Positive expression of E-cadherin suppresses cell adhesion to fibronectin via reduction of alpha5beta1 integrin in human breast carcinoma cells

E-cadherin mainly mediated the epithelial cell-cell adhesion, and integrin signaling can modulate the signaling pathway of E-cadherin in the different levels. Up to now, however, it is still unclear that whether E-cadherin could interfere with cell-matrix interaction, a typical adhesion through integrins. In this study we investigated the effects of E-cadherin on cell-matrix adhesion and alpha5beta1 integrin expression in human breast carcinoma cells. It was found that either mRNA or protein level of alpha5 and beta1 subunits of integrin decreased in E-cad-231 compared with Mock-231. Furthermore, the promoter activity of alpha5 gene was inhibited in E-cad-231 compared with Mock-231. Consistently, phosphorylated focal adhesion kinase, a closer key downstream protein kinase of integrin signaling, were also down-regulated in E-cad-231. Furthermore, distribution of beta-catenin was observed and data showed beta-catenin was accumulated in the nucleus in Mock-231, while disappeared from the nucleus and mainly accumulated near the cell surface membrane in E-cad-231. LiCl, a molecule that can inhibit the GSK-3beta activity and down-regulate beta-catenin degradation, could inversely stimulate expression of alpha5 and beta1 integrin. Taken together, these results indicated that positive expression of E-cadherin inhibits the cell adhesion to extracellular matrix mediated by alpha5beta1 integrin signaling.

Notoginsenoside R1 inhibits TNF-alpha-induced fibronectin production in smooth muscle cells via the ROS/ERK pathway

The matrix fibronectin protein plays an important role in vascular remodeling. Notoginsenoside R1 is the main ingredient with cardiovascular activity in Panax notoginseng; however, its molecular mechanisms are poorly understood. We report that notoginsenoside R1 significantly decreased TNF-alpha-induced activation of fibronectin mRNA, protein levels, and secretion in human arterial smooth muscle cells (HASMCs) in a dose-dependent manner. Notoginsenoside R1 scavenged hydrogen peroxide (H2O2) in a dose-dependent manner in the test tube. TNF-alpha significantly increased intracellular ROS generation and then ERK activation, which was blocked by notoginsenoside R1 or DPI and apocynin, inhibitors of NADPH oxidase, or the antioxidant NAC. Our data demonstrated that TNF-alpha-induced upregulation of fibronectin mRNA and protein levels occurs via activation of ROS/ERK, which was prevented by treatment with notoginsenoside R1, DPI, apocynin, NAC, or MAPK/ERK inhibitors PD098059 and U0126. Notoginsenoside R1 significantly inhibited H2O2-induced upregulation of fibronectin mRNA and protein levels and secretion; it also significantly inhibited TNF-alpha and H2O2-induced migration. These results suggest that notoginsenoside R1 inhibits TNF-alpha-induced ERK activation and subsequent fibronectin overexpression and migration in HASMCs by suppressing NADPH oxidase-mediated ROS generation and directly scavenging ROS.

Involvement of H- and N-Ras isoforms in transforming growth factor-beta1-induced proliferation and in collagen and fibronectin synthesis

Transforming growth factor beta1 (TGF-beta1) has a relevant role in the origin and maintenance of glomerulosclerosis and tubule-interstitial fibrosis. TGF-beta and Ras signaling pathways are closely related: TGF-beta1 overcomes Ras mitogenic effects and Ras counteracts TGF-beta signaling. Tubule-interstitial fibrosis is associated to increases in Ras, Erk, and Akt activation in a renal fibrosis model. We study the role of N- and H-Ras isoforms, and the involvement of the Ras effectors Erk and Akt, in TGF-beta1-mediated extracellular matrix (ECM) synthesis and proliferation, using embrionary fibroblasts from double knockout (KO) mice for H- and N-Ras (H-ras(-/-)/N-ras(-/-)) isoforms and from heterozygote mice (H-ras(+/-)/N-ras(+/-)). ECM synthesis is increased in basal conditions in H-ras(-/-)/N-ras(-/-) fibroblasts, this increase being higher after stimulation with TGF-beta1. TGF-beta1-induced fibroblast proliferation is smaller in H-ras(-/-)/N-ras(-/-) than in H-ras(+/-)/N-ras(+/-) fibroblasts. Erk activation is decreased in H-ras(-/-)/N-ras(-/-) fibroblasts; inhibition of Erk activation reduces fibroblast proliferation. Akt activation is higher in double KO fibroblasts than in heterozygotes; inhibition of Akt activation also inhibits ECM synthesis. We suggest that H- and N-Ras isoforms downregulate ECM synthesis, and mediate proliferation, in part through MEK/Erk activation. PI3K-Akt pathway activation may be involved in the increase in ECM synthesis observed in the absence of H- and N-Ras.

