CD95(APO-1/Fas)-mediated apoptosis: live and let die

Apoptotic potential of Fas-associated death domain on regulation of cell death regulatory protein cFLIP and death receptor mediated apoptosis in HEK 293T cells

Fas-associated death domain (FADD) is a common adaptor molecule which plays an important role in transduction of death receptor mediated apoptosis. The FADD provides DED motif for binding to both procaspase-8 and cFLIP molecules which executes death receptor mediated apoptosis. Dysregulated expression of FADD and cFLIP may contribute to inhibition of apoptosis and promote cell survival in cancer. Moreover elevated intracellular level of cFLIP competitively excludes the binding of procaspase-8 to the death effector domain (DED) of FADD at the DISC to block the activation of death receptor signaling required for apoptosis. Increasing evidence shows that defects in FADD protein expression are associated with progression of malignancies and resistance to apoptosis. Therefore, improved expression and function of FADD may provide new paradigms for regulation of cell proliferation and survival in cancer. In the present study, we have examined the potential of FADD in induction of apoptosis by overexpression of FADD in HEK 293T cells and validated further its consequences on the expression of pro and anti-apoptotic proteins besides initiation of death receptor mediated signaling. We have found deficient expression of FADD and elevated expression of cFLIP(L) in HEK 293T cells. Our results demonstrate that over expression of FADD attenuates the expression of anti-apoptotic protein cFLIP and activates the cascade of extrinsic caspases to execution of apoptosis in HEK 293T cells.

NF-κB directly regulates Fas transcription to modulate Fas-mediated apoptosis and tumor suppression

Fas is a member of the death receptor family. Stimulation of Fas leads to induction of apoptotic signals, such as caspase 8 activation, as well as "non-apoptotic" cellular responses, notably NF-κB activation. Convincing experimental data have identified NF-κB as a critical promoter of cancer development, creating a solid rationale for the development of antitumor therapy that suppresses NF-κB activity. On the other hand, compelling data have also shown that NF-κB activity enhances tumor cell sensitivity to apoptosis and senescence. Furthermore, although stimulation of Fas activates NF-κB, the function of NF-κB in the Fas-mediated apoptosis pathway remains largely undefined. In this study, we observed that deficiency of either Fas or FasL resulted in significantly increased incidence of 3-methylcholanthrene-induced spontaneous sarcoma development in mice. Furthermore, Fas-deficient mice also exhibited significantly greater incidence of azoxymethane and dextran sodium sulfate-induced colon carcinoma. In addition, human colorectal cancer patients with high Fas protein in their tumor cells had a longer time before recurrence occurred. Engagement of Fas with FasL triggered NF-κB activation. Interestingly, canonical NF-κB was found to directly bind to the FAS promoter. Blocking canonical NF-κB activation diminished Fas expression, whereas blocking alternate NF-κB increased Fas expression in human carcinoma cells. Moreover, although canonical NF-κB protected mouse embryo fibroblast (MEF) cells from TNFα-induced apoptosis, knocking out p65 diminished Fas expression in MEF cells, resulting in inhibition of FasL-induced caspase 8 activation and apoptosis. In contrast, knocking out p52 increased Fas expression in MEF cells. Our observations suggest that canonical NF-κB is a Fas transcription activator and alternate NF-κB is a Fas transcription repressor, and Fas functions as a suppressor of spontaneous sarcoma and colon carcinoma.

Effect of nerve growth factor and its transforming tyrosine kinase protein and low-affinity nerve growth factor receptors on apoptosis of notochordal cells

PURPOSE

The disappearance of notochordal cells by apoptosis is thought to be the starting point of intervertebral disc degeneration. The aim of this study was to determine the apoptotic pathway of notochordal cells as well as the anti-apoptotic potential of caspase inhibitors.

METHODS

Rat notochordal cells were isolated, cultured, and placed in either 0 % (apoptosis-promoting condition) or 10 % (normal control) foetal bovine serum (FBS). We identified and quantified apoptotic cell deaths and caspase activities. In addition, we examined the cells for expression of nerve growth factor (NGF) and its two receptors--TrkA (survival signal) and p75 (apoptotic signal)--and downstream pathways. Finally, we analysed the degree of anti-apoptotic effects of caspase inhibitors on the cells.

RESULTS

The apoptotic rate and expressions of caspase-8 (extrinsic pathway), -9 (intrinsic pathway), and -3 (common executioner) of notochordal cells were increased in 0 % FBS compared with those in 10 % FBS. Expressions of NGF, p75 receptor and JNK downstream pathways were also increased in 0 % FBS. In contrast, expressions of the TrkA receptor and Akt and MAPK downstream pathways were decreased in 0 % FBS. Pancaspase, capase-9 and capase-8 inhibitors significantly reduced apoptotic cell death.

CONCLUSIONS

Our results suggest that notochordal cells undergo apoptosis through both the intrinsic and extrinsic pathways by activation of NGF, p75 receptor, and the JNK downstream pathway. We also found that apoptosis of notochordal cells can be attenuated by caspase inhibitors. Caspase inhibitors may play a therapeutic role in delaying the starting point of disc degeneration that is due to inappropriate or premature excessive apoptosis of notochordal cells.

