Interaction of interferon with other cytokines

Cytokine and protease glycosylation as a regulatory mechanism in inflammation and autoimmunity

Cytokines are locally produced hormones that alert the innate and specific immune systems. Many cytokines induce, enhance and govern the traffic of leukocytes. An important mechanism in cell trafficking and migration through endothelial basement membranes and connective tissues is the cytokine-regulated production of matrix degrading proteases. The latter include the serine proteinases of plasminogen activation and metalloproteinases such as collagenases, stromelysins and gelatinases. Many cytokines and all known matrix proteinases are glycoproteins and thus occur as sets of glycoforms. The relation between structures and functions of these glycoproteins has already been probed extensively at the protein level but not yet at the carbohydrate level. Attached oligosaccharides target the cytokines and proteinases to specific cellular receptors and matrix binding sites. In addition, a number of cytokines possess lectin-like functions and may thus interact with carbohydrates of the host or parasites. These intermolecular interactions influence for instance the compartmentalisation, the cell- and tissue-specific distribution and the pharmacokinetics of cytokines and proteinases. Attempts were done to deduce structure-function rules for the intramolecular effects of carbohydrates on cytokines and matrix proteinases. The relatively voluminous N-linked sugars downmodulate the specific activities of enzymes and cytokines. Because in host stress reactions (infection, inflammation, trauma) N-linked glycosylation is less efficient, glycosylation may constitute an important regulatory mechanism in the cytokine network and in multi-enzyme cascades.

Regulation of macrophage gene expression by T-cell-derived lymphokines

Cytokines secreted from antigen-specific T lymphocytes provide important positive and negative control of inflammation through their effects on non-antigen-specific inflammatory leukocytes. These effects often involve modulation of gene expression. Lymphokine-inducible macrophage gene expression is largely controlled at the level of transcription. Multiple cis-acting sequence motifs cooperate with one another to produce patterns of expression that are relatively unique to individual genes. Members of trans-acting transcription factor families, which recognize related regulatory sequence elements, participate frequently in complex protein-protein interactions that generate remarkable complexity in terms of the number of potential combinations and the consequential functional differences exhibited by each combination. Thus, the remarkable plasticity of immune-mediated inflammation derives from combinations of finite numbers of options at several points in the cellular and molecular sequence.

Interferon-alpha 2b inhibits proliferation of human Tenon's capsule fibroblasts

To evaluate the potential of interferon-alpha 2b (IFN-alpha) as an antifibrotic treatment after glaucoma filtering surgery, we studied its ability to inhibit mitogen-induced proliferation of human Tenon's capsule fibroblasts in vitro, as shown by [3H]-thymidine incorporation. IFN-alpha inhibited fetal calf serum-induced proliferation in a dose-dependent manner in concentrations ranging from 10 to 10,000 IU/ml (P < 0.001). Inhibition was also found when IFN-alpha was added prior to the mitogen (P = 0.001); this inhibitory effect lasted at least 3 days. We suggest that IFN-alpha deserves further evaluation as a possible agent for the control of ocular fibrosis.

Ethanol enhances immunosuppression induced by cocaine

Use of cocaine concurrently with alcohol is prevalent among cocaine addicts. Cocaine has been shown to inhibit phytohemagglutinin- and ConA-induced proliferation of T-lymphocytes, NK cell cytotoxicity, and phagocytic activity of peritoneal macrophages. In some studies no effects of cocaine on the immune response have been observed, although on the contrary, others show it increased the NK cell activity and serum antibody response to T-dependent antigen. Effects of cocaine on the immune system may be mediated by its neurostimulatory action on the hypothalamo-pituitary-adrenal axis. ACTH, beta-endorphine, and corticosterone released under the action of cocaine exert various inhibitory effects on the immune function. We studied the immunotoxic effect of cocaine, combination of cocaine with ethanol, and cocaethylene, a derivative formed from cocaine and ethanol in the body, on the mitogen-stimulated production of cytokines by splenocytes. C57BL mice were injected twice daily with 20 mg/kg cocaine or equivalent dose of cocaethylene and received a liquid Lieber-DeCarli diet containing ethanol (26% of total calories) or isocaloric amount of maltose-dextrin. After 3 weeks of treatment, cocaine and cocaethylene caused a significant decrease of the spleen weight and total number of splenocytes. In splenocytes isolated from the cocaine- or cocaethylene-treated mice, mitogen-stimulated production of gamma-interferon, tumor necrosis factor, and interleukin-2 was suppressed, in all cases more severely when cocaethylene was used. Thus, formation of cocaethylene during simultaneous consumption of cocaine and ethanol may enhance the immunotoxicity of cocaine.

