Possible Involvement Of Fas Research Articles

Inhibition of COX-2 induces apoptosis in hepatoma cells: possible involvement of Fas receptor/ligand system: Alfred S Cheng, Henry L Chan, Nathalie Wong, Philip J Johnson, Joseph J Sung, The Chinese University of Hong Kong, Hong Kong China

Inhibition of COX-2 induces apoptosis in hepatoma cells: possible involvement of Fas receptor/ligand system: Alfred S Cheng, Henry L Chan, Nathalie Wong, Philip J Johnson, Joseph J Sung, The Chinese University of Hong Kong, Hong Kong China

Fas and perforin are not required for thymus atrophy induced by Trypanosoma cruzi infection

In the acute phase of Trypanosoma cruzi infection there is a prominent thymus atrophy, which is determined by massive loss of immature CD4/CD8 double positive cells. Recently, the involvement of a parasite transialidase, which is shed from the parasite cell membrane and the activation of P2X 7, a purinergic receptor, were stated as important pathways leading to thymus atrophy. In this work we evaluated the possible involvement of Fas- and perforin-based cytotoxic pathways in the thymus atrophy induced by T. cruzi infection using gld/gld and perforin (−/−) mice. We found similar kinetics of thymus atrophy in mice competent or deficient in both cytotoxic pathways, indicating that both molecules are not directly involved in the thymus atrophy, either inducing cellular death or as co-stimulatory molecules.

Fas/FasL mediated apoptosis of thyrocytes in Graves' disease.

We examined in the present study the possible involvement of Fas and its ligand (FasL) in the process of Graves' disease. Immunohistochemical analysis showed that few normal thyrocytes expressed Fas but many thyrocytes in Graves' disease expressed this molecule. The percentage of FasL-positive thyrocytes in Graves' thyroids was, however, less than in normal thyroids. Several apoptotic thyrocytes and infiltrating mononuclear cells (MNCs) were detected scattered throughout Graves' thyroid tissues and abundant proliferating cell nuclear antigen (PCNA)-positive thyrocytes were present. Apoptotic cells, as well as PCNA-positive cells, were scarcely detectable in normal thyroid glands, however. In vitro treatment of thyrocytes by IL-1beta a cytokine found to be expressed in Graves' thyroid glands, increased Fas but reduced FasL expression. IL-1beta-stimulated thyrocytes became sensitive to apoptosis by anti-Fas IgM monoclonal antibody (mAb). Activated T cells, which strongly expressed FasL, showed cytotoxic activity toward IL-1beta-stimulated thyrocytes but not toward unstimulated thyrocytes. This cytotoxic activity involved the Fas/FasL pathway. Importantly, unstimulated thyrocytes could kill activated, but not resting, T cells. IL-1beta-stimulated thyrocytes, with down-regulated FasL expression, could not efficiently kill activated T cells. The cytotoxic activity of unstimulated thyrocytes toward activated T cells was inhibited by anti-FasL mAb. Interestingly, unstimulated thyrocytes induced apoptosis in IL-1beta-stimulated thyrocytes but not in unstimulated thyrocytes. These interactions were also blocked by anti-FasL mAb. Our results suggest that the apoptotic cell death of both thyrocytes and infiltrating MNCs found in Graves' thyroid glands is regulated by IL-1beta through Fas/FasL interactions.

Male germ cell death in mouse testes: possible involvement of Fas and Fas ligand.

Loss of germ cells is very common during various stages of mammalian spermatogenesis. Although cell death, particularly apoptosis, has been implicated, our understanding of the mechanisms underlying germ cell death is still limited. In order to elucidate the extent and mechanism of germ cell death, this review first covers what is known of germ cell degeneration in the normal testes of fetal, neonatal, and adult mice from electron microscopy (EM) and from terminal dUTP nick-end labeling (TUNEL) staining. The issue of whether the Fas and Fas ligand (FasL) system is involved in the induction of germ cell apoptosis in normal and damaged testes is then addressed, including consideration of both the ischemia-reperfusion model of testicular torsion and the estrogen-treated testis model of environmental endocrine disruption. Finally, this review proposes that different molecular pathways may be triggered to induce male germ cell apoptosis, depending upon the physiological and pathological states of the germ cells.

Enhanced cell death in NR-S1 tumor by photodynamic therapy: possible involvement of Fas and Fas ligand system.

