The interplay between mitochondrial complex I, dopamine and Sp1 in schizophrenia

Relation of ATPase6 Mutations and Telomere Length in Schizophrenia Patients

Objective

Schizophrenia is a serious mental disorder. Mutations in mitochondrial genes can change energy metabolism. Telomere is a tandem sequence at the end of chromosomes. Shorter telomere length has been shown in schizophrenia. The aim of this study was to determine the relationship between ATPase6 gene mutations and telomere length in schizophrenia patients.

Methods

Blood samples of 34 patients and 34 healthy controls were used. In this study conventional PCR, Sanger sequencing technic and real-time PCR were utilized.

Results

Five different mutations (A8860G, A8836, G8697A, C8676T, and A8701G) in the ATPase6 gene were identified in schizophrenia patients. The most seen mutation was A8860G (94%). Telomere length analysis indicated the relation of ATPase6 gene mutations and telomere length variations (p = 0.001). Patients carrying the A8860G mutation had shorter telomere lengths than patients carrying other mutations. Comparing telomere length between schizophrenia patients and healthy controls revealed that the mean telomere length of schizophrenia patients was shorter than healthy controls (p = 0.006). The demographic analysis demonstrated a significant relationship between marital status and telomere length (p = 0.011). Besides that, the duration of the illness is another factor that impacts telomere length (p = 0.044). There is no significant relation between telomere length and other clinical and demographic characteristics including education status, age, gender, etc.

Conclusion

In conclusion, telomere length and ATPase6 gene mutations have a significant relation. Studies with larger patient populations and investigation of other mitochondrial gene mutations will make the clearer link between telomere length and mitochondrial mutations.

Update of Mitochondrial Network Analysis by Imaging: Proof of Technique in Schizophrenia

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_m) 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 (Δψ_m). The other is MitoTracker^® Orange, a mitochondrion-selective probe which passively diffuses across the plasma membrane and accumulates in active mitochondria depending on their Δψ_m. We show that in addition to changes in Δψ_m, 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.

Dependence of Leydig Cell's Mitochondrial Physiology on Luteinizing Hormone Signaling

Knowledge about the relationship between steroidogenesis and the regulation of the mitochondrial bioenergetics and dynamics, in steroidogenic cells, is not completely elucidated. Here we employed in vivo and ex vivo experimental models to analyze mitochondrial physiology in Leydig cells depending on the different LH-cAMP environments. Activation of LH-receptor in rat Leydig cells ex and in vivo triggered cAMP, increased oxygen consumption, mitoenergetic and steroidogenic activities. Increased mitoenergetic activity i.e., ATP production is achieved through augmented glycolytic ATP production and a small part of oxidative phosphorylation (OXPHOS). Transcription of major genes responsible for mitochondrial dynamics was upregulated for Ppargc1a (regulator of mitogenesis and function) and downregulated for Drp1 (main fission marker), Prkn, Pink1 and Tfeb (mitophagy markers). Leydig cells from gonadotropin-treated rats show increased mitogenesis confirmed by increased mitochondrial mass, increased mtDNA, more frequent mitochondria observed by a transmission electron microscope and increased expression of subunits of respiratory proteins Cytc/CYTC and COX4. Opposite, Leydig cells from hypogonadotropic-hypogonadal rats characterized by low LH-cAMP, testosterone, and ATP production, reduced markers of mitogenesis and mitofusion (Mfn1/2, Opa1) associated with reduced mtDNA content. Altogether results underline LH-cAMP signaling as an important regulator of mitochondrial physiology arranging mitochondrial dynamics, bioenergetic and steroidogenic function in Leydig cells.

Leukocyte mitochondrial DNA copy number in schizophrenia

OBJECTIVE

Schizophrenia is a complex neuropsychiatric disorder with significant genetic predisposition. In a subset of schizophrenia patients, mitochondrial dysfunction could be explained by the genomic defects like mitochondrial DNA Copy Number Variations, which are considered as a sensitive index of cellular oxidative stress. Given the high energy demands for neuronal functions, altered Mitochondrial DNA copy number (mtDNAcn) and consequent impaired mitochondrial physiology would significantly influence schizophrenia pathogenesis. In this context, we have made an attempt to study mitochondrial dysfunction in schizophrenia by assessing mtDNAcn in antipsychotic-naïve/free schizophrenia patients.

METHOD

mtDNAcn was measured in 90 antipsychotic-naïve / free schizophrenia (SCZ) patients and 147 Healthy Controls (HC). The relative mtDNAcn was determined by quantitative real-time polymerase chain reaction (qPCR) using TaqMan® multiplex assay method.

RESULT

A statistically significant difference between groups [t = 5.22, P < 0.001] was observed, with significantly lower mtDNAcn in SCZ compared to HC. The group differences persisted even after controlling for age and sex [F (4, 232) = 22.68, P < 0.001, η2 = 0.09].

