Management of heparin-induced thrombocytopenia during continuous renal replacement therapy

Heparin-associated thrombocytopenia occurred in a patient during continuous renal replacement therapy (CRRT), resulting in repeated clotting of the extracorporeal circuit and spontaneous hemorrhage. The peripheral platelet count initially appeared to improve by changing to prostacyclin and dalteparin. However, repeated CRRT circuit clotting recurred, and the platelet count decreased once again. This time the synthetic heparinoid, Orgaran (danaparoid), was used and was associated with successful CRRT and return of the platelet count.

Sulfation of extracellular matrices modifies growth factor effects on type II cells on laminin substrata

The alveolar basement membrane contains a variety of extracellular matrix (ECM) molecules, including laminin and sulfated glycosaminoglycans of proteoglycans. These mixtures exist within microdomains of differing levels of sulfate, which may specifically interact to be key determinants of the known capacity of the type II cell to respond to certain growth factors. Isolated type II cells were exposed to either acidic fibroblast growth factor (FGF-1), basic fibroblast growth factor (FGF-2), or keratinocyte growth factor (KGF; FGF-7) on culture wells precoated with laminin alone or in combination with chondroitin sulfate (CS), high-molecular-weight heparin, or their desulfated forms. Desulfated heparin significantly elevated FGF-1- and FGF-2-stimulated DNA synthesis, whereas desulfated CS and N-desulfated heparin elevated FGF-7-stimulated DNA synthesis by type II cells on laminin substrata. When FGF-1 was mixed into the various test matrix substrata, DNA synthesis was significantly increased in all cases. These results demonstrated that decreased levels of sulfate in ECM substrata act to upregulate responses to heparin-binding growth factors by alveolar epithelial cells on laminin substrata.

Heparan sulfate oligosaccharides require 6-O-sulfation for promotion of basic fibroblast growth factor mitogenic activity

The interaction of heparan sulfate (HS) with basic fibroblast growth factor (bFGF) is influential in enabling the growth factor to bind to its cell surface tyrosine kinase receptor. In this study, we have investigated further the structural properties of HS required to mediate the activity of bFGF in a mitogenic assay. We have prepared a library of heparinase III-generated HS oligosaccharides fractionated by both their size (dp6-dp12) and sulfate content. The ability of these oligosaccharides to activate bFGF in a mitogenic assay was then correlated with their length and disaccharide composition. All octa- and hexasaccharide fractions tested were unable to activate bFGF. Dodeca- and decasaccharide fractions were found to contain both activating and non-activating oligosaccharides, and showed a clear correlation between total sulfate content and the level of activatory activity. Disaccharide analysis of a range of dodeca- and decasaccharide fractions showed that both activating and non-activating oligosaccharides were composed mainly of N-sulfated and IdoA(2S)-containing disaccharides. The only significant difference between activating and non-activating oligosaccharides was the content of 6-O-sulfated disaccharides, in particular the disaccharide IdoA(2S)alpha1,4GlcNSO3(6S). These results show that there is a requirement for 6-O-sulfation of N-sulfated glucosamine residues, in addition to the 2-O-sulfation of IdoA, for the promotion of bFGF mitogenic activity by naturally occurring HS oligosaccharides. Analysis of the structure-activity relationships in the dodecasaccharide fractions in particular, suggests that a minimum bFGF activation sequence exists which is dependent on the positioning of at least one 6-O-sulfate group.

Heparinase II from Flavobacterium heparinum. Role of cysteine in enzymatic activity as probed by chemical modification and site- directed mutagenesis

Heparinase II (no EC number) is one of three lyases isolated from Flavobacterium heparinum that degrade heparin-like complex polysaccharides. Heparinase II is unique among the heparinases in that it has broad substrate requirements and possesses the ability to degrade both heparin and heparan sulfate-like regions of glycosaminoglycans. This study set out to investigate the role of cysteines in heparinase II activity. Through a series of chemical modification experiments, it was found that one of the three cysteines in heparinase II is surface-accessible and possesses unusual chemical reactivity toward cysteine-specific chemical modifying reagents. Substrate protection experiments suggest that this surface-accessible cysteine is proximate to the active site, since addition of substrate shields the cysteine from modifying reagents. The cysteine, present in an ionic environment, was mapped by radiolabeling with N-[3H]ethylmaleimide and identified as cysteine 348. Site-directed mutagenesis of cysteine 348 to an alanine resulted in loss of activity toward heparin but not heparan sulfate, indicating that cysteine 348 is required for heparinase II activity toward heparin but is not essential for the breakdown of heparan sulfate. Furthermore, we show in this study that cysteine 164 and cysteine 189 are functionally unimportant for heparinase II.

