Interleukin 6 induces a liver-specific nuclear protein that binds to the promoter of acute-phase genes

Serum amyloid A expression in liver promotes synovial macrophage activation and chronic arthritis via NFAT5

Nuclear factor of activated T-cells 5 (NFAT5), an osmo-sensitive transcription factor, can be activated by isotonic stimuli, such as infection. It remains unclear, however, whether NFAT5 is required for damage-associated molecular pattern-triggered (DAMP-triggered) inflammation and immunity. Here, we found that several DAMPs increased NFAT5 expression in macrophages. In particular, serum amyloid A (SAA), primarily generated by the liver, substantially upregulated NFAT5 expression and activity through TLR2/4-JNK signalling pathway. Moreover, the SAA-TLR2/4-NFAT5 axis promoted migration and chemotaxis of macrophages in an IL-6- and chemokine ligand 2-dependent (CCL2-dependent) manner in vitro. Intraarticular injection of SAA markedly accelerated macrophage infiltration and arthritis progression in mice. By contrast, genetic ablation of NFAT5 or TLR2/4 rescued the pathology induced by SAA, confirming the SAA-TLR2/4-NFAT5 axis in vivo. Myeloid-specific depletion of NFAT5 also attenuated SAA-accelerated arthritis. Of note, inflammatory arthritis in mice strikingly induced SAA overexpression in the liver. Conversely, forced overexpression of the SAA gene in the liver accelerated joint damage, indicating that the liver contributes to bolstering chronic inflammation at remote sites by secreting SAA. Collectively, this study underscores the importance of the SAA-TLR2/4-NFAT5 axis in innate immunity, suggesting that acute phase reactant SAA mediates mutual interactions between liver and joints and ultimately aggravates chronic arthritis by enhancing macrophage activation.

Modulation of nuclear factor-kappa B activation by the endoplasmic reticulum stress sensor PERK to mediate estrogen-induced apoptosis in breast cancer cells

Stress responses are critical for estrogen (E₂)-induced apoptosis in E₂-deprived breast cancer cells. Nuclear factor-kappa B (NF-κB) is an important therapeutic target to prevent stress responses in chronic inflammatory diseases including cancer. However, whether E₂ activates NF-κB to participate in stress-associated apoptosis in E₂-deprived breast cancer cells is unknown. Here, we demonstrated that E₂ differentially modulates NF-κB activity according to treatment time. E₂ initially has significant potential to suppress NF-κB activation; it completely blocks tumor necrosis factor alpha (TNFα)-induced activation of NF-κB. We found that E₂ preferentially and constantly enhances the expression of the adipogenic transcription factor CCAAT/enhancer binding protein beta (C/EBPβ), which is responsible for the suppression of NF-κB activation by E₂ in MCF-7:5C cells. Interestingly, NF-κB p65 DNA-binding activity is increased when E₂ is administered for 48 h, leading to the induction of TNFα and associated apoptosis. Blocking the nuclear translocation of NF-κB can completely prevent the induction of TNFα and apoptosis induced by E₂. Further examination revealed that protein kinase RNA-like endoplasmic reticulum kinase (PERK), a stress sensor of unfolded protein response (UPR), plays an essential role in the late activation of NF-κB by E₂. This modulation between PERK and NF-κB is mainly mediated by a stress responsive transcription factor, transducer and activator of transcription 3 (STAT3), independently of the classic canonical IκBα signaling pathway. Thus, inhibition of PERK kinase activity completely blocks the DNA binding of both STAT3 and NF-κB, thereby preventing induction of NF-κB-dependent genes and E₂-induced apoptosis. All of these findings suggest that PERK is a key regulator to convey stress signals from the endoplasmic reticulum to the nucleus and illustrate a crucial role for the novel PERK/STAT3/NF-κB/TNFα axis in E₂-induced apoptosis in E₂-deprived breast cancer cells.

Paradoxical Immune Responses in Non-HIV Cryptococcal Meningitis

The fungus Cryptococcus is a major cause of meningoencephalitis in HIV-infected as well as HIV-uninfected individuals with mortalities in developed countries of 20% and 30%, respectively. In HIV-related disease, defects in T-cell immunity are paramount, whereas there is little understanding of mechanisms of susceptibility in non-HIV related disease, especially that occurring in previously healthy adults. The present description is the first detailed immunological study of non-HIV-infected patients including those with severe central nervous system (s-CNS) disease to 1) identify mechanisms of susceptibility as well as 2) understand mechanisms underlying severe disease. Despite the expectation that, as in HIV, T-cell immunity would be deficient in such patients, cerebrospinal fluid (CSF) immunophenotyping, T-cell activation studies, soluble cytokine mapping and tissue cellular phenotyping demonstrated that patients with s-CNS disease had effective microbiological control, but displayed strong intrathecal expansion and activation of cells of both the innate and adaptive immunity including HLA-DR+ CD4+ and CD8+ cells and NK cells. These expanded CSF T cells were enriched for cryptococcal-antigen specific CD4+ cells and expressed high levels of IFN-γ as well as a lack of elevated CSF levels of typical T-cell specific Th2 cytokines -- IL-4 and IL-13. This inflammatory response was accompanied by elevated levels of CSF NFL, a marker of axonal damage, consistent with ongoing neurological damage. However, while tissue macrophage recruitment to the site of infection was intact, polarization studies of brain biopsy and autopsy specimens demonstrated an M2 macrophage polarization and poor phagocytosis of fungal cells. These studies thus expand the paradigm for cryptococcal disease susceptibility to include a prominent role for macrophage activation defects and suggest a spectrum of disease whereby severe neurological disease is characterized by immune-mediated host cell damage.

Cryptococcus is an important cause of fungal meningitis with significant mortality globally. Susceptibility to the fungus in humans has been related to T-lymphocyte defects in HIV-infected individuals, but little is known about possible immune defects in non HIV-infected patients including previously healthy individuals. This latter group also has some of the worst response rates to therapy with almost a third dying in the United States, despite available therapy. Here we conducted the first detailed immunological analysis of non-HIV apparently immunocompetent individuals with active cryptococcal disease. In contrast to HIV-infected individuals, these studies identified a highly activated antigen-presenting dendritic cell population within CSF, accompanied by a highly active T-lymphocyte population with potentially damaging inflammatory cytokine responses. Furthermore, elevated levels of CSF neurofilament light chains (NFL), a marker of axonal damage in severe central nervous system infections suggest a dysfunctional role to this acute inflammatory state. Paradoxically, CSF macrophage proportions were reduced in patients with severe disease and biopsy and autopsy samples identified alternatively activated tissue macrophage populations that failed to appropriately phagocytose fungal cells. Our study thus provides new insights into the susceptibility to human cryptococcal disease and identifies a paradoxically active T-lymphocyte response that may be amenable to adjunctive immunomodulation to improve treatment outcomes in this high-mortality disease.

The warm temperature acclimation protein (Wap65) has an important role in the inflammatory response of turbot (Scophthalmus maximus)

Wap65 is a molecule similar to the mammalian hemopexin that is a serum glycoprotein produced mainly by the liver with high affinity to heme. Its primary role is participating in iron metabolism scavenging heme that is released into the plasma and transporting it to the liver. It has been reported an important role of hemopexin in the inflammation as an acute-phase protein and its production is up-regulated by pro-inflammatory cytokines. There are also some evidences suggesting this immune-induction in fish Wap65 genes. Most teleost species presents two Wap65 genes but their physiological functions have not been completely elucidated; in fact, the transcriptional patterns of Wap65 genes to stimulatory treatments are variable and contradictory. In the present study two Wap65 genes, Wap65-1 and Wap65-2, have been characterized for the first time in turbot (Scophthalmus maximus). Their constitutive expression and differential modulation by thermal treatments, immune challenges (bacterial and viral), as well as iron supplementation, have been investigated. Both genes were mainly expressed in liver, but they were detected in all tested tissues. Whereas Wap65-1 and Wap65-2 were up-regulated by temperature rise and bacterial challenge, VHSV infection inhibited the expression of both genes. Moreover, iron-dextran administration induced only the overexpression of Wap65-1. Interestingly, these induction were observed in head kidney buy not in liver. The effect of Wap65 protein purified from turbot serum by hemin-agarose affinity chromatography was also studied to demonstrate a possible anti-inflammatory role, analyzing its inhibitory effect on leucocytes migration induced by zymosan injection to the peritoneal cavity.

