Rapid regulation of neurite outgrowth and retraction by phospholipase A2-derived arachidonic acid and its metabolites

Fraction of C. d. collilineatus venom containing crotapotin protects PC12 cells against MPP + toxicity by activating the NGF-signaling pathway

Background

Parkinson's disease (PD) is the second most prevalent neurodegenerative disease. There is no effective treatment for neurodegenerative diseases. Snake venoms are a cocktail of proteins and peptides with great therapeutic potential and might be useful in the treatment of neurodegenerative diseases. Crotapotin is the acid chain of crotoxin, the major component of Crotalus durissus collilineatus venom. PD is characterized by low levels of neurotrophins, and synaptic and axonal degeneration; therefore, neurotrophic compounds might delay the progression of PD. The neurotrophic potential of crotapotin has not been studied yet.

Methods

We evaluated the neurotrophic potential of crotapotin in untreated PC12 cells, by assessing the induction of neurite outgrowth. The activation of the NGF signaling pathway was investigated through pharmacological inhibition of its main modulators. Additionally, its neuroprotective and neurorestorative effects were evaluated by assessing neurite outgrowth and cell viability in PC12 cells treated with the dopaminergic neurotoxin MPP+ (1-methyl-4-phenylpyridinium), known to induce Parkinsonism in humans and animal models.

Results

Crotapotin induced neuritogenesis in PC12 cells through the NGF-signaling pathway, more specifically, by activating the NGF-selective receptor trkA, and the PI3K/Akt and the MAPK/ERK cascades, which are involved in neuronal survival and differentiation. In addition, crotapotin had no cytotoxic effect and protected PC12 cells against the inhibitory effects of MPP+ on cell viability and differentiation.

Conclusion

These findings show, for the first time, that crotapotin has neurotrophic/neuroprotective/neurorestorative potential and might be beneficial in Parkinson's disease. Additional studies are necessary to evaluate the toxicity of crotapotin in other cell models.

Doxycycline inhibits dopaminergic neurodegeneration through upregulation of axonal and synaptic proteins

Doxycycline (DOX) is a widely used antibiotic that is able to cross the blood-brain barrier. Several studies have shown its neuroprotective effect against neurodegeneration and have associated it with antioxidant, anti-apoptotic, and anti-inflammatory mechanisms. We have recently demonstrated that DOX mimics nerve growth factor (NGF) signaling in PC12 cells. However, the involvement of this mechanism in the neuroprotective effect of DOX is unknown. Axonal degeneration and synaptic loss are key events at the early stages of neurodegeneration, and precede the neuronal death in neurodegenerative diseases, including Parkinson's disease (PD). Therefore, the regeneration of the axonal and synaptic network might be beneficial in PD. The effect of DOX in PC12 cells treated with the Parkinsonian neurotoxin 1-methyl-4-phenylpyridinium (MPP+) was addressed. Doxycycline reduced the inhibition of neuritogenesis induced by MPP+, even in cells deprived of NGF. The mechanism involved the upregulation of GAP-43, synapsin I, β-III-tubulin, F-actin, and neurofilament-200, proteins that are associated with axonal and synaptic plasticity. Considering the role of axonal degeneration and synaptic loss at the initial stages of PD, the recent advances in early diagnosis of neurodegeneration, and the advantages of drug repurposing, doxycycline is a promising candidate to treat PD.

The Neurotrophic-Like Effect of Carvacrol: Perspective for Axonal and Synaptic Regeneration

Carvacrol (CARV) is a phytochemical widely used as flavoring, preservative, and fragrance in food and cosmetic industries. CARV is able to cross the blood-brain barrier (BBB) and has demonstrated protective potential against neurodegenerative diseases by several mechanisms, including antioxidant, anti-inflammatory, anticholinesterase, and antiapoptotic effects. However, it is not known whether CARV is able to modulate axonal and synaptic plasticity, crucial events in cognition, memory, and learning. Abnormalities in axonal and synaptic plasticity, low levels of neurotrophins, and bioenergetic failure have been associated with the pathogenesis of neurodegenerative diseases, including Parkinson's (PD) and Alzheimer's diseases (ADs). Small lipophilic molecules with neurotrophic activity might be able to restore the axonal and synaptic networks that are lost in neurodegenerative processes. Therefore, this study investigated the neurotrophic potential of CARV in PC12 cell-based neuronal model. Carvacrol induced neurite outgrowth by activating the NGF high-affinity trkA receptor and the downstream PI3K-AKT and MAPK-ERK pathways, without depending on NGF. In addition, CARV increased the expression of proteins involved in neuronal plasticity (β-tubulin III, F-actin, 200-kDa neurofilament, GAP-43 and synapsin-I) and improved bioenergetics (AMPKα, p-AMPKα, and ATP). Our study showed, for the first time, a promising neurotrophic mechanism of CARV that could be beneficial in neurodegenerative and neurological diseases.

Neurotropic activity and safety of methylene-cycloalkylacetate (MCA) derivative 3-(3-allyl-2-methylenecyclohexyl) propanoic acid

Polyneuropathy is a disease involving multiple peripheral nerves injuries. Axon regrowth remains the major prerequisite for plasticity, regeneration, circuit formation, and eventually functional recovery and therefore, regulation of neurite outgrowth might be a candidate for treating polyneuropathies. In a recent study, we synthesized and established the methylene-cycloalkylacetate (MCAs) pharmacophore as a lead for the development of a neurotropic drug (inducing neurite/axonal outgrowth) using the PC12 neuronal model. In the present study we extended the characterizations of the in vitro neurotropic effect of the derivative 3-(3-allyl-2-methylenecyclohexyl) propanoic acid (MCA-13) on dorsal root ganglia and spinal cord neuronal cultures and analyzed its safety properties using blood biochemistry and cell counting, acute toxicity evaluation in mice and different in vitro "off-target" pharmacological evaluations. This MCA derivative deserves further preclinical mechanistic pharmacological characterizations including therapeutic efficacy in in vivo animal models of polyneuropathies, toward development of a clinically relevant neurotropic drug.

Stream of consciousness: Quantum and biochemical assumptions regarding psychopathology

The accepted paradigms of mainstream neuropsychiatry appear to be incompletely adequate and in various cases offer equivocal analyses. However, a growing number of new approaches are being proposed that suggest the emergence of paradigm shifts in this area. In particular, quantum theories of mind, brain and consciousness seem to offer a profound change to the current approaches. Unfortunately these quantum paradigms harbor at least two serious problems. First, they are simply models, theories, and assumptions, with no convincing experiments supporting their claims. Second, they deviate from contemporary mainstream views of psychiatric illness and do so in revolutionary ways. We suggest a possible way to integrate experimental neuroscience with quantum models in order to address outstanding issues in psychopathology. A key role is played by the phenomenon called the "stream of consciousness", which can be linked to the so-called "Gamma Synchrony" (GS), which is clearly demonstrated by EEG data. In our novel proposal, a unipolar depressed patient could be seen as a subject with an altered stream of consciousness. In particular, some clues suggest that depression is linked to an "increased power" stream of consciousness. It is additionally suggested that such an approach to depression might be extended to psychopathology in general with potential benefits to diagnostics and therapeutics in neuropsychiatry.

