Polar functional group-containing glycolipid CD1d ligands modulate cytokine-biasing responses and prevent experimental colitis.

The MHC class I-like molecule CD1d is a nonpolymorphic antigen-presenting glycoprotein, and its ligands include glycolipids, such as α-GalCer. The complexes between CD1d and ligands activate natural killer T cells by T cell receptor recognition, leading to the secretion of various cytokines (IFN-γ, IL-4, IL-17A, etc.). Herein, we report structure-activity relationship studies of α-GalCer derivatives containing various functional groups in their lipid acyl chains. Several derivatives have been identified as potent CD1d ligands displaying higher cytokine induction levels and/or unique cytokine polarization. The studies also indicated that flexibility of the lipid moiety can affect the binding affinity, the total cytokine production level and/or cytokine biasing. Based on our immunological evaluation and investigation of physicochemical properties, we chose bisamide- and Bz amide-containing derivatives 2 and 3, and evaluated their in vivo efficacy in a DSS-induced model of ulcerative colitis. The derivative 3 that exhibits Th2- and Th17-biasing responses, demonstrated significant protective effects against intestinal inflammation in the DSS-induced model, after a single intraperitoneal injection.

Design and Discovery of Covalent α-GalCer Derivatives as Potent CD1d Ligands.

CD1d is a nonpolymorphic antigen-presenting protein responsible for the regulation of natural killer T (NKT) cell activation. α-Galactosyl ceramide (α-GalCer, KRN7000) is the representative CD1d ligand that can bind to the CD1d protein. The resulting complex is recognized by the T cell receptors of the NKT cell, inducing various immune responses. Previous structure-activity relationship studies of α-GalCer have revealed that the ability of NKT cells to induce cytokines depends on the ligand structure, and in particular, ligands that form more stable complexes with CD1d display potent activity. We focused on the Cys residue of the large hydrophobic pockets of CD1d (A' pocket) and developed α-GalCer derivatives containing groups that can form covalent bonds. The assay results revealed that these ligands displayed higher levels of cytokine production and Th2 cell-type cytokine polarization response. Furthermore, the LC-MS/MS analysis indicated that the chloroacetylamide-containing ligand was covalently bound to Cys12 of CD1d, which suggests that the enhanced activities result from the formation of a stable CD1d-ligand complex. To our knowledge, this is the first ligand that allows covalent bond formation to CD1d under physiological conditions.

Structure-activity relationship studies of Bz amide-containing α-GalCer derivatives as natural killer T cell modulators.

CD1d is a non-polymorphic antigen-presenting glycoprotein that recognizes glycolipids as ligands. Ligands bind to the hydrophobic grooves of CD1d, and the resulting ligand-CD1d complexes activate natural killer T (NKT) cells by means of T cell receptor recognition, leading to the secretion of various cytokines. However, details of the ligand recognition mechanism of a large hydrophobic ligand binding pocket and the relationship between cytokine induction and ligand structure are unclear. We report the synthesis of α-GalCer derivatives containing a Bz amide group having various substituting groups in the ceramide moiety, and the analysis of the structure-activity relationships. The assays reveal that the Bz amide-containing CD1d ligands function as NKT cell modulators displaying Th2 cytokine biasing responses. Furthermore, molecular dynamics simulation studies suggest that the phenyl groups can interact with the aromatic amino acid residues in the lipid binding pocket of CD1d.

Potent Th2 Cytokine Bias of Natural Killer T Cell by CD1d Glycolipid Ligands: Anchoring Effect of Polar Groups in the Lipid Component.

Th2-biasing CD1d ligands are attractive potential candidates for adjuvants and therapeutic drugs. However, the number of potent ligands is limited, and their biasing mechanism remain unclear. Herein, a series of novel Th2-biasing CD1d glycolipid ligands, based on modification of their lipid part, have been identified. These have shown high binding affinities and efficient Th2 cytokine production. Importantly, the truncated acyl chain containing variants still retain their binding affinities and agonistic activities, which can be associated with an "anchoring effect," that is, formation of a buried hydrogen bond between a polar group on the acyl chain and the CD1d lipid-binding pocket. The analysis indicated that the appearance rates of ligand-CD1d complexes on the cell surface were involved in Th2-biasing responses. The designed ligands, having the anchor in the shorter lipid part, are one of the most potent Th2-biasing ligands among the known ligands.

Convergent Synthesis of Digalactosyl Diacylglycerols.

Efficient convergent chemical syntheses of digalactosyl diacylglycerols (DGDGs), which have both a galactose-galactose α(1→6)-linkage and a galactose-glycerol ß-linkage along with a diacylglycerol containing various kinds of fatty acids, have been accomplished. In order to achieve a concise synthesis, we chose to use allylic protective groups as permanent protective groups. We have also achieved α- and ß-selective glycosylations for the respective linkages with high yields as the key steps.

The relationship between the frequency of self-monitoring of blood glucose and glycemic control in patients with type 1 diabetes mellitus on continuous subcutaneous insulin infusion or on multiple daily injections.

AIMS/INTRODUCTION: We investigated the relationship between the frequency of self-monitoring of blood glucose (SMBG) and glycemic control in type 1 diabetes mellitus patients on continuous subcutaneous insulin infusion (CSII) or on multiple daily injections (MDI) using data management software. MATERIALS AND METHODS: We recruited 148 adult type 1 diabetes mellitus patients (CSII n = 42, MDI n = 106) and downloaded their SMBG records to the MEQNET™ SMBG Viewer software (Arkray Inc., Kyoto, Japan). The association between the SMBG frequency and the patients' hemoglobin A1c (HbA1c) levels was analyzed using the χ(2)-test and linear regression analysis was carried out to clarify their relationship. RESULTS: The odds ratio of achieving a target HbA1c level of <8% (63.9 mmol/mol) was significantly higher in subjects with SMBG frequencies of ≥3.5 times/day compared with those with SMBG frequencies of <3.5 times/day in the CSII group (odds ratio 7.00, 95% confidence interval 1.72-28.54), but not in the MDI group (odds ratio 1.35, 95% CI 0.62-2.93). A significant correlation between SMBG frequency and the HbA1c level was detected in the CSII group (HbA1c [%] = -0.24 × SMBG frequency [times/day] + 8.60 [HbA1c {mmol/L} = -2.61 × SMBG frequency {times/day} + 70.5], [r = -0.384, P = 0.012]), but not in the MDI group. CONCLUSIONS: A SMBG frequency of <3.5 times per day appeared to be a risk factor for poor glycemic control (HbA1c ≥8%) in type 1 diabetes mellitus patients on CSII.

Surface Tomonaga-Luttinger-Liquid State on Bi/InSb(001).

A 1D metallic surface state was created on an anisotropic InSb(001) surface covered with Bi. Angle-resolved photoelectron spectroscopy (ARPES) showed a 1D Fermi contour with almost no 2D distortion. Close to the Fermi level (E_{F}), the angle-integrated photoelectron spectra showed power-law scaling with the binding energy and temperature. The ARPES plot above E_{F}, obtained thanks to a thermally broadened Fermi edge at room temperature, showed a 1D state with continuous metallic dispersion across E_{F} and power-law intensity suppression around E_{F}. These results strongly suggest a Tomonaga-Luttinger liquid on the Bi/InSb(001) surface.