bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thrombin receptor activating peptides induce Ca2+ mobilization, barrier dysfunction, prostaglandin synthesis, and platelet‐derived growth factor mRNA expression in cultured endothelium
Authors: Garcia Joe G. N. , Patterson Carolyn , Bahler Chris , Aschner Judy , Hart C. Michael , English Denis 
Published: February 2005

AbstractEndothelial cell activation by thrombin is a key event in wound healing, Inflammation, and hemostasis. To better define thrombin‐endothelial cell interactions we synthesized several peptides of varying length corresponding to the initial 14 amino acid sequence of the cloned human platelet thrombin receptor after cleavage at an arginine41 site (R/SFLLRNPNDKYEPF). Thrombin receptor activating peptides (TRAPs) as short as 5 amino acids induced significant levels of PGl2 synthesis and expression of PDGF mRNA in human endothelium and produced dose‐dependent cellular contraction and permeability of confluent human umbilical vein and bovine pulmonary artery endothelial monolayers. To explore whether TRAPs utilized similar signal transducing pathways as α‐thrombin to accomplish endothelial cell activation, phospholipase C production of the Ca2+ secretagogue IP3 was measured and detected 10 seconds after either TRAP 7 or α‐thrombin. Furthermore, TRAPs ranging from 5‐14 residues induced significant dose‐dependent incsreases in Fura‐2 fluorescence indicative of Ca2+ 1 mobilization. These results indicate that thrombin‐mediated proteolytic cleavage of the human and bovine thrombin receptor initiates stimulus/coupling respones such phospholipase C activation, Ca2+ mobilization, and protein kinase C activation. The functional consequence of this cellular activation via the cleaved receptor is enhanced cellular contraction, barrier dysfunction, PGI2 synthesis, and expression of PDGF mRNA. © 1993 Wiley‐Liss, Inc.
Modulation of endothelial autacoid release by protein kinase C: Feedback inhition or non‐specific attenuation of receptor‐dependent cell activation?
Authors: Hecker Markus , Lückhoff Andreas , Busse Rudi 
Published: February 2005

AbstractReceptor‐mediated elevations of intracellular Ca2+ in endothelial cells may be controlled by a negative feedback mechanism through activation of protein kinase C (PKC). To test this hypothesis, we studied the effects of an activation or inhibition of PKC on the release of nitric oxide (NO) and prostacyclin (PGI2) from cultured bovine and porcine aortic endothelial cells (EC). Preincubation with the PKC activators phorbol‐12‐myristate‐13‐acetate (PMA) (3‐300 nM) or 1‐oleyl‐2‐acetyl‐glycerol (OAG) (30 μM) significantly attenuated the release of NO and PGI2 from EC stimulated with bradykinin (0.3–30 nM), whereas phorbol‐12, 13‐didecanoate (PDD) (30–300 nM), which does not activate PKC, had no effect. UCN‐01 (10 nM), a specific PKC inhibitor, significantly augmented the bradykinin‐stimulated release of NO from EC. These effects were correlated with a reduced (PMA) or enhanced (UCN‐01) elevation of intracellular Ca2+ in response to bradykinin in both types of EC. Neither the PKC activators nor the inhibitor had any effect on resting intracellular Ca2+ or basal endothelial autacoid release. Several isoforms of PKC (namely PKCα, PKCδ, PKCϵ, and PKCζ) were detected in bovine, human, and porcine EC by immunoblotting analysis with isotype‐specific anti‐PKC antibodies, which, except PKCϵ, were predominantly located in the cytosol. Incubation of bovine EC with PMA elicited a significant increase in membrane‐bound PKCα immunoreactivity, whereas there was no translocation of PKCα from the cytosolic to the membrane fraction with bradykinin. As determined by histone phosphorylation, PKC activity was similarly reduced in the cytosol, but increased in the membrane fraction of bovine EC exposed to PMA, whereas bradykinin had no significant effect. These findings indicate that endothelial autacoid release can be modulated by activators and inhibitors of PKC. However, stimulation of EC with bradykinin does not lead to a detectable activation of PKC, suggesting that PKC does not exert a negative feedback in the signal transduction pathway of this receptor‐dependent agonist. © 1993 Wiley‐Liss, Inc.
Substance P: A competence factor for human fibroblast proliferation that induces the release of growth‐regulatory arachidonic acid metabolites
Authors: Kähler Christian M. , Herold Manfred , Wiedermann Christian J. 
Published: February 2005

