Basic fibroblast growth factor inhibits radiation-induced apoptosis of HUVECs. II. The RAS/MAPK pathway and phosphorylation of BAD at serine 112.
Radiation-induced endothelial cell apoptosis is involved in the development of many radiation injuries, including radiation-induced skin ulcers. The proangiogenic growth factor basic fibroblast growth factor (bFGF, NUDT6) enhances endothelial cell survival. In the present study, we set up a model of apoptosis in which primary cultured human umbilical vein endothelial cells (HUVECs) were irradiated with (60)Co gamma rays to explore the effects of bFGF on radiation-induced apoptosis of HUVECs and the signaling pathways involved. We found that bFGF inhibited radiation-induced apoptosis of HUVECs, and that the effect was mediated in part by the RAS/MEK/ MAPK/RSK (p90 ribosomal S6 kinase)/BAD pathway. This pathway was activated by exposure of irradiated HUVECs to bFGF, involving phosphorylation of FGFR, MEK and p44/42 MAPK. The survival-enhancing effect of bFGF was partly inhibited by U0126 and PD98059. The fact that the anti-apoptosis effect of bFGF on irradiated HUVECs was not completely abrogated by U0126 and PD98059 suggests that other survival signaling pathways may exist. Transfection of a dominant-negative form of RSK2 (DN RSK2) partly blocked the anti-apoptosis effect of bFGF in irradiated HUVECs. Moreover, we provide evidence for the first time that bFGF induced BAD phosphorylation (at serine 112) and CREB (cAMP response element-binding protein) activation (phosphorylation at serine 133) in gamma-irradiated HUVECs. In our model, inhibition of MAPK signaling-dependent phosphorylation of BAD at serine 112 promoted increased association with BCL-X(L), suggesting that MAPK pathway-dependent serine 112 phosphorylation of BAD is critical for the effect of bFGF on cell survival. These results showed that RAS/MAPK/BAD pathway participated in the bFGF-induced effect on survival of HUVECs exposed to radiation. It is suggested that RAS/ MAPK pathway in tumor vascular endothelium could be a potential therapeutic target to enhance the efficacy of ionizing radiation.
Gu
Qingyang
Q
Beijing Institute of Radiation Medicine, Beijing, China. Guqy111@hotmail.com
Wang
Dewen
D
Wang
Xiaodan
X
Peng
Ruiyun
R
Liu
Jie
J
Deng
Hua
H
Wang
Zhaohai
Z
Jiang
Tao
T
D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects*; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects*; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism* / Q000494:pharmacology; D005720:Gamma Rays; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D011836:Radiation Tolerance / Q000187:drug effects / Q000502:physiology; D012694:Serine / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D013329:Structure-Activity Relationship; D014471:Umbilical Veins / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D051025:bcl-Associated Death Protein; D018631:ras Proteins / Q000378:metabolism*
C494819:BAD protein, human; D002352:Carrier Proteins; D051025:bcl-Associated Death Protein; D016222:Fibroblast Growth Factor 2; D012694:Serine; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins