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Biomedical subjects

A Meager

Publications and source records attributed to A Meager.

At least 19 recordsLinked to original sources
PubMed1999

Cytokine regulation of cellular adhesion molecule expression in inflammation.

Cellular adhesion molecules (CAMs) play an essential role in tethering circulating leukocytes to the vascular endothelium at sites of inflammation. They are also instrumental in enabling leukocytes to transmigrate from blood vessels into adjacent inflamed tissues. In the absence of signals to stimulate expression of CAMs, the adhesive forces between leukocytes and the vascular endothelium are below the threshold level required to tether leukocytes. Research in the last decade has shown that several cytokines, including tumour necrosis factor alpha (TNF alpha) and interleukin-1 beta (IL-1beta), potently increase the expression of many CAMs and thus increase the adhesiveness between leukocytes and the endothelium. The CAM-inducing activity of these cytokines is therefore crucial to the regulation of inflammatory processes. Overactivation of CAM expression is linked to a number of acute and chronic inflammatory conditions, and has led to the rationale of antagonising cytokine activity and or CAM expression in order to treat these conditions. The potential application of 'adhesion' antagonists for the therapy of acute chronic inflammatory conditions is briefly discussed.

Animals↗
PubMed1998

TRANK, a novel cytokine that activates NF-kappa B and c-Jun N-terminal kinase.

We searched the expressed sequence tag database using sequence homology and identified a novel cytokine, which we have named TRANK (thioredoxin peroxidase-related activator of NF-kappa B and c-Jun N-terminal kinase). The predicted amino acid sequence of TRANK was highly homologous to that of the thiol-specific antioxidant proteins. Unlike these proteins, however, TRANK had a putative secretory signal polypeptide and was found to be secreted by cells. TRANK was expressed in most tissues and cell lines, and the gene that encodes it was mapped to chromosome Xp21-22.1. TRANK activated NF-kappa B and induced the degradation of the inhibitory subunit of NF-kappa B. In addition, TRANK up-regulated the expression of NF-kappa B-dependent gene products, ICAM-1, and inducible nitric oxide synthase. TRANK also activated c-Jun N-terminal kinase and induced the proliferation of normal human foreskin fibroblasts. Its homology with antioxidant proteins, wide distribution in tissues, and ability to activate NF-kappa B and c-Jun N-terminal kinase suggest that TRANK plays an important role in inflammation.

Amino Acid Sequence↗
PubMed1998

Interferon alpha primes early proliferative response of bone marrow cells in vivo.

Using colony-forming assays, a number of previous studies established that interferon alpha (IFN-alpha) could cause bone marrow cell (BMC) suppression. In this study, the suppressive effect of IFN-alpha is however shown to be time-dependent, occurring only 7-8 days after transfer of BMC obtained from IFN-alpha-treated mice to growth factor-containing culture medium. In contrast, in the interval before suppression is observed, BMC obtained from IFN-alpha-treated mice initially proliferated more rapidly than BMC from placebo-treated mice. These findings suggest that IFN-alpha acts in vivo to prime the proliferative responses of BMC, a hitherto unexpected action which may have clinical relevance.

Animals↗
PubMed1997

Antitumor activity of the novel human breast cancer growth inhibitor, mammary-derived growth inhibitor-related gene, MRG.

A novel human tumor growth inhibitor was identified by differential cDNA sequencing. The predicted amino acid sequence of this tumor-suppressing factor has a significant sequence homology to mouse mammary-derived growth inhibitor and thus was named mammary-derived growth inhibitor-related gene (MRG). MRG was found to be expressed in normal and benign human breast tissues but not in breast carcinomas. In situ hybridization analysis demonstrated a stage-specific MRG expression as follows. MRG was barely detectable in breast carcinomas, showed partial and weak expression in benign hyperplasia, but was expressed at a high level in normal breast epithelial cells. To determine if MRG can modulate in vivo growth of human breast cancers, we transfected a full-length MRG cDNA into MDA-MB-231 human breast cancer cells and studied the orthotopic growth of MRG transfectants versus control transfectants in the mammary fat pad of athymic nude mice. Overexpression of MRG in human breast cancer cells significantly suppressed cell proliferation in vitro and tumor growth in an orthotopic nude mouse model. These results suggest that MRG has tumor-suppressing activity, and the loss of MRG expression may be involved in the development and progression of breast cancer.

