Hypoxia and apoptosis

Research description

HIF-1 (hypoxia-inducible factor-1) is the major transcription factor specifically activated by hypoxia. It induces the expression of different genes whose products play an adaptative role for hypoxic cells and tissues. Besides these protective responses, HIF-1 and/or hypoxia have also been shown to be either anti-apoptotic or pro-apoptotic, according to the cell type and experimental conditions. More severe or prolonged hypoxia rather induces apoptosis that is, at least in part, initiated by the direct association of HIF-1alpha and p53 and p53-induced gene expression. On the other hand, HIF-1alpha dimerized with ARNT, as an active transcription factor, can protect cells from apoptosis induced by several conditions. The aim of this project is to understand the different mechanisms that account for these opposite effects of HIF-1alpha. Proteins/genes overexpressed in hypoxic conditions are identified and their role in the protective effect of hypoxia against apoptosis is determined. In addition, the signal transduction pathways initiated by hypoxia and that lead to this overexpression are dissected.

Experimental models

• HepG2 incubated in the presence of ter-butyl hydroperoxide or etoposide

• L929 incubated in the presence of TNFa

Techniques

DNA ladder (agarose gel, ELISA), cytochrome c release (western blot, ELISA), PARP cleavage (western blot), caspase-3 activity (activity assay, ELISA), kinase phosphorylation (western blot), Bax and Bid translocation (confocal microscopy), DNA microarray, RPA