Acuity of selective mechanisms operating on ABO, Rh, and MN blood groups

Selection in ABO, Rh, and MN blood groups was studied in 216 matings and their children in an endogamous population. Incompatibility status with respect to these three systems was considered simultaneously. There is no effect of incompatibility on number of pregnancies. Analysis of variance between groups confirms that prenatal loss is associated with incompatibility, and it is greater when the matings are incompatible for any two systems. There is no significant intergenerational change in ABO and Rh polymorphisms. Segregation analysis for the ABO system suggests that there is no significant difference in the proportion of A, B, and O children, based on the compatibility of the parents, while analysis for Rh-D system showed a segregation distortion which is not related to the known antigenic specificities (mother-child incompatibility).     

Activation of the collagen-binding of endogenous serum vitronectin by heating, urea and glycosaminoglycans.

The present study describes that the collagen-binding activity of vitronectin in human serum increases by treatment with heparin, heating and urea. Vitronectin purified from human serum was bound to native collagen, whereas endogenous vitronectin in the serum was not. We have examined the conditions to change the collagen-binding activity of endogenous vitronectin. Endogenous vitronectin in human serum became considerably bound to collagen when the serum was boiled in 4-8 M urea for 5 min and mixed with heparin (0.5-5 micrograms/ml). Each treatment of heating, urea or heparin alone, and any combination of the two factors, inefficiently activated the binding. Dextran sulfate could substitute for heparin, but dermatan sulfate, keratan sulfate, chondroitin sulfate A and C, heparan sulfate and hyaluronan could not. Possible explanations for the activation of endogenous vitronectin are discussed.     

Effect of anticoagulants on the activity of trypsin-like proteinases in human blood plasma

Influence of some anticoagulants (heparin, sodium citrate, their mixture) on blood trypsin-like proteinases activity was examined. The activity was determined using synthetic substrate N-alpha-benzoyl-L-arginine-p-nitroanilide. It was shown that heparin greatly activated blood trypsin-like proteinases (at heparin concentration 5 unit/ml of blood, the enzyme activity in plasma was about 10 times higher than the activity in serum). Heparin added to serum caused the activation effect too, maximum of activation was reached at heparin concentration in serum 800 unit/ml, following increase of heparin concentration did not led to the activity change. Sodium citrate had no significant effect both on the trypsin-like proteinases activity and on the activation effect of heparin. It was found that investigated anticoagulants did not affect blood antitryptic activity.     

Structural mechanism for heparin-binding of the third Kunitz domain of human tissue factor pathway inhibitor.

Tissue factor pathway inhibitor (TFPI) inhibits the activity of coagulation factor VIIa and Xa through its K1 and K2 domain, respectively, and the inhibitory activity is enhanced by heparin. The function of the K3 domain of TFPI has not been established, but the domain probably harbors a heparin binding site (HBS-2). We determined the three-dimensional solution structure of the TFPI K3 domain (Glu182-Gly242) by heteronuclear multidimensional NMR. The results showed that the molecule is composed of one antiparallel beta-sheet and one alpha-helix, and in overall structure is very similar to the K2 domain, with the rms deviation of 1.55 A for the 58 defined C(alpha) positions. However, the surface electrostatic properties of both domains are different each other. The lack of inhibitory activity of the K3 domain is explained by the absence of electrostatic interaction with factor Xa over a large surface area. A titration experiment with size-fractionated heparin showed that a heparin binding site was located in the vicinity of the alpha-helix. In this region, a positively charged cluster is formed by Lys213, Lys232, and Lys240, and the negatively charged sulfate groups of heparin bind there. The enhancement of inhibitory activity by heparin probably was not due to a conformational change to TFPI itself. It is likely that heparin simply increases the local concentration of TFPI on the cell surface and stabilizes the initial complex that forms.     

Optical sensing of biomedically important polyionic drugs using nano-sized gold particles

A simple optical method for the sensing of biomedically important polyionic drugs, protamine and heparin based on the reversible aggregation and de-aggregation of gold nanoparticles (AuNPs) is described. The polycationic protamine induces the aggregation of negatively charged citrate-stabilized AuNPs, resulting in a shift in the surface plasmon (SP) band and a consequent color change of the AuNPs from red to blue. Addition of polyanionic heparin dissipates the aggregated AuNPs due to its strong affinity to protamine and the blue color changes to the native color. The color change was monitored using UV-vis spectrophotometry. The aggregation and de-aggregation was confirmed by transmission electron microscopic (TEM) measurements. The degree of aggregation and de-aggregation is proportional to the concentration of added protamine and heparin, allowing their quantitative detection. The change in the absorbance and SP band position has been used to monitor the concentration of protamine and heparin. This optical method can quantify protamine and heparin as low as 0.1 microg/ml and 0.6 microg/ml, respectively and the calibration is linear for a wide range of concentration.     

