Mouse blastocysts were exposed to doses of 0, 1 and 10 mumol/L retinoic acid (RA) for 24 h and the cytotoxic effect of RA on the mouse blastocysts in vitro was observed. FITC-labeled terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL-FITC) assay was employed to stain apoptotic cells and immunohistochemical S-P staining method was used to detect the expression of Fas protein in mouse blastocysts in vitro. The results showed that RA could induce apoptosis and increase the expression of Fas proteins of trophectoderm (TE) and inner cell mass (ICM) cells in blastocysts. Compared with the findings for the control blastocysts, exposure to RA (10 mumol/L) resulted in a more significant apoptosis and higher expression level of Fas proteins (P<0.01). It was concluded that RA could induce apoptosis, which may result in a significant reduction in the average number of total cells and the trophectoderm/inner cell mass in blastocysts and an increased expression of Fas protein, suggesting that RA had a cytotoxic effect on the growth and development of early embryos in mice.
Antigens, CD95/*biosynthesis ; Apoptosis/*drug effects ; Blastocyst/cytology ; Blastocyst/*metabolism ; Cell Culture Techniques/methods ; Cells, Cultured ; Gene Expression Regulation/*drug effects ; In Situ Nick-End Labeling ; RNA, Messenger/metabolism ; Tretinoin/*pharmacology

Neutrophils are also known to acquire the characteristics of dendritic cells (DCs) under the appropriate conditions. In this study, neutrophils were cultivated in vitro in the presence or absence of compounds modulating their survival in an attempt to characterize the expression profile of the DC markers. Higher MHC-II, CD80, CD86, CD83, and CD40 expression levels were detected on the surface of the cultured neutrophils for 24 h than on the freshly isolated cells. The annexin V-positive cells showed a higher expression level of the DC markers than the annexin V-negative cells. The population of neutrophils double stained with annexin V and the DC markers increased after being incubated with agonistic anti-Fas Ab. LPS, the anti-apoptotic compound, decreased the CD86 and MHC-II expression levels but 50-60% of the DC marker-positive cells were detected in the annexin V-positive cells. In contrast, CD80, CD86, CD83, and HLA-DR mRNA levels increased in the GM-CSF-treated neutrophils but not in the anti-Fas Ab-treated neutrophils. T cell proliferation was inhibited by co-culturing them with anti-Fas Ab- or LPS-treated neutrophils at a high neutrophil:T cell ratio. However, the superantigen-mediated T cell proliferation was increased by the LPS-treated neutrophils but decreased by the anti-Fas Ab-treated neutrophils. There was a lower level of interferon-gamma production in the T cells co-cultured with anti-Fas Ab-treated neutrophils than with the LPS-treated neutrophils. This suggests that apoptotic neutrophils express DC markers on their surface and the differential expression of DC markers might have a detrimental effect on the immune reaction.
Antigen Presentation ; Antigens, CD/biosynthesis ; Antigens, CD95/pharmacology ; Antigens, Differentiation/*biosynthesis ; *Apoptosis ; Cells, Cultured ; Dendritic Cells/*metabolism ; Humans ; Lipopolysaccharides/pharmacology ; Lymphocyte Activation ; Neutrophils/*metabolism/physiology ; T-Lymphocytes/immunology

Although the apoptosis of chondrocytes plays an important role in endochondral ossification, its mechanism has not been elucidated. In this study, we show that guanosine induces chondrocyte apoptosis based on the results of acridine orange/ ethidium bromide staining, caspase-3 activation, and sub-G1 fraction analysis. The potent inhibitory effect of dipyridamole, a nucleoside transporter blocker, indicates that extracellular guanosine must enter the chondrocytes to induce apoptosis. We found that guanosine promotes Fas-Fas ligand interaction which, in turn, leads to chondrocyte apoptosis. These findings indicate a novel mechanism for endochondral ossification via metabolic regulation.
Tumor Necrosis Factors/metabolism ; Signal Transduction/drug effects ; Receptors, Tumor Necrosis Factor/*metabolism ; Rats, Sprague-Dawley ; Rats ; Nucleoside Transport Proteins/metabolism ; Membrane Glycoproteins/metabolism ; Guanosine/*pharmacology/physiology ; Fas Ligand Protein ; Chondrocytes/*drug effects/metabolism ; Apoptosis/*drug effects ; Antigens, CD95 ; Animals

