Mammalian ABC transporters in health and disease

The association of ABC proteins with multidrug resistance in cancer

Multidrug resistance (MDR) poses one of the primary challenges for cancer treatment, especially in cases of metastatic disease. Various mechanisms contribute to MDR, including the overexpression of ATP-binding cassette (ABC) proteins. In this context, we reviewed the literature to establish a correlation between the overexpression of ABC proteins and MDR in cancer, considering both in vitro and clinical studies. Initially, we presented an overview of the seven subfamilies of ABC proteins, along with the subcellular localization of each protein. Subsequently, we identified a panel of 20 ABC proteins (ABCA1-3, ABCA7, ABCB1-2, ABCB4-6, ABCC1-5, ABCC10-11, ABCE1, ABCF2, ABCG1, and ABCG2) associated with MDR. We also emphasize the significance of drug sequestration by certain ABC proteins into intracellular compartments. Among the anticancer drugs linked to MDR, 29 were definitively identified as substrates for at least one of the three most crucial ABC transporters: ABCB1, ABCC1, and ABCG2. We further discussed that the most commonly used drugs in standard regimens for mainly breast cancer, lung cancer, and acute lymphoblastic leukemia could be subject to MDR mediated by ABC transporters. Collectively, these insights will aid in conducting new studies aimed at a deeper understanding of the clinical MDR mediated by ABC proteins and in designing more effective pharmacological treatments to enhance the objective response rate in cancer patients.

Structural insights into binding-site access and ligand recognition by human ABCB1

ABCB1 is a broad-spectrum efflux pump central to cellular drug handling and multidrug resistance in humans. However, how it is able to recognize and transport a wide range of diverse substrates remains poorly understood. Here we present cryo-EM structures of lipid-embedded human ABCB1 in conformationally distinct apo-, substrate-bound, inhibitor-bound, and nucleotide-trapped states at 3.4-3.9 Å resolution, in the absence of stabilizing antibodies or mutations. The substrate-binding site is located within one half of the molecule and, in the apo state, is obstructed by the transmembrane helix (TM) 4. Substrate and inhibitor binding are distinguished by major TM rearrangements and their ligand binding chemistry, with TM4 playing a central role in all conformational transitions. Furthermore, our data identify secondary structure-breaking residues that impart localized TM flexibility and asymmetry between the two transmembrane domains. The resulting structural changes and lipid interactions that are induced by substrate and inhibitor binding can predict substrate-binding profiles and may direct ABCB1 inhibitor design.

Parallel gene expansions drive rapid dietary adaptation in herbivorous woodrats

How mammalian herbivores evolve to feed on chemically defended plants remains poorly understood. In this study, we investigated the adaptation of two species of woodrats (Neotoma lepida and N. bryanti) to creosote bush (Larrea tridentata), a toxic shrub that expanded across the southwestern United States after the Last Glacial Maximum. We found that creosote-adapted woodrats have elevated gene dosage across multiple biotransformation enzyme families. These duplication events occurred independently across species and substantially increase expression of biotransformation genes, especially within the glucuronidation pathway. We propose that increased gene dosage resulting from duplication is an important mechanism by which animals initially adapt to novel environmental pressures.

Overview of the role of purinergic signaling and insights into its role in cancer therapy

Innovation of cancer therapy has received a dramatic acceleration over the last fifteen years thanks to the introduction of the novel immune checkpoint inhibitors (ICI). On the other hand, the conspicuous scientific knowledge accumulated in purinergic signaling since the early seventies is finally being transferred to the clinic. Several Phase I/II clinical trials are currently underway to investigate the effect of drugs interfering with purinergic signaling as stand-alone or combination therapy in cancer. This is supporting the novel concept of "purinergic immune checkpoint" (PIC) in cancer therapy. In the present review we will address a) the basic pharmacology and cell biology of the purinergic system; b) principles of its pathophysiology in human diseases; c) implications for cell death, cell proliferation and cancer; d) novel molecular tools to investigate nucleotide homeostasis in the extracellular environment; e) recent developments in the pharmacology of P1, P2 receptors and related ecto-enzymes; f) P1 and P2 ligands as novel diagnostic tools; g) current issues in PIC-based anti-cancer therapy. This review will provide an appraisal of the current status of purinergic signaling in cancer and will help identify future avenues of development.

Marein, a novel natural product for restoring chemo-sensitivity to cancer cells through competitive inhibition of ABCG2 function

The pivotal roles of ATP-binding cassette (ABC) transporters in drug resistance have been widely appreciated. Here we report that marein, a natural product from Coreopsis tinctoria Nutt, is a potent chemo-sensitizer in drug resistant cancer cells overexpressing ABCG2 transporter. We demonstrate that marein can competitively inhibit efflux activity of ABCG2 protein and increase the intracellular accumulation of the chemotherapeutic drugs that belong to substrate of this transporter. We further show that marein can bind to the conserved amino acid residue F439 of ABCG2, a critical site for drug-substrate interaction. Moreover, marein can significantly sensitize the ABCG2-expressing tumor cells to chemotherapeutic drugs such as topotecan, mitoxantrone, and olaparib. This study reveals a novel role and mechanism of marein in modulating drug resistance, and may have important implications in treatment of cancers that are resistant to chemotherapeutic drugs that belong to the substrates of ABCG2 transporters.

Plant-Based Products Originating from Serbia That Affect P-glycoprotein Activity

Our review paper evaluates the impact of plant-based products, primarily derived from plants from Serbia, on P-glycoprotein (P-gp) activity and their potential in modulating drug resistance in cancer therapy. We focus on the role and regulation of P-gp in cellular physiology and its significance in addressing multidrug resistance in cancer therapy. Additionally, we discuss the modulation of P-gp activity by 55 natural product drugs, including derivatives for some of them, based on our team's research findings since 2011. Specifically, we prospect into sesquiterpenoids from the genera Artemisia, Curcuma, Ferula, Inula, Petasites, and Celastrus; diterpenoids from the genera Salvia and Euphorbia; chalcones from the genera Piper, Glycyrrhiza, Cullen, Artemisia, and Humulus; riccardins from the genera Lunularia, Monoclea, Dumortiera, Plagiochila, and Primula; and diarylheptanoids from the genera Alnus and Curcuma. Through comprehensive analysis, we aim to highlight the potential of natural products mainly identified in plants from Serbia in influencing P-gp activity and overcoming drug resistance in cancer therapy, while also providing insights into future perspectives in this field.

P-glycoprotein inhibitors as an adjunct therapy for TB

The primary challenge in TB treatment is the emergence of multidrug-resistant TB (MDR-TB). One of the major factors responsible for MDR is the upregulation of efflux pumps. Permeation-glycoprotein (P-gp), an efflux pump, hinders the bioavailability of the administered drugs inside the infected cells. Simultaneously, angiogenesis, the formation of new blood vessels, contributes to drug delivery complexities. TB infection triggers a cascade of events that upregulates the expression of angiogenic factors and P-gp. The combined action of P-gp and angiogenesis foster the emergence of MDR-TB. Understanding these mechanisms is pivotal for developing targeted interventions to overcome MDR in TB. P-gp inhibitors, such as verapamil, and anti-angiogenic drugs, including bevacizumab, have shown improvement in TB drug delivery to granuloma. In this review, we discuss the potential of P-gp inhibitors as an adjunct therapy to shorten TB treatment.

Epigenetic modification of ferroptosis by non-coding RNAs in cancer drug resistance

The development of drug resistance remains a major challenge in cancer treatment. Ferroptosis, a unique type of regulated cell death, plays a pivotal role in inhibiting tumour growth, presenting new opportunities in treating chemotherapeutic resistance. Accumulating studies indicate that epigenetic modifications by non-coding RNAs (ncRNA) can determine cancer cell vulnerability to ferroptosis. In this review, we first summarize the role of chemotherapeutic resistance in cancer growth/development. Then, we summarize the core molecular mechanisms of ferroptosis, its upstream epigenetic regulation, and its downstream effects on chemotherapeutic resistance. Finally, we review recent advances in understanding how ncRNAs regulate ferroptosis and from such modulate chemotherapeutic resistance. This review aims to enhance general understanding of the ncRNA-mediated epigenetic regulatory mechanisms which modulate ferroptosis, highlighting the ncRNA-ferroptosis axis as a key druggable target in overcoming chemotherapeutic resistance.

