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Biomedical subjects

M N Thang

Publications and source records attributed to M N Thang.

At least 37 records · Page 2Linked to original sources
PubMed1988

Reduction of transferrin receptor expression by interferon gamma in a human cell line sensitive to its antiproliferative effect.

Interferon gamma (IFN gamma) reduced 125I-transferrin binding to WISH cells which are sensitive to its antiproliferative effect. IFN gamma did not affect transferrin binding to Daudi cells or phytohemagglutinin-stimulated human lymphocytes, neither of which respond to its antigrowth action. Scatchard analyses of the equilibrium binding of 125I-transferrin to WISH cells exposed to IFN gamma revealed a decrease in the number of cell surface receptors but no change in the apparent association constant compared with control cells. When 125I-transferrin binding was measured using detergent-extracted cells, the IFN-induced reduction of binding was smaller than with intact cells. This suggests that in WISH cells, IFN gamma not only reduced the total number of transferrin receptors, but also modified the process of receptor internalization and recycling. Labeling of newly synthesized receptors with [35S]-methionine indicated that a reduction in the biosynthesis might account for the decrease in the total number of transferrin receptors in IFN gamma-treated cells. Our results suggest that the antigrowth effect of IFN gamma is at least partly due to its inhibitory action on transferrin receptor expression leading to iron starvation.

Cell Division↗
PubMed1988

Effect of endogenous and exogenous interferons on the differentiation of human monocyte cell line U937.

The effect of interferons (IFNs) on the differentiation of hematopoietic cells was examined with the human monocyte cell line U937. The differentiation of U937 was induced by hydroxyvitamin D3 and was evaluated through the study of specific markers. The induction of the U937 differentiation was associated with a production of IFN and with a marked increase in (2'5') oligoadenylate synthetase. Addition of anti-IFN-alpha/beta antibodies inhibited the enhancement of (2'5') oligoadenylate synthetase and reduced the inhibitory effect of hydroxyvitamin D3 on cell growth. Nevertheless, neutralization of endogenous IFN excreted during U937 cell maturation did not modify the expression of the differentiation markers examined. Exogenous natural IFN-alpha, IFN-beta, or recombinant (r) IFN-gamma, when added to the culture medium, did not promote a "global" U937 differentiation. Most of the differentiation markers, except for reduction of nitroblue-tetrazolium, were not induced by IFN-alpha or -beta. However, rIFN-gamma was able to induce the appearance of several monocytic membrane markers at an extent comparable or slightly inferior to that elicited by hydroxyvitamin D3. Different effects on the expression of HLA antigens were obtained with these IFNs: IFN-alpha or -beta enhanced mainly class I HLA antigen expression, whereas rIFN-gamma increased selectively the expression of class II HLA DC1 but not HLA DR antigens. In contrast, phytohemagglutinin-leukocyte conditioned medium elicited a marked and selective enhancement of the expression of HLA-DR antigens. This induction of HLA DC1 antigens by rIFN-gamma was not observed in two other leukemic cell lines (HL60 and HEL). The present study shows that IFN-alpha or -beta may participate in the antiproliferative effect occurring during cellular differentiation, while IFN-gamma may be involved in the induction of the expression of specific monocytic markers involved in cellular immunoregulation.

2',5'-Oligoadenylate Synthetase↗
PubMed1988

Stimulation of natural killer cytotoxicity by long-term treatment with double-stranded polynucleotides without induction of hyporesponsiveness.

Treatment of Wistar/AG rats with a single i.p. injection of 1 mg/kg of synthetic double-stranded polynucleotides, either polyadenylic-polyuridylic acid (rAn.rUn), or a mismatched analogue of polyinosinic-polycytidylic acid (rIn.r(C12U)n), enhanced the cytotoxicity of natural killer (NK) cells among peripheral blood leukocytes and lung intracapillary leukocytes (LICL). The enhancement reached a peak 24 h after treatment and returned to control values after 4 days. In rats given repeated injections of double-stranded polynucleotides (2 per week), the NK cytotoxicity expressed by LICL reached more than ten times (in lytic units) the control levels between day 8, after 3 injections, and day 360, after 100 injections. No hyporesponsiveness was observed. Moreover, NK activity was frequently and significantly higher in rats given multiple injections than in those given a single injection. In rats with experimentally induced P77 lung fibrohistiocytoma colonies, repeated injections of rIn.r(C12U)n stimulated NK activity and reduced the number of metastatic nodules from 172 to 19. The same significant reduction (from 172 to 27) was also observed in animals given repeated injections of rAn.rUn. However, with two models of spontaneous metastases, significant reduction in lung metastases (M37 bronchioloalveolar carcinoma) or lack of effect (S4T19 rhabdomyosarcoma) were observed.

