Increase in nitric oxide levels and mitochondrial membrane potential in platelets of untreated patients with major depression

Antioxidants in neuropsychiatric disorder prevention: neuroprotection, synaptic regulation, microglia modulation, and neurotrophic effects

Oxidative stress, caused by an imbalance between the generation of reactive oxygen species (ROS) and the body's intrinsic antioxidant defenses, plays a critical role in neurodegenerative diseases such as Alzheimer's, Parkinson's, and Huntington's. Beyond these conditions, recent evidence indicates that dysregulated redox balance is implicated in neuropsychiatric disorders, including schizophrenia, major depressive disorder, and anxiety disorders. Preclinical and clinical studies have demonstrated the potential of antioxidants, such as N-acetylcysteine, sulforaphane, alpha-lipoic acid, L-carnitine, ascorbic acid, selenocompounds, flavones and zinc, in alleviating neuropsychiatric symptoms by mitigating excitotoxicity, enhancing synaptic plasticity, reducing microglial overactivation and promoting synaptogenesis. This review explores the role of oxidative stress in the pathogenesis of neuropsychiatric disorders. It provides an overview of the current evidence on antioxidant therapy's pharmacological effects, as demonstrated in animal models and clinical studies. It also discusses the underlying mechanisms and future directions for developing antioxidant-based adjuvant therapies. Given the limitations and side effects of existing treatments for neuropsychiatric disorders, antioxidant therapy presents a promising, safer alternative. Further research is essential to deepen our understanding and investigate the clinical efficacy and mechanisms underlying these therapies.

Unraveling the potential of vitamins C and D as adjuvants in depression treatment with escitalopram in an LPS animal model

Depression is linked with oxidative stress and inflammation, where key players include nitric oxide (NO), nuclear factor erythroid 2-related factor 2 (Nrf2), Brain-Derived Neurotrophic Factor (BDNF), and Heme Oxidase-1 (HO-1). Augmenting the efficacy of antidepressants represents a compelling avenue of exploration. We explored the potential of vitamins C and D as adjuncts to escitalopram (Esc) in a lipopolysaccharide (LPS)-induced depression model focusing on the aforementioned biomarkers. Male Swiss albino mice were stratified into distinct groups: control, LPS, LPS + Esc, LPS + Esc + Vit C, LPS + Esc + Vit D, and LPS + Esc + Vit C + Vit D. After a 7-day treatment period, a single LPS dose (2 mg/kg), was administered, followed by comprehensive assessments of behavior and biochemical parameters. Notably, a statistically significant (p < 0.05) alleviation of depressive symptoms was discerned in the Esc + Vit C + Vit D group versus the LPS group, albeit with concomitant pronounced sedation evident in all LPS-treated groups (p < 0.05). Within the cortex, LPS reduced (p < 0.05) the expression levels of NOx, Nrf2, BDNF, and HO-1, with only HO-1 being reinstated to baseline in the LPS + Esc + Vit D and the LPS + Esc + Vit C + Vit D groups. Conversely, the hippocampal NOx, Nrf2, and HO-1 levels remained unaltered following LPS administration. Notably, the combination of Esc, Vit C, and Vit D effectively restored hippocampal BDNF levels, which had been diminished by Esc alone. In conclusion, vitamins C and D enhance the therapeutic effects of escitalopram through a mechanism independent of Nrf2. These findings underscore the imperative need for in-depth investigations.

Platelet mitochondria, a potent immune mediator in neurological diseases

Dysfunction of the immune response is regarded as a prominent feature of neurological diseases, including neurodegenerative diseases, malignant tumors, acute neurotraumatic insult, and cerebral ischemic/hemorrhagic diseases. Platelets play a fundamental role in normal hemostasis and thrombosis. Beyond those normal functions, platelets are hyperactivated and contribute crucially to inflammation and immune responses in the central nervous system (CNS). Mitochondria are pivotal organelles in platelets and are responsible for generating most of the ATP that is used for platelet activation and aggregation (clumping). Notably, platelet mitochondria show marked morphological and functional alterations under heightened inflammatory/oxidative stimulation. Mitochondrial dysfunction not only leads to platelet damage and apoptosis but also further aggravates immune responses. Improving mitochondrial function is hopefully an effective strategy for treating neurological diseases. In this review, the authors discuss the immunomodulatory roles of platelet-derived mitochondria (PLT-mitos) in neurological diseases and summarize the neuroprotective effects of platelet mitochondria transplantation.

