Structure, hormonal regulation, and identification of the interleukin-6- and dexamethasone-responsive element of the rat haptoglobin gene

Haptoglobin Genotypes in Nasopharyngeal Carcinoma

Aim

Haptoglobin polymorphisms are associated with different cancers; however, the occurrence of nasopharyngeal carcinoma (NPC) in relation to haptoglobin polymorphisms has not been reported. In this study, the distribution of haptoglobin genotypes among patients with NPC was investigated and the prognostic significance of haptoglobin genotypes was further analyzed.

Material and methods

Haptoglobin genotypes were analyzed using polymerase chain reaction and electrophoresis. The genotypes were determined in the sera of 49 NPC patients and in 134 controls.

Results

The haptoglobin genotypes of patients with NPC were as follows: Hp 1–1, 2%; Hp 2–1, 39%; Hp 2–2, 59%. The frequency of the Hp 2–2 genotype was much higher in NPC patients than in control individuals (p=0.044). Furthermore, NPC patients with the Hp 2–2 genotype had advanced T stages (p=0.001) and larger primary tumor volumes (p=0.035) than those with Hp 2–1 or 1–1.

Conclusion

An increased frequency of the Hp 2–2 genotype was associated with NPC. The Hp 2 allele was also overexpressed in NPC patients. NPC patients with the Hp 2–2 genotype had advanced T stage and a larger primary tumor volume. Hp 2–2 may be a negative prognostic factor in NPC.

Anti-CD163-dexamethasone protects against apoptosis after ischemia/reperfusion injuries in the rat liver

Aim

The Pringle maneuver is a way to reduce blood loss during liver surgery. However, this may result in ischemia/reperfusion injury in the development of which Kupffer cells play a central role. Corticosteroids are known to have anti-inflammatory effects. Our aim was to investigate whether a conjugate of dexamethasone and antibody against the CD163 macrophage cell surface receptor could reduce ischemia/reperfusion injury in the rat liver.

Methods

Thirty-six male Wistar rats were used for the experiments. Animals were randomly divided into four groups of eight receiving anti-CD163-dexamethasone, high dose dexamethasone, low dose dexamethasone or placebo intravenously 18 h before laparotomy with subsequent 60 min of liver ischemia. After reperfusion for 24 h the animals had their liver removed. Bloods were drawn 30 min and 24 h post ischemia induction. Liver cell apoptosis and necrosis were analyzed by stereological quantification.

Results

After 24 h' reperfusion, the fraction of cell in non-necrotic tissues exhibiting apoptotic profiles was significantly lower in the high dose dexamethasone (p = 0.03) and anti-CD163-dex (p = 0.03) groups compared with the low dose dexamethasone and placebo groups. There was no difference in necrotic cell volume between groups. After 30 min of reperfusion, levels of haptoglobin were significantly higher in the anti-CD163-dex and high dose dexamethasone groups. Alanine aminotransferase and alkaline phosphatase were significantly higher in the high dose dexamethasone group compared to controls after 24 h' reperfusion.

Conclusions

We show that pharmacological preconditioning with anti-CD163-dex and high dose dexamethasone reduces the number of apoptotic cells following ischemia/reperfusion injury.

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We investigated the effect of pharmacologic preconditioning with HDD, LDD and anti-CD163-dex on ischemia/reperfusion injury.

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Liver cell apoptosis and necrosis were analyzed by stereological quantification.

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Anti-CD163-dex and high dose dexamethasone reduces the number of apoptotic cells following ischemia/reperfusion injury.

Haptoglobin, hemopexin, and related defense pathways-basic science, clinical perspectives, and drug development

Hemolysis, which occurs in many disease states, can trigger a diverse pathophysiologic cascade that is related to the specific biochemical activities of free Hb and its porphyrin component heme. Normal erythropoiesis and concomitant removal of senescent red blood cells (RBC) from the circulation occurs at rates of approximately 2 × 10⁶ RBCs/second. Within this physiologic range of RBC turnover, a small fraction of hemoglobin (Hb) is released into plasma as free extracellular Hb. In humans, there is an efficient multicomponent system of Hb sequestration, oxidative neutralization and clearance. Haptoglobin (Hp) is the primary Hb-binding protein in human plasma, which attenuates the adverse biochemical and physiologic effects of extracellular Hb. The cellular receptor target of Hp is the monocyte/macrophage scavenger receptor, CD163. Following Hb-Hp binding to CD163, cellular internalization of the complex leads to globin and heme metabolism, which is followed by adaptive changes in antioxidant and iron metabolism pathways and macrophage phenotype polarization. When Hb is released from RBCs within the physiologic range of Hp, the potential deleterious effects of Hb are prevented. However, during hyper-hemolytic conditions or with chronic hemolysis, Hp is depleted and Hb readily distributes to tissues where it might be exposed to oxidative conditions. In such conditions, heme can be released from ferric Hb. The free heme can then accelerate tissue damage by promoting peroxidative reactions and activation of inflammatory cascades. Hemopexin (Hx) is another plasma glycoprotein able to bind heme with high affinity. Hx sequesters heme in an inert, non-toxic form and transports it to the liver for catabolism and excretion. In the present review we discuss the components of physiologic Hb/heme detoxification and their potential therapeutic application in a wide range of hemolytic conditions.

Pulmonary haptoglobin and CD163 are functional immunoregulatory elements in the human lung

BACKGROUND

The acute-phase protein haptoglobin (Hp) and its receptor CD163 serve as immunomodulators and possess anti-inflammatory besides antioxidant functions.

OBJECTIVES

To further understand the role of the recently described pulmonary Hp (pHp) and its receptor CD163 in case of inflammation and infection, pHp and CD163 were investigated on mRNA and protein level to gain insight into the cellular events taking place upon stimulation with the inflammatory mediators LPS, Pam3, cytokine IL-6 and dexamethasone, and upon infection with respiratory pathogens (Haemophilus influenzae, Streptococcuspneumoniae and Chlamydia pneumoniae) by use of a human ex vivo tissue culture model and cell cultures of A549 and alveolar epithelial cells type II. In addition, pHp and CD163 expression in COPD and sarcoidosis was assessed.

METHODS

We conducted experiments using 942 ex vivo cultured lung samples applying immunohistochemistry, immunocytochemistry, in situ hybridization, immunofluorescence, real-time PCR, RT-PCR, slot and Western immunoblot analyses with tissue lysates and culture supernatants as well as ELISA and cytometric bead array analyses.

RESULTS

This study describes for the first time the expression, regulation and secretion of pHp and its receptor CD163 in the human lung. The release of soluble mediators from A549 cell line and human monocyte-derived macrophages was observed indicating that Hp differentially activates the release of soluble mediators and major chemoattractants.

