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Zheng S, Loreto R, Smith P, Patterson A, Hughes D, Wang L. Specialist and Generalist Fungal Parasites Induce Distinct Biochemical Changes in the Mandible Muscles of Their Host. Int J Mol Sci 2019; 20:E4589. [PMID: 31533250 PMCID: PMC6769763 DOI: 10.3390/ijms20184589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Revised: 09/09/2019] [Accepted: 09/10/2019] [Indexed: 11/24/2022] Open
Abstract
Some parasites have evolved the ability to adaptively manipulate host behavior. One notable example is the fungus Ophiocordyceps unilateralis sensu lato, which has evolved the ability to alter the behavior of ants in ways that enable fungal transmission and lifecycle completion. Because host mandibles are affected by the fungi, we focused on understanding changes in the metabolites of muscles during behavioral modification. We used High-Performance Liquid Chromatography-Mass/Mass (HPLC-MS/MS) to detect the metabolite difference between controls and O. unilateralis-infected ants. There was a significant difference between the global metabolome of O. unilateralis-infected ants and healthy ants, while there was no significant difference between the Beauveria bassiana treatment ants group compared to the healthy ants. A total of 31 and 16 of metabolites were putatively identified from comparisons of healthy ants with O. unilateralis-infected ants and comparisons of B. bassiana with O. unilateralis-infected samples, respectively. This result indicates that the concentrations of sugars, purines, ergothioneine, and hypoxanthine were significantly increased in O. unilateralis-infected ants in comparison to healthy ants and B. bassiana-infected ants. This study provides a comprehensive metabolic approach for understanding the interactions, at the level of host muscles, between healthy ants and fungal parasites.
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Affiliation(s)
- Shanshan Zheng
- Key Laboratory of Biopesticide and Chemical Biology, Ministry of Education, Fuzhou 350002, China.
- College of Plant Protection College, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
- Department of Entomology, Pennsylvania State University, University Park, PA 16802, USA.
| | - Raquel Loreto
- Center for Infectious Diseases Dynamics, Pennsylvania State University, University Park, PA 16802, USA.
- CAPES Foundation, Ministry of Education of Brazil, Brasilia 70040-020, DF, Brazil.
| | - Philip Smith
- Metabolomics Core Facility, Huck Institutes of Life Sciences, Pennsylvania State University, University Park, PA 16802, USA.
| | - Andrew Patterson
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University, University Park, PA 16802, USA.
| | - David Hughes
- Department of Entomology, Pennsylvania State University, University Park, PA 16802, USA.
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA.
| | - Liande Wang
- Key Laboratory of Biopesticide and Chemical Biology, Ministry of Education, Fuzhou 350002, China.
- College of Plant Protection College, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
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Welihinda AA, Kaur M, Raveendran KS, Amento EP. Enhancement of inosine-mediated A 2AR signaling through positive allosteric modulation. Cell Signal 2017; 42:227-235. [PMID: 29126977 DOI: 10.1016/j.cellsig.2017.11.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 10/20/2017] [Accepted: 11/06/2017] [Indexed: 12/14/2022]
Abstract
Inosine is an endogenous nucleoside that is produced by metabolic deamination of adenosine. Inosine is metabolically more stable (half-life 15h) than adenosine (half-life <10s). Inosine exerts anti-inflammatory and immunomodulatory effects similar to those observed with adenosine. These effects are mediated in part through the adenosine A2A receptor (A2AR). Relative to adenosine inosine exhibits a lower affinity towards the A2AR. Therefore, it is generally believed that inosine is incapable of activating the A2AR through direct engagement, but indirectly activates the A2AR upon metabolic conversion to higher affinity adenosine. A handful of studies, however, have provided evidence for direct inosine engagement at the A2AR leading to activation of downstream signaling events and inhibition of cytokine production. Here, we demonstrate that under conditions devoid of adenosine, inosine as well as an analog of inosine 6-S-[(4-Nitrophenyl)methyl]-6-thioinosine selectively and dose-dependently activated A2AR-mediated cAMP production and ERK1/2 phosphorylation in CHO cells stably expressing the human A2AR. Inosine also inhibited LPS-stimulated TNF-α, CCL3 and CCL4 production by splenic monocytes in an A2AR-dependent manner. In addition, we demonstrate that a positive allosteric modulator (PAM) of the A2AR enhanced inosine-mediated cAMP production, ERK1/2 phosphorylation and inhibition of pro-inflammatory cytokine and chemokine production. The cumulative effects of allosteric enhancement of adenosine-mediated and inosine-mediated A2AR activation may be the basis for the sustained anti-inflammatory and immunomodulatory effects observed in vivo and thereby provide insights into potential therapeutic interventions for inflammation- and immune-mediated diseases.
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Affiliation(s)
- Ajith A Welihinda
- Molecular Medicine Research Institute, 428 Oakmead Parkway, Sunnyvale, CA 94085.
| | - Manmeet Kaur
- Molecular Medicine Research Institute, 428 Oakmead Parkway, Sunnyvale, CA 94085
| | - Kaviya S Raveendran
- Molecular Medicine Research Institute, 428 Oakmead Parkway, Sunnyvale, CA 94085
| | - Edward P Amento
- Molecular Medicine Research Institute, 428 Oakmead Parkway, Sunnyvale, CA 94085
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Welihinda AA, Kaur M, Greene K, Zhai Y, Amento EP. The adenosine metabolite inosine is a functional agonist of the adenosine A2A receptor with a unique signaling bias. Cell Signal 2016; 28:552-60. [PMID: 26903141 DOI: 10.1016/j.cellsig.2016.02.010] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 02/10/2016] [Accepted: 02/15/2016] [Indexed: 01/12/2023]
Abstract
Inosine is an endogenous purine nucleoside that is produced by catabolism of adenosine. Adenosine has a short half-life (approximately 10s) and is rapidly deaminated to inosine, a stable metabolite with a half-life of approximately 15h. Resembling adenosine, inosine acting through adenosine receptors (ARs) exerts a wide range of anti-inflammatory and immunomodulatory effects in vivo. The immunomodulatory effects of inosine in vivo, at least in part, are mediated via the adenosine A2A receptor (A2AR), an observation that cannot be explained fully by in vitro pharmacological characterization of inosine at the A2AR. It is unclear whether the in vivo effects of inosine are due to inosine or a metabolite of inosine engaging the A2AR. Here, utilizing a combination of label-free, cell-based, and membrane-based functional assays in conjunction with an equilibrium agonist-binding assay we provide evidence for inosine engagement at the A2AR and subsequent activation of downstream signaling events. Inosine-mediated A2AR activation leads to cAMP production with an EC50 of 300.7μM and to extracellular signal-regulated kinase-1 and -2 (ERK1/2) phosphorylation with an EC50 of 89.38μM. Our data demonstrate that inosine produces ERK1/2-biased signaling whereas adenosine produces cAMP-biased signaling at the A2AR, highlighting pharmacological differences between these two agonists. Given the in vivo stability of inosine, our data suggest an additional, previously unrecognized, mechanism that utilizes inosine to functionally amplify and prolong A2AR activation in vivo.
