2-Hydroxyoleate, a nontoxic membrane binding anticancer drug, induces glioma cell differentiation and autophagy

Lysosomes in Cancer-At the Crossroad of Good and Evil

Although it has been known for decades that lysosomes are central for degradation and recycling in the cell, their pivotal role as nutrient sensing signaling hubs has recently become of central interest. Since lysosomes are highly dynamic and in constant change regarding content and intracellular position, fusion/fission events allow communication between organelles in the cell, as well as cell-to-cell communication via exocytosis of lysosomal content and release of extracellular vesicles. Lysosomes also mediate different forms of regulated cell death by permeabilization of the lysosomal membrane and release of their content to the cytosol. In cancer cells, lysosomal biogenesis and autophagy are increased to support the increased metabolism and allow growth even under nutrient- and oxygen-poor conditions. Tumor cells also induce exocytosis of lysosomal content to the extracellular space to promote invasion and metastasis. However, due to the enhanced lysosomal function, cancer cells are often more susceptible to lysosomal membrane permeabilization, providing an alternative strategy to induce cell death. This review summarizes the current knowledge of cancer-associated alterations in lysosomal structure and function and illustrates how lysosomal exocytosis and release of extracellular vesicles affect disease progression. We focus on functional differences depending on lysosomal localization and the regulation of intracellular transport, and lastly provide insight how new therapeutic strategies can exploit the power of the lysosome and improve cancer treatment.

Asymmetric Synthesis of Saturated and Unsaturated Hydroxy Fatty Acids (HFAs) and Study of Their Antiproliferative Activity

Hydroxy fatty acids (HFAs) constitute a class of lipids, distinguished by the presence of a hydroxyl on a long aliphatic chain. This study aims to expand our insights into HFA bioactivities, while also introducing new methods for asymmetrically synthesizing unsaturated and saturated HFAs. Simultaneously, a procedure previously established by us was adapted to generate new HFA regioisomers. An organocatalytic step was employed for the synthesis of chiral terminal epoxides, which either by alkynylation or by Grignard reagents resulted in unsaturated or saturated chiral secondary alcohols and, ultimately, HFAs. 7-(S)-Hydroxyoleic acid (7SHOA), 7-(S)-hydroxypalmitoleic acid (7SHPOA) and 7-(R)- and (S)-hydroxymargaric acids (7HMAs) were synthesized for the first time and, together with regioisomers of (R)- and (S)-hydroxypalmitic acids (HPAs) and hydroxystearic acids (HSAs), whose biological activity has not been tested so far, were studied for their antiproliferative activities. The unsaturation of the long chain, as well as an odd-numbered (C17) fatty acid chain, led to reduced activity, while the new 6-(S)-HPA regioisomer was identified as exhibiting potent antiproliferative activity in A549 cells. 6SHPA induced acetylation of histone 3 in A549 cells, without affecting acetylated α-tubulin levels, suggesting the selective inhibition of histone deacetylase (HDAC) class I enzymes, and was found to inhibit signal transducer and activator of transcription 3 (STAT3) expression.

A Phase 1/2A trial of idroxioleic acid: first-in-class sphingolipid regulator and glioma cell autophagy inducer with antitumor activity in refractory glioma

BACKGROUND

The first-in-class brain-penetrating synthetic hydroxylated lipid idroxioleic acid (2-OHOA; sodium 2-hydroxyoleate), activates sphingomyelin synthase expression and regulates membrane-lipid composition and mitochondrial energy production, inducing cancer cell autophagy. We report the findings of a multicentric first-in-human Phase 1/2A trial (NCT01792310) of 2-OHOA, identifying the maximum tolerated dose (MTD) and assessing safety and preliminary efficacy.

METHODS

We performed an open-label, non-randomised trial to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics and anti-tumour activity of daily oral treatment with 2-OHOA monotherapy (BID/TID) in 54 patients with glioma and other advanced solid tumours. A dose-escalation phase using a standard 3 + 3 design was performed to determine safety and tolerability. This was followed by two expansion cohorts at the MTD to determine the recommended Phase-2 dose (RP2D).

RESULTS

In total, 32 recurrent patients were enrolled in the dose-escalation phase (500-16,000 mg/daily). 2-OHOA was rapidly absorbed with dose-proportional exposure. Treatment was well-tolerated overall, with reversible grade 1-2 nausea, vomiting, and diarrhoea as the most common treatment-related adverse events (AEs). Four patients had gastrointestinal dose-limiting toxicities (DLTs) of nausea, vomiting, diarrhoea (three patients at 16,000 mg and one patient at 12,000 mg), establishing an RP2D at 12,000 mg/daily. Potential activity was seen in patients with recurrent high-grade gliomas (HGG). Of the 21 patients with HGG treated across the dose escalation and expansion, 5 (24%) had the clinical benefit (RANO CR, PR and SD >6 cycles) with one exceptional response lasting >2.5 years.

CONCLUSIONS

2-OHOA demonstrated a good safety profile and encouraging activity in this difficult-to-treat malignant brain-tumour patient population, placing it as an ideal potential candidate for the treatment of glioma and other solid tumour malignancies.

CLINICAL TRIAL REGISTRATION

EudraCT registration number: 2012-001527-13; Clinicaltrials.gov registration number: NCT01792310.

2-Hydroxyoleic Acid as a Self-Assembly Inducer for Anti-Cancer Drug-Centered Nanoparticles

A potent nontoxic antitumor drug, 2-hydroxyoleic acid (6, 2OHOA) used for membrane lipid therapy, was selected as a self-assembly inducer due to its ability to form nanoparticles (NPs) in water. For this purpose, it was conjugated with a series of anticancer drugs through a disulfide-containing linker to enhance cell penetration and to secure drug release inside the cell. The antiproliferative evaluation of the synthesized NP formulations against three human tumor cell lines (biphasic mesothelioma MSTO-211H, colorectal adenocarcinoma HT-29, and glioblastoma LN-229) showed that nanoassemblies 16-22a,bNPs exhibit antiproliferative activity at micromolar and submicromolar concentrations. Furthermore, the ability of the disulfide-containing linker to promote cellular effects was confirmed for most nanoformulations. Finally, 17bNP induced intracellular ROS increase in glioblastoma LN-229 cells similarly to free drug 8, and such elevated production was decreased by pretreatment with the antioxidant N-acetylcysteine. Also, nanoformulations 18bNP and 21bNP confirmed the mechanism of action of the free drugs.

Evolving Diagnostic and Treatment Strategies for Pediatric CNS Tumors: The Impact of Lipid Metabolism

Pediatric neurological tumors are a heterogeneous group of cancers, many of which carry a poor prognosis and lack a "standard of care" therapy. While they have similar anatomic locations, pediatric neurological tumors harbor specific molecular signatures that distinguish them from adult brain and other neurological cancers. Recent advances through the application of genetics and imaging tools have reshaped the molecular classification and treatment of pediatric neurological tumors, specifically considering the molecular alterations involved. A multidisciplinary effort is ongoing to develop new therapeutic strategies for these tumors, employing innovative and established approaches. Strikingly, there is increasing evidence that lipid metabolism is altered during the development of these types of tumors. Thus, in addition to targeted therapies focusing on classical oncogenes, new treatments are being developed based on a broad spectrum of strategies, ranging from vaccines to viral vectors, and melitherapy. This work reviews the current therapeutic landscape for pediatric brain tumors, considering new emerging treatments and ongoing clinical trials. In addition, the role of lipid metabolism in these neoplasms and its relevance for the development of novel therapies are discussed.

