Hypoxia inducible factor promotes murine allergic airway inflammation and is increased in asthma and rhinitis.

BACKGROUND: New therapies are necessary to address inadequate asthma control in many patients. This study sets out to investigate whether hypoxia-inducible factor (HIF) is essential for development of allergic airway inflammation (AAI) and therefore a potential novel target for asthma treatment. METHODS: Mice conditionally knocked out for HIF-1ß were examined for their ability to mount an allergic inflammatory response in the lung after intratracheal exposure to ovalbumin. The effects of treating wild-type mice with either ethyl-3,4-dihydroxybenzoate (EDHB) or 2-methoxyestradiol (2ME), which upregulate and downregulate HIF, respectively, were determined. HIF-1α levels were also measured in endobronchial biopsies and bronchial fluid of patients with asthma and nasal fluid of patients with rhinitis after challenge. RESULTS: Deletion of HIF-1ß resulted in diminished AAI and diminished production of ovalbumin-specific IgE and IgG(1) . EDHB enhanced the inflammatory response, which was muted upon simultaneous inhibition of vascular endothelial growth factor (VEGF). EDHB and 2ME antagonized each other with regard to their effects on airway inflammation and mucus production. The levels of HIF-1α and VEGF increased in lung tissue and bronchial fluid of patients with asthma and in the nasal fluid of patients with rhinitis after challenge. CONCLUSIONS: Our results support the notion that HIF is directly involved in the development of AAI. Most importantly, we demonstrate for the first time that HIF-1α is increased after challenge in patients with asthma and rhinitis. Therefore, we propose that HIF may be a potential therapeutic target for asthma and possibly for other inflammatory diseases.

The contrasting effects of CD8+ T cells on primary, established and Nippostrongylus brasiliensis-induced IgE responses.

Recent data have indicated that CD8+ T cells suppress rodent IgE responses. In this study we investigated the effect of CD8+ T cells on primary and established IgE responses in euthymic and athymic nude rats. Euthymic PVG rats were depleted of CD8+ T cells by intraperitoneal injection of a CD8-specific monoclonal antibody (OX8), which resulted in an apparent loss of 92% of splenic and 98% of peripheral blood CD8+ T cells. The CD8+ T-cell depleted animals failed to mount a significant IgE response compared with control animals given an irrelevant monoclonal antibody (OX21). Furthermore, PVG nude rats reconstituted with purified CD4+ thoracic duct lymphocytes (TDL) alone failed to mount a significant IgE response, while animals given unfractionated TDL (containing CD4+ and CD8+ T cells) did. Depletion of CD8+ T cells 7 days prior to immunization and subsequent reconstitution at the time of immunization restored the IgE response. In contrast, removal of CD8+ T cells 1 month after induction of IgE by immunization with ovalbumin (OVA) and ricin prolonged the IgE response. In all cases IgG antibody responses were unaffected by the presence or absence of CD8+ T cells. This study shows that some CD8+ T cells are required for IgE, but not IgG, production to soluble antigen in a primary immune response. However, later in the immune response CD8+ T cells were shown to inhibit IgE production. These effects were apparently restricted to the immune response to soluble antigen, as Hooded Lister rats infected with 9000 larvae of the nematode Nippostrongylus brasiliensis produced high sustained levels of circulating IgE, in excess of 10 micrograms/ml, regardless of whether CD8+ T cells were depleted before or 1 month after infection.