Heparin-like structures on respiratory syncytial virus are involved in its infectivity in vitro

Addition of heparin to the virus culture inhibited syncytial plaque formation due to respiratory syncytial virus (RSV). Moreover, pretreatment of the virus with heparinase or an inhibitor of heparin, protamine, greatly reduced virus infectivity. Two anti-heparan sulfate antibodies stained RSV-infected cells, but not noninfected cells, by immunofluorescence. One of the antibodies was capable of neutralizing RSV infection in vitro. These results prove that heparin-like structures identified on RSV play a major role in early stages of infection. The RSV G protein is the attachment protein. Both anti-heparan sulfate antibodies specifically bound to this protein. Enzymatic digestion of polysaccharides in the G protein reduced the binding, which indicates that heparin-like structures are on the G protein. Such oligosaccharides may therefore participate in the attachment of the virus.

The heparan sulfate suleparoide inhibits rat corneal angiogenesis and in vitro neovascularization

The purpose of this study was to evaluate the inhibitory activity of the heparan sulfate suleparoide on vascular cell growth in vitro and angiogenesis in vivo. Human HUV-EC-C endothelial cell proliferation and microvessel sprouting from cultured rat aortic rings were assayed by the bioreduction of 3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide. The inhibition of the neoforming capillary network in the chorioallantoic membrane of chick embryo (CAM) was evaluated by agarose disks containing suleparoide and applied on the CAM surface. AgNO3/KNO3 injury was used to induce corneal neovascularization and to evaluate the therapeutic effect of topical suleparoide, while the involvement of bFGF in angiogenesis was evidenced by immunohistochemistry of corneal tissue. Quantitation of angiogenesis in the CAM and the cornea was accomplished by image analysis. Suleparoide dose-dependently inhibited HUV-EC-C cell proliferation (50% inhibitory concentration [IC50], 197.5+/-15.2 microg ml-1) and reduced microvessel sprouting in vitro (IC50, 351+/-22 microg ml-1). Likewise, suleparoide 150 microg in agarose disks produced an avascular area of 19.7+/-2.7% of the total area of the CAM (P<0.05 as compared to controls). bFGF levels were significantly enhanced in the cornea after AgNO3/KNO3 injury, and the increase appeared to be time-dependent (25.6+/-1.8 and 43.2+/-7.4%, vs. uninjured controls after 24 hr and 48 hr, respectively, P<0.05). Suleparoide 4.8 mg eye-1 day-1 for six days reduced the length of blood vessels and the area of the cornea infiltrated by them (59.6+/-7.4% decrease vs. controls, P<0.05). These results demonstrate that suleparoide is an active agent against angiogenesis and suggest that the therapeutic effect of the drug could be of value to treat corneal neovascularization.

Pharmacokinetics of danaparoid sodium, dalteparin sodium and heparin determined by inhibitory effect on the activated coagulation factor X activity after single intravenous administration in rabbits

The inhibitory effect on the activated coagulation factor X activity (anti-Xa activity) in plasma and urine of danaparoid sodium (DAS, CAS 9005-49-6) was compared with that of dalteparin sodium (DLS, CAS 9041-08-1) and heparin (CAS 9005-49-6) after single intravenous administration at a dose of 640 anti-Xa U/kg to male rabbits. The elimination of half-life of DAS was 9.90 h and was 6.0 times longer than that of DLS and 16.5 times longer than that of heparin. The area under the plasma concentration-time curve (AUC) of DAS was 47.13 +/- 14.55 anti-Xa U.h/ml and was 2.4 times larger than that of DLS and 2.9 times larger than that of heparin. The urinary cumulative excretion of anti-Xa activity of DAS and DLS was 42.6 +/- 6.4% and 16.4 +/- 0.8% of dose, respectively, in 24 h after dosing, respectively. But the anti-Xa activity in urine was not detected at any sampling points after administration of heparin. DAS has a longer elimination half-life and a higher renal excretion of anti-Xa activity than that of DLS and heparin. Therefore, in comparison to DLS and heparin, it seems that the anticoagulant activity of DAS has a long duration.

