Superoxide, neuroleptics and the ubiquinone and cytochrome b5 reductases in brain and lymphocytes from normals and schizophrenic patients

Schizophrenia Synaptic Pathology and Antipsychotic Treatment in the Framework of Oxidative and Mitochondrial Dysfunction: Translational Highlights for the Clinics and Treatment

Schizophrenia is a worldwide mental illness characterized by alterations at dopaminergic and glutamatergic synapses resulting in global dysconnectivity within and between brain networks. Impairments in inflammatory processes, mitochondrial functions, energy expenditure, and oxidative stress have been extensively associated with schizophrenia pathophysiology. Antipsychotics, the mainstay of schizophrenia pharmacological treatment and all sharing the common feature of dopamine D2 receptor occupancy, may affect antioxidant pathways as well as mitochondrial protein levels and gene expression. Here, we systematically reviewed the available evidence on antioxidants' mechanisms in antipsychotic action and the impact of first- and second-generation compounds on mitochondrial functions and oxidative stress. We further focused on clinical trials addressing the efficacy and tolerability of antioxidants as an augmentation strategy of antipsychotic treatment. EMBASE, Scopus, and Medline/PubMed databases were interrogated. The selection process was conducted in respect of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. Several mitochondrial proteins involved in cell viability, energy metabolism, and regulation of oxidative systems were reported to be significantly modified by antipsychotic treatment with differences between first- and second-generation drugs. Finally, antioxidants may affect cognitive and psychotic symptoms in patients with schizophrenia, and although the evidence is only preliminary, the results indicate that further studies are warranted.

Mitochondria DNA copy number, mitochondria DNA total somatic deletions, Complex I activity, synapse number, and synaptic mitochondria number are altered in schizophrenia and bipolar disorder

Mitochondrial dysfunction is a neurobiological phenomenon implicated in the pathophysiology of schizophrenia and bipolar disorder that can synergistically affect synaptic neurotransmission. We hypothesized that schizophrenia and bipolar disorder share molecular alterations at the mitochondrial and synaptic levels. Mitochondria DNA (mtDNA) copy number (CN), mtDNA common deletion (CD), mtDNA total deletion, complex I activity, synapse number, and synaptic mitochondria number were studied in the postmortem human dorsolateral prefrontal cortex (DLPFC), superior temporal gyrus (STG), primary visual cortex (V1), and nucleus accumbens (NAc) of controls (CON), and subjects with schizophrenia (SZ), and bipolar disorder (BD). The results showed (i) the mtDNA CN is significantly higher in DLPFC of both SZ and BD, decreased in the STG of BD, and unaltered in V1 and NAc of both SZ and BD; (ii) the mtDNA CD is significantly higher in DLPFC of BD while unaltered in STG, V1, and NAc of both SZ and BD; (iii) The total deletion burden is significantly higher in DLPFC in both SZ and BD while unaltered in STG, V1, and NAc of SZ and BD; (iv) Complex I activity is significantly lower in DLPFC of both SZ and BD, which is driven by the presence of medications, with no alteration in STG, V1, and NAc. In addition, complex I protein concentration, by ELISA, was decreased across three cortical regions of SZ and BD subjects; (v) The number of synapses is decreased in DLPFC of both SZ and BD, while the synaptic mitochondria number was significantly lower in female SZ and female BD compared to female controls. Overall, these findings will pave the way to understand better the pathophysiology of schizophrenia and bipolar disorder for therapeutic interventions.

Recent Reports on Redox Stress-Induced Mitochondrial DNA Variations, Neuroglial Interactions, and NMDA Receptor System in Pathophysiology of Schizophrenia

Schizophrenia (SZ) is a chronic psychiatric disorder affecting several people worldwide. Mitochondrial DNA (mtDNA) variations could invoke changes in the OXPHOS system, calcium buffering, and ROS production, which have significant implications for glial cell survival during SZ. Oxidative stress has been implicated in glial cells-mediated pathogenesis of SZ; the brain comparatively more prone to oxidative damage through NMDAR. A confluence of scientific evidence points to mtDNA alterations, Nrf2 signaling, dynamic alterations in dorsolateral prefrontal cortex (DLPFC), and provocation of oxidative stress that enhance pathophysiology of SZ. Furthermore, the alterations in excitatory signaling related to NMDAR signaling were particularly reported for SZ pathophysiology. Current review reported the recent evidence for the role of mtDNA variations and oxidative stress in relation to pathophysiology of SZ, NMDAR hypofunction, and glutathione deficiency. NMDAR system is influenced by redox dysregulation in oxidative stress, inflammation, and antioxidant mediators. Several studies have demonstrated the relationship of these variables on severity of pathophysiology in SZ. An extensive literature search was conducted using Medline, PubMed, PsycINFO, CINAHL PLUS, BIOSIS Preview, Google scholar, and Cochrane databases. We summarize consistent evidence pointing out a plausible model that may elucidate the crosstalk between mtDNA alterations in glial cells and redox dysregulation during oxidative stress and the perturbation of NMDA neurotransmitter system during current therapeutic modalities for the SZ treatment. This review can be beneficial for the development of promising novel diagnostics, and therapeutic modalities by ascertaining the mtDNA variations, redox state, and efficacy of pharmacological agents to mitigate redox dysregulation and augment NMDAR function to treat cognitive and behavioral symptoms in SZ.

Oxidative Stress in Autism Spectrum Disorder-Current Progress of Mechanisms and Biomarkers

Autism spectrum disorder (ASD) is a type of neurodevelopmental disorder that has been diagnosed in an increasing number of children around the world. Existing data suggest that early diagnosis and intervention can improve ASD outcomes. However, the causes of ASD remain complex and unclear, and there are currently no clinical biomarkers for autism spectrum disorder. More mechanisms and biomarkers of autism have been found with the development of advanced technology such as mass spectrometry. Many recent studies have found a link between ASD and elevated oxidative stress, which may play a role in its development. ASD is caused by oxidative stress in several ways, including protein post-translational changes (e.g., carbonylation), abnormal metabolism (e.g., lipid peroxidation), and toxic buildup [e.g., reactive oxygen species (ROS)]. To detect elevated oxidative stress in ASD, various biomarkers have been developed and employed. This article summarizes recent studies about the mechanisms and biomarkers of oxidative stress. Potential biomarkers identified in this study could be used for early diagnosis and evaluation of ASD intervention, as well as to inform and target ASD pharmacological or nutritional treatment interventions.

