Intracellular delivery of ceramide lipids via liposomes enhances apoptosis in vitro

Apoptosis induction by ceramide derivatives and its potential mechanisms through domain formation

Ceramides, which are recognized as pivotal signaling agents in cell differentiation and proliferation, elicit apoptosis in response to anticancer drugs and stress. Although the 1-hydroxy group of ceramide is considered to play an important role in inducing apoptosis, the detailed mechanism underlying ceramide-induced apoptosis remains elusive. We previously synthesized ceramide derivatives by transforming the 1-hydroxy group into amino and carboxy groups, and assessed their ability to form domains in artificial membranes. In this study, we evaluated the apoptotic activities of these derivatives against living cells. Surprisingly, despite the lack of the 1-hydroxy group, most of the derivatives exhibited apoptotic activity, with some being more active than ceramide. Confocal microscopy using fluorescent-ceramide and coherent anti-Stokes Raman scattering microscopy utilizing deuterated ceramide suggested the formation of large domains on living cell membranes. These findings suggest a potential relationship between domain formation and apoptotic activity. Liquid chromatography-mass spectrometry showed that the differences in apoptotic activity among the derivatives were unlikely attributed to variations in cellular uptake. Consequently, we propose that these ceramide derivatives accumulate and form distinct domains within the cellular membranes, inducing apoptosis. Intracellular ceramides synthesized in response to external stimuli may trigger apoptosis through the same mechanism.

The effects of caffeine and adenosine on the microbiome and lipidome of the scalp

Hair loss is a complex multifactorial process. The mechanisms by which caffeine and adenosine act against hair loss have been extensively researched, but little is known about their effects on the microbiome and lipidome of the scalp. Hair loss may be associated with the status of scalp microbiota and lipids. Further investigation is warranted to determine whether caffeine and adenosine can regulate scalp microbiota and lipids and thus help to prevent hair loss. The objective of this study was to assess the effect of shampoo containing caffeine and adenosine on the scalp microbiome and lipidome in subjects experiencing hair loss who were aged between 18 and 60 years. The study was a randomized, single-blind and parallel comparison trial involving full scalp treatment, which was conducted among 30 subjects experiencing hair loss. Samples were collected from subjects at baseline and at 12 weeks (±3 days). Microbiomes were analysed via 16S rDNA and ITS1 sequencing. Lipidome analysis was carried out using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). At 12 weeks, significant clinical characteristics indicating an anti-hair loss effect were evident. Abundances of Pseudomonas, Escherichia-Shigella and Malassezia all decreased in the experimental group, whereas those of Talaromyces and Cutibacterium increased. In addition, levels of triglyceride (TG), diglyceride (DG), ceramide (Cer) and ceramide-1-phosphate (CerP) were all significantly impacted in the experimental group. Furthermore, abundances of lipid metabolites were tightly correlated with those of Escherichia-Shigella and Talaromyces. Caffeine and adenosine may enhance the anti-hair loss process through their effects on the lipidome and microbiome of the scalp.

Application of sphingolipid-based nanocarriers in drug delivery: an overview

Sphingolipids (SL) are well recognized for their cell signaling through extracellular and intracellular pathways. Based on chemistry different types of SL are biosynthesized in mammalian cells and have specific function in cellular activity. SL has an ampiphilic structure with have hydrophobic body attached to the polar head enables their use as a drug delivery agent in the form of nanocarriers. SL-based liposomes can improve the solubility of lipophilic drugs through host and drug complexes and are more stable than conventional liposomal formulations. Preclinical studies of SL nanocarriers are reported on topical delivery, oral delivery, ocular delivery, chemotherapeutic delivery, cardiovascular delivery and Alzheimer's disease. The commercial challenges and patents related to SL nanoformulations are highlighted in this article.

Solid Magnetoliposomes as Multi-Stimuli-Responsive Systems for Controlled Release of Doxorubicin: Assessment of Lipid Formulations

Stimuli-responsive liposomes are a class of nanocarriers whose drug release occurs, preferentially, when exposed to a specific biological environment, to an external stimulus, or both. This work is focused on the design of solid magnetoliposomes (SMLs) as lipid-based nanosystems aiming to obtain multi-stimuli-responsive vesicles for doxorubicin (DOX) controlled release in pathological areas under the action of thermal, magnetic, and pH stimuli. The effect of lipid combinations on structural, colloidal stability, and thermodynamic parameters were evaluated. The results confirmed the reproducibility for SMLs synthesis based on nine lipid formulations (combining DPPC, DSPC, CHEMS, DOPE and/or DSPE-PEG), with structural and colloidal properties suitable for biological applications. A loss of stability and thermosensitivity was observed for formulations containing dioleoylphosphatidylethanolamine (DOPE) lipid. SMLs PEGylation is an essential step to enhance both their long-term storage stability and stealth properties. DOX encapsulation (encapsulation efficiency ranging between 87% and 96%) in the bilayers lowered its pK_a, which favors the displacement of DOX from the acyl chains to the surface when changing from alkaline to acidic pH. The release profiles demonstrated a preferential release at acidic pH, more pronounced under mimetic mild-hyperthermia conditions (42 °C). Release kinetics varied with the lipid formulation, generally demonstrating hyperthermia temperatures and acidic pH as determining factors in DOX release; PEGylation was shown to act as a diffusion barrier on the SMLs surface. The integrated assessment and characterization of SMLs allows tuning lipid formulations that best respond to the needs for specific controlled release profiles of stimuli-responsive nanosystems as a multi-functional approach to cancer targeting and therapy.

Activation of neutral sphingomyelinase 2 through hyperglycemia contributes to endothelial apoptosis via vesicle-bound intercellular transfer of ceramides

Background

Pro-apoptotic and pro-inflammatory ceramides are crucially involved in atherosclerotic plaque development. Local cellular ceramide accumulation mediates endothelial apoptosis, especially in type 2 diabetes mellitus, which is a major cardiovascular risk factor. In recent years, large extracellular vesicles (lEVs) have been identified as an important means of intercellular communication and as regulators of cardiovascular health and disease. A potential role for lEVs as vehicles for ceramide transfer and inductors of diabetes-associated endothelial apoptosis has never been investigated.

