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)

Multiple mechanisms are necessary to spatially and temporally restrict and direct the effects of potent mediators of inflammation, immune reactions and tissue repair. Recent studies implicate alpha 2-macroglobulin (alpha 2M) as a protein that regulates the distribution and activity of many cytokines, including transforming growth factors-beta (TGFs-beta), tumor necrosis factor-alpha (TNF-alpha), platelet derived growth factor (PDGF), interleukin-6 (IL-6), nerve growth factor (NGF), fibroblast growth factor (b-FGF), and interleukin-1 beta (IL-1 beta). Some cytokines, including PDGF, NGF, and IL-6 bind preferentially to the native secreted form of alpha 2M, whereas the TGF-beta s, TNF-alpha and IL-1 beta bind preferentially to forms of alpha 2M that have been modified by proteinases such as plasmin. Cytokines bound to native alpha 2M retain much of their biologic activity in various bioassays, whereas cytokines bound to "activated" alpha 2Ms have decreased activity in some cell systems. Because native alpha 2M in circulation can escape into extravascular fluid during tissue injury and inflammation, alpha 2M is a putative cytokine carrier, especially in the presence of heparin or specific cytokine receptors that can displace non-covalently bound cytokines from native alpha 2M. However, proteinase or chemically modified alpha 2Ms become activated for receptor-mediated endocytosis (RME) when they undergo conformational alterations that expose a latent alpha 2M receptor-recognition domain. Circulating activated alpha 2Ms, together with bound cytokines, are rapidly removed by hepatic alpha 2M-receptors (alpha 2M-R) but also bind to other cells expressing alpha 2M-R. This suggests that diseases resulting from an apparent change in the production of one or several different cytokines might represent changes in either the production of alpha 2M "cytokine scavengers" or their alpha 2M-receptor-mediated clearance/targeting mechanisms. The sequence identity between the LDL-receptor related protein and the alpha 2M receptor (115) provides a theoretical basis for interference with cytokine clearance by association of competing lipoprotein ligands with this cytokine clearance pathway. Furthermore, activated alpha 2Ms or augmentation of alpha 2M-receptor-dependent cytokine clearance might be novel strategies for preventing the harmful systemic or local effects of excess cytokines such as TGF-beta s and TNF-alpha in vivo.
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PMID:Cytokine binding and clearance properties of proteinase-activated alpha 2-macroglobulins. 171 74

Lipoprotein (a) (Lp(a)) is a low density lipoprotein-like particle which contains the plasminogen-like apolipoprotein a. Lp(a) levels are elevated in patients with atherosclerotic coronary artery disease. Recent studies suggest that Lp(a) competitively inhibits plasminogen binding to the endothelial cell and interferes with surface-associated plasmin generation. In this study, we present evidence for the presence of Lp(a) in the microvasculature of inflamed tissue. In addition, we demonstrate that Lp(a) regulates endothelial cell synthesis of a major fibrinolytic protein, plasminogen activator inhibitor-1 (PAI-1). In cultured human endothelial cells, Lp(a) enhanced PAI-1 antigen, activity, and steady-state mRNA levels without altering tissue plasminogen activator activity or mRNA transcript levels. This effect was cell-specific. Although other lipoproteins did not coordinately raise PAI-1 mRNA levels in endothelial cells, low density lipoprotein treatment selectively raised the level of the 3.4-kilobase mRNA species of PAI-1 without a concomitant increase in PAI-1 activity or antigen. Endothelial cell exposure to Lp(a) did not cause generalized endothelial cell activation since the functional activity and mRNA levels for tissue factor, platelet-derived growth factor and interleukin-6 were not elevated following Lp(a) exposure. These data suggest a molecular mechanism whereby Lp(a) may support a specific prothrombotic endothelial cell phenotype, namely by increasing PAI-1 expression.
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PMID:Lipoprotein (a) regulates plasminogen activator inhibitor-1 expression in endothelial cells. A potential mechanism in thrombogenesis. 182 42

