The synthesis and characterization of a nuclear membrane affinity chromatography column for the study of human breast cancer resistant protein (BCRP) using nuclear membranes obtained from the LN-229 cells

High-Resolution Bioassay Profiling with Complemented Sensitivity and Resolution for Pancreatic Lipase Inhibitor Screening

How to rapidly and accurately screen bioactive components from complex natural products remains a major challenge. In this study, a screening platform for pancreatic lipase (PL) inhibitors was established by combining magnetic beads-based ligand fishing and high-resolution bioassay profiling. This platform was well validated using a mixture of standard compounds, i.e., (-)- epigallocatechin gallate (EGCG), luteolin and schisandrin. The dose-effect relationship of high-resolution bioassay profiling was demonstrated by the standard mixture with different concentrations for each compound. The screening of PL inhibitors from green tea extract at the concentrations of 0.2, 0.5 and 1.0 mg/mL by independent high-resolution bioassay profiling was performed. After sample pre-treatment by ligand fishing, green tea extract at the concentration of 0.2 mg/mL was specifically enriched and simplified, and consequently screened through the high-resolution bioassay profiling. As a result, three PL inhibitors, i.e., EGCG, (-)-Gallocatechin gallate (GCG) and (-)-Epicatechin gallate (ECG), were rapidly identified from the complex matrix. The established platform proved to be capable of enriching affinity binders and eliminating nonbinders in sample pre-treatment by ligand fishing, which overcame the technical challenges of high-resolution bioassay profiling in the aspects of sensitivity and resolution. Meanwhile, the high-resolution bioassay profiling possesses the ability of direct bioactive assessment, parallel structural analysis and identification after separation. The established platform allowed more accurate and rapid screening of PL inhibitors, which greatly facilitated natural product-based drug screening.

Subcellular drug distribution: mechanisms and roles in drug efficacy, toxicity, resistance, and targeted delivery

After administration, drug molecules usually enter target cells to access their intracellular targets. In eukaryotic cells, these targets are often located in organelles, including the nucleus, endoplasmic reticulum, mitochondria, lysosomes, Golgi apparatus, and peroxisomes. Each organelle type possesses unique biological features. For example, mitochondria possess a negative transmembrane potential, while lysosomes have an intraluminal delta pH. Other properties are common to several organelle types, such as the presence of ATP-binding cassette (ABC) or solute carrier-type (SLC) transporters that sequester or pump out xenobiotic drugs. Studies on subcellular drug distribution are critical to understand the efficacy and toxicity of drugs along with the body's resistance to them and to potentially offer hints for targeted subcellular drug delivery. This review summarizes the results of studies from 1990 to 2017 that examined the subcellular distribution of small molecular drugs. We hope this review will aid in the understanding of drug distribution within cells.

Selective GPR55 antagonism reduces chemoresistance in cancer cells

G protein-coupled receptor 55 (GPR55) possesses pro-oncogenic activity and its function can be competitively inhibited with (R,R')-4'-methoxy-1-naphthylfenoterol (MNF) through poorly defined signaling pathways. Here, the anti-tumorigenic effect of MNF was investigated in the human pancreatic cancer cell line, PANC-1, by focusing on the expression of known cancer biomarkers and the expression and function of multidrug resistance (MDR) exporters such as P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP). Incubation of PANC1 cells with MNF (1μM) for 24h significantly decreased EGF receptor, pyruvate kinase M2 (PKM2), and β-catenin protein levels and was accompanied by significant reduction in nuclear accumulation of HIF-1α and the phospho-active forms of PKM2 and β-catenin. Inhibition of GPR55 with either MNF or the GPR55 antagonist CID 16020046 lowered the amount of MDR proteins in total cellular extracts while diminishing the nuclear expression of Pgp and BCRP. There was significant nuclear accumulation of doxorubicin in PANC-1 cells treated with MNF and the pre-incubation with MNF increased the cytotoxicity of doxorubicin and gemcitabine in these cells. Potentiation of doxorubicin cytotoxicity by MNF was also observed in MDA-MB-231 breast cancer cells and U87MG glioblastoma cells, which express high levels of GPR55. The data suggest that inhibition of GPR55 activity produces antitumor effects via attenuation of the MEK/ERK and PI3K-AKT pathways leading to a reduction in the expression and function of MDR proteins.

