Fas Receptor (fa + receptor)

Distribution by Scientific Domains

Selected Abstracts

Involvement of mitochondrial signaling pathways in the mechanism of Fas-mediated apoptosis after spinal cord injury

Wen Ru Yu
Abstract Activation of the Fas receptor has been recently linked to apoptotic cell death after spinal cord injury (SCI). Although it is generally considered that Fas activation mediates apoptosis predominantly through the extrinsic pathway, we hypothesized that intrinsic mitochondrial signaling could be involved in the underlying mechanism of Fas-induced apoptosis after SCI. In the present study, we utilized the FejotaTM clip compression model of SCI at T5,6 in C57BL/6 Fas-deficient (lpr) and wild-type mice. Complementary studies were conducted using an in vitro model of trauma or a Fas-activating antibody to induce apoptosis in primary neuronal,glial mixed spinal cord cultures. After in vivo SCI, lpr mice, in comparison with wild-type mice, exhibited reduced numbers of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells at the lesion, reduced expression of truncation of Bid (tBid), apoptosis-inducing factor, activated caspase-9 and activated caspase-3, and increased expression of the antiapoptotic proteins Bcl-2 and Bcl-xL. After in vitro neurotrauma or the induction of Fas signaling by the Jo2 activating antibody, lpr spinal cord cultures showed an increased proportion of cells retaining mitochondrial membrane integrity and a reduction of tBid expression, caspase-9 and caspase-3 activation, and TUNEL-positive cells as compared to wild-type spinal cord cultures. The neutralization of Fas ligand (FasL) protected against traumatically induced or Fas-mediated caspase-3 activation and the loss of mitochondrial membrane potential and tBid expression in wild-type spinal cord cultures. However, in lpr spinal cord cultures, FasL neutralization had no protective effects. In summary, these data provide direct evidence for the induction of intrinsic mitochondrial signaling pathways following Fas activation after SCI. [source]

Fas ligand expressed in colon cancer is not associated with increased apoptosis of tumor cells in vivo

Aileen Houston
Abstract Expression of Fas ligand (FasL/CD95L) may help to maintain colon cancers in a state of immune privilege by inducing apoptosis of antitumor immune effector cells. Colon tumor-derived cell lines appear to be relatively insensitive to apoptosis mediated by their own or exogenous FasL in vitro, despite expression of cell surface Fas. In our present study, we sought to investigate if FasL upregulated in human colon cancers leads to any increase in apoptosis of the tumor cells in vivo. FasL and Fas receptor (APO-1/CD95) expression by tumor cells were detected immunohistochemically. Apoptotic tumor cell death was detected by immunohistochemistry for caspase-cleaved cytokeratin-18. FasL expression did not correlate with the extent of apoptosis of tumor cells. There was no significant local difference in the frequency of apoptosis of tumor cells between tumor nests that expressed FasL (mean = 2.4%) relative to those that did not (mean = 2.6%) (p = 0.625, n = 10; Wilcoxon signed rank). FasL expressed by the tumor cells appeared to be functional, since FasL expression in tumor nests correlated with diminished infiltration of tumor-infiltrating lymphocytes (TILs). TILs were detected using immunohistochemistry for CD45. Expression of FasL by tumor nests was associated with a mean 4-fold fewer TILs relative to FasL-negative nests (range 2.4,33-fold, n = 10, p < 0.003). Together, our results indicate that colon tumors are insensitive to FasL-mediated apoptosis in vivo. © 2003 Wiley-Liss, Inc. [source]

Lifeguard/neuronal membrane protein 35 regulates Fas ligand-mediated apoptosis in neurons via microdomain recruitment

