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Cheon Y, Kim HW, Igarashi M, Modi HR, Chang L, Ma K, Greenstein D, Wohltmann M, Turk J, Rapoport SI, Taha AY. Disturbed brain phospholipid and docosahexaenoic acid metabolism in calcium-independent phospholipase A(2)-VIA (iPLA(2)β)-knockout mice. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1821:1278-86. [PMID: 22349267 PMCID: PMC3393806 DOI: 10.1016/j.bbalip.2012.02.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 01/25/2012] [Accepted: 02/03/2012] [Indexed: 10/14/2022]
Abstract
Calcium-independent phospholipase A(2) group VIA (iPLA(2)β) releases docosahexaenoic acid (DHA) from phospholipids in vitro. Mutations in the iPLA(2)β gene, PLA2G6, are associated with dystonia-parkinsonism and infantile neuroaxonal dystrophy. To understand the role of iPLA(2)β in brain, we applied our in vivo kinetic method using radiolabeled DHA in 4 to 5-month-old wild type (iPLA(2)β(+/+)) and knockout (iPLA(2)β(-/-)) mice, and measured brain DHA kinetics, lipid concentrations, and expression of PLA(2), cyclooxygenase (COX), and lipoxygenase (LOX) enzymes. Compared to iPLA(2)β(+/+) mice, iPLA(2)β(-/-) mice showed decreased rates of incorporation of unesterified DHA from plasma into brain phospholipids, reduced concentrations of several fatty acids (including DHA) esterified in ethanolamine- and serine-glycerophospholipids, and increased lysophospholipid fatty acid concentrations. DHA turnover in brain phospholipids did not differ between genotypes. In iPLA(2)β(-/-) mice, brain levels of iPLA(2)β mRNA, protein, and activity were decreased, as was the iPLA(2)γ (Group VIB PLA(2)) mRNA level, while levels of secretory sPLA(2)-V mRNA, protein, and activity and cytosolic cPLA(2)-IVA mRNA were increased. Levels of COX-1 protein were decreased in brain, while COX-2 protein and mRNA were increased. Levels of 5-, 12-, and 15-LOX proteins did not differ significantly between genotypes. Thus, a genetic iPLA(2)β deficiency in mice is associated with reduced DHA metabolism, profound changes in lipid-metabolizing enzyme expression (demonstrating lack of redundancy) and of phospholipid fatty acid content of brain (particularly of DHA), which may be relevant to neurologic abnormalities in humans with PLA2G6 mutations.
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Affiliation(s)
- Yewon Cheon
- National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA.
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Ramadan E, Basselin M, Rao JS, Chang L, Chen M, Ma K, Rapoport SI. Lamotrigine blocks NMDA receptor-initiated arachidonic acid signalling in rat brain: implications for its efficacy in bipolar disorder. Int J Neuropsychopharmacol 2012; 15:931-43. [PMID: 21733229 PMCID: PMC3204186 DOI: 10.1017/s1461145711001003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
An up-regulated brain arachidonic acid (AA) cascade and a hyperglutamatergic state characterize bipolar disorder (BD). Lamotrigine (LTG), a mood stabilizer approved for treating BD, is reported to interfere with glutamatergic neurotransmission involving N-methyl-d-aspartate receptors (NMDARs). NMDARs allow extracellular calcium into the cell, thereby stimulating calcium-dependent cytosolic phospholipase A2 (cPLA2) to release AA from membrane phospholipid. We hypothesized that LTG, like other approved mood stabilizers, would reduce NMDAR-mediated AA signalling in rat brain. An acute subconvulsant dose of NMDA (25 mg/kg) or saline was administered intraperitoneally to unanaesthetized rats that had been treated p.o. daily for 42 d with vehicle or a therapeutically relevant dose of LTG (10 mg/kg.d). Regional brain AA incorporation coefficients k* and rates J in, and AA signals, were measured using quantitative autoradiography after intravenous [1-14C]AA infusion, as were other AA cascade markers. In chronic vehicle-treated rats, acute NMDA compared to saline increased k* and J in in widespread regions of the brain, as well as prostaglandin (PG)E2 and thromboxane B2 concentrations. Chronic LTG treatment compared to vehicle reduced brain cyclooxygenase (COX) activity, PGE2 concentration, and DNA-binding activity of the COX-2 transcription factor, NF-κB. Pretreatment with chronic LTG blocked the acute NMDA effects on AA cascade markers. In summary, chronic LTG like other mood stabilizers blocks NMDA-mediated signalling involving the AA metabolic cascade. Since markers of the AA cascade and of NMDAR signalling are up-regulated in the post-mortem BD brain, mood stabilizers generally may be effective in BD by dampening NMDAR signalling and the AA cascade.
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Affiliation(s)
- Epolia Ramadan
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA.
