The control of the balance between ceramide and sphingosine-1-phosphate by sphingosine kinase: Oxidative stress and the seesaw of cell survival and death

The impacts of dietary sphingomyelin supplementation on metabolic parameters of healthy adults: a systematic review and meta-analysis of randomized controlled trials

Background

Studies have shown that sphingomyelin (SM) and its metabolites play signaling roles in the regulation of human health. Endogenous SM is involved in metabolic syndrome (MetS), while dietary SM supplementation may maintain lipid metabolism and prevent or alleviate MetS. Therefore, we hypothesized that dietary SM supplementation is beneficial for human health.

Aims

In order to examine the impacts of dietary SM on metabolic indexes in adults without MetS, we performed a meta-analysis to test our hypothesis.

Methods

A comprehensive search was performed to retrieve randomized controlled trials that were conducted between 2003 and 2023 to examine the effects of dietary SM supplementation on metabolic parameters in the Cochrane Library, PubMed, Web of Science, Embase, and ClinicalTrials.gov databases. RevMan 5.4 and Stata 14.0 software were used for meta-analysis, a sensitivity analysis, the risk of bias, and the overall quality of the resulted evidence.

Results

Eventually, 10 articles were included in this meta-analysis. Dietary SM supplementation did not affect the endline blood SM level. When compared to the control, SM supplementation reduced the blood total cholesterol level [MD: -12.97, 95% CI: (-14.57, -11.38), p < 0.00001], low-density lipoprotein cholesterol level [MD: -6.62, 95% CI: (-10.74, -2.49), p = 0.002], and diastolic blood pressure [MD: -3.31; 95% CI (-4.03, -2.58), p < 0.00001] in adults without MetS. The supplementation also increased high-density lipoprotein level [MD:1.41, 95% CI: (0.94, 1.88), p < 0.00001] and muscle fiber conduction velocity [MD: 95% 1.21 CI (0.53, 1.88), p = 0.0005]. The intake of SM had no effect on the blood phospholipids and lyso-phosphatidylcholine, but slightly decreased phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol concentrations. Dietary SM supplementation reduced insulin level [MD: -0.63; 95% CI (-0.96, -0.31), p = 0.0001] and HOMA-IR [MD: -0.23; 95% CI (-0.31, -0.16), p < 0.00001] without affecting blood levels of glucose and inflammatory cytokines.

Conclusion

Overall, dietary SM supplementation had a protective effect on blood lipid profiles and insulin level, but had limited impacts on other metabolic parameters in adults without MetS. More clinical trials and basic research are required.

Systematic review registration

PROSPERO, identifier CRD42023438460.

Cell and rat serum, urine and tissue metabolomics analysis elucidates the key pathway changes associated with chronic nephropathy and reveals the mechanism of action of rhein

BACKGROUND

Rhein can significantly delay the progression of chronic nephropathy. However, its mechanism of action has not been adequately elaborated, which hinders its extensive clinical application. In this work, the effects of rhein on models of TGF-β-induced NRK-49F cellular fibrosis and rat renal ischemia-reperfusion fibrosis were evaluated using metabolomics and western blotting.

METHODS

The metabolic profiles of NRK-49F cells and rat urine, serum, and kidney tissues in the control, model, and rhein groups were investigated using UPLC-QTOF-MS. The levels of p-P65, p-IKK, p-AKT, p-P38, p-JNK and AP-1 in NRK-49F cells were measured using western blotting and immunofluorescence methods. Molecular docking and network pharmacology methods were employed to explore the relationship between the potential targets of rhein and key proteins in the NF-κB and MAPK signaling pathways.

RESULTS

Various potential metabolites, including sphingolipids, ceramides, phosphatidylcholine, and lysophosphatidylcholine,14-hydroxy-E4-neuroprostane E, and 5-HPETE, were present in the cell, tissue, urine, and serum samples; however, few metabolites matches exactly among the four type of biological samples. These differential metabolites can effectively differentiated between the control, model, and rhein groups. Pathway enrichment analysis of differential metabolites unveiled that sphingolipid metabolism, arachidonic acid metabolism, and glycerophospholipid metabolism were closely related to nephropathy. Phosphorylation levels of AKT, IKK, P65 and AP-1 in NRK-49F cells was reduced by rhein treatment. Network pharmacology and molecular docking showed that the potential targets of rhein might regulated the expression of MAPK and AKT in the NF-κB and MAPK signaling pathways.

CONCLUSION

In brief, rhein might delays the progression of chronic nephropathy via the metabolic pathways, NF-κB and MAPKs signaling pathways, which provides the foundation for its development and clinical application.

Ceramides in peripheral arterial plaque lead to endothelial cell dysfunction

Background

Peripheral arterial atheroprogression is increasingly prevalent, and is a risk factor for major limb amputations in individuals with risk factors such as diabetes. We previously demonstrated that bioactive lipids are significantly altered in arterial tissue of individuals with diabetes and advanced peripheral arterial disease.

Methods

Here we evaluated whether sphingolipid ceramide 18:1/16:0 (C16) is a cellular regulator in endothelial cells and peripheral tibial arterial tissue in individuals with diabetes.

Results

We observed that C16 is the single most elevated ceramide in peripheral arterial tissue from below the knee in individuals with diabetes (11% increase, P < .05). C16 content in tibial arterial tissue positively correlates with sphingomyelin (SPM) content in patients with and without diabetes (r2 = 0.5, P < .005; r2 = 0.17, P < .05; respectively). Tibial arteries of individuals with diabetes demonstrated no difference in CERS6 expression (encoding ceramide synthase 6; the predominate ceramide synthesis enzyme), but higher SMPD expression (encoding sphingomyelin phosphodiesterase that catalyzes ceramide synthesis from sphingomyelins; P < .05). SMPD4, but not SMPD2, was particularly elevated in maximally diseased (Max) tibial arterial segments (P < .05). In vitro, exogenous C16 caused endothelial cells (HUVECs) to have decreased proliferation (P < .03), increased apoptosis (P < .003), and decreased autophagy (P < .008). Selective knockdown of SMPD2 and SMPD4 decreased native production of C16 (P < .01 and P < .001, respectively), but only knockdown of SMPD4 rescued cellular proliferation (P < .005) following exogenous supplementation with C16.

Conclusions

Our findings suggest that C16 is a tissue biomarker for peripheral arterial disease severity in the setting of diabetes, and can impact endothelial cell viability and function.

Clinical relevance

Peripheral arterial disease and its end-stage manifestation known as chronic limb-threatening ischemia (CLTI) represent ongoing prevalent and intricate medical challenges. Individuals with diabetes have a heightened risk of developing CLTI and experiencing its complications, including wounds, ulcers, and major amputations. In the present study, we conducted a comprehensive examination of the molecular lipid composition within arterial segments from individuals with CLTI, and with and without diabetes. Our investigations unveiled a striking revelation: the sphingolipid ceramide 18:1/16:0 emerged as the predominant ceramide species that was significantly elevated in the peripheral arterial intima below the knee in patients with diabetes. Moreover, this heightened ceramide presence is associated with a marked impairment of endothelial cell function and viability. Additionally, our study revealed a concurrent elevation in the expression of sphingomyelin phosphodiesterases, enzymes responsible for catalyzing ceramide synthesis from sphingomyelins, within maximally diseased arterial segments. These findings underscore the pivotal role of ceramides and their biosynthesis enzymes in the context of CLTI, offering new insights into potential therapeutic avenues for managing this challenging disease process.

Gastrointestinal Degradation and Toxicity of Disinfection Byproducts in Drinking Water Using In Vitro Models and the Roles of Gut Microbiota

Disinfection byproducts (DBPs) in drinking water are mainly exposed to the human body after oral ingestion and degradation in the gastrointestinal tract. The role of gastrointestinal degradation in the toxic effects of DBPs still needs further investigation. In this study, the degradation of five categories of DBPs (22 DBPs) in the stomach and small intestine was investigated based on a semicontinuous steady-state gastrointestinal simulation system, and 22 DBPs can be divided into three groups based on their residual proportions. The degradation of chloroacetonitrile (CAN), dibromoacetic acid (DBAA), and tetrabromopyrrole (FBPy) was further analyzed based on the Simulator of the Human Intestinal Microbial Ecosystem inoculating the gut microbiota, and approximately 60% of CAN, 45% of DBAA, and 80% of FBPy were degraded in the stomach and small intestine, followed by the complete degradation of remaining DBPs in the colon. Meanwhile, gastrointestinal degradation can reduce oxidative stress-mediated DNA damage and apoptosis induced by DBPs in DLD-1 cells, but the toxicity of DBPs did not disappear with the complete degradation of DBPs, possibly because of their interferences on gut microbiota. This study provides new insights into investigating the gastrointestinal toxic effects and mechanisms of DBPs through oral exposure.