Methods and Results

A mass-spectrometric analysis of human coronary artery endothelial cells (HCAECs) and their lEVs revealed C16 ceramide (d18:1–16:0) to be the most abundant ceramide in lEVs and to be significantly increased in lEVs after hyperglycemic injury to HCAECs. The increased packaging of ceramide into lEVs after hyperglycemic injury was shown to be dependent on neutral sphingomyelinase 2 (nSMase2), which was upregulated in glucose-treated HCAECs. lEVs from hyperglycemic HCAECs induced apoptosis in the recipient HCAECs compared to native lEVs from untreated HCAECs. Similarly, lEVs from hyperglycemic mice after streptozotocin injection induced higher rates of apoptosis in murine endothelial cells compared to lEVs from normoglycemic mice. To generate lEVs with high levels of C16 ceramide, ceramide was applied exogenously and shown to be effectively packaged into the lEVs, which then induced apoptosis in lEV-recipient HCAECs via activation of caspase 3. Intercellular transfer of ceramide through lEVs was confirmed by use of a fluorescently labeled ceramide analogue. Treatment of HCAECs with a pharmacological inhibitor of nSMases (GW4869) or siRNA-mediated downregulation of nSMase2 abrogated the glucose-mediated effect on apoptosis in lEV-recipient cells. In contrast, for small EVs (sEVs), hyperglycemic injury or GW4869 treatment had no effect on apoptosis induction in sEV-recipient cells.

Conclusion

lEVs mediate the induction of apoptosis in endothelial cells in response to hyperglycemic injury through intercellular transfer of ceramides.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00018-021-04049-5.

Polyethylenimine quantity and molecular weight influence its adjuvanting properties in liposomal peptide vaccines

We recently reported that polyethylenimine (PEI; molecular weight of 600 Da) acted as a vaccine adjuvant for liposomal group A Streptococcus (GAS) vaccines, eliciting immune responses in vivo with IgG antibodies giving opsonic activity against five Australian GAS clinical isolates. However, to date, no investigation comparing the structure-activity relationship between the molecular weight of PEI and its adjuvanting activity in vaccine development has been performed. We hypothesized that the molecular weight and quantity of PEI in a liposomal vaccine will impact its adjuvanting properties. In this study, we successfully formulated liposomes containing different molecular weights of PEI (600, 1800, 10k and 25k Da) and equivalents of PEI (0.5, 1 and 2) of branched PEI. Outbred mice were administrated the vaccine formulations intranasally, and the mice that received a high ratio of PEI 600 reported a stronger immune response than the mice that received a lower ratio of PEI 600. Interestingly, mice that received the same quantity of PEI 600, PEI 10k and PEI 25k showed similar immune responses in vivo and in vitro. This comparative study highlights the ratio of PEI present in the liposome vaccines impacts adjuvanting activity, however, PEI molecular weight did not significantly enhance its adjuvanting properties. We also report that the stability of PEI liposomes is critical for vaccines to elicit the desired immune response.

Epidermal Delivery of Retinyl Palmitate Loaded Transfersomes: Penetration and Biodistribution Studies

The alteration of retinoids levels in the skin can cause different disorders in the maturation of epithelial skin cells. Topical administration of these lipophilic molecules is a challenge that can be addressed by encapsulation into drug delivery systems. In this study, retinyl palmitate transferosomes formulated in cream were developed and the increases in the penetration of the active ingredients as well as the biodistribution were evaluated in vitro and in vivo. Transfersomes demonstrated a significant increase in the administration of retinyl palmitate to the epidermis by quantification of the active ingredients in the different layers of the skin, as well as by fluorescence microscopy of biopsies of non-dermatomized pig-ear skin. These results suggest that transfersomes may be an efficient vehicle for the delivery of retinoids to inner layers of the skin, such as the epidermis.

Role of Ceramides in Drug Delivery

Ceramides belong to the sphingolipid group of lipids, which serve as both intracellular and intercellular messengers and as regulatory molecules that play essential roles in signal transduction, inflammation, angiogenesis, and metabolic disorders such as diabetes, neurodegenerative diseases, and cancer cell degeneration. Ceramides also play an important structural role in cell membranes by increasing their rigidity, creating micro-domains (rafts and caveolae), and altering membrane permeability; all these events are involved in the cell signaling. Ceramides constitute approximately half of the lipid composition in the human skin contributing to barrier function as well as epidermal signaling as they affect both proliferation and apoptosis of keratinocytes. Incorporation of ceramides in topical preparations as functional lipids appears to alter skin barrier functions. Ceramides also appear to enhance the bioavailability of drugs by acting as lipid delivery systems. They appear to regulate the ocular inflammation signaling, and external ceramides have shown relief in the anterior and posterior eye disorders. Ceramides play a structural role in liposome formulations and enhance the cellular uptake of amphiphilic drugs, such as chemotherapies. This review presents an overview of the various biological functions of ceramides, and their utility in topical, oral, ocular, and chemotherapeutic drug delivery.

Co-delivery of Doxorubicin and Ceramide in a Liposomal Formulation Enhances Cytotoxicity in Murine B16BL6 Melanoma Cell Lines

This study reports co-delivery of doxorubicin (DOX) and ceramide in a liposomal system in B16BL6 melanoma cell lines for enhanced cytotoxic effects. Different types of ceramides (C6-ceramide, C8-ceramide, and C8-glucosylceramide) and lipids (1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE)) were considered in the preparation of liposomes. DOX was encapsulated within liposome, and ceramide was used as the component of the lipid bilayer. The formulations were optimized for size and size distribution, zeta potential, and DOX encapsulation efficiency (EE). Cytotoxic effect on B16BL6 melanoma cell lines was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The ceramide based liposome formulations generally provided a mean diameter < 181 nm, a zeta potential, + 35 mV, and EE > 90% DOX EE. Co-delivery of DOX and C8-ceramide with DOTAP liposomes demonstrated significantly higher cytotoxicity as compared to DOX liposomes without ceramide (P < 0.001), and also showed enhanced cellular uptake by B16BL6 cell lines. This study provides basis for developing a co-delivery system of DOX and ceramide for lowering the dose and dose-related side effects of DOX for the treatment of melanoma.

Cisplatin-Membrane Interactions and Their Influence on Platinum Complexes Activity and Toxicity

Cisplatin and other platinum(II) analogs are widely used in clinical practice as anti-cancer drugs for a wide range of tumors. The primary mechanism by which they exert their action is through the formation of adducts with genomic DNA. However, multiple cellular targets by platinum(II) complexes have been described. In particular, the early events occurring at the plasma membrane (PM), i.e., platinum-membrane interactions seem to be involved in the uptake, cytotoxicity and cell-resistance to cisplatin. In fact, PM influences signaling events, and cisplatin-induced changes on membrane organization and fluidity were shown to activate apoptotic pathways. This review critically discusses the sequence of events caused by lipid membrane-platinum interactions, with emphasis on the mechanisms that lead to changes in the biophysical properties of the membranes (e.g., fluidity and permeability), and how these correlate with sensitivity and resistance phenotypes of cells to platinum(II) complexes.