Enhanced Phospholipase A2 Group 3 Expression by Oxidative Stress Decreases the Insulin-Degrading Enzyme

Oxidative stress has a ubiquitous role in neurodegenerative diseases and oxidative damage in specific regions of the brain is associated with selective neurodegeneration. We previously reported that Alzheimer disease (AD) model mice showed decreased insulin-degrading enzyme (IDE) levels in the cerebrum and accelerated phenotypic features of AD when crossbred with alpha-tocopherol transfer protein knockout (Ttpa^-/-) mice. To further investigate the role of chronic oxidative stress in AD pathophysiology, we performed DNA microarray analysis using young and aged wild-type mice and aged Ttpa^-/- mice. Among the genes whose expression changed dramatically was Phospholipase A2 group 3 (Pla2g3); Pla2g3 was identified because of its expression profile of cerebral specific up-regulation by chronic oxidative stress in silico and in aged Ttpa^-/- mice. Immunohistochemical studies also demonstrated that human astrocytic Pla2g3 expression was significantly increased in human AD brains compared with control brains. Moreover, transfection of HEK293 cells with human Pla2g3 decreased endogenous IDE expression in a dose-dependent manner. Our findings show a key role of Pla2g3 on the reduction of IDE, and suggest that cerebrum specific increase of Pla2g3 is involved in the initiation and/or progression of AD.

Chronic inhibition of brain phospholipase A2 in adult rats impairs the survival of newborn mature neurons in the hippocampus

Adult neurogenesis occurs in the hippocampal dentate gyrus (DG) and lateral ventricles, and includes cell proliferation and neuronal differentiation, maturation and survival. In vitro studies suggest a role for phospholipase A2 (PLA2) in neuronal differentiation/maturation and survival. This study aimed to investigate the effect of in vivo chronic inhibition of brain PLA2 in adult rats on the number of newborn mature neurons in the DG. Male Wistar rats were injected with BrdU (cell proliferation marker) and 2 weeks later (beginning of neuronal maturation) sham-operated or infused intracerebroventricularly with either vehicle (DMSO in saline) or PLA2 inhibitor (MAFP dissolved in the vehicle) for 14 days via osmotic minipump. The animals were euthanised 28 days post-BrdU and their brains immunostained for BrdU and BrdU plus NeuN (mature neuronal marker) for analysis of surviving cells. MAFP reduced the number of BrdU(+) cells in the ventral DG (p < 0.05 vs. sham; p < 0.01 vs. DMSO) and the number of BrdU(+)NeuN(+) cells in the ventral (p < 0.01 vs. sham and DMSO) and whole DG (p < 0.02 vs. sham and DMSO). There was no effect of MAFP in the dorsal DG. These findings show that chronic PLA2 inhibition in adult rat hippocampus decreases the number of newborn mature neurons in the ventral DG (reflecting in the whole DG), perhaps by impairing neuronal maturation and survival, and suggest that PLA2 inhibition reported in the hippocampus of Alzheimer disease subjects might partly contribute to the neurogenic abnormalities found in the DG in this disease.

Differential regulation of lipid metabolism genes in the brain of acetylcholinesterase knockout mice

Mice deficient in acetylcholinesterase (AChE; EC3.1.1.7) exhibited significant phenotypical and biochemical changes when compared with wild-type littermates. They showed a delay of growth in weight and size, immature external ears, and persistent body tremor, and they circled when walking. The molecular mechanisms underlying these changes have not been investigated yet. Here, we studied the profiles of both the messenger RNA (mRNA) and protein expression in the brain of AChE-deficient mice using mRNA microarray, quantitative PCR, and two-dimensional difference gel electrophoresis (2D DIGE) coupled to protein identification with matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry. Analysis of gene expression profile was conducted by DAVID ( http://david.abcc.ncifcrf.gov ) and Ingenuity Pathway Analysis (IPA, http://www.ingenuity.com ). Previous results implicated that there is a close relationship between lipid metabolisms which were associated with central nervous system development. Here, we demonstrated that the mRNA expressions of brain specific fatty acid protein 7 (fabp-7) and phospholipase A2 group IV (pla2g4) were significantly downregulated in AChE-deficient mice. These results suggested that AChE may play a role in neurogenesis and neurodegeneration by specifically regulating lipid metabolism in the brain.

Distribution of secretory phospholipase A2 XIIA in the brain and its role in lipid metabolism and cognition

Phospholipases A(2) (PLA(2)) catalyze the hydrolysis of membrane phospholipids to produce free fatty acids and lysophospholipids, which have important functions in cell signaling. The present study elucidated differential expression of PLA(2) isoforms in the rat cortex by quantitative reverse transcription PCR and demonstrated that sPLA(2)-XIIA had greater messenger RNA expression than iPLA(2)-VI or cPLA(2)-IVA in different brain regions, or compared to other sPLA(2) isoforms in the prefrontal cortex (PFC) and hippocampus. Western blots identified a 24-kDa band in different regions of the adult brain, and high levels of sPLA(2)-XIIA protein expression were detected in the PFC, striatum, and thalamus. Electron microscopy showed that sPLA(2)-XIIA is present in axon terminals and dendrites. Injection of antisense oligonucleotide to sPLA(2)-XIIA in the PFC and lipidomic analysis showed increase in phospholipid but decrease in lysophospholipid species consistent with decreased catalytic activity of the enzyme, changes in arachidonic acid release, and alterations in sphingolipids. sPLA(2)-XIIA knockdown also resulted in shorter latency timings in the passive avoidance test, and higher number of errors in the attention set-shifting task, indicating deficits in working memory and attention. Together, the results show an important role of sPLA(2)-XIIA in lipid metabolism, prefrontal cortical function, and cognition.

Abnormal circadian rhythm and cortisol excretion in autistic children: a clinical study

Aim

To determine the circadian rhythm alteration of cortisol excretion and the level of corticosteroids in children with different grades of autism severity.

Methods

The study included 45 children with different grades of autism severity (low [LFA], medium [MFA], and high functioning autism [HFA]), 15 in each group, and 45 age/sex-matched children with typical development. The urinary levels of free cortisol (at three phases of 24-hour cycle), corticosteroids, vanilylmandelic acid, and 5-hydroxyindole acetic acid were determined.

Results

Alteration in the pattern of cortisol excretion (Phases I, II, and III) was observed in children with LFA (Phase I: 43.8 ± 4.43 vs 74.30±8.62, P = 0.000; Phase II: 21.1±2.87 vs 62±7.68, P < 0.001; Phase III: 9.9 ± 1.20 vs 40 ± 5.73, P < 0.001) and MFA (Phase I: 43.8 ± 4.43 vs 52.6±7.90, P < 0.001; Phase II: 21.1±2.87 vs 27.4±4.05, P < 0.001; Phase III: 9.9 ± 1.20 vs 19 ± 2.50, P < 0.001) compared to the control group. The corticosteroids excretion levels were higher in all the groups of children with autism than in the control group. The level of 5-hydroxyindole acetic acid was significantly higher in children with LFA (8.2±1.48 vs 6.8±0.85, P < 0.001) and MFA (8.2±1.48 vs 7.4± 0.89, P = 0.001) and not significantly higher in children with HFA than in the control group. The changes were correlated with degrees of severity of the disorder.

Conclusion

These data suggest that altered cortisol excretion pattern and high level of corticosteroids in urine may probably be a consequence of altered hypothalamic-pituitary-adrenal axis function, which may contribute to the pathogenesis and affect the severity of autism.