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Ramadan E, Chang L, Chen M, Ma K, Hall FS, Uhl GR, Rapoport SI, Basselin M. Knocking out the dopamine reuptake transporter (DAT) does not change the baseline brain arachidonic acid signal in the mouse. Int J Neurosci 2012; 122:373-80. [PMID: 22376027 PMCID: PMC3464054 DOI: 10.3109/00207454.2012.665972] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND Dopamine transporter (DAT) homozygous knockout (DAT(-/-)) mice have a 10-fold higher extracellular (DA) concentration in the caudate-putamen and nucleus accumbens than do wildtype (DAT(+/+)) mice, but show reduced presynaptic DA synthesis and fewer postsynaptic D(2) receptors. One aspect of neurotransmission involves DA binding to postsynaptic D(2)-like receptors coupled to cytosolic phospholipase A(2) (cPLA(2)), which releases the second messenger, arachidonic acid (AA), from synaptic membrane phospholipid. We hypothesized that tonic overactivation of D(2)-like receptors in DAT(-/-) mice due to the excess DA would not increase brain AA signaling, because of compensatory downregulation of postsynaptic DA signaling mechanisms. METHODS [1-(14)C]AA was infused intravenously for 3 min in unanesthetized DAT(+/+), heterozygous (DAT(+/-)), and DAT(-/-) mice. AA incorporation coefficients k* and rates J(in), markers of AA metabolism and signaling, were imaged in 83 brain regions using quantitative autoradiography; brain cPLA(2)-IV activity also was measured. RESULTS Neither k* nor J(in) for AA in any brain region, or brain cPLA(2)-IV activity, differed significantly among DAT(-/-), DAT(+/-), and DAT(+/+) mice. CONCLUSIONS These results differ from reported increases in k* and J(in) for AA, and in brain cPLA(2) expression, in serotonin reuptake transporter (5-HTT) knockout mice, and suggest that postsynaptic dopaminergic neurotransmission mechanisms involving AA are downregulated despite elevated DA in DAT(-/-) mice.
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Affiliation(s)
- Epolia Ramadan
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA.
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Basselin M, Ramadan E, Rapoport SI. Imaging brain signal transduction and metabolism via arachidonic and docosahexaenoic acid in animals and humans. Brain Res Bull 2012; 87:154-71. [PMID: 22178644 PMCID: PMC3274571 DOI: 10.1016/j.brainresbull.2011.12.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 12/01/2011] [Accepted: 12/02/2011] [Indexed: 02/05/2023]
Abstract
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.
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Affiliation(s)
- Mireille Basselin
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA
| | - Epolia Ramadan
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA
| | - Stanley I. Rapoport
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA
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Ramadan E, Basselin M, Taha AY, Cheon Y, Chang L, Chen M, Rapoport SI. Chronic valproate treatment blocks D2-like receptor-mediated brain signaling via arachidonic acid in rats. Neuropharmacology 2011; 61:1256-64. [PMID: 21839100 PMCID: PMC3190603 DOI: 10.1016/j.neuropharm.2011.07.025] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 07/12/2011] [Accepted: 07/17/2011] [Indexed: 02/06/2023]
Abstract
BACKGROUND AND OBJECTIVE Hyperdopaminergic signaling and an upregulated brain arachidonic acid (AA) cascade may contribute to bipolar disorder (BD). Lithium and carbamazepine, FDA-approved for the treatment of BD, attenuate brain dopaminergic D(2)-like (D(2), D(3), and D(4)) receptor signaling involving AA when given chronically to awake rats. We hypothesized that valproate (VPA), with mood-stabilizing properties, would also reduce D(2)-like-mediated signaling via AA. METHODS An acute dose of quinpirole (1 mg/kg) or saline was administered to unanesthetized rats that had been treated for 30 days with a therapeutically relevant dose of VPA (200 mg/kg/day) or vehicle. Regional brain AA incorporation coefficients, k*, and incorporation rates, J(in), markers of AA signaling and metabolism, were measured by quantitative autoradiography after intravenous [1-(14)C]AA infusion. Whole brain concentrations of prostaglandin (PG)E(2) and thromboxane (TX)B(2) also were measured. RESULTS Quinpirole compared to saline significantly increased k* in 40 of 83 brain regions, and increased brain concentrations of PGE(2) in chronic vehicle-treated rats. VPA treatment by itself reduced concentrations of plasma unesterified AA and whole brain PGE(2) and TXB(2), and blocked the quinpirole-induced increments in k* and PGE(2). CONCLUSION These results further provide evidence that mood stabilizers downregulate brain dopaminergic D(2)-like receptor signaling involving AA.
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Affiliation(s)
- Epolia Ramadan
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA.
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Shichiri M, Yoshida Y, Ishida N, Hagihara Y, Iwahashi H, Tamai H, Niki E. α-Tocopherol suppresses lipid peroxidation and behavioral and cognitive impairments in the Ts65Dn mouse model of Down syndrome. Free Radic Biol Med 2011; 50:1801-11. [PMID: 21447382 DOI: 10.1016/j.freeradbiomed.2011.03.023] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2010] [Revised: 03/11/2011] [Accepted: 03/22/2011] [Indexed: 10/18/2022]
Abstract
It is widely accepted that oxidative stress is involved in the pathogenesis of Down syndrome, but the effectiveness of antioxidant treatment remains inconclusive. We tested whether chronic administration of α-tocopherol ameliorates the cognitive deficits exhibited by Ts65Dn mice, a mouse model of Down syndrome. α-Tocopherol was administered to pregnant Ts65Dn females, from the day of conception throughout the pregnancy, and to pups over their entire lifetime, from birth to the end of the behavioral testing period. Cognitive deficits were confirmed for Ts65Dn mice fed a control diet, revealing reduced anxiety or regardlessness in the elevated-plus maze task test and spatial learning deficits in the Morris water maze test. However, supplementation with α-tocopherol attenuated both cognitive impairments. In addition, we found that levels of 8-iso-prostaglandin F(2α) in brain tissue and hydroxyoctadecadienoic acid and 7-hydroxycholesterol in the plasma of Ts65Dn mice were higher than those of control mice. Supplementation with α-tocopherol decreased levels of lipid peroxidation products in Ts65Dn mice. Furthermore, we found out that α-tocopherol improved hypocellularity in the hippocampal dentate gyrus of Ts65Dn mice. These results imply that α-tocopherol supplementation from an early stage may be an effective treatment for the cognitive deficits associated with Down syndrome.
