Sphingosine kinase: Role in regulation of bioactive sphingolipid mediators in inflammation

Plantaginis semen ameliorates diabetic kidney disease via targeting the sphingosine kinase 1/sphingosine-1-phosphate pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Plantaginis Semen (PS) is widely utilized as a common herb in several Asian countries, particularly China, due to its diuretic, anti-hypertensive, anti-hyperlipidemic, and anti-hyperglycemic properties. Furthermore, it is acknowledged for its ability to mitigate renal complications associated with metabolic syndrome. Despite its extensive usage, there is limited systematic literature elucidating its therapeutic mechanisms, thus emphasizing the necessity for comprehensive investigations in this field.

AIM

This study aims to comprehensively evaluate the therapeutical potential of PS in treating diabetic kidney disease (DKD) and to elucidate the underlying mechanisms through in vivo and in vitro models.

METHODS

The main composition of PS were characterized using the UPLC-QTOF-MS method. For the in vivo investigation, a mouse model mediated by streptozocin (STZ) associated with a high-fat diet (HFD) and unilateral renal excision was established. The mice were split into 6 groups (n = 8): control group (CON group), DKD group, low-dose of Plantago asiatica L. seed extract group (PASE-L group, 3 g/kg/d), medium-dose of PASE group (PASE-M, 6 g/kg/d), high-dose of PASE group (PASE-H, 9 g/kg/d), and positive drug group (valsartan, VAS group, 12 mg/kg/d). After 8 weeks of treatment, the damage induced by DKD was evaluated by using relevant parameters of urine and blood. Furthermore, indicators of inflammation and factors associated with the SphK1-S1P signaling pathway were investigated. For the in vitro study, the cell line HBZY-1 was stimulated by high glucose (HG), they were then co-cultured with different concentrations of PASE, and the corresponding associated inflammatory and sphingosine kinase 1/sphingosine-1-phosphate (SphK1-S1P) factors were examined.

RESULTS

A total of 59 major components in PS were identified, including flavonoids, iridoids, phenylethanol glycosides, guanidine derivatives, and fatty acids. In the mouse model, PS was found to significantly improve body weight, decrease fasting blood glucose (FBG) levels, increased glucose tolerance and insulin tolerance, improved kidney-related markers compared to the DKD group, pathological changes in the kidneys also improved dramatically. These effects showed a dose-dependent relationship, with higher PASE concentrations yielding significantly better outcomes than lower concentrations. However, the effects of the low PASE concentration were not evident for some indicators. In the cellular model, the high dose of PASE suppressed high glucose (HG) stimulated renal mesangial cell proliferation, suppressed inflammatory factors and NF-κB, and decreased the levels of fibrillin-1(FN-1) and collagen IV(ColIV).

CONCLUSION

Our results indicate that PS exerts favorable therapeutic effects on DKD, with the possible mechanisms including the inhibition of inflammatory pathways, suppression of mRNA levels and protein expressions of SphK1 and S1P, consequently leading to reduced overexpression of FN-1 and ColIV, thereby warranting further exploration.

Sphingosine-1-phosphate signalling in the heart: exploring emerging perspectives in cardiopathology

Cardiometabolic disorders contribute to the global burden of cardiovascular diseases. Emerging sphingolipid metabolites like sphingosine-1-phosphate (S1P) and its receptors, S1PRs, present a dynamic signalling axis significantly impacting cardiac homeostasis. S1P's intricate mechanisms extend to its transportation in the bloodstream by two specific carriers: high-density lipoprotein particles and albumin. This intricate transport system ensures the accessibility of S1P to distant target tissues, influencing several physiological processes critical for cardiovascular health. This review delves into the diverse functions of S1P and S1PRs in both physiological and pathophysiological conditions of the heart. Emphasis is placed on their diverse roles in modulating cardiac health, spanning from cardiac contractility, angiogenesis, inflammation, atherosclerosis and myocardial infarction. The intricate interplays involving S1P and its receptors are analysed concerning different cardiac cell types, shedding light on their respective roles in different heart diseases. We also review the therapeutic applications of targeting S1P/S1PRs in cardiac diseases, considering existing drugs like Fingolimod, as well as the prospects and challenges in developing novel therapies that selectively modulate S1PRs.

Opaganib Downregulates N-Myc Expression and Suppresses In Vitro and In Vivo Growth of Neuroblastoma Cells

Neuroblastoma (NB), the most common cancer in infants and the most common solid tumor outside the brain in children, grows aggressively and responds poorly to current therapies. We have identified a new drug (opaganib, also known as ABC294640) that modulates sphingolipid metabolism by inhibiting the synthesis of sphingosine 1-phosphate (S1P) by sphingosine kinase-2 and elevating dihydroceramides by inhibition of dihydroceramide desaturase. The present studies sought to determine the potential therapeutic activity of opaganib in cell culture and xenograft models of NB. Cytotoxicity assays demonstrated that NB cells, including cells with amplified MYCN, are effectively killed by opaganib concentrations well below those that accumulate in tumors in vivo. Opaganib was shown to cause dose-dependent decreases in S1P and hexosylceramide levels in Neuro-2a cells, while concurrently elevating levels of dihydroceramides. As with other tumor cells, opaganib reduced c-Myc and Mcl-1 protein levels in Neuro-2a cells, and also reduced the expression of the N-Myc protein. The in vivo growth of xenografts of human SK-N-(BE)2 cells with amplified MYCN was suppressed by oral administration of opaganib at doses that are well tolerated in mice. Combining opaganib with temozolomide plus irinotecan, considered the backbone for therapy of relapsed or refractory NB, resulted in increased antitumor activity in vivo compared with temozolomide plus irinotecan or opaganib alone. Mice did not lose additional weight when opaganib was combined with temozolomide plus irinotecan, indicating that the combination is well tolerated. Opaganib has additive antitumor activity toward Neuro-2a tumors when combined with the checkpoint inhibitor anti-CTLA-4 antibody; however, the combination of opaganib with anti-PD-1 or anti-PD-L1 antibodies did not provide increased antitumor activity over that seen with opaganib alone. Overall, the data demonstrate that opaganib modulates sphingolipid metabolism and intracellular signaling in NB cells and inhibits NB tumor growth alone and in combination with other anticancer drugs. Amplified MYCN does not confer resistance to opaganib, and, in fact, the drug attenuates the expression of both c-Myc and N-Myc. The safety of opaganib has been established in clinical trials with adults with advanced cancer or severe COVID-19, and so opaganib has excellent potential for treating patients with NB, particularly in combination with temozolomide and irinotecan or anti-CTLA-4 antibody.

Signaling controversy and future therapeutical perspectives of targeting sphingolipid network in cancer immune editing and resistance to tumor necrosis factor-α immunotherapy

Anticancer immune surveillance and immunotherapies trigger activation of cytotoxic cytokine signaling, including tumor necrosis factor-α (TNF-α) and TNF-related apoptosis-inducing ligand (TRAIL) pathways. The pro-inflammatory cytokine TNF-α may be secreted by stromal cells, tumor-associated macrophages, and by cancer cells, indicating a prominent role in the tumor microenvironment (TME). However, tumors manage to adapt, escape immune surveillance, and ultimately develop resistance to the cytotoxic effects of TNF-α. The mechanisms by which cancer cells evade host immunity is a central topic of current cancer research. Resistance to TNF-α is mediated by diverse molecular mechanisms, such as mutation or downregulation of TNF/TRAIL receptors, as well as activation of anti-apoptotic enzymes and transcription factors. TNF-α signaling is also mediated by sphingosine kinases (SphK1 and SphK2), which are responsible for synthesis of the growth-stimulating phospholipid, sphingosine-1-phosphate (S1P). Multiple studies have demonstrated the crucial role of S1P and its transmembrane receptors (S1PR) in both the regulation of inflammatory responses and progression of cancer. Considering that the SphK/S1P/S1PR axis mediates cancer resistance, this sphingolipid signaling pathway is of mechanistic significance when considering immunotherapy-resistant malignancies. However, the exact mechanism by which sphingolipids contribute to the evasion of immune surveillance and abrogation of TNF-α-induced apoptosis remains largely unclear. This study reviews mechanisms of TNF-α-resistance in cancer cells, with emphasis on the pro-survival and immunomodulatory effects of sphingolipids. Inhibition of SphK/S1P-linked pro-survival branch may facilitate reactivation of the pro-apoptotic TNF superfamily effects, although the role of SphK/S1P inhibitors in the regulation of the TME and lymphocyte trafficking should be thoroughly assessed in future studies.

Lipid metabolism-related genes are involved in the occurrence of asthma and regulate the immune microenvironment

BACKGROUND

Lipid metabolism plays a pivotal role in asthma pathogenesis. However, a comprehensive analysis of the importance of lipid metabolism-related genes (LMRGs) in regulating the immune microenvironment in asthma remains lacking. The transcriptome matrix was downloaded from the Gene Expression Omnibus (GEO) dataset. Differentially expressed analysis and weighted gene coexpression network analysis (WGCNA) were conducted on the GSE74986 dataset to select hub LMRGs, and gene set enrichment analysis (GSEA) was conducted to explore their biological functions. The CIBERSORT algorithm was used to determine immune infiltration in the asthma and control groups, and the correlation of diagnostic biomarkers and immune cells was performed via Spearman correlation analysis. Subsequently, a competitive endogenous RNA (ceRNA) network was constructed to investigate the hidden molecular mechanism of asthma. The expression levels of the hub genes were further validated in the GSE143192 dataset, and RT‒qPCR and immunofluorescence were performed to verify the reliability of the results in the OVA asthma model. Lastly, the ceRNA network was confirmed by qRT-PCR and RNAi experiments in the characteristic cytokine (IL-13)-induced asthma cellular model.

