In vitro expansion of U87-MG human glioblastoma cells under hypoxic conditions affects glucose metabolism and subsequent in vivo growth.

Hypoxia is a characteristic feature of solid tumors leading to the over expression of hypoxia-inducible factor (HIF)-1α protein and therefore to a specific cellular behavior. However, even though the oxygen tension in tumors is low (<5 %), most of the cell lines used in cancer studies are grown under 21 % oxygen tension. This work focuses on the impact of oxygen conditions during in vitro cell culture on glucose metabolism using 1-(13)C-glucose. Growing U87-MG glioma cells under hypoxic conditions leads to a two- to threefold reduction of labeled glutamine and an accumulation of fructose. However, under both hypoxic and normoxic conditions, glucose is used for de novo synthesis of pyrimidine since the (13)C label is found both in the uracil and ribose moieties. Labeling of the ribose ring demonstrates that U87-MG glioma cells use the reversible branch of the non-oxidative pentose phosphate pathway. Interestingly, stereotactic implantation of U87-MG cells grown under normoxia or mild hypoxia within the striatum of nude mice led to differential growth; the cells grown under hypoxia retaining an imprint of the oxygen adaptation as their development is then slowed down.

Lipid nanocapsule functionalization by lipopeptides derived from human papillomavirus type-16 capsid for nucleic acid delivery into cancer cells.

Plasmid DNA (pDNA) and small interfering RNAs (siRNAs) are very useful tools for the treatment of cancer. However, pDNA and siRNAs efficacy is restricted by their negative charge and susceptibility to degradation by endonucleases that prevent them penetrating tissue and cellular barriers such as the plasma and endolysosomal membranes. Viral vectors have some advantages but their use is largely limited by their immunogenicity. On the other hand, synthetic nanoparticles have advantage of being relatively non-immunogenic but their ability to deliver nucleic acids remains less efficient than their viral counterparts. The present study is focussed on the development and evaluation of biomimetic lipid nanocapsules (LNCs) functionalized with a L1 papillomavirus type-16 capsid-derived lipopeptide on their surface, for transfection of U87MG glioma cells and Caco-2 colorectal adenocarcinoma cells with pDNA or siRNAs. Since the L1-peptide has been described as a nuclear localization signal able to complex with nucleic acids and bind to heparan sulfate on the cell surface, the structure and function of L1-peptide bound to LNCs (L1-LNCs) were investigated. Although L1-LNCs were shown to complex with both pDNA and siRNAs, the pDNA-L1-LNC complexes showed only weak transfection efficiency. In contrast, siRNA-L1-LNC complexes appeared as effective repressors of targeted messengers.

Silencing of miR-21 by locked nucleic acid-lipid nanocapsule complexes sensitize human glioblastoma cells to radiation-induced cell death.

The recent discovery of microRNA (miRNA) as major post-transcriptional repressors prompt the interest of developing novel approaches to target miRNA pathways to improve therapy. In this context, although the most significant barrier to their widespread clinical use remains delivery, nuclease-resistant locked nucleic acid (LNA) that bind specifically and irreversibly to miRNA represent interesting weapons. Thus, by focusing on oncongenic miR-21 miRNA, which participate to cancer cell resistance to apoptotic signals, the aim of the present study was to investigate the possibility of silencing miRNA by LNA conjugated to lipid nanocapsules (LNCs) as miRNA-targeted nanomedicines in U87MG glioblastoma (GBM) cells. After synthesis of an amphiphilic lipopeptide affine for nucleic acids, a post-insertion procedure during the LNC phase inversion formulation process allowed to construct peptide-conjugated LNCs. Peptide-conjugated LNCs were then incubated with LNAs to allow the formation of complexes characterized in gel retardation assays and by their physicochemical properties. U87MG cell treatment by LNA-LNC complexes resulted in a marked reduction of miR-21 expression as assessed by RTqPCR. In addition, exposure of U87MG cells to LNA-LNC complexes followed by external beam radiation demonstrated a significant improvement of cell sensitivity to treatment and emphasizes the interest to investigate further this miRNA-targeted strategy.

Perfluorocarbon-loaded lipid nanocapsules as oxygen sensors for tumor tissue pO2 assessment.