CONCLUSION

Lower mtDNAcn in SCZ compared to HC suggests that mtDNAcn may hold potential to serve as an important proxy marker of mitochondrial function in antipsychotic-naïve/free SCZ patients.

Mitochondrial Dysfunction in Blood Platelets of Patients with Manic Episode of Bipolar Disorder

OBJECTIVES

The bipolar affective disorder (BAD) pathophysiology is multifactorial and has not been fully clarified.

METHOD

We measured selected mitochondrial parameters in peripheral blood components. The analyses were performed for patients suffering from a manic episode during remission and were compared to those performed for healthy controls. BAD was clinically evaluated using well-established diagnostic scales and questionnaires. Mitochondrial respiration was examined in intact and permeabilized blood platelets using high-resolution respirometry. The citrate synthase (CS) and electron transport system (ETS) complex (complex I, II, and IV) activities were examined in platelets.

RESULTS

The CS, complex II and complex IV activities were decreased in the BAD patients, complex I activity was increased, and the ratio of complex I to CS was significantly increased. In the intact platelets, respiration after complex I inhibition and residual oxygen consumption were decreased in the BAD patients compared to the healthy controls. In the permeabilized platelets, a decreased ETS capacity was found in the BAD patients. No significant differences were found between BAD patients in mania and remission.

CONCLUSION

Increased complex I activity can be a compensatory mechanism for decreased CS and complex II and IV activities. We conclude that complex I and its abnormal activity contribute to defects in cellular energy metabolism during a manic episode and that the deficiency in the complex's functioning, but not the availability of oxidative phosphorylation substrates, seems to be responsible for the decreased ETS capacity in BAD patients. The observed parameters can be further evaluated as 'trait' markers of BAD.

The Complex Interaction of Mitochondrial Genetics and Mitochondrial Pathways in Psychiatric Disease

While accounting for only 2% of the body's weight, the brain utilizes up to 20% of the body's total energy. Not surprisingly, metabolic dysfunction and energy supply-and-demand mismatch have been implicated in a variety of neurological and psychiatric disorders. Mitochondria are responsible for providing the brain with most of its energetic demands, and the brain uses glucose as its exclusive energy source. Exploring the role of mitochondrial dysfunction in the etiology of psychiatric disease is a promising avenue to investigate further. Genetic analysis of mitochondrial activity is a cornerstone in understanding disease pathogenesis related to metabolic dysfunction. In concert with neuroimaging and pathological study, genetics provides an important bridge between biochemical findings and clinical correlates in psychiatric disease. Mitochondrial genetics has several unique aspects to its analysis, and corresponding special considerations. Here, we review the components of mitochondrial genetic analysis - nuclear DNA, mitochon-drial DNA, mitochondrial pathways, pseudogenes, nuclear-mitochondrial mismatch, and microRNAs - that could contribute to an observable clinical phenotype. Throughout, we highlight psychiatric diseases that can arise due to dysfunction in these processes, with a focus on schizophrenia and bipolar disorder.

The Energy Metabolism Dysfunction in Psychiatric Disorders Postmortem Brains: Focus on Proteomic Evidence

Psychiatric disorders represent a great medical and social challenge and people suffering from these conditions face many impairments regarding personal and professional life. In addition, a mental disorder will manifest itself in approximately one quarter of the world's population at some period of their life. Dysfunction in energy metabolism is one of the most consistent scientific findings associated with these disorders. With this is mind, this review compiled data on disturbances in energy metabolism found by proteomic analyses of postmortem brains collected from patients affected by the most prevalent psychiatric disorders: schizophrenia (SCZ), bipolar disorder (BPD), and major depressive disorder (MDD). We searched in the PubMed database to gather the studies and compiled all the differentially expressed proteins reported in each work. SCZ studies revealed 92 differentially expressed proteins related to energy metabolism, while 95 proteins were discovered in BPD, and 41 proteins in MDD. With the compiled data, it was possible to determine which proteins related to energy metabolism were found to be altered in all the disorders as well as which ones were altered exclusively in one of them. In conclusion, the information gathered in this work could contribute to a better understanding of the impaired metabolic mechanisms and hopefully bring insights into the underlying neuropathology of psychiatric disorders.

Mitochondrial multifaceted dysfunction in schizophrenia; complex I as a possible pathological target

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.

