Cytosolic phospholipase A2 gene in human and rat: chromosomal localization and polymorphic markers

Four Variants of SLCO2A1 Identified in Three Chinese Patients with Chronic Enteropathy Associated with the SLCO2A1 Gene

BACKGROUND

Chronic enteropathy associated with the SLCO2A1 gene (CEAS) is an enteropathy characterized by multiple small intestinal ulcers of nonspecific histology, also known as chronic nonspecific multiple ulcers of the small intestine. The SLCO2A1 gene encodes a prostaglandin transporter (PGT).

AIMS

The aim of this study was to investigate the clinical characteristics of ten Chinese patients with intestinal ulcers of unknown origin, screen them for variants of SLCO2A1, and to investigate the expression of PGT in the small intestinal mucosa of patients with CEAS.

METHODS

Ten Chinese patients with intestinal ulcers of unknown origin were included in this study. Blood samples were collected for whole-exome sequencing and Sanger sequencing of candidate gene variants. Immunohistochemical staining was used to investigate the expression of PGT.

RESULTS

These ten patients were clinically diagnosed with intestinal ulcers of unknown origin based on criteria established according to earlier publications. Three of them were genetically diagnosed as having CEAS and four candidate variants of the SLCO2A1 gene were identified, among which c.941-1G>A, c.178G>A and c.1681C>T were detected in patients with CEAS for the first time. The terminal ileum was involved in all three patients with CEAS in our study, which was different from the results of Japanese patients. The expression of PGT in the vascular endothelial cells of the intestinal mucosa tissues of patients with CEAS was negative or intermediate.

CONCLUSION

We summarized the clinical data of ten Chinese patients with intestinal ulcers of unknown origin and identified three novel SLCO2A1 variants from three patients with CEAS. This study improves our understanding of CEAS and broadens the spectrum of SLCO2A1 variants known to cause CEAS.

Inflammation and JNK's Role in Niacin-GPR109A Diminished Flushed Effect in Microglial and Neuronal Cells With Relevance to Schizophrenia

Schizophrenia is a neuropsychiatric illness with no single definitive aetiology, making its treatment difficult. Antipsychotics are not fully effective because they treat psychosis rather than the cognitive or negative symptoms. Antipsychotics fail to alleviate symptoms when patients enter the chronic stage of illness. Topical application of niacin showed diminished skin flush in the majority of patients with schizophrenia compared to the general population who showed flushing. The niacin skin flush test is useful for identifying patients with schizophrenia at their ultra-high-risk stage, and understanding this pathology may introduce an effective treatment. This review aims to understand the pathology behind the diminished skin flush response, while linking it back to neurons and microglia. First, it suggests that there are altered proteins in the GPR109A-COX-prostaglandin pathway, inflammatory imbalance, and kinase signalling pathway, c-Jun N-terminal kinase (JNK), which are associated with diminished flush. Second, genes from the GPR109A-COX-prostaglandin pathway were matched against the 128-loci genome wide association study (GWAS) for schizophrenia using GeneCards, suggesting that G-coupled receptor-109A (GPR109A) may have a genetic mutation, resulting in diminished flush. This review also suggests that there may be increased pro-inflammatory mediators in the GPR109A-COX-prostaglandin pathway, which contributes to the diminished flush pathology. Increased levels of pro-inflammatory markers may induce microglial-activated neuronal death. Lastly, this review explores the role of JNK on pro-inflammatory mediators, proteins in the GPR109A-COX-prostaglandin pathway, microglial activation, and neuronal death. Inhibiting JNK may reverse the changes observed in the diminished flush response, which might make it a good therapeutic target.

BanI polymorphism of cytosolic phospholipase A2 gene and somatic symptoms in medication-free acute depressed patients

Somatic symptoms are commonly seen in patients with major depressive disorder (MDD) and might be associated with inflammatory activation. Cytosolic phospholipase A2 (cPLA2) and cyclo-oxygenase-2 (COX-2) are the key enzymes in the metabolism of polyunsaturated fatty acids (PUFAs), which in turn may play an important role in inflammation and somatic symptoms in depression. This study investigated the effects of BanI polymorphism of cPLA2 gene and COX-2 rs4648308 genotypes on somatic symptoms and inflammatory marker in patients with MDD. Eighty-two patients with MDD were assessed for their psychopathology including psychiatric and somatic symptoms, BanI polymorphism of cPLA2 and COX-2 rs4648308 genotypes and CRP levels. The results revealed that MDD patients with the cPLA2 BanI GG genotypes had higher somatic symptoms and higher levels of C-reactive protein (CRP), while no differences were found among the COX-2 rs4648308 genotypes. Inflammatory process, such as arachidonic acid cascade pathway, might help explain the effect of cPLA2 BanI polymorphism on the somatic symptoms, and may be a potential target for future investigation on treatment for MDD with somatic symptoms. However, the interpretation of the findings in this study is limited since we analyzed the data from a subset data from a larger study.

Synopsis of arachidonic acid metabolism: A review

Arachidonic acid (AA), a 20 carbon chain polyunsaturated fatty acid with 4 double bonds, is an integral constituent of biological cell membrane, conferring it with fluidity and flexibility. The four double bonds of AA predispose it to oxygenation that leads to a plethora of metabolites of considerable importance for the proper function of the immune system, promotion of allergies and inflammation, resolving of inflammation, mood, and appetite. The present review presents an illustrated synopsis of AA metabolism, corroborating the instrumental importance of AA derivatives for health and well-being. It provides a comprehensive outline on AA metabolic pathways, enzymes and signaling cascades, in order to develop new perspectives in disease treatment and diagnosis.

Targeting arachidonic acid pathway by natural products for cancer prevention and therapy

Arachidonic acid (AA) pathway, a metabolic process, plays a key role in carcinogenesis. Hence, AA pathway metabolic enzymes phospholipase A₂s (PLA₂s), cyclooxygenases (COXs) and lipoxygenases (LOXs) and their metabolic products, such as prostaglandins and leukotrienes, have been considered novel preventive and therapeutic targets in cancer. Bioactive natural products are a good source for development of novel cancer preventive and therapeutic drugs, which have been widely used in clinical practice due to their safety profiles. AA pathway inhibitory natural products have been developed as chemopreventive and therapeutic agents against several cancers. Curcumin, resveratrol, apigenin, anthocyans, berberine, ellagic acid, eugenol, fisetin, ursolic acid, [6]-gingerol, guggulsteone, lycopene and genistein are well known cancer chemopreventive agents which act by targeting multiple pathways, including COX-2. Nordihydroguaiaretic acid and baicalein can be chemopreventive molecules against various cancers by inhibiting LOXs. Several PLA₂s inhibitory natural products have been identified with chemopreventive and therapeutic potentials against various cancers. In this review, we critically discuss the possible utility of natural products as preventive and therapeutic agents against various oncologic diseases, including prostate, pancreatic, lung, skin, gastric, oral, blood, head and neck, colorectal, liver, cervical and breast cancers, by targeting AA pathway. Further, the current status of clinical studies evaluating AA pathway inhibitory natural products in cancer is reviewed. In addition, various emerging issues, including bioavailability, toxicity and explorability of combination therapy, for the development of AA pathway inhibitory natural products as chemopreventive and therapeutic agents against human malignancy are also discussed.

