Improvement on binding of chondroitin sulfate derivatives to midkine by increasing hydrophobicity.

The interactions between chondroitin sulfate (CS) and a wide number of proteins modulate important biological processes. Here, the binding properties to midkine and pleiotrophin of sulfated, fully protected intermediates, typically obtained in the chemical synthesis of CS oligosaccharides, were tested for the first time. Using a fluorescence polarization competition experiment, we discovered that these synthetic precursors strongly bound these two closely related cytokines involved in cancer and inflammation. The relative binding affinities of these intermediates were significantly higher than those displayed by the corresponding fully deprotected oligosaccharides, indicating that the presence of hydrophobic protecting groups strongly enhanced the binding of CS-like derivatives to midkine. These compounds offer novel opportunities for the development of potent inhibitors/activators of CS-protein interactions with potential therapeutic applications.

NMR structural studies of oligosaccharides related to cancer processes.

A summary of spectroscopic methods for structural and conformational elucidation of bioactive carbohydrates based on nuclear magnetic resonance (NMR) is described. The formation of carbohydrate-protein complexes is often the initial step of biological responses. Therefore, knowledge about the structural factors that stabilize the complex may be relevant and contribute to predict the structural/conformational requirements of new drugs acting as agonists. Two examples of medical significance in the cancer research field are discussed (1) conformational studies of glycoconjugates related to antitumour vaccines (2) conformational analysis of glycosaminoglycans and the interaction heparin-fibroblast growth factor (FGF).

Changes in the expression of tachykinin receptors in the rat uterus during the course of pregnancy.

In the mammalian female reproductive tract, tachykinin neuropeptides, such as substance P (SP), are localized to a population of sensory fibers and their precise physiological role is still unknown. The aim of the present study was to characterize the population of tachykinin receptors in the pregnant rat uterus and to assess their regulation during the course of pregnancy and after delivery. The expression of the tachykinin NK(1) receptor (NK(1)R), the tachykinin NK(2) receptor (NK(2)R), and the tachykinin NK(3) receptor (NK(3)R) in uteri from rats at different stages of pregnancy and on Day 1 postpartum was investigated by using a semiquantitative reverse transcription-polymerase chain reaction. The contractile effect of tachykinin receptor agonists acting selectively on the NK(1)R, the NK(2)R, or the NK(3)R was investigated by conventional organ bath techniques. Serum levels of estrogen and progesterone were measured by RIA. Our data show that the expression and function of NK(1)R and NK(3)R varied along the course of pregnancy and at postpartum. Uterine NK(2)R mRNA levels remain stable during the course of pregnancy and at Day 1 postpartum; and the contractions elicited by activating selectively the NK(2) receptor in the presence of the neutral endopeptidase inhibitor phosphoramidon (1 microM) were similar in early, mid, or late pregnancy. These results show that the expression and function of tachykinin receptors within the uterus vary with reproductive state and length of gestation, supporting a role for tachykinins in pregnancy and/or parturition in the rat.

Inositolphosphoglycan mediators structurally related to glycosyl phosphatidylinositol anchors: synthesis, structure and biological activity.

The preparation of the pseudopentasaccharide 1a, an inositol-phosphoglycan (IPG) that contains the conserved linear structure of glycosyl phosphatidylinositol anchors (GPI anchors), was carried out by using a highly convergent 2+3-block synthesis approach which involves imidate and sulfoxide glycosylation reactions. The preferred solution conformation of this structure was determined by using NMR spectroscopy and molecular dynamics simulations prior to carrying out quantitative structure--activity relationship studies in connection with the insulin signalling process. The ability of 1a to stimulate lipogenesis in rat adipocytes as well as to inhibit cAMP dependent protein kinase and to activate pyruvate dehydrogenase phosphatase was investigated. Compound 1a did not show any significant activity, which may be taken as a strong indication that the GPI anchors are not the precursors of the IPG mediators.