Keap1-Nrf2 signaling pathway confers resilience versus susceptibility to inescapable electric stress

Gut-brain axis modulation by sudachi peel extract enhances resilience to chronic social defeat stress in mice

BACKGROUND

Sudachitin, an anti-inflammatory compound from Citrus sudachi peel, may influence stress resilience. We examined whether sudachi peel extract affects depression-like behaviors and gut microbiota dysbiosis in mice subjected to chronic social defeat stress (CSDS).

METHODS

First, we examined the effect of sudachitin on depression-like behavior and plasma interleukin-6 (IL-6) levels following lipopolysaccharide (LPS, 0.5 mg/kg) administration. Next, we investigated whether supplementation with sudachi peel extract could modulate the gut microbiota dysbiosis induced by CSDS.

RESULTS

Sudachitin prevented LPS-induced depression-like behavior and the rise in plasma IL-6. In control mice, CSDS increased IL-6, induced splenomegaly, and caused anhedonia-like behavior. These changes were absent in the sudachi peel extract group. Although alpha-diversity of the gut microbiota remained abnormal under CSDS, beta-diversity was significantly altered by sudachi peel extract. Moreover, plasma IL-6 levels and Iba1 expression in the prefrontal cortex correlated with the relative abundance of certain gut bacteria.

LIMITATIONS

The exact mechanisms behind the resilience-promoting effects of sudachi peel extract remain unclear.

CONCLUSION

Sudachi peel extract supplementation enhances resilience to CSDS by preventing anhedonia, reducing plasma IL-6 levels and splenomegaly, and modulating gut microbiota composition. Further research is needed to clarify these anti-inflammatory pathways and the roles of additional pro-inflammatory cytokines.

Phytochemicals Targeting BDNF Signaling for Treating Neurological Disorders

Neurological disorders are defined by a deterioration or disruption of the nervous system's structure and function. These diseases, which include multiple sclerosis, Alzheimer's disease, Parkinson's disease, Huntington's disease, and schizophrenia, are caused by intricate pathological processes that include excitotoxicity, neuroinflammation, oxidative stress, genetic mutations, and compromised neurotrophic signaling. Although current pharmaceutical treatments relieve symptoms, their long-term efficacy is limited due to adverse side effects and weak neuroprotective properties. However, when combined with other neuroprotective drugs or adjunct therapy, they may offer additional benefits and improve treatment outcomes. Phytochemicals have emerged as attractive therapeutic agents due to their ability to regulate essential neurotrophic pathways, especially the brain-derived neurotrophic factor (BDNF) signaling cascade. BDNF is an important target for neurodegenerative disease (ND) treatment since it regulates neuronal survival, synaptic plasticity, neurogenesis, and neuroprotection. This review emphasizes the molecular pathways through which various phytochemicals-such as flavonoids, terpenoids, alkaloids, and phenolic compounds-stimulate BDNF expression and modulate its downstream signaling pathways, including GSK-3β, MAPK/ERK, PI3K/Akt/mTOR, CREB, and Wnt/β-catenin. This paper also highlights how phytochemical combinations may interact to enhance BDNF activity, offering new therapeutic options for ND treatment. Despite their potential for neuroprotection, phytochemicals face challenges related to pharmacokinetics, blood-brain barrier (BBB) permeability, and absorption, highlighting the need for further research into combination therapies and improved formulations. Clinical assessment and mechanistic understanding of BDNF-targeted phytotherapy should be the main goals of future studies. The therapeutic efficacy of natural compounds in regulating neurotrophic signaling is highlighted in this review, providing a viable approach to the prevention and treatment of NDs.

Inhalation of Curcumae Rhizoma volatile oil attenuates depression-like behaviours via activating the Nrf2 pathway to alleviate oxidative stress and improve mitochondrial dysfunction

OBJECTIVES

Curcumae Rhizoma (CR) is a traditional Chinese medicine used frequently in clinics, which contains volatile components that exhibit various active effects. This study explores the effect of Curcumae Rhizoma volatile oil (CRVO) on depressive mice and its possible mechanism of action.

METHODS

Chemical composition of CRVO was analysed by GC-MS. DPPH and ABTS free radical scavenging assays were used to evaluate the in vitro antioxidant capacity of CRVO. A chronic unpredictable mild stress (CUMS) model was used to evaluate the antidepressant effect of CRVO. The effects of CRVO on oxidative stress in vivo were investigated using Nissl staining, ELISA and transmission electron microscopy. The Nrf2/HO-1/NQO1 signalling pathway was detected by western blotting and immunofluorescence. ML385, a Nrf2 inhibitor was used to validate the effect of Nrf2 on CUMS mice with CRVO treatment.

KEY FINDINGS

Phytochemical analysis showed that CRVO is rich in its characteristic components, including curzerene (31.1%), curdione (30.56%), and germacrone (12.44%). In vivo, the administration of CRVO significantly ameliorated CUMS-induced depressive-like behaviours. In addition, inhalation of CRVO significantly alleviated the oxidative stress caused by CUMS and improved neuronal damage and mitochondrial dysfunction. The results of mechanistic studies showed that the mechanism of action is related to the Nrf2/HO-1/NQO1 pathway and the antioxidant and antidepressant effects of CRVO were weakened when ML385 was used.

CONCLUSIONS

In summary, by regulating the Nrf2 pathway, inhalation of CRVO can reduce oxidative stress in depressed mice, thereby reducing neuronal damage and mitochondrial dysfunction to alleviate depression-like behaviours. Our study offers a prospective research foundation to meet the diversity of clinical medication.

The role of BDNF transcription in the antidepressant-like effects of 18β-glycyrrhetinic acid in a chronic social defeat stress model

BACKGROUND

Xiaoyaosan (XYS), a traditional Chinese medicine formulation, has been used in the treatment of depression. However, no studies have yet identified the active compounds responsible for its antidepressant effects in the brain.

STUDY DESIGN

We investigated the antidepressants effects of XYS and identified 18β-glycyrrhetinic acid (18β-GA) as the primary compound present in the brain following XYS injection. Furthermore, we explored the molecular mechanisms underlying the antidepressant-like effects of both XYS and 18β-GA.

METHODS

To investigate the antidepressant-like effects of XYS and elucidate the associated molecular mechanisms, we employed various methodologies, including cell cultures, the chronic social defeat stress (CSDS) model, behavioral tests, immunoprecipitation, quantitative PCR (qPCR) assays, Western blotting assays, luciferase assays, chromatin immunoprecipitation (ChIP) assays, immunofluorescence staining, and dendritic spine analysis.

RESULTS

We identified 18β-GA as the primary compound in the brain following XYS injection. In vitro, 18β-GA was found to bind with ERK (extracellular signal-regulated kinase), subsequently activating ERK kinase activity toward both c-Jun and cAMP response element binding protein (CREB). Moreover, 18β-GA activated brain-derived neurotrophic factor (BDNF) transcription by stimulating nuclear factor-erythroid factor 2-related factor 2 (Nrf2), c-Jun, and CREB, while also inhibiting methyl CpG binding protein 2 (MeCP2) both in vitro and in vivo. Chronic intraperitoneal (i.p.) administration of 18β-GA exhibited prophylactic antidepressant-like effects in a CSDS model, primarily by activating BDNF transcription in the medial prefrontal cortex (mPFC). Interestingly, a single i.p. injection of 18β-GA produced rapid and sustained antidepressant-like effects in CSDS-susceptible mice by engaging the BDNF-tropomyosin receptor kinase B (TrkB) signaling pathway in the mPFC.

CONCLUSION

These findings suggest that the activation of BDNF transcription in the mPFC underlies the antidepressant-like effects of 18β-GA, a key component of XYS in the brain.

Transdiagnostic inflammatory and oxidative biomarkers with predictive capacity of self-injurious behavior in impulsive and unstable disorders

INTRODUCTION

Alterations in inflammatory processes have previously been reported in impulsive and unstable disorders, as well as in other psychiatric conditions. In order to investigate transdiagnostic biomarkers associated with various phenotypic features of these disorders, this study is designed to identify biomarkers of inflammatory and oxidative endophenotypes related to autolytic behavior.

METHODS

Peripheral blood mononuclear cells were collected from 35 patients with borderline personality disorder (BPD), 29 patients with restrictive eating disorder (rED), 21 patients with purging eating disorder (pED) and 23 control subjects. Plasma levels of different inflammatory and oxidative factors were measured by ELISA and the expression of selected proteins was by Western Blot. Principal component analysis (PCA) was performed to categorize the different inflammatory factors. Additionally, Ancova was performed to observe the differences in the principal components among the different groups and logistic regression analysis was conducted to assess the predictive capacity of these components for autolytic behaviors.

RESULTS

We found two inflammatory/oxidative components were associated with BPD, characterized by high levels of JNK and ERK and low levels of GPx, SOD and Keap1; and two other inflammatory/oxidative components were linked to pED, associated with more JNK, TBARS and TNF-α and less GPx and SOD. Two components, with more JNK and ERK and less GPx, SOD and Keap1, predicted non-suicidal self-injury and three components, with higher JNK, TBARS and TNF-α levels and lower GPx, SOD and iNOS levels, predicted suicide attempts.

CONCLUSIONS

These results strongly support the endophenotypic characterization of impulsivity and the identification of transdiagnostic inflammatory/oxidative biomarkers relevant to autolytic behavior in impulsive and unstable disorders. These dates lay the groundwork for developing of screening tests for these biomarker components to rapidly detect biological risk factors for specific impulse control disorders and future self-injurious behaviors.

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.

