Multi-Omic analyses characterize the ceramide/sphingomyelin pathway as a therapeutic target in Alzheimer's disease.

Dysregulation of sphingomyelin and ceramide metabolism have been implicated in Alzheimer's disease. Genome-wide and transcriptome-wide association studies have identified various genes and genetic variants in lipid metabolism that are associated with Alzheimer's disease. However, the molecular mechanisms of sphingomyelin and ceramide disruption remain to be determined. We focus on the sphingolipid pathway and carry out multi-omics analyses to identify central and peripheral metabolic changes in Alzheimer's patients, correlating them to imaging features. Our multi-omics approach is based on (a) 2114 human post-mortem brain transcriptomics to identify differentially expressed genes; (b) in silico metabolic flux analysis on context-specific metabolic networks identified differential reaction fluxes; (c) multimodal neuroimaging analysis on 1576 participants to associate genetic variants in sphingomyelin pathway with Alzheimer's disease pathogenesis; (d) plasma metabolomic and lipidomic analysis to identify associations of lipid species with dysregulation in Alzheimer's; and (e) metabolite genome-wide association studies to define receptors within the pathway as a potential drug target. We validate our hypothesis in amyloidogenic APP/PS1 mice and show prolonged exposure to fingolimod alleviated synaptic plasticity and cognitive impairment in mice. Our integrative multi-omics approach identifies potential targets in the sphingomyelin pathway and suggests modulators of S1P metabolism as possible candidates for Alzheimer's disease treatment.

Sphingomyelin-based PEGylation Cu (DDC)2 liposomes prepared via the dual function of Cu2+ for cancer therapy: Facilitating DDC loading and exerting synergistic antitumor effects.

The old alcohol-aversion drug disulfiram (DSF) has aroused wide attention as a drug repurposing strategy in terms of cancer therapy because of the high antitumor efficacy in combination with copper ion. However, numerous defects of DSF (e.g., the short half-life and acid instability) have limited the application in cancer treatment. Cu (DDC)2, the complex of diethyldithiocarbamate (DDC, DSF metabolite) and Cu2+, have been proven as the vital active component on cancer, which have aroused the attention of researchers from DSF to Cu (DDC)2. However, the poor water solubility of Cu (DDC)2 increase more difficulties to the treatment and in-depth investigations of Cu (DDC)2. In this study, sphingomyelin (SM)-based PEGylated liposomes (SM/Chol/DSPE-mPEG2000 (55:40:5, mole%)) were produced as the carriers for Cu (DDC)2 delivery to enhance the water solubility. DDC was added to Cu-containing liposomes with a higher encapsulation efficiency of more than 90%, and it reacted with Cu2+ to synthesize Cu (DDC)2. Due to the high phase transition temperature of SM and strong intermolecular hydrogen bonds with cholesterol, SM-based liposomes would be conducive to enhancing the stability of Cu (DDC)2 and preventing drug leakage during delivery. As proven by pharmacokinetic studies, loading Cu (DDC)2 into liposomes improve bioavailability, and the area under the curve (AUC0-t) and the mean elimination half-life (t1/2) increased 1.9-time and 1.3-time to those of free Cu (DDC)2, respectively. Furthermore, the anticancer effect of Cu (DDC)2 was enhanced by the liposomal encapsulation, thus resulting in remarkable cell apoptosis in vitro and a tumor-inhibiting rate of 77.88% in vivo. Thus, it was concluded that Cu (DDC)2 liposomes could be promising in cancer treatment.

Sphingomyelin maintains the cutaneous barrier via regulation of the STAT3 pathway.

