A collagen I derived matricryptin increases aorta vascular wall remodeling after induced thrombosis in mouse

Matricryptins are collagen fragments proteolytically released from the extracellular matrix (ECM) with biological activity that can regulate several processes involved in ECM remodeling. Vessel wall matrix reorganization after lesion is important to the recovery of vascular function. This study aimed to analyze the effect of the peptide p1158/59 (Lindsey, 2015) on thrombosis, neointimal formation, and vascular remodeling of C57BL6 mice abdominal aorta. We used a FeCl₃ induced vascular injury mice model and analyzed thrombus size, neointima formation, gelatinase activities in situ, re-endothelization, and collagen fibers organization on the arterial wall using polarization microscopy. As result, we observed that 2 days after injury the treatment with p1158/59 increased thrombus size and gelatinase activity, vascular lesion and it did not recover the endothelium loss induced by the chemical injury. We also observed that the peptide increased neointima growth and collagen birefringence, indicating collagen fibers reorganization. It also promoted increased re-endothelization and decreased activity of gelatinases 14 days after injury. Thus, we conclude that the peptide p1158/59 impaired the initial thrombosis recovery 2 days after injury but was able to induce vascular ECM remodeling after 14 days, improving vessel re-endothelization, collagen fibers deposition, and organization.

A new heparan sulfate from the mollusk Nodipecten nodosus inhibits merozoite invasion and disrupts rosetting and cytoadherence of Plasmodium falciparum

BACKGROUND

Despite treatment with effective antimalarial drugs, the mortality rate is still high in severe cases of the disease, highlighting the need to find adjunct therapies that can inhibit the adhesion of Plasmodium falciparum-infected erythrocytes (Pf-iEs).

OBJECTIVES

In this context, we evaluated a new heparan sulfate (HS) from Nodipecten nodosus for antimalarial activity and inhibition of P. falciparum cytoadhesion and rosetting.

METHODS

Parasite inhibition was measured by SYBR green using a cytometer. HS was assessed in rosetting and cytoadhesion assays under static and flow conditions using Chinese hamster ovary (CHO) and human lymphatic endothelial cell (HLEC) cells expressing intercellular adhesion molecule-1 (ICAM1) and chondroitin sulfate A (CSA), respectively.

FINDINGS

This HS inhibited merozoite invasion similar to heparin. Moreover, mollusk HS decreased cytoadherence of P. falciparum to CSA and ICAM-1 on the surface of endothelial cells under static and flow conditions. In addition, this glycan efficiently disrupted rosettes.

CONCLUSIONS

These findings support a potential use for mollusk HS as adjunct therapy for severe malaria.

Physical exercises decreases thrombus and neointima formation in atherosclerotic mice

The practice of physical exercise is highly indicated to prevent cardiovascular diseases and is directly related to the improvement of endothelial function and the regulation of arterial blood pressure. The objective of this study was to analyze the effect of physical exercise in vascular remodeling after FeCl₃ chemically induced arterial injury on atherosclerotic mice. To analyze the effect of exercises on thrombus formation, LDL receptor-deficient mice were fed for 6 weeks with a high-fat diet and performed or not physical exercises for 2 weeks before the arterial injury. To verify endothelium recovery the animals were exercised or not 2 weeks before the injury, and 3 weeks after it, when the vessels were analyzed. In this work, we observed that physical exercises done only before arterial injury reduced thrombosis time, protected the endothelial layer, promoted the recruitment of CD34 positive progenitor cells, increased the level of eNOS and gelatinases activities and decreased the number of inflammatory cells in the vessel, but do not avoid the growth of neointima. Otherwise exercises done before and continued after injury, increased gelatinase activities, reduced lipid deposition in the aortic arch and prevented neointima formation. Thus, we could conclude that physical exercises are done before and continued after endothelial injury stimulate endothelial recovery by promoting endothelial cell growth, matrix remodeling and decreasing inflammation in the vessel wall.

