FADD/MORT1 and caspase-8 are recruited to TRAIL receptors 1 and 2 and are essential for apoptosis mediated by TRAIL receptor 2

Apoptosis induced by tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL/APO-2L) has been shown to exert important functions during various immunological processes. The involvement of the death adaptor proteins FADD/MORT1, TRADD, and RIP and the apoptosis-initiating caspases-8 and -10 in death signaling by the two death-inducing TRAIL receptors 1 and 2 (TRAIL-R1 and TRAIL-R2) are controversial. Analysis of the native TRAIL death-inducing signaling complex (DISC) revealed ligand-dependent recruitment of FADD/MORT1 and caspase-8. Differential precipitation of ligand-stimulated TRAIL receptors demonstrated that FADD/MORT1 and caspase-8 were recruited to TRAIL-R1 and TRAIL-R2 independently of each other. FADD/MORT1- and caspase-8-deficient Jurkat cells expressing only TRAIL-R2 were resistant to TRAIL-induced apoptosis. Thus, FADD/MORT1 and caspase-8 are essential for apoptosis induction via TRAIL-R2.     

The adaptor molecule FADD from Xenopus laevis demonstrates evolutionary conservation of its pro-apoptotic activity

FADD is an adaptor protein that transmits apoptotic signals from death receptors such as Fas to downstream initiator caspases in mammals. We have identified and characterized the Xenopus orthologue of mammalian FADD (xFADD). xFADD contains both a death effector domain (DED) and a death domain (DD) that are structurally homologous to those of mammalian FADD. We observed xFADD binding to Xenopus caspase-8 and caspase-10 as well as to human caspase-8 and Fas through interactions with their homophilic DED and DD domains. When over-expressed, xFADD was also able to induce apoptosis in wild-type mouse embryonic fibroblasts (MEF), but not in caspase-8-deficient MEF cells. In contrast, DED-deficient xFADD (xFADDdn) acted as a dominant-negative mutant and prevented Fas-mediated apoptosis in mammalian cell lines. These results indicate that xFADD transmits apoptotic signals from Fas to caspase-8. Furthermore, we found that transgenic animals expressing xFADD in the developing heart or eye under the control of tissue-specific promoters show abnormal phenotypes. Taken together, these results suggest that xFADD can substitute functionally for its mammalian homologue in death receptor-mediated apoptosis, and we suggest that xFADD functions as a pro-apoptotic adaptor molecule in frogs. Thus, the structural and functional similarities between xFADD and mammalian FADD provide evidence that the apoptotic pathways are evolutionally conserved across vertebrate species.     

Apo2L/TRAIL-dependent recruitment of endogenous FADD and caspase-8 to death receptors 4 and 5

Fas (APO-1/CD95) and tumor necrosis factor receptor 1 (TNFR1) trigger apoptosis by recruiting the apoptosis initiator caspase-8 through the adaptor FADD. Fas binds FADD directly, whereas TNFR1 binds FADD indirectly, through TRADD. TRADD alternatively recruits the NF-kappaB-inducing adaptor RIP. The TNF homolog Apo2L/TRAIL triggers apoptosis through two distinct death receptors, DR4 and DR5; however, receptor over-expression studies have yielded conflicting results on the ligand's signaling mechanism. Apo2L/TRAIL induced homomeric and heteromeric complexes of DR4 and DR5 and stimulated recruitment of FADD and caspase-8 and caspase-8 activation in nontransfected cells. TRADD and RIP, which bound TNFR1, did not bind DR4 and DR5. Thus, Apo2L/TRAIL and FasL initiate apoptosis through similar mechanisms, and FADD may be a universal adaptor for death receptors.     

