Decrease of Bcl-xL and augmentation of thymocyte apoptosis in GILZ overexpressing transgenic mice.
Glucocorticoids promote thymocyte apoptosis and modulate transcription of numerous genes. GILZ (glucocorticoid-induced leucine zipper), being one of them, is strongly up-regulated in the thymus. To elucidate its function we generated transgenic mice overexpressing it specifically in the T-cell lineage and characterized its influence on thymus function. In young adult transgenic mice CD4(+)CD8(+) thymocyte number was significantly decreased and ex vivo thymocyte apoptosis was increased. Apoptotic pathway analysis detected reduced antiapoptotic B-cell leukemia XL (Bcl-xL) expression and increased activation of caspase-8 and caspase-3. Time-course experiments showed that in wild-type (WT) thymocytes GILZ up-regulation was followed by sequential Bcl-xL decreased expression and activation of caspase-8 and of caspase-3. Moreover, GILZ delivered inside WT thymocytes by a fusion protein with the transactivator of transcription (TAT) peptide decreased Bcl-xL and promoted their apoptosis. In aged mice perturbation of thymic subset numbers was amplified over time, as demonstrated by a further decrease in CD4(+)CD8(+) cells and increases in CD4(+)CD8(-), CD4(-)CD8(-), and CD8(+)CD4(-) cell counts. These results support the hypothesis that GILZ participates in the regulation of thymocyte apoptosis by glucocorticoids.
Section of Pharmacology, Department of Clinical and Experimental Medicine, University of Perugia, Via del Giochetto, 06122 Perugia, Italy. midelfin@unipg.it
Domenico Vittorio
DV
Delfino
Massimiliano
M
Agostini
Stefania
S
Spinicelli
Pasquale
P
Vito
Carlo
C
Riccardi
D000818:Animals; D017209:Apoptosis; D018801:CD2 Antigens / Q000235:genetics; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism; D018929:Cell Culture Techniques; D004261:DNA Replication; D005938:Glucocorticoids / Q000494:pharmacology; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008822:Mice, Transgenic; D012333:RNA, Messenger / Q000235:genetics; D013601:T-Lymphocytes / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology; D014157:Transcription Factors / Q000276:immunology*
D018801:CD2 Antigens; C498608:Dsip1 protein, mouse; D005938:Glucocorticoids; D012333:RNA, Messenger; C404226:TSC22D3 protein, human; D014157:Transcription Factors; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C505409:Casp3 protein, mouse; C505526:Casp8 protein, mouse; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases