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PubMed1997

Biological functions of haptoglobin--new pieces to an old puzzle.

Haptoglobin, an "acute phase" protein, has different functions, which display genetic polymorphism. The complex of haptoglobin with haemoglobin is metabolized in the heptic reticuloendothelial system. Biosynthesis of haptoglobin occurs not only in the liver, but also in adipose tissue and in lung; providing antioxidant and antimicrobial activity. Changes in the measured concentrations of haptoglobin in serum may help to assess the disease status of patients with inflammations, infections, malignancy etc. (increases) as well as in haemolytic conditions (decreases). Haptoglobin plays a role in stimulation of angiogenesis and has highly potent cholesterolcrystallization-promoting activity. Probably the most important biological function of haptoglobin consists in the host defence responses to infection and inflammation, acting as a natural antagonist for receptor-ligand activation of the immune system.

Animals↗
PubMed1997

[Content of haptoglobin in blood serum in patients after thoracic surgery for various indications].

Initial results are presented on the usefulness of haptoglobin content monitoring in blood serum of patients after thoracic operations performed for various indications. 57 patients were analysed and divided into 3 groups based on the type of disease. Group 1 consisted of patients operated for malignant neoplasm. Group 2 consisted of patients with inflammatory changes and purulent complications within the thorax. Group 3 consisted of patients operated from other indications. The experimental samples of further 30 operated patients have not been analysed yet due to a delay in shipment of plates from Boehringer. The control group consisted of 31 healthy volunteers. In the experimental groups blood was taken 1 day before and 1, 3, 7, 10 and 14 days after the surgical intervention and in the case of complications-21 and 30 days after surgery. Erythrocyte sedimentation, leucocyte level, serum haptoglobin content, clinical and radiological data were analysed. Haptoglobin content was measured using the radial immunodiffusion method according to Manchini. Results were analysed statistically. The increase in serum haptoglobin content in patients after thoracic surgeries and after purulent complications, shows that haptoglobin is a sensitive acute phase indicator and its monitoring may be useful in evaluating the disease process. In advanced neoplastic processes haptoglobin content is a reflection of the progression of the disease process.

Adult↗
PubMed1998

Development of a simple enzyme immunoassay for blood haptoglobin concentration in cattle and its application in improving food safety.

OBJECTIVE: To verify the role of haptoglobin, a major acute-phase reactant protein in cattle, as a marker to identify health/disease status in cattle and further assess its potential in improving food safety. SAMPLE POPULATION: Serum samples from various cattle groups: clinically normal cattle comprising steers (n = 157) and culled dairy cows (n = 92) before death (antemortem [AM]); retained carcasses (n = 57) railed off the line during postmortem (PM) inspection; and apparently AM normal culled dairy cows (n = 57). PROCEDURE: Efficacy of the simplified monoclonal antibody-based enzyme immunoassay was established by comparing results of haptoglobin tests performed independently on aliquots of serum samples by 3 laboratories. RESULTS: Haptoglobin concentration was significantly (P< or = 0.0001) different between the PM retained carcass group (n = 57) and the AM steer (n = 157) and culled dairy cow (n = 92) groups. In addition, haptoglobin concentration in AM steers (n = 157) and culled dairy cows (n = 92) was significantly (P < or = 0.0012) different, possibly reflecting a higher percentage of underlying pathologic or inflammatory conditions in animals of the latter group. Evaluation in 3 laboratories of sera from a group of culled dairy cows (n = 57), each laboratory performing a different test procedure, indicated that correlation of haptoglobin concentrations was good between the reported test procedure and the unmodified test and the classical hemoglobin-binding assay that measures peroxidase activity. CONCLUSION: Haptoglobin determination is effective in identifying diseased and healthy cattle. It may be a potentially important tool for application at the farm and slaughterhouse as an aid in improving food safety.

Animals↗
PubMed1996

Measurement of serum haptoglobin in neonatal farm-raised and bob veal calves using two immunoassay methods.

