[Metastatic lung cancer origin from osteosarcoma of mandible invading tracheal lumen]

A 52-year-old woman underwent the surgical treatment for osteosarcoma of the left mandible in 2003 and was followed up afterward. She suffered from dry cough and bloody sputum, and was admitted to our hospital in April 2007. Computed tomography (CT) revealed several nodules in bilateral lung, and bronchofiberscopy showed the endobronchial tumor obstructing in the right main bronchus. The metastatic tumor progressed in the right main bronchus from the right S6 lung segment. The tumor rapidly progressed in the right bronchus in comparison with the CT findings in about 2 weeks, and the possibility of the tracheal obstruction was considered. She underwent the right middle and lower lobectomy, and the endobronchial tumor was pulled through the right main bronchus. The postoperative course was uneventful, the patient was discharged on 14th postoperative day, and the chemotherapy using cisplatin (CDDP) and adriamycin (ADR) is on-going.

[Thymic carcinoma involving aortic arch; report of a case]

Adenocarcinoma of the thymus is a very rare malignant tumor. The standard treatment for advanced thymic carcinoma has not yet been established, and the prognosis is poor. We report a case of thymic carcinoma that involving the aortic arch and the innominate vein. A 78-year-old woman was admitted to our hospital complaining of hoarseness in April 2007. The computed tomography (CT) scan showed an anterior mediastinal tumor contiguous to the aortic arch and the innominate vein with swelling lymphnodes. Microspcopic examinations of specimens obtained by CT-guided needle biopsy revealed poorly differenciated adenocarcinoma. The carcinoembryonic antigen (CEA) level of serum elevated at 54.9 ng/ml. Thymic carcinoma was diagnosed. The chemoradiotherapy [concurrent, carboplatin (CBDCA) + paclitaxel(TXL)-->vinorelbine (NVB), 60 Gy] was performed, but the effect of the therapy was limited. The resection of the tumor with a part of aortic arch and other peripheral tissues was performed in Augast 2007. The postoperative course was uneventful and the CEA level of serum lowered to the normal. She was discharged 30 days after surgery.

Mechanism of NKT cell activation by intranasal coadministration of alpha-galactosylceramide, which can induce cross-protection against influenza viruses

In a nasal vaccine against influenza, the activation of natural killer T (NKT) cells by intranasal coadministration of alpha-galactosylceramide (alpha-GalCer) can potently enhance protective immune responses. The results of this study show that the NKT cell-activated nasal vaccine can induce an effective cross-protection against different strains of influenza virus, including H5 type. To analyze the mechanism of NKT cell activation by this nasal vaccine, we prepared fluorescence-labeled alpha-GalCer by which we detect a direct interaction between NKT cells and alpha-GalCer-stored dendritic cells in nasal mucosa-associated tissues. Accordingly, although very few NKT cells exist at mucosa, the nasal vaccination induced a localized increase in NKT cell population, which is partly dependent on CXCL16/CXCR6. Furthermore, we found that NKT cell activation stimulates mucosal IgA production by a mechanism that is dependent on interleukin (IL)-4 production. These results strengthen the basis of nasal vaccination via NKT cell activation, which can induce immune cross-protection.

Serine protease Omi/HtrA2 targets WARTS kinase to control cell proliferation

The serine protease Omi/HtrA2 was initially regarded as a proapoptotic molecule that proteolyses several proteins to induce cell death. Recent studies, however, indicate that loss of Omi protease activity increases susceptibility to stress-induced cell death. These complicated findings suggest that the protease activity of Omi is involved not only in apoptosis but also in cellular homeostasis. However, the targets which Omi uses to mediate this novel process are unknown. Previously, we showed that WARTS (WTS)/large tumor-suppressor 1 mitotic kinase interacts with the protein/discs-large protein/zonula (PDZ) domain of Omi and promotes its protease activity. We now report that WTS is a substrate for Omi protease activity, thus it is not only a regulator but also a downstream target of this protease. Interaction with Omi PDZ domain is required for WTS to be proteolysed. When caspase-9-deficient mouse embryonic fibroblasts (MEFs) were treated with staurosporine, WTS was proteolysed by activated endogenous Omi without induction of cell death. Therefore, protease activity of Omi and proteolysis of WTS are not necessarily required for cell death. We found that depletion of Omi from HeLa cells results in accelerated cell proliferation despite no significant change in the duration of mitosis. The depletion of WTS showed the same effect on S phase progression. Therefore, WTS proteolytic fragment(s) generated by Omi may act as an inhibitor of G1/S progression. Our data reveal a role for Omi-mediated processing of WTS in negative regulation of cell cycle progression at interphase, suggesting a novel function of Omi other than apoptosis.

Sensitization of osteosarcoma cells to death receptor-mediated apoptosis by HDAC inhibitors through downregulation of cellular FLIP

Fas-mediated apoptosis plays an important role in elimination of tumor cells in vivo, but some tumor-derived cells are resistant to this mechanism. Here, we show that treatment with the histone deacetylase (HDAC) inhibitor FR901228 renders Fas-resistant osteosarcoma cell lines sensitive to Fas-mediated apoptosis by downregulating expression of cellular FLIP (cellular FLICE-inhibitory protein), an inhibitor of Fas-mediated activation of caspase-8. Moreover, sensitization to Fas-mediated apoptosis was also induced in Fas-resistant osteosarcoma cells by suppressing FLIP expression using FLIP-specific RNA interference. HDAC inhibitors including FR901228 were shown to induce downregulation of cellular FLIP through inhibiting generation of FLIP mRNA, rather than stimulating degradation at either protein or mRNA level, and the inhibition was independent of de novo protein synthesis. These results clearly indicate that some tumor cells exhibit a phenotype resistant to death receptor-mediated apoptosis by expressing cellular FLIP, and that HDAC inhibitors sensitize such resistant tumor cells by directly downregulating cellular FLIP mRNA.

Involvement of death receptor Fas in germ cell degeneration in gonads of Kit-deficient Wv/Wv mutant mice

Kit and its ligand stem cell factor (SCF) play a fundamental role in hematopoiesis, melanogenesis and gametogenesis. Homozygous W(v) mutant mice with a mutation in kit show abnormalities in these cell lineages. Fas is a member of the death receptor family inducing apoptosis. In this study, we generated double-mutant mice (W(v)/W(v):Fas(-/-)) and analyzed histologically their reproductive organs. In testes and ovaries of the double-mutant mice, testicular germ cells and oocytes were detected, respectively, whereas the same-aged W(v)/W(v) mice contained neither cells. In addition, inhibition of Kit signals by administration of anti-Kit mAb, which induces degeneration of testicular germ cells in vivo in wild-type mice, did not cause degeneration in Fas-deficient mice. In testicular germ cells of W(v)/W(v) mutant mice, an increase of Fas expression was observed in spermatogonia. Further, in vitro treatment with SCF was shown to downregulate Fas on fibroblasts expressing exogenous Kit through activation of PI3-kinase/Akt. All the results clearly indicate that Fas-mediated apoptosis is involved in germ cell degeneration accompanied by defects in Kit-mediated signals, and Kit signaling negatively regulates Fas-mediated apoptosis in vivo.