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Affiliation(s)
- Mototada Shichiri
- Health Research Institute, National Institute of Advanced Industrial Science and Technology, Ikeda, Osaka 563-8577, Japan.
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Basselin M, Rosa AO, Ramadan E, Cheon Y, Chang L, Chen M, Greenstein D, Wohltmann M, Turk J, Rapoport SI. Imaging decreased brain docosahexaenoic acid metabolism and signaling in iPLA(2)β (VIA)-deficient mice. J Lipid Res 2010; 51:3166-73. [PMID: 20686114 DOI: 10.1194/jlr.m008334] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ca(2+)-independent phospholipase A(2)β (iPLA(2)β) selectively hydrolyzes docosahexaenoic acid (DHA, 22:6n-3) in vitro from phospholipid. Mutations in the PLA2G6 gene encoding this enzyme occur in patients with idiopathic neurodegeneration plus brain iron accumulation and dystonia-parkinsonism without iron accumulation, whereas mice lacking PLA2G6 show neurological dysfunction and neuropathology after 13 months. We hypothesized that brain DHA metabolism and signaling would be reduced in 4-month-old iPLA(2)β-deficient mice without overt neuropathology. Saline or the cholinergic muscarinic M(1,3,5) receptor agonist arecoline (30 mg/kg) was administered to unanesthetized iPLA(2)β(-/-), iPLA(2)β(+/-), and iPLA(2)β(+/+) mice, and [1-(14)C]DHA was infused intravenously. DHA incorporation coefficients k* and rates J(in), representing DHA metabolism, were determined using quantitative autoradiography in 81 brain regions. iPLA(2)β(-/-) or iPLA(2)β(+/-) compared with iPLA(2)β(+/+) mice showed widespread and significant baseline reductions in k* and J(in) for DHA. Arecoline increased both parameters in brain regions of iPLA(2)β(+/+) mice but quantitatively less so in iPLA(2)β(-/-) and iPLA(2)β(+/-) mice. Consistent with iPLA(2)β's reported ability to selectively hydrolyze DHA from phospholipid in vitro, iPLA(2)β deficiency reduces brain DHA metabolism and signaling in vivo at baseline and following M(1,3,5) receptor activation. Positron emission tomography might be used to image disturbed brain DHA metabolism in patients with PLA2G6 mutations.
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Affiliation(s)
- Mireille Basselin
- Brain Physiology and Metabolism Section, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
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Lee HJ, Bazinet RP, Rapoport SI, Bhattacharjee AK. Brain arachidonic acid cascade enzymes are upregulated in a rat model of unilateral Parkinson disease. Neurochem Res 2009; 35:613-9. [PMID: 19997776 DOI: 10.1007/s11064-009-0106-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/25/2009] [Indexed: 10/20/2022]
Abstract
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.
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Affiliation(s)
- Ho-Joo Lee
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA
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Rapoport SI, Basselin M, Kim HW, Rao JS. Bipolar disorder and mechanisms of action of mood stabilizers. ACTA ACUST UNITED AC 2009; 61:185-209. [PMID: 19555719 DOI: 10.1016/j.brainresrev.2009.06.003] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 06/03/2009] [Accepted: 06/15/2009] [Indexed: 11/30/2022]
Abstract
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.
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Affiliation(s)
- Stanley I Rapoport
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA.
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Basselin M, Fox MA, Chang L, Bell JM, Greenstein D, Chen M, Murphy DL, Rapoport SI. Imaging elevated brain arachidonic acid signaling in unanesthetized serotonin transporter (5-HTT)-deficient mice. Neuropsychopharmacology 2009; 34:1695-709. [PMID: 19145225 PMCID: PMC2700347 DOI: 10.1038/npp.2008.227] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Certain polymorphisms reduce serotonin (5-HT) reuptake transporter (5-HTT) function and increase susceptibility to psychiatric disorders. Heterozygous (5-HTT(+/-))-deficient mice, models for humans with these polymorphisms, have elevated brain 5-HT concentrations and behavioral abnormalities. As postsynaptic 5-HT(2A/2C) receptors are coupled to cytosolic phospholipase A(2) (cPLA(2)), which releases arachidonic acid (AA) from membrane phospholipid, 5-HTT-deficient mice may have altered brain AA signaling and metabolism. To test this hypothesis, signaling was imaged as an AA incorporation coefficient k(*) in unanesthetized homozygous knockout (5-HTT(-/-)), 5-HTT(+/-) and wild-type (5-HTT(+/+)), mice following saline (baseline) or 1.5 mg/kg s.c. DOI, a partial 5-HT(2A/2C) receptor agonist. Enzyme activities, metabolite concentrations, and head-twitch responses to DOI were also measured. Baseline k(*) was widely elevated by 20-70% in brains of 5-HTT(+/-) and 5-HTT(-/-) compared to 5-HTT(+/+) mice. DOI increased k(*) in 5-HTT(+/+) mice, but decreased k(*) in 5-HTT-deficient mice. Brain cPLA(2) activity was elevated in 5-HTT-deficient mice; cyclooxygenase activity and prostaglandin E(2) and F(2alpha) and thromboxane B(2) concentrations were reduced. Head-twitch responses to DOI, although robust in 5-HTT(+/+) and 5-HTT(+/-) mice, were markedly fewer in 5-HTT(-/-) mice. Pretreatment with para-chlorophenylalanine, a 5-HT synthesis inhibitor, restored head twitches in 5-HTT(-/-) mice to levels in 5-HTT(+/+) mice. We propose that increased baseline values of k(*) in 5-HTT-deficient mice reflect tonic cPLA(2) stimulation through 5-HT(2A/2C) receptors occupied by excess 5-HT, and that reduced k(*) and head-twitch responses to DOI reflected displacement of receptor-bound 5-HT by DOI with a lower affinity. Increased baseline AA signaling in humans having polymorphisms with reduced 5-HTT function might be identified using positron emission tomography.
