Biochemistry and cell biology of bacterial endotoxins

Anti-Inflammatory Effects of a Novel Acetonitrile-Water Extract of Lens Culinaris against LPS-Induced Damage in Caco-2 Cells

Natural compounds like flavonoids preserve intestinal mucosal integrity through their antioxidant, anti-inflammatory, and antimicrobial properties. Additionally, some flavonoids show prebiotic abilities, promoting the growth and activity of beneficial gut bacteria. This study investigates the protective impact of Lens culinaris extract (LE), which is abundant in flavonoids, on intestinal mucosal integrity during LPS-induced inflammation. Using Caco-2 cells as a model for the intestinal barrier, the study found that LE did not affect cell viability but played a cytoprotective role in the presence of LPS. LE improved transepithelial electrical resistance (TEER) and tight junction (TJ) protein levels, which are crucial for barrier integrity. It also countered the upregulation of pro-inflammatory genes TRPA1 and TRPV1 induced by LPS and reduced pro-inflammatory markers like TNF-α, NF-κB, IL-1β, and IL-8. Moreover, LE reversed the LPS-induced upregulation of AQP8 and TLR-4 expression. These findings emphasize the potential of natural compounds like LE to regulate the intestinal barrier and reduce inflammation's harmful effects on intestinal cells. More research is required to understand their mechanisms and explore therapeutic applications, especially for gastrointestinal inflammatory conditions.

Advances in endotoxin analysis

The outer membrane of gram-negative bacteria is primarily composed of lipopolysaccharide (LPS). In addition to protection, LPS defines the distinct serogroups used to identify bacteria specifically. Furthermore, LPS also act as highly potent stimulators of innate immune cells, a phenomenon essential to understanding pathogen invasion in the body. The complex multi-step process of LPS binding to cells involves several binding partners, including LPS binding protein (LBP), CD14 in both membrane-bound and soluble forms, membrane protein MD-2, and toll-like receptor 4 (TLR4). Once these pathways are activated, pro-inflammatory cytokines are eventually expressed. These binding events are also affected by the presence of monomeric or aggregated LPS. Traditional techniques to detect LPS include the rabbit pyrogen test, the monocyte activation test and Limulus-based tests. Modern approaches are based on protein, antibodies or aptamer binding. Recently, novel techniques including electrochemical methods, HPLC, quartz crystal microbalance (QCM), and molecular imprinting have been developed. These approaches often use nanomaterials such as gold nanoparticles, quantum dots, nanotubes, and magnetic nanoparticles. This chapter reviews current developments in endotoxin detection with a focus on modern novel techniques that use various sensing components, ranging from natural biomolecules to synthetic materials. Highly integrated and miniaturized commercial endotoxin detection devices offer a variety of options as the scientific and technologic revolution proceeds.

Effects of Escherichia coli LPS Structure on Antibacterial and Anti-Endotoxin Activities of Host Defense Peptides

The binding of Host Defense Peptides (HDPs) to the endotoxin of Gram-negative bacteria has important unsolved aspects. For most HDPs, it is unclear if binding is part of the antibacterial mechanism or whether LPS actually provides a protective layer against HDP killing. In addition, HDP binding to LPS can block the subsequent TLR4-mediated activation of the immune system. This dual activity is important, considering that HDPs are thought of as an alternative to conventional antibiotics, which do not provide this dual activity. In this study, we systematically determine, for the first time, the influence of the O-antigen and Lipid A composition on both the antibacterial and anti-endotoxin activity of four HDPs (CATH-2, PR-39, PMAP-23, and PMAP36). The presence of the O-antigen did not affect the antibacterial activity of any of the tested HDPs. Similarly, modification of the lipid A phosphate (MCR-1 phenotype) also did not affect the activity of the HDPs. Furthermore, assessment of inner and outer membrane damage revealed that CATH-2 and PMAP-36 are profoundly membrane-active and disrupt the inner and outer membrane of Escherichia coli simultaneously, suggesting that crossing the outer membrane is the rate-limiting step in the bactericidal activity of these HDPs but is independent of the presence of an O-antigen. In contrast to killing, larger differences were observed for the anti-endotoxin properties of HDPs. CATH-2 and PMAP-36 were much stronger at suppressing LPS-induced activation of macrophages compared to PR-39 and PMAP-23. In addition, the presence of only one phosphate group in the lipid A moiety reduced the immunomodulating activity of these HDPs. Overall, the data strongly suggest that LPS composition has little effect on bacterial killing but that Lipid A modification can affect the immunomodulatory role of HDPs. This dual activity should be considered when HDPs are considered for application purposes in the treatment of infectious diseases.

Recombinant antibodies by phage display for bioanalytical applications

Antibody phage display, aimed at preparing antibodies to defined antigens, is a useful replacement for hybridoma technology. The phage system replaces all work stages that follow animal immunization with simple procedures for manipulating DNA and bacteria. It enables the time needed to generate stable antibody-producing clones to be shortened considerably, making the process noticeably cheaper. Antibodies prepared by phage display undergo several affinity selection steps and can be used as selective receptors in biosensors. This article briefly describes the techniques used in the making of phage antibodies to various antigens. The possibilities and prospects are discussed of using phage antibodies as selective agents in analytical systems, including biosensors.

Lactobacillus plantarum improves LPS-induced Caco2 cell line intestinal barrier damage via cyclic AMP-PKA signaling

Lactobacillus plantarum (LP) has been shown to exhibit protective effects on intestinal barrier function in septic rats, although the regulatory mechanism has not been established. We determined whether LP imparts such protective effects in a lipopolysaccharide (LPS)-induced Caco2 cell monolayer model and whether cAMP-PKA signaling is the underlying mechanism of action. The cyclic adenosine monophosphate (cAMP) agonist, forskolin (FSK), and the protein kinase A (PKA) inhibitor, HT89, were used to study the protective effect of LP on the destruction of the tight junction (TJ) structure of cells treated with LPS and the corresponding changes in cAMP-PKA signaling. Our experimental results demonstrated that LP promoted the expression of TJ proteins between Caco2 cells after LPS treatment, and increased the electrical barrier detection (TEER) between Caco2 cells. Moreover, transmission electron microscopy (TEM) revealed that the TJ structural integrity of cells treated with LPS + LP was improved compared to cells treated with LPS alone. In addition, our findings were consistent between the FSK and LP intervention group, while HT89 inhibited LP influence. Taken together, our results indicate that LP has an improved protective effect on LPS-induced damage to the monolayer membrane barrier function of Caco2 cells and is regulated by the cAMP-PKA pathway.

