Synthesis Of Acute Phase Proteins Research Articles

Regulation of metabolism and growth during immune challenge: an overview of cytokine function.

Commercially reared food animals encounter serial pathogenic and nonpathogenic immune challenges throughout production. Because of the diversion of nutrients away from growth in support of immune-related processes, immune challenge is considered a major obstacle to animals' achieving their genetic potential for growth or efficiency of gain. Scientists now recognize that many metabolic processes respond directly or indirectly to proinflammatory cytokines. This cytokine-mediated "reprogramming" of metabolism is a homeorhetic mechanism that ensures an adequate supply of nutrients for proliferation of lymphocyte and macrophage populations, antibody production, and hepatic synthesis of acute phase proteins. Proinflammatory cytokines have been linked to altered nutrient uptake and utilization. Anabolic processes are interrupted, and companion catabolic activities are amplified. Furthermore, cytokines may influence prenatal growth and development, and to the extent that postnatal proliferation and differentiation of myogenic and adipogenic cells contribute to postnatal growth, cytokine regulation of these events may ultimately influence growth. The following discussion is an overview of the impact of immune challenge and proinflammatory cytokines on metabolism and growth.

Effects of anabolic steroids on acute phase responses in intra‐abdominal sepsis

The acute phase response is an important adaptive response to sepsis and injury. As anabolic steroids increase protein synthesis we postulated that these agents might also increase hepatic acute phase protein synthesis. Male Wistar rats were pretreated with testosterone or danazol for 48 h prior to caecal ligation and puncture (CLP). Thirty-six h following surgery the animals were killed and blood taken for full blood count, total protein, albumin, α, β and γ globulin fractions on serum electrophoresis, complement C3 and transferrin levels. Danazol increased the α1, α2 and β1 globulin serum protein fractions in comparison with no surgery and CLP alone groups. These results indicate that danazol increases plasma acute phase proteins, as measured by electrophoresis, in this model of intra-abdominal sepsis.

Le rétrocontrôle négatif de l'inflammation: rôle des cytokines antiinflammatoires

Summary Transforming growth factor-β (TGFβ), interferon-α (IFNα), interleukin-4 (IL4), IL10 and IL13 have the capacity for inhibiting the production of inflammatory cvtokines such as IL1, IL6, tumour necrosis factor (TNFα), IL8 and the other chemokines. Consequently, these cytokines have been designated antimflammatory cytokines. In addition, they can counteract the proinflammatory activities of IL1 and TNF, such as tissue factor induction involved in coagulation, or the expression of adhesion molecules on the endothelial cell surface. Furthermore, IL4, IL10, IL13, TGFβ and IFNα can induce the production of IL1 receptor antagonists (IL1ra) which specifically limit the activity of IL1. The main natural inhibitors of TNF are the soluble TNF receptors, the release of which is enhanced during inflammation. Corticoids also repress the production of proinflammatory cytokines but do not affect or even enhance the production of antimflammatory cytokines. IL6, as the main inducer of acute phase protein synthesis, can be considered an antiinflammatory cytokine. However, all proinflammatory producing cells are not similarly sensitive to the effects of antiinflammatory cytokines. In addition, the nature and sequence of messages acting on the target cell may modify its reactivity to the negative signals delivered by the antiinflammatory cytokines. Finally, wide individual heterogeneity amplifies the diversity of the inflammatory responses. Thus, the world of cytokines is a complex one, and the nature of signals and of responding cells as well as the sequences of events are the unique characteristics of an inflammatory process induced by infectious and non-infectious stimuli.

