Masataka Sasada

Affinity labeling displays the stepwise activation of ICE-related proteases by Fas, staurosporine, and CrmA-sensitive caspase-8.

The activation of multiple interleukin-1β converting enzyme-related proteases (caspases) in apoptotic mammalian cells raises questions as to whether the multiple active caspases have distinct roles in apoptotic execution as well as how these proteases are organized in apoptotic signaling pathways. Here we used an affinity-labeling agent, YV(bio)KD-aomk, to investigate the caspases activated during apoptotic cell death. YV(bio)KD-aomk identified six distinct polypeptides corresponding to active caspases in Fas-stimulated Jurkat T cells. On staurosporine treatment, four polypeptides were detected. Competition experiments showed that the labeled caspases have distinct substrate preferences. Stepwise appearance of the labeled caspases in each cell death event was consistent with the view that the activated caspases are organized into protease cascades. Moreover, we found that stepwise activation of caspases similar to that induced by Fas ligation is triggered by exposing non-apoptotic Jurkat cell extracts to caspase-8 (MACH/FLICE/Mch5). Conversely, CrmA protein, a viral suppressor of Fas-induced apoptosis, inhibited the protease activity of caspase-8. Overall, these findings provide evidence that caspase-8, a CrmA-sensitive protease, is responsible for initiating the stepwise activation of multiple caspases in Fas-stimulated cells.

Candidacidal activity of monocyte-derived human macrophages: relationship between Candida killing and oxygen radical generation by human macrophages.

Freshly isolated human monocytes ingested and killed Candida albicans, and generated O‐ 2 H2O2 and .OH efficiently. When monocytes were cultured in vitro, these cells transformed into macrophages. Cultured monocytes retained their ingestive activity but lost their candidacidal activity almost completely after day 3. The release of O‐ 2 by monocytes decreased slightly with culture and that of .OH was markedly decreased on day 3 of culture. The activity of myeloperoxidase in the monocytes decreased with culture. These results suggested that the loss of candidacidal activity is due to the decrease of .OH generation and myeloperoxidase activity in cultured monocytes.

Leukotriene B4-activated human endothelial cells promote transendothelial neutrophil migration.

We explored the effect of leukotriene B4 (LTB4) on endothelial cells in LTB4‐induced transendothelial migration (TEM) of neutrophils as an in vitro model of neutrophil extravasation. Chemotactic response of human neutrophils to LTB4 was significantly lower than that in response to N‐formyl‐methionyl‐leucyl‐phenylalanine (fMLP), whereas the extent of TEM in response to LTB4 was significantly higher than that to fMLP. The study on random migration induced by LTB4 and fMLP also showed similar results, which indicated that LTB4 might affect the human umbilical cord vein endothelial cell (HUVEC) barrier. Neutrophil TEM was induced by pretreatment of HUVEC monolayer with LTB4 but not with fMLP. Treatment of endothelial cells by ONO‐4057, a LTB4 receptor antagonist, abolished the effect of LTB4 almost completely whereas neutrophils treated with ONO‐4057 could transmigrate through HUVEC treated with LTB4. These findings indicated that LTB4 could induce neutrophil TEM by acting on HUVEC. J. Leukoc. Biol. 62: 203–209; 1997.

Ozone production by amino acids contributes to killing of bacteria

Reactive oxygen species produced by phagocytosing neutrophils are essential for innate host defense against invading microbes. Previous observations revealed that antibody-catalyzed ozone formation by human neutrophils contributed to the killing of bacteria. In this study, we discovered that 4 amino acids themselves were able to catalyze the production of an oxidant with the chemical signature of ozone from singlet oxygen in the water-oxidation pathway, at comparable level to antibodies. The resultant oxidant with the chemical signature of ozone exhibited significant bactericidal activity in our distinct cell-free system and in human neutrophils. The results also suggest that an oxidant with the chemical signature of ozone produced by neutrophils might potentiate a host defense system, when the host is challenged by high doses of infectious agents. Our findings provide biological insights into the killing of bacteria by neutrophils.

