Mitochondria: A Connecting Link in the Major Depressive Disorder Jigsaw

The Role of Mitochondrial Dysfunction-Mediated Changes in Immune Cytokine Expression in the Pathophysiology and Treatment of Major Depressive Disorder

Recent studies have demonstrated an association between major depressive disorder (MDD) and both mitochondrial dysfunction and alterations in pro-inflammatory cytokine expression, suggesting that such changes may be key drivers of MDD pathogenesis. Mechanistically, changes in mitochondrial function are related to endoplasmic reticulum stress, reactive oxygen species production, oxidative phosphorylation, apoptosis, and disrupted calcium ion homeostasis, all of which trigger the activation of signaling cascades that affect the expression of pro-inflammatory cytokines, including tumor necrosis factor alpha, interleukin 1, interleukin 6, and interferons. Certain factors present in the gut microbiota ecosystem can influence communication between microorganisms and the brain through the neuroendocrine, immune, and autonomic nervous systems, thereby altering mitochondrial function and cytokine production. This review article explores the means through which mitochondria regulate immune cytokine expression and the role of mitochondrial dysfunction in the pathogenesis and treatment of MDD to provide new perspectives for the diagnosis of this disease and the development of novel therapeutic interventions with greater efficacy and improved safety profiles.

Chronic stress induces depression-like behavior in rats through affecting brain mitochondrial function and inflammation

Chronic stress is involved in pathophysiology of depression, and causes some neurochemical alterations in brain. Both mitochondrial dysfunction and neuroinflammation are implicated in mediating the depression-like behavior. The objectives of present study were, at first, to confirm that chronic unpredictable mild stress (CUMS) induces depression-like behavior and alters mitochondrial function and inflammatory responses within the brain, and then to explore the role of mitochondria in the development of this depression-like behavior. It has been found that CUMS exposure induced depression-like behavior, mitochondrial dysfunction, increased IL-1, IL-6, IFN-γ and TNF-α levels in hippocampus and PFC. Moreover, the level of ATP, the key index of mitochondrial function, was inversely correlated with the levels of proinflammatory cytokine. Intracerebroventricular (ICV) injection of the mitochondrial targeted antioxidant MnTBAP significantly alleviated depression-like behavior in CUMS group. These findings suggested that CUMS results in depression-like behavior, mitochondrial dysfunction as well as neuroinflammation, and mitochondria dysfunction contributes to depression-like behavior caused by CUMS.

An Updated Bio-Behavioral Profile of the Flinders Sensitive Line Rat: Reviewing the Findings of the Past Decade

The Flinders sensitive line (FSL) rat is an accepted rodent model for depression that presents with strong face, construct, and predictive validity, thereby making it suitable to investigate novel antidepressant mechanisms. Despite the translatability of this model, available literature on this model has not been reviewed for more than ten years. The PubMed, ScienceDirect and Web of Science databases were searched for relevant articles between 2013 and 2024, with keywords relating to the Flinders line rat, and all findings relevant to treatment naïve animals, included. Following screening, 77 studies were included and used to create behavioral reference standards and calculate FSL favor ratios for the various behavioral parameters. The GRADE and SYRCLE risk of bias tools were used to scale the quality of these studies. Based on these results, FSL rats display reliable and reproducible depressive-like behavior in the forced swim test, together with hyperlocomotor activity across various behavioral tests. Despite reports of increased anhedonia, anxiety-like behavior, and cognitive dysfunction, the reviewed findings indicate that these parameters are comparable between strains. For the various neuro- and biological constructs, oxidative stress, energy production, and glutamatergic, noradrenergic and serotonergic neurotransmission received the most support for strain differences. Taken together, the FSL remains a reliable, popular, and translatable rodent model of depression, with strong face and construct validity. As for predictive validity, similar review approaches should be considered to establish whether the mentioned behavioral aspects and neurochemical constructs may be more sensitive (or resistant) to certain antidepressant strategies.

Mitochondrial Dysfunction as a Biomarker of Illness State in Bipolar Disorder: A Critical Review

Mitochondria are organelles involved in different cellular functions, especially energy production. A relationship between mitochondrial dysfunction and mood disorders, especially bipolar disorder (BD), has been reported in the scientific literature, which suggests altered energy production and higher levels of oxidative stress compared to healthy controls. Specifically, in BD, the hypothesis of a biphasic pattern of energy availability has been postulated according to mood states. Current evidence highlights the presence of mitochondrial dysfunction in BD and variations between the manic, depressive, and euthymic phases. These findings need to be confirmed in future studies to identify biomarkers that may lead to individualized management of patients with BD and also to identify profiles with a higher risk of presenting an unfavorable course of illness, which would enable the design of preventive and therapeutic strategies in determined subpopulations of patients with BD. The limitations of this review include the non-systematic methodology, variety of mitochondrial-related functions associated with BD, heterogeneous study designs, preliminary evidence for specific findings, and limited recommendations regarding the use of mitochondrial modulators in BD.

Major depressive disorder is associated with mitochondrial ND6 T14502C mutation in two Han Chinese families

BACKGROUND

Globally, the World Health Organization ranks major depressive disorder (MDD) as the leading cause of disability. However, MDD molecular etiology is still poorly understood.

AIM

To explore the possible association between mitochondrial ND6 T14502C mutation and MDD.

METHODS

Clinical data were collected from two pedigrees, and detailed mitochondrial genomes were obtained for the two proband members. The assessment of the resulting variants included an evaluation of their evolutionary conservation, allelic frequencies, as well as their structural and functional consequences. Detailed mitochondrial whole genome analysis, phylogenetic, and haplotype analysis were performed on the probands.

RESULTS

Herein, we reported the clinical, genetic, and molecular profiling of two Chinese families afflicted with MDD. These Chinese families exhibited not only a range of onset and severity ages in their depression but also extremely low penetrances to MDD. Sequence analyses of mitochondrial genomes from these pedigrees have resulted in the identification of a homoplasmic T14502C (I58V) mutation. The polymorphism is located at a highly conserved isoleucine at position 58 of ND6 and distinct mitochondrial DNA (mtDNA) polymorphisms originating from haplogroups M10 and H2.

