RESUMO
Xenorhabdus nematophila is a symbiotic Gammaproteobacterium that produces diverse natural products that facilitate mutualistic and pathogenic interactions in their nematode and insect hosts, respectively. The interplay between X. nematophila secondary metabolism and symbiosis stage is tuned by various global regulators. An example of such a regulator is the LysR-type protein transcription factor LrhA, which regulates amino acid metabolism and is necessary for virulence in insects and normal nematode progeny production. Here, we utilized comparative metabolomics and molecular networking to identify small molecule factors regulated by LrhA and characterized a rare γ-ketoacid (GKA) and two new N-acyl amides, GKA-Arg (1) and GKA-Pro (2) which harbor a γ-keto acyl appendage. A lrhA null mutant produced elevated levels of compound 1 and reduced levels of compound 2 relative to wild type. N-acyl amides 1 and 2 were shown to be selective agonists for the human G-protein-coupled receptors (GPCRs) C3AR1 and CHRM2, respectively. The CHRM2 agonist 2 deleteriously affected the hatch rate and length of Steinernema nematodes. This work further highlights the utility of exploiting regulators of host-bacteria interactions for the identification of the bioactive small molecule signals that they control. IMPORTANCE: Xenorhabdus bacteria are of interest due to their symbiotic relationship with Steinernema nematodes and their ability to produce a variety of natural bioactive compounds. Despite their importance, the regulatory hierarchy connecting specific natural products and their regulators is poorly understood. In this study, comparative metabolomic profiling was utilized to identify the secondary metabolites modulated by the X. nematophila global regulator LrhA. This analysis led to the discovery of three metabolites, including an N-acyl amide that inhibited the egg hatching rate and length of Steinernema carpocapsae nematodes. These findings support the notion that X. nematophila LrhA influences the symbiosis between X. nematophila and S. carpocapsae through N-acyl amide signaling. A deeper understanding of the regulatory hierarchy of these natural products could contribute to a better comprehension of the symbiotic relationship between X. nematophila and S. carpocapsae.
Assuntos
Amidas , Proteínas de Bactérias , Simbiose , Fatores de Transcrição , Xenorhabdus , Xenorhabdus/genética , Xenorhabdus/metabolismo , Xenorhabdus/fisiologia , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Amidas/farmacologia , Amidas/metabolismo , Fatores de Transcrição/metabolismo , Fatores de Transcrição/genética , Regulação Bacteriana da Expressão Gênica , Humanos , Nematoides/microbiologiaRESUMO
OBJECTIVES: Currently, there are no studies that have established the self-perceived cognitive trajectories experienced by breast cancer patients (BCPs) post-chemotherapy. Therefore, we characterized the long-term trajectory of self-perceived cognitive function among Asian early-stage BCPs using the minimal clinically important difference of a subjective measure of cognitive function. METHODS: Early-stage BCPs who received chemotherapy were recruited and assessed at 4 time points: Before chemotherapy initiation (T1), 6 weeks post-chemotherapy initiation (T2), 12 weeks post-chemotherapy initiation (T3), and 15-months post-chemotherapy initiation (T4). All assessments were performed approximately within 2 weeks post-chemotherapy. Subjective and objective cognitive function were assessed using Functional Assessment of Cancer Therapy-Cognitive (version 3) and Headminder™. RESULTS: A total of 166 BCPs were recruited, of whom 131 completed assessment at all time points. Using the minimal clinically important difference of Functional Assessment of Cancer Therapy-Cognitive, 5 distinct cognitive trajectories were established. Of the 131 patients, 70 (53.4%) did not report any clinically significant cognitive impairment. Twenty-one (16.0%) patients reported acute cognitive changes during chemotherapy (T2 and/or T3) but not at T4. Forty patients (30.5%) reported clinically significant cognitive impairment at T4, of whom 18 did not report any cognitive impairment at earlier time points. Fifteen (11.5%) patients reported persistent cognitive impairment throughout all time points, while 7 (5.3%) patients reported intermittent cognitive impairment at T2 and T4 but not at T3. CONCLUSION: This is the first study to establish the existence of heterogeneous cognitive trajectories based on clinically significant thresholds of self-perceived cognitive impairment. The findings have important implications on the window for screening and management of post-chemotherapy cognitive impairment.