Decitabine and vorinostat cooperate to sensitize colon carcinoma cells to Fas ligand-induced apoptosis in vitro and tumor suppression in vivo

The death receptor Fas and its physiological ligand (FasL) regulate apoptosis of cancerous cells, thereby functioning as a critical component of the host cancer immunosurveillance system. To evade Fas-mediated apoptosis, cancer cells often downregulate Fas to acquire an apoptosis-resistant phenotype, which is a hallmark of metastatic human colorectal cancer. Therefore, targeting Fas resistance is of critical importance in Fas-based cancer therapy and immunotherapy. In this study, we demonstrated that epigenetic inhibitors decitabine and vorinostat cooperate to upregulate Fas expression in metastatic human colon carcinoma cells. Decitabine also upregulates BNIP3 and Bik expression, whereas vorinostat decreased Bcl-x(L) expression. Altered expression of Fas, BNIP3, Bik, and Bcl-x(L) resulted in effective sensitization of the metastatic human colon carcinoma cells to FasL-induced apoptosis. Using an experimental metastasis mouse model, we further demonstrated that decitabine and vorinostat cooperate to suppress colon carcinoma metastasis. Analysis of tumor-bearing lung tissues revealed that a large portion of tumor-infiltrating CD8(+) T cells are FasL(+), and decitabine and vorinostat-mediated tumor-suppression efficacy was significantly decreased in Fas(gld) mice compared with wild-type mice, suggesting a critical role for FasL in decitabine and vorinostat-mediated tumor suppression in vivo. Consistent with their function in apoptosis sensitization, decitabine and vorinostat significantly increased the efficacy of CTL adoptive transfer immunotherapy in an experimental metastasis mouse model. Thus, our data suggest that combined modalities of chemotherapy to sensitize the tumor cell to Fas-mediated apoptosis and CTL immunotherapy is an effective approach for the suppression of colon cancer metastasis.

Caspase-mediated programmed cell death pathways as potential therapeutic targets in cancer

The caspase family is well characterized as playing a crucial role in modulation of programmed cell death (PCD), which is a genetically regulated, evolutionarily conserved process with numerous links to many human diseases, most notably cancer. In this review, we focus on summarizing the intricate relationships between some members of the caspase family and their key apoptotic mediators, involving tumour necrosis factor receptors, the Bcl-2 family, cytochrome c, Apaf-1 and IAPs in cancer initiation and progression. We elucidate new emerging types of cross-talk between several caspases and autophagy-related genes (Atgs) in cancer. Moreover, we focus on presenting several PCD-modulating agents that may target caspases-3, -8 and -9, and their substrates PARP-1 and Beclin-1, which may help us harness caspase-modulated PCD pathways for future drug discovery.

Immune responses and ultrastructural changes of hemocytes in freshwater crab Sinopotamon henanense exposed to elevated cadmium

Cadmium (Cd) is one of the most toxic heavy metals that can impact immunological parameters in aquatic animals. To investigate the immunotoxicity and ultrastructural changes of hemocytes, specimens of Sinopotamon henanense were exposed to different concentrations of cadmium and the differences in immunologic parameters between Cd exposure groups and control groups were investigated. Total hemocyte count (THC) in Cd-exposure groups were decreased significantly when compared with the control groups, especially in the groups treated with higher Cd concentrations and longer exposure time, while no significant differences were observed in the proportions of the three types of hemocytes. Phenoloxidase (PO) activities were significantly higher in Cd-exposure groups than the control groups. Superoxide dismutase (SOD) activities gradually increased in 7.25 and 14.5 mg L⁻¹ Cd groups, but in other higher Cd groups, they showed first increase and following decrease with the exposure time prolonged. Acid phosphatase (ACP) activities were induced at 48 h, and then decreased, while alkaline phosphatase (AKP) activities increased gradually until 96 h. Electron microscopic results showed that nucleus, mitochondria and rough endoplasm recutulum (rER) of three types of hemocytes were sensitive to acute Cd toxicity. In Cd-exposed groups, chromatin condensation, nucleus deformation and nucleus envelope rupture were noted. Additionally, mitochondrial dilation and rER degranulation were observed in Cd-treated crabs. These results suggested that immune response and organelles of hemocyte of S. henanense were impacted by Cd exposure, and the changes of these immunologic parameters reflect changes in crab immune response capability consequent to Cd exposure.

Bystander-type effects mediated by long-lived inflammatory signaling in irradiated bone marrow

Radiation-induced bystander and abscopal effects, in which DNA damage is produced in nonirradiated cells as a consequence of communication with irradiated cells, indicate mechanisms of inducing damage and cell death additional to the conventional model of deposition of energy in the cell nucleus at the time of irradiation. In this study we show that signals generated in vivo in the bone marrow of mice irradiated with 4 Gy γ rays 18 h to 15 months previously are able to induce DNA damage and apoptosis in nonirradiated bone marrow cells but that comparable signals are not detected at earlier times postirradiation or at doses below 100 mGy. Bone marrow cells of both CBA/Ca and C57BL/6 genotypes exhibit responses to signals produced by either irradiated CBA/Ca or C57BL/6 mice, and the responses are mediated by the cytokines FasL and TNF-α converging on a COX-2-dependent pathway. The findings are consistent with indirect inflammatory signaling induced as a response to the initial radiation damage rather than to direct signaling between irradiated and nonirradiated cells. The findings also demonstrate the importance of studying tissue responses when considering the mechanisms underlying the consequences of radiation exposures.

Long-lived inflammatory signaling in irradiated bone marrow is genome dependent

Ionizing radiation is carcinogenic, but genotype is a key determinant of susceptibility. Mutational DNA damage is generally attributed to cause disease, but irradiation also affects multicellular interactions as a result of poorly understood bystander effects that may influence carcinogenic susceptibility. In this study, we show that the bone marrow of irradiated mice will retain the ability to kill hemopoietic clonogenic stem cells and to induce chromosomal instability for up to 3 months after irradiation. Chromosomal instability was induced in bone marrow cells derived from CBA/Ca mice, a strain that is susceptible to radiation-induced acute myeloid leukemia (r-AML), but not in C57BL6 mice that are resistant to r-AML. Similarly, clonogenic cell lethality was exhibited in C57BL/6 mice but not CBA/Ca mice. Mechanistic investigations revealed that these genotype-dependent effects involved cytokine-mediated signaling and were mediated by a cyclooxygenase-2-dependent mechanism. Thus, our results suggested that inflammatory processes were responsible for mediating and sustaining the durable effects of ionizing radiation observed on bone marrow cells. Because most exposures to ionizing radiation are directed to only part of the body, our findings imply that genotype-directed tissue responses may be important determinants of understanding the specific consequence of radiation exposure in different individuals.

Expression of Fas receptor and apoptosis in vertebral endplates with degenerative disc diseases categorized as Modic type I or II

STUDY DESIGN

Vertebral endplate tissues were obtained from patients with degenerated lumbar disc classified as Modic type 1 or type 2 and investigated with immunohistochemical staining and the DNA nick end labelling techniques.