CONCLUSIONS

The findings indicate a native function of pHp and CD163 as functional pulmonary defense elements due to local expression, regulation and secretion during lung infection and as part of the inflammatory immune response of the respiratory system.

Hemoglobin and heme scavenger receptors

Heme, the functional group of hemoglobin, myoglobin, and other hemoproteins, is a highly toxic substance when it appears in the extracellular milieu. To circumvent potential harmful effects of heme from hemoproteins released during physiological or pathological cell damage (such as hemolysis and rhabdomyolysis), specific high capacity scavenging systems have evolved in the mammalian organism. Two major systems, which essentially function in a similar way by means of a circulating latent plasma carrier protein that upon ligand binding is recognized by a receptor, are represented by a) the hemoglobin-binding haptoglobin and the receptor CD163, and b) the heme-binding hemopexin and the receptor low density lipoprotein receptor-related protein/CD91. Apart from the disclosure of the molecular basis for these important heme scavenging systems by identifying the functional link between the carrier proteins and the respective receptors, research over the last decade has shown how these systems, and the metabolic pathways they represent, closely relate to inflammation and other biological events.

Regulation of rat haptoglobin gene expression is coordinated by the nuclear matrix

Using computer stress-induced duplex destabilization (SIDD) analysis and binding experiments, we identified a S/MAR element (-599/-200 bp) (Hp-S/MAR) adjacent to the cis-element (-165/-56 bp) in the rat haptoglobin gene. We examined its functional interactions with the lamins and lamin-associated proteins in the basal state and during acute-phase (AP) response-induced increased transcription. Colocalization, electrophoretic mobility shift assay (EMSA), and re-electrophoresis of nucleoprotein complexes, South-Western and Western blot analysis and coimmunoprecipitation experiments revealed that the lamins, PARP-1, C/EBP beta, and Hp-S/MAR assembled higher order complexes through direct lamin-Hp-S/MAR and probably PARP-1-Hp-S/MAR interactions although C/EBP beta did not bind to the Hp-S/MAR but established direct interaction with PARP-1. The transition from constitutive to increased haptoglobin gene transcription during the AP response was associated with quantitative and qualitative changes in Hp-S/MAR-protein interactions, respectively, observed as increased association of the lamin(s) with the Hp-S/MAR and as the appearance of a 90 kDa Hp-S/MAR-binding protein. Also, during the AP response the contact between C/EBP beta and PARP-1 established in the basal state was lost. DNA chromatography with the haptoglobin cis-element and Western blot analysis suggests that PARP-1 was a coactivator during constitutive and elevated transcription. The results show that the lamin components of the nuclear matrix form a network of functional, dynamic protein-protein and protein-Hp-S/MAR associations with multiple partners, and underline the involvement of PARP-1 in the regulation of haptoglobin gene transcription. We concluded that the interplay of these interactions fine tunes haptoglobin gene expression to meet the changing requirements of liver cells.

MPTP administration increases plasma levels of acute phase proteins in non-human primates (Macaca fascicularis)

Parkinson's disease (PD) is characterized by the loss of dopaminergic neurons in the Substantia Nigra pars compacta (SNpc). Parkinsonian patients and animal models of PD show inflammatory phenomena such as microglial activation and cytokine production that could modulate the progression of the disease, since they play a crucial role in the degenerative process. Since acute phase proteins (APPs) are involved in a number of homeostatic alterations and inflammatory processes, we analyzed the levels of APPs in primates before and after treatment with MPTP. A significant increase in C-reactive protein (CRP), serum amyloid A (SAA) and haptoglobin (HP) levels after MPTP treatment. These results demonstrate that MPTP induces a systemic generalized inflammatory reaction after specific dopaminergic neurotoxicity insult, suggesting that the inflammatory process in Parkinsonism may affect other immune-inflammatory responses outside the brain.

Regulation of C/EBPdelta-dependent transactivation by histone deacetylases in intestinal epithelial cells

The C/EBPdelta transcription factor is involved in the positive regulation of the intestinal epithelial cell acute phase response. C/EBPdelta regulation by histone deacetylases (HDACs) during the course of inflammation remains to be determined. Our aim was to examine the effect of HDACs on C/EBPdelta-dependent regulation of haptoglobin, an acute phase protein induced in intestinal epithelial cells in response to pro-inflammatory cytokines. HDAC1, HDAC3, and HDAC4 were expressed in intestinal epithelial cells, as determined by Western blot. GST pull-down assays showed specific HDAC1 interactions with the transcriptional activation and the b-ZIP C/EBPdelta domains, while the co-repressor mSin3A interacts with the C-terminal domain. Immunoprecipitation assays confirmed the interaction between HDAC1 and the N-terminal C/EBPdelta amino acid 36-164 domain. HDAC1 overexpression decreased C/EBPdelta transcriptional activity of the haptoglobin promoter, as assessed by transient transfection and luciferase assays. Chromatin immunoprecipitation analysis showed a displacement of HDAC1 from the haptoglobin promoter in response to inflammatory stimuli and an increased acetylation of histone H3 and H4. HDAC1 silencing by shRNA expression increased both basal and IL-1beta-induced haptoglobin mRNA levels in epithelial intestinal cells. Our results suggest that interactions between C/EBPs and HDAC1 negatively regulate C/EBPdelta-dependent haptoglobin expression in intestinal epithelial cells.

The action of interleukin 6 and leukaemia inhibitory factor on liver cells

The hepatic action of cytokines has generally been analysed in terms of the acute-phase response of the liver. The qualitative and quantitative changes in the expression of plasma proteins serve as defining criteria for cytokine function. Interleukin 6 (IL-6) and leukaemia inhibitory factor (LIF) are representatives of a group of cytokines which display strikingly similar effects in both human and rodent liver cells. Hallmarks of the action of these cytokines are the stimulation of type 2 acute-phase plasma proteins and enhancement of the effect of interleukin 1 (IL-1) or tumour necrosis factor alpha (TNF-alpha) on type 1 acute-phase plasma proteins. The transcriptional activation of the various acute-phase plasma protein genes involves common cis-acting regulatory elements whose sequences and location relative to the transcription start site vary from gene to gene. The activity of the IL-6- and LIF-responsive genes depends in part on transcription factors including several members of the C/EBP family, JunB and the glucocorticoid receptor. The expression of these transcription factors is in turn under cytokine-specific control. In a few cases, expression is temporally correlated with the activation of 'late' acute-phase protein genes. The finding that structurally distinct cytokines interact with separate receptors but elicit an almost identical liver cell response demands a reassessment of the contribution of each factor to the in vivo acute-phase response.