Cervico-vaginal foetal fibronectin: a predictor of cervical response at pre-induction cervical ripening

CONTEXT

Not all pregnant women with an "unripe" cervix can be successfully ripened by the cervical ripening agents; therefore tests with predictive information are justified.

OBJECTIVES

To examine the effect of the presence of foetal fibronectin (FFN) in the cervico-vaginal secretions on pre-induction cervical ripening with either intravaginal Misoprostol or transcervical Foley catheter.

METHODOLOGY

Twenty (20) patients managed at a tertiary health institution in South-western Nigeria between March and May 2003 were randomised for cervical ripening by either intravaginal Misoprostol or Transcervical Foley catheters. Cervico-vaginal secretions were assessed for presence of FFN with Foetal Fibronectin Enzyme Immunoassay Kit (Adeza Corp.) prior to commencement of cervical ripening.

MAIN OUTCOME MEASURES

FFN status, Pre-ripening and Pre-induction modified Bishop scores and duration of cervical ripening.

RESULTS

Ten of the fifteen patients with positive membrane immunoassay for FFN achieved ripened cervix (modified Bishop score > or = 6) within 6 - 12 hours of exposure to the agents of cervical ripening. In the FFN negative group, only 2 of the five patients achieved ripe cervix within the >12 - 18 hours period, the rest being in the >18 - 24 hours period.

CONCLUSION

Foetal fibronectin test may offer useful predictive information prior to institution of processes of cervical ripening in patients with unfavourable cervices.

Local simvastatin effects on mandibular bone growth and inflammation

BACKGROUND

Simvastatin has been shown to increase bone growth when applied topically to murine bone; however, it causes considerable soft tissue inflammation at high doses (2.2 mg), making future clinical use problematic. This study evaluated the effect of lower simvastatin doses and cyclooxygenase (COX) synthase inhibitors on tissue inflammation and bone growth in rats and gene expression in mice.

METHODS

Adult female rats were untreated or treated with a single dose of 0.1, 0.5, 1.0, 1.5, or 2.2 mg simvastatin in methylcellulose gel in a polylactic acid membrane (SIM) on the lateral aspect of the mandible. The contralateral mandible side was implanted with methylcellulose gel/polylactic acid membrane alone (GEL), and five rats in each dose pairing were evaluated histomorphometrically after 3, 7, and 24 days. Subsequent rats were similarly treated with 0.5 mg simvastatin (optimal dose) and daily intraperitoneal injections of COX-2 inhibitor (NS-398; 1 mg/kg x 7 days; N = 16), general COX inhibitor (indomethacin; 1 mg/kg x 7 days; N = 16), or no inhibitor (N = 10) and evaluated histomorphometrically after 7 or 24 days by analysis of variance (ANOVA). Gene arrays were also used to evaluate osteogenic gene expression from 0.5 mg simvastatin in murine calvaria (N = 12).

RESULTS

There was a 45% increase in bone area with 0.5 mg simvastatin versus gel control (P <0.001; similar to the 2.2-mg dose), and clinical swelling was reduced compared to the high simvastatin dose (P <0.05). The 0.1-mg simvastatin dose failed to stimulate significant bone growth. NS-398 and indomethacin reduced inflammation and bone growth. Simvastatin significantly upregulated procollagen, fibronectin, and matrix metalloproteinase-13 genes.

CONCLUSION

Reducing the simvastatin dose from 2.2 to 0.5 mg reduced inflammation to a more clinically acceptable level without sacrificing bone-growth potential, but COX-associated inflammation appears to be necessary for in vivo bone growth.

Effects of low molecular weight heparin in obstructed kidneys: decrease of collagen, fibronectin and TGF-β, and increase of chondroitin/dermatan sulfate proteoglycans and macrophage infiltration

BACKGROUND

Heparin exerts beneficial effects in different experimental models of nephropathy, as observed by the preservation of the structural morphology of the kidney after heparin therapy. Here we investigate molecular and cellular events involved in the protective effects of heparin in the progression of renal disease after unilateral ureteral obstruction.

METHODS

Thirty-six rats were divided into six groups: group C (control) was not subjected to any surgical manipulation; group S (sham) was subjected to surgical manipulation but without ureteral ligation; group UUO was subjected to ureteral obstruction and received no treatment; group UUO + S was subjected to ureteral obstruction and received saline subcutaneously (s.c.) once daily; group UUO + H was subjected to ureteral obstruction and received low molecular weight heparin (LMW-Hep; 4 mg/kg) s.c. once daily; and group C + H was not subjected to any surgical manipulation and received LMW-Hep (4 mg/kg) s.c. once daily. After 14 days, the content of collagen, fibronectin, total glycosaminoglycans (GAGS), chondroitin sulfate/dermatan sulfate proteoglycans (CS/DSPGs), transforming growth factor-beta (TGF-beta) and cellular infiltration were determined in the kidneys by immunohistochemical and biochemical techniques.