Oxidized graphene nanoparticles as a delivery system for the pro-apoptotic sphingolipid C6 ceramide

Sphingolipids such as ceramide have attracted much attention as possible anticancer agents due to their potent pro-apoptotic effects. However, due to their extreme hydrophobicity, there is currently no clinically approved delivery method for in vivo use as a therapeutic agent. To this end, we have developed a novel method for loading the short-chain C₆ ceramide onto oxidized graphene nanoribbons (O-GNRs) and graphene nanoplatelets (GNPs). Mass spectrometry revealed loading efficiencies of 57% and 51.5% for C₆ ceramide onto O-GNRs and GNPs, respectively. The PrestoBlue viability assay revealed that 100 µg/mL of C₆ ceramide-loaded O-GNRs and C₆ ceramide-loaded GNPs reduced HeLa cell viability by approximately 93% and approximately 76%, respectively, compared to untreated HeLa cells, while equal concentrations of these nanoparticles without C₆ ceramide did not significantly reduce HeLa cell viability. We confirmed that this cytotoxicity was apoptotic in nature via capase-3 activity and Hoechst staining. Using live-cell confocal imaging with the fluorescent NBD-ceramide loaded on O-GNRs, we observed robust uptake into HeLa cells within 30 min while NBD-ceramide on its own was uptaken much more rapidly. Transmission electron microscopy confirmed that C₆ ceramide-loaded O-GNRs were actually entering cells. Taken together, these data show that O-GNRs are a promising delivery agent for ceramide. To our knowledge, this study is the first to use such a loading method. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 25-37, 2019.

Novel glucosylceramide synthase inhibitor based prodrug copolymer micelles for delivery of anticancer agents

In order to improve the efficacy of chemotherapy for cancers, we have developed a novel prodrug micellar formulation to co-deliver ceramide-generating anticancer agents and ceramide degradation inhibitor (PPMP). The prodrug nanocarrier is based on a well-defined POEG-b-PPPMP diblock copolymer. The hydrophilic block of POEG-b-PPPMP is POEG, and the hydrophobic block is composed of a number of PPMP units, which could work synergistically with loaded anticancer drugs. POEG-b-PPPMP was readily synthesized via a one-step reversible addition-fragment transfer (RAFT) polymerization from a PPMP monomer. The newly synthesized polymers were self-assembled into micelles and served as a carrier for several hydrophobic anticancer drugs including DOX, PTX and C6-ceramide. POEG-b-PPPMP prodrug polymer exhibited intrinsic antitumor activity in vitro and in vivo. In addition, POEG-b-PPPMP prodrug polymer was comparable to free PPMP in selectively enhancing the production of pro-apoptotic ceramide species as well as down-regulating the mRNA expression of GCS. DOX-loaded POEG-b-PPPMP micelles exhibited an excellent stability of 42 days at 4 °C. Moreover, DOX loaded in POEG-b-PPPMP micelles showed higher levels of cytotoxicity than DOX loaded in a pharmacologically inert polymer (POEG-b-POM) and Doxil formulation in several tumor cell lines. Consistently, in a 4T1.2 murine breast cancer model, the tumor inhibition followed the order of DOX/POEG-b-PPPMP > DOX/POEG-b-POM ≥ Doxil > POEG-b-PPPMP > POEG-b-POM. Our data suggest that POEG-b-PPPMP micelles are a promising dual-functional carrier that warrants more studies in the future.

Selective induction of apoptosis in MCF7 cancer-cell by targeted liposomes functionalised with mannose-6-phosphate

Liposomes are versatile platforms to carry anticancer drugs in targeted drug delivery; they can be surface modified by different strategies and, when coupled with targeting ligands, are able to increase cellular internalisation and organelle-specific drug delivery. An interesting strategy of antitumoral therapy could involve the use of lysosomotropic ligand-targeted liposomes loaded with molecules, which can induce lysosomal membrane permeabilization (LMP), leakage of cathepsins into the cytoplasm and subsequent apoptosis. We have previously demonstrated the ability of liposomes functionalised with a mannose-6-phosphate to reach lysosomes; in this research we compare the behaviour of M6P-modified and non-functionalised liposomes in MCF7 tumour cell and in HDF normal cells. With this aim, we first demonstrated by Western blotting the overexpression of mannose-6-phosphate/insulin-like growth factor (M6P/IGF-II) receptor in MCF7. Then, we prepared calcein-loaded liposomes and we revealed the increased uptake of M6P-functionalised liposomes in MCF7 cells respect to HDF cells by flow cytometry analysis. Finally, we loaded functionalised and not functionalised liposomes with N-hexanoyl-d-erythro-sphingosine (C6Cer), able to initiate LMP-induced apoptosis; after having studied the stability of both vesicles in the presence of serum by Dynamic Light Scattering and Spectrophotometric turbidity measurements, we showed that ceramide-loaded M6P-liposomes significantly increased apoptosis in MCF7 with respect to HDF cells.

Metabolic Conversion of Ceramides in HeLa Cells - A Cholesteryl Phosphocholine Delivery Approach

Ceramides can be delivered to cultured cells without solvents in the form of complexes with cholesteryl phosphocholine. We have analysed the delivery of three different radiolabeled D-erythro-ceramides (C6-Cer, C10-Cer and C16-Cer) to HeLa cells, and followed their metabolism as well as the cell viability. We found that all three ceramides were successfully taken up by HeLa cells when complexed to CholPC in an equimolar ratio, and show that the ceramides show different rates of cellular uptake and metabolic fate. The C6-Cer had the highest incorporation rate, followed by C10-Cer and C16-Cer, respectively. The subsequent effect on cell viability strongly correlated with the rate of incorporation, where C6-Cer had the strongest apoptotic effects. Low-dose (1 μM) treatment with C6-Cer favoured conversion of the precursor to sphingomyelin, whereas higher concentrations (25–100 μM) yielded increased conversion to C6-glucosylceramide. Similar results were obtained for C10-Cer. In the lower-dose C16-Cer experiments, most of the precursor was degraded, whereas at high-dose concentrations the precursor remained un-metabolized. Using this method, we demonstrate that ceramides with different chain lengths clearly exhibit varying rates of cellular uptake. The cellular fate of the externally delivered ceramides are clearly connected to their rate of incorporation and their subsequent effects on cell viability may be in part determined by their chain length.

