Sialyl LewisX glycomimetics bearing an extended anionic chain targeting E- and P- selectin binding sites.

Neutrophil binding to vascular P- and E-selectin is the rate-limiting step in the recruitment of immune cells to sites of inflammation. Many diseases, including sickle cell anemia, post-myocardial infarction reperfusion injury, and acute respiratory distress syndrome are characterized by dysregulated inflammation. We have recently reported sialyl Lewisx analogues as potent antagonists of P- and E-selectin and demonstrated their in vivo immunosuppressive activity. A key component of these molecules is a tartrate diester that serves as an acyclic tether to orient the fucoside and the galactoside moiety in the required gauche conformation for optimal binding. The next stage of our study involved attaching an extended carbon chain onto one of the esters. This chain could be utilized to tether other pharmacophores, lipids, and contrast agents in the context of enhancing pharmacological applications through the sialyl Lewisx / receptor-mediated mechanism. Herein, we report our preliminary studies to generate a small library of tartrate based sialyl Lewisx analogues bearing extended carbon chains. Anionic charged chemical entities are attached to take advantage of proximal charged amino acids in the carbohydrate recognition domain of the selectin receptors. Starting with a common azido intermediate, synthesized using copper-catalyzed Huisgen 1,3-dipolar cycloadditions, these molecules demonstrate E- and P-selectin binding properties.

Synthesis of Sialyl LewisX Mimetics with E- and P-Selectin Binding Properties and Immunosuppressive Activity.

E- and P-selectins are adhesion proteins implicated in immune cell recruitment at sites of infection, making them important drug targets for diseases involving excessive and uncontrolled inflammation. In this study, we developed an efficient strategy to synthesize bicyclic galactopyranosides through a key stereoselective equatorial C4-propiolate addition and TMSCN axial C-glycosidation. The nitrile group can then be converted to the carboxyl and different bioisosteres at a late stage in the synthesis, allowing for various derivatizations to potentially enhance biological activity. The sialyl LewisX glycomimetic featuring this rigidified bicyclic galactopyranoside moiety prevents neutrophil adhesion to endothelial cells in vitro by binding to both E- and P-selectins. We show here that the axial carboxyl analogue blocks immune cell recruitment in vivo, demonstrating its potential as an immunomodulator.

GATA6 is a regulator of sinus node development and heart rhythm.

The sinus node (SAN) is the primary pacemaker of the human heart, and abnormalities in its structure or function cause sick sinus syndrome, the most common reason for electronic pacemaker implantation. Here we report that transcription factor GATA6, whose mutations in humans are linked to arrhythmia, is highly expressed in the SAN and its haploinsufficiency in mice results in hypoplastic SANs and rhythm abnormalities. Cell-specific deletion reveals a requirement for GATA6 in various SAN lineages. Mechanistically, GATA6 directly activates key regulators of the SAN genetic program in conduction and nonconduction cells, such as TBX3 and EDN1, respectively. The data identify GATA6 as an important regulator of the SAN and provide a molecular basis for understanding the conduction abnormalities associated with GATA6 mutations in humans. They also suggest that GATA6 may be a potential modifier of the cardiac pacemaker.

Synthesis of Sialyl LewisX Glycomimetics Bearing a Bicyclic 3- O,4- C-Fused Galactopyranoside Scaffold.

Reported herein is the synthesis of sialyl LewisX analogues bearing a trans-bicyclo[4.4.0] dioxadecane-modified 3- O,4- C-fused galactopyranoside scaffold that locks the carboxylate pharmacophore in either the axial or equatorial position. This novel series of bicyclic galactopyranosides are prepared through a stereocontrolled intramolecular cyclization reaction that has been evaluated both experimentally and by density functional theory calculations. The cyclization precursors are obtained from ß-d-galactose pentaacetate in a nine-step sequence featuring a highly diastereoselective equatorial alkynylation and Cu(I) catalyzed formation of the acetylenic α-ketoester moiety. Preliminary biological evaluations indicate improved activity as P-selectin antagonists for the axially configured analogues as compared to their equatorial counterparts.