Transforming growth factor-beta induces selective increase of proteoglycan production and changes in the copolymeric structure of dermatan sulphate in human skin fibroblasts

Domain Mapping of Chondroitin/Dermatan Sulfate Glycosaminoglycans Enables Structural Characterization of Proteoglycans

Of all posttranslational modifications known, glycosaminoglycans (GAGs) remain one of the most challenging to study, and despite the recent years of advancement in MS technologies and bioinformatics, detailed knowledge about the complete structures of GAGs as part of proteoglycans (PGs) is limited. To address this issue, we have developed a protocol to study PG-derived GAGs. Chondroitin/dermatan sulfate conjugates from the rat insulinoma cell line, INS-1832/13, known to produce primarily the PG chromogranin-A, were enriched by anion-exchange chromatography after pronase digestion. Following benzonase and hyaluronidase digestions, included in the sample preparation due to the apparent interference from oligonucleotides and hyaluronic acid in the analysis, the GAGs were orthogonally depolymerized and analyzed using nano-flow reversed-phase LC-MS/MS in negative mode. To facilitate the data interpretation, we applied an automated LC-MS peak detection and intensity measurement via the Proteome Discoverer software. This approach effectively provided a detailed structural description of the nonreducing end, internal, and linkage region domains of the CS/DS of chromogranin-A. The copolymeric CS/DS GAGs constituted primarily consecutive glucuronic-acid-containing disaccharide units, or CS motifs, of which the N-acetylgalactosamine residues were 4-O-sulfated, interspersed by single iduronic-acid-containing disaccharide units. Our data suggest a certain heterogeneity of the GAGs due to the identification of not only CS/DS GAGs but also of GAGs entirely of CS character. The presented protocol allows for the detailed characterization of PG-derived GAGs, which may greatly increase the knowledge about GAG structures in general and eventually lead to better understanding of how GAG structures are related to biological functions.

•

Protocol developed to structurally characterize glycosaminoglycans of proteoglycans.

•

Comprehensive characterization of cellular glycosaminoglycan structures.

•

Relative quantification of nonreducing end, internal, and linkage region domains.

•

Overall chondroitin/dermatan sulfate glycosaminoglycan structures of chromogranin-A.

Plasma Glycosaminoglycan Profiles in Systemic Sclerosis: Associations with MMP-3, MMP-10, TIMP-1, TIMP-2, and TGF-Beta

The aim of the study was to determine whether plasma levels of total glycosaminoglycans (GAGs), matrix metalloproteinases (MMPs) (MMP-3, MMP-10), and their tissue inhibitors (TIMPs) (TIMP-1, TIMP-2) as well as transforming growth factor β (TGF-β) differ in the patients with systemic sclerosis (SSc) in relation to the healthy subjects. Plasma samples were obtained from 106 people (64 patients with SSc and 42 healthy individuals) and measured for MMP-3, MMP-10, TIMP-1, TIMP-2, and TGF-β levels using ELISA methods. GAGs isolated from plasma samples were quantified using a hexuronic acid assay. The plasma levels of total GAGs, TIMP-1, TIMP-2, and TGF-β were significantly higher, while MMP-3 was significantly decreased in SSc patients compared to the controls. We have revealed a significant correlation between plasma GAGs and TGF-β (r = -0.47) and TIMP-2 (r = 0.38), respectively. The results of this study revealed that remodeling of the extracellular matrix, reflected by quantitative changes in plasma glycosaminoglycans, occurs during systemic sclerosis. Thus, the alterations in GAG metabolism connected with SSc may lead to systemic changes in the properties of the connective tissue extracellular matrix.

Nutricosmetics: A brief overview

The nutricosmetics are products and ingredients that act as nutritional supplements to care skin, nails, and hair natural beauty. They work from the inside to promote beauty from within. Nutricosmetic is the latest trend in the beauty industry. This tendency rapidly gained many followers because it fits with the modern culture: Today, consumers are very careful with the food that they introduce into their body, and there is also an increasing demand for natural products able to enhance one's health and beauty without side effects and significant traction before use. However, many nutricosmetic products are considered effective due to the historical use and word of mouth. Comprehensive analysis of the global nutricosmetics market is conducted considering form, end-user applications, and some product components such as collagen, peptides, proteins, vitamins, carotenes, minerals, and omega-3 fatty acid are reported. Plant extract ingredients used in nutricosmetic are also described.

Glycosaminoglycans: A Link Between Development and Regeneration in the Lung

What can we learn from embryogenesis to increase our understanding of how regeneration of damaged adult lung tissue could be induced in serious lung diseases such as chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and asthma? The local tissue niche determines events in both embryogenesis and repair of the adult lung. Important constituents of the niche are extracellular matrix (ECM) molecules, including proteoglycans and glycosaminoglycans (GAGs). GAGs, strategically located in the pericellular and extracellular space, bind developmentally active growth factors (GFs) and morphogens such as fibroblast growth factors (FGFs), transforming growth factor-β (TGF-β), and bone morphogenetic proteins (BMPs) aside from cytokines. These interactions affect activities in many cells, including stem cells, important in development and tissue regeneration. Moreover, it is becoming clear that the "inherent code," such as sulfation of disaccharides of GAGs, is a strong determinant of cellular outcome. Sulfation patterns, deacetylations, and epimerizations of GAG chains function as tuning forks in gradient formation of morphogens, growth factors, and cytokines. Learning to tune these fine instruments, that is, interactions between GFs, chemokines, and cytokines with the specific disaccharide code of GAGs in the adult lung, could become the key to unlock inherent regenerative forces to override pathological remodeling. This review aims to provide an overview of the role GAGs play during development and similar events in regenerative efforts in the adult lung.

Roles of chondroitin sulfate and dermatan sulfate in the formation of a lesion scar and axonal regeneration after traumatic injury of the mouse brain

Dermatan sulfate (DS) is synthesized from chondroitin sulfate (CS) by epimerization of glucuronic acid of CS to yield iduronic acid. In the present study, the role of CS and DS was examined in mice that received transection of nigrostriatal dopaminergic pathway followed by injection of glycosaminoglycan degrading enzymes into the lesion site. Two weeks after injury, fibrotic and glial scars were formed around the lesion, and transected axons did not regenerate beyond the fibrotic scar. Injection of chondroitinase ABC (ChABC), which degrades both CS and DS, completely suppressed the fibrotic scar formation, reduced the glial scar, and promoted the regeneration of dopaminergic axons. Injection of the DS-degrading enzyme chondroitinase B (ChB) also yielded similar results. By contrast, injection of chondroitinase AC (ChAC), a CS-degrading enzyme, did not suppress the fibrotic and glial scar formation, but reduced CS immunoreactivity and promoted the axonal regeneration. Addition of transforming growth factor-β1 (TGF-β1) to a co-culture of meningeal fibroblasts and cerebral astrocytes induces a fibrotic scar-like cell cluster. The effect of TGF-β1 on cluster formation was suppressed by treatment with ChABC or ChB, but not by ChAC. TGF-β1-induced cell cluster repelled neurites of neonatal cerebellar neurons, but addition of ChABC or ChAC suppressed the inhibitory property of clusters on neurite outgrowth. The present study is the first to demonstrate that DS and CS play different functions after brain injury: DS is involved in the lesion scar formation, and CS inhibits axonal regeneration.

Splicosomal and serine and arginine-rich splicing factors as targets for TGF-β

Background

Transforming growth factor-β₁ (TGF-β₁) is a potent regulator of cell growth and differentiation. TGF-β₁ has been shown to be a key player in tissue remodeling processes in a number of disease states by inducing expression of extracellular matrix proteins. In this study a quantitative proteomic analysis was undertaken to investigate if TGF-β₁ contributes to tissue remodeling by mediating mRNA splicing and production of alternative isoforms of proteins.

Methodology/Principal findings

The expression of proteins involved in mRNA splicing from TGF-β₁-stimulated lung fibroblasts was compared to non-stimulated cells by employing isotope coded affinity tag (ICAT^TM) reagent labeling and tandem mass spectrometry. A total of 1733 proteins were identified and quantified with a relative standard deviation of 11% +/− 8 from enriched nuclear fractions. Seventy-six of these proteins were associated with mRNA splicing, including 22 proteins involved in splice site selection. In addition, TGF-β₁ was observed to alter the relative expression of splicing proteins that may be important for alternative splicing of fibronectin. Specifically, TGF-β₁ significantly induced expression of SRp20, and reduced the expression of SRp30C, which has been suggested to be a prerequisite for generation of alternatively spliced fibronectin. The induction of SRp20 was further confirmed by western blot and immunofluorescence.