Epidermal tissues play vital roles in maintaining homeostasis and preventing the dysregulation of the cutaneous barrier. Sphingomyelin (SM), a sphingolipid synthesized by sphingomyelin synthase (SMS) 1 and 2, is involved in signal transduction via modulation of lipid-raft functions. Though the implications of SMS on inflammatory diseases have been reported, its role in dermatitis has not been clarified. In this study, we investigated the role of SM in the cutaneous barrier using a dermatitis model established by employing Sgms1 and 2 deficient mice. SM deficiency impaired the cutaneous inflammation and upregulated signal transducer and activator of transcription 3 (STAT3) phosphorylation in epithelial tissues. Furthermore, using mouse embryonic fibroblast cells, the sensitivity of STAT3 to Interleukin-6 stimulation was increased in Sgms-deficient cells. Using tofacitinib, a clinical JAK inhibitor, the study showed that SM deficiency might participate in STAT3 phosphorylation via JAK activation. Overall, these results demonstrate that SM is essential for maintaining the cutaneous barrier via the STAT3 pathway, suggesting SM could be a potential therapeutic target for dermatitis treatment.

Ameliorating Effects of Sphingomyelin-Based Liposomes on Sarcopenia in Senescence-Accelerated Mice.

The effects of orally administered sphingomyelin-based liposomes (SM-lipo) on muscle function were investigated in senescence-accelerated mice prone 1 (SAMP1) for the purpose of protection against or treatment of sarcopenia. SM-lipo were prepared by thin lipid-film hydration followed by extrusion. Their spherical shape was observed by transmission electron microscopy. The obtained liposomes were stable in gastric liquid and intestinal fluid models as well as in water. In in vitro tests liposomalization of sphingomyelin significantly increased its transport into human intestinal epithelial Caco-2 cells. In addition, SM-lipo upregulated the proliferation of murine C2C12 myoblasts compared with free sphingomyelin or phosphatidylcholine-based liposomes (PC-lipo). Finally, SM-lipo orally administered to SAMP1 for 10 weeks significantly increased quadriceps femoris weight and extended swimming time until fatigue compared with PC-lipo. In conclusion, these findings indicate that SM-lipo are well absorbed into the body and improve muscle weakness caused by senescence.

Sweet buttermilk intake reduces colonisation and translocation of Listeria monocytogenes in rats by inhibiting mucosal pathogen adherence.

The bovine milk fat globule membrane (MFGM) contains several antimicrobial components with proven efficacy in vitro, but in vivo evidence is scarce. The present study was performed to determine the efficacy of the bovine MFGM in vivo. Rats were fed diets based on bovine skimmed milk powder (low in MFGM) or bovine sweet buttermilk powder (high in MFGM). After dietary adaptation, rats were orally infected with Salmonella enteritidis or Listeria monocytogenes. Whereas sweet buttermilk powder did not protect rats against infection with S. enteritidis, it protected against L. monocytogenes, as shown by a lower colonisation and translocation of this pathogen. Protection coincided with higher listericidal capacity of gastric and caecal contents. The digestion products of phosphoglycerides and sphingomyelin are bactericidal in vitro. To study their role, rats were fed diets containing either 0·1 % phosphatidylcholine or sphingomyelin, or a control diet. After dietary adaptation, rats were infected with L. monocytogenes. Since Listeria colonisation was not affected by these diets, phosphoglycerides and sphingomyelin are not involved in the protective effect of sweet buttermilk. Additional in vitro experiments were performed to further explore the mechanism of the beneficial effects of sweet buttermilk. Inhibition of the adherence of L. monocytogenes to the intestinal mucosa is the most likely explanation, since sweet buttermilk powder inhibited the binding of L. monocytogenes in both a haemagglutination assay and a Caco-2 cell adherence assay. In conclusion, sweet buttermilk powder, which is rich in MFGM, protects against L. monocytogenes infection in rats, probably by preventing adherence of this pathogen to the intestinal mucosa.

The apolipoprotein A-I mimetic peptide, ETC-642, reduces chronic vascular inflammation in the rabbit.