Clinical relevance of abstruse transport phenomena in haemodialysis

Haemodialysis (HD) utilizes the bidirectional properties of semipermeable membranes to remove uraemic toxins from blood while simultaneously replenishing electrolytes and buffers to correct metabolic acidosis. However, the nonspecific size-dependent transport across membranes also means that certain useful plasma constituents may be removed from the patient (together with uraemic toxins), or toxic compounds, e.g. endotoxin fragments, may accompany electrolytes and buffers of the dialysis fluids into blood and elicit severe biological reactions. We describe the mechanisms and implications of these undesirable transport processes that are inherent to all HD therapies and propose approaches to mitigate the effects of such transport. We focus particularly on two undesirable events that are considered to adversely affect HD therapy and possibly impact patient outcomes. Firstly, we describe how loss of albumin (and other essential substances) can occur while striving to eliminate larger uraemic toxins during HD and why hypoalbuminemia is a clinical condition to contend with. Secondly, we describe the origins and mode of transport of biologically active substances (from dialysis fluids with bacterial contamination) into the blood compartment and biological reactions they elicit. Endotoxin fragments activate various proinflammatory pathways to increase the underlying inflammation associated with chronic kidney disease. Both phenomena involve the physical as well as chemical properties of membranes that must be selected judiciously to balance the benefits with potential risks patients may encounter, in both the short and long term.

Analysis of the Taxonomy and Pathogenic Factors of Pectobacterium aroidearum L6 Using Whole-Genome Sequencing and Comparative Genomics

Soft rot pectobacteria are devastating plant pathogens with a global distribution and a broad host range. Pectobacterium aroidearum L6, previously isolated from leaves of Syngonium podophyllum, is a pectolytic bacterial pathogen that causes typical soft rot on S. podophyllum. There is a shortage for genome data of P. aroidearum, which seriously hinders research on classification and pathogenesis of Pectobacterium. We present here the complete genome sequence of P. aroidearum L6. The L6 strain carries a single 4,995,896-bp chromosome with 53.10% G + C content and harbors 4,306 predicted protein-coding genes. We estimated in silico DNA-DNA hybridization and average nucleotide identity values in combination with the whole-genome-based phylogeny from 19 Pectobacterium strains including P. aroidearum L6. The results showed that L6 and PC1 formed a population distinct from other populations of the Pectobacterium genus. Phylogenetic analysis based on 16S rRNA and genome sequences showed a close evolutionary relationship among Pectobacterium species. Overall, evolutionary analysis showed that L6 was in the same branch with PC1. In comparison with 18 Pectobacterium spp. reference pathogens, strain L6 had 2,712 gene families, among which 1,632 gene families were identified as orthologous to those strains, as well as 1 putative unique gene family. We discovered 478 genes, 10.4% of the total of predicted genes, that were potentially related to pathogenesis using the Virulence Factors of Pathogenic Bacteria database. A total of 25 genes were related to toxins, 35 encoded plant cell-wall degrading enzymes, and 122 were involved in secretion systems. This study provides a foundation for a better understanding of the genomic structure of P. aroidearum and particularly offers information for the discovery of potential pathogenic factors and the development of more effective strategies against this pathogen.

Interaction of nanoparticles with endotoxin Importance in nanosafety testing and exploitation for endotoxin binding

The interaction between engineered nanoparticles and the bacterial lipopolysaccharide, or endotoxin, is an event that warrants attention. Endotoxin is one of the most potent stimulators of inflammation and immune reactions in human beings, and is a very common contaminant in research labs. In nanotoxicology and nanomedicine, the presence of endotoxin on the nanoparticle surface affects their biological properties leading to misinterpretation of results. This review discusses the importance of detecting the endotoxin contamination on nanoparticles, focusing on the current method of endotoxin detection and their suitability for nanoparticulate materials. Conversely, the capacity of nanoparticles to bind endotoxin can be enhanced by functionalization with endotoxin-capturing molecules, opening the way to the development of novel endotoxin detection assays.

The effects of lactobacilli (L. rhamnosus, L. reuteri, L. Plantarum) on LPS-induced memory impairment and changes in CaMKII-α and TNF-α genes expression in the hippocampus of rat

In recent years, some investigations have focused on the relationship between gut microbiota and brain function in healthy and disease conditions. Moreover, changes in the gut microbiome may affect memory, behavior, and cognition. This study aimed to evaluate the effect of lactobacilli on passive avoidance learning, hippocampal CaMKII-α, and TNF-α genes expression in one experimental model of neuroinflammtion. Male wistar rats (220-240 g) received daily oral gavage of different lactobacilli including L. rhamnosus, L. reuteri, and L. plantarum for 21 days. At the next step, behavioral test was performed and 4 hours after acute injection of LPS (1mg/kg, ip) retrieval was evaluated. Then the hippocampi were extracted and kept at _80°C. Finally CaMKII-α and TNF-α mRNA levels were evaluated by Real-time PCR. Our results showed that consumption of L. rhamnosus, L.reuteri, or L. plantarum significantly prevented LPS-induced enhancement of TNF-α mRNA and memory deterioration. Furthermore, L. rhamnosus significantly prevented changes induced by LPS on CaMKII-α mRNA levels. It seems the lactobacilli used in this study can affect brain function and memory performance by their immune-modulatory properties.

Interaction between Macrophages and Nanoparticles: In Vitro 3D Cultures for the Realistic Assessment of Inflammatory Activation and Modulation of Innate Memory

Understanding the modes of interaction between human monocytes/macrophages and engineered nanoparticles is the basis for assessing particle safety, in terms of activation of innate/inflammatory reactions, and their possible exploitation for medical applications. In vitro assessment of nanoparticle-macrophage interaction allows for examining the response of primary human cells, but the conventional 2D cultures do not reproduce the three-dimensional spacing of a tissue and the interaction of macrophages with the extracellular tissue matrix, conditions that shape macrophage recognition capacity and reactivity. Here, we have compared traditional 2D cultures with cultures on a 3D collagen matrix for evaluating the capacity gold nanoparticles to induce monocyte activation and subsequent innate memory in human blood monocytes in comparison to bacterial LPS. Results show that monocytes react to stimuli almost in the same way in 2D and 3D cultures in terms of production of TNFα and IL-6, but that notable differences are found when IL-8 and IL-1Ra are examined, in particular in the recall/memory response of primed cells to a second stimulation, with the 3D cultures showing cell activation and memory effects of nanoparticles better. In addition, the response variations in monocytes/macrophages from different donors point towards a personalized assessment of the nanoparticle effects on macrophage activation.

