Ceramide: a simple sphingolipid with unique biophysical properties

Simultaneous metabolomics and lipidomics analysis based on 4in1 online analysis system reveal metabolic signatures in atherosclerotic mice

Developing efficient and comprehensive analysis methods for metabolomics and lipidomics in the biological tissues and body fluids is essential for understanding the disease mechanisms. Although various two-dimensional liquid chromatography-mass spectrometry (2D-LC-MS) methods have been proposed to expand metabolite coverage, achieving higher efficiency in integrated metabolomics and lipidomics studies remains a technical challenge. In this work, a novel 4in1 online analysis system with excellent reproducibility and mass accuracy was constructed for metabolomics and lipidomics study in various biological samples from atherosclerotic mice. This system enabled the simultaneous detection in both positive and negative ion modes with extensive polarity separation in a single analytical run. Using the 4in1 online analysis system, we identified distinct but complementary metabolic signatures associated with atherosclerosis in different biological samples. Specifically, a total of 230 and 170 differential metabolites or lipids were detected in mice plasma samples and aortic tissue samples, respectively, including glycerophospholipids, sphingolipids, fatty acyls, glycerolipids, carboxylic acids, and pyrimidine nucleosides. Additionally, atherosclerosis-related metabolic pathways involved in biosynthesis of unsaturated fatty acids, sphingolipid metabolism, cholesterol metabolism, glycerophospholipid metabolism, and choline metabolism further revealed. These findings demonstrate that the novel 4in1 online analysis system is a faithful, stable and powerful tool for comprehensive metabolomics and lipidomics studies in complex biological matrices.

Lysosphingolipids in ceramide-deficient skin lipid models

Ceramides are key components of the skin's permeability barrier. In atopic dermatitis, pathological hydrolysis of ceramide precursors - glucosylceramides and sphingomyelin - into lysosphingolipids, specifically glucosylsphingosine (GS) and sphingosine-phosphorylcholine (SPC), and free fatty acids (FFAs) has been proposed to contribute to impaired skin barrier function. This study investigated whether replacing ceramides with lysosphingolipids and FFAs in skin lipid barrier models would exacerbate barrier dysfunction. When applied topically to human stratum corneum sheets, SPC and GS increased water loss, decreased electrical impedance, and slightly disordered lipid chains. In lipid models containing isolated human stratum corneum ceramides, reducing ceramides by ≥ 30% significantly increased permeability to four markers, likely due to loss of long-periodicity phase (LPP) lamellae and phase separation within the lipid matrix, as revealed by X-ray diffraction and infrared spectroscopy. However, when the missing ceramides were replaced by lysosphingolipids and FFAs, no further increase in permeability was observed. Conversely, these molecules partially mitigated the negative effects of ceramide deficiency, particularly with 5%-10% SPC, which reduced permeability even compared to control with "healthy" lipid composition. These findings suggest that while ceramide deficiency is a key factor in skin barrier dysfunction, the presence of lysosphingolipids and FFAs does not aggravate lipid structural or functional damage, but may provide partial compensation, raising further questions about the behavior of lyso(sphingo)lipids in rigid multilamellar lipid environments, such as the stratum corneum, that warrant further investigation.

The serine palmitoyltransferase core subunit StLcb2 regulates sphingolipid metabolism and promotes Setosphaeria turcica pathogenicity by modulating appressorium development

The fungal pathogen Setosphaeria turcica (S. turcica) causes northern corn leaf blight (NCLB), resulting in significant yield and economic losses in maize. To elucidate the metabolic pathways essential for its pathogenicity, we investigated the metabolome of S. turcica during appressorium development, a critical stage for host infection. Our analysis indicated a substantial enrichment of sphingosine and related compounds during this phase. The application of chemical inhibitors to disrupt sphingolipid metabolism confirmed their pivotal role in appressorium formation and pathogenicity. Additionally, silencing of the serine palmitoyl transferase (Spt) core subunit gene StLCB2 led to significant alterations in fungal morphology and growth, accompanied by changes in cell membrane integrity, surface hydrophobicity, melanin, and sphingosine synthesis. These findings underscore the importance of sphingolipids in the pathogenicity of S. turcica and suggest that targeting specific components of the sphingolipid pathway could aid in developing novel fungicides or genetically engineered maize varieties with increased resistance to NCLB.

Sphingolipid metabolism and regulated cell death in malignant melanoma

Malignant melanoma (MM) is a highly invasive and therapeutically resistant skin malignancy, posing a significant clinical challenge in its treatment. Programmed cell death plays a crucial role in the occurrence and progression of MM. Sphingolipids (SP), as a class of bioactive lipids, may be associated with many kinds of diseases. SPs regulate various forms of programmed cell death in tumors, including apoptosis, necroptosis, ferroptosis, and more. This review will delve into the mechanisms by which different types of SPs modulate various forms of programmed cell death in MM, such as their regulation of cell membrane permeability and signaling pathways, and how they influence the survival and death fate of MM cells. An in-depth exploration of the role of SPs in programmed cell death in MM aids in unraveling the molecular mechanisms of melanoma development and holds significant importance in developing novel therapeutic strategies.

Ion Mobility QTOF-MS Untargeted Lipidomics of Human Serum Reveals a Metabolic Fingerprint for GNE Myopathy

GNE myopathy, also known as hereditary inclusion body myopathy (HIBM), is a rare genetic muscle disorder marked by a gradual onset of muscle weakness in young adults. GNE myopathy (GNEM) is caused by bi-allelic variants in the UDP-N-acetylglucosamine 2-epimerase (UDP-GlcNAc 2-epimerase)/N-acetylmannosamine kinase (ManNAc kinase) gene (GNE), clinically resulting in the loss of ambulation within 10-20 years from the onset of the initial symptoms. The disease's mechanism is poorly understood and non-invasive biomarkers are lacking, hindering effective therapy development. Based on the available evidence, we employed a lipidomic approach to study the serum lipid profile of GNE patients. The multivariate statistical analysis revealed a downregulation of carnitines, as well as of lysophosphatidylcholines, in sera samples derived from GNEM patients. Furthermore, we identified lower levels of sphingomyelins and, concomitantly, high levels of ceramides in serum samples from GNEM patients when compared to control samples derived from healthy donors. Moreover, the GNEM serum samples showed the upregulation of Krebs cycle intermediates, in addition to a decrease in oxaloacetic acid. The correlated data gathered in this study can offer a promising diagnostic panel of complex lipids and polar metabolites that can be used in clinic for GNEM in terms of a metabolic fingerprint measurable in a minimally invasive manner.

Multiomics approach discloses lipids and metabolites profiles associated to Parkinson's disease stages and applied therapies

Profiling circulating lipids and metabolites in Parkinson's disease (PD) patients could be useful not only to highlight new pathways affected in PD condition but also to identify sensitive and effective biomarkers for early disease detection and potentially effective therapeutic interventions. In this study we adopted an untargeted omics approach in three groups of patients (No L-Dopa, L-Dopa and DBS) to disclose whether long-term levodopa treatment with or without deep brain stimulation (DBS) could reflect a characteristic lipidomic and metabolomic signature at circulating level. Our findings disclosed a wide up regulation of the majority of differentially regulated lipid species that increase with disease progression and severity. We found a relevant modulation of triacylglycerols and acyl-carnitines, together with an altered profile in adiponectin and leptin, that can differentiate the DBS treated group from the others PD patients. We found a highly significant increase of exosyl ceramides (Hex2Cer) and sphingoid bases (SPB) in PD patients mainly in DBS group (p < 0.0001), which also resulted in a highly accurate diagnostic performance. At metabolomic level, we found a wide dysregulation of pathways involved in the biosynthesis and metabolism of several amino acids. The most interesting finding was the identification of a specific modulation of L-glutamic acid in the three groups of patients. L-glutamate levels increased slightly in No L-Dopa and highly in L-Dopa patients while decreased in DBS, suggesting that DBS therapy might have a beneficial effect on the glutamatergic cascade. All together, these data provide novel insights into the molecular and metabolic alterations underlying PD therapy and might be relevant for PD prediction, diagnosis and treatment.

Bioactive sphingolipids as emerging targets for signal transduction in cancer development

Sphingolipids, crucial components of cellular membranes, play a vital role in maintaining cellular structure and signaling integrity. Disruptions in sphingolipid metabolism are increasingly implicated in cancer development. Key bioactive sphingolipids, such as ceramides, sphingosine-1-phosphate (S1P), ceramide-1-phosphate (C1P), and glycosphingolipids, profoundly impact tumor biology. They influence the behavior of tumor cells, stromal cells, and immune cells, affecting tumor aggressiveness, angiogenesis, immune modulation, and extracellular matrix remodeling. Furthermore, abnormal expression of sphingolipids and their metabolizing enzymes modulates the secretion of tumor-derived extracellular vesicles (TDEs), which are key players in creating an immunosuppressive tumor microenvironment, remodeling the extracellular matrix, and facilitating oncogenic signaling within in situ tumors and distant pre-metastatic niches (PMNs). Understanding the role of sphingolipids in the biogenesis of tumor-derived extracellular vesicles (TDEs) and their bioactive contents can pave the way for new biomarkers in cancer diagnosis and prognosis, ultimately enhancing comprehensive tumor treatment strategies.

Extracellular Vesicle Preparation and Analysis: A State-of-the-Art Review

In recent decades, research on Extracellular Vesicles (EVs) has gained prominence in the life sciences due to their critical roles in both health and disease states, offering promising applications in disease diagnosis, drug delivery, and therapy. However, their inherent heterogeneity and complex origins pose significant challenges to their preparation, analysis, and subsequent clinical application. This review is structured to provide an overview of the biogenesis, composition, and various sources of EVs, thereby laying the groundwork for a detailed discussion of contemporary techniques for their preparation and analysis. Particular focus is given to state-of-the-art technologies that employ both microfluidic and non-microfluidic platforms for EV processing. Furthermore, this discourse extends into innovative approaches that incorporate artificial intelligence and cutting-edge electrochemical sensors, with a particular emphasis on single EV analysis. This review proposes current challenges and outlines prospective avenues for future research. The objective is to motivate researchers to innovate and expand methods for the preparation and analysis of EVs, fully unlocking their biomedical potential.

Comprehensive assessment of the anti-obesity effects of highland barley total, insoluble, and soluble dietary fiber through multi-omics analysis

The impact of different forms of dietary fiber (total, insoluble or soluble) derived from the same source on health remains incompletely understood. In this study, the effects of total, insoluble, and soluble dietary fiber extracted from highland barley (HDF, HIDF, and HSDF) on combating obesity were evaluated and compared. A high-fat diet (HFD) was used to induce obesity in a murine model, followed by gavage administration of HDF, HIDF, or HSDF, and a comprehensive multi-omics approach was utilized to assess and compare the effects of these dietary fibers on obesity-related parameters. The results showed that all three dietary fibers significantly reduced body weight, modified blood lipid profiles, and ameliorated tissue damage in HFD-fed mice. Additionally, 16S rRNA sequencing analysis of mice feces showed that three types of dietary fiber exerted varying degrees of impact on the composition and abundance of gut microbiota while simultaneously promoting the biosynthesis of short-chain fatty acids. Specifically, HDF supplementation remarkably enhanced the abundance of Coprococcus, while HIDF and HSDF supplementation elevated the levels of Akkermansia and Allobaculum, respectively. Transcriptomic and proteomic results suggested the PPAR signaling pathway as a central regulatory mechanism influenced by these fibers. HDF and HIDF were particularly effective in modulating biological processes related to triglyceride and fatty acid metabolism, identifying Abcc3 and Dapk1 as potential targets. Conversely, HSDF primarily affected processes related to membrane lipids, ceramides, and phospholipids metabolism, with Pck1 identified as a potential target. Collectively, HDF, HIDF, and HSDF demonstrated distinct mechanisms in exerting exceptional anti-obesity properties. These insights may inform the development of personalized dietary interventions for obesity.

β-Sitosterol Inhibits Tumor Growth and Amplifies Rituximab Sensitivity through Acid Sphingomyelinase/Ceramide Signaling in Diffuse Large B-Cell Lymphoma

Rituximab (RTX) resistance is a notable challenge in treating diffuse large B-cell lymphoma (DLBCL). β-Sitosterol (β-ST) is a plant sterol that has been found in a broad variety of fruits, spices, and medicinal plants. The antineoplastic properties of β-ST are established in various solid malignancies; however, its effect on DLBCL is uncharted. This study investigates the role of β-ST in DLBCL as well as the underlying mechanisms. Our findings indicated that β-ST impeded DLBCL cell proliferation in a concentration- and time-dependent manner. β-ST appeared to alter sphingolipid metabolism, facilitate acid sphingomyelinase (ASM) translocation to the plasma membrane, augment ceramide platforms through increased ceramide synthesis, and consequently induce apoptosis in DLBCL cells. Furthermore, we found that RTX initiated both apoptotic and survival pathways in vitro, with the former contingent on the transient activation of the ASM, and β-ST could amplify the anti-DLBCL efficacy of RTX by modulating ASM/Ceramide (Cer) signaling. Collectively, our findings elucidate the mechanistic role of β-ST in DLBCL and underscore its potential in amplifying the antineoplastic efficacy of RTX via ASM activation, proposing a potential avenue to improve the efficacy of RTX therapy.

Intrathecal Fumagillin Alleviates Chronic Neuropathy-Induced Nociceptive Sensitization and Modulates Spinal Astrocyte-Neuronal Glycolytic and Angiogenic Proteins

Nociceptive sensitization is accompanied by the upregulation of glycolysis in the central nervous system in neuropathic pain. Growing evidence has demonstrated glycolysis and angiogenesis to be related to the inflammatory processes. This study investigated whether fumagillin inhibits neuropathic pain by regulating glycolysis and angiogenesis. Fumagillin was administered through an intrathecal catheter implanted in rats with chronic constriction injury (CCI) of the sciatic nerve. Nociceptive, behavioral, and immunohistochemical analyses were performed to evaluate the effects of the inhibition of spinal glycolysis-related enzymes and angiogenic factors on CCI-induced neuropathic pain. Fumagillin reduced CCI-induced thermal hyperalgesia and mechanical allodynia from postoperative days (POD) 7 to 14. The expression of angiogenic factors, vascular endothelial growth factor (VEGF) and angiopoietin 2 (ANG2), increased in the ipsilateral lumbar spinal cord dorsal horn (SCDH) following CCI. The glycolysis-related enzymes, pyruvate kinase M2 (PKM2) and lactate dehydrogenase A (LDHA) significantly increased in the ipsilateral lumbar SCDH following CCI on POD 7 and 14 compared to those in the control rats. Double immunofluorescence staining indicated that VEGF and PKM2 were predominantly expressed in the astrocytes, whereas ANG2 and LDHA were predominantly expressed in the neurons. Intrathecal infusion of fumagillin significantly reduced the expression of angiogenic factors and glycolytic enzymes upregulated by CCI. The expression of hypoxia-inducible factor-1α (HIF-1α), a crucial transcription factor that regulates angiogenesis and glycolysis, was also upregulated after CCI and inhibited by fumagillin. We concluded that intrathecal fumagillin may reduce the expression of ANG2 and LDHA in neurons and VEGF and PKM2 in the astrocytes of the SCDH, further attenuating spinal angiogenesis in neuropathy-induced nociceptive sensitization. Hence, fumagillin may play a role in the inhibition of peripheral neuropathy-induced neuropathic pain by modulating glycolysis and angiogenesis.

Association of plasma ceramide with decline in kidney function in patients with type 2 diabetes

Circulating ceramide levels are dysregulated in kidney disease. However, their associations with rapid decline in kidney function (RDKF) and end-stage kidney disease (ESKD) in patients with type 2 diabetes (T2D) are unknown. In this prospective study of 1746 T2D participants, we examined the association of plasma ceramide Cer16:0, Cer18:0, Cer24:0, and Cer24:1 with RDKF, defined as an estimated glomerular filtration rate (eGFR) decline of 5 ml/min/1.73 m2 per year or greater, and ESKD defined as eGFR <15/min/1.73 m2 for at least 3 months, on dialysis or renal death at follow-up. During a median follow-up period of 7.7 years, 197 patients experienced RDKF. Ceramide Cer24:0 (odds ratio [OR] = 0.71, 95% CI 0.56-0.90) and ratios Cer16:0/Cer24:0 (OR = 3.54 [1.70-7.35]), Cer18:0/Cer24:0 (OR = 1.89 [1.10-3.25]), and Cer24:1/Cer24:0 (OR = 4.01 [1.93-8.31]) significantly associated with RDKF in multivariable analysis; 124 patients developed ESKD. The ratios Cer16:0/Cer24:0 (hazard ratio [HR] = 3.10 [1.44-6.64]) and Cer24:1/Cer24:0 (HR = 4.66 [1.93-11.24]) significantly associated with a higher risk of ESKD. The Cer24:1/Cer24:0 ratio improved risk discrimination for ESKD beyond traditional risk factors by small but statistically significant margin (Harrell C-index difference: 0.01; P = 0.022). A high ceramide risk score also associated with RDKF (OR = 2.28 [1.26-4.13]) compared to lower risk score. In conclusion, specific ceramide levels and their ratios are associated with RDKF and conferred an increased risk of ESKD, independently of traditional risk factors, including baseline renal functions in patients with T2D.

Therapeutic potential of exosomes in spermatogenesis regulation and male infertility

BACKGROUND

Spermatogenesis is a fundamental process crucial for male reproductive health and fertility. Exosomes, small membranous vesicles released by various cell types, have recently garnered attention for their role in intercellular communication.

OBJECTIVE

This review aims to comprehensively explore the role of exosomes in regulating spermatogenesis, focusing on their involvement in testicular development and cell-to-cell communication.

METHODS

A systematic examination of literature was conducted to gather relevant studies elucidating the biogenesis, composition, and functions of exosomes in the context of spermatogenesis.

RESULTS

Exosomes play a pivotal role in orchestrating the complex signaling networks required for proper spermatogenesis. They facilitate the transfer of key regulatory molecules between different cell populations within the testes, including Sertoli cells, Leydig cells, and germ cells.

CONCLUSION

The emerging understanding of exosome-mediated communication sheds light on novel mechanisms underlying spermatogenesis regulation. Further research in this area holds promise for insights into male reproductive health and potential therapeutic interventions.

A guide to the expanding field of extracellular vesicles and their release in regulated cell death programs

Homeostasis disruption is visible at the molecular and cellular levels and may often lead to cell death. This vital process allows us to maintain the more extensive system's integrity by keeping the different features (genetic, metabolic, physiologic, and individual) intact. Interestingly, while cells can die in different manners, dying cells still communicate with their environment. This communication was, for a long time, perceived as only driven by the release of soluble factors. However, it has now been reconsidered with the increasing interest in extracellular vesicles (EVs), which are discovered to be released during different regulated cell death programs, with the observation of specific effects. EVs are game changers in the paradigm of cell-cell communication with tremendous implications in fundamental research with regard to noncell autonomous functions, as well as in biomarkers research, all of which are geared toward diagnostic and therapeutic purposes. This review is composed of two main parts. The first is a comprehensive presentation of the state of the art of the EV field at large. In the second part, we focus on EVs discovered to be released during different regulated cell death programs, also known as cell death EVs (cdEVs), and EV-associated specific effects on recipient cells in the context of cell death and inflammation/inflammatory responses.

Emerging Roles of Neuronal Extracellular Vesicles at the Synapse

Extracellular vesicles (EVs) are secreted from most, if not all, cell types and are implicated in short- and long-distance signaling throughout the body. EVs are also secreted from neurons and represent an emergent neuronal communication platform. Understanding the functional implications of EV signaling to recipient neurons and glia requires understanding the cell biology involved in EV biogenesis, cargo loading, secretion, uptake, and signal transduction in the recipient cell. Here we review these major questions of EV biology while highlighting recent new insights and examples within the nervous system, such as modulating synaptic function or morphogenesis in recipient neurons.

Dysregulation of sphingolipid metabolism in pain

Pain is a clinical condition that is currently of great concern and is often caused by tissue or nerve damage or occurs as a concomitant symptom of a variety of diseases such as cancer. Severe pain seriously affects the functional status of the body. However, existing pain management programs are not fully satisfactory. Therefore, there is a need to delve deeper into the pathological mechanisms underlying pain generation and to find new targets for drug therapy. Sphingolipids (SLs), as a major component of the bilayer structure of eukaryotic cell membranes, also have powerful signal transduction functions. Sphingolipids are abundant, and their intracellular metabolism constitutes a huge network. Sphingolipids and their various metabolites play significant roles in cell proliferation, differentiation, apoptosis, etc., and have powerful biological activities. The molecules related to sphingolipid metabolism, mainly the core molecule ceramide and the downstream metabolism molecule sphingosine-1-phosphate (S1P), are involved in the specific mechanisms of neurological disorders as well as the onset and progression of various types of pain, and are closely related to a variety of pain-related diseases. Therefore, sphingolipid metabolism can be the focus of research on pain regulation and provide new drug targets and ideas for pain.

Neutral Sphingomyelinase 2 Inhibition Limits Hepatic Steatosis and Inflammation

Non-alcoholic fatty liver disease (NAFLD) is manifested by hepatic steatosis, insulin resistance, hepatocyte death, and systemic inflammation. Obesity induces steatosis and chronic inflammation in the liver. However, the precise mechanism underlying hepatic steatosis in the setting of obesity remains unclear. Here, we report studies that address this question. After 14 weeks on a high-fat diet (HFD) with high sucrose, C57BL/6 mice revealed a phenotype of liver steatosis. Transcriptional profiling analysis of the liver tissues was performed using RNA sequencing (RNA-seq). Our RNA-seq data revealed 692 differentially expressed genes involved in processes of lipid metabolism, oxidative stress, immune responses, and cell proliferation. Notably, the gene encoding neutral sphingomyelinase, SMPD3, was predominantly upregulated in the liver tissues of the mice displaying a phenotype of steatosis. Moreover, nSMase2 activity was elevated in these tissues of the liver. Pharmacological and genetic inhibition of nSMase2 prevented intracellular lipid accumulation and TNFα-induced inflammation in in-vitro HepG2-steatosis cellular model. Furthermore, nSMase2 inhibition ameliorates oxidative damage by rescuing PPARα and preventing cell death associated with high glucose/oleic acid-induced fat accumulation in HepG2 cells. Collectively, our findings highlight the prominent role of nSMase2 in hepatic steatosis, which could serve as a potential therapeutic target for NAFLD and other hepatic steatosis-linked disorders.

Ceramides: a potential cardiovascular biomarker in young adult childhood cancer survivors?

Aims

The aim of this study was to investigate circulating ceramides involved in cardiovascular disease (CVD) in young adult childhood cancer survivors (CCS) and their correlations to previously reported adverse cardiovascular changes in this cohort.

Methods and results

Fifty-seven CCS and 53 healthy controls (age 20-30 years) were studied. Plasma long-chain ceramides, known to be cardiotoxic (C16:0, C18:0, C24:0, and C24:1), were analysed by mass spectrometry. The coronary event risk test 2 (CERT2) score was calculated from the ceramide data. Cardiac and carotid artery ultrasound data and lipid data available from previous studies of this cohort were used to study partial correlations with ceramide and CERT2 score data. All four analysed ceramides were elevated in CCS compared with controls (P ≤ 0.012). The greatest difference was noted for C18:0, which was 33% higher in CCS compared with controls adjusted for sex, age, and body mass index (BMI) (P < 0.001). The CERT2 score was higher in CCS compared with controls (P < 0.001). In the CCS group, 35% had a high to very high CERT2 score (7-12) when compared with 9% in the control group (P < 0.001). The CCS subgroup with a CERT2 score ≥ 7 had higher heart rate, systolic blood pressure, and higher levels of apolipoprotein B compared with CCS with a CERT2 score < 6 (P ≤ 0.011). When adjusted for age, sex, and BMI, CERT2 score was significantly correlated with arterial stiffness, growth hormone, and cranial radiotherapy (P < 0.044).

Conclusion

Ceramides could be important biomarkers in understanding the pathophysiology of CVD and in predicting CVD disease risk in young adult CCS.

Ceramide regulation of autophagy: A biophysical approach

Specific membrane lipids play unique roles in (macro)autophagy. Those include phosphatidylethanolamine, to which LC3/GABARAP autophagy proteins become covalently bound in the process, or cardiolipin, an important effector in mitochondrial autophagy (or mitophagy). Ceramide (Cer), or N-acyl sphingosine, is one of the simplest sphingolipids, known as a stress signal in the apoptotic pathway. Moreover, Cer is increasingly being recognized as an autophagy activator, although its mechanism of action is unclear. In the present review, the proposed Cer roles in autophagy are summarized, together with some biophysical properties of Cer in membranes. Possible pathways for Cer activation of autophagy are discussed, including specific protein binding of the lipid, and Cer-dependent perturbation of bilayer properties. Cer generation of lateral inhomogeneities (domain formation) is given special attention. Recent biophysical results, including fluorescence and atomic force microscopy data, show Cer-promoted enhanced binding of LC3/GABARAP to lipid bilayers. These observations could be interpreted in terms of the putative formation of Cer-rich nanodomains.

The relevance between abnormally elevated serum ceramide and cognitive impairment in Alzheimer's disease model mice and its mechanism

RATIONALE

The plasma ceramide levels in Alzheimer's disease (AD) patients are found abnormally elevated, which is related to cognitive decline.

OBJECTIVES

This research was aimed to investigate the mechanisms of aberrant elevated ceramides in the pathogenesis of AD.

