Membrane phospholipid composition, alterations in neurotransmitter systems and schizophrenia

High throughput lipidomic profiling of schizophrenia and bipolar disorder brain tissue reveals alterations of free fatty acids, phosphatidylcholines, and ceramides

A mass spectrometry based high throughput approach was employed to profile white and gray matter lipid levels in the prefrontal cortex (Brodmann area 9) of 45 subjects including 15 schizophrenia and 15 bipolar disorder patients as well as 15 controls samples. We found statistically significant alterations in levels of free fatty acids and phosphatidylcholine in gray and white matter of both schizophrenia and bipolar disorder samples compared to controls. Also, ceramides were identified to be significantly increased in white matter of both neuropsychiatric disorders as compared to control levels. The patient cohort investigated in this study includes a number of drug naive as well as untreated patients, allowing the assessment of drug effects on lipid levels. Our findings indicate that while gray matter phosphatidylcholine levels were influenced by antipsychotic medication, this was not the case for phosphatidylcholine levels in white matter. Changes in free fatty acids or ceramides in either white or gray matter also did not appear to be influenced by antipsychotic treatment. To assess lipid profiles in the living patient, we also profiled lipids of 40 red blood cell samples, including 7 samples from drug naive first onset patients. We found significant alterations in the concentrations of free fatty acids as well as ceramide. Overall, our findings suggest that lipid abnormalities may be a disease intrinsic feature of both schizophrenia and bipolar disorder reflected by significant changes in the central nervous system as well as peripheral tissues.

BanI polymorphism of cytosolic phospholipase A2 gene is associated with age at onset in male patients with schizophrenia and schizoaffective disorder

The enzymes phospholipases A2 are believed to be involved in the pathology of schizophrenia. We investigated allelic and genotype frequencies of PLA2G4A BanI polymorphism and the rs4375 in PLA2G6A in Croatian schizophrenic patients (n=81) and controls (n=182), using PCR/RFLP. Genotype and allelic frequencies of both loci, alone or in combination did not show significant difference (chi2-test). Allele-wise and genotype-wise meta-analyses of BanI polymorphism in case-control and family-based studies also revealed no significant association with schizophrenia. Multiple logistic regression analyses revealed statistically significant association between several items from PANSS general psychopathology scale and BanI polymorphism in PLA2G4A. BanI polymorphism further showed a significant impact on mean age of the onset of disease in males (betaA1=0.351, P=0.021; Spearman's rA1=0.391, P=0.010) indicating lower mean age at admission in homozygous A2A2 males.

Brain-derived neurotropic factor/TrkB signaling in the pathogenesis and novel pharmacotherapy of schizophrenia

The role of neurotropins, predominantly brain-derived neurotropic factor (BDNF), has been implicated in the pathophysiology as well as treatment outcome of schizophrenia. Both human and rodent studies indicate that the beneficial effects of antipsychotic drugs are mediated, at least in part, through BDNF and its receptor, TrkB. This review will discuss the available data on the levels of BDNF and TrkB in subjects with schizophrenia and in animals with and without conventional antipsychotics. The data concerning the impact of the antipsychotic drugs on BDNF/TrkB signaling will also be discussed. More importantly, this review will provide future perspective on BDNF/TrkB signaling as a novel molecular target to correct the pathogenesis and improve the long-term clinical outcome by treatments with conventional and adjunctive drugs.

Retinal dysfunctions in schizophrenia

The purpose of this study was to investigate the earliest stages of visual information processing using electroretinography (ERG) in patients with schizophrenia and bipolar disorder and to compare these values with those of healthy control volunteers. In the acute stage of the illness, patients with schizophrenia exhibited decreased a-wave amplitude (a measure of photoreceptor function) as compared with healthy controls. In patients with bipolar disorder, ERG measures were intact. At the baseline assessment, there was a significant negative relationship between a-wave amplitude and positive symptoms. After an 8-week follow-up period, clinical symptoms showed significant improvement and the amplitude of the a-wave significantly increased in patients with schizophrenia. At the follow-up assessment, there was no significant difference between patients with schizophrenia and controls. These results indicate that retinal dysfunctions are specific for schizophrenia, as compared with bipolar disorder, and are confined to the acute stage of the illness.

