Recent advances and perspectives in the design and development of polymyxins

The rise of bacterial pathogens with acquired resistance to almost all available antibiotics is becoming a serious public health issue. Polymyxins, antibiotics that were mostly abandoned a few decades ago because of toxicity concerns, are ultimately considered as a last-line therapy to treat infections caused by multi-drug resistant Gram-negative bacteria. This review surveys the progress in understanding polymyxin structure, chemistry, mechanisms of antibacterial activity and nephrotoxicity, biomarkers, synergy and combination with other antimicrobial agents and antibiofilm properties. An update of recent efforts in the design and development of a new generation of polymyxin drugs is also discussed. A novel approach considering the modification of the scaffold of polymyxins to integrate metabolism and detoxification issues into the drug design process is a promising new line to potentially prevent accumulation in kidney and reduce nephrotoxicit

Unveiling the Membrane and Cell Wall Action of Antimicrobial Cyclic Lipopeptides: Modulation of the Spectrum of Activity

Antibiotic resistance is a major public health challenge, and Gram-negative multidrug-resistant bacteria are particularly dangerous. The threat of running out of active molecules is accelerated by the extensive use of antibiotics in the context of the COVID-19 pandemic, and new antibiotics are urgently needed. Colistin and polymyxin B are natural antibiotics considered as last resort drugs for multi-resistant infections, but their use is limited because of neuro- and nephrotoxicity. We previously reported a series of synthetic analogues inspired in natural polymyxins with a flexible scaffold that allows multiple modifications to improve activity and reduce toxicity. In this work, we focus on modifications in the hydrophobic domains, describing analogues that broaden or narrow the spectrum of activity including both Gram-positive and Gram-negative bacteria, with MICs in the low µM range and low hemolytic activity. Using biophysical methods, we explore the interaction of the new molecules with model membranes that mimic the bacterial inner and outer membranes, finding a selective effect on anionic membranes and a mechanism of action based on the alteration of membrane function. Transmission electron microscopy observation confirms that polymyxin analogues kill microbial cells primarily by damaging membrane integrity. Redistribution of the hydrophobicity within the polymyxin molecule seems a plausible approach for the design and development of safer and more selective antibiotics

Recent Advances in Pharmaceutical Sciences VIII

This E-book is the eighth volume of a series that compiles contributions from different areas of the multidisciplinary field of Pharmaceutical Sciences. The E-book consists of 7 chapters that cover the areas of organic chemistry, health and environmental management, plant physiology, food science, toxicology, botany, parasitology, physiology, biochemistry and molecular biology, microbiology, and pharmacology

Membrane association and contact formation by a synthetic analogue of polymyxin B and its fluorescent derivatives

sP-B is a synthetic analogue of the natural lipopeptide antibiotic polymyxin B (PxB) that maintains the ability of the parent compound to form vesicle-vesicle contacts and induce lipid exchange. Exchange is selective, and only monoanionic phospholipids such as 1-palmitoyl-2-oleoyl-glycero-sn-3-phosphoglycerol (POPG) are transferred, whereas dianionic phospholipids such as 1-palmitoyl-2-oleoyl-glycero-sn-3-phosphate (POPA) are not, as shown by fluorescence experiments based on the excimer/monomer ratio of pyrene-labeled phospholipids. Synthetic fluorescent analogues of sP-B are used to investigate the peptide position and orientation in the intermembrane contacts: sP-Bw, an analogue that contains D-tryptophan (D-Trp) instead of the naturally occurring D-phenylalanine, and sP-Bpy, incorporating a pyrene group at the N-terminus. Tryptophan fluorescence, anisotropy, and quenching measurements performed with sP-Bw indicate that the peptide binds and inserts in anionic vesicles of POPG and POPA. However, significant differences are seen depending on the lipid composition, as also demonstrated by fluorescence resonance energy transfer (FRET) experiments from Trp to 7-nitro-2-1,3-benzoxadiazol (NBD) groups at the interface. Intermolecular FRET using sP-Bw as the donor and sP-Bpy as the acceptor indicates self-association of the peptide, possibly forming dimers, when bound to POPG vesicles at concentrations that induce the vesicle-vesicle contacts

