Mitochondria and Mood: Mitochondrial Dysfunction as a Key Player in the Manifestation of Depression

Cognitive functioning and mental health in mitochondrial disease: A systematic scoping review

Mitochondrial diseases (MDs) are rare, heterogeneous, hereditary and progressive in nature. In addition to the serious somatic symptoms, patients with MD also experience problems regarding their cognitive functioning and mental health. We provide an overview of all published studies reporting on any aspect of cognitive functioning and/or mental health in patients with MD and their relatives. A total of 58 research articles and 45 case studies were included and critically reviewed. Cognitive impairments in multiple domains were reported. Mental disorders were frequently reported, especially depression and anxiety. Furthermore, most studies showed impairments in self-reported psychological functioning and high prevalence of mental health problems in (matrilineal) relatives. The included studies showed heterogeneity regarding patient samples, measurement instruments and reference groups, making comparisons cautious. Results highlight a high prevalence of cognitive impairments and mental disorders in patients with MD. Recommendations for further research as well as tailored patientcare with standardized follow-up are provided. Key gaps in the literature are identified, of which studies on natural history are of highest importance.

A Review on Potential Footprints of Ferulic Acid for Treatment of Neurological Disorders

Ferulic acid is being screened in preclinical settings to combat various neurological disorders. It is a naturally occurring dietary flavonoid commonly found in grains, fruits, and vegetables such as rice, wheat, oats, tomatoes, sweet corn etc., which exhibits protective effects against a number of neurological diseases such as epilepsy, depression, ischemia-reperfusion injury, Alzheimer's disease, and Parkinson's disease. Ferulic acid prevents and treats different neurological diseases pertaining to its potent anti-oxidative and anti-inflammatory effects, beside modulating unique neuro-signaling pathways. It stays in the bloodstream for longer periods than other dietary polyphenols and antioxidants and easily crosses blood brain barrier. The use of novel drug delivery systems such as solid-lipid nanoparticles (SLNs) or its salt forms (sodium ferulate, ethyl ferulate, and isopentyl ferulate) further enhance its bioavailability and cerebral penetration. Based on reported studies, ferulic acid appears to be a promising molecule for treatment of neurological disorders; however, more preclinical (in vitro and in vivo) mechanism-based studies should be planned and conceived followed by its testing in clinical settings.

Inflammation-Related Changes in Mood Disorders and the Immunomodulatory Role of Lithium

Mood disorders are chronic, recurrent diseases characterized by changes in mood and emotions. The most common are major depressive disorder (MDD) and bipolar disorder (BD). Molecular biology studies have indicated an involvement of the immune system in the pathogenesis of mood disorders, and showed their correlation with altered levels of inflammatory markers and energy metabolism. Previous reports, including meta-analyses, also suggested the role of microglia activation in the M1 polarized macrophages, reflecting the pro-inflammatory phenotype. Lithium is an effective mood stabilizer used to treat both manic and depressive episodes in bipolar disorder, and as an augmentation of the antidepressant treatment of depression with a multidimensional mode of action. This review aims to summarize the molecular studies regarding inflammation, microglia activation and energy metabolism changes in mood disorders. We also aimed to outline the impact of lithium on these changes and discuss its immunomodulatory effect in mood disorders.

HEME: a neglected player in nociception?

Despite increasing progress in the understanding of the pathophysiology of pain, current management of pain syndromes is still unsatisfactory. The recent discovery of novel pathways associated with pain insensitivity in humans represents a unique opportunity to improve our knowledge on the pathophysiology of pain. Heme metabolism recently emerged as a crucial regulator of nociception. Of note, alteration of heme metabolism has been associated with pain insensitivity as well as with acute and chronic pain in porphyric neuropathy and hemolytic diseases. However, the molecular mechanisms linking heme to the pain pathways still remain unclear. The review focuses on the major heme-regulated processes relevant for sensory neurons' maintenance, peripheral and central sensitization as well as for pain comorbidities, like anxiety and depression. By discussing the body of knowledge on the topic, we provide a novel perspective on the molecular mechanisms linking heme to nociception.

Pregnancy swimming prevents early brain mitochondrial dysfunction and causes sex-related long-term neuroprotection following neonatal hypoxia-ischemia in rats

Neonatal hypoxia-ischemia (HI) is a major cause of cognitive impairments in infants. Antenatal strategies improving the intrauterine environment can have high impact decreasing pregnancy-derived intercurrences. Physical exercise alters the mother-fetus unity and has been shown to prevent the energetic challenge imposed by HI. This study aimed to reveal neuroprotective mechanisms afforded by pregnancy swimming on early metabolic failure and late cognitive damage, considering animals' sex as a variable. Pregnant Wistar rats were submitted to daily swimming exercise (20' in a tank filled with 32 °C water) during pregnancy. Neonatal HI was performed in male and female pups at postnatal day 7. Electron chain transport, mitochondrial mass and function and ROS formation were assessed in the right brain hemisphere 24 h after HI. From PND45, reference and working spatial memory were tested in the Morris water maze. MicroPET-FDG images were acquired 24 h after injury (PND8) and at PND60, following behavioral analysis. HI induced early energetic failure, decreased enzymatic activity in electron transport chain, increased production of ROS in cortex and hippocampus as well as caused brain glucose metabolism dysfunction and late cognitive impairments. Maternal swimming was able to prevent mitochondrial dysfunction and to improve spatial memory. The intergenerational effects of swimming were sex-specific, since male rats were benefited most. In conclusion, maternal swimming was able to affect the mitochondrial response to HI in the offspring's brains, preserving its function and preventing cognitive damage in a sex-dependent manner, adding relevant information on maternal exercise neuroprotection and highlighting the importance of mitochondria as a therapeutic target for HI neuropathology.

Oxidative eustress: On constant alert for redox homeostasis

In the open metabolic system, redox-related signaling requires continuous monitoring and fine-tuning of the steady-state redox set point. The ongoing oxidative metabolism is a persistent challenge, denoted as oxidative eustress, which operates within a physiological range that has been called the 'Homeodynamic Space', the 'Goldilocks Zone' or the 'Golden Mean'. Spatiotemporal control of redox signaling is achieved by compartmentalized generation and removal of oxidants. The cellular landscape of H₂O₂, the major redox signaling molecule, is characterized by orders-of-magnitude concentration differences between organelles. This concentration pattern is mirrored by the pattern of oxidatively modified proteins, exemplified by S-glutathionylated proteins. The review presents the conceptual background for short-term (non-transcriptional) and longer-term (transcriptional/translational) homeostatic mechanisms of stress and stress responses. The redox set point is a variable moving target value, modulated by circadian rhythm and by external influence, summarily denoted as exposome, which includes nutrition and lifestyle factors. Emerging fields of cell-specific and tissue-specific redox regulation in physiological settings are briefly presented, including new insight into the role of oxidative eustress in embryonal development and lifespan, skeletal muscle and exercise, sleep-wake rhythm, and the function of the nervous system with aspects leading to psychobiology.

Increasing Nrf2 Activity as a Treatment Approach in Neuropsychiatry

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

A dopamine metabolite stabilizes neurotoxic amyloid-β oligomers

Aberrant soluble oligomers formed by the amyloid-β peptide (Aβ) are major pathogenic agents in the onset and progression of Alzheimer's disease. A variety of biomolecules can influence the formation of these oligomers in the brain, although their mechanisms of action are still largely unknown. Here, we studied the effects on Aβ aggregation of DOPAL, a reactive catecholaldehyde intermediate of dopamine metabolism. We found that DOPAL is able to stabilize Aβ oligomeric species, including dimers and trimers, that exert toxic effects on human neuroblastoma cells, in particular increasing cytosolic calcium levels and promoting the generation of reactive oxygen species. These results reveal an interplay between Aβ aggregation and key biochemical processes regulating cellular homeostasis in the brain.

