cyclic-gmp and Astrocytoma

The brain as well as other mammalian tissues contains several different forms of cyclic nucleotide phosphodiesterase separable by polyacrylamide gel electrophoresis. Each tissue and each individual type of cell has its own distinctive pattern and ratio of these multiple forms of phosphodiesterase. The different forms have several distinguishing properties and characteristics, and their activities may be differentially regulated both acutely and chronically. The enzyme forms have different stabilities, kinetic properties, substrate specificities, and sensitivities to an endogenous activator and to several inhibitors of phosphodiesterase. The phosphodiesterase inhibitors studied not only inhibit the different forms of phosphodiesterase to different degrees but apparently do so by different mechanisms. Thus whereas theophylline, cyclic GMP, and low concentrations of papaverine inhibit the phosphodiesterases by competing with the substrate (cyclic AMP), trifluoperazine apparently inhibits phosphodiesterase by interfering with the phosphodiesterase activator. This confers a great deal of specificity to this drug, since only one form of phosphodiesterase is markedly activated by the activator. Chronically, a specific form of phosphodiesterase appears to be inducible. This induction is probably controlled by the intracellular cyclic AMP concentration. The phosphodiesterase activator also appears to be regulatable, the age of the animal being one of the factors controlling its activity. Finally, since different types of cells have different relative amounts of the phosphodiesterases and since these forms of the enzyme can be differentially inhibited by drugs, it may be possible to develop drugs which will selectively increase the cyclic AMP concentration in discrete cell types. Evidence that cyclic AMP is involved in certain disease states suggests further that by selectively altering the concentration of cyclic AMP in these cells, one might be able to alter the course of the disease.

Topics: Adenylyl Cyclases; Animals; Astrocytoma; Brain; Cyclic AMP; Cyclic GMP; Enzyme Activation; Isoenzymes; Kinetics; Nerve Tissue Proteins; Neuroblastoma; Organ Specificity; Papaverine; Phosphoric Diester Hydrolases; Rats; Trifluoperazine

Angiogenesis is a prerequisite for tumour progression and is highly regulated by growth factors and cytokines a number of which also stimulate the production of nitric oxide. Asymmetric dimethylarginine is an endogenous inhibitor of nitric oxide synthesis. Asymmetric dimethylarginine is metabolised by dimethylarginine dimethylaminohydrolase. To study the effect of dimethylarginine dimethylaminohydrolase on tumour growth and vascular development, the rat C6 glioma cell line was manipulated to overexpress the rat gene for dimethylarginine dimethylaminohydrolase I. Enhanced expression of dimethylarginine dimethylaminohydrolase I increased nitric oxide synthesis (as indicated by a two-fold increase in the production of cGMP), expression and secretion of vascular endothelial cell growth factor, and induced angiogenesis in vitro. Tumours derived from these cells grew more rapidly in vivo than cells with normal dimethylarginine dimethylaminohydrolase I expression. Immunohistochemical and magnetic resonance imaging measurements were consistent with increased tumour vascular development. Furthermore, dimethylarginine dimethylaminohydrolase activity was detected in a series of human tumours. This data demonstrates that dimethylarginine dimethylaminohydrolase plays a pivotal role in tumour growth and the development of the tumour vasculature by regulating the concentration of nitric oxide and altering vascular endothelial cell growth factor production.

Topics: Amidohydrolases; Animals; Astrocytoma; Blotting, Northern; Blotting, Western; Brain Neoplasms; Cell Division; Cell Movement; Cells, Cultured; Cyclic GMP; DNA Primers; Endothelial Growth Factors; Endothelium, Vascular; Enzyme-Linked Immunosorbent Assay; Female; Glioblastoma; Glioma; Humans; Lymphokines; Mice; Mice, Nude; Neoplasm Transplantation; Neoplasms, Experimental; Neovascularization, Pathologic; Nitric Oxide; Rats; Reverse Transcriptase Polymerase Chain Reaction; Transfection; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