Trends in Pharmaceutical and Food Sciences I

Podeu consultar el llibre complet a: https://medwinpublishers.com/OAJPR/OAJPR16000eB001.pdfTrends in Pharmaceutical and Food Sciences I is the first issue of an open access E-book devoted to scientific and technical research that covers the entire spectrum of drug and food research, including medicinal chemistry, pharmacology, drug delivery, microbiology and biochemical studies, as well as relevant developments in nutrition, food safety and analytical innovation. The first chapter, Different techniques to detect G protein coupled receptor heteromers, describes state of the art techniques based in biophysical principles applied to detect oligomeric aggregates formed by G-protein coupled receptors in the cell membrane, and describes how the knowledge generated can be applied to design new compounds for the treatment of neurological and mental diseases. Obesity has become a worldwide problem and it is well known that causes and exacerbates many health problems by promoting profound changes in physiological functions. Chapter 2, Analysis of the role of diet in the appearance of neurodegenerative processes, reviews the consequences of these metabolic alterations while considering their effects in the development of Type 2 Diabetes Mellitus, and their role in the appearance of cognitive impairments such as the sporadic forms of Alzheimer’s disease. The development of new cultivars facing climate change is an issue of great interest for the agrochemical industry and can be approached in different ways. Chapter 3, Arabidopsis Thaliana A Model for the Study of Plant Speciation, reviews different aspects of the plant immune system and the different layers of the plant immune response and signaling. The emerging field in plant research that studies how soil microbiota influences plant basic mechanisms is also discussed. Chagas disease is endemic in Latin America, but recently and due to human migrations, it is becoming a global health problem. In chapter 4, Trypanosoma cruzi infection diagnosis: New insights, challenges and perspectives, a group of experts from several institutions describe the different techniques that can be used for the serological diagnosis of the infection and the characterization of Trypanosoma cruzi, discuss the advantages and drawbacks of each method and propose improvements that would entail important savings for health institutions. Chapter 5, Nutrients, Control of Gene Expression and Metabolic Homeostasis, focuses on the molecular mechanisms that control metabolism by means of regulating gene expression in response to dietary inputs, to design new therapeutic strategies based on nutritional interventions against metabolic diseases. In this context, involvement of FGF21 hormone in the regulation of lipid metabolism during amino acid starvation is described, thus reinforcing its important role as an endocrine factor in coordinating energy homeostasis under a variety of nutritional conditions. This raises the possibility of dietary modulation of circulating levels of FGF21 as an alternative approach to its pharmacological administration. Biodegradable polymeric nanoparticles encapsulating neuroprotective drugs have enormous potential to treat neurodegenerative diseases, including Alzheimer´s disease and glaucoma. Recent advances in the field are described in chapter 6, Polymeric nanoparticles for the treatment of neurodegenerative diseases: Alzheimer’s disease and glaucoma, specifically the preparation of engineered polymeric nanoparticles with attached peptides or antibodies to increase their bioavailability, favoring their transport through the blood brain barrier and the blood retinal barrier, avoiding at the same time possible drug adverse and toxic effects. The last chapter, Pentacyclic triterpenes in table olives: Determination of their composition and bioavailability by LC-M, is a review on the pentacyclic triterpenes contained in table olives, natural compounds of enormous interest due to their beneficial effects on human health, including hepatoprotective, anti-diabetic, antiviral, cardioprotective and antitumor activities. Authors describe a selective and sensitive LC–MS method for the simultaneous determination of the main triterpenic compounds present in Olea europaea L. This opens the possibility to bioavailability studies after consumption of different foods, or administration of plants widely used in traditional medicine, with the aim of studying in depth the beneficial effects of these compounds in human beings. We hope that this new volume will attract the interest of all the scientific community, especially those working in the fields of pharmaceutical, medical, biological, chemical and food sciences

Tryptophan-containing lipopeptide antibiotics derived from polymyxin B with activity against Gram positive and Gram negative bacteria

Resistance to all known antibiotics is a growing concern worldwide, and has renewed the interest in antimicrobial peptides, a structurally diverse class of amphipathic molecules that essentially act on the bacterial membrane. Propelled by the antimicrobial potential of this compound class, we have designed three new lipopeptides derived from polymyxin B, sp-34, sp-96 and sp-100, with potent antimicrobial activity against both Gram positive and Gram negative bacteria. The three peptides bind with high affinity to lipopolysaccharide as demonstrated by monolayer penetration and dansyl-displacement. The interaction with the cytoplasmic membrane has been elucidated by biophysical experiments with model membranes of POPG or POPE/POPG (6:4), mimicking the Gram positive and Gram negative bacterial membrane. Trp-based fluorescence experiments including steady-state, quenching, anisotropy and FRET, reveal selectivity for anionic phospholipids and deep insertion into the membrane. All three lipopeptides induce membrane fusion and leakage from anionic vesicles, a process that is favored by the presence of POPE. The molecules bind to zwitterionic POPC vesicles, a model of the eukaryotic membrane, but in a different way, with lower affinity, less penetration into the bilayer and no fusion or permeabilization of the membrane. Results in model membranes are consistent with flow cytometry experiments in Escherichia coli and Staphylococcus aureus using a membrane potential sensitive dye (bis-oxonol) and a nucleic acid dye (propidium iodide), suggesting that the mechanism of action is based on membrane binding and collapse of membrane integrity by depolarization and permeabilization. (C) 2015 Elsevier B.V. All rights reserved

