The Experts below are selected from a list of 2541 Experts worldwide ranked by ideXlab platform
Takao Kataoka - One of the best experts on this subject based on the ideXlab platform.
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the Caspase 8 Inhibitor c flipl modulates t cell receptor induced proliferation but not activation induced cell death of lymphocytes
Molecular and Cellular Biology, 2002Co-Authors: Susanne Lens, Takao Kataoka, Karen A Fortner, Antoine Tinel, Isabel Ferrero, Robson Macdonald, Michel Hahne, Friedrich Beermann, Antoine AttingerAbstract:The Caspase 8 Inhibitor c-FLIP(L) can act in vitro as a molecular switch between cell death and growth signals transmitted by the death receptor Fas (CD95). To elucidate its function in vivo, transgenic mice were generated that overexpress c-FLIP(L) in the T-cell compartment (c-FLIP(L) Tg mice). As anticipated, FasL-induced apoptosis was inhibited in T cells from the c-FLIP(L) Tg mice. In contrast, activation-induced cell death of T cells in c-FLIP(L) Tg mice was unaffected, suggesting that this deletion process can proceed in the absence of active Caspase 8. Accordingly, c-FLIP(L) Tg mice differed from Fas-deficient mice by showing no accumulation of B220(+) CD4(-) CD8(-) T cells. However, stimulation of T lymphocytes with suboptimal doses of anti-CD3 or antigen revealed increased proliferative responses in T cells from c-FLIP(L) Tg mice. Thus, a major role of c-FLIP(L) in vivo is the modulation of T-cell proliferation by decreasing the T-cell receptor signaling threshold.
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Expression level of c-FLIP versus Fas determines susceptibility to Fas ligand-induced cell death in murine thymoma EL-4 cells.
Experimental Cell Research, 2002Co-Authors: Takao Kataoka, Ralph C Budd, Jürg Tschopp, Kazuo NagaiAbstract:The Caspase-8 Inhibitor c-FLIP blocks death receptor-mediated cell death and plays an essential role in the regulation of lymphocyte homeostasis and the immune escape of tumors. The murine thymoma cell line EL-4 was resistant to Fas ligand (FasL)-induced apoptosis by constitutive expression of FLIP (L). Cycloheximide downregulated the expression of FLIP (L) and markedly sensitized EL-4 cells to FasL-induced apoptosis. In contrast, DNA-damaging agents sensitized EL-4 cells to FasL-induced cell death via an increase of cell-surface Fas without any influence on FLIP (L) expression. Enforced expression of transfected Fas rendered EL-4 cells highly susceptible to FasL-induced cell death. These findings demonstrate that susceptibility to FasL-induced cell death mainly depends on the expression level of c-FLIP versus cell-surface Fas.
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the Caspase 8 Inhibitor flip promotes activation of nf κb and erk signaling pathways
Current Biology, 2000Co-Authors: Takao Kataoka, Ralph C Budd, Nils Holler, Margot Thome, Fabio Martinon, Martin Irmler, Kimberly Burns, Michael Hahne, Norman J KennedyAbstract:BACKGROUND: Activation of Fas (CD95) by its ligand (FasL) rapidly induces cell death through recruitment and activation of Caspase-8 via the adaptor protein Fas-associated death domain protein (FADD). However, Fas signals do not always result in apoptosis but can also trigger a pathway that leads to proliferation. We investigated the level at which the two conflicting Fas signals diverge and the protein(s) that are implicated in switching the response. RESULTS: Under conditions in which proliferation of CD3-activated human T lymphocytes is increased by recombinant FasL, there was activation of the transcription factors NF-kappaB and AP-1 and recruitment of the Caspase-8 Inhibitor and FADD-interacting protein FLIP (FLICE-like Inhibitory protein). Fas-recruited FLIP interacts with TNF-receptor associated factors 1 and 2, as well as with the kinases RIP and Raf-1, resulting in the activation of the NF-kappaB and extracellular signal regulated kinase (Erk) signaling pathways. In T cells these two signal pathways are critical for interleukin-2 production. Increased expression of FLIP in T cells resulted in increased production of interleukin-2. CONCLUSIONS: We provide evidence that FLIP is not simply an Inhibitor of death-receptor-induced apoptosis but that it also mediates the activation of NF-kappaB and Erk by virtue of its capacity to recruit adaptor proteins involved in these signaling pathways.
