Role of Ceramides and Sphingolipids in Parkinson's Disease

Sphingolipids, including the basic ceramide, are a subset of bioactive lipids that consist of many different species. Sphingolipids are indispensable for proper neuronal function, and an increasing number of studies have emerged on the complexity and importance of these lipids in (almost) all biological processes. These include regulation of mitochondrial function, autophagy, and endosomal trafficking, which are affected in Parkinson’s disease (PD). PD is the second most common neurodegenerative disorder and is characterized by the loss of dopaminergic neurons. Currently, PD cannot be cured due to the lack of knowledge of the exact pathogenesis. Nonetheless, important advances have identified molecular changes in mitochondrial function, autophagy, and endosomal function. Furthermore, recent studies have identified ceramide alterations in patients suffering from PD, and in PD models, suggesting a critical interaction between sphingolipids and related cellular processes in PD. For instance, autosomal recessive forms of PD cause mitochondrial dysfunction, including energy production or mitochondrial clearance, that is directly influenced by manipulating sphingolipids. Additionally, endo-lysosomal recycling is affected by genes that cause autosomal dominant forms of the disease, such as VPS35 and SNCA. Furthermore, endo-lysosomal recycling is crucial for transporting sphingolipids to different cellular compartments where they will execute their functions.This review will discuss mitochondrial dysfunction, defects in autophagy, and abnormal endosomal activity in PD and the role sphingolipids play in these vital molecular processes.     

Anti-inflammatory action of lipid nanocarrier-delivered myriocin: therapeutic potential in cystic fibrosis

Background

Sphingolipids take part in immune response and can initiate and/or sustain inflammation. Various inflammatory diseases have been associated with increased ceramide content, and pharmacological reduction of ceramide diminishes inflammation damage in vivo. Inflammation and susceptibility to microbial infection are two elements in a vicious circle. Recently, sphingolipid metabolism inhibitors were used to reduce infection. Cystic fibrosis (CF) is characterized by a hyper-inflammation and an excessive innate immune response, which fails to evolve into adaptive immunity and to eradicate infection. Chronic infections result in lung damage and patient morbidity. Notably, ceramide content in mucosa airways is higher in CF mouse models and in patients than in control mice or healthy subjects.

Methods

The therapeutic potential of myriocin, an inhibitor of the sphingolipid de novo synthesis rate limiting enzyme (Serine Palmitoyl Transferase, SPT),was investigated in CF cells and mice models.

Results

We treated CF human respiratory epithelial cells with myriocin, This treatment resulted in reduced basal, as well as TNFα-stimulated, inflammation. In turn, TNFα induced an increase in SPT in these cells, linking de novo synthesis of ceramide to inflammation. Furthermore, myriocin-loaded nanocarrier, injected intratrachea prior to P. aeruginosa challenge, enabled a significant reduction of lung infection and reduced inflammation.

Conclusions

The presented data suggest that de novo ceramide synthesis is constitutively enhanced in CF mucosa and that it can be envisaged as pharmacological target for modulating inflammation and restoring effective innate immunity against acute infection.

General significance

Myriocin stands as a powerful immunomodulatory agent for inflammatory and infectious diseases.     

LC3 as a potential therapeutic target in hypoxia-induced pulmonary hypertension

Recent research suggests that microtubule-associated protein 1 light chain 3B (LC3B) confers protection against hypoxia-induced pulmonary hypertension (HPH) by inhibiting proliferation of pulmonary artery (PA) wall cells. We recently demonstrated that 17β-estradiol (E2), a sex hormone with known protective properties in HPH, increases lung LC3-II expression in chronically hypoxic male Sprague-Dawley rats. Stimulatory E2 effects on LC3-II were recapitulated in isolated hypoxic (1% O₂ for 48 h), but not room air-exposed primary rat PA endothelial cells (PAECs), and were accompanied by hypoxia-specific inhibitory effects on other parameters involved in proproliferative signaling (MAPK3/ERK1-MAPK1/ERK2 activation, VEGF secretion), as well as inhibitory effects on PAEC proliferation. Taken together, these results suggest that E2 mediates hypoxia-specific antiproliferative effects in PAECs, and that stimulation of autophagy may be one of the underlying mechanisms of E2-mediated protection in HPH. Viewed in the context of previously published data, these results indicate that LC3 1) exerts protective effects in the pathogenesis of HPH, and 2) may represent a potential target for future therapeutic interventions in HPH.     

