Radiation-induced interleukin-6 expression through MAPK/p38/NF-kappaB signaling pathway and the resultant antiapoptotic effect on endothelial cells through Mcl-1 expression with sIL6-Ralpha.
OBJECTIVE
To investigate the mechanism of interleukin-6 (IL-6) activity induced by ionizing radiation.


METHODS
Human umbilical vascular endothelial cells (HUVECs) were irradiated with different doses to induce IL-6. The IL-6 promoter assay and reverse transcriptase-polymerase chain reaction (RT-PCR) were used to examine transcriptional regulation. Specific chemical inhibitors, decoy double-stranded oligodeoxynucleotides, and Western blotting were conducted to investigate the signal transduction pathway. Recombinant soluble human IL-6 receptor alpha-chain (sIL6-Ralpha) and specific small interfering RNA were used to evaluate the biologic function of radiation-induced IL-6.


RESULTS
Four grays of radiation induced the highest level of IL-6 protein. The promoter assay and RT-PCR data revealed that the induction of IL-6 was mediated through transcriptional regulation. The p38 inhibitor SB203580, by blocking nuclear factor-kappaB (NF-kappaB) activation, prevented both the transcriptional and translational regulation of radiation-induced IL-6 expression. The addition of sIL6-Ralpha rescued HUVECs from radiation-induced death in an IL-6 concentratio-dependent manner. The antiapoptotic effect of combined sIL6-Ralpha and radiation-induced IL-6 was inhibited by mcl-1-specific small interfering RNA.


CONCLUSIONS
Radiation transcriptionally induces IL-6 expression in endothelial cells through mitogen-activated protein kinase/p38-mediated NF-kappaB/IkappaB (inhibitor of NF-kappaB) complex activation. In the presence of sIL6-Ralpha, radiation-induced IL-6 expression acts through Mcl-1 expression to rescue endothelial cells from radiation-induced death.
Chou
Chia-Hung
CH
Graduate Institute of Oncology, National Taiwan University College of Medicine, Taipei, Taiwan.
Chen
Shee-Uan
SU
Cheng
Jason Chia-Hsien
JC
D017209:Apoptosis / Q000235:genetics; D002470:Cell Survival / Q000502:physiology; D004307:Dose-Response Relationship, Radiation; D042783:Endothelial Cells / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression; D006575:Heterocyclic Compounds, 3-Ring / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D016328:NF-kappa B / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D019947:Receptors, Interleukin-6 / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology / Q000528:radiation effects; D018808:Transcription Factor AP-1 / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
D004791:Enzyme Inhibitors; D006575:Heterocyclic Compounds, 3-Ring; D007093:Imidazoles; D015850:Interleukin-6; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D016328:NF-kappa B; C456319:PS1145; D019253:Proto-Oncogene Proteins c-bcl-2; D011725:Pyridines; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D019947:Receptors, Interleukin-6; D018808:Transcription Factor AP-1; C113250:interleukin-6 receptor alpha; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580