C/EBP transcription factors regulate NADPH oxidase in human aortic smooth muscle cells

In atherosclerosis, oxidative stress-induced vascular smooth muscle cells (SMCs) dysfunction is partially mediated by up-regulated NADPH oxidase (Nox); the mechanisms of enzyme regulation are not entirely defined. CCAAT/enhancer-binding proteins (C/EBP) regulate cellular proliferation and differentiation, and the expression of many inflammatory and immune genes. We aimed at elucidating the role of C/EBP in the regulation of Nox in SMCs exposed to pro-inflammatory conditions. Human aortic SMCs were treated with interferon-γ (IFN-γ) for up to 24 hrs. Lucigenin-enhanced chemiluminescence, real-time PCR, Western blot, promoter-luciferase reporter analysis and chromatin immunoprecipitation assays were employed to investigate Nox regulation. IFN-γ dose-dependently induced Nox activity and expression, nuclear translocation and up-regulation of C/EBPα, C/EBPβ and C/EBPδ protein expression levels. Silencing of C/EBPα, C/EBPβ or C/EBPδ reduced significantly but differentially the IFN-γ-induced up-regulation of Nox activity, gene and protein expression. In silico analysis indicated the existence of typical C/EBP sites within Nox1, Nox4 and Nox5 promoters. Transient overexpression of C/EBPα, C/EBPβ or C/EBPδ enhanced the luciferase level directed by the promoters of the Nox subtypes. Chromatin immunoprecipitation demonstrated the physical interaction of C/EBPα, C/EBPβ and C/EBPδ proteins with the Nox1/4/5 promoters. C/EBP transcription factors are important regulators of Nox enzymes in IFN-γ-exposed SMCs. Activation of C/EBP may induce excessive Nox-derived reactive oxygen species formation, further contributing to SMCs dysfunction and atherosclerotic plaque development. Pharmacological targeting of C/EBP-related signalling pathways may be used to counteract the adverse effects of oxidative stress.

CCAAT/enhancer-binding protein α is a crucial regulator of human fat mass and obesity associated gene transcription and expression

Several susceptibility loci have been reported associated with obesity and T2DM in GWAS. Fat mass and obesity associated gene (FTO) is the first gene associated with body mass index (BMI) and risk for diabetes in diverse patient populations. FTO is highly expressed in the brain and pancreas, and is involved in regulating dietary intake and energy expenditure. While much is known about the epigenetic mutations contributing to obesity and T2DM, less is certain with the expression regulation of FTO gene. In this study, a highly conserved canonical C/EBPα binding site was located around position −45~−54 bp relative to the human FTO gene transcriptional start site. Site-directed mutagenesis of the putative C/EBPα binding sites decreased FTO promoter activity. Overexpression and RNAi studies also indicated that C/EBPα was required for the expression of FTO. Chromatin immunoprecipitation (ChIP) experiment was carried out and the result shows direct binding of C/EBPα to the putative binding regions in the FTO promoter. Collectively, our data suggest that C/EBPα may act as a positive regulator binding to FTO promoter and consequently, activates the gene transcription.

Genetic organization of two types of flounder warm-temperature acclimation-associated 65-kDa protein and their gene expression profiles

We isolated and characterized two cDNA clone encoding warm-temperature acclimation-associated 65-kDa proteins (PoWap65-1 and PoWap65-2) from the olive flounder, Paralichthys olivaceus. The deduced amino acid sequences of PoWap65s showed overall identities of 33-73% with other fish Wap65 and mammalian hemopexin-like proteins. The 5'-flanking regions of both PoWap65-encoding genes contained various putative transcriptional elements. While PoWap65-1 and PoWap65-2 were structurally similar, they exhibited highly differential patterns of expression. PoWap65-1 was expressed only in the liver, whereas PoWap65-2 transcripts were detected in a wide range of tissues. The accumulation of PoWap65s mRNA was expressed differentially during development. Expression of them in warm temperatures also differed in flounder embryonic cells. PoWap65-1 was upregulated by temperature stimulation whereas PoWap65-2 was not detected. PoWap65s were highly regulated by Edwardsiella tarda infection and hypoxia. Pathogen challenge induced PoWap65-2 expression in the liver whereas PoWap65-1 was downregulated. Hypoxia induced the expression of both PoWap65s in the liver of juvenile fish.

IL-1beta and IL-6 modulate apolipoprotein E gene expression in rat hepatocyte primary culture

Incubation of rat hepatocytes in primary culture with IL-1β at a concentration of 2.5 units/ml resulted in an increase (+80%) in the amount of apoE mRNA without any effect upon apoE synthesis. IL-6 at a low concentration (10 units/ml) induced a decrease (−35%) in the amount of apoE mRNA, but increased apoE synthesis (+28%). No effect was observed with higher concentrations of IL-1β (10 units/ml) or IL-6 (100 units/ml). These results suggest that inflammatory cytokines IL-1β and IL-6 modulate the expression of apoE gene in cultured rat hepatocytes, at a concentration that does not induce the acute phase response.

Oct-1 acts as a transcriptional repressor on the C-reactive protein promoter

C-reactive protein (CRP), a plasma protein of the innate immune system, is produced by hepatocytes. A critical regulatory region (-42 to -57) on the CRP promoter contains binding site for the IL-6-activated transcription factor C/EBPβ. The IL-1β-activated transcription factor NF-κB binds to a κB site located nearby (-63 to -74). The κB site overlaps an octamer motif (-59 to -66) which is the binding site for the constitutively active transcription factor Oct-1. Oct-1 is known to function both as a transcriptional repressor and as an activator depending upon the promoter context. Also, Oct-1 can regulate gene expression either by binding directly to the promoter or by interacting with other transcription factors bound to the promoter. The aim of this study was to investigate the functions of Oct-1 in regulating CRP expression. In luciferase transactivation assays, overexpressed Oct-1 inhibited (IL-6+IL-1β)-induced CRP expression in Hep3B cells. Deletion of the Oct-1 site from the promoter drastically reduced the cytokine response because the κB site was altered as a consequence of deleting the Oct-1 site. Surprisingly, overexpressed Oct-1 inhibited the residual (IL-6+IL-1β)-induced CRP expression through the promoter lacking the Oct-1 site. Similarly, deletion of the Oct-1 site reduced the induction of CRP expression in response to overexpressed C/EBPβ, and overexpressed Oct-1 inhibited C/EBPβ-induced CRP expression through the promoter lacking the Oct-1 site. We conclude that Oct-1 acts as a transcriptional repressor of CRP expression and it does so by occupying its cognate site on the promoter and also via other transcription factors by an as yet undefined mechanism.

Emergence of the acute-phase protein hemopexin in jawed vertebrates

When released from damaged erythrocytes free heme not only provides a source of iron for invading bacteria but also highly toxic due to its ability to catalyze free radical formation. Hemopexin (Hx) binds free heme with very high-affinity and thus protects against heme toxicity, sequesters heme from pathogens, and helps conserve valuable iron. Hx is also an acute-phase serum protein (APP), whose expression is induced by inflammation. To date Hx has been identified as far back in phylogeny as bony fish where it is called warm-temperature acclimation-related 65 kDa protein (WAP65), as serum protein levels are increased at elevated environmental temperatures as well as by infection. During analysis of nurse shark (Ginglymostoma cirratum) plasma we isolated a Ni(2+)-binding serum glycoprotein and characterized it as the APP Hx. We subsequently cloned Hx from nurse shark and another cartilaginous fish species, the little skate Leucoraja erinacea. Functional analysis showed shark Hx, like that of mammals, binds heme but is found at unusually high levels in normal shark serum. As an Hx orthologue could not be found in the genomes of jawless vertebrates or lower deuterostomes it appears to have arisen just prior to the emergence of jawed vertebrates, coincident with the second round of genome-wide duplication and the appearance of tetrameric hemoglobin (Hb).

Interleukin-1beta stimulates acute phase response and C-reactive protein synthesis by inducing an NFkappaB- and C/EBPbeta-dependent autocrine interleukin-6 loop

Cytokines interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) are involved in acute phase response (APR). C-reactive protein (CRP), the prototype acute phase protein, may represent an important component in the pathogenesis of arteriosclerosis and may also be a target for drug development. Inhibition of CRP synthesis is one potential strategy. Understanding CRP synthesis, however, is a prerequirement for the development of CRP-inhibitors. From studies in hepatoma cell lines, IL-1beta and IL-6 were considered as equal inductors of APR and CRP. We investigated IL-1beta- and IL-6-effects on primary human hepatocytes (PHH) and Hep3B-cells. Kupffer cell contamination in PHH preparations was <3%. In PHH, several APP like CRP, haptoglobin (HP), lipopolysaccharide-binding protein (LBP) or hepcidin (HAMP) were regulated similarly by IL-1beta and IL-6, though signal transduction pathways of these cytokines are different. In Hep3B-cells, APP were regulated exclusively by IL-6. IL-1beta induced IL-6-synthesis in PHH but not in Hep3B-cells. C/EBPbeta-overexpression in Hep3B-cells reconstituted IL-1beta-mediated IL-6/CRP inducibility. In PHH and in C/EBPbeta-overexpressing Hep3B-cells, neutralizing anti-IL-6-antibodies blocked IL-1beta-mediated APR. Inhibition of protein synthesis and NFkappaB-signalling blocked IL-1beta- but not IL-6-mediated CRP-expression in PHH, whereas Janus-Kinase-1-inhibition blocked IL-1beta- and IL-6-mediated APR. IL-1beta induces APR in PHH via an NFkappaB- and C/EBPbeta-dependent autocrine IL-6-loop. These findings partly reconcile the understanding of APR and may help to design a transcriptional suppressor of CRP for the treatment of cardiovascular disease.

