Ketamine induces rapid antidepressant effects via the autophagy-NLRP3 inflammasome pathway

Molecular mechanism of programmed cell death in drug-induced neuronal damage: A special focus on ketamine-induced neurotoxicity

In recent years, the abuse of ketamine as a recreational drug has been growing, and has become one of the most widely abused drugs. Continuous using ketamine poses a risk of drug addiction and complications such as attention deficit disorder, memory loss and cognitive decline. Ketamine-induced neurotoxicity is thought to play a key role in the development of these neurological complications. In this paper, we focus on the molecular mechanisms of ketamine-induced neurotoxicity. According to our analyses, drugs in causing neurotoxicity are closely associated with programmed cell death (PCD) such as apoptosis, autophagy, necroptosis, pyroptosis, and Ferroptosis. Therefore, this review will collate the existing mechanisms of programmed death in ketamine-induced neurotoxicity as well as explore the possible mechanisms by outlining the mechanisms of programmed death in other drug-induced neurotoxicity, which may be helpful in identifying potential therapeutic targets for neurotoxicity induced by ketamine abuse.

Ginsenoside Rg1 ameliorates stress-exacerbated Parkinson's disease in mice by eliminating RTP801 and α-synuclein autophagic degradation obstacle

Emerging evidence shows that psychological stress promotes the progression of Parkinson's disease (PD) and the onset of dyskinesia in non-PD individuals, highlighting a potential avenue for therapeutic intervention. We previously reported that chronic restraint-induced psychological stress precipitated the onset of parkinsonism in 10-month-old transgenic mice expressing mutant human α-synuclein (αSyn) (hαSyn A53T). We refer to these as chronic stress-genetic susceptibility (CSGS) PD model mice. In this study we investigated whether ginsenoside Rg1, a principal compound in ginseng notable for soothing the mind, could alleviate PD deterioration induced by psychological stress. Ten-month-old transgenic hαSyn A53T mice were subjected to 4 weeks' restraint stress to simulate chronic stress conditions that worsen PD, meanwhile the mice were treated with Rg1 (40 mg· kg-1 ·d-1, i.g.), and followed by functional magnetic resonance imaging (fMRI) and a variety of neurobehavioral tests. We showed that treatment with Rg1 significantly alleviated both motor and non-motor symptoms associated with PD. Functional MRI revealed that Rg1 treatment enhanced connectivity between brain regions implicated in PD, and in vivo multi-channel electrophysiological assay showed improvements in dyskinesia-related electrical activity. In addition, Rg1 treatment significantly attenuated the degeneration of dopaminergic neurons and reduced the pathological aggregation of αSyn in the striatum and SNc. We revealed that Rg1 treatment selectively reduced the level of the stress-sensitive protein RTP801 in SNc under chronic stress conditions, without impacting the acute stress response. HPLC-MS/MS analysis coupled with site-directed mutation showed that Rg1 promoted the ubiquitination and subsequent degradation of RTP801 at residues K188 and K218, a process mediated by the Parkin RING2 domain. Utilizing αSyn A53T+; RTP801-/- mice, we confirmed the critical role of RTP801 in stress-aggravated PD and its necessity for Rg1's protective effects. Moreover, Rg1 alleviated obstacles in αSyn autophagic degradation by ameliorating the RTP801-TXNIP-mediated deficiency of ATP13A2. Collectively, our results suggest that ginsenoside Rg1 holds promise as a therapeutic choice for treating PD-sensitive individuals who especially experience high levels of stress and self-imposed expectations.

The immune regulatory mechanism of ketamine-induced psychiatric disorders: A new perspective on drug-induced psychiatric symptoms

Ketamine, a psychoactive substance strictly regulated by international drug conventions, is classified as a "new type drug" due to its excitatory, hallucinogenic, or inhibitory effects. The etiology of ketamine-induced psychiatric symptoms is multifaceted, with the immune regulatory mechanism being the most prominent among several explanatory theories. In recent years, the interaction between the immune system and nervous system have garnered significant attention in neuropsychiatric disorder research. Notably, the infiltration of peripheral lymphocytes into the central nervous system has emerged as an early hallmark of certain neuropsychiatric disorders. However, a notable gap exists in the current literature, regarding the immune regulatory mechanisms, specifically the peripheral immune alterations, associated with ketamine-induced psychiatric symptoms. To address this void, this article endeavors to provide a comprehensive overview of the pathophysiological processes implicated in psychiatric disorders or symptoms, encompassing those elicited by ketamine. This analysis delves into aspects such as nerve damage, alterations within the central immune system, and the regulation of the peripheral immune system. By emphasizing the intricate crosstalk between the peripheral immune system and the central nervous system, this study sheds light on their collaborative role in the onset and progression of psychiatric diseases or symptoms. This insight offers fresh perspectives on the underlying mechanisms, diagnosis and therapeutic strategies for mental disorders stemming from drug abuse.

