Biomedical subjects

Gert Storm

Publications and source records attributed to Gert Storm.

At least 37 records · Page 2Linked to original sources

PubMed2006

ICS-283: a system for targeted intravenous delivery of siRNA.

ICS-283 was developed within Intradigm Corporation as a system that is designed for the systemic delivery of therapeutic small interfering (siRNA) to sites of pathological angiogenesis. The non-viral siRNA delivery system is based on synthetic nanoparticles, known as Targe (Intradigm Corporation), which functions as a broad-platform technology to deliver siRNA to specific target cells in diseased tissues. The system is constructed to incorporate different functionalities that address critical needs for successful nucleic acid delivery. The TargeTran synthetic vector is a self-assembling, layered nanoparticle that protects and targets siRNA to specific cell types in pathological tissues. At present, ICS-283 is the only antiangiogenic siRNA delivery system that is designed for intravenous administration to treat angiogenesis-driven diseases.

Animals↗

PubMed2006

Effect of intratumoral injection on the biodistribution and the therapeutic potential of HPMA copolymer-based drug delivery systems.

The direct intratumoral (i.t.) injection of anticancer agents has been evaluated extensively in the past few decades. Thus far, however, it has failed to become established as an alternative route of administration in routine clinical practice. In the present report, the impact of i.t. injection on the biodistribution and the therapeutic potential of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-based drug delivery systems was investigated. It was found that, compared to intravenous injection, both the tumor concentrations and the tumor-to-organ ratios of carriers improved substantially. In addition, compared to intravenously and intratumorally applied free doxorubicin and to intravenously applied poly(HPMA)-glycylphenylalanylleucylglycine-doxorubicin, intratumorally injected poly(HPMA)-glycylphenylalanylleucylglycine-doxorubicin presented a significantly increased antitumor efficacy, as well as an improved therapeutic index. Based on these findings, we propose intratumorally injected carrier-based chemotherapy as an interesting alternative to routinely used chemotherapy regimens and routes of administration.

Acrylamides↗

PubMed2005

Effect of physicochemical modification on the biodistribution and tumor accumulation of HPMA copolymers.

Copolymers of N-(2-hydroxypropyl)methacrylamide (HPMA) are prototypic and well-characterized polymeric drug carriers that are being broadly implemented in the delivery of anticancer therapeutics. To better predict the in vivo potential of the copolymers and to describe the biodistributional consequences of functionalization, 13 physicochemically different HPMA copolymers were synthesized, varying in molecular weight and in the nature and amount of functional groups introduced. Upon radiolabeling, the copolymers were injected i.v., and their circulation kinetics, tissue distribution and tumor accumulation were monitored in rats bearing subcutaneous Dunning AT1 tumors. It was found that increasing the average molecular weight of HPMA copolymers resulted in prolonged circulation times and in increased tumor concentrations. Conjugation of carboxyl and hydrazide groups, as well as introduction of spacer, drug and peptide moieties reduced the long-circulating properties of the copolymers and as a result, lower levels were found in tumors and in all organs other than kidney. Interestingly, however, in spite of the reduced (absolute) tumor concentrations, hardly any reduction in the relative levels localizing to tumors was found. Tumor-to-organ ratios were comparable to unmodified control for the majority of chemically modified copolymers, indicating that functionalization does not necessarily affect the tumor targeting ability of the copolymers and suggesting that HPMA copolymer-based drug delivery systems may prove to be attractive tools for more effectively treating various forms of advanced solid malignancy.

Animals↗

PubMed2005

MR molecular imaging and fluorescence microscopy for identification of activated tumor endothelium using a bimodal lipidic nanoparticle.