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.

Altered estradiol-dependent cellular Ca2+ homeostasis and endoplasmic reticulum stress response in Premenstrual Dysphoric Disorder

Premenstrual Dysphoric Disorder (PMDD) is characterized by debilitating mood symptoms in the luteal phase of the menstrual cycle. Prior studies of affected women have implicated a differential response to ovarian steroids. However, the molecular basis of these patients' differential response to hormone remains poorly understood. We performed transcriptomic analyses of lymphoblastoid cell lines (LCLs) derived from women with PMDD and asymptomatic controls cultured under untreated (steroid-free), estradiol-treated (E2), and progesterone-treated (P4) conditions. Weighted gene correlation network analysis (WGCNA) of transcriptomes identified four gene modules with significant diagnosis x hormone interactions, including one enriched for neuronal functions. Next, in a gene-level analysis comparing transcriptional response to hormone across diagnoses, a generalized linear model identified 1522 genes differentially responsive to E2 (E2-DRGs). Among the top 10 E2-DRGs was a physically interacting network (NUCB1, DST, GCC2, GOLGB1) involved in endoplasmic reticulum (ER)-Golgi function. qRT-PCR validation reproduced a diagnosis x E2 interaction (F(1,24)=7.01, p = 0.014) for NUCB1, a regulator of cellular Ca²⁺ and ER stress. Finally, we used a thapsigargin (Tg) challenge assay to test whether E2 induces differences in Ca²⁺ homeostasis and ER stress response in PMDD. PMDD LCLs had a 1.36-fold decrease in Tg-induced XBP1 splicing response compared to controls, and a 1.62-fold decreased response (p = 0.005), with a diagnosis x treatment interaction (F(3,33)=3.51, p = 0.026) in the E2-exposed condition. Altered hormone-dependent in cellular Ca²⁺ dynamics and ER stress may contribute to the pathophysiology of PMDD.

Severe life stress, mitochondrial dysfunction, and depressive behavior: A pathophysiological and therapeutic perspective

Mitochondria are responsible for providing our cells with energy, as well as regulating oxidative stress and apoptosis, and considerable evidence demonstrates that mitochondria-related alterations are prevalent during chronic stress and depression. Here, we discuss how chronic stress may induce depressive behavior by potentiating mitochondrial allostatic load, which ultimately decreases energy production, elevates the generation of harmful reactive oxygen species, damages mitochondrial DNA and increases membrane permeability and pro-apoptotic factor release. We also discuss how mitochondrial insults can exacerbate the immune response, contributing to depressive symptomology. Furthermore, we illustrate how depression symptoms are associated with specific mitochondrial defects, and how targeting of these defects with pharmacological agents may be a promising avenue for the development of novel, more efficacious antidepressants. In summary, this review supports the notion that severe psychosocial stress induces mitochondrial dysfunction, thereby increasing the vulnerability to developing depressive symptoms.

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.

Mediators of mitophagy that regulate mitochondrial quality control play crucial role in diverse pathophysiology

Mitochondria are double membrane-bound cellular work-horses constantly functioning to regulate vital aspects of cellular metabolism, bioenergetics, proliferation and death. Biogenesis, homeostasis and regulated turnover of mitochondria are stringently regulated to meet the bioenergetic requirements. Diverse external and internal stimuli including oxidative stress, diseases, xenobiotics and even age profoundly affect mitochondrial integrity. Damaged mitochondria need immediate segregation and selective culling to maintain physiological homeostasis. Mitophagy is a specialised form of macroautophagy that constantly checks mitochondrial quality followed by elimination of rogue mitochondria by lysosomal targeting through multiple pathways tightly regulated and activated in context-specific manners. Mitophagy is implicated in diverse oxidative stress-associated metabolic, proliferating and degenerative disorders owing to the centrality of mitopathology in diseases as well as the common mandate to eliminate damaged mitochondria for restoring physiological homeostasis. With improved health care and growing demand for precision medicine, specifically targeting the keystone factors in pathogenesis, more exploratory studies are focused on mitochondrial quality control as underlying guardian of cellular pathophysiology. In this context, mitophagy emerged as a promising area to focus biomedical research for identifying novel therapeutic targets against diseases linked with physiological redox perturbation. The present review provides a comprehensive account of the recent developments on mitophagy along with precise discussion on its impact on major diseases and possibilities of therapeutic modulation.

Mitochondria under the spotlight: On the implications of mitochondrial dysfunction and its connectivity to neuropsychiatric disorders

Neuropsychiatric disorders (NPDs) such as bipolar disorder (BD), schizophrenia (SZ) and mood disorder (MD) are hard to manage due to overlapping symptoms and lack of biomarkers. Risk alleles of BD/SZ/MD are emerging, with evidence suggesting mitochondrial (mt) dysfunction as a critical factor for disease onset and progression. Mood stabilizing treatments for these disorders are scarce, revealing the need for biomarker discovery and artificial intelligence approaches to design synthetically accessible novel therapeutics. Here, we show mt involvement in NPDs by associating 245 mt proteins to BD/SZ/MD, with 7 common players in these disease categories. Analysis of over 650 publications suggests that 245 NPD-linked mt proteins are associated with 800 other mt proteins, with mt impairment likely to rewire these interactions. High dosage of mood stabilizers is known to alleviate manic episodes, but which compounds target mt pathways is another gap in the field that we address through mood stabilizer-gene interaction analysis of 37 prescriptions and over-the-counter psychotropic treatments, which we have refined to 15 mood-stabilizing agents. We show 26 of the 245 NPD-linked mt proteins are uniquely or commonly targeted by one or more of these mood stabilizers. Further, induced pluripotent stem cell-derived patient neurons and three-dimensional human brain organoids as reliable BD/SZ/MD models are outlined, along with multiomics methods and machine learning-based decision making tools for biomarker discovery, which remains a bottleneck for precision psychiatry medicine.

Molecular correlates of mitochondrial dysfunctions in major depression: Evidence from clinical and rodent studies

Major depressive disorder (MDD) is one of the most prevalent stress-related mental disorders worldwide. Several biological mechanisms underlying the pathophysiology of MDD have been proposed, including endocrine disturbances, neurotransmitter deficits, impaired neuronal plasticity, and more recently, mitochondrial dysfunctions. In this review, we provide an overview of relevant molecular correlates of mitochondrial dysfunction in MDD, based on findings from clinical studies and stress-induced rodent models. We also compare differences and similarities between the phenotypes of MDD patients and animal models. Our analysis of the literature reveals that both MDD and stress are associated, in humans and animals, with changes in mitochondrial biogenesis, redox imbalance, increased oxidative damages of cellular macromolecules, and apoptosis. Yet, a considerable amount of conflicting data exist and therefore, the translation of findings from clinical and preclinical research to novel therapies for MDD remains complex. Further studies are needed to advance our understanding of the molecular networks and biological mechanisms involving mitochondria in the pathophysiology of MDD.

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.

