Hirotaka Miyamoto

Publications of Hirotaka Miyamoto

• Evaluation of changes in hepatic disposition of phenolsulfonphthalein, indocyanine green and fluorescein isothiocyanate-dextran at low temperatures using a rat liver perfusion system.

  Authors: Hirotaka Miyamoto, Hideaki Miyake, Naoki Yoshikawa, Haruna Hirata, Yuichi Ohwaki, Shintaro Fumoto, Hitoshi Sasaki, Junzo Nakamura, Koyo Nishida

  The Journal of pharmacy and pharmacology. 06/2012; 64(6):848-54.

  Objectives  The aim of this study was to determine the factor changing the hepatic disposition of a drug during hypothermia using a rat liver perfusion system. Methods  The livers of male Wistar ratsObjectives  The aim of this study was to determine the factor changing the hepatic disposition of a drug during hypothermia using a rat liver perfusion system. Methods  The livers of male Wistar rats were perfused at 37, 32 or 28°C in the single-pass mode. Venous outflow dilution patterns and biliary excretion rate patterns of phenolsulfonphthalein (PSP), indocyanine green (ICG) and fluorescein isothiocyanate (FITC)-dextran (FD-4, MW 4400) after the injection of a bolus into the perfused rat liver were analysed based on statistical moment theory. Key findings  The first-pass extraction ratio (E(h) ) of PSP was significantly decreased at 32 and 28°C compared with 37°C. The biliary recovery of PSP and its conjugate was decreased and the biliary excretion was kept at a high concentration and was prolonged by low perfusion temperatures. ICG was almost extracted by a single-pass through the liver even at 32 and 28°C. The biliary recovery of ICG was significantly decreased at low temperature. Although the distribution volume of FD-4 as a vascular reference was not changed by perfusion temperature, the E(h) of FD-4 was decreased at 28°C although not markedly. Conclusion  The change in hepatic disposition of a drug at low perfusion temperatures differed according to disposition processes under hypothermia.

• Multiple components in serum contribute to hepatic transgene expression by lipoplex in mice.

  Authors: Naoki Yoshikawa, Keiko Sakamoto, Sachiyo Mizuno, Junichiro Sakaguchi, Hirotaka Miyamoto, Toyoharu Mine, Hitoshi Sasaki, Shintaro Fumoto, Koyo Nishida

  The journal of gene medicine. 11/2011; 13(11):632-43.

  Interaction of cationic liposome/plasmid DNA complex (lipoplex) with serum was not a limiting factor for in vivo transfection. After intraportal injection of lipoplex, hepatic transgene expressionInteraction of cationic liposome/plasmid DNA complex (lipoplex) with serum was not a limiting factor for in vivo transfection. After intraportal injection of lipoplex, hepatic transgene expression was enhanced by interaction with serum in mice. In the present study, we analyzed the mechanism of enhanced hepatic transgene expression of lipoplex by interaction with serum components. Lipoplexes were incubated with several serum components for 5  min at 37  ° C before administration. Transfection efficiency of lipoplexes was measured 6  h after intraportal injection of lipoplex in mice. Depletion of divalent cation from serum decreased hepatic transgene expression. The addition of calcium ion to divalent cation-depleted serum restored transgene expression. Heat-inactivated serum and bovine serum albumin diminished the enhancing effect of serum on hepatic transgene expression. On the other hand, removal of anionic proteins from serum using an anion-exchanging column was critical for the enhancing effect of serum on transgene expression. Among the serum components tested, fibronectin and complement component C3 enhanced hepatic transgene expression. Hepatic transgene expression by lipoplex was enhanced by interaction with multiple components in serum. Interaction of lipoplex with serum could be an important factor for successful in vivo gene transfer. Hence, the information obtained in the present study is valuable for the future development of effective gene carriers.

• Relationship between lipophilicity and absorption from the liver surface of paraben derivatives and antipyrine in rats.

  Authors: Koyo Nishida, Masanori Kobayashi, Hirotaka Miyamoto, Naoki Yoshikawa, Shintaro Fumoto, Hitoshi Sasaki, Junzo Nakamura

  The Journal of pharmacy and pharmacology. 05/2011; 63(5):736-40.

  The importance of drug lipophilicity on absorption from the liver surface was examined in rats using paraben derivatives, antipyrine, Sudan III, and Sudan blue. The log partition coefficient (PC) ofThe importance of drug lipophilicity on absorption from the liver surface was examined in rats using paraben derivatives, antipyrine, Sudan III, and Sudan blue. The log partition coefficient (PC) of n-octanol/water ranged from -1.39 to 4.62. The compounds were applied to the rat liver surface using a cylindrical diffusion cell (i.d. 9 mm). The rate of absorption at 15 min was calculated to be 13.9% for paraben, much lower than that for its derivatives methylparaben, propylparaben and butylparaben (∼ 80%). The obtained first-order absorption rate constant (k(a) ) of paraben, methylparaben, propylparaben and antipyrine increased according to lipophilicity. Further lipophilicity resulted in a fall in k(a) , implying the importance of affinity for lipids and water in absorption from the liver surface. Thus, a compound with a log PC of around 2.5 is considered to have maximum absorbability from the rat liver surface. A good relationship (r(2) = 0.97) was recognized between the log k(a) and log reciprocal value with the square root of molecular weight of the compounds with a log PC below 2.5. The rate of absorption of a drug from the liver surface could be estimated from physicochemical properties such as lipophilicity and molecular weight.

• Rubbing gastric serosal surface enhances naked plasmid DNA transfer in rats and mice.

  Authors: Toyoharu Mine, Hiroki Ishii, Sayuri Nakajima, Naoki Yoshikawa, Hirotaka Miyamoto, Mikiro Nakashima, Junzo Nakamura, Shintaro Fumoto, Koyo Nishida

  Biological & pharmaceutical bulletin. 01/2011; 34(9):1514-7.

  We have developed in vivo gene transfer to mesothelial cells on the peritoneal organs, including the stomach. Simple instillation of naked plasmid DNA onto the gastric serosal surface in miceWe have developed in vivo gene transfer to mesothelial cells on the peritoneal organs, including the stomach. Simple instillation of naked plasmid DNA onto the gastric serosal surface in mice resulted in effective but transient transgene expression. Here, we developed a simple method to improve not only the transfection efficiency but also the duration of transgene expression. Rubbing the gastric serosal surface using a medical spoon immediately after instillation of naked plasmid DNA onto the gastric serosal surface resulted in 59-fold higher transgene expression 24 h after administration in rats. Without rubbing, transgene expression decreased under the detection limit 7 d after administration. On the other hand, rubbing the gastric serosal surface with a medical spoon after instillation of plasmid DNA prolonged transgene expression for one month. Mechanistic study in mice revealed that improved transfection should not be due to stimulation of cell function such as macropinocytosis by rubbing because rubbing before instillation of plasmid DNA did not improve transfection. Plasmid DNA should enter effectively into cells during rubbing. These findings are valuable to develop an effective method of in vivo gene transfer into peritoneal organs.

• Rac-Mediated Macropinocytosis Is a Critical Route for Naked Plasmid DNA Transfer in Mice.

  Authors: Shintaro Fumoto, Junya Nishi, Hiroki Ishii, Xuan Wang, Hirotaka Miyamoto, Naoki Yoshikawa, Mikiro Nakashima, Junzo Nakamura, Koyo Nishida

  Molecular pharmaceutics. 07/2009;

  We have recently discovered the potential for in vivo naked plasmid DNA (pDNA) transfer into gastric serosal surface cells in mice. As pDNA are huge molecules, the mechanism of gene transfer withoutWe have recently discovered the potential for in vivo naked plasmid DNA (pDNA) transfer into gastric serosal surface cells in mice. As pDNA are huge molecules, the mechanism of gene transfer without carriers and physical forces is of great biological interest. The endocytic route for naked pDNA transfer into gastric mesothelial cells was not clathrin- or caveolae-mediated endocytosis, but macropinocytosis. Naked pDNA transfer required both actin polymerization and myosin-based contraction. Upstream kinases of Rho family GTPases, Syk, Src family kinases and PI-3K were involved in naked pDNA transfer. Furthermore, the intracellular signaling pathway was not mediated via the Rho pathway, but by the Rac pathway. Downstream molecules of Rac, PAK and WAVE2 co-operated with naked pDNA transfer. Overall, it was demonstrated that the Rac signaling pathway regulated the macropinocytosis of naked pDNA. The information in this study would be helpful to clarify in vivo cell functions and to improve in vivo transfection efficiency.