Inhibition Of P-glycoprotein Activity Research Articles

Co-administration of herbal inhibitors of P-glycoprotein with renal drugs enhance their bioavailability– In silico approach

Introduction: Multidrug resistance (MDR) is primarily associated with reduced intracellular drug accumulation owing to overexpression of p-glycoprotein, an active efflux transporter. Competitive inhibition or allosteric modulation of p-glycoprotein may alter the pharmacokinetics of the drugs that serve as substrates, resulting in enhanced drug bioavailability and tissue penetration. This study endeavors to assess the efficacy of the components of reno-protective herbs in the inhibition of p-glycoprotein activity thereby enhancing the possibility of the retention of co-administered renal medications inside the target cells. Methods: Drug-likeness and pharmacokinetic properties were determined to ensure the safety and efficacy of herbal constituents. Molecular docking employing the CDOCKER module of Discovery Studio was performed to investigate the binding affinity between the active constituents and the p-glycoprotein receptor (6C0V). Molecular dynamics simulation was utilized to further assess the stability of the complex of receptors with the component bearing its maximal affinity. Results: The analyses suggested that the inhibitors viz., atisine, kutkin, and embelin from Aconitum heterophyllum, phylloquinone from Calendula officinalis, stigmasterol from Paederia foetida, and convallamarogenin from Convallaria majalis demonstrated maximum binding affinity towards p-glycoprotein. Conclusion: Atisine may thus be identified as the lead compound in the augmentation of drug bioavailability inside the cell, along with its reno-protective efficacy.

Short- and long-term single and combined effects of microplastics and chromium on the freshwater water flea Daphnia magna

In this study, we investigated the individual and combined effects of microplastics (MPs) and chromium (Cr) on the freshwater water flea Daphnia magna by measuring mortality, bioaccumulation, antioxidative response, multixenobiotic resistance activity, and sestrin-related mitochondrial biogenesis in short-term assays and in vivo endpoints including reproduction and adult survival rate in long-term assays. Exposure to MPs, Cr, and their combination caused significant deleterious effects and acute toxicity in D. magna. Alterations in oxidative stress occurred in the groups treated with MPs and Cr alone and together. However, upon co-exposure to MPs, the Cr concentration, measured by inductively coupled plasma optical emission spectroscopy, decreased, suggesting that MPs and Cr interact with each other. Based on enzymatic activities, we noted a decrease in MP egestion via inhibition of P-glycoprotein activity in the MP-exposed groups, and multidrug resistance–associated protein activity increased in some of the MP-exposed animals depending on Cr concentration. On the other hand, MP exposure seemed to lead to mitochondrial transcription dysfunction induced by Cr via sestrin-related mitochondrial biogenesis. Overall, these results indicate that co-exposure to MPs and Cr causes acute toxicity in D. magna but lacks the chronic toxicity (21 days) and mitochondrial dysfunction caused by Cr exposure alone.

Cellular pharmacokinetics and pharmacodynamics mechanisms of ginkgo diterpene lactone and its modulation of P‐glycoprotein expression in human SH‐SY5Y cells

Ginkgo diterpene lactone (GDL) is the raw material for ginkgo diterpene lactone meglumine injection, which is used for treating cerebral ischemia. The aims of this study were to explore the cellular pharmacokinetics of GDL in whole cells and subcellular fractions, and detect cellular pharmacodynamics on the human SH-SY5Y cells induced by oxygen-glucose deprivation and reoxygenation (OGD/R). Firstly, a simple, sensitive and reliable liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for assessing the amount of ginkgolide A (GA), B (GB) and K (GK) in cellular/subcellular samples. Then, phosphatidylserine and mitochondria membrane potential were assayed to evaluate the extent of apoptosis effect. The study showed that the cellular/subcellular accumulation of GA and GB were increased in a concentration-dependent manner; the levels of GA and GB in cytosol were the highest among these subcellular organelles. Meanwhile, GDL also attenuated the OGD/R-induced increases in the percentage of apoptotic and mitochondria membrane potential. In addition, verapamil increased the rate and amount of GA and GB entering cellular/subcellular compartments through inhibition of P-glycoprotein activity, and promoted the protective effect of GDL. The present study reports the cellular pharmacokinetics profiles of GA and GB in normal and OGD/R-induced SH-SY5Y cells in vitro for the first time, which provided valuable information for clinical safety application.