Multiple functions of FADD in apoptosis,NF‐κB‐related signaling,and heart development in Xenopus embryos

FADD is an adaptor protein that transmits apoptotic signals from death receptors. Additionally, FADD has been shown to play a role in various functions including cell proliferation. However, the physiological role of FADD during embryonic development remains to be delineated. Here, we show the novel roles FADD plays in development and the molecular mechanisms of these roles in Xenopus embryos. By whole‐mount in situ hybridization and RT‐PCR analysis, we observed that fadd is constantly expressed in early embryos. The upregulation or downregulation of FADD proteins by embryonic manipulation resulted in induction of apoptosis or size changes in the heart during development. Expression of a truncated form of FADD, FADDdd, which lacks pro‐apoptotic activity, caused growth retardation of embryos associated with dramatic expressional fluctuations of genes that are regulated by NF‐κB. Moreover, we isolated a homolog of mammalian cullin‐4 (Cul4), a component of the ubiquitin E3 ligase family, as a FADDdd‐interacting molecule in Xenopus embryos. Thus, our study shows that FADD has multiple functions in embryos; it plays a part in the regulation of NF‐κB activation and heart formation, in addition to apoptosis. Furthermore, our findings provide new insights into how Cul4‐based ligase is related to FADD signaling in embryogenesis.     

The NS3 protein of hepatitis C virus induces caspase-8-mediated apoptosis independent of its protease or helicase activities

Apoptosis has been implicated in the pathogenesis of hepatitis C virus (HCV)-related disease. Here, we show that expression of HCV NS3, or the NS2/NS3 precursor protein, in mammalian cells results in induction of apoptosis and activation of caspases. HCV NS3-induced apoptosis was blocked by a caspase-8, but not a caspase-9-specific inhibitor. HCV NS3 coimmunoprecipitated with caspase-8, but not with other caspases or with FADD. Coexpression of HCV NS3 and caspase-8 resulted in aggregation of the caspase in punctate structures that colocalized with HCV NS3. Cell lines stably expressing low levels HCV NS3 showed increased sensitivity to Fas-induced cell death. Point mutations of NS3 showed that the pro-apoptotic function of the protein is distinct from its protease and helicase activities. These findings suggest that HCV NS3 promotes caspase-8 induced apoptosis at a pathway site distal to FADD, and that flavivirus NS3 may represent a new class of pro-apoptotic proteins.     

The death effector domains (DEDs) of the molluscum contagiosum virus MC159 v-FLIP protein are not functionally interchangeable with each other or with the DEDs of caspase-8

The molluscum contagiosum virus (MCV) MC159 protein contains two death effector domains (DEDs) that bind to the DEDs of caspase-8 and FADD and inhibit apoptosis. We constructed MC159 truncation mutants and found that the amino-terminal region before the first DED and nearly all the carboxyl terminus after the second DED were dispensable for the antiapoptotic activity of MC159. We also engineered tandem repeats of two identical MC159 DEDs, MC159 DEDs in the reverse orientation, and MC159-caspase-8 chimeras in which a DED of MC159 was replaced with the corresponding DED of caspase-8. Each of these constructs bound to caspase-8, but was unable to bind to FADD or block apoptosis. In addition, we constructed mutants containing only a single DED of MC159. These mutants bound to both FADD and caspase-8, but could not block apoptosis or the formation of death effector filaments. Thus, the DEDs of MC159 are not functionally interchangeable with each other or with those of caspase-8.     

Leptospira interrogans Induces Apoptosis in Macrophages via Caspase-8- and Caspase-3-Dependent Pathways

Apoptosis of host cells plays an important role in modulating the pathogenesis of many infectious diseases. It has been reported that Leptospira interrogans, the causal agent of leptospirosis, induces apoptosis in macrophages and hepatocytes. However, the molecular mechanisms responsible for host cell death remained largely unknown. Here we demonstrate that L. interrogans induced apoptosis in a macrophage-like cell line, J774A.1, and primary murine macrophages in a time- and dose-dependent manner. Apoptosis was associated with the activation of cysteine aspartic acid-specific proteases (caspase-3, caspase-6, and caspase-8), the increased expression of Fas-associated death domain (FADD), and the cleavage of the caspase substrates poly(ADP-ribose) polymerase (PARP) and nuclear lamina protein (lamin A and lamin C). Caspase-9 was activated to a lesser extent, whereas no release of cytochrome c from mitochondria was detectable. Inhibition of caspase-8 impaired L. interrogans-induced caspase-3 and -6 activation, as well as PARP and lamin A/C cleavage and apoptosis, suggesting that apoptosis is initiated via caspase-8 activation. Furthermore, caspase-3 was required for the activation of caspase-6 and seemed to be involved in caspase-9 activation through a feedback amplification loop. These data indicate that L. interrogans-induced apoptosis in macrophages is mediated by caspase-3 and -6 activation through a FADD-caspase-8-dependent pathway, independently of mitochondrial cytochrome c-caspase-9-dependent signaling.     

