Fig. 4. Mechanistic understanding of PAR2 antagonists.

Concentration–response curves for PAR2 agonists, 2f-LIGRL-NH₂ or trypsin, were measured in the presence of increasing concentrations of the two antagonists AZ8838 and AZ3451 in CHO-hPAR2 cells. AZ8838 was a competitive antagonist against a 2f-LIGRL-NH₂ (n = 4) and b trypsin (n = 3). In contrast, AZ3451 was a non-competitive antagonist against c 2f-LIGRL-NH₂ (n = 3) and d trypsin (n = 3). Data were analysed using Gaddum/Schild EC₅₀ global fitting competitive model and the calculated Schild slopes are shown. By comparing the calculated Schild slope of AZ8838 and AZ3451 versus a hypothetical Schild slope = 1 using extra-sum of squares F-test, the p-values for AZ8838 against 2f-LIGRL-NH₂ and trypsin are >0.05 indicating that the calculated Schild slope for AZ8838 is not statistically distinguishable from a hypothetical Schild slope = 1. While the p-values for AZ3451 against 2f-LIGRL-NH₂ and trypsin are <0.001 indicating that the calculated Schild slope for AZ3451 is statistically distinguishable from a hypothetical Schild slope = 1. Data are presented as individual data points with error bar denoting s.e.m. of n > 3 independent experiments.