Red blood cell nitric oxide levels in patients with schizophrenia

The relationship between neuropsychiatric disorders and aging: A review on telomere length, oxidative stress, and inflammation

Aging is the group of time-independent changes that occur in an organism and that ultimately end in death. The relationship between aging and neuropsychiatric disorders is complex. Not only does the incidence of several neuropsychiatric disorders rise with age, but also these disorders are linked with premature mortality and are even thought to be syndromes of accelerated biological aging. Oxidative stress, inflammation and telomere length are factors commonly used to assess biological aging. The purpose of this review is to sum up the existing information about the state of those factors in schizophrenia, depression, bipolar disorder and anxiety disorders, and to summarize the effects of treatment on telomere length in patients with those neuropsychiatric disorders. The main focus, however, is on telomere length seeing the highly controversial study results on this biomarker in neuropsychiatric disorders. There is no scientific consensus on the state of those factors in the mentioned neuropsychiatric disorders or on the effects of treatment on telomere length, thus further research is needed where confounding variables are controlled. Regarding telomere length, it is highly important to explore whether short telomeres lead to the development of neuropsychiatric disorders or vice versa, as it carries huge clinical potential.

Importance of oxidative stress in the pathogenesis, diagnosis, and monitoring of patients with neuropsychiatric disorders, a review

Oxidative stress is defined as the persistent imbalance between the activity of toxic reactive forms of both oxygen and nitrogen and the antioxidant defense. In low concentrations, they are essential for the proper functioning of the body. Still, their excessive amount contributes to the damage of the biomolecules, consequently leading to various pathologies of the organism. Due to the lipid-rich brain structure, enormous oxygen consumption, and the lack of a sufficient antioxidant barrier make it highly susceptible to oxidative imbalance. Hence, oxidative stress has been linked to various psychiatric disorders. These diseases include all behavioral, emotional, and cognitive abnormalities associated with a significant impediment to social life. Each of the diseases in question: Alzheimer's disease, schizophrenia, depression, and bipolar disorder, is characterized by excessive oxidative stress. Considerable damages to DNA, RNA, proteins, lipids, and mitochondrial dysfunction, are observed. All conditions show increased lipid peroxidation, which appears to be typical of psychiatric disorders because the brain contains large amounts of these types of molecules. In addition, numerous abnormalities in the antioxidant defense are noted, but the results of studies on the activity of antioxidant enzymes differ significantly. The most promising biomarkers seem to be GSH in Alzheimer's disease as an early-stage marker of the disease and thioredoxin in schizophrenia as a marker for therapy monitoring. Data from the literature are consistent with the decrease in antioxidants such as vitamin C, E, uric acid, albumin, etc. Despite these numerous inconsistencies, it seems that oxidative stress is present in the course of psychiatric diseases. Still, it cannot be conclusively determined whether it is the direct cause of development, a consequence of other abnormalities at the biochemical or molecular level, or the result of the disease itself.

Genetic Factors of Nitric Oxide's System in Psychoneurologic Disorders

According to the recent data, nitric oxide (NO) is a chemical messenger that mediates functions such as vasodilation and neurotransmission, as well as displaying antimicrobial and antitumoral activities. NO has been implicated in the neurotoxicity associated with stroke and neurodegenerative diseases; neural regulation of smooth muscle, including peristalsis; and penile erections. We searched for full-text English publications from the past 15 years in Pubmed and SNPedia databases using keywords and combined word searches (nitric oxide, single nucleotide variants, single nucleotide polymorphisms, genes). In addition, earlier publications of historical interest were included in the review. In our review, we have summarized information regarding all NOS1, NOS2, NOS3, and NOS1AP single nucleotide variants (SNVs) involved in the development of mental disorders and neurological diseases/conditions. The results of the studies we have discussed in this review are contradictory, which might be due to different designs of the studies, small sample sizes in some of them, and different social and geographical characteristics. However, the contribution of genetic and environmental factors has been understudied, which makes this issue increasingly important for researchers as the understanding of these mechanisms can support a search for new approaches to pathogenetic and disease-modifying treatment.

Association between leptin levels and severity of suicidal behaviour in schizophrenia spectrum disorders

OBJECTIVE

Associations between suicidality and lipid dysregulation are documented in mental illness, but the potential role of leptin remains unclear. We examined the association between leptin and suicidal behaviour in schizophrenia, together with the influence of other clinical and biological indices.

METHOD

We recruited a sample of 270 participants with schizophrenia spectrum diagnoses. Blood samples were analysed for leptin, while symptom severity was assessed by Positive and Negative Syndrome Scale (PANSS) and Inventory of Depressive Symptomatology (IDS-C). Patients' history of suicidal behaviour was categorized into three subgroups based on IDS-C suicide subscale: No suicidal behaviour, mild/moderate suicidal behaviour and severe suicidal behaviour with/without attempts.

RESULTS

Mild/moderate suicidal behaviour was present in 17.4% and severe suicidal behaviour in 34.8%. Both groups were significantly associated with female gender (OR = 6.0, P = 0.004; OR = 5.9, P = 0.001), lower leptin levels (OR = 0.4, P = 0.008; OR = 0.5, P = 0.008) and more severe depression (OR = 1.2, P < 0.001; OR = 1.1, P < 0.001) respectively. Smoking (OR = 2.6, P = 0.004), younger age of onset (OR = 0.9, P = 0.003) and less use of leptin-increasing medications (OR = 0.5, P = 0.031) were associated with severe/attempts group, while higher C-reactive protein CRP (OR = 1.3, P = 0.008) was associated with mild/moderate group.

CONCLUSION

Lower leptin levels were associated with higher severity of suicidal behaviour in schizophrenia.

Effects of sodium nitroprusside in the acute dizocilpine (MK-801) animal model of schizophrenia

Schizophrenia treatment remains a major challenge, especially the associated cognitive impairments, as these are not consistently alleviated by conventional antipsychotics. Recent animal and clinical studies suggest that the nitric oxide (NO) donor sodium nitroprusside (SNP) reduces the psychiatric symptoms and cognitive deficits of schizophrenia. The present study was designed to investigate the efficacy of SNP against schizophrenia-like behavioral and cognitive deficits in the dizocilpine (MK-801) rat model. We used the rotarod and open field tests to identify the SNP dose which had no adverse effects on rat's exploratory and motor behavior, then established the schizophrenia model by injecting adult Sprague-Dawley rats intraperitoneally with MK-801 (0.4 mg/kg) with or without SNP pre-treatment. Behavioral changes were examined after 10 min. Prepulse inhibition (PPI) and the Y maze tests were conducted to assess cognitive deficits, and elevated plus maze and open field tests to assess anxiety-like behaviors. Preliminary rotarod and open field tests demonstrated that 2.5 mg/kg SNP had no effect on motor performance. Acute MK-801 treatment induced both cognitive deficits and anxiety. Co-administration of SNP (2.5 mg/kg) failed to improve these schizophrenia-like abnormalities. Sodium nitroprusside appears unable to improve schizophrenia-like symptoms and cognitive deficits induced by MK-801, inconsistent with the effectiveness of SNP as an adjunct therapy for anxiety disorders and working memory impairments in schizophrenia patients. Future studies are required to define an effective dose range for SNP monotherapy and adjunct therapy in different rodent models.

