Chronic lithium treatment decreases brain phospholipase A2 activity

Dynamics of Choline-Containing Phospholipids in Traumatic Brain Injury and Associated Comorbidities

The incidences of traumatic brain injuries (TBIs) are increasing globally because of expanding population and increased dependencies on motorized vehicles and machines. This has resulted in increased socio-economic burden on the healthcare system, as TBIs are often associated with mental and physical morbidities with lifelong dependencies, and have severely limited therapeutic options. There is an emerging need to identify the molecular mechanisms orchestrating these injuries to life-long neurodegenerative disease and a therapeutic strategy to counter them. This review highlights the dynamics and role of choline-containing phospholipids during TBIs and how they can be used to evaluate the severity of injuries and later targeted to mitigate neuro-degradation, based on clinical and preclinical studies. Choline-based phospholipids are involved in maintaining the structural integrity of the neuronal/glial cell membranes and are simultaneously the essential component of various biochemical pathways, such as cholinergic neuronal transmission in the brain. Choline or its metabolite levels increase during acute and chronic phases of TBI because of excitotoxicity, ischemia and oxidative stress; this can serve as useful biomarker to predict the severity and prognosis of TBIs. Moreover, the effect of choline-replenishing agents as a post-TBI management strategy has been reviewed in clinical and preclinical studies. Overall, this review determines the theranostic potential of choline phospholipids and provides new insights in the management of TBI.

Omega-3 fatty acids and mood stabilizers alter behavioral and oxidative stress parameters in animals subjected to fenproporex administration

Studies have shown that oxidative stress is involved in the pathophysiology of bipolar disorder (BD). It is suggested that omega-3 (ω3) fatty acids are fundamental to maintaining the functional integrity of the central nervous system. The animal model used in this study displayed fenproporex-induced hyperactivity, a symptom similar to manic BD. Our results showed that the administration of fenproporex, in the prevent treatment protocol, increased lipid peroxidation in the prefrontal cortex (143%), hippocampus (58%) and striatum (181%), and ω3 fatty acids alone prevented this change in the prefrontal cortex and hippocampus, whereas the co-administration of ω3 fatty acids with VPA prevented the lipoperoxidation in all analyzed brain areas, and the co-administration of ω3 fatty acids with Li prevented this increase only in the prefrontal cortex and striatum. Moreover, superoxide dismutase (SOD) activity was decreased in the striatum (54%) in the prevention treatment, and the administration of ω3 fatty acids alone or in combination with Li and VPA partially prevented this inhibition. On the other hand, in the reversal treatment protocol, the administration of fenproporex increased carbonyl content in the prefrontal cortex (25%), hippocampus (114%) and striatum (91%), and in prefrontal coxter the administration of ω3 fatty acids alone or in combination with Li and VPA reversed this change, whereas in the hippocampus and striatum only ω3 fatty acids alone or in combination with VPA reversed this effect. Additionally, the administration of fenproporex resulted in a marked increase of TBARS in the hippocampus and striatum, and ω3 fatty acids alone or in combination with Li and VPA reversed this change. Finally, fenproporex administration decreased SOD activity in the prefrontal cortex (85%), hippocampus (52%) and striatum (76%), and the ω3 fatty acids in combination with VPA reversed this change in the prefrontal cortex and striatum, while the co-administration of ω3 fatty acids with Li reversed this inhibition in the hippocampus and striatum. In conclusion, our results support other studies showing the importance of ω3 fatty acids in the brain and the potential for these fatty acids to aid in the treatment of BD.

Long-Term Lithium Treatment Increases cPLA₂ and iPLA₂ Activity in Cultured Cortical and Hippocampal Neurons

Background: Experimental evidence supports the neuroprotective properties of lithium, with implications for the treatment and prevention of dementia and other neurodegenerative disorders. Lithium modulates critical intracellular pathways related to neurotrophic support, inflammatory response, autophagy and apoptosis. There is additional evidence indicating that lithium may also affect membrane homeostasis. Objective: To investigate the effect of lithium on cytosolic phospholipase A₂ (PLA₂) activity, a key player on membrane phospholipid turnover which has been found to be reduced in blood and brain tissue of patients with Alzheimer’s disease (AD). Methods: Primary cultures of cortical and hippocampal neurons were treated for 7 days with different concentrations of lithium chloride (0.02 mM, 0.2 mM and 2 mM). A radio-enzymatic assay was used to determine the total activity of PLA₂ and two PLA₂ subtypes: cytosolic calcium-dependent (cPLA₂); and calcium-independent (iPLA₂). Results: cPLA₂ activity increased by 82% (0.02 mM; p = 0.05) and 26% (0.2 mM; p = 0.04) in cortical neurons and by 61% (0.2 mM; p = 0.03) and 57% (2 mM; p = 0.04) in hippocampal neurons. iPLA₂ activity was increased by 7% (0.2 mM; p = 0.04) and 13% (2 mM; p = 0.05) in cortical neurons and by 141% (0.02 mM; p = 0.0198) in hippocampal neurons. Conclusion: long-term lithium treatment increases membrane phospholipid metabolism in neurons through the activation of total, c- and iPLA₂. This effect is more prominent at sub-therapeutic concentrations of lithium, and the activation of distinct cytosolic PLA₂ subtypes is tissue specific, i.e., iPLA₂ in hippocampal neurons, and cPLA₂ in cortical neurons. Because PLA₂ activities are reported to be reduced in Alzheimer’s disease (AD) and bipolar disorder (BD), the present findings provide a possible mechanism by which long-term lithium treatment may be useful in the prevention of the disease.

Potential application of lithium in Parkinson's and other neurodegenerative diseases

Lithium, the long-standing hallmark treatment for bipolar disorder, has recently been identified as a potential neuroprotective agent in neurodegeneration. Here we focus on introducing numerous in vitro and in vivo studies that have shown lithium treatment to be efficacious in reducing oxidative stress and inflammation, increasing autophagy, inhibiting apoptosis, and decreasing the accumulation of α-synulcein, with an emphasis on Parkinson's disease. A number of biological pathways have been shown to be involved in causing these neuroprotective effects. The inhibition of GSK-3β has been the mechanism most studied; however, other modes of action include the regulation of apoptotic proteins and glutamate excitotoxicity as well as down-regulation of calpain. This review provides a framework of the neuroprotective effects of lithium in neurodegenerative diseases and the putative mechanisms by which lithium provides the protection. Lithium-only treatment may not be a suitable therapeutic option for neurodegenerative diseases due to inconsistent efficacy and potential side-effects, however, the use of low dose lithium in combination with other potential or existing therapeutic compounds may be a promising approach to reduce symptoms and disease progression in neurodegenerative diseases.

Common biological mechanisms between bipolar disorder and type 2 diabetes: Focus on inflammation

INTRODUCTION

Bipolar disorder (BD) patients present a 3-5 fold greater risk of developing type 2 diabetes (T2D) compared to general population. The underlying mechanisms for the increased prevalence of T2D in BD population are poorly understood.

OBJECTIVES

The purpose of this review is to critically review evidence suggesting that inflammation may have an important role in the development of both BD and T2D.

RESULTS

The literature covered in this review suggests that inflammatory dysregulation take place among many BD patients. Such dysregulated and low grade chronic inflammatory process may also increase the prevalence of T2D in BD population. Current evidence supports the hypothesis of dysregulated inflammatory processes as a critical upstream event in BD as well as in T2D.

CONCLUSIONS

Inflammation may be a factor for the development of T2D in BD population. The identification of inflammatory markers common to these two medical conditions will enable researchers and clinicians to better understand the etiology of BD and develop treatments that simultaneously target all aspects of this multi-system condition.

