Biomaterials releasing silver (Ag) are of interest because of their ability to inhibit pathogenic bacteria including antibiotic-resistant strains. In order to investigate the potential of ...nanometre-thick Ag polymer (Ag/amino-hydrocarbon) nanocomposite plasma coatings, we studied a comprehensive range of factors such as the plasma deposition process and Ag cation release as well as the antibacterial and cytocompatible properties. The nanocomposite coatings released most bound Ag within the first day of immersion in water yielding an antibacterial burst. The release kinetics correlated with the inhibitory effects on the pathogens Pseudomonas aeruginosa or Staphylococcus aureus and on animal cells that were in contact with these coatings. We identified a unique range of Ag content that provided an effective antibacterial peak release, followed by cytocompatible conditions soon thereafter. The control of the in situ growth conditions for Ag nanoparticles in the polymer matrix offers the possibility to produce customized coatings that initially release sufficient quantities of Ag ions to produce a strong adjacent antibacterial effect, and at the same time exhibit a rapidly decaying Ag content to provide surface cytocompatibility within hours/days. This approach seems to be favourable with respect to implant surfaces and possible Ag-resistance/tolerance built-up.
Abstract
Deciphering translation is of paramount importance for the understanding of many diseases, and antibiotics played a pivotal role in this endeavour. Blasticidin S (BlaS) targets translation ...by binding to the peptidyl transferase center of the large ribosomal subunit. Using biochemical, structural and cellular approaches, we show here that BlaS inhibits both translation elongation and termination in Mammalia. Bound to mammalian terminating ribosomes, BlaS distorts the 3′CCA tail of the P-site tRNA to a larger extent than previously reported for bacterial ribosomes, thus delaying both, peptide bond formation and peptidyl-tRNA hydrolysis. While BlaS does not inhibit stop codon recognition by the eukaryotic release factor 1 (eRF1), it interferes with eRF1’s accommodation into the peptidyl transferase center and subsequent peptide release. In human cells, BlaS inhibits nonsense-mediated mRNA decay and, at subinhibitory concentrations, modulates translation dynamics at premature termination codons leading to enhanced protein production.
Type III secretion systems (T3SSs) are essential devices in the virulence of many Gram-negative bacterial pathogens. They mediate injection of protein effectors of virulence from bacteria into ...eukaryotic host cells to manipulate them during infection. T3SSs involved in virulence (vT3SSs) are evolutionarily related to bacterial flagellar protein export apparatuses (fT3SSs), which are essential for flagellar assembly and cell motility. The structure of the external and transmembrane parts of both fT3SS and vT3SS is increasingly well-defined. However, the arrangement of their cytoplasmic and inner membrane export apparatuses is much less clear. Here we compare the architecture of the cytoplasmic regions of the vT3SSs of Shigella flexneri and the vT3SS and fT3SS of Salmonella enterica serovar Typhimurium at ~5 and ~4 nm resolution using electron cryotomography and subtomogram averaging. We show that the cytoplasmic regions of vT3SSs display conserved six-fold symmetric features including pods, linkers and an ATPase complex, while fT3SSs probably only display six-fold symmetry in their ATPase region. We also identify other morphological differences between vT3SSs and fT3SSs, such as relative disposition of their inner membrane-attached export platform, C-ring/pods and ATPase complex. Finally, using classification, we find that both types of apparatuses can loose elements of their cytoplasmic region, which may therefore be dynamic.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Pseudomonas aeruginosa est un pathogène opportuniste responsable d'infections graves chez les personnes immunodéprimées, les grands brûlés et les patients atteints de la mucoviscidose. Cette ...pathogénicité repose sur de nombreux facteurs de virulence dont le système de sécrétion de type III (SSTT).Nous avons observé une protéine précédemment identifiée, PsrA, nécessaire pour la pleine activation de l'expression du SSTT chez P. aeruginosa. Les analyses par retard de migration électrophorétique de fragments du promoteur de l'operon régulateur exsCEBA ont montré que la protéine recombinante PsrA pourrait se fixer sur celui-ci. Le mutant DpsrA a montré une diminution marquée de la sécrétion des effecteurs de type III et une faible résistance à la bactéricidie par des cellules de type phagocytaires, PLB-985. L'ensemble des résultats suggèrent que PsrA est un nouvel activateur qui est impliqué dans l'expression du SSTT en augmentant le niveau de la transcription d'exsCEBA.Dans un second temps, nous avons mis en évidence qu'un signal inhibiteur, de type quorum sensing inconnu et produit dans la phase stationnaire de la culture, peut réprimer l'expression du SSTT in vitro. L'analyse de milliers de mutants de transposition a montré que la production de ce signal dépend du tryptophane, qui est le précurseur de nombreux métabolites dont l'acide d'indole-3-acétic (IAA). IAA-Na et un autre membre de cette famille de molécules, le acide 1-naphthalenacétique (NAA-K) aux concentrations millimolaires peuvent en effet inhiber l'expression et la sécrétion du SSTT. L'identification précise de ce signal nécessite des investigations plus poussées.
