Plasma orosomucoid 2 as a potential risk marker of cholangiocarcinoma.

BACKGROUND: Cholangiocarcinoma (CCA), a malignant tumor of the biliary epithelium, is a tumor with an ineffective diagnosis and poor prognosis. We have previously identified an overexpression of orosomucoid 2 (ORM2) along with CCA development in hamsters using a proteomics technique. OBJECTIVE: To evaluate plasma ORM2 as a candidate risk biomarker for CCA in humans. METHODS: Overexpression of ORM2 in CCA patients was assessed by western blotting and immunohistochemistry. The diagnostic efficacy of ORM2 was investigated in the plasma of patients with hepatobiliary diseases - including 46 cholangitis patients and 70 CCA patients - compared with 20 healthy individuals, using enzyme-linked immunosorbent assay (ELISA). RESULTS: Overexpression of ORM2 was observed in the cytoplasm of bile duct tumor cells and in the adjacent normal hepatocytes at a much higher intensity than in normal bile duct cells. Western blot analysis revealed that its expression was significantly higher in the plasma of CCA patients compared with that of healthy individuals (P < 0.01). ELISA showed that plasma ORM2 levels were significantly elevated in CCA and cholangitis groups compared with healthy individuals (P < 0.0001). The sensitivity and specificity of ORM2 in distinguishing CCA patients from healthy patients were 92.86% and 73.68%, respectively. CONCLUSIONS: Plasma ORM2 could serve as a new risk marker for CCA.

Regulation of alpha-1 acid glycoprotein synthesis by porcine hepatocytes in monolayer culture.

Alpha-1 acid glycoprotein (AGP, orosomucoid, ORM-1) is a highly glycosylated mammalian acute-phase protein, which is synthesized primarily in the liver and represents the major serum protein in newborn pigs. Recent data have suggested that the pig is unique in that AGP is a negative acute-phase protein in this species, and its circulating concentration appears to be associated with growth rate. The purpose of the present study was to investigate the regulation of AGP synthesis in hepatocytes prepared from suckling piglets and to provide a framework to compare its regulation with that of haptoglobin (HP), a positive acute-phase protein. Hepatocytes were isolated from preweaned piglets and maintained in serum-free monolayer culture for up to 72 h. The influences of hormones, cytokines, and redox modifiers on the expression and secretion of AGP and HP were determined by relative polymerase chain reaction and by measuring the concentration of each protein secreted into culture medium. The messenger RNA abundance and/or secretion of AGP protein was enhanced by interleukin (IL)-17a, IL-1, and resveratrol and inhibited by tumor necrosis factor-α (TNF), oncostatin M, and thyroid hormone (P < 0.05). HP expression and synthesis were upregulated by oncostatin M, IL-6, and dexamethasone and downregulated by TNF (P < 0.01). The overall messenger RNA expression at 24 h was in agreement with the secreted protein patterns confirming that control of these proteins in hepatocytes is largely transcriptional. Moreover, these data support the consideration that AGP is a negative acute-phase reactant and appears to be regulated by cytokines (with the exception of TNF) and hormones primarily in a manner opposite to that of the positive acute-phase protein, HP.

The hepatic orosomucoid/α1-acid glycoprotein gene cluster is regulated by the nuclear bile acid receptor FXR.

The α-1-acid glycoprotein/orosomucoids (ORMs) are members of the lipocalin protein family. Encoded by 3 polymorphic genes in mouse (2 in man, 1 in rat), ORMs are expressed in hepatocytes and function as acute-phase proteins secreted in plasma under stressful conditions. In addition to their role of nanocarrier, ORMs are involved in several pathophysiological processes such as immunosuppression, cardioprotection, and inflammatory bowel disease. The nuclear bile acid receptor farnesoid X receptor (FXR) regulates bile acid homeostasis and lipid and glucose metabolism and is an important modulator of enterohepatic functions. Here we report that hepatic FXR deletion in mice affects the expression of several members of the lipocalin family, among which ORMs are identified as direct FXR target genes. Indeed, a FXR response element upstream of the mouse Orm1 promoter was identified to which hepatic, but not ileal, FXR can bind and activate ORM expression in vitro and in vivo. However, ORMs are regulated in a species-specific manner because the ORM cluster is regulated by FXR neither in human nor rat cell lines. Consistent with these data, chromatin immunoprecipitation sequencing analysis of the FXR genomic binding sites did not detect any FXR response element in the vicinity of the human or rat ORM gene cluster. Thus, bile acids and their cognate nuclear receptor, FXR, are regulators of ORM expression, with potential implications for the species-specific metabolic and inflammation control by FXR because the expression of the proinflammatory genes in epididymal white adipose tissue was dependent on liver FXR activation.