RESULTS

Collagen, fibronectin, total GAGS, CS/DSPGs, TGF-beta and cellular infiltration increased significantly in group UUO. LMW-Hep treatment reduced collagen, fibronectin and TGF-beta, but induced an increase in the content of total GAGS, CS/DSPGs and macrophage infiltration in group UUO + H when compared with group UUO.

CONCLUSIONS

LMW-Hep diminishes fibrosis in obstructed kidneys by downregulating the synthesis of collagen, fibronectin and TGF-beta. The mechanisms underlying the overproduction of CS/DSPGs and the increase in cellular infiltration upon LMW-Hep administration remain to be elucidated.

Requirement for glutamine in the expression of alpha-actin and type IV collagen in mesangial cells

The importance of glutamine for the synthesis of proteins of the extracellular matrix was investigated in cultured mesangial cells. Glutamine at 2 mM elicited an increase in smooth muscle cell alpha-actin, alpha(1)-type IV collagen and fibronectin transcripts (19.0-, 16.7-, and 4.3-fold, respectively) accompanied by an increase in alpha-actin stress fibres compared to cells grown in absence of glutamine. The specificity for the glutamine requirement is suggested by the fact that mRNA levels of tenascin were not altered by addition of glutamine. This suggests that glutamine is required for the expression of important proteins of the extracellular matrix in cultured mesangial cells.

Endothelial-monocyte activating polypeptide II alters fibronectin based endothelial cell adhesion and matrix assembly via alpha5 beta1 integrin

Mature Endothelial-Monocyte Activating Polypeptide (mEMAP) II functions as a potent antiangiogenic peptide. Although the anti-tumor effect of mEMAP II has been described, little is known regarding its mechanism of action. Observations that mEMAP II induced apoptosis only in a subset of migrating and proliferating endothelial cells (EC) suggests a targeted effect on cells engaged in angiogenic activities which are known to rely upon cell adhesion and migration. Indeed, we demonstrate that mEMAP II inhibited fibronectin (FN) dependent microvascular EC (MEC) adhesion and spreading and we show that this depends upon the alpha5 beta1 integrin. Immunofluorescence analysis demonstrated that mEMAP II-dependent blockade of FN-alpha5 beta1 interactions was associated with disassembly of both actin stress fiber networks and FN matrix. These findings suggest that mEMAP II blocks MEC adhesion and spreading on fibronectin, via a direct interaction with the integrin alpha5 beta1, thus implicating that alpha5 integrin may be a mediator of mEMAP II's antiangiogenic function.

Effect of biomaterial surface properties on fibronectin-alpha5beta1 integrin interaction and cellular attachment

The ability of fibronectin (Fn) to mediate cell adhesion through binding to alpha(5)beta(1) integrins is dependent on the conditions of its adsorption to the surface. Using a model system of alkylsilane SAMs with different functional groups (X=OH, COOH, NH(2) and CH(3)) and an erythroleukemia cell line expressing a single integrin (alpha(5)beta(1)), the effect of surface properties on the cellular adhesion with adsorbed Fn layers was investigated. (125)I-labeled Fn, a modified biochemical cross-linking/extraction technique and a spinning disc apparatus were combined to quantify the Fn adsorption, integrin binding and adhesion strength, respectively. This methodology allows for a binding equilibrium analysis that more closely reflects cellular adhesion found in stable tissue constructs in vivo. Differences in detachment strength and integrin binding were explained in terms of changes in the adhesion constant (psi, related to affinity) and binding efficiency of the adsorbed Fn for the alpha(5)beta(1) integrins (CH(3) approximately NH(2)<COOH approximately OH) and the resulting average bond strength. Fn interacted more strongly with alpha(5)beta(1) integrins when adsorbed on COOH vs. OH surfaces suggesting that negative charge may be a critical component of inducing efficient cellular adhesion. As evident by the low psi values, Fn adsorbed on NH(2) and CH(3) surfaces interacted inefficiently with alpha(5)beta(1) integrins and also possessed significant non-specific components to adhesion. Lastly, comparison of cellular adhesion to Fn adsorbed onto smooth and rough surfaces showed that nano-scale roughness altered cellular adhesion by increasing the surface density of adsorbed Fn.