RESULTS

ASAH1, ACER3 and SGPP1 were identified as hub LMRGs and were mainly involved in protein secretion, mTORC1 signaling, and fatty acid metabolism. We found more infiltration of CD8+ T cells, activated NK cells, and monocytes and less M0 macrophage infiltration in the asthma group than in the healthy control group. In addition, ASAH1, ACER3, and SGPP1 were negatively correlated with CD8+ T cells and activated NK cells, but positively correlated with M0 macrophages. Within the ceRNA network, SNHG9-hsa-miR-615-3p-ACER3, hsa-miR-212-5p and hsa-miR-5682 may play crucial roles in asthma pathogenesis. The low expression of ASAH1 and SGPP1 in asthma was also validated in the GSE74075 dataset. After SNHG9 knockdown, miR-615-3p expression was significantly upregulated, while that of ACER3 was significantly downregulated.

CONCLUSION

ASAH1, ACER3 and SGPP1 might be diagnostic biomarkers for asthma, and are associated with increased immune system activation. In addition, SNHG9-hsa-miR-615-3p-ACER3 may be viewed as effective therapeutic targets for asthma. Our findings might provide a novel perspective for future research on asthma.

Integrative roles of sphingosine kinase in liver pathophysiology

Bioactive sphingolipids and enzymes that metabolize sphingolipid-related substances have been considered as critical messengers in various signaling pathways. One such enzyme is the crucial lipid kinase, sphingosine kinase (SphK), which mediates the conversion of sphingosine to the potent signaling substance, sphingosine-1-phosphate. Several studies have demonstrated that SphK metabolism is strictly regulated to maintain the homeostatic balance of cells. Here, we summarize the role of SphK in the course of liver disease and illustrate its effects on both physiological and pathological conditions of the liver. SphK has been implicated in a variety of liver diseases, such as steatosis, liver fibrosis, hepatocellular carcinoma, and hepatic failure. This study may advance the understanding of the cellular and molecular foundations of liver disease and establish therapeutic approaches via SphK modulation.

Assessment of Toxoplasma gondii lytic cycle and the impact of a gene deletion using 3D label-free optical diffraction holotomography

Toxoplasma gondii is a widespread single-celled intracellular eukaryotic apicomplexan protozoan parasite primarily associated with mammalian foetal impairment and miscarriage, including in humans. Is estimated that approximately one third of the human population worldwide is infected by this parasite. Here we used cutting-edge, label-free 3D quantitative optical diffraction holotomography to capture and evaluate the Toxoplasma lytic cycle (invasion, proliferation and egress) in real-time based on the refractive index distribution. In addition, we used this technology to analyse an engineered CRISPR-Cas9 Toxoplasma mutant to reveal differences in cellular physical properties when compared to the parental line. Collectively, these data support the use of holotomography as a powerful tool for the study of protozoan parasites and their interactions with their host cells.

Lipidomic profiling of the Brazilian yellow scorpion venom: new insights into inflammatory responses following Tityus serrulatus envenomation

Due to the high prevalence and clinical relevance, scorpionism is a critical public health issue in several Brazilian regions. Tityus serrulatus, commonly known as the Brazilian yellow scorpion, is the most venomous genus found in Brazilian fauna and associated with severe clinical manifestations such as localized pain, hypertension, sweating, tachycardia and complex hyperinflammatory responses. In general, T. serrulatus venom contains a complex mixture of active compounds, including proteins, peptides, and amino acids. Although knowledge of the protein fractions of scorpion venom is available, venom lipid components are not yet comprehensively known. The aim of the present study was to determine and characterize the lipid constituents/profile of the T. serratus venom utilizing liquid chromatography coupled with high-resolution mass spectrometry. Lipid species (164 in total) belonging to 3 different lipid categories, glycerophospholipids, sphingolipids, and glycerolipids, were identified. A further search on MetaCore/MetaDrug platform, which is based upon a manually curated database of molecular interactions, molecular pathways, gene-disease associations, chemical metabolism, and toxicity information, exhibited several metabolic pathways for 24 of previously identified lipid species, including activation of nuclear factor kappa B and oxidative stress pathways. Further several bioactive compounds, such as plasmalogens, lyso-platelet-activating factors, and sphingomyelins, associated with systemic responses triggered by T. serrulatus envenomation were detected. Finally, lipidomic data presented provide advanced and valuable information to better comprehend the mechanisms underlying the complex pathophysiology induced by T. serrulatus envenomation.

The Regulation of Neutrophil Migration in Patients with Sepsis: The Complexity of the Molecular Mechanisms and Their Modulation in Sepsis and the Heterogeneity of Sepsis Patients

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Common causes include gram-negative and gram-positive bacteria as well as fungi. Neutrophils are among the first cells to arrive at an infection site where they function as important effector cells of the innate immune system and as regulators of the host immune response. The regulation of neutrophil migration is therefore important both for the infection-directed host response and for the development of organ dysfunctions in sepsis. Downregulation of CXCR4/CXCL12 stimulates neutrophil migration from the bone marrow. This is followed by transmigration/extravasation across the endothelial cell barrier at the infection site; this process is directed by adhesion molecules and various chemotactic gradients created by chemotactic cytokines, lipid mediators, bacterial peptides, and peptides from damaged cells. These mechanisms of neutrophil migration are modulated by sepsis, leading to reduced neutrophil migration and even reversed migration that contributes to distant organ failure. The sepsis-induced modulation seems to differ between neutrophil subsets. Furthermore, sepsis patients should be regarded as heterogeneous because neutrophil migration will possibly be further modulated by the infecting microorganisms, antimicrobial treatment, patient age/frailty/sex, other diseases (e.g., hematological malignancies and stem cell transplantation), and the metabolic status. The present review describes molecular mechanisms involved in the regulation of neutrophil migration; how these mechanisms are altered during sepsis; and how bacteria/fungi, antimicrobial treatment, and aging/frailty/comorbidity influence the regulation of neutrophil migration.

Neuroinflammation, Energy and Sphingolipid Metabolism Biomarkers Are Revealed by Metabolic Modeling of Autistic Brains

Autism spectrum disorders (ASD) are a heterogeneous group of neurodevelopmental disorders generally characterized by repetitive behaviors and difficulties in communication and social behavior. Despite its heterogeneous nature, several metabolic dysregulations are prevalent in individuals with ASD. This work aims to understand ASD brain metabolism by constructing an ASD-specific prefrontal cortex genome-scale metabolic model (GEM) using transcriptomics data to decipher novel neuroinflammatory biomarkers. The healthy and ASD-specific models are compared via uniform sampling to identify ASD-exclusive metabolic features. Noticeably, the results of our simulations and those found in the literature are comparable, supporting the accuracy of our reconstructed ASD model. We identified that several oxidative stress, mitochondrial dysfunction, and inflammatory markers are elevated in ASD. While oxidative phosphorylation fluxes were similar for healthy and ASD-specific models, and the fluxes through the pathway were nearly undisturbed, the tricarboxylic acid (TCA) fluxes indicated disruptions in the pathway. Similarly, the secretions of mitochondrial dysfunction markers such as pyruvate are found to be higher, as well as the activities of oxidative stress marker enzymes like alanine and aspartate aminotransferases (ALT and AST) and glutathione-disulfide reductase (GSR). We also detected abnormalities in the sphingolipid metabolism, which has been implicated in many inflammatory and immune processes, but its relationship with ASD has not been thoroughly explored in the existing literature. We suggest that important sphingolipid metabolites, such as sphingosine-1-phosphate (S1P), ceramide, and glucosylceramide, may be promising biomarkers for the diagnosis of ASD and provide an opportunity for the adoption of early intervention for young children.

Phase I study of opaganib, an oral sphingosine kinase 2-specific inhibitor, in relapsed and/or refractory multiple myeloma

Multiple myeloma (MM) remains an incurable disease and there is an unmet medical need for novel therapeutic drugs that do not share similar mechanisms of action with currently available agents. Sphingosine kinase 2 (SK2) is an innovative molecular target for anticancer therapy. We previously reported that treatment with SK2 inhibitor opaganib inhibited myeloma tumor growth in vitro and in vivo in a mouse xenograft model. In the current study, we performed a phase I study of opaganib in patients with relapsed/refractory multiple myeloma (RRMM). Thirteen patients with RRMM previously treated with immunomodulatory agents and proteasome inhibitors were enrolled and treated with single-agent opaganib at three oral dosing regimens (250 mg BID, 500 mg BID, or 750 mg BID, 28 days as a cycle). Safety and maximal tolerated dose (MTD) were determined. Pharmacokinetics, pharmacodynamics, and correlative studies were also performed. Opaganib was well tolerated up to a dose of 750 mg BID. The most common possibly related adverse event (AE) was decreased neutrophil counts. There were no serious AEs considered to be related to opaganib. MTD was determined as at least 750 mg BID. On an intent-to-treat basis, one patient (7.7%) in the 500 mg BID dose cohort showed a very good partial response, and one other patient (7.7%) achieved stable disease for 3 months. SK2 is an innovative molecular target for antimyeloma therapy. The first-in-class SK2 inhibitor opaganib is generally safe for administration to RRMM patients, and has potential therapeutic activity in these patients. Clinicaltrials.gov: NCT02757326.

Lamiophlomis rotata attenuates rheumatoid arthritis by regulating sphingolipid and steroid hormone metabolism

Rheumatoid arthritis (RA) is a chronic and progressive autoimmune disease. Lamiophlomis rotata (L. rotata) (Benth.) Kudo, an essential medicinal plant in traditional Tibetan medicine, is useful in treating RA. The purpose of this study was to evaluate L. rotata's anti-RA effect and to analyze its serum metabolites and lipids to predict the possible action pathways. Female and male rats were immunized with CFA to induce arthritis. Paw volumes were measured, and arthritis index analysis and histological analysis were performed to check the effects of L. rotata. ELISA was used to measure the levels of inflammatory cytokines (IL-1β, TNF-α, IL-6, and IL-10) and oxidative stress (MDA, SOD, GSH, and CAT). UPLC/Q-Orbitrap-MS was used to identify untargeted metabolites and lipids in serum. Metabolite validation was performed using UPLC/QQQ-MS. L. rotata application significantly reduced arthritis indices and paw swelling in AIA rats, and diminished inflammation and bone fractures in joint tissues. Sphingolipid (SP) and steroid hormone biosynthesis was found to be closely related to L. rotata's intervention in RA. In addition, our experiments also confirmed that females were more likely than males to develop RA. These findings provide clues and a scientific basis for the mechanism of L. rotata in treating RA.

Sphingosine 1-Phosphate as Essential Signaling Molecule in Inflammatory Skin Diseases

Sphingolipids are crucial molecules of the mammalian epidermis. The formation of skin-specific ceramides contributes to the formation of lipid lamellae, which are important for the protection of the epidermis from excessive water loss and protect the skin from the invasion of pathogens and the penetration of xenobiotics. In addition to being structural constituents of the epidermal layer, sphingolipids are also key signaling molecules that participate in the regulation of epidermal cells and the immune cells of the skin. While the importance of ceramides with regard to the proliferation and differentiation of skin cells has been known for a long time, it has emerged in recent years that the sphingolipid sphingosine 1-phosphate (S1P) is also involved in processes such as the proliferation and differentiation of keratinocytes. In addition, the immunomodulatory role of this sphingolipid species is becoming increasingly apparent. This is significant as S1P mediates a variety of its actions via G-protein coupled receptors. It is, therefore, not surprising that dysregulation in the signaling pathways of S1P is involved in the pathophysiological conditions of skin diseases. In the present review, the importance of S1P in skin cells, as well as the immune cells of the skin, is elaborated. In particular, the role of the molecule in inflammatory skin diseases will be discussed. This is important because interfering with S1P signaling pathways may represent an innovative option for the treatment of inflammatory skin diseases.

Genetic Tools for Studying the Roles of Sphingolipids in Viral Infections

Sphingolipids are a critical family of membrane lipids with diverse functions in eukaryotic cells, and a growing body of literature supports that these lipids play essential roles during the lifecycles of viruses. While small molecule inhibitors of sphingolipid synthesis and metabolism are widely used, the advent of CRISPR-based genomic editing techniques allows for nuanced exploration into the manners in which sphingolipids influence various stages of viral infections. Here we describe some of these critical considerations needed in designing studies utilizing genomic editing techniques for manipulating the sphingolipid metabolic pathway, as well as the current body of literature regarding how viruses depend on the products of this pathway. Here, we highlight the ways in which sphingolipids affect viruses as these pathogens interact with and influence their host cell and describe some of the many open questions remaining in the field.

Metabolomic transition trajectory and potential mechanisms of N-nitrosomethylbenzylamine induced esophageal squamous cell carcinoma in rats

Esophageal squamous cell carcinoma (ESCC) is an environment-relevant malignancy with a high mortality. Nitrosamines, a class of nitrogen-containing environmental carcinogens, are widely suggested as a risk factor for ESCC. However, how nitrosamines affect metabolic regulation to promote ESCC tumorigenesis is largely unknown. In this study, the transition trajectory of serum metabolism in the course of ESCC induced by N-nitrosomethylbenzylamine (NMBA) in rats was depicted by an untargeted metabolomic analysis, and the potential molecular mechanisms were revealed. The results showed that the metabolic alteration in rats was slight at the basal cell hyperplasia (BCH) stage, while it became apparent when the esophageal lesion developed into dysplasia (DYS) or more serious conditions. Moreover, serum metabolism of severe dysplasia (S-DYS) showed more similar characteristics to that of carcinoma in situ (CIS) and invasive cancer (IC). Aberrant nicotinate (NA) and nicotinamide (NAM) metabolism, tryptophan (TRP) metabolism, and sphingolipid metabolism could be the key players favoring the malignant transformation of esophageal epithelium induced by NMBA. More particularly, NA and NAM metabolism in the precancerous stages and TRP metabolism in the cancerous stages were demonstrated to replenish NAD⁺ in different patterns. Furthermore, both the IDO1-KYN-AHR axis mediated by TRP metabolism and the SPHK1-S1P-S1PR1 axis by sphingolipid metabolism provided an impetus to create the pro-inflammatory yet immune-suppressive microenvironment to facilitate the esophageal tumorigenesis and progression. Together, these suggested that NMBA exerted its carcinogenicity via more than one pathway, which may act together to produce combination effects. Targeting these pathways may open up the possibility to attenuate NMBA-induced esophageal carcinogenesis. However, the interconnection between different metabolic pathways needs to be specified further. And the integrative and multi-level systematic research will be conducive to fully understanding the mechanisms of NMBA-induced ESCC.

Host-microbial co-metabolites modulated by human milk oligosaccharides relate to reduced risk of respiratory tract infections

Human milk oligosaccharides (HMOs) are structurally diverse oligosaccharides present in breast milk, supporting the development of the gut microbiota and immune system. Previously, 2-HMO (2'fucosyllactose, lacto-N-neotetraose) compared to control formula feeding was associated with reduced risk of lower respiratory tract infections (LRTIs), in part linked to lower acetate and higher bifidobacteria proportions. Here, our objective was to gain further insight into additional molecular pathways linking the 2-HMO formula feeding and LRTI mitigation. From the same trial, we measured the microbiota composition and 743 known biochemical species in infant stool at 3 months of age using shotgun metagenomic sequencing and untargeted mass spectrometry metabolomics. We used multivariate analysis to identify biochemicals associated to 2-HMO formula feeding and LRTI and integrated those findings with the microbiota compositional data. Three molecular pathways stood out: increased gamma-glutamylation and N-acetylation of amino acids and decreased inflammatory signaling lipids. Integration of stool metagenomic data revealed some Bifidobacterium and Bacteroides species to be implicated. These findings deepen our understanding of the infant gut/microbiome co-metabolism in early life and provide evidence for how such metabolic changes may influence immune competence at distant mucosal sites such as the airways.

Skin fibroblast metabolomic profiling reveals that lipid dysfunction predicts the severity of Friedreich's ataxia

Friedreich's ataxia (FRDA) is an autosomal recessive neurodegenerative disorder caused by a triplet guanine-adenine-adenine (GAA) repeat expansion in intron 1 of the FXN gene, which leads to decreased levels of the frataxin protein. Frataxin is involved in the formation of iron-sulfur (Fe-S) cluster prosthetic groups for various metabolic enzymes. To provide a better understanding of the metabolic status of patients with FRDA, here we used patient-derived fibroblast cells as a surrogate tissue for metabolic and lipidomic profiling by liquid chromatography-high resolution mass spectrometry. We found elevated HMG-CoA and β-hydroxybutyrate-CoA levels, implying dysregulated fatty acid oxidation, which was further demonstrated by elevated acyl-carnitine levels. Lipidomic profiling identified dysregulated levels of several lipid classes in FRDA fibroblast cells when compared with non-FRDA fibroblast cells. For example, levels of several ceramides were significantly increased in FRDA fibroblast cells; these results positively correlated with the GAA repeat length and negatively correlated with the frataxin protein levels. Furthermore, stable isotope tracing experiments indicated increased ceramide synthesis, especially for long-chain fatty acid-ceramides, in FRDA fibroblast cells compared with ceramide synthesis in healthy control fibroblast cells. In addition, PUFA-containing triglycerides and phosphatidylglycerols were enriched in FRDA fibroblast cells and negatively correlated with frataxin levels, suggesting lipid remodeling as a result of FXN deficiency. Altogether, we demonstrate patient-derived fibroblast cells exhibited dysregulated metabolic capabilities, and their lipid dysfunction predicted the severity of FRDA, making them a useful surrogate to study the metabolic status in FRDA.

