1,803 research outputs found
Thioredoxin-interacting protein, hematopoietic stem cells, and hematopoiesis
No full textPURPOSE OF REVIEW: Reactive oxygen species (ROS) can regulate diverse signaling pathways and functions in hematopoietic cells. Thioredoxin-interacting protein (TXNIP) plays an important role in mammalian cells by inhibiting thioredoxin (TRX) under oxidative stress conditions. TXNIP is expressed in hematopoietic stem cells (HSCs), and its expression decreases as HSCs differentiate into precursor cells. However, this reduction in expression does not sufficiently explain the function of TXNIP in hematopoietic cells under oxidative stress conditions. Here, we review how ROS can regulate hematopoiesis by focusing on the function of TXNIP in hematopoietic cells under oxidative stress conditions. RECENT FINDINGS: Studies of Txnip mice have demonstrated an antioxidant function of TXNIP in hematopoietic cells or immune cells. This antioxidant function differs from the conventional pro-oxidant activity of TXNIP observed in other cell types under oxidative stress. The data suggest a context-dependent function of TXNIP under oxidative stress conditions and, in particular, a differential function of TXNIP in hematopoietic cells via its direct interaction with other redox regulatory proteins. SUMMARY: The regulation of ROS is important in determining cellular fate decisions. TXNIP acts as a negative regulator of TRX via direct interaction, and it increases the levels of ROS under oxidative stress. However, TXNIP has an antioxidant function in hematopoietic cells or immune cells, as ROS levels are elevated and induce apoptosis in Txnip hematopoietic cells. These results suggest that the amount of TXNIP is inversely associated with ROS levels, and the loss of TXNIP can increase ROS levels in immune cells or hematopoietic cells.open
Generation and characterization of 1H8 monoclonal antibody against human bone marrow stromal cells
No full textBackground: Bone marrow stromal cells (BMSCs) express many cell surface molecules, which regulate the proliferation and differentiation of immune cells within the bone marrow. Methods: To identify cell surface molecules, which can regulate cell proliferation through cell interaction, monoclonal antibodies (MoAbs) against BMSCs were produced. Among them, 1H8 MoAb, which recognized distinctly an 80 kDa protein, abolished myeloma cell proliferation that was induced by co-culturing with BMSCs. Results: IL-6 gene expression was increased when myeloma or stromal cells were treated with 1H8 MoAb . In addition, the expression of IL-6 receptor and CD40 was up-regulated by 1H8 treatment, suggesting that the molecule recognized by 1H8 MoAb is involved in cell proliferation by modulating the expression of cell growth-related genes. Myeloma cells contain high levels of reactive oxygen species (ROS), which are related to gene expression and tumorigenesis. Treatment with 1H8 decreased the intracellular ROS level and increased PAG antioxidant gene concomitantly . Finally, 1H8 induced the tyrosine phosphorylation of several proteins in U266. Conclusion: Taken together, 1H8 MoAb recognized the cell surface molecule and triggered the intracellular signals, which led to modulate gene expression and cell proliferation.open
Protein Phosphatase 2A Modulates the Proliferation of Human Multiple Myeloma Cells via Regulation of the Production of Reactive Oxygen Intermediates and Anti-Apoptotic Factors
No full textTo understand the roles of reactive oxygen intermediates (ROI) in Fas-mediated apoptosis of myeloma cells, the effects of antioxidants were tested. Fas-mediated apoptosis was further increased in the presence of antioxidants such as N-acetyl-L-cysteine and glutathione, but it was decreased when hydrogen peroxide was added. The intracellular ROI level was significantly decreased in myeloma cells treated with okadaic acid, an inhibitor of protein phosphatases 1 and 2A (PP1/PP2A). To clarify the direct roles of PP2A in myeloma cell growth, the PP2A transfected cell lines, sense- or antisense-PP2A transfectants, were established. Spontaneous cell growth of antisense-PP2A transfectants was reduced compared with that of vector transfectants. The intracellular ROI level was significantly decreased in antisense-PP2A transfectants but increased in sense-PP2A transfectants compared with vector controls. In addition, anti-apoptotic factors such as bcl-2 and IL-6 were reduced in antisense-PP2A transfectants. Taken together, these results indicate that PP2A is an essential factor for survival and growth of myeloma cells via regulation of intracellular ROI and anti-apoptotic factors.open
The regulation of NK cell function and development