Coordinated gene expression of neuroinflammatory and cell signaling markers in dorsolateral prefrontal cortex during human brain development and aging

BACKGROUND

Age changes in expression of inflammatory, synaptic, and neurotrophic genes are not well characterized during human brain development and senescence. Knowing these changes may elucidate structural, metabolic, and functional brain processes over the lifespan, as well vulnerability to neurodevelopmental or neurodegenerative diseases.

HYPOTHESIS

Expression levels of inflammatory, synaptic, and neurotrophic genes in the human brain are coordinated over the lifespan and underlie changes in phenotypic networks or cascades.

METHODS

We used a large-scale microarray dataset from human prefrontal cortex, BrainCloud, to quantify age changes over the lifespan, divided into Development (0 to 21 years, 87 brains) and Aging (22 to 78 years, 144 brains) intervals, in transcription levels of 39 genes.

RESULTS

Gene expression levels followed different trajectories over the lifespan. Many changes were intercorrelated within three similar groups or clusters of genes during both Development and Aging, despite different roles of the gene products in the two intervals. During Development, changes were related to reported neuronal loss, dendritic growth and pruning, and microglial events; TLR4, IL1R1, NFKB1, MOBP, PLA2G4A, and PTGS2 expression increased in the first years of life, while expression of synaptic genes GAP43 and DBN1 decreased, before reaching plateaus. During Aging, expression was upregulated for potentially pro-inflammatory genes such as NFKB1, TRAF6, TLR4, IL1R1, TSPO, and GFAP, but downregulated for neurotrophic and synaptic integrity genes such as BDNF, NGF, PDGFA, SYN, and DBN1.

CONCLUSIONS

Coordinated changes in gene transcription cascades underlie changes in synaptic, neurotrophic, and inflammatory phenotypic networks during brain Development and Aging. Early postnatal expression changes relate to neuronal, glial, and myelin growth and synaptic pruning events, while late Aging is associated with pro-inflammatory and synaptic loss changes. Thus, comparable transcriptional regulatory networks that operate throughout the lifespan underlie different phenotypic processes during Aging compared to Development.

Coordination of gene expression of arachidonic and docosahexaenoic acid cascade enzymes during human brain development and aging

Background

The polyunsaturated arachidonic and docosahexaenoic acids (AA and DHA) participate in cell membrane synthesis during neurodevelopment, neuroplasticity, and neurotransmission throughout life. Each is metabolized via coupled enzymatic reactions within separate but interacting metabolic cascades.

Hypothesis

AA and DHA pathway genes are coordinately expressed and underlie cascade interactions during human brain development and aging.

Methods

The BrainCloud database for human non-pathological prefrontal cortex gene expression was used to quantify postnatal age changes in mRNA expression of 34 genes involved in AA and DHA metabolism.

Results

Expression patterns were split into Development (0 to 20 years) and Aging (21 to 78 years) intervals. Expression of genes for cytosolic phospholipases A₂ (cPLA₂), cyclooxygenases (COX)-1 and -2, and other AA cascade enzymes, correlated closely with age during Development, less so during Aging. Expression of DHA cascade enzymes was less inter-correlated in each period, but often changed in the opposite direction to expression of AA cascade genes. Except for the PLA2G4A (cPLA₂ IVA) and PTGS2 (COX-2) genes at 1q25, highly inter-correlated genes were at distant chromosomal loci.

Conclusions

Coordinated age-related gene expression during the brain Development and Aging intervals likely underlies coupled changes in enzymes of the AA and DHA cascades and largely occur through distant transcriptional regulation. Healthy brain aging does not show upregulation of PLA2G4 or PTGS2 expression, which was found in Alzheimer's disease.

Cryptogenia multifocal ulcerous stenosing enteritis: an entity on its own as a cause of abdominal pain, iron deficiency anemia and protein-losing enteropathy

We studied a patient with edema secondary to protein losing enteropathy, and recurrent bouts of bloating and abdominal pain secondary to intestinal subocclusion episodes. After the clinical study, the patient was diagnosed of cryptogenic multifocal ulcerous stenosing enteritis (CMUSE), that is a rare disease, probably caused by mutations in the gene PLA2G4A, and characterized by multiple short stenosis of the small bowel with superficial ulcers, which do not exceed the submucosa layer. Inflammatory bowel disease (Chron's disease), intestinal tuberculosis and intestinal ulcers secondary to non-steroidal anti-inflammatory drugs are the main differential diagnosis. To sum up, physicians should included CMUSE in the differential diagnosis of recurrent abdominal pain, iron deficiency anaemia, occult intestinal bleeding, edema and protein losing enteropathy.

Translational studies on regulation of brain docosahexaenoic acid (DHA) metabolism in vivo

One goal in the field of brain polyunsaturated fatty acid (PUFA) metabolism is to translate the many studies that have been conducted in vitro and in animal models to the clinical setting. Doing so should elucidate the role of PUFAs in the human brain, and effects of diet, drugs, disease and genetics on this role. This review discusses new in vivo radiotracer kinetic and neuroimaging techniques that allow us to do this, with a focus on docosahexaenoic acid (DHA). We illustrate how brain PUFA metabolism is influenced by graded reductions in dietary n-3 PUFA content in unanesthetized rats. We also show how kinetic tracer techniques in rodents have helped to identify mechanisms of action of mood stabilizers used in bipolar disorder, how DHA participates in neurotransmission, and how brain DHA metabolism is regulated by calcium-independent iPLA₂β. In humans, regional rates of brain DHA metabolism can be quantitatively imaged with positron emission tomography following intravenous injection of [1-¹¹C]DHA.

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.

Gender-specific genomic profiling in metastatic colorectal cancer patients treated with 5-fluorouracil and oxaliplatin

AIMS

Survival and response rates in metastatic colorectal cancer remain poor, despite advances in drug development. There is increasing evidence to suggest that gender-specific differences may contribute to poor clinical outcome. We tested the hypothesis that genomic profiling of metastatic colorectal cancer is dependent on gender.

MATERIALS & METHODS

A total of 152 patients with metastatic colorectal cancer who were treated with oxaliplatin and continuous infusion 5-fluorouracil were genotyped for 21 polymorphisms in 13 cancer-related genes by PCR. Classification and regression tree analysis tested for gender-related association of polymorphisms with overall survival, progression-free survival and tumor response.

RESULTS

Classification and regression tree analysis of all polymorphisms, age and race resulted in gender-specific predictors of overall survival, progression-free survival and tumor response. Polymorphisms in the following genes were associated with gender-specific clinical outcome: estrogen receptor β, EGF receptor, xeroderma pigmentosum group D, voltage-gated sodium channel and phospholipase A2.

CONCLUSION

Genetic profiling to predict the clinical outcome of patients with metastatic colorectal cancer may depend on gender.

