Apparent involvement of the A(2A) subtype adenosine receptor in the anti-inflammatory interactions of CGS 21680, cyclopentyladenosine, and IB-MECA with human neutrophils.
This study was undertaken to identify the adenosine receptor (AR) subtypes which down-regulate the proinflammatory activities of human neutrophils, as well as the involvement of adenosine 3',5'-cyclic monophosphate (cAMP) and its relationship to cellular handling of Ca(2+) in mediating these effects. Neutrophils were treated with varying concentrations (0.01-1 microM) of AR agonists operative at A(1) (N(6)-cyclopentyladenosine, CPA), A(2A) (2(4-[(2-carboxyethyl)phenyl]ethylamino)-5'-N-ethylcarboxamidoadenosi ne, CGS 21680), and A(3) (N(6)-(3-iodobenzyl-5'-N-methylcarbamoyladenosine, IB-MECA) receptors, after which they were activated with the chemoattractant, N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP, 1 microM). Intracellular cAMP, superoxide, and elastase were assayed using radioimmunoassay, lucigenin-enhanced chemiluminescence (LECL), and colorimetric procedures, respectively, while changes in the concentrations of cytosolic Ca(2+) were monitored by fura-2-based spectrofluorimetry. CGS 21680, at all concentrations tested, inhibited superoxide production in a dose-related manner, while CPA and IB-MECA were effective only at the highest concentrations tested (0.5-1 microM). The release of elastase from activated neutrophils was also inhibited by all three AR agonists, but was more sensitive to CGS 21680 and IB-MECA than was superoxide production. The inhibitory effects of all 3 agonists on superoxide production and elastase release were associated with accelerated clearance of Ca(2+) from the cytosol of activated neutrophils, and were effectively neutralized by pretreatment of the cells with the highly selective A(2A)R antagonist, ZM 241385 (4-(2-[7-amino-2-(2-furyl)[1, 2,4]triazolo[2,3-a][1,3,5]triazin-5yl amino]ethyl)phenol). Increased cAMP was detected in neutrophils treated with CGS 21680 and IB-MECA (1 microM). These data support the involvement of the A(2A)R subtype in the suppression of superoxide production and degranulation by activated human neutrophils, probably by cAMP-mediated alterations in Ca(2+) handling.
Visser
S S
SS
Division of Pulmonology, Department of Internal Medicine and Medical Research Council Unit for Inflammation and Immunity, University of Pretoria, Pretoria, South Africa.
Theron
A J
AJ
Ramafi
G
G
Ker
J A
JA
Anderson
R
R
D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D015550:Cell Degranulation / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism; D016257:Fura-2 / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D009504:Neutrophils / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010196:Pancreatic Elastase / Q000378:metabolism; D010627:Phenethylamines / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D043705:Receptor, Adenosine A2A; D018047:Receptors, Purinergic P1 / Q000187:drug effects / Q000378:metabolism*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D010627:Phenethylamines; D017382:Reactive Oxygen Species; D043705:Receptor, Adenosine A2A; D018047:Receptors, Purinergic P1; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; C084956:N(6)-(3-iodobenzyl)-5'-N-methylcarboxamidoadenosine; C048599:N(6)-cyclopentyladenosine; D000242:Cyclic AMP; D010196:Pancreatic Elastase; D000241:Adenosine; D016257:Fura-2