CONCLUSION

Identifying the T14502C mutation in two individuals with no genetic relation who exhibit symptoms of depression provides compelling evidence that this mutation may be implicated in MDD development. Nonetheless, the two Chinese pedigrees that carried the T14502C mutation did not exhibit any functionally significant mutations in their mtDNA. Therefore, the phenotypic expression of the T14502C mutation related to MDD may be influenced by the nuclear modifier gene(s) or environmental factors.

Extremely Low-Frequency Electromagnetic Field (ELF-EMF) Increases Mitochondrial Electron Transport Chain Activities and Ameliorates Depressive Behaviors in Mice

Compromised mitochondrial electron transport chain (ETC) activities are associated with depression in humans and rodents. However, the effects of the enhancement of mitochondrial ETC activities on depression remain elusive. We recently reported that an extremely low-frequency electromagnetic field (ELF-EMF) of as low as 10 μT induced hormetic activation of mitochondrial ETC complexes in human/mouse cultured cells and mouse livers. Chronic social defeat stress (CSDS) for 10 consecutive days caused behavioral defects mimicking depression in mice, and using an ELF-EMF for two to six weeks ameliorated them. CSDS variably decreased the mitochondrial ETC proteins in the prefrontal cortex (PFC) in 10 days, which were increased by an ELF-EMF in six weeks. CSDS had no effect on the mitochondrial oxygen consumption rate in the PFC in 10 days, but using an ELF-EMF for six weeks enhanced it. CSDS inactivated SOD2 by enhancing its acetylation and increased lipid peroxidation in the PFC. In contrast, the ELF-EMF activated the Sirt3-FoxO3a-SOD2 pathway and suppressed lipid peroxidation. Furthermore, CSDS increased markers for mitophagy, which was suppressed by the ELF-EMF in six weeks. The ELF-EMF exerted beneficial hormetic effects on mitochondrial energy production, mitochondrial antioxidation, and mitochondrial dynamics in a mouse model of depression. We envisage that an ELF-EMF is a promising therapeutic option for depression.

Chronic stress dysregulates the Hippo/YAP/14-3-3η pathway and induces mitochondrial damage in basolateral amygdala in a mouse model of depression

Rationale: Recent evidence highlights the pivotal role of mitochondrial dysfunction in mood disorders, but the mechanism involved remains unclear. We studied whether the Hippo/YAP/14-3-3η signaling pathway mediates mitochondrial abnormalities that result in the onset of major depressive disorder (MDD) in a mouse model. Methods: The ROC algorithm was used to identify a subpopulation of mice that were exposed to chronic unpredictable mild stress (CUMS) and exhibited the most prominent depressive phenotype (Dep). Electron microscopy, biochemical assays, quantitative PCR, and immunoblotting were used to evaluate synaptic and mitochondrial changes in the basolateral amygdala (BLA). RNA sequencing was used to explore changes in the Hippo pathway and downstream target genes. In vitro pharmacological inhibition and immunoprecipitation was used to confirm YAP/14-3-3η interaction and its role in neuronal mitochondrial dysfunction. We used virus-mediated gene overexpression and knockout in YAP transgenic mice to verify the regulatory effect of the Hippo/YAP/14-3-3η pathway on depressive-like behavior. Results: Transcriptomic data identified a large number of genes and signaling pathways that were specifically altered from the BLA of Dep mice. Dep mice showed notable synaptic impairment in BLA neurons, as well as mitochondrial damage characterized by abnormal mitochondrial morphology, compromised function, impaired biogenesis, and alterations in mitochondrial marker proteins. The Hippo signaling pathway was activated in Dep mice during CUMS, and the transcriptional regulatory activity of YAP was suppressed by phosphorylation of its Ser127 site. 14-3-3η was identified as an important co-regulatory factor of the Hippo/YAP pathway, as it can respond to chronic stress and regulate cytoplasmic retention of YAP. Importantly, the integrated Hippo/YAP/14-3-3η pathway mediated neuronal mitochondrial dysfunction and depressive behavior in Dep mice. Conclusion: The integrated Hippo/YAP/14-3-3η pathway in the BLA neuron is critical in mediating depressive-like behaviors in mice, suggesting a causal role for this pathway in susceptibility to chronic stress-induced depression. This pathway therefore may present a therapeutic target against mitochondrial dysfunction and synaptic impairment in MDD.

CB1 receptor mediates anesthetic drug ketamine‑induced neuroprotection against glutamate in HT22 cells

The anesthetic drug, ketamine (KTM) has been shown to induce therapeutic effects against major depressive disorder (MDD), however the related underlying mechanisms remain unclear. In the present study, HT22 neuronal cells were treated with glutamate to imitate oxidative stress injury in MDD, and it was hypothesized that the cannabinoid type 1 (CB1) receptor mediates KTM-induced neuroprotection via ameliorating mitochondrial function in glutamate-treated neuronal cells. Compared with the control, glutamate decreased cell viability and intracellular antioxidants, including glutathione (GSH), catalase and superoxide dismutase 2 levels, and inhibited mitochondrial function simultaneously. Moreover, glutamate increased lactate dehydrogenase release, cellular apoptosis level, cleaved caspase-3 expression and intracellular oxidants, such as reactive oxygen species, oxidized GSH and mitochondrial superoxide in the cells. The presence of KTM, however, significantly decreased the glutamate-induced oxidative stress injury, ameliorated the antioxidant/oxidant levels in the cells, enhanced mitochondrial function and upregulated CB1 receptor expression (P<0.05). Co-administration of the CB1 receptor antagonist AM251 markedly abolished the KTM-induced cytoprotective effects and ameliorations of antioxidant/oxidant levels and mitochondrial function, and also reversed CB1 upregulation (P<0.05). These observations indicated that KTM decreases the oxidative stress injury caused by glutamate in HT22 neuronal cells, and the neuroprotective effects may be mediated by the CB1 receptor.

