Induction of HIF-1alpha in response to hypoxia is instantaneous.

SPECIFIC AIMSDespite the pivotal role the hypoxia-inducible factor 1α (HIF-1α) plays in physiological and pathological processes, little is known regarding the time frame and mechanisms involved in its regulation. The aim of this study was to gain insight into the sequential events occurring in the nucleus immediately after hypoxic exposure and reoxygenation by determining the kinetics of HIF-1α induction and degradation, and comparison with its dimerization partner ARNT (aryl hydrocarbon receptor nuclear translocator) and nuclear levels of NF-κB (nuclear factor kappa B), c-Fos, c-Jun, Ref-1 (redox factor 1), and Trx (thioredoxin) over a range of pathophysiological oxygen concentrations.PRINCIPAL FINDINGS1. Within 2 min of anoxic/hypoxic exposure, HIF-1α protein accumulates in the nucleusTonometers were used to expose HeLaS3 cells to 0%, 0.02%, 0.1%, 0.5%, and 5% oxygen for 0, 2, 5, 10, 32, and 60 min. Western blot analysis of nuclear extracts did not detect HIF-1α protein at any zero time points (equival...