ER stress induces caspase-8 activation, stimulating cytochrome c release and caspase-9 activation

Excess ER stress induces caspase-12 activation and/or cytochrome c release, causing caspase-9 activation. Little is known about their relationship during ER stress-mediated cell death. Upon ER stress, P19 embryonal carcinoma (EC) cells showed activation of various caspases, including caspase-3, caspase-8, caspase-9, and caspase-12, and extensive DNA fragmentation. We examined the relationship between ER stress-mediated cytochrome c/caspase-9 and caspase-12 activation by using caspase-9- and caspase-8-deficient mouse embryonic fibroblasts and a P19 EC cell clone [P19-36/12 (-) cells] lacking expression of caspase-12. Caspase-9 and caspase-8 deficiency inhibited and delayed the onset of DNA fragmentation but did not inhibit caspase-12 processing induced by ER stress. P19-36/12 (-) cells underwent apoptosis upon ER stress, with cytochrome c release and caspase-8 and caspase-9 activation. The dominant negative form of FADD and z-VAD-fmk inhibited caspase-8, caspase-9, Bid processing, cytochrome c release, and DNA fragmentation induced by ER stress, suggesting that caspase-8 and caspase-9 are the main caspases involved in ER stress-mediated apoptosis of P19-36/12 (-) cells. Caspase-8 deficiency also inhibited the cytochrome c release induced by ER stress. Thus, in parallel with the caspase-12 activation, ER stress triggers caspase-8 activation, resulting in cytochrome c/caspase-9 activation via Bid processing.

Ex vivo whole-embryo culture of caspase-8-deficient embryos normalize their aberrant phenotypes in the developing neural tube and heart

Caspase-8 plays the role of initiator in the caspase cascade and is a key molecule in death receptor-induced apoptotic pathways. To investigate the physiological roles of caspase-8 in vivo, we have generated caspase-8-deficient mice by gene targeting. The first signs of abnormality in homozygous mutant embryos were observed in extraembryonic tissue, the yolk sac. By embryonic day (E) 10.5, the yolk sac vasculature had begun to form inappropriately, and subsequently the mutant embryos displayed a variety of defects in the developing heart and neural tube. As a result, all mutant embryos died at E11.5. Importantly, homozygous mutant neural and heart defects were rescued by ex vivo whole-embryo culture during E10.5-E11.5, suggesting that these defects are most likely secondary to a lack of physiological caspase-8 activity. Taken together, these results suggest that caspase-8 is indispensable for embryonic development.

Expression of scavenger receptor for phosphatidylserine and oxidized lipoprotein (SR-PSOX) in human atheroma

Recently, we identified a novel macrophage cell-surface receptor for oxidized low-density lipoprotein (Ox-LDL), designated SR-PSOX (scavenger receptor for phosphatidylserine and oxidized lipoprotein). Here we examine SR-PSOX expression in human atherosclerotic lesions using carotid endarterectomy specimens from 21 patients, directional coronary atherectomy specimens from 11 patients, and normal aortas from 2 patients. RT-PCR analysis demonstrated that SR-PSOX expression was upregulated in atherosclerotic lesions, but undetectable in normal aortas. Immunohistochemistry showed that SR-PSOX was abundantly expressed by macrophages in the intima of atherosclerotic lesions. Taken together, SR-PSOX may be involved in Ox-LDL uptake and subsequent foam cell transformation in macrophages in vivo and therefore may play important roles in human atherosclerotic lesion formation.

Expression of SR-PSOX, a novel cell-surface scavenger receptor for phosphatidylserine and oxidized LDL in human atherosclerotic lesions

Receptor-mediated endocytosis of oxidized low density lipoprotein (Ox-LDL) by macrophages and the subsequent foam cell transformation in the arterial intima are key events in early atherogenesis. Recently, we have identified a novel macrophage cell-surface receptor for Ox-LDL by expression cloning from a cDNA library of phorbol 12-myristate 13-acetate-stimulated THP-1 cells, designated as the scavenger receptor for phosphatidylserine and oxidized lipoprotein (SR-PSOX). Here, we examined SR-PSOX expression in human atherosclerotic lesions. Total cellular RNA and fresh frozen sections were prepared from human carotid endarterectomy specimens (from 21 patients) and directional coronary atherectomy specimens (from 11 patients). Fragments of human aortas of 2 patients without visible atherosclerotic lesions served as negative controls. Quantitative reverse transcription-polymerase chain reaction demonstrated that SR-PSOX mRNA expression was prominent in atherosclerotic lesions but undetectable in normal aortas. Immunohistochemistry showed that SR-PSOX was predominantly expressed by lipid-laden macrophages in the intima of atherosclerotic plaques in carotid endarterectomy and directional coronary atherectomy specimens, although its expression was not detectable in normal arterial wall. Double-labeled immunohistochemistry confirmed that SR-PSOX is expressed by intimal macrophages. Taken together, SR-PSOX may be involved in Ox-LDL uptake and subsequent foam cell transformation in macrophages in vivo and thus may play important roles in human atherosclerotic lesion formation.

Difference in the way of macrophage recognition of target cells depending on their apoptotic states

Dying cells are selectively eliminated from the organism by phagocytosis. Previous studies suggested the existence of some other phagocytosis marker(s) that function together with phosphatidylserine, the best-characterized phagocytosis marker. We obtained here a monoclonal antibody named PH2 that inhibited macrophage phagocytosis of late apoptotic or necrotic cells, but not of early apoptotic cells. On the other hand, phagocytosis of cells at any time during the process of apoptosis was inhibitable by phosphatidylserine-containing liposomes. Inhibition occurred even when target cells were preincubated with PH2 and separated from unbound antibodies. Moreover, PH2 bound to apoptotic cells at late stages more efficiently than to those at early stages, and it did not bind to normal cells unless their plasma membrane was permeabilized. These results suggest that the putative PH2 antigen is a novel phagocytosis marker that translocates to the cell surface at late stages of apoptosis, resulting in maximal recognition and engulfment by macrophages.

Lectin-like oxidized low density lipoprotein receptor-1 (LOX-1) supports cell adhesion to fibronectin

Lectin-like oxidized lipoprotein receptor-1 (LOX-1) is a specific receptor for atherogenic oxidized low density lipoprotein (OxLDL) which belongs to the scavenger receptor family. In the present report, we show that LOX-1 can also support cell adhesion to fibronectin (FN) in a divalent cation-independent fashion. CHO-K1 cells stably expressing bovine LOX-1 (BLOX-1-CHO), but not untransfected CHO-K1 cells, can adhere to FN-coated plates, but not to collagen-coated plates, in the presence of EDTA. BLOX-1-CHO adhesion to FN-coated plates can also be suppressed by scavenger receptor ligands, such as OxLDL, polyinosinic acid (poly I), and dextran sulfate, but not by native LDL, acetylated LDL, polycytidylic acid (poly C), or chondroitin sulfate. Cultured bovine aortic endothelial cells can similarly adhere to FN-coated plates, which was inhibited by OxLDL, poly I, and dextran sulfate in the presence of EDTA. LOX-1 may play an important role in cell adhesion to FN in an integrin-independent manner.

