Hypoxia stimulates release of the soluble form of fas ligand that inhibits endothelial cell apoptosis.
Fas ligand (FasL), an apoptosis-inducing cytokine, is constitutively expressed on endothelial cells (EC). Here, we report that the soluble form of FasL (sFasL) is released from EC and inhibits hypoxia-induced EC apoptosis. For hypoxia experiments, human EC were exposed to low oxygen tension in airtight chambers flushed with preanalyzed gas mixtures (1% oxygen, 5% CO2, 94% N2) at 37 degrees C. Exposure of cultured EC to hypoxia transiently increased FasL mRNA and protein levels. The maximum increase was observed at 3 and 6 hours after exposure to hypoxia, respectively. Although sFasL protein was not detected in the supernatant from EC without hypoxia, sFasL protein level in the supernatant was transiently increased from 6 hours and disappeared again at 24 hours after the exposure to hypoxia. Interestingly, the supernatant from hypoxia-exposed EC inhibited EC apoptosis induced by hypoxia, which was abolished by a neutralizing antibody against FasL. In addition, incubation with KB8301, an inhibitor of metalloproteinase, suppressed the release of sFasL from EC and enhanced hypoxia-induced apoptosis in EC. Furthermore, exogenously added recombinant sFasL inhibited hypoxia-induced apoptosis. These findings indicate that sFasL released from EC may inhibit hypoxia-induced EC apoptosis. Therefore, the shedding of FasL could be a new therapeutic target in regulating hypoxia-induced EC injury.
Department of Geriatric Medicine, Osaka University Medical School, Suita, Japan.
M
M
Mogi
K
K
Fukuo
J
J
Yang
T
T
Suhara
T
T
Ogihara
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000235:genetics; D015687:Cell Hypoxia / Q000502:physiology*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology* / Q000502:physiology*; D053222:Fas Ligand Protein; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins / Q000235:genetics / Q000502:physiology*; D051379:Mice; D014176:Protein Biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D014471:Umbilical Veins; D019014:fas Receptor / Q000502:physiology
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; C506387:Cflar protein, mouse; C505661:FASLG protein, human; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D019014:fas Receptor