Adenosine analogs and electromagnetic fields inhibit prostaglandin E2 release in bovine synovial fibroblasts.
OBJECTIVE
To investigate the role of adenosine analogs and electromagnetic field (EMF) stimulation on prostaglandin E(2) (PGE(2)) release and cyclooxygenase-2 (COX-2) expression in bovine synovial fibroblasts (SFs).


METHODS
SFs isolated from synovia were cultured in monolayer. Saturation and binding experiments were performed by using typical adenosine agonists: N6-cyclohexyladenosine (CHA, A(1)), 2-[p-(2-carboxyethyl)-phenetyl-amino]-5'-N-ethylcarboxamidoadenosine (CGS 21680, A(2A)), 5'-N-ethylcarboxamidoadenosine (NECA, non-selective), N6-(3-iodobenzyl)2-chloroadenosine-5'-N-methyluronamide (Cl-IB-MECA, A(3)). SFs were treated with TNF-alpha (10 ng/ml) and lipopolysaccharide (LPS) (1 microg/ml) to activate inflammatory response. Adenosine analogs were added to control and TNF-alpha- or LPS-treated cultures both in the absence and in the presence of adenosine deaminase (ADA) which is used to deplete endogenous adenosine. Parallel cultures were exposed to EMFs (75 Hz, 1.5 mT) during the period in culture (24h). PGE(2) release was measured by immunoassay. COX-2 expression was evaluated by RT-PCR.


RESULTS
TNF-alpha and LPS stimulated PGE(2) release. All adenosine agonists, except for Cl-IB-MECA, significantly inhibited PGE(2) production. EMFs inhibited PGE(2) production in the absence of adenosine agonists and increased the effects of CHA, CGS 21680 and NECA. In ADA, the inhibition on PGE(2) release induced by CHA, CGS and NECA was stronger than in the absence of ADA and the EMF-inhibitory effect was lost. Changes in PGE(2) levels were associated to modification of COX-2 expression.


CONCLUSIONS
This study supports anti-inflammatory activities of A(1) and A(2A) adenosine receptors and EMFs in bovine SFs. EMF activity appears mediated by an EMF-induced up-regulation of A(2A) receptors. Biophysical and/or pharmacological modulation of adenosine pathways may play an important role to control joint inflammation.
De Mattei
M
M
Department of Morphology and Embryology, University of Ferrara, Ferrara, Italy. dmm@unife.it
Varani
K
K
Masieri
F F
FF
Pellati
A
A
Ongaro
A
A
Fini
M
M
Cadossi
R
R
Vincenzi
F
F
Borea
P A
PA
Caruso
A
A
D000241:Adenosine / Q000819:agonists* / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D002417:Cattle; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D051546:Cyclooxygenase 2 / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004574:Electromagnetic Fields; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D018047:Receptors, Purinergic P1 / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013582:Synovial Fluid / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D008070:Lipopolysaccharides; D018047:Receptors, Purinergic P1; D014409:Tumor Necrosis Factor-alpha; D005576:Colforsin; D051546:Cyclooxygenase 2; D000241:Adenosine; D015232:Dinoprostone