Glucose-induced Akt1 activation mediates fibronectin synthesis in endothelial cells

AIMS/HYPOTHESIS

Increased expression and decreased degradation of extracellular matrix (ECM) proteins are key features of chronic diabetic complications. Fibronectin, a predominant ECM protein, has been shown to be overexpressed in all target organs of diabetic complications and in endothelial cells cultured in high levels of glucose. The present study was designed to elucidate the role of protein kinase B (Akt/PKB) in glucose-induced fibronectin mRNA expression and protein production in vascular endothelial cells.

METHODS

Human umbilical vein endothelial cells were cultured in the presence of high glucose to study Akt/PKB activation. The upstream and downstream mediators in the Akt/PKB pathway were also investigated using dominant negative transfections and specific inhibitors of signalling pathways. Cells were subjected to real time RT-PCR, western blotting, and confocal microscopy to assess Akt1/PKBalpha activation and fibronectin mRNA expression and protein production. To detect transcription factor activation, electrophoretic mobility shift assay was carried out.

RESULTS

Our data demonstrate that fibronectin mRNA expression and protein production that are induced by high glucose are mediated via activation of Akt/PKB, which is modulated by mitogen-activated protein kinase, phosphatidylinositol 3-kinase, and protein kinase C. Glucose-induced fibronectin mRNA expression and protein production are also mediated by Akt1/PKBalpha-dependent activation of the transcription factors nuclear factor-kappaB and activating protein-1.

CONCLUSIONS/INTERPRETATION

Our study provides insight into the mechanical basis of glucose-induced increases in fibronectin mRNA expression and protein production. High levels of glucose may increase fibronectin mRNA expression and protein production by activating Akt/PKB.

Estrogen and raloxifene, a selective estrogen receptor modulator, ameliorate renal damage in db/db mice

Despite the potentially protective effects of estrogen on bone and cardiovascular tissue as well as against kidney diseases, its effects on diabetic nephropathy are unknown. Here, we examined the therapeutic effectiveness of 17beta-estradiol and raloxifene, a selective estrogen receptor modulator, for preventing functional and histological alterations in the kidneys of db/db mice, a model of type 2 diabetes. In the first experiment, ovariectomized female db/db mice were treated with 17beta-estradiol for 8 weeks. The treatment significantly ameliorated albuminuria, attenuated weight gain, and reduced hyperglycemia in diabetic ovariectomized db/db mice. Histologically, the increases in mesangial area and the accumulation of fibronectin were significantly inhibited by 17beta-estradiol. In the second experiment, mice were administered vehicle or raloxifene hydrochloride (3 mg/kg/day) for 8 weeks. Raloxifene significantly reduced mesangial expansion and fibronectin accumulation in db/db mice, but in contrast to 17beta-estradiol, it failed to affect body weight or hyperglycemia. An in vitro experiment further demonstrated that raloxifene inhibited transforming growth factor beta-1-induced fibronectin transcription and AP-1 activity. Thus, our findings suggest that raloxifene, which lacks the harmful effects of estrogen, is useful for the treatment of diabetic nephropathy.

Effects of a new pathogen-reduction technology (Mirasol PRT) on functional aspects of platelet concentrates

BACKGROUND

Several strategies are being developed to reduce the risk of pathogen transmission associated with platelet (PLT) transfusion.

STUDY DESIGN AND METHODS

The impact of a new technology for pathogen reduction based on riboflavin plus illumination (Mirasol PRT, Navigant Biotechnologies, Inc.) at 6.2 and 12.3 J per mL on functional and biochemical characteristics of PLTs was evaluated. PLT concentrates (PCs) obtained by apheresis were treated with Mirasol PRT and stored at 22 degrees C. Modifications in major PLT glycoproteins (GPIbalpha, GPIV, and GPIIb-IIIa), adhesive ligands (von Willebrand factor [VWF], fibrinogen [Fg], and fibronectin), activation antigens (P-selectin and LIMP), and apoptotic markers (annexin V binding and factor [F]Va) were analyzed by flow cytometry. Adhesive and cohesive PLT functions were evaluated with well-established perfusion models. Studies were performed on the preparation day (Day 0) and during PCs storage (Days 3 and 5).

RESULTS

Levels of glycoproteins remained stable during storage in PCs treated with 6.2 J per mL pathogen reduction technology (PRT) and similar to those observed in nontreated PCs. When 12.3 J per mL PRT was applied, however, levels of GPIbalpha moderately decreased on Days 3 and 5. VWF, Fg, and FVa were not modified in their expression levels, either by treatment or by storage period. Fibronectin appeared more elevated in all PRT samples. A progressive increase in P-selectin and LIMP expression and in annexin V binding was observed during storage of PRT-treated PCs. Functional studies indicated that 6.2 J per mL Mirasol PRT-treated PLTs preserved adhesive and cohesive functions to levels compatible with those observed in the respective control PCs.

