title: Signaling through the vascular endothelial growth factor receptor VEGFR-2 protects hippocampal neurons from mitochondrial dysfunction and oxidative stress.
abstract: Vascular endothelial growth factor VEGF (VEGF-A or VEGF₁₆₅) is a potent angiogenic factor that also signals neuroprotection through activation of its cognate receptor VEGFR-2. In this capacity, VEGF signaling can rescue neurons from the damage induced by stressful stimuli many of which elicit oxidative stress. However, the regulatory role that VEGFR-2 plays in providing neuroprotection remains elusive. Therefore, we investigated the effects of VEGFR-2 inhibition on primary cultures of mature hippocampal neurons undergoing nutritional stress. We found that neurons cultured under nutritional stress had increased expression of VEGF and its receptors, VEGFR-1, VEGFR-2, and NP-1, as well as enhanced levels of VEGFR-2 phosphorylation. These neurons also showed increased activation of the prosurvival pathways for MEK/ERK1/2 and PI3K/Akt, enhanced phosphorylation (inactivation) of the proapoptotic BAD, and higher levels of the antiapoptotic protein Bcl-xL, all of which were augmented by treatments with exogenous VEGF and blocked by VEGFR-2 inhibition. The blockade of VEGFR-2 function also elicited a cytotoxicity that was accompanied by caspase-3 activation, induction of hemeoxygenase-1 (HO-1), oxidative stress, and a collapse in the mitochondrial membrane potential (ΔΨ(m)). Knockdown of VEGFR-2 by siRNA generated a similar pattern of redox change and mitochondrial impairment. Pretreatments with VEGF, VEGF-B, or the antioxidant N-acetylcysteine (NAC) rescued SU1498 or siRNA-treated neurons from the mitochondrial dysfunction and oxidative stress induced by VEGFR-2 inhibition in a timely fashion. These findings suggested that VEGF or VEGF-B can provide neuroprotection by signaling through an alternate VEGF receptor. Together, our findings suggest that VEGF signaling through VEGFR-2 plays a critical regulatory role in protecting stressed hippocampal neurons from the damaging effects of an oxidative insult. These findings also implicate VEGFR-1 or NP-1 as compensatory receptors that mediate neuroprotection when VEGFR-2 function is blocked.
authors.affiliation: Department of Biological Sciences, Hunter College and the Graduate Center of The City University of New York, 695 Park Ave, New York, NY 10065, USA.
authors.forename: Tianfeng
authors.initials: T
authors.lastname: Hao
authors.forename: Patricia
authors.initials: P
authors.lastname: Rockwell
mesh_terms: D000818:Animals; D005786:Gene Expression Regulation; D006624:Hippocampus / Q000378:metabolism / Q000473:pathology; D008928:Mitochondria / Q000378:metabolism / Q000473:pathology*; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D018696:Neuroprotective Agents / Q000378:metabolism; D018384:Oxidative Stress; D010766:Phosphorylation; D034741:RNA, Small Interfering; D051381:Rats; D015398:Signal Transduction; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000378:metabolism; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051025:bcl-Associated Death Protein / Q000378:metabolism; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: C494821:Bad protein, rat; C494813:Bcl2l1 protein, rat; D018696:Neuroprotective Agents; D034741:RNA, Small Interfering; D042461:Vascular Endothelial Growth Factor A; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; D040281:Vascular Endothelial Growth Factor Receptor-1; D040301:Vascular Endothelial Growth Factor Receptor-2
keywords: 6-carboxy-2′,7′-dichlorodihydrofluorescein diacetate; GCM; Hippocampal neurons; MAP; MEK; Mitochondrial dysfunction; N-acetylcysteine; NAC; NB; NP-1, NP-2; Neurobasal; Neuropilin-1 and -2; Oxidative stress; PI3K; TMRE; VEGF; VEGF-B; VEGFR-2; carboxy-H(2)DCFCA; glial-conditioned medium; microtubule-associated protein; mitogen-activated protein kinase; phosphatidylinositol 3-kinase; tetramethylrhodamine methyl; vascular endothelial growth factor