To investigate the effect of photodynamic therapy (PDT) on cell death in malignant tumor tissue, the frequency of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells and the possible involvement of Fas and Fas ligand system were evaluated. NR-S1 tumor-bearing C3H/HeNCrj mice were treated by PDT with Photofrin(R) (12 mg/kg body weight) and Nd:YAG dye laser (630 nm, 10 Hz, 150 J/cm(2)). Paraffin-embedded tissue sections from the excised tumor tissues at 6, 12, 24, 48 hours after PDT were analyzed by TUNEL for the occurrence of apoptosis and by immunohistochemistry for Fas and Fas ligand (FasL) expression. TUNEL-positive cells as well as Fas- or FasL-positive cells were counted and expressed as a percentage of positive cells per total cells. Based on the percent area of tumor necrotic foci, the most effective conditions for PDT were first determined. Under these conditions, PDT increased the number of TUNEL-positive tumor cells at 12 hours after irradiation. In parallel with the increase in TUNEL-positive cells, Fas-positive tumor cells were also found in the same area where many TUNEL-positive tumor cells were found. The expression of Fas ligand was found in the tumor cells surrounding TUNEL-positive cells on serial sections. A significant increase in FasL-positive lymphocytes was observed at 12 hours, whereas the infiltration of such lymphocytes into the area where TUNEL-positive tumor cells were observed was rare. The possible role of Fas/FasL system in the cell death induced by PDT with Photofrin(R) and Nd:YAG dye laser was suggested. Moreover, the role of infiltrated lymphocytes seemed not to be so much in this model.

Enhanced cell death in NR‐S1 tumor by photodynamic therapy: Possible involvement of Fas and Fas ligand system

Enhanced cell death in NR‐S1 tumor by photodynamic therapy: Possible involvement of Fas and Fas ligand system

Induction of apoptosis in placentas of pregnant mice exposed to lipopolysaccharides: possible involvement of Fas/Fas ligand system.

To explore the pathogenesis in placental dysfunction and abruptio placentae, we analyzed the occurrence of placental cell apoptosis and the role of Fas and Fas ligand (L) in that process in an inflammatory placental dysfunction model of pregnant mice, using lipopolysaccharides (LPS). In the present study, Day 13 pregnant mice were injected i.p. with LPS (50 microg/kg) or saline as a control, and the placentas were isolated at various time points after the injection. Analysis of the isolated DNA in agarose-gel electrophoresis revealed a typical ladder pattern of bands consisting of 180-200 base pairs (bp), which is regarded as a hallmark of apoptosis. The intensity of the bands increased time-dependently, reaching a maximum level at 12 h after LPS injection. In accord with the biochemical data, histochemical analysis using terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) revealed that nuclei positive for double-stranded DNA breaks were found in decidua, diploid trophoblasts in the basal zone, and spongiotrophoblasts. The number of positive nuclei was maximized at 12 h after LPS injection. As a next step, we investigated the possible involvement of Fas and Fas L in the induction of apoptosis of the placental cells after LPS injection. Western blot analysis indicated that LPS increased the expression of Fas and Fas L in the placenta by about 4-fold at 12 h and 18 h, respectively, after injection. The cells expressing Fas and Fas L were identified, using immunohistochemistry and nonradioactive in situ hybridization, as decidua, diploid trophoblasts in the basal zone, and spongiotrophoblasts. Furthermore, when the expression of 4-hydroxy-2-nonenal (HNE)-modified proteins was assessed to evaluate the relation of oxidative stress elicited by LPS to the induction of apoptosis, once again decidua, diploid trophoblasts in the basal zone, and spongiotrophoblasts were positive. Therefore, the placental dysfunction by LPS may be brought about by the Fas-mediated apoptosis of various placental cells in a paracrine/autocrine fashion, possibly under the influence of oxidative stress.

Apoptotic Role of Fas/Fas Ligand System in the Regulation of Erythropoiesis

The possible involvement of Fas and Fas ligand (FasL) in the regulation of erythropoiesis was evaluated. Immunohistochemistry of normal bone marrow specimens revealed that several immature erythroblasts undergo apoptosis in vivo. Analysis of bone marrow erythroblasts and purified progenitors undergoing unilineage erythroid differentiation showed that Fas is rapidly upregulated in early erythroblasts and expressed at high levels through terminal maturation. However, Fas crosslinking was effective only in less mature erythroblasts, particularly at basophilic level, where it induced apoptosis antagonized by high levels of erythropoietin (Epo). In contrast, FasL was selectively induced in late differentiating Fas-insensitive erythroblasts, mostly at the orthochromatic stage. FasL is functional in mature erythroblasts, as it was able to kill Fas-sensitive lymphoblast targets in a Fas-dependent manner. Importantly, FasL-bearing mature erythroblasts displayed a Fas-based cytotoxicity against immature erythroblasts, which was abrogated by high levels of Epo. These findings suggest the existence of a negative regulatory feedback between mature and immature erythroid cells, whereby the former cell population might exert a cytotoxic effect on the latter one in the erythroblastic island. Hypothetically, this negative feedback operates at low Epo levels to moderate the erythropoietic rate; however, it is gradually inhibited at increasing Epo concentrations coupled with enhanced erythrocyte production. Thus, the interaction of Fas and FasL may represent an apoptotic control mechanism for erythropoiesis, contributing to the regulation of red blood cell homeostasis.

