-independent obesity in approximately 20% of animals, and it involved inflammatory responses in peripheral and central nervous system as well as hyperactivation of the hypothalamic-pituitary-adrenal signaling and of microglia in the hippocampus, which were associated with cognitive deficits and impaired hippocampal neurogenesis. It significantly increased in relative abundance at the phylum level (Firmicutes), at the family level (Prevotellaceae ucg - 001 and Lachnospiraceae NK4a136), at the genus level (Dubosiella and Turicibacter) for some enteric flora, while reducing the relative abundance at the family level (Lactobacillaceae and Erysipelotrichaceae), at the genus level (Bacteroidota, Alistipes, Alloprevotella, Bifidobacterium and Desulfovibrio) for some enteric flora. These results suggest that stress, independently of diet, can induce obesity and cognitive decline that involve dysfunctional gut microbiota. These insights imply that mitigation of hypothalamic-pituitary-adrenal signaling and microglial activation as well as remodeling of gut microbiota may reverse stress-induced obesity and associated cognitive decline.

The long non-coding RNA GAS5 contributes to the suppression of inflammatory responses by inhibiting NF-κB activity

INTRODUCTION

Nuclear factor kappa B (NF-κB) is a key regulator of immune and inflammatory responses. Glucocorticoid drugs (GC) act through the glucocorticoid receptor (GR) as immunosuppressant also in pediatric patients inhibiting NF-κB activity. The long non-coding RNA GAS5 interacts with the GR, influencing GC activity. No data on the role of GAS5 on GR-dependent inhibition of NF-κB activity have been published.

METHODS

This study investigated the impact of GAS5 on NF-κB activity in HeLa cells overexpressing GAS5, both under basal conditions and during GC treatment. The study used EMSA, RNA-immunoprecipitation (RIP), Western blotting, and bioinformatic analyses to assess NF-κB DNA binding, GAS5-p65 interaction, and NF-κB signaling pathway modulation.

RESULTS

GAS5 overexpression increased NF-κB DNA binding activity in untreated cells. RNA-IP confirmed a direct interaction between GAS5 and the NF-κB subunit p65, suggesting a potential regulatory mechanism. GAS5 overexpression led to downregulation of NF-κB target genes, TNF-α, and NR3C1. GC treatment reduced NF-κB DNA binding activity in GAS5-overexpressing cells, indicating a potential synergistic effect. Furthermore, GAS5 overexpression increased IκB levels and reduced p-p65/pan-p65 levels during GC treatment.

DISCUSSION

GAS5 appears to modulate NF-κB activity in a complex manner, influencing both basal and GC-induced signaling. The interaction between GAS5, GCs, and NF-κB is multi-faceted, and further research is needed to fully elucidate the underlying mechanisms. These findings suggest that GAS5 could be a potential target for personalized therapy, particularly in pediatric patients with inflammatory conditions.

Escin alleviates cerebral ischemia-induced intestinal pyroptosis via the GR-dependent p38 MAPK/NF-κB signaling and NLRP3 inflammasome activation

Cerebral ischemia-induced systemic inflammation and inflammasome-dependent pyroptotic cell death in ileum, causing serious intestinal injury. Glucocorticoid receptor (GR) mediates the effects of glucocorticoids and participates in inflammation. Escin has corticosteroid-like, neuroprotective, and anti-intestinal dysfunction effects. This study aimed to investigate the effect of Escin on the intestinal barrier injury in rats subjected to middle cerebral artery occlusion (MCAO) and on Caco-2 cells exposed to lipopolysaccharides. The MCAO-caused brain injury was evaluated by assessing neurological function, cerebral infarct volume, and plasma corticosterone (Cort) levels. Intestinal injury was evaluated by observing the histopathological changes, assessing the intestinal barrier function, and determining blood FD4, endotoxin and IL-1β levels. The levels of the tight-junction proteins such as claudin-1, occludin, and ZO-1, and proteins involved in the GR/p38 MAPK/NF-κB pathway and NLRP3-inflammasome activation were evaluated using western blotting or immunofluorescence. Administration of Escin suppressed the cerebral ischemia-induced increases in Garcia-test scores and infarct volume, alleviated the injury to the intestinal barrier, and decreased the levels of Cort, endotoxin, and IL-1β. Additionally, Escin upregulated GR and downregulated phospho(p)-p65, p-p38MAPK, NLRP3, GSDMD-N, and cleaved-caspase-1 in the intestine. The effects of Escin could be suppressed by the GR antagonist RU486 or enhanced by the p38 MAPK antagonist SB203580. We revealed details how Escin improves cerebral ischemia-induced intestinal barrier injury by upregulating GR and thereby inhibiting the pyroptosis induced by NF-κB-mediated NLRP3 activation. This study will provide a experimental foundation for the features of glucocorticoid-like activity and the discovery of new clinical application for Escin.

Unmoving and uninflamed: Characterizing neuroinflammatory dysfunction in the Wistar-Kyoto rat model of depression

Reductionistic research on depressive disorders has been hampered by the limitations of animal models. Recently, it has been hypothesized that neuroinflammation is a key player in depressive disorders. The Wistar-Kyoto (WKY) rat is an often-used animal model of depression, but no information so far exists on its neuroinflammatory profile. As such, we compared male young adult WKY rats to Wistar (WS) controls, with regard to both behavioral performance and brain levels of key neuroinflammatory markers. We first assessed anxiety- and depression-like behaviors in a battery consisting of the Elevated Plus Maze (EPM), the Novelty Suppressed Feeding (NSFT), Open Field (OFT), Social Interaction (SIT), Forced Swim (FST), Sucrose Preference (SPT), and Splash tests (ST). We found that WKY rats displayed increased NSFT feeding latency, decreased OFT center zone permanence, decreased EPM open arm permanence, decreased SIT interaction time, and increased immobility in the FST. However, WKY rats also evidenced marked hypolocomotion, which is likely to confound performance in such tests. Interestingly, WKY rats performed similarly, or even above, to WS levels in the SPT and ST, in which altered locomotion is not a significant confound. In a separate cohort, we assessed prefrontal cortex (PFC), hippocampus and amygdala levels of markers of astrocytic (GFAP, S100A10) and microglial (Iba1, CD86, Ym1) activation status, as well as of three key proinflammatory cytokines (IL-1β, IL-6, TNF-α). There were no significant differences between strains in any of these markers, in any of the regions assessed. Overall, results highlight that behavioral data obtained with WKY rats as a model of depression must be carefully interpreted, considering the marked locomotor activity deficits displayed. Furthermore, our data suggest that, despite WKY rats replicating many depression-associated neurobiological alterations, as shown by others, this is not the case for neuroinflammation-related alterations, thus representing a novel limitation of this model.

