Effects of stimulation of adenosine A2A receptors on lipopolysaccharide-induced production of reactive oxygen species by equine neutrophils.
OBJECTIVE
To assess the anti-inflammatory effects of an adenosine analogue on lipopolysaccharide (LPS)-stimulated equine neutrophils.


METHODS
Neutrophils obtained from 10 healthy horses.


METHODS
An adenosine analogue (5'-N-ethylcarboxamidoadenosine [NECA]) was tested for its ability to inhibit production of reactive oxygen species (ROS) in LPS-stimulated equine neutrophils. Selective adenosine receptor antagonists were used to identify the receptor subtype responsible for effects. To assess the mechanism of action of NECA, cAMP concentrations were measured, and effects of dibutyryl cAMP (a stable analogue of cAMP) and rolipram (a type 4 phosphodiesterase inhibitor) were investigated.


RESULTS
NECA elicited concentration-dependent inhibition of ROS production that was inhibited by ZM241385, a selective adenosine A(2A) receptor antagonist; this effect of NECA was not affected by the adenosine A(2B) receptor antagonist MRS1706. Also, ZM241385 blocked NECA-induced increases in cAMP concentrations, whereas MRS1706 did not alter this effect of NECA. Rolipram potentiated NECA-induced inhibition of ROS production, and dibutyryl cAMP also inhibited ROS production.


CONCLUSIONS
Activation of adenosine A(2A) receptors inhibited ROS production by LPS-stimulated equine neutrophils in a cAMP-dependent manner. These results suggest that stable adenosine A(2A) receptor agonists may be developed as suitable anti-inflammatory drugs in horses.
Sun
Wan-chun
WC
Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA.
Moore
James N
JN
Hurley
David J
DJ
Vandenplas
Michel L
ML
Murray
Thomas F
TF
D058908:Adenosine A2 Receptor Agonists; D058917:Adenosine A2 Receptor Antagonists; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000494:pharmacology*; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006736:Horses / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D043705:Receptor, Adenosine A2A / Q000378:metabolism*; D020889:Rolipram / Q000494:pharmacology; D014227:Triazines / Q000494:pharmacology; D014230:Triazoles / Q000494:pharmacology
D058908:Adenosine A2 Receptor Agonists; D058917:Adenosine A2 Receptor Antagonists; D008070:Lipopolysaccharides; D017382:Reactive Oxygen Species; D043705:Receptor, Adenosine A2A; D014227:Triazines; D014230:Triazoles; C097270:ZM 241385; D019830:Adenosine-5'-(N-ethylcarboxamide); D000242:Cyclic AMP; D020889:Rolipram