RESULTS

The ICR mice intracerebroventricularly injected with Aβ1-42 and APP/PS1 transgenic mice were employed as AD mice. The cognitive deficiency, impaired episodic and spatial memory were observed without altered spontaneous ability. The serum levels of p-tau and ceramide were evidently elevated. The modified expressions and activities of glycogen synthase kinase-3β (GSK-3β) and protein phosphatase 2A (PP2A) influenced the serum content of p-tau. The levels of ceramide synthesis-related genes including sptlc1, sptlc2, cers2, and cers6 in the liver of AD mice were increased, while the ceramide degradation-related gene asah2 did not significantly change. The regulations of these genes were conducted by activated nuclear factor kappa-B (NF-κB) signaling. NF-κB, promoted by free fatty acid (FFA), also increased the hepatic concentrations of proinflammatory cytokines. The FFA amount was modulated by fatty acid synthesis-related genes acc1 and srebp-1c. Besides, the decreased levels of pre-proopiomelanocortin (pomc) mRNA and increased agouti-related protein (agrp) mRNA were found in the hypothalamus without significant alteration of melanocortin receptor 4 (MC4R) mRNA. The bioinformatic analyses proved the results using GEO datasets and AlzData.

CONCLUSIONS

Ceramide was positively related to the increased p-tau and impaired cognitive function. The increased generation of ceramide and endoplasmic reticulum stress in the hypothalamus was positively related to fatty acid synthesis and NF-κB signaling via brain-liver axis.

Plant-derived exosomes: a green approach for cancer drug delivery

Plant-derived exosomes (PDEs) are natural extracellular vesicles (EVs). In the current decade, they have been highlighted for cancer therapeutic development. Cancer is a global health crisis and it requires an effective, affordable, and less side effect-based treatment. Emerging research based on PDEs suggests that they have immense potential to be considered as a therapeutic option. Research evidences indicate that PDEs' internal molecular cargos show impressive cancer prevention activity with less toxicity. PDEs-based drug delivery systems overcome several limitations of traditional drug delivery tools. Extraction of PDEs from plant sources employ diverse methodologies, encompassing ultracentrifugation, immunoaffinity, size-based isolation, and precipitation, each with distinct advantages and limitations. The core constituents of PDEs comprise of lipids, proteins, DNA, and RNA. Worldwide, a few clinical trials on plant-derived exosomes are underway, and regulatory affairs for their use as therapeutic agents are still not understood with clarity. This review aims to comprehensively analyze the current state of research on plant-derived exosomes as a promising avenue for drug delivery, highlighting anticancer activity, challenges, and future orientation in effective cancer therapeutic development.

Diagnostic value of sphingolipid metabolism-related genes CD37 and CXCL9 in nonalcoholic fatty liver disease

The development of nonalcoholic fatty liver disease (NAFLD) has been reported to be caused by sphingolipid family inducing insulin resistance, mitochondrial dysfunction, and inflammation, which can be regulated by multiple sphingolipid metabolic pathways. This study aimed to explore the molecular mechanism of crucial sphingolipid metabolism related genes (SMRGs) in NAFLD. Firstly, the datasets (GSE48452, GSE126848, and GSE63067) from the Gene Expression Omnibus database and sphingolipid metabolism genes (SMGs) from previous research were collected for this study. The differentially expressed genes (DEGs) between different NAFLD and controls were acquired through "limma," and the SMRGs were authenticated via weighted gene co-expression network analysis (WGCNA). After overlapping the DEGs and SMRGs, the causality between the intersection genes (DE-SMRGs) and NAFLD was explored to sort out the candidate biomarkers by Mendelian randomization (MR) study. The receiver operating characteristic (ROC) curves of candidate biomarkers in GSE48452 and GSE126848 were yielded to determine the biomarkers, followed by the nomogram construction and enrichment analysis. Finally, the immune infiltration analysis, the prediction of transcription factors (TFs) and drugs targeting biomarkers were put into effect. A total of 23 DE-SMRGs were acquired based on the differential analysis and weighted gene co-expression network analysis (WGCNA), of which 3 DE-SMRGs (CD37, CXCL9 and IL7R) were picked out for follow-up analysis through univariate and multivariate MR analysis. The values of area under ROC curve of CD37 and CXCL9 were >0.7 in GSE48452 and GSE126848, thereby being regarded as biomarkers, which were mainly enriched in amino acid metabolism. With respect to the Spearman analysis between immune cells and biomarkers, CD37 and CXCL9 were significantly positively associated with M1 macrophages (P < .001), whose proportion was observably higher in NAFLD patients compared with controls. At last, TFs (ZNF460 and ZNF384) of CD37 and CXCL9 and a total of 79 chemical drugs targeting CD37 and CXCL9 were predicted. This study mined the pivotal SMRGs, CD37 and CXCL9, and systematically explored the mechanism of action of both biomarkers based on the public databases, which could tender a fresh reference for the clinical diagnosis and therapy of NAFLD.

Sphingolipids: drivers of cardiac fibrosis and atrial fibrillation

Sphingolipids (SLs) are vital constituents of the plasma membrane of animal cells and concurrently regulate numerous cellular processes. An escalating number of research have evinced that SLs assume a crucial part in the progression of tissue fibrosis, a condition for which no efficacious cure exists as of now. Cardiac fibrosis, and in particular, atrial fibrosis, is a key factor in the emergence of atrial fibrillation (AF). AF has become one of the most widespread cardiac arrhythmias globally, with its incidence continuing to mount, thereby propelling it to the status of a major public health concern. This review expounds on the structure and biosynthesis pathways of several pivotal SLs, the pathophysiological mechanisms of AF, and the function of SLs in cardiac fibrosis. Delving into the influence of sphingolipid levels in the alleviation of cardiac fibrosis offers innovative therapeutic strategies to address cardiac fibrosis and AF.

Optimization of Fermentation Process for New Anti-Inflammatory Glycosylceramide Metabolite from Aspergillus sp

A novel ceramide compound, named Aspercerebroside A (AcA), was successfully isolated from the ethyl acetate layer of the marine symbiotic fungus Aspergillus sp. AcA exhibited notable anti-inflammatory activity by effectively inhibiting the production of nitric oxide (NO) in RAW 264.7 cells at concentrations of 30 μg/mL and 40 μg/mL, offering a promising avenue for the treatment of inflammatory diseases. To optimize the yield of glycosylceramide (AcA), a series of techniques, including single-factor experiments, orthogonal experiments, and response surface optimization, were systematically employed to fine-tune the composition of the fermentation medium. Initially, the optimal carbon source (sucrose), nitrogen source (yeast extract powder), and the most suitable medium salinity (14 ppt) were identified through single-factor experiments. Subsequently, orthogonal experiments, employing an orthogonal table for planning and analyzing multifactor experiments, were conducted. Finally, a mathematical model, established using a Box-Behnken design, comprehensively analyzed the interactions between the various factors to determine the optimal composition of the fermentation medium. According to the model's prediction, when the sucrose concentration was set at 37.47 g/L, yeast extract powder concentration at 19.66 g/L, and medium salinity at 13.31 ppt, the predicted concentration of glycosylceramide was 171.084 μg/mL. The experimental results confirmed the model's accuracy, with the actual average concentration of glycosylceramide under these conditions measured at 171.670 μg/mL, aligning closely with the predicted value.

The chemokine receptor CCR5: multi-faceted hook for HIV-1

Chemokines are cytokines whose primary role is cellular activation and stimulation of leukocyte migration. They perform their various functions by interacting with G protein-coupled cell surface receptors (GPCRs) and are involved in the regulation of many biological processes such as apoptosis, proliferation, angiogenesis, hematopoiesis or organogenesis. They contribute to the maintenance of the homeostasis of lymphocytes and coordinate the function of the immune system. However, chemokines and their receptors are sometimes hijacked by some pathogens to infect the host organism. For a given chemokine receptor, there is a wide structural, organizational and conformational diversity. In this review, we describe the evidence for structural variety reported for the chemokine receptor CCR5, how this variability can be exploited by HIV-1 to infect its target cells and what therapeutic solutions are currently being developed to overcome this problem.