Miriam Fernández
Abstract Fas ligand (FasL)-receptor system plays an essential role in regulating cell death in the developing nervous system, and it has been implicated in neurodegenerative and inflammatory responses in the CNS. Lifeguard (LFG) is a protein highly expressed in the hippocampus and the cerebellum, and it shows a particularly interesting regulation by being up-regulated during postnatal development and in the adult. We show that over-expression of LFG protected cortical neurons from FasL-induced apoptosis and decreased caspase-activation. Reduction of endogenous LFG expression by small interfering RNA sensitized cerebellar granular neurons to FasL-induced cell death and caspase-8 activation, and also increased sensitivity of cortical neurons. In differentiated cerebellar granular neurons, protection from FasL-induced cell death could be attributed exclusively to LFG and appears to be independent of FLICE inhibitor protein. Thus, LFG is an endogenous inhibitor of FasL-mediated neuronal death and it mediates the FasL resistance of CNS differentiated neurons. Finally, we also demonstrate that LFG is detected in lipid rafts microdomains, where it may interact with Fas receptor and regulate FasL-activated signaling pathways. [source]

Apoptosis of human intervertebral discs after trauma compares to degenerated discs involving both receptor-mediated and mitochondrial-dependent pathways

Sven K. Tschoeke
Abstract Post-traumatic disc degeneration with consecutive loss of reduction and kyphosis remains a debatable issue within both the operative and nonoperative treatment regimen of thoracolumbar spine fractures. Intervertebral disc (IVD) cell apoptosis has been suggested to play a vital role in promoting the degeneration process. To evaluate and compare apoptosis-regulating signaling mechanisms, IVDs were obtained from patients with thoracolumbar spine fractures (n,=,21), patients suffering from symptomatic IVD degeneration (n,=,6), and from patients undergoing surgical resection of a primary vertebral tumor (n,=,3 used as control samples). All tissues were prospectively analyzed in regards to caspase-3/7, -8, and -9 activity, apoptosis-receptor expression levels, and gene expression of the mitochondria-bound apoptosis-regulating proteins Bax and Bcl-2. Morphologic changes characteristic for apoptotic cell death were confirmed by H&E staining. Statistical significance was designated at p,<,0.05 using the Student's t -test. Both traumatic and degenerative IVD demonstrated a significant increase of caspase-3/7 activity with evident apoptosis. Although caspase-3/7 activation was significantly greater in degenerated discs, both showed equally significant activation of the initiator caspases 8 and 9. Traumatic IVD alone demonstrated a significant increase of the Fas receptor (FasR), whereas the TNF receptor I (TNFR I) was equally up-regulated in both morbid IVD groups. Only traumatic IVD showed distinct changes in up-regulated TNF expression, in addition to significantly down-regulated antiapoptotic Bcl-2 protein. Our results suggest that post-traumatic disc changes may be promoted and amplified by both the intrinsic mitochondria-mediated and extrinsic receptor-mediated apoptosis signaling pathways, which could be, in part, one possible explanation for developing subsequent disc degeneration. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:999,1006, 2008 [source]

Inhibition of Caspases In Vivo Protects the Rat Liver Against Alcohol-Induced Sensitization to Bacterial Lipopolysaccharide

ALCOHOLISM, Issue 6 2001
Ion V. Deaciuc
Background: The mechanisms of liver sensitization by alcohol to Gram-negative bacterial lipopolysaccharide (LPS) remain elusive. The purpose of this study was two-fold: (1) to test the hypothesis that alcohol-enhanced liver apoptosis may be a sensitizing mechanism for LPS and (2) to further characterize the liver apoptotic response to alcohol. Methods: Rats were fed a high-fat, alcohol-containing liquid diet for 14 weeks, treated with LPS (1.0 mg/kg of body weight, intravenously) or saline, followed by injection of a pan-caspase inhibitor {IDN1965;N -[(1,3-dimethylindole-2-carbonyl)-valinyl]-3-amino-4-oxo-5-fluoropentanoic acid; 10 mg/kg of body weight, intraperitoneally} or vehicle, and killed. The following parameters were assessed: plasma aspartate: 2-oxoglutarate aminotransferase activity (AST); liver histology and terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) response; caspase-3, ,8, and ,9 activity; and mRNA and protein expression for two apoptosis-signaling molecules: Fas receptor and Fas ligand; and three apoptosis adaptors: Bax, Bcl-XL, and Bcl-2. Results: Alcohol-feeding-induced liver steatosis, slightly increased caspases' activity, the number of TUNEL-positive nuclei, and facilitated the LPS necrotic effect without affecting mRNA expression of apoptosis signals and adaptors. LPS induced a significant increase in AST and the number of TUNEL-positive nuclei, both effects being more pronounced in alcohol-treated rats. LPS produced hepatic necrosis only in alcohol-treated rats. LPS effects were associated with up-regulation of mRNA expression for both apoptosis adaptors and signaling molecules. IDN1965 administration 3 hr after LPS injection strongly inhibited caspases' activity, particularly that of caspase-3. IDN1965 also abolished the increase in TUNEL-positive nuclei, reversed the effect of LPS on plasma AST in alcohol-treated rats, and prevented LPS-induced necrosis. Conclusions: (1) Alcohol-enhanced liver apoptosis may not involve regulatory steps at the transcriptional level. LPS-induced liver apoptosis seems to involve transcriptional regulation of several apoptosis adaptors. Therefore, alcohol and LPS may enhance liver apoptosis through different mechanisms. (2) Alcohol-enhanced liver apoptosis precedes and may facilitate the hepatic effects of LPS. LPS superimposed on alcohol further elevates the rate of apoptosis in the liver. This may exceed the phagocytosing capacity of the liver so that all the apoptotic cells are not phagocytosed, but rather die of necrosis. [source]

