Differences in bone mineral density, markers of bone turnover and extracellular matrix and daily life muscular activity among patients with recent motor-incomplete versus motor-complete spinal cord injury.

Spinal cord injury (SCI) leads to severe bone loss, but the associated mechanisms are poorly described in incomplete SCI individuals. The purpose of the study is to compare alterations in bone mineral density (BMD) and serum biomarkers of bone turnover in recent motor-incomplete to -complete SCI men, as well as to describe their physical activity and spasticity. We studied 31 men with acute SCI. Whole-body DXA scans, serum biomarkers and self-reported activity and spasticity were examined 1 and/or 3 and 12 months after the injury. We observed a decrease in proximal femur BMD (p < 0.02) in both the groups. Serum phosphate and carboxy-terminal-collagen crosslinks were significantly lower in motor-incomplete versus complete SCI men, whereas albumin-corrected Ca(2+) (p = 0.02) were lower only 3 months after injury. When data from all 31 SCI participants were pooled, we observed increased serum matrix metalloproteinase-2 (MMP-2) and tissue inhibitors of MMP-2 (TIMP-2) (p < 0.02) whereas TIMP-1 decreased (p = 0.03). BMD correlated positively with self-reported activity (r = 0.59, p = 0.04) and negatively with spasticity (r = 0.74, p = 0.02) 12 months after injury. As a summary, men with motor-incomplete SCI developed significant proximal femur bone loss 12 months after injury and exhibited increased bone resorption throughout the first year after the injury. Compared with complete SCI men, incomplete SCI men show attenuated bone resorption. Our pooled data show increased turnover of extracellular matrix after injury and that increased exercise before and after injury correlated with reduced bone loss.

Biocompatibility and pathways of initial complement pathway activation with Phisio- and PMEA-coated cardiopulmonary bypass circuits during open-heart surgery.

A randomized open-heart surgery study comprising 30 patients was undertaken to compare the biocompatibility of Phisio-(phosphorylcholine) and PMEA-(poly-2-methoxyethyl acrylate) coated cardiopulmonary bypass (CPB) circuits and to assess the initial complement pathway activation during open-heart surgery. Blood samples were obtained at five time points, from the start of surgery to 24 hours postoperatively. The following analyses were performed: haemoglobin, lactate dehydrogenase, leukocyte and platelet counts, myeloperoxidase and neutrophil-activating peptide-2, thrombin-anti-thrombin complexes, syndecan-1 and the complement activation products C1rs-C1-inhibitor complexes, C4bc, C3bc, C3bBbP and the terminal complement complex (TCC). No significant inter-group difference was found in any parameters, except for the concentration of TCC which was moderately lower in the PMEA group at termination of CPB. Complement activation during open-heart surgery was mainly mediated through the alternative pathway. In conclusion, PMEA- and Phisio-coated circuits displayed similar biocompatibility with respect to inflammatory and haemostatic responses during and after open-heart surgery.

Serglycin--structure and biology.

Serglycin is a proteoglycan found in hematopoietic cells and endothelial cells. It has important functions related to formation of several types of storage granules. In connective tissue mast cells the covalently attached glycosaminoglycan is heparin, whereas mucosal mast cells and activated macrophages contain oversulfated chondroitin sulfate (type E). In mast cells, serglycin interact with histamine, chymase, tryptase and carboxypeptidase, in neutrophils with elastase, in cytotoxic T cells with granzyme B, in endothelial cells with tissue-type plasminogen activator and in macrophages with tumor necrosis factor-alpha. Serglycin is important for the retention of key inflammatory mediators inside storage granules and secretory vesicles. Serglycin can further modulate the activities of partner molecules in different ways after secretion from activated immune cells, through protection, transport, activation and interactions with substrates or target cells. Serglycin is a proteoglycan with important roles in inflammatory reactions.

Decreasing the metastatic potential in cancers--targeting the heparan sulfate proteoglycans.