Endothelial cells play an important role in the regulation of fibrinolysis by the production of several key regulatory proteins. The cytokines tumor necrosis factor (TNF), lymphotoxin, and interleukin-1 (IL-1), but not interleukin-6, increase the production of plasminogen activator inhibitor-1 (PAI-1) by endothelial cells, whereas they have no stimulatory effect on the production of tissue-type plasminogen activator (t-PA). Primary cultures of human endothelial cells release very little urokinase-type plasminogen activator (u-PA). We report here that TNF and lymphotoxin induce, in a concentration-dependent way, the production of both cellular and secreted u-PA antigen in primary and subcultured human endothelial cells. The TNF-induced increase was accompanied by a more than 10-fold increase in u-PA mRNA. Upon stimulation of early passage umbilical vein endothelial cells by TNF, u-PA was predominantly secreted at the basolateral side, whereas PAI activity and t-PA were found in more equal amounts at the apical and basolateral sides of the cell monolayers. TNF-stimulated u-PA secretion by subcultured human aorta endothelial cells showed only a marginal polarity. The u-PA antigen was present in a plasmin-activatable form (single chain u-PA) and in a nonactivatable form (probably u-PA: PAI-1 complex). During the induction of u-PA by TNF, the ratio between plasmin-activatable u-PA and total u-PA decreased markedly. This may indicate that TNF also increases the degree of u-PA activation. The parallel induction of the synthesis and secretion of both u-PA and PAI-1 by endothelial cells adds a new aspect to the alterations of the fibrinolytic system caused by inflammatory mediators. This aspect may be significant for the regulation of cell-associated and interstitial plasminogen activator activity.
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PMID:Tumor necrosis factor induces the production of urokinase-type plasminogen activator by human endothelial cells. 214 60

Human peripheral blood monocytes isolated by centrifugation with Mono-Poly resolving medium, and human alveolar macrophages obtained by lung lavage during fiberoscopic bronchoscopy, were cultured in RPMI containing 2% foetal calf serum. The cultures were exposed to modified human proteins: alpha-1-antitrypsin cleaved with papain, fibrinogen degradation products (fraction D) purified from plasmin digest, and non-enzymatically glycosylated (glycated) serum albumin. Conditioned macrophage media were tested for the contents of acute phase cytokines by bioassay with hepatoma cells, and the concentration of interleukin-6 was determined with ELISA. Modified proteins stimulated macrophages to produce acute phase cytokines and the response was not abrogated by polymyxin B in distinction to stimulation of macrophages by endotoxin. Our data indicate that some proteolytically damaged proteins or the end glycosylation products formed in pathological states (acute inflammation, diabetes) may be responsible for the appearance of cytokines in the circulation.
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PMID:Origin of circulating acute phase cytokines: modified proteins may trigger IL-6 production by macrophages. Preliminary report. 804 10

Tumor necrosis factor (TNF) is considered to be a pivotal mediator of endotoxin-induced lethality. To assess the intermediate role of TNF in specific systemic inflammatory responses known to contribute to tissue injury in endotoxemia, eight healthy adult chimpanzees were intravenously injected with Escherichia coli endotoxin (4 ng/kg). In four of these animals the administration of endotoxin was followed immediately by a bolus intravenous injection of an anti-TNF monoclonal antibody (15 mg/kg). Treatment with anti-TNF completely prevented the endotoxin-induced increase in serum TNF activity, and profoundly reduced the appearance of interleukin-6 and -8 (both P < .05). Neutrophilia and lymphopenia were not affected by anti-TNF, whereas neutrophil degranulation, as measured by the plasma concentrations of elastase-alpha 1-antitrypsin complexes, was only slightly reduced (peak levels after endotoxin alone 31.0 +/- 3.4 ng/mL, versus 25.5 +/- 3.4 ng/mL after endotoxin with anti-TNF; P < .05). Anti-TNF did not influence endotoxin-induced activation of the coagulation system, as reflected by unchanged increases in the plasma concentrations of the prothrombin fragment F1 + 2 and thrombin-antithrombin III complexes. In contrast, anti-TNF strongly attenuated the activation of the fibrinolytic system, ie, peak plasma levels of plasmin-alpha 2-antiplasmin were 33.8 +/- 11.1 nmol/L after endotoxin alone and 17.0 +/- 2.9 nmol/L after endotoxin with anti-TNF (P < .05). These results suggest that TNF is not the common mediator of systemic inflammatory changes in low-grade endotoxemia. Moreover, the finding that in this mild model anti-TNF specifically inhibited fibrinolysis suggests that treatment with anti-TNF potentially may enhance the tendency towards microvascular thrombosis in sepsis.
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PMID:Differential effects of anti-tumor necrosis factor monoclonal antibodies on systemic inflammatory responses in experimental endotoxemia in chimpanzees. 828 42