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Affiliation(s)
- Ajith A Welihinda
- Molecular Medicine Research Institute, 428 Oakmead Parkway, Sunnyvale, CA 94085, United States.
| | - Manmeet Kaur
- Molecular Medicine Research Institute, 428 Oakmead Parkway, Sunnyvale, CA 94085, United States
| | - Kelly Greene
- Molecular Medicine Research Institute, 428 Oakmead Parkway, Sunnyvale, CA 94085, United States
| | - Yongjiao Zhai
- Molecular Medicine Research Institute, 428 Oakmead Parkway, Sunnyvale, CA 94085, United States
| | - Edward P Amento
- Molecular Medicine Research Institute, 428 Oakmead Parkway, Sunnyvale, CA 94085, United States
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Antonioli L, Csóka B, Fornai M, Colucci R, Kókai E, Blandizzi C, Haskó G. Adenosine and inflammation: what's new on the horizon? Drug Discov Today 2014; 19:1051-68. [DOI: 10.1016/j.drudis.2014.02.010] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 02/06/2014] [Accepted: 02/25/2014] [Indexed: 12/18/2022]
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Gomes CV, Kaster MP, Tomé AR, Agostinho PM, Cunha RA. Adenosine receptors and brain diseases: neuroprotection and neurodegeneration. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:1380-99. [PMID: 21145878 DOI: 10.1016/j.bbamem.2010.12.001] [Citation(s) in RCA: 303] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Revised: 11/30/2010] [Accepted: 12/01/2010] [Indexed: 02/06/2023]
Abstract
Adenosine acts in parallel as a neuromodulator and as a homeostatic modulator in the central nervous system. Its neuromodulatory role relies on a balanced activation of inhibitory A(1) receptors (A1R) and facilitatory A(2A) receptors (A2AR), mostly controlling excitatory glutamatergic synapses: A1R impose a tonic brake on excitatory transmission, whereas A2AR are selectively engaged to promote synaptic plasticity phenomena. This neuromodulatory role of adenosine is strikingly similar to the role of adenosine in the control of brain disorders; thus, A1R mostly act as a hurdle that needs to be overcame to begin neurodegeneration and, accordingly, A1R only effectively control neurodegeneration if activated in the temporal vicinity of brain insults; in contrast, the blockade of A2AR alleviates the long-term burden of brain disorders in different neurodegenerative conditions such as ischemia, epilepsy, Parkinson's or Alzheimer's disease and also seem to afford benefits in some psychiatric conditions. In spite of this qualitative agreement between neuromodulation and neuroprotection by A1R and A2AR, it is still unclear if the role of A1R and A2AR in the control of neuroprotection is mostly due to the control of glutamatergic transmission, or if it is instead due to the different homeostatic roles of these receptors related with the control of metabolism, of neuron-glia communication, of neuroinflammation, of neurogenesis or of the control of action of growth factors. In spite of this current mechanistic uncertainty, it seems evident that targeting adenosine receptors might indeed constitute a novel strategy to control the demise of different neurological and psychiatric disorders.
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Affiliation(s)
- Catarina V Gomes
- Center for Neurosciences of Coimbra, University of Coimbra, Coimbra, Portugal
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Coelho JE, Rebola N, Fragata I, Ribeiro JA, de Mendonça A, Cunha RA. Hypoxia-induced desensitization and internalization of adenosine A1 receptors in the rat hippocampus. Neuroscience 2006; 138:1195-203. [PMID: 16442739 DOI: 10.1016/j.neuroscience.2005.12.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Revised: 10/21/2005] [Accepted: 12/02/2005] [Indexed: 12/20/2022]
Abstract
Activation of A1 adenosine receptors is important for both the neuromodulatory and neuroprotective effects of adenosine. However, short periods of global ischemia decrease A1 adenosine receptor density in the brain and it is not known if a parallel loss of functional efficiency of A1 adenosine receptors occurs. We now tested if hypoxia leads to changes in the density and efficiency of A1 adenosine receptors to inhibit excitatory synaptic transmission in rat hippocampal slices. In control conditions, the adenosine analog 2-chloroadenosine, inhibited field excitatory post-synaptic potentials with an EC50 of 0.23 microM. After hypoxia (95% N2 and 5% CO2, for 60 min) and reoxygenation (30 min), the EC50 increased to 0.73 microM. This EC50 shift was prevented by the presence of the A1 adenosine receptor antagonist 8-phenyltheophyline, but not by the A(2A)R antagonist 7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2,4-triazolo[1,5-c] pyrimidine, during the hypoxic period. This decreased efficiency of A1 adenosine receptors was not paralleled by a global change of A1 adenosine receptor density or affinity (as evaluated by the binding parameters obtained in nerve terminal membranes). However, the density of biotinylated A1 adenosine receptors at the plasma membrane of nerve terminals was reduced by 30% upon hypoxia/reoxygenation, in a manner prevented by the A1 adenosine receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine and mimicked by prolonged (60 min) supra-maximal activation of A1 adenosine receptors with 2-chloroadenosine (10 microM). These results indicate that hypoxia leads to a rapid (<90 min) homologous desensitization of A1 adenosine receptor-mediated inhibition of synaptic transmission that is likely due to an internalization of A1 adenosine receptors in nerve terminals.
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Affiliation(s)
- J E Coelho
- Laboratory of Neurosciences, Institute of Molecular Medicine, Faculty of Medicine, University of Lisbon, 1649-028 Lisboa, Portugal
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Cunha RA. Neuroprotection by adenosine in the brain: From A(1) receptor activation to A (2A) receptor blockade. Purinergic Signal 2005; 1:111-34. [PMID: 18404497 PMCID: PMC2096528 DOI: 10.1007/s11302-005-0649-1] [Citation(s) in RCA: 404] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2004] [Accepted: 11/10/2004] [Indexed: 12/11/2022] Open
Abstract
Adenosine is a neuromodulator that operates via the most abundant inhibitory adenosine A(1) receptors (A(1)Rs) and the less abundant, but widespread, facilitatory A(2A)Rs. It is commonly assumed that A(1)Rs play a key role in neuroprotection since they decrease glutamate release and hyperpolarize neurons. In fact, A(1)R activation at the onset of neuronal injury attenuates brain damage, whereas its blockade exacerbates damage in adult animals. However, there is a down-regulation of central A(1)Rs in chronic noxious situations. In contrast, A(2A)Rs are up-regulated in noxious brain conditions and their blockade confers robust brain neuroprotection in adult animals. The brain neuroprotective effect of A(2A)R antagonists is maintained in chronic noxious brain conditions without observable peripheral effects, thus justifying the interest of A(2A)R antagonists as novel protective agents in neurodegenerative diseases such as Parkinson's and Alzheimer's disease, ischemic brain damage and epilepsy. The greater interest of A(2A)R blockade compared to A(1)R activation does not mean that A(1)R activation is irrelevant for a neuroprotective strategy. In fact, it is proposed that coupling A(2A)R antagonists with strategies aimed at bursting the levels of extracellular adenosine (by inhibiting adenosine kinase) to activate A(1)Rs might constitute the more robust brain neuroprotective strategy based on the adenosine neuromodulatory system. This strategy should be useful in adult animals and especially in the elderly (where brain pathologies are prevalent) but is not valid for fetus or newborns where the impact of adenosine receptors on brain damage is different.
