Search Results (1,211)

In this review we propose the hypothesis that an energy-dissipating process precedes the continuous stimulation of insulin secretion by glucose. This process is mediated by connexin 36 hemichannels (Cx36H), or Cx36 connexons. Cx36H oligomers are expressed at the plasma membrane, and their gating activity (opening) is activated by plasma membrane depolarization after the closure of K⁺ATP channels by glucose (>5 mM) metabolism. This initial depolarization (1st step) might be responsible for the first phase of insulin secretion, with the subsequent opening of Cx36H increasing β-cell plasma membrane permeability, allowing for the efflux of metabolites (less than 1KD) (GABA, adenine nucleotides) and K⁺ (2nd step). This provokes a breakdown of oxidative glucose metabolism and the repolarization of the plasma membrane. As the extracellular glucose concentration increases further (>>5 mM), it exerts a progressive inhibition effect on Cx36H opening, allowing for the continuous stimulation of insulin secretion (3d step, second phase,). The glucose feature of regulating Cx36H closing with sigmoidal kinetics (8 mM IC₅₀ and around 20 mM at maximum) has been confirmed in mouse Cx36 connexin expression in Xenopus oocytes and in mouse islets stimulated by a range of glucose concentrations in the presence of 70 mM KCl. This gating activity was also inhibited by some non-metabolized glucose analogs. Glucose inhibition of Cx3H opening might not only contribute to making the insulin secretory response more specific for glucose but might also play a role in the pulsatility of sustained insulin secretion. Cx36H opening also offers the opportunity to potentiate the secretory effect in vivo by, permeant or not, metabolic stimuli. Confirmation of this novel physiological role for Cx36H in β-cells would place them as new susceptibility locus for type 1 and type 2 diabetes, whose physiological implication in the mechanism of insulin secretion regulation should be evaluated by in vivo studies in diabetic patients. Full article

Upon reacting with cellular components, Hg(II) ions elicit the production of reactive oxygen species (ROS). While the ROS-promoted cytotoxic and genotoxic effects induced by Hg(II) have been widely described in eukaryotes, such effects have been less studied in bacteria. In this work, the prokaryotic environmental model Bacillus subtilis was employed to evaluate the cytotoxic and genotoxic impact of Hg(II) over strains proficient or deficient in SOS, general stress and antioxidant responses, as well as the global transcriptional response elicited by this ion. The exposure to HgCl₂ significantly increased the mutation frequency to rifampicin resistance (Rif^R) in WT and mutant strains, suggesting a major contribution of these pathways in counteracting the genotoxic effects of Hg(II). Detection of A → T and C → G transversion mutations in the rpoB gene of Hg(II)-exposed cells suggested the generation of 8-oxo-guanines (8-OxoGs) and other oxidized DNA bases. The RNA-seq study revealed upregulation of genes involved in efflux and/or reduction of metal ions, synthesis of sulfur-containing molecules, and downregulation of genes implicated in iron metabolism and cell envelope stress. Therefore, our results indicate that metal extrusion and scavenging of Hg(II) by thiol-rich molecules may constitute a line of defense of B. subtilis that counteracts the noxious effects of ROS resulting from an imbalance in iron metabolism elicited by this ion. Full article

