Enhanced production and extracellular deposition of the endothelial-type plasminogen activator inhibitor in cultured human lung fibroblasts by transforming growth factor-beta

Cytoskeleton regulates expression of genes for transforming growth factor-beta 1 and extracellular matrix proteins in dermal fibroblasts

Cytoskeleton not only controls cell morphology but also regulates cell growth, migration, differentiation, and gene expression, events which are fundamental to embryogenesis, carcinogenesis, and wound healing. We have recently reported that reorganization of cytoskeleton induces expression of mRNA for transforming growth factor-beta 1 (TGF-beta 1), collagenase, and tissue inhibitor of metalloproteinase-I (TIMP-I) in dermal fibroblasts. In this report we have examined the role of gene transcription in this induction. As judged by nuclear run-on assay, trypsin, EGTA (ethylene glycol-bis (beta-aminoethyl ether) N, N, N', N', tetra-acetic acid), or cytochalasin C (Chs) increased the rate of transcription of the TGF-beta 1 gene by 2.0, 2.7, and 1.6 fold, respectively, and of the collagenase gene by 5.3, 6.2, and 3.3 fold. The rate of transcription of the TIMP-I gene was increased by trypsin (4.3 fold) or EGTA (3.8 fold) but unaffected by Chs. Cytochalasin induced an increase in the rate of transcription of procollagen I (alpha 1), procollagen I (alpha 2), and fibronectin genes by 1.4, 1.5, and 1.9 fold respectively, while trypsinization or EGTA treatment had no or little effects on these gene. Since transcription of the TGF-beta 1 gene is believed to be largely governed by the activating protein 1 (AP1) complex, we also examined the expression of mRNA for c-fos and c-jun protoon-coproteins. Trypsinization induced rapid (within 30 min) and transient expression of c-fos mRNA. A 2.4 fold increase in c-jun mRNA was apparent after 4 hr and persisted for at least 24 hr. Actinomycin D (Act D) suppressed the induction of TGF-beta 1 mRNA by Chs but had less effect on the TGF-beta 1 mRNA in trypsinized cells which had been replated for 4 hr, suggesting that the half life of TGF-beta 1 mRNA is reduced in cells with a disassembled cytoskeleton. Simultaneous treatment with Chs and cycloheximide (Cxm) resulted in a superinduction of TGF-beta 1 mRNA by 88 +/- 23% (n = 4, P < 0.05), which was abrogated by preexposure to Act D. In contrast, the induction of collagenase mRNA by Chs was totally blocked by Cxm, indicating that the Cxm-mediated superinduction is selective and that protein synthesis is required for induction of this mRNA. Our results suggest that the activities of genes for proteins involved in the structure (Type I collagen and fibronectin), turnover (collagenase and TIMP-1) and regulation (TGF-beta 1) of extracellular matrix (ECM), are all governed at least in part by the status of the cytoskeleton. Since the cytoskeleton is reorganized during cell division, migration, and differentiation, these results may have implications for the regulation of ECM during such processes as embryogenesis, carcinogenesis, and wound healing.

Role of transforming growth factor-beta 1 and -beta 2 in ddY mouse nephropathy

We investigated the glomerular distribution of transforming growth factor-beta (TGF-beta 1 and TGF-beta 2) protein and the expression of its mRNA, and related factors, in ddY mice, aged 5-60 weeks, before and after the onset of nephropathy, TGF-beta 1 protein expression was observed from the age of 20 weeks onwards, peaking at 50 weeks, and then declining. Expression of TGF-beta 2 protein gradually increased from 5 to 60 weeks. TGF-beta 1 and TGF-beta 2 mRNA were both detected from 5 to 60 weeks. The mesangial matrix expansion index (MMEI) was significantly higher in mice with nephropathy than in those without nephropathy, as was the expression of TGF-beta 1 and TGF-beta 2 proteins (P < 0.05). TGF-beta 2 was significantly positively correlated with the MMEI (P < 0.05). Infiltration of CD68-positive monocytes/macrophages gradually increased until 60 weeks, and was significantly correlated with the expression of TGF-beta 1 (P < 0.05) and TGF-beta 2 (P < 0.01). These findings indicate that TGF-beta 1 and TGF-beta 2 were overexpressed in ddY mice with overt nephropathy compared with pre-nephropathic mice. TGF-beta 2 may be an important mediator of mesangial matrix expansion in ddY mouse nephropathy.

TGFbeta1 regulates gene expression of its own converting enzyme furin

TGFbeta1 is known for its potent and diverse biological effects, including immune regulation, and cell growth and differentiation. We have recently shown that TGFbeta1 precursor is processed by human furin COOH-terminal to the R-H-R-R278 cleavage site to generate authentic mature TGFbeta1. In the present study, we demonstrate that steady-state furin mRNA levels are increased in rat synovial cells by 2 and 20 ng/ml TGFbeta1. Stimulation with TGFbeta1 results in a significant increase in furin mRNA levels, starting at 3 h with the peak effect observed at 12 h (2.5-fold increase +/-0.4). TGFbeta1 did not increase furin mRNA stability, and treatment of synovial cells with actinomycin D, before TGFbeta1 addition prevented the increase in fur gene expression, suggesting that the observed regulation occurs at the level of gene transcription. Treatment of synovial and NRK-49F fibroblastic cells with exogenous TGFbeta1 (5 ng/ml) or TGFbeta2 (10 ng/ml) translates into an increase in pro-TGFbeta1 processing as evidenced by the appearance of a 40-kD immunoreactive band corresponding to the TGFbeta1 NH2-terminal pro-region. Furin processing activity stimulated by TGFbeta2 correlates with significant increase in extracellular mature and heat-activable TGFbeta1 as determined by an isoform-specific ELISA assay. Taken together, these results demonstrate for the first time that TGFbeta1 upregulates gene expression of its own converting enzyme, and that this expression is translated into augmented processing of the TGFbeta1 precursor form. Such adaptive responsiveness of the TGFbeta1 convertase may represent an important aspect of TGFbeta1 bioavailibility in TGFbeta1-related processes and pathological conditions.

Effect of tension-force on plasminogen activator activity from human periodontal ligament cells

The plasminogen activator (PA)-plasmin proteolytic system has recently received considerable attention because of its participation in a wide variety of biological activities and in pathological conditions involving tissue destruction. Excessive mechanical stress such as occlusal trauma is associated with alveolar bone loss in severe periodontitis. Therefore, mechanical stress may involve degradation of the extracellular matrix by occlusal trauma through activation of the PA-plasmin proteolytic system. We examined the effects of mechanical stress on PA activity, gene expressions of tissue type (t) PA, urokinase type (u) PA and PA inhibitor-1 (PAI-1) in human PDL cells. Human PDL cells were cultured on flexible-bottomed culture plates and placed on a Flexercell Strain Unit. The cells were flexed at 6 cycles (5 s strain, 5 s relaxation) at 9% and 18% elongation for 5 d. Application of tension-force induced significantly higher PA activity in stressed PDL cells than in non-stressed controls, and did so in a time- and magnitude-dependent manner (p < 0.001, ANOVA). Western-blot analysis revealed that the high level of activity was due to tPA and not uPA. Gene expression of tPA mRNA in stressed PDL cells, as examined by RT-PCR, increased on d 5. These findings suggest that tPA may be involved in periodontal metabolism in response to mechanical stress.

Low density lipoprotein receptor-related protein modulates the expression of tissue-type plasminogen activator in human colon fibroblasts

Human colon fibroblasts (HCF) produce tissue-type plasminogen activator (t-PA) in culture, but after 24-48 h, t-PA ceases to accumulate in the medium. Here, we report negative feedback regulation of t-PA expression, exerted by t-PA or complexes of t-PA with its physiological inhibitor, plasminogen activator inhibitor type 1 (PAI-1). Inhibition of t-PA expression could be induced by addition of exogenous t-PA or t-PA.PAI-1 complexes and reversed by monoclonal antibody directed against the active site of t-PA. Analysis of metabolically radiolabeled protein and cellular mRNA showed that both t-PA protein and mRNA levels declined considerably after 24 h. When 125I-labeled t-PA or t-PA.PAI-1 complexes were incubated with HCF, monensin-inhibitable endocytosis and catabolism were observed. The low density lipoprotein receptor-related protein (LRP) was found to be expressed by HCF and to mediate these events. Addition of the 39-kDa receptor-associated protein (RAP), an antagonist for ligand interactions with LRP, removed the block to t-PA expression and restored its accumulation in the medium. Moreover, RAP completely prevented the degradation of exogenous 125I-labeled t-PA by HCF, suggesting that LRP is the endocytic receptor for t-PA in these cells. These results demonstrate that cellular modulation of t-PA expression in HCF involves LRP receptor-mediated clearance of t-PA. This LRP receptor-mediated event results in down-regulation of t-PA expression at the mRNA level.