Effects of lithium on inflammation

Lithium is an effective medication for the treatment of bipolar affective disorder. Accumulating evidence suggests that inflammation plays a role in the pathogenesis of bipolar disorder and that lithium has anti-inflammatory effects that may contribute to its therapeutic efficacy. This article summarizes the studies which examined the effects of lithium on pro- and anti-inflammatory mediators. Some of the summarized data suggest that lithium exerts anti-inflammatory effects (e.g., suppression of cyclooxygenase-2 expression, inhibition of interleukin (IL)-1β and tumor necrosis factor-α production, and enhancement of IL-2 and IL-10 synthesis). Nevertheless, there is a large body of data which indicates that under certain experimental conditions lithium also exhibits pro-inflammatory properties (e.g., induction of IL-4, IL-6 and other pro-inflammatory cytokines synthesis). The reviewed studies utilized various experimental model systems, and it is thus difficult to draw an unequivocal conclusion regarding the effect of lithium on specific inflammatory mediators.

Plasma phosphatidylcholine and sphingomyelin concentrations are associated with depression and anxiety symptoms in a Dutch family-based lipidomics study

The central nervous system has the second highest concentration of lipids after adipose tissue. Alterations in neural membrane phospho- and sphingolipid composition can influence crucial intra- and intercellular signalling and alter the membrane's properties. Recently, the polyunsaturated fatty acids (PUFA) hypothesis for depression suggests that phospho- and sphingolipid metabolism includes potential pathways for the disease. In 742 people from a Dutch family-based study, we assessed the relationships between 148 different plasma phospho- and sphingolipid species and depression/anxiety symptoms as measured by the Hospital Anxiety and Depression Scales (HADS-A and HADS-D) and the Centre for Epidemiological Studies Depression Scale (CES-D). We observed significant differences in plasma sphingomyelins (SPM), particularly the SPM 23:1/SPM 16:0 ratio, which was inversely correlated with depressive symptom scores. We observed a similar trend for plasma phosphatidylcholines (PC), particularly the molar proportion of PC O 36:4 and its ratio to ceramide CER 20:0. Absolute levels of PC O 36:4 were also associated with depression symptoms in an independent replication. To our knowledge this is the first study on depressive symptoms that focuses on specific phospho- and sphingolipid molecules in plasma rather than total PUFA concentrations. The findings of this lipidomic study suggests that plasma sphingomyelins and ether phospholipids should be further studied for their potential as biomarkers and for a better understanding of the underlying mechanisms of this systemic disease.

cPLA2α knockout mice exhibit abnormalities in the architecture and synapses of cortical neurons

Cytosolic phospholipase A2α (cPLA2α) affects membrane fluidity and permeability by catalyzing the hydrolysis of membrane phospholipids. We hypothesize that cPLA2α deficiency induces rigidity and architectural changes in cell membranes, especially in large cortical neurons. These membrane changes are discernible using light and electron microscopy. Through careful comparison with wild-type counterparts, we observed significant morphological changes in cortical neurons of cPLA2α knockout mice. These changes included the following: (1) increased numbers of nucleoli and enlarged nuclei, (2) narrower spaces between the inner and outer nuclear membranes, (3) reduced numbers of nuclear pores and altered nuclear pore structure, and (4) morphological changes in synaptic clefts. These results further suggest that cPLA2α and its cleaved arachidonic acids play important roles in cortical neuronal maturation and in normal neurochemical processes.

Chronic lithium feeding reduces upregulated brain arachidonic acid metabolism in HIV-1 transgenic rat

HIV-1 transgenic (Tg) rats, a model for human HIV-1 associated neurocognitive disorder (HAND), show upregulated markers of brain arachidonic acid (AA) metabolism with neuroinflammation after 7 months of age. Since lithium decreases AA metabolism in a rat lipopolysaccharide model of neuroinflammation, and may be useful in HAND, we hypothesized that lithium would dampen upregulated brain AA metabolism in HIV-1 Tg rats. Regional brain AA incorporation coefficients k* and rates J ( in ), markers of AA signaling and metabolism, were measured in 81 brain regions using quantitative autoradiography, after intravenous [1-(14) C]AA infusion in unanesthetized 10-month-old HIV-1 Tg and age-matched wildtype rats that had been fed a control or LiCl diet for 6 weeks. k* and J ( in ) for AA were significantly higher in HIV-1 Tg than wildtype rats fed the control diet. Lithium feeding reduced plasma unesterified AA concentration in both groups and J ( in ) in wildtype rats, and blocked increments in k* (19 of 54 regions) and J ( in ) (77 of 81 regions) in HIV-1 Tg rats. These in vivo neuroimaging data indicate that lithium treatment dampened upregulated brain AA metabolism in HIV-1 Tg rats. Lithium may improve cognitive dysfunction and be neuroprotective in HIV-1 patients with HAND through a comparable effect.

Imaging brain signal transduction and metabolism via arachidonic and docosahexaenoic acid in animals and humans

The polyunsaturated fatty acids (PUFAs), arachidonic acid (AA, 20:4n-6) and docosahexaenoic acid (DHA, 22:6n-3), important second messengers in brain, are released from membrane phospholipid following receptor-mediated activation of specific phospholipase A(2) (PLA(2)) enzymes. We developed an in vivo method in rodents using quantitative autoradiography to image PUFA incorporation into brain from plasma, and showed that their incorporation rates equal their rates of metabolic consumption by brain. Thus, quantitative imaging of unesterified plasma AA or DHA incorporation into brain can be used as a biomarker of brain PUFA metabolism and neurotransmission. We have employed our method to image and quantify effects of mood stabilizers on brain AA/DHA incorporation during neurotransmission by muscarinic M(1,3,5), serotonergic 5-HT(2A/2C), dopaminergic D(2)-like (D(2), D(3), D(4)) or glutamatergic N-methyl-d-aspartic acid (NMDA) receptors, and effects of inhibition of acetylcholinesterase, of selective serotonin and dopamine reuptake transporter inhibitors, of neuroinflammation (HIV-1 and lipopolysaccharide) and excitotoxicity, and in genetically modified rodents. The method has been extended for the use with positron emission tomography (PET), and can be employed to determine how human brain AA/DHA signaling and consumption are influenced by diet, aging, disease and genetics.

Novel insights into lithium's mechanism of action: neurotrophic and neuroprotective effects

The monovalent cation lithium partially exerts its effects by activating neurotrophic and neuroprotective cellular cascades. Here, we discuss the effects of lithium on oxidative stress, programmed cell death (apoptosis), inflammation, glial dysfunction, neurotrophic factor functioning, excitotoxicity, and mitochondrial stability. In particular, we review evidence demonstrating the action of lithium on cyclic adenosine monophosphate (cAMP)-mediated signal transduction, cAMP response element binding activation, increased expression of brain-derived neurotrophic factor, the phosphatidylinositide cascade, protein kinase C inhibition, glycogen synthase kinase 3 inhibition, and B-cell lymphoma 2 expression. Notably, we also review data from clinical studies demonstrating neurotrophic effects of lithium. We expect that a better understanding of the clinically relevant pathophysiological targets of lithium will lead to improved treatments for those who suffer from mood as well as neurodegenerative disorders.

Brain arachidonic acid uptake and turnover: implications for signaling and bipolar disorder

PURPOSE OF REVIEW

Arachidonic acid was first detected in the brain in 1922. Although earlier work examined the role of arachidonic acid in growth and development, more recent advancements have elucidated roles for arachidonic acid in brain health and disease.

