ATP and UTP activate calcium-mobilizing P2U-like receptors and act synergistically with interleukin-1 to stimulate prostaglandin E2 release from human rheumatoid synovial cells.
OBJECTIVE
To pharmacologically and functionally characterize calcium-mobilizing purine receptors on adherent human rheumatoid synovial cells.


METHODS
Fura-2-loaded synovial cells were screened for changes in cytosolic calcium concentration after the addition of purine receptor agonists. Release of interleukin-1 (IL-1) and prostaglandin E2 (PGE2) was assessed by enzyme-linked immunosorbent assay (ELISA) and radioimmunoassay, respectively. The effect of IL-1 prestimulation on purine-mediated PGE2 release was determined.


RESULTS
ATP (1-100 microM) and UTP (1-100 microM), but not 2-methylthio-ATP or adenosine, stimulated mobilization of calcium from intracellular stores in synovial cells. ATP and UTP stimulated a small, but significant, increase in PG release from resting synoviocytes and a dramatic increase in PG release from synoviocytes prestimulated with recombinant human IL-1alpha. Neither ATP nor UTP stimulated synoviocyte release of IL-1 as measured by specific ELISA. The effects of ATP and UTP on PG secretion were mimicked by phorbol 12-myristate 13-acetate and thapsigargin, and blocked by BAPTA buffering of cytosolic calcium.


CONCLUSIONS
Adherent human rheumatoid synovial cells mobilize intracellular calcium via a P2U-like purine receptor. P2U receptor agonists stimulate PGE2 release from synoviocytes, an effect that is greatly enhanced by IL-1alpha prestimulation and blocked by intracellular calcium buffering.
Loredo
G A
GA
University of California, Davis 95616, USA.
Benton
H P
HP
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000293:Adolescent; D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000378:metabolism* / Q000473:pathology; D002021:Buffers; D002118:Calcium / Q000378:metabolism*; D015232:Dinoprostone / Q000378:metabolism*; D004357:Drug Synergism; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D008875:Middle Aged; D058913:Purinergic Agonists; D011983:Receptors, Purinergic / Q000187:drug effects / Q000378:metabolism*; D013583:Synovial Membrane / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014544:Uridine Triphosphate / Q000494:pharmacology
D002021:Buffers; D007375:Interleukin-1; D058913:Purinergic Agonists; D011983:Receptors, Purinergic; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D015232:Dinoprostone; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; D014544:Uridine Triphosphate