Haptoglobin phenotype and risk of cervical neoplasia: a case-control study

BACKGROUND

Haptoglobin is an acute-phase glycoprotein that influences host response to infections and tumours. The haptoglobin locus is polymorphic with 2 classes of alleles (Hp(1) and Hp(2)) yielding 3 phenotypes: Hp1-1, Hp2-2, and Hp2-1 with structurally and functionally distinct protein products, suggesting that haptoglobin polymorphism may influence susceptibility to infections and cancers.

METHODS

We examined the relation between haptoglobin phenotype and high-grade cervical intraepithelial neoplasia (CIN) in a hospital-based case-control study. Cases (n = 307) were women with biopsy-confirmed CIN-2 or CIN-3. Controls (n = 358) were a random sample of women with normal cytology. The PGMY polymerase chain reaction and reverse line blot methods were used for HPV detection and genotyping. Haptoglobin phenotype was determined by polyacrylamide gel electrophoresis.

RESULTS

Among controls, phenotype distribution corresponded to allele frequencies of 0.39 for Hp(1) and 0.61 for Hp(2) with no significant deviation from the Hardy-Weinberg equilibrium (p=0.66). With all women included in the analysis, the Hp1-1 phenotype was associated with increased risk of CIN (OR contrasting Hp1-1 vs. Hp2-2 = 1.0; 95% CI: 0.6-1.5). However, in analyses restricted to HPV-positive participants, the Hp1-1 phenotype was associated with 2.7-fold (95% CI: 1.0-7.2) higher risk of CIN.

CONCLUSIONS

If confirmed, these findings indicate an increased risk of CIN among women with the Hp1-1 phenotype.

Dual effect of butyrate on IL-1beta--mediated intestinal epithelial cell inflammatory response

Butyrate (NaBu), a product of intestinal microbial metabolism, has been proposed as an anti-inflammatory agent for treating inflammatory bowel diseases. However, the molecular mechanisms implicated in the modulation of intestinal epithelial cell inflammatory response to NaBu remain unknown. Here, microarray analysis performed on nontransformed human crypt intestinal epithelial cells (HIEC) shows that NaBu regulated specifically the short-term IL-1beta -dependent induction of different inflammatory genes. While NaBu significantly increased the IL-1beta -induction of genes like SAA2, C3, and IL-1alpha , other inflammatory genes like CXCL5, CXCL11, and IL-1beta were decreased. Induction of various genes such as CXCL8, CCL20, and IL-6 was unaffected by NaBu. We show that, compared to genes that are upregulated or downregulated by NaBu, genes that are unaffected by NaBu were induced more rapidly after IL-1beta treatment and contained a higher concentration of transcription factor binding sites in their promoter region. In addition, transient treatment with IL-1beta was sufficient for subsequent induction of NaBu-upregulated and NaBu-unaffected classes of genes, while a continuous presence of IL-1beta was required for NaBu-downregulated gene expression. In conclusion, our results suggest that fundamental differences predispose inflammatory genes to specific regulation by NaBu in intestinal epithelial cells, thereby allowing precise control of inflammation.

Synergy between deacetylase inhibitors and IL-1beta in activation of the serum amyloid A2 gene promoter

Butyrate (NaBu) regulates intestinal inflammatory gene expression in part through inhibition of deacetylase activity, but the exact mechanisms involved remain to be determined. In this study, we showed by Northern blot a synergistic induction of the acute phase protein gene SAA2 with a combination of deacetylase inhibitors (Trichostatin A or NaBu) and IL-1beta in the colon carcinoma cell line Caco-2. While the NF-kappa B DNA-binding site was essential for SAA2 regulation by IL-1beta and deacetylase inhibitors, the C/EBP DNA-binding site modulated SAA2 expression levels, as assessed by transient transfection assays and mutagenesis studies. NaBu was sufficient to induce SAA2 expression after transient treatment with IL-1beta and, conversely, IL-1beta induced SAA2 after transient treatment with NaBu. These data suggest that pretreatment with either NaBu or IL-1beta predisposes the SAA2 promoter to further stimulation. Indeed, both NaBu and IL-1beta led to increased recruitment of NF-kappa B p65, C/EBPbeta, and C/EBP delta, and decreased NF-kappa B p50 and C/EBP alpha DNA-binding to the proximal SAA2 promoter, as assessed by chromatin immunoprecipitation assays. Interestingly, while IL-1beta, in contrast to NaBu, induced histone H4 acetylation, addition of IL-1beta and NaBu increased histone H4 acetylation and both C/EBPbeta and NF-kappa B p65 DNA-binding. Therefore, these results suggest that NaBu and IL- 1beta mediate SAA2 synergistic induction by establishing and maintaining similar and complementary chromatin modifications and transcription factor recruitment as well. In addition to global effects, NaBu specifically regulate gene expression, as exemplified by SAA2.

IL-1 beta-dependent regulation of C/EBP delta transcriptional activity

We have previously shown that the transcription factor C/EBP delta is involved in the intestinal inflammatory response. C/EBP delta regulates several inflammatory response genes, such as haptoglobin, in the rat intestinal epithelial cell line IEC-6 in response to IL-1. However, the different C/EBP delta domains involved in IL-1 beta-mediated transcriptional activation and the kinases implicated have not been properly defined. To address this, we determined the role of the p38 MAP kinase in the regulation of C/EBP delta transcriptional activity. The IL-1-dependent induction of the acute phase protein gene haptoglobin in IEC-6 cells was decreased in response to the p38 MAP kinase inhibitor SB203580, as determined by Northern blot. Transcriptional activity of C/EBP delta was repressed by the specific inhibitor of the p38 MAP kinase, as assessed by transient transfection assays. Mutagenesis studies and transient transfection assays revealed an important domain for transcriptional activation between amino acids 70 and 108. This domain overlapped with a docking site for the p38 MAP kinase, between amino acids 75 and 85, necessary to insure C/EBP delta phosphorylation. Deletion of this domain led to a decrease in basal transcriptional activity of C/EBP delta and in p300-dependent transactivation, as assessed by transient transfection assays, and in IL-1-dependent haptoglobin induction. This unusual arrangement of a kinase docking site within a transactivation domain may functionally be important for the regulation of C/EBP delta transcriptional activity.