Lysosomal glycosaminoglycan storage as induced by dicationic amphiphilic drugs: investigation into the mechanisms underlying the slow reversibility

Several dicationic amphiphilic compounds, such as the immunomodulator tilorone and analogues, impair the lysosomal catabolism of sulphated glycosaminoglycans (GAGs). Thereby they cause lysosomal GAG storage in rats and in cultured fibroblasts of several species including man. The GAG storage is rather slowly reversible in vivo; it persists for months after discontinuance of drug treatment. In the present study, we investigated the mechanisms underlying the slow reversibility. Cultured bovine corneal fibroblasts were pretreated for 4 days with tilorone (5 and 20 microM) or with compound CL-90.100 (3 and 10 microM) and further cultured in drug-free medium for periods up to 11 days. The intracellular GAG storage was analysed biochemically and demonstrated histochemically. The subcellular drug distribution (CL-90.100) was demonstrated by fluorescence microscopy. Dermatan sulphate (DS) provided the predominant contribution towards the GAG storage. After pretreatments with the low, as well as the high concentrations of either drug, the storage of DS was irreversible during the period of observation, whereas the minor storage of heparan sulphate was resolved. The enhanced secretion of the lysosomal enzyme beta-hexosaminidase (E.C. 3.2.1.52) caused by pretreatment with the high concentration of tilorone was also readily reversible. Thus, enzyme deprivation could not be the explanation for the sustained DS storage. The localization of the drug-related fluorescence within perinuclear cell organelles, presumably lysosomes, resembled that of the stored GAGs as visualized by histochemical staining. Both, the fluorescence and the positive GAG staining persisted with unchanged intracellular distribution throughout the recovery period. The present results suggest that the persistence of the DS storage is due to the formation of long-lived, non-degradable DS-drug complexes within the lysosomes.

Molecular features of the collagen V heparin binding site

A heparin binding region is known to be present within the triple helical part of the alpha1(V) chain. Here we show that a recombinant alpha1(V) fragment (Ile824 to Pro950), referred to as HepV, is sufficient for heparin binding at physiological ionic strength. Both native individual alpha1(V) chains and HepV are eluted at identical NaCl concentrations (0.35 M) from a heparin-Sepharose column, and this binding can be inhibited specifically by the addition of free heparin or heparan sulfate. In contrast, a shorter 23-residue synthetic peptide, containing the putative heparin binding site in HepV, fails to bind heparin. Interestingly, HepV promotes cell attachment, and HepV-mediated adhesion is inhibited specifically by heparin or heparan sulfate, indicating that this region might behave as an adhesive binding site. The same site is equally functional on triple helical molecules as shown by heparin-gold labeling. However, the affinities for heparin of each of the collagen V molecular forms tested are different and increase with the number of alpha1(V) chains incorporated in the molecules. Molecular modeling of a sequence encompassing the putative HepV binding sequence region shows that all of the basic residues cluster on one side of the helical face. A highly positively charged ring around the molecule is thus particularly evident for the alpha1(V) homotrimer. This could strengthen its interaction with the anionic heparin molecules. We propose that a single heparin binding site is involved in heparin-related glycosaminoglycans-collagen V interactions, but the different affinities observed likely modulate cell and matrix interactions between collagen V and heparan sulfate proteoglycans in tissues.

Inhibition of DNA topoisomerase I activity by heparan sulfate and modulation by basic fibroblast growth factor

Eukaryotic DNA topoisomerase I catalyzes changes in the superhelical state of duplex DNA by transiently breaking single strands thereby allowing relaxation of both positively and negatively supercoiled DNA. Topoisomerase I is a nuclear enzyme localized at active sites of transcription, and abnormal levels of the enzyme have been observed in a variety of neoplasms. Because the enzyme binds heparin and, given the presence of heparan sulfate within the nuclei of mammalian cells, we sought to investigate the interaction between topoisomerase I and sulfated glycosaminoglycans isolated from normal and neoplastic human liver. The results demonstrated that low concentrations (approximately 100 nM) of heparan sulfate from normal liver but not from its malignant counterpart effectively blocked relaxation of supercoiled DNA driven by either purified holoenzyme or topoisomerase I activity present in nuclear extracts of three malignant cell lines. Heparin acted at even lower (approximately 10 nM) concentrations. Moreover, we show that basic fibroblast growth factor could interfere with this heparan sulfate/heparin-driven inhibition and that both basic fibroblast growth factor and heparin-binding sites co-localized in the nuclei of U937 leukemic cells. Our results suggest that DNA topoisomerase I activity may be modulated in vivo by specific heparan sulfate moieties present in normal cells but markedly reduced or absent in their transformed counterparts.

