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Antibiotics (Basel, Switzerland) Dec 2023Antibiotics, which hit the market with astounding impact, were once called miracle drugs, as these were considered the ultimate cure for infectious diseases in the... (Review)
Review
Antibiotics, which hit the market with astounding impact, were once called miracle drugs, as these were considered the ultimate cure for infectious diseases in the mid-20th century. However, today, nearly all bacteria that afflict humankind have become resistant to these wonder drugs once developed to stop them, imperiling the foundation of modern medicine. During the COVID-19 pandemic, there was a surge in macrolide use to treat secondary infections and this persistent use of macrolide antibiotics has provoked the emergence of macrolide resistance. In view of the current dearth of new antibiotics in the pipeline, it is essential to find an alternative way to combat drug resistance. Antibiotic potentiators or adjuvants are non-antibacterial active molecules that, when combined with antibiotics, increase their activity. Thus, potentiating the existing antibiotics is one of the promising approaches to tackle and minimize the impact of antimicrobial resistance (AMR). Several natural and synthetic compounds have demonstrated effectiveness in potentiating macrolide antibiotics against multidrug-resistant (MDR) pathogens. The present review summarizes the different resistance mechanisms adapted by bacteria to resist macrolides and further emphasizes the major macrolide potentiators identified which could serve to revive the antibiotic and can be used for the reversal of macrolide resistance.
PubMed: 38136749
DOI: 10.3390/antibiotics12121715 -
Nature Communications Jun 2021Memory is supported by a specific collection of neurons distributed in broad brain areas, an engram. Despite recent advances in identifying an engram, how the engram is...
Memory is supported by a specific collection of neurons distributed in broad brain areas, an engram. Despite recent advances in identifying an engram, how the engram is created during memory formation remains elusive. To explore the relation between a specific pattern of input activity and memory allocation, here we target a sparse subset of neurons in the auditory cortex and thalamus. The synaptic inputs from these neurons to the lateral amygdala (LA) are not potentiated by fear conditioning. Using an optogenetic priming stimulus, we manipulate these synapses to be potentiated by the learning. In this condition, fear memory is preferentially encoded in the manipulated cell ensembles. This change, however, is abolished with optical long-term depression (LTD) delivered shortly after training. Conversely, delivering optical long-term potentiation (LTP) alone shortly after fear conditioning is sufficient to induce the preferential memory encoding. These results suggest a synaptic plasticity-dependent competition rule underlying memory formation.
Topics: Animals; Basolateral Nuclear Complex; Brain; Conditioning, Classical; Evoked Potentials, Auditory; Fear; Halorhodopsins; Learning; Long-Term Potentiation; Memory; Mice, Inbred C57BL; Neuronal Plasticity; Neurons; Optogenetics; Mice
PubMed: 34168140
DOI: 10.1038/s41467-021-24269-4 -
Journal of Controlled Release :... Oct 2023Growth factors are key molecules involved in angiogenesis, a process critical for tissue repair and regeneration. Despite the potential of growth factor delivery to...
Growth factors are key molecules involved in angiogenesis, a process critical for tissue repair and regeneration. Despite the potential of growth factor delivery to stimulate angiogenesis, limited clinical success has been achieved with this approach. Growth factors interact with the extracellular matrix (ECM), and particularly heparan sulphate (HS), to bind and potentiate their signalling. Here we show that engineered short forms of perlecan, the major HS proteoglycan of the vascular ECM, bind and signal angiogenic growth factors, including fibroblast growth factor 2 and vascular endothelial growth factor-A. We also show that engineered short forms of perlecan delivered in porous chitosan biomaterial scaffolds promote angiogenesis in a rat full thickness dermal wound model, with the fusion of perlecan domains I and V leading to superior vascularisation compared to native endothelial perlecan or chitosan scaffolds alone. Together, this study demonstrates the potential of engineered short forms of perlecan delivered in chitosan scaffolds as next generation angiogenic therapies which exert biological activity via the potentiation of growth factors.
Topics: Rats; Animals; Vascular Endothelial Growth Factor A; Chitosan; Heparan Sulfate Proteoglycans; Extracellular Matrix Proteins
PubMed: 37648081
DOI: 10.1016/j.jconrel.2023.08.052 -
Cellular and Molecular Neurobiology May 2018Acid-sensing ion channels (ASICs) are modulated by various classes of ligands, including the recently described hydrophobic monoamines, which inhibit and potentiate...