Cancer stem cells and chemoresistance: The smartest survives the raid

Chemoresistant metastatic relapse of minimal residual disease plays a significant role for poor prognosis of cancer. Growing evidence supports a critical role of cancer stem cell (CSC) behind the mechanisms for this deadly disease. This review briefly introduces the basics of the conventional chemotherapies, updates the CSC theories, highlights the molecular and cellular mechanisms by which CSC smartly designs and utilizes multiple lines of self-defense to avoid being killed by chemotherapy, and concisely summarizes recent progress in studies on CSC-targeted therapies in the end, with the hope to help guide future research toward developing more effective therapeutic strategies to eradicate tumor cells in the patients.

The development of mitochondrial membrane affinity chromatography columns for the study of mitochondrial transmembrane proteins

Mitochondrial membrane fragments from U-87 MG (U87MG) and HEK-293 cells were successfully immobilized onto immobilized artificial membrane (IAM) chromatographic support and surface of activated open tubular (OT) silica capillary, resulting in mitochondrial membrane affinity chromatography (MMAC) columns. Translocator protein (TSPO), located in mitochondrial outer membrane as well as sulfonylurea and mitochondrial permeability transition pore (mPTP) receptors, localized to the inner membrane, were characterized. Frontal displacement experiments with multiple concentrations of dipyridamole (DIPY) and PK-11195 were run on MMAC (U87MG) column, and the binding affinities (Kd) determined were 1.08±0.49 and 0.0086±0.0006μM, respectively, consistent with previously reported values. Furthermore, binding affinities (Ki) for DIPY binding site were determined for TSPO ligands, PK-11195, mesoporphyrin IX, protoporphyrin IX, and rotenone. In addition, the relative ranking of these TSPO ligands based on single displacement studies using DIPY as marker on MMAC (U87MG) was consistent with the obtained Ki values. The immobilization of mitochondrial membrane fragments was also confirmed by confocal microscopy.

Prospects for multitarget lipid-raft-coated silica beads: a remarkable online biomaterial for discovering multitarget antitumor lead compounds

Application of lipid raft biomaterial with multiple cancer-related receptors for screening novel multitarget antitumour lead compounds.

Multiple protein stationary phases: a review

Cellular membrane affinity chromatography stationary phases have been extensively used to characterize immobilized proteins and provide a direct measurement of multiple binding sites, including orthosteric and allosteric sites. This review will address the utilization of immobilized cellular and tissue fragments to characterize multiple transmembrane proteins co-immobilized onto a stationary phase. This approach will be illustrated by demonstrating that multiple transmembrane proteins were immobilized from cell lines and tissue fragments. In addition, the immobilization of individual compartments/organelles within a cell will be discussed and the changes in the proteins binding/kinetics based on their location.

Solid-phase biological assays for drug discovery

In the past 30 years, there has been a significant growth in the use of solid-phase assays in the area of drug discovery, with a range of new assays being used for both soluble and membrane-bound targets. In this review, we provide some basic background to typical drug targets and immobilization protocols used in solid-phase biological assays (SPBAs) for drug discovery, with emphasis on particularly labile biomolecular targets such as kinases and membrane-bound receptors, and highlight some of the more recent approaches for producing protein microarrays, bioaffinity columns, and other devices that are central to small molecule screening by SPBA. We then discuss key applications of such assays to identify drug leads, with an emphasis on the screening of mixtures. We conclude by highlighting specific advantages and potential disadvantages of SPBAs, particularly as they relate to particular assay formats.

Comparative normal/failing rat myocardium cell membrane chromatographic analysis system for screening specific components that counteract doxorubicin-induced heart failure from Acontium carmichaeli

Cell membrane chromatography (CMC) derived from pathological tissues is ideal for screening specific components acting on specific diseases from complex medicines owing to the maximum simulation of in vivo drug-receptor interactions. However, there are no pathological tissue-derived CMC models that have ever been developed, as well as no visualized affinity comparison of potential active components between normal and pathological CMC columns. In this study, a novel comparative normal/failing rat myocardium CMC analysis system based on online column selection and comprehensive two-dimensional (2D) chromatography/monolithic column/time-of-flight mass spectrometry was developed for parallel comparison of the chromatographic behaviors on both normal and pathological CMC columns, as well as rapid screening of the specific therapeutic agents that counteract doxorubicin (DOX)-induced heart failure from Acontium carmichaeli (Fuzi). In total, 16 potential active alkaloid components with similar structures in Fuzi were retained on both normal and failing myocardium CMC models. Most of them had obvious decreases of affinities on failing myocardium CMC compared with normal CMC model except for four components, talatizamine (TALA), 14-acetyl-TALA, hetisine, and 14-benzoylneoline. One compound TALA with the highest affinity was isolated for further in vitro pharmacodynamic validation and target identification to validate the screen results. Voltage-dependent K⁺ channel was confirmed as a binding target of TALA and 14-acetyl-TALA with high affinities. The online high throughput comparative CMC analysis method is suitable for screening specific active components from herbal medicines by increasing the specificity of screened results and can also be applied to other biological chromatography models.

Identification of metabolites of propyrisulfuron in rats

The metabolites found in the urine, feces and bile of male and female rats administered with (14)C-labeled herbicide, propyrisulfuron [1-(2-chloro-6-propylimidazo[1,2-b]pyridazin-3-ylsulfonyl)-3- (4,6-dimethoxypyrimidin-2-yl)urea] were identified by high-performance liquid chromatography (HPLC) with the ultraviolet (UV) and radioisotope (RI) detectors, tandem mass spectrometry and nuclear magnetic resonance (NMR). Administered (14)C was excreted into the urine (5.7-29.8%) and feces (64.6-97.4%). Urine and bile samples were concentrated and purified using a solid-phase extraction cartridge, and fecal homogenates were extracted using acetonitrile. Conjugates were hydrolyzed with enzyme or hydrochloric acid solution for identification. The proposed major metabolic reactions of propyrisulfuron are as follows: (1) hydroxylation of the pyrimidine ring, propyl group, and imidazopyridazine ring, (2) O-demethylation, (3) cleavage of the pyrimidine ring, and (4) glucuronic acid and sulfate conjugation. The metabolic patterns found are not different among sulfonylurea herbicides.

Characterization of a multiple endogenously expressed adenosine triphosphate-binding cassette transporters using nuclear and cellular membrane affinity chromatography columns

Glioblastoma multiforme is an aggressive form of human astrocytoma, with poor prognosis due to multi-drug resistance to a number of anticancer drugs. The observed multi-drug resistance is primarily due to the efflux activity of ATP-Binding Cassette (ABC) efflux transporters such as Pgp, MRP1 and BCRP. The expression of these transporters has been demonstrated in nuclear and cellular membranes of the LN-229 human glioblastoma cell line. Nuclear membrane and cellular membrane fragments from LN-229 cells were immobilized on the IAM stationary phase to create nuclear and cellular membrane affinity chromatography columns, (NMAC(LN-229)) and (CMAC(LN-229)), respectively. Pgp, MRP1 and BCRP transporters co-immobilized on both columns were characterized and compared by establishing the binding affinities for estrone-3-sulfate (3.8 vs. 3.7μM), verapamil (0.6 vs. 0.7μM) and prazosin (0.099 vs. 0.033μM) on each column and no significant differences were observed. Since the marker ligands had overlapping selectivities, the selective characterization of each transporter was carried out by saturation of the binding sites of the non-targeted transporters. The addition of verapamil (Pgp and MRP1 substrate) to the mobile phase allowed the comparative screening of eight compounds at the nuclear and cellular BCRP using etoposide as the marker ligand. AZT increased the retention of etoposide (+15%), a positive allosteric interaction, on the CMAC(LN-229) column and decreased it (-5%) on the NMAC(LN-229), while the opposite effect was produced by rhodamine. The results indicate that there are differences between the cellular and nuclear membrane expressed BCRP and that NMAC and CMAC columns can be used to probe these differences.