Neutrophil haptotaxis induced by the lectin KM+

KM+ is a D-mannose binding lectin from Artocarpus integrifolia that induces neutrophil migration in vitro and in vivo. This attractant activity was shown to be caused by haptotaxis rather than chemotaxis. The inhibition by D-mannose of the neutrophil attraction exerted by KM+, both in vitro and in vivo, supports the idea that haptotaxis is triggered in vivo by the sugar binding sites interacting with glycoconjugates located on the neutrophil surface and in the extracellular matrix. In the present study an in vivo haptotaxis assay was performed by intradermally (i.d.) injecting 125I-KM+ (200 ng), which led to a selective staining of loose connective tissue and vascular endothelium. The radiolabelled area exhibited a maximum increase (five-fold) in neutrophil infiltration 3 h after injection, relative to i.d. 200 ng 125I-BSA. We characterized the ex vivo binding of KM+ to tissue elements by immunohistochemistry, using paraformaldehyde-fixed, paraffin-embedded, untreated rat skin. Bound KM+ was detected with an affinity-purified rabbit IgG anti-KM+ and visualized with an alkaline phosphatase based system. KM+ binding to connective tissue and vascular endothelium was inhibited by preincubating KM+ with 0.4 mM D-mannose and was potentiated by heparan sulfate (100 microg ml(-1)). An in vitro assay carried out in a Boyden microchamber showed that heparan sulfate potentiated the attractant effect of 10 microg KM+ by 34%. The present data suggest that KM+ induces neutrophil migration in vivo by haptotaxis and that the haptotactic gradient could be provided by the interaction of the KM+ carbohydrate recognition site(s) with mannose-containing glycoconjugate(s) in vascular endothelium and connective tissue. Heparan sulfate would act as an accessory molecule, enhancing the KM+ tissue binding and potentiating the induced neutrophil haptotaxis.

Heparin potentiates in vivo neutrophil migration induced by IL-8

Chemokine IL-8 attracts neutrophils by a haptotactic gradient, made possible by its interaction with proteoglycans of the extracellular matrix. Heparan sulfate, but not heparin, potentiates the attraction exerted in vitro by IL-8. In the present study we first confirmed this in vitro phenomenon, observing that IL-8 activity was potentiated 100% by heparan sulfate, but not by heparin. Then, we evaluated the interference of heparan sulfate or heparin on in vivo neutrophil migration induced by IL-8. The activity of rat IL-8 (3.5 microg/animal) preincubated with heparan sulfate (50 microg/animal) or heparin (77 microg/animal) was assayed on the rat dorsal air pouch. Contrary to in vitro experiments, heparin, but not heparan sulfate, potentiated the in vivo IL-8 activity two-fold. We investigated the relationship between this observation and that reported by others, that IL-8-induced migration depends on the presence of mast cells, which contain heparin-rich granules. We studied the neutrophil migration induced by IL-8 (3.5 microg/animal) into the rat peritoneal cavity depleted of mast cells. Neutrophil migration was reduced by 32% when compared to that observed in normal animals. The response of depleted rats was reconstituted by preincubation of IL-8 with heparin (77 microg/animal). These data suggest that heparin released from cytoplasmic granules may be the contribution of mast cells to IL-8-induced neutrophil migration.

Regulation of interleukin-8 binding and function by heparin and alpha2-macroglobulin

BACKGROUND

Increased expression of interleukin-8 (IL-8), a potent neutrophil chemoattractant, is associated with a number of inflammatory diseases. Interleukin-8 binds to the glycosaminoglycan (GAG) heparin and the protease inhibitor alpha2-macroglobulin, molecules which regulate the function of a number of cytokines. Heparan sulphate was previously shown to enhance neutrophil chemotactic responses to IL-8.

OBJECTIVE

The purpose of this study was to investigate the effect of heparin, heparan sulphate and alpha2-macroglobulin on IL-8 binding to neutrophils and subsequent functional effects in vitro.