PF543-like compound, a promising sphingosine kinase 1 inhibitor: Structure-based virtual screening and molecular dynamic simulation approaches

Sphingosine kinase 1 (SphK1) has been widely recognized as a significant contributor to various types of cancer, including breast, lung, prostate, and hematological cancers. This research aimed to find a potential SphK1 inhibitor through a step-by-step virtual screening of PF543 (a known SphK1 inhibitor)-like compounds obtained from the PubChem library with the Tanimoto threshold of 80 %. The virtual screening process included several steps, namely physicochemical and ADMET evaluation, PAINS filtering, and molecular docking, followed by molecular dynamics (MD) simulation and principal component analysis (PCA). The results showed that compound CID:58293960 ((3R)-1,1-dioxo-2-[[3-[(4-phenylphenoxy)methyl]phenyl]methyl]-1,2-thiazolidine-3-carboxylic acid) demonstrated high potential as SphK1 inhibitor. All-atom MD simulations were performed for 100 ns to evaluate the stability and structural changes of the docked complexes in an aqueous environment. The analysis of the time evolution data of structural deviations, compactness, PCA, and free energy landscape (FEL) indicated that the binding of CID:58293960 with SphK1 is relatively stable throughout the simulation. The results of this study provide a platform for the discovery and development of new anticancer therapeutics targeting SphK1.

Identification of a Specific Plasma Sphingolipid Profile in a Group of Normal-Weight and Obese Subjects: A Novel Approach for a "Biochemical" Diagnosis of Metabolic Syndrome?

Metabolic syndrome is nosographically defined by using clinical diagnostic criteria such as those of the International Diabetes Federation (IDF) ones, including visceral adiposity, blood hypertension, insulin resistance and dyslipidemia. Due to the pathophysiological implications of the cardiometabolic risk of the obese subject, sphingolipids, measured in the plasma, might be used to biochemically support the diagnosis of metabolic syndrome. A total of 84 participants, including normal-weight (NW) and obese subjects without (OB-SIMET-) and with (OB-SIMET+) metabolic syndrome, were included in the study, and sphingolipidomics, including ceramides (Cer), dihydroceramides (DHCer), hexosyl-ceramides (HexCer), lactosyl-ceramides (LacCer), sphingomyelins (SM) and GM3 ganglosides families, and sphingosine-1-phosphate (S1P) and its congeners, was performed in plasma. Only total DHCers and S1P were significantly higher in OB-SIMET+ than NW subjects (p < 0.05), while total Cers decreased in both obese groups, though statistical significance was reached only in OB-SIMET- (vs. NW) subjects (p < 0.05). When considering the comparisons of the single sphingolipid species in the obese groups (OB-SIMET- or OB-SIMET+) vs. NW subjects, Cer 24:0 was significantly decreased (p < 0.05), while Cer 24:1, DHCer 16:0, 18:0, 18:1 and 24:1, and SM 18:0, 18:1 and 24:1 were significantly increased (p < 0.05). Furthermore, taking into account the same groups for comparison, HexCer 22:0 and 24:0, and GM3 22:0 and 24:0 were significantly decreased (p < 0.05), while HexCer 24:1 and S1P were significantly increased (p < 0.05). After having analyzed all data via a PLS-DA-based approach, the subsequent determination of the VIP scores evidenced the existence of a specific cluster of 15 sphingolipids endowed with a high discriminating performance (i.e., VIP score > 1.0) among the three groups, including DHCer 18:0, DHCer 24:1, Cer 18:0, HexCer 22:0, GM3 24:0, Cer C24:1, SM 18:1, SM 18:0, DHCer 18:1, HexCer 24:0, SM 24:1, S1P, SM 16:0, HexCer 24:1 and LacCer 22:0. After having run a series of multiple linear regressions, modeled by inserting each sphingolipid having a VIP score > 1.0 as a dependent variable, and waist circumference (WC), systolic/diastolic blood pressures (SBP/DBP), homeostasis model assessment-estimated insulin resistance (HOMA-IR), high-density lipoprotein (HDL), triglycerides (TG) (surrogates of IDF criteria) and C-reactive protein (CRP) (a marker of inflammation) as independent variables, WC was significantly associated with DHCer 18:0, DHCer 24:1, Cer 18:0, HexCer 22:0, Cer 24:1, SM 18:1, and LacCer 22:0 (p < 0.05); SBP with Cer 18:0, Cer 24:1, and SM 18:0 (p < 0.05); HOMA-IR with DHCer 18:0, DHCer 24:1, Cer 18:0, Cer 24:1, SM 18:1, and SM 18:0 (p < 0.05); HDL with HexCer 22:0, and HexCer 24:0 (p < 0.05); TG with DHCer 18:1, DHCer 24:1, SM 18:1, and SM 16:0 (p < 0.05); CRP with DHCer 18:1, and SP1 (p < 0.05). In conclusion, a cluster of 15 sphingolipid species is able to discriminate, with high performance, NW, OB-SIMET- and OB-SIMET+ groups. Although (surrogates of) the IDF diagnostic criteria seem to predict only partially, but congruently, the observed sphingolipid signature, sphingolipidomics might represent a promising "biochemical" support for the clinical diagnosis of metabolic syndrome.

ACER2 forms a cold tumor microenvironment and predicts the molecular subtype in bladder cancer: Results from real-world cohorts

Background: ACER2 is a critical gene regulating cancer cell growth and migration, whereas the immunological role of ACER2 in the tumor microenvironment (TME) is scarcely reported. Thus, we lucubrate the potential performance of ACER2 in bladder cancer (BLCA). Methods: We initially compared ACER2 expressions in BLCA with normal urothelium tissues based on data gathered from the Cancer Genome Atlas (TCGA) and our Xiangya cohort. Subsequently, we systematically explored correlations between ACER2 with immunomodulators, anti-cancer immune cycles, tumor-infiltrating immune cells, immune checkpoints and the T-cell inflamed score (TIS) to further confirm its immunological role in BLCA TME. In addition, we performed ROC analysis to illustrate the accuracy of ACER2 in predicting BLCA molecular subtypes and explored the response to several cancer-related treatments. Finally, we validated results in an immunotherapy cohort and Xiangya cohort to ensure the stability of our study. Results: Compared with normal urinary epithelium, ACER2 was significantly overexpressed in several cell lines and the tumor tissue of BLCA. ACER2 can contribute to the formation of non-inflamed BLCA TME supported by its negative correlations with immunomodulators, anti-cancer immune cycles, tumor-infiltrating immune cells, immune checkpoints and the TIS. Moreover, BLCA patients with high ACER2 expression were inclined to the luminal subtype, which were characterized by insensitivity to neoadjuvant chemotherapy, chemotherapy and radiotherapy but not to immunotherapy. Results in the IMvigor210 and Xiangya cohort were consistent. Conclusion: ACER2 could accurately predict the TME and clinical outcomes for BLCA. It would be served as a promising target for precision treatment in the future.

Systemic inflammation factors as survival prognosis markers in ovarian neoplasm and the relationship with cancer-associated inflammatory mediators-a review

At the level of the genital system, ovarian neoplasm is the most frequent cause of morbidity and mortality. In the specialized literature, the coexistence of an inflammatory process is admitted from the early stages of the evolution of this pathology. Starting from the importance of this process, both in determinism and in the evolution of carcinogenesis and summarizing the field of knowledge, for this study we considered two objectives: the first was the presentation of the pathogenic mechanism, through which chronic +ovarian inflammation is involved in the process of carcinogenesis, and the second is the justification of the clinical utility of the three parameters, accepted as biomarkers of systemic inflammation: neutrophil-lymphocyte ratio, platelet lymphocyte ratio, and lymphocyte-monocyte ratio in the assessment of prognosis. The study highlights the acceptance of these hematological parameters, with practical utility, as prognostic biomarkers in ovarian cancer, based on the intrinsic link with cancer-associated inflammatory mediators. Based on the data from the specialized literature, the conclusion is that in ovarian cancer, the inflammatory process induced by the presence of the tumor, induces changes in the types of circulating leukocytes, with immediate effects on the markers of systemic inflammation.