RECENT FINDINGS

In this review, we summarize evidence demonstrating that unesterified arachidonic acid in the plasma pool, which is supplied in part from adipose, is readily taken up and incorporated into brain phospholipids. By labeling plasma unesterified arachidonic acid, it is possible to trace the subsequent release of arachidonic acid from brain phospholipids upon neuroreceptor-mediated release by phospholipase A2 in response to drugs and neuroinflammation in rodents. With the synthesis of 11C labeled fatty acids, brain arachidonic acid signaling can now be measured in humans with position emission tomography. Arachidonic acid signals are known to regulate important biological functions, including neuroinflammation and excitotoxicity, and we focus on how the brain arachidonic acid cascade is a common target of drugs used to treat bipolar disorder (e.g. lithium, carbamazepine and valproate).

SUMMARY

A better understanding of the regulation of arachidonic acid uptake into the brain and the brain arachidonic acid cascade could lead to new imaging techniques and the identification of novel therapeutic targets in excitotoxicity, neuroinflammation and bipolar disorder.

Is phosphoadenosine phosphate phosphatase a target of lithium's therapeutic effect?

Lithium, which is approved for treating patients with bipolar disorder, is reported to inhibit 3'(2')-phosphoadenosine-5'-phosphate (PAP) phosphatase activity. In yeast, deletion of PAP phosphatase results in elevated PAP levels and in inhibition of sulfation and of growth. The effect of lithium on PAP phosphatase is remarkable for the low Ki (approximately 0.2 mM), suggesting that this system would be almost completely shut down in vivo with therapeutic levels of 1 mM lithium, thereby elevating PAP levels. To test the hypothesis that lithium inhibition of PAP phosphatase is pharmacologically relevant to bipolar disorder, we fed rats LiCl for 6 weeks, and assayed brain PAP levels after subjecting the brain to high-energy microwaving. We also measured PAP phosphatase mRNA and protein levels in frozen brain tissue of lithium-treated mice. Brain adenosine phosphates were extracted by trichloroacetic acid and assayed by HPLC with a gradient system of two phases. PAP phosphatase mRNA was measured by RT-PCR, and PAP phosphatase protein was measured by Western blotting. Brain PAP levels were below detection limit of 2 nmol/g wet weight, even following lithium treatment. Lithium treatment also did not significantly change brain PAP phosphatase mRNA or protein levels. These results question the relevance of PAP phosphatase to the therapeutic mechanism of lithium. A statistically significant 25% reduced brain ADP/ATP ratio was found following lithium treatment in line with lithium's suggested neuroprotective effects.

Deficits in docosahexaenoic acid and associated elevations in the metabolism of arachidonic acid and saturated fatty acids in the postmortem orbitofrontal cortex of patients with bipolar disorder

Previous antemortem and postmortem tissue fatty acid composition studies have observed significant deficits in the omega-3 fatty acid docosahexaenoic acid (DHA, 22:6n-3) in red blood cell (RBC) and postmortem cortical membranes of patients with unipolar depression. In the present study, we determined the fatty acid composition of postmortem orbitofrontal cortex (OFC, Brodmann area 10) of patients with bipolar disorder (n=18) and age-matched normal controls (n=19) by gas chromatography. After correction for multiple comparisons, DHA (-24%), arachidonic acid (-14%), and stearic acid (C18:0) (-4.5%) compositions were significantly lower, and cis-vaccenic acid (18:1n-7) (+12.5%) composition significantly higher, in the OFC of bipolar patients relative to normal controls. Based on metabolite:precursor ratios, significant elevations in arachidonic acid, stearic acid, and palmitic acid conversion/metabolism were observed in the OFC of bipolar patients, and were inversely correlated with DHA composition. Deficits in OFC DHA and arachidonic acid composition, and elevations in arachidonic acid metabolism, were numerically (but not significantly) greater in drug-free bipolar patients relative to patients treated with mood-stabilizer or antipsychotic medications. OFC DHA and arachidonic acid deficits were greater in patients plus normal controls with high vs. low alcohol abuse severity. These results add to a growing body of evidence implicating omega-3 fatty acid deficiency as well as the OFC in the pathoaetiology of bipolar disorder.

In Vitro Interaction of Lithium on Phospholipids in Human Erythrocytes

Lithium salts are used in the treatment of mania and as prophylaxis against manic depressive disorder. The aim of these studies was the in vitro investigation of the effect of lithium on phospholipids of human erythrocyte membranes. Erythrocytes were treated with lithium for 1 h. Phospholipids phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylocholine (PC) were separated from erythrocyte ghosts and determined by HPLC. Blood samples from healthy adults were investigated. A very strong decrease in PC content in erythrocyte membranes due to lithium in vitro treatment was found, as well as a statistically significant increase in PI content.

Omega-3 fatty acid deficiency augments amphetamine-induced behavioral sensitization in adult mice: prevention by chronic lithium treatment

OBJECTIVES

Emerging data suggests that omega-3 fatty acid deficiency may be a risk factor for bipolar disorder. In the present study, we determined the effects of chronic dietary-induced omega-3 fatty acid deficiency and/or concomitant chronic lithium chloride (LiCl) treatment on amphetamine (AMPH)-induced behavioral sensitization, a phenomenon that may recruit neuroplastic mechanisms relevant to the pathophysiology of bipolar disorder.

METHOD

Adult male C57BL/6J mice were randomly assigned to one four diets: Control (alpha-linolenic-fortified), Control+LiCl (0.255%), alpha-linolenic-Deficient, or Deficient+LiCl (0.255%), and behavioral testing initiated 65 days later. Locomotor activity was determined following 3 intermittent (separated by 7d) injections of amphetamine (AMPH) (1mg/kg). After behavioral testing, red blood cell (RBC) and regional brain (prefrontal cortex, hippocampus, ventral striatum) fatty acid composition was determined by gas chromatography.

RESULTS

Each diet group exhibited comparable locomotor activity following acute AMPH treatment. However, the development of sensitization following repeated AMPH treatment was significantly augmented in Deficient mice relative to controls, and this augmented response was prevented by chronic LiCl treatment. Relative to controls, Deficient mice exhibited deficits in RBC and regional brain docosahexaenoic acid (DHA, 22:6n-3) composition, reciprocal elevations in vaccenic acid (18:1n-7), arachidonic acid (AA, 20:4n-6), and docosapentaenoic acid (DPA, 22:5n-6) compositions, and elevations in AA:DHA, oleic acid:DHA, and DPA:DHA ratios. The fatty acid abnormalities in Deficient mice were not altered by concurrent chronic lithium treatment. Mice fed the Control+LiCl diet exhibited a significant increase in AA composition in RBC and all brain regions, and an elevated AA:DHA ratio in the prefrontal cortex and hippocampus, relative to Controls. Fatty acid composition in RBC and different brain regions were predominantly positively correlated. Within the ventral striatum, DHA composition was inversely correlated, and AA:DHA and oleic acid:DHA ratios positively correlated, with total distance traveled following the final AMPH treatment.

CONCLUSION

These data indicate that alterations in fatty acid composition resulting from dietary-induced omega-3 fatty acid deficiency augment the development of AMPH-induced behavioral sensitization in a manner that is prevented by chronic lithium treatment. The implications of these findings for understanding the contribution of omega-3 fatty acid deficiency to the pathophysiology and progression of bipolar disorder are discussed.

Omega-3 fatty acids on the forced-swimming test

OBJECTIVES

Based on the findings of epidemiological data and recent clinical trials, omega-3 fatty acids seem to have a preventive and therapeutic effect on depression.

METHOD

We examined the effect of omega-3 fatty acids on the forced-swimming test (FST) in two groups of Sprague-Dawley rats after a six-week treatment with two different diets. Behavioral responses were observed and recorded during the 5-min test. The fatty acid composition from the whole brain tissue and the RBC membrane of the rats were analyzed.