The Role of Gasotransmitter-Dependent Signaling Mechanisms in Apoptotic Cell Death in Cardiovascular, Rheumatic, Kidney, and Neurodegenerative Diseases and Mental Disorders

Cardiovascular, rheumatic, kidney, and neurodegenerative diseases and mental disorders are a common cause of deterioration in the quality of life up to severe disability and death worldwide. Many pathological conditions, including this group of diseases, are based on increased cell death through apoptosis. It is known that this process is associated with signaling pathways controlled by a group of gaseous signaling molecules called gasotransmitters. They are unique messengers that can control the process of apoptosis at different stages of its implementation. However, their role in the regulation of apoptotic signaling in these pathological conditions is often controversial and not completely clear. This review analyzes the role of nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H₂S), and sulfur dioxide (SO₂) in apoptotic cell death in cardiovascular, rheumatic, kidney, and neurodegenerative diseases. The signaling processes involved in apoptosis in schizophrenia, bipolar, depressive, and anxiety disorders are also considered. The role of gasotransmitters in apoptosis in these diseases is largely determined by cell specificity and concentration. NO has the greatest dualism; scales are more prone to apoptosis. At the same time, CO, H₂S, and SO₂ are more involved in cytoprotective processes.

The tryptophan catabolite or kynurenine pathway in major depressive and bipolar disorder: A systematic review and meta-analysis

Background

There is now evidence that affective disorders including major depressive disorder (MDD) and bipolar disorder (BD) are mediated by immune-inflammatory and nitro-oxidative pathways. Activation of these pathways may be associated with activation of the tryptophan catabolite (TRYCAT) pathway by inducing indoleamine 2,3-dioxygenase (IDO, the rate-limiting enzyme) leading to depletion of tryptophan (TRP) and increases in tryptophan catabolites (TRYCATs).

Aims

To systematically review and meta-analyze central and peripheral (free and total) TRP levels, its competing amino-acids (CAAs) and TRYCATs in MDD and BD.

Methods

This review searched PubMed, Google Scholar and SciFinder and included 121 full-text articles and 15470 individuals, including 8024 MDD/BD patients and 7446 healthy controls.

Results

TRP levels (either free and total) and the TRP/CAAs ratio were significantly decreased (p < 0.0001) in MDD/BD as compared with controls with a moderate effect size (standardized mean difference for TRP: SMD = -0.513, 95% confidence interval, CI: -0.611; -0.414; and TRP/CAAs: SMD = -0.558, CI: -0.758; -0.358). Kynurenine (KYN) levels were significantly decreased in patients as compared with controls with a small effect size (p < 0.0001, SMD = -0.213, 95%CI: -0.295; -0.131). These differences were significant in plasma (p < 0.0001, SMD = -0.304, 95%CI: -0.415, -0.194) but not in serum (p = 0.054) or the central nervous system (CNS, p = 0.771). The KYN/TRP ratio, frequently used as an index of IDO activity, and neurotoxicity indices based on downstream TRYCATs were unaltered or even lowered in MDD/BD.

Conclusions

Our findings suggest that MDD and BD are accompanied by TRP depletion without IDO and TRYCAT pathway activation. Lowered TRP availability is probably the consequence of lowered serum albumin during the inflammatory response in affective disorders.

