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Epilepsy is a prevalent neurological disorder characterized by neuronal hypersynchronous discharge in the brain, leading to central nervous system (CNS) dysfunction. Despite the availability of anti‐epileptic drugs (AEDs), resistance to AEDs is the greatest challenge in treating epilepsy. The role of sphingosine‐1‐phosphate‐receptor 1 (S1PR1) in drug‐resistant epilepsy is unexplored. This study investigated the effects of SEW2871, a potent S1PR1 agonist, on a phenobarbitone (PHB)‐resistant pentylenetetrazol (PTZ)‐kindled Wistar rat model. We measured the messenger ribonucleic acid (mRNA) expression of multi‐drug resistance 1 (MDR1) and multi‐drug resistance protein 5 (MRP5) as indicators for drug resistance. Rats received PHB + PTZ for 62 days to develop a drug‐resistant epilepsy model. From day 48, SEW2871 (0.25, 0.5, 0.75 mg/kg, intraperitoneally [i.p.]) was administered for 14 days. Seizure scoring, behaviour, oxidative markers like reduced glutathione, catalase, superoxide dismutase, inflammatory markers like interleukin 1 beta tumour necrosis factor alpha, interferon gamma and mRNA expression (MDR1 and MRP5) were assessed, and histopathological assessments were conducted. SEW2871 demonstrated dose‐dependent improvements in seizure scoring and neurobehavioral parameters with a reduction in oxidative and inflammation‐induced neuronal damage. The S1PR1 agonist also downregulated MDR1 and MRP5 gene expression and significantly decreased the number of dark‐stained pyknotic nuclei and increased cell density with neuronal rearrangement in the rat brain hippocampus. These findings suggest that SEW2871 might ameliorate epileptic symptoms by modulating drug resistance through downregulation of MDR1 and MRP5 gene expression. [ABSTRACT FROM AUTHOR]

Objective(s): A new series of quinoline analogs of ketoprofen was designed and synthesized as multidrug resistance protein 2 (MRP2) inhibitors using ketoprofen as the lead compounds.Materials and Methods: The cytotoxic activity of the compounds was evaluated againt two cancer cell lines including A2780/RCIS (MRP2-overexpressing ovarian carcinoma), A2780, drug-sensitive ovarian carcinoma using MTT assay. Compounds showing low toxicity in MTT test were selected to investigate their MRP inhibition activity. MRP2 inhibitory potency was evaluated by determination of the uptake amount of fluorescent 5-carboxy fluorescein diacetate (5-CFDA) substrate, by A2780/RCIS in the presence of the selected compounds. Mode of interaction between synthesized ligands and homology modeled MRP2 was investigated by MOE software. Results: Compound 6d, a 4-carboxy quinoline possessing dimethoxy phenyl in position 2 of quinoline ring, showed the most MRP2 inhibition activity among all the quinolines and more than the reference drug ketoprofen. MRP2 inhibition activity of compound 7d was less in comparison to that of compound 6d, indicating that carboxyl group in position 4 of quinoline may interact with MRP2. Docking studies showed that compound 7d methyl ester of 6d, interacted less compared to its parent 6d, which is consistent with biological results.Conclusion: This study indicates that 6- or 8-benzoyl-2-arylquinoline is a suitable scaffold to design MRP2 inhibitors. The position of benzoyl in quinoline ring is important in inhibition of MRP2. Generally, MRP2 inhibition activity of compound 7d was less in comparison to that of 6d, indicating that carboxyl group in position 4 of quinoline may interact with MRP2.