Chronic restraint stress induces abnormal behaviors in pain sensitivity and cognitive function in mice: the role of Keap1/Nrf2 pathway

Stress is a series of physical and psychological responses to external and internal environmental stimuli. Growing studies have demonstrated the detrimental impacts of acute restraint stress (ARS) and chronic restraint stress (CRS) on animal behavior. However, the related pathogenesis and therapeutic mechanisms remain unclear. Hence, the present study aimed to examine whether unfolded protein response (UPR) and Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid 2 related factor 2 (Nrf2) pathway are associated with ARS- and CRS- induced abnormal behaviors of pain sensitivity and cognitive function. We here used four behavioral tests to evaluate pain sensitivity and cognitive function in ARS and CRS mice. CRS markedly decreased Paw Withdrawal Mechanical Threshold (PWMT) and Tail-flick Latency (TFL) scores, whereas ARS altered TFL but had no effect on PWMT scores. Additionally, CRS, but not ARS, significantly changed behaviors in nest building behavior and MWMT. Intriguingly, the expression of Keap1 and Nrf2 protein were decreased in the spinal cord and hippocampus in CRS mice, but not in ARS mice. Moreover, neither the ARS nor the CRS groups significantly differed from the control group in terms of endoplasmic reticulum stress (ERS). Taken together, this study demonstrated that CRS could induce abnormal pain sensitivity and cognitive function probably via Keap1/Nrf2 pathway in spinal cord and hippocampus. It is therefore likely that effective intervention of Keap1/Nrf2 pathway may contribute to preventing and treating hyperalgesia and cognitive dysfunction in CRS.

Nrf2 regulates iron-dependent hippocampal synapses and functional connectivity damage in depression

Neuronal iron overload contributes to synaptic damage and neuropsychiatric disorders. However, the molecular mechanisms underlying iron deposition in depression remain largely unexplored. Our study aims to investigate how nuclear factor-erythroid 2 (NF-E2)-related factor 2 (Nrf2) ameliorates hippocampal synaptic dysfunction and reduces brain functional connectivity (FC) associated with excessive iron in depression. We treated mice with chronic unpredictable mild stress (CUMS) with the iron chelator deferoxamine mesylate (DFOM) and a high-iron diet (2.5% carbonyl iron) to examine the role of iron overload in synaptic plasticity. The involvement of Nrf2 in iron metabolism and brain function was assessed using molecular biological techniques and in vivo resting-state functional magnetic resonance imaging (rs-fMRI) through genetic deletion or pharmacologic activation of Nrf2. The results demonstrated a significant correlation between elevated serum iron levels and impaired hippocampal functional connectivity (FC), which contributed to the development of depression-induced CUMS. Iron overload plays a crucial role in CUMS-induced depression and synaptic dysfunction, as evidenced by the therapeutic effects of a high-iron diet and DFOM. The observed iron overload in this study was associated with decreased Nrf2 levels and increased expression of transferrin receptors (TfR). Notably, inhibition of iron accumulation effectively attenuated CUMS-induced synaptic damage mediated by downregulation of brain-derived neurotrophic factor (BDNF). Nrf2-/- mice exhibited compromised FC within the limbic system and the basal ganglia, particularly in the hippocampus, and inhibition of iron accumulation effectively attenuated CUMS-induced synaptic damage mediated by downregulation of brain-derived neurotrophic factor (BDNF). Activation of Nrf2 restored iron homeostasis and reversed vulnerability to depression. Mechanistically, we further identified that Nrf2 deletion promoted iron overload via upregulation of TfR and downregulation of ferritin light chain (FtL), leading to BDNF-mediated synapse damage in the hippocampus. Therefore, our findings unveil a novel role for Nrf2 in regulating iron homeostasis while providing mechanistic insights into poststress susceptibility to depression. Targeting Nrf2-mediated iron metabolism may offer promising strategies for developing more effective antidepressant therapies.

Inflammatory and oxidative endophenotypes in borderline personality disorder: A biomarker cluster analysis

OBJECTIVES

This study is designed to search for aggrupation of inflammatory/oxidative biomarker alterations in borderline personality disorder (BPD) and their association with phenotypic features.

METHODOLOGY

Inflammatory/nitrosative proteins were measures in plasma and peripheral blood mononuclear cells obtained from BPD patients. Patients were assessed on different clinical dimensions of BPD. Oxidative damage was tested by measuring TBARS, nitrites, catalase, GPx and SOD. Protein expression of IκBα, NFκB, iNOS, COX-2, PPARγ, Keap1, NQO1, Nrf2 and α7nAChR was also determined. Western blot and ELISA were used for measurements and a cluster analysis of inflammatory/oxidative biomarkers alterations was performed to investigate subgroups of patients with similar alterations and its relationship with clinical features of BPD.

RESULTS

69 patients were included in the study. Two inflammatory/nitrosative clusters of patients were found: Cluster 1 patients showed significantly higher levels of GPx, IκBα, keap1, NQO1, PPARγ, α7nAChR and Nrf2 than cluster 2 patients. These patients had significantly longer duration of illness, milder anxiety symptoms and lower prescription of antipsychotic drugs than cluster 2.

CONCLUSIONS

Two clusters of BPD patients according to the inflammatory/nitrosative profiles were identified. Cluster 1 had increased antioxidant and anti-inflammatory biomarkers and was characterised by greater chronicity of illness but less acute symptomatic severity.

NRF2, KEAP1 and GSK-3 levels in autism spectrum disorder: a case control study

Recent studies show that oxidative stress has an important role in the etiology of autism. In our study, Nrf2, which is the main regulator of cellular antioxidant response, and Keap1 and Gsk-3β, which are the main proteins that regulate this pathway, were compared between children with autism and healthy controls. To the best of our knowledge, our study is the first in which Nrf2, Keap1 and Gsk-3β levels were evaluated together in children with ASD. In our study, Nrf2 level was found to be lower and Keap1 level higher in children with autism. Although GSK-3β is increased in many psychiatric and neurodegenerative diseases, it was found to be low in the autistic group in accordance with the literature. In conclusion, considering the versatile modulation of the Nrf2 pathway, this article does not provide any mechanistic insight into the pathway, but it suggests that Nrf2, Keap1 and Gsk-3β, which have central roles in oxidative stress, may play a role in the pathophysiology of autism.

Nrf2: An all-rounder in depression

The balance between oxidation and antioxidant is crucial for maintaining homeostasis. Once disrupted, it can lead to various pathological outcomes and diseases, such as depression. Oxidative stress can result in or aggravate a battery of pathological processes including mitochondrial dysfunction, neuroinflammation, autophagical disorder and ferroptosis, which have been found to be involved in the development of depression. Inhibition of oxidative stress and related pathological processes can help improve depression. In this regard, the nuclear factor erythroid 2-related factor 2 (Nrf2) in the antioxidant defense system may play a pivotal role. Nrf2 activation can not only regulate the expression of a series of antioxidant genes that reduce oxidative stress and its damages, but also directly regulate the genes related to the above pathological processes to combat the corresponding alterations. Therefore, targeting Nrf2 has great potential for the treatment of depression. Activation of Nrf2 has antidepressant effect, but the specific mechanism remains to be elucidated. This article reviews the key role of Nrf2 in depression, focusing on the possible mechanisms of Nrf2 regulating oxidative stress and related pathological processes in depression treatment. Meanwhile, we summarize some natural and synthetic compounds targeting Nrf2 in depression therapy. All the above may provide new insights into targeting Nrf2 for the treatment of depression and provide a broad basis for clinical transformation.

Nrf2 regulates the arginase 1+ microglia phenotype through the initiation of TREM2 transcription, ameliorating depression-like behavior in mice

The expression of the triggering receptor on myeloid cell-2 (TREM2) knockdown in microglia from the lateral habenula (LHb) reportedly induces depression-like behaviors in mice. However, the key molecular mechanism that mediates major depressive disorder (MDD) pathogenesis remains elusive. We herein show that Nrf2 regulates TREM2 transcription and effects TREM2 mRNA and protein expression. The activation of Nrf2 by sulforaphane (Nrf2 activator) increases the microglial arginase 1⁺ phenotype by initiating TREM2 transcription in the medial prefrontal cortex (mPFC) and ameliorates depression-like behavior in CSDS mice. The knockout of Nrf2 decreases TREM2 and the microglial arginase 1⁺ phenotype in the mPFC of Nrf2 KO mice with depression-like behavior. Downregulating TREM2 expression decreases the microglial arginase 1⁺ phenotype in the mPFC, resulting in depression-like behavior in SFN-treated CSDS mice. Finally, the knockout of Nrf2 and downregulation of TREM2 expression decreases the microglial arginase 1⁺ phenotype in the mPFC of Nrf2 KO mice and SFN-treated CSDS mice were associated with the brain-derived neurotrophic factor (BDNF)-tropomyosin receptor kinase B (TrkB) signaling pathway. These data indicate that alterations in the interaction between Nrf2 and TREM2 may play a role in the pathophysiology of depression-like behavior in mice.

The role of MeCP2 and the BDNF/TrkB signaling pathway in the stress resilience of mice subjected to CSDS

RATIONALE

There is accumulating evidence to support the idea that brain-derived neurotrophic factor (BDNF) is involved in stress resilience. However, the precise molecular mechanisms underlying resilience in major depressive disorder (MDD) remain unknown.

OBJECTIVE

The objective of this study was to explore the role of methyl CpG binding protein 2 (MeCP2) and the BDNF/tropomyosin-receptor-kinase B (TrkB) signaling pathway in the stress resilience to chronic social defeat stress (CSDS) in mice.

