In vivo induction of IL-6 by administration of exogenous cytokines and detection of de novo serum levels of IL-6 in tumor-bearing mice

We investigated the capacity of several recombinant cytokines to induce IL-6 in vivo in both normal and tumor-bearing (TB) mice. Intravenous administration of human rhTNF-alpha, rhIL-1, rhIL-2, rhIFN-alpha A/D, and rmIFN-gamma were all capable of inducing circulating IL-6. rhTNF-alpha administration caused the greatest induction of IL-6. TB animals consistently produced more IL-6 in response to rhTNF-alpha than did normal mice (2 h after 4 micrograms rhTNF-alpha, TB = 24,100 HGF U/ml, non-TB = 3600 HGF U/ml of IL-6). A single daily i.v. dose of rhTNF-alpha (4 micrograms/mouse/day) for 5 days led to decreased IL-6 induction in TB animals by day 3 of treatment (peak levels of IL-6, day 1 = 72,800 HGF U/ml, day 3 = 23,400 HGF U/ml, day 5 = 26,400 HGF U/ml). rhIL-1 administration also resulted in considerable IL-6 production, although peak values were less than those resulting from administration of rhTNF-alpha. Administration of rhIL-1 induced similar IL-6 levels (TB = 10,025 and non-TB = 10,600 HGF U/ml) in TB and normal mice. Single high doses of rhIL-2, rhIFN-alpha A/D, and rmIFN-gamma induced lower but consistent levels of circulating IL-6 in mice with and without tumor. In addition, the sera of untreated TB mice contained levels of IL-6 which paralleled the extent of tumor burden (serum IL-6 in day 30 MCA 106 TB mice = 420 HGF U/ml). The detection of de novo IL-6 was also confirmed in animals bearing tumors of different histologies (the MCA 102 sarcoma, MCA 38 adenocarcinoma, and B16 melanoma). At no time was IL-6 measurable in the sera of untreated normal mice. The identification of IL-6 was verified by neutralization studies using specific antimurine IL-6 antibody. Although the exact role of IL-6 in TB animals remains to be elucidated, its known pleotrophic immune and metabolic effects may be important in the host response to malignancy.     

Ciliary neurotrophic factor induces acute-phase protein expression in hepatocytes.

During inflammatory states, hepatocytes are induced to synthesize and secrete a group of proteins called acute-phase proteins. It has recently been shown that besides interleukin-6 (IL-6), related cytokines such as leukemia inhibitory factor, oncostation M and interleukin-11 are also mediators of the hepatic acute-phase response. All these mediators belong to the hematopoietic family of alpha-helical cytokines. Here we show that an additional member of this cytokine family, ciliary neurotrophic factor (CNTF), induces the hepatic acute-phase protein genes haptoglobin, alpha 1-antichymotrypsin, alpha 2-macroglobulin and beta-fibrinogen in human hepatoma cells (HepG2) and in primary rat hepatocytes with a time course and dose-response comparable with that of IL-6. Our next aim was to define the receptor components used by CNTF on hepatic cells. Using a cell-free binding assay we exclude that CNTF binds to the 80 kDa IL-6 receptor, a protein with significant homology to the CNTF receptor which has recently been cloned from neuroblastoma cells. In human hepatoma cells (Hep3B) which lack the leukemia inhibitory factor receptor, CNTF was not able to induce acute-phase protein synthesis, indicating that this receptor protein may be part of the functional CNTF receptor on hepatic cells.     

Paradoxical synergistic effects of tumour necrosis factor and interleukin 1 in murine gut-derived sepsis with Pseudomonas aeruginosa.