Background/Objectives: This study investigated the flavonoid enrichment and antimicrobial activity of the ethyl acetate fraction (EAF) obtained from Croton blanchetianus (Euphorbiaceae) leaves against Staphylococcus aureus, including the methicillin-resistant strains (MRSA) that were isolated, as well as its possible mechanism of action. Methods: Croton blanchetianus leaves were extracted with ethanol:water (50%), then the extract was spray-dried and partitioned (8×) with ethyl acetate. Phytochemical analysis was performed using thin layer chromatography (TLC), while antibacterial activity was conducted using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods. Results: Chemical profiling (TLC) confirmed multiple flavonoid bands and the presence of hyperoside; the total flavonoid content in the EAF reached 25.3% (≈2.28× the spray-dried extract and 6.65× the aqueous fraction). The MIC and MBC assays against S. aureus ATCC 29213 and six clinical isolates showed an MIC of 4–32 μg/mL and an MBC of 16–64 μg/mL for EAF. The combination of EAF with chloramphenicol showed a complete synergistic effect for S. aureus ATCC 29213 and S. aureus UFPEDA 705, a partial effect for S. aureus UFPEDA-659 and S. aureus UFPEDA-671, antagonistic effect for S. aureus UFPEDA 731 and S. aureus UFPEDA 802, and no effect for S. aureus UFPEDA-691. Growth curves indicated time- and concentration-dependent inhibition. Membrane integrity assays revealed K⁺ efflux and release of DNA/RNA and proteins, suggesting bacterial membrane destabilization as a likely mechanism. Conclusions: The flavonoid-rich fraction of C. blanchetianus exhibits potent anti-S. aureus activity, including MRSA. Furthermore, it was observed that EAF has a synergistic effect with chloramphenicol and acts through membrane damage, making it a candidate for a phytoderived adjuvant in antimicrobial therapies. Full article

Dermatophilosis, caused by the Gram-positive, filamentous bacterium Dermatophilus congolensis, is an important skin disease that adversely affects cattle health and productivity. It also affects other domestic and wild animals and occasionally humans. This review provides a detailed overview of the molecular characteristics and resistome profile of D. congolensis, highlighting recent advances in genomic research. We examine the bacterium’s genome architecture, including its genome size, GC content, gene composition, and phylogenetic placement within the Actinomycetales. Key virulence factors are discussed, including proteolytic enzymes, hyphal invasion, zoospore motility, and the gene products of nasp and agac, emphasizing their roles in tissue invasion, pathogenesis, and diagnostic detection. Furthermore, we analyze resistome, focusing on identified antibiotic resistance genes, diverse resistance mechanisms such as efflux pumps and beta-lactamases, and the contribution of mobile genetic elements to horizontal gene transfer. The implications of these molecular insights for accurate diagnosis, effective treatment, and antibiotic stewardship in cattle production are critically evaluated. Finally, we highlight future research priorities aimed at deepening our understanding of D. congolensis biology and improving strategies for disease control. This review underscores the importance of integrating molecular surveillance with antimicrobial monitoring to safeguard cattle health and promote sustainable livestock management. Full article

Resistance to conventional anti-tumor drugs is one of the significant challenges in oncology, responsible for treatment failure and patient death. Introduction of the targeted drugs (e.g., small molecule tyrosine kinase inhibitors (TKIs) and monoclonal antibodies) in cancer therapy significantly improved overall survival (OS) and progression-free survival (PFS) rates for selected groups of cancer patients and delayed the progression of advanced forms of human malignancies. However, the development of secondary resistance to the targeted drugs remains an unbeatable obstacle to a successful outcome in the long run, thereby making prognosis unfavorable for cancer patients with advanced, recurrent, and metastatic forms of disease. The review focuses on several mechanisms that regulate cancer resistance to conventional chemotherapies. This includes the upregulation of main types of ABC transporters (e.g., ABCB1, ABCC1, and ABCG2), which provides the efflux of chemotherapeutic agents from cancer cells. Additionally, the activation of diverse DNA damage repair (DDR) pathways, epithelial-to-mesenchymal transition (EMT), and the population of cancer stem cells (CSCs) are also discussed in detail, thereby illustrating the diverse molecular mechanisms of cancer sensitivity to chemotherapies. Recently, several TKIs, including those that were initially developed to specifically target FGFR and VEGFR pathways, have also been reported to exhibit “off-target” effects by interacting with ABC transporters and inhibiting their function. This, in turn, illustrates their potency in retaining chemotherapeutic agents within cancer cells and possessing a chemosensitizing function. Of note, FGFR and VEGFR inhibitors may behave as inhibitors or substrates of ABC transporters, depending on the expression of specific pumps and affinity for them, concentrations, and types of co-administered agents, thereby disclosing the complexity of this scenario. Additionally, the aforementioned RTKI can interfere with the other molecular mechanisms regulating tumor sensitivity to conventional chemotherapies, including the regulation of diverse DDR pathways, EMT, and the population of CSCs. Thereby, the aforementioned “off-target” functions of FGFR and VEGFR inhibitors can open novel approaches towards anti-cancer therapies and strategies aimed at counteracting cancer multidrug resistance (MDR), which is important especially as second- or third-line treatments in patients who have progressed on modern chemotherapeutic regimens. Notably, the strategy of using TKIs to potentiate the clinical efficacy of chemotherapies can extend beyond inhibitors of FGFR and VEGFR signaling pathways, thereby providing a rationale for repurposing existing TKIs as an attractive therapeutic approach to overcome cancer chemoresistance. Full article

Bacteriocins from lactic acid bacteria have attracted considerable attention as natural alternatives to conventional antimicrobial agents. Weissellicin LM85, a bacteriocin purified from Weissella confusa LM85, has been less extensively studied in terms of its mechanism of action and potential applications. In this study, purified weissellicin LM85 exhibited potent inhibitory effects against Gram-positive bacteria, with minimum inhibitory and bactericidal concentrations determined against Micrococcus luteus MTCC106. Time-kill assays and fluorescence staining indicated a concentration-dependent reduction in cell viability, accompanied by membrane disruption. Further analyses revealed potassium ion efflux, dissipation of membrane potential (Δψ) and pH gradient (ΔpH), genomic DNA fragmentation, and pronounced morphological alterations in target cells. These findings are strongly suggestive of membrane-targeted bactericidal activity, likely involving pore-forming effects. In addition, weissellicin LM85 inhibited both growth and biofilm formation of Salmonella enterica subsp. enterica serovar Typhimurium ATCC13311 and Staphylococcus aureus subsp. aureus ATCC25923. Mechanistic analyses revealed the disruption of cell membrane integrity, leakage of potassium ions, cytoplasmic contents, and non-specific DNA degradation, indicating a multifaceted antibacterial mode of action. These findings highlight weissellicin LM85 as a promising natural antimicrobial with potential applications in food preservation and the control of foodborne pathogens and biofilm-associated infections. Further studies on cytotoxicity and in vivo efficacy are required to advance its practical application. Full article

The escalating global threat of antimicrobial resistance (AMR) necessitates innovative therapeutic strategies beyond traditional antibiotic development. Drug repurposing offers a rapid, cost-effective approach by identifying new antibacterial applications for existing non-antibiotic drugs with established safety profiles. Emerging evidence indicates that diverse classes of non-antibiotic drugs, including non-steroidal anti-inflammatory drugs (NSAIDs), statins, antipsychotics, calcium channel blockers and antidepressants, exhibit intrinsic antibacterial activity, or potentiate antibiotic efficacy. This review critically explores the mechanisms by which drugs that are not recognised as antibiotics exert antibacterial effects, including efflux pump inhibition, membrane disruption, biofilm inhibition, and quorum sensing interference. We discuss specific examples that demonstrate reductions in minimum inhibitory concentrations (MICs) of antibiotics when combined with these drugs, underscoring their potential as antibiotic adjuvants. Furthermore, we examine pharmacokinetic considerations, toxicity challenges, and clinical feasibility for repurposing these agents as standalone antibacterials or in combination therapies. Finally, we highlight future directions, including the integration of artificial intelligence and machine learning to prioritise drug candidates for repurposing, and the development of targeted delivery systems to enhance bacterial selectivity while minimising host toxicity. By exploring the overlooked potential of non-antibiotic drugs, this review seeks to stimulate translational research aimed at leveraging these agents in combating resistant bacterial infections. Nonetheless, it is crucial to acknowledge that such drugs may also pose unintended risks, including gut microbiota disruption and facilitation of resistance development. Hence, future research should pursue these opportunities with equal emphasis on efficacy, safety, and resistance mitigation. Full article