RESULTS

We found that the overexpression of MeCP2 inhibited BDNF transcription, resulting in BDNF mRNA and protein downregulation in neuro-2a cells. The overexpression of MeCP2 increased S80-MeCP2 and decreased S421-MeCP2, BDNF, the ratio of S133-cyclic AMP response element binding protein (CREB)/CREB and p-TrkB/TrkB expression in neuro-2a cells. In addition, using the CSDS mouse model, we found that MeCP2 mRNA levels were decreased in the medial prefrontal cortex (mPFC) of resilient mice and increased in the hippocampus of susceptible mice. BDNF exon IV promoter and BDNF mRNA levels were decreased in the mPFC and hippocampus of susceptible mice. Finally, MeCP2 and S80-MeCP2 protein levels were increased in the mPFC and hippocampus of susceptible mice, whereas the protein expression of S421-MeCP2 and BDNF, the ratio of S133-CREB/CREB, and the levels of p-TrkB/TrkB were decreased in susceptible mice.

CONCLUSIONS

These data suggest that the overexpression of MeCP2 inhibits BDNF transcription in neuro-2a cells. The inhibition of MeCP2 expression and activation of the BDNF/TrkB signaling pathway may confer stress resilience in CSDS mice.

Long-lasting beneficial effects of maternal intake of sulforaphane glucosinolate on gut microbiota in adult offspring

Mounting evidence suggests the impact of maternal diet on the health of offspring. We reported that maternal diet of sulforaphane glucosinolate (SGS) could prevent behavioral abnormalities in offspring after maternal immune activation. The present study was designed to investigate whether the dietary intake of SGS during pregnancy and lactation influences the composition of gut microbiota in the offspring. The dietary intake of SGS during pregnancy and lactation caused significant changes in the α-diversity and β-diversity of gut microbiota in 3-week-old offspring (SGS-3W group) and 10-week-old offspring (SGS-10W group). The LEfSe algorithm identified several microbes as important phylotypes in the SGS-3W or SGS-10W groups. Predictive functional metagenomes showed that the maternal intake of SGS caused several KEGG pathways alterations with respect to the genetic information processing and metabolism. Furthermore, the plasma levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in the SGS-10W group after the injection of lipopolysaccharide (LPS: 0.5 mg/kg) were significantly lower than those of the CON-10W group. It is noteworthy that there were positive correlations between the relative abundance of the genus Blautia and IL-6 (or TNF-α) in adult offspring. Moreover, there were sex differences of gut microbiota composition in offspring. In conclusion, these data suggest that the dietary intake of SGS during pregnancy and lactation might produce long-lasting beneficial effects in adult offspring through the persistent modulation of gut microbiota. It is likely that the modulation of gut microbiota by maternal nutrition may confer resilience versus vulnerability to stress-related psychiatric disorders in the offspring.

Regulation of BDNF transcription by Nrf2 and MeCP2 ameliorates MPTP-induced neurotoxicity

Mounting evidence suggests the key role of brain-derived neurotrophic factor (BDNF) in the dopaminergic neurotoxicity of Parkinson’s disease (PD). Activation of NF-E2-related factor-2 (Nrf2) and inhibition of methyl CpG-binding protein 2 (MeCP2) can regulate BDNF upregulation. However, the regulation of BDNF by Nrf2 and MeCP2 in the PD pathogenesis has not been reported. Here, we revealed that Nrf2/MeCP2 coordinately regulated BDNF transcription, reversing the decreased levels of BDNF expression in 1-methyl-4-phenylpyridinium (MPP⁺)-treated SH-SY5Y cells and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice. Repeated administration of sulforaphane (SFN, an Nrf2 activator) attenuated dopaminergic neurotoxicity in MPTP-treated mice through activation of BDNF and suppression of MeCP2 expression. Furthermore, intracerebroventricular injection of MeCP2-HDO, a DNA/RNA heteroduplex oligonucleotide (HDO) silencing MeCP2 expression, ameliorated dopaminergic neurotoxicity in MPTP-treated mice via activation of Nrf2 and BDNF expression. Moreover, we found decreased levels of Nrf2 and BDNF, and increased levels of MeCP2 protein expression in the striatum of patients with dementia with Lewy bodies (DLB). Interesting, there were correlations between BDNF and Nrf2 (or MeCP2) expression in the striatum from DLB patients. Therefore, it is likely that the activation of BDNF transcription by activation of Nrf2 and/or suppression of MeCP2 could be a new therapeutic approach for PD.

Biological mechanisms and clinical efficacy of sulforaphane for mental disorders

Current clinical management of major mental disorders, such as autism spectrum disorder, depression and schizophrenia, is less than optimal. Recent scientific advances have indicated that deficits in oxidative and inflammation systems are extensively involved in the pathogenesis of these disorders. These findings have led to expanded considerations for treatment. Sulforaphane (SFN) is a dietary phytochemical extracted from cruciferous vegetables. It is an effective activator of the transcription factor nuclear erythroid-2 like factor-2, which can upregulate multiple antioxidants and protect neurons against various oxidative damages. On the other hand, it can also significantly reduce inflammatory response to pathological states and decrease the damage caused by the immune response via the nuclear factor-κB pathway and other pathways. In this review, we introduce the biological mechanisms of SFN and the pilot evidence from its clinical trials of major mental disorders, hoping to promote an increase in psychiatric clinical studies of SFN.

Targeting NRF2 in Type 2 diabetes mellitus and depression: Efficacy of natural and synthetic compounds

Evidence supports a strong bidirectional association between depression and Type 2 diabetes mellitus (T2DM). The harmful impact of oxidative stress and chronic inflammation on the development of both disorders is widely accepted. Nuclear factor erythroid 2-related factor 2 (NRF2) is a pertinent target in disease management owing to its reputation as the master regulator of antioxidant responses. NRF2 influences the expression of various cytoprotective phase 2 antioxidant genes, which is hampered in both depression and T2DM. Through interaction and crosstalk with several signaling pathways, NRF2 endeavors to contain the widespread oxidative damage and persistent inflammation involved in the pathophysiology of depression and T2DM. NRF2 promotes the neuroprotective and insulin-sensitizing properties of its upstream and downstream targets, thereby interrupting and preventing disease advancement. Standard antidepressant and antidiabetic drugs may be powerful against these disorders, but unfortunately, they come bearing distressing side effects. Therefore, exploiting the therapeutic potential of NRF2 activators presents an exciting opportunity to manage such bidirectional and comorbid conditions.

Sulforaphane activates anti-inflammatory microglia, modulating stress resilience associated with BDNF transcription

Sulforaphane (SFN) is an organic isothiocyanate and an NF-E2-related factor-2 (Nrf2) inducer that exerts prophylactic effects on depression-like behavior in mice. However, the underlying mechanisms remain poorly understood. Brain-derived neurotrophic factor (BDNF), a neurotrophin, is widely accepted for its antidepressant effects and role in stress resilience. Here, we show that SFN confers stress resilience via BDNF upregulation and changes in abnormal dendritic spine morphology in stressed mice, which is accompanied by rectifying the irregular levels of inflammatory cytokines. Mechanistic studies demonstrated that SFN activated Nrf2 to promote BDNF transcription by binding to the exon I promoter, which is associated with increased Nrf2, and decreased methyl-CpG binding protein-2 (MeCP2), a transcriptional suppressor of BDNF, in BV2 microglial cells. Furthermore, SFN inhibited the pro-inflammatory phenotype and activated the anti-inflammatory phenotype of microglia, which was associated with increased Nrf2 and decreased MeCP2 expression in microglia of stressed mice. Hence, our findings support that Nrf2 induces BDNF transcription via upregulation of Nrf2 and downregulation of MeCP2 in microglia, which is associated with changes in the morphology of damaged dendritic spines in stressed mice. Meanwhile, the data presented here provide evidence for the application of SFN as a candidate for the prevention and intervention of depression.

Inflammation and Nitro-oxidative Stress as Drivers of Endocannabinoid System Aberrations in Mood Disorders and Schizophrenia

The endocannabinoid system (ECS) is composed of the endocannabinoid ligands anandamide (AEA) and 2-arachidonoylgycerol (2-AG), their target cannabinoid receptors (CB₁ and CB₂) and the enzymes involved in their synthesis and metabolism (N-acyltransferase and fatty acid amide hydrolase (FAAH) in the case of AEA and diacylglycerol lipase (DAGL) and monoacylglycerol lipase (MAGL) in the case of 2-AG). The origins of ECS dysfunction in major neuropsychiatric disorders remain to be determined, and this paper explores the possibility that they may be associated with chronically increased nitro-oxidative stress and activated immune-inflammatory pathways, and it examines the mechanisms which might be involved. Inflammation and nitro-oxidative stress are associated with both increased CB₁ expression, via increased activity of the NADPH oxidases NOX4 and NOX1, and increased CNR1 expression and DNA methylation; and CB₂ upregulation via increased pro-inflammatory cytokine levels, binding of the transcription factor Nrf2 to an antioxidant response element in the CNR2 promoter region and the action of miR-139. CB₁ and CB₂ have antagonistic effects on redox signalling, which may result from a miRNA-enabled negative feedback loop. The effects of inflammation and oxidative stress are detailed in respect of AEA and 2-AG levels, via effects on calcium homeostasis and phospholipase A₂ activity; on FAAH activity, via nitrosylation/nitration of functional cysteine and/or tyrosine residues; and on 2-AG activity via effects on MGLL expression and MAGL. Finally, based on these detailed molecular neurobiological mechanisms, it is suggested that cannabidiol and dimethyl fumarate may have therapeutic potential for major depressive disorder, bipolar disorder and schizophrenia.