MST, a physiological caspase substrate, highly sensitizes apoptosis both upstream and downstream of caspase activation

The human serine/threonine kinase, mammalian STE20-like kinase (MST), is considerably homologous to the budding yeast kinases, SPS1 and STE20, throughout their kinase domains. The cellular function and physiological activation mechanism of MST is unknown except for the proteolytic cleavage-induced activation in apoptosis. In this study, we show that MST1 and MST2 are direct substrates of caspase-3 both in vivo and in vitro. cDNA cloning of MST homologues in mouse and nematode shows that caspase-cleaved sequences are evolutionarily conserved. Human MST1 has two caspase-cleavable sites, which generate biochemically distinct catalytic fragments. Staurosporine activates MST either caspase-dependently or independently, whereas Fas ligation activates it only caspase-dependently. Immunohistochemical analysis reveals that MST is localized in the cytoplasm. During Fas-mediated apoptosis, cleaved MST translocates into the nucleus before nuclear fragmentation is initiated, suggesting it functions in the nucleus. Transiently expressed MST1 induces striking morphological changes characteristic of apoptosis in both nucleus and cytoplasm, which is independent of caspase activation. Furthermore, when stably expressed in HeLa cells, MST highly sensitizes the cells to death receptor-mediated apoptosis by accelerating caspase-3 activation. These findings suggest that MST1 and MST2 play a role in apoptosis both upstream and downstream of caspase activation.

Therapeutic effect of anti-Fas antibody on a collagen induced arthritis model

OBJECTIVE

To investigate the therapeutic effect of anti-Fas monoclonal antibody (Mab, RK-8) in collagen induced arthritis (CIA).

METHODS

CD1F1 mice were immunized with bovine type II collagen to induce CIA and were treated with RK-8 intravenously. The effect of RK-8 was monitored by visual scoring. ELISA to detect serum anti-type II collagen antibody was performed on Day 47 and 70. Histopathological analysis was performed on Days 31 and 72. Digital micrography was performed on Day 72.

RESULTS

RK-8 treatment almost completely prevented CIA. This suppressive effect continued after RK-8 was discontinued. RK-8 significantly suppressed the serum anti-type II collagen antibody level on Day 47. Histological analysis revealed that RK-8 significantly reduced joint histopathology, as determined by the infiltration of inflammatory cells and cartilage damage, consistent with digital micrography.

CONCLUSION

Administration of anti-Fas Mab may be a useful therapeutic strategy for rheumatoid arthritis if used early in the disease.

LOX-1 supports adhesion of Gram-positive and Gram-negative bacteria

Adhesion of bacteria to vascular endothelial cells as well as mucosal cells and epithelial cells appears to be one of the initial steps in the process of bacterial infection, including infective endocarditis. We examined whether lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1), a member of scavenger receptor family molecules with C-type lectin-like structure, can support adhesion of Gram-positive and Gram-negative bacteria. Chinese hamster ovary-K1 (CHO-K1) cells stably expressing LOX-1 can support binding of FITC-labeled Staphylococcus aureus and Escherichia coli, which was suppressed by poly(I) and an anti-LOX-1 mAb. Adhesion of these bacteria to LOX-1 does not require divalent cations or serum factors and can be supported under both static and nonstatic conditions. Cultured bovine aortic endothelial cells (BAEC) can also support adhesion of FITC-labeled S. aureus, which was similarly suppressed by poly(I) and an anti-LOX-1 mAb. In contrast, binding of FITC-labeled E. coli to BAEC was partially inhibited by the anti-LOX-1 mAb, and poly(I) did not block FITC-labeled E. coli adhesion to BAEC, but, rather, enhanced it under a static condition. TNF-alpha increased LOX-1-dependent adhesion of E. coli, but not that of S. aureus, suggesting that S. aureus adhesion to BAEC may require additional molecules, which cooperate with LOX-1 and suppressed by TNF-alpha. Taken together, LOX-1 can work as a cell surface receptor for Gram-positive and Gram-negative bacteria, such as S. aureus and E. coli, in a mechanism similar to that of class A scavenger receptors; however, other unknown molecules may also be involved in the adhesion of E. coli to BAEC, which is enhanced by poly(I).

Apoptosis-inducing protein, AIP, from parasite-infected fish induces apoptosis in mammalian cells by two different molecular mechanisms

AIP (apoptosis-inducing protein) is a protein purified and cloned from Chub mackerel infected with the larval nematode, Anisakis simplex, which induces apoptosis in various mammalian cells including human tumor cell lines. AIP has shown structural and functional homology to L-amino acid oxidase (LAO) which oxidizes several L-amino acids including L-lysine and AIP-induced apoptosis has been suggested to be mediated by H2O2 generated by LAO activity of AIP. In this study, we confirmed that recombinant AIP generated enough H2O2 in culture medium to induce rapid apoptosis in cells and this apoptosis was clearly inhibited by co-cultivation with antioxidants such as catalase and N-acetyl-cysteine. Surprisingly, however, we found that AIP still could induce H2O2-independent apoptosis more slowly than H2O2-dependent one in HL-60 cells even in the presence of antioxidants. In addition, the HL-60-derived cell line HP100-1, which is a H2O2-resistant variant, underwent apoptosis on treatment with AIP with a similar delayed time course. The latter apoptosis was completely blocked by addition of L-lysine to the culture medium, which is the best substrate of AIP as LAO, indicating that decreased concentration of L-lysine in the culture medium by AIP-treatment induced apoptosis. We also showed that the both apoptosis by AIP were associated with the release of cytochrome c from mitochondria and activation of caspase-9, and overexpressed Bcl-2 could inhibit both of the AIP-induced apoptosis. These results indicate that AIP induces apoptosis in cells by two distinct mechanisms; one rapid and mediated by H2O2, the other delayed and mediated by deprivation of L-lysine, both of which utilize caspase-9/cytochrome c system.

High-pressure NMR study of cis-1,n-disubstituted[n]paracyclophanes. Effect of increased pressure on the hindered internal rotation

The effect of hydrostatic pressure on the rate of internal rotation of title compounds has been examined by the DNMR method. Quartz pressure-resisting NMR cells were used to realize the high-pressure experiments up to 390 (line shape measurements) and 450 MPa (chemical shift measurements). Application of hydrostatic pressure was found to accelerate the rotation of the benzene ring, while pressure-induced low-frequency chemical shifts of bridge methylene protons indicated that there is a considerable shrinkage of the methylene bridge structure upon pressurization.

Molecular cloning of a novel scavenger receptor for oxidized low density lipoprotein, SR-PSOX, on macrophages

Receptor-mediated endocytosis of oxidized low density lipoprotein (OxLDL) by macrophages has been implicated in foam cell transformation in the process of atherogenesis. Although several scavenger receptor molecules, including class A scavenger receptors and CD36, have been identified as OxLDL receptors on macrophages, additional molecules on macrophages may also be involved in the recognition of OxLDL. From a cDNA library of phorbol 12-myristate 13-acetate-stimulated THP-1 cells, we isolated a cDNA encoding a novel protein designated SR-PSOX (scavenger receptor that binds phosphatidylserine and oxidized lipoprotein), which acts as a receptor for OxLDL. SR-PSOX was a type I membrane protein consisting of 254 amino acids, expression of which was shown on human and murine macrophages with a molecular mass of 30 kDa. SR-PSOX could specifically bind with high affinity, internalize, and degrade OxLDL. The recognition of OxLDL was blocked by polyinosinic acid and dextran sulfate but not by acetylated low density lipoprotein. Taken together, SR-PSOX is a novel class of molecule belonging to the scavenger receptor family, which may play important roles in pathophysiology including atherogenesis.