Two immunoassays using an anti-bovine haptoglobin monoclonal antibody, Hap 1, were used to measure serum haptoglobin levels in neonatal farm-raised and bob veal calves. Bob veal calves were grouped into condemned, normal, and icteric groups based on the appearance of the carcass and viscera at postmortem examination. The competitive inhibition assay was more sensitive than the direct hemoglobin binding assay in detecting low levels of haptoglobin in all groups of calves. A significant number of bob veal calves with gross postmortem lesions other than icterus had detectable haptoglobin levels. The low levels of haptoglobin that were detected were not useful in distinguishing the relative severity of the inflammatory or degenerative process; however, the predictive values of a positive and negative test suggest haptoglobin measurement may be useful as a supplemental tool in evaluating the health status of the neonatal calf.

Journal Article↗
PubMed1985

Changes in plasma haptoglobin and alpha-2-macroglobulin in hemophiliacs receiving factor replacement therapy.

Plasma proteins were studied in 84 patients with hemophilia A, who were receiving factor replacement therapy. Compared with age-matched controls, 63 patients (75%) had subnormal haptoglobin and 58 (69%) had elevated alpha-2-macroglobulin. Causes for depressed haptoglobin were sought by correlating ABO blood types, liver function tests, factor VIII procoagulant levels, and intensity of yearly exposure to clotting factor products. Subnormal haptoglobin levels in chronically transfused patients may relate in part to hemolysis from AB incompatability. However, depressed haptoglobin levels were also found in group O hemophiliacs without other evidence of hemolysis. Most patients lacked evidence of active liver disease, making synthetic deficiency unlikely. There was close correlation between depressed haptoglobin and severity of clotting factor deficiency. The degree of alpha-2-macroglobulin elevation correlated with severity of procoagulant deficiency but not with intensity of clotting factor replacement therapy. Since alpha-2-macroglobulin plays a major role in the catabolism of fibrinogen, elevated levels may represent a compensatory increase in response to exogenous fibrinogen contained in the clotting factor concentrates. Alternatively, since alpha-2-macroglobulin has potent immunosuppressive properties, the elevation may represent a response to transfused alloantigens. Whatever the underlying cause, it is likely the elevations are due to endogenous production rather than to transfusions since clotting factor concentrates contain minimal amounts of alpha-2-macroglobulin.

ABO Blood-Group System↗
PubMed1997

Cancer cells release a covalent complex containing disulfide-linked domains from urinary plasminogen activator, neural cell adhesion molecule, and haptoglobin alpha and beta chains.

We have previously reported on the secretion of a family of high Mr plasminogen activators (PAs) by a human lung cancer cell line [Harvey et al. (1991) Biochim. Biophys. Acta 1078, 360-368]. We have now extended these studies to several human cancer cell lines and a human embryonic lung cell line. In the present study with HPL-SK-1 lung cancer, A431 epidermoid cancer, ovarian carcinoma, and embryonic lung cell lines, we show that the 900- and the 660-kDa PAs are disulfide-bonded multiprotein oligomeric complexes. They are functionally and immunologically related to human urinary PA (uPA). Their size and PA activity are not destroyed by strong denaturants such as 8 M urea or 2% sodium dodecyl sulfate (SDS), suggesting that the uPA moiety is covalently associated with the rest of the molecule. It is only under strong denaturing conditions with 1.4 M beta-mercaptoethanol and 2% SDS that the uPA moiety could be released as a 21- to 23-kDa fragment along with two major polypeptide chains of 70 and 40 kDa, respectively. The presence of the uPA active center in the reduced PA660 was demonstrated by [3H]diisopropylphosphorofluoridate labeling and by Western blot using a monoclonal antibody to uPA B chain. N-terminal amino acid sequencing of the 70- and 40-kDa polypeptides, respectively, showed homology to the neural cell adhesion molecule and the beta chain of haptoglobin. A minor fragment of 18 kDa obtained under strong reduction conditions was also sequenced and shown to share homology with the alpha chain of haptoglobin. Western blot analysis of the reduced PAs with monoclonal antibody to the neural cell adhesion molecule and rabbit anti-haptoglobin confirmed the homologies obtained by the sequence data. Further, immobilized monoclonal antibodies to the neural cell adhesion molecule, uPA B chain, and rabbit anti-haptoglobin bound the multiprotein complexes with uPA activity, from A431, ovarian cancer, and embryonic lung cell lines. The bound material, after dissociation, exhibited PA activity that was inhibited by monoclonal antibody to the uPA B chain. These data suggest that in tumor and embryonal cell lines, in addition to proper folding and assembly of proteins by intramolecular disulfide bond formation in the endomembrane compartment, intermolecular disulfide bonds could also occur, producing multiprotein oligomers as in the present case. Formation of such oligomers may have a selective advantage for such cells in the focalization of proteolytic activity through the interaction of the neural cell adhesion molecule domain with the extracellular matrix and in immunosuppression of lymphocytes by the haptoglobin portion of the complex.

