140,038 research outputs found
Different approaches to optimize the antimicrobial properties of cationic peptides: substitution by non-coded amino acids and conjugation to nanoparticles
No full textAntimicrobial peptides are small, cationic and amphipathic peptides produced by virtually all living organisms as key components of the innate immune system. Importantly, they hold promise for the development of new broad-spectrum anti-infective agents. These are urgently needed, due to the growing emergence of microorganisms that are resistant to the available therapeutic agents. In recent years, research has focused on the characterization and optimization of these molecules. Albeit thousands of peptides have been isolated and characterized, only a reduced number of them has entered into clinical phases, because of some limitations. Among them: (i) the poor peptide bioavailability, (ii) the toxicity at high doses (iii) the high susceptibility to proteolytic degradation (iv) the inefficient peptide delivery to the target site at high concentration.
Nowadays, thanks to advances in biochemical research, computational studies and nanotechnologies it has become possible to overcome some of these problems.
Recently, a frog-skin derived AMP, named Esc(1-21), has been investigated for its potent activity against the Gram-negative bacterium Pseudomonas aeruginosa and immunomodulatory properties. However, it showed a weaker activity against Gram-positive bacteria and some cytotoxic effect on mammalian cells.
In this thesis work, with the aim to optimize the biological properties of AMPs, e.g. Esc(1-21), three different approaches have been used:
- Design and synthesis of an analog of Esc(1-21) carrying three alpha-aminoisobutyric acid (Aib) residues. When inserted into the primary structure of
peptides, Aib residues are expected to increase the alpha-helical content of the peptides, due to their strong helicogenicity. Importantly, a stabilized alpha-helical structure is known to be a crucial parameter to improve the AMPs’ activity against Gram-positive bacteria but also to increase their toxicity against mammalian cells. The Aib-containing peptide has been studied for its structural and biological properties and compared with the parent peptide Esc(1-21).
- Design and synthesis of a diastereomer of Esc(1-21), named Esc(1-21)-1c, by replacing two L-amino acids in the C-terminal portion, i.e. L-Leu14 and L-Ser17, with the corresponding D-enantiomers. Besides making a peptide more resistant to proteolytic degradation, the insertion of D- amino acids is expected to disrupt the peptide’s alpha-helical content and to reduce its cytotoxicity. The effect(s) of D-amino acids incorporation on the structural/biological properties of the peptide have been investigated.
- Design and production of two different types of nanoparticles to protect the AMP from proteolytic degradation and to allow its delivery to the target site at high concentration without altering the antimicrobial properties: (i) inorganic gold nanoparticles (AuNPs) coated with Esc(1-21) and (ii) nano-embedded microparticles for pulmonary delivery of a model cationic antimicrobial peptide, i.e. colistin.
As expected, the Aib-analog of Esc(1-21) resulted to be more active against Gram-positive bacteria, but also more cytotoxic against mammalian cells, due to its higher alpha-helical content in the secondary structure.
Differently, the insertion of two D-amino acids provoked a disruption of the alpha-helix and, as a consequence, a significant reduction in the peptide’s cytotoxic effect. In addition, the diastereomer resulted to be more active against the biofilm form of P. aeruginosa and more stable in human serum.
The conjugation of Esc(1-21) to AuNPs, led to an increase of the antimicrobial activity of the peptide and to a greater stability to proteolytic degradation, without interfering with the mechanism of membrane perturbation. In addition, the conjugation onto AuNPs did not affect the wound-healing properties of the free peptide and AuNPs@Esc(1-21) were not found to be toxic against human keratinocytes.
Finally, the engineered biocompatible and biodegradable polymeric microparticles designed as a delivery system for an AMP model, i.e. colistin, resulted to have a prolonged activity against P. aeruginosa biofilm in comparison with the free peptide. This was likely due to their ability to penetrate into bacterial biofilm and to sustain colistin release inside it.