Gelatin beads as platforms for targeting molecule and anti-Fas antibody: two major properties of cytotoxic T lymphocytes

OBJECTIVE

Cytotoxic T lymphocytes (CTL) initially recognize target cells using the T-cell receptor (TCR), then strongly adhere to these cells by accessory molecules, and finally induce apoptosis by Fas ligand (FasL)/Fas or lyse by the granzyme/perforin system. We describe the development of gelatin beads carrying anti-tumor monoclonal antibody (mAb) and anti-Fas mAb mimicking the TCR and FasL, respectively. We hypothesized that these antibody-coated beads can be therapeutically utilized for the elimination of tumor cells.

MATERIALS AND METHODS

We evaluated the cytotoxic activity of gelatin beads bearing CH11 (anti-Fas mAb) after incubation with several human leukemia cell lines. Cytotoxic activities were measured using colorimetric DNA fragmentation assay and lactate dehydrogenase (LDH) release assay.

RESULTS

We demonstrated that the cytotoxic effects of anti-Fas mAb were markedly enhanced by fixation on gelatin beads. Microscopic examination showed that the beads attached to the target cells and induced their apoptosis. These effects were enhanced further by adding tumor-specific mAb. These in vitro properties of the beads were well reconstituted in the peritoneal cavity of mice.

CONCLUSION

Although antibody-coated gelatin beads lack several important properties of natural CTL, such as differentiation, proliferation, and the functions of adhesion molecules, they mimic well the targeting and cytotoxic functions of natural CTL. Our findings suggest that antibody-carrying gelatin beads may be the first step toward the development of artificial CTL and can be applied, for example, to artificial dendritic and stroma cells for the development of novel biotherapeutic approaches.

Reduction of thymocyte numbers in transgenic mice expressing viral FLICE-inhibitory protein in a Fas-independent manner

A viral FLIP (FLICE/caspase-8-Inhibitory Protein), equine herpesvirus type 2 E8 protein, has been shown to inhibit Death receptor-induced apoptosis by suppressing the activation of FLICE/caspase-8. We generated transgenic mice specifically expressing E8 in thymocytes under the control of lck-proximal promoter. Although E8-expressing thymocytes were resistant to Fas-mediated apoptosis, the total number of thymocytes in 4-8-week-old E8 transgenic mice was more than 3-fold less than that in control littermates. This reduction was also observed in E8 transgenic mice with a Fas-/- background suggesting the reduction to be independent of Fas. The thymocytes of the transgenic mice, however, could similarly respond to CD3-mediated stimulation, indicating that the reduction of thymocyte numbers might be independent of T cell receptor complex-mediated stimulation. Thus, the Death receptor-mediated signaling pathway is too complex to be regarded as only an executor for apoptosis.

Cloning and expression of a novel murine anti-human Fas antibody

Agonistic anti-human Fas antibodies that can induce apoptosis are thought to have therapeutic effects for various diseases resulting from an abnormality of the Fas/FasL system. However, some anti-Fas antibodies show toxicity, and it is difficult to investigate their therapeutic and toxicological effect using animals because of their species specificity. We previously obtained a murine anti-human Fas mAb, HFE7A. HFE7A reacted with both human and murine Fas, and mitigated lymphadenopathy without any sign of hepatotoxicity in MRLgld/gld mice. It is suggested that humanized HFE7A would be a therapeutic treatment for various diseases resulting from an abnormality of the Fas/FasL system. Here we isolated the cDNAs that code for the heavy and light chains of HFE7A and identified the corresponding nucleotide sequences. The recombinant HFE7A was indistinguishable in binding and apoptosis-inducing activity to that from a hybridoma cell line. These data provide essential information for the humanization and clinical application of the humanized HFE7A.

Execution of apoptosis signal-regulating kinase 1 (ASK1)-induced apoptosis by the mitochondria-dependent caspase activation

ASK1 activates JNK and p38 mitogen-activated protein kinases and constitutes a pivotal signaling pathway in cytokine- and stress-induced apoptosis. However, little is known about the mechanism of how ASK1 executes apoptosis. Here we investigated the roles of caspases and mitochondria in ASK1-induced apoptosis. We found that benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (zVAD-fmk), a broad-spectrum caspase inhibitor, mostly inhibited ASK1-induced cell death, suggesting that caspases are required for ASK1-induced apoptosis. Overexpression of ASK1DeltaN, a constitutively active mutant of ASK1, induced cytochrome c release from mitochondria and activation of caspase-9 and caspase-3 but not of caspase-8-like proteases. Consistently, caspase-8-deficient (Casp8 (-/-)) cells were sensitive to ASK1-induced caspase-3 activation and apoptosis, suggesting that caspase-8 is dispensable for ASK1-induced apoptosis, whereas ASK1 failed to activate caspase-3 in caspase-9-dificient (Casp9 (-/-)) cells. Moreover, mitochondrial cytochrome c release, which was not inhibited by zVAD-fmk, preceded the onset of caspase-3 activation and cell death induced by ASK1. ASK1 thus appears to execute apoptosis mainly by the mitochondria-dependent caspase activation.

Significance of Fas antigen-mediated apoptosis in human fulminant hepatic failure

OBJECTIVE

The aim of this study was to elucidate the role of apoptosis in human fulminant hepatic failure. We studied the expression of Fas antigen on liver tissues, Fas ligand in lymphocytes, and soluble Fas ligand in patients' serum.

METHODS

On finding apoptotic cells in fulminant hepatic failure liver, we first examined them using the TUNEL method. Subsequently, the expression of Fas was studied by immunostaining. Simultaneously, Fas ligand presenting on both liver-infiltrated cells and peripheral lymphocytes was studied by reverse transcription-polymerase chain reaction, and soluble Fas ligand in sera was measured by ELISA.

RESULTS

By using the TUNEL method, we first demonstrated that many apoptotic cells existed in fulminant hepatic failure but not in normal ones. Our immunohistochemistry study showed that many hepatocytes in fulminant hepatic failure strongly expressed Fas. In addition, Fas ligand on both liver-infiltrating lymphocytes and peripheral lymphocytes in fulminant hepatic failure patients was detected. The serum level of soluble Fas ligand was significantly increased in fulminant hepatic failure (mean value, 2.91 ng/ml in fulminant hepatic failure [n = 10], 1.62 ng/ml in acute hepatitis [n = 10], and 0.27 ng/ml in healthy controls [n = 10]). Furthermore, this serum level of sFas ligand was significantly associated with prothrombin time both in acute hepatitis and fulminant hepatic failure.

CONCLUSIONS

The present results indicate that Fas-mediated apoptosis may be one of the triggers for the induction of fulminant hepatic failure.