Efficacy of Artemisia annua L. extract for recovery of acute liver failure

Artemisia annua L. is an annual herb belonging to the Asteraceae family. It is commonly grown in parts of Asia, including Korea and China, and is called by its nickname Gae-ddong-ssuk, or Chung-ho. The herb is well known for its positive effects on fever and hemostasis, as well as its antibiotic effects. To evaluate the protective properties of A. annua L. on the liver, an acute liver failure animal model was set up with intraperitoneal injection of lipopolysaccharide (LPS) and D-galactosamine (D-galN) in C57BL/6J mice, showing increased levels of AST (aspartate transaminase) and ALT (alanine transaminase). Oral administration of the extract of A. annua L. (EAA) for 2 weeks reduced the level of AST and ALT up to 50% of the levels in the negative control group treated with water vehicle. The efficacy of EAA was more effective than that in a comparative positive control group treated with milk thistle extract. Moreover, EAA protected hepatic cells and tissues from oxidative stresses and inflammatory damages, showing downregulation of inflammatory cytokines such as interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α). We also found that LPS stimulated the mouse macrophage cell line, Raw264.7, and secreted a tremendous level of proinflammatory cytokines and the secretion of these cytokines was reduced with EAA treatment via downregulation of mitogen-activated protein kinase phosphorylation and p65 translocation. This study demonstrated that A. annua L. extract is a promising treatment for protection against and recovery from liver damage, as well as maintenance of liver health.

Synthetic Glucocorticoid-Induced Leucine Zipper Peptide Inhibits Lipopolysaccharide-Induced Ocular Inflammation in Rats

PURPOSE

To demonstrate the anti-inflammatory action of a synthetic glucocorticoid-induced leucine zipper (GILZ98-134) peptide (GILZ-p) in a model of endotoxin-induced uveitis (EIU) in rats.

METHODS

The EIU model was induced in Sprague Dawley rats with an intravitreal injection of lipopolysaccharide (LPS). Synthetic GILZ-p was injected intravitreally 6 h after the LPS injection. To evaluate the anti-inflammatory effects of GILZ-p, the inflammatory response in the anterior chamber and iris of the rat eyes was evaluated with a slitlamp microscope on days 0, 1, 2, 3, and 4 after GILZ-p injection. The retinal expression of inflammatory cytokines was measured on days 0, 1, 2, 3, and 4 after GILZ-p injection. Müller cell gliosis was also detected at planned time points after GILZ-p injection.

RESULTS

Anterior segment inflammation peaked at 24 h after LPS injection in the EIU model. Compared with the controls, intravitreal GILZ-p significantly suppressed LPS-induced anterior segment inflammation in the EIU rats. The levels of retinal inflammatory factors IL-1β, TNF-α, MCP-1, and ICAM-1 were simultaneously reduced by the intravitreal GILZ-p injection. The expression of vimentin in the EIU retina was significantly reduced by GILZ-p, and the downregulated aquaporin 4 in the EIU retina was significantly restored by GILZ-p.

CONCLUSION

The synthetic GILZ-p inhibited the inflammatory reaction in the EIU model and may have utility in the treatment of inflammatory ocular disease.

Structure and function of lipid A-modifying enzymes

Lipopolysaccharides are complex molecules found in the cell envelop of many Gram-negative bacteria. The toxic activity of these molecules has led to the terminology of endotoxins. They provide bacteria with structural integrity and protection from external environmental conditions, and they interact with host signaling receptors to induce host immune responses. Bacteria have evolved enzymes that act to modify lipopolysaccharides, particularly the lipid A region of the molecule, to enable the circumvention of host immune system responses. These modifications include changes to lipopolysaccharide by the addition of positively charged sugars, such as N-Ara4N, and phosphoethanolamine (pEtN). Other modifications include hydroxylation, acylation, and deacylation of fatty acyl chains. We review the two-component regulatory mechanisms for enzymes that carry out these modifications and provide details of the structures of four enzymes (PagP, PagL, pEtN transferases, and ArnT) that modify the lipid A portion of lipopolysaccharides. We focus largely on the three-dimensional structures of these enzymes, which provide an understanding of how their substrate binding and catalytic activities are mediated. A structure-function-based understanding of these enzymes provides a platform for the development of novel therapeutics to treat antibiotic resistance.

Use of an electro-optical sensor and phage antibodies for immunodetection of Herbaspirillum

A sheep single-chain antibody-fragment library (Griffin.1, UK) was used to obtain miniantibodies to the lipopolysaccharide of Herbaspirillum seropedicae Z78. Using electro-optical analysis and electron microscopy, we recorded a biospecific interaction of antigenic determinants on the cell surface with phage antibodies against the LPS of H. seropedicae Z78 (mini-Abs_LPS). Control experiments were run to rule out nonspecific binding of the mini-Abs_LPS to cells of Azospirillum brasilense Sp245. Use of the highly specific mini-Abs_LPS enabled the lipopolysaccharide of H. seropedicae Z78 to be detected in a mixture of bacterial cells by electro-optical means (analysis time, ∼5 min). This report is the first to show the possibility of rapid detection of Herbaspirillum on the basis of electro-optical analysis coupled with the use of mini-Abs_LPS. The results are promising for the development of biosensor-based methods to detect potentially human-harmful prokaryotes whose structures either have not been studied or are absent from commercial databases.