Dietary n-6 PUFA deprivation downregulates arachidonate but upregulates docosahexaenoate metabolizing enzymes in rat brain

BACKGROUND

Dietary n-3 polyunsaturated fatty acid (PUFA) deprivation increases expression of arachidonic acid (AA 20:4n-6)-selective cytosolic phospholipase A(2) (cPLA(2)) IVA and cyclooxygenase (COX)-2 in rat brain, while decreasing expression of docosahexaenoic acid (DHA 22:6n-3)-selective calcium-independent iPLA(2) VIA. Assuming that these enzyme changes represent brain homeostatic responses to deprivation, we hypothesized that dietary n-6 PUFA deprivation would produce changes in the opposite directions.

METHODS

Brain expression of PUFA-metabolizing enzymes and their transcription factors was quantified in male rats fed an n-6 PUFA adequate or deficient diet for 15weeks post-weaning.

RESULTS

The deficient compared with adequate diet increased brain mRNA, protein and activity of iPLA(2) VIA and 15-lipoxygenase (LOX), but decreased cPLA(2) IVA and COX-2 expression. The brain protein level of the iPLA(2) transcription factor SREBP-1 was elevated, while protein levels were decreased for AP-2α and NF-κB p65, cPLA(2) and COX-2 transcription factors, respectively.

CONCLUSIONS

With dietary n-6 PUFA deprivation, rat brain PUFA metabolizing enzymes and some of their transcription factors change in a way that would homeostatically dampen reductions in brain n-6 PUFA concentrations and metabolism, while n-3 PUFA metabolizing enzyme expression is increased. The changes correspond to reported in vitro enzyme selectivities for AA compared with DHA.

cPLA2 is protective against COX inhibitor-induced intestinal damage

Cytosolic phospholipase A(2) (cPLA(2)) is the rate-limiting enzyme responsible for the generation of prostaglandins (PGs), which are bioactive lipids that play critical roles in maintaining gastrointestinal (GI) homeostasis. There has been a long-standing association between administration of cyclooxygenase (COX) inhibitors and GI toxicity. GI injury is thought to be induced by suppressed production of GI-protective PGs as well as direct injury to enterocytes. The present study sought to determine how pan-suppression of PG production via a genetic deletion of cPLA(2) impacts the susceptibility to COX inhibitor-induced GI injury. A panel of COX inhibitors including celecoxib, rofecoxib, sulindac, and aspirin were administered via diet to cPLA(2)(-/-) and cPLA(2)(+/+) littermates. Administration of celecoxib, rofecoxib, and sulindac, but not aspirin, resulted in acute lethality (within 2 weeks) in cPLA(2)(-/-) mice, but not in wild-type littermates. Histomorphological analysis revealed severe GI damage following celecoxib exposure associated with acute bacteremia and sepsis. Intestinal PG levels were reduced equivalently in both genotypes following celecoxib exposure, indicating that PG production was not likely responsible for the differential sensitivity. Gene expression profiling in the small intestines of mice identified drug-related changes among a panel of genes including those involved in mitochondrial function in cPLA(2)(-/-) mice. Further analysis of enterocytic mitochondria showed abnormal morphology as well as impaired ATP production in the intestines from celecoxib-exposed cPLA(2)(-/-) mice. Our data demonstrate that cPLA(2) appears to be an important component in conferring protection against COX inhibitor-induced enteropathy, which may be mediated through affects on enterocytic mitochondria.

Study of association between genetic polymorphisms of phospholipase A2 enzymes and Alzheimer's disease

Several genes have been related to late-onset Alzheimer's disease (LOAD). Phospholipases A2 (PLA2) influence the processing and secretion of the amyloid precursor protein, which gives rise to the beta-amyloid peptide, the major component of the amyloid plaque in AD. Hence, in the present study, polymorphisms of three genes encoding PLA2 enzymes group (cytosolic PLA2: BanI cPLA2 polymorphism; calcium-independent PLA2: AvrII iPLA2 polymorphism; PAFAH: Val279Phe PAFAH polymorphism) were analysed in a case-control sample using 58 patients with LOAD and 107 matched healthy controls. There was a genotypic association between the BanI cPLA2 polymorphism and LOAD (χ2=6.25, 2df, p=0.04), however there was no allelic association. There were no associations between AvrII iPLA2 and Val279Phe PAFAH polymorphisms and LOAD. These data suggest that the BanI cPLA2 polymorphism may play a role in the susceptibility for LOAD in our Brazilian sample.

Aryl hydrocarbon receptor-mediated induction of the cytosolic phospholipase A(2)alpha gene by 2,3,7,8-tetrachlorodibenzo-p-dioxin in mouse hepatoma Hepa-1c1c7 cells

Upon binding to ligands such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an aryl hydrocarbon receptor (AhR) is activated to form a heterodimer with an aryl hydrocarbon receptor nuclear translocator (Arnt). This complex binds to DNA. It has been shown that the AhR bonds to a DNA sequence called the dioxin response element (DRE), which controls the expression of battery genes. It is reported that TCDD releases arachidonic acid from membrane phospholipids via activation of phospholipase A(2)s (PLA(2)s) in various cell types. Recently, we demonstrated that the TCDD-activated AhR binds to the second intron of the Pla2g4a gene, which encodes cytosolic phospholipase A(2)alpha (cPLA(2)alpha), in mouse hepatoma Hepa-1c1c7 cells. This result suggests that Pla2g4a appears to be a target gene of the AhR. In the present study, we investigated whether the transcriptional regulation of Pla2g4a is dependent on the AhR in Hepa-1c1c7 cells. Treatment of the cells with TCDD increased mRNA expression of Pla2g4a and enzymatic activity of PLA(2,) while this increased expression was not observed in AhR-defective c12 cells. After transient transfection of an Ahr gene-expressing plasmid into the c12 cells, expression of Pla2g4a was increased by TCDD. These results indicate that Pla2g4a may be a novel target gene of the AhR, and its transcriptional induction is mediated through binding of the AhR to the second intron of Pla2g4a, although this target site does not have a typical DRE sequence.

Brain arachidonic acid cascade enzymes are upregulated in a rat model of unilateral Parkinson disease

Arachidonic acid (AA) signaling is upregulated in the caudate-putamen and frontal cortex of unilaterally 6-hydroxydopamine (6-OHDA) lesioned rats, a model for asymmetrical Parkinson disease. AA signaling can be coupled to D(2)-like receptor initiated AA hydrolysis from phospholipids by cytosolic phospholipase A(2) (cPLA(2)) and subsequent metabolism by cyclooxygenase (COX)-2. In unilaterally 6-OHDA- and sham-lesioned rats, we measured brain expression of cPLA(2), other PLA(2) enzymes, and COX-2. Activity and protein levels of cPLA(2) were significantly higher as was COX-2-protein in caudate-putamen, frontal cortex and remaining brain on the lesioned compared to intact side of the 6-OHDA lesioned rats, and compared to sham brain. Secretory sPLA(2) and Ca(2+)-independent iPLA(2) expression did not differ between sides or groups. Thus, the tonically increased ipsilateral AA signal in the lesioned rat corresponds to upregulated cPLA(2) and COX-2 expression within the AA metabolic cascade, which may contribute to symptoms and pathology in Parkinson disease.

