Identification of a new Mpl-interacting protein, Atp5d.

Thrombopoietin (TPO) can regulate hematopoiesis and megakaryopoiesis via activation of its receptor, c-Mpl, and multiple downstream signal transduction pathways. Using the cytoplasmic domain of Mpl as bait, we performed yeast two-hybrid screening, and found that the protein Atp5d might associate with Mpl. Atp5d is known as the δ subunit of mitochondrial ATP synthase, but little is known about the function of dissociative Atp5d. The interaction between Mpl and Atp5d was confirmed by the yeast two-hybrid system, mammalian two-hybrid assay, pull-down experiment, and co-immunoprecipitation study in vivo and in vitro. An additional immunofluorescence assay showed that the two proteins can colocalize along the plasma membrane in the cytoplasm. Using the yeast two-hybrid system, we tested a series of cytoplasmic truncated mutations for their ability to bind Atp5d and found an association between Atp5d and the Aa98-113 domain of Mpl. The dissociation of Atp5d from Mpl after TPO stimulation suggests that Atp5d may be a new component of TPO signaling.

Inhibition of STAT3 and ErbB2 suppresses tumor growth, enhances radiosensitivity, and induces mitochondria-dependent apoptosis in glioma cells.

PURPOSE: Constitutively activated signal transducer and activator of transcription 3 (STAT3) and ErbB2 are involved in the pathogenesis of many tumors, including astrocytoma. Inactivation of these molecules is reported to result in radiosensitization. The purpose of this study was to investigate whether inhibition of STAT3, ErbB2, or both could enhance radiotherapy in the human glioma model (U251 and U87 cell lines). METHODS AND MATERIALS: The RNAi plasmids targeting STAT3 or ErbB2 were constructed, and their downregulatory effects on target proteins were examined by immunoblotting. After combination treatment of RNAi with or without irradiation, the cell viability was determined using 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and clonogenic assays. The in vivo effect of combined treatment was determined using the U251 xenograft model. The apoptosis caused by the inhibition of STAT3 and ErbB2 was detected, and the mechanism involved in the apoptosis was investigated, including increases in caspase proteins, mitochondrial damage, and the expression of key modulating protein of different apoptosis pathways. RESULTS: Transfection of U251 cells with STAT3 or ErbB2 siRNA plasmids specifically reduced their target gene expressions. Inhibition of STAT3 or ErbB2 greatly decreased glioma cell survival after 2, 4, or 6 Gy irradiation. Inhibition of STAT3 and ErbB2 also enhanced radiation-induced tumor growth inhibition in the U251 xenograft model. Furthermore, the suppression of either STAT3 or ErbB2 could induce U251 cell apoptosis, which was related primarily to the mitochondrial apoptotic pathway. CONCLUSIONS: These results indicated that simultaneous inhibition of STAT3 and ErbB2 expression can promote potent antitumor activity and radiosensitizing activity in human glioma.

[Biological effect of gamma-rays and LPS on the murine macrophage cell line RAW264.7 in mice].

AIM: To explore the effect of activating the murine macrophage cell line RAW264.7 by both gamma-rays and lipopolysaccharide (LPS) and to study the expression of calcium-binding protein S100A8 induced by gamma-rays and LPS. METHODS: The RAW264.7 cells were observed by phase contrast microscope. The cell cycle and the level of reactive oxygen intermediates (ROIs) were detected by flow cytometry (FCM). The production of NO was measured by colorimetric Griess reaction. The mRNA expression of S100A8 was recorded by real-time quantitative RT-PCR method. RESULTS: The exposure of RAW264.7 cells to gamma-rays and LPS resulted in the morphological change of cells, the rise of cells number of aneuploid and apoptosis, and the rise of the level of ROI, NO and S100A8 mRNA. The effect of using both gamma-rays and LPS was stronger than that of single gamma-rays or LPS treatment. CONCLUSION: The mechanism of using both gamma-rays and LPS for activating macrophages is owing to the various biological effects including the change of cell cycle, the change of the level of messenger molecules and the expression of inflammation factor such as S100A8. The expression of S100A8 gene is closely correlated with the function and state of macrophages.

Melissoidesin G, a diterpenoid purified from Isodon melissoides, induces leukemic-cell apoptosis through induction of redox imbalance and exhibits synergy with other anticancer agents.

