Enhancing of GM3 synthase expression during differentiation of human blood monocytes into macrophages as in vitro model of GM3 accumulation in atherosclerotic lesion

Enhanced Anti-Atherosclerotic Efficacy of pH-Responsively Releasable Ganglioside GM3 Delivered by Reconstituted High-Density Lipoprotein

Recently, the atheroprotective role of endogenous GM3 and an atherogenesis-inhibiting effect of exogenous GM3 suggested a possibility of exogenous GM3 being recruited as an anti-atherosclerotic drug. This study seeks to endow exogenous GM3 with atherosclerotic targetability via reconstituted high-density lipoprotein (rHDL), an atherosclerotic targeting drug nanocarrier. Unloaded rHDL, rHDL loaded with exogenous GM3 at a low concentration (GM3_L-rHDL), and rHDL carrying GM3 at a relatively high concentration (GM3_H-rHDL) were prepared and characterized. The inhibitory effect of GM3-rHDL on lipid deposition in macrophages was confirmed, and GM3-rHDL did not affect the survival of red blood cells. In vivo experiments using ApoE^-/- mice fed a high fat diet further confirmed the anti-atherosclerotic efficacy of exogenous GM3 and demonstrated that GM3 packed in HDL nanoparticles (GM3-rHDL) has an enhanced anti-atherosclerotic efficacy and a reduced effective dose of GM3. Then, the macrophage- and atherosclerotic plaque-targeting abilities of GM3-rHD, most likely via the interaction of ApoA-I on GM3-rHDL with its receptors (e.g., SR-B1) on cells, were certified via a microsphere-based method and an aortic fragment-based method, respectively. Moreover, we found that solution acidification enhanced GM3 release from GM3-rHDL nanoparticles, implying the pH-responsive GM3 release when GM3-rHDL enters the acidic atherosclerotic plaques from the neutral blood. The rHDL-mediated atherosclerotic targetability and pH-responsive GM3 release of GM3-rHDL enhanced the anti-atherosclerotic efficacy of exogenous GM3. The development of the GM3-rHDL nanoparticle may help with the application of exogenous GM3 as a clinical drug. Moreover, the data imply that the GM3-rHDL nanoparticle has the potential of being recruited as a drug nanocarrier with atherosclerotic targetability and enhanced anti-atherosclerotic efficacy.

Sphingolipids in Hematopoiesis: Exploring Their Role in Lineage Commitment

Sphingolipids, associated enzymes, and the sphingolipid pathway are implicated in complex, multifaceted roles impacting several cell functions, such as cellular homeostasis, apoptosis, cell differentiation, and more through intrinsic and autocrine/paracrine mechanisms. Given this broad range of functions, it comes as no surprise that a large body of evidence points to important functions of sphingolipids in hematopoiesis. As the understanding of the processes that regulate hematopoiesis and of the specific characteristics that define each type of hematopoietic cells is being continuously refined, the understanding of the roles of sphingolipid metabolism in hematopoietic lineage commitment is also evolving. Recent findings indicate that sphingolipid alterations can modulate lineage commitment from stem cells all the way to megakaryocytic, erythroid, myeloid, and lymphoid cells. For instance, recent evidence points to the ability of de novo sphingolipids to regulate the stemness of hematopoietic stem cells while a substantial body of literature implicates various sphingolipids in specialized terminal differentiation, such as thrombopoiesis. This review provides a comprehensive discussion focused on the mechanisms that link sphingolipids to the commitment of hematopoietic cells to the different lineages, also highlighting yet to be resolved questions.