Fast-acting antidepressant-like effects of Reelin evaluated in the repeated-corticosterone chronic stress paradigm

The present report examines the effects of repeated or single intrahippocampal Reelin infusions on measures of depressive-like behavior, cognition, and hippocampal neurogenesis in the repeated-corticosterone (CORT) paradigm. Rats received subcutaneous injections of CORT for 3 weeks and Reelin was infused through an inserted canula in the left hippocampus on days 7, 14, and 21, or only on day 21 of CORT injections. CORT increased immobility in the forced-swim test and impaired object-location memory. Notably, these effects were reversed by both repeated and single-Reelin infusions. CORT decreased both the number and complexity of doublecortin-labeled maturing newborn neurons in the dentate gyrus subgranular zone, and a single-Reelin infusion increased the number but not complexity of newborn neurons, while repeated Reelin infusions restored both. Injection of the AMPA antagonist CNQX blocked the rescue of the behavioral phenotype by Reelin but did completely block the effects of Reelin on hippocampal neurogenesis. Reelin is able to rescue the deficits in AMPA, NMDA, GABAA receptors, mTOR and p-mTOR induced by CORT. These novel results demonstrate that a single intrahippocampal Reelin infusion into the dorsal hippocampus has fast-acting antidepressant-like effects, and that some of these effects may be at least partially independent of Reelin actions on hippocampal neurogenesis.

Traumatic stress history interacts with sex and chronic peripheral inflammation to alter mitochondrial function of synaptosomes

BACKGROUND

Repeated exposures to chronic stress can lead to long lasting negative behavioral and metabolic outcomes. Here, we aim to determine the impact of chronic stress and chronic low-level inflammation on behavior and synaptosomal metabolism.

METHODS

Male (n = 31) and female (n = 32) C57Bl/6 mice underwent chronic repeated predation stress or daily handling for two rounds of 15 consecutive days of exposure during the adolescent and early adult timeframes. Subsequently, mice were exposed to repeated lipopolysaccharide (LPS; 7.5 × 10⁵ EU/kg) or saline injections every third day for eight weeks. Exploratory and social behaviors were assessed in the open field and social interaction tests prior to examination of learning and memory with the Barnes Maze. Mitochondrial function and morphology were assessed in synaptosomes post-mortem using the Cell Mito Stress test and Seahorse XFe24 analyzer, TEM, and western analysis, respectively. In addition, expression of TNF-α, IL-1ß, and ROMO1 were examined in the hippocampus and prefrontal cortex with Taqman qPCR. Circulating pro- and anti-inflammatory cytokines in the periphery were assessed using the MSD V-plex Proinflammatory Panel 1 following the first and last LPS injection as well as at the time of tissue collection. Circulating ROMO1 was assessed in terminal samples via ELISA.

RESULTS

Exposure to repeated predatory stress increased time spent in the corners of the open field, suggestive of anxiety-like behavior, in both males and females. There were no significant group differences in the social interaction test and minimal effects were evident in the Barnes maze. A history of chronic stress interacted with chronic LPS in male mice to lead to a deficit in synaptosomal respiration. Female mice were more sensitive to both chronic stress and chronic LPS such that either a history of chronic stress or chronic LPS exposure was sufficient to disrupt synaptosomal respiration in females. Both stress and chronic LPS were sufficient to increase inflammation and reactive oxygen in males centrally and peripherally. Females had increased markers of peripheral inflammation following acute LPS but no evidence of peripheral or central increases in inflammatory factors or reactive oxygen following chronic exposures.

CONCLUSION

Collectively, these data suggest that while metrics of inflammation and reactive oxygen are disrupted in males following chronic stress and chronic LPS, only the combined condition is sufficient to alter synaptosomal respiration. Conversely, although evidence of chronic inflammation or chronic elevation in reactive oxygen is absent, females demonstrate profound shifts in synaptosomal mitochondrial function with either a history of chronic stress or a history of chronic inflammation. These data highlight that different mechanisms are likely in play between the sexes and that sex differences in neural outcomes may be precipitated by sex-specific effects of life experiences on mitochondrial function in the synapse.

The impact of chronic stress on energy metabolism

The brain is exceptionally demanding in terms of energy metabolism. Approximately 20% of the calories consumed are devoted to our cerebral faculties, with the lion's share provided in the form of glucose. The brain's stringent energy dependency requires a high degree of harmonization between the elements responsible for supplying- and metabolizing energetic substrates. However, chronic stress may jeopardize this homeostatic energy balance by disruption of critical metabolic processes. In agreement, stress-related mental disorders have been linked with perturbations in energy metabolism. Prominent stress-induced metabolic alterations include the actions of hormones, glucose uptake and mitochondrial adjustments. Importantly, fundamental stress-responsive metabolic adjustments in humans and animal models bear a striking resemblance. Here, an overview is provided of key findings, demonstrating the pervasive impact of chronic stress on energy metabolism. Furthermore, I argue that medications, aimed primarily at restoring metabolic homeostasis, may constitute a novel approach to treat mental disorders.

Sex differences in the genetic architecture of depression

The prevalence and clinical characteristics of depressive disorders differ between women and men; however, the genetic contribution to sex differences in depressive disorders has not been elucidated. To evaluate sex-specific differences in the genetic architecture of depression, whole exome sequencing of samples from 1000 patients (70.7% female) with depressive disorder was conducted. Control data from healthy individuals with no psychiatric disorder (n = 72, 26.4% female) and East-Asian subpopulation 1000 Genome Project data (n = 207, 50.7% female) were included. The genetic variation between men and women was directly compared using both qualitative and quantitative research designs. Qualitative analysis identified five genetic markers potentially associated with increased risk of depressive disorder in females, including three variants (rs201432982 within PDE4A, and rs62640397 and rs79442975 within FDX1L) mapping to chromosome 19p13.2 and two novel variants (rs820182 and rs820148) within MYO15B at the chromosome 17p25.1 locus. Depressed patients homozygous for these variants showed more severe depressive symptoms and higher suicidality than those who were not homozygotes (i.e., heterozygotes and homozygotes for the non-associated allele). Quantitative analysis demonstrated that the genetic burden of protein-truncating and deleterious variants was higher in males than females, even after permutation testing. Our study provides novel genetic evidence that the higher prevalence of depressive disorders in women may be attributable to inherited variants.

Antidepressant Effect and Modulation of the Redox System Mediated by Tannic Acid on Lipopolysaccharide-Induced Depressive and Inflammatory Changes in Mice

Depression is an emotional disorder that causes mental and physical changes, and has limited pharmacotherapy. Tannic acid (TA) is a polyphenol with previously described antioxidant and neuroprotective properties. The aim of this study was to evaluate the effects of TA on lipopolysaccharide (LPS)-induced depressive-like behavior, as well as oxidative stress parameters and TNF-α levels in the brains of mice. Animals were pretreated once daily, with TA (30 or 60 mg/kg), fluoxetine (20 mg/kg) or vehicle for 7 days. On the 7th day, the animals received a single injection of LPS (830 μg/kg). After 24 h, open field, forced swimming, tail suspension, and splash tests were conducted. The endotoxin induced depressive-like behavior in these mice and this was attenuated by TA. In the cerebral cortex, hippocampus, and striatum, LPS increased lipid peroxidation and reactive oxygen species production, and this was also prevented by TA administration. TA treatment also prevented a decrease in catalase activity within the striatum. Further, LPS administration caused increased levels of TNF-α in all brain structures, and this was prevented in the cortex by TA treatment. In conclusion, TA shows many neuroprotective properties, with demonstrated antioxidant, anti-inflammatory and antidepressant effects in this animal model of acute depressive-like behavior. Therefore, this compound could provide an alternative therapeutic approach for the treatment of depression.