Arachidonic acid derivatives and their role in peripheral nerve degeneration and regeneration

After peripheral nerve injury, a process of axonal degradation, debris clearance, and subsequent regeneration is initiated by complex local signaling, called Wallerian degeneration (WD). This process is in part mediated by neuroglia as well as infiltrating inflammatory cells and regulated by inflammatory mediators such as cytokines, chemokines, and the activation of transcription factors also related to the inflammatory response. Part of this neuroimmune signaling is mediated by the innate immune system, including arachidonic acid (AA) derivatives such as prostaglandins and leukotrienes. The enzymes responsible for their production, cyclooxygenases and lipooxygenases, also participate in nerve degeneration and regeneration. The interactions between signals for nerve regeneration and neuroinflammation go all the way down to the molecular level. In this paper, we discuss the role that AA derivatives might play during WD and nerve regeneration, and the therapeutic possibilities that arise.

G-protein-coupled receptors in adult neurogenesis

The importance of adult neurogenesis has only recently been accepted, resulting in a completely new field of investigation within stem cell biology. The regulation and functional significance of adult neurogenesis is currently an area of highly active research. G-protein-coupled receptors (GPCRs) have emerged as potential modulators of adult neurogenesis. GPCRs represent a class of proteins with significant clinical importance, because approximately 30% of all modern therapeutic treatments target these receptors. GPCRs bind to a large class of neurotransmitters and neuromodulators such as norepinephrine, dopamine, and serotonin. Besides their typical role in cellular communication, GPCRs are expressed on adult neural stem cells and their progenitors that relay specific signals to regulate the neurogenic process. This review summarizes the field of adult neurogenesis and its methods and specifies the roles of various GPCRs and their signal transduction pathways that are involved in the regulation of adult neural stem cells and their progenitors. Current evidence supporting adult neurogenesis as a model for self-repair in neuropathologic conditions, adult neural stem cell therapeutic strategies, and potential avenues for GPCR-based therapeutics are also discussed.

Inhibition of neuroblastoma cell proliferation with omega-3 fatty acids and treatment of a murine model of human neuroblastoma using a diet enriched with omega-3 fatty acids in combination with sunitinib

INTRODUCTION

We investigated the use of dietary omega-3 (ω-3) polyunsaturated fatty acids (PUFAs) in the treatment of neuroblastoma both as a sole agent and in combination with sunitinib, a broad-spectrum tyrosine kinase receptor inhibitor.

RESULTS

Substitution of all dietary fat with menhaden oil (ω-3 PUFA rich) resulted in a 40-70% inhibition of tumor growth and a statistically significant difference in the levels of several PUFAs (18:2 ω-6, 20:4 ω-6, 22:4 ω-6, 20:5 ω-3) as compared with a control diet. Furthermore, tumors from animals on the ω-3 fatty acid (FA)-enriched diet had an elevated triene/tetraene ratio suggestive of a change in local eicosanoid metabolism in these tissues similar to that seen with essential fatty acid deficiency. The ω-3 FA-enriched diet also decreased tumor-associated inflammatory cells and induced mitochondrial changes suggestive of mitochondrial damage. Combination treatment with sunitinib resulted in further reduction in tumor proliferation and microvessel density.

DISCUSSION

These findings suggest a potential role for ω-3 PUFAs in the combination treatment of neuroblastoma.

METHODS

We used a murine model of orthotopic and subcutaneous human neuroblastoma and diets that differ in the FA content to define the optimal dietary ω-3/omega-6 (ω-6) FA ratio required for the inhibition of these tumors.

A case of montelukast-induced churg-strauss syndrome associated with liver dysfunction

A 64-year-old woman was admitted to hospital due to protracted diarrhea and liver dysfunction. The patient was diagnosed as Churg-Strauss syndrome (CSS) due to asthma, paranasal sinusitis, hypereosinophilia, and polyneuropathy. There was a history of taking montelukast, a leukotriene receptor antagonist (LTRA), which is thought to have some relationship with CSS. The liver biopsy specimen showed eosinophilic infiltration and centrolobular fatty change. In this paper, we review the relationship between LTRA and CSS. Several lines of evidence suggest that leukotriene plays an important role in maintaining neural tissues. We also review the potential relationship between centrolobular fatty change and pivoxil-containing antibiotics, which was prescribed for sinusitis before admission. Carnitine deficiency induced by pivoxil-containing agents may cause impaired fatty acid oxidation in mitochondria.

Differential roles of phospholipases A2 in neuronal death and neurogenesis: implications for Alzheimer disease

The involvement of phospholipase A(2) (PLA(2)) in Alzheimer disease (AD) was first investigated nearly 15 years ago. Over the years, several PLA(2) isoforms have been detected in brain tissue: calcium-dependent secreted PLA(2) or sPLA(2) (IIA, IIC, IIE, V, X, and XII), calcium-dependent cytosolic PLA(2) or cPLA(2) (IVA, IVB, and IVC), and calcium-independent PLA(2) or iPLA(2) (VIA and VIB). Additionally, numerous in vivo and in vitro studies have suggested the role of different brain PLA(2) in both physiological and pathological events. This review aimed to summarize the findings in the literature relating the different brain PLA(2) isoforms with alterations found in AD, such as neuronal cell death and impaired neurogenesis process. The review showed that sPLA(2)-IIA, sPLA(2)-V and cPLA(2)-IVA are involved in neuronal death, whereas sPLA(2)-III and sPLA(2)-X are related to the process of neurogenesis, and that the cPLA(2) and iPLA(2) groups can be involved in both neuronal death and neurogenesis. In AD, there are reports of reduced activity of the cPLA(2) and iPLA(2) groups and increased expression of sPLA(2)-IIA and cPLA(2)-IVA. The findings suggest that the inhibition of cPLA(2) and iPLA(2) isoforms (yet to be determined) might contribute to impaired neurogenesis, whereas stimulation of sPLA(2)-IIA and cPLA(2)-IVA might contribute to neurodegeneration in AD.

Fasudil protects cultured N1E-115 cells against lysophosphatidic acid-induced neurite retraction through inhibition of Rho-kinase

The aim of this study was to investigate the possible effects of the Rho-kinase inhibitor, fasudil, on the lysophosphatidic acid (LPA)-induced neurite retraction in N1E-115 cells. In cultured N1E-115 cells, LPA produced a marked increase in the population of rounded cells. Fasudil or hydroxyfasudil, an active metabolite of fasudil, blocked cell rounding in a concentration-dependent manner at levels between 1 and 10 μM, with IC₅₀ values of 1.7 or 1.6 μM, respectively. Fasudil or hydroxyfasudil concentration-dependently inhibited phosphorylation of the myosin binding subunit of myosin phosphatase in N1E-115 cells. These results indicate that Rho-kinase is essential for LPA-induced neurite retraction in N1E-115 cells and that inactivation of Rho-kinase by a Rho-kinase inhibitor, such as fasudil, eliminates cell rounding and promotes neurite outgrowth, thus improving neurological function in the brain damage.