AbstractSubstance P (SP) was recognized to stimulate cell growth. The mechanisms of growth control by SP are unknown. We, therefore, investigated mechanisms of the effect of SP on proliferation of human skin fibroblasts. SP did not stimulate proliferation of fibroblasts growth arrested by serum starvation over 48 hours. However, in the presence of acetylsalicylic acid SP potently stimulated fibroblast growth. A bell‐shaped dose‐response curve with maximal stimulation at picomolar concentrations was found. Specificity of the mitogenic effect was analyzed by use of synthetic SP analogs. Only neurokinin‐1 receptor agonists were active, whereas a specific neurokinin‐2 receptor analog did not exhibit mitogenicity. Analyzing the supernatants of growth‐arrested fibroblasts treated with SP indicated that SP provokes release of the arachidonic acid metabolites, prostaglandin E2, and prostacyclin but not thromboxane B2 or leukotriene B4. Since similar response patterns in proliferation and arachidonic acid metabolite release have been described for several proinflammatory cytokines, some of which are known to act as competence factors in proliferation, we characterized the mitogenic effect of SP. Results established that SP stimulates fibroblast growth in a manner typical of competence factors. We conclude that arachidonic acid metabolites are involved in the cell cycle‐dependent mitogenic action of SP on human skin fibroblasts. © 1993 Wiley‐Liss, Inc.
Early induction of LDL receptor gene during rat liver regeneration
Authors: Bocchetta M. , Bruscalupi G. , Castellano F. , Trentalance A. , Komaromy M. , Fong L. G. , Cooper A. D. 
Published: February 2005

AbstractAfter partial hepatectomy in the rat, there is substantial lipid accumulation in the liver. No information is available on the possible role of receptor‐mediated endocytosis in this process. Since the low density lipoprotein (LDL) receptor is stimulated as a part of an early growth response in cell culture (Ellsworth et al.: Biochem. J. 279:175–187, 1991), the metabolism of this receptor during liver regeneration was studied. The mRNA and membrane protein level of the receptor were measured in the liver and in the adrenal glands at different times after partial hepatectomy, corresponding to different phases of the cell cycle. A discontinuous pattern of receptor expression is detectable in the regenerating liver; a large increase of mRNA and membrane protein occurs at an early time (2–4 h), suggesting that there is induction of LDL receptor gene transcription shortly after partial hepatectomy. This response seems specific for the liver following injury since the adrenal receptor does not show a different pattern in partially hepatectomized rats and sham‐operated controls. After returning to control levels, the LDL receptor again increases slightly above control at 24 h, a time when cell replication begins. © 1993 Wiley‐Liss, Inc.
Bradykinin‐stimulated transient modulation of epidermal growth factor receptors in A‐431 human epidermoid carcinoma cells
Authors: Hosoi Kazuo , Kurihara Kinji , Ueha Takao 
Published: February 2005