The authors evaluated the synergistic effect of tumour necrosis factor (TNF) and interleukin 1 (IL-1) in gut-derived sepsis in mice. After colonization of Pseudomonas aeruginosa strain D4 in the gastrointestinal tract, cyclophosphamide was administered to induce bacterial translocation of the P. aeruginosa and thereby to cause gut-derived sepsis. In this model, treatment either with 8 microg/kg of recombinant human TNF-alpha (rhTNF-alpha) or 2 microg/kg of recombinant human interleukin 1alpha (rhIL-1alpha) solely did not affect the mortality, whereas combined administration of the same doses of rhTNF-alpha and rhIL-1alpha significantly increased the mortality rate in comparison with saline-treated mice. Bacterial counts in liver and blood were significantly higher in rhTNF-alpha and rhIL-1alpha treated mice than in saline-treated mice. Endogenous TNF-alpha and IL-1beta productions were stimulated after combined treatment with rhTNF-alpha and rhIL-1alpha. On the contrary to these adverse effects, combined treatment with 500 microg/kg of rhTNF-alpha and 50 microg/kg of rhIL-1alpha on the day before the administration of cyclophosphamide significantly reduced the mortality from septic infection. We conclude that TNF and IL-1 synergistically affect the mortality of mice after gut-derived sepsis due to P. aeruginosa in mice and the timing of treatment with these cytokines causes both extremes in their effects.     

Effects of IFN on human eosinophils in comparison with other cytokines. A novel class of eosinophil activators with delayed onset of action.

Extracellular killing is regarded as one of the main functions of eosinophils. Therefore, a cytotoxicity assay against antibody-coated Daudi-lymphoma cells was established to measure cytokine effects on peripheral blood eosinophils from healthy volunteers. Optimal time of exposure to cytokines and half optimal concentrations (EC50) were determined and the capability of various cytokines to enhance cytotoxicity of eosinophils was compared. Thus, after 24 h with cytokine, the highest activation of eosinophils was observed with recombinant human rhIFN-gamma (EC50 = 0.2 U/ml), followed by the known activators of eosinophils recombinant human granulocyte/macrophage CSF (rhGM-CSF), rhIL-3, and murine IL-5 (mIL-5). rhIFN-alpha and natural human IFN-beta (nhIFN-beta) enhanced cytotoxicity as well. On the other hand, in short term assays, eosinophils were not stimulated by IFN and the strongest stimulator was rhGM-CSF (EC50 = 0.2 U/ml), followed by rhIL-3, mIL-5, rhTNF, and rhIL-4. With rhTNF-alpha enhancement was more pronounced on freshly isolated eosinophils (EC50 = 0.6 U/ml) and declined with time. No significant stimulation was detected with rhG-CSF, rhIL-1 beta, rhIL-2, rhIL-6, and rhIL-8. On neutrophils, rhIL-8 enhanced cytotoxicity, but the stimulation was weak in relation to other neutrophil activators. Studies on the mechanism of cytotoxic activity revealed that cytotoxicity required opsonization of targets with specific antibody. FMF analysis was performed demonstrating that freshly isolated eosinophils express Fc-gamma RII (CD32), small amounts of Fc-gamma RIII (CD16), but not Fc-gamma RI (CD64). In experiments with blocking antibodies to Fc-gamma R cytotoxicity was restricted to Fc-gamma RII. Expression of Fc-gamma RII was not enhanced by rhGM-CSF, rhTNF-alpha, and mIL-5, but a significant increase in the number of positive cells was observed after incubation with rhIFN-gamma for 24 h (p less than 0.05). In addition, enhanced viability of eosinophils was observed when cultured in the presence of rhIFN-gamma, rhIFN-alpha, rhGM-CSF, and rhTNF-alpha, but not of rhG-CSF and rhIL-2. Thus, IFN appear to be another class of activators of eosinophils, characterized by their delayed type of action.     

Recombinant human interleukin-6 (IL-6/BSF-2/HSF) regulates the synthesis of acute phase proteins in human hepatocytes