Omega-3 Polyunsaturated Fatty Acids (n-3 PUFAs) in Cardiovascular Diseases (CVDs) and Depression: The Missing Link?

Background. Based on epidemiological data, clinical trials, and meta-analytic reviews, omega-3 polyunsaturated fatty acids (n-3 PUFAs) seem to be a biological link between depression and cardiovascular diseases (CVDs). Presentation. Involvement of n-3 PUFAs in depression and CVDs may be associated with a chronic, low-grade, inflammation. We hypothesize that n-3 PUFAs link depression and CVDs via “PUFA-prostaglandin E2 (PGE2) cascade.” Testing. To further support our hypothesis, case-control studies are needed to test the role of COX2 and PLA2 functions in depression and in CVDs. In addition, the effects of n-3 PUFAs on cardiovascular markers in depression and on depressive symptoms in CVDs should be investigated in clinical trials. Finally, the effects of manipulating COX2 and PLA2 functions on depression-like behaviors and cardiovascular functions could be explored in animal studies. Implications. n-3 PUFAs might be a promising treatment for both cardiovascular diseases and depression via its anti-inflammatory, cardioprotective, and neuroprotective effects.

Ceramide 1-phosphate is required for the translocation of group IVA cytosolic phospholipase A2 and prostaglandin synthesis

Little is known about the regulation of eicosanoid synthesis proximal to the activation of cytosolic phospholipase A(2)alpha (cPLA(2)alpha), the initial rate-limiting step. The current view is that cPLA(2)alpha associates with intracellular/phosphatidylcholine-rich membranes strictly via hydrophobic interactions in response to an increase of intracellular calcium. In opposition to this accepted mechanism of two decades, ceramide 1-phosphate (C1P) has been shown to increase the membrane association of cPLA(2)alpha in vitro via a novel site in the cationic beta-groove of the C2 domain (Stahelin, R. V., Subramanian, P., Vora, M., Cho, W., and Chalfant, C. E. (2007) J. Biol. Chem. 282, 20467-204741). In this study we demonstrate that C1P is a proximal and required bioactive lipid for the translocation of cPLA(2)alpha to intracellular membranes in response to inflammatory agonists (e.g. calcium ionophore and ATP). Last, the absolute requirement of the C1P/cPLA(2)alpha interaction was demonstrated for the production of eicosanoids using murine embryonic fibroblasts (cPLA(2)alpha(-/-)) coupled to "rescue" studies. Therefore, this study provides a paradigm shift in how cPLA(2)alpha is activated during inflammation.

Bipolar disorder and mechanisms of action of mood stabilizers

Bipolar disorder (BD) is a major medical and social burden, whose cause, pathophysiology and treatment are not agreed on. It is characterized by recurrent periods of mania and depression (Bipolar I) or of hypomania and depression (Bipolar II). Its inheritance is polygenic, with evidence of a neurotransmission imbalance and disease progression. Patients often take multiple agents concurrently, with incomplete therapeutic success, particularly with regard to depression. Suicide is common. Of the hypotheses regarding the action of mood stabilizers in BD, the "arachidonic acid (AA) cascade" hypothesis is presented in detail in this review. It is based on evidence that chronic administration of lithium, carbamazepine, sodium valproate, or lamotrigine to rats downregulated AA turnover in brain phospholipids, formation of prostaglandin E(2), and/or expression of AA cascade enzymes, including cytosolic phospholipase A(2), cyclooxygenase-2 and/or acyl-CoA synthetase. The changes were selective for AA, since brain docosahexaenoic or palmitic acid metabolism, when measured, was unaffected, and topiramate, ineffective in BD, did not modify the rat brain AA cascade. Downregulation of the cascade by the mood stabilizers corresponded to inhibition of AA neurotransmission via dopaminergic D(2)-like and glutamatergic NMDA receptors. Unlike the mood stabilizers, antidepressants that increase switching of bipolar depression to mania upregulated the rat brain AA cascade. These observations suggest that the brain AA cascade is a common target of mood stabilizers, and that bipolar symptoms, particularly mania, are associated with an upregulated cascade and excess AA signaling via D(2)-like and NMDA receptors. This review presents ways to test these suggestions.

Leukotriene pathway genetics and pharmacogenetics in allergy

Leukotrienes (LT) are biologically active lipid mediators known to be involved in allergic inflammation. Leukotrienes have been shown to mediate diverse features of allergic conditions including inflammatory cell chemotaxis/activation and smooth muscle contraction. Cysteinyl leukotrienes (LTC(4), LTD(4) and, LTE(4)) and the dihydroxy leukotriene LTB(4) are generated by a series of enzymes/proteins constituting the LT synthetic pathway or 5-lipoxygenase (5-LO) pathway. Their function is mediated by interacting with multiple receptors. Leukotriene receptor antagonists (LTRA) and LT synthesis inhibitors (LTSI) have shown clinical efficacy in asthma and more recently in allergic rhinitis. Despite growing knowledge of leukotriene biology, the molecular regulation of these inflammatory mediators remains to be fully understood. Genes encoding enzymes of the 5-LO pathway (i.e. ALOX5, LTC4S and LTA4H) and encoding for LT receptors (CYSLTR1/2 and LTB4R1/2) provide excellent candidates for disease susceptibility and severity; however, their role remains unclear. Preliminary data also suggest that 5-LO pathway/receptor gene polymorphism can predict patient responses to LTSI and LTRA; however, the exact mechanisms require elucidation. The aim of this review was to summarize the recent advances in the knowledge of these important mediators, focusing on genetic and pharmacogenetic aspects in the context of allergic phenotypes.

Inherited human cPLA(2alpha) deficiency is associated with impaired eicosanoid biosynthesis, small intestinal ulceration, and platelet dysfunction

Cytosolic phospholipase A2alpha (cPLA2alpha) hydrolyzes arachidonic acid from cellular membrane phospholipids, thereby providing enzymatic substrates for the synthesis of eicosanoids, such as prostaglandins and leukotrienes. Considerable understanding of cPLA2alpha function has been derived from investigations of the enzyme and from cPLA2alpha-null mice, but knowledge of discrete roles for this enzyme in humans is limited. We investigated a patient hypothesized to have an inherited prostanoid biosynthesis deficiency due to his multiple, complicated small intestinal ulcers despite no use of cyclooxygenase inhibitors. Levels of thromboxane B2 and 12-hydroxyeicosatetraenoic acid produced by platelets and leukotriene B4 released from calcium ionophore-activated blood were markedly reduced, indicating defective enzymatic release of the arachidonic acid substrate for the corresponding cyclooxygenase and lipoxygenases. Platelet aggregation and degranulation induced by adenosine diphosphate or collagen were diminished but were normal in response to arachidonic acid. Two heterozygous single base pair mutations and a known SNP were found in the coding regions of the patient's cPLA2alpha genes (p.[Ser111Pro]+[Arg485His; Lys651Arg]). The total PLA2 activity in sonicated platelets was diminished, and the urinary metabolites of prostacyclin, prostaglandin E2, prostaglandin D2, and thromboxane A2 were also reduced. These findings characterize what we believe is a novel inherited deficiency of cPLA2.