AbstractOf nine biological factors (ATP, bradykinin, vasopressin, substance P, angiotensin II, norepinephrine, epinephrine, 12‐tetradecanoylphorbol 13‐acetate (TPA), and A23187 calcium ionophore) examined, bradykinin, as well as ATP, TPA, and A23187, significantly increased the phosphorylation of epidermal growth factor (EGF) receptors and reduced the binding of EGF to their high‐affinity site. The reduction in EGF binding by bradykinin, ATP, and TPA was similarly reversed by concomitant incubation with staurosporine, a protein kinase C inhibitor, implying that the phosphorylation of EGF receptors was catalyzed probably by a protein kinase C of the same or similar type in each case. This possibility was confirmed by the fact that the major phosphorylation site of EGF receptors by the stimulation with either bradykinin, ATP or TPA was the same (Thi‐654). Different from the stimulations with ATP and TPA, the effect of bradykinin of decreasing the high‐affinity EGF binding was transient (a minimum binding at 2.5 min); the reduced EGF binding was, however, sustained for up to 30 min in the presence of calyculin A, a phosphoprotein phosphatase inhibitor. Moreover, the homogenate prepared from bradykinin‐stimulated A‐431 cells had stronger dephosphorylation activity for phosphorylated EGF receptors than that from control cells. These results suggest that bradykinin stimulates both the protein kinase C system and a phosphoprotein phosphatase(s) activity in A‐431 cells. Such biphasic effects of bradykinin to phosphorylate and dephosphorylate EGF receptors via protein kinase C and a phosphoprotein phosphatase, respectively, imply a homeostatic control of receptor function in regulating phosphorylation level by the same bioactive factor. © 1993 Wiley‐Liss, Inc.
Vascular smooth muscle cells synthesize two forms of insulin‐like growth factor binding proteins which are regulated differently by the insulin‐like growth factors
Authors: Cohick Wendie S. , Gockerman Amy , Clemmons David R. 
Published: February 2005

AbstractVascular smooth muscle cells (SMC) synthesize insulin‐like growth factor‐I (IGF‐I), which is a mitogen for this cell type in vitro. Since IGF binding proteins (IGFBP) modulate IGF bioactivity, we determined which IGFBPs were secreted by porcine SMC. Porcine SMC secreted 34,000 and 24,000 Mr forms of IGFBPs which were identified as IGFBP‐2 and IGFBP‐4, respectively, by immunoblotting. Northern blot analysis showed single transcripts of 1.6 kb and 2.4 kb for IGFBP‐2 and IGFBP‐4, respectively. Secretion of IGFBP‐2 was not regulated to a significant degree, with insulin, IGF‐II, IGF‐I, forskolin, and dibutyryl cyclic adenosine monophosphate (cAMP) inducing minimal changes in IGFBP‐2 secretion of less than 30% by radioimmunoassay (RIA). Insulin increased (2.8 ± 0.1‐fold) the abundance of IGFBP‐4 protein in conditioned media (CM) and increased IGFBP‐4 mRNA levels. Growth factors for SMC such as platelet‐derived growth factor (PDGF), fibroblast growth factor (FGF), epidermal growth factor (EGF), and transforming growth factor beta‐1 (TGFβ‐1) were without effect on either IGFBP‐2 or −4. IGF‐I treatment decreased the amount of IGFBP‐4 present in CM, but a corresponding decrease in IGFBP‐4 mRNA levels was not observed. In order to determine if IGFBP‐4 could modulate IGF‐I bioactivity, IGFBP‐4 was added to pSMCs with and without IGF‐I. IGF‐I alone (20 ng/ml) induced a 1.6 to threefold increase in 3H‐thymidine incorporation. Addition of IGFBP‐4 (between 50 and 250 ng/ml) to cultures containing IGF‐I (20 ng/ml) had no effect on DNA synthesis compared to that observed with IGF‐I alone, while 500 ng/ml consistently caused a small decrease (15 ± 5%; mean ± SE). Immunoblotting of the CM obtained at the end of the 3H‐thymidine assay showed a loss of intact IGFBP‐4 in the cultures containing IGF‐I. This corresponded with an increase in the abundance of a 16,000 Mr immunoreactive fragment that did not bind IGF‐I. Coincubation with insulin had no effect on the amount of IGFBP‐4 that was converted to fragment, suggesting that the reaction was dependent upon IGF‐I binding to IGFBP‐4. In contrast, addition of IGFBP‐4 (500 ng/ml) to human fibroblast cultures with IGF‐I (20 ng/ml) almost completely inhibited the stimulatory effect of IGF‐I on DNA synthesis and no increase in fragment was detected in the CM. In summary, SMC secrete IGFBP‐2 and IGFBP‐4, both of which have been shown to regulate IGF‐mediated DNA synthesis. The factors that regulate the abundance of the two forms of IGFBPs differ suggesting that differential regulation of these substances may be an important mechanism by which SMC growth is regulated. © 1993 Wiley‐Liss, Inc.
Down‐regulation of retinoic acid receptor activity associated with decreased α and γ isoforms expression in F9 embryonal carcinoma cells differentiated by retinoic acid
Authors: Lazega David , Schenker Esther , Busso Nathalie , Zelent Arthur , Chen Alex , Waxman Samuel 
Published: February 2005

