Tryptase activation of urothelial cell mitogen‐activated protein kinase

We determined whether mitogen‐activated protein (MAP) kinases are activated in response to tryptase stimulation of urothelial cells derived from human normal and interstitial cystitis/painful bladder syndrome (IC/PBS) bladders. Urothelial cells isolated from normal (PD07i and PD08i) and IC/PBS (SR22A and SM28A) bladders were stimulated with tryptase (20 ng/ml) and MAP kinase activation and phosphorylation was determined. Phospholipase A 2 (PLA 2 ) activity was measured in the absence of calcium using (16:0, [ 3 H]18:1) plasmenylcholine as substrate. Tryptase stimulation of normal urothelial cells (PD07i and PD08i) resulted in a significant increase in extracellular signal regulated kinase 1/2 (ERK 1/2). A much greater increase in ERK 1/2 activity was observed in urothelial cells isolated from IC/PBS bladders (SR22A and SM28A). A smaller, but significant, increase in p38 MAP kinase was observed in all cells following tryptase stimulation. Treatment with PD 98059 to inhibit ERK 1/2 or SB 203580 to inhibit p38 MAP kinase did not block tryptase‐stimulated iPLA 2 activation, but treatment with lysoplasmenylcholine increased ERK 1/2 activity, suggesting that iPLA 2 activation is upstream of ERK 1/2. Activation of ERK 1/2 in response to tryptase stimulation may facilitate wound healing or cell proliferation in areas of inflammation associated with IC/PBS.