Mitochondrial dynamics dysfunction: Unraveling the hidden link to depression

Depression is a common mental disorder and its pathogenesis is not fully understood. However, more and more evidence shows that mitochondrial dynamics dysfunction may play an important role in the occurrence and development of depression. Mitochondria are the centre of energy production in cells, and are also involved in important processes such as apoptosis and oxidative stress. Studies have found that there are abnormalities in mitochondrial function in patients with depression, including mitochondrial morphological changes, mitochondrial dynamics disorders, mitochondrial DNA damage, and impaired mitochondrial respiratory chain function. These abnormalities may cause excessive free radicals and oxidative stress in mitochondria, which further damage cells and affect the balance of neurotransmitters, causing or aggravating depressive symptoms. Studies have shown that mitochondrial dynamics dysfunction may participate in the occurrence and development of depression by affecting neuroplasticity, inflammation and neurotransmitters. This article reviews the effects of mitochondrial dynamics dysfunction on the pathogenesis of depression and its potential molecular pathway. The restorers for the treatment of depression by regulating the function of mitochondrial dynamics were summarized and the possibility of using mitochondrial dynamics as a biomarker of depression was discussed.

Serotonin regulation of mitochondria in kidney diseases

Serotonin, while conventionally recognized as a neurotransmitter in the CNS, has recently gained attention for its role in the kidney. Specifically, serotonin is not only synthesized in the kidney, but it also regulates glomerular function, vascular resistance, and mitochondrial homeostasis. Because of serotonin's importance to mitochondrial health, this review is focused on the role of serotonin and its receptors in mitochondrial function in the context of acute kidney injury, chronic kidney disease, and diabetic kidney disease, all of which are characterized by mitochondrial dysfunction and none of which has approved pharmacological treatments. Evidence indicates that activation of certain serotonin receptors can stimulate mitochondrial biogenesis (MB) and restore mitochondrial homeostasis, resulting in improved renal function. Serotonin receptor agonists that induce MB are therefore of interest as potential therapeutic strategies for renal injury and disease. SIGNIFICANCE STATEMENT: Mitochondrial dysfunction is associated with many human renal diseases such as acute kidney injury, chronic kidney disease, and diabetic kidney disease, which are associated with increased morbidity and mortality. Unfortunately, none of these pathologies has an FDA-approved pharmacological intervention, underscoring the urgency of identifying new therapeutics for such disorders. Studies show that induction of mitochondrial biogenesis via serotonin (5-hydroxytryptamine, 5-HT) receptors reduces kidney injury markers, restores mitochondrial and renal function after kidney injury, and decreases mortality, suggesting that targeting 5-HT receptors may be a promising therapeutic avenue for mitochondrial dysfunction in kidney diseases. While numerous reviews describe the importance of mitochondria and mitochondrial quality control mechanisms in kidney disease, the relevance of 5-HT receptor-mediated mitochondrial metabolic modulation in the kidney has yet to be thoroughly explored.

Ndufs4 KO mice: A model to study comorbid mood disorders associated with mitochondrial dysfunction

The Ndufs4 knockout (KO) mouse is a validated and robust preclinical model of mitochondrial diseases (specifically Leigh syndrome), that displays a narrow window of relative phenotypical normality, despite its inherent mitochondrial complex I dysfunction and severe phenotype. Preclinical observations related to psychiatric comorbidities that arise in patients with mitochondrial diseases and indeed in Leigh syndrome are, however, yet to be investigated in this model. Strengthening this narrative is the fact that major depression and bipolar disorder are known to present with deficits in mitochondrial function. We therefore screened the behavioural profile of male and female Ndufs4 KO mice (relative to heterozygous; HET and wildtype; WT mice) between postnatal days 28 and 35 for locomotor, depressive- and anxiety-like alterations and linked it with selected brain biomarkers, viz. serotonin, kynurenine, and redox status in brain areas relevant to psychiatric pathologies (i.e., prefrontal cortex, hippocampus, and striatum). The Ndufs4 KO mice initially displayed depressive-like behaviour in the tail suspension test on PND31 but not on PND35 in the forced swim test. In the mirror box test, increased risk resilience was observed. Serotonin levels of KO mice, compared to HET controls, were increased on PND36, together with increased tryptophan to serotonin and kynurenine turnover. Kynurenine to kynurenic acid turnover was however decreased, while reduced versus oxidized glutathione ratio (GSH/GSSG) was increased. When considering the comorbid psychiatric traits of patients with mitochondrial disorders, this work elaborates on the neuropsychiatric profile of the Ndufs KO mouse. Secondly, despite locomotor differences, Ndufs4 KO mice present with a behavioural profile not unlike rodent models of bipolar disorder, namely variable mood states and risk-taking behaviour. The model may elucidate the bio-energetic mechanisms underlying mood disorders, especially in the presence of mitochondrial disease. Studies are however required to further validate the model's translational relevance.

Overview of metabolomic aspects in postpartum depression

Along with the typical biochemical alterations that occur during pregnancy, certain metabolic changes might be associated with the development of several psychiatric disorders, including postpartum depression (PPD), which is the most common type of psychiatric disorder during pregnancy or first postpartum year, and it develops in about 15% of women. Metabolomics is a rapidly developing discipline that deals with the metabolites as the final products of all genetically controlled biochemical pathways, highly influenced by external and internal changes. The aim of this paper was to review the published studies whose results suggest or deny a possible association between the fine regulation of the metabolome and PPD, enabling conclusions about whether metabolomics could be a useful tool in defining the biochemical pathways directly involved in the etiology, diagnosis and course of PPD. Beside numerous hormonal changes, a lot of different metabolic pathways have been discovered to be affected in women with PPD or associated with its development, including alterations in the energy metabolism, tryptophan and amino acid metabolism, steroid metabolism, purine cycle, as well as neurotransmitter metabolism. Additionally, metabolomics helped in defining the association between PPD and the exposure to various endocrine disrupting metabolites during pregnancy. Finally, metabolome reflects different PPD therapies and exposure of fetus or breastfed infants to pharmacotherapy prescribed to a mother suffering from PPD. This review can help in creating the picture about metabolomics' broad application in PPD studies, but it also implies that its potential is still not completely used.

