A highly purified vegetal fraction able to modulate HMGB1 and to attenuate septic shock in mice

High-mobility group box protein 1 (HMGB1) is an intracellular protein that may be released actively from monocytes and macrophages or passively from necrotic or damaged cells. Its inhibition in animal experiments, even in the late phase of septic shock, significantly enhanced the survival rate of rodents. The aim of our study was to investigate the effect of a vegetal fraction isolated and highly purified from Helleborus purpurascens regarding the modulation of HMGB1 release either from tumor cells or human blood mononuclear cells. Our results showed that the vegetal fraction was able to down-regulate the release of HMGB1 from activated human blood mononuclear cells (PBMCs) and tumor cells. By combining the purified fraction with Cyclophosphamide the release of HMGB1 from tumor cells was strongly decreased. This synergism was not noticed when the ve getal product was associated with Doxorubicin. We also studied the effect of the purified fraction in mice with septic shock induced by cecal ligation and puncture (CLP) method. The tested vegetal product increased significantly the survival rate of animals compared to the mice not treated with it. Our data suggest that the purified vegetal fraction may modulate inflammation by down-regulating the HMGB1, which can also explain its efficacy in septic shock in mice.     

CD40 stimulation provides an IFN-gamma-independent and IL-4-dependent differentiation signal directly to human B cells for IgE production.

IgE induction from human cells has generally been considered to be T cell dependent and to require at least two signals: IL-4 stimulation and T cell/B cell interaction. In the present study we report a human system of T cell-independent IgE production from highly purified B cells. When human cells were co-stimulated with a mAb directed against CD40 (mAb G28-5), there was induction of IgE secretion from purified blood and tonsil B cells as well as unfractionated lymphocytes. Anti-CD40 alone failed to induce IgE from blood mononuclear cells or purified B cells. The effect of the combination of anti-CD40 and IL-4 on IgE production was very IgE isotype specific as IgG, IgM, and IgA were not increased. Furthermore, anti-CD40 with IL-5 or PWM did not co-stimulate IgG, IgM, or IgA and in fact strongly inhibited PWM-stimulated IgG, IgM and IgA production from blood or tonsil cells. IgE synthesis induced by anti-CD40 plus IL-4 was IFN-gamma independent as is the in vivo production of IgE in humans; the doses of IFN-gamma that profoundly suppressed IgG synthesis induced by IL-4, or IL-4 plus IL-6, had no inhibitory effect on anti-CD40-induced IgE production. Anti-CD23 and anti-IL-6 also could not block anti-CD40 plus IL-4-induced IgE production, but anti-IL-4 totally blocked their effect. IgE production via CD40 was not due to IL-5, IL-6 or nerve growth factor as none of these synergized with IL-4 to induce IgE synthesis by purified B cells. Finally, we observed that CD40 stimulation alone could enhance IgE production from in vivo-driven IgE-producing cells from patients with very high IgE levels; cells that did not increase IgE production in response to IL-4. Taken together, our data suggest that the signals delivered for IgE production by IL-4 and CD40 stimulation may mimic the pathway for IgE production seen in vivo in human allergic disease.     

Preparation of target antigens specifically recognized by human natural killer cells

In an attempt to identify target cell membrane molecules recognized by natural killer (NK) cells, artificial membranes were prepared from detergent-solubilized plasma membranes of NK target cells and synthetic lipids. Such reconstituted membranes from human and rat NK target cells were shown to inhibit both human and rat NK-target cell conjugates in a species-specific fashion; these reconstituted membranes failed to inhibit NK cytotoxicity. The detergent-solubilized material from the human NK target K562 was subjected to various procedures prior to reconstitution and the conjugate inhibition assay. Conjugate inhibitory activity was lost upon trypsin digestion and incubation at 65 degrees C. This inhibition activity was absorbed to concanavalin A agarose and could subsequently be eluted with alpha-methylmannoside, resulting in approximately 20-fold purification. Gel filtration of this material on an AcA-34 column in detergent gave a broad activity peak with maximal activity in the molecular weight range of 30,000-165,000. Gel electrophoresis of purified membranes demonstrated multiple molecular weight bands in lipid membranes. The K562 membrane material, purified by concanavalin A agarose and gel filtration, inhibited conjugates between human NK cells and any of four human target cells, but not of conjugates with (1) human large granular lymphocytes and antibody-coated mouse tumor cells nor (2) rat NK cells and their target cells. Thus the purified glycoproteins from K562 retain the property of specific inhibition of human NK-target conjugates.     

