Protease-Activated Receptor-2–Mediated Inhibition for Ca2+ Response to Lipopolysaccharide in Guinea Pig Tracheal Epithelial Cells

The protease-activated receptor-2 (PAR-2) has been implicated in airway inflammation. Here, we examined the interaction between PAR-2 and lipopolysaccharide (LPS), a major proinflammatory factor, using cultured guinea pig tracheal epithelial cells. In fura2-loaded cells, LPS (1 μg/ml) transiently increased intracellular Ca2+ concentrations ([Ca2+]i), this effect being abolished by a Ca2+ channel blocker, verapamil, and Ca2+ removal. Prestimulation of PAR-2 with trypsin (0.1–1 U/ml) or an agonist peptide (SLIGRL-NH2, 1 μM) for 60 min inhibited the LPS-induced [Ca2+]i increase. Such an inhibitory effect of trypsin was abolished by inhibitors of protein kinase C (PKC), chelerythrine and staurosporine. A PKC activator, phorbol 12,13-dibutylate, also reduced the LPS response. Trypsin also inhibited a transient increase in [Ca2+]i caused by a Ca2+ channel opener, Bay K 8644. When the trypsin-pretreated cells were incubated in normal buffer for 10–60 min before LPS exposure, the effect of trypsin on the Ca2+ res...