Dual effects of angiotensin II on the plasminogen/plasmin system in rat mesangial cells

Previous studies indicate that angiotensin II (Ang II) stimulates extracellular matrix synthesis through induction of transforming growth factor-beta (TGF-beta) expression. Here we investigate Ang II effects on the plasmin protease system. Plasmin both degrades extracellular matrix itself and activates metalloproteinases which then degrade collagens. Plasmin production is determined by the balance between plasminogen activators (PA) and their inhibitors (PAI-1,2). The data presented here indicate that Ang II treatment of mesangial cells in culture markedly increases PAI-1 gene transcription and PAI-1 mRNA levels but does not change the half life of PAI-1 mRNA. Increased PAI-1 protein was detected 24 hours after Ang II stimulation with a concomitant decrease of PA activity. To determine whether these effects were mediated by TGF-beta, cells were coincubated with Ang II and neutralizing antibody to TGF-beta. Induction of PAI-1 at four hours was not altered but the prolonged effect of Ang II on PAI-1 protein synthesis was markedly diminished. Thus, Ang II acts both through rapid, direct transcriptional up-regulation of the PAI-1 gene and through induction of TGF-beta, providing sustained changes in the PAI-1/PA system, which would favor extracellular matrix accumulation by inhibiting turnover. These data provide further evidence that Ang II can act as a potent fibrogenic molecule independent of its effects on blood pressure.

Effects of transforming growth factor-beta 1 and phorbol ester on PAI-1 and PA genes in human lung cells

Transforming growth factor-beta (TGF-beta) mediates the production of extracellular matrix proteins, proteases and protease inhibitors in epithelial cells. Both TGF-beta and phorbol-12-myristate-13-acetate (PMA) exert both positive and negative effects on mitogenesis in these as well as other cell types. Phorbol esters act through stimulation of protein kinase C (PKC) and are among the most potent tumor promoters known. The present study was conducted to determine whether the effect of TGF-beta in human non-small cell lung cancer (NSCLC) and normal human bronchial epithelial (NHBE) cells parallels that of the phorbol esters and whether this effect of TGF-beta involves PKC. TGF-beta 1 and PMA increased expression of TGF-beta 1 mRNA 24 hr after their addition to both NSCLC and NHBE cells. The effects of these agents on expression of the mRNAs for TGF-beta 2 and TGF-beta 3 were more complex; while TGF-beta 2 and TGF-beta 3 mRNAs increased transiently in response to TGF-beta 1 in NHBE cells and TGF-beta 3 mRNA increased transiently in some NSCLC cells, expression of these mRNAs decreased in most of these cells in response to PMA with the exception of the carcinoid NCI-H727 where TGF-beta 2 mRNA increased dramatically, TGF-beta 1 and PMA both caused a persistent increase in expression of the mRNAs for both plasminogen activator inhibitor-1 (PAI-1) and plasminogen activator (PA) up to 24 hr in most NSCLC cells, with the increase in PAI-1 mRNA beginning several hours before that of PA mRNA. In contrast, while TGF-beta 1 also increased expression of PAI-1 mRNA in NHBE cells, the expression of PA mRNA decreased simultaneously. The effect of PMA on PAI-1 and PA mRNAs was opposite of TGF-beta 1 in these cells, with expression of PAI-1 mRNA decreasing and PA mRNA increasing after addition of PMA. These data show that there is parallel regulation of the genes for TGF-beta 1, PAI-1 and PA by TGF-beta 1 and PMA in NSCLC, but differential regulation of the genes for PAI-1 and PA by these agents in NHBE cells. The responses of the mRNAs and proteins of TGF-beta 1, PAI-1 and PA to TGF-beta 1 and PMA were inhibited by the serine/ threonine kinase inhibitor H7 in NSCLC cells. Treatment of NSCLC cells with TGF-beta 1 and PMA resulted in a persistent increase in the expression of fibronectin mRNA and protein. This response was blocked by the addition of H7. Inhibition of these effects by H7 in NSCLC cells suggests that H7 blocks TGF-beta responses by inhibiting a protein serine/threonine kinase(s). Because the effects of TGF-beta and PMA on the different TGF-beta isoforms, PA, PAI and fibronectin in NHBE and NSCLC cells are complex, our data suggest that there are distinct mechanisms for controlling the different TGF-beta isoforms, PA, PAI and extracellular matrix proteins in normal lung and lung cancer cells.

Modulation of neutral protease expression in human mesangial cells by hyperglycaemic culture

We report on the effect of prolonged hyperglycaemic (11 and 30 mM D-glucose) culture conditions on human mesangial cell matrix metalloproteinases (MMPs), plasminogen activators and their inhibitors. The results indicate that hyperglycaemic conditions modulate the potential proteolytic activity of the enzymes secreted by confluent cultures of these cells. Gelatinase A (MMP-2) activity was always higher in cultures maintained under hyperglycaemic than under normoglycaemic conditions (4 mM D-glucose). In contrast, gelatinase B (MMP-9) activity was decreased under the same conditions. Matrilysin (MMP-7) activity was decreased by up to 100% under hyperglycaemic conditions. Reverse transcriptase-PCR and Western-blotting analyses indicate that in all cases both the transcripts and the protein level were correlated with enzymic activity. One tissue inhibitor of metalloproteinases, TIMP-2, was barely detectable under hyperglycaemic conditions (30 mM D-glucose). In contrast, TIMP-1 increased during the initial 2 weeks of culture in hyperglycaemic conditions and remained elevated to the end of the experiment (4 weeks). Under normoglycaemic conditions TIMP-1 decreased after 2 weeks of culture. Hyperglycaemic conditions also decreased markedly the activity of tissue plasminogen activator (t-PA). This seemed to be due to increased synthesis of its inhibitor, plasminogen activator inhibitor 1, under these conditions rather than to decreased expression of the t-PA enzyme.

Protease nexin 1 in the murine kidney: glomerular localization and up-regulation in glomerulopathies

Protease nexin 1 (PN-1), a potent serpin-class antiprotease, is thought to be synthesized in the murine kidney. However, neither the cellular localization of PN-1 synthesis nor its role has yet been defined. To address these questions, we determined by in situ hybridizations RNase protection assay and immunoblotting, the sites of PN-1 mRNA accumulation in normal mouse kidneys and the modulation of PN-1 expression in several pathological conditions. In normal kidneys, PN-1 mRNA was detected primarily in glomeruli, most likely in mesangial cells. The glomerular expression of PN-1 was substantially enhanced not only in lupus-like glomerulonephritis (induced by IgG3 monoclonal rheumatoid factors or occurring spontaneously in lupus-prone mice), but also in mild glomerular lesions associated with intracapillary thrombi induced by IgG3 anti-trinitrophenyl monoclonal antibodies. In contrast, no modulation of PN-1 mRNA levels was observed during the course of lipopolysaccharide-induced acute tubular necrosis. A constitutive PN-1 gene expression and its up-regulation during glomerular injury suggest a possible role for PN-1 in glomerular biology. In view of its high inhibitory activity towards thrombin, mesangial PN-1 may be involved in the control of glomerular coagulation following initial glomerular injuries.

