Distribution and Functions of Sterols and Sphingolipids

Sterols and sphingolipids are considered mainly eukaryotic lipids even though both are present in some prokaryotes, with sphingolipids being more widespread than sterols. Both sterols and sphingolipids differ in their structural features in vertebrates, plants, and fungi. Interestingly, some invertebrates cannot synthesize sterols de novo and seem to have a reduced dependence on sterols. Sphingolipids and sterols are found in the plasma membrane, but we do not have a clear picture of their precise intracellular localization. Advances in lipidomics and subcellular fractionation should help to improve this situation. Genetic approaches have provided insights into the diversity of sterol and sphingolipid functions in eukaryotes providing evidence that these two lipid classes function together. Intermediates in sphingolipid biosynthesis and degradation are involved in signaling pathways, whereas sterol structures are converted to hormones. Both lipids have been implicated in regulating membrane trafficking.Typical examples of eukaryotic lipids, sterols, and sphingolipids can both be found in membranes from simple unicellular fungi and protists to multicellular animals and plants. Their versatile use as structural elements but also as signaling molecules has probably played an important role during the evolution of this large and diverse group of organisms. There are also many eukaryotes that have lost the ability to synthesize sterols de novo including nematodes, insects, and marine invertebrates, which have to take up sterols with their diet. Sterol biosynthesis has also been reported in a number of bacteria. Sphingolipids are more widely spread among prokaryotes than sterols and also show a greater variety of structures among the different eukaryotes.In this short review we will first give an overview about the diversity of sterol and sphingolipid structures and their distribution in nature. Then we will discuss their subcellular distribution. A brief technical section will add some information on the separation and detection of these lipid molecules. Subsequently, we will summarize different genetic approaches to study the functions of sterols and sphingolipids, and finally, we will discuss the functional and possible physical interactions of the two lipid classes within the cell. Far from being comprehensive, we will focus only on a few interesting aspects and try to give new view points, which are less frequently discussed.     

Rationale for the Use of Histone Deacetylase Inhibitors as a Dual Therapeutic Modality in Multiple Sclerosis

Major recent advances in the field of chromatin remodeling have dramatically changed our understanding of the ways in which genes are regulated. Epigenetic regulators such as histone deacetylases (HDACs) and histone acetyltransferases (HATs) are increasingly being implicated as direct or indirect components in the regulation of expression of neuronal, immune and other tissue specific genes. HDACs and HATs have been shown to play important roles in cell growth, cell cycle control, development, differentiation and survival. Mutations in genes that encode HDAC-binding proteins cause neurological disorders, such as MeCP2 mutations in Rett's syndrome. Mutations of CBP, a gene with HAT function, cause the mental retardation-associated Rubinstein-Taybi syndrome. Recently, HDAC inhibitors have been found to ameliorate progression of the spinal muscular atrophy (SMA) motor neuron disease and the Huntington disease mouse models. The neuroprotective role of HDAC inhibitors seems to extend to other diseases that share mechanisms of oxidative stress, inflammation and neuronal cell apoptosis. HDAC inhibitors also have widespread modulatory effects on gene expression within the immune system and have been used successfully in the lupus and rheumatoid arthritis autoimmune disease models. Recently, we demonstrated the efficacy of the HDAC inhibitor Trichostatin A in ameliorating disease in the multiple sclerosis (MS) animal model, experimental autoimmune encephalomyelitis (EAE). In this review we describe the current literature surrounding these inhibitors and propose a rationale for harnessing both their neuroprotective and anti-inflammatory effects to treat MS, an autoimmune, demyelinating and degenerative disease of the human central nervous system (CNS).      

HIF-NOS信号通路对哺乳动物卵巢NO依赖性功能的调控作用

一氧化氮(NO)作为气体明星分子和信号分子,在哺乳动物体内不同的生理调节过程中具有非常重要的作用,尤其是哺乳动物卵巢功能的调控.一氧化氮合酶(NOS)是NO合成的限速酶,是调节NO合成的关键环节,也是NO依赖性功能调控的重要环节.因此,调节NOS转录/合成的信号通路对哺乳动物卵巢NO依赖性功能具有至关重要的调控作用.最近的研究发现,缺氧诱导因子(HIF)作为转录因子,参与许多与缺氧相关靶基因的转录调控,如NOS和血管内皮生长因子(VEGF)等.本文一方面描述了NO合成及其调控的分子机制,另一方面阐明了HIF作为转录因子对NOS的转录调控,从而揭示HIF在NO依赖性卵巢功能调控中的重要作用,同时为进一步研究哺乳动物卵巢功能的调控提供新的研究方向和理论基础.     

Fingolimod Increases CD39-Expressing Regulatory T Cells in Multiple Sclerosis Patients

Background

Multiple sclerosis (MS) likely results from an imbalance between regulatory and inflammatory immune processes. CD39 is an ectoenzyme that cleaves ATP to AMP and has been suggested as a novel regulatory T cells (Treg) marker. As ATP has numerous proinflammatory effects, its degradation by CD39 has anti-inflammatory influence. The purpose of this study was to explore regulatory and inflammatory mechanisms activated in fingolimod treated MS patients.

Methods and Findings

Peripheral blood mononuclear cells (PBMCs) were isolated from relapsing-remitting MS patients before starting fingolimod and three months after therapy start. mRNA expression was assessed in ex vivo PBMCs. The proportions of CD8, B cells, CD4 and CD39-expressing cells were analysed by flow cytometry. Treg proportion was quantified by flow cytometry and methylation-specific qPCR. Fingolimod treatment increased mRNA levels of CD39, AHR and CYP1B1 but decreased mRNA expression of IL-17, IL-22 and FOXP3 mRNA in PBMCs. B cells, CD4⁺ cells and Treg proportions were significantly reduced by this treatment, but remaining CD4⁺ T cells were enriched in FOXP3⁺ cells and in CD39-expressing Tregs.

Conclusions

In addition to the decrease in circulating CD4⁺ T cells and CD19⁺ B cells, our findings highlight additional immunoregulatory mechanisms induced by fingolimod.     

Alternative Signaling Pathways as Potential Therapeutic Targets for Overcoming EGFR and c-Met Inhibitor Resistance in Non-Small Cell Lung Cancer

The use of tyrosine kinase inhibitors (TKIs) against EGFR/c-Met in non-small cell lung cancer (NSCLC) has been shown to be effective in increasing patient progression free survival (PFS), but their efficacy is limited due to the development of resistance and tumor recurrence. Therefore, understanding the molecular mechanisms underlying development of drug resistance in NSCLC is necessary for developing novel and effective therapeutic approaches to improve patient outcome. This study aims to understand the mechanism of EGFR/c-Met tyrosine kinase inhibitor (TKI) resistance in NSCLC. H2170 and H358 cell lines were made resistant to SU11274, a c-Met inhibitor, and erlotinib, an EGFR inhibitor, through step-wise increases in TKI exposure. The IC₅₀ concentrations of resistant lines exhibited a 4–5 and 11–22-fold increase for SU11274 and erlotinib, respectively, when compared to parental lines. Furthermore, mTOR and Wnt signaling was studied in both cell lines to determine their roles in mediating TKI resistance. We observed a 2–4-fold upregulation of mTOR signaling proteins and a 2- to 8-fold upregulation of Wnt signaling proteins in H2170 erlotinib and SU11274 resistant cells. H2170 and H358 cells were further treated with the mTOR inhibitor everolimus and the Wnt inhibitor XAV939. H358 resistant cells were inhibited by 95% by a triple combination of everolimus, erlotinib and SU11274 in comparison to 34% by a double combination of these drugs. Parental H2170 cells displayed no sensitivity to XAV939, while resistant cells were significantly inhibited (39%) by XAV939 as a single agent, as well as in combination with SU11274 and erlotinib. Similar results were obtained with H358 resistant cells. This study suggests a novel molecular mechanism of drug resistance in lung cancer.     

Visual Search as a Tool for a Quick and Reliable Assessment of Cognitive Functions in Patients with Multiple Sclerosis

Background

Despite the high frequency of cognitive impairment in multiple sclerosis, its assessment has not gained entrance into clinical routine yet, due to lack of time-saving and suitable tests for patients with multiple sclerosis.

Objective

The aim of the study was to compare the paradigm of visual search with neuropsychological standard tests, in order to identify the test that discriminates best between patients with multiple sclerosis and healthy individuals concerning cognitive functions, without being susceptible to practice effects.

Methods

Patients with relapsing remitting multiple sclerosis (n = 38) and age-and gender-matched healthy individuals (n = 40) were tested with common neuropsychological tests and a computer-based visual search task, whereby a target stimulus has to be detected amongst distracting stimuli on a touch screen. Twenty-eight of the healthy individuals were re-tested in order to determine potential practice effects.