Gene environment interaction in periphery and brain converge to modulate behavioral outcomes: Insights from the SP1 transient early in life interference rat model

It is generally assumed that behavior results from an interaction between susceptible genes and environmental stimuli during critical life stages. The present article reviews the main theoretical and practical concepts in the research of gene environment interaction, emphasizing the need for models simulating real life complexity. We review a novel approach to study gene environment interaction in which a brief post-natal interference with the expression of multiple genes, by hindering the activity of the ubiquitous transcription factor specificity protein 1 (Sp1) is followed by later-in-life exposure of rats to stress. Finally, this review discusses the role of peripheral processes in behavioral responses, with the Sp1 model as one example demonstrating how specific behavioral patterns are linked to modulations in both peripheral and central physiological processes. We suggest that models, which take into account the tripartite reciprocal interaction between the central nervous system, peripheral systems and environmental stimuli will advance our understanding of the complexity of behavior.

Inflammation in schizophrenia: A question of balance

In the past decade, there has been renewed interest in immune/inflammatory changes and their associated oxidative/nitrosative consequences as key pathophysiological mechanisms in schizophrenia and related disorders. Both brain cell components (microglia, astrocytes, and neurons) and peripheral immune cells have been implicated in inflammation and the resulting oxidative/nitrosative stress (O&NS) in schizophrenia. Furthermore, down-regulation of endogenous antioxidant and anti-inflammatory mechanisms has been identified in biological samples from patients, although the degree and progression of the inflammatory process and the nature of its self-regulatory mechanisms vary from early onset to full-blown disease. This review focuses on the interactions between inflammation and O&NS, their damaging consequences for brain cells in schizophrenia, the possible origins of inflammation and increased O&NS in the disorder, and current pharmacological strategies to deal with these processes (mainly treatments with anti-inflammatory or antioxidant drugs as add-ons to antipsychotics).

The Neuro-Immune Pathophysiology of Central and Peripheral Fatigue in Systemic Immune-Inflammatory and Neuro-Immune Diseases

Many patients with systemic immune-inflammatory and neuro-inflammatory disorders, including depression, rheumatoid arthritis, systemic lupus erythematosus, Sjögren's disease, cancer, cardiovascular disorder, Parkinson's disease, multiple sclerosis, stroke, and chronic fatigue syndrome/myalgic encephalomyelitis, endure pathological levels of fatigue. The aim of this narrative review is to delineate the wide array of pathways that may underpin the incapacitating fatigue occurring in systemic and neuro-inflammatory disorders. A wide array of immune, inflammatory, oxidative and nitrosative stress (O&NS), bioenergetic, and neurophysiological abnormalities are involved in the etiopathology of these disease states and may underpin the incapacitating fatigue that accompanies these disorders. This range of abnormalities comprises: increased levels of pro-inflammatory cytokines, e.g., interleukin-1 (IL-1), IL-6, tumor necrosis factor (TNF) α and interferon (IFN) α; O&NS-induced muscle fatigue; activation of the Toll-Like Receptor Cycle through pathogen-associated (PAMPs) and damage-associated (DAMPs) molecular patterns, including heat shock proteins; altered glutaminergic and dopaminergic neurotransmission; mitochondrial dysfunctions; and O&NS-induced defects in the sodium-potassium pump. Fatigue is also associated with altered activities in specific brain regions and muscle pathology, such as reductions in maximum voluntary muscle force, downregulation of the mitochondrial biogenesis master gene peroxisome proliferator-activated receptor gamma coactivator 1-alpha, a shift to glycolysis and buildup of toxic metabolites within myocytes. As such, both mental and physical fatigue, which frequently accompany immune-inflammatory and neuro-inflammatory disorders, are the consequence of interactions between multiple systemic and central pathways.

Analysis of mitochondrial network by imaging: proof of technique in 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.

Transcriptome alterations of mitochondrial and coagulation function in schizophrenia by cortical sequencing analysis

Background

Transcriptome sequencing of brain samples provides detailed enrichment analysis of differential expression and genetic interactions for evaluation of mitochondrial and coagulation function of schizophrenia. It is implicated that schizophrenia genetic and protein interactions may give rise to biological dysfunction of energy metabolism and hemostasis. These findings may explain the biological mechanisms responsible for negative and withdraw symptoms of schizophrenia and antipsychotic-induced venous thromboembolism.

We conducted a comparison of schizophrenic candidate genes from literature reviews and constructed the schizophrenia-mediator network (SCZMN) which consists of schizophrenic candidate genes and associated mediator genes by applying differential expression analysis to BA22 RNA-Seq brain data. The network was searched against pathway databases such as PID, Reactome, HumanCyc, and Cell-Map. The candidate complexes were identified by MCL clustering using CORUM for potential pathogenesis of schizophrenia.

Results

Published BA22 RNA-Seq brain data of 9 schizophrenic patients and 9 controls samples were analyzed. The differentially expressed genes in the BA22 brain samples of schizophrenia are proposed as schizophrenia candidate marker genes (SCZCGs). The genetic interactions between mitochondrial genes and many under-expressed SCZCGs indicate the genetic predisposition of mitochondria dysfunction in schizophrenia. The biological functions of SCZCGs, as listed in the Pathway Interaction Database (PID), indicate that these genes have roles in DNA binding transcription factor, signal and cancer-related pathways, coagulation and cell cycle regulation and differentiation pathways.