Growth factors in skeletal muscle regeneration

Adult skeletal muscles are able to regenerate after injury. This process is due to the activation of quiescent muscle precursor cells, also called satellite cells, which proliferate and differentiate to form new myotubes. In this regeneration process, several growth factors which come from the muscle and/or from the motor nerve and inflammatory cells have been shown to play key roles. However, most of our knowledge comes from in vitro studies, where, during myogenesis, proliferation of satellite cells is regulated by FGFs, TGF beta s, PDGF, IGF-I and II, while differentiation appears to be promoted mainly by IGFs. During regeneration in vivo, most of these factors have been shown to operate and interact. Other factors also appear to condition the regeneration process, such as LIF, which acts predominantly as a proliferative factor; and HARP/PTN/HB-GAM and other neurotrophic factors, which may be necessary for the formation of new neuromuscular junctions. TGF beta has a major influence on the reorganisation of the extracellular matrix. This review presents a critical summary of the known effects of growth factors on skeletal muscle regeneration.

The proteolytic potential of normal human melanocytes: comparison with other skin cells and melanoma cell lines

To understand the contribution of epidermal melanocytes in the proteolytic potential of human skin, we have studied melanocytes grown in a low-serum medium deprived of phorbol esters, cholera toxin, and other non-physiological supplements. We focused on the plasminogen activation system and certain matrix metalloproteinases (gelatinases). Supposing that the proteolytic activity of cells can influence binding to collagen matrix and its reorganization, we have analyzed these parameters as well. We found that human melanocytes secreted tissue-type plasminogen activator and utilised it to generate cell-bound plasmin. No urokinase-type plasminogen activator was detected in the cultures but its receptor was found in cell extracts. Both the 72 kDa and 92 kDa gelatinases were secreted by the cells and in equal amounts. In addition, melanocytes secreted the wide-spectrum proteinase inhibitor alpha-2-macroglobulin. Melanocytes cast into collagen matrices retained a rounded morphology, did not extend processes, and were unable to contract collagen lattices. As a control, these parameters were investigated in parallel in cultures of human keratinocytes, dermal fibroblasts, and two melanoma cell lines. The obtained characteristics suggest that normal human melanocytes are proteolytically active cells. This function may pertain to skin physiology and pathophysiology.

Stimulation of fibroblast cell growth, matrix production, and granulation tissue formation by connective tissue growth factor

Connective tissue growth factor (CTGF) is a 36-to 38-kDa peptide that is selectively induced by transforming growth factor-beta (TGF-beta) in fibroblastic cell types. We compared the biologic activities of CTGF with TGF-beta on fibroblasts in culture and in animal models of fibroplasia. CTGF was active as a mitogen in monolayer cultures of normal rat kidney fibroblasts. CTGF did not stimulate anchorage-independent growth of NRK fibroblasts, however, or inhibit the growth of mink lung epithelial cells, distinguishing CTGF's growth-regulatory activities from those of TGF-beta. In NRK fibroblasts, both TGF-beta and CTGF significantly increased the transcripts encoding alpha 1 type I collagen, alpha 5 integrin, and fibronectin. Stimulation of type I collagen and fibronectin protein synthesis by TGF-beta and CTGF was confirmed by pulse labeling of cells with [35S]methionine. Subcutaneous injection of TGF-beta and CTGF into neonatal NIH Swiss mice resulted in a large stimulation of granulation tissue and fibrosis at the site of injection. In situ hybridization studies revealed that TGF-beta injection induced high levels of CTGF mRNA in the dermal fibroblasts at the injection site, demonstrating that TGF-beta can induce the expression of CTGF in connective tissue cells in vivo. No CTGF transcripts were detected in the epidermal cells in either control or TGF-beta-injected skin or in fibroblasts in control (saline-injected) skin. These results demonstrate that, like TGF-beta, CTGF can induce connective tissue cell proliferation and extracellular matrix synthesis.

Epidermal growth factor in gingival crevicular fluid and its binding capacity in inflamed and non-inflamed human gingiva

Epidermal growth factor (EGF) is a pro-inflammatory small peptide (6000 Da) with a variety of biological activities including stimulation of cell differentiation and mediation of proteolysis by binding to its specific receptor on the cell surface. The purpose of this study was to determine the levels of EGF in gingival crevicular fluid (GCF) and the EGF-binding capacity to its receptor in gingival tissue. The GCF samples were collected from six patients by inserting paper strips into shallow (< 5 mm) and deep pockets (> or = 5 mm) for 30 s. The strips were soaked in 0.2 M acetate for extraction and the EGF in the supernatants was analysed by radioimmunoassay. To determine the binding capacity of EGF to its receptor, inflamed gingival tissues (pocket depth > or = 5 mm, Gingival Index = 1, 2 or 3) were collected during periodontal flap surgery and non-inflamed gingival tissues (pocket depth < 5 mm, Gingival Index = 0) were collected during surgical "crown lengthening' for aesthetic purposes. The tissues were pooled by group, homogenized for membrane preparation and the supernatants obtained after centrifugation were used in a 125IEGF binding assay. To determine the effect of inflammation on gingival EGF receptor, inflamed and non-inflamed gingival tissues were collected from six patients and prepared similarly to the binding assay. Gingival preparations were then electrophoresed for Western blot analysis with EGF receptor antiserum. The EGF level in GCF was significantly lower (P < 0.05) in the samples collected from pockets > or = 5 mm (0.9 +/- 0.6 ng/ml) than in those from pockets < 5 mm (2.4 +/- 2.1 ng/ml). The average Gingival Index was higher (2.6 +/- 0.6) in pockets > or = 5 mm than in pockets < 5 mm (1.4 +/- 1.0). Specific binding of 125I-EGF to its receptor in inflamed gingiva was 2.7-fold higher than in non-inflamed gingiva (14.4 +/- 4.9 vs 5.4 +/- 1.8 fmol/g wet tissue). Western blot analysis showed two major immunoreactive bands (180 and 120 kDa), which represent EGF receptor and its degradation products, in inflamed gingiva. The findings show that inflammation activates EGF binding capacity in gingiva and that the up-regulation of EGF receptor in inflamed gingiva might be associated with a lowered concentration of EGF in GCF produced adjacent to inflamed gingiva. This up-regulation of EGF receptor during inflammation might be an important mechanism in the pathogenesis of periodontal disease.

Role of stromal myofibroblasts infiltrating colon cancer in tumor invasion

In the normal colon, myofibroblasts are closely apposed to colonocytes where they deposit type IV collagen, the main basement membrane component. In colon carcinomas, this epithelial-mesenchymal association is physically disrupted, leading to the production of an abnormal, type IV collagen defective, basement membrane. Tumor-infiltrating myofibroblasts are migratory cells that accumulate at the invasive front of the colorectal carcinomas. They produce lytic enzymes able to degrade the basement membrane surrounding tumor glands. They also participate in the synthesis of the extracellular matrix components of the tumor stroma, which could subsequently alter the adhesive and migratory properties of the epithelial colon cancer cells. These results suggest that tumor-infiltrating myofibroblasts play a role in the invasion and metastasis of colorectal tumor cells.

Gene expression of TGF-beta 1 and elaboration of extracellular matrix using in situ hybridization and EM radioautography during dentinogenesis

BACKGROUND AND METHODS

The expressions of TGF-beta 1 and Type I collagen mRNA were studied by in situ hybridization and immunohistochemistry then the secretory pathway of dentin phosphoprotein was investigated electron microscopic radioautography in rat incisors.

RESULTS AND CONCLUSIONS

Expression of TGF-beta 1 mRNA was observed in dental papilla cells before dentin formation. The signals were most intense in pre- and postodontoblasts and during dentinogenesis, but became weaker in the secretory region during the dentin formation. Type I collagen mRNA was expressed in essentially the same as that of TGF-beta 1. These results suggest that TGF-beta 1 plays an important role in the differentiation of, and collagen synthesis by odontoblasts. Radioautography showed radioactivity in the rough endoplasmic reticulum 5 min after injection of 3H-serine. Silver grains were observed over the cylindrical portions of the cis-face of the Golgi apparatus at 10 min and over the cylindrical portions of the transface at 20 min. The secretory granules showed the strongest reaction between 20 min and 1 h after injection. At 45 min, a significant labeled band appeared at the mineralization front. The pathway of 3H-proline was essentially the same as that of 3H-serine, but 3H-proline moved more slowly. Secretory granules were heavily labeled from 30 min; no labeling was found at the mineralization front at 45 min. The labeling pattern with 3H-serine appears to be closely related to the localization of phosphoproteins. Dentin phosphoproteins are related to secretory granules and are secreted by odontoblasts as the mineralization front, being involved in the process of dentin mineralization.

