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  • CELL  (60)
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  • 1
    Keywords: APOPTOSIS ; CELLS ; EXPRESSION ; IN-VITRO ; CELL ; Germany ; human ; IN-VIVO ; MODEL ; PATHWAY ; PATHWAYS ; VITRO ; SYSTEM ; DEATH ; DISTINCT ; TIME ; COMPLEX ; COMPLEXES ; primary ; T cell ; T cells ; T-CELL ; T-CELLS ; culture ; activation-induced cell death ; CELL-DEATH ; UP-REGULATION ; CYCLE PROGRESSION ; DISPLAY ; SIGNALING PATHWAY ; SIGNALING PATHWAYS ; B-CELLS ; immune response ; IMMUNE-RESPONSE ; IL-2 ; INITIATION ; FAS-MEDIATED APOPTOSIS ; DISC ; SIGNALING COMPLEX ; ANTIGEN RECEPTOR ; C-FLIPSHORT ; CD95 ; COMPLEX DISC ; FLICE-INHIBITORY PROTEIN ; INTERLEUKIN-2 RECEPTOR
    Abstract: The CD95 (APO-1/Fas) system plays a critical role in activation-induced cell death (AICD) of T cells. We previously described two distinct CD95 (APO-1/Fas) signaling pathways: 1) type I cells show strong death-inducing signaling complex (DISC) formation and mitochondria-independent apoptosis and 2) DISC formation is reduced in type II cells, leading to mitochondria-dependent apoptosis. To investigate the relevance of these pathways, we set up an in vitro model that mimics the initiation and the down phase of an immune response, respectively. Freshly activated human T cells (initiation) are resistant toward CD95-mediated AICD despite high expression of CD95. We previously reported that these T cells show reduced DISC formation. In this study, we show that freshly activated T cells are CD95-type II cells that show high expression levels of Bcl-x(L) and display a block in the mitochondrial apoptosis pathway. Furthermore, we show that, upon prolonged culture (down phase), human T cells undergo a switch from type II to type I cells that renders T cells sensitive to CD95-mediated AICD. Finally, we demonstrate that this switch is dependent on the presence of IL-2. Our observations reveal for the first time that the existence of coexisting CD95 signaling pathways is of physiological relevance
    Type of Publication: Journal article published
    PubMed ID: 12960316
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  • 2
    Keywords: CELLS ; EXPRESSION ; tumor ; CELL ; Germany ; IN-VIVO ; INHIBITION ; VIVO ; DISEASE ; SITE ; SITES ; GENE ; transcription ; DIFFERENTIATION ; NF-KAPPA-B ; ACTIVATION ; FAMILY ; TRANSCRIPTION FACTOR ; AP-1 ; T cell ; T cells ; T-CELL ; T-CELLS ; BINDING ; RESPONSE ELEMENT ; TRANSCRIPTION FACTORS ; PROMOTER ; BETA ; immune response ; IMMUNE-RESPONSE ; LIVING CELLS ; CD28 ; C-REL ; T lymphocyte,transcription factor,cytokine
    Abstract: IL-4 plays a pivotal role in the development of the Th2 cell mediated humoral immune response and causes IgE-dependent allergic inflammatory diseases. Expression of IL-4 in differentiated Th2 cells is regulated by transcription factors such as NF-AT AP-1 and NF-IL6. Recently, increasing evidence indicates that the pro-inflammatory transcription factor NF-kappaB,13 may also participate in IL-4 expression. In this study, we show that the IL-4 promoter is synergistically activated by NF-kappaB, NF-AT and NF-IL6 at the NF-kappaB/NF-AT/NF-IL6 composite sites. In addition, we performed the chromatin immunoprecipitation technique to determine the functional relevance of NF-kappaB in the activation of the IL-4 gene in vivo. We demonstrate that NF-kappaB binds to the IL-4 promoter in vivo upon T cell activation. Inhibition of NF-kappaB nuclear translocation in living cells blocked binding of NF-kappaB to the IL-4 promoter. The data provide first evidence that NF-kappaB is directly involved in IL-4 transcription