State-of-the-Art: Inflammatory and Metabolic Markers in Mood Disorders

Mounting evidence highlights the involvement of inflammatory/immune systems and their relationships with neurotransmitters and different metabolic processes in mood disorders. Nevertheless, there is a general agreement that available findings are still inconclusive. Therefore, further investigations are required, aimed at deepening the role of possible alterations of biomarkers in the pathophysiology of mood disorders that might lead to more focused and tailored treatments. The present study is a comprehensive review on these topics that seem to represent intriguing avenues for the development of real innovative therapeutic strategies of mood disorders.

Vitamin C, Pain and Opioid Use Disorder

Vitamin C (ascorbic acid, AA) is an essential nutrient in humans. It is vital to a multitude of metabolic pathways, including those affecting mental health, stress response, and pain perception. This paper provides a review of the literature and a theoretical perspective on the potential roles of AA in the treatment of pain and opioid use disorder (OUD). A powerful antioxidant and anti-inflammatory agent involved in glutathione recycling, AA is a cofactor in adrenal steroidogenesis and catecholamine biosynthesis. AA supports the synthesis of serotonin, modulates synaptic dopamine and glutamate, and may also enhance the synthesis of endomorphins and endorphins. In animal models, AA reduces and prevents opioid drug tolerance and physical dependency. It irreversibly inactivates opioid stereospecific binding, while increasing the antinociceptive effects of pain medications. In clinical trials, AA has been proven safe and effective in acute and chronic pain relief, including ambulatory, surgical, and oncological settings. AA may temper the need for opioids, which raises the question of whether it can help reduce the risk of OUD onset. High, frequent doses of AA may also abort cravings and opioid withdrawal symptoms in those with OUD and has better tolerability than other OUD treatments. Further clinical trials on the potential of AA in the prevention and treatment of OUD are warranted.

Mitochondria as a target for neuroprotection: role of methylene blue and photobiomodulation

Mitochondrial dysfunction plays a central role in the formation of neuroinflammation and oxidative stress, which are important factors contributing to the development of brain disease. Ample evidence suggests mitochondria are a promising target for neuroprotection. Recently, methods targeting mitochondria have been considered as potential approaches for treatment of brain disease through the inhibition of inflammation and oxidative injury. This review will discuss two widely studied approaches for the improvement of brain mitochondrial respiration, methylene blue (MB) and photobiomodulation (PBM). MB is a widely studied drug with potential beneficial effects in animal models of brain disease, as well as limited human studies. Similarly, PBM is a non-invasive treatment that promotes energy production and reduces both oxidative stress and inflammation, and has garnered increasing attention in recent years. MB and PBM have similar beneficial effects on mitochondrial function, oxidative damage, inflammation, and subsequent behavioral symptoms. However, the mechanisms underlying the energy enhancing, antioxidant, and anti-inflammatory effects of MB and PBM differ. This review will focus on mitochondrial dysfunction in several different brain diseases and the pathological improvements following MB and PBM treatment.

Depression-like behaviors are accompanied by disrupted mitochondrial energy metabolism in chronic corticosterone-induced mice

Stress exerts its negative effects by interference with mitochondrial energy production in rodents, and is able to impair mitochondrial bioenergetics. However, the underlying mechanism that stress hormone impacts depression-like behaviors and mitochondrial energy metabolism is still not well understood. Here, we investigated the changes of depression-like behaviors and mitochondrial energy metabolism induced by chronic corticosterone (CORT). The results showed that after treatment with CORT for 6 weeks, mice displayed depression-like behaviors, which were identified by tail suspension test, forced swimming test and open field test. Then, the livers were isolated and tested by RNA sequencing and metabolome analysis. RNA sequencing showed 354 up-regulated genes and 284 down-regulated genes, and metabolome analysis revealed 280 metabolites with increased abundances and 193 metabolites with reduced abundances in the liver of mice after CORT, which were closely associated with lipid metabolism and oxidative phosphorylation in mitochondria. Based on these findings, the changes of mitochondrial energy metabolism were investigated, and we revealed that CORT condition inhibited glycolysis and fatty acid degradation pathway, and activated synthesis of triacylglycerol, leading to the reduced levels of acetyl-CoA and attenuated TCA cycle. Also, the pathways of NAD⁺ synthesis were inhibited, resulting in the reduced activity of sirtuin 3 (SIRT3). Thus, all of these observations disrupted the function of mitochondria, and led to the decrease of ATP production. Our findings uncover a novel mechanism of stress on depression-like behaviors and mitochondrial energy metabolism in rodents.

Nicotinamide Mononucleotide: A Promising Molecule for Therapy of Diverse Diseases by Targeting NAD+ Metabolism

NAD+, a co-enzyme involved in a great deal of biochemical reactions, has been found to be a network node of diverse biological processes. In mammalian cells, NAD+ is synthetized, predominantly through NMN, to replenish the consumption by NADase participating in physiologic processes including DNA repair, metabolism, and cell death. Correspondingly, aberrant NAD+ metabolism is observed in many diseases. In this review, we discuss how the homeostasis of NAD+ is maintained in healthy condition and provide several age-related pathological examples related with NAD+ unbalance. The sirtuins family, whose functions are NAD-dependent, is also reviewed. Administration of NMN surprisingly demonstrated amelioration of the pathological conditions in some age-related disease mouse models. Further clinical trials have been launched to investigate the safety and benefits of NMN. The NAD+ production and consumption pathways including NMN are essential for more precise understanding and therapy of age-related pathological processes such as diabetes, ischemia–reperfusion injury, heart failure, Alzheimer’s disease, and retinal degeneration.

Sex differences in brain gene expression among suicide completers

BACKGROUND

Suicide rates vary substantially by sex. Suicides committed by males significantly outnumber female suicides. Disparities in community and social factors provide a partial explanation for this phenomenon. Thus, the evaluation of sex differences at a biological level might contribute to the elucidation of the factors involved in this imbalance. The aim of the present study was to evaluate sex-specific gene expression patterns in the suicidal brain.

METHODS

postmortem samples from the dorsolateral prefrontal cortex (DLPFC) of 75 Latino individuals were analyzed. We considered the following groups: i) male suicides (n = 38), ii) female suicides (n = 10), iii) male controls (n = 20), and iv) female controls (n = 7). Gene expression profiles were evaluated by microarrays. Differentially expressed genes among the groups were identified with a linear model. Similarities and differences in the gene sets between the sexes were identified.

RESULTS

Differentially expressed genes were identified between suicides and controls of each sex: 1,729 genes in females and 1,997 genes in males. Female-exclusive suicide genes were related to cell proliferation and immune response. Meanwhile, male-exclusive suicide genes were associated to DNA binding and ribonucleic protein complex. Sex-independent suicide genes showed enrichment in mitochondrial and vesicular functions.

LIMITATIONS

Relatively small sample size. Our diagnosis approach was limited to information found on coroner's records. The analysis was limited to a single brain area (DLPFC) and we used microarrays.

CONCLUSION

Previously unexplored sex differences in the brain gene expression of suicide completers were identified, providing valuable foundation for the evaluation of sex-specific factors in suicide.