LC3 as a potential therapeutic target in hypoxia-induced pulmonary hypertension

Recent research suggests that microtubule-associated protein 1 light chain 3B (LC3B) confers protection against hypoxia-induced pulmonary hypertension (HPH) by inhibiting proliferation of pulmonary artery (PA) wall cells. We recently demonstrated that 17β-estradiol (E2), a sex hormone with known protective properties in HPH, increases lung LC3-II expression in chronically hypoxic male Sprague-Dawley rats. Stimulatory E2 effects on LC3-II were recapitulated in isolated hypoxic (1% O₂ for 48 h), but not room air-exposed primary rat PA endothelial cells (PAECs), and were accompanied by hypoxia-specific inhibitory effects on other parameters involved in proproliferative signaling (MAPK3/ERK1-MAPK1/ERK2 activation, VEGF secretion), as well as inhibitory effects on PAEC proliferation. Taken together, these results suggest that E2 mediates hypoxia-specific antiproliferative effects in PAECs, and that stimulation of autophagy may be one of the underlying mechanisms of E2-mediated protection in HPH. Viewed in the context of previously published data, these results indicate that LC3 1) exerts protective effects in the pathogenesis of HPH, and 2) may represent a potential target for future therapeutic interventions in HPH.     

Differential expression of (dihydro)ceramide synthases in mouse brain: oligodendrocyte-specific expression of CerS2/Lass2

Synthesis of dihydroceramide is catalyzed by a family of (dihydro)ceramide synthases (CerS), first identified in yeast as longevity-assurance genes. Six members (CerS1–6; Lass1–6) of this gene family have been identified in mammals. We examined expression of CerS genes during postnatal development in mouse brain by means of Northern blot analysis, real-time RT-PCR, and in situ-hybridization. In situ-hybridization experiments showed that CerS1 was the predominant CerS in neurons throughout the brain. This observation is in line with the high levels of C18:0-ceramide in neurons and the substrate specificity of CerS1. A similar distribution, but lower expression levels, were found for CerS4 and CerS6. Only low or undetectable amounts of CerS1, CerS4 and CerS6 were, however, present in white matter. In contrast, CerS5 mRNA was detected in most cells within gray and white matter of all brain regions, suggesting ubiquitous expression of this palmitoyl-CoA specific CerS. Expression of CerS2 was transiently increased during the period of active myelination. Furthermore, expression of CerS2 was specifically localized to white matter tracts of the brain. Furthermore, CerS2 was the predominant CerS in Schwann cells of sciatic nerves. These data suggest that CerS2 is important for the synthesis of dihydroceramide used for synthesis of myelin sphingolipids.     

E2F是疾病治疗的潜在靶点

竞争性寡聚脱氧核糖核酸识别转录因子的DNA结合域,抑制了转录因子对基因的转录调控,转录因子E2F作为潜在的治疗靶点,可以用于抑制肾小球系膜细胞和血管内皮细胞的增生,在部分异常增生的疾病中显示了一定的应用前景。     

解脂假丝酵母中神经酰胺的鉴别和定量分析

采用制备型薄层板分离解脂假丝酵母 (Yarrowialipolitica)中与神经酰胺标样近似的脂类成分 ,将其用于二级质谱分析 ,确认了其结构为脂肪酸碳链长度为 2 4的神经酰胺。结合高效液相色谱 蒸发光散射检测器 (HPLC ELSD)的检测方法 ,首次定量报道了解脂假丝酵母中神经酰胺的含量为 2 5‰。     