In oncological research, there is a great need for imaging techniques that specifically identify angiogenic blood vessels in tumors on the basis of differences in the expression level of biomolecular markers. In the angiogenic cascade, different cell surface receptors, including the alphavbeta3-integrin, are strongly expressed on activated endothelial cells. In the present study, we aimed to image angiogenesis by detecting the expression of alphavbeta3 in tumor bearing mice with a combination of magnetic resonance imaging (MRI) and fluorescence microscopy. To that end, we prepared MR-detectable and fluorescent liposomes, which carry approximately 700 alphavbeta3-specific RGD peptides per liposome. RGD competition experiments and RAD-conjugated liposomes were used as controls for specificity. In vivo, both RAD liposomes and RGD liposomes gave rise to signal increase on T1-weighted MR images. It was established by the use of ex vivo fluorescence microscopy that RGD liposomes and RAD liposomes accumulated in the tumor by different mechanisms. RGD liposomes were specifically associated with activated tumor endothelium, while RAD liposomes were located in the extravascular compartment. This study demonstrates that MR molecular imaging of angiogenesis is feasible by using a targeted contrast agent specific for the alphavbeta3-integrin, and that the multimodality imaging approach gave insight into the exact mechanism of accumulation in the tumor.

Animals↗

PubMed2005

Application of poly(2-(dimethylamino)ethyl methacrylate)-based polyplexes for gene transfer into human ovarian carcinoma cells.

Previously, attempts were made in our laboratory to transfect human ovarian cancer (OVCAR-3) cells, growing in the peritoneal cavity of nude mice, by intraperitoneal administration of poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA)-based polyplexes. However, hardly any transfection of the OVCAR-3 cells was observed. The aim of the present study was to examine whether pDMAEMA-polyplexes can transfect OVCAR-3 cells in vivo at DNA doses much higher than used previously [J. Gene Med. 1 (1999) 156-158]. We also explored a specific targeting strategy based on the use of folic acid (FA) as a targeting ligand directed against the folate receptor overexpressed on OVCAR-3 cells. Luciferase expression by OVCAR-3 cells mediated by pDMAEMA-based polyplexes was evaluated in the mouse i.p. OVCAR-3 xenograft model of ovarian cancer. By virtue of new formulation options, we were able to administer polyplex dispersions into OVCAR-3 bearing mice at much larger doses (75-120 microg DNA) than used previously (15 microg). The feasibility of folate-mediated targeting of the polyplexes was studied after coupling of FA to preformed polyplexes with poly(ethylene glycol) (PEG) as a spacer. Intraperitoneal administration of naked pLuc plasmid did not result in significant gene expression by the tumor cells. Administration of uncoated, positively charged pDMAEMA-based polyplexes at a DNA dose of 75-120 microg yielded significant transfection activity. However, also considerable gene expression was observed in non-target cells. To avoid transfection of non-target cells, an active targeting strategy based on the use of FA was studied. At a dose of 75 microg DNA (N/P 5), the folate-targeting approach yielded about 10-fold lower luciferase transfection levels in organs lined by the mesenthelial layer. This beneficial site-avoidance effect was achieved without compromising the degree of tumor cell transfection. Successful transfection of OVCAR-3 cells growing in the peritoneal cavity of nude mice can be achieved by i.p. administration of polyplexes at doses between 75 and 120 microg DNA. It was further demonstrated that active targeting of polyplexes to OVCAR-3 cells growing in the peritoneal cavity of mice is a realistic possibility to avoid transfection of non-target cells.

Animals↗

PubMed2005

Strategies for cytosolic delivery of liposomal macromolecules.

Potential approaches to achieve cytosolic delivery of liposomal macromolecules are presented. These approaches include: (1) the co-encapsulation of fusogenic peptides into targeted drug-containing liposomes (2) coupling of the HIV-1-derived cell-penetrating peptide TAT to the surface of liposomes and (3) photochemical internalization, based on photochemically inducible permeabilization of endocytic vesicles.

Chemistry, Pharmaceutical↗

PubMed2005

Coformulated N-octanoyl-glucosylceramide improves cellular delivery and cytotoxicity of liposomal doxorubicin.

The anticancer agent doxorubicin is in certain cases administered as a long-circulating liposomal formulation. Due to angiogenesis-related structural abnormalities in the endothelial lining of many neoplasms, these complexes tend to extravasate and accumulate in the tumor stroma. However, delivery of doxorubicin is still not optimal since liposomes are not taken up directly by tumor cells. Instead, doxorubicin is gradually released into the interstitial space, and the subsequent uptake by surrounding cells is a limiting step in the delivery process. We recently demonstrated that plasma membrane-inserted short-chain sphingomyelin facilitates the cellular uptake of free doxorubicin. Here, we report that N-octanoyl-glucosylceramide acts equally potent but is itself less toxic. When coformulated with liposomal doxorubicin, this short-chain glycosphingolipid administered to cultured A431 epidermoid carcinoma cells led to superior (up to 4-fold) cellular doxorubicin accumulation and cytotoxicity, compared with control doxorubicin liposomes. These results were fully reproducible when N-octanoyl-glucosylceramide was postinserted into Caelyx, a commercial liposomal doxorubicin preparation. The doxorubicin-potentiating effect of N-octanoyl-glucosylceramide-enriched liposomes proved relatively insensitive to high serum concentrations, indicating that in vivo application is a feasible option. N-Octanoyl-glucosylceramide enrichment might thus represent a major improvement of conventional liposomal doxorubicin formulations.

Antibiotics, Antineoplastic↗

PubMed2005

In vivo tumor transfection mediated by polyplexes based on biodegradable poly(DMAEA)-phosphazene.

In recent years, increasing interest is being paid to the design of transfectants based on non-toxic and biodegradable polymers for gene therapy purposes. We recently reported on a novel, biodegradable polymer, poly(2-dimethylamino ethylamino)phosphazene (p(DMAEA)-ppz) for use in non-viral gene delivery. In this study, the biodistribution and in vivo transfection efficiency of polyplexes composed of plasmid DNA and p(DMAEA)-ppz were investigated after intravenous administration in tumor bearing mice. Data were compared with those of polyplexes based on the non-biodegradable polyethylenimine (PEI 22kDa). Both polyplex systems were rapidly cleared from the circulation (<7% ID, at 60 min after administration) and showed considerable disposition in the liver and the lung, all in line with earlier work on cationic polyplex systems. The lung disposition is attributed to aggregates formed by interaction of the polyplexes with blood constituents. Redistribution of the polyplexes from the lung was observed for both polyplex formulations. Importantly, both polyplex systems showed a substantial tumor accumulation of 5% and 8% ID/g for p(DMAEA)-ppz and PEI22 polyplexes, respectively, at 240 min after administration. The tumor disposition of the p(DMAEA)-ppz and PEI22 polyplexes was associated with considerable expression levels of the reporter gene. In contrast to PEI22 polyplexes, p(DMAEA)-ppz polyplexes did not display substantial gene expression in the lung or other organs (organ gene expression<1/100 of tumor gene expression). The observed preferential tumor gene expression mediated by the p(DMAEA)-ppz polyplexes enables the application of this polymer to deliver therapeutic genes to tumors.

Animals↗

PubMed2005

Alveolar macrophages have a dual role in a rat model for trimellitic anhydride-induced occupational asthma.

Occupational exposure to low molecular weight chemicals, like trimellitic anhydride (TMA), can result in occupational asthma. Alveolar macrophages (AMs) are among the first cells to encounter inhaled compounds. These cells can produce many different mediators that have a putative role in asthma. In this study, we examined the role of AMs in lung function and airway inflammation of rats exposed to TMA. Female Brown Norway rats were sensitized by dermal application of TMA or received vehicle alone on days 0 and 7. One day before challenge, rats received intratracheally either empty or clodronate-containing liposomes to deplete the lungs of AMs. On day 21, all rats were challenged by inhalation of TMA in air. Lung function parameters were measured before, during, within 1 h after, and 24 h after challenge. IgE levels and parameters of inflammation and tissue damage were assessed 24 h after challenge. Sensitization with TMA led to decreased lung function parameters during and within 1 h after challenge as compared to non-sensitized rats. AM depletion alleviated the TMA-induced drop in lung function parameters and induced a faster recovery compared to sham-depleted TMA-sensitized rats. It also decreased the levels of serum IgE 24 h after challenge, but did not affect the sensitization-dependent increase in lung lavage fluid IL-6 and tissue TNF-alpha levels. In contrast, AM depletion augmented the TMA-induced tissue damage and inflammation 24 h after challenge. AMs seem to have a dual role in this model for TMA-induced occupational asthma since they potentiate the immediate TMA-induced decrease in lung function but tended to dampen the TMA-induced inflammatory reaction 24 h later.

Allergens↗

PubMed2005

Transporting silence: design of carriers for siRNA to angiogenic endothelium.

The recently developed siRNA oligonucleotides are an attractive alternative to antisense as a therapeutic modality because of their robust, gene selective silencing of drug target protein expression. To achieve therapeutic success, however, several hurdles must be overcome including rapid clearance, nuclease degradation, and inefficient intracellular localization. In this presentation, we discuss design strategies for development of self-assembling nanoscale carriers for neovasculature targeted delivery of siRNA inhibiting tumor or ocular angiogenesis.

Angiogenesis Inhibitors↗

PubMed2005

Thermosensitive and biodegradable polymeric micelles for paclitaxel delivery.

The preparation, release and in vitro cytotoxicity of a novel polymeric micellar formulation of paclitaxel (PTX) were investigated. The micelles consisted of an AB block copolymer of poly(N-(2-hydroxypropyl) methacrylamide lactate) and poly(ethylene glycol) (pHPMAmDL-b-PEG). Taking advantage of the thermosensitivity of pHPMAmDL-b-PEG, the loading was done by simply mixing of a small volume of a concentrated PTX solution in ethanol and an aqueous polymer solution and subsequent heating of the resulting solution above the critical micelle temperature of the polymer. PTX could be almost quantitatively loaded in the micelles up to 2 mg/mL. By dynamic light scattering and cryo-transmission electron microscopy, it was shown that PTX-loaded micelles have a mean size around 60 nm with narrow size distribution. At pH 8.8 and 37 degrees C, PTX-loaded micelles destabilized within 10 h due to the hydrolysis of the lactic acid side group of the pHPMAmDL. Because the hydrolysis of the lactic acid side groups is first order in hydroxyl ion concentration, the micelles were stable for about 200 h at physiological conditions. The presence of serum proteins did not have an adverse effect on the stability of the micelles during at least 15 h. Interestingly, the dissolution kinetics of pHPMAmDL-b-PEG micelles was retarded by incorporation of PTX, indicating a strong interaction between PTX and the pHPMAmDL block. The PTX-loaded micelles showed a release of the incorporated 70% of PTX during 20 h at 37 degrees C and at pH 7.4. PTX-loaded pHPMAmDL-b-PEG micelles showed comparable in vitro cytotoxicity against B16F10 cells compared to the Taxol standard formulation containing Cremophor EL, while pHPMAmDL-b-PEG micelles without PTX were far less toxic than the Cremophor EL vehicle. Confocal laser-scanning microscopy (CLSM) and fluorescence activated cell sorting (FACS) analysis of fluorescently labelled micelles showed that pHPMAmDL-b-PEG micelles were internalized by the B16F10 cells. The present results suggest that pHPMAmDL-b-PEG block copolymer micelles are a promising delivery system for the parenteral administration of PTX.

Animals↗

PubMed2005

CD134 as target for specific drug delivery to auto-aggressive CD4+ T cells in adjuvant arthritis.

