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At least 271 records · Page 15Linked to original sources
PubMed1997

HR 720, a novel angiotensin receptor antagonist inhibits the angiotensin II-induced trophic effects, fibronectin release and fibronectin-EIIIA+ expression in rat aortic vascular smooth muscle cells in vitro.

The aim of this study was to evaluate the direct trophic effects of angiotensin II (AII) on rat vascular smooth muscle cells obtained from a single cellular isolate. Cell volume, protein synthesis, fibronectin (FN) release and FN-EIIIA+ mRNA isoform expression were analyzed in parallel. The effects of HR 720, a novel AT1 angiotensin receptor antagonist with some AT2 receptor affinity, were compared with those of selective AT1 antagonist EXP 3174. Both HR 720 and EXP 3174 inhibited in a concentration-dependent manner the maximum increase in cell volume induced by 10(-9) M Sar1-All (IC50 = 0.49 x 10(-9) M and 0.79 x 10(-9) M, respectively). Maximum [3H]leucine incorporation was also achieved at 10(-9) M All. HR 720 blocked the increase in protein synthesis with potency similar to EXP 3174; the respective IC50 values were 1.04 x 10(-9) M and 1.36 x 10(-9) M. All dose-dependently increased FN release, which was also equally inhibited by about 50% with both compounds at 10(-6) M. Furthermore, All enhanced FN-EIIIA+ mRNA in rat vascular smooth muscle cells (VSMC), which indicated a modulation of FN isoform expression which was inhibited by angiotensin II antagonists. In conclusion, All induced parallel and concentration-dependent increases in cell volume, protein synthesis, FN release and FN-EIIIA+ mRNA expression in vascular smooth muscle cells. These effects appeared to be essentially mediated by AT1 receptor stimulation as indicated by the equal inhibitory effects of HR 720 and EXP 3174.

Angiotensin II↗
PubMed1998

Growth-supporting activities of fibronectin on hematopoietic stem/progenitor cells in vitro and in vivo: structural requirement for fibronectin activities of CS1 and cell-binding domains.

Fibronectin (FN) is supposed to play important roles in various aspects of hematopoiesis through binding to very late antigen 4 (VLA4) and VLA5. However, effects of FN on hematopoietic stem cells are largely unknown. In an effort to determine if FN had a growth-supporting activity on hematopoietic stem cells, human CD34(+)/VLA4(bright)/VLA5(dull) hematopoietic stem cells and a murine stem cell factor (SCF)-dependent multipotent cell line, EML-C1, were treated with or without FN in a serum and growth-factor-deprived medium, and then subjected to clonogenic assay in the presence of hematopoietic growth factors. The pretreatment of the CD34(+) cells with FN gave rise to significantly increased numbers of granulocyte-macrophage colony-forming units (CFU-GM), erythroid burst colony-forming units, and mixed erythroid-myeloid colony-forming units. In addition, the numbers of blast colony-forming units and CFU-GM that developed after culture of EML-C1 cells with SCF and the combination of SCF and interleukin-3, respectively, were augmented by the pretreatment with FN. The augmented colony formation by FN was completely abrogated by the addition of CS1 fragment, but not of GRGDSP peptide, suggesting an essential role of FN-VLA4 interaction in the FN effects. Furthermore, the effects of various FN fragments consisting of RGDS-containing cell-binding domain (CBD), heparin-binding domain (HBD), and/or CS1 portion were tested on clonogenic growth of CD34(+) cells. Increased colony formation was induced by CBD-CS1 and CBD-HBD-CS1 fragments, but not with other fragments lacking CBD or CS1 domains, suggesting that both CS1 and CBD of FN were required for the augmentation of clonogenic growth of hematopoietic stem/progenitor cells in vitro. In addition to the in vitro effects, the in vivo administration of CBD-CS1 fragment into mice was found to increase the numbers of hematopoietic progenitor cells in bone marrow and spleen in a dose-dependent manner. Thus, FN may function on hematopoietic stem/progenitor cells as a growth-supporting factor in vitro and in vivo.

Amino Acid Sequence↗
PubMed1991

A modified Arg-Asp-Val (RDV) peptide derived during the synthesis of Arg-Glu-Asp-Val (REDV), a tetrapeptide derived from an alternatively spliced site in fibronectin, inhibits the binding of fibrinogen, fibronectin, von Willebrand factor and vitronectin to activated platelets.

Characterization of a side-product obtained during the synthesis of Arg-Glu-Asp-Val (REDV) with inhibitory activity in thrombin-activated platelet aggregation was carried out. The semipreparative column fractionation of REDV peptide was rechromatographed on an analytical HPLC column and revealed two peaks which were re-tested for inhibitory activity. Using amino acid analysis with sequencing and fast atom bombardment mass spectrometry (FABMS), the first peak was determined to be REDV with molecular mass of 517 Da, and the second peak was determined to be a modified RDV with a mass of 608 Da. The modified RDV peptide inhibited thrombin-induced platelet aggregation with an IC50 of 200 microM, and complete inhibition occurred at 600 microM. However, the REDV peptide did not inhibit platelet aggregation up to 1 mM concentration. The modified RDV peptide eluted platelet glycoprotein IIb-IIIa complex that had been bound to GRGDSP-agarose. These studies show that the modified RDV peptide interacts with the platelet glycoprotein IIb-IIIa complex. Based on the collision-induced dissociation (CID) mass spectral data analysis, the modified RDV peptide has been characterized to contain an N-terminus blocking group on the Arg residue. The origin of this blocking group is presumed to have originated from decomposition products of the phenylacetamidomethyl (PAM) resin used in the solid-phase synthesis of the target peptide Arg-Glu-Asp-Val.

Amino Acid Sequence↗