OBJECTIVE

To examine the expression of fas receptor (FasR) and apoptosis in the endplate cells isolated from patients with degenerative disc disease and to see whether they are associated with the pathological change of endplate.

METHODS

Fifty-six degenerated lumbar endplate specimens were obtained from the patients with degenerative disc disease categorized as type Modic I or II in magnetic resonance imaging (MRI) and eight nondegenerated specimens as control (vertebra burst fracture patients without degenerative change in MRI) during surgical procedures. Immunohistochemical staining was performed to determine the presence of FasR and apoptosis in sections of those endplate tissues. To investigate whether the FasR expression and apoptosis in endplate were influenced by degeneration and ageing of the discs, the level of FasR expression and apoptosis in the changed and unchanged endplates was analysed.

RESULTS

FasR were expressed in the cytoplasm of the endplate cells. A higher degree of FasR expression and apoptosis in endplate cells in degenerated discs was found than that in nondegenerated discs. In cell culture, the level of FasR expression and apoptosis in cells from the degenerative endplates was higher than those in unchanged endplates. The percentage of FasR-positive endplate and apoptotic endplate cells correlated significantly with the patient's age (r=0.301, p<0.05; r=0.307, p<0.05. respectively), but not with the degree of disc degeneration in MRI (r=0.047, p>0.05; r=0.066, p>0.05, respectively).

CONCLUSION

This is the first study to compare the expression of FasR and apoptosis on vertebral endplate cells in degenerated disc with in nondegenerated disc. The results show that the endplate in degenerated disc may undergo fas-mediated apoptosis and vice versa, endplate degenerative changes may promotes apoptosis of the endplate cells within degenerated disc.

Apoptosis in displaced temporomandibular joint disc with and without reduction: an immunohistochemical study

Internal derangement (ID) of the temporomandibular joint (TMJ) is due to an abnormal relationship of the articular disc to the mandibular condyle, glenoid fossa and articular eminence. The two most common types of internal derangement are anterior disc displacement with (ADDwR) and without reduction (ADDwoR). Disc displacement is associated with degenerative tissue changes. The histological features of discs from patients with TMJ ID reflect a general remodelling caused by abnormal loading. A correlation has been demonstrated between TMJ ID and apoptosis. Few investigations have addressed the role of apoptosis or caspase activity in TMJ ID. The apoptosis activation process was studied in different areas of discs from 18 patients with ID (both ADDwR and ADDwoR) and four cadavers (controls), with emphasis on the expression of caspase 3, whose activation makes the death process irreversible. The results showed a greater proportion of caspase 3-positive cells in ADDwR and ADDwoR than in control discs. Immunopositivity also varied between disc areas; in particular, in ADDwoR sections labelled cells were significantly more numerous (P < 0.01) in the posterior disc attachment than in the anterior and intermediate bands. In addition, a significantly greater proportion of labelled cells was seen in the anterior (+) and intermediate (++) band of ADDwR compared with ADDwoR discs both bands (P < 0.05). These data suggest the importance of programmed cell death in the progression of TMJ ID.

Role of apoptosis resistance in immune evasion and metastasis of colorectal cancer

The host immune system functions as a guardian against tumor development. It has been demonstrated that cytotoxic T lymphocyte (CTL)-mediated cytotoxic pathways function to inhibit or delay human colorectal cancer development. However, the host anti-tumor immune responses also 'edit' the tumor and select for more aggressive variants, resulting in immune evasion and tumor escape. Fas is a death receptor that mediates one of the major cytotoxic effector mechanisms of the CTLs. Fas is highly expressed in normal human colon epithelial cells but is frequently silenced in colorectal carcinoma, especially in metastatic colorectal carcinoma, suggesting that loss of Fas expression and function may be an immune evasion and tumor escape mechanism. In addition, recent studies indicated that Fas also mediates cellular proliferation signaling pathways to promote tumor development. Therefore, the death receptor Fas may not only transduce death signals to suppress tumor development but also activate cellular proliferation and the migration process to promote tumor growth and progression. Thus, understanding the mechanisms by which the Fas receptor and its associated protein complex transduces the death and survival signals may identify molecular targets for the development of therapeutic strategy to enhance the Fas-mediated death signals to increase the efficacy of cancer immunotherapy.

Compounds from Viburnum sargentii Koehne and evaluation of their cytotoxic effects on human cancer cell lines

Compounds were isolated from a methanol extract of the dried stem barks of Viburnum sargentii Koehne. The structures of the compounds, namely 9'-O-methylvibsanol (3), furcatoside A (4) and lareciresinol (5) were elucidated by analysis of spectroscopic data and comparison with values for previously known analogues. In addition, (+)-catechin (1), (+)-epicatechin (2) were also isolated. This work also examined the cytotoxic effects of three compounds 3-5 (25-100 µM) in MCF-7 and A549 cells after 24, 48 and 72 h of exposure. Our results showed that 9'-O-methylvibsanol (3) exhibited strong concentration-dependent anticancer effects according to the MTT assay and produced morphological changes consistent with apoptosis, as confirmed by Ho3342 staining analysis revealed that more apoptotic cells were observed after 9'-O-methylvibsanol (3) treatment.

Gentamicin-induced spiral ganglion cell death: apoptosis mediated by ROS and the JNK signaling pathway

CONCLUSION

Reactive oxygen species (ROS) and the c-Jun N-terminal kinase (JNK) signaling pathway may be involved in secondary apoptosis of spiral ganglion cells (SGCs) induced by intracochlear gentamicin injection.

OBJECTIVES

The purpose of this study was to ascertain the role of ROS and the JNK signaling pathway in secondary apoptosis of SGCs induced by intracochlear gentamicin treatment.

METHODS

Gentamicin (40 mg/ml) was injected into the cochlea of guinea pigs (n = 18) to destroy the hair cells and induce secondary apoptosis of SGCs. At 1 (n = 6), 2 (n = 6), and 3 (n = 6) weeks after gentamicin treatment, the cochleas were removed and stained with hematoxylin and eosin, and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling to observe the morphologic changes and apoptosis of SGCs. A dihydroethidium (DHE) assay was performed to detect ROS generation, and RT-PCR and Western blot analysis were used to assess the expression of Fas ligand (FasL), JNK, and c-Jun.