问号钩端螺旋体在体外诱导细胞凋亡及相关信号通路的研究

目的 了解问号钩端螺旋体诱导不同宿主细胞凋亡的作用及相关胞内信号传导通路.方法 建立问号钩体黄疸出血群赖型赖株小鼠单核-巨噬样细胞J774A.1、人脐静脉内皮细胞EVC304和人Ⅱ型肺泡上皮细胞A549感染模型.采用FITC-Annexin V/PI荧光标记流式细胞术检测细胞凋亡或坏死情况.分别采用荧光比色法和Western blot检测感染的J774A.1细胞caspase-3,-8,-9活性和凋亡相关蛋白FADD(Fas-associated death domain)表达水平.结果 问号钩体赖株感染1～6 h后,36.70%～63.70%的J774A.1细胞可H{现明显的早期凋亡,感染12 h时转变为晚期凋亡或坏死为主(53.68%).78.52%问号钩体赖株感染的A549细胞仪出现晚期凋亡或坏死.问号钩体赖株感染的EVC304细胞无细胞凋亡或坏死现象.感染的J774A.1细胞caspase-3和-8最大活性分别为(1453.41±36.07)和(1402.15±59.09)Fu,是未感染细胞的16.38和29.99倍.感染的J774A.1细胞caspase-9虽略有升高为(89.42±5.08)Fu,但明显低于caspase-3和-8(P<0.001).随着感染时间的延长,感染的J774A.1细胞FADD蛋白表达量逐步增加.结论 问号钩体诱导宿主细胞凋亡的效应町因细胞种类不同而有明显差异,FADD→caspase-8→caspase-3是介导问号钩体感染J774A.1细胞凋亡的主要信号通路.     

Increased activity of caspase 3 and caspase 8 in anti-Fas-induced apoptosis in lymphocytes from ageing humans.

We have previously shown an increased susceptibility of T cell subsets to anti-Fas-induced apoptosis in human ageing [1]. In this study, we have examined the role of downstream mediators, including caspases, in Fas-mediated apoptosis in lymphocytes from ageing humans. The cleavage activity of caspase-8 and caspase-3 was compared between ageing and young subjects at different times following anti-Fas treatment, using colorimetric detection analysis. The expression of Fas-associated death domain (FADD), caspase-8, and caspase-3 in lymphocytes was compared at the protein level using Western blotting, and at the mRNA level by Northern blot analysis. In lymphocytes from ageing subjects, there was an early increase in the cleavage activity of caspase-8 and caspase-3 compared with young controls. Furthermore, increased protein expression of FADD, caspase-8 and caspase-3 at the basal level was observed in lymphocytes from ageing humans. Our results suggest that the altered expression and activity of molecules in the Fas/FasL signalling pathway may play a role in increased Fas-induced apoptosis and T cell deficiency in ageing humans.     

Apoptosis in spermatocytic and usual seminomas: a light microscopic and immunohistochemical study.

Despite its alarming appearance, spermatocytic seminoma virtually never metastasizes. We hypothesized that this paradox may at least be partially related to increased apoptosis compared to metastasizing germ cell tumors since high expression of proapoptotic factors correlates with indolent behavior in other tumor systems, notably CD30-positive cutaneous lymphoma, another neoplasm where phenotype and behavior do not match. We therefore compared apoptosis and apoptotic regulators in 17 spermatocytic seminomas (2 with sarcoma) and 18 usual seminomas by light microscopy and using immunostains for caspase-3, p53, bcl-2, bcl-xL, FADD, FAS and survivin. We found significantly greater numbers of apoptotic cells and activated caspase-3-positive cells in spermatocytic seminoma compared to usual seminoma (P<0.01). There was over a 10-fold range in apoptotic cells in usual seminoma but only a 4-fold variation in spermatocytic seminoma. Spermatocytic seminoma had decreased p53 expression compared to usual seminoma, with marked variation in bcl-2 expression and increased FADD. The two sarcomas in spermatocytic seminoma, however, showed decreased apoptosis and caspase-3 reactivity, with upregulation of p53 and bcl-2 and decreased FADD expression. We conclude that apoptosis, caspase-3 and FADD expression are increased in spermatocytic seminoma compared to usual seminoma. Apoptotic parameters are decreased in sarcomatous transformation of spermatocytic seminoma. The increased apoptosis of spermatocytic seminoma, possibly mediated by FAS independent activation of the death receptor pathway, may provide some insight into its excellent prognosis. The variation in apoptosis of usual seminomas merits investigation as a prognostic parameter.     