Implications for reactive oxygen species in schizophrenia pathogenesis

Oxidative stress is a well-recognized participant in the pathophysiology of multiple brain disorders, particularly neurodegenerative conditions such as Alzheimer's and Parkinson's diseases. While not a dementia, a wide body of evidence has also been accumulating for aberrant reactive oxygen species and inflammation in schizophrenia. Here we highlight roles for oxidative stress as a common mechanism by which varied genetic and epidemiologic risk factors impact upon neurodevelopmental processes that underlie the schizophrenia syndrome. While there is longstanding evidence that schizophrenia may not have a single causative lesion, a common pathway involving oxidative stress opens the possibility for intervention at susceptible phases.

Neuronal nitric oxide synthase (NOS1) and its adaptor, NOS1AP, as a genetic risk factors for psychiatric disorders

Nitric oxide (NO) is a gaseous transmitter produced by nitric oxide synthases (NOSs). The neuronal isoform (NOS-I, encoded by NOS1) is the main source of NO in the central nervous system (CNS). Animal studies suggest that nitrinergic dysregulation may lead to behavioral abnormalities. Unfortunately, the large number of animal studies is not adequately reflected by publications concerning humans. These include post-mortem studies, determination of biomarkers, and genetic association studies. Here, we review the evidence for the role of NO in psychiatric disorders by focusing on the human NOS1 gene as well as biomarker studies. Owing to the complex regulation of NOS1 and the varying function of NOS-I in different brain regions, no simple, unidirectional association is expected. Rather, the 'where, when and how much' of NO formation is decisive. Present data, although still preliminary and partially conflicting, suggest that genetically driven reduced NO signaling in the prefrontal cortex is associated with schizophrenia and cognition. Both NOS1 and its interaction partner NOS1AP have a role therein. Also, reduced NOS1 expression in the striatum determined by a length polymorphism in a NOS1 promoter (NOS1 ex1f-VNTR) goes along with a variety of impulsive behaviors. An association of NOS1 with mood disorders, suggested by animal models, is less clear on the genetic level; however, NO metabolites in blood may serve as biomarkers for major depression and bipolar disorder. As the nitrinergic system comprises a relevant target for pharmacological interventions, further studies are warranted not only to elucidate the pathophysiology of mental disorders, but also to evaluate NO function as a biomarker.

Cognitive psychotherapy treatment decreases peripheral oxidative stress parameters associated with major depression disorder

INTRODUCTION

Studies have already pointed out the contribution of oxidative stress in the pathophysiology of major depressive disorder (MDD). The aim of the present study was to investigate the oxidative-antioxidative systems in MDD and in response to cognitive psychotherapies. Oxidative stress were analyzed in 49 MDD patients at baseline, post-treatment, and follow-up; and 49 control subjects without history of psychiatric disorders.

RESULTS

MDD subjects presented an increase in oxidative damage related to control subjects for thiobarbituric acid reactive species (TBARS), nitric oxide, and a decrease in total thiol content. Cognitive psychotherapies were able to counteract peripheral oxidative stress in MDD patients, reducing TBARS levels (p<0.001) in the follow-up, nitric oxide (p<0.001) in the post-treatment and follow-up, and increasing the total thiol content (p<0.01) in the post-treatment and follow-up.

CONCLUSION

Oxidative stress was associated with MDD and the regulation of these parameters might represent an important mechanism associated with the clinical improvement of cognitive psychotherapy.

Paliperidone regulates intracellular redox system in rat brain: Role of purine mechanism

OBJECTIVE

The treatment of schizophrenia is multifactorial, with antipsychotic medications comprising a major part of treatment. Paliperidone is a newly commercialized antipsychotic whose formulation includes the principal active metabolite risperidone, 9-hydroxyrisperidone. Ever since the relationship between schizophrenia and oxidative stress was first demonstrated, many studies have been conducted in order to probe the potential protective effects of antipsychotic drugs on the oxidant-antioxidant system and lipid peroxidation. The basic aim of this study is to determine the effects of the newly marketed drug paliperidone on the activities of the enzymes adenosine deaminase (ADA), xanthine oxidase (XO), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) as well as on malondialdehyde (MDA) and nitric oxide (NO) levels in rat brain tissues.

METHODS

Twenty male Sprague-Dawley rats were used for the study, which were divided into two equal groups. The first was the control group (n = 10) and the second was the paliperidone group (n = 10). Saline was administered once daily for 14 days in the control group. In the paliperidone group, paliperidone was administered once daily with a dose of 1 mg/kg for 14 days. All rats were sacrificed at the end of the fourteenth day. Brain samples were collected and then analyzed.

RESULTS

Our results demonstrated that paliperidone significantly decreased the activities of ADA (P = 0.015), XO (P = 0.0001), and CAT (P = 0.004) while insignificantly increasing the activity of SOD (P = 0.49), MDA (P = 0.71), and NO (P = 0.26) levels in rat brain tissues. In addition, paliperidone insignificantly decreased the activity of GSH-Px (P = 0.30) compared to the control group in rat brain tissues.

DISCUSSION

In conclusion, the data obtained in this study suggest that paliperidone can positively alter antioxidant status and, accordingly, can offer positive outcomes in the treatment of schizophrenia by reducing activity in the enzymes ADA and XO, which are associated with purine metabolism. We believe that such a comprehensive approach used with other antipsychotic drugs warrants further study.

Leptin and the brain: influences on brain development, cognitive functioning and psychiatric disorders

Receptors of leptin, the prototypical adipokine, are expressed throughout the cortex and several other areas of the brain. Although typically studied for its role in energy intake and expenditure, leptin plays a critical role in many other neurocognitive processes and interacts with various other hormones and neurotransmitters to perform these functions. Here, we review the literature on how leptin influences brain development, neural degradation, Alzheimer's disease, psychiatric disorders, and more complicated cognitive functioning and feeding behaviors. We also discuss modulators of leptin and the leptin receptor as they relate to normal cognitive functioning and may mediate some of the actions of leptin in the brain. Although we are beginning to better understand the critical role leptin plays in normal cognitive functioning, there is much to be discovered.

Oxidative stress and psychological disorders

Oxidative stress is an imbalance between cellular production of reactive oxygen species and the counteracting antioxidant mechanisms. The brain with its high oxygen consumption and a lipid-rich environment is considered highly susceptible to oxidative stress or redox imbalances. Therefore, the fact that oxidative stress is implicated in several mental disorders including depression, anxiety disorders, schizophrenia and bipolar disorder, is not surprising. Although several elegant studies have established a link between oxidative stress and psychiatric disorders, the causal relationship between oxidative stress and psychiatric diseases is not fully determined. Another critical aspect that needs much attention and effort is our understanding of the association between cellular oxidative stress and emotional stress. This review examines some of the recent discoveries that link oxidative status with anxiety, depression, schizophrenia and bipolar disorder. A discussion of published results and questions that currently exist in the field regarding a causal relationship between oxidative and emotional stress is also provided.