Animals↗
PubMed1987

Cloned human interferons alpha: differential affinities for polyinosinic acid and relationship between molecular structure and species specificity.

The HuIFN-alpha A and HuIFN-alpha D interferons, produced by two independent recombinant bacterial clones, have different affinities for polyinosinic acid (poly I). The monomeric form HuIFN-alpha A (FMM), but not the HuIFN-alpha D, binds to poly (I)-agarose and is protected by poly (I) from thermal inactivation. Other subtypes of HuIFN-alpha A including the monomer SMM and oligomers have no affinity for this polynucleotide. In addition, these interferons show different target cell preferences in agreement with our previous suggestion (23) that the polynucleotide binding domain may be responsible for species specificity. Two significant observations are 1) the fractions of HuIFN-alpha D and HuIFN-alpha A unbound on poly (I)-agarose show higher antiviral inducing activity on heterologous (MDBK) than on homologous (WISH) cells, whereas they induce about the same activity of 2'5' oligoadenylate synthetase in these two cell lines. These fractions are also active on L929 cells. 2) The bound fraction of HuIFN-alpha A induces almost the same antiviral and 2'5' oligoadenylate synthetase activities in MDBK and in WISH cells but neither activity in L929 cells.

2',5'-Oligoadenylate Synthetase↗
PubMed1987

2',5'-Oligoadenylate synthetase expression is induced in response to heat shock.

Hyperthermia (45 degrees C) induced the synthesis of a characteristic heat-shock protein of 70,000 daltons (70 hsp) in Madin-Darby bovine kidney (MDBK) cells. In addition, subsequent to heat shock, there was a substantial increase in the 2',5'-oligoadenylate synthetase (2',5'-A synthetase) activity in both MDBK and human WISH cells. However, in contrast to 70 hsp synthesis, which reached its maximum 3 h after cell transfer from 45 to 37 degrees C, increase in 2',5'-A synthetase expression, conspicuous after 6 h, attained its maximum only 18 h after transfer. Another interesting observation is that, during recovery at 37 degrees C, the cells released into the medium heat-shock-induced factor(s) (HSIF) capable of inducing an increase in 2',5'-A synthetase activity in fresh MDBK cells. HSIF behaves as a polypeptide with a molecular weight of more than 5,000; it is relatively heat stable and sensitive to acidic treatment. HISF seems different from interferon (IFN) since: 1) no detectable antiviral state developed after infection in cells treated with HSIF; 2) antibovine IFN antibodies did not abolish the inducing capacity of HSIF; 3) IFN had an additive effect on the inducing capacity of HSIF, and 4) HSIF released from bovine cells induced a net enhancement of 2',5'-A synthetase activity in human WISH cells. The first three of these observations applied also to heat-shocked MDBK cells.

2',5'-Oligoadenylate Synthetase↗
PubMed1987

Relationship between inhibition of cell growth and of transferrin receptor expression by interferon (IFN) alpha: studies in IFN-sensitive and IFN-resistant Daudi cells.