Background: Multidrug resistance (MDR), primarily driven by P-glycoprotein (P-gp)-mediated drug efflux, presents a significant challenge in cancer therapy, contributing to chemotherapy failure and poor patient outcomes. Objectives: In this study, we explored the potential of manidipine (MA), a clinically approved calcium channel blocker, to reverse P-gp-mediated MDR through modulation of calcium signaling via nuclear factor of activated T cells 2 (NFAT2). Methods: Paclitaxel (PTX) resistance ABCB1-overexpressing cancer in vitro and in vivo were used for evualting the anti-MDR effects of MA, as well as the underlying mechanism with siRNA of NFAT2. Results: We found that MA at non-toxic concentrations (0.6–5.4 μM) significantly sensitize drug-resistant colorectal (HCT-8/T) and non-small cell lung (A549/T) cells to PTX, reducing its IC₅₀ by up to 1328-fold in vitro models. Mechanistically, MA inhibited P-gp efflux activity without altering its expression, as shown by an increased intracellular accumulation of doxorubicin and Flutax-2 (2.3- and 3.1-fold, respectively) and dose-dependent modulation of ATPase activity (EC₅₀ = 4.16 μM). Notably, MA reduced intracellular calcium levels (52% reduction, p < 0.001) and downregulated NFAT2, an oncogene overexpressed in resistant cells. In vivo, MA (3.5 mg/kg) synergizes with PTX to inhibit tumor growth by 68% (p < 0.001) in A549/T xenograft model, without an observable decrease in weight. Conclusions: In sum, all these results position MA as a novel NFAT2 inhibitor to overcome P-gp-mediated MDR via modulating calcium signaling, which points to further investigation for its clinical applications. Full article

Background/Objectives: Urinary tract infections (UTIs) represent a major healthcare challenge due to antimicrobial resistance and biofilm formation. Our aim was to evaluate whether repurposed drugs and efflux pump inhibitors (EPIs) could provide alternative strategies by investigating their antibacterial, anti-biofilm, and resistance-modifying properties against Gram-negative uropathogens under varying pH conditions. Methods: Clinical isolates of Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis were tested. Minimum inhibitory concentrations (MICs) of thioridazine (TZ), promethazine (PMZ), fluoxetine (Fx), sertraline (Sr), phenylalanine arginine β-naphthylamide (PAβN), carbonyl cyanide m-chlorophenyl hydrazone (CCCP), and the glutamine uptake inhibitor V9302 were determined at pH 5–8. Biofilm inhibition was assessed by crystal violet staining, while MIC reduction assays tested antibiotic combinations. Efflux pump inhibition was examined using an ethidium bromide accumulation assay. Results: TZ reduced biofilm formation in sensitive K. pneumoniae at all pH levels and enhanced ciprofloxacin (CIP) activity, whereas PMZ showed a weaker effect, limited mainly to neutral pH. Fx and Sr exhibited pH-dependent anti-biofilm activity, with Fx particularly effective against P. mirabilis at alkaline pH. PAβN consistently decreased biofilm biomass in both sensitive and resistant K. pneumoniae and, at pH 7–8, potentiated CIP activity with a 16-fold MIC reduction in the sensitive strain. CCCP showed pH-dependent activity, with stronger effects under acidic conditions, notably in E. coli and P. mirabilis. V9302 was a potent biofilm inhibitor in K. pneumoniae and resistant E. coli and interfered with efflux activity, showing strong effects in acidic environments. Conclusions: Repurposed drugs and EPIs may be useful as antibiotic adjuvants or biofilm inhibitors in treating resistant UTIs. Full article

Antimicrobial resistance (AMR) is traditionally discussed in the context of horizontally acquired resistance genes and point mutations at target loci. However, this gene-centred model fails to account for a large number of clinically important modalities of resistance. There is now substantial evidence implicating bacteria in the ability to escape the effects of antibiotics in a variety of non-canonical ways, which are not considered in traditional diagnostic and surveillance pipelines. Among these factors, we can list those arising from global regulatory networks, phase variability, epigenetic tuning, small RNAs, genome structural variability, and phenotypic states like tolerance and persistence. This review will blend the current knowledge on these alternative pathways of resistance and underscore how they intersect with canonical genetic determinants. We will highlight cases where resistance emerges in the absence of known resistance genes, analyse the role of regulatory plasticity in efflux pump expression and membrane remodelling, and examine the contributions of bacterial stress responses and post-transcriptional control. Additionally, we will address methodological gaps in the detection of these mechanisms and their implications for clinical treatment failure, resistance surveillance, and drug development. By integrating insights from molecular microbiology, systems biology, and genomics, this review aims to offer a framework for understanding AMR as a multifaceted, context-dependent phenotype, not merely a genotype. We conclude by identifying knowledge gaps and suggesting priorities for research and diagnostic innovation in this evolving field. Full article

