Ami Ben Ya'acov

Glycolipids as Immune Modulatory Tools

NKT cells are a subset of regulatory lymphocytes characterized by co-expression of the NK cell receptor-CD161 and an invariant TCR-alpha chain (Valpha14-Jalpha28). They are most abundant in the liver, spleen, and bone marrow. NKT lymphocytes have been implicated in the regulation of autoimmune processes in both mice and humans. Activation of NKT lymphocytes leads to rapid amplification of either IFNgamma or IL4, endowing these cells with the capability to mediate both pro-inflammatory and anti-inflammatory immune responses. Activation of this subset of cells is associated with significant liver damage in the Concanavalin A immune mediated hepatitis model. Administration of CD1d ligand has a protective role in collagen-induced arthritis in mice. Disease amelioration was associated with a shift in the immune balance from a pathological Th1 type response towards a protective Th2 type response. In humans, patients with SLE, scleroderma, diabetes, multiple sclerosis, and rheumatoid arthritis have lower numbers of peripheral NKT cells. NKT lymphocytes promote tumor rejection in experimental models of tumor immunotherapy. In contrast, NKT lymphocyte-related anti-tumor activity is associated with pro-inflammatory Th1-type immune responses. NKT cells were shown to have a role in suppression of hepatocellular carcinoma (HCC) via immune regulation towards tumor derived antigens, and adoptive transfer of dendritic cells pulsed ex vivo with the same antigens. NKT lymphocytes are activated by interaction of their TCR with glycolipids presented by CD1d, a nonpolymorphic, MHC class I-like molecule expressed by antigen presenting cells, and also by hepatocytes. Several possible ligands for NKT cells have recently been suggested including CD1d bound Glucocerebroside. Glucocerebroside (GC, beta-glucosylceramide), a naturally occurring glycolipid, is a metabolic intermediate in the anabolic and catabolic pathways of complex glycosphingolipids. Its synthesis from ceramide is catalyzed by the enzyme glucosylceramide synthase. Inherited deficiency of glucocerebrosidase, a lysosomal hydrolase, results in Gauchers disease. Patients with Gauchers disease have altered humoral and cellular immune profiles and increased peripheral blood NKT lymphocytes. CD1d-bound glucocerebroside does not activate NKT cells directly, and may inhibit activation of NKT cells by alpha-GalCer. On the other hand, glucosylceramide-synthase deficiency was shown to lead to defective ligand presentation by CD1d, with secondary inhibition of NKT cell activation. Recent studies have suggested that a number of glycolipids, including GC, have an immune modulatory effect in several immune mediated disorders. The ability to alter NKT lymphocyte function in various settings and the potential application of natural glycolipids for treatment are discussed.

Gastric stimulation for weight loss

The prevalence of obesity is growing to epidemic proportions, and there is clearly a need for minimally invasive therapies with few adverse effects that allow for sustained weight loss. Behavior and lifestyle therapy are safe treatments for obesity in the short term, but the durability of the weight loss is limited. Although promising obesity drugs are in development, the currently available drugs lack efficacy or have unacceptable side effects. Surgery leads to long-term weight loss, but it is associated with morbidity and mortality. Gastric electrical stimulation (GES) has received increasing attention as a potential tool for treating obesity and gastrointestinal dysmotility disorders. GES is a promising, minimally invasive, safe, and effective method for treating obesity. External gastric pacing is aimed at alteration of the motility of the gastrointestinal tract in a way that will alter absorption due to alteration of transit time. In addition, data from animal models and preliminary data from human trials suggest a role for the gut-brain axis in the mechanism of GES. This may involve alteration of secretion of hormones associated with hunger or satiety. Patient selection for gastric stimulation therapy seems to be an important determinant of the treatments outcome. Here, we review the current status, potential mechanisms of action, and possible future applications of gastric stimulation for obesity.

β-Glycosphingolipids-mediated lipid raft alteration is associated with redistribution of NKT cells and increased intrahepatic CD8+ T lymphocyte trapping

The aim of this study was to determine the effect of beta-glycosphingolipids on intra-hepatic natural killer T (NKT) lymphocyte regulatory function and on lymphocyte trapping via alteration of cell membrane lipid rafts. Immune-mediated colitis was induced by intracolonic instillation of trinitrobenzene sulfonic acid. Mice were treated with beta-lactosylceramide (LC), beta-glucosylceramide (GC), beta-galactosylceramide, ceramide, or a combination of both GC and LC (IGL), or solvent alone. Lipid rafts were investigated by fluorescence-activated cell sorting analysis of ganglioside-GM1 and fluorescence microscopy of structure. Administration of beta-glycosphingolipids resulted in an increased intrahepatic/peripheral NKT ratio, increased intrahepatic CD8+ lymphocyte trapping, decreased serum interferon-gamma (IFN-gamma) levels and decreased serum IFN-gamma/interleukin-10 ratio. Administration of GC, LC, or IGL significantly altered the levels of GM1, a key marker of lipid rafts, on NKT regulatory lymphocytes. The immune modulatory effect of beta-glycosphingolipids was associated with increased survival and significant alleviation of colitis as determined by improvement in both the macroscopic and microscopic scores. In conclusion, administration of beta-glycosphingolipids increased NKT regulatory lymphocyte redistribution and intrahepatic CD8(+) T lymphocyte trapping, resulting in alleviation of immune-mediated colitis. The effects of these naturally occurring compounds were associated with modification of the T lymphocyte lipid raft structure, which is a site for immune modulation.