This chapter presents a general overview of type III secretion system (T3SS) regulation in the main pathogenic bacteria, and focuses on the different aspects of the regulation of T3SS gene expression ...in Pseudomonas aeruginosa. Pathogenic bacteria occupy very different infection foci; for instance, the animal pathogens Shigella spp. and Salmonella spp. live intracellularly after successful invasion, whereas Yersinia spp., P. aeruginosa, and enteropathogenic Escherichia coli (EPEC) predominantly remain extracellular. Therefore, different stimuli could be used to up or downregulate the expression of T3SS genes: temperature, divalent cations, host cell contact, serum, or other factors. Although the mechanism by which metabolic pathways influence virulence gene expression in bacteria is unclear, the example of P. aeruginosa detailed could facilitate progress in that field. It has been shown that T3SS expression is dependent on cell density and that exsCEBA operon expression decreases rapidly in the second part of stationary phase, and also that indole‐3‐acetic acid (IAA), naphthalenacetic, and 3‐hydroxykynurenine inhibit exsCEBA operon expression at millimolar concentrations. In 2005, Wu and coworkers proposed that the opportunistic pathogen P. aeruginosa could adapt to the host by sensing alterations in the host immune function and respond by enhancing the virulence phenotype. Despite the large number of genes that influence the regulation of the expression of T3SS genes in P. aeruginosa, only a minority have been shown to have a precise role. Both fundamental and applied research can make the inhibition of T3SS expression as one of the first new antibacterial therapeutics.
Bladder cancer is associated with high recurrence and mortality rates due to metastasis. The elucidation of metastasis suppressors may offer therapeutic opportunities if their mechanisms of action ...can be elucidated and tractably exploited. In this study, we investigated the clinical and functional significance of the transcription factor activating transcription factor 3 (ATF3) in bladder cancer metastasis. Gene expression analysis revealed that decreased ATF3 was associated with bladder cancer progression and reduced survival of patients with bladder cancer. Correspondingly, ATF3 overexpression in highly metastatic bladder cancer cells decreased migration in vitro and experimental metastasis in vivo. Conversely, ATF3 silencing increased the migration of bladder cancer cells with limited metastatic capability in the absence of any effect on proliferation. In keeping with their increased motility, metastatic bladder cancer cells had increased numbers of actin filaments. Moreover, ATF3 expression correlated with expression of the actin filament severing protein gelsolin (GSN). Mechanistic studies revealed that ATF3 upregulated GSN, whereas ATF3 silencing reduced GSN levels, concomitant with alterations in the actin cytoskeleton. We identified six ATF3 regulatory elements in the first intron of the GSN gene confirmed by chromatin immunoprecipitation analysis. Critically, GSN expression reversed the metastatic capacity of bladder cancer cells with diminished levels of ATF3. Taken together, our results indicate that ATF3 suppresses metastasis of bladder cancer cells, at least in part through the upregulation of GSN-mediated actin remodeling. These findings suggest ATF3 coupled with GSN as prognostic markers for bladder cancer metastasis.