Targeting Inflammatory-Mitochondrial Response in Major Depression: Current Evidence and Further Challenges

The prevalence of psychiatric disorders has increased in recent years. Among existing mental disorders, major depressive disorder (MDD) has emerged as one of the leading causes of disability worldwide, affecting individuals throughout their lives. Currently, MDD affects 15% of adults in the Americas. Over the past 50 years, pharmacotherapy, psychotherapy, and brain stimulation have been used to treat MDD. The most common approach is still pharmacotherapy; however, studies show that about 40% of patients are refractory to existing treatments. Although the monoamine hypothesis has been widely accepted as a molecular mechanism to explain the etiology of depression, its relationship with other biochemical phenomena remains only partially understood. This is the case of the link between MDD and inflammation, mitochondrial dysfunction, and oxidative stress. Studies have found that depressive patients usually exhibit altered inflammatory markers, mitochondrial membrane depolarization, oxidized mitochondrial DNA, and thus high levels of both central and peripheral reactive oxygen species (ROS). The effect of antidepressants on these events remains unclear. Nevertheless, the effects of ROS on the brain are well known, including lipid peroxidation of neuronal membranes, accumulation of peroxidation products in neurons, protein and DNA damage, reduced antioxidant defenses, apoptosis induction, and neuroinflammation. Antioxidants such as ascorbic acid, tocopherols, and coenzyme Q have shown promise in some depressive patients, but without consensus on their efficacy. Hence, this paper provides a review of MDD and its association with inflammation, mitochondrial dysfunction, and oxidative stress and is aimed at thoroughly discussing the putative links between these events, which may contribute to the design and development of new therapeutic approaches for patients.

Hippocampal mitochondrial dysfunction and psychiatric-relevant behavioral deficits in spinocerebellar ataxia 1 mouse model

Spinocerebellar ataxia 1 (SCA1) is a devastating neurodegenerative disease associated with cerebellar degeneration and motor deficits. However, many patients also exhibit neuropsychiatric impairments such as depression and apathy; nevertheless, the existence of a causal link between the psychiatric symptoms and SCA1 neuropathology remains controversial. This study aimed to explore behavioral deficits in a knock-in mouse SCA1 (SCA1^154Q/2Q) model and to identify the underlying neuropathology. We found that the SCA1 mice exhibit previously undescribed behavioral impairments such as increased anxiety- and depressive-like behavior and reduced prepulse inhibition and cognitive flexibility. Surprisingly, non-motor deficits characterize the early SCA1 stage in mice better than does ataxia. Moreover, the SCA1 mice exhibit significant hippocampal atrophy with decreased plasticity-related markers and markedly impaired neurogenesis. Interestingly, the hippocampal atrophy commences earlier than the cerebellar degeneration and directly reflects the individual severity of some of the behavioral deficits. Finally, mitochondrial respirometry suggests profound mitochondrial dysfunction in the hippocampus, but not in the cerebellum of the young SCA1 mice. These findings imply the essential role of hippocampal impairments, associated with profound mitochondrial dysfunction, in SCA1 behavioral deficits. Moreover, they underline the view of SCA1 as a complex neurodegenerative disease and suggest new avenues in the search for novel SCA1 therapies.

Severe hydroxymethylbilane synthase deficiency causes depression-like behavior and mitochondrial dysfunction in a mouse model of homozygous dominant acute intermittent porphyria

Acute intermittent porphyria (AIP) is an autosomal dominant inborn error of heme biosynthesis due to a pathogenic mutation in the Hmbs gene, resulting in half-normal activity of hydroxymethylbilane synthase. Factors that induce hepatic heme biosynthesis induce episodic attacks in heterozygous patients. The clinical presentation of acute attacks involves the signature neurovisceral pain and may include psychiatric symptoms. Here we used a knock-in mouse line that is biallelic for the Hmbs c.500G > A (p.R167Q) mutation with ~ 5% of normal hydroxymethylbilane synthase activity to unravel the consequences of severe HMBS deficiency on affective behavior and brain physiology. Hmbs knock-in mice (KI mice) model the rare homozygous dominant form of AIP and were used as tool to elucidate the hitherto unknown pathophysiology of the behavioral manifestations of the disease and its neural underpinnings. Extensive behavioral analyses revealed a selective depression-like phenotype in Hmbs KI mice; transcriptomic and immunohistochemical analyses demonstrated aberrant myelination. The uncovered compromised mitochondrial function in the hippocampus of knock-in mice and its ensuing neurogenic and neuroplastic deficits lead us to propose a mechanistic role for disrupted mitochondrial energy production in the pathogenesis of the behavioral consequences of severe HMBS deficiency and its neuropathological sequelae in the brain.

Inhibition of Uncoupling Protein 2 Enhances the Radiosensitivity of Cervical Cancer Cells by Promoting the Production of Reactive Oxygen Species

Objective

The mechanism of enhanced radiosensitivity induced by mitochondrial uncoupling protein UCP2 was investigated in HeLa cells to provide a theoretical basis as a novel target for cervical cancer treatment.

Methods

HeLa cells were irradiated with 4 Gy X-radiation at 1.0 Gy/min. The expression of UCP2 mRNA and protein was assayed by real-time quantitative polymerase chain reaction and western blotting. UCP2 siRNA and negative control siRNA fragments were constructed and transfected into HeLa cells 24 h after irradiation. The effect of UCP2 silencing and irradiation on HeLa cells was determined by colony formation, CCK-8 cell viability, γH2AX immunofluorescence assay of DNA damage, Annexin V-FITC/PI apoptosis assay, and propidium iodide cell cycle assay. The effects on mitochondrial structure and function were investigated with fluorescent probes including dichlorodihydrofluorescein diacetate (DCFH-DA) assay of reactive oxygen species (ROS), rhodamine 123, and MitoTracker Green assay of mitochondrial structure and function.

Results

Irradiation upregulated UCP2 expression, and UCP2 knockdown decreased the survival of irradiated HeLa cells. UCP2 silencing sensitized HeLa cells to irradiation-induced DNA damage and led to increased apoptosis, cell cycle arrest in G2/M, and increased mitochondrial ROS. Increased radiosensitivity was associated with an activation of P53, decreased Bcl-2, Bcl-xl, cyclin B, CDC2, Ku70, and Rad51 expression, and increased Apaf-1, cytochrome c, caspase-3, and caspase-9 expression.

Conclusions

UCP2 inhibition augmented the radiosensitivity of cervical cancer cells, and it may be a potential target of radiotherapy of advanced cervical cancer.

Psychiatric drugs impact mitochondrial function in brain and other tissues

Mitochondria have been linked to the etiology of schizophrenia (SZ). However, studies of mitochondria in SZ might be confounded by the effects of pharmacological treatment with antipsychotic drugs (APDs) and other common medications. This review summarizes findings on relevant mitochondria mechanisms underlying SZ, and the potential impact of psychoactive drugs including primarily APDs, but also antidepressants and anxiolytics. The summarized data suggest that APDs impair mitochondria function by decreasing Complex I activity and ATP production and dissipation of the mitochondria membrane potential. At the same time, in the brains of patients with SZ, antipsychotic drug treatment normalizes gene expression modules enriched in mitochondrial genes that are decreased in SZ. This indicates that APDs may have both positive and negative effects on mitochondria. The available evidence suggests three conclusions i) alterations in mitochondria functions in SZ exist prior to APD treatment, ii) mitochondria alterations in SZ can be reversed by APD treatment, and iii) APDs directly cause impairment of mitochondria function. Overall, the mechanisms of action of psychiatric drugs on mitochondria are both direct and indirect; we conclude the effects of APDs on mitochondria may contribute to both their therapeutic and metabolic side effects. These studies support the hypothesis that neuronal mitochondria are an etiological factor in SZ. Moreover, APDs and other drugs must be considered in the evaluation of this pathophysiological role of mitochondria in SZ. Considering these effects, pharmacological actions on mitochondria may be a worthwhile target for further APD development.

