Oxidative stress and superoxide dismutase in schizophrenia

Oxidative Stress and Emergence of Psychosis

Treatment and prevention strategies for schizophrenia require knowledge about the mechanisms involved in the psychotic transition. Increasing evidence suggests a redox imbalance in schizophrenia patients. This narrative review presents an overview of the scientific literature regarding blood oxidative stress markers’ evolution in the early stages of psychosis and chronic patients. Studies investigating peripheral levels of oxidative stress in schizophrenia patients, first episode of psychosis or UHR individuals were considered. A total of 76 peer-reviewed articles published from 1991 to 2022 on PubMed and EMBASE were included. Schizophrenia patients present with increased levels of oxidative damage to lipids in the blood, and decreased levels of non-enzymatic antioxidants. Genetic studies provide evidence for altered antioxidant functions in patients. Antioxidant blood levels are decreased before psychosis onset and blood levels of oxidative stress correlate with symptoms severity in patients. Finally, adjunct treatment of antipsychotics with the antioxidant N-acetyl cysteine appears to be effective in schizophrenia patients. Further studies are required to assess its efficacy as a prevention strategy. Redox imbalance might contribute to the pathophysiology of emerging psychosis and could serve as a therapeutic target for preventive or adjunctive therapies, as well as biomarkers of disease progression.

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

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

Interrelationships Between BDNF, Superoxide Dismutase, and Cognitive Impairment in Drug-Naive First-Episode Patients With Schizophrenia

The pathogenesis and etiology of schizophrenia (SCZ) remains unclear. Accumulating studies showed that complex interrelationships between brain-derived neurotrophic factor (BDNF) and an imbalanced redox system has a crucial role in the psychopathology of SCZ. However, the influence of the interrelationships of BDNF and superoxide dismutase (SOD) on cognitive impairment and clinical symptomatology in drug-naive first-episode (DNFE) SCZ patients has not been studied thoroughly. Serum BDNF levels, plasma total SOD, manganese-SOD (Mn-SOD), copper/zinc-containing SOD (CuZn-SOD) activities, and malondialdehyde (MDA) levels were measured in 327 DNFE patients with SCZ and 391 healthy controls. Cognitive functions were measured using the Repeatable Battery for the Assessment of Neuropsychological status (RBANS) and clinical symptoms were evaluated by the Positive and Negative Syndrome Scale (PANSS). Compared with the controls, the DNFE patients had increased activities of total SOD and CuZn-SOD, and reduced levels of BDNF and MDA. BDNF levels were positively correlated with CuZn-SOD activity in patients. In addition, we found that elevated Mn-SOD and CuZn-SOD activities were related to PANSS depression factor. Moreover, an interactive effect of BDNF levels and Mn-SOD activity was associated with attentional index score in the patients. Therefore, our findings suggested that interrelationships between BDNF and antioxidant mechanisms might underlie the pathological mechanisms of cognitive impairments and symptomatology in the DNFE patients with SCZ.

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.

Cognitive function, plasma MnSOD activity, and MnSOD Ala-9Val polymorphism in patients with schizophrenia and normal controls

Excessive reactive oxygen species are thought to produce oxidative damage that underlies neurodegeneration and cognitive impairment in several disorders including schizophrenia. The functional Ala-9Val polymorphism of the mitochondrial enzyme manganese superoxide dismutase (MnSOD), which detoxifies superoxide radicals to hydrogen peroxide, has been associated with schizophrenia. However, no study has reported its role in cognitive deficits of schizophrenia as mediated through MnSOD activity. We recruited 923 schizophrenic inpatients and 566 healthy controls and compared them on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), plasma MnSOD activity, and the MnSOD Ala-9Val polymorphism. We assessed patient psychopathology using the Positive and Negative Syndrome Scale. We showed that the MnSOD Ala-9Val polymorphism may not contribute directly to the susceptibility to schizophrenia. The Ala variant was associated with worse attention performance among chronic schizophrenic patients but not among normal controls. Plasma MnSOD activity was significantly decreased in patients compared with that in normal controls. Moreover, MnSOD activity among the schizophrenic Ala allele carriers was correlated with the degree of cognitive impairments, especially attention and RBANS total score. We demonstrated an association between the MnSOD Ala-9Val variant and poor attention in schizophrenia. The association between higher MnSOD activity and cognitive impairment in schizophrenia is dependent on the MnSOD Ala-9Val polymorphism.

