Search

Ample evidence implicate mitochondria in early brain development. However, to the best of our knowledge, there is only circumstantial data for mitochondria involvement in late brain development occurring through adolescence, a critical period in the pathogenesis of various psychiatric disorders, specifically schizophrenia. In schizophrenia, neurodevelopmental abnormalities and mitochondrial dysfunction has been repeatedly reported. Here we show a causal link between mitochondrial transplantation in adolescence and brain functioning in adulthood. We show that transplantation of allogenic healthy mitochondria into the medial prefrontal cortex of adolescent rats was beneficial in a rat model of schizophrenia, while detrimental in healthy control rats. Specifically, disparate initial changes in mitochondrial function and inflammatory response were associated with opposite long-lasting changes in proteome, neurotransmitter turnover, neuronal sprouting and behavior in adulthood. A similar inverse shift in mitochondrial function was also observed in human lymphoblastoid cells deived from schizophrenia patients and healthy subjects due to the interference of the transplanted mitochondria with their intrinsic mitochondrial state. This study provides fundamental insights into the essential role of adolescent mitochondrial homeostasis in the development of normal functioning adult brain. In addition, it supports a therapeutic potential for mitochondria manipulation in adolescence in disorders with neurodevelopmental and bioenergetic deficits, such as schizophrenia, yet emphasizes the need to monitor individuals’ state including their mitochondrial function and immune response, prior to intervention.

Parkinson's disease (PD) and schizophrenia (SZ) are two CNS disorders in which dysfunctions in the dopaminergic system and mitochondria are major pathologies. The symptomology of both, PD a neurodegenerative disorder and SZ a neurodevelopmental disorder, is completely different. However, the pharmacological treatment of each of the diseases can cause a shift of symptoms into those characteristic of the other disease. In this review, I describe a pathological interaction between dopamine and mitochondria in both disorders, which due to differences in the extent of oxidative stress leads either to cell death and tissue degeneration as in PD substantia nigra pars compacta or to distorted neuronal activity, imbalanced neuronal circuitry and abnormal behavior and cognition in SZ. This review is in the honor of Moussa Youdim who introduced me to the secrets of research work. His enthusiasm, curiosity and novelty-seeking inspired me throughout my career. Thank you Moussa.

Mitochondria, similar to living cells and organelles, have a negative membrane potential, which ranges between (-108) and (150) mV as compared to (-70) and (-90) mV of the plasma membrane. Therefore, permeable lipophilic cations tend to accumulate in the mitochondria. Those cations which exhibit fluorescence activity after accumulation into energized systems are widely used to decipher changes in membrane potential by imaging techniques. Here we describe the use of two different dyes for labeling mitochondrial membrane potential (Δψ

Mitochondria, similar to living cells and organelles, have a negative membrane potential, which ranges between (-108) and (150) mV as compared to (-70) and (-90) mV of the plasma membrane. Therefore, permeable lipophilic cations tend to accumulate in the mitochondria. Those cations which exhibit fluorescence activity after accumulation into energized systems are widely used to decipher changes in membrane potential by imaging techniques. Here we describe the use of two different dyes for labeling mitochondrial membrane potential (Δψm) in live cells. One is the lipophilic cation 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazol-carbocyanine iodide (JC-1), which alters reversibly its color from green (J-monomer, at its low concentration in the cytosol) to red (J-aggregates, at its high concentration in active mitochondria) with increasing mitochondrial membrane potential (Δψm). The other is MitoTracker® Orange, a mitochondrion-selective probe which passively diffuses across the plasma membrane and accumulates in active mitochondria depending on their Δψm. We show that in addition to changes in Δψm, these specific dyes can be used to follow alterations in mitochondrial distribution and mitochondrial network connectivity. We suggest that JC-1 is a preferable probe to compare between different cell types and cell state, as a red to green ratio of fluorescence intensities is used for analysis. This ratio depends only on the mitochondrial membrane potential and not on other cellular and/or mitochondrial-dependent or independent factors that may alter, for example, due to treatment or disease state. However, in cells labeled either with green or red fluorescence protein, JC-1 cannot be used. Therefore, other dyes are preferable. We demonstrate various applications of JC-1 and MitoTracker Orange staining to study mitochondrial abnormalities in different cell types derived from schizophrenia patients and healthy subjects.

Heme plays a role in major cellular processes such as signal transduction, protein synthesis, and complex assembly and regulation of transcription and translation. As such, it is essential for brain metabolism, oxygen sensing, and neuronal survival. Its synthesis is composed of eight distinct steps; the first and last three steps take place in the mitochondria. Accumulating evidence point at mitochondrial dysfunction and altered heme metabolism in neuropsychiatric disorders. Here, we will review the growing number of experimental data demonstrating deficits in heme, mitochondria, and specifically the first complex (Co-I) of the electron transport chain in three neuropsychiatric disorders—Alzheimer’s disease (AD), Parkinson’s disease (PD), and schizophrenia (SZ). Furthermore, we will provide evidence for an association between mitochondrial Co-I dysfunction and heme metabolism and suggest their potential to become additional therapeutic targets that will improve the efficiency of the current treatments.

Chemotherapy-induced cognitive changes is a major burden on a substantial number of cancer survivors. The mechanism of this sequel is unknown. In this study, we followed long-term effects of early in life mithramycin (MTR) treatment on behaviour and on the normal course of alterations of gene expression in brain. Between post-natal days (PND) 7 and 10, male rats were divided into 2 groups, 1 receiving MTR (0.1 mg/kg s.c. per day) and the other receiving saline. At PND11, frontal cortex tissue samples were dissected from 4 rats from each group. At PND 65 the remaining rats underwent behavioural tests after which all the rats were decapitated and their prefrontal cortex incised. Rats treated transiently with MTR early in life, showed impairments in spatial working memory and anxious-like behaviour in adulthood. The immediate molecular effect of MTR was expressed in a limited number of altered genes of different unconnected trajectories, which were simultaneously distorted by the drug. In contrast, 3 months later we observed a change in the expression of more than 1000 genes that converged into specific cellular processes. Time-dependent gene expression dynamics of several genes was significantly different between treated and untreated rats. The differences in the total number of altered genes and in gene expression trends, immediately and long after MTR treatment cessation, suggest the evolution of a new cellular homeostatic set point, which can lead to behavioural abnormalities following chemotherapy treatment.