Recent Reports on Redox Stress-Induced Mitochondrial DNA Variations, Neuroglial Interactions, and NMDA Receptor System in Pathophysiology of Schizophrenia

Schizophrenia (SZ) is a chronic psychiatric disorder affecting several people worldwide. Mitochondrial DNA (mtDNA) variations could invoke changes in the OXPHOS system, calcium buffering, and ROS production, which have significant implications for glial cell survival during SZ. Oxidative stress has been implicated in glial cells-mediated pathogenesis of SZ; the brain comparatively more prone to oxidative damage through NMDAR. A confluence of scientific evidence points to mtDNA alterations, Nrf2 signaling, dynamic alterations in dorsolateral prefrontal cortex (DLPFC), and provocation of oxidative stress that enhance pathophysiology of SZ. Furthermore, the alterations in excitatory signaling related to NMDAR signaling were particularly reported for SZ pathophysiology. Current review reported the recent evidence for the role of mtDNA variations and oxidative stress in relation to pathophysiology of SZ, NMDAR hypofunction, and glutathione deficiency. NMDAR system is influenced by redox dysregulation in oxidative stress, inflammation, and antioxidant mediators. Several studies have demonstrated the relationship of these variables on severity of pathophysiology in SZ. An extensive literature search was conducted using Medline, PubMed, PsycINFO, CINAHL PLUS, BIOSIS Preview, Google scholar, and Cochrane databases. We summarize consistent evidence pointing out a plausible model that may elucidate the crosstalk between mtDNA alterations in glial cells and redox dysregulation during oxidative stress and the perturbation of NMDA neurotransmitter system during current therapeutic modalities for the SZ treatment. This review can be beneficial for the development of promising novel diagnostics, and therapeutic modalities by ascertaining the mtDNA variations, redox state, and efficacy of pharmacological agents to mitigate redox dysregulation and augment NMDAR function to treat cognitive and behavioral symptoms in SZ.

Importance of oxidative stress in the pathogenesis, diagnosis, and monitoring of patients with neuropsychiatric disorders, a review

Oxidative stress is defined as the persistent imbalance between the activity of toxic reactive forms of both oxygen and nitrogen and the antioxidant defense. In low concentrations, they are essential for the proper functioning of the body. Still, their excessive amount contributes to the damage of the biomolecules, consequently leading to various pathologies of the organism. Due to the lipid-rich brain structure, enormous oxygen consumption, and the lack of a sufficient antioxidant barrier make it highly susceptible to oxidative imbalance. Hence, oxidative stress has been linked to various psychiatric disorders. These diseases include all behavioral, emotional, and cognitive abnormalities associated with a significant impediment to social life. Each of the diseases in question: Alzheimer's disease, schizophrenia, depression, and bipolar disorder, is characterized by excessive oxidative stress. Considerable damages to DNA, RNA, proteins, lipids, and mitochondrial dysfunction, are observed. All conditions show increased lipid peroxidation, which appears to be typical of psychiatric disorders because the brain contains large amounts of these types of molecules. In addition, numerous abnormalities in the antioxidant defense are noted, but the results of studies on the activity of antioxidant enzymes differ significantly. The most promising biomarkers seem to be GSH in Alzheimer's disease as an early-stage marker of the disease and thioredoxin in schizophrenia as a marker for therapy monitoring. Data from the literature are consistent with the decrease in antioxidants such as vitamin C, E, uric acid, albumin, etc. Despite these numerous inconsistencies, it seems that oxidative stress is present in the course of psychiatric diseases. Still, it cannot be conclusively determined whether it is the direct cause of development, a consequence of other abnormalities at the biochemical or molecular level, or the result of the disease itself.

Andrographolide improves PCP-induced schizophrenia-like behaviors through blocking interaction between NRF2 and KEAP1

Schizophrenia is one of the foremost psychological illness around the world, and recent evidence shows that inflammation and oxidative stress may play a critical role in the etiology of schizophrenia. Andrographolide is a diterpenoid lactone from Andrographis paniculate, which has shown anti-inflammation and anti-oxidative effects. In this study, we explored whether andrographolide can improve schizophrenia-like behaviors through its inhibition of inflammation and oxidative stress in Phencyclidine (PCP)-induced mouse model of schizophrenia. We found that abnormal behavioral including locomotor activity, forced swimming and novel object recognition were ameliorated following andrographolide administration (5 mg/kg and 10 mg/kg). Andrographolide inhibited PCP-induced production of inflammatory cytokines, decreased p-p65, p-IκBα, p-p38 and p-ERK1/2 in the prefrontal cortex. Andrographolide significantly declined the level of MDA and GSH, as well as elevated the activity of SOD, CAT and GCH-px. In addition, andrographolide increased expression of NRF-2, HO-1 and NQO-1, promoted nuclear translocation of NRF-2 through blocking the interaction between NRF-2 and KEAP1, which may be associated with directly binding to NRF-2. Furthermore, antioxidative effects and anti-schizophrenia-like behaviors of andrographolide were compromised by the application of NRF-2 inhibitor ML385. In conclusion, these results suggested that andrographolide improved oxidative stress and schizophrenia-like behaviors induced by PCP through increasing NRF-2 pathway.

Exposure to footshock stress downregulates antioxidant genes and increases neuronal apoptosis in an Aβ(1-42) rat model of Alzheimer's disease

Post-traumatic stress disorder (PTSD) is a neuropsychiatric disorder that develops from exposure to trauma, mostly when normal psychological mechanisms fail. Studies have shown that people who have PTSD are susceptible to developing dementia, mostly Alzheimer's disease (AD), suggesting common underlying risk factors in the comorbidity. However, data elucidating links between these conditions is scarce. Here we show that footshock stress exacerbates AD-like pathology. To induce a trauma-like condition, the rats were exposed to multiple intense footshocks followed by a single reminder. This was followed by bilateral intrahippocampal lesions with amyloid-beta (Aβ) (1-42), to model AD-like pathology. We found that footshocks increased anxiety behavior and impaired fear memory extinction in Aβ(1-42) lesioned rats. We also found a reduced expression of nuclear factor erythroid 2-related factor 2 (Nrf2), NAD (P) H: quinone oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1), and an increased expression of Kelch-like ECH-associated protein 1 (Keap1) in the amygdala and hippocampus. Furthermore, oxidative stress level was sustained, which was associated with increased apoptosis in the amygdala and hippocampus. Our finding suggests that AD-like pathology can induce oxidative changes in the amygdala and hippocampus, which can be exaggerated by footshock stress.

Polyphenols as adjunctive treatments in psychiatric and neurodegenerative disorders: Efficacy, mechanisms of action, and factors influencing inter-individual response

The pathophysiology of psychiatric and neurodegenerative disorders is complex and multifactorial. Polyphenols possess a range of potentially beneficial mechanisms of action that relate to the implicated pathways in psychiatric and neurodegenerative disorders. The aim of this review is to highlight the emerging clinical trial and preclinical efficacy data regarding the role of polyphenols in mental and brain health, elucidate novel mechanisms of action including the gut microbiome and gene expression, and discuss the factors that may be responsible for the mixed clinical results; namely, the role of interindividual differences in treatment response and the potentially pro-oxidant effects of some polyphenols. Further clarification as part of larger, well conducted randomized controlled trials that incorporate precision medicine methods are required to inform clinical efficacy and optimal dosing regimens.

The regulation of animal behavior by cellular stress responses

Cellular stress responses exist to detect the effects of stress on cells, and to activate protective mechanisms that promote resilience. As well as acting at the cellular level, stress response pathways can also regulate whole organism responses to stress. One way in which animals facilitate their survival in stressful environments is through behavioral adaptation; this review considers the evidence that activation of cellular stress responses plays an important role in mediating the changes to behavior that promote organismal survival upon stress.

Minocycline inhibits sleep deprivation-induced aberrant microglial activation and Keap1-Nrf2 expression in mouse hippocampus

Sleep deprivation (SD) is a hallmark of modern society and associated with many neuropsychiatric disorders, including depression and anxiety. However, the cellular and molecular mechanisms underlying SD-associated depression and anxiety remain elusive. Does the neuroinflammation play a role in mediating the effects of SD? In this study, we investigated SD-induced cellular and molecular alterations in the hippocampus and asked whether treatment with an anti-inflammatory drug, minocycline, could attenuate these alterations. We found that SD animals exhibit activated microglia and decreased levels of Keap1 and Nrf2 (antioxidant and anti-inflammatory factors) in the hippocampus. In vivo local field potential recordings show decreased theta and beta oscillations, but increased high gamma oscillations, as a result of SD. Behavioral analysis revealed increased immobility time in the forced swim and tail suspension tests, and decreased sucrose intake in SD mice, all indicative of depressive-like behavior. Moreover, open field test and elevated plus maze test results indicated that SD increases anxiety-like behavior. Interestingly, treatment with the microglial modulator minocycline prevented SD-induced microglial activation, restored Keap1 and Nrf2 levels, normalized neuronal oscillations, and alleviated depressive-like and anxiety-like behavior. The present study reveals that microglial activation and Keap1-Nrf2 signaling play a crucial role in SD-induced behavioral alteration, and that minocycline treatment has a protective effect on these alterations.

