Value of quantifying ABC transporters by mass spectrometry and impact on in vitro-to-in vivo prediction of transporter-mediated drug-drug interactions of rivaroxaban

Unveiling the mechanisms and challenges of cancer drug resistance

Cancer treatment faces many hurdles and resistance is one among them. Anti-cancer treatment strategies are evolving due to innate and acquired resistance capacity, governed by genetic, epigenetic, proteomic, metabolic, or microenvironmental cues that ultimately enable selected cancer cells to survive and progress under unfavorable conditions. Although the mechanism of drug resistance is being widely studied to generate new target-based drugs with better potency than existing ones. However, due to the broader flexibility in acquired drug resistance, advanced therapeutic options with better efficacy need to be explored. Combination therapy is an alternative with a better success rate though the risk of amplified side effects is commonplace. Moreover, recent groundbreaking precision immune therapy is one of the ways to overcome drug resistance and has revolutionized anticancer therapy to a greater extent with the only limitation of being individual-specific and needs further attention. This review will focus on the challenges and strategies opted by cancer cells to withstand the current therapies at the molecular level and also highlights the emerging therapeutic options -like immunological, and stem cell-based options that may prove to have better potential to challenge the existing problem of therapy resistance. Video Abstract.

Research Methods and New Advances in Drug-Drug Interactions Mediated by Renal Transporters

The kidney is critical in the human body's excretion of drugs and their metabolites. Renal transporters participate in actively secreting substances from the proximal tubular cells and reabsorbing them in the distal renal tubules. They can affect the clearance rates (CLr) of drugs and their metabolites, eventually influence the clinical efficiency and side effects of drugs, and may produce drug-drug interactions (DDIs) of clinical significance. Renal transporters and renal transporter-mediated DDIs have also been studied by many researchers. In this article, the main types of in vitro research models used for the study of renal transporter-mediated DDIs are membrane-based assays, cell-based assays, and the renal slice uptake model. In vivo research models include animal experiments, gene knockout animal models, positron emission tomography (PET) technology, and studies on human beings. In addition, in vitro-in vivo extrapolation (IVIVE), ex vivo kidney perfusion (EVKP) models, and, more recently, biomarker methods and in silico models are included. This article reviews the traditional research methods of renal transporter-mediated DDIs, updates the recent progress in the development of the methods, and then classifies and summarizes the advantages and disadvantages of each method. Through the sorting work conducted in this paper, it will be convenient for researchers at different learning stages to choose the best method for their own research based on their own subject's situation when they are going to study DDIs mediated by renal transporters.

Ivermectin induces chicken BCRP/ABCG2 expression and function: Involvement of CXR signaling pathway and mRNA stabilization

Ivermectin is a macrocyclic lactone antiparasitic drug widely used in human and veterinary medicine. Previous studies indicated that ivermectin could interact with P-glycoprotein, being a good inducer and substrate; however, it is unknown whether ivermectin affects BCRP of chicken. In this study, we found that ivermectin distinctly affected the expression of BCRP in a time- and concentration-dependent up-regulatory way in chicken primary hepatocytes. Subsequent series of experiments showed that the BCRP induction is related with the increase of CXR expression and, promoting CXR translocations to the nucleus and enhancing the stability of Abcg2 mRNA at the post-transcriptional level by ivermectin. Furthermore, we observed that ivermectin also enhanced the stability of Abcg2 mRNA at the post-transcriptional level by Act-D chase assay. We got the similar results by in vivo test that ivermectin-induced BCRP and CXR expression in pharmacologically important tissues, and decreased the apparent permeability coefficient of florfenicol (substrate of chicken BCRP). In conclusion, the results indicated that ivermectin could induce chicken BCRP expression and function through the transcriptional CXR signaling pathway and post-transcriptional mRNA stabilization.

TNF-α and IL-1β Exposure Modulates the Expression and Functionality of P-Glycoprotein in Intestinal and Renal Barriers

Inflammation is characterized by an increased secretion of proinflammatory cytokines known to alter the expression and functionality of drug transporters. Since P-glycoprotein (P-gp) plays a key role in the pharmacokinetics of several drugs, these modulations could further affect drug exposure. In this context, this study aims to investigate the impact of in vitro cytokine exposure on the expression and activity of P-gp using the intestinal model Caco-2 and the human renal cells RPTEC/TERT1. Cells were exposed to various concentrations of tumor necrosis factor (TNF)-α and interleukin (IL)-1β for 24 or 72 h. Gene expression was then assessed by RT-qPCR followed by absolute quantification of P-gp using liquid chromatography coupled with mass spectrometry. Then, the activity of P-gp was assessed by the intracellular accumulation of rhodamine 123. TNF-α increased both the gene expression and P-gp activity by 15-40% in each model. Minor modulations were observed at the protein level with increases of up to 8% for RPTEC/TERT1 cells and 24% for Caco-2 cells. Conversely, IL-1β led to a downregulation of gene, protein, and functionality by 48 and 25% in intestinal and renal cells, respectively. Taken together, these data highlighted that gene expression levels and functional activity of P-gp are altered by the pro-inflammatory cytokines in intestinal and renal cells. Such pronounced changes in human P-gp could result in altered exposure to drug substrates. Further in vivo studies are needed to confirm the impact of inflammation on drug pharmacokinetics.

In Vitro Evaluation of P-gp-Mediated Drug-Drug Interactions Using the RPTEC/TERT1 Human Renal Cell Model

BACKGROUND AND OBJECTIVES

In vitro evaluation of the P-glycoprotein (P-gp) inhibitory potential is an important issue when predicting clinically relevant drug-drug interactions (DDIs). Located within all physiological barriers, including intestine, liver, and kidneys, P-gp plays a major role in the pharmacokinetics of various therapeutic classes. However, few data are available about DDIs involving renal transporters during the active tubular secretion of drugs. In this context, the present study was designed to investigate the application of the human renal cell line RPTEC/TERT1 to study drug interactions mediated by P-gp.

METHODS

The P-gp inhibitory potentials of a panel of drugs were first determined by measuring the intracellular accumulation of rhodamine 123 in RPTEC/TERT1 cells. Then four drugs were selected to assess the half-maximal inhibitor concentration (IC50) values by measuring the intracellular accumulation of two P-gp-substrate drugs, apixaban and rivaroxaban. Finally, according to the FDA guidelines, the [I₁]/IC50 ratio was calculated for each combination of drugs to assess the clinical relevance of the DDIs.

RESULTS

The data showed that drugs which are known P-gp inhibitors, including cyclosporin A, ketoconazole, and verapamil, caused great increases in rhodamine 123 retention, whereas noninhibitors did not affect the intracellular accumulation of the P-gp substrate. The determined IC50 values were in accordance with the inhibition profiles observed in the rhodamine 123 accumulation assays, confirming the reliability of the RPTEC/TERT1 model.

CONCLUSIONS

Taken together, the data demonstrate the feasibility of the application of the RPTEC/TERT1 model for evaluating the P-gp inhibitory potentials of drugs and consequently predicting renal drug interactions.

Strategies for Structural Modification of Small Molecules to Improve Blood-Brain Barrier Penetration: A Recent Perspective

In the development of central nervous system (CNS) drugs, the blood-brain barrier (BBB) restricts many drugs from entering the brain to exert therapeutic effects. Although many novel delivery methods of large molecule drugs have been designed to assist transport, small molecule drugs account for the vast majority of the CNS drugs used clinically. From this perspective, we review studies from the past five years that have sought to modify small molecules to increase brain exposure. Medicinal chemists make it easier for small molecules to cross the BBB by improving diffusion, reducing efflux, and activating carrier transporters. On the basis of their excellent work, we summarize strategies for structural modification of small molecules to improve BBB penetration. These strategies are expected to provide a reference for the future development of small molecule CNS drugs.