Impaired NK response of cancer patients to IFN-alpha but not to IL-2: correlation with serum immunosuppressive acidic protein (IAP) and role of suppressor macrophage

In vitro NK responses of cancer patients (N = 21) to rIFN-alpha A and rIL-2 were examined. The serum concentration of IAP (immunosuppressive acidic protein) was determined in parallel. Five out of seven patients whose serum IAP contents were within the normal range (270 micrograms/ml to 470 micrograms/ml), had their NK activities significantly augmented by rIFN-alpha A and rIL-2. On the other hand, NK cells from ten out of fifteen patients whose serum IAP concentrations were 650 micrograms/ml or more, were not activated by rIFN-alpha A. NK cells of these fifteen patients yet were capable of responding to rIL-2. NK cells from cancer patients, however, became responsive to rIFN-alpha A by either removal of adherent cells or treatment with indomethacin. Therefore, macrophages in PBMC of cancer patients with high serum IAP levels seem to selectively suppress NK response to rIFN-alpha A by an indomethacin-sensitive mechanisms. It was further shown that PGE2 was not the mediator of this suppression.

Cytokines involved in monocyte mediated tumor cell death and growth inhibition in serum-free medium

In a serum-free culture system, the release of TNF, lI-1, lI-6, IFN-alpha, and IFN-beta during interaction of elutriated human monocytes (MO) with human tumor cells (TC) was studied by ELISA-technique. Contributions of these cytokines to inhibition of TC-growth and to induction of TC-death by supernatants (SU) gained from such MO/TC-interaction cultures were investigated using affinity chromatography for removal of individual cytokines. Although the TC used are relatively insensitive to recombinant human TNF, withdrawal of TNF causes 50% to 75% reduction of SU-induced TC-death rates, suggesting that susceptibility to TNF is raised during MO/TC-interaction by the other cytokines. Individual removal of other cytokines does not cause reduction of SU-mediated TC-death. However, combined withdrawal of lI-1 and IFN-alpha/beta causes in 2 of 4 TC-lines significant reduction of TC-death. Combined removal of TNF, IFN-alpha/beta, lI-1, and lI-6 leads to complete prevention of SU-mediated growth inhibitory and lytic effects, suggesting that besides these cytokines other signals are not involved significantly. SU-effects can be mimicked by appropriate combinations of authentic cytokines. The response of TC to SU- or cytokine-exposure is strikingly dependent on TC-density, leading at subconfluent TC-density exclusively to inhibition of growth and at postconfluent TC-density to induction of cell death. The principal effect of SU or cytokine combinations in this context seems to be the activation of growth inhibitory signal transduction pathways leading to TC-death in postconfluent TC-populations exclusively if growth stimulatory pathways are activated at the same time. Mouse L cells do not follow this reaction pattern: Their death is exclusively dependent on the presence of TNF in SU and they die upon SU-exposure at postconfluent as well as at subconfluent cell density.

Cytokines and proteases in invasive processes: molecular similarities between inflammation and cancer

Tumor-derived serine proteinases and metalloproteinases have been associated with invasion and metastasis of cancer cells. Leukocytes, particularly monocytes/macrophages and neutrophils, actively synthesize and store these proteolytic enzymes. The production by tumor cells of chemotactic factors that attract white blood cells raises questions that are important for the basic researcher as well as the clinical scientist. Are the proteinases, which have the capacity to dissolve the extracellular matrix and by this solubilization promote cell migration, the same in tumor cells as in normal cells? Is the production of chemotactic factors by tumor cells a coincident epiphenomenon of the malignant state or a selective way to parasitize the host? Does the early attraction of leukocytes to the tumor site contribute to early host defense against cancer? Does our knowledge about mechanisms of action of cytokines have implications for therapy of the cancer patient? Recent experimental data give hints to the answers to these questions and make it possible to deduce a fundamental model of cytokine mediated proteolysis in tissue remodelling.

Interferon-gamma and interleukin-1 beta inhibit adipoconversion in cultured rodent preadipocytes

Cytokines like tumor necrosis factor (TNF), interferon-gamma (IFN-gamma), and interleukin-1 (IL-1) are known to interfere with the differentiation of cultured cell lines of adipocyte precursors. In the present study, the effect of mouse and rat IFN-gamma, as well as human IL-1 beta, was investigated on rodent preadipocytes in primary cultures, either in the presence of fetal bovine serum (FBS, 10%) or in serum-free defined medium. IFN-gamma exerted an antiproliferative action that was more pronounced when cells reached confluency than during the growth phase of the culture. Morphological observation and quantifications of undifferentiated and differentiating cells revealed that IFN-gamma caused a decrease in the proportion of cells devoid of lipid droplets which would correspond to fibroblast-like cells, whereas preadipocytes remained unaffected. IFN-gamma induced a marked retardation of adipoconversion, resulting in a partial inhibition of lipoprotein lipase (LPL) activity and a severe decrease in glycerol-3-phosphate dehydrogenase (GPDH) activity. The antiproliferative and anti-LPL effects of IFN-gamma were neutralized by adding anti-IFN-gamma antibodies, while these antibodies prevented only partially the depressing effect of IFN-gamma on GPDH activity. Contrary to IFN-gamma, IL-1 beta slightly enhanced the proliferation in preadipocyte cultures. IL-1 beta also depressed adipoconversion, inhibited markedly LPL activity, and partially reduced GPDH activity. These results show that the influence of cytokines on adipoconversion observed in preadipocyte cell lines can be found in normal preadipocytes in culture.