Potential role of autophagy induced by FLT3-ITD and acid ceramidase in acute myeloid leukemia chemo-resistance: new insights

Acute myeloid leukemia (AML) is a type of leukemia with a poor prognosis and survival characterized by abnormal cell proliferation and differentiation. Despite advances in treatment, AML still has a low complete remission rate, particularly in elderly patients, and recurrences are frequently seen even after complete remissions. The major challenge in treating AML is the resistance of leukemia cells to chemotherapy drugs. Thus, to overcome this issue, it can be crucial to conduct new investigations to explore the mechanisms of chemo-resistance in AML and target them. In this review, the potential role of autophagy induced by FLT3-ITD and acid ceramidase in chemo-resistance in AML patients are analyzed. With regard to the high prevalence of FLT3-ITD mutation (about 25% of AML cases) and high level of acid ceramidase in these patients, we hypothesized that both of these factors could lead to chemo-resistance by inducing autophagy. Therefore, pharmacological targeting of autophagy, FLT3-ITD, and acid ceramidase production could be a promising therapeutic approach for such AML patients to overcome chemo-resistance.

Effects of sphingolipid metabolism disorders on endothelial cells

Many cardiovascular disorders, including atherosclerosis, hypertension, coronary heart disease, diabetes, etc., are characterized by endothelial cell dysfunction. Endothelial cell function is closely related to sphingolipid metabolism, and normal sphingolipid metabolism is critical for maintaining endothelial cell homeostasis. Sphingolipid metabolites or key enzymes in abnormal situation, including sphingosine, ceramide (Cer), sphingosine-1-phosphate (S1P), serine, sphingosine kinase (SPHK), ceramide kinase (Cerk), sphingosine-1-phosphate lyase (S1PL) etc., may have a protective or damaging effect on the function of endothelial cells. This review summarizes the effects of sphingolipid metabolites and key enzymes disordering in sphingolipid metabolism on endothelial cells, offering some insights into further research on the pathogenesis of cardiovascular diseases and corresponding therapeutic targets.

Targeting the Sphingolipid Rheostat in Gliomas

Gliomas are highly aggressive cancer types that are in urgent need of novel drugs and targeted therapies. Treatment protocols have not improved in over a decade, and glioma patient survival remains among the worst of all cancer types. As a result, cancer metabolism research has served as an innovative approach to identifying novel glioma targets and improving our understanding of brain tumors. Recent research has uncovered a unique metabolic vulnerability in the sphingolipid pathways of gliomas that possess the IDH1 mutation. Sphingolipids are a family of lipid signaling molecules that play a variety of second messenger functions in cellular regulation. The two primary metabolites, sphingosine-1-phosphate (S1P) and ceramide, maintain a rheostat balance and play opposing roles in cell survival and proliferation. Altering the rheostat such that the pro-apoptotic signaling of the ceramides outweighs the pro-survival S1P signaling in glioma cells diminishes the hallmarks of cancer and enhances tumor cell death. Throughout this review, we discuss the sphingolipid pathway and identify the enzymes that can be most effectively targeted to alter the sphingolipid rheostat and enhance apoptosis in gliomas. We discuss each pathway’s steps based on their site of occurrence in the organelles and postulate novel targets that can effectively exploit this vulnerability.

Ceramide and Sphingosine-1-Phosphate in Neurodegenerative Disorders and Their Potential Involvement in Therapy

Neurodegenerative disorders (ND) are progressive diseases of the nervous system, often without resolutive therapy. They are characterized by a progressive impairment and loss of specific brain regions and neuronal populations. Cellular and animal model studies have identified several molecular mechanisms that play an important role in the pathogenesis of ND. Among them are alterations of lipids, in particular sphingolipids, that play a crucial role in neurodegeneration. Overall, during ND, ceramide-dependent pro-apoptotic signalling is promoted, whereas levels of the neuroprotective spingosine-1-phosphate are reduced. Moreover, ND are characterized by alterations of the metabolism of complex sphingolipids. The finding that altered sphingolipid metabolism has a role in ND suggests that its modulation might provide a useful strategy to identify targets for possible therapies. In this review, based on the current literature, we will discuss how bioactive sphingolipids (spingosine-1-phosphate and ceramide) are involved in some ND (Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis) and their possible involvement in therapies.

Sphingolipid Metabolism and Signaling in Lung Cancer: A Potential Therapeutic Target

Sphingolipids are important bioactive lipids that not only play an important role in maintaining the barrier function and fluidity of cell membranes but also regulate multiple processes in cancer development by controlling multiple signaling pathways in the signal transduction network. Dysregulation of sphingolipid metabolism is thought to be one of the most important dysregulated pathways in lung cancer, the most prevalent type of cancer in terms of incidence and mortality worldwide. This article focuses on lung cancer, reviewing the important lipids in sphingolipid metabolism and the related enzymes in relation to lung cancer progression and their effects on the tumor microenvironment and discussing their roles in the diagnosis and treatment of lung cancer.

Comparative metabolomic analysis in plasma and cerebrospinal fluid of humans and in plasma and brain of mice following antidepressant-dose ketamine administration

Subanesthetic-dose racemic (R,S)-ketamine (ketamine) produces rapid, robust, and sustained antidepressant effects in major depressive disorder (MDD) and bipolar disorder (BD) and has also been shown to effectively treat neuropathic pain, complex regional pain syndrome, and post-traumatic stress disorder (PTSD). However, to date, its mechanism of action remains unclear. Preclinical studies found that (2 R,6 R;2 S,6 S)-hydroxynorketamine (HNK), a major circulating metabolite of ketamine, elicits antidepressant effects similar to those of ketamine. To help determine how (2 R,6 R)-HNK contributes to ketamine's mechanism of action, an exploratory, targeted, metabolomic analysis was carried out on plasma and CSF of nine healthy volunteers receiving a 40-minute ketamine infusion (0.5 mg/kg). A parallel targeted metabolomic analysis in plasma, hippocampus, and hypothalamus was carried out in mice receiving either 10 mg/kg of ketamine, 10 mg/kg of (2 R,6 R)-HNK, or saline. Ketamine and (2 R,6 R)-HNK both affected multiple pathways associated with inflammatory conditions. In addition, several changes were unique to either the healthy human volunteers and/or the mouse arm of the study, indicating that different pathways may be differentially involved in ketamine's effects in mice and humans. Mechanisms of action found to consistently underlie the effects of ketamine and/or (2 R,6 R)-HNK across both the human metabolome in plasma and CSF and the mouse arm of the study included LAT1, IDO1, NAD+, the nitric oxide (NO) signaling pathway, and sphingolipid rheostat.

A Rheostat of Ceramide and Sphingosine-1-Phosphate as a Determinant of Oxidative Stress-Mediated Kidney Injury

Reactive oxygen species (ROS) modulate sphingolipid metabolism, including enzymes that generate ceramide and sphingosine-1-phosphate (S1P), and a ROS-antioxidant rheostat determines the metabolism of ceramide-S1P. ROS induce ceramide production by activating ceramide-producing enzymes, leading to apoptosis, while they inhibit S1P production, which promotes survival by suppressing sphingosine kinases (SphKs). A ceramide-S1P rheostat regulates ROS-induced mitochondrial dysfunction, apoptotic/anti-apoptotic Bcl-2 family proteins and signaling pathways, leading to apoptosis, survival, cell proliferation, inflammation and fibrosis in the kidney. Ceramide inhibits the mitochondrial respiration chain and induces ceramide channel formation and the closure of voltage-dependent anion channels, leading to mitochondrial dysfunction, altered Bcl-2 family protein expression, ROS generation and disturbed calcium homeostasis. This activates ceramide-induced signaling pathways, leading to apoptosis. These events are mitigated by S1P/S1P receptors (S1PRs) that restore mitochondrial function and activate signaling pathways. SphK1 promotes survival and cell proliferation and inhibits inflammation, while SphK2 has the opposite effect. However, both SphK1 and SphK2 promote fibrosis. Thus, a ceramide-SphKs/S1P rheostat modulates oxidant-induced kidney injury by affecting mitochondrial function, ROS production, Bcl-2 family proteins, calcium homeostasis and their downstream signaling pathways. This review will summarize the current evidence for a role of interaction between ROS-antioxidants and ceramide-SphKs/S1P and of a ceramide-SphKs/S1P rheostat in the regulation of oxidative stress-mediated kidney diseases.