The assessment of tumor oxygenation is a crucial factor in cancer therapy and may be carried out using fluorine MRI once fluorine probes have been distributed within the tumor. However, the deposit of those highly fluorinated compounds often jeopardizes anatomical image quality and requires emulsification of the probes. Due to the high density and the high lipophilicity of perfluorocarbons, nanoemulsion of these molecules usually requires high-energy processes. In the present work, we discuss the synthesis and the physico-chemical characterization of perfluorocarbon nanocapsules using a low-energy phase-inversion process. The nanocapsules were tested on a mouse tumor brain model to assess oxygenation.

Smart nanocarriers for pH-triggered targeting and release of hydrophobic drugs.

The use of hybrid pH-sensitive micelles based mainly on the (PEO)(129)(P2VP)(43)(PCL)(17) ABC miktoarm star copolymer as potential triggered drug delivery systems was investigated. Co-micellization of this star copolymer with a second copolymer labeled by a targeting ligand, i.e. biotin, on the pH sensitive block (poly-2-vinylpyridine) is considered here in order to impart possible active targeting of the tumor cells. Two architectures were studied for these labeled copolymers, i.e. a miktoarm star or a linear ABC terpolymer, and the respective hybrid micelles are compared in terms of cytotoxicity (cells viability) and cellular uptake (using fluorescent dye loaded micelles). Finally, the triggered drug release in the cytosol of tumor cells was investigated by studying, on the one hand, the lysosomal integrity after internalization and, on the other hand, the release profile in function of the pH.

Development and characterization of immuno-nanocarriers targeting the cancer stem cell marker AC133.

In the context of targeted therapy, we addressed the possibility of developing a drug delivery nanocarrier capable to specifically reach cancer cells that express the most prominent marker associated with cancer stem cell (CSC) phenotype, AC133. For this purpose, 100nm lipid nanocapsules (LNCs) were functionalized with a monoclonal antibody (mAb) directed against AC133 according to two distinct methods: firstly, post-insertion within 100nm LNCs of a lipid poly(ethylene glycol) functionalized with reactive-sulfhydryl maleimide groups (DSPE-PEG(2000)-maleimide) followed by thiolated mAb coupling, and, secondly, creation of a thiolated lipo-immunoglobulin between DSPE-PEG(2000)-maleimide and AC133, then post-inserted within LNCs. Due to the reduced number of purification steps, lower amounts of DSPE-PEG(2000)-maleimide that were necessary as well as lower number of free maleimide functions present onto the surface of immuno-LNC, the second method was found to be more appropriate. Thus, 126nm AC133-LNC with a zeta potential of -22mV while keeping a narrow distribution were developed. Use of the IgG1κ isotype control-immunoglobulins produced similar control IgG1-LNCs. Micro-Bradford colorimetric assay indicated a fixation of about 40 immunoglobulins per LNC. Use of human Caco-2 cells that constitutively express AC133 (Caco-2-AC133(high)) allowed addressing the behavior of the newly functionalized immuno-LNCs. siRNA knockown strategy permitted to obtain Caco-2-AC133(low) for comparison. Immunofluorescence-combined flow cytometry analysis demonstrated that the epitope-recognition function of AC133 antibody was preserved when present on immuno-LNCs. Although grafting of immunoglobulins onto the surface of LNCs repressed their internalization within Caco-2 cells as evaluated by flow cytometry, AC133-specific cellular binding was obtained with AC133-LNC as assessed by computer-assisted fluorescence microscopy. In conclusion, interest of AC133-LNCs as niche carriers is discussed toward the development of CSC targeted chemo- or radio-nanomedicines.

Mitochondrial targeting by use of lipid nanocapsules loaded with SV30, an analogue of the small-molecule Bcl-2 inhibitor HA14-1.

