No abstract

In inflammation, extensive cell death may occur, which results in the release of chromatin components into the extracellular environment. Individually, the purified chromatin components double stranded (ds)DNA and histones have been demonstrated, both in vitro and in vivo, to display various immunostimulatory effects, for example, histones induce cytotoxicity and proinflammatory signaling through toll-like receptor (TLR)2 and 4, while DNA induces signaling through TLR9 and intracellular nucleic acid sensing mechanisms. However, DNA and histones are organized in nucleosomes in the nucleus, and evidence suggests that nucleosomes are released as such in inflammation. The cytotoxicity and proinflammatory signaling induced by nucleosomes have not been studied as extensively as the separate effects brought about by histones and dsDNA, and there appear to be some marked differences. Remarkably, little distinction between the different forms in which histones circulate has been made throughout literature. This is partly due to the limitations of existing techniques to differentiate between histones in their free or DNA-bound form. Here we review the current understanding of immunostimulation induced by extracellular histones, dsDNA and nucleosomes, and discuss the importance of techniques that in their detection differentiate between these different chromatin components.

Effects of thermal processing (toasting or extrusion) of untoasted soybean meal on growth performance, apparent ileal nutrient digestibilities, and chyme characteristics were studied in broiler chicks fed diets with soybean meal as the main protein source. Effects of increasing shear forces during extrusion as well as enzyme treatments (protease and carbohydrase) were also studied. When compared with toasting, extrusion significantly improved feed conversion ratio (1.56 vs 1.62) and apparent ileal digestibilities of CP and nonstarch polysaccharides (87.5 vs 82.2% and 26.7 vs 11.4%, respectively). Enzyme treatment improved apparent ileal digestibility of CP and nonstarch polysaccharide compared with no enzyme treatment (85.2 vs 83.7% and 20.6 vs 14.5%, respectively); however, enzyme treatments did not result in a better growth performance of the chicks. Among the enzyme treatments, no differences were found in growth performance and apparent ileal CP digestibility, whereas the carbohydrase significantly improved apparent ileal nonstarch polysaccharide digestibility compared with the other enzyme treatments. Extrusion of SBM at the highest shear level caused a significant increase in the water-holding capacity, chyme viscosity, and concentration of soluble nonstarch polysaccharides in the chyme compared with extrusion of SBM at lower shear levels. The increase in chyme viscosity did not affect growth performance, nor did it influence apparent ileal nutrient digestibilities.

The in vitro accessibility of the water unextractable solids (WUS) from untreated, toasted, and extruded soybean meals toward different enzyme activities was studied. WUS was incubated with seven commercial enzyme preparations. Two enzyme preparations were selected for further research. Upon addition of Neutrase, the extruded sample yielded considerably more solubilized protein compared with the toasted and untreated soybean meals. Energex solubilized high amounts of neutral sugars after heat treatments compared with the untreated meal. Cell wall polysaccharides solubilized by the enzymes were released as small oligosaccharides and monosaccharides. SDS−PAGE analysis showed that after enzyme addition to the extruded sample, proteins were more rapidly and completely degraded compared with enzyme addition to the toasted and untreated soybean meals. Neutrase degraded both β-conglycinin and glycinin. Energex could only, partly, degrade β-conglycinin. The basic polypeptide from glycinin showed the highest resistance against proteolytic activity. Keywords: Soybean meal; toasting; extrusion; enzymes; protein; cell wall components

Objective. Removal of dead cells is essential in the maintenance of tissue homeostasis, and efficient removal prevents exposure of intracellular content to the immune system, which could lead to autoimmunity. The plasma protease factor VII-activating protease (FSAP) can release nucleosomes from late apoptotic cells. FSAP circulates as an inactive single-chain protein, which is activated upon contact with either apoptotic cells or necrotic cells. The purpose of this study was to investigate the role of FSAP in the release of nucleosomes from necrotic cells.Methods. Necrotic Jurkat cells were incubated with serum, purified 2-chain FSAP, and/or DNase I. Nucleosome release was analyzed by flow cytometry, and agarose gel electrophoresis was performed to detect DNA breakdown.Results. Incubation with serum released nucleosomes from necrotic cells. Incubation with FSAPdeficient serum or serum in which FSAP was inhibited by a blocking antibody was unable to release nucleosomes from necrotic cells, confirming that FSAP is indeed the essential serum factor in this process. Together with serum DNase I, FSAP induced the release of DNA from the cells, the appearance of nucleosomes in the supernatant, and the fragmentation of chromatin into eventually mononucleosomes.Conclusion. FSAP and DNase I are the essential serum factors that cooperate in necrotic cell DNA degradation and nucleosome release. We propose that this mechanism may be important in the removal of potential autoantigens.