Sex Differences in Cardiovascular Diseases: A Matter of Estrogens, Ceramides, and Sphingosine 1-Phosphate

The medical community recognizes sex-related differences in pathophysiology and cardiovascular disease outcomes (CVD), culminating with heart failure. In general, pre-menopausal women tend to have a better prognosis than men. Explaining why this occurs is not a simple matter. For decades, sex hormones like estrogens (Es) have been identified as one of the leading factors driving these sex differences. Indeed, Es seem protective in women as their decline, during and after menopause, coincides with an increased CV risk and HF development. However, clinical trials demonstrated that E replacement in post-menopause women results in adverse cardiac events and increased risk of breast cancer. Thus, a deeper understanding of E-related mechanisms is needed to provide a vital gateway toward better CVD prevention and treatment in women. Of note, sphingolipids (SLs) and their metabolism are strictly related to E activities. Among the SLs, ceramide and sphingosine 1-phosphate play essential roles in mammalian physiology, particularly in the CV system, and appear differently modulated in males and females. In keeping with this view, here we explore the most recent experimental and clinical observations about the role of E and SL metabolism, emphasizing how these factors impact the CV system.

Systems genetics in the rat HXB/BXH family identifies Tti2 as a pleiotropic quantitative trait gene for adult hippocampal neurogenesis and serum glucose

Neurogenesis in the adult hippocampus contributes to learning and memory in the healthy brain but is dysregulated in metabolic and neurodegenerative diseases. The molecular relationships between neural stem cell activity, adult neurogenesis, and global metabolism are largely unknown. Here we applied unbiased systems genetics methods to quantify genetic covariation among adult neurogenesis and metabolic phenotypes in peripheral tissues of a genetically diverse family of rat strains, derived from a cross between the spontaneously hypertensive (SHR/OlaIpcv) strain and Brown Norway (BN-Lx/Cub). The HXB/BXH family is a very well established model to dissect genetic variants that modulate metabolic and cardiovascular diseases and we have accumulated deep phenome and transcriptome data in a FAIR-compliant resource for systematic and integrative analyses. Here we measured rates of precursor cell proliferation, survival of new neurons, and gene expression in the hippocampus of the entire HXB/BXH family, including both parents. These data were combined with published metabolic phenotypes to detect a neurometabolic quantitative trait locus (QTL) for serum glucose and neuronal survival on Chromosome 16: 62.1-66.3 Mb. We subsequently fine-mapped the key phenotype to a locus that includes the Telo2-interacting protein 2 gene (Tti2)-a chaperone that modulates the activity and stability of PIKK kinases. To verify the hypothesis that differences in neurogenesis and glucose levels are caused by a polymorphism in Tti2, we generated a targeted frameshift mutation on the SHR/OlaIpcv background. Heterozygous SHR-Tti2+/- mutants had lower rates of hippocampal neurogenesis and hallmarks of dysglycemia compared to wild-type littermates. Our findings highlight Tti2 as a causal genetic link between glucose metabolism and structural brain plasticity. In humans, more than 800 genomic variants are linked to TTI2 expression, seven of which have associations to protein and blood stem cell factor concentrations, blood pressure and frontotemporal dementia.

Metabolism disorder promotes isoproterenol-induced myocardial injury in mice with high temperature and high humidity and high-fat diet

Background

Isoproterenol (ISO), a synthetic on selective β-adrenergic agonist, provides a simple and non-invasive method for inducing myocardial injury with lower mortality and higher reproducibility. Phlegm-damp syndrome, as known as “Tanshi” in Chinese, is one of Traditional Chinese Medicine (TCM) syndrome differentiation, which plays an important role in the development of cardiovascular diseases. However, the underlying mechanism remains unknown.

Methods

In our present study, a myocardial injury mouse model was introduced by ISO administration combined with high temperature and high humidity and high-fat diet to simulate phlegm-damp syndrome. Nontargeted metabolomics with LC–MS/MS was adopted to reveal serum metabolism profile for elucidating the possible molecular mechanism.

Results

The results of our study showed that phlegm-damp syndrome promoted ISO-induced myocardial injury by aggravating left ventricular hypertrophy and fibrosis, and increasing cardiac index. Our study also confirmed the presence of specific metabolites and disturbed metabolic pathways by comparing ISO mice and Tanshi mice, mainly including glycerophospholipid metabolism, arginine–proline metabolism, and sphingolipid signaling pathway. The lysoPCs, PCs, SMs, Sphingosine, and L-Arginine were the main metabolites that showed a difference between ISO and Tanshi mice, which might be the result of the underlying mechanism in the promotion of ISO-induced myocardial injury in mice with high temperature and high humidity and high-fat diet.

Conclusion

Our current study provides new insights into contribution of metabolism disorder in promotion of ISO-induced myocardial injury in mice with high temperature and high humidity and high-fat diet, and new targets for clinical diagnosis and pharmacologic treatment of cardiovascular disease with phlegm-damp syndrome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02583-z.

Staphylococcus aureus β-Toxin Exerts Anti-angiogenic Effects by Inhibiting Re-endothelialization and Neovessel Formation

Staphylococcus aureus causes severe, life-threatening infections that often are complicated by severe local and systemic pathologies with non-healing lesions. A classic example is S. aureus infective endocarditis (IE), where the secreted hemolysin β-toxin potentiates the disease via its sphingomyelinase and biofilm ligase activities. Although these activities dysregulate human aortic endothelial cell activation, β-toxin effect on endothelial cell function in wound healing has not been addressed. With the use of the ex vivo rabbit aortic ring model, we provide evidence that β-toxin prevents branching microvessel formation, highlighting its ability to interfere with tissue re-vascularization and vascular repair. We show that β-toxin specifically targets both human aortic endothelial cell proliferation and cell migration and inhibits human umbilical vein endothelial cell rearrangement into capillary-like networks in vitro. Proteome arrays specific for angiogenesis-related molecules provided evidence that β-toxin promotes an inhibitory profile in endothelial cell monolayers, specifically targeting production of TIMP-1, TIMP-4, and IGFBP-3 to counter the effect of a pro-angiogenic environment. Dysregulation in the production of these molecules is known to result in sprouting defects (including deficient cell proliferation, migration, and survival), vessel instability and/or vascular regression. When endothelial cells are grown under re-endothelialization/wound healing conditions, β-toxin decreases the pro-angiogenic molecule MMP-8 and increases the anti-angiogenic molecule endostatin. Altogether, the data indicate that β-toxin is an anti-angiogenic virulence factor and highlight a mechanism where β-toxin exacerbates S. aureus invasive infections by interfering with tissue re-vascularization and vascular repair.

Role of Ceramides in the Molecular Pathogenesis and Potential Therapeutic Strategies of Cardiometabolic Diseases: What we Know so Far

Ceramides represent a class of biologically active lipids that are involved in orchestrating vital signal transduction pathways responsible for regulating cellular differentiation and proliferation. However, accumulating clinical evidence have shown that ceramides are playing a detrimental role in the pathogenesis of several diseases including cardiovascular disease, type II diabetes and obesity, collectively referred to as cardiometabolic disease. Therefore, it has become necessary to study in depth the role of ceramides in the pathophysiology of such diseases, aiming to tailor more efficient treatment regimens. Furthermore, understanding the contribution of ceramides to the pathological molecular mechanisms of those interrelated conditions may improve not only the therapeutic but also the diagnostic and preventive approaches of the preceding hazardous events. Hence, the purpose of this article is to review currently available evidence on the role of ceramides as a common factor in the pathological mechanisms of cardiometabolic diseases as well as the mechanism of action of the latest ceramides-targeted therapies.

Effects of Sex, Age, and Apolipoprotein E Genotype on Brain Ceramides and Sphingosine-1-Phosphate in Alzheimer's Disease and Control Mice

Apolipoprotein ε4 (APOE)4 is a strong risk factor for the development of Alzheimer’s disease (AD) and aberrant sphingolipid levels have been implicated in AD. We tested the hypothesis that the APOE4 genotype affects brain sphingolipid levels in AD. Seven ceramides and sphingosine-1-phosphate (S1P) were quantified by LC-MSMS in hippocampus, cortex, cerebellum, and plasma of <3 months and >5 months old human APOE3 and APOE4-targeted replacement mice with or without the familial AD (FAD) background of both sexes (145 animals). APOE4 mice had higher Cer(d18:1/24:0) levels in the cortex (1.7-fold, p = 0.002) than APOE3 mice. Mice with AD background showed higher levels of Cer(d18:1/24:1) in the cortex than mice without (1.4-fold, p = 0.003). S1P levels were higher in all three brain regions of older mice than of young mice (1.7-1.8-fold, all p ≤ 0.001). In female mice, S1P levels in hippocampus (r = −0.54 [−0.70, −0.35], p < 0.001) and in cortex correlated with those in plasma (r = −0.53 [−0.71, −0.32], p < 0.001). Ceramide levels were lower in the hippocampus (3.7–10.7-fold, all p < 0.001), but higher in the cortex (2.3–12.8-fold, p < 0.001) of female than male mice. In cerebellum and plasma, sex effects on individual ceramides depended on acyl chain length (9.5-fold lower to 11.5-fold higher, p ≤ 0.001). In conclusion, sex is a stronger determinant of brain ceramide levels in mice than APOE genotype, AD background, or age. Whether these differences impact AD neuropathology in men and women remains to be investigated.

Human serum metabolomic analysis reveals progression for high blood pressure in type 2 diabetes mellitus

INTRODUCTION

Type 2 diabetes mellitus (T2DM) is one of the most ordinary metabolic disorders and manifests as a high blood sugar level; 80%-90% of patients with T2DM will develop high blood pressure (HBP), which exacerbates irreversible organ damage. Understanding the metabolic basis of HBP is essential to facilitating early diagnosis and prompt treatments of diabetic complications.

RESEARCH DESIGN AND METHODS

34 patients who originally had T2DM and then developed HBP within 1 year were selected from physical examination participants. Using ultrahigh-performance liquid chromatography quadrupole time-of-flight metabolomic analysis, we compared the metabolomic profile of patients with 30 healthy controls. The results showed a clear discrimination in metabolomic profiles between T2DM and T2DM+HBP when employing orthogonal projection to latent structure with discriminant analysis with electrospray ionization modes.

RESULTS

Eight differential metabolites changed significantly during disease progression, among which L-isoleucine, L-glutamic acid, pyroglutamic acid and linoleic acid decreased, while sphinganine, Cer(d18:0/16:0), Cer(d18:0/18:0), and citric acid increased. These metabolites are associated with the γ-glutamyl cycle, tricarboxylic acid cycle, and ceramide metabolism.

CONCLUSIONS

These novel serum biomarkers may improve the management of T2DM and HBP complications, thus reducing the use of incorrect medical care.

Dihydrosphingosine driven enrichment of sphingolipids attenuates TGFβ induced collagen synthesis in cardiac fibroblasts

The sphingolipid de novo synthesis pathway, encompassing the sphingolipids, the enzymes and the cell membrane receptors, are being investigated for their role in diseases and as potential therapeutic targets. The intermediate sphingolipids such as dihydrosphingosine (dhSph) and sphingosine (Sph) have not been investigated due to them being thought of as precursors to other more active lipids such as ceramide (Cer) and sphingosine 1 phosphate (S1P). Here we investigated their effects in terms of collagen synthesis in primary rat neonatal cardiac fibroblasts (NCFs). Our results in NCFs showed that both dhSph and Sph did not induce collagen synthesis, whilst dhSph reduced collagen synthesis induced by transforming growth factor β (TGFβ). The mechanisms of these inhibitory effects were associated with the increased activation of the de novo synthesis pathway that led to increased dihydrosphingosine 1 phosphate (dhS1P). Subsequently, through a negative feedback mechanism that may involve substrate-enzyme receptor interactions, S1P receptor 1 expression (S1PR1) was reduced.

Age-Related Transcriptional Deregulation of Genes Coding Synaptic Proteins in Alzheimer's Disease Murine Model: Potential Neuroprotective Effect of Fingolimod

Alzheimer's disease (AD) induces time-dependent changes in sphingolipid metabolism, which may affect transcription regulation and neuronal phenotype. We, therefore, analyzed the influence of age, amyloid β precursor protein (AβPP), and the clinically approved, bioavailable sphingosine-1-phosphate receptor modulator fingolimod (FTY720) on the expression of synaptic proteins. RNA was isolated, reverse-transcribed, and subjected to real-time PCR. Expression of mutant (V717I) AβPP led to few changes at 3 months of age but reduced multiple mRNA coding for synaptic proteins in a 12-month-old mouse brain. Complexin 1 (Cplx1), SNAP25 (Snap25), syntaxin 1A (Stx1a), neurexin 1 (Nrxn1), neurofilament light (Nefl), and synaptotagmin 1 (Syt1) in the hippocampus, and VAMP1 (Vamp1) and neurexin 1 (Nrxn1) in the cortex were all significantly reduced in 12-month-old mice. Post mortem AD samples from the human hippocampus and cortex displayed lower expression of VAMP, synapsin, neurofilament light (NF-L) and synaptophysin. The potentially neuroprotective FTY720 reversed most AβPP-induced changes in gene expression (Cplx1, Stx1a, Snap25, and Nrxn1) in the 12-month-old hippocampus, which is thought to be most sensitive to early neurotoxic insults, but it only restored Vamp1 in the cortex and had no influence in 3-month-old brains. Further study may reveal the potential usefulness of FTY720 in the modulation of deregulated neuronal phenotype in AD brains.

Recent Insights into the Interplay of Alpha-Synuclein and Sphingolipid Signaling in Parkinson's Disease

Molecular studies have provided increasing evidence that Parkinson’s disease (PD) is a protein conformational disease, where the spread of alpha-synuclein (ASN) pathology along the neuraxis correlates with clinical disease outcome. Pathogenic forms of ASN evoke oxidative stress (OS), neuroinflammation, and protein alterations in neighboring cells, thereby intensifying ASN toxicity, neurodegeneration, and neuronal death. A number of evidence suggest that homeostasis between bioactive sphingolipids with opposing function—e.g., sphingosine-1-phosphate (S1P) and ceramide—is essential in pro-survival signaling and cell defense against OS. In contrast, imbalance of the “sphingolipid biostat” favoring pro-oxidative/pro-apoptotic ceramide-mediated changes have been indicated in PD and other neurodegenerative disorders. Therefore, we focused on the role of sphingolipid alterations in ASN burden, as well as in a vast range of its neurotoxic effects. Sphingolipid homeostasis is principally directed by sphingosine kinases (SphKs), which synthesize S1P—a potent lipid mediator regulating cell fate and inflammatory response—making SphK/S1P signaling an essential pharmacological target. A growing number of studies have shown that S1P receptor modulators, and agonists are promising protectants in several neurological diseases. This review demonstrates the relationship between ASN toxicity and alteration of SphK-dependent S1P signaling in OS, neuroinflammation, and neuronal death. Moreover, we discuss the S1P receptor-mediated pathways as a novel promising therapeutic approach in PD.

Loss of sphingosine kinase 1 increases lung metastases in the MMTV-PyMT mouse model of breast cancer

Breast cancer is a very heterogeneous disease, and ~30% of breast cancer patients succumb to metastasis, highlighting the need to understand the mechanisms of breast cancer progression in order to identify new molecular targets for treatment. Sphingosine kinase 1 (SK1) has been shown to be upregulated in patients with breast cancer, and several studies have suggested its involvement in breast cancer progression and/or metastasis, mostly based on cell studies. In this work we evaluated the role of SK1 in breast cancer development and metastasis using a transgenic breast cancer model, mouse mammary tumor virus-polyoma middle tumor-antigen (MMTV-PyMT), that closely resembles the characteristics and evolution of human breast cancer. The results show that SK1 deficiency does not alter tumor latency or growth, but significantly increases the number of metastatic lung nodules and the average metastasis size in the lung of MMTV-PyMT mice. Additionally, analysis of Kaplan-Meier plotter of human disease shows that high SK1 mRNA expression can be associated with a better prognosis for breast cancer patients. These results suggest a metastasis-suppressing function for SK1 in the MMTV-PyMT model of breast cancer, and that its role in regulating human breast cancer progression and metastasis may be dependent on the breast cancer type.

Platelet extracellular vesicles mediate transfusion-related acute lung injury by imbalancing the sphingolipid rheostat

Transfusion-related acute lung injury (TRALI) is a hazardous transfusion complication with an associated mortality of 5% to 15%. We previously showed that stored (5 days) but not fresh platelets (1 day) cause TRALI via ceramide-mediated endothelial barrier dysfunction. As biological ceramides are hydrophobic, extracellular vesicles (EVs) may be required to shuttle these sphingolipids from platelets to endothelial cells. Adding to complexity, EV formation in turn requires ceramide. We hypothesized that ceramide-dependent EV formation from stored platelets and EV-dependent sphingolipid shuttling induces TRALI. EVs formed during storage of murine platelets were enumerated, characterized for sphingolipids, and applied in a murine TRALI model in vivo and for endothelial barrier assessment in vitro. Five-day EVs were more abundant, had higher long-chain ceramide (C16:0, C18:0, C20:0), and lower sphingosine-1-phosphate (S1P) content than 1-day EVs. Transfusion of 5-day, but not 1-day, EVs induced characteristic signs of lung injury in vivo and endothelial barrier disruption in vitro. Inhibition or supplementation of ceramide-forming sphingomyelinase reduced or enhanced the formation of EVs, respectively, but did not alter the injuriousness per individual EV. Barrier failure was attenuated when EVs were abundant in or supplemented with S1P. Stored human platelet 4-day EVs were more numerous compared with 2-day EVs, contained more long-chain ceramide and less S1P, and caused more endothelial cell barrier leak. Hence, platelet-derived EVs become more numerous and more injurious (more long-chain ceramide, less S1P) during storage. Blockade of sphingomyelinase, EV elimination, or supplementation of S1P during platelet storage may present promising strategies for TRALI prevention.