Recombinant human IL-6 (rhIL-6) is a potent inducer of the synthesis of acute phase proteins in adult human hepatocytes. A wide spectrum of acute phase proteins is regulated by this mediator. After labeling of rhIL-6 stimulated human hepatocytes with [35S]methionine acute phase protein synthesis was measured by immunoprecipitation. Serum amyloid A, C-reactive protein, haptoglobin, alpha 1-antichymotrypsin and fibrinogen were strongly induced (26-, 23-, 8.6-, 4.6- and 3.8-fold increases, respectively). Moderate increases were found for alpha 1-antitrypsin (2.7-fold) and alpha 1-acid glycoprotein (2.7-fold). RhIL-6 had no effect on alpha 2-macroglobulin, whereas fibronectin, albumin and transferrin decreased to 64, 56 and 55% of controls. In the cases of serum amyloid A, haptoglobin, alpha 1-antichymotrypsin, alpha 1-antitrypsin and alpha 1-acid glycoprotein, dexamethasone enhanced the action of rhIL-6. We conclude that rhIL-6 controls the acute phase response in human liver cells.     

Liver receptor homolog 1 is a negative regulator of the hepatic acute-phase response

The orphan nuclear receptor liver receptor homolog 1 (LRH-1) has been reported to play an important role in bile acid biosynthesis and reverse cholesterol transport. Here, we show that LRH-1 is a key player in the control of the hepatic acute-phase response. Ectopic expression of LRH-1 with adenovirus resulted in strong inhibition of both interleukin-6 (IL-6)- and IL-1beta-stimulated haptoglobin, serum amyloid A, and fibrinogen beta gene expression in hepatocytes. Furthermore, induction of the hepatic inflammatory response was significantly exacerbated in HepG2 cells expressing short hairpin RNA targeting LRH-1 expression. Moreover, transient-transfection experiments and electrophoretic mobility shift and chromatin immunoprecipitation assays revealed that LRH-1 regulates this cytokine-elicited inflammatory response by, at least in part, antagonizing the CCAAT/enhancer binding protein beta signaling pathway. Finally, we show, by using LRH-1 heterozygous mice, that LRH-1 is involved in the control of the inflammatory response at the hepatic level in vivo. Taken together, our results outline an unexpected role for LRH-1 in the modulation of the hepatic acute-phase response.     

Dual function of interleukin-1beta for the regulation of interleukin-6-induced suppressor of cytokine signaling 3 expression

Interleukin-6 (IL-6) exerts pro- as well as anti-inflammatory activities in response to infection, injury, or other stimuli that affect the homeostasis of the organism. IL-6-induced expression of acute-phase protein genes in the liver is tightly regulated through both IL-6-induced feedback inhibitors and the activity of pro-inflammatory cytokines such as tumor necrosis factor alpha and interleukin-1beta. In previous studies mechanisms for how IL-1beta counteracts IL-6-dependent acute-phase protein gene induction have been proposed. Herein we analyzed IL-1beta-mediated regulation of IL-6-induced expression of the feedback inhibitor SOCS3. In hepatocytes IL-1beta alone does not induce SOCS3 expression, but it counteracts SOCS3-promoter activation in long term studies. Surprisingly, short term stimulation revealed IL-1beta to be a potent enhancer of SOCS3 expression in concert with IL-6. This activity of IL-1beta does not depend on IL-1beta-dependent STAT1-serine phosphorylation but on NF-kappaB-dependent gene induction. Such a regulatory network allows IL-1beta to counteract IL-6-dependent expression of acute-phase protein genes without inhibiting IL-6-induced SOCS3 expression and provides a reasonable mechanism for the IL-1beta-dependent inhibition of acute-phase gene induction, because reduced SOCS3 expression would lead to enhanced IL-6 activity.     

Reduction of the acetylcholine-induced K+ current in identifiedAplysia neurons by human interleukin-1 and interleukin-2

1. Effects of bath-applied recombinant human interleukin-1 (rhIL-1) and interleukin-2 (rhIL-2) on the acetylcholine (ACh)-induced K+ current recorded from identified neurons (R9 and R10) of Aplysia kurodai were investigated with voltage-clamp and pressure ejection techniques. 2. Bath-applied rhIL-1 and rhIL-2 (10-40 U/ml) reduced the ACh-induced current in the neurons without affecting the resting membrane conductance and holding current. 3. The suppressing effects of these cytokines on the current were completely reversible. 4. Heat-inactivated rhIL-1 and rhIL-2 were without effect. 5. These results suggest that the immunomodulators, IL-1 and IL-2, can modulate the ACh-induced response in the nervous system.     