Association between BanI genotype and increased phospholipase A2 activity in schizophrenia

Phospholipases A2 (PLA2) are a family of key enzymes in the metabolism of membrane phospholipids. Several studies reported on increased blood and brain PLA2 activity in schizophrenia, which suggest a disordered phospholipid metabolism in the disease. In addition, a genetic variant of a cytosolic PLA2 gene has been reported to be associated with schizophrenia. These data indicate that variants of PLA2 encoding genes are plausible candidates for increasing the susceptibility for schizophrenia. In this study, we investigated a possible association between PLA2 activity in platelets and a polymorphic site for BanI in the PLA2 (group 4A) gene on chromosome 1q25. Seventy-five schizophrenic patients (DSM-IV) and 68 healthy controls were recruited and the PCR assays were performed. A radioenzymatic assay for the cytosolic PLA2 activity in platelets was used. The allele A2 and the genotype A2A2 were more frequent in schizophrenic patients than in controls (p<0.005 and p<0.05 respectively). When we assorted the subjects according to their genotypes, we found that PLA2 activity was significantly higher in patients with the A2A2 genotype (29.6+/-5.1 pMol/mg protein/min) than in those with the A1A2 (20.8+/-3.6 pMol/mg protein/min, p<0.001) or A1A1 genotype (15.9+/-5.1 pMol/mg protein/min, p<0.001). Also in controls, carriers of the A2 allele (A1A2 and A2A2) had higher PLA2 activity than the A1A1 group (p=0.004 for both). Our data suggest an association between BanI genotype and PLA2G4A activity in platelets and that the presence of the allele A2 may increase risk for schizophrenia through an increment of PLA2 activity.

Flurbiprofen, A Cyclooxygenase Inhibitor, Reduces the Brain Arachidonic Acid Signal in Response to the Cholinergic Muscarinic Agonist, Arecoline, in Awake Rats

Cholinergic muscarinic receptors, when stimulated by arecoline, can activate cytosolic phospholipase A(2) (cPLA(2)) to release arachidonic acid (AA) from membrane phospholipid. This signal can be imaged in the brain in vivo using quantitative autoradiography following the intravenous injection of radiolabeled AA, as an increment in a regional brain AA incorporation coefficient k*. Arecoline increases k* significantly in brain regions having muscarinic M(1,3,5) receptors in wild-type but not in cyclooxygenase (COX)-2 knockout mice. To further clarify the roles of COX enzymes in the AA signal, in this paper we imaged k* following arecoline (5 mg/kg i.p.) or saline in each of 81 brain regions of unanesthetized rats pretreated 6 h earlier with the non-selective COX inhibitor flurbiprofen (FB, 60 mg/kg s.c.) or with vehicle. Baseline values of k* were unaffected by FB treatment, which however reduced by 80% baseline brain concentrations of prostaglandin E(2) (PGE(2)) and thromboxane B(2) (TXB(2)), eicosanoids preferentially derived from AA via COX-2 and COX-1, respectively. In vehicle-pretreated rats, arecoline increased the brain PGE(2) but not TXB(2) concentration, as well as values for k* in 77 of the 81 brain regions. FB-pretreatment prevented these arecoline-provoked changes. These results and those reported in COX-2 knockout mice suggest that the AA released in brain following muscarinic receptor-mediated activation is lost via COX-2 to PGE(2) but not via COX-1 to TXB(2), and that increments in k* following arecoline largely represent replacement by unesterified plasma AA of this loss.

Survival signalling in Alzheimer's disease

Significant advancements in our understanding of cell-survival signalling in AD (Alzheimer's disease) stem from recent investigations into the metabolism, trafficking and fate of the essential omega-3 fatty acid DHA (docosahexaenoic acid) (C(22:6), n=3). Brain synaptic terminals and neuronal plasma membranes are highly enriched in DHA, and deficiencies in this polyunsaturated fatty acid are characteristic of AD-affected brain. Oxidative stress, targeting phospholipids containing DHA, and age-related DHA depletion are associated with the progressive erosion of normal cognitive function in AD. Current studies support the idea that DHA itself and novel DHA-derived neural synapse- and membrane-derived lipid messengers have considerable potential to modulate cell survival signalling in stressed cultured neural cell models in vitro and in mammalian models of learning, memory and AD in vivo. Key players in this intrinsic rescue system include the alpha-secretase-processed neurotrophin sAPPalpha [soluble APPalpha (amyloid precursor protein alpha)] peptide, the DHA-derived 10,17S-docosatriene NPD1 (neuroprotectin D1), a tandem brain cytosolic phospholipase A(2) and 15-lipoxygenase enzymatic system that biosynthesizes NPD1, and a small family of anti-apoptotic neuroprotective genes that encode Bcl-2, Bcl-X(L) and Bfl-1 (A1). This paper reviews current ideas regarding DHA and the oxygenated DHA derivative NPD1, intrinsically triggered biolipid neuroprotectants that along with their associated rescue pathways, contribute to life-or-death decisions of brain cells during homoeostasis, aging and neurodegenerative disease.

Ex vivo analysis of antineoplastic agents in precision-cut tissue slices of human origin: effects of cyclooxygenase-2 inhibition in hepatocellular carcinoma

Cultures of precision-cut tissue slices allow the investigation of substance effects on human tissues under in vivo-like conditions over a limited time span. We have adapted the model for direct analyses of antineoplastic substances on tumor tissues. We have recently demonstrated that selective cyclooxygenase-2 (COX-2) inhibitors strongly suppress growth of human hepatocellular carcinoma (HCC) cells in vitro and nude mouse HCC implants by inducing apoptosis and reducing proliferation. We have now analyzed the effects of COX-2 inhibition on human tumor tissue. Three hundred micrometer slices of tumorous and non-tumorous liver tissue from three surgically resected HCCs were cultured with increasing concentrations of the selective COX-2 inhibitor Meloxicam (20-200 microM) for 6, 12, 24, and 48 h. The cultured tissue slices were analysed morphologically and by immunohistology for proliferation (Ki-67), apoptosis (M30), and COX-2 expression. COX-2 was expressed in all HCCs and in the non-tumorous liver tissue. Cytoplasmic COX-2 immunoreactivity in HCCs increased during culturing time. In two of three cases, COX-2 inhibition significantly increased tumor cell apoptosis in HCCs, whereas the low basal apoptosis rate in the non-tumorous liver parenchyma did not change. Tumor cell proliferation was mildly reduced, but the changes did not reach statistical significance. These results demonstrate that the precision-cut tissue slice culture model is a useful tool to analyze directly drug-dependent antitumorous or unwanted organ-specific effects. The analysis of COX-2 inhibition lends further support to the antineoplastic effects previously demonstrated in vitro and in animal models.

