title: Dual upregulation of Fas and Bax promotes alloreactive T cell apoptosis in IL-10 gene targeting of cardiac allografts.
abstract: Activation-induced cell death and cytokine deprivation are demonstrated by peripheral T cell populations at the conclusion of natural immune responses, and each of these processes is modulated by the immunosuppressive cytokine interleukin (IL)-10 in vitro. This study employs a clinically relevant in vivo model of IL-10 gene transfer with heterotopically transplanted cardiac allografts to determine the mechanisms of the effects of IL-10 on T cell survival. IL-10 protein overexpression within allografts 4-5 days after gene transfer augments apoptosis of CD4+ and CD8+ graft-infiltrating lymphocytes by 7.1-fold (P < 0.001) and 6.0-fold (P < 0.001), respectively. Graft-infiltrating T cells express 10-fold more proapoptotic Fas (P < 0.01) and 30-fold more Bax (P < 0.01) than controls. The fractions of activated caspase-8 (FADD-like IL-1beta-converting enzyme) and activated caspase-9 were increased 7- and 2.3-fold, respectively, in IL-10 gene-treated allografts at postoperative day 4-5. These changes in the Fas-Fas ligand pathway and Bcl-2 mitochondrial apoptosis regulation are enhanced by complete suppression of antiapoptotic FADD-like IL-1beta-converting enzyme inhibitory protein (FLIP) (from 30.5 to 0.0%, P < 0.01) and Bcl-xL (from 22.5 to 0.1%, P = 0.03) expression among these cells from the earliest days after gene transfer. Although changes in proteins of Fas- and Bcl-2-mediated apoptosis signaling occur, only the levels of Fas and FLIP correlate to the rate of apoptosis of graft-infiltrating CD3 lymphocytes and histological rejection scores. These results indicate that dichotomous apoptosis-regulatory pathways are affected by IL-10 gene therapy, but Fas-mediated mechanisms of activation-induced cell death more substantially contribute to the greater cell death of graft-infiltrating T cells after ex vivo IL-10 gene transfer.
authors.affiliation: Division of Cardiothoracic Surgery, Department of Surgery, UCLA Medical Center, David Geffen School of Medicine, University of California-Los Angeles, 10833 Leconte Avenue, Los Angeles, CA 90095-1679, USA.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Tung
authors.forename: Kiyohiro
authors.initials: K
authors.lastname: Oshima
authors.forename: Guanggen
authors.initials: G
authors.lastname: Cui
authors.forename: Hillel
authors.initials: H
authors.lastname: Laks
authors.forename: Luyi
authors.initials: L
authors.lastname: Sen
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D017252:CD3 Complex / Q000032:analysis; D002352:Carrier Proteins / Q000378:metabolism; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D015316:Genetic Therapy / Q000379:methods; D006084:Graft Rejection / Q000276:immunology / Q000517:prevention & control / Q000628:therapy; D006085:Graft Survival / Q000276:immunology; D016027:Heart Transplantation / Q000276:immunology*; D006801:Humans; D016753:Interleukin-10 / Q000235:genetics*; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011817:Rabbits; D013601:T-Lymphocytes / Q000737:chemistry / Q000166:cytology* / Q000378:metabolism; D014184:Transplantation, Homologous; D015854:Up-Regulation / Q000276:immunology; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D019014:fas Receptor / Q000378:metabolism*
chemical_list: C494826:BAX protein, human; C494811:BCL2L1 protein, human; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D017252:CD3 Complex; C506386:CFLAR protein, human; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D019014:fas Receptor; D016753:Interleukin-10; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases