Multidrug Resistance Protein Research Articles

The ATP-Binding Cassette Transporter-Mediated Efflux Transport of Ganciclovir at the Blood-Brain Barrier.

Recent studies have highlighted the key role of the ATP-binding cassette (ABC) transporters, including theP-glycoprotein (P-gp), the breast cancer resistance protein (BCRP), and the multi-drug resistance protein 4 (MRP4) in limiting the brain distribution of several antiviral agents. In this study, we investigated whether the inhibition of these transporters increases the permeability of the blood-brain barrier (BBB) to ganciclovir. A microdialysis and high-performance liquid chromatographic method was developed to monitor the concentrations of unbound ganciclovir in the brain interstitial fluid and plasma, with and without the administration of ABC transporter inhibitors. Pharmacokinetic parameters, including the area under the plasma concentration-time curve from time 0 to time of the last measurable analyte concentration (AUC0-t,plasma), the area under the brain interstitial fluid concentration-time curve from time 0 to time of the last measurable analyte concentration (AUC0-t,brain), and the unbound brain-to-plasma concentration ratio (Kp,uu,brain) were calculated. The mean AUC0-t,plasma, AUC0-t,brain, and Kp,uu,brain in rats who received ganciclovir (30 mg/kg, intraperitoneal) alone were 1090 min·µg/mL, 150 min·µg/mL, and 14%, respectively. After the administration of tariquidar (inhibitor of P-gp), Ko143 (inhibitor of BCRP), or MK-571 (inhibitor of MRP4), the Kp,uu,brain of ganciclovir increased to 31 ± 2.1%, 26 ± 1.3%, and 32 ± 2.0%, respectively. The findings of this studysuggest that ABC transporters P-gp, BCRP, and MRP4 mediate the efflux of ganciclovir at the BBB and that the inhibition of these transporters facilitates the penetration of the BBB by ganciclovir.

Picroside II promotes HSC apoptosis and inhibits the cholestatic liver fibrosis in Mdr2−/− mice by polarizing M1 macrophages and balancing immune responses

Liver fibrosis is characterized by chronic inflammatory responses and progressive fibrous scar formation. Macrophages play a central role in the pathogenesis of hepatic fibrosis by reconstructing the immune microenvironment. Picroside II (PIC II), extracted from Picrorhizae Rhizoma, has demonstrated therapeutic potential for various liver damage. However, the mechanisms by which macrophage polarization initiates immune cascades and contributes to the development of liver fibrosis, and whether this process can be influenced by PIC II, remain unclear. In the current study, RNA sequencing and multiple molecular approaches were utilized to explore the underlying mechanisms of PIC II against liver fibrosis in multidrug-resistance protein 2 knockout (Mdr2−/−) mice. Our findings indicate that PIC II activates M1-polarized macrophages to recruit natural killer cells (NK cells), potentially via the CXCL16-CXCR6 axis. Additionally, PIC II promotes the apoptosis of activated hepatic stellate cells (aHSCs) and enhances the cytotoxic effects of NK cells, while also reducing the formation of neutrophil extracellular traps (NETs). Notably, the anti-hepatic fibrosis effects associated with PIC II were largely reversed by macrophage depletion in Mdr2−/− mice. Collectively, our research suggests that PIC II is a potential candidate for halting the progression of liver fibrosis.

Optimization of diastereomeric dihydropyridines as antimalarials

The increase in research funding for the development of antimalarials since 2000 has led to a surge of new chemotypes with potent antimalarial activity. High-throughput screens have delivered several thousand new active compounds in several hundred series, including the 4,7-diphenyl-1,4,5,6,7,8-hexahydroquinolines, hereafter termed dihydropyridines (DHPs). We optimized the DHPs for antimalarial activity. Structure-activity relationship studies focusing on the 2-, 3-, 4-, 6-, and 7-positions of the DHP core led to the identification of compounds potent (EC50 < 10 nM) against all strains of P. falciparum tested, including the drug-resistant parasite strains K1, W2, and TM90-C2B. Evaluation of efficacy of several compounds in vivo identified two compounds that reduced parasitemia by >75 % in mice 6 days post-exposure following a single 50 mg/kg oral dose. Resistance acquisition experiments with a selected dihydropyridine led to the identification of a single mutation conveying resistance in the gene encoding for Plasmodium falciparum multi-drug resistance protein 1 (PfMDR1). The same dihydropyridine possessed transmission blocking activity. The DHPs have the potential for the development of novel antimalarial drug candidates.

