Effect of the novel antipsychotic drug perospirone on P-glycoprotein function and expression in Caco-2 cells

The potentiation of menadione on imatinib by downregulation of ABCB1 expression

Imatinib was the first BCR-ABL inhibitor used in clinical practice to treat chronic myeloid leukaemia (CML) and significantly improve the life expectancy of CML patients in the chronic phase. However, a portion of CML patients are resistant to imatinib. This study aimed to determine whether menadione (Vitamin K3) can improve imatinib efficacy in CML and to thoroughly explore the combination regimen mechanism between imatinib and menadione. Menadione improved imatinib efficacy in K562 cells by downregulating ABCB1 expression and increased the intracellular concentration of imatinib, which confirmed that this combination regimen is more effective than imatinib monotherapy. The results demonstrate that menadione and imatinib combination therapy may be a promising approach to refractory CML.

Tailoring of P-glycoprotein for effective transportation of actives across blood-brain-barrier

P-Glycoprotein serves as a gatekeeper in the blood-brain-barrier wherein, it shows a vital part in the elimination of xenobiotics, drugs, foreign molecules etc. and guards the central nervous system from infections and external toxic molecules by functioning as an efflux transporter. It plays an essential role in various brain-related conditions like Parkinsonism, Alzheimer's disease, depression, cancer, etc. and terminates the entry of therapeutic agents across blood-brain-barrier which remains a significant challenge serving as major hindrance in pharmacotherapy of disease. The physiological structure and topology of P-glycoprotein and its relation with blood-brain-barrier and central nervous system gives an idea for targeting nanocarriers across the barrier into brain. This review article provides an overview of current understanding of the nanoformulations-based P-gp trafficking strategies like nanocarriers, stem cell therapy, drugs, substrates, polymeric materials, chemical compounds as well as naturally occurring active constituents for improving drug transport in brain across blood-brain-barrier and contributing in effective nanotherapeutic development for treatment of CNS disorders.

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.

Validation of Thiosemicarbazone Compounds as P-Glycoprotein Inhibitors in Human Primary Brain-Blood Barrier and Glioblastoma Stem Cells

P-glycoprotein (Pgp) is highly expressed on blood-brain barrier (BBB) and glioblastoma (GB) cells, particularly on cancer stem cells (SC). Pgp recognizes a broad spectrum of substrates, limiting the therapeutic efficacy of several chemotherapeutic drugs in eradicating GB SC. Finding effective and safe inhibitors of Pgp that improve drug delivery across the BBB and target GB SC is open to investigation. We previously identified a series of thiosemicarbazone compounds that inhibit Pgp with an EC₅₀ in the nanomolar range, and herein, we investigate the efficacy of three of them in bypassing Pgp-mediated drug efflux in primary human BBB and GB cells. At 10 nM, the compounds were not cytotoxic for the brain microvascular endothelial hCMEC/D3 cell line, but they markedly enhanced the permeability of the Pgp-substrate doxorubicin through the BBB. Thiosemicarbazone derivatives increased doxorubicin uptake in GB, with greater effects in the Pgp-rich SC clones than in the differentiated clones derived from the same tumor. All compounds increased intratumor doxorubicin accumulation and consequent toxicity in GB growing under competent BBB, producing significant killing of GB SC. The compounds crossed the BBB monolayer. The most stable derivative, 10a, had a half-life in serum of 4.2 h. The coadministration of doxorubicin plus 10a significantly reduced the growth of orthotopic GB-SC xenografts, without eliciting toxic side effects. Our work suggests that the thiosemicarbazone compounds are able to transform doxorubicin, a prototype BBB-impermeable drug, into a BBB-permeable drug. Bypassing Pgp-mediated drug efflux in both BBB and GB SC, thiosemicarbazones might increase the success of chemotherapy in targeting GB SC, which represent the most aggressive and difficult components to eradicate.

New Tetrahydroisoquinoline Derivatives Overcome Pgp Activity in Brain-Blood Barrier and Glioblastoma Multiforme in Vitro

P-glycoprotein (Pgp) determines resistance to a broad spectrum of drugs used against glioblastoma multiforme (GB). Indeed, Pgp is highly expressed in GB stem cells and in the brain-blood barrier (BBB), the peculiar endothelium surrounding the brain. Inhibiting Pgp activity in the BBB and GB is still an open challenge. Here, we tested the efficacy of a small library of tetrahydroisoquinoline derivatives with an EC₅₀ for Pgp ≤ 50 nM, in primary human BBB cells and in patient-derived GB samples, from which we isolated differentiated/adherent cells (AC, i.e., Pgp-negative/doxorubicin-sensitive cells) and stem cells (neurospheres, NS, i.e., Pgp-positive/doxorubicin-resistant cells). Three compounds used at 1 nM increased the delivery of doxorubicin, a typical substrate of Pgp, across BBB monolayer, without altering the expression and activity of other transporters. The compounds increased the drug accumulation within NS, restoring doxorubicin-induced necrosis and apoptosis, and reducing cell viability. In co-culture systems, the compounds added to the luminal face of BBB increased the delivery of doxorubicin to NS growing under BBB and rescued the drug’s cytotoxicity. Our work identified new ligands of Pgp active at low nanomolar concentrations. These compounds reduce Pgp activity in BBB and GB and improve in vitro chemotherapy efficacy in this tumor.

GMZ-1 is a podophyllotoxin derivative that suppresses growth and induces apoptosis in adriamycin-resistant K562/A02 cells through modulation of MDR1 expression

The incidence of multidrug resistance (MDR) during cancer chemotherapy is a major challenge for treatment. With the aim of identifying drugs that are capable of targeting treatment‑resistant cancer cells, the present study evaluated the efficacy of GMZ‑1 in cancer chemotherapy using K562/A02, an MDR leukemia cell line. Cell viability and apoptosis were measured by MTT assay and flow cytometry/Giemsa staining, respectively. The expression levels of the MDR protein 1 (MDR1) gene transcript and protein in K562/A02 cells were determined by reverse transcription‑quantitative polymerase chain reaction and western blot analyses, respectively. GMZ‑1 suppressed the viability of various human cancer cell lines and induced apoptosis in the K562/A02 cell line in a time‑ and concentration‑dependent manner. GMZ‑1 toxicity may be associated with a decrease in MDR gene expression. These findings demonstrated that GMZ‑1 may have efficacy as a potential antitumor drug to overcome leukemia cell resistance to apoptosis induced by chemotherapy.

Relationship between P-glycoprotein and second-generation antipsychotics

The membrane transport protein P-glycoprotein (P-gp) is an interesting candidate for individual differences in response to antipsychotics. To present an overview of the current knowledge of P-gp and its interaction with second-generation antipsychotics (SGAs), an internet search for all relevant English original research articles concerning P-gp and SGAs was conducted. Several SGAs are substrates for P-gp in therapeutic concentrations. These include amisulpride, aripiprazole, olanzapine, perospirone, risperidone and paliperidone. Clozapine and quetiapine are not likely to be substrates of P-gp. However, most antipsychotics act as inhibitors of P-gp, and can therefore influence plasma and brain concentrations of other substrates. No information was available for sertindole, ziprasidone or zotepine. Research in animal models demonstrated significant differences in antipsychotic brain concentration and behavior owing to both P-gp knockout and inhibition. Results in patients are less clear, as several external factors have to be accounted for. Patients with polymorphisms which decrease P-gp functionality tend to perform better in clinical settings. There is some variability in the findings concerning adverse effects, and no definitive conclusions can be drawn at this point.

Pharmacokinetics and metabolism update for some recent antipsychotics

INTRODUCTION

The search for drugs that reduce psychotic symptoms, with minimal adverse effects, has led to the development of new agents that act somewhat differently from their older antipsychotic counterparts. These agents, which include aripiprazole, lurasidone and perospirone, act by targeting both D₂ and 5-HT(1A) receptors, in addition to other characteristic receptors.

AREAS COVERED

This article covers the pharmacokinetics and metabolism of aripiprazole, perospirone, lurasidone and cariprazine. The review also describes the effects of physiological and pathological variables on these drugs as well as potential drug interactions. The author provides the reader with knowledge of the fundamental pharmacokinetic characteristics and metabolic pathways of these new antipsychotics, emphasizing the clinically important common features and differences compared to other older agents.

EXPERT OPINION

Aripiprazole, perospirone, lurasidone and cariprazine share some of the pharmacokinetic characteristics of older, lipophilic antipsychotics and, like these, each has some distinct pharmacokinetic features that are clinically beneficial and some that are not. We await the results of future practical effectiveness trials of these new antipsychotics and their follow-on derivatives to learn more about their benefit/risk profile compared with established antipsychotics. It is hoped that some of these newer antipsychotics will not only increase the range of pharmacotherapeutic options, but decisively improve the expectations of psychotherapy for schizophrenia.

Effect of MDR modulators verapamil and promethazine on gene expression levels of MDR1 and MRP1 in doxorubicin-resistant MCF-7 cells

PURPOSE

One of the major problems of cancer chemotherapy is the development of multidrug resistance (MDR) phenotype. Among the numerous mechanisms of MDR, a prominent one is the increased expression of membrane transporter proteins, the action of which leads to decreased intracellular drug concentration and cytotoxicity of drugs. Among them, P-gp and MRP1, encoded by MDR1 and MRP1 genes, respectively, have been associated with MDR phenotype. Chemical modulators can be used to reverse MDR. These chemicals can either modulate MDR due to their substrate analogy (such as calcium channel blocker verapamil) or interact with phospholipid membranes (such as antihistaminic drug promethazine). This study focuses on the effect of verapamil and promethazine on the expression levels of MDR1 and MRP1 genes and the drug transport activity in doxorubicin-resistant MCF-7 breast carcinoma cell line.

METHODS

Doxorubicin-resistant MCF-7 (MCF-7/Dox) cells were incubated with either verapamil or promethazine, and total RNA was isolated. Real-time PCR (qPCR) was carried out by using specific primers for MDR1, MRP1, and β-actin genes. Intracellular doxorubicin accumulation was also examined by confocal laser scanning microscopy in treated cells.

RESULTS

Results demonstrated a significant decrease in both MDR1 and MRP1 expression levels after promethazine applications. It has also been shown that treatment of the cells with verapamil results in significant decrease in MDR1 mRNA levels. Confocal laser scanning microscopy images demonstrated that the intracellular accumulation of doxorubicin was increased after verapamil treatment in MCF-7/Dox cells.

CONCLUSIONS

The present study gives an idea about the efficiency of verapamil and promethazine on MDR reversal both in gene expression and in transport activity levels.