Binding Sites↗
PubMed1999

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.

Animals↗
PubMed1975

Serum haptoglobin type and liver cirrhosis.

Haptoglobin phenotypes were studied by a polyacrylamide gel electrophoresis on 200 blood donors and 105 patients with liver cirrhosis, of which 79% belonged to non-alcoholic etiology. Though no difference of haptoglobin types could be found between blood donors with positive and negative hepatitis B antigen, the cirrhois patients had an excess haptoglobin gene 1. The patients with haptoglobin gene 1 were associated with severe liver dysfunction. Since the family pedigrees of the patients with type 1--1 excluded individuals with type 2--2, the phenotypes seemed to be stable in the cirrhotic process. The possibility that the haptoglobin 2 gene offered resistence to the non-alcoholic cirrhosis was discussed.

Adult↗
PubMed1976

Studies on the binding of haemoglobin by haptoglobin using electrofocusing and gradient electrophoresis.

1. Gel electrofocusing followed by gel gradient electrophoresis separated the haptoglobins and their complexes with haemoglobin into characteristic two-dimensional patterns of protein bands. 2. Molecular weights of 107 000, 139 000 and 168 000 were obtained for the three bands seen after a purified preparation of haptoglobin type 1 was partially saturated with haemoglobin. This indicated that free haptoglobin, the intermediate haptoglobin-haemoglobin complex containing one half-haemoglobin and the saturated complex with two half-haemoglobins were present. 3. The three proteins showed considerable microheterogeneity and gave a number of isoelectric points in the pH ranges 4.58-4.77, 5.20-5.40 and 5.74-5.93, free haptoglobin type 1 being the lowest group. These ranges were all 0.15-0.30pH units lower if other values were taken for the isoelectric points of markers used to calibrate the pH gradient. 4. All three proteins were present over a wide range of haemoglobin concentrations, from 0.5% to 92% of that required for saturation. This would be expected if both binding sites have similar affinities for haemoglobin.

Binding Sites↗
PubMed1991

Haptoglobin synergistically potentiates bradykinin and thrombin induced prostaglandin biosynthesis in isolated osteoblasts.

Haptoglobin of two different phenotypes (Hp 1-1 and Hp 2-1) dose-dependently (1-4 mg/ml) stimulated the formation of prostaglandin E2 (PGE2) in osteoblast-like cells isolated from neonatal mouse calvarial bones. The degree of stimulation obtained by haptoglobins (4 mg/ml) on PGE2 biosynthesis was in the same range as that caused by bradykinin (1 mumol/l). Pretreatment of osteoblasts with Hp 1-1 or Hp 2-1 (1-4 mg/ml) resulted in a dose-dependent, synergistic potentiation of the stimulatory effect of bradykinin (1 mumol/l) on PGE2 formation. Thrombin (7 U/ml) stimulated PGE2 formation in the osteoblast-like cells by a mechanism that was also synergistically potentiated by haptoglobin (2 mg/ml). These data show that haptoglobin per se stimulates PGE2 biosynthesis in isolated osteoblasts and, in addition, synergistically potentiates the effect of bradykinin and thrombin. Consequently, the enhanced production of haptoglobin seen in different inflammatory processes may contribute to the destruction of bone by inducing the formation of prostanoids capable of stimulating bone resorption.

Animals↗
PubMed1979

Is immunochemical determination of haptoglobin phenotype dependent?

Immunochemical methods have been used to determine the concentration of haptoglobins. The dependence on the phenotype was tested with highly purified Hp 2-1, Hp 2-2 and Hp 1-1, by immunonephelometry and radial immunodiffusion (RID). Measurements with three different instruments: automated immunonephelometer (AIP, Technicon), laser nephelometer (LN, Behring) and immunochemistry system (ICS, Beckman) were performed. For each type of apparatus antisera against a pool of haptoglobins were provided by the respective manufacturers. Some experiments were done with an antiserum to the haptoglobin heavy chain prepared in the laboratory. This study shows that haptoglobin determination depends neither on the physical geometry of the instruments or on the type of antiserum used in this work. In contrast, the data display a dependence on haptoglobin phenotype. When Hp 2-1, the most common phenotype, is taken as a standard, thd values obtained for Hp 2-2 are in good agreement with those obtained for Hp 2-1. However, the values obtained for Hp 1-1 are overestimated unless they are corrected by an experimental factor which has been determined in this study.