Inhibition and transport mechanisms of the ABC transporter hMRP5

Human multidrug resistance protein 5 (hMRP5) effluxes anticancer and antivirus drugs, driving multidrug resistance. To uncover the mechanism of hMRP5, we determine six distinct cryo-EM structures, revealing an autoinhibitory N-terminal peptide that must dissociate to permit subsequent substrate recruitment. Guided by these molecular insights, we design an inhibitory peptide that could block substrate entry into the transport pathway. We also identify a regulatory motif, comprising a positively charged cluster and hydrophobic patches, within the first nucleotide-binding domain that modulates hMRP5 localization by engaging with membranes. By integrating our structural, biochemical, computational, and cell biological findings, we propose a model for hMRP5 conformational cycling and localization. Overall, this work provides mechanistic understanding of hMRP5 function, while informing future selective hMRP5 inhibitor development. More broadly, this study advances our understanding of the structural dynamics and inhibition of ABC transporters.

Unraveling the Mechanism of Curculiginis Rhizoma in Suppressing Cisplatin Resistance in Non-Small Cell Lung Cancer: An Experimental Study.

Non-small cell lung cancer (NSCLC) stands as one of the most prevalent malignancies, and chemotherapy remains the primary treatment for advanced stages. However, the high expression of ABC binding cassette transporters, including MRP, P-gp, and LRP, along with multidrug resistance proteins, has been identified as a significant factor contributing to decreased chemotherapy drug sensitivity. This study aims to explore the impact and underlying mechanisms of Curculiginis Rhizoma [Hypoxidaceae; Curculigo orchioides Gaertn.] (CR) in combination with cisplatin on improving chemoresistance mediated by ABC binding cassette transporters and multidrug resistance proteins in NSCLC. To unravel the relationship between JNK, MRP, P-gp, and LRP in NSCLC and gain insights into the regulatory mechanism of CR, this study employs an integrated approach encompassing bioinformatics, molecular docking, molecular dynamics, animal and cellular experiments. Bioinformatics analysis revealed a significant increase in the expression levels of JNK, MRP, P-gp, and LRP subtypes in multidrug-resistant non-small cell lung cancer. Subsequent animal experiments have shown that the combination of CR with cisplatin can improve the survival rate of lung cancer mice. Molecular docking and molecular dynamics analyses demonstrated favorable binding interactions between curculigoside and the aforementioned subtypes of JNK, MRP, P-gp, and LRP. In cellular experiments, the combination of cisplatin with both curculigoside and CR extract resulted in a notable decrease in cell viability and downregulation of the expression of JNK1, JNK2, MRP1, MRP2, MRP4, P-gp, and LRP1 in A549/cis cells. Remarkably, curculigoside exerted a significant downregulation effect on the expression levels of JNK1, MRP1, MRP2, MRP4, and LRP1. CR, particularly its main effective metabolite, curculigoside, has the potential to enhance the sensitivity of non-small cell lung cancer to cisplatin by regulating levels of JNK/MRP/LRP/P-gp and mitigating multidrug resistance.

Transporter Genes and statin-induced Hepatotoxicity.

Hepatotoxicity has emerged as a major cause of statin treatment interruption. Although organic anion-transporting polypeptide 1B1 (SLCO1B1), multidrug resistance protein 1 (ABCB1), and breast cancer resistance protein (ABCG2) have been identified as transporters of statins, knowledge of their role in statin-associated hepatotoxicity remains limited. Therefore, we aimed to conduct a comprehensive analysis to elucidate the association between hepatotoxicity and SLCO1B1, ABCB1, and ABCG2 polymorphisms. This study retrospectively analyzed prospectively collected samples. We selected 10 single nucleotide polymorphisms (SNPs) of SLCO1B1, 9 SNPs of ABCB1, and 12 SNPs of ABCG2. We developed two models for multivariable analyses (Model I: clinical factors only; Model II: both clinical and genetic factors), and the attributable risk (%) of variables in Model II was determined. Among 851 patients, 66 (7.8%) developed hepatotoxicity. In Model I, lipophilic statins, atrial fibrillation (Afib), and diabetes mellitus showed a significant association with hepatotoxicity. In Model II, lipophilic statins and Afib, SLCO1B1 rs11045818 A allele, SLCO1B1 rs4149035 T allele, and ABCG2 rs2622629 TT genotype were associated with higher hepatotoxicity risk. Among them, the SLCO1B1 rs11045818 A allele exhibited the highest attributable risk (93.2%). The area under the receiver operating characteristic curve in Model I was 0.62 (95% CI: 0.55-0.69), and it was increased to 0.71 in Model II (95% CI: 0.64-0.77). This study investigated the correlation between hepatotoxicity and polymorphisms of transporter genes in patients taking statins. The findings could help improve personalized treatments for patients receiving statin therapy.