Hypoxia-sensitive domain in the human cytosolic phospholipase A2 promoter

Transcription from the human cytosolic phospholipase A2 gene has been observed to be hypoxia sensitive in endothelial cells cultured from the human cerebral microvasculature. DNA sequence analysis of the cytosolic phospholipase A2 promoter revealed the presence of a distal cluster of potential hypoxia-inducible factor-1-DNA binding sites homologous to 5'-NCGTG-3', located between -1087 and -996 bp of the major start of transcription at +1 bp (Genbank U08374). Gel shift assay showed strong hypoxia-inducible factor-1-DNA binding to only a single site within this cluster, and promoter deletion analysis indicated the functional importance of this chromatin domain in conveying oxygen sensitivity to cytosolic phospholipase A2 gene transcription. Non-functional hypoxia inducible factor-1-DNA binding sites flanking a single functional hypoxia-inducible factor-1-DNA binding site in this hypoxia-sensitive domain may promote oxygen sensitivity via transcription factor clustering or Circe effects.

Resting and arecoline-stimulated brain metabolism and signaling involving arachidonic acid are altered in the cyclooxygenase-2 knockout mouse

Abstract Studies were performed to determine if cyclooxygenase (COX)-2 regulates muscarinic receptor-initiated signaling involving brain phospholipase A2 (PLA2) activation and arachidonic acid (AA; 20 : 4n-6) release. AA incorporation coefficients, k* (brain [1-14C]AA radioactivity/integrated plasma radioactivity), representing this signaling, were measured following the intravenous injection of [1-14C]AA using quantitative autoradiography, in each of 81 brain regions in unanesthetized COX-2 knockout (COX-2(-/-)) and wild-type (COX-2(+/+)) mice. Mice were administered arecoline (30 mg/kg i.p.), a non-specific muscarinic receptor agonist, or saline i.p. (baseline control). At baseline, COX-2(-/-) compared with COX-2(+/+) mice had widespread and significant elevations of k*. Arecoline increased k* significantly in COX-2(+/+) mice compared with saline controls in 72 of 81 brain regions, but had no significant effect on k* in any region in COX-2(-/-) mice. These findings, when related to net incorporation rates of AA from brain into plasma, demonstrate enhanced baseline brain metabolic loss of AA in COX-2(-/-) compared with COX-2(+/+) mice, and an absence of a normal k* response to muscarinic receptor activation. This response likely reflects selective COX-2-mediated conversion of PLA2-released AA to prostanoids.

Ceramide 1-Phosphate Acts as a Positive Allosteric Activator of Group IVA Cytosolic Phospholipase A2α and Enhances the Interaction of the Enzyme with Phosphatidylcholine

Previous findings from our laboratory have demonstrated that cPLA(2)alpha is directly activated by the emerging bioactive sphingolipid, ceramide 1-phosphate (C-1-P) (1). In this study, a Triton X-100/phosphatidylcholine (PC) mixed micelle assay was utilized to determine the kinetics and specificity of this lipid-enzyme interaction. Using this assay, the addition of C-1-P induced a dramatic increase in the activity of cPLA(2)alpha (>15-fold) with a K(a) of 2.4 mol % C-1-P/Triton X-100 micelle. This activation was highly specific as the addition of other lipids had insignificant effects on cPLA(2)alpha activity. Studies using surface-dilution kinetics revealed that C-1-P had no effect on the Michaelis-Menten constant, K(m)(B), but decreased the dissociation constant (K (A)(s)) value by 87%. Thus, C-1-P not only increases the membrane affinity of cPLA(2)alpha but also may act as an allosteric activator of the enzyme. Surface plasmon resonance analysis of the C-1-P/cPLA(2)alpha interaction verified a decrease in the dissociation constant, demonstrating that cPLA(2)alpha bound PC vesicles containing C-1-P with increased affinity (5-fold) compared with PC vesicles alone. The effect on the dissociation rate of cPLA(2)alpha was also found to be lipid-specific with the exception of phosphatidylinositol 4,5-bisphosphate, which caused a modest increase in vesicle affinity (2-fold). Lastly, the binding site for C-1-P was determined to be within the C2-domain of cPLA(2)alpha, unlike phosphatidylinositol 4,5-bisphosphate. These data demonstrate a novel interaction site for C-1-P and suggest that C-1-P may function to recruit cPLA(2)alpha to intracellular membranes as well as allosterically activate the membrane-associated enzyme.

Genetic association between the phospholipase A2 gene and unipolar affective disorder: a multicentre case-control study

The co-segregation in one pedigree of bipolar affective disorder with Darier's disease whose gene is on chromosome 12q23-q24.1, and findings from linkage and association studies with the neighbouring gene of phospholipase A2 (PLA2) indicate that PLA2 may be considered as a candidate gene for affective disorders. All relevant genetic association studies, however, were conducted on bipolar patients. In the present study, the possible association between the PLA2 gene and unipolar affective disorder was examined on 321 unipolar patients and 604 controls (all personally interviewed), recruited from six countries (Belgium, Bulgaria, Croatia, Germany, Greece, and Italy) participating in the European Collaborative Project on Affective Disorders. After controlling for population group and gender, one of the eight alleles of the investigated marker (allele 7) was found to be more frequent among unipolar patients with more than three major depressive episodes than among controls (P<0.01); genotypic association was also observed, under the dominant model of genetic transmission (P<0.02). In addition, presence of allele 7 was correlated with a higher frequency of depressive episodes (P<0.02). These findings suggest that structural variations at the PLA2 gene or the chromosomal region around it may confer susceptibility for unipolar affective disorder.

The role of TFIID, the initiator element and a novel 5' TFIID binding site in the transcriptional control of the TATA-less human cytosolic phospholipase A2-alpha promoter

Human cytosolic phospholipase A2-alpha (cPLA2-alpha) is a critical enzyme in the liberation of arachidonic acid (AA) from cellular membranes and the subsequent formation of prostaglandins (PGs), leukotrienes (LTs), hydroxyeicosatetraenoic acids (HETEs) and platelet activating factor in many different cell types. Much is known of the effect of posttranslational phosphorylation and calcium binding events on the enzymatic activity of cPLA2-alpha, but to date little is known about its specific transcriptional control. Through the use of reporter gene constructs and eletrophoretic mobility shift assays (EMSAs), this study determined the minimal promoter required for basal transcriptional activity of the human cPLA2-alpha promoter to include base pairs -40 through the transcription start site (TSS). In addition, it confirms the importance of an initiator (Inr) element at the TSS by deletion reporter gene analysis, and further identifies bases -3 (C) and -2 (T) as critical bases in the Inr function by mutation reporter gene analysis. Finally, this study describes a novel AAGGAG motif at -30 to -35 which is bound by TATA-box binding protein (TBP) and is critical for basal transcriptional activity.

