Novel effects mediated by bradykinin and  pharmacological characterization of bradykinin B2  receptor antagonism in human synovial fibroblasts.
OBJECTIVE
Bradykinin (BK) and B2 receptors have been implicated in the pathophysiology of osteoarthritis (OA), and synovitis is one of its hallmarks. Here, the selective B2 receptor antagonists MEN16132 and icatibant have been pharmacologically characterized in human synovial cells.


METHODS
Radioligand and functional studies (inositol phosphate (IP) accumulation, interleukin (IL)-6 and IL-8 release) were performed in cultured synoviocytes.


RESULTS
[3H]-BK saturation studies indicated receptor density (Bmax) and K(d) values of 121,550 sites per cell and 1.14 nM respectively. In synoviocytes, MEN16132 (pK(I) 8.9) was threefold more potent than icatibant (pK(I) 8.4). Both antagonists showed competitive antagonism in the BK-induced IP assay (control EC50 0.45 nM), with pK(B) values of 9.9 (MEN16132) and 8.1 (icatibant). 24h incubation with BK induced IL-6 (EC50 216 nM) and IL-8 (EC50 53 nM) release. Both MEN16132 (IL-6: pIC50 8.1; IL-8: pIC50 8.4) and icatibant (IL-6: pIC50 6.6; IL-8: pIC50 6.7) completely prevented this BK-induced release. Indomethacin did not affect the basal or the IL-6/IL-8 release induced by BK, whereas nordihydroguaiaretic acid decreased the basal release, although BK still increased IL-6 and IL-8 production. BK-induced IL-8 release was attenuated by inhibitors of phospholipase C (U73122), p38 (SB203580), JNK (SP600125), ERK 1/2 (PD98059) MAPKs, phosphoinositide 3-kinase (LY294002), NF-kappaB (BAY-117085) and by the glucocorticoid dexamethasone.


CONCLUSIONS
Bradykinin via B2 receptors can participate in inflammatory events in synovitis. MEN16132 is a highly potent B2 receptor antagonist capable of blocking pro-inflammatory responses to BK evoked in human synoviocytes.
Bellucci
F
F
Department of Pharmacology, Menarini Ricerche SpA, Florence, Italy.
Cucchi
P
P
Catalani
C
C
Giuliani
S
S
Meini
S
S
Maggi
C A
CA
D001920:Bradykinin / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D065094:Bradykinin B2 Receptor Antagonists; D002478:Cells, Cultured; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D020128:Inhibitory Concentration 50; D007295:Inositol Phosphates / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D009952:Ornithine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D011869:Radioligand Assay; D043782:Receptor, Bradykinin B2 / Q000378:metabolism; D013449:Sulfonamides / Q000008:administration & dosage / Q000494:pharmacology*; D013583:Synovial Membrane / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013585:Synovitis / Q000188:drug therapy / Q000503:physiopathology
C506838:(4-amino-5-(4-(4-(2,4-dichloro-3-(2,4-dimethyl-8-quinolyloxymethyl)phenylsulfonamido)tetrahydro-2H-4-pyranoylcarbonyl)piperazino)-5-oxopentyl)(trimethyl)ammonium; D065094:Bradykinin B2 Receptor Antagonists; D007295:Inositol Phosphates; D015850:Interleukin-6; D016209:Interleukin-8; D043782:Receptor, Bradykinin B2; D013449:Sulfonamides; C065679:icatibant; D009952:Ornithine; D001920:Bradykinin