Melissoidesin G (MOG) is a new diterpenoid purified from Isodon melissoides, a plant used in Chinese traditional medicine as antitumor and anti-inflammatory agents. In our study, MOG was shown to specifically inhibit the growth of human leukemia cell lines and primary acute myeloid leukemia (AML) blasts via induction of apoptosis, with the evidence of mitochondrial DeltaPsim loss, reactive oxygen species production, caspases activation and nuclear fragmentation. Furthermore, it was shown that thiol-containing antioxidants completely blocked MOG-induced mitochondrial DeltaPsim loss and subsequent cell apoptosis, while the inhibition of apoptosis by benzyloxy-carbonyl-Val-Ala-Asp-fluoromethylketone only partially attenuated mitochondrial DeltaPsim loss, indicating that MOG-induced redox imbalance is an early event upstream to mitochondrial DeltaPsim loss and caspase-3 activation. Consistently, it was found that MOG rapidly decreased the intracellular glutathione (GSH) content in a dose-dependent manner and the significance of GSH depletion in MOG-induced apoptosis was further supported by the protective effects of tert-butylhydroquinone (tBHQ) and the facilitative effects of DL-buthionine (S,R)-sulfoximine (BSO). Furthermore, it was showed that GSH depletion induced by MOG rendered some leukemia cell lines more sensitive to arsenic trioxide (As2O3), doxorubicin or cisplatin. Additionally, the synergistic apoptotic effects of MOG with As2O3 were detected in HL-60 and primary AML cells, but not in normal cells, suggesting the selective toxicity of their combination to the malignant cells. Together, we proposed that MOG alone or administered with other anticancer agents may provide a novel therapeutic strategy for leukemia.

[Apoptotic characteristics of spleen lymphocyte in mice irradiated by lethal dose and its relationship to the expression of Bax and Bcl-XL proteins].

OBJECTIVE: To observe the apoptotic characteristics of mouse spleen lymphocyte after lethal dose gamma-irradiation and its relationship to the expression of Bax and Bcl-XL proteins. METHODS: Two hundred and twenty-five second-grade C57 mice were randomly divided into six groups of 0, 6, 9, 12, 15 and 20 Gy. They were sacrificed by dislocation and samples were taken on 1-28 days after whole body single gamma-irradiation. Lymphocyte apoptosis and necrosis were analyzed by TdT-mediated dUTP nick end labeling (TUNEL) and flow cytometry (FCM) techniques. The expression of Bax and Bcl-XL proteins were estimated by immunohistochemical method. RESULTS: (1) The number of peripheral white blood cells of mice increased temporarily at 6 hours after radiation, thereafter, began to decrease rapidly, which reached the minimum on day 7 and recovered normal level basically one month after 6 Gy gamma-irradiation. (2) Apoptotic rate of spleen lymphocytes increased significantly, peaking at 6 hours after radiation, which was found to have a dose-response relationship during 6-24 hours after < or =12 Gy irradiation, but decreased after > or =15 Gy irradiation. (3) It was confirmed by FCM that the apoptotic rate of spleen lymphocytes increased along with the elevation of radiation dose. However, the apoptotic rate began to decrease and the necrotic rate rose distinctively after > or =15 Gy irradiation. The analysis of DNA gel electrophoresis supported above-mentioned results. (4) The expression of Bax protein in spleen lymphocyte enhanced at 6 hours after 6 Gy gamma-irradiation and peaked by 12 Gy-irradiation, showing a dose-dependent pattern, but which was not be found after > or =15 Gy gamma-irradiation. On the other hand, the expression of Bcl-XL protein reduced persistently with the increase of radiation dose, and also presented a better dose-dependent effect after < or =12 Gy irradiation. CONCLUSION: After 6-12 Gy gamma-irradiation, the apoptosis is the major death way of spleen lymphocyte, while both necrosis and apoptosis are important death pathways after > or =15 Gy irradiation. Pro-apoptotic Bax and anti-apoptotic Bcl-XL play an important role in the apoptotic regulation of spleen lymphocytes induced by lethal dose radiation.

[The effects of acute large dose of gamma-irradiation on immune function of mice].