Topoisomerase activity is associated with purified SV40 T antigen.

Purified SV40 T antigen has been assayed for topoisomerase activity. The ability to relax negatively-supercoiled SV40 DNA was found in preparations of T antigen purified either from human 293 cells infected with Ad5-SVR111 virus or from insect Sf9 cells infected with recombinant baculovirus 941T. The T antigen-associated relaxing activity was stimulated by MgCl2 and was not dependent on ATP, suggesting that it is not due to cellular topoisomerase II. The topoisomerase activity was immunoprecipitated by a monoclonal antibody specific for T antigen, but not by a control monoclonal antibody. In addition, immunoblotting of purified T antigen from human 293 cells with antihuman topoisomerase I and anti-human topoisomerase II antibodies failed to detect cellular topoisomerases I or II. Sedimentation analysis of purified T antigen revealed that the topoisomerase activity co-sedimented with the hexameric form of T antigen at 23S. The topoisomerase activity is, therefore, either inherent to T antigen or due to a cellular topoisomerase I tightly bound to, and co-purifying with, T antigen.     

Purification and properties of an endothelial cell growth factor from human platelets

An endothelial cell growth factor has been purified about 1,000,000-fold to homogeneity from human platelets by a seven-step procedure. The purified product has an apparent Mr on sodium dodecyl sulfate-polyacrylamide gels of 45,000. The mobility in sodium dodecyl sulfate gel electrophoresis was similar in the presence or absence of reducing agents, indicating that the factor consists of a single polypeptide chain. Maximal stimulation by the purified protein was achieved at a concentration of about 20 ng/ml (440 pM). Heparin did not potentiate the activity, nor did the factor bind to heparin immobilized on Sepharose. The purified factor was heat- and acid-labile; it was active on porcine and human endothelial cells, but not on human foreskin fibroblasts. Chromatofocusing revealed that the pI of the factor was 4.6. The structural and functional characteristics of the platelet-derived endothelial cell growth factor are distinct from previously characterized endothelial cell mitogens with affinities for heparin.     

Biosynthesis of lactosylceramide and paragloboside by human lactose synthase A protein

Lactosylceramide and paragloboside were synthesized from their precursor glycolipids and UDP-galactose by lactose synthase A protein [UDP-Gal : GlcNAc beta-4-galactosyltransferase, EC 2.4.1.22] purified to homogeneity from human plasma. The partially purified human liver enzyme and an extract from human lymphoblastoid cells also exhibited the above activities. Rabbit antibody against the purified human plasma lactose synthase A protein neutralized the glycolipid synthesis activity as well as the activity for lactose synthesis by the enzyme preparations from plasma, liver and lymphoblastoid cells. These results suggest that lactose synthase A protein existing in plasma, liver and lymphoblastoid cells can synthesize not only lactose but also lactosylceramide and paragloboside in vitro. The enzyme could play a role in the synthesis of these two glycolipids in vivo.     

A growth inhibitory protein secreted by human diploid fibroblasts. Partial purification and characterization

We have identified and partially purified a growth inhibitor protein secreted by human diploid fibroblast cells. This protein is not secreted constitutively but only after induction with the double stranded hetero duplex polyriboinosinic:polyribocytidylic acid. The growth inhibitory activity has been purified 3,800-fold and has an estimated molecular mass of 12,000 daltons. The protein will inhibit the growth in culture of human diploid fibroblast cells, human cells derived from tumors, and mouse L cells. Although interferon-beta is secreted with the growth inhibitory protein, the partially purified growth inhibitory protein has no antiviral activity, and its activity is not neutralized by antibodies to interferon-alpha, interferon-beta, and interferon-gamma. We believe this growth inhibitory activity to reside in a newly defined protein and have named it fibroblast-derived growth inhibitor.     

A novel cell surface antigen, 4C8, is expressed on human eosinophils

BACKGROUND: A novel monoclonal antibody, anti-4C8, reacted with human peripheral lymphocytes and monocytes but not with neutrophils. In this study, we investigated whether the 4C8 antigen is expressed on human peripheral eosinophils. METHODS: Expression of the 4C8 antigen on eosinophils was analyzed by flow cytometry and molecular analysis of the antigen was performed with eosinophils by Western blotting. RESULTS: Among human peripheral granulocytes, the 4C8 antigen was expressed on CD16-negative cells but not on CD16-positive cells. The 4C8 antigen also appeared to be expressed on eosinophils. To confirm the latter finding, eosinophils were purified from peripheral blood. On flow cytometric analysis, anti-4C8 antibody reacted with purified eosinophils. On Western blotting analysis, anti-4C8 reacted with a single band of 80 kDa in lysates from purified eosinophils. The correlation between the percentage of eosinophils determined by May-Giemsa staining and the percentage of 4C8-positive/CD16-negative cells among granulocytes was good (r = 0.91, P < 0.0001). CONCLUSIONS: Only a few cell surface antigens are available to distinguish human peripheral eosinophils from neutrophils. The novel cell surface antigen, 4C8, is a useful new marker of human eosinophils.     

Rabbit B spleen lymphocytes and T helper cells. I. Responsiveness to mitogens of B cell subpopulations of different sedimentation velocities and subpopulations bearing or lacking Fcgamma receptors.

The response to anti-allotype (anti-Ab4), Nocardia Water Soluble Mitogen (NWSM), pneumococcal polysaccharide type III (SSS III), and human Fc fragments of various purified and unfractionated rabbit spleen cell populations was determined in terms of 3H-thymidine up-take. B cells were isolated either from untreated suspensions of spleen cells or from suspensions from which adherent and phagocytic cells were removed. The purification factor was greater than the enhancement of 3H-thymidine uptake by anti-Ab4, NWSM, and SSS III as compared with the response of unfractionated spleen cells. It thus appears that a helper cell was involved: the mitogen response of purified B cells was enhanced by the addition of T cells. B subpopulations were separated by sedimentation or by rosetting, which allowed us to separate Fcgamma receptor-bearing cells from cells that did not possess this receptor. There were differences between cells responding to B mitogens not only in sedimentation velocity but also in the absolute number of cells. B cells bearing the Fcgamma receptor were less responsive to anti-Ab4 and more responsive to SSS III, NWSM, and human Fc than were B cells lacking the Fcgamma receptor.     

Induction of interferon-gamma production by human natural killer cells stimulated by hydrogen peroxide

Interferon (IFN)-inducing activity of hydrogen peroxide in human peripheral mononuclear cells was investigated. Among the mononuclear cells, purified nonadherent cells produced IFN, but not B cells and monocytes. The maximal titer of IFN by purified nonadherent cells was observed after a 72-hr cultivation in the presence of 10(-2) mM H2O2 without affecting their viability. Furthermore, the purified nonadherent cells, but not the unpurified mononuclear cells, showed an augmented cytotoxicity to K562 when stimulated with hydrogen peroxide. By using Percoll discontinuous density gradient centrifugation, peripheral blood nonphagocytic and nonadherent mononuclear cells were divided into the low and high density fractions for which natural killer (NK) cells and T cells were enriched, respectively. The NK-enriched low density fractions, but not the T cell-enriched high density fractions, showed IFN production by the stimulation of hydrogen peroxide. IFN production as well as large granular lymphocytes and HNK-1+, Leu-11+ cells of the NK-enriched fractions were abrogated by treatment of the cells with monoclonal antibody against human NK cells (HNK-1+) but not against T cells (OKT3) in the presence of complement. Moreover, hydrogen peroxide-inducing IFN production seems to be regulated by monocytes. The antiserum neutralizing IFN-alpha and IFN-beta failed to neutralize substantially IFN-produced NK cells. The treatment with either pH 2 or antiserum-neutralizing human IFN-gamma resulted in marked reduction, indicating that a major part of IFN was IFN-gamma. The purified nonadherent cells showed IFN production and augmented cytotoxicity when cultured separately from activated macrophages by opsonized zymosan; furthermore, both IFN production and enhancement of cytotoxicity were abrogated by catalase. These results suggest that both exogenous and endogenous hydrogen peroxide might be responsible for a part of immunoregulation.     

Characterization of lysozyme synthesized by differentiated mouse myeloid leukemia cells.