AbstractF9 embryonal carcinoma cells differentiate in response to retinoic acid (RA). To investigate the regulation of RA receptors (RARs) expression during this process, cDNA probes specific for the major RAR isoforms were used. In contrast to the level of RARβ2 mRNA which was high in cells treated 5 days with RA and below detection in untreated cells, as previously described, the steady state levels of RARα1, α2, γl, and γ2 mRNAs were markedly decreased in the RA‐differentiated cells as compared to untreated cells. The down‐regulation of the RA‐responsive system in differentiated cells was also evident in gel shift assays as a marked decrease in binding capacity to a retinoid acid response element (βRARE), as well as in chloramphenicol acetyltransferase (CAT) assays as a sixfold decrease in RA‐mediated transacting activity via this element. The down‐regulation of RAR DNA‐binding and transacting activity coincided with the burst in tissue plasminogen activator secretion and thus, occurred at the hinge between early and late differentiation. The down‐regulation of RA responsiveness may constitute an important event in the transition between early and late differentiation stage in F9 cells. © 1993 Wiley‐Liss, Inc.
Increased epidermal growth factor receptor in an estrogen‐responsive, adriamycin‐resistant MCF‐7 cell line
Authors: Dickstein Bruce , Valverius Eva M. , Wosikowski Katja , Saceda Miguel , Pearson Jack W. , Martin Mary Beth , Bates Susan E. 
Published: February 2005

AbstractWe examined the expression of the estrogen and epidermal growth factor (EGF) receptors in a drug‐resistant subline of MCF‐7 cells in order to study potential alterations in hormone dependence or in the growth factor pathway that could be related to the development of drug resistance in human breast cancer. The drug‐resistant subline was derived from MCF‐7 cells by selection with Adriamycin in the presence of the P‐giycoprotein antagonist, verapamil, to prevent acquisition of the classical multidrug resistance phenotype. The Adriamycin‐resistant cells retain estrogen‐binding, estrogen‐responsive monolayer growth, and estrogen‐dependent tumorigenesis. Estrogen‐binding studies demonstrate 1.4 × 106 sites per cell with unaltered affinity when compared to parental MCF‐7 cells, which have 2.7 × 105 sites per cell. An increase in expression of EGF receptor, eight to 12‐fold, occurred early in the selection for drug resistance, and appears to be unrelated to verapamil exposure, since cells maintained in Adriamycin without verapamil also have increased EGF receptor expression. Partially drug‐sensitive revertants carried a verapamil, but out of Adriamycin, demonstrate a decline in EGF receptor expression. We postulate that activation of growth factor pathways in drug‐resistant cells may enhance mechanisms of drug resistance, or provide mitogenic stimuli for cells to recover after damage by drug exposure. © 1993 Wiley‐Liss, Inc.
Induction of the murine “W phenotype” in long‐term cultures of human cord blood cells by c‐kit antisense oligomers
Authors: Migliaccio Anna Rita , Migliaccio Giovanni , Mancini Giancarlo , Ratajczak Mariusz , Gewirtz Alan M. , Adamson John W. 
Published: February 2005

