Cytokine-induced release of ceramide-enriched exosomes as a mediator of cell death signaling in an oligodendroglioma cell line

Unique Lipid Signatures of Extracellular Vesicles from the Airways of Asthmatics

Asthma is a chronic inflammatory disease process involving the conductive airways of the human lung. The dysregulated inflammatory response in this disease process may involve multiple cell-cell interactions mediated by signaling molecules, including lipid mediators. Extracellular vesicles (EVs) are lipid membrane particles that are now recognized as critical mediators of cell-cell communication. Here, we compared the lipid composition and presence of specific lipid mediators in airway EVs purified from the bronchoalveolar lavage (BAL) fluid of healthy controls and asthmatic subjects with and without second-hand smoke (SHS) exposure. Airway exosome concentrations were increased in asthmatics, and correlated with blood eosinophilia and serum IgE levels. Frequencies of HLA-DR⁺ and CD54⁺ exosomes were also significantly higher in asthmatics. Lipidomics analysis revealed that phosphatidylglycerol, ceramide-phosphates, and ceramides were significantly reduced in exosomes from asthmatics compared to the non-exposed control groups. Sphingomyelin 34:1 was more abundant in exosomes of SHS-exposed asthmatics compared to healthy controls. Our results suggest that chronic airway inflammation may be driven by alterations in the composition of lipid mediators within airway EVs of human subjects with asthma.

Role of sphingolipids in the biogenesis and biological activity of extracellular vesicles

Extracellular vesicles (EVs) are membrane vesicles released by both eukaryotic and prokaryotic cells; they not only serve physiological functions, such as disposal of cellular components, but also play pathophysiologic roles in inflammatory and degenerative diseases. Common molecular mechanisms for EV biogenesis are evident in different cell biological contexts across eukaryotic phyla, and inhibition of this biogenesis may provide an avenue for therapeutic research. The involvement of sphingolipids (SLs) and their enzymes on EV biogenesis and release has not received much attention in current research. Here, we review how SLs participate in EV biogenesis by shaping membrane curvature and how they contribute to EV action in target cells. First, we describe how acid and neutral SMases, by generating the constitutive SL, ceramide, facilitate biogenesis of EVs at the plasma membrane and inside the endocytic compartment. We then discuss the involvement of other SLs, such as sphingosine-1-phosphate and galactosyl-sphingosine, in EV formation and cargo sorting. Last, we look ahead at some biological effects of EVs mediated by changes in SL levels in recipient cells.

Lower plasma choline levels are associated with sleepiness symptoms

Sleepiness and cardiovascular disease share common molecular pathways; thus, metabolic risk factors for sleepiness may also predict cardiovascular disease risk. Daytime sleepiness predicts mortality and cardiovascular disease, although the mechanism is unidentified. This study explored the associations between subjective sleepiness and metabolite concentrations in human blood plasma within the oxidative and inflammatory pathways, in order to identify mechanisms that may contribute to sleepiness and cardiovascular disease risk.

METHODS

An exploratory case-control sample of 36 subjects, categorized based on the Epworth Sleepiness Scale (ESS) questionnaire as sleepy (ESS ≥ 10) or non-sleepy (ESS < 10), was recruited among subjects undergoing an overnight sleep study for suspected sleep apnea at the University of Pennsylvania Sleep Center. The average age was 42.4 ± 10.5 years, the mean body mass index (BMI) was 40.0 ± 9.36 kg/m², median Apnea Hypopnea Index (AHI) was 8.2 (IQR: 2.5-26.5), and 52% were male. Fasting morning blood plasma samples were collected after an overnight sleep study. Biomarkers were explored in subjects with sleepiness versus those without using the multiple linear regression adjusting for age, BMI, smoking, Apnea Hypopnea Index (sleep apnea severity), study cohort, and hypertension.

RESULTS

The level of choline is significantly lower (P = 0.003) in sleepy subjects (N = 18; mean plasma choline concentration of 8.19 ± 2.62 μmol/L) compared with non-sleepy subjects (N = 18; mean plasma choline concentration of 9.14 ± 2.25 μmol/L). Other markers with suggestive differences (P < 0.1) include isovalerylcarnitine, Alpha-Amino apidipic acid, Spingosine 1 Phosphate, Aspartic Acid, Propionylcarnitine, and Ceramides (fatty acids; C14-C16 and C-18).