Running from depression: the antidepressant-like potential of prenatal and pre-pubertal exercise in adolescent FSL rats exposed to an early-life stressor

OBJECTIVE

We aimed to answer the questions of whether early-life (perinatal and/or juvenile) exercise can induce antidepressant-like effects in a validated rodent model of depression, and whether such early-life intervention could prevent or reverse the adverse effects of early-life stress in their offspring.

METHODS

Male and female Flinders sensitive line rats born to a dam that exercised during gestation, or not, were either maternally separated between PND02 and 16 and weaned on PND17 or not. Half of these animals then underwent a fourteen-day low-intensity exercise regimen from PND22. Baseline depressive-like behaviour was assessed on PND21 and then reassessed on PND36, whereafter hippocampal monoamine levels, redox state markers and metabolic markers relevant to mitochondrial function were measured.

RESULTS

Pre-pubertal exercise was identified as the largest contributing factor to the observed effects, where it decreased immobility time in the FST by 6%, increased time spent in the open arms of the EPM by 9%. Hippocampal serotonin and norepinephrine levels were also increased by 35% and 26%, respectively, whilst nicotinic acid was significantly decreased.

CONCLUSION

These findings suggest that pre-pubertal low-intensity exercise induces beneficial biological alterations that could translate into antidepressant behaviour in genetically susceptible individuals.

Mitochondria of intestinal epithelial cells in depression: Are they at a crossroads of gut-brain communication?

The role of gut dysbiosis in depression is well established. However, recent studies have shown that gut microbiota is regulated by intestinal epithelial cell (IEC) mitochondria, which has yet to receive much attention. This review summarizes the recent developments about the critical role of IEC mitochondria in actively maintaining gut microbiota, intestinal metabolism, and immune homeostasis. We propose that IEC mitochondrial dysfunction alters gut microbiota composition, participates in cell fate, mediates oxidative stress, activates the peripheral immune system, causes peripheral inflammation, and transmits peripheral signals through the vagus and enteric nervous systems. These pathological alterations lead to brain inflammation, disruption of the blood-brain barrier, activation of the hypothalamic-pituitary-adrenal axis, activation of microglia and astrocytes, induction of neuronal loss, and ultimately depression. Furthermore, we highlight the prospect of treating depression through the mitochondria of IECs. These new findings suggest that the mitochondria of IECs may be a newly found important factor in the pathogenesis of depression and represent a potential new strategy for treating depression.

Resveratrol Attenuates Chronic Unpredictable Mild Stress-Induced Alterations in the SIRT1/PGC1α/SIRT3 Pathway and Associated Mitochondrial Dysfunction in Mice

Environmental challenges, specifically chronic stress, have long been associated with neuropsychiatric disorders, including anxiety and depression. Sirtuin-1 (SIRT1) is a NAD+-dependent deacetylase that is widely distributed in the cortex and is involved in stress responses and neuropsychiatric disorders. Nevertheless, how chronic stress modulates the SIRT1 pathway and associated signaling remains unclear. In this study, we first explored the impact of chronic unpredictable mild stress (CUMS) on the SIRT1/PGC1α/SIRT3 pathway, on GABAergic mechanisms, and on mitophagy, autophagy and apoptosis in mice. We also asked whether activation of SIRT1 by resveratrol (RSV) can attenuate CUMS-induced molecular and behavioral alterations. Two-month-old C57/BL6J mice were subjected to three weeks of CUMS and one week of RSV treatment (30 mg/kg; i.p.) during the third week of CUMS. CUMS caused downregulation of the SIRT1/PGC1α/SIRT3 pathway leading to impaired mitochondrial morphology and function. CUMS also resulted in a reduction in numbers of parvalbumin-positive interneurons and increased oxidative stress leading to reduced expression of autophagy- and mitophagy-related proteins. Strikingly, activation of SIRT1 by RSV ameliorated expression of SIRT1/PGC1α/SIRT3, and also improved mitochondrial function, GABAergic mechanisms, mitophagy, autophagy and apoptosis. RSV also rescued CUMS-induced anxiety-like and depressive-like behavior in mice. Our results raise the compelling possibility that RSV treatment might be a viable therapeutic method of blocking stress-induced behavioral alterations.

Plasma acetyl-l-carnitine and l-carnitine in major depressive episodes: a case-control study before and after treatment

BACKGROUND

Major depressive disorder (MDD) is the main cause of disability worldwide, its outcome is poor, and its underlying mechanisms deserve a better understanding. Recently, peripheral acetyl-l-carnitine (ALC) has been shown to be lower in patients with major depressive episodes (MDEs) than in controls. l-Carnitine is involved in mitochondrial function and ALC is its short-chain acetyl-ester. Our first aim was to compare the plasma levels of l-carnitine and ALC, and the l-carnitine/ALC ratio in patients with a current MDE and healthy controls (HCs). Our second aim was to assess their changes after antidepressant treatment.

METHODS

l-Carnitine and ALC levels and the carnitine/ALC ratio were measured in 460 patients with an MDE in a context of MDD and in 893 HCs. Depressed patients were re-assessed after 3 and 6 months of antidepressant treatment for biology and clinical outcome.

RESULTS

As compared to HC, depressed patients had lower ALC levels (p < 0.00001), higher l-carnitine levels (p < 0.00001) and higher l-carnitine/ALC ratios (p < 0.00001). ALC levels increased [coefficient: 0.18; 95% confidence interval (CI) 0.12-0.24; p < 0.00001], and l-carnitine levels (coefficient: -0.58; 95% CI -0.75 to -0.41; p < 0.00001) and l-carnitine/ALC ratios (coefficient: -0.41; 95% CI -0.47 to -0.34; p < 0.00001), decreased after treatment. These parameters were completely restored after 6 months of antidepressant. Moreover, the baseline l-carnitine/ALC ratio predicted remission after 3 months of treatment (odds ratio = 1.14; 95% CI 1.03-1.27; p = 0.015).

