Auswahl der wissenschaftlichen Literatur zum Thema „Aminoglycosides uptake“

Aminoglycosides bind to apical and basolateral (BL) membranes of renal epithelial cells. However, little is known regarding differential uptake and intracellular processing after internalization across these distinct surface membrane domains. To examine these processes independently, LLC-PK1 cells were grown on porous filters, which allow selective access to both domains. Apical and BL membrane uptakes of gentamicin (0.5 mM), quantified using [3H]gentamicin, were linear from 2 to 24 h (r = 0.99). The 4-h apical gentamicin uptake was 667 +/- 59 pmol/mg protein, the BL 748 +/- 26 pmol/mg protein, and concurrent apical and BL uptake 1,389 +/- 22 pmol/mg protein. Aminoglycoside uptake, documented using indirect immunogold techniques, occurred via the apical and BL endocytic systems and colocalized with cationic ferritin. Aminoglycosides internalized via the apical (gentamicin) and BL (tobramycin) membrane converged at the lysosomal level. Gentamicin incorporated via either domain significantly decreased lysosomal N-acetylglucosaminidase below control values (P < 0.05). We conclude that, after binding, aminoglycosides are internalized equally across apical and BL membranes of LLC-PK1 cells via receptor-mediated endocytosis, colocalize within the lysosomal compartment, and alter cellular function similarly.

A spontaneous kanamycin-resistant Escherichia coli mutant, showing cross resistance to five other aminoglycosides and absence of the OppA protein was isolated. [3H]-dihydrostreptomycin uptake is reduced in this mutant, implying that the oligopeptide transport system is involved in accumulation of aminoglycosides, although apparently not related with aminoglycoside permeability alteration due to bacterial adaptation to osmotic changes.

ABSTRACTOur investigations have identified a mechanism by which exogenous production of nitric oxide (NO) induces resistance of Gram-positive and -negative bacteria to aminoglycosides. An NO donor was found to protectSalmonellaspp. against structurally diverse classes of aminoglycosides of the 4,6-disubstituted 2-deoxystreptamine group. Likewise, NO generated enzymatically by inducible NO synthase of gamma interferon-primed macrophages protected intracellularSalmonellaagainst the cytotoxicity of gentamicin. NO levels that elicited protection against aminoglycosides repressedSalmonellarespiratory activity. NO nitrosylated terminal quinol cytochrome oxidases, without exerting long-lasting inhibition of NADH dehydrogenases of the electron transport chain. The NO-mediated repression of respiratory activity blocked both energy-dependent phases I and II of aminoglycoside uptake but not the initial electrostatic interaction of the drug with the bacterial cell envelope. As seen inSalmonella, the NO-dependent inhibition of the electron transport chain also afforded aminoglycoside resistance to the clinically important pathogensPseudomonas aeruginosaandStaphylococcus aureus. Together, these findings provide evidence for a model in which repression of aerobic respiration by NO fluxes associated with host inflammatory responses can reduce drug uptake, thus promoting resistance to several members of the aminoglycoside family in phylogenetically diverse bacteria.

All bactericidal antibiotics were recently proposed to kill by inducing reactive oxygen species (ROS) production, causing destabilization of iron-sulfur (Fe-S) clusters and generating Fenton chemistry. We find that the ROS response is dispensable upon treatment with bactericidal antibiotics. Furthermore, we demonstrate that Fe-S clusters are required for killing only by aminoglycosides. In contrast to cells, using the major Fe-S cluster biosynthesis machinery, ISC, cells using the alternative machinery, SUF, cannot efficiently mature respiratory complexes I and II, resulting in impendence of the proton motive force (PMF), which is required for bactericidal aminoglycoside uptake. Similarly, during iron limitation, cells become intrinsically resistant to aminoglycosides by switching from ISC to SUF and down-regulating both respiratory complexes. We conclude that Fe-S proteins promote aminoglycoside killing by enabling their uptake.