Attenuation of TNF-induced neutrophil adhesion by simvastatin is associated with the inhibition of Rho-GTPase activity, p50 activity and morphological changes

Neutrophil adhesion to the vasculature in response to potent inflammatory stimuli, such as TNF-α (TNF), can contribute to atheroprogression amongst other pathophysiological mechanisms. Previous studies have shown that simvastatin, a statin with known pleiotropic anti-inflammatory properties, can partially abrogate the effects of TNF-induced neutrophil adhesion, in association with the modulation of β₂-integrin expression. We aimed to further characterize the effects of this statin on neutrophil and leukocyte adhesive mechanisms in vitro and in vivo. A microfluidic assay confirmed the ability of simvastatin to inhibit TNF-induced human neutrophil adhesion to fibronectin ligand under conditions of shear stress, while intravital imaging microscopy demonstrated an abrogation of leukocyte recruitment by simvastatin in the microvasculature of mice that had received a TNF stimulus. This inhibition of neutrophil adhesion was accompanied by the inhibition of TNF-induced RhoA activity in human neutrophils, and alterations in cell morphology and β₂-integrin activity. Additionally, TNF augmented the activity of the p50 NFκB subunit in human neutrophils and TNF-induced neutrophil adhesion and β₂-integrin activity could be abolished using pharmacological inhibitors of NFκB translocation, BAY11-7082 and SC514. Accordingly, the TNF-induced elevation of neutrophil p50 activity was abolished by simvastatin. In conclusion, our data provide further evidence of the ability of simvastatin to inhibit neutrophil adhesive interactions in response to inflammatory stimuli, both in vivo and in vitro. Simvastatin appears to inhibit neutrophil adhesion by interfering in TNF-induced cytoskeletal rearrangements, in association with the inhibition of Rho A activity, NFκB translocation and, consequently, β₂-integrin activity.

Inhibition of hypoxia-associated response and kynurenine production in response to hyperbaric oxygen as mechanisms involved in protection against experimental cerebral malaria

Cerebral malaria (CM) is a multifactorial syndrome involving an exacerbated proinflammatory status, endothelial cell activation, coagulopathy, hypoxia, and accumulation of leukocytes and parasites in the brain microvasculature. Despite significant improvements in malaria control, 15% of mortality is still observed in CM cases, and 25% of survivors develop neurologic sequelae for life-even after appropriate antimalarial therapy. A treatment that ameliorates CM clinical signs, resulting in complete healing, is urgently needed. Previously, we showed a hyperbaric oxygen (HBO)-protective effect against experimental CM. Here, we provide molecular evidence that HBO targets brain endothelial cells by decreasing their activation and inhibits parasite and leukocyte accumulation, thus improving cerebral microcirculatory blood flow. HBO treatment increased the expression of aryl hydrocarbon receptor over hypoxia-inducible factor 1-α (HIF-1α), an oxygen-sensitive cytosolic receptor, along with decreased indoleamine 2,3-dioxygenase 1 expression and kynurenine levels. Moreover, ablation of HIF-1α expression in endothelial cells in mice conferred protection against CM and improved survival. We propose that HBO should be pursued as an adjunctive therapy in CM patients to prolong survival and diminish deleterious proinflammatory reaction. Furthermore, our data support the use of HBO in therapeutic strategies to improve outcomes of non-CM disorders affecting the brain.-Bastos, M. F., Kayano, A. C. A. V., Silva-Filho, J. L., Dos-Santos, J. C. K., Judice, C., Blanco, Y. C., Shryock, N., Sercundes, M. K., Ortolan, L. S., Francelin, C., Leite, J. A., Oliveira, R., Elias, R. M., Câmara, N. O. S., Lopes, S. C. P., Albrecht, L., Farias, A. S., Vicente, C. P., Werneck, C. C., Giorgio, S., Verinaud, L., Epiphanio, S., Marinho, C. R. F., Lalwani, P., Amino, R., Aliberti, J., Costa, F. T. M. Inhibition of hypoxia-associated response and kynurenine production in response to hyperbaric oxygen as mechanisms involved in protection against experimental cerebral malaria.

