Background and Purpose Asthma is a heterogenous disease strongly associated with inflammation that has many different causes and triggers. Current asthma treatments target symptoms such as bronchoconstriction and airway inflammation. Despite recent advances in biological therapies, there remains a need for new classes of therapeutic agents with novel, upstream targets. The proteinase‐activated receptor‐2 (PAR2) has long been implicated in allergic airway inflammation and asthma and it remains an intriguing target for novel therapies. Here, we describe the actions of C781, a newly developed low MW PAR2 biased antagonist, in vitro and in vivo in the context of acute allergen exposure. Experimental Approach A human bronchial epithelial cell line expressing PAR2 (16HBE14o‐ cells) was used to evaluate the modulation in vitro, by C781, of physiological responses to PAR2 activation and downstream β‐arrestin/MAPK and Gq/Ca2+ signalling. Acute Alternaria alternata sensitized and challenged mice were used to evaluate C781 as a prophylactically administered modulator of airway hyperresponsiveness, inflammation and mucus overproduction in vivo. Key Results C781 reduced in vitro physiological signalling in response to ligand and proteinase activation. C781 effectively antagonized β‐arrestin/MAPK signalling without significant effect on Gq/Ca2+ signalling in vitro. Given prophylactically, C781 modulated airway hyperresponsiveness, airway inflammation and mucus overproduction of the small airways in an acute allergen‐challenged mouse model. Conclusion and Implications Our work demonstrates the first biased PAR2 antagonist for β‐arrestin/MAPK signalling. C781 is efficacious as a prophylactic treatment for allergen‐induced airway hyperresponsiveness and inflammation in mice. It exemplifies a key pharmacophore for PAR2 that can be optimized for clinical development.

Asthma is a complex disease characterized by airway hyperresponsiveness (AHR) inflammation, and mucus overproduction, and has differential presentation in males and females. There exists strong demand to improve upon current asthma treatments by targeting upstream signaling pathways, including the G-protein coupled receptor protease-activated receptor-2 (PAR2). We have recently shown effectiveness of full (C391) and ß-arrestin biased (C781) PAR2 antagonism in limiting allergen-induced asthma indicators in mouse models (C57Bl/6 and Balb/C). To better test PAR2 antagonists as asthma drugs, we have developed a transgenic mouse model that expresses human PAR2 without mouse PAR2 expression in a C57Bl/6 background (htgPAR2). The htgPAR2 mice have heightened responses to asthma allergens [house dust mite (HDM) or Alternaria alternata] following acute exposure. Limited sex differences were observed in the HDM challenge model. However, when challenged with A. alternata there was significantly higher AHR in the male mice and significantly higher inflammatory and mucus responses in the female mice. The full and ß-arrestin biased PAR2 antagonists also displayed differential effects with C781 providing broader control of allergen-induced indicators (AHR, inflammation and mucus overproduction). We conclude that the htgPAR2 mouse model is a promising tool for preclinical in vivo screening of potential asthma treatments targeting PAR2. Grants from the National Institute of Health (NS098826, AI140257, HL16024, HL152942) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

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