METHODS

The binding of 125I-IL-8 to normal neutrophils at 4 degrees C was studied and the IL-8 induced neutrophil chemotactic response was investigated using micro-Boyden chambers. Complexation of IL-8 with alpha2-macroglobulin was confirmed using gel filtration chromatography.

RESULTS

Heparin, but not heparan sulphate, inhibited the binding of 125I-IL-8 to neutrophils (IC50=26 microg/mL) and IL-8 induced neutrophil chemotactic responses (IC50=4 microg/mL). The specific inhibitory effect of heparin was apparently due to an interaction with IL-8 which was charge-dependent, since dextran sulphate had a greater inhibitory effect on chemotactic responses (IC50=2 microg/mL) and FITC-heparin did not bind to neutrophils. The heparin-induced inhibition of IL-8 binding and chemotactic responses was reversed in a dose-dependent manner in the presence of alpha2-macroglobulin. The binding of 125I-IL-8 to neutrophils in the presence of alpha2-macroglobulin appears to be, in part, through the specific IL-8 receptor.

CONCLUSION

These results point to an anti-inflammatory role for heparin and a novel, potentially, pro-inflammatory role for alpha2-macroglobulin which together indicate the importance of cytokine-binding macromolecules in determining net cytokine function.

Structural comparison of fibroblast growth factor-specific heparan sulfates derived from a growing or differentiating neuroepithelial cell line

Heparan sulfate (HS) glycosaminoglycans are essential modulators of fibroblast growth factor (FGF) activity both in vivo and in vitro, and appear to act by cross-linking particular forms of FGF to appropriate FGF receptors. We have recently isolated and characterized two separate HS pools derived from immortalized embryonic day 10 mouse neuroepithelial 2.3D cells: one from cells in log growth phase, which greatly potentiates the activity of FGF-2, and the other from cells undergoing contact-inhibition and differentiation, which preferentially activates FGF-1. These two pools of HS have very similar functional activities to those species isolated from primary neuroepithelial cells at corresponding stages of active proliferation or differentiation. We present here a structural comparison between these cell line HS species to establish the nature of the changes that occur in the biosynthesis of HS. A combination of chemical and enzymatic cleavage, low pressure chromatography and strong anion-exchange HPLC were used to generate full chain models of each species. Overall, the HS pools synthesized in the dividing cell line pools possessed less complex sulfation than those derived from more differentiated, growth arrested cells.

Sulfated glycosaminoglycans enhance tumor cell invasion in vitro by stimulating plasminogen activation

Metastasizing tumor cells invade host tissues by degrading extracellular matrix constituents. We report here that the highly sulfated glycosaminoglycans, heparin and heparan sulfate, as well as the sulfated polysaccharide, fucoidan, significantly enhanced tumor cell invasion in vitro into fibrin, the basement membrane extract, Matrigel, or through a basement membrane-like extracellular matrix. The enhancement of tumor cell invasion was due to a stimulation of the proteolytic cascade of plasminogen activation since the effect required plasminogen activation and was abolished by inhibitors of urokinase-type plasminogen activator (uPA) or plasmin. Sulfated polysaccharides enhanced five reactions of tumor-cell initiated plasminogen activation in a dose-dependent manner. They amplified plasminogen activation in culture supernatants up to 70-fold by stimulating (i) pro-uPA activation by plasmin and (ii) plasminogen activation by uPA. (iii) In addition, sulfated polysaccharides partially protected plasmin from inactivation by alpha 2-antiplasmin. Sulfated polysaccharides also stimulated tumor-cell associated plasminogen activation, e.g., (iv) cell surface pro-uPA activation by plasmin and (v) plasminogen activation by cell surface uPA. These results suggest that sulfated glycosaminoglycans liberated by tumor-cell mediated extracellular matrix degradation in vivo might amplify pericellular plasminogen activation and locally enhance tumor cell invasion in a positive feedback manner.