#2899 Role of the Th17.1 cells in IgA nephropathy

Abstract Background and Aims T helper (Th) cells play a crucial role in glomerulonephritis, including IgA nephropathy (IgAN). Recently identified Th17.1 cells, which are elevated in sarcoidosis, lupus, and Takayasu arteritis, express chemokine receptors CCR6 and CXCR3. These receptors are implicated in inflammatory cell infiltration and fibrosis in glomerulonephritis models. Notably, Th17.1 cells express MDR-1 (multidrug resistance protein) and the drug efflux protein p-glycoprotein, associated with corticosteroid resistance. However, the exact role of Th17.1 cells in IgAN remains unclear. Intriguingly, Th17.1 cells produce INF-γ and IL-17, cytokines implicated in IgAN pathogenesis. Method In this retrospective cross-sectional study, we examined circulating Th17.1 cells in 18 confirmed IgAN patients. Antibodies such as anti-CXCR3-FITC and anti-CCR6-PCy7 (Biolegend, U.S.A.) were used to stain Th subpopulations. We also used combinations of the following antibodies: anti-CD45-FITC, anti-CD4-PE, anti-CD8-ECD, anti-CD3-PCy5, anti-CD56-PCy5, anti-CD3-PCy7, anti-CD19-ECD, anti-CD127-FITC, anti-CD25-PCy5, and anti-CD4-PCy7 (Coulter Immunotech, France) to evaluate T, B, NK, and Treg cells. Multicolor flow cytometry was performed using a Navios cytometer, and data were analyzed using Kaluza software (Beckman Coulter, U.S.A.). Th effector subpopulations of CD4+ lymphocytes were identified based on chemokine receptor expression: Th17.1 (CXCR3+CCR6+). Th17.1 cells were quantified as a percentage of CD4+ lymphocytes. Th1, Th2, and Treg cells were also evaluated. We explored correlations between Th17.1 cell counts, estimated glomerular filtration rate (eGFR, mL/min/1.73 m²), and proteinuria (24-hour collection). Among the patients, 5 were classified as refractory (progressive eGFR decline &amp;gt; 5 mL/min/1.73 m² and 24-hour proteinuria &amp;gt; 1g despite steroid and immunosuppressant therapy). Results The study included 18 patients. The mean (95% CI) Th17.1 cell count was 20% (16-23), and the 24-hour proteinuria was 2.1g (1.4-2.7). A significant direct correlation was observed between Th17.1 cells and proteinuria (g/L, adjusted for 24 hours) (r = 0.50, P = 0.03). Refractory patients exhibited higher Th17.1 levels compared to others (25% [95% CI: 17-33] vs. 18% [95% CI: 14-21], P = 0.02) (Fig. 1). Patients with proteinuria &amp;lt; 0.5g/24 h had lower Th17.1 cell counts compared to those with higher proteinuria (16% [95% CI: 12-20] vs. 21% [95% CI: 17-25], P = 0.06. No correlation was found between eGFR, proteinuria, and Th1, Th2, Th17, or Treg cells. Conclusion These findings suggest that Th17.1 cells may contribute to the pathogenesis of IgAN and could potentially indicate the response to steroids or immunosuppressants in treatment. While the direct involvement of Th17.1 cells in kidney tissue remains unexplored, further investigation is warranted due to its therapeutic and prognostic implications.

Alkaliptosis induction counteracts paclitaxel-resistant ovarian cancer cells via ATP6V0D1-mediated ABCB1 inhibition.

