Search Results (59)

Dental enamel, the final product of amelogenesis, is a highly mineralized bioceramic that becomes acellular and non-regenerating after tooth eruption. This paper reviews literature that explores inorganic phosphate (Pi) transport during the process of enamel formation or amelogenesis. Evidence from transcriptomics, immunolocalization, and physiology implicates ameloblast-specific sodium-dependent Pi uptake by type III sodium–phosphate cotransporters SLC20A1 (PiT1) and SLC20A2 (PiT2), and by type IIb sodium–phosphate cotransporter SLC34A2 (NaPi-IIb) with stage-specific basal (proximal) or apical (distal) enrichment, and pH-dependent expression. Controlled Pi efflux to the enamel space has been partly attributed to xenotropic and polytropic retrovirus receptor (XPR1) mediated Pi export during maturation-stage amelogenesis. These amelogenesis-specific Pi fluxes operate within a polarized cellular framework in which Ca²⁺ delivery and extrusion, together with bicarbonate-based buffering regulated by cystic fibrosis transmembrane conductance regulator (CFTR), Solute carrier family 26 (SLC26) exchangers, anion exchanger 2 (AE2), and electrogenic sodium bicarbonate cotransporter 1 (NBCe1), at-least partially contribute to cellular Pi activity, and neutralize protons generated as the extracellular hydroxyapatite-based enamel matures. Disruption of phosphate handling reduces crystal growth and final mineral content of enamel, and produces hypomineralized or hypomature enamel with opacities, post-eruptive breakdown, and greater caries susceptibility. This review integrates multi-modal findings to appraise established features of ameloblast Pi handling, define constraints imposed by pH control and Ca²⁺ transport, and identify gaps in ion transporter topology and trafficking dynamics. Full article

This review conducts a bibliometric analysis of scientific literature on antibiotic resistance in Helicobacter pylori (H. Pylori), aiming to map scientific production, identify trends and key themes, analyze collaboration models, and highlight research gaps to inform research priorities and guide public health policies, amidst the growing challenge of multidrug resistance affecting treatment success. Background/Objectives: H. Pylori infection is usually contracted during childhood and often becomes chronic and asymptomatic in 80–90% of cases. Eradication requires complex treatments involving proton pump inhibitors and multiple antibiotics, but success rates have declined due to increased antibiotic resistance caused by genetic mutations, efflux mechanisms, altered membrane permeability, and biofilm formation. Reports indicate an alarming increase in multidrug resistance, affecting the effectiveness of treatments. Methods: The bibliometric analysis was performed using the Web of Science Core Collection (WoS) database, which provides comprehensive bibliographic data. Filters were applied for articles in English, reducing the set to 39,879 papers. The analysis was performed using the VOSviewer program (v1.6.20) to visualize co-author networks, citations, and keyword co-occurrence, and Microsoft Excel for processing and organization. Results: Editorial Trends: Over the last decade (2016–2025), interest in this topic has increased, with over 4000 publications annually in 2020, although a slight decline was observed in 2023. Leading Contributors: China is the most prolific author, followed by the USA and Japan. Cited Articles and Key Publications: Articles by prominent authors are frequently cited in 2022 and 2023, indicating their high relevance. Bibliographic Coupling Analysis: This revealed three main thematic clusters centered around research by specific authors. Keyword Analysis: A total of 57,462 terms were identified, of which 5292 appeared at least five times; “Helicobacter pylori” was the most frequent, followed by “infection” and “eradication.” Visualized terms highlight central areas of interest, such as “risk,” “cancer,” and “resistance”. Conclusions: This bibliometric analysis underscores a rising research focus on H. pylori antibiotic resistance, with recent publications providing essential clinical guidelines and epidemiological insights into the infection’s global impact. China leads in contributions, followed by the US and Japan. Significant articles by notable authors received many citations, emphasizing their significance. Full article