    Type of Publication: Journal article published
    PubMed ID: 15048722
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  • 3
    Keywords: APOPTOSIS ; CELLS ; EXPRESSION ; INHIBITOR ; tumor ; CELL ; Germany ; human ; IN-VIVO ; MODEL ; DEATH ; PROTEIN ; PROTEINS ; ACTIVATION ; COMPLEX ; RESPONSES ; COMPLEXES ; primary ; DENDRITIC CELLS ; T cell ; T cells ; T-CELL ; T-CELLS ; DOWN-REGULATION ; culture ; IMMUNE-RESPONSES ; resistance ; CELL-DEATH ; UP-REGULATION ; immune response ; IMMUNE-RESPONSE ; CASPASE 8 ; FAS-MEDIATED APOPTOSIS ; SIGNALING COMPLEX ; EFFECTOR ; Bcl-2 ; FLICE-INHIBITORY PROTEIN ; CASPASE-8 ACTIVATION ; ACQUIRE
    Abstract: In the early phase of an immune response, T cells are activated and acquire effector functions. Whereas these short term activated T cells are resistant to CD95-mediated apoptosis, activated T cells in prolonged culture are readily sensitive, leading to activation-induced cell death and termination of the immune response. The translation inhibitor, cycloheximide, partially overcomes the apoptosis resistance of short term activated primary human T cells. Using this model we show in this study that sensitization of T cells to apoptosis occurs upstream of mitochondria. Neither death-inducing signaling complex formation nor expression of Bcl-2 proteins is altered in sensitized T cells. Although the caspase-8 inhibitor c-FLIPlong was only slightly down-regulated in sensitized T cells, c-FLIPshort became almost undetectable. This correlated with caspase-8 activation and apoptosis. These data suggest that c-FLIPshort, rather than c-FLIPlong, confers resistance of T cells to CD95-mediated apoptosis in the context of immune responses
    Type of Publication: Journal article published
    PubMed ID: 14764686
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  • 4
    Keywords: APOPTOSIS ; CELLS ; EXPRESSION ; IN-VITRO ; proliferation ; tumor ; CELL ; Germany ; VITRO ; DEATH ; PATIENT ; MECHANISM ; ANTIGEN ; T cell ; T cells ; T-CELL ; T-CELLS ; SUSCEPTIBILITY ; CD95 ligand ; CELL-DEATH ; LYMPHOCYTES ; INDIVIDUALS ; sensitivity ; MULTIPLE-SCLEROSIS ; GUIDELINES ; CD95 ; AUTOIMMUNE ENCEPHALOMYELITIS ; PROGRAM ; COSTIMULATION ; CD95-MEDIATED APOPTOSIS ; multiple sclerosis ; function ; DEFECT ; regulatory T cells ; EXPANSION ; regulatory T cell ; healthy individuals ; auto immunity ; DIAGNOSTIC-CRITERIA
    Abstract: Impaired suppressive function of CD4(+)CD25(high) regulatory T cells (T-reg) has been reported as a novel pathogenetic mechanism in Multiple sclerosis (MS). We addressed if high apoptosis sensitivity of MS-T-reg could explain this functional T-reg defect. T-reg from treatmentnaive MS patients showed high sensitivity towards CD95Ligand-mediated apoptosis and exhibited enhanced cell death to IL-2 and TCR-signal deprivation. Since susceptibility of T-reg to cell death was similar in MS patients and healthy controls, this cannot explain the inhibitory dysfunction of T-reg associated with MS. Furthermore, as cell death is not enhanced, therapeutic expansion of MS-T-reg in vitro should be a reasonable and novel therapeutic option. (c) 2006 Elsevier B.V. All rights reserved
    Type of Publication: Journal article published
    PubMed ID: 17092518
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  • 5