Structural Basis of the Interaction of the G Proteins, Gαi1, Gβ1γ2 and Gαi1β1γ2, with Membrane Microdomains and Their Relationship to Cell Localization and Activity

GPCRs receive signals from diverse messengers and activate G proteins that regulate downstream signaling effectors. Efficient signaling is achieved through the organization of these proteins in membranes. Thus, protein-lipid interactions play a critical role in bringing G proteins together in specific membrane microdomains with signaling partners. Significantly, the molecular basis underlying the membrane distribution of each G protein isoform, fundamental to fully understanding subsequent cell signaling, remains largely unclear. We used model membranes with lipid composition resembling different membrane microdomains, and monomeric, dimeric and trimeric Gi proteins with or without single and multiple mutations to investigate the structural bases of G protein-membrane interactions. We demonstrated that cationic amino acids in the N-terminal region of the Gαi₁ and C-terminal region of the Gγ₂ subunit, as well as their myristoyl, palmitoyl and geranylgeranyl moieties, define the differential G protein form interactions with membranes containing different lipid classes (PC, PS, PE, SM, Cho) and the various microdomains they may form (Lo, Ld, PC bilayer, charged, etc.). These new findings in part explain the molecular basis underlying amphitropic protein translocation to membranes and localization to different membrane microdomains and the role of these interactions in cell signal propagation, pathophysiology and therapies targeted to lipid membranes.

The anti-tumor drug 2-hydroxyoleic acid regulates the oncogenic potassium channel Kv10.1

Background

2-hydroxyoleic acid (2OHOA) is a synthetic fatty acid with antitumor properties that alters membrane composition and structure, which in turn influences the functioning of membrane proteins and cell signaling. In this study, we propose a novel antitumoral mechanism of 2OHOA accomplished through the regulation of Kv10.1 channels. We evaluated the effects of 2OHOA on Kv10.1 channels expressed in HEK-293 cells by using electrophysiological techniques and a cell proliferation assay.

Results

2OHOA increased Kv10.1 channel currents in a voltage-dependent manner, shifted its conductance-voltage relationship towards negative potentials, and accelerated its activation kinetics. Moreover, 2OHOA reduced proliferation of cells that exogenously (HEK-293) and endogenously (MCF-7) expressed Kv10.1 channels. It is worth noting that the antiproliferative effect of 2OHOA was maintained in HEK-293 cells expressing a non-conducting mutant of Kv10.1 channel (Kv10.1-F456A), while it did not affect HEK-293 cells not expressing Kv10.1 channels, suggesting that 2OHOA interferes with a non-conducting function of Kv10.1 channels involved in cell proliferation. Finally, we found that 2OHOA can act synergistically with astemizole, a Kv10.1 channel blocker, to decrease cell proliferation more efficiently.

Conclusion

Our data suggest that 2OHOA decreases cell proliferation, at least in part, by regulating Kv10.1 channels.

Targeting Oncogenic Rewiring of Lipid Metabolism for Glioblastoma Treatment

Glioblastoma (GBM) is the most malignant primary brain tumor. Despite increasing research on GBM treatment, the overall survival rate has not significantly improved over the last two decades. Although recent studies have focused on aberrant metabolism in GBM, there have been few advances in clinical application. Thus, it is important to understand the systemic metabolism to eradicate GBM. Together with the Warburg effect, lipid metabolism has emerged as necessary for GBM progression. GBM cells utilize lipid metabolism to acquire energy, membrane components, and signaling molecules for proliferation, survival, and response to the tumor microenvironment. In this review, we discuss fundamental cholesterol, fatty acid, and sphingolipid metabolism in the brain and the distinct metabolic alterations in GBM. In addition, we summarize various studies on the regulation of factors involved in lipid metabolism in GBM therapy. Focusing on the rewiring of lipid metabolism will be an alternative and effective therapeutic strategy for GBM treatment.

Mass spectrometry imaging discriminates glioblastoma tumor cell subpopulations and different microvascular formations based on their lipid profiles

Glioblastoma is a prevalent malignant brain tumor and despite clinical intervention, tumor recurrence is frequent and usually fatal. Genomic investigations have provided a greater understanding of molecular heterogeneity in glioblastoma, yet there are still no curative treatments, and the prognosis has remained unchanged. The aggressive nature of glioblastoma is attributed to the heterogeneity in tumor cell subpopulations and aberrant microvascular proliferation. Ganglioside-directed immunotherapy and membrane lipid therapy have shown efficacy in the treatment of glioblastoma. To truly harness these novel therapeutics and develop a regimen that improves clinical outcome, a greater understanding of the altered lipidomic profiles within the glioblastoma tumor microenvironment is urgently needed. In this work, high resolution mass spectrometry imaging was utilized to investigate lipid heterogeneity in human glioblastoma samples. Data presented offers the first insight into the histology-specific accumulation of lipids involved in cell metabolism and signaling. Cardiolipins, phosphatidylinositol, ceramide-1-phosphate, and gangliosides, including the glioblastoma stem cell marker, GD3, were shown to differentially accumulate in tumor and endothelial cell subpopulations. Conversely, a reduction in sphingomyelins and sulfatides were detected in tumor cell regions. Cellular accumulation for each lipid class was dependent upon their fatty acid residue composition, highlighting the importance of understanding lipid structure-function relationships. Discriminating ions were identified and correlated to histopathology and Ki67 proliferation index. These results identified multiple lipids within the glioblastoma microenvironment that warrant further investigation for the development of predictive biomarkers and lipid-based therapeutics.

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.

Anti-Tumorigenic Effect of a Novel Derivative of 2-Hydroxyoleic Acid and the Endocannabinoid Anandamide on Neuroblastoma Cells

Modulation of the endogenous cannabinoid system has been suggested as a potential anticancer strategy. In the search for novel and less toxic therapeutic options, structural modifications of the endocannabinoid anandamide and the synthetic derivative of oleic acid, Minerval (HU-600), were done to obtain 2-hydroxy oleic acid ethanolamide (HU-585), which is an HU-600 derivative with the anandamide side chain. We showed that treatment of SK-N-SH neuroblastoma cells with HU-585 induced a better anti-tumorigenic effect in comparison to HU-600 as evidenced by 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide assay, colony-forming assay, and migration assay. Moreover, HU-585 demonstrated pro-apoptotic properties shown by increased levels of activated caspase-3 following treatment and a better senescence induction effect in comparison to HU-600, as demonstrated by increased activity of lysosomal β-galactosidase. Finally, we observed that combined treatment of HU-585 with the senolytic drugs ABT-263 in vitro, and ABT-737 in vivo resulted in enhanced anti-proliferative effects and reduced neuroblastoma xenograft growth in comparison to treatment with HU-585 alone. Based on these results, we suggest that HU-585 is a pro-apoptotic and senescence-inducing compound, better than HU-600. Hence, it may be a beneficial option for the treatment of resistant neuroblastoma especially when combined with senolytic drugs that enhance its anti-tumorigenic effects.

Bilayer Forming Phospholipids as Targets for Cancer Therapy

Phospholipids represent a crucial component for the structure of cell membranes. Phosphatidylcholine and phosphatidylethanolamine are two phospholipids that comprise the majority of cell membranes. De novo biosynthesis of phosphatidylcholine and phosphatidylethanolamine occurs via the Kennedy pathway, and perturbations in the regulation of this pathway are linked to a variety of human diseases, including cancer. Altered phosphatidylcholine and phosphatidylethanolamine membrane content, phospholipid metabolite levels, and fatty acid profiles are frequently identified as hallmarks of cancer development and progression. This review summarizes the research on how phospholipid metabolism changes over oncogenic transformation, and how phospholipid profiling can differentiate between human cancer and healthy tissues, with a focus on colorectal cancer, breast cancer, and non-small cell lung cancer. The potential for phospholipids to serve as biomarkers for diagnostics, or as anticancer therapy targets, is also discussed.