Paclitaxel serves as the cornerstone chemotherapy for ovarian cancer, yet its prolonged administration frequently culminates in drug resistance, presenting a substantial challenge. Here we reported that inducing alkaliptosis, rather than apoptosis or ferroptosis, effectively overcomes paclitaxel resistance. Mechanistically, ATPase H+ transporting V0 subunit D1 (ATP6V0D1), a key regulator of alkaliptosis, plays a pivotal role by mediating the downregulation of ATP-binding cassette subfamily B member 1 (ABCB1), a multidrug resistance protein. Both ATP6V0D1 overexpression through gene transfection and pharmacological enhancement of ATP6V0D1 protein stability using JTC801 effectively inhibit ABCB1 upregulation, resulting in growth inhibition in drug-resistant cells. Additionally, increasing intracellular pH to alkaline (pH 8.5) via sodium hydroxide application suppresses ABCB1 expression, whereas reducing the pH to acidic conditions (pH 6.5) with hydrochloric acid amplifies ABCB1 expression in drug-resistant cells. Collectively, these results indicate a potentially effective therapeutic strategy for targeting paclitaxel-resistant ovarian cancer by inducing ATP6V0D1-dependent alkaliptosis.

ABCB1-mediated docetaxel resistance reversed by erastin in prostate cancer.

Docetaxel (Doc) currently serves as the primary first-line treatment for patients with castrate-resistant prostate cancer (CRPC). Erastin, a small molecule compound, can trigger inhibition of the cystine-glutamate reverse transport system and other pathways, leading to iron-dependent cell death (ferroptosis). Beyond its role in inducing cancer cell death, erastin demonstrates potential when combined with chemotherapy drugs to heighten cancer cell drug susceptibility. However, the augmentation by erastin of the effects of Doc treatment on prostate cancer, and the underlying mechanisms involved, remain unclear. In the present study, we determined the role and the underlying molecular mechanism of erastin against CRPC. The results showed that CRPC cell lines were resistant to Doc, and the expression of ferroptosis-related factors in drug-resistant cell lines was downregulated. Erastin, in synergy with Doc, exerts a pro-apoptotic effect. Erastin significantly inhibited the activity of ATP-binding cassette subfamily B member 1 (ABCB1) but did not change its protein expression and localization. Finally, in mice, erastin treatment dramatically reduced tumor growth in vivo. Taken together, our findings demonstrate that erastin enhances Doc-induced apoptosis to a certain extent and reverses Doc resistance in prostate cancer by inhibiting the activity of multidrug-resistant protein ABCB1.

Deciphering the functional role of clinical mutations in ABCB1, ABCC1, and ABCG2 ABC transporters in endometrial cancer.

ATP-binding cassette transporters represent a superfamily of dynamic membrane-based proteins with diverse yet common functions such as use of ATP hydrolysis to efflux substrates across cellular membranes. Three major transporters-P-glycoprotein (P-gp or ABCB1), multidrug resistance protein 1 (MRP1 or ABCC1), and breast cancer resistance protein (BCRP or ABCG2) are notoriously involved in therapy resistance in cancer patients. Despite exhaustive individual characterizations of each of these transporters, there is a lack of understanding in terms of the functional role of mutations in substrate binding and efflux, leading to drug resistance. We analyzed clinical variations reported in endometrial cancers for these transporters. For ABCB1, the majority of key mutations were present in the membrane-facing region, followed by the drug transport channel and ATP-binding regions. Similarly, for ABCG2, the majority of key mutations were located in the membrane-facing region, followed by the ATP-binding region and drug transport channel, thus highlighting the importance of membrane-mediated drug recruitment and efflux in ABCB1 and ABCG2. On the other hand, for ABCC1, the majority of key mutations were present in the inactive nucleotide-binding domain, followed by the drug transport channel and membrane-facing regions, highlighting the importance of the inactive nucleotide-binding domain in facilitating indirect drug efflux in ABCC1. The identified key mutations in endometrial cancer and mapped common mutations present across different types of cancers in ABCB1, ABCC1, and ABCG2 will facilitate the design and discovery of inhibitors targeting unexplored structural regions of these transporters and re-engineering of these transporters to tackle chemoresistance.