Changes in oxidative stress markers in patients with schizophrenia: the effect of antipsychotic drugs

The aim of this study was to investigate the serum levels or activities of oxidative stress markers in patients with schizophrenia in acute phase and evaluate the changes in superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH) and thiobarbituric acid-reactive substances (TBARS) after treatment. We consecutively enrolled 41 patients with schizophrenia in acute phase, and 27 patients were followed up with a 4-week antipsychotic treatment. Serum oxidative stress markers were measured with assay kits. We found that Positive and Negative Syndrome Scale (PANSS) total scores were significantly negatively correlated with serum GPx activity and GSH levels and positively correlated with serum SOD activity in patients with schizophrenia in acute phase. In addition, serum GPx activity had a positive correlation with GSH levels and negative correlation with SOD activity. We also found that serum SOD activity was significantly negatively correlated with TBARS levels in patients in acute phase. Furthermore, we found significantly increased changes only in GPx activity in female patients receiving the 4-week treatment (P=0.006). In conclusion, our results suggest that SOD, GPX and GSH might be indicators of schizophrenia severity in acute phase. Furthermore, antipsychotic drugs might affect serum GPx activity in female patients receiving the 4-week treatment.

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.

The effects of ziprasidone, clozapine and haloperidol on lipid peroxidation in human plasma (in vitro): comparison

Oxidative injury in schizophrenia can be caused by the disease itself and probably by antipsychotics treatment. The aim of the study was to establish whether there is a difference between ziprasidone, clozapine and haloperidol effect on lipid peroxidation in human plasma, measured by the level of thiobarbituric acid reactive substances (TBARS). The samples of plasma from healthy subjects were incubated with the drugs (1 and 24 h) and compared with control samples. The levels of TBARS were measured spectrophotometrically, according to the Rice-Evans method. The multifactorial variance analysis ANOVA II test showed that the differences in TBARS levels significantly depended on the studied drugs (ziprasidone 40 ng/ml, haloperidol 4 ng/ml and clozapine 350 ng/ml) (F = 3.248 p = 0.047) and (ziprasidone 139 ng/ml, haloperidol 20 ng/ml and clozapine 420 ng/ml) (F = 2.248, p = 2.9 × 10(-5)). Statistically increased levels of TBARS after 24 h incubation of plasma with ziprasidone 139 ng/ml and haloperidol 20 ng/ml (p < 0.001, p < 0.05 respectively) in comparison with control samples were observed. Clozapine did not significantly (p > 0.05) increase TBARS level in plasma in comparison with control samples. The results obtained in the study showed that ziprasidone and haloperidol contrary to clozapine induced a significant increase in plasma lipid peroxidation.

Behavioral phenotyping of glutathione-deficient mice: relevance to schizophrenia and bipolar disorder

Redox-dysregulation represents a common pathogenic mechanism in schizophrenia (SZ) and bipolar disorder (BP). It may in part arise from a genetically compromised synthesis of glutathione (GSH), the major cellular antioxidant and redox-regulator. Allelic variants of the genes coding for the rate-limiting GSH synthesizing enzyme glutamate-cysteine-ligase modifier (GCLM) and/or catalytic (GCLC) subunit have been associated with SZ and BP. Using mice knockout (KO) for GCLM we have previously shown that impaired GSH synthesis is associated with morphological, functional and neurochemical anomalies similar to those in patients. Here we asked whether GSH deficit is also associated with SZ- and BP-relevant behavioral and cognitive anomalies. Accordingly, we subjected young adult GCLM-wildtype (WT), heterozygous and KO males to a battery of standard tests. Compared to WT, GCLM-KO mice displayed hyperlocomotion in the open field and forced swim test but normal activity in the home cage, suggesting that hyperlocomotion was selective to environmental novelty and mildly stressful situations. While spatial working memory and latent inhibition remained unaffected, KO mice showed a potentiated hyperlocomotor response to an acute amphetamine injection, impaired sensorymotor gating in the form of prepulse inhibition and altered social behavior compared to WT. These anomalies resemble important aspects of both SZ and the manic component of BP. As such our data support the notion that redox-dysregulation due to GSH deficit is implicated in both disorders. Moreover, our data propose the GCLM-KO mouse as a valuable model to study the behavioral and cognitive consequences of redox dysregulation in the context of psychiatric disease.

