A simplified approach to determining P-glycoprotein expression in peripheral blood mononuclear cell subsets

Qualifying P-glycoprotein in drug-resistant ovarian cancer cells: a dual-mode aptamer probe approach

Drug resistance presents a significant obstacle in treating human ovarian cancer. The development of effective methods for detecting drug-resistant cancer cells is pivotal for tailoring personalized therapies and prognostic assessments. In this investigation, we introduce a dual-mode detection technique employing a fluorogenic aptamer probe for the qualification of P-glycoprotein (P-gp) in drug-resistant ovarian cancer cells. The probe, initially in an "off" state due to the proximity of a quencher to the fluorophore, exhibits increased fluorescence intensity upon binding with the target. The fluorescence enhancement shows a linear correlation with both the concentration of P-gp and the presence of P-gp in drug-resistant ovarian cancer cells. This correlation is quantifiable, with detection limits of 1.56 nM and 110 cells per mL. In an alternate mode, the optimized fluorophores, attached to the aptamer, form larger complexes upon binding to the target protein, which diminishes the rotation speed, thereby augmenting fluorescence polarization. The alteration in fluorescence polarization enables the quantitative analysis of P-gp in the cells, ranging from 100 to 1500 cells per milliliter, with a detection limit of 40 cells per mL. Gene expression analyses, protein expression studies, and immunofluorescence imaging further validated the reliability of our aptamer-based probe for its specificity towards P-gp in drug-resistant cancer cells. Our findings underscore that the dual-mode detection approach promises to enhance the diagnosis and treatment of multidrug-resistant ovarian cancer.

Some pharmacogenetic aspects of the <i>ABCB1</i> gene in lopinavir / ritonavir concentration variability in children with HIV infection: A pilot study

   Polymorphic variants of the multidrug resistance gene (ABCB1 or MDR1) are associated with changes in the absorption and transport of drugs in the body. One of the substrates of the ABCB1 transporter is an antiretroviral drug from the class of protease inhibitors, lopinavir.   The aim. To research the effect of polymorphic variants C1236T and C3435T in the ABCB1 gene on the plasma concentration of lopinavir / ritonavir in children and adolescents living with HIV infection.   Methods. The genotypes of polymorphic variants of the ABCB1 gene were identified in 136 HIV infected children and adolescents; median age – 10 [7–12] years. The plasma concentration of lopinavir / ritonavir was measured from blood taken during the next scheduled appointment as part of dispensary observation at the Irkutsk Regional AIDS Centre using high performance liquid chromatography.   Results. The average duration of lopinavir/ritonavir use as part of an antiretroviral therapy was 55 months. Median viral load in patients was 1 [1–2.03] log 10  copies/ mL; the number of CD4 +  T cells – 38.36 %. The frequency of occurrence of the 3435T and 1236T alleles of the ABCB1 gene was ~50 %. In carriers of the 3435TT genotype, the median lopinavir concentrations 2 and 12 hours after drug intake were 5050.8 [3615.8–5847.7] and 2665.5 [216–4896.3] ng/mL, respectively. In carriers of the 1236TT genotype, median lopinavir concentrations 2 and 12 hours after drug intake were 4913.5 [3355.1–5733.7] and 3290.6 [159.1–4972.5] ng/mL, respectively.   Conclusions. The study did not reveal a significant relationship between the carriage of the C3435T and C1236T genotypes of the ABCB1 gene and the concentrations of lopinavir and ritonavir 2 and 12 hours after drug intake.

Drug efflux transporters and metabolic enzymes in human circulating and testicular T-cell subsets: relevance to HIV pharmacotherapy

OBJECTIVES

ATP-binding cassette (ABC) drug efflux transporters and drug metabolic enzymes could reduce antiretroviral concentrations in HIV target cells. The testis has been demonstrated to be a sanctuary site, displaying suboptimal antiretroviral concentrations and persistent HIV infection. Therefore, we compared the expression and function of ABC transporters and metabolic enzymes in CD4 and CD8 T cells isolated from human testis and peripheral blood mononuclear cells (PBMCs), and assessed their expression in circulating naive and memory CD4 T-cell phenotypes.