Effects of hepatic zonal oxygen levels on hepatocyte stress responses

BACKGROUND

Hepatocytes spend their lifetimes in a gradient of oxygen, hormones, and enzymes. We used a three-dimensional Matrigel model to determine whether hepatocytes cultured at perivenous (zone 3) oxygen levels differed in susceptibility to anoxia-induced cell injury compared with hepatocytes cultured at periportal (zone 1) oxygen levels.

MATERIALS AND METHODS

Hepatocytes were harvested from Sprague Dawley rats and cultured at 9% oxygen (hepatic zone 1) or 5% oxygen (hepatic zone 3) and stressed at 0% oxygen. Microscopy, real-time reverse transcriptase-polymerase chain reaction, and enzyme-linked immunosorbent assay were used to assess cell viability, mitochondrial potential, acute phase responses, and membrane blebbing.

RESULTS

Hepatocytes cultured in Matrigel with HepatoZyme medium at zone 1 and zone 3 oxygen conditions were viable for 1 wk and showed acute phase responses as measured by interleukin-6-induced fibrinogen production. In response to 3 h anoxia, cells maintained at the perivenous oxygen level showed increased membrane blebbing and increased loss of mitochondrial membrane potential in comparison to the periportal oxygen cultured cells. Cells at perivenous oxygen also showed a reduced ability to recover following reoxygenation.

CONCLUSIONS

Hepatocytes can remain viable and functional for extended periods in culture at low oxygen levels that mimic the hepatic perivenous environment, yet these cells are more susceptible to anoxia-induced damage than hepatocytes cultured at the periportal oxygen level. The small population of perivenous hepatocytes may be critical in determining the fate of the liver during ischemia/reperfusion since hepatocytes cultured at that concentration appear to be more labile in response to anoxia.

Regulation of expression of the interleukin 6 gene: structure and function of the transcription factor NF-IL6

The interleukin 6 (IL-6) promoter is rapidly and transiently activated by other cytokines, including IL-1 and tumour necrosis factor (TNF), as well as by phorbol esters and cyclic AMP agonists. Studies using promoter mutants suggested that an IL-1-responsive element mapped within the -180 to -123 region of the IL-6 promoter. A nuclear factor (NF-IL6) that recognized a unique sequence containing an inverted repeat, ACATTGCACAATCT, was identified within the region. Direct cloning of the human NF-IL6 revealed its similarity to C/EBP, a liver- and adipose tissue-specific transcription factor. C/EBP and NF-IL6 recognize the same nucleotide sequence, but exhibit distinct patterns of expression. NF-IL6 is expressed at a low level in normal tissues, but is rapidly and drastically induced by bacterial lipopolysaccharide (LPS) or inflammatory cytokines such as IL-1, TNF and IL-6. Recently, NF-IL6 has been shown to be identical to IL-6DBP, the DNA-binding protein which is responsible for IL-6-mediated induction of several acute-phase proteins. Evidence that NF-IL6 DNA-binding activity is increased after IL-6 stimulation without increased NF-IL6 protein synthesis demonstrates the importance of post-translational modification. There are some results indicating that phosphorylation is involved in transcriptional and binding activities of NF-IL6. Taken together, these findings indicate that NF-IL6 may be an important transcription factor on the signal transduction pathways of IL-1 and IL-6.

The occurrence of two types of hemopexin-like protein in medaka and differences in their affinity to heme

Full-length cDNA clones encoding two types of hemopexin-like protein, mWap65-1 and mWap65-2, were isolated from the HNI inbred line of medaka Oryzias latipes. The deduced amino acid sequence of mWap65-2 resembled mammalian hemopexins more closely than that of mWap65-1. Histidine residues required for the high affinity of hemopexins for hemes were conserved in mWap65-2, but not in mWap65-1. Surprisingly, mWap65-1, but not mWap65-2, showed heme-binding ability as revealed by hemin-agarose affinity chromatography, even though mWap65-1 lacked the essential histidine residues. Furthermore, RT-PCR analysis of different tissues demonstrated that the transcripts of mWap65-2 were restricted to liver, whereas those of mWap65-1 were found in various tissues including liver, eye, heart and brain. Quantitative RT-PCR revealed that transcripts of mWap65-2 were expressed earlier than those of mWap65-1 during ontogeny. However, the accumulated mRNA levels of both mWap65-1 and mWap65-2 did not differ significantly in fish acclimated to either 10 degrees C or 30 degrees C for 5 weeks. These characteristics suggest that the two proteins have different physiological functions and that mWap65-2 is not a hemopexin.

Thalidomide reduces serum C-reactive protein and interleukin-6 and induces response to IL-2 in a fraction of metastatic renal cell cancer patients who failed IL-2-based therapy

Interleukin-2 (IL-2) has some antitumor activity in patients with renal cell carcinoma. It has been noted that response to IL-2 and prognosis may be adversely affected by elevated serum levels of C-reactive protein (CRP) or interleukin-6 (IL-6). We used thalidomide to treat patients with cancer-induced cachexia and noted that the drug significantly reduced serum levels of CRP and IL-6 to normal or near normal levels in a substantial fraction of patients. We tested whether thalidomide might potentiate the response of patients with renal cell carcinoma to IL-2. Four patients with metastatic renal cell carcinoma and high serum levels of CRP and IL-6 who had experienced disease progression on IL-2 were retreated with the same IL-2 regimen combined with thalidomide 300 mg p.o. daily. Two patients achieved good partial responses and 2 patients had prolonged disease stabilization with the combination of IL-2 plus thalidomide. The regimen was well tolerated without increased IL-2-associated toxicity. Reduction of serum CRP or IL-6 levels with thalidomide may enhance the responsiveness of renal cell carcinoma to IL-2. A Phase II study of the combination is in order. It is possible that the thalidomide-induced normalization of serum acute phase proteins might improve the response of other types of malignancy to IL-2 or other immune-based therapies.

In vitro and in vivo comparative study of chimeric liver-specific promoters

Targeting therapeutic genes to the liver is essential to improve gene therapy protocols of hepatic diseases and of some hereditary disorders. Transcriptional targeting can be achieved using liver-specific promoters. In this study we have made chimeric constructs combining promoter and enhancer regions of the albumin, alpha 1-antitrypsin, hepatitis B virus core protein, and hemopexin genes. Tissue specificity, activity, and length of gene expression driven from these chimeric regulatory sequences have been analyzed in cultured cells from hepatic and nonhepatic origin as well as in mice livers and other organs. We have identified a collection of liver-specific promoters whose activities range from twofold to less than 1% of the CMV promoter in human hepatoma cells. We found that the best liver specificity was attained when both enhancer and promoter sequences of hepatic genes were combined. In vivo studies were performed to analyze promoter function during a period of 50 days after gene transfer to the mouse liver. We found that among the various chimeric constructs tested in this work, the alpha1-antitrypsin promoter alone or linked to the albumin or hepatitis B enhancers is the most potent in directing stable gene expression in liver cells.

Down-regulation of human CYP3A4 by the inflammatory signal interleukin-6: molecular mechanism and transcription factors involved

The hepatic drug-metabolizing cytochrome P-450 (CYP) enzymes are down-regulated during inflammation. In vitro studies with hepatocytes have shown that the cytokines released during inflammatory responses are largely responsible for this CYP repression. However, the signaling pathways and the cytokine-activated factors involved remain to be properly identified. Our research has focused on the negative regulation of CYP3A4 (the major drug-metabolizing human CYP) by interleukin 6 (IL-6) (the principal regulator of the hepatic acute-phase response). CYP3A4 down-regulation by IL-6 requires activation of the glycoprotein receptor gp130; however, it does not proceed through the JAK/STAT pathway, as demonstrated by the overexpression of a dominant-negative STAT3 factor by means of an adenoviral vector. The involvement of IL-6-activated kinases such as extracellular signal-regulated kinase ERK1/2 or p38 is also unlikely, as evidenced by the use of specific chemical inhibitors. It is noteworthy that IL-6 caused a moderated induction in the mRNA of the transcription factor C/EBPbeta (CCAAT-enhancer binding protein beta) and a marked increase in the translation of C/EBPbeta-LIP, a 20-kDa C/EBPbeta isoform lacking a transactivation domain. Adenovirus-mediated expression of C/EBPbeta-LIP caused a dose-dependent repression of CYP3A4 mRNA, whereas overexpression C/EBPalpha and C/EBPb-LAP (35 kDa) caused a significant induction. Our results support the idea that IL-6 down-regulates CYP3A4 through translational induction of C/EBPbeta-LIP, which competes with and antagonizes constitutive C/EBP transactivators. From a clinical point of view, these findings could be relevant in the development of therapeutic cytokines with a less repressive effect on hepatic drug-metabolizing enzymes.