Sphingosine-1-Phosphate (S1P) and S1P Signaling Pathway Modulators, from Current Insights to Future Perspectives

Sphingosine-1-phosphate (S1P) and S1P receptors (S1PR) are bioactive lipid molecules that are ubiquitously expressed in the human body and play an important role in the immune system. S1P-S1PR signaling has been well characterized in immune trafficking and activation in both innate and adaptive immune systems. Despite this knowledge, the full scope in the pathogenesis of autoimmune disorders is not well characterized yet. From the discovery of fingolimod, the first S1P modulator, until siponimod, the new molecule recently approved for the treatment of secondary progressive multiple sclerosis (SPMS), there has been a great advance in understanding the S1P functions and their involvement in immune diseases, including multiple sclerosis (MS). Modulation on S1P is an interesting target for the treatment of various autoimmune disorders. Improved understanding of the mechanism of action of fingolimod has allowed the development of the more selective second-generation S1PR modulators. Subtype 1 of the S1PR (S1PR1) is expressed on the cell surface of lymphocytes, which are known to play a major role in MS pathogenesis. The understanding of S1PR1’s role facilitated the development of pharmacological strategies directed to this target, and theoretically reduced the safety concerns derived from the use of fingolimod. A great advance in the MS treatment was achieved in March 2019 when the Food and Drug Association (FDA) approved Siponimod, for both active secondary progressive MS and relapsing–remitting MS. Siponimod became the first oral disease modifying therapy (DMT) specifically approved for active forms of secondary progressive MS. Additionally, for the treatment of relapsing forms of MS, ozanimod was approved by FDA in March 2020. Currently, there are ongoing trials focused on other new-generation S1PR1 modulators. This review approaches the fundamental aspects of the sphingosine phosphate modulators and their main similarities and differences.

Sphingosine-1-phosphate: metabolism, transport, atheroprotection and effect of statin treatment

PURPOSE OF REVIEW

To better define the metabolism of sphingosine-1-phosphate (S1P), its transport in plasma and its interactions with S1P receptors on vascular cells, and to evaluate the effect of statin treatment on the subnormal plasma levels of high-density lipoprotein (HDL)-bound S1P characteristic of the atherogenic dyslipidemia of metabolic syndrome (MetS).

RECENT FINDINGS

Neither clinical intervention trials targeted to raising high-density lipoprotein-cholesterol (HDL-C) levels nor human genome-wide association studies (GWAS) studies have provided evidence to support an atheroprotective role of HDL. Recently however a large monogenic univariable Mendelian randomization on the N396S mutation in the gene encoding endothelial lipase revealed a causal protective effect of elevated HDL-C on coronary artery disease conferred by reduced enzyme activity. Given the complexity of the HDL lipidome and proteome, components of HDL other than cholesterol may in all likelihood contribute to such a protective effect. Among HDL lipids, S1P is a bioactive sphingolipid present in a small proportion of HDL particles (about 5%); indeed, S1P is preferentially enriched in small dense HDL3. As S1P is bound to apolipoprotein (apo) M in HDL, such enrichment is consistent with the elevated apoM concentration in HDL3. When HDL/apoM-bound S1P acts on S1P1 or S1P3 receptors in endothelial cells, potent antiatherogenic and vasculoprotective effects are exerted; those exerted by albumin-bound S1P at these receptors are typically weaker. When HDL/apoM-bound S1P binds to S1P2 receptors, proatherogenic effects may potentially be induced. Subnormal plasma levels of HDL-associated S1P are typical of dyslipidemic individuals at high cardiovascular risk and in patients with coronary heart disease. International Guidelines recommend statin treatment as first-line lipid lowering therapy in these groups. The cardiovascular benefits of statin therapy are derived primarily from reduction in low-density lipoprotein (LDL)-cholesterol, although minor contributions from pleiotropic actions cannot be excluded. Might statin treatment therefore normalize, directly or indirectly, the subnormal levels of S1P in dyslipidemic subjects at high cardiovascular risk? Our unpublished findings in the CAPITAIN study (ClinicalTrials.gov: NCT01595828), involving a cohort of obese, hypertriglyceridemic subjects (n = 12) exhibiting the MetS, showed that pitavastatin calcium (4 mg/day) treatment for 180days was without effect on either total plasma or HDL-associated S1P levels, suggesting that statin-mediated improvement of endothelial function is not due to normalization of HDL-bound S1P. Statins may however induce the expression of S1P1 receptors in endothelial cells, thereby potentiating increase in endothelial nitric oxide synthase response to HDL-bound S1P, with beneficial downstream vasculoprotective effects.

SUMMARY

Current evidence indicates that S1P in small dense HDL3 containing apoM exerts antiatherogenic effects and that statins exert vasculoprotective effects through activation of endothelial cell S1P1 receptors in response to HDL/apoM-bound S1P.

Sphingolipids and Lymphomas: A Double-Edged Sword

Lymphomas are a highly heterogeneous group of hematological neoplasms. Given their ethiopathogenic complexity, their classification and management can become difficult tasks; therefore, new approaches are continuously being sought. Metabolic reprogramming at the lipid level is a hot topic in cancer research, and sphingolipidomics has gained particular focus in this area due to the bioactive nature of molecules such as sphingoid bases, sphingosine-1-phosphate, ceramides, sphingomyelin, cerebrosides, globosides, and gangliosides. Sphingolipid metabolism has become especially exciting because they are involved in virtually every cellular process through an extremely intricate metabolic web; in fact, no two sphingolipids share the same fate. Unsurprisingly, a disruption at this level is a recurrent mechanism in lymphomagenesis, dissemination, and chemoresistance, which means potential biomarkers and therapeutical targets might be hiding within these pathways. Many comprehensive reviews describing their role in cancer exist, but because most research has been conducted in solid malignancies, evidence in lymphomagenesis is somewhat limited. In this review, we summarize key aspects of sphingolipid biochemistry and discuss their known impact in cancer biology, with a particular focus on lymphomas and possible therapeutical strategies against them.

Tumor Necrosis Factor-α Induces a Preeclamptic-like Phenotype in Placental Villi via Sphingosine Kinase 1 Activation

Preeclampsia (PE) involves inadequate placental function. This can occur due to elevated pro-inflammatory tumor necrosis factor-α (TNF-α). In other tissues, TNF-α signals via sphingosine kinase 1 (SphK1). SphK1 hinders syncytial formation. Whether this occurs downstream of TNF-α signaling is unclear. We hypothesized that placental SphK1 levels are higher in PE and elevated TNF-α decreases syncytial function, increases syncytial shedding, and increases cytokine/factor release via SphK1 activity. Term placental biopsies were analyzed for SphK1 using immunofluorescence and qRT-PCR. Term placental explants were treated after 4 days of culture, at the start of syncytial regeneration, with TNF-α and/or SphK1 inhibitors, PF-543. Syncytialization was assessed by measuring fusion and chorionic gonadotropin release. Cell death and shedding were measured by lactate dehydrogenase release and placental alkaline phosphatase-positive shed particles. Forty-two cytokines were measured using multiplex assays. Placental SphK1 was increased in PE. Increased cell death, shedding, interferon-α2, IFN-γ-induced protein 10, fibroblast growth factor 2, and platelet-derived growth factor-AA release induced by TNF-α were reversed upon SphK1 inhibition. TNF-α increased the release of 26 cytokines independently of SphK1. TNF-α decreased IL-10 release and inhibiting SphK1 reversed this effect. Inhibiting SphK1 alone decreased TNF-α release. Hence, SphK1 partially mediates the TNF-α-induced PE placental phenotype, primarily through cell damage, shedding, and specific cytokine release.

Sphingosine-1-Phosphate Levels Are Higher in Male Patients with Non-Classic Fabry Disease

Fabry disease is an X-linked lysosomal disease in which defects in the alpha-galactosidase A enzyme activity lead to the ubiquitous accumulation of glycosphingolipids. Whereas the classic disease is characterized by neuropathic pain, progressive renal failure, white matter lesions, cerebral stroke, and hypertrophic cardiomyopathy (HCM), the non-classic phenotype, also known as cardiac variant, is almost exclusively characterized by HCM. Circulating sphingosine-1-phosphate (S1P) has controversially been associated with the Fabry cardiomyopathy. We measured serum S1P levels in 41 patients of the FFABRY cohort. S1P levels were higher in patients with a non-classic phenotype compared to those with a classic phenotype (200.3 [189.6−227.9] vs. 169.4 ng/mL [121.1−203.3], p = 0.02). In a multivariate logistic regression model, elevated S1P concentration remained statistically associated with the non-classic phenotype (OR = 1.03; p < 0.02), and elevated lysoGb3 concentration with the classic phenotype (OR = 0.95; p < 0.03). S1P levels were correlated with interventricular septum thickness (r = 0.46; p = 0.02). In a logistic regression model including S1P serum levels, phenotype, and age, age remained the only variable significantly associated with the risk of HCM (OR = 1.25; p = 0.001). S1P alone was not associated with cardiac hypertrophy but with the cardiac variant. The significantly higher S1P levels in patients with the cardiac variant compared to those with classic Fabry suggest the involvement of distinct pathophysiological pathways in the two phenotypes. S1P dosage could allow the personalization of patient management.

