Effects of nonsteroidal anti-inflammatory drugs on the expression and function of P-Glycoprotein/MDR1 in Caco-2 cells

Translational veterinary epilepsy: A win-win situation for human and veterinary neurology

Epilepsy is a challenging multifactorial disorder with a complex genetic background. Our current understanding of the pathophysiology and treatment of epilepsy has substantially increased due to animal model studies, including canine studies, but additional basic and clinical research is required. Drug-resistant epilepsy is an important problem in both dogs and humans, since seizure freedom is not achieved with the available antiseizure medications. The evaluation and exploration of pharmacological and particularly non-pharmacological therapeutic options need to remain a priority in epilepsy research. Combined efforts and sharing knowledge and expertise between human medical and veterinary neurologists are important for improving the treatment outcomes or even curing epilepsy in dogs. Such interactions could offer an exciting approach to translate the knowledge gained from people and rodents to dogs and vice versa. In this article, a panel of experts discusses the similarities and knowledge gaps in human and animal epileptology, with the aim of establishing a common framework and the basis for future translational epilepsy research.

Antimicrobial Activity of a Library of Thioxanthones and Their Potential as Efflux Pump Inhibitors

The overexpression of efflux pumps is one of the causes of multidrug resistance, which leads to the inefficacy of drugs. This plays a pivotal role in antimicrobial resistance, and the most notable pumps are the AcrAB-TolC system (AcrB belongs to the resistance-nodulation-division family) and the NorA, from the major facilitator superfamily. In bacteria, these structures can also favor virulence and adaptation mechanisms, such as quorum-sensing and the formation of biofilm. In this study, the design and synthesis of a library of thioxanthones as potential efflux pump inhibitors are described. The thioxanthone derivatives were investigated for their antibacterial activity and inhibition of efflux pumps, biofilm formation, and quorum-sensing. The compounds were also studied for their potential to interact with P-glycoprotein (P-gp, ABCB1), an efflux pump present in mammalian cells, and for their cytotoxicity in both mouse fibroblasts and human Caco-2 cells. The results concerning the real-time ethidium bromide accumulation may suggest a potential bacterial efflux pump inhibition, which has not yet been reported for thioxanthones. Moreover, in vitro studies in human cells demonstrated a lack of cytotoxicity for concentrations up to 20 µM in Caco-2 cells, with some derivatives also showing potential for P-gp modulation.

Intravenous pharmacokinetics of moxifloxacin following simultaneous administration with flunixin meglumine or diclofenac in sheep

In this study, the pharmacokinetics of moxifloxacin (5 mg/kg) was determined following a single intravenous administration of moxifloxacin alone and co-administration with diclofenac (2.5 mg/kg) or flunixin meglumine (2.2 mg/kg) in sheep. Six healthy Akkaraman sheep (2 ± 0.3 years and 53.5 ± 5 kg of body weight) were used. A longitudinal design with a 15-day washout period was used in three periods. In the first period, moxifloxacin was administered by an intravenous (IV) injection. In the second and third periods, moxifloxacin was co-administered with IV administration of diclofenac and flunixin meglumine, respectively. The plasma concentration of moxifloxacin was assayed by high-performance liquid chromatography. The pharmacokinetic parameters were calculated using a two-compartment open pharmacokinetic model. Following IV administration of moxifloxacin alone, the mean elimination half-life (t_1/2β ), total body clearance (Cl_T ), volume of distribution at steady state (V_dss ) and area under the curve (AUC) of moxifloxacin were 2.27 hr, 0.56 L h^-1  kg^-1 , 1.66 L/kg and 8.91 hr*µg/ml, respectively. While diclofenac and flunixin meglumine significantly increased the t_1/2β and AUC of moxifloxacin, they significantly reduced the Cl_T and V_dss . These results suggest that anti-inflammatory drugs could increase the therapeutic efficacy of moxifloxacin by altering its pharmacokinetics.

