ATP-binding Cassette Transporter Research Articles

Native mass spectrometry and structural studies reveal modulation of MsbA–nucleotide interactions by lipids

The ATP-binding cassette (ABC) transporter, MsbA, plays a pivotal role in lipopolysaccharide (LPS) biogenesis by facilitating the transport of the LPS precursor lipooligosaccharide (LOS) from the cytoplasmic to the periplasmic leaflet of the inner membrane. Despite multiple studies shedding light on MsbA, the role of lipids in modulating MsbA-nucleotide interactions remains poorly understood. Here we use native mass spectrometry (MS) to investigate and resolve nucleotide and lipid binding to MsbA, demonstrating that the transporter has a higher affinity for adenosine 5’-diphosphate (ADP). Moreover, native MS shows the LPS-precursor 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo)2-lipid A (KDL) can tune the selectivity of MsbA for adenosine 5’-triphosphate (ATP) over ADP. Guided by these studies, four open, inward-facing structures of MsbA are determined that vary in their openness. We also report a 2.7 Å-resolution structure of MsbA in an open, outward-facing conformation that is not only bound to KDL at the exterior site, but with the nucleotide binding domains (NBDs) adopting a distinct nucleotide-free structure. The results obtained from this study offer valuable insight and snapshots of MsbA during the transport cycle.

MiR-223 accelerates lipid droplets clearance in microglia following spinal cord injury by upregulating ABCA1

BackgroundSpinal cord injury (SCI) is characterized by extensive demyelination and inflammatory responses. Facilitating the clearance of lipid droplets (LDs) within microglia contributes to creating a microenvironment that favors neural recovery and provides essential materials for subsequent remyelination. Therefore, investigating MicroRNAs (miRNAs) that regulate lipid homeostasis after SCI and elucidating their potential mechanisms in promoting LDs clearance in microglia have become focal points of SCI research.MethodsWe established a subacute C5 hemicontusion SCI model in mice and performed transcriptomic sequencing on the injury epicenter to identify differentially expressed genes and associated pathways. Confocal imaging was employed to observe LDs accumulation. Multi-omics analyses were conducted to identify differentially expressed mRNA and miRNA post-SCI. Pathway enrichment analysis and protein-protein interaction network construction were performed using bioinformatics methods, revealing miR-223-Abca1 as a crucial miRNA-mRNA pair in lipid metabolism regulation. BV2 microglia cell lines overexpressing miR-223 were engineered, and immunofluorescence staining, western blot, and other techniques were employed to assess LDs accumulation, relevant targets, and inflammatory factor expression, confirming its role in regulating lipid homeostasis in microglia.ResultsHistopathological results of our hemicontusion SCI model confirmed LDs aggregation at the injury epicenter, predominantly within microglia. Our transcriptomic analysis during the subacute phase of SCI in mice implicated ATP-binding cassette transporter A1 (Abca1) as a pivotal gene in lipid homeostasis, cholesterol efflux and microglial activation. Integrative mRNA-miRNA multi-omics analysis highlighted the crucial role of miR-223 in the neuroinflammation process following SCI, potentially through the regulation of lipid metabolism via Abca1. In vitro experiments using BV2 cells overexpressing miR-223 demonstrated that elevated levels of miR-223 enhance ABCA1 expression in myelin debris and LPS-induced BV2 cells. This promotes myelin debris degradation and LDs clearance, and induces a shift toward an anti-inflammatory M2 phenotype.ConclusionsIn summary, our study unveils the critical regulatory role of miR-223 in lipid homeostasis following SCI. The mechanism by which this occurs involves the upregulation of ABCA1 expression, which facilitates LDs clearance and myelin debris degradation, consequently alleviating the lipid burden, and inhibiting inflammatory polarization of microglia. These findings suggest that strategies to enhance miR-223 expression and target ABCA1, thereby augmenting LDs clearance, may emerge as appealing new clinical targets for SCI treatment.