Background: Gold nanoparticles (AuNPs) have several beneficial properties that make them effective as intracellular drug carriers, and their potential for various diagnostic and therapeutic applications is gaining recognition. Depending on their size and shape, AuNPs can cross the central nervous system (CNS) through the blood–brain barrier (BBB). In the CNS, they can exert a variety of influences on neuronal and glial cells, which can be both supportive—promoting cell health and function—and cytotoxic, potentially leading to cellular damage. The hypothalamus (HT) is the first region where nanoparticles (NPs) interact, as this neuroendocrine center is particularly sensitive to factors in the systemic circulation due to its function and location. This area is affected by systemic factors, including pro-opiomelanocortin (POMC) neurons, which regulate metabolic function and maintain homeostasis. The activity of mitochondria within these cells influences their response to both external factors and the presence of AuNPs, thereby facilitating a complex interplay between nanoparticle interactions and cellular metabolism in this vital brain region. Aims: This study investigates how AuNPs, at different concentrations and exposure times under in vitro conditions, affect the mitochondrial activity of POMC neurons, aiming to provide a comprehensive understanding of the mechanisms in the HT. Methods: The study investigates the effect of varying gold nanoparticle concentrations on the mitochondrial activity of POMC neurons over treatment periods of 1, 15, 24, and 48 h. Mitochondrial activity was measured using a Seahorse XFp Analyzer to provide high-resolution insights. Additionally, mitochondrial functionality was assessed through the detection of reactive oxygen species (ROS) and cell viability. Results: The findings indicated that the effects of gold nanoparticles on mitochondrial activity depend significantly on their concentration and exposure time. Specifically, exposure leads to an increase in early response systems, the citric acid cycle, and proton efflux, ultimately resulting in the inhibition of mitochondrial function and ATP production in POMC cells. This disruption may affect hypothalamic regulation and energy metabolism. Full article

Helicobacter pylori is a Gram-negative bacterium that infects almost half of the global population and is linked to gastric conditions like peptic ulcers and gastric cancer, as well as other diseases such as neurological disorders, cardiovascular problems, and iron deficiency anemia. Its survival in the acidic stomach environment is due to virulence factors like urease, flagella, and adhesion proteins (BabA, SabA). Current treatments involve a combination of antibiotics (clarithromycin, metronidazole, amoxicillin, tetracycline) and proton pump inhibitors, but increasing antibiotic resistance, especially to clarithromycin and metronidazole, poses a major challenge. Resistance mechanisms include mutations in drug targets, efflux pump overexpression, and enzymatic degradation of antibiotics. This has prompted exploration of alternative therapies targeting bacterial processes like urease activity, biofilm formation, and metabolic pathways (energy production, amino acid synthesis, iron acquisition). Natural compounds, such as chitosan and plant extracts, show promise in combating H. pylori growth and virulence. Vaccine development is also ongoing, with DNA vaccines showing potential for broad immune responses. However, no vaccine is yet close to widespread clinical use. Full article

Background: The efflux system is one of the resistance mechanisms that bacteria use to reduce the effectiveness of antibiotics, leading to the development of multidrug resistance. To evaluate other treatment choices, esomeprazole (ESO), omeprazole (OME), pantoprazole (PAN), vitamin D (VD), and vitamin K (VK) were tested for potential efflux pump (EP)-inhibiting activity. Methods: The minimum inhibitory concentrations (MICs) of the tested drugs were determined against K. pneumoniae ATCC 51503 and P. aeruginosa PAO1. Quantitative estimation of the EP-inhibiting activity of the tested medications was phenotypically investigated with a semi-automated fluorometric system and genotypically confirmed by real-time polymerase chain reaction (RT-PCR). Data were confirmed through docking study. Results: K. pneumoniae ATCC 51503 and P. aeruginosa PAO1 were positive efflux standard strains. VD and VK revealed an MIC_VD of 625–1250 µg/mL and MIC_VK of 2500–5000 µg/mL, lower than what was detected for PPIs (MIC_PPIs = 16,000–32,000 µg/mL). Vitamins showed powerful anti-efflux activity with remarkable ethidium bromide accumulation in K. pneumoniae ATCC 51503 and P. aeruginosa PAO1. Also, VD and VK significantly lowered the MIC of ciprofloxacin by 64-fold. On the molecular level, OME showed a notable decrease in the relative expression of the efflux-encoding genes acrB and mexA by 91.5% and 99.7% in ATCC 51503 and PAO1, respectively. Conclusion: This study highlights the anti-efflux activity of ESO, OME, PAN, VD, and VK against the tested Gram-negative strains. Hence, these PPIs and vitamins could be valuable adjuvant treatments to enhance the effectiveness of curing infections caused by MDR strains. Full article