The promising results obtained by these different approaches, have made it possible to take a step forward in the optimization of a cationic peptide for the development of potential new antibacterial drugs
Análisis de técnicas, formas y estéticas de composición en dos obras de jazz contemporáneo de Shai Maestro
No full textLa presente investigación tiene como propósito identificar y analizar el conjunto de recursos
musicales que generan nuevas estéticas de composición en el repertorio del pianista de jazz
israelí, Shai Maestro. Este análisis propone definir la estructura de las obras y descomponer
sus elementos constituyentes, pues esto permite la comprensión de la función de cada recurso
utilizado dentro de dicha estructura. La complejidad inherente a las piezas escogidas para este
trabajo brinda un panorama musical lleno de elementos que son el resultado de la fusión de
distintas culturas musicales. Con influencias tanto occidentales como orientales, Shai Maestro
recrea la diversidad de estímulos musicales con la que actualmente crecen los compositores
gracias a la globalización. Teniendo la métrica de 7/4 como único elemento en común, las
piezas a estudiar fueron elegidas porque ofrecen dos estilos y técnicas de composición que
contrastan dramáticamente. El resultado de este trabajo aporta herramientas para la
comprensión y asimilación del uso de los diversos recursos musicales en las obras de
Maestro. Asimismo, ofrece nuevas opciones para la utilización y manipulación de ideas
musicales en una pieza de jazz contemporáneo a quienes estén interesados en desarrollar
habilidades de composición en este género
LPS is a Key Molecule in the Synergistic Effect of Temporins on Gram-Negative Bacteria
No full textThe growing emergence of multidrug-resistant microbes requires the discovery of new antibiotics with new modes of action. Naturally occurring antimicrobial peptides (AMPs), which are produced by almost all forms of life, represent promising candidates [1].
There is compelling evidence that unlike conventional antibiotics, most AMPs interact and increase the permeability of the bacterial membrane as part of their killing mechanism. However, before reaching it, they need to cross the cell wall that, in Gram-negative bacteria, is surrounded by the lipopolysaccharide (LPS)-outer membrane, which forms a very efficient barrier against a variety of hydrophilic and hydrophobic molecules [2, 3].
In Amphibia, temporins are among the shortest (10 to 16 residues) AMPs, with up to ten isoforms within the same specimen [4]. However, the biological significance of the coexistence of so many isoforms in a single living organism is not clear. We addressed this question using temporins A, B and L isolated from Rana temporaria skin secretion.
In this study, we show that temporins A and B, which are only weakly active on Gram-negative bacteria, can synergize, when combined each with temporin L, to overcome the bacterial resistance imposed by the LPS protective layer. Furthermore, this effect is highly dependent on the type of LPS. To understand the underlying mechanism, we investigated the effect of two types of LPS (from E. coli O111:B4 and O26:B6) on the organization of temporins, alone and when mixed one with each other. Our data indicate that the synergism between temporins is related to the ability of temporin L to prevent the oligomerization of A and B when in contact with LPS O111:B4, thus allowing their traslocation across the bacterial cell wall into the target cytoplasmic membrane [5].
Overall, such studies should contribute to the development of new peptide-based anti-infective therapeutic strategies, urgently needed because of the increasing microbial resistance to the available antibiotics.
References
1. Zasloff, M. 2002. Antimicrobial peptides of multicellular organisms. Nature. 415: 389-395.
2. Nikaido, H. 1994. Prevention of drug access to bacterial targets: permeability barriers and active efflux. Science. 264: 382-8.
3. Papo, N. and Y. Shai. 2005.A molecular mechanism for lipopolysaccharide protection of Gram-negative bacteria from antimicrobial peptides. J Biol Chem. 280: 10378-87.