Amino Acid Sequence↗
PubMed1997

Treatment of metastatic renal cell carcinoma with subcutaneous interleukin 2: evidence for non-renal clearance of cytokines.

The circulating cytokine concentrations following administration of subcutaneous recombinant interleukin 2 (IL-2) in combination with interferon alpha and 5-fluorouracil used to treat advanced renal cancer were studied. One patient was anephric and on dialysis, and seven had normal biochemical renal function, although five had undergone single nephrectomy. The pharmacokinetics of IL-2 and changes in IL-6 and tumour necrosis factor (TNF)-alpha were essentially similar in all patients including the anephric patient, irrespective of the periods of dialysis, although at some time points, IL-2 concentrations were slightly higher in the anephric patient than in the others. These results show that for subcutaneous administration of low-dose IL-2, renal clearance of IL-2 is not important. This contrasts with high-dose, intravenous IL-2 where blood concentrations are higher and renal clearance seems to occur, perhaps because of saturation of the non-renal mechanisms of clearance. The subcutaneous route is certainly preferred if IL-2 is used in anephric patients and in those with impaired renal function, and it may be generally preferred for most purposes.

Adult↗
PubMed1997

Transforming growth factor-beta induced by live or ultraviolet-inactivated equid herpes virus type-1 mediates immunosuppression in the horse.

Up to 21 days after exposure to live or ultraviolet-inactivated equid herpesvirus type-1 (EHV-1) autologous serum from ponies caused an immunosuppressive effect if incorporated into T-cell proliferation assays to EHV-1. The suppressive factor in the sera of ponies also inhibited T-cell response to phytohaemagglutinin. Increased levels of circulating activated transforming growth factor-beta 1 (TGF-beta 1) were detected, and the suppressive activity of the serum could be reversed by antibody to TGF-beta 1. In a challenge experiment the ponies which exhibited circulating TGF-beta 1 activity succumbed to infection while the ones with similar magnitudes of T-cell responses, but no TGF-beta 1 activity, were protected. A definition of this immunosuppressive mechanism and its mode of induction must be central to the design of vaccines and to an understanding of the pathogenesis of EHV-1.

Animals↗
PubMed1997

Interferon standardization and designations.

A large number of different human and nonhuman interferon (IFN) preparations are now available for either research purposes or commercial use. Consistency of results can be achieved only through rigorous application of biologic standards and individual species designation. International standards for the potency determinations of these preparations have been produced in accordance with World Health Organization (WHO) guidelines and are available for calibrating assays. Until recently, potency has been assessed purely as a measure of antiviral activity expressed in international units. Other biologic properties are now also being considered, including antiproliferation and immunomodulation. Indirect methods of measuring IFN, such as radioimmunoassay or enzyme immunoassay, if fully validated, may also provide useful estimates of function. Reference antisera are useful for characterizing IFN preparations and for monitoring neutralization assays for detecting anti-IFN antibodies but should not have a function in assay calibration. Factors to be considered when referring to specific designations for pure IFN species include distinctions for the species of origin, any mutant or hybrid forms, the method of production, and the presence of additional glycosylation.

Animals↗
PubMed1997

Natural autoantibodies to interferons.