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The Caspase-8 Inhibitor FLIP promotes activation of NF-κB and Erk signaling pathways
Current Biology, 2000Co-Authors: Takao Kataoka, Ralph C Budd, Nils Holler, Margot Thome, Fabio Martinon, Martin Irmler, Kimberly Burns, Michael Hahne, Norman J Kennedy, M. KovacsovicsAbstract:Abstract Background: Activation of Fas (CD95) by its ligand (FasL) rapidly induces cell death through recruitment and activation of Caspase-8 via the adaptor protein Fas-associated death domain protein (FADD). However, Fas signals do not always result in apoptosis but can also trigger a pathway that leads to proliferation. We investigated the level at which the two conflicting Fas signals diverge and the protein(s) that are implicated in switching the response. Results: Under conditions in which proliferation of CD3-activated human T lymphocytes is increased by recombinant FasL, there was activation of the transcription factors NF-κB and AP-1 and recruitment of the Caspase-8 Inhibitor and FADD-interacting protein FLIP (FLICE-like Inhibitory protein). Fas-recruited FLIP interacts with TNF-receptor associated factors 1 and 2, as well as with the kinases RIP and Raf-1, resulting in the activation of the NF-κB and extracellular signal regulated kinase (Erk) signaling pathways. In T cells these two signal pathways are critical for interleukin-2 production. Increased expression of FLIP in T cells resulted in increased production of interleukin-2. Conclusions: We provide evidence that FLIP is not simply an Inhibitor of death-receptor-induced apoptosis but that it also mediates the activation of NF-κB and Erk by virtue of its capacity to recruit adaptor proteins involved in these signaling pathways.
Anthony M Jevnikar - One of the best experts on this subject based on the ideXlab platform.
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Anti-IL-2 receptor antibody decreases cytokine-induced apoptosis of human renal tubular epithelial cells (TEC)
Nephrology Dialysis Transplantation, 2010Co-Authors: Shuang Wang, Zhu-xu Zhang, Bertha Garcia, Xuyan Huang, Philip D. Acott, Anthony M JevnikarAbstract:Background. Transplant rejection is mediated by T-cell activation which is modulated by interleukin-2 (IL-2) binding to IL-2R (CD25). Monoclonal anti-IL-2 receptor antibody is used in renal transplantation to reduce rejection. Interestingly, proximal tubular epithelial cells (TEC) express CD25, similar to T cells. We have demonstrated that IL-2 induces murine TEC apoptosis through down-regulation of the Caspase-8 Inhibitor protein c-FLIP. Anti-CD25 antibody may be useful clinically to limit renal injury, but this has not been tested in human TEC. Methods. Human PT-2 TEC were isolated and cloned from the urine of transplant patients. Apoptosis was determined by FACS with Annexin-V FITC. Protein expression was studied using western blot, and mRNA levels by quantitative real-time (PR-PCR). Results. We demonstrated that the morphology of a human kidney cell line (PT-2) cloned from urine was consistent with proximal TEC and expresses alkaline phosphatase, cytokeratin, vimentin, CD13, CD26, and low levels of E-cadherin. Basal IL-2 receptor (CD25) was up-regulated by IL-2/IFN-γ stimulation, and cytokine exposure induced apoptosis in a dose-dependent manner. Apoptosis with IL-2/IFN-γ was associated with increased Caspase-8 activity and decreased endogenous Caspase-8 Inhibitor c-FLIP mRNA and protein expression. IL-2/IFN-γ-induced apoptosis could be blocked by pre-treatment of PT-2 with anti IL-2R antibody (basiliximab) but not control IgG antibody. Conclusions. These data demonstrate for the first time in human TEC that IL-2 and IFN-γ can induce TEC apoptosis which can be blocked by CD25 blockade antibody. These data suggest that anti-CD25 mAb might similarly attenuate inflammation-induced TEC injury in vivo. Kidney-expressed CD25 may represent a clinically important new target for attenuating early inflammatory injury in donor kidneys and preserving renal function during antirejection therapy.