Assuntos
Povo Asiático/psicologia , Neoplasias da Mama/psicologia , Sobreviventes de Câncer/psicologia , Disfunção Cognitiva/psicologia , Autoimagem , Adulto , Idoso , Cognição , Progressão da Doença , Feminino , Humanos , Estudos Longitudinais , Pessoa de Meia-Idade , Estudos Prospectivos , SingapuraRESUMO
A strategy for the production of side-chain-to-tail cyclic peptides from ribosomally derived polypeptide precursors is reported. Two genetically encodable unnatural amino acids, bearing either an aryl or alkyl amino group, were investigated for their efficiency toward promoting the formation of medium to large-sized peptide macrocycles via intein-mediated side-chain-to-C-terminus cyclization. While only partial cyclization was observed with precursor proteins containing para-amino-phenylalanine, efficient peptide macrocyclization could be achieved using O-2-aminoethyl-tyrosine as the reactive moiety. Conveniently, the latter was generated upon quantitative, post-translational reduction of the azido-containing counterpart, O-2-azidoethyl-tyrosine, directly in E. coli cells. This methodology could be successfully applied for the production of a 12 mer cyclic peptide with enhanced binding affinity for the model target protein streptavidin as compared to the acyclic counterpart (KD: 5.1 µM vs. 22.4 µM), thus demonstrating its utility toward the creation and investigation of novel, functional macrocyclic peptides.
Assuntos
Aminoácidos/metabolismo , Peptídeos Cíclicos/biossíntese , Peptídeos Cíclicos/química , Ribossomos/metabolismo , Aminoacil-tRNA Sintetases/metabolismo , Ciclização , Escherichia coli/citologia , Escherichia coli/metabolismo , Inteínas , Estreptavidina/metabolismoRESUMO
Escherichia coli is a common inhabitant of the human microbiota and a beacon model organism in biology. However, an understanding of its signaling systems that regulate population-level phenotypes known as quorum sensing remain incomplete. Here, we define the structure and biosynthesis of autoinducer-3 (AI-3), a metabolite of previously unknown structure involved in the pathogenesis of enterohemorrhagic E. coli (EHEC). We demonstrate that novel AI-3 analogs are derived from threonine dehydrogenase (Tdh) products and "abortive" tRNA synthetase reactions, and they are distributed across a variety of Gram-negative and Gram-positive bacterial pathogens. In addition to regulating virulence genes in EHEC, we show that the metabolites exert diverse immunological effects on primary human tissues. The discovery of AI-3 metabolites and their biochemical origins now provides a molecular foundation for investigating the diverse biological roles of these elusive yet widely distributed bacterial signaling molecules.
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Although in recent years there has been an increased awareness of the widespread nature of biofluorescence in the marine environment, the diversity of the molecules responsible for this luminescent phenotype has been mostly limited to green fluorescent proteins (GFPs), GFP-like proteins, and fluorescent fatty acid-binding proteins (FABPs). In the present study, we describe a previously undescribed group of brominated tryptophan-kynurenine small molecule metabolites responsible for the green biofluorescence in two species of sharks and provide their structural, antimicrobial, and spectral characterization. Multi-scale fluorescence microscopy studies guided the discovery of metabolites that were differentially produced in fluorescent versus non-fluorescent skin, as well as the species-specific structural details of their unusual light-guiding denticles. Overall, this study provides the detailed description of a family of small molecules responsible for marine biofluorescence and opens new questions related to their roles in central nervous system signaling, resilience to microbial infections, and photoprotection.
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AIM: Observation with close follow-up ("watch and wait") is a recognized treatment option in patients who achieve a complete clinical response to long course chemoradiotherapy. This review of a prospective database aims to evaluate the clinical outcomes among patients with a complete clinical response managed with observation. METHODS: A prospective study of 32 patients who achieved a complete clinical response was undertaken. The primary outcomes measured were overall and recurrence-free survival, and rate of organ preservation in patients who deferred immediate surgery. RESULTS: Seven patients developed local regrowth over a median follow-up period of 38 months (range, 9-91 months). Median time to detection was 12 months. All seven underwent salvage surgery with complete surgical clearance. One patient developed combined local and systemic recurrence following a low anterior resection. Organ preservation was possible in 25 (78%) patients who sustained a complete clinical response with no evidence of local regrowth or disease recurrence. Among the patients who sustained a complete response, two developed isolated systemic disease. Overall and recurrence-free survival was 95.7% and 87.0%, respectively. CONCLUSION: The majority of patients with rectal cancer who achieved a complete clinical response after chemoradiotherapy and managed with a "watch and wait" approach preserved their rectum and did not develop cancer relapse. Salvage surgery was achieved in all patients who developed local regrowth. The study supports a period of observation in rectal cancer patients who achieve a complete clinical response.