Intracellular Ca(2+) mobilization and release into mammal CSF plays a fundamental role in the etiogenesis of fever induced by the proinflammatory cytokine interleukin-1beta (IL-1beta) and other pyrogens. The source and mechanism of IL-1beta-induced intracellular Ca(2+) mobilization was investigated using two experimental models. IL-1beta (10 ng/ml) treatment of rat striatal slices preloaded with (45)Ca(2+) elicited a delayed (30 min) and sustained increase (125-150%) in spontaneous (45)Ca(2+) release that was potentiated by l-arginine (300 microm) and counteracted by N-omega-nitro-l-arginine methyl ester (l-NAME) (1 and 3 mm). The nitric oxide (NO) donors diethylamine/NO complex (sodium salt) (0.3 and 1 mm) and spermine/NO (0.1 and 0.3 mm) mimicked the effect of IL-1beta on Ca(2+) release. IL-1beta stimulated tissue cGMP concentration, and dibutyryl cGMP enhanced Ca(2+) release. The guanyl cyclase inhibitors 1H-[1,2, 4]oxadiazole[4,3-a] quinoxalin-1-one (100 microm) and 6-[phenylamino]-5,8 quinolinedione (50 microm) counteracted Ca(2+) release induced by 2.5 but not 10 ng/ml IL-1beta. Ruthenium red (50 microm) and, to a lesser extent, heparin (3 mg/ml) antagonized IL-1beta-induced Ca(2+) release, and both compounds administered together completely abolished this response. Similar results were obtained in human astrocytoma cells in which IL-1beta elicited a delayed (30 min) increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) (402 +/- 71.2% of baseline), which was abolished by 1 mm l-NAME. These data indicate that the NO/cGMP-signaling pathway is part of the intracellular mechanism transducing IL-1beta-evoked Ca(2+) mobilization in glial and striatal cells and that the ryanodine and the inositol-(1,4,5)-trisphosphate-sensitive Ca(2+) stores are involved.

Topics: Aminoquinolines; Animals; Arginine; Astrocytoma; Calcium; Corpus Striatum; Cyclic GMP; Dibutyryl Cyclic GMP; Dose-Response Relationship, Drug; Enzyme Inhibitors; Guanylate Cyclase; Heparin; Humans; Hydrazines; In Vitro Techniques; Interleukin-1; Intracellular Fluid; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Donors; Nitrogen Oxides; Oxadiazoles; Quinoxalines; Rats; Rats, Sprague-Dawley; Ruthenium Red; Spermine; Tumor Cells, Cultured

The role of the L-arginine-NO pathway on the formation of PGE2 by human cultured astroglial cells incubated with NMDA has been investigated. Preincubation of T 67 astroglial cell line with NMDA (10-600 microM) produced a significant dose-dependent increase of both nitrite (the breakdown product of NO), PGE2 and cGMP levels in cell supernatant. This effect was inhibited by coincubation of cells with L-NAME (20-300 microM), an inhibitor of NO synthase showing that the release of PGE2 subsequent to NMDA receptor stimulation was driven by NO. The release of PGE2 but not elevation of nitrite and cGMP levels was affected by indomethacin (10 microM), an inhibitor of cyclooxygenase. The inhibitory effect of L-NAME on PGE2 release by NMDA-pretreated astroglial cells was reverted by arachidonic acid, showing that the effect of NO on PGE2 release occurred at the cyclo-oxygenase level. Thus, the present experiments demonstrate that the release of PGE2 by astroglial cells pretreated with NMDA is driven by activation of the L-arginine-NO pathway, and this may be relevant in the pathophysiological mechanisms where glutamatergic neurotransmission is involved.

Topics: Arachidonic Acid; Arginine; Astrocytes; Astrocytoma; Cell Line; Cyclic GMP; Dinoprostone; Dose-Response Relationship, Drug; Enzyme Inhibitors; Humans; Kinetics; N-Methylaspartate; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitrites; Nitroprusside; Oxyhemoglobins; Receptors, N-Methyl-D-Aspartate; Tumor Cells, Cultured

Methylene blue (MB), a known inhibitor of guanylyl cyclase, induced cytotoxicity in SK-N-MC human neuroblastoma and U-373 MG human astrocytoma cells in a dose-dependent manner. MB did not significantly alter cellular levels of cGMP in both cells. 8-Br cGMP, a membrane-permeable analogue of cGMP, did not decrease MB-induced cytotoxicity, indicating that cGMP may not be a major target of the cytotoxic action of MB. However, hydroxyl radical scavengers or intracellular Ca2+ modulators effectively blocked the MB-induced cytotoxicity. These results suggest that hydroxyl radical and intracellular Ca2+ may have an important involvement in the cytotoxic action of MB. These results further suggest that the treatment with MB may be useful for the therapeutic applications of human brain tumors.