Multifaceted Analyses of Isolated Mitochondria Establish the Anticancer Drug 2-Hydroxyoleic Acid as an Inhibitor of Substrate Oxidation and an Activator of Complex IV-Dependent State 3 Respiration

The synthetic fatty acid 2-hydroxyoleic acid (2OHOA) has been extensively investigated as a cancer therapy mainly based on its regulation of membrane lipid composition and structure, activating various cell fate pathways. We discovered, additionally, that 2OHOA can uncouple oxidative phosphorylation, but this has never been demonstrated mechanistically. Here, we explored the effect of 2OHOA on mitochondria isolated by ultracentrifugation from U118MG glioblastoma cells. Mitochondria were analyzed by shotgun lipidomics, molecular dynamic simulations, spectrophotometric assays for determining respiratory complex activity, mass spectrometry for assessing beta oxidation and Seahorse technology for bioenergetic profiling. We showed that the main impact of 2OHOA on mitochondrial lipids is their hydroxylation, demonstrated by simulations to decrease co-enzyme Q diffusion in the liquid disordered membranes embedding respiratory complexes. This decreased co-enzyme Q diffusion can explain the inhibition of disjointly measured complexes I–III activity. However, it doesn’t explain how 2OHOA increases complex IV and state 3 respiration in intact mitochondria. This increased respiration probably allows mitochondrial oxidative phosphorylation to maintain ATP production against the 2OHOA-mediated inhibition of glycolytic ATP production. This work correlates 2OHOA function with its modulation of mitochondrial lipid composition, reflecting both 2OHOA anticancer activity and adaptation to it by enhancement of state 3 respiration.

Tri-2-Hydroxyarachidonein Induces Cytocidal Autophagy in Pancreatic Ductal Adenocarcinoma Cancer Cell Models

Cell proliferation in pancreatic cancer is determined by a complex network of signaling pathways. Despite the extensive understanding of these protein-mediated signaling processes, there are no significant drug discoveries that could considerably improve a patient’s survival. However, the recent understanding of lipid-mediated signaling gives a new perspective on the control of the physiological state of pancreatic cells. Lipid signaling plays a major role in the induction of cytocidal autophagy and can be exploited using synthetic lipids to induce cell death in pancreatic cancer cells. In this work, we studied the activity of a synthetic lipid, tri-2-hydroxyarachidonein (TGM4), which is a triacylglycerol mimetic that contains three acyl moieties with four double bonds each, on cellular and in vivo models of pancreatic cancer. We demonstrated that TGM4 inhibited proliferation of Mia-PaCa-2 (human pancreatic carcinoma) and PANC-1 (human pancreatic carcinoma of ductal cells) in in vitro models and in an in vivo xenograft model of Mia-PaCa-2 cells. In vitro studies demonstrated that TGM4 induced cell growth inhibition paralleled with an increased expression of PARP and CHOP proteins together with the presence of sub-G0 cell cycle events, indicating cell death. This cytocidal effect was associated with elevated ER stress or autophagy markers such as BIP, LC3B, and DHFR. In addition, TGM4 activated peroxisome proliferator-activated receptor gamma (PPAR-γ), which induced elevated levels of p-AKT and downregulation of p-c-Jun. We conclude that TGM4 induced pancreatic cell death by activation of cytocidal autophagy. This work highlights the importance of lipid signaling in cancer and the use of synthetic lipid structures as novel and potential approaches to treat pancreatic cancer and other neoplasias.

Fundamentals of Membrane Lipid Replacement: A Natural Medicine Approach to Repairing Cellular Membranes and Reducing Fatigue, Pain, and Other Symptoms While Restoring Function in Chronic Illnesses and Aging

Membrane Lipid Replacement (MLR) uses natural membrane lipid supplements to safely replace damaged, oxidized lipids in membranes in order to restore membrane function, decrease symptoms and improve health. Oral MLR supplements contain mixtures of cell membrane glycerolphospholipids, fatty acids, and other lipids, and can be used to replace and remove damaged cellular and intracellular membrane lipids. Membrane injury, caused mainly by oxidative damage, occurs in essentially all chronic and acute medical conditions, including cancer and degenerative diseases, and in normal processes, such as aging and development. After ingestion, the protected MLR glycerolphospholipids and other lipids are dispersed, absorbed, and internalized in the small intestines, where they can be partitioned into circulating lipoproteins, globules, liposomes, micelles, membranes, and other carriers and transported in the lymphatics and blood circulation to tissues and cellular sites where they are taken in by cells and partitioned into various cellular membranes. Once inside cells, the glycerolphospholipids and other lipids are transferred to various intracellular membranes by lipid carriers, globules, liposomes, chylomicrons, or by direct membrane-membrane interactions. The entire process appears to be driven by 'bulk flow' or mass action principles, where surplus concentrations of replacement lipids can stimulate the natural exchange and removal of damaged membrane lipids while the replacement lipids undergo further enzymatic alterations. Clinical studies have demonstrated the advantages of MLR in restoring membrane and organelle function and reducing fatigue, pain, and other symptoms in chronic illness and aging patients.

Lipids in Pathophysiology and Development of the Membrane Lipid Therapy: New Bioactive Lipids

Membranes are mainly composed of a lipid bilayer and proteins, constituting a checkpoint for the entry and passage of signals and other molecules. Their composition can be modulated by diet, pathophysiological processes, and nutritional/pharmaceutical interventions. In addition to their use as an energy source, lipids have important structural and functional roles, e.g., fatty acyl moieties in phospholipids have distinct impacts on human health depending on their saturation, carbon length, and isometry. These and other membrane lipids have quite specific effects on the lipid bilayer structure, which regulates the interaction with signaling proteins. Alterations to lipids have been associated with important diseases, and, consequently, normalization of these alterations or regulatory interventions that control membrane lipid composition have therapeutic potential. This approach, termed membrane lipid therapy or membrane lipid replacement, has emerged as a novel technology platform for nutraceutical interventions and drug discovery. Several clinical trials and therapeutic products have validated this technology based on the understanding of membrane structure and function. The present review analyzes the molecular basis of this innovative approach, describing how membrane lipid composition and structure affects protein-lipid interactions, cell signaling, disease, and therapy (e.g., fatigue and cardiovascular, neurodegenerative, tumor, infectious diseases).

SMS2 deficiency impairs PKCδ-regulated B cell tolerance in the germinal center

B cell tolerance prevents autoimmunity by deleting or deactivating autoreactive B cells that otherwise may cause autoantibody-driven disorders, including systemic lupus erythematosus (lupus). Lupus is characterized by immunoglobulin Gs carrying a double-stranded (ds)-DNA autospecificity derived mainly from somatic hypermutation in the germinal center (GC), pointing to a checkpoint breach of GC B cell tolerance that leads to lupus. However, tolerance mechanisms in the GC remain poorly understood. Here, we show that upregulated sphingomyelin synthase 2 (SMS2) in anti-dsDNA GC B cells induces apoptosis by directly activating protein kinase C δ (PKCδ)'s pro-apoptotic activity. This tolerance mechanism prevents lupus autoimmunity in C57/BL6 mice and can be stimulated pharmacologically to inhibit lupus pathogenesis in lupus-prone NZBWF1 mice. Patients with lupus consistently have substantially reduced SMS2 expression in B cells and to an even greater extent in autoimmune-prone, age-associated B cells, suggesting that patients with lupus have insufficient SMS2-regulated B cell tolerance.

Cationic amphiphilic drugs induce elevation in lysoglycerophospholipid levels and cell death in leukemia cells

INTRODUCTION

Repurposing of cationic amphiphilic drugs (CADs) emerges as an attractive therapeutic solution against various cancers, including leukemia. CADs target lysosomal lipid metabolism and preferentially kill cancer cells via induction of lysosomal membrane permeabilization, but the exact effects of CADs on the lysosomal lipid metabolism remain poorly illuminated.

OBJECTIVES

We aimed to systematically monitor CAD-induced alterations in the quantitative lipid profiles of leukemia cell lines in order to chart effects of CADs on the metabolism of various lipid classes present in these cells.