DESIGN

Testicular tissue and blood were collected from 15 uninfected donors undergoing gender affirmation surgery. Testicular interstitial cells were isolated by enzymatic digestion, whereas PBMCs were isolated from blood by density gradient centrifugation. The expression and/or function of ABC transporters and metabolic enzymes were examined in blood and testicular T-cell subsets by flow cytometry.

RESULTS

ABC transporters (P-gp, BCRP, MRP1) and metabolic enzymes (CYP3A4, UGT1A1) were expressed in testicular and circulating CD4 and CD8 T cells, as well as in circulating naive, central, transitional, and effector memory T-cell phenotypes. MRP1 demonstrated lower frequencies in T cells from testis compared with PBMCs, as well as in circulating naive T cells compared with the memory T-cell phenotypes. Functional activity of P-gp and BCRP was detected in T-cell subsets from testis and PBMCs.

CONCLUSION

Our findings demonstrate for the first time that antiretroviral drug efflux transporters and metabolic enzymes are functionally expressed in T-cell subsets infiltrating the human testis. These transporters and enzymes can reduce antiretroviral intracellular concentrations, potentially contributing to residual HIV replication in the testis, and negatively impact HIV cure strategies.

Excessive Cyclosporine-Associated Immunosuppression in a Dog Heterozygous for the MDR1 (ABCB1-1Δ) Mutation

Pharmacodynamic monitoring was used to titrate cyclosporine dosing in a dog with immune-mediated hemolytic anemia. Development of a suspected secondary infection, with subsequent discovery of an unexpectedly high level of T-cell suppression despite a relatively low cyclosporine dose, prompted an investigation into the cause of possible excessive immunosuppression. Blood cyclosporine concentrations were within expected target ranges, and the dog was determined to be heterozygous for the multidrug resistance protein 1 (MDR1; ATP-binding cassette sub family B member 1-1Δ) gene mutation. The MDR1 mutation was suspected to have contributed to the excessive immunosuppression experienced by this patient. This case highlights the need to monitor immunosuppressive therapy in the individual patient, especially when the patient is not responding to therapy at typical dosages or when secondary infections develop at dosages lower than expected to cause significant immunosuppression. Pharmacodynamic monitoring can be used to help identify unexpected excessive immunosuppression in dogs receiving cyclosporine, and MDR1 genotyping should be further explored as a potential method of predicting and preventing its occurrence.

Expression levels of P-glycoprotein in peripheral blood CD8+ T lymphocytes from HIV-1-infected patients on antiretroviral therapy

In this study, we aimed to measure P-glycoprotein (P-gp) expression in CD8(+) T lymphocytes of HIV-1-infected patients, to investigate how P-gp levels are affected by antiretroviral therapy (ART) in HIV-1 infection, and to assess the value of using P-gp expression to predict virologic response to ART. Peripheral blood mononuclear cells (PBMCs) were obtained from a cohort of HIV-1‑infected patients in China: 140 patients on ART, and 49 ART-naïve patients. We also enrolled 24 healthy blood donors as the controls. The expression levels of P-gp in CD8(+) T cells of HIV-1-infected patients were evaluated by quantitative reverse transcription PCR, ELISA and flow cytometry. A high inter-individual variability was observed in the CD8(+) T cells of both HIV-1-infected patients and healthy donors; however, the expression levels of P-gp were significantly higher in the HIV-1-infected group on ART compared to the ART-naïve group. The relative proportion of P-gp(+)CD8(+) T cells inversely correlated with the blood CD4(+) T cell count in the HIV-1‑infected patients on ART (r=-0.3343, P=0.0375). Groups of both good and poor responders showed significantly elevated levels of P-gp(+)CD8(+) T cells. The percentage of P-gp(+)CD8(+) T cells appeared to provide a sensitive estimate of the virologic response to ART compared to the CD4(+) T cell count. Our results suggest that P-gp expression varies among HIV-1‑infected patients, but is significantly higher in HIV-1‑infected patients on ART. The overexpression of P-gp is involved in ART initiation during HIV-1 infection, and P-gp(+)CD8(+) T cells may be an additional criterion for the evaluation of the antiretroviral response to ART.