Nucleolin overexpression in breast cancer cell sub-populations with different stem-like phenotype enables targeted intracellular delivery of synergistic drug combination

Breast cancer stem cells (CSC) are thought responsible for tumor growth and relapse, metastization and active evasion to standard chemotherapy. The recognition that CSC may originate from non-stem cancer cells (non-SCC) through plastic epithelial-to-mesenchymal transition turned these into relevant cell targets. Of crucial importance for successful therapeutic intervention is the identification of surface receptors overexpressed in both CSC and non-SCC. Cell surface nucleolin has been described as overexpressed in cancer cells as well as a tumor angiogenic marker. Herein we have addressed the questions on whether nucleolin was a common receptor among breast CSC and non-SCC and whether it could be exploited for targeting purposes. Liposomes functionalized with the nucleolin-binding F3 peptide, targeted simultaneously, nucleolin-overexpressing putative breast CSC and non-SCC, which was paralleled by OCT4 and NANOG mRNA levels in cells from triple negative breast cancer (TNBC) origin. In murine embryonic stem cells, both nucleolin mRNA levels and F3 peptide-targeted liposomes cellular association were dependent on the stemness status. An in vivo tumorigenic assay suggested that surface nucleolin overexpression per se, could be associated with the identification of highly tumorigenic TNBC cells. This proposed link between nucleolin expression and the stem-like phenotype in TNBC, enabled 100% cell death mediated by F3 peptide-targeted synergistic drug combination, suggesting the potential to abrogate the plasticity and adaptability associated with CSC and non-SCC. Ultimately, nucleolin-specific therapeutic tools capable of simultaneous debulk multiple cellular compartments of the tumor microenvironment may pave the way towards a specific treatment for TNBC patient care.

Differential apoptotic effect and metabolism of N-acetylsphingosine and N-hexanoylsphingosine in CHP-100 human neurotumor cells

The cytotoxic effects of N-acetylsphingosine (C2-Cer) and N-hexanoylsphingosine (C6-Cer) were compared together with their specific intracellular accumulation profiles and metabolism in human CHP-100 neuroepithelioma cells. The two short-chain ceramides, administered in the culture medium at an equimolar concentration, evoked a differential apoptotic response, with C6-Cer showing markedly more cytotoxic than C2-Cer. Apoptosis, that was suppressed in both cases by inhibition of caspase-9, but not of caspase-8, associated with a higher intracellular accumulation of C6-Cer over C2-Cer, notwithstanding C6-Cer was actively metabolized by direct glucosylation or by conversion to natural ceramide via the sphingosine salvage pathway, whereas C2-Cer was apparently metabolically inhert. C2-Cer cytotoxicity was markedly enhanced by increasing its concentration in the culture medium, and this response associated with a higher intracellular accumulation of this compound, in the absence of any natural ceramide elevation. These results support the notion that the differential apoptotic effect evoked by C2-Cer and C6-Cer in CHP-100 cells is driven by their differential intracellular accumulation profiles, but not by their differential property to generate natural ceramide via the sphingosine salvage pathway.

Unsaturation of very-long-chain ceramides protects plant from hypoxia-induced damages by modulating ethylene signaling in Arabidopsis

Lipid remodeling is crucial for hypoxic tolerance in animals, whilst little is known about the hypoxia-induced lipid dynamics in plants. Here we performed a mass spectrometry-based analysis to survey the lipid profiles of Arabidopsis rosettes under various hypoxic conditions. We observed that hypoxia caused a significant increase in total amounts of phosphatidylserine, phosphatidic acid and oxidized lipids, but a decrease in phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Particularly, significant gains in the polyunsaturated species of PC, PE and phosphatidylinositol, and losses in their saturated and mono-unsaturated species were evident during hypoxia. Moreover, hypoxia led to a remarkable elevation of ceramides and hydroxyceramides. Disruption of ceramide synthases LOH1, LOH2 and LOH3 enhanced plant sensitivity to dark submergence, but displayed more resistance to submergence under light than wild type. Consistently, levels of unsaturated very-long-chain (VLC) ceramide species (22:1, 24:1 and 26:1) predominantly declined in the loh1, loh2 and loh3 mutants under dark submergence. In contrast, significant reduction of VLC ceramides in the loh1-1 loh3-1 knockdown double mutant and lacking of VLC unsaturated ceramides in the ads2 mutants impaired plant tolerance to both dark and light submergences. Evidence that C24:1-ceramide interacted with recombinant CTR1 protein and inhibited its kinase activity in vitro, enhanced ER-to-nucleus translocation of EIN2-GFP and stabilization of EIN3-GFP in vivo, suggests a role of ceramides in modulating CTR1-mediated ethylene signaling. The dark submergence-sensitive phenotypes of loh mutants were rescued by a ctr1-1 mutation. Thus, our findings demonstrate that unsaturation of VLC ceramides is a protective strategy for hypoxic tolerance in Arabidopsis.

Liposomal codelivery of a synergistic combination of bioactive lipids in the treatment of acute myeloid leukemia

Aim: The aim of this work was to develop a liposomal formulation to facilitate delivery of a synergistic safingol/C2-ceramide combination in the treatment of acute myeloid leukemia (AML). Materials & methods: Liposomes were prepared using the extrusion method and the bioactive lipids were encapsulated passively. Drug concentrations were determined by liquid chromatography tandem mass spectrometry. Antileukemic activity was evaluated using human leukemic cell lines, patient samples and U937 leukemic xenograft models. Results: A stable liposome formulation was developed to coencapsulate safingol and C2-ceramide at 1:1 molar ratio with >90% encapsulation efficiency. The liposomal safingol/C2-ceramide was effective in AML cell lines, patient samples and murine xenograft models of AML, compared with liposomal safingol or liposomal C2-ceramide alone despite a dose reduction of 33%. Conclusion: Our study provided proof-of-concept evidence to deliver synergistic combination of bioactive lipid to achieve complete remission in AML.

Original submitted: 27 February 2013; Revised submitted: 25 June 2013

Nanodrug delivery in reversing multidrug resistance in cancer cells

Different mechanisms in cancer cells become resistant to one or more chemotherapeutics is known as multidrug resistance (MDR) which hinders chemotherapy efficacy. Potential factors for MDR includes enhanced drug detoxification, decreased drug uptake, increased intracellular nucleophiles levels, enhanced repair of drug induced DNA damage, overexpression of drug transporter such as P-glycoprotein(P-gp), multidrug resistance-associated proteins (MRP1, MRP2), and breast cancer resistance protein (BCRP). Currently nanoassemblies such as polymeric/solid lipid/inorganic/metal nanoparticles, quantum dots, dendrimers, liposomes, micelles has emerged as an innovative, effective, and promising platforms for treatment of drug resistant cancer cells. Nanocarriers have potential to improve drug therapeutic index, ability for multifunctionality, divert ABC-transporter mediated drug efflux mechanism and selective targeting to tumor cells, cancer stem cells, tumor initiating cells, or cancer microenvironment. Selective nanocarrier targeting to tumor overcomes dose-limiting side effects, lack of selectivity, tissue toxicity, limited drug access to tumor tissues, high drug doses, and emergence of multiple drug resistance with conventional or combination chemotherapy. Current review highlights various nanodrug delivery systems to overcome mechanism of MDR by neutralizing, evading, or exploiting the drug efflux pumps and those independent of drug efflux pump mechanism by silencing Bcl-2 and HIF1α gene expressions by siRNA and miRNA, modulating ceramide levels and targeting NF-κB. “Theragnostics” combining a cytotoxic agent, targeting moiety, chemosensitizing agent, and diagnostic imaging aid are highlighted as effective and innovative systems for tumor localization and overcoming MDR. Physical approaches such as combination of drug with thermal/ultrasound/photodynamic therapies to overcome MDR are focused. The review focuses on newer drug delivery systems developed to overcome MDR in cancer cell.