AbstractThe murine white (W) spotting locus is the site of the c‐kit gene and encodes a tyrosine kinase receptor while the complementary Steel (Sl) iocus encodes its ligand. Mutations at either locus have profound effects on hematopoiesis, particularly erythroid and mast cell proliferation. We added c‐kit antisense oligonucleotides to long‐term suspension cultures of enriched human umbilical cord progenitor cells. This resulted in the suppression of c‐kit gene expression and the preferential suppression of the generation of erythroid burst‐forming cells (BFU‐E) which extended over the life of the culture (3 weeks). The results provide an in vitro model of the “W phenotype” in human hematopoiesis and confirm the importance of c‐kit gene function in early erythropoiesis. Because the generation of BFU‐E was suppressed even after c‐kit gene expression had recovered, this gene product may be critical to the erythroid commitment process. © 1993 Wiley‐Liss, Inc.
Asymmetric origins of the mature glomerular basement membrane
Authors: Lee Larry K. , Pollock Allan S. , Lovett David H. 
Published: February 2005

AbstractRenal plasma filtration is a critical physiologic function that depends upon the precise composition and arrangement of the constituent extracellular matrix proteins within the glomerular basement membrane (GBM). The GBM develops during renal embryogenesis by the fusion of discrete basement membranes produced independently by endothelial and visceral epithelial cells, and, possibly from matrix secreted by the mesangial cells. In the mature animal, however, the epithelial cell has generally been accepted as the sole source of all GBM constituent proteins. Although the final structures and distributions of the component proteins have been defined by histochemical techniques, the individual contributions of the three resident glomerular cell types to the maintenance and turnover of the mature GBM remain uncertain. We report the application of a new technique, in situ reverse transcription (ISRT), for the localization of RNA transcripts of nine major GBM protein components within the closely apposed cells of the glomerulus. Using this technique, we demonstrate that in normal adult rat glomeruli the RNA transcripts for heparan sulfate proteoglycan and the laminin‐S chain are primarily expressed by visceral epithelial cells, while Type IV α‐1 and α‐2 collagen transcripts were restricted to the endothelial cells in a heterogeneous pattern. RNA transcripts for entactin and the laminin‐A and ‐B2 chains were expressed by all three glomerular cell types, while laminin‐B1 and fibronectin transcripts were limited to the mesangium. These findings demonstrate that GBM synthesis in the mature animal is not restricted to the epithelial cell and that all intrinsic glomerular cells contribute to the production of GBM protein components. The ISRT technique also provided the additional, and unexpected, finding that appreciable synthetic heterogeneity exists within individual glomerular cell types. © 1993 Wiley‐Liss, Inc.
Role of glucose in interleukin‐1β production by lipopolysaccharide‐activated human monocytes
Authors: Orlinska Urszula , Newton Robert C. 
Published: February 2005

AbstractWhen monocytes are activated with endotoxin (lipopolysaccharide [LPS]), they make and release several mediators, including interleukin‐1β (IL‐1β). This study was undertaken to investigate the role of glucose in IL‐1β production by these cells. IL‐1β was produced in a dose‐dependent manner to glucose concentration in the culture medium. The uptake of (3H)2‐deoxyglucose in monocytes was stimulated by LPS 1,554% after 10 minutes, 6,095% after 2 hours, then gradually declined after 4 hours of incubation. The inhibition of the uptake of (3H)2‐deoxyglucose by either 10 μM cytochaiasin B or phloretin, added at the time of monocyte activation, was accompanied by significant reduction in ATP/ADP ratio and the inhibition of the production of IL‐1β by activated monocytes. The synthesis of total protein did not change in monocytes activated in the absence of glucose in the culture medium, nor in the presence of either 10 μM cytochalasin B or phloretin. The export of IL‐1β from LPS‐activated monocytes was not inhibited by either 10 μM cytochalasin B or phloretin, nor in the absence of glucose in the culture medium. These data suggest that (1) glucose is required for LPS‐induced IL‐1β production by monocytes; (2) glucose is the major source of ATP for IL‐1β production; (3) glucose transporter (GLUT 1) does not control the export of IL‐1β. © 1993 Wiley‐Liss, Inc.
Recombinant insulin‐like growth factor binding protein‐1 inhibits IGF‐I, serum, and estrogen‐dependent growth of MCF‐7 human breast cancer cells
Authors: Figueroa José A. , Sharma Jivesh , Jackson James G. , McDermott Martin J. , Hilsenbeck Susan G. , Yee Douglas 
Published: February 2005