The Tryptophan Catabolite or Kynurenine Pathway in a Major Depressive Episode with Melancholia, Psychotic Features and Suicidal Behaviors: A Systematic Review and Meta-Analysis

Major depressive disorder (MDD) and bipolar disorder (BD) with melancholia and psychotic features and suicidal behaviors are accompanied by activated immune-inflammatory and oxidative pathways, which may stimulate indoleamine 2,3-dioxygenase (IDO), the first and rate-limiting enzyme of the tryptophan catabolite (TRYCAT) pathway resulting in increased tryptophan degradation and elevated tryptophan catabolites (TRYCTAs). The purpose of the current study is to systematically review and meta-analyze levels of TRP, its competing amino acids (CAAs) and TRYCATs in patients with severe affective disorders. Methods: PubMed, Google Scholar and SciFinder were searched in the present study and we recruited 35 studies to examine 4647 participants including 2332 unipolar (MDD) and bipolar (BD) depressed patients and 2315 healthy controls. Severe patients showed significant lower (p < 0.0001) TRP (standardized mean difference, SMD = -0.517, 95% confidence interval, CI: -0.735; -0.299) and TRP/CAAs (SMD = -0.617, CI: -0.957; -0.277) levels with moderate effect sizes, while no significant difference in CAAs were found. Kynurenine (KYN) levels were unaltered in severe MDD/BD phenotypes, while the KYN/TRP ratio showed a significant increase only in patients with psychotic features (SMD = 0.224, CI: 0.012; 0.436). Quinolinic acid (QA) was significantly increased (SMD = 0.358, CI: 0.015; 0.701) and kynurenic acid (KA) significantly decreased (SMD = -0.260, CI: -0.487; -0.034) in severe MDD/BD. Patients with affective disorders with melancholic and psychotic features and suicidal behaviors showed normal IDO enzyme activity but a lowered availability of plasma/serum TRP to the brain, which is probably due to other processes such as low albumin levels.

The kynurenine pathway in major depressive disorder, bipolar disorder, and schizophrenia: a meta-analysis of 101 studies

The importance of tryptophan as a precursor for neuroactive compounds has long been acknowledged. The metabolism of tryptophan along the kynurenine pathway and its involvement in mental disorders is an emerging area in psychiatry. We performed a meta-analysis to examine the differences in kynurenine metabolites in major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia (SZ). Electronic databases were searched for studies that assessed metabolites involved in the kynurenine pathway (tryptophan, kynurenine, kynurenic acid, quinolinic acid, 3-hydroxykynurenine, and their associate ratios) in people with MDD, SZ, or BD, compared to controls. We computed the difference in metabolite concentrations between people with MDD, BD, or SZ, and controls, presented as Hedges' g with 95% confidence intervals. A total of 101 studies with 10,912 participants were included. Tryptophan and kynurenine are decreased across MDD, BD, and SZ; kynurenic acid and the kynurenic acid to quinolinic acid ratio are decreased in mood disorders (i.e., MDD and BD), whereas kynurenic acid is not altered in SZ; kynurenic acid to 3-hydroxykynurenine ratio is decreased in MDD but not SZ. Kynurenic acid to kynurenine ratio is decreased in MDD and SZ, and the kynurenine to tryptophan ratio is increased in MDD and SZ. Our results suggest that there is a shift in the tryptophan metabolism from serotonin to the kynurenine pathway, across these psychiatric disorders. In addition, a differential pattern exists between mood disorders and SZ, with a preferential metabolism of kynurenine to the potentially neurotoxic quinolinic acid instead of the neuroprotective kynurenic acid in mood disorders but not in SZ.

Association of depressive disorder with biochemical and anthropometric indices in adult men and women