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il 2 mediated apoptosis of kidney tubular epithelial cells is regulated by the Caspase 8 Inhibitor c flip
Kidney International, 2005Co-Authors: Caigan Du, Qiunong Guan, Robert Zhong, Anthony M JevnikarAbstract:IL-2–mediated apoptosis of kidney tubular epithelial cells is regulated by the Caspase-8 Inhibitor c-FLIP. Background Tubular epithelial cells (TECs) are essential in the maintenance of kidney function. Apoptosis of TECs occur during acute and chronic renal allograft rejection as well as other forms of renal injury, including autoimmune nephritis. The regulation of TEC apoptosis by proinflammatory cytokines associated with renal inflammation [e.g., interleukin (IL)-2 and interferon-gamma (IFN-γ)] has not been extensively investigated. Methods Apoptosis in murine TECs was determined by FACS with annexin-V or ligation-mediated-polymerase chain reaction (LM-PCR) and mRNA levels by reverse transcription (RT)-PCR or Northern blot. Protein expression was observed using Western blot. Results IL-2R (CD25) was expressed by murine TECs and up-regulated by IL-2. Both IL-2 and IFN-γ induced TEC apoptosis and activated Caspase-8. Apoptosis with IL-2 was concentration-dependent and blocked by z-IETD-fmk, a specific Caspase-8 Inhibitor. Apoptosis with IFN-γ was associated with increased surface expression of Fas, while IL-2 had no effect on Fas. IL-2 did not induce apoptosis in Fas-deficient TECs (M3.1- lpr ) suggesting IL-2 regulation of Caspase-8 activity requires Fas. Consistent with this, IL-2 but not IFN-γ was found to decrease mRNA and protein expression of c-FLIP, an endogenous Caspase-8 Inhibitor in murine TECs. Overexpression of c-FLIP in TECs (CS3.7-FLIP) blocked apoptosis and Caspase-8 activation with both IFN-γ and IL-2. c-FLIP expression was found in kidney cortex, primary and cloned TECs, suggesting c-FLIP is likely a key regulator of Caspase-8–mediated apoptosis in vivo. Conclusion This is the first report of c-FLIP regulation by IL-2 in renal TECs. Augmentation of c-FLIP in TECs may enhance an endogenous mechanism by which TECs normally resist injury to Caspase-8–mediated apoptosis and thus may be a useful and novel strategy to prevent tubular injury in transplant rejection and autoimmune nephritis.
Martin Zörnig - One of the best experts on this subject based on the ideXlab platform.
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transgenic overexpression of the Caspase 8 Inhibitor flipshort leads to impaired t cell proliferation and an increased memory t cell pool after staphylococcal enterotoxin b injection
European Journal of Immunology, 2005Co-Authors: Ina Oehme, Frank Neumann, Susanne Bösser, Martin ZörnigAbstract:The cellular homologues of the viral anti-apoptotic v-FLIP proteins exist as a long (c-FLIPL) and a short (c-FLIPS) splice variant. While c-FLIPS and v-FLIP are composed solely of two death effector domains, c-FLIPL contains an (inactive) Caspase-like domain in addition to these two death effector domains, thereby structurally resembling pro-Caspase-8. Both c-FLIPL and c-FLIPS suppress apoptosis by inhibiting Caspase-8 activation, although at different levels of pro-Caspase-8 processing. To analyze the consequences of deregulated c-FLIPS expression in vivo, we established lck FLIPS-transgenic mice overexpressing the transgene in thymocytes and in mature T cells. As expected, CD95L-induced apoptosis was impaired in lck FLIPS-transgenic T cells, indicating the functionality of the FLIPS transgene. Remarkably, activation-induced cell death of transgenic T cells was unaffected, despite the observed inhibition of CD95-induced T cell death. Thymic and splenic cell numbers as well as CD4/CD8 cellularity were normal in lck FLIPS-transgenic animals, which in contrast to CD95-deficient mice do not accumulate Thy1+ B220+ CD4– CD8– peripheral T cells. c-FLIPS overexpression leads to a significant decrease in activation-induced T cell proliferation in vitro. Despite the capacity of FLIPS to inhibit CD95-induced apoptosis, T cell lymphomagenesis is not observed in lck FLIPS-transgenic mice. Interestingly, the Vβ8+ memory T cell pool is enlarged upon staphylococcal enterotoxin B injections, suggesting a specific in vivo function for FLIPS in the maintenance of restimulated T cells.
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Transgenic overexpression of the Caspase‐8 Inhibitor FLIPshort leads to impaired T cell proliferation and an increased memory T cell pool after staphylococcal enterotoxin B injection
European Journal of Immunology, 2005Co-Authors: Ina Oehme, Frank Neumann, Susanne Bösser, Martin ZörnigAbstract:The cellular homologues of the viral anti-apoptotic v-FLIP proteins exist as a long (c-FLIPL) and a short (c-FLIPS) splice variant. While c-FLIPS and v-FLIP are composed solely of two death effector domains, c-FLIPL contains an (inactive) Caspase-like domain in addition to these two death effector domains, thereby structurally resembling pro-Caspase-8. Both c-FLIPL and c-FLIPS suppress apoptosis by inhibiting Caspase-8 activation, although at different levels of pro-Caspase-8 processing. To analyze the consequences of deregulated c-FLIPS expression in vivo, we established lck FLIPS-transgenic mice overexpressing the transgene in thymocytes and in mature T cells. As expected, CD95L-induced apoptosis was impaired in lck FLIPS-transgenic T cells, indicating the functionality of the FLIPS transgene. Remarkably, activation-induced cell death of transgenic T cells was unaffected, despite the observed inhibition of CD95-induced T cell death. Thymic and splenic cell numbers as well as CD4/CD8 cellularity were normal in lck FLIPS-transgenic animals, which in contrast to CD95-deficient mice do not accumulate Thy1+ B220+ CD4– CD8– peripheral T cells. c-FLIPS overexpression leads to a significant decrease in activation-induced T cell proliferation in vitro. Despite the capacity of FLIPS to inhibit CD95-induced apoptosis, T cell lymphomagenesis is not observed in lck FLIPS-transgenic mice. Interestingly, the Vβ8+ memory T cell pool is enlarged upon staphylococcal enterotoxin B injections, suggesting a specific in vivo function for FLIPS in the maintenance of restimulated T cells.