T cells have an important role during the development of autoimmune diseases. In adjuvant arthritis, a model for rheumatoid arthritis, we found that the percentage of CD4+ T cells expressing the activation marker CD134 (OX40 antigen) was elevated before disease onset. Moreover, these CD134+ T cells showed a specific proliferative response to the disease-associated epitope of mycobacterial heat shock protein 60, indicating that this subset contains auto-aggressive T cells. We studied the usefulness of CD134 as a molecular target for immune intervention in arthritis by using liposomes coated with a CD134-directed monoclonal antibody as a drug targeting system. Injection of anti-CD134 liposomes subcutaneously in the hind paws of pre-arthritic rats resulted in targeting of the majority of CD4+CD134+ T cells in the popliteal lymph nodes. Furthermore, we showed that anti-CD134 liposomes bound to activated T cells were not internalized. However, drug delivery by these liposomes could be established by loading anti-CD134 liposomes with the dipalmitate-derivatized cytostatic agent 5'-fluorodeoxyuridine. These liposomes specifically inhibited the proliferation of activated CD134+ T cells in vitro, and treatment with anti-CD134 liposomes containing 5'-fluorodeoxyuridine resulted in the amelioration of adjuvant arthritis. Thus, CD134 can be used as a marker for auto-aggressive CD4+ T cells early in arthritis, and specific liposomal targeting of drugs to these cells via CD134 can be employed to downregulate disease development.

Animals↗

PubMed2005

Effects of treatment with small interfering RNA on joint inflammation in mice with collagen-induced arthritis.

OBJECTIVE: RNA interference is a process in which genes can be silenced sequence-specifically. In mammals, RNA interference can be invoked by introduction of small (19-21-nucleotide) double-stranded RNA molecules known as small interfering RNA (siRNA) into cells. Thereby, siRNA offers promise as a novel therapeutic modality. However, siRNA is a relatively large, highly charged molecule and does not readily enter cells. This study was undertaken to investigate the use of electroporation for in vivo transfection of siRNA into joint tissue in arthritic mice to achieve local RNA interference. METHODS: Proof of principle that siRNA is able to inhibit gene expression in vivo in the mouse joint was studied by local injection and electroporation of siRNA designed to silence reporter genes. In mice with collagen-induced arthritis (CIA), the disease-modulating activity of siRNA designed to silence tumor necrosis factor alpha (TNFalpha) was investigated. RESULTS: Luciferase activity could be reduced by >90% with luciferase-specific siRNA as compared with the activity measured after electroporation without siRNA or with irrelevant siRNA. The effect was observed only locally. In mice with CIA, electroporation of siRNA designed to inhibit TNFalpha strongly inhibited joint inflammation, whereas electroporation of irrelevant siRNA or injection of siRNA against TNFalpha without electroporation failed to produce therapeutic effects. CONCLUSION: Local electroporation of siRNA in joint tissue can inhibit CIA in mice. These results offer promise for the use of siRNA as a new strategy for therapeutic intervention in rheumatoid arthritis and may serve as a tool to study arthritis disease pathways through loss-of-function phenotypes.

Animals↗

PubMed2005

Long-circulating sterically stabilized liposomes in the treatment of infections.

The administration of antimicrobial agents encapsulated in long-circulating sterically stabilized liposomes results in a considerable enhancement of therapeutic efficacy compared with the agents in the free form. After liposomal encapsulation, the pharmacokinetics of the antimicrobial agents is significantly changed. An increase in circulation time and reduction in toxic side effects of the agents are observed. In contrast to other types of long-circulating liposomes, an important characteristic of these sterically stabilized liposomes is that their prolonged blood circulation time is, to a high degree, independent of liposome characteristics such as liposome particle size, charge and lipid composition (rigidity) of the bilayer, and lipid dose. This provides the opportunity to manipulate antibiotic release from these liposomes at the site of infection, which is important in view of the differences in pharmacodynamics of different antibiotics and can be done without compromising blood circulation time and degree of target localization of these liposomes. Depending on the liposome characteristics and the agent encapsulated, antibiotic delivery to the infected site is achieved, or the liposomes act as a micro-reservoir function for the antibiotic. In experimental models of localized or disseminated bacterial and fungal infections, the sterically stabilized liposomes have successfully been used to improve antibiotic treatment using representative agents of various classes of antibacterial agents such as the beta-lactams, the aminoglycosides, and the quinolones or the antifungal agent amphotericin B. Extensive biodistribution studies have been performed. Critical factors that contribute to liposome target localization in infected tissue have been elucidated. Liposome-related factors that were investigated were poly(ethylene glycol) density, particle size, bilayer fluidity, negative surface charge, and circulation kinetics. Host-related factors focused on the components of the inflammatory response.

