PubMed Health⌕ Search

Biomedical subjects

T N Wight

Publications and source records attributed to T N Wight.

At least 19 recordsLinked to original sources

Platelet-derived growth factor stimulates the formation of versican-hyaluronan aggregates and pericellular matrix expansion in arterial smooth muscle cells.

Hyaluronan and versican-rich pericellular matrices form around arterial smooth muscle cells (ASMC) preferentially during the detachment phase of proliferation and migration. PDGF is a potent mitogen and chemotactic agent for ASMC and also stimulates the production of extracellular matrix molecules which may regulate the proliferative and migratory capacity of the cells. We have examined the effect of PDGF on the formation of hyaluronan-dependent pericellular matrices, and on the synthesis and interaction of several major pericellular coat constituents. As demonstrated using a particle exclusion assay, PDGF stimulated the formation of pericellular matrices and was seen both in an increased proportion of cells with a coat and a greater coat size. This increase was accompanied by a transient increase in hyaluronan synthase 2 (HAS2) expression and an increase in hyaluronan synthesis and polymer length. PDGF also increased the synthesis of versican and link protein as measured at the mRNA and protein levels. The amount of native versican-hyaluronan aggregates and link-stabilized aggregate was also increased following PDGF treatment. Time lapse imaging showed that pericellular matrix formation occurred around trailing cell processes prior to their detachment. These data suggest that PDGF modulates the synthesis and organization of ASMC pericellular coat-forming molecules such as versican, hyaluronan, and link protein, which leads to extracellular matrix expansion and alterations in ASMC phenotype.

Aorta↗

Mechanical strain induces specific changes in the synthesis and organization of proteoglycans by vascular smooth muscle cells.

In the mechanically active environment of the artery, cells sense mechanical stimuli and regulate extracellular matrix structure. In this study, we explored the changes in synthesis of proteoglycans by vascular smooth muscle cells in response to precisely controlled mechanical strains. Strain increased mRNA for versican (3.2-fold), biglycan (2.0-fold), and perlecan (2.0-fold), whereas decorin mRNA levels decreased to a third of control levels. Strain also increased versican, biglycan, and perlecan core proteins, with a concomitant decrease in decorin core protein. Deformation did not alter the hydrodynamic size of proteoglycans as evidenced by molecular sieve chromatography but increased sulfate incorporation in both chondroitin/dermatan sulfate proteoglycans and heparan sulfate proteoglycans (p < 0.05 for both). Using DNA microarrays, we also identified the gene for the hyaluronan-linking protein TSG6 as mechanically induced in smooth muscle cells. Northern analysis confirmed a 4.0-fold increase in steady state mRNA for TSG6 following deformation. Size exclusion chromatography under associative conditions showed that versican-hyaluronan aggregation was enhanced following deformation. These data demonstrate that mechanical deformation increases specific vascular smooth muscle cell proteoglycan synthesis and aggregation, indicating a highly coordinated extracellular matrix response to biomechanical stimulation.

Aorta↗

Versican V1 proteolysis in human aorta in vivo occurs at the Glu441-Ala442 bond, a site that is cleaved by recombinant ADAMTS-1 and ADAMTS-4.

Mature human aorta contains a 70-kDa versican fragment, which reacts with a neoepitope antiserum to the C-terminal peptide sequence DPEAAE. This protein therefore appears to represent the G1 domain of versican V1 (G1-DPEAAE(441)), which has been generated in vivo by proteolytic cleavage at the Glu(441)-Ala(442) bond, within the sequence DPEAAE(441)-A(442)RRGQ. Because the equivalent aggrecan product (G1-NITEGE(341)) and brevican product (G1-EAVESE(395)) are generated by ADAMTS-mediated cleavage of the respective proteoglycans, we tested the capacity of recombinant ADAMTS-1 and ADAMTS-4 to cleave versican at Glu(441)-Ala(442). Both enzymes cleaved a recombinant versican substrate and native human versican at the Glu(441)-Ala(442) bond and the mature form of ADAMTS-4 was detected by Western analysis of extracts of aortic intima. We conclude that versican V1 proteolysis in vivo can be catalyzed by one or more members of the ADAMTS family of metalloproteinases.

ADAM Proteins↗

Perlecan inhibits smooth muscle cell adhesion to fibronectin: role of heparan sulfate.