Microglial NLRP3 inflammasome-mediated neuroinflammation and therapeutic strategies in depression

Previous studies have demonstrated a bidirectional relationship between inflammation and depression. Activation of the nucleotide-binding oligomerization domain, leucine-rich repeat, and NLR family pyrin domain-containing 3 (NLRP3) inflammasomes is closely related to the pathogenesis of various neurological diseases. In patients with major depressive disorder, NLRP3 inflammasome levels are significantly elevated. Understanding the role that NLRP3 inflammasome-mediated neuroinflammation plays in the pathogenesis of depression may be beneficial for future therapeutic strategies. In this review, we aimed to elucidate the mechanisms that lead to the activation of the NLRP3 inflammasome in depression as well as to provide insight into therapeutic strategies that target the NLRP3 inflammasome. Moreover, we outlined various therapeutic strategies that target the NLRP3 inflammasome, including NLRP3 inflammatory pathway inhibitors, natural compounds, and other therapeutic compounds that have been shown to be effective in treating depression. Additionally, we summarized the application of NLRP3 inflammasome inhibitors in clinical trials related to depression. Currently, there is a scarcity of clinical trials dedicated to investigating the applications of NLRP3 inflammasome inhibitors in depression treatment. The modulation of NLRP3 inflammasomes in microglia holds promise for the management of depression. Further investigations are necessary to ascertain the efficacy and safety of these therapeutic approaches as potential novel antidepressant treatments.

Remote-controlled dexamethasone-duration on eye-surface with a micelle-magnetic nanoparticulate co-delivery system for dry eye disease

Dexamethasone (DEX) is used to treat ocular surface diseases. However, regulating DEX duration in tears while preventing its absorption into the anterior chamber is critical for balancing its therapy effects and the side effects. In this study, a novel magnetic nanoparticle (MNP)-micelle (MC) co-delivery system (MMDS) was developed. The MC moiety in the MMDS served as the carrier for DEX and the MNP part endowed the MMDS with magnetic-responsive properties. To extend its residency, the MMDS was magnetically attracted by an external magnet after instilling, which acted as a precorneal drug-depot enabling a sustainable release of DEX in tears. With combination of magnet treatment, the topical instillation of MMDS@DEX significantly prolonged the DEX-retention in tears and increased the DEX-concentration in the cornea and conjunctiva, as well as concurrently reduced the DEX-level in the aqueous humor, when compared with the commercial DEX eye drop treatment. The combination of MMDS@DEX and magnet treatment exerted significantly better therapeutic effects against DED with smaller side effects than conventional treatments including DEX suspension, commercial DEX eye drops, as well as the MMDS@DEX treatment alone. The present work provided a new method for the effective delivery of DEX to ocular surface tissues while reducing its side effects, which will be beneficial to the treatments of a wide range of ocular surface diseases.

Potential role of gut microbiota in major depressive disorder: A review

Interactions between the gut microbiota and host immunity are sophisticated, dynamic, and host-dependent. Scientists have recently conducted research showing that disturbances in the gut bacterial community can lead to a decrease in some metabolites and, consequently, to behaviors such as depression. Exposure to stressors dropped the relative abundance of bacteria in the genus Bacteroides while soaring the relative abundance of bacteria in the genus Clostridium, Coprococcus, Dialister, and Oscillibacter, which were also reduced in people with depression. Microbiota and innate immunity are in a bilateral relationship. The gut microbiota has been shown to induce the synthesis of antimicrobial proteins such as catalysidins, type C lectins, and defensins. Probiotic bacteria can modulate depressive behavior through GABA signaling. The gut microbiome produces essential metabolites such as neurotransmitters, tryptophan metabolites, and short-chain fatty acids (SCFAs) that can act on the CNS. In the case of dysbiosis, due to mucin changes, the ratio of intestinal-derived molecules may change and contribute to depression. Psychotropics, including Bifidobacterium longum NCC3001, Clostridium butyricum CBM588, and Lactobacillus acidophilus, have mental health benefits, and can have a positive effect on the host-brain relationship, and have antidepressant effects. This article reviews current studies on the association between gut microbiota dysbiosis and depression. Comprehensively, these findings could potentially lead to novel approaches to improving depressive symptoms via gut microbiota alterations, including probiotics, prebiotics, and fecal microbiota transplantation.

Inflammation and Connexin 43 profiles in the prefrontal cortex are relevant to stress susceptibility and resilience in mice

Depression is a major chronic mental illness worldwide, characterized by anhedonia and pessimism. Exposed to the same stressful stimuli, some people behave normally, while others exhibit negative behaviors and psychology. The exact molecular mechanisms linking stress-induced depressive susceptibility and resilience remain unclear. Connexin 43 (Cx43) forms gap junction channels between the astrocytes, acting as a crucial role in the pathogenesis of depression. Cx43 dysfunction could lead to depressive behaviors, and depression down-regulates the expression of Cx43 in the prefrontal cortex (PFC). Besides, accumulating evidence indicates that inflammation is one of the most common pathological features of the central nervous system dysfunction. However, the roles of Cx43 and peripheral inflammation in stress-susceptible and stress-resilient individuals have rarely been investigated. Thus, animals were classified into the chronic unpredictable stress (CUS)-susceptible group and the CUS-resilient group based on the performance of behavioral tests following the CUS protocol in this study. The protein expression of Cx43 in the PFC, the Cx43 functional changes in the PFC, and the expression levels including interleukin (IL)-1β, tumor necrosis factor-α, IL-6, IL-2, IL-10, and IL-18 in the peripheral serum were detected. Here, we found that stress exposure triggered a significant reduction in Cx43 protein expression in the CUS-susceptible mice but not in the CUS-resilient mice accompanied by various Cx43 phosphorylation expression and the changes of inflammatory signals. Stress resilience is associated with Cx43 in the PFC and fluctuation in inflammatory signaling, showing that therapeutic targeting of these pathways might promote stress resilience.

Melatonin modulates neuroinflammatory response and microglial activation in mice exposed to dim blue light at night

Objectives

Dim light at night contributes to neurodegenerative diseases by causing neuroinflammation. In the central nervous system, the activation of microglia is a significant contributor to neuroinflammation. Therefore, there is an urgent need to find an intervention to treat the neuroinflammatory response caused by dim light at night. Melatonin is a rhythmic hormone whose synthesis is suppressed during the day. In this study, we attempt to explore whether and how melatonin improves hippocampal neuroinflammation in mice exposed to dim blue light at night.

Materials and Methods

In vivo, a total of 36 male C57BL6/J mice that exposed to no light at night, dim blue light at night, and dim blue light at night with melatonin treatment. In vitro, the corticosterone-induced BV2 cells with or without melatonin treatment were used.

Results

Both in vivo and in vitro experiments showed melatonin treatment significantly reduced dim blue light -induced hippocampal microglial activation and the expression of inflammatory factors IL-1β and TNF-α. This improved effect of melatonin is related to its receptor MT2 rather than MT1. The MT2 blockers significantly increased mRNA levels of M1-type activation marker CD86 and inflammatory cytokines IL-1β and TNF-α in melatonin-treated BV2 cells. Binding of melatonin to its receptor MT2 downregulated the expression of inflammatory proteins P-P65 and NLRP3, consequently inhibited the CD80 expression and M1-type activation in microglia. Furthermore, consistent with the decrease in microglial activation and inflammatory response after melatonin treatment, we also observed a reduction in hippocampal neuron loss and damage to the HT22 cells.