Haptoglobins↗
PubMed1988

Properties of sulfanilazo-haptoglobin.

1. Tyrosine and two structural isomers of histidine residues in human haptoglobin were modified with diazotized sulfanilic acid. Sulfanilazo-derivatives of haptoglobin obtained by increasing the reagent/protein molar ration showed gradual decrease of peroxidase activity when complexed with hemoglobin. 2. Formation of haptoglobin derivatives with ten mono(sulfanilazo)-tyrosines and two mono (sulfanilazo)histidines resulted in the blockage of one out of six antigenic determinants, whereas immunoreactivity of the derivative with fourteen azotyrosines, one C-4, and two C-2 azohistidines was decreased by half. 3. Removal of sialic acid from oligosaccharide chains of haptoglobin made the molecule more accessible to diazotized sulfanilic acid. 4. Sulfanilazo-modification of tyrosine and histidine residues was practically of no effect in the reaction of haptoglobin with plant lectin, concanavalin A.

Haptoglobins↗
PubMed1979

A general affinity chromatographic method for preparing monospecific antibody to mammalian serum haptoglobin.

A general affinity chromatographic method for preparation of monospecific antibody to serum haptoglobin of any species is described. Hemoglobin prepared from the species to be immunized is coupled to an organomercurical substituted agarose gel support (Affi-Gel 501). The immobilized hemoglobin binds haptoglobin with great affinity and allows removal of other serum proteins by extensive washing. The haptoglobin-hemoglobin complexes are then specifically eluted by buffers containing dithiothreitol or other thiols and are further purified by chromatography on concanavalin A-agarose and Sephacryl S-200 columns. The pure complexes are very effective immunogens. Potent monospecific antisera to rabbit and to human haptoglobin have been prepared. The potential usefulness of affinity chromatography support media with specifically cleavable ligand sites in studies of haptoglobin and in other biological studies is discussed.

Animals↗
PubMed1989

Complement genes C1r and C1s feature an intronless serine protease domain closely related to haptoglobin.

The exon-intron structure of the human complement C1s gene displays a striking similarity with that of the gene encoding haptoglobin, a peculiar transport protein distantly related to the serine proteases. While the protease regions of the serine zymogens are typically encoded by multiple exons, the protease domains of C1s and of its genetically linked and functionally interacting homolog C1r are encoded as intronless domains, not unlike a region of haptoglobin, which in fact is devoid of proteolytic activity. The close similarity of the C1s gene with haptoglobin includes the precise conservation of exon-intron junctions and it extends to upstream exons encoding the short repeats typical of several complement components, but found also in other functionally unrelated proteins. Additional evidence of the common ancestry of C1r, C1s and haptoglobin is the presence, within the protease domain, of a set of sequence markers that distinguish these three proteins from all known serine proteases. The finding of vertebrate serine protease genes with an uninterrupted protease-encoding exon supports the definition of a novel evolutionary branch of this gene family and rules out the hypothesis that regards this unusual exon as an irrelevant byproduct of the extravagant functional divergence of haptoglobin.

Amino Acid Sequence↗
PubMed1984

Studies on haptoglobin binding to concanavalin A.

Ascitic fluid haptoglobins 1-1, 2-1 and 2-2 and their tryptic glycopeptides were fractionated by affinity chromatography on Con A-Sepharose. Three peaks were obtained, corresponding to non-binding, weakly binding and strongly binding fractions. Concanavalin A-non-binding and concanavalin A-binding fractions of haptoglobin and of glycopeptide III 2-2 consisted of a series of polymers with increasing molecular mass, except for the non-binding fraction of glycopeptide III 1-1. After reduction there was no difference between the subunit composition of the glycopeptides and their concanavalin A fraction. Concanavalin A-non-binding fractions from haptoglobin 2-1 and glycopeptides III 1-1 and III 2-2 did not form an active complex with hemoglobin and, in crossed immunodiffusion, showed a reaction of partial identity with haptoglobin 2-1, glycopeptides III 1-1, III 2-2 and their concanavalin A-binding fractions. Concanavalin A-binding fractions of the above preparations exhibited with hemoglobin higher peroxidase activity than before their separation on Con A-Sepharose and immunodiffusion gave a reaction of identity among themselves and with unfractionated preparations. The concanavalin A-binding glycopeptide III is the biologically active part of the haptoglobin beta-chain.

