Megumu Higaki

The Jikei University School of Medicine, Edo, Tōkyō, Japan

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Publications (56)154.25 Total impact

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    ABSTRACT: The therapeutic effects of betamethasone phosphate (BP) encapsulated in biocompatible and biodegradable blended nanoparticles of poly(lactic acid) (PLA) homopolymers and PEG-block-PLA copolymers (stealth nanosteroids) were examined in an experimental autoimmune uveoretinitis (EAU) model in Lewis rats. EAU was induced by S-antigen peptide in Lewis rats. Accumulation of systemically administered Cy7-labeled stealth nanoparticles in inflamed eyes of rats with EAU was assessed using in vivo fluorescence imaging, and the therapeutic effect of stealth nanosteroids, nonstealth nanosteroids, or saline on EAU was examined. The eyes were obtained 7 days after the treatment, and the histologic score was determined using pathologic findings. The expression of inflammatory cytokines including IL-6, IL-17, and VEGF was determined immunohistochemically. Cy7-stealth nanoparticles accumulated in inflamed eyes of rats with EAU and remained in situ for a 3-day period. Systemically administered stealth nanosteroids (100 μg of BP) reduced the clinical scores of rats with EAU within 1 day and maintained the effect for 2 weeks. This treatment also decreased the histologic scores and the expression of inflammatory cytokines in the retina of EAU. The strong therapeutic benefit on EAU obtained with the stealth nanosteroids may have been due to prolonged blood circulation and targeting to the inflamed uvea and retina, in addition to sustained release in situ.
    No preview · Article · Dec 2010 · Investigative ophthalmology & visual science
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    ABSTRACT: This study aimed to investigate the efficacy of encapsulating steroids, which is a primary choice for the treatment of sensorineural hearing loss, in polyethylene glycol-coated polylactic acid nanoparticles for drug delivery to the cochlea. We prepared polyethylene glycol-coated polylactic acid nanoparticles encapsulating rhodamine or betamethasone phosphate (BP), and administered them systemically to CBA/N mice previously exposed to intense noise. We assessed nanoparticle distribution using rhodamine fluorescence, BP concentrations in tissues, nuclear translocation of glucocorticoid receptors and the function and histology of the mouse cochleae. Polyethylene glycol-coated polylactic acid nanoparticles delivered BP to cochleae over a sustained period, resulting in significant reductions in histological and functional damage to cochleae and indicating the potential therapeutic benefits of these nanoparticles for enhancing the delivery of BP in acute sensorineural hearing loss.
    Full-text · Article · Nov 2010 · Nanomedicine
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    ABSTRACT: Aim: Early disappearance of serum hepatitis C virus (HCV) RNA is the prerequisite for achieving sustained virological response (SVR) in peg-interferon (PEG-IFN) plus ribavirin (RBV) therapy for chronic hepatitis C. This study aimed to develop a decision tree model for the pre-treatment prediction of response. Methods: Genotype 1b chronic hepatitis C treated with PEG-IFN alpha-2b and RBV were studied. Predictive factors of rapid or complete early virological response (RVR/cEVR) were explored in 400 consecutive patients using a recursive partitioning analysis, referred to as classification and regression tree (CART) and validated. Results: CART analysis identified hepatic steatosis (<30%) as the first predictor of response followed by low-density-lipoprotein cholesterol (LDL-C) (≥100 mg/dL), age (<50 and <60 years), blood sugar (<120 mg/dL), and gamma-glutamyltransferase (GGT) (<40 IU/L) and built decision tree model. The model consisted of seven groups with variable response rates from low (15%) to high (77%). The reproducibility of the model was confirmed by the independent validation group (r2 = 0.987). When reconstructed into three groups, the rate of RVR/cEVR was 16% for low probability group, 46% for intermediate probability group and 75% for high probability group. Conclusions: A decision tree model that includes hepatic steatosis, LDL-C, age, blood sugar, and GGT may be useful for the prediction of response before PEG-IFN plus RBV therapy, and has the potential to support clinical decisions in selecting patients for therapy and may provide a rationale for treating metabolic factors to improve the efficacy of antiviral therapy.