GFI1-Dependent Repression of SGPP1 Increases Multiple Myeloma Cell Survival

Simple Summary

New therapies have greatly improved the progression-free and overall survival for patients with “standard risk” multiple myeloma (MM). However, patients with “high risk” MM, in particular patients whose MM cells harbor non-functional p53, have very short survival times because of the early relapse and rapid development of highly therapy-resistant MM. In this report, we identify a novel mechanism responsible for Growth Factor Independence-1 (GFI1) regulation of the growth and survival of MM cells through its modulation of sphingolipid metabolism, regardless of their p53 status. We identify the Sphingosine-1-Phosphate Phosphatase (SGPP1) gene as a novel direct target of GFI1 transcriptional repression in MM cells, thus increasing intracellular sphingosine-1-phosphate levels, which stabilizes c-Myc. Our results support GFI1 as an attractive therapeutic target for all types of MM, including the “high risk” patient population with non-functional p53, as well as a possible therapeutic approach for other types of cancers expressing high levels of c-Myc.

Abstract

Multiple myeloma (MM) remains incurable for most patients due to the emergence of drug resistant clones. Here we report a p53-independent mechanism responsible for Growth Factor Independence-1 (GFI1) support of MM cell survival by its modulation of sphingolipid metabolism to increase the sphingosine-1-phosphate (S1P) level regardless of the p53 status. We found that expression of enzymes that control S1P biosynthesis, SphK1, dephosphorylation, and SGPP1 were differentially correlated with GFI1 levels in MM cells. We detected GFI1 occupancy on the SGGP1 gene in MM cells in a predicted enhancer region at the 5’ end of intron 1, which correlated with decreased SGGP1 expression and increased S1P levels in GFI1 overexpressing cells, regardless of their p53 status. The high S1P:Ceramide intracellular ratio in MM cells protected c-Myc protein stability in a PP2A-dependent manner. The decreased MM viability by SphK1 inhibition was dependent on the induction of autophagy in both p53WT and p53mut MM. An autophagic blockade prevented GFI1 support for viability only in p53mut MM, demonstrating that GFI1 increases MM cell survival via both p53WT inhibition and upregulation of S1P independently. Therefore, GFI1 may be a key therapeutic target for all types of MM that may significantly benefit patients that are highly resistant to current therapies.

Targeting Chronic Inflammation of the Digestive System in Cancer Prevention: Modulators of the Bioactive Sphingolipid Sphingosine-1-Phosphate Pathway

Incidence of gastrointestinal (GI) cancers is increasing, and late-stage diagnosis makes these cancers difficult to treat. Chronic and low-grade inflammation are recognized risks for most GI cancers. The GI mucosal immune system maintains healthy homeostasis and signalling molecules made from saturated fats, bioactive sphingolipids, play essential roles in healthy GI immunity. Sphingosine-1-phosphate (S1P), a bioactive sphingolipid, is a key mediator in a balanced GI immune response. Disruption in the S1P pathway underlies systemic chronic metabolic inflammatory disorders, including diabetes and GI cancers, providing a strong rationale for using modulators of the S1P pathway to treat pathological inflammation. Here, we discuss the effects of bioactive sphingolipids in immune homeostasis with a focus on S1P in chronic low-grade inflammation associated with increased risk of GI carcinogenesis. Contemporary information on S1P signalling involvement in cancers of the digestive system, from top to bottom, is reviewed. Further, we discuss the use of novel S1P receptor modulators currently in clinical trials and their potential as first-line drugs in the clinic for chronic inflammatory diseases. Recently, ozanimod (Zeposia^TM) and etrasimod have been approved for clinical use to treat ulcerative colitis and eosinophilic oesophagitis, respectively, which may have longer term benefits in reducing risk of GI cancers.

Podocyte Sphingolipid Signaling in Nephrotic Syndrome

Podocytes play a vital role in the pathogenesis of nephrotic syndrome (NS), which is clinically characterized by heavy proteinuria, hypoalbuminemia, hyperlipidemia, and peripheral edema. The pathogenesis of NS has evolved through several hypotheses ranging from immune dysregulation theory and increased glomerular permeability theory to the current concept of podocytopathy. Podocytopathy is characterized by dysfunction or depletion of podocytes, which may be caused by unknown permeability factor, genetic disorders, drugs, infections, systemic disorders, and hyperfiltration. Over the last two decades, numerous studies have been done to explore the molecular mechanisms of podocyte injuries or NS and to develop the novel therapeutic strategies targeting podocytopathy for treatment of NS. Recent studies have shown that normal sphingolipid metabolism is essential for structural and functional integrity of podocytes. As a basic component of the plasma membrane, sphingolipids not only support the assembly of signaling molecules and interaction of receptors and effectors, but also mediate various cellular activities, such as apoptosis, proliferation, stress responses, necrosis, inflammation, autophagy, senescence, and differentiation. This review briefly summarizes current evidence demonstrating the regulation of sphingolipid metabolism in podocytes and the canonical or noncanonical roles of podocyte sphingolipid signaling in the pathogenesis of NS and associated therapeutic strategies.

Elephant Genomes Reveal Accelerated Evolution in Mechanisms Underlying Disease Defenses

Disease susceptibility and resistance are important factors for the conservation of endangered species, including elephants. We analyzed pathology data from 26 zoos and report that Asian elephants have increased neoplasia and malignancy prevalence compared with African bush elephants. This is consistent with observed higher susceptibility to tuberculosis and elephant endotheliotropic herpesvirus (EEHV) in Asian elephants. To investigate genetic mechanisms underlying disease resistance, including differential responses between species, among other elephant traits, we sequenced multiple elephant genomes. We report a draft assembly for an Asian elephant, and defined 862 and 1,017 conserved potential regulatory elements in Asian and African bush elephants, respectively. In the genomes of both elephant species, conserved elements were significantly enriched with genes differentially expressed between the species. In Asian elephants, these putative regulatory regions were involved in immunity pathways including tumor-necrosis factor, which plays an important role in EEHV response. Genomic sequences of African bush, forest, and Asian elephant genomes revealed extensive sequence conservation at TP53 retrogene loci across three species, which may be related to TP53 functionality in elephant cancer resistance. Positive selection scans revealed outlier genes related to additional elephant traits. Our study suggests that gene regulation plays an important role in the differential inflammatory response of Asian and African elephants, leading to increased infectious disease and cancer susceptibility in Asian elephants. These genomic discoveries can inform future functional and translational studies aimed at identifying effective treatment approaches for ill elephants, which may improve conservation.

Inflammatory interactions between degenerated intervertebral discs and microglia: Implication of sphingosine-1-phosphate signaling

The etiology of intervertebral disc degeneration is largely unknown, but local neuroinflammation may exert a crucial role through activation of cells as microglia and pro-inflammatory cytokines production. We aimed to compare the effect of degenerated and normal intervertebral disc microenvironment on microglial cells and the potential role of sphingosine-1-phosphate, a pro-inflammatory sphingolipid, in their crosstalk. Human degenerated intervertebral discs (Pfirrmann grade IV) were obtained at surgery for spondylolisthesis. Normal intervertebral discs were collected from cadaveric normal lumbar spines. Normal and degenerated-intervertebral discs were kept in culture to obtain media conditioning. Then, microglial cells were cocultured with conditioned media and viability, proliferation, migration, chemotaxis, and inflammatory gene expression were evaluated. The results demonstrate that conditioned media from degenerated intervertebral discs activate microglial cells, increasing chemotaxis, migration, and pro-inflammatory mediators release to a great extent than normal discs. In addition, we show that the administration of sphingosine-1-phosphate to normal intervertebral disc/microglia coculture mimicked degenerative effects. Interestingly, sphingosine-1-phosphate content in conditioned media from degenerated discs was significantly higher than that from normal ones. In addition, FTY720, a functional antagonist of sphingosine-1-phosphate, potently inhibited the effect of degenerated intervertebral discs on microglial inflammatory factor transcription and migration. Our data report, for the first time, that sphingosine-1-phosphate is involved as signal in the microenvironment of human degenerated intervertebral discs. Sphingosine-1-phosphate signaling modulation by FTY720 may induce beneficial effects in counteracting microglial activation during intervertebral disc degeneration.

Sphingosine 1-phosphate-induced nitric oxide production simultaneously controls endothelial barrier function and vascular tone in resistance arteries

The regulations of endothelial permeability and vascular tone by sphingosine 1-phosphate (S1P) have been well-studied independently. Little is known about whether the effects of S1P on endothelial permeability can directly influence vascular tone in resistance arteries, which impact blood flow. The endothelium forms a partial barrier that regulates access of circulating agonists to underlying vascular smooth muscle cells (VSMCs). We hypothesized that physiological concentrations of circulating S1P simultaneously control endothelial barrier function and vascular tone through endothelial production of nitric oxide (NO). We adapted the pressure myograph system to simultaneously measure both functions in pressurized mesenteric compared to uterine resistance arteries from wild-type and eNOS KO mice. We established that: 1) S1P interacting directly with the endothelium inside pressurized arteries generates NO that limits endothelial permeability; 2) an intact endothelium forms a partial physical barrier that regulates access of intraluminal S1P to the underlying VSMCs and 3) S1P infused lumenally also generates NO through eNOS that counterbalances the constriction induced by S1P that is able to access VSMCs and this is critical to control vascular tone. We conclude that targeting the S1P signaling system, particularly the capacity to produce NO could be clinically important in the treatment of vascular diseases.