The cell surface proteoglycan syndecan-1 mediates fibroblast growth factor-2 binding and activity

Binding of fibroblast growth factors (FGFs) to receptor tyrosine kinases (FGFRs) and signaling is facilitated by binding of FGF to heparan sulfate proteoglycans (HSPGs). There are multiple families of HSPGs, including extracellular and cell surface forms. An important and potentially controversial question is whether cell surface forms of HSPGs act as positive or negative regulators of FGF signaling. This study examines the ability of the cell surface HSPG syndecan-1 to regulate FGF binding and signaling. HSPG-deficient Raji lymphoma cells, expressing a transfected syndecan-1 cDNA (Raji S1 cells), were used as HSPG "donor" cells. BaF3 cells, expressing an FGFR1 cDNA (FR1C-11 cells), were used as FGFR "reporter" cells. Using Raji S1 cells preincubated with FGF, it was found that they formed heterotypic aggregates with FR1C-11 cells in the presence of FGF-2, but not FGF-1. In addition, the FR1C-11 cells demonstrated FGF-2, but not FGF-1, dependent survival when cultured on fixed Raji S1 cells. Thus, Raji syndecan-1 1) differentially regulates the binding and signaling of FGFs 1 and 2 and 2) acts as a positive regulator of FGF-2 signaling.

Intraoperative monitoring of danaparoid sodium anticoagulation during cardiovascular operations

PURPOSE

Patients with cardiovascular disorders frequently need anticoagulation for diagnostic studies, surgical procedures, and therapy. Heparin-induced thrombocytopenia is a relatively common complication of heparin therapy that can result in thrombosis and subsequent limb loss or death, necessitating use of alternative anticoagulants.

METHODS

Two patients who needed cardiac surgery had thrombocytopenia induced by exposure to heparin and heparin-coated tubing. Several assays were examined for their ability to monitor intraoperative anticoagulation of a factor Xa inhibitor, danaparoid sodium.

RESULTS

In vitro, celite and kaolin activated dotting times and activated partial thromboplastin time were prolonged linearly in the presence of increasing concentrations of danaparoid sodium. Aprotinin did not alter the linearity of the response but did alter its slope. In vivo, activated clotting times and activated partial thromboplastin time were insensitive to clinically significant changes in danaparoid sodium plasma levels during cardiopulmonary bypass. Correction in activated partial thromboplastin time lagged 2 hours behind clinically important changes in anti-factor Xa levels. Only anti-factor Xa levels were adequate to monitor intraoperative danaparoid sodium levels.

CONCLUSION

Anticoagulation for cardiopulmonary bypass can be successfully performed with danaparoid sodium and intraoperative anti-factor Xa monitoring.

Different classes of proteoglycans contribute to the attachment of Borrelia burgdorferi to cultured endothelial and brain cells

The Lyme disease spirochete, Borrelia burgdorferi, infects multiple tissues, such as the heart, joint, skin, and nervous system and has been shown to recognize heparan sulfate and dermatan sulfate proteoglycans. In this study, we examined the contribution of different classes of proteoglycans to the attachment of the infectious B. burgdorferi strain N40 to several immortalized cell lines and primary cultured cells, including endothelial cells and brain cells. Bacterial attachment was inhibited by exogenous proteoglycans or by treatment of host cells with inhibitors of proteoglycan synthesis or sulfation, indicating that proteoglycans play a critical role in bacterial binding to diverse cell types. Binding to primary bovine capillary endothelial cells or a human endothelial cell line was also inhibited by digestion with heparinase or heparitinase but not with chondroitinase ABC. In contrast, binding to glial cell-enriched brain cell cultures or to a neuronal cell line was inhibited by all three lyases. Binding of strain N40 to immobilized heparin could be completely inhibited by dermatan sulfate, and conversely, binding to dermatan sulfate could be completely blocked by heparin. As measured by 50% inhibitory dose, heparin was a better inhibitor of binding than dermatan sulfate, regardless of whether the substrate was heparin or dermatan sulfate. These results are consistent with the hypotheses that the species of proteoglycans recognized by B. burgdorferi vary with cell type and that bacterial recognition of different proteoglycans is mediated by the same bacterial molecule(s).

Interleukin-5 binds to heparin/heparan sulfate. A model for an interaction with extracellular matrix

Interleukin-5 (IL-5) is the major cytokine regulating eosinophil production. In allergic disease tissue damage is primarily caused by eosinophils. Heparan sulfate proteoglycans are components of the bone marrow stroma, which supports hemopoietic cell differentiation and proliferation. We show that at low IL-5 concentrations heparan sulfate enhances the proliferation of an IL-5-dependent cell line. To investigate a mechanism for this effect we used an artificial proteoglycan to establish an enzyme-linked immunosorbent assay for the binding of heparin to proteins. Using this assay we demonstrate that IL-5 binds to heparin. The IL-5/heparin interaction is inhibited by ethylenediaminetetraacetate and enhanced by low concentrations of zinc ions. IL-5 interacts with iduronic acid containing glycosaminoglycans, and heparan sulfate preparations that have numerous N-sulfated domains per chain are especially efficient at inhibiting heparin binding. Both IL-5/heparin binding and the synergistic effect of IL-5 and heparan sulfate on cell proliferation were inhibited by an anti-IL-5 monoclonal antibody. These data suggest that the binding of IL-5 to heparan sulfate modulates IL-5 activity.