Trypanosoma cruzi tryparedoxin II interacts with different peroxiredoxins under physiological and oxidative stress conditions

Trypanosoma cruzi, the etiologic agent of Chagas disease, has to cope with reactive oxygen and nitrogen species during its life cycle in order to ensure its survival and infection. The parasite detoxifies these species through a series of pathways centered on trypanothione that depend on glutathione or low molecular mass dithiol proteins such as tryparedoxins. These proteins transfer reducing equivalents to peroxidases, including mitochondrial and cytosolic peroxiredoxins, TcMPx and TcCPx, respectively. In T. cruzi two tryparedoxins have been identified, TXNI and TXNII with different intracellular locations. TXNI is a cytosolic protein while TXNII due to a C-terminal hydrophobic tail is anchored in the outer membrane of the mitochondrion, endoplasmic reticulum and glycosomes. TXNs have been suggested to be involved in a majority of biological processes ranging from redox mechanisms to protein translation. Herein, a comparison of the TXNII interactomes under physiological and oxidative stress conditions was examined. Under physiological conditions, apart from the proteins with unknown biological process annotation, the majority of the identified proteins are related to cell redox homeostasis and biosynthetic processes, while under oxidative stress conditions, are involved in stress response, cell redox homeostasis, arginine biosynthesis and microtubule based process. Interestingly, although TXNII interacts with both peroxiredoxins under physiological conditions, upon oxidative stress, TcMPx interaction prevails. The relevance of the interactions is discussed opening a new perspective of TXNII functions.

Losartan and captopril treatment rescue normal thrombus formation in microfibril associated glycoprotein-1 (MAGP1) deficient mice

INTRODUCTION

MAGP1 is a glycoprotein present in the elastic fibers and is a part of the microfibrils components. MAGP1 interacts with von Willebrand factor and the active form of TGF-β and BMP. In mice lacking MAGP1, thrombus formation is delayed, increasing the occlusion time of carotid artery despite presenting normal blood coagulation in vitro. MAGP1-containing microfibrils may play a role in hemostasis and thrombosis. In this work, we evaluated the function of MAGP1 and its relation to TGF-β in the arterial thrombosis process.

METHODS AND RESULTS

We analyzed thrombus formation time in wild type and MAGP1-deficient mice comparing Rose Bengal and Ferric Chloride induced arterial lesion. The potential participation of TGF-β in this process was accessed when we treated both wild type and MAGP1-deficient mice with losartan (an antihypertensive drug that decreases TGF-β activity) or captopril (an angiotensin converting enzyme inhibitor that was used as a control antihypertensive drug). Besides, we evaluated thrombus embolization and the gelatinolytic activity in the arterial walls in vitro and ex vivo. Losartan and captopril were able to recover the thrombus formation time without changing blood pressure, activated partial thromboplastin time (aPTT), PT (prothrombin time), platelet aggregation and adhesion, but decreased gelatinase activity.

CONCLUSIONS

Our results suggest that both treatments are effective in the prevention of the sub-endothelial ECM degradation, allowing the recovery of normal thrombus formation.

Trypanosoma cruzi mitochondrial tryparedoxin peroxidase is located throughout the cell and its pull down provides one step towards the understanding of its mechanism of action

Trypanosoma cruzi depends on the effectiveness of redox metabolism to survive and ensure infection in the host. Homeostasis of redox metabolism in T. cruzi is achieved by the actions of several proteins that differ in many aspects from host proteins. Although extensive research has been performed examining hydroperoxide cytosolic antioxidant defense centered on trypanothione, the mechanisms of mitochondrial antioxidant defense are not yet known. The aim of this study was to elucidate the partners of TcMPx antioxidant pathway and to determine the influence of the cellular context (physiological versus oxidative stress). Through co-precipitation coupled with a mass spectrometry approach, a variety of proteins were detected under physiological and oxidative stress conditions. Interestingly, functional category analysis of the proteins identified under physiological conditions showed that they were involved in the stress response, oxidoreduction, thiol transfer, and metabolic processes; this profile is distinct under oxidative stress conditions likely due to structural alterations. Our findings help to elucidate the reactions involving TcMPx and most importantly also reveal that this protein is present throughout the cell and that its interaction partners change following oxidative stress exposure. The involvement and significance of the proteins found to interact with TcMPx and other possible functions for this protein are discussed widening our knowledge regarding T. cruzi mitochondrial antioxidant defenses.

Dermatan sulfate and bone marrow mononuclear cells used as a new therapeutic strategy after arterial injury in mice

BACKGROUND AIMS

Previously, we have demonstrated that administration of dermatan sulfate (DS) suppresses neointima formation in the mouse carotid artery by activating heparin co-factor II. A similar suppressive effect was observed by increasing the number of progenitor cells in circulation. In this study, we investigated the combination of DS and bone marrow mononuclear cells (MNC), which includes potential endothelial progenitors, in neointima formation after arterial injury.