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Affiliation(s)
- Mireille Basselin
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA.
| | - Meredith A. Fox
- Laboratory of Clinical Science, National Institute of Mental Health. National Institutes of Health, Bethesda, MD, 20892, USA
| | - Lisa Chang
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Jane M. Bell
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Dede Greenstein
- Child Psychiatry Branch, National Institute of Mental Health. National Institutes of Health, Bethesda, MD, 20892, USA
| | - Mei Chen
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Dennis L. Murphy
- Laboratory of Clinical Science, National Institute of Mental Health. National Institutes of Health, Bethesda, MD, 20892, USA
| | - Stanley I. Rapoport
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD, 20892, USA
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Chang L, Rapoport SI, Nguyen HN, Greenstein D, Chen M, Basselin M. Acute nicotine reduces brain arachidonic acid signaling in unanesthetized rats. J Cereb Blood Flow Metab 2009; 29:648-58. [PMID: 19142197 PMCID: PMC2704339 DOI: 10.1038/jcbfm.2008.159] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Nicotine exerts its central effects by activating pre- and postsynaptic nicotinic acetylcholine receptors (nAChRs). Presynaptic nAChRs modulate the release of many neurotransmitters that bind to postsynaptic receptors. These may be coupled to the activation of cytosolic phospholipase A(2) (cPLA(2)), which hydrolyzes arachidonic acid (AA) from membrane phospholipids. We hypothesized that nicotine would modify brain signaling involving AA by binding to nAChRs. Nicotine (0.1 mg/kg, subcutaneously) or saline was injected 2 or 10 mins before infusing [1-(14)C]AA in unanesthetized rats. The AA incorporation coefficient k(*) (a marker of the AA signal) was measured in 80 brain regions by quantitative autoradiography. Nicotine, compared to saline, when administrated 2 mins before [1-(14)C]AA infusion, significantly decreased k(*) for AA in 26 regions, including cerebral cortex, thalamus, and habenula-interpeduncular regions, by 13% to 45%. These decreases could be entirely prevented by pretreatment with mecamylamine (1.0 mg/kg, subcutaneously). When administered 10 mins before [1-(14)C]AA infusion, nicotine did not alter any value of k(*). In summary, nicotine given to unanesthetized rats rapidly reduces signaling involving AA in brain regions containing nAChRs, likely by modulating the presynaptic release of neurotransmitters. The effect shows rapid desensitization and is produced at a nicotine dose equivalent to smoking one cigarette in humans.
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Affiliation(s)
- Lisa Chang
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892, USA
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Basselin M, Nguyen HN, Chang L, Bell JM, Rapoport SI. Acute but not chronic donepezil increases muscarinic receptor-mediated signaling via arachidonic acid in unanesthetized rats. J Alzheimers Dis 2009; 17:369-82. [PMID: 19363262 PMCID: PMC2790024 DOI: 10.3233/jad-2009-1058] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Donepezil, an acetylcholinesterase (AChE) inhibitor used for treating Alzheimer's disease patients, is thought to act by increasing brain extracellular acetylcholine (ACh), and ACh binding to cholinergic receptors. Muscarinic receptors are coupled to cytosolic phospholipase A2 (cPLA2) activation and arachidonic acid (AA) release from synaptic membrane phospholipid. This activation can be imaged in rodents as an AA incorporation coefficient k*, using quantitative autoradiography. Acute and chronic effects of donepezil on the AA signal, k* for AA, were measured in 81 brain regions of unanesthetized rats. Twenty min after a single oral dose (3.0 mg/kg) of donepezil, k* was increased significantly in 37 brain regions, whereas k* did not differ from control 7 h afterwards or following chronic (21 days) of donepezil. Pretreatment with atropine prevented the 20-min increments in k* following donepezil. Donepezil also increased the brain ACh concentration and reduced brain AChE activity, but did not change cPLA2 activity, regardless of administration regimen. These results show that donepezil acutely increases the brain AA signal that is mediated by ACh acting at muscarinic receptors, but that this signal is rapidly desensitized despite continued elevated brain ACh concentration. In contrast, the AA signal in response to arecoline was not altered following donepezil.
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Affiliation(s)
- Mireille Basselin
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bldg. 9, Room 1S126, Bethesda, MD 20892, USA.