Lipophilic tail modifications of 2-(hydroxymethyl)pyrrolidine scaffold reveal dual sphingosine kinase 1 and 2 inhibitors

The sphingosine 1-phosphate (S1P) signaling pathway is an attractive target for pharmacological manipulation due to its involvement in cancer progression and immune cell chemotaxis. The synthesis of S1P is catalyzed by the action of sphingosine kinase 1 or 2 (SphK1 or SphK2) on sphingosine and ATP. While potent and selective inhibitors of SphK1 or SphK2 have been reported, development of potent dual SphK1/SphK2 inhibitors are still needed. Towards this end, we report the structure-activity relationship profiling of 2-(hydroxymethyl)pyrrolidine-based inhibitors with 22d being the most potent dual SphK1/SphK2 inhibitor (SphK1 K_i = 0.679 μM, SphK2 K_i = 0.951 μM) reported in this series. 22d inhibited the growth of engineered Saccharomyces cerevisiae and decreased S1P levels in histiocytic lymphoma myeloid cell line (U937 cells), demonstrating inhibition of SphK1 and 2 in vitro. Molecular modeling studies of 22d docked inside the Sph binding pocket of both SphK1 and SphK2 indicate essential hydrogen bond between the 2-(hydroxymethyl)pyrrolidine head to interact with aspartic acid and serine residues near the ATP binding pocket, which provide the basis for dual inhibition. In addition, the dodecyl tail adopts a "J-shape" conformation found in crystal structure of sphingosine bound to SphK1. Collectively, these studies provide insight into the intermolecular interactions in the SphK1 and 2 active sites to achieve maximal dual inhibitory activity.

Inflammasome activation in acute lung injury

Inflammasomes are multiprotein complexes tasked with sensing endogenous or exogenous inflammatory signals and integrating this signal into a downstream response. Inflammasome activation has been implicated in a variety of pulmonary diseases, including pulmonary hypertension, bacterial pneumonia, COPD, and asthma. Of increasing interest is the contribution of inflammasome activation in the context of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Inflammasome activation in both the lung parenchyma and resident immune cells generates intereukin-1β (IL-1β) and IL-18, both of which drive the cascade of lung inflammation forward. Blockade of these responses has been shown to be beneficial in animal models and is a focus of translational research in the field. In this review, we will discuss the assembly and regulation of inflammasomes during lung inflammation, highlighting therapeutically viable effector steps. We will examine the importance of IL-1β and IL-18, two key products of inflammasome activation, in ALI, as well as the contribution of the pulmonary endothelial cell to this process. Finally, we will explore translational research moving toward anti-inflammasome therapies for ALI/ARDS and speculate toward future directions for the field.

Sphingosine 1-phosphate in sepsis and beyond: Its role in disease tolerance and host defense and the impact of carrier molecules

Sphingosine 1-phosphate (S1P) is an important immune modulator responsible for physiological cellular responses like lymphocyte development and function, positioning and emigration of T and B cells and cytokine secretion. Recent reports indicate that S1P does not only regulate immunity, but can also protect the function of organs by inducing disease tolerance. S1P also influences the replication of certain pathogens, and sphingolipids are also involved in pathogen recognition and killing. Certain carrier molecules for S1P like serum albumin and high density lipoproteins contribute to the regulation of S1P effects. They are able to associate with S1P and modulate its signaling properties. Similar to S1P, both carrier molecules are also decreased in sepsis patients and likely contribute to sepsis pathology and severity. In this review, we will introduce the concept of disease tolerance and the involvement of S1P. We will also discuss the contribution of S1P and its precursor sphingosine to host defense mechanisms against pathogens. Finally, we will summarize current data demonstrating the influence of carrier molecules for differential S1P signaling. The presented data may lead to new strategies for the prevention and containment of sepsis.

Cardioprotective Effects of Taurisolo® in Cardiomyoblast H9c2 Cells under High-Glucose and Trimethylamine N-Oxide Treatment via De Novo Sphingolipid Synthesis

In addition to high plasma glucose, increased levels of trimethylamine N-oxide (TMAO) have been found in obese subjects, where are considered as a novel risk factor for cardiovascular diseases. The present study aimed to investigate the effect of a novel nutraceutical formulation based on grape polyphenols (registered as Taurisolo®) in counteracting TMAO- and high glucose (HG)-induced cytotoxicity in cardiomyoblast H9c2 cells. Cell damage was induced with HG (HG-H9c2) and HG+TMAO (THG-H9c2); both experimental cell models were, thus, incubated for 72 h in the presence or absence of Taurisolo®. It was observed that Taurisolo® significantly increased the cell viability and reduced lactate dehydrogenase and aspartate transaminase release in both HG- and THG-H9c2 cells. Additionally, through its antioxidant activity, Taurisolo® modulated cell proliferation via ERK activation in THG-H9c2. Furthermore, Taurisolo® was able to induce autophagic process via increasing the expression of LC3II, a protein marker involved in formation of autophagosome and ex novo synthesis of sphingomyelin, ceramides, and their metabolites both in HG- and THG-H9c2 cells. Finally, Taurisolo® reduced hypertrophy and induced differentiation of HG-H9C2 cells into cardiomyocyte-like cells. These data suggest that Taurisolo® counteracts the toxicity induced by TMAO and HG concentrations increasing autophagic process and activating de novo sphingolipid synthesis, resulting in a morphological cell remodeling. In conclusion, our results allow speculating that Taurisolo®, combined with energy restriction, may represent a useful nutraceutical approach for prevention of cardiomyopathy in obese subjects.

New strategies to treat AML: novel insights into AML survival pathways and combination therapies

The effective treatment of acute myeloid leukemia (AML) is very challenging. Due to the immense heterogeneity of this disease, treating it using a "one size fits all" approach is ineffective and only benefits a subset of patients. Instead, there is a shift towards more personalized treatment based on the patients' genomic signature. This shift has facilitated the increased revelation of novel insights into pathways that lead to the survival and propagation of AML cells. These AML survival pathways are involved in drug resistance, evasion of the immune system, reprogramming metabolism, and impairing differentiation. In addition, based on the reports of enhanced clinical efficiencies when combining drugs or treatments, deeper investigation into possible pathways, which can be targeted together to increase treatment response in a wider group of patients, is warranted. In this review, not only is a comprehensive summary of targets involved in these pathways provided, but also insights into the potential of targeting these molecules in combination therapy will be discussed.

Sphingolipid Pathway as a Source of Vulnerability in IDH1mut Glioma

In addition to providing integrity to cellular structure, the various classes of lipids participate in a multitude of functions including secondary messengers, receptor stimulation, lymphocyte trafficking, inflammation, angiogenesis, cell migration, proliferation, necrosis and apoptosis, thus highlighting the importance of understanding their role in the tumor phenotype. In the context of IDH1mut glioma, investigations focused on metabolic alterations involving lipidomics' present potential to uncover novel vulnerabilities. Herein, a detailed lipidomic analysis of the sphingolipid metabolism was conducted in patient-derived IDH1mut glioma cell lines, as well as model systems, with the of identifying points of metabolic vulnerability. We probed the effect of decreasing D-2HG levels on the sphingolipid pathway, by treating these cell lines with an IDH1mut inhibitor, AGI5198. The results revealed that N,N-dimethylsphingosine (NDMS), sphingosine C17 and sphinganine C18 were significantly downregulated, while sphingosine-1-phosphate (S1P) was significantly upregulated in glioma cultures following suppression of IDH1mut activity. We exploited the pathway using a small-scale, rational drug screen and identified a combination that was lethal to IDHmut cells. Our work revealed that further addition of N,N-dimethylsphingosine in combination with sphingosine C17 triggered a dose-dependent biostatic and apoptotic response in a panel of IDH1mut glioma cell lines specifically, while it had little effect on the IDHWT cells probed here. To our knowledge, this is the first study that shows how altering the sphingolipid pathway in IDH1mut gliomas elucidates susceptibility that can arrest proliferation and initiate subsequent cellular death.