Spontaneous and cytokine regulated c-fos gene expression in rheumatoid synovial cells: resistance to cytokine stimulation when the c-fos gene is overexpressed

OBJECTIVE

To study the effect of cytokines on the transactivation of the c-fos gene in relation to the contribution of overexpression of c-fos/AP-1 in rheumatoid joint destruction.

METHODS

The promoter region (-447 to +109) of the human c-fos gene was integrated upstream of the chloramphenicol acetyltransferase (CAT) reporter gene, and the effect of cytokines on the expression of the c-fos gene was studied in the rheumatoid synovial cells of early (3-4) or late (14-18) passages, in the presence or absence of cytokines, by the transient transfection assay.

RESULTS

Expression of c-fos gene was enhanced by tumour necrosis factor alpha (TNF alpha) and interleukin 6 (IL6) in the synovial cells of early passage, whereas it was not enhanced in the synovial cells of late passage. The c-fos gene expression was also enhanced by 13-O-tetradecanoyl phorbol-13-acetate (TPA) in early passage but was somewhat suppressed in the late passage. It was found that the c-fos gene and c-Fos protein were both increased in the synovial cells of late passage. Similarly, c-fos gene expression was also not increased by TPA or cytokine stimulation in the stable c-fos transformants (fos-pH8) or H-ras transformed NIH3T3 cells (NIH H-ras cells) that constitutively expressed c-fos genes.

CONCLUSIONS

Although TNF alpha and IL6 augmented c-fos gene expression of rheumatoid synovial cells, transactivation of c-fos gene became resistant against cytokine stimulation under prolonged expression of c-fos gene, which may impart a tumour-like characteristic to rheumatoid synovial cells.

Purification and cloning of an apoptosis-inducing protein derived from fish infected with Anisakis simplex, a causative nematode of human anisakiasis

While investigating the effect of marine products on cell growth, we found that visceral extracts of Chub mackerel, an ocean fish, had a powerful and dose-dependent apoptosis-inducing effect on a variety of mammalian tumor cells. This activity was strikingly dependent on infection of the C. mackerel with the larval nematode, Anisakis simplex. After purification of the protein responsible for the apoptosis-inducing activity, we cloned the corresponding gene and found it to be a flavoprotein. This protein, termed apoptosis-inducing protein (AIP), was also found to possess an endoplasmic reticulum retention signal (C-terminal KDEL sequence) and H2O2-producing activity, indicating that we had isolated a novel reticuloplasimin with potent apoptosis-inducing activity. AIP was induced in fish only after infection with larval nematode and was localized to capsules that formed around larvae to prevent their migration to host tissues. Our results suggest that AIP may function to impede nematode infection.

A novel murine anti-human Fas mAb which mitigates lymphadenopathy without hepatotoxicity

Defects in Fas-mediated apoptosis are implicated in autoimmune diseases including rheumatoid arthritis (RA). Although induction of Fas-mediated apoptosis could have therapeutic effects on these diseases, it might cause deleterious effects in liver as Fas ligand or an agonistic anti-murine Fas antibody Jo2 causes severe hepatic injury in mice. We report here on the interesting characteristics of the newly obtained anti-Fas mAb, HFE7A, which cross-reacts with the Fas molecules of various species ranging from human to mouse and mitigates autoimmune symptoms without hepatotoxicity in mice. The administration of HFE7A to mice induced apoptosis in the thymocytes, although administration of HFE7A to mice or to marmosets did not induce any sign of hepatitis. The effect of HFE7A on liver is different from that of anti-murine Fas antibody Jo2, which causes acute and lethal hepatic injury to mice. Administration of HFE7A reduced lymphadenopathy and abnormal T cells in MRL-gld/gld mice. HFE7A induced apoptosis in synovial cells prepared from RA patients. Surprisingly, HFE7A protected mice from fulminant hepatitis induced by Jo2. Therefore, HFE7A is a potential therapeutic antibody not only for autoimmune diseases including RA but also for fulminant hepatitis.

Effects of anti-Fas antibodies on lymphocytes and other organs: preparation of original and new monoclonal antibodies and amelioration of systemic autoimmune disease

Fifteen and ten years have passed since original anti-human Fas mAb CH-11 with associated apoptosis-inducing activity was prepared in 1984 and reported in 1989, respectively. Fas antigen (FS-7 cell-associated cell surface antigen) has been shown to be a cell surface receptor molecule (Fas) which can introduce apoptosis-inducing signals into Fas-bearing cells. Studies on lpr (lymphoproliferation) and gld (generalized lymphoproliferative disease) mice, which are loss-of-function mutant mice of Fas and Fas ligand (FasL), respectively, show that these mutations are responsible for the early onset of systemic autoimmune disease in MRL mice, suggesting that autoreactive immunocytes are eliminated by the function of Fas/FasL system ("physiological function" of Fas). Fas/FasL system, however, plays an important role in not only prevention but also aggravation of autoimmune disease. Fas/FasL was shown to be involved in the mechanisms responsible for tissue disruption in autoimmune diseases ("pathological function" of Fas). Studies on the in vivo administration of anti-mouse Fas mAbs, Jo2 and RK-8, emphasized pathological and physiological functions of Fas, respectively: Jo2 induces fulminant hepatitis and RK-8 ameliorates systemic autoimmune disease without the induction of fulminant hepatitis. The different in vivo effects of Jo2 and RK-8 coincide well with different target cell specificity of these mAbs in vitro. Similarly, I observed different target cell specificity on anti-human Fas mAbs. In this review, I propose new strategy of therapeutic use of anti-Fas mAb as specific suppressor for activated immune system on autoimmune disease and other diseases.

Role of apoptosis induction in both peripheral lymph nodes and thymus in progressive loss of CD4+ cells in SHIV-infected macaques

To investigate the role of apoptosis in the progressive loss of CD4+ lymphocytes in HIV infection, we have used macaques infected with SHIV, a hybrid virus of HIV and simian immunodeficiency virus (SIV). In the present study, we sequentially analyzed apoptosis induction in the acute phase of SHIV infection. Four macaques infected with a pathogenic SHIV, SHIV89.6P, and four macaques infected with a nonpathogenic SHIV, NM-3rN, were analyzed during the first 2 or 4 weeks postinfection. In the 89.6P-infected macaques the number of peripheral CD4+ cells sharply decreased at 2 weeks postinfection and was maintained below 50/microl until 4 weeks postinfection, while in the NM-3rN-infected macques the number of the CD4+ cells did not change significantly. Plasma viral loads peaked at 2 and 2-3 weeks postinfection, and the peak values were about 1 x 10(9) and 10(6)-10(7) copies/ml in the 89.6P- and the NM-3rN-infected macaques, respectively. In the 89.6P-infected macaques, Fas antigen expression and the extent of apoptosis in PBMCs and peripheral lymph nodes increased at 1-2 weeks postinfection. A high number of apoptotic cells was also observed in thymus sections 2 and 4 weeks postinfection. On the other hand, apoptosis was scarcely induced in the NM-3rN-infected macaques. These results suggest that the extent of apoptosis induction is closely correlated with the pathogenicity of SHIV and that the apoptosis induction in peripheral lymphoid tissues and thymus, where T cell maturation occurs, may play an important role in the depletion of CD4+ lymphocytes in 89.6P infection.