Acute phase response to recombinant interleukin-6 and macrophage- and fibroblast-derived crude cytokine preparations in primary cultures of mouse hepatocytes

A number of acute phase proteins were determined by electroimmunoassay in media from CBA mouse hepatocytes cultured for 2 days with human recombinant IFN beta 2/IL-6, as well as with conditioned media from LPS-stimulated rat macrophages, and of murine L fibroblasts. It was found that human recombinant IL-6 caused three-fold increase in secretion of fibrinogen, while haptoglobin, complement C3 and transferrin were increased respectively, to 168 per cent, 151 per cent, and 145 per cent of the control. DEX(10(-7) M) in DMEM supplemented with 5 per cent FCS, enhanced the IL-6 effect on the three positive acute phase proteins. IL-6 elevated haptoglobin mRNA in mouse hepatocytes to a degree comparable with the concentration of the protein in the culture medium. The effect of conditioned media from murine fibroblasts and peritoneal rat macrophages was generally similar to that of recombinant IL-6. However, both natural preparations of the cytokines caused decrease in albumin and alpha-1-proteinase inhibitor secretion.     

Sequential appearance of IL-1 and IL-6 activities in rat carrageenin-induced pleurisy.

IL-1 and IL-6 activities were measured in the pleural exudate of rats during carrageenin-induced pleurisy to examine the relationship of the local production of cytokines to the inflammatory reaction. Time courses of appearance of the cytokines and inflammatory parameters in the exudate were compared. IL-1 activity and exudate volume started to increase at 1 h after the carrageenin injection, and then slightly later IL-6 activity and leukocyte number began to increase. IL-1 showed peak activity of approximately 700 U at 3 h and IL-6, of 6000 U at 5 h in the exudate, whereas exudate volume and number of polymorphonuclear leukocytes continued to increase thereafter. Furthermore, IL-6 level in the plasma of the carrageenin-injected rats showed a peak at 4 h (30 U/ml), and when rhIL-1 alpha (100,000 U) was intrapleurally injected, the more rapid increase in plasma IL-6 level was demonstrated at 1 h (30 U/ml). This latter rise was neutralized with simultaneous injection of anti-rhIL-1 alpha antibody. These facts indicate the possibility that IL-1 produced in the exudate or injected could rapidly propagate a signal to induce IL-6 production in the circulation. It took several hours to transmit an inflammatory signal that stimulated the liver to synthesize the acute-phase protein, T-kininogen. The time lag from the peak induction of IL-1 to the T-kininogen-increase in the pleurisy corresponded well to the interval for T-kininogen-increase by exogenous rhIL-1 alpha injection. These results strongly suggest that the initial inflammatory stimulus induces sequentially IL-1, IL-6, and T-kininogen production in this carrageenin inflammation.     

Regulation of synthesis and secretion of major rat acute-phase proteins by recombinant human interleukin-6 (BSF-2/IL-6) in hepatocyte primary cultures

The regulation of the three major acute-phase proteins alpha 2-macroglobulin, cysteine proteinase inhibitor and alpha 1-antitrypsin by recombinant human interleukin-1 beta, recombinant human interleukin-6 and recombinant human tumor necrosis factor alpha was studied in rat hepatocyte primary cultures. Synthesis and secretion of the acute-phase proteins was measured after labeling with [35S]methionine and immunoprecipitation. Incubation of hepatocytes with interleukin-6 led to dose-dependent and time-dependent changes in the synthesis of the three major acute-phase proteins and albumin, similar to those occurring in vivo during experimental inflammation. alpha 2-Macroglobulin and cysteine proteinase inhibitor synthesis was induced 54-fold and 8-fold, respectively, 24 h after the addition of 100 units/ml interleukin-6. At the same time synthesis of the negative acute-phase protein albumin was reduced to 30% of controls. Half-maximal effects were achieved with 4 units interleukin-6/ml. Interleukin-1 beta had only a partial effect on the regulation of the four patients studied: only a twofold stimulation of alpha 2-macroglobulin and a 60% reduction of albumin synthesis were observed. Tumor necrosis factor alpha did not alter the synthesis of acute-phase proteins. The stimulation of alpha 2-macroglobulin and cysteine proteinase inhibitor synthesis by interleukin-6 was inhibited by interleukin-1 beta in a dose-dependent manner. In pulse-chase experiments the effect of interleukin-1 beta, interleukin-6 and tumor necrosis factor alpha on the secretion of acute-phase proteins was examined. Interleukin-6 markedly accelerated the secretion of total proteins and alpha 2-macroglobulin, whereas the secretion of cysteine proteinase inhibitor, alpha 1-antitrypsin and albumin was not affected. The inhibition of N-glycosylation by tunicamycin abolished the effect of interleukin-6 on the secretion of alpha 2-macroglobulin, indicating a possible role of interleukin-6 on N-glycosylation.     

