Acute administration of ketamine reverses the inhibition of mitochondrial respiratory chain induced by chronic mild stress

A mitochondrial nexus in major depressive disorder: Integration with the psycho-immune-neuroendocrine network

Nervous system processes, including cognition and affective state, fundamentally rely on mitochondria. Impaired mitochondrial function is evident in major depressive disorder (MDD), reflecting cumulative detrimental influences of both extrinsic and intrinsic stressors, genetic predisposition, and mutation. Glucocorticoid 'stress' pathways converge on mitochondria; oxidative and nitrosative stresses in MDD are largely mitochondrial in origin; both initiate cascades promoting mitochondrial DNA (mtDNA) damage with disruptions to mitochondrial biogenesis and tryptophan catabolism. Mitochondrial dysfunction facilitates proinflammatory dysbiosis while directly triggering immuno-inflammatory activation via released mtDNA, mitochondrial lipids and mitochondria associated membranes (MAMs), further disrupting mitochondrial function and mitochondrial quality control, promoting the accumulation of abnormal mitochondria (confirmed in autopsy studies). Established and putative mechanisms highlight a mitochondrial nexus within the psycho-immune neuroendocrine (PINE) network implicated in MDD. Whether lowering neuronal resilience and thresholds for disease, or linking mechanistic nodes within the MDD pathogenic network, impaired mitochondrial function emerges as an important risk, a functional biomarker, providing a therapeutic target in MDD. Several treatment modalities have been demonstrated to reset mitochondrial function, which could benefit those with MDD.

Targeting mitophagy for depression amelioration: a novel therapeutic strategy

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

Mitochondrial dysfunction in animal models of PTSD: Relationships between behavioral models, neural regions, and cellular maladaptation

Post-traumatic stress disorder (PTSD) is a trauma-related condition that produces distressing fear memory intrusions, avoidance behaviors, hyperarousal, stress responses, insomnia and other symptoms. This review of rodent models of PTSD examines trauma effects on fear-related learning, cognition, and avoidance, emotional and arousal behaviors and on mitochondrial dysfunction in relevant neural pathways. The review focuses on research that includes four elements: consensus PTSD rodent models, behavioral phenotyping, mitochondrial dysfunction within key neural regions. This approach allows for the integration of behavioral, neural and cellular findings in PTSD models. The PTSD models reviewed include fear conditioning, predator/social stress, chronic restraint stress, single prolonged stress, social isolation, chronic unpredictable stress and early life stress. These models produce a variety of PTSD-related behaviors that include associative and non-associative fear- and stress-related responses, hyperarousal, avoidance behaviors, cognitive disturbances, social withdrawal, compulsive behaviors, anhedonia-, anxiety- and depression-related behaviors. Neural regions included fear- and stress-related regions of the prefrontal cortex, hippocampal, amygdala, nucleus accumbens and hypothalamus. PTSD models produced mitochondrial dysfunction that includes dysregulation of oxidative phosphorylation and other metabolic pathways including β-oxidation of fatty acids and the tricarboxylic acid pathway. These models generated neural reactive oxygen species that damage DNA, proteins, and lipids. Trauma models further altered mitochondrial structure and replication and affected neuroinflammatory responses, signal transduction and apoptosis. Antidepressant medications used for the treatment of PTSD reversed stress-induced changes in some PTSD-like behaviors and many elements of brain mitochondrial dysfunction. Future studies can develop PTSD models which are ecologically valid and result in a broader manifestation of PTSD-related behaviors as it is clinically defined. This review highlights mitochondrial mechanisms associated with PTSD-like behaviors that have been produced in an array of consensus PTSD models and identifies putative circuit-based targets for more effective treatment for this debilitating disorder.

Combined Low Dose of Ketamine and Social Isolation: A Possible Model of Induced Chronic Schizophrenia-Like Symptoms in Male Albino Rats

While animal models for schizophrenia, ranging from pharmacological models to lesions and genetic models, are available, they usually mimic only the positive symptoms of this disorder. Identifying a feasible model of chronic schizophrenia would be valuable for studying the possible underlying mechanism and to investigate emerging treatments. Our hypothesis starts from the observation that combining ketamine with isolation could result in long-lasting neuro-psychological deficits and schizophrenia-like features; thus, it could probably be used as the first model of chronic schizophrenia that emphasizes the characteristic of having a multifactorial etiology. By the means of this study, we investigated the effects of ketamine administration combined with isolation in inducing schizophrenia-like symptoms in male albino rats and the brain reactive oxygen species levels. Our results showed that the number of lines crossings in the open field test, the number of open arm entries in the elevated plus maze, and the spontaneous alternations percentage in the Y-maze were significantly lower in the ketamine + isolation group compared to both the control and ketamine + social housing group (p < 0.05). Furthermore, the ketamine + isolation intervention significantly increased the MDA levels and decreased the GPx levels both in the hippocampus and the cortex of the rats. In addition, our premise of creating a model capable of exhibiting both positive and negative symptoms of schizophrenia was also based on adding the aripiprazole treatment to a group of rats. Therefore, we compared the ketamine + social isolation group with the ketamine + social isolation + aripiprazole group in order to attempt to discover if the antipsychotic drug would significantly decrease the potential positive schizophrenia-like symptoms induced by social isolation and ketamine. Given that we obtained significant results, we cautiously presume that this might be an important step in developing our animal model capable of illustrating both positive and negative symptoms of schizophrenia. This study could be a first step towards the creation of a complex animal model capable of exhibiting the multifactorial origin and manifestation of schizophrenia.