BACKGROUND: High-density lipoproteins (HDL) and their main apolipoprotein, apoA-I, exhibit anti-inflammatory properties. The development of peptides that mimic HDL apolipoproteins offers a promising strategy to reduce inflammatory disease. This study aimed to compare the anti-inflammatory effects of ETC-642, an apoA-I mimetic peptide, with that of discoidal reconstituted HDL (rHDL), consisting of full-length apoA-I complexed with phosphatidylcholine, in rabbits with chronic vascular inflammation. RESULTS: New Zealand White rabbits (n = 10/group) were placed on chow supplemented with 0.2% (w/w) cholesterol for 6-weeks. The animals received two infusions of saline, rHDL (8 mg/kg apoA-I) or ETC-642 (30 mg/kg peptide) on the third and fifth days of the final week. The infusions of rHDL and ETC-642 were able to significantly reduce cholesterol-induced expression of intracellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in the thoracic aorta (p < 0.05). When isolated rabbit HDL was pre-incubated with human coronary artery endothelial cells (HCAECs), prior to stimulation with TNF-α, it was found that HDL from ETC-642 treated rabbits were more effective at inhibiting the TNF-α-induced increase in ICAM-1, VCAM-1 and p65 than HDL isolated from saline treated rabbits (p < 0.05). There were, however, no changes in HDL lipid composition between treatment groups. CONCLUSIONS: Infusion of ETC-642 causes anti-inflammatory effects that are comparable to rHDL in an animal model of chronic vascular inflammation and highlights that apoA-I mimetic peptides present a viable strategy for the treatment of inflammatory disease.

Dihydrosphingomyelin impairs HIV-1 infection by rigidifying liquid-ordered membrane domains.

The lateral organization of lipids in cell membranes is thought to regulate numerous cell processes. Most studies focus on the coexistence of two fluid phases, the liquid crystalline (l(d)) and the liquid-ordered (l(o)); the putative presence of gel domains (s(o)) is not usually taken into account. We show that in phospholipid:sphingolipid:cholesterol mixtures, in which sphingomyelin (SM) promoted fluid l(o) domains, dihydrosphingomyelin (DHSM) tended to form rigid domains. Genetic and pharmacological blockade of the dihydroceramide desaturase (Des1), which replaced SM with DHSM in cultured cells, inhibited cell infection by replication-competent and -deficient HIV-1. Increased DHSM levels gave rise to more rigid membranes, resistant to the insertion of the gp41 fusion peptide, thus inhibiting viral-cell membrane fusion. These results clarify the function of dihydrosphingolipids in biological membranes and identify Des1 as a potential target in HIV-1 infection.

Dietary sphingomyelin alleviates experimental inflammatory bowel disease in mice.

The effect of dietary sphingomyelin (SM) on inflammatory bowel disease (IBD) induced with dextran sodium sulfate (DSS) was examined in mice. Although the severity of IBD as expressed by the disease activity index (DAI) markedly increased with DSS administration, feeding a diet containing SM lowered the DAI value significantly. Myeloperoxidase (MPO) activity in colonic tissue also increased with DSS administration, suggesting the development of inflammation. Because simultaneous administration of SM with DSS prevented the MPO activity increase, we concluded that SM could suppress the development of inflammation. These results provide novel evidence that dietary supplementation with SM can alleviate the symptoms of IBD in mice. Dietary SM also increased the amount of IgA in the large intestine, suggesting that SM promotes IgA secretion into the large intestine. These results suggest that the mechanism of IBD mitigation by SM is complex and involves the immune system.

The potential of sphingomyelin as a chemopreventive agent in AOM-induced colon cancer model: wild-type and p53+/- mice.