Ilexgenin A inhibits lipid accumulation in macrophages and reduces the progression of atherosclerosis through PTPN2/ERK1/2/ABCA1 signalling pathway

Macrophage lipid accumulation indicates a pathological change in atherosclerosis. Ilexgenin A (IA), a pentacyclic triterpenoid compound, plays a role in preventing inflammation, bacterial infection, and fatty liver and induces a potential anti-atherogenic effect. However, the anti-atherosclerotic mechanism remains unclear. The present study investigated the effects of IA on lipid accumulation in macrophage-derived foam cells and atherogenesis in apoE−/− mice. Our results indicated that the expression of adenosine triphosphate-binding cassette transporter A1 (ABCA1) was up-regulated by IA, promoting cholesterol efflux and reducing lipid accumulation in macrophages, which may be regulated by the protein tyrosine phosphatase non-receptor type 2 (PTPN2)/ERK1/2 signalling pathway. IA attenuated the progression of atherosclerosis in high-fat diet-fed apoE−/− mice. PTPN2 knockdown with siRNA or treatment with an ERK1/2 agonist (Ro 67–7476) impeded the effects of IA on ABCA1 upregulation and cholesterol efflux in macrophages. These results suggest that IA inhibits macrophage lipid accumulation and alleviates atherosclerosis progression via the PTPN2/ERK1/2 signalling pathway.

Glycolipid Metabolic Disorders, Metainflammation, Oxidative Stress, and Cardiovascular Diseases: Unraveling Pathways.

Glycolipid metabolic disorders (GLMDs) are various metabolic disorders resulting from dysregulation in glycolipid levels, consequently leading to an increased risk of obesity, diabetes, liver dysfunction, neuromuscular complications, and cardiorenal vascular diseases (CRVDs). In patients with GLMDs, excess caloric intake and a lack of physical activity may contribute to oxidative stress (OxS) and systemic inflammation. This study aimed to review the connection between GLMD, OxS, metainflammation, and the onset of CRVD. GLMD is due to various metabolic disorders causing dysfunction in the synthesis, breakdown, and absorption of glucose and lipids in the body, resulting in excessive ectopic accumulation of these molecules. This is mainly due to neuroendocrine dysregulation, insulin resistance, OxS, and metainflammation. In GLMD, many inflammatory markers and defense cells play a vital role in related tissues and organs, such as blood vessels, pancreatic islets, the liver, muscle, the kidneys, and adipocytes, promoting inflammatory lesions that affect various interconnected organs through their signaling pathways. Advanced glycation end products, ATP-binding cassette transporter 1, Glucagon-like peptide-1, Toll-like receptor-4, and sphingosine-1-phosphate (S1P) play a crucial role in GLMD since they are related to glucolipid metabolism. The consequences of this is system organ damage and increased morbidity and mortality.

Direct lactic acid production from raw jerusalem artichoke powder by Lacticaseibacillus paracasei NJ and the comparative transcriptomic profiling of inulin and monosaccharide utilization

A feasible fermentation process for the production of lactic acid (LA), one of the most important food additives, from non-crop feedstocks would help alleviate the challenges of food safety. In this study, 215 g/L inulin-rich Jerusalem artichoke powder (JAP) were directly converted into LA without exogenous nitrogen addition under non-sterile conditions via selected Lacticaseibacillus paracasei NJ. The LA concentration, yield, and average productivity reached 144.08 g/L, 0.67 g/g, and 4.37 g/L/h, respectively, which can be scalable from 5 L to 50 L bioreactors. The viable counts of Lacticaseibacillus reached to 142.30–301.50 × 108 CFU/mL, allowing the products a promising probiotic in food additives. Transcriptional analysis revealed that strain NJ utilized inulin mainly via extracellular β-fructosidase and fructose transporters encoded by the fosRABCDXE operon, and the gene expression within the phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS), pyruvate metabolism, and fatty acid synthesis was significantly altered. For strain NJ grown on JAP, the expressions of genes related to amino acid biosynthesis and peptide/amino acid relevant ATP-binding cassette (ABC) transport system were upregulated to fit nitrogen limitation. We found the availability of L. paracasei NJ for high-yield lactic acid from raw JAP and explores the inner changes of gene expression by utilizing inulin, which provide both promising food additives and new perspectives on the understanding of inulin metabolism in Lacticaseibacillus.

