Multidrug resistance (MDR) is a serious obstacle encountered in cancer treatment, in which the overexpression of P-glycoprotein (P-gp) plays an important role. Here, a novel α-hederagenin derivative, ...designated H6, was designed, synthesized and evaluated for its ability to reverse MDR. Our results showed that H6 could sensitize KBV and MCF7/T cells to paclitaxel and vincristine. Meanwhile, H6 could increase both rhodamine 123 and paclitaxel accumulation in MDR cells without affecting the expression of P-gp. Interestingly, siRNA knockdown of MDR1 further sensitized the cytotoxic activity of paclitaxel when co-administrated with H6. In addition, H6 could directly stimulate P-gp ATPase activity in vitro. Importantly, H6 enhanced the efficacy of paclitaxel against KBV cancer cell-derived xenograft tumors in nude mice. Finally, H6 showed high binding affinity with P-gp with a high docking score. Overall, we show H6 is a novel and potent MDR reversal agent, which has the potential to be administered in combination with conventional anticancer drugs.
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•H6 is one novel synthesized α-hederagenin derivative.•H6 demonstrates robust reversal activity against MDR in vitro and in vivo.•H6 could directly stimulate P-gp ATPase activity via binding with p-gp.•H6 might be co-administered against drug resistance in clinic.
A promising strategy to overcome multidrug resistance is the use of inhibitors of ABC drug transporters. For this reason, we evaluated the polyoxovanadates (POVs) V10O286– (V10), H6V14O38(PO4)5− ...(V14), V15O36Cl6− (V15) and V18O42I7− (V18) as inhibitors of three major multidrug resistance‐linked ABC transporters: P‐glycoprotein (P‐gp), ABCG2 and MRP1. All of the POVs selectively inhibited P‐gp. V10 and V18 were the two most promising compounds, with IC50 values of transport inhibition of 25.4 and 22.7 µm, respectively. Both compounds inhibited P‐gp ATPase activity, with the same IC50 value of 1.26 µm. V10 and V18 triggered different conformational changes in the P‐gp protein with time‐dependent inhibition, which was confirmed using the synthesized salt of V10 with rhodamine B, RhoB‐V10. The hydrophilic nature of POVs supports the hypothesis that these compounds target an unusual ligand‐binding site, opening new possibilities in the development of potent modulators of ABC transporters.
One of the main challenges in cancer treatment is the resistance mediated by P‐glycoprotein (P‐gp). We described polyoxovanadates (POVs) as new selective P‐gp inhibitors. The two best compounds were V10O286– (V10) and V18O42(I)7− (V18). These compounds were not transported, inhibited the ATPase activity and triggered different protein conformational changes. In addition, compound RhoB‐V10 confirmed the time‐dependent intracellular accumulation of POVs.
The P‐glycoprotein (P‐gp) substrate status of antineoplastic drugs intended for veterinary patients is an important characteristic to define for two reasons. First, neoplastic cells expressing P‐gp ...can actively efflux drugs that are P‐gp substrates curtailing their efficacy. Second, antineoplastic drugs tend to have a narrow therapeutic index. Antineoplastic drugs that are P‐gp substrates can cause severe adverse reactions in animals with P‐gp dysfunction such as dogs with ABCB1‐1Δ and cats with ABCB11930_1931del TC. Animals with P‐gp dysfunction experience greater overall exposure to P‐gp substrate drugs due to mechanisms such as increased intestinal absorption, decreased biliary clearance and greater central nervous system penetration compared with animals with normal P‐gp function. Accordingly, knowing the P‐gp substrate status of antineoplastic drugs is an important safety consideration prior to use in canine or feline cancer patients. This study used a cell line overexpressing canine P‐gp to assess the P‐gp substrate status of verdinexor. Based on both a cytotoxicity assay and a competitive flow cytometry assay verdinexor is not a substrate for canine P‐gp.
Aim
Apixaban is an orally active inhibitor of coagulation factor Xa and is eliminated by multiple pathways, including renal and non‐renal elimination. Non‐renal elimination pathways consist of ...metabolism by cytochrome P450 (CYP) enzymes, primarily CYP3A4, as well as direct intestinal excretion. Two single sequence studies evaluated the effect of ketoconazole (a strong dual inhibitor of CYP3A4 and P‐glycoprotein P‐gp) and diltiazem (a moderate CYP3A4 inhibitor and a P‐gp inhibitor) on apixaban pharmacokinetics in healthy subjects.
Method
In the ketoconazole study, 18 subjects received apixaban 10 mg on days 1 and 7, and ketoconazole 400 mg once daily on days 4–9. In the diltiazem study, 18 subjects received apixaban 10 mg on days 1 and 11 and diltiazem 360 mg once daily on days 4–13.
Results
Apixaban maximum plasma concentration and area under the plasma concentration–time curve extrapolated to infinity increased by 62% (90% confidence interval CI, 47, 78%) and 99% (90% CI, 81, 118%), respectively, with co‐administration of ketoconazole, and by 31% (90% CI, 16, 49%) and 40% (90% CI, 23, 59%), respectively, with diltiazem.
Conclusion
A 2‐fold and 1.4‐fold increase in apixaban exposure was observed with co‐administration of ketoconazole and diltiazem, respectively.
P‐glycoprotein (P‐gp) is an efflux transporter at the blood–brain barrier (BBB) that hinders brain access of substrate drugs and clears endogenous molecules such as amyloid beta (Aβ) from the brain. ...As biometals such as copper (Cu) modulate many neuronal signalling pathways linked to P‐gp regulation, it was hypothesised that the bis(thiosemicarbazone) (BTSC) Cu‐releasing complex, copper II glyoxal bis(4‐methyl‐3‐thiosemicarbazone) (CuIIGTSM), would enhance P‐gp expression and function at the BBB, while copper II diacetyl bis(4‐methyl‐3‐thiosemicarbazone) (CuIIATSM), which only releases Cu under hypoxic conditions, would not modulate P‐gp expression. Following treatment with 25–250 nM CuII(BTSC)s for 8–48 h, expression of P‐gp mRNA and protein in human brain endothelial (hCMEC/D3) cells was assessed by RT‐qPCR and Western blot, respectively. P‐gp function was assessed by measuring accumulation of the fluorescent P‐gp substrate, rhodamine 123 and intracellular Cu levels were quantified by inductively coupled plasma mass spectrometry. Interestingly, CuII(ATSM) significantly enhanced P‐gp expression and function 2‐fold and 1.3‐fold, respectively, whereas CuII(GTSM) reduced P‐gp expression 0.5‐fold and function by 200%. As both compounds increased intracellular Cu levels, the effect of different BTSC backbones, independent of Cu, on P‐gp expression was assessed. However, only the Cu‐ATSM complex enhanced P‐gp expression and this was mediated partly through activation (1.4‐fold) of the extracellular signal‐regulated kinase 1 and 2, an outcome that was significantly attenuated in the presence of an inhibitor of the mitogen‐activated protein kinase regulatory pathway. Our findings suggest that CuII(ATSM) and CuII(GTSM) have the potential to modulate the expression and function of P‐gp at the BBB to impact brain drug delivery and clearance of Aβ.
P‐glycoprotein (P‐gp) expressed at the blood–brain barrier (BBB) acts as a gatekeeper regulating the transport of molecules into and out of the brain. Two similar copper complexes, CuII(ATSM) and CuII(GTSM), have opposite modulatory effects on the expression and function of this efflux transporter that is responsible for keeping the brain a protected sanctuary as well as to clear unwanted molecules like amyloid beta (Aβ) from the brain. This involves the activation of MAPK signalling and MDR1 promoter regions regulating P‐gp. This has implications for enhancing brain drug delivery and clearance of Aβ in Alzheimer's disease.
Objective
In this study, we develop and apply a high‐throughput screening protocol to investigate the activity of non‐ionic surfactants, with a broad range of hydrophilic–lipophilic balance values, ...against ABCB1‐mediated efflux transport and ABCC2‐mediated efflux transport.
Methods
Caco‐2 cells were grown for 7 days in 96‐well plates, then washed and incubated with the test materials for 2 h in the presence of 2.5 μm of either rhodamine 123 (R‐123) or 5(6)‐Carboxy‐2′,7′ dichlorofluorescein diacetate as probes of ABCB1 and ABCC2, respectively.
Key findings
Of the surfactants tested, no activity against ABCC2 was detected and all surfactants showing efficacy against ABCB1 had a HLB value of 22 or below. Inhibition of ABCB1 was seen in the order of efficacy to be poloxamer 335 > poloxamer 40 > Crovol A‐70 > Myrj S‐40 > poloxamer 184 > poloxamer 182 > Etocas 40 > Tween 20 > Etocas 29 > Tween 80 > Acconon C‐44 > Span 20. With regard to this inhibition, the distribution of hydrophilic regions is more important than the HLB value.
Conclusion
This work demonstrates a high‐throughput protocol for detecting materials that can modulate ABCB1‐mediated efflux. These surfactants could be exploited to improve oral delivery of drugs prone to efflux.