A protective effect of sphingolipids on colorectal cancer (CRC) has been reported in certain mouse strains. It is unknown if sphingolipids are protective in a p53 deficiency mouse model of CRC. This study investigated the effect of sphingomyelin (SM) on intestinal sphingomyelinase (SMase) activity, colonic epithelial biology and azoxymethane (AOM)-induced CRC. Groups of wild-type (C57BL/6J) and p53+/- mice were fed 0.1% SM diet for 4 wk, administered a single AOM injection and then killed 6 h later to measure apoptosis and proliferation. Separately, both mouse types were fed 0.05% SM diet, administered three AOM injections and killed 33-38 wk later to measure tumour formation. SM significantly increased SMase activity and reduced proliferation (p < 0.05) in wild-type and p53+/- mice. SM did not regulate baseline apoptosis, apoptotic response to AOM or apoptosis in tumours, nor did it restore defective apoptosis in p53+/- mice. There was a nonsignificant trend to reduced tumour incidence with SM in wild-type (p = 0.15) and p53+/- (p = 0.12) mice. In conclusion, while increasing intestinal SMase activity and suppressing proliferation, SM did not promote any form of apoptosis and failed to achieve significant protection in these mice. Further investigation to understand the variable effect of SM in preventing CRC is warranted.

Inhibition of lipopolysaccharide-induced release of interleukin-8 from intestinal epithelial cells by SMA, a novel inhibitor of sphingomyelinase and its therapeutic effect on dextran sulphate sodium-induced colitis in mice.

Lipopolysaccharide (LPS) and inflammatory cytokines cause activation of sphingomyelinases (SMases) and subsequent hydrolysis of sphingomyelin (SM) to produce a lipid messenger ceramide. The use of SMase inhibitors may offer new therapies for the treatment of the LPS- and cytokines-related inflammatory bowel disease (IBD). We synthesized a series of difluoromethylene analogues of SM (SMAs). Here, we show that LPS efficiently increases the release of IL-8 from HT-29 intestinal epithelial cells by activating both neutral SMase and nuclear factor (NF)-kappaB in the cells. The addition of SMA-7 suppressed neutral SMase-catalyzed ceramide production, NF-kappaB activation, and IL-8 release from HT-29 cells caused by LPS. The results suggest that activation of neutral SMase is an underlying mechanism of LPS-induced release of IL-8 from the intestinal epithelial cells. Ceramide production following LPS-induced SM hydrolysis may trigger the activation of NF-kappaB in nuclei. Oral administration of SMA-7 (60 mg/kg) to mice with 2% dextran sulfate sodium (DSS) in their drinking water, for 21 consecutive days, reduced significantly the severity of colonic injury. This finding suggests a central role for SMase/ceramide signaling in the pathology of DSS-induced colitis in mice. The therapeutic effect of SMA-7 observed in mice may involve the suppression of IL-8 production from intestinal epithelial cells by LPS or other inflammatory cytokines.

[Synthesis of sphingomyelin analogues as a sphingomyelinase inhibitor and the application as a blocking agent of extracellular stress signaling].

Sphingomyelin (SM) pathway, where sphingomyelinase (SMase) hydrolyzes SM to produce ceramide, has recently been suggested to link to the signaling pathway that determines cell death. Therefore, elucidation of the mechanism by which SMase is activated and the regulation of SMase activity will be an important therapeutic strategy for various cytokine-related and ischemic diseases. We have synthesized nine difluoromethylene analogues of SM as SMase inhibitors and evaluated their inhibitory potencies. In this study, we show that the inhibitor suppresses ceramide production and cell death of PC-12 neurons that have been induced by deprivation of serum from the culture medium. The SMase inhibitor could also suppress neuronal cell death in a mouse model of brain ischemia. These results suggest a possibility that the prevention of various extracellular stress-induced cell death signalings is accomplished by inhibiting the cell membrane SMase.

Sphingomyelin enhances chemotherapy efficacy and increases apoptosis in human colonic tumor xenografts.

Evidence suggests that ceramide, generated from a distinct subcellular pool of sphingomyelin (SM) by the action of sphingomyelinases, may be used by cells to propagate apoptotic signals in response to a variety of cytotoxic agents. Since most tumor cells have altered lipid metabolism, it is possible that the intracellular pool of SM used for signaling is decreased. To overcome this, we have attempted to increase the SM content of all intracellular compartments with exogenous SM and examined the impact on 5-fluorouracil (5FU) and irinotecan chemosensitivity. Our data suggest that the efficacy of these two chemotherapeutics for the treatment of HT-29, HCT15 and GW-39 human colonic tumor xenografts can be enhanced by the use of exogenous SM. Furthermore, this enhancement may be due to a reversal of the attenuation of the apoptotic signal found in cancer cells without inducing significant hematopoietic, hepatic or renal toxicity.

