Expression of several TAS2Rs has previously been observed in human airway smooth muscle cells. In agreement with the latter find ings, we found that not only were expressed in intact bronchi. This result suggests that these four latter subtypes could be expressed by cells CHIR99021 mechanism other than smooth muscle cells in human bronchi, as has already been observed in epithelial cells. A number of TAS2R agonists were found to have re laxant properties in mouse airways and guinea pig tra chea. Furthermore, chloroquine and saccharin acted as relaxants in bronchial rings from three patients, although the latter compound was found to be inactive in another study. We further investigated TAS2R mediated relaxation in human bronchi by first confirming the relaxation of bronchi exposed to chloro quine.

In the present study, quinine, caffeine, strychnine and diphenidol were effective as relaxing agents, whereas saccharin, denatonium, colchicine Inhibitors,Modulators,Libraries and ofloxacin were devoid of effect. The tissue relaxation induced by bitter taste compounds was likely to be receptor mediated ef fect rather than a non specific toxic effect because wash ing the preparations after application of the highest concentration of the TAS2R agonists resulted in the re covery of basal tone and essentially pre exposure levels of contractility to acetylcholine. Given the current lack of TAS2R antagonists, we sought to determine which receptor subtypes were primarily involved in the relaxation by combining a receptor gene expression analysis with subtype selective agonist experiments.

In their extensive Inhibitors,Modulators,Libraries work with HEK cells transfected with plasmids harboring sequences cod ing for the different hTAS2R and stably expressing a chimeric G protein subunit, Meyerhof et al. described the molecular receptive ranges of the 25 human TAS2R with 104 natural or synthetic bitter com pounds. Calcium imaging analysis was used as a de tection method and quantitative values in this particular model of HEK cells were most often reported as the threshold concentration, defined as the minimal con centration that elicited responses from cells but only in rare exceptions were the results expressed as potency. This work was used as a basis for the choice of the different Inhibitors,Modulators,Libraries non selective or subtype selective Inhibitors,Modulators,Libraries agonists used in the present study for which threshold concentration or EC50 when available were detailed in Table 1.

These data obtained in a transfected renal cell line should only be cautiously ex trapolated to experiments performed on Inhibitors,Modulators,Libraries human bron chial preparations. For example, many free overnight delivery bitter compounds generated artificial calcium responses in HEK cells in the absence of transfected hTAS2R, and signalling pathways other than changes in intracellular calcium may be activated. Furthermore, the threshold concentrations assessed in HEK cells cannot be easily extrapolated to pharmaco logical potency.