Phenytoin (PHT) is a first‐line antiepileptic drug in clinics, which could decrease neuronal bioelectric activity by blocking the voltage‐operated sodium channels. However, the intrinsically low ...blood–brain‐barrier (BBB)‐crossing capability of PHT and upregulated expression level of the efflux transporter p‐glycoprotein (P‐gp) coded by the gene Abcb1 in epileptic neurons limit its efficacy in vivo. Herein, a nanointegrated strategy to overcome PHT resistance mechanisms for enhanced antiepileptic efficacy is reported. Specifically, PHT is first incorporated into calcium phosphate (CaP) nanoparticles through biomineralization, followed by the surface modification of the PEGylated BBB‐penetrating TAT peptide. The CaP@PHT‐PEG‐TAT nanoformulation could effectively cross the BBB to be taken in by epileptic neurons. Afterward, the acidic lysosomal environment would trigger their complete degradation to release Ca2+ and PHT into the cytosol. Ca2+ ions would inhibit mitochondrial oxidative phosphorylation to reverse cellular hypoxia to block hypoxia‐inducible factor‐1α (Hif1α)‐Abcb1‐axis, as well as disrupt adenosine triphosphate generation, leading to simultaneous suppression of the expression and drug efflux capacity of P‐gp to enhance PHT retention. This study offers an approach for effective therapeutic intervention against drug‐resistant epilepsy.
To maximize the therapeutic index of phenytoin (PHT) for epilepsy treatment, a nanointegrated PHT delivery system based on biocompatible and degradable amorphous calcium phosphate is developed, which can effectively and safely cross the blood–brain barrier and mechanistically block hypoxia‐inducible factor‐1α‐Abcb1 signaling, thus inhibiting the drug efflux potential of p‐glycoprotein and improving the neuronal retention of PHT.
Flavonoids, natural compounds found in plants and in plant‐derived foods and beverages, have been extensively studied with regard to their capacity to modulate metabolic enzymes and drug ...transporters. In vitro, flavonoids predominantly inhibit the major phase I drug‐metabolizing enzyme CYP450 3A4 and the enzymes responsible for the bioactivation of procarcinogens (CYP1 enzymes) and upregulate the enzymes involved in carcinogen detoxification (UDP‐glucuronosyltransferases, glutathione S‐transferases (GSTs)). Flavonoids have been reported to inhibit ATP‐binding cassette (ABC) transporters (multidrug resistance (MDR)–associated proteins, breast cancer–resistance protein) that contribute to the development of MDR. P‐glycoprotein, an ABC transporter that limits drug bioavailability and also induces MDR, was differently modulated by flavonoids. Flavonoids and their phase II metabolites (sulfates, glucuronides) inhibit organic anion transporters involved in the tubular uptake of nephrotoxic compounds. In vivo studies have partially confirmed in vitro findings, suggesting that the mechanisms underlying the modulatory effects of flavonoids are complex and difficult to predict in vivo. Data summarized in this review strongly support the view that flavonoids are promising candidates for the enhancement of oral drug bioavailability, chemoprevention, and reversal of MDR.
Malaria in pregnancy (MiP) induces intrauterine growth restriction (IUGR) and preterm labour (PTL). However, its effects on yolk sac morphology and function are largely unexplored. We hypothesized ...that MiP modifies yolk sac morphology and efflux transport potential by modulating ABC efflux transporters. C57BL/6 mice injected with Plasmodium berghei ANKA (5 × 105 infected erythrocytes) at gestational day (GD) 13.5 were subjected to yolk sac membrane harvesting at GD 18.5 for histology, qPCR and immunohistochemistry. MiP did not alter the volumetric proportion of the yolk sac's histological components. However, it increased levels of Abcb1a mRNA (encoding P‐glycoprotein) and macrophage migration inhibitory factor (Mif chemokine), while decreasing Abcg1 (P < 0.05); without altering Abca1, Abcb1b, Abcg2, Snat1, Snat2, interleukin (Il)‐1β and C‐C Motif chemokine ligand 2 (Ccl2). Transcripts of Il‐6, chemokine (C‐X‐C motif) ligand 1 (Cxcl1), Glut1 and Snat4 were not detectible. ABCA1, ABCG1, breast cancer resistance protein (BCRP) and P‐gp were primarily immunolocalized to the cell membranes and cytoplasm of endodermic epithelium but also in the mesothelium and in the endothelium of mesodermic blood vessels. Intensity of P‐gp labelling was stronger in both endodermic epithelium and mesothelium, whereas ABCA1 labelling increased in the endothelium of the mesodermic blood vessels. The presence of ABC transporters in the yolk sac wall suggests that this fetal membrane acts as an important protective gestational barrier. Changes in ABCA1 and P‐gp in MiP may alter the biodistribution of toxic substances, xenobiotics, nutrients and immunological factors within the fetal compartment and participate in the pathogenesis of malaria‐induced IUGR and PTL.
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