The role of mitochondria in the pathophysiology of schizophrenia: A critical review of the evidence focusing on mitochondrial complex one

There has been increasing interest in the role of mitochondrial dysfunction in the pathophysiology of schizophrenia. Mitochondrial complex one (MCI) dysfunction may represent a mechanism linking bioenergetic impairment with the alterations in dopamine signalling, glutamatergic dysfunction, and oxidative stress found in the disorder. New lines of evidence from novel approaches make it timely to review evidence for mitochondrial involvement in schizophrenia, with a specific focus on MCI. The most consistent findings in schizophrenia relative to controls are reductions in expression of MCI subunits in post-mortem brain tissue (Cohen's d> 0.8); reductions in MCI function in post-mortem brains (d> 0.7); and reductions in neural glucose utilisation (d= 0.3 to 0.6). Antipsychotics may affect glucose utilisation, and, at least in vitro, affect MC1. The findings overall are consistent with MCI dysfunction in schizophrenia, but also highlight the need for in vivo studies to determine the link between MCI dysfunction and symptoms in patients. If new imaging tools confirm MCI dysfunction in the disease, this could pave the way for new treatments targeting this enzyme.

Microsomal reductase activity in patients with thyroid neoplasms

OBJECTIVE

Cytochrome b5-reductase (CYB5R) and cytochrome P450 reductase (CYPOR) are important for cell metabolism; however, their role in thyroid hormonogenesis and carcinogenesis has not been elucidated yet. The activity of CYB5R correlates with the metastasis in breast cancer, but there are no similar studies for CYB5R and CYPOR for thyroid tumors. The aim of this study was to elucidate the activity of CYB5R and CYPOR changes in benign euthyroid and hyperthyroid neoplasms and in papillary thyroid cancer for their potential application as biomarkers for diagnosis and prognosis prediction of thyroid cancer.

METHODS

Thirty-six patients with thyroid diseases participated in the study. The control euthyroid nodular goiter group included ten patients; the thyrotoxic nodular or diffuse goiter group included 14 patients; the papillary thyroid cancer T1-2N0-1M0 (PTC) group included 12 patients. The activity of CYB5R and CYPOR was assessed with lucigenin-enhanced chemiluminescence stimulated by NADH and NADPH, respectively.

RESULTS

Compared to the control euthyroid nodular goiter group, activity of CYB5R and CYPOR increased ~5 and 10 times, respectively, in toxic goiter, and 15 and 30 times, respectively, in half of cases of PTC. The change in activity of CYPOR was more pronounced compared to CYB5R. Within the PTC group, the subgroups with low and high activities of microsomal reductases were identified. Microsomal reductases in follicular adenoma was 2-4-fold less active compared to the euthyroid nodular goiter and the low-activity PTC group.

CONCLUSIONS

Activity of tissue microsomal reductases varies in thyroid pathology and can be considered as a promising biomarker for differential diagnostics of benign and malignant thyroid tumors.

Interactions of zinc- and redox-signaling pathways

Zinc and cellular oxidants such as reactive oxygen species (ROS) each participate in a multitude of physiological functions. There is considerable overlap between the affected events, including signal transduction. While there is no obvious direct connection between zinc and ROS, mainly because the bivalent cation zinc does not change its oxidation state in biological systems, these are linked by their interaction with sulfur, forming the remarkable triad of zinc, ROS, and protein thiols. First, zinc binds to reduced thiols and can be released upon oxidation. Thereby, redox signals are translated into changes in the free zinc concentration, which can act as zinc signals. Second, zinc affects oxidation of thiols in several ways, directly as well as indirectly. A protein incorporating many of these interactions is metallothionein (MT), which is rich in cysteine and capable of binding up to seven zinc ions in its fully reduced state. Zinc binding is diminished after (partial) oxidation, while thiols show increased reactivity in the absence of bound metal ions. Adding still more complexity, the MT promoter is controlled by zinc (via metal regulatory transcription factor 1 (MTF-1)) as well as redox (via nuclear factor erythroid 2-related factor 2 (NRF2)). Many signaling cascades that are important for cell proliferation or apoptosis contain protein thiols, acting as centers for crosstalk between zinc- and redox-signaling. A prominent example for shared molecular targets for zinc and ROS are active site cysteine thiols in protein tyrosine phosphatases (PTP), their activity being downregulated by oxidation as well as zinc binding. Because zinc binding also protects PTP thiols form irreversible oxidation, there is a multi-faceted reciprocal interaction, illustrating that zinc- and redox-signaling are intricately linked on multiple levels.

The homeostatic role of hydrogen peroxide, superoxide anion and nitric oxide in the vasculature

Reactive oxygen and nitrogen species are produced in a wide range of physiological reactions that, at low concentrations, play essential roles in living organisms. There is a delicate equilibrium between formation and degradation of these mediators in a healthy vascular system, which contributes to maintaining these species under non-pathological levels to preserve normal vascular functions. Antioxidants scavenge reactive oxygen and nitrogen species to prevent or reduce damage caused by excessive oxidation. However, an excessive reductive environment induced by exogenous antioxidants may disrupt redox balance and lead to vascular pathology. This review summarizes the main aspects of free radical biochemistry (formation, sources and elimination) and the crucial actions of some of the most biologically relevant and well-characterized reactive oxygen and nitrogen species (hydrogen peroxide, superoxide anion and nitric oxide) in the physiological regulation of vascular function, structure and angiogenesis. Furthermore, current preclinical and clinical evidence is discussed on how excessive removal of these crucial responses by exogenous antioxidants (vitamins and related compounds, polyphenols) may perturb vascular homeostasis. The aim of this review is to provide information of the crucial physiological roles of oxidation in the endothelium, vascular smooth muscle cells and perivascular adipose tissue for developing safer and more effective vascular interventions with antioxidants.

Reactive Oxygen Species and Oxidative Stress in the Pathogenesis and Progression of Genetic Diseases of the Connective Tissue

Connective tissue is known to provide structural and functional “glue” properties to other tissues. It contains cellular and molecular components that are arranged in several dynamic organizations. Connective tissue is the focus of numerous genetic and nongenetic diseases. Genetic diseases of the connective tissue are minority or rare, but no less important than the nongenetic diseases. Here we review the impact of reactive oxygen species (ROS) and oxidative stress on the onset and/or progression of diseases that directly affect connective tissue and have a genetic origin. It is important to consider that ROS and oxidative stress are not synonymous, although they are often closely linked. In a normal range, ROS have a relevant physiological role, whose levels result from a fine balance between ROS producers and ROS scavenge enzymatic systems. However, pathology arises or worsens when such balance is lost, like when ROS production is abnormally and constantly high and/or when ROS scavenge (enzymatic) systems are impaired. These concepts apply to numerous diseases, and connective tissue is no exception. We have organized this review around the two basic structural molecular components of connective tissue: The ground substance and fibers (collagen and elastic fibers).

