Densimetric determination of equilibrium binding of sucrose octasulfate with basic fibroblast growth factor

Alleviation of experimental ulcerative colitis with the synthetic peptide, F2A4-K-NS (Fibratide)

Recombinant fibroblast growth factors (FGFs) maintain the integrity of the gut epithelium and reduce mucosal injury in experimental inflammatory bowel disease (IBD). Chemically synthesized FGF mimetics could potentially extend the utility of FGFs by tailoring them for optimal bioactivity and oral administration, for example. Here, F2A4-K-NS (Fibratide), a synthetic FGF mimetic peptide, alleviated dextran sulfate sodium (DSS)-induced ulcerative colitis in mice when delivered systemically and, to a lesser extent, orally. Intraperitoneal injection of Fibratide (1 or 5 mg/kg/day) ameliorated DSS-induced ulcerative colitis, resulting in reduced weight loss, decreased colon wall thickening, and increased colon length. Fibratide also improved epithelial integrity by reducing histological-detectable crypt damage and inflammation. Orally administered Fibratide (1 mg/kg/day) was also effective in ameliorating symptoms with effects generally similar to those of intraperitoneal injection. In vitro studies were conducted to help clarify how Fibratide might act in vivo. Fibratide exhibited a modest enhancement of epithelial cell proliferation. On the other hand, Fibratide doubled the rate of epithelial cells migration and restitution in a cell culture model of wound repair. Collectively, the results indicate that Fibratide reduced the severity of experimental ulcerative colitis and may be potentially useful in the treatment of IBD.

Structural basis for activation of fibroblast growth factor signaling by sucrose octasulfate

Sucrose octasulfate (SOS) is believed to stimulate fibroblast growth factor (FGF) signaling by binding and stabilizing FGFs. In this report, we show that SOS induces FGF-dependent dimerization of FGF receptors (FGFRs). The crystal structure of the dimeric FGF2-FGFR1-SOS complex at 2.6-A resolution reveals a symmetric assemblage of two 1:1:1 FGF2-FGFR1-SOS ternary complexes. Within each ternary complex SOS binds to FGF and FGFR and thereby increases FGF-FGFR affinity. SOS also interacts with the adjoining FGFR and thereby promotes protein-protein interactions that stabilize dimerization. This structural finding is supported by the inability of selectively desulfated SOS molecules to promote receptor dimerization. Thus, we propose that SOS potentiates FGF signaling by imitating the dual role of heparin in increasing FGF-FGFR affinity and promoting receptor dimerization. Hence, the dimeric FGF-FGFR-SOS structure substantiates the recently proposed "two-end" model, by which heparin induces FGF-FGFR dimerization. Moreover, the FGF-FGFR-SOS structure provides an attractive template for the development of easily synthesized SOS-related heparin agonists and antagonists that may hold therapeutic potential.

Topical use of Sucralfate Cream in second and third degree burns

This clinical study was undertaken to test the efficacy of topical Sucralfate Cream in second and third degree burns. Topical Sucralfate Cream has been used on a wide variety of lesions from radiation proctitis and dermatitis to keratoconjunctivitis with remarkable results. The study was carried out in two phases. The first phase comprised 60 patients, 30 of whom were treated with Sucralfate Cream while the other 30 were treated with other topical antimicrobial agents. Twenty-one of the patients in the study group had second-degree burns and nine patients' third degree burns. In the second phase, a double blind study was carried out on 25 patients where one area of burns was treated with Sucralfate Cream while another control area of the same patient was treated with a placebo ointment, containing the excipients used during preparation of the Sucralfate Cream, without Sucralfate. In the first phase, it was seen that the period of epithelialisation of second degree burns in the study group treated with Sucralfate Cream was 18.8 days compared with 24.6 days with other topical agents. This difference is statistically significant with a P value of <0.00001. In the double blind study, also healing in the areas treated with Sucralfate was more rapid than those treated with bland placebo ointment. The difference in the two rates of healing was statistically significant with a P value of 0.00067. Histopathological studies were also carried out in 10 patients of phase I of the trial. Sucralfate Cream promotes rapid epithelialisation of second degree burns with minimal said effects and offers another topical agent in the burn care specialist's armamentarium.

Heparin-induced self-association of fibroblast growth factor-2. Evidence for two oligomerization processes

Fibroblast growth factor-2 (FGF-2), a potent angiogenic factor, requires heparin for dimerization and activation of the FGF receptor tyrosine kinase. The binding of multiple fibroblast growth factors by heparin may be necessary for dimerization of the FGF receptor. Analytical ultracentrifugation of FGF-2 in the presence of heparin-derived saccharides shows that both an active heparin octasaccharide and an inactive heparin-like disaccharide induce fibroblast growth factor-2 self-association. Analysis of the data indicates that the heparin octasaccharide induces a monomer-dimer-tetramer assembly of FGF-2 while the disaccharide induces a monomer-dimer equilibrium. Evidence is presented indicating that the dimer conformation induced by the heparin octasaccharide is a side by side dimer with the FGF-2 molecules cis to the heparin, while the disaccharide-induced dimer is a head to head dimer in which FGF-2 molecules are trans to the ligand. These results, combined with previous studies, support the model that formation of a specific side by side heparin-induced FGF-2 dimer is required for activation of the FGF receptor.

A comparison of the conformation of sucrose octasulfate, free and bound to acidic fibroblast growth factor

The conformation of sucrose octasulfate free in solution has been determined based on high-resolution NMR spectroscopy. Three-bond 1H-1H scalar coupling constants, laboratory and rotating frame NOEs, long-range 1H-13C scalar coupling constants, and chemical-shift temperature and ionic-strength dependence were used, aided by molecular mechanics calculations. By modification of a pulse sequence designed for measuring long-range 1H-13C coupling constants, it was possible to obtain an accurate value for the 3JC2f-H1g despite the confounding presence of 3JHH of similar value. Free sucrose octasulfate appears to assume a conformation significantly different from any of the eight conformations observed bound to acidic fibroblast growth factor, as determined in a previous X-ray crystallographic study [X. Zhu, B.T. Hsu, and D.C. Rees, Structure, 1 (1993) 27-34]. Strong electrostatic interactions between guest and host may be the dominant factor in deformation of sucrose octasulfate. The implications of this study for protein-carbohydrate interactions and the effects of the presence of sulfate groups on the flexibility of sucrose are also discussed.

The importance of Arg40 and 45 in the mitogenic activity and structural stability of basic fibroblast growth factor: effects of acidic amino acid substitutions

High-affinity binding of basic fibroblast growth factor (bFGF) to the tyrosine kinase receptor requires cell-surface heparan sulfate proteoglycan or exogenous addition of heparin. The crystal structure of bFGF shows Arg40 and 45 on the surface opposite to the heparin-binding region, suggesting that these charged residues may be involved in the receptor binding. Therefore, these amino acids were mutated to aspartic acid separately or simultaneously, and also a simultaneous mutation to glutamic acid was introduced. These mutants displayed a mitogenic activity decreased greater than tenfold compared to the wild-type protein. Addition of heparin had no effect on the activity, while these mutants showed heparin-binding characteristics resembling those of the native sequence protein. The mutants exhibited decreased stability compared to the native sequence protein. Gradual changes in conformation were observed by circular dichroic and infrared spectroscopy. Heparin chromatography also showed the presence of denatured form for these mutants. However, in the presence of multivalent anions such as citrate, sucrose octasulfate, and heparin, the conformation of the mutants resembled that of the wild-type protein, as revealed by X-ray crystallography and circular dichroism spectra of the mutant with a Arg40-->Asp substitution.