Ketamine-Assisted Psychotherapy for Antisocial Personality Disorder: A Case Report

There are currently no evidence-based treatment guidelines for antisocial personality disorder (ASPD). Instead, treatment typically focuses on comorbid conditions. There is currently no literature documenting cases or research, theoretical or otherwise of using ketamine-assisted therapy or any other psychedelic therapy in cases of ASPD. In this case report, a 43-year-old man seeking ketamine-assisted psychotherapy (KAP) for alcoholism and depression was diagnosed with comorbid antisocial personality disorder. A series of psycholytic (low dose) ketamine therapy sessions and other integrative approaches over the course of 3 years results in resolution of severe alcoholism, reduction in violent thoughts about people and the world, and a reduction in depression symptoms. With additional precautions, utilizing a ketamine-assisted psychotherapy approach led to clinical improvements in depression, alcohol abuse, and ASPD traits.

Time- and Region-specific Effect of Vortioxetine on Central LPS-induced Transcriptional Regulation of NLRP3 Inflammasome

BACKGROUND

Inflammasome overactivation, multiprotein complexes that trigger inflammatory responses, plays a critical role in Major Depressive Disorder (MDD) pathogenesis and treatment responses. Indeed, different antidepressants alleviate depression-related behaviours by specifically counteracting the NLRP3 inflammasome signalling pathway. The immunomodulatory effects of vortioxetine (VTX), a multimodal antidepressant with cognitive benefits, were recently revealed to counter memory impairment induced by a peripheral lipopolysaccharide (LPS) injection 24 hours (h) postchallenge. The potential link between VTX and NLRP3, along with other inflammasomes, remains un-explored.

METHODS

The potential link between VTX and NLRP3, along with other inflammasomes, remains unexplored. Hence, adult C57BL/6J male mice (n = 73) were fed with a standard or VTX-enriched diet (600 mg/kg of food, 28 days), injected with LPS (830 μg/kg) or saline, and sacrificed 6/24 h post-LPS. At these time-points, transcriptional effects of LPS and VTX on NLRP3, NLRP1, NLRC4, AIM2 (inflammasomes), ASC and CASP1 (related subunits) and NEK7 mediator (NLRP3 regulator) were assessed in dorsal and ventral hippocampal subregions, frontal-prefrontal cortex and hypothalamus, brain regions serving behavioural-cognitive functions impaired in MDD.

RESULTS

Varied expression patterns of inflammasomes were revealed, with long-term NLRP3 and ASC transcriptional changes observed in response to LPS. It was demonstrated that VTX counteracted the LPS-mediated NLRP3 and ASC upregulation in memory-related brain areas like the dorsal hippocampus at 24 h time-point, potentially via regulating NEK7 expression. No VTX-mediated transcriptional effects were observed on other inflammasomes, reinforcing a potentially specific modulation on the NLRP3 inflammasome signalling pathway.

CONCLUSION

Thus, a novel VTX molecular mechanism in modulating the NLRP3 inflammasome in a time- and area-specific manner in the brain was highlighted, with significant clinical implications in treating depression and cognitive impairments.

Effect of subanesthetic dose of esketamine on early postoperative depression in elderly patients with Sarcopenia

OBJECTIVE

To explore the effects of subanesthetic dose of esketamine on serum inflammatory factor levels and depressive mood in elderly patients with sarcopenia postoperatively.

METHODS

This study retrospectively included 102 elderly patients who underwent elective total knee arthroplasty from April 2023 to June 2024 with skeletal muscle mass index (SMI) meeting the diagnostic criteria for sarcopenia (male SMI < 42.6 cm2/m2, female SMI < 30.6 cm2/m2). They were divided into two groups according to whether esketamine was used: esketamine group (ESK group, n = 51) and control group (CON group, n = 51). The Hamilton Depression Scale (HAMD) scores of the patients in the two groups were completed on preoperative day 1, postoperative day 1 and day 7, and serum ceramide (Cer), NOD-like receptor thermoprotein structural domain-related protein 3 (NLRP3) and interleukin-6 (IL-6) were detected. The length of hospital stay, time to first ambulation and pain VAS scores of 4 h, 8 h and 24 h after surgery were recorded. The incidence of adverse reactions was recorded in the postoperative period of 48 h.

RESULTS

There were no significant differences in HAMD scores, Cer, NLRP3 and IL-6 levels between the two groups preoperatively (P > 0.05). Compared with CON group, HAMD score, Cer, NLRP3 and IL-6 levels, and pain VAS scores (postoperative 4 h and 8 h) were significantly decreased in ESK group at postoperative day 1 and day 7 (P < 0.05). In addition, the number of postoperative remedial analgesia and length of hospital stay in the ESK group were significantly shorter than those in the CON group (P < 0.05). HAMD scores and levels of Cer, IL-6 and NLRP3 were higher at postoperative day 1 and day 7 than those preoperatively in both two groups (P < 0.05), and there was no statistically significant difference in the incidence of adverse reactions at postoperative 48 h between the two groups.

CONCLUSIONS

The subanesthetic dose of esketamine can effectively reduce the serum Cer, NLRP3 and IL-6 levels after knee arthroplasty in elderly patients with sarcopenia, and may improve the patients' depression in the early postoperative period.