The neurobiology of psychiatric disorders is still unclear, although changes in multiple neuronal systems, specifically the dopaminergic, glutamatergic, and gamma-aminobutyric acidergic systems as well as abnormalities in synaptic plasticity and neural connectivity, are currently suggested to underlie their pathophysiology. A growing body of evidence suggests multifaceted mitochondrial dysfunction in mental disorders, which is in line with their role in neuronal activity, growth, development, and plasticity. In this review, we describe the main endeavors toward development of treatments that will enhance mitochondrial function and their transition into clinical use in congenital mitochondrial diseases and chronic disorders such as types 1 and 2 diabetes, cardiovascular disorders, and cancer. In addition, we discuss the relevance of mitochondrial targeted treatments to mental disorders and their potential to become a novel therapeutic strategy that will improve the efficiency of the current treatments.

Mitochondria are key players in various essential cellular processes beyond being the main energy supplier of the cell. Accordingly, they are involved in neuronal synaptic transmission, neuronal growth and sprouting and consequently neuronal plasticity and connectivity. In addition, mitochondria participate in the modulation of gene transcription and inflammation as well in physiological responses in health and disease. Schizophrenia is currently regarded as a neurodevelopmental disorder associated with impaired immune system, aberrant neuronal differentiation and abnormalities in various neurotransmitter systems mainly the dopaminergic, glutaminergic and GABAergic. Ample evidence has been accumulated over the last decade indicating a multifaceted dysfunction of mitochondria in schizophrenia. Indeed, mitochondrial deficit can be of relevance for the majority of the pathologies observed in this disease. In the present article, we overview specific deficits of the mitochondria in schizophrenia, with a focus on the first complex (complex I) of the mitochondrial electron transport chain (ETC). We argue that complex I, being a major factor in the regulation of mitochondrial ETC, is a possible key modulator of various functions of the mitochondria. We review biochemical, molecular, cellular and functional evidence for mitochondrial impairments and their possible convergence to impact in-vitro neuronal differentiation efficiency in schizophrenia. Mitochondrial function in schizophrenia may advance our knowledge of the disease pathophysiology and open the road for new treatment targets for the benefit of the patients.

Dysfunction of mitochondria, key players in various essential cell processes, has been repeatedly reported in schizophrenia (SZ). Recently, several studies have reported functional recovery and cellular viability following mitochondrial transplantation, mostly in ischemia experimental models. Here, we aimed to demonstrate beneficial effects of isolated active normal mitochondria (IAN-MIT) transfer in vitro and in vivo, using SZ-derived induced pluripotent stem cells (iPSCs) differentiating into glutamatergic neuron, as well as a rodent model of SZ. First, we show that IAN-MIT enter various cell types without manipulation. Next, we show that IAN-MIT transfer into SZ-derived lymphoblasts induces long-lasting improvement in various mitochondrial functions including cellular oxygen consumption and mitochondrial membrane potential (Δ ψ m). We also demonstrate improved differentiation of SZ-derived iPSCs into neurons, by increased expression of neuronal and glutamatergic markers β3-tubulin, synapsin1, and Tbr1 and by an activation of the glutamate-glutamine cycle. In the animal model, we show that intra-prefrontal cortex injection of IAN-MIT in adolescent rats exposed prenatally to a viral mimic prevents mitochondrial Δ ψ m and attentional deficit at adulthood. Our results provide evidence for a direct link between mitochondrial function and SZ-related deficits both in vitro and in vivo and suggest a therapeutic potential for IAN-MIT transfer in diseases with bioenergetic and neurodevelopmental abnormalities such as SZ.

Pharmacological treatment of mental disorders is currently decided based on "trial and error" strategy. Mitochondrial multifaceted dysfunction is assumed to be a major factor in the pathophysiology and treatment of schizophrenia (SZ) and bipolar disorder (BD). This study aimed to explore the feasibility of using a profile of mitochondrial function parameters as a tool to predict the optimal drug for an individual patient (personalized medicine). Healthy controls (n = 40), SZ (n = 48) and BD (n = 27) patients were recruited. Mental and global state of the subjects, six mitochondrial respiration parameters and 14 mitochondrial function-related proteins were assessed in fresh lymphocytes following in-vitro or in-vivo treatment with five antipsychotic drugs and two mood-stabilizers. In healthy controls, hierarchal clustering shows a drug-specific effect profile on the different mitochondrial parameters following in-vitro exposure. Similar changes were observed in untreated SZ and BD patients with psychosis. Following a month of treatment of the latter patients, only responders showed a significant correlation between drug-induced in-vitro effect (prior to in-vivo treatment) and short-term in-vivo treatment effect for 45% of the parameters. Long- but not short-term psychotropic treatment normalized mitochondria-related parameters in patients with psychosis. Taken together, these data substantiate mitochondria as a target for psychotropic drugs and provide a proof of concept for selective mitochondrial function-related parameters as a predictive tool for an optimized psychotropic treatment in a given patient. This, however, needs to be repeated with an expanded sample size and additional mitochondria related parameters.

