Abstract Introduction Asthma is a chronic inflammatory airway disease affecting over 300 million people worldwide. Airway smooth muscle (ASM) plays a central role in bronchoconstriction through responses to mediators released by immune and structural cells. Several G protein-coupled receptors (GPCRs) expressed in ASM regulate smooth muscle contraction and contribute to asthma pathophysiology. Phosphatidylinositol 4-phosphate-5 kinase (PIP5K) generates phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2), a lipid mediator critical for GPCR signaling, but its role in asthma remains poorly defined. Here, we investigated whether targeting PIP5K modulates ASM function in vitro and features of allergic asthma in vivo. Methods A small-molecule inhibitor and siRNA-mediated knockdown of PIP5K were used to assess cell proliferation, calcium mobilization and downstream contractile signaling in immortalized human ASM and primary human ASM cells. For in vivo studies, mice received intranasal house dust mite (HDM) extract (25 µg daily for three weeks) with or without PIP5K inhibitor (1mg/Kg, 30 min before each challenge). Lung function was assessed using FlexiVent (Scireq, Canada), and bronchoalveolar lavage (BAL) fluid was analyzed for immune cell infiltration by flow cytometry and cytokines measurement by multiplex ELISA (Eve Technologies, Canada). Results Pharmacological and siRNA-mediated inhibition of PIP5K suppressed mitogen-induced proliferation of human ASM cells and reduced agonist-induced calcium mobilization. These effects were associated with decreased phospholipase C activity, reduced IP3 accumulation, and diminished phosphorylation of myosin light chain kinase, indicating impaired contractile signaling. In HDM-challenged mice, PIP5K inhibition markedly attenuated airway resistance, immune cell infiltration (myeloid and lymphoid subsets) and proinflammatory cytokines in BAL fluid. Conclusion These findings suggest that PIP5K contributes to ASM hyperresponsiveness and allergen-driven airway inflammation. Targeting PIP5K may represent a novel therapeutic strategy for asthma. This abstract is funded by: None
Roy et al. (Fri,) studied this question.