Hypoxia Inducible Factor-1α binding to HDAC2 and MIF promoter regions is associated with changes in gene expression levels in chronic ozone exposed mice

Ozone is an oxidizing environmental pollutant that significantly contributes to respiratory health risk. Exposure to increased ambient levels of ozone has been associated to worsening of symptoms of patients with lung diseases like asthma and COPD. In this study we investigate the chronic effects of ozone exposure on Hypoxia Inducible Factor (HIF)-1α binding to Histone Deacetylase (HDAC) 2 and Macrophage Migration Inhibitory Factor (MIF) promoter regions in vivo . C57BL/6J mice were exposed to ozone (2.5 ppm) for 3 hours a day, 2 times a week for a period of 6 weeks. After the last exposure mice were sacrificed for bronchoalveolar lavage (BAL) fluid and lung tissue collections. BAL total cell counts were elevated (predominately macrophages and neutrophils) and was associated with increased levels of cytokines (KC and TNFα) levels in ozone exposed mice indicating the presence of an inflammatory environment in the lung. Lung HIF-1α protein levels were increased in cytoplasm and nuclear fractions of ozone exposed mice compared to normal air exposed mice. Using chromatin immunoprecipitation assays were demonstrate that HIF-1α binds to the promoter regions of both HDAC2 and MIF genes in vivo . This was associated with a reduction in HDAC2 mRNA, protein and activity and an increase in MIF protein and mRNA levels. Ozone-induced HIF-1α protein is able to bind to HDAC2 and MIF promoter regions in vivo identifying these as two novel HIF-1α target genes. Funded by the Wellcome Trust.