Sei Yonezawa

Induction of Intensive Tumor Suppression by Antiangiogenic Photodynamic Therapy Using Polycation-Modified Liposomal Photosensitizer

The authors previously observed that antiangiogenic scheduling of photodynamic therapy (PDT) was effective in causing tumor regression through hemostasis. It would thus be expected that photosensitizer entrapped in polycation liposomes (PCLs) would be efficiently taken up in tumor‐derived angiogenic vascular endothelial cells due to the strong electrostatic adhesion between the polycation and the plasma membrane, thus resulting in enhanced phototherapeutic efficacy.

Disappearance of the angiogenic potential of endothelial cells caused by Argonaute2 knockdown

Argonaute2 (Ago2), a component protein of RNA-induced silencing complex, plays a central role in RNA interference. We focused on the involvement of Ago2 in angiogenesis. Human umbilical vein endothelial cells (HUVECs) stimulated with several growth factors such as vascular endothelial growth factor were used for angiogenesis assays. We applied polycation liposomes for transfection of small interfering RNA (siRNA) to determine the biological effects of siRNA for Ago2 (siAgo2) on HUVECs. The proliferation study indicated that siAgo2 significantly suppressed the growth of HUVECs compared with control siRNA. TUNEL staining showed a certain population of HUVECs treated with siAgo2 underwent apoptosis. Furthermore, the treatment with siAgo2 suppressed the tube formation of HUVECs and significantly reduced the length of the tubes. These present data demonstrate that siAgo2 inhibited indispensable events of angiogenesis in vitro. This is the first report suggesting that Ago2 is required for angiogenesis.

Suppression of immune response by antigen-modified liposomes encapsulating model agents: A novel strategy for the treatment of allergy

A specific antigen-sensitized animal has antigen-specific immune cells that recognize the antigen. Therefore, an antigen-modified drug carrier would be recognized by the immune cells. When such a carrier encapsulates certain drugs, these drugs should be specifically delivered to the immune cells. To examine this strategy, ovalbumin (OVA) was used as model antigen, and mice were presensitized with 100 μg of OVA with Alum. For preparing OVA-modified liposomes (OVA-lipo), OVA was incubated with DSPE-PEG-NHS and resulting DSPE-PEG-OVA was inserted into liposomes. OVA-specific IgG was produced 6-fold higher by intravenous injection of OVA-lipo thrice (10 μg as OVA in each injection) in OVA-sensitized mice, than that by the injection of control liposomes, suggesting that OVA-lipo was recognized by the antigen-specific immune cells. Moreover, intra-splenic accumulation of OVA-lipo was observed in OVA-sensitized mice, but not in naive mice. To achieve the delivery of a drug to specific immune cells, OVA-lipo encapsulated low dose of doxorubicin (DOX) as a model drug (20 μg DOX/mouse, Ca. 1 mg/kg) was injected in the sensitized mice. The injection of OVA-lipo encapsulating DOX suppressed the production of IgE against OVA, suggesting that the specific delivery of the drug to immune cells responsible for OVA recognition was achieved and that these immune cells were removed by the drug treatment. This strategy would be useful for the fundamental treatment of allergy by the use of immunosuppressing agents.

Specific delivery of an immunosuppressive drug to splenic B cells by antigen-modified liposomes and its antiallergic effect.

Abstract Background: Use of the reverse targeting drug delivery system (RT-DDS) is a new targeting strategy based on the specific delivery of drugs to immune cells in antigen-sensitized animals by using antigen-modified liposomes, and it is expected to be a curative treatment for allergic diseases. Purpose: Herein, we prepared ovalbumin (OVA)-modified liposomes encapsulating the immunosuppressive drug FK506 (OVA-LipFK) and aimed to demonstrate the delivery selectivity of the liposomes to splenic B cells, and its antiallergic effect in an OVA-sensitized allergic model mouse. Methods: Fluorescently labeled OVA-LipFK was intravenously injected into OVA-sensitized mice, and the intrasplenic localization of liposomes was observed. The antiallergic effect of OVA-LipFK in OVA-sensitized mice was examined by measuring the blood levels of OVA-specific IgE and IgG antibodies. Results and discussion: OVA-LipFK was co-localized to not only B cells but also germinal centers, in the spleen of OVA-sensitized mice. However, there was no accumulation of unmodified liposomes encapsulating FK506 (LipFK) in the splenic B-cell area. In a therapeutic study, OVA-LipFK significantly suppressed the production of both OVA-specific IgE and IgG antibodies in OVA-sensitized mice after the animals had been boosted with OVA, whereas LipFK showed little antiallergic effect. Conclusions: The present study suggested that the introduction of RT-DDS for use with immunosuppressive drugs could be useful for the treatment of allergic diseases.