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Quimiorradioterapia , Terapia Neoadjuvante , Recidiva Local de Neoplasia/terapia , Neoplasias Retais/terapia , Terapia de Salvação , Conduta Expectante , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Recidiva Local de Neoplasia/patologia , Estudos Observacionais como Assunto , Prognóstico , Estudos Prospectivos , Neoplasias Retais/patologia , Indução de RemissãoRESUMO
BACKGROUND: Over the last decade, there has been a shift towards endoscopic treatment of high-grade dysplasia (HGD) and T1 stage adenocarcinoma arising in Barrett's oesophagus. Although short-term outcomes are promising, longer-term outcomes remain uncertain and the role of these therapies versus surgery is debated, with surgical mortality rates assumed. However, few studies have specifically determined the outcome for oesophagectomy in the subgroup with HGD or T1 adenocarcinoma. To determine this, we evaluated experience with oesophagectomy for HGD and T1 adenocarcinoma in Barrett's oesophagus. METHODS: Data were analysed from a prospective audit database for oesophagectomy performed at two public and four associated private hospitals in Adelaide, South Australia. Patients with HGD, T1a and T1b adenocarcinoma who underwent oesophagectomy from 20 February 1998 to 17 February 2012 were identified, and their perioperative, post-operative and survival outcomes were determined. RESULTS: From 452 oesophagectomy procedures, 63 (13.9%) individuals who underwent surgery for HGD or T1 adenocarcinoma were identified; HGD - 19 (30.1%), T1a - 18 (28.5 %), T1b - 26 (41.3%). Major complications occurred in eight (12.7%) patients including one (1.6%) death following surgery. Five-year survival for HGD and T1a cancers using Kaplan-Meier analysis was not significantly different from a matched general population without cancer. CONCLUSION: Oesophagectomy for HGD and T1 stage adenocarcinoma in Barrett's oesophagus is associated with favourable outcomes. Outcomes following endoscopic treatments should be benchmarked against these outcomes, not those following oesophagectomy for advanced cancer.
Assuntos
Adenocarcinoma/cirurgia , Esôfago de Barrett/diagnóstico , Detecção Precoce de Câncer , Neoplasias Esofágicas/cirurgia , Esofagectomia/métodos , Estadiamento de Neoplasias , Lesões Pré-Cancerosas , Adenocarcinoma/diagnóstico , Adenocarcinoma/mortalidade , Adulto , Idoso , Neoplasias Esofágicas/diagnóstico , Neoplasias Esofágicas/mortalidade , Esofagoscopia , Feminino , Seguimentos , Humanos , Estimativa de Kaplan-Meier , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Austrália do Sul/epidemiologia , Taxa de Sobrevida/tendências , Resultado do TratamentoRESUMO
Organic dyes with their wide range of molecular structures and spectroscopic features show great promise for solar energy applications. Corroles, structural analogues to porphyrins, are highly fluorescent molecules with tunable properties. We have synthesized a series of structurally similar corroles chelating gallium and phosphorus, along with a ß-chlorinated phosphorus corrole, and determined their photophysical and electrochemical properties. The electrochemical potentials to oxidize the corroles range from 0.78 V vs NHE for the gallium corrole to 1.42 V for the ß-octachlorinated phosphorus corrole. We are interested in developing photosensitizers for water oxidation on a metal oxide-based photoanode, so the corroles were modified to contain a meso-phenyl-COOH substituent for binding to metal oxide surfaces. The ability of these corrole dyes to act as photosensitizers was assessed by comparing the corroles in a model dye sensitized solar cell design. Transient absorption spectroscopy was utilized to analyze recombination dynamics and determine the kinetics of iodide oxidation. The most efficient photoelectrochemical cell was achieved for the phosphorus corrole P-2 with electrochemical properties and kinetics suitable for both photoinduced electron injection into TiO2 and oxidation of iodide. This structure-function study highlights the wide window for tuning corrole electrochemical potentials while still maintaining desirable photophysical properties, important variables when designing dyes for applications in photoelectrochemical water-oxidation cells.