Natural antibodies that appear to have arisen in the absence of direct antigenic stimulation often are present in the circulation. In healthy individuals, they are of low prevalence and generally show low affinity to their respective antigens, whereas in autoimmune disease, their frequency and affinity toward specific antigens are in many cases increased. In some autoimmune disease, the spontaneous occurrence of autoantibodies to antigens that are apparently unrelated to symptoms or pathology has been observed. For example, antibodies to interferon-alpha (IFN-alpha) have been observed in patients with systemic lupus erythematosus but appear to be of no clinical significance. Natural autoantibodies to IFN-alpha have also been found in other patients, including those with insulin-dependent diabetes mellitus, heart disease, or cancer and patients who have just received allogeneic bone marrow transplantation. A major property of IFN-alpha autoantibodies is their capacity to both bind to and neutralize the biologic activity of a range of IFN-alpha subtypes and natural IFN-alpha preparations. Their origins and significance remain a matter for debate.

Antigen-Antibody Reactions↗
PubMed1996

An anti-cytokine bioactivity assay for interferons-alpha, -beta and -omega.

Interferons-alpha and -beta (IFN-alpha and -beta) are cytokines that are widely known to induce potent anti-viral activity. However, it has become increasingly apparent that IFN-alpha and -beta exert a variety of other biological effects, including anti-tumour and immunomodulatory activities and are increasingly used clinically to treat a range of malignancies, myelodysplasias and autoimmune diseases, e.g., IFN-beta for multiple sclerosis. The most widely used bioassays for the IFNs are based on their anti-viral activity, but these do not predict the biological activity of the IFNs in anti-tumour and immunomodulatory therapies. Thus, we have developed anti-cytokine-based bioassays that may be more reflective of such activity and which have several advantages over existing anti-viral bioassays. The anti-cytokine bioassay is based on the ability of IFN-alpha, -beta and -omega to inhibit granulocyte-macrophage-colony-stimulating factor (GM-CSF) induced proliferation of the erythroleukaemic cell line TF-1. This assay can take only 24 h, is sensitive to 200 fg (0.04 IU) IFN-alpha or -beta and 100 fg (0.02 IU) IFN-omega and is able to detect down to these levels in serum or plasma samples. The usefulness of anti-cytokine bioassays for IFN-alpha, -beta and -omega is not restricted to the GM-CSF/TF-1 cell format and other alternatives are available, such as erythropoietin (EPO)/TF-1 cells and EPO/UT-7-EPO cells. These assays can be made specific for each of the IFNs by including neutralising antibodies in the bioassay.

Humans↗
PubMed1996

Bioimmunoassays for proinflammatory cytokines involving cytokine-induced cellular adhesion molecule expression in human glioblastoma cell lines.

Twelve human glioblastoma/astrocytoma cell lines were tested for cellular adhesion molecule expression following cytokine induction in order to identify a cell line that would be suitable for functional cytokine bioimmunoassays. Many of the glioblastoma/astrocytoma cell lines were shown to inducibly express intercellular adhesion molecule-1 (ICAM-1, CD54) and vascular cell adhesion molecule-1 (VCAM-1) following stimulation with interleukin-1 alpha (IL-1 alpha), interleukin-1 beta (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha), tumour necrosis factor-beta (TNF-beta), and interferon-gamma (IFN-gamma), but not with any of the several other cytokines tested. The cell line U-138MG, a human glioblastoma-derived line, was the most sensitive one to IL-1 alpha/beta, TNF-alpha/beta and IFN-gamma for ICAM-1 expression, comparing well with proinflammatory cytokine-induced ICAM-1 expression in the endothelial cell hybrid EA-hy926 line, and was shown to be useful for the functional assay of the biological potencies of these individual cytokines. Such bioimmunoassays, which are developed by routine ELISA techniques, should provide valuable alternatives to existing bioassays for these cytokines.

Astrocytoma↗
PubMed1996

IL-4 and TNF-alpha-mediated proliferation of the human megakaryocytic line M-O7E is regulated by induced autocrine production of GM-CSF.

