Induction of alpha 1-acid glycoprotein by recombinant human interleukin-1 in rat hepatoma cells

Alpha-1-acid glycoprotein

Alpha-1-acid glycoprotein (AGP) or orosomucoid (ORM) is a 41-43-kDa glycoprotein with a pI of 2.8-3.8. The peptide moiety is a single chain of 183 amino acids (human) or 187 amino acids (rat) with two and one disulfide bridges in humans and rats,respectively. The carbohydrate content represents 45% of the molecular weight attached in the form of five to six highly sialylated complex-type-N-linked glycans. AGP is one of the major acute phase proteins in humans, rats, mice and other species. As most acute phase proteins, its serum concentration increases in response to systemic tissue injury, inflammation or infection, and these changes in serum protein concentrations have been correlated with increases in hepatic synthesis. Expression of the AGP gene is controlled by a combination of the major regulatory mediators, i.e. glucocorticoids and a cytokine network involving mainly interleukin-1 beta (IL-1 beta), tumour necrosis factor-alpha (TNF alpha), interleukin-6 and IL-6 related cytokines. It is now well established that the acute phase response may take place in extra-hepatic cell types, and may be regulated by inflammatory mediators as observed in hepatocytes. The biological function of AGP remains unknown; however,a number of activities of possible physiological significance, such as various immunomodulating effects, have been described. AGP also has the ability to bind and to carry numerous basic and neutral lipophilic drugs from endogenous (steroid hormones) and exogenous origin; one to seven binding sites have been described. AGP can also bind acidic drugs such as phenobarbital. The immunomodulatory as well as the binding activities of AGP have been shown to be mostly dependent on carbohydrate composition. Finally, the use of AGP transgenic animals enabled to address in vivo, functionality of responsive elements and tissue specificity, as well as the effects of drugs that bind to AGP and will be an useful tool to determine the physiological role of AGP.

Synergistic induction of mouse serum amyloid A3 promoter by the inflammatory mediators IL-1 and IL-6

Serum amyloid A (SAA), one of the major acute-phase proteins, increases several hundredfold in concentration in plasma following acute inflammation, primarily as a result of a 200-fold increase in its transcription rate. We have previously demonstrated that a 350-bp promoter fragment from the mouse SAA3 gene could confer conditioned medium-induced expression in cultured cells. The induction is mediated through a 42-bp distal response element (DRE) consisting of three functional regulatory elements. In this study, we show that interleukin-1 (IL-1) is the major cytokine in the conditioned medium responsible for SAA3 induction, and the induction by IL-1 can be effectively blocked by H-7, a protein kinase C inhibitor. Although IL-6 alone had no effect on SAA3 promoter activity, the addition of IL-6 and IL-1 resulted in dramatic synergistic activation of the reporter gene. We further show that the DRE is both necessary and sufficient to confer synergistic induction by IL-1 and IL-6. Moreover, individual mutation of the three regulatory elements within DRE either abolished or drastically reduced the synergistic induction. Our results indicate that synergistic activation of SAA3 promoter by IL-1 and IL-6 is achieved through integration of signals triggered by these two cytokines onto the DRE and that all three functionally distinct regulatory elements in the DRE are required to effectively and fully activate SAA3 gene transcription.

Inducible Expression and Regulation of the α1-Acid Glycoprotein Gene by Alveolar Macrophages: Prostaglandin E2 and Cyclic AMP Act as New Positive Stimuli

We have reported that α1-acid glycoprotein (AGP) gene expression was induced in lung tissue and in alveolar type II cells during pulmonary inflammatory processes, suggesting that local production of this immunomodulatory protein might contribute to the modulation of inflammation within the alveolar space. Because AGP may also be secreted by other cell types in the alveolus, we have investigated the expression and the regulation of the AGP gene in human and rat alveolar macrophages. Spontaneous AGP secretion by alveolar macrophages was increased 4-fold in patients with interstitial lung involvement compared with that in controls. In the rat, immunoprecipitation of [35S]methionine-labeled cell lysates showed that alveolar macrophages synthesize and secrete AGP. IL-1β had no effect by itself, but potentiated the dexamethasone-induced increase in AGP production. RNase protection assay demonstrated that AGP mRNA, undetectable in unstimulated cells, was induced by dexamethasone. Conditioned medium from LPS-stimulated macrophages as well as IL-1β had no effect by themselves, but potentiated the dexamethasone-induced increase in AGP mRNA levels. In addition to cytokines, PGE2 as well as dibutyryl cAMP increased AGP mRNA levels in the presence of dexamethasone. When AGP expression in other cells of the monocyte/macrophage lineage was examined, weak and no AGP production by human blood monocytes and by rat peritoneal macrophages, respectively, were observed. Our data showed that 1) AGP expression is inducible specifically in alveolar macrophages in vivo and in vitro; and 2) PGE2 and cAMP act as new positive stimuli for AGP gene expression.