Development of EGFR-targeted nanoemulsion for imaging and novel platinum therapy of ovarian cancer

PURPOSE

Platinum-based chemotherapy is the treatment of choice for malignant epithelial ovarian cancers, but generalized toxicity and platinum resistance limits its use. Theranostic nanoemulsion with a novel platinum prodrug, myrisplatin, and the pro-apoptotic agent, C6-ceramide, were designed to overcome these limitations.

METHODS

The nanoemulsions, including ones with an EGFR binding peptide and gadolinium, were made using generally regarded as safe grade excipients and a high shear microfluidization process. Efficacy was evaluated in ovarian cancer cells, SKOV3, A2780 and A2780CP.

RESULTS

The nanoemulsion with particle size <150 nm were stable in plasma and parenteral fluids for 24 h. Ovarian cancer cells in vitro efficiently took up the non-targeted and EGFR-targeted nanoemulsions; improved cytotoxicity was observed for the these nanoemulsions with the latter showing a 50-fold drop in the IC50 in SKOV3 cells as compared to cisplatin alone. The addition of gadolinium did not affect cell viability in vitro, but showed relaxation times comparable to Magnevist(®).

CONCLUSION

The myrisplatin/C6-ceramide nanoemulsion synergistically enhanced in vitro cytotoxicity. An EGFR binding peptide addition further increased in vitro cytotoxicity in EGFR positive cancer cells. The diagnostic version showed MR imaging similar to the clinically relevant Magnevist® and may be suitable as a theranostic for ovarian cancer.

PLGA/liposome hybrid nanoparticles for short-chain ceramide delivery

PURPOSE

Rapid premature release of lipophilic drugs from liposomal lipid bilayer to plasma proteins and biological membranes is a challenge for targeted drug delivery. The purpose of this study is to reduce premature release of lipophilic short-chain ceramides by encapsulating ceramides into liposomal aqueous interior with the aid of poly (lactic-coglycolicacid) (PLGA).

METHODS

BODIPY FL labeled ceramide (FL-ceramide) and BODIPY-TR labeled ceramide (TR-ceramide) were encapsulated into carboxy-terminated PLGA nanoparticles. The negatively charged PLGA nanoparticles were then encapsulated into cationic liposomes to obtain PLGA/liposome hybrids. As a control, FL-ceramide and/or TR ceramide co-loaded liposomes without PLGA were prepared. The release of ceramides from PLGA/liposome hybrids and liposomes in rat plasma, cultured MDA-MB-231 cells, and rat blood circulation was compared using fluorescence resonance energy transfer (FRET) between FL-ceramide (donor) and TR-ceramide (acceptor).

RESULTS

FRET analysis showed that FL-ceramide and TR-ceramide in liposomal lipid bilayer were rapidly released during incubation with rat plasma. In contrast, the FL-ceramide and TR-ceramide in PLGA/liposome hybrids showed extended release. FRET images of cells revealed that ceramides in liposomal bilayer were rapidly transferred to cell membranes. In contrast, ceramides in PLGA/liposome hybrids were internalized into cells with nanoparticles simultaneously. Upon intravenous administration to rats, ceramides encapsulated in liposomal bilayer were completely released in 2 min. In contrast, ceramides encapsulated in the PLGA core were retained in PLGA/liposome hybrids for 4 h.

CONCLUSIONS

The PLGA/liposome hybrid nanoparticles reduced in vitro and in vivo premature release of ceramides and offer a viable platform for targeted delivery of lipophilic drugs.

Complexation of c6-ceramide with cholesteryl phosphocholine - a potent solvent-free ceramide delivery formulation for cells in culture

Ceramides are potent bioactive molecules in cells. However, they are very hydrophobic molecules, and difficult to deliver efficiently to cells. We have made fluid bilayers from a short-chain D-erythro-ceramide (C6-Cer) and cholesteryl phosphocholine (CholPC), and have used this as a formulation to deliver ceramide to cells. C6-Cer complexed with CholPC led to much larger biological effects in cultured cells (rat thyroid FRTL-5 and human HeLa cells in culture) compared to C6-Cer dissolved in dimethyl sulfoxide (DMSO). Inhibition of cell proliferation and induction of apoptosis was significantly more efficient by C6-Cer/CholPC compared to C6-Cer dissolved in DMSO. C6-Cer/CholPC also permeated cell membranes and caused mitochondrial Ca²⁺ influx more efficiently than C6-Cer in DMSO. Even though CholPC was taken up by cells to some extent (from C6-Cer/CholPC bilayers), and was partially hydrolyzed to free cholesterol (about 9%), none of the antiproliferative effects were due to CholPC or excess cholesterol. The ceramide effect was not limited to D-erythro-C6-Cer, since L-erythro-C6-Cer and D-erythro-C6-dihydroCer also inhibited cell priolifereation and affected Ca²⁺ homeostasis. We conclude that C6-Cer complexed to CholPC increased the bioavailability of the short-chain ceramide for cells, and potentiated its effects in comparison to solvent-dissolved C6-Cer. This new ceramide formulation appears to be superior to previous solvent delivery approaches, and may even be useful with longer-chain ceramides.

pHLIP®-mediated delivery of PEGylated liposomes to cancer cells

We develop a method for pH-dependent fusion between liposomes and cellular membranes using pHLIP® (pH Low Insertion Peptide), which inserts into lipid bilayer of membrane only at low pH. Previously we establish the molecular mechanism of peptide action and show that pHLIP can target acidic diseased tissue. Here we investigate how coating of PEGylated liposomes with pHLIP might affect liposomal uptake by cells. The presence of pHLIP on the surface of PEGylated-liposomes enhanced membrane fusion and lipid exchange in a pH dependent fashion, leading to increase of cellular uptake and payload release, and inhibition of cell proliferation by liposomes containing ceramide. A novel type of pH-sensitive, "fusogenic" pHLIP-liposomes was developed, which could be used to selectively deliver various diagnostic and therapeutic agents to acidic diseased cells.

The therapeutic potential of nanoscale sphingolipid technologies

Nanotechnologies, while small in size, widen the scope of drug delivery options for compounds with problematic pharmacokinetics, such as bioactive sphingolipids. We describe the development of historical sphingolipid nanotechnologies, such as nanoliposomes, and project future uses for a broad repertoire of nanoscale sphingolipid therapy formulations. In particular, we describe sphingo-nanotherapies for treatment of cancer, inflammatory disease, and cardiovascular disease. We conclude with a discussion of the challenges associated with regulatory approval, scale-up, and development of these nanotechnology therapies for clinical applications.

Targeting glucosylceramide synthase synergizes with C6-ceramide nanoliposomes to induce apoptosis in natural killer cell leukemia

Abstract Natural killer (NK) cell leukemia is characterized by clonal expansion of CD3 - NK cells and comprises both chronic and aggressive forms. Currently no effective treatment exists, thus providing a need for identification of novel therapeutics. Lipidomic studies revealed a dysregulated sphingolipid metabolism as evidenced by decreased levels of overall ceramide species and increased levels of cerebrosides in leukemic NK cells, concomitant with increased glucosylceramide synthase (GCS) expression. GCS, a key enzyme of this pathway, neutralizes pro-apoptotic ceramide by transfer of a uridine diphosphate (UDP)-glucose. Thus, we treated both rat and human leukemic NK cells in combination with: (1) exogenous C6-ceramide nanoliposomes in order to target mitochondria and increase physiological pro-apoptotic levels of long chain ceramide, and (2) 1-phenyl-2-palmitoylamino-3-morpholino-1-propanol (PPMP), an inhibitor of GCS. Co-administration of C6-ceramide nanoliposomes and PPMP elicited an increase in endogenous long-chain ceramide species, which led to cellular apoptosis in a synergistic manner via the mitochondrial intrinsic cell death pathway in leukemic NK cells.

Trojan-horse nanotube on-command intracellular drug delivery

A major challenge to nanomaterial-based medicine is the ability to release drugs on-command. Here, we describe an innovative drug delivery system based on carbon nanotubes (CNTs), in which compounds can be released inside cells from within the nanotube "on-command" by inductive heating with an external alternating current or pulsed magnetic field. Without inductive heating the drug remains safely inside the CNTs, showing no toxicity in cell viability tests. Similar to the "Trojan-Horse" in function, we demonstrate the delivery of a combination of chemotherapeutic agents with low aqueous solubility, paclitaxel (Taxol), and C6-ceramide, to multidrug resistant pancreatic cancer cells. Nanotube encapsulation permitted the drugs to be used at a 100-fold lower concentration compared to exogenous treatment yet achieve a comparable ~70% cancer kill rate.

Increased apoptosis in cancer cells in vitro and in vivo by ceramides in transferrin-modified liposomes

Lysosomes are a promising therapeutic target for induction apoptosis in cancer cells due to lysosomal membrane permeabilization (LMP) leading to leakage of hydrolytic enzymes, especially the cathepsins, into the cytoplasm. We hypothesized that with the modification of the ceramide-loaded liposomes with transferrin (Tf), we would achieve both tumor targeting and increased delivery of lysosome-destabilizing agents, such as ceramides to lysosomes, to initiate LMP-induced apoptosis. We prepared Tf-modified (TL) and plain (PL) liposomes and loaded with short (C6)- or long (C16) N-acyl chain ceramides. Uptake, intracellular localization of liposomes, stability of the lysosomal membrane and release of cathepsin D were investigated on Hela cells by fluorescence microscopy and flow cytometry. Apoptosis was evaluated by binding of fluorescently-labeled Annexin V. Antitumor and pro-apoptotic effects of C6Cer-loaded Tf-liposomes were demonstrated in vivo in an A2780-ovarian carcinoma xenograft mouse model. TL were internalized specifically via the TfR-dependent endocytic pathway and localized within the endosome-lysosomal compartment. Ceramide-loaded Tf-liposomes significantly increased apoptosis compared with ceramide-free and ceramide-loaded non-modified liposomes. The treatment of cancer cells with TL led to increased LMP and cytoplasmic relocation of the intralysosomal cathepsin D. A strong antitumor and pro-apoptotic effect of C6Cer-loaded TL was also demonstrated in vivo in an A2780-ovarian carcinoma xenograft mouse model. The lysosomal accumulation of ceramides delivered by Tf-liposomes initiates the permeabilization of the lysosomal membranes required for the release of lysosomal cathepsins into the cytoplasm and initiation of the cancer cell apoptosis both in vitro and in vivo.

Ceramide--antiestrogen nanoliposomal combinations--novel impact of hormonal therapy in hormone-insensitive breast cancer

Although the sphingolipid ceramide exhibits potent tumor suppressor effects, efforts to harness this have been hampered by poor solubility, uptake, bioavailability, and metabolic conversion. Therefore, identification of avenues to improve efficacy is necessary for development of ceramide-based therapies. In this study, we used mutant p53, triple-negative breast cancer (TNBC) cells, a type of breast cancer highly refractory to treatment, and cell-permeable nanoliposomal C6-ceramide in conjunction with the antiestrogen tamoxifen, which has been shown to be an effective modulator of ceramide metabolism. We show for the first time that nanoliposomal tamoxifen enhances nanoliposomal C6-ceramide cytotoxicity in cultured TNBC cells, a response that was accompanied by induction of cell-cycle arrest at G(1) and G(2), caspase-dependent induction of DNA fragmentation, and enhanced mitochondrial and lysosomal membrane permeability at 18 and 2 hours, respectively. Tamoxifen metabolites were also effective. Only tamoxifen promoted lysosomal membrane permeability. In addition, we show for the first time that tamoxifen inhibits acid ceramidase, as measured in intact cell assays; this effect was irreversible. Together, our findings show that tamoxifen magnifies the antiproliferative effects of C6-ceramide via combined targeting of cell-cycle traverse and lysosomal and mitochondrial integrity. We adduce that C6-ceramide-induced apoptosis is amplified by tamoxifen's impact on lysosomes and perhaps accompanying inhibition of acid ceramidase, which could result in decreased levels of sphingosine 1-phosphate. This drug regimen could serve as a promising therapy for chemoresistant and triple-negative types of breast cancer, and thus represents an indication for tamoxifen, irrespective of estrogen receptor status.

Glucosylceramide synthase protects glioblastoma cells against autophagic and apoptotic death induced by temozolomide and Paclitaxel

Glioblastoma is a deadly cancer with intrinsic chemoresistance. Understanding this property will aid in therapy. Glucosylceramide synthase (GCS) is associated with resistance and poor outcome; little is known about glioblastomas. In glioblastoma cells, temozolomide and paclitaxel induce ceramide increase, which in turn promotes cytotoxicity. In drug-resistant cells, both drugs are unable to accumulate ceramide, increased expression and activity of GCS is present, and its inhibitors hinder resistance. Resistant cells exhibit cross-resistance, despite differing in marker expression, and cytotoxic mechanism. These findings suggest that GCS protects glioblastoma cells against autophagic and apoptotic death, and contributes to cell survival under chemotherapy.