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Bhattacharjee AK, Chang L, Chen M, White L, Bell JM, Bazinet RP, Rapoport SI. Chronic d-amphetamine depresses an imaging marker of arachidonic acid metabolism in rat brain. Int J Neuropsychopharmacol 2008; 11:957-69. [PMID: 18570702 PMCID: PMC2676692 DOI: 10.1017/s1461145708008833] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Acute d-amphetamine (d-Amph) administration to rats leads to the release of arachidonic acid (AA, 20:4n-6) as a second messenger following indirect agonism at dopamine D2-like receptors in the brain. We hypothesized that chronically administered d-Amph in rats also would alter brain AA metabolism and signalling. To test this, adult male rats were injected i.p. daily for 2 wk with saline or 2.5 mg/kg d-Amph. After a 1-d washout, the unanaesthetized rats were injected acutely with i.v. saline, 1 mg/kg quinpirole (a D2-like receptor agonist) or 5.0 mg/kg SKF-38393 (a D1-like receptor agonist), followed by i.v. [1-14C]AA. The AA incorporation coefficient k* (brain radioactivity/integrated plasma radioactivity), a marker of AA signalling and metabolism, was quantified using autoradiography in each of 62 brain regions. Compared with chronic saline, chronic d-Amph widely decreased baseline values of k* in brain regions having D2-like receptors. On the other hand, chronic amphetamine did not alter the k* responses to quinpirole seen in chronic saline-treated rats. SKF-38393 had minimal effects on k* in both chronic saline-treated and amphetamine-treated rats, consistent with D1-like receptors not being coupled to AA signalling. The ability of chronic d-Amph after 1-d washout to down-regulate baseline values of k* probably reflects neuroplastic changes in brain AA signalling, and may correspond to depressive behaviours noted following withdrawal from chronic amphetamine in humans and in rats.
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MESH Headings
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/pharmacology
- Animals
- Arachidonic Acid/metabolism
- Arachidonic Acid/pharmacokinetics
- Autoradiography
- Biomarkers/analysis
- Biomarkers/metabolism
- Brain Chemistry/drug effects
- Central Nervous System Stimulants/administration & dosage
- Central Nervous System Stimulants/pharmacology
- Depression, Chemical
- Dextroamphetamine/administration & dosage
- Dextroamphetamine/pharmacology
- Dopamine Agonists/pharmacology
- Fatty Acids, Nonesterified/blood
- Half-Life
- Image Processing, Computer-Assisted
- Injections, Intraperitoneal
- Male
- Quinpirole/pharmacology
- Rats
- Rats, Inbred F344
- Receptors, Dopamine D2/agonists
- Receptors, Phospholipase A2/drug effects
- Signal Transduction/drug effects
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Affiliation(s)
- Abesh K Bhattacharjee
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA.
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14
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Basselin M, Chang L, Chen M, Bell JM, Rapoport SI. Chronic administration of valproic acid reduces brain NMDA signaling via arachidonic acid in unanesthetized rats. Neurochem Res 2008; 33:2229-40. [PMID: 18461450 PMCID: PMC2564799 DOI: 10.1007/s11064-008-9700-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2008] [Accepted: 04/03/2008] [Indexed: 01/12/2023]
Abstract
Evidence that brain glutamatergic activity is pathologically elevated in bipolar disorder suggests that mood stabilizers are therapeutic in the disease in part by downregulating glutamatergic activity. Such activity can involve the second messenger, arachidonic acid (AA, 20:4n - 6). We tested this hypothesis with regard to valproic acid (VPA), when stimulating glutamatergic N-methyl-D: -aspartate (NMDA) receptors in rat brain and measuring AA and related responses. An acute subconvulsant dose of NMDA (25 mg/kg i.p.) or saline was administered to unanesthetized rats that had been treated i.p. daily with VPA (200 mg/kg) or vehicle for 30 days. Quantitative autoradiography following intravenous [1-(14)C]AA infusion was used to image regional brain AA incorporation coefficients k*, markers of AA signaling. In chronic vehicle-pretreated rats, NMDA compared with saline significantly increased k* in 41 of 82 examined brain regions, many of which have high NMDA receptor densities, and also increased brain concentrations of the AA metabolites, prostaglandin E(2) (PGE(2)) and thromboxane B(2) (TXB(2)). VPA pretreatment reduced baseline concentrations of PGE(2) and TXB(2), and blocked the NMDA induced increases in k* and in eicosanoid concentrations. These results, taken with evidence that carbamazepine and lithium also block k* responses to NMDA in rat brain, suggest that mood stabilizers act in bipolar disorder in part by downregulating glutamatergic signaling involving AA.
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Affiliation(s)
- Mireille Basselin
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bldg 9, Room 1S126, MSC 0947, 9 Memorial Drive, Bethesda, MD, 20892, USA.
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15
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Basselin M, Chang L, Chen M, Bell JM, Rapoport SI. Chronic carbamazepine administration attenuates dopamine D2-like receptor-initiated signaling via arachidonic acid in rat brain. Neurochem Res 2008; 33:1373-83. [PMID: 18302021 PMCID: PMC5240792 DOI: 10.1007/s11064-008-9595-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Accepted: 01/10/2008] [Indexed: 12/25/2022]
Abstract
Observations that dopaminergic antagonists are beneficial in bipolar disorder and that dopaminergic agonists can produce mania suggest that bipolar disorder involves excessive dopaminergic transmission. Thus, mood stabilizers used to treat the disease might act in part by downregulating dopaminergic transmission. In agreement, we reported that dopamine D2-like receptor mediated signaling involving arachidonic acid (AA, 20:4n-6) was downregulated in rats chronically treated with lithium. To see whether chronic carbamazepine, another mood stabilizer, did this as well, we injected i.p. saline or the D2-like receptor agonist, quinpirole (1 mg/kg), into unanesthetized rats that had been pretreated for 30 days with i.p. carbamazepine (25 mg/kg/day) or vehicle, and used quantitative autoradiography to measure regional brain incorporation coefficients (k*) for AA, markers of signaling. We also measured brain prostaglandin E2 (PGE2), an AA metabolite. In vehicle-treated rats, quinpirole compared with saline significantly increased k* for AA in 35 of 82 brain regions examined, as well as brain PGE2 concentration. Affected regions belong to dopaminergic circuits and have high D2-like receptor densities. Chronic carbamazepine pretreatment prevented the quinpirole-induced increments in k* and in PGE2. These findings are consistent with the hypothesis that effective mood stabilizers generally downregulate brain AA signaling via D2-like receptors, and that this signaling is upregulated in bipolar disorder.
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Affiliation(s)
- Mireille Basselin
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bldg. 9, Room 1S126, Bethesda, MD 20892, USA.
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Imaging apomorphine stimulation of brain arachidonic acid signaling via D2-like receptors in unanesthetized rats. Psychopharmacology (Berl) 2008; 197:557-66. [PMID: 18274730 DOI: 10.1007/s00213-008-1073-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2007] [Accepted: 01/02/2008] [Indexed: 10/22/2022]
Abstract
RATIONALE AND OBJECTIVE Because of the important role of dopamine in neurotransmission, it would be useful to be able to image brain dopamine receptor-mediated signal transduction in animals and humans. Administering the D1-D2 receptor agonist apomorphine may allow us to do this, as the D2-like receptor is reported to be coupled to cytosolic phospholipase A2 activation and arachidonic acid (AA) release from membrane phospholipid. METHODS Unanesthetized adult rats were given intraperitoneally apomorphine (0.5 mg/kg) or saline, with or without pretreatment with 6 mg/kg intravenous raclopride, a D2/D3 receptor antagonist. [1-14C]AA was injected intravenously, then AA incorporation coefficients k*--brain radioactivity divided by integrated plasma radioactivity--markers of AA signaling, were measured using quantitative autoradiography in 62 brain regions. RESULTS Apomorphine significantly elevated k* in 26 brain regions, including the frontal cortex, motor and somatosensory cortex, caudate-putamen, thalamic nuclei, and nucleus accumbens. Raclopride alone did not change baseline values of k*, but raclopride pretreatment prevented the apomorphine-induced increments in k*. CONCLUSIONS A mixed D1-D2 receptor agonist, apomorphine, increased the AA signal by activating only D2-like receptors in brain circuits containing regions with high D2-like receptor densities. Thus, apomorphine might be used with positron emission tomography to image brain D2-like receptor-mediated AA signaling in humans in health and disease.
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17
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Basselin M, Villacreses NE, Chen M, Bell JM, Rapoport SI. Chronic carbamazepine administration reduces N-methyl-D-aspartate receptor-initiated signaling via arachidonic acid in rat brain. Biol Psychiatry 2007; 62:934-43. [PMID: 17628508 PMCID: PMC2131715 DOI: 10.1016/j.biopsych.2007.04.021] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2006] [Revised: 04/11/2007] [Accepted: 04/11/2007] [Indexed: 01/16/2023]
Abstract
BACKGROUND Lithium and carbamazepine (CBZ) are used to treat mania in bipolar disorder. When given chronically to rats, both agents reduce arachidonic acid (AA) turnover in brain phospholipids and downstream AA metabolism. Lithium in rats also attenuates brain N-methyl-D-aspartic acid receptor (NMDAR) signaling via AA. We hypothesized that, like chronic lithium, chronic CBZ administration to rats would reduce NMDAR-mediated signaling via AA. METHODS We used our fatty acid method with quantitative autoradiography to image the regional brain incorporation coefficient k* of AA, a marker of AA signaling, in unanesthetized rats that had been given 25 mg/kg/day I.P. CBZ or vehicle for 30 days, then injected with NMDA (25 mg/kg I.P.) or saline. We also measured brain concentrations of two AA metabolites, prostaglandin E(2) (PGE(2)) and thromboxane B(2) (TXB(2)). RESULTS In chronic vehicle-treated rats, NMDA compared with saline increased k* significantly in 69 of 82 brain regions examined, but did not change k* significantly in any region in CBZ-treated rats. In vehicle- but not CBZ-treated rats, NMDA also increased brain concentrations of PGE(2) and TXB(2). CONCLUSIONS Chronic CBZ administration to rats blocks increments in the AA signal k*, and in PGE(2) and TXB(2) concentrations that are produced by NMDA in vehicle-treated rats. The clinical action of antimanic drugs might involve inhibition of brain NMDAR-mediated signaling involving AA and its metabolites.
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Affiliation(s)
- Mireille Basselin
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892, USA.
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18
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Basselin M, Villacreses NE, Lee HJ, Bell JM, Rapoport SI. Flurbiprofen, A Cyclooxygenase Inhibitor, Reduces the Brain Arachidonic Acid Signal in Response to the Cholinergic Muscarinic Agonist, Arecoline, in Awake Rats. Neurochem Res 2007; 32:1857-67. [PMID: 17562170 DOI: 10.1007/s11064-007-9372-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Accepted: 05/01/2007] [Indexed: 10/23/2022]
Abstract
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.
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Affiliation(s)
- Mireille Basselin
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bldg 9, Room 1S126, MSC 0947, 9 Memorial Drive, Bethesda, MD 20892, USA.