Ammonium Sulfate↗

PubMed2005

siRNA-mediated inhibition of angiogenesis.

Small interfering RNA (siRNA) has rapidly become the agent of choice for gene function analysis through loss-of-function phenotypes. Especially in complicated (patho)physiological processes such as angiogenesis, where vast numbers of proteinaceous factors are involved, the siRNA application allows relatively fast analysis of pathways and identification of new target genes. The first studies on the therapeutic effects of siRNA in angiogenesis show that this new 'drug' class holds great promise for therapeutic intervention. Two strategies emerge: the use of unmodified or the use of complexed, targeted and/or protected nucleic acids. The challenge for clinical application will be to control off-target effects and the transient character of the sequence-specific silencing effect, and to address the targeted delivery to the cell types involved in the various stages of angiogenesis. This is especially important as clinical studies indicate a profound heterogeneity of the angiogenic vasculature.

Animals↗

PubMed2005

Liposomes in the treatment of inflammatory disorders.

This review focuses on the therapeutic utility of liposomes in the treatment of inflammatory disorders, and aims to offer the reader an overview of the in vivo results obtained with liposomally encapsulated anti-inflammatory and immune suppressive drugs. The past 30 years has clearly indicated the added value of liposomes in the search for solutions for the delivery problems encountered. However, only a few liposomal anti-inflammatory therapeutics have entered the clinic. Reasons for the hurdles existing in the translation of promising preclinical findings to clinical studies are discussed.

Anti-Inflammatory Agents↗

PubMed2005

Liposome-encapsulated prednisolone phosphate inhibits growth of established tumors in mice.

Glucocorticoids can inhibit solid tumor growth possibly due to an inhibitory effect on angiogenesis. The antitumor effects of the free drugs have only been observed using treatment schedules based on high and frequent dosing for prolonged periods of time. As long-circulating liposomes accumulate at sites of malignancy, we investigated the tumor-inhibiting potential of liposome-encapsulated prednisolone phosphate. Liposomal prednisolone phosphate could inhibit tumor growth dose-dependently, with 80% to 90% tumor growth inhibition of subcutaneous B16.F10 melanoma and C26 colon carcinoma murine tumor models at 20 mg/kg by single or weekly doses. Prednisolone phosphate in the free form was completely ineffective at this low-frequency treatment schedule, even when administered at a dose of 50 mg/kg. In vitro studies did not show an inhibitory effect of prednisolone (phosphate) on tumor cell, nor on endothelial cell proliferation. Histologic evaluation revealed that liposomal prednisolone phosphate-treated tumors contained a center with areas of picnotic/necrotic cells, which were not apparent in untreated tumors or tumors treated with the free drug. In conclusion, the present study shows potent antitumor effects of liposomal formulations of glucocorticoids in a low dose and low-frequency schedule, offering promise for liposomal glucocorticoids as novel antitumor agents.

Animals↗

PubMed2005

Liposomal targeting of angiogenic vasculature.

Active targeting of angiogenic vasculature represents a promising therapeutic strategy to fight a variety of diseases. In particular, attention has been focused on inhibition of tumor growth. In this review, the recent progress in targeting liposomes to angiogenic endothelial cells is discussed.

Angiogenesis Inhibitors↗