Aggravation of gingival inflammatory symptoms during pregnancy associated with the concentration of plasminogen activator inhibitor type 2 (PAI-2) in gingival fluid

Gingival inflammatory symptoms are aggravated during pregnancy. In vitro studies suggest a hormonal influence on the plasminogen activator inhibitor type 2 (PAI-2), and a disturbed balance of the fibrinolytic system could help to explain pregnancy gingivitis. Gingival crevicular fluid (GCF) was sampled in 14 women in pregnant and post-pregnant states. The gingival condition was assessed by the gingival index of Løe & Silness (GI) and the amount of bacterial plaque by the plaque index of Silness & Løe (PI). The ratio of sites with gingivitis to sites with bacterial plaque was calculated (G/P-ratio). Antigen levels of tissue plasminogen activator (t-PA), urokinase-type plasminogen activator (u-PA), plasminogen activator inhibitors type 1 (PAI-1) and PAI-2 in GCF were determined with ELISAs and 17 beta-oestradiol and progesterone in serum with radioimmunoassays. For each individual the differences (delta) in hormone levels and PAs and PAIs between pregnancy and post-pregnancy were calculated. Based on differences in G/P-ratio between pregnancy and post-pregnancy, subgrouping was done into a high-reacting and a low-reacting group. For the total group, the mean G/P-ratio was 2.0 during and 1.2 after pregnancy (p = 0.064). A statistically significant correlation between delta progesterone and delta PAI-2 was noted: the higher delta progesterone, the lower delta PAI-2. No other significant correlations between hormone levels and components of the fibrinolytic system were found. For the total group of women, the concentrations of PAI-2, PAI-1 and t-PA were significantly higher during than after pregnancy. The individuals in the high-reacting group, however, showed a lower or unchanged production of PAI-2 during pregnancy, while those in the low-reacting group showed a greatly increased production. The lower inhibitory capacity in terms of a low production of PAI-2 during pregnancy in women with a higher inflammatory reaction indicates that the components of the fibrinolytic system may be involved in the development of pregnancy gingivitis and implies that PAI-2 serves as an inhibitor of importance for tissue proteolysis. The present finding contributes to the explanation of pregnancy gingivitis.

Type-1 plasminogen activator inhibitor in human renal cell carcinoma

In experimental models, plasminogen activator-mediated degradation of the extracellular matrix is inhibited by type-1 plasminogen activator inhibitor (PAI-1). PAI-1 has also been shown to protect tumour stromal tissue from autoproteolytic activities and may thus substantially promote tumour growth and metastasis formation. Human renal cell carcinoma (RCC) cells express significant amounts of plasminogen activator activity. In the present study, the expression of its specific inhibitor PAI-1 has been investigated in 32 cases of RCC and compared with adjacent non-tumour renal tissues. RCC tissue exhibited higher levels of PAI-1, determined at both the antigen and the mRNA level by ELISA and Northern blot analysis respectively. Immunohistochemical analysis showed that PAI-1 antigen was primarily confined to tumour cells and vascular endothelium, a distribution similar to that previously reported for plasminogen activator activity in RCC. The close co-localization with endogenous plasminogen activator activity may be important in the regulation of RCC-associated proteolysis. The increased expression of PAI-1 and its predominant localization within the tumour may help to conserve tumour tissue integrity and may thus promote RCC progression and metastasis formation.

Expression of transforming growth factor-beta isoforms in human glomerular diseases

Protein and mRNA expression of TGF-beta isoforms, TGF-beta 1, -beta 2 and -beta 3, and deposition of fibronectin containing extra domain A (fibronectin EDA+) and plasminogen activator inhibitor-1 (PAI-1) were studied in human chronic glomerulonephritis and diabetic nephropathy. Normal kidneys showed similar, weak immunostaining for all three TGF-beta isoforms. TGF-beta mRNA expression was weak for all isoforms with TGF-beta 1 > TGF-beta 3 >> TGF-beta 2. In thin basement membrane disease and minimal change disease, disorders where extracellular matrix accumulation is not a feature, immunoreactivity and mRNA expression did not differ from normal. In contrast, diseases characterized by extracellular matrix accumulation (IgA nephropathy, focal and segmental glomerulosclerosis, crescentic glomerulonephritis, lupus nephritis and diabetic nephropathy) all showed significantly increased expression of the three TGF-beta isoforms in glomeruli and the tubulointerstitium. While glomerular and tubulointerstitial deposition of two matrix components induced by TGF-beta, fibronectin EDA+ and PAI-1, was significantly elevated in all diseases with matrix accumulation, correlation analysis revealed a close relationship primarily with TGF-beta 1. We conclude that, for a spectrum of human glomerular disorders, increased protein expression of all three TGF-beta isoforms and proteins induced by TGF-beta is associated with pathological accumulation of extracellular matrix.

Transforming growth factor-beta system and its regulation by members of the steroid-thyroid hormone superfamily

TGF-beta s and their receptors are expressed ubiquitously, and they act as key regulators of many aspects of cell growth, differentiation, and function. Steroid action on target tissues is often associated with increase in TGF-beta isoforms. Regulation of TGF-beta expression and activation is crucial for normal development and growth control. The loss of responsiveness of different tumor cells to the antiproliferative effects of TGF-beta is a common feature in carcinogenesis. Multiple changes are required for the cells to gain complete resistance to TGF-beta growth inhibition (Fynan and Reiss, 1993; Kimchi et al., 1988; Samuel et al., 1992). Although many tumor cells are not growth inhibited by TGF-beta, they respond to TGF-beta treatment by changes in the expression of matrix components and enhanced proteolytic activity (KeskiOja et al., 1988). Agents that induce TGF-beta production in target tissues can have a chemopreventive or chemotherapeutic value for the management of epithelial malignancies. Conversely, data supporting a positive role for TGF-beta in established tumor progression are beginning to emerge (Arteaga et al., 1993a,b; Barrett-Lee et al., 1990; Arrick et al., 1992 ; E. A. Thompson et al., 1991). In later stages of tumor development, cell proliferation is often not inhibited by TGF-beta, and tumor cells secrete large amounts of this growth factor (Fynan and Reiss, 1993). In vivo TGF-beta secreted by tumor or stromal cells can influence host responses such as a natural killer cell function and thus indirctly support tumor cell viability (Arteaga et al., 1993b). TGF-beta may also affect tumor growth indirectly by stromal effects and promotion of angiogenesis. TGF-beta may also be involved in the progression of breast tumors from the steroid-sensitive to steroid-insensitive state (King et al., 1989). Understanding of the net effect of TGF-beta in different stages of tumor development is critical for the evaluation of its therapeutic value in cancer treatment.

Pre- and post-translational regulation of lysyl oxidase by transforming growth factor-beta 1 in osteoblastic MC3T3-E1 cells

The final enzymatic step required for collagen cross-linking is the extracellular oxidative deamination of peptidyl-lysine and -hydroxylysine residues by lysyl oxidase. A cross-linked collagenous extracellular matrix is required for bone formation. The goals of this study were to compare the transforming growth factor (TGF)-beta 1 regulation of lysyl oxidase enzyme activity and steady state mRNA levels to changes in COL1A1 mRNA levels in MC3T3-E1 osteoblastic cells. TGF-beta 1 increased steady state lysyl oxidase and COL1A1 mRNA levels in a dose- and time-dependent manner. The increase in lysyl oxidase mRNA levels was transient, peaking at 12 h and 8.8 times controls in cells treated with 400 pM TGF-beta 1. COL1A1 steady state mRNA levels increased maximally to 3.5-fold of controls. Development of increased lysyl oxidase enzyme activity was delayed and was of slightly lower magnitude than the increase in its mRNA levels. This suggested limiting post-translational processing of lysyl oxidase proenzyme. Pulse-labeling/immunoprecipitation studies demonstrated slow proenzyme secretion and proteolytic processing. Development and application of an independent assay for lysyl oxidase proenzyme proteolytic processing activity verified its proportionately lower stimulation by 400 pM TGF-beta 1. Thus, lysyl oxidase regulation by TGF-beta 1 in osteoblastic cell cultures occurs at both pre- and post-translational levels. This regulation is consistent with increased production of a collagenous extracellular matrix.

