The effects of fibroblast growth factors on ischemic kidney, liver and gut injuries.
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OBJECTIVE: To explore the possibility of reducing reperfusion injuries of internal organ with acidic and basic fibroblast growth factors (aFGF and bFGF). METHODS: Two kinds of ischemia and reperfusion animal models were used in this study. In rat model of superior mesenteric artery (SMA) occlusion, microvascular clamp was placed on the root of SMA to cut off the blood flow for 45 minutes, and then the clamp was removed. In rat model of bilateral renal ischemia and reperfusion, both renal arteries were clipped to get complete cessation of blood flow for 60 minutes, then the blood flow was allowed to return. At the onset of reperfusion, the doses of 4.0 micrograms/rat of bFGF in SMA occluded rats or 2.6 micrograms/rat of aFGF in rats with acute renal injury were administered through the jugular vein. The liver and renal function examination, tissue bacterial study and histopathological evaluation were done to evaluate the treatment results. RESULTS: The functional impairment of ischemic liver, gut and kidney were reduced with venous administration of aFGF or bFGF at the onset of reperfusion. The results of pathological and tissue bacterial examination supported the assertion of significant protective effects of FGFs. CONCLUSIONS: The protective effects of FGFs may come from the non-mitogenic effects of FGFs at the early and the mitogenic effects at the late stage of tissue repair. These results indicate a potential for clinical use of FGFs as a therapeutic modality in ischemic visceral organ injuries in the future. (+info)
Induction of the mesendoderm in the zebrafish germ ring by yolk cell-derived TGF-beta family signals and discrimination of mesoderm and endoderm by FGF.
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The endoderm forms the gut and associated organs, and develops from a layer of cells which emerges during gastrula stages in the vertebrate embryo. In comparison to mesoderm and ectoderm, little is known about the signals which induce the endoderm. The origin of the endoderm is intimately linked with that of mesoderm, both by their position in the embryo, and by the molecules that can induce them. We characterised a gene, zebrafish gata5, which is expressed in the endoderm from blastula stages and show that its transcription is induced by signals originating from the yolk cell. These signals also induce the mesoderm-expressed transcription factor no tail (ntl), whose initial expression coincides with gata5 in the cells closest to the blastoderm margin, then spreads to encompass the germ ring. We have characterised the induction of these genes and show that ectopic expression of activin induces gata5 and ntl in a pattern which mimics the endogenous expression, while expression of a dominant negative activin receptor abolishes ntl and gata5 expression. Injection of RNA encoding a constitutively active activin receptor leads to ectopic expression of gata5 and ntl. gata5 is activated cell-autonomously, whereas ntl is induced in cells distant from those which have received the RNA, showing that although expression of both genes is induced by a TGF-beta signal, expression of ntl then spreads by a relay mechanism. Expression of a fibroblast growth factor (eFGF) or a dominant negatively acting FGF receptor shows that ntl but not gata5 is regulated by FGF signalling, implying that this may be the relay signal leading to the spread of ntl expression. In embryos lacking both squint and cyclops, members of the nodal group of TGF-beta related molecules, gata5 expression in the blastoderm is abolished, making these factors primary candidates for the endogenous TGF-beta signal inducing gata5. (+info)
Fgf8 and Gbx2 induction concomitant with Otx2 repression is correlated with midbrain-hindbrain fate of caudal prosencephalon.