Mitochondria, endoplasmic reticulum and innate immune dysfunction in mood disorders: Do Mitochondria-Associated Membranes (MAMs) play a role?

Mood disorders like major depression and bipolar disorder (BD) are among the most prevalent forms of mental illness. Current knowledge of the neurobiology and pathophysiology of these disorders is still modest and clear biological markers are still missing. Thus, a better understanding of the underlying pathophysiological mechanisms to identify potential therapeutic targets is a prerequisite for the design of new drugs as well as to develop biomarkers that help in a more accurate and earlier diagnosis. Multiple pieces of evidence including genetic and neuro-imaging studies suggest that mood disorders are associated with abnormalities in endoplasmic-reticulum (ER)-related stress responses, mitochondrial function and calcium signalling. Furthermore, deregulation of the innate immune response has been described in patients diagnosed with mood disorders, including depression and BD. These disease-related events are associated with functions localized to a subdomain of the ER, known as Mitochondria-Associated Membranes (MAMs), which are lipid rafts-like domains that connect mitochondria and ER, both physically and biochemically. This review will outline the current understanding of the role of mitochondria and ER dysfunction under pathological brain conditions, particularly in major depressive disorder (MDD) and BD, that support the hypothesis that MAMs can act in these mood disorders as the link connecting ER-related stress response and mitochondrial impairment, as well as a mechanisms behind sterile inflammation arising from deregulation of innate immune responses. The role of MAMs in the pathophysiology of these pathologies and its potential relevance as a potential therapeutic target will be discussed.

Nicotinamide mononucleotide ameliorates the depression-like behaviors and is associated with attenuating the disruption of mitochondrial bioenergetics in depressed mice

BACKGROUND

Nicotinamide mononucleotide (NMN) has been shown to stimulate oxidative phosphorylation in mitochondria and to improve various pathologies in patients and mouse disease models. However, whether NMN mediates mitochondrial energy production and its mechanism of action in depressed animals remain unclear.

METHODS

Mice were subcutaneously injected with corticosterone (CORT; 20 mg/kg) each day for 6 weeks, while another group was given an additional dose of NMN (300 mg/kg) by oral gavage in the last 2 weeks. Then, transcriptome analyses, metabolome analyses and transient gene knockdown in primary mouse cells were performed.

RESULTS

NMN administration alleviated depression-like behavior and the liver weight to body weight ratio in a mouse model of CORT-induced depression. Transcriptome and metabolome analyses revealed that in depressed mice, NMN reduced the mRNA expression of genes involved in fatty acid synthesis, stimulation of β-oxidation and glycolysis, and increased production of acetyl-coenzyme A for the tricarboxylic acid cycle. Importantly, NMN supplementation increased NAD⁺ levels to enhance sirtuin (SIRT)3 activity, thereby improving mitochondrial energy metabolism in the hippocampus and liver of CORT-treated mice. Sirt3knockdown in primary mouse astrocytes reversed the effect of NMN by inhibiting energy production, although it did not affect NAD⁺ synthesis LIMITATIONS: Group sample sizes were small, and only one type of primary mouse cell was used CONCLUSION: These results provide evidence for the beneficial role of NMN in energy production and suggest that therapeutic strategies that increase the level of NMN can be an effective treatment for depression.

Carnitine Palmitoyl Transferase Deficiency in a University Immunology Practice

PURPOSE

This report describes the clinical manifestations of 35 patients sent to a University Immunology clinic with a diagnosis of fatigue and exercise intolerance who were identified to have low carnitine palmitoyl transferase activity on muscle biopsies.

RECENT FINDINGS

All of the patients presented with fatigue and exercise intolerance and many had been diagnosed with fibromyalgia. Their symptoms responded to treatment of the metabolic disease. Associated symptoms included bloating, diarrhea, constipation, gastrointestinal reflux symptoms, recurrent infections, arthritis, dyspnea, dry eye, visual loss, and hearing loss. Associated medical conditions included Hashimoto thyroiditis, Sjogren's syndrome, seronegative arthritis, food hypersensitivities, asthma, sleep apnea, and vasculitis. This study identifies clinical features that should alert physicians to the possibility of an underlying metabolic disease. Treatment of the metabolic disease leads to symptomatic improvement.

Dl-3-n-butylphthalide attenuates mouse behavioral deficits to chronic social defeat stress by regulating energy metabolism via AKT/CREB signaling pathway

Major depressive disorder (MDD) is a severe mental disorder associated with high rates of morbidity and mortality. Current first-line pharmacotherapies for MDD are based on enhancement of monoaminergic neurotransmission, but these antidepressants are still insufficient and produce significant side-effects. Consequently, the development of novel antidepressants and therapeutic targets is desired. Dl-3-n-butylphthalide (NBP) is a compound with proven efficacy in treating ischemic stroke, yet its therapeutic effects and mechanisms for depression remain unexplored. The aim of this study was to investigate the effect of NBP in a chronic social defeat stress model of depression and its underlying molecular mechanisms. Here, we examined depression-related behavior and performed a targeted metabolomics analysis. Real-time quantitative polymerase chain reaction and western blotting were used to examine key genes and proteins involved in energy metabolism and the AKT/cAMP response element-binding protein (CREB) signaling pathway. Our results reveal NBP attenuates stress-induced social deficits, anxiety-like behavior and despair behavior, and alters metabolite levels of glycolysis and tricarboxylic acid (TCA) cycle components. NBP affected gene expression of key enzymes of the TCA cycle, as well as protein expression of p-AKT and p-CREB. Our findings provide the first evidence showing that NBP can attenuate stress-induced behavioral deficits by modulating energy metabolism by regulating activation of the AKT/CREB signaling pathway.

Aspects of diastolic dysfunction in patients with new and recurrent depression

Objective

The main objective of this study was to evidence the potential impact of the intensity, duration and recurrence of depression on the development of arterial stiffness (AS) leading to left ventricular hypertrophy (LVH) and diastolic dysfunction (DD) in patients with new onset depression (NOD) and recurrent depression (RD) in comparison to 33 control subjects without depression. Another aim was to identify potential predictive factors regarding the occurrence of diastolic dysfunction (DD).

Methods

Our study group included 58 patients diagnosed with NOD and 128 diagnosed with RD, without any previously diagnosed significant heart diseases. The intensity of depression was evaluated by means of the Montgomery-Asberg Depression Rating Scale (MADRS). Assessment of pulse wave velocity (PWV), left ventricular mass index (LVMI) and echocardiographic parameters characterizing DD were performed for each patient.

Results

The cardiology evaluations suggested an increased prevalence of AS in all patients, of significantly higher rate than in controls (p<0.001), which was statistically correlated with the severity and duration of depression. Another significant finding was an increased prevalence of DD (29.31% and 63.28%, respectively; p<0.001) correlated with the MADRS score, total duration and number of recurrences/relapses. The multivariate logistic regression analysis identified PWV, the intensity and duration of depression as significant predictive factors for the occurrence of DD.