The outer membrane glycolipids of bacteria from cold environments: isolation, characterization, and biological activity

Lipopolysaccharides (LPSs) are the main components of the external leaflet of the outer membrane of Gram-negative bacteria. Microorganisms that colonize permanently or transiently cold habitats have evolved an array of structural adaptations, some of which involve components of bacterial membranes. These adaptations assure the perfect functionality of the membrane even at freezing or sub-freezing growth temperatures. This review summarizes the state-of-the-art information concerning the structural features of the LPSs produced by cold-adapted bacteria. The LPS structure has recently been elucidated from species mainly belonging to Gammaproteobacteria and Flavobacteriaceae. Although the reported structural heterogeneity may arise from the phylogenetic diversity of the analyzed source strains, some generalized trends can be deduced. For instance, it is clear that only a small portion of LPSs displays the O-chain. In addition, the biological activity of the lipid A portion from several cold-adapted strains is reported.

Divergent Effects of Metformin on an Inflammatory Model of Parkinson's Disease

The oral antidiabetic drug metformin is known to exhibit anti-inflammatory properties through activation of AMP kinase, thus protecting various brain tissues as cortical neurons, for example. However, the effect of metformin on the substantia nigra (SN), the main structure affected in Parkinson’s disease (PD), has not yet been studied in depth. Inflammation is a key feature of PD and it may play a central role in the neurodegeneration that takes place in this disorder. The aim of this work was to determine the effect of metformin on the microglial activation of the SN of rats using the animal model of PD based on the injection of the pro-inflammogen lipopolysaccharide (LPS). In vivo and in vitro experiments were conducted to study the activation of microglia at both the cellular and molecular levels. Our results indicate that metformin overall inhibits microglia activation measured by OX-6 (MHCII marker), IKKβ (pro-inflammatory marker) and arginase (anti-inflammatory marker) immunoreactivity. In addition, qPCR experiments reveal that metformin treatment minimizes the expression levels of several pro- and anti-inflammatory cytokines. Mechanistically, the drug decreases the phosphorylated forms of mitogen-activated protein kinases (MAPKs) as well as ROS generation through the inhibition of the NADPH oxidase enzyme. However, metformin treatment fails to protect the dopaminergic neurons of SN in response to intranigral LPS. These findings suggest that metformin could have both beneficial and harmful pharmacological effects and raise the question about the potential use of metformin for the prevention and treatment of PD.

Etiologic role of root canal infection in apical periodontitis and its relationship with clinical symptomatology

Evidence shows the polymicrobial etiology of endodontic infections, in which bacteria and their products are the main agents for the development, progression, and dissemination of apical periodontitis. Microbial factors in necrotic root canals (e.g., endotoxin) may spread into apical tissue, evoking and supporting a chronic inflammatory load. Thus, apical periodontitis is the result of the complex interplay between microbial factors and host defense against invasion of periradicular tissues. This review of the literature aims to discuss the complex network between endodontic infectious content and host immune response in apical periodontitis. A better understanding of the relationship of microbial factors with clinical symptomatology is important to establish appropriate therapeutic procedures for a more predictable outcome of endodontic treatment.

New virulence factor CSK29544_02616 as LpxA binding partner in Cronobacter sakazakii

Cronobacter sakazakii is an opportunistic pathogen that can cause meningitis and necrotizing enterocolitis in premature infants, but its virulence determinants remain largely unknown. In this study, a transposon-mediated random-mutant library of C. sakazakii was used to identify new virulence factors. Compared to wild-type bacteria, a mutant lacking CSK29544_02616 (referred to as labp) was defective in invasion into intestinal epithelial cells (by at least 1000-fold) and showed less phagocytosis by macrophages (by at least 50-fold). The lack of labp in C. sakazakii changed the profile of outer membrane proteins, decreased the production of lipopolysaccharides, and increased the production of membrane phospholipids. Bacterial physiological characteristics including surface hydrophobicity and motility were also altered in the absence of labp, presumably because of changes in the bacterial-envelope structure. To systematically determine the role of labp, ligand fishing was conducted using Labp as a bait, which revealed LpxA as a binding partner of Labp. LpxA is UDP-N-acetylglucosamine (GlcNAc) acyltransferase, the first enzyme in the pathway of lipid A biosynthesis. Labp increased the enzymatic activity of LpxA without influencing lpxA expression. Considering multifaceted roles of lipopolysaccharides in virulence regulation, Labp is a novel virulence factor that promotes the production of lipid A by LpxA in Cronobacter.

Capillary Electrophoresis Chips for Fingerprinting Endotoxin Chemotypes and Subclasses

Endotoxins (lipopolysaccharides, LPS; lipooligosaccharides, LOS) are components of the envelope of Gram-negative bacteria. These molecules, responsible for both advantageous and harmful biological activity of these microorganisms, are highly immunogenic and directly involved in numerous bacterial diseases in humans, such as Gram-negative sepsis. The characterization of endotoxins is of importance, since their physiological and pathophysiological effects depend on their chemical structure. The differences among the LPS from different bacterial serotypes and their mutants include variations mainly within the composition and length or missing of their O-polysaccharide chains. Microchip electrophoretic methodology enables the structural characterization of LPS molecules from several bacteria and the quantitative evaluation of components of endotoxin extracts. The improved microchip electrophoretic method is based on the direct labeling of endotoxins by covalent binding of a fluorescent dye. The classification of the S-type LPSs can be done according to their electrophoretic profiles, which are characteristics of the respective bacterial strains. According to the number, distribution, and the relative amounts of components in an endotoxin extract, it is possible to differentiate between the S-type endotoxins from different Gram-negative bacterial strains. The microchip electrophoresis affords high-resolution separation of pure and partially purified (e.g., obtained from whole-cell lysate) S and R endotoxins. This microchip technique provides a new, standardizable, fast, and sensitive method for the detection of endotoxins and for the quantitative evaluation of components of an endotoxin extract.

