Neuroprotective effect of exogenous vascular endothelial growth factor on rat spinal cord neurons in vitro hypoxia

Background Vascular endothelial growth factor (VEGF) is well known as a hypoxia-induced protein. That it markedly increased expression of VEGF and improvement of rat motor function after spinal cord injury suggested that VEGF could play a neuroprotective role in ischaemic tolerance. This study investigated whether vascular endothelial growth factor has direct neuroprotective effects on rat spinal cord neurons. Methods We employed primary cultures of embryonic rat spinal cord neurons, then administrated different concentrations of VEGF(164) in the culture medium before hypoxia when the number of neurons was counted and the cell viability was detected by MTT. The neuronal apoptosis and expression of VEGF and its receptor genes were evaluated by terminal deoxynucleotidyl transferase mediated dUTP nick-end labelling ( TUNEL) and immunohistochemistry. The VEGFR(2)/FLK-1 inhibitor, SU1498, was used to confirm whether the neuroprotective effect of VEGF was mediated through VEGFR(2)/Flk-1 receptors. Result In hypoxic conditions, the number and viability of neurons decreased progressively, while the number of TUNEL-positive cells increased along with the prolongation of hypoxic exposure. When the concentration of VEGF in cell culture medium reached 25 ng/ml, the cell viability increased 11% and neuronal apoptosis reduced to half, this effect was dose dependent and led to an approximately 25% increase in cell viability and about threefold decrease in TUNEL-positive cells at a maximally effective concentration of 100 ng/ml. In normal conditions, VEGF/Flk-1 but not VEGF/Flt-1 gene expressed at a low level: after hypoxia, the expression of VEGF/Flk-1, but not VEGF/Flt-1 was significantly increased. The protective effect of VEGF was blocked by the VEGFR(2)/Flk-1 receptor tyrosine kinase inhibitor, SU1498. Conclusions VEGF has direct neuroprotective effects on rat spinal cord neurons, which may be mediated in vitro through VEGFR(2)/Flk-1 receptors.