New Insights into Contradictory Changes in Brain-Derived Neurotrophic Factor (BDNF) in Rodent Models of Posttraumatic Stress Disorder (PTSD)

Post-traumatic stress disorder (PTSD) is a neuropsychiatric disorder that may develop after experiencing traumatic events. Preclinical studies use various methods to induce PTSD-like models such as fear-conditioning, single-prolonged stress (SPS), restraint stress, and social defeat. Brain-derived neurotrophic factor (BDNF) is a crucial neurotrophin in mood regulation. Evidence shows BDNF changes in different neuropsychiatric disorders particularly PTSD. This review examined BDNF alterations in preclinical rodent models of PTSD where we demonstrated a wide range of paradoxical changes in BDNF. We found that the fear-conditioning model produced the most inconsistent alterations in BDNF, and suggest that conclusions drawn from these changes be approached with caution. We suggest that BDNF maladaptive changes in social defeat and restraint stress models may be related to the duration of stress, while the SPS model appears to have more consistent results. Ultimately, we propose that evaluating BDNF alterations in the process of treating PTSD symptoms may not be a reliable factor.

Intranasal LAG3 antibody infusion induces a rapid antidepressant effect via the hippocampal ERK1/2-BDNF signaling pathway in chronically stressed mice

The decline of microglia in the dentate gyrus is a new phenomenon that may explain the pathogenesis of depression, and reversing this decline has an antidepressant effect. The development of strategies that restore the function of dentate gyrus microglia in under stressful conditions is becoming a new focus. Lymphocyte-activating gene-3 (LAG3) is an immune checkpoint expressed by immune cells including microglia. One of its functions is to suppress the expansion of immune cells. In a recent study, chronic systemic administration of a LAG3 antibody that readily penetrates the brain was reported to reverse chronic stress-induced hippocampal microglia decline and depression-like behaviors. We showed here that a single intranasal infusion of a LAG3 antibody (In-LAG3 Ab) reversed chronic unpredictable stress (CUS)-induced depression-like behaviors in a dose-dependent manner, which was accompanied by an increase in brain-derived neurotrophic factor (BDNF) in the dentate gyrus. Infusion of an anti-BDNF antibody into the dentate gyrus, construction of knock-in mice with the BDNF Val68Met allele, or treatment with the BDNF receptor antagonist K252a abolished the antidepressant effect of In-LAG3 Ab. Activation of extracellular signal-regulated kinase1/2 (ERK1/2) is required for the reversal effect of In-LAG3 Ab on CUS-induced depression-like behaviors and BDNF decrease in the dentate gyrus. Moreover, both inhibition and depletion of microglia prevented the reversal effect of In-LAG3 Ab on CUS-induced depression-like behaviors and impairment of ERK1/2-BDNF signaling in the dentate gyrus. These results suggest that In-LAG3 Ab exhibits an antidepressant effect through microglia-mediated activation of ERK1/2 and synthesis of BDNF in the dentate gyrus.

Shared effects of electroconvulsive shocks and ketamine on neuroplasticity: A systematic review of animal models of depression

Electroconvulsive shocks (ECS) and ketamine are antidepressant treatments with a relatively fast onset of therapeutic effects compared to conventional medication and psychotherapy. While the exact neurobiological mechanisms underlying the antidepressant response of ECS and ketamine are unknown, both interventions are associated with neuroplasticity. Restoration of neuroplasticity may be a shared mechanism underlying the antidepressant efficacy of these interventions. In this systematic review, literature of animal models of depression is summarized to examine the possible role of neuroplasticity in ECS and ketamine on a molecular, neuronal, synaptic and functional level, and specifically to what extent these mechanisms are shared between both interventions. The results highlight that hippocampal neurogenesis and brain-derived neurotrophic factor (BDNF) levels are consistently increased after ECS and ketamine. Moreover, both interventions positively affect glutamatergic neurotransmission, astrocyte and neuronal morphology, synaptic density, vasculature and functional plasticity. However, a small number of studies investigated these processes after ECS. Understanding the shared fundamental mechanisms of fast-acting antidepressants can contribute to the development of novel therapeutic approaches for patients with severe depression.

Whole-Genome Metagenomic Analysis of the Oral Microbiota in Patients with Obstructive Sleep Apnea Comorbid with Major Depressive Disorder

Background

Obstructive sleep apnea (OSA) patients commonly experience high rates of depression. This study aims to examine the oral microbiota characteristics of OSA and those with comorbid major depressive disorder (OSA+MDD) patients.

Methods

Participants were enrolled from Aug 2022 to Apr 2023. Polysomnography, psychiatrist interviews, and scales were used to diagnose OSA and MDD. Oral samples were collected from participants by rubbing swabs on buccal mucosa, palate, and gums. Oral microbiota was analyzed via whole-genome metagenomics and bioinformatic analysis followed sequencing. Venous blood was drawn to detect plasma inflammatory factor levels.