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.

Lipid peroxidation in patients with schizophrenia

AIMS

There is evidence that dysregulation of free radicals metabolism associated with abnormal activities of antioxidative enzymes in schizophrenia can lead to lipid peroxidation in plasma, erythrocytes, blood platelets and cerebrospinal fluid. Injury to neurons in schizophrenia may affect their function, i.e. membrane transport, impairment of energy production in mitochondria, changes in membrane phospholipid composition, alteration of receptors and transporters as well as neurotransmission. The purpose of the present study was to assess the total antioxidant capacity (TAC) and lipid peroxidation (expressed as the level of thiobarbituric acid reactive substances [TBARS]) in plasma from schizophrenic patients taking olanzapine or risperidone. The level of TBARS estimated according to the Rice-Evans method and TAC ([ABTS; 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation decolorization assay]) in plasma from schizophrenic patients (DSM-IV criteria for schizophrenia, n = 30, age 18-36) taking olanzapine or risperidone and from healthy volunteers (n = 30) were measured.

METHODS

The level of TBARS in plasma from healthy volunteers after incubation with olanzapine or risperidone was also estimated.

RESULTS

Significantly lower plasma TAC (P < 0.05) and significantly increased level of TBARS (P < 0.001) in schizophrenic patients were observed. The in vitro study showed that after olanzapine or risperidone (at final concentrations corresponding to doses used in acute episodes of schizophrenia treatment) no changes of plasma lipid peroxidation were found (P > 0.05). The obtained results indicate that the pro-oxidant disturbances occur in schizophrenic patients (acute episode) taking stable doses of olanzapine or risperidone.

CONCLUSION

It seems that second-generation antipsychotics (olanzapine and risperidone) are not responsible for increase of plasma lipid peroxidation.

Isoprostenes as indicators of oxidative stress in schizophrenia

OBJECTIVE

Free radicals induce oxidative stress and damage to all types of biological molecules and may be involved in pathology of schizophrenia. A cell membrane dysfunction caused by lipid peroxidation can be secondary to a free radical-mediated pathology and may contribute to specific aspects of schizophrenic symptomatology and complications of its treatment.

METHOD

The aim of our study was to estimate oxidative stress in a group of schizophrenic patients by using different biomarkers of free radicals-induced lipid peroxidation (isoprostanes, thiobarbituric acid reactive substances (TBARS)). We also determined the products of enzymatic peroxidation of arachidonic acid, such as thromboxane B2 (TXB2) and its metabolite 11-dehydrothromboxane B2. Isoprostanes (IPs) are a family of novel prostaglandin isomers and are produced in free radical-catalysed reactions from arachidonic acid. They are useful as a specific, sensitive, chemically stable, noninvasive index of free radical generation in vivo. We therefore assessed in schizophrenic patients and control subjects the level of urinary excretion of isoprostane--8-epi-prostaglandin F2 alpha, (8-isoPGF2 alpha)--a marker of lipid peroxidation induced by free radicals using an immunoassay kit. We also studied the level of the other marker of enzymatic arachidonic acid peroxidation--11-dehydrothromboxane B2--in urine from schizophrenic patients and healthy volunteers. Moreover, we estimated the production of TBARS and TXB2 in plasma from schizophrenic patients and the control group. Patients hospitalised in the II Psychiatric Department of Medical University in Lodz, Poland, were interviewed with a special questionnaire (treatment, course of diseases, dyskinesis and other EPS). According to DSM-IV criteria, all patients had diagnosis of paranoid type. All patients were treated with second-generation antipsychotic drugs (risperidone, clozapine, and olanzapine). Mean time of schizophrenia duration was about 2 years.