Haptoglobin expression and activity during coronary collateralization

Coronary collateral development relies on the coordinated secretion of growth factors. However, alone they are insufficient for permanent collateral growth. We utilized proteomics to identify other important proteins in the extracellular environment that could facilitate collateralization. Chronically instrumented dogs developed coronary collaterals by the repetitive occlusion method. Subendocardial (0.19 ± 0.04, 0.27 ± 0.06, 0.48 ± 0.10, and 0.81 ± 0.11 ml·min−1·g−1 on days 1, 7, 14, and 21, respectively) and subepicardial (0.14 ± 0.01, 0.36 ± 0.06, 0.51 ± 0.07, and 0.71 ± 0.08 ml·min−1·g−1 on days 1, 7, 14, and 21, respectively) blood flow increased in animals subjected to repetitive occlusion. Sham animals exhibited no changes in blood flow. Myocardial interstitial fluid (MIF) from both groups was analyzed by two-dimensional electrophoresis with matrix-assisted laser desorption/ionization time-of-flight identification. The acute-phase protein haptoglobin was identified in the group subjected to repetitive occlusion. ELISA of MIF showed haptoglobin to be elevated at all time points of collateral development compared with sham, with maximal production on day 7. Purified haptoglobin dose dependently stimulated endothelial cells to form tubes and vascular smooth muscle cells to migrate. Purified haptoglobin did not stimulate proliferation of either cell type. The relative contribution of haptoglobin to the chemotactic properties of MIF was tested using a neutralizing antibody. Neutralized MIF could not stimulate smooth muscle cells to migrate at any time during collateral development. Endothelial cell tube formation was inhibited after the midpoint of collateralization. Therefore, the acute-phase protein haptoglobin plays a critical role during coronary collateralization.

Expression, by functional proteomics, of spontaneous tolerance in rat orthotopic liver transplantation

Orthotopic liver transplants (OLT) performed in certain combinations of donor and recipient rat strains, such as DA (RT1a) to PVG (RT1c), without immunosuppressive drugs could completely overcome major histocompatibility complex barriers. Although other organs transplanted in a similar fashion within the same combination have been promptly rejected, 60 day post-OLT serum (POD 60) has been proven competent in rapidly reversing the established rejection in animal models. In order to understand the functional role of tolerogenic serum proteins and their involvement with immune response regulation, a comprehensive analysis surveying global changes in complex OLT systems by proteomic techniques was applied. The results display the varying protein expressions in sera extracted from naïve and transplanted animals on POD 60 with regard to immunosuppression. Among these proteins, haptoglobin (Hp) which is related to inhibition of T-cell proliferation was found to be up-regulated following OLT. In addition, the transcriptional expression level and intracellular localization of Hp correlated with the immune events. Hp also exhibited a strong in vitro immunosuppressive effect on the mixed lymphocyte reaction. In conclusion, the presence of Hp may play an important role in modulating the spontaneous tolerance of liver transplantation. Furthermore, the serum proteome map could provide guidance with respect to discovering potential protein targets in OLT tolerance and eventually prolong hepatic allograft survival in the future.

Nitric oxide synthesis is involved in arterial haptoglobin expression after sustained flow changes

The acute phase protein haptoglobin is highly expressed in arteries after sustained flow changes and involved in cell migration and arterial restructuring. In the liver, haptoglobin expression is mainly regulated by interleukin-6 (IL-6). In the artery, shear stress and NO influence IL-6 expression. In the present study, we demonstrate that NO synthesis is involved in the regulation of arterial haptoglobin expression after sustained flow changes. Decreased haptoglobin expression after NO inhibition coincided with decreased IL-6 levels. However, IL-6 knockout mice had normal arterial haptoglobin expression levels after sustained flow changes suggesting that other mediators may provide compensatory mechanisms for the regulation of arterial haptoglobin expression.

Haptoglobin, an inflammation-inducible plasma protein

Sterile tissue injury or infection initiates a local inflammatory response that mobilizes a systemic acute phase reaction resulting in, among other things, the induction of genes encoding the acute phase plasma proteins (APPs). In all vertebrates, a common set of APPs is increased and exerts essential protective functions. Haptoglobin (HP), one of the major APPs, acts as a high-affinity hemoglobin-binding protein and antioxidant. Liver is the major site of HP synthesis; however, regulated, low level expression is also detected in other organs. Induction of the Hp gene is mediated by interleukin-6-type cytokines and is synergistically enhanced by glucocorticoids. Growth stimulation of hepatic cells in vivo or in vitro suppresses the Hp gene-inducing effects of inflammatory cytokines. Receptors for IL-6 cytokines mediate induction of the Hp gene by the transcription factors signal transducer and activator of transcription-3 (STAT3) and CAAT/enhancer binding protein beta (C/EBPbeta), but attenuate the stimulation through co-activated STAT5 and mitogen-activated protein kinases, ERK-1 and ERK-2. The specificity by which the related cytokines, IL-6, oncostatin M, and leukemia inhibitory factor, regulate Hp gene transcription is determined by the profile of the cytokine receptor subunits expressed on the target cells and the relative extents by which these receptors activate the intracellular signaling pathways. The current hypothesis is that HP exerts an anti-inflammatory activity and that by the degree with which HP attenuates the inflammatory process, including the production of IL-6 cytokines, it determines the level and duration of acute phase expression of the Hp gene.

Relevance of apolipoproteins in the development of fatty liver and fatty liver-related peripartum diseases in dairy cows

Most metabolic diseases in dairy cows occur during the peripartum period and are suggested to be derived from fatty liver initially developed during the nonlactating stage. Fatty liver is induced by hepatic uptake of nonesterified fatty acids that are released in excess by adipose tissues attributable to negative energy balance. The fatty accumulation leads to impairment of lipoprotein metabolism in the liver, and the impairment in turn influences other metabolic pathways in extrahepatic tissues such as the steroid hormone production by the corpus luteum. Detailed understanding of the impaired lipoprotein metabolism is crucial for elucidation of the mechanistic bases of the development of fatty liver and fatty liver-related peripartum diseases. This review summarizes results on evaluation of lipoprotein lipid and protein concentrations and enzyme activity in cows with fatty liver and those with ketosis, left displacement of the abomasum, milk fever, downer syndrome and retained placenta. Obtained data strongly suggest that decreases in serum concentrations of apolipoprotein B-100, apolipoprotein A-I and apolipoprotein C-III, a reduction in activity of lecithin:cholesterol acyltransferase and induction of haptoglobin and serum amyloid A are intimately related to the development of fatty liver and fatty liver-related diseases. Moreover, determination of the apolipoprotein concentrations and enzyme activity during the peripartum period is useful for early diagnoses of these diseases.