Bioactive Sphingolipids as Major Regulators of Coronary Artery Disease

Atherosclerosis is the deposition of plaque in the main arteries. It is an inflammatory condition involving the accumulation of macrophages and various lipids (low-density lipoprotein [LDL] cholesterol, ceramide, S1P). Moreover, endothelial cells, macrophages, leukocytes, and smooth muscle cells are the major players in the atherogenic process. Sphingolipids are now emerging as important regulators in various pathophysiological processes, including the atherogenic process. Various sphingolipids exist, such as the ceramides, ceramide-1-phosphate, sphingosine, sphinganine, sphingosine-1-phosphate (S1P), sphingomyelin, and hundreds of glycosphingolipids. Among these, ceramides, glycosphingolipids, and S1P play important roles in the atherogenic processes. The atherosclerotic plaque consists of higher amounts of ceramide, glycosphingolipids, and sphingomyelin. The inhibition of the de novo ceramide biosynthesis reduces the development of atherosclerosis. S1P regulates atherogenesis via binding to the S1P receptor (S1PR). Among the five S1PRs (S1PR1-5), S1PR1 and S1PR3 mainly exert anti-atherosclerotic properties. This review mainly focuses on the effects of ceramide and S1P via the S1PR in the development of atherosclerosis. Moreover, it discusses the recent findings and potential therapeutic implications in atherosclerosis.

Vascular Diseases and Gangliosides

Vascular diseases, such as myocardial infarction and cerebral infarction, are most commonly caused by atherosclerosis, one of the leading causes of death worldwide. Risk factors for atherosclerosis include lifestyle and aging. It has been reported that lifespan could be extended in mice by targeting senescent cells, which led to the suppression of aging-related diseases, such as vascular diseases. However, the molecular mechanisms underlying the contribution of aging to vascular diseases are still not well understood. Several types of cells, such as vascular (endothelial cell), vascular-associated (smooth muscle cell and fibroblast) and inflammatory cells, are involved in plaque formation, plaque rupture and thrombus formation, which result in atherosclerosis. Gangliosides, a group of glycosphingolipids, are expressed on the surface of vascular, vascular-associated and inflammatory cells, where they play functional roles. Clarifying the role of gangliosides in atherosclerosis and their relationship with aging is fundamental to develop novel prevention and treatment methods for vascular diseases based on targeting gangliosides. In this review, we highlight the involvement and possible contribution of gangliosides to vascular diseases and further discuss their relationship with aging.

Exogenous GM3 ganglioside inhibits atherosclerosis via multiple steps: A potential atheroprotective drug

Atherosclerosis is one of the leading causes of morbidity and mortality worldwide. A significant increase in ganglioside GM3 content generally happens in atherosclerotic plaques causing a GM3-enriched microenvironment. It remains unclear whether the GM3-enriched microenvironment influences atherogenesis. This study sought to answer the question by investigating exogenous GM3 effects on multiple steps involved in atherogenesis. First, the physicochemical properties of native low-density lipoprotein (LDL) and LDL enriched with exogenous GM3 (GM3-LDL) were characterized by dynamic laser scattering, atomic force microscopy, and agarose gel electrophoresis. Then, electrophoretic mobility, conjugated diene and malondialdehyde production, and amino group blockage of GM3-LDL/LDL were measured to determine LDL oxidation degrees and cellular recognition/internalization of GM3-LDL/GM3-oxLDL were detected via confocal microscopy and flow cytometry. Subsequently, influences of exogenous GM3 addition on the monocyte-adhering ability of endothelial cells and on lipid deposition in macrophages were investigated. Finally, exogenous GM3 effect on atherogenesis was evaluated using apoE^-/- mice fed a high-fat diet. We found that exogenous GM3 addition increased the size, charge, and stability of LDL particles, reduced LDL susceptibility to oxidation and its cellular recognition/internalization, impaired the monocyte-adhering ability of endothelial cells and lipid deposition in macrophages. Moreover, exogenous GM3 treatment also significantly decreased blood lipid levels and atherosclerotic lesion areas in atherosclerotic mice. The data imply that exogenous GM3 had an inhibitory effect on atherogenesis, suggesting a protective role of a GM3-enriched microenvironment in atherosclerotic plaques and implying a possibility of exogenous GM3 as an anti-atherosclerotic drug.

Genome-Wide DNA Methylome and Transcriptome Analysis of Porcine Intestinal Epithelial Cells upon Deoxynivalenol Exposure

Deoxynivalenol (DON) is a type of mycotoxin that is disruptive to intestinal and immune systems. To better understand the molecular effects of DON exposure, we performed genome-wide comparisons of DNA methylation and gene expression from porcine intestinal epithelial cell IPEC-J2 upon DON exposure using reduced representation bisulfite sequencing and RNA-seq technologies. We characterized the methylation pattern changes and found 3030 differentially methylated regions. Moreover, 3226 genes showing differential expression were enriched in pathways of protein and nucleic acid synthesis and ribosome biogenesis. Integrative analysis identified 29 genes showing inverse correlations between promoter methylation and expression. Altered DNA methylation and expression of various genes suggested their roles and potential functional interactions upon DON exposure. Our data provided new insights into epigenetic and transcriptomic alterations of intestinal epithelial cells upon DON exposure and may advance the identification of biomarkers and drug targets for predicting and controlling the toxic effects of this common mycotoxin.