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19
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Toscano CD, Prabhu VV, Langenbach R, Becker KG, Bosetti F. Differential gene expression patterns in cyclooxygenase-1 and cyclooxygenase-2 deficient mouse brain. Genome Biol 2007; 8:R14. [PMID: 17266762 PMCID: PMC1839133 DOI: 10.1186/gb-2007-8-1-r14] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2006] [Revised: 11/09/2006] [Accepted: 01/31/2007] [Indexed: 12/30/2022] Open
Abstract
Microarray analysis of gene expression in the cerebral cortex and hippocampus of mice deficient in cyclooxygenase-1 or cyclooxygenase-2 reveals that the two enzymes differentially modulate brain gene expression. Background Cyclooxygenase (COX)-1 and COX-2 produce prostanoids from arachidonic acid and are thought to have important yet distinct roles in normal brain function. Deletion of COX-1 or COX-2 results in profound differences both in brain levels of prostaglandin E2 and in activation of the transcription factor nuclear factor-κB, suggesting that COX-1 and COX-2 play distinct roles in brain arachidonic acid metabolism and regulation of gene expression. To further elucidate the role of COX isoforms in the regulation of the brain transcriptome, microarray analysis of gene expression in the cerebral cortex and hippocampus of mice deficient in COX-1 (COX-1-/-) or COX-2 (COX-2-/-) was performed. Results A majority (>93%) of the differentially expressed genes in both the cortex and hippocampus were altered in one COX isoform knockout mouse but not the other. The major gene function affected in all genotype comparisons was 'transcriptional regulation'. Distinct biologic and metabolic pathways that were altered in COX-/- mice included β oxidation, methionine metabolism, janus kinase signaling, and GABAergic neurotransmission. Conclusion Our findings suggest that COX-1 and COX-2 differentially modulate brain gene expression. Because certain anti-inflammatory and analgesic treatments are based on inhibition of COX activity, the specific alterations observed in this study further our understanding of the relationship of COX-1 and COX-2 with signaling pathways in brain and of the therapeutic and toxicologic consequences of COX inhibition.
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Affiliation(s)
- Christopher D Toscano
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bldg. 9, Rm. 1S126, 9 Memorial Drive, Bethesda, Maryland 20892, USA
| | - Vinaykumar V Prabhu
- Gene Expression and Genomics Unit, National Institute on Aging, National Institutes of Health, Gerontology Research Center, 5600 Nathan Shock Drive, Baltimore, Maryland, 21224, USA
| | - Robert Langenbach
- Laboratory of Molecular Carcinogenesis, National Institute of Environmental Health Sciences, National Institutes of Health, 111 TW Alexander Drive, Research Triangle Park, North Carolina, 27709, USA
| | - Kevin G Becker
- Gene Expression and Genomics Unit, National Institute on Aging, National Institutes of Health, Gerontology Research Center, 5600 Nathan Shock Drive, Baltimore, Maryland, 21224, USA
| | - Francesca Bosetti
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bldg. 9, Rm. 1S126, 9 Memorial Drive, Bethesda, Maryland 20892, USA
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Bosetti F. Arachidonic acid metabolism in brain physiology and pathology: lessons from genetically altered mouse models. J Neurochem 2007; 102:577-86. [PMID: 17403135 PMCID: PMC2084377 DOI: 10.1111/j.1471-4159.2007.04558.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The arachidonic acid (AA) cascade involves the release of AA from the membrane phospholipids by a phospholipase A(2), followed by its subsequent metabolism to bioactive prostanoids by cyclooxygenases coupled with terminal synthases. Altered brain AA metabolism has been implicated in neurological, neurodegenerative, and psychiatric disorders. The development of genetically altered mice lacking specific enzymes of the AA cascade has helped to elucidate the individual roles of these enzymes in brain physiology and pathology. The roles of AA and its metabolites in brain physiology, with a particular emphasis on the phospholipase A(2)/cyclooxygenases pathway, are summarized, and the specific phenotypes of genetically altered mice relevant to brain physiology and neurotoxic models are discussed.
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Affiliation(s)
- Francesca Bosetti
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, Maryland, USA.
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Basselin M, Villacreses NE, Lee HJ, Bell JM, Rapoport SI. Chronic lithium administration attenuates up-regulated brain arachidonic acid metabolism in a rat model of neuroinflammation. J Neurochem 2007; 102:761-72. [PMID: 17488274 DOI: 10.1111/j.1471-4159.2007.04593.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Neuroinflammation, caused by a 6-day intracerebroventricular infusion of lipopolysaccharide (LPS) in rats, is associated with the up-regulation of brain arachidonic acid (AA) metabolism markers. Because chronic LiCl down-regulates markers of brain AA metabolism, we hypothesized that it would attenuate increments of these markers in LPS-infused rats. Incorporation coefficients k* of AA from plasma into brain, and other brain AA metabolic markers, were measured in rats that had been fed a LiCl or control diet for 6 weeks, and subjected in the last 6 days on the diet to intracerebroventricular infusion of artificial CSF or of LPS. In rats on the control diet, LPS compared with CSF infusion increased k* significantly in 28 regions, whereas the LiCl diet prevented k* increments in 18 of these regions. LiCl in CSF infused rats increased k* in 14 regions, largely belonging to auditory and visual systems. Brain cytoplasmic phospholipase A(2) activity, and prostaglandin E(2) and thromboxane B(2) concentrations, were increased significantly by LPS infusion in rats fed the control but not the LiCl diet. Chronic LiCl administration attenuates LPS-induced up-regulation of a number of brain AA metabolism markers. To the extent that this up-regulation has neuropathological consequences, lithium might be considered for treating human brain diseases accompanied by neuroinflammation.
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Affiliation(s)
- Mireille Basselin
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda 20892-0947, Maryland, USA.