    No preview · Article · Apr 2010 · Hepatology Research
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    ABSTRACT: We have prepared polymeric nanoparticles using a blend of poly(lactic acid) and monomethoxy-polyethyleneglycol(PEG)-polylactide block copolymer along with betamethasone disodium phosphate (BP). Nanoparticles have been screened for anti-inflammatory activity using experimental rat models of inflammation. In the present study, we examined the degradation of nanoparticles in vitro during incubation. We found that the nanoparticles lost the PEG chains present on their surfaces within a few days, and subsequently gradually released BP. Furthermore, we found that these nanoparticles preferentially accumulated in the inflammatory lesion in adjuvant arthritis rat models, and that the amount of BP gradually depleted from the lesion over 14 days. These results suggested the mechanism underlying the anti-inflammatory effect of the nanoparticles in vivo: the initial accumulation of BP in the lesion due to the enhanced permeability and retention effect, the subsequent internalization in inflammatory macrophages due to the loss of PEG, and the release of BP in cells during the hydrolysis of polymers. The nanoparticles were successfully prepared on a large-scale and stably stored in the form of a freeze-dried formulation for at least 69 weeks below 25 degrees C. These results suggest that the nanoparticles can be used as an anti-inflammatory pharmaceutical formulation in a clinical setting.
    No preview · Article · Oct 2009 · International Journal of Pharmaceutics
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    ABSTRACT: Although inhaled steroids are the treatment of first choice to control asthma, administration of systemic steroids is required for treatment of asthmatic exacerbation and intractable asthma. To improve efficacy and reduce side effects, we examine the effects of betamethasone disodium phosphate (BP) encapsulated in biocompatible, biodegradable blended nanoparticles (stealth nanosteroids) on a murine model of asthma. These stealth nanosteroids were found to accumulate at the site of airway inflammation and exhibit anti-inflammatory activity. Significant decreases in BALF eosinophil number were maintained for 7 days with a single injection of nanosteroids containing 40 microg BP. Airway responsiveness was also attenuated by the injection of stealth nanosteroids. A single injection of 40 microg of free BP and 8 microg of free BP once daily for 5 days did not show any significant effects. We conclude that stealth nanosteroids achieve prolonged and higher benefits at the site of airway inflammation compared to free steroids.
    No preview · Article · Sep 2009 · Cellular Immunology
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    ABSTRACT: The purpose of this study was to engineer nanoparticles with various sustained profiles of drug release and prolonged circulation by blending poly(D,L-lactic acid)/poly(D,L-lactic/glycolic acid) (PLA/PLGA) homopolymers and poly(ethylene glycol) (PEG)-block-PLA/PLGA copolymers encapsulating betamethasone disodium 21-phosphate (BP). Nanoparticles of different sizes, drug encapsulation/release profiles, and cellular uptake levels were obtained by mixing homopolymers and block copolymers with different compositions/molecular weights at various blend ratios by an oil-in-water solvent diffusion method. The in vitro release of BP increased with nanoparticles of smaller size or of PLGA homopolymers instead of PLA homopolymers. Furthermore, the uptake of nanoparticles by macrophage-like cells decreased with nanoparticles of higher PEG content, and nanoparticles of PEG-PLGA block copolymers were taken up earlier than those of PEG-PLA block copolymers after incubation with serum. In addition, prolonged blood circulation was observed with nanoparticles of smaller size with higher PEG content, and nanoparticles of PEG-PLA block copolymers remained longer in circulation than those of PEG-PLGA block copolymers. Analysis of BP concentration in organs revealed reduced liver distribution of blended nanoparticles compared with PLA nanoparticles. This is the first study to systematically design and characterize biodegradable PLA/PLGA and PEG-PLA/PLGA-blended nanoparticles encapsulating BP with different release profiles and stealthiness.
