Cytosolic phospholipase A2 regulates viability of irradiated vascular endothelium.
Radiosensitivity of various normal tissues is largely dependent on radiation-triggered signal transduction pathways. Radiation simultaneously initiates distinct signaling from both DNA damage and cell membrane. Specifically, DNA strand breaks initiate cell-cycle delay, strand-break repair or programmed cell death, whereas membrane-derived signaling through phosphatidylinositol 3-kinase/Akt and mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) enhances cell viability. Here, activation of cytosolic phospholipase A(2) (cPLA(2)) and production of the lipid second-messenger lysophosphatidylcholine were identified as initial events (within 2 min) required for radiation-induced activation of Akt and ERK1/2 in vascular endothelial cells. Inhibition of cPLA(2) significantly enhanced radiation-induced cytotoxicity due to an increased number of multinucleated giant cells and cell cycle-independent accumulation of cyclin B1 within 24-48 h of irradiation. Delayed programmed cell death was detected at 72-96 h after treatment. Endothelial functions were also affected by inhibition of cPLA(2) during irradiation resulting in attenuated cell migration and tubule formation. The role of cPLA(2) in the regulation of radiation-induced activation of Akt and ERK1/2 and cell viability was confirmed using human umbilical vein endothelial cells transfected with shRNA for cPLA(2)alpha and cultured embryonic fibroblasts from cPLA(2)alpha(-/-) mice. In summary, an immediate radiation-induced cPLA(2)-dependent signaling was identified that regulates cell viability and, therefore, represents one of the key regulators of radioresistance of vascular endothelial cells.
Department of Radiation Oncology, Vanderbilt University School of Medicine, Vanderbilt University, Nashville, TN 37232-5671, USA.
E M
EM
Yazlovitskaya
A G
AG
Linkous
D K
DK
Thotala
K C
KC
Cuneo
D E
DE
Hallahan
D000818:Animals; D002470:Cell Survival / Q000502:physiology*; D002478:Cells, Cultured; D003600:Cytosol / Q000201:enzymology*; D042783:Endothelial Cells / Q000166:cytology / Q000502:physiology* / Q000528:radiation effects*; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D054513:Group IV Phospholipases A2 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008244:Lysophosphatidylcholines / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology / Q000528:radiation effects*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism
D008244:Lysophosphatidylcholines; D034741:RNA, Small Interfering; D040301:Vascular Endothelial Growth Factor Receptor-2; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D054513:Group IV Phospholipases A2