View Abstract

A1332 - HIFα Subunits Alter Asthma Phenotype in a Murine Model
Author Block: L. Ma1, C. J. Javier1, R. Al Kolla1, A. Moshensky1, C. M. Bojanowski2, J. Shin1, L. E. Crotty Alexander3, V. Chun1; 1UCSD and VASDHS, San Diego, CA, United States, 2Pulmonary and Critical Care, La Jolla, CA, United States, 3Medicine, UCSD and VASDHS, San Diego, CA, United States.
Introduction:Asthma is a heterogeneous disease with different clinical phenotypes. Some asthmatics do not respond to conventional therapies, indicating that there are inflammatory pathways active in asthma pathogenesis that are not being targeted by current therapeutic agents. Hypoxia inducible factor (HIF)-1α is a transcription factor that regulates important inflammatory pathways and is upregulated in immune cells and lung tissues of asthmatic patients. Very little is known about the HIF-2α subunit. However, prior research suggests that HIF-2α may act in a complementary fashion with HIF-1α to promote inflammation. We hypothesize that, in asthma, both HIF-1α and HIF-2α promote the transmigration of eosinophils and TH2 lymphocytes into the lungs by increasing expression of adhesion molecules on the surface of pulmonary endothelial cells. We used the well characterized OVA mouse model of asthma for these studies. Methods:C57BL/6j mice with cre expressed solely in pulmonary endothelial cells (L1cre) were crossed with HIF-1α flox/flox, HIF-2α flox/flox and double HIF-1α and HIF-2α flox/flox mice to create three mouse lines: L1cre HIF-1αfl/fl, L1cre HIF-2αfl/fl, and L1cre HIF-1αfl/fl HIF-2αfl/fl. Cre- mice were used as experimental (wild-type) controls. Six to eight-week-old female and male mice underwent asthma induction by intraperitoneal (i.p.) injection of ovalbumin (OVA) 50μg in 200μL of phosphate buffered saline (PBS) on days 0 and 7. Mice were exposed to inhaled OVA (10μg in 50μL, intranasally) on days 18-21. On day 22, lung mechanics were assessed using the FlexiVent mouse ventilator, and methacholine challenge was performed to assess degree of airway reactivity. Bronchoalveolar lavage (BAL), blood, and bone marrow total cell count and differentials were performed. ELISAs were used to assay known TH2 cytokine profiles of BAL fluid and serum. Lung tissue gene expression was evaluated via qPCR. Results:Removal of HIF-1α and -2α from pulmonary endothelial cells altered asthma pathogenesis via changes in both airway inflammation (BAL cell counts, eosinophilia, and TH2 cytokines) and airway hyperreactivity in response to methacholine challenge. Conclusions:HIF-1α and -2α subunits in pulmonary endothelial cells play a role in regulating allergic inflammation in the lungs. These data suggest that HIF-1α and HIF-2α may be therapeutic targets in asthmatics who are non-responders to conventional therapy.