RESULTS

Comparing to control diet, omega-3 fatty acid diet significantly decreased the immobility time (218 +/- 16 vs. 183 +/- 19s, p = 0.001) and increased behaviors of swimming (32 +/- 7 vs. 45 +/- 9s, p = 0.012) and climbing (50 +/- 10 vs. 73 +/- 14s, p = 0.011) during the FST. The group in omega-3 fatty acid diet had higher levels of docosahexaenoic acid (DHA, 50% increase) and alpha-linolenic acid (ALA, 63% increase) in the brain, and of eicosapentaenoic acid (EPA, 27% increase) in the peripheral RBC membrane. The level of brain DHA is negatively correlated to the immobility time (r = -0.654, p = 0.006) and is positively correlated to the swimming time (r = 0.69, p = 0.003).

CONCLUSION

The result shows that omega-3 fatty acids have a beneficial effect on preventing the development of depression-like behaviors in rats with the FST.

Effect of chronic lithium administration on endothelium-dependent relaxation of rat mesenteric bed: role of nitric oxide

The mechanism of action of lithium, an effective treatment for bipolar disease, is still unknown. In this study, the mesenteric vascular beds of control rats and rats that were chronically treated with lithium were prepared by the McGregor method, and the mesenteric vascular bed vasorelaxation responses were examined. NADPH-diaphorase histochemistry was used to determine the activity of NOS (nitric oxide synthase) in mesenteric vascular beds. We demonstrated that ACh-induced vasorelaxation increased in the mesenteric vascular bed of rats treated with lithium. Acute Nο-nitro-l-arginine methyl ester (l-NAME) administration in the medium blocked ACh-induced vasorelaxation in the control group more effectively than in lithium-treated rats, while the vasorelaxant response to sodium nitroprusside, a NO donor, was not different between lithium-treated and control groups. Acute aminoguanidine administration blocked ACh-induced vasorelaxation of lithium-treated rats, but had no effect in the control rats. Furthermore, NOS activity, determined by NADPH-diaphorase staining, was significantly greater in the mesenteric vascular beds from chronic lithium-treated rats than in those from control rats. These data suggest that the enhanced ACh-induced endothelium-derived vasorelaxation in rat mesenteric bed from chronic lithium-treated rats might be associated with increased NOS activity, likely via iNOS. Simultaneous acute l-NAME and indomethacin administration suggests the possible upregulation of EDHF (endothelium-derived hyperpolarizing factor) in lithium-treated rats.

Chronic treatment of rats with sodium valproate downregulates frontal cortex NF-kappaB DNA binding activity and COX-2 mRNA

OBJECTIVES

Valproic acid (VPA) is used to treat bipolar disorder, but its mechanism of action is not clear. VPA shares many cellular and molecular targets with lithium, including reducing arachidonic acid turnover in rat brain phospholipids and cyclooxygenase-2 (COX-2) protein level and activity in rat brain.

METHODS

We examined the effect of chronic VPA administration (200 mg/kg body weight for 30 days) to produce therapeutically relevant plasma concentrations, on transcription factors (NF-kappaB, AP-1, AP-2, C/EBP, CREB, and ETS) that are known to regulate the COX-2 gene.

RESULTS

Chronic VPA significantly increased AP-1 DNA binding activity and decreased NF-kappaB DNA binding activity, p50 subunit protein and mRNA expression of COX-2 in frontal cortex compared with untreated control rats. It did not alter AP-2, C/EBP, ETS or CREB DNA binding activity.

CONCLUSIONS

VPA downregulates NF-kappaB DNA binding activity, likely by decreasing the p50 protein levels. This effect may explain its downregulation of COX-2 mRNA. The decrease in NF-kappaB activity by chronic VPA may affect other NF-kappaB-regulated genes and may be related to VPA's action in bipolar disorder. Chronic VPA may decrease the reported increased brain NF-kappaB components in bipolar patients.

Interactions between neural membrane glycerophospholipid and sphingolipid mediators: A recipe for neural cell survival or suicide

The neural membranes contain phospholipids, sphingolipids, cholesterol, and proteins. Glycerophospholipids and sphingolipids are precursors for lipid mediators involved in signal transduction processes. Degradation of glycerophospholipids by phospholipase A(2) (PLA(2)) generates arachidonic acid (AA) and docosahexaenoic acids (DHA). Arachidonic acid is metabolized to eicosanoids and DHA is metabolized to docosanoids. The catabolism of glycosphingolipids generates ceramide, ceramide 1-phosphate, sphingosine, and sphingosine 1-phosphate. These metabolites modulate PLA(2) activity. Arachidonic acid, a product derived from glycerophospholipid catabolism by PLA(2), modulates sphingomyelinase (SMase), the enzyme that generates ceramide and phosphocholine. Furthermore, sphingosine 1-phosphate modulates cyclooxygenase, an enzyme responsible for eicosanoid production in brain. This suggests that an interplay and cross talk occurs between lipid mediators of glycerophospholipid and glycosphingolipid metabolism in brain tissue. This interplay between metabolites of glycerophospholipid and sphingolipid metabolism may play an important role in initiation and maintenance of oxidative stress associated with neurologic disorders as well as in neural cell proliferation, differentiation, and apoptosis. Recent studies indicate that PLA(2) and SMase inhibitors can be used as neuroprotective and anti-apoptotic agents. Development of novel inhibitors of PLA(2) and SMase may be useful for the treatment of oxidative stress, and apoptosis associated with neurologic disorders such as stroke, Alzheimer disease, Parkinson disease, and head and spinal cord injuries.

Chronic lithium administration attenuates up-regulated brain arachidonic acid metabolism in a rat model of neuroinflammation

Neuroinflammation, caused by a 6-day intracerebroventricular infusion of lipopolysaccharide (LPS) in rats, is associated with the up-regulation of brain arachidonic acid (AA) metabolism markers. Because chronic LiCl down-regulates markers of brain AA metabolism, we hypothesized that it would attenuate increments of these markers in LPS-infused rats. Incorporation coefficients k* of AA from plasma into brain, and other brain AA metabolic markers, were measured in rats that had been fed a LiCl or control diet for 6 weeks, and subjected in the last 6 days on the diet to intracerebroventricular infusion of artificial CSF or of LPS. In rats on the control diet, LPS compared with CSF infusion increased k* significantly in 28 regions, whereas the LiCl diet prevented k* increments in 18 of these regions. LiCl in CSF infused rats increased k* in 14 regions, largely belonging to auditory and visual systems. Brain cytoplasmic phospholipase A(2) activity, and prostaglandin E(2) and thromboxane B(2) concentrations, were increased significantly by LPS infusion in rats fed the control but not the LiCl diet. Chronic LiCl administration attenuates LPS-induced up-regulation of a number of brain AA metabolism markers. To the extent that this up-regulation has neuropathological consequences, lithium might be considered for treating human brain diseases accompanied by neuroinflammation.