Conclusion

Our findings suggested that melatonin may regulate microglial polarization through MT2/NF-kB-NLRP3 pathway and improves dim blue light -induced hippocampal neuroinflammation in mice.

Liraglutide and Naringenin relieve depressive symptoms in mice by enhancing Neurogenesis and reducing inflammation

Depression is a debilitating mental disease that negatively impacts individuals' lives and society. Novel hypotheses have been recently proposed to improve our understanding of depression pathogenesis. Impaired neuroplasticity and upregulated neuro-inflammation add-on to the disturbance in monoamine neurotransmitters and therefore require novel anti-depressants to target them simultaneously. Recent reports demonstrate the antidepressant effect of the anti-diabetic drug liraglutide. Similarly, the natural flavonoid naringenin has shown both anti-diabetic and anti-depressant effects. However, the neuro-pharmacological mechanisms underlying their actions remain understudied. The study aims to evaluate the antidepressant effects and neuroprotective mechanisms of liraglutide, naringenin or a combination of both. Depression was induced in mice by administering dexamethasone (32 mcg/kg) for seven consecutive days. Liraglutide (200 mcg/kg), naringenin (50 mg/kg) and a combination of both were administered either simultaneously or after induction of depression for twenty-eight days. Behavioral and molecular assays were used to assess the progression of depressive symptoms and biomarkers. Liraglutide and naringenin alone or in combination alleviated the depressive behavior in mice, manifested by decrease in anxiety, anhedonia, and despair. Mechanistically, liraglutide and naringenin improved neurogenesis, decreased neuroinflammation and comparably restored the monoamines levels to that of the reference drug escitalopram. The drugs protected mice from developing depression when given simultaneously with dexamethasone. Collectively, the results highlight the usability of liraglutide and naringenin in the treatment of depression in mice and emphasize the different pathways that contribute to the pathogenesis of depression.

Stress, pain, anxiety, and depression in endometriosis-Targeting glial activation and inflammation

Endometriosis (EM) is a gynecological inflammatory disease often accompanied by stress, chronic pelvic pain (CPP), anxiety, and depression, leading to a diminished quality of life. This review aims to discuss the relationship between systemic and local inflammatory responses in the central nervous system (CNS), focusing on glial dysfunctions (astrocytes and microglia) as in critical brain regions involved in emotion, cognition, pain processing, anxiety, and depression. The review presents that EM is connected to increased levels of pro-inflammatory cytokines in the circulation. Additionally, chronic stress and CPP as stressors may contribute to the dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, depleting the production of inflammatory mediators in the circulatory system and the brain. The systemic cytokines cause blood-brain barrier (BBB) breakdown, activate microglia in the brain, and lead to neuroinflammation. Furthermore, CPP may induce neuronal morphological alterations in critical regions through central sensitization and the activation of glial cells. The activation of glial cells, particularly the polarization of microglia, leads to the activation of the NLRP3 inflammasome and the overproduction of inflammatory cytokines. These inflammatory cytokines interact with the signaling pathways involved in neural plasticity. Additionally, persistent inflammatory conditions in the brain lead to neuronal death, which is correlated with a reduced volume of key brain regions such as the hippocampus. This review highlights the involvement of glial cells in the pathogenesis of the mental comorbidities of EM (i.e., pain, anxiety, and depression) and to discuss potential therapeutic approaches for targeting the inflammation and activation of microglia in key brain regions.

Targeting inflammasome complexes as a novel therapeutic strategy for mood disorders

INTRODUCTION

Inflammasome complexes, especially NLRP3, have gained great attention as a potential therapeutic target in mood disorders. NLRP3 triggers a caspase 1-dependent release of the inflammatory cytokines IL-1β and IL-18, and seems to interact with purinergic and kynurenine pathways, all of which are implicated in mood disorders development and progression.

AREAS COVERED

Emerging evidence supports NLRP3 inflammasome as a promising pharmacological target for mood disorders. We discussed the available evidence from animal models and human studies and provided a reflection on drawbacks and perspectives for this novel target.

EXPERT OPINION

Several studies have supported the involvement of NLRP3 inflammasome in MDD. However, most of the evidence comes from animal models. The role of NLRP3 inflammasome in BD as well as its anti-manic properties is not very clear and requires further exploration. There is evidence of anti-manic effects of P2×R7 antagonists associated with reduction in the brain levels of IL-1β and TNF-α in a murine model of mania. The involvement of other NLRP3 inflammasome expressing cells besides microglia, like astrocytes, and of other inflammasome complexes in mood disorders also deserves further investigation. Preclinical and clinical characterization of NLRP3 and other inflammasomes in mood disorders is needed before considering translational approaches, including clinical trials.

Sex-Related and Brain Regional Differences of URB597 Effects on Modulation of MAPK/PI3K Signaling in Chronically Stressed Rats

Gender differences exist in depression incidence and antidepressant efficacy. In addition to the neurotransmission theory of depression, inflammation and disrupted signaling pathways play crucial roles in the pathophysiology of depression. Endocannabinoids offer a novel approach to treat inflammatory and emotional disorders like depression. URB597, a FAAH inhibitor, reduces endocannabinoids breakdown. In this study, URB597 effects were investigated on the pro-inflammatory cytokine interleukin-1β (IL-1β), nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3(NLRP3), and mitogen-activated protein kinase (MAPK)/ phosphatidylinositol 3-hydroxy kinase/ protein kinase B (PI3K) signaling in the hippocampus and the medial prefrontal cortex (mPFC) of male and female rats subjected to chronic unpredictable stress (CUS). The results show that CUS induces depression-like behaviors, and the URB597 exhibited antidepressant-like effects inboth sexes. URB597 reduced the CUS-induced NLRP3 and IL-1β increase in the hippocampus and mPFC of both sexes. URB597 increased the reduced pERK1/2 levels in the mPFC of both sexes and hippocampus of CUS males. URB597 also prevented the increase in p38 phosphorylation after chronic stress in the mPFC of both sexes and in the hippocampus of the females. The CUS suppressed the downstream Akt phosphorylation in the mPFC and hippocampi of both sexes. URB597 produced an up-regulation of the pAkt in the hippocampus of the CUS animals but did not affect the pAkt in the mPFC. These data demonstrated a sexual dimorphism in the neural cell signaling, and in the effects of endocannabinoids, and indicated these dimorphisms are region-specific.

The Metabolic Syndrome, a Human Disease

This review focuses on the question of metabolic syndrome (MS) being a complex, but essentially monophyletic, galaxy of associated diseases/disorders, or just a syndrome of related but rather independent pathologies. The human nature of MS (its exceptionality in Nature and its close interdependence with human action and evolution) is presented and discussed. The text also describes the close interdependence of its components, with special emphasis on the description of their interrelations (including their syndromic development and recruitment), as well as their consequences upon energy handling and partition. The main theories on MS's origin and development are presented in relation to hepatic steatosis, type 2 diabetes, and obesity, but encompass most of the MS components described so far. The differential effects of sex and its biological consequences are considered under the light of human social needs and evolution, which are also directly related to MS epidemiology, severity, and relations with senescence. The triggering and maintenance factors of MS are discussed, with especial emphasis on inflammation, a complex process affecting different levels of organization and which is a critical element for MS development. Inflammation is also related to the operation of connective tissue (including the adipose organ) and the widely studied and acknowledged influence of diet. The role of diet composition, including the transcendence of the anaplerotic maintenance of the Krebs cycle from dietary amino acid supply (and its timing), is developed in the context of testosterone and β-estradiol control of the insulin-glycaemia hepatic core system of carbohydrate-triacylglycerol energy handling. The high probability of MS acting as a unique complex biological control system (essentially monophyletic) is presented, together with additional perspectives/considerations on the treatment of this 'very' human disease.