Hemopexin: structure, function, and regulation

Hemopexin (HPX) is the plasma protein with the highest binding affinity to heme among known proteins. It is mainly expressed in liver, and belongs to acute phase reactants, the synthesis of which is induced after inflammation. Heme is potentially highly toxic because of its ability to intercalate into lipid membrane and to produce hydroxyl radicals. The binding strength between heme and HPX, and the presence of a specific heme-HPX receptor able to catabolize the complex and to induce intracellular antioxidant activities, suggest that hemopexin is the major vehicle for the transportation of heme in the plasma, thus preventing heme-mediated oxidative stress and heme-bound iron loss. In this review, we discuss the experimental data that support this view and show that the most important physiological role of HPX is to act as an antioxidant after blood heme overload, rather than to participate in iron metabolism. Particular attention is also put on the structure of the protein and on its regulation during the acute phase reaction.

The transcription factor C/EBPbeta is essential for inducible expression of the cox-2 gene in macrophages but not in fibroblasts

Cyclooxygenase-2 (COX-2) is the rate-limiting enzyme for the inducible synthesis of prostaglandins, and its up-regulated activity is thought to play a pathological role in diseases such as inflammatory bowel disease, rheumatoid arthritis, and cancer. Regulation of COX-2 expression is complex and appears to involve diversified mechanisms in different cell types and conditions. Here we make use of immortalized macrophages and fibroblasts that we have generated from C/EBPbeta-deficient mice to directly test and compare the specific role played by this factor in inducible COX-2 expression in these two cell types. We could demonstrate that COX-2 mRNA induction and promoter activity were profoundly impaired in C/EBPbeta(-/-) macrophages and could be rescued by expression of C/EBPbeta. The obligatory role of C/EBPbeta in COX-2 expression appeared to be mediated exclusively by the C/EBP element located at positions -138/-130 of the murine cox-2 promoter, and did not involve altered activity at the level of the other promoter elements described previously (the -402/-392 NF-kappaB site, the -59/-48 CRE/E box element, and a potential second C/EBP site located at positions -93/-85). In contrast, COX-2 induction was completely normal in C/EBPbeta-deficient fibroblasts, thus highlighting the diversity of cell-specific molecular mechanisms in determining inducible COX-2 expression and prostaglandins production.

Effect of cytokines, dexamethasone and the A/T-signal peptide polymorphism on the expression of alpha(1)-antichymotrypsin in astrocytes: significance for Alzheimer's disease

Proinflammatory cytokines and acute phase proteins, such as alpha(1)-antichymotrypsin, are over expressed in microglia and astrocytes in brain regions with abundant mature amyloid plaques, suggesting a glial cell-led brain acute phase response in the Alzheimer neuropathology. In this paper, we show that alpha(1)-antichymotrypsin gene expression in human astrocytes is elevated by interleukin-1 and interleukin-6, and further enhanced by glucocorticoid, while the homologous contrapsin gene in rat astrocytes is unaffected by these cytokines. These distinct gene regulation mechanisms might help to explain the differential susceptibility of humans and rodents to amyloid formation of the Alzheimer's type. In addition, we demonstrate that the alpha(1)-antichymotrypsin A-allele that encodes a different signal peptide and is a suggested risk factor for Alzheimer's disease gives rise to a reduced level of immature alpha(1)-antichymotrypsin in transfected cells. The physiological result would be an enhanced ability of the A-encoded alpha(1)-antichymotrypsin protein to become secreted and promote extracellular amyloid formation. We discuss our findings in terms of a model in which cytokine-induced alpha(1)-antichymotrypsin synthesis in astrocytes constitutes a specific inflammatory pathway that accelerates the development of Alzheimer's disease and could at least partly underlie the regional specificity and species restriction of the neuropathology.

The kallikrein-kininogen-kinin system: lessons from the quantification of endogenous kinins

The purpose of the present review is to describe the place of endogenous kinins, mainly bradykinin (BK) and des-Arg(9)-BK in the kallikrein-kininogen-kinin system, to review and compare the different analytical methods reported for the assessment of endogenous kinins, to explain the difficulties and the pitfalls for their quantifications in biologic samples and finally to see how the results obtained by these methods could complement and extend the pharmacological evidence of their pathophysiological role.

The link of biocompatibility to cytokine production

Recent studies suggest that chronic inflammation plays a role in the pathogenesis of cardiovascular disease. Cytokines released from jeopardized tissues stimulate the liver to synthesize acute phase proteins, including C-reactive protein (CRP). Baseline levels of CRP in apparently healthy persons or in persons with unstable angina constitute an independent risk factor for cardiovascular events. More recently, it has been suggested that CRP is useful not only as a marker of the acute phase response, but is also involved in the pathogenesis of the disease. CRP may, in fact, directly interact with the atherosclerotic vessels or ischemic myocardium by activation of the complement system, thereby promoting inflammation and thrombosis. Several studies in uremic patients have implicated CRP as a marker of malnutrition, resistance to erythropoietin, and chronic stimulation in hemodialysis. An increased cytokine production secondary to blood interaction with bioincompatible dialysis components has been reported by several studies; interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-alpha), and mainly IL-6 are the three proinflammatory cytokines involved in the pathogenesis of hemodialysis-related disease. We have provided evidence for the occurrence of high CRP and IL-6 levels in chronic dialytic patients exposed to contaminate dialysate and suggest that backfiltration may induce a chronic, slowly developing inflammatory state that may be abrogated by avoiding backfiltration of contaminate dialysate. Therefore, CRP is implicated as a marker linking bioincompatibility associated with backfiltration and increased cytokine production with a clinical state of chronic inflammation.

Defective Recovery and Severe Renal Damage After Acute Hemolysis in Hemopexin-Deficient Mice

Hemopexin (Hx) is a plasma glycoprotein mainly expressed in liver and, less abundantly, in the central and peripheral nervous systems. Hx has a high binding affinity with heme and is considered to be a major transport vehicle of heme into the liver, thus preventing both heme-catalyzed oxidative damage and heme-bound iron loss. To determine the physiologic relevance of heme-Hx complex formation, Hx-deficient mice were generated by homologous recombination in embryonic stem (ES) cells. The Hx-deficient mice were viable and fertile. Their plasma iron level and blood parameters were comparable to those of control mice and they showed no evidence of tissue lesions caused by oxidative damage or abnormal iron deposits. Moreover, they were sensitive to acute hemolysis, as are wild-type mice. Nevertheless, Hx-null mice recovered more slowly after hemolysis and were seen to have more severe renal damage than controls. After hemolytic stimulus, Hx-deficient mice presented prolonged hemoglobinuria with a higher kidney iron load and higher lipid peroxidation than control mice. Moreover, Hx-null mice showed altered posthemolysis haptoglobin (Hp) turnover in as much as Hp persisted in the circulation after hemolytic stimulus. These data indicate that, although Hx is not crucial either for iron metabolism or as a protection against oxidative stress under physiologic conditions, it does play an important protective role after hemolytic processes.

Defective Recovery and Severe Renal Damage After Acute Hemolysis in Hemopexin-Deficient Mice

Hemopexin (Hx) is a plasma glycoprotein mainly expressed in liver and, less abundantly, in the central and peripheral nervous systems. Hx has a high binding affinity with heme and is considered to be a major transport vehicle of heme into the liver, thus preventing both heme-catalyzed oxidative damage and heme-bound iron loss. To determine the physiologic relevance of heme-Hx complex formation, Hx-deficient mice were generated by homologous recombination in embryonic stem (ES) cells. The Hx-deficient mice were viable and fertile. Their plasma iron level and blood parameters were comparable to those of control mice and they showed no evidence of tissue lesions caused by oxidative damage or abnormal iron deposits. Moreover, they were sensitive to acute hemolysis, as are wild-type mice. Nevertheless, Hx-null mice recovered more slowly after hemolysis and were seen to have more severe renal damage than controls. After hemolytic stimulus, Hx-deficient mice presented prolonged hemoglobinuria with a higher kidney iron load and higher lipid peroxidation than control mice. Moreover, Hx-null mice showed altered posthemolysis haptoglobin (Hp) turnover in as much as Hp persisted in the circulation after hemolytic stimulus. These data indicate that, although Hx is not crucial either for iron metabolism or as a protection against oxidative stress under physiologic conditions, it does play an important protective role after hemolytic processes.