RESULTS

After gentamicin was injected into the cochlea, apoptosis and progressive loss of SGCs were observed. RT-PCR and Western blot analysis showed increased expression of FasL after gentamicin treatment. ROS generation detected by DHE fluorescence increased progressively, and the expression of JNK, phospho-JNK, c-Jun, and phospho-c-Jun also increased.

Toxicological evaluation of z24, a novel indolin-2-ketone compound, in cultured human liver cells using toxicogenomic techniques

The current study was designed to investigate the toxicity of 3Z-3-[((1)H-pyrrol-2-yl)-methylidene]-1-(1-piperidinylmethyl)-1, 3-2H-indol-2-one (Z24), a novel synthetic indolin-2-ketone small molecule compound, using toxicogenomic techniques (complementary DNA [cDNA] microarray). Bioinformatic analysis suggested that the main functions of genes with altered expression were consistent with liver cell regeneration, apoptosis, metabolism of energy and fat, and the death receptor (DR)-mediated apoptosis-signaling pathway. Death receptor 4, Bcl-2, Bcl-xl, caspase 3, and cytochrome C, which are involved in the DR-mediated apoptosis-signaling pathway, were altered after Z24 treatment as determined by Western blotting analysis. When hepatocarcinoma cell line (HepG2 cells) treated with Z24 at 0.248 mmol/L for 24 hours, DNA fragmentation reached a maximum, and examination of cell morphology showed typical signs of apoptosis. These results indicate that Z24 can initiate apoptosis in hepatocytes, which in turn causes hepatotoxicity. A possible toxicological mechanism is that apoptosis was induced in hepatocytes by initiating the DR-mediated signal transduction pathway. Apoptosis of hepatocytes might lead to impairment of energy and lipid metabolism and provoke hepatocyte necrosis or inflammation, resulting in hepatotoxicity.

Monocytes and macrophages regulate immunity through dynamic networks of survival and cell death

Monocytes and macrophages are central cells of the innate immune system, responsible for defending against diverse pathogens. While they originate from a common myeloid precursor and share functions in innate immunity, each has a very distinct life span finely tuned by the apoptotic caspases. Normally, circulating monocytes are short-lived and undergo spontaneous apoptosis on a daily basis. Macrophages, however, have a longer life span. In chronic inflammatory diseases and, as recently recognized, in the tumor microenvironment, the inhibition of the apoptotic program promotes monocyte survival contributing to the accumulation of macrophages and the persistence of an inflammatory milieu. A complex network of differentiation factors and inflammatory stimuli determine monocyte/macrophage life span by blocking the apoptotic pathway and activating a myriad of survival pathways. Our understanding of apoptosis has flourished over the last decade, and its relevance in the regulation of the immune system is now indisputable. Nevertheless, how the complicated networks of survival and apoptotic regulators are integrated to determine cellular life span remains elusive. This review summarizes the contribution of the caspases and their regulators in monocyte/macrophage cell fate and discusses how these molecules orchestrate the initiation, maintenance, and resolution of inflammation. More provocatively, we discuss possible strategies to control inflammation by manipulating leukocyte life span.

Up-regulation of the Apo/Fas (CD95) complex on neutrophils harvested during cardiac surgery: distinct findings in patients operated on with or without the use of cardiopulmonary bypass

Aims: In a group of patients undergoing cardiac surgery performed both with (“on-pump”) and without the use (“offpump”) of cardiopulmonary bypass (CPB), we studied the changes of neutrophil membrane apoptosis-inducing complex Apo/Fas.

Methods: Expression of Apo/Fas (CD95) on leukocytes was evaluated by flow cytometry.

Results: In “on-pump” patients, we found an increase in the expression of CD95 median intensity fluorescence (MFI) on granulocytes from a baseline level median=56, (Q 1=45.5, Q3=64) to a median=88, (Q1=62, Q 3=109.5; p<0.01) at the 3rd postoperative day and median=74, (Q1=63, Q3=84.5; p<0.01) at the 7th postoperative day. In “off-pump” patients, granulocyte CD95 MFI was median=55, (Q1=51, Q3=84) before surgery. The significant increase was found on the 3rd postoperative day only; median=90, (Q 1=66; Q3=98; p<0.05). A similar pattern in the CD95 expression was also found if percentage changes of granulocyte CD95 MFI were followed. Moreover, the significantly increased Apo/Fas expression expressed as a percentage change of CD95 MFI was found in “on-pump” patients compared to “off-pump” patients, both at the 3rd postoperative day (p<0.05) and at the 7th postoperative day (p<0.01).

Conclusions: This is the first direct evidence of increasing densities of the Apo/Fas complex on neutrophils in cardiac surgical patients.

Chronic cigarette smoke extract treatment selects for apoptotic dysfunction and mitochondrial mutations in minimally transformed oral keratinocytes

Cigarette smoke demonstrates a carcinogenic effect through chronic exposure, not acute exposures. However, current cell line models study only the acute effects of cigarette smoke. Using a cell line model, we compared the effects of acute versus chronic cigarette smoke extract (CSE) on mitochondria in minimally transformed oral keratinocytes (OKF6). OKF6 cells were treated with varying concentrations of CSE for 6 months. Cells were analyzed monthly by flow cytometry for mitochondrial membrane potential (MMP), cytochrome c release, caspase 3 activation and viability after CSE exposure. At each time point, the same assays were performed after 24 hr of valinomycin (MMP-depolarizing agent) treatment. The mitochondrial DNA of chronically CSE-treated cells was sequenced. After 6 months of CSE treatment, the cells were increasingly resistant to CSE-mediated and valinomycin-induced cell death. In addition, chronic CSE treatment caused chronic depolarization of MMP, cytochrome c release and caspase activation. Cells grown in the presence of only CSE vapor also exhibited the same resistance and chronic baseline apoptotic activation. Mitochondrial DNA sequencing found that chronic CSE-treated cells had more amino acid-changing mitochondrial mutations than acutely treated cells. CSE treatment of normal cells select for apoptotic dysfunction as well as mitochondrial mutations. These findings suggest that chronic tobacco exposure induces carcinogenesis via selection of apoptosis resistance and mitochondrial mutation in addition to previously known genotoxic effects that were found by acute treatments. Chronic models of tobacco exposure on upper aerodigestive epithelia may be more insightful than models of acute exposure in studying head and neck carcinogenesis.