Depression is a common psychiatric disorder. Although many risk factors for depression have been reported, the associations of biochemical and anthropometric indices with depressive disorder remain unclear. The objective of this study was to assess whether there are significant associations of depressive disorder with biochemical and obesity indices. This study was based on data from the Korea National Health and Nutrition Examination Survey from 2007 to 2018, and logistic regression was performed to examine the association of depression with biochemical and obesity indices. A total of 33,993 subjects were included in the analyses. Study subjects consisted of 13,178 men in the control group (mean age of 51.12 years), 509 men in the depression group (53.67), 18,279 women in the control group (50.5), and 2027 women in the depression group (55.39). Among men, the depression group was significantly more likely to have a lower height and weight than the control group. Compared to the control group, the depression group was more likely to have higher triglyceride levels and tended to have lower hematocrit and blood urea nitrogen (BUN) levels. Among women, the depression group was more likely to have higher triglyceride, aspartate aminotransferase (AST), BUN, and creatinine levels and lower high-density lipoprotein cholesterol (HDL-C), hematocrit, and red blood cell counts. Several biochemical and anthropometric indices used in this study were associated with depressive disorder, but these associations may differ according to sex.

Depression and Cardiovascular Disease: The Viewpoint of Platelets

Depression is a major cause of morbidity and low quality of life among patients with cardiovascular disease (CVD), and it is now considered as an independent risk factor for major adverse cardiovascular events. Increasing evidence indicates not only that depression worsens the prognosis of cardiac events, but also that a cross-vulnerability between the two conditions occurs. Among the several mechanisms proposed to explain this interplay, platelet activation is the more attractive, seeing platelets as potential mirror of the brain function. In this review, we dissected the mechanisms linking depression and CVD highlighting the critical role of platelet behavior during depression as trigger of cardiovascular complication. In particular, we will discuss the relationship between depression and molecules involved in the CVD (e.g., catecholamines, adipokines, lipids, reactive oxygen species, and chemokines), emphasizing their impact on platelet activation and related mechanisms.

Molecular markers of neuroendocrine function and mitochondrial biogenesis associated with early life stress

OBJECTIVE

Glucocorticoid receptor gene (NR3C1) promoter methylation influences cellular expression of the glucocorticoid receptor and is a proposed mechanism by which early life stress impacts neuroendocrine function. Mitochondria are sensitive and responsive to neuroendocrine stress signaling through the glucocorticoid receptor, and recent evidence with this sample and others shows that mitochondrial DNA copy number (mtDNAcn) is increased in adults with a history of early stress. No prior work has examined the role of NR3C1 methylation in the association between early life stress and mtDNAcn alterations.

METHODS

Adult participants (n = 290) completed diagnostic interviews and questionnaires characterizing early stress and lifetime psychiatric symptoms. Medical conditions, active substance abuse, and prescription medications other than oral contraceptives were exclusionary. Subjects with a history of lifetime bipolar, obsessive-compulsive, or psychotic disorders were excluded; individuals with other forms of major psychopathology were included. Whole blood mtDNAcn was measured using qPCR; NR3C1 methylation was measured via pyrosequencing. Multiple regression and bootstrapping procedures tested NR3C1 methylation as a mediator of effects of early stress on mtDNAcn.

RESULTS

The positive association between early adversity and mtDNAcn (p = .02) was mediated by negative associations of early adversity with NR3C1 methylation (p = .02) and NR3C1 methylation with mtDNAcn (p < .001). The indirect effect involving early adversity, NR3C1 methylation, and mtDNAcn was significant (95 % CI [.002, .030]).

CONCLUSIONS

NR3C1 methylation significantly mediates the association between early stress and mtDNAcn, suggesting that glucocorticoid receptor signaling may be a mechanistic pathway underlying mtDNAcn alterations of interest for future longitudinal work.

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

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

Mitochondrial DNA copy number, damage, repair and degradation in depressive disorder

Objectives: We aimed to explore mitochondrial DNA (mtDNA) copy number, damage, repair and degradation in peripheral blood mononuclear cells (PBMCs) of patients with depression and to compare the results with healthy subjects.Methods: Total genomic DNA was isolated from PBMCs of 25 depressed and 60 healthy subjects before, immediately after, and 3 h after the exposure to H₂O₂. Evaluation of mtDNA copy number was performed using real-time PCR and 2-ΔCt methods. Semi-long run real-time PCR was used to estimate the number of mtDNA lesions.Results: Baseline mtDNA copy number did not differ in cells of healthy and depressed subjects; however, it was negatively correlated with the severity of the episode. After a 10-min challenge with hydrogen peroxide (H₂O₂), depressed patients' PBMCs exhibited slower changes of the copy number, indicating a lower efficiency of mtDNA degradation compared to controls. Moreover, a significantly higher number of mtDNA lesions was found in depressed patients at the baseline as well as at other experimental time points. mtDNA lesions were also elevated in depressed patient cells immediately after H₂O₂ exposure. Induction of oxidative stress had no significant influence on the cells of controls.Conclusions: We are the first to show that impairment in repair and degradation of mtDNA may be involved in the pathophysiology of depression.