Rapid-acting and long-lasting antidepressant-like action of (R)-ketamine in Nrf2 knock-out mice: a role of TrkB signaling

The transcription nuclear factor-erythroid factor 2-related factor 2 (Nrf2) plays a key role in inflammation that is involved in depression. We previously reported that Nrf2 knock-out (KO) mice exhibit depression-like phenotypes through systemic inflammation. (R)-ketamine, an enantiomer of ketamine, has rapid-acting and long-lasting antidepressant-like effects in rodents. We investigated whether (R)-ketamine can produce antidepressant-like effects in Nrf2 KO mice. Effects of (R)-ketamine on the depression-like phenotypes in Nrf2 KO mice were examined. Furthermore, the role of TrkB in the antidepressant-like actions of (R)-ketamine was also examined. In the tail-suspension test (TST) and forced swimming test (FST), (R)-ketamine (10 mg/kg) significantly attenuated the increased immobility times of TST and FST in the Nrf2 KO mice. In the sucrose preference test (SPT), (R)-ketamine significantly ameliorated the reduced preference of SPT in Nrf2 KO mice. Decreased expression of synaptic proteins (i.e., GluA1 and PSD-95) in the medial prefrontal cortex (mPFC) of Nrf2 KO mice was significantly ameliorated after a single injection of (R)-ketamine. Furthermore, the pre-treatment with the TrkB antagonist ANA-12 (0.5 mg/kg) significantly blocked the rapid and long-lasting antidepressant-like effects of (R)-ketamine in Nrf2 KO mice. Furthermore, ANA-12 significantly antagonized the beneficial effects of (R)-ketamine on decreased expression of synaptic proteins in the mPFC of Nrf2 KO mice. These findings suggest that (R)-ketamine can produce rapid and long-lasting antidepressant-like actions in Nrf2 KO mice via TrkB signaling.

Understanding the role of the cytoprotective transcription factor nuclear factor erythroid 2-related factor 2-lessons from evolution, the animal kingdom and rare progeroid syndromes

The cytoprotective transcriptor factor nuclear factor erythroid 2– related factor 2 (NRF2) is part of a complex regulatory network that responds to environmental cues. To better understand its role in a cluster of inflammatory and pro-oxidative burden of lifestyle diseases that accumulate with age, lessons can be learned from evolution, the animal kingdom and progeroid syndromes. When levels of oxygen increased in the atmosphere, mammals required ways to protect themselves from the metabolic toxicity that arose from the production of reactive oxygen species. The evolutionary origin of the NRF2–Kelch-like ECH-associated protein 1 (KEAP1) signalling pathway from primitive origins has been a prerequisite for a successful life on earth, with checkpoints in antioxidant gene expression, inflammation, detoxification and protein homoeostasis. Examples from the animal kingdom suggest that superior antioxidant defense mechanisms with enhanced NRF2 expression have been developed during evolution to protect animals during extreme environmental conditions, such as deep sea diving, hibernation and habitual hypoxia. The NRF2–KEAP1 signalling pathway is repressed in progeroid (accelerated ageing) syndromes and a cluster of burden of lifestyle disorders that accumulate with age. Compelling links exist between tissue hypoxia, senescence and a repressed NRF2 system. Effects of interventions that activate NRF2, including nutrients, and more potent (semi)synthetic NRF2 agonists on clinical outcomes are of major interest. Given the broad-ranging actions of NRF2, we need to better understand the mechanisms of activation, biological function and regulation of NRF2 and its inhibitor, KEAP1, in different clinical conditions to ensure that modulation of this thiol-based system will not result in major adverse effects. Lessons from evolution, the animal kingdom and conditions of accelerated ageing clarify a major role of a controlled NRF2–KEAP1 system in healthy ageing and well-being.

The Nrf2 pathway in psychiatric disorders: pathophysiological role and potential targeting

Introduction: All psychiatric disorders exhibit excitotoxicity, mitochondrial dysfunction, inflammation, oxidative stress, and neural damage as their common characteristic. The endogenous nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway is implicated in the defense mechanism against oxidative stress and has a significant role in psychiatric disorders.Areas covered: We explore the role of Nrf2 pathway and its modulators in psychiatric disorders. The literature was searched utilizing various databases such as Embase, Medline, Web of Science, Pub-Med, and Google Scholar from 2010 to 2020. The search included research articles, clinical reports, systematic reviews, and meta-analyses.Expert opinion: Environmental factors and genetic predisposition can be a trigger for the development of psychiatric disorders. Nrf2 downregulates certain inflammatory pathways and upregulates various antioxidant enzymes to maintain a balance. However, its intricate balance with NF-Kβ (Nuclear factor kappa light chain enhancer of activated B cells) and its crosstalk with the transcription factor Nrf2 is critical in severe oxidative stress. Several Nrf2 modulators are now in clinical trials and can help reduce oxidative stress and neuroinflammation. There are immense potential opportunities for these modulators to become a novel therapeutic option.

Activation of BDNF by transcription factor Nrf2 contributes to antidepressant-like actions in rodents

The transcription factor erythroid 2-related factor 2 (Nrf2) and brain-derived neurotrophic factor (BDNF) play a key role in depression. However, the molecular mechanisms underlying the crosstalk between Nrf2 and BDNF in depression remain unclear. We examined whether Nrf2 regulates the transcription of Bdnf by binding to its exon I promoter. Furthermore, the role of Nrf2 and BDNF in the brain regions from mice with depression-like phenotypes was examined. Nrf2 regulated the transcription of Bdnf by binding to its exon I promoter. Activation of Nrf2 by sulforaphane (SFN) showed fast-acting antidepressant-like effects in mice by activating BDNF as well as by inhibiting the expression of its transcriptional repressors (HDAC2, mSin3A, and MeCP2) and revising abnormal synaptic transmission. In contrast, SFN did not affect the protein expression of BDNF and its transcriptional repressor proteins in the medial prefrontal cortex (mPFC) and hippocampus, nor did it reduce depression-like behaviors and abnormal synaptic transmission in Nrf2 knockout mice. In the mouse model of chronic social defeat stress (CSDS), protein levels of Nrf2 and BDNF in the mPFC and hippocampus were lower than those of control and CSDS-resilient mice. In contrast, the protein levels of BDNF transcriptional repressors in the CSDS-susceptible mice were higher than those of control and CSDS-resilient mice. These data suggest that Nrf2 activation increases the expression of Bdnf and decreases the expression of its transcriptional repressors, which result in fast-acting antidepressant-like actions. Furthermore, abnormalities in crosstalk between Nrf2 and BDNF may contribute to the resilience versus susceptibility of mice against CSDS.

Oxidative Stress-Related Mechanisms in Schizophrenia Pathogenesis and New Treatment Perspectives

Schizophrenia is recognized to be a highly heterogeneous disease at various levels, from genetics to clinical manifestations and treatment sensitivity. This heterogeneity is also reflected in the variety of oxidative stress-related mechanisms contributing to the phenotypic realization and manifestation of schizophrenia. At the molecular level, these mechanisms are supposed to include genetic causes that increase the susceptibility of individuals to oxidative stress and lead to gene expression dysregulation caused by abnormal regulation of redox-sensitive transcriptional factors, noncoding RNAs, and epigenetic mechanisms favored by environmental insults. These changes form the basis of the prooxidant state and lead to altered redox signaling related to glutathione deficiency and impaired expression and function of redox-sensitive transcriptional factors (Nrf2, NF-κB, FoxO, etc.). At the cellular level, these changes lead to mitochondrial dysfunction and metabolic abnormalities that contribute to aberrant neuronal development, abnormal myelination, neurotransmitter anomalies, and dysfunction of parvalbumin-positive interneurons. Immune dysfunction also contributes to redox imbalance. At the whole-organism level, all these mechanisms ultimately contribute to the manifestation and development of schizophrenia. In this review, we consider oxidative stress-related mechanisms and new treatment perspectives associated with the correction of redox imbalance in schizophrenia. We suggest that not only antioxidants but also redox-regulated transcription factor-targeting drugs (including Nrf2 and FoxO activators or NF-κB inhibitors) have great promise in schizophrenia. But it is necessary to develop the stratification criteria of schizophrenia patients based on oxidative stress-related markers for the administration of redox-correcting treatment.

Molecular pathology associated with altered synaptic transcriptome in the dorsolateral prefrontal cortex of depressed subjects

Disrupted synaptic plasticity is the hallmark of major depressive disorder (MDD), with accompanying changes at the molecular and cellular levels. Often, the maladaptive molecular changes at the synapse are the result of global transcriptional reprogramming dictated by activity-dependent synaptic modulation. Thus far, no study has directly studied the transcriptome-wide expression changes locally at the synapse in MDD brain. Here, we have examined altered synaptic transcriptomics and their functional relevance in MDD with a focus on the dorsolateral prefrontal cortex (dlPFC). RNA was isolated from total fraction and purified synaptosomes of dlPFC from well-matched 15 non-psychiatric controls and 15 MDD subjects. Transcriptomic changes in synaptic and total fractions were detected by next-generation RNA-sequencing (NGS) and analyzed independently. The ratio of synaptic/total fraction was estimated to evaluate a shift in gene expression ratio in MDD subjects. Bioinformatics and network analyses were used to determine the biological relevance of transcriptomic changes in both total and synaptic fractions based on gene-gene network, gene ontology (GO), and pathway prediction algorithms. A total of 14,005 genes were detected in total fraction. A total of 104 genes were differentially regulated (73 upregulated and 31 downregulated) in MDD group based on 1.3-fold change threshold and p < 0.05 criteria. In synaptosomes, out of 13,236 detectable genes, 234 were upregulated and 60 were downregulated (>1.3-fold, p < 0.05). Several of these altered genes were validated independently by a quantitative polymerase chain reaction (qPCR). GO revealed an association with immune system processes and cell death. Moreover, a cluster of genes belonged to the nervous system development, and psychological disorders were discovered using gene-gene network analysis. The ratio of synaptic/total fraction showed a shift in expression of 119 genes in MDD subjects, which were primarily associated with neuroinflammation, interleukin signaling, and cell death. Our results suggest not only large-scale gene expression changes in synaptosomes, but also a shift in the expression of genes from total to synaptic fractions of dlPFC of MDD subjects with their potential role in immunomodulation and cell death. Our findings provide new insights into the understanding of transcriptomic regulation at the synapse and their possible role in MDD pathogenesis.