Omega-3 polyunsaturated fatty acids increase the neurite outgrowth of rat sensory neurones throughout development and in aged animals

Polyunsaturated fatty acids (PUFA) of the omega-3 series and omega-6 series modulate neurite outgrowth in immature neurones. However, it has not been determined if their neurotrophic effects persist in adult and aged tissue. We prepared cultures of primary sensory neurones from male and female rat dorsal root ganglia (DRG), isolated at different ages: post-natal day 3 (P3) and day 9 (P9), adult (2-4 months) and aged (18-20 months). Cultures were incubated with the omega-6 PUFA arachidonic acid (AA) and the omega-3 PUFA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), at 0.8, 4, 8 and 40muM. PUFA increased neurite outgrowth throughout the developmental stages studied. The effects of omega-3 PUFA, in particular DHA, were still prominent in aged tissue. The amplitude of the effects was comparable to that of nerve growth factor (NGF; 50ng/ml) and all-trans-retinoic acid (ATRA; 0.1muM). The effects of PUFA were similar in cells positive or negative for the N52 neurofilament marker. Our results show that omega-3 PUFA have a marked neurite-promoting potential in neurones from adult and aged animals.

Docosahexaenoic acid promotes hippocampal neuronal development and synaptic function

Docosahexaenoic acid (DHA, 22:6n-3), the major polyunsaturated fatty acid accumulated in the brain during development, has been implicated in learning and memory, but underlying cellular mechanisms are not clearly understood. Here, we demonstrate that DHA significantly affects hippocampal neuronal development and synaptic function in developing hippocampi. In embryonic neuronal cultures, DHA supplementation uniquely promoted neurite growth, synapsin puncta formation and synaptic protein expression, particularly synapsins and glutamate receptors. In DHA-supplemented neurons, spontaneous synaptic activity was significantly increased, mostly because of enhanced glutamatergic synaptic activity. Conversely, hippocampal neurons from DHA-depleted fetuses showed inhibited neurite growth and synaptogenesis. Furthermore, n-3 fatty acid deprivation during development resulted in marked decreases of synapsins and glutamate receptor subunits in the hippocampi of 18-day-old pups with concomitant impairment of long-term potentiation, a cellular mechanism underlying learning and memory. While levels of synapsins and NMDA receptor subunit NR2A were decreased in most hippocampal regions, NR2A expression was particularly reduced in CA3, suggesting possible role of DHA in CA3-NMDA receptor-dependent learning and memory processes. The DHA-induced neurite growth, synaptogenesis, synapsin, and glutamate receptor expression, and glutamatergic synaptic function may represent important cellular aspects supporting the hippocampus-related cognitive function improved by DHA.

Phospholipase A2 activation as a therapeutic approach for cognitive enhancement in early-stage Alzheimer disease

RATIONALE

Alzheimer disease (AD) is the leading cause of dementia in the elderly and has no known cure. Evidence suggests that reduced activity of specific subtypes of intracellular phospholipases A2 (cPLA2 and iPLA2) is an early event in AD and may contribute to memory impairment and neuropathology in the disease.

OBJECTIVE

The objective of this study was to review the literature focusing on the therapeutic role of PLA2 stimulation by cognitive training and positive modulators, or of supplementation with arachidonic acid (PLA2 product) in facilitating memory function and synaptic transmission and plasticity in either research animals or human subjects.

METHODS

MEDLINE database was searched (no date restrictions) for published articles using the keywords Alzheimer disease (mild, moderate, severe), mild cognitive impairment, healthy elderly, rats, mice, phospholipase A(2), phospholipid metabolism, phosphatidylcholine, arachidonic acid, cognitive training, learning, memory, long-term potentiation, protein kinases, dietary lipid compounds, cell proliferation, neurogenesis, and neuritogenesis. Reference lists of the identified articles were checked to select additional studies of interest.

RESULTS

Overall, the data suggest that PLA2 activation is induced in the healthy brain during learning and memory. Furthermore, learning seems to regulate endogenous neurogenesis, which has been observed in AD brains. Finally, PLA2 appears to be implicated in homeostatic processes related to neurite outgrowth and differentiation in both neurodevelopmental processes and response to neuronal injury.

CONCLUSION

The use of positive modulators of PLA2 (especially of cPLA2 and iPLA2) or supplementation with dietary lipid compounds (e.g., arachidonic acid) in combination with cognitive training could be a valuable therapeutic strategy for cognitive enhancement in early-stage AD.

The XLMR gene ACSL4 plays a role in dendritic spine architecture

ACSL4 is a gene involved in non-syndromic X-linked mental retardation. It encodes for a ubiquitous protein that adds coenzyme A to long-chain fatty acids, with a high substrate preference for arachidonic acid. It presents also a brain-specific isoform deriving from an alternative splicing and containing 41 additional N-terminal amino acids. To start to unravelling the link between ACSL4 and mental retardation, we have performed molecular and cell biological studies. By retro-transcription polymerase chain reaction analyses we identified a new transcript with a shorter 5'-UTR region. By immunofluorescence microscopy in embryonic rat hippocampal neurons we report that ACSL4 is associated preferentially to endoplasmic reticulum tubules. ACSL4 knockdown by siRNAs in hippocampal neurons indicated that this protein is largely dispensable for these cells' gross architectural features (i.e. axonal and dendritic formation and final length) yet it is required for the presence of normal spines. In fact, reduced levels of ACSL4 led to a significant reduction in dendritic spine density and an alteration in spine/filopodia distribution. The possible mechanisms behind this phenotype are discussed.

The cytotoxic effect of bromoenol lactone, a calcium-independent phospholipase A2 inhibitor, on rat cortical neurons in culture

This study characterized the phospholipase A(2) (PLA(2)) activity in cerebral cortex of fetal rat brain and investigated effects of chemical inhibition of Ca(2+)-independent PLA(2) (iPLA(2)) on neurite outgrowth and cell development of cortical neurons in vitro. The PLA(2) activity in fetal brain was insensitive to a Ca(2+)-chelator EGTA and was significantly impaired by an iPLA(2) inhibitor, bromoenol lactone (BEL). Following treatment with BEL, cortical neurons showed acute loss of neurites and impaired cell body, which were clearly dose- and time-dependent. Nuclear staining revealed nuclear regression (shrinkage), but not fragmentation, in BEL-treated cells. The cytotoxic effect of BEL was additive with arachidonic acid (AA) and AA alone also induced neurite demise. BEL treatment resulted in increased production of prostaglandin E(2). Overall data suggest that iPLA(2), a primary PLA(2) isoform in cerebral cortex, displays a housekeeping role in development and neurite outgrowth in cortical neurons in vitro probably via maintaining phospholipid membrane remodeling rather than generating free fatty acids and lysophospholipids.

Inhibition of phospholipase A2 reduces neurite outgrowth and neuronal viability

Phospholipase A2 (PLA(2)) has been implicated in neurodevelopmental processes and in the early development of the nervous system. We investigated the effects of the inhibition of calcium-dependent and calcium-independent subtypes of cytosolic PLA2 (cPLA2 and iPLA2) on the development and viability of primary cultures of cortical and hippocampal neurons. PLA2 in these cultures was continuously inhibited with methylarachidonyl-fluorophosphonate (MAFP), an irreversible inhibitor of cPLA2 and iPLA2, or with bromoenol lactone (BEL), an irreversible selective iPLA2 inhibitor. The effect of PLA2 inhibitors on the development of neuronal cultures was ascertained by total cell count and morphological characterisation. Neuronal viability was quantified with MTT assays. Inhibition of PLA2 resulted in reduction of neuritogenesis and neuronal viability, disrupting neuronal homeostasis and leading to neuronal death. We conclude that the functional integrity of both calcium-dependent and calcium-independent cytosolic PLA2 is necessary for the in vitro development of cortical and hippocampal neurons.