UPMODULATION OF MULTINUCLEATED CELL FORMATION IN LONG-TERM HUMAN BONE MARROW CULTURES BY LEUKAEMIA INHIBITORY FACTOR (LIF)

Inflammatory processes are mediated by many cellular events involving different cell types (leukocytes, monocytes, stromal cells, etc.). Numerous soluble mediators regulate these reactions, including leukaemia inhibitory factor (LIF), a cytokine which may play an important role in inducing acute-phase protein synthesis by hepatocytes during inflammation. This study was designed to determine the effects of LIF on the human monocyte/macrophage lineage and provide a better definition of its behaviour during systemic inflammation. In-vitro exposure of human long-term bone marrow cultures to recombinant human LIF significantly increased (about two-fold) the number of multinucleated cells (MNC) formed after three weeks of culture. These LIF-induced MNC expressed tartrate-resistant acid phosphatase, and LIF increased this intracellular activity by about 50%. MNC displayed phagocytotic activity but were unable to degrade sperm whale dentin or respond to human calcitonin. They did not possess the main characteristics of osteoclasts and were in fact macrophage polykaryons. Our results demonstrate for the first time that LIF can induce macrophage polykaryon formation from human bone marrow culture, suggesting that this factor not only produces leukocytes but also has a direct influence on the monocyte/macrophage lineage.

Reduction of hepatic acute phase response after partial hepatectomy in elderly patients.

The hepatic capacity for acute phase protein synthesis after partial hepatectomy in the elderly patients was prospectively studied. Forty-one patients who consecutively underwent a partial hepatectomy were grouped according to age of greater or less than 70 years; 12 were in the older group and 29 in the younger. The changes in the levels of serum interleukin-6, alpha 1-antitrypsin, alpha 1-acid glycoprotein, haptoglobin, and plasma fibrinogen were measured after surgery. The postoperative changes in standard liver function tests were also measured. The incidence of postoperative infected complications was 25% in the older group and 7% in the younger (P = 0.28). Although postoperative levels of serum interleukin-6 were similar between the two groups, those of serum alpha 1-antitrypsin, alpha 1-acid glycoprotein, and haptoglobin were significantly lower in the elderly (P < 0.05). Postoperative levels of serum alpha 1-antitrypsin and plasma fibrinogen showed an increase of about 30% compared with the preoperative values (P < 0.05) in the younger group, but no significant increase in the older. Postoperative deterioration of serum albumin levels and hepaplastin test values was also significantly more severe in the older group (P < 0.05). We conclude that in the older patients, a reduction of acute phase protein synthesis occurs after partial hepatectomy as a result of a global deterioration of liver function, and may render patients liable to infection.

Acute-Phase Protein Synthesis in Rats Is Influenced by Alterations in Plasma and Muscle Free Amino Acid Pools Related to Lower Plasma Volume Following Trauma

Acute-Phase Protein Synthesis in Rats Is Influenced by Alterations in Plasma and Muscle Free Amino Acid Pools Related to Lower Plasma Volume Following Trauma

Dual Oncostatin M (OSM) Receptors: CLONING AND CHARACTERIZATION OF AN ALTERNATIVE SIGNALING SUBUNIT CONFERRING OSM-SPECIFIC RECEPTOR ACTIVATION

Oncostatin M (OSM) is a cytokine whose structural and functional features are similar to other members of the interleukin (IL)-6 family of cytokines (IL-6, IL-11, leukemia inhibitory factor (LIF), granulocyte colonystimulating factor, ciliary neurotrophic factor, and cardiotrophin-1), many of which utilize gp130 as a common receptor subunit. A biologically active OSM receptor has been previously described that consists of a heterodimer of leukemia inhibitory factor receptor (LIFR) and gp130. This LIFR.gp130 complex is also a functional receptor for LIF. We have cloned and characterized an alternative subunit (OSMRbeta) for an OSM receptor complex (a heterodimer of gp130 and OSMRbeta) that is activated by OSM but not by LIF. The signaling capability of specific receptor subunit combinations was analyzed by independent assays measuring cell proliferation or induction of acute phase protein synthesis. Our results demonstrate that both LIF and OSM cause tyrosine phosphorylation and activation of the gp130.LIFR combination, but the gp130.OSMRbeta complex is activated by OSM only. OSM-induced cellular responses, initiated through low affinity binding to gp130, are mediated by two heterodimeric receptor complexes that utilize alternative signal transducing subunits that confer different cytokine specificities to the receptor complex.