CD95 death-inducing signaling complex formation and internalization occur in lipid rafts of type I and type II cells

We investigated the membrane localization of CD95 in type I and type II cells, which differ in their ability to recruit and activate caspase-8. We found that CD95 was preferentially located in lipid rafts of type I cells, while it was present both in raft and non-raft plasma membrane sub-domains of type II cells. After stimulation, CD95 located in phospholipid-rich plasma membrane was recruited to lipid rafts in both types of cells. Similarly, CD95 cross-linking resulted in caspase-independent translocation of FADD/MORT1 and caspase-8 to the lipid rafts, which was prevented by a death domain-defective receptor. CD95 internalization was then rapid in type I and delayed in type II cells and showed a substantial correlation with the kinetics of Fas-associated death domain (FADD)and caspase-8 recruitment to lipid rafts. Finally, electron microscopy analysis showed that after CD95 stimulation lipid rafts aggregated in large clusters that were internalized in endosomal vesicles, where caspase-8 underwent massive processing. Taken together, our data demonstrate that CD95 death-inducing signaling complex formation and internalization in type I and type II cells occur in lipid rafts, which are a major site of caspase-8 activation.     

Novel Roles for Caspase-8 in IL-1β and Inflammasome Regulation

Caspase-8 is an initiator and apical activator caspase that plays a central role in apoptosis. Caspase-8–deficient mice are embryonic lethal, which makes study of caspase-8 in primary immune cells difficult. Recent advances have rescued caspase-8–deficient mice by crossing them to mice deficient in receptor-interacting serine-threonine kinase 3 (RIPK3). These genetic tools have made it possible to study the role of caspase-8 in vivo and in primary immune cells. Several recent studies have identified novel roles for caspase-8 in modulating IL-1β and inflammation, showing that caspase-8 directly regulates IL-1β independent of inflammasomes or indirectly through the regulation of inflammasomes, depending on the stimulus or stimuli that initiate the signaling cascade. Here, we address recent findings on caspase-8 and its role in modulating IL-1β and inflammation.Caspase-8 is an initiator and apical activator caspase that plays a central role in apoptosis. It consists of two N-terminal death effector domains (DEDs), which are followed by a large (p18) and a small (p10) protease subunit at the C-terminal end (Figure 1). First described in 1996, caspase-8 is essential for death receptor–induced activation of the extrinsic cell-death pathway.^1,2 On activation of death receptors (CD95, TNFR1, or DR5), caspase-8 is recruited to the receptors via the adaptor protein FAS-associated death domain (FADD). Caspase-8 and FADD both contain DEDs, which mediate DED–DED homotypic interactions and coordinate complex formation of death receptors. Caspase-8 homodimer formation in this complex results in activation and autocleavage, which further stabilizes the active dimer. Active caspase-8 then processes and cleaves downstream executioner caspases, or the BCL2 family member BID, to initiate apoptosis. Because apoptosis is central for development and survival of the host, caspase-8 activation is tightly regulated. cFLIP, a homolog of caspase-8, blocks caspase-8 apoptotic function by forming heterodimeric complexes³ (Figure 1). It has also been proposed that caspase-8 is cleaved, and in some instances activated by other caspases, such as caspase-3^4,5 and caspase-6,^5,6 as well as by the proteases granzyme B⁷ and cathepsin D.⁸Open in a separate windowFigure 1Role for caspase-8 (CASP8) in inducing apoptosis and regulating signaling pathways. A: Procaspase-8 consists of two N-terminal death-effector domain (DED) prodomains, which are followed by the catalytic subunits p18 and p10, respectively. On dimerization, caspase-8 is cleaved at the sites between the DED and p18, and between p18 and p10. B: Death receptor (CD95, TNFR1, DR5) engagement with the respective ligand [CD95L, tumor necrosis factor alpha (TNF-α), TNF-related apoptosis inducing ligand (TRAIL)] results in recruitment of FAS-associated death domain (FADD) and caspase-8 homodimers. Activation of caspase-8 results in induction of apoptosis. cFLIP can bind to caspase-8 to form cFLIP–caspase-8 heterodimers. The formation of cFLIP–caspase-8 heterodimers inhibits apoptosis. C: Activation of Toll-like receptor 4 (TLR4) or TLR2 results in recruitment of TIR domain-containing adaptor-inducing interferon-β (TRIF) and myeloid differentiation primary response protein MyD88 (MyD88) to the receptors. TRIF and MyD88 signaling results in downstream nuclear factor-κB (NF-κB) signaling events that induce mRNA expression of pro–IL-1β and NLRP3. Evidence suggests that FADD and caspase-8 are required for optimal expression of pro–IL-1β and NLRP3 mRNA, possibly through their role in NF-κB activation. LPS, lipopolysaccharide; PGN, peptidoglycan.The importance of caspase-8 is highlighted by the fact that knockout mice die at approximately embryonic day 10.5.⁹ In seminal studies, the Mocarski¹⁰ and Green¹¹ research groups showed that deletion of receptor-interacting serine-threonine kinase 3 (RIPK3, involved in necroptotic cell death) rescues caspase-8 deficient mice. These studies established a nonapoptotic role for caspase-8, namely, to rescue the lethality induced by RIPK3-mediated pathways. The generation of double-knockout Ripk3^−/−Casp8^−/− mice has provided an invaluable tool for investigating the role of caspase-8 in vivo and in primary immune cells.Here, we discuss inflammasome-mediated IL-1β production and the novel roles of caspase-8 in modulating inflammasomes, IL-1β, and inflammation.     

