Analysis of SM4 sulfatide as a P-selectin ligand using model membranes

Sphingolipid Metabolism in Tumor Cells

Sphingolipids are a diverse family of complex lipids typically composed of a sphingoid base bound to a fatty acid via amide bond. The metabolism of sphingolipids has long remained out of focus of biochemical studies. Recently, it has been attracting an increasing interest of researchers because of different and often multidirectional effects demonstrated by sphingolipids with a similar chemical structure. Sphingosine, ceramides (N-acylsphingosines), and their phosphorylated derivatives (sphingosine-1-phosphate and ceramide-1-phosphates) act as signaling molecules. Ceramides induce apoptosis and regulate stability of cell membranes and cell response to stress. Ceramides and sphingoid bases slow down anabolic and accelerate catabolic reactions, thus suppressing cell proliferation. On the contrary, their phosphorylated derivatives (ceramide-1-phosphate and sphingosine-1-phosphate) stimulate cell proliferation. Involvement of sphingolipids in the regulation of apoptosis and cell proliferation makes them critically important in tumor progression. Sphingolipid metabolism enzymes and sphingolipid receptors can be potential targets for antitumor therapy. This review describes the main pathways of sphingolipid metabolism in human cells, with special emphasis on the properties of this metabolism in tumor cells.

Prognostic and immunological role of sulfatide-related lncRNAs in hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver. Long non-coding RNAs (lncRNAs) play important roles in the occurrence and development of HCC through multiple pathways. Our previous study reported the specific molecular mechanism for sulfatide regulation of integrin αV expression and cell adhesion in HCC cells through lncRNA AY927503. Next, it is necessary to identify more sulfatide-related lncRNAs, explore their clinical signifcance, and determine new targeted treatment strategies.

Methods

Microarrays were used to screen a complete set of lncRNAs with different expression profiles in sulfatide-treated cells. Sulfatide-related lncRNAs expression data and corresponding HCC patient survival information were obtained from the The Cancer Genome Atlas (TCGA) database, and the prognosis prediction model was constructed based on Cox regression analysis. Methylated RNA immunoprecipitation with next generation sequencing (MeRIP-seq) was used to detemine the effect of sulfatide on lncRNAs m6A modification. Tumor Immune Estimation Resource (TIMER) and Gene set nnrichment analysis (GSEA) were utilized to enrich the immune and functional pathways of sulfatide-related lncRNAs.

Results

A total of 85 differentially expressed lncRNAs (|Fold Change (FC)|>2, P<0.05) were screened in sulfatide-treated HCC cells. As a result, 24 sulfatide-related lncRNAs were highly expressed in HCC tissues, six of which were associated with poor prognosis in HCC patients. Based on thses data, a sulfatide-related lncRNAs prognosis assessment model for HCC was constructed. According to this risk score analysis, the overall survival (OS) curve showed that the OS of high-risk patients was significantly lower than that of low-risk patients (P<0.05). Notably, the expression difference in sulfatide-related lncRNA NRSN2-AS1 may be related to sulfatide-induced RNA m6A methylation. In addition, the expression level of NRSN2-AS1 was significantly positively correlated with immune cell infiltration in HCC and participated in the peroxisome and Peroxisome proliferator-activated receptor (PPAR) signaling pathways.

Conclusions

In conclusion, sulfatide-related lncRNAs might be promising prognostic and therapeutic targets for HCC.

Preparation of sulfatide mimicking oleic acid sulfated chitosan as a potential inhibitor for metastasis

Sulfatide is associated with numerous health problems, affecting different parts of the human body, including the metastasis; however, the underlying mechanisms are yet to be fully elucidated. Sulfatide has been used to potential inhibitor for tumor cell metastasis. In the present study we synthesized oleic acid sulfated chitosan (OlcShCs). It shows structural similarity to sulfatide because of its functional groups (sulfate and fatty acyl chains). Chitosan has smart properties such as biocompatibility, biodegradability and non-toxicity. We have prepared oleic acid sulfated chitosan (OlcShCs) by chitosan modification to mimic sulfatide. Its structure was characterized by FT-IR, H-NMR, and thermogravimetric analysis. After characterization studies its antimicrobial, antifungal and cytotoxic properties were investigated. Oleic acid sulfated chitosan (OlcShCs) was tested for its anti-cancer potential against human cancer cell lines (HeLa (ATCC® CCL-2™)) for 24 h, 48 h and 72 h using the MTT assays. This new material which is soluble at physiological conditions, is a potential candidate for further metastasis inhibition investigations.