Conclusions

The results show that TGF-β₁ induces the expression of proteins involved in mRNA splicing and RNA processing in human lung fibroblasts. This may have an impact on the production of alternative isoforms of matrix proteins and can therefore be an important factor in tissue remodeling and disease progression.

Bruch's membrane changes in transgenic mice overexpressing the human biglycan and apolipoprotein b-100 genes

Age-Related Macular Degeneration (AMD) is characterized by the accumulation of lipid- and protein-rich deposits in Bruch's Membrane (BrM). A consequent decrease in hydraulic conductivity and impairment of transport through BrM may play a central role in the pathogenesis of AMD. The mechanism of deposit formation in AMD had been suggested to show similarities to the formation of atherosclerotic plaques in which the interactions of extracellular matrix proteoglycans with apolipoprotein-B 100 (apoB-100) play an important role. A prime candidate for this interaction is the small leucin-rich proteoglycan biglycan. The aim of our study was to test the effect of the simultaneous overexpression of human apoB-100 and biglycan genes in combination with a high-cholesterol diet on BrM morphology in transgenic mice. Six-weeks-old homozygous apoB-100 or biglycan, hemizygous apoB-100/biglycan transgenic and wild-type C57Bl/6 mice were fed either a standard chow or a diet supplemented with 2% cholesterol for 17 weeks. Animals were sacrificed, serum lipid levels were measured and eyes were processed for transmission electron microscopy (TEM) according to standard protocol. Morphometric analysis of digitally acquired TEM images of BrM showed that in apoB-100 and double transgenic animals fed a high-cholesterol diet, the BrM thickness was significantly increased compared to wild-type animals. Both groups had electron-lucent profiles in clusters, scattered throughout the collagenous layers of BrM, and focal nodules of an amorphous material of intermediate electron-density between the plasma and basement membranes of the retinal pigment epithelium (RPE). BrM thickness in these two groups correlated well with elevated cholesterol levels. Unexpectedly, animals overexpressing biglycan alone showed a marked, diet-independent increase in BrM thickness associated with a layer of a basement membrane-like material in outer BrM. The effects of biglycan overexpression are intriguing and further investigations are needed to elucidate the underlying mechanisms.

The importance of fibroblasts in remodelling of the human uterine cervix during pregnancy and parturition

It is well established that fibroblasts play a crucial role in pathophysiological extracellular matrix remodelling. The aim of this project is to elucidate their role in normal physiological remodelling. Specifically, the remodelling of the human cervix during pregnancy, resulting in an enabled passage of the child, is used as the model system. Fibroblast cultures were established from cervices of non-pregnant women, women after 36 weeks of pregnancy and women directly after partus. The cells were immunostained and quantified by western blots for differentiation markers. The cultures were screened for cytokine and metalloproteinase production and characterized by global proteome analysis. The cell cultures established from partal donors differ significantly from those from non-pregnant donors, which is in accordance with in vivo findings. A decrease in alpha-smooth actin and prolyl-4-hydroxylase and an increase in interleukin (IL)-6, IL-8 and matrix metalloproteinases (MMP)-1 and MMP-3 were observed in cultures from partal donors. 2D-gel electrophoresis followed by mass spectrometry showed that the expression of 59 proteins was changed significantly in cultures of partal donors. The regulated proteins are involved in protein kinase C signalling, Ca2+ binding, cytoskeletal organization, angiogenesis and degradation. Our data suggest that remodelling of the human cervix is orchestrated by fibroblasts, which are activated or recruited by the inflammatory processes occurring during the ripening cascade.

Lung fibroblast proteoglycan production induced by serum is inhibited by budesonide and formoterol

Proteoglycans contribute to extracellular matrix remodeling in asthmatic airways. We investigated the effects of budesonide, a glucocorticoid, and formoterol, a long-acting beta2-adrenergic agonist, on serum-induced proteoglycan production by human lung fibroblasts. In 10% serum, total proteoglycan production was increased 1.5-fold (P < 0.01) compared with basal production in 0.4% serum. Budesonide (10(-8) M) reduced this increase by 44% (P < 0.01) and, whereas formoterol (10(-10)-10(-8) M) had no inhibitory effects, the drug combination abolished the increase (P < 0.01) without affecting fibroblast proliferation. This synergistic effect required functional glucocorticoid and beta-adrenergic receptors. The production of the proteoglycans decorin, biglycan, perlecan, and versican was increased 2.5- to 5-fold (P < 0.01) in 10% serum. Combination treatment with budesonide (10(-8) M) and formoterol (10(-10) M) abolished this increase to a significantly greater extent than either drug alone. In 10% serum, only versican mRNA was increased 1.4-fold (P < 0.05), whereas decorin mRNA was reduced to 39% (P < 0.01) of basal expression. These serum effects were counteracted by the drug combination, but there were no significant differences between the combination and either drug alone. Thus, the budesonide and formoterol combination seems to synergistically control serum-induced proteoglycan production, primarily at the post-transcriptional level. In conclusion, the proteoglycan upregulation characteristic of asthmatic airways may be limited by combination therapy with budesonide and formoterol.

Inhibition of astroglial nuclear factor kappaB reduces inflammation and improves functional recovery after spinal cord injury

In the central nervous system (CNS), the transcription factor nuclear factor (NF)-kappaB is a key regulator of inflammation and secondary injury processes. After trauma or disease, the expression of NF-kappaB-dependent genes is highly activated, leading to both protective and detrimental effects on CNS recovery. We demonstrate that selective inactivation of astroglial NF-kappaB in transgenic mice expressing a dominant negative (dn) form of the inhibitor of kappaB alpha under the control of an astrocyte-specific promoter (glial fibrillary acidic protein [GFAP]-dn mice) leads to a dramatic improvement in functional recovery 8 wk after contusive spinal cord injury (SCI). Histologically, GFAP mice exhibit reduced lesion volume and substantially increased white matter preservation. In parallel, they show reduced expression of proinflammatory chemokines and cytokines, such as CXCL10, CCL2, and transforming growth factor-beta2, and of chondroitin sulfate proteoglycans participating in the formation of the glial scar. We conclude that selective inhibition of NF-kappaB signaling in astrocytes results in protective effects after SCI and propose the NF-kappaB pathway as a possible new target for the development of therapeutic strategies for the treatment of SCI.

Regulation of the chondroitin/dermatan fine structure by transforming growth factor-beta1 through effects on polymer-modifying enzymes

The chondroitin/dermatan sulfate proteoglycans (CS/DSPGs), biglycan, decorin, and versican play several important roles in extracellular matrix influencing matrix organization, cell proliferation, and recruitment. Moreover, they bind and regulate growth factors in the extracellular matrix. We have previously shown that cultured human lung fibroblasts treated with transforming growth factor-beta (TGF-beta) alone or in combination with epidermal growth factor and platelet-derived growth factor, increase the production of these PGs. In this report, we describe that the structure of their galactosaminoglycan side chains is altered, albeit there is no alteration of polysaccharide length. The findings showed that iduronic acid content is reduced by 50% in decorin and biglycan, whereas 4-O-sulfation is increased 2-fold in versican. To unravel the mechanism behind these changes, the activities of chondroitin C-5 epimerase and of O-sulfotransferases in cellular fractions prepared from fibroblasts were quantitated, and transcript levels of the relevant sulfotransferases were measured by real time polymerase chain reaction (RT-PCR). The C-5 epimerase activity was reduced by 25% in TGF-beta1 treated cells and 50% in fibroblasts treated with the growth factor combination. No change in activity in dermatan 4-O sulfotransferase was observed, and only a minor decrease in dermatan 4-O-sulfotransferase-1 (D4ST-1) mRNA was observed. On the other hand, chondroitin 4-O sulfotransferase activity increased 2-fold upon TGF-beta1 treatment and 3-fold upon treatment with the growth factor combination. This is in agreement with a 2-fold up-regulation of chondroitin-4-O-sulfotransferase 1 (C4ST-1) mRNA, and no changes in chondroitin-4-O-sulfotransferase 2 (C4ST-2) mRNA. Thus, cellular activity and transcript level correlated well with the changes in the structure of the dermatan/chondroitin sulfate chains.