METHODS

We conducted this study on eight cultured cell lines representing two leukemia types, acute lymphoblastic leukemia and acute myeloid leukemia. Mass spectrometry-based quantitative shotgun lipidomics was employed to quantify the levels of around 400 lipid species of 26 lipid classes in the leukemia cell lines treated or untreated with a CAD, siramesine.

RESULTS

The two leukemia types displayed high, but variable sensitivities to CADs and distinct profiles of cellular lipids. Treatment with siramesine rapidly altered the levels of diverse lipid classes in both leukemia types. These included sphingolipid classes previously reported to play key roles in CAD-induced cell death, but also lipids of other categories. We demonstrated that the treatment with siramesine additionally elevated the levels of numerous cytolytic lysoglycerophospholipids in positive correlation with the sensitivity of individual leukemia cell lines to siramesine.

CONCLUSIONS

Our study shows that CAD treatment alters balance in the metabolism of glycerophospholipids, and proposes elevation in the levels of lysoglycerophospholipids as part of the mechanism leading to CAD-induced cell death of leukemia cells.

Exploiting Sphingo- and Glycerophospholipid Impairment to Select Effective Drugs and Biomarkers for CMT1A

In Charcot-Marie-Tooth type 1A (CMT1A), Schwann cells exhibit a preponderant transcriptional deficiency of genes involved in lipid biosynthesis. This perturbed lipid metabolism affects the peripheral nerve physiology and the structure of peripheral myelin. Nevertheless, the identification and functional characterization of the lipid species mainly responsible for CMT1A myelin impairment currently lack. This is critical in the pathogenesis of the neuropathy since lipids are many and complex molecules which play essential roles in the cell, including the structural components of cellular membranes, cell signaling, and membrane trafficking. Moreover, lipids themselves are able to modify gene transcription, thereby affecting the genotype-phenotype correlation of well-defined inherited diseases, including CMT1A. Here we report for the first time a comprehensive lipid profiling in experimental and human CMT1A, demonstrating a previously unknown specific alteration of sphingolipid (SP) and glycerophospholipid (GP) metabolism. Notably, SP, and GP changes even emerge in biological fluids of CMT1A rat and human patients, implying a systemic metabolic dysfunction for these specific lipid classes. Actually, SP and GP are not merely reduced; their expression is instead aberrant, contributing to the ultrastructural abnormalities that we detailed by X-ray diffraction in rat and human internode myelin. The modulation of SP and GP pathways in myelinating dorsal root ganglia cultures clearly sustains this issue. In fact, just selected molecules interacting with these pathways are able to modify the altered geometric parameters of CMT1A myelinated fibers. Overall, we propose to exploit the present SP and GP metabolism impairment to select effective drugs and validate a set of reliable biomarkers, which remain a challenge in CMT1A neuropathy.

Ceramide/Sphingomyelin Rheostat Regulated by Sphingomyelin Synthases and Chronic Diseases in Murine Models

Ceramide and sphingomyelin (SM) are major components of the double membrane-bound sphingolipids. Ceramide is an essential bioactive lipid involved in numerous cell processes including apoptosis, necrosis, and autophagy-dependent cell death. Inversely, SM regulates opposite cellular processes such as proliferation and migration by changing receptor-mediated signal transduction in the lipid microdomain. SM is generated through a transfer of phosphocholine from phosphatidylcholine to ceramide by SM synthases (SMSs). Research during the past several decades has revealed that the ceramide/SM balance in cellular membranes regulated by SMSs is important to decide the cell fate, survival, and proliferation. In addition, recent experimental studies utilizing SMS knockout mice and murine disease models provide evidence that SMS-regulated ceramide/SM balance is involved in human diseases. Here, we review the basic structural and functional characteristics of SMSs and focus on their cellular functions through the regulation of ceramide/SM balance in membrane microdomains. In addition, we present the pathological or physiological implications of SMSs by analyzing their role in SMS-knockout mice and human disease models. This review finally presents evidence indicating that the regulation of ceramide/SM balance through SMS could be a therapeutic target for human disorders.

The Implications for Cells of the Lipid Switches Driven by Protein-Membrane Interactions and the Development of Membrane Lipid Therapy

The cell membrane contains a variety of receptors that interact with signaling molecules. However, agonist-receptor interactions not always activate a signaling cascade. Amphitropic membrane proteins are required for signal propagation upon ligand-induced receptor activation. These proteins localize to the plasma membrane or internal compartments; however, they are only activated by ligand-receptor complexes when both come into physical contact in membranes. These interactions enable signal propagation. Thus, signals may not propagate into the cell if peripheral proteins do not co-localize with receptors even in the presence of messengers. As the translocation of an amphitropic protein greatly depends on the membrane's lipid composition, regulation of the lipid bilayer emerges as a novel therapeutic strategy. Some of the signals controlled by proteins non-permanently bound to membranes produce dramatic changes in the cell's physiology. Indeed, changes in membrane lipids induce translocation of dozens of peripheral signaling proteins from or to the plasma membrane, which controls how cells behave. We called these changes "lipid switches", as they alter the cell's status (e.g., proliferation, differentiation, death, etc.) in response to the modulation of membrane lipids. Indeed, this discovery enables therapeutic interventions that modify the bilayer's lipids, an approach known as membrane-lipid therapy (MLT) or melitherapy.

A Virulence-Associated Glycolipid with Distinct Conformational Attributes: Impact on Lateral Organization of Host Plasma Membrane, Autophagy, and Signaling

Mycobacterium tuberculosis (Mtb) serves as the epitome of how lipids-next to proteins-are utilized as central effectors in pathogenesis. It synthesizes an arsenal of structurally atypical lipids (C60-C90) to impact various membrane-dependent steps involved in host interactions. There is a growing precedent to support insertion of these exposed lipids into the host membrane as part of their mode of action. However, the vital role of specific virulence-associated lipids in modulating cellular functions by altering the host membrane organization and associated signaling pathways remain unanswered questions. Here, we combined chemical synthesis, biophysics, cell biology, and molecular dynamics simulations to elucidate host membrane structure modifications and modulation of membrane-associated signaling using synthetic Mycobacterium tuberculosis sulfoglycolipids (Mtb SL). We reveal that Mtb SL reorganizes the host cell plasma membrane domains while showing higher preference for fluid membrane regions. This rearrangement is governed by the distinct conformational states sampled by SL acyl chains. Physicochemical assays with SL analogues reveal insights into their structure-function relationships, highlighting specific roles of lipid acyl chains and headgroup, along with effects on autophagy and cytokine profiles. Our findings uncover a mechanism whereby Mtb uses specific chemical moieties on its lipids to fine-tune host lipid interactions and confer control of the downstream functions by modifying the cell membrane structure and function. These findings will inspire development of chemotherapeutics against Mtb by counteracting their effects on the host-cell membrane.

Targeting Cancer Lysosomes with Good Old Cationic Amphiphilic Drugs

Being originally discovered as cellular recycling bins, lysosomes are today recognized as versatile signaling organelles that control a wide range of cellular functions that are essential not only for the well-being of normal cells but also for malignant transformation and cancer progression. In addition to their core functions in waste disposal and recycling of macromolecules and energy, lysosomes serve as an indispensable support system for malignant phenotype by promoting cell growth, cytoprotective autophagy, drug resistance, pH homeostasis, invasion, metastasis, and genomic integrity. On the other hand, malignant transformation reduces the stability of lysosomal membranes rendering cancer cells sensitive to lysosome-dependent cell death. Notably, many clinically approved cationic amphiphilic drugs widely used for the treatment of other diseases accumulate in lysosomes, interfere with their cancer-promoting and cancer-supporting functions and destabilize their membranes thereby opening intriguing possibilities for cancer therapy. Here, we review the emerging evidence that supports the supplementation of current cancer therapies with lysosome-targeting cationic amphiphilic drugs.