METHODS

Arterial injury was induced by mechanical dilation of the left common carotid artery. We analyzed the extension of endothelial lesion, thrombus formation, P-selectin expression and CD45(+) cell accumulation 1 and 3 days post-injury, and neointima formation 21 days post-injury. Animals were injected with MNC with or without DS during the first 48 h after injury.

RESULTS

The extension of endothelial lesion was similar in all groups 1 day after surgery; however, in injured animals treated with MNC and DS the endothelium recovery seemed to be more efficient 21 days after lesion. Treatment with DS inhibited thrombosis, decreased CD45(+) cell accumulation and P-selectin expression at the site of injury, and reduced the neointimal area by 56%. Treatment with MNC reduced the neointimal area by 54%. The combination of DS and MNC reduced neointima formation by more than 91%. In addition, DS promoted a greater accumulation of MNC at the site of injury.

CONCLUSIONS

DS inhibits the initial thrombotic and inflammatory processes after arterial injury and promotes migration of MNC to the site of the lesion, where they may assist in the recovery of the injured endothelium.

Deficiency in microfibril-associated glycoprotein-1 leads to complex phenotypes in multiple organ systems

Microfibril-associated glycoprotein-1 (MAGP-1) is a small molecular weight component of the fibrillin-rich microfibril. Gene-targeted inactivation of MAGP-1 reveals a complex phenotype that includes increased body weight and size due to excess body fat, an altered wound healing response in bone and skin, and a bleeding diathesis. Elastic tissues rich in MAGP-1-containing microfibrils develop normally and show normal function. The penetrance of MAGP-1-null phenotypes is highly variable and mouse strain-dependent, suggesting the influence of modifier genes. MAGP-1 was found to bind active transforming growth factor-beta (TGF-beta) and BMP-7 with high affinity, suggesting that it may be an important modulator of microfibril-mediated growth factor signaling. Many of the phenotypic traits observed in MAGP-1-deficient mice are consistent with loss of TGF-beta function and are generally opposite those associated with mutations in fibrillin-1 that result in enhanced TGF-beta signaling. Increased body size and fat deposition in MAGP-1-mutant animals are particularly intriguing given the localization of obesity traits in humans to the region on chromosome 1 containing the MAGP-1 gene.

Tropoelastin Interacts with Cell-surface Glycosaminoglycans via Its COOH-terminal Domain

Using a biochemical and cell biological approach, we have identified a cell interaction site at the carboxyl terminus of tropoelastin. Cell interactions with the COOH-terminal sequence are not through the elastin-binding protein (EBP67) because neither VGVAPG-like peptides nor galactoside sugars altered adhesion. Our results also show that cell adhesion to tropoelastin is not promoted by integrins. Through the use of mutant Chinese hamster ovary cell lines defective in glycosaminoglycan biosynthesis, as well as competition studies and enzymatic removal of specific cell-surface glycosaminoglycans, the tropoelastin-binding moieties on the cell surface were identified as heparan and chondroitin sulfate-containing glycosaminoglycans, with heparan sulfate being greatly preferred. Heparin affinity chromatography combined with cell adhesion assays identified the last 17 amino acids as the sequence element at the carboxyl terminus of tropoelastin responsible for the adhesive activity.

The Pro-regions of lysyl oxidase and lysyl oxidase-like 1 are required for deposition onto elastic fibers

These studies were undertaken to determine how lysyl oxidase (LOX) and lysyl oxidase like-1 (LOXL) enzymes are targeted to their substrates in the extracellular matrix. Full-length LOX/LOXL and constructs containing just the pro-regions of each enzyme localized to elastic fibers when expressed in cultured cells. However, the LOXL catalytic domain without the pro-region was secreted into the medium but did not associate with matrix. Ligand blot and mammalian two-hybrid assays confirmed an interaction between tropoelastin and the pro-regions of both LOX and LOXL. Immunofluorescence studies localized both enzymes to elastin at the earliest stages of elastic fiber assembly. Our results showed that the pro-regions of LOX and LOXL play a significant role in directing the deposition of both enzymes onto elastic fibers by mediating interactions with tropoelastin. These findings confirmed that an important element of substrate recognition lies in the pro-domain region of the molecule and that the pro-form of the enzyme is what initially interacts with the matrix substrate. These results have raised the interesting possibility that sequence differences between the pro-domain of LOX and LOXL account for some of the functional differences observed for the two enzymes.