Complex I (NADH dehydrogenase, NDU) and complex IV (cytochrome-c-oxidase, COX) of the mitochondrial electron transport chain have been implicated in the pathophysiology of major psychiatric disorders, such as major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia (SZ), as well as in neurodegenerative disorders, such as Alzheimer disease (AD) and Parkinson disease (PD). We conducted meta-analyses comparing complex I and IV in each disorder MDD, BD, SZ, AD, and PD, as well as in normal aging. The electronic databases Pubmed, EMBASE, CENTRAL, and Google Scholar, were searched for studies published between 1980 and 2018. Of 2049 screened studies, 125 articles were eligible for the meta-analyses. Complex I and IV were assessed in peripheral blood, muscle biopsy, or postmortem brain at the level of enzyme activity or subunits. Separate meta-analyses of mood disorder studies, MDD and BD, revealed moderate effect sizes for similar abnormality patterns in the expression of complex I with SZ in frontal cortex, cerebellum and striatum, whereas evidence for complex IV alterations was low. By contrast, the neurodegenerative disorders, AD and PD, showed strong effect sizes for shared deficits in complex I and IV, such as in peripheral blood, frontal cortex, cerebellum, and substantia nigra. Beyond the diseased state, there was an age-related robust decline in both complexes I and IV. In summary, the strongest support for a role for complex I and/or IV deficits, is in the pathophysiology of PD and AD, and evidence is less robust for MDD, BD, or SZ.

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-HT2A, 5-HT2C, 5-HT3A) 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.

Mitochondria together with other cellular components maintain a constant crosstalk, modulating transcriptional and posttranslational processes. We and others demonstrated mitochondrial multifaceted dysfunction in schizophrenia, with aberrant complex I (CoI) as a major cause. Here we show deficits in CoI activity and homeostasis in schizophrenia-derived cell lines. Focusing on a core CoI subunit, NDUFV2, one of the most severely affected subunits in schizophrenia, we observed reduced protein level and functioning, with no change in mRNA transcripts. We further show that NDUFV2 pseudogene (NDUFV2P1) expression is increased in schizophrenia-derived cells and in postmortem brain specimens. In schizophrenia and controls pooled samples, NDUFV2P1 level demonstrated a significant inverse correlation with NDUFV2 pre- and matured protein level and with CoI-driven cellular respiration. Our data suggest a role for a pseudogene in its parent-gene regulation and possibly in CoI dysfunction in schizophrenia. The abnormal expression of the pseudogene may be one element of a vicious circle in which CoI deficits lead to mitochondrial dysfunction potentially affecting genome-wide regulation of gene expression, including the expression of pseudogenes.

Complex I (NADH dehydrogenase) and complex IV (cytochrome-c-oxidase) of the mitochondrial electron transport chain 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. Meta-analyses revealed that selected antidepressants increase or decrease complex I and IV, antipsychotics and stimulants primarily decrease complex I but increase complex IV, whereas anxiolytics, mood stabilizers, antidementia and antiparkinsonian drugs preserve or even enhance both complex I and IV. To determine potential contributors to the drug effects, we meta-analyzed the drugs' neurotransmitter receptor profiles and found that affinity to adrenergic, dopaminergic (D1/2), glutaminergic (NMDA1,3), histaminergic (H1), muscarinic (M1,3), opioid (OP1-3), serotonergic (5-HT2A, 5-HT2C, 5-HT3A) and sigma receptors contributed most to the effects. We discuss the drug effects in relation to pharmacological mechanisms of action that might have relevance for clinical and research applications. Funding: No specific funding. Declaration of Interest: J.J.M. receives royalties for commercial use of the C-SSRS from the Research Foundation of Mental Hygiene. The remaining authors declare no competing interests. Keywords: meta-analysis; psychotropic drugs; NADH dehydrogenase; cytochrome-c-oxidase

Mitochondrial transplantation is currently being explored as a means to repair and restore proper organelle function in a variety of inherited and acquired disorders of energy metabolism. The optimal preparation and application of donor mitochondria is unknown, but most studies in vivo have used injection techniques or, for tissue studies, unpackaged mitochondria (organelles isolated and suspended in buffer) in transplant experiments. Packaging in lipid rafts can increase recipient cell uptake of some compounds and objects. We present the first data comparing recipient cell uptake of unpackaged mitochondria to recipient cell uptake of mitochondria packaged in cell membrane lipids. Mitochondria and membranes were prepared from autologous cells and applied to cells (fibroblasts) in culture. Both unpackaged and lipid-packaged mitochondria were taken into recipient cells and the donor mitochondria showed evidence, in each case, of retained functionality and the ability to merge with the recipient mitochondrial matrix. However, lipid packaging appeared to enhance the uptake of functional mitochondria. Current studies of mitochondrial transplantation in animal models might fruitfully explore the utility and efficacy of lipid-packaged mitochondria in transplant experiments.

There is compelling evidence that aminoglycoside (AG) antibiotics can induce the mammalian ribosome to suppress disease-causing nonsense mutations and partially restore the expression of functional proteins. However, prolonged AG treatment can cause detrimental side effects in patients, including most prominently, ototoxicity. Recent mechanistic discussions have considered the relative contributions of mitochondrial and cytoplasmic protein synthesis inhibition to AG-induced ototoxicity. We show that AGs inhibit mitochondrial protein synthesis in mammalian cells and perturb cell respiration, leading to a time- and dose-dependent increase in superoxide overproduction and accumulation of free ferrous iron in mitochondria caused by oxidative damage of mitochondrial aconitase, ultimately leading to cell apoptosis via the Fenton reaction. These deleterious effects increase with the increased potency of AG to inhibit the mitochondrial rather than cytoplasmic protein synthesis, which in turn correlates with their ototoxic potential in both murine cochlear explants and the guinea pig in vivo. The deleterious effects of AGs were alleviated in synthetic derivatives specially designed for the treatment of genetic diseases caused by nonsense mutations and possessing low affinity toward mitochondrial ribosomes. This work highlights the benefit of a mechanism-based drug redesign strategy that can maximize the translational value of "readthrough therapy" while mitigating drug-induced side effects. This approach holds promise for patients suffering from genetic diseases caused by nonsense mutations.