Targeting S1PRs as a Therapeutic Strategy for Inflammatory Bone Loss Diseases-Beyond Regulating S1P Signaling

As G protein coupled receptors, sphingosine-1-phosphate receptors (S1PRs) have recently gained attention for their role in modulating inflammatory bone loss diseases. Notably, in murine studies inhibiting S1PR2 by its specific inhibitor, JTE013, alleviated osteoporosis induced by RANKL and attenuated periodontal alveolar bone loss induced by oral bacterial inflammation. Treatment with a multiple S1PRs modulator, FTY720, also suppressed ovariectomy-induced osteoporosis, collagen or adjuvant-induced arthritis, and apical periodontitis in mice. However, most previous studies and reviews have focused mainly on how S1PRs manipulate S1P signaling pathways, subsequently affecting various diseases. In this review, we summarize the underlying mechanisms associated with JTE013 and FTY720 in modulating inflammatory cytokine release, cell chemotaxis, and osteoclastogenesis, subsequently influencing inflammatory bone loss diseases. Studies from our group and from other labs indicate that S1PRs not only control S1P signaling, they also regulate signaling pathways induced by other stimuli, including bacteria, lipopolysaccharide (LPS), bile acid, receptor activator of nuclear factor κB ligand (RANKL), IL-6, and vitamin D. JTE013 and FTY720 alleviate inflammatory bone loss by decreasing the production of inflammatory cytokines and chemokines, reducing chemotaxis of inflammatory cells from blood circulation to bone and soft tissues, and suppressing RANKL-induced osteoclast formation.

Multi-Omics Analysis of Brain Metastasis Outcomes Following Craniotomy

Background

The incidence of brain metastasis continues to increase as therapeutic strategies have improved for a number of solid tumors. The presence of brain metastasis is associated with worse prognosis but it is unclear if distinctive biomarkers can separate patients at risk for CNS related death.

Methods

We executed a single institution retrospective collection of brain metastasis from patients who were diagnosed with lung, breast, and other primary tumors. The brain metastatic samples were sent for RNA sequencing, proteomic and metabolomic analysis of brain metastasis. The primary outcome was distant brain failure after definitive therapies that included craniotomy resection and radiation to surgical bed. Novel prognostic subtypes were discovered using transcriptomic data and sparse non-negative matrix factorization.

Results

We discovered two molecular subtypes showing statistically significant differential prognosis irrespective of tumor subtype. The median survival time of the good and the poor prognostic subtypes were 7.89 and 42.27 months, respectively. Further integrated characterization and analysis of these two distinctive prognostic subtypes using transcriptomic, proteomic, and metabolomic molecular profiles of patients identified key pathways and metabolites. The analysis suggested that immune microenvironment landscape as well as proliferation and migration signaling pathways may be responsible to the observed survival difference.

Conclusion

A multi-omics approach to characterization of brain metastasis provides an opportunity to identify clinically impactful biomarkers and associated prognostic subtypes and generate provocative integrative understanding of disease.

Sphingosine 1-phosphate metabolism and insulin signaling

Insulin is the main anabolic hormone secreted by β-cells of the pancreas stimulating the assimilation and storage of glucose in muscle and fat cells. It modulates the postprandial balance of carbohydrates, lipids and proteins via enhancing lipogenesis, glycogen and protein synthesis and suppressing glucose generation and its release from the liver. Resistance to insulin is a severe metabolic disorder related to a diminished response of peripheral tissues to the insulin action and signaling. This leads to a disturbed glucose homeostasis that precedes the onset of type 2 diabetes (T2D), a disease reaching epidemic proportions. A large number of studies reported an association between elevated circulating fatty acids and the development of insulin resistance. The increased fatty acid lipid flux results in the accumulation of lipid droplets in a variety of tissues. However, lipid intermediates such as diacylglycerols and ceramides are also formed in response to elevated fatty acid levels. These bioactive lipids have been associated with the pathogenesis of insulin resistance. More recently, sphingosine 1-phosphate (S1P), another bioactive sphingolipid derivative, has also been shown to increase in T2D and obesity. Although many studies propose a protective role of S1P metabolism on insulin signaling in peripheral tissues, other studies suggest a causal role of S1P on insulin resistance. In this review, we critically summarize the current state of knowledge of S1P metabolism and its modulating role on insulin resistance. A particular emphasis is placed on S1P and insulin signaling in hepatocytes, skeletal muscle cells, adipocytes and pancreatic β-cells. In particular, modulation of receptors and enzymes that regulate S1P metabolism can be considered as a new therapeutic option for the treatment of insulin resistance and T2D.

Metformin alleviates inflammation in oxazolone induced ulcerative colitis in rats: plausible role of sphingosine kinase 1/sphingosine 1 phosphate signaling pathway

OBJECTIVES

Ulcerative colitis (UC) is a chronic inflammatory bowel disease that is associated with high sphingosine kinase 1(SPHK1) expression in the colon, however its role in pathogenesis of UC is not clearly understood so, the aim of the present study was to clarify the role of SPHK1 and investigate whether the anti-inflammatory effects of metformin in UC is mediated by Sphingosine kinase 1/sphingosine 1 phosphate (S1P) signaling pathway.

MATERIAL AND METHODS

Colitis was induced in adult male wistar rats by intra rectal administration of oxazolone in the fifth and seventh days from initial presensitization. Oxazolone treated rats were divided into untreated oxazolone group, metformin and mesalazine treated groups both in a dose of 100 mg/kg/day orally for 21 days. Along with these groups normal control and saline groups were used .Colitis was assessed by colon length, disease activity index (DAI) and histological examination of colontissue. Plasma samples were used to measure S1P.SPHK1 activity, signal transducer and activator of transcription -3(STAT-3), interleukin-6 (IL-6), nitric oxide (NO), myeloperoxidase activity (MPO), reduced glutathione (GSH) and tissue expression of intracellular cell adhesion molecule -1(ICAM-1) and caspase-3 genes were measured in tissue.

RESULTS

Metformin successfully attenuated oxazolone colitis by increasing colon length, decreasing DAI and improved colon histologic picture. Metformin also induced a significant decrease in Plasma SIP, SPHK1 activity, inflammatory, oxidative stress markers, ICAM-1 and Caspase-3 genes expression compared to oxazolone group.

CONCLUSION

It is revealed that metformin alleviated inflammation and underlying mechanism may result from inhibition of SPHK1/S1P signaling pathway.

Signal Transduction in Immune Cells and Protein Kinases

Immune response relies upon several intracellular signaling events. Among the protein kinases involved in these pathways, members of the protein kinase C (PKC) family are prominent molecules because they have the capacity to acutely and reversibly modulate effector protein functions, controlling both spatial distribution and dynamic properties of the signals. Different PKC isoforms are involved in distinct signaling pathways, with selective functions in a cell-specific manner.In innate system, Toll-like receptor signaling is the main molecular event triggering effector functions. Various isoforms of PKC can be common to different TLRs, while some of them are specific for a certain type of TLR. Protein kinases involvement in innate immune cells are presented within the chapter emphasizing their coordination in many aspects of immune cell function and, as important players in immune regulation.In adaptive immunity T-cell receptor and B-cell receptor signaling are the main intracellular pathways involved in seminal immune specific cellular events. Activation through TCR and BCR can have common intracellular pathways while others can be specific for the type of receptor involved or for the specific function triggered. Various PKC isoforms involvement in TCR and BCR Intracellular signaling will be presented as positive and negative regulators of the immune response events triggered in adaptive immunity.

Transcriptional Regulation of Sphingosine Kinase 1

Once thought to be primarily structural in nature, sphingolipids have become increasingly appreciated as second messengers in a wide array of signaling pathways. Sphingosine kinase 1, or SK1, is one of two sphingosine kinases that phosphorylate sphingosine into sphingosine-1-phosphate (S1P). S1P is generally pro-inflammatory, pro-angiogenic, immunomodulatory, and pro-survival; therefore, high SK1 expression and activity have been associated with certain inflammatory diseases and cancer. It is thus important to develop an understanding of the regulation of SK1 expression and activity. In this review, we explore the current literature on SK1 transcriptional regulation, illustrating a complex system of transcription factors, cytokines, and even micro-RNAs (miRNAs) on the post transcriptional level.