Prognostic value of PINI index in patients with multiple myeloma.

BACKGROUND: The Prognostic Inflammatory and Nutritional Index (PINI) is a simple scoring system that aggregates two blood markers of inflammatory [C-reactive protein (CRP) and orosomucoid] and of nutritional (albumin and prealbumin) states. It is used in routine practice in geriatric medicine, especially in hospitalized elderly patients. This study was undertaken to evaluate the usefulness of PINI index in multiple myeloma (MM), a malignancy of the elderly. METHOD: The PINI score was determined in 231 previously untreated patients with MM, of whom 112 were ≥65 yrs old. The serum albumin, prealbumin, orosomucoid (human α1-acid glycoprotein), and hsCRP are measured routinely by immunonephelometry. RESULTS: In the overall population and the elderly subset, PINI ≥ 4 ('high PINI') was correlated with a shorter median survival, 26 vs. 65 months in the high and low PINI groups, respectively. The prognostic impact of PINI index was dramatic in the elderly MM subgroup, 6 and 45 months, respectively. The high PINI index also predicted for shorter survival in various groups with good prognostic, such as low International Staging System (ISS) stages, low b2m, and absence of del17p and t(4;14), further demonstrating its prognostic impact on overall survival. In multivariate analysis, PINI index provided additional survival prognostic information to b2m in a b2m/PINI model. CONCLUSION: PINI index appears to be a useful and easy-to-perform marker in routine to determine the prognosis of patients with MM, especially in the elderly population. PINI might represent an alternative to ISS score, especially in elderly patients, in the future.

Orosomucoid serum concentrations and fat depot-specific mRNA and protein expression in humans.

Obesity is associated with chronic low-grade inflammation, which contributes to systemic metabolic irregularities and obesity-linked metabolic disorders. Orosomucoid (ORM), an acute phase reactant protein, was shown to be produced in response to metabolic and inflammatory signals in the adipose tissue of obese mice, which protects them from severe inflammation and subsequent metabolic dysfunction. In this study, we examined whether there are site-specific differences between visceral and subcutaneous adipose tissue (VAT and SAT, respectively) ORM gene and protein expression from individuals with a wide range of obesity and the relationship between expressed and circulating ORM levels and measures of adiposity, insulin resistance, and pro- and anti-inflammatory markers and adipokines. The level of circulating ORM correlated positively with BMI, body fat mass, and serum leptin. It also correlated with fasting insulin, HOMA-IR values and C-reactive protein in men. There were no site-specific differences in ORM mRNA and protein expression between VAT and SAT, nor did we find a relationship between circulating ORM levels and its mRNA expression in either fat depot. We found that ORM mRNA expression correlated with mRNA expression of TNF-α, IL-6, and adiponectin in VAT, and with TNF-α and adiponectin in SAT. These observations are the first description linking adipose tissue ORM and pro- and anti-inflammatory molecules in humans. The close links of ORM and measures of adiposity, insulin resistance, and adipose tissue inflammation in humans reinforce previous experimental data and warrant further studies to explore a possible role of ORM in the pathogenesis of obesity-associated metabolic derangements.

Relationship between production of acute-phase proteins and strength of inflammatory stimulation in rats.