Lung fibroblast clones from normal and fibrotic subjects differ in hyaluronan and decorin production and rate of proliferation

Development of fibrosis involves an increase in the deposition of connective tissue components including collagens, fibronectin and proteoglycans. One hypothesis to account for matrix deposition in fibrosis is that fibroblast with differing matrix producing capacity are involved in the fibrotic process. To test this hypothesis, primary fibroblast cultures and clones derived from these primary lines were established from the lung tissue of control patients and patients with pulmonary fibrosis. The primary lines and derived clones were studied in relation to their capacity to proliferate and to produce proteoglycans and hyaluronan. Primary fibroblast cultures and clones from normal subjects and patients with lung fibrosis differed considerably, with up to 13-fold difference, in both hyaluronan and proteoglycan production. The major proteoglycan produced was decorin in both controls and cultures from fibrotic patients, while cultures from patients with lung fibrosis had a higher expression of mRNA for both collagen and decorin. Clones derived from a primary line from a fibrotic patient secreted 3-fold greater amounts of decorin than those from a control subject. Furthermore, a negative correlation between proliferation and synthesis of decorin was noted. We suggest that different fibroblast clones accumulate in the lung, and that specific cell populations of high decorin producing fibroblasts may exist which are crucial in the pathogenesis of fibrosis.

Combined administration of basic fibroblast growth factor protein and the hepatocyte growth factor gene enhances the regeneration of dermis in acute incisional wounds

Hepatocyte growth factor (HGF) is a ligand for the c-Met receptor tyrosine kinase. This study was aimed to characterize the role of the HGF gene combined with basic fibroblast growth factor (bFGF) protein in wound healing by administering both of them locally to acute incisional skin wounds created on the backs of rats. The bFGF protein and the HGF gene were administered intradermally after incisional surgery. Apoptotic cells in wound lesions were identified by the terminal deoxynucleotide transferase-mediated nick-end labeling method, as well as by immunological detection of active caspase-3. While there was almost complete suppression of apoptosis with well-organized wound healing in animals treated with the HGF gene, the combination of bFGF protein and the HGF gene paradoxically resulted in less scarring along with the promotion of apoptosis. Histopathological examination revealed that scar formation was least apparent in rats treated with both bFGF and the HGF gene compared with controls or those treated with the bFGF or the HGF gene alone. It is thought that the combined administration of bFGF and the HGF gene immediately after skin incision may make the healing process occur closer to tissue regeneration through the induction of apoptosis, which occurred 1 week after surgery. HGF supplementation through gene therapy combined with bFGF protein may be an effective strategy for treating wounds, as it increases the apparent regeneration of the dermis to allow for "scarless wound healing."

Versican undergoes speci?c alterations in the ?ne molecular structure and organization in human aneurysmal abdominal aortas

Versican is the major matrix proteoglycan in aortic wall and participates in various biological functions of the tissue. In the present study the molecular characteristics of versican isolated from normal human aorta as well as those of versican expressed in aneurysmal aortic tissue were examined. Versican was isolated by combined anion-exchange and gel permeation chromatography and was further characterized by high-performance liquid chromatography, polyacrylamide gel electrophoresis and immunoblotting. In both tissues versican is exclusively substituted with chondroitin sulfate chains, in contrast to other human tissues where both chondroitin and dermatan sulfate chains are attached onto versican core proteins. Except for the significant decrease in the concentration of versican in the aneurysmal tissue, this PG undergoes specific alterations in the aneurysmal tissue. The molecular size of versican isolated from diseased tissue is decreased with a simultaneous increase in the ratio of glycosaminoglycan to protein in this tissue. The latter reflect the extensive fragmentation of versican in the diseased tissue and most probably the generation of shorter peptides enriched to glycosaminoglycan chains. Although the size of chondroitin sulfate chains is identical in both versican preparations, a significant increase in the percentage of 6-sulfated disaccharides is observed in chondroitin sulfate chains of versican in aneurysmal aortas, which is accompanied by decrease in 4-sulfated and non-sulfated units.

Correlation between airway responsiveness and proteoglycan production by bronchial fibroblasts from normal and asthmatic subjects

Asthma is characterized by an airway remodeling process involving altered extracellular matrix deposition such as collagen, fibronectin and proteoglycans. Proteoglycans determine tissue mechanical properties and are involved in many important biological aspects. Not surprisingly, it has been suggested that proteoglycan deposition may alter airway properties in asthma including airway hyperresponsiveness. In chronically inflamed airway tissues, fibroblasts likely represent an activated fibrotic phenotype that contributes to the excessive deposition of different extracellular matrix components. To investigate whether this was the case for proteoglycans, the production of hyaluronan, perlecan, versican, small heparan sulphate proteoglycans (HSPGs), decorin and biglycan was quantified in the culture medium of primary bronchial fibroblast cultures, established from four normal and six asthmatic subjects. Values were further correlated to the airway responsiveness (PC(20) methacholine) of donor subjects. Fibroblasts from subjects with the most hyperresponsive airways produced up to four times more total proteoglycans than cells from subjects with less hyperresponsive or normoresponsive airways. We observed a significant negative correlation between the PC(20) and perlecan, small HSPGs and biglycan, while such correlation was absent for decorin and close to significant for hyaluronan and versican. Altered proteoglycan metabolism by bronchial fibroblasts may contribute to the increased proteoglycan deposition in the bronchial mucosa and to airway hyperresponsiveness characterizing asthma.

Dermatan sulfate: new functions from an old glycosaminoglycan

Glycosaminoglycans constitute a considerable fraction of the glycoconjugates found on cellular membranes and in the extracellular matrix of virtually all mammalian tissues. Their ability to bind and alter protein-protein interactions or enzymatic activity has identified them as important determinants of cellular responsiveness in development, homeostasis, and disease. Although heparan sulfate tends to be emphasized as the most biologically active glycosaminoglycan, dermatan sulfate is a particularly attractive subject for further study because it is expressed in many mammalian tissues and it is the predominant glycan present in skin. Dermatan and dermatan sulfate proteoglycans have also been implicated in cardiovascular disease, tumorigenesis, infection, wound repair, and fibrosis. Growing evidence suggests that this glycosaminoglycan, like the better studied heparin and heparan sulfate, is an important cofactor in a variety of cell behaviors.

Biglycan isoforms with differences in polysaccharide substitution and core protein in human lung fibroblasts

Biglycan is widely distributed in the extracellular matrix and is a member of the small proteoglycan family characterized by a core protein with leucine-rich repeat motifs. We show in this paper for the first time that biglycan from human lung fibroblasts can be expressed as different isoforms. These isoforms can be separated from the predominant form of biglycan by hydrophobic interaction chromatography, where the more hydrophobic isoforms are retarded. The newly found isoforms of biglycan have a smaller core protein substituted with smaller glycosaminoglycan chains, migrating on SDS/PAGE at between 110 and 200 kDa. These molecules were identified as biglycan using MALDI-TOF MS. Identification of C-terminal peptides together with glycosylation of the N-terminal glycosaminoglycan sites excludes the possibility of terminal proteolytic cleavage. The biglycan isoforms are N-glycosylated, which demonstrates that a lack in N-glycosylation is not the reason for a smaller core. Two components revealed by RT-PCR indicate alternative splicing, which could be located in regions of the protein that have not been identified, with the exclusion of sites of glycosylations. Analyses of glycosaminoglycan chain length of the isoforms show that besides the normally occurring glycosaminoglycan chains, there is a mixture of shorter glycosaminoglycan chains. Structural analysis shows that these glycosaminoglycan chains contain a lower proportion of iduronic acid (61%) relative to glucuronic acid when compared to the glycosaminoglycan chain of the predominant form of biglycan (71%). We can anticipate that variation in structure of biglycan can cause changes in the connective tissue formation depending on its ability to bind matrix molecules, as well as cytokines.