Identification of a major microfibril-associated glycoprotein-1-binding domain in fibrillin-2

Using yeast two-hybrid, ligand blotting, and solid phase binding assays, we have shown that microfibril-associated glycoprotein-1 (MAGP-1) interacts with the 8-cysteine motif of fibrillin-2 encoded by exon 24. Binding to this sequence was demonstrated for full-length MAGP-1 as well as for the MAGP-1 matrix-binding domain encoded by exons 7 and 8. The matrix-binding domain, but not the full-length protein, also bound to regions of fibrillin-2 defined by exons 16 and 17, exon 20, and exons 23 and 24. Interestingly, no binding was detected to sequences near the N or C terminus where MAGP-1 and MAGP-2, respectively, were shown to interact with fibrillin-1. The localization of MAGP-1 binding to the 8-Cys domain encoded by exon 24 suggests that the bead structure of microfibrils consists of exon 24 and portions of the central region of fibrillin-2. Exon 24 in fibrillin lies in the region of the molecule where mutations produce the most severe phenotypes associated with Marfan syndrome (fibrillin-1) and congenital contractural arachnodactyly (fibrillin-2). It is possible that these mutations alter the ability of fibrillin to bind MAGP-1, which may contribute to the severity of the disease.

Fibrillin-1 and -2 contain heparin-binding sites important for matrix deposition and that support cell attachment

Fibrillin-1 and -2 are large modular extracellular matrix glycoproteins found in many vertebrate organ systems and are known to be key components of the elastic fibre. In the present study, we identify a new heparin-binding region in fibrillin-2 between exons 18 and 24. Additionally, we have narrowed the location of heparin-binding activity previously identified in fibrillin-1 to the last 17 residues of the mature proteolytically processed protein. This domain demonstrated higher activity as a multimer than as a monomer. The fibrillin-1 C-terminal site supported cell attachment in each of nine cell types tested. Attachment was shown to be mediated by cell-surface heparan sulphate proteoglycans. Fibrillin-1 has been shown previously to have heparin-binding activity that is important for matrix deposition of the molecule by fibroblasts. This function in deposition was confirmed in two additional fibrillin-producing cell types (osteosarcoma and epithelial cells) for the deposition of both fibrillin-1 and -2 into the extracellular matrix.

Molecular size distribution analysis of human gingival glycosaminoglycans in cyclosporin- and nifedipine-induced overgrowths

Glycosaminoglycans are thought to accumulate in formative lesions like drug-induced gingival overgrowth. Recent evidences, however, suggest that the amounts of glycosaminoglycans are comparable in overgrown and healthy gingiva. Besides, alterations in the size distribution of glycosaminoglycan molecules isolated from phenytoin-induced overgrown samples have also been suggested. Therefore, we sought to determine possible differences in molecular size distribution of gingival glycosaminoglycans in other types of drug-induced overgrowths. Purified gingival glycosaminoglycans from healthy and cyclosporin- and nifedipine-induced overgrown gingival tissues were analyzed by agarose gel electrophoresis and their molecular-size distribution was evaluated by both gel filtration chromatography and polyacrylamide gel electrophoresis. Our results on the gingival glycosaminoglycan composition showed presence of chondroitin sulfate, dermatan sulfate, heparan sulfate and hyaluronic acid in all types of gingival tissues examined. In addition, hyaluronic acid was predominantly of a large size eluting near to the void volume of a Superose-6 column, while the sulfated glycosaminoglycans were mainly composed of low molecular size glycosaminoglycans. Our results show no differences in the molecular-size distribution of hyaluronic acid and sulfated glycosaminoglycans among healthy and drug-induced overgrown gingival tissues.