A study of roflumilast treatment on functional and structural changes in hippocampus in depressed Adult male Wistar rats

Depression is a common stress disability disorder that affects higher mental functions including emotion, cognition, and behavior. It may be mediated by inflammatory cytokines that interfere with neuroendocrine function, and synaptic plasticity. Therefore, reductions in inflammation might contribute to treatment response. The current study aims to evaluate the role of Protein Kinase (PKA)- cAMP response element-binding protein (CREB)- brain derived neurotropic factor (BDNF) signaling pathway in depression and the effects of roflumilast (PDE4 inhibitor) as potential antidepressant on the activity of the PKA-CREB-BDNF signaling pathway, histology, and pro-inflammatory cytokine production. Forty Adult male Wistar rats were divided into 4 groups: Control group, Positive Control group: similar to the controls but received Roflumilast (3 mg / kg / day) by oral gavage for the last 4 weeks of the experiment, Depressed group which were exposed to chronic stress for 6 weeks, and Roflumilast-treated group which were exposed to chronic stress for 6 weeks and treated by Roflumilast (3 mg / kg / day) by oral gavage for the last 4 weeks of the experiment. The depressed group showed significant increase in immobility time with significant decrease in swimming and struggling times, significant decrease in hippocampal PKA, CERB, BDNF, Dopamine, Cortisone, and Superoxide dismutase while hippocampal Phosphodiesterase-E4, Interleukin-6, and Malondialdhyde levels were significantly elevated. These findings were significantly reversed upon Roflumilast treatment. Therefore, it could be concluded that depression is a neurodegenerative inflammatory disease and oxidative stress plays a key role in depression. Roflumilast treatment attenuated the depression behavior in rats denoting its neuroprotective, and anti-inflammatory effects.

NLRP3 inflammatory pathway. Can we unlock depression?

Depression holds the title of the largest contributor to worldwide disability, with the numbers expected to continue growing. Currently, there are neither reliable biomarkers for the diagnosis of the disease nor are the current medications sufficient for a lasting response in nearly half of patients. In this comprehensive review, we analyze the previously established pathophysiological models of the disease and how the interplay between NLRP3 inflammasome activation and depression might offer a unifying perspective. Adopting this inflammatory theory, we explain how NLRP3 inflammasome activation emerges as a pivotal contributor to depressive inflammation, substantiated by compelling evidence from both human studies and animal models. This inflammation is found in the central nervous system (CNS) neurons, astrocytes, and microglial cells. Remarkably, dysregulation of the NLRP3 inflammasome extends beyond the CNS boundaries and permeates into the enteric and peripheral immune systems, thereby altering the microbiota-gut-brain axis. The integrity of the brain blood barrier (BBB) and intestinal epithelial barrier (IEB) is also compromised by this inflammation. By emphasizing the central role of NLRP3 inflammasome activation in depression and its far-reaching implications, we go over each area with potential modulating mechanisms within the inflammasome pathway in hopes of finding new targets for more effective management of this debilitating condition.

(-)-Epigallocatechin gallate alleviates chronic unpredictable mild stress-induced depressive symptoms in mice by regulating the mTOR autophagy pathway and inhibiting NLRP3 inflammasome activation

Depression is a global public health issue that is widely studied due to the large number of people it affects and its serious consequences. Clinical studies have shown that regular tea consumption may reduce depression risk. (-)-Epigallocatechin gallate (EGCG), the main tea polyphenol, was observed to alleviate depression, but the underlying mechanism has not been elucidated. In this study, chronic unpredictable mild stress (CUMS) was used to induce depression-like behavior in mice, and behavioral tests, such as sucrose preference test and forced swim test, were performed. Then, ELISA, western blot and QT-PCR tests were used to assess the expression of the key components of the NLRP3 inflammasome and its downstream inflammatory effectors (e.g., IL-1β, IL-18), autophagy markers (Beclin-1, LC3, P62) and apoptosis markers (Bax, Bcl-2) in mouse brain tissues. Changes in serum lipid levels were also assessed. EGCG alleviated CUMS-induced depression-like behavioral changes in mice, reduced activation of the NLRP3 inflammasome, inhibited the mTOR signaling pathway, restored autophagy levels, reduced apoptosis marker expression and attenuated abnormal changes in blood lipid levels. Our study demonstrates that EGCG exerts antidepressive effects through multiple mechanisms, providing new insight into the pathological mechanism of depression and laying the foundation for the development of new therapeutic measures.

Neurodevelopmental and Neuropsychiatric Disorders

This chapter will focus on microglial involvement in neurodevelopmental and neuropsychiatric disorders, particularly autism spectrum disorder (ASD), schizophrenia and major depressive disorder (MDD). We will describe the neuroimmune risk factors that contribute to the etiopathology of these disorders across the lifespan, including both in early life and adulthood. Microglia, being the resident immune cells of the central nervous system, could play a key role in triggering and determining the outcome of these disorders. This chapter will review preclinical and clinical findings where microglial morphology and function were examined in the contexts of ASD, schizophrenia and MDD. Clinical evidence points out to altered microglial morphology and reactivity, as well as increased expression of pro-inflammatory cytokines, supporting the idea that microglial abnormalities are involved in these disorders. Indeed, animal models for these disorders found altered microglial morphology and homeostatic functions which resulted in behaviours related to these disorders. Additionally, as microglia have emerged as promising therapeutic targets, we will also address in this chapter therapies involving microglial mechanisms for the treatment of neurodevelopmental and neuropsychiatric disorders.

Restraint stress promotes nonalcoholic steatohepatitis by regulating the farnesoid X receptor/NLRP3 signaling pathway

Psychological stress promotes nonalcoholic steatohepatitis (NASH) development. However, the pathogenesis of psychological stress-induced NASH remains unclear. This study aims to explore the underlying mechanism of restraint stress-induced NASH, which mimics psychological stress, and to discover potential NASH candidates. Methionine choline deficient diet- and high fat diet-induced hepatosteatotic mice are subjected to restraint stress to induce NASH. The mice are administrated with Xiaoyaosan granules, NOD-like receptor family pyrin domain containing 3 (NLRP3) inhibitors, farnesoid X receptor (FXR) agonists, or macrophage scavengers. Pathological changes and NLRP3 signaling in the liver are determined. These results demonstrate that restraint stress promotes hepatic inflammation and fibrosis in hepatosteatotic mice. Restraint stress increases the expressions of NLRP3, Caspase-1, Gasdermin D, interleukin-1β, cholesterol 7α-hydroxylase, and sterol 12α-hydroxylase and decreases the expression of FXR in NASH mice. Xiaoyaosan granules reverse hepatic inflammation and fibrosis and target FXR and NLRP3 signals. In addition, inhibition of NLRP3 reduces the NLRP3 inflammasome and liver damage in mice with restraint stress-induced NASH. Elimination of macrophages and activation of FXR also attenuate inflammation and fibrosis by inhibiting NLRP3 signaling. However, NLRP3 inhibitors or macrophage scavengers fail to affect the expression of FXR. In conclusion, restraint stress promotes NASH-related inflammation and fibrosis by regulating the FXR/NLRP3 signaling pathway. Xiaoyaosan granules, NLRP3 inhibitors, FXR agonists, and macrophage scavengers are potential candidates for the treatment of psychological stress-related NASH.