IL-6 stimulates osteoclast-like multinucleated cell formation in long term human marrow cultures by inducing IL-1 release

IL-6 enhances the differentiation of pluripotent hematopoietic stem cells but predominantly affects the differentiation of hematopoietic cells in the granulocyte-macrophage lineage. We have previously shown that multinucleated cells (MNC) with many features of the osteoclast phenotype form in long term human marrow cultures. Addition of rhIL-6 (10 to 100 pg/ml) to these cultures significantly increased MNC formation, with greater than 80% of the MNC expressing an Ag that cross-reacts with the mAb 23c6. This antibody preferentially binds to osteoclasts. rhIL-6 did not enhance MNC formation in marrow cultures treated with 1,25 dihydroxyvitamin D3, a potent stimulator of MNC formation, but significantly increased the percentage of MNC that cross-reacted with the 23c6 mAb. Addition of antihuman IL-1 to cultures treated with rhIL-6 totally inhibited the increase in MNC formation stimulated by rhIL-6. In contrast, anti-IL-1 did not affect MNC formation stimulated by 1,25 dihydroxyvitamin D3. Further, conditioned media from marrow cultures exposed to rhIL-6 contained elevated levels of IL-1 beta (500 pg/ml compared to 23 pg/ml in control cultures 15 h after IL-6 addition). These results suggest that the capacity of rhIL-6 to stimulate formation of MNC which cross-react with 23c6 is mediated by induction of release of IL-1 beta.     

抗人IL-6单克隆抗体的制备及鉴定

用基因重组人IL-6免疫Balb/c小鼠,采用小鼠杂交瘤技术,筛选克隆到分泌抗人重组IL-6单克隆抗体的杂交瘤细胞株,并对其中2H₂、 1D₂ 和4B₄瘤细胞株进行了鉴定.其抗体类别均为IgG,亚类分别为IgG1和IgG2a.用多种细胞因子和无关蛋白的鉴别试验结果证实它们均特异地识别rhIL-6.免疫转染结果显示,该单抗识别分子质量为21 ku的IL-6单一条带.IL-6单克隆抗体的亲和常数K_aff= 1.62×10⁹ (mol/L)^-1.     

Angiotensinogen production by rat hepatoma cells is stimulated by B cell stimulatory factor 2/interleukin-6

Angiotensinogen has been identified as one of the acute-phase reactants. In vitro studies were carried out using the Reuber H35 hepatoma cell line to identify the species of cytokines contributing to the increased synthesis of angiotensinogen in the liver. Angiotensinogen secretion by H35 cells was maximally increased 4-fold by the addition of 10(-7) M dexamethasone. Under this condition, angiotensinogen secretion was further stimulated by B cell stimulatory factor 2/interleukin-6 (IL-6, 50 U/ml), but not by interleukin-1 or interferon-alpha. In the absence of glucocorticoid, IL-6 did not affect angiotensinogen secretion by H35 cells, indicating that the presence of glucocorticoid is required for the stimulatory activity of IL-6. These results suggest that IL-6 is a mediator responsible for the increased synthesis of angiotensinogen in the liver during acute inflammation.     