The relationship between intensity of inflammatory stimulation and production of α(2)-macroglobulin (α2M) and α(1)-acid glycoprotein (AAG) in rats was investigated. Sprague-Dawley rats were injected with turpentine oil at doses of 0.05, 0.2 or 0.4 mL/rat. Serum levels of α2M, interleukin (IL)-6 and cytokine-induced neutrophil chemoattractant-1 (CINC-1) were measured by enzyme-linked immunosorbent assay, and AAG was measured by single radial immunodiffusion. Peak serum levels of α2M and AAG in rats injected at 0.05 mL/rat were significantly lower than those at 0.2 or 0.4 mL/rat. However, no significant differences were observed for peak serum levels of these acute-phase proteins between 0.2 and 0.4 mL/rat. Furthermore, peak serum levels of IL-6 and CINC-1 in rats injected at 0.05 mL/rat were significantly lower than those at 0.2 or 0.4 mL/rat. Thus, the production of these acute-phase proteins has upper limits, even under increased strength of inflammatory stimulation in rats injected with turpentine oil.

Extra hepatic expression of the acute phase protein alpha 1-acid glycoprotein in normal bovine tissues.

Combined quantitative (real-time) polymerase chain reaction and immunohistochemistry were used to evaluate the expression of the minor acute phase protein alpha 1-acid glycoprotein (AGP, orosomucoid) in bovine extrahepatic tissues. AGP was produced mainly in the salivary glands and spleen, whereas minor expression was detected in all other tissues sampled, including lung, lymph nodes, uterus, ovary, kidney and tongue. The findings were consistent with immunohistochemical results. In view of the immunomodulatory and direct antibacterial activity of AGP, its expression in the salivary glands may signal an involvement in the regulation of the local immunity, even in non-pathological conditions.

Alpha(1)-acid glycoprotein is contained in bovine neutrophil granules and released after activation.

The present study was designed to investigate the capability of bovine neutrophil granulocytes to produce the minor acute phase protein alpha(1)-acid glycoprotein (AGP, Orososmucoid). Bovine neutrophils contain a high MW (50-60kDa) AGP isoform (PMN-AGP), as determined by Western blotting and confirmed by fluorescence microscopy. The presence of AGP in bovine neutrophils has been confirmed by fluorescence immunocytometry. In addition, bovine neutrophils contain also a 42-45kDa isoform, which has the same MW as plasma-, liver-delivered, AGP. cDNA sequence of plasma- and PMN-AGP revealed that (i) the two proteins are products of the same gene; (ii) the differences in molecular weight are due do different post-translational modifications. This result was confirmed by deglycosylation of the two glycoforms. Exocytosis studies showed that isolated neutrophils exposed to several challengers, including Zymosan activated serum (ZAS) and phorbol 12-myristate 13-acetate (PMA), which mimic the inflammatory activation, released PMN-AGP as early as 15min. AGP's mRNA is physiologically expressed by mature resting neutrophils. Real-time PCR on LPS, ZAS and PMA challenged cells revealed that the level of expression apparently does not increase after inflammatory activation. Collectively, the findings reported in this paper proved that PMN-AGP: (i) is a hyperglycosylated glycoform of plasma AGP, (ii) is stored in granules, and (iii) is released by neutrophils in response to activation. Due to its anti-inflammatory activity, PMN-AGP may work as a fine tuning of the neutrophils functions in the inflammatory focus, i.e. it can reduce the damages caused by an excess of inflammatory response.

Alpha-1-acid glycoprotein, its local production and immunopathological participation in experimental pulmonary tuberculosis.

Alpha-1-acid glycoprotein (AGP) is one of the major acute-phase proteins (APPs). Hepatic production and serum concentrations increase in response to systemic injury, inflammation, or infection. We reported previously that expression of the AGP gene is induced in the liver during experimental pulmonary tuberculosis. Since AGP may also be produced at the infection site and has some immunomodulatory properties, we used a model of progressive pulmonary tuberculosis in Balb/c mice to study the kinetics of AGP production in the lung and its influence on immunopathology. We found that AGP was produced in the lung during experimental tuberculosis. Alveolar macrophages and type II pneumocytes were the most important cellular sources during early infection (days 1-14). From day 21 postinfection, during the progressive phase of the infection, foamy macrophages located in pneumonic areas were the most important source of AGP and 10-fold higher concentrations were found on day 60. In a second part of the study, AGP was inactivated during the progressive phase by the administration of specific blocking antibodies. In comparison with control infected animals, tuberculous mice treated with blocking AGP antibodies showed higher expression of interferon gamma (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and inducible nitric oxide synthase (iNOS) in association with significantly reduced bacillary loads and tissue damage. Thus, AGP is produced in the lung during experimental pulmonary tuberculosis and it has immunomodulatory activities, suppressing cell-mediated immunity and facilitating growth of bacilli and disease progression.