Computational Modeling of Sodium Fluorescein Disposition in Ex Vivo, Machine-Perfused Livers with Ischemia-Reperfusion Injury

Rationale: Quantitation of bile formation machinery activity through biliary sodium fluorescein (SF) clearance is useful for assessing liver viability. Studies have shown that the bile-to-plasma SF ratio is inversely correlated with warm ischemia time (WIT) in rats, which is associated with ischemia-reperfusion injury (IRI)-induced intracellular internalization of the multidrug resistance protein 2 (MRP2) transporter (doi: 10.1152/ajpgi.00038.2022). Computational modeling studies by Monti et al. have demonstrated the sensitivity of biliary SF clearance to MRP2 transporter activity in vivo (doi: 10.48550/arXiv.2302.05511). In vivo experimentation is pertinent for establishing physiological variations occurring during IRI, but transplantation often requires a period of ex vivo machine perfusion (MP). The effects of total hepatectomy, WIT, cold ischemia time (CIT), and MP on biliary function remain unclear. We aim to develop a model for quantitative interpretation of biliary SF clearance kinetics in MP livers to estimate parameters descriptive of the dominant processes determining hepatic SF uptake kinetics in MP livers subjected to different periods of WIT. We hypothesize that increasing WIT will lead to a decrease in the maximal transport velocity (Vmax) parameter for MRP2, which is reflective of decreased biliary SF clearance and diminished liver viability. Methods: Using established protocols (doi: 10.3389/frtra.2023.1215182), livers (n = 3-5) were obtained from anesthetized, male, Sprague-Dawley rats and subjected to 0-, 10-, 20-, or 30-min WIT through ligation of the portal vein and hepatic artery. Livers were removed and subjected to 3 hours of CIT on ice. Livers were attached to a custom normothermic MP system, 0.4 mg/kg SF were added to the MP system’s perfusate-containing reservoir, and SF fluorescence measurements in perfusate and bile were obtained and converted to concentration measurements using standard curves. We modified the liver-centric model described in Monti et al. to account for MP by replacing the liver input functions with ordinary differential equations for SF and its conjugate SF glucuronide (SFG) kinetics in the MP system’s reservoir. The model also accounts for three liver regions (sinusoid, hepatocytes, bile) and major processes, including hepatic transporter kinetics and SF metabolism into SFG, which govern SF dynamics in different model regions. We fit the model solutions using a pseudo-Monte Carlo parameter estimation strategy to each of the datasets by allowing the Vmax parameters to vary, while others were fixed to physiologic values. Results: Time course data for IRI conditions showed a modest decrease in biliary SF with 10- and 20-min WIT and a marked change in biliary SF kinetics with 30-min WIT when compared to control. The MP model was fit to each dataset individually and the model was able to provide a good fit to each dataset. Comparison of Vmax parameters estimated from fitting showed a decrease in MRP2’s Vmax with increasing WIT relative to control. Sensitivity analysis supported our finding by demonstrating that MRP2’s Vmax­ was the most sensitive model parameter. Conclusions: We modified an existing in vivo biliary SF clearance model to account for MP livers and fit the new model to biliary SF clearance data for ex vivo MP livers with varying amounts of WIT. We found that the new model was able to fit biliary SF clearance data for ex vivo MP livers and that the Vmax for MRP2 decreased during MP with increasing WIT. Funded in part by 1F30AI179084-01 to C.M. and NSF DMS 2153387 to R.D. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Evaluating the Dynamics of Cyp3a11, MRP2 and MDR1 Modulation by IL-22

Background: IL-22 is a cytokine produced by a number of immune cell populations, including type 3 innate lymphoid cells. We have shown previously that IL-22 suppresses the expression Cyp3a11 in the mouse intestine, a gene that encodes a drug metabolizing. In addition, IL-22 reduces the expression of MRP2 and MDR1, the gene that encodes as Multidrug resistance protein 2 or 1 involve in the drug detoxification. Modulation of these proteins can influence the oral bioavailability of drugs. Aims: The aim of this study was to define the existence of reversible modulation of IL-22 on Cyp3a11, MRP2 and MDR1 expression and protein level or activity in the intestinal epithelium. Methods: In vitro enteroids of the mouse small intestine were cultured in 3D in the presence/absence of IL-22 for 5 days. Cyp3a11, MRP2 and MDR1 transcript expression was evaluated by qPCR followed by protein analysis to define their modulation and activity at varying timepoints after IL-22 treatment cessation. Results: IL-22 reduced the expression and activity of Cyp3a11 which normalized soon after stopping IL-22 treatment. This action of IL-22 are made without any modulation of protein level of Cyp3a11. In the same way, IL-22 reduces the expression and the protein level of MRP2 and MDR1, an effect normalizes after treatment cessation. Conclusions: IL-22 suppresses the expression and the activity of Cyp3a11 without any modulation of the protein level unlike at the level of MRP2 and MDR1 which are reduced. These data suggest that regulation of gene expression, protein or enzyme activity by IL-22 may have variable effects: Cyp3a11 is ATP-independent, whereas MRP2 and MDR1 are ATP-dependent. This direct or indirect enzymatic modulation of these proteins must be taken into account when assessing the role of the drug in the biology of the intestinal mucosa. Dr. Lloyd Sutherland Chair in IBD/GI Research/Weston Foundation. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Physiological and proteomic characterization revealed the response mechanisms underlying aluminium tolerance in lentil (Lens culinaris Medikus).