Abstract Objectives Frailty is a prevalent geriatric condition that significantly impacts the health of older adults. This study aimed to examine the prevalence of frailty among older Chinese adults ...aged ≥ 65 years and to assess its association with adverse geriatric outcomes. Method This study included 20,724 older adults aged ≥ 65 years in Jiangsu Province, China, utilizing a random, stratified, multistage cluster sampling approach. Frailty was assessed using the 5-item FRAIL scale. Geriatric outcomes, such as independence in activities of daily living (ADL), cognitive impairment, and frequent fall events (occurring four or more times in the preceding year), were evaluated. Logistic regression models were employed to evaluate the association between frailty and geriatric outcomes, with results presented as odds ratios (ORs) and 95% confidence intervals (CIs). Results The mean age of the participants was 73.4 ± 6.4 years. The standardized prevalence of prefrailty and frailty was 35.2% and 10.3%, respectively. Individuals identified as prefrail or frail tended to live in rural areas, have lower educational levels, be widowed, have lower incomes, and engage in less physical activity. Prefrailty and frailty were associated with an increased risk of limitations in BADL (OR: 9.62, 95% CI: 7.43–12.46; and OR: 29.25, 95% CI: 22.42–38.17, respectively) and IADL (OR: 2.54, 95% CI 2.35–2.74; and OR: 5.19, 95% CI 4.66–5.78, respectively), positive cognitive impairment screening (OR: 1.23, 95% CI: 1.16–1.31; and OR: 1.72, 95% CI: 1.56–1.91, respectively), and frequent falls (occurring four or more times in the preceding year) (OR: 3.38, 95% CI: 2.50–4.56; and OR: 8.37, 95% CI: 6.01–11.65). The association between frailty and both limitations in BADL and falls was notably more pronounced among the younger age groups (p for interaction < 0.001). Conclusions According to the 5-item FRAIL scale, frailty was associated with limitations in BADLs and IADLs, positive cognitive impairment screening, and recent falls among older adults living in the community. Screening for frailty in younger age groups has the potential to prevent declines in physical function and falls.
Streptococcus pneumoniae (S. pneumoniae) is a leading agent worldwide, which could cause community-acquired pneumonia, bacteraemia, and meningitis. However, the pathogeneses remain unclear. This ...study was conducted to investigate gene pneumococcal surface antigen A (psaA) expression and the adhesion differences of various S. pneumoniae strains. A total of 24 (N) S. pneumoniae strains were collected: 11 from blood (bd-SP), 12 from sputum (sd-SP) and one was ATCC49619. One millilitre of A549 pneumocytes (3.3×108/L) and 100 µl of each S. pneumoniae strain at 1.0 McFarland were mixed and incubated under 37oC and 5% CO2 for three hours. The cells were centrifuged and extracted for psaA mRNA analysis. The former experiment was redone. After culture, the adherent cells were collected and cultured on blood agar plates. The △CT values of psaA were 18.9, 29.9±2.5, 29.6±2.0 and 16.0, 17.0±3.3, 18.6±3.8 for ATCC49619, bd-SP and sd-SP before and after stimulation respectively, with the colony units of 23, 68.4±6.7 and 59.1±7.7, which showed equal adhesion between bd-SP and sd-SP. Moderate psaA expression and adhesion of S. pneumoniae might facilitate its pathogenesis, excess of which induces faster S. pneumoniae clearance.
Abstract The transcription factor Foxp3 plays a key role in CD4+ CD25+ regulatory T (Treg) cell function. A correlation has been shown between survival and the frequency of tumor-infiltrating ...Foxp3-positive Treg cells in cancer patients. However, few studies have characterized the regulation of Foxp3 expression and function in Treg cells, which are known to comprise distinct subsets, with different roles in the complex tumor microenvironment. Here, we show that significantly more Foxp3-positive Treg cells accumulated in gastric tumors. In addition, we found increased expression of Foxp3 protein per cell in tumor-infiltrating Treg cells. Moreover, elevated Foxp3 expression in tumor-infiltrating Treg cells was associated with the TNM stage in gastric cancer patients. Importantly, further investigation within the tumor microenvironment showed that expression of Foxp3 in Treg cells correlated with expression of cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2 ). Furthermore, Treg cells with higher levels of Foxp3 were able to suppress the proliferation of autologous CD4+ CD25− T cells. The suppression of the effector T-cell response was reversed by COX inhibitors and PGE2 receptor-specific antagonists. Our data demonstrate a mechanism by which tumor-infiltrating Treg cells with increased Foxp3 expression can mediate immune suppression via COX-2/PGE2 production in the gastric cancer microenvironment. Thus, we provide new insights into overcoming regulatory T-cell activity, which may be beneficial for the treatment of human gastric cancer.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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