Topics: Astrocytoma; Brain Neoplasms; Calcium; Cell Division; Cyclic GMP; Humans; Intracellular Fluid; Kinetics; Methylene Blue; Neuroblastoma; Reactive Oxygen Species; Tumor Cells, Cultured

Inflammatory cytokines (interleukin 1 alpha, 1 beta and tumor necrosis factor-alpha) induce the formation of nitrite by C6 astrocytoma cells in a manner that was blocked by inhibitors of NO synthase such as NG-monomethylarginine. They increase the formation of cGMP. This action was potentiated by isobutylmethylxanthine and was inhibited by NG-monomethylarginine. Interleukin-6 and interferon-gamma were inactive. It is concluded that the nitridergic signalling pathway is active in C6 cells and is a major target for inflammatory cytokines.

Topics: 1-Methyl-3-isobutylxanthine; Arginine; Astrocytoma; Cyclic GMP; Interleukin-1; Nitrites; omega-N-Methylarginine; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha

The present studies were performed in order to examine the possible role of cyclic GMP-stimulated phosphodiesterase (cGMP-PDE) activity in the inhibitory action of the inflammatory peptide bradykinin on cyclic AMP (cAMP) accumulation in D384 cells. Bradykinin decreased the forskolin-stimulated cAMP accumulation in the presence of the phosphodiesterase inhibitor rolipram, and caused a transient 50% rise in cellular cGMP in the presence of the nonselective PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX). Both basal and bradykinin-stimulated cGMP accumulation were about 8 times higher in the presence of IBMX than in the presence of rolipram. Sodium nitroprusside, which caused a 20-70-fold increase in cGMP levels reduced forskolin stimulated cAMP accumulation, whereas hydroxylamine, which maximally caused a 16-fold increase in cGMP, did not. 8-bromo-cGMP or dibutyryl cGMP had no effect on cAMP accumulation induced by forskolin. The inhibitory effect of nitroprusside was totally reversed by blocking the soluble guanylate cyclase activity by methylene blue treatment; however, the inhibitory action of bradykinin on cAMP accumulation was not changed by this treatment. Additionally, inhibition of nitric oxide synthesis, which is known to be regulated by Ca2+ and in turn stimulates cGMP production, by N omega-nitro-L-arginine (L-NAME) treatment did not alter the inhibitory effect of bradykinin on forskolin-induced cAMP accumulation. These results indicate that large increases in cGMP may regulate cAMP via cGMP-PDE whereas the small increase induced by bradykinin is insufficient and that cGMP is not involved in the inhibitory action of bradykinin on cAMP levels in D384 cells.

Topics: 1-Methyl-3-isobutylxanthine; Arginine; Astrocytoma; Bradykinin; Colforsin; Cyclic AMP; Cyclic GMP; Dose-Response Relationship, Drug; Humans; Hydroxylamine; Hydroxylamines; Kinetics; NG-Nitroarginine Methyl Ester; Nitroprusside; Pyrrolidinones; Rolipram; Tumor Cells, Cultured

1. The inhibitory activity of astrocytoma cells (0.25-3 x 10(5)) treated with indomethacin (10 microM) on platelet aggregation was enhanced by incubating the cells with E. coli lipopolysaccharide (LPS, 0.5 micrograms ml-1) for 18 h. This effect was attenuated when cycloheximide (10 micrograms ml-1) was incubated together with LPS. The inhibition of platelet aggregation by cells treated with LPS was potentiated by superoxide dismutase (60 u ml-1) and ablated by oxyhaemoglobin (oxyHb, 10 microM) or NG-monomethyl-L-arginine (L-NMMA, 30-300 microM). The effects of L-NMMA were reversed by co-incubation with L-arginine (L-Arg, 100 microM) but not D-arginine (D-Arg, 100 microM). LPS also increased the levels of nitrite in the culture media and this increase was ablated by co-incubation with L-NMMA (300 microM) or cycloheximide (10 micrograms ml-1). 2. Astrocytoma cells (0.5 x 10(5)) treated with indomethacin (10 microM) enhanced the platelet inhibitory activity of glyceryl trinitrate (GTN, 11-352 microM) but not that of sodium nitroprusside (4 microM). Furthermore, when incubated with GTN (200 microM) a 4 fold increase in the levels of guanosine 3':5'-cyclic monophosphate (cyclic GMP) was observed. These effects were abrogated by co-incubation with oxyHb (10 microM) but not with L-NMMA (300 microM). Treatment of the cells with LPS (0.5 micrograms ml-1) for 18 h did not enhance their capacity to form NO from GTN. 3. Thus, in cultured astrocytoma cells, LPS enhances the formation of nitric oxide from endogenous L-arginine.In addition, these cells can metabolize GTN to nitric oxide but this process is not enhanced by LPS stimulation.