Aluminium (Al) toxicity causes major plant distress, affecting root growth, nutrient uptake and, ultimately, agricultural productivity. Lentil, which is a cheap source of vegetarian protein, is recognized to be sensitive to Al toxicity. Therefore, it is important to dissect the physiological and molecular mechanisms of Al tolerance in lentil. To understand the physiological system and proteome composition underlying Al tolerance, two genotypes [L-4602 (Al-tolerant) and BM-4 (Al-sensitive)] were studied at the seedling stage. L-4602 maintained a significantly higher root tolerance index and malate secretion with reduced Al accumulation than BM-4. Also, label-free proteomic analysis using ultra-performance liquid chromatography-tandem mass spectrometer exhibited significant regulation of Al-responsive proteins associated with antioxidants, signal transduction, calcium homeostasis, and regulation of glycolysis in L-4602 as compared to BM-4. Functional annotation suggested that transporter proteins (transmembrane protein, adenosine triphosphate-binding cassette transport-related protein and multi drug resistance protein), antioxidants associated proteins (nicotinamide adenine dinucleotide dependent oxidoreductase, oxidoreductase molybdopterin binding protein & peroxidases), kinases (calmodulin-domain kinase & protein kinase), and carbohydrate metabolism associated proteins (dihydrolipoamide acetyltransferase) were found to be abundant in tolerant genotype providing protection against Al toxicity. Overall, the root proteome uncovered in this study at seedling stage, along with the physiological parameters measured, allow a greater understanding of Al tolerance mechanism in lentil, thereby assisting in future crop improvement programmes.

Distinguishing Molecular Properties of OAT, OATP, and MRP Drug Substrates by Machine Learning.

The movement of organic anionic drugs across cell membranes is partly governed by interactions with SLC and ABC transporters in the intestine, liver, kidney, blood-brain barrier, placenta, breast, and other tissues. Major transporters involved include organic anion transporters (OATs, SLC22 family), organic anion transporting polypeptides (OATPs, SLCO family), and multidrug resistance proteins (MRPs, ABCC family). However, the sets of molecular properties of drugs that are necessary for interactions with OATs (OAT1, OAT3) vs. OATPs (OATP1B1, OATP1B3) vs. MRPs (MRP2, MRP4) are not well-understood. Defining these molecular properties is necessary for a better understanding of drug and metabolite handling across the gut-liver-kidney axis, gut-brain axis, and other multi-organ axes. It is also useful for tissue targeting of small molecule drugs and predicting drug-drug interactions and drug-metabolite interactions. Here, we curated a database of drugs shown to interact with these transporters in vitro and used chemoinformatic approaches to describe their molecular properties. We then sought to define sets of molecular properties that distinguish drugs interacting with OATs, OATPs, and MRPs in binary classifications using machine learning and artificial intelligence approaches. We identified sets of key molecular properties (e.g., rotatable bond count, lipophilicity, number of ringed structures) for classifying OATs vs. MRPs and OATs vs. OATPs. However, sets of molecular properties differentiating OATP vs. MRP substrates were less evident, as drugs interacting with MRP2 and MRP4 do not form a tight group owing to differing hydrophobicity and molecular complexity for interactions with the two transporters. If the results also hold for endogenous metabolites, they may deepen our knowledge of organ crosstalk, as described in the Remote Sensing and Signaling Theory. The results also provide a molecular basis for understanding how small organic molecules differentially interact with OATs, OATPs, and MRPs.

