Acidic glycolipids from dolphin kidney

Syntheses of α(2,8) Sialosides Containing NeuAc and NeuGc by Using Double Carbonyl-Protected N-Acyl Sialyl Donors

We report on the syntheses of NeuAc and NeuGc-containing glycosides via the use of double carbonyl-protected N-acetyl sialyl donors. The 7-O,9-O-carbonyl protection of an N-acyl-5-N,4-O-carbonyl-protected sialyl donor markedly increased the α-selectivity during glycosylation, particularly when glycosylating the C-8 hydroxyl group of sialic acids. The N-acyl carbamates were selectively opened with ethanethiol under basic conditions to provide N-acyl amines. It is noteworthy that N-glycolyl carbamate was more reactive to nucleophiles by comparison with the N-acetyl carbamate due to the electron-withdrawing oxygen in the N-acyl group and however, allowed selective opening of the carbamates without the loss of N-glycolyl groups. To demonstrate the utility of the approach, we began by synthesizing α(2,3) and α(2,6) sialyl galactosides. Glycosylation of the hydroxy groups of galactosides at the C-6 position with the NeuAc and NeuGc donors provided the corresponding sialyl galactoses in good yields with excellent α-selectivity. However, glycosylation of the 2,3-diol galactosyl acceptor selectively provided Siaα(2,2)Gal. Next, we prepared a series of α(2,8) disialosides composed of NeuAc and NeuGc. Glycosylation of NeuGc and NeuAc acceptors at the C-8 hydroxyl group with NeuGc and NeuAc sialyl donors provided the corresponding α(2,8) disialosides, and no significant differences were detected in the reactivities of these acceptors.

Vascularized cardiac tissue construction with orientation by layer-by-layer method and 3D printer

Herein, we report the fabrication of native organ-like three-dimensional (3D) cardiac tissue with an oriented structure and vascular network using a layer-by-layer (LbL), cell accumulation and 3D printing technique for regenerative medicine and pharmaceutical applications. We firstly evaluated the 3D shaping ability of hydroxybutyl chitosan (HBC), a thermoresponsive polymer, by using a robotic dispensing 3D printer. Next, we tried to fabricate orientation-controlled 3D cardiac tissue using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) and normal human cardiac fibroblasts (NHCF) coated with extracellular matrix (ECM) nanofilms by layer-by-layer technique. These cells were seeded in the fabricated rectangular shape HBC gel frame. After cultivation of the fabricated tissue, fluorescence staining of the cytoskeleton revealed that hiPSC-CM and NHCF were aligned in one direction. Moreover, we were able to measure its contractile behavior using a video image analysis system. These results indicate that orientation-controlled cardiac tissue has more remarkable contractile function than uncontrolled cardiac tissue. Finally, co-culture with human cardiac microvascular endothelial cells (HMVEC) successfully provided a vascular network in orientation-controlled 3D cardiac tissue. The constructed 3D cardiac tissue with an oriented structure and vascular network would be a useful tool for regenerative medicine and pharmaceutical applications.

Metabolism of vertebrate amino sugars with N-glycolyl groups: resistance of α2-8-linked N-glycolylneuraminic acid to enzymatic cleavage

The sialic acid (Sia) N-acetylneuraminic acid (Neu5Ac) and its hydroxylated derivative N-glycolylneuraminic acid (Neu5Gc) differ by one oxygen atom. CMP-Neu5Gc is synthesized from CMP-Neu5Ac, with Neu5Gc representing a highly variable fraction of total Sias in various tissues and among different species. The exception may be the brain, where Neu5Ac is abundant and Neu5Gc is reported to be rare. Here, we confirm this unusual pattern and its evolutionary conservation in additional samples from various species, concluding that brain Neu5Gc expression has been maintained at extremely low levels over hundreds of millions of years of vertebrate evolution. Most explanations for this pattern do not require maintaining neural Neu5Gc at such low levels. We hypothesized that resistance of α2-8-linked Neu5Gc to vertebrate sialidases is the detrimental effect requiring the relative absence of Neu5Gc from brain. This linkage is prominent in polysialic acid (polySia), a molecule with critical roles in vertebrate neural development. We show that Neu5Gc is incorporated into neural polySia and does not cause in vitro toxicity. Synthetic polymers of Neu5Ac and Neu5Gc showed that mammalian and bacterial sialidases are much less able to hydrolyze α2-8-linked Neu5Gc at the nonreducing terminus. Notably, this difference was not seen with acid-catalyzed hydrolysis of polySias. Molecular dynamics modeling indicates that differences in the three-dimensional conformation of terminal saccharides may partly explain reduced enzymatic activity. In keeping with this, polymers of N-propionylneuraminic acid are sensitive to sialidases. Resistance of Neu5Gc-containing polySia to sialidases provides a potential explanation for the rarity of Neu5Gc in the vertebrate brain.