The heterogeneity of proteoglycans (PG)s contributes to their functional diversity. Many functions depend on their ability to bind and modulate the activity of components of the extracellular matrix (ECM). The ability of PGs to interact with other molecules, such as growth factors, is largely determined by the fine structure of the glycosaminoglycan (GAG) chains. Tumorigenesis is associated with changes in the PG synthesis. Heparan sulfate (HS) PGs are involved in several aspects of cancer biology including tumor progression, angiogenesis, and metastasis. PGs can have both tumor promoting and tumor suppressing activities depending on the protein core, the GAG attached, molecules they associate with, localization, the tumor subtype, stages, and degree of tumor differentiation. Perlecan is an angiogenic factor involved in tumor invasiveness. The C-terminal domain V of perlecan, named endorepellin, has however been shown to inhibit angiogenesis. Another angiogenic factor is endostatin, the COOH-terminal domain of the part-time PG collagen XVIII. Glypicans and syndecans may promote local cancer cell growth in some cancer tissues, but inhibit tissue invasion and metastasis in others. The GAG hyaluronan (HA) promotes cancer growth by providing a loose matrix for migrating tumor cells and mediates adhesion of cancer cells. HSPG degrading enzymes like heparanase, heparitinase, and other enzymes such as hyaluronidase and MMP are also important in tumor metastasis. Several different treatment strategies that target PGs have been developed. They have the potential to be effective in reducing tumor growth and inhibit the formation of metastases. PGs are also valuable tumor markers in several cancers.

The AGE product N epsilon-(carboxymethyl)lysine serum albumin is a modulator of proteoglycan expression in polarized cultured kidney epithelial cells.

AIMS/HYPOTHESIS: Changes in kidney function in diabetes could be due to changes in the kidney basement membranes. Proteoglycans are important constituents of this kidney extracellular matrix. This study explored the possibility that advanced glycation end products affect proteoglycan synthesis in cultured kidney epithelial cells. METHODS: Madin Darby Canine Kidney (MDCK) epithelial cells were cultured with either low glucose (5 mmol/l), low glucose with 10 micrograms/ml of N epsilon-(carboxymethyl)lysine bovine serum albumin (CML-BSA) or high glucose (25 mmol/l). From day 7-8 cells were labelled with either [35S]sulphate or [3H]glucosamine for 24 h. Labelled macromolecules were purified by gel and ion exchange chromatography, and isolated proteoglycans analysed by gel chromatography and electrophoresis. RESULTS: The CML-BSA treatment reduced the proteoglycan synthesis in MDCK cells. Neither the type of glycosaminoglycan chains made nor the molecular size of the chains was affected. CONCLUSION/INTERPRETATION: At concentrations found in the plasma of diabetes patients CML-BSA, decreases proteoglycan expression in kidney epithelial cells. Advanced glycation end products could, accordingly, promote pathological changes in kidneys of diabetics.

Proteoglycan synthesis is increased in cells with impaired clathrin-dependent endocytosis.

Overexpression of a GTPase deficient dynamin mutant in HeLa dynK44A cells causes a block in clathrin-dependent endocytosis. When endocytosis is inhibited, these cells incorporate higher levels of [(35)S]sulfate into both cellular and secreted macromolecules and larger amounts of proteoglycans such as syndecan and perlecan are immunoprecipitated from [(35)S]sulfate-labelled lysates. Gel filtration and ion-exchange chromatography revealed that the increased [(35)S]sulfate incorporation into proteoglycans was not due to significant differences in size or density of negative charge of glycosaminoglycan chains attached to proteoglycan core proteins. On the other hand, measurements of the syndecan-1 mRNA level and of [(3)H]leucine-labelled perlecan after immunoprecipitation supported the idea that the increased [(35)S]sulfate incorporation into proteoglycans was due to a selective increase in the synthesis of proteoglycan core proteins. Interestingly, the activity of protein kinase C was increased in cells expressing mutant dynamin and inhibition of protein kinase C with BIM reduced the differences in [(35)S]sulfate incorporation between cells with normal and impaired clathrin-dependent endocytosis. Thus, the activation of protein kinase C observed upon inhibition of clathrin-dependent endocytosis may be responsible for the increased synthesis of proteoglycans.

Macrophages secrete matrix metalloproteinase 9 covalently linked to the core protein of chondroitin sulphate proteoglycans.

Matrix metalloproteinases (MMPs) secreted from the leukemic macrophage cell-line THP-1 have been investigated. Under serum-free conditions, this cell-line synthesizes and secretes proMMP-9, which was detected in the culture medium as a monomer of 92 kDa, and in dimeric forms, including a homodimer of approximately 225 kDa. In addition, a new heterodimer complex is described, in which proMMP-9 is covalently linked to the core protein of chondroitin sulphate proteoglycan (CSPG) through one or more disulphide bridges. After SDS-PAGE electrophoresis, at least two forms of this complex were detected, a large form in the stacking gel and a smaller form with an estimated size of 300 kDa. When the CS chains were removed by chondroitin ABC lyase treatment, heterodimers of proMMP-9/CSPG core protein of approximately 145, 127 and 109 kDa were found, based on zymography and Western blots. Since as much as 10-15 % of the total proMMP-9 secreted from THP-1 cells was covalently linked to CSPG, this association may have important implications for transport, targetting and regulation of the enzyme activity.

Lithocholic acid and sulphated lithocholic acid differ in the ability to promote matrix metalloproteinase secretion in the human colon cancer cell line CaCo-2.

The human colon carcinoma cell line CaCo-2 has the ability to sulphate the secondary bile acid lithocholic acid (LA), whereas other primary or secondary bile acids were not sulphated [Halvorsen, Kase, Prydz, Gharagozlian, Andresen and Kolset (1999) Biochem. J. 343, 533--539]. To study the biological implications of this modification, CaCo-2 cells were incubated with either LA or sulphated lithocholic acid (3-sulpholithocholic acid, SLA), and in some experiments with taurine-conjugated lithocholic acid. Increased secretion of matrix metalloproteinases (MMPs) correlates with transformation of colon epithelial cells. When CaCo-2 cells were incubated with LA, the secretion of MMP-2 was found to increase approx. 60% when analysed by gelatin zymography, and 80% when analysed by Western blotting. SLA, in contrast, did not affect the level of MMP-2 secretion, and after zymography the level of enzyme activity was 78% of control values after 18 h incubation. The secretion of MMPs is linked to increased cellular invasion and, in tumours, to increased capacity for metastasis. The ability of CaCo-2 cells to invade in a chamber assay was stimulated after exposure to LA, whereas SLA-treated cells did not differ from control cells. LA therefore seems to induce a more invasive CaCo-2 cell phenotype, as judged by the two parameters tested, whereas the sulphated counterpart, SLA, did not have these effects. Sulphation of LA in the colon may be an important mechanism to decrease the potential LA has to promote a malignant epithelial phenotype.

Sulphation of lithocholic acid in the colon-carcinoma cell line CaCo-2.

High levels of bile acids in the colon may correlate with an increased risk of colon cancer, but the underlying mechanisms are not known. Proteoglycan structures have been shown to change when human colon cells differentiate in vitro. The expression of [(35)S]sulphated molecules was used as a phenotypic marker to study the effects of bile acids on the human-colon-carcinoma cell line CaCo-2. [(35)S]sulphated compounds were isolated from the medium of cell fractions of cells metabolically labelled with [(35)S]sulphate in the absence and presence of cholic acid, deoxycholic acid, chenodeoxycholic acid and lithocholic acid (LA). Labelled molecules were analysed by gel chromatography, HPLC and SDS/PAGE in combination with chemical and enzymic methods. The expression of (35)S-labelled proteoglycans was not affected by any of the bile acids tested. However, the level of sulphated metabolites increased 7-18-fold in different experiments during a 22 h labelling period in the presence of an LA concentration of 10 microg/ml (26.6 nmol/ml) compared with controls. Further analyses showed that this was due, at least in part, to the sulphation of LA itself. This sulphation of LA was a rapid process followed by secretion back to the medium. Brefeldin A did not reduce the sulphation of LA, indicating that this conversion takes place in the cytosol, rather than in the Golgi apparatus of the CaCo-2 cells. LA in colon may be sulphated efficiently by the colonocytes to reduce the toxic effects of this particular bile acid. Sulphation may possibly be an important protective mechanism in the colon.

Stimulation of serglycin and CD44 mRNA expression in endothelial cells exposed to TNF-alpha and IL-1alpha.

Serglycin is a widely distributed proteoglycan, previously assumed to be hematopoietic cell specific. However, the results presented show that serglycin mRNA is expressed outside the hematopoietic cell system. High levels of serglycin mRNA were detected in endothelial cells and smooth muscle cells, whereas low levels were detected in skin fibroblasts. To further analyze the importance of serglycin in endothelial cells, the expression of serglycin mRNA was measured following activation of an endothelial cell line derived from human umbilical cord vein (HUV-EC-C), by the proinflammatory cytokines TNF-alpha and IL-1alpha. The level of serglycin mRNA increased in a time- and dose-dependent way. TNF-alpha (7 ng/ml) was the most potent inducer, increasing the level of serglycin mRNA 2.5 times after 24 h of stimulation. Serglycin has been shown to be a ligand for CD44, a membrane protein expressed in endothelial cells. Following stimulation of the endothelial cells, the level of CD44 mRNA also increased. Again, TNF-alpha (7 ng/ml) turned out to be the most potent inducer, increasing the level of CD44 mRNA 5.5 times after 24 h of stimulation. Both TNF-alpha and IL-1alpha stimulation of the endothelial cells resulted in an increase in the total incorporation of [(35)S]sulfate into macromolecules, which probably indicates an increase in the total production of proteoglycans. A stimulation of endothelial cells by proinflammatory agents resulted in an increase in both serglycin and CD44 mRNA expression, indicating that serglycin, as well as CD44, may participate in the inflammatory process of leukocyte migration.

Cell surface heparan sulfate proteoglycans and lipoprotein metabolism.

Cell surface heparan sulfate proteoglycans are involved in several aspects of the lipoprotein metabolism. Most of the biological activities of these proteoglycans are mediated via interactions of their heparan sulfate moieties with various protein ligands, including lipoproteins and lipases. The binding of lipoproteins to heparan sulfate is largely determined by their apoprotein composition, and apoproteins B and E display the highest affinity for heparan sulfate. Interactions of lipoproteins with heparan sulfate are important for the cellular uptake and turnover of lipoproteins, in part by enhancing the accessibility of lipoproteins to lipoprotein receptors and lipases. Apoprotein B may interact with receptors without involving heparan sulfate. Heparan sulfate has been further implicated in presentation and stabilization of lipoprotein lipase and hepatic lipase on cell surfaces and in the transport of lipoprotein lipase from extravascular cells to the luminal surface of the endothelia. In atherosclerosis, heparan sulfate is intimately involved in several events important to the pathophysiology of the disease. Heparan sulfate thus binds and regulates the activity of growth factors, cytokines, superoxide dismutase and antithrombin, which contribute to aberrant cell proliferation, migration and matrix production, scavenging of reactive oxygen radicals and thrombosis. In this review we discuss the various roles of heparan sulfate proteoglycans in vascular biology, with emphasis on interactions of heparan sulfate with lipoproteins and lipases and the molecular basis of such interactions.

Cell proliferation, apoptosis and accumulation of lipid droplets in U937-1 cells incubated with eicosapentaenoic acid.