Correlation of tacrolimus levels in peripheral blood mononuclear cells with histological staging of rejection after liver transplantation: preliminary results of a prospective study

Therapeutic drug monitoring of tacrolimus (TAC) is characterized by a complex relationship between trough blood TAC concentrations and therapeutic efficacy. This prospective study evaluates the predictive value of intrahepatic, peripheral blood mononuclear cells (PBMCs) and blood TAC concentrations during the early postliver transplantation (LT) period. In a cohort of 90 adult liver recipients under TAC-based monotherapy, liver biopsies were performed at day 7 post-LT, and PBMCs TAC concentrations were measured at day 1, 3, 5, and 7 post-LT. Both intrahepatic and PBMCs TAC concentrations were determined. All biopsies were graded following the Banff scoring. Intrahepatic, and day 3, 5, 7 PBMCs concentrations correlated very well with day 7 liver Banff rejection scores (P < 0.05). Clinical rejection was characterized by significantly lower mean TAC PBMCs concentrations at day 5 and 7 (P < 0.05) and tended to be associated to lower mean intrahepatic TAC concentrations at day 7 (P = 0.059). Intrahepatic TAC concentrations at day 7 significantly correlated with TAC PBMCs concentrations from day 5 post-LT (P < 0.05). TAC PBMCs concentrations might be reliable markers of immunosuppression efficacy during the early phase after LT. This finding could represent an additional tool to individualize more precisely early immunosuppressive schemes after liver transplantation.

The role of cytokines in the regulation of drug disposition: extended functional pleiotropism?

INTRODUCTION

Drug disposition, metabolism and drug-drug interactions are important considerations for most drugs. Cytokines are integral to the successful resolution of many diseases. Data are emerging on a role for cytokines in regulation of the expression and activity of drug transporters and drug metabolising enzymes. Investigation of the interaction between pharmacological and immunological responses is key to understanding the complex relationships involved in patient response to therapy.

AREAS COVERED

Evidence detailing the ability of cytokines to regulate drug disposition and metabolism is reviewed in the context of different cell and tissue types. The literature search undertaken provides an overview of the current understanding of the interrelationship between pharmacological and immunological factors which may influence successful drug therapy.

EXPERT OPINION

Dysregulation of cytokines and cytokine networks is a hallmark of a number of diseases such as HIV and cancer. The mechanisms by which the immune system can influence drug disposition are relatively understudied but recent work has highlighted the necessity for examining its impact on pharmacokinetics and pharmacodynamics. A more comprehensive approach in clinical studies will allow better determination of the impact of cytokines on drug disposition. In addition, determining the mechanisms that underpin the differential effects of cytokines across different cell types will clarify the responses reported in these studies.

Tegillarca granosa extract Haishengsu inhibits the expression of P-glycoprotein and induces apoptosis in drug-resistant K562/ADM cells

This study was designed to investigate the effect and molecular mechanisms of Haishengsu (HSS), a protein extract from a shellfish Tegillarca granosaL., on a drug resistant leukemia cell line. Cultured K562/Adriamycin (ADM) cells were treated with HSS at 10, 20 and 40 microg/mL, respectively. The apoptosis and expression of p-glycoprotein was evaluated by flow cytometry. Expressions of caspase-3 and Bcl-2 were also evaluated. There was a significant dose-dependent increase in the apoptosis in the HSS treated K562/ADM cells (P < 0.05 and 0.01, respectively). The p-glycoprotein expression in the 40 microg/mL HSS group (14.8%) was lower than in the control (16.9%, P < 0.05) and the 10 microg/mL HSS group (7.3%, P < 0.05), but it was similar to the HSS 20 microg/mL group (10.7%, P > 0.05). The expressions of apoptosis-stimulating protein caspase-3 protein were increased, whereas the expressions of apoptosis-suppressing Bcl-2 were decreased in the HSS groups, as compared with the levels in the control group (P < 0.05). We conclude that HSS induces apoptosis of the Adriamycin-resistant K562/ADM cells. The enhanced expressions in caspase-3 and the reduced expressions in Bcl-2 protein may have contributed to the apoptosis-stimulating effect of HSS. The inhibition of p-glycoprotein suggests that HSS may diminish the resistance to Adriamycin and potentially enhance the therapeutic effects.