Biochemical characterization of heparan sulfate derived from murine hemopoietic stromal cell lines: a bone marrow-derived cell line S17 and a fetal liver-derived cell line AFT024

Heparan sulfate (HS) present on the surface of hemopoietic stromal cells has important roles in the control of adhesion and growth of hemopoietic stem and progenitor cells. Recent studies have characterized several different heparan sulfate proteoglycans (HSPGs) from both human and murine bone marrow stromal cells. In the present study, we have compared the molecular structure of HS, metabolically labeled with [(35)S]-sulfate produced by two distinct preparations of murine hemopoietic stromal cell lines. These comprised a bone marrow-derived cell line S17 and a fetal liver-derived cell line AFT024. [(35)S]-HS was examined in the cell layers and in the culture medium. We identified and measured the relative proportions of the various glycosaminoglycans (GAGs) in the two stromal cell lines. Chondroitin sulfate (CS) was preponderantly secreted by the stromal cell lines, while HS was relatively more abundant in the cell-associated fractions. The two types of stromal cells differ in their HS composition, mainly due to different patterns of N- and O-sulfation. The two stromal cell lines expressed mRNA for different HSPGs. Data from reverse transcription PCR revealed that the two stromal cell lines expressed mRNA for glypican and syndecan4. Only AFT024 cell line expressed mRNA for betaglycan. There was no evidence for expression of mRNA for both syndecan1 and syndecan2. [(35)S]-sulfated macromolecules could be released from the cell surface of both stromal cell lines by phosphatidylinositol phospholipase C (PI-PLC), which is consistent with the expression of glypican detected by PCR experiments.

Comparative biochemistry of human skin: glycosaminoglycans from different body sites in normal subjects and in patients with localized scleroderma

OBJECTIVES

The aim of this investigation is to compare the relative proportions of disaccharides of chondroitinase-digestible glycosaminoglycans (GAGs) among the different body sites in control human skin and in the skin lesions of patients with localized scleroderma.

METHODS

The disaccharide relative proportions were determined using high-performance liquid chromatography (HPLC).

RESULTS

DeltaDi-4S, the main disaccharide unit of dermatan sulphate (DS), was the major skin GAG disaccharide (approximately 70% of the total) in control skin among all different body sites studied here. In scleroderma there was an increase in the relative proportion of both deltaDi-HA, the main disaccharide unit of hyaluronic acid (HA), and deltaDi-diS(B) (alpha-deltaUA(2SO4)-1-->3-GalNAc(4SO4)), derived from DS, and a decrease in deltaDi-4S, as compared with the uninvolved skin or the site-matched control skin.

CONCLUSION

DS is the major GAG species in normal skin from different body sites. In addition, our results suggest a decrease and also a structural change in DS and an increase in the proportion of HA in scleroderma skin.

Embryos of the sea urchin Strongylocentrotus purpuratus synthesize a dermatan sulfate enriched in 4-O- and 6-O-disulfated galactosamine units

Unfertilized eggs of the sea urchin Strongylocentrotus purpuratus are surrounded by a gelatinous layer rich in sulfated fucan. Shortly after fertilization this polysaccharide disappears, but 24 h later the embryos synthesize high amounts of dermatan sulfate concomitantly with the mesenchyme blastula-early gastrula stage when the larval gut is forming. This glycosaminoglycan has the same backbone structure [4-alpha-L-IdoA-1-->3-beta-D-GalNAc-1](n) as the mammalian counterpart but possesses a different sulfation pattern. It has a high content of 4-O- and 6-O-disulfated galactosamine units. In addition, chains of this dermatan sulfate are considerable longer than those of vertebrate tissues. Adult sea urchin tissues contain high concentrations of sulfated polysaccharides, but dermatan sulfate is restricted to the adult body wall where it accounts for approximately 20% of the total sulfated polysaccharides. In addition, sulfation at the 4-O-position decreases markedly in the dermatan sulfate from adult sea urchin when compared with the glycan from larvae. Overall, these results demonstrate the occurrence of dermatan sulfates with unique sulfation patterns in this marine invertebrate. The physiological implication of these oversulfated dermatan sulfates is unclear. One hypothesis is that interactions between components of the extracellular matrix in marine invertebrates occur at higher salt concentrations than in vertebrates and therefore require glycosaminoglycans with increased charge density.