CONCLUSION

PLT function was well preserved in PCs treated with 6.2 J per mL Mirasol PRT and stored for 5 days.

Actions of the functional upstream domain of protein F1 of Streptococcus pyogenes on the conformation of fibronectin

Fibronectin (Fn), discovered by Harvard's Plasma Protein Program as plasma "cold-insoluble globulin" in the 1940s, has attracted much interest over the past three decades. One of the most interesting features of Fn is its ability to change shape in response to various environmental conditions and interactions with other substances found in the extra-cellular space. Here we examine the potential of the functional upstream domain (FUD) of Streptococcus pyogenes protein F1 to bring about changes in structure of Fn. In particular, we investigate the accessibility of Fn's 10th type III module that contains the integrin binding RGD motif. By use of monoclonal antibodies in a competitive ELISA assay, we found that FUD interacts with the amino-terminal type I modules of Fn to unveil the cell-binding region of Fn. This conformational change was achieved at sub-equimolar ratios of FUD/Fn monomer. We discuss the functional relevance of the interaction for both Fn and S. pyogenes and correlate the results with a conformational model of Fn that arose out of a collaboration between our laboratory and that of John Ferry.

Dystrophin Dp71 in PC12 cell adhesion

Previously, we reported that PC12 cells with decreased Dp71 expression (antisense-Dp71 cells) display deficient nerve-growth-factor-induced neurite outgrowth. In this study, we show that disturbed neurite outgrowth of antisense-Dp71 cells is accompanied by decreased adhesion activity on laminin, collagen and fibronectin. In wild-type cells, the immunostaining of Dp71 and beta1-integrin overlaps in the basal area contacting the substrate, but staining of both proteins decrease in the antisense-Dp71 cells. Morphology of antisense-Dp71 cells at the electron microscopic level is characterized by the lack of filopodia, cellular projections involved in adhesion. Our findings suggest that Dp71 is required for the efficient PC12 cell attachment to beta1-integrin-dependent substrata and that decreased adhesion activity of the antisense-Dp71 cells could determine their deficiency to extend neurites.

Angiotensin-converting enzyme inhibitor captopril prevents volume overload cardiomyopathy in experimental chronic aortic valve regurgitation

The efficacy of angiotensin-converting enzyme inhibitors (ACEIs) in the treatment of chronic aortic regurgitation (AR) is not well established and remains controversial. The mechanisms by which ACEIs may protect against left-ventricular (LV) volume overload are not well understood, and clinical trials performed until now have yielded conflicting results. This study was therefore performed to assess the effectiveness of two different doses of the ACEI captopril in a rat model of chronic AR. We compared the effects of a 6-month low-dose (LD) (25 mg/kg) or higher dose (HD) (75 mg/kg) treatment with captopril on LV function and hypertrophy in Wistar rats with severe AR. Untreated animals developed LV eccentric hypertrophy and systolic dysfunction. LD treatment did not prevent hypertrophy and provided modest protection against systolic dysfunction. HD treatment preserved LV systolic function and dimensions and tended to slow hypertrophy. The cardiac index remained high and similar among all AR groups, treated or not. Tissue renin-angiotensin system (RAS) analysis revealed that ACE activity was increased in the LVs of AR animals and that only HD treatment significantly decreased angiotensin II receptor mRNA levels. Fibronectin expression was increased in the LV or AR animals, but HD treatment almost completely reversed this increase. The ACE inhibitor captopril was effective at high doses in this model of severe AR. These effects might be related to the modulation of tissue RAS and the control of fibrosis.

A specific alpha5beta1-integrin conformation promotes directional integrin translocation and fibronectin matrix formation

Integrin adhesion receptors are structurally dynamic proteins that adopt a number of functionally relevant conformations. We have produced a conformation-dependent anti-alpha5 monoclonal antibody (SNAKA51) that converts alpha5beta1 integrin into a ligand-competent form and promotes fibronectin binding. In adherent fibroblasts, SNAKA51 preferentially bound to integrins in fibrillar adhesions. Clustering of integrins expressing this activation epitope induced directional translocation of alpha5beta1, mimicking fibrillar adhesion formation. Priming of alpha5beta1 integrin by SNAKA51 increased the accumulation of detergent-resistant fibronectin in the extracellular matrix, thus identifying an integrin conformation that promotes matrix assembly. The SNAKA51 epitope was mapped to the calf-1/calf-2 domains. We propose that the action of the antibody causes the legs of the integrin to change conformation and thereby primes the integrin to bind ligand. These findings identify SNAKA51 as the first anti-integrin antibody to selectively recognize a subset of adhesion contacts, and they identify an integrin conformation associated with integrin translocation and fibronectin matrix formation.

