title: Regulation of A2B adenosine receptor functioning by tumour necrosis factor a in human astroglial cells.
abstract: Low-affinity A2B adenosine receptors (A2B ARs), which are expressed in astrocytes, are mainly activated during brain hypoxia and ischaemia, when large amounts of adenosine are released. Cytokines, which are also produced at high levels under these conditions, may regulate receptor responsiveness. In the present study, we detected A2B AR in human astrocytoma cells (ADF) by both immunoblotting and real-time PCR. Functional studies showed that the receptor stimulated adenylyl cyclase through Gs proteins. Moreover, A2B ARs were phosphorylated and desensitized following stimulation of the receptors with high agonist concentration. Tumour necrosis factor alpha (TNF-alpha) treatment (24- h) increased A2B AR functional response and receptor G protein coupling, without any changes in receptor protein and mRNA levels. TNF-alpha markedly reduced agonist-dependent receptor phosphorylation on threonine residues and attenuated agonist-mediated A2B ARs desensitization. In the presence of TNF-alpha, A2B AR stimulation in vitro induced the elongation of astrocytic processes, a typical morphological hallmark of in vivo reactive astrogliosis. This event was completely prevented by the selective A2B AR antagonist MRS 1706 and required the presence of TNF-alpha. These results suggest that, in ADF cells, TNF-alpha selectively modulates A2B AR coupling to G proteins and receptor functional response, providing new insights to clarify the pathophysiological role of A2B AR in response to brain damage.
authors.affiliation: Department of Psychiatry, Neurobiology, Pharmacology and Biotechnology, University of Pisa, Pisa, Italy.
authors.forename: Maria L
authors.initials: ML
authors.lastname: Trincavelli
authors.forename: Matteo
authors.initials: M
authors.lastname: Marroni
authors.forename: Daniela
authors.initials: D
authors.lastname: Tuscano
authors.forename: Stefania
authors.initials: S
authors.lastname: Ceruti
authors.forename: Alessia
authors.initials: A
authors.lastname: Mazzola
authors.forename: Nico
authors.initials: N
authors.lastname: Mitro
authors.forename: Maria P
authors.initials: MP
authors.lastname: Abbracchio
authors.forename: Claudia
authors.initials: C
authors.lastname: Martini
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives*; D058917:Adenosine A2 Receptor Antagonists; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects*; D001254:Astrocytoma; D015153:Blotting, Western / Q000379:methods; D048708:Cell Growth Processes / Q000187:drug effects; D045744:Cell Line, Tumor; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000493:pharmacokinetics; D006801:Humans; D047468:Immunoprecipitation / Q000379:methods; D018696:Neuroprotective Agents / Q000494:pharmacology; D010627:Phenethylamines; D011687:Purines / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D011869:Radioligand Assay / Q000379:methods; D043704:Receptor, Adenosine A2B / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013912:Threonine / Q000378:metabolism; D013997:Time Factors; D014162:Transfection / Q000379:methods; D014230:Triazoles / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: C098657:5-amino-7-(2-phenylethyl)-2-(2-furyl)pyrazolo(4,3-e)-1,2,4-triazolo(1,5-c)pyrimidine; D058917:Adenosine A2 Receptor Antagonists; D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; C496145:N-(4-acetylphenyl)-2-(4-(2,3,6,7-tetrahydro-2,6-dioxo-1,3-dipropyl-1H-purin-8-yl)phenoxy)acetamide; D018696:Neuroprotective Agents; D010627:Phenethylamines; D011687:Purines; D011743:Pyrimidines; D012333:RNA, Messenger; D043704:Receptor, Adenosine A2B; D014230:Triazoles; D014409:Tumor Necrosis Factor-alpha; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D013912:Threonine; D019830:Adenosine-5'-(N-ethylcarboxamide); D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000242:Cyclic AMP; D000241:Adenosine