The expression of co-stimulatory molecules and their relationship to the prognosis of human acute myeloid leukaemia : poor prognosis of B7-2-positive leukaemia

We examined the expression of co‐stimulatory molecules on leukaemic cells of 52 adult patients with acute myeloid leukaemia (AML) (34 men and 18 women) and analysed the relationship between these expressions and the patients prognosis. B7‐1 was not expressed in any of the 23 patients investigated, whereas B7‐2 was expressed in 26/52 patients (50.0%). B7‐2 was expressed in all AML patients with monocytic morphology (M4 or M5) and in 16/42 cases without monocytic morphology. CD54 was expressed in 28/37 patients examined (75.7%), and CD58 was expressed in all of the AML patients except one (M7). The overall survival of the 26 B7‐2‐positive leukaemia patients (1–24 months, median survival 11.5 months) was significantly shorter than that of the 26 B7‐2‐negative leukaemia patients (1–71+ months, median 35.1 months) (P = 0.0080). In addition, the B7‐2‐positive patients exhibited significantly shorter disease‐free survival periods compared to the B7‐2‐negative patients (P = 0.021). There was no significant difference in age, sex, haematological data and complete remission rate between the B7‐2‐positive and B7‐2‐negative patients. Our results indicated that B7‐2 is one of the most crucial factors in the prognosis of adult acute leukaemia and can be expected to have an important role in tumour immunity.

Defective bactericidal activity and absence of specific granules in neutrophils from a patient with recurrent bacterial infections

Recent studies have suggested that specific granules and/or their contents may have a role in neutrophil adherence, oxidative metabolism, and other aspects of cell function. In the current report, we studied neutrophil function in a 13-year-old female with recurrent pyogenic infections and absent specific granules previously documented by electron microscopy. Levels of cobalamin (vitamin B12)-binding protein and lactoferrin were markedly decreased in this patients neutrophils. Bactericidal activity againstEscherichia coli was decreased at 60 and 120 min (percentage organisms killed: patient neutrophils, 48 and 33%; control neutrophils, 90 and 99%, respectively). Defective killing ofStaphylococcus aureus was also documented. Degranulation and adherence were normal. Levels of lactoferrin and cobalamin-binding protein were decreased in plasma but normal in saliva, indicating that the defect was specific for hematopoietic tissue. Superoxide anion production was normal in the patient, while hydroxyl radical generation was decreased in response to opsonized zymosan. The data support the concept that specific granules and their contents are important for oxidative metabolism and other neutrophil functions.

E148Q/M694I mutation in 3 Japanese patients with familial Mediterranean fever

We describe 3 unrelated Japanese patients with familial Mediterranean fever (FMF) due to a compound heterozygous E148Q/M694I mutation in the MEFV gene.The first patient is a 38-year-old man who also has chronic myelogenous leukemia (CML). Because genomic DNA analysis of the patient’s nail revealed the E148Q/M694I mutation, we concluded that the individual mutations were obtained congenitally. Interferon therapy was effective against not only the CML but also the FMF. The second patient is a 42-year-old man with consanguineous parents and a 14-year history of recurrent lower abdominal and back pain associated with fever. He successfully responded to colchicine treatment. The third patient is a 23-year-old woman who has a family history of FMF and since the age of 11 years has had recurrent chest and abdominal pain with fever. The onset of FMF was at an early age in this case, in contrast with the late onset of the disease in the first 2 cases. This patient’s mother also has a heterozygous M694I mutation and experienced the same symptoms until 30 years of age. Our data suggest that it should be recognized that there are more FMF patients in Japan than previously expected and that the frequency of the E148Q/M694I mutation may be significant in Japanese FMF patients.

