Mouse heparin proteoglycan. Synthesis by mast cell-fibroblast monolayers during lymphocyte-dependent mast cell proliferation

Mast cell proteoglycans

Mast cells are versatile effector cells of the immune system, contributing to both innate and adaptive immunity toward pathogens but also having profound detrimental activities in the context of inflammatory disease. A hallmark morphological feature of mast cells is their large content of cytoplasmic secretory granules, filled with numerous secretory compounds, including highly negatively charged heparin or chondroitin sulfate proteoglycans of serglycin type. These anionic proteoglycans provide the basis for the strong metachromatic staining properties of mast cells seen when applying various cationic dyes. Functionally, the mast cell proteoglycans have been shown to have an essential role in promoting the storage of other granule-contained compounds, including bioactive monoamines and different mast cell-specific proteases. Moreover, granule proteoglycans have been shown to regulate the enzymatic activities of mast cell proteases and to promote apoptosis. Here, the current knowledge of mast cell proteoglycans is reviewed.

The Hemolymph of the Ascidian Styela plicata (Chordata-Tunicata) Contains Heparin inside Basophil-like Cells and a Unique Sulfated Galactoglucan in the Plasma

The hemolymph of ascidians (Chordata-Tunicata) contains different types of hemocytes embedded in a liquid plasma. In the present study, heparin and a sulfated heteropolysaccharide were purified from the hemolymph of the ascidian Styela plicata. The heteropolysaccharide occurs free in the plasma, is composed of glucose ( approximately 60%) and galactose ( approximately 40%), and is highly sulfated. Heparin, on the other hand, occurs in the hemocytes, and high performance liquid chromatography of the products formed by degradation with specific lyases revealed that it is composed mainly by the disaccharides DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4)) (39.7%) and DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4))(6SO(4)) (38.2%). Small amounts of the 3-O-sulfated disaccharides DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4))(3SO(4)) (9.8%) and DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4))(3SO(4))(6SO(4)) (3.8%) were also detected. These 3-O-sulfated disaccharides were demonstrated to be essential for the binding of the hemocyte heparin to antithrombin III. Electron microscopy techniques were used to characterize the ultrastructure of the hemocytes and to localize heparin and histamine in these cells. At least five cell types were recognized and classified as univacuolated and multivacuolated cells, amebocytes, hemoblasts, and granulocytes. Immunocytochemistry showed that heparin and histamine co-localize in intracellular granules of only one type of hemocyte, the granulocyte. These results show for the first time that in ascidians, a sulfated galactoglucan circulates free in the plasma, and heparin occurs as an intracellular product of a circulating basophil-like cell.

Apposition of fibroblasts to mast cells and lymphocytes in normal human lung and in cryptogenic fibrosing alveolitis. Ultrastructure and cell perimeter measurements

The perimeters of mast cells and lymphocytes in human lungs were measured in electron micrographs by digitizer to determine the percentage of perimeter apposed to fibroblast (PPAF). Fibroblasts were apposed to the majority of mast cells. The median PPAF for mast cells in normal lung was 50.3 per cent, and in cryptogenic fibrosing alveolitis (CFA), 35.7 per cent. Although the value in CFA was lower, the difference was not statistically significant (median difference 11.8; 95 per cent confidence interval (-19.6, 25.1); P = 0.65). The PPAF range overall was 3.8-94.1 per cent. There was similar apposition of fibroblasts to lymphocytes, and no statistical differences were found when median PPAF results for mast cells and lymphocytes were compared for normal and CFA lung. The high degree of percentage apposition, accurately quantified in this study, shows that fibroblasts, mast cells, and lymphocytes are ideally arranged structurally in normal alveolar walls, to facilitate the many physiological interactions which are currently being uncovered. The present study also shows that apposition persists in pathological states, e.g., CFA lung, but because all these cells are increased in number in CFA lung, apposition is easier to identify here than in normal lung.

Recent advances in the cellular and molecular biology of mast cells

The mast cell is now considered to play a pivotal role not only in allergic reactions but also in a number of inflammatory disorders. After immunological activation via the IgE receptor, the mast cell releases a variety of cytokines, lipid-derived mediators, amines, proteases and proteoglycans--all of which can regulate adjacent cells and the metabolism of the extra-cellular matrix of connective tissues. While it had been known for some time that mast cells differ in a number of properties in varied tissue sites, it was not known why or how this heterogeneity occurred. The development of in-vitro techniques to culture mast cells and the reconstitution of mast-cell-deficient mice are two major approaches that have facilitated analyses of how the tissue microenvironment regulates the phenotype of mast cells. In this review by Richard L. Stevens and K. Frank Austen, some of the recent findings on the molecular biology of mast cell secretory granule proteins and proteoglycans, and the interaction of mast cells with fibroblasts in the presence and absence of interleukin 3(IL-3) are highlighted.