The hepatoprotective effect and mechanism of lotus leaf on liver injury induced by Genkwa Flos

OBJECTIVES

As a traditional Chinese medicine, lotus leaf was reported to have significant hepatoprotective effect. To explore the hepatoprotective mechanism of lotus leaf, a rapid and reliable UPLC-MS/MS method was conducted to simultaneously determine six specific endogenous substances including 5-oxoproline, phenylalanine, tryptophan, C₁₈ -phytosphingosine, lysophosphatidylcholine (16 : 0) and lysophosphatidylcholine (18 : 1).

METHODS

With the help of HPLC-FT-ICR-MS, the chemical constituents of louts leaf extract were elucidated. By observing histopathological changes and determining hepatotoxicity-related biochemical indicators, rat model of liver injury was developed and the hepatoprotective effect of lotus leaf was verified. With the developed UPLC-MS/MS method, six endogenous metabolites related to hepatotoxicity were monitored to investigate the hepatoprotective mechanism of lotus leaf.

KEY FINDINGS

In the qualitative analysis, a total of twenty compounds including ten flavonoids, nine alkaloids and one proanthocyanidin were identified. Based on the results of determining six endogenous metabolites related to hepatotoxicity, it was predicted that the hepatoprotective mechanism of lotus leaf might be related to glutathione metabolism, phenylalanine metabolism, tryptophan metabolism, sphingolipid metabolism and phospholipid metabolism.

CONCLUSIONS

This study could be a meaningful investigation to provide mechanistic insights into the hepatoprotective effect of lotus leaf and further lay a theoretical basis for the clinical application of lotus leaf.

Sphingolipids and Diagnosis, Prognosis, and Organ Damage in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that involves multiple organs and disproportionality affects females, especially African Americans from 15 to 44 years of age. SLE can lead to end organ damage including kidneys, lungs, cardiovascular and neuropsychiatric systems, with cardiovascular complications being the primary cause of death. Usually, SLE is diagnosed and its activity is assessed using the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), Systemic Lupus International Collaborating Clinics Damage Index (SLICC/ACR), and British Isles Lupus Assessment Group (BILAG) Scales, which unfortunately often occurs after a certain degree of systemic involvements, disease activity or organ damage already exists. There is certainly a need for the identification of early biomarkers to diagnose and assess disease activity as well as to evaluate disease prognosis and response to treatment earlier in the course of the disease. Here we review advancements made in the area of sphingolipidomics as a diagnostic/prognostic tool for SLE and its co-morbidities. We also discuss recent reports on differential sphingolipid metabolism and blood sphingolipid profiles in SLE-prone animal models as well as in diverse cohorts of SLE patients. In addition, we address targeting sphingolipids and their metabolism as a method of treating SLE and some of its complications. Although such treatments have already shown promise in preventing organ-specific pathology caused by SLE, further investigational studies and clinical trials are warranted.

Pro-Survival Lipid Sphingosine-1-Phosphate Metabolically Programs T Cells to Limit Anti-tumor Activity

Sphingosine 1-phosphate (S1P), a bioactive lysophospholipid generated by sphingosine kinase 1 (SphK1), regulates lymphocyte egress into circulation via S1P receptor 1 (S1PR1) signaling, and it controls the differentiation of regulatory T cells (Tregs) and T helper-17 cells. However, the mechanisms by which receptor-independent SphK1-mediated intracellular S1P levels modulate T cell functionality remains unknown. We show here that SphK1-deficient T cells maintain central memory phenotype and exhibit higher mitochondrial respiration and reduced differentiation to Tregs. Mechanistically, we discovered a direct correlation between SphK1-generated S1P and lipid transcription factor PPARγ (peroxisome proliferator-activated receptor gamma) activity, which in turn regulates lipolysis in T cells. Genetic and pharmacologic inhibition of SphK1 improved metabolic fitness and anti-tumor activity of T cells against murine melanoma. Further, inhibition of SphK1 and PD1 together led to improved control of melanoma. Overall, these data highlight the clinical potential of limiting SphK1/S1P signaling for enhancing anti-tumor-adoptive T cell therapy.

An adiponectin-S1P autocrine axis protects skeletal muscle cells from palmitate-induced cell death

Background

The prevalence of type 2 diabetes, obesity and their various comorbidities have continued to rise. In skeletal muscle lipotoxicity is well known to be a contributor to the development of insulin resistance. Here it was examined if the small molecule adiponectin receptor agonist AdipoRon mimicked the effect of adiponectin to attenuate palmitate induced reactive oxygen species (ROS) production and cell death in L6 skeletal muscle cells.

Methods

L6 cells were treated ±0.1 mM PA, and ± AdipoRon, then assays analyzing reactive oxygen species (ROS) production and cell death, and intracellular and extracellular levels of sphingosine-1 phosphate (S1P) were conducted. To determine the mechanistic role of S1P gain (using exogenous S1P or using THI) or loss of function (using the SKI-II) were conducted.

Results

Using both CellROX and DCFDA assays it was found that AdipoRon reduced palmitate-induced ROS production. Image-IT DEAD, MTT and LDH assays all indicated that AdipoRon reduced palmitate-induced cell death. Palmitate significantly increased intracellular accumulation of S1P, whereas in the presence of AdipoRon there was increased release of S1P from cells to extracellular medium. It was also observed that direct addition of extracellular S1P prevented palmitate-induced ROS production and cell death, indicating that S1P is acting in an autocrine manner. Pharmacological approaches to enhance or decrease S1P levels indicated that accumulation of intracellular S1P correlated with enhanced cell death.

Conclusion

This data indicates that increased extracellular levels of S1P in response to adiponectin receptor activation can activate S1P receptor-mediated signaling to attenuate lipotoxic cell death. Taken together these findings represent a possible novel mechanism for the protective action of adiponectin.

The role of sphingolipids in endoplasmic reticulum stress

The endoplasmic reticulum (ER) is an important intracellular compartment in eukaryotic cells and has diverse functions, including protein synthesis, protein folding, lipid metabolism and calcium homeostasis. ER functions are disrupted by various intracellular and extracellular stimuli that cause ER stress, including the inhibition of glycosylation, disulphide bond reduction, ER calcium store depletion, impaired protein transport to the Golgi, excessive ER protein synthesis, impairment of ER-associated protein degradation and mutated ER protein expression. Distinct ER stress signalling pathways, which are known as the unfolded protein response, are deployed to maintain ER homeostasis, and a failure to reverse ER stress triggers cell death. Sphingolipids are lipids that are structurally characterized by long-chain bases, including sphingosine or dihydrosphingosine (also known as sphinganine). Sphingolipids are bioactive molecules long known to regulate various cellular processes, including cell proliferation, migration, apoptosis and cell-cell interaction. Recent studies have uncovered that specific sphingolipids are involved in ER stress. This review summarizes the roles of sphingolipids in ER stress and human diseases in the context of pathogenic events.

The imbalance in the aortic ceramide/sphingosine-1-phosphate rheostat in ovariectomized rats and the preventive effect of estrogen

Background

The prevalence of hypertension in young women is lower than that in age-matched men while the prevalence of hypertension in women is significantly increased after the age of 50 (menopause) and is greater than that in men. It is already known that sphingosine-1-phosphate (S1P) and ceramide regulate vascular tone with opposing effects. This study aimed to explore the effects of ovariectomy and estrogen supplementation on the ceramide/S1P rheostat of the aorta in rats, and to explore a potential mechanism for perimenopausal hypertension and a brand-new target for menopausal hormone therapy to protect vessels.

Methods

In total, 30 female adult SD rats were randomly divided into three groups: The sham operation group (SHAM), ovariectomy group (OVX) and ovariectomy plus estrogen group (OVX + E). After 4 weeks of treatment, the blood pressure (BP) of the rats was monitored by a noninvasive system; the sphingolipid content (e.g., ceramide and S1P) was detected by liquid chromatography-mass spectrometry (LC-MS); the expression of the key enzymes involved in ceramide anabolism and catabolism was measured by real-time fluorescence quantitative polymerase chain reaction (qPCR); and the expression of key enzymes and proteins in the sphingosine kinase 1/2 (SphK1/2)-S1P-S1P receptor 1/2/3 (S1P1/2/3) signaling pathway was detected by qPCR and western blotting.

Results

In the OVX group compared with the SHAM group, the systolic BP (SBP), diastolic BP (DBP) and pulse pressure (PP) increased significantly, especially the SBP and PP (P < 0.001). For aortic ceramide metabolism, the mRNA level of key enzymes involved in anabolism and catabolism decreased in parallel 2–3 times, while the contents of total ceramide and certain long-chain subtypes increased significantly (P < 0.05). As for the S1P signaling pathway, SphK1/2, the key enzymes involved in S1P synthesis, decreased significantly, and the content of S1P decreased accordingly (P < 0.01). The S1P receptors showed various trends: S1P1 was significantly down-regulated, S1P2 was significantly up-regulated, and S1P3 showed no significant difference. No significant difference existed between the SHAM and OVX + E groups for most of the above parameters (P > 0.05).