Lycopene Alleviates Chronic Stress-Induced Hippocampal Microglial Pyroptosis by Inhibiting the Cathepsin B/NLRP3 Signaling Pathway

Lycopene (LYC) exerts a strong neuroprotective and antipyroptotic effects. This study explored the effects and mechanisms of LYC on chronic stress-induced hippocampal microglial damage and depression-like behaviors. The caspase-1 inhibitor VX-765 attenuated chronic restrain stress (CRS)-induced hippocampal microglial pyroptosis and depression-like behaviors. Moreover, the alleviation of CRS-induced hippocampal microglial pyroptosis and depression-like behaviors by LYC was associated with the cathepsin B/NLRP3 pathway. In vitro, the caspase-1 inhibitor Z-YVAD-FMK alleviated pyroptosis in highly aggressively proliferating immortalized (HAPI) cells. Additionally, the alleviation of corticosterone-induced HAPI cell damage and pyroptosis by LYC was associated with the cathepsin B/NLRP3 pathway. Furthermore, the cathepsin B agonist pazopanib promoted HAPI cell pyroptosis, whereas LYC inhibited pazopanib-induced pyroptosis via the cathepsin B/NLRP3 pathway. Similarly, Z-YVAD-FMK inhibited pazopanib-induced HAPI cell pyroptosis. These results suggest that LYC alleviates chronic stress-induced hippocampal microglial pyroptosis via the cathepsin B/NLRP3 pathway inhibition. This study provides a new strategy for treating chronic stress encephalopathy.

Chia seeds oil ameliorate chronic immobilization stress-induced neurodisturbance in rat brains via activation of the antioxidant/anti-inflammatory/antiapoptotic signaling pathways

Chronic immobilization stress plays a key role in several neuropsychiatric disorders. This investigation assessed the possible ameliorative effect of chia seed oil (CSO) against the neurodisturbance-induced in rats by chronic immobilization. Rats were randomly allocated into control, CSO (1 ml/kg b.wt./orally), restrained (6 h/day), CSO pre-restraint, and CSO post-restraint for 60 days. Results revealed a significant reduction in serum corticosterone level, gene expression of corticotrophin-releasing factor, pro-inflammatory cytokines, and oxidative biomarkers in restrained rats treated with CSO. The histopathological findings revealed restoring necrosis and neuronal loss in CSO-treated-restraint rats. The immunohistochemical evaluation revealed a significant reduction in the immuno-expression of caspase-3, nuclear factor kappa B, interleukin-6, and cyclooxygenase-2 (COX-2), and an elevation of calbindin-28k and synaptophysin expression compared to non-treated restraint rats. The molecular docking showed the CSO high affinity for several target proteins, including caspase-3, COX-2, corticotropin-releasing hormone binding protein, corticotropin-releasing factor receptors 1 and 2, interleukin-1 receptor types 1 and 2, interleukin-6 receptor subunits alpha and beta. In conclusion, CSO emerges as a promising candidate against stress-induced brain disruptions by suppressing inflammatory/oxidative/apoptotic signaling pathways due to its numerous antioxidant and anti-inflammatory components, mainly α-linolenic acid. Future studies are necessary to evaluate the CSO therapeutic impacts in human neurodisturbances.

Effects of elevated emotional symptoms on metabolic disease development: a 10-year follow-up study

Background

In recent decades, the relationship between emotional disorders (i.e., depression and anxiety) and alterations in physiological functions (i.e., inflammation or metabolism) have been well supported. However, studies on a symptom-based approach have provided mixed results. Our study aims to gain insight into how subclinical statuses, featured by elevated depressive and/or anxious symptoms, may influence immunometabolic alterations in the concurrent relationship; and the development of metabolic diseases at 10-year follow-up: diabetes, hypertension and hypercholesterolemia.

Methods

Data from 758 Greek adults [394 men (aged 41 ± 10 years) and 364 women (aged 37 ± 12 years)] were used. Four groups were created according to the levels of depressive and anxiety symptoms: (1) control group (CG), (2) depressive group (DG), (3) anxiety group (AG) and (4) depressive and anxiety group (DAG). Multi-indicator multi-causes (MIMIC) modeling was used to estimate metabolic function and inflammatory response scores, on a wide selection of blood biomarkers. Finally, a binary logistic regression was carried out to study the influence of symptoms on the development of the aforementioned metabolic diseases on a 10-year follow-up.

Results

Group membership was not associated with metabolic function score. Conversely, DAG membership was related with higher inflammatory response score (B = 0.20, CI95 = 0.01, 0.40), with respect to the CG (p < 0.05). Both age and sex were significant variables in the calculation of both scores. Regarding disease at 10-year follow-up effect, risk of developing diabetes, hypertension and hypercholesterolemia was associated with age and socioeconomic status. Moreover, DG membership was significant for diabetes risk (OR = 2.08, CI95 = 1.00, 4.22) and DAG for hypercholesterolemia (OR = 1.68, CI95 = 1.16, 2.43).

Limitations

Data on anti-inflammatory drugs and psychopharmacological medication were not collected in this study.

Conclusions

Elevated symptoms of depression and anxiety accounts for inflammatory alterations at concurrent relationship and a higher risk of 10-year follow-up metabolic diseases.

Noteworthy perspectives on microglia in neuropsychiatric disorders

Microglia are so versatile that they not only provide immune surveillance for central nervous system, but participate in neural circuitry development, brain blood vessels formation, blood-brain barrier architecture, and intriguingly, the regulation of emotions and behaviors. Microglia have a profound impact on neuronal survival, brain wiring and synaptic plasticity. As professional phagocytic cells in the brain, they remove dead cell debris and neurotoxic agents via an elaborate mechanism. The functional profile of microglia varies considerately depending on age, gender, disease context and other internal or external environmental factors. Numerous studies have demonstrated a pivotal involvement of microglia in neuropsychiatric disorders, including negative affection, social deficit, compulsive behavior, fear memory, pain and other symptoms associated with major depression disorder, anxiety disorder, autism spectrum disorder and schizophrenia. In this review, we summarized the latest discoveries regarding microglial ontogeny, cell subtypes or state spectrum, biological functions and mechanistic underpinnings of emotional and behavioral disorders. Furthermore, we highlight the potential of microglia-targeted therapies of neuropsychiatric disorders, and propose outstanding questions to be addressed in future research of human microglia.