Ascites↗
PubMed1992

Expression of haptoglobin receptors in human hepatoma cells.

The uptake of radio-labeled hemoglobin-haptoglobin complex (Hb-Hp) by human hepatoma PLC/PRF/5 and HepG2 cells was investigated in an attempt to characterize the uptake process and intracellular transport. Human hepatoma cells took up Hb-Hp in a receptor-mediated manner. Scatchard analysis of binding revealed that PLC/PRF/5 and HepG2 cells exhibited about 21,000 and 63,000 haptoglobin receptors/cell, with a dissociation constant (Kd) of 8.0 and 17 nM, respectively. Human hepatocytes in primary culture also expressed about 84,000 receptors/cells, with a Kd of 7.4 nM. The hemoglobin-haptoglobin complex was internalized and subsequently the internalized Hb-Hp was slowly degraded in the cells. Preincubation of the cells with Hb-Hp resulted in a decrease in binding of the radioactive Hb-Hp to the cell surface, and was accompanied with an accumulation of intracellular receptors. The uptake of Hb-Hp by the cells was not inhibited by 100 microM chloroquine or by 10 mM methylamine, but was inhibited by 50 microM monodansylcadaverine. Hemoglobin-heme taken up by the cells induced microsomal heme oxygenase. Thus, human hepatoma PLC/PRF/5 and HepG2 cells can take up Hb-Hp by haptoglobin receptor-mediated endocytosis and Hb-Hp probably causes translocation of the haptoglobin receptors from the cell surface to the cell interior where they can be degraded. The internalized heme-moiety of hemoglobin can regulate the expression of heme oxygenase.

Biological Transport↗
PubMed2003

Haptoglobin phenotype in age-related macular degeneration patients.

PURPOSE: To investigate a possible role of the haptoglobin phenotype in the development of exudative age-related macular degeneration (AMD) in human subjects. DESIGN: Prospective, observational, comparative population study. METHODS: The study was carried out in an institutional setting. All patients referred because of exudative AMD in one eye during an 18-month period were included in the study group. A group of patients treated for other ocular diseases and not having AMD in either eye served as control. Haptoglobin phenotype was determined from a blood sample drawn from each patient in both the study and control groups. The main outcome measure was the distribution of the haptoglobin phenotype in the study and control group. RESULTS: One hundred eighty-five participants were included in the study. Ninety-eight had exudative AMD, and 87 were AMD-free. The difference between the study and control groups in distribution of the haptoglobin phenotype was found to be statistically insignificant. CONCLUSIONS: Our results suggest that the haptoglobin phenotype has no effect on the prevalence of exudative AMD.

Aged↗
PubMed1984

Re-evaluation of the haptoglobin reference values with the radial immunodiffusion technique.

The reference values of the three main types of serum haptoglobin Hp 1-1, Hp 2-1, and Hp 2-2, as determined by radial immunodiffusion and with phenotype determination on polyacrylamide gel electrophoresis have been re-evaluated for both sexes. For that purpose about 500 serum samples were collected from normal, healthy Dutch volunteers. The relative occurrence of the three main types of serum haptoglobin in Dutch men and women was found to be comparable to that reported for other whites, with the Hp 2-1 phenotype predominating in the Dutch population and phenotype Hp 0-0 being absent. The observed overall reference range of haptoglobin for the Dutch population, irrespective of the phenotype, was 0.50-3.30 g/L serum. As reported by other investigators we found that the reference values for the three main types of haptoglobin significantly differed (Hp 1-1: 1.40 +/- 0.51; Hp 2-1: 2.10 +/- 0.76; and Hp 2-2: 1.65 +/- 0.73 g/L serum, mean +/- SD). However, in contrast to the data available in the literature, the reference values of haptoglobin for men and for women, as determined by the radial immunodiffusion technique, were not significantly different.

Adolescent↗