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Chick/quail transplantation experiments were performed to analyse possible factors involved in the regionalisation of the midbrain-hindbrain domain. The caudal prosomeres, expressing Otx2, were transplanted at stage HH10 into rostrocaudal levels of the midbrain-hindbrain domain, either straddling the intra-metencephalic constriction (type 1 grafts), or at rostral and medial levels of pro-rhombomere A1 (type 2 and 3 grafts, respectively); thus, in all situations, one border of the graft was in contact with the host Gbx2- and Fgf8-expressing domains. The area containing the graft, recognised by QCPN immunohistochemistry, was first analysed 48 hours after transplantation for Otx2, Gbx2, En2 and Fgf8. Although in all three situations, a large part of the graft maintained Otx2 expression, another part became Otx2 negative and was induced to express Gbx2 and Fgf8. These inductive events occurred exclusively at the interface between the Otx2-positive transplanted domain and the ipsilateral host Gbx2-positive rhombomere 1, creating a new Otx2-Gbx2 boundary within the grafted territory. In type 1 and 2 grafts, the induced Fgf8 domain is in continuity with the host Fgf8 isthmic domain, whereas for type 3 grafts, these two domains are separate. High levels of En2 expression were also induced in the area expressing Gbx2 and Fgf8, and Wnt1 and Pax2 expressions, analysed in type 3 grafts, were induced at the intragraft Otx2-Gbx2 new boundary. Moreover, at later embryonic stages, the graft developed meso-isthmo-cerebellar structures. Thus, gene expressions induced in the grafted prosencephalon not only mimicked the pattern observed in the normal midbrain-hindbrain domain, but is followed by midbrain-hindbrain cytodifferentiation, indicating that not only Fgf8 but also confrontation of Otx2 and Gbx2 may play an essential role during midbrian-hindbrain regionalisation. (+info)
Comparison of the intracellular signaling responses by three chimeric fibroblast growth factor receptors in PC12 cells.
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Stably transfected PC12 cell lines expressing similar amounts of chimeric receptors composed of the extracellular domain of the human platelet-derived growth factor (PDGF)beta receptor and the transmembrane and intracellular domains of the fibroblast growth factor receptors (FGFRs) 1, 3, and 4 undergo ligand-induced differentiation. The FGFR1 chimera (PFR1) is the most potent of the three, and PFR4 requires more frequent (every 24 hr) addition of ligand to maintain the response. Both PFR1 and -3 also show significant ligand-independent autophosphorylation but PFR4 does not. All of the chimeras activated phospholipase Cgamma, Shc, FGFR substrate (FRS)2, and the mitogen-activated protein kinases, ERK1 and 2. PFR4 was moderately weaker in stimulating these effects as well; PFR1 and -3 were comparable. None of the chimeras induced Sos association or were coprecipitated with Shc. Cotransfection of a dominant-negative Shc derivative, with tyrosine at 239, 240, and 317 replaced with phenylalanine, in the PFR-expressing cells was without effect on PDGF-induced neurite outgrowth. The same derivative substantially inhibited the response of these cells to NGF. These results indicate that FGFR1, 3, and 4 (i) are capable of signaling in a similar fashion; (ii) primarily use FRS2 and, perhaps, PLCgamma; and (iii) do not utilize Shc. The results also suggest that the principal difference between FGFR1, 3, and 4 is in the strength of the tyrosine kinase activity and that qualitative differences in signaling capacity are likely to be less important. (+info)
Genomic structure, mapping, activity and expression of fibroblast growth factor 17.
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Fibroblast growth factors are essential molecules for development. Here we characterize Fgfl7, a new member of the fibroblast growth factor (FGF) family. The Fgfl7 gene maps to mouse chromosome 14 and is highly conserved between mouse and human (93% identity). It exhibits 60% amino acid identity with Fgf8 and 50% identity with Fgf8. Both Fgf8 and Fgf17 have a similar structure and a similar pattern of alternative splicing in the 5' coding region. When expressed in 3T3 fibroblasts, mouse FGF17 is transforming, indicating that it can activate the 'c' splice form of either FGF receptor (FGFR) one or two. During midgestation embryogenesis, in situ hybridization analysis localized Fgf17 expression to specific sites in the midline structures of the forebrain, the midbrain-hindbrain junction, the developing skeleton and in developing arteries. Comparison to Fgf8 revealed a striking similarity in expression patterns, especially in the central nervous system (CNS), suggesting that both genes may be important for CNS development, although Fgf17 is expressed somewhat later than Fgf8. In the developing skeleton, both genes are expressed in costal cartilage while Fgf8 is preferentially expressed in long bones. In the developing great vessels Fgfl7 is preferentially expressed, suggesting that it may have a more prominent role in vascular growth. (+info)
Efficacy of keratinocyte growth factor-2 in dextran sulfate sodium-induced murine colitis.