Identification of gangliosides recognized by IgG anti-GalNAc-GD1a antibodies in bovine spinal motor neurons and motor nerves

The presence of immunoglobulin G (IgG)-type antibodies to the ganglioside, N-acetylgalactosaminyl GD1a (GalNAc-GD1a), is closely associated with the pure motor type of Guillain-Barré syndrome (GBS). In the present study, we isolated disialogangliosides from the motor neurons and motor nerves of bovine spinal cords by DEAE-Sephadex column chromatography. The disialoganglioside fraction contained GD1a, GD2, GD1b, and three gangliosides, designated X1, X2 and X3. Serum from a patient with axonal GBS with IgG anti-GalNAc-GD1a antibody yielded positive immunostaining with X1, X2, and X3. When isolated by preparative thin-layer chromatography (TLC), X1 migrated at the same position as GalNAc-GD1a from Tay-Sachs brain, suggesting that X1 is GalNAc-GD1a containing N-acetylneuraminic acid (NeuAc). TLC of isolated X2 revealed that it migrated between GD1a and GD2. On the other hand, X3 had a migratory rate on TLC between and GD1b and GT1b. Since both X2 and X3 were recognized by IgG anti-GalNAc-GD1a antibody, the results suggest that X2 is a GalNAc-GD1a species containing a mixture containing a NeuAc-and an N-glycolylneuraminic acid (NeuGc) species, and X3 is a GalNAc-GD1a species with two NeuGc. This evidence indicating the specific localization of GalNAc-GD1a and its isomers in spinal motor neurons should be useful in elucidating the pathogenic role of IgG anti-GalNAc-GD1a antibody in pure motor-type GBS.

Isolation and characterization of acidic glycosphingolipids from the gill of the Pacific Salmon (Oncorhynchus keta): A novel hybrid-type ganglioside with isoglobo- and neolacto-Series

Monosialosyl gangliosides and sulfoglycolipids in the gill of pacific salmon, Oncorhynchus keta, have been prepared by solvent extraction and DEAE-Sephadex column chromatography. Acidic glycolipid bands (M1-M13) detected by thin layer chromatography were separated by Iatrobeads column chromatography and 13 components were characterized by TLC, compositional analysis, methylation analysis, chemical and enzymatic degradation, liquid secondary ion mass spectrometry and (1)H nuclear magnetic resonance spectroscopy. In addition to the acidic glycolipids with known structures (SM4s, SM3, GM3, LM1, GM1b and V(3)alphaFuc,IV(3)betaGalNAc-GM1a), two fractions (M11 and M13) of unknown monosialosyl gangliosides with TLC mobility slower than GM1a were isolated and characterized as having the following structure with a hybrid of isoglobo- and neolacto-series. [formula: see text] Analysis of fatty acid indicated predominance of C24:1 fatty acid in the upper band (M11) and shorter chain saturated fatty acids in the lower band (M13). The tissue concentrations of M11 and M13 were 1.15 and 0.96 mumol/kg wet weight, respectively.

Unique disialosyl gangliosides from salmon kidney: Characterization of V3αFuc, IV3βGalNAc, II3(αNeuAc)2-Gg4Cer and its analogue with 4-O-acetyl-N-acetylneuraminic acid

Four unidentified acidic glycolipids (X3-X6) were isolated from the kidney of the Pacific salmon on an anion exchange column and by high performance liquid chromatography using a silica bead (Iatrobeads) column. Based on methylation analysis, chemical and enzymatic degradation, proton nuclear magnetic resonance spectroscopy and mass spectrometry, the glycon structure of X5 and X6 was identified as a unique disialosyl fucosyl-N-acetylgalactosaminyl ganglio-N-tetraose:Fucalpha3GalNAcbeta3Galbeta3GalNAcbeta4[NeuAcalpha8NeuAcalpha3] Galbeta4Glcbeta1Cer. NMR showed that X3 and X4 were analogues of X5 and X6 and contained O-acetyl groups on C4 of the outer N-acetylneuraminic acid, first disialosyl gangliosides containing 4-O-acetyl-N-acetylneuraminic acid. The ceramides of X3 and X5 contained predominantly C24: 1, and X4 and X6 contained saturated fatty acids (C14: 0, C16: 0 and C18: 0), whereas the long chain base was exclusively sphingenine. The concentrations of X3 and X4 were 0.13 and 0.16 nmol/g of kidney respectively and those of X5 and X6, were 0.07 nmol/g each.

Conformational studies on a unique bis-sulfated glycolipid using NMR spectroscopy and molecular dynamics simulations

The time-averaged solution conformation of a unique bis-sulfated glycolipid (HSO3)2-2,6Manalpha-2Glcalpha-1-sn-2,3-O-alkylglycerol , was studied in terms of the torsional angles of two glycosidic linkages, phi (H1-C1-O-Cx) and psi (C1-O-Cx-Hx), derived from heteronuclear three-bond coupling constants (3JC,H), and inter-residual proton-proton distances from J-HMBC 2D and ROESY experiments, respectively. The dihedral angles of Glcalpha1Gro in glycolipids were determined for the first time. The C1-C4 diagonal line of the alpha-glucose ring makes an angle of approximately 120 degrees with the glycerol backbone, suggesting that the alpha-glucose ring is almost parallel to the membrane surface in contrast with the perpendicular orientation of the beta-isomer. Furthermore, minimum-energy states around the conformation were estimated by Monte Carlo/stochastic dynamics (MCSD) mixed-mode simulations and the energy minimization with assisted model building and energy refinement (AMBER) force field. The Glcalpha1Gro linkage has a single minimum-energy structure. On the other hand, three conformers were observed for the Manalpha2Glc linkage. The flexibility of Manalpha2Glc was further confirmed by the absence of inter-residual hydrogen bonds which were judged from the temperature coefficients of the chemical shifts, ddelta/dT (-10-3 p.p.m. degrees C-1), of hydroxy protons. The conformational flexibility may facilitate interaction of extracellular substances with both sulfate groups.