Increase in portal blood interleukin-6 soon after the commencement of digestive surgery

To determine whether cytokines produced in the operative field during digestive surgery selectively spill over into the portal blood, the changes in interleukin-6 (IL-6) levels in portal and peripheral venous blood were assayed at several points in time from the commencement of surgery until 14 days later, in 11 patients. Similar changes in the IL-6 levels were observed in the portal and peripheral blood samples; however, the IL-6 levels in the portal blood reached a maximum 6-12h after the commencement of surgery, being earlier than in the peripheral venous blood. In fact, between 3 and 12h after the commencement of surgery, the IL-6 levels were higher in the portal blood by 33-81 pg/ml. By 24h or more after the commencement of surgery, the IL-6 levels did not differ significantly in the two types of blood samples. Moreover, the C-reactive protein levels 2 days after surgery were even more closely correlated to the maximum IL-6 levels in the portal blood than to those in the peripheral venous blood. These results suggest that IL-6 produced during intra-abdominal digestive surgery initially enters the portal blood, being trapped by IL-6 receptors in the liver, where it may regulate the synthesis of acute-phase proteins as a hepatocyte-stimulating factor.

Characterization and biologic activities of recombinant rat soluble interleukin-6 receptor.

The soluble interleukin-6 receptor (sIL-6R) consists of the extracellular domain of the membrane-bound IL-6 receptor (gp80) found on many types of cells. Contrary to most other soluble cytokine receptors, it possesses in vitro agonistic properties, yet its physiologic role remains unknown. We have generated a cDNA encoding the rat sIL-6R and have expressed and purified the protein using Escherichia coli and baculovirus systems. Analysis of purified protein by electrophoresis and silver staining showed a single band migrating at 35 kDa for E. coli (nonglycosylated) and at 47 kDa for baculovirus-derived material. The purified protein is biologically active, as determined by the ability to convert human hepatoma cells (HepG2) from nonresponsive to responsive to rat IL-6 and induce acute-phase protein synthesis. Most important, we show that rat sIL-6R directly induces proliferation of the IL-6-dependent murine hybridoma cell line (B9) in an IL-6-like manner, with 50% proliferation induced by 100 ng/ml of baculovirus-derived receptor protein. Physiologic concentrations of sIL-6R dramatically enhance the sensitivity of B9 cells to IL-6, indicating that the bioassay for IL-6 is susceptible to modulation by the presence of sIL-6R in rodent serum samples. This sIL-6R-dependent B9 cell proliferation is fully abrogated by antibodies directed against rodent IL-6 and indicates autocrine production of low amounts of IL-6 by the B9 cell line.

Are cytokines possible mediators of cancer cachexia?

The possible role of cytokines in the development of cancer cachexia was reviewed from the literature. Tumor necrosis factor (TNF)-alpha, interleukin (IL)-1, IL-6, interferon (IFN)-gamma and leukemia inhibitory factor (LIF) can elicit many but not all host changes seen in cancer cachexia, including loss of appetite, loss of body weight, and the induction of acute-phase protein synthesis. However, these cytokines are not always demonstrated in the circulation of the cancer patients. The inability to detect circulating cytokines may be due to their low rate of production, their short half-life and rapid clearance from plasma, or their mode of action (autocrine or paracrine). Different cytokines are induced to stimulate the same response. This is very different from hormonal regulation, where a hormone acts on a cell directly through a specific receptor without depending on other mediators. Specific antibodies including anti-IFN-gamma, anti-TNF and anti-IL-6 antibodies, as well as the cyclooxygenase inhibitor indomethacin, have been used to reverse cancer cachexia. Overlapping physiologic activities make it unlikely that a single substance is the sole cause of cancer cachexia. It is hoped that further investigation on other cytokines and their possible relationships with hormones will help to clarify the mechanisms of cancer cachexia in the near future.