In this study, the authors examined the effects of recombinant human interleukin 4 (rhIL-4) and recombinant human tumour necrosis factor alpha (rhTNF-alpha) alone or in combination on proliferation of the human cytokine dependent myeloid cell line, M-O7e. While rhIL-4 or rhTNF-alpha alone induced only a weak proliferative response, a synergistic proliferative signal was clearly evident on stimulation of cells with a combination of both cytokines. The stimulatory effect of rhTNF-alpha is mediated predominantly by the 55-kDa TNF receptor because the agonistic monoclonal antibody htr-9 and the Trp32 Thr86 TNF-alpha mutant protein specific for this receptor type produced similar results to rhTNF-alpha. In contrast, the Asn143 Arg145 TNF-alpha mutant protein specific for the 75-kDa TNF receptor produced only minimal proliferation of M-O7e cells. Using RT-PCR, we found that rhTNF-alpha rapidly and strongly induced granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNA production, while rhIL-4 was a slow and less efficient inducer of GM-CSF mRNA. However, there was little evidence of the TNF-alpha/IL-4 combination acting synergistically on GM-CSF mRNA production as the levels of GM-CSF mRNA increased only marginally compared with IL-4 or TNF-alpha alone. Thus, the observed synergistic effect of TNF-alpha/IL-4 costimulation of M-O7e cells seems to be mediated via induction of GM-CSF secretion rather than an enhanced production of GM-CSF mRNA. Higher levels of GM-CSF were detectable in supernatants of cells treated with both rhIL-4 and rhTNF-alpha than in cells stimulated with either cytokine alone. Furthermore, addition of a neutralising antibody against GM-CSF abrogated the observed synergistic effect of rhIL-4 and rhTNF-alpha treatment, indicating that the rhIL-4/TNF-alpha combination acts to significantly increase GM-CSF release which then acts in an autocrine manner to enhance the proliferation of M-O7e cells.

Antibodies, Monoclonal↗
PubMed1996

The biological properties, assay, and standardization of interferon-alpha: a need for a WHO collaborative study.

Interferon-alpha (IFN-alpha) exists as a range of closely related, biologically active proteins and has been the subject of extensive research and clinical investigation. Standardization of IFN-alpha and the uniform reporting of IFN-alpha activity in International Units (IU) is critical to preclinical research and the clinical development of IFN-alpha products as therapeutic agents. Currently, several different IFN-alpha-containing reference preparations, established as World Health Organization (WHO) International Standards (IS) for particular IFN-alpha proteins (mixtures or single molecular species) are available for assay calibration. Nevertheless, the heterogeneous nature of IFN-alpha has raised standardization issues relating to the activity of individual IFN-alpha proteins, hence-forth termed subtypes, in the various biologic assays used for determining IFN-alpha levels. These issues include the question of parallelism of dose-response curves among particular IFN-alpha subtypes and different, naturally produced IFN-alpha subtype mixtures, for example, leukocyte IFN-alpha, and the applicability of IU of IFN-alpha activity defined by antiviral assays to alternative biologic assays, for example, antiproliferative assays. To address such issues, a WHO Consultative Group on Cytokine Standardization requested that the National Institute for Biological Standards and Control (NIBSC) and the Centre for Biologics Evaluation and Research (CBER) organize an international collaborative study to compare the activities and relative potencies of the several available IFN-alpha preparations, including those derived from human cells containing mixtures of IFN-alpha subtypes and those derived by rDNA methods containing single IFN-alpha subtypes, in different assays. To date, 111 participants in 32 countries have been recruited to the study and have agreed to assay a total of 17 different natural and recombinant IFN-alpha preparations or a defined subset thereof in specific in-house assays. The assay results generated will be statistically analyzed and evaluated to address the stated issues and to assess whether any individual IFN-alpha preparation is suitable to serve as an IS for all IFN-alpha preparations or whether more than one IS will be needed for this purpose.

Animals↗
PubMed1996

Effect of cyclo-oxygenase inhibitors and modulators of cyclic AMP formation on lipopolysaccharide-induced neutrophil infiltration in mouse lung.