Effect of neuropsychiatric medications on mitochondrial function: For better or for worse

Individuals with mitochondrial disease often present with psychopathological comorbidity, and mitochondrial dysfunction has been proposed as the underlying pathobiology in various psychiatric disorders. Several studies have suggested that medications used to treat neuropsychiatric disorders could directly influence mitochondrial function. This review provides a comprehensive overview of the effect of these medications on mitochondrial function. We collected preclinical information on six major groups of antidepressants and other neuropsychiatric medications and found that the majority of these medications either positively influenced mitochondrial function or showed mixed effects. Only amitriptyline, escitalopram, and haloperidol were identified as having exclusively adverse effects on mitochondrial function. In the absence of formal clinical trials, and until such trials are completed, the data from preclinical studies reported and discussed here could inform medication prescribing practices for individuals with psychopathology and impaired mitochondrial function in the underlying pathology.

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.

Chronic fluoxetine or ketamine treatment differentially affects brain energy homeostasis which is not exacerbated in mice with trait suboptimal mitochondrial function

Antidepressants have been shown to influence mitochondrial function directly, and suboptimal mitochondrial function (SMF) has been implicated in complex psychiatric disorders. In the current study, we used a mouse model for trait SMF to test the hypothesis that chronic fluoxetine treatment in mice subjected to chronic stress would negatively impact brain bioenergetics, a response that would be more pronounced in mice with trait SMF. In contrast, we hypothesized that chronic ketamine treatment would positively impact mitochondrial function in both WT and mice with SMF. We used an animal model for trait SMF, the Ndufs4^GT/GT mice, which exhibit 25% lower mitochondrial complex I activity. In addition to antidepressant treatment, mice were subjected to chronic unpredictable stress (CUS). This paradigm is widely used to model complex behaviours expressed in various psychiatric disorders. We assayed several physiological indices as proxies for the impact of chronic stress and antidepressant treatment. Furthermore, we measured brain mitochondrial complex activities using clinically validated assays as well as established metabolic signatures using targeted metabolomics. As hypothesized, we found evidence that chronic fluoxetine treatment negatively impacted brain bioenergetics. This phenotype was, however, not further exacerbated in mice with trait SMF. Ketamine did not have a significant influence on brain mitochondrial function in either genotype. Here we report that trait SMF could be a moderator for an individual's response to antidepressant treatment. Based on these results, we propose that in individuals with SMF and comorbid psychopathology, fluoxetine should be avoided, whereas ketamine could be a safer choice of treatment.

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.

The Therapeutic Effect of Exercise on Anxiety and Bowel Oxidative Stress in the Maternal Separation Animal Model

Introduction:

According to evidence, Early-Life Stress (ELS), mood disorders, and medical comorbidities, i.e. Irritable Bowel Syndrome (IBS), are correlated; however, the direct contribution of ELS to IBS manifestations is less understood. The current study aimed at evaluating the effect of voluntary exercise on the mitochondrial dysfunction of the bowel fibroblasts, following the confirmation of anxiety behavior.

Methods:

In this study, Postnatal Day (PND) rats underwent Maternal Separation (MS), as a valid animal model of the brain-gut axis dysfunction, in the days 2–14; three hours daily. On day 21, the study animals were divided into 4 groups, as follows: control, Running Wheel (RW) exercise, MS, and MS+RW groups. The study groups were housed in separate cages (4 rats per cage) until the onset of intervention. On day 60, the elevated plusmaze was used to assess anxiety-like behaviors; the level of oxidative stress biomarkers, i.e. Reactive Oxygen Species (ROS), Glutathione (GSH), as well as Adenosine Triphosphate (ATP) was measured to determine the gut mitochondrial function.

Results:

Findings revealed that ELS affected the gut energy metabolism in the studied rats; the negative effects of MS on anxiety and the gut mitochondrial dysfunction decreased via RW exercise during adolescence.

Conclusion:

Overall, anxiety behaviors and ROS production, leading to increased GSH and ATP levels, improved after RW exercise; this significantly impacts the function of colon secretory mitochondria. According to the positive effects of RW exercise on mitochondrial dysfunction in an ELS animal model, a potential relationship was found between the brain and gut in the study rats.

Mitochondria: A Connecting Link in the Major Depressive Disorder Jigsaw

Background

Depression is a widespread phenomenon with varying degrees of pathology in different patients. Various hypotheses have been proposed for the cause and continuance of depression. Some of these include, but not limited to, the monoamine hypothesis, the neuroendocrine hypothesis, and the more recent epigenetic and inflammatory hypotheses.

Objective

In this article, we review all the above hypotheses with a focus on the role of mitochondria as the connecting link. Oxidative stress, respiratory activity, mitochondrial dynamics and metabolism are some of the mitochondria-dependent factors which are affected during depression. We also propose exogenous ATP as a contributing factor to depression.

Result

Literature review shows that pro-inflammatory markers are elevated in depressive individuals. The cause for elevated levels of cytokines in depression is not completely understood. We propose exogenous ATP activates purinergic receptors which in turn increase the levels of various pro-inflammatory factors in the pathophysiology of depression.