Dietary Modulation of Amino Acid Transport in Rat and Human Liver

Specialized diets enriched in the amino acids glutamine and arginine have been shown to benefit surgical patients. In the liver, glutamine supports glutathione biosynthesis, arginine regulates nitric oxide synthesis, and both of these amino acids serve as precursors for ureagenesis, gluconeogenesis, and acute phase protein synthesis. The effects of a diet enriched with glutamine and arginine on hepatic plasma membrane transport activity have not been studied in humans. We hypothesized that feeding supradietary amounts of these nutrients would enhance the activities of the specific carriers which mediate their transmembrane transport in the liver. We fed surgical patients (n= 8) and rats (n= 6) one of three diets: a) a regular diet, b) an enteral liquid diet containing arginine and glutamine, or c) an enteral diet supplemented with pharmacologic amounts of glutamine and arginine. Diets were isocaloric and were administered for 3 days. Hepatic plasma membrane vesicles were prepared from rat liver and from human wedge biopsies obtained at laparotomy. The transport of glutamine and arginine by rat and human vesicles was assayed. Vesicle integrity and functionality were verified by osmolarity plots, enzyme marker enrichments, and time courses. Provision of both a standard enteral liquid diet and one enriched with glutamine and arginine increased the activities of Systems N (glutamine) and y+(arginine) in rat and human liver compared to a control diet. The diet supplemented with glutamine and arginine was the most effective in increasing transport activity. We conclude that the liver responds to diets enriched with specific amino acids by increasing membrane transport activity. This adaptive response provides essential precursors for hepatocytes which may enhance hepatic synthetic functions during catabolic states. This study provides insights into the mechanisms by which enteral nutrition regulates nutrient transport at the cellular level and may provide a biochemical rationale for the use of formulas which are enriched with conditionally essential nutrients.

The hepatocyte growth factor regulates the synthesis of acute-phase proteins in human hepatocytes: Divergent effect on interleukin-6-stimulated genes

Our study addressed the role of the human hepatocyte growth factor (HGF), a potent mitogen for mature rat and human hepatocytes, in the regulation of specific hepatic genes. The experimental evidence obtained in primary cultured human hepatocytes indicates that HGF regulates the synthesis of plasma proteins in a dose-response fashion. It stimulates the synthesis of the negative acute-phase proteins albumin, transferrin, and fibronectin, decreases that of alpha1-antichymotrypsin (ACT) and haptoglobin, and stimulates that of alpha2-macroglobulin (AMG), which in man is insensitive to inflammatory mediators. HGF had no effect on C-reactive protein (CRP) synthesis. These effects differ from those elicited by interleukin-6 (IL-6). The effects of HGF on fibrinogen and alpha1-antitrypsin were, however, similar to those induced by IL-6. The effects of HGF were also observed at the messenger RNA (mRNA) level. Time-course induction experiments showed that the effects of HGF on protein synthesis were delayed by about 48 to 72 hours, in contrast with the 12-hour lag found after IL-6 stimulation. Although the presence of glucocorticoids was not absolutely necessary for HGF to affect plasma protein synthesis, it moderately extended the effects. In pulse-chase experiments, it was found that the action of HGF was not due to an alteration of the rate of secretion of the proteins. The effects of HGF on the synthesis of albumin, transferrin, fibronectin, alpha1-antichymotrypsin, and haptoglobin could be counteracted by the simultaneous presence of IL-6 in the incubation media. A clear additive effect was observed only in the case of fibrinogen. No interaction was observed in the cases of CRP and AMG. The results of this study indicate that the effects of HGF on human hepatocytes may not simply be limited to its mitogenic activity, but that it also regulates hepatic-specific genes and antagonizes, in part, the action of IL-6.

The hepatocyte growth factor regulates the synthesis of acute-phase proteins in human hepatocytes: Divergent effect on interleukin-6-stimulated genes