Induction of plasminogen activator inhibitor type 1 in murine lupus-like glomerulonephritis

Three major components of the plasminogen activators (PA)/plasmin system are synthesized physiologically in glomeruli, and can be involved in glomerular proteolysis and extracellular matrix metabolism: tissue-type PA (tPA), urokinase (uPA) and PA inhibitor type 1 (PAI-1). To explore the possible role of a dysregulation of the plasmin protease system in the development and progression of lupus-like glomerulonephritis, we studied the expression of the renal plasmin protease components during the course of the disease, either acute, induced by IgG3 monoclonal cryoglobulins, or chronic, occurring spontaneously in three different lupus-prone mice: (NZBxNZW)F1, BXSB and MRL-lpr/lpr. RNase protection assays and in situ hybridizations revealed a marked glomerular induction of PAI-1 mRNA abundance without any significant changes in renal tPA and uPA mRNA levels in the two different types of lupus-like glomerulonephritis. The overexpression of PAI-1 mRNA occurred in parallel with a significant decrease in glomerular tPA-catalyzed enzymatic activity as determined by zymographic analysis. In addition, a concomitant increase in glomerular expression of transforming growth factor beta 1 (TGF-beta 1) mRNA was observed. The demonstration of a close correlation between the PAI-1 and TGF-beta 1 mRNA levels and the severity of lupus-like glomerular lesions suggests that a pertubation of the glomerular PA/PAI balance, resulting from a marked TGF-beta 1-mediated induction of PAI-1 gene expression, plays an important role in the progression of lupus-like glomerular lesions, leading to glomerulosclerosis.

Role of angiotensin II in the expression and regulation of transforming growth factor-beta in obstructive nephropathy

Unilateral ureteral obstruction (UUO) leads to fibrosis of the obstructed kidney. We tested the hypothesis that interstitial fibrosis in UUO results, at least in part, from enhanced expression of transforming growth factor-beta (TGF-beta) which in turn is regulated by local angiotensin II (Ang II) generation. (The generic name TGF-beta is used to discuss properties shared by all isoforms, but special reference to other isoforms is made when specifically needed.) Using Northern blot and immunohistochemical analysis, we examined the expression of TGF-beta in rat kidneys after 24 hours (aUUO) and one week (cUUO) of obstruction. Obstructed kidneys from both periods had increased interstitial and perivascular TGF-beta immunoreactivity compared to contralateral and sham kidneys, in which immunostaining was confined to the inner medulla. Relative abundance of all TGF-beta mRNA isoforms were higher in the obstructed than in contralateral and sham kidneys in both aUUO and cUUO. Expression of TGF-beta isoforms varied according to site (cortex vs. medulla), segment of the nephron, type of cells and duration of the obstruction. The increase in TGF-beta immunoreactivity and mRNA levels in aUUO and cUUO was almost totally abolished by pretreatment with losartan. We conclude that in UUO: (a) TGF-beta gene expression is increased and differentially regulated; (b) Ang II, at least partially, mediates the overexpression of TGF-beta gene; and (c) Ang II may play a central role in fibrogenesis in this and other models of tubulointerstitial disease.

Accumulation of extracellular matrix and developmental dysregulation in the pancreas by transgenic production of transforming growth factor-beta 1

Transgenic mice expressing transforming growth factor-beta 1 (TGF-beta 1) in the pancreatic beta-islet cells directed by human insulin promoter were produced to study in vivo effects of TGF-beta 1. Fibroblast proliferation and abnormal deposition of extracellular matrix were observed from birth onward, finally replacing almost all the exocrine pancreas. Cellular infiltrates comprising macrophages and neutrophils were also observed. Plasminogen activator inhibitor was induced in the transgenic pancreas as well as fibronectin and laminin, partly explaining accumulation of extracellular matrix. TGF-beta 1 inhibited proliferation of acinar cells in vivo as evidenced by decreased bromodeoxyuridine incorporation. Development of pancreatic islets was dysregulated, resulting in small islet cell clusters without formation of normal adult islets; however, the overall islet cell mass was not significantly diminished. Additional transgenic lines with less pronounced phenotypes had less expression of TGF-beta 1 transgene. These findings suggest that TGF-beta 1 might be a mediator of diseases associated with extracellular matrix deposition such as chronic pancreatitis, and this mouse model will be useful for further analysis of the in vivo effects of TGF-beta 1, including its potential for immunosuppression.

Human mast cell chymase and leukocyte elastase release latent transforming growth factor-beta 1 from the extracellular matrix of cultured human epithelial and endothelial cells

Monolayer cultures of human epithelial and endothelial cells were used to study the association of latent transforming growth factor-beta 1 (TGF-beta 1) to extracellular matrices and its release and activation during matrix degradation. Human umbilical vein endothelial cells and embryonic lung fibroblasts produced relatively high levels of TGF-beta 1, its propeptide (beta 1-latency-associated protein), and latent TGF-beta-binding protein and incorporated latent TGF-beta 1 into their matrices as shown by immunoblotting. Amnion epithelial cells produced lower levels of these proteins. Confluent cultures of epithelial cells were exposed to matrix-degrading proteases and glycosidases. Mast cell chymase, leukocyte elastase, and plasmin efficiently released matrix-bound latent TGF-beta 1 complexes, while chondroitinase ABC and heparitinases were ineffective. The ability of the proteases to activate recombinant latent TGF-beta 1 was tested using growth inhibition assays and a novel sodium deoxycholate-polyacrylamide gel electrophoresis followed by immunoblotting. Sodium deoxycholate solubilized M(r) 25,000 TGF-beta 1 but did not dissociate high M(r) latent TGF-beta 1 complexes, allowing separation of these forms by polyacrylamide gel electrophoresis. Mast cell chymase and leukocyte elastase did not activate latent TGF-beta 1, suggesting that its release from matrix and activation are controlled by different mechanisms. The release of TGF-beta from the matrix by leukocyte and mast cell enzymes may contribute to the accumulation of connective tissue in inflammation.

Effect of Campylobacter rectus LPS on plasminogen activator-plasmin system in human gingival fibroblast cells

The plasminogen activator (PA)-plasmin system is implicated in the degradation of the extracellular matrix in inflammation through activation of metalloproteases and prekallikrein. We examined the activation of the PA-plasmin system in human gingival fibroblast cells (Gin-1 cells) following treatment with lipopolysaccharide (LPS) from Campylobacter rectus, which is frequently detected at sites of periodontal disease. The C. rectus LPS stimulated the plasmin activity in the conditioned medium of Gin-1 cells in a time- and dose-dependent manner, and C. rectus LPS also stimulated the PA activity in the conditioned medium. The PA produced by Gin-1 cells was determined to be urokinase PA (uPA), as preincubation of Gin-1 conditioned medium with anti-uPA antiserum completely inhibited the PA activity while that with anti-tPA antiserum had no inhibitory effect. The concentration of PA inhibitor-1 (PAI-1) in the conditioned medium was decreased by the addition of C. rectus LPS. Therefore, the enhancement of plasmin activity in the conditioned medium was dependent on increased uPA activity via the decrease of the PAI-1 level of Gin-1 cells treated with C. rectus LPS. Furthermore, the conditioned medium of Gin-1 cells treated with C. rectus LPS showed significantly increased kallikrein activity, indicating the conversion of prekallikrein to kallikrein, which converts kininogen into kinin. These findings suggest that C. rectus LPS is a potent stimulator of inflammation of gingival tissue which acts through stimulation of the PA-plasmin system.