Generation of inflammatory cytokines in zymosan-induced pleurisy in rats: TNF induces IL-6 and cytokine-induced neutrophil chemoattractant (CINC) in vivo

Levels of inflammatory cytokines tumour necrosis factor (TNF), interleukin 1 (IL-1), IL-6, and cytokine-induced neutrophil chemoattractant (CINC), which is a member of the alpha-chemokine family in rats, were measured in the pleural exudates during zymosan-induced pleurisy to examine the relationship between the local production of cytokines and the inflammatory reaction. All four cytokine levels in the pleural exudate began to increase after 1-2 h, preceding the influx of neutrophils, and peaked after 4-5 h. Thereafter, these cytokine levels declined after 24 h, whereas the exudate volume still continued to increase and leukocyte number reached a plateau. Concomitant injection of actinomycin D (10 microg) with zymosan markedly suppressed the neutrophil infiltration, parallel with CINC production in the pleural exudate at 4 h. A transient elevation of IL-6 level, peaking at 5 h, and subsequent rise in the level of an acute-phase protein, T-kininogen, were also observed in the plasma. When recombinant human TNF-alpha (rhTNF-alpha) (20 000 U) was intrapleurally injected a rapid increase in pleural CINC level, followed by neutrophil infiltration, and a sharp rise in IL-6 level in the plasma, followed by an increase in T-kininogen, were demonstrated. These results suggest that CINC produced in the pleural exudate may participate in neutrophil infiltration, that IL-6 induced in the plasma stimulates T-kininogen production, and that endogenous TNF may be partly involved in the induction of CINC and IL-6 in this zymosan inflammation.     

Interleukin-6 is the major regulator of acute phase protein synthesis in adult human hepatocytes

The three monokines interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha (TNF alpha), and interleukin-6 (IL-6) modulate acute phase plasma protein synthesis in adult human hepatocytes. Only IL-6 stimulates the synthesis of the full spectrum of acute phase proteins as seen in inflammatory states in humans, i.e. synthesis and secretion of C-reactive protein, serum amyloid A, fibrinogen, alpha 1-antitrypsin, alpha 1-antichymotrypsin and haptoglobin are increased while albumin, transferrin and fibronectin are decreased. IL-1 beta as well as TNF alpha, although having a moderate effect on the positive acute phase proteins and inhibiting the synthesis of fibrinogen, albumin and transferrin, fail to induce serum amyloid A and C-reactive protein. These data suggest that IL-6 plays the key role in the regulation of acute phase protein synthesis in human hepatocytes.     

Modulation of IL-1 inflammatory and immunomodulatory properties by IL-6.

Among the major cytokines present in inflammatory lesions interleukin-1 (IL-1), tumor necrosis factor alpha (TNF alpha) and interleukin-6 (IL-6) share many biological activities. Since IL-1 alpha, IL-1 beta and TNF alpha have been previously demonstrated to play an important role in connective tissue destruction by stimulating the production of prostaglandin E2 (PGE2) and collagenase, these functions were investigated in the presence or absence of natural human IL-6 (nhIL-6) or recombinant human IL-6 (rhIL-6). IL-6 was found 1 degree to stimulate immunoglobulin A production by the CESS B cell line up to 19 fold without being affected by the presence of IL-1 beta and 2 degrees to stimulate murine thymocytes proliferation up to 2-4 fold, with an increase up to 60-fold in costimulation with either IL-1 alpha or beta. IL-6 alone, even at very high concentrations (up to 200 U/ml and 50 ng/ml), did not induce PGE2 production by fibroblasts and synovial cells. However, IL-1 alpha or beta induced PGE2 production by human dermal fibroblasts and by human synovial cells was inhibited (in 5/8 experiments) up to 62% by addition of IL-6. On the contrary in 2/4 experiments TNF alpha-induced PGE2 production was increased (approximately 2 fold) by the addition of IL-6. IL-1 and TNF alpha-induced collagenase production in synovial cells remained unchanged in the presence of IL-6.(ABSTRACT TRUNCATED AT 250 WORDS)