Tumor specific cytotoxicity of beta-glucosylceramide: structure-cytotoxicity relationship and anti-tumor activity in vivo

Antiviral activity of glucosylceramide synthase inhibitors in alphavirus infection of the central nervous system

Virus-induced CNS diseases impose a considerable human health burden worldwide. For many viral CNS infections, neither antiviral drugs nor vaccines are available. In this study, we examined whether the synthesis of glycosphingolipids, major membrane lipid constituents, could be used to establish an antiviral therapeutic target. We found that neuroinvasive Sindbis virus altered the sphingolipid levels early after infection in vitro and increased the levels of gangliosides GA1 and GM1 in the sera of infected mice. The alteration in the sphingolipid levels appears to play a role in neuroinvasive Sindbis virus replication, as treating infected cells with UDP-glucose ceramide glucosyltransferase (UGCG) inhibitors reduced the replication rate. Moreover, the UGCG inhibitor GZ-161 increased the survival rates of Sindbis-infected mice, most likely by reducing the detrimental immune response activated by sphingolipids in the brains of Sindbis virus-infected mice. These findings suggest a role for glycosphingolipids in the host immune response against neuroinvasive Sindbis virus and suggest that UGCG inhibitors should be further examined as antiviral therapeutics for viral infections of the CNS.

Oncosuppressive and oncogenic activity of the sphingolipid-metabolizing enzyme β-galactosylceramidase

β-galactosylceramidase (GALC) is a lysosomal enzyme that removes β-galactose from β-galactosylceramide, leading to the formation of the oncosuppressor metabolite ceramide. Recent observations have shown that GALC may exert opposite effects on tumor growth by acting as an oncosuppressive or oncogenic enzyme depending on the different experimental approaches, in vitro versus in vivo observations, preclinical versus clinical findings, and tumor type investigated. This review will recapitulate and discuss the contrasting experimental evidence related to the impact of GALC on the biological behavior of cancer and stromal cells and its contribution to tumor progression.

Intracellular metabolite β-glucosylceramide is an endogenous Mincle ligand possessing immunostimulatory activity

Sensing and reacting to tissue damage is a fundamental function of immune systems. Macrophage inducible C-type lectin (Mincle) is an activating C-type lectin receptor that senses damaged cells. Notably, Mincle also recognizes glycolipid ligands on pathogens. To elucidate endogenous glycolipids ligands derived from damaged cells, we fractionated supernatants from damaged cells and identified a lipophilic component that activates reporter cells expressing Mincle. Mass spectrometry and NMR spectroscopy identified the component structure as β-glucosylceramide (GlcCer), which is a ubiquitous intracellular metabolite. Synthetic β-GlcCer activated myeloid cells and induced production of inflammatory cytokines; this production was abrogated in Mincle-deficient cells. Sterile inflammation induced by excessive cell death in the thymus was exacerbated by hematopoietic-specific deletion of degrading enzyme of β-GlcCer (β-glucosylceramidase, GBA1). However, this enhanced inflammation was ameliorated in a Mincle-deficient background. GBA1-deficient dendritic cells (DCs) in which β-GlcCer accumulates triggered antigen-specific T-cell responses more efficiently than WT DCs, whereas these responses were compromised in DCs from GBA1 × Mincle double-deficient mice. These results suggest that β-GlcCer is an endogenous ligand for Mincle and possesses immunostimulatory activity.

Structure of Sphingolipids From Sea Cucumber Cucumaria frondosa and Structure-Specific Cytotoxicity Against Human HepG2 Cells