Astroglial cells derived from lateral and medial midbrain sectors differ in their synthesis and secretion of sulfated glycosaminoglycans

Astroglial cells derived from lateral and medial midbrain sectors differ in their abilities to support neuritic growth of midbrain neurons in cocultures. These different properties of the two types of cells may be related to the composition of their extracellular matrix. We have studied the synthesis and secretion of sulfated glycosaminoglycans (GAGs) by the two cell types under control conditions and beta-D-xyloside-stimulated conditions, that stimulate the ability to synthesize and release GAGs. We have confirmed that both cell types synthesize and secrete heparan sulfate and chondroitin sulfate. Only slight differences were observed between the proportions of the two GAGs produced by the two types of cells after a 24-h labeling period. However, a marked difference was observed between the GAGs produced by the astroglial cells derived from lateral and medial midbrain sectors. The medial cells, which contain derivatives of the tectal and tegmental midline radial glia, synthesized and secreted approximately 2.3 times more chondroitin sulfate than lateral cells. The synthesis of heparan sulfate was only slightly modified by the addition of beta-D-xyloside. Overall, these results indicate that astroglial cells derived from the two midbrain sectors have marked differences in their capacity to synthesize chondroitin sulfate. Under in vivo conditions or a long period of in vitro culture, they may produce extracellular matrix at concentrations which may differentially affect neuritic growth.

Sulfated glycosaminoglycans from ovary of Rhodnius prolixus

We have characterized sulfated glycosaminoglycans from ovaries of the blood-sucking insect Rhodnius prolixus, and determined parameters of their synthesis and distribution within this organ by biochemical and histochemical procedures. The major sulfated glycosaminoglycan is heparan sulfate while chondroitin 4-sulfate is a minor component. These glycosaminoglycans are concentrated in the ovarian tissue and are not found inside the oocytes. Besides this, we detected the presence of a sulfated compound distinguished from sulfated glycosaminoglycans and possibly derived from sulfated proteins. Conversely to the compartmental location of sulfated glycosaminoglycans, the unidentified sulfated compound is located in the ovarian tissue as well as inside the oocytes. Based on these and other findings, the possible roles of ovarian sulfated glycosaminoglycans on the process of oogenesis in these insects are discussed.

Is there a glycosaminoglycan-related heterogeneity of the thymic epithelium?

We determined the synthesis and secretion of glycosaminoglycans by three distinct preparations of mouse cultured thymic epithelial cells. These comprised primary cultures of thymic nurse cells (TNCs), which are normally located within the cortex of the thymic lobules, as well as two murine thymic epithelial cells, bearing a mixed, yet distinct, cortico-medullary phenotype. We first identified and measured the relative proportions of the various glycosaminoglycans in the three epithelial cells. Non-sulfated glycosaminoglycans are preponderantly secreted by the TNCs, while the sulfated glycans (particularly heparan sulfate) are relatively more abundant on the cell surface. The three types of epithelial cells differ markedly in their heparan sulfate composition, mainly due to different patterns of N- and O-sulfation. In addition, the cells differ in the synthesis and secretion of other glycosaminoglycans. Thus, TNCs secrete high amounts of dermatan sulfate + chondroitin sulfate to the culture medium. IT-76M1 cells secrete high proportions of heparan sulfate while 2BH4 cells show a more equilibrated proportion of dermatan sulfate/chondroitin sulfate and heparan sulfate. The three epithelial cells also differ in their capacity to produce hyaluronic acid and 2BH4 cells are distinguished by their high rate of synthesis of this glycosaminoglycan. In conclusion, our results show that distinct thymic epithelial cells can synthesize different types of glycosaminoglycans. Although it remains to be definitely determined whether these differences reflect the in vivo situation, our data provide new clues for further understanding of how glycosaminoglycan-mediated interactions behave in the thymus.

Patterns of synthesis and secretion of sulfated glycosaminoglycans in primary cortical and cerebellar astrocytes in vitro

We determined the amounts of [35S]-glycosaminoglycans (GAGs) found on the intracellular, pericellular and extracellular compartments of primary cultures of astrocytes derived from newborn rat cortex and cerebellum in vitro. Our results show that the greatest portion of newly synthesized GAGs were found in different cellular compartments, depending on the source of the astrocytes. In the cells derived from the cerebellum, the proportion of [35S]-GAGs secreted to the culture medium preponderates over the amount found in the two other compartments, whereas cells derived from the cortex accumulated higher proportions of [35S]-GAGs in the intracellular compartment than in the two other compartments. Cortical and cerebellar glial cells synthesised and secreted heparan sulfate (HS) and chondroitin 4-sulfate (C-4S). HS was predominantly accumulated on the pericellular surface, while C-4S was mostly secreted to the culture medium. Beside the difference on the distribution of total [35S]-GAGs among the three cellular compartments, no difference was observed on the relative proportions of HS and C-4S within each compartment. By defining the source of GAGs, the present study may help to complement and extend information on biosynthesis of these compounds by mammalian glial cells.