Synthesis and degradation of connective tissue macromolecules in pachydermoperiostosis (PDP): evidence for altered processing of plasminogen activator inhibitor-1 (PAI-1)

Pachydermoperiostosis (PDP) is a hereditary disease with hyperostosis, clubbing of fingers, coarse skin and thickening of bones. Previous studies have disclosed some abnormality in the connective tissue in these patients. The purpose of the present study was to investigate connective tissue pathology in one family with PDP using fibroblast cultures. Fibroblastic cells were established from both the affected and healthy looking skin of 2 patients with PDP, and the expression of types I and III collagen, 92 kDa and 72 kDa gelatinases, metalloproteinase inhibitor (TIMP-1), human retinoic acid receptor and transforming growth factor beta (TGF beta) was analyzed. The modulation of glycoprotein synthesis, and of plasminogen activators and their inhibitors by TGF beta in vitro were also studied. The results indicated that collagen genes and gelatinases were similarly expressed in PDP and control cells, as well as the human retinoic acid receptor. TGF beta stimulated, both in PDP cells and normal cells, the synthesis of fibronectin, procollagen and plasminogen activator inhibitor-l (PAI-1), but qualitative differences could not be found. Proteolytically processed forms of PAI-1 were detected in PDP cell lines.

The relationship between the immunodetection of transforming growth factor-beta in lung adenocarcinoma and longer survival rates

We immunohistochemically examined the expression of transforming growth factor-beta (TGF-beta) on tissue specimens from primary 124 human lung adenocarcinoma, using a polyclonal antibody. The overall mean immunoreactivity of TGF-beta was 25.7 +/- 22.9, therefore we separated patients into two groups according to their mean immunoreactivity. There were 59 (48%) with a high TGF-beta and 65 (52%) with a low TGF-beta. No correlation was observed between the expression of TGF-beta and clinicopathological factors except for degree of differentiation. The 5-year survival rates of patients with high and low TGF-beta were 71% and 37%, respectively (P < 0.05). A multivariate analysis using the Cox life table regression model showed TGF-beta to be a significantly independent factor. We thus concluded, based on our findings, that the expression of TGF-beta was found to be related to a better prognosis. Therefore, estimating the negative cell proliferation activity induced by TGF-beta on immunohistochemical technique is considered to be useful for determining the patients' prognosis in cases of lung adenocarcinoma.

Alteration in cell morphology triggers transforming growth factor-beta 1, collagenase, and tissue inhibitor of metalloproteinases-I expression in normal and hypertrophic scar fibroblasts

Using immunocytochemistry and Northern blot analysis, we investigated the role of cell morphology and reorganization of the cytoskeleton in the expression of transforming growth factor-beta 1 (TGF-beta 1) in human dermal fibroblasts. Disruption of the cytoskeleton was induced by three different agents--trypsin, ethyl-eneglycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), or cytochalasin--and was confirmed by staining with rhodamine-labeled phalloidin. Immunocytochemical staining with antibodies specific for TGF-beta 1 revealed a cell-shape-related induction of TGF-beta 1. Northern blot analysis of total RNA showed a significant increase in the expression of TGF-beta 1 mRNA as early as 4 h and peaking at 12 h after disruption of the cytoskeleton. Quantitative analysis of TGF-beta 1 mRNA expression at 4 h after treatment with trypsin, EGTA, or cytochalasin C showed increases of 2.6-, 3.3-, and 2.6-fold, respectively. Disruption of the cytoskeleton by trypsin, EGTA, or cytochalasin C increased mRNA for collagenase by 3.8-fold, 2.3-fold, or 2.5-fold, respectively. The expression of mRNA for tissue inhibitor of metalloproteinases I (TIMP-I) also showed a 3.2-fold increase by trypsin, a 3.6-fold increase by EGTA, and a 2.5-fold increase by cytochalasin C. Cell-shape-related induction of TGF-beta 1, collagenase, and TIMP-I genes appears to be selective, as the levels of mRNA for fibronectin and type I procollagen were not significantly altered. These data suggest that gene expression of TGF-beta 1, collagenase, and TIMP-I is governed by the status of the cytoskeleton microfilament organization, which may be a mechanism of gene regulation during cell division, migration, and differentiation, events fundamental to wound healing.

Many roads lead to atheroma

For many years cholesterol was seen as the worst enemy of coronary arteries. Recent advances show that interactions between lipoproteins, coagulation and growth factors are important in atherosclerosis.

Reorganization of endothelial cord-like structures on basement membrane complex (Matrigel): involvement of transforming growth factor beta 1

The formation of capillary-like network structures by cultured vascular endothelial cells on reconstituted basement membrane matrix, Matrigel, models endothelial cell differentiation, the final step of angiogenesis (Kubota et al., 1988; Grant et al., 1989). When endothelial cells derived from bovine aorta and brain capillaries were plated on Matrigel, DNA synthesis was suppressed and a network of capillary-like structures rapidly formed in 8-12 h. With time, the network broke down, resulting in dense cellular cords radiating from multiple cellular clusters in 16-24 h. Finally, multicellular aggregates of cells were formed as the network underwent further retraction. Network regression was prevented when either dithiothreitol (DTT) or anti-TGF-beta 1 antibodies were added during the assay. The addition of exogenous TGF-beta 1 promoted the regression of endothelial cells into the clusters. This response to TGF-beta 1 was blocked by potent serine threonine protein kinase inhibitors, H-7 and HA100. TGF-beta 1 was released from polymerized Matrigel by incubation with Dulbecco's modified eagle's medium (DMEM) in the absence of cells. The Matrigel-conditioned DMEM inhibited endothelial DNA synthesis even in the presence of anti-TGF-beta 1 antibodies. These results suggest that TGF-beta 1 and possibly other soluble factors from Matrigel may be important for differentiation and remodeling of endothelial cells in a capillary network with possible implications for wound healing and development.

Renal TGF-beta regulation in spontaneously diabetic NOD mice with correlations in mesangial cells

Diabetic nephropathy is characterized by excessive glomerular matrix accumulation, basement membrane thickening and sclerosis. Although it is clear that systemic metabolic disturbances precipitate such renal changes, the signals and pathways involved in this process are not fully elucidated. Recent evidence suggests that growth factors/cytokines are intimately involved in the pathogenesis of diabetic nephropathy. Because of its prosclerotic properties, transforming growth factor-beta (TGF-beta) is a prime candidate mediator of diabetic nephrosclerosis. We examined perfused kidney tissues isolated from spontaneously diabetic, non-obese diabetic mice (NOD) for TGF-beta content. By using murine isotype specific TGF-beta probes, we demonstrate that within 5 to 10 days of hyperglycuria renal TGF-beta 2 mRNA and protein content increases. By immunohistochemical analysis, de novo TGF-beta immunoreactivity was detected within both glomeruli and the interstitium. In order to determine the signals involved in promoting kidney TGF-beta content in vivo, TGF-beta regulation was examined in renal mesangial cells in vitro. Murine mesangial cells stimulated with glycosylated protein secrete bioactive TGF-beta and demonstrate a disproportionate increase in the steady state levels of TGF-beta 2 mRNA. These data suggest that a major early renal response in NOD mice to hyperglycemia or to glycosylated proteins is characterized by increases in TGF-beta.

Effects of cytokines on gingival fibroblasts in vitro are modulated by the extracellular matrix

Fibroblast function in gingival tissue is thought to be regulated by the local cellular environment--both the extracellular matrix and soluble factors. In an attempt to artificially re-create this situation fibroblasts have been cultured within 3-dimensional collagen gels in an environment more physiologically comparable to connective tissue. Using such a model we investigated the effects of the extracellular matrix on gingival fibroblast growth and synthetic activity and on the cellular responsiveness to 4 soluble factors--epidermal growth factor (EGF), platelet-derived growth factor (PDGF), transforming growth factor-beta (TGF-beta 1) and interleukin-1 beta (IL-1 beta). Fibroblasts cultured within collagen gels showed similar growth rates, an increased production of collagen but reduced levels of hyaluronan synthesis in comparison to cells in monolayer culture. Cellular responsiveness to soluble mediators was also modulated by the collagen matrix, with a generalised reduction in response by cells embedded within the matrix. The stimulatory effects of EGF and PDGF on cell growth in monolayer over a 14-day period were only found during the initial stages of culture within gels. Similarly the stimulation of matrix production by cells induced by TGF-beta 1 on plastic was reduced or even negated when cells were cultured in collagen gels. On plastic IL-1 beta significantly stimulated cell growth but had no effect on either collagen or hyaluronan production by fibroblasts. In gel cultures, this cytokine had no effect on cell proliferation, but significantly inhibited both collagen and hyaluronan synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasminogen activator inhibitor-1 in the pathogenesis of delayed radiation damage in rat spinal cord in vivo

