Hyo-Kyung Han

Improved oral bioavailability of alendronate via the mucoadhesive liposomal delivery system

This study aimed to design the chitosan coated liposomes of alendronate and optimize their in vitro/in vivo characteristics to improve the bioavailability as well as potentially to reduce the mucosal irritation of alendronate. Liposomes of alendronate were prepared with DSPC/DSPG by using thin layer film hydration method and then the surface of anionic liposomes was coated by chitosan. In vitro characteristics of liposomes (e.g., stability in various biological media, mucoadhesiveness and cellular uptake profiles) were evaluated along with the pharmacokinetic studies in rats. Lipid vesicles of 200 nm size were obtained with narrow size distribution (PI<0.1) and subsequently coated with chitosan. Chitosan coated liposomes were stable for 24 h without either size change or drug leakage in various biological fluids including simulated gastric fluids and intestinal fluids. Furthermore, it exhibited strong mucoadhesive properties. Compared to the untreated drug (non-liposome), the chitosan coated liposomes indicated significantly (p<0.05) increased cellular uptake of alendronate in Caco-2 cells and also 2.6-fold enhancement in oral bioavailability of alendronate in rats. Taken all together, the mucoadhesive liposomes for the oral delivery of alendronate was prepared by using DSPC and DSPG with narrow size distribution and appeared to be effective to enhance the bioavailability of alendronate in rats.

Role of FoxO1 activation in MDR1 expression in adriamycin-resistant breast cancer cells.

The development of multidrug resistance 1 (MDR1) can be mediated by a number of different mechanisms but elevated gene expression of MDR1 (P-glycoprotein) has often been a major cause of chemoresistance in many cancer cells. Therefore, the present study aimed to investigate the role of forkhead box-containing protein, O subfamily (FoxO), transcription factors in regulating the MDR1 gene expression. The proximal promoter region of the human MDR1 contained a putative FoxO-binding site, which partially overlapped with the enhancer/enhancer-binding protein beta-binding region. Gel shift and immunoblot analysis of subcellular fractions revealed that nuclear levels of FoxO1 and its DNA-binding activity were selectively enhanced in MCF-7/ADR cells, which was reversed by a FoxO1 antibody. Reporter gene assays showed that the transcription of MDR1 gene is stimulated by FoxO1 overexpression. Moreover, both MDR1 expression and doxorubicin resistance in MCF-7/ADR cells were reversed by FoxO1 small interfering RNA (siRNA). The MDR1 expression in MCF-7/ADR cells was also inhibited by insulin, a functional FoxO1 inactivator. In conclusion, FoxO1 is a novel transcriptional activator of MDR1 and is crucial for MDR1 induction in MCF-7/ADR cells.

Preparation and in vitro–in vivo evaluation of Witepsol® H35 based self-nanoemulsifying drug delivery systems (SNEDDS) of coenzyme Q10

Coenzyme Q(10) (CoQ(10)) was formulated into self-nanoemulsifying drug delivery systems (SNEDDS) to overcome low bioavailability attributed to hydrophobic nature of the drug. Screening of oil phase, surfactants and co-surfactants were performed to select Witepsol H35, Solutol HS15 and Lauroglycol FCC, respectively. Ternary phase diagrams were drawn to identify nanoemulsifying region followed by optimization of SNEDDS formulation. The optimized formulation, CoQ(10), Witepsol H35, Solutol HS15 and Lauroglycol FCC in the weight ratio of 1:0.7:4:2, respectively, emulsified readily at 37 degrees C with mean emulsion droplet size of 32.4 nm. The stability test of the optimized formulation in pH 1.2 and 6.8 buffers confirmed no pH effect on emulsion droplet size. In vitro dissolution (emulsification) test and in vivo animal study of the formulation elucidated the complete emulsification of drug and improved oral bioavailability of poorly soluble CoQ(10).

Inhibition of liver fibrosis by solubilized coenzyme Q10: role of Nrf2 activation in inhibiting transforming growth factor-β1 expression.

Coenzyme Q10 (CoQ10), an endogenous antioxidant, is important in oxidative phosphorylation in mitochondria. It has anti-diabetic and anti-cardiovascular disease effects, but its ability to protect against liver fibrosis has not been studied. Here, we assessed the ability of solubilized CoQ10 to improve dimethylnitrosamine (DMN)-induced liver fibrogenesis in mice. DMN treatments for 3 weeks produced a marked liver fibrosis as assessed by histopathological examination and tissue 4-hydroxyproline content. Solubilized CoQ10 (10 and 30 mg/kg) significantly inhibited both the increases in fibrosis score and 4-hydroxyproline content induced by DMN. Reverse transcription-polymerase chain reaction and Western blot analyses revealed that solubilized CoQ10 inhibited increases in the transforming growth factor-beta1 (TGF-beta1) mRNA and alpha-smooth muscle actin (alpha-SMA) protein by DMN. Interestingly, hepatic glutamate-cysteine ligase (GCL) and glutathione S-transferase A2 (GSTA2) were up-regulated in mice treated with CoQ10. Solubilized CoQ10 also up-regulated antioxidant enzymes such as catalytic subunits of GCL and GSTA2 via activating NF-E2 related factor2 (Nrf2)/antioxidant response element (ARE) in H4IIE hepatoma cells. Moreover, CoQ10s inhibition of alpha-SMA and TGF-beta1 expressions disappeared in Nrf2-null MEF cells. In contrast, Nrf2 overexpression significantly decreased the basal expression levels of alpha-SMA and TGF-beta1 in Nrf2-null MEF cells. These results demonstrated that solubilized CoQ10 inhibited DMN-induced liver fibrosis through suppression of TGF-beta1 expression via Nrf2/ARE activation.

Enhancement of solubility and dissolution of coenzyme Q10 using solid dispersion formulation.

This study aimed to develop a stable solid dispersion of Coenzyme Q(10) (CoQ(10)) with high aqueous solubility and dissolution rate. Among various carriers screened, poloxamer 407 was most effective to form a superior solid dispersion of CoQ(10) having significantly enhanced solubility. Particularly, solid dispersion of CoQ(10) with poloxamer 407 in the weight ratio of 1:5 prepared by melting method enhanced the solubility of CoQ(10) to the greatest extent. However, it exhibited poor stability and hence Aerosil 200 (colloidal silicon dioxide) was incorporated into the solid dispersion as an adsorbent to inhibit the recrystallization process. The solid dispersion of CoQ(10), poloxamer 407 and Aerosil 200 in the weight ratio of 1:5:6 exhibited improved stability with no significant change in solubility during the 1-month stability test. Moreover, the solid dispersion formulation containing Aerosil 200 significantly enhanced the extent of drug release (approx. 75% release) as well as the dissolution rate of CoQ(10). In conclusion, the present study has developed the stable solid dispersion formulation of CoQ(10) with poloxamer 407 and Aerosil 200 for the enhanced solubility and dissolution of CoQ(10), which could also offer some additional advantages including ease of preparation, good flowability and cost-effectiveness.

Amurensin G, a Potent Natural SIRT1 Inhibitor, Rescues Doxorubicin Responsiveness via Down-Regulation of Multidrug Resistance 1

The transition from a chemotherapy-responsive cancer to a chemotherapy-resistant one is accompanied by increased expression of multidrug resistance 1 (MDR1, p-glycoprotein), which plays an important role in the efflux from the target cell of many anticancer agents. We recently showed that a Forkhead box-containing protein of the O subfamily 1 (FoxO1) is a key regulator of MDR1 gene transcription. Because nuclear localization of FoxO1 is regulated by silent information regulator two ortholog 1 (SIRT1) deacetylase, we wondered whether SIRT1 dominates MDR1 gene expression in breast cancer cells. Overexpression of SIRT1 enhanced both FoxO reporter activity and nuclear levels of FoxO1. Protein expression of MDR1 and gene transcriptional activity were also up-regulated by SIRT1 overexpression. In addition, SIRT1 inhibition reduced both nuclear FoxO1 levels and MDR1 expression in doxorubicin-resistant breast cancer cells (MCF-7/ADR) cells. A potent SIRT1 inhibitor, amurensin G (from Vitis amurensis), was identified by screening plant extracts and bioassay-guided fractionation. The compound suppressed FoxO1 activity and MDR1 expression in MCF-7/ADR cells. Moreover, pretreatment of MCF-7/ADR cells with 1 μg/ml amurensin G for 24 h increased cellular uptake of doxorubicin and restored the responsiveness of MCF-7/ADR cells to doxorubicin. In xenograft studies, injection of 10 mg/kg i.p. amurensin G substantially restored the ability of doxorubicin to inhibit MCF-7/ADR-induced tumor growth. These results suggest that SIRT1 is a potential therapeutic target of MDR1-mediated chemoresistance and that it may be possible to develop amurensin G as a useful agent for chemoresistance reversal.

The roles of acidifiers in solid dispersions and physical mixtures

The roles of acidifiers in polyvinylpyrrolidone-based solid dispersions and physical mixtures were originally investigated on dissolution rate of drug, acidifier release, structural crystallinity and micro-environmental pH. A poorly water-soluble and weakly basic isradipine was used as a model drug. The solid dispersion and physical mixtures were prepared with drug and polyvinylpyrrolidone without or with pH modifiers using the solvent evaporation method and then compressed into tablet. The dissolution rate of drug from solid dispersions containing acidifiers were more pronounced when compared to physical mixtures. The dissolution rate of isradipine from solid dispersion was ranked by acidifiers in a decreasing order: fumaric acid, citric acid, glycolic acid and malic acid. In contrast, the acidifiers in physical mixtures had no significant difference in drug dissolution rate. It was attributed by the rank of acidifiers leading to the decrease of micro-environmental pH and slower release rate of acidifier as well as the maintenance of structural amorphousness. The selection of acidifiers with optimal micro-environmental pH, retarded release rate and maintaining structural amorphousness of drug could maximize the dissolution rate of weakly basic drug in solid dispersion.

Effect of piperine, a major component of black pepper, on the intestinal absorption of fexofenadine and its implication on food-drug interaction.

The present study aimed to investigate the effect of piperine, a major component of black pepper, on the oral exposure of fexofenadine in rats. Pharmacokinetic parameters of fexofenadine were determined in rats following an oral (10 mg/kg) or intravenous (5 mg/kg) administration of fexofenadine in the presence and absence of piperine (10 or 20 mg/kg, given orally). Compared to the control group given fexofenadine alone, the combined use of piperine increased the oral exposure (AUC) of fexofenadine by 180% to 190% while there was no significant change in C(max) and T(1/2) of fexofenadine in rats. The bioavailability of fexofenadine was increased by approximately 2-folds via the concomitant use of piperine. Furthermore, T(max) tends to be increased which might be attributed to the delayed gastric emptying in the presence of piperine. In contrast, piperine did not alter the intravenous pharmacokinetics of fexofenadine, implying that piperine may increase mainly the gastrointestinal absorption of fexofenadine rather than reducing hepatic extraction. In conclusion, piperine significantly enhanced the oral exposure of fexofenadine in rats likely by the inhibition of P-glycoprotein-mediated cellular efflux during the intestinal absorption, suggesting that the combined use of piperine or piperine-containing diet with fexofenadine may require close monitoring for potential drug-diet interactions.

Magnesium and calcium organophyllosilicates: synthesis and in vitro cytotoxicity study.

Synthesis of multifunctional hybrid nanomaterials for biomedical applications has received great attention. Herein, we examine the potential toxicity of organophyllosilicates on cells from different organs such as A549 (lung epithelial cancer), HT-29 (colon epithelial cancer), MRC-5 (lung fibroblast) and CCD-986sk (skin fibroblast) cells. For this, aminopropyl functionalized magnesium phyllosilicate (AMP clay) and aminopropyl functionalized calcium phyllosilicate (ACP clay) were prepared using one-pot direct sol-gel method. Toxic effects of these organoclays on normal fibroblast and tumor cells were examined under varying concentrations and exposure times. MTT and LDH assays indicated that both organoclays had little cytotoxicity in all of the cells tested at concentrations as high as 500 μg/mL. Even at high concentration (1000 μg/mL), the toxicity of both organoclays on cell viability and membrane damage was not severe and appeared to be cell type specific. In addition, organoclays did not induce apoptosis at concentrations as high as 1000 μg/mL.

Enhanced dissolution and bioavailability of biochanin A via the preparation of solid dispersion: In vitro and in vivo evaluation

The present study aimed to improve the bioavailability of biochanin A, a poorly soluble bioflavonoid, via the preparation of solid dispersion (SD) using Solutol HS15 and HPMC 2910. Solubility of biochanin A was enhanced by 8-60 folds as the drug-carrier ratio was increased in SDs. Furthermore, compared to pure biochanin A or physical mixture (PM), SDs significantly improved the dissolution rate and the extent of drug release. Particularly, SDs (Drug:Solutol HS15:HPMC 2910=1:5:5 or 1:10:10) achieved the rapid and complete drug release (approximately 100% within 1h) at pH 6.8. The XRD patterns indicated that SDs might enhance the solubility of biochanin A by changing the drug crystallinity to amorphous state in addition to the solubilizing effect of hydrophilic carriers. The improved dissolution of biochanin A via SD formulation appeared to be well correlated with the enhanced oral exposure of biochanin A in rats. After an oral administration of SD (Drug:Solutol HS15:HPMC 2910=1:10:10), C(max) and AUC of biochanin A were increased by approximately 13 and 5 folds, respectively, implying that SDs could be effective to improve the bioavailability of biochanin A. In conclusion, solid dispersion with Solutol HS15 and HPMC 2910 appeared to be promising to improve the dissolution and oral exposure of biochanin A.