Conclusions

Ovariectomy resulted in the imbalance of the aortic ceramide/S1P rheostat in rats, which may be a potential mechanism underlying the increase in SBP and PP among perimenopausal women. Besides, the ceramide/S1P rheostat may be a novel mechanism by which estrogen protects vessels.

Fingolimod Affects Transcription of Genes Encoding Enzymes of Ceramide Metabolism in Animal Model of Alzheimer's Disease

The imbalance in sphingolipid signaling may be critically linked to the upstream events in the neurodegenerative cascade of Alzheimer’s disease (AD). We analyzed the influence of mutant (V717I) amyloid β precursor protein (AβPP) transgene on sphingolipid metabolism enzymes in mouse hippocampus. At 3 months of age AβPP/Aβ presence upregulated enzymes of ceramide turnover on the salvage pathway: ceramide synthases (CERS2, CERS4, CERS6) and also ceramidase ACER3. At 6 months, only CERS6 was elevated, and no ceramide synthase was increased at 12 months. However, sphingomyelin synthases, which utilize ceramide on the sphingomyelinase pathway, were reduced (SGMS1 at 12 and SGMS2 at 6 months). mRNAs for sphingomyelin synthases SGMS1 and SGMS2 were also significantly downregulated in human AD hippocampus and neocortex when compared with age-matched controls. Our findings suggest early-phase deregulation of sphingolipid homeostasis in favor of ceramide signaling. Fingolimod (FTY720), a modulator of sphingosine-1-phosphate receptors countered the AβPP-dependent upregulation of hippocampal ceramide synthase CERS2 at 3 months. Moreover, at 12 months, FTY720 increased enzymes of ceramide-sphingosine turnover: CERS4, ASAH1, and ACER3. We also observed influence of fingolimod on the expression of the sphingomyelinase pathway enzymes. FTY720 counteracted the AβPP-linked reduction of sphingomyelin synthases SGMS1/2 (at 12 and 6 months, respectively) and led to elevation of sphingomyelinase SMPD2 (at 6 and 12 months). Therefore, our results demonstrate potentially beneficial, age-specific effects of fingolimod on transcription of sphingolipid metabolism enzymes in an animal model of AD.

The Important Role of Adiponectin and Orexin-A, Two Key Proteins Improving Healthy Status: Focus on Physical Activity

Exercise represents the most important integrative therapy in metabolic, immunologic and chronic diseases; it represents a valid strategy in the non-pharmacological intervention of lifestyle linked diseases. A large body of evidence indicates physical exercise as an effective measure against chronic non-communicable diseases. The worldwide general evidence for health benefits are both for all ages and skill levels. In a dysregulated lifestyle such as in the obesity, there is an imbalance in the production of different cytokines. In particular, we focused on Adiponectin, an adipokine producted by adipose tissue, and on Orexin-A, a neuropeptide synthesized in the lateral hypothalamus. The production of both Adiponectin and Orexin-A increases following regular and structured physical activity and both these hormones have similar actions. Indeed, they improve energy and glucose metabolism, and also modulate energy expenditure and thermogenesis. In addition, a relevant biological role of Adiponectin and Orexin A has been recently highlighted in the immune system, where they function as immune-suppressor factors. The strong connection between these two cytokines and healthy status is mediated by physical activity and candidates these hormones as potential biomarkers of the beneficial effects induced by physical activity. For these reasons, this review aims to underly the interconnections among Adiponectin, Orexin-A, physical activity and healthy status. Furthermore, it is analyzed the involvement of Adiponectin and Orexin-A in physical activity as physiological factors improving healthy status through physical exercise.

Lysophospholipids and Their G-Coupled Protein Signaling in Alzheimer's Disease: From Physiological Performance to Pathological Impairment

Lysophospholipids (LPLs) are bioactive signaling lipids that are generated from phospholipase-mediated hydrolyzation of membrane phospholipids (PLs) and sphingolipids (SLs). Lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are two of the best-characterized LPLs which mediate a variety of cellular physiological responses via specific G-protein coupled receptor (GPCR) mediated signaling pathways. Considerable evidence now demonstrates the crucial role of LPA and S1P in neurodegenerative diseases, especially in Alzheimer’s disease (AD). Dysfunction of LPA and S1P metabolism can lead to aberrant accumulation of amyloid-β (Aβ) peptides, the formation of neurofibrillary tangles (NFTs), neuroinflammation and ultimately neuronal death. Summarizing LPA and S1P signaling profile may aid in profound health and pathological processes. In the current review, we will introduce the metabolism as well as the physiological roles of LPA and S1P in maintaining the normal functions of the nervous system. Given these pivotal functions, we will further discuss the role of dysregulation of LPA and S1P in promoting AD pathogenesis.

The role of the sphingolipid pathway in liver fibrosis: an emerging new potential target for novel therapies

Sphingolipids (SL) are a family of bioactive lipids and a major cellular membrane structural component. SLs include three main compounds: ceramide (Cer), sphingosine (Sp), and sphingosine-1-phosphate (S-1P), all of which have emerging roles in biological functions in cells, especially in the liver. They are under investigation in various liver diseases, including cirrhosis and end-stage liver disease. In this review, we provide an overview on the role of SLs in liver pathobiology and focus on their potential role in the development of hepatic fibrosis. We describe recent evidence and suggest SLs are a promising potential therapeutic target for the treatment of liver disease and fibrosis.

Unbalanced Sphingolipid Metabolism and Its Implications for the Pathogenesis of Psoriasis

Sphingolipids (SLs), which have structural and biological responsibilities in the human epidermis, are importantly involved in the maintenance of the skin barrier and regulate cellular processes, such as the proliferation, differentiation and apoptosis of keratinocytes (KCs). As many dermatologic diseases, including psoriasis (PsO), intricately characterized by perturbations in these cellular processes, are associated with altered composition and unbalanced metabolism of epidermal SLs, more education to precisely determine the role of SLs, especially in the pathogenesis of skin disorders, is needed. PsO is caused by a complex interplay between skin barrier disruption, immune dysregulation, host genetics and environmental triggers. The contribution of particular cellular compartments and organelles in SL metabolism, a process related to dysfunction of lysosomes in PsO, seems to have a significant impact on lysosomal signalling linked to a modulation of the immune-mediated inflammation accompanying this dermatosis and is not fully understood. It is also worth noting that a prominent skin disorder, such as PsO, has diminished levels of the main epidermal SL ceramide (Cer), reflecting altered SL metabolism, that may contribute not only to pathogenesis but also to disease severity and/or progression. This review provides a brief synopsis of the implications of SLs in PsO, aims to elucidate the roles of these molecules in complex cellular processes deregulated in diseased skin tissue and highlights the need for increased research in the field. The significance of SLs as structural and signalling molecules and their actions in inflammation, in which these components are factors responsible for vascular endothelium abnormalities in the development of PsO, are discussed.

NADPH Oxidase-Mediated Activation of Neutral Sphingomyelinase Is Responsible for Diesel Particulate Extract-Induced Keratinocyte Apoptosis

Human epidermis is positioned at the interface with the external environment, protecting our bodies against external challenges, including air pollutants. Emerging evidence suggests that diesel particulate extract (DPE), a major component of air pollution, leads to impairment of diverse cellular functions in keratinocytes (KC). In this study, we investigated the cellular mechanism underlying DPE-induced KC apoptosis. We first addressed cell death occurring in KC exposed to DPE, paralleled by increased activation of NADPH oxidases (NOXs) and subsequent ROS generation. Blockade of NOX activation with a specific inhibitor attenuated the expected DPE-induced KC apoptosis. In contrast, pre-treatment with a specific inhibitor of reactive oxygen species (ROS) generation did not reverse DPE/NOX-mediated increase in KC apoptosis. We next noted that NOX-mediated KC apoptosis is mainly attributable to neutral sphingomyelinase (SMase)-mediated stimulation of ceramides, which is a well-known pro-apoptotic lipid. Moreover, we found that inhibition of NOX activation significantly attenuated DPE-mediated increase in the ratio of ceramide to its key metabolite sphingosine-1-phosphate (S1P), an important determinant of cell fate. Together, these results suggest that activation of neutral SMase serves as a key downstream signal for the DPE/NOX activation-mediated alteration in ceramide and S1P productions, and subsequent KC apoptosis.