Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P05231 (interleukin-6)
 23,907 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new mutein of interleukin-6, called delta 22-IL-6 Cys 3,4, characterized by the deletion of the first 22 amino acids at the N-terminal end and by the substitution of the first two cysteines (Cys23 and Cys29) with serine residues, was produced in Escherichia coli and was found to maintain the structural and functional properties of the human native form. A partially purified preparation still showed in isoelectric focusing a minor acidic component (pI 6.10) and a more basic component (pI 6.70), the native form having a pI of 6.56. This preparation was further fractionated in a multi-compartment electrolyser with isoelectric membranes, which allowed the collection of the more alkaline species for characterization. Mass spectra of the pI 6.70 form gave an additional mass of 32 atomic mass units (amu), suggesting the addition of two oxygen atoms (a potential oxidation of two methionine residues to sulphoxide). However, the five methionine residues in this higher pI form were identified after enzymatic hydrolysis and peptide mapping and were found to be in a reduced state. In addition, the pI 6.70 form was quickly converted into the native form by mild reductive treatment. On digestion and fingerprinting, the peptide from residues 50 to 65 of the pI 6.70 species (containing the only two cysteine residues of the molecule) exhibited a more hydrophobic behaviour in reversed-phase high-performance liquid chromatography and retained a mass increase of 32 amu. These experimental findings more likely suggest the addition of an extra sulphur atom to the only disulphide bridge to give an unusual protein trisulphide molecule.
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PMID:Detection of traces of a trisulphide derivative in the preparation of a recombinant truncated interleukin-6 mutein. 758 42

Aggregation studies have become a useful criterion for analyzing leukocyte motility and activation in vitro. The T-cell-derived lymphokine human leukocyte inhibitory factor (LIF) is a modulator of many important polymorphonuclear (PMN) functions in addition to aggregation such as chemotaxis, lysosomal degranulation, phagocytosis, bactericidal killing, augmented antibody-dependent cellular cytotoxicity (ADCC), induction of neutrophil Fc-gamma, complement type-1 and FMLP receptors, and production of superoxide and H2O2. Our investigations focused on the ability of LIF to modulate the aggregation of macrophages (MO) induced by calcium ionophore A23187. The ionophore A23187 directly induced potent aggregation of macrophages, which was markedly enhanced when the cells were pretreated with LIF. However, the addition of LIF in the absence of other costimuli did not directly induce MO aggregation. LIF was shown to enhance PMN aggregation induced by N-formyl-Met-Leu-Phe (FMLP), but did not augment the aggregation of FMLP-stimulated macrophages, indicating a cellular specificity of aggregation-inducing costimuli following LIF priming. Additional cytokines examined for possibly inducing MO aggregation were interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF), and interleukin-6 (IL-6); all proved to be incapable of inducing aggregation directly, nor did they enhance the effect of A23187 ionophore on macrophage aggregation. Additionally, we found that LIF can directly stimulate MO to activate specific pathways of the arachidonic acid cascade, inducing the synthesis and release of thromboxanes and leukotriene B4. LIF did not augment the potent ability of A23187 to induce increased production of LTB4 or TxA2 by human MO. These new results coupled with our previously published data indicate that LIF can enhance the activation of both MO and PMN leukocytes when exposed to either A23187 or FMLP, respectively. Moreover, these data suggest that LIF can contribute directly to monocyte-macrophage leukocyte activation, in addition to PMN activation, during inflammatory responses, resulting in greater cell aggregation, activation, and specific proinflammatory arachidonic acid product release.
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PMID:Leukocyte inhibitory factor (LIF) potentiates human macrophage aggregation and activation responses to calcium ionophore A23187 and directly induces leukotriene B4 and thromboxane A2 release. 829 72