Helicobacter pylori is a Gram-negative bacterium from the Epsilonproteobacteria class, associated with various gastric diseases, including gastric cancer. It infects both adults and children, with a high prevalence in developing countries due to poor health conditions. The International Agency for Research on Cancer has classified H. pylori as a class I carcinogen, linked not only to gastric cancer but also to neurological disorders. Current treatment involves proton pump inhibitors combined with antibiotics for 10 to 14 days, but patient non-compliance can lead to increased antibiotic resistance. This review examines studies from the past decade that explore flavonoids as potential future treatments for H. pylori. Flavonoids like kaempferol, rutin, quercetin, myricetin, catechin, epicatechin, eupatilin, chrysin, apigenin, and hesperetin have been shown to regulate the expression of key H. pylori genes, alter cell membrane permeability, and affect proton efflux. These biomolecules, found in various plants, have demonstrated the potential to inhibit H. pylori, even in resistant strains. Gene expression and molecular docking studies reveal how these flavonoids interact with the membrane, bacterial genes, and proteins, affecting host cell transcription, translation, and bacterial adherence. While promising, clinical trials are needed to better understand their mechanisms and efficacy. Full article

Collateral sensitivity is an evolutionary trade-off for bacteria where acquiring resistance to one antibiotic results in an increased sensitivity to another antibiotic. This study was designed to evaluate the collateral sensitivity of methicillin-resistant Staphylococcus aureus (MRSA) to β-lactam antibiotics induced by the evolution of resistance to apramycin. Collateral sensitivity to ampicillin, cephazolin, ceftriaxone, cefotaxime, cefepime and cefquinome occurred after MRSA were exposed to apramycin and induced to acquire resistance. This sensitivity was associated with reduced β-lactamase activity and decreased expression of the mecA gene. We also found a decrease in the proton motive force and decreased efflux activity. These results provide new insights into collateral sensitivity-based strategies for the treatment of MRSA. Full article

Cation-pumping membrane pyrophosphatases (mPPases; EC 7.1.3.1) vary in their transport specificity from obligatory H⁺ transporters found in all kingdoms of life, to Na⁺/H⁺-co-transporters found in many prokaryotes. The available data suggest a unique “direct-coupling” mechanism of H⁺ transport, in which the transported proton is generated from nucleophilic water molecule. Na⁺ transport is best rationalized by assuming that the water-borne proton propels a prebound Na⁺ ion through the ion conductance channel (“billiard” mechanism). However, the “billiard” mechanism, in its simple form, is not applicable to the mPPases that simultaneously transport Na⁺ and H⁺ without evident competition between the cations (Na⁺,H⁺-PPases). In this study, we used a pyranine-based fluorescent assay to explore the relationship between the cation transport reactions catalyzed by recombinant Bacteroides vulgatus Na⁺,H⁺-PPase in membrane vesicles. Under appropriately chosen conditions, including the addition of an H⁺ ionophore to convert Na⁺ influx into equivalent H⁺ efflux, the pyranine signal measures either H⁺ or Na⁺ translocation. Using a stopped-flow version of this assay, we demonstrate that H⁺ and Na⁺ are transported by Na⁺,H⁺-PPase in a ratio of approximately 1:8, which is independent of Na⁺ concentration. These findings were rationalized using an “extended billiard” model, whose most likely variant predicts the kinetic limitation of Na⁺ delivery to the pump-loading site. Full article

Understanding carboxylate transport through lipid membranes under physiological conditions is critical in biomedicine and biotechnology, as it allows for the emulation of biological membrane functions and can enhance the absorption of hydrophobic carboxylate-based drugs. However, the structural diversity of carboxylates has made it challenging to study their transport, and the limited available examples do not provide a comprehensive understanding of the role of the organic moiety in this process. Here, we present an in-depth analysis of the diffusion and transport of various aliphatic and aromatic carboxylates into liposomes. We assessed the influence of their size, number of carboxylate groups, and presence of hydroxyl groups. Our findings from fluorescence assays, using lucigenin and HPTS as probes, revealed that most carboxylates can spontaneously diffuse into liposomes in their protonated state, facilitated by the efflux of HNO₃ when using NaNO₃ solutions at pH 7. The Cl-ISE assay showed chloride/carboxylate exchange by a synthetic anion transporter. Clear trends were observed when the organic moiety was systematically varied, with a particular enhancement of anion transport by the presence of hydroxyl groups in the aromatic carboxylates. Our findings provide insights into the processes by which carboxylates can enter liposomes, which can contribute to understanding the transport of other biologically relevant organic anions. Full article