Human herpesvirus 8 interleukin-6 (vIL-6) signals through gp130 but has structural and receptor-binding properties distinct from those of human IL-6

Human herpesvirus 8 (HHV-8) has been associated with classical, endemic (African), and AIDS-related Kaposi's sarcoma (KS), body cavity-based primary effusion lymphomas, and multicentric Castleman's disease (MCD). HHV-8 encodes a functional homologue of interleukin-6 (IL-6), a cytokine that promotes the growth of KS and myeloma cells and is found at elevated levels in MCD lesions and patient sera. We have previously reported that the viral IL-6 (vIL-6) gene product can support the growth of the IL-6-dependent murine hybridoma cell line, B9, and that the gp80 (IL-6 receptor [IL-6R]) component of the IL-6 receptor-signal transducer (gp180) complex plays a role in mediating this activity. However, it has been shown by others that vIL-6 can function in human cells independently of IL-6R. Here we have extended our functional studies of vIL-6 by identifying transcription factors and pathways used in human Hep3B cells, investigating the utilization of gp130 and IL-6R by vIL-6, and undertaking mutational analyses of vIL-6 and gp130. The data presented here establish that vIL-6, in common with its endogenous counterparts, can mediate signal transduction through gp130 and activate multiple transcription factors, map residues within the vIL-6 protein that are and are not important for vIL-6 signalling, and identify a gp130 mutant that is nonfunctional with respect to vIL-6 signalling in the absence of IL-6R but that retains the ability to mediate vIL-6 and human IL-6 (hIL-6) signal transduction when IL-6R is coexpressed. The data presented demonstrate functional and mechanistic similarities between vIL-6 and endogenous IL-6 proteins but also highlight differences in the structural and receptor-binding properties of vIL-6 relative to its human counterpart.

Regulation of angiogenin expression in human HepG2 hepatoma cells by mediators of the acute-phase response

Angiogenin is a potent inducer of neovascularization in vivo. However, like other angiogenic molecules, its specific physiologic roles and mechanisms regulating its expression remain to be elucidated. Angiogenin is a liver-derived component of normal serum whose concentration can increase in various disease states. This suggests that it might participate in the acute-phase response. In an initial study we showed that angiogenin protein and mRNA levels transiently increased in mice following an acute inflammatory stimulus. We now report that IL-6, a major inducer of acute-phase proteins, stimulates the synthesis and secretion of angiogenin protein in human HepG2 cells within 24 hr following treatment, an effect enhanced by dexamethasone. IL-6 also increases the amount of angiogenin mRNA without altering its half-life. This increase, suppressible by cycloheximide, peaks at 12 hr following stimulation and returns to basal levels by 48 hr. IL-1 alone slightly decreases the basal production of angiogenin protein and mRNA, but essentially abolishes the response to IL-6 in the absence or presence of dexamethasone. This antagonistic effect by IL-1 on IL-6 activity is not a result of changes in mRNA stability nor is it dependent on new protein synthesis. Thus, the combined effects of IL-6, IL-1, glucocorticoids, and perhaps other related factors may specifically control angiogenin expression. Since angiogenin is regulated in a manner similar to that of acute phase proteins both in vitro and in vivo, it may play a role in the host response to injury.

Recombinant human growth hormone alters acute phase reactant proteins, cytokine expression, and liver morphology in burned rats

BACKGROUND

The effects of exogenous recombinant human growth hormone (rhGH) on hepatic acute phase reactant proteins, cytokine expression, and liver morphology were studied in thermally injured rats to define whether rhGH alters the acute phase response.

MATERIALS AND METHODS

Sprague-Dawley rats (56 males) receiving a 60% TBSA third-degree scald burn were randomly divided into two groups to receive either 2.5 mg/kg/day sc rhGH or saline. Rats were sacrificed on Postburn Days 1, 2, 5, and 7. Serum acute phase reactant proteins and cytokines TNF-alpha, IL-1alpha, IL-1beta, and IL-6 were measured. Hepatocyte proliferation, hepatic cytokine gene expression, and liver protein concentrations were determined.

RESULTS

Recombinant hGH increased serum albumin on Days 5 and 7 after burn (P < 0.05). Serum haptoglobin and alpha1-acid glycoprotein levels decreased at 2, 5, and 7 days after burn compared to saline (P < 0.05). In rats treated with rhGH, serum IL-1beta decreased 1 day postburn, while serum TNF-alpha increased 5 days after burn compared to saline (P < 0.05). Serum IL-6 and IL-1alpha did not change. Hepatic RNA levels for TNF-alpha were significantly elevated on Day 1 postburn compared to saline (P < 0. 05). Hepatic protein content increased on Days 2, 5, and 7 postburn compared to saline (P < 0.05). Hepatocyte proliferation in rhGH-treated rats increased on Day 5 after burn (P < 0.05).

CONCLUSION

Data indicate that rhGH alters the hepatic acute phase response by decreasing type I acute phase proteins and modulating IL-1-like cytokine expression. These changes are associated with increased hepatocyte mitosis and serum and total liver protein concentrations.

Regulation of serum amyloid A protein expression during the acute-phase response

The acute-phase (AP) serum amyloid A proteins (A-SAA) are multifunctional apolipoproteins which are involved in cholesterol transport and metabolism, and in modulating numerous immunological responses during inflammation and the AP response to infection, trauma or stress. During the AP response the hepatic biosynthesis of A-SAA is up-regulated by pro-inflammatory cytokines, and circulating concentrations can increase by up to 1000-fold. Chronically elevated A-SAA concentrations are a prerequisite for the pathogenesis of secondary amyloidosis, a progressive and fatal disease characterized by the deposition in major organs of insoluble plaques composed principally of proteolytically cleaved A-SAA, and may also contribute to physiological processes that lead to atherosclerosis. There is therefore a requirement for both positive and negative control mechanisms that permit the rapid induction of A-SAA expression until it has fulfilled its host-protective function(s) and subsequently ensure that its expression can be rapidly returned to baseline. These mechanisms include modulation of promoter activity involving, for example, the inducer nuclear factor kappaB (NF-kappaB) and its inhibitor IkappaB, up-regulatory transcription factors of the nuclear factor for interleukin-6 (NF-IL6) family and transcriptional repressors such as yin and yang 1 (YY1). Post-transcriptional modulation involving changes in mRNA stability and translation efficiency permit further up- and down-regulatory control of A-SAA protein synthesis to be achieved. In the later stages of the AP response, A-SAA expression is effectively down-regulated via the increased production of cytokine antagonists such as the interleukin-1 receptor antagonist (IL-1Ra) and of soluble cytokine receptors, resulting in less signal transduction driven by pro-inflammatory cytokines.

Cytokine-mediated transcriptional induction of the human inducible nitric oxide synthase gene requires both activator protein 1 and nuclear factor kappaB-binding sites

The involvement of AP-1 and NF-kappaB transcription factors in cytokine-mediated induction of human inducible nitric oxide synthase (hiNOS) promoter activity was examined. Luciferase reporter plasmids, containing mutations in AP-1 and NF-kappaB sites, in a hiNOS promoter extending from -8.3 kilobase pairs (kb) to +168, were transiently expressed in A549 cells, and promoter activity was determined after treatment with a cytokine mixture (CM) containing interleukin 1-beta, interferon-gamma, and tumor necrosis factor-alpha. Mutation of the AP-1 heptad located -5301 base pairs upstream decreased gene activation by 90% in a -8.3-kb promoter and a shorter -5.574-kb promoter. Disruption of AP-1 (at -5115) or NF-kappaB (at -115 and -8283) sites reduced promoter activity by 45, 67, and 52%, respectively. Responsiveness to CM was decreased by 85% in constructs mutated in both NF-kappaB sites. By gel retardation analyses, CM increased AP-1- and NF-kappaB binding. Supershift analysis identified Jun D and Fra-2 as components of AP-1 complexes. Each kappaB site bound different complements of NF-kappaB/Rel family members (downstream site, Rel A/p50; upstream site, Rel A/Rel A). Rel A was maximally, whereas IkappaB-alpha was minimally, expressed in nuclei after 1 h of CM treatment, corresponding with the peak in NF-kappaB inding activity. Thus, AP-1 and NF-kappaB are important cis-elements for induction of hiNOS gene transcription.

