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Biomedical subjects

Tatsuhiro Ishida

Publications and source records attributed to Tatsuhiro Ishida.

28 records · Page 2Linked to original sources
PubMed2003

Accelerated clearance of a second injection of PEGylated liposomes in mice.

We recently reported that the firstly injected PEGylated liposomes dramatically affected the rate of blood clearance of secondly injected PEGylated liposomes in rats in a time interval of injection dependent manner [J. Control. Release (2003)]. Mice are frequently used in evaluations of the therapeutic efficacy of PEGylated liposomal formulations, but the pharmacokinetics of repeatedly injected PEGylated liposomes in mice is not fully understood. In this study, therefore, we examined in mice the effect of the repeated injection of PEGylated liposomes on their pharmacokinetics. An intravenous pretreatment with PEGylated liposomes produced a striking change in the biodistribution of the second dose which was given several days after the first injection. The first dose resulted in a reduction in the circulation half-life of the second dose. The degree of alteration was dependent on the time interval between the injections. The rapid clearance of the second dose was strongly related to hepatic clearance (CLh). This finding suggests that a considerable increase in hepatic accumulation accounts for this phenomenon. But, no liver injury or an increase in the number of Kupffer cells were detected in histopathological evaluations. Collectively, although the multiple injections of the PEGylated liposomes had no obvious physical effects, such as inflammation, their pharmacokinetic behavior was clearly altered in mice. The results obtained here have important implications not only with respect to the design and engineering of liposomes for human use, but for evaluating the therapeutic efficacy of liposomal formulations in experimental animal models as well.

Animals↗
PubMed2003

Accelerated clearance of PEGylated liposomes in rats after repeated injections.

Polyethylene glycol-modified liposomes (PEGylated liposomes) represent promising carrier systems for therapeutic agents. Herein, we report on a study of the effect of repeated injection of PEGylated liposomes on their pharmacokinetics in rats. The first dose resulted in a reduction in the circulation time and an increase in hepatic accumulation of the second dose in a time-interval of injection-dependent manner. No significant increases in the number of Kupffer cells were detectable, although the liver most likely played an important role in the accelerated clearance. Interestingly, the acceleration in clearance became less pronounced, when the third dose was injected at 4, 7 or 14 days after the second injection (the second dose was given 5 weeks after the first injection). An accelerated clearance was evoked in normal rats by the transfusion of serum from rats that had received PEGylated liposomes 5 days earlier, indicating that humoral serum factor(s) are also involved in causing the accelerated clearance. A complement consumption assay indicated that the complement system is not the factor. In summary, multiple injections of PEGylated liposomes clearly altered their pharmacokinetic behavior in rats. It is likely that cellular immunity (Kupffer cells) and humoral immunity are required to cause the phenomenon. The results reported here have a considerable impact in and important implications on the clinical application, design and engineering of PEGylated liposomes for use in repeated intravenous administration.

Animals↗
PubMed2003

Culture time-dependent gene expression in isolated primary cultured rat hepatocytes by transfection with the cationic liposomal vector TFL-3.

The development of a carrier system that enables the transfer of a functional exogenous gene to non- or less frequently dividing mammalian cells is essential for increasing the available options for the treatment of various diseases. The issue of whether TFL-3, a recently developed cationic liposome, can be successfully used to achieve gene expression in primary cultured rat hepatocytes was examined. The hepatocytes were transfected for 4 h with plasmid DNA (pDNA) in TFL-3 at various time points after 4-h preculture. The transfection efficiency was determined at various times posttransfection with pDNA coding for chloramphenicol acetyltransferase (CAT), luciferase, or beta-galactosidase. The amount of intranuclear pDNA present, as a consequence of the lipofection, was also quantitatively determined. Successful lipofections were observed for all pDNA tested, and the efficiencies were superior to that of commercially available LIPOFECTAMINE under our experimental conditions. The degree and rate of gene expression were dependent on incubation time prior to lipofection as well as on the density of the cells per dish, but this relationship did not hold for the amount of gene delivered to the nuclei. These results indicate that TFL-3 could be a useful vector for achieving sufficient gene expression in rat hepatocytes and suggest that the culture time prior to and following lipofection, which is related to the biological condition of the cells, may be one major factor affecting efficient gene expression in nondividing cells.

Animals↗
PubMed2002

HEPC-based liposomes trigger cytokine release from peripheral blood cells: effects of liposomal size, dose and lipid composition.

The immune response caused by liposome stimulation was studied by assessing the level of several cytokines released from human peripheral blood cells. Liposome stimulation resulted in the release of IL-6, IL-10, IL-1beta, TNF-alpha and IFN-gamma. The size of the liposomes affected the degree of the cytokine releases with larger sized liposomes causing higher levels of cytokine induction. In addition, it appears that the lipid composition of liposomes had no effect on the degree of cytokine release. The release of cytokines occurred even in the absence of serum, suggesting that serum proteins did not contribute to liposome stimulation in peripheral blood cells. The release of cytokines induced by liposome stimulation was inhibited by the presence of either protein kinase-C (PKC) or protein tyrosine kinase (PTK) inhibitor, but not by the presence of an endocytosis inhibitor. This indicates that signal transduction via PKC or PTK is necessary, in order for human peripheral blood cells to release cytokines (IL-6, IL-10, IL-1beta, TNF-alpha and IFN-gamma) as the result of liposome stimulation. These quantitative data on the release of cytokines by liposomal stimulation provide useful information for the development of rational drug delivery systems and the safety of cytokine induction via the use of liposomes.

Cytokines↗
PubMed2002

Encapsulation of an antivasospastic drug, fasudil, into liposomes, and in vitro stability of the fasudil-loaded liposomes.

The objectives of this work were to develop a liposomal fasudil, an antivasospastic drug, as a possible means to deliver the encapsulated drug to the brain, and to characterize the stability of the liposomal formulation in vitro. Transmembrane electrochemical gradients of H+ or ammonium sulfate were created, and their effect on the uptake of fasudil into preformed hydrogenated soy phosphatidylcholine/cholesterol (HSPC/CHOL) liposomes were examined. Fasudil was successfully loaded into preformed liposomes in response to sulfate ion (SO4(2-)) and, in part, by H+. Encapsulation levels approaching 100% could be achieved up to a drug to lipid ratio of 0.364 (mol/mol). A stability study of the fasudil-loaded liposomes was performed by storage at 4 degrees C in 4-(2-hydroxyethyl)-1-piperazineethanesulphonic acid (HEPES)-buffer (pH 7.4) and by incubation in human cerebrospinal fluid (CSF) at 37 degrees C. The formulations were stable with respect to drug retention as well as size alteration, for the period studied. A leakage study clearly showed the sustained release properties of the fasudil-loaded liposomes in human CSF. We recently reported that the intrathecal administration of liposomal fasudil significantly decreased ischemia, with no obvious adverse effect in a rat model [Neurol. Med. Chir. 41 (2001) 109]. Taken together, efficient encapsulation of fasudil into preformed liposomes, their long-term stability at 4 degrees C and the sustained release characteristics in CSF indicate that fasudil-loaded liposomes could be potential candidates for further clinical evaluation.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed2002

Use of the post-insertion technique to insert peptide ligands into pre-formed stealth liposomes with retention of binding activity and cytotoxicity.

PURPOSE: Simple methods for the large-scale manufacture of ligand-targeted liposomes will be needed if clinical trials are to proceed. We tested a recently developed technology for inserting peptide ligands into preformed Stealth liposomes. Antagonist G-targeted liposomes (PLG) were prepared and loaded with doxorubicin and their cellular association and cytotoxicity were evaluated using the human small cell lung cancer H69 cell line. METHODS: The hexapeptide antagonist G was covalently coupled via a thioether bond to the terminus of polyethylene glycol (PEG) in micelles formed from maleimide-derivatized poly(ethylene glycol) (Mr 2000) distearoylphosphatidylethanolamine followed by transfer into preformed liposomes during a one-step incubation. For cellular association, we used radiolabeled liposomes. Cytotoxicity was evaluated using the MTT in vitro proliferation assay. RESULTS: The postinsertion approach to the formation of peptide-targeted liposomes led to the production of PLG bearing a maximum of approximately 0.3 microg antagonist G/micromol phospholipid. These liposomes had increased cellular association to H69 cells relative to nontargeted liposomes and, when loaded with doxorubicin, they resulted in similar levels of cytotoxicity to those obtained by conventional coupling techniques. CONCLUSIONS: The postinsertion technique is a simple, effective means for the production of biologically active peptide-targeted liposomes.

Binding Sites↗
PubMed2002

Liposome clearance.

The clearance rate of liposomal drugs from the circulation is determined by the rate and extent of both drug release and uptake of liposomes by cells of the mononuclear phagocyte system (MPS). Intravenously injected liposomes initially come into contact with serum proteins. The interaction of liposomes with serum proteins is thought to play a critical role in the liposome clearance. Therefore, in this review, we focus on the role of serum proteins, so-called opsonins, that enhance the clearance of liposomes, when bound to liposomes. In addition to opsonin-dependent liposome clearance, opsonin-independent liposome clearance is also reviewed. As opposed to the conventional (non-surface modification) liposomes, we briefly address the issue of the accelerated clearance of PEGylated-liposomes (sterically stabilized liposomes, long-circulating liposomes) on repeated injection, a process that has recently been observed.

Animals↗
PubMed2002

Effect of cationic liposomes in an in vitro transcription and translation system.

The effects of cationic liposomes complexed with plasmid DNA on the process of transcription was examined using a recently developed rapid cell free translation system. The findings indicate that the liposome itself inhibited the process when the ratio of DNA/liposome typically used in transfection studies was used.

Amino Acid Sequence↗
PubMed2002

Pharmacokinetics of targeting with liposomes.

The optimization of drug disposition in the body leads to an increase in its therapeutic effect and to a decrease in adverse effects. Liposomes can serve as a potential drug carrier for achieving this. However, the behavior of a drug carrier system under in vivo conditions is complex. Therefore, a more complete understanding of the pharmacokinetics of liposomes themselves, as well as that of the encapsulated drug, is required. The optimization of the pharmacokinetics of liposomes can be performed by linking a pharmacodynamic model of the free drugs that are encapsulated into liposomes. Sensitivity analysis was applied to optimize the delivery system to maximize the antitumor effect of liposomal doxorubicin (DOX). Advanced technology for ligand-mediated selective targeting and intracellular targeting is also introduced for antitumor agents and for gene delivery systems.

Animals↗