Sweet complementarity: the functional pairing of glycans with lectins

Carbohydrates establish the third alphabet of life. As part of cellular glycoconjugates, the glycans generate a multitude of signals in a minimum of space. The presence of distinct glycotopes and the glycome diversity are mapped by sugar receptors (antibodies and lectins). Endogenous (tissue) lectins can read the sugar-encoded information and translate it into functional aspects of cell sociology. Illustrated by instructive examples, each glycan has its own ligand properties. Lectins with different folds can converge to target the same epitope, while intrafamily diversification enables functional cooperation and antagonism. The emerging evidence for the concept of a network calls for a detailed fingerprinting. Due to the high degree of plasticity and dynamics of the display of genes for lectins the validity of extrapolations between different organisms of the phylogenetic tree yet is inevitably limited.

Pericellular proteolysis by matrix metalloproteinase-7 is differentially modulated by cholesterol sulfate, sulfatide, and cardiolipin

Matrix metalloproteinase (MMP)-7 binds to cell surface cholesterol sulfate (CS) and acts as a membrane-associated protease. We have previously found that CS modulates the substrate preference of MMP-7, thereby regulating its pericellular proteolytic action. MMP-7 potentially associates with the cell surface via sulfatide (SM4) and cardiolipin (CL) when they are overexpressed on the cell surface. Here, we investigated the molecular interaction between these acidic lipids and MMP-7 or its substrates, and their effects on the activity of MMP-7. Studies using MMP-7 variants with low CS-binding ability suggested that these lipids interact with a similar site on MMP-7. The hydroxamate-based MMP inhibitor TAPI-1 markedly reduced the affinity of MMP-7 for CS and CL, whereas that for SM4 was not affected by TAPI-1. These three acidic lipids also had different effects on the hydrolytic activity of MMP-7 towards a small peptide substrate: SM4, CL and CS reduced the activity to 80%, 92%, and 20%, respectively. Nevertheless, SM4 and CS similarly accelerated the MMP-7-catalyzed degradation of fibronectin and laminin-332, whereas CL did not. The increased proteolysis of substrate was observed only when both substrate and enzyme had affinity for the lipid, suggesting that the lipids probably bring the reactants into closer proximity. Furthermore, MMP-7 bound to cell surface SM4 or CS cleaved specific cell surface proteins and released similar fragments, whereas the cleavage was not stimulated by cell surface CL-bound MMP-7. This study provides a novel mechanism by which acidic lipids differentially regulate pericellular proteolysis by MMP-7 through allosteric alteration of the substrate-binding site and their inherent affinities for MMP-7 substrates.

Ligand-functionalized nanoliposomes for targeted delivery of galantamine

The purpose of this study was to design ligand-functionalized nanoliposomes that are proficient in providing effective intracellular delivery of an alkaloid drug (galantamine) into PC12 neuronal cells in response to managing Alzheimer's disease (AD). Ligand-functionalized nanoliposomes were produced and validated for their physicochemical properties, in silico molecular mechanics energy relationships, ex vivo cytotoxicity, peptide coupling efficiency (PCE), drug entrapment efficiency (DEE), drug release, fluorometry and confocal microscopy. Particle sizes of the nanoliposomes ranged from 127 nm to 165 nm (PdI=0.39-0.03), zeta potential values of -18 mV to -36 mV, PCE from 40% to 78% while DEE ranged from 42% to 79%. The surface morphology of the nanoliposomes was stable, spherically and uniform in shape. Thermal behavior and Fourier transform infrared (FTIR) analyses confirmed that galantamine and the peptide-ligand were incorporated into the inner core and surface of the nanoliposomes, respectively. The optimized formulation showed sustained drug release (30% of drug released within 48 h). Fluorometry and confocal microscopy revealed that the ligand-functionalized nanoliposomes facilitated galantamine uptake into PC12 neuronal cells via the Serpin Enzyme Complex Receptor in a mediated manner. CytoTox-Glo™ cytotoxicity assay established the low cytotoxicity on PC12 neuronal cells when exposed to native nanoliposomes and the ligand-functionalized nanoliposomes. Response surface analysis demonstrated there was a high degree of correlation between the experimental and fitted values. Furthermore, ex vivo studies showed that the high galantamine accumulation into PC12 neuronal cells was influenced by the post-engineering of peptides on the surface of the galantamine-loaded nanoliposomes. MMER analysis aptly corroborated the experimental findings.

The application of tetrahydroisoquinoline-3-carbonyl-TARGD(F)F as an anti-thrombotic agent having dual mechanisms of action