    Keywords: CELLS ; EXPRESSION ; IRRADIATION ; tumor ; CELL ; COMBINATION ; Germany ; DISEASE ; EXPOSURE ; TISSUE ; PATIENT ; NITRIC-OXIDE SYNTHASE ; NITRIC-OXIDE ; MECHANISM ; IMPACT ; mechanisms ; SKIN ; T cell ; T cells ; T-CELL ; T-CELLS ; FIELD ; LESIONS ; UP-REGULATION ; DAMAGE ; RECRUITMENT ; CLEARANCE ; FUTURE ; inflammation ; PROGRAM ; RE ; SYNTHASE ; chemokines ; REGULATORY T-CELLS ; SUBTYPES ; APOPTOTIC CELLS ; TESTS ; EVENTS ; SLE ; function ; nitric oxide ; regulatory T cells ; regulatory T cell ; PROTECTS ; CD4(+)CD25(+) ; ENVIRONMENTAL-FACTORS ; SKIN-LESIONS ; LUPUS-ERYTHEMATOSUS
    Abstract: The pathophysiology of cutaneous lupus erythematosus (CLE) has been investigated in numerous studies demonstrating that the combination of specific cellular and molecular events is leading to inflammation and tissue damage in this disease. However, a complete understanding of the diverse pathophysiological mechanisms and interactions does not exist. Various environmental factors influence the clinical expression of CLE and a striking relationship has emerged between sunlight exposure and the various subtypes of this disease. In the past years, photoprovocation tests with different ultraviolet (UV) wavelengths have been approved to be an optimal way to evaluate photosensitivity in patients with CLE. Furthermore, research on the pathogenetic mechanisms of UV-induced skin lesions has become an increasingly dynamic field and several new aspects of this disease could be identified. In this review, the impact of UV exposure that contributes to the manifestations of CLE is discussed and recently reported mechanisms in the pathophysiology of this disease are considered including the clearance of apoptotic cells, expression of inducible nitric oxide synthase, function of CD4(+)CD25(+) regulatory T cells, and the role of chemokines for lymphocyte recruitment. Elucidation of the relevant factors might lead to future development of effective strategies to prevent abnormal reactivity in patients with CLE
    Type of Publication: Journal article published
    PubMed ID: 16987823
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  • 6
    Keywords: RECEPTOR ; APOPTOSIS ; CANCER ; IN-VITRO ; tumor ; CELL ; IN-VIVO ; MODEL ; MODELS ; PATHWAY ; PATHWAYS ; VITRO ; VIVO ; SYSTEM ; SYSTEMS ; DEATH ; GENE ; GENES ; microarray ; PROTEIN ; transcription ; EPITHELIA ; TUMORS ; validation ; MICE ; TRANSCRIPTION FACTOR ; KERATINOCYTES ; SKIN ; BIOLOGY ; cell cycle ; CELL-CYCLE ; CYCLE ; TARGET ; ISOFORM ; ENCODES ; PROMOTER ; PROMOTERS ; REQUIRES ; DNA-DAMAGE ; BAX ; HUMAN KERATINOCYTES ; SQUAMOUS-CELL CARCINOMA ; TARGETS ; RECEPTORS ; MICROARRAY ANALYSIS ; epidermis ; TRAIL ; DEATH RECEPTORS ; tetramer ; CD95 ; chemoresistance ; review ; TUMOR-SUPPRESSOR ; keratinocyte ; LIGHT ; TUMORIGENESIS ; development ; STRATIFIED EPITHELIA ; TARGET GENES ; analysis ; P63 ; death receptor ; EPITHELIUM ; EPITHELIAL TUMORS ; KINASE C-ABL ; P53-DEPENDENT APOPTOSIS ; REGULATES P73 ; USA ; function ; in vivo ; E ; PROTECTS ; MAINTENANCE ; inactive ; cornification ; FAMILY-MEMBER GENES ; GENE ENCODES ; IKK alpha ; ISOFORM EXPRESSION ; P53 HOMOLOG P63