Cell Death Induced by Cationic Amphiphilic Drugs Depends on Lysosomal Ca2+ Release and Cyclic AMP

Repurposing cationic amphiphilic drugs (CAD) for cancer treatment is emerging as an attractive means to enhance the efficacy of chemotherapy. Many commonly used CADs, including several cation amphiphilic antihistamines and antidepressants, induce cancer-specific, lysosome-dependent cell death and sensitize cancer cells to chemotherapy. CAD-induced inhibition of lysosomal acid sphingomyelinase is necessary, but not sufficient, for the subsequent lysosomal membrane permeabilization and cell death, while other pathways regulating this cell death pathway are largely unknown. Prompted by significant changes in the expression of genes involved in Ca2+ and cyclic AMP (cAMP) signaling pathways in CAD-resistant MCF7 breast cancer cells, we identified here an early lysosomal Ca2+ release through P2X purinergic receptor 4 (P2RX4) and subsequent Ca2+- and adenylyl cyclase 1 (ADCY1)-dependent synthesis of cAMP as a signaling route mediating CAD-induced lysosomal membrane permeabilization and cell death. Importantly, pharmacologic and genetic means to increase cellular cAMP levels either by activating cAMP-inducing G-protein-coupled receptors (GPR3 or β2 adrenergic receptor) or ADCY1, or by inhibiting cAMP-reducing guanine nucleotide-binding protein G(i) subunit α2, C-X-C motif chemokine receptor type 4, or cAMP phosphodiesterases, sensitized cancer cells to CADs. These data reveal a previously unrecognized lysosomal P2RX4- and ADCY1-dependent signaling cascade as a pathway essential for CAD-induced lysosome-dependent cell death and encourage further investigations to find the most potent combinations of CADs and cAMP-inducing drugs for cancer therapy.

Membrane Dynamics in Health and Disease: Impact on Cellular Signalling

Biological membranes display a staggering complexity of lipids and proteins orchestrating cellular functions. Superior analytical tools coupled with numerous functional cellular screens have enabled us to query their role in cellular signalling, trafficking, guiding protein structure and function-all of which rely on the dynamic membrane lipid properties indispensable for proper cellular functions. Alteration of these has led to emergence of various pathological conditions, thus opening an area of lipid-centric therapeutic approaches. This perspective is a short summary of the dynamic properties of membranes essential for proper cellular functions, dictating both protein and lipid functions, and mis-regulated in diseases. Towards the end, we focus on some challenges lying ahead and potential means to tackle the same, mainly underscored by multi-disciplinary approaches.

Studies on the Interactions of 2-Hydroxyoleic Acid with Monolayers and Bilayers Containing Cationic Lipid: Searching for the Formulations for More Efficient Drug Delivery to Cancer Cells

Drug delivery in cationic liposomes seems to be a promising therapeutic approach in cancer treatment. The rational design of the positively charged lipid vesicles as anticancer drug carriers should be supported by a detailed analysis of the interactions of the carrier components with anticancer drugs. In the present work, 2-hydroxyoleic acid (2OHOA; Minerval), a membrane lipid therapy drug, was incorporated into positively charged mono- and bilayer membranes containing 1-palmitoyl-2-oleoyl- sn-glycero-3-ethylphosphocholine (EPOPC), the synthetic cationic lipid, and 1,2-dioleoyl- sn-glycero-3-phosphocholine (DOPC). The intermolecular interactions, fluidity, and miscibility of the studied monolayers were analyzed by utilizing Langmuir balance experiments. The morphology of two-dimensional films was inspected using a Brewster angle microscopy technique. The properties of the liposomes were investigated by dynamic light scattering (DLS) and zeta potential measurements, steady-state fluorescence anisotropy experiments, and the spectrofluorimetric titration of calcein-encapsulated vesicles with a lysis-inducing agent. According to the collected results, 2OHOA intercalation into films of pure phospholipids or a binary EPOPC/DOPC film is thermodynamically favorable. Surprisingly, no significant effect of the presence of unsaturated 2OHOA chains on the EPOPC/DOPC monolayer order was observed. The experiments carried out for 2OHOA-inserted cationic EPOPC/DOPC (1:4) liposomes indicate effective incorporation of the drug into the liposome bilayer and the formation of stable vesicles without affecting their properties markedly. On the basis of the obtained results, EPOPC/DOPC/2OHOA cationic liposomes with 15% 2OHOA content in the phospholipid bilayer seem to be the most suitable for potential biomedical applications.

pH-Responsive Nano-Self-Assemblies of the Anticancer Drug 2-Hydroxyoleic Acid

pH-responsive lipid nanocarriers have the potential to selectively target the acidic extracellular pH environment of cancer tissues and may further improve the efficacy of chemotherapeutics by minimizing their toxic side-effects. Here, we present the design and characterization of pH-sensitive nano-self-assemblies of the poorly water-soluble anticancer drug 2-hydroxyoleic acid (2OHOA) with glycerol monooleate (GMO). pH-triggered nanostructural transformations from 2OHOA/GMO nanoparticles with an internal inverse hexagonal structure (hexosomes) at pH around 2.0-3.0, via nanocarriers with an internal inverse bicontinuous cubic structure (cubosomes) at pH 2.0-4.5, to vesicles at pH 4.5-7.4 were observed with synchrotron small-angle X-ray scattering, and cryogenic transmission electron microscopy. ζ-potential measurements highlight that the pH-driven deprotonation of the carboxylic group of 2OHOA, and the resulting charge-repulsions at the lipid-water interface account for these nanostructural alterations. The study provides detailed insight into the pH-dependent self-assembly of 2OHOA with GMO in excess buffer at physiologically relevant pH values, and discusses the effects of pH alterations on modulating their nanostructure. The results may guide the further development of pH-responsive anticancer nanocarriers for the targeted delivery of chemotherapeutics to the local microenvironment of tumor cells.

Impact of extremely low-frequency electromagnetic field (100 Hz, 100 G) exposure on human glioblastoma U87 cells during Temozolomide administration

Glioblastoma multiforme (GBM) is a highly malignant brain tumor with an extremely dismal prognosis, a median survival is12 months. Temozolomide (TMZ) is an alkylating agent widely used to treat cancer, resistance to this drug is often found. One unexplored possibility for overcoming this resistance is a treatment based on concomitant exposure to electromagnetic fields (EMF) and TMZ. Indeed, many evidences show that EMF affects cancer cells and drug performance. Therefore, the present study was carried out to evaluate the potential synergistic effect of 100 µM TMZ and EMF (100 Hz, 100 G) on human glioma cell line U87 U87 cells with four experimental groups (I-IV) were exposed to ELF-EMF and TMZ for 120 and 144 h, as follows: (I) control; (II) ELF-EMF; (III) TMZ; (IV) ELF-PEMFs / TMZ. mRNA expression of genes such as (Nestin,CD133, Notch4 and GFAP) were investigated by Real-time PCR and western blot. We also evaluated, SOD activity, MDA and calcium concentration by ELISA assay. Co-treatment synergistically decreased the expression of Nestin,CD133, and Notch4 and increased the GFAP genes. We also observed an increase in Superoxide dismutase (SOD) activity, Malondialdehyde (MDA) and Ca2+concentration in comparison to controls.TMZ prevents cancer progression not only through the induction of cell death, but also by inducing differentiation in cancer cells. In addition, our data demonstrate ELF-EMF (100 Hz, 100 G) can significantly enhance the effects of TMZ on human glioblastoma U87 cell. These findings may open new window for future studies.

Membrane Lipid Composition: Effect on Membrane and Organelle Structure, Function and Compartmentalization and Therapeutic Avenues

Biological membranes are key elements for the maintenance of cell architecture and physiology. Beyond a pure barrier separating the inner space of the cell from the outer, the plasma membrane is a scaffold and player in cell-to-cell communication and the initiation of intracellular signals among other functions. Critical to this function is the plasma membrane compartmentalization in lipid microdomains that control the localization and productive interactions of proteins involved in cell signal propagation. In addition, cells are divided into compartments limited by other membranes whose integrity and homeostasis are finely controlled, and which determine the identity and function of the different organelles. Here, we review current knowledge on membrane lipid composition in the plasma membrane and endomembrane compartments, emphasizing its role in sustaining organelle structure and function. The correct composition and structure of cell membranes define key pathophysiological aspects of cells. Therefore, we explore the therapeutic potential of manipulating membrane lipid composition with approaches like membrane lipid therapy, aiming to normalize cell functions through the modification of membrane lipid bilayers.

The triacylglycerol, hydroxytriolein, inhibits triple negative mammary breast cancer cell proliferation through a mechanism dependent on dihydroceramide and Akt

The plasma membrane is an attractive target for new anticancer drugs, not least because regulating its lipid structure can control multiple signaling pathways involved in cancer cell proliferation, differentiation and survival. Accordingly, the novel anticancer drug hydroxytriolein (HTO) was designed to interact with and regulate the composition and structure of the membrane, which in turn controls the interaction of amphitropic signaling membrane proteins with the lipid bilayer. Changes in signaling provoked by HTO impair the growth of triple negative breast cancer (TNBC) cells, aggressive breast tumor cells that have a worse prognosis than other types of breast cancers and for which there is as yet no effective targeted therapy. HTO alters the lipid composition and structure of cancer cell membranes, inhibiting the growth of MDA-MB-231 and BT-549 TNBC cells in vitro. Depending on the cellular context, HTO could regulate two pathways involved in TNBC cell proliferation. On the one hand, HTO might stimulate ERK signaling and induce TNBC cell autophagy, while on the other, it could increase dihydroceramide and ceramide production, which would inhibit Akt independently of EGFR activation and provoke cell death. In vivo studies using a model of human TNBC show that HTO and its fatty acid constituent (2-hydroxyoleic acid) impair tumor growth, with no undesired side effects. For these reasons, HTO appears to be a promising anticancer molecule that targets the lipid bilayer (membrane-lipid therapy). By regulating membrane lipids, HTO controls important signaling pathways involved in cancer cell growth, the basis of its pharmacological efficacy and safety.

Sphingomyelin synthase 2 promotes an aggressive breast cancer phenotype by disrupting the homoeostasis of ceramide and sphingomyelin

Breast cancer is the most common type of carcinoma in women worldwide, but the mechanisms underlying tumour development and progression remain unclear. Sphingomyelin synthase 2 (SGMS2) is a crucial regulator involved in ceramide (Cer) and sphingomyelin (SM) homoeostasis that is mostly studied for its role in lipid metabolism. Our primary study indicated that high SGMS2 expression is associated with breast cancer metastasis. Gain- and loss-of-function assays in vitro and in vivo revealed that SGMS2 promotes cancer cell proliferation by suppressing apoptosis through a Cer-associated pathway and promotes cancer cell invasiveness by enhancing epithelial-to-mesenchymal transition (EMT) initiation through the TGF-β/Smad signalling pathway. Further study determined that SGMS2 activated the TGF-β/Smad signalling pathway primarily by increasing TGF-β1 secretion, which was likely associated with aberrant expression of SM. Thus, our findings indicate that SGMS2-mediated activation of the TGF-β/Smad signalling pathway is important in breast cancer progression, which provides new insight into the mechanisms underlying breast cancer metastasis and suggests a possible anticancer therapy for breast cancer.

Quantitative biophysical analysis defines key components modulating recruitment of the GTPase KRAS to the plasma membrane

The gene encoding the GTPase KRAS is frequently mutated in pancreatic, lung, and colorectal cancers. The KRAS fraction in the plasma membrane (PM) correlates with activation of the mitogen-activated protein kinase (MAPK) pathway and subsequent cellular proliferation. Understanding KRAS's interaction with the PM is challenging given the complexity of the cellular environment. To gain insight into key components necessary for KRAS signal transduction at the PM, we used synthetic membranes such as liposomes and giant unilamellar vesicles. Using surface plasmon resonance (SPR) spectroscopy, we demonstrated that KRAS and Raf-1 proto-oncogene Ser/Thr kinase (RAF1) domains interact with these membranes primarily through electrostatic interactions with negatively charged lipids reinforced by additional interactions involving phosphatidyl ethanolamine and cholesterol. We found that the RAF1 region spanning RBD through CRD (RBDCRD) interacts with the membrane significantly more strongly than the isolated RBD or CRD domains and synergizes KRAS partitioning to the membrane. We also found that calmodulin and phosphodiesterase 6 delta (PDE6δ), but not galectin3 previously proposed to directly interact with KRAS, passively sequester KRAS and prevent it from partitioning into the PM. RAF1 RBDCRD interacted with membranes preferentially at nonraft lipid domains. Moreover, a C-terminal O-methylation was crucial for KRAS membrane localization. These results contribute to a better understanding of how the KRAS-membrane interaction is tuned by multiple factors whose identification could inform drug discovery efforts to disrupt this critical interaction in diseases such as cancer.

Hsp70 interactions with membrane lipids regulate cellular functions in health and disease

Beyond guarding the cellular proteome the major stress inducible heat shock protein Hsp70 has been shown to interact with lipids. Non-cytosolic Hsp70 stabilizes membranes during stress challenges and, in pathophysiological states, facilitates endocytosis, counteracts apoptotic mechanisms, sustains survival pathways or represents a signal that can be recognized by the immune system. Disease-coupled lipid-associated functions of Hsp70 may be targeted via distinct subcellular localizations of Hsp70 itself or its specific interacting lipids. With a special focus on interacting lipids, here we discuss localization-dependent roles of the membrane-bound Hsp70 in the context of its therapeutic potential, particularly in cancer and neurodegenerative diseases.

Minerval (2-hydroxyoleic acid) causes cancer cell selective toxicity by uncoupling oxidative phosphorylation and compromising bioenergetic compensation capacity

This work tests bioenergetic and cell-biological implications of the synthetic fatty acid Minerval (2-hydroxyoleic acid), previously demonstrated to act by activation of sphingomyelin synthase in the plasma membrane (PM) and lowering of phosphatidylethanolamine (PE) and phosphatidylcholine (PC) and their carcinogenic signaling. We show here that Minerval also acts, selectively in cancer cell lines, as an ATP depleting uncoupler of mitochondrial oxidative phosphorylation (OxPhos). As a function of its exposure time, Minerval compromised the capacity of glioblastoma U87-MG cells to compensate for aberrant respiration by up-modulation of glycolysis. This effect was not exposure time-dependent in the lung carcinoma A549 cell line, which was more sensitive to Minerval. Compared with OxPhos inhibitors FCCP (uncoupler), rotenone (electron transfer inhibitor), and oligomycin (F1F0-ATPase inhibitor), Minerval action was similar only to that of FCCP. This similarity was manifested by mitochondrial membrane potential (MMP) depolarization, facilitation of oxygen consumption rate (OCR), restriction of mitochondrial and cellular reactive oxygen species (ROS) generation and mitochondrial fragmentation. Additionally, compared with other OxPhos inhibitors, Minerval uniquely induced ER stress in cancer cell lines. These new modes of action for Minerval, capitalizing on the high fatty acid requirements of cancer cells, can potentially enhance its cancer-selective toxicity and improve its therapeutic capacity.

The Opposing Contribution of SMS1 and SMS2 to Glioma Progression and Their Value in the Therapeutic Response to 2OHOA

Background: 2-Hydroxyoleic acid (2OHOA) is particularly active against glioblastoma multiforme (GBM) and successfully finished a phase I/IIA trial in patients with glioma and other advanced solid tumors. However, its mechanism of action is not fully known. Methods: The relationship between SMS1 and SMS2 expressions (mRNA) and overall survival in 329 glioma patients was investigated, and so was the correlation between SMS expression and 2OHOA's efficacy. The opposing role of SMS isoforms in 2OHOA's mechanism of action and in GBM cell growth, differentiation and death, was studied overexpressing or silencing them in human GBM cells. Results: Patients with high-SMS1 plus low-SMS2 expression had a 5-year survival ~10-fold higher than patients with low-SMS1 plus high-SMS2 expression. SMS1 and SMS2 also had opposing effect on GBM cell survival and 2OHOA's IC₅₀ correlated with basal SMS1 levels and treatment induced changes in SMS1/SMS2 ratio. SMSs expression disparately affected 2OHOA's cancer cell proliferation, differentiation, ER-stress and autophagy. Conclusions: SMS1 and SMS2 showed opposite associations with glioma patient survival, glioma cell growth and response to 2OHOA treatment. SMSs signature could constitute a valuable prognostic biomarker, with high SMS1 and low SMS2 being a better disease prognosis. Additionally, low basal SMS1 mRNA levels predict positive response to 2OHOA.

2-Hydroxy-oleic acid does not activate sphingomyelin synthase activity

2-Hydroxy-oleic acid (2OHOA) is a potent anticancer drug that induces cancer cell cycle arrest and apoptosis. Previous studies have suggested that 2OHOA's anticancer effect is mediated by SMS activation in cancer cells, including A549 and U118 cells. To confirm this phenomenon, in this study, we treated both A549 and U118 cells with 2OHOA and measured SMS activity. To our surprise, we found neither 2OHOA-mediated SMS activation nor sphingomyelin accumulation in the cells. However, we noted that 2OHOA significantly reduces phosphatidylcholine in these cells. We also did not observe 2OHOA-mediated SMS activation in mouse tissue homogenates. Importantly, 2OHOA inhibited rather than activated recombinant SMS1 (rSMS1) and rSMS2 in a dose-dependent fashion. Intra-gastric treatment of C57BL/6J mice with 2OHOA for 10 days had no effects on liver and small intestine SMS activities and plasma sphingomyelin levels. The treatment inhibited lysophosphatidylcholine acyltransferase (LPCAT) activity, consistent with the aforementioned reduction in plasma phosphatidylcholine. Because total cellular phosphatidylcholine is used as a predictive biomarker for monitoring tumor responses, the previously reported 2OHOA-mediated cancer suppression could be related to this phosphatidylcholine reduction, which may influence cell membrane structure and properties. We conclude that 2OHOA is not a SMS activator and that its anticancer property may be related to an effect on phosphatidylcholine metabolism.

Beneficial effects of n-3 polyunsaturated fatty acids administration in a partial lesion model of Parkinson's disease: The role of glia and NRf2 regulation

Omega-3 polyunsaturated fatty acids (n-3 PUFAs) have been widely associated to beneficial effect over different neurodegenerative diseases. In the present study, we tested the potential therapeutic effect of docohexanoic acid (DHA) and its hydroxylated derivate, DHAH, in a partial lesion model of Parkinson's disease (PD). One month before and four months after the striatal lesion with 6-OHDA was made, the animals were daily treated with DHA (50 mg/kg), DHAH (50 mg/kg), vehicle or saline, by intragastric administration. Animal groups under n-3 PUFA treatments exhibited a trend to improve in amphetamine-induced rotations and cylinder test. The beneficial effect seen in behavioral studies were confirmed with TH immunostaining. TH⁺ fibers and TH⁺ neurons increased in the experimental groups treated with both n-3 PUFAs, DHA and DHAH. Moreover, the n-3 PUFAs administration decreased the astrogliosis and microgliosis, in both the striatum and substantia nigra (SN), with a higher decrease of GFAP⁺ and Iba-1⁺ cells for the DHAH treated group. This experimental group also revealed a positive effect on Nrf2 pathway regulation, decreasing the positive Nrf2 immmunostaining in the striatum and SN, which revealed a potential antioxidant effect of this compound. Taking together, these data suggest a positive effect of n-3 PUFAs administration, and more concretely of DHAH, for PD treatment as it exhibited positive results on dopaminergic system, neuroinflammation and oxidative stress.

Autophagy in glioma cells: An identity crisis with a clinical perspective

Over the last decade, autophagy has emerged as one of the critical cellular systems that control homeostasis. Besides management of normal homeostatic processes, autophagy can also be induced by tissue damage stress or by rapidly progressing tumors. During tumor progression, autophagy mediates a cellular reaction to the changes inside and outside of cells, which leads to tumor adaptation. Even though the regulation of autophagy seems universal and is a well-described process, its dysregulation and role in glioma progression remain an important topic of investigation. In this review, we summarize recent evidence of autophagy regulation in brain tumor tissues and possible interconnection between signaling pathways that govern cellular responses. This perspective may help to assess the qualitative differences and various outcomes in response to autophagy stimulation.

The anti-tumor drug 2-hydroxyoleic acid (Minerval) stimulates signaling and retrograde transport

2-hydroxyoleic acid (OHOA, Minerval^®) is an example of a substance used for membrane lipid therapy, where the cellular membranes rather than specific proteins constitute the therapeutical target. OHOA is thought to mediate its anti-tumor effect by affecting the biophysical properties of membranes, which leads to altered recruitment and activation of amphitropic proteins, altered cellular signaling, and eventual cell death. Little is known about the initial signaling events upon treatment with OHOA, and whether the altered membrane properties would have any impact on the dynamic intracellular transport system. In the present study we demonstrate that treatment with OHOA led to a rapid release of intracellular calcium and activation of multiple signaling pathways in HeLa cells, including the PI3K-AKT1-MTOR pathway and several MAP kinases, in a process independent of the EGFR. By lipidomics we confirmed that OHOA was incorporated into several lipid classes. Concomitantly, OHOA potently increased retrograde transport of the plant toxin ricin from endosomes to the Golgi and further to the endoplasmic reticulum. The OHOA-stimulated ricin transport seemed to require several amphitropic proteins, including Src, phospholipase C, protein kinase C, and also Ca²⁺/calmodulin. Interestingly, OHOA induced a slight increase in endosomal localization of the retromer component VPS35. Thus, our data show that addition of a lipid known to alter membrane properties not only affects signaling, but also intracellular transport.

2-Hydroxyoleic acid-inserted liposomes as a multifunctional carrier of anticancer drugs

Studies have shown that insertion of oleic acid into lipid bilayers can modulate the membrane properties of liposomes so as to improve their function as drug carriers. Considering that 2-hydroxyoleic acid (2OHOA), a potential antitumor agent currently undergoing clinical trials, is a derivative of oleic acid, we explored the possibility of developing 2OHOA-inserted liposomes as a multifunctional carrier of antitumor drugs in the present study. The insertion of 2OHOA into lipid bilayers was confirmed by surface charge determination and differential scanning calorimetry. 2OHOA insertion greatly decreased the order of dimyristoylphosphatidylcholine packing, produced a nanosized (<100 nm) dispersion, and improved the colloidal stability of liposomes during storage. Moreover, 2OHOA-inserted liposome forms exhibited greater growth inhibitory activity against cancer cells compared with free 2OHOA, and the growth-inhibitory activity of liposomal 2OHOA was selective for tumor cells. 2OHOA insertion greatly increased the liposome-incorporated concentration of hydrophobic model drugs, including mitoxantrone, paclitaxel, and all-trans retinoic acid (ATRA). The in vitro anticancer activity of ATRA-incorporated/2OHOA-inserted liposomes was significantly higher than that of ATRA-incorporated conventional liposomes. In a B16-F10 melanoma syngeneic mouse model, the tumor growth rate was significantly delayed in mice treated with ATRA-incorporated/2OHOA-inserted liposomes compared with that in the control group. Immunohistochemical analyses revealed that the enhanced antitumor activity of ATRA-incorporated/2OHOA-inserted liposomes was due, at least in part, to increased induction of apoptosis. Collectively, our findings indicate that 2OHOA-inserted liposomes exhibit multiple advantages as antitumor drug carriers, including the ability to simultaneously deliver two anticancer drugs - 2OHOA and incorporated drug - to the tumor tissue.