Receptor-interacting protein shuttles between cell death and survival signaling pathways

Cross-talk between apoptosis and survival signaling pathways is crucial for regulating tissue processes and mitigating disease. We report that anoikis-apoptosis triggered by loss of extracellular matrix contacts-activates a CD95/Fas-mediated signaling pathway regulated by receptor-interacting protein (RIP), a kinase that shuttles between CD95/Fas-mediated cell death and integrin/focal adhesion kinase (FAK)-mediated survival pathways. RIP's death domain was critical for RIP and Fas association to mediate anoikis. Fas or RIP attenuation reduced this association and suppressed anoikis, whereas their overexpression had the reverse effect. Overexpressing FAK restored RIP and FAK association and inhibited anoikis. Thus, RIP shuttles between CD95/Fas death and FAK survival signaling to mediate anoikis.

Reduced Liver Apoptosis After Venous Systemic Oxygen Persufflation in Non-Heart-Beating Donors

Graft injury caused by warm ischemia in livers from non-heart-beating donors (NHBDs) strongly affects posttransplantation outcome and is associated with liver apoptosis, which is mediated by death receptors, such as Fas, a surface receptor of the tumor necrosis factor (TNF)-alpha family. The aim of this study was to test the ability of venous systemic oxygen persufflation (VSOP) to reduce apoptotic changes and Fas activation in the liver after warm ischemic insult in vivo. Livers of male Wistar rats were harvested 30 min after cardiac arrest from non-heart-beating donors (NHBD) with (NHBD + O2) or without (NHBD) application of gaseous oxygen during the cold storage period via the suprahepatic caval vein. After 24 h of storage in University of Wisconsin solution at 4 degrees C, viability of the livers was assessed upon isolated reperfusion in vitro. Conventional signs of tissue damage like enzyme release and bile production showed a significantly elevated nonspecific cell injury in the NHBD group. TUNEL staining revealed increased DNA fragmentation of sinusoidal endothelial cells in the NHBD group and more apoptotic hepatocytes than in the control group. All these alterations could be almost abrogated by the use of VSOP in the NHBD + O2 group. The immunohistochemical staining of Fas antigen expression showed a significantly elevated Fas receptor expression in the NHBD and NHBD + O2 groups, in accord with an eightfold increase of Fas receptor mRNA detected by real-time reverse-transcription polymerase chain reaction (RT-PCR). These results demonstrate that the postischemic apoptotic rate of sinusoidal endothelial cells in NHBD livers can be reduced by the use of VSOP. A significant improvement in liver integrity and viability was obtained with this technique, without influencing the expression of Fas expression.

Expression of TRAIL and the death receptors DR4 and DR5 correlates with progression of degeneration in human intervertebral disks

Intervertebral disks degenerate far earlier than other musculoskeletal tissues and apoptosis has been suggested to have a vital function in promoting the degeneration process that is strongly associated with back pain. However, the molecular mediators of apoptosis in the intervertebral disk are poorly understood. Fas/FasL, TRAIL/DR4, TRAIL/DR5 and TNF-alpha/TNFR1 are ligand/receptor pairs of the tumor necrosis factor/nerve growth factor family, which are able to induce apoptosis by trimerization of the receptor by its corresponding ligand. We investigated which of these molecules are expressed in intervertebral disks and whether their expression correlates to disk degeneration. Intervertebral disks from 28 donors (age 12-70 years) suffering from scoliosis, vertebrae fracture or disk degeneration were scored histologically for degeneration and analyzed for gene expression of FasL/Fas, TRAIL/DR4, TNF-alpha/TNFR1 and caspase 8. Protein expression of FasL and TRAIL was assessed by immunohistology and apoptotic cell death was quantified by poly(ADP-ribose) polymerase (PARP) p85 staining. Isolated disk cells were analyzed by flow cytometry for Fas, FasL, TRAIL, DR4 and DR5 expression. Gene expression of TRAIL (P=0.002) and caspase 8 (P=0.027) significantly correlated with degeneration. TRAIL expression further correlated with cellularity (P=0.04), muccoid matrix changes (P=0.009) and tears and cleft formation (P=0.019). FasL and TRAIL expression was confirmed by immunohistology and PARP cleavage was significantly associated with degeneration (P=0.027). Flow cytometry on isolated disk cells revealed correlations between DR4 and degeneration (P=0.014), DR4/DR5 double-positive cells and degeneration (P=0.019), as well as DR5 and changes in tissue granularity (P=0.03). This is the first study that shows that intervertebral disk cells express TRAIL, DR4 and DR5, which correlate to the degenerative state of the disk. Therefore, disk cells inherit the molecular machinery to induce and undergo cellular apoptosis, and the frequency of cytokine expression suggests that the TRAIL/DR4/DR5 axis is an important molecular mediator of apoptosis induction in disk tissue.

Bile acids: regulation of apoptosis by ursodeoxycholic acid

Bile acids are a group of molecular species of acidic steroids with peculiar physical-chemical and biological characteristics. At high concentrations they become toxic to mammalian cells, and their presence is pertinent in the pathogenesis of several liver diseases and colon cancer. Bile acid cytoxicity has been related to membrane damage, but also to nondetergent effects, such as oxidative stress and apoptosis. Strikingly, hydrophilic ursodeoxycholic acid (UDCA), and its taurine-conjugated form (TUDCA), show profound cytoprotective properties. Indeed, these molecules have been described as potent inhibitors of classic pathways of apoptosis, although their precise mode of action remains to be clarified. UDCA, originally used for cholesterol gallstone dissolution, is currently considered the first choice therapy for several forms of cholestatic syndromes. However, the beneficial effects of both UDCA and TUDCA have been tested in other experimental pathological conditions with deregulated levels of apoptosis, including neurological disorders, such as Alzheimer's, Parkinson's, and Huntington's diseases. Here, we review the role of bile acids in modulating the apoptosis process, emphasizing the anti-apoptotic effects of UDCA and TUDCA, as well as their potential use as novel and alternate therapeutic agents for the treatment of apoptosis-related diseases.