Objective To explore the effect of long noncoding RNA cancer susceptibility 2 (lncRNA CASC2) on the sensitivity of glioma cells to temazolamide (TMZ) and investigate the underling mechanism. Methods Forty glioma tissue samples derived from the 40 patients undergoing surgical treatment in our department from July 2018 to March 2020 were enrolled in this study. The expression of lncRNA CASC2 in the glioma tissues was detected with RT-PCR, and the results were analyzed with pathological grades and compared between the patients with isocitrate dehydrogenase (IDH) 1/2 mutant (n=17) and IDH 1/2 wild type (n=9). Glioma cells U251 were cultured and transfected with plasmid pc-CASC2 to overexpress lncRNA CASC2 and/or interfering RNA of multi-drug resistance protein ABCG2. CCK-8 assay and flow cytometry were used to detect the cell viability and apoptotic rate in above cell groups after 30 μg/mL TMZ treatment. After mouse intracranial glioma model was established, high performance liquid chromatography was adopted to determine the concentration of TMZ. The correlation between lncRNA CASC2 and ABCG2 was detected by immunofluorescence staining and RNA immunoprecipitation. Results LncRNA CASC2 level was decreased in the glioma tissues with IDH 1/2 wild type, and had a negative correlation with pathological grade of glioma. LncRNA CASC2 overexpression resulted in significantly lower IC50 to TMZ (36.7±4.2 μg/mL) than the U251 cells after pc-Null transfection (t=4.41, P < 0.05). Under 30 μg/mL TMZ stimulation, the cell viability was reduced and the proportion of apoptotic cells was increased after lncRNA-CASC2 overexpression. In the mouse intracranial glioma model, the concentration of intracellular TMZ active product was increased after lncRNA-CASC2 overexpression. LncRNA CASC2 and ABCG2 were evenly distributed in the cytoplasm, and RNA immunoprecipitation showed that the content of lncRNA CASC2 in ABCG2 antibody group was higher than that in IgG control group. In addition, down-regulation of intracellular ABCG2 by siRNA decreased the TMZ sensitivity of U251 cells that could enhanced by lncRNA CASC2. Conclusion LncRNA CASC2 improves the sensitivity of glioma U251 cells to TMZ. However, ABCG2 inhibition by siRNA attenuates the above effects of lncRNA CASC2.

Colorectal cancer (CRC) is one of the most fatal types of cancers that is seen in both men and women. CRC is the third most common type of cancer worldwide. Over the years, several drugs are developed for the treatment of CRC; however, patients with advanced CRC can be resistant to some drugs. P-glycoprotein (P-gp) (also known as Multidrug Resistance 1, MDR1) is a well-identified membrane transporter protein expressed by ABCB1 gene. The high expression of MDR1 protein found in several cancer types causes chemotherapy failure owing to efflux drug molecules out of the cancer cell, decreases the drug concentration, and causes drug resistance. As same as other cancers, drug-resistant CRC is one of the major obstacles for effective therapy and novel therapeutic strategies are urgently needed. Network-based approaches can be used to determine specific biomarkers, potential drug targets, or repurposing approved drugs in drug-resistant cancers. Drug repositioning is the approach for using existing drugs for a new therapeutic purpose; it is a highly efficient and low-cost process. To improve current understanding of the MDR-1-related drug resistance in CRC, we explored gene co-expression networks around ABCB1 gene with different network sizes (50, 100, 150, 200 edges) and repurposed candidate drugs targeting the ABCB1 gene and its co-expression network by using drug repositioning approach for the treatment of CRC. The candidate drugs were also assessed by using molecular docking for determining the potential of physical interactions between the drug and MDR1 protein as a drug target. We also evaluated these four networks whether they are diagnostic or prognostic features in CRC besides biological function determined by functional enrichment analysis. Lastly, differentially expressed genes of drug-resistant (i.e., oxaliplatin, methotrexate, SN38) HT29 cell lines were found and used for repurposing drugs with reversal gene expressions. As a result, it is shown that all networks exhibited high diagnostic and prognostic performance besides the identification of various drug candidates for drug-resistant patients with CRC. All these results can shed light on the development of effective diagnosis, prognosis, and treatment strategies for drug resistance in CRC.