New molecule in the etiology of schizophrenia: urotensin II

AIMS

Urotensin II (U-II) is a cyclic peptide that was first isolated from the caudal neurosecretory system of goby fish. U-II receptors were detected in the vascular endothelium, brain and kidney cortex. Urotensin is by far the most powerful vasoconstrictor identified. U-II molecules were previously isolated from the brain of rats and were shown to have an impact on rat behavior. The aim of the present study was to measure the level of U-II molecule in schizophrenia patients and to investigate whether the U-II level is associated with the etiology of schizophrenia.

METHODS

Forty schizophrenia patients who were followed at Gaziantep University Faculty of Medicine Department of Psychiatry Psychotic Disorders Unit and 40 healthy volunteers were enrolled in this study. Blood samples were taken from the antecubital vein after 12-h fasting. U-II level was measured on ELISA.

RESULTS

The U-II level in schizophrenia patients was significantly higher than in the control group. U-II level was not different with regard to gender in either group. U-II level was not different between subgroups of schizophrenia. No significant correlation was found between U-II level, Positive and Negative Syndrome Scale and Clinical Global Impression-Severity scale scores.

CONCLUSION

U-II level was higher in schizophrenia patients, indicating that U-II level may be related to the etiology of the disease.

Evidences for a progressive microglial activation and increase in iNOS expression in rats submitted to a neurodevelopmental model of schizophrenia: reversal by clozapine

Schizophrenia was proposed as a progressive neurodevelopmental disorder. In this regard herein we attempted to determine progressive inflammatory and oxidative alterations induced by a neonatal immune challenge and its possible reversal by clozapine administration. For this end, Wistar rats at postnatal day (PN) 5-7 were administered the viral mimetic polyriboinosinic-polyribocytidilic acid (polyI:C) or saline. A distinct group of animals additionally received the antipsychotic drug clozapine (25mg/kg) from PN60 to 74. At PN35 (periadolescence), 60 (adult) and 74 (adulthood) the animals were submitted to behavioral determinations of prepulse inhibition of the startle (PPI) and Y maze task for working memory evaluation. At PN35 and 74 the animals were sacrificed and the hippocampus (HC), prefrontal cortex (PFC) and striatum (ST) immunostained for Iba-1, a microglial marker, and inducible nitric oxide synthase (iNOS). At PN74 oxidative stress parameters, such as, reduced glutathione levels (GSH) and lipid peroxidation were determined. The results showed a progressive increase of microglial activation and iNOS immunostaining from PN35 to PN74 mainly in the CA2 and CA3 regions of the HC and in the ST. At PN74 neonatal challenge also induced an oxidative imbalance. These inflammatory alterations were accompanied by deficits in PPI and working memory only in adult life that were reversed by clozapine. Clozapine administration reversed microglial activation and iNOS increase, but not the alterations of oxidative stress parameters. Taken together these results give further evidences for a neuroprogressive etiology and course of schizophrenia and that clozapine may partly alleviate this process.

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.

Schizophrenia shows a unique metabolomics signature in plasma

Schizophrenia is a severe complex mental disorder affecting 0.5-1% of the world population. To date, diagnosis of the disease is mainly based on personal and thus subjective interviews. The underlying molecular mechanism of schizophrenia is poorly understood. Using targeted metabolomics we quantified and compared 103 metabolites in plasma samples from 216 healthy controls and 265 schizophrenic patients, including 52 cases that do not take antipsychotic medication. Compared with healthy controls, levels of five metabolites were found significantly altered in schizophrenic patients (P-values ranged from 2.9 × 10(-8) to 2.5 × 10(-4)) and in neuroleptics-free probands (P-values ranging between 0.006 and 0.03), respectively. These metabolites include four amino acids (arginine, glutamine, histidine and ornithine) and one lipid (PC ae C38:6) and are suggested as candidate biomarkers for schizophrenia. To explore the genetic susceptibility on the associated metabolic pathways, we constructed a molecular network connecting these five aberrant metabolites with 13 schizophrenia risk genes. Our result implicated aberrations in biosynthetic pathways linked to glutamine and arginine metabolism and associated signaling pathways as genetic risk factors, which may contribute to patho-mechanisms and memory deficits associated with schizophrenia. This study illustrated that the metabolic deviations detected in plasma may serve as potential biomarkers to aid diagnosis of schizophrenia.

Biological understanding of the cardiovascular risk associated with major depression and panic disorder is important

INTRODUCTION

Panic disorder (PD) and major depressive disorders (MDD) are serious mental disorders but the mechanisms underlying the pathophysiology are poorly understood. Nitric oxide (NO) is a gas considered to play an important role in mediating anxiety and stress response and is synthesised from nitric oxide synthase (NOS). The endothelial isoform (eNOS) has been found also in platelets. Homocysteine (Hcy) is an amino acid which naturally occurs in the human body. Elevated levels are linked to increased risk of cardiovascular, neurological and psychiatric diseases. In this study we aimed to evaluate NO, platelet aggregation and Hcy levels in PD and MDD patients.

MATERIALS AND METHODS

Nineteen PD and 18 MDD patients participated in this study. NO levels were measured spectrophotometrically, platelet aggregation levels were measured in an aggregometer and Hcy levels were measured by HPLC.

RESULTS

NO levels were significantly lower in patients with MDD and PD than in control subjects (P < 0.05). Hcy and platelet aggregation levels were significantly higher in patients with MDD and PD than in control subjects (P < 0.05).

CONCLUSION

Further more detailed studies are needed to find out the effects of drugs on these parameters or to disclose the exact mechanism underlying the alteration of these parameters.

Genetic dysregulation of glutathione synthesis predicts alteration of plasma thiol redox status in schizophrenia

Genetic studies have shown an association between schizophrenia and a GAG trinucleotide repeat (TNR) polymorphism in the catalytic subunit (GCLC) of the glutamate cysteine ligase (GCL), the key enzyme for glutathione (GSH) synthesis. The present study was aimed at analyzing the influence of a GSH dysregulation of genetic origin on plasma thiols (total cysteine, homocysteine, and cysteine-glycine) and other free amino acid levels as well as fibroblast cultures GSH levels. Plasma thiols levels were also compared between patients and controls. As compared with patients with a low-risk GCLC GAG TNR genotype, patients with a high-risk genotype, having an impaired GSH synthesis, displayed a decrease of fibroblast GSH and plasma total cysteine levels, and an increase of the oxidized form of cysteine (cystine) content. Increased levels of plasma free serine, glutamine, citrulline, and arginine were also observed in the high-risk genotype. Taken together, the high-risk genotypes were associated with a subgroup of schizophrenia characterized by altered plasma thiols and free amino acid levels that reflect a dysregulation of redox control and an increased susceptibility to oxidative stress. This altered pattern potentially contributes to the development of a biomarker profile useful for early diagnosis and monitoring the effectiveness of novel drugs targeting redox dysregulation in schizophrenia.