Topics: Arginine; Astrocytoma; Cyclic GMP; Escherichia coli; Humans; Indomethacin; Lipopolysaccharides; Nitric Oxide; Nitroglycerin; omega-N-Methylarginine; Platelet Aggregation; Tumor Cells, Cultured

Sodium nitroprusside (SNP) stimulates cGMP formation to a greater extent in 20,000 g supernatant fractions of the human neuroblastoma clones NB1-G and SH-SY5Y than in the human astrocytoma clone D384. This suggests that these cell lines contain the soluble form of guanylate cyclase. Arachidonic, 8,11,14- and 11,14,17-eicosatrienoic acids inhibit SNP (10(-4) M)-stimulated cGMP formation more potently than the C18 unsaturated fatty acids linolenic and linoleic acids in D384 and NB1-G. In contrast the C20 saturated fatty acid, arachidic acid had little effect even at 10(-4) M concentration. In addition arachidonic and 8,11,14-eicosatrienoic acids inhibited basal guanylate cyclase activity, in NB1-G, over the same concentration range as they inhibited SNP-stimulated cGMP formation. No evidence could be obtained for the stimulation of guanylate cyclase by arachidonic acid in either NB1-G or D384. These results provide further support for suggestions that arachidonic acid or its metabolites may be important regulators of cGMP formation in the nervous system.

Topics: 8,11,14-Eicosatrienoic Acid; Arachidonic Acid; Arachidonic Acids; Astrocytoma; Cyclic GMP; Fatty Acids, Unsaturated; Ferricyanides; Guanylate Cyclase; Humans; Linoleic Acid; Linoleic Acids; Linolenic Acids; Neuroblastoma; Nitroprusside; Tumor Cells, Cultured

Specific high-affinity binding sites (dissociation constant 100 pmol/l) for atrial natriuretic peptide (ANP) have been identified in the clone D384 derived from the human astrocytoma cell line G-CCM. Unrelated peptides such as angiotensin II, vasopressin and bradykinin did not compete for these sites. Of the atrial natriuretic peptides studied, both the human and rat ANP competed equally, while peptides with either C- or N-terminal residue missing or with no internal -S-S-bond either competed less effectively or did not compete at all. Human ANP stimulated the cells to increase their intracellular level of cyclic GMP in a time- and dose-dependent manner with maximum stimulation being approached but not reached at concentrations of 1 mumol/l. These results support both the notion that ANP has an important functional role within the brain and the concept of neurotransmitter/neuromodulator communication between neurones and glia.

Topics: Astrocytoma; Atrial Natriuretic Factor; Binding Sites; Brain Neoplasms; Cyclic GMP; Humans; Receptors, Atrial Natriuretic Factor; Receptors, Cell Surface; Tumor Cells, Cultured

The effects of various neurotransmitters and cyclic nucleotides on 45Ca2+ efflux in cultured human glioma cells were investigated. Glutamate and glycine, but not GABA, stimulated 45Ca2+ release from the cells. Stimulation of beta-adrenergic receptors but not alpha-adrenergic receptors also increased 45Ca2+ efflux. Cholinergic receptor stimulation by carbachol had the same effect. The stimulatory effect of carbachol was abolished in the presence of either atropine or hexamethonium. C-AMP and c-GMP increased the 45Ca2+ efflux, suggesting that these agents are involved in the transmitter-stimulated release of 45Ca2+ from the cell. Kinetic analysis of the efflux revealed four calcium compartments. The carbachol-stimulated efflux represented a net release of calcium and could be ascribed to the slowest compartment. The physiological role of the transmitter-stimulated calcium release is discussed in terms of calcium-regulated stimulus-response coupling in glial-neural interaction during excitation.

Topics: Astrocytoma; Atropine; Calcium; Calcium Radioisotopes; Carbachol; Cells, Cultured; Cyclic AMP; Cyclic GMP; Glutamates; Glutamic Acid; Glycine; Hexamethonium; Hexamethonium Compounds; Humans; Neoplasms, Experimental; Nicotine; Norepinephrine; Oxotremorine; Prostaglandins E; Time Factors

Topics: Astrocytoma; Brain Neoplasms; Cyclic AMP; Cyclic GMP; Glioblastoma; Glioma; Humans; Meningeal Neoplasms; Meningioma

Studies on the level of cyclic nucleotides (cAMP and cGMP) in human and animal glial tumours showed that the content of both nucleotides, especially that of cAMP, decreases in all the tumours. The cAMP/cGMP ratio also drops down. Concurrently it appears to be the most consistent parameter of nucleotide metabolism both in brain tissue and in human or animal glial tumours. The growing tumour affects cAMP and cGMP metabolism not only in the involved but also in the other hemisphere. No principal differences between human and animal tumours have been revealed in the content of cyclic nucleotides and its variation in tumour tissue.