CONCLUSIONS

Our data suggest a decreased mitochondrial metabolism of l-carnitine into ALC during MDE. This decreased mitochondrial metabolism is restored after a 6-month antidepressant treatment. Moreover, the magnitude of mitochondrial dysfunction may predict remission after 3 months of antidepressant treatment. New strategies targeting mitochondria should be explored to improve treatments of MDD.

Neurobiological Mechanisms Of Depression Following Traumatic Brain Injury

OBJECTIVE

Depression is among the most pervasive and debilitating neuropsychiatric sequelae experienced by patients following a traumatic brain injury (TBI). While the individual mechanisms underlying depression and TBI have been widely studied, the neurobiological bases of depression after TBI remain largely unknown. This article highlights the potential mechanisms of action implicated in depression after TBI.

RESULTS

We review putative mechanisms of action including neuroinflammation, neuroendocrine dysregulation, metabolic abnormalities, and neurotransmitter and circuitry dysfunction. We also identify the current limitations in the field and propose directions for future research.

CONCLUSION

An improved understanding of the underlying mechanisms will aid the development of precision-guided and personalized treatments for patients suffering from depression after TBI.

Therapeutic Potential of the Purinergic System in Major Depressive Disorder Associated with COVID-19

Neuroinflammation is closely related to the development of depression, since the latter is caused, among other factors, by inflammatory processes, mainly related to the activation of microglia and expression of specific genes, which occurs during the neuroinflammatory process. Thus, COVID-19 is an important risk factor for the development of depression, since in addition to generating the feeling of stress, which also increases the activity of the immune system, it is also the cause of pathological processes and physiological ones that lead to the development of neuroinflammation, microglial activation, gene expression dysfunction and decreased concentration of available serotonin. That said, drugs are being used to combat COVID-19 to reduce the oxidative stress presented in the disease. Thus, tramadol and fluoxetine are highlighted as drugs used, however, although they present some positive results, such as the reduction of pro-inflammatory cytokines, they are also associated with negative effects such as dependence, pulmonary, cardiac and brain impairment. From this, the purinergic system is highlighted in the literature as a possible therapeutic target. This is because its mechanisms are related to the regulation of microglia, astrocytes and the physiology of important neurotransmitters and hormones. Added to this, there is a modulation of inflammatory activity, especially with regard to the P2X7 receptors of this system. The latter is an important target for the treatment of depression and COVID-19, since positive results were obtained through the genetic exclusion of this receptor and the use of selective antagonists.

Maternal Metabolites Indicative of Mental Health Status during Pregnancy

Approximately 25% of individuals report poor mental health during their pregnancy or postpartum period, which may impact fetal neurodevelopment, birth outcomes, and maternal behaviors. In the present study, maternal serum samples were collected from pregnancies at 28-32 weeks gestation from the All Our Families (Alberta, Canada) cohort and assessed using nuclear magnetic resonance spectroscopy (¹H-NMR) and inductively coupled plasma-mass spectrometry (ICP-MS). Individuals with poor mental health at 34-36 weeks gestation were age-matched with mentally healthy pregnant controls. Metabolites were examined against validated self-reported mental health questionnaires for associations with depressive symptoms (Edinburgh Perinatal Depression Scale) and anxiety symptoms (Spielberger State-Trait Anxiety Inventory). ¹H-NMR metabolites were identified for depression (alanine, leucine, valine, methionine, phenylalanine, glucose, lactate, 3-hydroxybutyrate, and pyruvate) and anxiety (3-hydroxybutyrate). For ICP-MS, antimony and zinc were significant for depression and anxiety, respectively. Upon false discovery rate (FDR) correction at 10%, five ¹H-NMR metabolites (alanine, leucine, lactate, glucose, and phenylalanine) for depression remained significantly increased. Although results warrant further validation, the identified metabolites may serve as a predictive tool for assessing mental health during pregnancy as earlier identification has the potential to aid intervention and management of poor mental health symptomology, thus avoiding harmful consequences to both mother and offspring.

Forgetful, sad and old: Do vascular cognitive impairment and depression share a common pre-disease network and how is it impacted by ageing?

Vascular cognitive impairment (VCI) and depression frequently coexist in geriatric populations and reciprocally increase disease risks. We assert that a shared pre-disease state of the psycho-immune-neuroendocrine (PINE) network model mechanistically explains bidirectional associations between VCI and depression. Five pathophysiological sub-networks are identified that are shared by VCI and depression: neuroinflammation, kynurenine pathway imbalance, hypothalamic-pituitary-adrenal (HPA) axis overactivity, impaired neurotrophic support and cerebrovascular dysfunction. These do not act independently, and their complex interactions necessitate a systems biology approach to better define disease pathogenesis. The PINE network is already established in the context of non-communicable diseases (NCDs) such as depression, hypertension, atherosclerosis, coronary heart disease and type 2 diabetes mellitus. We build on previous literature to specifically explore mechanistic links between MDD and VCI in the context of PINE pathways and discuss key mechanistic commonalities linking these comorbid conditions and identify a common pre-disease state which precedes transition to VCI and MDD. We expand the model to incorporate bidirectional interactions with biological ageing. Diathesis factors for both VCI and depression feed into this network and the culmination of shared mechanisms (on an ageing substrate) lead to a critical network transition to one or both disease states. A common pre-disease state underlying VCI and depression can provide clinicians a unique opportunity for early risk assessment and intervention in disease development. Establishing the mechanistic elements and systems biology of this network can reveal early warning or predictive biomarkers together with novel therapeutic targets. Integrative studies are recommended to elucidate the dynamic networked biology of VCI and depression over time.