Results

The study enrolled 33 OSA patients, 28 OSA+MDD patients, and 28 healthy controls. Significant differences were found in 8 phyla, 229 genera, and 700 species of oral microbiota among the three groups. Prevotellaceae abundance in the OSA and OSA+MDD groups was significantly lower than that in healthy controls. Linear discriminant analysis effect size (LEfSe) analysis showed that Streptococcaceae and Actinobacteria were the characteristic oral microbiota of the OSA and OSA+MDD groups, respectively. KEGG analysis indicates 30 pathways were changed in the OSA and OSA+MDD groups compared with healthy controls, and 23 pathways were changed in the OSA group compared with the OSA+MDD group. Levels of IL-6 in the OSA+MDD group were significantly higher than in the healthy group, correlating positively with the abundance of Schaalia, Campylobacter, Fusobacterium, Alloprevotella, and Candidatus Nanosynbacter in the oral, as well as with Hamilton Anxiety Rating Scale and Hamilton Depression Rating Scale scores.

Conclusion

Significant differences in oral microbiota populations and gene function were observed among the three groups. OSA patients were characterized by a decreased abundance of Prevotellaceae and an increased abundance of Streptococcaceae. OSA+MDD patients had an increased abundance of Actinobacteria. IL-6 might regulate the relationship between depression and the oral microbiota in OSA+MDD patients.

Paeoniflorin alleviates depression by inhibiting the activation of NLRP3 inflammasome via promoting mitochondrial autophagy

Depression ranks among the most common neuropsychiatric disorders globally. Current studies examining the roles of inflammation and mitochondrial autophagy in the antidepressant efficacy of paeoniflorin (PF) are sparse. This study aimed to elucidate PF's antidepressant mechanism by promoting autophagy and inhibiting NLRP3 inflammasome activation using chronic unpredictable mild stimulation (CUMS)-induced C57BL/6 mouse models in vivo and corticosterone (CORT)-induced HT22 cell models in vitro. Results demonstrated that PF enhanced the viability of HT22 cells following CORT exposure, restored mitochondrial membrane potential (MMP), reduced reactive oxygen species accumulation, increased LC3 fluorescence intensity, and suppressed inflammatory cytokine secretion and inflammation activation. Additionally, PF ameliorated depressive behaviors induced by CUMS and improved damage in hippocampal neurons. It also reduced the expression of NLRP3, ASC, Caspase-1, IL-1β, and the assembly of the NLRP3 inflammasome. Moreover, PF upregulated the expression of autophagy-related proteins in the hippocampus, facilitating the clearance of damaged mitochondria and enhancing autophagy. The role of autophagy in PF's antidepressant effects was further confirmed through the use of the autophagy inhibitor 3-methyladenine (3-MA), which reduced the efficacy of PF. In conclusion, PF effectively improved depressive behaviors in CUMS-induced mice and reduced NLRP3-mediated inflammation both in vivo and in vitro, likely via the induction of autophagy.

Targeting Large-Conductance Calcium-Activated Potassium Channels to Ameliorate Lipopolysaccharide-Induced Depressive-Like Behavior in Mice

Neuroinflammation plays crucial role in the development and progression of depression. Large conductance calcium- and voltage-dependent potassium (BK) channels mediate the activation of microglia. Herein, we investigated whether BK channels could serve as a target for the treatment of inflammation-associated depression. Lipopolysaccharide (LPS, 0.83 mg/kg) was injected intraperitoneally (i.p.) to induce neuroinflammation and depressive-like behavior in 6-8 week ICR mice. Adeno-associated virus (AAV) constructs (AAV9-Iba1p-BK shRNA-EGFP (BK shRNA-AAV) or AAV9-Iba1p-NC shRNA-EGFP (NC shRNA-AAV)) were unilaterally injected intracerebroventricularly to selectively knock down BK channels in microglia. The tail suspension test (TST) and forced-swim test (FST) were used to evaluate depressive-like behavior in mice 24 h after LPS challenge. The morphology of microglia, expression of BK channels, levels of cytokines, and expression and activity of indoleamine 2,3-dioxygenase (IDO) were measured by immunohistochemistry, western blot, quantitative real time PCR, and enzyme-linked immunosorbent assay (ELISA), respectively. Either paxilline (i.p.), a specific BK channel blocker, or BK shRNA-AAV effectively inhibited the activation of microglia, reduced the production of IL-1β in the hippocampus and suppressed the expression and activity of IDO in the hippocampus and prefrontal cortex, resulting in the amelioration of depressive-like behavior in mice. These data suggest for the first time that BK channels are involved in LPS-induced depressive-like behaviors. Thus, microglia BK channels may be a potential drug target for the depression treatment.

Role of Inflammatory Mechanisms in Major Depressive Disorder: From Etiology to Potential Pharmacological Targets

The involvement of central and peripheral inflammation in the pathogenesis and prognosis of major depressive disorder (MDD) has been demonstrated. The increase of pro-inflammatory cytokines (interleukin (IL)-1β, IL-6, IL-18, and TNF-α) in individuals with depression may elicit neuroinflammatory processes and peripheral inflammation, mechanisms that, in turn, can contribute to gut microbiota dysbiosis. Together, neuroinflammation and gut dysbiosis induce alterations in tryptophan metabolism, culminating in decreased serotonin synthesis, impairments in neuroplasticity-related mechanisms, and glutamate-mediated excitotoxicity. This review aims to highlight the inflammatory mechanisms (neuroinflammation, peripheral inflammation, and gut dysbiosis) involved in the pathophysiology of MDD and to explore novel anti-inflammatory therapeutic approaches for this psychiatric disturbance. Several lines of evidence have indicated that in addition to antidepressants, physical exercise, probiotics, and nutraceuticals (agmatine, ascorbic acid, and vitamin D) possess anti-inflammatory effects that may contribute to their antidepressant properties. Further studies are necessary to explore the therapeutic benefits of these alternative therapies for MDD.