Smooth muscle cell migration, proliferation, and deposition of extracellular matrix are key events in atherogenesis and restenosis development. To explore the mechanisms that regulate smooth muscle cell function, we have investigated whether perlecan, a basement membrane heparan sulfate proteoglycan, modulates interaction between smooth muscle cells and other matrix components. A combined substrate of fibronectin and perlecan showed a reduced adhesion of rat aortic smooth muscle cells by 70-90% in comparison to fibronectin alone. In contrast, perlecan did not interfere with cell adhesion to laminin. Heparinase treated perlecan lost 60% of its anti-adhesive effect. Furthermore, heparan sulfate as well as heparin reduced smooth muscle cell adhesion when combined with fibronectin whereas neither hyaluronan nor chondroitin sulfate had any anti-adhesive effects. Addition of heparin as a second coating to a preformed fibronectin matrix did not affect cell adhesion. Cell adhesion to the 105- and 120 kDa cell-binding fragments of fibronectin, lacking the main heparin-binding domains, was also inhibited by heparin. In addition, co-coating of fibronectin and (3)H-heparin showed that heparin was not even incorporated in the substrate. Morphologically, smooth muscle cells adhering to a substrate prepared by co-coating of fibronectin and perlecan or heparin were small, rounded, lacked focal contacts, and showed poorly developed stress fibers of actin. The results show that the heparan sulfate chains of perlecan lead to altered interactions between smooth muscle cells and fibronectin, possibly due to conformational changes in the fibronectin molecule. Such interactions may influence smooth muscle cell function in atherogenesis and vascular repair processes.

Animals↗

Biglycan, a vascular proteoglycan, binds differently to HDL2 and HDL3: role of apoE.

Lipoprotein retention by vascular extracellular matrix proteoglycans is important in atherogenesis. Proteoglycans bind apolipoprotein (apo)B- and apoE-containing lipoproteins. However, the colocalization of apoA-I and apoE with biglycan in atherosclerotic lesions suggests that vascular proteoglycans also may trap high density lipoproteins (HDLs). Because the major HDL subclasses may be atheroprotective to different degrees, we investigated the role of apoE in mediating HDL(2) and HDL(3) binding to the extracellular vascular proteoglycan, biglycan. ApoE-free HDL(2) and HDL(3) did not bind to purified [(35)S]SO(4)-biglycan, whereas apoE-containing HDL(2) and HDL(3) (HDL+E) did. The extent of binding correlated positively with the apoE content for both HDL(2) and HDL(3), although HDL(2)+E had a 3.5-fold higher affinity than did HDL(3)+E. ApoE on HDL(3) was cleaved into 22- and 12-kDa fragments, whereas apoE on HDL(2) remained intact. These results suggest that the cleaved apoE on HDL(3) results in diminished biglycan binding of HDL(3)+E relative to HDL(2)+E. Reducing positive charges on lysine and arginine residues on HDL+E eliminated biglycan binding, suggesting an ionic interaction. Thus, apoE is an important determinant of HDL binding to extracellular vascular proteoglycans and may play a role in HDL retention in the artery wall.

Apolipoprotein A-I↗

Retroviral overexpression of decorin differentially affects the response of arterial smooth muscle cells to growth factors.

Decorin is a member of the family of small leucine-rich proteoglycans that are present in blood vessels and synthesized by arterial smooth muscle cells (ASMCs). This proteoglycan accumulates in topographically defined regions of atherosclerotic lesions and may play a role in the development of this disease. However, little is known about whether decorin has specific effects on the cellular events that contribute to atherosclerotic lesion formation. In the present study, rat ASMCs were transduced with a retroviral vector (LDSN) that carries the bovine decorin gene. Compared with vector control cells (LXSN), these cells constitutively overexpress decorin, as verified by Northern and Western analysis and by metabolic labeling. Experiments were performed to examine the responsiveness of decorin-overexpressing rat ASMCs to platelet-derived growth factor (PDGF) and transforming growth factor-beta1 (TGF-beta1), 2 growth factors that affect cell proliferation and extracellular matrix production in atherosclerosis. Decorin-overexpressing cells had decreased [(3)H]thymidine incorporation into DNA and increased the levels of the cyclin-dependent kinase inhibitors p21 and p27 in the first 24 hours of response to serum and PDGF-BB. However, these effects of decorin were not apparent at 48 or 72 hours after plating and did not result in reduced growth of decorin-overexpressing cells in response to serum and PDGF-BB. In contrast, the growth response of decorin-overexpressing ASMCs to TGF-beta1, as well as the expression of TGF-beta1-responsive genes, such as plasminogen activator inhibitor-1 and versican (an extracellular matrix proteoglycan), was diminished. These results indicate that decorin selectively inhibits the responsiveness of rat ASMCs to TGF-beta1 and suggests that the induction of constitutive decorin overexpression by ASMCs in vivo may have therapeutic value in the inhibition of TGF-beta1-mediated effects on the development of atherosclerotic lesions.