Psychiatric drugs impact mitochondrial function in brain and other tissues

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

ROS Generation and Antioxidant Defense Systems in Normal and Malignant Cells

Reactive oxygen species (ROS) are by-products of normal cell activity. They are produced in many cellular compartments and play a major role in signaling pathways. Overproduction of ROS is associated with the development of various human diseases (including cancer, cardiovascular, neurodegenerative, and metabolic disorders), inflammation, and aging. Tumors continuously generate ROS at increased levels that have a dual role in their development. Oxidative stress can promote tumor initiation, progression, and resistance to therapy through DNA damage, leading to the accumulation of mutations and genome instability, as well as reprogramming cell metabolism and signaling. On the contrary, elevated ROS levels can induce tumor cell death. This review covers the current data on the mechanisms of ROS generation and existing antioxidant systems balancing the redox state in mammalian cells that can also be related to tumors.

Dopamine perturbation of gene co-expression networks reveals differential response in schizophrenia for translational machinery

The dopaminergic hypothesis of schizophrenia (SZ) postulates that positive symptoms of SZ, in particular psychosis, are due to disturbed neurotransmission via the dopamine (DA) receptor D2 (DRD2). However, DA is a reactive molecule that yields various oxidative species, and thus has important non-receptor-mediated effects, with empirical evidence of cellular toxicity and neurodegeneration. Here we examine non-receptor-mediated effects of DA on gene co-expression networks and its potential role in SZ pathology. Transcriptomic profiles were measured by RNA-seq in B-cell transformed lymphoblastoid cell lines from 514 SZ cases and 690 controls, both before and after exposure to DA ex vivo (100 μM). Gene co-expression modules were identified using Weighted Gene Co-expression Network Analysis for both baseline and DA-stimulated conditions, with each module characterized for biological function and tested for association with SZ status and SNPs from a genome-wide panel. We identified seven co-expression modules under baseline, of which six were preserved in DA-stimulated data. One module shows significantly increased association with SZ after DA perturbation (baseline: P = 0.023; DA-stimulated: P = 7.8 × 10^-5; ΔAIC = -10.5) and is highly enriched for genes related to ribosomal proteins and translation (FDR = 4 × 10^-141), mitochondrial oxidative phosphorylation, and neurodegeneration. SNP association testing revealed tentative QTLs underlying module co-expression, notably at FASTKD2 (top P = 2.8 × 10^-6), a gene involved in mitochondrial translation. These results substantiate the role of translational machinery in SZ pathogenesis, providing insights into a possible dopaminergic mechanism disrupting mitochondrial function, and demonstrates the utility of disease-relevant functional perturbation in the study of complex genetic etiologies.

Mitochondrial function in individuals at clinical high risk for psychosis

Alterations in mitochondrial function have been implicated in the etiology of schizophrenia. Most studies have investigated alterations in mitochondrial function in patients in which the disorder is already established; however, whether mitochondrial dysfunction predates the onset of psychosis remains unknown. We measured peripheral mitochondrial complex (I–V) function and lactate/pyruvate levels in 27 antipsychotic-naïve individuals at clinical high risk for psychosis (CHR) and 16 healthy controls. We also explored the association between mitochondrial function and brain microglial activation and glutathione levels using a translocator protein 18 kDa [¹⁸F]FEPPA PET scan and ¹H-MRS scan, respectively. There were no significant differences in mitochondrial complex function and lactate/pyruvate levels between CHR and healthy controls. In the CHR group, mitochondrial complex III function (r = −0.51, p = 0.008) and lactate levels (r = 0.61, p = 0.004) were associated with prodromal negative symptoms. As previously reported, there were no significant differences in microglial activation and glutathione levels between groups, however, mitochondrial complex IV function was inversely related to microglial activation in the hippocampus in CHR (r = −0.42, p = 0.04), but not in healthy controls. In conclusion, alterations in mitochondrial function are not yet evident in CHR, but may relate to the severity of prodromal symptoms, particularly negative symptoms.

Neuropsychiatric Features in Primary Mitochondrial Disease

Mitochondrial diseases are a clinically heterogeneous group of disorders that ultimately result from dysfunction of the mitochondrial respiratory chain. There is some evidence to suggest that mitochondrial dysfunction plays a role in neuropsychiatric illness; however, the data are inconclusive. This article summarizes the available literature published in the area of neuropsychiatric manifestations in both children and adults with primary mitochondrial disease, with a focus on autism spectrum disorder in children and mood disorders and schizophrenia in adults.

Mitochondrial Oxidative Phosphorylation System (OXPHOS) Deficits in Schizophrenia: Possible Interactions with Cellular Processes

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.

Mitochondrial reactive oxygen species and inflammation: Molecular mechanisms, diseases and promising therapies

Over the last few decades, many different groups have been engaged in studies of new roles for mitochondria, particularly the coupling of alterations in the redox pathway with the inflammatory responses involved in different diseases, including Alzheimer's disease, Parkinson's disease, atherosclerosis, cerebral cavernous malformations, cystic fibrosis and cancer. Mitochondrial dysfunction is important in these pathological conditions, suggesting a pivotal role for mitochondria in the coordination of pro-inflammatory signaling from the cytosol and signaling from other subcellular organelles. In this regard, mitochondrial reactive oxygen species are emerging as perfect liaisons that can trigger the assembly and successive activation of large caspase-1- activating complexes known as inflammasomes. This review offers a glimpse into the mechanisms by which inflammasomes are activated by mitochondrial mechanisms, including reactive oxygen species production and mitochondrial Ca²⁺ uptake, and the roles they can play in several inflammatory pathologies.

The Role of Mitochondrial Reactive Oxygen Species in Cardiovascular Injury and Protective Strategies

Ischaemia/reperfusion (I/R) injury of the heart represents a major health burden mainly associated with acute coronary syndromes. While timely coronary reperfusion has become the established routine therapy in patients with ST-elevation myocardial infarction, the restoration of blood flow into the previously ischaemic area is always accompanied by myocardial injury. The central mechanism involved in this phenomenon is represented by the excessive generation of reactive oxygen species (ROS). Besides their harmful role when highly generated during early reperfusion, minimal ROS formation during ischaemia and/or at reperfusion is critical for the redox signaling of cardioprotection. In the past decades, mitochondria have emerged as the major source of ROS as well as a critical target for cardioprotective strategies at reperfusion. Mitochondria dysfunction associated with I/R myocardial injury is further described and ultimately analyzed with respect to its role as source of both deleterious and beneficial ROS. Furthermore, the contribution of ROS in the highly investigated field of conditioning strategies is analyzed. In the end, the vascular sources of mitochondria-derived ROS are briefly reviewed.