Reactivity to traumatic stress varies between individuals and only a minority of those exposed to trauma develops stress-induced psychopathologies. Currently extensive effort is made to unravel the specific mechanisms predisposing to vulnerability vs. resilience to stress. We investigated in rats the role of β-endorphin metabolism in vulnerability to acute traumatic stress. Responders (showing extreme anxiety; n=7) and resilient non-responders (not differing from the non-stressed individuals; n=8) to traumatic foot-shock stress were compared for their blood levels of stress hormones as well as brain levels and activity of two opioid-degrading enzymes. β-endorphin is a substrate to insulin degrading enzyme, which also degrades insulin. Therefore, the effects of insulin application on behavioral and hormonal responses and on β-endorphin degradation were tested. Pre- and post-stress levels of serum corticosterone, and post-stress plasma β-endorphin concentration differentiated between the responders and the non-responders. In brain, responders showed enhanced degradation rates of β-endorphin, assessed by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS), in hippocampal and amygdalar slices as compared to non-responders. Application of insulin to the amygdala, prior to exposure to traumatic stress, reduced post-stress anxiety and serum corticosterone levels only in the responders. In parallel, amygdalar β-endorphin degradation rate was also reduced by insulin. These results suggest that slowing down β-endorphin degradation rate may constitute an integral part of the normal stress-response, upon a failure of which an extreme anxiety develops. Modulation of opioid degradation may thus present a potential novel target for interference with extreme anxiety.

Negative symptoms in schizophrenia are associated with decreased dopaminergic activity in the prefrontal cortex (PFC). It is hypothesized that increasing dopamine levels would alleviate negative symptoms. Termination of dopamine activity in the PFC is mainly via catechol-O-methyl tranferase (COMT) activity. Hence, inhibition of COMT activity with entacapone should reverse PFC dopaminergic transmission. To assess the efficacy of entacapone addition to antipsychotic treatment in patients with residual schizophrenia, we conducted a double-blind, randomised, placebo-controlled study for 12 wk of treatment with entacapone or placebo. Clinical measures (PANSS, CGI and QLS) were obtained at baseline and at weeks 4, 8 and 12 and cognitive functions were assessed by the RBANSS. Significant improvement over time in PANSS and QLS scores was observed in both groups. However, entacapone did not demonstrate a beneficial effect compared to placebo. Therefore, this study does not support a therapeutic role for entacapone in residual schizophrenia.

Background It is currently accepted that complex behavior and mental disorder results from a combination of biological susceptibility and exposure to environmental stimuli. Most of the gene–environment interaction models focus on the interaction between the stimuli and a single candidate gene. We suggest that an alternative approach is interference with the expression of multiple genes followed by exposure to environmental insults. Methods Early interference with gene transcription was performed by treatment of 7 days old Wistar male rats for 4 days with the Sp1/DNA binding inhibitor, mithramycin. Environmental insult was mimicked by exposing these rats during adulthood (34 days) to sub-chronic (12 days, n = 30) or chronic stress (28 days, n = 48). The effects of mithramycin and stress treatment on the behavioral response and serum corticosterone concentration were assessed. Results Exposure of mithramycin treated rats to sub-chronic stress led to anxious behavior in the open field test, high startle response, low sucrose preference, indifference to novel objects and high serum corticosterone concentration. However, exposure to chronic stress resulted in normal sucrose preference, startle response and serum corticosterone, novelty seeking behavior and reduced anxiety. In saline treated rats the extension of stress duration led to behavioral and hormonal adaptation to stress. Conclusion Our study suggests that postnatal temporal interference with multiple gene expression can lead to hyper-responsiveness to environmental stimuli, the features of which affects the phenotypic outcomes. Such a paradigm may be used to model gene–environmental interaction in the etiology of behavioral disorders.

Mitochondria are key players in the generation and regulation of cellular bioenergetics, producing the majority of adenosine triphosphate molecules by the oxidative phosphorylation system (OXPHOS). Linked to numerous signaling pathways and cellular functions, mitochondria, and OXPHOS in particular, are involved in neuronal development, connectivity, plasticity, and differentiation. Impairments in a variety of mitochondrial functions have been described in different general and psychiatric disorders, including schizophrenia (SCZ), a severe, chronic, debilitating illness that heavily affects the lives of patients and their families. This article reviews findings emphasizing the role of OXPHOS in the pathophysiology of SCZ. Evidence accumulated during the past few decades from imaging, transcriptomic, proteomic, and metabolomic studies points at OXPHOS deficit involvement in SCZ. Abnormalities have been reported in high-energy phosphates generated by the OXPHOS, in the activity of its complexes and gene expression, primarily of complex I (CoI). In addition, cellular signaling such as cAMP/protein kinase A (PKA) and Ca+2, neuronal development, connectivity, and plasticity have been linked to OXPHOS function and are reported to be impaired in SCZ. Finally, CoI has been shown as a site of interaction for both dopamine (DA) and antipsychotic drugs, further substantiating its role in the pathology of SCZ. Understanding the role of mitochondria and the OXPHOS in particular may encourage new insights into the pathophysiology and etiology of this debilitating disorder.