Background/Objectives: Homotypic targeting refers to the ability of cells to preferentially interact with other cells of the same type. An understanding of how cells use homotypic targeting (self-homing) characteristics for tumor-targeting purposes may aid in the effective delivery of radionuclides or other drugs for imaging or therapeutic applications. Additionally, studies investigating the targeting properties of cells from the same lineage may shed light on this interesting mechanism, allowing it to be harnessed for other applications. The objective of this study was to assess the tumor-self targeting potential of PC3 prostate cancer and 4T1 breast cancer cells using a direct cell labeling technique, with a focus on evaluation of cellular labeling efficiency, cell viability, cellular efflux, and in vivo tumor-self targeting capability using both identical and dissimilar tumor models. Methods: [⁸⁹Zr]Zr-oxine was prepared and utilized for the labeling of PC3 and 4T1 cells. Following the assessment of cell labeling efficacy, viability, and efflux, PET/CT imaging and biodistribution studies were conducted with [⁸⁹Zr]Zr-oxine labeled PC3 and 4T1 cells in PC3 and 4T1 tumor-bearing mice models. Results: Both PC3 cells and 4T1 cells were radiolabeled with [⁸⁹Zr]oxine, with PC3 cells illustrating a higher labeling efficiency (86.55 ± 0.38%) than 4T1 cells (46.95 ± 1.47%). Notably, radiolabeled PC3 cells illustrated significant uptake in PC3 tumors (7.54 ± 1.07%ID/gram at 24 h and 6.95 ± 3.56%ID/gram at 48 h) with lower tumor uptake in the 4T1 xenograft model (1.79 ± 0.29%ID/gram at 24 h and 1.42 ± 0.71%ID/gram at 48 h), illustrating the potential of self-targeting. Conclusions: Both PC3 and 4T1 cells followed a similar pattern of biodistribution, with labeled PC3 cells demonstrating lower blood retention and reduced uptake in non-target organs such as lungs and heart. Taken together, these results may indicate that PC3 cells illustrate homotypic targeting, warranting further investigation of this phenomenon. Full article

The treatment of azole-resistant Trichophyton indotineae poses a significant challenge for clinicians worldwide. Resistance mechanisms include amino acid substitutions in the sterol 14-α demethylase gene Erg11B, as well as overexpression of Erg11B. Additionally, efflux mechanisms mediated by fungal transporter proteins contribute to antifungal resistance. Therefore, the inhibition of fungal efflux transporters using known inhibitors could be a promising strategy to prevent treatment failure. The inhibitory effects of itraconazole in combination with various efflux pump inhibitors were evaluated. Co-treatment with quinine hydrochloride and itraconazole did not lead to a significant reduction in the inhibitory concentration (IC) values in T. indotineae isolates. In contrast, ritonavir lowered IC values by approximately 50% without affecting fungal growth when applied as monotherapy. The most pronounced effect was observed with sertraline, which demonstrated intrinsic antifungal activity at higher concentrations. When combined with itraconazole, sertraline reduced IC values to below 10% in both susceptible and resistant strains, enhancing itraconazole efficacy markedly. The increasing prevalence of antifungal resistance is a growing global health concern. These findings suggest that sertraline holds considerable potential as an adjunctive therapy for the treatment of dermatomycoses. Full article

