mrs-1220 and 8-cyclopentyl-1-3-dimethylxanthine

Actions of adenosine 5'-monophosphate (AMP) on electrical and synaptic behavior of submucosal neurons in guinea pig small intestine were studied with "sharp" intracellular microelectrodes. Application of AMP (0.3-100 microM) evoked slowly activating depolarizing responses associated with increased excitability in 80.5% of the neurons. The responses were concentration dependent with an EC(50) of 3.5 +/- 0.5 microM. They were abolished by the adenosine A(2A) receptor antagonist ZM-241385 but not by pyridoxal-phosphate-6-azophenyl-2,4-disulfonic acid, trinitrophenyl-ATP, 8-cyclopentyl-1,3-dimethylxanthine, suramin, or MRS-12201220. The AMP-evoked responses were insensitive to AACOCF3 or ryanodine. They were reduced significantly by 1) U-73122, which is a phospholipase C inhibitor; 2) cyclopiazonic acid, which blocks the Ca(2+) pump in intraneuronal membranes; and 3) 2-aminoethoxy-diphenylborane, which is an inositol (1,4,5)-trisphosphate receptor antagonist. Inhibitors of PKC or calmodulin-dependent protein kinase also suppressed the AMP-evoked excitatory responses. Exposure to AMP suppressed fast nicotinic ionotropic postsynaptic potentials, slow metabotropic excitatory postsynaptic potentials, and slow noradrenergic inhibitory postsynaptic potentials in the submucosal plexus. Inhibition of each form of synaptic transmission reflected action at presynaptic inhibitory adenosine A(1) receptors. Slow excitatory postsynaptic potentials, which were mediated by the release of ATP and stimulation of P2Y(1) purinergic receptors in the submucosal plexus, were not suppressed by AMP. The results suggest an excitatory action of AMP at adenosine A(2A) receptors on neuronal cell bodies and presynaptic inhibitory actions mediated by adenosine A(1) receptors for most forms of neurotransmission in the submucosal plexus, with the exception of slow excitatory purinergic transmission mediated by the P2Y(1) receptor subtype.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Action Potentials; Adenosine; Adenosine A1 Receptor Antagonists; Adenosine A2 Receptor Antagonists; Adenosine Diphosphate; Adenosine Monophosphate; Animals; Boron Compounds; Enzyme Inhibitors; Estrenes; Excitatory Postsynaptic Potentials; Guinea Pigs; Ileum; Indoles; Male; Maleimides; Norepinephrine; Phenethylamines; Pyrrolidinones; Quinazolines; Receptor, Adenosine A1; Receptor, Adenosine A2A; Signal Transduction; Submucous Plexus; Synaptic Transmission; Tetrodotoxin; Theophylline; Triazines; Triazoles

Gliomas are the most common and devastating primary tumors of the central nervous system. Ecto-NTPDases and ecto-5'-nucleotidase/CD73 can control extracellular ATP/adenosine levels, which have been described as proliferation factors. Here, we investigate the influence of indomethacin on the enzyme cascade that catalyses the interconversion of purine nucleotides in U138-MG and C6 glioma cell lines. Exposure of glioma cells to 100 microM indomethacin for 48 h caused increases of 52% (P < 0.05) and 62% (P < 0.05) in the AMP hydrolysis rate in C6 and U138-MG cell lines, respectively. Indomethacin treatments also increased ATP hydrolysis. Significant increase in ecto-5'-nucleotidase/CD73 mRNA and protein levels were observed after treatment with indomethacin. Pretreatment of glioma cells with a specific antagonist of the adenosine A(3) receptor, MRS1220 (1 microM; 9-Chloro-2-(2-furanyl)-5-((phenylacetyl)amino)-[1,2,4]triazolo[1,5-c]quinazoline), significantly reduced the inhibition of cell proliferation induced by indomethacin. In addition, a significant increase in mRNA levels of the adenosine A(3) receptor was observed after treatment with indomethacin. In conclusion, our data indicate that adenosine A(3) receptors and the enzyme, ecto-5'-nucleotidase/CD73, are involved in the anti-proliferative effect of indomethacin in glioma cells.

Topics: 5'-Nucleotidase; Actins; Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Anti-Inflammatory Agents, Non-Steroidal; Cell Line, Tumor; Cell Proliferation; Dimethyl Sulfoxide; Dose-Response Relationship, Drug; Enzyme Activation; Flow Cytometry; Gene Expression Regulation, Enzymologic; Glioma; Humans; Indomethacin; Purinergic P1 Receptor Agonists; Purinergic P1 Receptor Antagonists; Quinazolines; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Theophylline; Time Factors; Triazoles; Xanthines