The Involvement of Neuroinflammation in the Onset and Progression of Parkinson's Disease

Parkinson's disease is a neurodegenerative disease exhibiting the fastest growth in incidence in recent years. As with most neurodegenerative diseases, the pathophysiology is incompletely elucidated, but compelling evidence implicates inflammation, both in the central nervous system and in the periphery, in the initiation and progression of the disease, although it is not yet clear what triggers this inflammatory response and where it begins. Gut dysbiosis seems to be a likely candidate for the initiation of the systemic inflammation. The therapies in current use provide only symptomatic relief, but do not interfere with the disease progression. Nonetheless, animal models have shown promising results with therapies that target various vicious neuroinflammatory cascades. Translating these therapeutic strategies into clinical trials is still in its infancy, and a series of issues, such as the exact timing, identifying biomarkers able to identify Parkinson's disease in early and pre-symptomatic stages, or the proper indications of genetic testing in the population at large, will need to be settled in future guidelines.

Emphasizing the Crosstalk Between Inflammatory and Neural Signaling in Post-traumatic Stress Disorder (PTSD)

Post-traumatic stress disorder (PTSD) is a chronic incapacitating condition with recurrent experience of trauma-related memories, negative mood, altered cognition, and hypervigilance. Agglomeration of preclinical and clinical evidence in recent years specified that alterations in neural networks favor certain characteristics of PTSD. Besides the disruption of hypothalamus-pituitary-axis (HPA) axis, intensified immune status with elevated pro-inflammatory cytokines and arachidonic metabolites of COX-2 such as PGE2 creates a putative scenario in worsening the neurobehavioral facet of PTSD. This review aims to link the Diagnostic and Statistical Manual of mental disorders (DSM-V) symptomology to major neural mechanisms that are supposed to underpin the transition from acute stress reactions to the development of PTSD. Also, to demonstrate how these intertwined processes can be applied to probable early intervention strategies followed by a description of the evidence supporting the proposed mechanisms. Hence in this review, several neural network mechanisms were postulated concerning the HPA axis, COX-2, PGE2, NLRP3, and sirtuins to unravel possible complex neuroinflammatory mechanisms that are obscured in PTSD condition.

Ethyl pyruvate prevents long-term stress-induced cognitive decline and modulates Akt/GSK-3β signaling

Stress is an inevitable part of life and, simultaneously, a stimulus that can trigger various neuropsychiatric disorders. Therefore, proper stress management is essential for maintaining a healthy life. In this study, we investigated the suppression of stress-induced cognitive deficit by controlling changes in synaptic plasticity caused by stress and confirmed that ethyl pyruvate (EP) has such an effect. Corticosterone, a stress hormone, suppresses long-term potentiation (LTP) in mouse acute hippocampal slices. EP blocked the LTP inhibitory effect of corticosterone by regulating GSK-3β function. Restraint stress for 2 weeks increased the anxiety levels and caused the cognitive decline in the experimental animals. Administration of EP for 14 days did not affect the increase in anxiety caused by stress but improved cognitive decline caused by stress. In addition, the decrease in neurogenesis and synaptic function deficits in the hippocampus, which cause of cognitive decline due to stress, were improved by EP administration. These effects appear via regulation of Akt/GSK-3β signaling, as in in vitro studies. These results suggest that EP prevents stress-induced cognitive decline through the modulation of Akt/GSK-3β-mediated synaptic regulation.

Inherited stress resiliency prevents the development of metabolic alterations in diet-induced obese mice

OBJECTIVE

Chronic stress promotes obesity and metabolic comorbidities. The ability of individuals to cope with stress may serve as an important parameter in the development of obesity-related metabolic outcomes. The aim of this study was to clarify whether differences in stress response affect metabolic health under obesity.

METHODS

The study was performed in a selectively bred mouse model of social dominance (Dom) and submissiveness (Sub), which exhibit stress resilience or vulnerability, respectively. Mice were given a high-fat diet (HFD) or standard diet, followed by physiological, histological, and molecular analyses.

RESULTS

The HFD caused hyperleptinemia, glucose intolerance, insulin resistance, steatosis of the liver and pancreas, and brown adipose tissue whitening in Sub mice, whereas Dom mice were protected from these consequences of the HFD. The HFD increased circulating levels of interleukin (IL)-1β and induced the expression of proinflammatory genes in the liver and in epididymal white adipose tissue of Sub mice, with no changes in Dom mice. The Cox2 inhibitor celecoxib (15 mg/kg/d) reduced serum IL-1β, improved glucose tolerance and insulin sensitivity, and prevented hepatic and brown adipose tissue whitening in HFD-fed Sub mice.

CONCLUSIONS

The extent of stress resiliency is associated with inflammation and contributes to population heterogeneity in the development of healthy or unhealthy obesity.

Telmisartan Alleviates Alzheimer's Disease-Related Neuropathologies and Cognitive Impairments

BACKGROUND

Alzheimer's disease (AD) is the most common type of neurodegenerative disorder. There are few effective medications for halting the progression of AD. Telmisartan (TEL) is a widely used anti-hypertensive drug approved by FDA. Aside from treating hypertension, TEL has been revealed to provide protection against AD. However, the underlying mechanisms remain unclear.

OBJECTIVE

To investigate the mechanisms underlying the beneficial effects of TEL against AD.

METHODS

Eight-month-old APP/PS1 mice were administered with 5 mg/kg TEL once per day for 4 successive months. Nesting test, Y-maze test, and Morris water maze test were employed to assess the cognitive and executive functions. Neuronal and synaptic markers, Aβ pathology, neuroinflammation, and oxidative stress in the brains were measured. Specifically, components involved in amyloid-β (Aβ) production and degradation pathway were analyzed to explore the mechanisms underlying the therapeutic effect of TEL against Aβ pathology. The primary microglia were used to uncover the mechanisms underlying the anti-inflammatory effects of TEL in AD. Additionally, the preventive effect of TEL against AD were investigated using 4-month-old APP/PS1 mice.

RESULTS

TEL treatment ameliorated cognitive and executive impairments, neuronal and synaptic injury, Aβ pathology, neuroinflammation, and oxidative stress in APP/PS1 mice. The favorable effects of TEL on Aβ pathology were achieved by inhibiting enzymatic Aβ production and facilitating enzymatic and autophagic Aβ degradation. Meanwhile, the anti-inflammatory effects of TEL were accomplished via microglial PPARγ/NLRP3 pathway. The administration of TEL prior to symptom onset prevented AD-related cognitive decline and neuropathologies.

CONCLUSION

TEL represents a promising agent for AD prevention and treatment.

Microglial Responses to Stress-Induced Depression: Causes and Consequences

Chronic stress is a major risk factor for various psychiatric diseases, including depression; it triggers various cellular and structural changes, resulting in the alteration of neurocircuitry and subsequent development of depression. Accumulating evidence suggests that microglial cells orchestrate stress-induced depression. Preclinical studies of stress-induced depression revealed microglial inflammatory activation in regions of the brain that regulate mood. Although studies have identified several molecules that trigger inflammatory responses in microglia, the pathways that regulate stress-induced microglial activation remain unclear. Understanding the exact triggers that induce microglial inflammatory activation can help find therapeutic targets in order to treat depression. In the current review, we summarize the recent literature on possible sources of microglial inflammatory activation in animal models of chronic stress-induced depression. In addition, we describe how microglial inflammatory signaling affects neuronal health and causes depressive-like behavior in animal models. Finally, we propose ways to target the microglial inflammatory cascade to treat depressive disorders.