Taking advantage from the development of SV30, a new analogue of the pro-apoptotic molecule HA14-1, the aim of this study was to functionally evaluate SV30 and to develop safe nanocarriers for its administration. By using an inversion phase process, 57nm organic solvent-free lipid nanocapsules loaded with SV30 (SV30-LNCs) were formulated. Biological performance of SV30 and SV30-LNCs were evaluated on F98 cells that express Bax and Bcl-2, through survival assays, HPLC, flow cytometry, confocal microscopy and spectral imaging. We observed that SV30 alone or in combination with paclitaxel, etoposide or beam radiation could trigger cell death in a similar fashion to HA14-1. Although partially blocked by Z-VAD-fmk, this effect was coincident to caspase-3 activation. Hence, we established that SV30-LNCs improved SV30 biological activity together with a potentiation of the mitochondrial membrane potential decrease. Interestingly, flow cytometry and confocal analysis indicated that SV30 itself conferred to LNCs improved mitochondrial targeting skills that may present a great interest toward the development of mitochondria targeted nanomedicines.

Reciprocal competition between lipid nanocapsules and P-gp for paclitaxel transport across Caco-2 cells.

Lipid nanocapsules (LNCs) have been shown to improve paclitaxel (Ptx) bioavailability and transport across an intestinal barrier model. In the present study, the interaction between P-glycoprotein (P-gp) and LNC transport across Caco-2 cells are investigated. Transport experiments have been performed on Caco-2 cells displaying different P-gp activities (early and later cell passages). The permeability of Ptx encapsulated in LNCs has been studied in the presence of P-gp inhibitors (verapamil and vinblastin) or unloaded LNCs. The uptake of dye-labelled LNCs was also observed in the presence of the same inhibitors. It was found that the permeability of Ptx varied depending on the passages with later ones showing higher absolute values (5.74+/-1.21 cms(-1) vs 133.41+/-5.74 cms(-1)). P-gp inhibition obtained with verapamil or vinblastin improved Ptx transport up to 98%. LNCs have also demonstrated their capacity to increase their own transport. Experiments performed with dye-labelled LNCs demonstrated an enhancement of the uptake of dye (Nile red), only in the presence of verapamil. These results demonstrated an effect of P-gp on the transport of Ptx when loaded in LNCs and support a direct effect of P-gp on their endocytosis in Caco-2 cells. These finding may assist in the development of new nanomedicine for oral administration.

Lipid nanocarriers improve paclitaxel transport throughout human intestinal epithelial cells by using vesicle-mediated transcytosis.

The use of lipid nanocapsules (LNCs) has enabled an improvement of the oral bioavailability of paclitaxel (Ptx). However, mechanisms that support this recent observation are not yet understood. By focusing on the well defined in vitro Caco-2 model, the purpose of this study was to evaluate the transport of LNCs across a model intestinal barrier. Firstly, four sizes of paclitaxel or dye (Nile Red)-loaded LNCs were formulated and LNCs with sizes between 26.3+/-2.7 nm and 132.7+/-5.5 nm were obtained. Different transport and uptake experiments were then performed across a Caco-2 cells culture model using these LNCs. Paclitaxel-loaded LNCs improved permeability of Ptx across intestinal epithelium compared with free Ptx or Taxol by a factor of 3.5. At 37 degrees C particle size did not influence transport efficiency. However, at 4 degrees C a decrease in Ptx transport was observed with increasing size of LNCs. Thus, with LNCs of 25 nm size, the apparent permeability coefficient (P(app)) was 5.3+/-1.1 cm s(-1) at 37 degrees C and 2.2+/-0.4 cm s(-1) at 4 degrees C. In comparison in LNCs of 130 nm size, the P(app) decreased from 5.8+/-0.8 cm s(-1) at 37 degrees C to 0.5+/-0.1 cm s(-1) at 4 degrees C. The uptake of LNCs by Caco-2 cells and the incapacity of LNCs to open tight junctions were also demonstrated. Furthermore, experiment transports were performed in the presence of different inhibitors of endocytosis. Findings indicated a reduction of Ptx transport of 30+/-6% when cell cholesterol was depleted, 65+/-12% when caveolae-mediated endocytosis was inhibited and 20+/-8% when clathrin-mediated endocytosis was inhibited. Finally, transmission electronic microscopy showed the presence of nano-objects on the basolateral side of the Caco-2 cell monolayers when LNCs were applied on the apical side.

[Local chemotherapy of malignant glioma: from syringe injections to nanotechnology]. / Chimiothérapie locale dans les gliomes malins: de l'injection à la seringue aux nanotechnologies.

Many arguments support the development of local therapies for malignant gliomas. Simple injections of antimitotic agents into the surgical cavity has been replaced by more sophisticated systems. Tissues can be infused with complex prolonged-release polymeric or lipidic systems with macroscopic, microscopic and now even nanometric particles. But, as for any drug, the developments of these new agents has been long and only very few reach the stage of the clinic trials.

Development and characterization of interleukin-18-loaded biodegradable microspheres.

Immunostimulation represents a promising approach designed to specifically eradicate malignant cells. Since glioma tumour cells hole up in the central nervous system (CNS) in a particularly inauspicious milieu to antitumour immune reactions we here propose a new strategy to revert the properties of this microenvironment by administering an antitumour cytokine into the CNS tumour itself. Thus, biodegradable poly(D,L-lactide-co-glycolide) (PLGA) sustained-release microspheres for stereotaxic implantation loaded with interleukin-18 (IL-18), that is known to exert antitumour activity and trigger immune cell-mediated cytotoxicity, were developed. Different tests for assessing IL-18 bioactivity were set-up and evaluated. A specific bioassay was considered as the most reliable test. The stability and integrity of IL-18 was then verified during the encapsulation process. Consequently, two procedures of IL-18 encapsulation in PLGA microparticles (W/O/W and S/O/W) were investigated. As determined by radiolabelling studies using 125I-IL-18 and a continuous flow system, the in vitro release profile of IL-18 was optimum with S/O/W method with a moderate burst effect and a subsequent progressive discharge of 16.5+/-8.4 ng/day during the next 21 days against 6.1+/-4.2 ng/day with the W/O/W method. Considering analytical testing of IL-18 together with its preserved biological activity after release from microspheres, amounts of the active cytokine obtained with S/O/W method were relevant to plan in vivo evaluation to validate the therapeutic strategy.

In vitro investigation of lipid implants as a controlled release system for interleukin-18.

Operating on the inductive and effective phases of an anti-tumor immune response and uncovering pivotal functions that may reduce cancer cell growth, interleukin-18 (IL-18) appears to be an attractive candidate for the sustained local adjuvant immunotherapeutic treatment of brain gliomas. The objective of this work was to develop IL-18 loaded lipid implants as a controlled delivery system. For the preparation of protein loaded triglyceride matrix material, a solid-in-oil (s/o) dispersion technique was chosen for which protein particles in the micrometer range were first prepared by co-lyophilization with polyethylene glycol (PEG). Implants of 1 mm diameter, 1.8 mm height and 1.8 mg weight were manufactured by compression of the powder mixture in a specially designed powder compacting tool. The in vitro release behavior of 125I-Bolton-Hunter-radiolabeled IL-18 was assessed in a continuous-flow system. A cell culture assay was established for the determination of bioactivity of released IL-18. Implants showed a continuous release of 10-100 ng IL-18 per day for 12 days. A progressive integrity loss was observed with ongoing release, which would be related to protein degradation during incubation. The initially released fraction proved complete retention of bioactivity, indicating that the manufacturing procedure had no detrimental effects on protein stability.

Development of new polymer-based particulate systems for anti-glioma vaccination.

Biodegradable and biocompatible microspheres represent a promising alternative to conventional adjuvants for anti-tumour vaccination. Focusing on glioma, we developed two poly(D,L-lactide-co-glycolide) (PLGA)-based particulate systems presenting tumour antigens associated with plasma membranes or with cell lysates. Glioma cell fractions were prepared for adsorption onto poly-D-lysine (PDL)-coated PLGA microspheres formulated using a double-emulsion procedure. Adsorption was followed by (125)I-radiolabelling, Western blot and confocal laser scanning microscopy. Only a panel (34%) of the proteins isolated from both cell fractions adsorbed onto PDL-coated PLGA microspheres. The integrity of the epitopes after loading was preserved, as shown by identification of plasma membrane and cytoplasmic markers. Finally, one of the major potential advantages of those particulate systems resides in the fact they not only serve as injectable adjuvant matrices presenting tumour antigens to antigen presenting cells, but also as potential reservoirs for controlled delivery of active immunostimulant molecules.

Knockout mice reveal a contribution of the extracellular matrix molecule tenascin-C to neural precursor proliferation and migration.