To investigate the relationship between structure and activity, three glucocerebroside series (CFC-1, CFC-2 and CFC-3), ceramides (CF-Cer) and long-chain bases (CF-LCB) of sea cucumber Cucumaria frondosa (C. frondosa) were isolated and evaluated in HepG2 cells. The molecular species of CFC-1, CFC-2 and CFC-3 and CF-Cer were identified using reversed-phase liquid chromatography with heated electrospray ionization coupled to high-resolution mass spectrometry (RPLC-HESI-HRMS), and determined on the basis of chemical and spectroscopic evidence: For the three glucocerebroside series, fatty acids (FA) were mainly saturated (18:0 and 22:0), monounsaturated (22:1, 23:1 and 24:1) and 2-hydroxyl FA (2-HFA) (23:1 h and 24:1 h), the structure of long-chain bases (LCB) were dihydroxy (d17:1, d18:1 and d18:2) and trihydroxy (t16:0 and t17:0), and the glycosylation was glucose; For CF-Cer, FA were primarily saturated (17:0) and monounsaturated (16:1 and 19:1), the structure of LCB were dihydroxy (d17:1 and d18:1), and trihydroxy (t16:0). The results of cell experiment indicated that all of three glucocerebroside series, CF-Cer and CF-LCB exhibited an inhibitory effects on cell proliferation. Moreover, CFC-3 was most effective in three glucocerebrosides to HepG-2 cell viability. The inhibition effect of CF-LCB was the strongest, and the inhibition effect of CF-Cer was much stronger than glucocerebrosides.

Transport and uptake effects of marine complex lipid liposomes in small intestinal epithelial cell models

Transport and uptake effects of marine complex lipid liposomes in Caco-2 and M cell monolayer models.

Sea cucumber cerebrosides and long-chain bases from Acaudina molpadioides protect against high fat diet-induced metabolic disorders in mice

Sea cucumber cerebrosides and long-chain bases fromAcaudina molpadioidesefficiently protected against high fat diet-induced metabolic disorders in mice.

Beta-glucosidase 2 knockout mice with increased glucosylceramide show impaired liver regeneration

BACKGROUND AND AIMS

Glycolipids have been shown to serve specialized functions in cell signalling, proliferation and differentiation processes, which are all important during liver regeneration. We previously generated beta-glucosidase 2 (GBA2) knockout mice that accumulate the glycolipid glucosylceramide in various tissues, including the liver. The present study addressed the role of GBA2-deficiency and subsequent glucosylceramide accumulation in liver regeneration.

METHODS

Gba2 knockout and wild-type mice were subjected to two-third partial hepatectomy. Mice were sacrificed at different time points, blood was collected, and the remnant liver was removed. Glucosylceramide and ceramide were quantified using mass spectrometry from whole liver and isolated hepatocytes. Serum and hepatocytic supernatant of IL-6, TNF-α and TGF-β levels were measured using ELISA. Cell signalling proteins were analysed using immunoblots.

RESULTS

Regenerating liver after partial hepatectomy showed a significant increase of hepatic glucosylceramide in GBA2-deficient mice compared to controls. Accumulation of glucosylceramide was associated with a delay in liver regeneration and reduced serum levels of IL-6 and TNF-α. Furthermore, reduced IL-6 led to decreased expression of the phosphorylated form of the signal transducer and activator of transcription 3 (P-STAT3).

CONCLUSIONS

We conclude that increased glucosylceramide affects cytokine- and growth factor-mediated signalling pathways during liver regeneration. Thus, the repression of IL-6/STAT3 signalling pathway seems to be one of the mechanisms for the delay of liver regeneration in GBA2-deficient mice.

Three Glucocerebroside Molecular Species from the Sea Cucumber Apostichopus japonicus

Three glucocerebroside molecular species, AJC-1, AJC-2 and AJC-3, have been isolated from the less lipid fraction of the chloroform–methanol extract of the sea cucumber Apostichopus japonica by repeated column chromatography. The structures of these glucocerebroside molecular species were determined on the basis of chemical and spectroscopic evidence. The composition of three glucocerebrosides (AJC-1, AJC-2 and AJC-3): fatty acids were mainly saturated (C18:0), monounsaturated (C24:1) and α-hydroxyl fatty acids (C24:1h, C23:0h and C22:0h), the structures of long-chain base were dihydroxy (d18:2, d17:1 and d17:0) and trihydroxy (t17:0), and the glycosylation was mainly glucose. Three glucocerebroside molecular species were evaluated for activity in vitro assays for the cytotoxic activities against human colonic cancer cell line (Caco-2).