Interactions between macrophage membrane and lipid mediators during cardiovascular diseases with the implications of scavenger receptors

The onset and progression of cardiovascular diseases with the major underlying cause being atherosclerosis, occur during chronic inflammatory persistence in the vascular system, especially within the arterial wall. Such prolonged maladaptive inflammation is driven by macrophages and their key mediators are generally attributed to a disparity in lipid metabolism. Macrophages are the primary cells of innate immunity, endowed with expansive membrane domains involved in immune responses with their signalling systems. During atherosclerosis, the membrane domains and receptors control various active organisations of macrophages. Their scavenger/endocytic receptors regulate the trafficking of intracellular and extracellular cargo. Corresponding influence on lipid metabolism is mediated by their dynamic interaction with scavenger membrane receptors and their integrated mechanisms such as pinocytosis, phagocytosis, cholesterol export/import, etc. This interaction not only results in the functional differentiation of macrophages but also modifies their structural configurations. Here, we reviewed the association of macrophage membrane biomechanics and their scavenger receptor families with lipid metabolites during the event of atherogenesis. In addition, the membrane structure of macrophages and the signalling pathways involved in endocytosis integrated with lipid metabolism are detailed. This article establishes future insights into the scavenger receptors as potential targets for cardiovascular disease prevention and treatment.

A comprehensive review on recent nanosystems for enhancing antifungal activity of fenticonazole nitrate from different routes of administration

This review aims to comprehensively highlight the recent nanosystems enclosing Fenticonazole nitrate (FTN) and to compare between them regarding preparation techniques, studied factors and responses. Moreover, the optimum formulae were compared in terms of in vitro, ex vivo and in vivo studies in order to detect the best formula. FTN is a potent antifungal imidazole compound that had been used for treatment of many dangerous fungal infections affecting eye, skin or vagina. FTN had been incorporated in various innovative nanosystems in the recent years in order to achieve significant recovery such as olaminosomes, novasomes, cerosomes, terpesomes and trans-novasomes. These nanosystems were formulated by various techniques (ethanol injection or thin film hydration) utilizing different statistical designs (Box-Behnken, central composite, full factorial and D-optimal). Different factors were studied in each nanosystem regarding its composition as surfactant concentrations, surfactant type, amount of oleic acid, cholesterol, oleylamine, ceramide, sodium deoxycholate, terpene concentration and ethanol concentration. Numerous responses were studied such as percent entrapment efficiency (EE%), particle size (PS), poly-dispersity index (PDI), zeta potential (ZP), and in vitro drug release. Selection of the optimum formula was based on numerical optimization accomplished by Design-Expert® software taking in consideration the largest EE %, ZP (as absolute value) and in vitro drug release and lowest PS and PDI. In vitro comparisons were done employing different techniques such as Transmission electron microscopy, pH determination, effect of gamma sterilization, elasticity evaluation and docking study. In addition to, ex vivo permeation, in vivo irritancy test, histopathological, antifungal activity and Kinetic study.

Glucagon-like peptide-1 receptor agonist regulates fat browning by altering the gut microbiota and ceramide metabolism

Studies have shown that antidiabetic drugs can alter the gut microbiota. The hypoglycemic effects of the drugs can be attributed in part to certain species in the gut microbiome that help the drugs work more effectively. In addition, increasing energy expenditure via the induction of adipose tissue browning has become an appealing strategy to treat obesity and associated metabolic complications. Currently, glucagon-like peptide-1 receptor agonist (GLP-1 RA) treatment for metabolic disorders such as obesity and type 2 diabetes has been widely studied. To determine the mechanism of a long-acting GLP-1 RA affects adipose tissue browning and the gut microbiome, we treated high-fat diet mice with GLP-1 RA and demonstrated that the drug can regulate adipose tissue browning. 16S rRNA and untargeted metabolomics assays suggested that it increased the abundance of bacterium Lactobacillus reuteri and decreased serum ceramide levels in mice. L. reuteri was negatively correlated with ceramide. We found that the mechanism of ceramide decline was alkaline ceramidase 2 (Acer2) overexpression. Moreover, L. reuteri can play a therapeutic synergistic role with GLP-1 RA, suggesting that gut microbiota can be used as a part of the treatment of diabetes.

Molecular basis for the catalytic mechanism of human neutral sphingomyelinases 1 (hSMPD2)

Enzymatic breakdown of sphingomyelin by sphingomyelinase (SMase) is the main source of the membrane lipids, ceramides, which are involved in many cellular physiological processes. However, the full-length structure of human neutral SMase has not been resolved; therefore, its catalytic mechanism remains unknown. Here, we resolve the structure of human full-length neutral SMase, sphingomyelinase 1 (SMPD2), which reveals that C-terminal transmembrane helices contribute to dimeric architecture of hSMPD2 and that D111 - K116 loop domain is essential for substrate hydrolysis. Coupled with molecular docking, we clarify the binding pose of sphingomyelin, and site-directed mutagenesis further confirms key residues responsible for sphingomyelin binding. Hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamic (MD) simulations are utilized to elaborate the catalysis of hSMPD2 with the reported in vitro substrates, sphingomyelin and lyso-platelet activating fator (lyso-PAF). Our study provides mechanistic details that enhance our knowledge of lipid metabolism and may lead to an improved understanding of ceramide in disease and in cancer treatment.

The separation and identification of circulating small extracellular vesicles from endurance-trained, strength-trained and recreationally active men

Small extracellular vesicles (EV) are membrane-encapsulated particles that carry bioactive cargoes, are released by all cell types and are present in all human biofluids. Changes in EV profiles and abundance occur in response to acute exercise, but this study investigated whether individuals with divergent histories of exercise training (recreationally active controls - CON; endurance-trained - END; strength-trained - STR) presented with varied abundances of small EVs in resting samples and whether the abundance of small EVs differed within each group across two measurement days. Participants (n = 38, all male; CON n = 12, END n = 13, STR n = 13) arrived at the lab on two separate occasions in a rested, overnight fasted state, with standardisation of time of day of sampling, recent dietary intake, time since last meal and time since last exercise training session (∼40 h). Whole blood samples were collected and separated into plasma from which small EVs were separated using size exclusion chromatography and identified in accordance with the Minimal Information For Studies of Extracellular Vesicles (MISEV) guidelines. No differences in the abundance of small EVs were observed within or between groups across multiple methods of small EV identification (nanoparticle tracking analysis, flow cytometry, immunoblot of specific EV markers). Targeted metabolomics of the small EV preparations identified 96 metabolites that were associated with the structure and function of small EVs, with no statistically significant differences in concentrations observed across groups. The results of the current study suggest that the abundance and metabolomic profile of small EVs derived from men with divergent histories of exercise training are similar to those in resting blood samples. KEY POINTS: Extracellular vesicles (EV) are membrane-encapsulated particles that are present in circulation and carry bioactive materials as 'cargo'. The abundance and profile of small EVs are responsive to acute exercise, but little is known about the relationship between small EVs and exercise training. This study examined the abundance, and a targeted metabolomic profile, of small EVs separated from the blood of endurance athletes, strength athletes and recreationally active controls at rest (∼40 h after the most recent exercise session) on two separate but identical lab visits. No differences were observed in the abundance or metabolomic profile of small EV preparations between the groups or between the lab visits within each group. Further research should determine whether the bioactive cargoes (e.g. RNA, protein and additional metabolites) carried within EVs are altered in individuals with divergent histories of exercise training or in response to exercise training interventions.

Exosomes in Cancer Progression and Therapy Resistance: Molecular Insights and Therapeutic Opportunities

The development of therapy resistance still represents a major hurdle in treating cancers, leading to impaired treatment success and increased patient morbidity. The establishment of minimally invasive liquid biopsies is a promising approach to improving the early diagnosis, as well as therapy monitoring, of solid tumors. Because of their manifold functions in the tumor microenvironment, tumor-associated small extracellular vesicles, referred to as exosomes, have become a subject of intense research. Besides their important roles in cancer progression, metastasis, and the immune response, it has been proposed that exosomes also contribute to the acquisition and transfer of therapy resistance, mainly by delivering functional proteins and RNAs, as well as facilitating the export of active drugs or functioning as extracellular decoys. Extensive research has focused on understanding the molecular mechanisms underlying the occurrence of resistance and translating these into strategies for early detection. With this review, we want to provide an overview of the current knowledge about the (patho-)biology of exosomes, as well as state-of-the-art methods of isolation and analysis. Furthermore, we highlight the role of exosomes in tumorigenesis and cancer treatment, where they can function as therapeutic agents, biomarkers, and/or targets. By focusing on their roles in therapy resistance, we will reveal new paths of exploiting exosomes for cancer diagnosis and treatment.

Natural Products and Small Molecules Targeting Cellular Ceramide Metabolism to Enhance Apoptosis in Cancer Cells

Molecular targeting strategies have been used for years in order to control cancer progression and are often based on targeting various enzymes involved in metabolic pathways. Keeping this in mind, it is essential to determine the role of each enzyme in a particular metabolic pathway. In this review, we provide in-depth information on various enzymes such as ceramidase, sphingosine kinase, sphingomyelin synthase, dihydroceramide desaturase, and ceramide synthase which are associated with various types of cancers. We also discuss the physicochemical properties of well-studied inhibitors with natural product origins and their related structures in terms of these enzymes. Targeting ceramide metabolism exhibited promising mono- and combination therapies at preclinical stages in preventing cancer progression and cemented the significance of sphingolipid metabolism in cancer treatments. Targeting ceramide-metabolizing enzymes will help medicinal chemists design potent and selective small molecules for treating cancer progression at various levels.