Lysozyme was induced by dexamethasone during normal differentiation of cultured mouse myeloid leukemia cells (M1) to macrophages and granulocytes. A large amount of lysozyme was produced by macrophage-like line cells (Mm-1), established from spontaneously differentiated macrophage-like cells from a clonal line of M1 cells. Lysozyme purified from the culture medium of these Mm-1 cells (Mm-1 lysozyme) had a molecular weight of 15,000, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and showed maximal activity at pH 6.6 with an optimal NaCl concentration of 0.04 M. Its mobility on polyacrylamide gel electrophoresis at pH 4.5 was distinctly lower than those of lysozymes from hen egg white and human urine. Rabbit anti-Mm-1 lysozyme serum inhibited the activities of lysozyme preparations from peritoneal macrophages of normal mice and rats and dexamethasone-induced differentiated M1 cells, but not those of preparations from hen egg white and human urine. Lysozyme was also purified from normal mouse lung, which is rich in alveolar macrophages and was found to be similar to lysozyme purified from the culture medium of Mm-1 cells in size and electrophoretic mobility and in its pH optimum, trypsin peptide map, and antigenicity. Thus the molecular structure of the lysozyme induced in differentiated mouse myeloid leukemia cells is similar to that of lysozyme produced by normal cells.     

The degradation of bovine parathyroid hormone by leukocytes

Human peripheral leukocytes catalyse an elastase-like cleavage of bovine parathyroid hormone, with an identical specificity to that previously observed with a neutral proteinase (EC 3.4.21-) isolated from the outer surface of plasma membranes from human leukocytes. Parathyroid hormone is not hydrolysed by human erythrocytes, and polymorphonuclear leukocytes are much more effective in hormone degradation than lymphocytes. Despite the fact that purified human leukocyte granular elastase (EC 3.4.21.37) catalyses an identical cleavage reaction, the hydrolysis observed with intact cells is clearly not due to proteinases secreted by the cells. The reaction is inhibited by human serum and by purified human alpha-1-antitrypsin, but not by antibodies to human leukocyte granular elastase. The possible significance of these phenomena to the in vivo metabolism of parathyroid hormone are discussed.     

Functional activities of acidic isoferritins and lactoferrin in vitro and in vivo

The functional activities of acidic isoferritins (AIF) and lactoferin (LF) were evaluated. The inhibitory activity of AIF (AIFIA) was inactivated by preincubation with a monoclonal antibody (2A4) against AIF, but AIFIA was not inactivated by another monoclonal antibody against AIF (1C5), by a monoclonal antibody (3A5) against basic isoferritins, or by a heteroantiserum (LFT) against basic isoferritins. Monoclonal 2A4 also inactivated the inhibitory activity against colony formation by granulocyte-macrophage (CFU-GM) progenitor cells that was constitutively released by human monocytes or induced by human monocytes in the presence of OKT4+ lymphocytes. In addition to OKT4+ lymphocytes, the release of AIFIA from human monocytes was modulated by iron-saturated human LF and OKT8+ lymphocytes, both of which suppressed the release of AIFIA. Evidence for the physiologic relevance of AIF as a regulator of myelopoiesis was presented, in that human AIF suppressed the numbers of CFU-GM, BFU-E, and CFU-GEMM per femur and the cycling status of these cells in mice recovering from a sublethal dosage of Cytoxan. Abnormalities in LF and AIF interactions were found with cells from a pediatric patient with neutrophilia of unknown etiology that were consistent with the disease manifestations of neutrophilia. Polymorphonuclear neutrophils (PMN) from the patient contained low levels (1%-10% of control) of immunologically reactive LF and the LF found was ineffective as a suppressor molecule for the release of GM-CSF from normal mononuclear blood cells. In addition, the patient's GM-CSF releasing mononuclear blood cells were insensitive to the suppressive effects of purified LF, and colony formation by the patient's CFU-GM, but not BFU-E or CFU-GEMM, were insensitive to the suppressive effects of purified AIF. When the activity of purified AIF was assessed against mouse bone marrow cells under serum-free conditions, it was apparent that serum was not needed for the suppressive activity of AIF and that in some cases, serum actually masked the effects of AIF. Human monoblast cell line U937 was found to be a good model in vitro for the actions of LF and AIF; U937 cells induced for Ia-antigens by human gamma interferon were separated into populations of Ia-antigen+ and Ia-antigen- cells by fluorescence activated cell sorting (FACS), and LF and AIF suppressed colony formation only by the Ia-antigen+ U937 cells. A comparative analysis of bovine and human LF against release of GM-CSF from human mononuclear cells demonstrated that both were active in their iron-saturated form.(ABSTRACT TRUNCATED AT 400 WORDS)     

Purification and characterization of a protein antigen (p94) from human brain and its identification in other species.