P-glycoprotein activation by 1-(propan-2-ylamino)-4-propoxy-9H-thioxanthen-9-one (TX5) in rat distal ileum: ex vivo and in vivo studies

In vitro studies showed that 1-(propan-2-ylamino)-4-propoxy-9H-thioxanthen-9-one (TX5) increases P-glycoprotein (P-gp) expression and activity in Caco-2 cells, preventing xenobiotic toxicity. The present study aimed at investigating TX5 effects on P-gp expression/activity using Wistar Han rats: a) in vivo, evaluating intestinal P-gp activity; b) ex vivo, evaluating P-gp expression in ileum brush border membranes (BBM) and P-gp activity in everted intestinal sacs; c) ex vivo, evaluating P-gp activity in everted intestinal sacs of the distal and proximal ileum. TX5 (30 mg/kg, b.w.), gavage, activated P-gp in vivo, given the significant decrease in the AUC of digoxin (0.25 mg/kg, b.w.). The efflux of rhodamine 123 (300 μM), a P-gp fluorescent substrate, significantly increased in TX5-treated everted sacs from the distal portion of the rat ileum, when P-gp activity was evaluated in the presence of TX5 (20 μM), an effect abolished by the P-gp inhibitor verapamil (100 μM). No increases on P-gp expression or activity were found in TX5-treated BBM of the distal ileum and everted distal sacs, respectively, 24 h after TX5 (10 mg/kg, b.w.) administration. In vivo, no differences were found on digoxin portal concentration between control (digoxin 0.025 mg/kg, b.w., intraduodenal) and TX5-treated (digoxin+TX5 20 μM, intraduodenal) rats. The observed discrepancies in digoxin results can be related to differences in TX5 dose administered and used methodologies. Thus, the results show that TX5 activates P-gp at the distal portion of the rat ileum, and, at the higher dose tested (30 mg/kg, b.w.), seems to modulate in vivo the AUC of P-gp substrates.

ABC Transporters in Extrahepatic Tissues: Pharmacological Regulation in Heart and Intestine

ATP binding cassette (ABC) transporters are transmembrane proteins expressed in secretory epithelia like the liver, kidneys and intestine, in the epithelia exhibiting barrier function such as the blood-brain barrier and placenta, and to a much lesser extent, in tissues like reproductive organs, lungs, heart and pancreas, among others. They regulate internal distribution of endogenous metabolites and xenobiotics including drugs of therapeutic use and also participate in their elimination from the body. We here describe the function and regulation of ABC transporters in the heart and small intestine, as examples of extrahepatic tissues, in which ABC proteins play clearly different roles. In the heart, they are involved in tissue pathogenesis as well as in protecting this organ against toxic compounds and druginduced oxidative stress. The small intestine is highly exposed to therapeutic drugs taken orally and, consequently, ABC transporters localized on its surface strongly influence drug absorption and pharmacokinetics. Examples of the ABC proteins currently described are Multidrug Resistance-associated Proteins 1 and 2 (MRP1 and 2) for heart and small intestine, respectively, and P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP) for both organs.

Nonsteroidal Anti-inflammatory Drugs Sensitize CD44-Overexpressing Cancer Cells to Hsp90 Inhibitor Through Autophagy Activation

Recently, novel therapeutic strategies have been designed with the aim of killing cancer stem-like cells (CSCs), and considerable interest has been generated in the development of specific therapies that target stemness-related marker of CSCs. In this study, nonsteroidal anti-inflammatory drugs (NSAIDs) significantly potentiated Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG)-mediated cytotoxicity through apoptotic and autophagic cell death induction, but COX-2-inhibitory function was not required for NSAID-induced autophagy in CD44-overexpressing human chronic myeloid leukemia K562 (CD44^highK562) cells. Importantly, we found that treatment with NSAIDs resulted in a dose-dependent increase in LC3-II level and decrease in p62 level and simultaneous reduction in multiple stemness-related markers including CD44, Oct4, c-Myc, and mutant p53 (mutp53) in CD44^highK562 cells, suggesting that NSAIDs could induce autophagy, which might mediate degradation of stemness-related marker proteins. Activation of AMPK and inhibition of Akt/mTOR/p70S6K/4EBP1 participated in NSAID-induced autophagy in CD44^highK562 cells. In addition, treatment of CD44^highK562 cells with NSAIDs inhibited expression of HSF1/Hsps, which resulted in suppression of 17-AAG-induced activation of Hsp70, leading to reversal of 17-AAG resistance and sensitization of CD44^highK562 cells to 17-AAG by NSAIDs. In conclusion, combining NSAIDs with Hsp90 inhibitor may offer one of the most promising strategies for eradication of CD44-overexpressing CSCs.

Effects of diclofenac on the pharmacokinetics of celastrol in rats and its transport

CONTEXT

Diclofenac and celastrol are always used together for the treatment of rheumatoid arthritis; the herb-drug interaction potential between diclofenac and celastrol is still unknown.

OBJECTIVE

This study investigates the effects of diclofenac on the pharmacokinetics of celastrol in rats.