Time and Dose Effects of Mitomycin C on Extracellular Matrix Fibroblasts and Proteins

OBJECTIVES/HYPOTHESIS

The objective was to determine treatment dose and time-dependent effects of injected mitomycin C on extracellular matrix fibroblasts, collagen, and fibronectin, important mediators in the wound healing response, in a rat cutaneous wound model.

STUDY DESIGN

A prospective, controlled animal study.

METHODS

Forty rats were injected with three different doses (0.4, 2.3, and 5.0 mg/mL) of mitomycin C at three different wound sites with a fourth wound site receiving saline as a control. The rats were grouped to have their tissue harvested at five different dates ranging from 1 week to 8 weeks. After death, samples from the wound site underwent Western blot analysis for collagen and fibronectin and histological analysis measuring fibroblast apoptosis.

RESULTS

Over an 8-week period, collagen and fibronectin significantly decreased and fibroblast apoptosis significantly increased. No correlation was found between the injected dose of mitomycin C and either the extracellular matrix protein concentration or the rate of fibroblast apoptosis.

CONCLUSION

Mitomycin C demonstrated a long-term effect in a wound, inhibiting collagen and fibronectin production and inducing apoptosis. Use of mitomycin C in excess of 0.4 mg/mL did not alter protein concentrations or rate of apoptosis.

In vivo antitumor effect of ascorbic acid, lysine, proline and green tea extract on human prostate cancer PC-3 xenografts in nude mice: evaluation of tumor growth and immunohistochemistry

BACKGROUND

Matrix metalloproteinases (MMPs), vascular endothelial growth factor (VEGF), Ki 67 (proliferative protein) and constituents of ECM play a critical role in angiogenesis, and are crucial in neoplastic invasion and metastasis. Based on the antitumor properties of certain nutrients, we investigated the effect of a diet containing lysine, proline, arginine, ascorbic acid and green tea extract on the growth of tumors induced by implanting human prostate cancer PC-3 cells in athymic nude mice and on the expression of MMPs, VEGF, Ki 67 and fibronectin in these tumors, as well as the production of mucin (by PAS staining).

MATERIALS AND METHODS

Male nude mice (n =12) were inoculated with 3x10(6) prostate cancer PC-3 cells and randomly divided into two groups; Group A was fed a regular diet and Group B was fed a regular diet supplemented with 0.5% of the nutrient mixture (NM). Four weeks later, tumors were excised, weighed and processed for histology.

RESULTS

The results showed inhibition of tumor growth in Group B. Histological studies revealed inhibition of MMP-9 and VEGF secretion and mitosis in Group B tissues.

CONCLUSION

Nutrient supplementation strongly suppressed the growth of tumors without any adverse effects in nude mice, suggesting strong potential as an anticancer agent.

Fibronectin matrix turnover occurs through a caveolin-1-dependent process

Extracellular matrix remodeling occurs during development, tissue repair, and in a number of pathologies, including fibrotic disorders, hypertension, and atherosclerosis. Extracellular matrix remodeling involves the complex interplay between extracellular matrix synthesis, deposition, and degradation. Factors that control these processes are likely to play key roles in regulating physiological and pathological extracellular matrix remodeling. Our data show that fibronectin polymerization into the extracellular matrix regulates the deposition and stability of other extracellular matrix proteins, including collagen I and thrombospondin-1 (Sottile and Hocking, 2002. Mol. Biol. Cell 13, 3546). In the absence of continual fibronectin polymerization, there is a loss of fibronectin matrix fibrils, and increased levels of fibronectin degradation. Fibronectin degradation occurs intracellularly after endocytosis and can be inhibited by chloroquine, an inhibitor of lysosomal degradation, and by caveolae-disrupting agents. Down-regulation of caveolin-1 by RNAi inhibits loss of fibronectin matrix fibrils, fibronectin internalization, and fibronectin degradation; these processes can be restored by reexpression of caveolin-1. These data show that fibronectin matrix turnover occurs through a caveolin-1-dependent process. Caveolin-1 regulation of fibronectin matrix turnover is a novel mechanism regulating extracellular matrix remodeling.

Inhibition of human embryonic palatal mesenchymal cell cycle by secalonic acid D: a probable mechanism of its cleft palate induction

OBJECTIVE

To assess the mechanism(s) of cleft palate induction by secalonic acid D (SAD) in human embryonic palatal mesenchymal (HEPM) cells and compare them with those evaluated in the murine embryonic palate.