The cytokine-protease connection: identification of a 96-kD THP-1 gelatinase and regulation by interleukin-1 and cytokine inducers

The induction of proteolytic enzymes is an important mechanism in the migration of monocytes into tissues and body fluids. The monocytic cell line THP-1 was used as a model system to study the production of a particular gelatinase. Upon stimulation with phorbol myristate acetate (PMA) the cells differentiated to the adherent phenotype and produced significant amounts of a 96-kD gelatinase in a dose-dependent way. The secretion rate was maximal between 12 and 24 h after induction. Study of gelatinase mRNA steady state levels showed that the synthesis of THP-1 gelatinase is regulated by PMA at transcriptional or posttranscriptional levels. Stimulation of signal transduction pathways with other substances, including calcium ionophore A 23187, dibutyryl cyclic AMP, and dexamethasone, were ineffective in inducing gelatinase mRNA or enzyme activity. However, THP-1 cells were responsive to the cytokine interleukin (IL)-1 beta, to bacterial lipopolysaccharide (LPS), and the lectin concanavalin A (Con A), the kinetics of gelatinase induction being similar to those of induction by PMA. The THP-1 cells did not synthesize and/or secrete detectable levels of IL-6 after stimulation with PMA, Con A, LPS, or IL-1 beta. The 96-kD monocytic THP-1 gelatinase was shown to be a neutral metalloproteinase that cross-reacted with hepatoma-derived and neutrophil gelatinases in immunoprecipitation experiments. The active enzyme produced by THP-1 cells consistently showed, however, a molecular mass different from that of normal granulocyte-, monocyte-, and tumor cell-derived gelatinases.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular and functional analysis of the virus- and interferon-inducible human MxA promoter

The virus- and interferon-inducible human MxA (IFI-78k) gene is a homologue of the murine influenza resistance gene Mx1. Three overlapping human cosmid clones covering most of the gene including its promoter region were isolated. Sequencing the 5' MxA cDNA derived by RT-PCR (reverse transcriptase-polymerase chain reaction) confirmed the most 5' putative transcriptional start site. The MxA promoter does not contain a TATA or CCAAT box but has three Interferon Stimulated Response Element (ISRE) motifs. Strong induction with type I interferons was demonstrated with a fragment containing only two ISREs in human L132 cells. This induced expression was not adversely affected by 2-aminopurine. However, the promoter showed constitutive expression in transiently or stably transfected murine LM cells.

Effects of cytokines on the liver

Cytokines are essential for the communication not only between the liver and extrahepatic sites but also within the liver itself. Cytokines regulate the intermediary metabolism of amino acids, proteins, carbohydrates, lipids and minerals. Cytokines partially interact with classical hormones such as glucocorticoids, resulting in a complex network of mutual control. Since many cytokines exert growth factor-like activities in addition to their specific proinflammatory effects, the distinction between cytokines and growth factors is somewhat artificial. The liver is an important site of synthesis and the major clearance organ for several cytokines. In liver disease, cytokines are involved in the onset of intrahepatic immune responses (e.g., during viral hepatitis), in liver regeneration (e.g., after partial hepatectomy) and in the fibrotic and cirrhotic transformation of the liver such as chronic chemical injury or viral infection. Further studies of cytokine actions may lead to a better understanding of liver diseases and to the development of new immunomodulating therapeutic options.

The human leukemia cell line, THP-1: a multifacetted model for the study of monocyte-macrophage differentiation

THP-1 is a human monocytic leukemia cell line. After treatment with phorbol esters, THP-1 cells differentiate into macrophage-like cells which mimic native monocyte-derived macrophages in several respects. Compared to other human myeloid cell lines, such as HL-60, U937, KG-1, or HEL cell lines, differentiated THP-1 cells behave more like native monocyte-derived macrophages. Because of these characteristics, the THP-1 cell line provides a valuable model for studying the mechanisms involved in macrophage differentiation, and for exploring the regulation of macrophage-specific genes as they relate to physiological functions displayed by these cells.