Colorectal cancer (CRC) is one of the most fatal types of cancers that is seen in both men and women. CRC is the third most common type of cancer worldwide. Over the years, several drugs are developed for the treatment of CRC; however, patients with advanced CRC can be resistant to some drugs. P-glycoprotein (P-gp) (also known as Multidrug Resistance 1, MDR1) is a well-identified membrane transporter protein expressed by ABCB1 gene. The high expression of MDR1 protein found in several cancer types causes chemotherapy failure owing to efflux drug molecules out of the cancer cell, decreases the drug concentration, and causes drug resistance. As same as other cancers, drug-resistant CRC is one of the major obstacles for effective therapy and novel therapeutic strategies are urgently needed. Network-based approaches can be used to determine specific biomarkers, potential drug targets, or repurposing approved drugs in drug-resistant cancers. Drug repositioning is the approach for using existing drugs for a new therapeutic purpose; it is a highly efficient and low-cost process. To improve current understanding of the MDR-1-related drug resistance in CRC, we explored gene co-expression networks around ABCB1 gene with different network sizes (50, 100, 150, 200 edges) and repurposed candidate drugs targeting the ABCB1 gene and its co-expression network by using drug repositioning approach for the treatment of CRC. The candidate drugs were also assessed by using molecular docking for determining the potential of physical interactions between the drug and MDR1 protein as a drug target. We also evaluated these four networks whether they are diagnostic or prognostic features in CRC besides biological function determined by functional enrichment analysis. Lastly, differentially expressed genes of drug-resistant (i.e., oxaliplatin, methotrexate, SN38) HT29 cell lines were found and used for repurposing drugs with reversal gene expressions. As a result, it is shown that all networks exhibited high diagnostic and prognostic performance besides the identification of various drug candidates for drug-resistant patients with CRC. All these results can shed light on the development of effective diagnosis, prognosis, and treatment strategies for drug resistance in CRC. [ABSTRACT FROM AUTHOR]

The intracellular levels of cyclic GMP are controlled by its rate of formation through nitric oxide-mediated stimulation of soluble guanylate cyclase (sGC) and its degradation by phosphodiesterases. Multidrug resistance protein 4 (MRP4) expressed in human platelets pumps cyclic nucleotides out of cells. In search for new antiplatelet strategies, we tested the hypothesis that sGC activation concomitant with MRP4 inhibition confers higher antiplatelet efficacy compared with monotherapy alone. This study was undertaken to investigate the pharmacological association of the sGC activator BAY 60-2770 with the MRP4 inhibitor MK571 on human washed platelets. Collagen- and thrombin-induced platelet aggregation and ATP-release reaction assays were performed. BAY 60-2770 (0.001–10 µM) produced significant inhibitions of agonist-induced platelet aggregation accompanied by reduced ATP-release. Pre-incubation with 10 µM MK571 alone had no significant effect on platelet aggregation and ATP release, but it produced a left displacement by about of 10–100-fold in the concentration-response curves to BAY 60-2770. Pre-incubation with MK571increased and decreased, respectively, the intracellular and extracellular levels of cGMP to BAY 60-2770, whereas the cAMP levels remained unchanged. The increased VASP-serine 239 phosphorylation in BAY 60-2770-treated platelets was enhanced by MK571. In Fluo-4-loaded platelets, BAY 60-2770 reduced the intracellular Ca2+ levels, an effect significantly potentiated by MK571. Flow cytometry assays showed that BAY 60-2770 reduces the αIIbβ3 integrin activation, which was further reduced by MK571 association. Blocking the MRP4-mediated efflux of cGMP may be a potential mechanism to enhance the antiplatelet efficacy of sGC activators. [ABSTRACT FROM AUTHOR]

Introduction Pharmacological P-glycoprotein (P-gp) inhibition with tariquidar (TQD) is considered a promising strategy for the augmentation of radiotracer brain uptake. However, a region-dependent effect may compromise the robustness of quantitative studies. For this reason, we studied the effect of a TQD pretreatment on 5-HT2A imaging with [ 123 I]R91150 and compared results with those obtained in Mdr1a knock-out (KO) rats. Methods Ex vivo autoradiography was performed in TQD (15 mg/kg) pretreated wild-type (WT-TQD), Mdr1a knock-out (KO) and untreated WT rats for Specific Binding Ratio (SBR) estimation. In vivo dynamic SPECT imaging with serial arterial blood sampling was performed in the former two groups of rats and kinetic analysis was performed with a one tissue-compartment (1TC) model and the Specific Uptake Ratio (SUR). Results were analyzed statistically using repeated measures ANOVA. Results SBR values differed between WT-TQD, Mdr1a KO and WT rats in a region-dependent manner (p < 0.0001). In vivo brain uptake of radiotracer did not differ between groups. Similarly, kinetic analysis provided distribution volume (V T ) values that did not differ significantly between groups. SUR binding potential (BP ND ) values from both groups highly correlated with corresponding V T (r = 0.970, p < 0.0001 and r = 0.962, p < 0.0001, respectively). However, SUR measured over averaged images between 100 and 120 min, using cerebellum as reference region, demonstrated values that were, by average, 2.99 ± 0.53 times higher in the WT-TQD group, with the difference between groups being region-dependent (p < 0.001). In addition, coefficient of variation of the SUR BP ND values across brain regions was significantly higher in the WT-TQD rats (41.25% ± 9.63% versus 11.13% ± 5.59%, p < 0.0001). Conclusion P-gp inhibition with TQD leads to region-dependent effect in the rat brain, with probably sub-optimal effect in cerebellum. This warrants attention when it is used as a reference region for quantitative studies. [ABSTRACT FROM AUTHOR]

Prion protein (PrP) plays crucial roles in regulating antioxidant systems to improve cell defenses against cellular stress. Here, we show that the interactions of PrP with the excitatory amino acid transporter 3 ( EAAT3), γ-glutamyl transpeptidase (γ- GT), and multi-drug resistance protein 1 ( MRP1) in astrocytes and the interaction between PrP and EAAT3 in neurons regulate the astroglial and neuronal metabolism of the antioxidant glutathione. Ablation of PrP in astrocytes and cerebellar neurons leads to dysregulation of EAAT3-mediated uptake of glutamate and cysteine, which are precursors for the synthesis of glutathione. In PrP-deficient astrocytes, levels of intracellular glutathione are increased, and under oxidative stress, levels of extracellular glutathione are increased, due to (i) increased glutathione release via MRP1 and (ii) reduced activity of the glutathione-degrading enzyme γ- GT. In PrP-deficient cerebellar neurons, cell death is enhanced under oxidative stress and glutamate excitotoxicity, when compared to wild-type cerebellar neurons. These results indicate a functional interplay of PrP with EAAT3, MRP1 and γ- GT in astrocytes and of PrP and EAAT3 in neurons, suggesting that these interactions play an important role in the metabolic cross-talk between astrocytes and neurons and in protection of neurons by astrocytes from oxidative and glutamate-induced cytotoxicity. [ABSTRACT FROM AUTHOR]

Auxin transport is mediated at the cellular level by three independent mechanisms that are characterised by the PIN-formed (PIN), P-glycoprotein (ABCB/PGP) and AUX/LAX transport proteins. The PIN and ABCB transport proteins, best represented by PIN1 and ABCB19 (PGP19), have been shown to coordinately regulate auxin efflux. When PIN1 and ABCB19 coincide on the plasma membrane, their interaction enhances the rate and specificity of auxin efflux and the dynamic cycling of PIN1 is reduced. However, ABCB19 function is not regulated by the dynamic cellular trafficking mechanisms that regulate PIN1 in apical tissues, as localisation of ABCB19 on the plasma membrane was not inhibited by short-term treatments with latrunculin B, oryzalin, brefeldin A (BFA) or wortmannin – all of which have been shown to alter PIN1 and/or PIN2 plasma membrane localisation. When taken up by endocytosis, the styryl dye FM4-64 labels diffuse rather than punctuate intracellular bodies in abcb19 ( pgp19), and some aggregations of PIN1 induced by short-term BFA treatment did not disperse after BFA washout in abcb19. Although the subcellular localisations of ABCB19 and PIN1 in the reciprocal mutant backgrounds were like those in wild type, PIN1 plasma membrane localisation in abcb19 roots was more easily perturbed by the detergent Triton X-100, but not other non-ionic detergents. ABCB19 is stably associated with sterol/sphingolipid-enriched membrane fractions containing BIG/TIR3 and partitions into Triton X-100 detergent-resistant membrane (DRM) fractions. In the wild type, PIN1 was also present in DRMs, but was less abundant in abcb19 DRMs. These observations suggested a rationale for the observed lack of auxin transport activity when PIN1 is expressed in a non-plant heterologous system. PIN1 was therefore expressed in Schizosaccharomyces pombe, which has plant-like sterol-enriched microdomains, and catalysed auxin transport in these cells. These data suggest that ABCB19 stabilises PIN1 localisation at the plasma membrane in discrete cellular subdomains where PIN1 and ABCB19 expression overlaps. [ABSTRACT FROM AUTHOR]

