Mechanisms of P-gp inhibition and effects on membrane fluidity of a new rifampicin derivative, 1,8-dibenzoyl-rifampicin

Progress in Research of Nanotherapeutics for Overcoming Multidrug Resistance in Cancer

Chemotherapy has been widely applied in oncotherapy. However, the development of multidrug resistance (MDR) has diminished the effectiveness of anticancer drugs against tumor cells. Such resistance often results in tumor recurrence, metastasis, and patient death. Fortunately, nanoparticle-based drug delivery systems provide a promising strategy by codelivery of multiple drugs and MDR reversal agents and the skillful, flexible, smart modification of drug targets. Such systems have demonstrated the ability to bypass the ABC transporter biological efflux mechanisms due to drug resistance. Hence, how to deliver drugs and exert potential antitumor effects have been successfully explored, applied, and developed. Furthermore, to overcome multidrug resistance, nanoparticle-based systems have been developed due to their good therapeutic effect, low side effects, and high tumor metastasis inhibition. In view of this, we systematically discuss the molecular mechanisms and therapeutic strategies of MDR from nanotherapeutics. Finally, we summarize intriguing ideas and future trends for further research in overcoming MDR.

Regulation of P-Glycoprotein during Oxidative Stress

P-glycoprotein (Pgp, ABCB1, MDR1) is an efflux transporter protein that removes molecules from the cells (outflow) into the extracellular space. Pgp plays an important role in pharmacokinetics, ensuring the absorption, distribution, and excretion of drugs and its substrates, as well as in the transport of endogenous molecules (steroid and thyroid hormones). It also contributes to tumor cell resistance to chemotherapy. In this review, we summarize the mechanisms of Pgp regulation during oxidative stress. The currently available data suggest that Pgp has a complex variety of regulatory mechanisms under oxidative stress, involving many transcription factors, the main ones being Nrf2 and Nf-kB. These factors often overlap, and some can be activated under certain conditions, such as the deposition of oxidation products, depending on the severity of oxidative stress. In most cases, the expression of Pgp increases due to increased transcription and translation, but under severe oxidative stress, it can also decrease due to the oxidation of amino acids in its molecule. At the same time, Pgp acts as a protector against oxidative stress, eliminating the causative factors and removing its by-products, as well as participating in signaling pathways.

Fiscalin Derivatives as Potential Neuroprotective Agents

Neurodegenerative diseases (ND) share common molecular/cellular mechanisms that contribute to their progression and pathogenesis. In this sense, we are here proposing new neuroprotection strategies by using marine-derived compounds as fiscalins. This work aims to evaluate the protective effects of fiscalin derivatives towards 1-methyl-4-phenylpyridinium (MPP⁺)- and iron (III)-induced cytotoxicity in differentiated SH-SY5Y cells, an in vitro disease model to study ND; and on P-glycoprotein (P-gp) transport activity, an efflux pump of drugs and neurotoxins. SH-SY5Y cells were simultaneously exposed to MPP⁺ or iron (III), and noncytotoxic concentrations of 18 fiscalin derivatives (0–25 μM), being the cytotoxic effect of both MPP⁺ and iron (III) evaluated 24 and 48 h after exposure. Fiscalins 1a and 1b showed a significant protective effect against MPP⁺-induced cytotoxicity and fiscalins 1b, 2b, 4 and 5 showed a protective effect against iron (III)-induced cytotoxicity. Fiscalins 4 and 5 caused a significant P-gp inhibition, while fiscalins 1c, 2a, 2b, 6 and 11 caused a modest increase in P-gp transport activity, thus suggesting a promising source of new P-gp inhibitors and activators, respectively. The obtained results highlight fiscalins with promising neuroprotective effects and with relevance for the synthesis of new derivatives for the treatment/prevention of ND.