MATERIALS AND METHODS

Twelve male Sprague-Dawley rats were divided into two groups and received celastrol (1 mg/kg) or both celastrol (1 mg/kg) and diclofenac (10 mg/kg) by oral gavage, and blood samples were collected via the oculi chorioideae vein and determined using the LC-MS method developed in this study. Additionally, the effects of diclofenac on the transport of celastrol were investigated using a Caco-2 cell transwell model.

RESULTS

Diclofenac could significantly (p < 0.05) decrease the C_max (from 66.93 ± 10.28 to 41.25 ± 8.06 ng/mL) and AUC_0-t (from 765.84 ± 163.61 to 451.33 ± 110.88 μg × h/L) of celastrol in rats. The efflux ratio of celastrol increased significantly (p < 0.05) from 3.12 to 4.55 with the treatment of diclofenac.

DISCUSSION AND CONCLUSION

These results indicated that diclofenac could decrease the system exposure of celastrol in rats when they are co-administered, and these effects might be exerted via decreasing its absorption in intestine.

Chiral Thioxanthones as Modulators of P-glycoprotein: Synthesis and Enantioselectivity Studies

Recently, thioxanthone derivatives were found to protect cells against toxic P-glycoprotein (P-gp) substrates, acting as potent inducers/activators of this efflux pump. The study of new P-gp chiral modulators produced from thioxanthone derivatives could clarify the enantioselectivity of this ABC transporter towards this new class of modulators. The aim of this study was to evaluate the P-gp modulatory ability of four enantiomeric pairs of new synthesized chiral aminated thioxanthones (ATxs) 1–8, studying the influence of the stereochemistry on P-gp induction/ activation in cultured Caco-2 cells. The data displayed that all the tested compounds (at 20 μM) significantly decreased the intracellular accumulation of a P-gp fluorescent substrate (rhodamine 123) when incubated simultaneously for 60 min, demonstrating an increased activity of the efflux, when compared to control cells. Additionally, all of them except ATx 3 (+), caused similar results when the accumulation of the P-gp fluorescent substrate was evaluated after pre-incubating cells with the test compounds for 24 h, significantly reducing the rhodamine 123 intracellular accumulation as a result of a significant increase in P-gp activity. However, ATx 2 (−) was the only derivative that, after 24 h of incubation, significantly increased P-gp expression. These results demonstrated a significantly increased P-gp activity, even without an increase in P-gp expression. Therefore, ATxs 1–8 were shown to behave as P-gp activators. Furthermore, no significant differences were detected in the activity of the protein when comparing the enantiomeric pairs. Nevertheless, ATx 2 (−) modulates P-gp expression differently from its enantiomer, ATx 1 (+). These results disclosed new activators and inducers of P-gp and highlight the existence of enantioselectivity in the induction mechanism.

Sensitization of multidrug-resistant cancer cells to Hsp90 inhibitors by NSAIDs-induced apoptotic and autophagic cell death

NSAIDs (non-steroidal anti-inflammatory drugs) have potential use as anticancer agents, either alone or in combination with other cancer therapies. We found that NSAIDs including celecoxib (CCB) and ibuprofen (IBU) significantly potentiated the cytotoxicity of Hsp90 inhibitors in human multidrug-resistant (MDR) cells expressing high levels of mutant p53 (mutp53) protein and P-glycoprotein (P-gp), and reversed Hsp90 inhibitor resistance caused by activation of heat shock factor 1 (HSF1) and by up-regulation of heat shock proteins (Hsps) and P-gp. Inhibition of Akt/mTOR and STAT3 pathways by CCB induced autophagy, which promoted the degradation of mutp53, one of Hsp90 client proteins, and subsequently down-regulated HSF1/Hsps and P-gp. Inhibition of autophagy prevented mutp53 degradation and CCB-induced apoptosis, and inhibition of caspase-3-mediated apoptotic pathway by Z-DEVD-FMK did not completely block CCB-induced cell death in MDR cells, suggesting that autophagic and apoptotic cell death may contribute to CCB-induced cytotoxicity in MDR cells. Furthermore, CCB and IBU suppressed Hsp90 inhibitor-induced HSF1/Hsp70/P-gp activity and mutp53 expression in MDR cells. Our results suggest that NSAIDs can be used as potential Hsp90 inhibitor chemosensitizers and reverse resistance of MDR cells to Hsp90 inhibitors via induction of apoptosis and autophagy. These results might enable the use of lower, less toxic doses of Hsp90 inhibitors and facilitate the design of practically applicable, novel combination therapy for the treatment of MDR cancer.