Antioxidants, redox signaling, and pathophysiology in schizophrenia: an integrative view

Schizophrenia (SZ) is a brain disorder that has been intensively studied for over a century; yet, its etiology and multifactorial pathophysiology remain a puzzle. However, significant advances have been made in identifying numerous abnormalities in key biochemical systems. One among these is the antioxidant defense system (AODS) and redox signaling. This review summarizes the findings to date in human studies. The evidence can be broadly clustered into three major themes: perturbations in AODS, relationships between AODS alterations and other systems (i.e., membrane structure, immune function, and neurotransmission), and clinical implications. These domains of AODS have been examined in samples from both the central nervous system and peripheral tissues. Findings in patients with SZ include decreased nonenzymatic antioxidants, increased lipid peroxides and nitric oxides, and homeostatic imbalance of purine catabolism. Reductions of plasma antioxidant capacity are seen in patients with chronic illness as well as early in the course of SZ. Notably, these data indicate that many AODS alterations are independent of treatment effects. Moreover, there is burgeoning evidence indicating a link among oxidative stress, membrane defects, immune dysfunction, and multineurotransmitter pathologies in SZ. Finally, the body of evidence reviewed herein provides a theoretical rationale for the development of novel treatment approaches.

A follow-up case-control association study of tractable (druggable) genes in recurrent major depression

The High-Throughput Disease-specific target Identification Program (HiTDIP) aimed to study case-control association samples for 18 common diseases. Here we present the results of a follow-up case-control association study of HiTDIP in major depressive disorder (MDD). The HiTDIP in MDD was conducted in a sample of 974 cases of recurrent MDD of white German origin collected at the Max-Planck Institute (MP-GSK) and 968 ethnically matched controls screened for lifetime absence of depression. Six genes were identified as of interest for a follow-up, based on the strength of the association and based on the interest as potential candidate target for developing new treatment for depression: Solute Carrier Family 4 Member 10 (SLC4A10), Dipeptidyl Peptidase IV (DPP4), Dopamine Receptor D3 (DRD3), Zinc Finger Protein 80 (ZNF80), Nitric Oxide Synthase 2A (NOS2A) and Peroxisome Proliferator-Activated Receptor-Gamma, Coactivator 1, Alpha (PPARGC1A). Within the current study, we attempted to follow-up these findings in a sample from the UK, the Depression Case Control (DeCC) sample consisting of 1,196 cases and 842 screened controls, phenotyped using exactly the same methods as the MP-GSK sample. Performing Cochran-Mantel-Haenzel statistics to test for genotypic and/or allelic differences between the DeCC and MP-GSK samples, we found no significant differences, thus being able to combine the two samples for association testing. In the combined sample of 2,170 MDD cases and 1,810 controls, there were positive findings in the Nitric Oxide Synthase 2A (NOS2A) gene both using single SNP analysis and haplotype analysis.

Acute and chronic effects of electroconvulsive treatment on oxidative parameters in schizophrenia patients

Electroconvulsive therapy (ECT) is an effective treatment alternative for schizophrenia. Previous studies have already indicated the possible effects of oxidative stress in this disorder. However, there have been no previous studies evaluating the effects of ECT on the oxidative stress in these patients. We therefore aimed to investigate the acute and chronic effects of ECT on serum levels of oxidant and antioxidant molecules in schizophrenia patients (n=28). The serum MDA and CAT levels of the patients with schizophrenia were higher than that of the controls before ECT (n=20) but there was no significant difference in the serum NO and GSH levels of the patient groups compared to the controls. We found that the NO levels of the patients were higher than the controls in the group experiencing their first episode but not in the chronic group. There was a significant clinical improvement in the patients in terms of BPRS, SANS and SAPS reduction after the 9th ECT, but not the 1st ECT. Serum MDA levels were significantly reduced compared to the baseline after the 9th ECT session although there was no significant difference after the 1st session. Separate evaluation of the patient groups revealed that the significant MDA decrease following ECT was in the patients experiencing their first episode and not in the chronic group. No significant difference was noted in the serum levels of other oxidant and antioxidant molecules after either the 1st or 9th ECT session. These results suggest that ECT does not produce any negative effect on oxidative stress in patients with schizophrenia.

Oxidative stress in schizophrenia

Increasing evidence indicates that oxidative damage exists in schizophrenia. Available literature about possible mechanisms of oxidative stress induction was reviewed. Furthermore, possibilities of measuring biomarkers of schizophrenia outside the central nervous system compartment, their specificity for different types of schizophrenia and potential therapeutic strategies to prevent oxidative injuries in schizophrenia were discussed. Data were extracted from published literature found in Medline, Embase, Biosis, Cochrane and Web of Science, together with hand search of references. Search terms were: schizophrenia, oxidative stress, antipsychotics, antioxidants and fatty acids. Finding a sensitive, specific and non invasive biomarker of schizophrenia, which could be measured in peripheral tissue, still stays an important task. Antioxidant enzymes, markers of lipid peroxidation, oxidatively modified proteins and DNA are most commonly used. As it considers the supplemental therapy, according to our meta-analysis vitamin E could potentially improve tardive dyskinesia, while for the effect of therapy with polyunsaturated fatty acids there is no clear evidence. Oxidative stress is a part of the pathology in schizophrenia and appears as a promising field to develop new therapeutic strategies. There is a need for well designed, placebo controlled trials with supplementation therapy in schizophrenia.

A putative cis-acting polymorphism in the NOS1 gene is associated with schizophrenia and NOS1 immunoreactivity in the postmortem brain

Schizophrenia is a devastating neurodevelopmental disorder whose genetic influences remain elusive. Recent genome-wide scans revealed that rare structural variants disrupted multiple genes in neurodevelopmental pathways, which strongly implicate nitric oxide (NO) signaling in schizophrenia. NO acts as a second messenger of N-methyl-D aspartate receptor activation, which further interacts with both dopaminergic and serotonergic pathways. NO is mainly synthesized by neuronal nitric oxide synthase (NOS1) in the brain, and its gene locus, 12q24.2, has attracted much attention as a major linkage region for schizophrenia. Genetic variations of NOS1 have also been associated with schizophrenia, and differential expression of NOS1 was observed in the postmortem brain of schizophrenic patients. Here, we explored the hypothesis that a putative cis-acting G-84A single nucleotide polymorphism (SNP; rs41279104) in the exon 1c promoter region of the NOS1 gene is associated with the levels of NOS1 immunoreactivity in postmortem prefrontal cortex specimens regardless of disease phenotype. Individuals with the A-allele of this SNP showed significantly lower levels of NOS1 immunoreactivity than did GG homozygotes (p=0.002). Furthermore, a case-control study using 720 individuals in a Japanese population revealed a significant association between the SNP and schizophrenia (genotypic p=0.0013 and allelic p=0.0011). Additionally, the average of onset age in schizophrenic patients with the A-allele was significantly earlier than GG homozygotes (p=0.018). When the analyses took gender into account, this significance was more significant for female. These findings provide further evidences that NOS1 is associated with a biological susceptibility gene to schizophrenia.