Structural insight into binding site access and ligand recognition by human ABCB1

ABCB1 is a broad-spectrum efflux pump central to cellular drug handling and multidrug resistance in humans. However, its mechanisms of poly-specific substrate recognition and transport remain poorly resolved. Here we present cryo-EM structures of lipid embedded human ABCB1 in its apo, substrate-bound, inhibitor-bound, and nucleotide-trapped states at 3.4-3.9 Å resolution without using stabilizing antibodies or mutations and each revealing a distinct conformation. The substrate binding site is located within one half of the molecule and, in the apo state, is obstructed by transmembrane helix (TM) 4. Substrate and inhibitor binding are distinguished by major differences in TM arrangement and ligand binding chemistry, with TM4 playing a central role in all conformational transitions. Our data offer fundamental new insights into the role structural asymmetry, secondary structure breaks, and lipid interactions play in ABCB1 function and have far-reaching implications for ABCB1 inhibitor design and predicting its substrate binding profiles.

High-throughput BCRP inhibitors screening system based on styrene maleic acid polymer membrane protein stabilization strategy and surface plasmon resonance biosensor

Multidrug resistance (MDR) is a dominant challenge in cancer chemotherapy failure. The over-expression of breast cancer resistance protein (BCRP) in tumorous cells, along with its extensive substrate profile, is a leading cause of tumor MDR. Herein, on the basis of styrene maleic acid (SMA) polymer membrane protein stabilization strategy and surface plasmon resonance (SPR) biosensor, a novel high-throughput screening (HTS) system for BCRP inhibitors has been established. Firstly, LLC-PK1 and LLC-PK1/BCRP cell membranes were co-incubated with SMA polymers to construct SMA lipid particles (SMALPs). PK1-SMALPs were thus immobilized in channel 1 of the L1 chip as the reference channel, and BCRP-SMALPs were immobilized in channel 2 as the detection channel to establish the BCRP-SMALPs-SPR screening system. The methodological investigation demonstrated that the screening system was highly specific and stable. Three active compounds were screened out from 26 natural products and their affinity constants with BCRP were determined. The KD of xanthotoxin, bergapten, and naringenin were 5.14 μM, 4.57 μM, and 3.72 μM, respectively. The in vitro cell verification experiments demonstrated that xanthotoxin, bergapten, and naringenin all significantly increased the sensitivity of LLC-PK1/BCRP cells to mitoxantrone with possessing reversal BCRP-mediated MDR activity. Collectively, the developed BCRP-SMALPs-SPR screening system in this study has the advantages of rapidity, efficiency, and specificity, providing a novel strategy for the in-depth screening of BCRP inhibitors with less side effects and higher efficacy.

ISTransbase: an online database for inhibitor and substrate of drug transporters

Drug transporters, integral membrane proteins found throughout the human body, play critical roles in physiological and biochemical processes through interactions with ligands, such as substrates and inhibitors. The extensive and disparate data on drug transporters complicate understanding their complex relationships with ligands. To address this challenge, it is essential to gather and summarize information on drug transporters, inhibitors and substrates, and simultaneously develop a comprehensive and user-friendly database. Current online resources often provide fragmented information and have limited coverage of drug transporter substrates and inhibitors, highlighting the need for a specialized, comprehensive and openly accessible database. ISTransbase addresses this gap by amassing a substantial amount of data from literature, government documents and open databases. It includes 16 528 inhibitors and 4465 substrates of 163 drug transporters from 18 different species, resulting in a total of 93 841 inhibitor records and 51 053 substrate records. ISTransbase provides detailed insights into drug transporters and their inhibitors/substrates, encompassing transporter and molecule structure, transporter function and distribution, as well as experimental methods and results from transport or inhibition experiments. Furthermore, ISTransbase offers three search strategies that allow users to retrieve drugs and transporters based on multiple selectable constraints, as well as perform checks for drug-drug interactions. Users can also browse and download data. In summary, ISTransbase (https://istransbase.scbdd.com/) serves as a valuable resource for accurately and efficiently accessing information on drug transporter inhibitors and substrates, aiding researchers in exploring drug transporter mechanisms and assisting clinicians in mitigating adverse drug reactions Database URL: https://istransbase.scbdd.com/.

BI-2865, a pan-KRAS inhibitor, reverses the P-glycoprotein induced multidrug resistance in vitro and in vivo

BACKGROUND

Multidrug resistance (MDR) limits successful cancer chemotherapy. P-glycoprotein (P-gp), BCRP and MRP1 are the key triggers of MDR. Unfortunately, no MDR modulator was approved by FDA to date. Here, we will investigate the effect of BI-2865, a pan-KRAS inhibitor, on reversing MDR induced by P-gp, BCRP and MRP1 in vitro and in vivo, and its reversal mechanisms will be explored.

METHODS

The cytotoxicity of BI-2865 and its MDR removal effect in vitro were tested by MTT assays, and the corresponding reversal function in vivo was assessed through the P-gp mediated KBv200 xenografts in mice. BI-2865 induced alterations of drug discharge and reservation in cells were estimated by experiments of Flow cytometry with fluorescent doxorubicin, and the chemo-drug accumulation in xenografts' tumor were analyzed through LC-MS. Mechanisms of BI-2865 inhibiting P-gp substrate's efflux were analyzed through the vanadate-sensitive ATPase assay, [125I]-IAAP-photolabeling assay and computer molecular docking. The effects of BI-2865 on P-gp expression and KRAS-downstream signaling were detected via Western blotting, Flow cytometry and/or qRT-PCR. Subcellular localization of P-gp was visualized by Immunofluorescence.

RESULTS

We found BI-2865 notably fortified response of P-gp-driven MDR cancer cells to the administration of chemo-drugs including paclitaxel, vincristine and doxorubicin, while such an effect was not observed in their parental sensitive cells and BCRP or MRP1-driven MDR cells. Importantly, the mice vivo combination study has verified that BI-2865 effectively improved the anti-tumor action of paclitaxel without toxic injury. In mechanism, BI-2865 prompted doxorubicin accumulating in carcinoma cells by directly blocking the efflux function of P-gp, which more specifically, was achieved by BI-2865 competitively binding to the drug-binding sites of P-gp. What's more, at the effective MDR reversal concentrations, BI-2865 neither varied the expression and location of P-gp nor reduced its downstream AKT or ERK1/2 signaling activity.

CONCLUSIONS

This study uncovered a new application of BI-2865 as a MDR modulator, which might be used to effectively, safely and specifically improve chemotherapeutic efficacy in the clinical P-gp mediated MDR refractory cancers.

Maternal exposure to polystyrene nanoplastics causes defective retinal development and function in progeny mice by disturbing metabolic profiles

Microplastics (MPs) and nanoplastics (NPs) are widely spreading in our living environment, accumulating in the human body and potentially threating human health. The retina, which is a terminally differentiated extension of the central nervous system, is essential for the visual system. However, the effects and molecular mechanisms of MPs/NPs on retina development and function are still unclear. Here, we investigated the effects and modes of action of polystyrene NPs (PS-NPs) on the retina using mice as a mammalian model species. Maternal PS-NP exposure (100 nm) at an environmentally realistic concentration of 10 mg L-1 (or 2.07 *1010 particles mL-1) via drinking water from the first day of pregnancy till the end of lactation (21 days after birth) caused defective neural retinal development in the neonatal mice, by depositing in the retinal tissue and reducing the number of retinal ganglion cells and bipolar cells. Exposure to PS-NPs retarded retinal vascular development, while abnormal electroretinogram (ERG) responses and an increased level of oxidative stress were also observed in the retina of the progeny mice after maternal PS-NP exposure. Metabolomics showed significant dysregulation of amino acids that are pivotal to neuron retinal function, such as glutamate, aspartate, alanine, glycine, serine, threonine, taurine, and serotonin. Transcriptomics identified significantly dysregulated genes, which were enriched in processes of angiogenesis, visual system development and lens development. Regulatory analysis showed that Fos gene mediated pathways could be a potential key target for PS-NP exposure in retinal development and function. Our study revealed that maternal exposure to PS-NPs generated detrimental effects on retinal development and function in progeny mice, offering new insights into the visual toxicity of PS-NPs.

Overcoming drug resistance with specific nano scales to targeted therapy: Focused on metastatic cancers

Metastatic cancer, which accounts for the majority of cancer fatalities, is a difficult illness to treat. Currently used cancer treatments include radiation therapy, chemotherapy, surgery, and targeted treatment (immune, gene, and hormonal). The disadvantages of these treatments include a high risk of tumor recurrence and surgical complications that may result in permanent deformities. On the other hand, most chemotherapy drugs are small molecules, which usually have unfavorable side effects, low absorption, poor selectivity, and multi-drug resistance. Anticancer drugs can be delivered precisely to the cancer spot by encapsulating them to reduce side effects. Stimuli-responsive nanocarriers can be used for drug release at cancer sites and provide target-specific delivery. As previously stated, metastasis is the primary cause of cancer-related mortality. We have evaluated the usage of nano-medications in the treatment of some metastatic tumors.