Platelet surface glycoproteins P-selectin and GPIIb/IIIa are implicated in the formation of platelet-fibrin-leukocyte thrombus and platelet-fibrin-platelet thrombus, respectively. In the current study, taking N-(3S-tetrahydroisoquinoline-3-carbonyl)-Thr-Ala-Arg-Gly-Asp-(Phe)-Phe (IQCA-TAFF) as a model compound, the molecular modeling, synthesis, and an evaluation system for a novel anti-thrombotic agent were investigated. The synthesis of IQCA-TAFF was achieved by coupling 3S-tetrahydro-isoquinoline-3-carboxylic acid (IQCA) and Thr-Ala-Arg-Gly-Asp(Phe)-Phe (TAFF). The molecular modeling indicated that IQCA-TAFF was able to occupy the active site pocket of P-selectin with its IQCA moiety and to block GPIIb/IIIa fibrinogen-binding sites with its TAFF moiety, respectively. These are consistent with the dual inhibition of the expressions of P-selectin and GPIIb/IIIa, and with the in vitro anti-platelet aggregation activity of IQCA-TAFF. Besides, the dual suppression of P-selectin and GPIIb/IIIa leads to significant in vivo efficacy of IQCA-TAFF, 500-fold higher than those of IQCA and TAFF, respectively. Transmission electron microscopy (TEM) images indicated that in water, IQCA-TAFF concentration-dependently formed nano-globes. The molecular modeling, in vitro bioassay, in vivo bioassay, action mechanism investigation, and nano-image visualization together constitute a model system to characterize the anti-thrombotic agent capable of simultaneously inhibiting P-selectin and GPIIb/IIIa mediated thrombosis.

Sulfatides inhibit adhesion, migration, and invasion of murine melanoma B16F10 cell line in vitro

Endogenous sulfatide, such as 3-sulfated galactosylceramide (3-sulfatide) has been reported to be involved in neuronal development and regulation of tumor cell metastasis. Recently, a new 6-sulfated glucosylceramide (6-sulfatide) has been isolated from the ascidian, Ciona intestinalis. To determine the antitumor function of the new sulfatide, we examined the effects of synthetic 6-sulfatide and 3-sulfatide on the metastatic features of a murine melanoma cell line, B16F10. Both sulfatides significantly inhibited the adhesion of melanoma cells onto fibronectin-coated tissue plates and, the motility and invasion of the cells, with 6-sulfatide showing stronger inhibitory activities. In addition, both sulfatides inhibited α(5)-, and β(1)- but not α(v)- or β(3)-integrin expression. Furthermore, these sulfatides inhibited the activation of focal adhesion kinase, Akt, and extracellular signal-regulated kinase signaling pathways, which are thought to be important for cell migration and invasion. Therefore, these sulfatides may serve as promising drug candidates for the treatment of cancer metastasis.

Expression of E-selectin ligands on circulating tumor cells: cross-regulation with cancer stem cell regulatory pathways?

Although significant progress has been made in the fight against cancer, successful treatment strategies have yet to be developed to combat those tumors that have metastasized to distant organs. Poor characterization of the molecular mechanisms of cancer spread is a major impediment to designing predictive diagnostics and effective clinical interventions against late stage disease. In hematogenous metastasis, it is widely suspected that circulating tumor cells (CTCs) express specific adhesion molecules that actively initiate contact with the vascular endothelium lining the vessel walls of the target organ. This "tethering" is mediated by ligands expressed by CTCs that bind to E-selectin expressed by endothelial cells. However, it is currently unknown whether expression of functional E-selectin ligands on CTCs is related to cancer stem cell regulatory or maintenance pathways, particularly epithelial-to-mesenchymal transition and the reverse, mesenchymal-to-epithelial transition. In this hypothesis and theory article, we explore the potential roles of these mechanisms on the dynamic regulation of selectin ligands mediating CTC trafficking during metastasis.

Role of sulfatide in normal and pathological cells and tissues

Sulfatide is 3-O-sulfogalactosylceramide that is synthesized by two transferases (ceramide galactosyltransferase and cerebroside sulfotransferase) from ceramide and is specifically degraded by a sulfatase (arylsulfatase A). Sulfatide is a multifunctional molecule for various biological fields including the nervous system, insulin secretion, immune system, hemostasis/thrombosis, bacterial infection, and virus infection. Therefore, abnormal metabolism or expression change of sulfatide could cause various diseases. Here, we discuss the important biological roles of sulfatide in the nervous system, insulin secretion, immune system, hemostasis/thrombosis, cancer, and microbial infections including human immunodeficiency virus and influenza A virus. Our review will be helpful to achieve a comprehensive understanding of sulfatide, which serves as a fundamental target of prevention of and therapy for nervous disorders, diabetes mellitus, immunological diseases, cancer, and infectious diseases.

A review on composite liposomal technologies for specialized drug delivery

The combination of liposomes with polymeric scaffolds could revolutionize the current state of drug delivery technology. Although liposomes have been extensively studied as a promising drug delivery model for bioactive compounds, there still remain major drawbacks for widespread pharmaceutical application. Two approaches for overcoming the factors related to the suboptimal efficacy of liposomes in drug delivery have been suggested. The first entails modifying the liposome surface with functional moieties, while the second involves integration of pre-encapsulated drug-loaded liposomes within depot polymeric scaffolds. This attempts to provide ingenious solutions to the limitations of conventional liposomes such as short plasma half-lives, toxicity, stability, and poor control of drug release over prolonged periods. This review delineates the key advances in composite technologies that merge the concepts of depot polymeric scaffolds with liposome technology to overcome the limitations of conventional liposomes for pharmaceutical applications.