Fucosylation of serum alpha1-acid glycoprotein in rheumatoid arthritis patients treated with infliximab.

To analyze fucosylation of alpha(1)-acid glycoprotein (AGP) and to identify relations between AGP fucosylation and clinical and biochemical indices of disease activity in patients with rheumatoid arthritis (RA) treated with monoclonal antitumor necrosis factor (TNF) antibody infliximab, we examined 22 patients with RA who underwent a 54-week treatment with infliximab according to ATTRACT protocol. Blood samples were collected at baseline and before every infusion of infliximab. AGP fucosylation was measured using lectin-binding enzyme-linked immunosorbent assay utilizing fucose-specific lectin Aleuria aurantia (AAL). Moreover, the clinical status/activity, erythrocyte sedimentation rate, serum C-reactive protein (CRP), antitrypsin, alpha(1)-antichymotrypsin, AGP reactivity with concanavalin A, serum C3 and C4 complement components, and serum concentrations of TNF and soluble TNF type 1 and type 2 receptors were determined. In most patients, the fucosylation of AGP decreased rapidly after first infusion of infliximab and remained low during the 54-week therapy (p < 0.001). The decrease in AGP affinity to AAL closely followed changes in clinical and laboratory activity of RA and correlated with pretreatment concentrations of CRP (r = 0.4986, p < 0.05) and TNF (r = 0.5181, p < 0.05). The fucosylation of AGP can be a part of a negative feedback loop regulating migration of inflammatory cells and collagenase-3 activity in RA. The decrease in AGP fucosylation accompanied by improvement in clinical and biochemical parameters of RA could possibly reflect reduced migration of inflammatory cells to inflamed joints and AGP-mediated inhibition of collagenase-3 as a response to infliximab treatment.

Peroxisome proliferator-activated receptor gamma agonists inhibit adipocyte expression of alpha1-acid glycoprotein.

alpha1-Acid glycoprotein (alpha1-AGP) is an acute phase protein that can potentiate cytokine secretion by mononuclear cells and may induce thrombosis by stabilizing the inhibitory activity of plasminogen activator inhibitor-1. Thus, alpha1-AGP may promote pathobiologies associated with type 2 diabetes mellitus (T2DM) including insulin resistance and cardiovascular disease. Here, we demonstrate that antidiabetic peroxisome proliferator-activated receptor gamma (PPARgamma) agonists inhibited expression of 3T3-L1 adipocyte alpha1-AGP in a concentration- and time-dependent manner via an apparent PPARgamma-mediated mechanism. As a result, synthesis and secretion of the glycoprotein was reduced. While PPARgamma agonist regulation of genes with functional peroxisome proliferator response elements in their promoter such as phosphoenolpyruvate carboxykinase were unaffected when cellular protein synthesis was inhibited, downregulation of alpha1-AGP mRNA was ablated thereby supporting the proposition that PPARgamma activation inhibits alpha1-AGP expression indirectly. These results suggest a potential novel adipocytic mechanism by which PPARgamma agonists may ameliorate T2DM-associated insulin resistance and cardiovascular disease.

Microheterogeneity of acute phase proteins in patients with ulcerative colitis.

AIM: To estimate the serum alpha1-antichymotrypsin (ACT), alpha1-acid glycoprotein (AGP) and transferrin (Tf) concentrations and to evaluate the microheterogeneity of these acute phase proteins in patients with ulcerative colitis. METHODS: Twenty-seven patients with ulcerative colitis (UC) and 17 healthy control subjects were studied. The patients were categorised as severe (n = 9), moderate (n = 10) and mild groups (n = 8) using Truelove and Witts' classification of ulcerative colitis. Microheterogeneity of ACT, AGP and Tf was analysed by crossed immunoaffinity electrophoresis (CIAE) with concanavalin A. In all serum samples standard electrophoresis of serum proteins was performed, iron (Fe) concentration, total iron binding capacity (TIBC) and C-reactive protein (CRP) were also measured. RESULTS: Our patients suffering from ulcerative colitis had significantly higher serum ACT and AGP concentrations and lower serum transferrin concentration in comparison to healthy subjects. Changes in concentrations of acute phase proteins were dependent on the activity of the inflammatory process. The glycosylation patterns of transferrin were related to the inflammation status. We also observed the correlation between ACT and AGP concentrations, patterns of transferrin glycosylation and changes in standard protein electrophoresis or blood cell count. CONCLUSION: The glycosylation patterns of transferrin obtained from patients suffering from ulcerative colitis are highly branched and sialylated compared with those obtained from healthy subjects. In contrast, the glycosylation patterns of transferrin do not differ according to the activity index of ulcerative colitis. The microheterogeneity patterns of AGP and ACT are similar in ulcerative colitis patients and healthy subjects.

Highly glycosylated alpha1-acid glycoprotein is synthesized in myelocytes, stored in secondary granules, and released by activated neutrophils.

Alpha-1-acid glycoprotein (AGP) is an acute-phase protein produced by hepatocytes and secreted into plasma in response to infection/injury. We recently assessed the transcriptional program of terminal granulocytic differentiation by microarray analysis of bone marrow (BM) populations highly enriched in promyelocytes, myelocytes/metamyelocytes (MYs), and BM neutrophils. These analyses demonstrated a transient, high mRNA expression of genuine secondary/tertiary granule proteins and AGP in MYs. In agreement with this, immunocytochemistry revealed the presence of AGP protein and the secondary granule protein lactoferrin in cells from the MY stage and throughout granulocytic differentiation. Immunoelectron microscopy demonstrated the colocalization of AGP and lactoferrin in secondary granules of neutrophils. This finding was substantiated by the failure to detect AGP and lactoferrin in blood cells from a patient with secondary/tertiary (specific) granule deficiency. In addition, Western blot analysis of subcellular fractions isolated from neutrophils revealed that neutrophil-derived AGP, localized in secondary granules, was abundant and highly glycosylated compared with endocytosed, plasma-derived AGP localized in secretory vesicles. Exocytosis studies further demonstrated a marked release of AGP and lactoferrin by activated neutrophils. Finally, induction of CCAAT/enhancer-binding protein (C/EBP)-epsilon in a myeloid cell line was shown to increase AGP transcript levels, indicating that AGP expression in myeloid cells, like in hepatocytes, is partially regulated by members of the C/EBP family. Overall, these findings define AGP as a genuine secondary granule protein of neutrophils. Hence, neutrophils, which constitute the first line of defense, are likely to serve as the primary local source of AGP at sites of infection or injury.

Circadian rhythm of acute phase proteins under the influence of bright/dim light during the daytime.

We investigated the influence of two different light intensities, dim (100 lx) and bright (5000 lx), during the daytime on the circadian rhythms of selected acute phase proteins of C-reactive protein (CRP), alpha1-acid glycoprotein (AGP), alpha1-antichymotrypsin (ACT), transfferin (TF), alpha2-macroglobulin (alpha2-m), haptoglobin (HP), and ceruloplasmin (CP). Serum samples were collected from 7 healthy volunteers at 4 h intervals during two separate single 24 h spans during which they were exposed to the respective light intensity conditions. A circadian rhythm was detected only in ACT concentration in the bright light condition. The concentration of ACT, a positive acute phase protein (APP), increased (significantly significant differences in the ACT concentration were detected at 14:00 and 22:00 h) and AGP showed a tendency to be higher under the daytime bright compared to dim light conditions. There were no significant differences between the time point means under daytime dim and bright light conditions for alpha2-M, AGP, Tf, Cp, or Hp. The findings suggest that some, but not all, APP may be influenced by the environmental light intensity.

Peroxisome proliferator-activated receptor alpha physically interacts with CCAAT/enhancer binding protein (C/EBPbeta) to inhibit C/EBPbeta-responsive alpha1-acid glycoprotein gene expression.