Sphingosine 1-Phosphate in Malaria Pathogenesis and Its Implication in Therapeutic Opportunities

Sphingosine 1-Phosphate (S1P) is a bioactive lipid intermediate in the sphingolipid metabolism, which exist in two pools, intracellular and extracellular, and each pool has a different function. The circulating extracellular pool, specifically the plasma S1P is shown to be important in regulating various physiological processes related to malaria pathogenesis in recent years. Although blood cells (red blood cells and platelets), vascular endothelial cells and hepatocytes are considered as the important sources of plasma S1P, their extent of contribution is still debated. The red blood cells (RBCs) and platelets serve as a major repository of intracellular S1P due to lack, or low activity of S1P degrading enzymes, however, contribution of platelets toward maintaining plasma S1P is shown negligible under normal condition. Substantial evidences suggest platelets loss during falciparum infection as a contributing factor for severe malaria. However, platelets function as a source for plasma S1P in malaria needs to be examined experimentally. RBC being the preferential site for parasite seclusion, and having the ability of trans-cellular S1P transportation to EC upon tight cell-cell contact, might play critical role in differential S1P distribution and parasite growth. In the present review, we have summarized the significance of both the S1P pools in the context of malaria, and how the RBC content of S1P can be channelized in better ways for its possible implication in therapeutic opportunities to control malaria.

Role of Inflammation in the Development of Colorectal Cancer

Chronic inflammation can lead to the development of many diseases, including cancer. Inflammatory bowel disease (IBD) that includes both ulcerative colitis (UC) and Crohnmp's disease (CD) are risk factors for the development of colorectal cancer (CRC). Many cytokines produced primarily by the gut immune cells either during or in response to localized inflammation in the colon and rectum are known to stimulate the complex interactions between the different cell types in the gut environment resulting in acute inflammation. Subsequently, chronic inflammation, together with genetic and epigenetic changes, have been shown to lead to the development and progression of CRC. Various cell types present in the colon, such as enterocytes, Paneth cells, goblet cells, and macrophages, express receptors for inflammatory cytokines and respond to tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, and other cytokines. Among the several cytokines produced, TNF-α and IL-1β are the key pro-inflammatory molecules that play critical roles in the development of CRC. The current review is intended to consolidate the published findings to focus on the role of pro-inflammatory cytokines, namely TNF-α and IL-1β, on inflammation (and the altered immune response) in the gut, to better understand the development of CRC in IBD, using various experimental model systems, preclinical and clinical studies. Moreover, this review also highlights the current therapeutic strategies available (monotherapy and combination therapy) to alleviate the symptoms or treat inflammation-associated CRC by using monoclonal antibodies or aptamers to block pro-inflammatory molecules, inhibitors of tyrosine kinases in the inflammatory signaling cascade, competitive inhibitors of pro-inflammatory molecules, and the nucleic acid drugs like small activating RNAs (saRNAs) or microRNA (miRNA) mimics to activate tumor suppressor or repress oncogene/pro-inflammatory cytokine gene expression.

Isoflurane versus sevoflurane for early brain injury and expression of sphingosine kinase 1 after experimental subarachnoid hemorrhage

The first step to treat aneurysmal subarachnoid hemorrhage (SAH) is aneurysmal obliteration under general anesthesia but not treat the SAH itself and the secondary effects. However, the identification of anesthetics with properties that help to attenuate post-SAH brain injury can be useful for improving outcomes of SAH patients. We examined whether 2% isoflurane and 3% sevoflurane posttreatment are protective against early brain injury (EBI) after SAH. This study used 87 8-week-old male CD-1 mice. We induced SAH by endovascular perforation in mice. Animals were randomly divided into 4 groups: sham-operated (n = 16), SAH + vehicle-medical air (n = 26), SAH + 2% isoflurane (n = 22), and SAH + 3% sevoflurane (n = 23). Neurobehavioral function, brain water content and Western blotting were evaluated at 24 h. The expression of sphingosine kinase (SphK), cleaved caspase-3 and cyclooxygenase-2 (COX2) was determined by Western blotting. Cell death was examined by terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end-labeling staining. Both 2% isoflurane and 3% sevoflurane significantly improved neurobehavioral function, and brain edema at 24 h after SAH and attenuated cell death, associated with an increase in SphK1, a decrease in cleaved caspase-3 and COX2. The neuroprotective effects were similar between 2% isoflurane and 3% sevoflurane. These findings suggest that both 2% isoflurane and 3% sevoflurane significantly inhibited EBI by suppressing post-SAH apoptosis and brain inflammation possibly via the SphK1-related pathway.

The potential of metabolic and lipid profiling in inflammatory bowel diseases: A pilot study

Inflammatory bowel diseases (IBDs) are conditions that still pose significant problems. A third of the patients are either misdiagnosed or a proper diagnosis of Crohn’s disease (CD) or ulcerative colitis (UC) cannot be made. We need new biomarkers, so that we can offer patients the best treatment and keep the disease in an inactive state for as long as possible. Alterations in metabolic profiles have been incriminated in the pathophysiology of IBD. The aim of the present study was to identify molecules that could serve as biomarkers for a positive diagnosis of IBD as well as to discriminate UC from colonic CD. Twenty-two patients with active colonic IBD (UC = 17, CD = 5) and 24 age- and gender-matched healthy controls were enrolled. Plasma lipid and metabolic profiles were quantified using ultra-high-performance liquid chromatography combined with mass spectrometry. Univariate and multivariate statistical tests were employed. Six lipid species and 7 metabolites were significantly altered in IBD patients compared to healthy controls, with the majority belonging to glycerophospholipid, linoleic acid, and sphingolipid metabolisms. Five lipid species and only 1 metabolite were significantly increased in UC compared to CD. This preliminary study suggests that lipid and metabolic profiling of serum can become diagnostic tools for IBD. In addition, they can be used to differentiate between CD and UC.

Reduction of Sphingosine Kinase 1 Phosphorylation and Activity in Plasmodium-Infected Erythrocytes

Sphingosine-1-phosphate (S1P), a bioactive lipid mediator is involved in an array of biological processes and linked to pathological manifestations. Erythrocyte is known as the major reservoir for S1P as they lack S1P-degrading enzymes (S1P lyase and S1P phosphohydrolase) and harbor sphingosine kinase-1 (SphK-1) essential for sphingosine conversion to S1P. Reduced S1P concentration in serum was correlated with disease severity in patients with Plasmodium falciparum and Plasmodium vivax infections. Herein, we aimed to identify the underlying mechanism and contribution of host erythrocytes toward depleted S1P levels in Plasmodium-infected patients vs. healthy individuals. The level and activity of SphK-1 were measured in vitro in both uninfected and cultured P. falciparum-infected erythrocytes. Infected erythrocytes demonstrated a significant decrease in SphK-1 level in a time-dependent manner. We found that 10–42 h post invasion (hpi), SphK1 level was predominantly reduced to ∼50% in rings, trophozoites, and schizonts compared to uninfected erythrocytes. We next analyzed the phosphorylation status of SphK-1, a modification responsible for its activity and S1P production, in both uninfected control and Plasmodium-infected erythrocytes. Almost ∼50% decrease in phosphorylation of SphK-1 was observed that could be corroborated with significant reduction in the production and release of S1P in infected erythrocytes. Serum S1P levels were studied in parallel in P. falciparum (N = 15), P. vivax (N = 36)-infected patients, and healthy controls (N = 6). The findings revealed that S1P concentration was significantly depleted in uncomplicated malaria cases and was found to be lowest in complicated malaria and thrombocytopenia in both P. falciparum and P. vivax-infected groups (^∗∗p < 0.01). The lower serum S1P level could be correlated with the reduced platelet count defining the role of S1P level in platelet formation. In conclusion, erythrocyte SphK-1 and S1P levels were studied in Plasmodium-infected individuals and erythrocytes that helped in characterizing the complications associated with malaria and thrombocytopenia, providing insights into the contribution of host erythrocyte biology in malaria pathogenesis. Finally, this study proposes the use of S1P and its analog as a novel adjunct therapy for malaria complications.

Small molecule oral targeted therapies in ulcerative colitis

The incidence and prevalence of ulcerative colitis are increasing globally. Although the exact cause and pathogenesis of this disease is unclear, research has led to a better understanding of the condition and to identification of new targets for therapy, which in turn has encouraged the development of new therapies. As well as biologic therapies, which have changed the way inflammatory bowel disease is managed, small molecules have been developed for the treatment of ulcerative colitis. These small molecule treatments are orally administered and are likely to bring a substantial shift in the way this chronic disease is treated. Oral therapies offer many advantages over infusion therapies, such as ease of use, increased acceptability by patients, and reduction of cost. This Review focuses not only on oral therapies that have been approved for use in ulcerative colitis, but also on those that are in development, providing a comprehensive overview for clinicians of available oral therapies and drugs that are likely to become available. We have also reviewed drugs that have shown promise in preclinical studies and could be effective future therapies.

Potential osteomyelitis biomarkers identified by plasma metabolome analysis in mice

Osteomyelitis, which often arises from a surgical-site infection, is a serious problem in orthopaedic surgery. However, there are no specific biomarkers for osteomyelitis. Here, to identify specific plasma biomarkers for osteomyelitis, we conducted metabolome analyses using a mouse osteomyelitis model and bioluminescence imaging. We divided adult male pathogen-free BALB/C mice into control, sham-control, and infected groups. In the infected group, a bioluminescent Staphylococcus aureus strain was inoculated into the femur, and osteomyelitis was detected by bioluminescence imaging. We next analysed the metabolome, by comprehensively measuring all of the small molecules. This analysis identified 279 metabolites, 12 of which were significantly higher and 45 were significantly lower in the infected group than in the sham-control and control groups. Principal component analysis identified sphingosine as the highest loading factor. Several acyl carnitines and fatty acids, particularly ω-3 and ω-6 polyunsaturated fatty acids, were significantly lower in the infected group. Several metabolites in the tricarboxylic acid cycle were lower in the infected group than in the other groups. Thus, we identified two sphingolipids, sphinganine and sphingosine, as positive biomarkers for mouse osteomyelitis, and two components in the tricarboxylic acid cycle, two-oxoglutarate and succinic acid, as negative biomarkers.