Apoptotic cell death induced by p53 occurs at a late G1 cell cycle checkpoint termed the restriction(R)point, and it has been proposed that p53-induced apoptosis causes upregulation of CD95. However, as cells with defective in CD95 signaling pathway are still sensitive to p53-induced apoptosis, CD95 cannot be the sole factor resulting in apoptosis. In addition, unlike p53-induced apoptosis, the relationship between CD95-mediated apoptosis and the cell cycle is not clearly understood. It would there-fore be worth investigating whether CD95-mediated cell death is pertinent with p53-induced apoptosis in view of cell cycle related molecules. In this report, biochemical analysis showed that etoposide-induced apoptosis caused the induction and the nuclear translocation of effector molecules involved in G1 cell cycle checkpoint. However, there was no such translocation in the case of CD95-mediated death. Thus, although both types of apoptosis involved caspase activation, the cell cycle related proteins responded differently. This argues against the idea that p53-induced apoptosis occurs through the induction of CD95/CD95L expression.
Active Transport, Cell Nucleus ; Antigens, CD95/*metabolism ; *Apoptosis ; Cell Cycle ; Cell Nucleus/metabolism ; Coculture ; Dose-Response Relationship, Drug ; Down-Regulation ; Etoposide/pharmacology ; Flow Cytometry ; Human ; Immunoblotting ; Jurkat Cells ; Nucleic Acid Synthesis Inhibitors/pharmacology ; Protein Binding ; Protein Transport ; Protein p53/*metabolism ; Signal Transduction ; Up-Regulation

A20 murine lymphoma cells undergoing Fas-mediated apoptosis showed increase in the activity of phospholipase D (PLD), which is involved in proliferative or mitogenic cellular responses. Using A20 cell lines that were resistant to Fas-induced apoptosis, we investigated the differential effects of Fas cross-linking on PLD activity and sphingolipid metabolism. The basal PLD activities in all of the selected three Fas-resistant clones (#5, #8, and #11) were about 2~4 folds higher than that of wild type A20 cells. Among the PLD isoforms, PLD2 expression was increased in all of the selected Fas-resistant clones. The Fas downstream signaling events triggered by Fas cross-linking, including the activations of PLD, phosphatidy-lcholine-specific phospholipase C (PC-PLC), sphingomyelinase (SMase), the increase in diacylglycerol (DAG) and protein phosphorylation levels, and the translocation of protein kinase C to membrane were not changed in both of Fas-resistant clone #5 and #8. In contrast, Fas cross-linking stimulated the activity of PLD, PC-PLC, and SMase, translocation of PKC, and protein phosphorylation in Fas-resistant clone #11, similar to that of wild type cells. We also found that clone #11 had a different Fas sequence encoding Fas B which has been known to inhibit Fas-induced apoptosis. These findings suggest that increased PLD2 expression resulting in increased basal PLD activity and the blockade of Fas downstream signaling cascades may be involved to limit apoptosis induced by Fas cross-linking.
Animals ; Antibodies, Monoclonal/immunology/pharmacology ; Antigens, CD95/immunology/*metabolism ; Base Sequence ; Carrier Proteins/metabolism ; Clone Cells ; Cross-Linking Reagents/pharmacology ; Diglycerides/metabolism ; Enzyme Activation/drug effects ; Lipids/*metabolism ; Mice ; Molecular Sequence Data ; Phospholipase D/*metabolism ; Phosphorylation/drug effects ; Protein Kinase C/metabolism ; *Signal Transduction/drug effects ; Sphingomyelin Phosphodiesterase/metabolism ; Tumor Cells, Cultured