Recently, the role of the peroxisome proliferator-activated receptor alpha (PPARalpha) in the hepatic inflammatory response has been associated to the decrease of acute phase protein transcription, although the molecular mechanisms are still to be elucidated. Here, we were interested in the regulation by Wy-14643 (PPARalpha agonist) of alpha1-acid glycoprotein (AGP), a positive acute phase protein, after stimulation by Dexamethasone (Dex), a major modulator of the inflammatory response. In cultured rat hepatocytes, we demonstrate that PPARalpha inhibits at the transcriptional level the Dex-induced AGP gene expression. PPARalpha exerts this inhibitory effect by antagonizing the CCAAT/enhancer binding protein (C/EBPbeta) transcription factor that is involved in Dex-dependent up-regulation of AGP gene expression. Overexpression of C/EBPbeta alleviates the repressive effect of PPARalpha, thus restoring the Dex-stimulated AGP promoter activity. Furthermore, glutathione-S-transferase GST pull-down and coimmunoprecipitation experiments evidenced, for the first time, a physical interaction between PPARalpha and the C-terminal DNA binding region of C/EBPbeta, thus preventing it from binding to specific sequence elements of the AGP promoter. Altogether, these results provide an additional molecular mechanism of negative regulation of acute phase protein gene expression by sequestration of the C/EBPbeta transcription factor by PPARalpha and reveal the high potency of the latter in controlling inflammation.

Activated human PMN synthesize and release a strongly fucosylated glycoform of alpha1-acid glycoprotein, which is transiently deposited in human myocardial infarction.

Alpha1-acid glycoprotein (AGP) is a major acute-phase protein present in human plasma as well as in polymorphonuclear leukocytes (PMN). In this report, we show that PMN synthesize a specific glycoform of AGP, which is stored in the specific and azurophilic granules. Activation of PMN results in the rapid release of soluble AGP. PMN AGP exhibits a substantially higher apparent molecular weight than plasma AGP (50-60 kD vs. 40-43 kD), owing to the presence of strongly fucosylated and sialylated polylactosamine units on its five N-linked glycans. PMN AGP is also released in vivo from activated PMN, as appeared from studies using well-characterized myocard slices of patients that had died within 2 weeks after an acute myocardial infarction. AGP was found deposited transiently on damaged cardiomyocytes in areas with infiltrating PMN only. It is interesting that this was inversely related to the deposition of activated complement C3. Strongly fucosylated and sialylated AGP glycoforms have the ability to bind to E-selectin and to inhibit complement activation. We suggest that AGP glycoforms in PMN provide an endogenous feedback-inhibitory response to excessive inflammation.

Proteomic analysis to identify breast cancer biomarkers in nipple aspirate fluid.

PURPOSE: Proteomic analysis of breast nipple aspirate fluid (NAF) holds promise as a noninvasive method to identify markers of breast cancer. The objectives of the study were to: (a) describe the NAF proteome, (b) identify candidate markers of breast cancer in NAF by using proteomic analysis, and (c) validate the markers identified by using a quantitative, high-throughput ELISA analysis. EXPERIMENTAL DESIGN: For proteome analysis, NAF proteins from a single subject without breast cancer were separated by two-dimensional PAGE and were subjected to matrix-assisted laser desorption ionization time-of-flight mass spectometry identification. A total of 41 different proteins were identified, 25 of which were known to be secreted. To identify breast cancer markers, we separated 20 NAF samples (10 normal, 10 cancer) by two-dimensional PAGE. Three protein spots were detected that were up-regulated in three or more cancer samples. These spots were identified to be gross cystic disease fluid protein (GCDFP)-15, apolipoprotein D (apoD), and alpha1-acid glycoprotein (AAG). To validate these three potential biomarkers, 105 samples (53 from benign breasts and 52 from breasts with cancer) were analyzed using ELISA. RESULTS: Among all of the subjects, GCDFP-15 levels were lower (P <0.001) and AAG levels were higher (P=0.001) in breasts with cancer. This was also true in premenopausal (GCDFP-15, P=0.011; AAG, P=0.002) but not in postmenopausal women. GCDFP-15 levels were lowest (P=0.003) and AAG levels highest (P <0.001) in women with ductal carcinoma in situ (DCIS). Menopausal status influenced GCDFP-15 and AAG more in women without breast cancer than in women with breast cancer. apoD levels did not correlate significantly with breast cancer. CONCLUSIONS: Our study revealed that the NAF proteome, as defined by two-dimensional PAGE, consists of a limited number of proteins, and that the expression of AAG and GCDFP-15 correlates with disease presence and stage.

