Weakly acidic pH-responsive liposomal content release induced by histidine-modified agents.

Internal stimuli-responsive controlled release from liposomal vesicles is an innovative approach for site-specific delivery of therapeutic drugs. In this study, to enhance the endosomal pH control of drug release from liposomes, a series of histidine-modified pH-sensitive Cn-His (n = 8, 12, 18) agents were designed and utilized as triggers for liposomal content release. The pH-dependent properties of Cn-His-incorporated liposomes were characterized using dynamic light scattering, ζ-potential, and fluorescence spectroscopy. The liposomes maintained a relatively uniform size across all pH conditions. However, the ζ-potential exhibited positive values at endosomal acidic pH levels and neutral or negative values at physiological pH levels. Furthermore, acidic pH-dependent release of both polar content (carboxyfluorescein) and nonpolar content (Nile red) was observed from the Cn-His-incorporated liposomes. Notably, with C12-His as the pH sensitizer, the pH dependence of liposomal content release was significantly evident. This work establishes endosomal pH-controllable liposome platforms, laying the groundwork for developing clinically applicable triggered release formulations.

Decrease in prostate specific antigen secretion correlated with docetaxel-induced growth inhibition and apoptosis in human prostate tumor cells.

The antitumor activity of docetaxel in human prostate tumor cells and correlation between cell-growth inhibition and prostate specific antigen (PSA) secretion were investigated. Cultured human prostate tumor cell lines (LNCaP, DU1 45 and PC-3) were treated with test drugs,after which the number of viable cells and PSA levels in the medium were determined. Apoptosis was assessed by changes in chromatin structure, DNA fragmentation, terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) and Annexin V assay. Docetaxel inhibited cell proliferation in a dose-dependent fashion in all cell lines,with IC50 levels from 0.90 to 4.2 nM,which were similar to those of paclitaxel,but more potent than mitoxantrone,estramustine,or cisplatin. Docetaxel-treated cells underwent cell-cycle arrest in the G2/M phase and apoptosis as indicated by chromatin condensation and DNA fragmentation. In docetaxel-treated LNCaP cells,there was a linear correlation between growth inhibition and the decline in PSA level in the culture medium. It was demonstrated that docetaxel had potent antitumor activity against human prostate tumor cells,and the decrease in cell growth was associated with a decrease in PSA secretion,suggesting that PSA would be a useful biological marker for monitoring the efficacy of docetaxel in a clinical setting.

Identification of estrogenic/anti-estrogenic compounds in diesel exhaust particulate extract.

Diesel exhaust particulate extract (DEPE) was obtained from diesel exhaust particulates with Soxhlet extraction using dichloromethane. After separating DEPE into 11 fractions by liquid-liquid extraction, the neutral fraction (N) showed anti-estrogenic activity and the weak acid (phenol) fraction (WA(P)) showed estrogenic and anti-estrogenic activities by a yeast two-hybrid assay system expressing human estrogen receptor alpha. Both fractions were thoroughly fractionated by silica gel column chromatography and reversed-phase HPLC. In the WA(P) fraction, 3-methyl-4-nitrophenol and 2,6-dimethyl-4-nitrophenol were identified by LC-MS/MS as estrogenic compounds. This is the first study to identify 2,6-dimethyl-4-nitrophenol in DEPE and the first study to show that it is an estrogenic compound. In the N fraction, 1-hydroxypyrene was also identified by LC-MS/MS as an anti-estrogenic compound.

[Antitumor effect of docetaxel against human endometrial tumor cell lines].

The antitumor effect of docetaxel against human endometrial tumor cell lines was investigated in vitro and in vivo. In the in vitro study,docetaxel showed concentration-dependent inhibition of the growth of 4 tumor cell lines having different degrees of differentiation (AN3 CA, KLE, HEC-1-A and HEC-1-B), with IC(50) values ranging from 2.48 to 82.40 ng/ml. These values represent ca. 1/900-1/30 of the mean maximum plasma concentration of 2.27 microg/ml attained when the recommended dose of 70 mg/m(2) for patients with endometrial cancer was administered to patients with various types of cancer in phase I trial. In addition, the activity was nearly equal to paclitaxel, and much more potent than fluorouracil, cisplatin and doxorubicin. Docetaxel also showed strong antitumor activity against xenografts of the AN3 CA human endometrial adenocarcinoma cell line in nude mice. In the docetaxel treated group at its MTD (33 mg/kg/dose, q 6 d x 3, iv), all of the animals were tumor-free survivors on Day 62 after xenografting. The antitumor effect in the MTD-administered group was the strongest of all of the tested anticancer drug groups (cyclophosphamide, mitomycin C, fluorouracil, cisplatin, doxorubicin). Even at two docetaxel dosages below its MTD (20.5 and 12.5 mg/kg/day), the drug showed a marked cytotoxic activity. These results demonstrated that docetaxel shows potent antitumor efficacy against human endometrial tumor cell lines, leading to the expectation that it will be useful as a therapeutic agent for endometrial cancer.