Diet-derived and diet-related endogenously produced palmitic acid: Effects on metabolic regulation and cardiovascular disease risk

Palmitic acid is the predominant dietary saturated fatty acid (SFA) in the US diet. Plasma palmitic acid is derived from dietary fat and also endogenously from de novo lipogenesis (DNL) and lipolysis. DNL is affected by excess energy intake resulting in overweight and obesity, and the macronutrient profile of the diet. A low-fat diet (higher carbohydrate and/or protein) promotes palmitic acid synthesis in adipocytes and the liver. A high-fat diet is another source of palmitic acid that is taken up by adipose tissue, liver, heart and skeletal muscle via lipolytic mechanisms. Moreover, overweight/obesity and accompanying insulin resistance increase non-esterified fatty acid (NEFA) production. Palmitic acid may affect cardiovascular disease (CVD) risk via mechanisms beyond increasing low-density lipoprotein-cholesterol (LDL-C), notably synthesis of ceramides and possibly through branched fatty acid esters of hydroxy fatty acids (FAHFAs) from palmitic acid. Ceramides are positively associated with incident CVD, whereas the role of FAHFAs is uncertain. Given the new evidence about dietary regulation of palmitic acid metabolism there is interest in learning more about how diet modulates circulating palmitic acid concentrations and, hence, potentially CVD risk. This is important because of the heightened interest in low carbohydrate (carbohydrate controlled) and high carbohydrate (low-fat) diets coupled with the ongoing overweight/obesity epidemic, all of which can increase plasma palmitic acid levels by different mechanisms. Consequently, learning more about palmitic acid biochemistry, trafficking and how its metabolites affect CVD risk will inform future dietary guidance to further lower the burden of CVD.

Sphingolipids: From structural components to signaling hubs

In late November 2019, Prof. Lina M. Obeid passed away from cancer, a disease she spent her life researching and studying its intricate molecular underpinnings. Along with her husband, Prof. Yusuf A. Hannun, Obeid laid down the foundations of sphingolipid biochemistry and oversaw its remarkable evolution over the years. Lipids are a class of macromolecules that are primarily associated with cellular architecture. In fact, lipids constitute the perimeter of the cell in such a way that without them, there cannot be cells. Hence, much of the early research on lipids identified the function of this class of biological molecules as merely structural. Nevertheless, unlike proteins, carbohydrates, and nucleic acids, lipids are elaborately diverse as they are not made up of monomers in polymeric forms. This diversity in structure is clearly mirrored by functional pleiotropy. In this chapter, we focus on a major subset of lipids, sphingolipids, and explore their historic rise from merely inert structural components of plasma membranes to lively and necessary signaling molecules that transmit various signals and control many cellular processes. We will emphasize the works of Lina Obeid since she was an integral pillar of the sphingolipid research world.

Biogenesis, Isolation, and Detection of Exosomes and Their Potential in Therapeutics and Diagnostics

The increasing research and rapid developments in the field of exosomes provide insights into their role and significance in human health. Exosomes derived from various sources, such as mesenchymal stem cells, cardiac cells, and tumor cells, to name a few, can be potential therapeutic agents for the treatment of diseases and could also serve as biomarkers for the early detection of diseases. Cellular components of exosomes, several proteins, lipids, and miRNAs hold promise as novel biomarkers for the detection of various diseases. The structure of exosomes enables them as drug delivery vehicles. Since exosomes exhibit potential therapeutic applications, their efficient isolation from complex biological/clinical samples and precise real-time analysis becomes significant. With the advent of microfluidics, nano-biosensors are being designed to capture exosomes efficiently and rapidly. Herein, we have summarized the history, biogenesis, characteristics, functions, and applications of exosomes, along with the isolation, detection, and quantification techniques. The implications of surface modifications to enhance specificity have been outlined. The review also sheds light on the engineered nanoplatforms being developed for exosome detection and capture.

Ceramide Risk Score in the Evaluation of Metabolic Syndrome: An Additional or Substitutive Biochemical Marker in the Clinical Practice?

Ceramide risk score (CERT1, ceramide test 1), based on specific ceramides (Cers) and their corresponding ratios in the plasma, has been reported as a promising biochemical marker for primary and secondary prediction of cardiovascular disease (CVD) risk in different populations of patients. Thus far, limited attention has been paid to metabolic syndrome, a condition considered at high CVD risk. The aim of the present study was to evaluate CERT1 in a group of obese subjects without (OB-MetS-) and with (OB-MetS+) metabolic syndrome (according to the International Diabetes Federation (IDF) diagnostic criteria), compared to an age- and sex-matched normal-weight (NW) group. In all participants, plasma levels of Cer 16:0, Cer 18:0, Cer 24:1, and Cer 24:0 were measured, and the corresponding ratios Cer 16:0/24:0, Cer 18:0/24:0, and Cer 24:1/24:0 were calculated together with CERT1. Subjects with obesity showed higher CERT1 values than the NW group (p < 0.05), with no difference between OB-MetS- and OB-MetS+ groups. Waist circumference (WC), homeostatic model assessment of insulin-resistance (HOMA-IR) (surrogates of IDF diagnostic criteria for metabolic syndrome), and C reactive protein (CRP) (a marker of inflammation) were predictors of CERT1 (p < 0.05), with the contribution of the other IDF criteria such as arterial hypertension and dyslipidemia being negligible. Adjustment for WC resulted in a loss of the difference in CERT1 between OB-MetS- and NW subjects, with the combination of WC and HOMA-IR or CRP as covariates being necessary to yield the same effect for the difference in CERT1 between OB-MetS+ and NW subjects. Importantly, an association was found between CERT1 and vascular age (VA) (p < 0.05). Proportions of NW, OB-MetS- and OB-MetS+ subjects appeared to be distributed according to the CERT1-based risk groups (i.e., low, moderate, increased, and high risk; p < 0.05), with some OB-MetS- subjects included in the increased/high-risk group and some OB-MetS+ in the low/moderate-risk one. In conclusion, the clinical diagnosis of metabolic syndrome seems to be inaccurate to assess CVD risk in the obese population; however, further studies are needed before considering CERT1 as an additional or substitutive biochemical marker in clinical practice.

Inhibition of neutral sphingomyelinase 2 impairs HIV-1 envelope formation and substantially delays or eliminates viral rebound

Although HIV-1 Gag is known to drive viral assembly and budding, the precise mechanisms by which the lipid composition of the plasma membrane is remodeled during assembly are incompletely understood. Here, we provide evidence that the sphingomyelin hydrolase neutral sphingomyelinase 2 (nSMase2) interacts with HIV-1 Gag and through the hydrolysis of sphingomyelin creates ceramide that is necessary for proper formation of the viral envelope and viral maturation. Inhibition or depletion of nSMase2 resulted in the production of noninfectious HIV-1 virions with incomplete Gag lattices lacking condensed conical cores. Inhibition of nSMase2 in HIV-1-infected humanized mouse models with a potent and selective inhibitor of nSMase2 termed PDDC [phenyl(R)-(1-(3-(3,4-dimethoxyphenyl)-2, 6-dimethylimidazo[1,2-b]pyridazin-8-yl) pyrrolidin-3-yl)-carbamate] produced a linear reduction in levels of HIV-1 in plasma. If undetectable plasma levels of HIV-1 were achieved with PDDC treatment, viral rebound did not occur for up to 4 wk when PDDC was discontinued. In vivo and tissue culture results suggest that PDDC selectively kills cells with actively replicating HIV-1. Collectively, this work demonstrates that nSMase2 is a critical regulator of HIV-1 replication and suggests that nSMase2 could be an important therapeutic target with the potential to kill HIV-1-infected cells.