RETRACTED: Chronic administration of carbamazepine down-regulates AP-2 DNA-binding activity and AP-2alpha protein expression in rat frontal cortex

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of author Stanley Rapoport, with approval from Biological Psychiatry Editor, John H. Krystal, MD. The National Institutes of Health has found that Dr. Jagadeesh S. Rao engaged in research misconduct by falsifying data in Figures 1, 3, and 5 of the aforementioned manuscript. No other authors were implicated in the data falsification

Inhibitors of brain phospholipase A2 activity: their neuropharmacological effects and therapeutic importance for the treatment of neurologic disorders

The phospholipase A(2) family includes secretory phospholipase A(2), cytosolic phospholipase A(2), plasmalogen-selective phospholipase A(2), and calcium-independent phospholipase A(2). It is generally thought that the release of arachidonic acid by cytosolic phospholipase A(2) is the rate-limiting step in the generation of eicosanoids and platelet activating factor. These lipid mediators play critical roles in the initiation and modulation of inflammation and oxidative stress. Neurological disorders, such as ischemia, spinal cord injury, Alzheimer's disease, multiple sclerosis, prion diseases, and epilepsy are characterized by inflammatory reactions, oxidative stress, altered phospholipid metabolism, accumulation of lipid peroxides, and increased phospholipase A(2) activity. Increased activities of phospholipases A(2) and generation of lipid mediators may be involved in oxidative stress and neuroinflammation associated with the above neurological disorders. Several phospholipase A(2) inhibitors have been recently discovered and used for the treatment of ischemia and other neurological diseases in cell culture and animal models. At this time very little is known about in vivo neurochemical effects, mechanism of action, or toxicity of phospholipase A(2) inhibitors in human or animal models of neurological disorders. In kainic acid-mediated neurotoxicity, the activities of phospholipase A(2) isoforms and their immunoreactivities are markedly increased and phospholipase A(2) inhibitors, quinacrine and chloroquine, arachidonyl trifluoromethyl ketone, bromoenol lactone, cytidine 5-diphosphoamines, and vitamin E, not only inhibit phospholipase A(2) activity and immunoreactivity but also prevent neurodegeneration, suggesting that phospholipase A(2) is involved in the neurodegenerative process. This also suggests that phospholipase A(2) inhibitors can be used as neuroprotectants and anti-inflammatory agents against neurodegenerative processes in neurodegenerative diseases.

Modulation of phosphoinositide-protein kinase C signal transduction by omega-3 fatty acids: implications for the pathophysiology and treatment of recurrent neuropsychiatric illness

The phosphoinositide (PI)-protein kinase C (PKC) signal transduction pathway is initiated by pre- and postsynaptic Galphaq-coupled receptors, and regulates several clinically relevant neurochemical events, including neurotransmitter release efficacy, monoamine receptor function and trafficking, monoamine transporter function and trafficking, axonal myelination, and gene expression. Mounting evidence for PI-PKC signaling hyperactivity in the peripheral (platelets) and central (premortem and postmortem brain) tissues of patients with schizophrenia, bipolar disorder, and major depressive disorder, coupled with evidence that PI-PKC signal transduction is down-regulated in rat brain following chronic, but not acute, treatment with antipsychotic, mood-stabilizer, and antidepressant medications, suggest that PI-PKC hyperactivity is central to an underlying pathophysiology. Evidence that membrane omega-3 fatty acids act as endogenous antagonists of the PI-PKC signal transduction pathway, coupled with evidence that omega-3 fatty acid deficiency is observed in peripheral and central tissues of patients with schizophrenia, bipolar disorder, and major depressive disorder, support the hypothesis that omega-3 fatty acid deficiency may contribute to elevated PI-PKC activity in these illnesses. The data reviewed in this paper outline a potential molecular mechanism by which omega-3 fatty acids could contribute to the pathophysiology and treatment of recurrent neuropsychiatric illness.

Chronic lithium chloride administration attenuates brain NMDA receptor-initiated signaling via arachidonic acid in unanesthetized rats

It has been proposed that lithium is effective in bipolar disorder (BD) by inhibiting glutamatergic neurotransmission, particularly via N-methyl-D-aspartate receptors (NMDARs). To test this hypothesis and to see if the neurotransmission could involve the NMDAR-mediated activation of phospholipase A2 (PLA2), to release arachidonic acid (AA) from membrane phospholipid, we administered subconvulsant doses of NMDA to unanesthetized rats fed a chronic control or LiCl diet. We used quantitative autoradiography following the intravenous injection of radiolabeled AA to measure regional brain incorporation coefficients k* for AA, which reflect receptor-mediated activation of PLA2. In control diet rats, NMDA (25 and 50 mg/kg i.p.) compared with i.p. saline increased k* significantly in 49 and 67 regions, respectively, of the 83 brain regions examined. The regions affected were those with reported NMDARs, including the neocortex, hippocampus, caudate-putamen, thalamus, substantia nigra, and nucleus accumbens. The increases could be blocked by pretreatment with the specific noncompetitive NMDA antagonist MK-801 ((5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate) (0.3 mg/kg i.p.), as well by a 6-week LiCl diet sufficient to produce plasma and brain lithium concentrations known to be effective in BD. MK-801 alone reduced baseline values for k* in many brain regions. The results show that it is possible to image NMDA signaling via PLA2 activation and AA release in vivo, and that chronic lithium blocks this signaling, consistent with its suggested mechanism of action in BD.

Serum calcium-independent phospholipase A2 activity in bipolar affective disorder

OBJECTIVE

Phospholipases A2 (PLA2) are a family of enzymes involved in membrane phospholipid metabolism and cell signalling. The gene encoding one form, type VI calcium-independent phospholipase A2, is located in a region of DNA that may contain a gene important in the aetiology of psychosis. Moreover, the activity of calcium-independent PLA2 is reported to be elevated in the blood and brain of patients with schizophrenia. In this study we determined whether a similar change takes place in patients with bipolar disorder with and without a history of psychosis.

METHODS

Serum calcium-independent and -dependent PLA2 activities were determined in 24 patients with bipolar I disorder.

RESULTS

Serum calcium-independent and -dependent PLA2 activities in bipolar cases did not differ significantly from that in healthy volunteers (HVs). However, calcium-independent PLA2 activity was significantly (p < 0.05) higher in patients with a history of psychosis compared with those with no history of psychosis (by 55%) or to HVs (by 31%).

CONCLUSIONS

Our data suggest that a subset of bipolar I disorder patients with a history of psychosis have elevated calcium-independent PLA2 activity. Given that this enzyme activity is also increased in schizophrenia, elevated rates of phospholipid turnover mediated by the enzyme could represent a common biochemical feature of psychotic illness.

A Module Map Showing Interaction between Apolipoprotein E and Phospholipase A2 Polymorphism in Lipid Profiles

OBJECTIVE

Establish a possible conceptual relationship among Apo E and PLA2 polymorphism and lipid profiles.

METHODS

Five hundred subjects aged 65 to 74 years were randomly selected from a community in southern Taiwan to assess the relationship between Apo E and PLA2 polymorphisms and lipid profiles. Two hundred fifty-six participants agreed to have venous blood drawn for DNA studies.

RESULTS

By multiple linear regression, the PLA2 A2 allele showed a statistically significant influence on LDL-C (p = 0.0097), and the Apo epsilon2 allele showed a statistically significant influence on HDL-C (p = 0.0004), however, the interaction between the PLA2 A2 allele and the Apo epsilon2 allele was found to be significant in the blood fraction of HDL-C (p = 0.0388) and LDL-C (p = 0.0002). Decreasing HDL-C and increasing LDL-C were found when the PLA2 A2 and Apo epsilon2 allele co-existed.

CONCLUSION

The presence of a physiologic balance contributes significantly to homeostatic and compensatory responses regulating blood HDL-C and LDL-C profiles. A module map of the generation-control cycle and conditional activity among Apo E, PLA2, and lipid levels is presented, and both behaviours and biological perspectives under the consilience model may suggest a new approach to many kinds of complex disorders.

Efficacy of ethyl-eicosapentaenoic acid in bipolar depression: randomised double-blind placebo-controlled study

BACKGROUND

Epidemiological and clinical studies suggest that increased intake of eicosapentaenoic acid (EPA) alleviates unipolar depression.

AIMS

To examine the efficacy of EPA in treating depression in bipolar disorder.