Repositioning VU-0365114 as a novel microtubule-destabilizing agent for treating cancer and overcoming drug resistance

Microtubule-targeting agents represent one of the most successful classes of anticancer agents. However, the development of drug resistance and the appearance of adverse effects hamper their clinical implementation. Novel microtubule-targeting agents without such limitations are urgently needed. By employing a gene expression-based drug repositioning strategy, this study identifies VU-0365114, originally synthesized as a positive allosteric modulator of human muscarinic acetylcholine receptor M5 (M5 mAChR), as a novel type of tubulin inhibitor by destabilizing microtubules. VU-0365114 exhibits a broad-spectrum in vitro anticancer activity, especially in colorectal cancer cells. A tumor xenograft study in nude mice shows that VU-0365114 slowed the in vivo colorectal tumor growth. The anticancer activity of VU-0365114 is not related to its original target, M5 mAChR. In addition, VU-0365114 does not serve as a substrate of multidrug resistance (MDR) proteins, and thus, it can overcome MDR. Furthermore, a kinome analysis shows that VU-0365114 did not exhibit other significant off-target effects. Taken together, our study suggests that VU-0365114 primarily targets microtubules, offering potential for repurposing in cancer treatment, although more studies are needed before further drug development.

In-depth metaproteomics analysis of tongue coating for gastric cancer: a multicenter diagnostic research study

BACKGROUND

Our previous study revealed marked differences in tongue images between individuals with gastric cancer and those without gastric cancer. However, the biological mechanism of tongue images as a disease indicator remains unclear. Tongue coating, a major factor in tongue appearance, is the visible layer on the tongue dorsum that provides a vital environment for oral microorganisms. While oral microorganisms are associated with gastric and intestinal diseases, the comprehensive function profiles of oral microbiota remain incompletely understood. Metaproteomics has unique strength in revealing functional profiles of microbiota that aid in comprehending the mechanism behind specific tongue coating formation and its role as an indicator of gastric cancer.

METHODS

We employed pressure cycling technology and data-independent acquisition (PCT-DIA) mass spectrometry to extract and identify tongue-coating proteins from 180 gastric cancer patients and 185 non-gastric cancer patients across 5 independent research centers in China. Additionally, we investigated the temporal stability of tongue-coating proteins based on a time-series cohort. Finally, we constructed a machine learning model using the stochastic gradient boosting algorithm to identify individuals at high risk of gastric cancer based on tongue-coating microbial proteins.

RESULTS

We measured 1432 human-derived proteins and 13,780 microbial proteins from 345 tongue-coating samples. The abundance of tongue-coating proteins exhibited high temporal stability within an individual. Notably, we observed the downregulation of human keratins KRT2 and KRT9 on the tongue surface, as well as the downregulation of ABC transporter COG1136 in microbiota, in gastric cancer patients. This suggests a decline in the defense capacity of the lingual mucosa. Finally, we established a machine learning model that employs 50 microbial proteins of tongue coating to identify individuals at a high risk of gastric cancer, achieving an area under the curve (AUC) of 0.91 in the independent validation cohort.

CONCLUSIONS

We characterized the alterations in tongue-coating proteins among gastric cancer patients and constructed a gastric cancer screening model based on microbial-derived tongue-coating proteins. Tongue-coating proteins are shown as a promising indicator for identifying high-risk groups for gastric cancer. Video Abstract.

Probing the allosteric NBD-TMD crosstalk in the ABC transporter MsbA by solid-state NMR

The ABC transporter MsbA plays a critical role in Gram-negative bacteria in the regulation of the outer membrane by translocating core-LPS across the inner membrane. Additionally, a broad substrate specificity for lipophilic drugs has been shown. The allosteric interplay between substrate binding in the transmembrane domains and ATP binding and turnover in the nucleotide-binding domains must be mediated via the NBD/TMD interface. Previous studies suggested the involvement of two intracellular loops called coupling helix 1 and 2 (CH1, CH2). Here, we demonstrate by solid-state NMR spectroscopy that substantial chemical shift changes within both CH1 and CH2 occur upon substrate binding, in the ATP hydrolysis transition state, and upon inhibitor binding. CH2 is domain-swapped within the MsbA structure, and it is noteworthy that substrate binding induces a larger response in CH2 compared to CH1. Our data demonstrate that CH1 and CH2 undergo structural changes as part of the TMD-NBD cross-talk.

Multimodal Phenomap of Stargardt Disease Integrating Structural, Psychophysical, and Electrophysiologic Measures of Retinal Degeneration

Objective

To cluster the diverse phenotypic features of Stargardt disease (STGD) using unsupervised clustering of multimodal retinal structure and function data.

Design

Retrospective cross-sectional study.

Subjects

Eyes of subjects with STGD and fundus autofluorescence (FAF), OCT, electroretinography (ERG), and microperimetry (MP) data available within 1 year of the baseline evaluation.

Methods

A total of 46 variables from FAF, OCT, ERG, and MP results were recorded for subjects with STGD as defined per published criteria. Factor analysis of mixed data identified the most informative variables. Unsupervised hierarchical clustering and silhouette analysis identified the optimal number of clusters to classify multimodal phenotypes.

Main Outcome Measures

Phenotypic clusters of STGD subjects and the corresponding cluster features.

Results

We included 52 subjects and 102 eyes with a mean visual acuity (VA) at the time of multimodal testing of 0.69 ± 0.494 logarithm of minimum angle of resolution (20/63 Snellen). We identified 4 clusters of eyes. Compared to the other clusters, cluster 1 (n = 16) included younger subjects, VA greater than that of clusters 2 and 3, normal or moderately low total macular volume (TMV), greater preservation of scotopic and photopic ERG responses and fixation stability, less atrophy, and fewer flecks. Cluster 2 (n = 49) differed from cluster 1 mainly with less atrophy and relatively stable fixation. Cluster 3 (n = 10) included older subjects than clusters 1 and 2 and showed the lowest VA, TMV, ERG responses, and fixation stability, with extensive atrophy. Cluster 4 (n = 27) showed better VA, TMV similar to clusters 1 and 2, moderate ERG activity, stable fixation, and moderate-high atrophy and flecks.

Conclusions

Reflecting the phenotypic complexity of STGD, an unsupervised clustering approach incorporating phenotypic measures can be used to categorize STGD eyes into distinct clusters. The clusters exhibit differences in structural and functional measures including quantity of flecks, extent of retinal atrophy, visual fixation accuracy, and ERG responses, among other features. If novel pharmacologic, gene, or cell therapy modalities become available in the future, the multimodal phenomap approach may be useful to individualize treatment decisions, and its utility in aiding prognostication requires further evaluation.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

Association of ABCG5 and ABCG8 Transporters with Sitosterolemia

Sitosterolemia is a rare genetic lipid disorder, mainly characterized by the accumulation of dietary xenosterols in plasma and tissues. It is caused by inactivating mutations in either ABCG5 or ABCG8 subunits, a subfamily-G ATP-binding cassette (ABCG) transporters. ABCG5/G8 encodes a pair of ABC half transporters that form a heterodimer (G5G8). This heterodimeric ATP-binding cassette (ABC) sterol transporter, ABCG5/G8, is responsible for the hepatobiliary and transintestinal secretion of cholesterol and dietary plant sterols to the surface of hepatocytes and enterocytes, promoting the secretion of cholesterol and xenosterols into the bile and the intestinal lumen. In this way, ABCG5/G8 function in the reverse cholesterol transport pathway and mediate the efflux of cholesterol and xenosterols to high-density lipoprotein and bile salt micelles, respectively. Here, we review the biological characteristics and function of ABCG5/G8, and how the mutations of ABCG5/G8 can cause sitosterolemia, a loss-of-function disorder characterized by plant sterol accumulation and premature atherosclerosis, among other features.

Immunosuppression for older liver transplant recipients

Older liver transplant recipients have a lower risk of acute rejection than younger patients (9% for patients aged ≥65 years versus 23% for those aged 18-34 years) and are more vulnerable to immunosuppression-related complications. The number of liver transplant recipients ≥65 years has risen to 22% in Europe and the US, but limited information is available on the optimal immunosuppressive regimen for these patients. In this review, we discuss the appropriate management of immunosuppressive agents in older adults to minimize adverse events while avoiding acute rejection. The way the body processes drugs greatly depends on age. In the case of calcineurin inhibitor drugs, aging reduces hepatic metabolism, leading to changes in their pharmacokinetics. Corticosteroids also show decreased clearance as the patient ages. In severe cases of hypoalbuminemia, dose adjustment of mycophenolate acid derivatives may be necessary. However, the pharmacokinetic profiles of the mammalian target of rapamycin inhibitors, basiliximab, and rabbit anti-thymocyte globulin remain unaffected by age. Furthermore, age-related frailty may impact drug metabolism and require tailored interventions and closer follow-up. Although there is limited research, elderly liver transplant recipients require less immunosuppression with double or triple-agent regimens, lower exposure to calcineurin inhibitors, and a shorter course of corticosteroids. The usage of mammalian target of rapamycin inhibitors in older transplant populations has not been specifically investigated, and thus their usage should align with indications for younger patient groups.

Green Approach Toward Triazole Forming Reactions for Developing Anticancer Drugs

Compounds containing triazole have many significant applications in the dye and ink industry, corrosion inhibitors, polymers, and pharmaceutical industries. These compounds possess many antimicrobial, antioxidant, anticancer, antiviral, anti-HIV, antitubercular, and anticancer activities. Several synthetic methods have been reported for reducing time, minimizing synthetic steps, and utilizing less hazardous and toxic solvents and reagents to improve the yield of triazoles and their analogues synthesis. Among the improvement in methods, green approaches towards triazole forming biologically active compounds, especially anticancer compounds, would be very important for pharmaceutical industries as well as global research community. In this article, we have reviewed the last five years of green chemistry approaches on click reaction between alkyl azide and alkynes to install 1,2,3-triazole moiety in natural products and synthetic drug-like molecules, such as in colchicine, flavanone cardanol, bisphosphonates, thiabendazoles, piperazine, prostanoid, flavonoid, quinoxalines, C-azanucleoside, dibenzylamine, and aryl-azotriazole. The cytotoxicity of triazole hybrid analogues was evaluated against a panel of cancer cell lines, including multidrug-resistant cell lines.

The transport activity of the multidrug ABC transporter BmrA does not require a wide separation of the nucleotide-binding domains

ATP-binding cassette (ABC) transporters are ubiquitous membrane proteins responsible for the translocation of a wide diversity of substrates across biological membranes. Some of them confer multidrug or antimicrobial resistance to cancer cells and pathogenic microorganisms, respectively. Despite a wealth of structural data gained in the last two decades, the molecular mechanism of these multidrug efflux pumps remains elusive, including the extent of separation between the two nucleotide-binding domains (NBDs) during the transport cycle. Based on recent outward-facing structures of BmrA, a homodimeric multidrug ABC transporter from Bacillus subtilis, we introduced a cysteine mutation near the C-terminal end of the NBDs to analyze the impact of disulfide-bond formation on BmrA function. Interestingly, the presence of the disulfide bond between the NBDs did not prevent the ATPase, nor did it affect the transport of Hoechst 33342 and doxorubicin. Yet, the 7-amino-actinomycin D was less efficiently transported, suggesting that a further opening of the transporter might improve its ability to translocate this larger compound. We solved by cryo-EM the apo structures of the cross-linked mutant and the WT protein. Both structures are highly similar, showing an intermediate opening between their NBDs while their C-terminal extremities remain in close proximity. Distance measurements obtained by electron paramagnetic resonance spectroscopy support the intermediate opening found in these 3D structures. Overall, our data suggest that the NBDs of BmrA function with a tweezers-like mechanism distinct from the related lipid A exporter MsbA.

Structure-based discovery of novel P-glycoprotein inhibitors targeting the nucleotide binding domains

P-glycoprotein (P-gp), a membrane transport protein overexpressed in certain drug-resistant cancer cells, has been the target of numerous drug discovery projects aimed at overcoming drug resistance in cancer. Most characterized P-gp inhibitors bind at the large hydrophobic drug binding domain (DBD), but none have yet attained regulatory approval. In this study, we explored the potential of designing inhibitors that target the nucleotide binding domains (NBDs), by computationally screening a large library of 2.6 billion synthesizable molecules, using a combination of machine learning-guided molecular docking and molecular dynamics (MD). 14 of the computationally best-scoring molecules were subsequently tested for their ability to inhibit P-gp mediated calcein-AM efflux. In total, five diverse compounds exhibited inhibitory effects in the calcein-AM assay without displaying toxicity. The activity of these compounds was confirmed by their ability to decrease the verapamil-stimulated ATPase activity of P-gp in a subsequent assay. The discovery of these five novel P-gp inhibitors demonstrates the potential of in-silico screening in drug discovery and provides a new stepping point towards future potent P-gp inhibitors.

Site-specific delivery of cisplatin and paclitaxel mediated by liposomes: A promising approach in cancer chemotherapy

The site-specific delivery of drugs, especially anti-cancer drugs has been an interesting field for researchers and the reason is low accumulation of cytotoxic drugs in cancer cells. Although combination cancer therapy has been beneficial in providing cancer drug sensitivity, targeted delivery of drugs appears to be more efficient. One of the safe, biocompatible and efficient nano-scale delivery systems in anti-cancer drug delivery is liposomes. Their particle size is small and they have other properties such as adjustable physico-chemical properties, ease of functionalization and high entrapment efficiency. Cisplatin is a chemotherapy drug with clinical approval in patients, but its accumulation in cancer cells is low due to lack of targeted delivery and repeated administration results in resistance development. Gene and drug co-administration along with cisplatin/paclitaxel have resulted in increased sensitivity in tumor cells, but there is still space for more progress in cancer therapy. The delivery of cisplatin/paclitaxel by liposomes increases accumulation of drug in tumor cells and impairs activity of efflux pumps in promoting cytotoxicity. Moreover, phototherapy along with cisplatin/paclitaxel delivery can increase potential in tumor suppression. Smart nanoparticles including pH-sensitive nanoparticles provide site-specific delivery of cisplatin/paclitaxel. The functionalization of liposomes can be performed by ligands to increase targetability towards tumor cells in mediating site-specific delivery of cisplatin/paclitaxel. Finally, liposomes can mediate co-delivery of cisplatin/paclitaxel with drugs or genes in potentiating tumor suppression. Since drug resistance has caused therapy failure in cancer patients, and cisplatin/paclitaxel are among popular chemotherapy drugs, delivery of these drugs mediates targeted suppression of cancers and prevents development of drug resistance. Because of biocompatibility and safety of liposomes, they are currently used in clinical trials for treatment of cancer patients. In future, the optimal dose of using liposomes and optimal concentration of loading cisplatin/paclitaxel on liposomal nanocarriers in clinical trials should be determined.

Elucidating the structural and functional prophecy of the Rv2326c gene, an ABC transporter of Mycobacterium tuberculosis H37Rv through computational approach

Tuberculosis is a fatal disease caused by Mycobacterium tuberculosis. M. tuberculosis becoming drug-resistant day by day, necessitating to know the mechanism behind the drug resistance and how to overcome this deadly malady. Drug resistance and reduced drug bioavailability are caused by a class of transporter proteins called the ATP-binding cassette (ABC) transporters, which pump a range of medicines out of cells at the price of ATP hydrolysis. By using computational approaches, we tried to elaborate the probable function of the Rv2326c gene of M. tuberculosis, perhaps involved in drug resistance mechanism. The presence of the signature motif of ABC transporters (LSGGELQRLALAAAL and LSGGQMRRVVLAGLL) and ATP binding motif (GXXXXGKT and GXXXXGKS) in the protein sequence signifying its importance in the ATP binding and transportation of molecules. Further, this manuscript elaborated about tertiary structure and validation, functional category, localization, phosphorylation site prediction, mutational analysis of conserved motifs. Ligand docking study shows the highest affinity with ATP than GTP justified its function as an ATP binding protein. The Rv2326c protein is present in the inner membrane and working as an ATP binding protein and might be playing a dynamic role in transportation. In this study, we found that Rv2326c protein might be working as an ABC transporter by which the drugs and other molecules are imported or exported into the bacterium. As a result, the current study provides a means to better understand its normal functioning and basic biology, which can help in the development of novel therapeutic targeting approaches for Rv2326c protein.

MDR1-EXPRESSING CD4+ T CELLS WITH TH1.17 FEATURES RESIST TO NEOADJUVANT CHEMOTHERAPY AND ARE ASSOCIATED WITH BREAST CANCER CLINICAL RESPONSE

BACKGROUND

Multidrug resistance-1 (MDR1) transporter limits the intracellular accumulation of chemotherapies (paclitaxel, anthracyclines) used in breast cancer (BC) treatment. In addition to tumor cells, MDR1 is expressed on immune cell subsets in which it confers chemoresistance. Among human T cells, MDR1 is expressed by most CD8+ T cells, and a subset of CD4+ T helper (Th) cells. Here we explored the expression, function and regulation of MDR1 on CD4+ T cells and investigated the role of this population in response to neoadjuvant chemotherapy (NAC) in BC.