It is known that CD95 (APO-1/Fas) is expressed on the cell surface, and apoptotic cell death can be induced by the CD95 ligation in the cultured, proliferating human retinal pigment epithelial (RPE) cells. However, little is known about CD95 on the non-proliferating RPE cells. In this study, human RPE cells were cultured up to 4 weeks after they reached the confluence, to simulate the non-proliferating RPE cells in situ. There was no significant difference in CD95 expression on the cell surface between the predominantly proliferating, preconfluent cells and predominantly non-proliferating, postconfluent cells in flow cytometric assays. However, unlike proliferating cells, no cellular death occurred in the predominantly non-proliferating cells after the treatment of agonistic anti-CD95 antibody with cycloheximide, pretreated with interferon-gamma. Our results suggest that the CD95/CD95L system probably plays a physiologic role in vivo to remove the abnormal, proliferating RPE cells, and factors other than the surface expression of CD95 may determine the sensitivity to the CD95 signals.
Antigens, CD95/*pharmacology ; Apoptosis/*physiology ; Cells, Cultured ; Human ; Pigment Epithelium of Eye/cytology/*drug effects/*physiology ; Sensitivity and Specificity

Both Fas and PMA can activate phospholipase D via activation of protein kinase Cbeta in A20 cells. Phospholipase D activity was increased 4 fold in the presence of Fas and 2.5 fold in the presence of PMA. The possible involvement of tyrosine phosphorylation in Fas-induced activation of phospholipase D was investigated. In five minute after Fas cross-linking, there was a prominent increase in tyrosine phosphorylated proteins, and it was completely inhibited by D609, a specific inhibitor of phosphatidylcholine-specific phospholipase C (PC-PLC). A tyrosine kinase inhibitor, genistein, can partially inhibit Fas-induced phospholipase D activation. There were no effects of genistein on Fas-induced activation of PC-PLC and protein kinase C. These results strongly indicate that tyrosine phosphorylation may in part account for the increase in phospholipase D activity by Fas cross-linking and D609 can block not only PC-PLC activity but also tyrosine phosphorylation involved in Fas-induced phospholipase D activation.
Animal ; Antibodies, Monoclonal/immunology/*pharmacology ; Antigens, CD95/immunology/*metabolism ; Bridged Compounds/*pharmacology ; Cell Line ; Cross-Linking Reagents ; Dose-Response Relationship, Immunologic ; Enzyme Activation ; Genistein/pharmacology ; Hydrolysis ; Lymphoma/pathology ; Mice ; Phospholipase C/*antagonists & inhibitors ; Phospholipase D/*metabolism ; Phosphorylation ; Phosphorylcholine/metabolism ; Solubility ; Thiones/*pharmacology ; Tumor Cells, Cultured ; Tyrosine/*metabolism ; Water/chemistry

Both Fas and PMA can activate phospholipase D via activation of protein kinase Cbeta in A20 cells. Phospholipase D activity was increased 4 fold in the presence of Fas and 2.5 fold in the presence of PMA. The possible involvement of tyrosine phosphorylation in Fas-induced activation of phospholipase D was investigated. In five minute after Fas cross-linking, there was a prominent increase in tyrosine phosphorylated proteins, and it was completely inhibited by D609, a specific inhibitor of phosphatidylcholine-specific phospholipase C (PC-PLC). A tyrosine kinase inhibitor, genistein, can partially inhibit Fas-induced phospholipase D activation. There were no effects of genistein on Fas-induced activation of PC-PLC and protein kinase C. These results strongly indicate that tyrosine phosphorylation may in part account for the increase in phospholipase D activity by Fas cross-linking and D609 can block not only PC-PLC activity but also tyrosine phosphorylation involved in Fas-induced phospholipase D activation.
Animal ; Antibodies, Monoclonal/immunology/*pharmacology ; Antigens, CD95/immunology/*metabolism ; Bridged Compounds/*pharmacology ; Cell Line ; Cross-Linking Reagents ; Dose-Response Relationship, Immunologic ; Enzyme Activation ; Genistein/pharmacology ; Hydrolysis ; Lymphoma/pathology ; Mice ; Phospholipase C/*antagonists & inhibitors ; Phospholipase D/*metabolism ; Phosphorylation ; Phosphorylcholine/metabolism ; Solubility ; Thiones/*pharmacology ; Tumor Cells, Cultured ; Tyrosine/*metabolism ; Water/chemistry