Xanthones as P-glycoprotein modulators and their impact on drug bioavailability

Introduction: P-glycoprotein (P-gp) is an important efflux pump responsible for the extruding of many endogenous and exogenous substances out of the cells. P-gp can be modulated by different molecules - including xanthone derivatives - to surpass the multidrug resistance (MDR) phenomenon through P-gp inhibition, or to serve as an antidotal strategy in intoxication scenarios through P-gp induction/activation.Areas covered: This review provides a perspective on P-gp modulators, with particular focus on xanthonic derivatives, highlighting their ability to modulate P-gp expression and/or activity, and the potential impact of these effects on the pharmacokinetics, pharmacodynamics and toxicity of P-gp substrates.Expert opinion: Xanthones, of natural or synthetic origin, are able to modulate P-gp, interfering with its protein synthesis or with its mechanism of action, by decreasing or increasing its efflux capacity. These modulatory effects make the xanthonic scaffold a promising source of new derivatives with therapeutic potential. However, the mechanisms beyond the xanthones-mediated P-gp modulation and the chemical characteristics that make them more potent P-gp inhibitors or inducers/activators are still understudied. Furthermore, a new window of opportunity exists in the neuropathologies field, where xanthonic derivatives with potential to modulate P-gp should be further explored to optimize the prevention/treatment of brain pathologies.

Design and characterization of Nanostructured lipid carriers (NLC) and Nanostructured lipid carrier-based hydrogels containing Passiflora edulis seeds oil

This study aims to design and characterize Nanostructured lipid carriers (NLC) and Nanostructured lipid carrier-based hydrogels with Passiflora edulis seeds oil, a by-product from Madeira Island food industry. NLC were prepared by the ultrasonication technique, using passion fruit seeds oil as a liquid lipid and glyceryl distearate as a solid lipid. These NLC were then gelled with Poly (acrylic acid). Long-term stability studies were conducted with NLC and NLC-based hydrogels stored for 12 months. The following tests were performed: morphology, encapsulation efficiency, particle size analysis, polydispersity index analysis, zeta potential, pH measurement, color analysis, viscosity studies, texture analysis, in vitro occlusion test, ex vivo skin penetration study, tyrosinase inhibition activity, in vitro skin permeation experiments and in vitro cytotoxicity studies. The developed NLC had spherical shape and narrow particle sizes distribution with mean sizes in the range of 150 nm and PDI below 0.3, Zeta potential values around -30 mV and high Encapsulation efficiency. The tyrosinase inhibitory activity and skin retention of the nanoparticles was superior to that of the non-encapsulated oil. The developed formulations did not show cytotoxicity towards HaCat cells and presented suitable viscosity and texture properties for skin application, proving to be good candidates as depigmenting agent.

New marine-derived indolymethyl pyrazinoquinazoline alkaloids with promising antimicrobial profiles

Due to the emergence of multidrug-resistant pathogenic microorganisms, the search for novel antimicrobials is urgent. Inspired by marine alkaloids, a series of indolomethyl pyrazino [1,2-b]quinazoline-3,6-diones was prepared using a one-pot microwave-assisted multicomponent polycondensation of amino acids. The compounds were evaluated for their antimicrobial activity against a panel of nine bacterial strains and five fungal strains. Compounds 26 and 27 were the most effective against Staphylococcus aureus ATCC 29213 reference strain with MIC values of 4 μg mL⁻¹, and a methicillin-resistant Staphylococcus aureus (MRSA) isolate with MIC values of 8 μg mL⁻¹. It was possible to infer that enantiomer (−)-26 was responsible for the antibacterial activity (MIC 4 μg mL⁻¹) while (+)-26 had no activity. Furthermore, compound (−)-26 was able to impair S. aureus biofilm production and no significant cytotoxicity towards differentiated and non-differentiated SH-SY5Y cells was observed. Compounds 26, 28, and 29 showed a weak antifungal activity against Trichophyton rubrum clinical isolate with MIC 128 μg mL⁻¹ and presented a synergistic effect with fluconazole.

Indolomethyl pyrazino [1,2-b]quinazoline-3,6-diones were prepared using a one-pot multicomponent polycondensation of amino acids and were evaluated for their antimicrobial activity against a panel of nine bacterial strains and five fungal strains.

Pessaries containing nanostructured lipid carriers (NLC) for prolonged vaginal delivery of progesterone