Sunitinib DDI with paracetamol, diclofenac, mefenamic acid and ibuprofen shows sex-divergent effects on the tissue uptake and distribution pattern of sunitinib in mice

PURPOSE

Pharmacokinetic interaction of sunitinib with diclofenac, paracetamol, mefenamic acid and ibuprofen was evaluated due to their P450 mediated metabolism and OATP1B1, OATP1B3, ABCB1, ABCG2 transporters overlapping features.

METHODS

Male and female mice were administered 6 sunitinib doses (60 mg/kg) PO every 12 h and 30 min before the last dose were administered vehicle (control groups), 250 mg/kg paracetamol, 30 mg/kg diclofenac, 50 mg/kg mefenamic acid or 30 mg/kg ibuprofen (study groups), euthanized 6 h post last administration and sunitinib plasma, liver, kidney, brain concentrations analyzed.

RESULTS

Ibuprofen halved sunitinib plasma concentration in female mice (p < 0.01) and showed 59 % lower concentration than male mice (p < 0.05). Diclofenac and paracetamol female mice showed 45 and 25 % higher plasma concentrations than male mice which were 27 % lower in mefenamic acid female mice. Paracetamol increased 2.2 (p < 0.05) liver and 1.4-fold (p < 0.05) kidney sunitinib concentrations in male mice that were lower in female mice (p < 0.01, p < 0.001, respectively). Ibuprofen increased 2.9-fold (p < 0.01) liver concentration in male mice that were higher than in female mice (p < 0.001). Female control mice had 35 % higher sunitinib brain concentration than male mice but the concentration decreased 37, 33, 10 and 57 % in the diclofenac, paracetamol, mefenamic acid and ibuprofen (p < 0.001), respectively. Tissue-plasma concentrations correlations were nonsignificant in control, paracetamol, mefenamic acid and ibuprofen groups but was significant in the diclofenac group in male mice (liver, brain) and female mice (liver, kidney).

CONCLUSIONS

These results portray gender-based sunitinib pharmacokinetic differences and NSAIDs selective effects on male or female mice, with potential clinical translatability.

Effect of lapatinib on oral digoxin absorption in patients

The potential for an interaction between lapatinib and absorption of the P-glycoprotein (ABCB1) substrate digoxin at a therapeutic dose in breast cancer patients was characterized. Seventeen women with HER2-positive metastatic breast cancer received a single oral 0.5-mg dose of digoxin on days 1 and 9 and oral lapatinib 1500 mg once daily on days 2 through 9. Digoxin pharmacokinetic parameters were determined on day 1 (digoxin administration alone) and on day 9 (coadministration of lapatinib and digoxin), and parameters were compared to determine the effects of lapatinib on digoxin absorption. Concomitant medications that could affect ABCB1 were accounted for. Lapatinib 1500 mg/day increased digoxin absorption approximately 80%, implicating lapatinib inhibition of intestinal ABCB1-mediated efflux. In summary, coadministration of lapatinib with narrow therapeutic index drugs that are substrates of ABCB1 should be undertaken with caution and dose adjustment should be considered.

Modulation of P-glycoprotein efflux pump: induction and activation as a therapeutic strategy

P-glycoprotein (P-gp) is an ATP-dependent efflux pump encoded by the MDR1 gene in humans, known to mediate multidrug resistance of neoplastic cells to cancer therapy. For several decades, P-gp inhibition has drawn many significant research efforts in an attempt to overcome this phenomenon. However, P-gp is also constitutively expressed in normal human epithelial tissues and, due to its broad substrate specificity, to its cellular polarized expression in many excretory and barrier tissues, and to its great efflux capacity, it can play a crucial role in limiting the absorption and distribution of harmful xenobiotics, by decreasing their intracellular accumulation. Such a defense mechanism can be of particular relevance at the intestinal level, by significantly reducing the intestinal absorption of the xenobiotic and, consequently, avoiding its access to the target organs. In this review, the current knowledge on this important efflux pump is summarized, and a new focus is brought on the therapeutic interest of inducing and/or activating P-gp for limiting the toxicity caused by its substrates. Several in vivo and in vitro studies validating the use of such a therapeutic strategy are discussed. An extensive literature search for reported P-gp inducers/activators and for the experimental models used in their characterization was conducted. Those studies demonstrate that effective antidotal pathways can be achieved by efficiently promoting the P-gp-mediated efflux of deleterious xenobiotics, resulting in a significant reduction in their intracellular levels and, consequently, in a significant reduction of their toxicity.