The monocytic cell line U937-1 was cultured in the presence of eicosapentaenoic acid (20:5, n-3) (EPA) or oleic acid (18:1, n-9) (OA). EPA caused a dose-dependent inhibition of cell proliferation, whereas OA had no effect. At the highest EPA concentrations, 120 and 240 microM, inhibition of cell proliferation was accompanied by initiation of apoptosis. A concentration of 60 microM EPA caused a 35% reduction in cell proliferation without inducing apoptosis, and was therefore used for further studies. Addition of antioxidants or inhibitors of eicosanoid synthesis had no influence on the reduced cell proliferation after EPA treatment. The inhibition required continuous presence of EPA in the incubation medium as the cells resumed a normal proliferation rate when they were placed in EPA-free medium. The inhibition of proliferation was not accompanied by differentiation into macrophage-like cells, as expression of serglycin and the ability to perform respiratory burst was unaffected by EPA. Expression of CD23 mRNA increased when the cells were incubated with EPA, but to a smaller extent than after retinoic acid (RA) or PMA treatment. Furthermore, expression of the monocytic differentiation markers CD36 and CD68 was lower in cells treated with EPA or OA when compared with untreated cells. The cell cycle distribution of U937-1 cells was similar in cells incubated with EPA or PMA, whereas RA-treated cells accumulated in the G1 phase. Side scatter increased in cells incubated with EPA and OA, which was ascribed to an accumulation of lipid droplets after examination of the cells by electron microscopy. The number of droplets per cell was higher in cells exposed to EPA than OA. The cellular triacylglycerol (TAG) increased 5.5- and 15.5-fold after incubation with OA and EPA respectively. No difference in the cellular content of cholesterol compared with untreated cells was observed. The TAG fraction in EPA-treated cells contained high amounts of EPA and docosapentaenoic acid and minor amounts of docosahexaenoic acid, whereas OA-treated cells had high levels of OA in the TAG. In cells incubated with a sulphur-substituted EPA, only minor effects on cell proliferation and no accumulation of cellular TAG were observed. These findings may indicate the existence of other mechanisms for regulation of cell behaviour by very-long-chain polyunsaturated n-3 fatty acids than the well established lipid peroxide and eicosanoid pathways.

Differentiation-associated modulation of heparan sulfate structure and function in CaCo-2 colon carcinoma cells.

Heparan sulfate species expressed by different cell and tissue types differ in their structural and functional properties. Limited information is available on differences in regulation of heparan sulfate biosynthesis within a single tissue or cell population under different conditions. We have approached this question by studying the effect of cell differentiation on the biosynthesis and function of heparan sulfate in human colon carcinoma cells (CaCo-2). These cells undergo spontaneous differentiation in culture when grown on semipermeable supports; the differentiated cells show phenotypic similarity to small intestine enterocytes. Metabolically labeled heparan sulfate was isolated from the apical and basolateral media from cultures of differentiated and undifferentiated cells. Compositional analysis of disaccharides, derived from the contiguous N-sulfated regions of heparan sulfate, indicated a greater proportion of 2-O-sulfated iduronic acid units and a smaller amount of 6-O-sulfated glucosamine units in differentiated than in undifferentiated cells. By contrast, the overall degree of sulfation, the chain length and the size distribution of the N-acetylated regions were similar regardless the differentiation status of the cells. The structural changes were found to affect the binding of heparan sulfate to the long isoform of platelet-derived growth factor A chain but not to fibroblast growth factor 2. These findings show that heparan sulfate structures change during cell differentiation and that heparan sulfate-growth factor interactions may be affected by such changes.

Multiplication and death-type of leukemia cell lines exposed to very long-chain polyunsaturated fatty acids.

Polyunsaturated fatty acids (PUFA) may reduce cell multiplication in cultures of normal, as well as transformed, white blood cells. We assessed the sensitivity of 14 different leukemia cell lines to PUFA by measuring cell number after 3 days of incubation. Ten of the examined cell lines were sensitive to 30, 60 and/or 120 microM of arachidonic, eicosapentaenoic and docosahexaenoic acid, whereas four cell lines were resistant. The sensitivity to PUFA was not associated with any particular cell lineage, clinical origin or specific mRNA pattern of bcl-2 and c-myc. Effects on cell viability were assessed by studying cell membrane integrity, DNA fragmentation and cell morphology. The sensitive cell lines Raji and Ramos died by necrosis and apoptosis, respectively, during incubation with eicosapentaenoic acid, whereas the viability of the resistant U-698 cell line was unaffected. The effects of EPA on Raji cells, was counteracted by vitamin E, indicating that lipid peroxidation was involved. However, apoptosis induced by eicosapentaenoic acid in Ramos cells, was unaffected by vitamin E, as well as eicosanoid synthesis inhibitors. In conclusion, our results indicate that a majority of leukemia cell lines are sensitive to PUFA. This sensitivity may be caused by induction of apoptosis or necrosis by very long-chain polyunsaturated fatty acids.

Serglycin expression during monocytic differentiation of U937-1 cells.