Requirement for cooperative interaction of interleukin-6 responsive element type 2 and glucocorticoid responsive element in the synergistic activation of mouse metallothionein-I gene by interleukin-6 and glucocorticoid

Metallothionein (MT)-inducing activity of interleukin (IL)-6 depends on the presence of glucocorticoid in hepatic cells. The synergistic action of IL-6 and glucocorticoid was observed in the transcriptional activation of the mouse MT (mMT)-I gene. We found that a 281-bp promoter was sufficient for IL-6 and glucocorticoid stimulation. Our inspection of this region revealed the putative type 1 and 2 IL-6 responsive elements (REs). Functional analyses of these regions were performed using luciferase reporter constructs, and it was observed that the type 2 IL-6RE exerted the major response to the IL-6 signal. The transcriptional factor binding to type 1 IL-6RE, nuclear factor-IL-6, hardly contributed to the activation of the mMT-I promoter by IL-6 and glucocorticoid. A glucocorticoid responsive element (GRE) was also required for the synergistic activation by IL-6 and glucocorticoid. Interestingly, this synergism was not observed when the type 2 IL-6RE and the GRE were kept apart. Therefore, the synergistic activation of the mMT-I gene by IL-6 and glucocorticoid may require not only that signal transducers and activators 3 (Stat3) and the glucocorticoid receptor (GR) bind to their respective responsive elements, but also that Stat3 and the GR physically interact with one another.

Expression of the protective proteins hemopexin and haptoglobin by cells of the neural retina

The blood-retinal barrier, consisting of retinal pigment epithelial cells and retinal endothelial cells, prevents hemopexin and haptoglobin, anti-oxidant protective plasma proteins normally synthesized by the liver, from entering the neural retina. If present, these proteins must, therefore, be made locally. The cell types within the retina in which hemopexin and haptoglobin mRNAs are made have been investigated. RNA was extracted from both the neural retina and pigment epithelium obtained by dissection of human donor eyes as well as from cultured pigment epithelial and photoreceptor cells. The mRNAs for both haptoglobin and hemopexin were detected, using reverse-transcriptase polymerase chain reaction, in the neural retina and cultured photoreceptors but not in pigment epithelial cells. The cellular location of these mRNAs was determined using in situ hybridization of sections of human retina which revealed that haptoglobin mRNA was located principally in the photoreceptor cells, cells of the inner nuclear layer and some cells of the ganglion cell layer. Hemopexin mRNA, previously shown to be made in the human neural retina (Hunt et al., 1996. Journal of Cellular Physiology 168: 71-80), is expressed by most of the cells of neural retina including the photoreceptors and, notably, the ganglion cells.

Renal expression of IL-6 and TNFalpha genes in lupus nephritis

These studies were carried out to examine the presence of the inflammatory cytokines IL-6 and TNFalpha in kidneys of patients with lupus nephritis as an indicator of their possible role in its pathogenesis. A total of 19 kidney biopsies from patients with type III or IV lupus nephritis were processed by direct immunofluorescence using monoclonal anti-IL-6 and TNFalpha antibodies. Local expression of these genes was demonstrated both by in situ hybridization and by reverse transcriptase-PCR amplification of total RNA isolated from kidney tissue. Fifty-two percent of the biopsies exhibited IL-6 and TNFalpha deposited along the glomeruli and tubules; in situ expression of these cytokines was demonstrated in 6 biopsies with type IV, and 1 with type III nephritis. Inflammatory cytokines are actively synthesized in the kidneys of patients with lupus nephritis and therefore, may play a role in its pathogenesis.

Characterization of transcriptional regulatory elements in the promoter region of the murine blood coagulation factor VII gene

To identify the 5' sequences of the murine coagulation factor VII (fVII) gene that resulted in its efficient transcription, a variety of 5'-flanking sequences up to 7 kilobase pairs upstream of the translation ATG initiation codon were fused to the reporter gene, bacterial chloramphenicol acetyltransferase, and relative expression levels of this gene in mouse Hepa 1-6 cells were determined. It was found that the 5' region extending approximately 85 base pairs (bp) upstream of the transcriptional initiation site served as the minimal DNA region that provided full relative promoter activity for chloramphenicol acetyltransferase expression. This region of the gene also contains consensus sequences for liver-enriched transcription factors, C/EBP beta and HNF4, as well as for the ubiquitous protein factors, AP1, H4TF1, NF1, and Sp1. In vitro DNase I footprinting of the 200-bp proximal region of the promoter with a murine Hepa 1-6 cell nuclear extract revealed a clear footprint of a region corresponding to -80 to -28 bp of the murine fVII gene, suggesting that liver factors interact with this region of the DNA. Competitive gel shift and supershift assays with different synthetic oligonucleotide probes demonstrate that proteins contained in the nuclear extract, identified as C/EBP beta, H4TF1, and HNF4, bind to a region of the murine fVII DNA from 85 to 32 bp upstream of the transcription start site. Purified Sp1 also interacts with this region of the DNA at a site that substantially overlaps, but is not identical to, the H4TF1 binding locus. Binding of Sp1 to the mouse DNA was not observed with the nuclear extract as the source of the transcription factors, suggesting that Sp1 is likely displaced from its binding site by H4TF1 in the crude extract. In vivo dimethyl sulfate footprint analysis confirmed the existence of these sites and additionally revealed two other binding regions slightly upstream of the CCAAT/enhancer-binding protein (C/EBP) binding locus that are homologous to NF1 binding sequences. The data demonstrate that appropriate transcription factor binding sites exist in the proximal promoter region of the murine fVII gene that are consistent with its strong liver-based expression in a highly regulated manner.

Activation of CAAT enhancer-binding protein delta (C/EBPdelta) by interleukin-1 negatively influences apolipoprotein C-III expression

Tissue-specific transcription of the apolipoprotein C-III (apoC-III) gene is mainly regulated by synergistic interactions between the liver-enriched transcription factor HNF-4, which binds to the proximal promoter, and ubiquitous factors, which bind to the upstream enhancer region. Here we show that apoC-III expression in HepG2 cells is negatively regulated in response to interleukin-1 (IL-1), and this inhibition is mainly due to transcriptional repression. CAAT enhancer-binding protein delta (C/EBPdelta) was found to be the main mediator of IL-1-induced suppression. Analysis of the apoC-III promoter revealed two IL-1 response elements. The first is located in the proximal promoter region D and the second in the distal enhancer region I. Proximal element D is a high affinity binding site for C/EBPdelta, while the enhancer element I is not directly recognized by this transcription factor. Functional analysis of different combinations of homologous and heterologous promoter constructs revealed that indirect interaction of C/EBPdelta with site I, in the context of the full promoter, leads to repression. C/EBPdelta is activated by phosphorylation during IL-1-induced signal transduction pathway. This modification is important for both DNA binding activity and indirect transrepression of the apoC-III promoter.

Kaposi's sarcoma-associated human herpesvirus-8 encodes homologues of macrophage inflammatory protein-1 and interleukin-6

Human herpesvirus-8 (HHV-8) has been detected in Kaposi's sarcoma (KS) lesions of all types (AIDS-related, classical and endemic), in body-cavity-based B-cell lymphomas (BCBLs) and in lesions of multicentric Castleman's disease (MCD). We have identified a major gamma-herpesvirus-divergent locus (DL-B) in HHV-8 DNA encoding several HHV-8 unique open reading frames (ORFs), including a homologue of interleukin-6 (IL-6) and two homologues of macrophage inflammatory protein MIP-1. We show that the HHV-8-encoded IL-6 homologue (vIL-6) shares functional properties with endogenous IL-6 proteins and that both vIL-6 and vMIP-1 transcripts are present at high levels following butyrate induction of an HHV-8' BCBL cell line. Low amounts of constitutive vIL-6, but not vMIP-1, mRNA were also detected. The presence of a functional IL-6 homologue encoded by HHV-8 may provide a mechanistic model for the hypothesized role of HHV-8 in KS, MCD and BCBL that involves the mitogenic effects of vIL-6 on surrounding cells. MIP-1 proteins may enhance these effects through the chemotactic recruitment of endogenous cytokine-producing cells into affected tissues and could potentially influence HIV disease progression in coinfected individuals through interactions with the HIV co-receptor CCR-5.