The cholesterol-lowering effects and mechanisms of novel milk casein-derived peptides in hyperlipidemia and hypercholesterol mice

Food-derived cholesterol-lowering peptides have the practical benefit of inhibiting lipid absorption and regulating systemic cholesterol homeostasis. This work aimed to explore the antihyperlipidemia function of milk casein-derived peptides Leu-Gln-Pro-Glu (LQPE), Val-Leu-Pro-Val-Pro-Gln (VLPVPQ), and Val-Ala-Pro-Phe-Pro-Glu (VAPFPE) and investigated whether the function of these peptides affected the gut microbiome. According to the experimental findings, lipid metabolism disorder in hyperlipidemia mice was improved to various degrees by all three peptides, which dramatically lowered the levels of low-density lipoprotein cholesterol (LDL-C) and triglyceride (TG) in the serum and inhibited the buildup of lipids in the liver and the development of steatosis. VAPFPE was found to reduce intestinal cholesterol absorption and the formation of cholesterol esters by inhibiting hepatocyte nuclear factor 4α (HNF4α), niemann-pick C1-like 1 (NPC1L1), and acetyl coenzyme A acetyltransferase 2 (ACAT2) expression and increase intestinal cholesterol efflux through up-regulation of ATP-binding cassette transporter G8 (ABCG8). VAPFPE also maintained cholesterol homeostasis by up-regulating liver low-density lipoprotein receptor (LDL-R) expression. The 16S rRNA analysis revealed that all three peptides improve the gut microbial composition, and VAPFPE specifically encouraged a rise in the proportional abundance of Bifidobacterium. The results shed light on the potential applications of bioactive peptides as functional health foods for lowering cholesterol.

AZGs: a new family of cytokinin transporters.

Cytokinins (CKs) are phytohormones structurally similar to purines that play important roles in various aspects of plant physiology and development. The local and long-distance distribution of CKs is very important to control their action throughout the plant body. Over the past decade, several novel CK transporters have been described, many of which have been linked to a physiological function rather than simply their ability to transport the hormone in vitro. Purine permeases, equilibrative nucleotide transporters and ATP-binding cassette transporters are involved in the local and long-range distribution of CK. In addition, members of the Arabidopsis AZA-GUANINE RESISTANT (AZG) protein family, AZG1 and AZG2, have recently been shown to mediate CK uptake at the plasma membrane and endoplasmic reticulum. Despite sharing ∼50% homology, AZG1 and AZG2 have unique transport mechanisms, tissue-specific expression patterns, and subcellular localizations that underlie their distinct physiological functions. AZG2 is expressed in a small group of cells in the overlying tissue around the lateral root primordia, where its expression is induced by auxins and it is involved in the regulation of lateral root growth. AZG1 is ubiquitously expressed, with high levels in the division zone of the root apical meristem. Here, it binds and stabilises the auxin efflux carrier PIN1, thereby shaping root architecture, particularly under salt stress. This review highlights the latest findings on the protein properties, transport mechanisms and cellular functions of this new family of CK transporters and discusses perspectives for future research in this field.

RNA thermometers are widespread upstream of ABC transporter genes in bacteria

RNA thermometers are temperature-sensing non-coding RNAs that regulate the expression of downstream genes. A well-characterized RNA thermometer motif discovered in bacteria is the ROSE-like element (repression of heat shock gene expression). ATP-binding cassette (ABC) transporters are a superfamily of transmembrane proteins that harness ATP hydrolysis to facilitate the export and import of substrates across cellular membranes. Through structure-guided bioinformatics, we discovered that ROSE-like RNA thermometers are widespread upstream of ABC transporter genes in bacteria. X-ray crystallography, biochemistry, and cellular assays indicate that these RNA thermometers are functional regulatory elements. This study expands the known biological role of RNA thermometers to these key membrane transporters.

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.

Impact of Reduced Acidic Earwax pH and Earwax-Determinant Genotypes in Acquired Middle Ear Cholesteatoma.