In the query-query protein-protein interaction (QQPPI) network of SCZCGs, TP53, PRKACA, STAT3 and SP1 were identified as the central "hub" genes. Mitochondrial function was modulated by dopamine inhibition of respiratory complex I activity. The genetic interaction between mitochondria function and schizophrenia may be revealed by DRD2 linked to NDUFS7 through protein-protein interactions of FLNA and ARRB2.

The biological mechanism of signaling pathway of coagulation cascade was illustrated by the PPI network of the SCZCGs and the coagulation-associated genes. The relationship between antipsychotic target genes (DRD2/3 and HTR2A) and coagulation factor genes (F3, F7 and F10) appeared to cascade the following hemostatic process implicating the bottleneck of coagulation genetic network by the bridging of actin-binding protein (FLNA).

Conclusions

It is implicated that the energy metabolism and hemostatic process have important roles in the pathogenesis for schizophrenia. The cross-talk of genetic interaction by these co-expressed genes and reached candidate genes may address the key network in disease pathology. The accuracy of candidate genes evaluated from different quantification tools could be improved by crosstalk analysis of overlapping genes in genetic networks.

Increased SP4 and SP1 transcription factor expression in the postmortem hippocampus of chronic schizophrenia

Altered levels of transcription factor specificity protein 4 (SP4) and 1 (SP1) in the cerebellum, prefrontal cortex and/or lymphocytes have been reported in severe psychiatric disorders, including early psychosis, bipolar disorder, and chronic schizophrenia subjects who have undergone long-term antipsychotic treatments. SP4 transgenic mice show altered hippocampal-dependent psychotic-like behaviours and altered development of hippocampal dentate gyrus. Moreover, NMDAR activity regulates SP4 function. The aim of this study was to investigate SP4 and SP1 expression levels in the hippocampus in schizophrenia, and the possible effect of antipsychotics and NMDAR blockade on SP protein levels in rodent hippocampus. We analysed SP4 and SP1 expression levels in the postmortem hippocampus of chronic schizophrenia (n = 14) and control (n = 11) subjects by immunoblot and quantitative RT-PCR. We tested the effect of NMDAR blockade on SP factors in the hippocampus of mouse treated with an acute dose of MK801. We also investigated the effect of subacute treatments with haloperidol and clozapine on SP protein levels in the rat hippocampus. We report that SP4 protein and both SP4 and SP1 mRNA expression levels are significantly increased in the hippocampus in chronic schizophrenia. Likewise, acute treatment with MK801 increased both SP4 and SP1 protein levels in mouse hippocampus. In contrast, subacute treatment with haloperidol and clozapine did not significantly alter SP protein levels in rat hippocampus. These results suggest that SP4 and SP1 upregulation may be part of the mechanisms deregulated downstream of glutamate signalling pathways in schizophrenia and might be contributing to the hippocampal-dependent cognitive deficits of the disorder.

Genetic variant in NDUFS1 gene is associated with schizophrenia and negative symptoms in Han Chinese

Abnormalities in mitochondrial complex I, which is responsible for controlling mitochondrial function, have been implicated in a variety of diseases associated with mitochondrial dysfunction, potentially including schizophrenia. The NADH dehydrogenase Fe-S protein 1 (NDUFS1) is the largest subunit of complex I. To explore whether the encoding NDUFS1 gene confers susceptibility to schizophrenia or is associated with the severity of typical symptoms of schizophrenia, we recruited 519 stable schizophrenia patients receiving clozapine treatment and 594 healthy controls for genotyping to investigate the association of four selected tagging single-nucleotide polymorphisms (SNPs) of NDUFS1 and both schizophrenia risk and symptom severity. The severity of psychotic symptoms was evaluated using the Positive and Negative Syndrome Scale and then tested for association with the four SNPs. The SNP rs1044120 showed significant association with schizophrenia (adjusted P=0.032). The frequency of the G allele of rs1044120 was significantly higher in patients than among the healthy controls (adjusted P=0.008). Stratification by sex revealed a significant association between the rs1044120 polymorphism and schizophrenia among males (adjusted P=0.036 and 0.008 in genotypic and allelic comparisons, respectively). We also observed a significant difference in the negative symptom scores among the three genotypes among these males (adjusted P=0.036). Post hoc comparisons showed that rs1044120 G/G carriers had higher negative symptom scores than those with G/T and T/T carriers (raw P=0.035 and 0.005, respectively). Our findings suggest that NDUFS1 may confer susceptibility to schizophrenia in male subjects, acting as a causative factor for the severity of negative symptoms in schizophrenia.