Transcranial Photobiomodulation For The Management Of Depression: Current Perspectives

Major depressive disorder (MDD) is a prevalent condition associated with high rates of disability, as well as suicidal ideation and behavior. Current treatments for MDD have significant limitations in efficacy and side effect burden. FDA-approved devices for MDD are burdensome (due to repeated in-office procedures) and are most suitable for severely ill subjects. There is a critical need for device-based treatments in MDD that are efficacious, well-tolerated, and easy to use. In this paper, we review a novel neuromodulation strategy, transcranial photobiomodulation (t-PBM) with near-infrared light (NIR). The scope of our review includes the known biological mechanisms of t-PBM, as well as its efficacy in animal models of depression and in patients with MDD. Theoretically, t-PBM penetrates into the cerebral cortex, stimulating the mitochondrial respiratory chain, and also significantly increases cerebral blood flow. Animal and human studies, using a variety of t-PBM settings and experimental models, suggest that t-PBM may have significant efficacy and good tolerability in MDD. In aggregate, these data support the need for large confirmatory studies for t-PBM as a novel, likely safe, and easy-to-administer antidepressant treatment.

DNA damage and repair in neuropsychiatric disorders. What do we know and what are the future perspectives?

Over the past two decades, extensive research has been done to elucidate the molecular etiology and pathophysiology of neuropsychiatric disorders. In majority of them, including Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS), bipolar disorder (BD), schizophrenia and major depressive disorder, increased oxidative and nitrosative stress was found. This stress is known to induce oxidative damage to biomolecules, including DNA. Accordingly, increased mitochondrial and nuclear DNA, as well as RNA damage, were observed in patients suffering from these diseases. However, recent findings indicate that the patients are characterised by impaired DNA repair pathways, which may suggest that these DNA lesions could be also a result of their insufficient repair. In the current systematic, critical review, we aim to sum up, using available literature, the knowledge about the involvement of nuclear and mitochondrial DNA damage and repair, as well as about damage to RNA in pathoetiology of neuropsychiatric disorders, i.e., AD, PD, ALS, BD, schizophrenia and major depressive disorder, as well as the usefulness of the discussed factors as being diagnostic markers and targets for new therapies. Moreover, we also underline the new directions to which future studies should head to elucidate these phenomena.

Activities of mitochondrial respiratory chain complexes in platelets of patients with Alzheimer's disease and depressive disorder

We analyzed activities of complex I, II, III, and IV, and citrate synthase (CS) in patients with major depressive disorder (MDD) or Alzheimer's disease (AD) presenting with or without depression. Associations of these parameters with disease or disease severity were observed in both AD and MDD; however, mean values of mitochondrial parameters were significantly altered in AD but not in MDD. Potential mitochondrial dysfunction in MDD seems not to be caused by disturbed activity of CS or respiratory complexes. In AD, a decrease in the activity of CS and complex IV may cause mitochondrial dysfunction, whereas an increase in activities of other mitochondrial complexes or their ratios to CS may be an adaptive response. The data indicate that comorbid depression in AD is associated with increased complex II activity. The mitochondrial parameters measured can be included in the panel of biomarkers of AD.