Histochemical heterogeneity of dermal mast cells in athymic and normal rats

Mucosal mast cells (MMC) and connective tissue mast cells (CTMC) of the rat contain different proteoglycans, which can be distinguished using histochemical methods. The chondroitin sulphate proteoglycan of the MMC, unlike the heparin of the CTMC, does not show fluorescent berberine binding, is susceptible to aldehyde fixatives and stains preferentially with Alcian Blue in a staining sequence with Safranin. The majority of the dermal mast cells are typical CTMC and are located in the deep part of the dermis. Subepidermal mast cells are comparatively few in normal rats but numerous in athymic rats and mice. These cells differ from other dermal mast cells in that they stain preferentially with Alcian Blue and they appear to contain little histamine. We examined some of the histochemical properties of the skin mast cells of female PVG-rnu/rnu rats and their heterozygous littermates aged from 5 to 29 weeks. The thiazine dye-binding of the subepidermal mast cells was partially blocked by formaldehyde fixation and only about half of them showed a weakly fluorescent berberine binding. The critical electrolyte concentration of the Alcian Blue staining of the subepidermal mast cells was between that of CTMC and MMC. Deaminative cleavage with nitrous acid abolished the staining of all skin mast cells, while that of the MMC was unaffected. There were no statistically significant differences in the staining patterns of the dermal mast cells between different ages or groups of rat. These results indicate that the subepidermal mast cells contain a heparin proteoglycan which is, however, different from that of the typical CTMC of other sites. They thus appear to represent a second example of a mast cell within a defined anatomical location exhibiting a distinct proteoglycan expression.

Degranulation of in vitro differentiated mast cells stimulated by two monoclonal IgE specificities

Confluent spread of mature nondividing mast cells is obtained after 1 month's growth of lymph node cells taken from mice immunized with horse serum and plated on embryonic fibroblast monolayers. The degranulation capacity of these mast cells and histamine release stimulated by monoclonal IgE antibodies and their antigens were studied. The mast cells were first incubated with either anti-2,4-dinitrophenyl (DNP) IgE or with anti-ovalbumin (OVA) IgE and then with the other IgE to study the ability of one IgE specificity to saturate the receptors and block the ability of the other IgE to bind and evoke degranulation. Saturation of the receptors and maximal histamine release (86-92%) were obtained within 2-3 h incubation with excess IgE (1-10 micrograms/ml). No histamine was released after incubation for 3-4 h with the other IgE (0.38-4.0% histamine release). Seventeen days after the excess, unbound, saturating IgE anti-DNP was washed away, 75% of the histamine was still released after antigen DNP-bovine serum albumin was added. However, these mast cells were still effectively blocked from sensitization with IgE anti-OVA (1.71% histamine release). The blocking could be broken if the second IgE molecules were allowed to stay longer than 4 h in culture. From 10 h onwards, the degranulation capacity steadily increased (from 59.6% histamine release after 10 h to 79.5% after 42 h). In studies with 125I-labeled IgE, there was a direct correlation between the rate of binding of the second IgE to the mast cells (from 1.7% binding after 3 h to 75% after 48 h) and the increase in degranulation rate with the second antigen (from 2.40% histamine release to 65.4%). In contrast, only slight binding of the 125I-labeled IgE of the saturating specificity occurred (4.2% after 3 h to 12.7% binding after 48 h). Incubation of mast cells, previously saturated with 125I-labeled IgE, with cold IgE of either specificity did not proportionally reduce the cell-bound label. This suggests that no substitution of IgE molecules on the receptors occurred. When the mast cells saturated with anti-OVA were incubated with IgE anti-DNP together with tunicamycin, the development of the degranulation capacity by DNP-bovine serum albumin was inhibited. The results suggest that IgE molecules of the other specificity stimulated the appearance of new receptors on the mast cell surface.

Extensive proliferation of mature connective-tissue type mast cells in vitro

There are two phenotypically distinct subpopulations of mast cells in rodents: connective tissue-type mast cells (CTMC) and mucosal mast cells (MMC). These populations differ in their location, cell size, staining characteristics, ultrastructure, mediator content and T-cell dependency. Several investigators recently reported a further subclass of mast cells which arise when normal mouse haematopoietic cells are cultured with interleukin-3 (IL-3); IL-3 is an activity similar or identical to mast-cell growth factor, histamine-producing factor, or P-cell stimulating factor. These cultured mast cells are in many ways similar to MMC; they stain with Alcian blue but not safranin, contain chondroitin sulphate E proteoglycan rather than heparin proteoglycan and have relatively low histamine content, as do MMC. Although proliferation of MMC is known to be T-cell dependent in vivo and thought to be IL-3-dependent in vitro, the factors on which CTMC proliferation depends remain elusive. Here we show that mature CTMC purified from mouse peritoneal cells can proliferate in vitro in methylcellulose culture and maintain the appearance and function of CTMC. We also present evidence that mature CTMC cannot proliferate in the presence of pure IL-3 alone.