[Ketamine and suicidal behavior: Contribution of animal models of aggression-impulsivity to understanding its mechanism of action]

More than two-thirds of suicides occur during a major depressive episode. Acting out prevention measures and therapeutic options to manage the suicidal crisis are limited. The impulsive-aggressive dimensions are vulnerability factors associated with suicide in patients suffering from a characterized depressive episode: this can be a dimension involved in animals. Impulsive and aggressive rodent models can help analyze, at least in part, the neurobiology of suicide and the beneficial effects of treatments. Ketamine, a glutamatergic antagonist, by rapidly improving the symptoms of depressive episodes, would help reduce suicidal thoughts in the short term. Animal models share with humans impulsive and aggressive endophenotypes modulated by the serotonergic system (5-HTB receptor, MAO-A enzyme), neuroinflammation or the hypothalamic-pituitary-adrenal axis and stress. Significant effects of ketamine on these endophenotypes remain to be demonstrated.

BNIP3L/NIX-mediated mitophagy alleviates passive stress-coping behaviors induced by tumor necrosis factor-α

Recent studies based on animal models of various neurological disorders have indicated that mitophagy, a selective autophagy that eliminates damaged and superfluous mitochondria through autophagic degradation, may be involved in various neurological diseases. As an important mechanism of cellular stress response, much less is known about the role of mitophagy in stress-related mood disorders. Here, we found that tumor necrosis factor-α (TNF-α), an inflammation cytokine that plays a particular role in stress responses, impaired the mitophagy in the medial prefrontal cortex (mPFC) via triggering degradation of an outer mitochondrial membrane protein, NIP3-like protein X (NIX). The deficits in the NIX-mediated mitophagy by TNF-α led to the accumulation of damaged mitochondria, which triggered synaptic defects and behavioral abnormalities. Genetic ablation of NIX in the excitatory neurons of mPFC caused passive coping behaviors to stress, and overexpression of NIX in the mPFC improved TNF-α-induced synaptic and behavioral abnormalities. Notably, ketamine, a rapid on-set and long-lasting antidepressant, reversed the TNF-α-induced behavioral abnormalities through activation of NIX-mediated mitophagy. Furthermore, the downregulation of NIX level was also observed in the blood of major depressive disorder patients and the mPFC tissue of animal models. Infliximab, a clinically used TNF-α antagonist, alleviated both chronic stress- and inflammation-induced behavioral abnormalities via restoring NIX level. Taken together, these results suggest that NIX-mediated mitophagy links inflammation signaling to passive coping behaviors to stress, which underlies the pathophysiology of stress-related emotional disorders.

Does decreased autophagy and dysregulation of LC3A in astrocytes play a role in major depressive disorder?

Astrocytic dysfunction contributes to the molecular pathogenesis of major depressive disorder (MDD). However, the astrocytic subtype that mainly contributes to MDD etiology and whether dysregulated autophagy in astrocytes is associated with MDD remain unknown. Using a single-nucleus RNA sequencing (snRNA-seq) atlas, three astrocyte subtypes were identified in MDD, while C2 State-1Q astrocytes showed aberrant changes in both cell proportion and most differentially expressed genes compared with other subtypes. Moreover, autophagy pathways were commonly inhibited in astrocytes in the prefrontal cortices (PFCs) of patients with MDD, especially in C2 State-1Q astrocytes. Furthermore, by integrating snRNA-seq and bulk transcriptomic data, we found significant reductions in LC3A expression levels in the PFC region of CUMS-induced depressed mice, as well as in postmortem PFC tissues and peripheral blood samples from patients with MDD. These results were further validated by qPCR using whole-blood samples from patients with MDD and healthy controls. Finally, LC3A expression in the whole blood of patients with MDD was negatively associated with the severity of depressive symptoms. Overall, our results underscore autophagy inhibition in PFC astrocytes as a common molecular characteristic in MDD and might reveal a novel potential diagnostic marker LC3A.

Antidepressant pharmacological mechanisms: focusing on the regulation of autophagy

The core symptoms of depression are anhedonia and persistent hopelessness. Selective serotonin reuptake inhibitors (SSRIs) and their related medications are commonly used for clinical treatment, despite their significant adverse effects. Traditional Chinese medicine with its multiple targets, channels, and compounds, exhibit immense potential in treating depression. Autophagy, a vital process in depression pathology, has emerged as a promising target for intervention. This review summarized the pharmacological mechanisms of antidepressants by regulating autophagy. We presented insights from recent studies, discussed current research limitations, and proposed new strategies for basic research and their clinical application in depression.