The pathophysiology of radiation-induced damage to the central nervous system (CNS) is poorly understood. Preliminary data suggest that fibrinolytic inhibitors are involved in the development of necrosis. In this study, cervical spinal cord irradiation was studied in 90 rats by measuring plasminogen activator inhibitor (PAI)-1 on Days 2, 7, 30, 60, 90, 120, 130, or 145 after irradiation. Paralysis due to radiation necrosis developed in all animals kept alive for 140 to 150 days. Assay of PAI-1 was by Western blot, enzyme-linked immunosorbent assay (ELISA), and complex formation with 125I-labeled urokinase. No PAI-1 was detected in normal spinal cord tissue or in irradiated spinal cord up to Day 90. However, PAI-1 was detected at Day 120 and was marked by elevated ELISA levels at the time of paralysis. Western blot showed detectable PAI-1 (51 kD) at Day 120 and very significant levels at the time of paralysis. Complex formation with 125I-labeled urokinase was also detected at Day 120 with similar results. Immunohistochemical studies showed that PAI-1 was highly concentrated within and immediately adjacent to zones of necrosis at 145 days and was absent in normal tissue. This study adds considerable weight to the proposal that PAI-1 is closely associated with the pathogenesis of CNS radiation necrosis.

Expression of fibrogenic cytokines in rat small intestine after fractionated irradiation

The molecular and cellular mechanisms that regulate the radiation-induced fibrotic response in the intestine are not known. In addition to increased amounts of connective tissue, inflammatory cell aggregates are often found, especially in conjunction with acute or chronic mucosal ulcerations. These inflammatory cells are a major source of cytokines that influence connective tissue metabolism. Hence, a possible link may exist between the cellular inflammatory response and fibrosis. This preclinical study examined the influence of fractionated irradiation on the expression of three inflammatory/fibrogenic cytokines in rat small intestine. A rat intestinal transposition model was used for localized fractionated irradiation of a 3-4-cm segment of small bowel. Fifty-nine male Sprague-Dawley rats were irradiated or sham irradiated with 9 daily fractions of 5.2 Gy. Expression of Interleukin 1 alpha (IL-1 alpha), Transforming growth factor beta 1 (TGF-beta 1), and Platelet derived growth factor-AA (PDGF-AA) was assessed by immunohistochemistry. Irradiated and unirradiated intestine was examined 24 h, 14 days, and 26 weeks after completion of irradiation. Unirradiated intestine exhibited immunohistochemical expression of IL-1 alpha, TGF-beta 1 and PDGF-AA that conformed to known staining patterns in normal tissue. Irradiated intestine showed increased expression of all three cytokines at all assessment times. The increased cytokine expression correlated with fibrosis and inflammatory cell infiltrates in irradiated intestine. This was particularly evident in areas with mucosal ulcerations. Fractionated irradiation of small intestine elicits increased expression of IL-1 alpha, TGF-beta 1, and PDGF-AA in areas of acute and chronic radiation injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Type I receptors specify growth-inhibitory and transcriptional responses to transforming growth factor beta and activin

Transforming growth factor beta (TGF-beta) and activin bind to receptor complexes that contain two distantly related transmembrane serine/threonine kinases known as receptor types I and II. The type II receptors determine ligand binding specificity, and each interacts with a distinct repertoire of type I receptors. Here we identify a new type I receptor for activin, ActR-IB, whose kinase domain is nearly identical to that of the recently cloned TGF-beta type I receptor, T beta R-I. ActR-IB has the structural and binding properties of a type I receptor: it binds activin only in the presence of an activin type II receptor and forms a heteromeric noncovalent complex with activin type II receptors. In Mv1Lu lung epithelial cells, ActR-IB and T beta R-I signal a common set of growth-inhibitory and transcriptional responses in association with their corresponding ligands and type II receptors. The transcriptional responses include elevated expression of fibronectin and plasminogen activator inhibitor 1. Although T beta R-I and ActR-IB are nearly identical in their kinase domains (90% amino acid sequence identity), their corresponding type II receptor kinase domains are very different from each other (42% amino acid sequence identity). Therefore, signaling of a specific set of responses by TGF-beta and activin correlates with the presence of similar type I kinases in their complex. Indeed, other TGF-beta and activin type I receptors (TSR-I and ActR-I) whose kinase domains significantly diverge from those of T beta R-I and ActR-IB do not substitute as mediators of these growth-inhibitory and extracellular matrix transcriptional responses. Hence, we conclude that the type I receptor subunits are primary specifiers of signals sent by TGF-beta and activin receptor complexes.

Type I receptors specify growth-inhibitory and transcriptional responses to transforming growth factor beta and activin

Transforming growth factor beta (TGF-beta) and activin bind to receptor complexes that contain two distantly related transmembrane serine/threonine kinases known as receptor types I and II. The type II receptors determine ligand binding specificity, and each interacts with a distinct repertoire of type I receptors. Here we identify a new type I receptor for activin, ActR-IB, whose kinase domain is nearly identical to that of the recently cloned TGF-beta type I receptor, T beta R-I. ActR-IB has the structural and binding properties of a type I receptor: it binds activin only in the presence of an activin type II receptor and forms a heteromeric noncovalent complex with activin type II receptors. In Mv1Lu lung epithelial cells, ActR-IB and T beta R-I signal a common set of growth-inhibitory and transcriptional responses in association with their corresponding ligands and type II receptors. The transcriptional responses include elevated expression of fibronectin and plasminogen activator inhibitor 1. Although T beta R-I and ActR-IB are nearly identical in their kinase domains (90% amino acid sequence identity), their corresponding type II receptor kinase domains are very different from each other (42% amino acid sequence identity). Therefore, signaling of a specific set of responses by TGF-beta and activin correlates with the presence of similar type I kinases in their complex. Indeed, other TGF-beta and activin type I receptors (TSR-I and ActR-I) whose kinase domains significantly diverge from those of T beta R-I and ActR-IB do not substitute as mediators of these growth-inhibitory and extracellular matrix transcriptional responses. Hence, we conclude that the type I receptor subunits are primary specifiers of signals sent by TGF-beta and activin receptor complexes.

Transient production of TGF-beta 2 by postnatal cerebellar neurons and its effect on neuroblast proliferation

The beta transforming growth factors (TGF-beta) are suggested to regulate developmental processes since they are distinctly expressed during embryogenesis and exert pleiotropic effects on cell growth and differentiation, In the present study the expression of TGF-beta isoforms was investigated in the postnatal and adult mouse brain. As shown by in situ hybridization, TGF-beta 2 was expressed in the choroid plexus, hippocampus, dentate gyrus and cerebellar Purkinje neurons, both postnatally and in adults. Furthermore, TGF-beta 2 expression was observed postnatally in immature cerebellar neurons of both the external and internal granule cell layers. In the external granule cell layer, the frequency of TGF-beta2 transcripts increased until postnatal day 10 and declined thereafter. In contrast to TGF-beta 2, no TGF-beta 1 mRNA was detected in cerebellar granule cells. TGF-beta 3 expression was widely distributed in postnatal brains although at very low levels. The significance of TGF-beta 2 production by cerebellar granule cells was further investigated using cultures of small cerebellar neurons. In these cultures reverse polymerase chain reaction analysis revealed expression of TGF-beta 2 but low or almost undetectable levels of TGF-beta 1 or -beta 3 mRNAs. Likewise, only TGF-beta 2 protein in its latent form was identified in the culture supernatant; the release of TGF-beta 2 was maximal during the second day in vitro. Furthermore, TGF-beta was found to inhibit the proliferation of cultured small cerebellar neurons. Taken together, these data suggest that TGF-beta 2 is involved in the regulation of postnatal development of the cerebellum.