Conclusion

Mitochondria are integral to the function of neurons and undergo dysfunction in major depressive disorder patients. This dysfunction is reflected in all the various hypotheses that have been proposed for depression. Among the newer targets identified, which also involve mitochondria, includes the role of exogenous ATP. The diversity of purinergic receptors, and their differential expression among various individuals in the population, due to genetic and environmental (prenatal) influences, may influence the susceptibility and severity of depression. Identifying specific receptors involved and using patient-specific purinergic receptor antagonist may be an appropriate therapeutic course in the future.

Psychotropic and neurological medication effects on mitochondrial complex I and IV in rodent models

Mitochondrial complex I (NADH-dehydrogenase) and complex IV (cytochrome-c-oxidase) are reported to be affected by drugs used to treat psychiatric or neurodegenerative diseases, including antidepressants, antipsychotics, anxiolytics, mood stabilizers, stimulants, antidementia, and antiparkinsonian drugs. We conducted meta-analyses examining the effects of each drug category on complex I and IV. The electronic databases Pubmed, EMBASE, CENTRAL, and Google Scholar were searched for studies published between 1970 and 2018. Of 3105 screened studies, 68 articles covering 53 drugs were included in the meta-analyses. All studies assessed complex I and IV in rodent brain at the level of enzyme activity. Results revealed that selected antidepressants increase or decrease complex I and IV, antipsychotics and stimulants decrease complex I but increase complex IV, whereas anxiolytics, mood stabilizers, antidementia, and antiparkinsonian drugs preserve or even enhance both complex I and IV. Potential contributions to the drug effects were found to be related to the drugs' neurotransmitter receptor profiles with adrenergic (α1B), dopaminergic (D1/2), glutaminergic (NMDA1,3), histaminergic (H1), muscarinic (M1,3), opioid (OP1-3), serotonergic (5-HT_2A, 5-HT_2C, 5-HT_3A) and sigma (σ1) receptors having the greatest effects. The findings are discussed in relation to pharmacological mechanisms of action that might have relevance for clinical and research applications.

The cerebellum under stress

Stress-related psychiatric conditions are one of the main causes of disability in developed countries. They account for a large portion of resource investment in stress-related disorders, become chronic, and remain difficult to treat. Research on the neurobehavioral effects of stress reveals how changes in certain brain areas, mediated by a number of neurochemical messengers, markedly alter behavior. The cerebellum is connected with stress-related brain areas and expresses the machinery required to process stress-related neurochemical mediators. Surprisingly, it is not regarded as a substrate of stress-related behavioral alterations, despite numerous studies that show cerebellar responsivity to stress. Therefore, this review compiles those studies and proposes a hypothesis for cerebellar function in stressful conditions, relating it to stress-induced psychopathologies. It aims to provide a clearer picture of stress-related neural circuitry and stimulate cerebellum-stress research. Consequently, it might contribute to the development of improved treatment strategies for stress-related disorders.

Mitochondrial Dysfunction in Depression

Abstract: Background

Depression is the most debilitating neuropsychiatric disorder with significant impact on socio-occupational and well being of individual. The exact pathophysiology of depression is still enigmatic though various theories have been put forwarded. There are evidences showing that mitochondrial dysfunction in various brain regions is associated with depression. Recent findings have sparked renewed appreciation for the role of mitochondria in many intracellular processes coupled to synaptic plasticity and cellular resilience. New insights in depression pathophysiology are revolving around the impairment of neuroplasticity. Mitochondria have potential role in ATP production, intracellular Ca²⁺ signalling to establish membrane stability, reactive oxygen species (ROS) balance and to execute the complex processes of neurotransmission and plasticity. So understanding the various concepts of mitochondrial dysfunction in pathogenesis of depression indubitably helps to generate novel and more targeted therapeutic approaches for depression treatment.

Objective

The review was aimed to give a comprehensive insight on role of mitochondrial dysfunction in depression.

Result

Targeting mitochondrial dysfunction and enhancing the mitochondrial functions might act as potential target for the treatment of depression.

Conclusion

Literature cited in this review highly supports the role of mitochondrial dysfunction in depression. As impairment in the mitochondrial functions lead to the generation of various insults that exaggerate the pathogenesis of depression. So, it is useful to study mitochondrial dysfunction in relation to mood disorders, synaptic plasticity, neurogenesis and enhancing the functions of mitochondria might show promiscuous effects in the treatment of depressed patients.