Hartmut Jaeschke - One of the best experts on this subject based on the ideXlab platform.
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protection against fas receptor mediated apoptosis in hepatocytes and nonparenchymal cells by a Caspase 8 Inhibitor in vivo evidence for a postmitochondrial processing of Caspase 8
Toxicological Sciences, 2000Co-Authors: Mary Lynn Bajt, Judy A Lawson, S L Vonderfecht, Jaspreet S Gujral, Hartmut JaeschkeAbstract:Lymphocytes can kill target cells including hepatocytes during various inflammatory diseases by Fas receptor-mediated apopto- sis. Caspase-8 is activated at the receptor level, thereby initiating the processing of downstream effector Caspases. The aim of this study was to investigate the time course of Caspase-8 activation and to evaluate the efficacy of the Caspase-8 Inhibitor IETD-CHO in a model of Fas-induced apoptosis in vivo. C3Heb/FeJ mice were treated with the anti-Fas antibody Jo-2 (0.6 mg/kg). Western blot analysis demonstrated increased cytochrome c in the cytosol (20 min), which was followed by the progressive activation of Caspase-3, -9 (40 -120 min), and Caspase-8 (120 min). At 90 and 120 min, extensive hemorrhage was observed, indicating damage to sinusoidal lining cells. In addition, high plasma ALT levels (997 6 316 U/L) and histological evaluation indicated severe parenchymal cell injury. Parenchymal and nonparenchymal cells showed a similar increase in Caspase-3 activity and DNA fragmen- tation. Treatment with IETD-CHO (10 mg/kg) attenuated the increase in Caspase-3 activity and DNA fragmentation by 80 -90% and completely prevented hemorrhage and parenchymal cell dam- age. IETD-CHO also prevented the early release of mitochondrial cytochrome c and the processing of Caspase-3, -8, and -9. Thus, our data support the hypothesis that Fas-mediated apoptosis is depen- dent on Caspase-8 activation in hepatocytes and nonparenchymal cells. However, the bulk of proCaspase-8 is processed late, suggest- ing that only a small amount of proCaspase-8 may actually be activated at the Fas receptor. This initial signal may be amplified by further activation of Caspase-8 by effector Caspases, i.e., after mitochondrial activation. Caspase-8 is a promising therapeutic
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Protection against Fas Receptor–Mediated Apoptosis in Hepatocytes and Nonparenchymal Cells by a Caspase-8 Inhibitor in Vivo: Evidence for a Postmitochondrial Processing of Caspase-8
Toxicological Sciences, 2000Co-Authors: Mary Lynn Bajt, Judy A Lawson, S L Vonderfecht, Jaspreet S Gujral, Hartmut JaeschkeAbstract:Lymphocytes can kill target cells including hepatocytes during various inflammatory diseases by Fas receptor-mediated apopto- sis. Caspase-8 is activated at the receptor level, thereby initiating the processing of downstream effector Caspases. The aim of this study was to investigate the time course of Caspase-8 activation and to evaluate the efficacy of the Caspase-8 Inhibitor IETD-CHO in a model of Fas-induced apoptosis in vivo. C3Heb/FeJ mice were treated with the anti-Fas antibody Jo-2 (0.6 mg/kg). Western blot analysis demonstrated increased cytochrome c in the cytosol (20 min), which was followed by the progressive activation of Caspase-3, -9 (40 -120 min), and Caspase-8 (120 min). At 90 and 120 min, extensive hemorrhage was observed, indicating damage to sinusoidal lining cells. In addition, high plasma ALT levels (997 6 316 U/L) and histological evaluation indicated severe parenchymal cell injury. Parenchymal and nonparenchymal cells showed a similar increase in Caspase-3 activity and DNA fragmen- tation. Treatment with IETD-CHO (10 mg/kg) attenuated the increase in Caspase-3 activity and DNA fragmentation by 80 -90% and completely prevented hemorrhage and parenchymal cell dam- age. IETD-CHO also prevented the early release of mitochondrial cytochrome c and the processing of Caspase-3, -8, and -9. Thus, our data support the hypothesis that Fas-mediated apoptosis is depen- dent on Caspase-8 activation in hepatocytes and nonparenchymal cells. However, the bulk of proCaspase-8 is processed late, suggest- ing that only a small amount of proCaspase-8 may actually be activated at the Fas receptor. This initial signal may be amplified by further activation of Caspase-8 by effector Caspases, i.e., after mitochondrial activation. Caspase-8 is a promising therapeutic
Ina Oehme - One of the best experts on this subject based on the ideXlab platform.