Acid-sensing ion channels (ASICs) are modulated by various classes of ligands, including the recently described hydrophobic monoamines, which inhibit and potentiate ASICs in a subunit-specific manner. In particular, memantine inhibits ASIC1a and potentiates ASIC2a homomers. The aim of the present work was to characterize action mechanism of memantine on recombinant ASIC1a expressed in CHO (Chinese hamster ovary) cells. We have demonstrated that effect of memantine on ASIC1a strongly depends on membrane voltage, conditioning pH value and application protocol. When applied simultaneously with activating acidification at hyperpolarized voltages, memantine caused the strongest inhibition. Surprisingly, application of memantine between ASIC1a activations at zero voltage caused significant potentiation. Analysis of the data suggests that memantine produces two separate effects, voltage-dependent open-channel block and shift of steady-state desensitization curve to more acidic values. Putative binding sites are discussed based on the computer docking of memantine to the acidic pocket and the pore region.
Topics: Acid Sensing Ion Channels; Animals; Binding Sites; CHO Cells; Cell Line; Cricetulus; Hydrogen-Ion Concentration; Memantine; Neurons; Rats
PubMed: 29058095
DOI: 10.1007/s10571-017-0561-6 -
The Journal of Steroid Biochemistry and... Sep 2020The family of ATP-gated purinergic P2X receptors comprises seven bunits (P2X1-7) that are unevenly distributed in the central and peripheral nervous systems as well as...
The family of ATP-gated purinergic P2X receptors comprises seven bunits (P2X1-7) that are unevenly distributed in the central and peripheral nervous systems as well as other organs. Endogenous modulators of P2X receptors are phospholipids, steroids and neurosteroids. Here, we analyzed whether bile acids, which are natural products derived from cholesterol, affect P2X receptor activity. We examined the effects of primary and secondary bile acids and newly synthesized derivatives of lithocholic acid on agonist-induced responses in HEK293T cells expressing rat P2X2, P2X4 and P2X7 receptors. Electrophysiology revealed that low micromolar concentrations of lithocholic acid and its structural analog 4-dafachronic acid strongly inhibit ATP-stimulated P2X2 but potentiate P2X4 responses, whereas primary bile acids and other secondary bile acids exhibit no or reduced effects only at higher concentrations. Agonist-stimulated P2X7 responses are significantly potentiated by lithocholic acid at moderate concentrations. Structural modifications of lithocholic acid at positions C-3, C-5 or C-17 abolish both inhibitory and potentiation effects to varying degrees, and the 3α-hydroxy group contributes to the ability of the molecule to switch between potentiation and inhibition. Lithocholic acid allosterically modulates P2X2 and P2X4 receptor sensitivity to ATP, reduces the rate of P2X4 receptor desensitization and antagonizes the effect of ivermectin on P2X4 receptor deactivation. Alanine-scanning mutagenesis of the upper halve of P2X4 transmembrane domain-1 revealed that residues Phe48, Val43 and Tyr42 are important for potentiating effect of lithocholic acid, indicating that modulatory sites for lithocholic acid and ivermectin partly overlap. Lithocholic acid also inhibits ATP-evoked currents in pituitary gonadotrophs expressing native P2X2, and potentiates ATP currents in nonidentified pituitary cells expressing P2X4 receptors. These results indicate that lithocholic acid is a bioactive steroid that may help to further unveil the importance of the P2X2, and P2X4 receptors in many physiological processes.
Topics: Animals; Female; HEK293 Cells; Humans; Hypothalamus; Ion Channel Gating; Lithocholic Acid; Male; Neurons; Pituitary Gland, Anterior; Purinergic P2X Receptor Agonists; Purinergic P2X Receptor Antagonists; Rats, Wistar; Receptors, Purinergic P2X2; Receptors, Purinergic P2X4; Receptors, Purinergic P2X7
PubMed: 32652201
DOI: 10.1016/j.jsbmb.2020.105725 -
Applied and Environmental Microbiology Apr 2021The emergence and spread of extended-spectrum β-lactamases (ESBLs), metallo-β-lactamases (MBLs), or variant low-affinity penicillin-binding proteins (PBPs) pose a...
The emergence and spread of extended-spectrum β-lactamases (ESBLs), metallo-β-lactamases (MBLs), or variant low-affinity penicillin-binding proteins (PBPs) pose a major threat to our ability to treat bacterial infection using β-lactam antibiotics. Although combinations of β-lactamase inhibitors with β-lactam agents have been clinically successful, there are no MBL inhibitors in current therapeutic use. Furthermore, recent clinical use of new-generation cephalosporins targeting PBP2a, an altered PBP, has led to the emergence of resistance to these antimicrobial agents. Previous work shows that natural polyphenols such as cranberry-extracted proanthocyanidins (cPAC) can potentiate non-β-lactam antibiotics against Gram-negative bacteria. This study extends beyond previous work by investigating the effect of cPAC in overcoming ESBL-, MBL-, and PBP2a-mediated β-lactam resistance. The results show that cPAC exhibit variable potentiation of different β-lactams against β-lactam-resistant clinical isolates as well as ESBL- and MBL-producing We also discovered that cPAC have broad-spectrum inhibitory properties on the activity of different classes of β-lactamases, including CTX-M3 ESBL and IMP-1 MBL. Furthermore, we observe that cPAC selectively potentiate oxacillin and carbenicillin against methicillin-resistant but not methicillin-sensitive staphylococci, suggesting that cPAC also interfere with PBP2a-mediated resistance. This study motivates the need for future work to identify the most bioactive compounds in cPAC and to evaluate their antibiotic-potentiating efficacy The emergence of β-lactam-resistant and staphylococci compromises the effectiveness of β-lactam-based therapy. By acquisition of ESBLs, MBLs, or PBPs, it is highly likely that bacteria may become completely resistant to the most effective β-lactam agents in the near future. In this study, we described a natural extract rich in proanthocyanidins which exerts adjuvant properties by interfering with two different resistance mechanisms. By their broad-spectrum inhibitory ability, cranberry-extracted proanthocyanidins could have the potential to enhance the effectiveness of existing β-lactam agents.