Role of specific CCAAT/enhancer-binding protein isoforms in intestinal epithelial cells

Intestinal epithelial cells participate in the acute phase response in response to inflammation. We have shown that acute phase protein genes are induced during intestinal acute phase response, and that the CCAAT/enhancer binding protein family of transcription factors are involved. To address the role of specific C/EBP isoforms, we generated IEC-6 rat intestinal epithelial cell lines expressing different C/EBP isoforms, by retroviral infection. Overexpression of C/EBPalpha p30 and C/EBPdelta led to increases in C/EBPbeta LAP and C/EBPbeta LIP endogenous protein levels, as determined by electrophoretic mobility shift assays and Western blot. Inhibition of C/EBP activity with dominant negative C/EBPs (C/EBPbeta LIP, 3hF, 4hF) decreased glucocorticoid-, cAMP- and IL-1 responsiveness of the endogenous haptoglobin gene, while overexpression of each C/EBP isoform increased the responsiveness to these regulators. In contrast, dominant negative C/EBPs or C/EBP isoforms did not alter the expression of alpha-acid glycoprotein in response to dexamethasone and of C/EBPbeta and C/EBPdelta in response to various regulators as assessed by Northern blot. These data show that the three C/EBP isoforms are involved in the regulation of haptoglobin and that C/EBPbeta, C/EBPdelta, and alpha-acid glycoprotein expression are not induced by C/EBP isoforms in contrast to other cell types. C/EBPbeta LAP-expressing cells showed an inhibition of cell growth characterized by a delay in p27(Kip1) decrease in response to serum and a decrease in cyclin D isoforms and cyclin E protein levels. Finally, C/EBP isoforms interact with the E2F4 transcription factor. Thus, specific C/EBP isoforms are involved in the differential expression of acute phase protein genes in response to hormones and cytokines. Furthermore, C/EBP isoforms may play a role in the control of cell cycle progression.

Short-chain ceramide regulates hepatic methionine adenosyltransferase expression

BACKGROUND

The metabolism of methionine plays an important role in regulating hepatic cellular function. Methionine adenosyltransferase (MAT) is the enzyme that catalyses the biosynthesis of S-adenosylmethionine (AdoMet) from ATP and methionine. Liver-specific MAT I/III levels are down-regulated in the regenerating rat liver after partial hepatectomy. Tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) are two cytokines fundamental for liver regeneration. TNF-alpha stimulates sphingomyelin metabolism and ceramide generation in a variety of cell systems.

AIMS

The role of exogenous cell-permeable ceramide in modifying MAT I/III mRNA levels and its association with TNF-alpha and IL-6 actions were investigated in rat hepatocytes and H35 hepatoma cells.

RESULTS

C2-ceramide (N-acetylsphingosine) at 1-10 microM decreased MAT I/III expression. The effect was maximum after 2 h of treatment and it was maintained up to 24 h. MAT I/III protein levels also decreased. IL-6 (1-10 ng/ml) potentiated C2-ceramide effects in cultured hepatocytes while decreasing by itself MAT I/III levels with a similar time-response curve in both cell types. C2-ceramide actions were not associated with an increase in cell death. TNF-alpha was also a potent antagonist for MAT I/III expression, at 1-20 ng/ml decreased MAT I/III levels and induced endogenous ceramide generation. The decrease of MAT I/III mRNA levels (in all the cases) was not due to a decrease in mRNA half-life which suggests a regulation at the transcriptional level. Finally, the decrease in MAT I/III mRNA levels correlated to a decrease in MAT activity.

CONCLUSION

This work demonstrates that short-chain ceramide can be used as a novel exogenous agonist that can modulate hepatic methionine metabolism in association with cytokines.

Inhibition by deacetylase inhibitors of IL-1-dependent induction of haptoglobin involves CCAAT/Enhancer-binding protein isoforms in intestinal epithelial cells

Intestinal epithelial cells participate in an acute phase response (APR) by responding to cytokines and by expressing acute phase protein genes. We hypothesized that butyrate, a fermentation product of the bacterial intestinal flora with deacetylase activity, affects the APR in intestinal epithelial cells. Sodium butyrate (NaBu) and Trichostatin A (TSA) induced alkaline phosphatase activity and histone H4 acetylation in IEC-6 rat intestinal epithelial cells treated with or without interleukin-1beta (IL-1). In contrast, both NaBu and TSA attenuated the IL-1-dependent induction of the acute phase protein gene haptoglobin, as well as C/EBPbeta and C/EBPdelta transcription factors mRNAs. Gel shift and supershift assays showed a strong decrease in the IL-1-induced C/EBPbeta and C/EBPdelta containing complexes binding to the HaptoA C/EBP DNA-binding site of the haptoglobin promoter, by NaBu and TSA. Furthermore, site-specific mutation of the HaptoA site abolished the NaBu- and TSA-dependent inhibition of haptoglobin, as determined by transient transfection assays. These results suggest that deacetylase inhibitors may regulate the IL-1 dependent induction of haptoglobin by down-regulating C/EBP isoforms, and that C/EBPs represent a target for the action of butyrate in the control of the APR of intestinal epithelial cells.

Receptor subunit-specific action of oncostatin M in hepatic cells and its modulation by leukemia inhibitory factor

The related cytokines, interleukin-6 (IL-6), oncostatin M (OSM), and leukemia inhibitory factor (LIF) direct the formation of specific heteromeric receptor complexes to achieve signaling. Each complex includes the common signal-transducing subunit gp130. OSM and LIF also recruit the signaling competent, but structurally distinct OSMRbeta and LIFRalpha subunits, respectively. To test the hypothesis that the particularly prominent cell regulation by OSM is due to signals contributed by OSMRbeta, we introduced stable expression of human or mouse OSMRbeta in rat hepatoma cells which have endogenous receptors for IL-6 and LIF, but not OSM. Both mouse and human OSM engaged gp130 with their respective OSMRbeta subunits, but only human OSM also acted through LIFR. Signaling by OSMRbeta-containing receptors was characterized by highest activation of STAT5 and ERK, recruitment of the insulin receptor substrate and Jun-N-terminal kinase pathways, and induction of a characteristic pattern of acute phase proteins. Since LIF together with LIFRalpha appear to form a more stable complex with gp130 than OSM with gp130 and OSMRbeta, co-activation of LIFR and OSMR resulted in a predominant LIF-like response. These results suggest that signaling by IL-6 cytokines is not identical, and that a hierarchical order of cytokine receptor action exists in which LIFR ranks as dominant member.

Modulation of hepatic acute phase gene expression by epidermal growth factor and Src protein tyrosine kinases in murine and human hepatic cells

As part of systemic inflammatory reactions, interleukin 6 (IL-6) induces acute phase protein (APP) genes through the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway. Epidermal growth factor (EGF), which contributes to the regenerative process after liver injury and also activates STATs, does not induce but attenuates IL-6-stimulated expression of several APP genes in primary mouse hepatocytes. The APP-modifying action of EGF receptor (EGFR) was characterized in HepG2 cells. Although EGF less effectively engages STAT proteins in these cells, it reduces expression of fibrinogen and haptoglobin, but stimulates production of alpha(1)-antichymotrypsin and induces transcription through the alpha(1)-antichymotrypsin and C-reactive protein promoter. The stimulatory EGFR signal is insensitive to inhibition of JAKs and appears to involve Src kinases and STAT proteins as shown by inhibition through overexpression of C-terminal Src kinase (Csk) and transdominant negative STAT3, respectively. A mediator role of Src is supported by the ability of c-Src and v-Src to activate STATs and induce transcription through APP promoters. Src kinases have been observed in association with the IL-6 receptor; however, inhibition of Src kinases by Csk enhances IL-6-induced transcription. The Csk effect is attributed to prevention of Src kinases from phosphorylating gp130 at the docking site for the signal-moderating protein tyrosine phosphatase SHP-2. The inhibitory EGFR signal on APP expression correlates with the activation of Erk1 and Erk2. The study shows a dual signaling function for EGFR and suggests that the ratio of receptor-activated STATs and Erks influence the level of stimulated or inhibited expression of individual APPs.