Apoptotic Role of Fas/Fas Ligand System in the Regulation of Erythropoiesis

AbstractThe possible involvement of Fas and Fas ligand (FasL) in the regulation of erythropoiesis was evaluated. Immunohistochemistry of normal bone marrow specimens revealed that several immature erythroblasts undergo apoptosis in vivo. Analysis of bone marrow erythroblasts and purified progenitors undergoing unilineage erythroid differentiation showed that Fas is rapidly upregulated in early erythroblasts and expressed at high levels through terminal maturation. However, Fas crosslinking was effective only in less mature erythroblasts, particularly at basophilic level, where it induced apoptosis antagonized by high levels of erythropoietin (Epo). In contrast, FasL was selectively induced in late differentiating Fas-insensitive erythroblasts, mostly at the orthochromatic stage. FasL is functional in mature erythroblasts, as it was able to kill Fas-sensitive lymphoblast targets in a Fas-dependent manner. Importantly, FasL-bearing mature erythroblasts displayed a Fas-based cytotoxicity against immature erythroblasts, which was abrogated by high levels of Epo. These findings suggest the existence of a negative regulatory feedback between mature and immature erythroid cells, whereby the former cell population might exert a cytotoxic effect on the latter one in the erythroblastic island. Hypothetically, this negative feedback operates at low Epo levels to moderate the erythropoietic rate; however, it is gradually inhibited at increasing Epo concentrations coupled with enhanced erythrocyte production. Thus, the interaction of Fas and FasL may represent an apoptotic control mechanism for erythropoiesis, contributing to the regulation of red blood cell homeostasis.

Radiation and stress-induced apoptosis: a role for Fas/Fas ligand interactions.

The lpr gene encodes a defective form of Fas, a cell surface protein that mediates apoptosis. This defect blocks apoptotic deletion of autoreactive T and B cells, leading to lymphoproliferation and lupus-like autoantibody production. The effects of the lpr Fas mutation on other kinds of physiologically relevant apoptosis are largely undocumented. To assess whether some of the apoptosis known to occur after ionizing radiation might be mediated by Fas/Fas ligand (FasL) interactions, we quantitated in vitro apoptosis by flow cytometry measurement of DNA content in splenic T and B cells from irradiated 5- to 8-month-old B6/lpr mice. Total apoptosis of both lpr and control cells was substantial after treatment; however there was a significant difference between B6 (73%) and lpr (25%) lymphocyte apoptosis. Thy1, CD4, CD8, and IgM cells from lpr showed much lower levels of apoptosis than control cells after irradiation. Apoptosis induced by heat shock was also impaired in lpr. The finding that gamma-irradiation increased Fas expression on B6 cells and that irradiation-induced apoptosis could be blocked with a Fas-Fc fusion protein further supported the possible involvement of Fas in this form of apoptosis. Fas/FasL interactions may thus play an important role in identifying and eliminating damaged cells after gamma-irradiation and other forms of injury.

Mouse islet cell lysis mediated by interleukin-1-induced Fas.

This study was conducted to investigate the possible involvement of Fas in beta-cell death in insulitis of Type 1 (insulin-dependent) diabetes mellitus. Although primary cultured Balb/c mouse islet cells did not express Fas mRNA, 4-12 hours of treatment with 10(2)-10(3) U/l of mouse interleukin-1 alpha (IL-1 alpha) induced the expression of Fas mRNA. Surface Fas expression was detected by immunofluorescence flow cytometry using a non-cytolytic anti-Fas monoclonal antibody after 6 or 12 h of incubation with 10(3) U/l of IL-1 alpha. Primary islet cells were resistant to an agonistic anti-Fas monoclonal antibody. However, 12 h pretreatment with IL-1 alpha sensitized islet cells to its cytolytic effect. Significant cell death was observed 24 h after the addition of anti-Fas, and progressively increased until 72 h, when specific 51Cr release was 72 +/- 6%. Agarose gel electrophoresis of DNA extracted from cells exposed to IL-1 alpha and agonistic anti-Fas showed internucleosomal DNA fragmentation, a hallmark of apoptotic cell death. Since the Fas antibody showed no cross-reactive activity of tumour necrosis factor (TNF), the cytotoxic effect was not mediated by TNF receptors. A protein synthesis inhibitor cycloheximide augmented Fas-mediated islet cell death. The Fas-mediated killing of islet cells was not L-arginine-dependent, or blocked by N(G)-monomethyl-L-arginine. beta-TC1 cells also expressed Fas mRNA when exposed to IL-1 alpha or IL-1 alpha plus interferon-gamma. These observations suggest that Fas-mediated apoptosis may be a mechanism of islet cell death in autoimmune insulitis.