1 uM iberiotoxin, 0. 1 uM thapsigargin, 1 mM tetraethylammonium and 1 uM U73122 on the relaxation induced by the bitter taste receptor sellectchem agonists chloroquine and phe nanthroline. None of the inhibitors altered the observed relaxations. We then focused on other signalling pathways involved in cAMP dependent human bronchus relaxation. Adeny lyl cyclase activation triggers bronchial smooth muscle relaxation following the stimulation of B2 adrenergic re ceptors. it has been reported that TAS2R agonists inhibit the phosphodiesterases responsible for cyclic nucleotide degradation. The downstream effectors activated via a cAMP dependent mechanism include protein kin ase A, the recently described Epacs and potassium channels.

However, our over night incubation of human bronchi with the PKA in hibitor H89 or with the Epac inhibitor brefeldin A did not Inhibitors,Modulators,Libraries inhibit chloroquine and phenanthroline induced relaxation. In contrast, the isoproterenol concentration effect curves were right shifted Inhibitors,Modulators,Libraries by about 0. 8 log units with H89. Recent findings suggested that the relaxation induced by chloroquine in mouse airways may be related to blockade of L type voltage gated calcium channels. We thus explored the effects of 1 uM BAY K8644, an acti vator of L type voltage gated calcium channels as well as those of 10 uM ouabain, an inhibitor of Na K ATPAse, which both induce calcium entry in the cell. Response profiles were similar with both drugs, which induced a right shift of Inhibitors,Modulators,Libraries concentration response curves to chloroquine and phenanthroline, whereas the response to dapsone and flufenamic acid was unaffected.

We then explored the involvement of the epithelium and epithelium dependent signalling pathways, with a focus on prostanoids and nitric oxide. Removal of the bronchial epithelium had no impact on the concentration response curve for chloroquine. In contrast, Inhibitors,Modulators,Libraries the concentration response curve for phenanthroline was right shifted in the absence of epithelium, resulting in a lower pD2. Pre incubation of the bronchi with 3 mM L NAME or 1 uM indomethacin did not significantly alter the response to chloroquine or phenanthroline. Table 3 Maximum relaxation of human bronchi and potency observed with chloroquine or phenanthroline in the presence or absence of U73122, iberiotoxin, thapsigargin, tetraethylammonium, H89, brefeldin A, indomethacin and L NAME We lastly investigated the role of phosphoinositide 3 kinases, which were previously shown to regu late calcium flux in airway smooth muscle cells and to be involved in the IL 13 induced increase in tracheal contractility in mouse.

Wortmanin and PI 828 potentiated the relaxation to chloro Inhibitors,Modulators,Libraries quine and phenanthroline, which selleckchem translated into a significant increase in pD2 for relaxation to chloroquine in bronchi treated with PI 828 only. On the other hand, the relaxation to iso proterenol was unaffected by either wortmanin or PI 828.