Human gingival glycosaminoglycans in cyclosporin-induced overgrowth

Glycosaminoglycans in normal and cyclosporin-induced gingival overgrowth were extracted by papain digestion and purified by Mono Q-FPLC chromatography. The purified glycosaminoglycans were analyzed by agarose gel electrophoresis and by the pattern of degradation products formed by chondroitin lyases on HPLC chromatography. Our results on the glycosaminoglycan composition showed presence of chondroitin 4- and 6-sulfate, dermatan sulfate, heparan sulfate and hyaluronic acid in both normal gingiva and cyclosporin-induced gingival overgrowth. The total and relative amounts of glycosaminoglycans were similar between normal and overgrown gingiva. This suggests that the glycosaminoglycan composition is not changed in cyclosporin-induced gingival overgrowth. Our present biochemical results conflict with histochemical and biosynthetic data previously reported by other groups. Those studies suggested that the affected tissues contained higher levels of glycosaminoglycans and that cyclosporin induced comparably high levels of these compounds in in vitro cultures of gingival fibroblasts. Therefore, these discrepant results suggest that a cyclosporin-induced increase on gingival glycosaminoglycans still remains an open question. The implications of these conflicting results are discussed.

Thymic epithelial cells synthesize a heparan sulfate with a highly sulfated region

Epithelial cells are important components of the thymus microenvironment and are involved in thymocyte differentiation. The production and secretion of sulfated glycosaminoglycans by these cells grown in culture were investigated using labeling with radioactive 35S-Na2SO4 and 3H-glucosamine. The major glycosaminoglycans synthesized by these cells are heparan sulfate and hyaluronic acid. The structure of the heparan sulfate was investigated by the pattern of degradation products formed by deaminative cleavage with nitrous acid. The ratio 35S-sulfate/ H-glucosamine is high in the segments of the heparan sulfate released during the deaminative cleavage with nitrous acid but low in the resistant portion of the molecule. Thus, the heparan sulfate synthesized by the thymic epithelial cells contains a highly sulfated region. Digestion with heparitinase reveals that this highly sulfated region is a heparin-like segment of the molecule. The heparan sulfate is rapidly incorporated into the cell surface but its secretion to the extracellular medium requires a longer incubation period. Finally, heparin was used to mimic the possible effect of this heparan sulfate with a highly sulfated region, as ascertained by its ability to modulate thymocyte adhesion to thymic epithelial cells. Since heparin actually enhanced thymocyte adhesion, it is suggested that the heparan sulfate described herein, secreted by the thymic epithelium, may play a role upon intrathymic heterotypic cellular interactions.

Highly sulfated dermatan sulfates from Ascidians. Structure versus anticoagulant activity of these glycosaminoglycans

Dermatan sulfates with the same backbone structure [4-alpha-L-IdceA-1-->3-beta-D-GalNAc-1]n but with different patterns of sulfation substitutions have been isolated from the ascidian body. All the ascidian dermatan sulfates have a high content of 2-O-sulfated alpha-L-iduronic acid residues but differ in the pattern of sulfation of the N-acetyl-beta-D-galactosamine units. Styela plicata and Halocynthia pyriformis have 4-O-sulfated units, but in Ascidian nigra they are 6-O-sulfated. This collection of ascidian dermatan sulfates (together with native and oversulfated mammalian dermatan sulfate), where the extent and position of sulfate substitution have been fully characterized, were tested in anticoagulant assays. Dermatan sulfate from A. nigra has no discernible anticoagulant activity, which indicates that 4-O-sulfation of the N-acetyl-beta-D-galactosamine is essential for the anticoagulant activity of this glycosaminoglycan. In contrast dermatan sulfates from S. plicata and H. pyriformis are potent anticoagulants due to potentiation of thrombin inhibition by heparin cofactor II. These ascidian dermatan sulfates have approximately 10-fold and approximately 6-fold higher activity with heparin cofactor II than native and an oversulfated mammalian dermatan sulfate, respectively. They have no effect on thrombin or factor Xa inhibition by antithrombin. These naturally oversulfated ascidian dermatan sulfates are sulfated at selected sites required for interaction with heparin cofactor II and thus have specific and potent anticoagulant activity.