Vascular endothelial growth factor protects motoneurons from serum deprivation–induced cell death through phosphatidylinositol 3-kinase-mediated p38 mitogen-activated protein kinase inhibition

Abstract

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the selective degeneration and death of motoneurons in the spinal cord, brainstem and motor cortex which causes progressive muscle weakness and paralysis. Although the molecular mechanisms causing the disease remain unknown, excitotoxicity and loss of trophic support have been proposed as causes of degeneration.The present study was designed to elucidate the mechanisms of motoneuron death induced by serum deprivation and the potential neuroprotective effects of vascular endothelial growth factor (VEGF) in dissociated and organotypic rat spinal cord cultures. Serum withdrawal induced apoptotic cell death in dissociated spinal cord cultures, which was prevented in the presence of VEGF. In organotypic spinal cord cultures, low serum-induced motoneuron death was mediated by the stress-related kinase p38 mitogen-activated protein kinase (p38MAPK), as it was reversed by the p38MAPK inhibitor SB203580. In these cultures, exposure to VEGF blocked p38MAPK phosphorylation and prevented the demise of motoneurons. These effects of VEGF were mediated through the phosphatidylinositol 3-kinase/Akt (PI3-K/Akt) signal transduction pathway, as they were blocked in the presence of the PI3-K inhibitor LY294002. In addition, serum deprivation induced down-regulation of the anti-apoptotic protein Bcl-2 and this effect was prevented both by SB203580 and by VEGF via the PI3-K/Akt pathway. Therefore, Bcl-2 could also play an important role in the neuroprotection induced by VEGF in spinal cord cultures. Together, these findings indicate that VEGF prevents motoneuron death induced by serum deprivation blocking the activity of p38MAPK via the PI3-K/Akt signaling pathway.