Exome sequencing and metabolomic analysis of a chronic kidney disease and hearing loss patient family revealed RMND1 mutation induced sphingolipid metabolism defects

Mitochondrial disorders (MIDs) shows overlapping clinical presentations owing to the genetic and metabolic defects of mitochondria. However, specific relationship between inherited mutations in nuclear encoded mitochondrial proteins and their functional impacts in terms of metabolic defects in patients is not yet well explored. Therefore, using high throughput whole exome sequencing (WES), we screened a chronic kidney disease (CKD) and sensorineural hearing loss (SNHL) patient, and her family members to ascertain the mode of inheritance of the mutation, and healthy population controls to establish its rare frequency. The impact of mutation on biophysical characteristics of the protein was further studied by mapping it in 3D structure. Furthermore, LC-MS tandem mass spectrophotometry based untargeted metabolomic profiling was done to study the fluctuations in plasma metabolites relevant to disease causative mutations and kidney damage. We identified a very rare homozygous c.631G > A (p.Val211Met) pathogenic mutation in RMND1 gene in the proband, which is inherited in an autosomal recessive fashion. This gene is involved in the mitochondrial translational pathways and contribute in mitochondrial energy metabolism. The p.Val211Met mutation is found to disturb the structural orientation (RMSD is −2.95 Å) and stability (ΔΔG is −0.552 Kcal/mol) of the RMND1 protein. Plasma metabolomics analysis revealed the aberrant accumulation of metabolites connected to lipid and amino acid metabolism pathways. Of these metabolites, pathway networking has discovered ceramide, a metabolite of sphingolipids, which plays a role in different signaling cascades including mitochondrial membrane biosynthesis, is highly elevated in this patient. This study suggests that genetic defects in RMND1 gene alters the mitochondrial energy metabolism leading to the accumulation of ceramide, and subsequently promote dysregulated apoptosis and tissue necrosis in kidneys.     

MicroRNA-34a: a potential therapeutic target in human cancer

MicroRNAs (miRs) are small noncoding RNAs that negatively regulate gene expression by binding to the three untranslated regions of their target mRNAs. Deregulations of miRs were shown to play pivotal roles in tumorigenesis and progression. Recent research efforts have been devoted to translating these basic discoveries into applications that could improve the therapeutic outcome of patients with cancer. MiR-34a is a highly conserved miR throughout many different species. In humans, there are three homologs (hsa-miR34a, hsa-miR-34b and hsa-miR-34c). Early studies have shown that miR-34a acts as a tumor-suppressor gene by targeting many oncogenes related to proliferation, apoptosis and invasion. In this review, we provide a complex overview of miR-34a, including regulating its expression, its known functions in cancer and future challenges as a potential therapeutic target in human cancers.     

High-density lipoprotein functionality and breast cancer: A potential therapeutic target

Breast cancer is a major cause of death globally, and particularly in developed countries. Breast cancer is influenced by cholesterol membrane content, by affecting the signaling pathways modulating cell growth, adherence, and migration. Furthermore, steroid hormones are derived from cholesterol and these play a key role in the pathogenesis of breast cancer. Although most findings have reported an inverse association between serum high-density lipoprotein (HDL)-cholesterol level and the risk of breast cancer, there have been some reports of the opposite, and the association therefore remains unclear. HDL is principally known for participating in reverse cholesterol transport and has an inverse relationship with the cardiovascular risk. HDL is heterogeneous, with particles varying in composition, size, and structure, which can be altered under different circumstances, such as inflammation, aging, and certain diseases. It has also been proposed that HDL functionality might have a bearing on the breast cancer. Owing to the potential role of cholesterol in cancer, its reduction using statins, and particularly as an adjuvant during chemotherapy may be useful in the anticancer treatment, and may also be related to the decline in cancer mortality. Reconstituted HDLs have the ability to release chemotherapeutic drugs inside the cell. As a consequence, this may be a novel way to improve therapeutic targeting for the breast cancer on the basis of detrimental impacts of oxidized HDL on cancer development.     

