Biophysical Mechanisms of the Neutralization of Endotoxins by Lipopolyamines

Endotoxins (lipopolysaccharides, LPS) are one of the strongest immunostimulators in nature, responsible for beneficial effects at low, and pathophysiological effects at high concentrations, the latter frequently leading to sepsis and septic shock associated with high mortality in critical care settings. There are no drugs specifically targeting the pathophysiology of sepsis, and new therapeutic agents are therefore urgently needed. The lipopolyamines are a novel class of small molecules designed to sequester and neutralize LPS. To understand the mechanisms underlying the binding and neutralization of LPS toxicity, we have performed detailed biophysical analyses of the interactions of LPS with candidate lipopolyamines which differ in their potencies of LPS neutralization. We examined gel-to-liquid crystalline phase behavior of LPS and of its supramolecular aggregate structures in the absence and presence of lipopolyamines, the ability of such compounds to incorporate into different membrane systems, and the thermodynamics of the LPS:lipopolyamine binding. We have found that the mechanisms which govern the inactivation process of LPS obey similar rules as found for other active endotoxin neutralizers such as certain antimicrobial peptides

Peptide interactions with bacterial lipopolysaccharides

Peptide and protein interactions with (lipo)polysaccharides are important in various biological contexts, including lipoprotein deposition at proteoglycan-covered endothelial surfaces in atherosclerosis, lectin functionality, and the interaction of antimicrobial and anti-inflammatory peptides and proteins with (lipo)polysaccharides. The latter of these areas, which is the topic of this review, has attracted considerable interest during the last few years, since antimicrobial peptides may offer novel therapeutic opportunities in an era of growing problems with antibiotic resistance, and persisting problems with both acute and chronic inflammation. In the present overview, physicochemical factors affecting peptide interactions with bacterial (lipo)polysaccharides are discussed, both in solution and at membrane interfaces. In doing so, an attempt is made to illustrate how physicochemical factors affect the antimicrobial and anti-endotoxic functionality of such peptides, and how knowledge on this can be translated into therapeutic opportunities, e.g., in sepsis. (C) 2013 Elsevier Ltd. All rights reserved

ДОСЛІДЖЕННЯ ЕКОНОМІЧНОЇ ПРИРОДИ АМОРТИЗАЦІЇ

В статті досліджується амортизація як економічна категорія і реальний процес господарської діяльності підприємств. Виділені основні проблеми, що виникають під час її обліку та стоять на заваді використання амортизації як джерела нагромадження основного капіталу. Запропоновано напрямки перетворення її у власне інвестиційне джерело підприємств. Depreciation as an economic category and real process of enterprises’ activity are investigated in the article. The author determines the main problems, which are the obstacles for depreciation’s calculating as well as using it as the source of the fixed capital accumulation, and suggests the ways of transformation it into own investment source of the enterprises

The synthetic antimicrobial peptide 19-2.5 attenuates septic cardiomyopathy and prevents down-regulation of SERCA2 in polymicrobial sepsis

LM has received grants by the Faculty of Medicine at the RWTH Aachen University (START 15/14 and START 46/16) and the Deutsche Forschungsgemeinschaft (DFG, MA 7082/1–1). This work was supported by the Immunohistochemistry and Confocal Microscopy Unit, a core facility of the Interdisciplinary Centre for Clinical Research (IZKF) Aachen, within the Faculty of Medicine at the RWTH Aachen University and the RWTH centralized Biomaterial Database (RWTH cBMB) of the University Hospital RWTH Aachen. We are very grateful to Antons Martincuks M.Sc. and Professor Gerhard Müller-Newen for live-cell imaging. This work was supported, in part, by the University of Turin (ex-60% 2015A and B) and by the William Harvey Research Foundation and forms part of the research themes contributing to the translational research portfolio of Barts and the London Cardiovascular Biomedical Research Unit that is supported and funded by the National Institute for Health Research. This work also contributes to the Organ Protection research theme of the Barts Centre for Trauma Sciences supported by the Barts and The London Charity (Award 753/1722)

Biophysical mechanisms of endotoxin neutralization by cationic amphiphilic peptides

Bacterial endotoxins (lipopolysaccharides (LPS)) are strong elicitors of the human immune system by interacting with serum and membrane proteins such as lipopolysaccharide-binding protein (LBP) and CD14 with high specificity. At LPS concentrations as low as 0.3 ng/ml, such interactions may lead to severe pathophysiological effects, including sepsis and septic shock. One approach to inhibit an uncontrolled inflammatory reaction is the use of appropriate polycationic and amphiphilic antimicrobial peptides, here called synthetic anti-LPS peptides (SALPs). We designed various SALP structures and investigated their ability to inhibit LPS-induced cytokine secretion in vitro, their protective effect in a mouse model of sepsis, and their cytotoxicity in physiological human cells. Using a variety of biophysical techniques, we investigated selected SALPs with considerable differences in their biological responses to characterize and understand the mechanism of LPS inactivation by SALPs. Our investigations show that neutralization of LPS by peptides is associated with a fluidization of the LPS acyl chains, a strong exothermic Coulomb interaction between the two compounds, and a drastic change of the LPS aggregate type from cubic into multilamellar, with an increase in the aggregate sizes, inhibiting the binding of LBP and other mammalian proteins to the endotoxin. At the same time, peptide binding to phospholipids of human origin (e.g., phosphatidylcholine) does not cause essential structural changes, such as changes in membrane fluidity and bilayer structure. The absence of cytotoxicity is explained by the high specificity of the interaction of the peptides with LPS

Bacterial cell wall compounds as promising targets of antimicrobial agents I. Antimicrobial peptides and lipopolyamines

The first barrier that an antimicrobial agent must overcome when interacting with its target is the microbial cell wall. In the case of Gram-negative bacteria, additional to the cytoplasmic membrane and the peptidoglycan layer, an outer membrane (OM) is the outermost barrier. The OM has an asymmetric distribution of the lipids with phospholipids and lipopolysaccharide (LPS) located in the inner and outer leaflets, respectively. In contrast, Gram-positive bacteria lack OM and possess a much thicker peptidoglycan layer compared to their Gram-negative counterparts. An additional class of amphiphiles exists in Gram-positives, the lipoteichoic acids (LTA), which may represent important structural components. These long molecules cross-bridge the entire cell envelope with their lipid component inserting into the outer leaflet of the cytoplasmic membrane and the teichoic acid portion penetrating into the peptidoglycan layer. Furthermore, both classes of bacteria have other important amphiphiles, such as lipoproteins, whose importance has become evident only recently. It is not known yet whether any of these amphiphilic components are able to stimulate the immune system under physiological conditions as constituents of intact bacteria. However, all of them have a very high pro-inflammatory activity when released from the cell. Such a release may take place through the interaction with the immune system, or with antibiotics (particularly with those targeting cell wall components), or simply by the bacterial division. Therefore, a given antimicrobial agent must ideally have a double character, namely, it must overcome the bacterial cell wall barrier, without inducing the liberation of the pro-inflammatory amphiphiles. Here, new data are presented which describe the development and use of membrane-active antimicrobial agents, in particular antimicrobial peptides (AMPs) and lipopolyamines. In this way, essential progress was achieved, in particular with respect to the inhibition of deleterious consequences of bacterial infections such as severe sepsis and septic shock