Comparative Pharmacology of Risperidone and Paliperidone

Antipsychotics, risperidone, and risperidone’s active metabolite, paliperidone (9-hydroxyrisperidone), are related molecules used for the treatment of schizophrenia and related disorders. Differences in receptor binding, 5-HT_2A/D₂ (serotonin/dopamine) binding ratios, and mitochondrial proteomics suggest that the effects of risperidone and paliperidone on neuronal firing, regulation of mitochondrial function, and movement are different. This review seeks to explore the most significant differences at the molecular level between risperidone and paliperidone, as reported in preclinical studies. Although risperidone shows higher affinity for 5-HT receptors, paliperidone does not fit this profile. Thus, the risperidone 5-HT_2A/D₂ binding ratio is significantly lower than the paliperidone 5-HT_2A/D₂ binding ratio. Paliperidone, similar to lithium and valproate, affects expression levels and phosphorylation of complex I and V proteins in synaptoneurosomal preparations of rat prefrontal cortex, suggesting that paliperidone behaves as a mood stabilizer. It is apparent that the presence of a hydroxyl group in the paliperidone molecule confers increased hydrophilicity to this drug compared with its parent, risperidone; thus, this contributes to differential effects on mitochondrial movement, protein expression, and phosphorylation. These differences are reflected in synaptic plasticity and neuronal firing and have only recently been implicated in the mechanisms of mitochondrial function and movement.

Reactive oxygen species and energy machinery: an integrated dynamic model

The role of several important reactive oxygen species (ROS) on the Krebs cycle, the electron transport chain (ETC) and the two important shuttles has been modelled. Major part of the ROS is produced during oxygen reduction in the ETC, which has been kinetically simulated, and the changes in the final concentrations of several important metabolites were found. The simulation is based on chemical kinetics equation, and the associated set of differential equations was solved by the ordinary differential equation package in Octave. The validity of the model is checked by comparing the experimental results available in the literature with the simulations when a part of the ETC is blocked (80%) in the script. The present approach is versatile and flexible and has potential applications in various simulations. It is easy to study the change in concentrations of various metabolites when a particular enzyme or pathway is blocked (say by a drug). The Octave script is presented in the text.

Mitochondria: Much ado about nothing? How dangerous is reactive oxygen species production?

For more than 50 years, reactive oxygen species have been considered as harmful agents, which can attack proteins, lipids or nucleic acids. In order to deal with reactive oxygen species, there is a sophisticated system developed in mitochondria to prevent possible damage. Indeed, increased reactive oxygen species levels contribute to pathomechanisms in several human diseases, either by its impaired defense system or increased production of reactive oxygen species. However, in the last two decades, the importance of reactive oxygen species in many cellular signaling pathways has been unraveled. Homeostatic levels were shown to be necessary for correct differentiation during embryonic expansion of stem cells. Although the mechanism is still not fully understood, we cannot only regard reactive oxygen species as a toxic by-product of mitochondrial respiration anymore.

This article is part of a Directed Issue entitled: Energy Metabolism Disorders and Therapies.

Mitochondrial reactive oxygen species (ROS) and ROS-induced ROS release

Byproducts of normal mitochondrial metabolism and homeostasis include the buildup of potentially damaging levels of reactive oxygen species (ROS), Ca(2+), etc., which must be normalized. Evidence suggests that brief mitochondrial permeability transition pore (mPTP) openings play an important physiological role maintaining healthy mitochondria homeostasis. Adaptive and maladaptive responses to redox stress may involve mitochondrial channels such as mPTP and inner membrane anion channel (IMAC). Their activation causes intra- and intermitochondrial redox-environment changes leading to ROS release. This regenerative cycle of mitochondrial ROS formation and release was named ROS-induced ROS release (RIRR). Brief, reversible mPTP opening-associated ROS release apparently constitutes an adaptive housekeeping function by the timely release from mitochondria of accumulated potentially toxic levels of ROS (and Ca(2+)). At higher ROS levels, longer mPTP openings may release a ROS burst leading to destruction of mitochondria, and if propagated from mitochondrion to mitochondrion, of the cell itself. The destructive function of RIRR may serve a physiological role by removal of unwanted cells or damaged mitochondria, or cause the pathological elimination of vital and essential mitochondria and cells. The adaptive release of sufficient ROS into the vicinity of mitochondria may also activate local pools of redox-sensitive enzymes involved in protective signaling pathways that limit ischemic damage to mitochondria and cells in that area. Maladaptive mPTP- or IMAC-related RIRR may also be playing a role in aging. Because the mechanism of mitochondrial RIRR highlights the central role of mitochondria-formed ROS, we discuss all of the known ROS-producing sites (shown in vitro) and their relevance to the mitochondrial ROS production in vivo.

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.

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.

Antioxidants as potential therapeutics for neuropsychiatric disorders

Oxidative stress has been implicated in the pathophysiology of many neuropsychiatric disorders such as schizophrenia, bipolar disorder, major depression etc. Both genetic and non-genetic factors have been found to cause increased cellular levels of reactive oxygen species beyond the capacity of antioxidant defense mechanism in patients of psychiatric disorders. These factors trigger oxidative cellular damage to lipids, proteins and DNA, leading to abnormal neural growth and differentiation. Therefore, novel therapeutic strategies such as supplementation with antioxidants can be effective for long-term treatment management of neuropsychiatric disorders. The use of antioxidants and PUFAs as supplements in the treatment of neuropsychiatric disorders has provided some promising results. At the same time, one should be cautious with the use of antioxidants since excessive antioxidants could dangerously interfere with some of the protective functions of reactive oxygen species. The present article will give an overview of the potential strategies and outcomes of using antioxidants as therapeutics in psychiatric disorders.

Meta-analysis of oxidative stress in schizophrenia

BACKGROUND

Schizophrenia is associated with impaired antioxidant defense, including abnormal serum, plasma, and red blood cell (RBC) oxidative stress parameters. We performed a meta-analysis of these associations, considering the effect of clinical status and antipsychotic treatment after an acute exacerbation of psychosis.

METHODS

We identified articles by searching PubMed, PsychInfo, and Institute for Scientific Information, and the reference lists of identified studies.

