title: A role for caspases in controlling IL-4 expression in T cells.
abstract: Although caspase activation is critical for T cell proliferation following activation, the role of caspases in T cell differentiation is unclear. In this study, we have examined the effect of inhibition of caspases on the process of Th1/Th2 differentiation. Naive CD4+ T cells activated under neutral differentiation conditions in the presence of the pan caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp (Z-VAD) fluoromethylketone showed increased Th2 cell differentiation concomitant with an up-regulation of GATA-3. Z-VAD induced optimal Th2 differentiation when T cells were stimulated under strong primary activation conditions. Treatment of naive CD4+ T cells with Z-VAD under strong activation conditions led to a 6-fold increase in IL-4 mRNA compared with control-treated T cells. The Z-VAD-induced increase in IL-4 transcription occurred within 24 h of activation and was independent of Stat6. IFN-gamma mRNA expression was not affected by Z-VAD at the 24-h time point. Z-VAD did not augment IL-4 expression from a committed Th2 cell, suggesting that caspases regulate IL-4 expression specifically during primary T cell activation. Z-VAD did not augment IL-12-driven Th1 differentiation. Activation of T cells in the presence of Z-VAD led to a specific increase in the expression of the transcription factor c-fos. Lastly, retrovirus-mediated expression of the antiapoptotic protein Bcl-2 resulted in an enhancement of Th2 cytokine expression, suggesting that inhibition of caspase activation by Bcl-2 can also modulate IL-4 expression. These findings reveal a novel regulatory mechanism of cytokine expression by caspases, and may explain how signaling pathways that inhibit apoptosis tend to promote Th2 differentiation.
authors.affiliation: Department of Microbiology and Immunology, The Walther Oncology Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
authors.forename: Sarita
authors.initials: S
authors.lastname: Sehra
authors.forename: Dipak
authors.initials: D
authors.lastname: Patel
authors.forename: Saritha
authors.initials: S
authors.lastname: Kusam
authors.forename: Zheng-Yu
authors.initials: ZY
authors.lastname: Wang
authors.forename: Cheong-Hee
authors.initials: CH
authors.lastname: Chang
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Dent
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001483:Base Sequence; D061945:Caspase Inhibitors; D020169:Caspases / Q000276:immunology* / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004247:DNA / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D050990:GATA3 Transcription Factor; D005786:Gene Expression Regulation; D019254:Genes, bcl-2; D016762:Genes, fos / Q000187:drug effects; D007371:Interferon-gamma / Q000235:genetics; D015847:Interleukin-4 / Q000235:genetics*; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D050800:STAT6 Transcription Factor; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology*; D018417:Th1 Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000276:immunology; D018418:Th2 Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000276:immunology; D015534:Trans-Activators / Q000172:deficiency / Q000235:genetics / Q000276:immunology / Q000378:metabolism
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D004268:DNA-Binding Proteins; D050990:GATA3 Transcription Factor; C494748:Gata3 protein, mouse; D012333:RNA, Messenger; D050800:STAT6 Transcription Factor; C494100:Stat6 protein, mouse; D015534:Trans-Activators; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D015847:Interleukin-4; D007371:Interferon-gamma; D004247:DNA; D020169:Caspases