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Esposito G, Giovacchini G, Der M, Liow JS, Bhattacharjee AK, Ma K, Herscovitch P, Channing M, Eckelman WC, Hallett M, Carson RE, Rapoport SI. Imaging signal transduction via arachidonic acid in the human brain during visual stimulation, by means of positron emission tomography. Neuroimage 2006; 34:1342-51. [PMID: 17196833 PMCID: PMC2040045 DOI: 10.1016/j.neuroimage.2006.11.018] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2006] [Revised: 10/20/2006] [Accepted: 11/01/2006] [Indexed: 10/23/2022] Open
Abstract
BACKGROUND Arachidonic acid (AA, 20:4n-6), an important second messenger, is released from membrane phospholipid following receptor mediated activation of phospholipase A(2) (PLA(2)). This signaling process can be imaged in brain as a regional brain AA incorporation coefficient K*. HYPOTHESIS K* will be increased in brain visual areas of subjects submitted to visual stimulation. SUBJECTS AND METHODS Regional values of K* were measured with positron emission tomography (PET), following the intravenous injection of [1-(11)C]AA, in 16 healthy volunteers subjected to visual stimulation at flash frequencies 2.9 Hz (8 subjects) or 7.8 Hz (8 subjects), compared with the dark (0 Hz) condition. Regional cerebral blood flow (rCBF) was measured with intravenous [(15)O]water under comparable conditions. RESULTS During flash stimulation at 2.9 Hz or 7.8 Hz vs. 0 Hz, K* was increased significantly by 2.3-8.9% in Brodmann areas 17, 18 and 19, and in additional frontal, parietal and temporal cortical regions. rCBF was increased significantly by 3.1-22%, often in comparable regions. Increments at 7.8 Hz often exceeded those at 2.9 Hz for both K* and rCBF. Decrements in both parameters also were produced, particularly in frontal brain regions. CONCLUSIONS AA plays a role in signaling processes provoked by visual stimulation, since visual stimulation at flash frequencies of 2.9 and 7.8 Hz compared to 0 Hz modifies both K* for AA and rCBF in visual and related areas of the human brain. The two-stimulus condition paradigm of this study might be used with PET to image effects of other functional activations and of drugs on brain signaling via AA.
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Affiliation(s)
- Giuseppe Esposito
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD
| | - Giampiero Giovacchini
- PET Department, Warren Magnusson Clinical Center, National Institutes of Health, Bethesda, MD
- Department of Radiology, University of Pisa, Pisa, Italy
| | - Margaret Der
- PET Department, Warren Magnusson Clinical Center, National Institutes of Health, Bethesda, MD
| | - Jeih-San Liow
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD
| | - Abesh K. Bhattacharjee
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD
| | - Kaizong Ma
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD
| | - Peter Herscovitch
- PET Department, Warren Magnusson Clinical Center, National Institutes of Health, Bethesda, MD
| | - Michael Channing
- PET Department, Warren Magnusson Clinical Center, National Institutes of Health, Bethesda, MD
| | - William C. Eckelman
- PET Department, Warren Magnusson Clinical Center, National Institutes of Health, Bethesda, MD
- Molecular Tracer, LLC, Snow Point Drive, Bethesda MD
| | - Mark Hallett
- Human Motor Control Section, Medical Neurology Branch, National Institute of Neurological Disease and Stroke; National Institutes of Health, Bethesda, MD
| | - Richard E. Carson
- PET Department, Warren Magnusson Clinical Center, National Institutes of Health, Bethesda, MD
- Department of Diagnostic Radiology and Biomedical Engineering, Yale University, New Haven, CT
| | - Stanley I. Rapoport
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD
- *Corresponding Author: Brain Physiology and Metabolism Section, Bldg. 9, Rm. 1S128, National Institute on Aging, National Institutes of Health, 9 Memorial Drive, Bethesda, MD 20892, Tel: 301 496 1765, Fax: 301 402 0074, E-mail:
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Bhattacharjee AK, Chang L, White L, Bazinet RP, Rapoport SI. D-Amphetamine stimulates D2 dopamine receptor-mediated brain signaling involving arachidonic acid in unanesthetized rats. J Cereb Blood Flow Metab 2006; 26:1378-88. [PMID: 16511499 DOI: 10.1038/sj.jcbfm.9600290] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In rat brain, dopaminergic D(2)-like but not D(1)-like receptors can be coupled to phospholipase A(2) (PLA(2)) activation, to release the second messenger, arachidonic acid (AA, 20:4n-6), from membrane phospholipids. In this study, we hypothesized that D-amphetamine, a dopamine-releasing agent, could initiate such AA signaling. The incorporation coefficient, k* (brain radioactivity/integrated plasma radioactivity) for AA, a marker of the signal, was determined in 62 brain regions of unanesthetized rats that were administered i.p. saline, D-amphetamine (2.5 or 0.5 mg/kg i.p.), or the D(2)-like receptor antagonist raclopride (6 mg/kg, i.v.) before saline or 2.5 mg/kg D-amphetamine. After injecting [1-(14)C]AA intravenously, k* was measured by quantitative autoradiography. Compared to saline-treated controls, D-amphetamine 2.5 mg/kg i.p. increased k* significantly in 27 brain areas rich in D(2)-like receptors. Significant increases were evident in neocortical, extrapyramidal, and limbic regions. Pretreatment with raclopride blocked the increments, but raclopride alone did not alter baseline values of k*. In independent experiments, D-amphetamine 0.5 mg/kg i.p. increased k* significantly in only seven regions, including the nucleus accumbens and layer IV neocortical regions. These results indicate that D-amphetamine can indirectly activate brain PLA(2) in the unanesthetized rat, and that activation is initiated entirely at D(2)-like receptors. D-Amphetamine's low-dose effects are consistent with other evidence that the nucleus accumbens, considered a reward center, is particularly sensitive to the drug.
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Affiliation(s)
- Abesh K Bhattacharjee
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892, USA.
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