Sphingomyelin potentiates chemotherapy of human cancer xenografts.

We propose that one manifestation of altered sphingolipid metabolism within tumor cells may be a reduced sensitivity to anti-cancer therapies because of an inability to produce a sufficient apoptotic signal via sphingomyelin hydrolysis to ceramide. If so, then sphingomyelin administration could reverse this effect and increase a tumor's sensitivity to chemotherapy. In vivo, intravenous sphingomyelin (10 mg/day, 7 days) potentiated 5-fluorouracil chemotherapy (0.45 mg/day, 5 days) when co-administered to HT29 human colonic xenograft-bearing nude mice. In vitro, sphingomyelin (SM) at its maximum tolerated concentration increased 5-fluorouracil and doxorubicin sensitivity of HCT15 and MOSER (1 mg/ml SM) and LS174T and SW480 human colonic tumor cells (0.1 mg/ml) approximately 100-300%. At 1 mg/ml SM, however, no effect was seen using HT29, LoVo and WiDr cells. There was no sensitization of normal human umbilical cord endothelial cells. Thus, sphingomyelin co-administration may be one method to improve the selective efficacy of chemotherapy in some tumors, possibly through enhancement of the apoptotic response.

Cows' milk fat components as potential anticarcinogenic agents.

The optimum approach to conquering cancer is prevention. Although the human diet contains components which promote cancer, it also contains components with the potential to prevent it. Recent research shows that milk fat contains a number of potential anticarcinogenic components including conjugated linoleic acid, sphingomyelin, butyric acid and ether lipids. Conjugated linoleic acid inhibited proliferation of human malignant melanoma, colorectal, breast and lung cancer cell lines. In animals, it reduced the incidence of chemically induced mouse epidermal tumors, mouse forestomach neoplasia and aberrant crypt foci in the rat colon. In a number of studies, conjugated linoleic acid, at near-physiological concentrations, inhibited mammary tumorigenesis independently of the amount and type of fat in the diet. In vitro studies showed that the milk phospholipid, sphingomyelin, through its biologically active metabolites ceramide and sphingosine, participates in three major antiproliferative pathways influencing oncogenesis, namely, inhibition of cell growth, and induction of differentiation and apoptosis. Mice fed sphingomyelin had fewer colon tumors and aberrant crypt foci than control animals. About one third of all milk triacylglycerols contain one molecule of butyric acid, a potent inhibitor of proliferation and inducer of differentiation and apoptosis in a wide range of neoplastic cell lines. Although butyrate produced by colonic fermentation is considered important for colon cancer protection, an animal study suggests dietary butyrate may inhibit mammary tumorigenesis. The dairy cow also has the ability to extract other potential anticarcinogenic agents such as beta-carotene, beta-ionone and gossypol from its feed and transfer them to milk. Animal studies comparing the tumorigenic potential of milk fat or butter with linoleic acid-rich vegetable oils or margarines are reviewed. They clearly show less tumor development with dairy products.

Suppression of aberrant colonic crypt foci by synthetic sphingomyelins with saturated or unsaturated sphingoid base backbones.