Hepatocyte differentiation of WIF-B cells includes a high capacity of interleukin-6-mediated induction of alpha 1-acid glycoprotein and alpha 2-macroglobulin

Responsiveness to cytokine-mediated acute inflammatory stimuli of the highly differentiated and polarized WIF-B hybrid cell line was studied by measuring the induction of alpha 1-acid glycoprotein and alpha 2-macroglobulin mRNAs after interleukin-1, interleukin-6 and tumor necrosis factor-alpha treatments in the presence of dexamethasone. Compared with their Fao parent, WIF-B cells were 10 times more responsive to 24-h interleukin-6 induction regarding alpha 2-macroglobulin induction. At variance from the response measured in Fao cells, the late effects of interleukin-6 treatment confirmed the higher sensitivity of WIF-B cells to this cytokine as a 72-h treatment as 10 times more effective than a 24-h treatment at inducting alpha 1-acid glycoprotein mRNA. These findings highlight the hepatocyte differentiation of WIF-B cells compared with other hepatoma cell lines, with respect to the regulation of acute-phase protein gene expression. They also make WIF-B cells a convenient model to study the molecular effects of interleukin-6 in terms of transduction and/or transcription, and the many cross-talks that occur during the regulation of acute-phase protein gene expression.

Inducible Expression of the α1-Acid Glycoprotein by Rat and Human Type II Alveolar Epithelial Cells

α1-Acid glycoprotein (AGP) is a major acute phase protein in rat and human. AGP has important immunomodulatory functions that are potentially important for pulmonary inflammatory response. The liver is the main tissue for AGP synthesis in the organism, but the expression of AGP in the rat lung has not been investigated. We show that AGP mRNA was induced in the lung of dexamethasone-, turpentine-, or LPS-treated rats, whereas AGP mRNA was not detected in the lung of control rats. In the lung of animals treated intratracheally with LPS, in situ hybridization showed that AGP gene expression was restricted to cells located in the corners of the alveolus, consistent with an alveolar type II (ATII) cell localization. The inducible expression of the AGP gene was confirmed in vitro with SV40 T2 cells and rat ATII cells in primary culture: maximal expression required the presence of dexamethasone. IL-1 and the conditioned medium of alveolar macrophages acted synergistically with dexamethasone. Rat ATII cells secreted immunoreactive AGP in vitro when stimulated with dexamethasone or with a combination of dexamethasone and the conditioned medium of alveolar macrophages. In vivo, in the human lung, we detected immunoreactive AGP in hyperplastic ATII cells, whereas we did not detect AGP in the normal lung. We conclude that AGP is expressed in the lung in cases of inflammation and that ATII cells are the main source of AGP in the lung.

Acute phase proteins and transformed cells

Acute phase proteins (APP) are plasma proteins whose concentration and glycosylation alters in response to tissue injury, inflammation, or tumor growth. Significant interspecies and sex differences in APP response exist. APP are produced mainly by hepatocytes, and their synthesis and glycosylation are controlled by a network consisting of cytokines, their soluble receptors, and glucocorticoids. The major cytokines involved in these processes belong to a group of interleukin-6-type cytokines that act through the hematopoietin receptor complex on hepatocytes and JAK-STAT signal transduction pathway. Transformed cells (hepatoma) display significant differences in synthesis of APP, cytokine responsiveness, expression of cytokine-receptor subunits and signal-transduction machinery. The most striking variability relates to the glycosylation alterations induced by cytokines. However, transformed cells (hepatoma) form a basic model for studying and understanding mechanisms controlling the synthesis and glycosylation of APP. Furthermore, APP may be secreted by transformed (tumor) cells of various origins and may display a growth factor-like function in certain cancer types.