Targeting mitophagy for depression amelioration: a novel therapeutic strategy

Major depressive disorder is a global psychiatric condition characterized by persistent low mood and anhedonia, which seriously jeopardizes the physical and mental well-being of affected individuals. While various hypotheses have been proposed to explicate the etiology of depression, the precise pathogenesis and effective treatment of this disorder remain elusive. Mitochondria, as the primary organelles responsible for cellular energy production, possess the ability to meet the essential energy demands of the brain. Research indicated that the accumulation of damaged mitochondria is associated with the onset of depression. Mitophagy, a type of cellular autophagy, specifically targets and removes excess or damaged mitochondria. Emerging evidence demonstrated that mitophagy dysfunction was involved in the progression of depression, and several pharmacological interventions that stimulating mitophagy exerted excellent antidepressant actions. We provided an overview of updated advancements on the regulatory mechanism of mitophagy and the mitophagy abnormality in depressed patients and animals, as well as in cell models of depression. Meanwhile, various therapeutic strategies to restore mitophagy for depression alleviation were also discussed in this review.

PM2.5 induces the inflammatory response in rat spleen lymphocytes through autophagy activation of NLRP3 inflammasome

Recent evidence has suggested that fine particulate matter (PM2.5) can induce inflammatory injury in spleen. However, the underlying mechanisms of injury remain enigmatic. In this study, we aim to clarify the inflammatory injury mechanisms of PM2.5 through investigating the crosstalk between autophagy and nod-like receptor protein 3 (NLRP3) inflammasome. The spleen lymphocytes were extracted from SD rats and subjected to PM2.5 and its water-soluble components. The CCK-8 assay was utilized to explore the effects of PM2.5 and its water-soluble components on lymphocytes. Then, the effects of PM2.5 and its water-soluble components exposure on autophagy and NLRP3 inflammasome were detected by qRT-PCR, western blotting, and immunofluorescence staining. The autophagosome production was observed under the transmission electron microscope. The autophagy inhibitor 3-methyladenine (3MA) following PM2.5 water-soluble components was used to investigate the regulation of NLRP3 inflammasome by autophagy. We found that PM2.5 and its water-soluble components decreased the viability of spleen lymphocytes in a dose-dependent manner. PM2.5 exposure and its water-soluble components exposure activated the autophagy and NlRP3 inflammasome, as indicated by an increased expression of LC3, P62, NLRP3, Caspase-1 p10, and increased release of IL-1β. Furthermore, the treatment with autophagy inhibitor 3MA attenuated the production of autophagosome and NLRP3 inflammasome induced by PM2.5 water-soluble components with decreased expression of NLRP3, Caspase-1 p10, and diminished production of IL-1β. These results suggested that PM2.5 and its water-soluble components could induce autophagy and inflammatory response through NLRP3 inflammasome in spleen lymphocytes, while the NLRP3 inflammasome induced by PM2.5 could be significantly alleviated by inhibition of autophagy, further providing new insights for the understanding of spleen injury caused by PM2.5.

A comparative analysis of antidepressant and anti-suicidal effects of repeated ketamine infusions in elderly and younger adults with depression

OBJECTIVES

This study aims to investigate the differences in safety and antidepressant effects of multi-infusion ketamine treatment between elderly and young adults with depression.

METHODS

The safety, antidepressant, and anti-suicidal effects of multi-infusion ketamine were compared between 19 elderly (≥50 years) and 116 younger (<50 years) adults with depression; all were treated with six ketamine infusions (0.5 mg/kg). Montgomery-Åsberg Depression Rating Scale (MADRS) was used to measure the depressive symptoms, and suicidal ideation was measured with Beck Scale for Suicide Ideation (SSI)-part 1, Hamilton Rating Scale for Depression (HAMD) item 3, and (MADRS) item 10. Dissociative and psychotomimetic symptoms were evaluated based on the Clinician-Administered Dissociative States Scale (CADSS) and the Brief Psychiatric Rating Scale (BPRS)-four items.

RESULTS

Multi-Ketamine infusions resulted in a lower (trend) antidepressant response (37.1 % versus 57.8 %) and antidepressant remission (15.8 % versus 47.4 %) in elderly patients with depression compared with younger patients with depression (all ps > 0.05). Interestingly, elderly patients with depression had a higher MADRS score after six ketamine infusions compared with younger patients (p = 0.04). No significant differences in SSI-part 1 scores, HAMD item 3 scores, MADRS item 10 scores, CADSS scores, and BPRS-four items scores were found between the two groups at any assessment point (all ps > 0.05).

CONCLUSION

Our study shows that repeated-dose infusions of ketamine may be a feasible treatment strategy in elderly Chinese patients with depression; however, elderly patients with depression may be less responsive to ketamine compared with younger adults with depression.

Changes in synaptic markers after administration of ketamine or psychedelics: a systematic scoping review

Background

Ketamine and psychedelics have abuse liability. They can also induce "transformative experiences" where individuals experience enhanced states of awareness. This enhanced awareness can lead to changes in preexisting behavioral patterns which could be beneficial in the treatment of substance use disorders (SUDs). Preclinical and clinical studies suggest that ketamine and psychedelics may alter markers associated with synaptic density, and that these changes may underlie effects such as sensitization, conditioned place preference, drug self-administration, and verbal memory performance. In this scoping review, we examined studies that measured synaptic markers in animals and humans after exposure to ketamine and/or psychedelics.