The extracellular matrix glycoprotein tenascin-C is widely expressed in the vertebrate central nervous system (CNS) during development and repair. Despite multiple effects of tenascin-C on cell behaviour in culture, no structural abnormalities of the CNS and other organs have been found in adult tenascin-C-null mice, raising the question of whether this glycoprotein has a significant role in vivo. Using a transgenic approach, we have demonstrated that tenascin-C regulates both cell proliferation and migration in oligodendrocyte precursors during development. Knockout mice show increased rates of oligodendrocyte precursor migration along the optic nerve and reduced rates of oligodendrocyte precursor proliferation in different regions of the CNS. Levels of programmed cell death were reduced in areas of myelination at later developmental stages, providing a potential corrective mechanism for any reduction in cell numbers that resulted from the proliferation phenotype. The effects on cell proliferation are mediated via the alphavbeta3 integrin and an interaction with the platelet-derived growth factor-stimulated mitogenic pathway, emphasising the importance of both CNS extracellular matrix and integrin growth factor interactions in the regulation of neural precursor behaviour.

Myelination and behaviour of tenascin-C null transgenic mice.

The extracellular matrix glycoprotein tenascin-C is widely expressed during development and repair, making it surprising that few abnormalities have been found in transgenic mice lacking this molecule. We have therefore re-examined the transgenic mice described by Saga et al. [Saga, Y., Yagi, T., Ikawa, Y., Sakakura, T. & Aizawa, S. (1992) Genes Dev., 6 1821-1831] in which tenascin-C was knocked-out by homologous recombination, focusing on two aspects of the nervous system likely to reveal any abnormalities that might follow the loss of tenascin-C. First, we have determined the pattern of myelin and distribution of oligodendrocyte precursor cells in those areas, such as the optic nerve and retina where local concentrations of tenascin-C have been proposed to act as barriers to oligodendrocyte precursor migration and so prevent inappropriate myelination. Secondly, we have examined the behaviour of the mice in a number of well-characterized tests, e.g. beam-walking, passive avoidance and the Morris water maze. We find no abnormalities of myelination or oligodendrocyte precursor distribution in adult mice, showing that local concentrations of tenascin-C are not the sole mechanism responsible for the pattern of myelination in these regions of CNS. However, we do find a number of behavioural abnormalities in these mice and show that hyperlocomotion and deficits in coordination during beam walking can be ascribed to tenascin-C deficiency. The effects on coordination are, however, not seen on a 129 genetic background. Taken together, these results significantly extend the phenotype associated with tenascin-C deficiency but argue against a role in myelination.

1,25-dihydroxyvitamin D3 regulates the synthesis of gamma-glutamyl transpeptidase and glutathione levels in rat primary astrocytes.

Astrocytes play a pivotal role in CNS detoxification pathways, where glutathione (GSH) is involved in the elimination of oxygen and nitrogen reactive species such as nitric oxide. We have previously demonstrated that the specific activity of gamma-glutamyl transpeptidase (gamma-GT), an enzyme of central significance in GSH metabolism, is regulated in vivo in astrocytes by 1,25-dihydroxyvitamin D3 (1,25-D3). The aim of the present work was to investigate, in primary cultures of newborn rat astrocytes, the effects of this hormone on gamma-GT synthesis and on GSH and nitrite levels after lipopolysaccharide (LPS) treatment. This study demonstrates that both gamma-GT gene expression and specific activity, induced by LPS, are potentiated by 1,25-D3. In contrast, 1,25-D3 does not regulate the expression of other enzymes involved in astrocyte detoxification processes, such as superoxide dismutase or GSH peroxidase. In parallel, 1,25-D3 enhanced intracellular GSH pools and significantly reduced nitrite production induced by LPS. Taken together, these results suggest that gamma-GT, GSH, and 1,25-D3 play a fundamental role in astrocyte detoxification pathways.

Expression of inducible nitric oxide synthase during rat brain inflammation: regulation by 1,25-dihydroxyvitamin D3.

This study, based on in situ hybridization and immunolabeling experiments, presents the time-course and cellular distribution of inducible NO synthase (iNOS) expression in a rat model of brain inflammation. Both intrahippocampal injection of lipopolysaccharide (LPS) or of buffer (stab lesion) induce an early, transient, and restricted expression of iNOS mRNA and immunoreactivity in the rat CNS. The topographic and phenotypic characteristics of iNOS-producing cells are distinct. After stab lesion, iNOS mRNAs, expressed at 5 h mainly in cells in the interventricular junction and in a few cells in brain parenchyma, were no more detectable from 15 h onwards, whereas the protein was faintly expressed in parenchymal cells at 15 h and 24 h. In contrast, after LPS injection, iNOS-mRNAs were detected from 5 to 24 h. iNOS-immunoreactivity was highly induced and sequentially observed first in choroid plexus and ependymal cells at 5 h, in monocytes and activated/reactive microglia at 15 h and 24 h, and finally in astrocytes at 72 h. In order to investigate potential regulatory effects of 1,25-dihydroxyvitamin D3 (1,25-D3) on iNOS expression, we have delivered this hormone with LPS or buffer into the rat hippocampus. 1,25-D3 significantly inhibits iNOS expression, at both the mRNA and immunoreactive protein levels, 15 h and 24 h after LPS injection, in the cells of the monocyte lineage. Moreover, 72 h after LPS injection, the addition of 1,25-D3 leads to a 6-fold increase in the number of macrophages around the lesion site, that correlates with a decrease in the proportion of apoptotic cells. Since 1,25-D3 can be produced by activated macrophages/microglia and since NO stimulates 1,25-D3 synthesis by macrophages, our results support the hypothesis that this hormone might be synthesized endogenously during CNS inflammatory reactions, thus explaining the transient and restricted iNOS expression observed after LPS intracerebral injection.

1,25-Dihydroxyvitamin D3 inhibits the expression of inducible nitric oxide synthase in rat central nervous system during experimental allergic encephalomyelitis.

The inducible form of nitric oxide synthase (iNOS) generates nitric oxide of which the excessive production is associated with central nervous system (CNS) inflammatory diseases. The investigation of iNOS expression during experimental allergic encephalomyelitis (EAE) of the Lewis rat demonstrated iNOS immunoreactivity and mRNA both during inflammatory bursts (days 12 and 23 post-immunization) and during the remission phase (day 18). iNOS expression was region-specific and expanded with time along a caudo-rostral axis, thus, correlating with the development of inflammatory infiltrates. Whereas cells of the monocyte/macrophage lineage continuously contributed to iNOS expression, astrocytes only expressed iNOS immunoreactivity or mRNA during the relapse (day 23). In order to investigate possible regulatory effects of 1,25-dihydroxyvitamin D3 (1,25-D3) on iNOS expression, rats were treated with the hormone after the beginning of clinical signs (days 11, 13, 19, 21 and 23 post-immunization), and areas of the CNS were examined at day 23. 1,25-D3 exerted a drastic inhibitory effect on iNOS expression, both at the protein and the mRNA levels. However, this effect was region-specific, and was most pronounced in the cerebellum and brainstem, but non-existent in cerebral cortex. iNOS down-regulation occurred in macrophages, activated microglia and astrocytes. The inhibition of iNOS expression in some CNS structures could account for the improvement of clinical signs observed in EAE-rats treated with 1,25-D3. Since 1,25-D3 can be synthesized by activated macrophages or microglia, our results support the hypothesis that this hormone might be implicated in the control of the CNS-specific immune responses. 1,25-D3 or its analogues could, thus, be of therapeutic value in the management of iNOS-associated diseases of the CNS.

1,25-Dihydroxyvitamin D3 regulates gamma 1 transpeptidase activity in rat brain.

gamma-Glutamyl transpeptidase (gamma-GT), primarily described as a kidney enzyme, is also expressed in several cell types of the central nervous system (CNS). It is involved in the glutathione cycle and in cysteine transport. Here we report that the specific activity of this enzyme is transiently increased in the rat brain, following a treatment with 1,25-dihydroxyvitamin D3 (1,25-D3), the active form of vitamin D. In vitro experiments showed that this positive regulatory effect does not affect endothelial cells of the brain microvessels, but does affect pericytes and parenchymal astrocytes. Changes in the specific activity of gamma-GT were not correlated with any important modification of brain amino acid concentrations. Since gamma-GT is though to participate in the scavenging of reactive oxygen species, these data suggest that 1,25-D3 could be an effector controlling detoxification processes in the brain.