METHOD

In a12-week, double-blind study individuals with bipolar depression were randomly assigned to adjunctive treatment with placebo (n=26) or with 1 g/day (n=24) or 2 g/day (n=25) of ethyl-EPA. Primary efficacy was assessed by the Hamilton Rating Scale for Depression (HRSD), with changes in the Young Mania Rating Scale and Clinical Global Impression Scale (CGI) as secondary outcome measures.

RESULTS

There was no apparent benefit of 2 g over 1 g ethyl-EPA daily. Significant improvement was noted with ethyl-EPA treatment compared with placebo in the HRSD (P=0.04) and the CGI (P=0.004) scores. Both doses were well tolerated.

CONCLUSIONS

Adjunctive ethyl-EPA is an effective and well-tolerated intervention in bipolar depression.

Decrease in the AP-2 DNA-binding activity and in the protein expression of AP-2 alpha and AP-2 beta in frontal cortex of rats treated with lithium for 6 weeks

Lithium chloride (LiCl), when fed to rats for 6 weeks, has been reported to decrease brain mRNA, protein, and activity levels of arachidonic acid (AA)-selective cytosolic phospholipase A2 (cPLA2), without affecting secretory sPLA2 or Ca2+-independent iPLA2. We investigated whether transcription factors known to regulate cPLA2 gene expression are modulated by chronic lithium treatment. Male Fischer-344 rats were fed a LiCl-containing diet for 6 weeks to produce a therapeutically relevant brain lithium concentration. Control animals were fed a LiCl-free diet. Using a gelshift assay, we found that LiCl significantly decreased activating protein 2 (AP-2)-binding activity, and protein levels of the AP-2 alpha and AP-2 beta but not of the AP-2 gamma subunits in the frontal cortex. Activating protein 1 (AP-1)-binding activity was increased, whereas glucocorticoid response element, polyoma enhancer activator 3, and nuclear factor kappa B DNA-binding activities were not changed significantly. Since both cPLA2 and AP-2 can be activated by protein kinase C (PKC), we examined the frontal cortex protein levels of PKC alpha and PKC epsilon, as well as AA-dependent PKC activity. The protein levels of PKC alpha and PKC epsilon were decreased significantly, as was AA-dependent PKC activity, in the lithium-treated compared to control rats. Our results suggest that the reported decrease in brain gene expression of cPLA2 by chronic lithium may be mediated by reduced AP-2 transcriptional activity, and that decreased expression of PKC alpha and PKC epsilon contributes to lowering the AP-2 activity.

Increased arachidonic acid concentration in the brain of Flinders Sensitive Line rats, an animal model of depression

Depression may be associated with impaired membrane PUFA composition, especially decreased n-3 PUFA. This assumption has not been tested at the level of brain tissue. Moreover, most studies were confounded by dietary variability. We examined the FA composition of selected brain areas in an animal model of depression, the Flinders Sensitive Line (FSL) rat, and compared the findings with those in controls fed identical diets. In all brain regions studied, the concentration of arachidonic acid (AA) was significantly higher in the FSL rats: in the hypothalamus by 21%, in the nucleus accumbens by 24%, in the prefrontal cortex by 31%, and in the striatum by 23%. No significant differences were observed for n-3 PUFA or for the saturated and monounsaturated FAs. Our results confirm the existence of altered brain PUFA composition in an animal model of depression. The finding of increased AA, an n-6 PUFA, rather than decreased n-3 PUFA, emphasizes the importance of both PUFA families in the pathophysiological processes underlying depression. The FSL rat is a useful tool for further elucidation of the FA disturbances in depression.

Arachidonic acid incorporation and turnover is decreased in sympathetically denervated rat heart

Heart sympathetic denervation can accompany Parkinson's disease, but the effect of this denervation on cardiac lipid-mediated signaling is unknown. To address this issue, rats were sympathetically denervated with 6-hydroxydopamine (6-OHDA, 50 mg/kg ip) and infused with 170 muCi/kg of either [1-(14)C]palmitic acid ([1-(14)C]16:0) or [1-(14)C]arachidonic acid ([1-(14)C]20:4 n-6), and kinetic parameters were assessed using a steady-state radiotracer model. Heart norepinephrine and epinephrine levels were decreased 82 and 85%, respectively, in denervated rats, and this correlated with a 34% reduction in weight gain in treated rats. Fatty acid tracer uptake was not significantly different between groups for either tracer, although the dilution coefficient lambda was increased in [1-(14)C]20:4 n-6-infused rats, which indicates that less 20:4 n-6 was recycled in denervated rats. In [1-(14)C]16:0-infused rats, incorporation rate and turnover values of 16:0 in stable lipid compartments were unchanged, which is indicative of preservation of beta-oxidation. In [1-(14)C]20:4 n-6-infused rats, there were dramatic reductions in incorporation rate (60-84%) and turnover value (56-85%) in denervated rats that were dependent upon the lipid compartment. In addition, phospholipase A(2) activity was reduced 40% in treated rats, which is consistent with the reduction observed in 20:4 n-6 turnover. These results demonstrate marked reductions in 20:4 n-6 incorporation rate and turnover in sympathetic denervated rats and thereby suggest an effect on lipid-mediated signal transduction mediated by a reduction in phospholipase A(2) activity.

Chronic carbamazepine selectively downregulates cytosolic phospholipase A2 expression and cyclooxygenase activity in rat brain

BACKGROUND

Carbamazepine is a mood stabilizer used as monotherapy or as an adjunct to lithium in the treatment of acute mania or the prophylaxis of bipolar disorder. Based on evidence that lithium and valproate, other mood stabilizers, reduce brain arachidonic acid turnover and its conversion via cyclooxygenase to prostaglandin E(2) in rat brain, one possibility is that carbamazepine also targets the arachidonic acid cascade.

METHODS

To test this hypothesis, carbamazepine was administered to rats by intraperitoneal injection at a daily dose of 25 mg/kg for 30 days.

RESULTS

Carbamazepine decreased brain phospholipase A(2) activity and cytosolic phospholipase A(2) protein and messenger RNA levels without changing significantly protein and activity levels of calcium-independent phospholipase A(2) or secretory phospholipase A(2). Cyclooxygenase activity was decreased in carbamazepine-treated rats without any change in cyclooxygenase-1 or cyclooxygenase-2 protein levels. Brain prostaglandin E(2) concentration also was reduced. The protein levels of other arachidonic acid metabolizing enzymes, 5-lipoxygenase and cytochrome P450 epoxygenase, were not significantly changed nor was the brain concentration of the 5-lipoxygenase product leukotriene B(4).

CONCLUSIONS

Carbamazepine downregulates cytosolic phospholipase A(2)-mediated release of arachidonic acid and its subsequent conversion to prostaglandin E(2) by cyclooxygenase. These effects may contribute to its therapeutic actions in bipolar disorder.

Emerging experimental therapeutics for bipolar disorder: insights from the molecular and cellular actions of current mood stabilizers

Bipolar disorder afflicts approximately 1-3% of both men and women, and is coincident with major economic, societal, medical, and interpersonal consequences. Current mediations used for its treatment are associated with variable rates of efficacy and often intolerable side effects. While preclinical and clinical knowledge in the neurosciences has expanded at a tremendous rate, recent years have seen no major breakthroughs in the development of novel types of treatment for bipolar disorder. We review here approaches to develop novel treatments specifically for bipolar disorder. Deliberate (ie not by serendipity) treatments may come from one of two general mechanisms: (1) Understanding the mechanism of action of current medications and thereafter designing novel drugs that mimics these mechanism(s); (2) Basing medication development upon the hypothetical or proven underlying pathophysiology of bipolar disorder. In this review, we focus upon the first approach. Molecular and cellular targets of current mood stabilizers include lithium inhibitable enzymes where lithium competes for a magnesium binding site (inositol monophosphatase, inositol polyphosphate 1-phosphatase, glycogen synthase kinase-3 (GSK-3), fructose 1,6-bisphosphatase, bisphosphate nucleotidase, phosphoglucomutase), valproate inhibitable enzymes (succinate semialdehyde dehydrogenase, succinate semialdehyde reductase, histone deacetylase), targets of carbamazepine (sodium channels, adenosine receptors, adenylate cyclase), and signaling pathways regulated by multiple drugs of different classes (phosphoinositol/protein kinase C, cyclic AMP, arachidonic acid, neurotrophic pathways). While the task of developing novel medications for bipolar disorder is truly daunting, we are hopeful that understanding the mechanism of action of current mood stabilizers will ultimately lead clinical trials with more specific medications and thus better treatments those who suffer from this devastating illness.