Construction of expression system for human alpha 1-acid glycoprotein in Pichia pastoris and evaluation of its drug-binding properties.

Human alpha1-acid glycoprotein (hAGP) is a plasma glycoprotein that functions as a major carrier of basic ligands. This is the first report of the recombinant hAGP (rhAGP). In this study, rhAGP was expressed in the methylotropic yeast Pichia pastoris (GS115) using the expression vector, pPIC9, and then purified by anionic exchange, hydrophobic interaction, and gel filtration chromatography. The molecular weight of rhAGP was much lower than that of hAGP, because of the difference in glycan chain content. Results of glycopeptidase F digestion suggest that the peptide moiety of rhAGP was the same as that of hAGP. The results of circular dichroism spectra measurement indicated that rhAGP predominantly formed a beta-sheet-rich structure that was the same as that of hAGP and typical of the lipocalin family. From the experiments using AGP-binding drugs (chlorpromazine, warfarin, and progesterone) and quinaldine red as a probe for the binding site, it was indicated that rhAGP also had the same ligand-binding capacity and binding site structure as hAGP. These findings strongly suggest that this recombinant hAGP (rhAGP) is very useful for the exploration of the ligand-binding site and biological function of hAGP.

Retinoids increase alpha-1 acid glycoprotein expression at the transcriptional level through two distinct DR1 retinoic acid responsive elements.

In the present study, we analyzed the influence of retinoic acids on the expression of alpha-1 acid glycoprotein (AGP). We show that in rat primary hepatocytes, 9-cis retinoic acid and all-trans retinoic acid increase AGP gene expression at the transcriptional level. Transient transfections of rat primary hepatocytes with a reporter construct driven by the rat AGP gene promoter indicated that retinoids regulate AGP gene expression via the -763/-138 region of the AGP promoter. Furthermore, cotransfection experiments with retinoic acid receptor alpha (RARalpha) and retinoid X receptor alpha (RXRalpha) expression vectors in NIH3T3 cells demonstrated that both RXRalpha/RXRalpha homodimer and RXRalpha/RARalpha heterodimer are competent for ligand-induced transactivation of the AGP promoter. Unilateral deletion and site-directed mutagenesis identified two retinoic-acid responsive elements (RARE), RARE-I and RARE-II, which interestingly correspond to a direct repeat of two TGACCT-related hexanucleotides separated by a single bp only (DR1-type response element). Cotransfection assays showed that RXRalpha and RARalpha activate AGP gene transcription through these two elements either as a homodimer (RXRalpha/RXRalpha) or as a heterodimer (RXRalpha/RARalpha). The RXRalpha/RXRalpha homodimer acts most efficiently through the RARE-I response element to promote AGP transactivation, whereas the RXRalpha/RARalpha heterodimer mediates transactivation better via the RARE-II responsive element.

Distinct glycoforms of human alpha1-acid glycoprotein have comparable synthesis rates: a [13C]valine-labelling study in healthy humans.

Various alpha1-acid glycoprotein (AGP) glycoforms are present in plasma differing in extent of branching and/or fucosylation of their 5 N-linked glycans, as well as in concentration. It is assumed that hepatic synthesis determines the relative occurrence of the AGP-glycoforms in plasma, but experimental evidence is lacking. In this study, we have investigated the contribution of fractional synthesis rates to the plasma concentration of AGP-glycoforms that differed in relative occurrence in healthy human plasma. During a [13C]valine infusion, AGP was isolated from the plasma of healthy volunteers. Four AGP-glycoforms, differing strongly in plasma concentration were obtained by sequential affinity chromatography over concanavalin-A- and Aleuria aurantia -agarose columns. The incorporation of the [13C]valine tracer into the AGP-glycoforms was measured by gas chromatography combustion isotope ratio mass spectrometry. The mean fractional synthesis rates of the four AGP-glycoforms did not differ significantly between each other as well between individuals. The results indicated a renewal of about 15%/day of the plasma pools of each of the AGP-glycoforms. This is in support to the assumption that the differences in plasma concentration of the AGP-glycoforms are a reflection of the state of the hepatic glycosylation process.