Disease-specific induced pluripotent stem cells (iPSC) allow unprecedented experimental platforms for basic research as well as high-throughput screening. This may be particularly relevant for neuropsychiatric disorders, in which the affected neuronal cells are not accessible. Keratinocytes isolated from hair follicles are an ideal source of patients' cells for reprogramming, due to their non-invasive accessibility and their common neuroectodermal origin with neurons, which can be important for potential epigenetic memory. From a small number of plucked human hair follicles obtained from two healthy donors we reprogrammed keratinocytes to pluripotent iPSC. We further differentiated these hair follicle-derived iPSC to neural progenitors, forebrain neurons and functional dopaminergic neurons.This study shows that human hair follicle-derived iPSC can be differentiated into various neural lineages, suggesting this experimental system as a promising in vitro model to study normal and pathological neural developments, avoiding the invasiveness of commonly used skin biopsies.

Evidence concerning ion-channel abnormalities in the pathophysiology of common psychiatric disorders is still limited. Given the significance of ion channels in neuronal activity, neurotransmission and neuronal plasticity we hypothesized that the expression patterns of genes encoding different ion channels may be altered in schizophrenia, bipolar and unipolar disorders. Frozen samples of striatum including the nucleus accumbens (Str-NAc) and the lateral cerebellar hemisphere of 60 brains from depressed (MDD), bipolar (BD), schizophrenic and normal subjects, obtained from the Stanley Foundation Brain Collection, were assayed. mRNA of 72 different ion-channel subunits were determined by qRT-PCR and alteration in four genes were verified by immunoblotting. In the Str-NAc the prominent change was observed in the MDD group, in which there was a significant up-regulation in genes encoding voltage-gated potassium-channel subunits. However, in the lateral cerebellar hemisphere (cerebellum), the main change was observed in schizophrenia specimens, as multiple genes encoding various ion-channel subunits were significantly down-regulated. The impaired expression of genes encoding ion channels demonstrates a disease-related neuroanatomical pattern. The alterations observed in Str-NAc of MDD may imply electrical hypo-activity of this region that could be of relevance to MDD symptoms and treatment. The robust unidirectional alteration of both excitatory and inhibitory ion channels in the cerebellum may suggests cerebellar general hypo-transcriptional activity in schizophrenia.

Schizophrenia is currently believed to result from variations in multiple genes, each contributing a subtle effect, which combines with each other and with environmental stimuli to impact both early and late brain development. At present, schizophrenia clinical heterogeneity as well as the difficulties in relating cognitive, emotional and behavioral functions to brain substrates hinders the identification of a disease-specific anatomical, physiological, molecular or genetic abnormality. Mitochondria play a pivotal role in many essential processes, such as energy production, intracellular calcium buffering, transmission of neurotransmitters, apoptosis and ROS production, all either leading to cell death or playing a role in synaptic plasticity. These processes have been well established as underlying altered neuronal activity and thereby abnormal neuronal circuitry and plasticity, ultimately affecting behavioral outcomes. The present article reviews evidence supporting a dysfunction of mitochondria in schizophrenia, including mitochondrial hypoplasia, impairments in the oxidative phosphorylation system (OXPHOS) as well as altered mitochondrial-related gene expression. Abnormalities in mitochondrial complex I, which plays a major role in controlling OXPHOS activity, are discussed. Among them are schizophrenia specific as well as disease-state-specific alterations in complex I activity in the peripheral tissue, which can be modulated by DA. In addition, CNS and peripheral abnormalities in the expression of three of complex I subunits, associated with parallel alterations in their transcription factor, specificity protein 1 (Sp1) are reviewed. Finally, this review discusses the question of disease specificity of mitochondrial pathologies and suggests that mitochondria dysfunction could cause or arise from anomalities in processes involved in brain connectivity.

Stressors differ in their physiological and behavioral outcomes. One of the major mechanisms by which stressors affect the brain and behavior is alteration in neuronal plasticity. We investigated in the rat the effects of a single exposure to psychophysical (electrical foot shock) vs. psychological (social defeat) stressors on anxiety- and depression-related behaviors, serum levels of corticosterone and the expression of plasticity-related genes CAM-L1, CREB, GAP-43, and laminin in the prefrontal cortex (PFC), the amygdala and the hippocampus. Rats were examined for 24 h or 1 week after the exposure to stress. Footshocks enhanced anxiety-related behaviors, whereas social defeat induced depression-related behaviors at both time points and less pronounced anxiety 1 week post-exposure. Serum corticosterone concentrations were enhanced 24 h after shocks, but only 1 week after exposure to the social stressor. Moreover, the shock-stressed rats exhibited decreased CAM-L1 protein level in the hippocampus 24 h post-exposure and decreased GAP-43 protein level in the PFC 1 week post-exposure. By contrast, the social stressor enhanced expression of the plasticity-related proteins in the amygdala and the hippocampus, mostly 1 week after the exposure. These results indicate stressor-specific time-dependent changes in different neuronal pathways, and suggest consideration of a cause-specific approach to the treatment of stress-related disorders.

Several independent lines of evidence suggest mitochondrial dysfunction in schizophrenia in brain and periphery, including mitochondrial hypoplasia, dysfunction of the oxidative phosphorylation system, and altered mitochondrial-related gene expression. In an attempt to decipher whether mitochondrial complex I abnormality in schizophrenia is a core pathophysiological process or is attributable to medication, we studied two animal models of schizophrenia related to the neurodevelopmental hypothesis of this disorder. Protein levels of complex I subunits, 24, 51, and 75 kDa, were assessed in neonatal ventral hippocampal lesion rat model and in rats exposed to hypoxia at a neonatal age. In the prefrontal cortex, a major anatomical substrate of schizophrenia, neonatal ventral hippocampal lesion induced a significant prepubertal increase and postpubertal decrease in all three subunits of complex I as compared to sham-treated rats, while no change was observed in the cingulate cortex. Neonatal exposure to hypoxia did not affect protein levels of any of the three subunits in the prefrontal cortex. An age-dependent increase in the expression of complex I subunits was observed, which was distorted in the prefrontal cortex by the neonatal ventral hippocampal lesion. Complex I alterations in schizophrenia-related neurodevelopmental rat models appear to be brain region and animal model dependent. The results of this study support previous findings suggesting abnormal complex I expression as a pathological characteristic of schizophrenia rather than an effect of medication.