In the small intestine, nutrients from ingested food are absorbed and broken down by enterocytes, which constitute over 95% of the intestinal epithelium. Enterocytes demonstrate diet- and segment-dependent metabolic flexibility, enabling them to take up large amounts of glutamine and glucose to meet their energy needs and transfer these nutrients into the bloodstream. During glycolysis, ATP, lactate, and H⁺ ions are produced within the enterocytes. Based on extensive but incomplete glutamine oxidation large amounts of alanine or lactate are produced. Lactate, in turn, promotes hypoxia-inducible factor-1α (Hif-1α) activation and Hif-1α-dependent transcription of various proton channels and exchangers, which extrude cytoplasmic H⁺-ions into the intestinal lumen. In parallel, the vitamin C-dependent and duodenal cytochrome b-mediated conversion of ferric iron into ferrous iron progresses. Finally, the generated electrochemical gradient is utilized by the divalent metal transporter 1 for H⁺-coupled uptake of non-heme Fe²⁺-ions. Iron efflux from enterocytes, subsequent binding to the plasma protein transferrin, and systemic distribution supply a wide range of cells with iron, including erythroid precursors essential for erythropoiesis. In this review, we discuss the impact of vitamin C on the redox capacity of human erythrocytes and connect enterocyte function with iron metabolism, highlighting its effects on erythropoiesis. Full article

The opening of the Torpedo CLC-0 chloride (Cl⁻) channel is known to be regulated by two gating mechanisms: fast gating and slow (common) gating. The structural basis underlying the fast-gating mechanism is better understood than that of the slow-gating mechanism, which is still largely a mystery. Our previous study on the intracellular proton (H⁺_i)-induced inhibition of the CLC-0 anionic current led to the conclusion that the inhibition results from the slow-gate closure (also called inactivation). The conclusion was made based on substantial evidence such as a large temperature dependence of the H⁺_i inhibition similar to that of the channel inactivation, a resistance to the H⁺_i inhibition in the inactivation-suppressed C212S mutant, and a similar voltage dependence between the current recovery from the H⁺_i inhibition and the recovery from the channel inactivation. In this work, we further examine the mechanism of the H⁺_i inhibition of wild-type CLC-0 and several mutants. We observe that an anion efflux through the pore of CLC-0 accelerates the recovery from the H⁺_i-induced inhibition, a process corresponding to the slow-gate opening. Furthermore, various inactivation-suppressed mutants exhibit different current recovery kinetics, suggesting the existence of multiple inactivated states (namely, slow-gate closed states). We speculate that protonation of the pore of CLC-0 increases the binding affinity of permeant anions in the pore, thereby generating a pore blockage of ion flow as the first step of inactivation. Subsequent complex protein conformational changes further transition the CLC-0 channel to deeper inactivated states. Full article

Advanced urothelial bladder cancer (UBC) patients are tagged by a dismal prognosis and high mortality rates, mostly due to their poor response to standard-of-care platinum-based therapy. Mediators of chemoresistance are not fully elucidated. This work aimed to study the metabolic profile of advanced UBC, in the context of cisplatin resistance. Three isogenic pairs of parental cell lines (T24, HT1376 and KU1919) and the matching cisplatin-resistant (R) sublines were used. A set of functional assays was used to perform a metabolic screening on the cells. In comparison to the parental sublines, a tendency was observed towards an exacerbated glycolytic metabolism in the cisplatin-resistant T24 and HT1376 cells; this glycolytic phenotype was particularly evident for the HT1376/HT1376R pair, for which the cisplatin resistance ratio was higher. HT1376R cells showed decreased basal respiration and oxygen consumption associated with ATP production; in accordance, the extracellular acidification rate was also higher in the resistant subline. Glycolytic rate assay confirmed that these cells presented higher basal glycolysis, with an increase in proton efflux. While the results of real-time metabolomics seem to substantiate the manifestation of the Warburg phenotype in HT1376R cells, a shift towards distinct metabolic pathways involving lactate uptake, lipid biosynthesis and glutamate metabolism occurred with time. On the other hand, KU1919R cells seem to engage in a metabolic rewiring, recovering their preference for oxidative phosphorylation. In conclusion, cisplatin-resistant UBC cells seem to display deep metabolic alterations surpassing the Warburg effect, which likely depend on the molecular signature of each cell line. Full article

