Delineating signaling pathways that protect against harmful insults that trigger cell death would be beneficial for developing strategies to delay or halt the neurodegenerative process. Vascular endothelial growth factor (VEGF) is a well established endothelial growth factor which also has neuroprotective properties. While certain pathways of VEGF-induced neuroprotection are known, the downstream signaling intermediates that suppress cell death and promote survival remain elusive. We found that VEGF activated its receptor VEGFR2 in serum deprived neuronal cells to protect against a caspase-dependent cell death that is regulated in part by the p38 mitogen activated protein kinase. VEGFR2 directed neuroprotection through the activation of a Phosphatidylinositol 3'-kinase/Protein Kinase B/Akt/mammalian Target of Rapamycin (PI3-K/Akt/mTOR) and the mitogen-activated protein kinase kinase/extracellular signal-regulated protein kinases (MEK/ERK1/2) pathways. We propose to delineate the downstream events activated by ERK1/2 and mTOR in response to serum deprivation in vitro and epileptic seizures in vivo with the objective of understanding how signaling cascades that are activated by VEGF protect neuronal cells from harmful insults. To this end, we will use RT- PCR, Western blotting, immunofluorescent and gene reporter assays to identify transcriptional-dependent and -independent mechanisms that are regulated by activated ERK1/2 in vitro to prevent cell death using a neuronal cell line and primary cultures (Specific Aim 1). Pharmacological and gene silencing approaches in combination with immunoprecipitation and kinase assays will be employed to identify components of the mTOR pathway that contribute to VEGF-mediated survival in vitro (Specific Aim 2). Western blotting and immunofluorescent assays of hippocampal tissue from control and VEGF treated rats undergoing epileptic seizures will determine whether activation of mTOR and its downstream targets are associated with VEGF- mediated neuroprotection in vivo (Specific Aim 3). Using the experimental approaches described for Specific Aim 1, we will also identify the regulatory components of the cell death mechanisms that VEGF suppresses in response to serum deprived neuronal cells (Specific Aim 4). It is conceivable that the mechanisms that trigger cell death (Specific Aim 4) are those targeted by activated ERK1/2 (Specific Aim 1).
TO PUBLIC HEALTH: Identifying signaling pathways that provide neuroprotection against damaging insults would be beneficial for the development of therapeutic strategies to treat neurodegenerative disorders. A delineation of molecular intermediates of neuroprotective pathways that signal survival by suppressing cell death mechanisms would be desirable to halt or delay the progressive cell damage associated with the neurodegenerative process.
|Hao, Tianfeng; Rockwell, Patricia (2013) Signaling through the vascular endothelial growth factor receptor VEGFR-2 protects hippocampal neurons from mitochondrial dysfunction and oxidative stress. Free Radic Biol Med 63:421-31|
|Edelstein, Jacob; Rockwell, Patricia (2012) Okadaic acid induces Akt hyperphosphorylation and an oxidative stress-mediated cell death in serum starved SK-N-SH human neuroblastoma cells that are augmented by rapamycin. Neurosci Lett 531:74-9|
|Edelstein, Jacob; Hao, Tianfeng; Cao, Qin et al. (2011) Crosstalk between VEGFR2 and muscarinic receptors regulates the mTOR pathway in serum starved SK-N-SH human neuroblastoma cells. Cell Signal 23:239-48|