The Role of Glycosphingolipids in Immune Cell Functions

Glycosphingolipids (GSLs) exhibit a variety of functions in cellular differentiation and interaction. Also, they are known to play a role as receptors in pathogen invasion. A less well-explored feature is the role of GSLs in immune cell function which is the subject of this review article. Here we summarize knowledge on GSL expression patterns in different immune cells. We review the changes in GSL expression during immune cell development and differentiation, maturation, and activation. Furthermore, we review how immune cell GSLs impact membrane organization, molecular signaling, and trans-interactions in cellular cross-talk. Another aspect covered is the role of GSLs as targets of antibody-based immunity in cancer. We expect that recent advances in analytical and genome editing technologies will help in the coming years to further our knowledge on the role of GSLs as modulators of immune cell function.

Expression of leukocyte adhesion-related glycosyltransferase genes in acute coronary syndrome patients

INTRODUCTION

Acute coronary syndrome (ACS) is caused by destabilization and rupture of atherosclerotic plaque in the coronary artery via mechanisms affecting leukocyte signaling, rolling, adhesion, extravasation and inflammation-promoting factors. The majority of cellular communication takes place on the membrane surface that is covered with glycoproteins and glycolipids synthesized by glycosyltransferases. The aim of this study was to determine the mRNA expression of leukocyte adhesion-related glycosyltransferases in patients during the onset and the chronic phase of ACS and to compare the expression with matching subjects without coronary disease.

SUBJECTS AND METHODS

The study included 26 ACS patients and 26 ACS-free matched-pair controls. Blood samples were collected at the time of hospital admittance and 8 days later. Expression analysis of six fucosyltransferases and six sialyltransferases was performed by a real-time polymerase chain reaction.

RESULTS

At the time of admittance ACS subjects had lower expression levels of FUT4, ST6GalNac4, ST6Gal1 and GM3 synthase (p < 0.05) than the control subjects, and moreover, after 8 days down-regulation of FUT7 and ST6GalNac3 was also observed (p < 0.05). When compared to the initial gene expression, after treatment and stabilization of ACS subjects, FUT7, ST6GalNac2 and ST6GalNac3 were down-regulated, whereas ST6GalNac1 was up-regulated. Expression levels of FUT7, ST6GalNac1, ST6GalNac2 and ST6GalNac3 were predicted by several drugs and medical history.

CONCLUSION

Expression of glycosyltransferase genes differs in ACS and control subjects. During the course of the ACS study we established further changes in gene expression levels. Medical history was predictive of gene expression levels while drugs were shown to modulate expression levels.

Activation of ganglioside GM3 biosynthesis in human blood mononuclear cells in atherosclerosis

Using blood monocytes and lymphocytes from atherosclerotic patients and healthy subjects we have investigated activity of GM3 synthase, cellular levels of ganglioside GM3 and its role in monocyte adhesion to cultured human umbilical vein endothelial cells (HUVEC). The results showed that activity of GM3 synthase and cellular levels of ganglioside GM3 in blood mononuclear cells from atherosclerotic patients were several-fold higher than those from healthy subjects. In monocytes the activity of GM3 synthase was one an order of magnitude higher than in lymphocytes from both groups studied; this suggests the major contribution of monocytes to enhanced biosynthesis and levels of GM3 in mononuclear cells in atherosclerosis. Enrichment of monocytes from healthy subjects with ganglioside GM3 by incubation in medium containing this ganglioside increased adherence of these monocytes to HUVEC up to the values typical for monocytes from atherosclerotic patients. In addition, an increase in CD11b integrin expression was observed that was comparable to that seen in lipopolysaccharide-activated monocytes. It is suggested that in atherosclerosis the enhanced cellular levels of GM3 in monocytes and lymphocytes may be an important element of cell activation that facilitates their adhesion to endothelial cells and penetration into intima.