P-glycoprotein, breast cancer resistance protein, and multidrug resistance proteins have physiological functions in placental tissue. Several antidepressants, antipsychotics, and anti-epileptic drugs have been found to be substrates of P-glycoprotein and other transporters. The extent that drugs pass through the placental barrier is likely influenced by drug transporters. The rational choice of psychoactive drugs to treat mental illness in women of child-bearing age should incorporate knowledge of both drug disposition as well as expected pharmacologic effects. This review summarizes the current data on drug transporters in the placental passage of medications, with a focus on medications used in clinical psychopharmacology. [ABSTRACT FROM AUTHOR]

Abstract: Because agricultural productivity can be severely limited in saline soils, many different approaches are necessary to efficiently manipulate plant salt tolerance. Yeast cadmium factor 1 (YCF1), which sequesters glutathione-chelates of heavy metals and xenobiotics into vacuoles, has been introduced into Arabidopsis thaliana plants to improve heavy metal tolerance. Here, we show that transgenic A. thaliana plants expressing YCF1 are enhanced in salt or xenobiotic chemical (1-chloro-2, 4-dinitrobenzene, CDNB) tolerance as well. Two lines of evidence suggest that this enhanced tolerance may be partially due to sequestration of salts or xenobiotic chemical into vacuoles. First, YCF1 transgenic plants treated with high salt were capable of accumulating higher levels of sodium ions than wild-type. Second, the salt tolerance of the YCF1 plants was abolished when these plants were exposed to salt in the presence of buthionine sulfoximine (BSO), an inhibitor of gamma-glutamylcysteine synthase, the first enzyme of glutathione biosynthesis. In line with these results, high salt treated YCF1 plants seem to experience a reduced level of salt stress compared to the wild-type, since salt stress-responsive genes such as COR15A and KIN1 were less strongly induced in these transgenic plants. Therefore, in addition to the previously shown increase in heavy metal tolerance by YCF1, our results clearly demonstrate that YCF1 gene can be used to improve salt and xenobiotic chemical tolerance, expanding our repertoire of methods for improving the ability of plants to cope with various abiotic stresses. [Copyright &y& Elsevier]

Hyperbilirubinemia is a frequent side effect induced by long-term therapy with the antibiotic fusidate. The aim of this study was to elucidate the molecular mechanisms of fusidate-induced hyperbilirubinemia by investigating its influence on hepatic transport systems in the canalicular membrane. Using canalicular membrane vesicles from rat liver, we determined the effect of fusidate on the adenosine 5′-triphosphate (ATP)-dependent transport of substrates of the apical conjugate export pump, multi-drug resistance protein 2 (Mrp2, symbol Abcc2) and the bile salt export pump (Bsep, symbol Abcb11). Fusidate inhibited the ATP-dependent transport of the Mrp2 substrates 17β-glucuronosyl estradiol and leukotriene C4, and the transport of cholyltaurine by Bsep with Ki values of 2.2±0.3, 7.6±1.3, and 5.5±0.8 μM, respectively. To elucidate the in vivo implication of these findings, the effect of fusidate treatment on the elimination of intravenously administered tracer doses of 17β-glucuronosyl estradiol and cholyltaurine into bile was studied in rats. Treatment with fusidate (100 μmol/kg body weight) reduced the biliary excretion rate of 17β-glucuronosyl [3H]estradiol and [3H]cholyltaurine by 75 and 80%, respectively. Extended treatment of rats with fusidate (100 μmol/kg body weight, three times daily i.p. for 3 days) reduced hepatic Mrp2 protein levels by 61% (P<0.001). Our data suggest that there are at least two different mechanisms involved in the impairment of transport processes and hepatobiliary elimination by fusidate, direct inhibition of transport of Mrp2 and Bsep substrates by competitive interaction and impairment by a decreased level of hepatic Mrp2. [Copyright &y& Elsevier]

