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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: 88] [Impact Index Per Article: 11.0] [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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Castillo CA, León D, Ruiz MA, Albasanz JL, Martín M. Modulation of adenosine A1 and A2A receptors in C6 glioma cells during hypoxia: involvement of endogenous adenosine. J Neurochem 2010; 105:2315-29. [PMID: 18315561 DOI: 10.1111/j.1471-4159.2008.05314.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
During hypoxia, extracellular adenosine levels are increased to prevent cell damage, playing a neuroprotective role mainly through adenosine A(1) receptors. The aim of the present study was to analyze the effect of hypoxia in both adenosine A(1) and A(2A) receptors endogenously expressed in C6 glioma cells. Two hours of hypoxia (5% O(2)) caused a significant decrease in adenosine A(1) receptors. The same effect was observed at 6 h and 24 h of hypoxia. However, adenosine A(2A) receptors were significantly increased at the same times. These effects were not due to hypoxia-induced alterations in cells number or viability. Changes in receptor density were not associated with variations in the rate of gene expression. Furthermore, hypoxia did not alter HIF-1alpha expression in C6 cells. However, HIF-3alpha, CREB and CREM were decreased. Adenosine A(1) and A(2A) receptor density in normoxic C6 cells treated with adenosine for 2, 6 and 24 h was similar to that observed in cells after oxygen deprivation. When C6 cells were subjected to hypoxia in the presence of adenosine deaminase, the density of receptors was not significantly modulated. Moreover, DPCPX, an A(1) receptor antagonist, blocked the effects of hypoxia on these receptors, while ZM241385, an A(2A) receptor antagonist, was unable to prevent these changes. These results suggest that moderate hypoxia modulates adenosine receptors and cAMP response elements in glial cells, through a mechanism in which endogenous adenosine and tonic A(1) receptor activation is involved.
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Affiliation(s)
- Carlos A Castillo
- Departamento de Química Inorgánica, Orgánica y Bioquímica, Facultad de Químicas, Centro Regional de Investigaciones Biomédicas, Universidad de Castilla-La Mancha, Ciudad Real, Spain
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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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Phillis JW, O'Regan MH. In vivo studies of the release of adenine 5?-nucleotides, adenosine, and its metabolites from the rat brain. Drug Dev Res 2003. [DOI: 10.1002/ddr.10173] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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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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Feng JD, Yeung PK. A simple high-performance liquid chromatography assay for simultaneous measurement of adenosine, guanosine, and the oxypurine metabolites in plasma. Ther Drug Monit 2000; 22:177-83. [PMID: 10774630 DOI: 10.1097/00007691-200004000-00007] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
To study the effect of pharmacologic agents on the biologic fate of adenosine, a reversed-phase high-performance liquid chromatography (HPLC) assay coupled with a solid-phase extraction (SPE) method was developed for simultaneous determination of plasma adenosine, hypoxanthine, xanthine, inosine, guanosine, and uric acid. The HPLC system consisted of a reversed phase C18 column, UV detector set at 254 nm, and a mobile phase composed of 0.01 M ammonium phosphate: methanol (9.5 : 0.5) vol/vol with the final pH adjusted to 3.9. The standard curves were linear between 0.1-2 microg/mL for all the analytes (except uric acid 50-400 microg/mL), with r2 > 0.99. The absolute recoveries were >60% and accuracy >85% in almost all cases. The limit of detection was <1 ng based on absolute injection of the analytes. The intraassay variations were <10% and interassay variations <15%. The presence of a wide range of medications in plasma samples did not interfere with the assay. The assay was applied successfully to measure plasma adenosine and the oxypurine metabolites in humans and rats. It was noted that plasma concentrations of adenosine and the oxypurine metabolites can vary considerably depending on the method of blood sample collection, and that species differences are apparent.