Pancreatic ductal adenocarcinoma (PDAC) is a highly heterogeneous cancer with a severe stromal reaction mediated by pancreatic stellate cells (PSCs), leading to increased resistance to chemotherapy and radiotherapy. Following a repurposing concept, this preclinical study investigates the potential of approved drugs, known to be modulators of cellular copper transport, in combination with cisplatin for therapeutic approaches in PDAC. Two major strategies were pursued: (i) inhibiting copper transporters ATP7A and B with tranilast (TR) and omeprazole (OM) to block the cellular copper and, potentially, also cisplatin efflux, and (ii) using the chelator elesclomol (ES) to elevate intracellular copper and cisplatin levels. Human cell lines PanC-1 (PDAC), HPaSteC (PSC), and their co-culture, as well as the hepatocellular carcinoma cell line HepG2 as a reference model, were used. In addition to an analysis of the expression of copper transport proteins, the dynamics of cellular copper uptake and transport were monitored using a [⁶⁴Cu]CuCl₂ radiotracer approach. In vitro, all drugs enhanced cellular copper uptake and/or reduced copper efflux. Moreover, all drugs contributed to the enhanced cellular anticancer activity of cisplatin, with ES being the most effective compound. The results suggest that the targeted modulation of copper transport mechanisms may offer novel adjuvant approaches for the treatment of PDAC. Full article

Background:Klebsiella pneumoniae is a highly dangerous microorganism that presents significant challenges to effectively eliminate in food production facilities, making it a serious and urgent public health concern. The wet markets of Hong Kong represent a considerable yet insufficiently explored source for the spread of microorganisms. Methods: This investigation employed whole-genome sequencing and comparative genomics to assess the genomic variation and adaptive traits of K. pneumoniae extracted from wooden cutting boards in these marketplaces. We examined four wet market isolates in conjunction with 39 publicly accessible genomes from diverse origins. Results: Pan-genome analysis revealed a diverse and open genetic structure significantly shaped by horizontal gene transfer. Phylogenetic reconstruction did not categorize the wet market isolates into a singular clade, indicating varied contamination sources; nonetheless, certain market isolates exhibited close phylogenetic affiliations with high-risk clinical clones, implying possible spillover events. These isolates exhibited a concerning variety of antimicrobial resistance genes (ARGs), chiefly encoding efflux pumps (acrAB, oqxAB), which confer resistance to numerous drug categories. Moreover, the evaluation for pathogenicity attributes uncovered genes associated with robust biofilm development (fim and mrk operons) and efficient iron procurement strategies. Conclusions: The existence of these genetically adaptable isolates, possessing multidrug resistance and virulence factors, renders wet markets potential amplifiers and reservoirs for the spread of resistant pathogens. These findings present the initial genomic evidence of such risks in Hong Kong’s wet markets and emphasize the immediate necessity for improved hygiene protocols and comprehensive One Health surveillance to reduce transmission at the human–animal–environment interface. Full article

Urinary tract infections (UTIs) remain a major global health concern, with rising antimicrobial resistance prompting the search for alternative therapies. Selenium nanoparticles (Se NPs) are promising antimicrobial agents due to their unique physicochemical properties and ability to disrupt bacterial physiology. This study evaluated the antibacterial efficacy of Se NPs against four uropathogens and conducted comparative proteomic analyses to elucidate stress responses. Enumeration assays showed that Se NPs effectively inhibited bacterial growth, with Pseudomonas aeruginosa being the most susceptible and Proteus mirabilis the most resistant. Microscopy revealed Se NP-induced membrane rupture and cellular deformation across all species. Proteomic and bioinformatic analyses showed more pronounced protein regulation in P. mirabilis than in P. aeruginosa. Cluster of Orthologous Groups (COG) analysis revealed both shared and species-specific responses, while Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated activation of key stress pathways. Virulence-associated proteins were modulated in both species, with P. mirabilis uniquely upregulating stress survival and exotoxin-related proteins. Both regulated efflux pumps, suggesting active transport mitigates Se NP toxicity. P. aeruginosa showed mercury resistance, while P. mirabilis expressed tellurite resistance proteins. These findings highlight distinct yet overlapping strategies and support the potential of Se NPs in novel antimicrobial development. Full article