Increased thioredoxin-interacting protein in brain of mice exposed to chronic stress

Chronic stress is a key contributor to depression. Previous studies have shown that oxidative stress and inflammation are increased by chronic stress and in subjects with depression. Thioredoxin is a small redox protein that regulates cellular redox balance and signaling. This protein can reverse protein cysteine oxidative modifications such as sulfenylation and nitrosylation, and inhibit stress-regulated apoptosis signal-regulating kinase 1 pathway. Therefore thioredoxin plays an important role in cellular defense against oxidative stress. Thioredoxin-interacting protein is an endogenous thioredoxin inhibitor. In the present study, to understand the role of thioredoxin in chronic stress and depression, we have investigated thioredoxin, thioredoxin-interacting protein, sulfenylation, nitrosylation and apoptosis signal-regulating kinase 1 phosphorylation in brain of mice exposed to chronic unpredictable stress (CUS). We found that mice exposed to CUS displayed decreased exploratory, increased anhedonic and increased despair depressive-like behaviours. We also found that although CUS had no effect on thioredoxin protein levels, it significantly increased levels of thioredoxin-interacting protein in mouse hippocampus and frontal cortex. CUS also increased protein cysteine sulfenylation, protein cysteine nitrosylation and apoptosis signal-regulating kinase 1 phosphorylation in mouse hippocampus and frontal cortex. These findings suggest that chronic stress may upregulate thioredoxin-interacting protein, subsequently inhibiting thioredoxin activity and enhancing oxidative protein cysteine modification and apoptosis signal-regulating kinase 1 pathway. These results also indicate that thioredoxin-interacting protein may have potential for depression treatment.

Intervention mechanism of repeated oral GABA administration on anxiety-like behaviors induced by emotional stress in rats

The purpose of this study was to investigate the effects and mechanism of repeated oral administration of gamma-aminobutyric acid (GABA) on anxiety-like behaviors induced by emotional stress. Male Sprague-Dawley rats were randomly divided into five groups (8 rats each): control, emotional stress model, three emotional stress + GABA-treated groups (0.5, 1, 2 mg/kg). The rats were given empty water bottles after the training of drinking water to induce emotional stress. Each group was treated with saline or different doses of GABA respectively for 21 consecutive days. Then open field and elevated plus maze were used to assess anxiety-like behaviors. Both frontal cortex and plasma NO metabolites nitrate and nitrite (NO_x) levels were determined spectrophotometrically. Results showed that oral administration of GABA significantly reversed the stress-induced anxiety-like negative responses dose-dependently. The frontal cortex NO_x levels were lower in stressed rats than in control group (P < 0.05), but higher in 2 mg/kg GABA-treated group than stress model group (P < 0.05). On the other hand, NOx levels in plasma showed a gradual decline trend. Collectively, these results suggest that short repeated oral administration of GABA has an anxiolytic-like effect possibly via preventing NO reduction caused by stress and improving availability of NO in the frontal cortex.

Ketamine upregulates eNOS expression in human astroglial A172 cells: Possible role in its antidepressive properties

Ketamine is a potent anti-depressive agent. Nitric oxide plays an essential role in neuronal transmission and cerebral blood flow and has been implicated in the pathophysiology of major depressive disorder as well as cardiovascular functioning. We investigated the effect of ketamine on eNOS expression in human A172 astroglial cells. Ketamine (50-500μM) increased eNOS expression at 4-24h in a concentration-dependent manner. This effect was mediated by NMDA receptor, Akt inhibition and ERK1/2 activation and was synergistically augmented by rapamycin. The combined effect on the vascular, immune and neuronal systems may be relevant to the rapid antidepressive effect of ketamine.

Higher mitochondrial potential and elevated mitochondrial respiration are associated with excessive activation of blood platelets in diabetic rats

AIMS

The high glucose concentration observed in diabetic patients is a recognized factor of mitochondrial damage in various cell types. Its impact on mitochondrial bioenergetics in blood platelets remains largely vague. The aim of the study was to determine how the metabolism of carbohydrates, which has been impaired by streptozotocin-induced diabetes may affect the functioning of platelet mitochondria.