Association of genetic variation at the beta-fibrinogen gene locus and plasma fibrinogen levels; interaction between allele frequency of the G/A-455 polymorphism, age and smoking

The beta-fibrinogen G/A-455 polymorphism genotype along with plasma fibrinogen levels was determined in 482 healthy middle-aged men, of whom 231 were smokers. Smokers had the highest plasma fibrinogen levels (2.92 g/l), ex-smokers the next (2.73 g/l), and never-smokers the lowest levels (2.66 g/l, P < 0.001). Those with one or two A-455 alleles had significantly higher plasma fibrinogen levels in never-smokers and ex-smokers (8.2% and 9.0%, respectively, P < 0.05), and the effect was larger in younger men (45 < 55 years, 11.6%, P = 0.002) than older men (> 65 years, 4.5%, NS), and was not significant in smokers (2.4%, P > 0.05). Allele frequencies were calculated and compared across age groups and between smokers and non-smokers. The difference in frequency of the A-455 allele between smokers and non-smokers varied significantly with age (P < 0.01), with the frequency of the A-455 allele being significantly lower in smokers than in non-smokers in subjects aged > 65 years (P < 0.05), but not in younger men. This demonstrates an interaction between age, smoking and allele frequency of the G/A-455 polymorphism in this population-based sample.

Effect of thermal injury on the expression of transcription factors that regulate acute phase response genes: the response of C/EBP alpha, C/EBP beta, and C/EBP delta to thermal injury

BACKGROUND

Eukaryotic organisms possess natural defense mechanisms that protect against stress stimuli. One such mechanism is the activation of families of stress response genes (e.g., the acute phase response). Transcription of many of these genes is regulated by the leucine zipper or bZIP proteins (CCAAT binding/enhancer binding proteins [C/EBPs]). The aim of this study was to show that the C/EBP transcription factor genes respond to thermal injury.

METHODS

Age- and weight-matched male Buffalo, Sprague-Dawley, and Fischer 344 12- to 16-week-old rats (275 to 325 gm) received a 40% total body surface area scald burn. Total RNA was isolated from livers at 0, 2, 5, 12, 24, and 48 hours. Northern blot hybridization was performed with 32P-labeled C/EBP alpha, C/EBP beta, and C/EBP delta cDNAs. Relative amounts of each mRNA were determined by densitometric analyses. For Western analyses liver nuclear and cytoplasmic protein extracts were prepared from burned and control rats. Nuclear protein extracts were resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, blotted onto a PVDF membrane, and detected by using an enhanced chemiluminescence detection kit.

RESULTS

Expression of C/EBP genes is regulated in response to 40% total body surface area scald burn. A simultaneous decrease in C/EBP alpha and an increase in C/EBP beta and C/EBP delta mRNA levels occur in response to thermal injury. Western analyses detect changes in C/EBP alpha and C/EBP beta pool levels that suggest a differential regulation of these genes in response to thermal injury.

CONCLUSIONS

The responses of C/EBP alpha, C/EBP beta, and C/EBP delta are similar in Buffalo, Sprague-Dawley, and Fischer rats. The induced level, however, of C/EBP beta mRNA was highest in the Sprague-Dawley strain and lowest in the Buffalo strain and correlates well with the mortality of these strains. Because C/EBP beta is associated with the transactivation of stress response genes, this may explain the intensity of the response in the susceptible strains. This agrees with our hypothesis that the higher degree of sensitivity of the Sprague-Dawley rat to stress relative to the Buffalo strain may be due to inherently higher levels of factors such as C/EBP whose functions are associated with activation of stress response genes.

Evidence for posttranscriptional regulation of C/EBPalpha and C/EBPbeta isoform expression during the lipopolysaccharide-mediated acute-phase response

The mRNAs of the CCAAT/enhancer-binding trans-activator proteins (C/EBPalpha and C/EBPbeta) serve as templates for the differential translation of several isoforms which have specific transcriptional regulatory functions. By using an oligonucleotide corresponding to the C/EBP binding site of the mouse alpha1-acid glycoprotein promoter, we detected multiple forms of C/EBPalpha and C/EBP++ beta proteins in the mouse liver that have DNA-binding activity. By using specific antisera, we detected C/EBPalphas with molecular masses of 42, 38, 30, and 20 kDa that have DNA-binding activity. The pool levels of the 42- and 30-kDa isoforms were high in control nuclear extracts and decreased significantly after lipopolysaccharide (LPS) treatment. The binding activity and protein levels of the 20-kDa isoform are low in controls and increase dramatically after LPS treatment. C/EBPbeta isoforms with molecular masses of 35, 20, and 16 kDa were also detected. The 35-kDa pool level did not change whereas the 20-kDa isoform was strongly induced in response to LPS. Western (immunoblot) and Southwestern (DNA-protein) analyses show that p42 C/EBPalpha forms specific complexes with the alpha1-acid glycoprotein oligonucleotide in control nuclear extract and that p20 C/EBP beta forms complexes in LPS-treated liver. Our studies suggest that synthesis of specific C/EBPalpha and C/EBPbeta isoforms occurred in the normal liver in vivo and that LPS mediated a differential initiation and inhibition of translation at specific AUG sites within each mRNA. The qualitative and quantitative changes in C/EBPalpha and C/EBPbeta isoform pool levels suggest that LPS or an LPS-stimulated factor can regulate the selection of AUG start sites for both activation and repression of translation. This regulation appears to involve an LPS-mediated down-regulation of initiation at the first AUG codon of the 42-kDa C/EBPalpha and dramatic translational up-regulation at the fifth AUG codon of the 20-kDa C/EBPalpha and the third AUG codon of the 20-kDa C/EBPbeta. These regulatory events suggest the existence of proteins that may act as translational trans-acting factors.

A novel cis-acting element is essential for cytokine-mediated transcriptional induction of the serum amyloid A gene in nonhepatic cells

Serum amyloid A (SAA) is a plasma protein which has been associated with several diseases, including amyloidosis, arthritis, and atherosclerosis, and its abnormal expression, particularly in nonhepatic cells, is implicated in the pathogenesis of these diseases. Transfection and DNA-binding studies were performed to investigate the mechanism controlling cytokine-induced, nonhepatic expression of the SAA gene. We have identified a novel promoter, located between positions -280 and 224, that confers interleukin-6 (IL-6) inducibility to an SAA-chloramphenicol acetyltransferase reporter gene in both nonhepatic and hepatic cells. DNase I protection assays revealed, within this region, three homologous highly pyrimidine rich octanucleotide sequence motifs, termed SAA-activating sequences (SAS). Specific mutations within these three SAS motifs severely reduced IL-6-mediated induction of the reporter gene in transfected nonhepatic cells but not in liver cells. A nuclear factor activated by IL-6 in both hepatic and nonhepatic cells efficiently interacts with the SAS. The induction kinetics and cycloheximide sensitivity of this SAS-binding factor (SAF) suggested that de novo synthesis of this factor itself or an activator protein is essential. Loss of DNA-binding ability as a result of in vitro dephosphorylation, induction of SAA-chloramphenicol acetyltransferase reporter gene activity in the presence of genistein, a protein kinase inhibitor, further indicate that a phosphorylation step is necessary for the activation of SAF. Our results suggest that SAF is a key regulator of cytokine-mediated SAA gene expression in some nonhepatic cells.

Adenovirus-mediated transfer of CCAAT/enhancer-binding protein-alpha identifies a dominant antiproliferative role for this isoform in hepatocytes

CCAAT/enhancer-binding protein (C/EBP) isoforms are thought to be important regulators of the hepatocyte phenotype. However, the specific physiological roles of different isoforms are poorly understood because hepatocytes express multiple C/EBPs, and various isoforms have overlapping functions. To identify the functions of C/EBPalpha in mature hepatocytes, replication-defective adenovirus vectors were used to efficiently and homogeneously overexpress the mouse C/EBPalpha gene in a SV40 virus-conditionally transformed rat hepatocyte line that can be induced to express C/EBPbeta and C/EBPdelta but that has little endogenous C/EBPalpha expression. Hepatocytes were infected with a recombinant adenovirus vector carrying the cDNA for C/EBPalpha driven by Rous sarcoma virus promoter elements (AdCEBPalpha) or a similar vector carrying the Escherichia coli lacZ gene (Adbetagal). Staining for beta-galactosidase demonstrated an infection efficiency of 100% at a multiplicity of infection of 25 plaque-forming units/cell and persistence of foreign gene expression for at least 9 days. Cultures infected with AdCEBPalpha had 50-fold higher levels of C/EBPalpha mRNA and protein than those infected with Ad-beta-gal, but similar expression of C/EBP-beta. Infection with AdCEBPalpha inhibited proliferation in cells expressing little C/EBPbeta, even when proliferation was driven by the SV40 transforming antigen, and also blunted mitogenic induction of the c-myc proto-oncogene in nontransformed cells with high levels of C/EBPbeta. Although overexpression of C/EBPalpha consistently increased C/EBPalpha DNA binding activity, it was not sufficient for albumin expression. Infection with AdCEBPalpha only increased albumin mRNA levels in nontransformed cells that also expressed relatively high levels of C/EBPbeta. Thus, in hepatocytes, C/EBPalpha has a dominant antiproliferative function, but must interact with other factors to regulate hepatocyte-specific gene expression.

