Tetsuo Hoshino

Enhancement of fracture repair in rats with streptozotocin-induced diabetes by a single injection of biodegradable microcapsules containing a bone formation stimulant, TAK-778

The feasibility of using microcapsules containing a bone formation stimulant, (2R,4S)-(-)-N-(4-diethoxyphosphorylmethylphenyl)-1,2,4, 5-tetrahydro-4-methyl-7, 8-methylenedioxy-5-oxo-3-benzothiepin-2-carboxamide (TAK-778) to enhance fracture repair was assessed in rats with streptozotocin-induced diabetes. The release profile of the microcapsules was designed to mimic a dosing regimen of multiple injections of TAK-778 solution. The solution was injected locally every third day from day 0 (the day of operation) to day 27 according to several dosing regimens, and fracture repair was assessed at day 28. The production of callus was most prominent when TAK-778 solution was injected so that 50-75% of the total dose (5 mg TAK-778/site) was administered during the first half of the treatment period. Thus, injectable microcapsules of 30 micrometer in mean diameter were prepared in order to release TAK-778 over 4 weeks using a biodegradable polymer, poly(d,l-lactic/glycolic) acid, with a copolymer ratio of 85:15 (mol/mol) and an average molecular weight of 14,000. A single local injection of the microcapsules markedly enhanced fracture repair, which resulted in recovery of destructive bending strength of the bone at day 28. Histologically, the injection of TAK-778 microcapsules stimulated both fibrous and cartilaginous proliferation and periosteal ossification in the callus at day 7; bony bridge formation was observed at day 28. At day 56, the callus was remodeled and cortical bony union was evidenced in the microcapsule-treated fractures compared with the controls, which showed only fibrous union.

Receptor-binding, in vitro cytotoxicity, and in vivo distribution of transferrin-bound cis-platinum (II) of differing molar ratios

Abstract Complexes of cis-diamminedichloroplatinum(II) (cisplatin) and transferrin (Tf(Fe)2) of differing molar ratios ( Pt Tf 3:1, 7:1, and 15:1 mol/mol) were prepared. Tf-receptor binding studies showed that the reactivity of Tf(Fe)2 to Tf receptors on A431 cells was reduced as the binding ratio of Pt to Tf(Fe)2 increased. The complexes of Pt Tf 3:1 and Pt Tf 7:1 inhibited the binding of 125I-Tf(Fe)2 to A431 cells with Ki values of 26 nM and 73 nM, respectively, while the complex of Pt Tf 15:1 did not show any inhibitory activity. The in vitro cytotoxicity of Pt against A431 cells also reduced as the ratio of Pt to Tf(Fe)2 increased, and IC50 of Pt were 15 μM, 13 μM, and 44 μM, for the complex of Pt Tf 3:1, Pt Tf 7:1, and Pt Tf 15:1, respectively. The pharmacokinetic analysis showed that the Pt-elimination from blood was delayed when Pt was administered in the form of the complex, while the Pt-elimination rate became higher in proportion as the ratio of Pt to Tf(Fe)2 increased. Thus, it was concluded that the receptor-binding activity, the cytotoxicity, and in vivo distribution of the complex could be optimized by altering the binding ratio of Pt to Tf(Fe)2, and the complex of Pt Tf 3:1 seemed to be most appropriate for the tumor-specific delivery of Pt.

Reduction in antiviral activity of human interferon-γ in acidic media with reference to structural change

The fluorescence intensity of a unique tryptophan 36 in human interferon-gamma was drastically decreased below pH 4 with a concomitant decrease of antiviral activity. The region of residues 32-42 of human interferon-gamma was found by calculation to have a low hydrophobicity together with a high helical hydrophobic moment, and the net electric charge of this region having an amphiphilic helical structure changed significantly near pH 4. These results suggest that the region of residues 32-42 plays an important role in exhibiting antiviral activity.