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The purpose of this study was to determine the efficacy of a novel human protein, keratinocyte growth factor-2 (KGF-2), in a model of murine colitis induced by ad libitum exposure to a 4% solution of dextran sulfate sodium (DSS) in the drinking water. Initial evaluation of KGF-2 was based on its ability to reduce weight loss, stool score, and histological score in mice exposed to DSS for 7 days. When KGF-2 (0.1-10.0 mg/kg i.p. or s.c.) was injected daily into DSS-treated mice from day 0 to 7, it significantly reduced all three parameters in a dose-response fashion, with a minimum effective dose of between 1 and 3 mg/kg. When KGF-2 was given therapeutically, starting 4 days after initiation of the 7-day DSS treatment, the 3- but not the 0.5-mg/kg dose significantly enhanced weight recovery after discontinuation of DSS treatment. When DSS treatment was prolonged beyond the normal 7 days, therapeutic intervention on day 2 or 4 also significantly reduced mortality, weight loss, and stool score at the 1- and 3-mg/kg dose. Therapeutic treatment also resulted in reduction of colon myloperoxidase levels by more than 50%. These experiments suggest that KGF-2 may be clinically useful in the treatment of inflammatory bowel diseases such as ulcerative colitis and Crohn's disease. (+info)
Association of atypical protein kinase C isotypes with the docker protein FRS2 in fibroblast growth factor signaling.
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FRS2 is a docker protein that recruits signaling proteins to the plasma membrane in fibroblast growth factor signal transduction. We report here that FRS2 was associated with PKC lambda when Swiss 3T3 cells were stimulated with basic fibroblast growth factor. PKC zeta, the other member of the atypical PKC subfamily, could also bind FRS2. The association between FRS2 and PKC lambda is likely to be direct as shown by yeast two-hybrid analysis. The C-terminal fragments of FRS2 (amino acid residues 300-508) and SNT2 (amino acids 281-492), an isoform bearing 50% identity to FRS2, interacted with PKC lambda at a region (amino acids 240-562) that encompasses the catalytic domain. In vitro kinase assays revealed neither FRS2 nor SNT2 was a substrate of PKC lambda or zeta. Mutation of the alanine residue (Ala-120) to glutamate in the pseudo-substrate region of PKC lambda results in a constitutively active kinase that exhibited more than 2-fold greater binding to FRS2 in vitro than its "closed" wild-type counterpart. Tyrosine phosphorylation of FRS2 did not affect its binding to the constitutively active PKC lambda mutant, suggesting that the activation of PKC lambda is necessary and sufficient for its association with FRS2. It is likely that FRS2 serves as an anchoring protein for targeting activated atypical PKCs to the cell plasma membrane in signaling pathways. (+info)
Manipulation of outer root sheath cell survival perturbs the hair-growth cycle.
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Transgenic mice that overexpress the anti-apoptotic gene bcl-xL under the control of the keratin 14 promoter have significantly shorter hair than non-transgenic littermates. The deficit in hair length correlated with a decrease in the duration of anagen, the growth phase of the hair cycle. A prolongation in telogen, the resting phase of the hair cycle, was also observed in adult animals. In the developing hair bulb, bcl-xL transgene expression was observed exclusively in the outer root sheath (ORS) cells. Bcl-xL expression enhanced the survival of ORS cells treated with apoptotic stimuli. The results suggest that preventing the apoptotic death of ORS cells during anagen leads to a more rapid termination of progenitor cell commitment/proliferation, while the increased survival of ORS cells during telogen delays the initiation of a new hair cycle. ORS cells produce fibroblast growth factor-5 (FGF-5), which acts in a paracrine fashion to terminate precursor cell division during anagen. The short hair phenotype of bcl-xL transgenic mice was substantially reversed in FGF-5-deficient mice. Thus, the production of growth inhibitory factors by ORS cells may provide a mechanism through which the hair-growth cycle is regulated by cell survival. (+info)