Serglycin is the major proteoglycan in most hematopoietic cells, including monocytes and macrophages. The monoblastic cell line U937-1 was used to study the expression of serglycin during proliferation and differentiation. In unstimulated proliferating U937-1 cells serglycin mRNA is nonconstitutively expressed. The level of serglycin mRNA was found to correlate with the synthesis of chondroitin sulfate proteoglycan (CSPG). The U937-1 cells were induced to differentiate into different types of macrophage-like cells by exposing the cells to PMA, RA, or VitD3. These inducers of differentiation affected the expression of serglycin mRNA in three different ways. The initial upregulation seen in the normally proliferating cells was not observed in PMA treated cells. In contrast, RA increased the initial upregulation, giving a reproducible six times increase in serglycin mRNA level from 4 to 24 h of incubation, compared to a four times increase in the control cells. VitD3 had no effect on the expression of serglycin mRNA. The incorporation of (35S)sulfate into CSPG decreased approximately 50% in all three differentiated cell types. Further, the (35S)CSPGs expressed were of larger size in PMA treated cells than controls, but smaller after RA treatment. This was due to the expression of CSPGs, with CS-chains of 25 and 5 kDa in PMA and RA treated cells, respectively, compared to 11 kDa in the controls. VitD3 had no significant effect on the size of CSPG produced. PMA treated cells secreted 75% of the (35S)PGs expressed, but the major portion was retained in cells treated with VitD3 or RA. The differences seen in serglycin mRNA levels, the macromolecular properties of serglycin and in the PG secretion patterns, suggest that serglycin may have different functions in different types of macrophages.

Proteoglycans in macrophages: characterization and possible role in the cellular uptake of lipoproteins.

The murine macrophage cell line J774 was incubated with [35S]sulphate. The cell-associated 35S-labelled macromolecules were shown to be proteoglycans and glycosaminoglycans in similar amounts. The possible presence of cell-surface proteoglycans was investigated by incubating [35S]sulphate-labelled cells with trypsin for 15 min. The released material contained approx. 70% free glycosaminoglycan chains and 30% proteoglycans. The latter component was demonstrated by HNO2 treatment to contain heparan sulphate. In the total cell fraction not treated with trypsin a small but significant portion was shown to be chondroitin sulphate proteoglycan. The cell-associated glycosaminoglycans contained both chondroitin sulphate and heparan sulphate. To investigate possible biological functions of cell-surface proteoglycans in macrophages, cells were incubated with NaClO3 to inhibit sulphation of proteoglycans and beta-d-xyloside to abrogate proteoglycan expression. The uptake of oxidized 125I-tyraminylcellobiose-labelled low-density lipoprotein (125I-TC-LDL) was typically two to three times higher than that of native 125I-TC-LDL in untreated J774 cells. The cellular uptake at 37 degreesC of native 125I-TC-LDL was decreased 25% after both NaClO3 and xyloside treatment, whereas the uptake of oxidized 125I-TC-LDL was decreased 35% after both types of treatment. The mRNA levels for the scavenger receptor A-II and the LDL receptor were not affected by NaClO3 or xyloside treatment. Furthermore, fluid-phase endocytosis, measured as uptake of horseradish peroxidase, and receptor-mediated endocytosis, measured as uptake of 125I-TC-ovalbumin, were not affected by NaClO3 treatment of J774 cells. Removal of cell-surface chondroitin sulphate with chondroitinase ABC decreased only the binding of native 125I-TC-LDL, whereas removal of heparan sulphate with heparitinase decreased the binding of both oxidized and native 125I-TC-LDL. Addition of lipoprotein lipase increased the uptake of oxidized 125I-TC-LDL 1.7 times and the uptake of native 125I-TC-LDL 2.1 times. The binding of the former was more sensitive to NaClO3 treatment than the latter. The results presented support the notion that some of the uptake pathways for lipoproteins in the foam-cell-forming macrophages depend on the presence of cell-surface heparan sulphate and chondroitin sulphate.

[Proteoglycans and pathology--new aspects]. / Proteoglykaner og patologi--nye aspekter.