Dose related effects of LPS on endometrial epithelial cell populations from dioestrus cows

Lipopolysaccharides (LPS) from Gram negative bacteria are involved in the pathogeny of uterine diseases in cows. This study aimed to investigate LPS effects on the growth of bovine endometrial epithelial cells (bEEC) and relationships between LPS response and tissue characteristics. Uteri from 35 females were characterized for parity and stage of oestrous cycle. Densities of glandular tissue (dGT), CD11b+ cells and Ki67+ cells were measured in the endometrial tissue. Cells from 13 dioestrus cows were exposed to 0, 2, 4, 8, 12, 16 or 24μg/mL LPS. Effects of parity and stage of the oestrous cycle on tissue characteristics and effects of LPS dosage, cow and tissue characteristics on changes in cell numbers were analyzed by ANOVA. The dGT was higher in metoestrus and dioestrus samples than in pro-oestrus ones whereas densities of CD11b+ and Ki67+ cells were higher at pro-oestrus (p<0.05-p<0.01). LPS influenced bEEC populations in a dose related manner. An increase in number of live cells was observed for dosages ranging from 2 to 12μg/mL LPS (p<0.0001 vs controls). No effect was found on numbers and frequencies of dead cells. With higher dosages, the numbers of live cells did not increase but the numbers of dead did increase. No relationships were observed between cow or tissue characteristics and growth patterns or frequencies of viable bEEC in controls nor in the response to LPS. To conclude this model is suitable for further studies on dysregulations induced by LPS in endometrial tissue.

Identification of meningococcal LPS as a major monocyte activator in IL-10 depleted shock plasmas and CSF by blocking the CD14-TLR4 receptor complex

We have examined the in vitro stimulatory effects of lipopolysaccharide (LPS)-containing samples (meningococcal shock plasma, n = 10; non-shock plasma, n = 10; cerebrospinal fluid (CSF), n = 7) before and after immunodepletion of interleukin (IL)-10 in a monocyte target assay. We also studied the stimulatory effects of plasma collected from 3 patients with lethal septicemia caused by Streptococcus pneumoniae without detectable LPS but with 100-fold increased levels of heat-shock protein 70 (HSP70). HSP70 may, like LPS, activate monocytes via the Toll-like receptor 4 (TLR4). The samples were analyzed for LPS, tumor necrosis factor (TNF)-α, IL-10 and HSP70; applied on human monocytes (purity > 95%) before and after IL-10 immunodepletion, in the absence or presence of CD14 blocking mAb (60bca) or the lipid A antagonist, Rhodobacter sphaeroides diphosphoryl lipid A (RsDPLA) which blocks TLR4. Monocyte activation was measured by increased TNF-α secretion and tissue factor (TF) up-regulation by monocyte procoagulant activity (PCA). There was a positive correlation between patientplasma LPS levels ( n = 10) and increases in TNF-α secretion by the monocytes after immunodepletion of IL-10 ( r = 0.82). Pretreatment of the monocytes with mAbCD14 or RsDPLA reduced TNF-α secretion to median 5% and 12%, respectively, of the levels before the receptor complex was blocked. The median levels of HSP70 were 543 ng/ml (range, 468—962 ng/ml) in pneumococcal shock plasma, 81.5 ng/ml (range, 41—331 ng/ml) in meningococcal shock plasma and 24 ng/ml (range, < 0.8—41 ng/ml) in meningococcal non-shock plasma. Pneumococcal septic shock plasmas with significantly higher levels of HSP70 ( P < 0.05) did not induce TNF-α secretion in the monocytes. The results strongly suggest that LPS in meningococcal shock plasma is the major activator of monocytes whereas HSP70 (in plasma concentrations up to 963 ng/ml) does not activate monocytes in this assay.

Deletion of caspase-8 in mouse myeloid cells blocks microglia pro-inflammatory activation and confers protection in MPTP neurodegeneration model

Increasing evidence involves sustained pro-inflammatory microglia activation in the pathogenesis of different neurodegenerative diseases, particularly Parkinson's disease (PD). We recently uncovered a completely novel and unexpected role for caspase-8 and its downstream substrates caspase-3/7 in the control of microglia activation and associated neurotoxicity to dopaminergic cells. To demonstrate the genetic evidence, mice bearing a floxed allele ofCASP8 were crossed onto a transgenic line expressing Cre under the control of Lysozyme 2 gene. Analysis of caspase-8 gene deletion in brain microglia demonstrated a high efficiency in activated but not in resident microglia. Mice were challenged with lipopolysaccharide, a potent inducer of microglia activation, or with MPTP, which promotes specific dopaminergic cell damage and consequent reactive microgliosis. In neither of these models, CASP8 deletion appeared to affect the overall number of microglia expressing the pan specific microglia marker, Iba1. In contrast, CD16/CD32 expression, a microglial pro-inflammatory marker, was found to be negatively affected upon CASP8 deletion. Expression of additional proinflammatory markers were also found to be reduced in response to lipopolysaccharide. Of importance, reduced pro-inflammatory microglia activation was accompanied by a significant protection of the nigro-striatal dopaminergic system in the MPTP mouse model of PD.

Structural characterization of the lipid A from the LPS of the haloalkaliphilic bacterium Halomonas pantelleriensis

Halomonas pantelleriensis DSM9661(Τ) is a Gram-negative haloalkaliphilic bacterium isolated from the sand of the volcanic Venus mirror lake, closed to seashore in the Pantelleria Island in the south of Italy. It is able to optimally grow in media containing 3-15 % (w/v) total salt and at pH between 9 and 10. To survive in these harsh conditions, the bacterium has developed several strategies that probably concern the bacteria outer membrane, a barrier regulating the exchange with the environment. In such a context, the lipopolysaccharides (LPSs), which are among the major constituent of the Gram-negative outer membrane, are thought to contribute to the restrictive membrane permeability properties. The structure of the lipid A family derived from the LPS of Halomonas pantelleriensis DSM 9661(T) is reported herein. The lipid A was obtained from the purified LPS by mild acid hydrolysis. The lipid A, which contains different numbers of fatty acids residues, and its partially deacylated derivatives were completely characterized by means of ESI FT-ICR mass spectrometry and chemical analysis. Preliminary immunological assays were performed, and a comparison with the lipid A structure of the phylogenetic proximal Halomonas magadiensis is also reported.

Polyclonal antibodies for specific detection of tobacco host cell proteins can be efficiently generated following RuBisCO depletion and the removal of endotoxins

The production of biopharmaceutical proteins in plants requires efficient downstream processing steps that remove impurities such as host cell proteins (HCPs) and adventitious endotoxins produced by bacteria during transient expression. We therefore strived to develop effective routines for endotoxin removal from plant extracts and the subsequent use of the extracts to generate antibodies detecting a broad set of HCPs. At first, we depleted the superabundant protein ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) for which PEG precipitation achieved the best results, preventing a dominant immune reaction against this protein. We found that a mixture of sera from rabbits immunized with pre-depleted or post-depleted extracts detected more HCPs than the individual sera used alone. We also developed a powerful endotoxin removal procedure using Polymyxin B for extracts from wild type plants or a combination of fiber-flow filtration and EndoTrap Blue for tobacco plants infiltrated with Agrobacterium tumefaciens. The antibodies we generated will be useful for quality and performance assessment in future process development and the methods we present can easily be transferred to other expression systems rendering them useful in the field of plant molecular farming.