The development of acquired middle ear cholesteatoma is associated with a single nucleotide polymorphism, 538G>A, in the human adenosine triphosphate-binding cassette transporter C11 (ABCC11) gene, which is a determinant of the earwax morphotype, such as wet- and dry-type earwax; however, the mechanism underlying this association is unclear. We focused on the earwax pH and aimed to elucidate the mechanism between ABCC11 genotypes and acquired middle ear cholesteatoma. Prospective observational study. Single-center, academic hospital. We recruited 40 patients with acquired middle ear cholesteatoma who underwent surgery and 115 controls with no history of middle ear cholesteatoma. We assessed the earwax pH and ABCC11 genotypes in all participants. Clinical information was collected from the patients with cholesteatoma. The earwax pH was significantly less acidic in patients with cholesteatoma and those carrying wet earwax genotypes (ABCC11 538G/G or 538G/A) than in the controls and those carrying the dry earwax genotype (ABCC11 538A/A), respectively. Furthermore, earwax pH was significantly positively correlated with high preoperative cholesteatoma stages in the patients with cholesteatoma. Our results show that the less acidic earwax pH was significantly related to the development and progression of acquired middle ear cholesteatoma. The less acidic earwax pH may play an important role in the mechanism underlying the association between acquired middle ear cholesteatoma and the ABCC11 gene at site 538.

Nongenomic ERα-AMPK Signaling Regulates Sex-Dependent Bcrp Transport Activity at the Blood-Brain Barrier.

The blood-brain barrier (BBB) is an extensive capillary network that protects the brain from environmental and metabolic toxins while limiting drug delivery to the central nervous system (CNS). The ATP-binding cassette transporter breast cancer resistance protein (Bcrp) reduces drug delivery across the BBB by actively transporting its clinical substrates back into peripheral circulation before their entry into the CNS compartment. 17β-Estradiol (E2)-elicited changes in Bcrp transport activity and expression have been documented previously. We report a novel signaling mechanism by which E2 decreases Bcrp transport activity in mouse brain capillaries via rapid nongenomic signaling through estrogen receptor α. We extended this finding to investigate the effects of different endocrine-disrupting compounds (EDCs) and selective estrogen receptor modulators (SERMs) on Bcrp transport function. We also demonstrate sex-dependent expression of Bcrp and E2-sensitive Bcrp transport activity at the BBB ex vivo. This work establishes an explanted tissue-based model by which to interrogate EDCs and SERMs as modulators of nongenomic estrogenic signaling with implications for sex and hormonal regulation of therapeutic delivery into the CNS.

Proton-pumping photoreceptor controls expression of ABC transporter by regulating transcription factor through light

Light is a significant factor for living organisms with photosystems, like microbial rhodopsin—a retinal protein that functions as an ion pump, channel, and sensory transduction. Gloeobacter violaceus PCC7421, has a proton-pumping rhodopsin gene, the Gloeobacter rhodopsin (GR). The helix-turn-helix family of transcriptional regulators has various motifs, and they regulate gene expression in the presence of various metal ions. Here, we report that active proton outward pumping rhodopsin interacted with the helix-turn-helix transcription regulator and regulated gene expression. This interaction is confirmed using ITC analysis (KD of 8 μM) and determined the charged residues required. During in vitro experiments using fluorescent and luciferase reporter systems, ATP-binding cassette (ABC) transporters and the self-regulation of G. violaceus transcriptional regulator (GvTcR) are regulated by light, and gene regulation is observed in G. violaceus using the real-time polymerase chain reaction. These results expand our understanding of the natural potential and limitations of microbial rhodopsin function.

Integrative metabolomics dictate distinctive signature profiles in patients with Tetralogy of Fallot.

Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease (CCHD) with multifactorial etiology. We aimed to investigate the metabolic profiles of CCHD and their independent contributions to TOF. A cohort comprising 42 individuals with TOF and atrial septal defect (ASD) was enrolled. Targeted ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) was employed to systematically analyze metabolite levels and identify TOF-associated metabolic profiles. Of 370 identified metabolites in tissue and 284 in plasma, over one-third of metabolites showed an association with microbiome. Differential metabolic pathways including amino acids biosynthesis, ABC (ATP-binding cassette) transporters, carbon metabolism, and fatty acid biosynthesis, shed light on TOF biological phenotypes. Additionally, ROC curves identified potential biomarkers, such as erythronic acid with an AUC of 0.868 in plasma, and 3-β-hydroxy-bisnor-5-cholenic acid, isocitric acid, glutaric acid, ortho-Hydroxyphenylacetic acid, picolinic acid with AUC close to 1 in tissue, whereas the discriminative performance of those substances significantly improved when combined with clinical phenotypes. Distinct metabolic profiles exhibited robust discriminatory capabilities, effectively distinguishing TOF from ASD patients. These metabolites may serve as biomarkers or key molecular players in the intricate metabolic pathways involved in CCHD development. Distinct metabolic profiles exhibited robust discriminatory capabilities, effectively distinguishing Tetralogy of Fallot from atrial septal defect patients. Similar profiling but inconsistent differential pathways between plasma and tissue. More than one-third metabolites in plasma and tissue are associated with the microbiome. The discovery of biomarkers is instrumental in facilitating early detection and diagnosis of Tetralogy of Fallot. Disturbed metabolism offers insights into interpretation of pathogenesis of Tetralogy of Fallot.

Parachlorometaxylenol stress caused multidrug-type antibiotic resistance genes proliferation via simultaneously reshaping microbial community and interfering metabolic traits during wastewater treatment process

Despite biological wastewater treatment processes (e.g., sequencing batch reactors (SBR)) being able to reduce the dissemination of antibiotic resistance genes (ARGs), the variation of ARGs under exogenous pollutant stress is an open question. This work investigated the impacts of para-chloro-meta-xylenol (PCMX, typical antibacterial contaminants) on ARGs spread in long-term SBR operation. Although the SBR process inherently decreased ARGs abundance, the presence of PCMX substantially amplified both the prevalence (mainly multidrug) and abundance of total ARGs (1.17-fold of the control). Further analysis demonstrated that PCMX disintegrated sludge structures as well as increased membrane permeability, facilitating the release of mobile genetic elements and subsequent horizontal transfer of ARGs. In addition, PCMX selectively enriched potential ARG hosts, notably Nitrospira and Candidatus Accumulibacter, which predominantly served as multidrug ARG hosts. Concurrently, the self-adaptive functions of ARGs hosts in the PCMX-exposed SBR system were activated via quorum sensing, two-component regulatory system, ATP-binding cassette transporters, and bacterial secretion system. The upregulation of these metabolic pathways also contributed to the dissemination of ARGs.

Metabolism-Based Herbicide Resistance to Mesosulfuron-methyl and Identification of Candidate Genes in Bromus japonicus.

The evolved resistance of Bromus japonicus Houtt. to ALS-inhibiting herbicides is well established. Previous studies have primarily focused on target-site resistance; however, non-target-site resistance has not been well characterized. This investigation demonstrated that ALS gene sequencing did not detect any previously known resistance mutations in a mesosulfuron-methyl-resistant (MR) population, and notably, treatment with the P450 monooxygenase (P450) inhibitor malathion markedly heightened susceptibility to mesosulfuron-methyl. Utilizing UPLC-MS/MS analysis confirmed elevated mesosulfuron-methyl metabolism in MR plants. The integration of Isoform Sequencing (Iso-Seq) and RNA Sequencing (RNA-Seq) facilitated the identification of candidate genes associated with non-target sites in a subpopulation with two generations of herbicide selection. Through qRT-PCR analysis, 21 differentially expressed genes were characterized, and among these, 10 genes (comprising three P450s, two glutathione S-transferases, one glycosyltransferase, two ATP-binding cassette transporters, one oxidase, and one hydrolase) exhibited constitutive upregulation in resistant plants. Our findings substantiated that increased herbicide metabolism is a driving force behind mesosulfuron-methyl resistance in this B. japonicus population.