Regulation of plasminogen activation by interleukin-6 in human lung fibroblasts

We determined that exposure of cultured lung fibroblasts (HEL-299) to recombinant human interleukin-6 (0-400 ng/ml) resulted in a dose- and time-dependent increase in secreted and cell lysate PAI-1 and total tPA levels (maximal increase of 2.6-fold and 1.7-fold, respectively). Specificity of this response was indicated when increases in PAI-1 levels were inhibited by neutralizing polyclonal antibodies to IL-6, but not with non-specific antibodies. Inhibition of the response to IL-6 by cycloheximide and alpha-amanitin indicates that increases in PAI-1 are dependent on both protein and RNA synthesis. The addition of IL-6 to HEL-299 cells also stimulated a dose- and time-dependent increase in steady-state PAI-1 mRNA levels (3.8 to 15.1 pg/micrograms total RNA by 24 h). A rapid increase (5-6-fold) in PAI-1 mRNA levels was found between 3 and 12 h. Nuclear run-on assays using a maximum dose of IL-6 showed that IL-6 increases a 4-fold rate of transcription of the PAI-1 gene. We further showed that LPS induces a 70% increase in secreted IL-6 and a 50% increase in PAI-1 protein levels. Increasing doses of anti-IL-6 completely blocked the effect of LPS on PAI-1 while non-specific antibodies had no effect. These studies suggest an autocrine role for IL-6 in regulating localized proteolysis and modulating tissue remodeling during acute inflammatory conditions by fibroblasts.

The recovery of articular cartilage in explant culture from interleukin-1 alpha: effects on proteoglycan synthesis and degradation

The cytokine interleukin-1 (IL-1) strongly inhibits proteoglycan biosynthesis and increases extracellular proteoglycan degradation in cartilage. In this study we investigated how quickly proteoglycan turnover recovered after IL-1 treatment. Porcine articular cartilage in explant culture was incubated with recombinant human (rh) IL-1 alpha, rh insulin-like growth factor (IGF)-1 or rh-transforming growth factor (TGF)-beta 1 for 3 days. RhIL-1 alpha strongly inhibited synthesis and promoted matrix degradation over 3 days, whereas rhIGF-1 stimulated proteoglycan synthesis, and rhTGF-beta 1 had no significant effect on synthesis. In the absence of serum, the recovery of proteoglycan synthesis after IL-1 treatment (10 ng/ml) for 3 days was extremely slow, and it remained 30% inhibited even after a further 8 days of recovery. Matrix degradation of proteoglycan assessed from the rate of release of glycosaminoglycan into the culture medium recovered more quickly and was greatly reduced within 3 days. Shorter exposure of explants to IL-1 alpha (8 h) resulted in less inhibition of synthesis, but it did not result in a more rapid rate of recovery following its removal. Treatment of cartilage with IGF-1 (20 ng/ml) or TGF-beta (10 ng/ml) during the recovery period increased the rate of recovery of both synthesis and degradation. Synthesis recovered to control rates within 6 days and degradation within 2 days. TGF-beta (10 ng/ml) was slightly more potent than IGF-1. Fetal calf serum (10% v/v) also promoted recovery in a similar way to the growth factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Transforming growth factor-beta 1 and -beta 2 promote neurite sprouting and elongation of cultured rat hippocampal neurons

Transforming growth factor-beta (TGF-beta) is known as a potent regulator of cell proliferation and differentiation. In the present study, we investigated the effects of TGF-beta 1 and -beta 2 on the survival, neurite sprouting and process elongation of primary cultured hippocampal neurons obtained from rat embryos. Addition of TGF-beta 1 little affected the total number of surviving neurons, but clearly increased the number of neurons bearing processes, indicating that TGF-beta 1 promotes neurite sprouting rather than neuronal survival. Furthermore, TGF-beta 1 significantly promoted the elongation of axon-like processes, but did not affect the process branching and the number of dendrite-like processes. TGF-beta 2 also promoted the neurite sprouting and stimulated the elongation of axons without affecting the branching. The effects of TGF-beta 2 were very similar to those of TGF-beta 1 in terms of both effective concentrations (0.1-1 ng/ml) and maximal effects. It is possible that TGF-beta 1 and -beta 2 play roles in the formation of neuritic networks in the central nervous system.

Sustained expression of TGF-beta 1 underlies development of progressive kidney fibrosis

We found that TGF-beta 1 expression and increased matrix production is transient and self-limited in nephritic glomeruli from rats with acute, reversible glomerulonephritis induced by a single injection of an antibody reactive with glomerular mesangial cells. In contrast, in rats given a second antibody injection, one week later, the glomerular expression of TGF-beta 1 mRNA and TGF-beta 1 protein remained elevated through 18 weeks and was associated with a large infiltration of mononuclear cells, with staining features of fibroblastic/myofibroblastic cells, strongly expressing TGF-beta 1 in the tubulointerstitium of the kidney. By 18 weeks kidneys from animals receiving two antibody injections showed glomerulosclerosis and tubulointerstitial fibrosis with striking deposition of collagens type I and III, whereas kidney tissue from animals given one antibody injection was indistinguishable from normal control. The histological changes were accompanied by persistent proteinuria and elevated levels of blood urea nitrogen. Extracellular matrix markers of TGF-beta 1 activity, a special isoform of fibronectin, tenascin, biglycan and plasminogen activator inhibitor-1, were significantly elevated in kidneys undergoing fibrosis. These data suggest that sustained TGF-beta 1 expression contributes to the development of progressive kidney fibrosis.

Effects of transforming growth factor beta 1 on scar production in the injured central nervous system of the rat

In the central nervous system (CNS), nerve regeneration after traumatic injury fails. The formation of a dense fibrous scar is thought to restrict in part the growth of axonal projections, providing one of the many reasons that complete lesions of neural pathways in the adult mammalian CNS are rarely followed by significant functional recovery. In order to determine which mechanisms mediate scar formation in the CNS and to investigate whether they can be modulated in vivo, we have attempted to define the potential role of trophic factors. Our previous studies have shown the focal elevation of transforming growth factor beta 1 (TGF beta 1) expression in lesioned CNS tissue. In the studies described here, we demonstrate that TGF beta 1 participates in the scarring response in the rat brain. First, the elevated protein levels of TGF beta 1 are localized to specific populations of injury-responsive cells in the traumatized CNS. Furthermore, the injection of TGF beta 1 into the brains of injured rats causes a dramatic increase in the scarring response. Conversely, when neutralizing TGF beta 1 antibodies are administered, the deposition of fibrous scar tissue and the formation of a limiting glial membrane that borders the lesion is significantly attenuated, thus establishing a role for the endogenous growth factor in regulation of the non-glial component of the scar. In implicating TGF beta 1 in the scarring response in the CNS, the potential use for TGF beta 1 antagonists as inhibitors of scar formation in the injured mammalian CNS is self-evident.

TGF beta 1 and IL-4 have opposing effects on the proliferation of chronic phase chronic myeloid leukaemic cells stimulated by G-CSF in vitro

The effects of transforming growth factor beta 1 (TGF beta 1) have been studied in vitro on the clonogenicity of haemopoietic progenitor cells (CFU-CML) from 14 patients with chronic myeloid leukaemia (CML) in chronic phase and 13 normal donors. In 14/14 patients with CML, 5 ng of TGF beta 1/dish decreased CFU-CML-formation in cultures stimulated with 15 ng of granulocyte colony-stimulating factor (G-CSF)/dish (p < 0.0005) and in 13/14 patients TGF beta 1 reduced CFU-CML-formation induced by G-CSF in combination with 5 ng of recombinant human interleukin-4 (rhIL-4)/dish (p < 0.005). In 10/14 samples the number of CFU-CML were reduced to levels lower than in cultures containing G-CSF alone (p < 0.01). In contrast, TGF beta 1 had no significant inhibitory effect on the G-CSF-directed proliferation of normal donor mononuclear cells (MNC) either alone or in combination with rhIL-4. RhIL-4 increased G-CSF-induced colony formation in 13/14 CML samples (p < 0.001), but did not have the same effect in the normal donor samples. The in vitro clonogenicity of CML peripheral blood MNC stimulated with 15 ng of G-CSF could not be correlated with the white cell count or the percentage of CD34+ cells at diagnosis.