Modulation of hSlo BK current inactivation by fatty acid esters of CoA

Lipid metabolism influences membrane proteins, including ion channels, in health and disease. Fatty acid esters of CoA are important intermediates in fatty acid metabolism and lipid biosynthesis. In the present study, we examined the effect of acyl-CoAs on hSlo BK currents. Arachidonoyl-CoA (C(20)-CoA) induced beta2-dependent inhibition of hSlo-alpha current when applied intracellularly but not extracellularly. This action was also mimicked by other long-chain acyl-CoAs such as oleoyl-CoA (C(18)-CoA) and palmitoyl-CoA (C(16)-CoA), but not acetyl-CoA (C(2)-CoA, shorter chain), suggesting that the length of acyl chains, rather than CoA headgroups, is critical. When hSlo-alpha inactivation was induced by a free synthetic cationic beta2 NH2-terminus inactivation ball peptide, long-chain acyl-CoAs inhibited hSlo-alpha current and facilitated inactivation. The precursor fatty acids also facilitated the ball peptide-induced inactivation in a chain length-dependent manner, whereas sphingosine (positively charged) slowed this inactivation. When the beta2-induced inactivation was compared with that of the ball peptide, there was a negative shift in the steady state inactivation, slower recovery, and a reduced voltage-dependence of inactivation onset. These data suggest that electrostatic interactions with the cytosolic inactivation domain of beta2 mediate acyl-CoA modulation of BK currents. BK channel inactivation may be a specific target for lipid modulation in physiological and pathophysiological conditions.

Reduction of gangliosides, phospholipids and cholesterol content in cerebral cortex of rats caused by chronic hypermethioninemia

Neurological dysfunction is observed in patients with severe hypermethioninemia, whose physiopathology is still poorly understood. In the current study we investigated the effect of chronic administration of methionine on the content and species of gangliosides and phospholipids, as well as on the concentration of cholesterol in rat cerebral cortex. Wistar rats received subcutaneous injections of methionine (1.34-2.68 micromol/g of body weight), twice a day, from the 6th to the 28th day of age and controls received saline. Animals were killed 12h after the last injection. Results showed that methionine administration significantly decreased the total content of lipids in cerebral cortex of rats. We also observed that this amino acid significantly reduced the absolute quantity of the major brain gangliosides (GM1, GD1a, GD1b and GT1b) and phospholipids (sphingomyelin, phosphatidylcholine and phosphatidylethanolamine). We also showed that Na+,K+-ATPase activity and TBARS were changed in cerebral cortex of rats subjected to hypermethioninemia. If confirmed in human beings, these data could suggest that the alteration in lipid composition, Na+,K+-ATPase activity and TBARS caused by methionine might contribute to the neurophysiopathology observed in hypermethioninemic patients.

Deficits in social behavior and sensorimotor gating in mice lacking phospholipase Cbeta1

Abnormal phospholipid metabolism has been implicated in the pathogenesis of schizophrenia, and it was reported that phospholipase C (PLC) beta1 is reduced in specific brain areas of patients with schizophrenia. However, the causal relationship of the PLCbeta1 gene with behavioral symptoms of schizophrenia remains unclear. To address this issue, we have examined the mutant mice lacking PLCbeta1 for schizophrenia-related phenotypes by performing various behavioral tests, including general locomotor activity, sensorimotor gating, social behaviors, and learning and memory. Phospholipase C beta1 knockout mice showed hyperactivities in an open field. They showed impaired prepulse inhibition of acoustic startle response, which was ameliorated by a systemic administration of an antipsychotic D2-receptor antagonist, haloperidol. In addition, they showed abnormal social behaviors, such as lack of barbering behavior, socially recessive trait and lack of nesting behavior. Furthermore, they showed impaired performance in the delayed-non-match-to-sample T-maze test. The present results show that the PLCbeta1 mutant mice share some of the behavioral abnormalities that have been reported in patients with schizophrenia. Thus, the PLCbeta1-linked signaling pathways may be involved in the neural system whose function is disrupted in the pathogenesis of schizophrenia.

Enhanced cAMP/PKA pathway by seabuckthorn fatty acids in aged rats

Seabuckthorn fatty acids were extracted by crushing and centrifuging from china seabuckthorn fruit. We detected cyclic nucleotides concentration in serum of different stages in aged rats (from 16 to 21 months), cyclic nucleotides concentration, PKA activity and PDE activity in hepatic tissue in aged rats by seabuckthorn fatty acids. Our data showed that the serum cAMP concentration decreased, accompany with the cGMP concentration increased and the imbalance of the cAMP/cGMP ratio in aged process. This kind of change equally in the hepatic tissue, the cAMP concentration decreased, PKA activity also decreased, but no change of the cAMP particularity PDE activity. And the SBFAs raised serum cAMP level in different stages, and raised the cAMP concentration and PKA activity of hepatic tissue, but did not effect the cAMP particularity PDE activity. Our study demonstrated that it is imbalance of the cAMP/cGMP ratio in aged process. SBFAs enhanced the cAMP/PKA pathway, regulated cAMP/cGMP ratio in aged rats.