Effects of insulin, dexamethasone and cytokines on alpha 1-acid glycoprotein gene expression in primary cultures of normal rat hepatocytes

While the effects of insulin, dexamethasone and cytokines on alpha 1-acid glycoprotein gene expression have been investigated in various hepatoma cell lines, the individual and combined effects of these components on the expression of this gene have been rarely studied in cultured normal rat hepatocytes. In this cell model, we have shown that mRNA levels of alpha 1-acid glycoprotein were not decreased at least during the first 24 h of culture under basal conditions. During these short-term cultures, the expression of alpha 1-acid glycoprotein in normal hepatocytes showed a high degree of responsiveness to dexamethasone alone (20-fold increase) and to dexamethasone associated with various cytokines (interleukin-1 beta, interleukin-6 and tumor necrosis factor alpha) with a 40 to 100-fold increase depending on the cytokine. Insulin alone did not modify alpha 1-acid glycoprotein mRNA; however, this hormone exerted a positive effect (about 50% increase) in the presence of dexamethasone or dexamethasone with cytokines. These results indicate that the regulation of alpha 1-acid glycoprotein in cultured normal rat hepatocytes presents major differences when compared to reported observations in rat hepatoma cell lines.

Alpha 1-acid glycoprotein expression in human leukocytes: possible correlation between alpha 1-acid glycoprotein and inflammatory cytokines in rheumatoid arthritis

alpha 1-Acid glycoprotein is an acute-phase reactant that becomes markedly elevated in serum during inflammation and has an immunosuppressive effect on lymphocyte functions. Patients with collagen diseases had significant increases of alpha 1-acid glycoprotein in their serum and on the surface of peripheral leukocytes compared with controls. The levels from patients with rheumatoid arthritis were higher than those from patients with systemic lupus erythematosus, mixed connective tissue disease, and Behçet's disease. In patients with rheumatoid arthritis, the value of serum alpha 1-acid glycoprotein correlated with disease activity. Among leukocyte subpopulations, monocytes showed more alpha 1-acid glycoprotein on their surface than polymorphonuclear leukocytes and lymphocytes. The cell surface expression of alpha 1-acid glycoprotein on cultured monocytes surface peaked after 48 h. Interleukin-1 beta and tumor necrosis factor-alpha stimulated the production of alpha 1-acid glycoprotein RNA message in peripheral blood mononuclear cells over 18-24 h during cell culture. The results show that serum alpha 1-acid glycoprotein reflects systemic disease activity in rheumatoid arthritis. Furthermore, monocytes may serve as a source of production of alpha 1-acid glycoprotein.

Transforming growth factors type-beta and dexamethasone attenuate group II phospholipase A2 gene expression by interleukin-1 and forskolin in rat mesangial cells

Treatment of rat mesangial cells with interleukin-1 beta (IL-1 beta) and forskolin induced, in a synergistic fashion, the expression of group II phospholipase A2 (PLA2) mRNA, with subsequent increased synthesis and secretion of PLA2. In contrast, interleukin-6 did not increase PLA2 mRNA levels of PLA2 activity. Transforming growth factor (TGF) beta 1, TGF beta 2 and TGF beta 3 equipotently attenuated the IL-1 beta- and forskolin-induced elevation of PLA2 mRNA, as well as PLA2 synthesis and secretion. The glucocorticoid dexamethasone only partially suppressed the IL-1 beta- and forskolin-induced elevation of PLA2 mRNA, but totally inhibited PLA2 synthesis and secretion.