Increased number of mast cells in the testis of neonatally estrogenized rats

The presence of increased numbers of mast cells in the testis of adult neonatally estrogenized rats is reported. The histometric study revealed significant differences between control and estrogenized animals for two ages considered (45 and 90 days). This increase might be related with the development of connective tissue in estrogenized rats.

Mast cell heterogeneity: evidence and implications

Mast cells and basophils play a fundamental role in the pathogenesis of allergic disease, although their physiologic role is largely unknown. A large body of evidence now indicates that the properties of mast cells are dependent on the tissue and species from which they are derived. Such mast cell heterogeneity encompasses differences in morphology, development, cytochemistry, and function. The evidence for such heterogeneity, and some of its clinical implications, is discussed.

Structural features and some binding properties of proteoheparan sulfate enzymatically labeled by calf brain microsomes

Previous studies established that brain microsomes catalyze the transfer of [35S]sulfate from 3'-phosphoadenosine 5'-phospho[35S]sulfate to an O-linked oligosaccharide chain of a membrane glycoprotein and sulfamino groups of a membrane-associated proteoheparan sulfate (R. R. Miller and C. J. Waechter (1979) Arch. Biochem. Biophys. 198, 31-41). A large fraction of the proteoheparan [35S]sulfate can be released by treating the enzymatically labeled membranes from calf brain with 1 M NaCl. The salt-extracted 35S-labeled proteoglycan has been partially purified by a combination of ion-exchange and gel filtration chromatography. Based on chromatographic analyses, the 35S-labeled proteoglycan labeled in vitro is proposed to be a family of proteoheparan [35S]sulfates having an average molecular weight estimated to be 55,000. Variation in the length of the 35S-labeled polysaccharide chains partially accounts for the differences in molecular size of the proteoheparan [35S]sulfates. Binding studies reveal that the intact proteoheparan [35S]sulfates, as well as the free 35S-labeled polysaccharides released by mild alkali treatment, rapidly reassociate with calf brain membrane preparations. The association with calf brain membranes is saturable and reversible. Consistent with the binding being a specific interaction, only iduronic acid-containing glycosaminoglycans inhibit the association of the 35S-labeled proteoglycan with calf brain membranes and facilitate the disassociation. Neither the binding of the 35S-labeled proteoglycan to membranes nor the displacement was affected by hyaluronic acid, chondroitin 4-sulfate, or chondroitin 6-sulfate. The binding of the enzymatically labeled proteoheparan sulfate is reduced by preincubating membranes with either trypsin or chymotrypsin, but not with neuraminidase or phospholipase D. These results suggest that at least one class of proteoheparan sulfates could be specifically bound to one or more brain membrane proteins. The results also suggest a role for iduronosyl residues, and perhaps the stereochemical relationship of the carboxyl group to the O-sulfate moiety at C-2, in the recognition process.

Effector cell heterogeneity in immediate hypersensitivity reactions

Histologic heterogeneity in the basophil and mast cell populations has been apparent for many years. The advent of tissue culture and cell separation procedures has now made it possible to explore distinct populations of basophils and mast cells, as should be evident from this review. In fact, the logical extension of such technology is the requirement that cell preparations used in exploring basophil and mast cell function be carefully defined to permit comparison of data from one laboratory to another. While this is a practical application of the knowledge of the characteristics of heterogeneity, the implications for future developments in the understanding of basophil and mast cell function are more theoretical. While both basophils and mast cells respond to degranulating stimuli and antiallergic compounds in a similar fashion, as a rule, this review has noted several exceptions including the failure of disodium cromoglycate to prevent rat mucosal mast cell degranulation induced by immunologic stimuli. Such observations suggest that the ability of given drugs to inhibit allergic responses in one target organ and not in another may be due in part to differing mast cell responses. This hypothesis can be extended to variation in response among infants, children, and adults to such drugs as antihistamines. Furthermore, the variety of symptoms seen in individuals may be a reflection of differing responses of those individuals' mast cells from organ to organ. For instance, one subject with ragweed sensitivity might express this sensitivity as asthma, and a second subject with ragweed sensitivity might express this sensitivity as rhinitis. This would depend upon the ability of their pulmonary and upper airway mast cells to bind ragweed-specific IgE, degranulate to IgE-mediated stimuli, or to be regulated by intrinsic control mechanisms. Of a yet more speculative nature is the attempt to discern the basis for basophil, and particularly mast cell, heterogeneity. The function of the mast cell is unknown, but theories include the rejection of parasites; regulation and repair of connective tissue; regulation of the microvasculature; regulation of gastric acid secretion; limitation of delayed hypersensitivity reactions; and detoxification of surrounding tissues. Any or all of these theories may be correct, however, such a diversity of possible biologic roles for the mast cell suggests that mast cell subpopulations may have highly specialized functions reflected in stimuli that lead to their proliferation, their response to degranulating stimuli, and their mediator content.(ABSTRACT TRUNCATED AT 400 WORDS)