Analysis and comparison of glucocerebroside species from three edible sea cucumbers using liquid chromatography-ion trap-time-of-flight mass spectrometry

Sphingolipids constitute a highly diverse and complex class of molecules and exhibit important physiological functions. Glucocerebrosides are anticipated to play a positive role in human nutrition. In this study, complicated glucocerebrosides from three specimens of edible sea cucumbers, specifically, Acaudina molpadioides, Cucumaria frondosa, and Apostichopus japonicus, were rapidly identified using liquid chromatography-ion trap-time-of-flight mass spectrometry (LCMS-IT-TOF), which is a powerful analysis tool. [M + H](+), [M + Na](+), and [M + H - H(2)O](+) in positive electrospray ionization (ESI) mode were used for MS/MS analysis to obtain product ion spectra. Various long-chain bases of glucocerebrosides were found in these sea cucumbers. Two of the most common long-chain bases were 2-amino-1,3-dihydroxy-4-heptadecene (d17:1) and 4,8-sphingadienine (d18:2), which were acylated to form saturated and monounsaturated nonhydroxy and monohydroxy fatty acids with 18-25 carbon atoms. The glucocerebroside molecular species were the most complicated in the sea cucumber C. frondosa and were the simplest in the sea cucumber A. molpadioides.

Therapy for minimal residual tumor disease: beta-galactosylceramide inhibits the growth of recurrent HPV16-associated neoplasms after surgery and chemotherapy

Natural killer T (NKT) cells are potent modulators of antitumor immunity. Their protective effects can be achieved upon their activation by glycolipid ligands presented in the context of the CD1d molecule. These CD1d-binding glycolipid antigens have been described as potent therapeutic agents against tumors, infections, as well as autoimmune diseases. Immunoregulatory and therapeutic effects of glycolipid ligands depend on their structure and modes of administration. Therefore, more studies are needed for optimization of the particular therapeutic settings. This study was focused on the tumor-inhibitory effects of 12 carbon acyl chain beta-galactosyl ceramide (C12 beta-D-Galactosyl Ceramide; beta-GalCer(C12)) on the growth of human papillomavirus type 16 (HPV16)-associated neoplasms transplanted in syngeneic mice. Treatment of tumor-bearing mice with beta-GalCer(C12) 3-14 days after tumor cell transplantation significantly inhibited the growth of the major histocompatibility complex (MHC) Class I-positive (TC-1), as well as MHC Class I-deficient (TC-1/A9) HPV16-associated tumors. Moreover, administration of beta-GalCer(C12) after surgical removal of TC-1 tumors inhibited the growth of tumor recurrences. Similar results were obtained in the treatment of tumors after chemotherapy. beta-GalCer(C12) treatment turned out to be also synergistic with immunotherapy based on administration of IL-12-producing cellular vaccines. These results suggest that beta-GalCer(C12), whose antitumor effects have so far not been studied in detail, can be effective for the treatment of minimal residual tumor disease as well as an adjuvant for cancer immunotherapy.

Beta-glucosylceramide ameliorates liver inflammation in murine autoimmune cholangitis

We have demonstrated spontaneous development of autoimmune cholangitis, similar to human primary biliary cirrhosis, in mice expressing a dominant negative form of the transforming growth factor-beta receptor (dnTGF-betaRII) restricted to T cells. The autoimmune cholangitis appears to be mediated by autoreactive CD8(+) T lymphocytes that home to the portal tracts and biliary system. Because the liver pathology is primarily secondary to CD8(+) T cells, we have determined herein whether administration of beta-glucosylceramide (GC), a naturally occurring plant glycosphingolipid, alters the natural history of disease in this model. We chose GC because previous work has demonstrated its ability to alter CD8(+) T cell responses and to down-regulate tissue inflammation. Accordingly, dnTGF-betaRII mice were treated with either GC or control for a period of 18 weeks beginning at 6 weeks of age. Importantly, in mice that received GC, there was a significant decrease in the frequency and absolute number of autoreactive liver-infiltrating CD8(+) T cells, accompanied by a significant decrease in activated CD44(high) CD8(+) T cell populations. Further, there was a significant reduction in portal inflammation in GC-treated mice. Interestingly, there were no changes in anti-mitochondrial antibodies, CD4(+) T cells, CD19(+) B cells or natural killer (NK) T cell populations, indicating further that the beneficial effects of GC on liver inflammation were targeted specifically to liver-infiltrating CD8(+) T cells. These data suggest that further work on GC in models of CD8(+) T-mediated inflammation are needed and point to a new therapeutic venue for potentially treating and/or modulating autoimmune disease.