title: Bradykinin activation of extracellular signal-regulated kinases in human trabecular meshwork cells.
abstract: Bradykinin stimulation of B(2) kinin receptors has been shown to promote matrix metallo-proteinase (MMP) secretion from trabecular meshwork cells and to increase conventional outflow facility. Because acute secretion of MMPs can be dependent on the activity of extracellular signal-regulated MAP kinases (ERK1/2), experiments were performed to determine bradykinin effects on ERK1/2 in cultured human trabecular meshwork cells and the relationship of these effects to MMP-9 release. Treatment of cells with bradykinin produced a rapid 4-to 6-fold increase in ERK1/2 phosphorylation. Stimulation of ERK1/2 activity peaked within 2 min and then declined to control levels by 60 min. The response maximum occurred with 100nM bradykinin and the estimated EC₅₀ was 0.7nM. Treatment of cells with the B₂ kinin receptor agonist, Tyr⁸- bradykinin, also stimulated ERK1/2 phosphorylation while the B₁ agonist, Lys- [Des-Arg⁹]- bradykinin had no significant effect. In addition, activation of ERK1/2 by bradykinin or Tyr⁸- bradykinin was blocked by the selective B₂ receptor antagonist, Hoe-140. Inhibition of MAP kinase kinase (MEK) with U0126 also blocked bradykinin-induced ERK1/2 phosphorylation. Suppression of protein kinase C activity with the nonselective inhibitor, GF109203X, or by down-regulation with phorbol ester, diminished, but did not eliminate, bradykinin activation of ERK1/2. A similar decrease of ERK1/2 stimulation was observed when Src kinase was inhibited by 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2). Finally, blockade of bradykinin-induced ERK1/2 activation substantially reduced the peptide's action to stimulate MMP-9 release into the extracellular environment. The data demonstrate that bradykinin promotes ERK1/2 activation in human trabecular meshwork cells. The effect is mediated by B₂ kinin receptors, involves two different signaling pathways, and results in increased secretion of MMP-9.
authors.affiliation: Department of Pharmacology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA. webbj@musc.edu
authors.forename: Jerry G
authors.initials: JG
authors.lastname: Webb
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Yang
authors.forename: Craig E
authors.initials: CE
authors.lastname: Crosson
mesh_terms: D001920:Bradykinin / Q000494:pharmacology*; D065094:Bradykinin B2 Receptor Antagonists; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D008875:Middle Aged; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D043783:Receptor, Bradykinin B1 / Q000819:agonists / Q000378:metabolism; D043782:Receptor, Bradykinin B2 / Q000378:metabolism; D014129:Trabecular Meshwork / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*
chemical_list: D065094:Bradykinin B2 Receptor Antagonists; D004791:Enzyme Inhibitors; D043783:Receptor, Bradykinin B1; D043782:Receptor, Bradykinin B2; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020780:Matrix Metalloproteinase 9; D001920:Bradykinin