Chronic treatment with coenzyme Q10 reverses restraint stress-induced anhedonia and enhances brain mitochondrial respiratory chain and creatine kinase activities in rats

Several recent studies suggest a close link between mitochondrial dysfunction and depression. Coenzyme Q10 (CoQ10) is a mobile electron carrier in the mitochondrial respiratory chain (MRC) with antioxidant and potential neuroprotective activities. This study investigated the effect of chronic administration of CoQ10 (50, 100, and 200 mg/kg/day, intraperitoneally, for 4 weeks) on anhedonia and on the activities of MRC complexes and creatine kinase in the frontal cortex and hippocampus of Wistar rats subjected to chronic restraint stress (CRS, 6 h × 28 days). Exposure to CRS-induced anhedonic-like behavior (decreased sucrose preference), reduced body weight gain and food intake, increased adrenal gland weight, and altered the activity of the MRC complexes in the brain areas tested. CoQ10 dose-dependently antagonized CRS-induced depressive behavior by increasing sucrose preference (reversal of anhedonia), body weight, and food intake and reducing adrenal gland weight. CoQ10 also enhanced the activities of MRC complexes (I-IV) and creatine kinase in the frontal cortex and hippocampus. Thus, the reversal of CRS-induced anhedonia may be partially mediated by amelioration of brain mitochondrial function. The findings also support the hypothesis that brain energy impairment is involved in the pathophysiology of depression and enhancing mitochondrial function could provide an opportunity for development of a potentially more efficient drug therapy for depression.

Enriched Flavonoid Fraction from Cecropia pachystachya Trécul Leaves Exerts Antidepressant-like Behavior and Protects Brain Against Oxidative Stress in Rats Subjected to Chronic Mild Stress

The purpose of this study was to assess the effect of an enriched C-glycosyl flavonoids fraction (EFF-Cp) from Cecropia Pachystachya leaves on behavior, mitochondrial chain function, and oxidative balance in the brain of rats subjected to chronic mild stress. Male Wistar rats were divided into experimental groups (saline/no stress, saline/stress, EFF-Cp/no stress, and EFF-Cp/stress). ECM groups were submitted to stress for 40 days. On the 35th ECM day, EFF-Cp (50 mg/kg) or saline was administrated and the treatments lasted until the 42nd day. On the 41st and 42nd days, the animals were submitted to the splash test and the forced swim test. After these behavioral tests, the enzymatic activity of mitochondrial chain complexes and oxidative stress were analyzed. EFF-Cp reversed the depressive-like behavior induced by ECM. It also reversed the increase in thiobarbituric acid reactive species, myeloperoxidase activity, and nitrite/nitrate concentrations in some brain regions. The reduced activities of the antioxidants superoxide dismutase and catalase in some brain regions were also reversed by EFF-Cp. The most pronounced effect of EFF-Cp on mitochondrial complexes was an increase in complex IV activity in all studied regions. Thus, it is can be concluded that EFF-Cp exerts an antidepressant-like effect and that oxidative balance may be an important physiological process underlying these effects.

Maternal deprivation disrupts mitochondrial energy homeostasis in the brain of rats subjected to ketamine-induced schizophrenia

Maternal deprivation (MD) appears to be one of the environmental factors involved in the pathophysiology of schizophrenia. A widely used animal model of the schizophrenia involves the administration of ketamine, a dissociative anesthetic, NMDA receptors noncompetitive antagonist, that induce symptoms such as schizophrenia. To clarify the molecular mechanism of schizophrenia induced by MD, we investigated alterations in energetic metabolism, oxidative stress and neurotrophic factor levels in the brain of rats following MD and/or a single administration of ketamine during adulthood. Male Wistar rats were subjected to MD for 10 days. Additionally, these animals received acute ketamine (5, 15 or 25 mg/kg by intraperitoneal route, i.p.) during adulthood, and 30 min later, they were killed and the prefrontal cortex (PFC), the hippocampus and the striatum were removed for molecular analyses. Ketamine 25 mg/kg and/or MD and Ketamine 15 and 5 mg/kg with MD decreased the creatine kinase (CK) activity in the hippocampus. The enzyme activity of succinate dehydrogenase (SDH) in the Krebs cycle had increased in the striatum following the administration of ketamine 25 mg/kg, MD per se or MD plus ketamine 5 and 15 mg/kg. MD per se or MD combined with ketamine in different doses increased the activity of mitochondrial complexes. The PFC of animals subjected to MD and administered with ketamine 5 mg/kg exhibited increased protein carbonyl content. In the hippocampus, ketamine 15 mg/kg, ketamine 25 mg/kg and MD each increased the carbonyl content. In the striatum, the TBARS levels were increased by the administration of ketamine 25 mg/kg. Finally, in the hippocampus, MD alone or in combination with ketamine reduced the Nerve Growth Factor (NGF) levels; however, the Brain-derived Neurotrophic Factor (BDNF) levels were unaltered. In the present study, we suggest that MD increased the risk of psychotic symptoms in adulthood, altering different parameters of energy and oxidative stress. Our results suggest that adverse experiences occurring early in life may sensitize specific neurocircuits to subsequent stressors, inducing vulnerability, and may help us understand the pathophysiological mechanisms involved in this disorder.

Minocycline protects against oxidative damage and alters energy metabolism parameters in the brain of rats subjected to chronic mild stress

Studies have been suggested that minocycline can be a potential new agent for the treatment of depression. In addition, both oxidative stress and energy metabolism present an important role in pathophysiology of depression. So, the present study was aimed to evaluate the effects of minocycline on stress oxidative parameters and energy metabolism in the brain of adult rats submitted to the chronic mild stress protocol (CMS). After CMS Wistar, both stressed animals as controls received twice ICV injection of minocycline (160 μg) or vehicle. The oxidative stress and energy metabolism parameters were assessed in the prefrontal cortex (PF), hippocampus (HIP), amygdala (AMY) and nucleus accumbens (Nac). Our findings showed that stress induced an increase on protein carbonyl in the PF, AMY and NAc, and mynocicline injection reversed this alteration. The TBARS was increased by stress in the PF, HIP and NAc, however, minocycline reversed the alteration in the PF and HIP. The Complex I was incrased in AMY by stress, and minocycline reversed this effect, however reduced Complex I activity in the NAc; Complex II reduced in PF and AMY by stress or minocycline; the Complex II-III increased in the HIP in stress plus minocycline treatment and in the NAc with minocycline; in the PF and HIP there were a reduced in Complex IV with stress and minocycline. The creatine kinase was reduced in AMY and NAc with stress and minocycline. In conclusion, minocycline presented neuroprotector effects by reducing oxidative damage and regulating energy metabolism in specific brain areas.

