Reversal of P-glycoprotein-mediated multidrug resistance by novel curcumin analogues in paclitaxel-resistant human breast cancer cells.

Multidrug resistance (MDR) is a major obstacle for successful cancer chemotherapy, and the main cause of MDR has been attributed to overexpression of P-glycoprotein (P-gp). In this present study, four P-gp modulators (E,E)-4,6-bis(styryl)-2-(substituted amino)-pyrimidines were evaluated for their activity in a breast cancer cell line overexpressing P-gp (LCC6MDR). The four modulators displayed significantly better P-gp modulating activity compared with the positive control verapamil (RF = 5.4), with a relative fold (RF) increase in activity ranging from 33.3 to 86.0. In contrast to compounds a and c that exhibited lower cytotoxicity, compounds b and d were nontoxic towards both cancer cells and normal cells, with IC50 values greater than 100 µmol/L. The qRT-PCR results demonstrated that after exposure to 2 µmol/L of compounds a, b, c, and d, the mRNA expression level of MDR1 in LCC6MDR cells decreased to 45%, 50%, 38%, and 51%, respectively. However, the Western-blot results indicated that compound c could reverse P-gp mediated MDR, but not via decreases in protein expression. DOX and Rh123 accumulation and efflux results further confirmed that the reversal of MDR activity happens via inhibition of P-gp efflux and increases in intracellular drug accumulation. These results demonstrated that compound c has low toxicity and is an efficient P-gp modulator, highlighting its potential as a promising candidate for P-gp-mediated reversal of MDR.

Reversal of P-glycoprotein-medicated multidrug resistance by LBM-A5 in vitro and a study of its pharmacokinetics in vivo.

The overexpression of P-glycoprotein (P-gp) in tumors leads to multidrug resistance (MDR), which is a significant obstacle in clinical cancer chemotherapy. The co-administration of anticancer drugs and MDR modulators is a promising strategy for overcoming this problem. Our study aimed to explore the reversal mechanism and safety of the MDR modulator LBM-A5 in vitro, and evaluate its pharmacokinetics and effects on doxorubicin metabolism in vivo. We evaluated an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay of anticancer agents mediated by LBM-A5, the effect of LBM-A5 on rhodamine123 intracellular accumulation, and the efflux in K562/DOX cells to investigate the reversal mechanisms of LBM-A5. The results showed that LBM-A5 inhibits rhodamine123 efflux and increases intracellular accumulation by inhibiting the efflux pump function of P-gp. Furthermore, the therapeutic index and CYP3A4 activity analysis in vitro suggested that LBM-A5 is reasonably safe to use. Also, LBM-A5 (10 mg/kg body mass) achieved the required plasma concentration in sufficient time to reverse MDR in vivo. Importantly, the LBM-A5 treatment group shared similar doxorubicin (DOX) pharmacokinetics with the free DOX group. Our results suggest that LBM-A5 effectively reverses MDR (EC50 = 483.6 ± 81.7 nmol·L(-1)) by inhibiting the function of P-gp, with relatively ideal pharmacokinetics and in a safe manner, and so may be a promising candidate for cancer chemotherapy research.

[PET imaging to study the functional impact of P-glycoprotein in neuropharmacokinetics]. / Imagerie TEP pour l'étude des répercussions fonctionnelles de la P-glycoprotéine en neuropharmacocinétique.

P-glycoprotein (P-gp) is a major efflux transporter at the blood-brain barrier (BBB) where it controls the brain distribution of many drugs. Clinical translation of preclinical data obtained using invasive methods in animals is difficult due to species differences in P-gp expression and function. Positron emission tomography (PET) is an imaging technique allowing for the determination of the tissue kinetics of microdose of radiolabeled compounds. Three radiolabeled substrates of the P-gp have been developed for clinical use: [11C]verapamil, [11C]-N-desmethyl-loperamide and [11C]metoclopramide. These innovative tools enabled the study of P-gp in humans in various patho-physiological conditions including neurological diseases. This approach is also useful to predict the risk for drug-drug interaction caused by P-gp inhibitors at the BBB and address its impact for neuropharmacokinetics in vivo in humans.

[Drug-food interactions in internal medicine: What physicians should know?]. / Interactions médicaments-aliments en médecine interne: quels messages pour le clinicien?

Orally administered medications may interact with various fruits, vegetables, herbal medicines, functional foods or dietary supplements. Drug-food interactions, which are mostly unknown from prescribers, including internists, may be responsible for changes in drug plasma concentrations, which may decrease efficacy or led to sometimes life-threatening toxicity. Aging, concomitant medications, transplant recipients, patients with cancer, malnutrition, HIV infection and those receiving enteral or parenteral feeding are at increased risk of drug-food interactions. This review focused on the most clinically relevant drug-food interactions, including those with grapefruit juice, Saint-John's Wort, enteral or parenteral nutrition, their respective consequences in the clinical setting in order to provide thoughtful information for internists in their routine clinical practice. Specific clinical settings are also detailed, such as the Ramadan or multiple medications especially in elderly patients. Drug-food interactions are also presented with respect to the main therapeutic families, including the non-steroidal anti-inflammatory drugs, analgesics, cardiovascular medications, warfarin as well as new oral anticoagulants, anticancer drugs and immunosuppressant medications. Considerable effort has been achieved to a better understanding of food-drug interactions and increase clinicians' ability to anticipate their occurrence and consequences in clinical practice. Describing the frequency of relevant food-drug interactions in internal medicine is paramount in order to optimize patient care and drug dosing on an individual basis as well as to increase patients and doctors information.