METHODS

Phenotypic and functional characteristics of MDR1+ CD4 Th cells were assessed on blood from healthy donors and patients with BC by flow cytometry. These features were extended to CD4+ Th cells from untreated breast tumor by flow cytometry and RNA-sequencing (RNA-seq). We performed in vitro polarization assays to decipher MDR1 regulation on CD4 Th cells. We evaluated in vitro the impact of chemotherapy agents on MDR1+ CD4+ Th cells. We analyzed the impact of NAC treatment on MDR1+ CD4+ Th cells from blood and tumors and their association with treatment efficacy in two independent BC cohorts and in a public RNA-seq data set of BC tumor biopsies before and after NAC. Finally, we performed single cell (sc) RNAseq of blood CD4+ memory T cells from NAC-treated patients and combined them with an scRNAseq public data set.

RESULTS

MDR1+ CD4 Th cells were strongly enriched in Th1.17 polyfunctional cells but also in Th17 cells, both in blood and untreated breast tumor tissues. Mechanistically, Tumor growth factor (TGF)-β1 was required for MDR1 induction during in vitro Th17 or Th1.17 polarization. MDR1 expression conferred a selective advantage to Th1.17 and Th17 cells following paclitaxel treatment in vitro and in vivo in NAC-treated patients. scRNAseq demonstrated MDR1 association with tumor Th1.17 and Th with features of cytotoxic cells. Enrichment in MDR1+ CD4+ Th1.17 and Th17 cells, in blood and tumors positively correlated with pathological response. Absence of early modulation of Th1.17 and Th17 in NAC-resistant patients, argue for its use as a biomarker for chemotherapy regimen adjustment.

CONCLUSION

MDR1 favored the enrichment of Th1.17 and Th17 in blood and tumor after NAC that correlated to clinical response.

ATP-dependent transporters: emerging players at the crossroads of immunity and metabolism

Nearly 50 ATP-binding cassette (ABC) transporters are encoded by mammalian genomes. These transporters are characterized by conserved nucleotide-binding and hydrolysis (i.e., ATPase) domains, and power directional transport of diverse substrate classes - ions, small molecule metabolites, xenobiotics, hydrophobic drugs, and even polypeptides - into or out of cells or subcellular organelles. Although immunological functions of ABC transporters are only beginning to be unraveled, emerging literature suggests these proteins have under-appreciated roles in the development and function of T lymphocytes, including many of the key effector, memory and regulatory subsets that arise during responses to infection, inflammation or cancers. One transporter in particular, MDR1 (Multidrug resistance-1; encoded by the ABCB1 locus in humans), has taken center stage as a novel player in immune regulation. Although MDR1 remains widely viewed as a simple drug efflux pump in tumor cells, recent evidence suggests that this transporter fills key endogenous roles in enforcing metabolic fitness of activated CD4 and CD8 T cells. Here, we summarize current understanding of the physiological functions of ABC transporters in immune regulation, with a focus on the anti-oxidant functions of MDR1 that may shape both the magnitude and repertoires of antigen-specific effector and memory T cell compartments. While much remains to be learned about the functions of ABC transporters in immunobiology, it is already clear that they represent fertile new ground, both for the definition of novel immunometabolic pathways, and for the discovery of new drug targets that could be leveraged to optimize immune responses to vaccines and cancer immunotherapies.

Symbiotic hemolymph bacteria reduce hexavalent chromium to protect the host from chromium toxicity in Procambarus clarkii

Hexavalent chromium (Cr(VI)) is a cytotoxic heavy metal pollutant that adversely affects all life forms. Interestingly, the crustacean Procambarus clarkii exhibits a relatively high tolerance to heavy metals. The underlying mechanisms remain unclear. In this study, we investigated the role of symbiotic bacteria in P. clarkii in alleviating Cr(VI)-induced damage and explored their potential mechanisms of action. Through transcriptomic analysis, we observed that Cr(VI) activated P. clarkii's antimicrobial immune responses and altered the bacterial composition in the hemolymph. After antibiotic treatment to reduce bacterial populations, Cr(VI)-induced intestinal and liver damage worsened, and crayfish exhibited lower levels of GSH/CAT/SOD activity. The Exiguobacterium, the symbiotic bacteria in the hemolymph of P. clarkii, were proved to be primary contributor to Cr(VI) tolerance. Further investigation suggested that it resists Cr(VI) through the activation of the ABC transporter system and the reduction of Cr(VI) via the reductase gene nfsA. To validate the role of Exiguobacterium in Cr(VI) tolerance, crayfish treated with antibiotics then supplemented with Exiguobacterium H6 and recombinant E. coli (with the nfsA gene), reduced Cr(VI)-induced ovarian damage. Overall, this study revealed that the symbiotic bacteria Exiguobacterium can absorb and reduce hexavalent chromium, mitigating Cr(VI)-induced damage in P. clarkii. These findings provide new insights into hexavalent chromium tolerance mechanisms in crustaceans.

Environmental endocrine disruptors and pregnane X receptor action: A review

The pregnane X receptor (PXR) is a kind of orphan nuclear receptor activated by a series of ligands. Environmental endocrine disruptors (EEDs) are a wide class of molecules present in the environment that are suspected to have adverse effects on the endocrine system by interfering with the synthesis, transport, degradation, or action of endogenous hormones. Since EEDs may modulate human/rodent PXR, this review aims to summarize EEDs as PXR modulators, including agonists and antagonists. The modular structure of PXR is also described, interestingly, the pharmacology of PXR have been confirmed to vary among different species. Furthermore, PXR play a key role in the regulation of endocrine function. Endocrine disruption of EEDs via PXR and its related pathways are systematically summarized. In brief, this review may provide a way to understand the roles of EEDs in interaction with the nuclear receptors (such as PXR) and the related pathways.

RNA modification: mechanisms and therapeutic targets

RNA modifications are dynamic and reversible chemical modifications on substrate RNA that are regulated by specific modifying enzymes. They play important roles in the regulation of many biological processes in various diseases, such as the development of cancer and other diseases. With the help of advanced sequencing technologies, the role of RNA modifications has caught increasing attention in human diseases in scientific research. In this review, we briefly summarized the basic mechanisms of several common RNA modifications, including m6A, m5C, m1A, m7G, Ψ, A-to-I editing and ac4C. Importantly, we discussed their potential functions in human diseases, including cancer, neurological disorders, cardiovascular diseases, metabolic diseases, genetic and developmental diseases, as well as immune disorders. Through the "writing-erasing-reading" mechanisms, RNA modifications regulate the stability, translation, and localization of pivotal disease-related mRNAs to manipulate disease development. Moreover, we also highlighted in this review all currently available RNA-modifier-targeting small molecular inhibitors or activators, most of which are designed against m6A-related enzymes, such as METTL3, FTO and ALKBH5. This review provides clues for potential clinical therapy as well as future study directions in the RNA modification field. More in-depth studies on RNA modifications, their roles in human diseases and further development of their inhibitors or activators are needed for a thorough understanding of epitranscriptomics as well as diagnosis, treatment, and prognosis of human diseases.

The Role of ATP-Binding Cassette Proteins in Stem Cell Pluripotency

Pluripotent stem cells (PSCs) are highly proliferative cells that can self-renew indefinitely in vitro. Upon receiving appropriate signals, PSCs undergo differentiation and can generate every cell type in the body. These unique properties of PSCs require specific gene expression patterns that define stem cell identity and dynamic regulation of intracellular metabolism to support cell growth and cell fate transitions. PSCs are prone to DNA damage due to elevated replicative and transcriptional stress. Therefore, mechanisms to prevent deleterious mutations in PSCs that compromise stem cell function or increase the risk of tumor formation from becoming amplified and propagated to progenitor cells are essential for embryonic development and for using PSCs including induced PSCs (iPSCs) as a cell source for regenerative medicine. In this review, we discuss the role of the ATP-binding cassette (ABC) superfamily in maintaining PSC homeostasis, and propose how their activities can influence cellular signaling and stem cell fate decisions. Finally, we highlight recent discoveries that not all ABC family members perform only canonical metabolite and peptide transport functions in PSCs; rather, they can participate in diverse cellular processes from genome surveillance to gene transcription and mRNA translation, which are likely to maintain the pristine state of PSCs.