Tobacco smoke is a usual form of oxidant aggression present in the domestic environment. In the present study, the in vitro acute effects of a 2-cigarette smoke gas phase were evaluated on cell viability and cytokine secretion by alveolar macrophages (AM) from guinea pigs and human healthy subjects. Cell injury was estimated immediately after smoke exposure by evaluation of ATP cell content (measured by bioluminescence) and lactic dehydrogenase (LDH) release in the culture medium. LDH release was also measured when the interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF) activities were evaluated. No cytotoxic effect was found: The ATP cell content of both guinea pig AM and human AM did not significantly change after tobacco smoke exposure. Similarly, the LDH release in the culture medium was unchanged both immediately after tobacco smoke exposure and at the time of the cytokine evaluation (18-20 h later) compared to cells cultured in the air. The total protein synthesis by the guinea pig AM evaluated by 35S-L-methionine labeling was unaffected by tobacco smoke exposure. The production of IL-6 and TNF activities was evaluated 18-20 h after smoke exposure. The IL-6 activity was measured by the proliferation test of 7TD1 hybridoma cell line; the TNF activity was evaluated by the L929 mouse fibroblast cytotoxic test and by an immunoradiometric assay (for human AM). A 2-cigarette smoke exposure decreased both activities significantly. The exposure of the guinea pig AM reduced IL-6 activity by 24.3 +/- 6.7%, 42.4 +/- 7.8%, and 39.7 +/- 9.6% and TNF activity by 33.8 +/- 10.4%, 35.1 +/- 10.7%, and 38.8 +/- 9.9% (respectively unstimulated cells and AM activated by 0.1 and 10 micrograms LPS/mL). The decrease in monokine production by the human AM was, respectively, 57.8 +/- 8.8%, 59.7 +/- 11.4%, and 49.9 +/- 10.5% of IL-6 activity and 37.4 +/- 14.6%, 17.6 +/- 9.6%, and 37.2 +/- 6.3% of TNF activity. The possible release of cytokine inhibitors was also investigated. The inhibitory activity against recombinant TNF and IL-6 was evaluated in culture medium from unstimulated AM exposed to tobacco smoke and did not significantly differ from that of AM exposed to air, demonstrating that the decrease of monokine levels could not be explained by the release of inhibitory factors.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:In vitro acute effects of tobacco smoke on tumor necrosis factor alpha and interleukin-6 production by alveolar macrophages. 831 4

Human promonocytic U937 cells have previously been shown to possess at their cell surface specific transmembrane serine proteases and N-terminal amino acid proteases as well as associated enzymes including elastase and cathepsin G. In this study, purified plasma membranes from U937 cells are reported to degrade the recombinant 21-kDa 125I-interleukin-6 (125I-IL-6) into 8-kDa products with loss of biological activity, as monitored by polyacrylamide gel electrophoresis and a cell-proliferation bioassay. Degradation of 125I-IL-6 by plasma membranes was completely prevented by the serine-protease inhibitor diisopropyl fluorophosphate, but was only partially impaired by alpha 1-protease inhibitor and antibody against cathepsin G. A similar incubation of 125I-IL-6 with cathepsin G purified from U937 cells caused hydrolysis of the cytokine into similar inactive 8-kDa fragments, whereas incubation with purified U937 cell elastase failed to degrade the peptide. These findings indicate that U937 cells hydrolyze IL-6 using cell-associated serine-protease activity and that cathepsin G partially participates in this degradation. Prolonged incubation of 8-kDa 125I-IL-6 fragments with purified U937 plasma membranes, led to a complete loss of IL-6 activity related to the transformation of the 8-kDa forms into a higher-molecular-mass complex (16 kDa). This complex was stable in SDS and 2-mercaptoethanol at 100 degrees C and was not dissociated by hydroxylamine treatment, indicating the formation of a covalent non-ester bond between the 8-kDa 125I-IL-6-derived peptide and an undetermined acceptor. An initial oxidative treatment of 125I-IL-6 partially prevented complex formation, suggesting the presence of one or more oxidizable methionine residues at the binding site of 8-kDa 125I-IL-6 peptide. The kinetics of complex formation (time dependence and plasma-membrane-concentration dependence), as well as its inhibition by a specific inhibitor of N-amino-peptidase activity, bestatin, suggest the participation of peptidyl-transferase activity in complex formation. Finally, a plasma-membrane fraction, corresponding to a molecular mass > or = 30 kDa, was able to convert the 8-kDa 125I-IL-6 forms into the 125I-labeled 16-kDa complex, suggesting that a > or = 30-kDa peptidyl-transferase enzyme catalyzes the reaction and provides the 125I-labeled 16-kDa peptide by dimerization of 8-kDa 125I-IL-6-derived intermediates. Further identification of the plasma-membrane-associated peptidyl transferase as a regulator of IL-6 proteolysis may be of physiological relevance for the control of IL-6 biological activity.
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PMID:Inactivation of interleukin-6 in vitro by monoblastic U937 cell plasma membranes involves both protease and peptidyl-transferase activities. 835 88