Topics: Animals; Astrocytoma; Cerebellar Cortex; Cerebral Cortex; Cyclic AMP; Cyclic GMP; Glioblastoma; Humans; Neoplasms, Experimental; Rabbits; Rats; Species Specificity

C-6 glial tumor cells treated with norepinephrine and sodium azide accumulated cyclic GMP to concentrations approximately 10-fold greater than the sum of the separate responses. Isoproterenol, but not phenylephrine, was an effective substitute for norepinephrine, and the response was blocked by propranolol and sotalol. Nitroprusside, but neither cyanide nor isobutyl-methylxanthine, replaced azide. The potentiation was not affected by removal of CA2+ OR Na+ from the extracellular medium and was not blocked by cocaine. The potentiative accumulation of cyclic GMP in C-6 cells differs from the recently described stimulation by catecholamines of soluble guanylate cyclase of renal cortex. The potentiative phenomenon is compared with the few known instances in which cyclic AMP augments cyclic GMP formation and may be associated with synergistic modifications of cellular functions.

Topics: Adenylyl Cyclases; Astrocytes; Astrocytoma; Azides; Calcium; Cell Line; Cyclic AMP; Cyclic GMP; Isoproterenol; Neoplasms, Experimental; Norepinephrine; Receptors, Adrenergic, beta

Recent evidence indicates that cyclic nucleotides are of importance for general and neurosurgical oncology, especially with respect to the contact-inhibition mechanisms and tumour cell growth. This preliminary report deals with the CSF levels of c-AMP and c-GMP in primary neoplasms in children and to problems related to the blood-brain barrier. Some cases of medulloblastoma were studied as well as a few cases of brain stem glioma and cystic astrocytoma. The importance of some rather unusual findings seems undebatable, i.e., the marked increase in c-GMP values usually observed in medulloblastoma and the decrease of c-AMP, that is fairly common in all malignant neoplasms. The main changes in the c-AMP/c-GMP ratio are also discussed.

Topics: Astrocytoma; Blood-Brain Barrier; Brain Neoplasms; Brain Stem; Cerebellar Neoplasms; Child; Child, Preschool; Cyclic AMP; Cyclic GMP; Glioma; Humans; Infant; Medulloblastoma

Since the effects of cyclic nucleotides are mediated via protein kinases activation, we have studied the properties and regulation of these enzymes in cytosol and particulate fraction of normal cerebral tissues and of some human brain tumors. We found that distribution and activity of cyclic nucleotide-dependent protein kinases are regulated differently among various brain tumors and in comparison to normal gray and white matter. Pathological tissues show an higher cGMP-dependent protein kinase and this biochemical pattern is particularly evident in tumors with more pronounced malignancy. These data further confirm the hypothesis of a correlation between the increase of cGMP function and cellular growth and malignancy.

Topics: Astrocytoma; Brain Neoplasms; Cyclic AMP; Cyclic GMP; Cytosol; Glioma; Humans; Kinetics; Neurilemmoma; Protein Kinases

Topics: Astrocytoma; Cell Line; Cyclic AMP; Cyclic GMP; Dose-Response Relationship, Drug; Epoprostenol; Neoplasms, Experimental; Neuroblastoma; Nucleotides, Cyclic; Prostaglandin Endoperoxides, Synthetic; Prostaglandins

Cyclic 3-5-adenosine-monophosphate and 3-5-guanosinemonophosphate concentrations were studied in the bioptate of brain tumors, examined during neurosurgical operation and in normal brain tissues. The correlations between cyclic nucleotides in the tumors appeared to be significantly decreased in comparison to the intact tissue, being a characteristic signs for all types of tumors. There were significant fluctuations in the level of cyclic nucleotides both in the tumours and nontumorous brain tissues. There were no correlations found between the level of cyclic adenosine-monophosphate and cyclic guanosine-monophosphate on the one hand and the duration of the disease, localization of the tumor, degree of the brain oedema and the type of narcosis on the other.

Topics: Adult; Arachnoid; Astrocytoma; Brain Neoplasms; Cerebellar Neoplasms; Cyclic AMP; Cyclic GMP; Female; Frontal Lobe; Humans; Male; Meningeal Neoplasms; Meningioma; Middle Aged; Parietal Lobe