Stromal-conditioned medium synergizes with thrombopoietin in stimulating megakaryocytopoiesis

We previously demonstrated that stromal cells release a soluble factor(s) that enhances thrombopoietin (TPO)-induced megakaryocyte (MK) production. We have now further characterized this enhancing activity of human bone marrow stroma and have also analyzed the role of direct contact of stromal cells with human bone marrow CD34+ cells on MK production. The three- to sixfold stromal-enhancing activity of conditioned media is constitutive and is not influenced by the presence of TPO. The addition of interleukins 3, 6 (IL-3, IL-6), stem cell factor (SCF), and TPO at concentrations found in stroma to a stroma-free system only enhanced by 58% the TPO-stimulated MK production. No influence of heparan sulfates on MK production was observed. In co-cultures of CD34+ cells in direct contact with stromal cells, nonadherent and adherent MK, and proplatelet structures were observed, either in the absence or presence of TPO. Direct contact did not further improve the enhancing activity of stromal cells on MK production induced by TPO. We conclude that the stromal enhancement of MK production is neither accounted for by stromal TPO, IL-3, IL-6, and SCF activities nor modified by physical contact.

Effect of basic fibroblast growth factor on angiogenesis in the infarcted porcine heart

Administration of growth factors is emerging as a new therapeutic approach for the enhancement of collateral vessel formation in the ischemic heart. We have investigated the effects of intramyocardial delivery of FGF-2 in the presence and absence of heparin on angiogenesis in a porcine model of myocardial infarction. Yorkshire pigs were subjected to myocardial infarction by the placement of an embolization coil in the left anterior descending artery (n = 5). Four to five weeks after creation of an infarct, FGF-2 (10 micrograms) alone or in complex with heparin, heparan sulfate, or heparin agarose beads was injected either into the normal myocardium or along the infarct border area. Histologic evaluation of each injection site was performed 4 to 5 weeks post-injection. The effect of FGF-2 on angiogenesis was evaluated by determining the number of capillaries (diameter < 20 microns (and arterioles (> 20 microns with tunica media) in each area observed. The number of capillaries were not affected by the treatment of FGF-2 both in normal myocardium and infarct border area. However, in the normal myocardium, the number of arterioles were increased with the treatment of FGF-2 alone (85 +/- 59%, P < 0.04), FGF-2 plus heparin (281 +/- 193%, P < 0.004) and FGF-2-coated heparin beads (241 +/- 141%, P < 0.01), as compared to control. Delivery of FGF-2 into the infarct border area, also increased the number of arterioles when FGF-2 was given with heparin (736 +/- 154%, P < 0.001) or heparin beads (700 +/- 109%, P < 0.001), as compared to control. FGF-2 administered with heparin was the most effective method of enhancing angiogenesis as compared to FGF-2 alone, FGF-2 plus heparan sulfate, or FGF-2 coated heparin agarose beads.

Induction of systemic lupus erythematosus-like disease in mice by immunization with heparan sulfate

Experimental systemic lupus erythematosus (SLE)-like disease was induced in BALB/c mice by immunization with heparan sulfate, the major glycosaminoglycan of glomerular basement membrane. Following booster injections with heparan sulfate (HS), high levels of anti-HS, anti-dsDNA, and anti-cardiolipin antibodies were detected in the sera of the immunized mice. An enzyme-linked immunospot (ELISPOT) assay indicted that IgG anti-HS and anti-dsDNA antibody-secreting cells were present in the kidneys and most likely contributed to antibody localization. Antibodies eluted from the kidneys of immunized mice were found to react strongly with HS and dsDNA when tested in vitro. The HS-immunized mice developed moderate to severe levels of proteinuria. Histologic examination of kidneys from HS-immunized mice revealed deposition of immunoglobulin in the kidneys. Our results describe the induction of SLE-like disease in normal mice following immunization with HS. This experimental model may be useful for understanding the immunologic basis for autoimmunity to HS.