Proteoglycans synthesized by arterial smooth muscle cells in the presence of transforming growth factor-beta1 exhibit increased binding to LDLs

The "response-to-retention" hypothesis of atherogenesis states that atherogenic lipoproteins, such as low density lipoprotein (LDL), are retained in vessels by proteoglycans and undergo proatherosclerotic modifications. Transforming growth factor (TGF)-beta1 has been identified in atherosclerotic vessels and has been shown to stimulate the synthesis of chondroitin sulfate- and dermatan sulfate-containing proteoglycans by arterial smooth muscle cells (ASMCs), but whether it promotes lipid retention has not been addressed. We investigated whether TGF-beta1 modulates the biosynthesis of proteoglycans by ASMCs in a manner that promotes binding to LDL. Proteoglycans isolated from TGF-beta1-treated ASMCs exhibited enhanced binding to native LDL compared with the binding of proteoglycans isolated from control cultures (K(d) 18 microg/mL LDL versus 81 microg/mL LDL, respectively). The increase in proteoglycan-LDL binding caused by TGF-beta1 could be attributed primarily to the glycosaminoglycan portion of the proteoglycans, since the glycosaminoglycan chains liberated from the core proteins of these proteoglycans synthesized in the presence of TGF-beta1 exhibited increased LDL binding as well. Furthermore, glycosaminoglycan chains initiated on xyloside (an initiator of glycosaminoglycan synthesis) in the presence of TGF-beta1 were longer and displayed enhanced binding to LDL compared with the LDL binding of xyloside-initiated glycosaminoglycan chains from control cultures. These results indicate that TGF-beta1 promotes LDL-proteoglycan interaction primarily by its effects on the glycosaminoglycan synthetic machinery of the ASMCs. Therefore, this study supports a proatherogenic role for TGF-beta1.

Identification of the major proteoglycans from human myometrium

BACKGROUND

During pregnancy and parturition a remodeling within the extracellular matrix of the cervix and the corpus uteri occurs, which is of fundamental importance to a normal labor. The aim of this study is to identify the major proteoglycans in corpus uteri of non-pregnant subjects.

METHODS

From human uterine tissue proteoglycans were extracted and purified using CsCl-density gradient centrifugation, gel and ion-exchange chromatography. The proteoglycans were quantified and identified by Alcian Blue before and after ABC-digestion and by Western blotting.

RESULTS

The results showed that the corpus uteri contains a substantial amount of proteoglycans, 1.825 microg/mg wet weight. Decorin is dominating, constituting 63% of the total amount of proteoglycans. Heparan sulphate proteoglycans accounted for 20% and biglycan for 16%. Less than 1% consisted of the large proteoglycan versican.

CONCLUSIONS

Further investigations must be performed to provide more information of the biological role of the proteoglycans in the uterus, especially during labor, by the presence of heparan sulphate proteoglycans and the minute presence of versican which indicate that the proteoglycan composition and organization is different to that of the cervix.

Dermatan sulphate is released by proteinases of common pathogenic bacteria and inactivates antibacterial alpha-defensin

Defensins represent an evolutionarily conserved group of small peptides with potent antibacterial activities. We report here that extracellular proteinases secreted by the human pathogens Pseudomonas aeruginosa, Enterococcus faecalis and Streptococcus pyogenes release dermatan sulphate by degrading dermatan sulphate-containing proteoglycans, such as decorin. Dermatan sulphate was found to bind to neutrophil-derived alpha-defensin, and this binding completely neutralized its bactericidal activity. During infection, proteoglycan degradation and release of dermatan sulphate may therefore represent a previously unknown virulence mechanism, which could serve as a target for novel antibacterial strategies.

Dermatan sulfates of normal and scarred fascia

We evaluated the composition of dermatan sulfates (DS) derived from 23 samples of normal and 23 samples of scarred fascia lata. We analyzed the molecular weight of intact DS chains and the length of chain regions comprising: (1) clusters of L-iduronate-containing disaccharides ("iduronic sections"); (2) clusters of D-glucuronate-containing disaccharides ("glucuronic sections"); and (3) copolymeric sections with both types of disaccharides. A portion of scarred fascia DS chains demonstrated higher molecular weight compared with those from normal tissue. Most disaccharides of DS chains derived from both fascia types form copolymeric segments - heterogeneous in size - with alternatively distributed single disaccharides with glucuronic residues and mainly single ones with iduronate. Only a small number of disaccharides form "glucuronic sections" of heterogeneous size or short "iduronic sections". However, the scarred fascia DS chains demonstrate an increased content of shorter "glucuronic sections" and shorter, often oversulfated, copolymeric segments. It seems that in normal fascia, the DS chain type with a single, long copolymeric region and a single, shorter "glucuronic section" is predominant, while in scarred tissue an increase in multidomain DS chain content may occur.

Expression of glycosaminoglycans and small proteoglycans in wounds: modulation by the tripeptide-copper complex glycyl-L-histidyl-L-lysine-Cu(2+)

Glycyl-histidyl-lysine-Cu(2+) is a tripeptide-copper complex previously shown to be an activator of wound healing. We have investigated the effects of glycyl-histidyl-lysine-Cu(2+) on the synthesis of glycosaminoglycans and small proteoglycans in a model of rat experimental wounds and in rat dermal fibroblast cultures. Repeated injections of glycyl-histidyl-lysine-Cu(2+) (2 mg per injection) stimulated the wound tissue production, as appreciated by dry weight and total protein measurements. This stimulation was accompanied by an increased production of type I collagen and glycosaminoglycans (assessed, respectively, by hydroxyproline and uronic acid contents of the chamber). Electrophoretic analysis of wound tissue glycosaminoglycans showed an accumulation of chondroitin sulfate and dermatan sulfate in control wound chambers, whereas the proportion of hyaluronic acid decreased with time. The accumulation of chondroitin sulfate and dermatan sulfate was enhanced by glycyl-histidyl-lysine-Cu(2+) treatment. The expression of two small proteoglycans of the dermis, decorin and biglycan, was analyzed by northern blot. The biglycan mRNA steady-state level in the chamber was maximal at day 12, whereas the decorin mRNA increased progressively until the end of the experiment (day 22). Glycyl-histidyl-lysine-Cu(2+) treatment increased the mRNA level of decorin and decreased those of biglycan. In dermal fibroblast cultures, the stimulation of decorin expression by glycyl-histidyl-lysine-Cu(2+) was also found. In contrast, biglycan expression was not modified. These results show that the expression of different proteoglycans in wound tissue are regulated in a different manner during wound healing. The glycyl-histidyl-lysine-Cu(2+) complex is able to modulate the expression of the extracellular matrix macromolecules differently during the wound repair process.

Differential expression of proteoglycans biglycan and decorin during neointima formation after stent implantation in normal and atherosclerotic rabbit aortas

Proteoglycans decorin and biglycan, which bind to TGF-beta, are thought to participate in regulation of extracellular matrix accumulation in arterial intimal hyperplasia. To investigate the correlation of these proteoglycans with the cellular localization and phenotypic modulation of smooth muscle cells (SMCs), we analyzed the spatial and chronological distribution of these proteoglycans and two cytokines, TGF-beta and IL-1beta, in the process of neointima formation after stent implantation in the aortas of rabbits fed a high-cholesterol diet (atherosclerotic group) or a regular diet (control group). We implanted metallic stents in the rabbit aortas and harvested the aortas 4-56 days later for immunohistochemical and mRNA in situ hybridization analyses. In the control group, TGF-beta and biglycan expression was in correspondence with the chronology and localization of embryonic SMCs. In the atherosclerotic group, TGF-beta and biglycan expression was sustained throughout the experimental period, which was in accord with the prolonged expression of embryonic SMCs. Decorin, which did not occur in neointima in the control group, appeared in the atherosclerotic aortas in the confined area of vascular SMCs surrounding the macrophages around the stent wire. These results indicate that biglycan and decorin kinetics during neointima formation after arterial injury are distinct, despite their similar construction; biglycan synthesis correlates with embryonic SMCs.

Developmental expression of dermatan sulfate proteoglycans in the elastic bovine nuchal ligament

The nuchal ligament of bovines is a useful system in which to study elastic fibre formation since it contains up to 83% elastin and undergoes a period of rapid elastinogenesis during the last trimester of fetal development and in the first four post-natal months. To identify proteoglycans (PGs) which may be involved in this process we initially investigated changes in the glycosaminoglycan (GAG) profiles during nuchal ligament development. In contrast to the collagenous Achilles tendon, nuchal ligament exhibited: (a) elevated hyaluronan (HA) levels in the peak period of elastin-associated microfibril (fibrillin) synthesis (130-200 days) which precedes elastinogenesis; and (b) markedly increased synthesis of a glucuronate-rich copolymeric form of dermatan sulfate (DS) in the period corresponding to elastin formation (200-270 days). Analysis of DSPGs isolated from 230-day nuchal ligament showed that this copolymer was predominantly associated with a glycoform of biglycan which was specifically elevated at this stage in development. This finding was consistent with Northern blot analysis which showed that steady-state biglycan mRNA levels increased significantly during the elastinogenic period. In contrast, the mRNA levels for decorin, the only other DSPG detected in this tissue, declined rapidly after 140 days of fetal development. In conclusion, the results suggest that HA may play a role in microfibril assembly and that a specific glycoform of biglycan may be associated with the elastinogenic phase of elastic fibre formation.