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transgenic overexpression of the Caspase 8 Inhibitor flipshort leads to impaired t cell proliferation and an increased memory t cell pool after staphylococcal enterotoxin b injection
European Journal of Immunology, 2005Co-Authors: Ina Oehme, Frank Neumann, Susanne Bösser, Martin ZörnigAbstract:The cellular homologues of the viral anti-apoptotic v-FLIP proteins exist as a long (c-FLIPL) and a short (c-FLIPS) splice variant. While c-FLIPS and v-FLIP are composed solely of two death effector domains, c-FLIPL contains an (inactive) Caspase-like domain in addition to these two death effector domains, thereby structurally resembling pro-Caspase-8. Both c-FLIPL and c-FLIPS suppress apoptosis by inhibiting Caspase-8 activation, although at different levels of pro-Caspase-8 processing. To analyze the consequences of deregulated c-FLIPS expression in vivo, we established lck FLIPS-transgenic mice overexpressing the transgene in thymocytes and in mature T cells. As expected, CD95L-induced apoptosis was impaired in lck FLIPS-transgenic T cells, indicating the functionality of the FLIPS transgene. Remarkably, activation-induced cell death of transgenic T cells was unaffected, despite the observed inhibition of CD95-induced T cell death. Thymic and splenic cell numbers as well as CD4/CD8 cellularity were normal in lck FLIPS-transgenic animals, which in contrast to CD95-deficient mice do not accumulate Thy1+ B220+ CD4– CD8– peripheral T cells. c-FLIPS overexpression leads to a significant decrease in activation-induced T cell proliferation in vitro. Despite the capacity of FLIPS to inhibit CD95-induced apoptosis, T cell lymphomagenesis is not observed in lck FLIPS-transgenic mice. Interestingly, the Vβ8+ memory T cell pool is enlarged upon staphylococcal enterotoxin B injections, suggesting a specific in vivo function for FLIPS in the maintenance of restimulated T cells.
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Transgenic overexpression of the Caspase‐8 Inhibitor FLIPshort leads to impaired T cell proliferation and an increased memory T cell pool after staphylococcal enterotoxin B injection
European Journal of Immunology, 2005Co-Authors: Ina Oehme, Frank Neumann, Susanne Bösser, Martin ZörnigAbstract:The cellular homologues of the viral anti-apoptotic v-FLIP proteins exist as a long (c-FLIPL) and a short (c-FLIPS) splice variant. While c-FLIPS and v-FLIP are composed solely of two death effector domains, c-FLIPL contains an (inactive) Caspase-like domain in addition to these two death effector domains, thereby structurally resembling pro-Caspase-8. Both c-FLIPL and c-FLIPS suppress apoptosis by inhibiting Caspase-8 activation, although at different levels of pro-Caspase-8 processing. To analyze the consequences of deregulated c-FLIPS expression in vivo, we established lck FLIPS-transgenic mice overexpressing the transgene in thymocytes and in mature T cells. As expected, CD95L-induced apoptosis was impaired in lck FLIPS-transgenic T cells, indicating the functionality of the FLIPS transgene. Remarkably, activation-induced cell death of transgenic T cells was unaffected, despite the observed inhibition of CD95-induced T cell death. Thymic and splenic cell numbers as well as CD4/CD8 cellularity were normal in lck FLIPS-transgenic animals, which in contrast to CD95-deficient mice do not accumulate Thy1+ B220+ CD4– CD8– peripheral T cells. c-FLIPS overexpression leads to a significant decrease in activation-induced T cell proliferation in vitro. Despite the capacity of FLIPS to inhibit CD95-induced apoptosis, T cell lymphomagenesis is not observed in lck FLIPS-transgenic mice. Interestingly, the Vβ8+ memory T cell pool is enlarged upon staphylococcal enterotoxin B injections, suggesting a specific in vivo function for FLIPS in the maintenance of restimulated T cells.