24-epibrassinolide as a multidimensional regulator of rice (Oryza sativa) physiological and molecular responses under isoproturon stress

Brassinosteroids (BRs) can regulate various processes in plant development and defense against environmental stress. In this study, the contribution of BRs in the degradation of isoproturon (IPU) in rice has been established. IPU has a significant effect on rice growth, chlorophyll content, and membrane permeability. When treated with 1.0 μmol/L 24-epibrassinolide (EBR), a BR analogue, the associated symptoms of rice poisoning were alleviated as the IPU levels in the rice and growth media were decreased. In the presence of EBR, the activities of several IPU-related detoxification enzymes were enhanced to cope with the stress due to IPU. An RNA-sequencing (RNA-Seq) has been performed to determine the variation of transcriptomes and metabolic mechanisms in rice treated with EBR, IPU, or IPU+EBR. Some of the differentially expressed genes (DEGs) were Phase I-III reaction components of plants, such as cytochrome P450 (CYP450), glutathione S-transferase (GST), glycosyltransferases (GTs), and the ATP-binding cassette transporter (ABC transporter). The expression of some signal transduction genes was significantly up-regulated. The relative content of low-toxicity IPU metabolites increased due to the presence of EBR as determined by UPLC/Q-TOF-MS/MS. The IPU metabolic pathways include enzyme-catalyzed demethylation, hydroxylation, hydrolysis, glycosylation, and amino acid conjugation processes. The results suggest that EBR plays a key role in the degradation and detoxification of IPU. This study has provided evidence that BRs regulate the metabolism and detoxification of IPU in rice, and offers a new approach to ensuring cleaner crops by eliminating pesticide residues in the environment.

Reprogramming of RNA m6A Modification Is Required for Acute Myeloid Leukemia Development.

Hematopoietic homeostasis is maintained by hematopoietic stem cells (HSCs), and it is tightly controlled at multiple levels to sustain the self-renewal capacity and differentiation potential of HSCs. Dysregulation of self-renewal and differentiation of HSCs leads to the development of hematologic diseases, including acute myeloid leukemia (AML). Thus, understanding the underlying mechanisms of HSC maintenance and the development of hematologic malignancies is one of the fundamental scientific endeavors in stem cell biology. N 6-methyladenosine (m6A) is a common modification in mammalian messenger RNAs (mRNAs) and plays important roles in various biological processes. In this study, we performed a comparative analysis of the dynamics of the RNA m6A methylome of hematopoietic stem and progenitor cells (HSPCs) and leukemia-initiating cells (LICs) in AML. We found that RNA m6A modification regulates the transformation of long-term HSCs into short-term HSCs and determines the lineage commitment of HSCs. Interestingly, m6A modification leads to reprogramming that promotes cellular transformation during AML development, and LIC-specific m6A targets are recognized by different m6A readers. Moreover, the very long chain fatty acid transporter ATP-binding cassette subfamily D member 2 (ABCD2) is a key factor that promotes AML development, and deletion of ABCD2 damages clonogenic ability, inhibits proliferation, and promotes apoptosis of human leukemia cells. This study provides a comprehensive understanding of the role of m6A in regulating cell state transition in normal hematopoiesis and leukemogenesis, and identifies ABCD2 as a key factor in AML development.

Silencing MUC1 to regulate intracellular lipid metabolism: Overcoming sunitinib resistance and inhibiting metastasis in renal cell carcinoma

Renal cell carcinoma (RCC) has been extensively studied and is a paradigmatic example of a malignancy distinguished by metabolic reprogramming. Reprogramming lipid metabolism is crucial for determining the response and resistance to chemotherapy. To overcome this, we developed a modified nanomicelle delivery system comprising polyethyleneimine (PEI) as a positive charge donor and ibuprofen as the hydrophobic end. The overall system, denoted as SPPI, is PEGylated, conjugated with sialic acid, and plays a targeting role. This system successfully delivered siRNA to cancer cells by overcoming systemic and cellular barriers. The resulting conjugates form uniform, spherical nanomicelles (37.8 ± 0.9 nm; 25.5 ± 1.4 mV) with targeting ability, stability, efficient delivery, and low toxicity. The complicated and indirect way cholesterol affects ATP-binding cassette transporters was investigated. Administering SPPI/siMUC1 resulted in significant suppression of MUC1 expression and a 3.25-fold decrease in cholesterol synthesis compared to the control, and it subsequently reversed resistance to sunitinib by modulating P-GP, ABCG2, and MRP1 activities. Importantly, SPPI/siMUC1 nanomicelles demonstrated outstanding growth inhibition (72.2 %) of sunitinib-resistant 786-O cell xenografts and remarkable inhibitory effects on tumor metastasis (45.0 %) without observable systemic toxicity according to tissue analysis and weight change evaluation. The efficacy and safety of SPPI/siMUC1 in the treatment of ccRCC were demonstrated, especially after drug resistance develops. Thus, this study introduces a novel strategy for addressing drug resistance in metabolically active cancers by targeting the lipid metabolism pathway.