The role of phospholipase A2 in neuronal homeostasis and memory formation: implications for the pathogenesis of Alzheimer's disease

Phospholipase A(2) (PLA(2)) is a key enzyme in cerebral phospholipid metabolism. Preliminary post-mortem studies have shown that PLA(2) activity is decreased in frontal and parietal areas of the AD brain, which is in accordance with recent (31)P-Magnetic Resonance Spectroscopy evidence of reduced phospholipid turnover in the pre-frontal cortex of moderately demented AD patients. Such abnormality may also be observed in peripheral cells, and reduced PLA(2) activity in platelet membranes of AD patients, and correlates with the severity of dementia. In rat hippocampal slices, PLA(2) has been implicated in mechanisms of synaptic plasticity. In adult rats, the stereotaxic injection of PLA(2) inhibitors in the CA1 area of hippocampus impaired, in a dose-dependent manner, the formation of short- and long-term memory. Additionally, such inhibition resulted in a reduction of the fluidity of hippocampal membranes. In primary cultures of cortical and hippocampal neurons, the inhibition of PLA(2) precluded neurite outgrowth, and the sustained inhibition of the enzyme in mature cultures lead to loss of viability. Taken together, these findings reinforce the involvement of PLA(2) enzymes in neurodevelopment and neurodegeneration processes, and further suggest that reduced PLA(2) activity, probably reducing membrane phospholipids breakdown, may contribute to the memory impairment in AD.

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.

sPLA2-X stimulates cutaneous melanocyte dendricity and pigmentation through a lysophosphatidylcholine-dependent mechanism

Photoprotection of the skin is provided by melanocytes, neural crest derived cells that synthesize melanin in specialized organelles that are transferred to keratinocytes. Secretory phospholipases comprise a large family of Ca2+-dependent enzymes that liberate arachidonic acid (AA), a precursor of prostaglandins, as well as lysophospholipids. The predominant secretory phospholipase expressed by keratinocytes is group X secretory phospholipase A2 (sPLA2), which liberates large amounts of AA and the lysophospholipid lysophosphatidylcholine (LPC), from membrane preparations. Recent work by our laboratory has shown that melanocytes express receptors for prostaglandins that upon activation stimulate melanocyte dendricity and activity of tyrosinase, a key enzyme in melanin biosynthesis. In the present study, we have treated human melanocytes with recombinant sPLA2-X and show that low levels of sPLA2-X stimulate both tyrosinase activity and melanocyte dendricity. We found that the effects of sPLA2-X are mediated predominantly by LPC, not AA, and we have demonstrated expression of the phospholipase A2 receptor and two G-protein-coupled receptors for LPC (G2A and GPR119) in human melanocytes. Because secretory phospholipases are released during inflammation and are regulated by UV irradiation, our data suggest an important role for sPLA2-X in cutaneous pigmentation through the release of LPC.

Nitric oxide alters arachidonic acid turnover in brain cortex synaptoneurosomes

Nitric oxide (NO) and arachidonic acid (AA) and also its metabolites are very important inter- and intracellular second messengers. They are involved in mechanisms of learning and memory. However, liberated in excessive amount in brain ischemia, Parkinson and Alzheimer diseases they are responsible for cell degeneration and death. Previously, we could show that Alzheimer disease's amyloid-beta protein enhanced nitric oxide liberation. The role of NO in AA metabolism is till now not well understood. Therefore, the aim of the present study was to investigate the mechanisms of NO-evoked activation of AA release and inhibition of AA incorporation into phospholipids of cortical rat brain synaptoneurosomes. The studies were carried out using NO donors, butyryl-cGMP (b-cGMP) and H2O2. All these compounds enhanced AA liberation from phosphatydilinositol (PI) and phosphatidylcholine (PC). Protein kinase ERK1/2, protein kinase C (PKC), cGMP-dependent protein kinase G (PKG) were involved in basal and NO-induced cytosolic phospholipase A2 (cPLA2) activation. Moreover, NO donors, b-cGMP and hydrogen peroxide (H2O2) exerted inhibitory effect on AA incorporation into PI and PC influencing arachidonyl-CoA transferase (AA-CoA-T) activity. AA-CoA synthase (AA-CoA-S) activity did not change. Specific inhibitors of protein kinase ERK1/2 (UO126), PKC (GF109203X), PKG (KT5823) had no effect on NO-mediated lowering of AA incorporation into PI and PC but inhibited the basal AA-CoA-S activity. Our data indicated that AA (10 microM) itself markedly decreased AA incorporation by about 50% into phospholipids of synaptoneurosomes membranes. Increasing release of AA and its metabolites causes the lowering of AA incorporation evoked by NO, b-cGMP and H2O2. Antioxidant, Resveratrol (100 microM) prevented NO- and cGMP-evoked inhibition of AA incorporation. These results suggest that NO affects the intracellular level of AA through alteration of cPLA2 and AA-CoA acyltransferase activities and may have an important implication in alterations of nerve endings properties and function.

Modulation of phospholipase A2 activity in primary cultures of rat cortical neurons

In neurons, phospholipase A2 (PLA2) plays a central role in the regulation of membrane phospholipid metabolism. We have addressed the pharmacological modulation of PLA2 in primary cultures of rat cortical neurons. Inhibition curves were obtained in 4 day-in-culture neurons treated for 30 minutes with either the dual PLA2 inhibitor methyl arachidonyl fluorophosphonate (MAFP), or the iPLA2 inhibitor bromoenol lactone (BEL). Full inhibition was achieved with 100 and 250 microM of MAFP, or 10 and 20 microM of BEL. Conversely, a dose-dependent activation of PLA2 was obtained with 10-20 microg/ml of melitin. PLA2 inhibition with MAFP or BEL was not acutely toxic for cultured neurons. However, sustained inhibition of the enzyme precluded the development of neurites, and resulted in long-term loss of neuronal viability. We present a model of pharmacological challenge of PLA2 in vitro, which can be further used to address the involvement of the enzyme in neurodevelopment and neurodegeneration models.