Catalpol Alleviates Depression by Inhibiting NLRP3 Inflammasome via TLR4/MAPK/NF-Kb Pathway

Background

We aimed to explore catalpol and NF-k. The role of antidepressant and anti-inflammatory effects of b inhibitor in depression induced by chronic unpredictable mild stress (CUMS).

Methods

Under the guidance of Qiqihar Medical University, from January 2020 to January 2021, the weight, sucrose consumption and rest time of mice during swimming were monitored, the neurobehavioral changes of rats under CUMS were used to determine the experimental model; ELISA detection of iNOS, ROS, caspase-1, IL-1 β And IL-18 expression level; Western blotting detection of TLR4, MAPK and NF-κB expression level; LPS-induced cell model. INOS, NLRP3, caspase-1, IL-1 in RT-qPCR and ELISA detection models β And IL-18 expression level; the TLR4, MAPK and NF-κB level were detected by Western blotting.

Results

CUMS can make rats lose weight, reduce sucrose consumption rate and prolong rest time. Catapol can enhance this effect; In the depression model, ROS, NLRP3, NF-κ B and iNOS were up-regulated Catalpol group MAPK, NF-κ Reduced expression of B and TLR4; ROS, caspase-1, IL-1β, IL-18 and iNOS protein increased. Cell model group TLR4, MAPK and NF-κ. The high protein content of B decreased in catalpol group.

Conclusion

Catalpol acts as anti-depressant and anti-inflammatory molecule indepression induced by CUMS. Combination of catalpol with NF-κB inhibitor might play a role in the treatment of depression through regulating the neuroinflammation.

Interplay between stress and cancer-A focus on inflammation

Stress is an integral part of life. While acute responses to stress are generally regarded as beneficial in dealing with immediate threats, chronic exposure to threatening stimuli exerts deleterious effects and can be either a contributing or an aggravating factor for many chronic diseases including cancer. Chronic psychological stress has been identified as a significant factor contributing to the development and progression of cancer, but the mechanisms that link chronic stress to cancer remain incompletely understood. Psychological stressors initiate multiple physiological responses that result in the activation of the hypothalamic-pituitary-adrenal (HPA) axis, sympathetic nervous system, and the subsequent changes in immune function. Chronic stress exposure disrupts the homeostatic communication between the neuroendocrine and immune systems, shifting immune signaling toward a proinflammatory state. Stress-induced chronic low-grade inflammation and a decline in immune surveillance are both implicated in cancer development and progression. Conversely, tumor-induced inflammatory cytokines, apart from driving a tumor-supportive inflammatory microenvironment, can also exert their biological actions distantly via circulation and therefore adversely affect the stress response. In this minireview, we summarize the current findings on the relationship between stress and cancer, focusing on the role of inflammation in stress-induced neuroendocrine-immune crosstalk. We also discuss the underlying mechanisms and their potential for cancer treatment and prevention.

Dulaglutide impedes depressive-like behavior persuaded by chronic social defeat stress model in male C57BL/6 mice: Implications on GLP-1R and cAMP/PKA signaling pathway in the hippocampus

AIM

There is a well-founded relation between bullying and depression, which may eventually lead to suicidal behavior. Repurposing of antidiabetic drugs for the treatment of depression started to glow, which open new horizons to introduce the antidiabetic medications as new treatment picks in depression. Dulaglutide has been approved as remedy of type 2 diabetes mellitus (T2DM). Consequently, our scope of work is to investigate the ability of dulaglutide to indulgence depression via deeply reconnoitering the Glucagon-like peptide-1 receptor and cAMP/PKA Signaling Pathway.

MATERIALS AND METHODS

Eighty mice were divided into two groups; one with and the other without the induction of chronic social defeat stress (CSDS). Each group was subdivided into two subsets; the first one was treated with saline for 42 days, while the other was treated with saline for 20 days, then with dulaglutide (0.6 mg/kg/week) for four weeks.

KEY FINDINGS

CSDS group showed a lessening in the social interaction ratio and sucrose consumption. They spent less exploration time in the open arms, and more time in the closed arms in elevated plus maze test as compared to controls. Furthermore, the CSDS group had a higher expression of NOD- like receptor protein-3 which explained the elevation in inflammatory biomarkers (IL-1β, IL-18, IL-6 and TNF-α) along with diminution in GLP-1R, cAMP/PKA levels. Treatment with dulaglutide markedly reversed the above-mentioned parameters via bolstering the GLP-1R/cAMP/PKA pathway.

SIGNIFICANCE

NLRP3 inflammasome activation expedites depression. Dulaglutide activates the GLP-1R/cAMP/PKA pathway, hence offering a novel therapeutic intervention to hinder depression.

NLRP3 inflammasome in depression: A review

The present article provides a detailed concept of the role of NLRP3 inflammasome in the pathophysiology of depression-like chronic diseases where inflammation and release of various cytokines plays a pivotal role in exaggerating the condition. The various pathways involved in NLRP3 activation are the main target of NLRP3 inhibitors for the therapeutic management of depression as per the recent clinical and research studies conducted so far. Further various drug inhibitors for NLRP3 available in preclinical and clinical trials have been discussed in detail. Hence, blockage of the action of NLRP3 inflammasome is crucial to anticipate the inflammatory cytokine release from the mediators that contributes to cause depression.

TRPV6 deficiency attenuates stress and corticosterone-mediated exacerbation of alcohol-induced gut barrier dysfunction and systemic inflammation

Introduction

Chronic stress is co-morbid with alcohol use disorder that feedback on one another, thus impeding recovery from both disorders. Stress and the stress hormone corticosterone aggravate alcohol-induced intestinal permeability and liver damage. However, the mechanisms involved in compounding tissue injury by stress/corticosterone and alcohol are poorly defined. Here we explored the involvement of the TRPV6 channel in stress (or corticosterone) 3and alcohol-induced intestinal epithelial permeability, microbiota dysbiosis, and systemic inflammation.

Methods

Chronic alcohol feeding was performed on adult wild-type and Trpv6-/- mice with or without corticosterone treatment or chronic restraint stress (CRS). The barrier function was determined by evaluating inulin permeability in vivo and assessing tight junction (TJ) and adherens junction (AJ) integrity by immunofluorescence microscopy. The gut microbiota composition was evaluated by 16S rRNA sequencing and metagenomic analyses. Systemic responses were assessed by evaluating endotoxemia, systemic inflammation, and liver damage.

Results

Corticosterone and CRS disrupted TJ and AJ, increased intestinal mucosal permeability, and caused endotoxemia, systemic inflammation, and liver damage in wild-type but not Trpv6-/- mice. Corticosterone and CRS synergistically potentiated the alcohol-induced breakdown of intestinal epithelial junctions, mucosal barrier impairment, endotoxemia, systemic inflammation, and liver damage in wild-type but not Trpv6-/- mice. TRPV6 deficiency also blocked the effects of CRS and CRS-mediated potentiation of alcohol-induced dysbiosis of gut microbiota.