To study the mechanism underlying the high lipoprotein (a) [Lp(a)] level in uremic patients on chronic hemodialysis, we investigated the levels of Lp(a), acute phase reactants (C-reactive protein and sialic acid), and interleukin-6 (IL-6) in 54 dialysis patients. The mean [95% CI] Lp(a) level was increased in the hemodialysis patients compared with the 30 controls (30 [25-36] vs. 18 [14-23] mg/dl, p < 0.005). Among dialysis patients, 46% had an Lp(a) level > 30 mg/dl, which was significantly higher than the percentage in the control group (17%). The levels of C-reactive protein, sialic acid, and IL-6 were also increased in dialysis subjects compared with controls (200 [134-299] vs. 37 [24-58] micrograms/dl, p < 0.0001; 63 [59-66] vs. 54 [52-56] mg/dl, p < 0.002; and 9.2 [7.8-11] vs. 5.5 [5.0-6.1] pg/ml, p < 0.0005, respectively). The Lp(a) level was positively correlated with that of C-reactive protein (r = 0.415, p < 0.002), sialic acid (r = 0.426, p < 0.002), and IL-6 (r = 0.298, p < 0.05) in the hemodialysis patients, but not in the controls or non-dialysis uremic patients. The Lp(a) level in the dialysis patients was also positively correlated with activation markers of coagulation (thrombin-antithrombin III complex and plasmin-alpha 2-plasmin inhibitor complex, p < 0.005). These results indicate that the Lp(a) level is closely related to the acute phase reaction and hypercoagulability in chronic hemodialysis patients.
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PMID:High lipoprotein (a) levels in chronic hemodialysis patients are closely related to the acute phase reaction. 856 Apr 4

In previous studies, we have shown that administration of monoclonal antibody (MoAb) C6B7 against human factor XII to baboons challenged with a lethal dose of Escherichia coli abrogates activation of the contact system and modulates secondary hypotension. To evaluate the contribution of activated contact proteases to the appearance of other inflammatory mediators in this experimental model of sepsis, we studied the effect of administration of MoAb C6B7 on activation of complement and fibrinolytic cascades, stimulation of neutrophil degranulation, and release of the proinflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6). Activation of the complement system, as reflected by circulating C3b/c and C4b/c levels, was significantly reduced in five animals that had received MoAb C6B7 before a lethal dose of E coli as compared with five control animals that had been given a lethal challenge only. Inhibition of contact activation also modulated the fibrinolytic response, since the release of tissue-type plasminogen activator (t-PA) and the appearance of plasmin-alpha2-antiplasmin (PAP) complexes into the circulation was significantly attenuated upon pretreatment with anti-factor XII MoAb. In contrast, plasma levels of plasminogen activator inhibitor (PAI) were modestly enhanced in the treatment group. Degranulation of neutrophils, as assessed by circulating elastase-alpha1-protease inhibitor complexes, and release of IL-6 but not of TNF-alpha was decreased in anti-factor XII-treated animals. Observed differences in the inflammatory response between treatment and control groups were not likely due to different challenges, since the number of E coli that had been infused, as well as circulating levels of endotoxin after the challenge, were similar for both groups. These data suggest that activation of the contact system modulates directly or indirectly various mediator systems involved in the inflammatory response during severe sepsis in nonhuman primates.
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PMID:Inhibition of factor XII in septic baboons attenuates the activation of complement and fibrinolytic systems and reduces the release of interleukin-6 and neutrophil elastase. 863 Mar 96

Twelve patients with acute pancreatitis admitted to our department between January 1993 and December 1994 were studied prospectively and classified into two groups (severe group, five patients; mild group, seven patients), according to the criteria for grading severity of acute pancreatitis proposed by the Research Committee for Intractable Diseases of the Pancreas, Japanese Ministry of Health and Welfare (1990). To evaluate markers for early estimation of the severity of acute pancreatitis, we measured serum changes in various parameters. In the severe group interleukin-6 (IL-6) levels were increased significantly 5, 24, 72, and 120 h after the onset (p < 0.01), compared with the mild group. C-reactive protein (CRP), thrombin antithrombin III, and alpha 2-plasmin inhibitor plasmin complex levels were significantly increased only at the 72-h time point. Peak values of interleukin-8 (IL-8) and soluble human E selectin were observed at 5 and 72 h, respectively, after the onset. There was a significant correlation between IL-6 at 5 h and both pancreatic secretory trypsin inhibitor (r = 0.85) and CRP (r = 0.94) at 72 h. We therefore conclude that IL-6 is a useful marker for assessment of the severity of acute pancreatitis in its early stages.
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PMID:Interleukin-6 is a useful marker for early prediction of the severity of acute pancreatitis. 959 21