Neuromelanin (NM) is a complex polymer pigment found primarily in the dopaminergic neurons of the human substantia nigra. The structure of NM is only partially characterized, and its synthesis pathway remains unknown. We used nuclear magnetic and infrared spectroscopy to examine the structure of human NM isolated from the substantia nigra compared with synthetic dopamine melanins. Biochemical analyses were used to investigate proteinaceous and dopaminergic components in these samples. Following acid hydrolysis of NM samples, small amounts of DOPA, dopamine, and a variety of amino acids were measured. These findings suggest a peptide component in NM structure. NM also appears to contain a variety of unidentified structural components possibly derived from the oxidation of dopamine. Human NM differs structurally from synthetic dopamine melanin, but both human and synthetic NM include an aromatic backbone. It is interesting that both human NM and synthetic melanin also contain a large proportion of aliphatic structures. Our results suggest that NM is a more complex pigment than synthetic dopamine melanin formed via dopamine autoxidation alone.

Deleterious effects of dopamine (DA) involving mitochondrial dysfunction have an important role in DA-associated neuronal disorders, including schizophrenia and Parkinson's disease. DA detrimental effects have been attributed to its ability to be auto-oxidized to toxic reactive oxygen species. Since, unlike Parkinson's disease, schizophrenia does not involve neurodegenerative processes, we suggest a novel mechanism by which DA impairs mitochondrial function without affecting cell viability. DA significantly dissipated mitochondrial membrane potential (Δ ψ m ) in SH-SY5Y cells. Bypassing complex I prevented the DA-induced depolarization. Moreover, DA inhibited complex I but not complex II activity in disrupted mitochondria, suggesting complex I participation in DA-induced mitochondrial dysfunction. We further demonstrated that intact mitochondria can accumulate DA in a saturated manner, with an apparent K m = 122.1 ± 28.6 nM and V max = 1.41 ± 0.15 pmol/mg protein/min, thereby enabling the interaction between DA and complex I. DA accumulation was an energy and Na + -dependent process. The pharmacological profile of mitochondrial DA uptake differed from that of other characterized DA transporters. Finally, relevance to schizophrenia is demonstrated by an abnormal interaction between DA and complex I in schizophrenic patients. These results suggest a non-lethal interaction between DA and mitochondria possibly via complex I, which can better explain DA-related pathological processes observed in non-degenerative disorders, such as schizophrenia.

Mitochondria, similar to living cells and organelles, have negative membrane potential and can therefore accumulate permeable lipophilic cations. Those cations which exhibit fluorescence activity after accumulation into energized systems are widely used to decipher changes in membrane potential by imaging techniques. Here we describe the use of the lipophilic cation 5,5',6,6'tetrachloro-1,1',3,3'-tetraethylbenzimidazol-carbocyanine iodide (JC-1), which alters reversibly its color from green (J-monomer, at its low concentration in the cytosol) to red (J-aggregates, at its high concentration in active mitochondria) with increasing mitochondrial membrane potential (Δψm). We show that in addition to changes in Δψm, this specific dye can be used to follow alterations in mitochondrial distribution and mitochondrial network connectivity. We suggest that JC-1 is a preferable probe to compare between treatment groups, as the ratio of green to red fluorescence intensities is used for analysis. This ratio depends only on the mitochondrial membrane potential and not on other mitochondrial dependent or independent factors. We demonstrate various applications of JC-1 staining to study mitochondrial abnormalities in different cell types derived from schizophrenia patients and healthy subjects.

Mitochondria, similar to living cells and organelles, have negative membrane potential and can therefore accumulate permeable lipophilic cations. Those cations which exhibit fluorescence activity after accumulation into energized systems are widely used to decipher changes in membrane potential by imaging techniques. Here we describe the use of the lipophilic cation 5,5',6,6'tetrachloro-1,1',3,3'-tetraethylbenzimidazol-carbocyanine iodide (JC-1), which alters reversibly its color from green (J-monomer, at its low concentration in the cytosol) to red (J-aggregates, at its high concentration in active mitochondria) with increasing mitochondrial membrane potential (Δψm). We show that in addition to changes in Δψm, this specific dye can be used to follow alterations in mitochondrial distribution and mitochondrial network connectivity. We suggest that JC-1 is a preferable probe to compare between treatment groups, as the ratio of green to red fluorescence intensities is used for analysis. This ratio depends only on the mitochondrial membrane potential and not on other mitochondrial dependent or independent factors. We demonstrate various applications of JC-1 staining to study mitochondrial abnormalities in different cell types derived from schizophrenia patients and healthy subjects.

Previously, we reported an ability of NE to promote processes of plasticity in neuroblastoma cells, as observed by morphological changes such as an elongated granule-rich cell body and neuritegenesis, in addition to a progressive decrease in the pluripotent marker Oct4 and an increase in the growth cone marker GAP-43. This was accompanied by the induction of three plasticity genes forming a functional cluster, the cell adhesion molecule L1 (CAM-L1), laminin, and CREB, all involved in neuronal plasticity and neurite outgrowth. In the present study, we hypothesized that the regulation of CAM-L1, laminin, and CREB/pCREB by NE could mediate processes of plasticity in the mode of action of antidepressants, as well as in the long-term effects of stress, in rats, given the association of both with NE alterations and neuronal plasticity. In the first experiment, rats were chronically administered with antidepressants (21 days). In the second experiment, rats were exposed to chronic stress and examined 4 months later, a model shown to exhibit behavioral indices of stress. We found brain region-specific alterations in mRNA and protein levels of CAM-L1, laminin, and pCREB in rats chronically treated with the noradrenergic antidepressant desipramine and, to a lesser extent, in those treated with fluoxetine. Stressed rats presented a decrease in CAM-L1, laminin, and pCREB, specifically in brain areas implicated in stress. Our findings suggest that noradrenergic-regulated plasticity genes such as CAM-L1, laminin, and CREB play an important role both in stress and in the treatment of depression.