The n-3 polyunsaturated fatty acid/dopamine hypothesis of schizophrenia

The dopamine hypothesis of schizophrenia has been the most influential since the 1970s. Normally, the prefrontal dopamine system suppressively controls the limbic dopamine system. Since the activities of prefrontal dopaminergic neurons are reduced in schizophrenia, the suppressive effect of the prefrontal area on the limbic system is reduced, and activities of the limbic dopamine system are enhanced. Reduced activities of the prefrontal dopamine system contribute to negative symptoms and cognitive disorders, and increased activities of the limbic dopamine system induce positive symptoms. While the dopamine hypothesis explains the relationship between dopamine kinetics and psychiatric symptoms in schizophrenia, it is not a direct explanation of its etiology. The cause of the abnormal activities of dopaminergic neurons in schizophrenia and its resultant symptoms are unknown. Since the late 1980s, it has been revealed that the n-3 fatty acid concentration is reduced in the plasma and erythrocyte membranes of schizophrenic patients and that the administration of n-3 fatty acids may be effective for the treatment of schizophrenia. Whether or not n-3 fatty acid deficiency plays a direct role in schizophrenia etiology, and the mechanisms underlying their therapeutic effect have yet to be clarified. Recently, the dopamine hypothesis and n-3 fatty acid hypothesis have been suggested to represent different aspects of the same pathology of schizophrenia. In schizophrenia, the brain concentrations of certain n-3 fatty acids are decreased. In rodents, n-3 fatty acid deficiency has been shown to cause decreases in dopamine concentration, number of vesicles and D2 receptors at prefrontal presynaptic terminals. The following minireview provides a summary of findings from n-3 fatty acid deficient animal models and their relevance to schizophrenia pathology is discussed.

β-Subunit–Dependent Modulation ofhSloBK Current by Arachidonic Acid

In this study, we examined the effect of arachidonic acid (AA) on the BK α-subunit with or without β-subunits expressed in Xenopus oocytes. In excised patches, AA potentiated the hSlo-α current and slowed inactivation only when β2/3 subunit was co-expressed. The β2-subunit–dependent modulation by AA persisted in the presence of either superoxide dismutase or inhibitors of AA metabolism such as nordihydroguaiaretic acid and eicosatetraynoic acid, suggesting that AA acts directly rather than through its metabolites. Other cis unsaturated fatty acids (docosahexaenoic and oleic acid) also enhanced hSlo-α + β2 currents and slowed inactivation, whereas saturated fatty acids (palmitic, stearic, and caprylic acid) were without effect. Pretreatment with trypsin to remove the cytosolic inactivation domain largely occluded AA action. Intracellularly applied free synthetic β2-ball peptide induced inactivation of the hSlo-α current, and AA failed to enhance this current and slow the inactivation. These results suggest that AA removes inactivation by interacting, possibly through conformational changes, with β2 to prevent the inactivation ball from reaching its receptor. Our data reveal a novel mechanism of β-subunit–dependent modulation of BK channels by AA. In freshly dissociated mouse neocortical neurons, AA eliminated a transient component of whole cell K+currents. BK channel inactivation may be a specific mechanism by which AA and other unsaturated fatty acids influence neuronal death/survival in neuropathological conditions.

Fish oil and mental health: the role of n-3 long-chain polyunsaturated fatty acids in cognitive development and neurological disorders

Epidemiological and experimental studies have indicated that consumption of more n-3 long-chain polyunsaturated fatty acids may reduce the risk for a variety of diseases, including cardiovascular, neurological and immunological disorders, diabetes and cancer. This article focuses on the role of marine n-3 long-chain polyunsaturated fatty acids in brain functions, including the development of the central nervous system and neurological disorders. An overview of the major animal studies and clinical trials is provided here, focusing on fatty acid supplementation during pregnancy and infancy, and prevention and management of Alzheimer's disease, schizophrenia, depression and attention deficit hyperactive disorder. Although an optimal balance in n-3/n-6 long-chain polyunsaturated fatty acid ratio is important for proper neurodevelopment and cognitive functions, results from randomized controlled trials are controversial and do not confirm any useful effect of supplementation on development of preterm and term infants. The relationship between fatty acid status and mental disorders is confirmed by reduced levels of n-3 long-chain polyunsaturated fatty acids in erythrocyte membranes of patients with central nervous system disorders. Nevertheless, there are very little data supporting the use of fish oil in those patients. The only way to verify whether n-3 long-chain polyunsaturated fatty acids are a potential therapeutic option in the management and prevention of mental disorders is to conduct a large definitive randomized controlled trials similar to those required for the licensing of any new pharmacological treatment.