MDR1 3435T and 1236T alleles delay disease progression to pediatric AIDS but have no effect on HIV-1 vertical transmission

BACKGROUND

Single nucleotide polymorphisms (SNPs) in the MDR1 gene, coding for the drug transporter P-glycoprotein, may modulate the response to antiretroviral therapy and susceptibility to HIV-1 infection. We investigated whether the MDR1 SNPs C1236T (exon 12) and C3435T (exon 26) affect HIV-1 vertical transmission and progression to pediatric AIDS.

METHODS

The MDR1 genotypes were identified by PCR-restriction fragment length polymorphism (RFLP) assays in 219 HIV-infected, 128 exposed uninfected children and 231 HIV-seronegative blood donors. Genotype and haplotype frequencies were estimated in the different groups. The median follow-up time of the infected cohort was 108 months and AIDS-free time was evaluated for the different MDR1 genotypes in 171 HIV-infected children.

RESULTS

We found that both C1236T and C3435T polymorphisms were highly frequent in the studied groups (approximately 0.44) and showed strong linkage disequilibrium. There was no association between MDR1 genotypes and HIV-1 vertical transmission. However, a protective effect against progression to AIDS was associated with MDR1 3435CT, 1236CT and 1236TT genotypes (P = 0.005, P = 0.024 and P = 0.026, respectively). Moreover, haplotype pairs' analysis showed that the 3435CT/1236CT and 3435CT/1236TT exerted a significant protection against progression to pediatric AIDS (P = 0.0025 and P = 0.006, respectively).

CONCLUSION

We conclude that in Argentinean children, MDR1 genotypes are associated with progression to AIDS, but they do not affect HIV-1 susceptibility by vertical transmission. These results support the notion that P-glycoprotein plays a role in HIV-1 infection independently from its role in drug transport.

Flow cytometric evaluation of multidrug resistance proteins

There are several ways to detect proteins on cells. One quite frequently used method is flow cytometry. This method needs fluorescently labeled antibodies that can attach selectively to the protein to be investigated for flow cytometric detection. Flow cytometry scans individual cells, virtually without their surrounding liquid, and can scan many cells in a very short time. Because of this advantage of flow cytometry, it was adapted to investigate transport proteins on normal and cancerous human cells and cell lines. These transport proteins play important roles in human metabolism. Absorption in the intestine, excretion at the kidney, protection of the CNS compartment and the fetus from xenobiotics, and other vital functions depend on these transporters. However, several transporters are overexpressed in cancer cells. These overexpressed transporters pump out anticancer drugs from the cells and prevent their curative effects. The detection and quantitation of these types of transporters in cancer cells is important for this reason. Here, we review literature on flow cytometric detection of the three most studied transporters: P-glycoprotein, multidrug resistance-associated proteins, and breast cancer resistance protein.

Relation between mRNA expression level of multidrug resistance 1/ABCB1 in blood cells and required level of tacrolimus in pediatric living-donor liver transplantation

It has been difficult to set an individualized therapeutic window of tacrolimus after organ transplantation, because of wide interindividual variation of responsiveness to immunosuppressive therapy. In this study, we examined the significance of multidrug resistance 1 (MDR1) in the peripheral blood cells by comparing the trough concentration of tacrolimus with the occurrence of acute cellular rejection (ACR) in retrospectively collected pediatric living-donor liver transplant patients, who were enrolled after obtaining written informed consent. No significant difference in the intraindividual variation in MDR1 mRNA expression in the peripheral blood cells was observed between postoperative days 3 and 7. The average trough concentration of tacrolimus during the 15-day postoperative period was significantly higher in the event-free patients than in those who experienced ACR (21 of 44 cases), and they had higher levels of blood MDR1 mRNA. In addition, the average trough concentration of tacrolimus significantly correlated with the logarithmically transformed MDR1 mRNA data from the blood cells in patients of both the event-free (r = 0.5406; P = 0.0077) and ACR (r = 0.4772; P = 0.0284). The cellular accumulation of [(14)C]tacrolimus in the peripheral blood mononuclear cells was 2-fold higher in mdr1a/1b-knockout mice than in wild-type mice (P = 0.0182). These results suggest that MDR1 in blood cells decreases the leukocytic concentration of tacrolimus, and it could be a useful marker to establish an individualized target concentration of tacrolimus to prevent ACR in pediatric patients after liver transplantation.