Association between plasma nitric oxide metabolites levels and negative symptoms of schizophrenia: a pilot study

Nitric oxide (NO) is involved in pathophysiology of psychiatric disorders such as depression and schizophrenia. We hypothesize that plasma levels of NO and its metabolites (NO(x)) are decreased in patients with schizophrenia. To examine the hypothesis, we compared plasma NO(x) levels between 30 schizophrenic patients (M/F: 18/12, age: 38 +/- 15 years) and age- and sex-matched 30 healthy controls (M/F: 18/12, age: 41 +/- 19 years), and we also examined the effects of risperidone on plasma NO(x) levels in schizophrenic patients. The baseline plasma NO(x) levels were significantly lower in the schizophrenia group (1.85 +/- 0.70 microM) than those in control group (3.37 +/- 2.27 microM). A significantly negative correlation was found between plasma NO(x) levels and PANSS-N scores before risperidone administration (rho = -0.385, p = 0.0416). Treatment with risperidone significantly increased the plasma NO(x) levels by 8 weeks (before; 1.85 +/- 0.70 microM, after; 2.25 +/- 1.00 microM, p = 0.0491). These results suggest that NO might be one of the candidates factors which are associated with the pathophysiology of negative symptoms of schizophrenia.

Family-based association study between NOS-I and -IIA polymorphisms and autism spectrum disorders in Korean trios

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder with a strong genetic component and environmental risk factors. Nitric oxide (NO), which is produced by nitric oxide synthase (NOS), may play a role in the development of ASD. We genotyped nine single nucleotide polymorphisms (SNPs) in the NOS-I gene and nine SNPs in the NOS-IIA gene and carried out the transmission disequilibrium test (TDT) and haplotype analysis in 151 Korean ASD trios. We found preferential transmission of the A allele of rs8068149 (P = 0.039) and G allele of rs1060826 (P = 0.035) of NOS-IIA in ASD and the haplotype analysis revealed that the two haplotypes had significant associations (P = 0.014 and 0.031, respectively). The behavioral subdomain score of failure to use nonverbal behaviors to regulate social interaction in Autism Diagnostic Interview-Revised (ADI-R) was significantly higher in subjects with the GG or AG allele in rs1060826 of NOS-IIA compared to those who had the AA allele (P = 0.027). These results provide significant but weak evidence for an association between NOS-IIA and ASD in the Korean population.

Evidence for association between the 5' flank of the NOS1 gene and schizophrenia in the Chinese population

Nitric oxide (NO) plays an important role in the dopaminergic and serotonergic system as the second messenger of the NMDA receptor and has possible roles in neurotransmission, neurosecretion, synaptic plasticity, and tissue injury in many neurological disorders, including schizophrenia. There is also genetic evidence to support the human NOS1 (neuronal nitric oxide synthase 1) gene as a promising candidate gene associated with schizophrenia. In this paper we conducted a case-control association study involving 1705 Chinese subjects and 12 genetic markers [11 single nucleotide polymorphisms (SNPs) and 1 microsatellite] mainly in the 5' flank region of the gene by direct sequencing and capillary electrophoresis. We identified SNP rs3782206 and several haplotypes derived from it as being significantly associated with schizophrenia and, specifically, in a paranoid subgroup. Our results strongly support a previous hypothesis that NOS1 contributes to the genetic risk of schizophrenia and suggest that further research on more NOS1 variants and its regular elements are warranted.

Reduced plasma nitric oxide metabolites before and after antipsychotic treatment in patients with schizophrenia compared to controls

BACKGROUND

Nitric oxide (NO) is believed to have a role in the pathophysiology of schizophrenia. We examined plasma levels of NO metabolites in patients with schizophrenia and normal controls. We also determined the impact of 6-week risperidone treatment on circulating NO metabolites in patients with schizophrenia.

METHOD

Plasma NO metabolite (NO(x)) levels were measured in 55 schizophrenia patients before and after 6-week treatment with risperidone and in 55 normal controls. Severity of schizophrenia and response to treatment were assessed with the positive and negative syndrome scale (PANSS) for schizophrenia. NO(x) levels were estimated by the Griess method.

RESULTS

Pre-treatment plasma NO(x) levels in schizophrenia patients (8.97+/-6.74 micromol/L) were lower than those of normal controls (14.51+/-6.30 micromol/L) (p<0.01). Schizophrenia patients had lower post-treatment NO(x) levels (10.99+/-8.31 micromol/L) than those of normal controls (p<0.01). There was marginal significant change between plasma NO(x) levels before and after 6-week treatment (p=0.056). Moreover, in 37 treatment responders (> or = 30% improvement in PANSS score), post-treatment plasma NO(x) significantly increased in comparison to pre-treatment NO(x) (p=0.028).

CONCLUSIONS

Plasma levels of NO(x) in patients with schizophrenia were significantly lower than normal controls both before and after the treatment. Our findings suggest that the improvement of psychiatric symptoms can lead to partially normalize a deficiency of NO after treatment in schizophrenia patients. Our findings support the hypothesis that the NO system is dampened in schizophrenia.

Imbalanced free radicals and antioxidant defense systems in schizophrenia: a comparative study

OBJECTIVE

To examine changes of blood oxidative-antiovidative level in schizophrenic patients and its relationship with clinical symptoms.

METHODS

Forty-six Chinese patients met DSM-IV (Diagnostic and Statistical Manual of Mental Disorders-IV) criteria for schizophrenia and fifty age- and sex-matched healthy controls were enrolled in the present study. Baseline psychiatric symptom severity was assessed with brief psychiatric rating scale, positive and negative syndrome scale on the blood draw day. Fresh blood samples were collected to measure levels of nitric oxide and lipid peroxide in plasma as well as activities of superoxide dismutase, catalase and glutathione peroxidase in red blood cells by spectrophotometric assays simultaneously.

RESULTS

Comparison of the biochemical parameters indicated that the level of nitric oxide and lipid peroxide increased in patient group, which represented a positive correlation with positive scale scores; while the activities of three critical enzymes decreased and showed a negative linear correlation.

CONCLUSION

This study showed that there are dysregulation of free radical metabolism and poor activities of the antioxidant defense systems in schizophrenic patients. Excess free radicals formation may play a critical role in the etiology of schizophrenia. Using antioxidants might be an effective therapeutic approach to partially alleviate or prevent the symptoms of schizophrenia.

Increased levels of nitric oxide, cortisol and adrenomedullin in patients with chronic schizophrenia

OBJECTIVE

To investigate the levels of serum cortisol, dehydroepiandrosterone sulfate (DHEA-S), nitric oxide (NO) and adrenomedullin (AM) in schizophrenic patients.

SUBJECTS AND METHODS

Sixty-six male patients with chronic schizophrenia and 28 normal male subjects participated in this study. The duration of disease was 145 +/- 120 (mean +/- SD) months. Serum levels of cortisol and DHEA-S were measured by electrochemiluminescence; plasma nitrite levels as an index of NO were measured with the Griess reaction, while plasma AM concentration was measured by using high-performance liquid chromatography.