No full textNK cells are the lymphocytes that are differentiated from hematopoietic stem cells in bone marrow (BM) through sequential acquisition of functional receptors. They are one of the critical components of innate immune system. The process of NK differentiation involves a variety of factors such as cytokines, membrane factors, and transcription factors in addition to BM microenvironment. NK cells express their own activating and inhibitory receptors. The cytolytic functions of NK cells against target cells are determined by the balance between theses activating and inhibitory receptors. NK cells discriminate self from non-self by MHC class I-binding inhibitory receptor. Once NK cell inhibitory receptors bound to their MHC class I-ligand, the target cells are protected from NK cell-mediated cytotoxicity. The cytolytic effector functions as well as the characteristic surface phenotypes of NK cells are acquired during the differentiation process. NK cells are emerging to apply as therapeutic agents against a variety of cancers by manipulating differentiation processes and intrinsic activities of the NK cell.open
Intracellular pH is a critical element in apoptosis triggered by GM-CSF deprivation in TF1 cells
No full textBackground: Hemopoietic cells require the constant presence of growth factors for survival in vitro and in vivo. Caspases have been known as central executors of apoptotic cell death. We have, therefore, investigated the pathways that regulate caspase activity and apoptosis using the CD34+ cell line, TF-1 which requires GM-CSF for survival. Methods: Apoptosis was measured by annexin V staining and mitochondrial membrane potential was measured by DiOC6 labelling. Intracellular pH was measured using pH sensitive fluorochrome, BCECF or SNARF-1, followed by flow cytometry analysis. Caspase activation was analyzed by PARP cleavage using anti-PARP antibody. Results: Removal of GM-CSF induceed PARP cleavage, a hallmark of caspase activity, concomitant with pHi acidification and a drop in mitochondrial potential. Treatment with ZVAD, a competitive inhibitor of caspases, partially rescued cell death without affecting pHi acidification and the reduction of mitochondrial potential, suggesting that both these events act upstream of caspases. Overexpression of Bcl-2 prevented cell death induced by GM-CSF deprivation as well as pHi acidification and the reduction in mitochondrial membrane potential. In parental cells maintained with GM-CSF, EIPA, a competitive inhibitor of Na+/H+ antiporter induced apoptosis, accompanied by a drastic reduction in mitochondrial potential. In contrast, EIPA induced apoptosis in Bcl-2 transfectants without causing mitochondrial membrane depolarization. Conclusion: Taken together, our results suggest that the regulation of H+fluxes, either through a mitochondriondependent or independent pathway, is central to caspase activation and apoptosis.open
Soluble ULBP suppresses natural killer cell activity via down-regulating NKG2D expression
No full textNKG2D is an activating receptor that is expressed on most natural killer (NK) cells and CD8+ T cells. MHC class I-related chain A(MICA) and UL16-binding protein (ULBP) 1, 2, and 3 are well-known ligands for NKG2D. Human gastric cancer cell lines, SNU216 and SNU638 cells which expressed UL16-binding protein (ULBP) were susceptible to NK cells in a NKG2D-dependent manner. However, SNU484 and SNU620 cells which had no ULBP on their surface were resistant to NK cells. ULBP 1, 2, and 3 are glycosylphosphatidylinositol (GPI)-anchored proteins which are sensitive to phosphatidylinositol-specific phospholipase C (PI-PLC). When SNU620 cells were treated with U73122, an inhibitor of PI-PLC, the surface expression of ULBP was elevated with increased NK susceptibility. Pre-incubating NK cells with culture supernatants of SNU620 or SNU638 cells, which contained soluble ULBP protein, reduced NK cell activity by decreasing surface expression of NKG2D in NK cells. Furthermore, recombinant ULBP-Fc induced the down-regulation of NKG2D expression in NK cells. Taken together, down-regulation of NKG2D by soluble ULBP provides a potential mechanism by which gastric cancer cells escape NKG2D-mediated attack by the immune cells.open
Direct exposure to 2,3,7,8-tetrachlodibenzo-p-dioxin(TCDD) increases infectivity of human erythrocytes to a malarial parasite
No full textDirect exposure to 10 nM 2,3,7,8-TCDD caused a 75% increase and a 2-fold increase in the infectivity of isolated human erythrocytes to P. falciparum after 48 hours when the parasites were in an unsynchronized or synchronized state of growth, respectively. Treatment of human erythrocytes with 10 μM sodium orthovanadate (NaOV), an inhibitor of plasma membrane Ca-ATPase and phosphotyrosine phosphatase, decreased parasitemia by 30%. Co-treatment of RBCs with TCDD and NaOV completely blocked the TCDD-induced increase in parasitemia. Because erythrocytes are anucleated, these results are discussed as evidence for biochemical changes by TCDD without requiring the activation of gene products.open