RESULTS

Forty-four studies met the inclusion criteria. Total antioxidant status seemed to be a state marker, because levels were significantly decreased in cross-sectional studies of serum and plasma in first-episode psychosis (FEP) and significantly increased in longitudinal studies of antipsychotic treatment for acute exacerbations of psychosis (p < .01 for each). The RBC catalase and plasma nitrite seemed to be state-related markers, because levels in cross-sectional studies were significantly decreased in FEP (p < .01) and significantly increased in stable outpatients (p = .01). In contrast, RBC superoxide dismutase seemed to be a trait marker for schizophrenia, because levels in cross-sectional studies were significantly decreased in acutely relapsed inpatients, FEP, and stable outpatients (p < .01 for each).

CONCLUSIONS

Oxidative stress abnormalities in FEP suggest an effect that might be independent of antipsychotic medications. Although some parameters (total antioxidant status, RBC catalase, and plasma nitrite) might be state markers for acute exacerbations of psychosis, others (RBC superoxide dismutase) might be trait markers; however, more longitudinal studies are needed. Our findings suggest that oxidative stress might serve as a potential biomarker in the etiopathophysiology and clinical course of schizophrenia.

New model of action for mood stabilizers: phosphoproteome from rat pre-frontal cortex synaptoneurosomal preparations

Background

Mitochondrial short and long-range movements are necessary to generate the energy needed for synaptic signaling and plasticity. Therefore, an effective mechanism to transport and anchor mitochondria to pre- and post-synaptic terminals is as important as functional mitochondria in neuronal firing. Mitochondrial movement range is regulated by phosphorylation of cytoskeletal and motor proteins in addition to changes in mitochondrial membrane potential. Movement direction is regulated by serotonin and dopamine levels. However, data on mitochondrial movement defects and their involvement in defective signaling and neuroplasticity in relationship with mood disorders is scarce. We have previously reported the effects of lithium, valproate and a new antipsychotic, paliperidone on protein expression levels at the synaptic level.

Hypothesis

Mitochondrial function defects have recently been implicated in schizophrenia and bipolar disorder. We postulate that mood stabilizer treatment has a profound effect on mitochondrial function, synaptic plasticity, mitochondrial migration and direction of movement.

Methods

Synaptoneurosomal preparations from rat pre-frontal cortex were obtained after 28 daily intraperitoneal injections of lithium, valproate and paliperidone. Phosphorylated proteins were identified using 2D-DIGE and nano LC-ESI tandem mass spectrometry.

Results

Lithium, valproate and paliperidone had a substantial and common effect on the phosphorylation state of specific actin, tubulin and myosin isoforms as well as other proteins associated with neurofilaments. Furthermore, different subunits from complex III and V of the electron transfer chain were heavily phosphorylated by treatment with these drugs indicating selective phosphorylation.

Conclusions

Mood stabilizers have an effect on mitochondrial function, mitochondrial movement and the direction of this movement. The implications of these findings will contribute to novel insights regarding clinical treatment and the mode of action of these drugs.

Mitochondria-ros crosstalk in the control of cell death and aging

Reactive oxygen species (ROS) are highly reactive molecules, mainly generated inside mitochondria that can oxidize DNA, proteins, and lipids. At physiological levels, ROS function as “redox messengers” in intracellular signalling and regulation, whereas excess ROS induce cell death by promoting the intrinsic apoptotic pathway. Recent work has pointed to a further role of ROS in activation of autophagy and their importance in the regulation of aging. This review will focus on mitochondria as producers and targets of ROS and will summarize different proteins that modulate the redox state of the cell. Moreover, the involvement of ROS and mitochondria in different molecular pathways controlling lifespan will be reported, pointing out the role of ROS as a “balance of power,” directing the cell towards life or death.

Perturbation in mitochondrial network dynamics and in complex I dependent cellular respiration in schizophrenia

BACKGROUND

Mitochondria have been suggested to be involved in the pathology of bipolar disorder (BD) and schizophrenia. However, the mechanism underlying mitochondrial dysfunction is unclear. Mitochondrial network dynamics, which reflects cellular metabolic state, is important for embryonic development, synapse formation, and neurodegeneration. This study aimed to investigate mitochondrial network dynamics and its plausible association with abnormal cellular oxygen consumption in schizophrenia.

METHODS

Viable Epstein-Barr virus (EBV)-transformed lymphocytes (lymphoblastoids) from DSM-IV diagnosed patients with schizophrenia (n = 17), BD (n = 15), and healthy control subjects (n = 15) were assessed for mitochondrial respiration, mitochondrial dynamics, and relevant protein levels by oxygraph, confocal microscopy, and immunoblotting, respectively.

RESULTS

Respiration of schizophrenia-derived lymphoblastoids was significantly lower compared with control subjects, and was twice as sensitive to dopamine (DA)-induced inhibition. Unlike DA, haloperidol inhibited complex I-driven respiration to a similar extent in both schizophrenia and the control cells. Both drugs interact with complex I but at different sites. At the site of DA interaction, we found alterations in protein levels of three subunits of complex I in schizophrenia. In addition, we observed structural and connectivity perturbations in the mitochondrial network, associated with alterations in the profusion protein OPA1, which was similarly reduced in schizophrenia prefrontal cortex specimens. None of these alterations were observed in the BD cells, which were similar to control cells.

CONCLUSIONS

We show impaired mitochondrial network dynamics associated with reduced cellular respiration and complex I abnormalities in schizophrenia but not in BD. If these findings represent disease-specific alterations, they may become an endophenotype biomarker for schizophrenia.

Altered interactions of tryptophan metabolites in first-episode neuroleptic-naive patients with schizophrenia

Schizophrenia is characterized by complex and dynamically interacting perturbations in multiple neurochemical systems. In the past, evidence for these alterations has been collected piecemeal, limiting our understanding of the interactions among relevant biological systems. Earlier, both hyper- and hyposerotonemia were variously associated with the longitudinal course of schizophrenia, suggesting a disturbance in the central serotonin (5-hydroxytryptamine (5-HT)) function. Using a targeted electrochemistry-based metabolomics platform, we compared metabolic signatures consisting of 13 plasma tryptophan (Trp) metabolites simultaneously between first-episode neuroleptic-naive patients with schizophrenia (FENNS, n=25) and healthy controls (HC, n=30). We also compared these metabolites between FENNS at baseline (BL) and 4 weeks (4w) after antipsychotic treatment. N-acetylserotonin was increased in FENNS-BL compared with HC (P=0.0077, which remained nearly significant after Bonferroni correction). N-acetylserotonin/Trp and melatonin (Mel)/serotonin ratios were higher, and Mel/N-acetylserotonin ratio was lower in FENNS-BL (all P-values<0.0029), but not after treatment, compared with HC volunteers. All three groups had highly significant correlations between Trp and its metabolites, Mel, kynurenine, 3-hydroxykynurenine and tryptamine. However, in the HC, but in neither of the FENNS groups, serotonin was highly correlated with Trp, Mel, kynurenine or tryptamine, and 5-hydroxyindoleacetic acid (5HIAA) was highly correlated with Trp, Mel, kynurenine or 3-hydroxykynurenine. A significant difference between HC and FENNS-BL was further shown only for the Trp-5HIAA correlation. Thus, some metabolite interactions within the Trp pathway seem to be altered in the FENNS-BL patients. Conversion of serotonin to N-acetylserotonin by serotonin N-acetyltransferase may be upregulated in FENNS patients, possibly related to the observed alteration in Trp-5HIAA correlation. Considering N-acetylserotonin as a potent antioxidant, such increases in N-acetylserotonin might be a compensatory response to increased oxidative stress, implicated in the pathogenesis of schizophrenia.

Expression analyses of the mitochondrial complex I 75-kDa subunit in early onset schizophrenia and autism spectrum disorder: increased levels as a potential biomarker for early onset schizophrenia

Searching for a peripheral biological marker for schizophrenia, we previously reported on elevated mitochondrial complex I 75-kDa subunit mRNA-blood concentrations in early onset schizophrenia (EOS). The aim of this study was to further evaluate the utility of this gene as a potential marker for schizophrenia. Both-schizophrenia and autism-are suggested to be neuronal maldevelopmental disorders with reports of mitochondrial dysfunction and increased oxidative stress. Therefore we have investigated the expression levels of mitochondrial complex I 75-kDa subunit mRNA in whole blood of children with autistic spectrum disorder (ASD) and a group of adolescent acute first-episode EOS patients in comparison to matched controls. We have found that compared to the respective controls only the group of EOS patients-and not the ASD group-showed a significantly altered expression of the complex I 75-kDa subunit mRNA. Although further studies are necessary to test for the specificity of this marker, our findings point to the potential use of the mitochondrial complex I as a biomarker for schizophrenia.

Homeostatic imbalance of purine catabolism in first-episode neuroleptic-naïve patients with schizophrenia

BACKGROUND

Purine catabolism may be an unappreciated, but important component of the homeostatic response of mitochondria to oxidant stress. Accumulating evidence suggests a pivotal role of oxidative stress in schizophrenia pathology.

METHODOLOGY/PRINCIPAL FINDINGS

Using high-pressure liquid chromatography coupled with a coulometric multi-electrode array system, we compared 6 purine metabolites simultaneously in plasma between first-episode neuroleptic-naïve patients with schizophrenia (FENNS, n = 25) and healthy controls (HC, n = 30), as well as between FENNS at baseline (BL) and 4 weeks (4w) after antipsychotic treatment. Significantly higher levels of xanthosine (Xant) and lower levels of guanine (G) were seen in both patient groups compared to HC subjects. Moreover, the ratios of G/guanosine (Gr), uric acid (UA)/Gr, and UA/Xant were significantly lower, whereas the ratio of Xant/G was significantly higher in FENNS-BL than in HC. Such changes remained in FENNS-4w with exception that the ratio of UA/Gr was normalized. All 3 groups had significant correlations between G and UA, and Xan and hypoxanthine (Hx). By contrast, correlations of UA with each of Xan and Hx, and the correlation of Xan with Gr were all quite significant for the HC but not for the FENNS. Finally, correlations of Gr with each of UA and G were significant for both HC and FENNS-BL but not for the FENNS-4w.

CONCLUSIONS/SIGNIFICANCE

During purine catabolism, both conversions of Gr to G and of Xant to Xan are reversible. Decreased ratios of product to precursor suggested a shift favorable to Xant production from Xan, resulting in decreased UA levels in the FENNS. Specifically, the reduced UA/Gr ratio was nearly normalized after 4 weeks of antipsychotic treatment. In addition, there are tightly correlated precursor and product relationships within purine pathways; although some of these correlations persist across disease or medication status, others appear to be lost among FENNS. Taken together, these results suggest that the potential for steady formation of antioxidant UA from purine catabolism is altered early in the course of illness.

The interplay between mitochondrial complex I, dopamine and Sp1 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.

A comparative proteomics analysis of rat mitochondria from the cerebral cortex and hippocampus in response to antipsychotic medications

An increasing number of experiments have found anomalies in mitochondria in the brains of psychotics, which suggests that mitochondrial dysfunction or abnormal cerebral energy metabolism might play an important role in the pathophysiology of schizophrenia (SCZ). We adopted a proteomic approach to identify the differential effects on the cerebral cortex and hippocampus mitochondrial protein expression of Sprague-Dawley (SD) rats by comparing exposure to typical and atypical antipsychotic medications. Differential mitochondrial protein expressions were assessed using two-dimensional (2D) gel electrophoresis for three groups with Chlorpromazine (CPZ), Clozapine (CLZ), quetiapine (QTP) and a control group. A total of 14 proteins, of which 6 belong to the respiratory electron transport chain (ETC) of oxidative phosphorylation (OXPHOS), showed significant changes in quantity including NADH dehydrogenase (ubiquinone) 1 alpha subcomplex 10 (Ndufa10), NADH dehydrogenase (ubiquinone) flavoprotein 2 (Ndufv2), NADH dehydrogenase (ubiquinone) Fe-S protein 3 (Ndufs3), F1-ATPase beta subunit (Atp5b), ATPase, H+ transporting, lysosomal, beta 56/58 kDa, isoform 2 (Atp6v1b2) and ATPase, H+ transporting, V1 subunit A, isoform 1 (Atp6v1a1). The differential proteins subjected to 2D were assessed for levels of mRNA using quantitative real time PCR (Q-RT-PCR), and we also made partial use of Western blotting for assessing differential expression. The results of our study may help to explain variations in SD rats as well as in human response to antipsychotic drugs. In addition, they should improve our understanding of both the curative effects and side effects of antipsychotics and encourage new directions in SCZ research.

NAD(P)H- and superoxide-dependent nitric oxide degradation by rat liver mitochondria

Mitochondria consume nitric oxide (NO) mainly through reaction with superoxide anion (O(2)(-)). Here, we analyzed the O(2)(-) sources for NO degradation by isolated rat liver mitochondria. Electron leakage from complex III and reverse electron transport to complex I accounted for O(2)(-)-dependent NO degradation by mitochondria in the presence of a protonmotive force. Mitochondria incubated with NAD(P)H also presented intense O(2)(-) generation and NO degradation rates that were insensitive to respiratory inhibitors and abolished after proteinase treatment. These results suggest that an outer membrane-localized NAD(P)H oxidase activity, in addition to the electron leakage from the respiratory chain, promotes O(2)(-)-dependent NO degradation in rat liver mitochondria.