Progesterone (PRG) plays a crucial role in the female reproductive system, being the vaginal route the most adequate for its administration, as this drug has an extensive hepatic first pass effect. Nonetheless, vaginal PRG dosage forms originate immediate drug release and requires repeated administrations, which is unpleasant. Thereby, it is necessary to develop alternative delivery systems for prolonged vaginal release of PRG. The objective of this work was the development of pessaries for the prolonged vaginal delivery of PRG. Studies began with the preparation of an aqueous dispersion of PRG-loaded NLC (NLC_PRG), followed by the evaluation of its biocompatibility in human immortalized keratinocytes (HaCat cells), using three different methods (neutral red uptake, resazurin reduction and sulforhodamine B assays). Finally, the NLC_PRG was incorporated into pessaries, which were further characterized according to the European Pharmacopoeia to assess their suitability to prolong PRG release through the vaginal route. The results showed that, after preparation, 90% of the NLC_PRG had sizes equal or lower than 315.60 ± 0.01 nm, and an EE of 96.42 ± 0.00%. All the assays used to assess the biocompatibility of NLC_PRG showed the absence of cytotoxicity towards HaCaT cells for concentrations up to 10 μg/mL. In all cytotoxicity assays, a cytotoxic effect was only observed for concentrations equal or higher than 25 μg/mL, which provides high confidence in the obtained results. The outcomes of this study suggest the suitability of using pessaries containing PRG-loaded NLC for sustained drug release, which is an innovative therapeutic strategy and constitutes a promising alternative for the vaginal use of PRG. However, further ex vivo and in vivo studies are needed to fully clarify the pharmacokinetic and toxicological profile before reaching the clinical use.

Evaluation of the biocompatibility and skin hydration potential of vitamin E-loaded lipid nanosystems formulations: In vitro and human in vivo studies

Lipid-based nanosystems, such as nanostructured lipid carriers (NLC) and nanoemulsions (NE) have been described as promising alternatives to conventional formulations for increase skin hydration. Besides, these systems have been used as efficient vehicles for lipophilic molecules that improve skin properties (e.g. vitamin E). In this study, we performed comparative investigations between hydrogels formulations containing vitamin E-loaded NLC (HG-NLC_VE) and vitamin E-loaded nanoemulsion (HG-NE_VE). The experiments started with particle size measurements, which showed no significant differences between nanoparticles/nanodroplets sizes after incorporation in the hydrogel net (386 nm vs. 397 nm for HG-NLC_VE and 402 nm vs. 514 nm for HG-NE_VE). Afterwards, in vitro biocompatibility studies in human keratinocytes were carried out, being observed that the lipid-based nanosystems were more cytotoxic for the cells before incorporation in the hydrogel. Finally, the formulations hydration potential and sensory attributes for skin application were evaluated by in vitro occlusion tests and in vivo human experiments. The results showed that the HG-NLC_VE exhibited the best occlusive properties, whereas the HG-NE_VE performed a faster skin hydration effect. Furthermore, the latter was selected as the most attractive for skin application, although the HG-NLC_VE was described as more suitable to obtain a long-lasting effect. This study demonstrated the in vitro and in vivo safety and hydration potential of hydrogels containing vitamin E-loaded lipid-based nanosystems. These results establish a basis to assess the cutaneous use of these systems, despite more in vivo experiments, for longer periods and in more volunteers, are required before commercialization.

Synthesis, docking and antibacterial studies of more potent amine and hydrazone rifamycin congeners than rifampicin

New rifamycin congeners (1-33) with incorporated amine and hydrazone substituents leading to lipophilic and/or basic nature and altered rigidity of modified C(3) arm were synthesized and structurally characterized in detail. NMR spectroscopic studies at different temperatures indicate two types of structures of rifamycin congeners that are realized in solution: zwitterionic and non-ionic forms in dependence of the basicity of modified C(3) arm. The presence of rifamycin congeners in these two possible forms has a significant impact on the physico-chemical parameters such as lipophilicity (clogP) and water solubility and different binding mode of the C(3) arm of antibiotic at RNAP binding pocket (molecular target) leading to different antibacterial potency. The highest antibacterial potency against S. aureus (including MRSA and MLSB strains) and S. epidermidis strains, even higher than reference rifampicin (Rif) and rifaximin (Rifx) antibiotics, was found for rifamycin congeners bearing at the C(3) arm relatively rigid and basic substituents (bipiperidine and guanidine groups). These modifications provide favorable docking mode and excellent water solubility resulting in high potency (MICs 0.0078 μg/mL what gives ∼ 8.5 nM), irrespective whether rifamycin congener is a tertiary amine (15) or hydrazone (29). In turn, for a higher antibacterial potency of rifamycin congeners against E. faecalis strain (MICs 0.5 μg/mL that is 0.6 μM) as compared to Rif and Rifx, the most crucial factors are: bulkiness and the lipophilic character of the end of the C(3) rebuilt arm.