Growth factors increase pericellular proteoglycans independently of their mitogenic effects on A10 rat vascular smooth muscle cells

Proliferation of vascular smooth muscle cells with the accumulation of proteoglycans in the extracellular matrix is one of the significant changes found in atherosclerotic lesions. In order to clarify the relationship between pericellular proteoglycan and cell growth, we established a simple method for quantitatively estimating the amount of pericellular proteoglycans and investigated the effects of various growth factors on the synthesis of pericellular proteoglycans by cultured A10 rat smooth muscle cells. Analysis of trypsin accessible [35SO4]-labeled material in the pericellular area of the A10 cell culture by Q-sepharose anion-exchange chromatography showed two peaks. One peak, eluted at 0.55 M NaCl, disappeared after treatment with 2 mU/ml of heparitinase, indicating that heparan sulfates (HS) were present. The other peak, which eluted at 0.65 M NaCl, disappeared with 20 mU/ml of chondroitinase ABC, indicating the presence of chondroitin sulfates and dermatan sulfates (CS/DS). We estimated the effects of several growth factors on the synthesis of the pericellular proteoglycans by measuring heparitinase- and chondroitinase-ABC-sensitive radioactivities. Although PDGF-AB significantly stimulated cell proliferation and the synthesis of pericellular CS/DS, its dose-dependent effect on the cell growth did not coincide with that on the proteoglycan synthesis. IGF-I (1 nM) increased pericellular CS/DS but not the cell number, while basic FGF (1 nM) and EGF (1 nM) increased the cell number but not pericellular CS/DS. All the growth factors we examined had no effect on the synthesis of pericellular HS. These results indicate that growth factors increase pericellular proteoglycans independently of their mitogenic effects.

Perlecan binds to the beta-amyloid proteins (A beta) of Alzheimer's disease, accelerates A beta fibril formation, and maintains A beta fibril stability

Perlecan is a specific heparan sulfate proteoglycan that accumulates in the fibrillar beta-amyloid (A beta) deposits of Alzheimer's disease. Perlecan purified from the Engelbreth-Holm-Swarm tumor was used to define perlecan's interactions with A beta and its effects on A beta fibril formation. Using a solid-phase binding immunoassay, freshly solubilized full-length A beta peptides bound immobilized perlecan at two sites, representing both high-affinity [K(D) = approximately 5.8 x 10(-11) M for A beta (1-40); K(D) = approximately 6.5 x 10(-12) M for A beta (1-42)] and lower-affinity [K(D) = 3.5 x 10(-8) M for A beta (1-40); K(D) = 4.3 x 10(-8) M for A beta (1-42)] interactions. An increase in the binding capacity of A beta (1-40) to perlecan correlated with an increase in A beta amyloid fibril formation during a 1-week incubation period. The high-capacity binding of A beta (1-40) to perlecan was similarly observed using perlecan heparan sulfate glycosaminoglycans and was completely abolished by heparin, but not by chondroitin-4-sulfate. Using a thioflavin T fluorometry assay, perlecan accelerated the rate of A beta (1-40) amyloid fibril formation, causing a significant increase in A beta fibril assembly over a 2-week incubation period at 1 h (2.8-fold increase), 1 day (3.6-fold increase), and 3 days (2.8-fold increase) in comparison with A beta (1-40) alone. Perlecan also initially accelerated the formation of A beta (1-42) fibrils within 1 h and maintained significantly higher levels of A beta (1-42) thioflavin T fluorescence throughout a 2-week experimental period in comparison with A beta (1-42) alone, suggesting perlecan's ability to maintain amyloid fibril stability. Perlecan's effects on A beta (1-40) fibril formation and maintenance of A beta (1-42) fibril stability occurred in a dose-dependent manner and was also mediated primarily by perlecan's glycosaminoglycan chains. Perlecan was the most effective enhancer and accelerator of A beta fibril formation when compared directly with other amyloid plaque components, including apolipoprotein E, alpha1-antichymotrypsin, P component, C1q, and C3. This study, therefore, demonstrates that perlecan not only binds to the predominant isoforms of A beta, but also accelerates A beta fibril formation and stabilizes amyloid fibrils once formed, confirming pivotal roles for perlecan in the pathogenesis of A beta amyloidosis in Alzheimer's disease.