P-glycoprotein induction in Caco-2 cells by newly synthetized thioxanthones prevents paraquat cytotoxicity

The induction of P-glycoprotein (P-gp), an ATP-dependent efflux pump, has been proposed as a strategy against the toxicity induced by P-gp substrates such as the herbicide paraquat (PQ). The aim of this study was to screen five newly synthetized thioxanthonic derivatives, a group known to interact with P-gp, as potential inducers of the pump's expression and/or activity and to evaluate whether they would afford protection against PQ-induced toxicity in Caco-2 cells. All five thioxanthones (20 µM) caused a significant increase in both P-gp expression and activity as evaluated by flow cytometry using the UIC2 antibody and rhodamine 123, respectively. Additionally, it was demonstrated that the tested compounds, when present only during the efflux of rhodamine 123, rapidly induced an activation of P-gp. The tested compounds also increased P-gp ATPase activity in MDR1-Sf9 membrane vesicles, indicating that all derivatives acted as P-gp substrates. PQ cytotoxicity was significantly reduced in the presence of four thioxanthone derivatives, and this protective effect was reversed upon incubation with a specific P-gp inhibitor. In silico studies showed that all the tested thioxanthones fitted onto a previously described three-feature P-gp induction pharmacophore. Moreover, in silico interactions between thioxanthones and P-gp in the presence of PQ suggested that a co-transport mechanism may be operating. Based on the in vitro activation results, a pharmacophore model for P-gp activation was built, which will be of further use in the screening for new P-gp activators. In conclusion, the study demonstrated the potential of the tested thioxanthonic compounds in protecting against toxic effects induced by P-gp substrates through P-gp induction and activation.

Inflammatory regulation of ATP binding cassette efflux transporter expression and function in microglia

ATP-binding cassette (ABC) efflux transporters, including multidrug resistance protein 1 (Mdr1), breast cancer resistance protein (Bcrp), and multidrug resistance-associated proteins (Mrps) extrude chemicals from the brain. Although ABC transporters are critical for blood-brain barrier integrity, less attention has been placed on the regulation of these proteins in brain parenchymal cells such as microglia. Prior studies demonstrate that inflammation after lipopolysaccharide (LPS) treatment alters transporter expression in the livers of mice. Here, we sought to determine the effects of inflammation on the expression and function of transporters in microglia. To test this, the expression and function of ABC efflux transport proteins were quantified in mouse BV-2 microglial cells in response to activation with LPS. Intracellular retention of fluorescent rhodamine 123, Hoechst 33342, and calcein acetoxymethyl ester was increased in LPS-treated microglia, suggesting that the functions of Mdr1, Bcrp, and Mrps were decreased, respectively. LPS reduced Mdr1, Bcrp, and Mrp4 mRNA and protein expression between 40 and 70%. Conversely, LPS increased expression of Mrp1 and Mrp5 mRNA and protein. Immunofluorescent staining confirmed reduced Bcrp and Mrp4 and elevated Mrp1 and Mrp5 protein in activated microglia. Pharmacological inhibition of nuclear factor κB (NF-κB) transcriptional signaling attenuated down-regulation of Mdr1a mRNA and potentiated up-regulation of Mrp5 mRNA in LPS-treated cells. Together, these data suggest that LPS stimulates microglia and impairs efflux of prototypical ABC transporter substrates by altering mRNA and protein expression, in part through NF-κB signaling. Decreased transporter efflux function in microglia may lead to the retention of toxic chemicals and aberrant cell-cell communication during neuroinflammation.

Differential involvement of mitochondrial dysfunction, cytochrome P450 activity, and active transport in the toxicity of structurally related NSAIDs

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used in the treatment of pain and inflammation. However, this group of drugs is associated with serious adverse drug reactions. Previously, we studied the mechanisms underlying toxicity of the NSAID diclofenac using Saccharomycescerevisiae as model system. We identified the involvement of several mitochondrial proteins, a transporter and cytochrome P450 activity in diclofenac toxicity. In this study, we investigated if these processes are also involved in the toxicity of other NSAIDs. We divided the NSAIDs into three classes based on their toxicity mechanisms. Class I consists of diclofenac, indomethacin and ketoprofen. Mitochondrial respiration and reactive oxygen species (ROS) play a major role in the toxicity of this class. Metabolism by cytochrome P450s further increases their toxicity, while ABC-transporters decrease the toxicity. Mitochondria and oxidative metabolism also contribute to toxicity of class II drugs ibuprofen and naproxen, but another cellular target dominates their toxicity. Interestingly, ibuprofen was the only NSAID that was unable to induce upregulation of the multidrug resistance response. The class III NSAIDs sulindac, ketorolac and zomepirac were relatively non-toxic in yeast. In conclusion, we demonstrate the use of yeast to investigate the mechanisms underlying the toxicity of structurally related drugs.