We previously showed that treatment of different cell lines with interferon-alpha (IFN-alpha) concurrently inhibited both cell growth and the rise observed in 125I-labelled transferrin binding when cells are exposed to culture conditions that stimulate proliferation. To gain insight into the relationship between these two IFN-induced inhibitory processes, we investigated the effect of IFN-alpha on the binding of 125I-labelled transferrin to Daudi cells sensitive or resistant to its antiproliferative action. We found a close correlation between the ability of IFN-alpha to inhibit cell growth and to inhibit transferrin receptor expression. Since growth inhibition induced by other agents is not always accompanied by an inhibition of transferrin receptor expression, the previous and present observations suggest that the inhibitory effect of IFN on this expression is at least one of the mechanisms by which IFN inhibits cell proliferation. We also observed that IFN-alpha did not modify transferrin receptor biosynthesis in IFN-sensitive Daudi cells, suggesting that IFN-alpha may change the processing of the transferrin receptor molecules, making them unable to bind transferrin.

Cell Cycle↗
PubMed1986

Multiple molecular forms of interferon display different specific activities in the induction of the antiviral state and 2'5' oligoadenylate synthetase.

Both Hu IFN-alpha A and Hu IFN-alpha D, produced by two independent recombinant bacterial clones, are mixtures of monomers, dimers and trimers. These forms, when assayed individually in heterologous MDBK cells, induced different degree of antiviral and 2'5' oligoadenylate synthetase (2'5' A synthetase) activities: the antiviral activity of the monomer is greater than that of the dimer and the trimer, whereas the activity of 2'5' A synthetase induction is lower with the monomer than with the dimer or the trimer. Similar differences are also observed on human cells. Compared to the mononeric form, the dimeric and the trimeric forms of Hu IFN-alpha A show higher antiviral inducing activity on heterologous MDBK cells than on homologous WISH cells, whereas the 2'5' A synthetase inducing activity in these two cell lines is about the same. Thus for the same antiviral activity, the trimer or the dimer compared to the monomer are much better inducers of the 2'5' A synthetase on human than on MDBK cells.

2',5'-Oligoadenylate Synthetase↗
PubMed1985

Chloroquine impairs the interferon-induced antiviral state without affecting the 2',5'-oligoadenylate synthetase.

Chloroquine, a weak base which raises the pH in acidic cellular compartments such as lysosomes and endosomes, counteracts the induction by interferon of the antiviral state but not that of the 2',5'-oligoadenylate synthetase in three different types of cell lines (MDBK, WISH, and L929). Active interferon is recovered in crude extracts of cells which have been treated with interferon and chloroquine together, but not in extracts of cells treated with interferon alone, indicating that chloroquine has inhibited the intralysosomal proteolysis of interferon. A low pH-dependent event in the intracellular fate of interferon (perhaps its intralysosomal degradation) is, therefore, necessary for the establishment of the antiviral state but not for the induction of the 2',5'-oligoadenylate synthetase.

2',5'-Oligoadenylate Synthetase↗
PubMed1985

Induction of (2'-5') oligoadenylate synthetase activity during granulocyte and monocyte differentiation.

Variations in the (2'-5') oligoadenylate synthetase (2-5 A synthetase) level were examined prior to and during the differentiation in culture of the human monocyte cell line U937 and the promyelocytic cell line HL60 in an attempt to reveal whether the enzyme is actively involved in hematopoietic cell maturation. The basal level of this enzyme was much higher in U937 than in HL60 cells. The activity of 2-5 A synthetase was enhanced in both cell lines in response to alpha, beta interferons. During cell differentiation, ten markers were measured. The level of the enzyme rose during the process of cellular maturation in both cell lines. The 2-5 A synthetase activity observed in differentiated HL60 and U937 cells was comparable to that observed in mature normal granulocytes and monocytes respectively. Induction of U937 differentiation by chemicals was associated with detectable production of IFN. The increase in enzyme activity observed was mostly dependent on endogenous production of interferon, since it was inhibited by interferon antibodies. Kinetic studies showed that in U937 cells 2-5 A synthetase was expressed prior to several of the differentiation markers. The rise in the enzyme's level observed during the differentiation of HL60 cells was independent of endogenous production of interferon, since it was not inhibited by the addition of anti-interferon antibodies. These results suggest that different biochemical and molecular mechanisms are responsible for the induction of 2-5 A synthetase observed during the differentiation of hematopoietic cells. In any case, 2-5 A synthetase can be considered as a biochemical marker of cell status and differentiation in hematopoietic cells.