PTH and phospholipase A2 in the aging process of intestinal cells

In this study we analyzed, for the first time, alterations in phospholipase A2 (PLA2) activity and response to parathyroid hormone (PTH) in rat enterocytes with aging. We found that PTH, rapidly stimulate arachidonic acid (AA) release in rat duodenal cells (+1- to 2-fold), an effect that is greatly potentiated by aging (+4-fold). We also found that hormone-induced AA release in young animals is Ca2+-dependent via cPLA2, while AA released by PTH in cells from aged rats is due to the activation of cPLA2 and the Ca2+-independent PLA2 (iPLA2). In enterocytes from 3 months old rats, PTH induced, in a time and dose-dependent fashion, the phosphorylation of cPLA2 on serine 505, with a maximum at 10 min (+7-fold). Basal levels of cPLA2 serine-phosphorylation were higher in old enterocytes, affecting the hormone response which was greatly diminished (+2-fold at 10 min). cPLA2 phosphorylation impairment in old animals was not related to changes of cPLA2 protein expression and did not explain the substantial increase on PTH-induced AA release with aging, further suggesting the involvement of a different PLA2 isoform. Intracellular Ca2+ chelation (BAPTA-AM, 5 microM) suppressed the serine phosphorylation of cPLA2 in both, young and aged rats, demonstrating that intracellular Ca2+ is required for full activation of cPLA2 in enterocytes stimulated with PTH. Hormone effect on cPLA2 was suppressed to a great extent by the MAP kinases ERK 1 and ERK2 inhibitor, PD 98059 (20 microM), the cAMP antagonist, Rp-cAMP, and the PKC inhibitor Ro31820 both, in young and aged animals. Enterocytes exposure to PTH also resulted in phospho-cPLA2 translocation from cytosol to nuclei and membrane fractions, where phospholipase substrates reside. Hormone-induced enzyme translocation is also modified by aging where, in contrast to young animals, part of phospho-cPLA2 remained cytosolic. Collectively, these data suggest that PTH activates in duodenal cells, a Ca2+-dependent cytosolic PLA2 and attendant AA release and that this activation requires prior stimulation of intracellular ERK1/2, PKA, and PKC. cPLA2 is the major enzyme responsible for AA release in young enterocytes while cPLA2 and the Ca2+-independent iPLA2, potentiate PTH-induced AA release in aged cells. Impairment of PTH activation of PLA2 isoforms upon aging may result in abnormal hormone regulation of membrane fluidity and permeability and thereby affecting intestinal cell membrane function.

Retinoic acid-mediated phospholipase A2 signaling in the nucleus

Retinoic acid modulates a wide variety of biological processes including proliferation, differentiation, and apoptosis. It interacts with specific receptors in the nucleus, the retinoic acid receptors (RARs). The molecular mechanism by which retinoic acid mediates cellular differentiation and growth suppression in neural cells remains unknown. However, retinoic acid-induced release of arachidonic acid and its metabolites may play an important role in cell proliferation, differentiation, and apoptosis. In brain tissue, arachidonic acid is mainly released by the action of phospholipase A2 (PLA2) and phospholipase C (PLC)/diacylglycerol lipase pathways. We have used the model of differentiation in LA-N-1 cells induced by retinoic acid. The treatment of LA-N-1 cells with retinoic acid produces an increase in phospholipase A2 activity in the nuclear fraction. The pan retinoic acid receptor antagonist, BMS493, can prevent this increase in phospholipase A2 activity. This suggests that retinoic acid-induced stimulation of phospholipase A2 activity is a retinoic acid receptor-mediated process. LA-N-1 cell nuclei also have phospholipase C and phospholipase D (PLD) activities that are stimulated by retinoic acid. Selective phospholipase C and phospholipase D inhibitors block the stimulation of phospholipase C and phospholipase D activities. Thus, both direct and indirect mechanisms of arachidonic acid release exist in LA-N-1 cell nuclei. Arachidonic acid and its metabolites markedly affect the neurite outgrowth and neurotransmitter release in cells of neuronal and glial origin. We propose that retinoic acid receptors coupled with phospholipases A2, C and D in the nuclear membrane play an important role in the redistribution of arachidonic acid in neuronal and non-nuclear neuronal membranes during differentiation and growth suppression. Abnormal retinoid metabolism may be involved in the downstream transcriptional regulation of phospholipase A2-mediated signal transduction in schizophrenia and Alzheimer disease (AD). The development of new retinoid analogs with diminished toxicity that can cross the blood-brain barrier without harm and can normalize phospholipase A2-mediated signaling will be important in developing pharmacological interventions for these neurological disorders.

Acyl-CoA synthetase 2 overexpression enhances fatty acid internalization and neurite outgrowth

During neurodevelopment neurons increase phospholipid synthesis to generate additional plasma membrane that makes up the growing neurites. Compared with most cell types, neurons contain a high percentage of the polyunsaturated fatty acids (PUFAs) arachidonic acid (AA) and docosahexaenoic acid (DHA). By utilizing PC12 cell lines as a model neuronal cell line, we examined the internalization rate of AA, DHA, and non-essential oleic acid (OA), as well as their effects on neurite outgrowth. When wild type cells were differentiated, the rate of AA and DHA internalization increased 50% more than the rate of OA internalization. When media were supplemented with AA or DHA, the average neurite length was increased by approximately 40%, but supplementation with the same amount of OA had no effect. We also increased the levels of acyl-CoA synthetase-1 (ACS1) and ACS2 proteins to determine whether they contribute to PUFA internalization or neurite outgrowth. Overexpression of ACS1 increased the rate of OA internalization by 55%, and AA and DHA uptake was increased by 25%, but there was no significant change in neurite outgrowth. In ACS2-overexpressing cells, in contrast, the rate of OA internalization increased by 90%, AA by 115%, and DHA by 70%. The average aggregate neurite length in ACS2-overexpressing cells was increased by approximately 40% when the media were supplemented with PUFAs, but there was no change with OA supplementation. Taken together, these results support the hypotheses that ACSs are rate-limiting for fatty acid internalization and that ACS2 enhances neurite outgrowth by promoting PUFA internalization.

From membrane phospholipid defects to altered neurotransmission: is arachidonic acid a nexus in the pathophysiology of schizophrenia?

Schizophrenia (SZ) is a devastating neuropsychiatric disorder affecting 1% of the general population, and is characterized by symptoms such as delusions, hallucinations, and blunted affect. While many ideas regarding SZ pathogenesis have been put forth, the majority of research has focused on neurotransmitter function, particularly in relation to altered dopamine activity. However, treatments based on this paradigm have met with only modest success, and current medications fail to alleviate symptoms in 30-60% of patients. An alternative idea postulated a quarter of a century ago by Feldberg (Psychol. Med. 6 (1976) 359) and Horrobin (Lancet 1 (1977) 936) involves the theory that SZ is associated in part with phospholipid/fatty acid abnormalities. Since then, it has been repeatedly shown that in both central and peripheral tissue, SZ patients demonstrate increased phospholipid breakdown and decreased levels of various polyunsaturated fatty acids (PUFAs), particularly arachidonic acid (AA). Given the diverse physiological function of membrane phospholipids and PUFAs, an elucidation of their role in SZ pathophysiology may provide novel strategies in the treatment of this disorder. The purpose of this review is to summarize the relevant data on membrane phospholipid/PUFA defects in SZ, the physiological consequence of altered AA signaling, and how they relate to the neurobiological manifestations of SZ and therapeutic outcome.

Ca2+-independent phospholipases A2 and production of arachidonic acid in nuclei of LA-N-1 cell cultures: a specific receptor activation mediated with retinoic acid

The LA-N-1 cell nucleus contains Ca2+-independent phospholipase A2 (PLA2) activity hydrolyzing plasmenylethanolamine (PlsEtn) and 1,2-diacyl-sn-glycero-3-phosphoethanolamine (PtdEtn). These enzymes hydrolyze glycerophospholipids to produce arachidonic acid and lysoglycerophospholipids. The treatment of LA-N-1 cell cultures with all-trans retinoic acid (atRA) results in time- and dose-dependent stimulation of PlsEtn-PLA2 and PtdEtn-PLA2 activities in the nuclear fraction. PLA2 activities in the non-nuclear fraction (microsomes) are not affected by atRA, whilst the pan retinoic acid receptor (RAR) antagonist, BMS493, blocks the PLA2 activities in the nuclear fraction. This indicates that the stimulation of PLA2 activities is a receptor-mediated process. Treatment of LA-N-1 cell cultures with cycloheximide has no effect on basal PLA2 activities. However, atRA-mediated stimulation of PLA2 activities in LA-N-1 cell nuclei is partially inhibited by cycloheximide indicating that this decrease in PLA2 activity is due to a general decreased protein synthesis. Our results also support earlier studies in which atRA induces morphologic differentiation through the stimulation of PLA2-generated second messengers such as arachidonic acid and eicosanoids.