RESULTS

We observed a statistically increased level of TBARS in plasma (P=0.000162) and isoprostanes (P=3.5 x 10(-12)) in urine of schizophrenic patients in comparison with the control group. The level of markers of enzymatic oxidation of arachidonic acid (TXB2 and its metabolite, 11-dehydrothromboxane B2) did not change. This indicates that free radicals induce peroxidation of unsaturated fatty acid in schizophrenic patients.

CONCLUSION

Considering the data presented in this study, we suggest that non-invasive measurement of 8-isoPGF2 alpha, is a valuable and sensitive (contrary to TBARS) indicator of oxidative stress status in vivo in schizophrenia.

Oxidative stress in blood platelets from schizophrenic patients

Oxidative stress in blood platelets is observed in various diseases, including neuropsychiatric disorders. The aim of our study was to evaluate oxidative stress in blood platelets from patients with schizophrenic disorders by measuring the activity of the platelet antioxidative enzyme, superoxide dismutase (SOD), concomitant with the level of thiobarbituric acid reactive species (TBARS). In blood platelets obtained from schizophrenic patients (with paranoid schizophrenia according to DSM-IV criteria) and from healthy volunteers the level of reactive oxygen species was also measured via chemiluminescence. In resting blood platelets from schizophrenic patients the chemiluminescence was higher than in platelets from control subjects (P < 0.05), but in thrombin-activated platelets an increase (about 53%) of chemiluminescence was observed, however this increase was lower than in thrombin-stimulated platelets from healthy subjects (101.5%). The results indicate that in platelets from schizophrenic patients generation of reactive oxygen species is enhanced. Moreover, we observed that SOD activity in blood platelets from schizophrenic patients was significantly lower than in control platelets and that a correlation exists between increased lipid peroxidation and inhibition of the activity of this antioxidative enzyme in schizophrenic platelets.

No association between Ala9Val functional polymorphism of MnSOD gene and schizophrenia in a representative Italian sample

Reactive oxygen species (ROS) have been suggested to play an important role in physiopathology of schizophrenia. The polymorphisms in the genes encoding antioxidant enzymes, such as manganese superoxide dismutase (MnSOD) should, thus, result in predisposition to this psychiatric disorder. A functional amino acid polymorphism (Ala9Val) has been described in the signal sequence of enzyme associated with a decreased defense capacity against oxidative stress. Preliminary evidence in a Turkey population indicated that this polymorphism contributes to physiopathogenesis of schizophrenia. The object of this study was to verify the association between Ala9Val and schizophrenia in a representative Italian sample. The polymorphism was genotyped by PCR amplification and Single-Stranded Conformational Polymorphism (SSCP) analysis in 212 DSMIV schizophrenic patients and 257 healthy volunteers. No association was observed between cases and controls (genotype and allele frequencies: p = 0.72, p = 0.55, respectively) even when a sample stratification for gender, age at onset and diagnostic subtypes was performed. This suggests that the gene variant could not be a risk factor for schizophrenia susceptibility in an Italian sample.

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.

Oxidative damage and schizophrenia: an overview of the evidence and its therapeutic implications

Free radicals are highly reactive chemical species generated during normal metabolic processes. which in excess can lead to membrane damage. Elaborate antioxidant defence systems exist to protect against oxidative stress. There is accumulating evidence of altered antioxidant capacity in schizophrenia. Membrane dysfunction can be secondary to free radical-mediated pathology, and may contribute to specific aspects of schizophrenic symptomatology and complications of its treatment. Specifically, free radical-mediated abnormalities may contribute to the development of a number of clinically significant consequences, including prominent negative symptoms, tardive dyskinesia, neurological 'soft' signs and parkinsonian symptoms. Our previous results showing altered membrane dynamics and antioxidant enzyme activities in schizophrenia, and findings from other investigators, are consistent with the notion of free radical-mediated neurotoxicity in schizophrenia. These findings provide a theoretical basis from which the development of novel therapeutic strategies such as fatty acid and antioxidant supplementation can occur in the future.