Structure and Mechanism of Human ABC Transporters

ABC transporters are essential for cellular physiology. Humans have 48 ABC genes organized into seven distinct families. Of these genes, 44 (in five distinct families) encode for membrane transporters, of which several are involved in drug resistance and disease pathways resulting from transporter dysfunction. Over the last decade, advances in structural biology have vastly expanded our mechanistic understanding of human ABC transporter function, revealing details of their molecular arrangement, regulation, and interactions, facilitated in large part by advances in cryo-EM that have rendered hitherto inaccessible targets amenable to high-resolution structural analysis. As a result, experimentally determined structures of multiple members of each of the five families of ABC transporters in humans are now available. Here we review this recent progress, highlighting the physiological relevance of human ABC transporters and mechanistic insights gleaned from their direct structure determination. We also discuss the impact and limitations of model systems and structure prediction methods in understanding human ABC transporters and discuss current challenges and future research directions.

NFR2/ABC transporter axis in drug resistance of breast cancer cells

Breast cancer is one of the most serious malignancies among women, accounting for about 12% of all cancers. The inherent complexity and heterogeneity of breast cancer results in failure to respond to treatment in the advanced stages of the disease. Breast cancer is caused by several genetic and environmental factors. One of the significant factors involved in the development of breast cancer is oxidative stress, which is generally regulated by nuclear factor erythroid 2-related factor 2 (NRF2). The level of NRF2 expression is low in healthy cells, which maintains the balance of the antioxidant system; however, its expression is higher in cancer cells, which have correlation characteristics such as angiogenesis, stem cell formation, drug resistance, and metastasis. Drug resistance increases with the upregulation of NRF2 expression, which contributes to cell protection. NRF2 controls this mechanism by increasing the expression of ATP-binding cassettes (ABCs). Considering the growing number of studies in this field, we aimed to investigate the relationship between NRF2 and ABCs, as well as their role in the development of drug resistance in breast cancer.

Cryo-EM structures of mitochondrial ABC transporter ABCB10 in apo and biliverdin-bound form

ABCB10, a member of ABC transporter superfamily that locates in the inner membrane of mitochondria, plays crucial roles in hemoglobin synthesis, antioxidative stress and stabilization of the iron transporter mitoferrin-1. Recently, it was found that ABCB10 is a mitochondrial biliverdin exporter. However, the molecular mechanism of biliverdin export by ABCB10 remains elusive. Here we report the cryo-EM structures of ABCB10 in apo (ABCB10-apo) and biliverdin-bound form (ABCB10-BV) at 3.67 Å and 2.85 Å resolution, respectively. ABCB10-apo adopts a wide-open conformation and may thus represent the apo form structure. ABCB10-BV forms a closed conformation and biliverdin situates in a hydrophobic pocket in one protomer and bridges the interaction through hydrogen bonds with the opposing one. We also identify cholesterols sandwiched by BVs and discuss the export dynamics based on these structural and biochemical observations.

Unfolding Individual Domains of BmrA, a Bacterial ABC Transporter Involved in Multidrug Resistance

The folding and stability of proteins are often studied via unfolding (and refolding) a protein with urea. Yet, in the case of membrane integral protein domains, which are shielded by a membrane or a membrane mimetic, urea generally does not induce unfolding. However, the unfolding of α-helical membrane proteins may be induced by the addition of sodium dodecyl sulfate (SDS). When protein unfolding is followed via monitoring changes in Trp fluorescence characteristics, the contributions of individual Trp residues often cannot be disentangled, and, consequently, the folding and stability of the individual domains of a multi-domain membrane protein cannot be studied. In this study, the unfolding of the homodimeric bacterial ATP-binding cassette (ABC) transporter Bacillus multidrug resistance ATP (BmrA), which comprises a transmembrane domain and a cytosolic nucleotide-binding domain, was investigated. To study the stability of individual BmrA domains in the context of the full-length protein, the individual domains were silenced by mutating the existent Trps. The SDS-induced unfolding of the corresponding constructs was compared to the (un)folding characteristics of the wild-type (wt) protein and isolated domains. The full-length variants BmrA_W413Y and BmrA_W104YW164A were able to mirror the changes observed with the isolated domains; thus, these variants allowed for the study of the unfolding and thermodynamic stability of mutated domains in the context of full-length BmrA.

Potential drug candidates as P-glycoprotein inhibitors to reverse multidrug resistance in cancer: an in silico drug discovery study

The failure of chemotherapy in the treatment of carcinoma is mainly due to the development of multidrug resistance (MDR), which is largely caused by the overexpression of P-glycoprotein (P-gp/ABCB1/MDR1). Until recently, the 3D structure of the P-gp transporter has not been experimentally resolved, which restricted the discovery of prospective P-gp inhibitors utilizing in silico techniques. In this study, the binding energies of 512 drug candidates in clinical or investigational stages were assessed as potential P-gp inhibitors employing in silico methods. On the basis of the available experimental data, the performance of the AutoDock4.2.6 software to predict the drug-P-gp binding mode was initially validated. Molecular docking and molecular dynamics (MD) simulations combined with molecular mechanics-generalized Born surface area (MM-GBSA) binding energy computations were subsequently conducted to screen the investigated drug candidates. Based on the current results, five promising drug candidates, namely valspodar, dactinomycin, elbasvir, temsirolimus, and sirolimus, showed promising binding energies against P-gp transporter with ΔGbinding values of -126.7, -112.1, -111.9, -102.9, and -101.4 kcal/mol, respectively. The post-MD analyses revealed the energetical and structural stabilities of the identified drug candidates in complex with the P-gp transporter. Furthermore, in order to mimic the physiological conditions, the potent drugs complexed with the P-gp were subjected to 100 ns MD simulations in an explicit membrane-water environment. The pharmacokinetic properties of the identified drugs were predicted and demonstrated good ADMET characteristics. Overall, these results indicated that valspodar, dactinomycin, elbasvir, temsirolimus, and sirolimus hold promise as prospective P-gp inhibitors and warrant further invitro/invivo investigations.

Pharmacogenetics of ABCB1, CDA, DCK, GSTT1, GSTM1 and outcomes in a cohort of pediatric acute myeloid leukemia patients from Colombia

BACKGROUND AND AIM

Different studies have shown pharmacogenetic variants related to drug toxicity in acute myeloid leukemia (AML) patients. Our aim was to identify the association between ABCB1, CDA, DCK, GSTT1, and GSTM1 variants with clinical outcomes and toxicity in pediatric patients with AML.

METHODS

Fifty-one confirmed de novo AML pediatric patients were included. A SNaPshot™ assay and conventional PCR were used to evaluate ABCB1, CDA, DCK, GSTT1, and GSTM1 variants. Clinical outcomes and toxicity associations were evaluated using odds ratios and Chi-square analysis.

RESULTS

Patients carrying ABCB1 (1236C > T, rs1128503) GG genotype in had a 6.8 OR (CI 95% 1.08-42.73, p = .044) for cardiotoxicity as compared to patients carrying either AA or GA genotypes 0.14 OR (CI 95% 0.023-0.92, p = .044). For ABCB1 (1236G > A rs1128503/2677C > A/T rs2032582/3435G > A rs1045642) AA/AA/AA combined genotypes had a strong association with death after HSTC OR 13.73 (CI 95% 1.94-97.17, p = .009). Combined genotypes GG/CC/GG with CDA (79A > C, rs2072671) CA genotype or CDA (-451G > A, rs532545) CT genotype, had a 4.11 OR (CI 95% 2.32-725, p = .007) and 3.8 OR (CI 95% 2.23-6.47, p = .027) with MRD >0.1% after first chemotherapy cycle, respectively.

CONCLUSION

Our results highlight the importance of pharmacogenetic analysis in pediatric AML, particularly in populations with a high degree of admixture, and might be useful as a future tool for patient stratification for treatment.

Pseudomonas Aeruginosa Theft Biofilm Require Host Lipids of Cutaneous Wound

OBJECTIVE

This work addressing complexities in wound infection, seeks to test the reliance of bacterial pathogen Pseudomonas aeruginosa (PA) on host skin lipids to form biofilm with pathological consequences.

BACKGROUND

PA biofilm causes wound chronicity. Both CDC as well as NIH recognizes biofilm infection as a threat leading to wound chronicity. Chronic wounds on lower extremities often lead to surgical limb amputation.

METHODS

An established preclinical porcine chronic wound biofilm model, infected with PA or Pseudomonas aeruginosa ceramidase mutant (PA ∆Cer ), was used.