Daxx inhibits stress-induced apoptosis in cardiac myocytes

The role of the death-associated protein Daxx in modulation of apoptosis induced in cardiac myocytes by oxidative stress was studied. Exposure of cultured cardiomyocyte-like cells to oxidative stress or simulated hypoxia increased the level of accumulated ROS and apoptosis. Under conditions of sub-apoptotic stimulation of cardiac myocytes, there was no increase in the level of the Daxx protein, but it translocated from the nucleus to the cytoplasm. Daxx overexpression protected the cells from apoptosis, while they were sensitised to cell death following its down-regulation by siRNA. Moreover, lowering the level of the Daxx protein sensitised cardiac myocytes to spontaneous apoptosis, suggesting that the protein may also have a pro-survival role under physiological conditions. Finally, it was shown that DJ-1, a protein suggested previously to sequester Daxx in the nucleus under conditions of oxidative stress (thereby preventing its cytosolic translocation), was localised solely in the cytoplasm of cardiac myocytes. This indicates that the protein does not modulate the apoptosis regulatory activity of Daxx in cardiac myocytes by its nuclear sequestration. Taken together, Daxx plays a protective role in cultured cardiomyocyte-like cells, at least under the conditions used.

Galectin-8 induces apoptosis in Jurkat T cells by phosphatidic acid-mediated ERK1/2 activation supported by protein kinase A down-regulation

Galectins have been implicated in T cell homeostasis playing complementary pro-apoptotic roles. Here we show that galectin-8 (Gal-8) is a potent pro-apoptotic agent in Jurkat T cells inducing a complex phospholipase D/phosphatidic acid signaling pathway that has not been reported for any galectin before. Gal-8 increases phosphatidic signaling, which enhances the activity of both ERK1/2 and type 4 phosphodiesterases (PDE4), with a subsequent decrease in basal protein kinase A activity. Strikingly, rolipram inhibition of PDE4 decreases ERK1/2 activity. Thus Gal-8-induced PDE4 activation releases a negative influence of cAMP/protein kinase A on ERK1/2. The resulting strong ERK1/2 activation leads to expression of the death factor Fas ligand and caspase-mediated apoptosis. Several conditions that decrease ERK1/2 activity also decrease apoptosis, such as anti-Fas ligand blocking antibodies. In addition, experiments with freshly isolated human peripheral blood mononuclear cells, previously stimulated with anti-CD3 and anti-CD28, show that Gal-8 is pro-apoptotic on activated T cells, most likely on a subpopulation of them. Anti-Gal-8 autoantibodies from patients with systemic lupus erythematosus block the apoptotic effect of Gal-8. These results implicate Gal-8 as a novel T cell suppressive factor, which can be counterbalanced by function-blocking autoantibodies in autoimmunity.

Alkaloids induce programmed cell death in bloodstream forms of trypanosomes (Trypanosoma b. brucei)

The potential induction of a programmed cell death (PCD) in Trypanosoma b. brucei by 55 alkaloids of the quinoline, quinolizidine, isoquinoline, indole, terpene, tropane, steroid, and piperidine type was studied by measuring DNA fragmentation and changes in mitochondrial membrane potential. For comparison, the induction of apoptosis by the same alkaloids in human leukemia cells (Jurkat APO-S) was tested. Several alkaloids of the isoquinoline, quinoline, indole and steroidal type (berberine, chelerythrine, emetine, sanguinarine, quinine, ajmalicine, ergotamine, harmine, vinblastine, vincristine, colchicine, chaconine, demissidine and veratridine) induced programmed cell death, whereas quinolizidine, tropane, terpene and piperidine alkaloids were mostly inactive. Effective PCD induction (EC(50) below 10 microM) was caused in T. brucei by chelerythrine, emetine, sanguinarine, and chaconine. The active alkaloids can be characterized by their general property to inhibit protein biosynthesis, to intercalate DNA, to disturb membrane fluidity or to inhibit microtubule formation.

Fas receptor expression in germinal-center B cells is essential for T and B lymphocyte homeostasis

Fas is highly expressed in activated and germinal center (GC) B cells but can potentially be inactivated by misguided somatic hypermutation. We employed conditional Fas-deficient mice to investigate the physiological functions of Fas in various B cell subsets. B cell-specific Fas-deficient mice developed fatal lymphoproliferation due to activation of B cells and T cells. Ablation of Fas specifically in GC B cells reproduced the phenotype, indicating that the lymphoproliferation initiates in the GC environment. B cell-specific Fas-deficient mice also showed an accumulation of IgG1(+) memory B cells expressing high amounts of CD80 and the expansion of CD28-expressing CD4(+) Th cells. Blocking T cell-B cell interaction and GC formation completely prevented the fatal lymphoproliferation. Thus, Fas-mediated selection of GC B cells and the resulting memory B cell compartment is essential for maintaining the homeostasis of both T and B lymphocytes.

CD4+T cells in CIKs (CD4+ CIKs) reversed resistance to fas-mediated apoptosis through CD40/CD40L ligation rather than IFN-gamma stimulation

BACKGROUND

Cytokine-induced killer cells (CIKs) are nonspecific antitumor effectors with superior advantages. CD4+ CIKs can induce Fas-dependent apoptosis in sensitive Raji cells. Here, a Fas-dependent apoptosis was detected in resistant breast cancer MDA-MB-231 cells, and underlying mechanisms were discriminated.