    No preview · Article · Jul 2009 · International Journal of Pharmaceutics
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    ABSTRACT: Polymeric micelles consisting of amphiphilic block copolymers have emerged as a promising carrier of various drugs, but unfortunately show a limited potential for encapsulating (solubilizing) such drugs. In this study, hybrid nanoparticles consisting of monomethoxypolyethyleneglycol-polylactide block copolymer (PEG-PLA) and oleic acid calcium salt were prepared to enhance the solubilization of poorly water-soluble drugs. Micelles made of a mixture of sodium oleate and PEG-PLA at various ratios were used as the template for preparation of the nanoparticles. These mixed micelles could efficiently solubilize poorly water-soluble drugs in aqueous media, when compared with polymeric micelles made of PEG-PLA alone. Addition of calcium to the mixed micelles induced the formation of oleic acid calcium salt, resulting in hybrid nanoparticles. These hybrid nanoparticles had a high colloidal stability, neutral zeta potential, and high drug entrapment efficiency. Drugs entrapped in nanoparticles made at a high PEG-PLA ratio were protected from enzymatic degradation in serum, while drugs entrapped in the mixed micelles were not, indicating that the hybrid nanoparticles show good drug retention. These results suggested that such hybrid nanoparticles may be used to expand the availability of poorly water-soluble drugs for various therapeutic applications.
    No preview · Article · Jul 2009 · Journal of Pharmaceutical Sciences
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    ABSTRACT: Prostaglandin E(1) (PGE(1)) is an effective treatment for peripheral vascular diseases. The encapsulation of PGE(1) in nanoparticles for its sustained-release would improve its therapeutic effect and quality of life (QOL) of patients. In order to encapsulate PGE(1) in nanoparticles prepared with a poly(lactide) homopolymer (PLA) and monomethoxy poly(ethyleneglycol)-PLA block copolymer (PEG-PLA), we synthesized a series of PGE(1) phosphate derivatives and tested their efficacy. Among them, PGE(1) 2-(phosphonooxy)ethyl ester sodium salt (C2) showed the most efficient hydrolysis to yield PGE(1) in human serum. An in vitro platelet aggregation assay showed that C2 inhibited aggregation only after pre-incubation in serum, suggesting that C2 is a prodrug of PGE(1). In vivo, intravenous administration of C2 caused increase in cutaneous blood flow. In the presence of zinc ions, all of the synthesized PGE(1) phosphate derivatives could be encapsulated in PLA-nanoparticles. Use of L-PLA instead of D,L-PLA, and high molecular weight PLA resulted in a slower release of C2 from the nanoparticles. We consider that C2-encapsulated nanoparticles prepared with L-PLA and PEG-D,L-PLA have good sustained-release profile of PGE(1), which is useful clinically.
    No preview · Article · Jun 2009 · Pharmaceutical Research
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    ABSTRACT: To achieve the effective intracellular delivery of siRNA and silence specific genes, various types of conjugates between cell-penetrating peptides (CPPs; Transportan, Penetratin, Tat) and cationic peptides were developed. Uptake, intracellular localization, cytotoxicity, and biological activity of siRNA were significantly dependent on the kind of CPP used and the length of the cationic peptides in the conjugate. Transportan-based conjugates yielded both high internalization of siRNA and strong gene silencing activity, while Penetratin- and Tat-based conjugates did not. These different properties of CPPs emphasize the importance of careful peptide selection and design when attempting the application of CPP technology.
    No preview · Article · May 2009 · Drug Delivery
  • Megumu Higaki · Yuko Higaki · Makoto Kawashima
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    ABSTRACT: Psoriasis is a chronic inflammatory skin disease characterized by epidermal hyperproliferation and infiltration of inflammatory leukocytes. The aim of this study was to clarify the role of innate immunity involving dendritic cells (DC) and keratinocytes in psoriasis. We immunohistochemically examined the expression of DC markers such as CD1a, CD83, CD207 (Langerin), CD208 (DC-LAMP) and CD209 (DC-SIGN) in psoriatic skin and gamma-interferon (IFN-gamma)/12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated keratinocytes in vitro. CD208 was strongly expressed in basal and suprabasal layer keratinocytes in addition to DC in the perivascular lesions of the psoriatic dermis. Furthermore, the enhanced expression of CD208 in the perinuclear lesions of IFN-gamma-/TPA-stimulated keratinocytes was observed in vitro. Because a defect of the granular layer in psoriatic lesions has been recognized, increased expression of lysosome-related CD208 in the basal and suprabasal keratinocytes of psoriatic lesions might represent aberrant epidermal differentiation. Additionally, these CD208-positive keratinocytes possessing putative antigen-processing activity might play a key role as antigen-presenting cells in psoriatic skin.
    No preview · Article · Apr 2009 · The Journal of Dermatology
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    Tsutomu Ishihara · Tetsushi Kubota · Tesu Choi · Megumu Higaki
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    ABSTRACT: We examined the therapeutic activity of betamethasone disodium 21-phosphate (BP) encapsulated in biocompatible and biodegradable blended nanoparticles of poly (D,L-lactic/glycolic acid) (PLGA)/poly(D,L-lactic acid) (PLA) homopolymers and polyethylene glycol (PEG)-block-PLGA/PLA copolymers (stealth nanosteroid) in experimental arthritis models. Various stealth nanosteroids with a size of 45 to 115 nm were prepared and then intravenously administered to rats with adjuvant arthritis (AA) rats and mice with anti-type II collagen antibody-induced arthritis (AbIA). The accumulation of stealth nanoparticles with Cy7 in inflamed joints was determined using an in vivo imaging system. The type A stealth nanosteroid, composed of PLA (2.6 kDa) and PEG (5 kDa)-PLA (3 kDa), with a PEG content of 10% and a diameter of 115 nm, exhibited the highest anti-inflammatory activity. In AA rats, a 35% decrease in paw inflammation was obtained in 1 day and maintained for 9 days with a single injection of the type A stealth nanosteroid (40 microg of BP), whereas the same does of nonstealth nanosteroid and 3 times higher free BP showed a significantly weaker response. In AbIA mice, a single injection of the type A stealth nanosteroid (3 microg of BP) resulted in complete remission of the inflammatory response after 1 week. Furthermore, in AbAI mice, the accumulation of type A stealth nanoparticles in inflamed joints was shown to parallel the severity of inflammation. The observed strong therapeutic benefit obtained with the type A stealth nanosteroid in experimental arthritis may have been due to prolonged blood circulation and targeting to the inflamed joint in addition to its sustained release in situ.
    Preview · Article · Mar 2009 · Journal of Pharmacology and Experimental Therapeutics
  • Megumu Higaki
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    ABSTRACT: The observed strong therapeutic benefit obtained with the stealth nanosteroid in experimental arthritis may have been due to prolonged blood circulation and targeting to the inflamed joint in addition to its sustained release in situ.
    No preview · Article · Jan 2009 · Drug Delivery System
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    Megumu Higaki

    Preview · Article · Jan 2009 · Inflammation and Regeneration
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    ABSTRACT: Solid nanoparticles consisting of biodegradable polymers have emerged as a promising carrier for various drugs, but unfortunately the encapsulation of drugs remains challenging. In this study, a technique for encapsulation of water-soluble drugs in solid nanoparticles was developed. Nanoparticles were prepared from a blend of biodegradable polymers, including poly(lactic acid) (PLA) and poly(lactic/glycolic acid) (PLGA), and monomethoxypolyethyleneglycol-polylactide block copolymer by an oil-in-water solvent diffusion method. Betamethasone sodium phosphate (BP) was not encapsulated by the nanoparticles due to its hydrophilicity, but it was effectively encapsulated in the presence of appropriate amounts of zinc and diethanolamine. It was found that BP formed an ionic complex with zinc at a certain pH range obtained by addition of diethanolamine. Furthermore, a carboxyl group located at the end of PLA/PLGA was shown to be essential for encapsulation of BP in nanoparticles, and the molar ratio among BP, zinc, and carboxyl groups in various nanoparticles was almost constant. These results strongly suggested that the encapsulation was promoted by zinc creating an ionic bridge between a carboxyl group on PLA/PLGA and a phosphate group on BP. This technique for entrapment of water-soluble drugs in solid biodegradable nanoparticles may expand the use of nanoparticles for various therapeutic applications.
    No preview · Article · Sep 2008 · International Journal of Pharmaceutics
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    ABSTRACT: Prostaglandins have potent and diverse biologic activities, but their clinical application is severely restricted, mainly due to rapid inactivation in vivo. In order to modulate the pharmacokinetics of prostaglandin E(1) (PGE(1)), we prepared biodegradable nanoparticles as a drug carrier. Nanoparticles encapsulating PGE(1) were prepared from a blend of poly(lactic acid) homopolymer and poly(ethylene glycol)-poly(lactide) block copolymer by the solvent diffusion method in the presence of iron. PGE(1) was efficiently and stably embedded in the nanoparticles through interaction with iron, despite being relatively hydrophilic and having unstable chemical properties. Depending on the isomers and molecular weight of poly(lactic acid) selected, PGE(1) was gradually released from the nanoparticles at various rates into diluted serum in vitro. Both stable retention of PGE(1) in the nanoparticles and coating of the nanoparticles with poly(ethylene glycol) led to an extremely extended blood residence time of PGE(1), as well as preferential accumulation in vascular lesions. These results suggest that the present strategy is useful to advance the clinical application of PGE(1) as a therapeutic agent for vascular disorders.
    No preview · Article · Aug 2008 · Pharmaceutical Research

  • No preview · Article · Jan 2008
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    ABSTRACT: This study investigated the molecular and pharmacokinetic mechanisms of the enhanced antiviral efficacy associated with pegylated interferon (PEG-IFN) alpha-2b and ribavirin. The study involved comparing the expression of serial double-stranded RNA-activated protein kinase (PKR) before and during treatment in 26 PEG-IFN alpha-2b and 26 conventional IFN alpha-2b recipients matched for age, body weight and dose of ribavirin. The pharmacokinetics of PEG-IFN alpha-2b and ribavirin was analysed in 15 of the 26 PEG-IFN recipients. There was a rapid increase in PKR expression in both treatment groups, although expression from day 2 onwards was maintained at a significantly higher level in the PEG-IFN recipients (P < 0.05). C(max) of PEG-IFN occurred 12-48 h after the initial administration, with t(1/2) and C(min) being 49 h and 190 pg/mL, respectively. In contrast to ribavirin, accumulation of PEG-IFN was minimal. There was no association between serum PEG-IFN and ribavirin levels and virological response. Although baseline expression of PKR before treatment was marginally higher in nonresponders (NRs), from day 2 onwards, sequential PKR expression in response to PEG-IFN was higher in sustained viral responders compared with the NRs (P < 0.05). Significant correlations were found between kinetics of PKR expression and viral decline rates in each phase of hepatitis C virus dynamics (first phase, r = 0.67, P = 0.0006; second phase, r = 0.67, P = 0.001). In conclusion, improvement in pharmacokinetics following pegylation led to higher intracellular PKR expression, which was associated with enhanced virological efficacy of PEG-IFN-based combination therapy. The concentrations of both ribavirin and PEG-IFN alpha-2b were not associated with viral response and PKR expression.
    No preview · Article · Jun 2007 · Journal of Viral Hepatitis
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    ABSTRACT: To detect dioxin using a quartz crystal microbalance (QCM) immunosensor, anti-2,3,7,8-tetrachloro-p-dibenzodioxin (TCDD) monoclonal antibodies (MAbs) were produced as types of IgG1 and IgM, with mono 6-(2,3,6,7-tetrachloroxanthene-9-ylidene) hexyl succinate (as a hapten) conjugated with bovine serum albumin (dioxin-BSA). Furthermore, ScFv was generated from hybridoma-producing IgG1 MAb. Among these antibodies, ScFv showed excellent capability for dioxin detection using QCM immunosensors.
    No preview · Article · Oct 2006 · Biosensors & Bioelectronics
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    ABSTRACT: This study evaluates the pharmacokinetic and pharmacodynamic effects of a transdermally delivered insulin using novel CaCO(3)-nanoparticles in normal mice and those with diabetes. CaCO3-nanoparticles encapsulating insulin (nanoinsulin) were transdermally applied to the back skin of normal ddY mice and dB/dB and kkAy mice with diabetes after fasting for 1 h. Serum insulin levels of ddY mice were analyzed by enzyme immunoassay, and blood glucose of normal mice and those with diabetes was monitored. Maximum serum insulin was 67.1 +/- 25.9 microIU/mL at 4 h with 200 microg of transdermal nanoinsulin in ddY mice, whereas that after subcutaneous injection of 3 microg of monomer insulin was 462 +/- 20.9 microIU/mL at 20 min. Transdermal nanoinsulin decreased glucose levels in a dose-dependent manner. A maximum decrease in blood glucose of 48.3 +/- 3.9% (ddY), 32.5 +/- 9.8% (dB/dB), and 26.2 +/- 7.6% (kkAy) after 6 h was observed with 200 microg of transdermal nanoinsulin, compared with 64.1+/-1.0% (ddY), 57.9 +/-3.4% (dB/dB), and 24.1 +/- 6.7% (kkAy) after 1 h with 3 microg of subcutaneous monomer insulin. Insulin bioavailability until 6 h with transdermal nanoinsulin in ddY mice was 0.9% based on serum insulin level and 2.0% on pharmacodynamic blood glucose-lowering effects. This CaCO(3)-nanoparticle system successfully delivered insulin transdermally, as evidenced by a significant sustained decrease in blood glucose in normal mice and those with diabetes. These results support the feasibility of developing transdermal nanoinsulin for human applications.
    No preview · Article · Jul 2006 · Diabetes Technology & Therapeutics
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    ABSTRACT: We have developed nanoparticles (NPs), which are capable of targeting a specific lesion and gradually releasing the agent at the site over a prolonged time period after a single intravenous administration. In this study, we evaluated the effects of intravenously administered poly(lactic acid) nanoparticles encapsulating betamethasone phosphate (BP-PLA NPs) on experimental autoimmune uveoretinitis (EAU) in Lewis rats. To determine the localization of NPs within the retina and choroid of rats with EAU, rhodamine (Rh)-encapsulated PLA NPs were injected intravenously and visualized by confocal microscopy. After the disease onset of EAU induced by S-antigen peptide in Lewis rats, either BP-PLA NPs, BP, or saline was injected intravenously, and the eyes were obtained 7 days following treatment and the histological score was determined. The clinical course of EAU was examined using pathological findings and the expression of the glial fibrillary acidic protein, rod opsin, and the surface markers of inflammatory cells (ED1 and pan T-cell) were immunohistochemically determined. Furthermore, T-cell proliferation and delayed-type hypersensitivity (DTH) to S-antigen were assessed. Intravenously injected Rh-PLA NPs accumulated in the retina and choroid of rats with EAU within 3 hr and remained over the succeeding 7-day-period. Furthermore, systemically administered BP-PLA NPs reduced the clinical scores of rats with EAU in 1 day, which were maintained for 2 weeks and decreased the histological scores. In addition, the ocular infiltration of activated T-cells and macrophages in addition to the hypertrophy of Müller cells were markedly reduced with this treatment. Meanwhile, T-cell proliferation and DTH of BP-PLA NPs-treated rats against S-antigen peptide were not significantly different from those of saline-treated rats. Systemically administered BP-PLA NPs inhibit the development of EAU due to the targeting and the sustained release of steroids in situ. The results of these studies suggest that the systemic administration of BP-PLA NPs may lead to a new therapeutic strategy in controlling intraocular inflammation.
    No preview · Article · May 2006 · Experimental Eye Research

Publication Stats

1k Citations
154.25 Total Impact Points


  • 2006-2010
    • The Jikei University School of Medicine
      • Research Center for Medical Science
      Edo, Tōkyō, Japan
  • 1996-2005
    • St. Marianna University School of Medicine
      • • Institute of Medical Science
      • • Department of Medicine
      Kawasaki Si, Kanagawa, Japan
  • 1990-1993
    • Tokyo Medical and Dental University
      • • Medical Research Institute
      • • Department of Immunology
      • • Department of Microbiology
      Edo, Tōkyō, Japan
  • 1992
    • Nippon Medical School
      Edo, Tokyo, Japan