Acute pain alters P-glycoprotein-containing protein complexes in rat cerebral microvessels: Implications for P-glycoprotein trafficking

P-glycoprotein (PgP) is the major drug efflux pump in human cerebral microvessels. PgP prevents pathogens, toxins and therapeutic drugs from entering the CNS. Understanding the molecular regulation of PgP activity will suggest novel mechanisms to improve CNS drug delivery. Previously, we found that during peripheral inflammatory pain (PIP) (3 h after λ carrageenan injection in the rat paw), PgP traffics to the cortical microvessel endothelial cell plasma membrane concomitant with increased PgP activity. In the current study, we measured the changes in composition of PgP-containing protein complexes after PIP in rat microvessel isolates. We found that a portion of the PgP is contained in a multi-protein complex that also contains the caveolar proteins CAV1, SDPR, PTRF and PRKCDBP. With PIP, total CAV1 bound to PgP was unchanged; however, phosphorylated CAV1 (Y14P-CAV1) in the complex increased. There were few PgP/CAV1 complexes relative to total PgP and CAV1 in the microvessels suggesting CAV1 bound to PgP is unlikely to affect total PgP activity. However, both PgP and CAV1 trafficked away from the nucleus in response to PIP. These data suggest that P-CAV1 bound to PgP potentially regulates PgP trafficking and contributes to the acute PgP activity increase after a PIP stimulus.

Targeting ABCB1 (MDR1) in multi-drug resistant osteosarcoma cells using the CRISPR-Cas9 system to reverse drug resistance

Background

Multi-drug resistance (MDR) remains a significant obstacle to successful chemotherapy treatment for osteosarcoma patients. One of the central causes of MDR is the overexpression of the membrane bound drug transporter protein P-glycoprotein (P-gp), which is the protein product of the MDR gene ABCB1. Though several methods have been reported to reverse MDR in vitro and in vivo when combined with anticancer drugs, they have yet to be proven useful in the clinical setting.

Results

The meta-analysis demonstrated that a high level of P-gp may predict poor survival in patients with osteosarcoma. The expression of P-gp can be efficiently blocked by the clustered regularly interspaced short palindromic repeats (CRISPR)-associated Cas9 system (CRISPR-Cas9). Inhibition of ABCB1 was associated with reversing drug resistance in osteosarcoma MDR cell lines (KHOSR2 and U-2OSR2) to doxorubicin.

Materials and Methods

We performed a meta-analysis to investigate the relationship between P-gp expression and survival in patients with osteosarcoma. Then we adopted the CRISPR-Cas9, a robust and highly efficient novel genome editing tool, to determine its effect on reversing drug resistance by targeting endogenous ABCB1 gene at the DNA level in osteosarcoma MDR cell lines.

Conclusion

These results suggest that the CRISPR-Cas9 system is a useful tool for the modification of ABCB1 gene, and may be useful in extending the long-term efficacy of chemotherapy by overcoming P-gp-mediated MDR in the clinical setting.

Influence of paeoniflorin and menthol on puerarin transport across MDCK and MDCK-MDR1 cells as blood–brain barrier in vitro model

Objective

Our objective of this research was (1) to investigate the transport characteristics of puerarin through MDCK-MDR1 and MDCK cells and (2) to evaluate the effects of paeoniflorin and menthol on puerarin transport so as to (3) explore the enhancement mechanism.

Methods

The cytotoxicity of drugs on MDCK and MDCK-MDR1 was evaluated by the MTT assay, and the transport studies were performed in both directions. The membrane fluidity was evaluated by fluorescence recovery after photobleaching, and the membrane potential was estimated by the accumulation of DiBAC4(3) in the cells.

Key findings

Puerarin showed relatively poor absorption and purely passive diffusion. However, the efflux ratio of puerarin was <2 in MDCK-MDR1 models, which suggested puerarin was not P-gp substrates so as to the P-glycoprotein activity determination of puerarin. With the existence of menthol, the transcellular transport of puerarin increased and puerarin transport significantly increased when co-administrated with paeoniflorin and menthol.

Conclusions

The enhancing effect of paeoniflorin and menthol may be attributed to the significant enhancement on cell membrane fluidity, the decrease in membrane potential. Immunostaining results indicated that menthol behaved as transport enhancer by disassembly effect on tight junction integrity.