Topics: Ampicillin; Anti-Bacterial Agents; Bacteria; Cefotaxime; Drug Synergism; Proanthocyanidins; Vaccinium macrocarpon; beta-Lactam Resistance
PubMed: 33712420
DOI: 10.1128/AEM.00127-21 -
Thrombosis Research Sep 2016Tyrosine kinase inhibitors (TKI) such as imatinib, nilotinib and dasatinib are now established as highly effective frontline therapies for chronic myeloid leukaemia...
Tyrosine kinase inhibitors (TKI) such as imatinib, nilotinib and dasatinib are now established as highly effective frontline therapies for chronic myeloid leukaemia (CML). Disease control is achieved in the majority of patients and survival is excellent such that recent focus has been on toxicities of these agents. Cumulative data have reported an excess of serious vascular complications, including arterial thrombosis and peripheral arterial occlusive disease, in patients receiving nilotinib in comparison with other TKIs, with resultant interest in delineating the pathophysiology and implications for rationale cardiovascular risk modification. To address this issue, we studied the effects of imatinib, nilotinib and dasatinib on platelet function and thrombus formation in human and mouse models using in vitro, ex vivo and in vivo approaches. In vitro studies demonstrated that dasatinib and imatinib but not nilotinib inhibited ADP, CRP, and collagen-induced platelet aggregation and moreover, that nilotinib potentiated PAR-1-mediated alpha granule release. Pretreatment of wild-type C57BL/6 mice with nilotinib but not imatinib or dasatinib, significantly increased thrombus growth and stability, on type I collagen under ex vivo arterial flow conditions and increased thrombus growth and stability following FeCl3-induced vascular injury of mesenteric arterioles and carotid artery injury in vivo. Whole blood from nilotinib-treated CML patients, demonstrated increased platelet adhesion ex vivo under flow, increased plasma soluble P- and E-selectin, sICAM-1, sVCAM-1, TNF-alpha, IL-6 levels and endogenous thrombin potential (ETP) levels in vivo, despite being on daily low-dose aspirin. These results demonstrate that nilotinib can potentiate platelet and endothelial activation and platelet thrombus formation ex vivo and in vivo.
Topics: Animals; Antineoplastic Agents; Disease Models, Animal; Humans; Mice; Mice, Inbred C57BL; Pyrimidines; Risk Factors; Thrombosis
PubMed: 27494773
DOI: 10.1016/j.thromres.2016.07.019 -
The Journal of General Physiology Dec 2017Cystic fibrosis (CF) is a channelopathy caused by loss-of-function mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which encodes a...
Cystic fibrosis (CF) is a channelopathy caused by loss-of-function mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which encodes a phosphorylation-activated and adenosine triphosphate (ATP)-gated chloride channel. In the past few years, high-throughput drug screening has successfully realized the first US Food and Drug Administration-approved therapy for CF, called ivacaftor (or VX-770). A more recent CFTR potentiator, GLPG1837 (-(3-carbamoyl-5,5,7,7-tetramethyl-4,7-dihydro-5-thieno[2,3-]pyran-2-yl)-1-pyrazole-3-carboxamide), has been shown to exhibit a higher efficacy than ivacaftor for the G551D mutation, yet the underlying mechanism of GLPG1837 remains unclear. Here we find that despite their differences in potency and efficacy, GLPG1837 and VX-770 potentiate CFTR gating in a remarkably similar manner. Specifically, they share similar effects on single-channel kinetics of wild-type CFTR. Their actions are independent of nucleotide-binding domain (NBD) dimerization and ATP hydrolysis, critical steps controlling CFTR's gate opening and closing, respectively. By applying the two reagents together, we provide evidence that GLPG1837 and VX-770 likely compete for the same site, whereas GLPG1837 and the high-affinity ATP analogue 2'-deoxy--(2-phenylethyl)-adenosine-5'--triphosphate (dPATP) work synergistically through two different sites. We also find that the apparent affinity for GLPG1837 is dependent on the open probability of the channel, suggesting a state-dependent binding of the drug to CFTR (higher binding affinity for the open state than the closed state), which is consistent with the classic mechanism for allosteric modulation. We propose a simple four-state kinetic model featuring an energetic coupling between CFTR gating and potentiator binding to explain our experimental results.