Abnormal age-related changes of plasma antioxidant proteins in schizophrenia

Albumin and bilirubin are metal-binding proteins, shown to possess free radical scavenging properties, and may thus be selective antioxidants. In the present study we examined whether individual plasma antioxidants such as albumin and bilirubin, which significantly contribute to total antioxidant status (TAS), are reduced in patients with schizophrenia. We prospectively studied plasma antioxidant proteins, i.e. albumin and bilirubin, in male veteran schizophrenic patients using a within-subject, repeated measures, on-off-on haloperidol treatment design, as well as age- and sex-matched healthy volunteers. Male patients with schizophrenia either during haloperidol treatment (n=46) or in a drug-free condition (n=35) had significantly lower levels of both plasma albumin and bilirubin compared with age- and sex-matched healthy volunteers (n=31). Such reductions of plasma antioxidant proteins in schizophrenic patients appear to be age-related changes, in contrast to those observed in healthy volunteers. On the other hand, levels of plasma albumin and bilirubin were not significantly affected by haloperidol treatment, haloperidol withdrawal, or length of drug-free period. Moreover, plasma TAS was not influenced significantly by cigarette smoking, even though it may selectively decrease plasma bilirubin but not albumin levels. The present findings, taken together with our previous results of reduced plasma TAS and uric acid, as well as an increased Red blood cell superoxide dismutase, lend further support to the hypothesis that a defect in the antioxidant defense system exists in schizophrenia that may lead to oxidative damage.

Comparisons of flux control exerted by mitochondrial outer-membrane carnitine palmitoyltransferase over ketogenesis in hepatocytes and mitochondria isolated from suckling or adult rats

The primary aim of this paper was to calculate and report flux control coefficients for mitochondrial outer-membrane carnitine palmitoyltransferase (CPT I) over hepatic ketogenesis because its role in controlling this pathway during the neonatal period is of academic importance and immediate clinical relevance. Using hepatocytes isolated from suckling rats as our model system, we measured CPT I activity and carbon flux from palmitate to ketone bodies and to CO2 in the absence and presence of a range of concentrations of etomoxir. (This is converted in situ to etomoxir-CoA which is a specific inhibitor of the enzyme.) From these data we calculated the individual flux control coefficients for CPT I over ketogenesis, CO2 production and total carbon flux (0.51 +/- 0.03; -1.30 +/- 0.26; 0.55 +/- 0.07, respectively) and compared them with equivalent coefficients calculated by similar analyses [Drynan, L., Quant, P.A. & Zammit, V.A. (1996) Biochem. J. 317, 791-795] in hepatocytes isolated from adult rats (0.85 +/- 0.20; 0.23 +/- 0.06; 1.06 +/- 0.29). CPT I exerts significantly less control over ketogenesis in hepatocytes isolated from suckling rats than those from adult rats. In the suckling systems the flux control coefficients for CPT I over ketogenesis specifically and over total carbon flux (< 0.6) are not consistent with the enzyme being rate-limiting. Broadly similar results were obtained and conclusions drawn by reanalysis of previous data {from experiments in mitochondria isolated from suckling or adult rats [Krauss, S., Lascelles, C.V., Zammit, V.A. & Quant, P.A. (1996) Biochem. J. 319, 427-433]} using a different approach of control analysis, although it is not strictly valid to compare flux control coefficients from different systems. Our overall conclusion is that flux control coefficients for CPT I over oxidative fluxes from palmitate (or palmitoyl-CoA) differ markedly according to (a) the metabolic state, (b) the stage of development, (c) the specific pathway studied and (d) the model system.