HEPARIN IN ACUTE MYOCARDIAL INFARCTION—Observations Indicating the Potential Advantages of Using It as the Sole Anticoagulant in Therapy

There is a considerable body of experimental evidence that heparin is superior as an anticoagulant to any prothrombin depressing drugs. Furthermore its lipemia-clearing action affords other benefits which result from the removal of fat from the bloodstream. Important among these beneficial effects is the increased tissue and myocardial oxygen consumption which results from the injection of heparin in atherosclerotic patients.Because of these advantages of heparin over oral anticoagulants, the use of heparin as the sole anticoagulant for three weeks in patients with severe acute myocardial infarction was evaluated as opposed to the customary therapy where heparin is given for several days and then oral anticoagulants are used. The mortality in the dicoumarin treated group was 38 per cent, as compared with 28 per cent in the patients who received only heparin for three weeks.     

Effect of heparin on thrombin inactivation by antithrombin-III.

The inactivation of thrombin by heat and by its physiological inhibitor, antithrombin-III, shows quite different dependence on heparin concentration. Heparin at 250 microgram/ml protects thrombin against heat inactivation, and thrombin behaves heterogeneously in this reaction. In the absence of heparin, the thermodynamic activation parameters change with temperature (deltaH+ = 733 kJ/mol and 210 kJ/mol at 50 and 58 degrees C respectively). When heparin is present, heat inactivation of the protected thrombin species proceeds with deltaH+ = 88 kJ/mol and is independent of temperature in the same range. On the other hand, heparin at 0.125-2.5 microgram/ml accelerates the thrombin-antithrombin-III reaction. Thrombin does not show heterogeneity in this reaction and the time courses at any heparin concentration and any temperature between 0 and 37 degrees C appear to follow first-order kinetics. Activation enthalpy is independent of heparin concentration or temperature, deltaH+ = 82-101 kJ/mol, varying slightly with antithrombin-III concentration and thrombin specific activity. Heparin seems to exert its effect by increasing activation entropy. On the basis of these data we suggest a mechanism of action of heparin in the thrombin-antithrombin-III reaction which accounts for all the important features of the latter and seems to unify the different hypotheses that have been advanced.     

Resistance of heparinase-derived heparin fragments to biotransformation

The biotransformation of heparinase-derived heparin fragments was examined via a combined approach using 35S-labeled heparin fragments as well as unlabeled chemically defined heparin fragments. Rats dosed with either [35S]di-, tetra-, hexa-, or octasaccharide fragments (2 mg/kg body weight, intravenously) excreted 63-69% of the injected radioactivity into the urine within 24 h with two-thirds being excreted during the first 6 h. Gel permeation chromatography of the urinary material shows that the tetra- and octasaccharides have undergone minor (approximately 5%) depolymerization whereas no change was observed for the di- and hexasaccharides. No N-desulfation was demonstrated for any of the substances. The hexa- and octasaccharide metabolites present in the urine 24 h after dosing exhibited the same antifactor Xa activity as that of the injected material. A chemically defined trisulfated disaccharide and a hexasulfated tetrasaccharide were prepared and dosed in a similar manner. Only one metabolite was recovered from animals dosed with disaccharide. This compound was characterized by anion exchange chromatography, proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectrometry, and mass spectrometry and shown to be identical to the injected disaccharide. Five metabolites were isolated from the urine of rats dosed with the hexasulfated tetrasaccharide. The major metabolite, consisting of at least 65% of the total, was characterized as described for the disaccharide and shown to be identical to the injected compound. The remaining material appeared to be disaccharides and, possibly, a tetrasaccharide conjugate. Taken together, our results show that the heparinase-derived heparin fragments are very resistant to biotransformation compared with heparin and endogenous heparin fragments. These fragments may therefore be useful in defining structure activity relationships in vivo.     

