cdw17-antigen and Inflammation

Diabetes contributes to about 30% morbidity and mortality world-wide and has tidal wave increases in several countries in Asia. Diabetes is a multi-factorial disease compounded by inflammation, dyslipidemia, atherosclerosis, and is sometimes accompanied with gains in body weight. Sphingolipid pathways that interplay in the enhancement of the pathology of this disease may be potential therapeutic targets. Thus, the application of advanced sphingolipidomics may help predict the progression of this disease and therapeutic outcomes in man. Pre-clinical studies using various experimental animal models of diabetes provide valuable information on the role of sphingolipid signaling networks in diabetes and the efficacy of drugs to determine the translatability of innovative discoveries to man. In this review, we discuss three major concepts regarding sphingolipids and diabetes. First, we discuss a possible involvement of a monosialodihexosylceramide (GM3) in insulin-insulin receptor interactions. Second, a potential role for ceramide (Cer) and lactosylceramide (LacCer) in apoptosis and mitochondrial dysfunction is proposed. Third, a larger role of LacCer in antioxidant status and inflammation is discussed. We also discuss how inhibitors of glycosphingolipid synthesis can ameliorate diabetes in experimental animal models.

Topics: Animals; Cardiovascular Diseases; Diabetes Mellitus; Glycosphingolipids; Inflammation; Lactosylceramides; Models, Animal; Oxidative Stress; Sphingolipids

Lactosylceramide (LacCer), also known as CD17/CDw17, is a member of a large family of small molecular weight compounds known as glycosphingolipids. It plays a pivotal role in the biosynthesis of glycosphingolipids, primarily by way of serving as a precursor to the majority of its higher homolog sub-families such as gangliosides, sulfatides, fucosylated-glycosphingolipids and complex neutral glycosphingolipids-some of which confer "second-messenger" and receptor functions. LacCer is an integral component of the "lipid rafts," serving as a conduit to transduce external stimuli into multiple phenotypes, which may contribute to mortality and morbidity in man and in mouse models of human disease. LacCer is synthesized by the action of LacCer synthase (β-1,4 galactosyltransferase), which transfers galactose from uridine diphosphate galactose (UDP-galactose) to glucosylceramide (GlcCer). The convergence of multiple physiologically relevant external stimuli/agonists-platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), stress, cigarette smoke/nicotine, tumor necrosis factor-α (TNF-α), and in particular, oxidized low-density lipoprotein (ox-LDL)-on β-1,4 galactosyltransferase results in its phosphorylation or activation, via a "turn-key" reaction, generating LacCer. This newly synthesized LacCer activates NADPH (nicotinamide adenine dihydrogen phosphate) oxidase to generate reactive oxygen species (ROS) and a highly "oxidative stress" environment, which trigger a cascade of signaling molecules and pathways and initiate diverse phenotypes like inflammation and atherosclerosis. For instance, LacCer activates an enzyme, cytosolic phospholipase A2 (cPLA2), which cleaves arachidonic acid from phosphatidylcholine. In turn, arachidonic acid serves as a precursor to eicosanoids and prostaglandin, which transduce a cascade of reactions leading to inflammation-a major phenotype underscoring the initiation and progression of several debilitating diseases such as atherosclerosis and cancer. Our aim here is to present an updated account of studies made in the field of LacCer metabolism and signaling using multiple animal models of human disease, human tissue, and cell-based studies. These advancements have led us to propose that previously unrelated phenotypes converge in a LacCer-centric manner. This LacCer synthase/LacCer-induced "oxidative stress" environment contributes to inflammation, atherosclerosis, skin conditions, hair greying, cardiovascu

Topics: Animals; Antigens, CD; Atherosclerosis; Cardiovascular Diseases; Cytokines; Diabetes Mellitus; Humans; Inflammation; Lactosylceramides; Mice; Oxidative Stress; Signal Transduction; Skin Diseases

Glycosphingolipids (GSLs) are membrane components consisting of hydrophobic ceramide and hydrophilic sugar moieties. GSLs cluster with cholesterol in cell membranes to form GSL-enriched lipid rafts. Biochemical analyses have demonstrated that GSL-enriched lipid rafts contain several kinds of transducer molecules, including Src family kinases. Among the GSLs, lactosylceramide (LacCer, CDw17) can bind to various microorganisms, is highly expressed on the plasma membranes of human phagocytes, and forms lipid rafts containing the Src family tyrosine kinase Lyn. LacCer-enriched lipid rafts mediate immunological and inflammatory reactions, including superoxide generation, chemotaxis, and non-opsonic phagocytosis. Therefore, LacCer-enriched membrane microdomains are thought to function as pattern recognition receptors (PRRs), which recognize pathogen-associated molecular patterns (PAMPs) expressed on microorganisms. LacCer also serves as a signal transduction molecule for functions mediated by CD11b/CD18-integrin (αM/β2-integrin, CR3, Mac-1), as well as being associated with several key cellular processes. LacCer recruits PCKα/ε and phospholipase A2 to stimulate PECAM-1 expression in human monocytes and their adhesion to endothelial cells, as well as regulating β1-integrin clustering and endocytosis on cell surfaces. This review describes the organizational and inflammation-related functions of LacCer-enriched lipid rafts.