Mitochondrial dysfunction in schizophrenia: an evolutionary perspective

Schizophrenia (SCZ) is a severe psychiatric illness with a lifetime prevalence of 0.4 %. A disturbance of energy metabolism has been suggested as part of the etiopathogenesis of the disorder. Several lines of evidence have proposed a connection between etiopathogenesis of SCZ and human brain evolution, which was characterized by an increase in the energy requirement, demanding a co-evolution of the mitochondrial system. Mitochondria are key players in brain energy homeostasis and multiple lines of evidence suggest that the system is disrupted in SCZ. In this review, we will describe the current knowledge on pathways/system involved in the human brain evolution as well as the main theories regarding the evolutionary origin of SCZ. We will furthermore discuss the role of mitochondria in the context of brain energy metabolism and its role in the etiopathogenesis of SCZ. Understanding SCZ in the context of human brain evolution opens a new perspective to elucidate pathophysiological mechanisms involved in the origin and/or portions of the complex symptomatology of this severe mental disorder.

Assessment of cytochrome C oxidase dysfunction in the substantia nigra/ventral tegmental area in schizophrenia

Perturbations in metabolism are a well-documented but complex facet of schizophrenia pathology. Optimal cellular performance requires the proper functioning of the electron transport chain, which is constituted by four enzymes located within the inner membrane of mitochondria. These enzymes create a proton gradient that is used to power the enzyme ATP synthase, producing ATP, which is crucial for the maintenance of cellular functioning. Anomalies in a single enzyme of the electron transport chain are sufficient to cause disruption of cellular metabolism. The last of these complexes is the cytochrome c oxidase (COX) enzyme, which is composed of thirteen different subunits. COX is a major site for oxidative phosphorylation, and anomalies in this enzyme are one of the most frequent causes of mitochondrial pathology. The objective of the present report was to assess if metabolic anomalies linked to COX dysfunction may contribute to substantia nigra/ventral tegmental area (SN/VTA) pathology in schizophrenia. We tested COX activity in postmortem SN/VTA from schizophrenia and non-psychiatric controls. We also tested the protein expression of key subunits for the assembly and activity of the enzyme, and the effect of antipsychotic medication on subunit expression. COX activity was not significantly different between schizophrenia and non-psychiatric controls. However, we found significant decreases in the expression of subunits II and IV-I of COX in schizophrenia. Interestingly, these decreases were observed in samples containing the entire rostro-caudal extent of the SN/VTA, while no significant differences were observed for samples containing only mid-caudal regions of the SN/VTA. Finally, rats chronically treated with antipsychotic drugs did not show significant changes in COX subunit expression. These findings suggest that COX subunit expression may be compromised in specific sub-regions of the SN/VTA (i.e. rostral regions), which may lead to a faulty assembly of the enzyme and a greater vulnerability to metabolic insult.

Reduced expression of SP1 and SP4 transcription factors in peripheral blood mononuclear cells in first-episode psychosis

Alterations of transcription factor specificity protein 4 (SP4) and 1 (SP1) have been linked to different neuropsychiatric diseases. Reduced SP4 and SP1 protein levels in the prefrontal cortex have been associated with bipolar disorder and schizophrenia, respectively, suggesting that both factors could be involved in the pathogenesis of disorders with psychotic features. The aim of this study was to investigate whether the reduction of SP1, SP4 and SP3 protein and mRNA expression in peripheral blood mononuclear cells in the early stages of psychosis may act as a potential biomarker of these disorders. A cross-sectional study of first-episode psychosis patients (n = 14) compared to gender- and age-matched healthy controls (n = 14) was designed. Patients were recruited through the adult mental health services of Parc Sanitari Sant Joan de Déu. Protein and gene expression levels of SP1, SP4 and SP3 were assessed in peripheral blood mononuclear cells of patients with first-episode psychosis and healthy control subjects. We report that protein levels of SP1 and SP4, but not SP3, are significantly reduced in patients compared to controls. In contrast, we did not observe any differences in expression levels for SP1, SP4 or SP3 genes between patient and control groups. In patients, SP4 protein levels were significantly associated with SP1 protein levels. No association was found, however, between protein and gene expression levels for each factor. Our study shows reduced SP1 and SP4 protein levels in first-episode psychosis in lymphocytes, suggesting that these transcription factors are potential peripheral biomarkers of psychotic spectrum disorders in the early stages.