Increasing Nrf2 Activity as a Treatment Approach in Neuropsychiatry

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor encoded by NFE2L2. Under oxidative stress, Nrf2 does not undergo its normal cytoplasmic degradation but instead travels to the nucleus, where it binds to a DNA promoter and initiates transcription of anti-oxidative genes. Nrf2 upregulation is associated with increased cellular levels of glutathione disulfide, glutathione peroxidase, glutathione transferases, thioredoxin and thioredoxin reductase. Given its key role in governing the cellular antioxidant response, upregulation of Nrf2 has been suggested as a common therapeutic target in neuropsychiatric illnesses such as major depressive disorder, bipolar disorder and schizophrenia, which are associated with chronic oxidative and nitrosative stress, characterised by elevated levels of reactive oxygen species, nitric oxide and peroxynitrite. These processes lead to extensive lipid peroxidation, protein oxidation and carbonylation, and oxidative damage to nuclear and mitochondrial DNA. Intake of N-acetylcysteine, coenzyme Q₁₀ and melatonin is accompanied by increased Nrf2 activity. N-acetylcysteine intake is associated with improved cerebral mitochondrial function, decreased central oxidative and nitrosative stress, reduced neuroinflammation, alleviation of endoplasmic reticular stress and suppression of the unfolded protein response. Coenzyme Q₁₀, which acts as a superoxide scavenger in neuroglial mitochondria, instigates mitohormesis, ameliorates lipid peroxidation in the inner mitochondrial membrane, activates uncoupling proteins, promotes mitochondrial biogenesis and has positive effects on the plasma membrane redox system. Melatonin, which scavenges mitochondrial free radicals, inhibits mitochondrial nitric oxide synthase, restores mitochondrial calcium homeostasis, deacetylates and activates mitochondrial SIRT3, ameliorates increased permeability of the blood-brain barrier and intestine and counters neuroinflammation and glutamate excitotoxicity.

Inflammation in Bipolar Disorder (BD): Identification of new therapeutic targets

Bipolar disorder (BD) is a chronic and cyclic mental disorder, characterized by unusual mood swings between mania/hypomania and depression, raising concern in both scientific and medical communities due to its deleterious social and economic impact. Polypharmacy is the rule due to the partial effectiveness of available drugs. Disease course is often unremitting, resulting in frequent cognitive deficits over time. Despite all research efforts in identifying BD-associated molecular mechanisms, current knowledge remains limited. However, the involvement of inflammation in BD pathophysiology is increasingly consensual, with the immune system and neuroinflammation playing a key role in disease course. Evidence includes altered levels of cytokines and acute-phase proteins, pathological microglial activation, deregulation of Nrf2-Keap1 system and changes in biogenic amines neurotransmitters, whose expression is regulated by TNF-α, a pro-inflammatory cytokine highly involved in BD, pointing out inflammation as a novel and attractive therapeutic target for BD. As result, new therapeutic agents including non-steroidal anti-inflammatory drugs, N-acetylcysteine and GSK3 inhibitors have been incorporated in BD treatment. Taking into consideration the latest pre-clinical and clinical trials, in this review we discuss recent data regarding inflammation in BD, unveiling potential therapeutic approaches through direct or indirect modulation of inflammatory response.

Mechanisms of repetitive transcranial magnetic stimulation for anti-depression: Evidence from preclinical studies

This review summarizes the anti-depressant mechanisms of repetitive transcranial magnetic stimulation in preclinical studies, including anti-inflammatory effects mediated by activation of nuclear factor-E2-related factor 2 signaling pathway, anti-oxidative stress effects, enhancement of synaptic plasticity and neurogenesis via activation of the endocannabinoid system and brain derived neurotrophic factor signaling pathway, increasing the content of monoamine neurotransmitters via inhibition of Sirtuin 1/monoamine oxidase A signaling pathway, and reducing the activity of the hypothalamic-pituitary-adrenocortical axis. We also discuss the shortcomings of transcranial magnetic stimulation in preclinical studies such as inaccurate positioning, shallow depth of stimulation, and difficulty in elucidating the neural circuit mechanism up- and down-stream of the stimulation target brain region.

Abnormal expression of colony stimulating factor 1 receptor (CSF1R) and transcription factor PU.1 (SPI1) in the spleen from patients with major psychiatric disorders: A role of brain-spleen axis

BACKGROUND

The colony stimulating factor 1 receptor (CSF1R) regulates microglia/macrophage proliferation, differentiation and survival; however, the precise role of this protein in psychiatric disorders is unknown. CSF1R is also known to interact with the transcription factor PU.1 (SPI1). Here we studied whether the expressions of CSF1R and SPI1 are altered in the postmortem samples (parietal cortex, cerebellum, spleen) from patients with major psychiatric disorders.

METHODS

Protein expression of CSF1R and SPI1 in the parietal cortex, cerebellum and spleen from control, major depressive disorder (MDD), schizophrenia (SZ), and bipolar disorder (BD) groups was measured.

RESULTS

Levels of CSF1R in the spleen, but not cerebellum and parietal cortex, from MDD and SZ groups were significantly lower than the control group. There was a positive correlation between CSF1R levels in the spleen and CSF1R levels in the parietal cortex in the all subjects from four groups. Furthermore, levels of SPI1 in the cerebellum and spleen from MDD and SZ groups were significantly higher than the control group. Levels of SPI1 in the parietal cortex were not different among the four groups. Interestingly, there was a negative correlation between CSF1R and SPI1 levels in the spleen of the all subjects from four groups. There was also a negative correlation between CSF1R and SPI1 levels in the spleen of MDD group.

LIMITATIONS

The small number in each group may limit our interpretation.

CONCLUSIONS

Abnormalities in CSF1R and SPI1 in the brain-spleen axis might, in part, play a role in the pathophysiology of MDD.

The efficacy and safety of sulforaphane as an adjuvant in the treatment of bipolar depressive disorder: Study protocol for a randomized, double-blinded, placebo-controlled, parallel-group clinical trial

BACKGROUND

Bipolar disorder (BD) is a chronic and disabling psychiatric disorder. The treatment of BD still remains a significant clinical challenge due to the complex nature of the disease. Nutraceutical therapy as adjunctive role is a promising therapy for BD. Sulforaphane (SFN), a broccoli extract, was reported to be effective for emotional problems and cognitive impairment. However, clinical research of SFN in the treatment of BD was rare. Therefore, this study is designed to evaluate the adjuvant role of SFN in the treatment of BD.

METHODS

This is a randomized, double-blinded, placebo-controlled, parallel-group clinical trial. A total of 100 patients who meet inclusion criteria will be assigned to receive quetiapine plus SFN or quetiapine plus placebo in a 1:1 ratio. The total duration of the study will be 12 weeks including 5 follow ups. The primary outcome is in the Montgomery-Asberg depression rating scale. The secondary outcomes are the quick inventory of depressive symptomatology-self report, Hamilton anxiety rating scale, young mania rating scale, cognitive function, inflammatory factors, and intestinal flora. Any adverse events will be recorded throughout the trial.

DISCUSSION

This trial will provide evidences to evaluate the efficacy and safety of SFN combined with quetiapine in the treatment of BD patients, as well as the adjuvant role of SFN in combination.

TRIAL REGISTRATION

This study protocol was registered at the Chinese clinical trial registry (ChiCTR2000028706).

The interplay between oxidative stress and bioenergetic failure in neuropsychiatric illnesses: can we explain it and can we treat it?

Nitro-oxidative stress and lowered antioxidant defences play a key role in neuropsychiatric disorders such as major depression, bipolar disorder and schizophrenia. The first part of this paper details mitochondrial antioxidant mechanisms and their importance in reactive oxygen species (ROS) detoxification, including details of NO networks, the roles of H₂O₂ and the thioredoxin/peroxiredoxin system, and the relationship between mitochondrial respiration and NADPH production. The second part highlights and identifies the causes of the multiple pathological sequelae arising from self-amplifying increases in mitochondrial ROS production and bioenergetic failure. Particular attention is paid to NAD⁺ depletion as a core cause of pathology; detrimental effects of raised ROS and reactive nitrogen species on ATP and NADPH generation; detrimental effects of oxidative and nitrosative stress on the glutathione and thioredoxin systems; and the NAD⁺-induced signalling cascade, including the roles of SIRT1, SIRT3, PGC-1α, the FOXO family of transcription factors, Nrf1 and Nrf2. The third part discusses proposed therapeutic interventions aimed at mitigating such pathology, including the use of the NAD⁺ precursors nicotinamide mononucleotide and nicotinamide riboside, both of which rapidly elevate levels of NAD⁺ in the brain and periphery following oral administration; coenzyme Q₁₀ which, when given with the aim of improving mitochondrial function and reducing nitro-oxidative stress in the brain, may be administered via the use of mitoquinone, which is in essence ubiquinone with an attached triphenylphosphonium cation; and N-acetylcysteine, which is associated with improved mitochondrial function in the brain and produces significant decreases in oxidative and nitrosative stress in a dose-dependent manner.

Increased expression of soluble epoxide hydrolase in the brain and liver from patients with major psychiatric disorders: A role of brain - liver axis

BACKGROUND

Soluble epoxide hydrolase (sEH) in the metabolism of polyunsaturated fatty acids might play a role in the pathogenesis of major psychiatric disorders. Here we studied whether expression of sEH protein is altered in the postmortem samples (parietal cortex, and liver) from patients with major psychiatric disorders.

METHODS

Protein expression of sEH in the parietal cortex and liver from control, major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia (SZ) groups was measured.

RESULTS

Levels of sEH in the parietal cortex and liver from MDD, BD, and SZ groups were significantly higher than the control group. Interestingly, there was a positive correlation between sEH protein in the parietal cortex and sEH protein the liver in all groups.

LIMITATIONS

The small number in each group may limit our interpretation.