Absorption properties and effects of caffeic acid phenethyl ester and its p-nitro-derivative on P-glycoprotein in Caco-2 cells and rats

CONTEXT

Caffeic acid phenethyl ester (CAPE), isolated from honeybee propolis, has pharmacological applications. A synthesized CAPE derivative, p-nitro-caffeic acid phenethyl ester (CAPE-NO₂), showed similar activities with CAPE. The pharmacological activities of CAPE and CAPE-NO₂ are related to their absorption properties.

OBJECTIVE

To understand the pharmacokinetic profiles of CAPE and CAPE-NO₂ in rats and investigate the absorption mechanisms and effects on P-glycoprotein in Caco-2 cells.

MATERIALS AND METHODS

The pharmacokinetic profiles of CAPE and CAPE-NO₂ were obtained after oral administration (10 mg/kg) to rats. Transport studies of CAPE and CAPE-NO₂ (5, 10, 20 μM) were performed in Caco-2 cell model. P-gp activities were assayed by rhodamine 123 cellular retention. Expression of P-gp was determined after the cells were administrated with CAPE and CAPE-NO₂ (5, 20 μM) for 48 and 72 h.

RESULTS

The AUC_(0-t) of CAPE-NO₂ (3239.9 ± 352 ng × h/mL) was two-time greater than CAPE (1659.6 ± 152 ng × h/mL) in rats. The P_app values of CAPE and CAPE-NO₂ were (4.86 ± 0.90) × 10^-6cm/s and (12.34 ± 1.6) × 10^-6cm/s, respectively. The accumulation of rhodamine 123 was increased by 1.3- to 1.9-fold and 1.4- to 2.3-fold in CAPE and CAPE-NO₂ groups after 1 h administration, respectively. However, CAPE and CAPE-NO₂ increased the P-gp levels by 2.1- and 1.7-fold, respectively.

CONCLUSION

The absorption of CAPE-NO₂ can be enhanced in rats and Caco-2 cells compared with CAPE. The two compounds are potential inhibitors of P-gp. The increased P-gp levels generated by CAPE and CAPE-NO₂ played a role as a defense mechanism by limiting intracellular xenobiotic levels.

P-glycoprotein traffics from the nucleus to the plasma membrane in rat brain endothelium during inflammatory pain

P-glycoprotein (PgP), a drug efflux pump in blood-brain barrier endothelial cells, is a major clinical obstacle for effective central nervous system drug delivery. Identifying PgP regulatory pathways that can be exploited clinically is critical for improving central nervous system drug delivery. We previously found that PgP activity increases in rat brain microvessels concomitant with decreased central nervous system drug delivery in response to acute peripheral inflammatory pain. In the current study, we tested the hypothesis that PgP traffics to the luminal plasma membrane of the microvessel endothelial cells from intracellular stores during peripheral inflammatory pain. Using immunofluorescence microscopy, we detected PgP in endothelial cell nuclei and in the luminal plasma membrane in control animals. Following peripheral inflammatory pain, luminal PgP staining increased while staining in the nucleus decreased. Biochemical analysis of nuclear PgP content confirmed our visual observations. Peripheral inflammatory pain also increased endothelial cell luminal staining of polymerase 1 and transcript release factor/cavin1 and serum deprivation response protein/cavin2, two caveolar scaffold proteins, without changing caveolin1 or protein kinase C delta binding protein/cavin3 location. Our data (a) indicate that PgP traffics from stores in the nucleus to the endothelial cell luminal membrane in response to peripheral inflammatory pain; (b) provide an explanation for our previous observation that peripheral inflammatory pain inhibits central nervous system drug uptake; and (c) suggest a novel regulatory mechanism for PgP activity in rat brain.

Cbl-b inhibits P-gp transporter function by preventing its translocation into caveolae in multiple drug-resistant gastric and breast cancers

The transport function of P-glycoprotein (P-gp) requires its efficient localization to caveolae, a subset of lipid rafts, and disruption of caveolae suppresses P-gp transport function. However, the regulatory molecules involved in the translocation of P-gp into caveolae remain unknown. In the present study, we showed that c-Src dependent Caveolin-1 phosphorylation promoted the translocation of P-gp into caveolae, resulting in multidrug resistance in adriamycin resistant gastric cancer SGC7901/Adr and breast cancer MCF-7/Adr cells. In a negative feedback loop, the translocation of Cbl-b from the nucleus to the cytoplasm prevented the localization of P-gp to caveolae resulting in the reversal of MDR through the ubiquitination and degradation of c-Src. Clinical data showed a significant positive relationship between Cbl-b expression and survival in P-gp positive breast cancer patients who received anthracycline-based chemotherapy. Our findings identified a new regulatory mechanism of P-gp transport function in multiple drug-resistant gastric and breast cancers.