Mitochondrial activity and oxidative stress markers in peripheral blood mononuclear cells of patients with bipolar disorder, schizophrenia, and healthy subjects

Evidence suggests that mitochondrial dysfunction is involved in the pathophysiology of psychiatric disorders such as schizophrenia (SZ) and bipolar disorder (BD). However, the exact mechanisms underlying this dysfunction are not well understood. Impaired activity of electron transport chain (ETC) complexes has been described in these disorders and may reflect changes in mitochondrial metabolism and oxidative stress markers. The objective of this study was to compare ETC complex activity and protein and lipid oxidation markers in 12 euthymic patients with BD type I, in 18 patients with stable chronic SZ, and in 30 matched healthy volunteers. Activity of complexes I, II, and III was determined by enzyme kinetics of mitochondria isolated from peripheral blood mononuclear cells (PBMCs). Protein oxidation was evaluated using the protein carbonyl content (PCC) method, and lipid peroxidation, the thiobarbituric acid reactive substances (TBARS) assay kit. A significant decrease in complex I activity was observed (p = 0.02), as well as an increase in plasma levels of TBARS (p = 0.00617) in patients with SZ when compared to matched controls. Conversely, no significant differences were found in complex I activity (p = 0.17) or in plasma TBARS levels (p = 0.26) in patients with BD vs. matched controls. Our results suggest that mitochondrial complex I dysfunction and oxidative stress play important roles in the pathophysiology of SZ and may be used in potential novel adjunctive therapy for SZ, focusing primarily on cognitive impairment and disorder progression.

Abnormal neuronal differentiation and mitochondrial dysfunction in hair follicle-derived induced pluripotent stem cells of schizophrenia patients

One of the prevailing hypotheses suggests schizophrenia as a neurodevelopmental disorder, involving dysfunction of dopaminergic and glutamatergic systems. Accumulating evidence suggests mitochondria as an additional pathological factor in schizophrenia. An attractive model to study processes related to neurodevelopment in schizophrenia is reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) and differentiating them into different neuronal lineages. iPSCs from three schizophrenia patients and from two controls were reprogrammed from hair follicle keratinocytes, because of their accessibility and common ectodermal origin with neurons. iPSCs were differentiated into Pax6(+)/Nestin(+) neural precursors and then further differentiated into β3-Tubulin(+)/tyrosine hydroxylase(+)/DAT(+) dopaminergic neurons. In addition, iPSCs were differentiated through embryonic bodies into β3-Tubulin(+)/Tbox brain1(+) glutamatergic neurons. Schizophrenia-derived dopaminergic cells showed severely impaired ability to differentiate, whereas glutamatergic cells were unable to maturate. Mitochondrial respiration and its sensitivity to dopamine-induced inhibition were impaired in schizophrenia-derived keratinocytes and iPSCs. Moreover, we observed dissipation of mitochondrial membrane potential (Δψm) and perturbations in mitochondrial network structure and connectivity in dopaminergic along the differentiation process and in glutamatergic cells. Our data unravel perturbations in neural differentiation and mitochondrial function, which may be interconnected, and of relevance to dysfunctional neurodevelopmental processes in schizophrenia.

Mitochondrial DNA (mtDNA) in brain samples from patients with major psychiatric disorders: gene expression profiles, mtDNA content and presence of the mtDNA common deletion

Several lines of evidence support a mitochondrial dysfunction in major psychiatric disorders. The objective of this study was to determine whether mitochondrial DNA (mtDNA) expression or content are implicated in the mitochondrial dysfunction observed in schizophrenia (SCH), bipolar disorder (BD), and major depressive disorder (MDD). MtDNA gene expression and mtDNA content (including the MT-ND4 deletion) were measured by RT-qPCR and qPCR, respectively. Post-mortem brain tissue from 60 subjects, divided evenly into four diagnostic groups (SCH, BD, MDD, and control (C)), was analyzed. MT-ND1 gene expression was significantly increased in the BD group compared with the C group. MDD and SCH patients showed a similar pattern of mtDNA expression, which was different from that in BD patients. Similarly, a larger number of MDD and SCH patients tended to have the MT-ND4 gene deleted compared with BD and C subjects. However, no other significant differences were observed in mtDNA gene expression and mtDNA content. Notably, high variability was observed in the mtDNA gene expression and content in each diagnostic group. Previous studies and the present work provide evidence for a role of mtDNA in SCH, BD and MDD. However, further studies with larger patient and control groups as well as by analyzing distinct brain regions are needed to elucidate the role of mtDNA in major psychiatric disorders.

