Gastrointestinal Hormone Cholecystokinin Increases P-Glycoprotein Membrane Localization and Transport Activity in Caco-2 Cells

A Non-Nutritive Feeding Intervention Alters the Expression of Efflux Transporters in the Gastrointestinal Tract

Intestinal interactions with nutrients, xenobiotics and endogenous hormones can influence the expression of clinically relevant membrane transporters. These changes in the gastrointestinal (GI) physiology can in turn affect the absorption of numerous drug substrates. Several studies have examined the effect of food on intestinal transporters in male and female humans and animal models. However, to our knowledge no studies have investigated the influence of a non-nutritive fibre meal on intestinal efflux transporters and key sex and GI hormones. Here, we show that a fibre meal increased the acute expression of P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and multidrug-resistance-associated protein-2 (MRP2) in small intestinal segments in both male and female Wistar rats. Enzyme-linked immunosorbent assays were used for the protein quantification of efflux transporters and hormonal plasma concentration. In male rats, the fibre meal caused the plasma concentration of the GI hormone cholecystokinin (CCK) to increase by 75% and the sex hormone testosterone to decrease by 50%, whereas, in contrast, the housing food meal caused a decrease in CCK by 32% and testosterone saw an increase of 31%. No significant changes in the hormonal concentrations, however, were seen in female rats. A deeper understanding of the modulation of efflux transporters by sex, food intake and time can improve our understanding of inter- and intra-variability in the pharmacokinetics of drug substrates.

Drug resistance via radixin-mediated increase of P-glycoprotein membrane expression during SNAI1-induced epithelial-mesenchymal transition in HepG2 cells

OBJECTIVES

Epithelial-mesenchymal transition (EMT) plays a role in cancer metastasis as well as in drug resistance through various mechanisms, including increased drug efflux mediated by P-glycoprotein (P-gp). In this study, we investigated the activation mechanism of P-gp, including its regulatory factors, during EMT in hepatoblastoma-derived HepG2 cells.

METHODS

HepG2 cells were transfected with SNAI1 using human adenovirus serotype 5 vector. We quantified mRNA and protein expression levels using qRT-PCR and western blot analysis, respectively. P-gp activity was evaluated by uptake assay, and cell viability was assessed by an MTT assay.

KEY FINDINGS

P-gp protein expression on plasma membrane was higher in SNAI1-transfected cells than in Mock cells, although there was no difference in P-gp protein level in whole cells. Among the scaffold proteins such as ezrin, radixin and moesin (ERM), only radixin was increased in SNAI1-transfected cells. Uptake of both Rho123 and paclitaxel was decreased in SNAI1-transfected cells, and this decrease was blocked by verapamil, a P-gp inhibitor. The reduced susceptibility of SNAI1-transfected cells to paclitaxel was reversed by elacridar, another P-gp inhibitor.

CONCLUSIONS

Increased expression of radixin during SNAI1-induced EMT leads to increased P-gp membrane expression in HepG2 cells, enhancing P-gp function and thereby increasing drug resistance.

Subcellular distribution of ezrin/radixin/moesin and their roles in the cell surface localization and transport function of P-glycoprotein in human colon adenocarcinoma LS180 cells

The ezrin/radixin/moesin (ERM) family proteins act as linkers between the actin cytoskeleton and P-glycoprotein (P-gp) and regulate the plasma membrane localization and functionality of the latter in various cancer cells. Notably, P-gp overexpression in the plasma membrane of cancer cells is a principal factor responsible for multidrug resistance and drug-induced mutagenesis. However, it remains unknown whether the ERM proteins contribute to the plasma membrane localization and transport function of P-gp in human colorectal cancer cells in which the subcellular localization of ERM has yet to be determined. This study aimed to determine the gene expression patterns and subcellular localization of ERM and P-gp and investigate the role of ERM proteins in the plasma membrane localization and transport function of P-gp using the human colon adenocarcinoma cell line LS180. Using real-time reverse transcription polymerase chain reaction and immunofluorescence analyses, we showed higher levels of ezrin and moesin mRNAs than those of radixin mRNA in these cells and preferential distribution of all three ERM proteins on the plasma membrane. The ERM proteins were highly colocalized with P-gp. Additionally, we show that the knockdown of ezrin, but not of radixin and moesin, by RNA interference significantly decreased the cell surface expression of P-gp in LS180 cells without affecting the mRNA expression of P-gp. Furthermore, gene silencing of ezrin substantially increased the intracellular accumulation of rhodamine123, a typical P-gp substrate, with no alterations in the plasma membrane permeability of Evans blue, a passive transport marker. In conclusion, ezrin may primarily regulate the cell surface localization and transport function of P-gp as a scaffold protein without influencing the transcriptional activity of P-gp in LS180 cells. These findings should be relevant for treating colorectal cancer, which is the second leading cause of cancer-related deaths in males and females combined.