Heparin decreases the degradation rate of lipoprotein lipase in adipocytes

The mechanism responsible for the stimulation of secretion of lipoprotein lipase by heparin in cultured cells was studied with avian adipocytes in culture. Immunoprecipitation followed by electrophoresis and fluorography were used to isolate and quantitate the radiolabeled enzyme, whereas total lipoprotein lipase was quantitated by radioimmunoassay. Rates of synthesis of lipoprotein lipase were not different for control or heparin treatments as judged by incorporation of L-[35S]methionine counts into lipoprotein lipase during a 20-min pulse. This observation was corroborated in pulse-chase experiments where the calculation of total lipoprotein lipase synthesis, based on the rate of change in enzyme-specific activity during the chase, showed no difference between control (8.13 +/- 3.1) and heparin treatments (9.1 +/- 5.3 ng/h/60-mm dish). Secretion rates of enzyme were calculated from measurements of the radioactivity of the secreted enzyme and the cellular enzyme-specific activity. Degradation rates were calculated by difference between synthesis and secretion rates of enzyme. In control cells 76% of the synthesized enzyme was degraded. Addition of heparin to the culture medium reduced the degradation rate to 21% of the synthetic rate. The presence of heparin in cell media resulted in a decrease in apparent intracellular retention half-time for secreted enzyme from 160 +/- 44 min to 25 +/- 1 min. The above data demonstrate that the increase in lipoprotein lipase protein secretion, observed upon addition of heparin to cultured adipocytes, is due to a decreased degradation rate with no change in synthetic rate. Finally, newly synthesized lipoprotein lipase in cultured adipocytes is secreted constitutively and there is no evidence that it is stored in an intracellular pool.     

No change of whole blood of plasma viscosity in cardiac patients after subcutaneous calcium heparin.

Whole blood viscosity, plasma viscosity and haematocrit were studied in a group of cardiac patients before and during subcutaneous heparin treatment. No significant change was noted in any of the parameters investigated. Relative viscosity (whole blood viscosity/plasma viscosity ratio) was also unaffected. These data indicate that heparin has no effect on the rheology of blood in vitro.     

Characterization of three distinct catalytic forms of human tryptase-beta: their interrelationships and relevance

Human tryptase-beta (HTbeta) is a serine protease that is isolated as a tetramer of four identical, catalytically active subunits (HTbeta-AT). Tetramer activity is not affected by protein-based physiological inhibitors but instead may be regulated by an autoinactivation process we have called spontaneous inactivation. Unless stabilized by heparin or high salt, the active tetramer converts to an inactive state consisting of an inactive-destabilized tetramer that reversibly dissociates to inactive monomers upon dilution. We refer to this mixture of inactive species as siHTbeta and show in this study that previous reports of monomeric catalytic forms are derived from this mixture. siHTbeta itself did not hydrolyze model substrates but unlike the tetramer did react slowly with the serpin alpha2-antiplasmin (alpha2-AP), suggesting a highly limited catalytic potential. In the presence of heparin (or other highly charged polysaccharides), we demonstrate that siHTbeta formed a well-defined complex with the heparin (siHTbeta-HC) that reacted 70-fold faster with alpha2-AP than siHTbeta and also hydrolyzed model substrates and fibrinogen. Formation of siHTbeta-HC was limited to dilute subunit solutions since high subunit concentrations resulted in the reformation of the active tetramer. By compensating for changes in the strength of heparin binding, siHTbeta-HC could be formed over the pH range of 6.0-8.5. The activity dependence on pH was bell-shaped with highest activity between pH 6.8 and pH 7.5. In contrast, HTbeta-AT activity showed no dependence upon heparin, increased over the pH range of 6.0-8.5, and was much higher than that of siHTbeta-HC especially above pH 6.8. HTbeta-AT incubated with excess heparin of different size (3-15 kDa) was functionally stable at 25 degrees C but lost activity regardless of heparin size at 37 degrees C above pH 6.8. The change in stability, which is likely due to weakened heparin binding, did not result in the formation of a stable catalytic monomer. These results confirm that siHTbeta is for the most part an inactive species and that any active monomer is a consequence of heparin binding to siHTbeta under dilute conditions where unfavorable thermodynamics and/or kinetics restrict formation of active tetramer. Heparin binding under these conditions drives a limited reorganization of the active site to a conformation that is catalytic but not the equivalent of a subunit within the active tetramer.     

Structure-activity relationship of antithrombotic polysaccharide derivatives

Heparin has been the drug of choice in clinical pre-surgical and post-surgical prophylaxis of thrombotic events. However, because of its side-effects, such as bleeding and other disadvantages (i.e. chemical inhomogeneity and variability of its physiological activities), alternatives to heparin are an important field of research. A necessary procedure in the development of new drugs is the evaluation of structure-activity relationships. Genuine neutral polysaccharides were chemically modified and examined for their anticoagulant activities. The linear β-1,3-glucan curdlan, an easily available bacterial polysaccharide, served as the basic polymer. It could be established that the anticoagulant activity was dependent on the degree of sulfation and the molecular weight. For heparin, the sulfation pattern, i.e. the actual location of the sulfate groups along the heparin chain, was of importance in addition to the degree of sulfation. Therefore, we investigated whether there was also a relationship between the substitution pattern of the curdlan sulfates and their anticoagulant activity. For determination of the substitution pattern of the sulfated polysaccharides, a method was developed that is based on synthesis of the partially alkylated alditol acetates of the polymer and examination of these derivatives using combined gas chromatographymass spectrometry. In addition to the analytical data, the structure-activity relationship of anticoagulative curdlan sulfates is presented.     

Blood compatible graphene/heparin conjugate through noncovalent chemistry

Blood compatible graphene/heparin conjugate is simply formulated through noncovalent interaction between chemically reduced graphene and heparin. Charge repulsion of negatively charged heparin on graphene plates renders hydrophobic graphene to be solublized in aqueous media without any precipitation or aggregation even after 6 months. Unfractioned heparin (UFH) with higher molecular weight was effective for graphene solubilization while low molecular weight heparin (LMWH) was not. Noncovalently interacting heparin chains on graphene plates preserve their anticoagulant activity after conjugation with graphene. Graphene/UFH conjugate shows much enhanced anti factor Xa (FXa) activity of 29.6 IU/mL compared with pristine graphene oxide (GO; 1.03 IU/mL).     

Synthesis of low-molecular-weight carbohydrate mimetics of heparin

Natural glycosaminoglycan heparin remains the most commonly prescribed anticoagulant for hospitalized patients in modern medical practice. Unfortunately, its administration can be accompanied by a series of clinical side effects, including thrombocytopenia and bleeding. This determines the urgency of the development of alternative anticoagulant drugs based on modified heparin and polyanionic oligo- and polysaccharide derivatives, such as sulfated glucans, phosphomannans, and fucoidans. Here we review work on the synthesis of oligosaccharides corresponding to low-molecular-weight heparin fragments and their derivatives, as well as oligosaccharides imitating parts of heparin chains that are responsible for biological activity. The reviewed works were aimed at developing pharmaceutical preparations lacking the aforementioned disadvantages of heparin.     

Modulation of adenylate cyclase activity by sulfated glycosaminoglycans. I. Inhibition by heparin of gonadotrophin-stimulated ovarian adenylate cyclase.

Heparin inhibits (I50 = 2 microgram/ml) the activity of luteinizing hormone and human chorionic gonadotropin-stimulated adenylate cyclase in purified rat ovarian plasma membranes. Unstimulated enzyme activity and activity stimulated by NaF, GTP or guanosine 5'-(beta,gamma-imido)triphosphate were inhibited to a lesser extent. Human chorionic gonadotropin binding to this membrane preparation was inhibited by heparin (I50 = 6 microgram/ml). The inhibition with respect to hormone concentration was of a mixed type for hormone binding and adenylate cyclase stimulation. Inhibition by heparin was not eliminated at saturating hormone concentration. The degree of inhibition was unaffected by the order in which enzyme, hormone and heparin were introduced into the assay system. Heparin (3 microgram/ml) did not affect the pH activity relationship of basal and hormone-stimulated adenylate cyclase activity and did not change the dependence of enzyme activity on magnesium ion concentration. The inhibitory action of heparin cannot be solely attributed to interference with either catalysis or hormone binding. The possibility is considered that the highly charged heparin molecule interferes with enzyme receptor coupling, by restricting the mobility of these components or by effecting their conformation.     

Conversion of cysteine to serine residues alters the activity, stability, and heparin dependence of acidic fibroblast growth factor.