Methods

A systematic search was conducted following PRISMA guidelines, through PubMed, EBSCO, Scopus, and Web of Science, based on a published protocol (Open Science Framework, DOI: 10.17605/OSF.IO/43FQ9). Both in vivo and in vitro studies were included. Studies on the following synaptic markers were included: dendritic structural changes, PSD-95, synapsin-1, synaptophysin-1, synaptotagmin-1, and SV2A.

Results

Eighty-four studies were included in the final analyses. Seventy-one studies examined synaptic markers following ketamine treatment, nine examined psychedelics, and four examined both. Psychedelics included psilocybin/psilocin, lysergic acid diethylamide, N,N-dimethyltryptamine, 2,5-dimethoxy-4-iodoamphetamine, and ibogaine/noribogaine. Mixed findings regarding synaptic changes in the hippocampus and prefrontal cortex (PFC) have been reported when ketamine was administered in a single dose under basal conditions. Similar mixed findings were seen under basal conditions in studies that used repeated administration of ketamine. However, studies that examined animals during stressful conditions found that a single dose of ketamine counteracted stress-related reductions in synaptic markers in the hippocampus and PFC. Repeated administration of ketamine also counteracted stress effects in the hippocampus. Psychedelics generally increased synaptic markers, but results were more consistently positive for certain agents.

Conclusion

Ketamine and psychedelics can increase synaptic markers under certain conditions. Heterogeneous findings may relate to methodological differences, agents administered (or different formulations of the same agent), sex, and type of markers. Future studies could address seemingly mixed results by using meta-analytical approaches or study designs that more fully consider individual differences.

Lipopolysaccharide-induced depression-like model in mice: meta-analysis and systematic evaluation

Depression is a complex and biologically heterogeneous disorder. Recent studies have shown that central nervous system (CNS) inflammation plays a key role in the development of depression. Lipopolysaccharide (LPS)-induced depression-like model in mice is commonly used to studying the mechanisms of inflammation-associated depression and the therapeutic effects of drugs. Numerous LPS-induced depression-like models in mice exist and differ widely in animal characteristics and methodological parameters. Here, we systematically reviewed studies on PubMed from January 2017 to July 2022 and performed cardinal of 170 studies and meta-analyses of 61 studies to support finding suitable animal models for future experimental studies on inflammation-associated depression. Mouse strains, LPS administration, and behavioral outcomes of these models have been assessed. In the meta-analysis, forced swimming test (FST) was used to evaluate the effect size of different mouse strains and LPS doses. The results revealed large effect sizes in ICR and Swiss mice, but less heterogeneity in C57BL/6 mice. For LPS intraperitoneal dose, the difference did not affect behavioral outcomes in C57BL/6 mice. However, in ICR mice, the most significant effect on behavioral outcomes was observed after the injection of 0.5 mg/kg LPS. Our results suggests that mice strains and LPS administration play a key role in the evaluation of behavioral outcomes in such models.

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.

Recent Developments in Protein Lactylation in PTSD and CVD: Novel Strategies and Targets

In 1938, Corneille Heymans received the Nobel Prize in physiology for discovering that oxygen sensing in the aortic arch and carotid sinus was mediated by the nervous system. The genetics of this process remained unclear until 1991 when Gregg Semenza while studying erythropoietin, came upon hypoxia-inducible factor 1, for which he obtained the Nobel Prize in 2019. The same year, Yingming Zhao found protein lactylation, a posttranslational modification that can alter the function of hypoxia-inducible factor 1, the master regulator of cellular senescence, a pathology implicated in both post-traumatic stress disorder (PTSD) and cardiovascular disease (CVD). The genetic correlation between PTSD and CVD has been demonstrated by many studies, of which the most recent one utilizes large-scale genetics to estimate the risk factors for these conditions. This study focuses on the role of hypertension and dysfunctional interleukin 7 in PTSD and CVD, the former caused by stress-induced sympathetic arousal and elevated angiotensin II, while the latter links stress to premature endothelial cell senescence and early vascular aging. This review summarizes the recent developments and highlights several novel PTSD and CVD pharmacological targets. They include lactylation of histone and non-histone proteins, along with the related biomolecular actors such as hypoxia-inducible factor 1α, erythropoietin, acid-sensing ion channels, basigin, and Interleukin 7, as well as strategies to delay premature cellular senescence by telomere lengthening and resetting the epigenetic clock.

Inflammation, stress and depression: An exploration of ketamine's therapeutic profile

Well-established animal models of depression have described a proximal relationship between stress and central nervous system (CNS) inflammation - a relationship mirrored in the peripheral inflammatory biomarkers of individuals with depression. Evidence also suggests that stress-induced proinflammatory states can contribute to the neurobiology of treatment-resistant depression. Interestingly, ketamine, a rapid-acting antidepressant, can partially exert its therapeutic effects via anti-inflammatory actions on the hypothalamic-pituitary adrenal (HPA) axis, the kynurenine pathway or by cytokine suppression. Further investigations into the relationship between ketamine, inflammation and stress could provide insight into ketamine's unique therapeutic mechanisms and stimulate efforts to develop rapid-acting, anti-inflammatory-based antidepressants.