4. Mangoni, M.L. 2006.Temporins, anti-infective peptides with expanding properties. Cell Mol Life Sci.
5. Rosenfeld, Y., D. Barra, M. Simmaco, Y. Shai and M.L. Mangoni. 2006. A synergism between temporins toward Gram-negative bacteria overcomes resistance imposed by the lipopolysaccharide protective layer. J Biol Chem. 281: 28565-74
Prevalence, trends and associated factors of malaria in the Shai-Osudoku District Hospital, Ghana
No full textAbstract Background Even though malaria is easily preventable and treatable, it continues to have a devastating impact on people’s health and livelihoods around the world. Sub-Saharan Africa carries a disproportionately high share of the global malaria burden. This study seeks to assess the prevalence, trends and factors associated with malaria in the Shai-Osudoku District Hospital, Ghana. Methods A cross-sectional study was conducted to determine the prevalence, trend, and factors associated with malaria in the Shai-Osudoku District Hospital; a 10-month secondary data was extracted from February to November 2020. The extracted data were entered into Epi Data version 6 and analysed using STATA version 16. Descriptive analysis was performed to determine the prevalence, trend and socio-demographic characteristics of study participants. Simple logistic regression at a 95% confidence level was performed to investigate socio-demographic factors associated with malaria infection. Tables and charts with summary statistics were used to present the results. Results Secondary data from 3896 individuals were included in the study. The age of the participants range from 0.8 to 101 years with a mean age of 32.5. The estimated prevalence of malaria during the study period is 20.9%. A majority (79.1%) of the participants who presented signs and symptoms of malaria were negative after testing. The prevalence of malaria cases increased progressively from 6.7 to 55.4% across the ten months. The simple logistic regression at a 95% confidence level revealed that age group, sex, residential status, religion, occupation and marital status were statistically significantly associated with malaria. The results shows that persons who tested positive for malaria were mostly treated with artemether-lumefantrine (46.1%), some malaria positive cases were given artesunate injection (11.6%), dihydroartemisinin-piperaquine (16.2%) and oral artemether-lumefantrine (6.5%). Surprisingly 19.6% of the malaria-positive cases were not given any form of malaria medication. Conclusion Factors found to influence malaria infection in the Shai-Osudoku District Hospital include participant’s age, sex, residential status, religious affiliation occupation and marital status. The findings of this study showed that malaria remains a serious public health problem in the Shai Osudoku District Hospital. The information obtained from this study can guide the implementation of malaria prevention, control and elimination strategies in Ghana
Synergism between temporins in Killing of Gram-negative bacteria and in neutralizing lipopolysaccharide-activation of macrophages
No full textA synergism between temporins toward gram-negative bacteria overcomes resistance imposed by the lipopolysaccharide protective layer
No full textTemporins are short and homologous antimicrobial peptides (AMPs) isolated from the frog skin of Rana genus. To date, very little is known about the biological significance of the presence of closely related AMPs in single living organisms. Here we addressed this question using temporins A, B, and L isolated from Rana temporaria. We found that temporins A and B are only weakly active toward Gram-negative bacteria. However, a marked synergism occurs when each is mixed with temporin L. To shed light on the underlying mechanisms involved in these activities, we used various experimental strategies to investigate: (i) the effect of the peptides' interaction on both the viability and membrane permeability of intact bacteria and spheroplasts; (ii) their interaction with lipopolysaccharides (LPS) and the effect of LPS on the oligomeric state of temporins, alone or combining one with another; (iii) their structure in solution and when bound to LPS, by using circular dichroism and ATR-FTIR spectroscopies. Our data reveal that temporin L synergizes with A and B by preventing their oligomerization in LPS. This should promote their translocation across the outer membrane into the cytoplasmic membrane. To the best of our knowledge, this is the first study that explains how a combination of native AMPs from the same species can overcome bacterial resistance imposed by the LPS leaflet
Chronic Radiodermatitis
No full textChronic radiodermatitis (CRD) is defi ned as a chronic infl ammation of the
skin associated with exposure to ionizing radiation. It usually presents in
individuals who, because of their profession, have been repeatedly exposed
to low doses of radiation over a long period of time without appropriate
protection. Few treatments have been found which affect the natural history
of this disease: topical 5-fl uorouracil, antibiotic cream, topical corticosteroids
and cryosurgery. Nevertheless, only surgery with excision and