NMDA receptor hypofunction induces dysfunctions of energy metabolism and semaphorin signaling in rats: a synaptic proteome study

There is considerable evidence to suggest that aberrations of synapse connectivity contribute to the pathophysiology of schizophrenia and that N-methyl-D-aspartate (NMDA) receptor-mediated glutamate transmission is especially important. Administration of MK-801 ([+]-5-methyl-10, 11-dihydro-5H-dibenzo-[a, d]-cycloheptene-5, 10-iminehydrogenmaleate) induces hypofunction of NMDA receptors in rats, which are widely used as a model for schizophrenia. We investigated synaptosomal proteome expression profiling of the cerebral cortex of MK-801-treated Sprague-Dawley rats using the 2-dimensional difference gel electrophoresis method, and 49 differentially expression proteins were successfully identified using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight/Time-of-Flight mass spectrometry. We carried out a literature search for further confirmation of subsynaptic locations and to explore the relevance to the diseases of differentially expressed proteins. Ingenuity Pathways Analysis (IPA) was used to further examine the underlying relationship between the changed proteins. The network encompassing "cell morphology, cell-to-cell signaling and interaction, nervous system development and function" was found to be significantly altered in the MK-801-treated rats. "Energy metabolism" and "semaphorin signaling in neurons" are the most significant IPA canonical pathways to be affected by MK-801 treatment. Using western blots, we confirmed the differential expression of Camk2a, Crmp2, Crmp5, Dnm1, and Ndufs3 in both synaptosome proteins and total proteins in the cerebral cortex of the rats. Our study identified the change and/or response of the central nervous transmission system under the stress of NMDA hypofunction, underlining the importance of the synaptic function in schizophrenia.

Modeling mitochondrial dysfunctions in the brain: from mice to men

The biologist Lewis Thomas once wrote: "my mitochondria comprise a very large proportion of me. I cannot do the calculation, but I suppose there is almost as much of them in sheer dry bulk as there is the rest of me". As humans, or indeed as any mammal, bird, or insect, we contain a specific molecular makeup that is driven by vast numbers of these miniscule powerhouses residing in most of our cells (mature red blood cells notwithstanding), quietly replicating, living independent lives and containing their own DNA. Everything we do, from running a marathon to breathing, is driven by these small batteries, and yet there is evidence that these molecular energy sources were originally bacteria, possibly parasitic, incorporated into our cells through symbiosis. Dysfunctions in these organelles can lead to debilitating, and sometimes fatal, diseases of almost all the bodies' major organs. Mitochondrial dysfunction has been implicated in a wide variety of human disorders either as a primary cause or as a secondary consequence. To better understand the role of mitochondrial dysfunction in human disease, a multitude of pharmacologically induced and genetically manipulated animal models have been developed showing to a greater or lesser extent the clinical symptoms observed in patients with known and unknown causes of the disease. This review will focus on diseases of the brain and spinal cord in which mitochondrial dysfunction has been proven or is suspected and on animal models that are currently used to study the etiology, pathogenesis and treatment of these diseases.

Mitochondria and reactive oxygen species. Which role in physiology and pathology?

Oxidative stress is among the major causes of toxicity due to interaction of Reactive Oxygen Species (ROS) with cellular macromolecules and structures and interference with signal transduction pathways. The mitochondrial respiratory chain, specially from Complexes I and III, is considered the main origin of ROS particularly under conditions of high membrane potential, but several other sources may be important for ROS generation, such as mitochondrial p66(Shc), monoamine oxidase, α-ketoglutarate dehydogenase, besides redox cycling of redox-active molecules. ROS are able to oxidatively modify lipids, proteins, carbohydrates and nucleic acids in mitochondria and to activate/inactivate signalling pathways by oxidative modification of redox-active factors. Cells are endowed with several defence mechanisms including repair or removal of damaged molecules, and antioxidant systems, either enzymatic or non-enzymatic. Oxidative stress is at the basis of ageing and many pathological disorders, such as ischemic diseases, neurodegenerative diseases, diabetes, and cancer, although the underlying mechanisms are not always completely understood.

Proteomics as a tool for understanding schizophrenia

Schizophrenia is likely to be a multifactorial disorder, consequence of alterations in gene and protein expression since the neurodevelopment that together to environmental factors will trigger the establishment of the disease. In the post-genomic era, proteomics has emerged as a promising strategy for revealing disease and treatment biomarkers as well as a tool for the comprehension of the mechanisms of schizophrenia pathobiology. Here, there is a discussion of the potential pathways and structures that are compromised in schizophrenia according to proteomic findings while studying five distinct brain regions of post-mortem tissue from schizophrenia patients and controls. Proteins involved in energy metabolism, calcium homeostasis, myelinization, and cytoskeleton have been recurrently found to be differentially expressed in schizophrenia brains. These findings may encourage new studies on the understanding of schizophrenia biochemical pathways and even new potential drug targets.