Our study addressed the role of the human hepatocyte growth factor (HGF), a potent mitogen for mature rat and human hepatocytes, in the regulation of specific hepatic genes. The experimental evidence obtained in primary cultured human hepatocytes indicates that HGF regulates the synthesis of plasma proteins in a dose-response fashion. It stimulates the synthesis of the negative acute-phase proteins albumin, transferrin, and fibronectin, decreases that of alpha1-antichymotrypsin (ACT) and haptoglobin, and stimulates that of alpha2-macroglobulin (AMG), which in man is insensitive to inflammatory mediators. HGF had no effect on C-reactive protein (CRP) synthesis. These effects differ from those elicited by interleukin-6 (IL-6). The effects of HGF on fibrinogen and alpha1-antitrypsin were, however, similar to those induced by IL-6. The effects of HGF were also observed at the messenger RNA (mRNA) level. Time-course induction experiments showed that the effects of HGF on protein synthesis were delayed by about 48 to 72 hours, in contrast with the 12-hour lag found after IL-6 stimulation. Although the presence of glucocorticoids was not absolutely necessary for HGF to affect plasma protein synthesis, it moderately extended the effects. In pulse-chase experiments, it was found that the action of HGF was not due to an alteration of the rate of secretion of the proteins. The effects of HGF on the synthesis of albumin, transferrin, fibronectin, alpha1-antichymotrypsin, and haptoglobin could be counteracted by the simultaneous presence of IL-6 in the incubation media. A clear additive effect was observed only in the case of fibrinogen. No interaction was observed in the cases of CRP and AMG. The results of this study indicate that the effects of HGF on human hepatocytes may not simply be limited to its mitogenic activity, but that it also regulates hepatic-specific genes and antagonizes, in part, the action of IL-6. (Hepatology 1996 Jun;23(6):1345-52)

Gp130 Transducing Receptor Cross-linking Is Sufficient to Induce Interleukin-6 Type Responses

gP130 transducing receptor is involved in the formation of high affinity receptors for the cytokines of the interleukin-6 (IL-6) family. Recruitment of gp130 by IL-6 associated to its receptor leads to the dimerization of the transducing component. In the present study we did characterize the B-S12 monoclonal antibody raised against gp130 and able to elicit IL-6 type biological activities. B-S12 antibody triggered strongly the proliferation of TF1 and XGI hematopoietic cell lines and was able to increase the synthesis of acute phase proteins in HepG2 hepatoma cell line. B-S12 also behaved as a synergistic factor with granulocyte-macrophage colony-stimulating factor for both proliferation and differentiation of CD34-positive hematopoietic cell progenitors. By using a symmetric enzyme-linked immunosorbent assay, allowing the detection of dimeric forms of soluble gp130, we found that addition of B-S12 to gp130 led to its dimerization. Analysis of the tyrosine phosphorylation events in gp130 and Jak kinase family members revealed that B-S12 quickly induced the phosphorylation of gp130 in a neural derived cell line, and that Jak1 and Jak2 were also recruited. In conclusion, we show that gp130 cross-linking with the B-S12 monoclonal antibody was sufficient to generate functional IL-6 type responses in hematopoietic, neural, and hepatic cells.

LUNG-LIVER INTERACTIONS IN SEPSIS AND MULTIPLE ORGAN FAILURE SYNDROME

This article examines interactions between the lungs and the liver during microbial sepsis from four interrelated elements of host defense: (1) control of systemic endotoxemia, bacteremia, and vasoactive by-products of sepsis via hepatic mononuclear phagocytic (Kupffer's) cell clearance; (2) biosynthesis and export of cytokine and eicosanoid inflammatory mediators into hepatic venous blood; (3) metabolic inactivation and detoxification of these mediators by Kupffer's cell-hepatocyte interactions at the hepatic sinusoidal interface; and (4) cytokine-driven synthesis of acute phase proteins, including α 2 -macroglobulin, C-reactive protein, and lipopolysaccharide-binding protein, that are capable of modifying sepsis-related changes in metabolism and inflammation.

Six different cytokines that share GP130 as a receptor subunit, induce serum amyloid A and potentiate the induction of interleukin-6 and the activation of the hypothalamus-pituitary-adrenal axis by interleukin-1