The pathogenesis of chronic cyclosporine A (CsA) nephrotoxicity has not been elucidated, but apoptosis is thought to play an important role in CsA induced tubular atrophy. Recently Fas-Fas ligand system mediated apoptosis has been frequently reported in many epithelial cells as well as in T lymphocytes. We investigated the ability of CsA to induce apoptosis in cultured human proximal tubular epithelial cells and also the effect of -MSH on them. Fas, Fas ligand, and an intracellular adaptor protein, Fas-associating protein with death domain (FADD) expression, and poly-ADP ribose polymerase (PARP) cleavage were also studied. CsA induced apoptosis in cultured tubular epithelial cells demonstrated by increased number of TUNEL positive cells and it was accompanied by a significant increase in Fas mRNA and Fas ligand protein expressions. FADD and the cleavage product of PARP also increased, indicating the activation of caspase. In -MSH co-treated cells, apoptosis markedly decreased with downregulation of Fas, Fas ligand and FADD expressions and also the cleavage product of PARP. In conclusion, these data suggest that tubular cell apoptosis mediated by Fas system may play a role in tubular atrophy in chronic CsA nephrotoxicity and pretreatment of -MSH may have a some inhibitory effect on CsA induced tubular cell apoptosis.
Antigens, CD95/genetics ; Apoptosis/*drug effects ; Carrier Proteins/biosynthesis ; Caspases/physiology ; Cells, Cultured ; Cyclosporine/*toxicity ; Human ; Immunosuppressive Agents/*toxicity ; Kidney Tubules, Proximal/cytology/*drug effects/metabolism ; Membrane Glycoproteins/biosynthesis ; NAD+ ADP-Ribosyltransferase/metabolism ; RNA, Messenger/analysis ; alpha-MSH/*pharmacology

Interleukin 15 (IL-15) is an important regulatory cytokine in cellular immunity. In vitro replacement of IL-15 has been shown to enhance immunity in Human immunodeficiency virus type 1 (HIV-1) infected lymphocytes. We evaluated the effect of IL-15 on the survival of peripheral blood mononuclear cells of HIV patients by examining in vitro lymphocyte apoptosis, and correlated the process with Bcl-2 and Fas gene regulation. Peripheral blood mononuclear cells (PBMC) from 21 HIV-infected adults and 24 HIV-seronegative healthy individuals were isolated and cultured to determine the effect of escalating doses of IL-15 (0, 1, 10, 100, 1000 ng/mL) on apoptosis. Lymphocyte proliferation assay with (3H) TdR was measured and Bcl-2 and Fas gene regulation was observed. The results were as follows: 1) IL-15 reduced culture induced lymphocyte apoptosis in HIV patients in a dose dependent manner, and reached a plateau level at a concentration of 100 ng/ml; 2) IL-15 significantly reduced the level of apoptosis after 3 days (14%) and 5 days (15%) of culture in HIV patients, while no difference was observed in HIV (-) donors; 3) The percentage of viable cells among the total number of lymphocytes was significantly enhanced by 25% in HIV patients with IL-15; 4) Bcl-2 expression was decreased in HIV patients (53.9 +/- 12.3%) compared to HIV (-) donors (93.0 +/- 3.7%), and IL-15 increased Bcl-2 expression by 21.2 +/- 5.2% in HIV patients; 5) Fas expression was increased in HIV patients (70.2 +/- 4.6%) compared to HIV (-) donors (32.4 +/- 4.3%), and IL-15 increased Fas expression by 8.4 +/- 1.2% in HIV (-) donors. Our findings indicate that IL-15 may influence immunologic abnormalities in HIV infection, particularly its ability to prevent apoptosis of lymphocytes by suppressing the down-modulation of Bcl-2. This may provide an experimental basis for IL-15 immunotherapy.
Antigens, CD95/genetics ; Apoptosis/drug effects* ; Cells, Cultured ; Gene Expression Regulation/physiology ; Genes, bcl-2/genetics ; HIV Infections/blood* ; Human ; Interleukin-15/pharmacology* ; Monocytes/drug effects*