The stimulation of adenosine 2A receptor reduces inflammatory response in mouse articular chondrocytes treated with hyaluronan oligosaccharides.
The adenosine 2A receptor (A(2A)R) is greatly involved in inflammation pathologies such as rheumatoid arthritis. By interacting with A(2A)R, the purine nucleoside adenosine acts as a potent endogenous inhibitor of the inflammatory process in a variety of tissues. Hyaluronan (HA) fragments act to prime inflammation via CD44 and the toll-like receptor 4 (TLR-4). The aim of this study was to investigate whether the inhibition/stimulation of A(2A)R modulates the inflammation cascade primed by small HA fragments in mouse articular chondrocytes. 6-mer HA treatment induced up-regulation of CD44, TLR4 and A(2A)R mRNA expression and the related protein levels, and NF-kB activation, that in turn increased TNF-α, IL-1β, and IL-6 and production. Treatment with a selective (2)A adenosine receptor agonist (2-phenylaminoadenosine) enhanced A(2A)R increase, as well as the inhibition of CD44 and TLR4 activity using two specific antibodies abolished up-regulation of CD44 and TLR4, and significantly reduced, especially by antibody inhibition, NF-kB activation and pro-inflammatory cytokine production. Furthermore, the exposure of chondrocytes to A(2A)R specific interference mRNA (A(2A)R siRNA) enhanced HA 6-mer induced NF-kB activation and inflammatory cytokine increase. Finally, the use of an exchange protein activated by cAMP (EPAC) siRNA and a specific PKA inhibitor showed a predominant EPAC involvement in the mediation of the anti-inflammatory activity exerted by A(2A)R stimulation. These data suggest that HA depolymerization occurring during inflammation contributes to priming of the inflammatory cascade, while endogenous adenosine, by exerting anti-inflammatory response via A(2A)R, could be a modulatory mechanism that attempts to attenuate the inflammation process.
Department of Biochemical, Physiological and Nutritional Sciences, Section of Medical Chemistry, School of Medicine, University of Messina, Policlinico Universitario, Messina, Italy. gcampo@unime.it
Giuseppe M
GM
Campo
Angela
A
Avenoso
Angela
A
D'Ascola
Vera
V
Prestipino
Michele
M
Scuruchi
Giancarlo
G
Nastasi
Alberto
A
Calatroni
Salvatore
S
Campo
D000241:Adenosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology; D058917:Adenosine A2 Receptor Antagonists / Q000494:pharmacology; D053674:Aggrecans / Q000378:metabolism; D000818:Animals; D002358:Cartilage, Articular / Q000276:immunology / Q000473:pathology*; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D024043:Collagen Type II / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism; D018960:Hyaluronan Receptors / Q000235:genetics / Q000378:metabolism; D006820:Hyaluronic Acid / Q000502:physiology; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D016328:NF-kappa B / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D058906:Purinergic P1 Receptor Agonists / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000235:genetics; D043683:Receptors, Adenosine A2 / Q000235:genetics / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism
D058917:Adenosine A2 Receptor Antagonists; D053674:Aggrecans; C476399:Cd44 protein, mouse; D024043:Collagen Type II; D016207:Cytokines; C482601:Epac protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D018960:Hyaluronan Receptors; D016328:NF-kappa B; D047428:Protein Kinase Inhibitors; D058906:Purinergic P1 Receptor Agonists; D034741:RNA, Small Interfering; D043683:Receptors, Adenosine A2; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D006820:Hyaluronic Acid; D017868:Cyclic AMP-Dependent Protein Kinases; C026708:2-phenylaminoadenosine; D000241:Adenosine