title: Activation of cytosolic phospholipase A2 downstream of the Src-phospholipase D1 (PLD1)-protein kinase C γ (PKCγ) signaling axis is required for hypoxia-induced pathological retinal angiogenesis.
abstract: In view of understanding the mechanisms of retinal neovascularization, we had reported previously that vascular endothelial growth factor (VEGF)-induced pathological retinal angiogenesis requires the activation of Src-PLD1-PKCγ signaling. In the present work, we have identified cytosolic phospholipase A(2) (cPLA(2)) as an effector molecule of Src-PLD1-PKCγ signaling in the mediation of VEGF-induced pathological retinal angiogenesis based on the following observations. VEGF induced cPLA(2) phosphorylation in a time-dependent manner in human retinal microvascular endothelial cells (HRMVECs). VEGF also induced arachidonic acid (AA) release in a dose-, time-, and cPLA(2)-dependent manner. Depletion of cPLA(2) levels inhibited VEGF-induced HRMVEC DNA synthesis, migration, and tube formation. In addition, the exogenous addition of AA rescued VEGF-induced HRMVEC DNA synthesis, migration, and tube formation from inhibition by down-regulation of cPLA(2). Inhibition of Src, PLD1, or PKCγ attenuated VEGF-induced cPLA(2) phosphorylation and AA release. Consistent with these findings, hypoxia induced cPLA(2) phosphorylation and activity in VEGF-Src-PLD1-PKCγ-dependent manner in a mouse model of oxygen-induced retinopathy. In addition, siRNA-mediated down-regulation of cPLA(2) levels in the retina abrogated hypoxia-induced retinal endothelial cell proliferation and neovascularization. These observations suggest that cPLA(2)-dependent AA release is required for VEGF-induced Src-PLD1-PKCγ-mediated pathological retinal angiogenesis.
authors.affiliation: Department of Physiology, The University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.
authors.forename: Qiuhua
authors.initials: Q
authors.lastname: Zhang
authors.forename: Dong
authors.initials: D
authors.lastname: Wang
authors.forename: Nikhlesh K
authors.initials: NK
authors.lastname: Singh
authors.forename: Venkatesh
authors.initials: V
authors.lastname: Kundumani-Sridharan
authors.forename: Laxmisilpa
authors.initials: L
authors.lastname: Gadiparthi
authors.forename: Ch Mohan
authors.initials: ChM
authors.lastname: Rao
authors.forename: Gadiparthi N
authors.initials: GN
authors.lastname: Rao
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D000860:Hypoxia / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D051379:Mice; D009389:Neovascularization, Pathologic / Q000378:metabolism / Q000473:pathology; D010100:Oxygen / Q000494:pharmacology; D010739:Phospholipase D / Q000378:metabolism*; D054510:Phospholipases A2, Cytosolic / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism*; D012160:Retina / Q000187:drug effects / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D015398:Signal Transduction / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology
chemical_list: D042461:Vascular Endothelial Growth Factor A; D016718:Arachidonic Acid; D004247:DNA; C087857:protein kinase C gamma; D016392:Proto-Oncogene Proteins pp60(c-src); D011493:Protein Kinase C; D054510:Phospholipases A2, Cytosolic; D010739:Phospholipase D; C106801:phospholipase D1; D010100:Oxygen