A pathway involving protein kinase Cδ up-regulates cytosolic phospholipase A2α in airway epithelium

Cytosolic phospholipase A(2)alpha (cPLA(2)alpha) catalyzes the hydrolysis of glycerophospholipids at the sn-2 position to liberate fatty acids. Although cPLA(2)alpha has been implicated in various cellular processes, the detailed mechanism of its expression remains to be elucidated. Here we report that phorbol 12-myristate 13-acetate (PMA) up-regulates cPLA(2)alpha in A549 airway epithelium cells, and that this effect is sensitive to rottlerin, a potent inhibitor of protein kinase Cdelta (PKCdelta). Consistent with this observation, a dominant negative mutant of PKCdelta reduced cPLA(2)alpha induction in response to PMA. Up-regulation of cPLA(2)alpha by PMA was also inhibited by PDTC, an inhibitor of nuclear factor-kappa B (NF-kappaB), and degradation of IkappaB and subsequent activation of NF-kappaB occurred in response to PMA treatment. These findings indicate that PMA induces expression of cPLA(2)alpha at the transcriptional level via an NF-kappaB-dependent mechanism. In addition, activation of the NF-kappaB promoter by PMA was diminished by pretreatment with DPI, a flavoenzyme inhibitor as well as by rottlerin, suggesting a role for reactive oxygen species (ROS) as well as PKCdelta. Consistent with this, PMA stimulated the production of ROS and this was blocked by inhibiting PKCdelta. Our results suggest that PKCdelta and ROS lie upstream of NF-kappaB, and we conclude that a PKCdelta-ROS-NF-kappaB cascade plays a pivotal role in cPLA(2)alpha induction by PMA.

BanI polymorphism of the cytosolic phospholipase A2 gene and mood disorders in the Korean population

Membrane phospholipid abnormalities have been proposed to be involved in the pathogenesis of mood disorders, and in signal transduction and neurotransmitter uptake. Cytosolic phospholipase A2 (cPLA2) is not only an essential enzyme in the metabolism of fatty acids but also in signaling process. Therefore, we examined the association between the BanI polymorphism of the cPLA2 gene and mood disorders. Sixty-two patients with major depressive disorder (MDD), 50 patients with bipolar I disorder (BID) and 117 healthy controls participated in this study. Genotyping was performed by using PCR-based methods. Genotype and allele distributions in MDD patients were significantly different from those of the controls. In particular, the A2 allele was associated with increased risk of MDD development (p = 0.007, odds ratio = 1.827; confidence interval = 1.141-2.927). However, the polymorphism was not different between BID patients and controls in genotype and allele distribution. This preliminary study indicates the need for further studies on the potential role of the cPLA2 gene polymorphism in the susceptibility to mood disorders.

BanI polymorphism of the cytosolic phospholipase A2 gene may confer susceptibility to the development of schizophrenia

Membrane phospholipid abnormalities have been proposed to be involved in the pathogenesis of schizophrenia. Cytosolic phospholipase A2 (cPLA2) plays a major role in the metabolism of fatty acids but is also found in abnormalities in patients with schizophrenia. This study examined the association between the cPLA2 gene BanI polymorphism and schizophrenia. Ninety-seven Korean schizophrenia patients and 117 healthy controls participated in this study. Genotyping was performed by using polymerase chain reaction (PCR)-based methods. Genotype and allele distributions were significantly different between the schizophrenia patients and controls. In particular, the A2 allele was associated with an increased risk of schizophrenia (p = 0.003; odds ratio (OR) = 1.799; confidence interval (CI) = 1.192-2.716). However, the polymorphism was not different when the patient group was subdivided by the presence or absence of family history and by positive and negative subgroups according to the positive and negative syndrome scale (PANSS) score on schizophrenia. The results of this study replicated those of previous findings from Western countries and indicates the need for further studies on the potential role of the cPLA2 gene polymorphism in the susceptibility to schizophrenia.

Phospholipase A2 isozymes in pregnancy and parturition

Mammalian cells contain several structurally different phospholipase (PLA2) enzymes that exhibit distinct localisation, function and mechanisms of regulation. PLA2 isozymes have been postulated to play significant roles in the parturition process. Both secretory and cytosolic PLA2 isozymes have been identified in human gestational tissues, and there is differential expression of these PLA2 isozymes in human fetal membranes and placenta obtained at preterm and term. The aims of this commentary are: (1) to review recent data concerning the expression, role and regulation of PLA2 isozymes in human gestational tissues; and (2) to present novel data demonstrating the regulation of PLA2 isozymes in human gestational tissues by nuclear factor-kappa B (NF-kappaB) and peroxisome proliferator-activated receptor (PPAR)-g.

Celecoxib: a potent cyclooxygenase-2 inhibitor in cancer prevention

Non-steroidal anti-inflammatory drugs (NSAIDs) are the most widely used therapeutic agents in the treatment of pain, inflammation and fever. They may also have a role in the management of cancer prevention, Alzheimer's disease and prophylaxis against cardiovascular disease. These drugs act primarily by inhibiting cyclooxygenase enzyme, which has two isoforms, cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). Selective COX-2 inhibitors provide potent anti-inflammatory and analgesic effects without the side effects of gastric and renal toxicity and inhibition of platelet function. Celecoxib is a potent COX-2 inhibitor being developed for the treatment of rheumatoid arthritis and osteoarthritis. Chemoprevention is the use of pharmacological or natural agents to prevent, suppress, interrupt or reverse the process of carcinogenesis. For this purpose, celecoxib is being used for different cancer types. The effects of NSAIDs on tumor growth remain unclear, but are most likely to be multifocal. In this article, we reviewed COX-2 selectivity, the pharmacological properties of celecoxib, the use of celecoxib for cancer prevention and the mechanisms of chemoprevention.

Ceramide 1-phosphate is a direct activator of cytosolic phospholipase A2

Recently, we demonstrated that ceramide kinase, and its product, ceramide 1-phosphate (Cer-1-P), were mediators of arachidonic acid released in cells in response to interleukin-1beta and calcium ionophore (Pettus, B. J., Bielawska, A., Spiegel, S., Roddy, P., Hannun, Y. A., and Chalfant, C. E. (2003) J. Biol. Chem. 278, 38206-38213). In this study, we demonstrate that down-regulation of cytosolic phospholipase A(2) (cPLA(2)) using RNA interference technology abolished the ability of Cer-1-P to induce arachidonic acid release in A549 cells, demonstrating that cPLA(2) is the key phospholipase A(2) downstream of Cer-1-P. Treatment of A549 cells with Cer-1-P (2.5 microm) induced the translocation of full-length cPLA(2) from the cytosol to the Golgi apparatus/perinuclear regions, which are known sites of translocation in response to agonists. Cer-1-P also induced the translocation of the CaLB/C2 domain of cPLA(2) in the same manner, suggesting that this domain is responsive to Cer-1-P either directly or indirectly. In vitro studies were then conducted to distinguish these two possibilities. In vitro binding studies disclosed that Cer-1-P interacts directly with full-length cPLA(2) and with the CaLB domain in a calcium- and lipid-specific manner with a K(Ca) of 1.54 microm. Furthermore, Cer-1-P induced a calcium-dependent increase in cPLA(2) enzymatic activity as well as lowering the EC(50) of calcium for the enzyme from 191 to 31 nm. This study identifies Cer-1-P as an anionic lipid that translocates and directly activates cPLA(2), demonstrating a role for this bioactive lipid in the mediation of inflammatory responses.