Cdc42 and Rac1 regulate the interaction of IQGAP1 with beta-catenin

IQGAP1, a target of Cdc42 and Rac1 small GTPases, directly interacts with beta-catenin and negatively regulates E-cadherin-mediated cell-cell adhesion by dissociating alpha-catenin from the cadherin-catenin complex in vivo (Kuroda, S., Fukata, M., Nakagawa, M., Fujii, K., Nakamura, T., Ookubo, T., Izawa, I., Nagase, T., Nomura, N., Tani, H., Shoji, I., Matsuura, Y., Yonehara, S., and Kaibuchi, K. (1998) Science 281, 832-835). Here we investigated how Cdc42 and Rac1 regulate the IQGAP1 function. IQGAP1 interacted with the amino-terminal region (amino acids 1-183) of beta-catenin, which contains the alpha-catenin-binding domain. IQGAP1 dissociated alpha-catenin from the beta-catenin-alpha-catenin complex in a dose-dependent manner in vitro. Guanosine 5'-(3-O-thio)triphosphate (GTPgammaS).glutathione S-transferase (GST)-Cdc42 and GTPgammaS. GST-Rac1 inhibited the binding of IQGAP1 to beta-catenin in a dose-dependent manner in vitro, whereas neither GDP.GST-Cdc42, GDP. GST-Rac1, nor GTPgammaS.GST-RhoA did. The coexpression of dominant active Cdc42 with IQGAP1 suppressed the dissociation of alpha-catenin from the cadherin-catenin complex induced by the overexpression of IQGAP1 in L cells expressing E-cadherin (EL cells). Consistent with this, the overexpression of either dominant negative Cdc42 or Rac1 resulted in the reduction of E-cadherin-mediated cell adhesive activity in EL cells. These results indicate that Cdc42 and Rac1 negatively regulate the IQGAP1 function by inhibiting the interaction of IQGAP1 with beta-catenin, leading to stabilization of the cadherin-catenin complex.

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.

Severe impairment of B cell function in lpr/lpr mice expressing transgenic Fas selectively on B cells

Transgenic lpr/lpr mice expressing functional Fas selectively on B cells were produced in an attempt to elucidate the role of Fas on B cells in the regulation of autoantibody production. The homozygous lpr/lpr mice carrying the transgene did not produce anti-double-stranded DNA antibodies throughout their lives, whereas the development of abnormal lpr T cells (double negative, B220(+)) was not suppressed. Further analyses, however, revealed that the expression of the transgenic Fas on B cells of lpr/lpr homozygous mice resulted in severe impairment of the B cell function. The defect was characterized by a decrease in the number of mature peripheral B cells, a reduction in the serum Ig level and the total failure of B cells to mount antibody responses to stimulations of T-dependent as well as T-independent antigens. Such a defect was prominent only when the transgene was expressed on the lpr/lpr homozygous background. On the contrary, B cells of the transgenic lpr/lpr mice were shown to be capable of producing Ig when stimulated with anti-CD40 in the presence of IL-4 and IL-5. Furthermore, lpr/lpr T cells showed enhanced non-specific cytolytic activity. These observations suggested that the observed B cell defect was probably attributable to the destruction of activated B cells expressing transgenic Fas by aggressive lpr/lpr T cells.

Fas-induced in vivo apoptosis in bone marrow: anti-Fas mAb-induced elimination and successive proliferation of Fas-expressing cells especially those of myeloid lineage

A single administration of agonistic anti-Fas mAb RK8 into mice decreased the number of bone marrow cells especially Mac1+ and Gr1+ cells of myeloid lineage. These cells, which were shown to be Fas-positive in normal bone marrow, were directly eliminated in vivo by Fas-mediated apoptosis. After the elimination of Fas-positive bone marrow cells, bone marrow was reconstituted by successive increase of numbers of Gr1(low) and Mac1(low) myeloid precursor cells expressing high levels of Fas, which are minor constituents in normal bone marrow. The increased cells consisted at least two components, Gr1(dull) Mac1+ cKit+ cells and Gr1(intermediate) Mac1+ cKit- cells, both of which were shown to be sensitive to Fas-induced apoptosis in vivo. Thus, Fas is functional in normal bone marrow and Fas-induced apoptosis in bone marrow enhances marked proliferation of Fas-expressing myeloid precursor cells in vivo.

Sequential analysis of apoptosis induction in peripheral blood mononuclear cells and lymph nodes in the early phase of pathogenic and nonpathogenic SIVmac infection

To investigate the role of apoptosis in the early phase of HIV infection, we used macaques infected with simian immunodeficiency virus strain mac (SIVmac) as a primate model and examined sequentially the characteristics of apoptosis of lymphocytes in peripheral blood mononuclear cells (PBMCs) and lymph nodes in the early phase of SIVmac infection. Five macaques infected with a pathogenic strain of SIV, SIVmac239, were analyzed during the first 4 weeks after infection. Peripheral CD4+ and CD8+ cells transiently decreased at 1 week postinfection. The percentage of apoptotic cells in cultured PBMCs increased from about 2 weeks postinfection. The number of apoptotic cells in lymph node sections was higher on days 13 and 28 postinfection than before infection and on day 5 postinfection. Fas antigen expression on peripheral lymphocytes was upregulated from day 8 postinfection. These results indicate that apoptosis is induced about 2 weeks after SIVmac239 infection, following the upregulation of Fas antigen expression on lymphocytes. Since apoptosis was induced about 1 week after the decrease in peripheral CD4+ and CD8+ cell counts, it appears that the apoptosis induction does not play an important role in the transient lymphopenia in the early phase of SIVmac infection. In macaques infected with a nonpathogenic derivative of SIVmac239, SIVmac delta nef, apoptosis of lymphocytes was induced as it was in SIVmac239-infected macaques, but to a lesser degree, suggesting a correlation between the extent of apoptosis induction in lymphocytes in the early phase of SIVmac infection and the pathogenicity of SIVmac.

The CED-4-homologous protein FLASH is involved in Fas-mediated activation of caspase-8 during apoptosis

Fas is a cell-surface receptor molecule that relays apoptotic (cell death) signals into cells. When Fas is activated by binding of its ligand, the proteolytic protein caspase-8 is recruited to a signalling complex known as DISC by binding to a Fas-associated adapter protein. A large new protein, FLASH, has now been identified by cloning of its complementary DNA. This protein contains a motif with oligomerizing activity whose sequence is similar to that of the Caenorhabditis elegans protein CED-4, and another domain (DRD domain) that interacts with a death-effector domain in caspase-8 or in the adapter protein. Stimulated Fas binds FLASH, so FLASH is probably a component of the DISC signalling complex. Transient expression of FLASH activates caspase-8, whereas overexpression of a truncated form of FLASH containing only one of its DRD or CED-4-like domains does not allow activation of caspase-8 and Fas-mediated apoptosis to occur. Overexpression of full-length FLASH blocks the anti-apoptotic effect of the adenovirus protein E1B19K. FLASH is therefore necessary for the activation of caspase-8 in Fas-mediated apoptosis.