Conclusions

These findings indicate an essential role of TRPV6 in stress, corticosterone, and alcohol-induced intestinal permeability, microbiota dysbiosis, endotoxemia, systemic inflammation, and liver injury. This study identifies TRPV6 as a potential therapeutic target for developing treatment strategies for stress and alcohol-associated comorbidity.

Lamotrigine protects against cognitive deficits, synapse and nerve cell damage, and hallmark neuropathologies in a mouse model of Alzheimer’s disease

Lamotrigine (LTG) is a widely used drug for the treatment of epilepsy. Emerging clinical evidence suggests that LTG may improve cognitive function in patients with Alzheimer’s disease. However, the underlying molecular mechanisms remain unclear. In this study, amyloid precursor protein/presenilin 1 (APP/PS1) double transgenic mice were used as a model of Alzheimer’s disease. Five-month-old APP/PS1 mice were intragastrically administered 30 mg/kg LTG or vehicle once per day for 3 successive months. The cognitive functions of animals were assessed using Morris water maze. Hyperphosphorylated tau and markers of synapse and glial cells were detected by western blot assay. The cell damage in the brain was investigated using hematoxylin and eosin staining. The levels of amyloid-β and the concentrations of interleukin-1β, interleukin-6 and tumor necrosis factor-α in the brain were measured using enzyme-linked immunosorbent assay. Differentially expressed genes in the brain after LTG treatment were analyzed by high-throughput RNA sequencing and real-time polymerase chain reaction. We found that LTG substantially improved spatial cognitive deficits of APP/PS1 mice; alleviated damage to synapses and nerve cells in the brain; and reduced amyloid-β levels, tau protein hyperphosphorylation, and inflammatory responses. High-throughput RNA sequencing revealed that the beneficial effects of LTG on Alzheimer’s disease-related neuropathologies may have been mediated by the regulation of Ptgds, Cd74, Map3k1, Fosb, and Spp1 expression in the brain. These findings revealed potential molecular mechanisms by which LTG treatment improved Alzheimer’s disease. Furthermore, these data indicate that LTG may be a promising therapeutic drug for Alzheimer’s disease.

Major depressive disorder (mdd): emerging immune targets at preclinical level

BACKGROUND

Major depressive disorder is a mental health disorder that is characterized by a persistently low mood and loss of interest. MDD is affecting over 3.8% of the global population as a major health problem. Its etiology is complex, and involves the interaction between a number of factors, including genetic predisposition and the presence of environmental stresses.

AREAS COVERED

The role of the immune and inflammatory systems in depression has been gaining interest, with evidence suggesting the potential involvement of pro-inflammatory molecules like TNF, interleukins, prostaglandins, and other cytokines, among others, has been put forth. Along with this, the potential of agents, from NSAIDs to antibiotics, are being evaluated in therapy for depression. The current review will discuss emerging immune targets at the preclinical level.

EXPERT OPINION

With increasing evidence to show that immune and inflammatory mediators are implicated in MDD, increasing research toward their potential as drug targets is encouraged. At the same time, agents acting on these mediators and possessing anti-inflammatory potential are also being evaluated as future therapeutic options for MDD, and increasing focus toward non-conventional drugs which can act through these mechanisms is important as regards the future prospects of the use of anti-inflammatory agents in depression.

The NLRP3 inflammasome in depression: Potential mechanisms and therapies

Increasing evidence suggests that the failure of clinical antidepressants may be related with neuroinflammation. The NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome is an intracellular multiprotein complex, and has been considered as a key contributor to the development of neuroinflammation. Inhibition of NLRP3 inflammasome is an effective method for depression treatment. In this review, we summarized current researches highlighting the role of NLRP3 inflammasome in the pathology of depression. Firstly, we discussed NLRP3 inflammasome activation in patients with depression and animal models. Secondly, we outlined the possible mechanisms driving the activation of NLRP3 inflammasome. Thirdly, we discussed the pathogenetic role of NLRP3 inflammasome in depression. Finally, we overviewed the current and potential antidepressants targeting the NLRP3 inflammasome. Overall, the inhibition of NLRP3 inflammasome activation may be a potential therapeutic strategy for inflammation-related depression.

NLRP3 Inflammasome: From Pathophysiology to Therapeutic Target in Major Depressive Disorder

Major depressive disorder (MDD) is a highly prevalent psychiatric disorder, whose pathophysiology has been linked to the neuroinflammatory process. The increased activity of the Nod-like receptor pyrin containing protein 3 (NLRP3) inflammasome, an intracellular multiprotein complex, is intrinsically implicated in neuroinflammation by promoting the maturation and release of proinflammatory cytokines such as interleukin (IL)-1β and IL-18. Interestingly, individuals suffering from MDD have higher expression of NLRP3 inflammasome components and proinflammatory cytokines when compared to healthy individuals. In part, intense activation of the inflammasome may be related to autophagic impairment. Noteworthy, some conventional antidepressants induce autophagy, resulting in less activation of the NLRP3 inflammasome. In addition, the fast-acting antidepressant ketamine, some bioactive compounds and physical exercise have also been shown to have anti-inflammatory properties via inflammasome inhibition. Therefore, it is suggested that modulation of inflammasome-driven pathways may have an antidepressant effect. Here, we review the role of the NLRP3 inflammasome in the pathogenesis of MDD, highlighting that pathways related to its priming and activation are potential therapeutic targets for the treatment of MDD.

The Interrelated Multifactorial Actions of Cortisol and Klotho: Potential Implications in the Pathogenesis of Parkinson's Disease

The pathogenesis of Parkinson's disease (PD) is complex, multilayered, and not fully understood, resulting in a lack of effective disease-modifying treatments for this prevalent neurodegenerative condition. Symptoms of PD are heterogenous, including motor impairment as well as non-motor symptoms such as depression, cognitive impairment, and circadian disruption. Aging and stress are important risk factors for PD, leading us to explore pathways that may either accelerate or protect against cellular aging and the detrimental effects of stress. Cortisol is a much-studied hormone that can disrupt mitochondrial function and increase oxidative stress and neuroinflammation, which are recognized as key underlying disease mechanisms in PD. The more recently discovered klotho protein, considered a general aging-suppressor, has a similarly wide range of actions but in the opposite direction to cortisol: promoting mitochondrial function while reducing oxidative stress and inflammation. Both hormones also converge on pathways of vitamin D metabolism and insulin resistance, also implicated to play a role in PD. Interestingly, aging, stress and PD associate with an increase in cortisol and decrease in klotho, while physical exercise and certain genetic variations lead to a decrease in cortisol response and increased klotho. Here, we review the interrelated opposite actions of cortisol and klotho in the pathogenesis of PD. Together they impact powerful and divergent mechanisms that may go on to influence PD-related symptoms. Better understanding of these hormones in PD would facilitate the design of effective interventions that can simultaneously impact the multiple systems involved in the pathogenesis of PD.