The effect of chronic lithium on arachidonic acid release and metabolism in rat brain does not involve secretory phospholipase A2 or lipoxygenase/cytochrome P450 pathways

The mood-stabilizer lithium, when chronically administered to rats at therapeutic concentrations, has been shown to downregulate brain arachidonic acid (AA) turnover and total phospholipase A2 (PLA2) activity, as well as protein and mRNA levels of cytosolic cPLA2. These effects are accompanied by a decrease in cyclooxygenase (COX)-2 protein level, COX activity, and brain prostaglandin E2 (PGE2) concentration. The involvement of Ca2+-dependent secretory PLA2 (sPLA2) in the mechanism of action of lithium has not been investigated. The purpose of this study was to examine, whether the effect of lithium is selectively directed to cPLA2 or it also affects sPLA2 protein and enzyme activity and whether other AA metabolizing enzymes (5-lipoxygenase and cytochrome P450 epoxygenase) were also altered. Furthermore, to determine if the reduction of brain PGE2 concentration was due only to downregulation of COX-2 protein or if it also involves the terminal PGE synthase, we determined brain microsomal PGE synthase protein level. Male Fischer-344 rats were fed lithium chloride for 6 weeks, whereas, control rats were fed lithium-free chow under parallel conditions. We found that chronic lithium did not significantly change sPLA2 activity or protein level. 5-Lipoxygenase and cytochrome P450 epoxygenase protein levels were unchanged, as were levels of the terminal PGE synthase. These results indicate that the effect of lithium selectively involves the cPLA2/COX-2 pathway, which might be responsible for the therapeutic effect in bipolar disorder.

Evidence for a role of the arachidonic acid cascade in affective disorders: a review

The treatment of affective disorders continues to present significant clinical challenges, notwithstanding the existence of available mood stabilizers and antidepressants. These difficulties include incomplete response, relapse, and intolerable medication side effects. Fundamental to the therapeutic impasse is incomplete knowledge concerning the neurobiology of mood disorders. Although some relevant biochemical pathways have been identified, including abnormalities of monoamine neurotransmission and of immunological functioning, a fuller understanding is likely to embrace other interrelated pathways. Arachidonic acid (AA) and prostaglandins (PGs) are important second messengers in the central nervous system that participate in signal transduction, inflammation and other vital processes. Their release, turnover, and metabolism represent the 'arachidonic acid cascade'. A significant body of diverse clinical and preclinical research suggests that the AA cascade may be important in affective states. This paper reviews the literature describing the association of affective illness with AA and its metabolites. Possible links between this and other prevailing hypotheses are considered, and implications for further research and for treatment are discussed.

Psychoses and creativity: is the missing link a biological mechanism related to phospholipids turnover?

Recent evidence suggests that genetic and biochemical factors associated with psychoses may also provide an increased propensity to think creatively. The evolutionary theories linking brain growth and diet to the appearance of creative endeavors have been made recently, but they lack a direct link to research on the biological correlates of divergent and creative thought. Expanding upon Horrobin's theory that changes in brain size and in neural microconnectivity came about as a result of changes in dietary fat and phospholipid incorporation of highly unsaturated fatty acids, we propose a theory relating phospholipase A2 (PLA2) activity to the neuromodulatory effects of the noradrenergic system. This theory offers probable links between attention, divergent thinking, and arousal through a mechanism that emphasizes optimal individual functioning of the PLA2 and NE systems as they interact with structural and biochemical states of the brain. We hope that this theory will stimulate new research in the neural basis of creativity and its connection to psychoses.

Allelic association study between phospholipase A2 genes and bipolar affective disorder

OBJECTIVES

In vivo studies demonstrating that lithium is a powerful phospholipase A2 (PLA2) inhibitor suggest that PLA2 activation, and subsequent cell signaling overactivation by increased fatty acid release may be the primary abnormality in bipolar affective disorder (BPAD), thus making PLA2 genes attractive candidates for the susceptibility to BPAD. The present study investigates polymorphisms in cytosolic phospholipase A2 (cPLA2), calcium-independent phospholipase A2 (iPLA2), and secretory phospholipase (sPLA2) genes in a Brazilian sample.

METHODS

A cross-sectional study was performed with 181 unrelated DSM-IIIR BPAD subjects and 312 controls. A polymerase chain reaction-restriction fragment length polymorphism assay for BanI cPLA2 and AvrII iPLA2 polymorphisms was performed, and an ATT repeat in sPLA2 was assessed using a semiautomated genetic analyzer (ALFexpress).

RESULTS

There was no significant difference observed in the allelic and genotypic distribution between the BPAD and control groups for cPLA2 (genotype: chi2 = 0.8, 2df, p = 0.6; allele chi2 = 0, 1df, p = 0.9), iPLA2 (genotype: chi2 = 1.7, 2df, p = 0.4; allele: chi2 = 0.3, 1df, p = 0.6), and sPLA2 (allele: chi2 = 3.6, 6df, p = 0.8).

CONCLUSION

Our results failed to demonstrate that the studied PLA2 polymorphisms were associated with an increased risk for BPAD in our sample.

Valproic acid down-regulates the conversion of arachidonic acid to eicosanoids via cyclooxygenase-1 and -2 in rat brain

Sodium valproate, a mood stabilizer, when chronically administered to rats (200 mg/kg i.p. daily for 30 days) significantly reduced the brain protein levels of cyclooxygenase (COX)-1 and COX-2, without altering the mRNA levels of these enzymes. COX activity was decreased, as were the brain concentrations of 11-dehydrothromboxane B2 and prostaglandin E2 (PGE2), metabolites of arachidonic acid (AA) produced via COX. In contrast, the brain protein level of 5-lipoxygenase and the concentration of its AA metabolite leukotriene B4 were unchanged. In view of published evidence that lithium chloride administered chronically to rats, like chronic valproate, reduces AA turnover within brain phospholipids, and that lithium post-transcriptionally down-regulates COX-2 but not COX-1 protein level and enzyme activity, these observations suggest that mood stabilizers generally modulate the release and recycling of AA within brain phospholipids, and the conversion of AA via COX-2 to PGE2 and related eicosanoids. If targeting this part of the 'AA cascade' accounts for their therapeutic action, non-steroidal anti-inflammatory drugs or selective COX-2 inhibitors might prove effective in bipolar disorder.

[Genes related to phospholipid metabolism as risk factors related to bipolar affective disorder]

The studies of genetic epidemiology provides consistent evidence of genetic factors having a major role on the risk for the bipolar affective disorder, although, vulnerability genes have not yet been identified in unequivocal form. The authors show that phospholipids play an important role in the cellular signalling processes, besides this, some studies with mood-stabilisers neurochemistry suggest that these drugs act in the phospholipase regulated signalling views. They conclude that analysis of gene variants that code enzymes of the phospholipids metabolism as potential susceptibility genes can extend the knowledge concerning the risk factors and the physiopatological mechanisms underling this mood disturbance.