Hydrogel Environment Supports Cell Culture Expansion of a Grade IV Astrocytoma

Malignant astrocytomas are aggressive cancers of glial origin that can develop into invasive brain tumors. The disease has poor prognosis and high recurrence rate. Astrocytoma cell lines of human origin are an important tool in the experimental pathway from bench to bedside because they afford a convenient intermediate system for in vitro analysis of brain cancer pathogenesis and treatment options. We undertook the current study to determine whether hydrogel culture methods could be adapted to support the growth of astrocytoma cell lines, thereby facilitating a system that may be biologically more similar to in vivo tumor tissue. Our experimental protocols enabled maintenance of Grade IV astrocytoma cell lines in conventional monolayer culture and in the extracellular matrix hydrogel, Geltrex™. Light and fluorescence microscopy showed that hydrogel environments promoted cellular reorganization from dispersed cells into multilayered aggregates. Transmission electron microscopy revealed the prevalence of autophagy and nuclear membrane distortions in both culture systems. Analysis of microarray Gene Expression Omnibus (GEO) DataSets highlighted expression of genes implicated in pathways for cancer progression and autophagy. A pilot quantitative polymerase chain reaction (qPCR) analysis of the autophagic biomarkers, Beclin 1 (BECN1) and microtubule-associated proteins 1A/1B light chain 3B (MAP1LC3B), with two reference genes (beta actin, ACTB; glyceraldehyde 3-phosphate dehydrogenase, GAPDH), uncovered a relative increase of BECN1 and LC3B in hydrogel cultures of astrocytoma as compared to the monolayer. Taken together, results establish that ultrastructural and molecular characteristics of autophagy are features of this astrocytoma cell line, and that hydrogel culture systems can afford novel opportunities for in vitro studies of glioma.

Molecular dynamics simulations of heterogeneous cell membranes in response to uniaxial membrane stretches at high loading rates

The chemobiomechanical signatures of diseased cells are often distinctively different from that of healthy cells. This mainly arises from cellular structural/compositional alterations induced by disease development or therapeutic molecules. Therapeutic shock waves have the potential to mechanically destroy diseased cells and/or increase cell membrane permeability for drug delivery. However, the biomolecular mechanisms by which shock waves interact with diseased and healthy cellular components remain largely unknown. By integrating atomistic simulations with a novel multiscale numerical framework, this work provides new biomolecular mechanistic perspectives through which many mechanosensitive cellular processes could be quantitatively characterised. Here we examine the biomechanical responses of the chosen representative membrane complexes under rapid mechanical loadings pertinent to therapeutic shock wave conditions. We find that their rupture characteristics do not exhibit significant sensitivity to the applied strain rates. Furthermore, we show that the embedded rigid inclusions markedly facilitate stretch-induced membrane disruptions while mechanically stiffening the associated complexes under the applied membrane stretches. Our results suggest that the presence of rigid molecules in cellular membranes could serve as “mechanical catalysts” to promote the mechanical destructions of the associated complexes, which, in concert with other biochemical/medical considerations, should provide beneficial information for future biomechanical-mediated therapeutics.

Changes in the plasma membrane in metabolic disease: impact of the membrane environment on G protein-coupled receptor structure and function

Drug development targeting GPCRs often utilizes model heterologous cell expression systems, reflecting an implicit assumption that the membrane environment has little functional impact on these receptors or on their responsiveness to drugs. However, much recent data have illustrated that membrane components can have an important functional impact on intrinsic membrane proteins. This review is directed toward gaining a better understanding of the structure of the plasma membrane in health and disease, and how this organelle can influence GPCR structure, function and regulation. It is important to recognize that the membrane provides a potential mode of lateral allosteric regulation of GPCRs and can affect the effectiveness of drugs and their biological responses in various disease states, which can even vary among individuals across the population. The type 1 cholecystokinin receptor is reviewed as an exemplar of a class A GPCR that is affected in this way by changes in the plasma membrane.

LINKED ARTICLES

This article is part of a themed section on Molecular Pharmacology of GPCRs. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.21/issuetoc.

Comparative Correlation Between Chemical Composition and Cytotoxic Potential of the Coral-Associated Fungus Aspergillus sp. 2C1-EGY Against Human Colon Cancer Cells

Cancer is a leading cause of death in several countries. In the search for new anticancer drugs, marine organisms have played an important role in the discovery of lead compounds and the development of new pharmaceuticals for their wide diversity of chemical structures and biological activities. In the present study, the cytotoxicity on colorectal cancer cells HCT116 exerted by marine fungus Aspergillus sp. 2C1-EGY extracts associated with the soft coral Sinularia sp. was investigated; the sub-fractions Fr 2c and Fr 2d had significantly high cytotoxic activity (88 and 85%, respectively). Moreover, the major hexadecanoic, octadecanoic, and octadecenoic acids as well as their methyl esters were isolated. GC/MS analysis revealed the identification of 46 major and minor compounds, from which 19 saturated and unsaturated fatty acids and eight fatty acid esters were identified.

Triacylglycerol mimetics regulate membrane interactions of glycogen branching enzyme: implications for therapy

Adult polyglucosan body disease (APBD) is a neurological disorder characterized by adult-onset neurogenic bladder, spasticity, weakness, and sensory loss. The disease is caused by aberrant glycogen branching enzyme (GBE) (GBE1Y329S) yielding less branched, globular, and soluble glycogen, which tends to aggregate. We explore here whether, despite being a soluble enzyme, GBE1 activity is regulated by protein-membrane interactions. Because soluble proteins can contact a wide variety of cell membranes, we investigated the interactions of purified WT and GBE1Y329S proteins with different types of model membranes (liposomes). Interestingly, both triheptanoin and some triacylglycerol mimetics (TGMs) we have designed (TGM0 and TGM5) markedly enhance GBE1Y329S activity, possibly enough for reversing APBD symptoms. We show that the GBE1Y329S mutation exposes a hydrophobic amino acid stretch, which can either stabilize and enhance or alternatively, reduce the enzyme activity via alteration of protein-membrane interactions. Additionally, we found that WT, but not Y329S, GBE1 activity is modulated by Ca²⁺ and phosphatidylserine, probably associated with GBE1-mediated regulation of energy consumption and storage. The thermal stabilization and increase in GBE1Y329S activity induced by TGM5 and its omega-3 oil structure suggest that this molecule has a considerable therapeutic potential for treating APBD.

Phytol-induced pathology in 2-hydroxyacyl-CoA lyase (HACL1) deficient mice. Evidence for a second non-HACL1-related lyase

2-Hydroxyacyl-CoA lyase (HACL1) is a key enzyme of the peroxisomal α-oxidation of phytanic acid. To better understand its role in health and disease, a mouse model lacking HACL1 was investigated. Under normal conditions, these mice did not display a particular phenotype. However, upon dietary administration of phytol, phytanic acid accumulated in tissues, mainly in liver and serum of KO mice. As a consequence of phytanic acid (or a metabolite) toxicity, KO mice displayed a significant weight loss, absence of abdominal white adipose tissue, enlarged and mottled liver and reduced hepatic glycogen and triglycerides. In addition, hepatic PPARα was activated. The central nervous system of the phytol-treated mice was apparently not affected. In addition, 2OH-FA did not accumulate in the central nervous system of HACL1 deficient mice, likely due to the presence in the endoplasmic reticulum of an alternate HACL1-unrelated lyase. The latter may serve as a backup system in certain tissues and account for the formation of pristanic acid in the phytol-fed KO mice. As the degradation of pristanic acid is also impaired, both phytanoyl- and pristanoyl-CoA levels are increased in liver, and the ω-oxidized metabolites are excreted in urine. In conclusion, HACL1 deficiency is not associated with a severe phenotype, but in combination with phytanic acid intake, the normal situation in man, it might present with phytanic acid elevation and resemble a Refsum like disorder.