Vascular endothelial growth factor C acts as a neurotrophic factor for dopamine neurons in vitro and in vivo

Neurotrophic factors regulate the development and maintenance of the nervous system and protect and repair dopaminergic neurons in animal models of Parkinson's disease (PD). Vascular endothelial growth factors A (VEGF-A) and B have also neurotrophic effects on various types of neurons, including dopaminergic neurons. We examined the ability of the key lymphangiogenic factor VEGF-C to protect dopaminergic cells in vitro and in vivo. The study was initiated by a finding from microarray profiling of Neuro2A-20 cells which revealed up-regulation of VEGF-C by glial cell-line-derived neurotrophic factor (GDNF). Next, we observed that VEGF-C can rescue embryonic dopaminergic neurons and activate the mitogen-activated protein kinase/extracellular signal regulated kinase (MAPK/ERK) pathway in vivo. VEGF receptors 1-2 and co-receptors, neuropilins 1-2, were expressed both in mouse embryonic cultures and adult midbrains. In vivo, VEGF-C had a robust functional effect in the rat unilateral 6-hydroxydopamine (6-OHDA) model of PD and there was a small additive effect on the survival of tyrosine hydroxylase (TH)-positive cells with GDNF. The neuroprotective effect of VEGF-C is most likely due to a combination of direct and indirect neurotrophic effects because, VEGF-C, unlike GDNF, induced also angiogenesis in the striatum following 6-OHDA insult as it did in human umbilical vein endothelial cells (HUVEC). However, we detected activation of astroglia and microglia as well as blood-brain barrier disruption after intracerebral delivery of VEGF-C, raising a concern of its safe usage as a therapeutic molecule. Our results provide evidence of VEGF-C as a neurotrophic factor that influences the dopaminergic system through multiple mechanisms.