title: N-cholesteryl sphingomyelin-A synthetic sphingolipid with unique membrane properties.
abstract: A sphingomyelin chimera in which the amide-linked acyl chain was replaced with cholesterol carbamate was prepared and its properties examined. The sphingomyelin/cholesterol chimera (N-cholesterol-D-erythro-sphingomyelin) was able to form unilamellar vesicles of defined size when extruded through 200nm pore size membranes. These N-cholesteryl sphingomyelin bilayers were resistant to solubilization by Triton X-100. When N-cholesteryl sphingomyelin was added to N-palmitoyl sphingomyelin (N-palmitoyl-d-erythro-sphingomyelin) bilayers, it increased acyl chain order as determined by 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy. N-cholesteryl sphingomyelin was, however, not as good an inducer of membrane order compared to cholesterol on a molar basis. Differential scanning calorimetry studies further showed that the miscibility of N-cholesteryl sphingomyelin with N-palmitoyl-d-erythro-sphingomyelin bilayers was non-ideal, and the effect of N-cholesteryl sphingomyelin on the N-palmitoyl-d-erythro-sphingomyelin gel-fluid transition enthalpy differed from that seen with cholesterol. Together with N-palmitoyl-d-erythro-sphingomyelin, the N-cholesteryl sphingomyelin chimera was able to form sterol-enriched ordered domains in a fluid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayer. N-cholesteryl sphingomyelin in the absence of N-palmitoyl-d-erythro-sphingomyelin was unable to form such sterol-enriched ordered domains in a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayer. However, N-cholesteryl sphingomyelin markedly increased the affinity of cholestatrienol for N-cholesteryl sphingomyelin containing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers, suggesting that N-cholesteryl sphingomyelin was able to somehow stabilize sterol interaction in fluid bilayers. Based on our results, we conclude that N-cholesteryl sphingomyelin behaved more like a cholesterol than a sphingolipid in fluid bilayer membranes. Because N-cholesteryl sphingomyelin increased bilayer order, conferred resistance against detergent solubilization, and is not degradable by phospholipases A(2), it could constitute a good lipocomplex matrix for drug delivery vehicles.
authors.affiliation: Department of Biosciences, Åbo Akademi University, Tykistökatu 6 A, FI-20520, Finland.
authors.forename: Christian
authors.initials: C
authors.lastname: Sergelius
authors.forename: Shou
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yamamoto
authors.forename: J Peter
authors.initials: JP
authors.lastname: Slotte
authors.forename: Shigeo
authors.initials: S
authors.lastname: Katsumura
mesh_terms: D002152:Calorimetry, Differential Scanning; D002784:Cholesterol / Q000737:chemistry*; D005454:Fluorescence Polarization; D008051:Lipid Bilayers / Q000737:chemistry*; D017830:Octoxynol / Q000737:chemistry; D012995:Solubility; D013053:Spectrophotometry; D013107:Sphingolipids / Q000737:chemistry*; D013109:Sphingomyelins / Q000737:chemistry*; D013696:Temperature; D053835:Unilamellar Liposomes / Q000737:chemistry
chemical_list: D008051:Lipid Bilayers; D013107:Sphingolipids; D013109:Sphingomyelins; D053835:Unilamellar Liposomes; D017830:Octoxynol; D002784:Cholesterol