Sex differences in the rapid and the sustained antidepressant-like effects of ketamine in stress-naïve and "depressed" mice exposed to chronic mild stress

During the past decade, one of the most striking discoveries in the treatment of major depression was the clinical finding that a single infusion of a sub-anesthetic dose of the N-methyl-d-aspartate receptor antagonist ketamine produces a rapid (i.e. within a few hours) and long-lasting (i.e. up to two weeks) antidepressant effect in both treatment-resistant depressed patients and in animal models of depression. Notably, converging clinical and preclinical evidence support that responsiveness to antidepressant drugs is sex-differentiated. Strikingly, research regarding the antidepressant-like effects of ketamine has focused almost exclusively on the male sex. Herein we report that female C57BL/6J stress-naïve mice are more sensitive to the rapid and the sustained antidepressant-like effects of ketamine in the forced swim test (FST). In particular, female mice responded to lower doses of ketamine (i.e. 3mg/kg at 30 min and 5mg/kg at 24h post-injection), doses that were not effective in their male counterparts. Moreover, tissue levels of the excitatory amino acids glutamate and aspartate, as well as serotonergic activity, were affected in a sex-dependent manner in the prefrontal cortex and the hippocampus, at the same time-points. Most importantly, a single injection of ketamine (10mg/kg) induced sex-dependent behavioral effects in mice subjected to the chronic mild stress (CMS) model of depression. Intriguingly, female mice were more reactive to the earlier effects of ketamine, as assessed in the open field and the FST (at 30 min and 24h post-treatment, respectively) but the antidepressant potential of the drug proved to be longer lasting in males, as assessed in the splash test and the FST (days 5 and 7 post-treatment, respectively). Taken together, present data revealed that ketamine treatment induces sex-dependent rapid and sustained neurochemical and behavioral antidepressant-like effects in stress-naïve and CMS-exposed C57BL/6J mice.

Ketamine reverses stress-induced depression-like behavior and increased GABA levels in the anterior cingulate: an 11.7 T 1H-MRS study in rats

Gamma-aminobutyric acid (GABA) is the major inhibitory amino acid neurotransmitter in the brain and is primarily responsible for modulating excitatory tone. Clinical neuroimaging studies show decreased GABA levels in the anterior cingulate of patients with mood disorders, including major depressive disorder. Chronic unpredictable stress (CUS) is an animal model thought to mimic the stressful events that may precipitate clinical depression in humans. In this study male Sprague-Dawley rats were subjected to a modified CUS paradigm that used a random pattern of unpredictable stressors twice daily for 10 days to explore the early developmental stages of depression-like endophenotypes. Control rats were handled daily for 10 days. Some rats from each treatment group received an injection of ketamine (40 mg/kg) after the final stressor. One day following the final stressor rats were tested for behavioral effects in the forced swim test and then euthanized to collect trunk blood and anterior cingulate brain samples. GABA levels were measured in anterior cingulate samples ex vivo using proton magnetic resonance spectroscopy ((1)H-MRS) at 11.7 T. Animals subjected to CUS had lower body weights, higher levels of blood corticosterone, and increased immobility in the forced swim test; all of which suggest that the stress paradigm induced a depression-like phenotype. GABA levels in the anterior cingulate were significantly increased in the stressed animals compared to controls. Administration of ketamine on the last day of treatment blunted the depression-like behavior and increased GABA levels in the anterior cingulate following CUS. These data indicate that stress disrupts GABAergic signaling, which may over time lead to symptoms of depression and ultimately lower basal levels of cortical (1)H-MRS GABA that are seen in humans with depression. Furthermore, the data suggests that ketamine modulates cortical GABA levels as a mechanism of its antidepressant activity.

A review of MR spectroscopy studies of pediatric bipolar disorder

Pediatric bipolar disorder is a severe mental illness whose pathophysiology is poorly understood and for which there is an urgent need for improved diagnosis and treatment. MR spectroscopy is a neuroimaging method capable of in vivo measurement of neurochemicals relevant to bipolar disorder neurobiology. MR spectroscopy studies of adult bipolar disorder provide consistent evidence for alterations in the glutamate system and mitochondrial function. In bipolar disorder, these 2 phenomena may be linked because 85% of glucose in the brain is consumed by glutamatergic neurotransmission and the conversion of glutamate to glutamine. The purpose of this article is to review the MR spectroscopic imaging literature in pediatric bipolar disorder, at-risk samples, and severe mood dysregulation, with a focus on the published findings that are relevant to glutamatergic and mitochondrial functioning. Potential directions for future MR spectroscopy studies of the glutamate system and mitochondrial dysfunction in pediatric bipolar disorder are discussed.