RESULTS

We observed that bacteria drew resource from host lipids to induce PA ceramidase expression by three orders of magnitude. PA utilized product of host ceramide catabolism to augment transcription of PA ceramidase. Biofilm formation was more robust in PA compared to PA ∆Cer . Downstream products of such metabolism such as sphingosine and sphingosine-1-phosphate were both directly implicated in the induction of ceramidase and inhibition of peroxisome proliferator-activated receptor (PPAR)δ, respectively. PA biofilm, in a ceram-idastin-sensitive manner, also silenced PPARδ via induction of miR-106b. Low PPARδ limited ABCA12 expression resulting in disruption of skin lipid homeostasis. Barrier function of the wound-site was thus compromised.

CONCLUSIONS

This work demonstrates that microbial pathogens must co-opt host skin lipids to unleash biofilm pathogenicity. Anti-biofilm strategies must not necessarily always target the microbe and targeting host lipids at risk of infection could be productive. This work may be viewed as a first step, laying fundamental mechanistic groundwork, toward a paradigm change in biofilm management.

Postoperative jaundice related to UGT1A1 and ABCB11 gene mutations: A case report and literature review

BACKGROUND

Patients with obstructive jaundice caused by intrahepatic bile duct stones can be effectively managed by surgery. However, some patients may develop postoperative complications, liver failure, and other life-threatening situations. Here, we report a patient with mutations in the uridine 5’-diphospho-glucuronosyltransferase 1A1 (UGT1A1) and bile salt export pump (adenosine triphosphate-binding cassette subfamily B member 11, ABCB11) genes who presented multiple intrahepatic bile duct stones and cholestasis, and the jaundice of the patient increased after partial hepatectomy.

CASE SUMMARY

A 52-year-old male patient admitted to the hospital on October 23, 2021, with a progressive exacerbation of jaundice, was found to have multiple intrahepatic bile duct stones with the diagnoses of obstructive jaundice and acute cholecystitis. Subsequently, the patient underwent left hepatectomy with biliary exploration, stone extraction, T-tube drainage, and cholecystectomy without developing any intraoperative complications. The patient had a dark urine color with worsening jaundice postoperatively and did not respond well to plasma exchange and other symptomatic and supportive treatments. Since the progressive increase in postoperative bilirubin could not be clinically explained with any potential reason, including, if not at all, viral infection, cholangitis, autoimmune liver disease, and other causes, the patient underwent whole-exon screening for any genetic diseases, which surprisingly identified UGT1A1 and ABCB11 gene mutations related to glucuronidation of indirect bilirubin as well as bile acid transport in hepatocytes, respectively. Thus, we hypothesized that postoperative refractory cholestasis might result from UGT1A1 and ABCB11 gene mutations and further recommended liver transplantation to the patient, who eventually declined it and died from liver failure six months later.

CONCLUSION

Surgery may aggravate cholestasis in patients with multiple intrahepatic bile duct stones and cholestasis associated with UGT1A1 and ABCB11 gene mutations. A liver transplant may be the best option if active medical treatment fails.

Inhibitors of ABCG2-mediated multidrug resistance: Lead generation through computer-aided drug design

Human breast cancer resistance protein (BCRP), known also as ABCG2, plays a major role in multiple drug resistance (MDR) in tumor cells. Through this ABC transporter, cancer cells acquire the ability of resistance to structurally and functionally unrelated anticancer drugs. Nowadays, the design of ABCG2 inhibitors as potential agents to enhance the chemotherapy efficacy is an interesting strategy. In this context, we have used computer-aided drug design (CADD) based on available data of a large series of potent inhibitors from our groups as an approach in guiding the design of effective ABCG2 inhibitors. We report therein the results on the use of the FLAPpharm method to elucidate the pharmacophoric features of one of the ABCG2 binding sites involved in the regulation of the basal ATPase activity of the transporter. The predictivity of the model was evaluated by testing three predicted compounds which were found to induce high inhibitory activity of BCRP, in the nanomolar range for the best of them.

Analysis of the Properties of 44 ABC Transporter Genes from Biocontrol Agent Trichoderma asperellum ACCC30536 and Their Responses to Pathogenic Alternaria alternata Toxin Stress

ATP-binding cassette (ABC) transporters are involved in transporting multiple substrates, such as toxins, and may be important for the survival of Trichoderma when encountering biotic toxins. In this study, genome searching revealed that there are 44 ABC transporters encoded in the genome of Trichoderma asperellum. These ABC transporters were divided into six types based on three-dimensional (3D) structure prediction, of which four, represented by 39 ABCs, are involved in transport and the remaining two, represented by 5 ABCs, are involved in regulating translation. The characteristics of nucleotide-binding domain (NBD) are important in the identification of ABC proteins. Even though the 3D structures of the 79 NBDs in the 44 ABCs are similar, multiple sequence alignment showed they can be divided into three classes. In total, 794 motifs were found in the promoter regions of the 44 ABC genes, of which 541 were cis-regulators related to stress responses. To characterize how their ABCs respond when T. asperellum interact with fungi or plants, T. asperellum was cultivated in either minimal media (MM) control, C-hungry, N-hungry, or poplar medium (PdPap) to simulate normal conditions, competition with pathogens, interaction with pathogens, and interaction with plants, respectively. The results show that 17 of 39 transport ABCs are highly expressed in at least one condition, whereas four of the five translation-regulating ABCs are highly expressed in at least one condition. Of these 21 highly expressed ABCs, 6 were chosen for RT-qPCR expression under the toxin stress of phytopathogen Alternaria alternata, and the results show ABC01, ABC04, ABC05, and ABC31 were highly expressed and may be involved in pathogen interaction and detoxifying toxins from A. alternata.

Bioavailability of tetracyclines is substantially increased by administration of cyclosporine A, a non-specific efflux-pump blocker

OBJECTIVES

To investigate how cyclosporine A, a nonspecific efflux-pump blocker, affects the plasma concentrations and oral bioavailability of tigecycline, oxytetracycline, chlortetracycline, doxycycline, minocycline, and tetracycline.

METHODS

Broiler chickens were used as an animal model. The tetracyclines (10 mg/kg BW) were administered intravenously, orally, and orally with cyclosporine A (50 mg/kg BW; administration: oral or intravenous). After administration, plasma samples were taken, and their concentrations of tetracyclines were measured using high-performance liquid chromatography coupled with tandem mass spectrometry. For pharmacokinetic analyses of mean plasma concentrations versus time, compartmental and non-compartmental analyses were used.

RESULTS

After oral administration of the tetracyclines, cyclosporine A administration (oral or intravenous) significantly (P < 0.05) increased the plasma concentrations, the bioavailability, the maximum plasma concentration, and the area under the curve of all the tetracyclines. Interestingly, the bioavailability of the tetracyclines was around two times higher after orally administering cyclosporine A than after intravenously administering it (P < 0.05).

CONCLUSIONS

Cyclosporine A administration increases the plasma concentrations of orally administered tetracyclines. Although cyclosporine A also inhibits renal and hepatic clearance, these results strongly suggest that efflux pumps in the intestinal epithelium are involved in the regulation of tetracycline absorption from the gastrointestinal tract.

The Role of Solute Carrier Transporters in Efficient Anticancer Drug Delivery and Therapy

Transporter-mediated drug resistance is a major obstacle in anticancer drug delivery and a key reason for cancer drug therapy failure. Membrane solute carrier (SLC) transporters play a crucial role in the cellular uptake of drugs. The expression and function of the SLC transporters can be down-regulated in cancer cells, which limits the uptake of drugs into the tumor cells, resulting in the inefficiency of the drug therapy. In this review, we summarize the current understanding of low-SLC-transporter-expression-mediated drug resistance in different types of cancers. Recent advances in SLC-transporter-targeting strategies include the development of transporter-utilizing prodrugs and nanocarriers and the modulation of SLC transporter expression in cancer cells. These strategies will play an important role in the future development of anticancer drug therapies by enabling the efficient delivery of drugs into cancer cells.

Case Report: Novel rare mutation c.6353C > G in the ABCA12 gene causing harlequin ichthyosis identified by whole exome sequencing

BACKGROUND

Harlequin ichthyosis (HI) is a severe rare genetic disease that mainly affects the skin. Neonates with this disease are born with thick skin and large diamond-shaped plates covering most of their bodies. Affected neonates lose the ability to control dehydration and regulate temperature and are more susceptible to infections. They also face respiratory failure and feeding problems. These clinical symptoms are factors associated with high mortality rates of neonates with HI. Until now, there are still no effective treatments for HI patients and most patients die in the newborn period. Mutation in the ABCA12 gene, which encodes an adenosine triphosphate-binding cassette (ABC) transporter, has been demonstrated as the major cause of HI.