Key Points• Free histones, not nucleosomes, are cytotoxic and are degraded by FSAP in serum to protect against cytotoxicity.• Free histone H3 was not detectable in sera of septic baboons and patients with meningococcal sepsis.Circulating histones have been implicated as major mediators of inflammatory disease because of their strong cytotoxic effects. Histones form the protein core of nucleosomes;however, it is unclear whether histones and nucleosomes are equally cytotoxic. Several plasma proteins that neutralize histones are present in plasma. Importantly, factor VII-activating protease (FSAP) is activated upon contact with histones and subsequently proteolyzes histones. We aimed to determine the effect of FSAP on the cytotoxicity of both histones and nucleosomes. Indeed, FSAP protected against histone-induced cytotoxicity of cultured cells in vitro. Upon incubation of serum with histones, endogenous FSAP was activated and degraded histones, which also prevented cytotoxicity. Notably, histones as part of nucleosome complexes were not cytotoxic, whereas DNA digestion restored cytotoxicity. Histones in nucleosomes were inefficiently cleaved by FSAP, which resulted in limited cleavage of histone H3 and removal of the N-terminal tail. The specific isolation of either circulating nucleosomes or free histones from sera of Escherichia coli challenged baboons or patients with meningococcal sepsis revealed that histone H3 was present in the form of nucleosomes, whereas free histone H3 was not detected. All samples showed signs of FSAP activation. Markedly, we observed that all histone H3 in nucleosomes from the patients with sepsis, and most histone H3 from the baboons, was N-terminally truncated, giving rise to a similarly sized protein fragment as through cleavage by FSAP.Taken together, our results suggest that DNA and FSAP jointly limit histone cytotoxicity and that free histone H3 does not circulate in appreciable concentrations in sepsis.

The lectin pathway (LP) of complement has a protective function against invading pathogens. Recent studies have also shown that the LP plays an important role in ischemia/reperfusion (I/R)-injury. MBL-associated serine protease (MASP)-2 appears to be crucial in this process. The serpin C1-inhibitor is the major inhibitor of MASP-2. In addition, aprotinin, a Kunitz-type inhibitor, was shown to inhibit MASP-2 activity in vitro.In this study we investigated whether the Kunitz-type inhibitor tissue factor pathway inhibitor (TFPI) is also able to inhibit MASP-2. Ex vivo LP was induced and detected by C4-deposition on mannan-coated plates. The MASP-2 activity was measured in a fluid-phase chromogenic assay. rTFPI in the absence or presence of specific monoclonal antibodies was used to investigate which TFPI-domains contribute to MASP-2 inhibition. Here, we identify TFPI as a novel selective inhibitor of MASP-2, without affecting MASP-1 or the classical pathway proteases C1s and C1r. Kunitz-2 domain of TFPI is required for the inhibition of MASP-2. Considering the role of MASP-2 in complement-mediated I/R-injury, the inhibition of this protease by TFPI could be an interesting therapeutic approach to limit the tissue damage in conditions such as cerebral stroke, myocardial infarction or solid organ transplantation.Keywords: Complement-coagulation crosstalk r Complement inhibition r MASP-2 r TFPI Additional supporting information may be found in the online version of this article at the publisher's web-site IntroductionThe complement system comprises over 30 different plasma proteins. The complement system consists of three activation pathways, each differing in their recognition mechanism while Correspondence: Mischa P. Keizer e-mail: m.keizer@sanquin.nl converging in a common terminal pathway at the level of complement component 3 (C3). The antibody-dependent classical pathway (CP) initiates the complement system via the binding of C1q to antibodies. Binding to specific sugar motifs by mannan-binding lectins (MBLs) or one of the ficolins activates the lectin pathway (LP) by subsequent activation of the MBL-associated serine proteases (MASPs). The alternative pathway activates spontaneously on surfaces that lack complement regulatory proteins and acts as amplification route for the other two pathways.www.eji-journal.eu Eur. J. Immunol. 2015. 45: 544-550 Innate immunity 545Besides the LP role as first line of defense against invading pathogens, by opsonization and induction of an inflammatory response, recent studies have shown that the LP also plays a prominent role in ischemia/reperfusion (I/R) injury. MBL-deficiency appears to be protective in human myocardial infarction [1], gastrointestinal I/R injury [1], and stroke [2]. This detrimental role of the LP in I/R injury has been confirmed in mice by selectively targeting MASP-2. MASP-2 knockout mice were protected from both gastrointestinal and myocardial I/R injury [3]. Together, these data indicate an important role for MASP-2 in aggravating cell damage in ischemi...

Staphylococcus aureus bi-component pore-forming leukocidins are secreted toxins that directly target and lyse immune cells. Intriguingly, one of the leukocidins, Leukocidin AB (LukAB), is found associated with the bacterial cell envelope in addition to secreted into the extracellular milieu. Here, we report that retention of LukAB on the bacterial cells provides S. aureus with a pre-synthesized active toxin that kills immune cells. On the bacteria, LukAB is distributed as discrete foci in two distinct compartments: membrane-proximal and surface-exposed. Through genetic screens, we show that a membrane lipid, lysyl-phosphatidylglycerol (LPG), and lipoteichoic acid (LTA) contribute to LukAB deposition and release. Furthermore, by studying non-covalently surface-bound proteins we discovered that the sorting of additional exoproteins, such as IsaB, Hel, ScaH, and Geh, are also controlled by LPG and LTA. Collectively, our study reveals a multistep secretion system that controls exoprotein storage and protein translocation across the S. aureus cell wall.