It is well documented that proteoglycans are involved in a wide range of pathological conditions. Recently published results in international journals provide new information on the role of proteoglycans in such conditions. A mutation in the gene encoding for a cell surface proteoglycan has been demonstrated in overgrowth syndromes. A proteoglycan has been isolated from urine and shown to induce cachexia in cancer patients. Furthermore, in both achondrogenesis and colon cancer, the reduced ability to sulphate proteoglycans is due to genetic defects in cellular sulfate transporters. Finally, fibrosis has been inhibited in glomerulonephritic mice by transferring the gene for decorin, a transforming growth factor beta-1 binding proteoglycan, into muscle tissue.

Uncoupling of stem cell inhibition from monocyte chemoattraction in MIP-1alpha by mutagenesis of the proteoglycan binding site.

We have studied the role of proteoglycans in the function of Macrophage Inflammatory Protein-1 alpha (MIP-1alpha), a member of the proteoglycan binding chemokine family. Sequence and peptide analysis has identified a basic region within MIP-1alpha which appears to be the major determinant of proteoglycan binding and we have now produced a mutant of MIP-1alpha lacking the basic charges on two of the amino acids within this proteoglycan binding site. This mutant (Hep Mut) appears to have lost the ability to bind to proteoglycans. Bioassay of Hep Mut indicates that it has retained stem cell inhibitory properties but has a compromised activity as a monocyte chemoattractant, thus suggesting uncoupling of these two properties of MIP-1alpha. Receptor studies have indicated that the inactivity of Hep Mut on human monocytes correlates with its inability to bind to CCR1, a cloned human MIP-1alpha receptor. In addition, studies using proteoglycan deficient cells transfected with CCR1 have indicated that the proteoglycan binding site in MIP-1alpha is a site that is also involved in the docking of MIP-1alpha to the monocyte receptor. The site for interaction with the stem cell receptor must therefore be distinct, suggesting that MIP-1alpha utilizes different receptors for these two different biological processes.

Serglycin-binding proteins in activated macrophages and platelets.

The major proteoglycan in macrophages and platelets is the chondroitin sulphate proteoglycan serglycin. To study the biological role of serglycin, its binding to secreted and cell-associated proteins from macrophages and blood platelets was examined. Affinity chromatography with serglycin-Sepharose and chondroitin sulphate-Sepharose was used to isolate proteoglycin-binding proteins from macrophages and platelets. Antibodies against human macrophage inflammatory protein-1 alpha (MIP-1 alpha) precipitated a 14-kDa 35S-methionine-labeled protein among the chondroitin sulfate binding proteins secreted from the macrophage-like U937 cells after stimulation. Two proteins from murine macrophage J774 cells with molecular masses of approximately 10 and 14 kDa were precipitated by an antiserum against the murine MIP-1 alpha. Protein sequencing of fragments obtained by trypsin digestion of a 14-kDa chondroitin sulfate-binding protein from cell extracts of stimulated U937 cells revealed 100% homology with lysozyme, a bacteriolytic enzyme. Fragment of one other protein with approximate molecular mass of 8 kDa showed high homology with bone morphogenetic protein. Inhibition studies showed that chondroitin 6-sulfate inhibited the bacteriolytic activity of lysozyme in a competitive manner more efficiently than heparin and chondroitin 4-sulphate. Amino-terminal sequencing of two proteins from platelet extracts that bound to serglycin-Sepharose revealed that they corresponded to multimeric forms of human platelet factor 4 (PE4). Chondroitin sulfate-Sepharose was shown to be equally efficient in retaining PF4 from platelet extracts as serglycin-Sepharose indicating that the glycosaminoglycan chains mediate the binding to PF4 in the intact proteoglycan molecule. Competition experiments showed that serglycin was as efficient as heparin sulfate in blocking the binding of [3H] chondrotin sulfate to PF4, whereas heparin was one order of magnitude more efficient. Affinity measurements using fluoresceinamine-labeled glycosaminoglycans showed that the affinity of heparin for PF4 is on the order of 30 nM, whereas chondroitin sulfate has an affinity of 260 nM. Both PF4, MIP-1 alpha, and lysozyme play important role in different types of inflammatory reactions. The interaction with serglycin may indicate that this proteoglycan is involved in the regulation of the inflammatory response.