Soo-Jeong Lim

Down-regulation of Mitochondrial F1F0-ATP Synthase in Human Colon Cancer Cells with Induced 5-Fluorouracil Resistance

5-Fluorouracil (5-FU) is widely used for treatment of advanced colorectal cancer. However, it is common for such patients to develop resistance to 5-FU, and this drug resistance becomes a critical problem for chemotherapy. The mechanisms underlying this resistance are largely unknown. To screen for proteins possibly responsible for 5-FU resistance, cells resistant to 5-FU were derived from human colon cancer cell lines and two-dimensional gel electrophoresis–based comparative proteomics was done. Two-dimensional gel electrophoresis data showed there was lower expression of the α subunit of mitochondrial F1F0-ATP synthase (ATP synthase) in 5-FU–resistant cells compared with parent cells. Western blotting showed that expression of other ATP synthase complex subunits was also lower in 5-FU–resistant cell lines and that these resistant cells also showed decreased ATP synthase activity and reduced intracellular ATP content. The ATP synthase inhibitor, oligomycin A, strongly antagonized 5-FU–induced suppression of cell proliferation. When 5-FU sensitivity was compared with ATP synthase activity in six different human colon cancer cell lines, a positive correlation has been found. Furthermore, suppressed ATP synthase d-subunit expression by siRNA transfection increased cell viability in the presence of 5-FU. Bioenergetic dysfunction of mitochondria has been reported as a hallmark of many types of cancers (i.e., down-regulation of ATP synthase β-subunit expression in liver, kidney, colon, squamous oesophageal, and lung carcinomas, as well as in breast and gastric adenocarcinomas). Our findings show that ATP synthase down-regulation may not only be a bioenergetic signature of colorectal carcinomas but may also lead to cellular events responsible for 5-FU resistance.

Novel gelatin microcapsule with bioavailability enhancement of ibuprofen using spray-drying technique.

A poorly water-soluble ibuprofen and ethanol can be encapsulated in gelatin microcapsule by spray-drying technique. To develop a novel ibuprofen-loaded gelatin microcapsule with bioavailability enhancement, the effect of spray-drying conditions, gelatin, ibuprofen and sodium lauryl sulfate on the ibuprofen solubility and the amount of ethanol encapsulated in gelatin microcapsule were investigated. The ibuprofen solubility and amount of encapsulated ethanol increased as inlet temperature and amount of sodium lauryl sulfate increased, reached maximum at 105 degrees C and 0.6%, respectively and after that followed a rapid decrease. Furthermore, they abruptly increased as the amount of gelatin increased, reaching maximum at 4% then remaining almost stable, but the encapsulated ethanol content decreased noticeably. Likewise, the ibuprofen solubility increased as the amount of ibuprofen increased, reaching maximum at 0.5% and beyond that, there was no change in the solubility. However, the encapsulated ethanol content hardly changed irrespective of the amount of ibuprofen. Furthermore, the formula of ibuprofen-loaded gelatin microcapsule at the ratio of gelatin/ibuprofen/sodium lauryl sulfate/water/ethanol of 4/0.5/0.6/30/70 showed ibuprofen solubility of about 290microg/ml and ethanol content of about 160microg/mg. This gelatin microcapsule dramatically increased the initial dissolution rate of ibuprofen compared to ibuprofen powder in pH 1.2 simulated gastric fluid. Moreover, it gave significantly higher initial plasma concentrations, Cmax and AUC of ibuprofen in rats than did ibuprofen powder, indicating that the drug from gelatin microcapsule could be more orally absorbed in rats. Our results suggested that the enhanced oral bioavailability of ibuprofen in the gelatin microcapsule was contributed by the marked increase in the absorption rate of ibuprofen due to the crystallinity change to amorphous form and increase in dissolution rate of ibuprofen in the gelatin microcapsule in rats. Thus, the ibuprofen-loaded gelatin microcapsule developed using spray-drying technique with gelatin would be useful to deliver ibuprofen in a pattern that allows fast absorption in the initial phase, leading to better absorption.

Reduced food-effect and enhanced bioavailability of a self-microemulsifying formulation of itraconazole in healthy volunteers

Self-microemulsifying drug delivery systems (SMEDDS) represent a possible alternative to traditional oral formulations of lipophilic compounds. This study was designed to compare the oral bioavailability and food-effect of SMEDDS of itraconazole (ITRA-GSMP capsule containing 50mg itraconazole) to that of the currently marketed formulation (Sporanox capsule containing 100mg itraconazole). Eight healthy volunteers received Sporanox or ITRA-GSMP capsule in the fasted state or after a high-fat diet on four separate dosing occasions with a 2-week washout period. Blood samples were collected and analyzed. After administration of the ITRA-GSMP capsule, AUC0-24 and Cmax were 1.9- and 2.5-fold higher in the fasted state and 1.5- and 1.3-fold higher in the fed state, respectively, than those of the Sporanox capsule. Moreover, ITRA-GSMP capsules yielded more reproducible blood-time profiles than Sporanox capsules. Food had a marked effect on itraconazole absorption from the Sporanox capsule, whereas the influence was less pronounced for the ITRA-GSMP capsule. Collectively, our data suggest that a new self-microemulsifying formulation may provide an alternative oral formulation for itraconazole with improved oral bioavailability and reduced food-effect.

Cyclooxygenase-independent down-regulation of multidrug resistance–associated protein-1 expression by celecoxib in human lung cancer cells

The recent finding of a link between cyclooxygenase-2 (COX-2) and p-glycoprotein expression suggests that COX-2 is involved in the development of the multidrug resistance (MDR) phenotype. MDR-associated protein 1 (MRP1) is another major MDR-related protein that is frequently overexpressed in cancer patients, including those with lung cancer. Based on our observation that among four human epithelial lung cell lines both MRP1 and COX-2 protein were highly expressed only in A549 cells, we have investigated whether COX-2 regulates the expression of MRP1. The COX-2 inhibitor celecoxib down-regulated the expression of MRP1 protein in A549 cells, which was accompanied by increased accumulation and enhanced cytotoxicity of doxorubicin, an MRP1 substrate. However, enforced expression of COX-2 in human H460 lung carcinoma cell lines, which express minimal level of COX-2, did not cause enhancement in MRP1 expression. Celecoxib down-regulation of MRP1 was observed independent of COX-2 expression. Moreover, in COX-2-overexpressing cell lines, celecoxib down-regulation of MRP1 was observed only at a concentration far exceeding that required for inhibiting COX activity, and exogenous addition of prostaglandin E2 did not restore MRP1 expression. These results suggest that celecoxib down-regulates MRP1 expression in human lung cancer cells in a COX-independent manner. The use of celecoxib for adjuvant therapy in lung cancer patients may contribute to their decreased resistance to chemotherapeutic drugs transported by MRP1.

Role of reactive oxygen species in the induction of apoptosis by α-tocopheryl succinate

α‐Tocopheryl succinate (TOS), a vitamin E analog, is a promising anticancer agent due to its abilities to inhibit proliferation and to induce apoptosis in a variety of human malignant cell lines, while being relatively less active toward normal cells. However, the molecular mechanisms underlying the apoptotic effects of TOS are not precisely understood. Reports that TOS can generate reactive oxygen species (ROS) prompted us to investigate the role of ROS in TOS‐induced apoptosis in cancer cells. We found that the human lung cancer A549 and H460 cell lines were much more sensitive to TOS‐induced apoptosis than the human glioblastoma T98G and U87MG cell lines. Our data suggested that the differential TOS sensitivity was not caused by differences in the uptake and retention of TOS between TOS‐sensitive and –resistant cancer cells. The differential ability of cancer cells to generate ROS in response to TOS appears to be an important factor in determining the susceptibility of cells to TOS‐induced apoptosis. Our results further suggest that TOS‐induced generation of ROS is involved in caspase‐independent apoptosis. Taken together, our findings suggest an important role of ROS generation in TOS‐induced, caspase‐independent apoptosis of cancer cells.

A structure-based virtual screening approach toward the discovery of histone deacetylase inhibitors: identification of promising zinc-chelating groups.

The inhibitors of histone deacetylases (HDACs) have drawn a great deal of attention due to their promising potential as small‐molecule therapeutics for the treatment of cancer. By means of virtual screening with docking simulations under consideration of the effects of ligand solvation, we were able to identify six novel HDAC inhibitors with IC50 values ranging from 1 to 100 μM. These newly identified inhibitors are structurally diverse and have various chelating groups for the active site zinc ion, including N‐[1,3,4]thiadiazol‐2‐yl sulfonamide, N‐thiazol‐2‐yl sulfonamide, and hydroxamic acid moieties. The former two groups are included in many drugs in current clinical use and have not yet been reported as HDAC inhibitors. Therefore, they can be considered as new inhibitor scaffolds for the development of anticancer drugs by structure–activity relationship studies to improve the inhibitory activities against HDACs. Interactions with the HDAC1 active site residues responsible for stabilizing these new inhibitors are addressed in detail.

Preparation and in vitro evaluation of anti-VCAM-1-Fab'-conjugated liposomes for the targeted delivery of the poorly water-soluble drug celecoxib.

When an inflammatory stimulus is given, vascular endothelial cells express various cell adhesion molecules including the vascular cell adhesion molecule (VCAM)-1. In this study, the possibility of specifically delivering anti-inflammatory drugs to activated endothelial cells by utilizing VCAM-1 as a target receptor was explored by loading celecoxib, a selective cyclooxygenase-2 inhibitor, into liposomes coupled to the Fab′ fragment against VCAM-1. Anti-VCAM-1-Fab′-conjugated liposomes were prepared by forming an amide linkage between amino groups of Fab′ and the carboxylic group of glutaryl-N-phosphatidylethanolamine in liposomes using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as a cross-linker in the presence of sulpho-N-hydroxysuccinimide. The coupling of Fab′ to phospholipids constituting liposomes was confirmed by SDS-PAGE analysis. Under our optimized conjugation conditions, 130.0 µg Fab′ was coupled to 1 µmol liposomes. Immunoblotting analysis showed that VCAM-1 protein expression could be induced by incubating human umbilical vein endothelial cells (HUVEC) with TNF-α. Confocal laser microsopy analysis revealed that Fab′ conjugation to liposomes selectively increased liposomal uptake in TNF-α-pre-stimulated (VCAM-1-expressed) HUVECs, but not in cells without VCAM-1 expression. The concentration of celecoxib loaded in Fab′-conjugated liposomes was 281.1 ± 29 µg/mL, suggesting that liposomal loading also helped to overcome the limitations in celecoxib administration caused by its poor water solubility. Celecoxib loaded in Fab′-conjugated liposomes inhibited prostaglandin E2 (PGE2) production induced by TNF-α-pre-stimulation more efficiently than when loaded in conventional liposomes. Therefore, Fab′-conjugated liposomes served as a drug delivery system with dual functions: targeted delivery and solubilizing capacity.

Wound healing evaluation of sodium fucidate-loaded polyvinylalcohol/sodium carboxymethylcellulose-based wound dressing

The cross-linked hydrogel films containing sodium fucidate were previously reported to be prepared polyvinyl alcohol (PVA) and sodium carboxymethylcellulose (Na-CMC) using the freeze-thawing method and their physicochemical property was investigated. For the development of novel sodium fucidate-loaded wound dressing, here its in vivo wound healing test and histopathology were performed compared with the conventional ointment product. In wound healing test, the sodium fucidate-loaded composed of 2.5% PVA, 1.125% Na-CMC and 0.2% drug showed faster healing of the wound made in rat dorsum than the hydrogel without drug, indicating the potential healing effect of sodium fucidate. Furthermore, from the histological examination, the healing effect of sodium fucidate-loaded hydrogel was greater than that of the conventional ointment product and hydrogel without drug, since it might gave an adequate level of moisture and build up the exudates on the wound area. Thus, the sodium fucidate-loaded wound dressing composed of 5% PVA, 1.125% Na-CMC and 0.2% drug is a potential wound dressing with excellent wound healing.

Metabolic inhibition and kinetics of raloxifene by pharmaceutical excipients in human liver microsomes

This study was originally undertaken to establish the in vitro metabolic conditions and then evaluate the effect of pharmaceutical excipients (PEs) on drug metabolism in uridine diphosphoglucuronic acid-supplemented human liver microsomes. Poorly bioavailable raloxifene was chosen as a model drug. Intact drug and its two glucuronide metabolites were successfully isolated using gradient HPLC analysis and LC/MS analysis. Formation of raloxifene metabolites was affected by buffer compositions, incubation time and initial raloxifene concentrations. Under optimized metabolic conditions, 41.0% of raloxifene was converted to its metabolites after 2h incubation. This metabolic inhibition of raloxifene by the PEs occurred in a dose-dependent manner and accordingly formed two glucuronide metabolites. In the metabolic kinetics using Lineweaver-Burk analyses, Cremophor EL competitively inhibited formation of metabolites while sodium lauryl sulfate (SLS), polyvinylpyrrolidone K30 (PVP) and Tween 80 significantly inhibited in a mixed competition. Although some PEs showed inhibition on glucuronidation of raloxifene in vitro, their effects on in vivo bioavailability of raloxifene need to be confirmed directly due to the dilution factors and other complicated situations influencing the bioavailability.

Liposome composition is important for retention of liposomal rhodamine in P-glycoprotein-overexpressing cancer cells

Multidrug resistance (MDR) caused by high expression of P-glycoprotein (Pgp) in cancer patients remains one of the major obstacles to successful therapy of cancer. Earlier studies have shown that the incorporation of Pgp-substrate drugs in liposomes may provide a strategy to circumvent Pgp-mediated drug efflux. The present study investigated the impact of liposome composition on the efflux of Pgp-substrate incorporated in liposomes. Liposomes with varying compositions were loaded with rhodamine 123, a fluorescent probe frequently used as a Pgp-substrate, and the retention of rhodamine was compared in two breast cancer cell lines: wild-type cells with no detectable Pgp expression (MCF-7/WT) and Pgp-expressing cells resulting from stable transfection of the MDR1 gene (MCF-7/Pgp). Pgp-expression decreased the rhodamine retention in MCF-7 cells, suggesting that Pgp is functional. Liposome loading increased rhodamine retention in MCF-7/Pgp cells, but not in MCF-7/WT cells. Surface charge of liposomes did not affect the rhodamine retention, whereas the incorporation of cholesterol and polyethyleneglycol-attached lipids was effective in further increasing the rhodamine retention in MCF-7/Pgp cells. Since further study demonstrated that the rate of rhodamine release from liposomes tended to be inversely correlated with rhodamine retention by cells, it seems likely that more rigid liposomes are able to sequester rhodamine more efficiently, thereby inhibiting direct interactions of rhodamine with Pgp proteins. Taken together, these findings suggest that Pgp-mediated MDR in cancer cells may be more effectively modulated by optimizing the composition of liposomes for loading Pgp-substrate anti-cancer drugs.