    Abstract: The epidermis is a multilayered stratified epithelium, continuously regenerated by differentiating keratinocytes, that requires the transcription factor p63 for its development and maintenance. The TP63 gene encodes two major protein isoforms, TAp63 and Delta Np63, which have both transactivating and transcriptional repressing activities and regulate a wide range of target genes. TAp63 shows clear pro-apoptotic activity, mediated both by death receptors (CD95, TNF, TRAIL) and mitochondrial (bax, puma) pathways. Conversely, DNp63 protects from apoptosis by directly competing for TAp63 target promoters or sequestering it, forming inactive tetramers. Accordingly, p63 is expressed in epithelial tumors, contributing to both tumorigenesis and chemoresistance. However, the predominant physiological role of p63 is in epithelial development, as demonstrated by the lack of epidermis and other epithelia in p63-deficient mice. The specific role of TAp63 and DNp63 isoforms in epithelial development remains mostly unclear. Nevertheless, recent work utilizing in vivo genetic complementation of TAp63 and/or DNp63 into a p63 null background has shed new light into the specific functions of the two isoforms and allowed the in vivo validation of several p63 transcriptional targets, originally identified by microarray analysis in in vitro systems. However, despite concerted efforts to address the role of p63 isoforms, several questions remain unanswered. The main aim of this review is to critically discuss the data available in the literature and thoroughly analyze the models proposed
    Type of Publication: Journal article published
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  • 7
    Keywords: APOPTOSIS ; CELLS ; BLOOD ; CELL ; Germany ; IN-VIVO ; KINASE ; PATHWAY ; PATHWAYS ; SYSTEM ; DEATH ; PROTEIN ; PROTEINS ; RNA ; MICE ; NF-KAPPA-B ; ACTIVATION ; MECHANISM ; FAMILY ; primary ; INDUCTION ; T cell ; T cells ; T-CELL ; T-CELLS ; MEMBER ; MEMBERS ; TRANSGENIC MICE ; CD95 ligand ; CELL-DEATH ; INDUCED APOPTOSIS ; LYMPHOCYTES ; B-CELLS ; SIGNALING COMPLEX ; Bcl-2 ; molecular ; MOLECULAR-BASIS ; RE ; FAMILIES ; LIFE ; LEVEL ; cell death ; ANTIGEN RECEPTORS ; progenitor ; SUPPRESSOR ; FAS LIGAND ; AICD ; HEMATOPOIETIC PROGENITOR KINASE-1 ; USA ; B-LYMPHOCYTES ; FATE ; FRAGMENT ; FAMILY-MEMBER BIM ; B-CELL ; KINASE-1 ; EXPANSION ; caspase-3 ; block ; B cells ; BCL-2 FAMILY ; COMPLEMENT ; FULL-LENGTH ; MEDIATED CLEAVAGE ; SMALL INTERFERING RNA
    Abstract: Life and death of peripheral lymphocytes is strictly controlled to maintain physiologic levels of T and B cells. Activation-induced cell death (AICD) is one mechanism to delete superfluous lymphocytes by restimulation of their immunoreceptors and it depends partially on the CD95/CD95L system. Recently, we have shown that hematopoietic progenitor kinase 1 (HPK1) determines T-cell fate. While full-length HPK1 is essential for NF-KB activation in T cells, the C-terminal fragment of HPK1, HPK1-C, suppresses NF-KB and sensitizes toward AICD by a yet undefined cell death pathway. Here we show that upon IL-2-driven expansion of primary T cells, HPK1 is converted to HPK1-C by a caspase-3 activity below the threshold of apoptosis induction. HPK1-C selectively blocks induction of NF-kappa B-dependent antiapoptotic Bcl-2 family members but not of the proapoptotic Bcl-2 family member Bim.Interestingly, T and B lymphocytes from HPK1-C transgenic mice undergo AICD independently of the CD95/CD95L system but involving caspase-9. Knock down of HPK1/HPK1-C or Bim by small interfering RNA shows that CD95L-dependent and HPK1/HPK1-C-dependent cell death pathways complement each other in AICD of primary T cells. Our results define HPK1-C as a suppressor of antiapoptotic Bcl-2 proteins and provide a molecular basis for our understanding of CD95L-independent AICD of lymphocytes
    Type of Publication: Journal article published
    PubMed ID: 17712048