Requirement of cooperative functions of two repeated death effector domains in caspase-8 and in MC159 for induction and inhibition of apoptosis, respectively

BACKGROUND: The death effector domain (DED), which functions as a domain for a homophilic protein interaction, plays a role in death receptor-mediated apoptosis. Two tandemly repeated DEDs in the prodomain of caspase-8 (Casp8NC-DED) and those in MC159 (viral FLIP) have been shown to positively and negatively regulate apoptosis, respectively, by binding to caspase-8 and/or Fas-associated death domain (FADD). However, characteristics of each DED in Casp8NC-DED and those in MC159 have not been well examined. RESULTS: We analysed deletion and chimera mutants of DEDs derived from Casp8NC-DED and MC159, and found that MC159 and Casp8NC-DED require the combined effects of the two repeated DEDs to exert their binding and biological activities. The carboxy-terminal DED of Casp8NC-DED (Casp8C-DED) has the potential to induce apoptosis, and the amino-terminal DED of MC159 showed a dominant inhibitory effect on apoptosis when combined with Casp8C-DED. In addition, the two repeated DEDs in Casp8NC-DED and MC159 were shown to regulate the activities of caspase differently from the caspase recruitment domain (CARD) in the prodomains of caspase-2, -9 and Apaf-1. CONCLUSIONS: Although each of the DEDs in Casp8NC-DED and MC159 has the potential to stimulate or inhibit apoptosis, the combination of the two-repeated DEDs is necessary for the DED-containing proteins to stimulate or inhibit apoptosis.     