Animals↗

Oxidized LDL bind to nonproteoglycan components of smooth muscle extracellular matrices.

Arterial wall lipid retention is believed to be due primarily to ionic interactions between lipoproteins and proteoglycans. Thus, oxidized low density lipoproteins (LDL), with decreased positive charge relative to native LDL, should have decreased interaction with negatively charged proteoglycans. However, oxidized LDL does accumulate within arterial lesions. Therefore, this study investigated the binding of native and oxidized LDL to a complex smooth muscle extracellular matrix and the role of ionic charge interactions in their binding. LDL was modified with 2,2-azo-bis(2-amidinopropane)-2HCl, hypochlorite, soybean lipoxygenase, and phospholipase or copper sulfate. The extracellular matrix had 15- to 45-fold greater binding capacity for the different forms of oxidized LDL than for native LDL. However, the affinity of binding for all forms of oxidized LDL was high (K(a) = approximately 10(-9) M) and was similar to that for native LDL. Preincubation of the lipoproteins with chondroitin sulfate decreased the binding of native LDL, but had no effect on the binding of oxidized LDL. Digestion of matrices with chondroitin ABC lyase and heparinase decreased the binding of native LDL, but increased the binding of oxidized LDL; matrix digestion with pronase or trypsin markedly reduced the binding of both native and oxidized LDL.Thus, the binding of native LDL involves matrix proteoglycans, whereas the binding of oxidized LDL involves a nonproteoglycan component(s) of the matrix. The markedly enhanced retention of oxidized LDL compared with native LDL may play an important role in the progression of atherosclerosis.

Animals↗

Retrovirally mediated expression of decorin by macrovascular endothelial cells. Effects on cellular migration and fibronectin fibrillogenesis in vitro.

Decorin is a member of the widely expressed family of small leucine-rich proteoglycans. In addition to a primary role as a modulator of extracellular matrix protein fibrillogenesis, decorin can inhibit the cellular response to growth factors. Decorin expression is induced in endothelial cells during angiogenesis, but not when migration and proliferation are stimulated. Thus, decorin may support the formation of the fibrillar pericellular matrix that stabilizes the differentiated endothelial phenotype during the later stages of angiogenesis. Therefore, we tested whether constitutive decorin expression alone could modify endothelial cell migration and proliferation or affect pericellular matrix formation. To this end, replication-defective retroviral vectors were used to stably express bovine decorin, which was detected by Northern and Western blotting. The migration of endothelial cells that express decorin is significantly inhibited in both monolayer outgrowth and microchemotaxis chamber assays. The inhibition of cell migration by decorin was not accompanied by decreased proliferation. In addition, endothelial cells that express decorin assemble an extensive fibrillar fibronectin matrix more rapidly than control cells as assessed by immunocytochemical and fibronectin fibrillogenesis assays. These observations suggest that cell migration may be modulated by the influence of decorin on the assembly of the cell-associated extracellular matrix.

Animals↗

Local expression of bovine decorin by cell-mediated gene transfer reduces neointimal formation after balloon injury in rats.