RESULTS

Patients (12.48 +/- 3.2 microg/dl), as compared to controls (10.31 +/- 3.1 microg/dl), had higher levels of baseline cortisol (p < 0.05). DHEA-S levels were lower in patients though this did not reach statistical significance (302 +/- 156 microg/dl compared to control, 322 +/- 96 microg/dl, p > 0.05). The mean levels of plasma AM and NO in the schizophrenic group (44.33 +/- 5.07 pmol/l and 36.27 +/- 17.6 micromol/l) were significantly higher than the levels in the control group (14.56 +/- 4.03 pmol/l and 32.54 +/- 7.14 micromol/l; p < 0.001, p < 0.03, respectively). There was a positive association between duration of disease and cortisol/DHEA-S ratio and cortisol level.

CONCLUSION

The data show that schizophrenia is associated with abnormal levels of cortisol, DHEA-S, NO and AM.

Nitric oxide levels in disruptive behavioral disorder

There are various evidences of the role of nitric oxide (NO) in several neuropsychiatric disorders. However, there is no clinical study which investigated the role of NO in disruptive behavioral disorders (DBD). The aim of this study is to investigate the relation between NO levels and DBD. NO levels were measured in serum from 45 patients diagnosed as having DBD (30 patients with a diagnosis of attention deficit and hyperactivity disorder [ADHD] and 15 with ADHD + oppositional defiant disorder [ODD]) and 51 healthy control subjects. It is statistically significant that the pure ADHD group's blood NO levels are lower than those of both the ADHD + ODD and control groups. There was no significant difference between the ADHD + ODD group and the controls. The difference of the NO levels in DBD may indicate the effect of NO in the etiology of this disorder spectrum.

Implication du stress oxydant dans la physiopathologie de la schizophrénie : revue de la literature

BACKGROUND

Schizophrenia is a devastating psychiatric disorder with a broad range of behavioural and biologic manifestations. There are several clinical characteristics of the illness that have been consistently associated with poor premorbid adjustment, long duration of psychosis prior to treatment and prominent negative symptoms. The etiopathogenic mechanisms of lack of insight in patients with schizophrenia are to date unknown, although several hypotheses have been suggested. A point of convergence for the theoretical models occurs with regard to the neuronal membrane. Neuronal membrane contains a high proportion of polyunsaturated fatty acid and is the site for oxidative stress. Oxidative stress is a state when there is unbalance between the generation of reactive oxygen species and antioxidant defence capacity of the body. It is closely associated with a number of diseases including Parkinson's disease, Alzheimer-type dementia and Huntington's chorea. Accumulating evidence points to many interrelated mechanisms that increase production of reactive oxygen or decrease antioxidant protection in schizophrenic patients.

OBJECTIVES

This review aims to summarize the perturbations in antioxidant protection systems during schizophrenia, their interrelationships with the characteristic clinics and therapeutics and the implications of these observations in the pathophysiology of schizophrenia are discussed.

LITERATURE FINDINGS

In schizophrenia there is evidence for deregulation of free radical metabolism, as detected by abnormal activity of critical antioxidant enzymes (superoxide dismutase, glutathione peroxidase and catalase). Many studies conclude in the decrease in the activity of key antioxidant enzymes in schizophrenia. A few studies have examined levels of non enzymatic antioxidants such as plasma antioxidant proteins (albumin, bilirubine, uric acid) and trace elements. How showed decreased levels in schizophrenic patients. Others studies have provided evidence of oxidative membrane damage by examining levels of lipid peroxidation products. Such abnormalities have been associated with certain clinical symptoms and therapeutic features. Negative symptoms have been associated with low levels of GSH-Px. Positive symptoms have been positively correlated with SOD activity. Plasma TAS was significantly lower in drug-free and haloperidol treated patients with schizophrenia. A low erythrocyte SOD activity has been found in never-treated patients, but with haloperidol treatment, SOD activity increased.

DISCUSSION

These results demonstrate altered membrane dynamics and antioxidant enzyme activity in schizophrenia. Membrane dysfunction can be secondary to free a radical-mediated pathology, and may contribute to specific aspects of the schizophrenia symptomatology. Membrane defects can significantly alter a broad range of membrane functions and presumably modify behavior through multiple downstream biological effects. Phospholipid metabolism in the brain may be perturbed in schizophrenia, with reduced amounts of phosphatidylcholins and phosphatidylethanolamine in post-mortem brain tissue from schizophrenic patients, and large amounts of lipofuscin-like materiel in the oligodendrocytes. The existence of these products within cell membranes results in an unstable membrane structure, altered membrane fluidity and permeability and impaired signal transduction. Recent findings suggest that multiple neurotransmitter systems may be faulty. CNS cells are more vulnerable to the toxic effects of free radicals because they have a high rate of catecholamine oxidative metabolic activity. Neurotransmitters, like glutamate, can induce the same metabolic processes that increase free radical production and can lead to impaired dopamine-glutamate balance. These results question the role of this imbalance in the biochemical basis evoked in the etipathogenic mechanisms of schizophrenia, as well as the role of antioxidants in the therapeutic strategy and their implication in preventive and early intervention approaches in populations at risk for schizophrenia.

Prevention of oxidative stress-mediated neuropathology and improved clinical outcome by adjunctive use of a combination of antioxidants and omega-3 fatty acids in schizophrenia

Schizophrenia is associated with a broad range of neurodevelopmental, structural and behavioral abnormalities that often progress with or without treatment. Evidence indicates that such neurodevelopmental abnormalities may result from defective genes and/or non-genetic factors such as pre-natal and neonatal infections, birth complications, famines, maternal malnutrition, drug and alcohol abuse, season of birth, sex, birth order and life style. Experimentally, these factors have been found to cause the cellular metabolic stress that often results in oxidative stress, such as increased cellular levels of reactive oxygen species (ROS) over the antioxidant capacity. This can trigger the oxidative cell damage (i.e., DNA breaks, protein inactivation, altered gene expression, loss of membrane lipid-bound essential polyunsaturated fatty acids [EPUFAs] and often apoptosis) contributing to abnormal neural growth and differentiation. The brain is preferentially susceptible to oxidative damage since it is under very high oxygen tension and highly enriched in ROS susceptible proteins, lipids and poor DNA repair. Evidence is increasing for increased oxidative stress and cell damage in schizophrenia. Furthermore, treatments with some anti-psychotics together with the lifestyle and dietary patterns, that are pro-oxidant, can exacerbate the oxidative cell damage and trigger progression of neuropathology. Therefore, adjunctive use of dietary antioxidants and EPUFAs, which are known to regulate the growth factors and neuroplasticity, can effectively improve the clinical outcome. The dietary supplementation of either antioxidants or EPUFAs, particularly omega-3 has already been found to improve some psychopathologies. However, a combination of antioxidants and omega-3 EPUFAs, particularly in the early stages of illness, when brain has high degree of neuroplasticity, potentially may be even more effective for long-term improved clinical outcome of schizophrenia.