Progression of hepatic stellate cell activation is associated with the level of oxidative stress rather than cytokines during CCl4-induced fibrogenesis
No full textIn order to identify a fibrogenic factor associated with the potential of hepatic stellate cells (HSC) activation that arises during the CCl4-induced fibrogenic process, the relationship between the activation of HSC and levels of several fibrogenic factors were investigated. After isolation of HSC from the liver at different stages of CCl4 intoxication, the activation of HSC was assessed by the expression of α-smooth muscle actin. Levels of cytokines and oxidative stress in liver homogenates and plasma were measured by enzyme linked immunosorbent assay and the colorimetric method. In primary culture, HSC isolated from a rat liver were gradually activated in a time-dependent manner according to CCl4 administration. The progression of HSC activation was closely correlated with parameters related to oxidative stress in liver homogenates rather than the tissue levels of several cytokines. Also, the levels of antioxidants and arginase activity were inversely correlated with HSC activation. In plasma, the levels of oxidative stress and cytokines in CCl4-treated rat livers were not associated with the activation of HSC found during the CCl4-induced fibrogenic process. The relationship between HSC activation and oxidative stress was also confirmed through several factor-treated HSC cultures. In conclusion, the activation of HSC was accelerated according to CCl4 administration, and the progression of HSC activation is absolutely related to the oxidative stress. These results show that enhanced oxidative stress is an important signal for activation of HSC in experimental liver fibrogenesis.open
Inhibition of fat storing cell proliferation by a monomeric arginase derived from perfused rat liver
No full textA fulminant hepatitis is associated with massive liver cell necrosis and a high mortality rate. But survivors regenerate a normal liver and do not have chronic liver disease. This clinical course suggests that the acutely injured livers release a factor that allows a recovery from chronic hepatitis or cirrhosis. The objective of this study was to isolate and characterize an anti-fibrotic factor from acutely damaged rat livers. The liver cell necrosis was prepared from rat by warm ischemical perfusion and the perfusates were assessed against the growth inhibition of fat-storing cells (FSC). A liver-derived growth inhibitory factor (LDGIF) was purified from ischemically damaged rat livers by chromatographies on Sephacryl S-300, CM Sepharose, hydroxyapatite, and Superose 12. The LDGIF was isolated with an overall purification of 194-fold and 40% recovery. Although LDGIF was identified as the rat liver arginase by N-terminal sequence analysis, LDGIF exists as a monomer and the purified native arginase has a trimer form. Furthermore, LDGIF has a lower enzyme activity on the hydrolysis of L-arginine and a higher inhibitory effect on proliferation of FSC than the normal rat liver arginase. The catalytic activity of LDGIF is ascribed to the monomeric characteristics of the LDGIF. Therefore, the inhibitory action of LDGIF might not be due to the arginine depletion by the catalytic activity of arginase. In conclusion, the presence of the LDGIF could interpret the clinical course that serious fibrosis is not found in the liver of patients recovering from severe hepatic necrosis due to fulminant hepatitis, suggesting that this LDGIF may provide a novel target for the prevention and treatment of hepatic fibrosis.open
Purification and characterization of a novel inhibitor of the proliferation of hepatic stellate cells
No full textAn inhibitor of the proliferation of hepatic stellate cells (HSC) was purified from rat liver by a combination of gel filtration and ion exchange chromatography. The molecular mass of this non-arginase growth inhibitory factor (NAGIF) was determined to be 38 kDa by sodium dodecyl sulfate- polyacrylamide gel electrophoresis and gel filtration. The proliferation of HSC was inhibited by NAGIF with a 50% inhibitory dose of 5 nmol/liter. The inhibitory activity of NAGIF was not limited to HSC but also affected the growth of bovine endothelial cells and 3T6 fibroblasts. However, the growth of B16 mouse melanoma was not inhibited by NAGIF. The NH2-terminal sequence of NAGIF, AEPVEPWS, is identical to an internal sequence of rat Zn-α2- glycoprotein. Although the action mode of this inhibitor remains to be investigated, it seems very likely that NAGIF is involved in the negative control mechanism of HSC growth.open
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