Corticosteroid-binding globulin (CBG) belongs to the superfamily of serine proteinase inhibitors which include alpha 1-antitrypsin, alpha 1-antichymotrypsin, and T4-binding globulin. Interleukin-6 (IL-6), the main mediator of the acute phase phenomenon, increases alpha 1-antitrypsin and alpha 1-antichymotrypsin synthesis and decreases T4-binding globulin synthesis by human hepatoblastoma-derived (Hep G2) cells. This effect is predominantly at a transcriptional level. When Hep G2 cells were exposed to different concentrations of IL-6 for variable time intervals, IL-6 caused a dose- and time-dependent decrease in the amount of [35S]methionine-labeled CBG immunoprecipitated in the culture medium. This effect could be greatly reduced by preincubation of IL-6 with its neutralizing antibody and reversed by removing the cytokine from the culture medium. The secretion rate of CBG was not affected by cell exposure to IL-6. CBG mRNA steady state levels were reduced; changes in mRNA were quantitatively similar to changes in secreted protein. Nuclear run-off assays failed to show a change in the rate of transcription of the CBG gene. These data indicate that IL-6 diminishes CBG synthesis by Hep G2 cells acting at a posttranscriptional level, presumably through a reduced stability of mRNA. In view of the role of IL-6 in the inflammatory process and other acute phase phenomena, these data suggest that its effects on CBG synthesis might influence the bioavailability of cortisol indirectly and play a role in regulating the homeostatic process during these conditions.
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PMID:Interleukin-6 inhibits corticosteroid-binding globulin synthesis by human hepatoblastoma-derived (Hep G2) cells. 839 24

cDNAs coding for the two receptor subunits of the interleukin-6 receptor have been stably expressed in Madine Darby canine kidney (MDCK) cells. The fate of the IL-6 binding protein (IL-6R) and of the signal transducing protein gp130 was studied independently. Both proteins were proteolytically cleaved from cells metabolically labeled with [35S]methionine/cysteine leading to the release of soluble receptor proteins of 55 kDa and 100 kDa, respectively. In contrast to the shedding of the IL-6R gp130 was inefficiently released from the cells and the process was not significantly stimulated by the phorbolester PMA. In addition we show that the soluble forms of the IL-6R and gp130 released by transfected cells can form a ternary complex with interleukin-6 indicating that such complexes also may occur in vivo.
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PMID:Differential shedding of the two subunits of the interleukin-6 receptor. 840 37

The concentration of plasma angiotensinogen increases upon induction of inflammation. Studies were carried out using serum samples collected from mice and rats after injection of lipopolysaccharide (LPS) to determine whether interleukin-6 (IL-6) is a mediator responsible for the inflammation-induced increase of angiotensinogen synthesis in liver cells. Serum collected from mice or rats 2 and 4 hr after injection of LPS contained a factor that stimulated [35S]methionine incorporation into angiotensinogen newly synthesized by rat hepatoma H4IIEC3 (H4) cells. Assay of IL-6 using an IL-6-dependent murine hybridoma, MH60.BSF2 cells, showed the presence of IL-6-like activity in sera of mice or rats 2 and 4 hr after injection of LPS. Anti-mouse IL-6 monoclonal antibody completely inhibited not only the IL-6-like activity present in LPS-treated mouse serum but also the ability of the serum to stimulate angiotensinogen synthesis of H4 cells. These results suggest that increased synthesis of angiotensinogen in the liver after induction of inflammation is mediated by IL-6, a cytokine important in immune reactions and the hepatic acute-phase response.
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PMID:Interleukin-6 as a mediator responsible for inflammation-induced increase in plasma angiotensinogen. 842 13