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  • 8
    Keywords: CELLS ; EXPRESSION ; BLOOD ; CELL ; Germany ; GENERATION ; POPULATION ; PATIENT ; MECHANISM ; MARKER ; DONOR ; mechanisms ; T cell ; T cells ; T-CELL ; T-CELLS ; SUPPRESSION ; DIFFERENCE ; resistance ; NUMBER ; AGE ; SURFACE ; BETA ; PHENOTYPE ; INDIVIDUALS ; TCR ; DE-NOVO ; PREVALENCE ; PERIPHERAL-BLOOD ; DECLINE ; MULTIPLE-SCLEROSIS ; GUIDELINES ; SUBPOPULATION ; DEFICIENCY ; SUBSET ; CAPACITY ; multiple sclerosis ; USA ; function ; correlation ; DEFECT ; immunology ; DEPLETION ; regulatory T cells ; HOMEOSTASIS ; EXPANSION ; DIAGNOSTIC-CRITERIA ; DYSFUNCTION ; GLATIRAMER ACETATE
    Abstract: The suppressive function of regulatory T cells (T-reg) is impaired in multiple sclerosis (MS) patients. The mechanism underlying the Treg functional defect is unknown. T-reg mature in the thymus and the majority of cells circulating in the periphery rapidly adopt a memory phenotype. Because our own previous findings suggest that the thymic output of T cells is impaired in MS, we hypothesized that an altered T-reg generation may contribute to the suppressive deficiency. We therefore determined the role of T-reg that enter the circulation as recent thymic emigrants (RTE) and, unlike their CD45RO(+) memory counterparts, express CD31 as typical surface marker. We show that the numbers of CD31(+)-coexpressing CD4(+)CD25(+)CD45RA(+)CD45RO-FOXP3(+) T-reg (RTE-T-g) within peripheral blood decline with age and are significantly reduced in MS patients. The reduced de novo generation of RTE-T-reg is compensated by higher proportions of memory T-reg, resulting in a stable cell count of the total T-reg population. Depletion of CD31(+) cells from T-reg diminishes the suppressive capacity of donor but not patient T-reg and neutralizes the difference in inhibitory potencies between the two groups. Overall, there was a clear correlation between T-reg-mediated suppression and the prevalence of RTE-T-reg, indicating that CD31-expressing naive T-reg contribute to the functional properties of the entire T-reg population. Furthermore, patient-derived T-reg, but not healthy T-reg, exhibit a contracted TCR V beta repertoire. These observations ggest that a shift in the homeostatic composition of T-reg subsets related to a reduced thymic-dependent de novo generation of RTE-T-reg with a compensatory expansion of memory Tmg may contribute to the Treg defect associated with MS
    Type of Publication: Journal article published
    PubMed ID: 17617625
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  • 9
    Keywords: CELLS ; EXPRESSION ; INHIBITOR ; tumor ; CELL ; Germany ; INHIBITION ; KINASE ; GENERATION ; DEATH ; PROTEIN ; RNA ; DRUG ; TIME ; COMPLEX ; COMPLEXES ; DNA ; INDUCTION ; T cell ; T cells ; T-CELL ; T-CELLS ; BIOLOGY ; PROTEIN-KINASE ; SIGNAL ; MITOCHONDRIA ; SUPEROXIDE ; OXYGEN ; FAS LIGAND EXPRESSION ; MULTIPLE-SCLEROSIS ; reactive oxygen species ; signaling ; PROGRAM ; RE ; assembly ; SUPEROXIDE-PRODUCTION ; HYDROGEN-PEROXIDE ; REACTIVE OXYGEN ; AICD ; CHAPERONE ; USA ; ROS ; PREVENTS ; CD95L ; block ; SMALL INTERFERING RNA ; superoxide dismutase ; COMPLEX-I ; DOPAMINERGIC-NEURONS ; HEART-MITOCHONDRIA ; LYMPHOCYTE-ACTIVATION ; RECEPTOR STIMULATION ; ROTENONE INHIBITION