In Parkinson's disease (PD) and its neurotoxin-induced models, 6-hydroxydopamine (6-OHDA) and N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), significant accumulation of iron occurs in the substantia nigra pars compacta. The iron is thought to be in a labile pool, unbound to ferritin, and is thought to have a pivotal role to induce oxidative stress-dependent neurodegeneration of dopamine neurons via Fenton chemistry. The consequence of this is its interaction with H(2)O(2) to generate the most reactive radical oxygen species, the hydroxyl radical. This scenario is supported by studies in both human and neurotoxin-induced parkinsonism showing that disposition of H(2)O(2) is compromised via depletion of glutathione (GSH), the rate-limiting cofactor of glutathione peroxide, the major enzyme source to dispose H(2)O(2) as water in the brain. Further, radical scavengers have been shown to prevent the neurotoxic action of the above neurotoxins and depletion of GSH. However, our group was the first to demonstrate that the prototype iron chelator, desferal, is a potent neuroprotective agent in the 6-OHDA model. We have extended these studies and examined the neuroprotective effect of intracerebraventricular (ICV) pretreatment with the prototype iron chelator, desferal (1.3, 13, 134 mg), on ICV induced 6-OHDA (250 micro g) lesion of striatal dopamine neurons. Desferal alone at the doses studied did not affect striatal tyrosine hydroxylase (TH) activity or dopamine (DA) metabolism. All three pretreatment (30 min) doses of desferal prevented the fall in striatal and frontal cortex DA, dihydroxyphenylacetic acid, and homovalinic acid, as well as the left and right striatum TH activity and DA turnover resulting from 6-OHDA lesion of dopaminergic neurons. A concentration bell-shaped neuroprotective effect of desferal was observed in the striatum, with 13 micro g being the most effective. Neither desferal nor 6-OHDA affected striatal serotonin, 5-hydroxyindole acetic acid, or noradrenaline. Desferal also protected against 6-OHDA-induced deficit in locomotor activity, rearing, and exploratory behavior (sniffing) in a novel environment. Since the lowest neuroprotective dose (1.3 micro g) of desferal was 200 times less than 6-OHDA, its neuroprotective activity may not be attributed to interference with the neurotoxin activity, but rather iron chelation. These studies led us to develop novel brain-permeable iron chelators, the VK-28 series, with iron chelating and neuroprotective activity similar to desferal for ironing iron out from PD and other neurodegenerative diseases, such as Alzheimer's disease, Friedreich's ataxia, and Huntington's disease.

Significant increase in iron occurs in the substantia nigra pars compacta of Parkinsonian subjects, and in 6-hydroxydopamine (6-OHDA) treated rats and monkeys. This increase in iron has been attributed to its release from ferritin and is associated with the generation of reactive oxygen species and the onset of oxidative stress-induced neurodegeneration. Several iron chelators with hydroxyquinoline backbone were synthesized and their ability to inhibit basal as well as iron-induced mitochondrial lipid peroxidation was examined. The neuroprotective potential of the brain permeable iron chelator, VK-28 (5-[4-(2-hydroxyethyl) piperazine-1-ylmethyl]-quinoline-8-ol), injected either intraventricularly (ICV) or intraperitoneally (IP), to 6-OHDA lesioned rats was investigated. VK-28 inhibited both basal and Fe/ascorbate induced mitochondrial membrane lipid peroxidation, with an IC(50) (12.7 microM) value comparable to that of the prototype iron chelator, desferal, which does not cross the blood brain barrier. At an ICV pretreatment dose as low as 1 microg, VK-28 was able to completely protect against ICV 6-OHDA (250 microg) induced striatal dopaminergic lesion, as measured by dopamine (DA), dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA) levels. IP injection of rats with VK-28 (1 and 5 mg/kg) daily for 10 and 7 days, respectively, demonstrated significant neuroprotection against ICV 6-OHDA at the higher dose, with 68% protection against loss of dopamine at 5mg/kg dosage of VK-28. The present study is the first to show neuroprotection with a brain permeable iron chelator. The latter can have implications for the treatment of Parkinson's disease and other neurodegenerative diseases (Alzheimer's disease, Friedreich ataxia, aceruloplasminemia, Hallervorden Spatz syndrome) where abnormal iron accumulation in the brain is thought to be associated with the degenerative processes.

Transcranial magnetic stimulation (TMS), which is produced by strong non-static magnetic fields, is a non-invasive means to stimulate the cerebral cortex. Studies from recent years show that TMS affects mood in healthy subjects and improves depressive symptoms in patients with major depression. However, the relationship between the clinical efficacy of TMS and stimulation parameters is still obscure. In the present study we have investigated the effects of different stimulation frequencies and number of treatments on catecholamine turnover in SH-SY5Y cell cultures. A single session of magnetic stimulation (1.7 T) caused a significant decrease in intracellular dopamine and L-DOPA and in noradrenaline (NE) release at a rate of 3 Hz for 10 s but increased NE release at a rate of 9 Hz. These alterations were associated with a reduction (47.8%) or an increase (48%) in tyrosine hydroxylase (TH) activity after 3 and 9 Hz magnetic stimulation, respectively. The latter may be related to the known sensitivity of TH to neuronal firing rates and NE concentrations. Higher stimulation frequencies (15, 20, 45 Hz) had no effect on catecholamine metabolism. Unlike 3 Hz acute treatment, chronic treatment (3 Hz, 11 sessions, for 4 d) had no effect on monoamines and TH activity was increased by 54.5% with no change in its protein level. The results of the present study demonstrate that in tissue culture system frequency and treatment duration of the magnetic stimulation are important factors in affecting catecholamine turnover. Considering the major role of catecholamine in the pathophysiology of depression, these findings may be of relevance to the application of rTMS in humans with major depression.