Decorin is an extracellular matrix (ECM) proteoglycan that may modify vascular smooth muscle cell (SMC) function by altering the response to growth factors and the accumulation of ECM proteins during vascular injury. To investigate these possibilities in vivo, decorin was overexpressed at the site of arterial injury by cell-mediated gene transfer. Fischer rat SMCs were transduced in vitro with a retroviral construct that contained the bovine decorin gene and were subsequently seeded into injured rat carotid arteries. A species-specific antibody to bovine decorin and polymerase chain reaction primers were used to detect bovine decorin and distinguish it from endogenous rat decorin. Immunohistochemical and Northern analyses of rat carotid arteries revealed only low levels of rat decorin expression up to 8 weeks after balloon injury. However, after cell-mediated transfer of bovine decorin, strong expression of bovine decorin was verified by immunohistochemistry and reverse transcriptase-polymerase chain reaction. Four weeks after injury, the intimal area in vessels seeded with bovine decorin-overexpressing SMCs was significantly reduced by 35+/-4% (mean+/-SEM, n=9; P<0.01). Decorin overexpression also induced a higher intimal nuclear density and decreased volume of ECM. Specifically, immunostaining for versican and fibronectin was markedly reduced. In contrast, immunostaining for collagen type I was increased, and electron microscopy confirmed that collagen accumulation was altered. Bromodeoxyuridine labeling indicated that intimal SMC proliferation was not affected by the expression of bovine decorin. In summary, we demonstrate that gene transfer of the ECM proteoglycan, decorin, into the injured arterial wall reduces intimal ECM volume and alters the composition of the ECM.

Animals↗

Oxidized low density lipoproteins regulate synthesis of monkey aortic smooth muscle cell proteoglycans that have enhanced native low density lipoprotein binding properties.

Oxidized low density lipoproteins (Ox-LDL) affect several biological processes involved in atherogenesis. However, it is not known whether Ox-LDL can regulate proteoglycan expression and thus affect arterial wall lipoprotein retention. This study evaluated whether Ox-LDL, as compared with native LDL, regulates proteoglycan expression by monkey arterial smooth muscle cells in vitro and whether proteoglycans synthesized in the presence of Ox-LDL exhibit altered lipoprotein binding properties. Ox-LDL stimulated glycosaminoglycan synthesis, as measured by (35)SO(4) incorporation, by 30-50% over that of native LDL. The effect was maximal after 72 h of exposure to 5 microg/ml of Ox-LDL. The molecular sizes of versican, biglycan, and decorin increased in response to Ox-LDL, as indicated by size exclusion chromatography and SDS-polyacrylamide gel electrophoresis. These effects could be mimicked by the lipid extract of Ox-LDL. These size increases were largely due to chain elongation and not to alterations in the ratio of (35)SO(4) to [(3)H]glucosamine incorporation. Affinity chromatography indicated that Ox-LDL stimulated the synthesis of proteoglycans with high affinity for native LDL. Ox-LDL also specifically stimulated mRNA expression for biglycan (but not versican or decorin), which was correlated with increased expression of secreted biglycan. Thus, Ox-LDL may influence lipoprotein retention by regulating synthesis of biglycan and also by altering glycosaminoglycan synthesis of vascular proteoglycans so as to enhance lipoprotein binding properties.

Animals↗

Cell density-dependent regulation of proteoglycan synthesis by transforming growth factor-beta(1) in cultured bovine aortic endothelial cells.

The regulation of vascular endothelial cell behavior during angiogenesis and in disease by transforming growth factor-beta(1) (TGF-beta(1)) is complex, but it clearly involves growth factor-induced changes in extracellular matrix synthesis. Proteoglycans (PGs) synthesized by endothelial cells contribute to the formation of the vascular extracellular matrix and also influence cellular proliferation and migration. Since the effects of TGF-beta(1) on vascular smooth muscle cell growth are dependent on cell density, it is possible that TGF-beta(1) also directs different patterns of PG synthesis in endothelial cells at different cell densities. In the present study, dense and sparse cultures of bovine aortic endothelial cells were metabolically labeled with [(3)H]glucosamine, [(35)S]sulfate, or (35)S-labeled amino acids in the presence of TGF-beta(1). The labeled PGs were characterized by DEAE-Sephacel ion exchange chromatography and Sepharose CL-4B molecular sieve chromatography. The glycosaminoglycan M(r) and composition were analyzed by Sepharose CL-6B chromatography, and the core protein M(r) was analyzed by SDS-polyacrylamide gel electrophoresis, before and after digestion with papain, heparitinase, or chondroitin ABC lyase. These experiments indicate that the effect of TGF-beta(1) on vascular endothelial cell PG synthesis is dependent on cell density. Specifically, TGF-beta(1) induced an accumulation of small chondroitin/dermatan sulfate PGs (CS/DSPGs) with core proteins of approximately 50 kDa in the medium of both dense and sparse cultures, but a cell layer-associated heparan sulfate PG with a core protein size of approximately 400 kDa accumulated only in dense cultures. Moreover, only in the dense cell cultures did TGF-beta(1) cause CS/DSPG hydrodynamic size to increase, which was due to the synthesis of CS/DSPGs with longer glycosaminoglycan chains. The heparan sulfate PG and CS/DSPG core proteins were identified as perlecan and biglycan, respectively, by Western blot analysis. The present data suggest that TGF-beta(1) promotes the synthesis of both perlecan and biglycan when endothelial cell density is high, whereas only biglycan synthesis is stimulated when the cell density is low. Furthermore, glycosaminoglycan chains are elongated only in biglycan synthesized by the cells at a high cell density.