CONCLUSIONS

This study shows that the increased expression of sEH in the brain and liver might play a role in the pathogenesis of major psychiatric disorders, suggesting a role of brain - liver axis in major psychiatric disorders.

Oxidation-reduction mechanisms in psychiatric disorders: A novel target for pharmacological intervention

While neurotransmitter dysfunction represents a key component in mental illnesses, there is now a wide agreement for a central pathophysiological hub that includes hormones, neuroinflammation, redox mechanisms as well as oxidative stress. With respect to oxidation-reduction (redox) mechanisms, preclinical and clinical evidence suggests that an imbalance in the pro/anti-oxidative homeostasis toward the increased production of substances with oxidizing potential may contribute to the etiology and manifestation of different psychiatric disorders. The substantial and continous demand for energy renders the brain highly susceptible to disturbances in its energy supply, especially following exposure to stressful events, which may lead to overproduction of reactive oxygen and nitrogen species under conditions of perturbed antioxidant defenses. This will eventually induce different molecular alterations, including extensive protein and lipid peroxidation, increased blood-brain barrier permeability and neuroinflammation, which may contribute to the changes in brain function and morphology observed in mental illnesses. This view may also reconcile different key concepts for psychiatric disorders, such as the neurodevelopmental origin of these diseases, as well as the vulnerability of selective cellular populations that are critical for specific functional abnormalities. The possibility to pharmacologically modulate the redox system is receiving increasing interest as a novel therapeutic strategy to counteract the detrimental effects of the unbalance in brain oxidative mechanisms. This review will describe the main mechanisms and mediators of the redox system and will examine the alterations of oxidative stress found in animal models of psychiatric disorders as well as in patients suffering from mental illnesses, such as schizophrenia and major depressive disorder. In addition, it will discuss studies that examined the effects of psychotropic drugs, including antipsychotics and antidepressants, on the oxidative balance as well as studies that investigated the effectiveness of a direct modulation of oxidative mechanisms in counteracting the behavioral and functional alterations associated with psychiatric disorders, which supports the promising role of the redox system as a novel therapeutic target for the improved treatment of brain disorders.

Induced Ketosis as a Treatment for Neuroprogressive Disorders: Food for Thought?

Induced ketosis (or ketone body ingestion) can ameliorate several changes associated with neuroprogressive disorders, including schizophrenia, bipolar disorder, and major depressive disorder. Thus, the effects of glucose hypometabolism can be bypassed through the entry of beta-hydroxybutyrate, providing an alternative source of energy to glucose. The weight of evidence suggests that induced ketosis reduces levels of oxidative stress, mitochondrial dysfunction, and inflammation-core features of the above disorders. There are also data to suggest that induced ketosis may be able to target other molecules and signaling pathways whose levels and/or activity are also known to be abnormal in at least some patients suffering from these illnesses such as peroxisome proliferator-activated receptors, increased activity of the Kelch-like ECH-associated protein/nuclear factor erythroid 2-related factor 2, Sirtuin-1 nuclear factor-κB p65, and nicotinamide adenine dinucleotide (NAD). This review explains the mechanisms by which induced ketosis might reduce mitochondrial dysfunction, inflammation, and oxidative stress in neuropsychiatric disorders and ameliorate abnormal levels of molecules and signaling pathways that also appear to contribute to the pathophysiology of these illnesses. This review also examines safety data relating to induced ketosis over the long term and discusses the design of future studies.

Inflammatory and antioxidant pathway dysfunction in borderline personality disorder

INTRODUCTION

This study investigates the alteration of the inflammatory/oxidative pathway in patients with borderline personality disorder (BPD) and its relationship with clinical features of the disorder.

METHODS

49 BPD patients and 33 healthy control subjects were studied. Plasma levels of TBARS, nitrites, and the antioxidant enzymes CAT, GPx and SOD were measured. In addition, peripheral blood mononuclear cells were obtained to investigate levels of intracellular components of the inflammatory/oxidative pathway including the IκBα, NFκB, iNOS, COX2, Keap1, NQO1, and HO1. Western Blot and ELISA were used to measure protein expression. Patients were assessed for different clinical dimensions of BPD with scales for depression, anxiety, impulsivity and functioning.

RESULTS

A significant decrease of IκBα levels and a significant increase of inflammatory factors, including NFκB, COX2 and iNOS levels were found in patients. On the other hand, a significant decrease was observed for all antioxidant enzymes in patients with BPD, except for HO1. The inflammatory factor NFκB showed a significant positive correlation with impulsivity scores.

CONCLUSIONS

Patients with BPD presented an increased activation of several components of the inflammatory pathways, as well as an inhibition of the antioxidant path. These alterations appear partially correlated with the impulsivity scores in these patients.

The compensatory antioxidant response system with a focus on neuroprogressive disorders

Major antioxidant responses to increased levels of inflammatory, oxidative and nitrosative stress (ONS) are detailed. In response to increasing levels of nitric oxide, S-nitrosylation of cysteine thiol groups leads to post-transcriptional modification of many cellular proteins and thereby regulates their activity and allows cellular adaptation to increased levels of ONS. S-nitrosylation inhibits the function of nuclear factor kappa-light-chain-enhancer of activated B cells, toll-like receptor-mediated signalling and the activity of several mitogen-activated protein kinases, while activating nuclear translocation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2 or NFE2L2); in turn, the redox-regulated activation of Nrf2 leads to increased levels and/or activity of key enzymes and transporter systems involved in the glutathione system. The Nrf2/Kelch-like ECH-associated protein-1 axis is associated with upregulation of NAD(P)H:quinone oxidoreductase 1, which in turn has anti-inflammatory effects. Increased Nrf2 transcriptional activity also leads to activation of haem oxygenase-1, which is associated with upregulation of bilirubin, biliverdin and biliverdin reductase as well as increased carbon monoxide signalling, anti-inflammatory and antioxidant activity. Associated transcriptional responses, which may be mediated by retrograde signalling owing to elevated hydrogen peroxide, include the unfolded protein response (UPR), mitohormesis and the mitochondrial UPR; the UPR also results from increasing levels of mitochondrial and cytosolic reactive oxygen species and reactive nitrogen species leading to nitrosylation, glutathionylation, oxidation and nitration of crucial cysteine and tyrosine causing protein misfolding and the development of endoplasmic reticulum stress. It is shown how these mechanisms co-operate in forming a co-ordinated rapid and prolonged compensatory antioxidant response system.

Abnormal composition of gut microbiota is associated with resilience versus susceptibility to inescapable electric stress

Increasing evidence indicates that abnormalities in the composition of gut microbiota might play a role in stress-related disorders. In the learned helplessness (LH) paradigm, ~60-70% rats are susceptible to LH in the face of inescapable electric stress. The role of gut microbiota in susceptibility in the LH paradigm is unknown. In this study, male rats were exposed to inescapable electric stress under the LH paradigm. The compositions of gut microbiota and short-chain fatty acids were assessed in fecal samples from control rats, non-LH (resilient) rats, and LH (susceptible) rats. Members of the order Lactobacillales were present at significantly higher levels in the susceptible rats than in control and resilient rats. At the family level, the number of Lactobacillaceae in the susceptible rats was significantly higher than in control and resilient rats. At the genus level, the numbers of Lactobacillus, Clostridium cluster III, and Anaerofustis in susceptible rats were significantly higher than in control and resilient rats. Levels of acetic acid and propionic acid in the feces of susceptible rats were lower than in those of control and resilient rats; however, the levels of lactic acid in the susceptible rats were higher than those of control and resilient rats. There was a positive correlation between lactic acid and Lactobacillus levels among these three groups. These findings suggest that abnormal composition of the gut microbiota, including organisms such as Lactobacillus, contributes to susceptibility versus resilience to LH in rats subjected to inescapable electric foot shock. Therefore, it appears likely that brain-gut axis plays a role in stress susceptibility in the LH paradigm.

Upregulating Nrf2 in the RVLM ameliorates sympatho-excitation in mice with chronic heart failure

Nuclear factor E2-related factor 2 (Nrf2) is a key transcription factor that maintains redox homeostasis by governing a broad array of antioxidant genes in response to oxidant stress. We hypothesized that overexpression of Nrf2 in the rostral ventrolateral medulla (RVLM) ameliorates sympatho-excitation in mice with coronary artery ligation-induced chronic heart failure (CHF). To address this, we overexpressed Nrf2 in the RVLM using an HIV-CamKIIa-Nrf2 lenti virus in C57BL/6 mice. In addition, we used a Lenti-Cre virus in Keap1^flox/flox mice to upregulate Nrf2 non-selectively in the RVLM. Arterial blood pressure (AP), heart rate (HR), and renal sympathetic nerve activity (RSNA) were recorded under conscious and anesthetized conditions, respectively. Protein expression was assayed using western blotting and immunofluorescence staining. We found that (1) Nrf2 and two target proteins, NQO1 and HO-1 in the RVLM were significantly lower in CHF compared to Sham mice. Nrf2 viral transfection of the RVLM upregulated Nrf2 protein. (2) Urinary NE excretion in CHF mice was markedly attenuated following Nrf2 upregulation (812 ± 133 vs 1120 ± 271 ng/24hr mean. ±SE, *p < 0.05, n = 8/group). (3) In the conscious state, CHF mice overexpressing Nrf2 exhibited an enhancement in spontaneous baroreflex gain and in phenylephrine-induced baroreflex control of HR. (4) Acute experiments under anesthetisa revealed a significant decrease in basal RSNA (44.0 ± 6.5 vs 64.7 ± 8.3% of Max. *P < 0.05 n = 8/group) and enhancement in baroreflex sensitivity (Maximal gain -1.8 ± 0.3 vs 1.1 ± 0.2 of mmHg. **p < 0.01. n = 6/group) in CHF mice that were virally transfected with Nrf2 compared with CHF mice transfected with Lenti-GFP. Finally, Lenti-Cre viral overexpression of Nrf2 in Keap1^flox/flox mice reduced Keap1 protein and increased Nrf2, NQO1, and HO-1 in the RVLM of Sham and CHF mice. CHF-Cre mice exhibited a significant decrease in baseline RSNA and plasma NE concentration (8.9 ± 1.1 vs 12.7 ± 0.9 ng/mL *P < 0.05 n = 6/group) as compared with CHF-GFP mice. Based on the above data, we conclude that upregulating Nrf2 selectively in the RVLM attenuates sympatho-excitation in CHF mice. Nrf2 may be an important central target for autonomic modulation in cardiovascular disease and during stress.