Actin polymerization in macrophages in response to oxidized LDL and apoptotic cells: role of 12/15-lipoxygenase and phosphoinositide 3-kinase

Formation of filamentous F-actin drives many cellular processes, including phagocytosis and cell spreading. We have recently reported that mouse macrophage 12/15-lipoxygenase (12/15-LO) activity promotes F-actin formation in filopodia during phagocytosis of apoptotic cells. Oxidized low-density lipoprotein (OxLDL) also stimulates robust F-actin formation and spreading of macrophages. However, unlike apoptotic cells, OxLDL did not cause specific translocation of 12/15-LO to the cell membrane, neither in macrophages nor in GFP-15LO-transfected COS-7 cells. Moreover, inhibition of 12/15-LO activity in macrophages by a specific inhibitor or by 12/15-LO gene disruption did not affect OxLDL-induced actin polymerization. Among LDL modifications modeling OxLDL, LDL modified by incubation with 15LO-overexpressing fibroblasts was as active in eliciting F-actin response as was OxLDL. This LDL modification is well known to produce minimally modified LDL (mmLDL), which is bioactive and carries lipid oxidation products similar to those produced by 12/15-LO catalysis. MmLDL activated phosphoinositide 3-kinase (PI3K), and PI3K inhibitors abolished mmLDL-induced macrophage spreading. We hypothesize that OxLDL and mmLDL may contribute oxidized lipids to the macrophage cell membrane and thereby mimic intracellular 12/15-LO activity, which leads to uncontrolled actin polymerization and dramatic cytoskeletal changes in macrophages.

Initial stages of neural regeneration in Helisoma trivolvis are dependent upon PLA2 activity

Neuronal regeneration after damage to an axon tract requires the rapid sealing of the injured plasma membrane and the subsequent formation of growth cones that can lead regenerating processes to their appropriate target. Membrane sealing and growth cone formation are Ca(2+)-dependent processes, but the signaling pathways activated by Ca(2+) to bring about these effects remain poorly understood. An in vitro injury model was employed in which neurites from identified snail neurons (Helisoma trivolvis) were transected with a glass microknife, and the formation of new growth cones from the distal portions of transected neurites was recorded at defined times after transection. This study presents three main results. First, phospholipase A(2) (PLA(2)), a calcium-activated enzyme, is necessary for membrane sealing in vitro. Second, PLA(2) activity is also required for the formation of a new growth cone after the membrane has sealed successfully. Thus, PLA(2) plays a dual role by affecting both growth cone formation and membrane sealing. Third, the injury-induced activation of PLA(2) by Ca(2+) controls growth cone formation through the production of leukotrienes, secondary metabolites of PLA(2) activity. Taken together, these results suggest that the injury-induced Ca(2+) influx acts via PLA(2) and leukotriene production to assure growth cone formation. These findings indicate that events that cause an inhibition of PLA(2) or lipoxygenases, enzymes that produce leukotrienes, could result in the inability of neurites to regenerate.

Investigation of antioxidant enzymes in children with autistic disorder

Impaired antioxidant mechanisms are unable to inactivate free radicals that may induce a number of pathophysiological processes and result in cell injury. Thus, any abnormality in antioxidant defence systems could affect neurodevelopmental processes and could have an important role in the etiology of autistic disorder. The plasma levels of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD), and erythrocyte levels of GSH-Px were investigated in 45 autistic children and compared with 41 normal controls. Levels of erythrocyte SOD, erythrocyte and plasma GSH-Px were assayed spectrophotometrically. Activities of erythrocyte SOD, erythrocyte and plasma GSH-Px in autistic children were significantly lower than normals. These results indicate that autistic children have low levels of activity of blood antioxidant enzyme systems; if similar abnormalities are present in brain, free radical accumulation could damage brain tissue.

Effect of retinoic acid on the Ca2+-independent phospholipase A2 in nuclei of LA-N-1 neuroblastoma cells

LA-N-1 neuroblastoma cell cultures contain Ca2+-independent phospholipases A2 hydrolyzing phosphatidylethanolamine and ethanolamine plasmalogens. These enzymes differ from each other in their molecular mass, substrate specificity, and kinetic properties. Subcellular distribution studies have indicated that the activity of these phospholipases is not only localized in the cytosol but also in non-nuclear membranes and in nuclei. The treatment of LA-N-1 neuroblastoma cell cultures with retinoic acid results in a marked stimulation of Ca2+-independent phospholipases A2 hydrolyzing phosphatidylethanolamine and plasmenylethanolamine. The increase of the activities of both enzymes was first observed in nuclei followed by those present in the cytosol. No effect of retinoic acid on either phospholipase activity could be observed in non-nuclear membranes. The stimulation of these enzymes may be involved in the generation and regulation of arachidonic acid and its metabolites during differentiation.

Red blood cell fatty acid compositions in a patient with autistic spectrum disorder: a characteristic abnormality in neurodevelopmental disorders?

The fatty acid compositions of red blood cell (RBC) phospholipids from a patient with autistic spectrum disorder (ASD) had reduced percentages of highly unsaturated fatty acids (HUFA) compared to control samples. The percentage of HUFA in the RBC from the autistic patient was dramatically reduced (up to 70%) when the sample was stored for 6 weeks at -20 degrees C. However, only minor HUFA reductions were recorded in control samples stored similarly, or when the autistic sample was stored at -80 degrees C. A similar instability in RBC HUFA compositions upon storage at -20 degrees C has been recorded in schizophrenic patients. In a number of other neurodevelopmental conditions, including attention deficit hyperactivity disorder (ADHD) and dyslexia, reduced concentrations of RBC HUFA have been recorded. The extent and nature of these aberrations require further assessment to determine a possible common biochemical origin of neurodevelopmental disorders in general. To facilitate this, a large scale assessment of RBC fatty acid compositions in patients with ASD, and related disorders, should be performed as a matter of urgency. Supplementing cells in culture with the tryptophan metabolite indole acrylic acid (IAA) affected the levels of cellular HUFA and prostaglandin production. Indole acroyl glycine (IAG), a metabolite of IAA excreted in urine, is found in high concentrations in patients with neurodevelopmental disorders including ASD, ADHD, dyslexia, Asperger's syndrome and obsessive compulsive disorder.

The potential role of fatty acids in attention-deficit/hyperactivity disorder

As currently defined, attention-deficit/hyperactivity disorder (ADHD) encompasses a broad constellation of behavioural and learning problems and its definition and diagnosis remain controversial. The aetiology of ADHD is acknowledged to be both complex and multifactorial. The proposal considered here is that at least some features of ADHD may reflect an underlying abnormality of fatty acid metabolism. Clinical and biochemical evidence is discussed which suggests that a functional deficiency of certain long-chain polyunsaturated fatty acids could contribute to many of the features associated with this condition. The implications in terms of fatty acid treatment proposals are also discussed; such a form of treatment is relatively safe compared to existing pharmacological interventions, although further studies are still needed in order to evaluate its potential efficacy in the management of ADHD symptoms.