DESIGN

Effect of SAD on HEPM cell proliferation was studied by obtaining dose response curves for cell numbers, uptake of 3H-thymidine and the expression of proliferating cell nuclear antigen (PCNA). Effects of SAD on cell cycle were assessed by flowcytometry. Cell-labeling with 3H-glucosamine and immunoblot analysis were conducted to study SAD effects on the synthesis of glycosaminogycans (GAG) and the expression of fibronectin and tenascin, respectively.

RESULTS

SAD induced a concentration-dependent decrease in HEPM cell number and 3H-thymidine uptake beginning at 0.1 microg of SAD/ml. Expression of PCNA and progression of cell cycle from G1 to S phase were inhibited following SAD exposure. Cell viability was significantly reduced only at 7.5 microg/ml of SAD or higher indicating that the reduction in cell numbers by SAD at lower concentrations is likely due to reduced proliferation and at higher concentrations due to both reduced proliferation and cell death. Synthesis of extra cellular matrix components (GAGs, fibronectin or tenascin) by HEPM cells, however, was not inhibited by SAD.

CONCLUSION

The results of these studies confirmed those of our previous studies with mice and the MEPM cells that SAD may induce cleft palate by reducing numbers of palatal mesenchymal cells by inhibition of their proliferation thereby leading to a reduction in the size of the developing palate shelves.

Regulation of fibronectin by thyroid hormone receptors

Thyroid hormones regulate growth, development, differentiation, and metabolic processes by interacting with and activating thyroid hormone receptors and associated pathways. We investigated the triiodothyronine (T3) modulation of gene expression, in human hepatocellular carcinoma cell lines, via a PCR-based cDNA subtraction method. Here we present further data on one of the T3-upregulated genes, fibronectin (FN). We demonstrate that the induction of FN protein expression by T3 in TRalpha1 and TRbeta1 over-expressing cells was time and dose-dependent at the mRNA and protein levels. Blockade of protein synthesis by cycloheximide almost completely inhibited the concomitant induction of FN mRNA by T3, indicating that T3 indirectly regulates FN. Furthermore, nuclear-run on and FN promoter assay clearly can specifically increase the number of FN transcriptional demonstrated that the presence of T3 initiations. In addition, we further confirmed that the up-regulation of FN by T3 was mediated, at least in part, by transforming growth factor-beta (TGF-beta), because the induction of FN was blocked in a dose-dependent manner by the addition of TGF-beta neutralizing antibody. In an effort to elucidate the we demonstrated the involvement of the signaling pathways involved in the activation of FN by T3, mitogen activated protein kinase/c-Jun N-terminal kinase/p38 MAPK (MAPK/JNK/p38) pathway. Although T3 induces the expression of TGF-beta, neither wild-type nor dominant-negative Smad3 or Smad4 over-expression affected the activation of FN by T3. Thus, we demonstrate that T3 regulates FN gene expression indirectly at the transcriptional level, with the participation of the MAPK/JNK/p38 pathway and the TGF-beta signaling pathway but independent of Smad3/4.

Adenosine down-regulates the surface expression of dipeptidyl peptidase IV on HT-29 human colorectal carcinoma cells: implications for cancer cell behavior

Dipeptidyl peptidase IV (DPPIV) is a multifunctional cell-surface protein that, as well as having dipeptidase activity, is the major binding protein for adenosine deaminase (ADA) and also binds extracellular matrix proteins such as fibronectin and collagen. It typically reduces the activity of chemokines and other peptide mediators as a result of its enzymatic activity. DPPIV is aberrantly expressed in many cancers, and decreased expression has been linked to increases in invasion and metastasis. We asked whether adenosine, a purine nucleoside that is present at increased levels in the hypoxic tumor microenvironment, might affect the expression of DPPIV at the cell surface. Treatment with a single dose of adenosine produced an initial transient (1 to 4 hours) modest (approximately 10%) increase in DPPIV, followed by a more profound (approximately 40%) depression of DPPIV protein expression at the surface of HT-29 human colon carcinoma cells, with a maximal decline being reached after 48 hours, and persisting for at least a week with daily exposure to adenosine. This down-regulation ofDPPIV occurred at adenosine concentrations comparable to those present within the extracellular fluid of colorectal tumors growing in vivo, and was not elicited by inosine or guanosine. Neither cellular uptake of adenosine nor its phosphorylation was necessary for the down-regulation of DPPIV. The decrease in DPPIV protein at the cell surface was paralleled by decreases in DPPIV enzyme activity, binding of ADA, and the ability of the cells to bind to and migrate on cellular fibronectin. Adenosine, at concentrations that exist within solid tumors, therefore acts at the surface of colorectal carcinoma cells to decrease levels and activities of DPPIV. This down-regulation of DPPIV may increase the sensitivity of cancer cells to the tumor-promoting effects of adenosine and their response to chemokines and the extracellular matrix, facilitating their expansion and metastasis.