ABSTRACT Antagonism of aminoglycosides by divalent cations is well documented for Pseudomonas aeruginosa and is regarded as one of the problems in aminoglycoside therapy. It is generally considered that divalent cations interfere with uptake of aminoglycosides at both the outer and inner membranes. It has been demonstrated recently that aminoglycosides can be removed from cells ofP. aeruginosa by the three-component multidrug resistance efflux pump MexXY-OprM. We sought to investigate the interplay between efflux and uptake in resistance to aminoglycosides inP. aeruginosa. To do so, we studied the effects of the divalent cations Mg2+ and Ca2+ on susceptibility to aminoglycosides in a wild-type strain of P. aeruginosa and in mutants either overexpressing or lacking the MexXY-OprM efflux pump. MICs of gentamicin, streptomycin, amikacin, apramycin, netilmicin, and arbekacin were determined in Mueller-Hinton broth in the presence of cations added at concentrations that varied from 0.125 to 8 mM. We found, unexpectedly, that while both Mg2+ and Ca2+ antagonized aminoglycosides (up to a 64-fold decrease in susceptibility at 8 mM), antagonism was seen only in the strains of P. aeruginosa that contained the functional MexXY-OprM efflux pump. Our results indicate that inhibition of the MexXY-OprM efflux pump should abolish the antagonism of aminoglycosides by divalent cations, regardless of its precise mechanism. This may significantly increase the therapeutic index of aminoglycosides and improve the clinical utility of this important class of antibiotics.

The clinical use of aminoglycosides often leads to renal magnesium wasting and hypomagnesemia. Of the nephron segments, both the thick ascending limb of Henle's loop and the distal tubule play significant roles in renal magnesium conservation but the distal convoluted tubule exerts the final control of urinary excretion. An immortalized mouse distal convoluted tubule (MDCT) cell line has been extensively used to study the cellular mechanisms of magnesium transport in this nephron segment. Peptide hormones, such as parathyroid hormone (PTH), glucagon, calcitonin, and arginine vasopressin (AVP) stimulate Mg2+ uptake in MDCT cells that is modulated by extracellular polyvalent cations, Ca2+ and Mg2+. The present studies determined the effect of aminoglycosides on parathyroid hormone (PTH)-mediated cAMP formation and Mg2+ uptake in MDCT cells. Gentamicin, a prototypic aminoglycoside, illicited transient increases in intracellular Ca2+ from basal levels of 102 ± 13 nM to 713 ± 125 nM, suggesting a receptor-mediated response. In order to determine Mg2+ transport, MDCT cells were Mg2+-depleted by culturing in Mg2+-free media for 16 h and Mg2+ uptake was measured by microfluorescence after placing the depleted cells in 1.0 mM MgCl2. The mean rate of Mg2+ uptake, d([Mg2+]i)/dt, was 138 ± 24 nM/s in control MDCT cells. Gentamicin (50 µM) did not affect basal Mg2+ uptake (105 ± 29 nM/s), but inhibited PTH stimulated Mg2+ entry, decreasing it from 257 ± 36 nM/s to 108 ± 42 nM/s. This was associated with diminished PTH-stimulated cAMP formation, from 80 ± 2.5 to 23 ± 1 pmol/mg protein·5 min. Other aminoglycosides such as tobramycin, streptomycin, and neomycin also inhibited PTH-stimulated Mg2+ entry and cAMP formation. As these antibiotics are positively charged, the data suggest that aminoglycosides act through an extracellular polyvalent cation-sensing receptor present in distal convoluted tubule cells. We infer from these studies that aminoglycosides inhibit hormone-stimulated Mg2+ absorption in the distal convoluted tubule that may contribute to the renal magnesium wasting frequently observed with the clinical use of these antibiotics.Key words: intracellular Mg2+, Mg2+ uptake, aminoglycosides, gentamicin, tobramycin, streptomycin, neomycin, parathyroid hormone, microfluorescence, cAMP measurements.

ABSTRACTBurkholderia cepaciacomplex (BCC) bacteria are opportunistic pathogens that can cause severe disease in cystic fibrosis (CF) patients and other immunocompromised individuals and are typically multidrug resistant. Here we observed that unlike other BCC species, most environmental and clinicalBurkholderia vietnamiensisisolates were intrinsically susceptible to aminoglycosides but not to cationic antimicrobial peptides or polymyxin B. Furthermore, strains acquired aminoglycoside resistance during chronic CF infection, a phenomenon that could be induced under tobramycin or azithromycin pressurein vitro. In comparing susceptible and resistantB. vietnamiensisisolates, no gross differences in lipopolysaccharide structure were observed, all had lipid A-associated 4-amino-4-deoxy-l-arabinose residues, and all were resistant to the permeabilizing effects of aminoglycosides, a measure of drug entry via self-promoted uptake. However, susceptible isolates accumulated 5 to 6 times more gentamicin than a resistant isolate, and aminoglycoside susceptibility increased in the presence of an efflux pump inhibitor.B. vietnamiensisis therefore unusual among BCC bacteria in its susceptibility to aminoglycosides and capacity to acquire resistance. Aminoglycoside resistance appears to be due to decreased cellular accumulation as a result of active efflux.