2',5'-Oligoadenylate Synthetase↗
PubMed1985

In vivo augmentation of rat lung natural killer cell activity and inhibition of experimental metastases by double-stranded polynucleotides.

The in vivo effect on natural killer cell activity of the compound rln X r(C12 X U)m, a mismatched nontoxic analogue of polyinosinic-polycytidylic acid [rln X rCn], was tested in inbred Wistar AG rats by measuring the natural killer cell activity of lymphocytes freshly isolated from lung capillaries. Lysis was measured in a 4-h chromium release assay using YAC-1 or syngeneic P77 lung tumor cells as target. Treatment of an animal with rln X r(C12 X U)n substantially enhanced natural killer cell activity to an extent comparable to the increase produced by rln X rCn. This boosting of natural killer activity was correlated closely with a decrease in the incidence of experimental pulmonary metastasis. However, the beneficial effect lasted for only a short period after stimulation, due to the transient nature of double stranded polynucleotide enhancement and to the concomitantly rapid extravasation of tumor cells into the lung parenchyma. It is concluded that natural killer cells are important in host defense against circulating tumor cells and can be boosted by nontoxic mismatched double stranded polynucleotides.

Animals↗
PubMed1984

(2'-5') Oligoadenylate synthetase in the maturation of rabbit reticulocytes.

The (2'-5') oligoadenylate synthetase normally found in interferon-treated cells has also been detected in considerable amounts in normal rabbit reticulocytes not exposed to interferon. The activity of this enzyme has been followed during the development of the reticulocytes to erythrocytes. A high level was found just after the formation of reticulocytes and this activity decayed with a half-life of about 3 days. In lymphocytes the (2'-5') oligoadenylate synthetase was found to stay at a constant level, which indicates the absence of interferon in the plasma.

2',5'-Oligoadenylate Synthetase↗
PubMed1983

Interferon affects intracellular calmodulin levels.

Interferon lowers calmodulin levels in two cell lines sensitive to its antiproliferative effect. Further, in synchronized cells, interferon strongly inhibits the increase in calmodulin observed when control cells enter the S phase, and concomitantly inhibits DNA synthesis. Calmodulin has been implicated in the control of cell proliferation and an increase in this protein seems to be necessary for the progression of cells into the S phase of the cell cycle. Therefore, the effect of interferon on calmodulin content might constitute part of the molecular mechanism by which interferon inhibits DNA synthesis.

Animals↗
PubMed1983

Purification of highly radioactive mouse interferon produced by Ehrlich ascites tumour cells induced by Sendai virus.

Mouse interferon (IFN) was produced to high titres after induction of Ehrlich ascites tumour cells with Sendai virus by using an improved procedure. The IFN molecules were labelled during their synthesis by the incorporation of [3H]leucine and [3H]lysine. Electrophoretically homogeneous labelled IFN with a molecular weight of 34000 was obtained after a two-step purification procedure using poly(I)-agarose and octyl-Sepharose column chromatography followed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The specific radioactivity of this IFN was about 10 ct/min/IFN unit.

Animals↗
PubMed1983

Clinical value of the determination of an interferon-induced enzyme activity: studies of the 2'5' oligoadenylate synthetase activity in peripheral blood lymphocytes of patients.

The 2'5' oligoadenylate synthetase (2'5' A synthetase) is one of the interferon-induced enzymes. The measurement of its activity may thus reveal the presence of interferon, which is one of the body's non-specific antiviral, antitumor, and immunoregulatory agents. We found a constant level of this enzyme activity (mean value: 0.31 units +/- 0.13 S. D.) when measured in the white blood cells of healthy subjects (104). The majority of the patients with viral (27/30), bacterial (13/16) and autoimmune (15/16) diseases showed a 2'5' A synthetase activity greater than 0.57 units (mean value of the control + S. D.). Conversely the 2'5' A synthetase activity level was normal or low in malignancies and in diseases depending on other aetiologies than those described above. Therefore this simple an rapid biochemical assay seems to be useful for clinical study of infectious and inflammatory diseases.

2',5'-Oligoadenylate Synthetase↗