Amino Acids↗

Detection of dissection and remodeling of atherosclerotic lesions in rabbits after balloon angioplasty by magnetic-resonance imaging.

OBJECTIVE: To assess the usefulness of magnetic-resonance imaging (MRI) for monitoring acute changes after angioplasty of preexisting lesions in rabbits with basal lesions similar to those observed in humans. METHODS: A combination of Fogarty balloon injury (1 week after initiation of diet) and a mildly hypercholesterolemic diet (0.2% cholesterol and 5% peanut oil) was used to promote the rapid formation of atherosclerotic lesions in 16 New Zealand white rabbits. After 5 months of the diet, angioplasty was performed on these lesions with a Grüntzig catheter in both iliac arteries and the abdominal aorta. MRI was used to monitor the initial formation of lesions after 3 and 5 months of the diet, and 2 days, 2 weeks, and 1 and 2 months after angioplasty. RESULTS: The combination of early Fogarty injury and mildly hypercholesterolemic diet induced fibroproliferative lesions similar to type Vb atherosclerotic lesions seen in humans. Angioplasty induced deep dissections at the shoulders of lesions in the majority of animals. These dissections often extended into the media. The cellular, proliferative response after angioplasty was localized and limited to sites of dissection. A significant increase in area of arterial wall was observed after angioplasty at sites of dissection without any loss of lumen. In contrast, proximal and distal to the sites of injury, there was no change in wall area but a transient reduction in lumen area. CONCLUSIONS: Comparison of MRI results with histology confirmed that changes in the wall and lumen, including small linear dissections in the lesions and arterial remodeling, are detectable by MRI.

Angioplasty, Balloon↗

Interaction of native and modified low-density lipoproteins with extracellular matrix.

Lipoprotein-matrix interactions play an important role in arterial disease. Extracellular matrix proteoglycans bind and retain specific positively charged domains on apolipoproteins B- and E-containing lipoproteins during atherogenesis. Retained lipoproteins can undergo several modifications, which may alter their interaction with extracellular matrix molecules. Growth factors, cytokines and oxidized low density lipoproteins influence proteoglycan structure, rendering them more likely to bind and retain lipoproteins during atherogenesis. Lipoproteins, native and modified, also can modulate the expression of several of the matrix degrading enzymes present in vascular tissue, thereby influencing plaque stability. Thus, the interaction of atherogenic lipoproteins with arterial wall matrix molecules can influence the genesis and progression of atherosclerosis and its complications.

Animals↗

Lipoprotein lipase enhances the binding of native and oxidized low density lipoproteins to versican and biglycan synthesized by cultured arterial smooth muscle cells.

Retention of low density lipoproteins (LDL) by vascular proteoglycans and their subsequent oxidation are important in atherogenesis. Lipoprotein lipase (LPL) can bind LDL and proteoglycans, although the effect of different proteoglycans to influence the ability of LPL to act as a bridge in the formation of LDL-proteoglycan complexes is unknown. Using an electrophoretic gel mobility shift assay, [(35)S]SO(4)-labeled versican and biglycan, two extracellular proteoglycans secreted by vascular cells, bound native LDL in a saturable fashion. The addition of bovine milk LPL dose-dependently increased the binding of native LDL to both versican and biglycan, approaching saturation at 30-40 microgram/ml LPL for versican and 20 microgram/ml LPL for biglycan. LDL was oxidized by several methods, including copper, 2, 2-azo-bis(2-amidinopropane)-2HCl and hypochlorite. Extensively copper- and hypochlorite-oxidized LDL bound poorly to versican and biglycan. Proteoglycan binding to LDL was correlated inversely with the extent of LDL; however, the addition of LPL to oxidized LDL together with biglycan or versican allowed the oxidized LDL to bind the proteoglycans in an LPL dose-dependent manner. Addition of LPL had a greater relative effect on the binding of extensively oxidized LDL to proteoglycans compared with native LDL. LPL had a slightly greater effect on increasing the binding of native and oxidized LDL to biglycan than versican. Thus, LPL in the artery wall might increase the atherogenicity of oxidized LDL, since it enables its binding to vascular biglycan and versican.