Acidic fibroblast growth factor (aFGF) is a broad spectrum mitogen that is stabilized by complexation with heparin and heparan proteoglycans. The monomeric human protein contains 3 reduced cysteine residues of unknown function, the first 2 of which are conserved among all seven known fibroblast growth factors. The influence of these free sulfhydryl groups on the level, stability, and heparin dependence of the mitogenic activity at physiological temperature and pH is characterized using a complete set of site-directed mutants in which either any 1, 2, or all 3 of the cysteine residues are converted to serines. Mutants of aFGF in which either any 2 or all 3 cysteine residues are substituted by serines are more active, have longer activity half-lives, and are less heparin dependent than wild-type aFGF. In contrast, wild-type aFGF and the three mutants that each retain 2 cysteine residues inactivate more rapidly in the absence of heparin by a nonproteolytic mechanism but are markedly stabilized by heparin. This cysteine-mediated destabilization of aFGF not only diminishes its activity in the absence of heparin in tissue culture but also could functionally restrict its activity in vivo to the vicinity of mast cell-derived heparins and heparan proteoglycans associated with cell surfaces and basement membranes.     

Heparin enhances fibrinolysis in B16 mouse melanoma cells

The fibrinolytic activity of two tumorigenic B16 mouse melanoma lines was stimulated by exogenous hog mucosal or beef lung heparin. In contrast, the activity of two normal fibroblast lines was unaffected. The degradation of ¹²⁵l-fibrin was increased up to 3.6-fold by the addition of heparin. Chondroitin-4-sulfate or dextran sulfate did not change the fibrinolytic activity of three of the cell lines, but, at concentrations where enhancement by heparin was much reduced, the activity of one of the B16 melanoma lines was somewhat elevated. Antithrombin III did not alter the plasminogen activator activity of the B16 cell lines, but, in the presence of exogenous heparin, the enhancement of fibrinolysis was greatly reduced. The polymers were not cytotoxic during the assay period, and, had little affect on the plating efficiencies of the lines.     

Histidine-rich glycoprotein modulation of the anticoagulant activity of heparin. Evidence for a mechanism involving competition with both antithrombin and thrombin for heparin binding

Heparin binding to rabbit histidine-rich glycoprotein (HRG) was studied in a purified system, allowing for determination of a heparin dissociation constant of approximately 5.5 X 10(-8) M for the interaction with HRG at pH 7.0. The strong interaction between heparin and HRG was demonstrated to be competitive with the binding of both antithrombin and thrombin to the heparin chain. HRG was further tested as a modulator of the anticoagulant activity of heparin by comparing rates of the heparin-catalyzed reaction between antithrombin and thrombin in the presence and absence of added HRG. The heparin-antithrombin-thrombin reaction was modeled using the formalism of a two-substrate enzyme-catalyzed reaction with heparin as the enzyme and HRG analyzed as an enzyme inhibitor. HRG was shown to compete with both antithrombin and thrombin for binding to heparin by this kinetic analysis. Thus, both the kinetic and heparin-binding data indicate that the mechanism by which HRG modulates heparin anticoagulant activity involves competition for heparin with both the inhibitor and the protease. Inhibition by HRG of the heparin-catalyzed reaction was found to be highly dependent on pH, with a sharp increase in inhibition from about 15% to greater than 90% observed as pH was lowered from 7.4 to 7.0. Since little change in the rate of the heparin-catalyzed inhibition of thrombin by antithrombin occurs in this pH region, the dramatic change in HRG inhibition seen upon pH titration may reflect increasing ionic interaction between heparin and HRG due to the protonation of histidine residues which occurs in this pH region.     

Molecular characterization of recombinant human acidic fibroblast growth factor produced in E. coli: comparative studies with human basic fibroblast growth factor.

Synthetic cDNA coding for human acidic fibroblast growth factor (haFGF) was expressed in E. coli under the control of the T7 promoter. The haFGF produced was purified extensively using heparin-Sepharose and phenyl-Sepharose columns. The mitogenic activity of haFGF on 3T3 and endothelial cells was significantly potentiated in the presence of heparin (10-50 micrograms/ml), while angiogenic activity was observed on chick embryo chorioallantoic membrane without exogenously added heparin. This significant potentiation of mitogenic activity was observed specifically with haFGF, not human basic fibroblast growth factor (hbFGF). Circular dichroism spectra of haFGF was not affected by the presence of heparin. The affinity of haFGF for heparin was examined using heparin affinity HPLC and was precisely confirmed to be relatively lower than that of hbFGF. These results implied that haFGF was potentiated by heparin and that this potentiation did not involve a significant change in the conformation of the haFGF molecule. The affinity of haFGF for copper was also confirmed to be higher than that of hbFGF using a copper affinity HPLC column. In addition, under acidic conditions, haFGF appeared more stable than hbFGF and was further stabilized in the presence of heparin.