Effect of the Sphingosine Kinase 1 Selective Inhibitor, PF543 on Dextran Sodium Sulfate-Induced Colitis in Mice

Ulcerative colitis (UC) is a chronic relapsing inflammatory bowel disease, which often affects colon or rectum or both. It is now well recognized that sphingosine kinases-1/sphingosine-1-phosphate (S1P) signaling may have a very significant potential as targets for therapeutic intervention in UC. Compared with the pure dextran sodium sulfate group, administration of PF543 significantly reduced clinical symptoms with less weight loss, diarrhea, and shortening of the colon. The severity of colitis was improved with reduced disease activity index and degree of histological damage in colon. Moreover, treatment with PF543 not only decreased S1P but also inhibited mRNA expression of proinflammatory factors such as interleukin (IL)-1β and IL-6. This suggests that PF543 might exhibit an anti-inflammatory function against colitis through inhibition of expression of proinflammatory factors.

Pro-Inflammatory Role of S1P3 in Macrophages

Sphingosine kinase 1 and its product, sphingosine 1-phosphate (S1P), as well as their receptors, have been implicated in inflammatory responses. The functions of receptors S1P₁ and S1P₂ on cell motility have been investigated. However, the function of S1P₃ has been poorly investigated. In this study, the roles of S1P₃ on inflammatory response were investigated in primary perito-neal macrophages. S1P₃ receptor was induced along with sphingosine kinase 1 by stimulation of lipopolysaccharide (LPS). LPS treatment induced inflammatory genes, such iNOS, COX-2, IL-1β, IL-6 and TNF-α. TY52156, an antagonist of S1P₃ suppressed the induction of inflammatory genes in a concentration dependent manner. Suppression of iNOS and COX-2 induction was further confirmed by western blotting and NO measurement. Suppression of IL-1β induction was also confirmed by western blotting and ELISA. Caspase 1, which is responsible for IL-1β production, was similarly induced by LPS and suppressed by TY52156. Therefore, we have shown S1P₃ induction in the inflammatory conditions and its pro-inflammatory roles. Targeting S1P₃ might be a strategy for regulating inflammatory diseases.

Sphingolipids as Emerging Mediators in Retina Degeneration

The sphingolipids ceramide (Cer), sphingosine-1-phosphate (S1P), sphingosine (Sph), and ceramide-1-phosphate (C1P) are key signaling molecules that regulate major cellular functions. Their roles in the retina have gained increasing attention during the last decade since they emerge as mediators of proliferation, survival, migration, neovascularization, inflammation and death in retina cells. As exacerbation of these processes is central to retina degenerative diseases, they appear as crucial players in their progression. This review analyzes the functions of these sphingolipids in retina cell types and their possible pathological roles. Cer appears as a key arbitrator in diverse retinal pathologies; it promotes inflammation in endothelial and retina pigment epithelium (RPE) cells and its increase is a common feature in photoreceptor death in vitro and in animal models of retina degeneration; noteworthy, inhibiting Cer synthesis preserves photoreceptor viability and functionality. In turn, S1P acts as a double edge sword in the retina. It is essential for retina development, promoting the survival of photoreceptors and ganglion cells and regulating proliferation and differentiation of photoreceptor progenitors. However, S1P has also deleterious effects, stimulating migration of Müller glial cells, angiogenesis and fibrosis, contributing to the inflammatory scenario of proliferative retinopathies and age related macular degeneration (AMD). C1P, as S1P, promotes photoreceptor survival and differentiation. Collectively, the expanding role for these sphingolipids in the regulation of critical processes in retina cell types and in their dysregulation in retina degenerations makes them attractive targets for treating these diseases.

Antibiotic therapy with metronidazole reduces endometriosis disease progression in mice: a potential role for gut microbiota

STUDY QUESTION

Does altering gut microbiota with antibiotic treatment have any impact on endometriosis progression?

SUMMARY ANSWER

Antibiotic therapy reduces endometriosis progression in mice, possibly by reducing specific gut bacteria.

WHAT IS KNOWN ALREADY

Endometriosis, a chronic condition causing abdominal pain and infertility, afflicts up to 10% of women between the ages of 25 and 40, ~5 million women in the USA. Current treatment strategies, including hormone therapy and surgery, have significant side effects and do not prevent recurrences. We have little understanding of why some women develop endometriosis and others do not.

STUDY DESIGN, SIZE, DURATION

Mice were treated with broad-spectrum antibiotics or metronidazole, subjected to surgically-induced endometriosis and assayed after 21 days.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The volumes and weights of endometriotic lesions and histological signatures were analysed. Proliferation and inflammation in lesions were assessed by counting cells that were positive for the proliferation marker Ki-67 and the macrophage marker Iba1, respectively. Differences in faecal bacterial composition were assessed in mice with and without endometriosis, and faecal microbiota transfer studies were performed.

MAIN RESULTS AND THE ROLE OF CHANCE

In mice treated with broad-spectrum antibiotics (vancomycin, neomycin, metronidazole and ampicillin), endometriotic lesions were significantly smaller (~ 5-fold; P < 0.01) with fewer proliferating cells (P < 0.001) than those in mice treated with vehicle. Additionally, inflammatory responses, as measured by the macrophage marker Iba1 in lesions and IL-1β, TNF-α, IL-6 and TGF-β1 in peritoneal fluid, were significantly reduced in mice treated with broad-spectrum antibiotics (P < 0.05). In mice treated with metronidazole only, but not in those treated with neomycin, ectopic lesions were significantly (P < 0.001) smaller in volume than those from vehicle-treated mice. Finally, oral gavage of faeces from mice with endometriosis restored the endometriotic lesion growth and inflammation (P < 0.05 and P < 0.01, respectively) in metronidazole-treated mice.

LARGE-SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

These findings are from a mouse model of surgically-induced endometriosis. Further studies are needed to determine the mechanism by which gut bacteria promote inflammation, identify bacterial genera or species that promote disease progression and assess the translatability of these findings to humans.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings suggest that gut bacteria promote endometriosis progression in mice. This finding if translated to humans, could aid in the development of improved diagnostic tools and personalised treatment strategies.

STUDY FUNDING AND COMPETING INTEREST(S)

This work was funded, in part, by: a National Institutes of Health (NIH)/ National Institute of Child Health and Human Development (NICHD) grant (R00HD080742) to RK; Washington University School of Medicine start-up funds to RK; an Endometriosis Foundation of America Research Award to R.K.; and an NIH/NICHD grant (R01HD091218) to IUM. The authors report no conflict of interest.

Sphingolipids in neurodegeneration (with focus on ceramide and S1P)

For many decades, research on sphingolipids associated with neurodegenerative disease focused on alterations in glycosphingolipids, particularly glycosylceramides (cerebrosides), sulfatides, and gangliosides. This seemed quite natural since many of these glycolipids are constituents of myelin and accumulated in lipid storage diseases (sphingolipidoses) resulting from enzyme deficiencies in glycolipid metabolism. With the advent of recognizing ceramide and its derivative, sphingosine-1-phosphate (S1P), as key players in lipid cell signaling and regulation of cell death and survival, research focus shifted toward these two sphingolipids. Ceramide and S1P are invoked in a plethora of cell biological processes participating in neurodegeneration such as ER stress, autophagy, dysregulation of protein and lipid transport, exosome secretion and neurotoxic protein spreading, neuroinflammation, and mitochondrial dysfunction. Hence, it is timely to discuss various functions of ceramide and S1P in neurodegenerative disease and to define sphingolipid metabolism and cell signaling pathways as potential targets for therapy.

Multi-hierarchical profiling the structure-activity relationships of engineered nanomaterials at nano-bio interfaces

Increasing concerns over the possible risks of nanotechnology necessitates breakthroughs in structure-activity relationship (SAR) analyses of engineered nanomaterials (ENMs) at nano-bio interfaces. However, current nano-SARs are often based on univariate assessments and fail to provide tiered views on ENM-induced bio-effects. Here we report a multi-hierarchical nano-SAR assessment for a representative ENM, Fe2O3, by metabolomics and proteomics analyses. The established nano-SAR profile allows the visualizing of the contributions of seven basic properties of Fe2O3 to its diverse bio-effects. For instance, although surface reactivity is responsible for Fe2O3-induced cell migration, the inflammatory effects of Fe2O3 are determined by aspect ratio (nanorods) or surface reactivity (nanoplates). These nano-SARs are examined in THP-1 cells and animal lungs, which allow us to decipher the detailed mechanisms including NLRP3 inflammasome pathway and monocyte chemoattractant protein-1-dependent signaling. This study provides more insights for nano-SARs, and may facilitate the tailored design of ENMs to render them desired bio-effects.