Recent Advances in the Early Intervention in Schizophrenia: Future Direction from Preclinical Findings

PURPOSE OF REVIEW

In the past decade, there has been increasing interest in the potential benefit of early intervention in schizophrenia. Patients with schizophrenia show cognitive impairment for several years preceding the onset of psychosis. The author discusses the recent topics on prevention of schizophrenia.

RECENT FINDINGS

Preclinical findings suggest that maternal immune activation (MIA) produces cognitive deficits as a prodromal symptom in juvenile offspring in rodents. Treatment with anti-inflammatory compounds, such as D-serine, 7,8-dihydroxyflavone (a TrkB agonist), sulforaphane (or its precursor glucoraphanin), and TPPU (1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea: a soluble epoxide hydrolase inhibitor), during adolescence might prevent the onset of behavioral abnormalities and parvalbumin immunoreactivity in the medial prefrontal cortex of adult offspring after MIA. Based on the role of inflammation and cognitive impairment in the prodromal state, early intervention using anti-inflammatory compounds (i.e., D-serine, sodium benzoate, TrkB agonist, Nrf2 agonist, soluble epoxide hydrolase inhibitor) may reduce the risk of subsequent transition to schizophrenia.

Melatonin Attenuates LPS-Induced Acute Depressive-Like Behaviors and Microglial NLRP3 Inflammasome Activation Through the SIRT1/Nrf2 Pathway

Inflammation is a crucial component of various stress-induced responses that contributes to the pathogenesis of major depressive disorder (MDD). Depressive-like behavior (DLB) is characterized by decreased mobility and depressive behavior that occurs in systemic infection induced by Lipopolysaccharide (LPS) in experimental animals and is considered as a model of exacerbation of MDD. We assessed the effects of melatonin on behavioral changes and inflammatory cytokine expression in hippocampus of mice in LPS-induced DLB, as well as its effects on NLR Family Pyrin Domain Containing 3 (NLRP3) inflammasome activation, oxidative stress and pyroptotic cell death in murine microglia in vitro. Intraperitoneal 5 mg/kg dose of LPS was used to mimic depressive-like behaviors and melatonin was given at a dose of 500 mg/kg for 4 times with 6 h intervals, starting at 2 h before LPS administration. Behavioral assessment was carried out at 24 h post-LPS injection by tail suspension and forced swimming tests. Additionally, hippocampal cytokine and NLRP3 protein levels were estimated. Melatonin increased mobility time of LPS-induced DLB mice and suppressed NLRP3 expression and interleukin-1β (IL-1β) cleavage in the hippocampus. Immunofluorescence staining of hippocampal tissue showed that NLRP3 is mainly expressed in ionized calcium-binding adapter molecule 1 (Iba1) -positive microglia. Our results show that melatonin prevents LPS and Adenosine triphosphate (ATP) induced NLRP3 inflammasome activation in murine microglia in vitro, evidenced by inhibition of NLRP3 expression, Apoptosis-associated speck-like protein containing a CARD (ASC) speck formation, caspase-1 cleavage and interleukin-1β (IL-1β) maturation and secretion. Additionally, melatonin inhibits pyroptosis, production of mitochondrial and cytosolic reactive oxygen species (ROS) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling. The beneficial effects of melatonin on NLRP3 inflammasome activation were associated with nuclear factor erythroid 2–related factor 2 (Nrf2) and Silent information regulator 2 homolog 1 (SIRT1) activation, which were reversed by Nrf2 siRNA and SIRT1 inhibitor treatment.

Dietary intake of glucoraphanin prevents the reduction of dopamine transporter in the mouse striatum after repeated administration of MPTP

Aims

Parkinson's disease (PD) is a chronic and progressive neurodegenerative disorder. Although diet may influence the development of PD, the precise mechanisms underlying relationship between diet and PD pathology are unknown. Here, we examined whether dietary intake of glucoraphanin (GF), the precursor of a natural antioxidant sulforaphane in cruciferous vegetables, can affect the reduction of dopamine transporter (DAT) in the mouse striatum after repeated administration of MPTP (1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine).

Methods

Normal food pellet or 0.1% GF food pellet was given into male mice for 28 days from 8‐week‐old. Subsequently, saline (5 mL/kg × 3, 2‐hour interval) or MPTP (10 mg/kg × 3, 2‐hour interval) was injected into mice. Immunohistochemistry of DAT in the striatum was performed 7 days after MPTP injection.

Results

Repeated injections of MPTP significantly decreased the density of DAT‐immunoreactivity in the mouse striatum. In contrast, dietary intake of 0.1% GF food pellet significantly protected against MPTP‐induced reduction of DAT‐immunoreactivity in the striatum.

Conclusion

This study suggests that dietary intake of GF food pellet could prevent MPTP‐induced dopaminergic neurotoxicity in the striatum of adult mice. Therefore, dietary intake of GF‐rich cruciferous vegetables may have beneficial effects on prevention for development of PD.

Oxidative stress plays a role in the neurotoxicity of MPTP in the striatum. Dietary intake of glucoraphanin could prevent the MPTP‐induced neurotoxicity in mouse striatum. Dietary intake of glucoraphanin‐rich vegetables may have beneficial effects on prevention of Parkinson's disease.

Increased expression of inwardly rectifying Kir4.1 channel in the parietal cortex from patients with major depressive disorder

BACKGROUND

The inwardly rectifying K⁺ channel subtype Kir4.1 has been well studied in the astrocyte within brain; however, the precise role of this protein in psychiatric disorders is unknown. Kir4.1 is also known to interact with GABA_B receptors which may be implicated in psychiatric disorders. Here we studied whether expression of Kir4.1 and GABA_B receptors was altered in the postmortem brain samples (parietal cortex and cerebellum) from patients with major psychiatric disorders.

METHODS

Protein expression of Kir4.1 and GABA_B receptors in the parietal cortex and cerebellum from control, major depressive disorder (MDD), schizophrenia (SZ), and bipolar disorder (BD) groups was measured.

RESULTS

Levels of Kir4.1 in the parietal cortex from MDD group, but not SZ and BD groups, were significantly higher than the control group. Furthermore, levels of GABA_B receptor subunit 1 in the parietal cortex from MDD group and SZ group, but not BD group, were also significantly higher than the control group. Interestingly, there was a positive correlation between Kir4.1 protein and GABA_B receptor subunit 1 in the parietal cortex from control group, but not MDD group.

LIMITATIONS

The small number in each group may limit our interpretation. Only two brain regions were analyzed.

CONCLUSIONS

Abnormalities in the interaction of Kir4.1 and GABA_B receptor in the parietal cortex might play a role in the pathophysiology of MDD.

Essential Role of Keap1-Nrf2 Signaling in Mood Disorders: Overview and Future Perspective

Depression is one of the most common mood disorders with a high rate of relapse. Accumulating evidence suggests that the transcription factor Kelch-like erythroid cell-derived protein with CNC homology (ECH)-associated protein 1 (Keap1)-Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) system plays a key role in inflammation which is involved in depression. Preclinical studies demonstrated that the protein expressions of Keap1 and Nrf2 in the prefrontal cortex (PFC), CA3 and dentate gyrus (DG) of hippocampus in mice with depression-like phenotype were lower than control mice. In the learned helplessness paradigm, the protein levels of Keap1 and Nrf2 in the PFC and DG of hippocampus from rats with depression-like phenotype were also lower than control and resilient rats. Furthermore, rodents with depression-like phenotype have higher levels of pro-inflammatory cytokines. Interestingly, Nrf2 knock-out (KO) mice exhibit depression-like phenotype, and higher serum levels of pro-inflammatory cytokines compared with wild-type mice. Furthermore, Nrf2 KO mice have lower expression of brain-derived neurotrophic factor (BDNF) in the PFC, and CA3 and DG of hippocampus compared to wild-type mice. 7,8-Dihydroxyflavone, a TrkB agonist, showed antidepressant effects in Nrf2 KO mice, by stimulating BDNF-TrkB in the PFC, CA3, and DG. Pretreatment with sulforaphane, a naturally occurring Nrf2 activator, prevented depression-like phenotype in mice after inflammation, or chronic social defeat stress. Interestingly, dietary intake of 0.1% glucoraphanin (a precursor of sulforaphane) containing food during juvenile and adolescent stages of mice could prevent depression-like phenotype in adulthood after chronic social defeat stress. Moreover, the protein expressions of Keap1 and Nrf2 in the parietal cortex from major depressive disorder and bipolar disorder were lower than controls. These findings suggest that Keap1-Nrf2 system plays a key role in the stress resilience which is involved in the pathophysiology of mood disorders. It is, therefore, possible that dietary intake of cruciferous vegetables including glucoraphanin (or SFN) may prevent or minimize relapse from remission, induced by stress and/or inflammation in depressed patients. In the review, the author would like to discuss the role of Keap1-Nrf2 system in mood disorders.