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Affiliation(s)
- Rodrigo A Cunha
- Center for Neuroscience of Coimbra, Institute of Biochemistry, Faculty of Medicine, University of Coimbra, Coimbra, Portugal,
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Abstract
OBJECTIVES This review summarizes the 30 year effort of my collaborator and mentor Dr J. W. Phillis to establish the role of adenosine in the regulation of cerebral blood flow. METHODS While most of the experiments described utilized the rat cerebral cortex as a model, several different and complementary methodologies were employed. Superfusate samples were collected from the cortical surface and analysed for purines using HPLC. Laser-Doppler flowmetry was utilized to measure blood flow in the pial vasculature, while pial diameters were monitored by videomicroscopy. An additional series of experiments looked at coronary blood flow in a Langendorff preparation. RESULTS Adenosine is released from the cortex in response to decreased nutrient supply (hypoxia/ ischemia) and during conditions that mimic alterations in the extracellular environment associated with increased metabolism. The application of pharmacological agents that alter adenosine metabolism resulted in the appropriate alterations in ECF adenosine levels and also in blood flow. Selective blockade of the adenosine A(2A) receptor reduced the pial vasodilation evoked by hypercapnoea. Results from the isolated rat heart, utilizing similar agents, support a role for adenosine in the regulation of coronary blood flow during respiratory and metabolic acidosis. DISCUSSION Adenosine is released when there is a mismatch between supply and demand. If the effects of adenosine are blocked with receptor antagonists, the vasodilation is also reduced. However, the effects of adenosine on the hyperemia evoked by hypercapnoea are complicated by the arousal evoked by adenosine receptor antagonists and the effects of upstream regulation.
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Affiliation(s)
- Michael O'Regan
- Department of Biomedical Sciences, School of Dentistry, University of Detroit Mercy, 8200 W. Outer Drive, P.O. Box 19900 Detroit, MI 48219-0900, USA.
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Buck LT. Adenosine as a signal for ion channel arrest in anoxia-tolerant organisms. Comp Biochem Physiol B Biochem Mol Biol 2005; 139:401-14. [PMID: 15544964 DOI: 10.1016/j.cbpc.2004.04.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2003] [Revised: 03/31/2004] [Accepted: 04/05/2004] [Indexed: 11/18/2022]
Abstract
Certain freshwater turtles and fish are extremely anoxia-tolerant, capable of surviving hours of anoxia at high temperatures and weeks to months at low temperatures. There is great interest in understanding the cellular mechanisms underlying anoxia-tolerance in these groups because they are anoxia-tolerant vertebrates and because of the far-reaching medical benefits that would be gained. It has become clear that a pre-condition of prolonged anoxic survival must involve the matching of ATP production with ATP utilization to maintain stable ATP levels during anoxia. In most vertebrates, anoxia leads to a severe decrease in ATP production without a concomitant reduction in utilization, which inevitably leads to the catastrophic events associated with cell death or necrosis. Anoxia-tolerant organisms do not increase ATP production when faced with anoxia, but rather decrease utilization to a level that can be met by anaerobic glycolysis alone. Protein synthesis and ion movement across the plasma membrane are the two main targets of regulatory processes that reduce ATP utilization and promote anoxic survival. However, the oxygen sensing and biochemical signaling mechanisms that achieve a coordinated reduction in ATP production and utilization remain unclear. One candidate-signaling compound whose extracellular concentration increases in concert with decreasing oxygen availability is adenosine. Adenosine is known to have profound effects on various aspects of tissue metabolism, including protein synthesis, ion pumping and permeability of ion channels. In this review, I will investigate the role of adenosine in the naturally anoxia-tolerant freshwater turtle and goldfish and give an overview of pathways by which adenosine concentrations are regulated.
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Affiliation(s)
- Leslie Thomas Buck
- Department of Zoology, University of Toronto, 25 Harbord St., Toronto, ON, Canada M5S 3G5.
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Latini S, Pedata F. Adenosine in the central nervous system: release mechanisms and extracellular concentrations. J Neurochem 2001; 79:463-84. [PMID: 11701750 DOI: 10.1046/j.1471-4159.2001.00607.x] [Citation(s) in RCA: 549] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Adenosine has several functions within the CNS that involve an inhibitory tone of neurotransmission and neuroprotective actions in pathological conditions. The understanding of adenosine production and release in the brain is therefore of fundamental importance and has been extensively studied. Conflicting results are often obtained regarding the cellular source of adenosine, the stimulus that induces release and the mechanism for release, in relation to different experimental approaches used to study adenosine production and release. A neuronal origin of adenosine has been demonstrated through electrophysiological approaches showing that neurones can release significant quantities of adenosine, sufficient to activate adenosine receptors and to modulate synaptic functions. Specific actions of adenosine are mediated by different receptor subtypes (A(1), A(2A), A(2B) and A(3)), which are activated by various ranges of adenosine concentrations. Another important issue is the measurement of adenosine concentrations in the extracellular fluid under different conditions in order to know the degree of receptor stimulation and understand adenosine central actions. For this purpose, several experimental approaches have been used both in vivo and in vitro, which provide an estimation of basal adenosine levels in the range of 50-200 nM. The purpose of this review is to describe pathways of adenosine production and metabolism, and to summarize characteristics of adenosine release in the brain in response to different stimuli. Finally, studies performed to evaluate adenosine concentrations under physiological and hypoxic/ischemic conditions will be described to evaluate the degree of adenosine receptor activation.