Convergent synthesis of 4,5-branched inner-core oligosaccharides of lipopoly- and lipooligosaccharides

The convergent synthesis of branched inner-core oligosaccharides of lipopoly- and lipooligosaccharide with a 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) disaccharide acceptor was achieved. The l-glycero-d-manno-heptopyranose (Hep) units for the branched core oligosaccharide Galβ(1-4)Glcβ(1-4)Hep and Hepα(1-3)Hep were prepared from the corresponding Hep building blocks. To obtain 4,5-branched core oligosaccharide structures, the common acceptor Kdoα(2-4)Kdo was glycosylated with the Hep units.

Lipopolysaccharide-promoted proliferation of Caco-2 cells is mediated by c-Src induction and ERK activation

As a major component of the cell wall of Gram-negative bacteria, lipopolysaccharide (LPS) can be released into the bloodstream to cause a spectrum of pathophysiological reactions. Despite the fact that colon epithelium cells in situ are continuously exposed to LPS, their biological responses as provoked by LPS as well as the underlying mechanisms are poorly defined. In the present study, we observed that LPS directly stimulated growth of Caco-2 cells as well as enhanced the amounts of c-Src, which could be partly attributable to increased c-src transcript. Parallel to LPS-induced c-Src expression was FAK activation and ERK activation. Remarkably, activation of ERK and cellular proliferation by LPS could be inhibited by PP2, the specific Src inhibitor, implicating the essential role of c-Src in this process. To our knowledge, this is the first report indicating that LPS can increase cellular growth via upregulation of c-Src in colon epithelial cells.

Structures, dynamics, and water permeation free energy across bilayers of Lipid A and its analog studied with molecular dynamics simulation

Fundamental studies of the supramolecular layer structures, dynamics and water permeation free energy of hexa-acyl-chain Lipid A and its analogue of tetra-acyl chains would be useful for polymer membranes design for endotoxin removal in water treatment, drug delivery and other biotechnologies. In this work, we studied their supramolecular bilayer by using molecular dynamics simulations and efficient free energy computations. Our simulation accuracy was verified by the agreement between the bilayer structural properties (structure factor, bilayer thickness, and the area per lipid) and lateral diffusion coefficient in our simulation and experimental measurements. More importantly, our simulation for the first time illustrated hexagonal compact packing of the hydrocarbon acyl chains within a leaflet of Lipid A membrane (at 298 K and water content of 40 wt %), which is consistent with experiments. In contrast, Lipid A analogue is found with less ordered ripple structures at the same condition. Our study also demonstrated slower dynamics and larger and broader free energy barrier (∼23 kJ/mol) for water permeation for Lipid A, compared with that of Lipid A analogue. Moreover, the analysis of dynamics showed that highly hydrated hydrophilic diglucosamine backbone is structurally stable, whereas the interdigitated hydrophobic acyl chain tails inside the membrane with faster dynamics screen the aqueous environment from the lipid interior and also reinforce the membrane's structural stability.

Gram-negative marine bacteria: structural features of lipopolysaccharides and their relevance for economically important diseases

Gram-negative marine bacteria can thrive in harsh oceanic conditions, partly because of the structural diversity of the cell wall and its components, particularly lipopolysaccharide (LPS). LPS is composed of three main parts, an O-antigen, lipid A, and a core region, all of which display immense structural variations among different bacterial species. These components not only provide cell integrity but also elicit an immune response in the host, which ranges from other marine organisms to humans. Toll-like receptor 4 and its homologs are the dedicated receptors that detect LPS and trigger the immune system to respond, often causing a wide variety of inflammatory diseases and even death. This review describes the structural organization of selected LPSes and their association with economically important diseases in marine organisms. In addition, the potential therapeutic use of LPS as an immune adjuvant in different diseases is highlighted.

Vibrio vulnificus MO6-24/O lipopolysaccharide stimulates superoxide anion, thromboxane B₂, matrix metalloproteinase-9, cytokine and chemokine release by rat brain microglia in vitro

Although human exposure to Gram-negative Vibrio vulnificus (V. vulnificus) lipopolysaccharide (LPS) has been reported to result in septic shock, its impact on the central nervous system's innate immunity remains undetermined. The purpose of this study was to determine whether V. vulnificus MO6-24/O LPS might activate rat microglia in vitro and stimulate the release of superoxide anion (O₂⁻), a reactive oxygen species known to cause oxidative stress and neuronal injury in vivo. Brain microglia were isolated from neonatal rats, and then treated with either V. vulnificus MO6-24/O LPS or Escherichia coli O26:B6 LPS for 17 hours in vitro. O₂⁻ was determined by cytochrome C reduction, and matrix metalloproteinase-2 (MMP-2) and MMP-9 by gelatinase zymography. Generation of cytokines tumor necrosis factor alpha (TNF-α), interleukin-1 alpha (IL-1α), IL-6, and transforming growth factor-beta 1 (TGF-β1), chemokines macrophage inflammatory protein (MIP-1α)/chemokine (C-C motif) ligand 3 (CCL3), MIP-2/chemokine (C-X-C motif) ligand 2 (CXCL2), monocyte chemotactic protein-1 (MCP-1)/CCL2, and cytokine-induced neutrophil chemoattractant-2alpha/beta (CINC-2α/β)/CXCL3, and brain-derived neurotrophic factor (BDNF), were determined by specific immunoassays. Priming of rat microglia by V. vulnificus MO6-24/O LPS in vitro yielded a bell-shaped dose-response curve for PMA (phorbol 12-myristate 13-acetate)-stimulated O₂⁻ generation: (1) 0.1-1 ng/mL V. vulnificus LPS enhanced O₂⁻ generation significantly but with limited inflammatory mediator generation; (2) 10-100 ng/mL V. vulnificus LPS maximized O₂⁻ generation with concomitant release of thromboxane B2 (TXB2), matrix metalloproteinase-9 (MMP-9), and several cytokines and chemokines; (3) 1000-100,000 ng/mL V. vulnificus LPS, with the exception of TXB2, yielded both attenuated O₂⁻ production, and a progressive decrease in MMP-9, cytokines and chemokines investigated. Thus concentration-dependent treatment of neonatal brain microglia with V. vulnificus MO6-24/O LPS resulted in a significant rise in O₂⁻ production, followed by a progressive decrease in O₂⁻ release, with concomitant release of lactic dehydrogenase (LDH), and generation of TXB2, MMP-9, cytokines and chemokines. We hypothesize that the inflammatory mediators investigated may be cytotoxic to microglia in vitro, by an as yet undetermined autocrine mechanism. Although V. vulnificus LPS was less potent than E. coli LPS in vitro, inflammatory mediator release by the former was clearly more efficacious. Finally, we hypothesize that should V. vulnificus LPS gain entry into the CNS, it would be possible that microglia might become activated, resulting in high levels of O₂⁻ as well as neuroinflammatory TXB2, MMP-9, cytokines and chemokines.