Results

Mean reaction time reflecting visual attention and movement time indicating motor execution in the visual search task discriminated best between healthy individuals and patients with multiple sclerosis, without practice effects.

Conclusions

Visual search is a promising instrument for the assessment of cognitive functions and potentially cognitive changes in patients with multiple sclerosis thanks to its good discriminatory power and insusceptibility to practice effects.     

Microvesicles as Emerging Biomarkers and Therapeutic Targets in Cardiometabolic Diseases

Microvesicles (MVs, also known as microparticles) are small vesicles that originate from plasma membrane of almost all eukaryotic cells during apoptosis or activation. MVs can serve as extracellular vehicles to transport bioactive molecules from their parental cells to recipient target cells, thereby serving as novel mediators for intercellular communication. Importantly, more and more evidence indicates that MVs could play important roles in early pathogenesis and subsequent progression of cardiovascular and metabolic diseases. Elevated plasma concentrations of MVs, originating from red blood cells, leukocytes, platelets, or other organs and tissues, have been reported in various cardiometabolic diseases. Circulating MVs could serve as potential biomarkers for disease diagnosis or therapeutic monitoring. In this review, we summarized recently-published studies in the field and discussed the role of MVs in the pathogenesis of cardiometabolic diseases. The emerging values of MVs that serve as biomarker for non-invasive diagnosis and prognosis, as well as their roles as novel therapeutic targets in cardiometabolic diseases, were also described.     

Profiling the Surfaceome Identifies Therapeutic Targets for Cells with Hyperactive mTORC1 Signaling

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Highlights

• •Quantitative proteomes of the cellular surface changes induced by mTORC1 signaling.
• •Hit validation in human cancer cell lines and biopsies.
• •Functional studies showing new drug targets to which cancer cells with hyperactive mTORC1 may be addicted.
• •A new paradigm for drug development, namely targeting cell surface proteins regulated by mTORC1.

     

Cannabinoids and Multiple Sclerosis

This review discusses clinical and preclinical evidence that supports the use of cannabinoid receptor agonists for the management of multiple sclerosis. In addition, it considers preclinical findings that suggest that as well as ameliorating signs and symptoms of multiple sclerosis, cannabinoid CB₁ and/or CB₂ receptor activation may suppress some of the pathological changes that give rise to these signs and symptoms. Evidence that the endocannabinoid system plays a protective role in multiple sclerosis is also discussed as are potential pharmacological strategies for enhancing such protection in the clinic.     

Natalizumab Exerts Direct Signaling Capacity and Supports a Pro-Inflammatory Phenotype in Some Patients with Multiple Sclerosis

Natalizumab is a recombinant monoclonal antibody raised against integrin alpha-4 (CD49d). It is approved for the treatment of patients with multiple sclerosis (MS), a chronic inflammatory autoimmune disease of the CNS. While having shown high therapeutic efficacy, treatment by natalizumab has been linked to progressive multifocal leukoencephalopathy (PML) as a serious adverse effect. Furthermore, drug cessation sometimes induces rebound disease activity of unknown etiology. Here we investigated whether binding of this adhesion-blocking antibody to T lymphocytes could modulate their phenotype by direct induction of intracellular signaling events. Primary CD4⁺ T lymphocytes either from healthy donors and treated with natalizumab in vitro or from MS patients receiving their very first dose of natalizumab were analyzed. Natalizumab induced a mild upregulation of IL-2, IFN-γ and IL-17 expression in activated primary human CD4⁺ T cells propagated ex vivo from healthy donors, consistent with a pro-inflammatory costimulatory effect on lymphokine expression. Along with this, natalizumab binding triggered rapid MAPK/ERK phosphorylation. Furthermore, it decreased CD49d surface expression on effector cells within a few hours. Sustained CD49d downregulation could be attributed to integrin internalization and degradation. Importantly, also CD4⁺ T cells from some MS patients receiving their very first dose of natalizumab produced more IL-2, IFN-γ and IL-17 already 24 h after infusion. Together these data indicate that in addition to its adhesion-blocking mode of action natalizumab possesses mild direct signaling capacities, which can support a pro-inflammatory phenotype of peripheral blood T lymphocytes. This might explain why a rebound of disease activity or IRIS is observed in some MS patients after natalizumab cessation.