In addition, Lee et al. have reported that VEGF is a potent stimulator of inflammation, airway remodeling, and

physiologic dysregulation that augments antigen sensitization and Th2 inflammation 17. In addition, PI3K/Akt selleck inhibitor signaling has been shown to increase levels of HIF-1α protein 18. However, there are little data on the roles and molecular basis of HIF-1α activation in allergic airway diseases. In the current study, we investigated the signaling networks involved in HIF-1α activation and the role of HIF-1α in pathogenesis of allergic airway disease using primary mouse tracheal epithelial cells and a murine model of OVA-induced allergic airway disease. The results showed that HIF-1α is activated in antigen-induced airway disease through PI3K-δ signaling. Activation of HIF-1α induces VEGF expression that is abnormally enhanced in asthma. Involvement of HIF-1α activation in VEGF expression in bronchial epithelial cells from OVA-treated mice was evaluated using siRNA for HIF-1α. The levels of nuclear HIF-1α protein and VEGF protein in primary tracheal epithelial cells

isolated from OVA-treated mice were increased compared with the levels in tracheal epithelial cells from the control mice (Fig. 1A). RNA interference using siRNA for HIF-1α reduced the increased levels of HIF-1α and VEGF in bronchial epithelial cells of OVA-treated mice. Additionally, RT-PCR and real-time RT-PCR analyses revealed that the increased mRNA levels of HIF-1α and VEGF were substantially decreased by the transfection of siRNA targeting HIF-1α (Fig. 1B–D). Western blot analysis not showed that levels find more of nuclear HIF-2α protein and VEGF protein in primary tracheal epithelial cells isolated from OVA-treated mice were increased as compared with

the levels in tracheal epithelial cells from the control mice (Supporting Information Fig. 1A). The RNA interference with siRNA for HIF-2α reduced the increased levels of HIF-2α and VEGF in bronchial epithelial cells isolated from OVA-treated mice. Consistent with the results, RT-PCR and real-time RT-PCR analyses revealed that the increased mRNA levels of HIF-2α and VEGF were substantially decreased by the transfection of siRNA targeting HIF-2α (Supporting Information Fig. 1B–D). The effects of 2ME2, an inhibitor of HIF-1α translation, on HIF-1α protein levels were evaluated in nuclear protein extracts of lung tissues and primary tracheal epithelial cells isolated from OVA-treated and control mice. HIF-1α levels were increased in OVA-treated mice, as compared with the levels in the control mice (Fig. 2A, B, E, and F). The increased HIF-1α levels in nuclear protein extracts were decreased by in vitro treatment with 2ME2 (Fig. 2A and B) as well as by oral administration of 2ME2 (Fig. 2E and F). PI3K signaling has been shown to increase levels of HIF-1α protein 18.