Development and use of ceramide nanoliposomes in cancer

Integration of C₆-ceramide into stealth pegylated nanoliposomes has led to the development of a promising preclinical therapeutic alone and in combination with other agents for treatment of cancer. Ceramide itself has been implicated as a bioactive lipid second messenger mediating cell senescence, cell cycle arrest, and apoptosis. Recent lipidomic analyses have demonstrated that specific ceramide species are differentially metabolized in individual cancers. Therapeutics that increase ceramide levels in cancer tissues have shown increased cell death and tumor inhibition. However, the use of ceramide itself as therapeutic has been problematic due to its inherent hydrophobicity and insolubility, therefore limiting the application for intravenous administration. Pegylated nanoliposomes eliminate this issue and are able to enhance the intracellular delivery of ceramide to cancer cells.

Effect of ceramide acyl chain length on skin permeability and thermotropic phase behavior of model stratum corneum lipid membranes

Stratum corneum ceramides play an essential role in the barrier properties of skin. However, their structure-activity relationships are poorly understood. We investigated the effects of acyl chain length in the non-hydroxy acyl sphingosine type (NS) ceramides on the skin permeability and their thermotropic phase behavior. Neither the long- to medium-chain ceramides (8-24 C) nor free sphingosine produced any changes of the skin barrier function. In contrast, the short-chain ceramides decreased skin electrical impedance and increased skin permeability for two marker drugs, theophylline and indomethacin, with maxima in the 4-6C acyl ceramides. The thermotropic phase behavior of pure ceramides and model stratum corneum lipid membranes composed of ceramide/lignoceric acid/cholesterol/cholesterol sulfate was studied by differential scanning calorimetry and infrared spectroscopy. Differences in thermotropic phase behavior of these lipids were found: those ceramides that had the greatest impact on the skin barrier properties displayed the lowest phase transitions and formed the least dense model stratum corneum lipid membranes at 32°C. In conclusion, the long hydrophobic chains in the NS-type ceramides are essential for maintaining the skin barrier function. However, this ability is not shared by their short-chain counterparts despite their having the same polar head structure and hydrogen bonding ability.

Implication of sphingomyelin/ceramide molar ratio on the biological activity of sphingomyelinase

Sphingolipid signaling plays an important, yet not fully understood, role in diverse aspects of cellular life. Sphingomyelinase is a major enzyme in these signaling pathways, catalyzing hydrolysis of sphingomyelin to ceramide and phosphocholine. To address the related membrane dynamical structural changes and their feedback to enzyme activity, we have studied the effect of enzymatically generated ceramide in situ on the properties of a well-defined lipid model system. We found a gel-phase formation that was about four times faster than ceramide generation due to ceramide-sphingomyelin pairing. The gel-phase formation slowed down when the ceramide molar ratios exceeded those of sphingomyelin and stopped just at the solubility limit of ceramide, due to unfavorable pairwise interactions of ceramide with itself and with monounsaturated phosphatidylcholine. A remarkable correlation to in vitro experiments suggests a regulation of sphingomyelinase activity based on the sphingomyelin/ceramide molar ratio.

Metabolism of short-chain ceramide by human cancer cells--implications for therapeutic approaches

Due to recent use of short-chain ceramides in preclinical studies, we characterized C6-ceramide metabolism in cancer cell lines and assessed metabolic junctures for enhancing efficacy. MDA-MB-231 breast cancer cells decreased the amount of C6-ceramide metabolized to C6-sphingomyelin (C6-SM) and increased the amount metabolized to C6-glucosylceramide (C6-GC) in response to increasing concentrations. A similar trend was seen in DU-145 (prostate cancer), PANC-1 (pancreatic cancer), and LoVo (colorectal cancer) cells. KG-1 leukemia cells favored C6-SM synthesis at low (0.6muM) and high-dose (12muM) C6-ceramide. Partnering C6-ceramide with tamoxifen, a P-glycoprotein antagonist that impedes ceramide glycosylation, was an effective regimen for enhancing cytotoxicity in cells. Experiments to assess the mechanism of cell death using KG-1 cells showed that tamoxifen inhibited synthesis of C6-GC and C6-SM from C6-ceramide by 80% and 50%, respectively, which was accompanied by enhanced apoptosis. Radiolabeling of KG-1 cells with [(3)H]palmitic acid produced a 2-fold increase in (3)H-long-chain ceramides when unlabeled C6-ceramide was added and a 9-fold increase when C6-ceramide and tamoxifen were added. The increase in (3)H-palmitate radiolabeling of long-chain ceramides was blocked by inclusion of a ceramide synthase inhibitor; however, inhibiting synthesis of long-chain ceramide did not rescue cells. These studies show that tamoxifen enhances the apoptotic effects of C6-ceramide. The proposed mechanism involves blocking short-chain ceramide anabolism to favor hydrolysis and generation of sphingosine. We propose that use of tamoxifen and other P-glycoprotein antagonists can be an effective means for enhancing cytotoxic potential of short-chain ceramides in the treatment of cancer.

Targeting sphingolipid metabolism in head and neck cancer: rational therapeutic potentials

IMPORTANCE OF THE FIELD

Ceramide accumulation has been shown to be a conserved mechanism of apoptosis initiation in normal physiological processes as well as in response to cancer treatments. Therefore, it is unsurprising that many cancers develop aberrations of sphingolipid metabolism that prevent the accumulation of ceramide, whether by reduction of ceramide generation or by enhanced ceramide catabolism, particularly dangerous when catabolism leads to generation of pro-tumor sphingosine-1-phosphate and ceramide-1-phosphate. Numerous studies have now implicated dysregulation of sphingolipid metabolism in head and neck cancers.

AREAS COVERED IN THIS REVIEW

This review highlights the importance of sphingolipid metabolism and brings sphingolipid metabolism to the forefront in the investigation of novel therapies for head and neck cancer. It reviews sphingolipid-centric therapies under investigation in preclinical and clinical trials of cancers of the head and neck.

WHAT THE READER WILL GAIN

The roles of sphingolipids and sphingolipid metabolism in cancer are reviewed and the reader will be brought up to date with discoveries in the field of sphingolipid metabolism in head and neck cancer.

TAKE HOME MESSAGE

As treatments for head and neck cancers are currently limited, the potential of targeting sphingolipid metabolism should be taken into consideration as we seek novel ways to combat this group of tumors.