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.

Deconstructing breast cancer cell biology and the mechanisms of multidrug resistance

Cancer complexity constantly challenges the way that clinicians manage breast cancer therapy. Tumor heterogeneity and intratumoral stroma characteristics allow cells with different phenotypes and deregulated apoptotic, proliferative and migration abilities to co-exist contributing to a disappointing therapeutic response. While new approaches are being associated with conventional chemotherapy, such as hormonal therapy or target monoclonal antibodies, recurrence and metastasization are still observed. Membrane transporters are the cell's first line of contact with anticancer drugs having a major role in multidrug resistance events. This structural-based activity enables the cell to be drug-resistant by decreasing drug intracellular concentration through an efflux-transport mechanism, mainly associated with overexpression of ATP-binding cassette (ABC) proteins. This review focuses on some of the important structural and biological properties of the malignant cell and tumor microenvironment, addressing the role of the membrane ABC transporters in therapeutic outcomes, and highlighting related molecular pathways that may represent meaningful target therapies.

Enhancing effect of borneol and muscone on geniposide transport across the human nasal epithelial cell monolayer

Geniposide is widely used in the treatment of cerebral ischemic stroke and cerebrovascular diseases for its anti-thrombotic and anti-inflammatory effects. Recent studies demonstrated that geniposide could be absorbed promptly and thoroughly by intranasal administration in mice and basically transported into the brain. Here, we explored its transport mechanism and the effect of borneol and muscone on its transport by human nasal epithelial cell (HNEC) monolayer. The cytotoxicity of geniposide, borneol, muscone and their combinations on HNECs was evaluated by the MTT assay. Transcellular transport of geniposide and the influence of borneol and muscone were studied using the HNEC monolayer. Immunostaining and transepithelial electrical resistance were measured to assess the integrity of the monolayer. The membrane fluidity of HNEC was evaluated by fluorescence recovery after photobleaching. Geniposide showed relatively poor absorption in the HNEC monolayer and it was not a P-gp substrate. Geniposide transport in both directions significantly increased when co-administrated with increasing concentrations of borneol and muscone. The enhancing effect of borneol and muscone on geniposide transport across the HNEC may be attributed to the significant enhancement on cell membrane fluidity, disassembly effect on tight junction integrity and the process was reversible. These results indicated that intranasal administration has good potential to treat cerebrovascular diseases.

Development of novel rifampicin-derived P-glycoprotein activators/inducers. synthesis, in silico analysis and application in the RBE4 cell model, using paraquat as substrate

P-glycoprotein (P-gp) is a 170 kDa transmembrane protein involved in the outward transport of many structurally unrelated substrates. P-gp activation/induction may function as an antidotal pathway to prevent the cytotoxicity of these substrates. In the present study we aimed at testing rifampicin (Rif) and three newly synthesized Rif derivatives (a mono-methoxylated derivative, MeORif, a peracetylated derivative, PerAcRif, and a reduced derivative, RedRif) to establish their ability to modulate P-gp expression and activity in a cellular model of the rat’s blood–brain barrier, the RBE4 cell line P-gp expression was assessed by western blot using C219 anti-P-gp antibody. P-gp function was evaluated by flow cytometry measuring the accumulation of rhodamine123. Whenever P-gp activation/induction ability was detected in a tested compound, its antidotal effect was further tested using paraquat as cytotoxicity model. Interactions between Rif or its derivatives and P-gp were also investigated by computational analysis. Rif led to a significant increase in P-gp expression at 72 h and RedRif significantly increased both P-gp expression and activity. No significant differences were observed for the other derivatives. Pre- or simultaneous treatment with RedRif protected cells against paraquat-induced cytotoxicity, an effect reverted by GF120918, a P-gp inhibitor, corroborating the observed P-gp activation ability. Interaction of RedRif with P-gp drug-binding pocket was consistent with an activation mechanism of action, which was confirmed with docking studies. Therefore, RedRif protection against paraquat-induced cytotoxicity in RBE4 cells, through P-gp activation/induction, suggests that it may be useful as an antidote for cytotoxic substrates of P-gp.