Supplementation of the diet of CF1 mice with sphingomyelin isolated from milk has been shown to reduce the number of aberrant crypt foci (ACF) and the appearance of colonic adenocarcinoma induced by 1,2-dimethylhydrazine (Schmelz et al., Cancer Res 56, 4936-4941, 1996). The objective of this study was to determine whether chemically synthesized sphingomyelin reduces the appearance of ACF, one of the earliest morphological changes in the development of colonic tumors, and to investigate the specificity of this inhibition for the unsaturated sphingoid base backbone. 1,2-Dimethylhydrazine was administered intraperitoneally to female CF1 mice, then the animals were fed a semipurified AIN 76A diet without supplementation (controls) or supplemented with 0.1% (wt/wt) sphingomyelin isolated from skim milk powder, synthetic N-palmitoylsphingomyelin, or N-palmitoyldihydrosphingomyelin for four weeks. The number of ACF in the sphingomyelin-fed groups was significantly lower than in the control by 54% (p = 0.002), 52% (p = 0.002), and 70% (p < 0.0001) for milk sphingomyelin, synthetic sphingomyelin, and synthetic dihydrosphingomyelin, respectively. Suppression of ACF by the synthetic dihydrosphingomyelin was significantly greater than by synthetic sphingomyelin (p = 0.035). These findings establish that sphingomyelin, and not merely a possible contaminant of the naturally occurring sphingomyelin preparation used previously, suppresses ACF formation. Furthermore, the greater potency of dihydrosphingomyelin reveals that the 4,5-trans double bond of the sphingoid backbone is not required for this suppression.

Dietary sphingomyelin inhibits 1,2-dimethylhydrazine-induced colon cancer in CF1 mice.

Sphingolipids are in all eukaryotic cells and modulate cell growth, differentiation, and transformation; however, little is known about the physiological effects of their consumption. Mice were fed diets supplemented with milk sphingomyelin to determine effects on colon carcinogenesis. Cancer was initiated in CF1 mice by 1,2-dimethylhydrazine. Mice were then fed AIN76A diets supplemented with 0.025 to 0.1 g sphingomyelin/100 g for 28 wk until the supply of sphingomyelin was depleted and then fed unsupplemented diet for 24 wk. Sphingomyelin did not affect weight gain. Mice fed sphingomyelin had a 20% incidence of colon tumors compared with 47% in controls (P = 0.08 for all sphingomyelin-fed mice vs. controls). Tumors were adenomas or adenocarcinomas and located in the distal third of the colon. In shorter-term studies, colonic epithelial cell proliferation was significantly greater than controls in mice fed 0.025 g sphingomyelin/100 g diet, but not in those fed higher amounts of sphingomyelin. The number of aberrant crypts was significantly lower in 1,2-dimethylhydrazine-treated mice fed 0.05 g sphingomyelin/100 g diet than in controls. These results demonstrate that consumption of sphingomyelin affects the behavior of colonic cells. Because sphingolipids are present in food, the reduction in 1,2-dimethylhydrazine-induced premalignant lesions and the incidence of colon tumors in CF1 mice implies that these compounds may be another important class of nutritional modulators of carcinogenesis.

Enhancement of anti-tumor activity of 1-beta-D-arabinofuranosylcytosine by encapsulation in liposomes.

1-beta-D-Arabinofuranosylcytosine (ara-C) was encapsulated in four different types of unsonicated artificial vesicles of phospholipid (liposomes) to compare the anti-tumor effect on mouse leukemia L1210 inoculated in CD2F, mice with that of free ara-C. The anti-tumor activity of ara-C was markedly enhanced by encapsulation in liposomes when given in a single IP injection. Among the four types of liposomes, a physically stable and positively charged liposome consisting of sphingomyelin, stearylamine and cholesterol (20:2:15 molar ratio) most effectively enhanced the effect of ara-C. A single IP dose of 50 mg/kg of ara-C, encapsulated in this kind of liposome exhibited high activity, producing a survival rate of 60% of the treated mice at 60 days. This enhanced effect of ara-C encapsulated in liposomes was also demonstrated when the drug was administered either IV or SC, and the range between the minimum effective and the maximum tolerable doses was wide enough to allow the safe use of the encapsulated ara-C. Intraperitoneal administration of encapsulated ara-C induced a more prolonged survival of mice inocualted with L1210 than did free ara-C, regardless of whether it was given in single or multiple doses.