Attenuation of haptoglobin gene expression by TGFbeta requires the MAP kinase pathway

In addition to important roles in the regulation of cell growth and cell restitution, both pro- and anti-inflammatory effects have been ascribed to TGFbeta in intestinal epithelial cells. However, the mechanisms involved in TGFbeta-dependent anti-inflammatory activities remain to be determined. In the rat intestinal epithelial cell line IEC-6, TGFbeta attenuated the glucocorticoid-dependent increases in mRNA levels of the acute phase protein gene haptoglobin, and of C/EBP isoforms beta and delta. Supershift assays demonstrated a TGFbeta-mediated decrease in the binding of C/EBP isoforms beta and delta to the haptoA and haptoC C/EBP DNA-binding sites from the haptoglobin promoter. Mutations of both HaptoA and HaptoC sites abolished the glucocorticoid-dependent activation and the TGFbeta-mediated attenuation of the haptoglobin promoter, as assessed by transient transfection assays. TGFbeta induced p42/p44 MAP kinase activities. Treatment with the MEK 1/2 inhibitor PD 98059 abolished TGFbeta attenuation. These results suggest that C/EBP isoforms are involved both in the glucocorticoid-dependent induction and in the TGFbeta-mediated attenuation of haptoglobin expression. Furthermore, p42/p44 MAP kinases may function in a TGFbeta-dependent signaling pathway leading to attenuation of haptoglobin expression.

The STAT3-independent signaling pathway by glycoprotein 130 in hepatic cells

Interleukin (IL)-6 is a major regulator of hepatic acute-phase plasma protein (APP) genes. The membrane-proximal 133-amino acid cytoplasmic domain of glycoprotein (gp) 130, containing one copy of the Box3 motif, is sufficient to transmit a productive signal to endogenous APP genes in rat hepatoma H-35 cells. In contrast, a mutant gp130 domain lacking the Box3 motif activates Janus kinases to a normal level but fails to activate signal transducer and activator of transcription 3 and to up-regulate a number of APP genes, including thiostatin, fibrinogen, hemopexin, and haptoglobin. However, in the absence of Box3, gp130 still stimulates the expression of alpha2-macroglobulin and synergizes with IL-1 to up-regulate alpha1-acid glycoprotein. The Box3 motif is not required for activation of the SH2-containing protein tyrosine phosphatase 2 or the mitogen-activated protein kinase (MAPK), nor is the immediate induction of egr-1 and junB significantly altered. Surprisingly, gp130 without any functional Box3 stimulates prolonged activation of MAPK, leading to an extended period of up-regulation of egr-1 and to an extracellularly regulated kinase-mediated reduction in the IL-6-stimulated production of thiostatin. IL-6 reduces proliferation of H-35 cells through signaling by the Box3. In addition, cells expressing Box3-deficient gp130 showed distinct morphologic changes upon receptor activation. Taken together, these results indicate that Box3-derived and Box3-independent signals cooperate in the control of hepatic APP genes and that Box3 may be involved in the modulation of MAPK activity in gp130 signaling.

Activation of haptoglobin gene expression by cAMP involves CCAAT/enhancer-binding protein isoforms in intestinal epithelial cells

CCAAT/enhancer-binding protein (C/EBP) isoforms are expressed in rodent intestine and in the rat intestinal epithelial cell line IEC-6 but their role remains to be determined. Treatment of IEC-6 cells with the adenylate cyclase activator forskolin led to coordinate induction of C/EBP isoforms alpha, beta and delta at the mRNA and protein levels. Transient transfection assays showed that their expression is controlled at the transcriptional level. Forskolin treatment induced haptoglobin mRNA levels. Electrophoretic mobility shift and supershift assays demonstrated an increase in DNA-binding activities of the three C/EBP isoforms to the haptoA and haptoC C/EBP DNA-binding sites of the proximal haptoglobin promoter. Site-specific mutations of both sites led to a decrease in transcriptional induction by forskolin, suggesting that C/EBP isoforms are involved in the cAMP-dependent regulation of the acute-phase protein gene haptoglobin in intestinal epithelial cells.

Increased Susceptibility in Hp Knockout Mice During Acute Hemolysis

Haptoglobin, a conserved plasma glycoprotein, forms very stable soluble complexes with free plasma hemoglobin. Hemoglobin binding by haptoglobin is thought to be important in the rapid hepatic clearance of hemoglobin from the plasma and in the inhibition of glomerular filtration of hemoglobin. To evaluate these functions,Haptoglobin knockout (−/−) mice were created. These mice were viable but had a small, significant reduction in postnatal viability. Contrary to popular belief, the lack of haptoglobin did not impair clearance of free plasma hemoglobin in −/− mice. Induction of severe hemolysis by phenylhydrazine caused extensive hemoglobin precipitation in the renal tubular cells of both −/− and +/+ mice, with death occurring in 55% of −/− mice and in 18% of +/+ mice. In general, phenylhydrazine-treated −/− mice suffered greater tissue damage, as evidenced by the induction of hepatic acute phase response resulting in increased plasma alpha 1-acid glycoprotein (AGP) levels. Among −/− and +/+ mice that survived, −/− mice tend to suffer greater oxidative damage and failed to repair or regenerate damaged renal tissues, as indicated by their higher plasma malonaldehyde (MDA) and 4-hydroxy-2(E)-nonenal (HNE) levels and lower mitotic indices in their kidneys, respectively. This study suggested that a physiologically important role of hemoglobin-haptoglobin complex formation is the amelioration of tissue damages by hemoglobin-driven lipid peroxidation.

© 1998 by The American Society of Hematology.