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Affiliation(s)
- S Latini
- Department of Preclinical and Clinical Pharmacology, University of Florence, Florence, Italy
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Abstract
Cerebral ischemia studies demonstrating that stimulation of adenosine A1 receptors by either endogenously released adenosine or the administration of selective receptor agonists causes significant reductions in the morbidity and mortality associated with focal or global brain ischemias have triggered interest in the potential of purinergic therapies for the treatment of traumatic injuries to the brain and spinal cord. Preliminary findings indicate that activation of A1 adenosine receptors can ameliorate trauma-induced death of central neurons. Other avenues of approach include the administration of agents which elevate local concentrations of adenosine at injury sites by inhibiting its metabolism to inosine by adenosine deaminase, rephosphorylation to adenosine triphosphate by adenosine kinase; or re-uptake into adjacent cells. Amplification of the levels of endogenously released adenosine in such a 'site and event specific' fashion has the advantage of largely restricting the effect of such inhibitors to areas of injury-induced adenosine release. Another approach involving purinergic therapy has been applied to the problem of respiratory paralysis following high spinal cord injuries. In this instance, the adenosine antagonist theophylline has been used to enhance residual synaptic drive to spinal respiratory neurons by blocking adenosine A1 receptors. Theophylline induced, and maintained, hemidiaphragmatic recovery for prolonged periods after C2 spinal cord hemisection in rats and may prove to be beneficial in assisting respiration in spinal cord injury patients.
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Affiliation(s)
- J W Phillis
- Department of Physiology, Wayne State University School of Medicine, 540 E. Canfield, Detroit, MI 48201-1928, USA.
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Jiang N, Kowaluk EA, Lee CH, Mazdiyasni H, Chopp M. Adenosine kinase inhibition protects brain against transient focal ischemia in rats. Eur J Pharmacol 1997; 320:131-7. [PMID: 9059845 DOI: 10.1016/s0014-2999(96)00905-3] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Endogenous adenosine released locally during cerebral ischemia is neuroprotective, and agents which decrease adenosine inactivation may potentiate its protective effects. The effects of 5'-deoxy-5-iodotubercidin (5'd-5IT), an inhibitor of the adenosine-catabolizing enzyme, adenosine kinase, were studied in male Wistar rats subjected to 2 h of transient middle cerebral artery occlusion. 5'd-5IT or the vehicle (10% DMSO in saline) was administered i.p. 30 min before, and 2 h and 6 h after the induction of middle cerebral artery occlusion. The infarct volume was determine using 2,3,5-triphenyltetrazolium chloride staining 48 h after middle cerebral artery occlusion. The infarct volume was significantly reduced in rats treated with 1.85 mg/kg x 3 (57% reduction, P < 0.001) or 1.0 mg/kg x 3 (34% reduction, P < 0.05), but not 0.3 mg/kg x 3 5'd-5IT compared to vehicle-treated rats. The reduction of infarct volume was accompanied by a significant improvement in behavioral measures of neurological deficit. These data further support a role of adenosine in neuroprotection and suggest that adenosine kinase inhibition may be a useful approach to the treatment of focal cerebral ischemia.
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Affiliation(s)
- N Jiang
- Henry Ford Health Science Center, Department of Neurology, Detroit, MI 48202, USA
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Yavuz O, Türközkan N, Bilgihan A, Doğulu F, Aykol S. The effect of 2-chloroadenosine on lipid peroxide level during experimental cerebral ischemia-reperfusion in gerbils. Free Radic Biol Med 1997; 22:337-41. [PMID: 8958159 DOI: 10.1016/s0891-5849(97)82138-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Oxygen free radicals may be implicated in the pathogenesis of ischemia-reperfusion damage. It is known that 2-chloroadenosine (2-CADO) has neuromodulatory effects and prevents the neuronal damage seen in the period of postischemia reperfusion. However, direct effects of 2-CADO on lipid peroxidation have not been investigated previously. The attack on the cell membrane by free radicals leads to lipid peroxidation, which can be assayed by the malondialdehyde (MDA) level. The aim of this study was to determine the effect of 2-CADO therapy on lipid peroxidation in experimental forebrain ischemia and postischemia reperfusion in Mongolian gerbils. Cerebral ischemia was induced by a bilateral 30-mm occlusion of the common carotid arteries. 2-Chloroadenosine (0.6 mg/kg, IV) was administered 5 min subsequent to ischemia. Ischemia was followed by reperfusion for 30 min. The MDA level was measured by the thiobarbituric acid (TBA) test. Bilateral carotid artery occlusion for 30 min in gerbils resulted in no significant change in MDA level in the brain. The MDA level was higher in postischemia reperfusion than in the ischemic group. 2-Chloroadenosine treatment did not change the MDA level in the ischemic period. However, the MDA level recovered significantly upon 2-CADO therapy during reperfusion following ischemia. These results suggest that 2-CADO may offer some degree of protection against oxidative stress in cerebral ischemia-reperfusion damage.
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Affiliation(s)
- O Yavuz
- Department of Biochemistry, Faculty of Medicine, Gazi University, Beşevler, Ankara, Turkey
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von Lubitz DK, Carter MF, Beenhakker M, Lin RC, Jacobson KA. Adenosine: a prototherapeutic concept in neurodegeneration. Ann N Y Acad Sci 1995; 765:163-78; discussion 196-7. [PMID: 7486604 PMCID: PMC3437326 DOI: 10.1111/j.1749-6632.1995.tb16573.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- D K von Lubitz
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases/NIH, Bethesda, Maryland 20892, USA
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Zhu PJ, Krnjević K. Endogenous adenosine deaminase does not modulate synaptic transmission in rat hippocampal slices under normoxic or hypoxic conditions. Neuroscience 1994; 63:489-97. [PMID: 7891860 DOI: 10.1016/0306-4522(94)90545-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Field and intracellular potentials were recorded from CA1 pyramidal stratum in submerged slices (at 33 degrees). During "normal" oxygenation (95% O2 + 5% CO2), tonic depression of population spikes and field excitatory postsynaptic potentials by endogenous adenosine was demonstrated by (i) the marked enhancement by the adenosine antagonists 8-(p-sulfophenyl)theophylline (10 microM) and caffeine (0.2 mM), (ii) depression by the transport blocker dipyridamole (5 microM), and (iii) enhancement by exogenous adenosine deaminase (all tested by bath application). Thus, adenosine deaminase (0.5 units/ml) reduced by 10.7 +/- 3.0% (S.E.) the half-maximal stimulus intensity (for population spikes). The effects of adenosine deaminase were prevented by the specific inhibitor, deoxycoformycin (30 microM). In intracellular recordings, excitatory postsynaptic potentials were enhanced in a comparable manner by adenosine deaminase. By contrast, neither deoxycoformycin (5 and 30 microM) nor erythro-9-(2-hydroxy-3-nonyl)adenine (another adenosine deaminase inhibitor; 10 and 50 microM) had significant effects on population spikes. Superfusion with anoxic medium (saturated with 95% N2 + 5% CO2) for 2-3 min suppressed population spikes reversibly, by a mechanism involving adenosine, because 8-(p-sulfophenyl)theophylline (10 microM) and caffeine (0.2 mM) delayed the onset of anoxic block and accelerated the subsequent recovery, and the recovery was much slower or incomplete in the presence of dipyramidole (0.5 microM). However, the anoxic suppression of population spikes was not affected by deoxycoformycin (30 microM) or erythro-9-(2-hydroxy-3-nonyl)adenine (10 microM); the corresponding 50% postanoxic recovery times were also unchanged (e.g. 4.0 +/- 0.2 min for controls and 4.1 +/- 0.3 min in deoxycoformycin).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P J Zhu
- Anaesthesia Research Department, McGill University, Montréal, Québec, Canada
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Phillis JW, Sen S. Oxypurinol attenuates hydroxyl radical production during ischemia/reperfusion injury of the rat cerebral cortex: an ESR study. Brain Res 1993; 628:309-12. [PMID: 8313161 DOI: 10.1016/0006-8993(93)90970-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Free radical generation and release from the cerebral hemispheres of rats subjected to four vessel occlusion followed by reperfusion was monitored using a cortical cup technique in conjunction with the spin-trapping agent alpha(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN). Electron spin resonance (ESR) was used to detect the presence of free radical adducts of POBN in the cortical superfusates. 30 min of ischemia plus reperfusion resulted in the release of .OH radical adducts during the period of ischemia and, especially, during the initial phases of reperfusion. No radical adducts were detectable 90 min after the onset of reperfusion. Pretreatment with the xanthine oxidase inhibitor, oxypurinol (40 mg/kg i.p.), virtually abolished free radical formation and release. The results of this study are consistent with earlier evidence of free radical formation during ischemia/reperfusion and suggest that the cerebroprotective actions of oxypurinol may be related to its ability to prevent the cascade of free radical generation.