Fibronectin levels in chronic viral hepatitis and response of this protein to interferon therapy

BACKGROUND/AIMS

In this study, the plasma fibronectin levels in the cases of chronic hepatitis B and C infection and this protein's response to the interferon therapy were examined.

METHODOLOGY

Totally, 38 patients with chronic hepatitis, 21 of them being hepatitis B, 17 of them being hepatitis C; and 24 healthy blood donors, as the control group, took part in this study. The quantitative determinations of fibronectin in plasma samples were performed with the Bohring Nephelometer BN 100 (N Antiserum to Human Fibronectin, code no OUND, Dade Behring Marburg GmbH, Marburg Germany).

RESULTS

It was observed that the fibronectin plasma levels of the control group were significantly higher than those of the patient group before the therapy (p=0.043). After the interferon therapy of six months, the difference between the fibronectin levels of 16 examined patients before and after the treatment was found to be significant (p=0.001). A negative correlation was detected between the fibronectin levels before the therapy and the inflammatory grade as far as the histopathology of the illness was concerned (r=-0.49), which is a statically significant value (p=0.002). The correlation between the levels of fibronectin and the stage of the fibrosis was found to be insignificant statistically (p=0.225). When comparing the levels before and after the therapy, as far as ALT and AST values were concerned, it was observed that both parameters fell significantly after the therapy (p=0.002). However, no correlation was observed between the fibronectin levels and ALT, AST before and after the therapy.

CONCLUSIONS

Fibronectin can be a useful marker for showing the hepatic inflammation and damage in the cases of chronic hepatitis, and can also be used in the evaluation of the response to the interferon therapy like other biochemical parameters (ALT, prothrombin activity etc.).

Extracellular myocilin affects activity of human trabecular meshwork cells

The trabecular meshwork (TM), a specialized eye tissue, is a major site for regulation of the aqueous humor outflow. Malfunctioning of this tissue is believed to be responsible for development of glaucoma, a blinding disease. Myocilin is a gene linked to the most common form of glaucoma. The protein product has been localized to both intra and extracellular sites, but its function still remains unclear. This study was to determine whether extracellular myocilin presented in the matrix affects adhesion, morphology, and migratory and phagocytic activities of human TM cells in culture. Cell adhesion assays indicated that TM cells, while adhering readily on fibronectin, failed to attach on recombinant myocilin purified from bacterial cultures. Adhesion on fibronectin was also compromised by myocilin in a dose dependent manner. Myocilin in addition triggered TM cells to assume a stellate appearance with broad cell bodies and microspikes. Loss of actin stress fibers and focal adhesions was observed. TM cell migration on fibronectin/myocilin to scratched wounds was reduced compared to fibronectin controls. Myocilin, however, had little impact on phagocytic activities of TM cells. Cell attachment on fibronectin and migration of corneal fibroblasts, a control cell type, were not altered by myocilin. These results demonstrate that extracellular myocilin elicits anti-adhesive and counter-migratory effects on TM cells. Myocilin in the matrix of tissues could be exerting a similar influence on TM cells in vivo, impacting the flexibility and resilience required for maintenance of the normal aqueous outflow.

Adenosine 3', 5' cyclic monophosphate attenuates the production of fibronectin in the glomeruli of anti-glomerular basement membrane antibody-associated nephritic rats

1. Excessive production of extracellular matrix is thought to be involved in the progression of glomerulonephritis and glomerulosclerosis. In chronic glomerulonephritis, fibronectin has been shown to accumulate in the glomeruli, accompanied by cell proliferation. 2. Glomerulonephritis was induced in rats by the injection of anti-glomerular basement membrane antibody. The rats showed proteinuria and histological alterations in the glomeruli. An increase in fibronectin levels in the culture medium of isolated nephritic glomeruli was confirmed, and was associated with the development of nephritis. Immunohistochemical staining demonstrated a marked accumulation of fibronectin in the glomeruli of nephritic rats. 3. Attenuated generation of cyclic AMP was also observed in the nephritic glomeruli treated with forskolin, prostaglandin E1 or adenosine. 4. Forskolin, prostaglandin E2 and 8-bromo-cyclic AMP markedly reduced the production of fibronectin by the nephritic glomeruli compared with controls in a dose-dependent manner. 8-Bromo-cyclic AMP suppressed the production of fibronectin by cultured mesangial cells. 5. These findings suggest that the attenuated generation of cyclic AMP in response to ligands is connected to the augmented accumulation of fibronectin in nephritic glomeruli, and may facilitate the development of methods for treating glomerulonephritis and glomerulosclerosis.