Rapid Increase of Gastrointestinal P-Glycoprotein Functional Activity in Response to Etoposide Stimulation

We previously reported that exposure of human colon adenocarcinoma (Caco-2) cells to the bitter substance phenylthiocarbamide (PTC) rapidly enhanced the transport function of P-glycoprotein (P-gp). In this study, we investigated the short-term effect of etoposide, another bitter-tasting P-gp substrate, on P-gp transport function in the same cell line. We found that etoposide exposure significantly increased both the P-gp protein level in the plasma membrane fraction and the efflux rate of rhodamine123 (Rho123) in Caco-2 cells within 10 min. The efflux ratio (ratio of the apparent permeability coefficient in the basal-to-apical direction to that in the apical-to-basal direction) of Rho123 in etoposide-treated cells was also significantly increased compared with the control. These results indicated that etoposide rapidly enhances P-gp function in Caco-2 cells. In contrast, P-gp expression in whole cells at both the mRNA and protein level was unchanged by etoposide exposure, compared with the levels in non-treated cells. Furthermore, etoposide increased the level of phosphorylated ezrin, radixin and moesin (P-ERM) proteins in the plasma membrane fraction of Caco-2 cells within 10 min. P-gp functional changes were blocked by YM022, an inhibitor of cholecystokinin (CCK) receptor. These results suggest that etoposide induces release of CCK, causing activation of the CCK receptor followed by phosphorylation of ERM proteins, which recruit intracellular P-gp for trafficking to the gastrointestinal membrane, thereby increasing the functional activity of P-gp.

Functional Alterations of Multidrug Resistance-Associated Proteins 2 and 5, and Breast Cancer Resistance Protein upon Snail-Induced Epithelial-Mesenchymal Transition in HCC827 Cells

Our previous report indicated that Snail-induced epithelial-mesenchymal transition (EMT) enhanced P-glycoprotein (P-gp) function and drug resistance to P-gp substrate anticancer drug in a human non-small cell lung cancer (NSCLC) cell line, HCC827. Our objective is to evaluate the changes in the mRNA and protein expression levels and the functions of multidrug resistance-associated protein (MRP) 2, MRP5 and breast cancer resistance protein (BCRP). Snail-expressing HCC827 cells showed increased mRNA levels of Snail and a mesenchymal marker vimentin, and decreased mRNA levels of an epithelial marker E-cadherin after transduction, indicating that Snail had induced EMT consistent with our previous reports. The mRNA level of MRP2 was significantly decreased, while that of MRP5 remained unchanged, in Snail-expressing cells. The expression levels of MRP2 and MRP5 proteins in whole-cell homogenate were unchanged in Snail-expressing cells, but MRP5 protein showed significantly increased membrane localization. Snail-transduction increased the efflux transport of 5-(and-6)-carboxy-2',7'-dichlorofluorescein (CDCF), a substrate of MRP2, 3 and 5. This increase was blocked by MK571, which inhibits MRP1, 2, and 5. Toxicity of cisplatin, a substrate of MRP2 and 5, was significantly decreased in Snail-expressing cells. BCRP mRNA and protein levels were both decreased in Snail-expressing cells, which showed an increase in the intracellular accumulation of 7-ethyl-10-hydroxycamptothecin (SN-38), a BCRP substrate, resulting in reduced viability. These results suggested that MRP5 function appears to be increased via an increase in membrane localization, whereas the BCRP function is decreased via a decrease in the expression level in HCC827 cells with Snail-induced EMT.

Acute regulation of apical ABC transporters in the gut. Potential influence on drug bioavailability

The extensive intestinal surface offers an advantage regarding nutrient, ion and water absorptive capacity but also brings along a high exposition to xenobiotics, including drugs of therapeutic use and food contaminants. After absorption of these compounds by the enterocytes, apical ABC transporters play a key role in secreting them back to the intestinal lumen, hence acting as a transcellular barrier. Rapid and reversible modulation of their activity is a subject of increasing interest for pharmacologists. On the one hand, a decrease in transporter activity may result in increased absorption of therapeutic agents given orally. On the other hand, an increase in transporter activity would decrease their absorption and therapeutic efficacy. Although of less relevance, apical ABC transporters also contribute to disposition of drugs systemically administered. This review article summarizes the present knowledge on the mechanisms aimed to rapidly regulate the activity of the main apical ABC transporters of the gut: multidrug resistance protein 1 (MDR1), multidrug resistance-associated protein 2 (MRP2) and breast cancer resistance protein (BCRP). Regulation of these mechanisms by drugs, drug delivery systems, drug excipients and nutritional components are particularly considered. This information could provide the basis for controlled regulation of bioavailability of therapeutic agents and at the same time would help to prevent potential drug-drug interactions.

Deoxyshikonin inhibits cisplatin resistance of non-small-cell lung cancer cells by repressing Akt-mediated ABCB1 expression and function

Drug resistance is a large challenge for the treatment of non-small-cell lung cancer (NSCLC). Deoxyshikonin is the naphthoquinol compound with anticancer activity. However, the role and mechanism of deoxyshikonin in cisplatin resistance of NSCLC remain poorly understood. Cell viability was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay. Cell apoptosis was evaluated by flow cytometry and caspase-3 activity. We found that cisplatin-resistant A549/cis and H1299/cis cells had higher cisplatin resistance than A549 and H1299 cells, respectively. Deoxyshikonin contributed to cisplatin-induced viability inhibition and apoptosis in A549/cis and H1299/cis cells. Moreover, deoxyshikonin inhibited phosphorylation of Akt and the expression and function of ATP-binding cassette subfamily B member 1 (ABCB1). Activation of protein kinase B (Akt) pathway attenuated the effect of deoxyshikonin on cisplatin resistance and ABCB1 expression and function in A549/cis and H1299/cis cells. In conclusion, deoxyshikonin suppressed cisplatin resistance in cisplatin-resistant NSCLC cells by repressing Akt signaling-mediated ABCB1 expression.

Prediction of Maternal and Fetal Pharmacokinetics of Dolutegravir and Raltegravir Using Physiologically Based Pharmacokinetic Modeling

BACKGROUND

Predicting drug pharmacokinetics in pregnant women including placental drug transfer remains challenging. This study aimed to develop and evaluate maternal-fetal physiologically based pharmacokinetic models for two antiretroviral drugs, dolutegravir and raltegravir.

Regulation of breast cancer resistance protein and P-glycoprotein by ezrin, radixin and moesin in lung, intestinal and renal cancer cell lines

Objectives

Ezrin (Ezr), radixin (Rdx) and moesin (Msn) (ERM) proteins anchor other proteins to the cell membrane, serving to regulate their localization and function. Here, we examined whether ERM proteins functionally regulate breast cancer resistance protein (BCRP) and P-glycoprotein in cell lines derived from lung, intestinal and renal cancers.

Methods

ERM proteins were each silenced with appropriate siRNA. BCRP and P-gp functions were evaluated by means of efflux and uptake assays using 7-ethyl-10-hydroxycamptothecin (SN-38) and rhodamine123 (Rho123) as specific substrates, respectively, in non-small cell lung cancer HCC827 cells, intestinal cancer Caco-2 cells and renal cancer Caki-1 cells.

Key findings

In HCC827 cells, the efflux rates of SN-38 and Rho123 were significantly decreased by knockdown of Ezr or Msn, but not Rdx. However, BCRP function was unaffected by Ezr or Rdx knockdown in Caco-2 cells, which do not express Msn. In Caki-1 cells, Rdx knockdown increased the intracellular SN-38 concentration, while knockdown of Ezr or Msn had no effect.

Conclusions

Our findings indicate that regulation of BCRP and P-gp functions by ERM proteins is organ-specific. Thus, if the appropriate ERM protein(s) are functionally suppressed, accumulation of BCRP or P-gp substrates in lung, intestine or kidney cancer tissue might be specifically increased.

A bioinspired in vitro bioelectronic tongue with human T2R38 receptor for high-specificity detection of N-C=S-containing compounds

Detection and identification of bitter compounds draw great attention in pharmaceutical and food industry. Several well-known agonists of specific bitter taste receptors have been found to exhibit anti-cancer effects. For example, N-C=S-containing compounds, such as allyl-isothiocyanates, have shown cancer chemo-preventive effects. It is worth noting that human T2R38 receptor is specific for compounds containing N-C=S moiety. Here, a bioinspired cell-based bioelctronic tongue (BioET) is developed for the high-specificity isothiocyanate-induced bitter detection, utilizing human Caco-2 cells as a primary sensing element and interdigitated impedance sensor as a secondary transducer. As an intestinal carcinoma cell line, Caco-2 endogenously expresses human bitter receptor T2R38, and the activation of T2R38 induces the changes of cellular morphology which can be detected by electric cell-substrate impedance sensing (ECIS). After configuration and optimization of parameters including timing of compound administration and cell density, quantitative bitter evaluation models were built for two well-known bitter compounds, phenylthiocarbamide (PTC) and propylthiouracil (PROP). The bitter specific detection of this BioET is inhibited by probenecid and U-73122, and is not elicited by other taste modalities or bitter ligands that do not activate T2R38. Moreover, by combining different computational tools, we designed a ligand-based virtual screening (LBVS) protocol to select ligands that are likely to activate T2R38 receptor. Three computationally predicted agonists of T2R38 were selected using the LBVS protocol, and the BioET presented response to the predicted agonists, validating the capability of the LBVS protocol. This study suggests this unique cell-based BioET paves a general and promising way to specifically detect N-C=S-containing compounds that can be used for pharmaceutical study and drug development.