Characterization and functional analysis of the human inducible nitric oxide synthase gene promoter

BACKGROUND

Nitric oxide has a wide variety of homeostatic and pathological effects. Control of the production of nitric oxide by the inducible form of the enzyme resides in the 5' promoter region of the gene. Although control of the murine isoform has been investigated, little is known about the functional aspects of the human analog.

MATERIALS AND METHODS

A 3.9-kb 5' nontranslated region of the human gene was cloned, sequenced, and several reporter constructs prepared. The promoter-reporter constructs were transfected into human or murine monocytoid cells and reporter expression quantified following cytokine activation of the cells. The production of nitric oxide was also monitored.

RESULTS

Although a murine promoter-reporter functioned efficiently in both human and mouse cells, the human constructs functioned only in human cells. The activity of the mouse construct increased progressively with the addition of activating cytokines, but the human promoter-reporter did not. Although interleukin 1 beta drove expression of the human inducible nitric oxide synthase reporter, actual expression of nitric oxide required both interleukin 1 beta and interferon-gamma.

CONCLUSIONS

The data indicate that despite the significant homology between the human and mouse inducible nitric oxide synthase promoter sequence, control of the two genes is quite different. In addition to being more efficient in promoter activity, the murine promoter responds increasingly to cytokines that are not effective for the human analog. It is also apparent that human inducible nitric oxide synthase is controlled at both the level of transcription and post-translationally.

In vivo role of IL-6 on the viral load and on immunological abnormalities of HIV-infected patients

In vitro experiments have suggested that interleukin (IL)-6 may contribute to human immunodeficiency virus (HIV) burden and to immunological abnormalities in HIV-infected patients. We had the opportunity to directly address this question in vivo through the virological and immunological monitoring of HIV-infected patients treated with an anti-IL-6 monoclonal antibody (mAb) for a lymphoma (ANRS 018 trial). Sixteen courses of anti-IL-6 mAb administration, performed in 11 patients, were studied. All patients were at a late stage of HIV infection. The HIV load and the immunological status were determined at the initiation of each course and at its end, 21 days later. The mAb induced no significant change of HIV load, as evaluated by p24 antigenemia, plasma viremia, and quantification of circulating HIV RNA by reverse transcriptase-polymerase chain reaction and branched DNA techniques. The anti-IL-6 mAb also did not affect CD4+, CD8+, and CD19+ circulating cell counts, nor the serum concentrations of sIL-2R and of sCD8. In contrast, the mAb completely abrogated acute-phase reaction, as demonstrated by the normalization of C-reactive protein and fibrinogen circulating levels (p = 0.013 and p = 0.008, respectively). It increased serum albumin concentration. The latter effect was restricted to patients with a spontaneously low albuminemia (p = 0.01). It decreased B-lymphocyte hyperactivity, as reflected by decreased IgG and IgA serum levels (p = 0.008 and p < 0.001, respectively), and by a decreased production of IgG in vitro (p = 0.017). In contrast, the IgM hyperproduction was not affected by the mAb. Therefore, increased IL-6 production in HIV-infected patients at a late stage of the infection may not stimulate HIV replication in vivo, but it may represent a key mechanism contributing to the metabolic and immunological dysbalance of the disease.

Drugs affecting plasma fibrinogen levels. Implications for new antithrombotic strategies

Current evidence indicates that plasma fibrinogen is synthesized by the liver; that genetic and environmental factors regulate plasma fibrinogen levels; that interleukin-6 (IL-6) affects the synthesis of plasma fibrinogen by mechanisms involving protein kinase C, and that during the acute-phase response, monocytes generate a variety of monokines including IL-6. Certain drugs and nutrients have been reported to lower plasma fibrinogen levels. The mechanism(s) involved in this effect is poorly understood. However, since most of these substances quantitatively and/or qualitatively affect monocytes, the possibility that these drugs affect plasma fibrinogen levels via these cells should be considered. In addition to fibrinogen, IL-6 also regulates the synthesis of other acute-phase proteins. Especially when combined, major risk factors for atherosclerosis cause vascular injury that triggers inflammatory events. This raises the issue of whether high plasma fibrinogen levels are just the epiphenomenon of as yet unknown events in thrombosis and atherosclerosis. Thus, the issue to be addressed is whether high plasma fibrinogen concentrations should be lowered or should they serve to suggest strong interventions on established risk factors. As for other risk factors, fibrinogen measurements in population-based studies, in parallel with measurements of established risk factors will help define appropriate directions to be followed to gain insight into the issue and define new antithrombotic strategies.

The warm temperature acclimation-related 65-kDa protein, Wap65, in goldfish and its gene expression

cDNAs encoding a warm temperature acclimation-related protein (Wap65) were cloned from the muscle and hepatopancreas cDNA libraries of the warm temperature-acclimated goldfish Carassius auratus, and their nucleotide sequences containing 5'- and 3'-noncoding regions together with their polyadenylation signal were determined. The deduced amino acid sequence of Wap65 was 31% homologous to rat hemopexin. However, goldfish Wap65 lacked a few possible glycosylation sites and presumed functional histidine residues, implying that it may have different functions from hemopexin. Wap65 contained a leader peptide of 30 amino acids and a mature protein region of 415 amino acids. Southern blot analysis demonstrated that the protein is expressed by a single copy gene in the goldfish haploid genome. In RNA blot analysis using isolated cDNA clones, a single transcript of about 2.0 kilobases was detected in the hepatopancreas but not in brain, muscle, or hemocytes. The abundancy of this transcript markedly increased in the hepatopancreas as a result of warm temperature acclimation. Electrophoretic analysis of plasma proteins revealed a good correlation of plasma Wap65 levels to those of the corresponding transcript in the hepatopancreas, suggesting that serum Wap65 concentrations are regulated mainly by transcript levels in the hepatopancreas via the secretion process.

Expression of tumour necrosis factor-alpha, interleukin-6, and interleukin-2 mRNA in the jejunum of patients with coeliac disease

BACKGROUND

A T-cell-mediated immune response may be responsible for the enteropathy seen in coeliac disease (CD), but it is unclear whether this is initiated in the epithelium or the lamina propria. We studied the site and number of cells expressing mRNA encoding the cytokines interleukin-2 (IL-2), IL-6, and tumour necrosis factor-alpha in jejunal biopsy specimens from patients with untreated or treated CD and normal controls.

METHODS

Tissue sections were hybridized with 35S-labelled DNA oligonucleotide probes specific for each cytokine RNA sequence. Positive cells were counted in the lamina propria and epithelial compartments.

RESULTS

For each cytokine significantly greater numbers of positive cells were found in the lamina propria of untreated CD patients. Few positive cells were detected in the epithelium of all three groups.

CONCLUSIONS

This study shows that the immune response to gliadin appears to occur in the lamina propria and supports cell-mediated immunity in the pathogenesis of coeliac disease.

Interleukin (IL)-10 inhibits nuclear factor kappa B (NF kappa B) activation in human monocytes. IL-10 and IL-4 suppress cytokine synthesis by different mechanisms

Our previous studies in human monocytes have demonstrated that interleukin (IL)-10 inhibits lipopolysaccharide (LPS)-stimulated production of inflammatory cytokines, IL-1 beta, IL-6, IL-8, and tumor necrosis factor (TNF)-alpha by blocking gene transcription. Using electrophoretic mobility shift assays (EMSA), we now show that, in monocytes stimulated with LPS or TNF alpha, IL-10 inhibits nuclear stimulation of nuclear factor kappa B (NF kappa B), a transcription factor involved in the expression of inflammatory cytokine genes. Several other transcription factors including NF-IL-6, AP-1, AP-2, GR, CREB, Oct-1, and Sp-1 are not affected by IL-10. This selective inhibition by IL-10 of NF kappa B activation occurs rapidly and in a dose-dependent manner and correlates well with IL-10's cytokine synthesis inhibitory activity in terms of both kinetics and dose responsiveness. Furthermore, compounds such as tosylphenylalanyl chloromethyl ketone and pyrrolidinedithiocarbamate that are known to selectively inhibit NF kappa B activation block cytokine gene transcription in LPS-stimulated monocytes. Taken together, these results suggest that inhibition of NF kappa B activation may be an important mechanism for IL-10 suppression of cytokine gene transcription in human monocytes. IL-4, another cytokine that inhibits cytokine mRNA accumulation in monocytes, shows little inhibitory effect on LPS-induced NF kappa B activation. Further examination reveals that, unlike IL-10, IL-4 enhances mRNA degradation and does not suppress cytokine gene transcription. These data indicate that IL-10 and IL-4 inhibit cytokine production by different mechanisms.