Revealing the cerebral regions and networks mediating vulnerability to depression: oxidative metabolism mapping of rat brain

The large variety of available animal models has revealed much on the neurobiology of depression, but each model appears as specific to a significant extent, and distinction between stress response, pathogenesis of depression and underlying vulnerability is difficult to make. Evidence from epidemiological studies suggests that depression occurs in biologically predisposed subjects under impact of adverse life events. We applied the diathesis-stress concept to reveal brain regions and functional networks that mediate vulnerability to depression and response to chronic stress by collapsing data on cerebral long term neuronal activity as measured by cytochrome c oxidase histochemistry in distinct animal models. Rats were rendered vulnerable to depression either by partial serotonergic lesion or by maternal deprivation, or selected for a vulnerable phenotype (low positive affect, low novelty-related activity or high hedonic response). Environmental adversity was brought about by applying chronic variable stress or chronic social defeat. Several brain regions, most significantly median raphe, habenula, retrosplenial cortex and reticular thalamus, were universally implicated in long-term metabolic stress response, vulnerability to depression, or both. Vulnerability was associated with higher oxidative metabolism levels as compared to resilience to chronic stress. Chronic stress, in contrast, had three distinct patterns of effect on oxidative metabolism in vulnerable vs. resilient animals. In general, associations between regional activities in several brain circuits were strongest in vulnerable animals, and chronic stress disrupted this interrelatedness. These findings highlight networks that underlie resilience to stress, and the distinct response to stress that occurs in vulnerable subjects.

Antidepressant effects of ketamine: mechanisms underlying fast-acting novel antidepressants

Newer antidepressants are needed for the many individuals with major depressive disorder (MDD) that do not respond adequately to treatment and because of a delay of weeks before the emergence of therapeutic effects. Recent evidence from clinical trials shows that the NMDA antagonist ketamine is a revolutionary novel antidepressant because it acts rapidly and is effective for treatment-resistant patients. A single infusion of ketamine alleviates depressive symptoms in treatment-resistant depressed patients within hours and these effects may be sustained for up to 2 weeks. Although the discovery of ketamine's effects has reshaped drug discovery for antidepressants, the psychotomimetic properties of this compound limit the use of this therapy to the most severely ill patients. In order to develop additional antidepressants like ketamine, adequate preclinical behavioral screening paradigms for fast-acting antidepressants need to be established and used to identify the underlying neural mechanisms. This review examines the preclinical literature attempting to model the antidepressant-like effects of ketamine. Acute administration of ketamine has produced effects in behavioral screens for antidepressants like the forced swim test, novelty suppression of feeding and in rodent models for depression. Protracted behavioral effects of ketamine have been reported to appear after a single treatment that last for days. This temporal pattern is similar to its clinical effects and may serve as a new animal paradigm for rapid antidepressant effects in humans. In addition, protracted changes in molecules mediating synaptic plasticity have been implicated in mediating the antidepressant-like behavioral effects of ketamine. Current preclinical studies are examining compounds with more specific pharmacological effects at glutamate receptors and synapses in order to develop additional rapidly acting antidepressants without the hallucinogenic side effects or abuse potential of ketamine.

Synaptic plasticity in depression: molecular, cellular and functional correlates

Synaptic plasticity confers environmental adaptability through modification of the connectivity between neurons and neuronal circuits. This is achieved through changes to synapse-associated signaling systems and supported by complementary changes to cellular morphology and metabolism within the tripartite synapse. Mounting evidence suggests region-specific changes to synaptic form and function occur as a result of chronic stress and in depression. Within subregions of the prefrontal cortex (PFC) and hippocampus structural and synapse-related findings seem consistent with a deficit in long-term potentiation (LTP) and facilitation of long-term depression (LTD), particularly at excitatory pyramidal synapses. Other brain regions are less well-studied; however the amygdala may feature a somewhat opposite synaptic pathology including reduced inhibitory tone. Changes to synaptic plasticity in stress and depression may correlate those to several signal transduction pathways (e.g. NOS-NO, cAMP-PKA, Ras-ERK, PI3K-Akt, GSK-3, mTOR and CREB) and upstream receptors (e.g. NMDAR, TrkB and p75NTR). Deficits in synaptic plasticity may further correlate disrupted brain redox and bioenergetics. Finally, at a functional level region-specific changes to synaptic plasticity in depression may relate to maladapted neurocircuitry and parallel reduced cognitive control over negative emotion.

Synergist effects of n-acetylcysteine and deferoxamine treatment on behavioral and oxidative parameters induced by chronic mild stress in rats

A growing body of evidence has pointed to a relationship between oxidative stress and depression. Thus, the present study was aimed at evaluating the effects of the antioxidants n-acetylcysteine (NAC), deferoxamine (DFX) or their combination on sweet food consumption and oxidative stress parameters in rats submitted to 40days of exposure to chronic mild stress (CMS). Our results showed that in stressed rats treated with saline, there was a decrease in sweet food intake and treatment with NAC or NAC in combination with DFX reversed this effect. Treatment with NAC and DFX decreased the oxidative damage, which include superoxide and TBARS production in submitochondrial particles, and also thiobarbituric acid reactive substances (TBARS) levels and carbonyl proteins in the prefrontal cortex, amygdala and hippocampus. Treatment with NAC and DFX also increased the activity of the antioxidant enzymes, superoxide dismutase and catalase in the same brain areas. Even so, a combined treatment with NAC and DFX produced a stronger increase of antioxidant activities in the prefrontal cortex, amygdala and hippocampus. The results described here indicate that co-administration may induce a more pronounced antidepressant activity than each treatment alone. In conclusion, these results suggests that treatment with NAC or DFX alone or in combination on oxidative stress parameters could have positive effects against neuronal damage caused by oxidative stress in major depressive disorders.