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Affiliation(s)
- J W Phillis
- Department of Physiology, Wayne State University, Detroit, MI 48201
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17
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Latini S, Pedata F, Pepeu G. Effect of idebenone on adenosine outflow and adenine nucleotide level in hippocampal slices under ischemia-like conditions. Eur J Pharmacol 1993; 249:65-70. [PMID: 8282020 DOI: 10.1016/0014-2999(93)90662-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The effect of idebenone on the changes in adenosine and nucleotide metabolism occurring in hippocampal slices after ischemia-like conditions (superfusion with glucose-free Krebs solution gassed with 95% N2-5% CO2) and during reperfusion with normal Krebs solution was investigated by measuring adenosine and inosine outflow, and adenosine and adenine nucleotide levels by HPLC. Five minutes of ischemia-like conditions brought about an 8- and 4-fold increase in adenosine and inosine outflow 10 min after reperfusion and a 75% increase in the tissue level of adenosine, a 40% decrease in ATP, and a 50% increase in AMP at the end of the ischemic period. Ten minutes after reperfusion, ATP and AMP returned to control values. Idebenone (25-100 microM) brought about a concentration-dependent increase in adenosine and inosine outflow evoked by ischemia-like conditions. Idebenone (50 microM) also increased the adenosine content in hippocampal slices after both ischemia (+150%) and reperfusion (+320%). An 82% increase in ADP, 174% in AMP, and 56% in the total sum of nucleotides, 10 min after reperfusion were found in idebenone treated slices. These results suggest that idebenone enhances adenosine formation after ischemia-like conditions from sources other than AMP, and improves phosphorylating activity during reperfusion. Idebenone, by increasing adenosine and total nucleotide levels, may protect brain tissue from ischemic damage.
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Affiliation(s)
- S Latini
- Department of Preclinical and Clinical Pharmacology, University of Florence, Italy
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18
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Meno JR, Ngai AC, Winn HR. Changes in pial arteriolar diameter and CSF adenosine concentrations during hypoxia. J Cereb Blood Flow Metab 1993; 13:214-20. [PMID: 8436613 DOI: 10.1038/jcbfm.1993.26] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We measured the changes in pial arteriolar diameter and CSF concentrations of adenosine, inosine, and hypoxanthine during hypoxia in the absence and presence of topically applied dipyridamole (10(-6) M) and erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA; 10(-5) M). Closed cranial windows were implanted in halothane-anesthetized adult male Sprague-Dawley rats for the observation of the pial circulation and collection of CSF. The mean resting arteriolar diameter in mock CSF was 31.2 +/- 5.9 microns. Topically applied dipyridamole and EHNA, in combination, caused a slight but significant (p < 0.05) increase in resting arteriolar diameter (33.8 +/- 4.3 microns). With mock CSF, moderate hypoxia caused a 22.1 +/- 9.7% increase in pial vessel diameter. Topically applied dipyridamole and EHNA significantly (p < 0.01) potentiated pial arteriolar vasodilation in response to hypoxia. Moreover, the potentiating effects of dipyridamole and EHNA during hypoxia were completely abolished by theophylline (0.20 mumol/g, i.p.; p < 0.05), an adenosine receptor antagonist. Resting concentrations of adenosine, inosine, and hypoxanthine in the subwindow CSF were 0.18 +/- 0.09, 0.35 +/- 0.21, and 0.62 +/- 0.12 microM, respectively. In the absence of dipyridamole and EHNA, these levels were not affected by sustained moderate hypoxia (PaO2 = 36 +/- 6 mm Hg). However, in the presence of dipyridamole and EHNA, the concentration of adenosine in the CSF during hypoxia was significantly (p < 0.05) increased. Our data indicate that dipyridamole and EHNA potentiate hypoxic vasodilation of pial arterioles while simultaneously increasing extracellular adenosine levels, thus supporting the hypothesis that adenosine is involved in the regulation of cerebral blood flow.
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Affiliation(s)
- J R Meno
- Department of Neurological Surgery, University of Washington School of Medicine, Seattle
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19
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Phillis JW, Perkins LM, O'Regan MH. Potassium-evoked efflux of transmitter amino acids and purines from rat cerebral cortex. Brain Res Bull 1993; 31:547-52. [PMID: 8098653 DOI: 10.1016/0361-9230(93)90122-r] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Repeated applications of elevated K+ (50 or 75 mM) in cerebral cortical cup superfusates was used to evoke an efflux of gamma-aminobutyric acid (GABA), glutamate, aspartate, glycine, adenosine, and inosine from the in vivo rat cerebral cortex. K+ (50 mM) significantly elevated GABA levels in cup superfusates but had little effect on the efflux of glutamate, aspartate, glycine, adenosine, or inosine. K+ (75 mM) significantly enhanced the efflux of GABA, aspartate, adenosine, and inosine and caused nonsignificant increases in glutamate and glycine efflux. The adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA), applied in cup superfusates at a concentration of 10(-10) M had no effect on either basal or K(+)-evoked release of any of the amino acids or purines measured. At 10(-6) M CPA significantly enhanced aspartate release, and depressed GABA efflux. The selective A2 adenosine receptor agonist 2-p(2-carboxyethyl) phenethylamino-5'-N-ethyl-carboxamidoadenosine (CGS 21680) (10(-8) M) was without effect on either basal, or K(+)-evoked, efflux of amino acids or purines. The enhancement of aspartate (an excitotoxic amino acid) efflux by higher concentrations of CPA is likely due to activation of adenosine A2b receptors. This observation may be of relevance when selecting adenosinergic agents to treat ischemic or traumatic brain injuries. Overall, the results suggest that effects of adenosine receptor agonists on K(+)-evoked efflux of transmitter amino acids from the in vivo rat cerebral cortex may not be comparable to those observed with in vitro preparations.