IL10/AMPK pathway was associated with the hippocampal anti-inflammatory response to high-sugar and high-fat diet withdrawal

OBJECTIVE

The present experimental study aimed to evaluate the effect of consuming an obesogenic diet (OD) on serum and hippocampal inflammation and proteins related to energy metabolism, alongside, we evaluated how the same parameters responded to an OD withdrawal.

SUBJECTS

Thirty male 60-days-old Wistar rats were used.

METHODS

The control group (n = 10) was fed the control diet across the whole experiment. The remaining animals were fed a high-sugar/high-fat (HSHF) diet for 30 days (n = 20) and half of them were placed on the control diet for 48 h (n = 10) afterwards.

RESULTS

OD intake decreased hippocampal AMPK phosphorylation, although, it did not increase serum inflammation and only increased hippocampal pNFκBp65 levels without any increase in the cytokines assessed. Moreover, OD withdrawal led to higher inflammatory markers in the serum and hippocampus and higher hippocampal AMPK phosphorylation. The mediation models applied suggested that the effect of OD withdrawal on hippocampal inflammation was driven by serum inflammation, which activated the hippocampal IL10/AMPK anti-inflammatory pathway as a response.

CONCLUSION

Our analyses suggest that OD withdrawal increases serum inflammation with hippocampal consequent inflammatory alterations. Despite the general assumption that improving diet improves health, this may not be immediate.

New Mechanisms and Targets of Subarachnoid Hemorrhage: A Focus on Mitochondria

Spontaneous subarachnoid hemorrhage (SAH) accounts for 5-10% of all strokes and is a subtype of hemorrhagic stroke that places a heavy burden on health care. Despite great progress in surgical clipping and endovascular treatment for ruptured aneurysms, cerebral vasospasm (CVS) and delayed cerebral ischemia (DCI) threaten the long-term outcomes of patients with SAH. Moreover, there are limited drugs available to reduce the risk of DCI and adverse outcomes in SAH patients. New insight suggests that early brain injury (EBI), which occurs within 72 h after the onset of SAH, may lay the foundation for further DCI development and poor outcomes. The mechanisms of EBI mainly include excitotoxicity, oxidative stress, neuroinflammation, blood-brain barrier (BBB) destruction, and cellular death. Mitochondria are a double-membrane organelle, and they play an important role in energy production, cell growth, differentiation, apoptosis, and survival. Mitochondrial dysfunction, which can lead to mitochondrial membrane potential (Δψm) collapse, overproduction of reactive oxygen species (ROS), release of apoptogenic proteins, disorders of mitochondrial dynamics, and activation of mitochondria-related inflammation, is considered a novel mechanism of EBI related to DCI as well as post-SAH outcomes. In addition, mitophagy is activated after SAH. In this review, we discuss the latest perspectives on the role of mitochondria in EBI and DCI after SAH. We emphasize the potential of mitochondria as therapeutic targets and summarize the promising therapeutic strategies targeting mitochondria for SAH.

Metabolomics Based on Peripheral Blood Mononuclear Cells to Dissect the Mechanisms of Chaigui Granules for Treating Depression

Chaigui granules were a traditional Chinese medicine (TCM) preparation with antidepressant effects derived from a famous antidepressant prescription. It was of great significance to clarify the antidepressant mechanism of Chaigui granules for the clinical application of this drug. In this study, a chronic unpredictable mild stress (CUMS) depression model was successfully established, and behavioral indicators were used to evaluate the antidepressant effect. Second, the CD4+, CD8+, and CD4+/CD8+ levels were detected in peripheral blood. Meanwhile, the amount of inflammatory cytokines was determined in serum. Correspondingly, LC/MS-based peripheral blood mononuclear cell (PBMC) metabolomics was used to investigate vital metabolic pathways participating in the antidepressive effects of Chaigui granules. Finally, bioinformatics technology was further employed to discover the potential antidepressant mechanism of Chaigui granules regulating the immune system. The results suggested that the administration of Chaigui granules significantly improved CUMS-induced depressive symptoms. Chaigui granules could improve immune function by regulating T lymphocyte subsets, increasing anti-inflammatory cytokine levels of IL-2 and IL-10, and reducing pro-inflammatory cytokine levels of TNF-α, IL-1β, and IL-6. In addition, metabolomics results of PBMCs showed that Chaigui granules improved 14 of the 25 potential biomarkers induced by CUMS. Metabolic pathway analyses indicated that purine metabolism was the critical metabolic pathway regulated by Chaigui granules. Furthermore, correlation analysis indicated that 13 key biomarkers were related to immune-related indicators. The metabolite-gene network of 13 key biomarkers was investigated by using bioinformatics. The investigation showed that 10 targets (5'-nucleotidase ecto; 5'-nucleotidase, cytosolic IB; 5'-nucleotidase, cytosolic II; etc.), mainly belong to the purine metabolism, might be potential targets for Chaigui granules to exert their antidepressant effects by improving immune function impairment. Together, our results suggested that Chaigui granules might exert antidepressant effects by improving immune function and regulating the purine metabolic pathway in PBMCs. This work used PBMCs metabolomics as an entry point to study the antidepressant mechanism of Chaigui granules, which provided a new way to elucidate the mechanism of a traditional Chinese medicine prescription.

Depression and obesity among females, are sex specificities considered?

This study aimed to systematically review the relationship of obesity-depression in the female sex. We carried out a systematic search (PubMed, MEDLINE, Embase) to quantify the articles (controlled trials and randomized controlled trials) regarding obesity and depression on a female population or a mixed sample. Successively, we established whether the sex specificities were studied by the authors and if they reported on collecting data regarding factors that may contribute to the evolution of obesity and depression and that could be responsible for the greater susceptibility of females to those conditions. After applying the inclusion and exclusion criteria, we found a total of 20 articles with a female sample and 54 articles with a mixed sample. More than half of all articles (51.35%, n = 38) evaluated the relationship between depression and obesity, but only 20 (27.03%) evaluated this relationship among females; still, 80% of those (n = 16) presented supporting results. However, few articles considered confounding factors related to female hormones (12.16%, n = 9) and none of the articles focused on factors responsible for the binomial obesity-depression in the female sex. The resulting articles also supported that depression (and related impairments) influencing obesity (and related impairments) is a two-way road. This systematic review supports the concurrency of obesity-depression in females but also shows how sex specificities are ultimately under-investigated. Female sex specificity is not being actively considered when studying the binomial obesity-depression, even within a female sample. Future studies should focus on trying to understand how the female sex and normal hormonal variations influence these conditions.