Association among Fas expression in leucocytes, serum Fas and Fas-ligand concentrations and hepatic inflammation and fibrosis in chronic hepatitis C

Anatol Panasiuk
Abstract Background: Replication of the hepatitis C virus (HCV) in peripheral blood mononuclear cells (PBMC) may impair immune functions and establish persistent infection. The aim of this study was to assess the influence of HCV on PBMC and their susceptibility to apoptosis in relation to liver inflammation and fibrosis. Methods: Eighty-one patients with chronic hepatitis C (CHC) were enrolled in this study. Flow cytometry was used to determine the amount of T cells (CD4+, CD8+), B cells (CD19+), monocytes (CD14+) and natural killer cells (CD16+) in the peripheral blood and the expression of CD95+ (CD95/APO-1) in each subset. Serum concentrations of sFas and sFasL were assessed by the enzyme-linked immunosorbent assay method. Results: An increased expression of Fas was observed in CD4+ and CD8+ cells in CHC. There was a more prominent expression of Fas on CD4+ cells in HCV genotype 1b in contrast to 3a. Increased Fas expression on CD4+ cells was seen in advanced stages of liver disease. Fas expression on monocytes was lower in advanced stages of liver inflammation and fibrosis. Serum sFas concentration was higher in CHC compared with the control group. There was an association between sFasL concentration and inflammatory activity in the liver. Serum sFasL concentration correlated positively with the mean intensity of fluorescence of the Fas receptor in CD4+ and CD8+ cells, granulocytes and monocytes. Conclusion: These findings indicate that there is an increased susceptibility of PBMC to apoptosis, which can be attributed to the constant contact of leucocytes with the inflamed liver tissue, or from direct HCV influence. [source]

Intracellular Fas ligand is elevated in T lymphocytes in severe aplastic anaemia

Annette Luther-Wyrsch
Increased expression of Fas receptor by haemopoietic progenitors in aplastic anaemia (AA) suggests that excessive apoptosis contributes to multilineage bone marrow (BM) failure. To investigate the role of Fas ligand (FasL) in triggering progenitor cell death, we examined FasL levels in T lymphocytes of patients with severe untreated AA (n = 8). Expression of FasL on the surface of CD3+ cells was not detectable. However, flow cytometric analysis of saponin-permeabilized cells demonstrated higher levels of intracellular FasL in AA than in normal T cells (P < 0·005), both prior to and following activation with phytohaemagglutinin. Confocal microscopy revealed that FasL-specific signals overlapped with cathepsin D staining, indicating that intracellular FasL is stored in lysosomal granules. Levels of intracellular FasL in patients examined 1 month after immunosuppression with antilymphocyte globulin and cyclosporin A were lower than prior to treatment. The caspase inhibitors, DEVD and zVAD, enhanced colony formation and prolonged survival of AA BM cells in liquid cultures by about 10-fold (P < 0·05). Taken together, these data provide further evidence that apoptosis by the Fas/FasL system plays a role in the depletion of stem cells in AA. [source]