MATERIALS AND METHODS

Diabetes was induced in Sprague Dawley rats by intraperitoneal injection of streptozotocin. Platelet mitochondrial respiratory capacity was monitored as oxygen consumption (high-resolution respirometry). Mitochondrial membrane potential was assessed using a fluorescent probe, JC-1. Activation of circulating platelets was monitored by flow cytometry measuring of the expressions of CD61 and CD62P on a blood platelet surface. To determine mitochondrial protein density in platelets, Western Blot technique was used.

KEY FINDINGS

The results indicate significantly elevated mitochondria mass, increased mitochondrial membrane potential (ΔΨm) and enhanced respiration in STZ-diabetic animals, although the respiration control ratios appear to remain unchanged. Higher ΔΨm and elevated mitochondrial respiration were closely related to the excessive activation of circulating platelets in diabetic animals.

SIGNIFICANCE

Long-term diabetes can result in increased mitochondrial mass and may lead to hyperpolarization of blood platelet mitochondrial membrane. These alterations may be a potential underlying cause of abnormal platelet functioning in diabetes mellitus and hence, a potential target for antiplatelet therapies in diabetes.

Neuronal effects of a nickel-piperazine/NO donor complex in rodents

In the brain, NO is a very important molecule in the regulation of cerebral and extra cerebral cranial blood flow and arterial diameters. It is also importantly involved in many neuronal functions and innumerable roles of NO in many brain related disorders including epilepsy, schizophrenia, drug addiction, anxiety, major depression, have been postulated. The present study aimed to explore the neuronal role exerted by the metal-nonoate compound Ni(PipNONO)Cl, a novel NO donor whose vascular protective effects have been recently demonstrated. Ni(PipNONO)Cl showed antidepressant-like properties in the tail suspension test and antiamnesic activity in the passive avoidance test in the absence of any hypernociceptive response to a mechanical stimulus. These effects were related to the NO-releasing properties of the compound within the central nervous system as demonstrated by the increase of iNOS levels in the brain, spinal cord and dura mater. The modulation of neuronal functions appeared after acute and repeated treatment, showing the lack of any tolerance to neuronal effects. At the dose used (10 mg/kg i.p.), Ni(PipNONO)Cl did not induce any visible sign of toxicity and experiments were performed in the absence of locomotor impairments. In addition to the NO-related neuronal activities of Ni(PipNONO)Cl, the decomposition control compound Ni(Pip)Cl2 showed anxiogenic-like and procognitive effects. The present findings showed neuronal modulatory activity of Ni(PipNONO)Cl through a NO-mediated mechanism. The activities of the decomposition compound Ni(Pip)Cl2 attributed to Ni(PipNONO)Cl the capability to modulate additional neuronal functions independently from NO releasing properties extending and improving the therapeutic perspectives of the NO donor.

Brain changes associated with thromboxane receptor antagonist SQ 29,548 treatment in a mouse model

The purpose of this study was to characterize behavioral and physiological effects of a selective thromboxane (TP) receptor antagonist, SQ 29,548, in the C57Bl/6 mouse model. At 6 months of age, male mice were given either sham or drug i.p. injections for 3 days at a dose of 2 mg/kg each day. On the day after the final injection, mice were subjected to behavioral testing before brain collection. Left hemisphere hippocampi were collected from all mice for protein analysis via Western blot. Right brain hemispheres were fixed and embedded in gelatin and then serially sectioned. The sections were immunostained with anti-c-Fos antibodies. Prostaglandin analysis was performed from remaining homogenized brain samples, minus the hippocampi. Injection of SQ 29,548 decreased selective brain prostaglandin levels compared with sham controls. This correlated with robust increases in limbic-region c-Fos immunoreactivity in the SQ 29,548-injected mice. However, drug-treated mice demonstrated no significant changes in relevant hippocampal protein levels compared with sham treatments, as determined from Western blots. Surprisingly, injection of SQ 29,548 caused mixed changes in parameters of depression and anxiety-like behavior in the mice. In conclusion, the results indicate that administration of peripheral TP receptor antagonists alters brain levels of prostanoids and influences neuronal activity, with only minimal alterations of behavior. Whether the drug affects neurons directly or through a secondary pathway involving endothelium or other tissues remains unclear.