The Missing Piece? A Case for Microglia's Prominent Role in the Therapeutic Action of Anesthetics, Ketamine, and Psychedelics

There is much excitement surrounding recent research of promising, mechanistically novel psychotherapeutics - psychedelic, anesthetic, and dissociative agents - as they have demonstrated surprising efficacy in treating central nervous system (CNS) disorders, such as mood disorders and addiction. However, the mechanisms by which these drugs provide such profound psychological benefits are still to be fully elucidated. Microglia, the CNS's resident innate immune cells, are emerging as a cellular target for psychiatric disorders because of their critical role in regulating neuroplasticity and the inflammatory environment of the brain. The following paper is a review of recent literature surrounding these neuropharmacological therapies and their demonstrated or hypothesized interactions with microglia. Through investigating the mechanism of action of psychedelics, such as psilocybin and lysergic acid diethylamide, ketamine, and propofol, we demonstrate a largely under-investigated role for microglia in much of the emerging research surrounding these pharmacological agents. Among others, we detail sigma-1 receptors, serotonergic and γ-aminobutyric acid signalling, and tryptophan metabolism as pathways through which these agents modulate microglial phagocytic activity and inflammatory mediator release, inducing their therapeutic effects. The current review includes a discussion on future directions in the field of microglial pharmacology and covers bidirectional implications of microglia and these novel pharmacological agents in aging and age-related disease, glial cell heterogeneity, and state-of-the-art methodologies in microglial research.

NLRP3 Inflammasome’s Activation in Acute and Chronic Brain Diseases—An Update on Pathogenetic Mechanisms and Therapeutic Perspectives with Respect to Other Inflammasomes

Increasingly prevalent acute and chronic human brain diseases are scourges for the elderly. Besides the lack of therapies, these ailments share a neuroinflammation that is triggered/sustained by different innate immunity-related protein oligomers called inflammasomes. Relevant neuroinflammation players such as microglia/monocytes typically exhibit a strong NLRP3 inflammasome activation. Hence the idea that NLRP3 suppression might solve neurodegenerative ailments. Here we review the recent Literature about this topic. First, we update conditions and mechanisms, including RNAs, extracellular vesicles/exosomes, endogenous compounds, and ethnic/pharmacological agents/extracts regulating NLRP3 function. Second, we pinpoint NLRP3-activating mechanisms and known NLRP3 inhibition effects in acute (ischemia, stroke, hemorrhage), chronic (Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, MS, ALS), and virus-induced (Zika, SARS-CoV-2, and others) human brain diseases. The available data show that (i) disease-specific divergent mechanisms activate the (mainly animal) brains NLRP3; (ii) no evidence proves that NLRP3 inhibition modifies human brain diseases (yet ad hoc trials are ongoing); and (iii) no findings exclude that concurrently activated other-than-NLRP3 inflammasomes might functionally replace the inhibited NLRP3. Finally, we highlight that among the causes of the persistent lack of therapies are the species difference problem in disease models and a preference for symptomatic over etiologic therapeutic approaches. Therefore, we posit that human neural cell-based disease models could drive etiological, pathogenetic, and therapeutic advances, including NLRP3’s and other inflammasomes’ regulation, while minimizing failure risks in candidate drug trials.

Role of α-synuclein in microglia: autophagy and phagocytosis balance neuroinflammation in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disease, and is characterized by accumulation of α-synuclein (α-syn). Neuroinflammation driven by microglia is an important pathological manifestation of PD. α-Syn is a crucial marker of PD, and its accumulation leads to microglia M1-like phenotype polarization, activation of NLRP3 inflammasomes, and impaired autophagy and phagocytosis in microglia. Autophagy of microglia is related to degradation of α-syn and NLRP3 inflammasome blockage to relieve neuroinflammation. Microglial autophagy and phagocytosis of released α-syn or fragments from apoptotic neurons maintain homeostasis in the brain. A variety of PD-related genes such as LRRK2, GBA and DJ-1 also contribute to this stability process.

OBJECTIVES

Further studies are needed to determine how α-syn works in microglia.

METHODS

A keyword-based search was performed using the PubMed database for published articles.

CONCLUSION

In this review, we discuss the interaction between microglia and α-syn in PD pathogenesis and the possible mechanism of microglial autophagy and phagocytosis in α-syn clearance and inhibition of neuroinflammation. This may provide a novel insight into treatment of PD.

Ketamine, benzoate, and sarcosine for treating depression

Studies have demonstrated the beneficial therapeutic effects of sarcosine, benzoate, and ketamine (including esketamine and arketamine) on depression. These drugs mainly act by modulating N-methyl-d-aspartate glutamate receptors (NMDARs) and reducing inflammation in the brain. Although ketamine, benzoate, and sarcosine act differently as the antagonists or coagonists of NMDARs, they all have demonstrated efficacy in animal models or human trials. In vitro and in vivo studies have indicated that sarcosine, benzoate, and ketamine exert their anti-inflammatory effects by inhibiting microglial activity. This review summarizes and compares the efficacy of the possible therapeutic mechanisms of sarcosine, benzoate, ketamine, esketamine, and arketamine. These compounds act as both NMDAR modulators and anti-inflammatory drugs and thus can be effective in the treatment of depression.

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.

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.