Topics: Aminophenols; Animals; Binding Sites; CHO Cells; Chloride Channel Agonists; Cricetinae; Cricetulus; Cystic Fibrosis Transmembrane Conductance Regulator; Humans; Ion Channel Gating; Protein Binding; Quinolones
PubMed: 29079713
DOI: 10.1085/jgp.201711886 -
The Journal of Antimicrobial... Dec 2019We have shown previously that celecoxib enhances the antibacterial effect of antibiotics and has sensitized drug-resistant bacteria to antibiotics at low concentrations...
BACKGROUND
We have shown previously that celecoxib enhances the antibacterial effect of antibiotics and has sensitized drug-resistant bacteria to antibiotics at low concentrations using in vitro and in vivo model systems and also using clinically isolated ESKAPE pathogens.
OBJECTIVES
To identify the mechanism of action of celecoxib in potentiating the effect of antibiotics on bacteria.
METHODS
Toxicogenomic expression analysis of Staphylococcus aureus in the presence or absence of ampicillin, celecoxib or both was carried out by microarray followed by validation of microarray results by flow cytometry and real-time PCR analysis, cocrystal development and analysis.
RESULTS
The RNA expression map clearly indicated a change in the global transcriptome of S. aureus in the presence of cells treated with ampicillin alone, which was similar to that of celecoxib-treated cells in co-treated cells. Several essential, non-essential and virulence genes such as α-haemolysin (HLA), enterotoxins and β-lactamase were differentially regulated in co-treated cells. Further detailed analysis of the expression data indicated that the ion transporters and enzymes of the lipid biosynthesis pathway were down-regulated in co-treated cells leading to decreased membrane permeability and membrane potential. Cocrystal studies using Powder-X-Ray Diffraction (PXRD) and differential scanning calorimetry (DSC) indicated interactions between celecoxib and ampicillin, which might help in the entry of antibiotics.
CONCLUSIONS
Although further studies are warranted, here we report that celecoxib alters membrane potential and permeability, specifically by affecting the Na+/K+ ion transporter, and thereby increases the uptake of ampicillin by S. aureus.
Topics: Ampicillin; Anti-Bacterial Agents; Celecoxib; Cell Membrane Permeability; Drug Synergism; Ion Transport; Membrane Potentials; Microbial Sensitivity Tests; Oligonucleotide Array Sequence Analysis; Staphylococcal Infections; Staphylococcus aureus
PubMed: 31586409
DOI: 10.1093/jac/dkz391 -
Antimicrobial Agents and Chemotherapy May 2018kills more people than any other bacterial pathogen and is becoming increasingly untreatable due to the emergence of resistance. Verapamil, an FDA-approved calcium...
kills more people than any other bacterial pathogen and is becoming increasingly untreatable due to the emergence of resistance. Verapamil, an FDA-approved calcium channel blocker, potentiates the effect of several antituberculosis (anti-TB) drugs and This potentiation is widely attributed to inhibition of the efflux pumps of , resulting in intrabacterial drug accumulation. Here, we confirmed and quantified verapamil's synergy with several anti-TB drugs, including bedaquiline (BDQ) and clofazimine (CFZ), but found that the effect is not due to increased intrabacterial drug accumulation. We show that, consistent with its potentiating effects on anti-TB drugs that target or require oxidative phosphorylation, the cationic amphiphile verapamil disrupts membrane function and induces a membrane stress response similar to those seen with other membrane-active agents. We recapitulated these activities using inverted mycobacterial membrane vesicles, indicating a direct effect of verapamil on membrane energetics. We observed bactericidal activity against nonreplicating "persister" that was consistent with such a mechanism of action. In addition, we demonstrated a pharmacokinetic interaction whereby human-equivalent doses of verapamil caused a boost of rifampin exposure in mice, providing a potential explanation for the observed treatment-shortening effect of verapamil in mice receiving first-line drugs. Our findings thus elucidate the mechanistic basis for verapamil's potentiation of anti-TB drugs and and highlight a previously unrecognized role for the membrane of as a pharmacologic target.
Topics: Animals; Antitubercular Agents; Calcium Channel Blockers; Cell Membrane; Clofazimine; Diarylquinolines; Drug Synergism; Female; Humans; Mice; Microbial Sensitivity Tests; Mycobacterium tuberculosis; Verapamil
PubMed: 29463541
DOI: 10.1128/AAC.02107-17