Alteration of proteoglycan synthesis in human lung fibroblasts induced by interleukin-1beta and tumor necrosis factor-alpha

Important constituents of extracellular matrix are collagen, fibronectin, hyaluronan, and various types of proteoglycans, such as versican, perlecan, decorin, and biglycan. Remodeling of extracellular matrix occurs continuously and is affected by various cytokines. The aim of this study was to investigate how interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), separately and in combination, alter fibroblast proliferation, as well as the production of extracellular matrix molecules produced by human fibroblasts from lung. Fibroblast proliferation was inhibited significantly by all treatments, by 12% with IL-1beta and by 16% with TNF-alpha. The combination of IL-1beta and TNF-alpha increased the inhibition further, by 27%. Hyaluronan production was increased by all treatments: 1.7-fold by IL-1beta and 1.5-fold by TNF-alpha. The combination of the two gave a further increase (2.5-fold). Similarly, the production of total proteoglycans was increased. The small proteoglycans, decorin, and biglycan, were regulated differently. Decorin production was inhibited by about 34% by all treatments, while biglycan was upregulated 1.3-fold by TNF-alpha. Versican was upregulated by IL-1beta (1.7-fold), whereas TNF-alpha was without effect. Perlecan was mostly unaffected. The changes in protein production of the various proteoglycans were due to increased transcription, as mRNA levels were also changed to the same extent. Synthesis of mRNA for collagen type I was inhibited by up to 75% with the IL-1beta/TNF-alpha combination. The separate cytokines also decreased the level of collagen type I mRNA, but to a lesser extent: 60% with IL-1beta and 40% with TNF-alpha. In summary, our study indicates that these proinflammatory cytokines affect the regulation of extracellular matrix production, which is of importance for the inflammatory process.

Differential effects of interleukin-1 and transforming growth factor beta on the synthesis of small proteoglycans by rabbit articular chondrocytes cultured in alginate beads as compared to monolayers

Small proteoglycans (PGs) are supposed to play great roles in the assembly of cartilage matrix but the influence of cytokines and growth factors on their synthesis by articular chondrocytes is largely unknown. We investigated whether IL-1 and TGFbeta1 influence the production of small leucine-rich proteoglycans by chondrocytes cultured in a three-dimensional gel, as compared to the common monolayer system. Rabbit articular chondrocytes were cultured in alginate beads for 14 days or as monolayers for 7 days. The effect of 2 ng/ml IL-1beta or TGFbeta1 during the last two days in culture was determined, after [35S]methionine labeling over the last 24 h. Cell-associated and further-removed matrix compartments were separated by centrifugation after sodium citrate/EDTA treatment of alginate beads whereas medium and cell-layer fractions were isolated from monolayer cultures. Total newly synthesized PGs were first isolated by anion-exchange chromatography and the small PGs were further separated from aggrecans by gel-filtration (Sepharose CL-4B) and analyzed by SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Addition of TGFbeta1 resulted in an overall rise in neosynthesized small PG content in both culture systems. However, TGFbeta1 significantly increased to the same extent the percentage of small PGs laid down in the cell-associated and the further-removed matrix compartments of the beads culture (+60%) whereas it augmented the content of small PGs in the medium (+40%) and reduced that of the cell fraction (-35%) in the monolayer culture. By adding IL-1, the amount of total newly synthesized small PGs was decreased in monolayers while it increased in alginate beads. IL-1 was also shown to change the relative distribution of these molecules in the monolayer system in contrast to the alginate beads culture where the proportions were not significantly altered. Electrophoretic analysis of the 35S-labeled small PGs-containing fractions confirmed these effects at the level of the 45-50 kDa-related core proteins. This study demonstrates that TGFbeta and IL-1 differently influence small PG synthesis of rabbit articular chondrocytes depending on whether they are cultured in alginate beads or in monolayers. Moreover, the regulation of small PG expression appears to be different from that of high-molecular weight aggrecans. As these small molecules are playing major roles in matrix assembly and growth factor regulation, the data may have great relevance to the pathogenesis of osteoarthritis and repair of articular cartilage lesions.

Comparative effects of TGFbeta on proliferation of 7- and 14-day-old chick embryo fibroblasts and lack of involvement of the ODC/PA system in the TGFbeta signaling pathway

The growth regulatory activity of transforming growth factor beta (TGFbeta) on chick embryo skin fibroblasts was compared in two developmental ages, days 7 and 14. The time course of 3H-thymidine incorporation, an S-phase marker of replication, was determined during 36 hr of TGFbeta treatment. Seven-day-old cells showed a prereplicative phase of 6 hr, and 14-day-old cells showed a prereplicative phase of 12 hr. DNA synthesis peaked at 24 hr in 7-day-old fibroblasts and was 10 times higher than that in 14-day-old fibroblasts. Ornithine decarboxylase (ODC) activity and content of the natural polyamines spermine (Spm), spermidine (Spd), and putrescine (Put) differed during cell cycle. ODC activity peaked at 12 hr in 7-day-old cells and at 6 hr in 14-day-old cells. Its level was two times higher at day 7 and was associated with a greater content of ODC mRNA. The maximum of polyamine (PA) concentration was determined after 12 hr of treatment in 7-day-old cells and after 36 hr in 14-day-old cells. These findings indicate that the TGFbeta proliferative response of embryo fibroblasts changes during development and is associated with activation of the ODC/PA system. Cotreatment with alpha-difluoromethylornithine, an enzyme-activated irreversible inhibitor of ODC, did not reduced growth rate. Inhibition of ODC resulted in levels of Put and Spd comparable to that of quiescent fibroblasts, whereas Spm concentration remained higher. Because an altered ODC metabolism does not convey the effects of TGFbeta on DNA synthesis, the ODC/PA system may not play a role in the pathway of TGFbeta signaling.

Temporal changes in disaccharide composition of dermatan sulfate in the skin after epicutaneous application of hapten

Glycosaminoglycans change their amount, structure and distribution with age, differentiation and pathologic conditions. In order to investigate temporal changes in dermatan sulfate in the skin during inflammation and subsequent healing, 2,4-dinitrofluorobenzene (DNFB) was applied once to the dorsal skin of female BALB/cA mice, and the disaccharide composition of dermatan sulfate was examined. Application of DNFB induced a transient increase in the thickness of the dermis, which reached a maximum on day 15 and decreased to the control level on day 35. The total amount of unsaturated disaccharides from dermatan sulfate per cm2 in the DNFB-treated skin showed a temporal pattern similar to that of the thickness of the dermis. Mol% of 4,5-unsaturated 2-sulfo-hexuronic acid-4-sulfated N-acetylgalactosamine (deltaDi-diSB), the second most abundant unsaturated disaccharide from dermatan sulfate, decreased rapidly on day 3 in the DNFB-treated skin, remained less than the control on days 7 and 15, and returned to the control level on day 35. These results suggest that a single application of DNFB induces temporal changes not only in the amount but also in the structure of dermatan sulfate.

Cadmium inhibits proteoglycan and procollagen production by cultured human lung fibroblasts

Chronic inhalation of cadmium at the workplace or in cigarette smoke is associated with emphysema, a disease characterized by extensive disruption of lung connective tissue. We have previously shown that cadmium, at noncytotoxic doses, inhibits fibroblast procollagen production in vitro, with maximal inhibitory effects of 69 +/- 6% (P < 0.01) at 30 &microM cadmium chloride (CdCl2). In this paper we show that at similar doses, cadmium also inhibits proteoglycan synthesis, with values reduced by between 36 +/- 4% (P < 0.01) and 42 +/- 6% (P < 0.01) for proteoglycans secreted into the culture media and associated with the cell layer, respectively. The greatest inhibition was obtained for the major matrix-associated proteoglycans, versican, decorin, and the large heparan sulfate proteoglycans, with synthesis values reduced by between 60 and 70%. Biglycan and other heparan sulfate proteoglycans were also affected, with synthesis values reduced by between 25 and 45%. In contrast, total protein synthesis was unaffected. Furthermore, effects of cadmium at the protein level were mirrored by reduction in messenger RNA levels for alpha1(I) procollagen, versican, and decorin. These data support the hypothesis that cadmium may play an important role in the pathogenesis of emphysema associated with chronic inhalation of cadmium fumes by inhibiting the production of connective tissue proteins.