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Affiliation(s)
- J W Phillis
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201
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20
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Phillis JW, Smith-Barbour M. The adenosine kinase inhibitor, 5-iodotubercidin, is not protective against cerebral ischemic injury in the gerbil. Life Sci 1993; 53:497-502. [PMID: 8341136 DOI: 10.1016/0024-3205(93)90701-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
5-Iodotubercidin is a potent inhibitor of the enzyme adenosine kinase. It has a recognized ability to enhance interstitial fluid levels of the cerebroprotective purine, adenosine, in the hypoxic brain, and an anticonvulsant action, which is thought to be a consequence of its ability to increase extracellular adenosine levels. 5-Iodotubercidin (1 mg/kg, i.p.) was therefore tested for its ability to reduce cerebral ischemic injury in a gerbil model. Unanesthetized gerbils were subjected to a 5 min period of bilateral carotid artery occlusion and then maintained in an environmental chamber at 30 degrees C for 5 hr to counteract the hypothermia-inducing action of 5-iodotubercidin. As estimated from the extent of the increases in locomotor activity and the magnitude of hippocampal CAI layer pyramidal cell loss, 5-iodotubercidin (1 mg/kg) failed to have a cerebroprotective effect against ischemic injury.
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Affiliation(s)
- J W Phillis
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201
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21
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Phillis JW, O'Regan MH, Perkins LM. Actions of ethanol and acetate on rat cortical neurons: ethanol/adenosine interactions. Alcohol 1992; 9:541-6. [PMID: 1472311 DOI: 10.1016/0741-8329(92)90094-q] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Recent studies have suggested that ethanol may exert some of its central depressant actions by increasing the extracellular levels of adenosine in the brain. Ethanol can inhibit the cellular uptake of adenosine, thus increasing its extracellular concentration. After ethanol metabolism by the liver, blood acetate levels are elevated and acetate metabolism in the brain could also lead to the production of adenosine. Rat cerebral cortical cup release experiments failed to reveal any elevation in the extracellular levels of either adenosine or inosine following the intraperitoneal (IP) administration of ethanol (1.5 g/kg) or acetate (2 g/kg). IP-administered ethanol (0.5 and 1.0 g/kg) enhanced the magnitude and duration of the inhibition by iontophoretically applied adenosine of the spontaneous firing of rat cerebrocortical neurons; an action which would be consistent with the block of adenosine uptake. Acetate, applied iontophoretically, depressed the spontaneous firing of 63% of the cerebrocortical neurons tested. 8-p-Sulphophenyltheophylline, an adenosine antagonist, was ineffective at blocking these inhibitions, indicating that adenosine generation is unlikely to have played a major role in the acetate-evoked depression of cerebral cortical neurons.
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Affiliation(s)
- J W Phillis
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201
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22
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Centelles JJ, Cascante M, Canela EI, Franco R. A model for adenosine transport and metabolism. Biochem J 1992; 287 ( Pt 2):461-72. [PMID: 1445204 PMCID: PMC1133188 DOI: 10.1042/bj2870461] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
1. A model is presented for adenosine transport and metabolism in different steady states. The model considers steady-state equations for metabolic enzymes based on information from the literature on their kinetic behaviour. 2. Assuming that extracellular adenosine and inosine are translocated by three transporters, we have devised rate equations for these nucleoside transporters which are valid when both nucleosides are present. Since the Na(+)-independent transporter can either incorporate nucleosides into the cell or release them, various conditions have been simulated in which inosine was either incorporated or released. 3. Control analyses are reported which show that the fluxes towards intracellular adenine nucleosides are controlled by ecto-5'-nucleotidase in some circumstances and by the nucleoside transporters in others. The nucleoside transporter is responsible for five fluxes (two Na+ dependent adenosine transport mechanisms, a Na(+)-dependent inosine transport, a Na(+)-independent adenosine transport and a Na(+)-independent inosine influx or efflux) but the control is not always positive for all these fluxes. The control patterns of these five fluxes indicate that, in the presence of extracellular adenosine and inosine, the intracellular metabolism of adenine derivatives would be highly dependent on the extracellular and intracellular concentrations of both nucleosides, on the ectoenzymes (5'-nucleotidase and adenosine deaminase) and on the transporter. 4. Predictions of the model were examined. The results indicate that a change in one independent variable (extracellular AMP concentration) makes the system evolve towards a new steady state which is far from the initial one and has a different control pattern. In contrast, simulation of inhibition of the carriers produces only slight modification of the fluxes since the concentrations of the metabolites change to counteract the effect. Thus, for instance, a 50% inhibition of the three carriers does not affect the flux towards intracellular adenine nucleotides. Finally, our model has confirmed that the evolution of the concentration of extracellular adenosine, when an increase in extracellular AMP is produced, agrees with the behaviour expected for a neurohormone.
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Affiliation(s)
- J J Centelles
- Departament de Bioquímica, Facultat de Química, Universitat de Catalunya, Barcelona, Spain
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23
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Chen Y, Graham DI, Stone TW. Release of endogenous adenosine and its metabolites by the activation of NMDA receptors in the rat hippocampus in vivo. Br J Pharmacol 1992; 106:632-8. [PMID: 1354544 PMCID: PMC1907546 DOI: 10.1111/j.1476-5381.1992.tb14387.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
1. The effects of N-methyl-D-aspartate (NMDA), KCl, and veratridine on the release of endogenous adenosine and its metabolites, inosine and hypoxanthine, from the rat hippocampus have been studied by in vivo microdialysis. 2. In the hippocampus of rats anaesthetized with urethane the adenosine level reached a stable state estimated at 0.93 microM during the first 2 h after the implantation of the dialysis probe. NMDA (50 microM to 25 mM) in the perfusate evoked a concentration-dependent release of adenosine, inosine and hypoxanthine with an EC50 of 180 microM. The release was reduced by 93% by the specific NMDA receptor antagonist 2-amino-5-phosphonopentanoic acid (2-AP5) at 200 microM, indicating an NMDA receptor-mediated process. In addition, the 100 mM KCl-evoked release of adenosine was also substantially reduced by 77% by 2-AP5, suggesting that a large component of the K(+)-evoked release is NMDA-receptor-mediated. 3. Perfusion with zero-Ca2+ artificial cerebrospinal fluid attenuated the NMDA-evoked release of adenosine only by 16% (not significant) but depressed the K(+)-evoked release by 62%, indicating that most of the NMDA-evoked release is directly receptor-mediated, whereas a large component of the K(+)-evoked release could be via the release of an excitatory amino acid acting at the NMDA receptors.
