Aim: 

Hypoxia is an important regulatory stimulus in several physiological conditions, including angiogenesis. The vascular endothelial growth factor (VEGF) belongs to a group of hypoxia-sensitive proteins, which are regulated by hypoxia-inducible factor (HIF)-1a. It has been reported that in endothelial cells hypoxic induction of HIF-1a is mediated via Shc, and it contributes to endothelial cell migration. Under normal conditions, T lymphocytes do not express p66Shc; in fact, they acquire the capacity to express this protein in response to various apoptogenic stimuli, such as hypoxic stress.

Methods: 

Peripheral blood T-cells from healthy volunteers, Jurkat T-cells and relative transfectants expressing p66Shc were cultured under normoxic (20% O₂) and hypoxic (2% O₂) conditions. mRNA

and protein expression were evaluated by qRT-PCR and Western blot analysis, respectively. VEGF concentrations were assessed on cell-free supernatants by ELISA.

Results: 

We here show that hypoxia enhanced HIF-1a accumulation and expression of VEGF in T cells. p66Shc was expressed in hypoxic T cells. Using T-cell transfectants expressing p66Shc, we observed that hypoxic p66Shc-positive expressed higher level of HIF-1a than negative controls.

p66Shc-positive transfectants overexpressed VEGF, when compared with the negative controls. A mutated version of p66Shc, lacking serine 36, expressed levels of VEGF similar to the control transfectants.

Conclusion: 

p66Shc may play an important role in downstream hypoxic signalling, involving phosphorylation of the serine 36, HIF-1a protein accumulation and VEGF expression in T lymphocytes, with important implications for the regulation of the angiogenic process by T cells.