AbstractThe insulin‐like growth factors (IGFs) are potent mitogens for breast cancer cells and their activity is modulated by high affinity binding proteins (IGFBPs). We have recently shown that IGFBP‐1 purified from human amniotic fluid neutralizes IGF‐I‐dependent growth of MCF‐7 cells. In this study we examined the effects of recombinant IGFBP‐1 (rBP‐1) on IGF‐I, estradiol (E2), and serum‐induced monolayer and anchorage independent growth (AIG) of MCF‐7 cells. Under serum‐free conditions, rBP‐1 had no effect on MCF‐7 basal monolayer growth. However, 40 nM rBP‐1 completely blocked the mitogenic action of both IGF‐I and 5% charcoal stripped serum (CSS). This concentration of rBP‐1 partially inhibited E2‐induced growth, while 80 nM rBP‐1 completely abolished E2 mitogenicity. The addition of either excess IGF‐I or 5 nM [Arg3]IGF‐I, a species that does not bind IGFBPs, neutralized rBP‐1 inhibitory effects. In AIG assays, 80 nM rBP‐1 reduced colony number by at least 70% and decreased colony size in all treatment groups compared to control. We examined rBP‐1 effects on both IGF‐I binding to MCF‐7 membranes and activation of type I IGF receptor (IGFR1) and found that 80 nM rBP‐1 reduced IGF‐I receptor binding to levels of nonspecific binding and completely abolished ligand‐dependent IGFR, phosphorylation. However, neither treatment with 5% CSS nor exposure to E2 resulted in IGFR1 phosphorylation suggesting that different mechanism(s) are responsible for rBP‐1 inhibitory action under this condition. Our data suggest rBP‐1 may serve as an antagonist of human breast cancer growth by interfering with growth factor‐mediated cell proliferation. © 1993 Wiley‐Liss, Inc.
Cell substratum modulates responses of preosteoblasts to retinoic acid
Authors: Traianedes K. , Ng K. W. , Martin T. J. , Findlay D. M. 
Published: February 2005

AbstractThe aim of this study was to determine the role of ECM components of bone in regulating the differentiation and function of cells of the osteoblast lineage. Rat UMR 201 cells, phenotypically preosteoblast, were plated onto plastic tissue culture dishes or dishes coated with gelled type I collagen or reconstituted basement membrane (matrigel). Acute cell attachment assays showed that cells adhered to substrates in the following order: collagen > matrigel ≫ plastic. Proliferation rate up to 96 hr were similar on each substrate. However, if cells were treated with 10−6 M retinoic acid (RA), proliferation rates were reduced compared with control for cells grown on collagen and matrigel but not on plastic. Morphological changes were matrix‐specific; in subconfluent cultures, long thin processes were seen with cells grown on collagen and a pattern of interconnecting cell processes formed when cells were plated on matrigel. Striking differences were observed in the constitutive or RA‐induced gene expression of cells grown on the different substrates. When cells plated on collagen were treated with RA, induction of mRNA for alkaline phosphatase (ALP) as well as ALP enzyme activity were much less than with cells grown on plastic. In contrast, RA treatment induced osteopontin (OP) mRNA expression more strongly in cells plated on collagen compared with plastic within 24 hr and this was maintained for 72 hr. RA treatment produced a two fold increase of pro‐α 1(I) collagen mRNA in cells grown on plastic and matrigel but not in cells grown on collagen. Growth on collagen produced changes in the way UMR 201 cells responded to RA from which they did not fully recover in subsequent 48‐hr growth periods on plastic. These results indicate that ECM components regulate the function of and are capable of modulating RA‐induced differentiation of preosteoblasts. © 1993 Wiley‐Liss, Inc.