Rationale: The alarmins IL-33 and HMGB1 (high mobility group box 1) contribute to type 2 inflammation and asthma pathogenesis.

Objectives: To determine whether P2Y₁₃-R (P2Y₁₃ receptor), a purinergic GPCR (G protein–coupled receptor) and risk allele for asthma, regulates the release of IL-33 and HMGB1.

Methods: Bronchial biopsy specimens were obtained from healthy subjects and subjects with asthma. Primary human airway epithelial cells (AECs), primary mouse AECs, or C57Bl/6 mice were inoculated with various aeroallergens or respiratory viruses, and the nuclear-to-cytoplasmic translocation and release of alarmins was measured by using immunohistochemistry and an ELISA. The role of P2Y₁₃-R in AEC function and in the onset, progression, and exacerbation of experimental asthma was assessed by using pharmacological antagonists and mice with P2Y₁₃-R gene deletion.

Measurements and Main Results: Aeroallergen exposure induced the extracellular release of ADP and ATP, nucleotides that activate P2Y₁₃-R. ATP, ADP, and aeroallergen (house dust mite, cockroach, or Alternaria antigen) or virus exposure induced the nuclear-to-cytoplasmic translocation and subsequent release of IL-33 and HMGB1, and this response was ablated by genetic deletion or pharmacological antagonism of P2Y13. In mice, prophylactic or therapeutic P2Y₁₃-R blockade attenuated asthma onset and, critically, ablated the severity of a rhinovirus-associated exacerbation in a high-fidelity experimental model of chronic asthma. Moreover, P2Y₁₃-R antagonism derepressed antiviral immunity, increasing IFN-λ production and decreasing viral copies in the lung.

Conclusions: We identify P2Y₁₃-R as a novel gatekeeper of the nuclear alarmins IL-33 and HMGB1 and demonstrate that the targeting of this GPCR via genetic deletion or treatment with a small-molecule antagonist protects against the onset and exacerbations of experimental asthma.