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Affiliation(s)
- J D Feng
- Pharmacokinetics and Metabolism Laboratory, College of Pharmacy Faculty of Health Professions, Dalhousie University, Halifax, Nova Scotia, Canada
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Yeung PK, Buckley SJ, Hung OR, Pollak PT, Barclay KD, Feng JD, Klassen GA. Effect of diltiazem on plasma concentrations of oxypurines and uric acid. Ther Drug Monit 1997; 19:286-91. [PMID: 9200769 DOI: 10.1097/00007691-199706000-00008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
To determine the clinical effect of diltiazem on the metabolism of adenosine, and its importance in ischemic heart disease, arterial plasma concentrations of the purine metabolites were determined in 21 healthy volunteers (10 female and 11 male) and 19 patients with effort angina (8 female and 11 male) before, during, and immediately after standard treadmill exercise tests conducted before and after they had taken 60 mg diltiazem (Cardizem; Hoechst Marion Roussel, Laval, QC, Canada) four times a day for 1 week. The results showed that the cardiac patients had significantly lower mean plasma concentrations of uric acid (46.82 +/- 25.51 versus 95.47 +/- 35.41 micrograms/ml, p 0.05), inosine (0.25 +/- 0.19 versus 0.84 +/- 0.17 microgram/ml, p < 0.05), and hypoxanthine (0.28 +/- 0.35 versus 0.50 +/- 0.27 microgram/ml, p < 0.05). Diltiazem decreased the mean resting plasma concentrations of uric acid in patients (uric acid 43.47 +/- 22.26 versus 46.82 +/- 25.51 micrograms/ml, p < 0.05) and healthy volunteers (uric acid 85.68 +/- 26.71 versus 95.47 +/- 35.41 micrograms/ml, p < 0.05). There was no statistically significant change in the plasma concentrations of the purine metabolites during exercise (p < 0.05). Female subjects had significantly lower plasma concentrations of uric acid than males (patients, 34.87 +/- 26.93 versus 55.78 +/- 21.25 micrograms/ml; healthy volunteers, 84.79 +/- 32.07 versus 104.22 +/- 37.05 micrograms/ml; p < 0.05 for both). Results of the study suggest that normal therapeutic doses of diltiazem may modulate the metabolism of adenosine and that some of the purine metabolites may be useful markers for specific types of ischemic heart disease.
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Affiliation(s)
- P K Yeung
- College of Pharmacy, Department of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada
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de Carvalho RP, Braas KM, Adler R, Snyder SH. Developmental regulation of adenosine A1 receptors, uptake sites and endogenous adenosine in the chick retina. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1992; 70:87-95. [PMID: 1473280 DOI: 10.1016/0165-3806(92)90106-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Although adenosine A1 receptors mediate the inhibition of dopamine-dependent stimulation of adenylate cyclase activity in the developing chick retina, their localization and function are unknown. We have examined the localization of these receptors, and of endogenous adenosine and adenosine uptake sites at several stages of chick retinal development. A1 receptors were already localized predominantly to plexiform regions by embryonic day 12 (E12) with no gross changes at subsequent stages. Adenosine immunoreactivity was absent from retina at E8 but was detected at E12 in the ganglion cell layer, as well as cells in the inner nuclear cell layer and photoreceptors. At more advanced developmental stages the immunoreactivity was greater, but displayed similar localizations. Uptake sites labeled with [3H]nitrobenzylthioinosine (NBI) were detected even earlier using binding and autoradiographic methods. [3H]NBI binding was saturable, and Scatchard analysis demonstrated a single class of sites with a Kd of 0.91 nM and Bmax of 298 fmol/mg protein in E15 retinal membranes. The binding was displaced by unlabeled NBI and dipyridamole. NBI binding sites differentiated earlier than adenosine A1 receptors or endogenous adenosine immunoreactivity, showing a diffuse distribution at E8, but predominating in the plexiform layers of more developed retinas. The results indicate that elements of a putative purinergic system differentiate at specific localizations early in retinal development.
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Affiliation(s)
- R P de Carvalho
- Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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Paes de Carvalho R, Braas KM, Snyder SH, Adler R. Analysis of adenosine immunoreactivity, uptake, and release in purified cultures of developing chick embryo retinal neurons and photoreceptors. J Neurochem 1990; 55:1603-11. [PMID: 2213012 DOI: 10.1111/j.1471-4159.1990.tb04945.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
We have investigated the presence of endogenous adenosine and of mechanisms for adenosine uptake and release in chick embryo retinal neurons and photoreceptors grown in purified cultures in the absence of glial cells. Simultaneous autoradiographic and immunocytochemical analysis showed that endogenous adenosine and the uptake mechanism for this nucleoside colocalize in practically all the photoreceptors, but only in approximately 20% of the neurons. Approximately 25% of the neurons showed either immunocytochemical labeling or autoradiographic labeling, while greater than 50% of the neurons were unlabeled with both techniques. [3H]Adenosine uptake was saturable and could be inhibited by nitrobenzylthioinosine and dipyridamole and by pretreatment of the [3H]adenosine with adenosine deaminase. Although these observations indicate that the uptake is specific for adenosine, only 35% of accumulated radioactivity was associated with adenosine, with the remaining 65% representing inosine, hypoxanthine, and nucleotides plus uric acid. Adenosine as well as several of its metabolites were released by the cells under basal as well as K(+)-stimulated conditions. Potassium-enhanced release was blocked by 10 mM CoCl2 or in Ca2(+)-free, Mg2(+)-rich solutions. The results indicate that retinal cells that synthesize, store, and release adenosine differentiate early during embryogenesis and are therefore consistent with a hypothetical role for adenosine in retinal development.