Topics: Animals; Antigens, CD; Humans; Immunity, Innate; Inflammation; Lactosylceramides; Membrane Microdomains; Superoxides

Topics: Antigens, CD; Biomedical Research; Cardiomegaly; Enzyme Activation; Humans; Inflammation; Lactosylceramides; Models, Biological; Myocytes, Cardiac; Phospholipases A2

In the present study a possible role of glycosphingolipids (GSLs) in inducible nitric oxide synthase (iNOS) gene expression and nitric oxide (NO) production after spinal cord injury (SCI) in rats has been established. In primary rat astrocytes lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) treatment increased the intracellular levels of lactosylceramide (LacCer) and induced iNOS gene expression. d-Threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol.HCI (PDMP), a glucosylceramide synthase and LacCer synthase (galactosyltransferase, GalT-2) inhibitor, inhibited LPS/IFN-gamma induced iNOS expression, which was reversed by exogenously supplied LacCer, but not by other glycosphingolipids. LPS/IFN-gamma caused a rapid increase in the activity of GalT-2 and synthesis of LacCer. Silencing of GalT-2 gene with the use of antisense oligonucleotides resulted in decreased LPS/IFN-gamma-induced iNOS, TNF-alpha, and IL-1beta gene expression. The PDMP-mediated reduction in LacCer production and inhibition of iNOS expression correlated with decreased Ras and ERK1/2 activation along with decreased IkappaB phosphorylation, NF-kappaB DNA binding activity, and NF-kappaB-luciferase reporter activity. LacCer-mediated Ras activation was redox-mediated and was attenuated by antioxidants N-acetyl cysteine (NAC) and pyrrolidine dithiocarbamate (PDTC). In vivo administration of PDMP after SCI resulted in improved functional outcome (Basso, Beattie, Bresnahan score); inhibition of iNOS, TNF-alpha, and IL-1beta expression; decreased neuronal apoptosis; and decreased tissue necrosis and demyelination. The in vivo studies supported the conclusions drawn from cell culture studies and provided evidence for the possible role of GalT-2 and LacCer in SCI-induced inflammation and pathology. To our knowledge this is the first report of a role of LacCer in iNOS expression and the advantage of GSL depletion in attenuating post-SCI inflammation to improve the outcome of SCI.

Topics: Acetylcysteine; Animals; Antigens, CD; Antioxidants; Apoptosis; Astrocytes; Cells, Cultured; Demyelinating Diseases; Drug Evaluation, Preclinical; Enzyme Induction; Enzyme Inhibitors; Fatty Acids; Female; Gait Disorders, Neurologic; Galactosyltransferases; I-kappa B Proteins; Inflammation; Interferon-gamma; Lactosylceramides; Lipopolysaccharides; Morpholines; Nerve Tissue Proteins; NF-kappa B; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Oxidation-Reduction; Phosphorylation; Proline; Protein Processing, Post-Translational; Rats; Rats, Sprague-Dawley; Recombinant Proteins; Signal Transduction; Spinal Cord Injuries; Thiocarbamates; Transfection

We have characterized the major glycolipid constituents of the mouse peritoneal macrophage, and have demonstrated that alterations in the amount and in the accessibility of specific glycolipid species to galactose oxidase/NaB3H4 labeling, an indicator of glycolipid surface exposure, occur in response to inflammation and as a consequence of activation to a tumoricidal state. The key findings are: (a) Asialo GM1, a major neutral glycolipid constituent of all macrophage populations examined, is accessible to galactose oxidase/NaB3H4 labeling on the surface of TG-elicited and BCG-activated macrophages but not on resident macrophages; (b) GM1 is the predominant ganglioside constituent of the mouse macrophage. Resident macrophages contain two distinct GM1 species, as determined by cholera toxin binding, while TG-elicited and BCG-activated macrophages contain an additional GM1 species. Differences in the relative amounts of these GM1 species, as well as in their accessibility to galactose oxidase/NaB3H4 labeling, exist among the macrophage populations. These observations suggest that both a chemical and spatial reorganization of surface glycolipids occurs in response to inflammation and tumoricidal activation.

Topics: Animals; Antigens, CD; Ascitic Fluid; Female; G(M1) Ganglioside; Galactosylceramides; Glycolipids; Glycosphingolipids; Inflammation; Lactosylceramides; Leukemia, Experimental; Macrophage Activation; Macrophages; Membrane Lipids; Mice; Mice, Inbred C57BL