Striatal mitochondria in subjects with chronic undifferentiated vs. chronic paranoid schizophrenia

Schizophrenia (SZ) is a heterogeneous disease with a spectrum of symptoms, risk factors, and etiology. Abnormalities in mitochondria, the energy-producing organelles of the cell, have been observed in mixed cohorts of subjects with SZ. The purpose of the present study was to determine if striatal mitochondria were differentially affected in two different DSM-IV subgroups of SZ. Postmortem striatal tissue was examined from normal controls (NC), chronic paranoid SZs (SZP), and chronic undifferentiated SZs (SZU). Tissue was processed for calbindin immunohistochemistry to identify striosomal compartments, prepared for electron microscopy and analyzed using stereological methods. In both caudate and putamen, the density of mitochondria in the neuropil was decreased in SZP compared to both NCs and SZU. In the putamen, both the SZP and the SZU subgroups had fewer mitochondria per synapse than did NCs. When examining patch matrix compartments, striatal compartments associated with different circuitry and function, only the matrix exhibited changes. In the caudate matrix, the SZP subgroup had fewer mitochondria in the neuropil than did the SZU and NCs. In the putamen matrix, the SZP had fewer mitochondria in the neuropil as compared to NCs, but not the SZU. The numbers of mitochondria per synapse in both the SZP and the SZU groups were similar to each other and fewer than that of NCs. A decrease in mitochondrial density in the neuropil distinguishes the SZP from the SZU subgroup, which could be associated with the symptoms of paranoia and/or could represent a protective mechanism against some of the symptoms that are less pronounced in this subtype than in the SZU subgroup such as cognitive and emotional deficits.

Oxidative stress in schizophrenia: pathogenetic and therapeutic implications

Over a century, a wide-ranging variety of pathophysiological models and causal hypotheses have been conceptualized for schizophrenia. One among these is the role for free radical-mediated pathology in schizophrenia, indicating impaired antioxidant defense system (AODS) and presence of oxidative stress in patients with schizophrenia. For the past two decades, the whole investigative domain of AODS and oxidative stress has broadened to include the wider AODS components, direct central nervous system assays of AODS, chemical imaging studies, proteomics, genetics of AODS, and, of importance to sufferers of schizophrenia, antioxidant therapeutics. These are some of the perspectives that are reviewed by several articles in this Forum. Overall, there has been growing recognition of the importance of oxidative stress in the pathophysiology of schizophrenia and in treatment-related side effects. The totality of the evidence from biochemistry, metabolomics, proteomics, genetics, and in vivo brain imaging points to the presence of multifarious abnormalities in the AODS and redox signaling in schizophrenia.

The role of energy metabolism dysfunction and oxidative stress in schizophrenia revealed by proteomics

Schizophrenia is a psychiatric illness that affects approximately 30 million people worldwide. Converging lines of evidence suggest that mitochondrial function may be compromised in this disorder, and this can lead to perturbations in calcium buffering, oxidative phosphorylation, increased production of reactive oxygen species, and apoptotic factors, which can, in turn, affect neuronal processes such as neurotransmitter synthesis and synaptic plasticity. Proteomics studies in brain and peripheral tissues of schizophrenia patients have provided considerable evidence and identified biomarker fingerprints corresponding to such pathways. Here we review the results of these studies with a focus on the biomarker pattern depicting alterations in energy metabolism and oxidative stress in this debilitating illness.

Connectivity between mitochondrial functions and psychiatric disorders

Mitochondria provide most of the energy production in cells. They are involved in the regulation of free radicals, calcium buffering, and redox signaling and take part in the intrinsic pathway of apoptosis. Mutations or polymorphisms of mitochondrial DNA, mitochondria-mediated oxidative stress, decrease of adenosine triphosphate production, changes of intracellular calcium and oxidative stress are concerned in various diseases. There is increasing evidence that impaired functions of mitochondria are associated with mood disorders. It is suggested that disturbed energetic metabolism and/or reactive oxygen species production take part in the pathophysiology of mood disorders and could participate in the therapeutic effects or side-effects of antidepressants and mood stabilizers.

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.

Synaptic mitochondria in synaptic transmission and organization of vesicle pools in health and disease

Cell types rich in mitochondria, including neurons, display a high energy demand and a need for calcium buffering. The importance of mitochondria for proper neuronal function is stressed by the occurrence of neurological defects in patients suffering from a great variety of diseases caused by mutations in mitochondrial genes. Genetic and pharmacological evidence also reveal a role of these organelles in various aspects of neuronal physiology and in the pathogenesis of neurodegenerative disorders. Yet the mechanisms by which mitochondria can affect neurotransmission largely remain to be elucidated. In this review we focus on experimental data that suggest a critical function of synaptic mitochondria in the function and organization of synaptic vesicle pools, and in neurotransmitter release during intense neuronal activity. We discuss how calcium handling, ATP production and other mitochondrial mechanisms may influence synaptic vesicle pool organization and synaptic function. Given the link between synaptic mitochondrial function and neuronal communication, efforts toward better understanding mitochondrial biology may lead to novel therapeutic approaches of neurological disorders including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and psychiatric disorders that are at least in part caused by mitochondrial deficits.