METHODS

Amplification of CIKs and purification of CD4+ CIKs were performed in 15 patients with malignant solid tumors. The expression of CD40L and soluble cytokines in CD4+ CIKs were analyzed. The apoptotic rates of tumor cells and the expression of Fas on membranes were detected using flow cytometry assay. The specific blocking antibodies against FasL, CD40L, and interferon-gamma (IFN-gamma) were added to abolish their effects. The changes of 4 apoptosis-related genes (Bcl-2, Bax, Fas-associating protein with death domain [FADD], and FLICE inhibitory protein [c-FLIP]) in MDA-MB-231 cells cocultured with CD4+ CIKs were measured by real-time quantitative reverse-transcriptase polymerase chain reaction after 6 hours and 24 hours with or without blocking antibodies.

RESULTS

Upregulated expression of membrane-attached CD40L and dramatically increased secretion of soluble CD40L and IFN-gamma were identified in CD4+ CIK. The susceptibility to Fas-mediated apoptosis of insensitive MDA-MB-231 cells was elevated after being pretreated with supernatants from CD4+ CIK. After coculture with CD4+ CIK, apoptosis in MDA-MB-231 cells paralleled with enhanced expression of Fas was blocked fully by either anti-FasL or anti-CD40L, but only partly by anti-IFN-gamma antibodies. The anti-CD40L monoclonal antibody (McAb) rather than anti-IFN-gamma McAb induced significant increase of c-FLIP, which negatively correlated with the apoptosis observed in MDA-MB-231 cells.

CONCLUSIONS

Apoptosis in MDA-MB-231 cells induced by CD4+ CIK is Fas-dependent. The reversion of Fas resistance is mediated through CD40/CD40L ligation rather than IFN-gamma stimulation by inhibiting synthesis of c-FLIP.

Immunohistochemical study of proteins linked to apoptosis in rat fetal kidney cells following prepregnancy adriamycin administration in the mother

Adriamycin is an antibiotic of the anthracycline group. In a previous study, we showed that administration of a single dose of adriamycin (i.p. injection, 5mg/kg body weight) 4 weeks before pregnancy in female Wistar rats induced histological changes in the fetal renal cells typical of apoptosis and also over-expression of heat shock proteins (HSP70). Using a similar experimental model, we have now examined renal cells in fetuses (gestation day 20) to investigate the pathways of the transduction signal of apoptosis in these cells that is induced by prepregnancy maternal administration of adriamycin. Immunolocalization of several proteins - p53, Bax, Apaf-1 and caspase 9 - which take part in the mitochondrial pathway of apoptosis and caspase 12, which takes part in the endoplasmic reticulum pathway of apoptosis, was determined. The results showed that adriamycin administered to the mother rat before pregnancy subsequently induced changes in fetal kidneys involving both the mitochondrial pathway of apoptosis, with increased labeling of the proteins p53, Bax, Apaf-1 and caspase 9, and the endoplasmic reticulum pathway of apoptosis, with increased labeling of caspase 12. Immunolabeling of these proteins was quantified using an image analysis program.

Multistep pathogenesis of autoimmune disease

In the immune system, many tolerance checkpoints exist to prevent self-antigens from stimulating the relentless growth of self-reactive B and T lymphocytes. The genes and molecular pathways underpinning these checkpoints overlap with those involved in tumor suppression. As with an inherited predisposition to cancer, inherited defects in self-tolerance genes typically precipitate autoimmune disease stochastically after a latent phase. Multiple mutations, inherited and somatic, may be needed before a self-reactive clone bypasses sequential tolerance checkpoints resulting in the emergence of autoimmune disease.

The "Fas counterattack" is not an active mode of tumor immune evasion in colorectal cancer with high-level microsatellite instability

Microsatellite instability (MSI) is an alternative pathway of colorectal carcinogenesis. It is found in 10% to 15% of sporadic colorectal neoplasms and is characterized by failure of the DNA mismatch-repair system. High-level MSI (MSI-H) is associated with tumor-infiltrating lymphocytes (TILs) and a favorable prognosis. Expression of Fas ligand (FasL/CD95L) by cancer cells may mediate tumor immune privilege by inducing apoptosis of antitumor immune cells. The aim of this study was to investigate the relationship between FasL expression and MSI status in primary colon tumors. Using immunohistochemistry, we detected FasL expression in 91 colorectal carcinoma specimens, previously classified according to the level of MSI as MSI-H (n = 26), MSI-low (MSI-L) (n = 29), and microsatellite stable (n = 36). Tumor-infiltrating lymphocyte density was quantified by immunohistochemical staining for CD3. MSI-H tumors were significantly associated with reduced frequency (P = .04) and intensity (P = .066) of FasL expression relative to non-MSI-H (ie, microsatellite stable and MSI-L) tumors. Higher FasL staining intensity correlated with reduced TIL density (P = .059). Together, these findings suggest that the abundance of TILs found in MSI-H tumors may be due to the failure of these tumor cells to up-regulate FasL and may explain, in part, the improved prognosis associated with these tumors.

Acute effect of cadmium treatment on the kidney of rats: biochemical and ultrastructural studies

The present study was designed to explore the nephrotoxic effect of intraperitoneal acute administration of CdCl2 (2.5 and 5 mg kg(-1) b.w.) in rats. A number of toxicological parameters in kidney were examined including malondialdehyde (MDA) and endogenous antioxidants, e.g., catalase (CAT), superoxide dismutase (SOD) and Glutathione Peroxidase (GPx). The parameters that indicate tissue damage such as serum urea and creatinine were also determined, along with the ultrastructural changes of kidneys. A correlation was found between the dose and the intensity of changes. The results demonstrated that cadmium administration increased renal MDA but decreased CAT, SOD and GPx activities. In parallel, serum creatinine and urea elevated. The glomerular ultrastructural changes observed in cadmium-treated rats included narrowing of the capillary lumen and swelling of the capillary endothelium with occasional loss of fenestrae. The mesangium was wide with increased mesangial matrix. Loss of homogenous appearance of basement membrane displaying ondulation and thickening in many areas and deterioration of the slit membrane structures formed by the podocytes were also noted. The effects of cadmium on proximal cell ultrastructure were focal loss of brush border, nuclear membrane damage, chromatin condensation, swelling of the mitochondria with regression of mitochondrial cristae, degranulation and disintegration of protein-synthesizing structures such as rough endoplasmic reticulum, increased number of lysosomes and ultimately cell death.