A contribution to the regulation of proteoglycan production: modulation by TGF alpha, TGF beta and IL-1 of glycosaminoglycan biosynthesis on beta-D-xyloside in chick embryo fibroblasts

In order to elucidate the mechanisms determining the variability in the proteoglycan structure and the factors involved in this determination, we treated chick embryo skin fibroblasts with beta-D-xyloside to obtain glycosaminoglycan chains deprived of core proteins, and with different cytokines (transforming growth factor alpha and beta, interleukin-1) to produce variability. The different cytokines specifically regulate both cellular and extracellular amount and composition of glycosaminoglycans. Beta-D-xyloside treatment does not change protein content and protein synthesis, whereas it increases overall extracellular sulphated glycosaminoglycan production, heparan sulphate and chondroitin sulphate content, and reduces that of dermatan sulphate. This indicates that the core protein regulates quantitative proteoglycan production, and probably directs (with appropriate signals) the core oligosaccharide bound to it to the right synthesizing enzymes. The modulatory action of the different cytokines on sulphated glycosaminoglycan production and classes remains, even though the core protein is absent. This indicates that the cytokines also act on the glycosyltransferases. Our results suggest that the proteoglycan production may be subject to a double control, one of which is at the level of the core protein and the other, mediated by environmental signals, at the level of glycosaminoglycan synthesizing enzymes.

Expression of decorin and biglycan by rabbit articular chondrocytes. Effects of cytokines and phenotypic modulation

In this study, the levels of mRNAs coding for aggrecan, decorin and biglycan in rabbit articular chondrocytes were investigated, using both monolayer and 3D-alginate cultures treated with TGF-beta 1 and IL-1 beta. The cells were shown to express higher amounts of proteoglycan messages, specially the aggrecan, in gels than in monolayers. TGF-beta 1 increased aggrecan mRNA in both systems, whereas biglycan message was elevated only in alginate. It markedly decreased decorin expression in monolayer, either in primary or passaged cultures. In contrast, IL-1 beta had a weak inhibitory effect on both decorin and biglycan expression. Subculturing induced a dramatic decrease of aggrecan mRNA, while that of decorin augmented. Biglycan expression transiently increased after two passages, whereas it declined in further subcultures. Passaged chondrocytes transferred to alginate re-expressed high levels of aggrecan, decorin and biglycan. The data point to the influence of morphology, proliferative state and environment of the articular chondrocytes on their biosynthetic responses to cytokines. Although these immature cells do not fully reflect the adult chondrocytes present in the cartilage, this study may help in understanding the behaviour of these cells in osteoarticular diseases, where the surrounding extracellular matrix is profoundly altered.

Leucine-rich repeat glycoproteins of the extracellular matrix

The extracellular matrix plays an integral role in the pivotal processes of development, tissue repair, and metastasis by regulating cell proliferation, differentiation, adhesion, and migration. This review is focused on a family of related glycoproteins represented by at least one member in all specialized extracellular matrices. This family currently comprises nine members grouped together on the basis of their presence in the extracellular matrix and by virtue of a leucine-rich repeat motif that dominates the structure of the core protein. It is likely that most, if not all the members of this group exist as proteoglycans in some tissues, and thus have been termed the Small Leucine-Rich Proteoglycan family, or SLRPs. The leucine-rich repeat (LRR) is usually present in tandem array and has been described in an increasing number of proteins, giving rise to a LRR-superfamily. The LRR domain of the SLRP family is unique within the superfamily in that it is flanked by cysteine clusters, and the 24 amino acid consensus for SLRP members is x-x-I/V/L-x-x-x-x-F/P/L-x-x-L/P-x-x-L-x-x-L/I-x-L-x-x-N-x-I/L, where x is any amino acid. Enormous progress has been made in describing the membership, structure and localization of this family, and recently new insight has emerged into the putative function of these molecules not just as modulators of matrix assembly but also on their intriguing role in regulating cell growth, adhesion, and migration. Determination of membership, structure and putative function of this fascinating class of molecules is summarized in this review.

Differential expressions of mRNA for proteoglycans, collagens and transforming growth factor-beta in the human cervix during pregnancy and involution

During pregnancy and involution, an extensive remodelling of the human cervical connective tissue occurs. This cervical ripening is one of the most pronounced physiological remodelling processes known in human connective tissue. To investigate how the remodelling is accomplished, the levels of mRNA for collagen I and III, versican and three small proteoglycans, biglycan, decorin and fibromodulin, were evaluated using Northern blots at different stages of cervical ripening. In the corresponding biopsies the concentration of collagen and of small and large proteoglycans were determined. The role of transforming growth factor-beta (TGF-beta) as a mediator of the remodelling process was also investigated. The concentration of collagen decreased and 1 week before partus, 50% of the nonpregnant level was attained. No further decrease was noted after partus. The mRNA for collagen I and III did, however, not decrease in the term pregnant cervix 1 week before partus. Only 20-30% decrease during the final ripening just before partus was recorded. Neither did the mRNA levels of the small proteoglycans change significantly during the ripening, despite an almost 50% decrease in the concentration of the small proteoglycans. The message for versican was, however, 5-fold increased at partus and then gradually returned to nonpregnant levels within 4 days after delivery. These changes corresponded to similar changes in the concentration of the large proteoglycan. Thus, the remodelling of the cervical connective tissue is achieved by two different mechanisms, on one hand an increased turnover of collagen and the small proteoglycans, on the other a changed transcription followed by an increased production of versican. During the involution 2- to 3-fold increases in the messages for collagen I and III, and the small proteoglycans, biglycan and decorin, corresponded to increases in the concentration of the small proteoglycans and non-extractable collagen. The message for TGF-beta was increased 2-fold immediately after delivery compared with the term pregnant state. Thus, TGF-beta may be of importance for the reconstruction of the cervix, which starts immediately after partus.

Cytokine regulation of proteoglycan production in fibroblasts: separate and synergistic effects

We have studied the effects of cytokines, separately or in combination, on the production of proteoglycans in confluent cultures of fibroblasts. The cytokines used were the transforming growth factor-beta (TGF-beta), the platelet derived growth factor-AA (PDGF-AA), the platelet derived growth factor-BB (PDGF-BB) and the epidermal growth factor (EGF). Hyaluronan production increased in cells treated with TGF-beta, PDGF-AA and PDGF-BB. Combining pairs of factors did not contribute further to hyaluronan production, whereas the triple combination of EGF, TGF-beta and PDGF-BB induced an additional 1.9-fold increase. Proteoglycan production was only increased by TGF-beta alone. As for hyaluronan, combining pairs of the cytokines had no further effect on metabolism, whereas the combination of EGF, TGF-beta and PDGF-BB induced a further 1.6-fold increase in production and secretion. Compared with the control, an extensive increase in proteoglycan production was generated by the combination of EGF, TGF-beta and PDGF-BB, 7-fold for biglycan, approximately 5-fold for versican and hyaluronan and 2.4-4-fold for heparan sulfate proteoglycan and decorin. Compared with TGF-beta alone, this combination increased, in falling order, the production of heparan sulfate proteoglycan, hyaluronan, biglycan, decorin and versican. The mRNA levels for the various proteoglycans did not completely agree with the changes in production, suggesting that changes not only in synthesis but also in rate of degradation generate these variations. The data indicate that cytokines cooperate to produce a proper and physiological response, one needed by the organism during physiological and pathophysiological remodeling.

Differential expression of membrane-anchored proteoglycans in rabbit articular chondrocytes cultured in monolayers and in alginate beads. Effect of transforming growth factor-beta 1

Cell-surface proteoglycans (PGs) were extracted with Triton X-100 from rabbit articular chondrocytes cultured in monolayers and in alginate beads. They were first purified on DEAE-Trisacryl columns and the proportion of hydrophobic PGs was determined by both Octyl-Sepharose chromatography and partitioning in Triton X-114. These two methods revealed that the proportion of hydrophobic PGs was higher in monolayer culture system as compared to alginate beads (24 and 15%, respectively). Characterization of the PGs by Sepharose CL 6B gel filtration followed by electrophoresis indicated that the PGs isolated from monolayers were composed of three chondroitin sulfate (CS) PGs (core proteins of 180, 100 and 50 kDa) and a heparan sulfate (HS) PG (core protein of 60 kDa). In the alginate system. CSPGs with core proteins of 180, 45 and 32 kDa were observed, but no HSPG was present. In parallel, the effect of TGF-beta on the distribution of membrane-associated PGs was studied. The results showed that the synthesis of cell-surface PGs was stimulated by TGF-beta in monolayers whereas it was inhibited in alginate beads, but the amount of hydrophobic PGs was not altered by the growth factor. These data clearly indicate that TGF-beta induces a differential expression of the PG families present at the cell surface. Taken together, the results reveal the complex regulation of cell-surface PG distribution, which obviously depends on the culture method used and suggest that rabbit articular chondrocytes may differentially respond to extracellular ligands according to their morphological state and environment.