Interaction of interferons with skin reactive cytokines: from interleukin-1 to interleukin-8

The skin as an organ contains a large pool of cells, important for the production of various cytokines. This study focuses on interferon-beta (IFN-beta), interleukin-6 (IL-6), and interleukin-8 (IL-8) production by fibroblasts and epithelial cells in response to interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha). Both these primary cytokines show multiple biologic activities in the skin. Their antiviral activity on fibroblasts is mediated by IFN-beta and not by IL-6. In addition, TNF-alpha and IL-1 have a growth stimulatory effect on dermal fibroblasts, which is not mediated by IFN-beta or IL-6. IL-1, double-stranded RNA, or virus are potent inducers of IL-6 and IL-8 on dermal fibroblasts, but they are less efficient on epidermal cells. IL-8 has been discovered as an early acting skin reactive factor responsible for the chemotaxis of neutrophilic granulocytes. Furthermore, IL-1 possesses delayed skin reactivity upon intradermal injection which presumably is mediated by local release of IL-8. These findings demonstrate that cytokines also interact in the skin and that dermal fibroblasts play an important role in the regulation of aspecific host defense.

Haemopoietic receptors and helical cytokines

A bewitching interplay of proteins, variously clothed as chemical messengers and cellular receptors, control the pace of growth and the course of progressive differentiation in blood cell types. The messengers are lymphokines, interleukins, colony-stimulating factors, growth hormones and interferons: generically, the cytokines. The second components of the regulatory pairs are membrane-spanning receptor proteins: these molecules transduce the specific binding of cognate cytokines into a mitogenic cellular response. In this article, Fernando Bazan discusses a provocative structural model for cytokine-receptor interactions which, if correct, will alter perceptions of the evolutionary design of the haemopoietic system.

Stimulation of tumor necrosis factor secretion by purified influenza virus neuraminidase

We showed that purified neuraminidase (NA) of influenza virus, but not hemagglutinin (HA), possessed the potential to increase in vitro and in vivo the interleukin 1 (IL 1) activity of mouse peritoneal macrophages. In this study, we report the effect of NA and HA on the secretion of tumor necrosis factor (TNF) activity by murine peritoneal macrophages. TNF being a cytokine sharing many related and overlapping biological functions with IL 1. The two glycoproteins of the strain A/USSR/90/77 (H1N1) were purified electrophoretically and were tested in vitro at doses ranging from 0.5 to 5.0 micrograms using the adherent peritoneal macrophages of C3H/HeN mice elicited with thioglycolate. The TNF activity of culture supernatants, collected 24 hr after stimulation with viral protein, was evaluated by the standard cytolytic assay using L929 and WEHI.164 cells. No increase of the TNF activity was observed at 0.5 micrograms of NA (4.8 Units (U)/ml in the L929 assay and 20.4 U/ml in the WEHI assay) but further increase of NA to 1.0 microgram had a significant effect on the TNF activity (39.7 and 88.8 U/ml, respectively). Higher concentrations of NA (2.0 and 5.0 micrograms) did not improve the TNF activity. The addition of a rabbit anti-TNF-alpha serum to the assay system reduced the lysis of L929 cells by 85%, suggesting that the observed activity was due to TNF. In parallel, the enhancement of IL 1 activity due to NA was reverified using D10.G4.1 cells instead of the C3H/HeJ thymocytes assay used previously. NA augmented the IL 1 activity up to 1.0 micrograms (25.8 U/ml). The addition of monoclonal anti-IL 1 antibodies (100 neutralizing units) to the supernatants reduced the incorporation of [3H]-thymidine by 90 to 95%, suggesting that the observed activity was due to IL 1. Comparative results of NA and HA showed that only NA stimulated the TNF and IL 1 activities of murine macrophages.

Gamma interferon-like immunoreactivity in the rat nervous system

The presence of gamma interferon-like immunoreactivity in the peripheral nervous system and in some central nervous system neurons is described. The immunohistochemical evidence is based upon labeling of neurons with five different monoclonal antibodies against rat gamma interferon and one polyclonal antiserum. Immunoreactive material was abundantly present in the peripheral nervous system including small primary sensory neurons in dorsal root ganglia and postsynaptic neurons of the sympathetic and parasympathetic nervous system. Large neurons in dorsal root ganglia were not stained. Neurites stained with DB1 antibody against rat gamma interferon were found in most organs examined such as the gastrointestinal tract, heart, lungs, kidney, sexual organs and skin. In contrast, staining was weak in the central nervous system and restricted to a few neurons in the hypothalamus and in the midbrain. It is speculated that this newly discovered system containing a gamma interferon-like neuropeptide could be involved in the neuronal control of immunological processes in its target organs.