Differential inhibitory effects of two Raf-targeting drugs, sorafenib and PLX4720, on the growth of multidrug-resistant cells

B-Raf is the most frequently mutated protein kinase in the MAPK signaling cascade in human cancers, making it an important therapeutic target. Here, we describe the differential effects of two Raf-targeting drugs, sorafenib and PLX4720, on multidrug-resistant v-Ha-ras-transformed cells (Ras-NIH 3T3/Mdr). We demonstrate that the growth of the NIH 3T3/Mdr cell line was affected in a dose-dependent manner more significantly by the pan-Raf inhibitor sorafenib than by the selective mutant B-Raf inhibitor PLX4720. Despite their differential effects on LKB1/AMPK phosphorylation, both sorafenib and PLX4720 inhibited downstream mTOR signaling with concomitant induction of autophagy, implying that the differential effects of sorafenib and PLX4720 on multidrug-resistant cells might not be due to different levels of autophagy and apoptosis. Interestingly, sorafenib caused a dose-dependent increase in rhodamine 123 uptake and retention. More importantly, sorafenib reversed the resistance to paclitaxel in Ras-NIH 3T3/Mdr cells. Moreover, MEK/ERK signaling was hyperactivated by the selective mutant B-Raf inhibitor PLX4720 and inhibited by the pan-Raf inhibitor sorafenib. Our data suggest that sorafenib sensitivity in MDR cells is mediated through the inhibition of P-glycoprotein activity following strong inhibition of Raf/MEK/ERK signaling. Thus, Raf inhibition with sorafenib might be a promising approach to abrogate the multidrug resistance of cancer cells.

Tariquidar inhibition of P-glycoprotein activity in patients with temporal lobe epilepsy measured with PET and (R)-[C-11]Verapamil

Tariquidar inhibition of P-glycoprotein activity in patients with temporal lobe epilepsy measured with PET and (R)-[C-11]Verapamil

Inhibition of P-glycoprotein activity by limonin and other secondary metabolites from Citrus species in human colon and leukaemia cell lines

P-glycoprotein (P-gp), a membrane transporter encoded by the MDR1 gene in human cells, mediates drug efflux from cells and plays a major role in causing multidrug resistance; which is one of the most accepted mechanisms for failure of chemotherapy in cancer treatment. In this study, we investigated the effects of nine naturally occurring compounds isolated from Citrus jambhiri Lush and Citrus pyriformis Hassk (Rutaceae) for their potential to modulate the activity of P-gp in the multidrug-resistant human leukaemia cell line CEM/ADR5000. Limonin, deacetylnomilin, hesperidin, neohesperidin, stigmasterol and ß-sitosterol- O-glucoside inhibited the efflux of the P-gp substrate rhodamine 123 in a concentration-dependent manner. Some of these compounds were more active than verapamil, which was used as a positive control. Treatment of drug-resistant Caco-2 cells with the most active C. jambhiri and C. pyriformis compounds increased their sensitivity to doxorubicin and completely reversed doxorubicin resistance, which agrees with a decreased P-gp activity. Limonin was the most potent P-glycoprotein inhibitor — when it was applied at a non-toxic concentration of 20 µM, it significantly enhanced doxorubicin cytotoxicity 2.98-fold ( P < 0.001) and 2.2-fold ( P < 0.001) in Caco2 and CEM/ADR5000 cells, respectively. These isolated Citrus compounds could be considered as good candidates for the development of novel P-gp/MDR1 reversal agents which may enhance the accumulation and efficacy of chemotherapy agents.

Inhibition of P-glycoprotein activity by curcubitane-type triterpenes and their interaction with doxorubicine on resistant cancer cells

Inhibition of P-glycoprotein activity by curcubitane-type triterpenes and their interaction with doxorubicine on resistant cancer cells

Inhibition of P-glycoprotein Activity at the Primate Blood-Brain Barrier Increases the Distribution of Nelfinavir into the Brain but Not into the Cerebrospinal Fluid

P-glycoprotein (P-gp) expression at the rodent blood-brain barrier (BBB) limits the central nervous system (CNS) distribution of anti-human immunodeficiency virus (HIV) protease inhibitors (PIs). However, it is not clear whether P-gp activity at the human BBB is as effective as that in rodents in preventing the distribution of PIs into the CNS. If it is, inhibition of P-gp at the human BBB could increase the distribution of the PIs into the CNS and, therefore, their efficacy against HIV-associated dementia. Because the distribution of the PIs into the human brain cannot be directly measured, we conducted studies in a more representative animal, the nonhuman primate. Specifically we investigated the distribution of nelfinavir (a PI and a P-gp substrate; 6 mg/kg i.v.) into the brain and cerebrospinal fluid (CSF) of nonhuman primates (cynomolgus monkeys, Macaca fascicularis) in the presence and absence of the potent and selective P-gp inhibitor, zosuquidar, and whether changes in brain nelfinavir concentration, after inhibition of P-gp, paralleled those in the CSF. Our data indicate that nelfinavir has poor penetration into the macaque's brain and CSF, and P-gp inhibition at the BBB by zosuquidar enhanced the distribution of nelfinavir into the brain by 146-fold. However, the concentration of nelfinavir in the CSF was unaffected by coadministration of zosuquidar (p > 0.05). In conclusion, P-gp inhibition at the nonhuman primate BBB significantly enhanced the distribution of nelfinavir into the brain, and this effect was not observed in the CSF. Therefore, as is common in human studies investigating P-gp inhibition at the BBB, CSF concentration of a drug should not be used as a surrogate marker for brain drug concentration.