The effect of TGF-beta 1 on cell proliferation and proteoglycan production in human melanoma cells depends on the degree of cell differentiation

The effect of transforming growth factor beta 1 (TGF-beta 1) on cell proliferation, colony formation in soft agar and synthesis and structure of proteoglycans was studied in three human melanoma cell lines at different stages of differentiation: SK-mel-1.36-1-5 (early), SK-mel-3.44 (intermediate) and SK-mel-23 (late). TGF-beta 1 potently inhibited cell growth in monolayer as well as in soft agar. TGF-beta 1 increased the release of sulfated proteoglycans into the medium, including the cell-specific melanoma proteoglycan, mel-PG, and induced changes in disaccharide composition and sulfation of the glycosaminoglycan chains. In all the cases, the effect of TGF-beta 1 was more pronounced in the most undifferentiated cell line SK-mel-1.36-1-5 than in the SK-mel-3.44, whereas it had no effect on the most differentiated SK-mel-23 cells.

Immunohistochemical localization of transforming growth factor beta, basic fibroblast growth factor and heparan sulphate glycosaminoglycan in gingival hyperplasia induced by nifedipine and phenytoin

Although drug-induced gingival hyperplasia has been extensively studied, the pathogenesis of this disorder has not been clarified to date. Transforming growth factor beta (TGF beta) and basic fibroblast growth factor (bFGF) have been shown to be implicated in diverse fibrotic and hyperplastic diseases. Heparan sulphate proteoglycan (HSPG), which is composed of heparan sulphate glycosaminoglycan (HSGAG), has also been shown to play an important role in the pathogenesis of tissue overgrowth by enhancing the functions of bFGF. However, the possible implication of these growth factors in gingival hyperplasia has not been studied. Immunohistochemical localization of TGF beta, bFGF, their receptors and HSGAG was studied in 4 nifedipine-induced and 5 phenytoin-induced hyperplastic gingival tissues, and 5 non-hyperplastic control gingival tissues to elucidate the pathogenesis of this disease. Significant immunostaining against TGF beta, bFGF, the receptors of these two growth factors and HSGAG was observed in the lamina propria of hyperplastic gingival tissues while less immunostaining was observed in the controls. The mean numbers of immunostained cells against TGF beta, bFGF, their receptors in a square unit (0.1 x 0.1 mm) of the lamina propria, which were counted to 10 units of each hyperplastic gingival tissue, were significantly higher than those of the controls. The results suggest that the increased synthesis of TGF beta, bFGF, their receptors and HSGAG may be related to the pathogenesis of drug-induced gingival hyperplasia.

Human granulation-tissue fibroblasts show enhanced proteoglycan gene expression and altered response to TGF-beta 1

Granulation-tissue fibroblasts are phenotypically unique cells that play an important role in wound repair and the development of chronic inflammatory lesions in connective tissue. In the present study, we compared proteoglycan, type I, and type III procollagen gene expression by granulation-tissue fibroblasts from wound and chronically inflamed tissues with normal gingival fibroblasts. We also analyzed the effect of TGF-beta 1 on proteoglycan mRNA levels and macromolecule production by these cells. One granulation-tissue fibroblast strain that was composed exclusively of alpha-smooth-muscle actin-positive cells (myofibroblasts) expressed strongly elevated basal levels of biglycan, fibromodulin, and versican (the large chondroitin sulphate proteoglycan), as well as type I and III procollagen mRNA. TGF-beta 1 enhanced more potently the expression of types I and III procollagen, biglycan, and versican mRNA by these cells as compared with normal fibroblasts. Other granulation-tissue fibroblast strains, in which about half of the cells expressed alpha-smooth-muscle actin, also showed enhanced proteoglycan and types I and III procollagen expression as compared with normal fibroblasts. These results suggest that alterations in matrix composition during inflammation and wound healing are regulated partly by altered phenotypes of the cells that produce the matrix, and partly by altered responses of these cells to TGF-beta 1.

Interferon gamma differentially affects the synthesis of chondroitin/dermatan sulphate and heparan sulphate by human skin fibroblasts

Interferon gamma (IFN gamma) is often considered to be an antifibrotic cytokine because it inhibits collagen synthesis in fibroblasts. Here we report the effects of recombinant human IFN gamma on sulphated glycosaminoglycan chains produced by normal skin fibroblasts from adult donors. IFN gamma (250 i.u./ml) induced an increase in incorporation of D-[1-3H]glucosamine into glycosaminoglycans, either secreted into the culture medium or associated with the cell layer. The structures of these molecules were analysed by using various cleavage agents (heparinases I and II, heparitinase/chondroitinases ABC and AC/periodate oxidation) followed by size-exclusion and anion-exchange HPLC. No modification was detected in the structure of the heparan sulphate chains. In contrast, the cytokine induced changes in the microcomposition of chondroitin/dermatan sulphate chains. More precisely, we found a decrease in the iduronic acid content, associated with down-regulation of the 4-O-sulphation on the GalNAc residues. In contrast, the 6-O-sulphation on these GalNAc residues was potentiated by the cytokine. These results indicate that IFN gamma is able to modulate not only collagen but also the structure of galactosaminoglycans synthesized by human skin fibroblasts.

Rodent models of Alzheimer's disease: rat A beta infusion approaches to amyloid deposits

The development of rodent models for Alzheimer's disease is a critical step for both understanding the disease and developing therapeutic drugs. Transgenic and knockout mouse models will elucidate some important aspects of the etiology of the disease and the development of pharmaceutical treatments. Here, we will focus on the advantages of nontransgenic models. In nontransgenic rat models, intraventricular infusion of A beta 1-40 (alone) generally results in diffuse deposition of A beta with very few focal plaque-like amyloid deposits after a 30-day intraventricular infusion. However, we have recently found that large numbers of scattered A beta immunoreactive plaque-like deposits can be produced in retired female Sprague-Dawley rat breeders using intraventricular infusion of A beta combined with neuropil injection of transforming growth factor beta 1(TGF beta). A beta that was not associated with the large deposits was often immunolocalized with neurons and cell processes. Immunogold electron microscopy demonstrated the presence of A beta in endosome/lysosomes of neuronal processes and glia and basal lamina. In some cases this labeling was clearly in lysosomes of degenerating neurites. This model allows one to introduce A beta and other plaque-associated factors without overexpression of potentially confounding APP domains. We conclude that A beta infusion models will be a useful complement to transgenic approaches to Alzheimer's pathology.

Biosynthesis of dermatan sulphate. Defructosylated Escherichia coli K4 capsular polysaccharide as a substrate for the D-glucuronyl C-5 epimerase, and an indication of a two-base reaction mechanism

The capsular polysaccharide from Escherichia coli K4 consists of a chondroitin ([GlcA(beta 1-->3)GalNAc(beta 1-->4)]n) backbone, to which beta-fructofuranose units are linked to C-3 of D-glucuronic acid (GlcA) residues. Removal of the fructose units by mild acid hydrolysis provided a substrate for the GlcA C-5 epimerase, which is involved in the generation of L-iduronic acid (IdoA) units during dermatan sulphate biosynthesis. Incubation of this substrate with solubilized fibroblast microsomal enzyme in the presence of 3H2O resulted in the incorporation of tritium at C-5 of hexuronyl units. A Km of 67 x 10(-6) M hexuronic acid (equivalent to disaccharide units) was determined, which is similar to that (80 x 10(-6) M) obtained for dermatan (desulphated dermatan sulphate). Vmax was about 4 times higher with dermatan than with the K4 substrate. A defructosylated K4 polysaccharide isolated after incubation of bacteria with D-[5-3H]glucose released 3H2O on reaction with the epimerase, and thus could be used to assay the enzyme. Incubation of a K4 substrate with solubilized microsomal epimerase for 6 h in the presence of 3H2O resulted in the formation of about 5% IdoA and approximately equal amounts of 3H in GlcA and IdoA. A corresponding incubation of dermatan yielded approx. 22% GlcA, which contained virtually all the 3H label. These results are tentatively explained in terms of a two-base reaction mechanism, involving a monoprotic L-ido-specific base and a polyprotic D-gluco-specific base. Most of the IdoA residues generated by the enzyme occurred singly, although some formation of two or three consecutive IdoA-containing disaccharide units was observed.