Aminoglycoside antibiotics are essential for treating life-threatening bacterial infections, despite the risk of lifelong hearing loss. Infections induce inflammation and up-regulate expression of candidate aminoglycoside-permeant cation channels, including transient receptor potential vanilloid-1 (TRPV1). Heterologous expression of TRPV1 facilitated cellular uptake of (fluorescently tagged) gentamicin that was enhanced by agonists, and diminished by antagonists, of TRPV1. Cochlear TRPV1 was immunolocalized near the apical membranes of sensory hair cells, adjacent supporting cells, and marginal cells in the stria vascularis. Exposure to immunostimulatory lipopolysaccharides, to simulate of bacterial infections, increased cochlear expression of TRPV1 and hair cell uptake of gentamicin. Lipopolysaccharide exposure exacerbated aminoglycoside-induced auditory threshold shifts and loss of cochlear hair cells in wild-type, but not in heterozygous Trpv1+/− or Trpv1 knockout, mice. Thus, TRPV1 facilitates cochlear uptake of aminoglycosides, and bacteriogenic stimulation upregulates TRPV1 expression to exacerbate cochleotoxicity. Furthermore, loss-of-function polymorphisms in Trpv1 can protect against immunogenic exacerbation of aminoglycoside-induced cochleotoxicity.

The critical inhibition of ribosome function by aminoglycosides has long been established. But the binding of drug to ribosomes is reversible: why then are aminoglycosides bactericidal? Several groups have shown that irreversible action (lethality) results from irreversible uptake into susceptible cells; conversely, resistance in cases such as anaerobiosis is associated with the failure of uptake. Oddly, the pattern of results excludes all traditional transport mechanisms; most unusual is the apparent dependence of uptake on the interaction of drug with ribosomes. A traditional view that ribosomes may function during uptake as a "sink" for aminoglycosides cannot explain all the data. Instead, the alternative is considered that cycling ribosomes at the cell membrane help to induce "one-way endocytic pores." Although no detailed mechanism is formulated, the results do suggest a way that the permeation of antibiotics might be systematically controllable to render them more cidal.

Amphiphilic kanamycin is one of the promising class of compounds for the treatment of fungal infections in plants and animal. Factor that lead to the restricting of compounds for commercialization includes, the higher cost of production and poor stability of the compound. However, the new lead, identified from the synthesis and biological testing, can be synthesized on a large scale with a cost comparable to commercial antifungals. The newly reported lead is stable at the acidic and basic conditions. Additionally, this compound has an excellent activity towards Candida auris, a multidrug-resistant superbug. Heart disease is the leading cause of death in the United States most of which are caused by cardiac ischemia and arrhythmias. Abnormal opening of Cx43 hemichannel can damage the heart muscles and lead to these conditions. A compound which can selectively inhibit the opening of Cx43 hemichannel may pave the way to reducing the mortality rate of heart disease. A selective inhibitor towards Cx43 hemichannel is explored from the synthesis and biological testing of kanamycin derivatives. The synthesis of the new inhibitor is scalable and cost-effective.

