Ion transport regulated by protease‐activated receptor 2 in human airway Calu‐3 epithelia

Abstract

1 We examined the mechanisms underlying anion secretion mediated by protease-activated receptor 2 (PAR2) and its role in the regulation of ion transport, using polarized human airway Calu-3 cells. 2 PAR2 stimulation by trypsin and a PAR2-activating peptide (PAR2AP), especially from the basolateral aspect, caused transient Cl À secretion due to cytosolic Ca 2 þ mobilization. 3 Antagonists of PI-PLC (U73122, ET-18-OCH 3 ) and inositol 1,4,5-triphosphate (xestospongin C (Xest C)) were without effect on the PAR2AP-mediated Cl À secretion, whereas it was attenuated by D609 (a PC-PLC inhibitor) and phorbol 12-myristate 13 acetate (PMA, a PKC activator). 4 Even 30 min after removal of PAR2AP after a 10-min-exposure, cells were still poorly responsive to PAR2 stimulation, but the reduced responsiveness was upregulated by a PKC inhibitor, GF109203X (GFX). 5 Pretreatment with PAR2AP did not affect responses to anion secretagogues, such as isoproterenol, forskolin, thapsigargin, 1-ethyl-2-benzimdazolinone, and adenosine, but ATP-induced responses were significantly reduced. Nystatin permeabilization studies revealed that the presence of PAR2AP prevented ATP-induced increments in basolateral membrane K þ conductance without affecting apical membrane Cl À conductance. 6 ATP-elicited Ca 2 þ mobilization, which was sensitive to D609 and PMA, was inhibited by the pretreatment with PAR2AP, and this inhibition was blunted by the presence of GFX. 7 Collectively, stimulation of PAR2 generates a brief response of Cl À secretion through PC-PLCmediated pathway, followed by not only auto-desensitization of PAR2 itself but also crossdesensitization of a PC-PLC-coupled purinoceptor. The two types of desensitization seem likely to have PKC-mediated downregulation of PC-PLC in common.

Allergic sensitization enhances anion current responsiveness of murine trachea to PAR-2 activation

“…In this study, we showed that basolateral PAR-2 activation leads to a transient increase in short circuit current. These results are similar with previously published measurements in mouse tracheas [20], human epithelial cell lines [29,34] and primary human airway epithelial cells [11].…”

“…It blocks sodium absorption in cultured human bronchial epithelial cells [11] as well as intact mouse tracheas [20]. It increases intracellular calcium with subsequent activation of apical calciumactivated chloride channels (CaCC) and/or basolateral calcium-dependent potassium channels in human bronchial epithelial cells [6,11,20], calu-3 cells [29,34] and intact mouse tracheas [20]. PAR-2 activation also increases CFTR activity in calu-3 cells [29] and intact mouse tracheas [20], and may also increase mucin secretion [18,22].…”

Protease-activated receptor 2–dependent fluid secretion from airway submucosal glands by house dust mite extract

“…Because PAR2 is known to induce fluid secretion in various airway cells 10,19,20 and HDM has been shown to be capable of activating PAR2, 10 we hypothesized that PAR2 can be involved in the IgE-independent, nonspecific induction of fluid secretion triggered by HDM exposure in nasal glands. Immunostaining with anti-PAR2 mAb revealed weak expression of PAR2 in the serous acinar cells of the control group; however, PAR2 expression in the 3 diseased groups (the AR, CRS, and AR1CRS groups) was significantly greater than that in the control group (P 5 .0233, P 5.0005, and P 5.0013, respectively, t test; Fig 3).…”

Apical and basolateral pools of proteinase-activated receptor-2 direct distinct signaling events in the intestinal epithelium

“…Many of these studies suggest that inflammatory responses in the intestine can be induced by luminal introduction of PAR 2 -activating peptides and by serosal exposure to mast cell tryptase. While the specific cellular responses such as ion secretion and changes in transepithelial electrical resistance (R T ) have been reported in response to basolaterally administered agonist in cultured cells (19,41,45,(51)(52)(53), little is known about signaling via apical PAR 2 . Furthermore, the possibility that there are distinctions in signaling between the apical and basolateral receptor populations has not yet been addressed.…”