Ciliary neurotrophic factor (CNTF) and interleukin-6 (IL-6) potentiate the elevation of serum corticosterone induced by suboptimal doses of interleukin-1 (IL-1). CNTF also potentiates IL-1-induced serum IL-6. Here, we report that four other cytokines (leukemia inhibitory factor [LIF], oncostatin M [OSM], interleukin-11 and cardiotrophin-1) also potentiated the elevation of serum corticosterone and IL-6 levels induced by IL-1. Furthermore, all the six cytokines studied induced the acute-phase protein serum amyloid A when administered alone. Because these cytokines differ both in structure and in function, but share gp130 as a subunit of their receptors, these results indicate that signaling through gp130 mediates potentiation of IL-1 activities. The potentiation of IL-1-induced serum corticosterone levels is not a consequence of the increased serum IL-6 observed after IL-1 administration. In fact, in IL-6 deficient mice, IL-1 increased serum corticosterone to a level comparable to that observed in wild-type mice. Thus, either endogenous IL-6 does not mediate IL-1-induced corticosterone increase, or its role may be fulfilled by other cytokines. To the extent that gp130-dependent cytokines may serve this role, they may be important feedback regulators of inflammation through the activation of the hypothalamus-pituitary-adrenal axis and the potentiation of acute-phase protein synthesis.

Six Different Cytokines That Share GP130 as a Receptor Subunit, Induce Serum Amyloid A and Potentiate the Induction of InterIeukin-6 and the Activation of the Hypothalamus-Pituitary-Adrenal Axis by Interleukin-1

Ciliary neurotrophic factor (CNTF) and interleukin-6 (IL-6) potentiate the elevation of serum corticosterone induced by suboptimal doses of interleukin-1 (IL-1). CNTF also potentiates IL-1-induced serum IL-6. Here, we report that four other cytokines (leukemia inhibitory factor [LIF], oncostatin M [OSM], interleukin-11 and cardiotrophin-1) also potentiated the elevation of serum corticosterone and IL-6 levels induced by IL-1. Furthermore, all the six cytokines studied induced the acute-phase protein serum amyloid A when administered alone. Because these cytokines differ both in structure and in function, but share gp130 as a subunit of their receptors, these results indicate that signaling through gp130 mediates potentiation of IL-1 activities. The potentiation of IL-1-induced serum corticosterone levels is not a consequence of the increased serum IL-6 observed after IL-1 administration. In fact, in IL-6 deficient mice, IL-1 increased serum corticosterone to a level comparable to that observed in wild-type mice. Thus, either endogenous IL-6 does not mediate IL-1-induced corticosterone increase, or its role may be fulfilled by other cytokines. To the extent that gp130-dependent cytokines may serve this role, they may be important feedback regulators of inflammation through the activation of the hypothalamus-pituitary-adrenal axis and the potentiation of acute-phase protein synthesis.

Microheterogeneity of acute-phase glycoproteins in patients with pulmonary sarcoidosis.

This study was designed to investigate qualitative changes in the carbohydrate side-chains of two acute-phase glycoproteins, alpha 1-acid glycoprotein (AGP) and alpha 1-antichymotrypsin (ACT), in 37 patients with pulmonary sarcoidosis. The glycosylation profile of AGP and ACT was studied using affinity immunoelectrophoresis with the lectin concanavalin A (conA). Serum concentration of soluble receptor for interleukin-2 (sIL-2R) and activity of serum angiotensin converting enzyme (ACE) were measured by specific enzyme-linked immunosorbent assay (ELISA) and enzyme kinetic assay, respectively. Rocket immunoelectrophoresis and nephelometric assay were used to determine serum concentration of AGP, ACT and C-reactive protein (CRP). In 11 patients with active disease, a decreased reactivity of AGP with conA was found as compared with controls (n = 44) and patients with nonactive sarcoidosis (n = 26). A similar tendency was seen with ACT. In the same group, increased concentrations of serum AGP and higher levels of sIL-2R were detected compared with patients with nonactive sarcoidosis. In the entire sarcoidosis group, there was a negative correlation between ACE activity and AGP and ACT affinity for conA (r = -0.6358, and r = -0.5019, respectively) and a positive correlation with sIL-2R level (r = 0.8241). In nine patients with elevated concentrations of serum CRP, no differences were found in disease activity and glycosylation profile of AGP and ACT when compared to patients with normal serum CRP. The results suggest that in active pulmonary sarcoidosis changes in the glycosylation pattern of acute-phase glycoproteins exist, which are similar in trend and magnitude to those found in other chronic inflammatory diseases. The synthesis and glycosylation of acute-phase proteins in pulmonary sarcoidosis are probably regulated independently.