1. The adult respiratory distress syndrome (ARDS) is an acute lung inflammation developed after direct or indirect contact with pathogenic agents. In the present study, a mouse model was developed to mimic this condition using aerosolized bacterial lipopolysaccharide (LPS) and to investigate the mechanisms involved in the lung inflammatory response. 2. Inhalation of LPS led to a time and dose-dependent increase in tumour necrosis factor-alpha (TNF-alpha) production and neutrophil recruitment into the bronchoalveolar lavage fluid (BALF) of Balb/c mice. Under the same conditions, neutrophil infiltration was also found in the BALF of the LPS-sensitive mouse strain C3H/HeN, but was absent in the LPS-resistant strain C3H/HeJ. Intranasal administration of murine recombinant TNF-alpha also triggered neutrophil recruitment. 3. One hour after inhalation of LPS, half of the maximal level of TNF-alpha was measured in the BALF, but only a few neutrophils were detected at this time. The peak TNF-alpha concentration was reached at 3 h, when the neutrophil amount started to increase. At 24 h, maximal neutrophil number was found in the BALF and TNF-alpha was no longer present. 4. Pretreatment of mice under different experimental conditions demonstrated that: (a) cycloheximide almost completely blocks both neutrophil recruitment and TNF-alpha production; (b) anti TNF-alpha antibodies block neutrophil recruitment; (c) indomethacin or aspirin enhance by two fold neutrophil recruitment; (d) indomethacin significantly increases TNF-alpha production 1 h after inhalation of LPS; (e) dibutyryl cyclic AMP and prostaglandin E2 (PGE2) block both neutrophil recruitment and TNF-alpha production. 5. It is concluded that aerosolized LPS in mice triggers an acute lung inflammation which can be used as a potential model of inhalational ARDS and that, strategies leading to the elevation of cyclic AMP levels in vivo can be effective in modulating LPS-induced TNF-alpha synthesis and neutrophil recruitment.

Administration, Inhalation↗
PubMed1996

Activation of the tumor necrosis factor-alpha system in the liver in chronic hepatitis B virus infection.

To determine the status of the tumor necrosis factor-alpha (TNFalpha) system in the liver in chronic hepatitis B virus (HBV) infection, hepatic expression of TNFalpha, its two receptors (TNFR-A, TNFR-B), HLA class I antigens (HLA-I), and HBV core antigen (HBcAg) were studied by immunohistochemistry in 24 patients with chronic HBV infection. TNFalpha was detected exclusively in the infiltrating mononuclear cells (MNC) in 19 of 24 patients. The expression of TNFalpha in infiltrating MNC correlated with serum markers of HBV replication and liver histology. TNFR were detected in hepatocytes, sinusoidal cells, and infiltrating MNC. The expression of TNFR correlated with liver histology (p < 0.01) but had no bearing on viral replication. There was a parallel expression of TNFalpha and TNFR (p < 0.01). Hepatocytic expression of HLA-I was increased, and this was related to liver histology but not with TNF alpha nor TNFR. These data indicate that the TNFalpha system is activated in the liver in chronic HBV infection.

Adult↗
PubMed1995

Evaluation of assay designs for assays using microtitre plates: results of a study of in vitro bioassays and immunoassays for tumour necrosis factor (TNF).

Biological assays for tumour necrosis factor (TNF) are primarily based on its cytotoxic effect in tumour cell lines, and many of these bioassays are carried out using microtitre plates. Many immunoassays for TNF also routinely use microtitre plates. Data from an international collaborative study, carried out by twenty participants in nine countries, each of whom evaluated seven different ampouled preparations of human tumour necrosis factor alpha (hTNF-alpha), one ampouled preparation of human tumour necrosis beta (hTNF-beta) and one ampouled preparation of mouse tumour necrosis factor alpha (mTNF-alpha) provided a unique opportunity for a broadly based evaluation and comparison of assay designs and results. The results of this evaluation can be applied to a wide range of in vitro assays based on cell cytotoxicity or proliferation. The results of this evaluation indicated that although it is difficult to achieve control of all factors which contribute to the variability of assay responses, assays may be designed to provide measures of the variation due to some factors and to improve reliability of estimates of relative potency.

Animals↗