Antidepressant fluoxetine enhances glucocorticoid receptor function in vitro by modulating membrane steroid transporters.

1. Incubation of LMCAT fibroblast cells with antidepressants potentiates glucocorticoid receptor (GR)-mediated gene transcription in the presence of dexamethasone and cortisol, but not of corticosterone. We have shown that antidepressants do so by inhibiting the LMCAT cell membrane steroid transporter (which is virtually identical to the multidrug resistance P-glycoprotein) and thus by increasing dexamethasone or cortisol intracellular concentrations. However, previous experiments with the antidepressant fluoxetine in the presence of dexamethasone have produced negative results (Pariante et al. (2001). Br. J. Pharmacol., 134, 1335-1343). 2. We have since re-examined the effects of fluoxetine on GR-mediated gene transcription in the presence of dexamethasone. Moreover, we have examined the effects of fluoxetine on GR-mediated gene transcription in the presence of cortisol and corticosterone, and on the intracellular accumulation of radioactive cortisol and corticosterone. Finally, we have examined the effects of fluoxetine on inhibition of P-glycoprotein activity in Caco-2 cells. 3. We now find that fluoxetine (1-10 micro M) enhances GR-mediated gene transcription in the presence of dexamethasone and cortisol (+140-170%), but not of corticosterone, and increases the intracellular accumulation of (3)H-cortisol (+5-15%), but not of (3)H-corticosterone. Moreover, fluoxetine (10 micro M) induces approximately 30% inhibition of PGP activity in Caco-2 cells. 4. Our results show that fluoxetine, like other antidepressants, inhibits membrane steroid transporters.

Increase in Doxorubicin Cytotoxicity by Inhibition of P-glycoprotein Activity with Lomerizine.

Acquired resistance to chemotherapy is a major problem during cancer treatment. One mechanism for drug resistance is overexpression of the MDR (multidrug resistance)1 gene encoding the transmembrane efflux pump, P-glycoprotein (P-gp). Calcium channel blockers such as verapamil, nifedipine and nicardipine have been shown to reverse cellular drug resistance by inhibiting P-gp drug efflux. This study evaluated whether a new calcium channel blocker, lomerizine, influenced doxorubicin (Dox) cytotoxicity and P-gp activity in a P-gp-expressing cell line compared to a non-expressing subline. Verapamil, and even more markedly, lomerizine, increased cellular uptake of calcein transported by P-gp in a P-gp-expressing erythroleukemia cell line, K562-Dox. Ten microM of lomerizine reduced the IC50 of doxorubicin in the K562-Dox from 60000 ng/ml to 800 ng/ml, whereas the IC50 of doxorubicin in the K562 subline was only marginally affected by these drugs. Lomerizine showed greater reduction in P-gp efflux than verapamil at an equimolar concentration. These results suggest that lomerizine has the clinical potential to reverse tumor MDR involving the efflux protein P-gp.

Itraconazole as an alternative for ritonavir liquid formulation when combined with saquinavir

Itraconazole as an alternative for ritonavir liquid formulation when combined with saquinavir

Inhibition of P-Glycoprotein Activity and Chemosensitization of Multidrug-Resistant Ovarian Carcinoma 2780AD Cells by Hexanoylglucosylceramide

In the present study we show that neutral hexanoyl-(glyco)sphingolipids inhibit P-glycoprotein (Pgp) activity in human ovarian 2780AD cells. By contrast, hexanoylceramide and the gangliosides GM3 and GM2 had no effect on Pgp activity, whereas sphingosine had a stimulating effect. In the case of hexanoylglucosylceramide, inhibition of Pgp activity by was reflected by a regained doxorubicin sensitivity of cells, which were grown in medium supplemented with the lipid. Our results lead to the conclusion that a direct transmodulation of Pgp activity by glycolipids occurs, depending on lipid headgroup structure, which can result in reduced resistance to the chemotherapeutic agent doxorubicin.

