AIM To study activation of extracellular signal-regulated kinase-1/2(ERK1/2) and pro-matrix metalloproteinases(pro-MMPs) secretion from isolated primary human ciliary muscle(h-CM) cells in response to bradykinin(BK) and other agonists. METHODS Serum-starved h-CM cells were challenged with vehicle, BK agonists or antagonists. Cell lysates were evaluated for phosphorylated ERK1/2 using homogeneous timeresolved fluorescence technology based on a sandwich immunoassay. Rabbit polyclonal anti-pro-MMP antibodies were used to measure pro-MMPs using immunoblot analysis.RESULTS A 10 min incubation time using 5 × 104 h-CM cells/well was optimum condition for studying stimulation of ERK1/2 phosphorylation. BK(100 nmol/L) caused a 1.86 ± 0.26 fold(n = 3) increase in ERK1/2 phosphorylation above baseline. BK analogs, Met-Lys-BK and RMP-7(100 nmol/L), also stimulated ERK1/2 phosphorylation by 1.57 ± 0.04 and 1.55 ± 0.09 fold, respectively. However, DesArg9-Bradykinin, a B1 receptor-selective agonist(0.1-1 μmol/L), was essentially inactive. HOE-140 or WIN-64338(B2-antagonists) appreciably blocked phosphorylation of ERK1/2 induced by various BK agonists. Pre-treatmentof cells with a prostaglandin(PG) synthase inhibitor(bromfenac; 1 μmol/L) failed to alter kinin-induced ERK1/2 activation. BK and a non-peptide BK agonist(FR-190997)(10 nmol/L-1 μmol/L) also enhanced pro-MMPs secretion(pro-MMP-1 > pro-MMP-3 > pro-MMP-2; 1.45-1.75-fold over baseline) from h-CM cells. CONCLUSION These collective data suggest that B2 kinin receptors initiate signaling in h-CM cells by a relatively rapid mechanism(within minutes) involving ERK1/2 activation which in turn regulates MMPs production(within hours). The latter process does not involve PGs.
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