Ca(2+)-independent phospholipase A2 is required for alpha2-adrenergic-induced preadipocyte spreading

In the present study, we studied the involvement of A2 phospholipases (PLA2) in alpha2-adrenergic receptor-control of preadipocyte actin cytoskeleton. For that, various PLA2 inhibitors were tested on the ability of the selective alpha2-adrenergic agonist UK14304 to induce the spreading in alpha2AF2 preadipocytes. We observed that, whereas several Ca(2+)-dependent PLA2 blockers were ineffective, the Ca(2+)-independent phospholipase A2 (iPLA2) inhibitor, broenolactone (BEL), specifically blocked alpha2-adrenergic-dependent preadipocyte spreading without affecting the spreading activity of lysophosphatidic acid (LPA) or serum. BEL inhibition was completely restored by lysophosphatidic acid, but not by arachidonic acid or other fatty acids. The presence of the lysophospholipase (phospholipase B) suppressed the effect of LPA on preadipocyte spreading, but had no influence on alpha2-adrenergic-induced spreading. Thus, the extracellular production of LPA or fatty acids is not involved in iPLA2-dependent preadipocyte spreading. iPLA2 protein was found in preadipocytes but, conversely to cPLA2, did not exhibit any modification of its electrophoretic mobility after alpha2-adrenergic stimulation. We concluded that iPLA2 is involved in alpha2-adrenergic control of preadipocyte actin cytoskeleton.

Involvement of axonal phospholipase A2 activity in the outgrowth of adult mouse sensory axons in vitro

The effect on axonal outgrowth of inhibition of phospholipase A2 activity was studied in a recently developed in vitro model, where dorsal root ganglia with attached spinal roots and nerve stumps from young adult mice were cultured in an extracellular matrix material (Matrigel). The phospholipase A2 inhibitors 4-bromophenacyl bromide and oleyloxyethyl phosphorylcholine dose-dependently reduced axonal outgrowth from the sciatic nerve stump. A similar inhibitory effect was seen when only the cut nerve end was exposed to the inhibitors in a compartmental culture system. The local effect of phospholipase A2 inhibition was further investigated on axons established in culture, using time-lapse recording. Exposure to phospholipase A2 inhibitors caused the retraction of filopodia extensions and a reduction in growth cone motility within a few minutes. After removal of inhibition, normal growth cone motility and axonal growth were regained. Nerve cell bodies and axons, in contrast to Schwann cells, showed immunoreactivity after staining with an antiserum against secretory phospholipase A2, and elevated levels of the enzyme could be detected after culture for 24 h. The immunoreactive protein was of approximately 170,000 molecular weight (phospholipase A2-170) as determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and immunoblotting. The localization of phospholipase A2-170 in axons growing into the Matrigel was also demonstrated by use of a whole-mount technique. The results of this study show the importance of continuous phospholipase A2 activity for growth cone motility and axonal outgrowth in the mammalian peripheral nerve, and suggest the involvement of an axonally localized enzyme.

Inhibitors of intracellular phospholipase A2 activity: their neurochemical effects and therapeutical importance for neurological disorders

Intracellular phospholipases A2 (PLA2) are a diverse group of enzymes with a growing number of members. These enzymes hydrolyze membrane phospholipids into fatty acid and lysophospholipids. These lipid products may serve as intracellular second messengers or can be further metabolized to potent inflammatory mediators, such as eicosanoids and platelet-activating factors. Several inhibitors of nonneural intracellular PLA2 have been recently discovered. However, nothing is known about their neurochemical effects, mechanism of action or toxicity in human or animal models of neurological disorders. Elevated intracellular PLA2 activities, found in neurological disorders strongly associated with inflammation and oxidative stress (ischemia, spinal cord injury, and Alzheimer's disease), can be treated with specific, potent and nontoxic inhibitors of PLA2 that can cross blood-brain barrier without harm. Currently, potent intracellular PLA2 inhibitors are not available for clinical use in human or animal models of neurological disorders, but studies on this interesting topic are beginning to emerge. The use of nonspecific intracellular PLA2 inhibitors (quinacrine, heparin, gangliosides, vitamin E) in animal model studies of neurological disorders in vivo has provided some useful information on tolerance, toxicity, and effectiveness of these compounds.

Lipid metabolism, human evolution and schizophrenia

There are only small genetic differences between humans and the great apes. Yet these differences must be very important. Major known differences include the accumulation of subcutaneous fat, the expansion of breasts and buttocks, the growth of the brain and the connectivity of neurons. All these involve lipid metabolism yet, because fat leaves no fossils, lipids are rarely mentioned in discussions of human evolution. This paper attempts to identify some candidate areas of lipid metabolism which may be important in human evolution. It draws attention to abnormalities in phospholipid metabolism in schizophrenia and suggests that these may have proved important in enhancing brain connectivity in the later stages of evolution of modern humans.

The membrane phospholipid hypothesis as a biochemical basis for the neurodevelopmental concept of schizophrenia

The neurodevelopmental hypothesis of schizophrenia is becoming an important feature of research in the field. However, its major drawback is that it lacks any biochemical basis which might draw the diverse observations together. It is suggested that the membrane phospholipid hypothesis can provide such a biochemical basis and that the neurodevelopmental phospholipid concept offers a powerful paradigm to guide future research.

Schizophrenia: the illness that made us human

Any hypotheses concerning the origins of humans must explain many things. Among these are: 1, the growth in brain size around two million years ago; 2, the presence of subcutaneous fat; 3, the near absence of change or cultural progress for around 2 million years after the brain grew in size; 4, the cultural explosion which began somewhere between fifty thousand and one hundred thousand years ago with the emergence of art, music, religion and warfare; 5, the further cultural explosion around ten thousand to fifteen thousand years ago which developed with the emergence of agriculture and which has continued since. Since the brain, like subcutaneous fat, is particularly rich in lipids, and since the microconnections of the brain are substantially lipid in nature, it is suggested that changes in lipid metabolism are what differentiated humans from the great apes. The growth in brain size and in the quality of subcutaneous adipose tissue may have occurred because of changes in the proteins which regulate the rate of delivery of fatty acids to tissues, notably lipoprotein lipases and fatty acid binding proteins. The creativity which occurred one hundred thousand years ago may have resulted from changes in phospholipid-synthesizing, -remodelling and -degrading enzymes which largely determine the microconnectivity of neurons. Family studies and adoption studies indicate that schizophrenia in a family member is associated with an increased risk of the illness in other family members. It is also associated with an increased risk of schizotypy, manic-depression, dyslexia, sociopathy and psychopathy. On the other hand it is also an indication of an increased likelihood of high creativity, leadership qualities, achievements in many fields, high musical skills and an intense interest in religion. I propose that the characteristics which entered the human race about one hundred thousand years ago and which ended around two million years of cultural near-stagnation are precisely those shown by the families of people with schizophrenia. I propose that these features are caused by variations in phospholipid biochemistry which are responsible both for schizophrenia and for our humanity. This would help to explain why schizophrenia is present to approximately the same degree in all races. It is the illness which made us human prior to the separation of the races.