Methylation of PLK-1 Potentially Drives Bendamustine Resistance in Leukemia Cells.

Drug resistance remains a significant impediment in leukemia treatment. While Bendamustine hydrochloride (BH) stands out as a promising therapeutic agent for non-Hodgkin's lymphoma and mantle cell lymphoma, the mechanisms of resistance to BH are not yet fully understood. Our study focuses on elucidating the mechanisms behind bendamustine resistance in leukemia cells, with a specific emphasis on epigenetics. Bendamustine-resistant cells were cultivated from human B cell lymphoblastic leukemia cell lines through systematic and sustained exposure to bendamustine, using the limiting dilution method. Gene expression was assessed via real-time polymerase chain reaction, while the expression of the multidrug resistance protein 1 (MDR1) was evaluated using flow cytometry. Bendamustine-resistant leukemia cells exhibited a decreased RNA expression level for Polo-like kinase-1 (PLK-1). Notably, after treatment with the demethylating agent 5-aza-2'-deoxycytidine, PLK-1 gene expression surged significantly, enhancing bendamustine's cytotoxicity in the resistant leukemia cells. However, MDR1 expression, as determined by flow cytometry, remained consistent between parental and bendamustine-resistant leukemia cells. Our findings indicate that the methylation of the PLK-1 gene plays a pivotal role in modulating PLK-1 expression and is central to the development of bendamustine resistance in leukemia cells.

Novel small multidrug resistance protein Tmt endows the Escherichia coli with triphenylmethane dyes bioremediation capability.

Dye contamination in printing and dyeing wastewater has long been a major concern due to its serious impact on both the environment and human health. In the quest for bioremediation of these hazardous dyes, biological resources such as biodegradation bacteria and enzymes have been investigated in severely polluted environments. In this context, the triphenylmethane transporter gene (tmt) was identified in six distinct clones from a metagenomic library of the printing and dyeing wastewater treatment system. Escherichia coli expressing tmt revealed 98.1% decolorization efficiency of triphenylmethane dye malachite green within 24h under shaking culture condition. The tolerance to malachite green was improved over eightfold in the Tmt strain compared of the none-Tmt expressed strain. Similarly, the tolerance of Tmt strain to other triphenylmethane dyes like crystal violet and brilliant green, was improved by at least fourfold. Site-directed mutations, including A75G, A75S and V100G, were found to reinforce the tolerance of malachite green, and double mutations of these even further improve the tolerance. Therefore, the tmt has been demonstrated to be a specific efflux pump for triphenylmethane dyes, particularly the malachite green. By actively pumping out toxic triphenylmethane dyes, it significantly extends the cells tolerance in a triphenylmethane dye-rich environment, which may provide a promising strategy for bioremediation of triphenylmethane dye pollutants in the environments.

Human ABC and SLC Transporters: The Culprit Responsible for Unspecific PSMA-617 Uptake?

[177Lu]Lu-PSMA-617 has recently been successfully approved by the FDA, the MHRA, Health Canada and the EMA as Pluvicto®. However, salivary gland (SG) and kidney toxicities account for its main dose-limiting side-effects, while its corresponding uptake and retention mechanisms still remain elusive. Recently, the presence of different ATP-binding cassette (ABC) transporters, such as human breast cancer resistance proteins (BCRP), multidrug resistance proteins (MDR1), multidrug-resistance-related proteins (MRP1, MRP4) and solute cassette (SLC) transporters, such as multidrug and toxin extrusion proteins (MATE1, MATE2-K), organic anion transporters (OAT1, OAT2v1, OAT3, OAT4) and peptide transporters (PEPT2), has been verified at different abundances in human SGs and kidneys. Therefore, our aim was to assess whether [177Lu]Lu-PSMA-617 and [225Ac]Ac-PSMA-617 are substrates of these ABC and SLC transporters. For in vitro studies, the novel isotopologue ([α,β-3H]Nal)Lu-PSMA-617 was used in cell lines or vesicles expressing the aforementioned human ABC and SLC transporters for inhibition and uptake studies, respectively. The corresponding probe substrates and reference inhibitors were used as controls. Our results indicate that [177Lu]Lu-PSMA-617 and [225Ac]Ac-PSMA-617 are neither inhibitors nor substrates of the examined transporters. Therefore, our results show that human ABC and SLC transporters play no central role in the uptake and retention of [177Lu]Lu-PSMA-617 and [225Ac]Ac-PSMA-617 in the SGs and kidneys nor in the observed toxicities.