Chronic stress enhances microglia activation and exacerbates death of nigral dopaminergic neurons under conditions of inflammation

Background

Parkinson’s disease is an irreversible neurodegenerative disease linked to progressive movement disorders and is accompanied by an inflammatory reaction that is believed to contribute to its pathogenesis. Since sensitivity to inflammation is not the same in all brain structures, the aim of this work was to test whether physiological conditions as stress could enhance susceptibility to inflammation in the substantia nigra, where death of dopaminergic neurons takes place in Parkinson’s disease.

Methods

To achieve our aim, we induced an inflammatory process in nonstressed and stressed rats (subject to a chronic variate stress) by a single intranigral injection of lipopolysaccharide, a potent proinflammogen. The effect of this treatment was evaluated on inflammatory markers as well as on neuronal and glial populations.

Results

Data showed a synergistic effect between inflammation and stress, thus resulting in higher microglial activation and expression of proinflammatory markers. More important, the higher inflammatory response seen in stressed animals was associated with a higher rate of death of dopaminergic neurons in the substantia nigra, the most characteristic feature seen in Parkinson’s disease. This effect was dependent on glucocorticoids.

Conclusions

Our data demonstrate that stress sensitises midbrain microglia to further inflammatory stimulus. This suggests that stress may be an important risk factor in the degenerative processes and symptoms of Parkinson’s disease.

Lipopolysaccharides accelerate hepatic steatosis in the development of nonalcoholic fatty liver disease in Zucker rats

Nonalcoholic fatty liver disease (NAFLD) can develop into end-stage disease that includes cryptogenic cirrhosis and hepatocellular carcinoma. Bacterial endotoxin, for example lipopolysaccharide (LPS), plays an important role in the pathogenesis of NAFLD. The aim of this study was to assess the role of LPS in the development of NAFLD. Twenty-one male Zucker (fa/fa) rats were divided into three groups: rats fed for twelve weeks on a diet rich in disaccharide (D12 group), rats similarly managed but treated with LPS (LPS group), and those on the same diet for 24 weeks (D24 group). Histological examination demonstrated that this protocol induced hepatic steatosis in the LPS and D24 groups. Significant, marked accumulation of lipid droplets was observed in the LPS group, compared with the D24 group. Rats from the LPS group showed a decrease in plasma adiponectin levels, an increase in plasma leptin levels, and greater expression of FAS and SREBP-1c mRNA in the liver, compared with rats from the D24 group. These finding coincided with histological findings. We therefore suggest that LPS may accelerate the progression of hepatic steatosis.

Exploring the immunomodulatory potential of microbial-associated molecular patterns derived from the enteric bacterial microbiota

The human intestinal lumen represents one of the most densely populated microbial niches in the biological world and, as a result, the intestinal innate immune system exists in a constant state of stimulation. A key component in the innate defence system is the intestinal epithelial layer, which acts not only as a physical barrier, but also as an immune sensor. The expression of pattern recognition receptors, such as Toll-like receptors, in epithelial cells allows innate recognition of a wide range of highly conserved bacterial moieties, termed microbial-associated molecular patterns (MAMPs), from both pathogenic and non-pathogenic bacteria. To date, studies of epithelial immunity have largely concentrated on inflammatory pathogenic antigens; however, this review discusses the major types of MAMPs likely to be produced by the enteric bacterial microbiota and, using data from in vitro studies, animal model systems and clinical observations, speculates on their immunomodulatory potential.

Synergistic effects of pyrrolizidine alkaloids and lipopolysaccharide on preterm delivery and intrauterine fetal death in mice

Preterm birth is the leading cause of death for newborn infants, and lipopolysaccharide (LPS) is commonly used to induce preterm delivery in experimental animals. Pyrrolizidine alkaloids (PAs) are widespread and occur in foods, herbs, and other plants. This study was to investigate the synergistic effects of LPS and two representative PAs, retrorsine (RTS) and monocrotaline (MCT), on preterm delivery and fetal death. Pregnant Kunming mice were divided into seven groups: control, RTS, MCT, LPS, RTS+LPS and two MCT+LPS groups. Animals in PAs and PAs+LPS groups were dosed intragastrically with RTS (10mg/kg) or MCT (20 mg/kg or 60 mg/kg) from gestational day (GD) 9 to GD16; mice given LPS were injected intraperitoneally with 150 μg/kg on GD15.5. Latencies to delivery, numbers of pups live and dead at birth were recorded, and livers of live neonates were collected. The incidence of LPS-induced preterm birth was enhanced in dams pretreated with MCT, and combination of PAs and LPS increased fetal mortality from PAs. The enhancement of LPS-induced preterm delivery and fetal demise in animals exposed chronically to PAs and other substances found in foods and beverages consumed widely by humans merits further focused investigation.