Development of a new doubly-labeled fluorescent ceramide probe for monitoring the metabolism of sphingolipids in living cells

A new ceramide analog, 1, containing two fluorescent dyes, NBD in the N-acyl part and KFL5 in the alkyl part, was synthesized. The fluorescence from both NBD and KFL5 was detected in living cells in a time-dependent manner. A multi-wavelength fluorescence detector was used to detect ceramide metabolites including sphingosine, sphingosine-1-phosphate, glucosylceramide, and sphingomyelin, which are connected to the fluorescent dyes, simultaneously in a single TLC plate.     

ICAM-1 in acute myocardial infarction: a potential therapeutic target

Current treatments for AMI centre on prompt restoration of epicardial coronary blood flow. Despite improvements, AMI is still associated with significant morbidity and mortality. Novel approaches are therefore keenly sought. Intercellular adhesion molecule-1 (ICAM-1, CD54) is a member of the immunoglobulin superfamily. It is implicated in neutrophil and monocyte-endothelial cell adhesion, processes contributing to myocardial neutrophil infiltration and microvascular coronary slow flow, both viewed as important to the pathophysiologic responses in AMI. ICAM-1 would therefore appear an important potential therapeutic target in this context, and is the subject of this review.     

Tartrate-resistant acid phosphatase: a potential target for therapeutic gold

Gold compounds are disease-modifying agents for the treatment of rheumatoid arthritis. They act on the immune system but the mechanism is not fully understood. Gold has been shown to affect antigen processing by T-cells and also reduces expression of cytokines in macrophages. Tartrate-resistant acid phosphatase (TRAP), expressed by osteoclasts, macrophages and dendritic cells is an enzyme with roles in skeletal metabolism and the immune response. TRAP is able to degrade skeletal phosphoproteins including osteopontin, identical to the T-cell cytokine, Eta-1; we thus propose that TRAP regulates the Eta-1 pathway common to the immune system and skeleton. We compared the distribution of osteopontin and TRAP in sections of 18-day-old embryonic mice by immunohistochemistry. Both proteins occurred in the same locations. To determine whether gold compounds exert their effects by modification of TRAP activity, we examined the action of gold chloride and the prodrugs, aurothioglucose and aurothiomalate on the dephosphorylation of osteopontin by TRAP. Aurothioglucose and aurothiomalate had little effect on phosphatase activity; gold chloride was a potent non-competitive inhibitor (Ki < 47 x 10(-9) M). These findings indicate a possible molecular mechanism for the action of therapeutic gold and further implicate TRAP in the control of immunity.     

MicroRNA-148a: A potential therapeutic target for cancer

MicroRNA-148a (miR-148a) which suppresses tumor growth by directly decreasing DNMT1 expression has been demonstrated as an important role for cancer therapy. The mechanisms for miR-148a in cancer will become potential future researches.     

PI3K: a potential therapeutic target for cancer

Phosphatidylinositol 3-kinase (PI3K), one member of lipid kinase family, has been demonstrated to play a key role in regulating cell proliferation, adhesion, survival, and motility. Recent studies indicate that PI3K related signaling pathway is one of the most commonly activated pathways in human cancers. Accordingly, pharmacological inhibition of key nodes in this signaling cascade has been a focus in developmental therapeutics. To date, Inhibitors targeting PI3K or nodes in this pathway, AKT and mTOR, are best studied and have reached clinical trials. In this review, we will focus on recent progress on understanding of PI3Ks signaling pathway and the development of PI3K inhibitors.     