Genome-wide analysis of hepatic DNA methylation reveals impact of epigenetic aging on xenobiotic metabolism and transport genes in an aged mouse model

Hepatic xenobiotic metabolism and transport decline with age, while intact xenobiotic metabolism is associated with longevity. However, few studies have examined the genome-wide impact of epigenetic aging on these processes. We used reduced representation bisulfite sequencing (RRBS) to map DNA methylation changes in liver DNA from mice ages 4 and 24 months. We identified several thousand age-associated differentially methylated sites (a-DMS), many of which overlapped genes encoding Phase I and Phase II drug metabolizing enzymes, in addition to ABC and SLC classes of transporters. Notable genes harboring a-DMS were Cyp1a2, Cyp2d9, and Abcc2 that encode orthologs of the human drug metabolizing enzymes CYP1A2 and CYP2D6, and the multidrug resistance protein 2 (MRP2) transporter. Cyp2d9 hypermethylation with age was significantly associated with reduced gene expression, while Abcc2 expression was unchanged with age. Cyp1a2 lost methylation with age while, counterintuitively, its expression also reduced with age. We hypothesized that age-related dysregulation of the hepatic transcriptional machinery caused down-regulation of genes despite age-related hypomethylation. Bioinformatic analysis of hypomethylated a-DMS in our sample found them to be highly enriched for hepatic nuclear factor 4 alpha (HNF4α) binding sites. HNF4α promotes Cyp1a2 expression and is downregulated with age, which could explain the reduction in Cyp1a2 expression. Overall, our study supports the broad impact of epigenetic aging on xenobiotic metabolism and transport. Future work should evaluate the interplay between hepatic nuclear receptor function and epigenetic aging. These results may have implications for studies of longevity and healthy aging.

Development of an aptamer capable of multidrug resistance reversal for tumor combination chemotherapy

Multidrug resistance (MDR) is a major factor in the failure of many forms of tumor chemotherapy. Development of a specific ligand for MDR-reversal would enhance the intracellular accumulation of therapeutic agents and effectively improve the tumor treatments. Here, an aptamer was screened against a doxorubicin (DOX)-resistant human hepatocellular carcinoma cell line (HepG2/DOX) via cell-based systematic evolution of ligands by exponential enrichment. A 50 nt truncated sequence termed d3 was obtained with high affinity and specificity for HepG2/DOX cells. Multidrug resistance protein 1 (MDR1) is determined to be a possible recognition target of the selected aptamer. Aptamer d3 binding was revealed to block the MDR of the tumor cells and increase the accumulation of intracellular anticancer drugs, including DOX, vincristine, and paclitaxel, which led to a boost to the cell killing of the anticancer drugs and lowering their survival of the tumor cells. The aptamer d3-mediated MDR-reversal for effective chemotherapy was further verified in an in vivo animal model, and combination of aptamer d3 with DOX significantly improved the suppression of tumor growth by treating a xenograft HepG2/DOX tumor in vivo. This work demonstrates the feasibility of a therapeutic DNA aptamer as a tumor MDR-reversal agent, and combination of the selected aptamer with chemotherapeutic drugs shows great potential for liver cancer treatments.

Model of P-Glycoprotein Ligand Binding and Validation with Efflux Substrate Matched Pairs.

The blood-brain barrier (BBB) poses a significant obstacle in developing therapeutics for neurodegenerative diseases and central nervous system (CNS) disorders. P-glycoprotein (P-gp), a multidrug resistance protein, is a critical gatekeeper in the BBB and plays a role in cancer chemoresistance. This paper uses cryo-EM P-gp structures as starting points with an induced fit docking (IFD) model to evaluate 19 pairs of compounds with known P-gp efflux data. The study reveals significant differences in binding energy and sheds light on structural modifications' impact on efflux properties. In the cases examined, fluorine incorporation influences the efflux by altering the molecular conformation rather than proximal heteroatom basicity. Although there are limitations in addressing covalent interactions or when binding extends into the more flexible vestibule region of the protein, the results provide valuable insights and potential strategies to overcome P-gp efflux, contributing to the advancement of drug development for both CNS disorders and cancer therapies.