    Abstract: Reactive oxygen species (ROS) play a key role in regulation of activation-induced T-cell death (AICD) by induction of CD95L expression. However, the molecular source and the signaling steps necessary for ROS production are largely unknown. Here, we show that the proximal T-cell receptor-signaling machinery, including ZAP70 (zeta chain-associated protein kinase 70), IAT (linker of activated T cells), SLP76 (SH2 domain-containing leukocyte protein of 76 kDa), PLC gamma 1 (phospholipase C gamma 1), and PKC theta (protein kinase C theta), are crucial for ROS production. PKC theta is translocated to the mitochondria. By using cells depleted of mitochondrial DNA, we identified the mitochondria as the source of activation-induced ROS. Inhibition of mitochondrial electron transport complex I assembly by small interfering RNA (siRNA) -mediated knockdown of the chaperone NDUFAF1 resulted in a block of ROS production. Complex I-derived ROS are converted into a hydrogen peroxide signal by the mitochondrial superoxide dismutase. This signal is essential for CD95L expression, as inhibition of complex I assembly by NDUFAF1-specific siRNA prevents AICD. Similar results were obtained when metformin, an antidiabetic drug and mild complex I inhibitor, was used. Thus, we demonstrate for the first time that PKC theta-dependent ROS generation by mitochondrial complex I is essential for AICD
    Type of Publication: Journal article published
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  • 10
    Keywords: RECEPTOR ; APOPTOSIS ; CELLS ; EXPRESSION ; IN-VITRO ; IONIZING-RADIATION ; CELL ; IN-VIVO ; MODEL ; VITRO ; VIVO ; SYSTEM ; DEATH ; MICE ; NEUROBLASTOMA-CELLS ; NITRIC-OXIDE SYNTHASE ; NITRIC-OXIDE ; IFN-GAMMA ; DONOR ; INDUCTION ; tumour ; DOWN-REGULATION ; INDUCED APOPTOSIS ; UP-REGULATION ; SIGNALING PATHWAYS ; KAPPA-B ; FACTOR-I ; TNF-ALPHA ; CD95 ; INCREASE ; FAS ; SYNTHASE ; MEDIATED APOPTOSIS ; death receptor ; function ; CANDIDATE ; nitric oxide ; in vivo ; immunology
    Abstract: Both the function and regulation of Fas expression in tumours is poorly understood. Our laboratory has reported that cultured, low Fas-expressing tumours undergo massive, yet reversible, up-regulation of cell surface Fas expression when injected into mice. The present study was aimed at determining what causes this enhanced Fas expression and whether the newly expressed Fas functions as a death receptor. Newly expressed Fas is indeed capable of inducing apoptosis. Based on our observation that Fas induction is reduced when tumour cells are injected into immune-deficient mice, we propose that Fas up-regulation in vivo involves the host's immune system. Accordingly, Fas up-regulation occurs in vitro when low Fas-expressing tumour cells are cocultured with lymphoid cells. Furthermore ascitic fluid extracted from tumour-bearing mice trigger Fas up-regulation in low Fas expressing tumours. This last finding suggests that a soluble factor(s) mediates induction of Fas expression. The best candidate for this soluble factor is nitric oxide (NO) based on the following observations: the factor in the ascites is unstable; Fas expression is induced to a lesser degree after injection into inducible NO synthase (NOS)-deficient (iNOS(-/-)) mice when compared to control mice; similarly, coculture with iNOS(-/-) splenocytes induces Fas less effectively than coculture with control splenocytes; and finally, the NO donor SNAP induces considerable Fas up-regulation in tumours in vitro. Our model is that host lymphoid cells in response to a tumour increase NO synthesis, which in turn causes enhanced Fas expression in the tumour
    Type of Publication: Journal article published
    PubMed ID: 17343612
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