Liposomes for drug delivery to mitochondria

Efficacy of therapeutically active drugs known to act on intracellular targets can be enhanced by specific delivery to the site of action. Triphenylphosphonium cations can be used to create subcellular targeted liposomes that efficiently deliver drugs to mitochondria, thus enhancing their therapeutic action.

Synthesis of fluorescent C24-ceramide: evidence for acyl chain length dependent differences in penetration of exogenous NBD-ceramides into human skin

Topical skin lipid supplementation may provide opportunities for controlling ceramide (Cer) deficiency in skin diseases such as atopic dermatitis or psoriasis. Here we describe the synthesis of a long-chain 7-nitrobenzo[c][1,2,5]oxadiazol-4-yl (NBD)-labeled Cer and its different penetration through human skin compared to widely used short-chain fluorescent Cer tools.

Undulating tubular liposomes through incorporation of a synthetic skin ceramide into phospholipid bilayers

Nonspherical liposomes were prepared by doping L-alpha-phosphatidylcholine (PC) with ceramide VI (a skin lipid). Cryo-transmission electron microscopy shows the liposome shape changing from spherical to an undulating tubular morphology, when the amount of ceramide VI is increased. The formation of tubular liposomes is energetically favorable and is attributed to the association of ceramide VI with PC creating regions of lower curvature. Since ceramides are the major component of skin lipids in the stratum corneum, tubular liposomes containing ceramide may potentially serve as self-enhanced nanocarriers for transdermal delivery.

Use of liposomes as drug delivery vehicles for treatment of melanoma

Melanoma is a progressive disease that claims many lives each year due to lack of therapeutics effective for the long-term treatment of patients. Currently, the best treatment option is early detection followed by surgical removal. Better melanoma therapies that are effectively delivered to tumors with minimal toxicity for patients are urgently needed. Nanotechnologies provide one approach to encapsulate therapeutic agents leading to improvements in circulation time, enhanced tumor uptake, avoidance of the reticulo-endothelial system, and minimization of toxicity. Liposomes in particular are a promising nanotechnology that can be used for more effective delivery of therapeutic agents to treat melanoma. Liposomes delivering chemotherapies, siRNA, asODNs, DNA, and radioactive particles are just some of the promising new nanotechnology based therapies under development for the treatment of melanoma that are discussed in this review.

Effect of chain length on physicochemical properties and cytotoxicity of cationic vesicles composed of phosphatidylcholines and dialkyldimethylammonium bromides

This study investigated the physicochemical characteristics of cationic vesicles that were prepared from two phosphatidylcholines and three dialkyldimethylammonium bromides (DXDAB) with differing in dialkyl chain lengths, ranging from 2-C(14) to 2-C(18), by measuring particle size and zeta potential. The dependence of particle size, zeta potential and short-storage stability of mixed phosphatidylcholine/DXDAB vesicles on the chain length and composition were also elucidated. Transmission electron microscopy analysis verified that vesicles were formed as a phosphatidylcholine film to which DXDAB was added in a phosphate buffer saline (PBS, pH 7.4). Furthermore, the toxicity to the human keratinocytes (HaCaT) and squamous cell carcinomas (SCC25) cells that were incubated with these vesicles, evaluated by a cell viability assay, increased with the percentage of DXDAB that was incorporated and was inversely proportional to the chain length of DXDAB. The morphological features (round shape, chromatin condensation and apoptosis bodies) and results of flow cytometry analysis (increased sub-G(1) fraction) confirmed the induction of apoptosis in HaCaT and SCC25 cells by cationic vesicles. Apoptosis caused by cationic vesicles without the addition of any drugs was observed for the first time in HaCaT and SCC25 cells. The results of this investigation suggest that cytotoxicity is related to the zeta potential of the cationic vesicles.

Calcium phosphate nanocomposite particles for in vitro imaging and encapsulated chemotherapeutic drug delivery to cancer cells

Paradigm-shifting modalities to more efficiently deliver drugs to cancerous lesions require the following attributes: nanoscale-size, targetability, and stability under physiological conditions. Often, these nanoscale drug delivery vehicles are limited due to agglomeration, poor solubility, or cytotoxicity. Thus, we have designed a methodology to encapsulate hydrophobic antineoplastic chemotherapeutics within a 20-30 nm diameter, pH-responsive, nonagglomerating, nontoxic calcium phosphate nanoparticle matrix. In the present study, we report on calcium phosphate nanocomposite particles (CPNPs) that encapsulate both fluorophores and chemotherapeutics, are colloidally stable in physiological solution for an extended time at 37 degrees C and can efficaciously deliver hydrophobic antineoplastic agents, such as ceramide, in several cell model systems.

Combining nanoliposomal ceramide with sorafenib synergistically inhibits melanoma and breast cancer cell survival to decrease tumor development

PURPOSE

Deregulation of phosphatidylinositol 3-kinase/Akt and Ras/Raf/mitogen-activated protein kinase/extracellular signal-regulated kinase kinase/extracellular signal-regulated kinase pathways occurs in melanoma and breast cancer, deregulating normal cellular apoptosis and proliferation. Therapeutic cocktails simultaneously targeting these pathways could promote synergistically acting tumor inhibition. However, agents with manageable toxicity and mechanistic basis for synergy need identification. The purpose of this study is to evaluate the preclinical therapeutic efficacy and associated toxicity of combining sorafenib with nanoliposomal ceramide.

EXPERIMENTAL DESIGN

Effects of sorafenib and nanoliposomal ceramide as single and combinatorial agents were examined on cultured cells using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium salt assays and CalcuSyn software used to assess synergistic or additive inhibition. Western blotting measured cooperative effects on signaling pathways. Rates of proliferation, apoptosis, and angiogenesis were measured in size- and time-matched tumors to identify mechanistic basis for inhibition. Toxicity was evaluated measuring animal weight, blood toxicity parameters, and changes in liver histology.

RESULTS

Sorafenib and nanoliposomal ceramide synergistically inhibited cultured cells by cooperatively targeting mitogen-activated protein kinase and phosphatidylinositol 3-kinase signaling. A 1- to 2-fold increase in cellular apoptosis and 3- to 4-fold decrease in cellular proliferation were observed following combination treatment compared with single agents, which caused synergistically acting inhibition. In vivo, an approximately 30% increase in tumor inhibition compared with sorafenib treatment alone and an approximately 58% reduction in tumor size compared with nanoliposomal ceramide monotherapy occurred by doubling apoptosis rates with negligible systemic toxicity.

CONCLUSIONS

This study shows that nanoliposomal ceramide enhances effectiveness of sorafenib causing synergistic inhibition. Thus, a foundation is established for clinical trials evaluating the efficacy of combining sorafenib with nanoliposomal ceramide for treatment of cancers.