RESUMEN
Foxp3, which encodes the transcription factor scurfin, is indispensable for the development and function of CD4(+)CD25(+) regulatory T cells (Treg). Recent data suggest conversion of peripheral CD4(+)CD25(-) nai ve T cells to CD4(+)CD25(+) Treg by acquisition of Foxp3 through costimulation with TCR and TGF-beta or forced expression of the gene. One critical question is how Foxp3 causes T cells to become regulatory. In the present work, we demonstrate that Foxp3 can induce heme oxygenase-1 (HO-1) expression and subsequently such regulatory phenotypes as the suppression of nontransfected cells in a cell-cell contact-dependent manner as well as impaired proliferation and production of cytokines upon stimulation in Jurkat T cells. Moreover, we confirm the expression of both Foxp3 and HO-1 in peripheral CD4(+)CD25(+) Treg and suppressive function of the cells are relieved by the inhibition of HO-1 activity. In summary, we demonstrate that Foxp3 induces HO-1 expression and HO-1 engages in Foxp3-mediated immune suppression.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , Hemo Oxigenasa (Desciclizante)/metabolismo , Linfocitos T CD4-Positivos/inmunología , Proliferación Celular , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/inmunología , Factores de Transcripción Forkhead , Regulación Leucémica de la Expresión Génica , Hemo Oxigenasa (Desciclizante)/genética , Hemo-Oxigenasa 1 , Humanos , Tolerancia Inmunológica/inmunología , Células Jurkat , Proteínas de la Membrana , Receptores de Interleucina-2/inmunología , TransfecciónRESUMEN
In this study, we evaluated the possibility that the anti-proliferative effects of paclitaxel on vascular smooth muscle cells (VSMCs) of the rat might be due to the induction of HO-1 gene expression. Treatment of the cells with paclitaxel resulted in marked time- and dose-dependent inductions of HO-1 mRNA, followed by corresponding increases in HO-1 protein expression and HO enzymatic activities. Furthermore, paclitaxel rapidly activated the JNK, ERK, and p38 mitogen-activated protein kinase pathways. A specific inhibitor of JNK, SP600125, abolished paclitaxel-induced HO-1 mRNA expression, whereas PD98059, a specific inhibitor of ERK, and SB203580, a specific inhibitor of p38, had no significant effect. Finally, the suppression of platelet-derived growth factor induced VSMC proliferation was abolished by the HO inhibitor, ZnPP, as well as by the CO scavenger, hemoglobin. These results demonstrated that paclitaxel induces the expression of HO-1 via the JNK pathway in VSMC and that HO-1 expression might be responsible for the anti-proliferative effect of paclitaxel on VSMC.
Asunto(s)
División Celular/efectos de los fármacos , Hemo Oxigenasa (Desciclizante)/genética , Músculo Liso Vascular/enzimología , Paclitaxel/farmacología , Animales , Células Cultivadas , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Hemo Oxigenasa (Desciclizante)/metabolismo , Hemo-Oxigenasa 1 , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Músculo Liso Vascular/citología , Músculo Liso Vascular/efectos de los fármacos , Fosforilación , ARN Mensajero/genética , Ratas , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transcripción Genética/efectos de los fármacosRESUMEN
We recently demonstrated that heme oxygenase (HO)-1 is constitutively expressed in human CD4+CD25+ regulatory T cells and induced by anti-CD28 or anti-CD28/anti-CD3 stimulation, even in CD4+CD25- responder T cells. To study the effects of HO-1 expression on lymphocyte survival, we transfected the HO-1 gene or induced the gene to express HO-1 protein with cobalt protoporphyrin (CoPP) in Jurkat T cells. Consistently, anti-Fas antibody triggered apoptotic cell death in wild-type Jurkat T cells. Surprisingly, however, HO-1-overexpressing Jurkat T cells showed strong resistance to Fas-mediated apoptosis. In contrast, abrogation of HO-1 expression by antisense oligomer against HO-1 gene from CoPP-treated cells or depletion of iron by desferrioxamine from HO-1-transfected cells abolished the resistance. In addition, exogenously added iron rendered wild-type Jurkat T cells resistant. The resistance involved IkappaB kinase (IKK) activation via iron-induced reactive oxygen species formation, NF-kappaB activation by activated IKK, and c-FLIP expression by activated NF-kappaB. Primary CD4+ T cells induced by CoPP to express HO-1 also showed more resistance to Fas-mediated apoptosis than untreated cells. Our findings suggest that HO-1 plays a critical and nonredundant role in Fas-mediated activation-induced cell death of T lymphocytes.