Conclusions

In our study, diastolic dysfunction was a common finding among patients with RD, but it was also noted, to a lesser extent, in those suffering with NOD. DD was associated with altered AS, and strongly correlated with the intensity and the duration of depressive symptoms. The two latter factors, together with an increased PWV, were strong predictors for the occurrence of DD.

Tryptophan metabolite concentrations in depressed patients before and after electroconvulsive therapy

Tryptophan and kynurenine pathway (KP) metabolites are implicated in the pathophysiology of depression. We aimed to investigate their plasma concentrations in medicated patients with depression (n = 94) compared to age- and sex-matched healthy controls (n = 57), and in patients with depression after electroconvulsive therapy (ECT) in a real-world clinical setting, taking account of co-variables including ECT modality and heterogenous psychopathology. Depression severity was assessed using the Hamilton Depression Rating Scale (HAM-D24). Tryptophan (TRP) and kynurenine (KYN) metabolite concentrations [anthranilic acid (AA), 3-hydroxyanthranilic acid (3HAA), picolinic acid (PA), kynurenic acid (KYNA), and xanthurenic acid (XA)] and KYNA/KYN and KYNA/quinolinic acid (QUIN) ratios were lower in patients compared to controls. For the total group there was no significant change in KP metabolites post-ECT or correlations with mood ratings. However, improvements in mood score were correlated with increased KYN, 3-hydroxykynurenine (3HK), 3HAA, QUIN, and KYN/TRP in a subgroup of unipolar depressed patients. Additionally, in remitters baseline KYN, 3HK, and QUIN were associated with baseline HAM-D24 scores, and changes in 3HK and 3HAA concentrations post-ECT correlated with improvement in mood. KYN, KYNA, AA, 3HK, XA, PA, and QUIN were increased in a smaller 3-month follow-up group (n = 19) compared to pre-ECT concentrations. Overall, the results indicate that ECT mobilizes the KP, where a moderate association between selected metabolites and treatment response in unipolar depressed patients is evident.

Mood-related central and peripheral clocks

Mood disorders, including major depression, bipolar disorder, and seasonal affective disorder, are debilitating disorders that affect a significant portion of the global population. Individuals suffering from mood disorders often show significant disturbances in circadian rhythms and sleep. Moreover, environmental disruptions to circadian rhythms can precipitate or exacerbate mood symptoms in vulnerable individuals. Circadian clocks exist throughout the central nervous system and periphery, where they regulate a wide variety of physiological processes implicated in mood regulation. These processes include monoaminergic and glutamatergic transmission, hypothalamic-pituitary-adrenal axis function, metabolism, and immune function. While there seems to be a clear link between circadian rhythm disruption and mood regulation, the mechanisms that underlie this association remain unclear. This review will touch on the interactions between the circadian system and each of these processes and discuss their potential role in the development of mood disorders. While clinical studies are presented, much of the review will focus on studies in animal models, which are attempting to elucidate the molecular and cellular mechanisms in which circadian genes regulate mood.

Proteomic profiling of the neurons in mice with depressive-like behavior induced by corticosterone and the regulation of berberine: pivotal sites of oxidative phosphorylation

Chronic corticosterone (CORT) stress is an anxiety and depression inducing factor that involves the dysfunction of glucocorticoid receptor (GR), brain-derived neurotrophic factor (BDNF), and neuronal plasticity. However, the regulation of proteomic profiles in neurons suffering CORT stress is remaining elusive. Thus, the proteomic profiles of mouse neuronal C17.2 stem cells were comprehensively investigated by TMT (tandem mass tag)-labeling quantitative proteomics. The quantitative proteomics conjugated gene ontology analysis revealed the inhibitory effect of CORT on the expression of mitochondrial oxidative phosphorylation-related proteins, which can be antagonized by berberine (BBR) treatment. In addition, animal studies showed that changes in mitochondria by CORT can affect neuropsychiatric activities and disturb the physiological functions of neurons via disordering mitochondrial oxidative phosphorylation. Thus, the mitochondrial energy metabolism can be considered as one of the major mechanism underlying CORT-mediated depression. Since CORT is important for depression after traumatic stress disorder, our study will shed light on the prevention and treatment of depression as well as posttraumatic stress disorder (PTSD).

Synthetic Peptides as Therapeutic Agents: Lessons Learned From Evolutionary Ancient Peptides and Their Transit Across Blood-Brain Barriers

Peptides play a major role in the transmission of information to and from the central nervous system. However, because of their structural complexity, the development of pharmacological peptide-based therapeutics has been challenged by the lack of understanding of endogenous peptide evolution. The teneurin C-terminal associated peptides (TCAP) possess many of the required attributes of a practical peptide therapeutic. TCAPs, associated with the teneurin transmembrane proteins that bind to the latrophilins, members of the Adhesion family of G-protein-coupled receptors (GPCR). Together, this ligand-receptor unit plays an integral role in synaptogenesis, neurological development, and maintenance, and is present in most metazoans. TCAP has structural similarity to corticotropin-releasing factor (CRF), and related peptides, such as calcitonin and the secretin-based peptides and inhibits the (CRF)-associated stress response. Latrophilins are structurally related to the secretin family of GPCRs. TCAP is a soluble peptide that crosses the blood-brain barrier and regulates glucose transport into the brain. We posit that TCAP represents a phylogenetically older peptide system that evolved before the origin of the CRF-calcitonin-secretin clade of peptides and plays a fundamental role in the regulation of cell-to-cell energy homeostasis. Moreover, it may act as a phylogenetically older peptide system that evolved as a natural antagonist to the CRF-mediated stress response. Thus, TCAP's actions on the CNS may provide new insights into the development of peptide therapeutics for the treatment of CNS disorders.

Hippocampal proteomic changes of susceptibility and resilience to depression or anxiety in a rat model of chronic mild stress

Chronic stressful occurrences are documented as a vital cause of both depression and anxiety disorders. However, the stress-induced molecular mechanisms underlying the common and distinct pathophysiology of these disorders remains largely unclear. We utilized a chronic mild stress (CMS) rat model to differentiate and subgroup depression-susceptible, anxiety-susceptible, and insusceptible rats. The hippocampus was analyzed for differential proteomes by combining mass spectrometry and the isobaric tags for relative and absolute quantitation (iTRAQ) labeling technique. Out of 2593 quantified proteins, 367 were aberrantly expressed. These hippocampal protein candidates might be associated with susceptibility to stress-induced depression or anxiety and stress resilience. They provide the potential protein systems involved in various metabolic pathways as novel investigative protein targets. Further, independent immunoblot analysis identified changes in Por, Idh2 and Esd; Glo1, G6pdx, Aldh2, and Dld; Dlat, Ogdhl, Anxal, Tpp2, and Sdha that were specifically associated to depression-susceptible, anxiety-susceptible, or insusceptible groups respectively, suggesting that identical CMS differently impacted the mitochondrial and metabolic processes in the hippocampus. Collectively, the observed alterations to protein abundance profiles of the hippocampus provided significant and novel insights into the stress regulation mechanism in a CMS rat model. This might serve as the molecular basis for further studies that would contributed to a better understanding of the similarities and differences in pathophysiologic mechanisms underlying stress-induced depression or anxiety, and stress resiliency.

Major Depressive Disorder and Oxidative Stress: In Silico Investigation of Fluoxetine Activity against ROS

Major depressive disorder is a psychiatric disease having approximately a 20% lifetime prevalence in adults in the United States (U.S.), as reported by Hasin et al. in JAMA Psichiatry 2018 75, 336–346. Symptoms include low mood, anhedonia, decreased energy, alteration in appetite and weight, irritability, sleep disturbances, and cognitive deficits. Comorbidity is frequent, and patients show decreased social functioning and a high mortality rate. Environmental and genetic factors favor the development of depression, but the mechanisms by which stress negatively impacts on the brain are still not fully understood. Several recent works, mainly published during the last five years, aim at investigating the correlation between treatment with fluoxetine, a non-tricyclic antidepressant drug, and the amelioration of oxidative stress. In this work, the antioxidant activity of fluoxetine was investigated using a computational protocol based on the density functional theory approach. Particularly, the scavenging of five radicals (HO•, HOO•, CH3OO•, CH2=CHOO•, and CH3O•) was considered, focusing on hydrogen atom transfer (HAT) and radical adduct formation (RAF) mechanisms. Thermodynamic as well as kinetic aspects are discussed, and, for completeness, two metabolites of fluoxetine and serotonin, whose extracellular concentration is enhanced by fluoxetine, are included in our analysis. Indeed, fluoxetine may act as a radical scavenger, and exhibits selectivity for HO• and CH3O•, but is inefficient toward peroxyl radicals. In contrast, the radical scavenging efficiency of serotonin, which has been demonstrated in vitro, is significant, and this supports the idea of an indirect antioxidant efficiency of fluoxetine.

Serotonin regulates mitochondrial biogenesis and function in rodent cortical neurons via the 5-HT2A receptor and SIRT1-PGC-1α axis

Neuronal mitochondria are crucial organelles that regulate bioenergetics and also modulate survival and function under environmental challenges. Here, we show that the neurotransmitter serotonin (5-HT) plays an important role in the making of new mitochondria (mitochondrial biogenesis) in cortical neurons, through the 5-HT_2A receptor and via master regulators of mitochondrial biogenesis, SIRT1 and PGC-1α. Mitochondrial function is also enhanced by 5-HT, increasing cellular respiration and ATP, the energy currency of the cell. We found 5-HT reduces cellular reactive oxygen species and exerts potent neuroprotective action in neurons challenged with stress, an effect that requires SIRT1. These findings highlight a role for the mitochondrial effects of 5-HT in the facilitation of stress adaptation and identify drug targets to ameliorate mitochondrial dysfunction in neurons.

Mitochondria in neurons, in addition to their primary role in bioenergetics, also contribute to specialized functions, including regulation of synaptic transmission, Ca²⁺ homeostasis, neuronal excitability, and stress adaptation. However, the factors that influence mitochondrial biogenesis and function in neurons remain poorly elucidated. Here, we identify an important role for serotonin (5-HT) as a regulator of mitochondrial biogenesis and function in rodent cortical neurons, via a 5-HT_2A receptor-mediated recruitment of the SIRT1–PGC-1α axis, which is relevant to the neuroprotective action of 5-HT. We found that 5-HT increased mitochondrial biogenesis, reflected through enhanced mtDNA levels, mitotracker staining, and expression of mitochondrial components. This resulted in higher mitochondrial respiratory capacity, oxidative phosphorylation (OXPHOS) efficiency, and a consequential increase in cellular ATP levels. Mechanistically, the effects of 5-HT were mediated via the 5-HT_2A receptor and master modulators of mitochondrial biogenesis, SIRT1 and PGC-1α. SIRT1 was required to mediate the effects of 5-HT on mitochondrial biogenesis and function in cortical neurons. In vivo studies revealed that 5-HT_2A receptor stimulation increased cortical mtDNA and ATP levels in a SIRT1-dependent manner. Direct infusion of 5-HT into the neocortex and chemogenetic activation of 5-HT neurons also resulted in enhanced mitochondrial biogenesis and function in vivo. In cortical neurons, 5-HT enhanced expression of antioxidant enzymes, decreased cellular reactive oxygen species, and exhibited neuroprotection against excitotoxic and oxidative stress, an effect that required SIRT1. These findings identify 5-HT as an upstream regulator of mitochondrial biogenesis and function in cortical neurons and implicate the mitochondrial effects of 5-HT in its neuroprotective action.

Antidepressants affect gut microbiota and Ruminococcus flavefaciens is able to abolish their effects on depressive-like behavior

Accumulating evidence demonstrates that the gut microbiota affects brain function and behavior, including depressive behavior. Antidepressants are the main drugs used for treatment of depression. We hypothesized that antidepressant treatment could modify gut microbiota which can partially mediate their antidepressant effects. Mice were chronically treated with one of five antidepressants (fluoxetine, escitalopram, venlafaxine, duloxetine or desipramine), and gut microbiota was analyzed, using 16s rRNA gene sequencing. After characterization of differences in the microbiota, chosen bacterial species were supplemented to vehicle and antidepressant-treated mice, and depressive-like behavior was assessed to determine bacterial effects. RNA-seq analysis was performed to determine effects of bacterial treatment in the brain. Antidepressants reduced richness and increased beta diversity of gut bacteria, compared to controls. At the genus level, antidepressants reduced abundances of Ruminococcus, Adlercreutzia, and an unclassified Alphaproteobacteria. To examine implications of the dysregulated bacteria, we chose one of antidepressants (duloxetine) and investigated if its antidepressive effects can be attenuated by simultaneous treatment with Ruminococcus flavefaciens or Adlercreutzia equolifaciens. Supplementation with R. flavefaciens diminished duloxetine-induced decrease in depressive-like behavior, while A. equolifaciens had no such effect. R. flavefaciens treatment induced changes in cortical gene expression, up-regulating genes involved in mitochondrial oxidative phosphorylation, while down-regulating genes involved in neuronal plasticity. Our results demonstrate that various types of antidepressants alter gut microbiota composition, and further implicate a role for R. flavefaciens in alleviating depressive-like behavior. Moreover, R. flavefaciens affects gene networks in the brain, suggesting a mechanism for microbial regulation of antidepressant treatment efficiency.

Treadmill Exercise Ameliorates Depression-Like Behavior in the Rats With Prenatal Dexamethasone Exposure: The Role of Hippocampal Mitochondria

Prenatal exposure to synthetic glucocorticoids (sGCs) can increase the risk of affective disorders, such as depression, in adulthood. Given that exercise training can ameliorate depression and improve mitochondrial function, we sought to investigate whether exercise can ameliorate depression-like behavior induced by prenatal sGC exposure and mitochondria function contributes to that behavior. At first, we confirmed that prenatal dexamethasone (Dex) administration in late pregnancy resulted in depression-like behavior and elevated level of circulatory corticosterone in adult offspring. We then found that mRNA and protein expression of a number of mitochondrial genes was changed in the hippocampus of Dex offspring. Mitochondria in the hippocampus showed abnormal morphology, oxidative stress and dysfunction in Dex offspring. Intracerebroventricular (ICV) injection of the mitochondrial superoxide scavenger mitoTEMPO significantly alleviated depression-like behavior but did not significantly affect circulatory corticosterone level in Dex offspring. The adult Dex offspring treated with treadmill exercise starting at four-weeks of age showed ameliorated depressive-like behavior, improved mitochondrial morphology and function and reduced circulatory corticosterone level. Our data suggest mitochondria dysfunction contributes to depression-like behavior caused by prenatal sGC exposure. Intervention with exercise training in early life can reverse depression caused by prenatal Dex exposure, which is associated with improvement of mitochondrial function in the hippocampus.