The many faces of nitric oxide in schizophrenia. A review

Intense research has been conducted in an effort to identify specific biological markers of schizophrenia. The gas nitric oxide (NO) is one of the most important signaling molecules involved in a plethora of cellular events that take place in the cardiovascular, immune and nervous systems of animals. This survey aims to demonstrate that NO and its metabolites play important roles in schizophrenia and have a significant influence on our understanding of the development, progression and treatment of the disease. Special emphasis is given to the impact of NO metabolism on processes known to be disturbed in schizophrenia (i.e., cell migration, formation of synapses, NMDA receptor mediated neurotransmission, membrane pathology and cognitive abilities). However, when comparing data on the NO metabolism in the brain tissue and body fluids of schizophrenics with those obtained from patients with other neurological and psychiatric diseases, it becomes clear that alterations of NO metabolism are not unique to, or indicative of, schizophrenia. Thus, NO and its metabolites are not suitable diagnostic tools to distinguish schizophrenia from psychically healthy control cases or from other brain disorders.

Altered diurnal variation of nitric oxide production in patients with panic disorder

The aim of this prospective study was to investigate the diurnal change in serum nitric oxide (NO) levels in active and remission phases of patients with panic disorder. This study included 15 patients fulfilling the criteria for panic disorder of Diagnostic and Statistical Manual of Mental Disorders--Fourth Edition and 15 healthy controls matched for age and sex. All patients were receiving a selective serotonin reuptake inhibitor at therapeutic doses. The serum nitrite and nitrate levels of subjects were determined at 10:00 a.m. after overnight fasting and at 3:00 p.m. 2 hours after lunch. NO levels of all patients measured in the morning were significantly higher than those of controls. The patients were also divided into active and remission groups according to clinical status and Panic Agoraphobia Scale's cut-off point. There were no statistically significant differences in serum nitrite and nitrate levels of the active group between the 10:00 a.m. and 3:00 p.m. measurements. In contrast, statistically significant differences were found in the serum levels of nitrite (p<0.05) and nitrate (p<0.05) in the remission group. Notably, the afternoon nitrite and nitrate levels of the remission group were higher than those of the morning levels as seen in control subjects. Thus, diurnal variation of NO production is altered in patients with panic disorder but is resumed in the remission phase. The present study suggests that serum NO levels are a good marker for evaluation of panic disorder.

Effects of 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS) and chlorpromazine on NO3- transport via anion exchanger in erythrocytes: inertness of DIDS in whole blood

We examined the effects of chlorpromazine on NO(3)(-) transport between erythrocytes (RBCs) and extracellular fluid. Chlorpromazine (10 microg/ml) did not influence NO(3)(-) movement in both whole blood and RBC suspension. Though an anion exchanger (AE1) inhibitor DIDS (4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid, 100 microM) did not alter NO(3)(-) movement in whole blood, it inhibited the movement in a concentration-dependent manner in the RBC suspension. The inhibition was abrogated by plasma and albumin concentration-dependently. Our results indicated that chlorpromazine had no effect on NO(3)(-) transport through AE1 and that the inertness of DIDS on AE1 in whole blood is due to interference by albumin in plasma.

Repeated application of ketamine to rats induces changes in the hippocampal expression of parvalbumin, neuronal nitric oxide synthase and cFOS similar to those found in human schizophrenia

Treatment with the phencyclidine derivative ketamine, a non-competitive N-methyl-D-aspartate receptor antagonist and a well known anesthetic, has recently been introduced to mimic schizophrenia in animals. Using rats repeatedly treated with sub-anesthetic doses we demonstrate in the hippocampal formation the cellular distribution patterns of proteins being relevant to the pathogenesis of schizophrenia. Compared with controls an increase in the density of reduced nicotinamide adenine dinucleotide phosphate diaphorase-, neuronal nitric oxide synthase- and cFOS-positive hippocampal interneurons was found, whereas the density of parvalbumin expressing cells was decreased. Our experiments show that repeated injections of sub-anesthetic doses of ketamine induce significant changes in the nitrergic and GABAergic system which, in part, resemble those described in postmortem brains of human schizophrenics indicating that sub-chronic treatment with sub-anesthetic doses of ketamine might be a useful animal model to study schizophrenia.

Serum nitric oxide metabolite levels and the effect of antipsychotic therapy in schizophrenia

BACKGROUND

Recently it was proposed that nitric oxide metabolites (NO) may have a role in the pathophysiology of schizophrenia and major depressive disorders. The present study was performed to assess changes in serum nitric oxide metabolite levels in schizophrenic patients compared with healthy controls. Our secondary aim was to further evaluate the impact of psychopharmacologic treatment on circulating NO levels not assessed previously.

METHODS

Serum NO levels of patients with schizophrenia (n=20) before and after 6 weeks of treatment were compared with those of healthy controls (n=20). Severity of schizophrenia and response to treatment were assessed with positive and negative symptoms of schizophrenia. NO levels were estimated by Griess method in serum samples.

RESULTS

In patients with schizophrenia, pre-treatment serum NO levels were higher than those of control subjects (39.15 +/- 18.24 vs. 25.40 +/- 5.83 micromol/L, p=0.036) and also of post-treatment values (34.41 +/- 16.35 vs. 25.40 +/- 5.83 micromol/L, p=0.049), respectively. However, no significant difference was found between serum NO levels in pre- and post-treatment values.

CONCLUSIONS

Our findings of increased serum NO levels in schizophrenic patients confirmed the role of NO in the pathophysiology of schizophrenia. However, we found that antipsychotic drugs do not reveal significant effects on serum levels of NO in schizophrenia in a 6-week treatment regimen. Further studies with longer therapy periods may suggest some new clues for novel treatment strategies employing antioxidants and NOS inhibitors in schizophrenia.

Implication of steady state concentrations of nitrite and nitrate metabolites of nitric oxide in plasma and whole blood in healthy human subjects

1. The aim of the present study was to determine whether the steady state NOx concentration reflects NOx formation in vivo. 2. A NO3- load study was performed after achieving NOx steady state. Chronological changes in NOx concentrations in plasma and whole blood samples from nine healthy subjects were determined by the HPLC-Griess system and NOx concentrations in erythrocytes were estimated as a possible NOx compartment influential in regulating plasma NOx concentrations. 3. Analysis was performed using the first-order one-compartment open model and the NOx formation rate was subsequently calculated. 4. The mean (+/-SEM) steady state NOx concentration of plasma (15.5 +/- 1.6 micromol/L), whole blood (12.8 +/- 1.2 micromol/L) and erythrocytes (11.9 +/- 0.7 micromol/L) did not correlate with the NOx formation rate in the compartments (0.50 +/- 0.05, 0.61 +/- 0.04 and 0.91 +/- 0.17 micromol/kg per h, respectively), whereas a significant correlation was found between the steady state NOx concentration and NOx elimination rate (Kel) in plasma (r=-0.69; P=0.04) and whole blood (r=-0.79; P=0.01). 5. Although there was no direct correlation between steady state NOx concentrations and serum creatinine levels, the correlation between half-life and serum creatinine levels was significant (plasma: r=0.60, P=0.02; whole blood: r=0.49, P=0.04). 6. Plasma NOx concentrations correlated significantly with erythrocyte NOx concentrations (r=0.92, P <0.01; erythrocyte NOx=0.66 x plasma NOx). 7. The results of the present study indicate that NOx does not accumulate excessively into erythrocytes at steady state and during a NO3- load and that the steady state NOx concentration in whole blood and plasma preferentially implies NOx elimination (mainly depending on renal function) rather than NOx formation.

