Small molecule modulation of allergen-induced asthma via human protease-activated receptor-2 (PAR2) in vivo

Allergic asthma is characterized by airway hyperresponsiveness (AHR), inflammation (INF), and mucus overproduction (MUC). It can be triggered by house dust mites (HDM) and <italic>Alternaria alternata</italic> (<italic>Alt</italic>). PAR2 is a G-protein coupled receptor that activates Gq/Ca²⁺ and β-arrestin/MAPK signaling to establish cellular changes. Allergen-induced asthma indicators in vivo require PAR2 β-arrestin/MAPK signaling in male mouse models. We have introduced full biased PAR2 antagonists (C781 and C937; inhibit only β-arrestin/MAPK signaling) that limit these allergen-induced responses <italic>in vivo</italic>. We have created a transgenic mouse devoid of mouse PAR2 and expressing human PAR2 in a C57Bl/6 background (hTgPAR2). hTgPAR2 mice respond to acute HDM and <italic>Alt</italic> exposure with significantly increased AHR, INF and MUC, whereas the C57Bl/6 mice only displayed changes in INF and MUC. Sex differences in response to HDM were dependent on the lot used and mostly presented in the AHR, where males were more responsive. Sex differences in response to <italic>Alt</italic> were observed with the male hTgPAR2 mice driving the increased AHR and female hTgPAR2 mice driving the INF and MUC. The biased PAR2 antagonists, C781 and C937, demonstrated efficacy in controlling allergen-induced asthma indicators from either allergen with near full inhibition of AHR development and partial inhibition of airway INF and MUC. We conclude that the hTgPAR2 mouse can serve as a model for sex differences in allergic asthma and as an in vivo tool for evaluating PAR2 antagonists for the treatment of allergic asthma, with biased PAR2-β-arrestin/MAPK antagonism a promising therapeutic approach.