An investigation into nicotinic receptor involvement in mood disorders uncovers novel depression candidate genes

BACKGROUND

We have previously reported reduced expression of the cholinergic autoreceptor CHRM2 in Brodmann's Area (BA) 24 of the anterior cingulate cortex from subjects with major depressive disorder (MDD) and bipolar disorder (BD), consistent with a hypercholinergic state. This led us to investigate whether levels of the high affinity nicotinic acetylcholine receptors are also altered in BA 24.

METHODS

We measured the binding levels of a high-affinity nicotinic receptor-selective radioligand, [³H]epibatidine, in BA 24 from subjects with MDD (n = 20), BD (n = 18) and age- and sex-matched controls (n = 20). We used qPCR to measure mRNA expression of the high affinity nicotinic acetylcholine receptor subunit CHRNB2 in these subjects.

RESULTS

[³H]Epibatidine binding density and CHRNB2 mRNA expression were not significantly altered in either MDD or BD compared to control levels. While validating reference genes for our qPCR experiments, we found that the mRNA levels of 3 putative reference genes, TFB1M, PPIA and SNCA, were increased in MDD but not BD compared to controls. Further investigations in other cortical regions showed that these changes were specific to BA24.

LIMITATIONS

Cohort size and available patient data were limited due to standard constraints associated with post-mortem studies.

CONCLUSION

Our data suggest that decreased CHRM2 in BA24 in mood disorders is not associated with a corresponding change in high affinity nicotinic acetylcholine receptor expression. Our findings of increased TFB1M, PPIA and SNCA expression in MDD point to a broader derangement of several homeostatic pathways in MDD that are distinct from BD.

The Role of Mitochondria in Mood Disorders: From Physiology to Pathophysiology and to Treatment

Mitochondria are cellular organelles involved in several biological processes, especially in energy production. Several studies have found a relationship between mitochondrial dysfunction and mood disorders, such as major depressive disorder and bipolar disorder. Impairments in energy production are found in these disorders together with higher levels of oxidative stress. Recently, many agents capable of enhancing antioxidant defenses or mitochondrial functioning have been studied for the treatment of mood disorders as adjuvant therapy to current pharmacological treatments. A better knowledge of mitochondrial physiology and pathophysiology might allow the identification of new therapeutic targets and the development and study of novel effective therapies to treat these specific mitochondrial impairments. This could be especially beneficial for treatment-resistant patients. In this article, we provide a focused narrative review of the currently available evidence supporting the involvement of mitochondrial dysfunction in mood disorders, the effects of current therapies on mitochondrial functions, and novel targeted therapies acting on mitochondrial pathways that might be useful for the treatment of mood disorders.

Bag-1 mediates glucocorticoid receptor trafficking to mitochondria after corticosterone stimulation: Potential role in regulating affective resilience

Molecular abnormalities within the Glucocorticoid Receptor (GR) stress signaling pathway involved in dysfunction of mitochondria and confer vulnerability to stress-related psychiatric disorders. Bcl-2 associated athanogene (Bag-1) is a target for the actions of mood stabilizers. Bag-1 interacts with GR, thereby regulating glucocorticoid function. In this study, we investigate the potential role of Bag-1 in regulating GR translocation into mitochondria. Corticosterone (CORT) treatment significantly enhanced Bag-1/GR complex formation and GR mitochondrial translocation in cultured rat cortical neurons after treatment for 30 min and 24 hr. By contrast, after stimulation with CORT for 3 days, localization of the Bag-1/GR complex and mitochondrial GR were reduced. Similar results were obtained in mice, in which administrated CORT in drinking water for 21 days significantly impaired the GR levels in the mitochondria, while Bag-1 over-expression rescued this reduction. Furthermore, chronic CORT exposure led to anhedonia-like and depression-like behaviors in the sucrose-consumption test and forced swimming test, and these behaviors were rescued by Bag-1 over-expression. These results suggest that Bag-1 mediates GR trafficking to mitochondria and regulates affective resilience in response to a CORT increase and provide potential insight into the mechanisms by which Bag-1 and GR could contribute to the physiology and pathogenesis of psychiatric disorders in response to the change of stress hormone.

Clinical Evidence of Antidepressant Effects of Insulin and Anti-Hyperglycemic Agents and Implications for the Pathophysiology of Depression-A Literature Review

Close connections between depression and type 2 diabetes (T2DM) have been suggested by many epidemiological and experimental studies. Disturbances in insulin sensitivity due to the disruption of various molecular pathways cause insulin resistance, which underpins many metabolic disorders, including diabetes, as well as depression. Several anti-hyperglycemic agents have demonstrated antidepressant properties in clinical trials, probably due to their action on brain targets based on the shared pathophysiology of depression and T2DM. In this article, we review reports of clinical trials examining the antidepressant effect of these medications, including insulin, metformin, glucagon like peptide-1 receptor agonists (GLP-1RA), and peroxisome proliferator-activated receptor (PPAR)-γ agonists, and briefly consider possible molecular mechanisms underlying the associations between amelioration of insulin resistance and improvement of depressive symptoms. In doing so, we intend to suggest an integrative perspective for understanding the pathophysiology of depression.

Post-stroke depression: A 2020 updated review

BACKGROUND

Post-stroke depression (PSD) is common and associated with higher mortality, poorer recovery, more pronounced cognitive deficits, and lower quality of life than is stroke without depression. This manuscript will conduct an updated, comprehensive and clinically-useful review of the risk factors, pathophysiology, assessment, prevention, and treatment of PSD.