In vitro inhibition of mitochondrial respiratory rate by antidepressants

Mitochondria represent a possible drug target with unexplored therapeutic and toxicological potential. The possibility was suggested that antidepressants, mood stabilizers and other drugs may show some therapeutic and/or toxic effects through their action on mitochondrial functions. There are no sufficient data about the effect of these drugs on mitochondrial respiration in the brain. We investigated the in vitro effects of amitriptyline, fluoxetine, tianeptine, ketamine, lithium, valproate, olanzapine, chlorpromazine and propranolol on mitochondrial respiration in crude mitochondrial fractions of pig brains. Respiration was energized using substrates of complex I or complex II and dose dependent drug-induced changes in mitochondrial respiratory rate were measured by high-resolution respirometry. Antidepressants, but not mood stabilizers, ketamine and propranolol were found to inhibit mitochondrial respiratory rate. The effective dose of antidepressants reaching half the maximal respiratory rate was in the range of 0.07-0.46 mmol/L. Partial inhibition was found for all inhibitors. Differences between individual drugs with similar physicochemical properties indicate selectivity of drug-induced changes in mitochondrial respiratory rate. Our findings suggest that mood stabilizers do not interfere with brain mitochondrial respiration, whereas direct mitochondrial targeting is involved in mechanisms of action of pharmacologically different antidepressants.

Corticosterone reduces brain mitochondrial function and expression of mitofusin, BDNF in depression-like rodents regardless of exercise preconditioning

Both chronic mild stress and an injection of corticosterone induce depression-like states in rodents. To further link mitochondrial dysfunction to the pathophysiology of major depression, here we describe two rat models of a depressive-like state induced by chronic unpredictable mild stress (CUMS) or corticosterone treatment (CORT). It is also a model that allows the simultaneous study of effects of exercise preconditioning on behavioral, electrophysiological, biochemical and molecular markers in the same animal. Exercise preconditioning ahead of CUMS and CORT treatment prevents many behavioral abnormalities resulted from CUMS. The changes in mitochondrial activity in brain and reduced expressions of superoxide dismutase (SOD1, SOD2), mitofusin (Mfn1, Mfn2) as well as brain-derived neurotrophic factor (BDNF) suggest that both CORT and CUMS may impair mitochondrial function and/or expressions of mitofusion and antioxidant enzymes that, in turn, may increase oxidative stress and reduce energy production in brain with depression-like behaviors. These findings suggest an underlying mechanism by which CORT, as well as CUMS, induces brain mitochondrial dysfunction that is associated with depressive-like states. Remarkably, physical exercise is identified as a helpful and preventive measure to promote mitochondrial function and expressions of mitofusin, BDNF and antioxidant enzymes in brain, so as to protect brain energy metabolism against CUMS, rather than the compound of corticosterone.

Olanzapine plus fluoxetine treatment alters mitochondrial respiratory chain activity in the rat brain

Agostinho FR, Réus GZ, Stringari RB, Ribeiro KF, Ferreira GK, Jeremias IC, Scaini G, Rezin GT, Streck EL, Quevedo J. Olanzapine plus fluoxetine treatment alters mitochondrial respiratory chain activity in the rat brain.

Background:Evidence is emerging for the role of dysfunctional mitochondria in pathophysiology and treatment of mood disorders. In this study, we evaluated the effects of acute and chronic administration of fluoxetine (FLX), olanzapine (OLZ) and the combination of FLX/OLZ on mitochondrial respiratory chain activity in the rat brain.

Methods:For acute treatment, Wistar rats received one single injection of OLZ (3 or 6 mg/kg) and/or FLX (12 or 25 mg/kg) and for chronic treatment, rats received daily injections of OLZ (3 or 6 mg/kg) and/or FLX (12 or 25 mg/kg) for 28 days and we evaluated the activity of mitochondrial respiratory chain complexes I, II, II–III and IV in prefrontal cortex, hippocampus and striatum.

Results:Our results showed that both acute and chronic treatments with FLX and OLZ alone or in combination altered respiratory chain complexes activity in the rat brain, but in combination we observed larger alterations.

Conclusions:Finally, these findings further support the hypothesis that metabolism energy could be involved in the treatment with antipsychotics and antidepressants in combination to mood disorders.