Modifications of hepatic alpha-1-acid glycoprotein and albumin gene expression in rats treated with phenobarbital

The serum level of alpha 1-acid glycoprotein (alpha 1-AGP) is significantly increased in various animal species by treatment with cytokines, glucocorticoids and phenobarbital. The mechanisms responsible for the cytokine-induced and glucocorticoid-induced increases are now well documented, but not so in the case of phenobarbital. The main purpose of this study was to assess whether phenobarbital acts on alpha 1-AGP synthesis in the liver at the transcriptional or translational level. Male Dark Agouti rats received 70 mg phenobarbital/kg daily for 7 days. The analysis of total hepatic RNA showed that a single injection of phenobarbital induced an 11-fold increase in phenobarbital-dependent cytochrome P450IIB mRNA, whereas seven injections of phenobarbital were required to induce a maximum 5.5-fold increase in alpha 1-AGP mRNA. Concurrently, the transcription rate of the alpha 1-AGP gene rose 3.5-fold. Hepatocytes isolated after the seventh injection of phenobarbital showed a threefold increased capacity to secrete alpha 1-AGP, corresponding to a 3.2-fold increased alpha 1-AGP mRNA content in the liver. In conditions in which its effect on the induction of alpha 1-AGP synthesis was maximum, phenobarbital caused a 30% reduction in liver albumin mRNA and in albumin secretion by isolated hepatocytes, resulting from a 60-70% reduction in the rate of transcription of the albumin gene measured in isolated nuclei. We conclude that the effect of phenobarbital on alpha 1-AGP and albumin gene expression occurs at the transcriptional rather than the translational level.

Evidence for continuous stimulation of interleukin-6 production in Crohn's disease

Increased serum concentrations of acute-phase proteins can be found in active inflammatory bowel disease. Because interleukin 6 (IL-6) is one of the main mediators of acute-phase protein synthesis by the liver, the serum concentrations of IL-6 and the acute-phase proteins C-reactive protein, alpha 1-antitrypsin, and alpha 1-acid glycoprotein were determined in 70 patients with Crohn's disease (CD) and 23 patients with ulcerative colitis (UC). Disease activities were determined by established clinical activity indices. Serum IL-6 concentrations were significantly (P less than 0.005) increased in patients with CD (mean +/- SEM, 6.8 +/- 0.9 U/mL) compared with patients with UC (mean, less than 4 U/mL) and healthy controls (mean, less than 4 U/mL). Of patients with CD, 68.5% had serum IL-6 concentrations of greater than or equal to 4 U/mL, compared with 21.7% of patients with UC and 0% of healthy controls. There was a tendency toward higher serum IL-6 concentrations in patients with active CD than in patients with inactive disease. However, these differences were not statistically significant. There was no correlation between IL-6 serum concentrations and clinical activity indices, possibly because of the short circulatory lifetime and rapid hepatic clearance of IL-6 from the portal venous blood. In contrast to serum IL-6, acute-phase proteins, which have a longer circulatory lifetime, were significantly correlated with clinical activity indices. Only the follow-up of individual patients with initially highly active disease showed a further increase in IL-6 levels during acute exacerbations of the inflammatory process. The results show that most patients with even moderately active CD have significantly increased serum concentrations of IL-6, most probably reflecting a continuous stimulation of IL-6-producing cells.

Recombinant human C5a induces transcription but not translation of interleukin-1 beta mRNA in human monocytes

The effect of recombinant human C5a (rhC5a) on the synthesis of interleukin-1 beta (IL 1 beta) was investigated in highly purified human monocytes, isolated by leukapheresis and counter-current elutriation. RhC5a induced IL 1 beta mRNA synthesis in a dose- and time-dependent manner; maximal induction was achieved at 3 h with rhC5a concentrations of 200 to 500 ng/ml. The IL 1 beta mRNA induction with rhC5a was about 75% of the response observed using lipopolysaccharide (LPS) as the stimulus (300 ng/ml). On the other hand, rhC5a in optimal concentrations only weakly stimulated IL 1 beta protein synthesis, as measured by a two-site-directed enzyme-linked immunoassay. When LPS- or C5a-stimulated RNA was used to program IL 1 beta synthesis in an in vitro translation system from rabbit reticulocytes, no difference in translational efficiency was observed. Our results indicate that, in human monocytes, two signals for IL 1 beta gene expression are necessary, one signal for transcriptional activation and a second signal to induce translation of the mRNA.