Complete 1H and 13C NMR assignment of mono-sulfated galactosylceramides with four types of ceramides from human kidney

The full assignment of 1H and 13C NMR signals of galactosylceramide 3-sulfate (galactosyl sulfatide) and 1H signals of galactosylceramide 6-sulfate was achieved by using 1H-1H DQF-COSY and 1H-13C heteronuclear COSY. Analyses were performed on a mixture of galactosyl sulfatides with four representative ceramide types consisting of a combination of non-hydroxy or 2-hydroxy fatty acids and sphingenine or 4D-hydroxysphinganine (trihydroxysphinganine) as the long-chain bases. The 1H and 13C NMR parameters of galactosyl sulfatide with 4-hydroxysphinganine as well as 13C signals of complex lipids with 4-hydroxysphinganine were elucidated for the first time. Not only sulfation of the galactosyl residue, but also modification of the aglycon, including hydroxylation of fatty acids and hydration of the double bond in sphingoid bases, altered the chemical shifts substantially. In addition, the unique long-range coupling constants, 4J(H,H) and 5J(H,H), in the galactosyl residue of galactosyl sulfatide could be determined.

A NeuGc-containing trisialoganglioside of bovine brain

A N-glycolyneuraminic acid containing trisialoganglioside was isolated from bovine brains ganglioside mixture using Q-Sepharose. Its chemical structure was characterized as IV3NeuAc, II3NeuAc-NeuGc, Gg4Cer by gas-liquid chromatography, a permethylation study, sialidase degradation, TLC/enzyme-immunostaining, fast atom bombardment-mass spectrometry, fluorometric HPLC and proton nuclear magnetic resonance spectroscopy. This was unique in the mixed sialic acid constituents. (formula; see text) This accounted for 0.78% of the gangliosides. The ceramide structure was almost identical with those of major bovine brain ganglioside, as mainly composed of 18:0 fatty acid (90.9%) and d20:0 sphingosine base.

Accumulation of sulfoglycolipids in hyperosmosis-resistant clones derived from the renal epithelial cell line MDCK (Madin-Darby canine kidney cell)

1. Two clones (osmR-A and osmR-B) resistant to hyperosmotic media of 700 and 800 mosmol/l, respectively, were selected from Madin-Darby canine kidney (MDCK) cells. 2. When cultured in isosmotic medium (300 mosmol/l), the concentration of galactosyl sulfatide and lactosyl sulfatide in these hyperosmosis-resistant clones was 3.4-5.9 times higher than in the wild-type MDCK. The rate of incorporation of [35S]sulfate into sulfolipids of osmR-A and osmR-B was 1.9-6.7 times higher than MDCK. 3. The stimulation of incorporation into sulfolipids by hyperosmotic culture was completely inhibited by cycloheximide. The pulse-chase studies indicated decreased turnover rate of sulfolipids in osmR-A.

Adaptive changes in sulfoglycolipids of kidney cell lines by culture in anisosmotic media

(1) The effects of osmolarity environments on renal glycolipid composition were examined using established renal cell lines. The profile of glycosphingolipids of Madin-Darby canine kidney cells (MDCK) in culture with anisosmotic media showed that a hyposomotic medium reduced the concentration of GalCer I3-sulfate and LacCer II3-sulfate. (2) The concentrations of sulfoglycolipids were increased by maintaining the culture in a hyperosmotic media prepared by the addition of various sodium salts to the control isosmotic medium, while the contents of most of the neutral glycolipids were reduced. The hyperosomotic medium supplemented with nonelectrolytes, mannitol, sucrose or urea, also increased the concentration of sulfoglycolipids. (3) Both sulfoglycolipids were increased linearly with gradual increases of sodium chloride in the medium. Hyperosmolarity produced by the addition of a nonelectrolyte, mannitol, also increased the levels of sulfoglycolipids. In both series of media, the most prominent accumulation was observed in LacCer II3-sulfate. (4) The incorporation of radioactive sulfate into sulfoglycolipids was elevated in cells adapted to high NaCl or mannitol. The increase of the label was observed not only in MDCK but also in three other established cell lines of renal tubular origin, JTC-12, LLC-PK1 and MDBK. (5) It was established, using the culture system of homogeneous cell lines, that the mechanism of increasing the amount of sulfoglycolipids is independent of the integral regulatory mechanism of animals and resides in the renal epithelial cell itself. These results suggest that by culture in hyperosmotic media, the elevated level of intracellular cations stimulated the activity of GalCer and LacCer sulfotransferase, inducing the increased expression of sulfoglycolipids.