Xenopus oocytes represent one of the most versatile model systems for characterizing the properties of membrane transporters. However, for studying proton-coupled antiporters, the use of Xenopus oocytes has so far been limited to so-called injection-based transport assays. In such assays, where the compound is injected directly into the oocytes’ cytosol and transport is detected by monitoring substrate efflux, poor control over internal diffusion and concentration are incompatible with mechanistic characterizations. In this study, we present an inverse pH-gradient transport assay. Herein, an outward-facing proton gradient enables the characterization of proton antiporters via facile import-based transport assays. We describe two approaches for establishing sustained outward-facing proton gradients across the oocyte membrane, namely by applying alkaline external conditions or through surprisingly stable carbonyl cyanide m-chlorophenyl-hydrazone (CCCP)-mediated acidification of the cytosol. Previously, genetic evidence has shown that DTX18 from Arabidopsis thaliana is essential for the deposition of the hydroxycinnamic acid amide p-coumaroylagmatine (coumaroylagmatine) defence compound on the leaf surface. However, direct evidence for its ability to transport coumarol-agmatine has not been provided. Here, using Xenopus oocytes as expression hosts, we demonstrate DTX18’s ability to transport coumaroyl-agmatine via both injection-based and inverse pH-gradient transport assays. Notably, by showing that DTX18 is capable of accumulating its substrate against its concentration gradient, we showcase the compatibility of the latter with mechanistic investigations. Full article

Efflux pumps play important roles in bacterial detoxification and some of them are stress-response elements that are up-regulated when the host is treated with antibiotics. However, efflux pumps that are down-regulated by stimulations are rarely discovered. Herein, we analyzed multiple transcriptome data and discovered a special (Major Facilitator Superfamily) MFS efflux pump, KpsrMFS, from Klebsiella pneumoniae, which was down-regulated when treated with antibiotics or extra carbon sources. Interestingly, overexpression of kpsrmfs resulted in halted cell growth in normal conditions, while the viable cells were rarely affected. The function of KpsrMFS was further analyzed and this efflux pump was determined to be a proton-driven transporter that can reduce the intracellular tetracycline concentration. In normal conditions, the expression of kpsrmfs was at a low level, while artificial overexpression of it led to increased endogenous reactive oxygen species (ROS) production. Moreover, by comparing the functions of adjacent genes of kpsrmfs, we further discovered another four genes that can confer similar phenotypes, indicating a special regulon that regulates cell growth. Our work provides new insights into the roles of efflux pumps and suggests a possible regulon that may regulate cell growth and endogenous ROS levels. Full article

High concentrations of sodium (Na⁺), chloride (Cl⁻), calcium (Ca²⁺), and sulphate (SO₄²⁻) are frequently found in saline soils. Crop plants cannot successfully develop and produce because salt stress impairs the uptake of Ca²⁺, potassium (K⁺), and water into plant cells. Different intracellular and extracellular ionic concentrations change with salinity, including those of Ca²⁺, K⁺, and protons. These cations serve as stress signaling molecules in addition to being essential for ionic homeostasis and nutrition. Maintaining an appropriate K⁺:Na⁺ ratio is one crucial plant mechanism for salt tolerance, which is a complicated trait. Another important mechanism is the ability for fast extrusion of Na⁺ from the cytosol. Ca²⁺ is established as a ubiquitous secondary messenger, which transmits various stress signals into metabolic alterations that cause adaptive responses. When plants are under stress, the cytosolic-free Ca²⁺ concentration can rise to 10 times or more from its resting level of 50–100 nanomolar. Reactive oxygen species (ROS) are linked to the Ca²⁺ alterations and are produced by stress. Depending on the type, frequency, and intensity of the stress, the cytosolic Ca²⁺ signals oscillate, are transient, or persist for a longer period and exhibit specific “signatures”. Both the influx and efflux of Ca²⁺ affect the length and amplitude of the signal. According to several reports, under stress Ca²⁺ alterations can occur not only in the cytoplasm of the cell but also in the cell walls, nucleus, and other cell organelles and the Ca²⁺ waves propagate through the whole plant. Here, we will focus on how wheat and other important crops absorb Na⁺, K⁺, and Cl⁻ when plants are under salt stress, as well as how Ca²⁺, K⁺, and pH cause intracellular signaling and homeostasis. Similar mechanisms in the model plant Arabidopsis will also be considered. Knowledge of these processes is important for understanding how plants react to salinity stress and for the development of tolerant crops. Full article