A protein antigen was chromatographically purified from human brain by its immunoaffinity to 44E3 monoclonal IgG and its chemical nature was investigated. The yield of antigen was estimated at 71%, and a 3160-fold purification was achieved relative to the homogenate. The antigen preparation from brain showed a very high degree of purity when analysed by SDS/polyacrylamide-gel electrophoresis and was composed of a single polypeptide of Mr 94,000. Amino-sugar and neutral-sugar analyses indicated that the protein was not glycosylated. The amino acid composition of the purified protein from brain was compared with that of the analogous protein purified from an acute-lymphoblastic-leukaemic cell line, HOON. The compositions were very similar, suggesting that the two proteins were closely related. Both purified proteins were equivalent in their ability to inhibit the reactivity of monoclonal antibodies 44E3 and 44H4 with leukaemic cells. These two antibodies appear to recognize spatially related, if not identical, epitopes on the same molecule. The antibodies were shown to cross-react with a polypeptide of Mr 94,000 in homogenates of human, bovine and guinea-pig brain white matter. Indirect immunoperoxidase staining of human grey- and white-matter acetone-fixed tissue sections incubated with either antibody indicated that the antigen was present on neuronal and glial cells; the staining was seen as clusters in the cytoplasm, starting at the plasma membrane, but leaving the nucleus unstained. The concentration of the protein in human brain was shown to be similar throughout postnatal development and aging.     

High-quality RNA and DNA from flow cytometrically sorted human epithelial cells and tissues

Microarray technologies have made possible comprehensive analyses of nucleic acid sequence and expression. However, the technology to obtain efficiently high-quality RNA and DNA suitable for array analysis from purified populations of neoplastic cells from human tissues has not been well addressed. Microdissection can enrich for populations of cells present in various tumor tissues, but it is not easily automated or performed rapidly, and there are tissues in which cells of interest cannot be readily isolated based on morphologic criteria alone. Here we describe a protocol for efficient RNA and DNA isolation from flow cytometrically purified whole epithelial cells from primary tissue. The aqueous reagent, RNAlater, which preserves RNA, allows immunolabeling and purification of whole epithelial cells by flow sorting without special instrument preparation to reduce RNase activity. We used real-time PCR to determine RNA quality afterflow sorting. High-quality RNA and DNA suitable for expression and genotype analysis can be readily obtained from flow cytometrically purified populations of neoplastic cells from human tissues.     

Characterization of recombinant human granulocyte-colony-stimulating factor produced in mouse cells.

Mouse C127I cells were transformed with a chimeric plasmid consisting of bovine papillomavirus DNA and human granulocyte-colony-stimulating factor (G-CSF) cDNA placed under the control of the SV40 early promoter. The transformed cells secreted constitutively a high level of human G-CSF, 10-20 micrograms/ml in a low-serum medium. The secreted G-CSF has been purified to homogeneity by a two-step procedure including gel filtration and hydrophobic column chromatography. The purified recombinant G-CSF runs as a single band with an apparent Mr of 19,000 on a polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. This value corresponds to that of the native human G-CSF purified from the medium conditioned by human carcinoma CHU-2 cells. The recombinant human G-CSF was as active as native G-CSF in vitro in supporting proliferation of mouse NFS-60 cells and stimulating colony formation from human as well as mouse bone marrow cells. When the recombinant human G-CSF was subcutaneously administrated into mice, a remarkable stimulation of granulopoiesis and splenomegaly was observed.     

In vitro response of subpopulations of human lymphocytes. II. DNA synthesis induced by anti-immunoglobulin antibodies.