Novel functions of o-cymen-5-ol nanoemulsion in reversing colistin resistance in multidrug-resistant Klebsiella pneumoniae infections

Multidrug resistance (MDR) Klebsiella pneumoniae (K. pneumoniae) is a major emerging threat to human health, and leads to very high mortality rate. The effectiveness of colistin, the last resort against MDR Gram-negative bacteria, is significantly compromised due to the widespread presence of plasmid- or chromosome-mediated resistance genes. In this study, o-cymen-5-ol has been found to greatly restore colistin sensitivity in MDR K. pneumoniae. Importantly, this compound does not impact bacterial viability, induce resistance, or cause any noticeable cell toxicity. Various routes disclosed the potential mechanism of o-cymen-5-ol potentiating colistin activity against MDR K. pneumoniae. These include inhibiting the activity of plasmid-mediated mobile colistin resistance gene (mcr-1), accelerating lipopolysaccharide (LPS) − mediated membrane damage, and promoting the ATP-binding cassette (ABC) transporter pathway. To enhance the administration and bioavailability of o-cymen-5-ol, a nanoemulsion has been designed, which significantly improves the loading efficiency and solubility of o-cymen-5-ol, resulting in antimicrobial potentiation of colistin against K. pneumoniae infection. This study has revealed a new understanding of the o-cymen-5-ol nanoemulsion as a means to enhance the effectiveness of colistin against resistant factors. The finding also suggests that o-cymen-5-ol nanoemulsion could be a promising approach in the development of potential treatments for multidrug-resistant Gram-negative bacterial infections.

Coupling the role of lipids to the conformational dynamics of the ABC transporter P-glycoprotein

The ATP-binding cassette transporter P-glycoprotein (P-gp) is a multidrug efflux pump that is overexpressed in a variety of cancers and associated with the drug-resistance phenomenon. P-gp structures were previously determined in detergent and in nanodiscs, in which different transmembrane helix conformations were found, “straight” and “kinked,” respectively, indicating a possible role of the lipid environment on the P-gp structural ensemble. Here, we investigate the dynamic conformational ensembles and protein-lipid interactions of two human P-gp inward-open conformers, straight and kinked, employing all-atom molecular dynamics (MD) simulations in asymmetric multicomponent lipid bilayers that mimic the highly specialized hepatocyte membrane in which P-gp is expressed. The two conformers are found to differ in terms of the accessibility of the substrate cavity. The MD simulations show how cholesterol and different lipid species wedge, snorkel, and partially enter into the cavity of the straight P-gp conformer solved in detergent. However, access to the cavity of the kinked P-gp conformer solved in nanodiscs is restricted. Furthermore, the volume and dynamic fluctuations of the substrate cavity largely differ between the two P-gp conformers and are modulated by the presence (or absence) of cholesterol in the membrane and/or of ATP. From the mechanistic perspective, the findings indicate that the straight conformer likely precedes the kinked conformer in the functional working cycle of P-gp, with the latter conformation representing a post substrate-bound state. The inaccessibility of the main transmembrane cavity in the kinked conformer might be crucial in preventing substrate disengagement and transport withdrawal. Remarkably, in our unbiased MD simulations, one transmembrane helix (TM10) of the straight conformer underwent a spontaneous transition to a kinked conformation, underlining the relevance of both conformations in a native phospholipid environment and revealing structural descriptors defining the transition between the two P-gp conformers.