Mitochondrial complex I as a novel target for intraneuronal DA: modulation of respiration in intact cells

Accumulating evidence suggests a role for mitochondria in synaptic potentiation and neurotransmission as well as in morphogenesis and plasticity of spines and synapses. However, studies investigating the ability of neurotransmitters to reciprocally affect mitochondrial function are sparse. In the present study we investigated whether dopamine can affect mitochondrial function in intact neuronal cells. We have shown that short- or long-term exposure of human neuroblastoma SH-SY5Y cells to dopamine (DA) inhibited mitochondrial respiration. This inhibition was associated with an increase in DA intracellular levels, and was prevented by the DA membrane transporter inhibitors, cocaine and GBR-12909. DA inhibited respiration driven through complex I but not through complexes II or III, in line with DA ability to specifically inhibit complex I activity in mitochondrial preparations. The effect of DA on complex I was not associated with altered expression of three subunits of complex I, which were formerly reported abnormal in DA-related pathologies. DA effects on respiration were not due to its ability to form reactive oxygen species. Antipsychotic drugs, which compete with DA on its receptors and inhibit complex I activity, also decreased complex I driven mitochondrial respiration. These findings may suggest that DA, which is taken up by neurons, can affect mitochondria and thereby neurotransmission and synaptic plasticity. Such a mechanism may be of relevance to DA-related non-degenerative pathologies such as schizophrenia.

Mitochondrial variants in schizophrenia, bipolar disorder, and major depressive disorder

Background

Mitochondria provide most of the energy for brain cells by the process of oxidative phosphorylation. Mitochondrial abnormalities and deficiencies in oxidative phosphorylation have been reported in individuals with schizophrenia (SZ), bipolar disorder (BD), and major depressive disorder (MDD) in transcriptomic, proteomic, and metabolomic studies. Several mutations in mitochondrial DNA (mtDNA) sequence have been reported in SZ and BD patients.

Methodology/Principal Findings

Dorsolateral prefrontal cortex (DLPFC) from a cohort of 77 SZ, BD, and MDD subjects and age-matched controls (C) was studied for mtDNA sequence variations and heteroplasmy levels using Affymetrix mtDNA resequencing arrays. Heteroplasmy levels by microarray were compared to levels obtained with SNaPshot and allele specific real-time PCR. This study examined the association between brain pH and mtDNA alleles. The microarray resequencing of mtDNA was 100% concordant with conventional sequencing results for 103 mtDNA variants. The rate of synonymous base pair substitutions in the coding regions of the mtDNA genome was 22% higher (p = 0.0017) in DLPFC of individuals with SZ compared to controls. The association of brain pH and super haplogroup (U, K, UK) was significant (p = 0.004) and independent of postmortem interval time.

Conclusions

Focusing on haplogroup and individual susceptibility factors in psychiatric disorders by considering mtDNA variants may lead to innovative treatments to improve mitochondrial health and brain function.

Prominent synaptic and metabolic abnormalities revealed by proteomic analysis of the dorsolateral prefrontal cortex in schizophrenia and bipolar disorder

There is evidence for both similarity and distinction in the presentation and molecular characterization of schizophrenia and bipolar disorder. In this study, we characterized protein abnormalities in the dorsolateral prefrontal cortex in schizophrenia and bipolar disorder using two-dimensional gel electrophoresis. Tissue samples were obtained from 35 individuals with schizophrenia, 35 with bipolar disorder and 35 controls. Eleven protein spots in schizophrenia and 48 in bipolar disorder were found to be differentially expressed (P<0.01) in comparison to controls, with 7 additional spots found to be altered in both diseases. Using mass spectrometry, 15 schizophrenia-associated proteins and 51 bipolar disorder-associated proteins were identified. The functional groups most affected included synaptic proteins (7 of the 15) in schizophrenia and metabolic or mitochondrial-associated proteins (25 of the 51) in bipolar disorder. Six of seven synaptic-associated proteins abnormally expressed in bipolar disorder were isoforms of the septin family, while two septin protein spots were also significantly differentially expressed in schizophrenia. This finding represented the largest number of abnormalities from one protein family. All septin protein spots were upregulated in disease in comparison to controls. This study provides further characterization of the synaptic pathology present in schizophrenia and of the metabolic dysfunction observed in bipolar disorder. In addition, our study has provided strong evidence implicating the septin protein family of proteins in psychiatric disorders for the first time.

Neuroanatomical pattern of mitochondrial complex I pathology varies between schizophrenia, bipolar disorder and major depression

Background

Mitochondrial dysfunction was reported in schizophrenia, bipolar disorderand major depression. The present study investigated whether mitochondrial complex I abnormalities show disease-specific characteristics.

Methodology/Principal Findings

mRNA and protein levels of complex I subunits NDUFV1, NDUFV2 and NADUFS1, were assessed in striatal and lateral cerebellar hemisphere postmortem specimens and analyzed together with our previous data from prefrontal and parieto-occipital cortices specimens of patients with schizophrenia, bipolar disorder, major depression and healthy subjects. A disease-specific anatomical pattern in complex I subunits alterations was found. Schizophrenia-specific reductions were observed in the prefrontal cortex and in the striatum. The depressed group showed consistent reductions in all three subunits in the cerebellum. The bipolar group, however, showed increased expression in the parieto-occipital cortex, similar to those observed in schizophrenia, and reductions in the cerebellum, yet less consistent than the depressed group.

Conclusions/Significance

These results suggest that the neuroanatomical pattern of complex I pathology parallels the diversity and similarities in clinical symptoms of these mental disorders.

Mitochondrial complex I subunits are altered in rats with neonatal ventral hippocampal damage but not in rats exposed to oxygen restriction at neonatal age

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.