Chronic lithium downregulates cyclooxygenase-2 activity and prostaglandin E(2) concentration in rat brain

Rats treated with lithium chloride for 6 weeks have been reported to demonstrate reduced turnover of arachidonic acid (AA) in brain phospholipids, and decreases in mRNA and protein levels, and enzyme activity, of AA-selective cytosolic phospholipase A(2)(cPLA(2)). We now report that chronic lithium administration to rats significantly reduced the brain protein level and enzyme activity of cyclooxygenase-2 (COX-2), without affecting COX-2 mRNA. Lithium also reduced the brain concentration of prostaglandin E(2) (PGE(2)), a bioactive product of AA formed via the COX reaction. COX-1 and the Ca(2+)-independent iPLA(2) (type VI) were unaffected by lithium. These and prior results indicate that lithium targets a part of the AA cascade that involves cPLA(2) and COX-2. This effect may contribute to lithium's therapeutic action in bipolar disorder.

Lithium chloride, administered chronically to rats, does not affect the fractional phosphorylation of brain cytosolic phospholipase A2, while reducing its net protein level

Lithium, used to treat bipolar disorder, has been reported to decrease rat brain mRNA and protein levels of cytosolic phospholipase A(2) (cPLA(2)), an enzyme that selectively hydrolyzes arachidonic acid from the stereospecifically numbered (sn)-2 position of membrane phospholipids, and to decrease PLA(2) activity. cPLA(2) can be activated by being phosphorylated at its Ser-228, Ser-505, and Ser-727 sites. In this study, we show that the percent phosphorylated cPLA(2) protein in rat brain is unaffected by lithium. Male Fischer-344 rats were fed lithium chloride for 6 weeks, so as to produce a therapeutically equivalent brain lithium concentration; control rats were fed lithium-free chow under parallel conditions. cPLA(2) was immunoprecipitated from brain homogenate and phosphorylated cPLA(2) protein was quantified using an anti-phosphoserine antibody, and compared to net cPLA(2) protein. The mean ratio of phosphorylated/total cPLA(2) was not changed significantly in the lithium-treated compared to the control group. Thus, decreased brain PLA(2) enzyme activity caused by chronic lithium is likely a consequence only of lithium's downregulation of cPLA(2) transcription.

Brain lipid metabolism in the cPLA2 knockout mouse

We examined brain phospholipid metabolism in mice in which the cytosolic phospholipase A(2) (cPLA(2,) Type IV, 85 kDa) was knocked out (cPLA(2)(-/-) mice). Compared with controls, these mice demonstrated altered brain concentrations of several phospholipids, reduced esterified linoleate, arachidonate, and docosahexaenoate in choline glycerophospholipid, and reduced esterified arachidonate in phosphatidylinositol. Unanesthetized cPLA(2)(-/-) mice had reduced rates of incorporation of unlabeled arachidonate from plasma and from the brain arachidonoyl-CoA pool into ethanolamine glycerophospholipid and choline glycerophospholipid, but elevated rates into phosphatidylinositol. These differences corresponded to altered turnover and metabolic loss of esterified brain arachidonate. These results suggests that cPLA(2) is necessary to maintain normal brain concentrations of phospholipids and of their esterified polyunsaturated fatty acids. Reduced esterified arachidonate and docosahexaenoate may account for the resistance of the cPLA(2)(-/-) mouse to middle cerebral artery occlusion, and should influence membrane fluidity, neuroinflammation, signal transduction, and other brain processes.

Mood stabilizer psychopharmacology

Mood stabilizers represent a class of drugs that are efficacious in the treatment of bipolar disorder. The most established medications in this class are lithium, valproic acid, and carbamazepine. In addition to their therapeutic effects for treatment of acute manic episodes, these medications often are useful as prophylaxis against future episodes and as adjunctive antidepressant medications. While important extracellular effects have not been excluded, most available evidence suggests that the therapeutically relevant targets of this class of medications are in the interior of cells. Herein we give a prospective of a rapidly evolving field, discussing common effects of mood stabilizers as well as effects that are unique to individual medications. Mood stabilizers have been shown to modulate the activity of enzymes, ion channels, arachidonic acid turnover, G protein coupled receptors and intracellular pathways involved in synaptic plasticity and neuroprotection. Understanding the therapeutic targets of mood stabilizers will undoubtedly lead to a better understanding of the pathophysiology of bipolar disorder and to the development of improved therapeutics for the treatment of this disease. Furthermore, the involvement of mood stabilizers in pathways operative in neuroprotection suggests that they may have utility in the treatment of classical neurodegenerative disorders.

Lithium and antidepressants: inhibiting eicosanoids, stimulating immunity, and defeating microorganisms

Infection-emerging, reemerging, antibiotic-resistant, and bioengineered-increasingly threatens mankind. It is widely assumed that immunostimulating agents, were they to exist, would be ideal in battling microorganisms. Various investigators have established lithium and antidepressants as immunostimulants and antimicrobials and they have identified the mechanisms involved. Eicosanoids both depress immunity and activate microorganisms and lithium and antidepressants oppose eicosanoids. Such philosophers of science as Paul Feyerabend have argued that special interests invariably oppose revolutionary paradigms.

Chronic lithium chloride administration to rats decreases brain protein level of epsilon (epsilon) subunit of eukaryotic initiation factor-2B

The eukaryotic initiation factor-2B (eIF-2B) can regulate translation and protein synthesis. We used Western blot analysis to quantify the protein level of the catalytic epsilon (epsilon) subunit of eIF-2B in brains of rats fed lithium chloride (LiCl) for 6 weeks so as to produce a brain lithium concentration that is therapeutically effective in bipolar disorder. The ratio of eIF-2B (epsilon) to actin protein was significantly reduced (P<0.01) in LiCl-fed rats, 0.86+/-0.06 (SE) compared to 1.2+/-0.07 in control rats. These results suggest that a therapeutic level of lithium may downregulate the synthesis of proteins whose translation depends on eIF-2B.

A new category of psychotropic drugs: neuroactive lipids as exemplified by ethyl eicosapentaenoate (E-E)

New treatments for psychiatric disorders are urgently required. Recent reviews show that there have been no improvements in efficacy of drugs for either affective disorders or schizophrenia since the first compounds were introduced over 40 years ago. Neuroactive lipids represent an entirely novel class of psychotropic compounds. Ethyl eicosapentaenoate is the first example of this group. Placebo-controlled studies have found it to be effective in depression, in treatment-unresponsive schizophrenia and in tardive dyskinesia. It is extremely well tolerated with none of the usual side-effects of either antidepressants or neuroleptics. It probably works by modulating postreceptor signal transduction processes.

Chronic valproate treatment decreases the in vivo turnover of arachidonic acid in brain phospholipids: a possible common effect of mood stabilizers

Both (Li(+)) and valproic acid (VPA) are effective in treating bipolar disorder, but the pathway by which either works, and whether it is common to both drugs, is not agreed upon. We recently reported, using an in vivo fatty acid model, that Li(+) reduces the turnover rate of the second messenger arachidonic acid (AA) by 80% in brain phospholipids of the awake rat, without changing turnover rates of docosahexaenoic or palmitic acid. Reduced AA turnover was accompanied by down-regulation of gene expression and protein levels of an AA-specific cytosolic phospholipase A(2) (cPLA(2)). To see if VPA had the same effect on AA turnover, we used our in vivo fatty acid model in rats chronically administered VPA (200 mg/kg, i.p. for 30 days). Like Li(+), VPA treatment significantly decreased AA turnover within brain phospholipids (by 28-33%), although it had no effect on cPLA(2) protein levels. Thus, both mood stabilizers, Li(+) and VPA have a common action in reducing AA turnover in brain phospholipids, albeit by different mechanisms.