Transforming growth factor-beta 1 increases internalization of basic fibroblast growth factor by smooth muscle cells: implication of cell-surface heparan sulphate proteoglycan endocytosis

Basic fibroblast growth factor (bFGF) was internalized by smooth muscle cells (SMC) from pig aorta. Correlation between heparin inhibition of binding and late internalization (8 h) implicated low-affinity sites in bFGF internalization. Transforming growth factor-beta 1 (TGF-beta 1) induced a 38% increase in bFGF internalized between 4 and 8 h. While bFGF and/or TGF-beta 1 enhanced cell-surface proteoglycan synthesis, 35S-labelled proteoglycans of the extracellular matrix (ECM) were not affected. This might be explained by the different turnover rates displayed by the two populations of proteoglycans. Although bFGF and/or TGF-beta 1 induced a similar stimulation in cell-surface chondroitin sulphate/dermatan sulphate and heparan sulphate (HS) proteoglycan synthesis, only the turnover of HS proteoglycans was increased. Twice as much HS proteoglycan was internalized in the presence of TGF-beta 1 or bFGF. Furthermore, TGF-beta 1 induced a 43 +/- 12% increase in HS proteoglycan internalized in the presence of bFGF with a parallel 38% increase in bFGF internalization. Overall, the results indicated that bFGF bound to two HS proteoglycan populations. bFGF storage (70% of bFGF bound to SMC) was not affected by TGF-beta 1 under our conditions and involved ECM proteoglycans characterized by a low turnover. bFGF internalization up-regulated by TGF-beta 1 involved cell-surface HS proteoglycan characterized by a high turnover.

TGF-beta modulates the synthesis of proteoglycans by myocardial fibroblasts in culture

In this study we examined the production of proteoglycans by fibroblasts cultured from the left ventricular myocardium of normal adult rats. Various molecular species of proteoglycan were detected, either by labeling glycosaminoglycan chains with 35SO4 or by labeling the proteoglycan core protein with [35S]methionine. The medium of the cell cultures, which contained quantitatively most of the proteoglycans, appeared to consist mainly of biglycan, lesser amounts of decorin and proteoglycans of higher molecular weight. Biglycan and decorin were identified not only by the characteristic mobility of the intact protein and the core protein but also by immunolocation on Western blots. TGF-beta upregulated the synthesis of all these proteoglycans, coincident with elongation of glycosaminoglycan side chains observed for biglycan and decorin. The apparent molecular weight of the core protein of the two proteoglycans remained unaffected by TGF-beta. The results of these experiments suggest that with regard to proteoglycan synthesis and its regulation by TGF-beta, cultured fibroblasts originating from the myocardium share to a large extent the properties of cultured fibroblasts of other organs.

Interleukin-1 upregulates decorin production by arterial smooth muscle cells

An increase in dermatan sulfate-proteoglycan (DSPG) production occurs in cultured aortic smooth muscle cells exposed to macrophage-conditioned media, an effect that is abrogated by an antibody to interleukin-1 (IL-1). To determine which DSPG gene was regulated, cultured arterial smooth muscle cells from monkeys (Macaca fascicularis) were treated with 0 to 500 pg/mL human recombinant IL-1 alpha or IL-1 beta in the presence of [35S]sulfate and [3H]serine. Proteoglycans were isolated from the culture media and purified by selective precipitation and chromatography. Both recombinant IL-1 alpha and IL-1 beta caused a dose-response increase in DSPG production. Northern blot analysis of mRNA isolated from the cells identified 1.6-kb and 2.6-kb transcripts homologous to the cDNA encoding human decorin and biglycan, respectively. IL-1 treatment resulted in increases in the steady-state level of decorin mRNA as high as fourfold to sixfold at 500 pg/mL recombinant IL-beta. By contrast, mRNA for biglycan was unchanged. Western blotting confirmed a specific enhancement of the 45-kD decorin core protein. These data indicate that IL-1 has differential effects on the two DSPG genes and suggest that macrophages may be capable of modifying the extracellular matrix of the artery wall by enhancing smooth muscle cell decorin production.

Cytokines and proteoglycans

Cytokines play an important regulatory role in the metabolism of proteoglycans. Proteoglycans are found in plasma membranes, but predominantly in the extra-cellular matrix. In the latter they are quantitatively and qualitatively essential components. Especially in a tissue like cartilage without any blood vessels, the cells are dependent on cytokines for the communication among themselves in the extra-cellular matrix and also for communication with the 'outside world'. Various cytokines have been found to be able to penetrate the extra-cellular matrix and inhibit, respectively stimulate the proteoglycan synthesis. Also, the degradation of proteoglycans can be stimulated, respectively inhibited by several cytokines. In addition, some cytokines have been found which regulate the effects of the other cytokines. With respect to proteoglycan metabolism a complex cytokine network is emerging. Furthermore it is becoming increasingly clear that proteoglycans are connected to the cytokine network by their own bioactive functions. First, they possibly possess cytokine activities themselves. Second, they can function as receptors, protectors, inactivators and storage ligands for cytokines. So the proteoglycans are clearly involved in the feedback signalling from the extra-cellular matrix to the cells that are synthesizing this extra-cellular matrix. Together with agonistic or antagonistic cytokines they are involved in the regulation of proteoglycan turnover during balanced or unbalanced metabolism in normal, respectively pathological situations.

Altered expression of small proteoglycans, collagen, and transforming growth factor-beta 1 in developing bleomycin-induced pulmonary fibrosis in rats

The development of bleomycin-induced pulmonary fibrosis in rats was studied over a period of 21 d after an intratracheal instillation of bleomycin. The expression of three small proteoglycans (biglycan, decorin, and fibromodulin), collagen III and TGF-beta 1 was studied by RNA-transfer blot analysis. The proteoglycans were also studied by SDS-polyacrylamide gel electrophoresis and Western blots. TGF-beta 1 mRNA increased threefold already on day 3 and remained elevated until day 10. After the increase of TGF-beta 1 mRNA the messages for biglycan and collagen III steadily increased to reach a maximum 10 d after bleomycin instillation. The mRNA for biglycan increased maximally fourfold and that of collagen III 2.5-fold. Decorin mRNA, in contrast to biglycan decreased and reached 20% of control on day 10. The message for fibromodulin remained constant throughout the study period. The amounts of biglycan and decorin in the tissue changed in accordance with the mRNA levels. The results corroborate and extend previous in vitro studies concerning the effect of TGF-beta 1 on the metabolism of small proteoglycans and show that these macromolecules are regulated differently also in vivo. The marked alterations of biglycan and decorin during the development of fibrosis suggests that these proteoglycans have a regulating role in this process.

Cytokines and proteoglycans

Cytokines play an important regulatory role in the metabolism of proteoglycans. Proteoglycans are found in plasma membranes, but predominantly in the extra-cellular matrix. In the latter they are quantitatively and qualitatively essential components. Especially in a tissue like cartilage without any blood vessels, the cells are dependent on cytokines for the communication among themselves in the extra-cellular matrix and also for communication with the 'outside world'. Various cytokines have been found to be able to penetrate the extra-cellular matrix and inhibit, respectively stimulate the proteoglycan synthesis. Also, the degradation of proteoglycans can be stimulated, respectively inhibited by several cytokines. In addition, some cytokines have been found which regulate the effects of the other cytokines. With respect to proteoglycan metabolism a complex cytokine network is emerging. Furthermore it is becoming increasingly clear that proteoglycans are connected to the cytokine network by their own bioactive functions. First, they possibly possess cytokine activities themselves. Second, they can function as receptors, protectors, inactivators and storage ligands for cytokines. So the proteoglycans are clearly involved in the feedback signalling from the extra-cellular matrix to the cells that are synthesizing this extra-cellular matrix. Together with agonistic or antagonistic cytokines they are involved in the regulation of proteoglycan turnover during balanced or unbalanced metabolism in normal, respectively pathological situations.