Exosomes as Novel Diagnostic Biomarkers and Therapeutic Tools in Gliomas

Exosomes constitute small extracellular vesicles that contain lipids, proteins, nucleic acids, and glycoconjugates from the secreted cells and are capable of transmitting signals between cells and coordinating cellular communication. By this means, they are ultimately involved in physiology and disease, including development, homeostasis, and immune system regulation, as well as contributing to tumor progression and neurodegenerative diseases pathology. Recent studies have shown that gliomas secrete a panel of exosomes which have been associated with cell invasion and migration, tumor immune tolerance, potential for malignant transformation, neovascularization, and resistance to treatment. Exosomes have therefore emerged as intercellular communicators, which mediate the tumor-microenvironment interactions and exosome-regulated glioma cell stemness and angiogenesis. They may induce tumor proliferation and malignancy in normal cells by carrying pro-migratory modulators from cancer cells as well as many different molecular cancer modifiers, such as oncogenic transcripts, miRNAs, mutant oncoproteins, etc., which promote the communication of cancer cells with the surrounding stromal cells and provide valuable information on the molecular profile of the existing tumor. Moreover, engineered exosomes can provide an alternative system for drug delivery and enable efficient treatment. In the present review, we discuss the latest findings regarding the role of exosomes in glioma pathogenesis, their utility in non-invasive diagnosis, and potential applications to treatment.

Cell lipid droplet heterogeneity and altered biophysical properties induced by cell stress and metabolic imbalance

Lipid droplets (LD) are important regulators of lipid metabolism and are implicated in several diseases. However, the mechanisms underlying the roles of LD in cell pathophysiology remain elusive. Hence, new approaches that enable better characterization of LD are essential. This study establishes that Laurdan, a widely used fluorescent probe, can be used to label, quantify, and characterize changes in cell LD properties. Using lipid mixtures containing artificial LD we show that Laurdan GP depends on LD composition. Accordingly, enrichment in cholesterol esters (CE) shifts Laurdan GP from ~0.60 to ~0.70. Moreover, live-cell confocal microscopy shows that cells present multiple LD populations with distinctive biophysical features. The hydrophobicity and fraction of each LD population are cell type dependent and change differently in response to nutrient imbalance, cell density, and upon inhibition of LD biogenesis. The results show that cellular stress caused by increased cell density and nutrient overload increased the number of LD and their hydrophobicity and contributed to the formation of LD with very high GP values, likely enriched in CE. In contrast, nutrient deprivation was accompanied by decreased LD hydrophobicity and alterations in cell plasma membrane properties. In addition, we show that cancer cells present highly hydrophobic LD, compatible with a CE enrichment of these organelles. The distinct biophysical properties of LD contribute to the diversity of these organelles, suggesting that the specific alterations in their properties might be one of the mechanisms triggering LD pathophysiological actions and/or be related to the different mechanisms underlying LD metabolism.

Ellagic acid and its metabolites urolithins A/B ameliorate most common disease phenotypes in cellular and mouse models for lysosomal storage disorders by enhancing extracellular vesicle secretion

Niemann Pick diseases types A (NPDA) and C (NPDC) are lysosomal storage disorders (LSDs) leading to cognitive impairment, neurodegeneration, and early death. NPDA and NPDC have different genetic origins, being caused by mutations in the acid sphingomyelinase (ASM) or the cholesterol transport protein NPC1, respectively. However, they share a common pathological hallmark in the accumulation of lipids in the endolysosomal compartment. Here, we tested the hypothesis that polyphenols reduce lipid overload in NPD cells by enhancing the secretion of extracellular vesicles (ECVs). We show that among the polyphenols tested, the ellagic acid metabolites, urolithin A and B, were the safest and most efficient in increasing ECV secretion. They reduced levels of accumulating lipids and lysosomal size and permeabilization in cultured bone marrow-derived macrophages and neurons from ASMko and NPC1 mutant mice, which mimic NPDA and NPDC, respectively. Moreover, oral treatment with ellagic acid reduced lipid levels, ameliorated lysosomal alterations, and diminished microglia activation in the brain of NPD mice. These results support the therapeutic value of ECV secretion and polyphenols for NPDs, which may also help treat other LSDs characterized by intracellular lipid overload.

Exploring Pro-Inflammatory Immunological Mediators: Unraveling the Mechanisms of Neuroinflammation in Lysosomal Storage Diseases

Lysosomal storage diseases are a group of rare and ultra-rare genetic disorders caused by defects in specific genes that result in the accumulation of toxic substances in the lysosome. This excess accumulation of such cellular materials stimulates the activation of immune and neurological cells, leading to neuroinflammation and neurodegeneration in the central and peripheral nervous systems. Examples of lysosomal storage diseases include Gaucher, Fabry, Tay–Sachs, Sandhoff, and Wolman diseases. These diseases are characterized by the accumulation of various substrates, such as glucosylceramide, globotriaosylceramide, ganglioside GM2, sphingomyelin, ceramide, and triglycerides, in the affected cells. The resulting pro-inflammatory environment leads to the generation of pro-inflammatory cytokines, chemokines, growth factors, and several components of complement cascades, which contribute to the progressive neurodegeneration seen in these diseases. In this study, we provide an overview of the genetic defects associated with lysosomal storage diseases and their impact on the induction of neuro-immune inflammation. By understanding the underlying mechanisms behind these diseases, we aim to provide new insights into potential biomarkers and therapeutic targets for monitoring and managing the severity of these diseases. In conclusion, lysosomal storage diseases present a complex challenge for patients and clinicians, but this study offers a comprehensive overview of the impact of these diseases on the central and peripheral nervous systems and provides a foundation for further research into potential treatments.

The Intriguing Molecular Dynamics of Cer[EOS] in Rigid Skin Barrier Lipid Layers Requires Improvement of the Model

Omega-O-acyl ceramides such as 32-linoleoyloxydotriacontanoyl sphingosine (Cer[EOS]) are essential components of the lipid skin barrier, which protects our body from excessive water loss and the penetration of unwanted substances. These ceramides drive the lipid assembly to epidermal-specific long periodicity phase (LPP), structurally much different than conventional lipid bilayers. Here, we synthesized Cer[EOS] with selectively deuterated segments of the ultralong N-acyl chain or deuterated or ¹³C-labeled linoleic acid and studied their molecular behavior in a skin lipid model. Solid-state ²H NMR data revealed surprising molecular dynamics for the ultralong N-acyl chain of Cer[EOS] with increased isotropic motion towards the isotropic ester-bound linoleate. The sphingosine moiety of Cer[EOS] is also highly mobile at skin temperature, in stark contrast to the other LPP components, N-lignoceroyl sphingosine acyl, lignoceric acid and cholesterol, which are predominantly rigid. The dynamics of the linoleic chain is quantitatively described by distributions of correlation times and using dynamic detector analysis. These NMR results along with neutron diffraction data suggest an LPP structure with alternating fluid (sphingosine chain-rich), rigid (acyl chain-rich), isotropic (linoleate-rich), rigid (acyl-chain rich), and fluid layers (sphingosine chain-rich). Such an arrangement of the skin barrier lipids with rigid layers separated with two different dynamic "fillings" i) agrees well with ultrastructural data, ii) satisfies the need for simultaneous rigidity (to ensure low permeability) and fluidity (to ensure elasticity, accommodate enzymes or antimicrobial peptides), and iii) offers a straightforward way to remodel the lamellar body lipids into the final lipid barrier.

Structural diversity of photoswitchable sphingolipids for optodynamic control of lipid microdomains

Sphingolipids are a structurally diverse class of lipids predominantly found in the plasma membrane of eukaryotic cells. These lipids can laterally segregate with other rigid lipids and cholesterol into liquid-ordered domains that act as organizing centers within biomembranes. Owing the vital role of sphingolipids for lipid segregation, controlling their lateral organization is of utmost significance. Hence, we made use of the light-induced trans-cis isomerization of azobenzene-modified acyl chains to develop a set of photoswitchable sphingolipids with different headgroups (hydroxyl, galactosyl, phosphocholine) and backbones (sphingosine, phytosphingosine, tetrahydropyran-blocked sphingosine) that are able to shuttle between liquid-ordered and liquid-disordered regions of model membranes upon irradiation with UV-A (λ = 365 nm) and blue (λ = 470 nm) light, respectively. Using combined high-speed atomic force microscopy, fluorescence microscopy, and force spectroscopy, we investigated how these active sphingolipids laterally remodel supported bilayers upon photoisomerization, notably in terms of domain area changes, height mismatch, line tension, and membrane piercing. Hereby, we show that the sphingosine-based (Azo-β-Gal-Cer, Azo-SM, Azo-Cer) and phytosphingosine-based (Azo-α-Gal-PhCer, Azo-PhCer) photoswitchable lipids promote a reduction in liquid-ordered microdomain area when in the UV-adapted cis-isoform. In contrast, azo-sphingolipids having tetrahydropyran groups that block H-bonding at the sphingosine backbone (lipids named Azo-THP-SM, Azo-THP-Cer) induce an increase in the liquid-ordered domain area when in cis, accompanied by a major rise in height mismatch and line tension. These changes were fully reversible upon blue light-triggered isomerization of the various lipids back to trans, pinpointing the role of interfacial interactions for the formation of stable liquid-ordered domains.