Plasmin, the primary fibrinolytic enzyme, has a broad substrate spectrum and participates in other biological processes dependent upon proteolytic activity. Consequently, plasmin activity is tightly regulated by plasminogen activators and protease inhibitors. In this study, we examined whether regulation of plasminogen gene expression also might provide a new mechanism for controlling this system. We examined the effects of recombinant human interleukin-6 (rhIL-6), a pleiotropic cytokine, on plasminogen mRNA expression in primary murine hepatocytes and Hep3B human hepatoma cells. In primary hepatocytes, rhIL-6 and hydrocortisone separately increased plasminogen mRNA expression, but hydrocortisone did not markedly enhance the response to rhIL-6. Hep3B hepatoma cells exhibited more modest responses to rhIL-6. We used the polymerase chain reaction to amplify a 1,067-bp fragment of the human plasminogen promoter/5' flanking region. This fragment was cloned upstream of a luciferase reporter gene. Hep3B cells transiently transfected with this construct provided approximately 100-fold higher luciferase activity compared to cells transfected with control plasmids, and luciferase activity was increased approximately 4.5-fold when these cells were treated with rhIL-6. Furthermore, mice injected with rhIL-6 exhibited increases in hepatic plasminogen mRNA. Circulating plasminogen levels were significantly higher in the mice injected with rhIL-6 compared to mice injected with saline. Mice injected with lipopolysaccharide (an inducer of IL-6 in vivo) also showed increased hepatic plasminogen mRNA. Thus, plasminogen gene expression can be modulated by rhIL-6, suggesting a new mechanism for regulating biological systems that use plasmin.
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PMID:Regulation of plasminogen gene expression by interleukin-6. 911 83

Lung epithelial cells (A549) synthesize and secrete fibrinogen (FBG) in vitro when stimulated with interleukin-6 and dexamethasone. This FBG secretion is polarized in the basolateral direction, suggesting that FBG is a component of the extracellular matrix (ECM). Immunofluorescent staining of A549 cells showed a fibrillar pattern of FBG, similar to the staining detected using antibodies against the matrix constituents, collagen type IV and fibronectin (FN). The same pattern of staining was detected using antibodies against fibrinopeptides A and B, as well as with the T2G1 monoclonal antibody against the fibrin-specific epitope, beta15-21. Matrix staining was unaltered in the presence of the thrombin inhibitor, hirudin, or the plasmin inhibitor, aprotinin, consistent with the interpretation that matrix deposition of FBG does not require such enzymatic action. Metabolic labeling studies confirmed that FBG secreted from A549 cells or deposited into the ECM showed no evidence of thrombin or plasmin proteolytic processing or of transglutaminase-mediated covalent cross-linking (gamma-gamma dimers or alpha-polymers). Incubation of either A549 cell-derived or purified plasma FBG with cultures of human foreskin fibroblasts resulted in FBG deposition in the ECM that colocalized with matrix fibrils containing endogenously produced FN and laminin (LN). Binding of FBG to this exogenously produced matrix was unaltered by inhibition of thrombin and plasmin action, yet also exhibited exposure of the fibrin-specific epitope, beta15-21. The majority (approximately 70%) of newly synthesized and secreted FBG is bound to the cell surface as determined by its trypsin-sensitivity. Cell surface-bound FBG is initially deoxycholate-soluble, which, over time, becomes incorporated in the deoxycholate-insoluble ECM in a similar fashion to FN. These data suggest that matrix incorporation requires the binding of secreted FBG to cell-associated matrix assembly sites. However, unlike FN, FBG in the ECM is composed of the dimeric protamer (A alpha/B beta/gamma gamma) and not high molecular weight polymers indicative of fibrin. This study provides evidence that deposition of FBG in both endogenous and exogenously produced matrices results in conformational changes that occur independently of thrombin cleavage. This matrix-bound FBG, on which unique cell-reactive domains are likely exposed, could augment cellular response mechanisms evoked during injury and inflammation.
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PMID:Thrombin cleavage-independent deposition of fibrinogen in extracellular matrices. 932 31


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