Animals↗

The sulfate moieties of glycosaminoglycans are critical for the enhancement of beta-amyloid protein fibril formation.

Our previous studies have demonstrated that perlecan and perlecan-derived glycosaminoglycans (GAGs) not only bind beta-amyloid protein (Abeta) 1-40 and 1-42, but are also potent enhancers of Abeta fibril formation and stabilize amyloid fibrils once formed. However, it was not determined which moieties in perlecan heparan sulfate GAG chains may be responsible for the observed effects and whether other GAGs were also capable of a similar enhancement of Abeta fibril formation as observed with perlecan GAGs. In the present study, thioflavin T fluorometry (over a 1-week period) was used to extend our previous studies and to test the hypothesis that the sulfate moiety is critical for the enhancing effects of heparin/heparan sulfate GAGs on Abeta 1-40 fibrillogenesis. This hypothesis was confirmed when removal of all sulfates from heparin (i.e., completely desulfated N-acetylated heparin) led to a complete loss in the enhancement of Abeta fibrillogenesis as demonstrated in both thioflavin T fluorometry and Congo red staining studies. On the other hand, removal of O-sulfate from heparin (i.e., completely desulfated N-sulfated heparin), and to a lesser extent N-sulfate (i.e., N-desulfated N-acetylated heparin), resulted in only a partial loss of the enhancement of Abeta 1-40 fibril formation. These studies indicate that the sulfate moieties of GAGs are critical for enhancement of Abeta amyloid fibril formation. In addition, other sulfated molecules such as chondroitin-4-sulfate, dermatan sulfate, dextran sulfate, and pentosan polysulfate all significantly enhanced (greater than twofold by 3 days) Abeta amyloid fibril formation. These latter findings indicate that deposition and accumulation of other GAGs at sites of Abeta amyloid deposition in Alzheimer's disease brain may also participate in the enhancement of Abeta amyloidosis.

Alzheimer Disease↗

Formation of hyaluronan- and versican-rich pericellular matrix is required for proliferation and migration of vascular smooth muscle cells.

The accumulation of hyaluronan (HA) and the HA-binding proteoglycan versican around smooth muscle cells in lesions of atherosclerosis suggests that together these molecules play an important role in the events of atherogenesis. In this study we have examined the formation of HA- and versican-rich pericellular matrices by human aortic smooth muscle cells in vitro, using a particle-exclusion assay, and the role of the pericellular matrix in cell proliferation and migration. The structural dependence of the pericellular matrix on HA can be demonstrated by the complete removal of the matrix with Streptomyces hyaluronidase. The presence of versican in the pericellular matrix was confirmed immunocytochemically. By electron microscopy, the cell coat was seen as a tangled network of hyaluronidase-sensitive filaments decorated with ruthenium red-positive proteoglycan granules. Ninety percent of migrating cells in wounded cultures, and virtually all mitotic cells, displayed abundant HA- and versican-rich coats. Time-lapse video imaging revealed that HA- and versican-rich pericellular matrix formation is dynamic and rapid, and coordinated specifically with cell detachment and mitotic cell rounding. HA oligosaccharides, which inhibit the binding of HA to the cell surface and prevent pericellular matrix formation, significantly reduced proliferation and migration in response to platelet-derived growth factor, whereas larger HA fragments and high molecular weight HA had no effect. Treatment with HA oligosaccharides also led to changes in cell shape from a typical fusiform morphology to a more spread and flattened appearance. These data suggest that organization of HA- and versican-rich pericellular matrices may facilitate migration and mitosis by diminishing cell surface adhesivity and affecting cell shape through steric exclusion and the viscous properties of HA proteoglycan gels.

Aorta, Thoracic↗