The vulnerability of the dopaminergic neurons of the substantia nigra (SN) in Parkinson's disease has been related to the presence of the pigment neuromelanin (NM) in these neurons. It is hypothesised that NM may act as an endogenous storage molecule for iron, an interaction suggested to influence free radical production. The current study quantified and characterised the interaction between NM and iron. Iron-binding studies demonstrated that both NM and synthetically-produced dopamine melanin contain equivalent numbers of high and low-affinity binding sites for iron but that the affinity of NM for iron is higher than that of synthetic melanin. Quantification of the total iron content in iron-loaded NM and synthetic melanin demonstrated that the iron-binding capacity of NM is 10-fold greater than that of the model melanin. This data was in agreement with the larger iron cluster size demonstrated by Mössbauer spectroscopy in the native pigment compared with the synthetic melanin. These findings are consistent with the hypothesis that NM may act as an endogenous iron-binding molecule in dopaminergic neurons of the SN in the human brain. The interaction between NM and iron has implications for disorders such as Parkinson's disease where an increase in iron in the SN is associated with increased indices of oxidative stress.

Mitochondria are not only the principal source of high energy intermediates, but play an important role in intracellular calcium buffering, are main producers of reactive oxygen species, and are the source of pro- and antiapoptotic key factors. Moreover, the mitochondria are of a ubiquitous nature and the respiratory chain has a dual genetic basis, i.e. the mitochondrial and the nuclear DNAs. Thus mitochondrial impairment could provide an explanation for the tremendous heterogeneity of clinical and pathological manifestations in schizophrenia. This article reviews several independent lines of evidence that suggest an involvement of mitochondrial dysfunction in schizophrenia. Among them are altered cerebral energy metabolism, mitochondrial hypoplasia, dysfunction of the oxidative phosphorylation system and altered mitochondrial related gene expression. In addition, the interaction between dopamine, a predominant etiological factor in schizophrenia, and mitochondrial respiration is considered as a possible mechanism underlying the hyper- and hypo-activity cycling in schizophrenia. Understanding the role of mitochondria in schizophrenia may encourage novel treatment approaches, the identification of candidate genes and new insights into the pathophysiology and etiology of the disorder.

Dopamine, due to metabolism by monoamine oxidase or autoxidation, can generate toxic products such as hydrogen peroxide, oxygen-derived radicals, semiquinones, and quinones and thus exert its neurotoxic effects. Intracerebroventricular injection of dopamine into rats pretreated with the monoamine oxidase nonselective inhibitor pargyline caused mortality in a dose-dependent manner with LD50 = 90 micrograms. Norepinephrine was less effective with LD50 = 141 micrograms. The iron chelator desferrioxamine completely protected against dopamine-induced mortality. In the absence of pargyline more rats survived, indicating that the products of dopamine enzymatic metabolism are not the main contributors to dopamine-induced toxicity. Biochemical analysis of frontal cortex and striatum from rats that received a lethal dose of dopamine did not show any difference from control rats in lipid and protein peroxidation and glutathione reductase and peroxidase activities. Moreover, dopamine significantly reduced the formation of iron-induced malondialdehyde in vitro, thus suggesting that earlier events in cell damage are involved in dopamine toxicity. Indeed, dopamine inhibited mitochondrial NADH dehydrogenase activity with IC50 = 8 microM, and that of norepinephrine was twice as much (IC50 = 15 microM). Dopamine-induced inhibition of NADH dehydrogenase activity was only partially reversed by desferrioxamine, which had no effect on norepinephrine-induced inhibition. These results suggest that catecholamines can cause toxicity not only by inducing an oxidative stress state but also possibly through direct interaction with the mitochondrial electron transport system. The latter was further supported by the ability of ADP to reverse dopamine-induced inhibition of NADH dehydrogenase activity in a dose-dependent manner.

Recent research into depression has focused on the involvement of long-term intracellular processes, leading to abnormal neuronal plasticity in brains of depressed patients, and reversed by antidepressant treatment. Given a suggested decrease in noradrenergic transmission in depression, and an antidepressant induced increase in norepinephrine (NE) level, a possible role for NE in mediating alterations in neuronal morphology and plasticity was examined. Human neuroblastoma SH-SY5Y cells treated with 10-5 m NE presented an elongated granule-rich cell-body and increased number of neurites, when compared with non-treated cells. Moreover, cell survival was enhanced in the presence of NE, while proliferation was inhibited. The above effects suggest a role for NE in cell differentiation. Indeed similar effects on cell survival and neurite outgrowth were induced in SH-SY5Y cells by retinoic acid (RA), an established differentiating agent. Finally, NE treatment resulted in a progressive decrease in the pluripotent marker Oct4 and an increase in the neuronal growth cone marker, growth-associated-protein 43 (GAP-43). Alongside these effects, NE-treated cells presented alterations in the expression of 44 genes as observed in a neurobiology cDNA microarray. Among the altered genes, an increase in the expression level of two neurite-outgrowth promoting genes, neural cell adhesion molecule L1 and laminin, was confirmed by RT-PCR. Taken together, the results support a role for NE in processes of synaptic connectivity, and may point to a role for this neurotransmitter in mediating the suggested neuronal plasticity in depression and in antidepressant treatment.