Function of nuclear steroid receptors in apoptosis: role of ursodeoxycholic acid

Nuclear steroid receptors such as the glucocorticoid and the mineralocorticoid receptors modulate apoptosis in different cell types through transactivation-dependent and -independent mechanisms. They are involved in both the induction and prevention of apoptosis depending on cell type. However, it is unclear how nuclear steroid receptors can affect expression of the same gene in opposing ways for different cells. In addition to their function as modulators of gene expression, nuclear steroid receptors often act as nuclear transporters of other regulatory molecules, thus indirectly regulating several apoptosis-related genes. Curiously, nuclear steroid receptors are thought to cooperate with the antiapoptotic endogenous bile acid, ursodeoxycholic acid, to prevent programmed cell death. The next decade will almost certainly unveil the remarkable role of nuclear steroid receptors in modulating the life and death struggle of cells and organ systems in human development and function.

Dual roles of intermediate filaments in apoptosis

New roles have emerged recently for intermediate filaments (IFs), namely in modulating cell adhesion and growth, and providing resistance to various forms of stress and to apoptosis. In this context, we first summarize findings on the IF association with the cell response to mechanical stress and growth stimulation, in light of growth-related signaling events that are relevant to death-receptor engagement. We then address the molecular mechanisms by which IFs can provide cell resistance to apoptosis initiated by death-receptor stimulation and to necrosis triggered by excessive oxidative stress. In the same way, we examine IF involvement, along with cytolinker participation, in sequential caspase-mediated protein cleavages that are part of the overall cell death execution, particularly those that generate new functional IF protein fragments and uncover neoantigen markers. Finally, we report on the usefulness of these markers as diagnostic tools for disease-related aspects of apoptosis in humans. Clearly, the data accumulated in recent years provide new and significant insights into the multiple functions of IFs, particularly their dual roles in cell response to apoptotic insults.

Up-regulation of Fas (CD95) expression in tumour cells in vivo

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.

The apoptotic pathway as a therapeutic target in sepsis

Recent research has yielded many interesting and potentially important therapeutic targets in sepsis. Specifically, the effects of antagonistic anti-cytokine therapies (tumor necrosis factor-alpha [TNF-alpha], interleukin-1 [IL-1]) and anti-endotoxin strategies utilizing antibodies against endotoxin or endotoxin receptor/carrier molecules (anti-CD14 or anti-LPS-binding protein) have been studied. Unfortunately, these approaches often failed clinically, and in many cases, the efficacy of these treatments was dependent on the severity of sepsis. Recently, clinical trials using insulin to lock blood glucose levels and activated protein C treatment have showed that while they provided some survival benefit, their efficacy does not appear to be predicated solely upon anti-inflammatory effects. Here, we will review work done in animal models of polymicrobial sepsis and clinical findings that support the hypothesis that apoptosis in the immune system is a pathologic event in sepsis that can be a therapeutic target. In this respect, experimental studies looking at the septic animal suggest that loss of lymphocytes during sepsis may be due to dysregulated apoptosis and that this appears to be brought on by a variety of mediators effecting 'intrinsic' as well as 'extrinsic' cell death pathways. From a therapeutic perspective this has provided a number of novel targets for clinically successful current, as well as future therapies, such as caspases (caspase inhibition/protease inhibition), pro-apoptotic protein-expression (via administration and/or over-expression of Bcl-2) and the death receptor family Fas-FasL (via. FasFP [fas fusion protein] and the application of siRNA against a number pro-apoptotic factors).

TRAIL-induced apoptosis is enhanced by heat shock protein 70 expression

Heat shock protein 70 (Hsp70) is a well-known inhibitor of apoptotic pathways; however, a role for Hsp70 in the modulation of death receptor-mediated apoptosis remains largely unexplored. In this study, the ability of Hsp70 to modulate tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-induced apoptosis was examined in SW480 and CCRF-CEM cells. These lines exhibit the characteristics of type I cells (SW480, human colon adenocarcinoma), with no requirement for mitochondrial involvement to exhibit apoptosis following death receptor engagement and type II cells (CCRF-CEM, human leukemic T cell), which do require amplification of the signal through the mitochondria. Unexpectedly, expression of Hsp70 in the type II CCRF-CEM cells enhanced the extent of TRAIL-induced apoptosis, but in SW480, Hsp70 had no impact on TRAIL-induced apoptosis. The enhanced TRAIL-induced apoptosis was accompanied by an up-regulation of TRAIL receptors, R1 and R2, at the cell surface as determined by flow cytometry and at the transcriptional level as assessed by real-time polymerase chain reaction (PCR). Increased expression of Hsp70 led to up-regulated expression of p53, and chromatin immunoprecipitation combined with real-time PCR revealed increased binding of p53 to its consensus sequence in the TRAIL-R2 gene. In contrast, expression of Hsp70 in SW480 cells did not increase p53 or TRAIL-R1 or TRAIL-R2 surface expression. This result is in marked contrast to most apoptotic stresses, including TNFalpha and Fas ligand, where Hsp70 has been shown to inhibit apoptosis in type II cells. These findings suggest that in tumors retaining functional p53 and expressing high levels of Hsp70, TRAIL may be an effective therapy.

Discal cyst associated with myxoid change and apoptosis of herniated disc materials: a case report

Discal cyst is a lumbar intraspinal cyst communicating with intervertebral disc, and previously reported series described the wall of these cysts as consisting of dense fibrous connective tissue. We report a 29-year-old Japanese male with discal cyst showing unusual histological features. Clinical symptoms in the current case as well as imaging features including discography were similar to those previously reported.However, the wall of the cyst consisted of disc material with myxoid degeneration. In addition, apoptosis of chondrocytes was diffusely observed in the herniated disc material. The current case was considered a histological variant of discal cyst. Myxoid degeneration of herniated disc material with diffuse apoptotic change of chondrocytes was probably associated with the formation of discal cyst.