Omega-3 fatty acids and monoamine neurotransmission

We proposed several years ago that the behavioral effects of n-3 PUFA deficiency observed in animal models might be mediated through the dopaminergic and serotonergic systems that are very involved in the modulation of attention, motivation and emotion. We evaluated this hypothesis in an extended series of experiments on rats chronically diet-deficient in alpha-linolenic acid, the precursor of long-chain n-3 PUFA, in which we studied several parameters of these neurotransmission systems. The present paper synthesizes the main data we obtained on interactions between n-3 PUFA status and neurotransmission in animal models. We demonstrated that several parameters of neurotransmission were affected, such as the vesicular pool of dopamine and serotonin, thus inducing several regulatory processes such as modification of cerebral receptors in specific brain areas. We also demonstrated that (i) a reversal diet with adequate n-6 and n-3 PUFA given during the lactating period to rats originating from alpha-linolenic acid-deficient dams was able to restore both the fatty acid composition of brain membranes and several parameters of the dopaminergic and serotonergic neurotransmission, and (ii) when given from weaning, this reversal diet allowed partial recovery of biochemical parameters, but no recovery of neurochemical factors. The occurrence of profound n-3 PUFA deficiency during the lactating period could therefore be an environmental insult leading to irreversible damage to specific brain functions. Strong evidence is now showing that a profound n-3 PUFA experimental deficiency is able to alter several neurotransmission systems, at least the dopaminergic and serotonergic. Whether these experimental findings can be transposed to human pathophysiology must be taken cautiously, but reinforces the hypothesis that strong links exist between the PUFA status, aspects of brain function such as neurotransmission processes and behavior.

The protective effects of omega-3 fatty acids against MK-801-induced neurotoxicity in prefrontal cortex of rat

The aims of this study are to investigate the contribution effect of oxidative stress in MK-801-induced experimental psychosis model, and to show that prevention of oxidative stress may improve prognosis. Because oxidative damage has been suggested in the neuropathophysiology of schizophrenia, the possible protecting agents against lipid peroxidation are potential target for the studies in this field. For this purpose, Wistar Albino rats were divided into three groups: the first group was used as control, MK-801 was given to the rats in the second group and MK-801+omega-3 essential fatty acids (EFA) was given to the third group. MK-801 was given intraperitoneally at the dose of 0.5mg/(kgday) once a day for 5 days in experimental psychosis group. In the second group, 0.8g/(kgday), omega-3 FA (eicosapentaenoic acid, 18%, docosahexaenoic acid, 12%) was given to the rats while exposed MK-801. In control group, saline was given intraperitoneally at the same time. After 7 days, rats were killed by decapitation. Prefrontal brain area was removed for histological and biochemical analyses. As a result, malondialdehyde (MDA), as an indicator of lipid peroxidation, protein carbonyl (PC), as an indicator of protein oxidation, nitric oxide (NO) levels and superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activities as antioxidant enzymes, and xanthine oxidase (XO) and adenosine deaminase (AD) activities as an indicator of DNA oxidation was found to be increased significantly in prefrontal cortex (PFC) of MK-801 group (P<0.0001) compared to control group. In omega-3 FA treated rats, prefrontal tissue MDA, PC and NO levels as well as SOD, GSH-Px, XO, and AD enzyme activities were significantly decreased when compared to MK-801 groups (P<0.0001) whereas catalase (CAT) enzyme activity was not changed. Moreover, in the light of microscopic examination of MK-801 groups, a great number of apoptotic cells were observed. omega-3 FA supplementation decreased the apoptotic cell count in PFC. The results of this study revealed that oxidative stress and apoptotic changes in PFC may play an important role in the pathogenesis of MK-801-induced neuronal toxicity. This experimental study also provides some evidences for the protective effects of omega-3 FA on MK-801-induced changes in PFC of rats.