Methods: LAD2 human mast cells [1], primary human basophils, and THP-1 human myeloid cells were used for investigations of FcεRI, TLR ligand and SCF-induced responses. Quantitative real-time PCR, Western blot analysis, ELISA, fluorometry, luminometry and fluorescence microscopy were employed to run the assays.
Results: We observed that HIF-1 activation is differentially regulated in the cases of pro-allergic, TLR-dependent and SCF-induced cellular responses. While PI3K/mTOR and MAP kinase pathways were the major contributors to HIF-1 activation during allergic/SCF-dependent responses, TLR-mediated processes occurred mostly via redox-dependent mechanisms. Experiments with HIF-1α (the inducible subunit regulating HIF-1 transactivation) knockdown cells demonstrated that HIF-1 plays a crucial role in the expression of the primary angiogenic cytokine VEGF and controls intracellular energy metabolism by regulating glycolytic metabolic activity.
Conclusions: The HIF-1 transcription complex supports not only the survival of immune cells (mast cells, basophils, myeloid cells) in pathological environments but also determines their abilities to generate pro-allergic, pro-inflammatory as well as pro-angiogenic cytokines over sustained periods.
Reference
1. Kirshenbaum AS, Akin C, Wu Y, Rottem M, Goff JP, Beaven MA, et al. (2003) Leuk Res; 27:677-82.