Mitophagy,a potential therapeutic target for stroke

Mitochondria autophagy, termed as mitophagy, is a mechanism of specific autophagic elimination of mitochondria. Mitophagy controls the quality and the number of mitochondria, eliminating dysfunctional or excessive mitochondria that can generate reactive oxygen species (ROS) and cause cell death. Mitochondria are centrally implicated in neuron and tissue injury after stroke, due to the function of supplying adenosine triphosphate (ATP) to the tissue, regulating oxidative metabolism during the pathologic process, and contribution to apoptotic cell death after stroke. As a catabolic mechanism, mitophagy links numbers of a complex network of mitochondria, and affects mitochondrial dynamic process, fusion and fission, reducing mitochondrial production of ROS, mediated by the mitochondrial permeability transition pore (MPTP). The precise nature of mitophagy’s involvement in stroke, and its underlying molecular mechanisms, have yet to be fully clarified. This review aims to provide a comprehensive overview of the integration of mitochondria with mitophagy, also to introduce and discuss recent advances in the understanding of the potential role, and possible signaling pathway, of mitophagy in the pathological processes of both hemorrhagic and ischemic stroke. The author also provides evidence to explain the dual role of mitophagy in stroke.     

Transport of lipids by ABC proteins: Interactions and implications for cellular toxicity, viability and function

Members of the ATP-binding cassette (ABC) family of membrane-bound transporters are involved in multiple aspects of transport and redistribution of various lipids and their conjugates. Most ABC transporters localize to the plasma membrane; some are associated with liquid-ordered cholesterol-/sphingolipid-rich microdomains, and to a lesser extent the membranes of the Golgi and endoplasmic reticulum. Hence, ABC transporters are well placed to regulate plasma membrane lipid composition and the efflux and redistribution of structural phospholipids and sphingolipids during periods of cellular stress and recovery. ABC transporters can also modulate cellular sensitivity to extrinsic pro-apoptotic signals through regulation of sphingomyelin-ceramide biosynthesis and metabolism. The functionality of ABC transporters is, in turn, modulated by the lipid content of the microdomains in which they reside. Cholesterol, a major membrane microdomain component, is not only a substrate of several ABC transporters, but also regulates ABC activity through its effects on microdomain structure. Several important bioactive lipid mediators and toxic lipid metabolites are also effluxed by ABC transporters. In this review, the complex interactions between ABC transporters and their lipid/sterol substrates will be discussed and analyzed in the context of their relevance to cellular function, toxicity and apoptosis.     

Bioinformatic analysis of Helicobacter pylori XGPRTase: a potential therapeutic target

BACKGROUND: Xanthine-guanine phosphoribosyltransferase (XGPRTase) is an enzyme of purine nucleotide salvage synthesis. The gpt gene of Helicobacter pylori has been annotated as encoding an XGPRTase and proposed as essential for survival of the bacterium in vitro. The aims of this work were to investigate the structure of H. pylori XGPRTase and to compare the key features of the enzyme to other phosphoribosyltransferases employing computational, modelling, and bioinformatic tools. MATERIALS AND METHODS: XGPRTase activity was measured in the cytosolic fraction of H. pylori by (31)P-nuclear magnetic resonance spectroscopy, and also in recombinant XGPRTase produced by a cell-free expression system. Bioinformatics was employed to analyze the phylogeny of XGPRTase, and a structural model of the XGPRTase was built using threading techniques. The observed interactions of purine phosphoribosyltransferases with immucillin-GP were used to study the theoretical interactions of H. pylori XGPRTase with this transition-state analog. RESULTS: It was demonstrated that the gpt gene of H. pylori encodes a functional XGPRTase enzyme. Analyses of the XGPRTase sequence showed that the enzyme is significantly divergent from equivalent mammalian enzymes. Modelling served to identify specific features of the enzyme and key residues involved in catalysis. CONCLUSIONS: The H. pylori XGPRTase is structurally similar to other phosphoribosyltransferase enzymes, but there were significant differences between the hood domain of H. pylori XGPRTase and other purine salvage phosphoribosyltransferases. Significant differences were found between the interactions of the H. pylori and human enzymes with a purine phosphoribosyltransferase inhibitor.