Increased Susceptibility in Hp Knockout Mice During Acute Hemolysis

Haptoglobin, a conserved plasma glycoprotein, forms very stable soluble complexes with free plasma hemoglobin. Hemoglobin binding by haptoglobin is thought to be important in the rapid hepatic clearance of hemoglobin from the plasma and in the inhibition of glomerular filtration of hemoglobin. To evaluate these functions,Haptoglobin knockout (−/−) mice were created. These mice were viable but had a small, significant reduction in postnatal viability. Contrary to popular belief, the lack of haptoglobin did not impair clearance of free plasma hemoglobin in −/− mice. Induction of severe hemolysis by phenylhydrazine caused extensive hemoglobin precipitation in the renal tubular cells of both −/− and +/+ mice, with death occurring in 55% of −/− mice and in 18% of +/+ mice. In general, phenylhydrazine-treated −/− mice suffered greater tissue damage, as evidenced by the induction of hepatic acute phase response resulting in increased plasma alpha 1-acid glycoprotein (AGP) levels. Among −/− and +/+ mice that survived, −/− mice tend to suffer greater oxidative damage and failed to repair or regenerate damaged renal tissues, as indicated by their higher plasma malonaldehyde (MDA) and 4-hydroxy-2(E)-nonenal (HNE) levels and lower mitotic indices in their kidneys, respectively. This study suggested that a physiologically important role of hemoglobin-haptoglobin complex formation is the amelioration of tissue damages by hemoglobin-driven lipid peroxidation.

© 1998 by The American Society of Hematology.

Adrenalectomy and dexamethasone treatment alter the patterns of basal and acute phase response-induced expression of acute phase protein genes in rat liver

Hormonal requirements for full hepatic expression of alpha2-macroglobulin (alpha2M), alpha1-acid glycoprotein (AGP), haptoglobin (Hp) and gamma-fibrinogen (Fb) were assessed at the level of mRNA. Prior to exposure to turpentine-induced inflammation, rats were either depleted of glucocorticoids by adrenalectomy or supplemented with an excess of dexamethasone. Adrenalectomy alone did not affect the basal level of acute phase protein (APP) expression except for alpha2M mRNA, the level of which was enhanced. In contrast, dexamethasone treatment alone promoted full induction of alpha2M, significant, but not maximal increase of AGP and Hp mRNAs and suppression of Fb. In adrenalectomized rats, acute phase (AP)-cytokines, released in response to inflammation, promoted full expression of Fb and Hp and increased the level of AGP mRNA whereas alpha2M mRNA remained at the basal level. Inflammation in dexamethasone pretreated rats elicited changes which, in comparison to mRNA values for dexamethasone unpretreated inflamed rats, were seen as overexpression of alpha2M, full expression of AGP and incomplete expression of Hp, whereas Fb mRNA remained at the basal level. These data suggest that glucocorticoids are the principal inducers of alpha2M and AP-cytokines of Fb. For full induction of AGP, additive actions of glucocorticoids and AP-cytokines are required whereas expression of Hp is predominantly controlled by AP-cytokines.

Ascorbic acid deficiency changes hepatic gene expression of acute phase proteins in scurvy-prone ODS rats

The ODS rat (genotype od/od), which has a hereditary defect in ascorbic acid biosynthesis, was used to investigate the effects of ascorbic acid deficiency on the hepatic gene expression of both the positive acute phase proteins, haptoglobin and alpha1-acid glycoprotein, and the negative acute phase proteins, apolipoprotein A-I and albumin. Male ODS rats (6 wk old, body weight approximately 140 g) were fed a basal diet containing ascorbic acid (300 mg/kg diet) or a diet without ascorbic acid for 14 d. Ascorbic acid deficiency significantly elevated the serum concentration of haptoglobin and significantly lowered those of apolipoprotein A-I and albumin. The hepatic mRNA levels of haptoglobin and alpha1-acid glycoprotein in the ascorbic acid-deficient rats were significantly elevated on d 12, and reached 260 (P < 0.05) and 360% (P < 0.01) of respective values in the control rats on d 14. On the contrary, the hepatic mRNA levels of apolipoprotein A-I and albumin in the ascorbic acid-deficient rats were lowered to 68 (P < 0.01) and 71% (P < 0.05) of respective values in the control rats on d 14. Although ascorbic acid deficiency significantly elevated the serum corticosterone concentration on d 14, the changes in mRNA levels of haptoglobin, alpha1-acid glycoprotein, apolipoprotein A-I and albumin due to ascorbic acid deficiency were not affected by adrenalectomy, as assessed in a separate experiment. The serum concentration of interleukin-6, an inflammatory cytokine that stimulates gene expression of some acute phase proteins, was significantly higher in the ascorbic acid-deficient rats on d 14 than in the control rats. These results suggest that ascorbic acid deficiency causes physiologic changes similar to those that occur in the acute phase response.

Cloning and sequencing of cDNA encoding haptoglobin, an acute phase protein in Syrian hamster, Mesacricetus auratus

One of the most prominent acute phase proteins in Syrian hamster (Mesacricetus auratus) was identified as haptoglobin and cDNA encoding this protein was sequenced. The deduced amino acid sequence of the mature protein is 83.6, 80.5, 79.6, and 76.1% identical to those of mouse, rat, human (1 s isoform), and dog homologues, respectively. As compared with six known members of this family, including human haptoglobin-related protein, hamster haptoglobin had 11 unique substitutions and one unique codon deletion, that is, the corresponding residues have been conserved in all other members. This indicates that hamster haptoglobin gene has accumulated these unique mutations after the time of cricetid-murid split while the ancestral sequence has been conserved in all other species examined. Hamster haptoglobin, however, contains nine cysteine residues, all of which are found in conserved positions in primate and rodent homologues. Molecular phylogenetic trees of alpha- and beta-chains show that the alpha-chain is more divergent than the beta-chain and that the difference in genetic distance between canine and hamster alpha-chains is much greater than that of corresponding beta-chains.

Tissue, temporal and inducible expression pattern of haptoglobin in mice

Haptoglobin (Hp) is a member of the acute phase plasma proteins previously thought to be synthesized solely by the adult liver. The present study analyzes the tissue and temporal expression pattern of endogenous haptoglobin in the mouse and acute phase inducibility in various tissues. The liver is found to be the major site of haptoglobin expression but significant expression levels were also observed in the lung and skin. Acute phase induction by bacterial lipopolysaccharide (LPS) demonstrated that haptoglobin was induced not only in the liver but also in other tissues, including lung, skin, spleen, and kidney. Temporal analyses demonstrated that haptoglobin is expressed during embryogenesis in the liver and is inducible in various tissues surveyed throughout development. Transgenic mice that harbored a 1.05-kilobase (kb) region of the human haptoglobin promoter linked to two different reporter genes gave rise to lung-specific expression in the majority of transgenic lines with minimal liver expression. However, when induced with lipopolysaccharide, the 1.05-kb fragment contained the necessary elements for a response comparable to endogenous expression levels. In conclusion, these studies demonstrate that haptoglobin is not an adult liver specific gene, and its role as an acute phase reactant may well be more diverse than previously suspected.