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Affiliation(s)
- R Paes de Carvalho
- Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, Maryland
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O'Regan MH, Kocsis JD, Waxman SG. Depolarization-dependent actions of dihydropyridines on synaptic transmission in the in vitro rat hippocampus. Brain Res 1990; 527:181-91. [PMID: 1701335 DOI: 10.1016/0006-8993(90)91136-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Field potential and intracellular recordings were obtained in the in vitro hippocampal slice to study the effects on synaptic transmission of dihydropyridine (DHP) derivatives. Nimodipine or nifedipine by itself had little effect upon the postsynaptic response as determined by field potential analysis. However, facilitation became evident when DHP application was coupled with manipulations which induced a moderate degree of membrane depolarization. In accordance with the hydrophobic nature of these compounds, extensive washing in normal Krebs' solution failed to reverse the facilitation indicating that the DHP effects outlasted the induced depolarization. Nifedipine is photolabile and its actions were reversed when intense light was applied to the slice. Application of the DHP Bay K 8644, resulted in a similar depolarization-dependent increase in neuronal excitability which, upon washout and exposure to light, was at first attenuated and then reversed, resulting in a long-lasting depression of the EPSP that was sensitive to caffeine. This depressant action of Bay K 8644 appeared to be mediated at a site presynaptic to the pyramidal cell because the postsynaptic component of the field potential response to pulsed applications of glutamate was not altered. Intracellular recording from CA1 neurons supports a presynaptic locus for the depressant actions of Bay K 8644; spike threshold for synaptically evoked responses was greatly increased while spike threshold to direct depolarization of the soma was unchanged. These results indicate that DHPs can exert effects on synaptic transmission in hippocampal brain slice under conditions of moderate membrane depolarization.
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Affiliation(s)
- M H O'Regan
- Department of Neurology, Yale University School of Medicine, New Haven, CT
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Shank RP, Baldy WJ. Adenosine transport by rat and guinea pig synaptosomes: basis for differential sensitivity to transport inhibitors. J Neurochem 1990; 55:541-50. [PMID: 2370550 DOI: 10.1111/j.1471-4159.1990.tb04168.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Adenosine transport by rat and guinea pig synaptosomes was studied to establish the basis for the marked differences in the potency of some transport inhibitors in these species. An analysis of transport kinetics in the presence and absence of nitrobenzylthioinosine (NBTI) using synaptosomes derived from several areas of rat and guinea pig brain indicated that at least three systems contributed to adenosine uptake, the Km values of which were approximately 0.4, 3, and 15 microM in both species. In both species, the system with the Km of 3 microM was potently (IC50 of approximately 0.3 nM) and selectively inhibited by NBTI. This NBTI-sensitive system accounted for a greater proportion of the total uptake in the guinea pig than in the rat and was inhibited by dipyridamole, mioflazine, and related compounds more potently in the guinea pig. Preliminary experiments with other species indicate that adenosine transport in the mouse is similar to that in the rat, whereas in the dog and rabbit, it is more like that in the guinea pig. In the rat, none of the systems appeared to require Na+, but the two systems possessing the higher affinities for adenosine were inhibited by veratridine- and K(+)-induced depolarization. The transport systems were active over a broad pH range, with maximal activity between pH 6.5 and 7.0. Our results are consistent with the possibility that adenosine transport systems may be differentiated into uptake and release systems.