Deregulated miR-155 promotes Fas-mediated apoptosis in human intervertebral disc degeneration by targeting FADD and caspase-3

The role of apoptosis in the pathogenesis of intervertebral disc degeneration (IDD) remains enigmatic. Accumulating evidence has shown that the apoptotic machinery is regulated by miRNAs. We hypothesized that miRNAs might contribute to apoptosis in IDD. We have found that 29 miRNAs were differentially expressed and miR-155 was down-regulated in degenerative nucleus pulposus (NP). The deregulation of miR-155 was further verified using real-time PCR (0.56 fold, p < 0.05). Bioinformatics target prediction identified FADD and caspase-3 as putative targets of miR-155. Furthermore, miR-155 inhibited FADD and caspase-3 expression by directly targeting their 3'-UTRs, which was abolished by mutation of the miR-155 binding sites. In vitro up-regulation of miR-155 in human NP cells by transfection with lentiviral pre-miR-155 resulted in repression of FADD and caspase-3; whereas knockdown of miR-155 with lentiviral antigomiR-155 led to over-expression of FADD and caspase-3. Also, Fas-mediated apoptosis was increased when antagonizing miR-155 and decreased when using pre-miR-155 in human NP cells. In addition, we presented direct evidence of NP cells undergoing apoptosis in IDD tissues using transmission electron microscopy analysis. Moreover, a combination of in situ hybridization (ISH) and immunohistochemistry (IHC) revealed that miR-155 expressed in the cytoplasm of human NP cells with reverse correlation with FADD and caspase-3. In summary, this is the first study addressing the underlying mechanisms of IDD in terms of apoptosis and miRNAs. Furthermore, caspase-3 is identified as a novel target of miR-155. Our results suggest that deregulated miR-155 promotes Fas-mediated apoptosis in human IDD by targeting FADD and caspase-3, implicating an aetiological and therapeutic role of miR-155 in IDD.     

Apoptosis signaling pathways in lung diseases

Evidence that apoptosis plays an important role in the pathophysiology of lung diseases has been accumulated. Apoptosis signaling is classically composed of two principle pathways. One is a direct pathway from death receptor ligation to caspase cascade activation and cell death. Death receptor ligation triggers recruitment of the precursor form of caspase-8 to a death-inducing complex, through the adaptor protein FADD, which leads to caspase-8 activation. The other pathway triggered by stimuli such as drugs, radiation, infectious agents and reactive oxygen species is initiated in mitochondria. After cytochrome c is released into the cytosol from the mitochondria, it binds to Apaf1 and ATP, which then activate caspase-9. Recently, endoplasmic reticulum has also been shown to be the organelle to execute apoptosis. Further understanding of molecular mechanisms of apoptosis and its regulation by novel drugs may lead to the development of effective strategies against lung diseases. We overview the signaling pathways of apoptosis and discuss the involvement of apoptosis in the pathophysiology of various lung diseases.     

Enhancement of death-receptor induced caspase-8-activation in the death-inducing signalling complex by uncoupling of oxidative phosphorylation

Signalling through the death receptor CD95 induces apoptosis by formation of a signalling complex at the cell membrane and subsequent caspase-8 and caspase-3-activation. Treatment of Jurkat T cells with protonophores across the mitochondrial membrane such as 2,4-dinitrophenol (DNP) enhances the death-inducing capacity of CD95. In this study, we show that this enhancement is due to the specific acceleration of caspase-8-processing and activation at the CD95-receptor. DNP-treatment did not affect NF-kappaB-induction by CD95. Immunoprecipitation experiments showed that the amounts of the adapter FADD/MORT1 and pro-caspase-8 at the CD95-receptor were not altered by DNP. Subcellular fractionation studies revealed that the amount of mature caspase-8 but not pro-caspase at the membrane was increased following CD95-stimulation in the presence of DNP. As a consequence of caspase-activation, c-FLIP-levels in the cytosol decreased. In Jurkat cells overexpressing c-FLIPS, DNP was still able to enhance caspase-activation. The enhancing capacity of DNP was seen in some cell lines (Jurkat, CEM and HeLa) but not in SKW6 cells and was also found in mitogen-stimulated human T cells. Furthermore, the enhancement extended to TRAIL-induced caspase-activation. Thus, a mechanism exists by which caspase-8-activation can be accelerated at death receptors and this mechanism can be triggered by targeting mitochondrial oxidative phosphorylation.     