Transforming growth factor beta modulates growth and differentiation of fetal hepatocytes in primary culture

Fetal hepatocytes in primary culture are cells capable to carry out both proliferation and differentiation processes simultaneously. Previous studies have shown that these cells respond to mitogens, such as hepatocyte growth factor (HGF) or epidermal growth factor (EGF), inducing the expression of early genes, such as fos and myc. The transforming growth factor-beta (TGF-beta) family is one of the most influential groups of growth and differentiation factors. In this report, we show that TGF-beta 1 inhibits fetal hepatocyte proliferation, arresting these cells at G1 phase of the cell cycle. In addition, TGF-beta down-regulates the mitogen-induced myc early expression. However, TGF-beta has no effect on the expression of other protooncogenes, such as fos and H-ras. In addition to its inhibitory role on fetal hepatocyte growth, TGF-beta increases the mRNA levels of fibronectin, an extracellular matrix protein, and maintains the expression of some liver specific genes, such as albumin and alfafetoprotein, above control values. The analysis of the expression of some hepatocyte transcriptional factors has shown that TGF-beta increases HNF1 alpha and HNF1 beta mRNA levels. We conclude that TGF-beta may modulate liver growth and differentiation throughout fetal development.

The action of interleukin-2 receptor subunits defines a new type of signaling mechanism for hematopoietin receptors in hepatic cells and fibroblasts

The gene regulatory functions of the human IL-2 receptor (IL-2R) were reconstituted in transiently transfected hepatoma cells. The combination of IL-2R beta and -gamma mediated a strong stimulation via the cytokine response element of the alpha 1-acid glycoprotein gene and the hematopoietin receptor response element, but none via the IL-6 response element or the sis-inducible element. IL-2R alpha enhanced 10-fold the sensitivity of the IL-2R beta.gamma complex to respond to IL-2 or IL-15, but did not modify the specificity or the magnitude of maximal gene regulation. A homodimerizing chimeric receptor G-CSFR-IL-2R beta could mimic the IL-2R action. The IL-2R-mediated gene regulation was similar to that seen with receptors for IL-4 and IL-7, but differed from that for IL-6 type cytokines, thrombopoietin, erythropoietin, and growth hormone. The activation of STAT proteins by the IL-2R was assessed in transfected L-cells and COS-1 cells. Although IL-2R subunits were highly expressed in these cells, no STAT protein activation was detectable. Transient overexpression of JAK3 was unable to change the signaling specificity of the hematopoietin receptors in rat hepatoma, L-, and COS cells, but established a prominent activation of the IL-6 response elements by the IL-2R and IL-4R in HepG2 cells. The data support the model that the IL-2R and related hematopoietin receptors produce at least two separate signals which control gene expression.

Haptoglobin in Carnivora: a unique molecular structure in bear, cat and dog haptoglobins

Haptoglobin (Hp), a hemoglobin-binding protein in plasma, consists of alpha and beta subunits and has a tetra-chain arrangement (beta-alpha-alpha-beta) connected by disulfide bridges in most mammals so far examined. Dog Hp has been reported to be unique compared with other Hps in respect that (1) the two alpha beta units are joined by a non-covalent interaction rather than a disulfide bridge and (2) the alpha chain has an oligosaccharide-binding sequence (Asn-X-Ser/Thr) and is glycosylated. To determine whether the unique structures of dog Hp are common in the Carnivora, we purified Hps from sera of bear and cat, and analyzed their subunit structure and partial amino acid sequences. The analyses by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, under both reducing and non-reducing conditions, revealed that bear and cat Hps have similar subunit arrangements to dog Hp, suggesting the absence of a disulfide bridge between two alpha chains. This was confirmed by amino acid sequence analysis of the alpha chains: that is, Cys15 participating in the inter-alpha chain disulfide bridge was replaced by Val in bear or Leu in cat and dog. Thus, the unique subunit arrangement of Hp reported in dog may be common in the Carnivora. In contrast to dog Hp, however, alpha chains of bear and cat Hps were found not to have the typical oligosaccharide binding sequence on their alpha chains and were not glycosylated.

Acute phase-dependent changes in the binding of rat liver nucleoproteins to the cytokine response element of the rat haptoglobin gene

Hormones released during the acute phase reaction promote the transcriptional activation of the haptoglobin (Hp) gene and a consequent increase of Hp protein synthesis in the liver. The mechanisms underlying the alterations of basal transcription rates of eukaryotic genes are assumed to result from modulations of the binding affinities between nucleoproteins and specific DNA sequences in the enhancer and promoter elements. In order to characterize the changes in the interaction of nucleoproteins with the promoter that accompany the induction of the Hp gene, nuclear extracts from normal and inflamed livers were probed with hormone responsive element (HRE) of the rat Hp gene by gel mobility shift and Southwestern assays. Each of the three cis-acting sequences of the HRE, elements A, B, and C, recognized a distinct set of proteins. Together they conferred an additional level of specificity to the protein binding sites of the entire ABC-element. These sites were recognized by proteins in liver nuclear extracts isolated from both control and treated rats. The differences in the gel shift and Southwestern patterns of the corresponding DNA-protein complexes suggested that transcriptional activation of the Hp gene relied on changes in the concentrations and/or functional modifications of preexisting proteins rather than on the induction of new trans-acting factors.

Inflammation of the dam has different effects on the binding of maternal and fetal rat liver nucleoproteins to the rat haptoglobin gene promoter

Transcriptional regulation of binding interactions between nucleoproteins and the hormone response element (RE) of the rat haptoglobin (Hp) gene was investigated in adult and fetal livers of rats exposed to inflammation on day 19 of pregnancy. Nuclear extracts from the embryonal liver displayed a barely detectable binding-affinity for hormone RE, but in extracts from the adult liver it was noticeable. The acute phase reaction of the mother promoted an increase of Hp gene expression in both adult and fetal livers, relying on stage-specific changes in hormone RE binding activities of nucleoplasmic proteins. The results indicated that the elevation of Hp gene expression in fetal liver to the steady basal level found in adults required the induction of new trans-acting proteins, whereas an overexpression of this gene in adult acute phase liver relied essentially on an increase in the binding-affinity of the preexisting hormone RE binding proteins.

Insulin cooperates with IL-1 in regulating expression of alpha 1-acid glycoprotein gene in rat hepatoma cells

Insulin treatment of the rat hepatoma H-35 cells results in a reduced stimulation of acute phase plasma protein gene expression by IL-1- and IL-6-type cytokines. The cell response to insulin appears to involve both stimulatory and inhibitory regulatory mechanisms because a clonal variant line of the H-35 cells has been identified in which insulin increases specifically the IL-1 stimulation of alpha 1-acid glycoprotein (AGP) gene, while still reducing the expression of the other acute phase protein genes. The magnitude of insulin and cytokine effect is dependent upon the proliferation state of the cell culture. One of the genetic targets of the insulin stimulation has been located to the cytokine-response element of the AGP gene and involves a cooperativity with the 5' adjacent IL-1-responsive element. The molecular mechanism of insulin inhibition, however, remains to be identified.