Insulin modulation of acute-phase protein production in a human hepatoma cell line

Insulin is widely used as a growth factor in hepatocyte culture but its effect on the production of acute-phase proteins has not been studied. By measuring four positive (fibrinogen, alpha 1-antitrypsin, alpha 1-acid glycoprotein, and alpha 1-antichymotrypsin) and four negative (albumin, prealbumin, transferrin, and retinol binding protein) acute-phase proteins produced by the Hep G2 hepatoma cell line, we have shown that insulin is an important modulator of acute-phase protein production. Our data show that insulin is able to inhibit the synthesis of prealbumin, transferrin, and fibrinogen. The results also show a complex interaction between insulin, interleukin 6, and glucocorticoids because insulin is able to inhibit the dexamethasone induction of alpha 1-antichymotrypsin, and in the presence of interleukin 6, dexamethasone is able to regulate the production of fibrinogen and prealbumin. The regulatory role of insulin in fibrinogen production was confirmed by pulse chase labeling followed by immunoprecipitation and fluorography.

Murine tumor cells metastasizing selectively in the liver: ability to produce hepatocyte-activating cytokines interleukin-1 and/or -6

Increasing evidence suggests that an intimate correlation may exist between the production of a cytokine, granulocyte-macrophage colony-stimulating factor (GM-CSF) and the ability to metastasize spontaneously in the lungs in murine transplantable tumors. In the present study, we further examined the cytokine production by tumor cells with the ability to metastasize in the liver. Four out of 8 test tumors, which produced metastasis in the lungs but not in the liver, exhibited the ability to produce GM-CSF activity in culture. Three other tumors produced metastasis in the liver but not in the lungs. These tumor cells exhibited no ability to produce GM-CSF, but two of them expressed an interleukin-6 (IL-6) mRNA and also produced IL-6 activity in the culture fluids. One of the two IL-6-producing tumors and the remaining liver metastatic tumor produced interleukin-1 (IL-1) as revealed by bioassay and neutralization test. In the tumor cells producing pulmonary metastasis, neither IL-6 gene expression nor IL-1 production could be detected. The last test tumor, which produced no metastasis either in the lungs or liver, produced neither GM-CSF, IL-1 nor IL-6. Furthermore, injection of antisera reactive to recombinant murine IL-6 caused a marked decrease of the number of liver metastases of an IL-6-producing tumor, but not lung metastases of a GM-CSF-producing tumor, which could be markedly inhibited by injection of anti-recombinant murine GM-CSF sera. These results suggest the possibility that there may be a correlation between the cytokines produced by tumor cells and their organ specificity in spontaneous metastasis, and also indicate that these tumor models may provide a useful tool for studies on the role of cytokines in tumor metastasis.

PDGF suppresses the activation of group II phospholipase A2 gene expression by interleukin 1 and forskolin in mesangial cells

Treatment of rat mesangial cells with interleukin 1 beta (IL-1 beta) and forskolin greatly enhanced the expression of group II phospholipase A2 (PLA2) mRNA, with subsequent increased synthesis and secretion of PLA2, as detected by PLA2 activity measurements and immunoprecipitation of culture media of [35S]methionine-labelled mesangial cells. PDGF-BB dose-dependently suppressed the IL-1 beta- and forskolin-induced elevation of PLA2 mRNA, as well as PLA2 synthesis and secretion. In contrast, PDGF-AA had no inhibitory effect. The tyrosine kinase inhibitor genistein dose-dependently antagonized the inhibitory effect of PDGF-BB on IL-1 beta-stimulated PLA2 secretion, thus suggesting that tyrosine phosphorylation may be required for PDGF-BB inhibition of PLA2 gene expression in mesangial 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.

Acute-phase response of human hepatocytes: regulation of acute-phase protein synthesis by interleukin-6

Human hepatocytes in primary culture were used as a model system to investigate the mechanism(s) involved in the induction of the acute-phase response in human liver. Hepatocytes were incubated with increasing amounts of recombinant human interleukin-1 beta, recombinant interleukin-6 and tumor necrosis factor-alpha. Synthesis of C-reactive protein was studied at the mRNA and protein levels. Only recombinant interleukin-6 was capable of inducing C-reactive protein-mRNA and C-reactive protein-protein synthesis. Also, fibrinogen and alpha-1-antitrypsin synthesis measured by immunoprecipitation with specific antisera increased in a dose-dependent, time-dependent manner, whereas albumin synthesis decreased to about 50% of controls. Maximal effects were observed at 100 to 300 units of recombinant interleukin-6/ml culture medium after 20 hr of incubation. Although the synthetic glucocorticoid dexamethasone slightly modulated the effect of recombinant interleukin-6, it was not an absolute requirement for the induction of acute-phase protein synthesis in human hepatocytes. In pulse-chase experiments it was shown that the time course of the disappearance of the acute-phase proteins from the cells and their appearance in the medium is not influenced by recombinant interleukin-6. This finding suggests that recombinant interleukin-6 exerts its regulatory effect on acute-phase protein synthesis at the pretranslational level.