The Serum Cytokine Profiles of Lymphoma-associated Hemophagocytic Syndrome: A Comparative Analysis of B-Cell and T-Cell/Natural Killer Cell Lymphomas

To elucidate the differences in pathogenesis between lymphoma-associated hemophagocytic syndromes (LAHS) of theT-cell/ natural killer cell (T/NK) and B-cell (B) types,we comparatively analyzed the clinical features and serum cytokine profiles of 33 patients with LAHS registered in the Kyoto University Hematology/Oncology Study Group.The serum cytokine levels of each patient group (B-LAHS versusT/NK-LAHS) were expressed as the ratio of the median to the upper normal values of the respective cytokines and were as follows: 19.05 versus 13.99 for soluble interleukin 2 (IL-2) receptor, 0.67 versus 0.67 for granulocytemacrophage colony-stimulating factor (GM-CSF), 0.64 versus 1.26 for G-CSF, 5.70 versus 3.61 for M-CSF, 1.54 versus 3.39 for interferon γ (IFN-γ), 13.17 versus 1.17 for IL-6, 6.88 versus 1.58 for tumor necrosis factor α (TNF-α), 0.71 versus 0.41 for IL-1, 1.99 versus 0.21 for IL-12, and 105.32 versus 29.65 for IL-10.The serum levels of IL-6,TNF-α, and IL-10 were significantly higher in the B-LAHS group,whereas those of IFN-γ were significantly lower. These differences between the 2 groups may reflect a difference in the pathogenesis. Higher serum levels of IL-6, TNF-α, and IL-10 may be derived at least partly from neoplastic B-cells themselves. In addition, the extremely high serum levels of IL-10 suggest that a compensatory anti-inflammatory process may operate in both groups and give rise to a profound immunosuppressive state and a poor outcome.

6-formylpterin, a xanthine oxidase inhibitor, intracellularly generates reactive oxygen species involved in apoptosis and cell proliferation.

The chemical property of 6-formylpterin and its biological functions were examined. Polarographic studies revealed that 6-formylpterin reacted with NAD(P)H and consumed oxygen. In contrast, other conjugated pterins, such as biopterin and neopterin, showed no consumption of oxygen. The production analysis using high-performance liquid chromatography documented that 6-formylpterin catalyzes the conversion from NADH to NAD. Electroparamagnetic resonance spin trapping experiments demonstrated that this reaction is accompanied with the generation of reactive oxygen species (ROS), superoxide anion and hydrogen peroxide. When 6-formylpterin was administered to HL-60 cells, intracellular ROS generation was observed and apoptosis was induced. In contrast, other conjugated pterins induced neither intracellular ROS generation nor apoptosis in HL-60 cells. The intracellular ROS generation by 6-formylpterin was observed in other cells, such as PanC-1 cells and Jurkat cells. 6-formylpterin suppressed cell proliferation in PanC-1 cells and inhibited Fas-mediated apoptosis in Jurkat cells. These findings indicate that, among conjugated pterins, 6-formylpterin has the unique property to transfer electron from NAD(P)H to oxygen and that the property brings about intracellular ROS generation, which exerts various biological functions such as induction of apoptosis, suppression of cell proliferation, and inhibition of Fas-mediated apoptosis.

Short-term delay of Fas-stimulated apoptosis by GM-CSF as a result of temporary suppression of FADD recruitment in neutrophils: evidence implicating phosphatidylinositol 3-kinase and MEK1-ERK1/2 pathways downstream of classical protein kinase C

Granulocyte/macrophage colony‐stimulating factor (GM‐CSF) inhibits Fas‐induced apoptosis of neutrophils. However, the exact step in the apoptotic pathway blocked by GM‐CSF remained unclear. Here, we found that pretreatment of neutrophils with GM‐CSF inhibits the recruitment of Fas‐associated protein with death domain (FADD) to Fas, abolishing the formation of the death‐inducing signaling complex required for Fas‐induced apoptosis. Two‐dimensional electrophoresis revealed that GM‐CSF modifies the ratio of FADD subspecies. These GM‐CSF‐triggered changes were abrogated, and Fas‐induced apoptosis was restored by an inhibitor of classical protein kinase C (PKC), Gö6976, and by the combination of a phosphatidylinositol 3‐kinase (PI‐3K) inhibitor, LY294002, and an inhibitor of mitogen‐activated protein kinase kinase (MEK)1, PD98059. Gö6976 blocked GM‐CSF‐elicited phosphorylation of Akt/PKB and extracellular signal‐regulated kinase (ERK)1/2. These results indicated that GM‐CSF suppresses Fas‐induced neutrophil apoptosis by inhibiting FADD binding to Fas, through redundant actions of PI‐3K and MEK1‐ERK1/2 pathways downstream of classical PKC.