Apoptotic pathways in ovarian surface epithelium of human embryos during embryogenesis and carcinogenesis: Close relationship of developmental plasticity and neoplasm

Cell differentiation and different pathways of cell death were immunohistochemically analyzed in ovaries of six human embryos, 20 serous borderline tumors (SBT) and ovarian serous carcinomas (OSC) using markers for apoptosis (caspase-3, AIF, TUNEL) and stemness (Oct-4). In the 5–8-week ovaries, caspase-3 was absent in the ovarian surface epithelium (ose) and mildly positive in the ovarian stroma (os), AIF was expressed moderately, while Oct-4 expression gradually decreased during that period. Some ovarian cells expressed only caspase-3 or AIF together with TUNEL, while both caspase-3 and AIF were co-expressed in other ovarian cells. Mild expression of Oct-4 and caspase-3 characterized some cells of SBT, while their expression varied from mild to strong in OSC. AIF displayed mild to strong expression in ose of SBT and moderate to strong expression in OSC, while no expression of AIF was observed in os of both tumors. In the ose of both SBT and OSC, caspase-3 and AIF were co-expressed only occasionally, while AIF and Oct-4 were co-expressed strongly. Our study showed the presence of stemness cells and different pathways of cell death (caspase-3 and AIF-mediated) in the ovarian tissue during development and carcinogenesis, indicating the correlation between developmental plasticity in human embryonic ovaries and OSC.     

Caspase-8: regulating life and death

Roles for cell death in development, homeostasis, and the control of infections and cancer have long been recognized. Although excessive cell damage results in passive necrosis, cells can be triggered to engage molecular programs that result in cell death. Such triggers include cellular stress, oncogenic signals that engage tumor suppressor mechanisms, pathogen insults, and immune mechanisms. The best-known forms of programmed cell death are apoptosis and a recently recognized regulated necrosis termed necroptosis. Of the two best understood pathways of apoptosis, the extrinsic and intrinsic (mitochondrial) pathways, the former is induced by the ligation of death receptors, a subset of the TNF receptor (TNFR) superfamily. Ligation of these death receptors can also induce necroptosis. The extrinsic apoptosis and necroptosis pathways regulate each other and their balance determines whether cells live. Integral in the regulation and initiation of death receptor-mediated activation of programmed cell death is the aspartate-specific cysteine protease (caspase)-8. This review describes the role of caspase-8 in the initiation of extrinsic apoptosis execution and the mechanism by which caspase-8 inhibits necroptosis. The importance of caspase-8 in the development and homeostasis and the way that dysfunctional caspase-8 may contribute to the development of malignancies in mice and humans are also explored.     

HSP110, caspase-3 and -9 expression in physiological apoptosis and apoptosis induced by in vivo embryonic exposition to all-trans retinoic acid or irradiation during early mouse eye development

Apoptosis is an essential physiological process in embryonic development. In the developing eye of vertebrates, three periods of developmental apoptosis can be distinguished: early, intermediate and later. Within the apoptosis pathway, caspases play a crucial role. It has also been shown that HSP110 may have a potential role in apoptosis. The aim of this research was to study the expression of HSP110, caspase-3 and -9 in physiological, retinoic- or irradiation-induced apoptosis during early eye development. Seven pregnant C57Bl/6J mice received 80 mg kg(-1) of all-trans retinoic acid mixed with sesame oil. Seven pregnant NMRI mice received 2 Gy irradiation at the same gestational day. Control mice of both strains (seven mice of each) were not submitted to any treatment. Embryos were harvested at 3, 6, 12 and 24 h after exposition, fixed, dehydrated and embedded. Coronal sections (5 microm) were made. Slide staining occurred alternatively using anti-caspase-3, anti-caspase-9 and anti-HSP110 immunohistochemistry. HSP110 and caspase-3 expression presented similar topographic and chronological patterns, whereas expression of HSP110 was more precocious in retinoic acid-treated embryos. After retinoic exposure, caspase-3- and HSP110-positive cells were increased in the region of the optic vesicle. By contrast, after irradiation, caspase-3- and HSP110-positive cells were noticeably increased in the optic vesicle, peri-optical mesoderm but less in lens placode. HSP110 was expressed before caspase-3. By contrast, caspase-9 was expressed by a very small number of cells in the optic vesicle either under physiological or under teratogenic conditions. Thus, it seems that activation of caspase-9 is dispensable in early eye developmental apoptosis.