A mitochondrial bioenergetic basis of depression

Major depressive disorder (MDD) is an important public health problem affecting 350 million people worldwide. After decades of study, the pathophysiology of MDD remains elusive, resulting in treatments that are only 30-60% effective. This review summarizes the emerging evidence that implicates impaired mitochondrial bioenergetics as a basis for MDD. It is suggested that impaired mitochondrial bioenergetic function contributes to the pathophysiology of MDD via several potential pathways including: genetics/genomics, inflammation, oxidative stress, and alterations in neuroplasticity. A discussion of mitochondrial bioenergetic pathways that lead to MDD is provided. Evidence is reviewed regarding the mito-toxic or mito-protective impact of various antidepressant medications currently in use. Opportunities for further research on novel therapeutic approaches, including mitochondrial modulators, as stand-alone or adjunct therapy for reducing depression are suggested. In conclusion, while there is substantial evidence linking mitochondrial bioenergetics and MDD, there are currently no clear mitochondrial phenotypes or biomarkers to use as guides in targeting therapies beyond individuals with MDD and known mitochondrial disorders toward the general population of individuals with MDD. Further study is needed to develop these phenotypes and biomarkers, to identify therapeutic targets, and to test therapies aimed at improving mitochondrial function in individuals whose MDD is to some extent symptomatic of impaired mitochondrial bioenergetics.

Vagus Nerve Stimulation

The vagus nerve is a major component of the autonomic nervous system, has an important role in the regulation of metabolic homeostasis, and plays a key role in the neuroendocrine-immune axis to maintain homeostasis through its afferent and efferent pathways. Vagus nerve stimulation (VNS) refers to any technique that stimulates the vagus nerve, including manual or electrical stimulation. Left cervical VNS is an approved therapy for refractory epilepsy and for treatment resistant depression. Right cervical VNS is effective for treating heart failure in preclinical studies and a phase II clinical trial. The effectiveness of various forms of non-invasive transcutaneous VNS for epilepsy, depression, primary headaches, and other conditions has not been investigated beyond small pilot studies. The relationship between depression, inflammation, metabolic syndrome, and heart disease might be mediated by the vagus nerve. VNS deserves further study for its potentially favorable effects on cardiovascular, cerebrovascular, metabolic, and other physiological biomarkers associated with depression morbidity and mortality.

Neurovascular unit dysfunction with blood-brain barrier hyperpermeability contributes to major depressive disorder: a review of clinical and experimental evidence

About one-third of people with major depressive disorder (MDD) fail at least two antidepressant drug trials at 1 year. Together with clinical and experimental evidence indicating that the pathophysiology of MDD is multifactorial, this observation underscores the importance of elucidating mechanisms beyond monoaminergic dysregulation that can contribute to the genesis and persistence of MDD. Oxidative stress and neuroinflammation are mechanistically linked to the presence of neurovascular dysfunction with blood-brain barrier (BBB) hyperpermeability in selected neurological disorders, such as stroke, epilepsy, multiple sclerosis, traumatic brain injury, and Alzheimer’s disease. In contrast to other major psychiatric disorders, MDD is frequently comorbid with such neurological disorders and constitutes an independent risk factor for morbidity and mortality in disorders characterized by vascular endothelial dysfunction (cardiovascular disease and diabetes mellitus). Oxidative stress and neuroinflammation are implicated in the neurobiology of MDD. More recent evidence links neurovascular dysfunction with BBB hyperpermeability to MDD without neurological comorbidity. We review this emerging literature and present a theoretical integration between these abnormalities to those involving oxidative stress and neuroinflammation in MDD. We discuss our hypothesis that alterations in endothelial nitric oxide levels and endothelial nitric oxide synthase uncoupling are central mechanistic links in this regard. Understanding the contribution of neurovascular dysfunction with BBB hyperpermeability to the pathophysiology of MDD may help to identify novel therapeutic and preventative approaches.