Is the arginine-nitric oxide pathway involved in the pathogenesis of schizophrenia?

The reciprocal regulation of arginase and nitric oxide synthase (NOS) in L-arginine-metabolizing pathways has been demonstrated. There are various evidences of the role of the nitric oxide (NO) in several neuropsychiatric disorders including schizophrenia. However, there is no study which has investigated the role of arginase as an important part of the arginine regulatory system affecting NOS activity in schizophrenia. This study aims to investigate arginase, manganese (Mn) and total nitrite levels (a metabolite of NO) and their relationship to the arginine-NO pathway in patients with schizophrenia. Arginase activities, Mn and total nitrite levels were measured in plasma from 46 patients with schizophrenia and 32 healthy control subjects. Plasma arginase activities and Mn were found to be significantly lower and total nitrite level higher in patients with schizophrenia compared with controls. Our results suggest that the arginine-NO pathway is involved in the pathogenesis of schizophrenia.

Changes in nitric oxide levels and antioxidant enzyme activities may have a role in the pathophysiological mechanisms involved in autism

BACKGROUND

There is evidence that oxygen free radicals play an important role in the pathophysiology of many neuropsychiatric disorders. Although it has not been investigated yet, several recent studies proposed that nitric oxide (NO) and other parameters related to oxidative stress may have a pathophysiological role in autism.

METHODS

We assessed the changes in superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activities and thiobarbituric acid-reactive substances (TBARS) levels in plasma as well as NO levels in red blood cells (RBC) in patients with autism (n=27) compared to age- and sex-matched normal controls (n=30).

RESULTS

In the autistic group, increased RBC NO levels (p<0.0001) and plasma GSH-Px activity (p<0.0001) and unchanged plasma TBARS levels and SOD activity were detected.

CONCLUSIONS

These findings indicate a possible role of increased oxidative stress and altered enzymatic antioxidants, both of which may be relevant to the pathophysiology of autism.

Pathophysiological role of nitric oxide and adrenomedullin in autism

Several studies indicate that nitric oxide (NO) is involved in the aetiopathogenesis of many neuropsychiatric disorders such as schizophrenia, bipolar disorder, depression, Alzheimer's disease, Hungtington disease and stroke. Although it has not been investigated yet, several recent studies proposed that NO may have a pathophysiological role in autism. Adrenomedullin (AM), a recently discovered 52-amino acid peptide hormone, induces vasorelaxation by activating adenylate cyclase and also by stimulating NO release. AM immune reactivity is present in the brain consistent with a role as a neurotransmitter. It has been stated that NO and AM do function in the regulation of many neurodevelopmental processes. We hypothesized that NO and AM activities have been affected in autistic patients and aimed to examine these molecules. Twenty-six autistic patients and 22 healthy control subjects were included in this study. AM and total nitrite (a metabolite of NO) levels have been measured in plasma. The mean values of plasma total nitrite and AM levels in the autistic group were significantly higher than control values, respectively (p < 0.001, p = 0.028). There is no correlation between total nitrite and AM levels (r = 0.11, p = 0.31). Certainly, this subject needs much further research investigating autistic patients in earlier periods of life and with subtypes of the disorder.

The possible pathophysiological role of plasma nitric oxide and adrenomedullin in schizophrenia

Evidence is accumulating for a possible role of nitric oxide (NO) in schizophrenia. Adrenomedullin (AM) induces vasorelaxation by activating adenylate cyclase and also by stimulating the release of NO. AM immune reactivity is present in the brain consistent with a role as neurotransmitter. We aimed to examine plasma levels of nitrite (a metabolite of NO) and AM in schizophrenic patients. Eighty-two patients with schizophrenia and 21 healthy control subjects were included in this study. DSM-IV diagnosis of chronic schizophrenia was established on the basis of independent structured clinical interviews and review of records by two qualified psychiatrists which included the Brief Psychiatric Rating Scale (BPRS), The Scale for the Assessment of Negative Symptoms (SANS) and The Scale for the Assessment of Positive Symptoms (SAPS). Total nitrite and AM have been studied in plasma. The mean values of plasma nitrite and AM levels in schizophrenic group were significantly higher than control values, respectively (P=0.03, P<0.0001). AM levels of schizophrenic patients were three fold higher than controls. In correlation analyses, there were statistically significant positive correlations between AM level and SAPS-delusion subscale (r=0.27, P=0.04); SAPS-bizarre behavior subscale (r=0.28, P=0.03) and SAPS-total (r=0.36, P=0.005). There is no correlation between total nitrite and AM levels (r=0.11, P=0.31). Both NO and AM may have a pathophysiological role in schizophrenia, and clinically symptomatology and prognosis of schizophrenia. This subject needs further study including treatment response and subtypes of schizophrenia.

The indices of endogenous oxidative and antioxidative processes in plasma from schizophrenic patients. The possible role of oxidant/antioxidant imbalance

There is great evidence in recent years that oxygen free radicals play an important role in the pathophysiology of schizophrenia. The present study was performed to assess the changes in plasma nitric oxide (NO) and thiobarbituric acid-reactive substances (TBARS) levels, and superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and xanthine oxidase (XO) activities in schizophrenic patients compared to age- and sex-matched normal controls. A hundred patients with schizophrenia and 51 healthy volunteers were included in the study. XO, SOD, and GSH-Px activities as well as NO and TBARS levels were estimated by standard biochemical techniques in the plasma of normal healthy controls and schizophrenia patients. In schizophrenia, increased plasma XO activity (P < .0001) and NO levels (P < .0001), decreased SOD activity (P < .0001), and unchanged GSH-Px activity were detected compared to control group. Plasma TBARS levels were increased in schizophrenic patients (P < .01), especially in the residual subtype. TBARS levels in nonsmoker schizophrenic patients were found to be higher than nonsmoker controls. Although TBARS levels in both patients and controls were found to be higher in smokers as compared to nonsmokers, it was not statistically significant. No effects of duration of the illness, gender, and low and high dose of daily neuroleptic treatment equivalent to chlorpromazine on oxidant and antioxidant parameters were observed. Because the dose and the duration of treatment with drugs have no influence on the results, it can be interpreted that the findings are more likely to be related mainly to the underlying disease. These findings indicated a possible role of increased oxidative stress and diminished enzymatic antioxidants, both of which may be relevant to the pathophysiology of schizophrenia. On the other hand, increased NO production by nitric oxide synthetases (NOSs) suggests a possible role of NO in the pathophysiological process of schizophrenia. These findings may also suggest some clues for the new treatment strategies with antioxidants and NO synthase (NOS) inhibitors in schizophrenia.