siRNA was dissolved in a 5% glucose solution and in vivo-jetPEI to an N/P ratio of 7, and a total of 50 μl of the siRNA-jetPEI complex was administered intranasally to nude mice before the last challenge.

Hyperactivation of phosphoinositol 3-kinase (PI3K) has been suggested to be a potential mechanism for endoplasmic reticulum (ER) stress-enhanced airway hyperresponsiveness, and PI3K inhibitors have been examined as asthma therapeutics. However, the regulatory mechanism linking PI3K to ER stress and related pathological signals in asthma have not been defined. To elucidate these pathogenic pathways, we investigated the influence of a selective PI3Kdelta inhibitor, IC87114, on airway inflammation in an ovalbumin/lipopolysaccharide (OVA/LPS)-induced asthma model. In OVA/LPS-induced asthmatic mice, the activity of PI3K, downstream phosphorylation of AKT and activation of nuclear factor-kappaB (NF-kappaB) were all significantly elevated; these effects were reversed by IC87114. IC87114 treatment also reduced the OVA/LPS-induced ER stress response by enhancing the intra-ER oxidative folding status through suppression of protein disulfide isomerase activity, ER-associated reactive oxygen species (ROS) accumulation and NOX4 activity. Furthermore, inositol-requiring enzyme-1alpha (IRE1alpha)-dependent degradation (RIDD) of IRE1alpha was reduced by IC87114, resulting in a decreased release of proinflammatory cytokines from bronchial epithelial cells. These results suggest that PI3Kdelta may induce severe airway inflammation and hyperresponsiveness by activating NF-kappaB signaling through ER-associated ROS and RIDD-RIG-I activation. The PI3Kdelta inhibitor IC87114 is a potential therapeutic agent against neutrophil-dominant asthma.