Inhibition of P-glycoprotein activity and reversal of multidrug resistance in vitro by rosemary extract

The transmembrane transport pump P-glycoprotein (Pgp) causes the efflux of chemotherapeutic agents from cells and is believed to be an important mechanism in multidrug resistance (MDR) in mammary tumours. In the present study we demonstrate that an extract of the common dietary herb rosemary ( Rosemarinus officinalis Labiatae), increases the intracellular accumulation of commonly used chemotherapeutic agents, including doxorubicin (DOX) and vinblastine (VIN), in drug-resistant MCF-7 human breast cancer cells which express Pgp. Rosemary extract (RE) inhibits the efflux of DOX and VIN, which are known to be substrates of Pgp, but does not affect accumulation or efflux of DOX in wild type MCF-7 cells, which lack Pgp. Treatment of drug-resistant cells with RE increases their sensitivity to DOX, which is consistent with an increased intracellular accumulation of the drug. RE blocks the binding of the VIN analogue azidopine to Pgp. Thus, it appears that RE directly inhibits Pgp activity by inhibiting the binding of drugs to Pgp.

Pharmacological characterization of LY335979: A potent cyclopropyldibenzosuberane modulator of P-glycoprotein

The above data indicate that LY335979 displays the following characteristics of an ‘ideal modulator’ of Pgp-mediated multidrug resistance: high affinity binding to Pgp, high potency for in vitro reversal of drug resistance, high therapeutic index (activity was demonstrated at doses ranging from 1–30 mg/kg) observed in in vivo antitumor efficacy experiments, and a lack of pharmacokinetic interactions that alter the plasma concentration of coadministered oncolytic agents. These desirable features strongly suggest that LY335979 is an exciting new clinical agent to test the hypothesis that inhibition of P-glycoprotein activity will result in reversal of multidrug resistance in human tumors.

Influence of dexniguldipine-HCl on rhodamine-123 accumulation in a multidrug-resistant leukaemia cell line: Comparison with other chemosensitisers

In the clinical therapy of cancer, resistance to many cytostatic drugs is a major cause of treatment failure. Among other mechanisms, the expression and pumping activity of P-glycoprotein (PGP) in the membrane of resistant cancer cells is responsible for the reduced uptake of cytostatics. The blockade or inhibition of PGP activity by chemosensitisers seems to be a tenable way to restore sensitivity to antineoplastic drugs and therapeutic efficacy. In the present work the influence of the new chemosensitiser dexniguldipine on rhodamine-123 accumulation in multidrug-resistant leukaemia cells was investigated. Dexniguldipine increases cellular rhodamine-123 accumulation dose-dependently. p ec 50 values (−log concentration of drug showing a half maximal effect) in accumulation studies are dependent on pH of the test system and are in the range of 6.5 (pH 7.2) to 7.2 (pH 8.0) for dexniguldipine. In comparison with other chemosensitisers such as SDZ PSC 833, cyclosporin A, verapamil, dipyridamole, quinidine and amiodarone, dexniguldipine is the most potent drug in this test system. In addition to equilibrium measurements of rhodamine-123 accumulation, efflux of rhodamine-123 was analysed in the absence and presence of chemosensitisers. A clear dose-dependency was seen and, moreover, a dramatic decrease in efflux rates was achieved in the presence of chemosensitisers. The described system can be used to investigate PGP-mediated drug transport on a pharmacological and biochemical basis.

Treatment of acute myeloid leukaemia in a renal allograft recipient: implications of cyclosporin immunosuppressive treatment.

The clinical effects of cyclosporin were evaluated during cytotoxic treatment in a 61 year old man with acute myeloid leukaemia. He had required a renal transplant 18 months before presenting with acute myeloid leukaemia (FAB subtype M4). He had received cyclosporin 3.5-4.0 mg/kg daily to maintain a plasma cyclosporin concentration of 75-150 ng/ml. Cyclosporin was continued during induction chemotherapy with daunorubicin, cytarabine, and 6-thioguanine (DAT). He had fever and oropharyngeal candidiasis that was unresponsive to anti-bacterial drugs but responsive to systemic amphotericin. Bone marrow examination 14 days after chemotherapy showed complete haematological remission. Subsequently he tolerated consolidation treatment with DAT with no serious complications. Unfortunately he developed fatal septicaemia following a second consolidation with mitozantrone and cytarabine. Inhibition of P-glycoprotein activity by cyclosporin may not significantly increase the toxicity of aggressive chemotherapeutic regimens, and as benefit may be achieved by this approach further clinical evaluation is justified.