METHODS

This narrative review summarizes articles obtained on PubMed, Medline, EMBase, Google Scholar and the Cochrane Database. This review prioritized articles with a more robust level of evidence, such as original articles with longitudinal data and/or larger samples, randomized controlled trials, systematic reviews, and metaanalyses.

RESULTS

One hundred twenty-four articles were reviewed, of which 44 (35%) were published before 2016 and 80 (65%) that were published since 2016.

DISCUSSION

Rates of PSD range from 18 to 33%, yet it is vastly underdiagnosed and undertreated. Risk factors for PSD include female sex, history of psychiatric illness, large or multiple strokes, injuries in frontal/anterior areas or in the basal ganglia, stroke occurrence within the past year, poor social support, and pronounced disability. The pathophysiology of PSD is multifactorial and likely involves decreased levels of monoamines, abnormal neurotrophic response, increased inflammation with dysregulation of hypothalamic-pituitary-adrenal axis, and glutamate-mediated excitotoxicity. The evidence for preventive interventions for PSD is somewhat inconsistent and modest. The best treatment for PSD consists of the combination of pharmacological, psychosocial and stroke-focused interventions.

CONCLUSION

PSD is a common, treatable condition that is associated with several negative outcomes. Early detection and proper management are critical to obtain better outcomes in individuals with PSD.

Mangosteen Pericarp and Its Bioactive Xanthones: Potential Therapeutic Value in Alzheimer's Disease, Parkinson's Disease, and Depression with Pharmacokinetic and Safety Profiles

Alzheimer's disease (AD), Parkinson's disease (PD), and depression are growing burdens for society globally, partly due to a lack of effective treatments. Mangosteen (Garcinia mangostana L.,) pericarp (MP) and its xanthones may provide therapeutic advantages for these disorders. In this review, we discuss potential therapeutic value of MP-derived agents in AD, PD, and depression with their pharmacokinetic and safety profiles. MP-derived agents have shown multifunctional effects including neuroprotective, antioxidant, and anti-neuroinflammatory actions. In addition, they target specific disease pathologies, such as amyloid beta production and deposition as well as cholinergic dysfunction in AD; α-synuclein aggregation in PD; and modulation of monoamine disturbance in depression. Particularly, the xanthone derivatives, including α-mangostin and γ-mangostin, exhibit potent pharmacological actions. However, low oral bioavailability and poor brain penetration may limit their therapeutic applications. These challenges can be overcome in part by administering as a form of MP extract (MPE) or using specific carrier systems. MPE and α-mangostin are generally safe and well-tolerated in animals. Furthermore, mangosteen-based products are safe for humans. Therefore, MPE and its bioactive xanthones are promising candidates for the treatment of AD, PD, and depression. Further studies including clinical trials are essential to decipher their efficacy, and pharmacokinetic and safety profiles in these disorders.

Advances in understanding mechanisms and therapeutic targets to treat comorbid depression and cardiovascular disease

Chronic or repeated social stress exposure often precipitates the onset of depression and cardiovascular disease (CVD). Despite a clear clinical association between CVD and depression, the pathophysiology underlying these comorbid conditions is unclear. Chronic exposure to social stress can lead to immune system dysregulation, mitochondrial dysfunction, and vagal withdrawal. Further, regular physical exercise is well-known to exert cardioprotective effects, and accumulating evidence demonstrates the antidepressant effect of exercise. This review explores the contribution of inflammation, mitochondrial dysfunction, and vagal withdrawal to stress-induced depression and CVD. Evidence for therapeutic benefits of exercise, anti-inflammatory therapies, and vagus nerve stimulation are also reviewed. Benefits of targeted therapeutics of mitochondrial agents, anti-inflammatory therapies, and vagus nerve stimulation are discussed. Importantly, the ability of exercise to impact each of these factors is also reviewed. The current findings described here implicate a new direction for research, targeting the shared mechanisms underlying comorbid depression-CVD. This will guide the development of novel therapeutic strategies for the prevention and treatment of these stress-related pathologies, particularly within treatment-resistant populations.

[Exercise for depression treatment. Physiological mechanisms]

This literature review considers meta-analyzes, systematic reviews and original research over the last decade addressing a comprehensive analysis of the antidepressant effect of targeted physical exercise and physical activity in general. Exercise is a promising non-pharmacological treatment for depression, showing effects that are comparable or may even exceed other first-line treatments of depression. The article introduces modern ideas about the mechanisms of depression and mechanisms of exercise effects on depression manifestations. The structures of the central nervous system, changing with the effective exercise-based treatment of depression, are indicated. Physical activity stimulates the secretion of growth factors, maintenance of angio-, synapto-, and neurogenesis. The regulation of antioxidant protection of neuronal mitochondria, a decrease in pro-inflammatory reactions and stress reactivity are also observed in response to regular exercise. Physical activity has a multimodal effect that stimulates biochemical pathways and restores neuronal structures disturbed in depression.

Mitochondria could be a potential key mediator linking the intestinal microbiota to depression

The intestinal microbiota has been reported to affect depression, a common mental condition with severe health-related consequences. However, what mediates the effect of the intestinal microbiota on depression has not been well elucidated. We summarize the roles of the mitochondria in eliciting beneficial effects on the gut microbiota to ameliorate symptoms of depression. It is well known that mitochondria play a key role in depression. An important pathogenic factor, namely inflammatory response, may adversely impact mitochondrial functionality to maintain cellular homeostasis. Dysfunction of mitochondria not only affects neuronal function but also reduces neuron cell numbers. We posit that the intestinal microbiota could affect neuronal mitochondrial function through short-chain fatty acids such as butyrate. Brain inflammatory processes could also be affected through the modulation of gut permeability and blood lipopolysaccharide levels. Aberrant mitochondria functionality coupled to adverse cellular homeostasis could be a key mediator for the effect of the intestinal microbiota on the progression of depression.