Differential activity of interleukin 1 alpha and interleukin 1 beta in the stimulation of the immune response in vivo

The biological activities of human recombinant interleukin (IL) 1 alpha and IL 1 beta were compared in different biological systems. The two IL 1 forms were equally active in vitro in inducing proliferation of murine thymocytes and of the murine T helper clone D10.G4.1, and in triggering release of prostaglandin E2 from human skin fibroblasts. In vivo, IL 1 alpha and IL 1 beta were similarly pyrogenic both in rabbits and mice, and could equally increase the circulating levels of the acute phase protein serum amyloid A in mice. However, only IL 1 beta showed immunostimulatory activity in vivo, as it could enhance the number of specific antibody-producing cells in the spleen of mice immunized with either a T-dependent or a T-independent antigen. Although devoid of immunostimulatory activity, IL 1 alpha could efficiently compete immunostimulation induced by IL 1 beta, suggesting an effective interaction with the IL 1 receptor. Thus, IL 1 beta appears to have an important role in the positive regulation of immune responses, while IL 1 alpha may act as down-regulator of the IL 1 beta effect.

Differential effects of endotoxin and fibrinogen degradation products (FDPS) on liver synthesis of fibrinogen and albumin: evidence for the involvement of a novel monokine in the stimulation of fibrinogen synthesis induced by FDPS

1. Administration of endotoxin or fibrinogen degradation products (FDPs) in rats increase fibrinogen synthesis comparable to that found during the acute phase response. 2. An increased fibrinogen synthesis is also found in co-cultures of hepatocytes with peripheral blood mononuclear cells upon administration of endotoxin or FDPs, but not in primary cultures of hepatocytes alone. 3. However, the increased synthesis of fibrinogen by FDPs is not accompanied by a decreased albumin synthesis, as in the case of stimulated fibrinogen synthesis induced by endotoxin in vivo and in co-cultures of hepatocytes with peripheral blood mononuclear cells, or induced by monocytic products in vivo and in primary cultures of hepatocytes alone. 4. Since IL-1 and/or IL-6 could not be accounted for the stimulation of fibrinogen synthesis without a decreased albumin synthesis, a novel monokine produced by mononuclear cells upon FDP administration might be involved.

Fate and biological action of human recombinant interleukin 1 beta in the rat in vivo

The plasma half life of recombinant human interleukin 1 beta (rhIL 1 beta) was determined in rats by measuring the disappearance of the radioactivity of 125I-labeled rhIL 1 beta from the circulation. The plasma clearance showed a biphasic behavior: an initial fast disappearance (half life of about 3 min) was followed by a second slower one (half life of about 4 h). Twenty minutes after a single-dose injection of 125I-labeled rhIL 1 beta most of the radioactivity was concentrated in kidneys, liver and intestine. rhIL 1 beta induced the synthesis of alpha 1-acid glycoprotein (AGP), alpha 1-cysteine proteinase inhibitor (CPI) and beta-fibrinogen mRNA in liver. Half maximal stimulation was elicited by approximately 3000 U of rhIL 1 beta per animal. The mRNA changes for AGP and CPI were followed by corresponding protein increases in serum. Twenty hours after rhIL 1 beta injection, serum AGP rose from 0.7 to 2.5 mg/ml. CPI increased from 0.3 to 1.9 mg/ml 25 h after administration of rhIL 1 beta. Within 20 h after rhIL 1 beta injection, albumin serum concentration showed a strong decrease, preceded by a reduction in hepatic albumin mRNA levels. Neither changes in albumin synthesis nor degradation can explain this decrease suggesting that other mechanisms such as increased transvascular permeability are involved.