CONCLUSION

This pilot study is the first to show that lower levels of plasma choline metabolites are associated with sleepiness. Further exploration of choline and other noted metabolites and their associations with sleepiness will guide targeted symptom management.

Hydrogen Peroxide Stimulates Exosomal Cathepsin B Regulation of the Receptor for Advanced Glycation End-Products (RAGE)

Exosomes are nano-sized vesicles that are secreted into the extracellular environment. These vesicles contain various biological effector molecules that can regulate intracellular signaling pathways in recipient cells. The aim of this study was to examine a correlation between exosomal cathepsin B activity and the receptor for advanced glycation end-products (RAGE). Type 1 alveolar epithelial (R3/1) cells were treated with or without hydrogen peroxide and exosomes isolated from the cell conditioned media were characterized by NanoSight analysis. Lipidomic and proteomic analysis showed exosomes released from R3/1 cells exposed to oxidative stress induced by hydrogen peroxide or vehicle differ in their lipid and protein content, respectively. Cathepsin B activity was detected in exosomes isolated from hydrogen peroxide treated cells. The mRNA and protein expression of RAGE increased in cultured R3/1 cells treated with exosomes containing active cathepsin B while depletion of exosomal cathepsin B attenuated RAGE mRNA and protein expression. These results suggest exosomal cathepsin B regulates RAGE in type 1 alveolar cells under conditions of oxidative stress. J. Cell. Biochem. 119: 599-606, 2018. © 2017 Wiley Periodicals, Inc.

Autoimmunity in multiple sclerosis: role of sphingolipids, invariant NKT cells and other immune elements in control of inflammation and neurodegeneration

Multiple sclerosis (MS) is the most common demyelinating disease of the central nervous system. It is classified as being an autoimmune response in the genetically susceptible individual to a persistent but unidentified antigen(s). Both the adaptive and the innate immune systems are likely to contribute significantly to MS pathogenesis. This review summarizes current understanding of the characteristics of MS autoimmunity in the initiation and progression of the disease. In particular we find it timely to classify the autoimmune responses by focusing on the immunogenic features of myelin-derived lipids in MS including molecular mimicry; on alterations of bioactive sphingolipids mediators in MS; and on functional roles for regulatory effector cells, including innate lymphocyte populations, like the invariant NKT (iNKT) cells which bridge adaptive and innate immune systems. Recent progress in identifying the nature of sphingolipids recognition for iNKT cells in immunity and the functional consequences of the lipid-CD1d interaction opens new avenues of access to the pathogenesis of demyelination in MS as well as design of lipid antigen-specific therapeutics.

Is there a role for exosomes in foetoplacental endothelial dysfunction in gestational diabetes mellitus?

Gestational diabetes mellitus (GDM) is a disease of pregnancy associated with endothelial dysfunction in the foetoplacental vasculature. Foetoplacental endothelial dysfunction is characterized by changes in the l-arginine-adenosine signalling pathway and inflammation. The mechanisms involved in these alterations are suggested to be hyperglycaemia, hyperinsulinemia, and oxidative stress. These conditions increase the release of exosomes, nanovesicles that are generated from diverse cell types, including endothelial cells. Since exosomes can modulate vascular function, they may play an important role in foetoplacental endothelial dysfunction seen in GDM pregnancies. In this review, we summarized current knowledge on the potential role of exosomes in foetoplacental endothelial dysfunction seen in this disease of pregnancy.

Heparanase: Potential roles in multiple sclerosis

Heparanase is a heparan sulfate degrading enzyme that cleaves heparan sulfate (HS) chains present on HS proteoglycans (HSPGs), and has been well characterized for its roles in tumor metastasis and inflammation. However, heparanase is emerging as a contributing factor in the genesis and severity of a variety of neurodegenerative diseases and conditions. This is in part due to the wide variety of HSPGs on which the presence or absence of HS moieties dictates protein function. This includes growth factors, chemokines, cytokines, as well as components of the extracellular matrix (ECM) which in turn regulate leukocyte infiltration into the CNS. Roles for heparanase in stroke, Alzheimer's disease, and glioma growth have been described; roles for heparanase in other disease such as multiple sclerosis (MS) are less well established. However, given its known roles in inflammation and leukocyte infiltration, it is likely that heparanase also contributes to MS pathology. In this review, we will briefly summarize what is known about heparanase roles in the CNS, and speculate as to its potential role in regulating disease progression in MS and its animal model EAE (experimental autoimmune encephalitis), which may justify testing of heparanase inhibitors for MS treatment.