Caspases mediate tumor necrosis factor-alpha-induced neutrophil apoptosis and downregulation of reactive oxygen production

Tumor necrosis factor-alpha (TNF-alpha) exerts two separate effects on neutrophils, stimulating effector functions while simultaneously inducing apoptosis. We examined here the involvement of caspases in neutrophil apoptosis and the effect of TNF-alpha-induced apoptosis on reactive oxygen production. Immunoblotting and affinity labeling showed activation of caspase-8, caspase-3, and a caspase with a large subunit of 18 kD (T18) in TNF-alpha-treated neutrophils. Active caspase-6 and -7 were not detectable in this cell type. Caspase-8 activated caspase-3 and T18 in neutrophil cytoplasmic extracts. zVAD-fmk blocked neutrophil apoptosis, in parallel with the inhibition of caspase activation. TNF-alpha-induced caspase activation was accompanied by a decrease in the ability of neutrophils to release superoxide anion. Conversely, TNF-alpha treatment in the presence of zVAD-fmk caused a prolonged augmentation of superoxide release. Granulocyte-macrophage colony-stimulating factor inhibited TNF-alpha-induced caspase activation and apoptosis, while reversing the diminution in superoxide release. These observations not only suggest that a caspase cascade mediates apoptotic events and downregulates oxygen radical production in TNF-alpha-treated neutrophils, but also raise the possibility that suppression of caspase activation with enhanced proinflammatory actions of TNF-alpha may underlie the pathogenesis of inflammatory diseases.

The development of autoimmune inflammatory arthropathy in mice transgenic for the human T cell leukemia virus type-1 env-pX region is not dependent on H-2 haplotypes and modified by the expression levels of Fas antigen

Previously, we reported that human T cell leukemia virus type-1 env-pX region-introduced transgenic (pX-Tg) mice develop an inflammatory polyarthropathy. Although autoimmune pathogenesis was suggested, the detailed mechanisms remain to be elucidated. In this report, we examined effects of the MHC and fas genes on the development of the disease. When pX-Tg mice were backcrossed with different inbred strains, the incidence of arthritis differed among strains; 64% and 72% in BALB/cAn (H-2d), 25% and 46% in C3H/HeN (H-2k), and 0% and 2% in C57BL/6J (H-2b) background at 3 and 6 months of age, respectively. Rheumatoid factor levels in the serum correlated with the susceptibility to the disease, whereas IL-1beta and MHC gene expression were similarly elevated in all of these strains, suggesting involvement of immune regulatory genes in this strain difference. However, introduction of the H-2d locus into C57BL/6J pX-Tg mice did not increase the incidence of arthritis, and substitution of the BALB/cAn H-2 locus with the H-2b did not decrease it. The results indicate that the H-2 locus is not the major determinant of the disease. Then, since previous study indicated a defect in Fas-mediated apoptosis of transgenic T cells, the effects of fas gene modification on the disease were examined. The incidence increased when these pX-Tg mice were crossed with lpr/lpr mice, while it decreased when crossed with fas-transgenic mice. These observations suggest that aberration of Fas-mediated apoptosis of peripheral lymphocytes, rather than negative selection in the thymus, is involved in the development of autoimmune arthropathy in pX-Tg mice.

Redox regulation of caspase-3(-like) protease activity: regulatory roles of thioredoxin and cytochrome c

Oxidative stress induces a variety of cellular responses, including apoptosis, and caspase family proteases are known to be involved in apoptosis. Caspase-3(-like) protease activity was examined in Jurkat T cells to investigate the mechanism of apoptosis induced by a thioloxidant, diamide. Caspase-3 was activated when cells were cultured with 200 microM diamide that induced apoptosis, whereas no caspase-3 activation was detected with 500 microM diamide that induced necrosis. When apoptosis was induced in cells with exposure to 200 microM diamide, the intracellular thioredoxin (TRX) levels were maintained and the intracellular generation of reactive oxygen intermediates was marginal. The cytosolic fractions of cytochrome c were increased earlier than the activation of caspase-3. In contrast, when cells were exposed to 500 microM diamide, intracellular reactive oxygen intermediate generation was increased and processing of caspase-3 was not detected despite cytochrome c release, resulting in necrosis. Caspase-3 activity in cell lysate precultured with anti-Fas Ab was suppressed dose dependently by diamide and restored by thiol-reducing agents, DTT or TRX. When cells were precultured with 5 mM of buthionine sulfoximine, an inhibitor of glutathione synthesis, intracellular TRX levels were maintained, and as low as 20 microM diamide could induce apoptosis associated with the increase of cytosolic cytochrome c and the activation of caspase-3. These results indicate that the activation of caspase-3 in diamide-induced apoptosis is mediated, at least partly, by cytochrome c release from mitochondria, and the cellular reducing environment maintained by TRX, as well as glutathione, is required for caspase-3 activity to induce apoptosis.

Expression of fas antigen in the normal mouse brain

The Fas antigen (Fas/Apo-1/CD95) is a cell surface receptor protein that mediates apoptosis-inducing signals and plays an important role in the immune system. In the central nervous system, during the period of naturally occurring cell death many neurons appear to die by apoptosis. We investigated the involvement of Fas in these events. The expression of Fas transcripts and protein was examined in the juvenile mouse brain. By RT-PCR analysis, Fas mRNA was detected in the cerebrum, cerebellum, and hippocampus of the brain. By immunohistochemistry, we found Fas in neurons localized in the CA2 and CA3 sectors of the hippocampus and in the cortical III layer of the cerebrum, but not neurons in the cerebellum. Furthermore, Fas was expressed on the primary cultured hippocampal and cerebral cells using immunofluorescence and flow cytometry. These results suggest that Fas is specifically expressed on neurons in the mouse brain during postnatal development.

Role of IQGAP1, a target of the small GTPases Cdc42 and Rac1, in regulation of E-cadherin- mediated cell-cell adhesion

The small guanosine triphosphatases (GTPases) Cdc42 and Rac1 regulate E-cadherin-mediated cell-cell adhesion. IQGAP1, a target of Cdc42 and Rac1, was localized with E-cadherin and beta-catenin at sites of cell-cell contact in mouse L fibroblasts expressing E-cadherin (EL cells), and interacted with E-cadherin and beta-catenin both in vivo and in vitro. IQGAP1 induced the dissociation of alpha-catenin from a cadherin-catenin complex in vitro and in vivo. Overexpression of IQGAP1 in EL cells, but not in L cells expressing an E-cadherin-alpha-catenin chimeric protein, resulted in a decrease in E-cadherin-mediated cell-cell adhesive activity. Thus, IQGAP1, acting downstream of Cdc42 and Rac1, appears to regulate cell-cell adhesion through the cadherin-catenin pathway.