Synergistic antipseudomonal effects of synthetic peptide AMP38 and carbapenems

The aim was to explore the antimicrobial activity of a synthetic peptide (AMP38) and its synergy with imipenem against imipenem-resistant Pseudomonas aeruginosa. The main mechanism of imipenem resistance is the loss or alteration of protein OprD. Time-kill and minimal biofilm eradication concentration (MBEC) determinations were carried out by using clinical imipenem-resistant strains. AMP38 was markedly synergistic with imipenem when determined in imipenem-resistant P. aeruginosa. MBEC obtained for the combination of AMP38 and imipenem was of 62.5 μg/mL, whereas the MBEC of each antimicrobial separately was 500 μg/mL. AMP38 should be regarded as a promising antimicrobial to fight MDR P. aeruginosa infections. Moreover, killing effect and antibiofilm activity of AMP38 plus imipenem was much higher than that of colistin plus imipenem

A bioinspired peptide scaffold with high antibiotic activity and low in vivo toxicity

Bacterial resistance to almost all available antibiotics is an important public health issue. A major goal in antimicrobial drug discovery is the generation of new chemicals capable of killing pathogens with high selectivity, particularly multi-drug-resistant ones. Here we report the design, preparation and activity of new compounds based on a tunable, chemically accessible and upscalable lipopeptide scaffold amenable to suitable hit-to-lead development. Such compounds could become therapeutic candidates and future antibiotics available on the market. The compounds are cyclic, contain two D-amino acids for in vivo stability and their structures are reminiscent of other cyclic disulfide-containing peptides available on the market. The optimized compounds prove to be highly active against clinically relevant Gram-negative and Gram-positive bacteria. In vitro and in vivo tests show the low toxicity of the compounds. Their antimicrobial activity against resistant and multidrug-resistant bacteria is at the membrane level, although other targets may also be involved depending on the bacterial strain

Adaptación Metodológica al EEES de la asignatura de Técnicas Instrumentales del Grado de Farmacia de la Universidad de Barcelona

[cast] En el plan de estudios del Grado de Farmacia de la Universidad de Barcelona, la asignatura de Técnicas Instrumentales se imparte en el cuarto semestre, después de haber cursado Física, Fisicoquímica y Química Analítica. El equipo docente de la asignatura está integrado por once profesores que mediante trabajo colaborativo y adecuada coordinación organizan la docencia de la misma que se distribuye en clases teóricas y prácticas. Con el objetivo de adaptar la asignatura a las necesidades del Espacio Europeo de Educación Superior, se distribuyó en tres Bloques: I, Técnicas Espectroscópicas; II, Técnicas Electroquímicas y III, Técnicas de Separación. Las actividades teórico-prácticas se han planificado de manera secuencial. Así se inicia el ciclo con las clases teóricas del Bloque I y a continuación de manera paralela se imparten las clases prácticas del Bloque I y las clases teóricas del Bloque II y así sucesivamente, de manera que se termina la docencia con las prácticas del último Bloque. En este proceso adquiere especial relevancia tanto la formación práctica en el laboratorio como el trabajo tutorizado que debe realizar el estudiante. Se realiza un proceso de evaluación continuada teórico/práctico en cada uno de los Bloques. Se da especial relevancia a la adquisición de habilidades y destrezas que permitan una correcta realización de las prácticas de laboratorio, es decir la integración de los contenidos específicos a la aplicación de las diferentes técnicas instrumentales, la resolución de los cálculos numéricos y la interpretación de los resultados. [eng] In the new syllabus of the Pharmacy degree at the University of Barcelona, the subject Analytical Techniques is taught at the fourth semester, after the subjects Physics, Physical chemistry and Analytical chemistry. The teaching team of this subject is integrated by eleven teachers that by means of collaborative work and an appropriate coordination, organize the docent activity into practical and theoretical classes. With the aim to adapt this subject to the requirements of the European space for higher education, it has been designed in three blocs: I. Spectroscopic techniques, II. Electrochemical techniques and, III. Separation techniques, by planning the theoretical and practical activities in a sequential manner. Therefore, the cycle begins with the theory of the first bloc followed with the practice corresponding to it together with the theory of the second bloc, and so on. The course ends with the practical part of the third bloc. In this process is of great importance the tutorial work that the student should do. The evaluation of the theory and of the practical part of each bloc is done in a continuous way paying special focus on the acquisition of abilities and handiness that will allow the correct performance in the laboratory. In summary, the integration of the specific contents to the application of the different instrumental techniques, the resolution of the numerical calculations and the interpretation of the results

Estudio de encapsulación de gentamicina en liposomas

Tesi de Llicenciatura per a la obtenció del Grau de Farmàcia. Facultat de Farmàcia. Universitat de Barcelona. Director: Francisca Reig Isart, Ma. Asunción Alsina Esteller. 1988.Los liposomas son vesículas que contienen compartimentos acuosos concéntricos separados entre sí y del medio externo acuoso por bicapas concéntricas de lípidos anfifílicos (figura 1). El término liposoma fue utilizado por primera vez por Bangham y Horne (1) , al observar por microscopía electrónica una suspensión de fosfolípidos de origen celular aislados y purificados. Los liposomas pueden prepararse con una gran variedad de lípidos naturales o sintéticos, o bien con mezclas de ellos; los más comunmente utilizados son los fosfolípidos y el colesterol, cuya fórmula general se muestra en la figura