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Affiliation(s)
- Y Chen
- Department of Pharmacology, University of Glasgow
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24
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Lin Y, Phillis JW. Deoxycoformycin and oxypurinol: protection against focal ischemic brain injury in the rat. Brain Res 1992; 571:272-80. [PMID: 1611498 DOI: 10.1016/0006-8993(92)90665-v] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We have previously demonstrated that oxypurinol (40 mg/kg i.p.), a xanthine oxidase inhibitor, can reduce focal ischemic brain injury in the rat when applied pre-ischemically. By using a model of occlusion of the middle cerebral artery (MCA) in tandem with occlusion of the ipsilateral carotid artery, the present study further demonstrates that delayed (60 min) administration of oxypurinol also exhibits a protective action on ischemic damage in the stroked rat brain. Oxypurinol significantly reduced the ischemic cerebral infarct zone by preventing the development of brain damage primarily in areas distant to the central lesion core. A corresponding amelioration of brain swelling and attenuation of neurological deficits were evident. Similar protection against focal ischemic brain damage was evident when the adenosine deaminase inhibitor, deoxycoformycin (500 micrograms/kg), was administered prior to the onset of ischemia. However, with delayed (60 min) administration deoxycoformycin had no protective effect. These findings support the hypothesis that manipulation of adenosine catabolism can be an effective therapeutic approach to the prevention or treatment of brain injuries, such as those occurring during ischemic stroke or cardiac arrest.
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Affiliation(s)
- Y Lin
- Department of Physiology, Wayne State University, School of Medicine, Detroit, MI 48201
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25
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Padua RA, Geiger JD, Delaney SM, Nagy JI. Rat brain adenosine deaminase after 2'-deoxycoformycin administration: biochemical properties and evidence for reduced enzyme levels detected by 2'-[3H]deoxycoformycin ligand binding. J Neurochem 1992; 58:421-9. [PMID: 1729390 DOI: 10.1111/j.1471-4159.1992.tb09739.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Near total inhibition of brain adenosine deaminase (ADA) activity in rats injected with the potent ADA inhibitor 2'-deoxycoformycin (DCF) was previously shown to reduce enzyme activity for up to 50 days during which time the enzyme exhibited reduced sensitivity to in vivo inhibition by DCF. Here, we investigated the biochemical properties of ADA and the basis for its reduced activity after DCF treatment. It was found that much higher doses of DCF were required to inhibit ADA in DCF-treated compared with drug-naive animals. Fourteen days after DCF administration, reduced ADA activity in brain homogenates was due to a decrease in Vmax, rather than to an altered Km of ADA for adenosine. DCF treatment had no effect on Ki values for erythro-9-(2-hydroxy-3-nonyl)adenine inhibition of ADA. The IC50 value for DCF inhibition of ADA in hypothalamus was unchanged. However, the Ki for DCF inhibition of ADA in whole brain increased by fivefold. Sucrose gradient analysis of brain ADA revealed only one corresponding peak of activity and [3H]DCF-labeled ADA in DCF-treated and control rats. A radioligand filtration assay with [3H]DCF was developed to assess the effects of DCF on ADA protein levels. Over a roughly 200-fold range of ADA activities the binding of [3H]DCF was highly correlated with deaminase activity (r = 0.99). In brain tissues taken 8 and 33 days after treatment of rats with DCF, [3H]DCF binding was reduced to 27% and 48% of control levels, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- R A Padua
- Department of Pharmacology, University of Manitoba, Faculty of Medicine, Winnipeg, Canada
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26
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Phillis JW, O'Regan MH, Perkins LM. Measurement of rat plasma adenosine levels during normoxia and hypoxia. Life Sci 1992; 51:PL149-52. [PMID: 1528087 DOI: 10.1016/0024-3205(92)90363-t] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A stop solution containing EDTA, EGTA, dipyridamole, erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA) and d,l-alpha-glycerophosphate has been used to prevent adenosine formation and loss from rat femoral arterial blood samples prepared for measurement of plasma adenosine levels. The femoral arterial plasma adenosine concentration in normoxic rats was 79.2 +/- 12.7 nM. During a 5 min period of hypoxia (8% oxygen) plasma adenosine increased to 190.2 +/- 32.2 nM. A resting plasma adenosine level of circa 80 nM, which is 10X lower than most previous estimates, approximates the threshold levels of adenosine required for arterial dilation.
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Affiliation(s)
- J W Phillis
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201
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27
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Phillis JW, Walter GA, Simpson RE. Brain adenosine and transmitter amino acid release from the ischemic rat cerebral cortex: effects of the adenosine deaminase inhibitor deoxycoformycin. J Neurochem 1991; 56:644-50. [PMID: 1671090 DOI: 10.1111/j.1471-4159.1991.tb08198.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The effects of a potent adenosine deaminase inhibitor, deoxycoformycin, on purine and amino acid neuro-transmitter release from the ischemic rat cerebral cortex were studied with the cortical cup technique. Cerebral ischemia (20 min) was elicited by four-vessel occlusion. Purine and amino acid releases were compared from control ischemic animals and deoxycoformycin-pretreated ischemic rats. Ischemia enhanced the release of glutamate, aspartate, and gamma-aminobutyric acid into cortical perfusates. The levels of adenosine, inosine, hypoxanthine, and xanthine in the same perfusates were also elevated during and following ischemia. Deoxycoformycin (500 micrograms/kg) enhanced ischemia-evoked release of adenosine, indicating a marked rise in the adenosine content of the interstitial fluid of the cerebral cortex. Inosine, hypoxanthine, and xanthine levels were depressed by deoxycoformycin. Deoxycoformycin pretreatment failed to alter the pattern of amino acid neurotransmitter release from the cerebral cortex in comparison with that observed in control ischemic animals. The failure of deoxycoformycin to attenuate amino acid neurotransmitter release, even though it markedly enhanced adenosine levels in the extracellular space, implies that the amino acid release during ischemia occurs via an adenosine-insensitive mechanism. Inhibition of excitotoxic amino acid release is unlikely to be responsible for the cerebroprotective actions of deoxycoformycin in the ischemic brain.
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Affiliation(s)
- J W Phillis
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201
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28
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Phillis JW, Simpson RE, Walter GA. The effect of hyperglycemia on extracellular levels of adenosine in the hypoxic rat cerebral cortex. Brain Res 1990; 524:336-8. [PMID: 2292016 DOI: 10.1016/0006-8993(90)90712-k] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The levels of adenosine in rat cerebral cortical superfusates were studied in rats prior to, and after, the administration of saline or D-glucose (3 g/kg). Hypoxia-evoked increases in purine release were significantly attenuated after glucose administration. After glucose administration, the falls in arterial blood pressure, which normally accompany systemic hypoxia, were reduced. To ensure that this was not the reason for the decrease in adenosine release, blood was withdrawn from a second group of hyperglycemic rats so that the post-glucose hypoxia was equivalent to the original control. Adenosine release was still significantly attenuated. This decrease in the levels of adenosine, a cerebroprotective agent, in the cerebral cortical extracellular space, may be a contributing factor to the detrimental effects of hyperglycemia on recovery from cerebral ischemia.
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Affiliation(s)
- J W Phillis
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201
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29
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Dux E, Fastbom J, Ungerstedt U, Rudolphi K, Fredholm BB. Protective effect of adenosine and a novel xanthine derivative propentofylline on the cell damage after bilateral carotid occlusion in the gerbil hippocampus. Brain Res 1990; 516:248-56. [PMID: 2364291 DOI: 10.1016/0006-8993(90)90925-2] [Citation(s) in RCA: 144] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The role of adenosine in the development of ischemia induced pathological changes has been examined in Mongolian gerbils. A dramatic increase in the concentrations of adenosine, inosine and hypoxanthine was detected by microdialysis in the dorsal part of hippocampus and in the striatum immediately after 5 min bilateral occlusion of the carotid arteries. From a resting value of about 0.5 microM the concentration of adenosine increased to more than 10 microM. The adenosine levels became normalized within 30 min after ischemia. Inosine and hypoxanthine levels were higher and they increased and also returned towards control somewhat later than adenosine. A second occlusion resulted in a similar but somewhat smaller increase in purine levels. Carotid occlusion for up to 12 min had no major, lasting effect on the binding to adenosine A1-receptors in the CA-regions of the hippocampus, as determined by autoradiography. Neuronal and vascular changes (degeneration of neurons, mitochondrial destruction and ribosomal disaggregation, astroglial oedema) due to ischemia (3-12 min, followed by 48 h recirculation) was studied with light and electron microscopy in the selectively vulnerable CA1 area of hippocampus. In one series of experiments the adenosine antagonist theophylline (20 mg/kg i.p.), given 15 min prior to a 5 min occlusion, significantly enhanced the ischemia induced changes. In another experiment the adenosine uptake inhibitor propentofylline (HWA 285, 10 mg/kg), injected 15 min before a 12 min carotid occlusion, reduced the neuronal (90%) and astroglial changes (84%) due to ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- E Dux
- Laboratory of Molecular Neurobiology, Institute of Biophysics, Biological Research Center, Szeged, Hungary
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30
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Phillis JW, Walter GA. Effect of a brief hypoxic/hypotensive episode on the in vivo release of cerebral cortical gamma-aminobutyric acid and glycine. Brain Res 1989; 504:121-3. [PMID: 2598006 DOI: 10.1016/0006-8993(89)91606-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
gamma-Aminobutyric acid (GABA) and glycine levels in rat cerebral cortical superfusates rose during a 10-min period to reach stable concentrations of approximately 0.55 microM and approximately 12.3 microM, respectively. In cerebrospinal fluid withdrawn from the fourth ventricle, the GABA concentration was 0.1 microM, and that of glycine, 10.55 microM. GABA, and to a lesser extent glycine, concentrations increased in the cortical superfusates during and immediately following exposure of the rats to a 5-min period of 5% oxygen in nitrogen inhalation.
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Affiliation(s)
- J W Phillis
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201
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31
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Abstract
Oxypurinol, an inhibitor of the enzyme xanthine oxidase, reduced ischemic hippocampal damage and the associated hypermotility in Mongolian gerbils. Cerebral ischemia was induced in unanesthetized gerbils by a bilateral 5-min occlusion of the carotid arteries. Oxypurinol (40 mg/kg, IP), administered 20 min prior to carotid occlusion, prevented the increase in locomotor activity observed in saline-injected ischemic animals and significantly reduced the damage to, and loss of, CA1 hippocampal neurons observed 5 days postischemia. These findings suggest that oxypurinol may be useful for the prevention of cerebral ischemic damage.
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Affiliation(s)
- J W Phillis
- Department of Physiology, Wayne State University, School of Medicine, Detroit, MI 48201
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32
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Phillis JW, Walter GA. Hypoxia/hypotension evoked release of glutamate and aspartate from the rat cerebral cortex. Neurosci Lett 1989; 106:147-51. [PMID: 2573865 DOI: 10.1016/0304-3940(89)90217-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Glutamate and aspartate levels in cerebral cortical superfusates rose rapidly after introduction of artificial cerebrospinal fluid into cortical cups to reach stable levels within 5-10 min. These equilibrated levels (glutamate 1.33 +/- 0.1 microM; aspartate 0.29 +/- 0.04 microM), which are very similar to those in fourth ventricular CSF (glutamate, 1.5 +/- 0.2 microM; aspartate, 0.27 +/- 0.03 microM), are likely to reflect basal interstitial amino acid levels in the superficial layers of the cortex. During and following brief (5 min) hypoxemic/hypotensive episodes, release of both excitatory amino acids into the cortical superfusates was enhanced. The finding of an hypoxia/hypotension-evoked release of excitatory amino acids is consistent with recent speculation that these agents may play an important role in the destruction of neurons in ischemic regions of the brain.
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Affiliation(s)
- J W Phillis
- Department of Physiology, School of Medicine, Wayne State University, Detroit, MI 48201
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33
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Abstract
Deoxycoformycin, a potent and specific adenosine deaminase antagonist, reduced ischemic hippocampal damage and the associated hypermotility in Mongolian gerbils. Cerebral ischemia was induced by a bilateral 5 min occlusion of the carotid arteries. Deoxycoformycin (500 micrograms/kg IP), administered 15 min prior to ischemia, prevented the increase in locomotor activity normally observed with this model and significantly reduced the ischemia-induced damage to CA1 hippocampal neurons. The results suggest that deoxycoformycin may be useful in the prevention of brain damage due to cerebral ischemia.
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Affiliation(s)
- J W Phillis
- Department of Physiology, Wayne State University, School of Medicine, Detroit, MI 48201
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