β-Glycoglycosphingolipid-Induced Alterations of the STAT Signaling Pathways Are Dependent on CD1d and the Lipid Raft Protein Flotillin-2

Beta-glucosylceramide has been shown to affect natural killer T cell function in models of inflammation. We, therefore, investigated the effects of different beta-glycosphingolipids, including beta-glucosylceramide, on STAT (signal transducers and activators of transcription) signaling pathways and determined whether these effects were mediated by lipid raft microdomains and/or CD1d molecules. The effects of alpha- and beta-structured ligands on the lipid raft protein flotillin-2 were studied in both natural killer T hybridoma cells and leptin-deficient mice. To determine whether CD1d was involved in the effects of the beta-glycosphingolipids, an anti-CD1d blocking antibody was used in a cell proliferation assay system. The downstream effects on the protein phosphorylation levels of STAT1, STAT3, and STAT6 were examined in both immune-mediated hepatitis and hepatoma models. The effects of beta-glycosphingolipids on the STAT signaling pathways were found to be dependent on CD1d. Lipid rafts were affected by both the dose and ratio of the beta-glycosphingolipids and the acyl chain length, and these effects were followed by downstream effects on STAT proteins. Our results show that beta-glycosphingolipids have beneficial effects in natural killer T cell-dependent immune-mediated metabolic and malignant animal models in vivo.

Hepatoprotective effect of DT56a is associated with changes in natural killer T cells and regulatory T cells.

To determine the metabolic and immunological effects of the oral administration of DT56a, an enzymatic isolate of soybeans.

Administration of β-glycolipids overcomes an unfavorable nutritional dependent host milieu: a role for a soy-free diet and natural ligands in intrahepatic CD8+ lymphocyte trapping and NKT cell redistribution ☆

UNLABELLED Soy-based diets are a major source of sphingolipids and play a complicated role in various aspects of the immune system. Administration of beta-glycolipids, including beta-glucosylceramide (GC), beta-lactosylceramide (LC) and a 1:1 combination of GC and LC (IGL) were shown to exert immune-modulatory effects. AIM To examine the effects of a soy-free diet, and several beta-glycolipids on concanavalin A (ConA)-induced hepatitis in the presence of an altered host glycolipid milieu. METHODS ConA hepatitis was induced in C57BL/6 mice that were fed a soy-free diet (glycolipid content 200 micromol/kg). Two hours prior to administration of ConA, animals were injected IP with GC, LC, IGL or PBS. Animals were sacrificed 6 h after ConA administration. RESULTS Both a soy-free diet and administration of beta-glycolipids were associated with significant alterations in the distribution of NKT cells. Specifically, there was a decrease in intrahepatic and an increase in intrasplenic NKT lymphocytes. beta-glycolipids prevented the ConA-induced intrahepatic CD8 lymphocyte trapping, not seen in mice with only a soy-free diet. Both a soy-free diet and beta-glycolipids alleviated ConA-induced hepatitis by inhibiting IL10 secretion and increasing IL12 serum levels. The effect of IGL was clinically and immunological superior to that of either glycolipid alone. CONCLUSIONS Both a soy-free diet and beta-glycolipids can overcome the unfavorable host milieu in the setting of ConA hepatitis. The host glycolipid milieu profoundly influenced the immune and clinical effects of various insults, and suggests that alteration of the glycolipid background of the host can serve as a novel therapeutic tool.

Impaired liver regeneration by β-glucosylceramide is associated with decreased fat accumulation

To investigate the effect of β‐glucosylceramide (GC), a natural glycolipid, on hepatic fat accumulation and regenerative response after partial hepatectomy (PH).

Sulfatides for the treatment of autoimmune disorders

Natural killer T (NKT) cells are a subset of immune regulatory cells. Several glycolipids and phospholipids derived from mammalian, bacterial, protozoan and plant species have recently been identified as possible natural ligands for NKT cells. One such compound, sulfatide, which is a major glycolipid of myelin, has been shown to modulate NKT cell activity. This patent application claims to ameliorate or prevent symptoms of immune related disorders by application of sulfatides. Although preclinical studies have effectively targeted NKT cells for immunotherapy, little is known regarding the early in vivo response of these cells to antigenic stimulation. The data in support of the present patent may suggest that the naturally β-anomeric glycosphingolipids (sulfatides) may be ligands for NKT lymphocytes.