Purification, molecular cloning, and characterization of TRP32, a novel thioredoxin-related mammalian protein of 32 kDa

We purified a protein of 32 kDa from human thymoma HPB-ALL cells that was co-purified with a catalytic fragment of MST (mammalian STE-20-like), a kinase of the STE20 family, which is proteolytically activated by caspase in apoptosis (Lee, K.-K., Murakawa, M., Nishida, E., Tsubuki, S., Kawashima, S., Sakamaki, K., and Yonehara, S. (1998) Oncogene 16, in press). Molecular cloning of the gene encoding this 32-kDa protein (TRP32) reveals that it is a novel protein of 289 amino acid residues and contains an NH2-terminal thioredoxin domain with a conserved thioredoxin active site. The human and mouse TRP32 proteins have 99% homology, and the thioredoxin domains are completely identical. The thioredoxin domain of TRP32 has thioredoxin-like reducing activity, which can reduce the interchain disulfide bridges of insulin in vitro. However, the thioredoxin domain of TRP32 is more sensitive to oxidation than human thioredoxin. Northern blot analysis showed that TRP32 is expressed in all human tissues. Expression of TRP32 was also confirmed in all mammalian cell lines tested by Western blot analysis using anti-TRP32 monoclonal antibody. Subcellular fractionation and immunostaining analysis showed TRP32 is cytoplasmic protein. These findings suggest that TRP32 is a novel cytoplasmic regulator of the redox state in higher eukaryotes.

Potential withdrawal of rheumatoid synovium by the induction of apoptosis using a novel in vivo model of rheumatoid arthritis

OBJECTIVE

To investigate whether Fas-mediated apoptosis has potential as a new therapeutic strategy in rheumatoid arthritis (RA) by use of a novel model of RA in which human RA tissue is grafted into SCID mice.

METHODS

Fresh rheumatoid synovial tissue including joint cartilage was grafted subcutaneously into the backs of SCID mice. Six weeks after engraftment, anti-Fas monoclonal antibody was injected intraperitoneally. Time-related apoptotic changes caused by anti-Fas monoclonal antibody in grafted synovium were evaluated by nick end-labeling histochemistry.

RESULTS

Thirty-six hours after the injection, diffuse apoptotic changes were observed in the grafted synovia. Four weeks after the injection, rheumatoid synovial tissue diminished.

CONCLUSION

This is the first report concerning the present effectiveness of anti-Fas monoclonal antibody in diminishing rheumatoid synovium in vivo, and suggests the possibility of a new strategy for treating rheumatoid arthritis by inducing Fas-mediated apoptosis.

Fas antigen expression and apoptosis of lymphocytes in macaques infected with simian immunodeficiency virus strain mac

To investigate the role of apoptosis in the pathogenesis of HIV infection we used macaques infected with simian immunodeficiency virus (SIV) as a primate model and examined the characteristics of the apoptosis of lymphocytes in SIV mac-infected macaques. In vitro apoptosis was more strongly induced in peripheral blood mononuclear cells (PBMC) from SIV mac239-infected macaques than those from uninfected controls. We found that the frequency of Fas antigen-positive cells was higher in PBMC from SIV mac-infected macaques than from uninfected controls, and in vitro apoptosis of PBMC was suppressed by an inhibitor of the interleukin-1 beta converting enzyme (ICE) family proteases. In biopsied lymph nodes, the number of apoptotic nuclei in T cell-dependent areas was higher in SIV mac-infected macaques than in uninfected controls. A higher number of apoptotic nuclei in lymph nodes of SIV mac-infected macaques was observed in the stage of persistent general lymphadenopathy than in those with AIDS-related complex, while there was no significant difference in the extent of apoptosis of cultured PBMC among the SIV mac-infected macaques. These results suggest that in vitro apoptosis is mediated by the Fas/Fas ligand and ICE system and that apoptosis in lymph nodes may be more closely related to the stage of SIV mac infection than is that of cultured PBMC.

Proteolytic activation of MST/Krs, STE20-related protein kinase, by caspase during apoptosis

The Fas system has been extensively investigated as a model of apoptosis and the caspase cascade has been shown to be a characteristic mechanism of signaling of apoptosis. We have identified and purified a kinase that was activated after the stimulation of Fas on human thymoma-derived HPB-ALL cells. Partial amino acid sequencing of the purified kinase revealed it to be MST/Krs, member of the yeast STE20 family of protein kinases. MST/Krs was activated by proteolytic cleavage and proteolytic activation was blocked by the caspase inhibitor, Z-VAD-FK. A mutant MST with Asp-->Asn replacement at a putative caspase cleavage site was resistant to either the proteolytic cleavage or the activation of the kinase activity. These findings suggest that proteolytic activation is one activation mechanism of MST and plays a role in apoptosis.

Molecular cloning and characterization of mouse caspase-8

Fas (APO-1/CD95) is a transmembrane receptor protein which induces apoptosis upon activation. In apoptosis triggered by Fas, a subset of cysteine proteases designated caspases is activated, playing a central role as effector molecules. Among these caspases, human caspase-8 (FLICE/MACH/Mch5) has been isolated and shown to be indispensable for Fas-mediated apoptotic signaling. In this study, we isolated the mouse homologue to human caspase-8 from a BaF3 cell cDNA library. This molecule conserved the death effector domain (DED) and protease domain as detected in human caspase-8, and was capable of inducing apoptosis in KB and Rat-1 cells when overexpressed. Expression of caspase-8 was detected in the various tissues of adult mouse and in embryos at 9.5 days and 17.5 days of development by Northern-blot analysis. Further, we isolated a chromosomal gene for caspase-8 from a mouse genomic library and analyzed the genomic structure of the isolated gene. This gene consisted of eight exons and seven introns spanning about 26 kb in the coding region.

Caspases are activated in a branched protease cascade and control distinct downstream processes in Fas-induced apoptosis

Two novel synthetic tetrapeptides, VEID-CHO and DMQD-CHO, could selectively inhibit caspase-6 and caspase-3, respectively. We used these inhibitors to dissect the pathway of caspase activation in Fas-stimulated Jurkat cells and identify the roles of each active caspase in apoptotic processes. Affinity labeling techniques revealed a branched protease cascade in which caspase-8 activates caspase-3 and -7, and caspase-3, in turn, activates caspase-6. Both caspase-6 and -3 have major roles in nuclear apoptosis. Caspase-6 cleaves nuclear mitotic apparatus protein (NuMA) and mediates the shrinkage and fragmentation of nuclei. Caspase-3 cleaves NuMA at sites distinct from caspase-6, and mediates DNA fragmentation and chromatin condensation. It is also involved in extranuclear apoptotic events: cleavage of PAK2, formation of apoptotic bodies, and exposure of phosphatidylserine on the cell surface. In contrast, a caspase(s) distinct from caspase-3 or -6 mediates the disruption of mitochondrial membrane potential (permeability transition) and the shrinkage of cytoplasm. These findings demonstrate that caspases are organized in a protease cascade, and that each activated caspase plays a distinct role(s) in the execution of Fas-induced cell death.

CD95 predicts responsiveness to tretinoin in acute promyelocytic leukemia

We describe a predictive marker (CD95) for the responsiveness to tretinoin (RA) in acute promyelocytic leukemia (APL). Functional CD95 expression during RA treatment have been observed only in those patients who responded to RA. Expression of CD95 (Fas antigen), which plays a major role in apoptosis, was determined by fluorescence activated cell sorter (FACS) analysis. APL cases in which no enhancement of CD95 expression was observed showed no response to RA and did not obtain complete remission. We propose that CD95 can predict the clinical response to RA probably due to differentiation.