Interferon-gamma induces apoptosis and augments the expression of Fas and Fas ligand by microglia in vitro.
Activation of microglia by interferon-gamma (IFN-gamma) has been implicated in a number of central nervous system (CNS) inflammatory disease processes. Because IFN-gamma has also been shown to play a role in programmed cell death, we investigated its cytotoxicity and its effect on the Fas apoptotic pathway in microglia. Flow cytometry was used to quantify the IFN-gamma-mediated apoptotic response and Fas and Fas ligand (FasL) expression in two well-characterized murine microglia cell lines (BV-2 and N9). Nuclear fragmentation, suggestive of apoptosis, was noted within 24 h of incubation of microglia with IFN-gamma (10 U/ml). After a 72-h incubation, almost every BV-2 and N9 microglia, but not GL261 glioma cells, underwent cell death and detached from the culture plates. This cytotoxicity occurred even at low IFN-gamma concentrations (1 U/ml) and was inhibited by BAF, a pan-caspase inhibitor. Incubation of BV-2 and N9 microglia, but not GL261 glioma cells, with IFN-gamma also potentiated the expression of Fas and FasL in a similar dose-response and time-course manner, as seen for the apoptotic response. Whereas Fas expression increased by 100% in both microglia cells, FasL upregulation was more pronounced and increased by as much as 200% in the N9 cells. These findings suggest that in addition to its role as a microglia activator, IFN-gamma may also induce apoptosis of microglia, possibly through simultaneous upregulation of Fas and FasL. Interferon-gamma modulation of the Fas pathway and apoptosis in microglia may be important in the pathogenesis of inflammatory CNS disease processes.
Badie
B
B
Neuro-oncology Laboratory, School of Medicine, Madison, Wisconsin 53792, USA.
Schartner
J
J
Vorpahl
J
J
Preston
K
K
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D000954:Antigens, Surface / Q000096:biosynthesis; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D061945:Caspase Inhibitors; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D053222:Fas Ligand Protein; D005434:Flow Cytometry; D005910:Glioma / Q000378:metabolism* / Q000473:pathology; D007371:Interferon-gamma / Q000494:pharmacology*; D008024:Ligands; D008562:Membrane Glycoproteins / Q000096:biosynthesis*; D008565:Membrane Proteins / Q000096:biosynthesis; D051379:Mice; D017628:Microglia / Q000166:cytology / Q000378:metabolism*; D015854:Up-Regulation; D019014:fas Receptor / Q000096:biosynthesis*
D000590:Amino Acid Chloromethyl Ketones; D000954:Antigens, Surface; D061945:Caspase Inhibitors; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008024:Ligands; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C103192:butyloxycarbonyl-O-methyl-aspartyl-fluoromethyl ketone; D019014:fas Receptor; D007371:Interferon-gamma