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Affiliation(s)
- R P Shank
- Department of Biological Research, Janssen Research Foundation, Spring House, Pennsylvania 19477-0776
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Pickard JD, Murray GD, Illingworth R, Shaw MD, Teasdale GM, Foy PM, Humphrey PR, Lang DA, Nelson R, Richards P. Effect of oral nimodipine on cerebral infarction and outcome after subarachnoid haemorrhage: British aneurysm nimodipine trial. BMJ (CLINICAL RESEARCH ED.) 1989; 298:636-42. [PMID: 2496789 PMCID: PMC1835889 DOI: 10.1136/bmj.298.6674.636] [Citation(s) in RCA: 713] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
OBJECTIVE To determine the efficacy of oral nimodipine in reducing cerebral infarction and poor outcomes (death and severe disability) after subarachnoid haemorrhage. DESIGN Double blind, placebo controlled, randomised trial with three months of follow up and intention to treat analysis. To have an 80% chance with a significance level of 0.05 of detecting a 50% reduction in an incidence of cerebral infarction of 15% a minimum of 540 patients was required. SETTING Four regional neurosurgical units in the United Kingdom. PATIENTS In all 554 patients were recruited between June 1985 and September 1987 out of a population of 1115 patients admitted with subarachnoid haemorrhage proved by the results of lumbar puncture or computed tomography, or both. The main exclusion criterion was admission to the neurosurgical units more than 96 hours after subarachnoid haemorrhage. There were four breaks of code and no exclusions after entry. One patient was withdrawn and in 130 treatment was discontinued early. All patients were followed up for three months and were included in the analysis, except the patient who had been withdrawn. INTERVENTIONS Placebo or nimodipine 60 mg was given orally every four hours for 21 days to 276 and 278 patients, respectively. Treatment was started within 96 hours after subarachnoid haemorrhage. END POINTS Incidence of cerebral infarction and ischaemic neurological deficits and outcome three months after entry. MEASUREMENTS Demographic and clinical data, including age, sex, history of hypertension and subarachnoid haemorrhage, severity of haemorrhage according to an adaptation of the Glasgow coma scale, number and site of aneurysms on angiography, and initial findings on computed tomography were measured at entry. Deterioration, defined as development of a focal sign or fall of more than one point on the Glasgow coma scale for more than six hours, was investigated by using clinical criteria and by computed tomography, by lumbar puncture, or at necropsy when appropriate. All episodes of deterioration and all patients with a three month outcome other than a good recovery were assessed by a review committee. MAIN RESULTS Demographic and clinical data at entry were similar in the two groups. In patients given nimodipine the incidence of cerebral infarction was 22% (61/278) compared with 33% (92/276) in those given placebo, a significant reduction of 34% (95% confidence interval 13 to 50%). Poor outcomes were also significantly reduced by 40% (95% confidence interval 20 to 55%) with nimodipine (20% (55/278) in patients given nimodipine v 33% (91/278) in those given placebo). CONCLUSIONS Oral nimodipine 60 mg four hourly is well tolerated and reduces cerebral infarction snd improves outcome after subarachnoid haemorrhage.
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Affiliation(s)
- J D Pickard
- Wessex Neurological Centre, Southampton General Hospital
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Phillis JW, O'Regan MH, Walter GA. Effects of two nucleoside transport inhibitors, dipyridamole and soluflazine, on purine release from the rat cerebral cortex. Brain Res 1989; 481:309-16. [PMID: 2720383 DOI: 10.1016/0006-8993(89)90808-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The effects of two nucleoside transport inhibitors, dipyridamole and soluflazine, on adenosine, inosine and oxypurine release from the normoxic and hypoxic/ischemic rat cerebral cortex have been studied. Dipyridamole (500 micrograms/kg) enhanced adenosine release during hypoxic/ischemic challenges in comparison with saline-injected controls. It decreased the hypoxia/ischemia-elicited releases of inosine, hypoxanthine and xanthine. Both basal and hypoxia/ischemia-elicited releases of uric acid were elevated. Soluflazine, administered topically or systemically, failed to enhance adenosine release and did not consistently alter the hypoxia/ischemia-evoked releases of inosine, hypoxanthine and xanthine. Basal release of uric acid was elevated. The failure of either drug to elevate the basal or hypoxia/ischemia-evoked releases of adenosine above predrug levels illustrates one of the problems which may be inherent in the use of bidirectional nucleoside transport inhibitors for the manipulation of adenosine levels in the cerebral interstitial fluid.
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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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