Regulation of Sucrase-Isomaltase Gene Expression in Human Intestinal Epithelial Cells by Inflammatory Cytokines

Using metabolic labeling techniques in human intestinal epithelial cell lines in tissue culture and in situ hybridization techniques in normal and inflamed (Crohn's) intestine, recent studies have shown that there is synthesis of acute phase proteins in enterocytes. Moreover, these studies have shown that acute phase protein biosynthesis in enterocytes is regulated by inflammatory cytokines in a manner characteristic of the physiologic acute phase response. In the course of these studies it was noticed that one inflammatory cytokine, interleukin-6 (IL-6), mediated selective down-regulation of the enterocyte-specific, differentiation-dependent integral membrane protein sucrase-isomaltase (SI) in the Caco2 intestinal epithelial cell line. In the current study we examined the effect of several other inflammatory cytokines interleukin-1 (IL-1 beta), tumor necrosis factor alpha (TNF alpha), and interferon gamma (IFN gamma) on synthesis of SI in Caco2 cells, examined the possibility that inflammatory cytokines affect the synthesis of other enterocyte integral membrane proteins using lactase as a prototype, and examined the possibility that SI gene expression was down-regulated in villous enterocytes in vivo during the local inflammatory response of Crohn's disease. The results show that IL-6 and IFN gamma each mediate a decrease and TNF alpha mediates an increase in synthesis of SI in Caco2 cells. The magnitude of down-regulation by IL-6 and IFN gamma is significantly greater than the up-regulation by TNF alpha. IL-1 beta has no effect on synthesis of SI. Synthesis of lactase is not affected by any of the cytokines. There is a marked specific decrease in SI gene expression in villous enterocytes in acutely inflamed Crohn's ileum as compared to adjacent uninflamed ileum and normal ileum. Taken together, these data show that inflammatory cytokines have specific and selective effects on the expression of the brush border hydrolase SI in tissue culture and in vivo and provide evidence for a previously unrecognized mechanism for disaccharidase deficiency in intestinal inflammation.

Murine Cardiotrophin-1 Stimulates the Acute-Phase Response in Rat Hepatocytes and H35 Hepatoma Cells

Mouse cardiotrophin-1 (CT-1) is a hypertrophy-inducing factor for cardiac myocytes and interacts with cell surface receptors that incorporate the signaling molecule gp130. Because other cytokines utilizing this receptor subunit stimulate acute-phase protein synthesis, we tested cardiotrophin-1 in in vitro assays of protein synthesis by primary rat hepatocytes, rat hepatoma cells (H35), and human hepatoma cells (HepG2). CT-1 showed a dose-dependent induction of protein synthesis by primary rat hepatocytes, with effective concentrations ranging from 0.1 to 100 ng/ml. Production of a number of acute-phase proteins, including alpha 1-cysteine proteinase inhibitor ( alpha 1-CPI), alpha 1-proteinase inhibitor (alpha 1-Pi), alpha 2-macroglobulin, and alpha 1-acid glycoprotein, was markedly increased at 48 and 72 h of cytokine stimulation. In rat H35 cells, CT-1 stimulated alpha 1-Pi and alpha 1-CPI protein production and upregulated alpha 1-CPI mRNA levels with similar potency. Compared with other IL-6-type human cytokines at optimal concentrations in parallel assays, CT-1 induced similar levels of acute-phase proteins as human oncostatin M (OM) and leukemia inhibitory factor (LIF), whereas human IL-6 induced the greatest levels of alpha 1-CPI or alpha 1-Pi production by H35 cells. When tested on human HepG2 cells, murine CT-1 was far less effective, in that it stimulated alpha 1-antichymotrypsin production only at very high concentrations (100 ng/ml) but did not alter haptoglobin or alpha 1-Pi. Human OM and IL-6 were effective at lower concentrations and induced much higher levels of acute-phase protein synthesis, whereas LIF activity was similar to that to CT-1. These results show that murine CT-1 is a strong acute-phase mediator for rat hepatocytes in vitro and its activity is similar to LIF on rat hepatocytes, H35 cells, and HepG2 cells.