Ceramide kinase mediates cytokine- and calcium ionophore-induced arachidonic acid release

Despite the importance of prostaglandins, little is known about the regulation of prostanoid synthesis proximal to the activation of cytosolic phospholipase A2, the initial rate-limiting step. In this study, ceramide-1-phosphate (C-1-P) was shown to be a specific and potent inducer of arachidonic acid (AA) and prostanoid synthesis in cells. This study also demonstrates that two well established activators of AA release and prostanoid synthesis, the cytokine, interleukin-1beta (IL-1beta), and the calcium ionophore, A23187, induce an increase in C-1-P levels within the relevant time-frame of AA release. Furthermore, the enzyme responsible for the production of C-1-P in mammalian cells, ceramide kinase, was activated in response to IL-1beta and A23187. RNA interference targeted to ceramide kinase specifically down-regulated ceramide kinase mRNA and activity with a concomitant decrease of AA release in response to IL-1beta and A23187. Down-regulation of ceramide kinase had no effect on AA release induced by exogenous C-1-P. Collectively, these results indicate that ceramide kinase, via the formation of C-1-P, is an upstream modulator of phospholipase A2 activation. This study identifies previously unknown roles for ceramide kinase and its product, C-1-P, in AA release and production of eicosanoids and provides clues for potential new targets to block inflammatory responses.

In vivo approaches to quantifying and imaging brain arachidonic and docosahexaenoic acid metabolism

A novel in vivo fatty acid method has been developed to quantify and image brain metabolism of nutritionally essential polyunsaturated fatty acids (PUFAs). In unanesthetized rodents, a radiolabeled PUFA is injected intravenously, and its rate of incorporation into brain phospholipids is determined by chemical analysis or quantitative autoradiography. Results indicate that about 5% of brain arachidonic acid (20:4 n-6) and of docosahexaenoic acid (22:6 n-3) acid are lost daily by metabolism and are replaced from dietary sources through the plasma. Calculated turnover rates of PUFAs in brain phospholipids, due to deesterification by phospholipase A(2) (PLA(2)) followed by reesterification, are very rapid, consistent with active roles of PUFAs in signal transduction and other processes. Turnover rates of arachidonate and docosahexaenoate are independent of each other and probably are regulated by independent sets of enzymes. Brain incorporation of radiolabeled arachidonate can be imaged in response to drugs that bind to receptors coupled to PLA(2) through G proteins, thus measuring PLA(2)-initiated signal transduction. The in vivo fatty method is being extended for human studies using positron emission tomography.

Co-localization of cytosolic phospholipase A2 and cyclooxygenase-2 in Rhesus monkey cerebellum

Cytosolic phospholipase A2 (cPLA2), cyclooxygenase (COX)-1 and COX-2 play important and integrated roles in the release and subsequent metabolism of arachidonic acid, an important second messenger, in brain and other tissues. Antibodies to each of these enzymes were used to examine their cellular localization and expression in the cerebellum of the adult macaque, using Western blotting and immunohistochemical methods. COX-2 and cPLA2 immunoreactivities co-localized on the plasma membrane of Purkinje cells, and within punctate intracellular regions. In contrast, COX-1 immunoreactivity was relatively uniform in Purkinje cell cytoplasm, and was more homogeneous in cells of the granular cell layer and occasionally of the molecular layer. COX-1 immunoreactivity was not found on the cell surface. Labeling of Purkinje cell dendrites was not marked for any of the enzymes. cPLA2 and COX-2 have been shown to be functionally coupled in a number of cell systems, and in brain following lithium chloride administration to rats. The co-localization of cPLA2 and COX-2 is consistent with evidence of their functional coupling at brain synapses, and of the presence of an unesterified brain arachidonate pool released by cPLA2 which is the precursor for prostaglandin formation via COX-2.

The study of cytosolic phospholipase A2 gene polymorphism in schizophrenia using eye movement disturbances as an endophenotypic marker

Phospholipase A(2) (PLA2) is a key enzyme of the phospholipid metabolism which shows alteration in schizophrenia. Eye movement disturbances occur in a majority of patients with schizophrenia and in a proportion of their first-degree relatives, and they have been suggested as an endophenotypic marker in genetic studies of this illness. Here we report an association between the BAN I polymorphism of the cytosolic PLA2 gene (single nucleotide polymorphism in the first intron of the gene) and the intensity of eye movement disturbances (fixation and smooth pursuit) observed in 126 schizophrenic patients. The mean intensity of both kinds of eye movement disturbances was significantly higher in individuals homozygous for the A2 genotype compared with the remaining phenotypes. There was also a trend for greater A2 allele frequency in schizophrenic patients with a higher degree of eye movement disturbances. The relative frequency of the A2/A2 genotype was higher in patients with a greater degree of eye movement disturbances occurring during both fixation and smooth pursuit tests. Our results correspond to the other studies showing an association between the cPLA2 polymorphism and schizophrenia (predominance of the A2 allele in schizophrenic subjects).

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.

Proapoptotic and antiproliferative potential of selective cyclooxygenase-2 inhibitors in human liver tumor cells

Recent studies have shown increased levels of cyclooxygenase-2 (COX-2) in a variety of human malignancies, including hepatocellular carcinoma (HCC), but so far it is unknown whether COX-2 contributes to the malignant growth and whether inhibition of COX-2 function modifies the malignant potential of liver tumors. COX-1 and COX-2 expression was determined in 4 liver tumor cell lines (Hep 3B, HuH-7, Hep G2, Sk-hep1) by Northern hybridization and Western immunoblot. The functional effects of the nonselective inhibitor sulindac sulfide and the COX-2 selective inhibitors SC-58635 and meloxicam were examined by 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazoliumbromide (MTT)-assays and BrdU uptake, morphology, and TUNEL analysis of apoptosis. Apoptosis regulating proteins were analyzed by Western immunoblot. COX-1 and COX-2 expression was demonstrable in all tested liver tumor cell lines. Sulindac sulfide (50 to 400 micromol/L), SC-58635 (6,25 to 400 micromol/L), and meloxicam (6.25 to 400 micromol/L) led to a significant time- and dose-dependent reduction of cell numbers of up to 80% (P <.05). At equimolar concentrations the effect was more pronounced when COX-2 was selectively blocked. COX-2 inhibition induced apoptosis and reduced tumor cell proliferation. Apoptosis after COX-2 inhibition with SC-58635 (50 micromol/L) was independent of BCL-2, BAX, and the phosphorylation status of AKT/PKB and BAD, but correlated with activation of caspase-9, caspase-3, and caspase-6. In conclusion, selective inhibition of COX-2 leads to a marked growth inhibition of human liver tumor cells, based on the induction of apoptosis and inhibition of proliferation and, thus, may offer therapeutic and preventive potential in human hepatocarcinogenesis.

Association studies of cytosolic phospholipase A2 polymorphisms and schizophrenia among two independent family-based samples

An association between the cytosolic phospholipase A2 locus (cPLA2) and schizophrenia has been reported using two polymorphic DNA markers. In an attempt to replicate these results, two independent family-based samples were ascertained from the United States and India (86 and 159 families, respectively). No significant associations were detected in either sample.