CASE PRESENTATION

In this study, we report the case who is one infant that was born prematurely at 32 gestational weeks with the whole body covered with thick plate-like scales of skin. The infant was severely infected with mild edema, multiple cracked skins full of the body, yellow discharge, and necrosis of fingers and toes. The infant was suspected to be affected by HI. Whole exome sequencing (WES) was performed as a tool for detecting the novel mutation in one prematurely born Vietnam infant with HI phenotype. And after that, the mutation was confirmed by the Sanger sequencing method in the patient and the members of his family. In this case, one novel mutation c.6353C > G (p.S2118X, Hom) in the ABCA12 gene, was detected in the patient. The mutation has not been reported in any HI patients previously. This mutation was also found in a heterozygous state in the members of the patient's family, including his parents, an older brother, and an older sister who are no symptoms.

CONCLUSIONS

In this study, we identified a novel mutation in a Vietnamese patient with HI by whole exome sequencing. The results for the patient and the members of his family will be helpful in understanding the etiology of the disease, diagnosing carriers, assisting in genetic counseling, and emphasizing the need for DNA-based prenatal screening for families with a history of the disease.

ABC transporters affects tumor immune microenvironment to regulate cancer immunotherapy and multidrug resistance

Multidrug resistance (MDR) is the phenomenon in which cancer cells simultaneously develop resistance to a broad spectrum of structurally and mechanistically unrelated drugs. MDR severely hinders the effective treatment of cancer and is the major cause of chemotherapy failure. ATP-binding cassette (ABC) transporters are extensively expressed in various body tissues, and actively transport endogenous and exogenous substrates through biological membranes. Overexpression of ABC transporters is frequently observed in MDR cancer cells, which promotes efflux of chemotherapeutic drugs and reduces their intracellular accumulation. Increasing evidence suggests that ABC transporters regulate tumor immune microenvironment (TIME) by transporting various cytokines, thus controlling anti-tumor immunity and sensitivity to anticancer drugs. On the other hand, the expression of various ABC transporters is regulated by cytokines and other immune signaling molecules. Targeted inhibition of ABC transporter expression or function can enhance the efficacy of immune checkpoint inhibitors by promoting anticancer immune microenvironment. This review provides an update on the recent research progress in this field.

Human Breast Milk Contamination with Aflatoxins, Impact on Children's Health, and Possible Control Means: A Review

Aflatoxins are natural toxicants produced mainly by species of the Aspergillus genus, which contaminate virtually all feeds and foods. Apart from their deleterious health effects on humans and animals, they can be secreted unmodified or carried over into the milk of lactating females, thereby posing health risks to suckling babies. Aflatoxin M1 (AFM1) is the major and most toxic aflatoxin type after aflatoxin B1 (AFB1). It contaminates human breast milk upon direct ingestion from dairy products or by carry-over from the parent molecule (AFB1), which is hydroxylated in the liver and possibly in the mammary glands by cytochrome oxidase enzymes and then excreted into breast milk as AFM1 during lactation via the mammary alveolar epithelial cells. This puts suckling infants and children fed on this milk at a high risk, especially that their detoxifying activities are still weak at this age essentially due to immature liver as the main organ responsible for the detoxification of xenobiotics. The occurrence of AFM1 at toxic levels in human breast milk and associated health conditions in nursing children is well documented, with developing countries being the most affected. Different studies have demonstrated that contamination of human breast milk with AFM1 represents a real public health issue, which should be promptly and properly addressed to reduce its incidence. To this end, different actions have been suggested, including a wider and proper implementation of regulatory measures, not only for breast milk but also for foods and feeds as the upstream sources for breast milk contamination with AFM1. The promotion of awareness of lactating mothers through the organization of training sessions and mass media disclosures before and after parturition is of a paramount importance for the success of any action. This is especially relevant that there are no possible control measures to ensure compliance of lactating mothers to specific regulatory measures, which can yet be appropriate for the expansion of breast milk banks in industrialized countries and emergence of breast milk sellers. This review attempted to revisit the public health issues raised by mother milk contamination with AFM1, which remains undermined despite the numerous relevant publications highlighting the needs to tackle its incidence as a protective measure for the children physical and mental health.

Naturally occurring plant-based anticancerous candidates as prospective ABCG2 inhibitors: an in silico drug discovery study

ATP-binding cassette transporter G2 (ABCG2) is an efflux transporter related to the clinical multidrug resistance (MDR) phenomenon. Identifying ABCG2 inhibitors could help discover extraordinary curative strategies for carcinoma remediation. Hitherto, there is no medication drug inhibiting ABCG2 transporter, notwithstanding that a considerable number of drugs have been submitted to clinical-trial and investigational phases. In the search for unprecedented chemical compounds that could inhibit the ABCG2 transporter, an in silico screening was conducted on the Naturally Occurring Plant-based Anticancer Compound-Activity-Target (NPACT) database containing 1574 compounds. Inhibitor-ABCG2 binding affinities were estimated based on molecular docking and molecular minimization (MM) calculations and compared to a co-crystallized inhibitor (BWQ) acting as a reference inhibitor. Molecular dynamics (MD) simulations pursued by molecular mechanics-generalized Born surface area (MM-GBSA) binding energy estimations were further executed for compounds with MM-GBSA//MM binding energies lower than BWQ (calc. - 60.5 kcal/mol). NPACT00968 and NPACT01545 demonstrated auspicious inhibitory activities according to binding affinities (ΔGbinding) over the 100 ns MD simulations that were nearly one and a half folds compared to BWQ (- 100.4, - 94.7, and - 62.9 kcal/mol, respectively). Throughout the 100 ns MD simulations, structural and energetical analyses unveiled outstanding stability of the ABCG2 transporter when bound with NPACT00968 and NPACT01545. In silico calculations hold a promise for those two inhibitors as drug candidates of ABCG2 transporter and emphasize that further in vitro and in vivo experiments are guaranteed.

Extracellular Vesicles in Cancer Drug Resistance: Roles, Mechanisms, and Implications

Extracellular vesicles (EVs) are cell-derived nanosized vesicles that mediate cell-to-cell communication via transporting bioactive molecules and thus are critically involved in various physiological and pathological conditions. EVs contribute to different aspects of cancer progression, such as cancer growth, angiogenesis, metastasis, immune evasion, and drug resistance. EVs induce the resistance of cancer cells to chemotherapy, radiotherapy, targeted therapy, antiangiogenesis therapy, and immunotherapy by transferring specific cargos that affect drug efflux and regulate signaling pathways associated with epithelial-mesenchymal transition, autophagy, metabolism, and cancer stemness. In addition, EVs modulate the reciprocal interaction between cancer cells and noncancer cells in the tumor microenvironment (TME) to develop therapy resistance. EVs are detectable in many biofluids of cancer patients, and thus are regarded as novel biomarkers for monitoring therapy response and predicting prognosis. Moreover, EVs are suggested as promising targets and engineered as nanovehicles to deliver drugs for overcoming drug resistance in cancer therapy. In this review, the biological roles of EVs and their mechanisms of action in cancer drug resistance are summarized. The preclinical studies on using EVs in monitoring and overcoming cancer drug resistance are also discussed.

Cancer Stem Cell Formation Induced and Regulated by Extracellular ATP and Stanniocalcin-1 in Human Lung Cancer Cells and Tumors

Cancer stem cells (CSCs) are closely associated with metastasis and epithelial mesenchymal transition (EMT). We previously reported that extracellular ATP (eATP) induces and regulates EMT in cancer cells. We recently found that the gene stanniocalcin 1 (STC1) is significantly upregulated by eATP in human non-small lung cancer (NSCLC) A549 cells; however, the relationships among eATP, CSCs, and STC1 were largely unknown. In this study, we performed gene knockdown and knockout, and a wide variety of functional assays to determine if and how eATP and STC1 induce CSCs in NSCLC A549 and H1299 cells. Our data show that, in both cultured cells and tumors, eATP increased the number of CSCs in the cancer cell population and upregulated CSC-related genes and protein markers. STC1 deletion led to drastically slower cell and tumor growth, reduced intracellular ATP levels and CSC markers, and metabolically shifted STC1-deficient cells from an energetic state to a quiescent state. These findings indicate that eATP induces and regulates CSCs at transcriptional, translational, and metabolic levels, and these activities are mediated through STC1 via mitochondria-associated ATP synthesis. These novel findings offer insights into eATP-induced CSCs and identify new targets for inhibiting CSCs.