Le nombre de décès dus aux bactéries multirésistantes s'élevait à plus d'un million en 2019, démontrant que la lutte contre les bactéries pathogènes est un enjeu majeur de santé publique. Les aminoglycosides (AGs) sont des antibiotiques à large spectre, efficaces contre les bactéries Gram-négatives grâce à leur capacité à traverser la double barrière membranaire en utilisant la force proton motrice, mais le mécanisme précis reste à élucider. Notre laboratoire a découvert un nouveau mécanisme d'entrée des AGs dans V. cholerae par l'intermédiaire des transporteurs de sucre. Dans cette étude, nous avons montré que la surexpression chez Escherichia coli de plusieurs transporteurs de carbohydrates augmentait la sensibilité aux AGs alors que la délétion d'un seul transporteur avait peu d'impact sur la sensibilité, suggérant une redondance de ces transporteurs capables de se compenser mutuellement et de limiter l'apparition de la résistance. En utilisant un transporteur "preuve de concept" appelé CmtA, nous avons confirmé qu'une entrée différentielle des AGs était lié à la délétion ou la surexpression de ce transporteur. Ce mécanisme est partagé avec d'autres pathogènes, puisque la même sensibilité aux AGs a été observée lors de la surexpression des transporteurs de sucre chez Pseudomonas aeruginosa. Augmenter la production de ces transporteurs en réponse à la présence d'un substrat in vivo pourrait permettre une plus grande efficacité des thérapies aux AGs et une toxicité plus faible, en permettant une meilleure absorption par les bactéries. Nous avons donc cherché un substrat capable d'augmenter l'expression des transporteurs impliqués dans l'absorption des AGs, et nous avons identifié le ribonucléoside uridine comme un activateur. L'ajout d'uridine au milieu de culture permet une plus grande absorption des AGs dans E. coli et n'a pas montré d'apparence de mutant. En mimant une infection des voies urinaires avec un milieu synthétique, l'ajout d'uridine potentialise le traitement par AGs en diminuant la concentration minimale inhibitrice des AGs et en accélérant la cinétique de mort. Nous proposons l'uridine comme potentialisateur du traitement par AG, en co-administrant un AG avec de l'uridine pour stimuler son entrée. Cette étude ouvre la voie à l'amélioration de ces traitements par l'utilisation de carbohydrates pour stimuler l'absorption des molécules AGs
The number of deaths due to multidrug-resistant bacteria was over one million in 2019, demonstrating that the fight against pathogenic bacteria is a major public health issue. Aminoglycosides (AGs) are broad-spectrum antibiotics, effective against Gram-negative bacteria due to their ability to cross the double membrane barrier using the proton motive force, but the precise mechanism remains to be elucidated. Our laboratory has discovered a novel mechanism of entry of AGs into V. cholerae via sugar transporters. In this study, we showed that overexpression in Escherichia coli of multiple carbohydrate transporters increased sensitivity to AGs while deletion of a single transporter had little impact on sensitivity, suggesting a redundancy of these transporters capable of compensating for each other and limiting the development of resistance. Using a "proof-of-concept" transporter called CmtA, we confirmed that differential entry of AGs was linked to the deletion or overexpression of this transporter. This mechanism is shared with other pathogens, since the same sensitivity to AGs was observed upon overexpression of sugar transporters in Pseudomonas aeruginosa. Increasing the production of these transporters in response to the presence of a substrate in vivo could allow for greater efficacy and lower side effects of AG therapies by allowing better uptake by bacteria. We therefore sought a substrate capable of increasing the expression of transporters involved in AG uptake, and identified the ribonucleoside uridine as an activator. The addition of uridine to the culture medium allows for greater AG uptake in E. coli and did not show a mutant appearance. By mimicking a urinary tract infection with a synthetic medium, the addition of uridine potentiates AG treatment by decreasing the minimum inhibitory concentration of AGs and accelerating death kinetics. We propose uridine as a potentiator of GA treatment by co-administering an AG with uridine to stimulate its entry. This study paves the way for improving these treatments by using carbohydrates to stimulate AGs molecules uptake

Although antibiotic resistance has come to the fore in the media and clinical practice relatively recently, it is by no means a new issue; Alexander Fleming discussed the risks of penicillin resistance more than sixty years ago, but even he was behind the times. Bacteria have been competing with each other for millions of years, producing compounds which kill or inhibit other species—it is not surprising that bacteria have evolved defence mechanisms. Current major concerns are the rise of pan-drug resistant gram-negative organisms and the spread of multi-drug resistant TB. Bacterial cells turn over rapidly—this rate of reproduction leads to many errors in DNA replication. Many of these mutations are deleterious to the organism, but others confer new properties, such as changing the structure of an enzyme. The application of selection pressure in the form of antimicrobial therapy leads to the survival of mutants that have randomly acquired resistance mechanisms. There are two useful ways to categorize resistance mechanisms: by how bacterial cells acquire them and by the physical mechanism of action. The types of acquisition have important infection control ramifications. Resistance can be subdivided into three separate categories: ● Intrinsic resistance— mechanisms hard coded into all members of a bacterial species at the chromosomal level. If an organism’s antibiogram suggests susceptibility to an agent to which it should be intrinsically resistant, further work should be done to check that the identification is correct. Examples include gram-negative bacteria being resistant to glycopeptides due to the outer cell membrane, anaerobes being resistant to aminoglycosides due to lack of an uptake mechanism, and amoxicillin resistance in Klebsiella due to beta-lactamase production. ● Mutational resistance—resistance that arises randomly due to DNA replication errors in conjunction with selection pressure applied by antimicrobial agents. This is the basis of the majority of the mechanisms detailed in this chapter. ● Transferrable resistance— mutational resistance that is passed horizontally from the bacterium in which it arose to another cell, possibly of a different species entirely. This happens through either transposons (DNA that incorporates into the bacterial chromosome) or plasmids (rings of DNA that replicate independent of the main chromosome).