title: Differential regulation and function of the Fas/Fas ligand system in human trophoblast cells.
abstract: Trophoblast rejection, which is characterized by increased apoptosis, is mediated by T helper (Th)-1, or proinflammatory, cytokines, whereas Th-2, or anti-inflammatory, cytokines confer immune protection and facilitate implantation. We investigated the role of both types of cytokines on the expression and function of the Fas/Fas ligand (FasL) apoptotic pathway in trophoblast cells. First-trimester human trophoblast primary-culture cells as well as A3 and HTR/8 trophoblast cell lines were treated with proinflammatory cytokines such as interferon-gamma (IFN-gamma) and tumor necrosis factor alpha (TNFalpha) and with the anti-inflammatory cytokines interleukin (IL)-6 and IL-10. Sensitivity to Fas-mediated apoptosis was measured using an activating anti-Fas monoclonal antibody. Cell viability was evaluated using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) and CellTiter 96 assay. Fas/FasL mRNA and protein expression levels were determined using reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis, respectively. Trophoblast cells normally express FasL, but low levels of Fas, and they are resistant to Fas-mediated apoptosis. IFN-gamma and TNFalpha promote Fas expression and sensitivity, whereas IL-6 and IL-10 increase the resistance of trophoblast cells to Fas-mediated apoptosis. Furthermore, IL-10 treatment activates FLICE-like inhibitory protein (FLIP), a downstream inhibitor of Fas apoptotic signaling. Although trophoblast cells express Fas, susceptibility to Fas does not necessarily correlate with its expression. In this study, we demonstrate that Th-2 cytokines increase the resistance of trophoblast cells to Fas-mediated apoptosis either by inhibiting Fas expression or by inducing FLIP activation. This "trophoblast-cytokine-Fas/FasL triad" determines the ability of the Fas/FasL system to regulate trophoblast viability and, consequently, the success or failure of pregnancy.
authors.affiliation: Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
authors.forename: Sarit
authors.initials: S
authors.lastname: Aschkenazi
authors.forename: Shawn
authors.initials: S
authors.lastname: Straszewski
authors.forename: Karlijn M A
authors.initials: KM
authors.lastname: Verwer
authors.forename: Harald
authors.initials: H
authors.lastname: Foellmer
authors.forename: Thomas
authors.initials: T
authors.lastname: Rutherford
authors.forename: Gil
authors.initials: G
authors.lastname: Mor
mesh_terms: D017209:Apoptosis; D015153:Blotting, Western; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D053222:Fas Ligand Protein; D005260:Female; D005786:Gene Expression Regulation; D005865:Gestational Age; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D016753:Interleukin-10 / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000502:physiology*; D011247:Pregnancy; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018417:Th1 Cells / Q000378:metabolism; D018418:Th2 Cells / Q000378:metabolism; D014327:Trophoblasts / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D019014:fas Receptor / Q000235:genetics* / Q000502:physiology*
chemical_list: D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; D016207:Cytokines; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D015850:Interleukin-6; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; D016753:Interleukin-10; D007371:Interferon-gamma