Real-time quantitative polymerase chain reaction for BCRP, MDR1, and MRP1 mRNA levels in lymphocytes and monocytes

The expression levels of mRNAs for MDR1 (P-glycoprotein), multidrug resistance-associated proteins (MRP1), and BCRP (breast cancer resistance protein; mitoxantrone resistance protein) were quantitatively determined in lymphocytes and monocytes. Monocytes and lymphocytes were obtained from 3 healthy male and 2 healthy female volunteers. BCRP, MDR1, and MRP1 mRNA levels were determined by real-time quantitative reverse transcriptase polymerase chain reaction. In lymphocytes, relative concentrations of mRNAs for target proteins (BCRP, MDR1, and MRP1) were 1.00 +/- 0.478, 9.67 +/- 5.53, and 0.116 +/- 0.0613 respectively, and in monocytes 1.00 +/- 0.854, 0.821 +/- 0.263, and 0.090 +/- 0.052, respectively. The MDR1 mRNA level was cell type dependent, whereas there was no difference in BCRP and MRP1 expression levels between lymphocytes and monocytes. Comparison of mRNA levels for the three major multidrug-resistant efflux pumps reveals that MDR1 is the predominant form in lymphocytes and BCRP is the predominant form in monocytes.

The implications of P-glycoprotein in HIV: friend or foe?

P-glycoprotein (P-gp), coded by the ABCB1 gene, has a wide tissue distribution. The drug transporter is known to limit the bioavailability of a plethora of drugs and xenobiotics including the human immunodeficiency virus (HIV) protease inhibitors. There remains a considerable degree of debate in the literature with respect to the role of ABCB1 polymorphisms in HIV-treatment outcome and some studies have also implicated antiretroviral drugs as inducers of P-gp. Recent evidence indicates a role for P-gp in the inhibition of viral infectivity and/or release and cellular relationships with other infection-related proteins (and cholesterol). It is becoming increasingly clear that future studies on P-gp in HIV should consider both pharmacological and virological issues.

Functional correlation of P-glycoprotein expression and genotype with expression of the human immunodeficiency virus type 1 coreceptor CXCR4

The aim of this study was to investigate the relationship between lymphocyte P-glycoprotein (P-gp) expression and genotype in vivo and the expression of lymphocyte receptors critical in the life cycle of human immunodeficiency virus type 1 (HIV-1), i.e., CD4, CCR5, and CXCR4. Using flow cytometry to quantify each membrane receptor/transporter, we demonstrate a highly significant correlation between P-gp protein expression and the expression of CXCR4 (rho = 0.874; P < 0.0001). Furthermore, confocal microscopy showed colocalized expression of CXCR4 and P-gp in the lymphocyte membrane. This significant relationship was also apparent at the mRNA level by use of reverse transcription-PCR (rho = 0.61; P < 0.005) and was present in both phytohemagglutinin-stimulated and unstimulated peripheral blood mononuclear cells. Genotypic analysis of the C3435T single-nucleotide polymorphism of P-gp confirmed significantly higher levels of P-gp in C (range, 2.45 to 11.00 relative fluorescence units [RFU])- than in T (range, 0.25 to 5.00 RFU)-homozygous individuals (P = 0.0088; 95% confidence interval [95% CI], 0.7 to 6.3 RFU). An equivalent association between CXCR4 levels and C (range, 12.7 to 44.1 RFU) versus T (range, 3 to 18.9 RFU) genotype was also demonstrated (P = 0.0019; 95% CI, 5.4 to 23.7). Functionally, although these correlates had no impact on HIV-1 production from either X4- or R5-tropic virus, expression correlated significantly with the activity of the HIV-1 protease inhibitor (PI) saquinavir for both P-gp (rho = 0.75; P = 0.0019) and CXCR4 (rho = 0.71; P = 0.0041). This study defines an association between P-gp (expression and genotype) and CXCR4 that may have implications for the selection of viral tropism and the access of drugs to protease for specific tropic types. The interplay between these two proteins may also influence the viral genotypes which escape effective chemotherapy and which therefore have the opportunity to evolve resistance to PIs.

Distinct Inhibitory Effects of Tacrolimus and Cyclosporin A on Calcineurin Phosphatase Activity

We have compared the pharmacodynamic properties of calcineurin inhibitors tacrolimus and cyclosporin A in rats to clarify the different therapeutic drug monitoring strategy of both drugs in a clinical situation. In various tissue extracts, the inhibition of calcineurin activity by cyclosporin A was significantly greater than that by tacrolimus at the same drug concentration (1 microM) in the thymus, heart, liver, spleen, kidney, and testis (p < 0.05). The time profiles of blood concentrations and calcineurin activity in whole blood were examined after single or repeated administration of each drug in rats. A substantial time delay in the inhibition was observed following the single administration of tacrolimus or cyclosporin A, resulting in an anticlockwise hysteresis in the relationship between blood concentrations and calcineurin inhibition in whole blood. In contrast, such a hysteresis loop diminished after the repeated administration of each drug, and the recovery rate of calcineurin activity was greater for the inhibition induced by cyclosporin A than by tacrolimus. Furthermore, tacrolimus produced a comparable inhibition of calcineurin activity in whole blood at lower blood concentrations than cyclosporin A. Overall, the effect compartment model well described the time profiles of calcineurin activity in whole blood after the single and repeated administrations of each drug. These findings suggest that the properties of calcineurin inhibition differ between tacrolimus and cyclosporin A. Distinct pharmacodynamics may partly contribute to the therapeutic drug monitoring strategy in transplant patients receiving calcineurin inhibitors.

Intracellular and plasma pharmacokinetics of saquinavir-ritonavir, administered at 1,600/100 milligrams once daily in human immunodeficiency virus-infected patients

Ritonavir-boosted saquinavir (SQV/r) is currently licensed as a twice-daily regimen. Reducing the pill burden with once-daily dosing may improve adherence. Intracellular concentrations of drugs must be related to the clinical efficacy of protease inhibitors. The aims of the study were to determine the cellular and plasma saquinavir and ritonavir concentrations, to determine the half-lives (t(1/2)s) of the drugs in each compartment, and to examine relationships between drug accumulation and lymphocyte subset P glycoprotein (P-gp) expression. Venous blood samples from 12 human immunodeficiency virus-infected patients receiving a hard-gel formulation of SQV/r (1,600/100 mg once daily) were collected at 2, 6, 12, and 24 h after dosing. Peripheral blood mononuclear cells were separated by density gradient centrifugation, and P-gp expression was measured by dual-color flow cytometry. Plasma and intracellular (cell-associated) drug concentrations were measured by high-performance liquid chromatography-tandem mass spectrometry. The ratio of the intracellular drug area under the concentration-time curve from 0 to 24 h (AUC(0-24 h)) to plasma drug AUC(0-24 h) was calculated to determine cellular drug accumulation. The median (range) AUC(0-24 h) of saquinavir in plasma was 16.2 (5.7 to 39.3) mg. h. liter(-1), and that in cells was 46.3 (24.7 to 114.6) mg. h. liter(-1). Corresponding ritonavir values were 7.5 (1.5 to 14.6) mg. h. liter(-1) and 10.4 (3.2 to 13.7) mg. h. liter(-1), respectively. The median accumulation ratios of cellular AUC to plasma AUC for saquinavir and ritonavir were 3.31 (range, 1.49 to 6.69) and 1.46 (range, 0.83 to 4.15), respectively. Significant differences between the plasma and intracellular saquinavir t(1/2)s (4.5 h [range, 2.5 to 9.3 h] and 5.9 h [range, 4.0 to 17.7 h]; P = 0.034) and between the plasma and intracellular ritonavir t(1/2)s (4.1 h [range, 2.6 to 8.3 h] and 6.2 h [range, 3.9 to 18.6 h]; P = 0.032) were observed. No relationship was observed between the accumulation of saquinavir or ritonavir and lymphocyte subset P-gp expression. The intracellular t(1/2)s of saquinavir and ritonavir were longer than the plasma t(1/2)s, indicating that intracellular drug may be available at a time when concentrations in plasma are below the minimum effective concentration.