Metabonomic studies of schizophrenia and psychotropic medications: focus on alterations in CNS energy homeostasis

Schizophrenia is a severe neuropsychiatric disorder with a poorly understood etiology and progression. We and other research groups have found that energy metabolic pathways in the CNS are perturbed in many subjects with this disorder. Antipsychotic drugs that generally target neurotransmission are currently used for clinical management of the disorder, although these can also have marked effects on energy metabolism in the CNS and periphery. Recent proteomic and metabonomic studies have shown that molecular pathways associated with brain energy metabolism are altered in both the disorder and by antipsychotic treatments. This review focuses on discussion of these molecular alterations. Increased knowledge in this area could facilitate biomarker identification and drug discovery based on improving brain energy metabolism in this debilitating disorder.

Chronic variable stress alters inflammatory and cholinergic parameters in hippocampus of rats

In the present study we investigated the effect of chronic variable stress (CVS) on some parameters of the immune system, including levels of cytokines [interleukin 1β (IL-1 β), interleukin 6 (IL-6), tumor necrosis factor α (TNF- α)] and chemokine CCL2 (MCP-1) in the hippocampus of rats. Acetylcholinesterase activity was also evaluated. Sixty-day old Wistar rats were submitted to different mild stressors for 40 days. After the last stress section, the cytokines and MCP-1 were determined by immunoassay and acetylcholinesterase activity by colorimetric method. Results showed that chronic stress significantly increased the levels of IL-1β, IL-6 and TNF-α, but did not alter the levels of MCP-1. In addition, acetylcholinesterase activity was increased in the hippocampus of rats subjected to CVS. These findings suggest that inflammation and cholinergic dysfunction may be, at least in part, important contributors to the neurological dysfunction observed in some depressed patients.

Effect of chronic administration of ketamine on the mitochondrial respiratory chain activity caused by chronic mild stress

Rezin GT, Gonçalves CL, Daufenbach JF, Carvalho-Silva M, Borges LS, Vieira JS, Hermani FV, Comim CM, Quevedo J, Streck EL. Effect of chronic administration of ketamine on the mitochondrial respiratory chain activity caused by chronic mild stress.

OBJECTIVE

Recently, we reported that mitochondrial respiratory chain complexes I, III and IV were inhibited in the cerebral cortex and cerebellum of rats submitted to chronic mild stress (CMS) and that acute ketamine administration reversed this effect. Therefore, we investigated whether the inhibition of these enzymes may be reversed by chronic administration of ketamine.

METHODS

Adult male Wistar rats were submitted to CMS and chronically treated with ketamine. After 40 days of CMS, consumption of sweet food, adrenal gland weight, body weight and enzymatic activity of the complexes were measured.

RESULTS

We verified that CMS decreased the intake of sweet food, increased the adrenal gland weight and the control group gained weight after 40 days but the stressed group did not; ketamine administration reversed these effects. We also verified that chronic administration of ketamine reversed the inhibition of complexes I, III and IV in cerebral cortex. However, in cerebellum, only complex IV inhibition was reversed. The chronic ketamine administration partially reverses the inhibition caused by CMS.

CONCLUSION

We hypothesise that CMS inhibits complexes I, III and IV activities and that chronic administration of ketamine administration partially reverses such an effect. Therefore, it seems reasonable to propose that ketamine administration might be a useful therapy for patients affected by major depression.

A rodent model of schizophrenia reveals increase in creatine kinase activity with associated behavior changes

Schizophrenia is a debilitating mental disorder characterized by positive (delusions, hallucinations, disorganized speech) and negative (affective flattering, avolition and social withdrawal) symptoms as well as cognitive deficits. The frequency, severity and topography characterize the disorder as heterogeneous, the pathophysiology of schizophrenia is poorly understood. Sub-anesthetic doses of ketamine produce hyperactivity, stereotypy and abnormal social interaction and it is used as a model of schizophrenia. In this study, we induced an animal model by acute sub-anesthetic doses of ketamine and tested different behavioral parameters. We also evaluated the activity of creatine kinase (CK) in brain of rats treated with ketamine. Our results demonstrated that administration of 10, 25 and 50 mg/kg of ketamine induced an increase of covered distance in habituated and non-habituated rats to the behavioral apparatus. Ketamine administration induced significant social deficits and stereotypic behavioral in all doses tested. Finally we evaluated the effect of different doses of ketamine on creatinine kinase (CK) activity and we observed that CK activity is increased inspecific regions of the brain. Our study suggests that our animal model may be used as a model of schizophrenia and that cerebral energy metabolism might be altered in the brain of schizophrenic patients, probably leading to alterations that might be involved in the pathogenesis of schizophrenia.

Mitochondrial respiratory chain in the colonic mucosal of patients with ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory disease of the large bowel. Its pathogenesis remains unclear, but it appears to result from a deregulated immune response, with infiltration of leukocytes into the mucosal interstitium. Several studies link oxidative stress and mitochondrial dysfunction to the pathogenesis of UC. Thus, the aim of this study was to evaluate the activities of mitochondrial respiratory chain complexes in the colonic mucosal of UC patients. Colonic biopsies were obtained from UC patients (n = 13). The control specimens were taken from patients without any history of inflammatory bowel disease (n = 8). Colon mucosal was removed by colonoscopy and homogenized. Mitochondrial respiratory chain complexes activities were then measured. Our results showed that the activity of complex I was not altered in UC patients, when compared to the control group. On the other hand, complexes II, III, and IV were decreased around 50-60% in the colonic mucosal of UC patients. Based on the present findings, we hypothesize that mitochondrial dysfunction may play a role in pathogenesis of UC.