grafting provides satisfactory treatment for extensive radionecrosis. In
selected cases, cryosurgery seems to be a safe and useful treatment for
CRD because it eliminates pain and avoids surgical procedures
HER2-Low Breast Cancer: Current Landscape and Future Prospects
No full textYelena Shirman, Shlomit Lubovsky, Ayelet Shai Division of Oncology, Rambam Health Care Campus, Haifa, IsraelCorrespondence: Ayelet Shai, Division of Oncology, Rambam Health Care Campus, HaAliya HaShniya St 8, PO Box 9602, Haifa, 3109601, Israel, Tel +972-47776400, Email [email protected]: More than 50% of breast cancers are currently defined as “Human epidermal growth factor receptor 2 (HER2) low breast cancer (BC)”, with HER2 immunohistochemistry (IHC) scores of +1 or +2 with a negative fluorescence in situ hybridization (FISH) test. In most studies that compared the clinical and biological characteristics of HER2-low BC with HER2-negative BC, HER2-low was not associated with unique clinical and molecular characteristics, and it seems that the importance of HER2 in these tumors is being a docking site for the antibody portion of antibody drug conjugates (ADCs). Current pathological methods may underestimate the proportion of BCs that express low levels of HER2 due to analytical limitations and tumor heterogeneity. In this review we summarize and contextualize the most recent literature on HER2-low breast cancers, including clinical and translational studies We also review the challenges of assessing low HER2 expression in BC and discuss the current and future therapeutic landscape for these tumors.Keywords: HER2-low, ERBB2 low, breast cancer, HER2 targeted therapy, trastuzumab, trastuzumab-deruxtecan, T-DX
Functional coordination of alternative splicing in the mammalian central nervous system
No full textBACKGROUND: Alternative splicing (AS) functions to expand proteomic complexity and plays numerous important roles in gene regulation. However, the extent to which AS coordinates functions in a cell and tissue type specific manner is not known. Moreover, the sequence code that underlies cell and tissue type specific regulation of AS is poorly understood. RESULTS: Using quantitative AS microarray profiling, we have identified a large number of widely expressed mouse genes that contain single or coordinated pairs of alternative exons that are spliced in a tissue regulated fashion. The majority of these AS events display differential regulation in central nervous system (CNS) tissues. Approximately half of the corresponding genes have neural specific functions and operate in common processes and interconnected pathways. Differential regulation of AS in the CNS tissues correlates strongly with a set of mostly new motifs that are predominantly located in the intron and constitutive exon sequences neighboring CNS-regulated alternative exons. Different subsets of these motifs are correlated with either increased inclusion or increased exclusion of alternative exons in CNS tissues, relative to the other profiled tissues. CONCLUSION: Our findings provide new evidence that specific cellular processes in the mammalian CNS are coordinated at the level of AS, and that a complex splicing code underlies CNS specific AS regulation. This code appears to comprise many new motifs, some of which are located in the constitutive exons neighboring regulated alternative exons. These data provide a basis for understanding the molecular mechanisms by which the tissue specific functions of widely expressed genes are coordinated at the level of AS
Primary monocytes regulate endothelial cell survival through secretion of Angiopoietin-1 and activation of endothelial Tie2
No full textObjective—Monocyte recruitment and interaction with the endothelium is imperative to vascular recovery. Tie2 plays a key role in endothelial health and vascular remodeling. We studied monocyte-mediated Tie2/angiopoietin signaling following interaction of primary monocytes with endothelial cells and its role in endothelial cell survival.
Methods and Results—The direct interaction of primary monocytes with subconfluent endothelial cells resulted in transient secretion of angiopoietin-1 from monocytes and the activation of endothelial Tie2. This effect was abolished by preactivation of monocytes with tumor necrosis factor-α. Although primary monocytes contained high levels of both angiopoietin 1 and 2, endothelial cells contained primarily angiopoietin 2. Seeding of monocytes on serum-starved endothelial cells reduced caspase-3 activity by 46±5.1%, and 52±5.8% after tumor necrosis factor-α treatment and decreased detected single-stranded DNA levels by 41±4.2% and 40±3.5%, respectively. This protective effect of monocytes on endothelial cells was reversed by Tie2 silencing with specific short interfering RNA. The antiapoptotic effect of monocytes was further supported by the activation of cell survival signaling pathways involving phosphatidylinositol 3-kinase, STAT3, and AKT.
Conclusion—Monocytes and endothelial cells form a unique Tie2/angiopoietin-1 signaling system that affects endothelial cell survival and may play critical a role in vascular remodeling and homeostasis
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