Respiratory syncytial virus (RSV), the most common etiologic agent of epidemic pediatric respiratory disease, infects and replicates in the human airway epithelium, resulting in the induction of cellular gene products essential for immune and inflammatory responses. We describe the effect of RSV infection on nuclear factor-IL6 (NF-IL6) expression, a human basic domain-leucine zipper-containing transcription factor that alone in combination with other inducible transcription factors regulates the expression of cytokine and adhesion molecule genes. RSV-infected human type II pulmonary alveolar epithelial cells (A549) synthesize a single 45.7-kDa isoform of NF-IL6 rapidly and in a time-dependent manner. NF-IL6 is first detectable after 3 h of infection and continues to accumulate until 48 h (until the cells lose viability). NF-IL6 production could not be induced by UV-inactivated virus, demonstrating the requirement of viral replication for NF-IL6 synthesis. Immunoprecipitation after [35S]methionine metabolic labeling was done to investigate the mechanism for NF-IL6 production. There was robust NF-IL6 protein synthesis within RSV-infected (24 h) cells. Protein synthesis occurred without detectable changes in the abundance or size of the single 1.8-kb NF-IL6 mRNA. RNase protection assay of transfected chloramphenicol acetyltransferase reporter genes driven by either wild-type or mutated NF-IL6 binding sites show a virus-induced increase in NF-IL6-dependent transcription. These studies have demonstrated a novel inducible mechanism for translational control of NF-IL6 synthesis and identify this transcription factor as a potential effector of the host response to RSV infection.
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PMID:Inducible translational regulation of the NF-IL6 transcription factor by respiratory syncytial virus infection in pulmonary epithelial cells. 862 74

Endotoxin-induced hepatic acute-phase protein synthesis has been thought to be primarily regulated through cytokines such as interleukin-1 (IL-1) and interleukin-6 (IL-6). Previously, it was found that a 23-kDa murine acute-phase protein, the lipopolysaccharide (LPS)-induced protein (LIP), was synthesized following treatment of hepatocytes in vitro with LPS. Since this protein was also induced by IL-1 and IL-6, the present studies were undertaken to determine if the effect of endotoxin was mediated through these cytokines. Primary cultures of murine hepatocytes were treated with LPS, IL-1, IL-6, or an LPS-stimulated macrophage supernatant in the presence or absence of the IL-1 receptor antagonist (IL-1 RA) and/or an anti-IL-6 antibody. The cells were then radiolabeled with [35S]methionine. LIP was detected by electrophoresis and autoradiography of the secreted proteins. In vitro, IL-1 RA completely inhibited the stimulation of LIP synthesis elicited by IL-1 and the macrophage supernatant, but did not affect LPS-stimulated synthesis of this protein. The anti-IL-6 antibody inhibited IL-6-triggered synthesis of LIP, but had no effect on LPS-stimulated synthesis. Hepatocytes isolated from mice treated in vivo with both IL-1 RA and LPS synthesized LIP to the same degree as hepatocytes isolated from mice treated with LPS alone. LPS-stimulated synthesis of LIP in vitro does not require IL-1 or IL-6 as an obligatory intermediate. These results are consistent with the hypothesis that endotoxin can directly stimulate hepatocyte acute-phase protein synthesis in the absence of cytokines.
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PMID:Effects of cytokine antagonists on the hepatic acute-phase response. 918 75

Met and ron proto-oncogenes encode the cell surface receptors for hepatocyte growth factor (HGF) and hepatocyte growth factor-like (HLP) protein, respectively, and induce mitogenesis, motogenesis, morphogenesis, and metastatic activity in various cell types. Overexpression of met in human carcinoma has been reported by several groups including ours; however, the mechanisms that control met gene expression are thus far unclear. The present study focuses on the expression and regulation of the Met and Ron receptors in human hepatocellular carcinoma (HCC). We report here that abnormal expression of met and ron proteins occurs in some cases of human HCC. Using several HCC cell lines as a model system, we show that HGF, as well as other cytokines, such as epidermal growth factor (EGF), interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-alpha), induce met and ron expression. Using several chimeric constructs consisting of various lengths of the met promoter region fused to the reporter gene of chloramphenicol acetyl transferase (CAT), and by performing transient transfection of these constructs into HepG2 cells, we show that induction of met gene expression by HGF and other cytokines is, at least in part, through up-regulation of met gene promoter activity. The DNA region conferring responsiveness to cytokine induction was located within 0.2 kb of the met core promoter. Interestingly, EGF did not stimulate met promoter activity in any of the met-CAT chimeric constructs. These results provide evidence that met and ron are modulated in the liver by a similar cytokine network. In the case of met expression, the 0.2-kb region in the met gene promoter may play an important role in mediating its gene induction in response to HGF and other cytokines. Our results also suggest that unregulated expression of met and ron may be associated with pathological conditions, such as HCC, in the liver.
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PMID:Co-expression and regulation of Met and Ron proto-oncogenes in human hepatocellular carcinoma tissues and cell lines. 921 52


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