Structural characterization of bacterial lipopolysaccharides with mass spectrometry and on- and off-line separation techniques

The focus of this review is the application of mass spectrometry to the structural characterization of bacterial lipopolysaccharides (LPSs), also referred to as "endotoxins," because they elicit the strong immune response in infected organisms. Recently, a wide variety of MS-based applications have been implemented to the structure elucidation of LPS. Methodological improvements, as well as on- and off-line separation procedures, proved the versatility of mass spectrometry to study complex LPS mixtures. Special attention is given in the review to the tandem mass spectrometric methods and protocols for the analyses of lipid A, the endotoxic principle of LPS. We compare and evaluate the different ionization techniques (MALDI, ESI) in view of their use in intact R- and S-type LPS and lipid A studies. Methods for sample preparation of LPS prior to mass spectrometric analysis are also described. The direct identification of intrinsic heterogeneities of most intact LPS and lipid A preparations is a particular challenge, for which separation techniques (e.g., TLC, slab-PAGE, CE, GC, HPLC) combined with mass spectrometry are often necessary. A brief summary of these combined methodologies to profile LPS molecular species is provided.

Lipid A from lipopolysaccharide recognition: structure, dynamics and cooperativity by molecular dynamics simulations

Molecular dynamics simulations of Lipid A and its natural precursor Lipid IVA from E.coli have been carried out free in solution, bound to the myeliod differentiation protein 2 (MD2) and in the complex of MD2 with the toll like receptor 4 (TLR4). In addition, simulations of the ligand free MD2 and MD2-TLR4 complex were performed. A structural and energetic characterization of the bound and unbound states of Lipid A/IVA was generated. As the crystal structures depict, the main driving force for MD2-Lipid A/IVA are the hydrophobic interactions between the aliphatic tails and the MD2 cavity. The charged phosphate groups do strongly interact with positively charged residues, located at the surface of MD2. However, they are not essential for keeping the lipids in the cavity, indicating a more prominent role in binding recognition and ionic interactions with TLR4 at the MD2/TLR4 interface. Interestingly, in the absence of any ligand MD2 rapidly closes, blocking the binding cavity. The presence of TLR4, though changing the dynamics, was not able to impede the aforementioned closing event. We hypothesize that fluctuations of the H1 region are essential for this phenomenon, and it is plausible that an equilibrium between the open and closed states exists, although the lengths of our simulations are not sufficient to encompass the reversible process. The MD2/Lipid A-TLR4 complex simulations show that the presence of the ligand energetically stabilizes the complex relative to the ligand-free structures, indicating cooperativity in the binding process.

Immunity and inflammation in the uterus

Microbes often infect the uterus and particularly the endometrium of animals. Infections are most commonly associated with natural service, pregnancy and the post-partum period, leading to inflammation with the elaboration of cytokines, chemokines and prostaglandins. Clinical diseases such as metritis, endometritis and abortion are important causes of infertility. The adaptive immune response to infection has been characterized previously, so the present review aims to highlight the emerging role for innate immunity in the endometrium. The detection of microbes and the innate immune response depends on the detection of pathogen-associated molecular patterns by pattern recognition receptors. The main families of pattern recognition receptors are Toll-like receptors (TLRs), nucleotide oligomerization domain-like receptors, retinoic acid-inducible gene I-like receptors and C-type lectin receptors. These receptors are most often expressed by hematopoietic cells, but the epithelial and stromal cells of the endometrium also possess functional receptors. For example, endometrial cells express TLR4 for recognition of the lipopolysaccharide endotoxin of Gram-negative bacteria, leading to secretion of IL-6, IL-8 and prostaglandin E(2) . It is likely that the epithelial and stromal cells provide a first line of defence in the endometrium to alert hematopoietic cells to the presence of microbes within the uterus.

Measurement of endotoxins in bioaerosols at workplace: a critical review of literature and a standardization issue

Endotoxins are lipopolysaccharides found in the outer membrane of most Gram-negative bacteria and cyanobacteria. Worker exposure to endotoxins has been shown in a number of work situations and is associated with both respiratory and systemic pathologies. The lack of an occupational exposure limit is mainly due to the absence of a standard protocol at the international level for sampling and analyzing airborne endotoxins. The bibliographic review in this article takes an exhaustive look at the current knowledge on measuring airborne endotoxins. It shows that, despite several reference documents at the international level, the methods used to measure endotoxin exposure differ considerably from one laboratory to another. Standardization is necessary to reduce interlaboratory variability and, ultimately, to improve the use of interstudy data. The bibliographic review presents the current status of standardization for airborne endotoxin measurement methods in the workplace and summarizes areas for further research. This article is both a reference document for all operators wishing to use such methods and a working document to build international consensus around the measurement of airborne endotoxins.

Role of cerebral endothelial cells in the astrocyte swelling and brain edema associated with acute hepatic encephalopathy

Brain edema is an important complication of acute hepatic encephalopathy (AHE), and astrocyte swelling is largely responsible for its development. Elevated blood and brain ammonia levels have been considered as major etiological factors in this edema. In addition to ammonia, recent studies have suggested that systemic infection, inflammation (and associated cytokines (CKs)), as well as endotoxin (lipopolysaccharide (LPS)) are also involved in AHE-associated brain edema. As endothelial cells (ECs) are the first resident brain cells exposed to blood-borne "noxious agents" (i.e., ammonia, CKs, LPS) that are present in AHE, these cells may be in a critical position to react to these agents and trigger a process resulting in astrocyte swelling/brain edema. We therefore examined the effect of conditioned media (CM) from ammonia, LPS and cytokine-treated cultured brain ECs on cell swelling in cultured astrocytes. CM from ammonia-treated ECs when added to astrocytes caused significant cell swelling, and such swelling was potentiated when astrocytes were exposed to CM from ECs treated with a combination of ammonia, LPS and CKs. We also found an additive effect when astrocytes were exposed to ammonia along with CM from ammonia-treated ECs. Additionally, ECs treated with ammonia showed a significant increase in the production of oxy-radicals, nitric oxide (NO), as well as evidence of oxidative/nitrative stress and activation of the transcription factor nuclear factor kappa B (NF-κB). CM derived from ECs treated with ammonia, along with antioxidants (AOs) or the NF-κB inhibitor BAY 11-7082, when added to astrocytes resulted in a significant reduction in cell swelling, as compared to the effect of CM from ECs-treated only with ammonia. We also identified increased nuclear NF-κB expression in rat brain cortical ECs in the thioacetamide (TAA) model of AHE. These studies suggest that ECs significantly contribute to the astrocyte swelling/brain edema in AHE, likely as a consequence of oxidative/nitrative stress and activation of NF-κB.