A significant and constant increase in DNA synthesis was observed in human lymphocytes cultured in the presence of purified anti-immunoglobulin antibodies specific for human IgG, IgA, and IgM. This has been found in cultures of lymphocytes isolated from blood, tonsils, spleen, and lymph nodes. The optimal culture conditions for blood and tonsil lymphocytes were determined. As a rule 6-day cultures containing 2 x 10(6) cells/ml and 100 mug/ml of antibody yielded the highest 3H-thymidine uptake. Purified T cell cultures could not be stimulated, whereas a low response could be observed in most of the purified B cell cultures. Optimal culture conditions were the same for the B and total tonsil lymphocytes. However, when the purified B cells were totally depleted of T cells, no response was observed. A T and B cell synergy has been demonstrated by supplementing B cell cultures with purified T cells, whether treated or not with mitomycin. These experiments indicated a permissive and potentiating effect of T cells on the B cell response. Cultures containing mitomycin-treated B cells and purified T cells (mB + T) could be stimulated by a-Ig, thus indicating a T cell proliferation. In keeping with this finding was the observation of an increased response of total lymphocytes supplemented with T cells but not with B cells. Adherent cells are necessary for an optimal response to a-Ig; they enhanced the B cell proliferation observed in (Tm + B) cultures and suppressed the response of T cells in (T + Bm) cultures.     

Purification of a cell growth factor from a human lung cancer cell line: Its relationship with ferritin

We have purified a cell growth factor from a human lung cancer cell line, T3M-30, which was established in a protein-free chemically defined medium. The factor, designated carcinoma-derived growth factor (CD-GF), stimulated proliferation of a variety of cells, including human leukemia cells, HL-60, and melanoma cells, SK-28. Half-maximum stimulation by the purified CD-GF was achieved at a concentration of 40 ng/ml. In the purified CD-GF, two major protein bands of 24 kDa and 22 kDa were identified on a SDS polyacrylamide gel. The partial amino acid sequences of the 24 kDa protein were determined from two peptide fragments obtained by V8 protease treatment. The partial sequences were identical to those of heavy chain of human ferritin. The activity of the purified CD-GF was coprecipitated completely with a monoclonal antibody to heavy chain of ferritin. Ferritin has been considered to inhibit cell growth. However, human heart ferritin was capable of stimulating the growth of HL-60 cells. These results suggest that CD-GF is related to feritin and ferritin is a growth factor of HL-60 leukemia cells. © 1994 Wiley-Liss, Inc.     

Monoclonal antibodies to bovine and human acrosin

Monoclonal antibodies to human acrosin were required for studies of immunological interference with fertilization. Since human acrosin was not available in adequate amounts, monoclonal antibodies have been raised in mice against purified bovine acrosin and screened for cross-reaction with human sperm cells. Two of these antibodies are described, B4F6 and C2E5. Data from enzyme-linked immunosorbent assays, immunoblots, immunoprecipitation, and indirect immunofluorescence on sperm cells indicate that B4F6 binds only to bovine acrosin, and that C2E5 binds both to bovine and to human acrosin at a conformationally determined epitope. The antibodies do not inhibit the hydrolysis of benzoylarginine ethyl ester by acrosin, but C2E5 did inhibit the dissolution of the hamster zona pellucida by purified human acrosin. The antibodies have also been used for affinity purification of acrosin and proacrosin.     

THE EFFECT OF HUMAN ENDOTHELIAL CELL-DERIVED PROTEOGLYCANS ON HUMAN SMOOTH MUSCLE CELL GROWTH

Extracellular proteoglycans (PGs) purified from cultured human arterial endothelial cells were tested for their effects on the proliferation of human vascular smooth muscle cells (VSMC). Fractions containing perlecan, the basement membrane heparan sulphate (HS) PG, the large chondrotin sulphate (CS) proteoglycan from connective tissue and other immunoreactive CS did not inhibit the proliferation of human VSMC. Native endothelial extracellular matrix, which was shown to contain the same PGs, demonstrated a pronounced stimulatory effect on the proliferation of human VSMCs. This stimulatory effect was not removed by pre-incubation of the matrix with 1M NaCl, heparin, platelet extract or plasmin. These experiments demonstrate that PGs produced by human arterial endothelial cells do not inhibit the proliferation of VSMC. These data do not support the hypothesis that human endothelial cells, in vivo control the activation or proliferation of VSMCs directly by the secretion of a non-proliferative molecule. Instead they support the hypothesis that the endothelial cells counteract intimal hyperplasia of VSMC indirectly by providing a barrier from activating factors in the plasma.