Objective: The characteristics of T1 relaxation values and the expression levels of organic anion transport system (OATP) and multidrug resistance protein carrier (MRP) on hepatocyte surface membrane were quantitatively studied to evaluate liver function in normal C57BL/6 mice with gadoxetic disodium-enhanced MRI. Methods: Ten 6-weeks-old, normal C57BL/6 mice were included in this study. Gadoxetic disodium- enhanced MRI examination was performed. Longitudinal relaxation time images before and 20 min after contrast injection (hepatobiliary-specific phase) were acquired. T1-relaxation time, T1 relaxation time decline rate (△T) and rapid initial enhancement slope percentage in the first-pass study of the liver parenchyma before and after administration of gadoxetate disodium were measured. Liver parenchyma specimens were detected by Western blotting and the values ​​of OATP1, MRP2, and MRP3 were recorded. Statistical results were expressed in mean. Results: The mean T1 relaxation time of 10 normal C57BL/6 mice before and after enhancement was 659.13 ± 24.07, and 408.87 ± 27.21 ms. The mean T1 relaxation time decline rate and rapid initial enhancement slope percentage in the first-pass study was 37.12% ± 4.95% and 4.14% ± 0.96% ms. Furthermore, the mean value of OATP1, MRP2 and MRP3 were 29 952.1 ± 11 475.2, 34 376.4 ± 33 228.4 and 357 308.9 ± 64 646.5. Conclusion: T1-relaxation values, T1 relaxation time decline rate and rapid initial enhancement slope percentage in the first-pass study before and after gadoxetic disodium-enhanced MRI were determined in normal C57BL/6 mice as well as quantitative values of OATP1, MRP2 and MRP3 at the molecular level on the hepatocyte surface membrane were helpful for liver injury model with control study.

To investigate the effects of Gegen Qinlian decoction on the expression of P-glycoprotein (P-gp) and multi-drug resistance protein (MRP) in epithelial cells of human colon adenocarcinoma Caco-2 cells．The effects of different concentrations of Gegen Qinlian decoction on the expression levels of p-gp and MRP1-6 mRNA in Caco-2 cells were detected by real time quantitative reverse transcriptase PCR (qRT-PCR).12 h after drug treatment (5.00 g·L⁻¹), the expression levels of MDR1 and MRP1-6 were significantly down-regulated at concentration of 5.00 g·L⁻¹; the mRNA expression levels of MDR1，MRP1，MRP2，MRP4，MRP5 and MRP6 were significantly down-regulated at concentration of 2.50 g·L⁻¹; only the expression levels of MRP2 and MRP5 were significantly affected at concentration of 1.00 g·L⁻¹. The results showed that the expression levels of MDR1 and MRP1-6 mRNA in Caco-2 cells could be down-regulated in a dose-dependent manner. Gegen Qinlian decoction may reduce drug efflux by down-regulating the mRNA expression of cell transporters in Caco-2 cell, and increase the time of drug action, thereby enhancing the bioavailability of chemotherapeutic drugs., Competing Interests: The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose., (Copyright© by the Chinese Pharmaceutical Association.)

Multi Drug Resistance (MDR) is one of the major causes of chemotherapy failure in human malignancies. Curcumin, the active constituent of Curcuma longa is a proven anticancer agent potentially modulating the expression and function of these MDR proteins. In this study, we attempted to test curcumin for its potential to inhibit the expression and function of multidrug resistance associated protein 1 (MRP1) in retinoblastoma (RB) cell lines through western blot, RT-PCR and functional assays. In silico analysis were also performed to understand the molecular interactions conferred by curucmin on MRP1 in RB cells. Western blot and RTPCR analysis did not show any correlation of MRP1 expression with increase in concentration of curcumin. However, inhibitory effect of curcumin on MRP1 function was observed as a decrease in the efflux of fluorescent substrate. Moreover, Curcumin did not affect 8-azido-ATP-biotin binding to MRP1 and it also showed inhibition of ATP-hydrolysis stimulated by quercetin, which is indicative of curcumin's interaction with the substrate binding site of MRP1. Furthermore, homology modelling and docking simulation studies of MRP1 also provided deeper insights into the molecular interactions, thereby inferring the potential binding mode of curcumin into the substrate binding site of MRP1.