Liquid Biopsies, Novel Approaches and Future Directions

Cancer is among the leading causes of death worldwide. Early diagnosis and prognosis are vital to improve patients' outcomes. The gold standard of tumor characterization leading to tumor diagnosis and prognosis is tissue biopsy. Amongst the constraints of tissue biopsy collection is the sampling frequency and the incomplete representation of the entire tumor bulk. Liquid biopsy approaches, including the analysis of circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), circulating miRNAs, and tumor-derived extracellular vesicles (EVs), as well as certain protein signatures that are released in the circulation from primary tumors and their metastatic sites, present a promising and more potent candidate for patient diagnosis and follow up monitoring. The minimally invasive nature of liquid biopsies, allowing frequent collection, can be used in the monitoring of therapy response in real time, allowing the development of novel approaches in the therapeutic management of cancer patients. In this review we will describe recent advances in the field of liquid biopsy markers focusing on their advantages and disadvantages.

Novel insights into the mechanisms of hard exudate in diabetic retinopathy: Findings of serum lipidomic and metabolomics profiling

Objective

Retinal hard exudates (HEs) result from lipoproteins leaking from capillaries into extracellular retinal space, and are related to decreased visual acuity in diabetic retinopathy (DR). This study aims to identify differential serum lipids and metabolites associated with HEs.

Materials and methods

A cross-sectional study was conducted Jul 2017 ∼ Mar 2021. We assessed the amount of HEs using standard ETDRS photographs for comparison. HEs severity was rated as "no or questionable", "moderate" or "severe". Serum samples were processed via high coverage pseudotargeted lipidomics analysis, and untargeted liquid chromatography coupled with time-of-flight mass spectrometry for metabolomics study, respectively. Weighted gene co-expression network analyses, partial least squares-discriminant analysis, and multi-receiver operating characteristic analysis were applied.

Results

A total of 167 patients were included. Discovery group: 116 eyes (116 patients). Validation group: 51 eyes (51 patients). 888 lipids were detected and divided into 18 modules (MEs), ME1 ∼ ME18. Lipids in ME1 significantly increased in patients with HEs in DR (NPDR and PDR combined), NPDR, and PDR, respectively. ME1 enriched to triglycerides (29%), ceramides (17%), and N-acylethanolamines (15%). A combined model of 20 lipids was the best to discriminate HEs, area under curve = 0.804, 95% confidence interval = 0.674-0.916. For metabolomics analysis, 19 metabolites and 13 pathways associated with HEs were identified. Taurine and hypotaurine metabolism, cysteine and methionine metabolism were closely related to HEs (P < 0.01).

Conclusions

The lipids and metabolites identified may serve as prediction biomarkers in the early stage of HEs in DR.

Sphingolipids in neurodegenerative diseases

Neurodegenerative Diseases (NDDs) are a group of disorders that cause progressive deficits of neuronal function. Recent evidence argues that sphingolipid metabolism is affected in a surprisingly broad set of NDDs. These include some lysosomal storage diseases (LSDs), hereditary sensory and autonomous neuropathy (HSAN), hereditary spastic paraplegia (HSP), infantile neuroaxonal dystrophy (INAD), Friedreich's ataxia (FRDA), as well as some forms of amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD). Many of these diseases have been modeled in Drosophila melanogaster and are associated with elevated levels of ceramides. Similar changes have also been reported in vertebrate cells and mouse models. Here, we summarize studies using fly models and/or patient samples which demonstrate the nature of the defects in sphingolipid metabolism, the organelles that are implicated, the cell types that are initially affected, and potential therapeutics for these diseases.

Biochemistry of exosomes and their theranostic potential in human diseases

Exosomes are classified as special extracellular vesicles in the eukaryotic system having diameters ranging from 30 to 120 nm. These vesicles carry various endogenous molecules including DNA, mRNA, microRNA, circular RNA, and proteins, crucial for numerous metabolic reactions and can be proposed as therapeutic or diagnostic targets for several disorders. The donor exosomes release their content to recipient cells and further establish the significant intercellular communication showing biological effects by triggering environmental alterations. Exosomes derived from mesenchymal and dendritic cells have demonstrated their therapeutic potential against organ injury. Yet, various intricacies are involved in exosomal transport and its inclusion in cancer and other disease pathogenesis needs to be explored. The exosomes represent profound potential as diagnostic biomarkers and therapeutic carriers in various pathophysiological conditions such as neurodegenerative diseases, chronic cancers, infectious diseases, female reproductive diseases and cardiovascular diseases. In the current study, we demonstrate the advancements in the implication of exosomes as one of the irrefutable prognostic biological targets in human health and diseases.

Targeted Lipidomics and Inflammation Response to Six Weeks of Sprint Interval Training in Male Adolescents

Lipids play an important role in coordinating and regulating metabolic and inflammatory processes. Sprint interval training (SIT) is widely used to improve sports performance and health outcomes, but the current understanding of SIT-induced lipid metabolism and the corresponding systemic inflammatory status modification remains controversial and limited, especially in male adolescents. To answer these questions, twelve untrained male adolescents were recruited and underwent 6 weeks of SIT. The pre- and post-training testing included analyses of peak oxygen consumption (VO2peak), biometric data (weight and body composition), serum biochemical parameters (fasting blood glucose, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triacylglycerol, testosterone, and cortisol), inflammatory markers, and targeted lipidomics. After the 6-week SIT, the serum C-reactive protein (CRP), interleukin (IL)-1β, IL-2, IL-4, IL-10, tumor necrosis factor (TNF)-α, and transforming growth factor (TGF)-β significantly decreased (p < 0.05), whereas IL-6 and IL-10/TNF-α significantly increased (p < 0.05). In addition, the targeted lipidomics revealed changes in 296 lipids, of which 33 changed significantly (p < 0.05, fold change > 1.2 or <1/1.2). The correlation analysis revealed that the changes in the inflammatory markers were closely correlated with the changes in some of the lipids, such as LPC, HexCer, and FFA. In conclusion, the 6-week SIT induced significant changes in the inflammatory markers and circulating lipid composition, offering health benefits to the population.

Phospholipases and Membrane Curvature: What Is Happening at the Surface?

In this revision work, we emphasize the close relationship between the action of phospholipases and the modulation of membrane curvature and curvature stress resulting from this activity. The alteration of the tridimensional structure of membranes upon the action of phospholipases is analyzed based on studies on model lipid membranes. The transient unbalance of both compositional and physical membrane properties between the hemilayers upon phospholipase activity lead to curvature tension and the catalysis of several membrane-related processes. Several proteins' membrane-bound and soluble forms are susceptible to regulation by the curvature stress induced by phospholipase action, which has important consequences in cell signaling. Additionally, the modulation of membrane fusion by phospholipase products regulates membrane dynamics in several cellular scenarios. We commented on vesicle fusion in the Golgi-endoplasmic system, synaptic vesicle fusion to the plasma membrane, viral membrane fusion to host cell plasma membrane and gametes membrane fusion upon acrosomal reaction. Furthermore, we explored the modulation of membrane fusion by the asymmetric adsorption of amphiphilic drugs. A deep understanding of the relevance of lipid membrane structure, particularly membrane curvature and curvature stress, on different cellular events leads to the challenge of its regulation, which may become a powerful tool for pharmacological therapy.

The interaction of CD300lf and ceramide reduces the development of periodontitis by inhibiting osteoclast differentiation

AIM

The regulation of osteoclasts (OCs) by inhibitory immunoreceptors maintains bone homeostasis and is considered an important determinant of the extent of periodontal pathology. The aim of this study was to investigate the role of the inhibitory immunoreceptor CD300lf and its ligand ceramide in osteoclastogenesis in periodontitis.

MATERIALS AND METHODS

The expression of CD300lf was measured in vitro and in a ligature-induced periodontitis model. The effect of CD300lf ablation on osteoclastogenesis was examined in ligature-retained and ligature removal periodontitis models. The effect of ceramide, the ligand of CD300lf, was examined in osteoclastogenesis in vitro and in vivo by smearing 20 μg of ceramide dissolved in carboxymethylcellulose on teeth and gingiva every other day in an experimental periodontitis model and ligature removal model.

RESULTS

CD300lf expression was downregulated during osteoclastogenesis. Ablation of CD300lf in the ligature-induced periodontitis model increased the number of OCs and exacerbated bone damage. Bone resorption caused by CD300lf ablation was reversible following ligature removal. CD300lf-ceramide binding suppressed osteoclastogenesis in vitro and inhibited alveolar bone loss in a mouse periodontitis model.

CONCLUSIONS

Our findings reveal that CD300lf-ceramide binding plays a critical negative role in alveolar bone loss in periodontitis by inhibiting OCs differentiation.