Artificial Polysialic Acid Chains as Sialidase-Resistant Molecular-Anchors to Accumulate Particles on Neutrophil Extracellular Traps

Abstract

Neutrophils are involved in numerous immunological events. One mechanism of neutrophils to combat pathogens is the formation of neutrophil extracellular traps (NETs). Thereby, neutrophils use DNA fibers to form a meshwork of DNA and histones as well as several antimicrobial components to trap and kill invaders. However, the formation of NETs can lead to pathological conditions triggering among other things (e.g., sepsis or acute lung failure), which is mainly a consequence of the cytotoxic characteristics of accumulated extracellular histones. Interestingly, the carbohydrate polysialic acid represents a naturally occurring antagonist of the cytotoxic properties of extracellular histones. Inspired by polysialylated vesicles, we developed polysialylated nanoparticles. Since sialidases are frequently present in areas of NET formation, we protected the sensitive non-reducing end of these homopolymers. To this end, the terminal sialic acid residue of the non-reducing end was oxidized and directly coupled to nanoparticles. The covalently linked sialidase-resistant polysialic acid chains are still able to neutralize histone-mediated cytotoxicity and to initiate binding of these polysialylated particles to NET filaments. Furthermore, polysialylated fluorescent microspheres can be used as a bioanalytical tool to stain NET fibers. Thus, polySia chains might not only be a useful agent to reduce histone-mediated cytotoxicity but also an anchor to accumulate nanoparticles loaded with active substances in areas of NET formation.

Molecular Interactions of the Polysialytransferase Domain (PSTD) in ST8Sia IV with CMP-Sialic Acid and Polysialic Acid Required for Polysialylation of the Neural Cell Adhesion Molecule Proteins: An NMR Study

“…Several significant structural studies have been published providing insight into the importance of the DP of polySia in biochemical, physiological and molecular neurobiological processes. Among others, these studies include the dependency of the DP of polySia binding to neurotrophic factors, their interactions with lactoferrin, their regulation of fibroblast growth factor 2 (FGF) to modulate cell growth, and the cytotoxicity of histones [63][64][65][66][67][68][69][70].…”

“…Importantly, these new findings thus raise the fundamentally important question: "Is it the polydispersity in the length of the polySia moiety on the NCAM protein that helps explain how polySia can modulate such a surprisingly myriad of cell-cell adhesive and cell migration interactions and functions?" [6,8,13,21,24,25,31,33,67,68].…”

Nanotechnology and sialic acid biology

“…Neutrophils by forming neutrophil extracellular traps (NETs) with DNA fibers and histones can combat pathogens and antimicrobial components to kill pathogens, but NETs could lead to pathological conditions like sepsis or acute lung failure due to histone-mediated toxicity. Poly sialic acid NPs with property as an antagonist of the cytotoxic properties of extracellular histones neutralize histone-mediated cytotoxicity and initiate binding of these polysialylated particles to NET filaments [71].…”

The Bovine Antimicrobial Peptide Lactoferricin Interacts with Polysialic Acid without Loss of Its Antimicrobial Activity against Escherichia coli

“…In order to obtain polySia fractions with defined degrees of polymerization (DP), commercially available polySia (a heterogeneous mixture of different chain lengths) was separated by anion-exchange chromatography [46,47]. To receive greater amounts of shorter polySia chain lengths (for native agarose gel electrophoresis and competitive ELISA), polySia was previously partially hydrolyzed.…”

“…Besides the best known function of histones in the packaging of DNA, extracellular histones and their fragments are part of the innate immune system [40], and their antimicrobial capacities have been described in many animal classes, such as insects, fish, amphibians, birds, and mammals [41][42][43][44][45]. In the case of histones, it is known that polySia influences their interactions and/or activity in a chain-length-dependent manner [46][47][48]. However, this interaction does not necessarily have an effect on the functionality of the interaction partners.…”