AIM: To observe the effects of large dose of gamma-irradiation on immune function of mice. METHODS: 225 cleaning-grad C57 mice, weighing(20+/-2.0) g, were randomly divided into 6 groups, and treated with 0, 6, 9, 12, 15 and 20 Gy gamma-irradiation. At different times after irradiation, lymphocytes were collected and lymphocytic apoptosis and T cell subsets were analyzed by TUNEL, May-Grunwald Giemsa (MGG) staining and flow cytometry. RESULTS: (1)At early stage(1-14) d after radiation, the apoptotic rate of peripheral blood lymphocytes increased significantly and 12 Gy radiation resulted in the highest apoptotic rate. The number of T lymphocytes and T cell subsets decreased continuously in a dose-dependent manner. CD8(+) T cells were the most sensitive in T cell subsets to irradiation. These results suggested that early severe injury might be one of the important features of immune injury caused by acute radiation. (2) One month after radiation, the apoptotic rate of lymphocytes began to decrease and T lymphocytes and their subsets recovered gradually. However, neither the lymphocytic apoptotic rate nor the number of CD3(+) T cells and CD8(+) T cells, recovered to normal level, indicating that large dose of radiation had severe remote effects on immune function. CONCLUSION: Apoptosis of a large number of peripheral blood lymphocytes in early stage after radiation may result in sharp reduction of T cell number and late immune function depression.

[Radioprotection of recombinant human interleukin-3 and granulocyte-macrophage colony-stimulating factor on peripheral lymphocytes of rhesus monkey irradiated by 3.0 Gy gamma-rays].

OBJECTIVE: To observe the radioprotection of recombinant human interleukin-3 (rhIL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF) and rhIL-3 (rhIL-3+GM-CSF) on peripheral lymphocytes of rhesus monkey irradiated by 3.0 Gy gamma-rays, and attempt to provide evidence of cytokines used effectively in the therapy of acute radiation sickness. METHODS: Thirty rhesus monkey used in the experiment were randomly divided into six groups of rhIL-3 20 microg.kg -1.d -1, 60 microg.kg -1.d -1 GM-CSF 10 microg.kg -1.d -1 IL-3 20 microg.kg -1.d -1 +GM-CSF 10 microg.kg -1.d -1 radiation control and normal control. 21 d after whole body gamma-irradiation and subcutaneous injection of cytokines, T lymphocyte and its subsets, Bax/Bcl-2 proteins in lymphocytes were determined by immunohistochemical staining with alkaline phosphatase, and lymphocyte apoptosis was detected by TdT-mediated dUTP nick end labeling (TUNEL) technique. RESULTS: (1) After irradiation the quantities of peripheral lymphocyte, T cell and its subsets obviously decreased as compared with those of normal controls. For instance, the percentages of lymphocyte, T, T H and Ts cells in radiation control group reduced to 44 percent, 42 percent, 41 percent and 57 percent of normal controls, respectively. (2)After radiation the reduction of lymphocyte, T, T H and Ts cells were evidently improved by injection of GM-CSF and GM-CSF+IL-3, The T,T H cells in GM-CSF and GM-CSF+IL-3 groups were respectively elevated by 1.57 and 1.76 fold, as well as 1.48 and 1.72 fold of radiation controls. (3) A large amount of lymphocyte apoptosis was found after radiation, GM-CSF and GM-CSF+IL-3 treatment could distinctively inhibit abundant lymphocyte apoptosis induced by acute irradiation,the apoptotic rates of lymphocytes in GM-CSF and GM-CSF+IL-3 groups reduced to 41 percent and 48 percent respectively when compared with that of radiation controls. CONCLUSION: A definite dose of GM-CSF and GM-CSF+IL-3 could suppress the reduction of lymphocyte, T and T H cells and lymphocyte apoptosis induced by 3.0 Gy gamma-irradiation. It confirms that inhibition of GM-CSF and GM-CSF+IL-3 on lymphocyte reduction as well as apoptosis might be one of the major causes to alleviate radiation injury of lymphocytes and improve the immunological function.

Expression of alpha and beta Genes of Human Hemoglobin in Escherichia coli.

Total RNA was isolated from human erythrocyte. cDNA fragments coding for alpha and beta genes of human hemoglobins were obtained through RT-PCR and were ligated to plasmid pT7-Blue. Then fragments of alpha and beta genes were cut off and ligated with plasmid pBV220. Sequences identical compared with the published ones were confirmed by DNA sequencing. Bacteria harbouring expression plasmid were induced at 42 degrees, and a band of expressed protein of 16 kD was found in PAGE.