Up-regulation of ADM and SEPX1 in the lymphoblastoid cells of patients in monozygotic twins discordant for schizophrenia

The contribution of genetic factors to schizophrenia is well established and recent studies have indicated several strong candidate genes. However, the pathophysiology of schizophrenia has not been totally elucidated yet. To date, studies of monozygotic twins discordant for schizophrenia have provided insight into the pathophysiology of this illness; this type of study can exclude inter-individual variability and confounding factors such as effects of drugs. In this study we used DNA microarray analysis to examine the mRNA expression patterns in the lymphoblastoid (LB) cells derived from two pairs of monozygotic twins discordant for schizophrenia. From five independent replicates for each pair of twins, we selected five genes, which included adrenomedullin (ADM) and selenoprotein X1 (SEPX1), as significantly changed in both twins with schizophrenia. Interestingly, ADM was previously reported to be up-regulated in both the LB cells and plasma of schizophrenic patients, and SEPX1 was included in the list of genes up-regulated in the peripheral blood cells of schizophrenia patients by microarray analysis. Then, we performed a genetic association study of schizophrenia in the Japanese population and examined the copy number variations, but observed no association. These findings suggest the possible role of ADM and SEPX1 as biomarkers of schizophrenia. The results also support the usefulness of gene expression analysis in LB cells of monozygotic twins discordant for an illness.

Dopamine modulates mitochondrial function in viable SH-SY5Y cells possibly via its interaction with complex I: relevance to dopamine pathology in schizophrenia

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 (delta psi 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 Km=122.1+/-28.6 nM and Vmax=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.

Long-term antipsychotic treatments and crossover studies in rats: differential effects of typical and atypical agents on the expression of antioxidant enzymes and membrane lipid peroxidation in rat brain

Short-term (<45 days) treatment studies in rats have reported increased oxidative stress and oxidative (i.e., oxygen free radical-mediated) neural cell injury with typical antipsychotics such as haloperidol, but not with the atypicals such as clozapine, olanzapine or risperidone. However, now these and several other atypical antipsychotics that differ in their neurotransmitter receptor affinity profiles are being used for a long-term treatment of schizophrenia. Therefore, understanding of their long-term treatment effects on the expression of antioxidant enzymes and oxidative neural cell injury in rats may be important to explain the possible differential mechanisms underlying their long-term clinical and side effects profiles. The effect of 90 and 180 day exposure to haloperidol (HAL, 2mg/kg/day), a representative typical antipsychotic was compared to exposure to chlorpromazine (CPZ, 10mg/kg/day), ziprasidone (ZIP, 12mg/kg/day), risperidone (RISP, 2.5mg/kg/day), clozapine (CLOZ, 20mg/kg/day) or olanzapine (OLZ, 10mg/kg/day) on the expression of antioxidant defense enzymes and levels of lipid peroxidation in the rat brain. The drug-induced effects on various antioxidant defense enzymes; manganese-superoxide dismutase (MnSOD), copper-zinc superoxide dismutase (CuZnSOD) and catalase (CAT) were assessed by determination of their enzymatic activity and protein content. Immunohistochemical analysis was also carried out to assess the cellular levels of MnSOD and CuZnSOD and cellular morphology. The oxidative membrane damage was assessed by determination of levels of the lipid peroxidation product, hydroxyalkanals (HAEs) in the rat brain. Both 90 and 180 days of HAL treatment very significantly decreased the levels of MnSOD (50%) and CuZnSOD (80%) and increased the levels of HAEs compared to vehicle treatment. Smaller reduction was found in CAT (25%) and no change in the glutathione peroxidase (GSHPx). The levels of enzymatic activity correlated generally well with the levels of enzyme protein indicating that the changes were in the expression of net protein. Though atypical antipsychotics like ZIP, RISP and OLZ did not show any change in the HAEs levels up to 90 days, further treatment up to 180 days resulted in significantly increased levels of HAEs in CPZ, ZIP and RISP, but not in OLZ treated rats. Post-treatment with several atypical antipsychotics (OLZ=CLOZ>RISP) for 90 days after 90 day of HAL treatment significantly restored the HAL-induced loss in MnSOD and CuZnSOD activities and increase in lipid peroxidation products as well as cellular morphology. These data may be very helpful in planning long-term use as well as switch over of these antipsychotics for the management of schizophrenia.

Cerebral glucose utilization and platelet mitochondrial complex I activity in schizophrenia: A FDG-PET study

Altered cerebral energy metabolism and mitochondrial dysfunction in periphery and in brain are implicated in the pathophysiology of schizophrenia. This study investigated whether cerebral glucose metabolism (rCGM) abnormalities are linked to altered mitochondrial complex I activity in the periphery, in schizophrenia. Sixteen schizophrenic patients, 8 with total positive PANSS score >or=20 (high positive schizophrenics; HPS), and 8 with total positive score <or=12 (low positive schizophrenics; LPS), and 8 healthy subjects, were analyzed for their complex I activity in platelets mitochondria and underwent FDG-PET scans at rest. Complex I activity was significantly increased only in HPS and was positively correlated with positive PANSS scores. Images were spatially normalized to an SPM template, their intensities normalized based on average brain activity. Hypermetabolism was observed in the basal ganglia, thalamus, amygdala, and brainstem of both patient groups compared with controls, and in LPS patients extended to parts of cerebellum, left and right cingulate gyrus, parietal and frontal lobes. rCGM in basal ganglia and thalamus significantly and positively correlated with complex I activity in the HPS. In the LPS, a negative correlation was identified in the cerebellum and brainstem. In the control group, however, no areas demonstrated significant positive or negative correlation. These results suggest that the correlation between peripheral complex I activity and rCGM in regions implicated in schizophrenia, could be a pathological factor that is differentially expressed in subgroups of schizophrenic patients.

The ultrastructure of lymphocytes in schizophrenia

OBJECTIVE

Replicated abnormalities in schizophrenia include decreased cellular immunity. The aim of the study was to verify whether there are some abnormalities in the ultrastructure of lymphocytes in drug-free schizophrenic patients.

METHOD

Fifty-nine in-patients with paranoid schizophrenia (DSM-IV 295.30) and 31 normal controls were used. Psychosis severity was assessed by the PANSS psychotic cluster. Electron microscopy and morphometric methods were applied to estimate the frequency and ultrastructural parameters of small, large, large activated lymphocytes (LAL) (containing 10 and more mitochondria) and of atypical lymphocytes (lymphoblasts, LB).

RESULTS

The frequency of small lymphocytes in schizophrenic patients was lower and that of large lymphocytes, LAL and LB was higher than in controls (all p= < 0.01). The volume density (Vv) of mitochondria in LAL in individuals with schizophrenia was lower than in controls (p<0.05), correlated negatively with the frequency of LB, Vv and number of lysosomes in LB (all p<0.01) and with the psychosis severity (p<0.05). In schizophrenic patients a trend towards positive correlations between the frequency of LB and psychosis severity were found (p<0.07).

CONCLUSION

The data suggest that the excess of LB in schizophrenic patients is associated with the dysfunction of energy metabolism in LAL, and these abnormalities are related to schizophrenia.